H13钢外套在热装配完成后发生多处开裂。采用化学成分分析、力学性能测试、断口分析、金相检验以及硬度测试等方法对外套开裂的原因进行了分析。结果表明: 原材料在锻造过程中产生的过热现象和热处理回火不充分使得H13钢外套硬度超标, 韧性大大降低, 并且在组织中产生了较大的残余内应力; 同时, 在装配过程中对外套施加的向外扩张力大于材料的开裂抗力, 因此出现了早期开裂。

H13 steel casing was cracked after hot charging. The cracking reason was analyzed by means of chemical composition analysis, mechanical properties testing, fracture analysis, metallographic examination, hardness testing and so on. The results indicated that overheating phenomenon and heat treatment insufficient occurred in the forging process of raw materials, and it induced the excessive hardness of H13 steel casing, and toughness greatly reduced. Also, there was a greater residual stress in the tissue. At the same time, the outward expansion stress about steel casing in the assembly process was larger than material cracking resistance, so the casing was cracked in the early period.