High red heat hardness, high wear resistance and laser cutting ability, high impact toughness, fine and uniform grain size, high toughness. Tool industry: scraper, hobbing cutter, iron knife, drill bit, etc. Forging industry: forging mold, screw industry: hexagonal head forming mold, tooth tapping, punch temperature: temperature 800-880 ℃, 10-20 ℃, dHr furnace cooling to about 600 ℃, hardness above HB269. Stress relief: temperature 650-750 ℃, Furnace cooling C: 1.00~1.15Si: ≥ 0.65Mn: ≥ 0.40P: ≥ 0.030S: ≥ 0.030Cr: 3.50~4.50V: 0.95~1.35W: 1.15~1.85Mo: 9.0~10.0CO: 7.50~8.50 High speed steel generally does not undergo tensile strength testing, but mainly relies on metallographic and hardness testing.
After proper heat treatment, the Rockwell hardness of tungsten and molybdenum based high-speed steels can reach over 63, while that of cobalt based high-speed steels can reach over 65. The acid soaked macrostructure of steel shall not have visible shrinkage or peeling. The central porosity should generally be less than level 1. The metallographic examination mainly includes three items: decarburization layer, microstructure, and carbide unevenness.
High speed steel should not have obvious decarburization. The microstructure must not contain fishbone like eutectic ledeburite. The unevenness of carbides in high-speed steel has the greatest impact on quality, and currently the metallurgical and mechanical departments attach great importance to the level of unevenness of carbides. According to the different uses of steel, different levels of carbide unevenness can be required, usually less than level 3. Manufacturing cutting tools with high-speed steel not only has high hardness, high wear resistance, and sufficient toughness, but also has red hardness as an important factor.
Red hardness refers to the ability of the CNC cutting tool to resist softening in a red hot state during high-speed cutting. One method to measure the hardness of red is to first heat the steel to 580-650 ℃, hold it for 1 hour, and then cool it. Repeat this process four times before measuring its hardness value.
The quenching temperature of high-speed steel is generally close to the melting point of the steel, such as 1210~1240 ℃ for tungsten based high-speed steel and 1180~1210 ℃ for high molybdenum based high-speed steel. After quenching, it is generally necessary to temper 3 times between 540~560 ℃. Increasing the quenching temperature can increase the red hardness of steel. In order to improve the service life of high-speed steel cutting tools, surface strengthening treatments can be carried out, such as low-temperature cyaniding, nitriding, sulfur nitrogen co infiltration, etc.
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