Overheating 5160

I was just starting to forge a blade the other day, when I got a phone call and was called into the house. I expected the call to be shorter than it was, so I left the piece in the forge. When I came back out, it was a very bright yellow and was much hotter than I've ever forged anything before. The scale was coming off in large pieces. I think that I overheated this piece. I hadn't done any forging on it yet, but I forged it anyway for practice. I used a rolling mill to do the main drawing out and evening and hand forging for the rest. I'm gonna grind it down and heat treat it as I have been and then break the blade and see how it looks. What's the best way to tell if I overheated it? Large grain? Is it like 52100 where it will difficult to get and keep a good cutting edge?

Jamie

Over heating isn't good for any steel. 5160 will handle it as well as any of them. You might be able to save the blade with proper thermal treatments (normalize/anneals). Much would depend on how the blade was treated after the inital overheating occurred. Chances are fair that if you used care, and reduced the heats as you progressed, the blade might be salvagable. When you break it...... if the grain appears large (like shiny grains of sand), and they look angular, it's not a good thing. What you hope to see in any blade is the look of melted and swirled vanilla ice cream. Drop a post and let us know how it turns out.

Got around to finishing this one, and it turned out right. When forging, I do use reducing heats and I am very attentive to the temperature. (Well, with this one exception... After forging, I normalize once and anneal once. I did the same thing here. After grinding, I normalized again and then did a triple quench. I broke the blade and it has the real small grain size. It's about as you described, melted and swirled vanilla ice cream. It's comforting to know that the blades previous to this weren't heated to near this temperate and this grain ended up ok, so I'm not worried about the others.

On a side note, I took another blade that I heat treated the same way but also triple tempered. I wasn't happy with the overall look and grind of the blade, so I tested it too. I clamped it in the post vise and bent it until it touched the vice and it sprung back to less the 90 degrees. The edge is hard enough that a new file only bit with a lot of force.

Jamie

Great news! Sounds as if you've got the hang of things. Just keep on testing, and things will only get better.