41xx steel is a family of high-strength low-alloy steels (HSLA), 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 include structural tubing, bicycle frames, AK-47 receivers, clutch and flywheel components, and roll cages. They are also used in aircraft and therefore 41xx grade structural tubing is sometimes referred to as "aircraft tubing".
Properties
| 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 | |||||||
| 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 important characteristics of the 41xx 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
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