三、过热和过烧刀具在淬火加热时因温度高于正常加热温度而引起组织粗化的现象称为过热。随着过热程度的增加不但晶粒随之进一步长大;同时剩余碳化物的数量、形状和分布亦相应发生变化:数量逐渐减少;形状可能出现粘连、拖尾、从等轴状过渡到角状;碳化物沿晶界呈不连续网状或网状分布。由于淬火加 Third, overheating and over burning Tool in the quenching heating due to the temperature higher than the normal heating temperature caused by the phenomenon of tissue roughening called overheating. With the increase of the degree of overheating, not only the grains grow up, but also the amount, shape and distribution of remaining carbides: the number decreases gradually; the shape may appear sticking and trailing, and the transition from equiaxed to angular ; Carbide along the grain boundary was discontinuous mesh or mesh distribution. As quenching plus