41xx steel is a family of SAE steel grades, as specified by the Society of Automotive Engineers (SAE). Alloying

elements Element or elements may refer to: Science * Chemical element, a pure substance of one type of atom * Heating element, a device that generates heat by electrical resistance * Orbital elements, parameters required to identify a specific orbit of ...

include

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

molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...

, and as a result these materials are often informally referred to as chromoly steel (common variant stylings include ''chrome-moly'', ''cro-moly'', ''CrMo'', ''CRMO'', ''CR-MOLY'', and similar). They have an excellent strength to weight ratio and are considerably stronger and harder than standard 1020 steel, but are not easily welded, requiring thermal treatment both before and after welding to avoid cold cracking. While these grades of steel do contain chromium, it is not in great enough quantities to provide the corrosion resistance found in

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

. Examples of applications for 4130, 4140 and 4145 include structural tubing, bicycle frames, gas bottles for transportation of pressurized gases, firearm parts,

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

and flywheel components, and roll cages. 4150 stands out as being one of the steels accepted for use in M16 rifle and M4 carbine barrels by the United States military. These steels are also used in aircraft parts and therefore 41xx grade structural tubing is sometimes referred to as "aircraft tubing".

Properties

Other characteristics

One of the characteristics of this class of steel is the ability to be case hardened by

carburization Carburising, carburizing (chiefly American English), or carburisation is a heat treatment process in which iron or steel absorbs carbon while the metal is heated in the presence of a carbon-bearing material, such as charcoal or carbon monoxide. ...

of the surface. The core of the material retains its bulk properties, while the outer surface is significantly hardened to reduce wear and tear. This makes this grade of steel an excellent material for uses such as gears, piston pins, and

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...

4140 Steel

4140 Steel (Quenched and Tempered) Mechanical Properties

References

{{reflist Steels