Overheating???

[Hunter10139]

Okay guys what is going on? This is a section of a long, thinnish knife that I heat treated with my charcoal forge. Heated to reddish-yellow and quenched in canola oil. Did the blade get overheated? Did it sit too long under high heat?

[Hunter10139]

Sorry I forgot to mention it was etched with vinegar and then lightly sanded with 400 grit sandpaper. I've looked around online and everything seems to indicate that this is overheating. Can anyone confirm this?

[Doug Lester]

It is really hard to tell what's going on with that blade because of the quality of the photo. Could you repeat the photo without holding it in your hand?

Doug

[jmccustomknives]

Really the only way to tell for sure is to break, yes break it. The grain structure will tell the tale. You didn't say if it was forged. Did you use a magnet? What steel? There are a lot of variables that can go wrong. Like Doug said, a better pic and the info will help.

[Hunter10139]

It isn't forged. It's 1080 and I didn't use a magnet partly because I didn't have one when I was heat treating this one. I guess that was a mistake though. I'll upload another picture a little later today.

[Hunter10139]

Here's a better picture.

[jmccustomknives]

It's hard to say. Over heating will cause a lot of heavy scaling that can lead to pitting. Did you check it with a file? I would think since you didn't use a magnet to judge the temp then that's probably what went wrong. Old oil can cause problems too. Also note that reddish yellow in full sun is a lot hotter than the same color in the shade. If you really want to know and aren't afraid to do a little reshaping snap a little bit of the tip off and read the grain. You might also get the same steel and just do a test. Heat to the same color, do everything the same and break that piece.

[Hunter10139]

It's been a while since I heat treated it. I put off working on this knife for other projects. I believe I did do the file test on this one and it skated. I might break off the tip I guess. Thing is I heat treated other knives at the same time with my forge and I think they turned out fine. The only knives I've heat treated that turned out like this (when etched) were thin or very small bladed knives.

I've heat treated all my knives and did the magnet test on the first ones. I thought I had a pretty good idea of when the blades became non magnetic. I'm still a newbie though. Could using a charcoal forge cause any problems?

[WBE]

Any time you see yellow, it is too hot and too late to prevent grain growth. On the other end of the scale non-magnetic is not quite hot enough to produce a good carbon solution. A shade or two of red above non-magnetic is about the right heat. Non-magnetic is only 1414?. You should be aiming for about 1475?/1500? max with the 1080.