Effect of Heat Treating 4140 vs 10B21 Steel 1

[jmarkus]

We have a part which was specified as a 10B21 steel, to be heat treated to a Rockwell C of 28-37. Instead we got a 4140 steel heat treated (although to 42 HRC). If the 4140 was heat treated to 28-37 would there be any significant different in mechanical properties (notably ultimate tensile strength)?

Thanks,
J

 

[swall]

It depends on the section size (i.e. cross section) of your part. If the cross section of the 10B21 part was small enough that it hardened all the way to the center, then there would be no difference in mechanical properties with the 4140 part tempered back to the same hardness.But, if the 10B21 part was of sufficient section size that it did not harden all the way to the center, then the 4140 part could exhibit greater mechanical properties.