Thread: Case Hardening Steel

Case Hardening imparts carbon into the surface of the steel, I was thinking is a steel already has carbon, in it like 4140 I was wanting to see if more carbon can be put into it to make the surface even harder..

This is obviously not the case with 4140 at least.

The hotter you get the workpiece the more soluble carbon is in the steel.... One article I have here says at 920C carbon will migrate into steel at a rate of 0.01mm/minute.. I guess this is optimum results.. Carbon solubility in iron starts when the metal becomes a bit over 720C

It is really hard to get my head around all the methods as they operate at different temperatures..... Case hardening using a metallic salt bath, operates at a lower temperature and achieves results in a shorter time frame.. I am starting to suspect the dedicated hardening shops keep a witchdoctor on hand to make sure the process is a success every time.

I once read somewhere that back in the dark ages a good sword would be quenched in the urine of a boy. I thought that it was a joke but perhaps not after reading the comments about urine adding nitrogen. Although perhaps the part about the young boy is at least.

This thread makes very interesting reading. Good work on the kiln RC.