Argon + heat treat oven?

silver_pilate

silver_pilate

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Oct 30, 2002
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I've been toying with the idea of adding an argon source to my heat treating oven. For stainless, I use stainless foil and plate quench, but I was wondering if it would be worth the trouble to add argon for my carbon steels, mainly O-1, to limit any decarb forming during the soak. I haven't really had a problem up to this point with decarb beyond the most superficial exposed surface "scale", and I wonder if I would just be spinning my wheels with no real benefits.

What do you think? If it's worth it, do you have ideas on how I should go about setting it up?

Thanks!

--nathan
 
This will sound funny, but I think it might be *more* useful to you for carbon steel than stainless because it is good enough, you don't need much, and it addresses a problem with quenching carbon and foil.

My furnace uses argon, but I seldom use it. For stainless, foil works better because the blade is protected during quench too, and argon ain't cheap.

As you know, you can't quench carbon steel through the foil like you can stainless. The antiscale powder makes a mess of your furnace, and can be a PITA to apply and remove. Due to the shorter soak and lower temps decarb is less of a problem, so a bit of argon should do the trick.

I use a welding regulator set to below the scale where I can just barely hear the gas flow in the regulator off an argon tank on the TIG. You could probably find something better on ebay. Argon is dramatically heavier than air. The furnace has a (somewhat) sealed door and a small port on the top for air to escape.

Use a good oil and your parts should look pristine. Once you open the door and start pulling blades out the scale will start quickly, so this may not work well if you're doing a bunch...
 
I had been thinking of doing the same thing, would like to know how it works if you try it. sure sounds like it should work.
 
Nathan would know better than I, but it seems like a lot of cost/trouble for a little gain.
The oven door would have to be quite tight to keep hot argon gas in ( or the flow rate high). The chamber would have to be non permeable to hot argon gas,to ( completely sealed at all joints). Once you open the door, the gas is gone, so multiple blades are a problem.

I have had good success with Turco on carbon blades, so I am somewhat one sided on this. That, plus the small amount of actual de-carb on blades held at 1500F being easily removed in the finishing.

I would be interested in anyones results with use....Quantity of gas used,surface after quench, final finishing gain time, etc.

Just a thought, but wouldn't making/finding a stainless "box/tray" with an open top work ( like a whole fish cooker, or an autoclave tray)? Put the "box" in the oven with a ceramic knife rack in it. Place the blade in it , fill it with argon ( just a quick squirt), set the top on it ( just to keep any convection currents from lifting out the gas), and heat the whole thing. It would basically be a removable muffle tray ( it should also insure even heating of the blade). When the soak time is done, remove the top ( or take out the whole tray), take out the blade and quench.....Seems like it should be workable.
You could even weld pieces of 1/2" round tubing on the sides and make a 24" "fork" to safely and securely remove and/or insert the tray in the oven..... Like I said ,just a thought???
Stacy
 
bladsmth said:
Nathan would know better than I, but it seems like a lot of cost/trouble for a little gain.
The oven door would have to be quite tight to keep hot argon gas in ( or the flow rate high). The chamber would have to be non permeable to hot argon gas,to ( completely sealed at all joints). Once you open the door, the gas is gone, so multiple blades are a problem.

I have had good success with Turco on carbon blades, so I am somewhat one sided on this. That, plus the small amount of actual de-carb on blades held at 1500F being easily removed in the finishing.

I would be interested in anyones results with use....Quantity of gas used,surface after quench, final finishing gain time, etc.

Just a thought, but wouldn't making/finding a stainless "box/tray" with an open top work ( like a whole fish cooker, or an autoclave tray)? Put the "box" in the oven with a ceramic knife rack in it. Place the blade in it , fill it with argon ( just a quick squirt), set the top on it ( just to keep any convection currents from lifting out the gas), and heat the whole thing. It would basically be a removable muffle tray ( it should also insure even heating of the blade). When the soak time is done, remove the top ( or take out the whole tray), take out the blade and quench.....Seems like it should be workable.
You could even weld pieces of 1/2" round tubing on the sides and make a 24" "fork" to safely and securely remove and/or insert the tray in the oven..... Like I said ,just a thought???
Stacy
Click to expand...


That sounds like a good idea to me.
 
I set my oven up to use argon or nitrogen. Nitrogen should be considerably cheaper btw. I don't think a bit of a leaky door would be a big problem. Mine does have a Kaowool "seal" though. Once the oven is full of the inert gas and under even a tiny bit of positive pressure the O2 shouldn't move into the oven. I guess I need to fill up my Argo bottle and trade one of my oxygen bottles for a nitrogen and do some experiments. I have been using the stainless foil on my D2 and the scale has never really bothered me on the carbon, so I have never got around to trying the purge.

I would advice anyone who does this to have plenty of ventilation in the area you do it in. Argo is heavy as mentioned and you can actually get enough in the bottom of your lungs to lower the volume of your oxygen intake and pass out. 78% of the atmosphere is N2, but if you have a N2 flow you can displace the 02 in you work space and you will not notice it until it is to late. We use nitrogen to purge lots of vessels in the refining business. It kills the careless on occasion. Remember this stuff is not poison, but, can displace the correct atmosphere and kill you.
 
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All good thoughts. My HT oven is towards the rear of my shop (secondary to the shop's electrical setup) and in a corner, and though I keep a fan running all the time while I'm in the shop, I'd hate to think of building a decreased oxygen area outside of the oven. It doesn't take me too much extra to clean up after heat treat, so I will probably keep this in the back of my head for now. Though I do love the thought of a pristine carbon blade after heat treat. I definitely need to step up to a formulated quench oil at least.

I have also thought about the way many keep a reducing atmosphere in a muffle forge by placing a piece of charcoal or something similar in the muffle to reduce the oxygen. Would something like that be possible in an oven? Or would the mess not be worth it?

Thanks for the thoughts gentlemen.

--nathan
 
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