Two Large 52100 Blades Cracked Down Spine

Shaw Blades

Shaw Blades

Joined
May 18, 2009
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Hello all,

I was wondering if anyone had any input. I was trying a triple quench heat treat method for 52100 and when I came time to clean the blades up I found multiple hairline cracks starting at the spine of both blades.

These blades for forged, triple normalized, triple quenched in Parks AAA. I know there are different ways to heat treat 52100 but I wanted to try this. I've done this successfully with smaller blades but these were 15 inch knives overall length. They cracked very easy by me lightly banging the flats of the blade on my wooden workbench.

Does this picture mean anything to anyone?

2wn0bxi.jpg


Thanks for your help
 
These blades for forged, triple normalized, triple quenched in Parks AAA.

They cracked very easy by me lightly banging the flats of the blade on my wooden workbench.
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Did you temper before you banged ?
 
In my opinion parks is WAY to fast for 52100 (I heard its around 7-10 second oil..I believe?) I think you should find something slower..Ed Fowler uses a 18 second oil Texaco type A.
 
Daniel Rohde said:
In my opinion parks is WAY to fast for 52100 (I heard its around 7-10 second oil..I believe?) I think you should find something slower..Ed Fowler uses a 18 second oil Texaco type A.
Click to expand...

He said parks AAA not parks 50. AAA is a medium speed oil.
 
It may have happened during the forging process but I suspect the quenchers. What is your heat source for HT? I would consider not doing the triple quench, anymore. Refine your grain through normalization cycles. Ed uses Texaco 18 second oil but he also heats only the edge with a torch.
 
I used a paragon km18d for the hardening and tempering steps.

I'm not a 52100 devotee by any means I just wanted to try my ABS performance test with something besides 5160.
 
Following.
I don't forge 52100, but it's one of my favorite steels.
I'd like to hear more about your normalization routine. And when you say "triple quenched," is that a full quench to room temp from 1480 or so, repeated for a total of 3?
 
Suspect the multiple quench too, if I understand your "triple quench" title as being three quenches from austenizing heat. No need at all to do so with ANY steel. One quench is all ANY steel should need if everything is done correctly. However, the problem MAY lie somewhere else besides the triple quench routine. Could be something else altogether for sure....but "triple quench" is a place to start looking. Undoubtedly you have heard of triple quenching being done by some very well known smiths who work with 52100. And they are EDGE quenching. Quenching is about the most stressful thing our blade steel will see. The fewer, if done right, the better. Normalize with air cooling during the cycling, (refine the grain size), stay just under 1500F for hardening and a 10 minute soak, into a medium speed oil (parks 50 will work well...but is really too fast for 52100). One quench only, then temper.
 
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And he also heats the oil to 165 before the quench, which I would guess speeds it up some.
I have 10 gallons of Tex A and it is amazingly slow at room temp, and even up to 130.
All that said, I've never seen blades break in the thickest area of the blade and not the thinner areas.
Makes me not question the quench.
Or not.
I don't know.
I see everyone else's points here and quenching three times a fully austenized blade could have all sorts of ramifications.

Rick Marchand said:
It may have happened during the forging process but I suspect the quenchers. What is your heat source for HT? I would consider not doing the triple quench, anymore. Refine your grain through normalization cycles. Ed uses Texaco 18 second oil but he also heats only the edge with a torch.
Click to expand...
 
samuraistuart said:
Suspect the multiple quench too, if I understand your "triple quench" title as being three quenches from austenizing heat. No need at all to do so with ANY steel. One quench is all ANY steel should need if everything is done correctly. However, the problem MAY lie somewhere else besides the triple quench routine. Could be something else altogether for sure....but "triple quench" is a place to start looking. Undoubtedly you have heard of triple quenching being done by some very well known smiths who work with 52100. And they are EDGE quenching. Quenching is about the most stressful thing our blade steel will see. The fewer, if done right, the better. Normalize with air cooling during the cycling, (refine the grain size), stay just under 1500F for hardening and a 10 minute soak, into a medium speed oil (parks 50 will work well...but is really too fast for 52100). One quench only, then temper.
Click to expand...

I respectfully disagree. I've seen pretty notable grain refinement from 2 quenches, I wonder if the 3rd is necessary. I was going on strong advice from a mastersmith that is not Ed Fowler and this is what he recommended.

The knife was 3/16 thick Bo.

Thanks for the ideas everyone.
 
You will also see notable grain refinement from good normalization practices... without the added stresses of quenching multiple times.
 
I admit that throwing a quench as a last step in normalization/refining process may help both with defining a very fine structure and placing carbon into solution in preparation for the final austenitizing & quench, but it is not necessary IMHO.
To take real advantage from this, though, you need a quick heat ramp for the final austenitizing...better a forge than an oven, otherwise you allow the time to get part of the carbon out of solution before it diffuse equally into solution again, thus possibly creating uneven structure.
 
Shaw Blades said:
I respectfully disagree. I've seen pretty notable grain refinement from 2 quenches, I wonder if the 3rd is necessary. I was going on strong advice from a mastersmith that is not Ed Fowler and this is what he recommended.

The knife was 3/16 thick Bo.

Thanks for the ideas everyone.
Click to expand...

That is the issue....multiple quenches CAN POSSIBLY induce too much stress on the steel that it does not need to see. Multiple normalizations with an air cool in between do the job of refining grain quite well without the quench.
 
I don't doubt that it may be a rolling the dice situation. Worst thing is I now have 1 less nice new 60 grit cubitron I just ordered.
 
No... the worst thing would be having undetected stress cracks in knives that you have already put out to customers.
 
Shaw, can you share the details of your complete ht please? Just not to focus only on the 3 quenches as the culprit of that bad failure.
Also, you forged that blade, at what temp? etc...
 
stezann said:
Shaw, can you share the details of your complete ht please? Just not to focus only on the 3 quenches as the culprit of that bad failure.
Also, you forged that blade, at what temp? etc...
Click to expand...

I don't have a pyrometer but I forged it at normal colors I'm used to, descending heats.

Normalized @ 1600, 1400, 1200 (air cool)

Here are the instructions I was given:
Hold @ 1550 degrees for 15 minutes, quench
Hold @ 1500 degrees for 7-10 minutes, quench
Hold @ 1450-1475 degrees for 5-7 minutes, quench

temper immediately twice @ 400 degrees.

I had to wait about 2 hours for my oven to cool down before I tempered it. I think that might have been an issue too with the 52100 specifically.
 
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