Properties of high speed steel tool materials Ⅰ
Properties of high speed steel tool materials
1. Hardness and wear resistance
The hardness of universal high-speed steel after quenching and tempering is 63~66HRC, and the hardness of superhard high-speed steel can reach 67~70HRC. Increasing the hardness of high speed steel can improve its wear resistance and endurance limit, high hardness high speed steel after proper grinding and grinding, can obtain relatively small surface roughness, hardness can also reduce the tool and chip bonding and friction factor. The experimental results show that for high-speed steel, the room temperature hardness also represents an index of high temperature hardness, that is, when the room temperature hardness of high-speed steel is increased, the high temperature hardness is also increased. In addition, the compression yield limit of high speed steel also increases in direct proportion to the hardness. Therefore, even if the hardness is slightly reduced, it will cause certain plastic deformation under low stress. It can be seen from the above that the high-speed steel tool should be used in the higher hardness range of the steel. However, for a certain kind of high-speed steel, to improve its hardness, often accompanied by a reduction in toughness. The best combination of hardness and strength of high speed steel can be obtained by proper selection of steel composition and heat treatment regime. The hardness and wear resistance of high speed steel mainly depend on the carbon content of the steel. Increased carbon content, hardness and wear resistance are also improved.
The wear resistance of high speed steel also depends on the type and amount of carbides in the steel. The greater the number of carbides, the lower the loss rate (the ratio of wear volume to friction distance). The influence of alloying elements on the tolerance was enhanced in the order of Cr, WMo and V, and the effect ratio was 2:5:10:40. This shows that V has a great influence on the wear resistance of tool steel.
Commonly used high vanadium high speed steel, such as W6Mo5Cr4V3, W12Cr4V4Mo, hardness up to 67HRC, China has also developed several kinds of w(V) 5% superhard high speed steel, in cutting those workpiece materials with strong wear properties for the tool, such as fiber, hard rubber, plastic, etc., high vanadium high speed steel tools have a particularly high coefficient, k=22mm '/m. Although the hardness of high-speed steel is less than carbide, it is sufficient for the cutting of steel and cast iron with general hardness. Superhard high-speed tools can process hard workpieces with hardness up to 400HBW and hard to life. 48~54HRC hard face gear.
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