I need some tempering advice on ATS34/154CM

C

crguin

Joined
Oct 27, 2002
Messages
35
I've been playing around with the high temper for ATS34/154CM and so far I'm getting more consistent results.

I pre-heat in a 24" Paragon at 1500 deg F for 10 min.
Ramp to 1950 deg F, hold for 40 minutes.
Quench between 2" Aluminum plates while blowing forced air between.

here is the problem....

It takes about 45 minutes for the Paragon to cool down to a little below 1000 deg F. I don't want to wait that long before tempering. So I'm wondering what's going to happen when I temper at 400 deg F for 2 hours, and then use the 1000 deg F for the other 2 hours.

As I understand it, using Crucibles heat treating specs.... you gain that extra Rockwell point by using the 1950 hardening and then 1000 deg temper.

Also let me say that I am not using any Cryo; not that I am against it.....Although I do have my reservations....It's just not in my budget at the moment.

Will the steel take on a new structure by using the low temp on the first temper? Something that will be totally ruined if I bump it up to 1000 on the second?

I know the disadvantages of using the high temper. Lower corrosion resistance, lower toughness, etc. These are paring knives that I'm making by the way.

I've noticed that some peoples numbers are all over the board in the stainless arena. I'm having fits with it. My 440C hardens up great, sharpens great, tough as nails, holds a great edge too. Even with it there are hundreds of degree's difference in some peoples hardening and tempering recipes. It was a total crap shoot when I first started working with it. Some say temper for
1 hour at 300 deg F 2 times, others say temper at 400 deg F 2 hours 2 times.
Some say hold it at hardening temperature for 10 minutes, some say 30 minutes, some say an hour. See what I mean? And that for 440C!

I've searched, read, experimented, made some nice looking knives that don't hold an edge for nothing(not too many). I've blamed it on my foil, switched to the no carb dip stuff for high heat. The stainless just isn't impressing me like W2, 1084, 01 and the other Carbon steels did. Heat treating is the fun part for me.

Anyway, now that I'm all worked up, and everybody knows how I really feel, it's late and I need to go back out to the shop and get those blades out of the 400 deg F oven and dream about what I should do next.

If anybody has any words of wisdom, I'm all ears.

thanks

Chris
 
The 400F vs 1000F has been discussed at length. 1000 F is good for many industrial applications.This temperature involves formation of different carbides and is called secondary hardening. But there's no reason for not using 400 F for a knife.Many do it without problems !! I just ordered a CPM154 knife and specified 400 F !!
You can trust me I'm a metallurgist not a politician !
 
If you want to grind hot after heat treat then high-heat temper may be a good option. You could put the blade in the freezer until you're ready to temper or you could just snap temper in the oven/toaster oven. Afik, it's not going to hurt it to temper at the low heat temp first.
 
Just remember, the high temper will convert retained austenite. So, you will need two tempers at the high temp.

Jim
 
I believe you Mete and thanks for your input.

That's exactly the kind of info I was looking for. "Different type of carbide at the higher temperature".

Actually the secondary hardening point is what I wanted, and I also wanted a little red hardness. The blades that I have been doing have mostly been done out of 1/8" stock, most of them hollow ground, and at least a few were borderline too thin in my book. They were kitchen knives and folder blades.
I didn't want to have to worry about overheating them in cleanup.

I basically want to know which is the most fool-proof, the low temp (400) temper, or the high temp (1000).

My main concern is edge holding alone. I don't care about the tradeoffs in this case.:D

thanks

Chris
 
Over heating in clean-up ? Don't play that game , I've seen too many knives that tips broke off or edges that had been damaged from grinding.It's very easy to do. And I don't appreciate having to regrind a new knife. When the blade gets too hot to the touch it's time to cool it and that will still be under 400 F.
 
As a rule I try not to grind too much after heat treat. I dip in water after every pass but still get a flash blister every month or so. I don't use a push stick or gloves after it's been heat treated because I want to feel every temp change.

I hate to do it too, and I've ruined a tip or two.
I still have to remove the heat treat scale that forms. Sometimes it's a pass or 2 on a 220 grit. Others are much tougher. Especially on 440C it seems. I use the high heat antiscale dip from Brownells, usually about 2 coats. It seems to work great. It leaves a very uniform blued gunmetal finish that is tough as nails. No pitting, most comes off in quench, oil or air. I have foil too but the dip is easier for some things that I do.

Chris
 
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