Heat Treat Oven Element

Latinrascalrg1 said:
Ray can you add a shielding gas to the oven during a "heat" cycle that would help protect the elements and metal projects from oxidizing?
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Yes. My ovens fill argon from the bottom and have an extension tube and valve at the top. During a heat, every 10 minutes or so, I push a little argon through the system. You don't need a constant flow; I found that's unnecessary. When done this way, the metal comes out with a bluish tint and no precipitated surface carbon flakes at all. Don't use CO2.

@ddickey: What is the name/model you have or at least the newer one if you don't know yours.

Regards
 
Why not use N2? Must be cheaper.
Thermolyne 1500.
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A roll of A1 will cost 7 bucks and N2 will cost 5. The N2 will burn-out twice as often.

I'll do a little digging about that brand of oven. I presume you have something similar to the #1300 model?

Ray.
 
Ray C said:
Yes. My ovens fill argon from the bottom and have an extension tube and valve at the top. During a heat, every 10 minutes or so, I push a little argon through the system. You don't need a constant flow; I found that's unnecessary. When done this way, the metal comes out with a bluish tint and no precipitated surface carbon flakes at all. Don't use CO2.
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Not that I plan to go against your advice but i would like to know for the sake of getting educated, what would happen if co2 was used if you wouldn't mind sharing?
 
Latinrascalrg1 said:
Not that I plan to go against your advice but i would like to know for the sake of getting educated, what would happen if co2 was used if you wouldn't mind sharing?
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Don't mind at all...

Depending on the type of metal you're treating, it could actually reduce the carbon content of the metal near the surface. It's like the opposite of carburizing. Also, CO2 (as it's chemical symbol implies) has 2 oxygen atoms per carbon. Oxygen is your enemy at high temperatures and you'll end-up with a whole lot of some kind of oxide (depending on the metal) coating all over it. Inert gases can be used for shielding but reactive gasses will either oxidize or carburize. You can't really do gaseous carburization in a home-shop environment. It's done under high pressure and you really don't want to be playing games with highly pressurized gasses at 1550F.

As for carburizing... there are lot's of recipes for coatings to case harden low carbon steel. -My advice... Don't waste your time. In a home-shop environment, you'll be lucky if you get a half-thou of case.

EDIT: If you use carburizing coatings on high-carbon steel, I can virtually guarantee you'll pull the surface carbon out of the metal and weaken it. Last but not least, carburizing compounds gum-up your element wires and cause premature failure.


Regards

Ray C.
 
Thank you very much for that explanation Ray. I Figured about the 2 oxygen atoms causing an oxidation problem but i figured there was more to it then just that.
 
ddickey said:
Makes sense Latinrascalrg1.
Size is .0565"
Refer to post #16. That diagram looks like a series connection.
I could be wrong on the wattage. I can not find any info. The above was from a newer model.
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You need 75' of this stuff to give you the electrical specifications of 240v, 9.3A for 2.23KW.
https://www.ebay.com/itm/TEMCo-Kant...J0AAOSwi8xZ~LRG:sc:USPSFirstClass!21114!US!-1

It needs to be coiled and evenly spaced. One loop should not touch any other. A coil like this should last a long time because it's a relatively low amount of power coming off a fairly high surface area of the total length of the wire. I use exactly this same wire but, shorter pieces (remember, shorter pieces have less resistance so, current is higher and therefore Wattage increases). Short wires burn-out faster than long wires because the heat density is greater with short wire. I usually get 10-12 heats out of a wire set. My system is 4x more wattage than yours. At the very least, you should be getting 40 - 48 heats before the wire goes bad. In reality, you should get a good bit more than that because of the low power density.

Regards

Ray C.
 
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