A2 HT a success

Gossman Knives

Gossman Knives

Edged Toolmaker
Knifemaker / Craftsman / Service Provider
Joined
Apr 9, 2004
Messages
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Well I successfully HT'd my first A2 blade. That furnace is awesome. :D It took about 35 minutes to get it ready for the oil quench. Since this was experimental, I played it by ear as far as how long to leave it in the furnace. After I tempered it, I cleaned it up, sharpened it, put a cord wraped the handle and went outside and did some extensive cutting. I cut rope, chopped on a 2x4 and whittled a 10" thumb size round stick down to about 3" long. Edge holding was pretty good and it sharpened right back to shaving hair right quick. Now I have a third steel I can do myself. :D
Scott
 
Scott,
Oil quenching A2? You got my attention. So can I get your secrets? What temperature, for how long, and how did you temper it? Do you have a way of checking the RC hardness? I like A2 but have always had to send it out for HT. Thanks,

Ryan
 
Whit said:
Scott,
Oil quenching A2? You got my attention. So can I get your secrets? What temperature, for how long, and how did you temper it? Do you have a way of checking the RC hardness? I like A2 but have always had to send it out for HT. Thanks,

Ryan
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Larry, will do. I'll bring it along next week. Hell I might even sell it. :D
Ryan, according to Crucible's website A2 can be oil or air hardened. It follows the same recipe as O1, only it needs to be held at a higher temp. That's why I left it in longer then I do for my O1 blades. All I did was place the blade on the hearth plate in the furance, close the door and let the blade heat to full color. I let it stay in the furance at full color for 5 to 10 minutes, pulled it out and quenched verically point first all the way in. I tempered it for 2 hours at 400 degrees. It may not be the way other makers do it, but it did seem to work. I'm going to do some more testing of this blade but so far it seems to have worked out ok. As far as checking for hardness, I just skated a file across the edge comparing it to a 154CM blade I had TKS HT. It skated the same.
Scott
 
djolney said:
Do you think that oil quenching A2 would make it less prone to fine chipping?
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I don't think it makes a difference. I put a convex grind on this blade and wacked it pretty hard into a treated lumber 2x4 and had no chipping or edge deformation. I also jabbed it point first and moved it back and forth and the tip seemed to come through well. This HTing is still pretty new to me so it's all fun and experimentation with different steels. :)
Scott
 
Oil quenching is fine for that. At blade thicknesses A2 won't have to soak long compared to other air hardening steels we use, therefore protection from atmosphere is not as essential and oil quenching is an option.

Five to ten minutes is quit a course estimate of soak time. Do you have a pyrometer on that oven or did you have to go by color alone?

RL
 
Roger, I went by color alone. The whole deal was a gamble but I think it worked out fine.
Scott
 
You did very well on that. Does your oven have a pyrometer? What's your next steel?

RL
 
No pyrometer Roger. Not sure about the next steel, any suggestions? :)
Scott
 
http://www.bucorp.com/coldworksteels/aza_bohler_item.asp?iItem_Id=39

Note that as a high (medium high?) alloy steel, A2 requires an elevated temperature for hardening, 1700°F to 1780°F and a soak time from 40 minutes minimum at the lower end to 20 minutes minimum at the high end. With 5+% Cr and 1.1% Mo, its performance depends on dissolving the carbides.

You can get hardening with less than optimal heat treats on these steels, but they will not be up to the rated performance level if you do less than the required process.

According to Uddeholm, you can quench all of the tool steels in oil in simpler geometries. I have done it for years with both A2 and D2. I have found that large thin geometries tend to warp in oil. Lately I have been plate quenching the D2, but still oil quench A2. I have never had one crack.
 
shgeo said:
http://www.bucorp.com/coldworksteels/aza_bohler_item.asp?iItem_Id=39

Note that as a high (medium high?) alloy steel, A2 requires an elevated temperature for hardening, 1700°F to 1780°F and a soak time from 40 minutes minimum at the lower end to 20 minutes minimum at the high end. With 5+% Cr and 1.1% Mo, its performance depends on dissolving the carbides.

You can get hardening with less than optimal heat treats on these steels, but they will not be up to the rated performance level if you do less than the required process.

According to Uddeholm, you can quench all of the tool steels in oil in simpler geometries. I have done it for years with both A2 and D2. I have found that large thin geometries tend to warp in oil. Lately I have been plate quenching the D2, but still oil quench A2. I have never had one crack.
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Are you saying I should hold it at full color for twenty minutes? This furance's top temp is 1800 degrees. The reason I ask is the time I left it in, it had scale that was stuck on pretty good. I thought with a good HT the scale should flake off.
Scott
 
Check the Crucible data, 1750-1800F, 20-30 min .If you can't match that you won't get best performance !!! Don't go to the next steel until you have mastered the A2. Some of the stainless steels harden from above 1800F so you can't do them in your furnace.
 
mete said:
Check the Crucible data, 1750-1800F, 20-30 min .If you can't match that you won't get best performance !!! Don't go to the next steel until you have mastered the A2. Some of the stainless steels harden from above 1800F so you can't do them in your furnace.
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Thanks Mete, I think I can handle that. :) No stainless in this furnace. I can do only steels that max out to 1800 degrees.
Scott
 
Razorback - Knives said:
Are you saying I should hold it at full color for twenty minutes? This furance's top temp is 1800 degrees. The reason I ask is the time I left it in, it had scale that was stuck on pretty good. I thought with a good HT the scale should flake off.
Scott
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Get some SS foil and wrap it.

Remember high alloy steels are not the same breed of cat as Carbon steel.

My personal opinion is that A2 is a great steel that is underrated by most knifemakers. It is very fine grained and takes a wicked edge. It holds an edge better than O1 and is more corrosion resistant. It is about as tough as O1 and is easy to work.

I really like it for bowies and camp knives and for kitchen knives at 1/16" thickness.
 
Thanks again for the tips. I'm guessing S.S. foil is available from the knifemaking suppliers? Also how does it work for quenching in oil if it's foil wrapped? Do you quench with the blade in the foil or do you remove it first?
Scott
 
Since A2 is an air quench, you have time to pull it out of the foil and quench.

I can usually get it in the oil while it's still red/orange. You just have to work on wrapping it so that you can get it out fast.

Mosy of the knife supply places have foil. I think K&G has the best prices. Crucible also has it on their website, but they don't give prices and with their steel, at least charge a handling fee in addition to shipping. I have stuck with K&G so far.
 
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