火炮底板开裂分析

Cracking analysis of artillery bottom plate

某公司购买的热轧钢板用于制作火炮底板,经数控火焰切割后,在过渡圆弧角处出现裂纹。采用化学成分分析、力学性能检测、金相检验、扫描电镜观察等方法对裂纹形成原因进行分析。结果表明:底板的化学成分和主要力学性能指标正常,原始组织粗大降低了材料性能。底板经火焰切割后组织变化较大,产生了粗大贝氏体和马氏体等不良组织,综合分析认为,底板断裂的主要原因是经数控火焰切割后组织应力过大和在过渡圆弧角处存在应力集中。通过采用火焰切割前对底板进行正火处理,提高了材料性能,有效避免了底板的开裂失效。

A hot-rolled steel plate was purchased by a company and used as the bottom plater for artillery. After flame cutting using the numerically-controlled machine tool,the cracks were observed at the transition arc. The causes of crack formation were analyzed by chemical composition analysis,mechanical properties test,metallographic examination and scanning electron microscopy(SEM). The experimental results showed that the chemical composition and main mechanical properties of the bottom plate were normal. The cooarse original structure decreased the material perpormance. After the flame cutting,the microstructure of bottom had great changes. The undesirable structures including coarse bainite and martensite were generated. The comprehensive analysis indicated that the major reason for the cracking of the bottom plate was the excessive stress of structure after NC flame cutting and the stress concentration at the transition arc angle. The material performance could be enhanced by the normalizing treatment of bottom plate before flame cutting,thus effectively avoiding the cracking failure of bottom plate.