Stainless steel is an
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
of
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
that is resistant to
rust
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...
ing and
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
. It contains at least 11%
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
and may contain elements such as
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
, other
nonmetal
In chemistry, a nonmetal is a chemical element that generally lacks a predominance of metallic properties; they range from colorless gases (like hydrogen) to shiny solids (like carbon, as graphite). The electrons in nonmetals behave differentl ...
s and
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s to obtain other desired properties. Stainless steel's
resistance to corrosion results from the chromium, which forms a
passive film that can protect the material and
self-heal
''Prunella'' is a genus of herbaceous plants in the family Lamiaceae, also known as self-heals, heal-all, or allheal for their use in herbal medicine.
Habitat
Most are native to Europe, Asia, and North Africa, but ''Prunella vulgaris'' (common ...
in the presence of oxygen.
The alloy's properties, such as luster and resistance to corrosion, are useful in many applications. Stainless steel can be rolled into
sheets
A bed sheet is a rectangular piece of cloth used either singly or in a pair as bedding, which is larger in length and width than a mattress, and which is placed immediately above a mattress or bed, but below blankets and other bedding (such as ...
, plates, bars, wire, and tubing. These can be used in
cookware
Cookware and bakeware is food preparation equipment, such as cooking pots, pans, baking sheets etc. used in kitchens. Cookware is used on a stove or range cooktop, while bakeware is used in an oven. Some utensils are considered both cookware ...
,
cutlery
Cutlery (also referred to as silverware, flatware, or tableware), includes any hand implement used in preparing, serving, and especially eating food in Western culture. A person who makes or sells cutlery is called a cutler. The city of Sheffie ...
,
surgical instrument
A surgical instrument is a tool or device for performing specific actions or carrying out desired effects during a surgery or operation, such as modifying biological tissue, or to provide access for viewing it. Over time, many different kinds of ...
s,
major appliance
A major appliance, also known as a large domestic appliance or large electric appliance or simply a large appliance, large domestic, or large electric, is a non-portable or semi-portable machine used for routine housekeeping tasks such as cookin ...
s, vehicles, construction material in large buildings, industrial equipment (e.g., in
paper mill
A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags, and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt, ...
s,
chemical plant
A chemical plant is an industrial process plant that manufactures (or otherwise processes) chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transform ...
s,
water treatment
Water treatment is any process that improves the Water quality, quality of water to make it appropriate for a specific end-use. The end use may be drinking water, drinking, industrial water supply, irrigation, river flow maintenance, water recrea ...
), and storage tanks and tankers for chemicals and food products.
The biological
cleanability
Cleanability is a term used in clean productions (e.g. to assess the cleanability of technical surfaces).
Description
In order to ensure optimum cleanability of the surfaces of machines and equipment, they must fulfil certain requirements. Where ...
of stainless steel is superior to both
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
and copper, having a biological cleanability comparable to glass. Its cleanability, strength, and corrosion resistance have prompted the use of stainless steel in pharmaceutical and food processing plants.
Different types of stainless steel are labeled with an
AISI three-digit number,
The ISO 15510 standard lists the chemical compositions of stainless steels of the specifications in existing ISO,
ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
,
EN,
JIS, and
GB standards in a useful interchange table.
Properties
Conductivity
Like steel, stainless steels are relatively poor conductors of electricity, with significantly lower
electrical conductivities than copper. In particular, the
electrical contact resistance
The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance. This effect is describe ...
(ECR) of stainless steel arises as a result of the dense protective oxide layer and limits its functionality in applications as electrical connectors. Copper alloys and nickel-coated connectors tend to exhibit lower ECR values, and are preferred materials for such applications. Nevertheless, stainless steel connectors are employed in situations where ECR poses a lower design criteria and corrosion resistance is required, for example in high temperatures and oxidizing environments.
Melting point
As with all other alloys, the melting point of stainless steel is expressed in the form of a range of temperatures, and not a singular temperature. This temperature range goes from depending on the specific consistency of the alloy in question.
Magnetism
Martensitic
Martensite is a very hard form of steel crystalline structure. It is named after German metallurgist Adolf Martens. By analogy the term can also refer to any crystal structure that is formed by diffusionless transformation.
Properties
Mart ...
,
duplex and
ferritic stainless steel
Ferritic stainless steel forms one of the five stainless steel families, the other four being austenitic, martensitic, duplex stainless steels, and ''precipitation hardened''. For example, many of AISI 400-series of stainless steels are ferritic st ...
s are
magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...
, while
austenitic stainless steel
Austenitic stainless steel is one of the five classes of stainless steel by crystalline structure (along with ''ferritic'', ''martensitic, duplex and precipitation hardened''). Its primary crystalline structure is austenite (face-centered cubic) ...
is usually non-magnetic. Ferritic steel owes its magnetism to its
body-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
, in which iron atoms are arranged in cubes (with one iron atom at each corner) and an additional iron atom in the center. This central iron atom is responsible for ferritic steel's magnetic properties. This arrangement also limits the amount of carbon the steel can absorb to around 0.025%. Grades with low coercive field have been developed for electro-valves used in household appliances and for injection systems in internal combustion engines. Some applications require non-magnetic materials, such as
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
.
Austenitic
Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K ...
stainless steels, which are usually
non-magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...
, can be made slightly magnetic through
work hardening
In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context.
This strengt ...
. Sometimes, if austenitic steel is bent or cut, magnetism occurs along the edge of the stainless steel because the crystal structure rearranges itself.
Corrosion
The addition of nitrogen also improves resistance to pitting corrosion and increases mechanical strength.
Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure. Corrosion resistance can be increased further by the following means:
* increasing chromium content to more than 11%
* adding nickel to at least 8%
* adding molybdenum (which also improves resistance to
pitting corrosion
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation re ...
)
Wear
Galling
Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is cau ...
, sometimes called cold welding, is a form of severe adhesive wear, which can occur when two metal surfaces are in relative motion to each other and under heavy pressure. Austenitic stainless steel fasteners are particularly susceptible to thread galling, though other alloys that self-generate a protective oxide surface film, such as aluminium and titanium, are also susceptible. Under high contact-force sliding, this oxide can be deformed, broken, and removed from parts of the component, exposing the bare reactive metal. When the two surfaces are of the same material, these exposed surfaces can easily fuse. Separation of the two surfaces can result in surface tearing and even complete seizure of metal components or fasteners.
Galling can be mitigated by the use of dissimilar materials (bronze against stainless steel) or using different stainless steels (martensitic against austenitic). Additionally, threaded joints may be
lubricated to provide a film between the two parts and prevent galling.
Nitronic
Nitronic is the trade name for a collection of nitrogen-strengthened stainless steel alloys. They are austenitic stainless steels.
History
Nitronic alloys were developed by AK Steel, Armco Steel. The first of these alloys, Nitronic 40, was introd ...
60, made by selective alloying with manganese, silicon, and nitrogen, has demonstrated a reduced tendency to gall.
Density
The density of stainless steel can be somewhere between 7,500kg/m3 to 8,000kg/m3 depending on the alloy.
History
An announcement, as it appeared in the 1915 ''New York Times'', of the development of stainless steel in , England.">Sheffield, England.
The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the
French Academy
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
by
Louis Vauquelin
Prof. Louis Nicolas Vauquelin FRS(For) HFRSE (16 May 1763 – 14 November 1829) was a French pharmacist and chemist. He was the discoverer of both chromium and beryllium.
Early life
Vauquelin was born at Saint-André-d'Hébertot in Normandy, F ...
. In the early 1800s, British scientists James Stoddart,
Michael Faraday
Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...
, and
Robert Mallet
Robert Mallet (3 June 1810 – 5 November 1881) was an Irish geophysicist, civil engineer, and inventor who distinguished himself in research on earthquakes and is sometimes called the father of seismology. His son, Frederick Richard Mallet was ...
observed the resistance of chromium-iron alloys ("chromium steels") to
oxidizing agents
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
.
Robert Bunsen
Robert Wilhelm Eberhard Bunsen (;
30 March 1811
– 16 August 1899) was a German chemist. He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. The Bu ...
discovered chromium's resistance to strong acids. The corrosion resistance of iron-chromium alloys may have been first recognized in 1821 by
Pierre Berthier
Pierre Berthier (; 3 July 1782, Nemours, Seine-et-Marne – 24 August 1861) was a French geologist and mining engineer.
Pierre Berthier was born in Nemours. After studying at the École Polytechnique, he went to the École des Mines, where he bec ...
, who noted their resistance against attack by some acids and suggested their use in cutlery.
In the 1840s, both of Britain's
Sheffield
Sheffield is a city status in the United Kingdom, city in South Yorkshire, England, whose name derives from the River Sheaf which runs through it. The city serves as the administrative centre of the City of Sheffield. It is Historic counties o ...
steelmakers and then
Krupp
The Krupp family (see pronunciation), a prominent 400-year-old German dynasty from Essen, is notable for its production of steel, artillery, ammunition and other armaments. The family business, known as Friedrich Krupp AG (Friedrich Krup ...
of Germany were producing chromium steel with the latter employing it for cannons in the 1850s. In 1861,
Robert Forester Mushet
Robert Forester Mushet (8 April 1811 – 29 January 1891) was a British metallurgist and businessman, born on 8 April 1811, in Coleford, in the Forest of Dean, Gloucestershire, England. He was the youngest son of Scottish parents, Agnes Wilson ...
took out a patent on chromium steel in Britain.
These events led to the first American production of chromium-containing steel by J. Baur of the Chrome Steel Works of Brooklyn for the construction of bridges. A US patent for the product was issued in 1869.
This was followed with recognition of the corrosion resistance of chromium alloys by Englishmen John T. Woods and John Clark, who noted ranges of chromium from 5–30%, with added tungsten and "medium carbon". They pursued the commercial value of the innovation via a British patent for "Weather-Resistant Alloys".
[
In the late 1890s, German chemist ]Hans Goldschmidt
Johannes Wilhelm "Hans" Goldschmidt (18 January 1861 – 21 May 1923) was a German chemist notable as the discoverer of the Thermite reaction. He was also co-owner of the Chemische Fabrik Th. Goldschmidt, as of 1911 Th. Goldschmidt AG (later to be ...
developed an aluminothermic (thermite
Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brief ...
) process for producing carbon-free chromium.[ Between 1904 and 1911, several researchers, particularly ]Leon Guillet
Leon, Léon (French) or León (Spanish) may refer to:
Places
Europe
* León, Spain, capital city of the Province of León
* Province of León, Spain
* Kingdom of León, an independent state in the Iberian Peninsula from 910 to 1230 and again fro ...
of France, prepared alloys that would be considered stainless steel today.
In 1908, the Essen
Essen (; Latin: ''Assindia'') is the central and, after Dortmund, second-largest city of the Ruhr, the largest urban area in Germany. Its population of makes it the fourth-largest city of North Rhine-Westphalia after Cologne, Düsseldorf and D ...
firm Friedrich Krupp Germaniawerft Friedrich may refer to:
Names
*Friedrich (surname), people with the surname ''Friedrich''
*Friedrich (given name), people with the given name ''Friedrich''
Other
*Friedrich (board game), a board game about Frederick the Great and the Seven Years' ...
built the 366-ton sailing yacht ''Germania
Germania ( ; ), also called Magna Germania (English: ''Great Germania''), Germania Libera (English: ''Free Germania''), or Germanic Barbaricum to distinguish it from the Roman province of the same name, was a large historical region in north- ...
'' featuring a chrome-nickel steel hull, in Germany. In 1911, Philip Monnartz
Philip, also Phillip, is a male given name, derived from the Greek (''Philippos'', lit. "horse-loving" or "fond of horses"), from a compound of (''philos'', "dear", "loved", "loving") and (''hippos'', "horse"). Prominent Philips who popularize ...
reported on the relationship between chromium content and corrosion resistance. On 17 October 1912, Krupp
The Krupp family (see pronunciation), a prominent 400-year-old German dynasty from Essen, is notable for its production of steel, artillery, ammunition and other armaments. The family business, known as Friedrich Krupp AG (Friedrich Krup ...
engineers Benno Strauss and Eduard Maurer patented as Nirosta Outokumpu Nirosta is a business segment of Outokumpu, headquartered in Krefeld, Germany. It produces flats of stainless steel. Prior to January 2012, it was named ThyssenKrupp Nirosta and part of ThyssenKrupp AG. The unit has a plant in Bochum.
The ...
the austenitic stainless steel
Austenitic stainless steel is one of the five classes of stainless steel by crystalline structure (along with ''ferritic'', ''martensitic, duplex and precipitation hardened''). Its primary crystalline structure is austenite (face-centered cubic) ...
known today as 18/8 or AISI Type 304.[
Similar developments were taking place in the United States, where ]Christian Dantsizen
Christians () are people who follow or adhere to Christianity, a monotheistic Abrahamic religion based on the life and teachings of Jesus Christ. The words ''Christ'' and ''Christian'' derive from the Koine Greek title ''Christós'' (Χρι ...
of General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
and Frederick Becket Frederick may refer to:
People
* Frederick (given name), the name
Nobility
Anhalt-Harzgerode
*Frederick, Prince of Anhalt-Harzgerode (1613–1670)
Austria
* Frederick I, Duke of Austria (Babenberg), Duke of Austria from 1195 to 1198
* Frederi ...
(1875-1942) at Union Carbide
Union Carbide Corporation is an American chemical corporation wholly owned subsidiary (since February 6, 2001) by Dow Chemical Company. Union Carbide produces chemicals and polymers that undergo one or more further conversions by customers befor ...
were industrializing ferritic stainless steel. In 1912, Elwood Haynes
Elwood Haynes (October 14, 1857 – April 13, 1925) was an American inventor, metallurgist, automotive pioneer, entrepreneur and industrialist. He invented the metal alloy stellite and independently co-discovered martensitic stainless steel ...
applied for a US patent on a martensitic stainless steel alloy, which was not granted until 1919.
Harry Brearley
While seeking a corrosion-resistant alloy for gun barrels in 1912, Harry Brearley
Harry Brearley (18 February 1871 – 14 July 1948)
was an English metallurgist, credited with the invention of "rustless steel" (later to be called "stainless steel" in the anglophone world). Based in Sheffield, his invention brought affordabl ...
of the Brown-Firth research laboratory in Sheffield, England, discovered and subsequently industrialized a martensitic stainless steel
Martensitic stainless steel is a type of stainless steel alloy that has a martensite crystal structure. It can be hardened and tempered through aging and heat treatment. The other main types of stainless steel are ''austenitic'', ''ferritic'', '' ...
alloy, today known as AISI Type 420.[ The discovery was announced two years later in a January 1915 newspaper article in ''The New York Times''.]
The metal was later marketed under the "Staybrite" brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel
The Savoy Hotel is a luxury hotel located in the Strand in the City of Westminster in central London, England. Built by the impresario Richard D'Oyly Carte with profits from his Gilbert and Sullivan opera productions, it opened on 6 August 188 ...
in London in 1929. Brearley applied for a US patent during 1915 only to find that Haynes had already registered one. Brearley and Haynes pooled their funding and, with a group of investors, formed the American Stainless Steel Corporation, with headquarters in Pittsburgh
Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County, Pennsylvania, Allegheny County. It is the most populous city in both Allegheny County and Wester ...
, Pennsylvania.
Rustless steel
Brearley initially called his new alloy "rustless steel". The alloy was sold in the US under different brand names like "Allegheny metal" and "Nirosta steel". Even within the metallurgy industry, the name remained unsettled; in 1921, one trade journal called it "unstainable steel". Brearley worked with a local cutlery manufacturer, who gave it the name "stainless steel". As late as 1932, Ford Motor Company
Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...
continued calling the alloy rustless steel in automobile promotional materials.
In 1929, before the Great Depression, over 25,000 tons of stainless steel were manufactured and sold in the US annually.
Major technological advances in the 1950s and 1960s allowed the production of large tonnages at an affordable cost:
* AOD process (argon oxygen decarburization
Argon oxygen decarburization (AOD) is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as chromium and aluminum. After initial melting the metal is then transferred to an AOD vessel where ...
), for the removal of carbon and sulfur
*Continuous casting
Continuous casting, also called strand casting, is the process whereby molten metal is solidified into a "semifinished" billet, bloom, or slab for subsequent rolling in the finishing mills. Prior to the introduction of continuous casting in the ...
and hot strip rolling
* The Z-Mill, or Sendzimir cold rolling mill
* The Creusot-Loire Uddeholm
Creusot-Loire was a French engineering conglomerate, formed from factories in Le Creusot and Châteauneuf, Loire. The Creusot-Loire subsidiary of ArcelorMittal also includes an Innovation, Research and Development centre for the group.
History
Th ...
(CLU) and related processes which use steam instead of some or all of the argon
Types
There are five main families, which are primarily classified by their crystalline structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns th ...
: austenitic, ferritic, martensitic, duplex, and precipitation hardening.
Austenitic
Austenitic stainless steel is the largest family of stainless steels, making up about two-thirds of all stainless steel production. They possess an austenitic microstructure, which is a face-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
crystal structure. This microstructure is achieved by alloying steel with sufficient nickel and/or manganese and nitrogen to maintain an austenitic microstructure at all temperatures, ranging from the cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
region to the melting point. Thus, austenitic stainless steels are not hardenable by heat treatment since they possess the same microstructure at all temperatures.
Austenitic stainless steels sub-groups, 200 series and 300 series:
* 200 series are chromium-manganese-nickel alloys that maximize the use of manganese and nitrogen to minimize the use of nickel. Due to their nitrogen addition, they possess approximately 50% higher yield strength than 300 series stainless sheets of steel.
** Type 201 is hardenable through cold working.
** Type 202 is a general-purpose stainless steel. Decreasing nickel content and increasing manganese results in weak corrosion resistance.
* 300 series are chromium-nickel alloys that achieve their austenitic microstructure almost exclusively by nickel alloying; some very highly alloyed grades include some nitrogen to reduce nickel requirements. 300 series is the largest group and the most widely used.
** Type 304
Year 304 ( CCCIV) was a leap year starting on Saturday A leap year starting on Saturday is any year with 366 days (i.e. it includes 29 February) that begins on Saturday, 1 January, and ends on Sunday, 31 December. Its dominical letters hence ...
: The best-known grade is Type 304, also known as 18/8 and 18/10 for its composition of 18% chromium and 8% or 10% nickel, respectively.
** Type 316: The second most common austenitic stainless steel is Type 316. The addition of 2% molybdenum provides greater resistance to acids and localized corrosion caused by chloride ions. Low-carbon versions, such as 316L
SAE 316L grade stainless steel, sometimes referred to as A4 stainless steel or marine grade stainless steel, is the second most common austenitic stainless steel after 304/A2 stainless steel. Its primary alloying constituents after iron, are c ...
or 304L, have carbon contents below 0.03% and are used to avoid corrosion problems caused by welding.
Ferritic
Ferritic stainless steels possess a ferrite microstructure like carbon steel, which is a body-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
crystal structure, and contain between 10.5% and 27% chromium with very little or no nickel. This microstructure is present at all temperatures due to the chromium addition, so they are not hardenable by heat treatment. They cannot be strengthened by cold work to the same degree as austenitic stainless steels. They are magnetic. Additions of niobium (Nb), titanium (Ti), and zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...
(Zr) to Type 430 allow good weldability. Due to the near-absence of nickel, they are less expensive than austenitic steels and are present in many products, which include:
* Automobile exhaust pipes (Type 409 and 409 Cb are used in North America; stabilized grades Type 439 and 441 are used in Europe)
*Architectural and structural applications (Type 430, which contains 17% Cr)
*Building components, such as slate hooks, roofing, and chimney ducts
*Power plates in solid oxide fuel cell
A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte.
A ...
s operating at temperatures around (high-chromium ferritics containing 22% Cr)
Martensitic
Martensitic stainless steels have a body-centered cubic crystal structure, and offer a wide range of properties and are used as stainless engineering steels, stainless tool steels, and creep
Creep, Creeps or CREEP may refer to:
People
* Creep, a creepy person
Politics
* Committee for the Re-Election of the President (CRP), mockingly abbreviated as CREEP, an fundraising organization for Richard Nixon's 1972 re-election campaign
Art ...
-resistant steels. They are magnetic, and not as corrosion-resistant as ferritic and austenitic stainless steels due to their low chromium content. They fall into four categories (with some overlap):
* Fe-Cr-C grades. These were the first grades used and are still widely used in engineering and wear-resistant applications.
* Fe-Cr-Ni-C grades. Some carbon is replaced by nickel. They offer higher toughness and higher corrosion resistance. Grade EN 1.4303 (Casting grade CA6NM) with 13% Cr and 4% Ni is used for most Pelton, Kaplan Kaplan may refer to:
Places
* Kapłań, Poland
* Kaplan, Louisiana, U.S.
* Kaplan Medical Center, a hospital in Rehovot, Israel
* Kaplan Street, in Tel Aviv, Israel
* Mount Kaplan, Antarctica
* Kaplan Arena, at the College of William & Mary in W ...
, and Francis turbine
The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency.
The proces ...
s in hydroelectric power plants
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...
because it has good casting properties, good weldability and good resistance to cavitation
Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, cal ...
erosion.
* Precipitation hardening grades. Grade EN 1.4542 (also known as 17-4 PH), the best-known grade, combines martensitic hardening and precipitation hardening
Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and so ...
. It achieves high strength and good toughness and is used in aerospace among other applications.
* Creep-resisting grades. Small additions of niobium, vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
, boron
Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
, and cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
increase the strength and creep resistance up to about .
Martensitic stainless steels can be heat treated to provide better mechanical properties. The heat treatment typically involves three steps:
# Austenitizing, in which the steel is heated to a temperature in the range , depending on grade. The resulting austenite has a face-centered cubic crystal structure.
# Quenching
In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as pha ...
. The austenite is transformed into martensite, a hard body-centered tetragonal
In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squa ...
crystal structure. The quenched martensite is very hard and too brittle for most applications. Some residual austenite may remain.
# Tempering. Martensite is heated to around , held at temperature, then air-cooled. Higher tempering temperatures decrease yield strength
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
and ultimate tensile strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
but increase the elongation and impact resistance.
Replacing some carbon in martensitic stainless steels by nitrogen is a recent development. The limited solubility of nitrogen is increased by the pressure electroslag refining (PESR) process, in which melting is carried out under high nitrogen pressure. Steel containing up to 0.4% nitrogen has been achieved, leading to higher hardness and strength and higher corrosion resistance. As PESR is expensive, lower but significant nitrogen contents have been achieved using the standard AOD process.
Duplex
Duplex stainless steels have a mixed microstructure of austenite and ferrite, the ideal ratio being a 50:50 mix, though commercial alloys may have ratios of 40:60. They are characterized by higher chromium (19–32%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. Duplex stainless steels have roughly twice the yield strength
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
of austenitic stainless steel. Their mixed microstructure provides improved resistance to chloride stress corrosion cracking in comparison to austenitic stainless steel Types 304 and 316. Duplex grades are usually divided into three sub-groups based on their corrosion resistance: lean duplex, standard duplex, and super duplex. The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. The pulp and paper industry was one of the first to extensively use duplex stainless steel. Today, the oil and gas industry is the largest user and has pushed for more corrosion resistant grades, leading to the development of super duplex and hyper duplex grades. More recently, the less expensive (and slightly less corrosion-resistant) lean duplex has been developed, chiefly for structural applications in building and construction (concrete reinforcing bars, plates for bridges, coastal works) and in the water industry
The water industry provides drinking water and wastewater services (including sewage treatment) to residential, commercial, and industrial sectors of the economy. Typically public utilities operate water supply networks. The water industry doe ...
.
Precipitation hardening
Precipitation hardening
Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and so ...
stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than other martensitic grades. There are three types of precipitation hardening stainless steels:
* Martensitic 17-4 PH (AISI 630 EN 1.4542) contains about 17% Cr, 4% Ni, 4% Cu, and 0.3% Nb.
Solution treatment at about followed by quenching results in a relatively ductile martensitic structure. Subsequent aging treatment at precipitates Nb and Cu-rich phases that increase the strength up to above 1000 MPa yield strength. This outstanding strength level is used in high-tech applications such as aerospace (usually after remelting to eliminate non-metallic inclusions, which increases fatigue life). Another major advantage of this steel is that aging, unlike tempering treatments, is carried out at a temperature that can be applied to (nearly) finished parts without distortion and discoloration.
* Semi-austenitic 17-7 PH (AISI 631 EN 1.4568) contains about 17% Cr, 7.2% Ni, and 1.2% Al.
Typical heat treatment involves solution treatment and quenching
In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as pha ...
. At this point, the structure remains austenitic. Martensitic transformation is then obtained either by a cryogenic treatment at or by severe cold work (over 70% deformation, usually by cold rolling or wire drawing). Aging at — which precipitates the Ni3Al intermetallic phase—is carried out as above on nearly finished parts. Yield stress levels above 1400MPa are then reached.
* Austenitic A286(ASTM 660 EN 1.4980) contains about Cr 15%, Ni 25%, Ti 2.1%, Mo 1.2%, V 1.3%, and B 0.005%.
The structure remains austenitic at all temperatures.
Typical heat treatment involves solution treatment and quenching, followed by aging at . Aging forms Ni3Ti precipitates and increases the yield strength to about at room temperature. Unlike the above grades, the mechanical properties and creep resistance of this steel remain very good at temperatures up to . As a result, A286 is classified as an Fe-based superalloy
A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Several key characteristics of a superalloy are excellent mechanical strength, resistance to thermal creep deformation, g ...
, used in jet engines, gas turbines, and turbo parts.
Grades
There are over 150 grades of stainless steel, of which 15 are most commonly used. There are several systems for grading stainless and other steels, including US SAE steel grades
The SAE steel grades system is a standard alloy numbering system (SAE J1086 - Numbering Metals and Alloys) for steel grades maintained by SAE International.
In the 1930s and 1940s, the American Iron and Steel Institute (AISI) and SAE were both in ...
. The Unified Numbering System for Metals and Alloys
The unified numbering system (UNS) is an alloy designation system widely accepted in North America. Each UNS number relates to a specific metal or alloy and defines its specific chemical composition, or in some cases a specific mechanical or physic ...
(UNS) was developed by the ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
in 1970. The Europeans have developed EN 10088
En or EN may refer to:
Businesses
* Bouygues (stock symbol EN)
* Esquimalt and Nanaimo Railway (reporting mark EN, but now known as Southern Railway of Vancouver Island)
* Euronews, a news television and internet channel
Language and writing
* E ...
for the same purpose.[
]
Terminology
In its early history, stainless steel was sometimes called ''rustless steel''. Both adjectives, ''stainless'' and ''rustless'', are duly recognized and accepted as exaggerations: stainless steel is not literally incapable of rusting, but its established name is "stainless steel" nonetheless.
In technical datasets, stainless steel may sometimes be designated as ''inox'' ( inoxidizable), ''CRES'' (corrosion-resistant), or ''SS'' or ''SST'' (stainless steel). It may also be designated by subclass or grade without further specification, as for example 18–8, 17-4 PH, 316, 303, or 304.
Corrosion resistance
Unlike carbon steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
, stainless steels do not suffer uniform corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
when exposed to wet environments. Unprotected carbon steel rusts readily when exposed to a combination of air and moisture. The resulting iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...
surface layer is porous and fragile. In addition, as iron oxide occupies a larger volume than the original steel, this layer expands and tends to flake
Flake or Flakes may refer to:
People
* Floyd H. Flake (born 1945), A.M.E. minister, university administrator, former U.S. representative
* Jeff Flake (born 1962), American politician
* Christian "Flake" Lorenz, German musician and member of ...
and fall away, exposing the underlying steel to further attack. In comparison, stainless steels contain sufficient chromium to undergo passivation, spontaneously forming a microscopically thin inert surface film of chromium oxide by reaction with the oxygen in the air and even the small amount of dissolved oxygen in the water. This passive film prevents further corrosion by blocking oxygen diffusion to the steel surface and thus prevents corrosion from spreading into the bulk of the metal. /sup>">/sup> This film is self-repairing, even when scratched or temporarily disturbed by an upset condition in the environment that exceeds the inherent corrosion resistance of that grade.
The resistance of this film to corrosion depends upon the chemical composition of the stainless steel, chiefly the chromium content. It is customary to distinguish between four forms of corrosion: uniform, localized (pitting), galvanic, and SCC (stress corrosion cracking). Any of these forms of corrosion can occur when the grade of stainless steel is not suited for the working environment.
The designation "CRES" refers to corrosion-resistant steel.
Uniform
Uniform corrosion takes place in very aggressive environments, typically where chemicals are produced or heavily used, such as in the pulp and paper industries. The entire surface of the steel is attacked, and the corrosion is expressed as corrosion rate in mm/year (usually less than 0.1 mm/year is acceptable for such cases). Corrosion tables provide guidelines.
This is typically the case when stainless steels are exposed to acidic or basic solutions. Whether stainless steel corrodes depends on the kind and concentration of acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
or base and the solution temperature. Uniform corrosion is typically easy to avoid because of extensive published corrosion data or easily performed laboratory corrosion testing.
Acidic solutions can be put into two general categories: reducing acids, such as hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
and dilute sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
, and oxidizing acid
An oxidizing acid is a Brønsted acid that is a strong oxidizing agent. Most Brønsted acids can act as oxidizing agents, because the acidic proton can be reduced to hydrogen gas. Some acids contain other structures that act as stronger oxidizing ...
s, such as nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
and concentrated sulfuric acid. Increasing chromium and molybdenum content provides increased resistance to reducing acids while increasing chromium and silicon content provides increased resistance to oxidizing acids. Sulfuric acid is one of the most-produced industrial chemicals. At room temperature, Type 304 stainless steel is only resistant to 3% acid, while Type 316 is resistant to 3% acid up to and 20% acid at room temperature. Thus Type 304 SS is rarely used in contact with sulfuric acid. Type 904L and Alloy 20
Alloy 20 is an austenitic stainless steel containing less than 50% iron developed for applications involving sulfuric acid. Its corrosion resistance also finds other uses in the chemical, petrochemical, power generation, and plastics industries. A ...
are resistant to sulfuric acid at even higher concentrations above room temperature. Concentrated sulfuric acid possesses oxidizing characteristics like nitric acid, and thus silicon-bearing stainless steels are also useful. Hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
damages any kind of stainless steel and should be avoided.[ All types of stainless steel resist attack from ]phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
and nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
at room temperature. At high concentrations and elevated temperatures, attack will occur, and higher-alloy stainless steels are required. In general, organic acid
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are rel ...
s are less corrosive than mineral acids such as hydrochloric and sulfuric acid. As the molecular weight of organic acids increases, their corrosivity decreases. Formic acid
Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Es ...
has the lowest molecular weight and is a weak acid. Type 304 can be used with formic acid, though it tends to discolor the solution. Type 316 is commonly used for storing and handling acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
, a commercially important organic acid.
Type 304 and Type 316 stainless steels are unaffected by weak bases such as ammonium hydroxide
Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH3(aq). Although ...
, even in high concentrations and at high temperatures. The same grades exposed to stronger bases such as sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
at high concentrations and high temperatures will likely experience some etching and cracking. Increasing chromium and nickel contents provide increased resistance.
All grades resist damage from aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...
s and amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
s, though in the latter case Type 316 is preferable to Type 304; cellulose acetate
In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and ...
damages Type 304 unless the temperature is kept low. Fats and fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
s only affect Type 304 at temperatures above and Type 316 SS above , while Type 317 SS is unaffected at all temperatures. Type 316L is required for the processing of urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.
Urea serves an important r ...
.[
]
Localized
Localized corrosion can occur in several ways, e.g. pitting corrosion
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation re ...
and crevice corrosion
Crevice corrosion refers to corrosion occurring in occluded spaces such as interstices in which a stagnant solution is trapped and not renewed. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between pa ...
. These localized attacks are most common in the presence of chloride ions
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
. Higher chloride levels require more highly alloyed stainless steels.
Localized corrosion can be difficult to predict because it is dependent on many factors, including:
* Chloride ion concentration. Even when chloride solution concentration is known, it is still possible for localized corrosion to occur unexpectedly. Chloride ions can become unevenly concentrated in certain areas, such as in crevices (e.g. under gaskets) or on surfaces in vapor spaces due to evaporation and condensation.
* Temperature: increasing temperature increases susceptibility.
* Acidity: increasing acidity increases susceptibility.
* Stagnation: stagnant conditions increase susceptibility.
* Oxidizing species: the presence of oxidizing species, such as ferric and cupric ions, increases susceptibility.
Pitting corrosion is considered the most common form of localized corrosion. The corrosion resistance of stainless steels to pitting corrosion is often expressed by the PREN, obtained through the formula:
:,
where the terms correspond to the proportion of the contents by mass of chromium, molybdenum, and nitrogen in the steel. For example, if the steel consisted of 15% chromium %Cr would be equal to 15.
The higher the PREN, the higher the pitting corrosion resistance. Thus, increasing chromium, molybdenum, and nitrogen contents provide better resistance to pitting corrosion.
Though the PREN of certain steel may be theoretically sufficient to resist pitting corrosion, crevice corrosion can still occur when the poor design has created confined areas (overlapping plates, washer-plate interfaces, etc.) or when deposits form on the material. In these select areas, the PREN may not be high enough for the service conditions. Good design, fabrication techniques, alloy selection, proper operating conditions based on the concentration of active compounds present in the solution causing corrosion, pH, etc. can prevent such corrosion.
Stress
Stress corrosion cracking
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC ...
(SCC) is a sudden cracking and failure of a component without deformation. It may occur when three conditions are met:
* The part is stressed (by an applied load or by residual stress).
* The environment is aggressive (high chloride level, temperature above , presence of H2S).
* The stainless steel is not sufficiently SCC-resistant.
The SCC mechanism results from the following sequence of events:
# Pitting occurs.
# Cracks start from a pit initiation site.
# Cracks then propagate through the metal in a transgranular or intergranular mode.
# Failure occurs.
Whereas pitting usually leads to unsightly surfaces and, at worst, to perforation of the stainless sheet, failure by SCC can have severe consequences. It is therefore considered as a special form of corrosion.
As SCC requires several conditions to be met, it can be counteracted with relatively easy measures, including:
* Reducing the stress level (the oil and gas specifications provide requirements for maximal stress level in H2S-containing environments).
* Assessing the aggressiveness of the environment (high chloride content, temperature above , etc.).
* Selecting the right type of stainless steel: super austenitic such as grade 904L or super-duplex (ferritic stainless steel
Ferritic stainless steel forms one of the five stainless steel families, the other four being austenitic, martensitic, duplex stainless steels, and ''precipitation hardened''. For example, many of AISI 400-series of stainless steels are ferritic st ...
s and duplex stainless steel
Duplex stainless steels are a family of stainless steels. These are called duplex (or austenitic-ferritic) grades because their metallurgical structure consists of two phases, austenite (face-centered cubic lattice) and ferrite (body centered cubi ...
s are very resistant to SCC).
Galvanic
Galvanic corrosion
Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A sim ...
(also called "dissimilar-metal corrosion") refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. The most common electrolyte is water, ranging from freshwater to seawater. When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would alone, while the other becomes the cathode and corrodes slower than it would alone. Stainless steel, due to having a more positive electrode potential than for example carbon steel and aluminium, becomes the cathode, accelerating the corrosion of the anodic metal. An example is the corrosion of aluminium rivets fastening stainless steel sheets in contact with water. The relative surface areas of the anode and the cathode are important in determining the rate of corrosion. In the above example, the surface area of the rivets is small compared to that of the stainless steel sheet, resulting in rapid corrosion. However, if stainless steel fasteners are used to assemble aluminium sheets, galvanic corrosion will be much slower because the galvanic current density on the aluminium surface will be many orders of magnitude smaller. A frequent mistake is to assemble stainless steel plates with carbon steel fasteners; whereas using stainless steel to fasten carbon-steel plates is usually acceptable, the reverse is not. Providing electrical insulation between the dissimilar metals, where possible, is effective at preventing this type of corrosion.
High-temperature
At elevated temperatures, all metals react with hot gases. The most common high-temperature gaseous mixture is air, of which oxygen is the most reactive component. To avoid corrosion in air, carbon steel is limited to approximately . Oxidation resistance in stainless steels increases with additions of chromium, silicon, and aluminium. Small additions of cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...
and yttrium
Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...
increase the adhesion of the oxide layer on the surface. The addition of chromium remains the most common method to increase high-temperature corrosion resistance in stainless steels; chromium reacts with oxygen to form a chromium oxide scale, which reduces oxygen diffusion into the material. The minimum 10.5% chromium in stainless steels provides resistance to approximately , while 16% chromium provides resistance up to approximately . Type 304, the most common grade of stainless steel with 18% chromium, is resistant to approximately . Other gases, such as sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
, hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
, carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
, chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
, also attack stainless steel. Resistance to other gases is dependent on the type of gas, the temperature, and the alloying content of the stainless steel. With the addition of up to 5% aluminium, ferritic grades Fr-Cr-Al are designed for electrical resistance and oxidation resistance at elevated temperatures. Such alloys include Kanthal Kanthal may refer to :
* the historical name of Pratapgarh State, a princely state in India, until it was renamed after its capital Prtabgarh in 1698
* Kanthal (alloy)
Kanthal is the trademark for a family of iron-chromium-aluminium (FeCrAl) al ...
, produced in the form of wire or ribbons.
Standard finishes
Standard mill finishes can be applied to flat rolled stainless steel directly by the rollers and by mechanical abrasives. Steel is first rolled to size and thickness and then annealed to change the properties of the final material. Any oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
that forms on the surface (mill scale
Mill scale, often shortened to just scale, is the flaky surface of hot rolled steel, consisting of the mixed iron oxides iron(II) oxide (FeO), iron(III) oxide (), and iron(II,III) oxide (, magnetite).
Mill scale is formed on the outer surfaces o ...
) is removed by pickling
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called a ...
, and a passivation layer is created on the surface. A final finish can then be applied to achieve the desired aesthetic appearance.
The following designations are used in the U.S. to describe stainless steel finishes by ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
A480/A480M-18 (DIN):
* No. 0: Hot-rolled, annealed, thicker plates
* No. 1 (1D): Hot-rolled, annealed and passivated
* No. 2D (2D): Cold rolled, annealed, pickled and passivated
* No. 2B (2B): Same as above with additional pass through highly polished rollers
* No. 2BA (2R): Bright annealed (BA or 2R) same as above then bright annealed under oxygen-free atmospheric condition
* No. 3 (G-2G:) Coarse abrasive finish applied mechanically
* No. 4 (1J-2J): Brushed finish
* No. 5: Satin finish
* No. 6 (1K-2K): Matte finish (brushed but smoother than #4)
* No. 7 (1P-2P): Reflective finish
* No. 8: Mirror finish
* No. 9: Bead blast finish
* No. 10: Heat colored finish – offering a wide range of electropolished and heat colored surfaces
Joining
A wide range of joining processes are available for stainless steels, though welding
Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing Fusion welding, fusion. Welding is distinct from lower ...
is by far the most common.
The ease of welding largely depends on the type of stainless steel used. Austenitic stainless steels are the easiest to weld by electric arc
An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma (p ...
, with weld properties similar to those of the base metal (not cold-worked). Martensitic stainless steels can also be welded by electric-arc but, as the heat-affected zone (HAZ) and the fusion zone (FZ) form martensite upon cooling, precautions must be taken to avoid cracking of the weld. Improper welding practices can additionally cause sugaring (oxide scaling) and/or heat tint on the backside of the weld. This can be prevented with the use of back-purging gases, backing plates, and fluxes. Post-weld heat treatment is almost always required while preheating before welding is also necessary in some cases. Electric arc welding of Type 430 ferritic stainless steel results in grain growth in the HAZ, which leads to brittleness. This has largely been overcome with stabilized ferritic grades, where niobium, titanium, and zirconium form precipitates that prevent grain growth. Duplex stainless steel welding by electric arc is a common practice but requires careful control of the process parameters. Otherwise, the precipitation of unwanted intermetallic phases occurs, which reduces the toughness of the welds.
Electric arc welding processes include:
*Gas metal arc welding
Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) and metal active gas (MAG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal(s), which hea ...
, also known as MIG/MAG welding
*Gas tungsten arc welding
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atmo ...
, also known as tungsten inert gas (TIG) welding
*Plasma arc welding
Plasma arc welding (PAW) is an arc welding process similar to gas tungsten arc welding (GTAW). The electric arc is formed between an electrode (which is usually but not always made of sintered tungsten) and the workpiece. The key difference from ...
*Flux-cored arc welding Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux and a constant-voltage or, less commonly, a constant-current welding power s ...
*Shielded metal arc welding
Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding or informally as stick welding, is a manual arc welding process that uses a consumable electrode covered with a flux to lay the wel ...
(covered electrode)
*Submerged arc welding
Submerged arc welding (SAW) is a common arc welding process. The first SAW patent was taken out in 1935. The process requires a continuously fed consumable solid or tubular (metal cored) electrode. The molten weld and the arc zone are protect ...
MIG, MAG and TIG welding are the most common methods.
Other welding processes include:
*Stud welding
Stud welding is a technique similar to flash welding where a fastener or specially formed nut is welded onto another metal part, typically a base metal or substrate. The fastener can take different forms, but typically fall under threaded, unthre ...
*Resistance spot welding
A spot welder
Spot welding (or resistance spot welding) is a type of electric resistance welding used to weld various sheet metal products, through a process in which contacting metal surface points are joined by the heat obtained from resistance ...
*Resistance seam welding
Electric resistance welding (ERW) is a welding process where metal parts in contact are permanently joined by heating them with an electric current, melting the metal at the joint. Electric resistance welding is widely used, for example, in manufa ...
*Flash welding
Flash welding is a type of resistance welding that does not use any filler metals. The pieces of metal to be welded are set apart at a predetermined distance based on material thickness, material composition, and desired properties of the finished ...
*Laser beam welding
Laser beam welding (LBW) is a welding technique used to join pieces of metal or thermoplastics through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates. The process is frequen ...
*Oxy-acetylene welding
Principle of burn cutting
Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, ...
Stainless steel may be bonded with adhesives such as silicone, silyl modified polymers Silyl-modified polymers (SMP; also ''silane-modified polymers'', ''modified-silane polymers'', ''MS polymers'', ''silane-terminated polymers'', etc.) are polymers terminating with a silane, silyl group. SMPs are the main components in solvent-free a ...
, and epoxies
The Epoxies were an American New wave music, new wave band from Portland, Oregon, formed in 2000. Heavily influenced by new wave, the band jokingly described themselves as robot garage rock. Members included FM Static on synthesizers, guitarist ...
. Acrylic and polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethan ...
adhesives are also used in some situations.
Production
Most of the world's stainless steel production is produced by the following processes:
* Electric arc furnace
An electric arc furnace (EAF) is a furnace that heats material by means of an electric arc.
Industrial arc furnaces range in size from small units of approximately one-tonne capacity (used in foundries for producing cast iron products) up to ab ...
(EAF): stainless steel scrap, other ferrous scrap, and ferrous alloys (Fe Cr, Fe Ni, Fe Mo, Fe Si) are melted together. The molten metal is then poured into a ladle and transferred into the AOD process (see below).
* Argon oxygen decarburization
Argon oxygen decarburization (AOD) is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as chromium and aluminum. After initial melting the metal is then transferred to an AOD vessel where ...
(AOD): carbon in the molten steel is removed (by turning it into carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
gas) and other compositional adjustments are made to achieve the desired chemical composition.
* Continuous casting
Continuous casting, also called strand casting, is the process whereby molten metal is solidified into a "semifinished" billet, bloom, or slab for subsequent rolling in the finishing mills. Prior to the introduction of continuous casting in the ...
(CC): the molten metal is solidified into slabs for flat products (a typical section is thick and wide) or blooms (sections vary widely but is the average size).
* Hot rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
(HR): slabs and blooms are reheated in a furnace and hot-rolled. Hot rolling reduces the thickness of the slabs to produce about -thick coils. Blooms, on the other hand, are hot-rolled into bars, which are cut into lengths at the exit of the rolling mill, or wire rod, which is coiled.
* Cold finishing (CF) depends on the type of product being finished:
**Hot-rolled coils are pickled in acid solutions to remove the oxide scale on the surface, then subsequently cold rolled in Sendzimir rolling mills and annealed in a protective atmosphere until the desired thickness and surface finish is obtained. Further operations such as slitting and tube forming can be performed in downstream facilities.
**Hot-rolled bars are straightened, then machined to the required tolerance and finish.
**Wire rod coils are subsequently processed to produce cold-finished bars on drawing benches, fasteners on boltmaking machines, and wire on single or multipass drawing machines.
World stainless steel production figures are published yearly by the International Stainless Steel Forum. Of the EU production figures, Italy, Belgium and Spain were notable, while Canada and Mexico produced none. China, Japan, South Korea, Taiwan, India the US and Indonesia were large producers while Russia reported little production.
Breakdown of production by stainless steels families in 2017:
* Austenitic stainless steels Cr-Ni (also called 300-series, see "Grades" section above): 54%
* Austenitic stainless steels Cr-Mn (also called 200-series): 21%
* Ferritic and martensitic stainless steels (also called 400-series): 23%
Applications
Stainless steel is used in a multitude of fields including architecture, art, chemical engineering, food and beverage manufacture, vehicles, medicine, energy and firearms.
Life cycle cost
Life cycle cost (LCC) calculations are used to select the design and the materials that will lead to the lowest cost over the whole life of a project, such as a building or a bridge.
The formula, in a simple form, is the following:
:
where LCC is the overall life cycle cost, AC is the acquisition cost, IC the installation cost, OC the operating and maintenance costs, LP the cost of lost production due to downtime, and RC the replacement materials cost.
In addition, ''N'' is the planned life of the project, ''i'' the interest rate, and ''n'' the year in which a particular OC or LP or RC is taking place. The interest rate ''(i)'' is used to convert expenses from different years to their present value (a method widely used by banks and insurance companies) so they can be added and compared fairly. The usage of the sum formula () captures the fact that expenses over the lifetime of a project must be cumulated after they are corrected for interest rate.
Application of LCC in materials selection
Stainless steel used in projects often results in lower LCC values compared to other materials. The higher acquisition cost (AC) of stainless steel components are often offset by improvements in operating and maintenance costs, reduced loss of production (LP) costs, and the higher resale value of stainless steel components.
LCC calculations are usually limited to the project itself. However, there may be other costs that a project stakeholder may wish to consider:
* Utilities, such as power plants, water supply & wastewater treatment, and hospitals, cannot be shut down. Any maintenance will require extra costs associated with continuing service.
* Indirect societal costs (with possible political fallout) may be incurred in some situations such as closing or reducing traffic on bridges, creating queues, delays, loss of working hours to the people, and increased pollution by idling vehicles.
Sustainability–recycling and reuse
The average carbon footprint
A carbon footprint is the total greenhouse gas (GHG) emissions caused by an individual, event, organization, service, place or product, expressed as carbon dioxide equivalent (CO2e). Greenhouse gases, including the carbon-containing gases carbo ...
of stainless steel (all grades, all countries) is estimated to be 2.90 kg of CO2 per kg of stainless steel produced, of which 1.92 kg are emissions from raw materials (Cr, Ni, Mo); 0.54 kg from electricity and steam, and 0.44 kg are direct emissions (i.e., by the stainless steel plant). Note that stainless steel produced in countries that use cleaner sources of electricity (such as France, which uses nuclear energy) will have a lower carbon footprint. Ferritics without Ni will have a lower CO2 footprint than austenitics with 8% Ni or more. Carbon footprint must not be the only sustainability-related factor for deciding the choice of materials:
* Over any product life, maintenance, repairs or early end of life (planned obsolescence) can increase its overall footprint far beyond initial material differences. In addition, loss of service (typically for bridges) may induce large hidden costs, such as queues, wasted fuel, and loss of man-hours.
* How much material is used to provide a given service varies with the performance, particularly the strength level, which allows lighter structures and components.
Stainless steel is 100% recyclable
Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
. An average stainless steel object is composed of about 60% recycled material of which approximately 40% originates from end-of-life products, while the remaining 60% comes from manufacturing processes. What prevents a higher recycling content is the availability of stainless steel scrap, in spite of a very high recycling rate. According to the International Resource Panel
The International Resource Panel is a scientific panel of experts that aims to help nations use natural resources sustainably without compromising economic growth and human needs. It provides independent scientific assessments and expert advice on ...
's Metal Stocks in Society report
The report Metal Stocks in Society: Scientific Synthesis was the first of six scientific assessments on global metals to be published by the International Resource Panel (IRP) of the United Nations Environment Programme. The IRP provides independ ...
, the per capita stock of stainless steel in use in society is in more developed countries and in less-developed countries. There is a secondary market that recycles usable scrap for many stainless steel markets. The product is mostly coil, sheet, and blanks. This material is purchased at a less-than-prime price and sold to commercial quality stampers and sheet metal houses. The material may have scratches, pits, and dents but is made to the current specifications.
The stainless steel cycle starts with carbon steel scrap, primary metals, and slag. The next step is the production of hot-rolled and cold-finished steel products in steel mills. Some scrap is produced, which is directly reused in the melting shop. The manufacturing of components is the third step. Some scrap is produced and enters the recycling loop. Assembly of final goods and their use does not generate any material loss. The fourth step is the collection of stainless steel for recycling at the end of life of the goods (such as kitchenware, pulp and paper plants, or automotive parts). This is where it is most difficult to get stainless steel to enter the recycling loop, as shown in the table below:
Nanoscale stainless steel
Stainless steel nanoparticles have been produced in the laboratory. These may have applications as additives for high-performance applications. For example, sulfurization, phosphorization, and nitridation treatments to produce nanoscale stainless steel based catalysts could enhance the electrocatalytic performance of stainless steel for water splitting
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen:
:2 H2O → 2 H2 + O2
Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy, base ...
.
Health effects
There is extensive research indicating some probable increased risk of cancer (particularly lung cancer) from inhaling fumes while welding stainless steel.[Langård, S. and R.M. Stern]
"Nickel in welding fumes--a cancer hazard to welders? A review of epidemiological studies on cancer in welders,"
1984, ''IARC Scientific Publications IARC may refer to:
* International Aerial Robotics Competition
* International Age Rating Coalition
* International Agency for Research on Cancer
* International Arctic Research Center
* Israel Amateur Radio Club
* iArc IARC may refer to:
* Intern ...
'' 1984;(53):95-103, summarized on website of National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
, retrieved 16 March 2020[Lauritsen, J.M., K.S. Hansen, and A. Skytthe]
"Cancer incidence among mild steel and stainless steel welders and other metal workers,"
October 1996, ''American Journal of Industrial Medicine
The ''American Journal of Industrial Medicine'' is a monthly peer-reviewed medical journal covering occupational safety and health, as well as environmental health. It was established in 1980 and is published by Wiley-Blackwell. The editor-in-chi ...
,'' pp.373-82, summarized on website of National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
, retrieved 16 March 2020[Lauritsen, J.M. and K.S. Hansen]
"Lung cancer mortality in stainless steel and mild steel welders: a nested case-referent study,"
, October 1996, ''American Journal of Industrial Medicine
The ''American Journal of Industrial Medicine'' is a monthly peer-reviewed medical journal covering occupational safety and health, as well as environmental health. It was established in 1980 and is published by Wiley-Blackwell. The editor-in-chi ...
,'' summarized on website of National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
, retrieved 16 March 2020[Knudsen, L.E. and H. Burr]
"[Follow-up examination of Danish stainless steel welders previously examined in 1987],"
(article in Danish) 14 July 2003 '' Ugeskr Laeger,'' 165(29):2882-6, summarized on website of National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
, retrieved 16 March 2020[Rapaport, Lisa]
"More evidence welding fumes raise lung cancer risk"
, 21 May 2019, Reuters News Service
Reuters ( ) is a news agency owned by Thomson Reuters Corporation. It employs around 2,500 journalists and 600 photojournalists in about 200 locations worldwide. Reuters is one of the largest news agencies in the world.
The agency was establ ...
, retrieved 16 March 2020 Stainless steel welding is suspected of producing carcinogenic fumes from cadmium oxides, nickel, and chromium.["Welding and cancer,"](_blank)
in "Welding" on the website of the Cancer Council Australia
Cancer Council Australia is a national, nonprofit organisation which aims to promote cancer-control policies and to reduce the illness caused by cancer in Australia. It advises various groups, including the government, on cancer-related issues, ...
, retrieved 16 March 2020 According to Cancer Council Australia
Cancer Council Australia is a national, nonprofit organisation which aims to promote cancer-control policies and to reduce the illness caused by cancer in Australia. It advises various groups, including the government, on cancer-related issues, ...
, "In 2017, all types of welding fumes were classified as a Group 1 carcinogen."
Stainless steel is generally considered to be biologically inert. However, during cooking, small amounts of nickel and chromium leach out of new stainless steel cookware into highly acidic food. Nickel can contribute to cancer risks—particularly lung cancer
Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
and nasal cancer.[Safe Cookware: Does Stainless Steel Leach Chemicals?](_blank)
''healthybuildingscience.com'', accessed 28 January 2019["Nickel Compounds,"](_blank)
in "Cancer-Causing Substances", in "Risk Factors," in "Cancer Causes and Prevention," in "About Cancer," at the website of the National Cancer Institute
The National Cancer Institute (NCI) coordinates the United States National Cancer Program and is part of the National Institutes of Health (NIH), which is one of eleven agencies that are part of the U.S. Department of Health and Human Services. ...
, retrieved 16 March 2020 However, no connection between stainless steel cookware and cancer has been established.["Can Common Cookware Cause Cancer?"](_blank)
8 February 2015, '' UPMC HealthBeat,'' UPMC (University of Pittsburgh Medical Center
The University of Pittsburgh Medical Center (UPMC) is a $23billion integrated global nonprofit health enterprise that has 92,000 employees, 40 hospitals with more than 8,000 licensed beds, 800 clinical locations including outpatient sites and do ...
), retrieved 16 March 2020
See also
* AL-6XN
AL-6XN (unified numbering system, UNS designation N08367) is a type of welding, weldable stainless steel that consist of an alloy of nickel (24%), chromium (22%) and molybdenum (6.3%) with other trace elements such as nitrogen.
The high nickel and ...
* Cobalt-chrome
Cobalt-chrome or cobalt-chromium (CoCr) is a metal alloy of cobalt and chromium. Cobalt-chrome has a very high specific strength and is commonly used in gas turbines, dental implants, and orthopedic implants.
* Corrosion engineering
Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to mana ...
* Corrugated stainless steel tubing
Corrugated stainless steel tubing (CSST) is tubing made of stainless steel with corrugation on the inside or outside.
CSST is not FAC (Flexible Appliance Connector) tubing. Presently, CSST and FAC tubing both use corrugated stainless steel tubin ...
* List of blade materials
Blade materials are materials used to make the blade of a knife or other simple edged hand tool or weapon, such as a hatchet or sword.
Blades can be made from a variety of materials. The most common being carbon steel, stainless steel, tool stee ...
* List of steel producers
This is a list of the largest steel-producing companies in the world mostly based on the list by the World Steel Association. This list ranks steelmakers by volume of steel production in millions of tonnes and includes all steelmakers with producti ...
* Metallic fiber
Metallic fibers are manufactured fibers composed of metal, metallic alloys, plastic-coated metal, metal-coated plastic, or a core completely covered by metal.
Having their origin in textile and clothing applications, gold and silver fibers have ...
* Pilling–Bedworth ratio The Pilling–Bedworth ratio (P–B ratio), in corrosion of metals, is the ratio of the volume of the elementary cell of a metal oxide to the volume of the elementary cell of the corresponding metal (from which the oxide is created).
On the basis ...
* Rouging
Rouging is a form of corrosion found in stainless steel. It can be due to iron contamination of the stainless steel surface due to welding of non-stainless steel
Steel is an alloy made up of iron with added carbon to improve its strength and ...
* SAF 2205 SAF 2205, also known as Sandvik SAF 2205, is a Sandvik-owned trademark for a 22Cr duplex (ferritic-austenitic) stainless steel. ''SAF'' derives from ''S''andvik ''A''ustenite ''F''errite. The nominal chemical composition of SAF 2205 is 22% chromium ...
* Stainless steel soap
Stainless steel soap is a piece of stainless steel, in the form of a soap bar or other hand-held shape. Its purported purpose is to neutralize or reduce strong odors such as those from handling garlic, onion, durian, guava, salami, or fish.
...
Notes
References
Further reading
*
International Standard ISO15510:2014
*
*
External links
*
*
{{Authority control
1916 introductions
Biomaterials
Building materials
Chromium alloys
English inventions
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