Preventing Scale During Heat Treatment

[eperkins]

I have been playing around with a small heat treat oven I recently purchased, thinking it would add useful capabilities to my shop. To prevent scale formation and avoid surface pitting and dimensional changes, what is the best way to protect the parts? I know that stainless steel foils (which are very expensive) are used to wrap parts, and some anti scaling compounds are available. Any other methods? I am looking for answers before spending any money. Thanks.

Perk in Cincinnati

[x39]

I've always used the foil wrap. Yes, a roll is somewhat costly, but if you're working on a small scale, one roll should last you for many years. I'm still working on a roll I bought back in 1987. You can also buy foil pouches, less initial outlay, but more expensive over the long run.

[SGW]

I use Keep-Bryte Anti-Scale Compound, or whatever it's called. I find it works quite well.

[rklopp]

Be careful with anti-scaling compounds like Keep Bryte and Brownell's PBC. I have found the hard way that the fumes are corrosive to furnace elements and other metal parts. I have even had pitting on the parts being heat-treated when not cleaned carefully beforehand.

[Lynn Standish]

I don't know a lot about this subject, but I have used a paste or slurry made up of soap. I've used mostly the little bars from hotels/motels. I've only used it with a torch, but it seems to work okay. You do have to use steel wool to rub the residue off afterward, but I haven't had any pitting or scale that wouldn't come off that way. The parts have generally been small, though.

[Forrest Addy]

Crumble up a few charcoal briquets and pack the work in them. The charcoal will scavanege the oxygen and keep the work almost bright. The quick transfer from furnace to quench will darkent thee work but not cause it to scale to a significant degree.

This does evolve carbon monoxide gas and a mildly violent flare is possible when the furnace door is opened so run the oven out of doors and treat it with respect. Eyebrows take a couple of months to grow back.

[JCD]

I don’t know your heat source but, if the job is small and you are using a torch, adjust the flame to a carbonizing flame (rich in fuel), if using a gas furnace, do the same.
You can test the athmosphere in the furnace with a piece of pine board. Adjust air/gas ratio so that no flames are seen when the pine is placed in the furnace.
You can pack your part in cast Iron chips. A pot made from steel pipe will make a good pot. Heat pot with part and chips in it to temp. If you are hardening the part remove it from the pot to quench.
If you are annealing, leave the part in the pot to cool.
JCD

[snowman]

coat your kiln elements with ITC 213

add a bunsen burner to the bottom of your kiln, keep your kiln in reduction. (if you have a flame coming out the top, you've done it right)

-Jacob

[wierdscience]

I have never tried it but I heard that talc powder was good for that.

[snowman]

oh...in order to coat your elements, you need to buy new ones first.

Then clean them with a mild bleach solution.

Then coat them.

-Jacob