The Heat-Treating Processes Step 2: Austenization

Not many years ago, before heat-treating furnaces were commonplace, heat-treating was often accomplished in open forges. It may have looked peculiar but the craftsman would take a long steel rod with a magnet hanging from the end of the rod by a wire. He would lower the magnet unto the red hot steel. Once the magnet was no longer attracted to the steel, the craftsman knew the steel had reached its upper critical temperature. He would look at his pocket watch and start the timing of the soak. He understood that when the steel went in-solution, even though the part still held its physical shape, the carbon matrix and the alloy content were dissolving into a full solution, almost as a liquid. Thus, he knew because there was no longer any magnetism present. As the chemistry in steel became more complex, heat-treating furnaces and controllers were improved to give us more accurate control. In today's world we're fortunate to have very accurate heattreating furnaces with good temperature controllers and pyrometers to track and control the temperature of the steel within a few degrees.