Major classes of tool materials 4 tungstencemented

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Unformatted text preview: bon at high temperature in the Made ratio of 94% and 6% respectively, by weight. Then combined with cobalt and sintered at 1400C. High hardness value at temperature as high as 1200C. They cannot be shaped after sintering so they are used as inserts, either brazed on or clamped on. Major Classes of Tool Materials 4. Tungsten/Cemented Carbide Tools To improve crater resistance, tantalum carbide and titanium carbide To are added. Increasing cobalt content it increases toughness but reduces hardness. Type Type WC C TaC TiC Use 883 94.0 6.0 - - Cast Iron 350 70.7 4.5 12.2 12.6 Steels 330 46.4 - 9.5 30.1 Steels–Ni12 370 72.0 8.5 11.5 8.0 Mo-2 Major Classes of Tool Materials General Characteristics of Carbide Tools General In comparison with other tool materials (except oxide tools) these are as follows: 1. 2. 3. 4. 5. 6. 7. high hardness over a wide range of temperature (up to 900 C) very stiff (Young's modulus is about three 3 that of steel) no plastic flow to stress as high as 352 kg/mm2, low thermal expansion (compared to steel) high thermal conductivity low specific heat weaker in tension than in compression Major Classes of Tool Materials Classification of Cemented Carbides Classification There are three categories in ISO classification system: 1. P for steel-cutting grades 2. K for cast iron-cutting grades 3. M for ductile irons, hard steels, HSTR alloys, etc. ISO symbol Usage Gr...
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