用人工的方法诱导超前扩展点,可以使那些不容易产生超前扩展点、又难以获得交界线借用的表面冷却得更快。为加以区别,把这样诱导出来的超前扩展点称为人工超前扩展点,而把前面介绍的称为自然超前扩展点。现今开发的诱导超前扩展点的办法有两个:一是用诱导钉,二是向确定的表面点喷射淬火液,下面只介绍前一种方法。用诱导钉的做法和原理:淬火加热之前,在选定的部位焊一个直径很小的钉子。在随后的淬火冷却中,该 By artificially inducing advancement extension points, surfaces that are less prone to advanced extension points and are less accessible to the borderline can be cooled more quickly. To make a difference, the leading extension point so induced is called the artificial leading extension point, and the previous introduction is called the natural leading extension point. Nowadays, there are two ways to induce advanced extension point: one is to induce nail, the other is to spray quenching liquid to certain surface points, and only the former method will be introduced below. The use of induced nailing practices and principles: Quenching heated before welding in a selected site a small diameter nail. In the subsequent quench cooling, the