对45热轧圆钢室温顶锻试验中出现的裂纹进行了研究,分析了表面缺陷、变形温度、变形量、显微组织、夹杂物等对顶锻开裂的影响.结果表明:引起室温顶锻开裂的直接原因是钢中存在大量脆性氧化铝和塑性硫化物非金属夹杂物,该夹杂物沿轧制方向不均匀分布,对拉伸性能影响不大,但对顶锻开裂有较大的影响,特别是当夹杂物处在变形鼓形区附近时;脆性夹杂物造成应力集中,塑性夹杂物形成空洞,使夹杂物和基体界面处容易形成裂纹源,进而在应力作用下不断扩展并最终开裂;原始片状珠光体组织及热轧后的热应力加剧了夹杂物开裂倾向.

The influences of surface defects,deformation temperature,deformation amount,microstructure and nonmetallic inclusions on the cracking of 45 hot-rolled round steel during upset forging at room temperature were studied.The results showed that the brittle alumina and plastic sulfide nonmetallic inclusions were the direct cause of the cracking of 45 hot-rolled round steel during upset forging.These inclusions had little impact on the tensile properties,but had a great influence on the compression performance particularly when they lay in the vicinity of drum-shaped deformation zone.Brittle inclusions brought stress concentration and plastic inclusions formed hollows,resulting in generating crack initiation easily between inclusions and matrixe.Primary sheet pearlite and heat stress formation during hot rolling intensified the tendency of inclusion cracking.