When it comes to understanding any subject, and in particular heat treating, having reference material you can trust is invaluable. Over the years we have talked with a number of extremely knowledgeable heat treaters and metallurgists and from these discussions, we have compiled the following list of our “favorites.” Newer editions may exist, but exercise caution to ensure their contents are equal to or better than the originals. No heat treat library is complete without them. By Daniel H. Herring

Audits of the heat-treating department are a vital part of any good quality program - either as part of a self-assessment or ISO program for a captive shop or, of equal importance, as part of an evaluation of the capabilities of a commercial heat-treat supplier. In either case, the audit process needs to be formal in nature and follow specific guidelines. By Daniel H. Herring

Stainless steel is primarily used for applications where resistance to corrosion or heat, or both, is required. For their cost, the performance enhancement achieved by stainless steels is unmatched. In the past and continuing through today, there have been a number of ways developed to retard or prevent corrosion, the most common of these being painting or coating with metals and non-metals. Stainless steels offer an attractive alternative. By Daniel H. Herring

Once we’ve heated a piece of steel to elevated temperature, it must be cooled in order to complete its transformation into a useful engineering material. Understanding cooling transformations is another important responsibility of the heat treater. By Daniel H. Herring

If we were traveling from one city to another, we would need to input our destination into a GPS locating device, use an Internet website such as MapQuest® to plot our route or simply pull out a map to help us find our way. The Iron-Carbon, or perhaps more accurately the Iron-Iron Carbide phase diagram (Fig. 1), is nothing more than a roadmap for heat treaters. A phase diagram simply helps us predict what will happen to the internal structure of the steel. By Daniel H. Herring

For many heat treaters, the use of oil gives the best value based on a number of factors including:

• Overall performance (cooling rate or quench severity)
• Economics/cost (initial investment, maintenance, upkeep, life)
• Minimization of distortion (quench-system performance) Variability (controllable cooling rates)
• Environmental concerns (recycling, waste disposal)

One additional factor – performance over time – should be added to the list since we are always looking for ways to extend the life of our quenchants without sacrificing their performance. By Daniel H. Herring

Cooling curves, cooling-rate curves and oil analyses are provided by suppliers to help heat treaters better control an important process variable – quenching. Unfortunately, in many cases these reports are not well understood or, worse yet, filed to be used merely as ISO documents. It’s time to pull them out of the file cabinet and learn how to interpret them so we know what it is we are being told. By Daniel H. Herring