Experimental study on the prohibition of edge cracking of high-silicon steel strips during cold rolling

Two sets of roll profiles were designed such that the roll surface outline is larger in the centre than at the end and vice versa (i.e. convex and concave roll profiles) to simulate positive bending and negative bending profiles in actual cold rolling. Pilot cold rolling tests were then performed to show how waviness of high-silicon steel (3.0 per cent Si) specimens occurs during cold rolling and leads to edge cracking. A finite-element analysis was carried out to examine stress distributions in the region of the specimen where edge cracking initiates during cold rolling. Results show that these specially designed roll profiles create waviness in the specimen, even though the ratio of width to thickness of the specimen used in this study is 10. (Generally, the width to thickness ratio of actual high-silicon steel strip is greater than several 100s.) It has been found that the convex roll profile, corresponding to positive bending in the actual cold rolling, generates waviness in the specimen centre and subsequently the edges of the specimen start fracturing locally due to tensile stress in the rolling direction produced by the waviness. Hence, the best way to avoid edge cracking in actual cold rolling mills is to suppress occurrence of waviness in the centre of the high-silicon steel strip by controlling the roll bending profile.