SKH2 
 SKH2 Japan National Institute of Standards (JIS G4403) SKH2 commonly used tungsten as a high-speed steel, it belongs to ledeburite steel, high-speed steel is the most long-lasting one. Like other high-speed steel, often referred to as "white steel" "front steel" or "wind of steel" (air to quench). Chemical composition: carbon content of 0.7 - 0.8%, the amount of tungsten 17.5 - 19% chromium content 3.80 - 4.4% vanadium content 1.0 - 1.4%, less than 0.4% silicon content, manganese content less than 0.4% molybdenum content is less than 0.3%. Red hardness: cutting the temperature 540 degrees, cutting HRC66 hardness can maintain the temperature 600 degrees, can maintain HRC63 hardness advantages: versatility, sophisticated technology. Disadvantages: carbide segregation serious, thermoplastic low, tool hardness and red hardness can not meet the special hardware and special processing tough materials. Alloying element content and high cost. Cutting speed: 80 m / sec (600 degrees Celsius). Uses: complex shape of a small tool. SKH2 the nature and processing of steel 
 Composition characteristics 
 SKH2 in steel, carbon mainly chromium, tungsten, molybdenum and vanadium (carbide formation element) and the formation of carbides, in order to improve hardness, wear resistance and red hardness. Tungsten is to improve the red hardness of the main elements that form carbides in the steel. Heating, part of the carbon dissolved in austenite after quenching form contains a lot of tungsten and other alloying elements, the stability of a high tempered martensite. In tempering, the part of the tungsten carbide in the form of dispersion to precipitate, causing secondary hardening. When heated, the undissolved carbides play a role in preventing austenite grain growth. Vanadium can significantly improve high-speed steel red hardness, hardness and wear resistance. The formation of vanadium carbides in the heating, some integration into the austenite, tempering with a small particle dispersion precipitation, resulting in secondary hardening and improve red hardness of steel. Chromium in high-speed steel is to increase its hardenability while improving anti-oxidation and decarbonization of steel and corrosion resistance. Cobalt can also significantly increase the red hardness and hardness of steel. 
 Structure 
 SKH2 organizations, including the cast was a bone-shaped, carbide sheet with martensite or troostite arranged ledeburite white, and black organizations (δ segregation) and the white tissue (martensite and retained austenite) . High-speed steel cast structure and chemical composition in particular, uneven, and the heat treatment does not change, so the pressure must be processed, the coarse eutectic carbides break, and make it uniform, and then use to manufacture a variety of cutting tools and Edit this paragraph die forging process 
 High-speed steel when heated are prone to over-burning, forging close to this temperature range is prone to fragmentation, should strictly control the heating temperature. Forging temperature range SKH2 a high alloy steel, which is characterized by slow heating, forging a narrow temperature range. Before forging temperature of 1100 ~ 1150 ° C, the final forging temperature of 900 ~ 950 ° C. 2) the heating time to determine SKH2 poor thermal conductivity of steel, it generally takes the heating section. Low-temperature heating temperature of 800 ~ 900 ° C, heating time is generally based on 1mi n / mm calculations. Quickly when the heating temperature, heating time is generally at 0. 5mi n / mm calculations. Heating, in order to prevent overheating or burnt, to strictly control the maximum temperature. At the same time, the furnace billet furnace to be installed right amount, but also to keep turning, so that it evenly inside and outside temperature. 
 Heat Treatment 
 Heat treatment of 800 a 840 warm-up from 1270 a 1280 grading quenching temperature of 580 a 620 grade, then 560 degrees for three tempering, tempering heat 1 hour. SKH2 contain large amounts of alloying elements: plastic poor, poor thermal conductivity in the fast heating of the thermal stress to the deformation of cracking, so the heating to quenching temperature in 1280 degrees in 1270 a 800 a 840 warm-up, those of complex shape, but also an increase in a preheated 500 a 650 . V, W, etc. play a major increase from the red rigid elements only to be dissolved under high temperature, but too high a temperature will make the coarse grains, and the W, A, alloying elements are reduced, making the eutectoid temperature of eutectic increased and so has chosen 1270 a 1280 degree. direct air cooling, will analyze the secondary carbides precipitate, thereby reducing the red hardness of steel. quenched carbides ten organizations for M + residual A (up to 30%) in 550 a 570 degree of tempering caused by secondary hardening precipitation WC, A decomposition analysis of C, lower alloy element content, the Ms increase, resulting in secondary quenching, a tempering, and 15% of the residual A, second tempering residual A3% a 5%, three tempering, only 1% to 2%, M + eventually have to temper the organization a very small amount of residual carbide ten.