DIY Heat treat furnace

just 2 cents added here.
you can do that with a piece of paper causing CO2 to over take the O2
it also is heaver than O2
the problem starts when you take it out and the hot steel comes in contact with O2 just before you quench it. that is one of the reasons that salt HT is so good the salt insults the steel from O2..
 
Argon, yeah, it will stay in the oven. I used to weld in a heat exchanger shop. We put little shacks on the ends of the exchangers, so the air wouldn't disturb the tube weldors (TIG) We had to cut holes in the floor and sometimes us a vaccum to remove the argon if two weldors were in the same shack. The Guys would literally run out of oxygen. :eek:
 
Normal atmospheric temperature air is also heavier than air in a floating hot air balloon.

I have to admit that while I'm not 100% sure, I'd be quite surprised if 2000 Degree argon is more dense than ambient temperature air.
 
It may or may not be more dense than ambient temperature air, but I guarantee 2000 degree argon will be more dense than 2000 degree air. Your goal is to displace the air in the oven; most people using argon will run a trickle to keep a very slight positive pressure, or really just to keep any air from seeping in.

A 3+ year old thread....nice. Been using that search tool, huh? :) The link to the britishblades tutorial is actually the one I based my home built ht oven off of. I haven't opted for argon flow, as it likely won't be worth the trouble and cost for the types of steels I use, though it would be nice to protect my O1 from oxidation. Oh well, sanding off scale builds character. :D

--nathan
 
Yup, that is the tutorial I will use when I get the funds to build mine. I found a local source that has bricks for a good price, so I do not have to worry about broken bricks in the mail.
 
gixxer, I ended up buying a case of the bricks from a local refractory supplier. I had extra bricks left over, but it worked out perfect to be able to replace cracked bricks or mistakes while making the oven.

--nathan
 
Oh, and a tip for future reference. It looks as though he wrapped a loop of kanthal around the stainless bolts coming into the rear of the oven and tightened down a washer and nut to hold it tight. I did the same thing, sandwiching the loop between two washers and snugging down with a nut, and the oven worked well for about a year. Then, for some reason, the oven began to arc across the very small space between the washers. The arc worked its way around the space and eventually burned through the kanthal. It did this on both sides within a week of each other. So instead of tightening a nut to a loop of kanthal, I took my stainless bolts out, drilled a small hole through the bolt the size of the kanthal, and ran the kanthal through the hole, and tightened down a nut onto the wire as it passes through the hole to hold it tight. No problems since.

--nathan
 
Thanks for the heads up on that one. In the tutorial he provides no real specifics as to how far to space the two bolts. I had not given it that much though until you brought up your problem, but now I am gonna space the input bolts out as far as possible.
 
silver_pilate said:
most people using argon will run a trickle to keep a very slight positive pressure, or really just to keep any air from seeping in.

A 3+ year old thread....nice. Been using that search tool, huh? :)
--nathan
Click to expand...

Good point on the positive argon flow, makes sense.

Umm, yeah I used the search tool.. .in my defense, I did look at the last post and when I saw 12/12, I figured a month old, didn't see the 05 :p
 
silver_pilate said:
It may or may not be more dense than ambient temperature air, but I guarantee 2000 degree argon will be more dense than 2000 degree air. Your goal is to displace the air in the oven; most people using argon will run a trickle to keep a very slight positive pressure, or really just to keep any air from seeping in.

A 3+ year old thread....nice. Been using that search tool, huh? :) The link to the britishblades tutorial is actually the one I based my home built ht oven off of. I haven't opted for argon flow, as it likely won't be worth the trouble and cost for the types of steels I use, though it would be nice to protect my O1 from oxidation. Oh well, sanding off scale builds character. :D

--nathan
Click to expand...

I get good results putting a couple lumps of hardwood charcoal in to absorb oxygen. I control my kilns with PIDs and SSRs (just set the infinite to full on, let the pid run it) when I build my kiln based on the tutorial, the door will have a microswitch that cuts the 12v input to the SSR.

-Page
 
gixxer, it's not so much the spacing of the bolts, as long as you get them several inches apart with no chance of the kanthal wire jumping around and shorting out, you should be fine. The problem I had was on each single bolt. I made a loop of kanthal, and sandwhiched it between two washers and nuts for a tight connection. Unfortunately, the washers were close enough together (kind of tilted when tightened down on the wire) that after some use, they eventually developed an arc that worked around and burned through the kanthal. So I simplified the setup with the wire through the bolt and one nut tightened to it.

I used some micarta to secure the bolts to on the outside of the oven. It was developed as insulation board for electrical purposes, so it works great. Make sure you cut the metal frame of the oven to allow plenty of clearance for the bolt so that you dont make the metal frame of the oven "hot" with electricity.

If you need any help, feel free to drop me a line.

--nathan
 
Yea I scoped out the hi temp G10 on Mcmaster (imagine that, using G10 for what it's made for?), found the high temp hook up wire there for way cheaper than BCS and has a higher temp rating.
 
Top loaders strike me as easier to build, maintain, and access. If I were doing it again, that's the way I'd go.
 
I just cring at the thought of reaching over and into the top of a 2000F space. If you have good tongs and mount it so you can see into it from an angle, I bet it would be fine.

--nathan
 
For a top-loading oven, would you use door hinges or just a free-floating set of firebricks cemented together?
 
cotdt said:
... but she zapped herself with her oven.
Click to expand...

Not this one :) The one that zapped her was a commercially made investment casting oven, and turned out to have an electrical problem she had fixed. Those door cut-off switches wired through the SSR control circuit are the ticket to reduce the risk of shock.

I mainly included the link as one potential resource for building a top loader, that is currently in use, with a hinged door.
 
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