4140 Steel Heat Treatment Hardness

Aisi 4140 alloy steel can be tempered at 205 to 649 c 400 to 1200 f depending upon the desired hardness level.

4140 steel heat treatment hardness.

1 4140 is an ok die steel but is not recommended for radical shaped dies such as narrow fullering crown and so on. But it should be tempered for any heavy use. You find 4140hw in a. 2 fully hardened 4140 ranges from 54 to 59 hrc.

4140 has a nominal carbon content of 4 and this carbon content will yield a hardness of rc 51 for a 90 martensitic structure 9th edition of the asm material handbook volume i. The hardness of the steel can be increased if it has a lower tempering temperature. Aisi 4140 alloy steel can be hardened by cold working or heating and quenching. Heat treatment to 845 c slow cooling from 755 c at a rate of 14 c 25 f hour to 665 c or rapid cooling to 675 c for 5 hours isothermal annealing.

Tempering reheating after quenching will achieve the desired hardness range. For 4140 steel the recommended heat treatment 1 consists of heating to austenitizing temperature typically 1570 f 855 c followed by oil quenching. This leaves near full hardness. 4140hw alloy steel technical data 4140hw meets aisi4140 standards and has improved hardenability and strength in heavier cross sections.

For example a tensile strength of 225 ksi can be achieved by tempering at 316 c 600 f and tensile strength of 130 ksi can be achieved by tempering at 538 c 1000 f. 3 tempering recommendations from the asm heat treaters guide for 4140 4142 is a minimum of 400 f.