Analysis and Improvement of Bending Cracking of Low Alloy Steel Strip

LÜ Fuqiang

Abstract：Aiming at the failure problem of 90° bending cracking of 355 MPa grade low alloy hot-rolled steel strips,the cracking causes were analyzed through methods such as micro structure observation and mechanical property testing.The results show that the base material structure is mainly pearlite+ferrite and contains a small amount of bainite.The overall strength is relatively high.There are burr defects at the shear edge.Moreover,in the bending test,the bending radius is too small,resulting in stress concentration and causing the deformation of the outer metal to exceed the deformation limit,which is the main factor causing bending cracking.The micro structure abnormalities and surface quality defects formed by surface rust on the steel strip and pear lite segregation in the core further intensify the risk of cracking.The research suggests that in the smelting and rolling process,by reducing the billet drawing speed and optimizing the controlled rolling and controlled cooling process to control the uniformity of the micro structure,using indoor storage and covering with rain covers to prevent surface rust during storage,and optimizing the shearing process during bending processing to improve the edge cutting accuracy and avoid burrs,the cracking problem during the bending and pipe manufacturing of this type of steel strip can be effectively controlled.It provides a process optimization direction for improving the processing performance of low alloy steel strips.