The micro-cracks on the surface of steel saw pipe have a great influence on the product quality, which is not equal to deceleration. When decommissioning, especially the longitudinal direction of Nb, V and Ti, are the most prominent, which seriously affects the improvement of product quality and yield. This not only brings enormous economic losses to enterprises, but also restricts the development of plate production line varieties. Longitudinal surface micro-cracks mainly include edge cracks, longitudinal cracks and star-shaped cracks. The reasons are improper control of rolling process parameters, abnormal production in continuous casting process, inheritance of slab cracks and enrichment of residual elements.


Longitudinal surface microcracks seriously affect product quality. The main cause of longitudinal surface microcracks is the falling off of copper coating on continuous casting dies. This will lead to copper penetration into austenite grain boundary and grain boundary cracks in solidified shell. On the other hand, thermal stress cracks and crack sensitivity of titanium-bearing steel are particularly obvious. Control measures: improve the quality of die copper and copper, prevent dew; strengthen inspection before slab quality and production; improve the cleanliness of longitudinal steel through good casting and other measures of longitudinal protection.