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经过退火之钢料,在淬火之后,皆大大增加其硬度。其增加之程度,则因材料不同而异。除低炭钢在淬火后所增之硬度只有原来之250％外,其余如中炭钢及高炭钢,皆增加至300％以上。至合金钢则常增加至250％至300％之间;即低炭合金钢及不锈钢亦增加至200％以上。如增加之程度不够以上比例者,即系硬度不足。如工件上有局部之硬度不及上述比例者,即是发生了软点。凡此皆为淬火时必须避免之事。兹将其发生之原因,及其避免之方法,分为下列数点述之于后:——(甲)由于钢之显微组织不良或晶粒大小不当
After annealing of the steel, after quenching, all greatly increase its hardness. The extent of its increase, due to different materials vary. In addition to low carbon steel hardness after quenching increased by only 250% of the original, the other as carbon steel and high carbon steel, both increased to 300% or more. To the alloy steel is often increased to between 250% and 300%; that is, low carbon steel and stainless steel also increased to more than 200%. If the increase is not more than the proportion of those who are not enough hardness. If the workpiece has a local hardness less than the above ratio, that is, the occurrence of a soft spot. All of these are things that must be avoided when quenching. The reasons for its occurrence and the method of avoidance are to be divided as follows: - (a) Due to the poor microstructure of the steel or the improper grain size