Even More Questions

Alden Cole

Alden Cole

Well-Known Member
Hello all, some more questions!
Does everyone else's magnets crack when hardening or is mine just faulty?
I tried to ht a 1075 3/16 thick knife and I don't think I got it hardened. I could cut it with a file. I was hardening in canola oil, and someone mentioned that may not be the best to quench 1075 in.
 
I have only used 1075 a couple of times but I hardened it in canola with no trouble. How did you crack a magnet? I have never had that happen. Just touching the magnet to the steel. If you stuck the magnet to the hot steel and quenched causing the crack then I would guess your steel was not hot enough to harden completely.
 
In regards to the 1075......it depends on the source and the chemical composition.

If its low manganese stuff it will be very shallow hardening and require a really fast quench.

Steel thickness and blade geometry will play an important role too.
 
I think I have an idea of what may be happening here. The magnet is a very general and loose guide. There really is no substitute for training your eye to recognize decalescence. The magnet is only used to quickly check for the shift from ferro-magnetism to para-magnetism and is only touched to the steel long enough to confirm what your eyes are telling you about decalescence. In 3/16" maximum thickness 130°F canola oil should be able to harden 1075, if your heat is correct.
 
Here's what happened. I have a firebrick forge with quite a few bricks I took out of an old wood stove. I have only ever hardened 1080 1/8 thick knives in it, and it performs well enough for me for that. My brother pumps in air with a ball pump thing. I used a mapp gas torch, but I couldn't get it up to heat so I also grabbed a propane torch. I think I got it up to red orange, touched it to the magnet where it cracked and then quenched in canola. The thing that is odd to me is that it doesn't spark as much as the 1080. This should happen some though, right, because it has less carbon? Summed up, would it be better to reharden it, or should I go with it and see if it's good? Thanks all, I know I ask a lot of questions, thanks for answering them.
 
I am not trying to be difficult but I want to make sure I do not give you bad info. What do you mean by sparking? Are you spark testing (holding the steel to a grinder to see how many complex sparks fly)?
 
Just looking at the sparks on the grinder, seeing how much they "firework". Because hardened steel makes a whole bunch more sparks in my limited experience.
 
MAPP gas should burn hotter than propane, all other things being equal. Unless you're blowing in air from behind the burner, I'm not sure you're helping anything by adding the pumped air. The smaller your forge, the better, if you're just using a simple hand held torch to heat things up.

If the magnet isn't working, table salt melts around 1480F if I remember right. Try to heat your steel in a darker area if you're having trouble seeing the colors or decalescence.
 
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