W6Mo5Cr4V2钢制大规格机用丝锥的热处理

Heat Treatment of Large-Sized Machine Tap of W6Mo5Cr4V2 Steel

高速钢大规格机用丝锥由于尺寸较大，碳化物分布难以均匀，将影响丝锥的热处理质量。对于大规格W6Mo5Cr4V2钢机用丝锥，为确保其性能达到要求，应按下列工艺进行热处理：淬火加热前，依次于500～600℃、800～850℃和950～1000℃进行预热；淬火温度取下限，即1200～1225℃；以大于7℃／s的速度进行淬火冷却，最好进行多次分级冷却；充分回火。此外，为减小丝锥的开裂倾向，柄部应采用水淬空冷而不是水淬油冷工艺淬火。

Carbides in large-sized machine tap of high speed steel are difficult to be uniformly distributed, which will have an effect on its heat treatment quality. The large-sized machine tap made of W6MoSCr4V2 steel should be heat treated by being successively preheated at 500 to 600 ℃, 800 to 850℃ and 950 to 1000℃prior to austenitizing; quenched from austenitizing temperature on the low side, i. e., 1200 to 1225 ℃ and at rates of more than 7 ℃/s（preferably, subjected to multiple stage cooling） ;and sufficiently tempered, thus making certain that the tap conforms with property requirements. Furthermore, the handle of a tap is to be hardened by being first quenched in water then cooled in air instead of by first being quenched in water then cooled in oil to render possibility of the tap cracking less.