Formulation of reduction procedures for rough rolling of packaging steel strip

Formulation of reduction procedures for rough rolling of packaging steel strip
　　The rough rolling mill generally does not use multi-mill continuous rolling. Its main task is to open the billet and compress it to milk the slab into a strip. Therefore, the quality requirements are not high, and relative to the thickness and reduction of the rolled product. , The impact of the rolling mill's bounce is also small, so the setting calculation of its reduction schedule can be carried out in a relatively simple method.
　　The content of the reduction program calculation includes determining the thickness of the intermediate strip and the thickness of each pass of the rough rolling is only the roughing mill stand number.
　　 Hot strip rolling has two zones, rough rolling and finishing rolling, the first task of thickness distribution is to determine the exit thickness H of the rough rolling zone. The determination of H actually determines the load distribution between rough rolling and finishing rolling. When the ruler deduction value is large, the rough rolling load is reduced, and the finishing rolling load increases. The opposite is true when the value is small.
　　 In principle, as long as the precision unit has sufficient capacity, Hrc should be larger.
　　The increase in the thickness of the strip is beneficial to reduce the number of rough rolling passes, shorten the rough rolling time, and increase the opening temperature of the finishing rolling, but it may increase the load of the finishing rolling unit (has little effect on the finishing rolling time. The thickness should first be determined according to the thickness of the finished product. Generally speaking, if a thinner finished product needs to be rolled, the thickness of the strip will be reduced accordingly, but the thin strip will not be able to guarantee the finish rolling required for rolling thin finished products. Temperature, even if the finish rolling temperature is guaranteed, the load of the finish rolling mill will not decrease too much due to the low rolling temperature, and may even increase.
　　The thickness of the strip shall be determined through optimized design according to the actual layout of the rolling mill and the capacity of roughing and finishing rolling equipment.
　　 Starting from reducing the temperature drop to ensure the finish rolling temperature, and also in order to reduce the furnace temperature to save energy, modern hot continuous rolling has developed the following technologies:
　　 (1) Adopt powerful rough rolling mill and powerful finishing mill (especially F0-F3). Take 1700mm hot tandem rolling as an example, allowing the rolling force to be increased from 20 MN to 30 MN in the past, the main drive power of rough rolling from 5000 kW to 10000 kW, and the main drive of finishing rolling from 3500 kW to 8000 kW. Therefore, the reduction can be increased and the thickness of the strip for finishing rolling can be increased.
　　 (2) Insulation covers are used before and after the roughing mill and between the roughing and finishing rolling.
　　 (3) For the constant-speed finishing mills with low output, a hot coiling box is installed after rough rolling to reduce temperature drop, especially to make the strip temperature uniform and reduce head and tail temperature drop.
　　 (4) Thin slab continuous casting and rolling adopts a long tunnel furnace to increase the temperature of the strip into the rough and finish rolling.