anneal exhaust valve

[benmychree]

You may have case hardened it, but my guess is that you didn't get it hot enough.

You asked a great question so I had to look up the properties. It's probably 21-4N steel, very high temperature steel. Very high chromium and manganese content, about 21% and 9%. This is some tough stuff. It looks like you would have to heat it to around 1500 to 1600 F to anneal it, but the annealing temperature is not specified anywhere that I could find. It may not be possible to anneal it. I wonder how it would work as a HHS tool bit? Someone needs to give that a try just to see what happens.


http://www.azom.com/article.aspx?ArticleID=7648

In any event, whether or not it may have been carburized is not material, as it would have had to be quenched to have become hardened.