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So I have a little problem and I am kind of stymied... I bought a bundle of various sized 52100 round stock a few years ago at a blacksmithing event, can't remember the details at the moment.  I just recently pulled it out and tested a small piece for a slipjoint knife build.  I forged the shape, ground it to near the final thickness, normalized and hardened.  Low and behold I barely get 50 HRC...  Did it a second time and got virtually the same result---------so I see 3 possibilities: I got sold something that isn't 52100, my heat treat process was totally wrong, or I had massive decarb.

I don't think decarb is really the issue because I ground away the surface steel and put a wash of satanite on before the hardening (the second round was done without the satanite just in case that had botched the quench, but results were the same).

My heat treatment may have been a bit off, but I still wouldn't expect to get such low hardness.  Here is the procedure I used:

2 normalizing cycles at about 1475, held for about 2-3 minutes then air cooled. Bring up to 1500 then hold for 10-15 minutes and quench in 125 degree cooking oil--------as quenched hardness was only 50 HRC.  My temperature control should be pretty good, I use a thermocouple in my forge to monitor temp during heat treats.  I also used a similar process to harden some W1 (with  shorter soaking times) at the same time and I got a hardness of 65 HRC.  

So, any ideas what might be going wrong???

 

 

 

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I have read of similar problems in the past. Heat it to 1550 F and quench, then test. If that doesn't do the trick, bump it up another 50 F and try again.

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I  have no idea where you got your information a few minutes at 1475F does almost nothing.
HEAT TREATMENT of 52100
Normalizing:
Air cool from 1650-1700F
 
Spheroidize Anneal:
the following step down cycling is recommended
1500°F (815°C) for 3 hours, 1350°F (734°C) for 4 hours, 1250°F (675°C) for 3 hours then a slow cool to 1000°F (538°C) and then air cool.   Maximum annealed hardness: 207 HBW
 
Hardening
Quench in oil from 1500-1550°F (816-842°C).

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Buy a piece of new 52100 from a store, and put it in with a sample of what you already have as a test sample. If it comes out right, and the material you have now doesn't you may not have 52100 in the knife. Follow Steve's advice above, and you should be good.

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