The quenching temperature of the high-speed tool steel is very high, close to the melting point, its purpose is dissolved in the matrix of the alloy carbides more, so that the steel has a better ability to secondary hardening. High-speed tool steel, the hardness after quenching increases, this is first hardened, but the higher the quenching temperature, the lower the strength and toughness after tempering. Low temperature below 350 ℃ after quenching and tempering hardness decline in temperatures above 350 ℃ tempering hardness gradually improve, to the range of 520 ~ 580 ℃ tempering (chemical composition, tempering temperature) appear second hardness peak, and more than quenched hardness, this secondary hardening. This is an important characteristic of the high-speed tool steel.
In addition to the use of performance with high hardness, wear resistance, red hardness, high-speed tool steel thermoplastic, can grinding process performance.
Mostly the high-speed tool steel alloying elements tungsten, molybdenum-free or with a small amount of molybdenum. Its main characteristic is overheating sensitivity decarburization sensitivity over a wide temperature range of heat treatment and thermal processing, but coarse carbide particles, poor distribution uniformity, the impact toughness of steel and plastic.
Tungsten molybdenum high speed tool steel alloying elements tungsten and molybdenum. Its main feature is the degree and distribution of carbide particles are better than tungsten high-speed tool steel, decarburization sensitivity and thermal sensitivity below molybdenum high speed tool steel, and technological properties are good.
Molybdenum high speed tool steel alloying elements molybdenum, does not contain tungsten or with small amounts of tungsten. Its main feature is the fine carbide particles uniformly distributed, toughness is good, but the decarbonization sensitivity and thermal sensitivity, thermal processing and heat treatment range is narrow.
Containing drilling high-speed tool steel added a certain amount of cobalt on the basis of the general-purpose high-speed tool steel, can significantly increase the hardness, wear resistance and toughness of the steel.
Powder high-speed tool steel produced by powder metallurgy method. First take the low-oxygen high-speed tool steel prealloyed powder atomization method, and then washed with cold, hot isostatic presses the powder compaction sake dense billet, and then by forging, rolling timber. The small carbide powder high-speed tool steel, evenly distributed, toughness, grinding resistance and dimensional stability are good, can produce ingot a superhard high-speed tool steel may have a higher content of alloying elements. Powder high-speed tool steel can be divided into three categories, the first category cobalt high-speed tool steel, which is characterized by close to the hardness of the carbide, but also has good malleability, machinability, grindability and toughness . The second category is high cobalt, tungsten, molybdenum, vanadium superhard high-speed tool steel. The third category is the super wear-resistant high-speed tool steel. Its hardness is not too high, but the abrasion resistance is excellent, and is mainly used for working conditions requiring high wear and to withstand the impact load.