H13锻棒异常内裂的质量分析

Quality analysis on abnormal internal crack in H13 forging rod

利用具有保护气氛的抽锭式电渣炉生产Φ600 mm H13钢锭并锻造成Φ240 mm的圆棒,锻造后锯切发现锻棒内部出现纵裂。采用化学成分分析、金相检验、断口宏微观检测及酸洗检测等手段对该锻棒内部裂纹进行了全面分析,同时对原始电渣锭材料进行复查。结果表明：H13锻棒化学成分符合要求,无原材料冶金缺陷;裂纹内部无异物,裂纹附近无脱碳层,裂纹呈沿晶断裂特征,周边组织为均匀的球化珠光体。分析内部中心裂纹产生的原因是由于在平砧锻造H13锻棒时,锻棒心部拉应力过大,超过材料的强度极限。

Steel H13 ingot of Φ600 mm was forged into bar of Φ240 mm by gas-protective retracting-type ESR furnace,and longitudinal crack was found inside the forging rod by cutting after forging. Then,the internal crack of the forging rod was comprehensively studied by chemical component analysis,metallographic examination,macroscopic and microscopic observation of fracture and pickling test. Meanwhile,the original ESR ingot materials were inspected again. The results show that the chemical composition of H13 forging rod meets the requirements without metallurgical defects of original material,and there is no foreign body inside the crack and no decarburization near the crack. In addition,the crack is characterized by intergranular fracture with uniform spheroidal pearlite around. The reason of internal crack is that the central tensile stress exceeds the strength limit of material when H13 forging rod is forged by flat anvil.