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Show FERROUS METAL HEAT TREATINGA COMPARISON OF NATURAL GAS AND ALTERNATIVE TECHNOLOGIES Gayle Schlea Koch, James H. Williams Hagler, Bailly & Company Washington, D.C. USA ABSTRACT Ferrous metal heat treating technologies are identified for the following categories: through heat treating and selective heat treating. Current market profiles are developed for the various ferrous metal heat treating technologies segmented by furnace type and process type. Preliminary findings show an estimated population of over 52,000 heat treating furnaces. Of these, approximately 55 percent are fossil fuel-fired batch technologies (mainly natural gas), 15 percent are fossil fuelfired continuous technologies, and 30 percent are electric induction technologies. Significant R&D opportunities for improving the competitiveness of natural gas in the ferrous metal heat treating market are explored. FERROUS METALS are composed of an iron base alloyed with various other constituents such as carbon, silicon, manganese, sulfur, and phosphorous. The properties of a ferrous metal are determined by the metal's microstructure, which is primarily determined by the iron's carbon content and crystalline structure. Upon heating and cooling in the solid state, the sol ubi 1 i ty of carbon in iron and the atomic arrangement of the iron-carbon lattice change, resulting in various physical and mechanical properties. As illustrated in Figure 1, ferrous HEAT TIME Fig. 1 - Heat Treating Cycle metal heat treating incorporates those processes through which ferrous metals are heated, soaked at a given temperature, and cooled in a controlled manner to produce desired mechanical and physical properties such as softness, hatdness, tensile strength, shear strength, impac t strength, and wear resistance. HEAT TREATING PROCESSES As shown in Figure 2, the basic types of heat treating processes can be grouped into two categories: • Through heat treating • Selective heat treating. As its name implies, through heat treating involves heating and cooling of the entire metal part. Within the through heat treating category fall treatments that stabilize the metal structure and properties by removing effects of previous hot and cold working or fabricating and machining operations. These include heat treating processes such as: • Normalizing • Annealing • Spheroidizing • Stress relieving. Through heat treating also encompasses treatments that achieve the des ired phys ical propert ies of finished or semi-finished products, including heat treating processes such as: • Hardening • Tempering • Austempering • Martempering. Select i ve heat treat ing typica lly involves more selective surface treatments that maximize physical properties of the selected surfaces of 253 |