The Research Of New Technology Producing High Strength Hot -rolled Ribbed -steel Bar

With the rapid development of China's national economy, as a kind of important steel used in construction, the demand of 400MPa GradeⅢtwisted bar is increasing continuously. At present, the domestic 400Mpa GradeⅢtwisted bar mainly produced by micro-alloying. With significantly increasing alloy prices caused by alloy resources lack, the production of micro-alloyed GradeⅢtwisted bar profit margins is becoming lower and lower, which also does not comply with the demand for building a conservation-minded society. To research a new process of 400Mpa GradeⅢtwisted bar has become very urgent, which has great economic value and social benefits.Pan Cheng Bar Plant is a more production-scale enterprises specializing in the production of twisted bar by micro-alloyed 20MnSiV in the southwest. In this paper, according to practice demand, without transforming the existing equipment and increasing the mill capacity, a new process to produce 400Mpa GradeⅢtwisted bar which meet the national standard by controlled rolling and cooling is researched, which reduce costs and save resources by rational use of V content.Because of the weak devices capacity, combined with the CCT curve of 20MnSi with designed rational component that reducing the content of alloying elements Mn,Si,V in original steel, a technology program was put forward with adjusted open rolling temperature and fast intermittent water cooling after finishing.The finite element software Marc was used to simulate the different specifications of the steel cooling process after rolling, to provide intuitive and credible evidence for the development of controlled cooling processes and water-cooled design parameters. Calculations result show that the bar temperature on cooling bed can be cooled down from 1000℃to 700℃by specially designed equipment, and surface temperature can be controlled more than 400℃.The inspection of 400Mpa GradeⅢtwisted bar produced by controlled rolling and controlled cooling show that the performance of twisted bar meet national standards completely, and can be bulkly supply market.