The performance of turning tool materials and several commonly used turning tool materials

1. The required performance of the cutting part of the turning tool (1) Sufficient hardness The hardness of the cutting part of the turning tool must be higher than the hardness of the material to be processed, and the hardness of the tool must be above HRC60 at room temperature. (2) Good wear resistance The tool material has to withstand severe friction during the cutting process, so the cutting part of the turning tool must have good wear resistance. (3) Better toughness and strength When cutting, the turning tool bears impact and cutting forces, so higher impact toughness and bending strength are required. (4) Better heat resistance (red hardness). Heat resistance is an important indicator to measure the cutting performance of tool materials. A large amount of heat is generated during cutting. The performance of tool materials to maintain hardness at high temperatures directly affects the service life of the tool. Therefore, the better the heat resistance of the tool, the higher the cutting speed it can bear, and the processing efficiency is also significantly improved. (5) Good manufacturability and economy. The cutting tool should have good welding manufacturability, better heat treatment manufacturability, and better sharpening performance. At the same time, it should be reasonable and practical in terms of price and resource utilization. 2. Commonly used turning tool materials (1) High-speed steel High-speed steel is a tool steel containing more alloying elements such as tungsten, molybdenum, chromium, and vanadium, and has a white metallic luster. The hardness after heat treatment is HRC63-66, which has good toughness and strength and good manufacturability, can withstand greater impact, and is easy to sharpen to obtain sharp cutting edges, so it is called high-end steel, but heat-resistant It is poor and can only withstand a temperature of 600°C, so high-speed cutting is not possible. High-speed steel is especially suitable for manufacturing various complex forming tools, thread tools, drills, reamers, etc. When used as a turning train, it is mainly used as a fine turning tool. Commonly used high-speed steels mainly include W18Cr4V tungsten high-speed steel and W6M05Cr4V2 tungsten-molybdenum high-speed steel. ①W18Cr4V tungsten series high-speed steel, this high-speed steel, has good comprehensive properties and can be used to manufacture all kinds of complex tools and finishing tools, and is widely used. The disadvantage is that the thermoplasticity is poor and it is not suitable for making tools with large cross-sections. ②W6Mo5Cr4V2 tungsten-molybdenum series high-speed steel This high-speed steel is a widely used brand at home and abroad. Its flexural strength and toughness are better than W18Cr4V. Its disadvantage is that the quenching temperature range is narrow and the grinding performance is slightly worse. It is generally used to make hot-rolled tools. (2) Tungsten carbide and titanium carbide powder for cemented carbide hard alloy foot plus Co, Mo, Ni, etc. are powder metallurgical products made by powder smelting as a binder. Cemented carbide has very high hardness (89～93HRA, equivalent to 74～82HRC), good wear resistance, heat resistance temperature can reach 800～1000℃, but its toughness is poor, it is easy to brittle and cannot withstand big impact But it can be compensated by sharpening a reasonable tool angle. Cemented carbide is a widely used turning tool material, suitable for high-speed cutting. Commonly used cemented carbides are K type (tungsten drill type), P type (tungsten drill titanium type), M type [tungsten titanium tantalum (niobium) drill type. Category K is suitable for processing ferrous metals, non-ferrous metals and non-ferrous metals with short chips; Category P is suitable for processing ferrous metals with long chips; Category M is suitable for processing ferrous metals and non-ferrous metals with long chips or short chips. (3) Coated tool material Coated tool material is formed by coating a thin layer of metal chemical with high hardness and high wear resistance on the substrate of tool material (such as high-speed steel or cemented carbide). The coating material has high hardness, good chemical stability, is not easy to cause diffusion and wear, and has a small friction coefficient. It can significantly improve the cutting performance of the tool, and the service life is 1-3 times longer than that of uncoated carbide tools. However, coated tools also have disadvantages, such as the sharpness, toughness, and chipping resistance of the cutting tools are not as good as uncoated tools. (4) Cubic Boron Nitride Cubic boron nitride (CBN for short) has high hardness (8000～9000HV), second only to diamond, and its thermal stability is much higher than that of diamond. It can still be cut at 1300℃. Cubic boron nitride tools can process materials such as ordinary steel, chilled cast iron, hardened steel and high-temperature alloys, which can increase cutting speed and high productivity. CBN is a promising new tool material. Previous post: How should the stamping roll cylinder die be designed?