钢轨下腭轧疤缺陷形成机理研究

针对河北钢铁集团邯钢公司大型轧钢厂钢轨下腭轧疤缺陷问题,对缺陷形成机理进行了分析。结果表明,形成钢轨下腭轧疤缺陷的主要原因是轧件轨头和轨底部位金属量不均衡,在万能U₁EU₂轧机第1、第2道次轧制过程中轨头部位的延伸大于轨底部位,U₁E轧机第3道次轧出后轧件向轨底一侧偏斜且轨头部位前尖舌头较轨底部位长,咬入U₂轧机时轨头前尖撞击水平辊孔型下腭部位而导致辊面粘钢; 辊面粘结物粘结力较弱时,会形成咬入端非周期性下腭轧疤缺陷;辊面粘结物粘结力较强时,则形成周期性下腭轧疤缺陷。根据现场实际情况,提出了对轨形延伸孔轨底部位设计增加金属量约0.3%、轨形切深孔轨头部位设计减小金属量约0.1%、BD₁轧机帽形孔轧件高度设计减小约2%的治理方案,平衡了轨头、轨底部位的金属变形量,改进了万能U₁EU₂轧机各道次轧件前尖舌头形状,改善了咬入状态,彻底解决了钢轨下腭轧疤缺陷问题。

Research on the formation mechanism of rolling scar defect in the lower jaw of rail

Aiming at the rolling scar defect inthe jaw of rail in Heavy Section Rolling Mill of Hansteel Co.of HBIS Group, the formation mechanism of defects was analyzed. The results show that the main reason of forming rolling scar defect in the lower jaw of rail is the unbalanced amount of metal between rail head and rail base. In the first and second pass rolling process of universal tandem mill U₁EU₂, the extension of rail head position is larger than that of rail base position, after the third pass rolling of the U₁E mill, the rolled piece is deflected towards the rail base side, and tongue of the rail head is longer than that of the rail base. When the piece is biting into U₂ rolling mill, the front tip of the rail head hits the lower jaw of the horizontal roll groove, resulting in the small pieces of metal sticking to the roll surface, and the adhesion of metal is weak, an aperiodic rolling scar defect formed at the biting end of the rolled piece. The adhesion of metal is strong, an periodic rolling scar defect formed at the biting end of the rolled piece. According to the actual situation, a design was proposed to increase amount of metal by about 0.3% at the rail base position of the rail-shaped extension groove, and to reduce amount of metal by about 0.1% at the rail head position of the rail-shaped cut deep groove, and to reduce the height of rolled piece in the hat-shaped groove of BD₁ mill by about 2%. Based on it, the metal deformation amount of rail head position and rail base position is balanced, the tongue shape of each pass rolled piece of U₁EU₂ universal tandem mill was improved, the bite condition was improved too,and the defect problem of rolling scar defect in the lower jaw of rail was completely resolved.