Lateral cracks damaging the stability of tensile sheet during tandem rolling conveying

Abstract

In tandem cold-rolling production, sheet fractures are interrelated to both conveyance stress and transverse cracks during conveyance process. The residual tension or sheet contour cannot completely explain the early fracture problem. It is found that small lateral crack reduces fracture threshold of sheets destructively during cold rolling and coiling processes without rolling stress. Several lateral notches were machined on cold-rolled intermediates of silicon steel to simulate edge cracks in rolling processes. Based on tensile test and laser confocal microscope, the damages of lateral notches on tension resistance of sheets were investigated. Then, the shape effect and size effect of lateral notches were analyzed. The notch depth could negatively affect energy absorption capacity of sheets before tensile fracture. Meanwhile, the sharp notch could deteriorate elongation ability of sheets before necking. Both factors reduced fracture threshold of sheets and tensile redundancy and conveyance stably capacity of tandem rolling mills, promoting sheet fracture.