Abstract: It  was  indicated  by  analysis  on  bulge-like  inner  overlap  of  Φ245  mm×12  mm  casing  tube  of  steel 26CrMo4V(0.26C,0.95Cr,0. 16Mo,0.07V)that  the  defects  distributed  random  at  the  same  side  of  inner  wall  and  there was  Si-Mn-Fe  compound  oxide  layer in  overlap.It was  considered that the bonding  of eccentric  shrinkage  cavity in  cast  bloom was prevented in piercing by the stable oxide layer which formed at inner wall of eccentric shrinkage cavity,and the inner overlap defects formed at action of combined shear and tensile strains during piercing.With the technology measures such  as  lower  overheating  of liquid  steel,weak  secondary  water  cooling  and  controlling  casting  speed,the  reject  ratio  of tube with  inner  overlap  decreased to  5.95%  from  original  15.43%.

Key words: Steel 26CrMo4V,Casing Tube,Inner Overlap,Concasting Technology

摘要： 26CrMo4V钢(%:0.26C、0.95Cr、0.16Mo、0.07V)Φ245 mm×12 mm套管内壁凸包折叠的分析表明,该缺陷有沿套管内壁同侧随机分布的规律性,凸包内存在Si、Mn、Fe复合氧化层。认为在穿孔时,连铸坯中的偏心缩孔内壁形成的稳定氧化层阻止缩孔内壁界面的"焊合",在剪切-拉伸应变的作用下,形成内折叠缺陷。通过低过热度、弱二冷和控制拉坯速度等工艺措施,使内折报废率从15.43%降至5.95%。

关键词: 26CrMo4V钢, 套管, 内折叠 , 连铸工艺