Tool material selection

The material used for manufacturing tools must have high high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertness, good manufacturability (cutting, forging and heat treatment, etc.), and is not easy to deform. Usually when the material hardness is high, the wear resistance is also high; When the bending strength is high, the impact toughness is also high. However, the higher the hardness of the material, the lower its bending strength and impact toughness. Because of its high bending strength and impact toughness, as well as good machinability, high-speed steel is still the most widely used tool material in modern times, followed by carbide. Polycrystalline cubic boron nitride is suitable for cutting high hardness hardened steel and hard cast iron. Polycrystalline diamond is suitable for cutting ferrous metals, alloys, plastics and glass steel; Carbon tool steel and alloy tool steel are only used for tools such as files, dies and taps. Carbide indexable inserts have been coated with hard layers of titanium carbide, titanium nitride, alumina or composite hard layers by chemical vapor deposition. The developing physical vapor deposition method can be used not only for carbide tools, but also for high-speed steel tools, such as drills, hobs, taps and milling cutters. As a barrier that prevents chemical diffusion and heat conduction, the hard coating slows down the wear rate of the tool during cutting, and the life of the coated blade is about 1 to 3 times higher than that of the uncoated blade.