HQ-80钢再热裂纹机理

通过插销、冲击韧度等试验研究HQ-80钢的再热裂纹倾向，扫描电镜发现过热区晶界存在合金元素碳化物，电子能谱检测碳化物富含Cr、Mo。再热裂纹的机理是，高温过热——合金元素碳化物固溶，再热弱化——晶界析出大颗粒状合金元素碳化物导致晶粒表面的贫Cr、Mo合金元素层．晶界高温强度不足。影响再热裂纹三要素是：生成品界碳化物的Cr、Mo、C等合金元素，高温过热与再热弱化的热循环过程，一定的拘束应力。再热裂纹与再热脆化的机理相同，两者同时发生，降低应力防止再热裂纹并不能防止再热脆化。成功采用无缺口插销进行插销试验，弧形断口证明再热裂纹的主要影响因素是过热区敏化组织。

Mechanism of HQ-80 steel reheat crack

Carbonides were discovered in HQ-80 steel coarse grain boundary after reheating by scanning electron micrograph. Energy spectrum analysis tested high intensities of Cr,Mo in carbonides. Implant test and Charpy-V impact test for coarse grain zone were conducted. Mechanism of HQ-80 reheat crack is due to low grain boundary strength because of poor Cr and Mo layer by separating out carbonides in boundary. Three basic influelce factors on reheat crack are Cr,Mo,C elements reacting out carbonides, overheat and reheat cycles, restrain stress. Mechanism of reheat embrittlement and reheat crack is the same. Reheat embrittlement cannot be avoided by reducing stress. The implant test was successfully achieved by non-notch implant. The implant curve fracture verified that major factor on reheat crack is sensitive coarse grain in heat affected zone.