Research On Ultra-fast Cooling Of50Mn Narrow Strip

In recent years, with the continuous improvement of customer demand and fiercer competition, how to produce the products stably and low-costly to meet market become major issue which the iron and steel enterprises are facing. The controlled cooling of strip after rolling play an important role on processing performance, mechanical and physical properties. Therefore, the promotion and application in hot-rolled strip production line become more and more important. In the thesis, the50Mn narrow strip was used as the research object, thermal-mechanical simulating technology and hot rolling process were applied, continuous cooling transformation and the cooling process after rolling of test steel were researched.The main contents and results are as follows:(1) The single-pass compression was tested for the experimental steels. Through the flow stress-strain curves, the influence of the deforming temperature, strain value and strain rate on the austenite recrystallization were investigated, and the mathematical models of deformation resistance were also established.(2) The CCT curves were plotted by transformation temperatures determined on the dilatometric curves with the help of metallographic observation and Lever Rule. Process simulation showed that deformation temperature had little effect on the hardness when it was higher than850℃. There was only ferrite and pearlite when coiling temperature was higher than600℃, and the content of ferrite increased when the coiling temperature became higher.(3)The hot rolling and cooling test were carried out to study the effect of different starting cooling temperature, finishing cooling temperature and cooling rate on the microstructure and mechanical properties, the results showed that the strength was increased and elongation was reduced after water cooling compared with air cooling. The strength and hardness were increased, the elongation was decreased and the yield ratio was increased with the start cooling and coiling temperature decreasing. The strength and hardness of the test steel were increased and the elongation was decreased with the cooling rate increasing. (4)The hot rolling and cooling test showed that the performance of test steel was determined by the content of the ferrite and interlamellar spacing of pearlite. The strength and hardness of test steel was increased, and the elongation was decreased with the content of pearlite increasing and interlamellar spacing decreasing.