导轨钢带钢边部细线缺陷成因分析及控制措施  

Cause analysis and control measures of edge thin wire defects of guide rail steel strip

作　　者：韩乐[1] 曾立[1] 袁天祥[1,3] 朱国明 刘鸿明[1] 刘延强[1] HAN Le;ZENG Li;YUAN Tianxiang;ZHU Guoming;LIU Hongming;LIU Yanqiang(Shougang Jingtang United Iron and Steel Co.,Ltd.,Tangshan 063200,China;Beijing University of Science and Technology,Beijing 100083,China;School of Mechanical Engineering,Yanshan University,Qinhuangdao 066000,China)

机构地区：[1]首钢京唐钢铁联合有限责任公司,河北唐山063200 [2]北京科技大学,北京100083 [3]燕山大学机械工程学院,河北秦皇岛066000

出　　处：《轧钢》2023年第5期129-134,共6页Steel Rolling

摘　　要：针对边部细线缺陷导致亚包晶成分镀锌导轨钢形成批量降级风险大的问题,对导轨钢边部细线缺陷组织形貌、铸坯凝固组织、高温变形行为及中间坯温降情况进行了分析,探究了缺陷产生机理,并提出了控制措施。结果表明:缺陷的产生与钢种特性密切相关,板坯晶粒粗大、大量沿晶界析出的片条状碳化物的组织特点导致导轨钢高温塑性较差;板坯出加热炉后,在粗轧过程中由于边角部温降大而落入高温脆性区,发生奥氏体向先共析铁素体转变,外部应力在铁素体相集中,萌生裂纹并扩展,在粗轧立平轧制过程中侧翻形成边部细线缺陷。通过在连铸工序采取低碳钢生产工艺并限制最高连铸拉速,在热轧工序适当提高出炉温度、增加粗轧保温罩,对定宽机进行孔型优化并限制减宽量,以及提高立辊润滑油浓度等措施,边部细线缺陷得到有效控制,缺陷降级率由原来的1.09%降低至0,缺陷发生率由原来的近100%降低至14.3%。Aiming at the problem of high risk of batch degradation caused by edge thin wire defects in galvanized guide rail steel with hypo-peritectic composition,the microstructure and morphology of edge thin wire defects in guide rail steel strip,solidification structure and high temperaturedeformation behavior of casting billed,and temperature drop of intermediate billet were analyzed.The mechanism of the defects was explored and the control measures were proposed.The results show that the occurrence of defects is closely related to the characteristics of steel grade.The microstructure characteristics of coarse grain and a large number of strip like carbides precipitated along the grain boundaries in the casting billet result in poor high temperature plasticity of guide rail steel.After the slab is discharged from heating furnace,it falls into the high temperature brittle zone due to the large temperature drop at the edges and corners during the ronghing rolling process.Austenite is transformed to proeutectoid ferrite.The external stress is concentrated in the ferrite phase,cracks are initiated and extended,and the thin wire defects at the edges are formed by rollover during vertical and horizontal rolling of roughing rolling.By adopting low carbon steel production process in the continuous casting process,limiting the maximum continuous casting speed,taking measures such as appropriately increasing the reheating temperature,increasing the insulation cover for roughing rolling in the hot rolling process,optimizing the pass of the slab sizing press machine and limiting the width reduction,and increasing the lubricating oil concentration of the vertical roll,the edge thin wire defects are effectively controlled.The defect degradation rate has decreased from 1.09%to 0,and the defect occurrence rate has decreased from nearly 100%to 14.3%.

关 键 词：导轨钢 边部细线缺陷 亚包晶钢 组织形貌 中间坯温降 高温脆性区 控制措施 

分 类 号：TG335[金属学及工艺—金属压力加工]