Study On Cold-rolled Deep-drawable Sheet Steels Based On Ferritic Hot Rolling In FTSR Line

In a FTSR ( Flexible Thin Slab casting Rolling) line, it is possible to produce thin strip and the deep drawable sheet steel by adopting ferritic rolling. With the gradual perfectness of thin slab continuous casting, hot rolling and cold rolling in Benxi Iron and Steel Co., Ltd., how to use the newly built FTSR line to manufacture cold rolled deep-drawable steel sheet by ferritic rolling becomes one of the key problems of science and technical scheme in Benxi Steel. Thus, a new rolling technology with proprietary intellectual property rights can not only be obtained for ferritic rolling, but it is possible to have the high value-added products in production line of ferritic rolling-cold rolling-coated products as well. It is also significant in reducing production cost, extending product range and specifications of extra low carbon steel and improving product quality. In this thesis, under the background of practical production of thin slab ferritic rolling in Bengang, a theoretical analysis combined with experimental investigation is utilized to study the processing conditions of cold rolling products with various deep drawable properties. The following research results have been obtained.1) Based on the particularity of thin slab continuous casting and rolling, an analysis has been made for the elements in steel influencing the deep drawability in ferritic rolling. Steel compositions have been designed to adapt the various deep-drawabilities. Through optimization of the chemical composition and processing conditions, cold rolled deep-drwable sheet steels have been successfully manufactured.2) By using Gleeble-2000 thermo-mechanical simulator, the hot deformation behavior of extra low carbon steel in ferritic region has been studied and a model of resistance to deformation established for ferritic rolling. The variation of the resistance to deformation during ferritic hot rolling has been explored and the CCT curves for some typical steels have been provided.3) On the basis of the themo-mechanical simulation results, industrial trial production was carried out in Bengang's thin slab continuous casting and rolling production line. After a detaied analysis for the microstructures, textures and mechanical properties, the effect of hot rolling parameters on the microstructures textures and mechanical properties were elucided and optimal hot rolling parameters determined for producing cold rolling deep-drawable sheet steel. 4) By experiments of cold rolling and annealing on spot, the effect of cold rolling and annealing on the microstructures, textures and mechanical properties have been clarified. The DC04 cold rolling products have been successfully manufactured by bell type furnace as required.5) Considering the Bengang's practical conditions, the optimal ferritic rolling, cold rolling and annealing techniques are used to successfully manufacture DC06 cold rolling deep-drawable product with desired quality, which made high-grade cold rolling deep-drawable sheet steel become ture. This brings great economic and social profits for the enterpresis.