8620H Temper Depth

[tmoney99]

I have a part, 8620H, with an M20x1.5 OD thread on it. The part is to be machined and then quenched to 980MPA. It states the thread must not be hardened.

This isnt really a case depth type thing, I thought quenching was a metallurgical transformation (martensite?). Is there a level at which the hardening decreases?

Does anyone have experience with this type of situation?

The cross section is R20mm (.79) and about the same in length.

Thanks,
Tyler.

 

[unclesyd]

Can you post a picture or drawing of the part?

 

[swall]

The material and the stated requirements are in conflict. The stated mechanical property requirement of 980 MPa is roughly comparable to a grade 10.8 metric fastener and you can't get there without a fully hardened, quenched and tempered product. You also can't get there with SAE 8620H steel. The only time I have seen a requirement for non hardened threads on a heat treated product is a product that is induction hardened, with the threads left soft, i.e. something like a ball stud.

 

[tmoney99]

My apologies, this thread can be closed.

I assumed to much while reading the drawing.....Getting ahead of myself.

Thanks uncle and swall.

 

[yshgao]

FYI only.

This is a low carbon cast iron/steel. normally, the surface is carburized for higher hardness and wearing resistance. Then quenched and tempered. It does not make a sense to do the inductive hardening w/o carburizing.

 

[dbooker630]

Another option is to carburize the part followed by induction annealing of the thread section.