[Kevin R. Cashen]

The reason I have the insight that I do in Aldo’s 52100 is when he started carrying this particular product, he started getting phone calls from some folks about the lower hardness. This bothered him, Aldo wants to offer a good product and so he wanted to know what was going on, so he called me. We discussed it for a bit and I asked him for the certified chemistry, and then asked him to send me a sample. I also inquired about some of the folks that were having trouble, it is a small business and we tend to know each other and our particular approaches to working steel. I now had a pretty good picture of what was going on.

When the bar of steel arrived, I sliced a sample off and prepped it for metallography, it was between 95% and 98 % spheroidized with larger spheroids. I then heat treated like normal and could not push it above a 63HRC with standard heat treatment regardless of how far out I pushed the soak time. But samples of this under the scope showed lots of lower carbon lath martensite littered with undissolved spheroidal carbides; umm hmm, I said to myself.

I did another series of tests and gave Aldo a call. “How does 65.5-66 HRC sound to you?” I asked him. Obviously, he was very eager to hear what I had to say. I assured him that his 52100 was of excellent quality but was prepared for the easiest possible machining. All it needed was a good normalization at 1650°F to dissolve those large spheroids and homogenize the solution, with a subsequent heat treatment it would then respond as well as any other steel.

After normalization one can carefully refine grain if they want but they need to leave the carbides alone as much as possible, so they should avoid over doing it at lower temperatures. You see, one of the clues I was working with, before I even got the steel, was the folks who were having troubles, who happened to be bladesmiths. Forging should have the same effects as normalizing, but I knew some of the folks really like low temp cycles, in forging and normalizing. By not homogenizing with a good temp, the low temperature cycles were only making the problem worst. The divorced eutectoid reaction relies on particles to grow the spheroids on, existing spheroids will gladly volunteer, and grow quite fat in the process.