轧件内部裂纹的模拟实验方法与愈合行为

提出一种预置轧件内部裂纹的模拟实验新方法，即钻孔填充法，将其用于普碳钢中厚板内部裂纹的预置，并对其愈合行为进行轧制实验研究.研究了位于轧件中心、厚度方向三分之一处等位置的裂纹愈合情况.实验结果表明，压下率达到50%以上、开轧温度在1100℃时，内部裂纹可完全愈合；且位于轧件厚向中心位置裂纹的愈合程度好于其他位置，采用缓冷方式时裂纹的愈合程度好于空冷.对轧制过程中裂纹愈合的机理进行了分析，认为在轧制变形条件下，压应力状态为裂纹愈合提供了静力学条件，塑性变形过程中大量原子的定向运动，为裂纹愈合提供了物质补给条件，裂纹两侧的金属原子更容易找到新的平衡位置，形成统一的晶格点阵，从而实现裂纹愈合.

Experiment Method to Simulate Internal Cracks and Its Healing Behavior of Rolled Pieces

A new experiment method called hole filling method was proposed to simulate the internal cracks inside rolled pieces. The healing behavior of internal cracks in a mild steel plate during rolling was studied by presetting internal cracks in a sample. The crack healing tests in the center and 1/3 height of the plate were carried out. The results showed that internal cracks heal completely at the reduction of more than 50%and the rolling temperature 1100℃. The crack in the center of the plate healed better than that at other places， and cooling slowly after rolling was good for healing. The mechanism of crack healing in the rolling processes was analyzed. During the rolling deformation， the compressive stress state provides the static condition for crack healing. When the plastic deformation went on， as the huge atoms move towards one direction， which provided the material supply condition for crack healing， the atoms on two sides of the crack are easy to find a stable location to form a crystal lattice， then the crack heal.