Machinery's Handbook, 31st Edition
Cold-Work Tool Steels 449 Frequently Used Molybdenum Types: AISI H43: The principal constituents of this hot-work steel, chromium, molybdenum, and vanadium, provide excellent abrasion- and wear-resistant properties at elevated temperatures. H43 has a good resistance to the devel opment of heat checks and a toughness adequate for many different purposes. Applica- tions include tools and operations that tend to cause surface wear in high-temperature work, like hot headers, punch and die inserts, hot heading and hot nut dies, as well as different kinds of punches operating at high temperature in service involving consider - able wear. Cold-Work Tool Steels Tool steels of the cold-working category are primarily intended for die work, although their use is by no means restricted to that general field. Cold-work tool steels are exten sively used for tools whose regular service does not involve elevated temperatures. They are available in chemical compositions adjusted to the varying requirements of a wide range of different applications. According to their predominant properties, characterized either by the chemical composition or by the quenching medium in heat treatment, the cold-work tool steels are assigned to three different groups, as discussed below. Cold-Work Tool Steels, High-Carbon, High-Chromium Types.— The chemical com position of tool steels of this family is characterized by the very high chromium content, to the order of 12 to 13 percent, and the uncommonly high carbon content, in the range of about 1.50 to 2.30 percent. Additional alloying elements that are present in different amounts in some of the steel types of this group are vanadium, molybdenum, and cobalt, each of which contributes desirable properties. The predominant properties of the whole group are: 1) excellent dimensional sta- bility in heat treatment, where, with one exception, air quench is used; 2) great wear resistance, particularly in the types with the highest carbon content; and 3) rather good machinability. Frequently Used High-Carbon, High-Chromium Types: AISI D2: An air-hardening die steel with high-carbon, high-chromium content having several desirable tool steel properties, such as abrasion resistance, high hardness, and nondeforming characteristics. The carbon content of this type, although relatively high, is not particularly detrimental to its machining. The ease of working can be further improved by selecting the same basic type with the addition of sulfur. Several steel producers supply the sulfurized version of D2, in which the uniformly distributed sulfide particles substantially improve the machinability and the resulting surface finish. The applications comprise primarily cold- working press tools for shearing (blanking and stamping dies, punches, shear blades), for forming (bending, seaming), and for thread rolling dies, solid gages, and wear-resistant structural parts. Dies for hot trimming of forgings are also made of D2, which is then heated treated to a lower hardness for the purpose of increasing toughness. AISI D3: The high carbon content of this high-chromium tool steel type results in excel lent resistance to wear and abrasion and provides superior compressive strength as long as the pressure is applied gradually without exerting sudden shocks. In hardening, an oil quench is used without affecting the excellent nondeforming properties of this type. Its deep-hardening properties make it particularly suitable for tools that require repeated regrinding during their service life, such as different types of dies and punches. The more important applications comprise blanking, stamping, and trimming dies and punches for long production runs; forming, bending and drawing tools; and structural elements like plug and ring gages, and lathe centers, in applications where high wear resistance is important. Cold-Work Tool Steels, Oil-Hardening Types.— With a relatively low percentage of alloying elements, yet with a substantial amount of manganese, these less expensive types
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