SAE 4140 thermal treatment

Hi
I need to trea SAE 4140 thermally by induction and need to know what thermal procedure to use (forging, tempering, normalizing, hardening, etc) to reach three different properties:

1) HB 426 , tensile strengh 1531 MPa

2) HB 283 , tensile 931 MPa

3) HB 216 , tensile 689 MPa

thancks

 

[gunsmith]

I think we are tlaking 4140 (=42CrMo4) here with the material key number (German steel key) 1.7225 without additional sulphur content.

1.) You won´t reach 1531 N/mm^2 at any condition

2.) yield point or break point - what You are looking for

3.) mechanical property is also a function of diameter or dimension - what dimensions do You want to use

4.) Have a look to DIN 17200

If 1470 N/mm^2 are needed take 18CrNi8 (1.5920 - maximum number is 1470 N/mm^2 for diameter lower than 11 mm) instead of 42CrMo4 using a case hardening process.

Andreas

 

[TVP]

jimiexe,

Can you clarify what you intend to do with the induction heating procedure? Do you want to the 4140 steel to have the tensile strength/hardness values you listed BEFORE or AFTER the induction heating procedure? If it is BEFORE, then you can obtain 4140 steel bar at the various hardness levels from a steel bar vendor. The lowest hardness can be obtained by using a hot-rolled bar which is subsequently cold-drawn. Normalizing will produce a hardness of ~ 300 HB, annealing will produce a hardness of ~ 200 HB.

In order to attain HB 283 or 426, you will need to obtain the steel bar in the Quenched & Tempered condition. The tempering temperature is varied to produce the 2 different strength levels.

Andreas,

4140 or 42CrMo4 CAN be produced with a strength level of > 1500 N/mm₂, but it must be Quenched & Tempered, not just hot-rolled/cold-drawn or normalized. Also, DIN 17200 has been superceded by DIN EN 10083.