低合金钢弯折开裂的分析与经济性改善

Analysis and Economic Improvement of Bending Cracking of Low Alloy Steel strip

针对355 MPa级别低合金钢带弯折开裂的实际问题,采用金相组织观察、扫描电镜分析等方法对其开裂原因进行了综合分析。结果表明,钢带组织为珠光体和铁素体含少量贝氏体,晶粒约10级,细小均匀,力学性能偏高;钢带分剪后边缘存在毛刺,弯折半径较小,易形成应力集中诱发折裂,外层金属形变量大于形变极限是造成失效的主原,再者钢带表面质量较差,心部位置存在一定珠光体偏析,加剧了失效可能。实际生产中严控铸坯偏析,做好钢带表面清洁,优化切边精度处理,可避免该类问题;某制管企业,该强度级别钢带弯折制管产量约20万t,经计算,优化工艺后,每年可节省80余万元质量赔付,有效提高了产品质量及其经济性。

In view of the actual problem of bending cracking of grade 355 MPa low alloy steel strip,the cracking causes were analyzed by means of metallographic observation and scanning electron microscopy.The results show that the structure of the steel strip is pearlite and ferrite with a small amount of bainite,the grain size is about grade 1o,fine and uniform,and the mechanical properties are high.There are burrs on the edge of the steel strip after shearing,and the bending radius is small,which is easy to form stress concentration induced fracture.The outer metal shape variable is greater than the deformation limit,which is the main cause of failure.Moreover,the surface quality of the steel strip is poor,and there is a certain pearlite segregation at the heart,which aggravates the possibility of failure.In actual production,this kind of problem can be avoided by strictly controlling the segregation of casting billet,cleaning the surface of steel strip and optimizing the cutting precision.One pipe manufacturing enterprise can produce about 200,000 tons steel belt bending pipe with this strength steel,after calculation and optimizing the process,it can save the quality compensation more than 800,000 Yuan per year,and can improve product quality and economy.