HT foil question.

[Nylunds knives]

I will do my first own heattreating today in my new owen, I was going to HT some AEB-L blades that I asked about yesterday but then i forgot I don't have any HT foil.

My questions is, wich steels need to be protected with foil while heating?

Do I need to use foil for high carboons steel steels as well?

Do the scale damage the whole blade if foil is not used or is it just the surface that will get ugly?



Regards Jakob

 

[mete]

When hardening steel two things can happen - formation of scale [oxidation] and decarburization [ carbon near the surface is removed from the steel].The much higher hardening temperatures for stainless steel make the problem worse.
Carbon steels are often protected by coatings that are available.Stainless steels usually are protected by foil.

 

[galadduin]

It depends on the HT specs of the steel. If your steel is air hardening or plate quenching mostly the foil is used, if oil or water quenched you won't use foil, instead you can use some coatings to prevent scale. Also in electric kilns you have an oxidation atmosphere but on propane or coal forges you mostly have a reduction atmosphere at which there are no oxygen molecules free to bind to the surface of your blade. If you even HT a carbon steel (something like 1095 or W1) at low temps on an electric kiln you will have much more scale than a propane forge/kiln. I did a D2 HT in a electric kiln without foil just to experiment, it has soaked 1 hour at 1900 F. The blade has lost almost 40% of the steel via oxidation. It had to be much thinner and lighter than originally purposed.

 

[Nylunds knives]

Thank you very much!

I did HT the carbon steel blades today, I didin't use any foil or coatings but the oxidation wasn't bad at all.

On the next batch will I try the coating to see the diffrence.

Think I will have to buy some foil for the aeb-l blades.



Regards Jakob