Carbon tool steel
The carbon content of carbon tool steel is relatively high, between 0.65-1.35%. After heat treatment, the surface of carbon tool steel can obtain higher hardness and toughness, and the core has better processability; the annealing hardness is low (not more than HB207), the processing performance is good, but the red hardness is poor. When the working temperature reaches 250℃, the hardness and wear resistance of the steel drop sharply, and the hardness drops below HRC60. Carbon tool steel has low hardenability, and larger tools cannot be hardened (the diameter of hardening in water is 15mm). The hardness of the surface hardened layer and the center part is very different during water quenching, which is easy to deform or form cracks during quenching. In addition, its quenching temperature range is narrow, and the temperature should be strictly controlled during quenching. Prevent overheating, decarburization and deformation. Carbon tool steel is prefixed with “T” to avoid confusion with other steels: the number in the steel number indicates the carbon content, expressed in thousandths of the average carbon content.
Alloy tool steel
Refers to steel that has some alloying elements added to improve the performance of tool steel. Commonly used alloying elements include tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), titanium (Ti), etc. The total content of alloying elements generally does not exceed 5%. Alloy tool steel has higher hardenability, hardenability, wear resistance and toughness than carbon tool steel. According to the purpose, it can be roughly divided into three categories: cutting tools, molds and measuring tools. The output of mold steel accounts for about 80% of alloy tool steel. Among them, steel with high carbon content (wC greater than 0.80%) is mostly used to manufacture cutting tools, measuring tools and cold working molds. The hardness of this type of steel after quenching is above HRC60 and has sufficient wear resistance; steel with medium carbon content (wt0.35%~0.70%) is mostly used to manufacture hot working molds. The hardness of this type of steel after quenching is slightly lower, at HRC50~55, but with good toughness.
High-speed tool steel
Is a high-alloy tool steel, generally referring to high-speed steel. The carbon content is generally between 0.70 and 1.65%, and the alloying elements are relatively high, with a total amount of up to 10-25%, including C, Mn, Si, Cr, V, W, Mo, and Co. It can be used to make high-speed rotary cutting tools, with high red hardness, good wear resistance, and high strength, and the proportion of Cr, V, W, and Mo is relatively large. When the cutting temperature is as high as 600°C, the hardness still does not drop significantly. It is usually produced in an electric furnace and the powder metallurgy method is used to produce high-speed steel, so that the carbides are evenly distributed on the matrix in extremely fine particles, which can increase the service life. High-speed steel tools account for about 75% of the total domestic tool production.
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