52100 Heat Treat Problems

Big Chris

Big Chris

SAHD/Knifemaker
Knifemaker / Craftsman / Service Provider
Joined
Apr 1, 2010
Messages
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Tried heat treating some blades in 52100 last night and I thought things went well till I tested one out. On a 5" blade of .200" thick stock only the last 2.5" got hard. I ground my bevels to 3/4 their finish height and the edge was at a consistent .040".
My process was, wrapped in foil to cycle at 1650 for 10 minutes then cool to black, 1550 for 10 minutes then cool to black, 1400 for 10 minutes and cool to black.
I austenized at 1450 for roughly 8 to 10 minutes.
I was under a second from heat to oil and quenched in Parks 50.
I tested by chopping on an antler for the entire length of blade.
The inch closest to the plunge wrinkled quite badly and for the next inch and a half the wrinkling tapered off to none and remained shaving sharp.
Anyone have an idea what happened here?
Can I bring to temp and try the heat treat again without thermal cycling?
A bit of help would be much appreciated as there are some blades I want for Blade Show.
Thanks
 
To low austenitize temp and not enough soak time at temp.

Austenitizing temp should be 1500*f. Full hardness is not reached until ~1525*. 1450 doesn't even get you past Ac3.

Hoss
 
Even the guys using the LOW austenzing temp method are using 1475 IIRC.
 
I do 1650-1550-1450 & harden @ 1480 for 20 min.. A/Q hardness is 66-67 and the grain is so fine that you can't really even see any grain.
 
Thanks so much for the replies.
I must have wrote the wrong numbers down last time or just got really lucky that the knives hardened.
Thanks again for the help.
 
Just to be sure ... you are removing the blade from the foil wrap before the final austenitization heat and quench?

Also, .200" is a very thick blade. Are you using sufficient quenchant for that amount of mass?

Lastly, is the Parks #50 at room temp ( you don't heat parks #50).
 
Stacy,
Yes, I removed them from the foil for the last cycle at 1400 and for the quench.
I am using 5 gallons of oil, which doesn't seem to get too hot unless I am quenching 5 or more blades in quick succession.
No, I am not heating the oil. It's a little cool here right now so it is starting at around 60 degrees.
Thanks
 
I use 1475 too, and get a consistent Rc66 out of quench. Same normalizing and cycling that Darren uses.
 
It was a success this morning, they all got acceptably hard.
Still didn't get the 66 that some of you are saying but I am pleased.
I'll get them tempered and grind one out to do some testing with this afternoon.
 
70F is the minimum temp P50 is supposed to be used at, according to the data provided by Parks/Heatbath. I use it at ~90F...P50 works well with 52100 it seems to me (technically too fast for this steel). 1475F is apparently the go to aus temp for 52100, and any drop or bump in temp will give less than desirable HRC readings. Lower temps = not enough carbon in solution/low HRC. Hotter temps = higher levels of RA/low HRC. Should have a good soak of 10 minutes (even in a pearlite state) due to the Cr content.

1650F is a good normalizing temp for 52100. 1550F would be a good thermal cycle temp. 1400F is a bit low for a 2nd thermal cycle, as it is well below Ac3. Recommend 3 thermal cycles at or above Ac3/1475F after normalizing. Something like 1650F, 1550F, 1500F, 1475F, and if desired a final cycle at or just above Ac1/1350F.
 
You can deal with the retained austenitite with industry standard temps of 1550f or so, but you would need to sub zero treat the steel for full conversion. It's easier to use the 1475f austenitizing and avoid the retained austenitite.

The datasheets also recommend water quench for low austenitizing temps, so parks50 is good, and oil at higher temps.
 
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