Effect of the Temperature–Speed Hot-Rolling Conditions on Scale Formation

The influence of the parameters of a through technology on a rolled-in scale defect is analyzed. To study the influence of the temperature behind stand no. 6 of the 2000 hot-rolling mill in sheet rolling shop no. 10 of PAO MMK on the rejection according to this defect, the temperature in the range 1030–1070°C is maintained on rolled strips of steel grades 08Yu and 08(sp, ps, kp), and the products to be processed are then delivered to the 2000 cold-rolling mill in sheet rolling shop no. 5. To study the influence of the reeling temperature on the scale layer thickness, selective sampling from rolls wound with different reeling temperatures is carried out. An analysis of the production of semifinished rolled products for cold rolling with a rolled-in scale defect and metallographic studies have shown that the main cause for the formation of this defect during hot rolling is a high reeling temperature of 604.7 t (24%). The rolled-in scale defect depth is mainly no more than 0.02 mm and is 81 and 67% of the initial cause of scab and underpickling, respectively. An analysis of the influence of the strip temperature behind stand no. 6 on rolling semifinished rolled tin plates shows that a decrease in the temperature decreases the rejection according to the rolled-in scale defect in sheet rolling shop no. 3 and in the coating shop by 3.7 times for the semifinished rolled products upon annealing in bell furnaces and by 1.9 times for annealing in a continuous annealing furnace. The study of the influence of the reeling temperature on the scale layer thickness showed that a change in the reeling temperature from 560 to 730°C leads to an increase in the scale layer from 55.15 to 89.45 g/m2. To improve the surface quality of the finished electro-tinned tin, an experimental technology is proposed: the reeling temperature for semifinished rolled tin plates in the flow of annealing in bell furnaces decreases to 630–660°C instead of 660–690°C according to a standard technology.