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Thread: New zero warp heat treat method + vid

  1. #1
    Gunco Regular twistedneck's Avatar
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    Default New zero warp heat treat method + vid

    Figured out that a stress relieving step before heat treating completely eliminates warping. Confirmed the theory first with a bad ass metallurgist guy.

    See the vid.

    I quenched this 4130 receiver from 1600 right into brine, normally that warps it a bit, a bitch to straighten in that state.

    With this new method, zero warp..

    ----
    Update 3/25/07, I"ve had a home heat treat break through! In addition to the 750F for 2hr pre-heat treat stress relieve step, if you get your buddy to stir the living hell out of the brine tank, warping is almost gone! so the combination of very fast agitation in quench and pre-stress relieve is the best one for kiln and brine quench. Note, the direction of flow in your 5 gallon bucket should be INTO the receiver shell opening - that way brine flows into the receiver and cools the inside rail areas very quickly.

    You'll notice the back end of the receiver where you holding it does not want to dunk all the way - due to the circuating current.. that was a surprise to me - and the only place i got a litte warping becuase i didn't get it under until a second later.
    -----

    To harden, heat to 1600F but do not hold, remove, quench into brine @ 3lbs salt / 5gal bucket.

    Temper 750F for 1 hr, sets up 42Rc.

    Side benefit? The oxide layer formed during the stress relieve pre step protects the steel surface from scale build up & decarburization softening during the high temperature step.

    http://home.comcast.net/~jcheck10/akbrine.3g2
    Last edited by twistedneck; 03-25-2007 at 05:54 AM.

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    Gunco Regular resting's Avatar
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    Twistedneck, good stuff. What are you using for a kiln?

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    Gunco Regular twistedneck's Avatar
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    resting, its the evenheat kf22.5.. made in Caseville MI.

    http://www.evenheat-kiln.com/knifeovens/knifeovens.htm

    takes a beating! its been drilled, i sealed it, i even over pressureized it w/ argon last night and it let out a loud creaking noise..
    Last edited by twistedneck; 10-04-2006 at 09:46 PM.

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    Gunco Regular pupwag's Avatar
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    Why won't it work with the rails pre welded in?
    It's only metal, it's not magic.

  5. #5
    Gunco Regular twistedneck's Avatar
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    Having the rails welded in might work for some, i did work for me in molten salt.

    I had such a hideous time with oil / brine and rails causing warp i didn't try it. But with this new stress relieve method it might be worth a try..

    Problem is, having two surfaces of different thickness welded together even if they are the same steel type, metal crystals will grow or shrink more in one than the other. This step might fix that.. heck i really should try it.

    But now i'm pretty much out of extra receivers to test - i've got extra rail sets. I would have to fully normalize the super hard test receiver and then start from scratch, by that time it would be a scale covered mess.

    If you donate a junk receiver, I'll test that method.

    Its not necessary, just use a 750F temp crayon on the hammer and trigger holes.. when you weld the rails in, it shouldn't get that hot near the hammer. Depending upon where you place that lowish spot weld. If the crayon does not melt then you didn't loose any hardness and its fine.

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    Citizen, Patriot, Ranger bellson's Avatar
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    Quote Originally Posted by twistedneck
    Figured out that a stress relieving step before heat treating completely eliminates warping. Confirmed the theory first with a bad ass metallurgist guy.

    See the vid.

    I quenched this 4130 receiver from 1600 right into brine, normally that warps it a bit, a bitch to straighten in that state.

    With this new method, zero warp..

    Heat your kiln to 750F and put the receiver + rails in seperate.. hold for two hours @750. It will relax all of the built up stresses from forming drilling, and the heat effects from cutting and sanding.

    Next, let it cool down slow in the kiln. Once cool, heat to 1600F but do not hold, remove, quench into brine @ 3lbs salt / 5gal bucket.

    Temper again at the same 750F for 1 hr, sets up 42Rc.

    Side benefit? The oxide layer formed during the stress relieve pre step protects the steel surface from scale build up & decarburization softening during the high temperature step.

    You still got to be even and straight down when you quench, but its simple. Rails went in random orientation and had zero warp.

    The one negative thing, you can't heat treat with rails welded on like the molten salt method. That means some soft spots will form on the spot welds - generally localized and not in the functional area of the rail / ejector / hammer hole.

    This is the simplest method and it works.

    http://home.comcast.net/~jcheck10/akbrine.3g2

    see the problem with this method? I held the door open too long getting the rails out first and the back end of the receiver cooled off. That difference in temp across the receiver would usually cause a warp.
    Hi Twistedneck,

    A couple of questions:

    1. In the first heat soak step, do you load the oven up with the recievers first, then bring up the temp to 750 for two hours?

    2. For the cool down cycle, how long does that take?

    3. For the cool down cycle, do you leave the recievers in the oven?

    4. For the Martensite (1600 degree) cycle, do you laod up the recievers in the oven and then bring it up to 1600 degrees? How long do you hold it at 1600 degrees? 5 Min? 10 Min? 1 Min? Or out and quench ASAP?

    5. For the final temper, do you load up the recievers first and bring it up to 750?

    6. For the final temper, do you remove the recievers from the oven and allow to slow cool, or do you leave them in the oven?

    7. How long do you leave them in the oven (assuming that you do)?

    Sorry for the nit-picking tone, It has been about 25 years since my last metalurgy class. I am intrigued with the possibilities here....

    I'm doing AK's to develop and sharpen my skills. My end game is to develop a Public Domain design that I call "The Freedom Rifle". It's just a rough concept at this point, but I know that AK kits don't grow on trees. Sooner or later we will all need to "really" build our own weapons from scratch or domestic parts.

    Thanks in advance.

    Bells_on

  7. #7
    Gunco Regular twistedneck's Avatar
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    Belson:

    1. In the first heat soak step, do you load the oven up with the recievers first, then bring up the temp to 750 for two hours?

    I only load up one receiver at a time cause that's all i usually have done. For sure put them in at room temp and heat kiln and receivers at the same time. Its important not to shock the thin material into warping.

    2. For the cool down cycle, how long does that take?

    I just open the kiln door and let it sit until about 250 or so, then remove, air cool.

    3. For the cool down cycle, do you leave the recievers in the oven?

    Yes

    4. For the Martensite (1600 degree) cycle, do you laod up the recievers in the oven and then bring it up to 1600 degrees? How long do you hold it at 1600 degrees? 5 Min? 10 Min? 1 Min? Or out and quench ASAP?

    Remove right away and quench. Thin metal like this, not high alloy tool steel doesn't need long to setup the austenite crystal structure, just a few seconds. It takes a while for the kiln to get to 1600, so they are already pleanty heat soaked. Some say best temp for 4130 is 1575F anyway.

    5. For the final temper, do you load up the recievers first and bring it up to 750?

    Again, every step you should be slow and gradual - heat up and cool down. Thin recevers warp at the drop of a hat. The only quick temp change is the quench.

    6. For the final temper, do you remove the recievers from the oven and allow to slow cool, or do you leave them in the oven?

    Same thing, let em cool slow, usually you don't need to worry about that - but with these thin things i aint takin no chances.

    7. How long do you leave them in the oven (assuming that you do)? Same as the stress relieve cycle.

    Sorry for the nit-picking tone, It has been about 25 years since my last metalurgy class. I am intrigued with the possibilities here....

    -Nit picking? huh? naaa

    I'm doing AK's to develop and sharpen my skills. My end game is to develop a Public Domain design that I call "The Freedom Rifle". It's just a rough concept at this point, but I know that AK kits don't grow on trees. Sooner or later we will all need to "really" build our own weapons from scratch or domestic parts.

  8. #8
    Citizen, Patriot, Ranger bellson's Avatar
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    Default Cool!

    Thanks Twistedneck!!!

    I hate having to ask all of the numbskull questions, but I hate destroying good metal even more

    Your descriptions should make this an easy task!

    Thanks Again

    Bells_0n

  9. #9
    Gunco Regular my-rifle's Avatar
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    You should try my new method. First get a nuclear reactor ...

    :-0
    * This is My Rifle *

  10. #10
    Gunco Member Zoo9guy's Avatar
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    Postak Awesome!

    Twisted, your write up is exactly what I was looking for. I'm just a knuckle buster and some of the guy's here talk about heat treating like it's Diamond splitting in a nitro plant. Now I need to build that oven and start cook'n steel!!

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