222 CHAPTER 11 Heat-Treating Steels for Strength, Toughness, and Ductility CHAPTER OUTLINE 11.1 Heat Treatment—Metallurgical Effects and Equipment 11.1.1 Furnaces 11.1.2 Additional Methods for Heating 11.2 Thermal Processing—Moderate Cooling Rate 11.2.1 Annealing 11.2.2 Normalizing 11.2.3 Forced Air 11.2.4 Furnace Cooling 11.2.5 Cooling in a Vacuum 11.3 Thermal Processing—Rapid Cooling 11.3.1 Quenching Media and Techniques 11.3.2 The H Coefficient to Compare Cooling Rates 11.4 Effects of Process Variations 11.5 Tempering Martensite 11.5.1 Tempering Equipment and Procedures 11.6 Heat-Treating Procedures Summarized 11.7 Interrupted Quenching 11.7.1 Martempering 11.7.2 Austempering 11.8 Applications of Heat-Treated Steels 11.8.1 Blades 11.8.2 Forming Rolls 11.8.3 Drive Bits 11.8.4 Compression Springs 11.9 Drawbacks of Tempered Martensitic Steels 11.9.1 Low Ductility at Low Temperatures 11.9.2 Heat-Treated Steels Cannot Be Welded