Mainly used in the manufacture of cutting tools, dies, gauges, and other wear-resistant tool steel. Generally divided into carbon tool steel, alloy tool steel and high speed tool steel categories. Carbon tool steel is basically a high-quality or high quality high-carbon steel, carbon steel workers referred to. Its cold, thermal processing performance, highest quenching hardness can reach HRC66 ~ 67, but usually tempered hardness of HRC60 ~ 64, good wear resistance, low prices, wide range of uses, about half of the entire number of tool steel. The main disadvantage is that: ① low hardenability, only when water quenching hardenability sectional thickness no greater than 8mm gadget; ② poor heat resistance at 250 ℃, a sharp decline in hardness, it is generally limited below 200 ℃ use. Carbon content of carbon steel workers since 0.65 to 1.35% (grades T7 ~ T13), belongs hypoeutectoid steel and eutectoid steel (T7, T8), used in the manufacture of tools and simple shapes woodworking tools. Hypereutectoid largest amount of steel, especially T10, T11 higher wear resistance suitable for the manufacture of tools and Die, drawing dies, trimming die, taps and the shape of a simple low-precision measuring tools. Carbonaceous higher grades, although high abrasion resistance, but low toughness, the impact of intolerance, only suitable for manufacturing rasp, tap, knife, scissors and other hand tools. Carbon steel workers in the thermal processing has a flaky pearlite structure, high hardness, hard machining, and easy to form a coarse martensitic hardening, annealing must be the ball, usually heated at 740 ~ 770 ℃, 600 ~ 680 ℃ isothermal deal with. Annealed hardness HB157 ~ 197. High carbon content, the large size of the carbon tool steel, often in front of the ball annealing normalizing to eliminate network carbide. Quenching temperature carbon tool steel is generally 770 ~ 820 ℃, usually with salt - oil double quenching with accelerated cooling, cooling to about 100 ℃ to be quickly removed immediately tempered to prevent cracking and reduce deformation hardening. Complex shape thin small parts, can be 120 ~ 160 ℃ alkali bath quenching, tempering and more in the range of 140 ~ 220 ℃ conduct. Alloy tool steel carbon steel workers joined in the Cr, W, Mo, V, Si, Mn, Ni, Co and other alloying elements to improve the strength, hardness, wear resistance and heat resistance, in order to meet the needs of different uses. Divided by purpose: measuring, cutting of steel high carbon content (0.75 to 1.50%), with the desired high hardness (≥HRC60), each containing Cr, W, V, Si, Mn and other alloying elements, hardenability higher, the formation of alloy carbides significantly improved wear resistance of steel, thermal stability, and has a certain strength and impact toughness. Common gauge steel GCr15 and CrWMn more choice and so on. For measuring tools, heat treatment system of low alloy tool steel cutting tools substantially similar to the carbon steel workers. Because it contains alloying elements to improve hardenability, the general oil quenching. For deformation demanding nitrate quenching tool can also be Austempering. High dimensional stability requirements for measuring, should be cold treatment. Also must adopt a long time tempering or aging treatment to obtain a stable tempered martensite and austenite unconverted aging stability, so that the residual stress tools or to eliminate steady state. Impact resistant tool steel the carbon content in the range of 0.35 to 0.65% carbon-chromium-tungsten silicon (e.g. 5CrW2Si), after heat treatment has a high impact toughness, high fatigue strength and high wear resistance, suitable for manufacturing by the impact Load large tools, such as manual or pneumatic chisel. Cold work die steel high carbon content, mostly in the more than 0.85%, 2% more than the individual, with high hardness (HRC60 above) and wear resistance. The low, medium alloy type essentially measuring tools, cutting steel similar, such as 9Mn2V, CrWMn. Cr6WV ??and can be used for larger size Cr4W2MoV Die. The most representative is the micro-deformation tool steel Cr12 and Cr12MoV carbon high chromium. This kind of steel with high wear resistance, high hardenability and micro deformation hardening, suitable for manufacturing large precision cold mold. Cr12MoV two quenching system: one for the conventional low temperature (950 ~ 1050 ℃) quenching and low-temperature (150 ~ 200 ℃) tempering, to obtain a higher hardness and a smaller deformation; the other is a high temperature (1100 ~ 1130 ℃) quenching and high temperature (500 ~ 520 ℃) ??tempering, secondary hardening, in order to increase the hardness of the steel, to obtain a high red hardness and wear resistance, the mold suitable for production at 400 ~ 500 ℃ work . But Cr12 steel is generally only use the former quenching system. Since this type of steel is ledeburite, there will be a large number of network organization within the cast eutectic carbides, it must be broken in the plastic processing and evenly distributed in the matrix, in order to increase the wear resistance of steel to prevent high temperature quenching the steel grain growth and at the same time have enough toughness. Hot work tool steel carbon content mostly between 0.3 to 0.6%, and contains some of the alloying elements. The main characteristics of this type of steel is a good temper resistance, thermal contact with the workpiece in the state to maintain a higher hardness and strength, good thermal fatigue resistance and toughness, mainly used for the production of heat forging, hot stamping, hot extrusion, hot forging and die-casting molds. General forging die can be high toughness and heat resistance in general (350 ~ 375 ℃ or less) of die steel 5CrMnMo and 5CrNiMo. Hot forging and hot extrusion die because during operation (especially in copper extrusion and extrusion of steel) in contact with the hot metal is deformed in a long time, easy to heat softening, requiring high heat resistance, often using 3Cr2W8V, 4Cr5MoVSi, 4Cr5W2VSi. These steels are secondary hardening tempering, suitable for working at 500 ~ 650 ℃. Die Cast material must have excellent thermal fatigue resistance and thermal erosion resistance. 3Cr2W8V common good, such as die-casting zinc, aluminum and magnesium alloy low melting point metals. To require a higher heat resistance, precision forging die, die-casting refractory metals, the non-ordinary hot work die steel can be handled. Should be used in tungsten, molybdenum and other refractory alloys to improve die life. Plastic mold steel industry in recent years with the development of plastics, plastic mold steels have been developed. Due to the complexity of the plastic mold cavity, the size requirements of precision, so in addition to the requirements of the plastic mold steel wear and corrosion resistance than the particular requirements of processability and after heat treatment of steel micro deformation. Such a low carbon content steel, further contains chromium, nickel, molybdenum and other elements, and sometimes also contain aluminum, titanium, to produce age hardening. Matrix steel its chemical composition corresponds to the different types of high-speed tool steel after quenching and chemical composition of the matrix organization, hence the name. This kind of steel compared with the high-speed tool steel, its eutectic carbides are few and small particle size, distribution, and thus toughness, fatigue strength and cold, good thermal processing performance than high-speed steel, but also has a high two secondary hardening capacity, high heat resistance and wear resistance, suitable for the production of higher thermal loads (600 ~ 680 ℃) of the mold. Substrate steel 5Cr4W2Mo2VSi, 35Cr3Mo3W2V, 65Cr4W3Mo2VNb etc. are successfully developed China's first two production hot mold, the latter produced by cold mold, with favorable results. Matrix steel cold die than high speed steel toughness, wear resistance and compressive strength lower. The difference between the high-speed tool steel, high-speed characteristics of tool steel and alloy tool steel, tool steel and parameters of the process is an alloy tool steel, which contains C, Mn, Si, Cr, V, W, Mo, Co. And it can be used for high-speed rotary cutting tool that can resistant, high temperature, is one of Cr, V, W, Mo was relatively large proportion (you also peers, do not go into detail here) to W12Cr4V5Co5, for example, Cr-> 3.75% - 5%, V-> 4.5% -5.25%, W-> 11.75% -13%. which was the proportion of Cr and V shall not be less than 3%. P and S content was not greater than 0.030%. Processing methods alloy tool steel is mainly pressure processing steel and cutting tool steel. Alloy tool steel types and more, there are cold, hot, non-magnetic, plastic mold steel, etc., while Cr and V ratio can not be too low. Select the cold mold tool steel cold mold tool steel selection, in practical use in tool steel is selected based mold major failure mechanisms. Select the tool steel only have the knowledge of steel performance is not enough, you must also consider the number of production parts and materials to be processed factor type, thickness and hardness. A basic method is to first select the tool steel in addition to other failure mechanisms wear total exclusion, and then select the most suitable abrasion resistance comprising a tool steel, in order to meet the production volume requirements. Tool steel tool steel production of metallurgical high quality requirements, and more generally with the furnace melting, purity requirements can be applied at higher vacuum smelting furnace smelting or remelting. In order to reduce segregation, etc. to improve performance, high-temperature diffusion annealing ingot can. Thermal processing, eutectoid steel stop forging (rolling) temperature is lower (about 800 ℃). After wrought timber should quickly cooled to 700 ℃, in order to avoid precipitation of coarse carbide network, carried out in the following 700 ℃ slow cooling to prevent thermal stress cracking. Mold steel, compression ratio control in six or more, in order to ensure the quality and life of the mold. Levin's body for high carbon high chromium steel, in order to improve the distribution of eutectic carbides uniformity, increased thermal processing in the compression ratio, to receive good results. The best selection of large-size steel ingot remelting large (more than 350mm diameter), by a large compression ratio, you can get higher quality.