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well, I screwed up the heat treat again...

D

DaQo'tah Forge

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Aug 26, 2002
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Hi this is DaQo'tah,

heres the problem...
the steel is 52100 steel , purchased from Rex Walters who forged it down from 6inch bar stock

I ground it down to a oversize by 1/16 inch.

I gave it 3 heat treatments with a Oxy-Acetylene torch until it was Non-magnetic. I then quenched it in Texaco type "A" oil that was heated to 160 degrees.

I gave it 3 temperings at 400 degrees

I sharpened it on a mouse pad , up to 2000 grit with wet/dry sandpaper.

then I etched it

the etch shows the soft part of the steel's grain dips way down too far near the cutting edge.

heres the questions,

Does the etch reveal to me just the last Oxy-acetylene torch heat treating?
or does it show me the results of the combined 3 different heat treatings?



The reason I ask is that during the last Oxy-acetylene torch heath treating I kinda ran out of gas,,,so parts of the blade never actually reach the critical temperature.

at the time I thought, "The first 2 heat treatments were good, the last should not matter that much"...but now upon seeing the Horrible looking etch on this blade, I start to wonder just what the etch can show us?

I just keep thinking that there is just NO WAY I screwed the first 2 heat treatments up that badly....

but,,,did I?
 
I think that the 3rd heat treatment cancelled out the first 2. If you didn't heat it evenly the parts that had hardned the first and second time got tempered the third time and did not reach non-magnetic. I think that if you re-harden the whole blade and then re-temper you might be able to save it.
 
Yep I see it just like Stiper28. Quench it 3 more times and give it the 3 tempers. Buy more gas first
 
I wonder too (and this probably has nothing to do with the real problem you asked about) if it would be better to only pre-heat the quenching oil to about 140 - 145 F. instead of 160 F.

Roger
 
I like the oil at 130 for each quench. I know its hard to keep it there if you quench 3 times because it keeps raising. I have cool oil standing by and use a digital pyrometer to check it before each quench. Dont overheat the blade with the torch. I like to use a pipe in the forge and put the blade inside the pipe. It will give a more even heat to the blade. Just quench the edge.
 
The specks call for 130 degrees with Texaco "Type A" I go to 165 for the purpose of 'fine tuning' the quench rate. Most steels do well at 130, the way I forge and work the steel, the added 35 degrees provide a little faster quench. I had to do a lot of cutting to arrive at the temperature, it works for my blades, provides about 3% more cut. Over 200 degrees and it is much slower gives a tougher blade, but looses cut.
 
I was also taught by Tim Zowada to pull the blade out of the quench while the blade is still hot enough to cause the oil on it to smoke but not flame. Shooting for about 350 degrees F. blade temp after quench. For a full blade quench I count to seven as I swish it back and forth through the oil (in a cutting motion). You, I guess, are doing an edge quench. There will be less steel in the quench that way and I have not yet done an edge quench. I hope one of the more experienced fellows reads this and advises on quench timing for you.

Roger
 
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