| Analysis | Mechanical_Properties | Applications | Machineability_and_Weldability | Heat_Treating | Tolerances | Speedy Metals items |
4140 HRA is a chromium-molybdenun alloy steel that can be oil hardened to relatively high hardenability. The chromium content provides good hardness penetration, and the molybdenum imparts uniformity of hardness and high strength. Through variations in the method of heat treating 4140, an exceptionally wide range of properties can be attained. For this reason, it is often used as stock for forging, as 4140 has self scaling properties. 4140 responds readily to heat treatment and is comparatively easy to machine in the heat treated condition. 4140 resists creep in temperatures up to 1000° F and maintains its properties even after long exposure at these relatively high working temperatures. Other desirable properties include good wear resistance, excellent toughness and good ductility in the quenched and tempered condition. 4140 can attain high mechanical properties (260,000 psi tensile and 235,000 psi yield) in the hardened condition of 500 Brinell.
4140 hot roll bars conforms to ASTM A322; ASTM A331; ASTM A304
The above values are average and may be considered as representative of 4140 hot rolled annealed
4140 can be used for as wide variety of applications where greater toughness and wear resistance is needed over lower carbon grades. Typical applications include ejectors, back up and support tooling, cams, drill collars, bolts, stubs, couplings, reamer bodies, axles, shafting, piston rods, rams, hydraulic machinery shafts, gears, sprockets, gear racks, valves, chain links, spindles, tool bodies, tool holders, tie rods, boring bars, machinery parts and components, etc. This material roll threads, knurls, and may be plated
4140 has a machinability rating at 63% of B1112. Average cutting speed 110 ft/min.
4140 is difficult to weld, but can be welded by any of the common welding practices providing section is preheated, and stress relieved after welding.
4140 has a hardening range of 1525° -1625° F. Quench in oil. A wide range of mechanical properties can be obtained by tempering between 400° and 1300° F.
Forging
Heat to 2100° to 2200° F
Normalizing
Heat to 1600° - 1700° F. Cool in air. Average BHN 285
Annealing
Heat to 1450° - 1550° F. Cool slowly in furnace. Average BHN 187
| Over | under | out of rd | |
| To 5/16" incl | 0.005 | 0.005 | 0.008 |
| Over 5/16 to 7/16 incl | 0.006 | 0.006 | 0.009 |
| Over 7/16 to 5/8 incl | 0.007 | 0.007 | 0.010 |
| Over 5/8 to 7/8 incl | 0.008 | 0.008 | 0.013 |
| Over 7/8 to 1-1/8 incl | 0.010 | 0.010 | 0.015 |
| Over 1-1/8 to 1-1/4 incl | 0.011 | 0.011 | 0.016 |
| Over 1-1/4 to 1-3/8 incl | 0.012 | 0.012 | 0.018 |
| Over 1-3/8 to 1-1/2 incl | 0.014 | 0.014 | 0.021 |
| Over 1-1/2 to 2 incl | 0.015 | 0.015 | 0.023 |
| Over 2 to 2-1/2 incl | 0.031 | - | 0.023 |
| Over 2-1/2 to 3-1/2 incl | 0.047 | - | 0.035 |
| Over 3-1/2 to 4-1/2 incl | 0.063 | - | 0.046 |
| Over 4-1/2 to 5-1/2 incl | 0.078 | - | 0.058 |
| Over 5-1/2 to 6-1/2 incl | 0.125 | - | 0.070 |
| Over 6-1/2 to 8-1/2 incl | 0.156 | - | 0.085 |
| Over 8-1/2 to 9-1/2 incl | 0.188 | - | 0.100 |
| Over 9-1/2 to 10 incl | 0.250 | - | 0.120 |