Tungsten carbide dies materials need to have four major properties
1. High strength and toughness: The mold has to withstand complex loads such as extreme extrusion force, bending stress, and impact during the extrusion process. Therefore, it is required that the selected material should have high strength and toughness after heat treatment. Therefore, the mold material should have good hardenability, so as to ensure the mold can be hardenable and uniform structure. Large carbides and serious deflection, fiber orientation and non-metallic inclusions and other internal defects will reduce the strength and toughness of the mold, or cause stress concentration when loaded, and cause early failure of the mold.
2. Good wear resistance: the mold should have high wear resistance to ensure normal service life and produce large quantities of qualified extrusions. Generally speaking, the hardness of steel is directly proportional to the wear resistance under certain conditions. Therefore, mold materials are required not only to have sufficient hardenability, but also high hardenability. However, in addition to hardness, the wear resistance of steel is also determined by the thickness, composition, excess and amount, size, type, dispersion and red hardness of the matrix structure after heat treatment. For example, high-speed steel and low-alloy tool steel have the same hardness value after heat treatment. In actual use, the wear resistance of the former is much higher, and the wear resistance of cemented carbide containing more than 80% WC is higher than that of steel. ten times. Therefore, in mass extrusion production, in order to obtain a long service life of the mold, high-speed steel and cemented carbide with high price and complex process are still used as mold materials.
3. Sufficient thermal stability: When continuous production, the temperature rise of the mold sometimes reaches or exceeds 200°C. This will reduce the strength and hardness of the mold material that uses 160~180°C as the tempering temperature, so it is used for warming Higher mold materials should have good stability against tempering.
4. Good manufacturability: The cold extrusion die has a long manufacturing cycle, complex process and high precision requirements. Generally, it must undergo forging, cutting, heat treatment, grinding or other finishing. Therefore, only materials with relatively good manufacturability can meet the needs of production.
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