Friction welding (FRW) is a solid-state

welding Welding is a 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 is distinct from lower temperature techniques such as b ...

process that generates heat through mechanical

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

between workpieces in relative motion to one another, with the addition of a lateral force called "upset" to plastically displace and fuse the materials. Because no melting occurs, friction welding is not a fusion welding process, but a solid-state welding technique more like forge welding. Friction welding is used with metals and

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

s in a wide variety of aviation and automotive applications. ISO norm of friction welding is EN ISO 15620:2019 there is information about basic terms and definitions and table of weldability of metals and

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, ductili ...

History

Historical photo of double spindle machine

Some applications and patents connected with friction welding were dated back to the turn of the 20th century and rotary friction welding is the oldest of this methods. W. Richter patented the method of

linear friction welding Friction welding (FRW) is a solid-state welding process that generates heat through mechanical friction between workpieces in relative motion to one another, with the addition of a lateral force called "upset" to plastically displace and fuse the ...

(LFW) process in 1924 in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

and 1929 in

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...

, however, the description of the process was vague and H.Klopstock patented the same process in the USSR 1924. But first description and experiments related to

rotary friction welding Rotary friction welding (RFW) one of the methods of friction welding, the classic way of which uses the work of friction to create a not separable weld. Typically one welded element is rotated to the other and forge (pressed down by axial force). ...

took place in the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

in 1956, machinist named A. J. Chdikov has realized scientific studies and suggested the use of this welding method as a commercial process. The process was introduced to the USA in 1960. The American companies

Caterpillar Tractor Company Caterpillar Inc. (stock symbol CAT) is an American ''Fortune'' 500 corporation and the world's largest construction-equipment manufacturer. In 2018, Caterpillar was ranked number 65 on the ''Fortune'' 500 list and number 238 on the Global ''Fo ...

( Caterpillar - CAT),

Rockwell International Rockwell International was a major American manufacturing conglomerate involved in aircraft, the space industry, defense and commercial electronics, components in the automotive industry, printing presses, avionics and industrial products. R ...

, and American Manufacturing Foundry all developed machines for this process. Patents were also issued throughout

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and the former Soviet Union. The first studies of friction welding in England were carried out by the Welding Institute in 1961. The USA with Caterpillar Inc. and MTI developed an inertia process in 1962. Europe with KUKA AG and Thompson launches rotary friction welding for industrial applications in 1966, developed a direct-drive process and in 1974 builds rRS6 the double spindle machine for heavy truck

axle An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, beari ...

s. Another method was invented and experimentally proven at The Welding Institute (TWI) in the UK and patented in 1991

Friction stir welding Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material ...

(FSW) processThomas, W.M., Nicholas, E.D., Needham, J.C., Murch, M.G., Templesmith, P., Dawes, C. J., 1991. Improvements to Friction Welding. GB Patent Application No. 91259788. a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. In 2008 KUKA AG developed the friction welding machine SRS 1000 with a forged force of 1000 tons. An improved modification of the standard friction welding is als
Low Force Friction Welding
hybrid technology developed by EWI and Manufacturing Technology Inc. (MTI), "''uses an external energy source to raise the interface temperature of the two parts being joined, thereby reducing the process forces required to make a solid-state weld compared to traditional friction welding''". The process applies to both linear and rotary friction welding. Today, the friction welding research materials comes from many places around the

world In its most general sense, the term "world" refers to the totality of entities, to the whole of reality or to everything that is. The nature of the world has been conceptualized differently in different fields. Some conceptions see the worl ...

, including

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

and

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

, and

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

Metal techniques

Rotary friction welding

Rotary friction welding (RFW) is one of the methods of friction welding. One welded element is rotated to the other and pressed down. The heating of the material is caused by friction work and created not separable weld.

Linear friction welding

Linear friction welding (LFW) is similar to spin welding, except that the moving chuck oscillates laterally instead of spinning.

Friction stir welding

Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough.

Friction surfacing

Friction surfacing is a process derived from friction welding where a coating material is applied to a substrate. A rod composed of the coating material (called a mechtrode) is rotated under pressure, generating a plasticized layer in the rod at the interface with the substrate.

Thermoplastic technique

Linear vibration welding

In linear vibration welding the materials are placed in contact and put under pressure. An external vibration force is then applied to slip the pieces relative to each other, perpendicular to the pressure being applied.

Orbital friction welding

Orbital friction welding is similar to

spin welding Spin welding is a friction welding technique used on thermoplastic materials, in which the parts to be welded are heated by friction. The heat may be generated by turning on a lathe, a drill press, or a milling machine, where one part is driven by t ...

, but uses a more complex machine to produce an orbital motion in which the moving part rotates in a small circle, much smaller than the size of the joint as a whole.

Method list connected to friction welding

* Forge welding *

(FSW) * Friction stir spot welding (FSSW) * Linear friction welding (LFW) * Friction welding of pipeline girth welds (FRIEX) * Friction hydro pillar overlap processing (FHPPOW) * Friction hydro pillar processing (FHHP) * Linear vibration welding * Spin welding of polymers * Low Force Friction Welding

Other information

Welds tests for Friction Welding and description of zones

Quality requirements of welded joints depend on the form of application, e.g. in the space or fly industry weld errors are not allowed. There are many scientific articles describing the weld, weld quality tests assurance is performed, with measurements and numerical methods. Science tries to gets good quality welds. For example, an ultra fine

grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...

structure of alloy or metal which is obtained by techniques such as

severe plastic deformation Severe plastic deformation (SPD) is a generic term describing a group of metalworking techniques involving very large strains typically involving a complex stress state or high shear, resulting in a high defect density and equiaxed "ultrafine" gra ...

is desirable, and not changed by the high temperature, a large

heat affected zone In fusion welding, the heat-affected zone (HAZ) is the area of base material, either a metal or a thermoplastic, which is not melted but has had its microstructure and properties altered by welding or heat intensive cutting operations. The heat ...

is unnecessary. Moreover, in addition to changing the grain structure during metal joining cycles, by methods where high temperature affected zone was occur, are phase transformations structure. For example, in

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...

between

austenite 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 100 ...

, ferrite,

pearlite Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite form ...

, bainite,

cementite Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure. It is a hard, ...

and

martensite 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 M ...

, see: Iron-carbon phase diagram. In order to avoid changes solid state welding may be desired and large

is not needed if weakens the material properties.

Heat and mechanical affected zones in friction weld

Individual thermomechanical zones can be described by citing an example article: Anthony R.McAndrew, Paul A.Colegrove, Clement Bühr, Bertrand C.D., Flipo Achilleas Vairis,
A literature review of Ti-6Al-4V linear friction welding
, 2018. ''"Technically the WCZ and the TMAZ are both "thermo-mechanically affected zones" but due to the vastly different microstructures they possess they are often considered separately. The WCZ experiences significant dynamic recrystallisation (DRX), the TMAZ does not. The material in HAZ is not deformed mechanically but is affected by the heat. The region from one TMAZ/HAZ boundary to the other is often referred to as the "TMAZ thickness" or the plastically affected zone (PAZ). For the remainder of this article this region will be referred to as the PAZ."'' Zones: * WCZ– weld center zone, * HAZ –

, * TMAZ – Thermo-Mechanically Affected Zone, * BM – base material, parent material, * Flash. Similar terms exist in

Seizure resistance

Friction welding may unintentionally occur at sliding surfaces like bearings. This happens in particular if the lubricating oil film between sliding surfaces becomes thinner than the surface roughness, which may be due to low speed, low temperature, oil starvation, excessive clearance, low viscosity of the oil, high roughness of the surfaces, or a combination thereof. The seizure resistance is the ability of a material to resist friction welding. It is a fundamental property of bearing surfaces and in general of sliding surfaces under load.

Curiosities

* Frictional welding (μ FSW) was also performed using a CNC machine. which does not mean that it is safe and recommended for the milling machine. * Friction welding has also been shown to work on wood.

Terms and definitions, name shortcuts

To quote ISO ( the International Organization for Standardization)
ISO 15620:2019(en) Welding — Friction welding of metallic materials
"axial force - force in axial direction between components to be welded, burn-off length - loss of length during the friction phase, burn-off rate - rate of shortening of the components during the friction welding process, component - single item before welding, component induced braking - reduction in rotational speed resulting from friction between the interfaces, external braking - braking located externally reducing the rotational speed, faying surface - surface of one component that is to be in contact with a surface of another component to form a joint, forge force - force applied normal to the faying surfaces at the time when relative movement between the components is ceasing or has ceased, forge burn-off length - amount by which the overall length of the components is reduced during the application of the forge force, forge phase - interval time in the friction welding cycle between the start and finish of application of the forge force, forge pressure - pressure (force per unit area) on the faying surfaces resulting from the axial forge force, forge time - time for which the forge force is applied to the components, friction force - force applied perpendicularly to the faying surfaces during the time that there is relative movement between the components, friction phase - interval time in the friction welding cycle in which the heat necessary for making a weld is generated by relative motion and the friction forces between the components i.e. from contact of components to the start of deceleration, friction pressure - pressure (force per unit area) on the faying surfaces resulting from the axial friction force, friction time - time during which relative movement between the components takes place at rotational speed and under application of the friction forces, interface - contact area developed between the faying surfaces after completion of the welding operation, rotational speed - number of revolutions per minute of rotating component, stick-out - distance a component sticks out from the fixture, or chuck in the direction of the mating component, deceleration phase - interval in the friction welding cycle in which the relative motion of the components is decelerated to zero, deceleration time - time required by the moving component to decelerate from friction speed to zero speed, total length loss (upset) - loss of length that occurs as a result of friction welding, i.e. the sum of the burn-off length and the forge burn-off length, total weld time - time elapsed between component contact and end of forging phase, welding cycle - succession of operations carried out by the machine to make a weldment and return to the initial position, excluding component - handling operations, weldment - two or more components joined by welding."

References

{{Authority control Plastic welding Welding