Procedure for hardening A2?
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  1. #1
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    I acquired a couple of lengths of A2 yesterday. I've used O1 and W1 before, but not A2. In a small home shop, what is the procedure for hardening it? I know it is "air hardening" -- does that mean I just heat it up and then let it cool in free air, or does it need some kind of cool air on it, or ?? How hot does it need to be (cherry red?), and can it be/does it need to be tempered after using (and if so, how)?

    Many thanks for any info ...

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    Blacksmith method.

    Take to critical temperature (near where magnetic-non-magnetic change occurs) let cool in free air.
    This is assuming less than 1 inch cross section.
    A compressed air blast may be used for thicker material.
    Do not water or oil quench as this WILL cause cracking. DAHIK.
    If you want the "real" way to handle this material contact the manufacturer or your supplier.

    Phil

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    Generally you heat A-2 in a furnace to a temp of 1750-1775degrees F. It should be wrapped in heat treat foil to prevent scaling. Depending on desired hardness, it should be tempered anywhere from 300 to 800 degrees F.

    I heat treat A-2 on a daily basis, so feel free to e-mail me for any questions.

    Shan

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    You must protect A2 steel from oxygen by wrapping it in stainless steel heat treating wrap.If you buy any,get the kind that's good for higher temp.think the usual stuff is good for 1800 deg.I hope you have a pyrometer.Put a small pc. of brown paper into the envelope to burn up the air in it.Put the envelope in a cold electric furnace.Preheat to 1200 F.Hold for abt.15 minutes.Set the heat up to1750 F.Let it reach the temp.,and soak for a max.of 1 hour if the steel is 1" thick.30 minutes if 1/8" thick.The A2 will have a soft skin on it if you don't put it in the envelope.Have another oven ready when you pull the A2 out of the furnace.Other oven can be just a toaster oven,but you need to know what temperature it really is.I've used a high temp.thermometer from Brownell's,with a long shank on it,inserted through a 1/8" hole in the back of the toaster oven.DON'T trust the dial on the oven.Now,take the A2 out of the furnace,and cut the envelope open with some old scissors.Get the metal out as soon as possible.Dump it gently onto some soft firebrick surface,NOT METAL SURFACE.If it is a flat piece of metal,stand it up against a brick.Don't let it lay flat on the brick,or it will not cool quickly enough on one side,and may mot harden.Let it cool until you can barely hold it in your hand,and put it into the preheated 400 degree toaster oven.You can lay it on the metal rack inside the oven because it is already hot.Temper 2 hours for even 1/4" thick.If you don't get it into the second oven as explained,and let the metal get fully cooled,it won't be as good if the application is critical as to tool life.Otherwise,send it out to be heat treated!

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    P.S. The A2 will harden just fine in still air unless it is real thick.I've made lots of punches and dies 1" thick.I may set them in front of an exhaust fan.They've still hardened in still air,though 1" thick.The danger of using an air blast is that there is usually some amount of water mist in the air,and that can crack your A2.I'd stay away from air blast,also,because it will cool the steel more quickly,and can cause distortion to ruin your work.No offence to Fen2art.You need to get a book on heat treating tool steel,and the right equipment,or you may put a lot of work into something to find it ruined.The main virtues of A2 are that it doesn't distort much at all if handled correctly,and it has much better wear resistance that O1,or W1.The last two named can be very treacherous to distort unless it is something simple like a knife blade.Even then,you can really get into trouble.Study up.

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    You can leave it in the bag until the red color goes away without any noticeable difference in hardness. Makes for a cleaner part and less likely to singe the hair off your knuckles. An elevated piece of heavy screen is better than brick.

  7. #7
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    Screen is a good idea.Promotes all around air exposure.I always prop the part up to get air all around.Maybe I'll get a chemistry tripod and some screen.I use long blacksmith tongs to hold the envelope while cutting the bottom of it open.


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