4140 / 4142 Steel

As a low alloy steel, 4140/4142, 4140PH/4142PH relies on the added chromium, molybdenum and manganese to increase strength and hardenability, yet it has inadequate weldability characteristics. The chromium content in this heat-treatable steel provides hardness penetration, whereas the added molybdenum provides uniform hardness and strength. The added manganese lends itself to increase strength and hardenability. This alloy may be used for both low and high temperature applications and with the relevant heat treatment can be used in sour gas environments as well.

In the quenched and tempered (PH) condition, it provides good wear resistance and has a minimum of 27 HRC which may be increased by flame or induction hardening or alternatively may as well be nitrided. In this condition, it is ready to use but still machinable as well.

Applications

Applications for this heat-treatable steel include: arbors, flanges, collets, bending dies, crankshafts, clutch parts, forming rolls and short run stamping dies.

Corrosion resistance

Molybdenum tends to increase corrosion resistance though the presence of iron can still cause some rust when exposed to different conditions. 4140/4142, 4140PH/4142PH though has excellent resistance to corrosion, which can be attributed to a significant percentage of chromium and molybdenum. That in mind, if corrosion has started, it will sustain the same damages as other non-corrosion resistant steels.

Heat treatment

Annealing

Uniformly heat the work piece to 1256-1328°F (680-720°C) followed with a slow cooling in the furnace.

Stress relieving

4140/4142 should be heated to 1100-1300°F (593-705°C), hold at that temperature for 2 hours and then cool the work piece in air.

4140/4142PH is heated slowly through to 900°F (482°C) and soak for 1 hour per inch (25.4 mm) thickness, then cool the material in the furnace or air to room temperature.

Normalizing

This steel grade can be normalized before hardening. Heat to 1544-1616°F (840-880°C), followed by air cooling.

Hardening

4140PH/4142PH is pre-hardened material, to reach a higher hardness the material has to be annealed, as described above, and then it can be re-hardened.

4140/4142 should be heated slowly and uniformly to 1508-1580°F (820-860°C) following with water or oil quenching, depending on  the size and complexity of the work piece.

Quenching

4140/4142 can be quenched in oil to room temperature and should be tempered  immediately.

Tempering

Alloy 4140/4142 can be tempered at 1004-1256°F (540-680°C) subject to hardness and according to the properties required. Cool in air after the treatment.

Alloy 4140PH/4142PH does not require a tempering as it is pre-hardened. If this material should be re-hardened, follow the annealing and hardening process as described above.

For our tempering diagram, please click here

Hot working

This steel can be hot worked at 1500-1900°F (816-1038°C), it maintains its properties even after long exposure at the high working temperatures.

Cold work

In its annealed condition, this steel can be cold worked with all the conventional methods.

Machinablility

This grade is easily machinable after it has been heat treated to produce the microstructure required for the best machinability.

Welding

Welding may only be done in the annealed or normalized condition, which can be done by all the conventional techniques. In order to prevent cracking, preheat to 350-650°F (177-350°C). Due to the level of carbon in this steel, pre- and post-heat is recommended. Cool slowly to prevent/reduce embrittlement.

If welded in the heat-treated condition, which is normally only done for repairs, mechanical properties are affected and a post-weld heat treatment should be performed. Welding pre-heated parts, it is recommended to stress relieve the parts before at a temperature 60°F (15°C) below the original tempering temperature in order to prevent cracking.