Research On Controlled Rolling And Cooling Process Of Bar And Wire Rod Of Bearing Steel

This thesis is focused on the research of controlled rolling and cooling process of bearing steel in a new invested bar and wire rod mill. It has been proved by research that controlled rolling combined with cooling process is effective to reduce net carbide up to 2.0 grade (with reference to standard YJZ84) and not only to shorten spheroidizing annealing time but also to realize direct cold drawing of the wire rod without any further spheroidizing annealing.Made a study of the effects of the reduction rate and finishing rolling temperature on net carbide and grain size. It was finally found out that uniform fine grain and lower net carbide grade will be achieved by enough deformation or low finishing rolling temperature. Made an utilization of ANSYS software to carry out somecomputer-aided simulation on the temperature falling during the period of controlled cooling of bearing steel bar. After compared the simulated and actual measured values it was proved that it was feasible and reliable to study the temperature falling of bearing steel bar by using computer-aided simulation.The cooling system used in controlled rolling and cooling process was designed and developed. Meanwhile optimized the design for the reduction rate which aimed to carry out cotrolled rolling and cooling process of bearing steel bar and wire rod sucessfully.Further research on practical results of controlled rolling and cooling of bearing steel in new invested bar and wire rod mill has been tried on. It was found out the best process flow and parameters to reduce net carbide grade and shorten spheroidizing annealing time.Besides it was developed a new process for direct cold drawing of wire rod without extra spheroidizing annealing.The results achieved in this thesis have already been put into use and brought very good profit both in terms of economy and society.