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

LIU Shanshan; SUN Qian; XU Ruiliang; YIN Haiyuan; ZHANG Jinbo; WU Xiujun

Abstract：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 10,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.