High-speed tool steel tool steel category, tungsten, molybdenum, chromium, vanadium, and sometimes high carbon cobalt as the main alloying elements ledeburite high alloy steel, commonly used as a high-speed cutting tools, referred to as high-speed steel, commonly known as speed steel forming principle speed tool steel is mainly used in the manufacture of high efficient cutting tools. Because of its high red hardness, wear resistance, strength properties, but also for the manufacture of high performance requirements of mold, roll, high-temperature and high temperature bearing springs. High-speed tool steel hardness after heat treatment up to HRC63 or more, at an operating temperature of about 600 ℃ can still maintain high hardness, and its toughness, wear resistance and heat resistance are good. The main alloying elements in the annealed condition of high-speed tool steel tungsten, molybdenum, chromium, vanadium, and some high-speed tool steel is added to cobalt, aluminum and other elements. Such steel is carbon high alloy ledeburite, one of its main features is the organization contains a large number of carbide. Cast high speed tool steel carbide eutectic carbides, processed by heat stress broken into granular distribution in the steel, called a carbide; precipitation from the austenite and martensite matrix, said carbide secondary carbides. These carbides significant impact on the performance of high-speed tool steel, especially secondary carbides, which has great influence on the austenite grain size of steel and this secondary hardening properties. The number of carbides, type and chemical composition of steel, whereas the particle size and distribution of the carbide and related deformation of steel. Tungsten, molybdenum is the main alloying elements of high-speed tool steel, and other properties of secondary hardening steel plays an important role. Chromium hardenability, oxidation resistance and wear resistance of steel plays an important role, the secondary hardening also has a role. Vanadium secondary hardening and wear resistance of steel plays an important role, but can reduce the grinding performance. The main classification cobalt high speed tool steel is a certain amount of cobalt on the basis of the common high-speed tool steel, can significantly increase the hardness, wear resistance and toughness. High-speed tool steel powder is produced by powder metallurgy method. First, take legal hypoxia atomizing speed tool steel pre-alloy powder, then cold, hot isostatic press to fulfill dense compacted powder billet, and then by forging, rolling timber. Powder high speed tool steel. Carbide end speed tool steel fine, evenly distributed, toughness, grinding and good dimensional stability etc., to produce ingots method may produce a higher content of alloying elements of super-hard high speed tool steel. Powder high speed tool steel can be divided into three categories, the first category is cobalt high speed tool steel, which is characterized by having a close carbide hardness, but also has good formability, workability, strength and toughness and grindability . The second category is no cobalt high tungsten, molybdenum, vanadium super-hard high-speed tool steel. The third category is super wear-resistant high speed tool steel. Its hardness is not too high, but excellent wear resistance, mainly used for high wear and shock loading conditions of work. High-speed steel according to the alloying elements can be divided into: ① tungsten high speed steel (W 9 ~ 18%), ② tungsten molybdenum high-speed steels (W5 ~ 12%, Mo 2 ~ 6%), ③ high molybdenum high-speed steels ( W 0 ~ 2%, Mo 5 ~ 10%). Faculties and how much vanadium content can be divided into general vanadium content (V 1 ~ 2%) and high vanadium content (V 2.5 ~ 5%). Any high-speed steel cobalt (Co 5 ~ 10%) such as when, and classified cobalt high speed steel. High-speed steel use can be divided into two types of high-speed steel integrated general-purpose high-speed steel and specialty applications. Universal high-speed steel is widely used in the production of metal-cutting common tools (such as drills, taps, saw blade) and precision tools (such as hobs, shaper cutters, broaches). The hardness of the material to be cut general HB≤300. Special purpose high speed steel can be divided into high vanadium high speed steel, cobalt high speed steel and general super-hard (HRC 68 ~ 70) high-speed steel (Table 2). The main purpose is to create high-speed high-speed steel cutting tools, in addition to having a high hardness (generally greater than HRC 63, high up to HRC 68 ~ 70), high wear resistance and toughness enough outside, but also in high-speed cutting edge is not due to fever softened heat resistance. Heat resistance usually red hardness measure, which is in 580 ~ 650 ℃ heating the steel has four times, each time for 1 hour air-cooled, and then measure the hardness at room temperature. Toughness high-speed steel usually flexural strength and impact value to measure. High-speed steel used in manufacture of cold-working die, mainly in the use of performance requirements for high compressive yield strength, high wear resistance and toughness, and heat resistance are less demanding, so lower temperatures can be quenched . The main performance process performance is an important indicator of high speed steel. First, a good thermoplastic, in order to fully broken eutectic carbides and processing forming; secondly, there must be a low annealing hardness, high-speed tool steel high-speed tool steel for cold forming and machining in the production process. Other technological properties such as thermal insensitivity, decarbonization insensitivity, low deformation hardening resistance, resistance welding, and friction welding of carbon steel shank in combination with good weldability is also very important, especially grindability, for manufacturing complex tools is extremely important. Ensure adequate broken carbide, refining and evenly distributed (see photo), has always been a high-speed steel production process and improving the quality of key issues. To this end, high-speed steel cold casting process should be used, choosing a good ingot and steel products according to the specifications chosen large enough compression ratio. China high-speed steel ingot production using flat since 1965, and its advantages are significantly faster ingot solidification rate, thereby improving the carbide of steel and low magnification. Large steel ingot use of ESR. Forging billet, rolling timber technology will help improve quality. Thermal processing temperature, the amount of deformation and annealing system of high-speed steel, heat treatment properties of the steel, especially those with a significant effect on the grain size after quenching, must be strictly controlled. Thermal processing such as the final forging (rolling) temperature is too high, the amount of deformation has been inadequate or once hardened, but not fully annealing and quenching second, there will be a special flash naphthalene-shaped fracture (see metal macroscopic examination) to significantly reduce the toughness of steel, the tool brittle collapse. Also features fast forging hydraulic machine cogging, forging machine become useful new technology. High speed steel required to achieve the desired performance with a special heat treatment. Usually quenching temperature are close to the melting temperature of the steel, such as high-tungsten steel is 1270 ~ 1290 ℃, tungsten and molybdenum steel is 1210 ~ 1240 ℃, high molybdenum steel is 1180 ~ 1210 ℃, generally use 540 ~ 560 ℃ tempered three times to obtain secondary hardening of the best results. When toughness and red hardness have different requirements, quenching temperature can be adjusted. Powder metallurgy high-speed steel can ensure fine and uniform distribution of carbides, to improve carbon high vanadium high speed steel grinding, improved hot workability, reducing quenching distortion and provide excellent quality of the large size of carbide steel does have unique advantages; can produce higher alloy content and greater high-speed steel cutting ability. Vacuum heat treatment of high-speed steel cutting tools widely available; Tool oxygen nitride, oxygen permeation and other surface chemical treatment, are also widely used, especially the development of chemical vapor deposition and physical vapor deposition method, the tool can be further improved life. High speed tool steel quenching temperature, near the melting point, which aims to make more of alloy carbides dissolved matrix, the steel has better secondary hardening ability. High-speed tool steel after quenching hardness increased, this is the first time sclerosis, but the higher the quenching temperature, the lower the strength and toughness after tempering. After quenching and tempering below 350 ℃ decrease in hardness at temperatures above 350 ℃ tempering hardness gradually increased to the range of 520 ~ 580 ℃ tempered (chemical composition is different, different tempering temperature) appear second hardness peak, and more than quenching hardness, this is secondary hardening. This is an important characteristic of high speed tool steel. In addition to high-speed tool steel with high hardness, wear resistance, red hardness and other properties, but also has a thermoplastic, can process performance grinding and so on. Tungsten high speed tool steel is the main alloying elements tungsten, molybdenum, or with a small amount of molybdenum. Its main feature is the heat sensitivity of small, decarbonization sensitivity, heat treatment and thermal processing temperature range is wide, but the coarse carbide particles, uniformity is poor, the impact toughness of steel and plastic. The main alloying elements tungsten molybdenum high-speed tool steel is tungsten and molybdenum. Its main feature is the particle size and distribution of carbides are better than tungsten high speed tool steel, decarburization sensitivity and thermal sensitivity of less than molybdenum high-speed tool steel, the use of performance and process performance are good. The main alloying elements molybdenum high-speed tool steel is a molybdenum, tungsten-free or low-tungsten. Its main feature is the fine carbide particles, evenly distributed, good toughness, but decarburization sensitivity and thermal sensitivity of large, narrow range of thermal processing and heat treatment.