45钢半轴套管锻件端面撕裂原因分析

Causes analysis of the end face tearing of 45 steel half shaft casing forging

对45钢半轴套管锻件开裂原因进行了分析。结果表明,失效锻件开裂原因是由于棒料的加热温度过高,造成材料组织严重过热,甚至出现过烧特征的晶间熔洞组织。组织中晶间结合力急剧降低,锻造应力已经大于此时材料的抗破断强度,因而造成沿晶开裂的热裂纹,裂纹继续向端面扩展撕裂。由于锻造工艺不当,锻件端面外边缘形成尖角,该处的冷却速度加大,裂纹的撕裂断口由沿晶转变为穿晶,而且随着温度的降低,氧化脱碳也逐渐减弱。

Cracking cause of 45 steel half shaft casing forging was analyzed.The results show that the cracking of the failed forging is due to very high heating temperature which result in serious overheated structure,and even it appears burnt and intergranular melted hole.The intercrystal binding force decreases sharply,and forging stress is higher than anti-breaking strength,thus thermal crack along intergranular cracking and propagating to the end.Due to improper forging progress,the outer edge of forging end face forms sharp angle where cooling speed is quick.So the crack tearing transforms from intergranular fracture to transgranular,and with the decrease of temperature,oxidation and decarburization layer gradually disappear.