One of my favorite television programs (and I suspect many other heat treaters) shows and demonstrates the early forging techniques that were used to make knives, swords, axes, etc. It further demonstrates the importance of good heat treatment in order for the weapon to be functional.  However, I have observed quite a few omissions in the heat-treat procedure.

When the implement is quenched after austenitizing, there is very little agitation of the blade to break up the initial vapor blanket. This means (in my opinion) that the blade is not being effectively quenched for the first stage of the quench procedure. The second omission (and perhaps the most important) is there has yet to be a broadcast that demonstrates the most important thermal treatment to make the implement functional, which is tempering! If the implement is not tempered correctly, it can be too soft (and bend or not hold its edge) or too hard (and the implement chips or breaks).  Good heat treatment makes the product; bad heat treatment breaks the product. This particularly applies to the tempering procedure.


The as-quenched hardness is the first way to identify if the implement has responded to its given thermal treatment. You can simply check the hardness with a 6-inch fine-cut file. The file is usually heat treated to 62-64 HRC. If the file bites into the as-quenched steel, then it has not been fully transformed into martensite and is below 62 HRC. If the file skids off the as-quenched steel, it means that the appropriate transformation to martensite has occurred. It is a simple and quick test to observe if the appropriate transformation has occurred. This should be conducted prior to tempering the implement.

We will talk about tempering in part 2.