1. High hardness
The hardness of the tool material must be higher than the hardness of the workpiece material to be processed, otherwise under high temperature conditions, it can not maintain the sharp geometry of the tool, which is the basic characteristics of the tool material should have. At present, the hardness of carbon tool steel, the tool material with poor cutting performance, should be above 62HRC at room temperature. The hardness of HSS is 63 ~ 70HRC. The hardness of cemented carbide is 89 ~ 93HRA.
2. Adequate strength and toughness
Tool cutting part of the material in cutting to withstand a lot of cutting force and impact. For example, when turning 45 steel, when ap=4 mm,f=0.5 mm /r, the blade will bear about 4000N cutting force. Therefore, the tool material must have sufficient strength and toughness. Generally, the bending strength of the tool material (unit is Pa) represents its strength, and the impact toughness (unit is J/m2) represents its toughness, which reflects the ability of the tool material to resist brittle fracture and blade breakage.
3. High wear resistance and heat resistance
Abrasion resistance of tool materials refers to the ability to resist wear and tear. Generally speaking, the higher the hardness of the tool material, the better the wear resistance. In addition, the wear resistance of the tool material is also related to the chemical composition of the metallographic structure, the properties of the hard points, the quantity, the particle size and distribution. The more carbides in the metallographic structure, the finer the particles and the more uniform the distribution, the higher the wear resistance. There is a close relationship between abrasion resistance and heat resistance of tool materials. Its heat resistance is usually measured by its ability to maintain high hardness at high temperatures, namely high temperature hardness, or red hardness. The higher the high temperature hardness, the better the heat resistance, the tool material at high temperature resistance to plastic deformation, wear resistance ability is stronger. Because the hardness of the tool material with poor heat resistance decreases obviously at high temperature, it will cause rapid wear and even plastic deformation, and lose its cutting ability.
4. Good thermal conductivity
The thermal conductivity of the tool material is expressed by the thermal conductivity (W/ (m·k)). Large thermal conductivity means good thermal conductivity, and the heat capacity generated during cutting is easily transmitted out, thus reducing the temperature of the cutting part and reducing tool wear. In addition, the tool material with good thermal conductivity for intermittent cutting, especially in the processing of the workpiece with poor thermal conductivity is particularly important.
5. Good manufacturability and economy
In order to facilitate manufacturing, the tool material is required to have better machinability, including forging, welding, cutting, heat treatment, grinding and so on. Economy is one of the important indexes for evaluating and popularizing new tool materials. Tool material selection should be combined with domestic resources to reduce costs.
6. Bond resistance
Prevent the workpiece and the tool material molecules under the action of high temperature and high pressure adsorption bond.
7. Chemical stability
It means that the tool material is not easy to react with the surrounding medium at high temperature.
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