I need to clarify what I said a bit. We would specify 1050 material, not 1020 as I said earlier. The problem with the higher content carbon material is, when the casting is poured and starts to cool, it looses surface carbon in the casting. And for the product we used it for, we had to have the surface carbon so it would respond to heat treat using induction heat and quench. Without the carbon restoration, there would be a depth of about .01-.02" on the casting that would not respond to heat treatment because of the diffusion of the carbon loss in the cooling process of the casting. So what the casting house would do was put it into a carbon atmosphere, the same one as used for carburizing, but no quench. Once the carbon restoration was done, the temperature in the furnace would be brought down gradually until it got to a safe level then the parts were removed from the furnace an air cooled. It worked 95% of the time. Years pasted, new company owners tool over, this was thrown out the window and went to the simpler process of standard carburizing 1020 castings. Dropped our processing cost by almost half!