Overheating 5160

[Josh Blount]

Hey guys,

I was working in the forge today, wasn't paying close attention and I slightly overheated my 5160 . I say slightly because when I pulled it out there were only one or two sparks coming off. I let the piece cool back down to forging heats before I worked it. Do you think I did any damage to the blade? How can I tell if I've burnt the steel? Thanks guys!

Josh

[Tom Ferry]

Hi Josh,
Well in my experience if its sparking some part, maybe just the outer most layer is burnt. I watched a demo on grain growth at a hammer in where the smith let it get to the point of sparking because he was answering questions. Well he then hardened it and broke a piece which of course had massive grain growth, then he proceeded to thermal cycle it to reduce the grain. He re- hardened it and broke another piece. I would say 3/4 of the bar had reduced fine grain but on one side of the bar it still showed signs of being burnt from the original overheating. The only way to know for sure how bad it is would be to break the blade to observe the grain. If it were me I would just to see how bad it looks to prevent future problems and not to take the risk of having a bad product out there. Maybe someone else has more insight or suggestions.

[polarbearforge]

I did something similar a while back and posted a similar question. Mine didn't get sparking, but it was very close and had been there longer than it should have. The advice I was given, was to thermal cycle and then break it to check the grain so that if it happens again, I'd know if I could recover it or not.

With my piece, I forged it out to shape with decreasing heats, normalized it a few times, annealed it, ground it to shape, normalized three times, and then did the triple quench. I broke it and the grain was nice and small and smooth as silk. What this told me, was that if I needed to, I could work a piece hotter than usual at first, the rolling mill reduced it very quickly at that heat. And then with decreasing forging temps, and proper heat cycling I could still make it usable and worthwhile.

Jamie

[Josh Blount]

Tom and Jamie,
Thanks for the quick replies. I think that I'll go ahead and break this blade to examine grain structure. I already triple normalized and annealed coming out of the forging, so I should have good grain size in the part that wasn't overheated, at least. Thanks!

Josh