Posted by Bill S. on December 28, 2000 at 08:42:50:
In Reply to: cracks in induction heat treated gears posted by Rick Wilson on December 27, 2000 at 21:44:29:
I remember cracks in some shafts we made from C1144 Cold Roll bar stock. We didn't see it until heat treating and grinding. We were told that this was due to "sulphur stringers" that are common in C1144 cold drawn bar stock. However, we made and hardened a lot of shafts, gears, etc. from C1144 CD without the cracking problem. I think it was a bad bar of C1144 CD.
If you must induction HT the teeth only, you might consider C1144 Hot Rolled bar, which (I think) doesn't have the "sulphur stringer" problem. Or 4150 HR. If you must use Cold Drawn bar stock and can furnace HT, you might consider C1117L for high machinability/medium service or the higher strength 8620L. Never use 12L14 if you are heat treating!!
Also, I wouldn't recommend hardening C1144 to much over 40-45 Rc.
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