Heat Treating A2

P.Brewster

P.Brewster

Joined
Jul 25, 2007
Messages
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I have some A2 I want to make some spikes out of. The package says "Preheat to 1450, then raise to hardening temp 1725 to 1800 and soak uniformly." Soak in what? Oil?

Then "Quench in still air or dry air blast at 125 to 175, then temper immediately."

So after I soak it (in whatever), I let it cool in open air? Then to temper, I reheat to 500 degrees and let cool in open air a second time?

If I want a differential hardening (hard at tip, softer and tougher at tail), do I only heat the tip to hardening temperature, or do I only temper the tail?

I have 3/8" square stock. Can I do all the heat treating and tempering with a MAPP torch?

Thanks,

Patrick
 
Do not HT with a torch. Soak means hold at temperature ,1750 F. Preheat not necessary for that type of use.The 'A' means it's air quenched. Using stainless steel foil to wrap the blade is a good idea.Do not differentially harden.This is not a steel for beginers to HT.
 
A2 is an excellent steel when done right, but often you need two kilns with electronic temperature controls because it has to stay at that correct temperature between 1400 and 1800 degrees, otherwise excess grain growth may occur.Also, scale formations and decarbonizations occur at such a high temp easily. I think a press is nice especially when treating a long and thin air hardening blade (like a machete) If you want to heat treat at home, opt for oil quenching steel, O1 is what i use and I am loving it, L6 has good shock resistance as well as other good qualities. Oil makes a real nice quench. But for A2,send it out! Good luck :thumbup:
 
I use A2 alot...well only as a matter of fact and i'd suggest you grind the whatever to shape to about 90% of the cutting edge or I guess if you're gonna make it a spike you can grind it to whatever is the finished product.

Degrease the part with Acetone as if you don't it makes the A2 surface kind of weird almost giving it some sort of shadow pattern (hard to explain), but if you have degreased it correctly, after HT, the color(s) should be pretty even throughout the blade or tool. You're definately gonna get some sort of rainbow tone on the surface which can be easily buffed off with 300 or high grit buffing compound.

Put the part in stainless steel foil and crimp all edges 3 times folded over to ensure for a nice seal. Put a piece of kraft paper (market shopping brown bag) inside the envelope you have just made to help burn up the oxygen.

Austenizing temperatures range from 1680-1800+ degrees so you'll have to do a bit of reading up on what you're trying to achieve in hardness as quenched and then to temper say between 400-500 degrees if you want it around 60 RC...but that will vary depending on your austenizing temperature.

Like Mete says, it's not a steel for newbies to play with really and if you don't have some sort of electric kiln or vacuum furnace, you won't be heat treating it correctly as it takes atleast at the bare minimum 30 minutes of soak time at austenizing temperature say for something 1/8" thick, but the time goes up the thicker the part gets. kind of hard to explain in this little paragraph.

After your have soaked it (in the furnace) open the door when the time is up and take out the blade/tool. make sure all the visible red heat has disipated before you cut open the envelope otherwise oxygen will get in and the blade will decarb somewhat more.

Put on a cooling rack that is well ventilated. DO NOT let it cool on the floor as the floors temperature will probably be different then the air temperature and it could cause cracking or other undesired results. If it's a blade, hang it up or something...i'm sure you can figure it out.

When the part reaches 120-150 degrees (can hold in your hand, but will be somewhat uncomfortable) but it into a preheated tempering furnace at 400 degrees for 2 hours. take out of oven and let it air cool to room temperature. If you want a 2nd temper to make it somewhat stronger or tougher, lower tempering oven to 375' degrees for another 2 hours. take out and let it air cool. Austenizing at 1775 degrees with a 400 degree temper should yield a hardness of around 60 RC.

OR if you have none of the following tools that I just described and you're just goofing around technically you could heat treat it in an open coal forge and harden it. It won't be very uniformly heat treated, but it will still be HARD. I know this, because lol i've done it back in the days before I knew you had to protect the blade/part from decarburization and all that other stuff. But if you're just messing around, that's a way to do it too....heat it to a nice cherry red for around 10 minutes and then take it out and let it air cool and then temper it. or if you just want something hella hard, don't bother tempering it! will just be somewhat brittle, but if it's a spike and you're not gonna do anything psycho with it, then that doesn't really matter.

Have fun!
 
You could technically also quench the A2 in Oil. If you're that brave, I'd suggest you use WARM vegetable oil and it won't flash or flare up...heck i've actually take a MAPP torch to it and it didn't flash or anything....use a flat small cookie sheet with about 1/2" of oil. Good luck. Don't do anything crazy like motor oil or other crazy things people quench their blades in as that stuff gives off toxic fumes when the blade goes into it.
 
I have heat treated over 1000 blades in A2. Here is how I do it:
Wrap blades in SS foil, no combustible inside package.
You can preheat @ 1425-1450F for 10 minutes. Then, ramp as fast as possible to 1750F. Soak 30 min for 1/8 blade, 45 minutes for thicker stock.
A2 is very resistant to grain growth. Undersoaking is far more detrimental than oversoaking.
Press quench between Aluminum plates. Deep freeze in Ln2, or, proceed directly to temper @ 425-450F. Double temper. Aim hardness is Rc60.

RJ Martin
 
Thanks guys! I appreciate all the info, and I'm glad I asked.

Please note my stock is 3/8" x 3/8" SQUARE stock, and my product is a spike (with a pyramid tip). So this is not technically a blade or a knife. Sorry, I couldn't find spikeforums.com ha ha. My choice in A2 was purely an impulse buy (I was buying SS rod for use at work, one thing led to another).

I am making a throwing spike aka shuriken for throwing. That is why I only want the tip to be hard, and why I'm not feeling too perfectioninst about heat treating this. In fact I may throw the spikes as is to see just how bad the tip is getting beat up. If the tip is just getting small chips or minor mushrooming, I'll probably leave it. But if that tip folds over, I'll be looking to do something about it. I mostly throw with paddle/spade wood drill bits that I regrind (with water so I don't loose the hardening). I don't know what they are made of (I'm guessing HSS) or what the hardening is, but they are perfect. They bounce off concrete day after day, with no bending or breaking - just a very gradual dulling.

That being said, would you guys still advise against partial (differential) treating?

Leu custom, I appreciate the info about Austenizing, oil quenching, etc. I'm new to this but what you said seemed like common sense.

rj martin, thanks for your input. Would you agree that press quenching wouldn't be right on square stock? Whats Ln2 (not liquid nitrogen, right! If so, you are serious.)?

Keith, thanks also. Another shuriken maker I know uses O-1, I should look into it. Also, it seems like what would be a good steel for a machete would be good for a throwing implement, in terms of toughness. I've never heard of L6, but I'm all ears. Where do I buy this stuff?

So, is there anyone besides Paul Boss who I can hire for heat treating? I see what you guys mean, this isn't for beginners. I gather consistency in temperature is important for all the steps of heat treating. I may be able to get this thing up to 1750 with a torch, but I def can't keep it at a steady 1750 for 30 minutes, even with a infrared thermometer. I thought I could just heat this thing up, stick it in some oil, and go to town.

So if "A" means air, "O" means oil, what does "D" mean?

Thanks guys.
 
LN2=liquid nitrogen. Yes RJ is serious. Plate quench should work ok for square stock.A hardness of 57-58 HRc might work better for you. 'D ' as in D2 is a cold work DIE steel....L6 is very tough !
 
For a throwing spike, you could probably get away with heating the tip and oil quenching. but 3/8 x 3/8 isn't going to break if it's fully hardened, either.

Skip the cryo trreatment, too.

Press quench will work fine, and will require the least clean-up on your spike.
 
Patrick: there is a firm in Meadville, Pa. called Peters Heat Treating Inc. There address is PO. Box 624. There Ph.# is (814)333-1782, Ask for Gary Armour, He is the General Mgr. They are an Associate Member of The Knife Makers Guild. Hope this helps. Paul.
 
i'm sure he does single pieces up to 20 blades for a cost of $70.00 bucks if i remember correctly. =) But man if you're just making something like a spike i wouldn't go all that way and pay all that money for something you're probably just gonna play with for awhile and then never touch again.

i'm guessing most people don't have access to Liquid Nitrogen =) I'm guessing RJ has it at his house as he does this stuff all day long or definitely in his shop! REAL NICE LOOKING JAPANESE BLADES RJ!!!!
 
got a bit of a dumb question, if you press quench a blade A2 or whatever, don't you have to straighten it out first if it happens to warp in the cress kiln RJ? my logic would tell me that if it were warped and you press quenched it it would cool down but the minute you took the plates off, the warp would be there as well as if you just left it there to air cool? PLEASE correct me if i am wrong =) Every A2 blade I've made that's ever warped i've straightened in padded vise and just hung up to air cool to 120-150 before tempering.
 
If the blade is already warped in the furnace the plates will straighten it easily as it is in the plastic autenite range .The plates will also prevent warping during martensite transformation.
 
Leu: A2 is not a steel that is prone to warpage-even the chisel ground blades. I lay mine flat on a row of kiln bricks that run down the center of my furnace. I gouged out two troughs that match up with my "fork" so I can slide the fork under the foil packets for insertion/removal. As mete says, they come out flat.
I used to use an upright "rack" that I put individual foil packets in. Had many more problems with warpage back then.

Thanks for the compliment on my blades!

RJ
 
Guys,
I didn't ask the question to start but am always happy to learn from your answering another's questions.
Thank-you!
 
Patrick: Yes I do single blades, For one blade it would be about $20.00 for H.T. and return postage. Paul.
 
RJ: so if the foil envelopes are laying flat on the kiln brick, does it allow for even circulation of the heat around the envelope? and i'm guessing you wouldn't want the ends of the blades hanging too much over the brick incase for warpage towards the tip and end of the blade tang right? Or does that method of yours not matter that much? I'm guessing if I was going to do something that was 16 inches long overall, i'd either have to have a very wide kiln which mine is only 10 inches wide, but 27" inches long...so the whole fork method makes it rather difficult no? So far i've putting putting blades in the upright method and taking them out with heat treat tongs...love it when it feels like the hairs on your hands and arms are about to burn off or melt! Even with glove rated for 1800' degrees! Or maybe it's just my face feels like it's getting baked!

How fast does the CRESS you have/had get up to the 1750-1800 degree range? like any other kiln or faster? I personally use 2 even heat kilns.

Thanks RJ for the information! Learning anything new is always exciting!
 
Mr. Bos: Do you heat treat 01? and if so, how much to do a 7 inch blade and roughly around 13 inches overall? i'm guessing you Heat treat anything?
 
Leu: Put your blade in running the length of the furnace. make your foil packet wide enough so you can insert/remove it with your fork. My fork tines are about 3" apart.

Nothing wrong with using tongs, either, if your blade is robust. But, a big blade will bend under it's own weight if you don't do it right.

People often assume (incorrectly) that laying the blade on a firebrick will result in uneven heating. Above about 1400F, everything inside the furnace is radiating heat-the floor, the walls, the support bricks. And, everything is the same temperature.

Sag is not a problem-Just run the bricks down the length of the furnace. I have several bricks, and I reconfigure them as necessary.
 
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