Study On Increasing Yield Strength Of Q345B Plate In JISCO

This paper summarizes the new research status of low alloy high strength steel , and discusses the method and the mechanism that can enhance the yield strength of low alloy high strength steel. The mostly problems on the low alloy high strength steel's research and production have been indicated.By analyzing a great deal of data from the current production of Q345B plate in JISCO, the reason caused lower yield strength in Q345B plate is confirmed, which is the chemistry composition and rolling process of the steel. Based on this, this paper researches the influences of chemistry composition and rolling process on the yield strength of the steel. The main results are as follow. The yield strength of Q345B plate can increase averagely 20MPa ~ 30MPa by increasing lower limit of carbon content and add Ti. The yield strength of Q345B plate can increase averagely 60MPa~65MPa, when Mn content increase from 1.36% to 1.55%, and add, 0.0029%~0.014% AI, 0.00!2%~0.035%V and 0.001%~0.026%Nb. In the same condition of smelting process and chemistry composition, the final rolling temperature, the final cooling temperature and the soaking temperature are reduced averagely 35 C, 25 C and 40C respectively, the average yield strength of 16mm thickness plate and 25mm thickness plate can increase 38.8MPa, and 43.7MPa respectively.Based on above research results, a better rolling process that can increase the yield strength of Q345B plate is put forward.