15CrMnMoVA钢Φ610 mm电渣锭锻造表面裂纹及工艺改进

Forging surface crack and process improvement on 15CrMnMoVA steelΦ610 mm electroslag ingot

利用光学显微镜(OM)、扫描电子显微镜(SEM)等研究了15CrMnMoVA钢Φ610 mm钢锭锻造开坯过程中圆坯料表面裂纹产生的根本原因。结果表明:钢锭在锻造加热前,锭的中上部附近已经存在微小裂纹;锻造开坯前,钢锭在加热炉中长时间处于加热均温阶段,微小裂纹附近严重脱碳及富Cu相析出的综合作用恶化了钢锭在开坯过程中钢锭表面的热塑性;Φ610 mm钢锭开坯过程中钢锭中上部附近出现了明显的横向热裂纹,裂纹两侧附近脱碳严重,并且在热裂纹附近的晶界上出现了液膜状富Cu相。通过降低母电极中的Cu含量及延长电极在电渣重熔后的炉冷时间,有效地消除了Φ610 mm钢锭在锻造开坯过程中圆坯料的表面裂纹,提高了成品棒材的表面质量。

The root cause of round billet surface crack formed in forging and billeting process of 15CrMnMoVA steelΦ610 mm steel ingot was studied by means of optical microscope(OM)and scanning electron microscope(SEM).The results show that there are micro-cracks near the middle and upper part of the ingot before forging and heating,and the combined effect of severe decarburization and Cu-rich phase precipitation near micro-cracks deteriorates the thermoplasticity of the steel ingot surface during the billeting process of the steel ingot when the steel ingot is in the heating homogenization stage for a long time in the heating furnace before forging and billeting.Furthermore,the obvious transverse hot cracks appear near the middle and upper part of the steel ingot during the billeting process ofΦ610 mm steel ingot,the decarburization near both sides of the crack is serious,and the liquid film Cu-rich phase appears on the grain boundary near the hot crack.Therefore,by reducing the content of Cu in the mother electrode and prolonging the furnace cooling time of the electrode after electroslag remelting,the surface cracks of the round billet during the forging and billeting process ofΦ610 mm steel ingot are effectively eliminated,and the surface quality of the finished bar is improved.