41xx steel

41xx steel is a family of SAE steel grades, as specified by the Society of Automotive Engineers (SAE). Alloying elements include chromium and molybdenum, and as a result these materials are often referred to as chromoly steel or CRMO. They have an excellent strength to weight ratio, are easily welded and are considerably stronger and harder than standard 1020 steel.

While these grades of steel do contain chromium, it is not in great enough quantities to provide the corrosion resistance found in stainless steel.

Examples of applications for 4130 and 4140 include structural tubing, bicycle frames, firearms receivers, clutch 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

Alloy composition (by weight)^[1]

SAE grade	% Cr	% Mo	% C *	% Mn	% P (max)	% S (max)	% Si
4118	0.40–0.60	0.08–0.15	0.18–0.23	0.70–0.90	0.035	0.040	0.15–0.35
4120	0.40–0.60	0.13–0.20	0.18–0.23	0.90–1.20	0.035	0.040	0.15–0.35
4121	0.45–0.65	0.20–0.30	0.18–0.23	0.75–1.00	0.035	0.040	0.15–0.35
4130	0.80–1.10	0.15–0.25	0.28–0.33	0.40–0.60	0.035	0.040	0.15–0.35
4135	0.80–1.10	0.15–0.25	0.33–0.38	0.70–0.90	0.035	0.040	0.15–0.35
4137	0.80–1.10	0.15–0.25	0.35–0.40	0.70–0.90	0.035	0.040	0.15–0.35
4140	0.80–1.10	0.15–0.25	0.38–0.43	0.75–1.00	0.035	0.040	0.15–0.35
4142	0.80–1.10	0.15–0.25	0.40–0.45	0.75–1.00	0.035	0.040	0.15–0.35
4145	0.80–1.10	0.15–0.25	0.43–0.48	0.75–1.00	0.035	0.040	0.15–0.35
4147	0.80–1.10	0.15–0.25	0.45–0.50	0.75–1.00	0.035	0.040	0.15–0.35
4150	0.80–1.10	0.15–0.25	0.48–0.53	0.75–1.00	0.035	0.040	0.15–0.35
4161	0.70–0.90	0.25–0.35	0.56–0.64	0.75–1.00	0.035	0.040	0.15–0.35
* The carbon composition of the alloy is denoted by the last two digits of the SAE specification number, in hundredths of a percent

Mechanical properties

Material	Condition	Tensile strength [psi (MPa)]	Yield strength [psi (MPa)]	Elongation in 2" [%]	Hardness (Rockwell)
4130	Cold drawn—normalized[2]	85,000–110,000 psi (590–760 MPa)	70,000–85,000 psi (480–590 MPa)	20–30	B 90–96
4142	Hot rolled—annealed[2]	90,000–100,000 psi (620–690 MPa)	60,000–70,000 psi (410–480 MPa)	20–30	B 90–95
	Cold drawn—annealed[2]	105,000–120,000 psi (720–830 MPa)	85,000–95,000 psi (590–660 MPa)	15–25	B 96–100
4150	Hot rolled—annealed[2]	90,000–110,000 psi (620–760 MPa)	65,000–75,000 psi (450–520 MPa)	20–30	B 90–96

Other characteristics

One of the class of steels is their ability to be case hardened by carburization of the surface. The core of the material retains its bulk properties, while the outside is significantly hardened to reduce wear and tear on the part. This makes this grade of steel an excellent material for such uses as gears, piston pins, and crankshafts.^[1]

References

1. ^ ^{a b} Central Steel & Wire Company Catalog (2006-2008 ed.), p. 246 . Note: "For bar products; plate, sheet and tubing may be slightly different."
2. ^ ^{a b c d} Central Steel & Wire Company Catalog (2006-2008 ed.), p. 260 .