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Recently, some friends were using a new low temperature salt pot to heat treat some 15N20 kitchen knives. We were looking in the Heat Treaters Manual for the specs and I noticed that the manual states that 1095 could be treated in a low temperature salt pot, but it did not state that W-2 could be. With both 1095 and W-2 being shallow hardening steel, why would you be able to use this method with 1095 but not W-2. Kevin? Is it an error in the manual or is there actually a difference in the W-2 vs 1095 that prevents the forming of banite?

Yes, there is something but it affects both and it is called pearlite. 10XX series and W series will not fully harden in low temp salts. There are some makers who I would pay attention to who have said they have done it, but I have tried every combination I can think of, including the methods recommended by the ones who said they can do it, and I have never got satisfactory Rockwell, and metallography invariably shows pearlite formation. There is but one way that I managed to get 1084 to serviceable levels in low temp salt, it was by raising austenitizing temps, many say lower, but while the resulting blade was harder the grain size was also unacceptable. 1095 is often used for many things not at all resembling a knife where different properties are of greater value, in this case pearlite or upper bainite are not so much of a problem. Also there are many situations where the size of the stock changes things. There are also different salt based quenchants, some industrial applications even add water to low temp salts for speed, I see this as rather counter productive and with a vertical tube type setup it is VERY dangerous. I speak from personal experience when I tell you that water contamination in a vertical low temp salt tube is something you DO NOT want to have when you plunge a 1500F blade into it.

At one time I consulted with a large scale manufacturing company that made industrial blades that were very thin, perhaps a little over 1/16" that used an automated austempering line to do a 10XX series (I cannot be more specific, sorry). I was surprised with how well the parts came out but they were very thin and the temperatures were very precisely gaged by the computers to accomplish the goal.

All of my 10XX or W series steels are austenitized in the high temp salts and quenched in fast oil.