PRODUCTION TECHNOLOGY OF HOT ROLLED PLATE OF SPECIFIED QUALITY USING NEW TECHNICS OF LARGE SECTION SLABS CASTING

Development of new methods for production of continuous cast slab blanks shall not be based on low speed equilibrium crystallization processes in steel. Feeding melt into crystallizer side-wall layers through feed rising construction of submerged nozzle with eccentric outlet holes allows a significant increase in steel crystallization rate during slab casting. The main results of large section slabs casting using new technology providing improvement of their quality are given. When casting steel through an experimental nozzle, considerable decrease in width of columnar crystals zone and increase of disoriented crystals zone are observed, as well as decrease in index of centerline segregation. When casting with a new technology, heat transfer in crystallizer increases by 10 – 12  %. In impact test, a number of qualitative characteristics of metal have been identified that are not captured in other types of tests. The main regularities in metal structure formation in continuous finishing mill group of continuous wide strip mill (CWSM) and subsequent cooling were studied using physical modeling method. Wedge-shaped samples of industrial melted low-carbon steel, withdrawn from semi-finished rolled stock cooled on CWSM intermediate rolling table, were rolled in one and two passes on twohigh speed laboratory rolling mill with a bypass device. Geometric and kinematic resemblance of rolling process was observed. Rolled samples, after fixed exposures on air, were dropped by a special device onto the lateral edge for partial hardening in cooling solution. A  set of relative reductions were received longwise the sample, a set of cooling rates – edgewise. Based on results of physical modeling, the main formation regularities of low-carbon steel structure during rolling and accelerated cooling of strips on continuous wide strip mill were established. Using these regularities and the Hall-Petch equation, it is possible to provide specified structure and flow limit of the finished hot-rolled plate. By eliminating of additional heating of slabs for rolling and improving quality of rolled products, a significant economic effect can be obtained.

continuous casting, crystallization, slab, continuous wide strip mill, physical modeling, low-carbon steel, structure, heat transfer

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