Study On Thermo-mechanical Control Process Of X80 Wide And Heavy Pipeline Plate

The thesis is combined with the project of The steel grade development of Shougang Group by the State Key Laboratory of Rolling Technology and Automation of Northeastern University. Hot simulation experiments, hot rolling experiments in laboratory and industrial experiments had been carried out; the high temperature deformation behavior and effect of thermo-mechanical control process on microstructure and mechanical properties of X80 pipeline steel were investigated. Main studies are rendered as follows:1. The single pass thermo-simulation compression experiment was carried out using Gleeble2000 hot simulation machine. The true stress-strain curves were obtained. The high temperature deformation behavior was researched and the activation energy of dynamic recrystallization and parameter Z were counted out. Besides, the model of deformation resistance of tested steels had been established.2. Through hot rolling test in lab, the microstructures and mechanical properties of three tested steels with different chemical component were studied in different TMCP conditions. The results showed:tested steel with 0.045%C,1.778%Mn, 0.042%Nb,0.046%V,0.02%Ti in rerolling temperature 854℃, finishing temperature 802℃, cooling temperature 550℃and cooling rate 15.6℃/s can achieve good mechanical properties with Rto.5=605MPa,Rm=755MPa,A50mm%=46 and charp ballistic work 287J,section of shear 97%.3. Through off-line simulation on the rolling and on-line accelerated cooling experiments, the rolling and cooling capability of Shouqin 4300mm production line were checked. The results showed that the rolling and cooling capability could satisfy the demand of process of X80 pipeline steel.4. Through one industrial experiment, the relations between process parameter and mechanical properties were surveyed. The results showed that the content of acicular ferrite was decreasing and the content of polygonal ferrite was increasing with the lowering of finishing cooling temperature. Due to the high finishing cooling temperature in the experiment, the content of acicular ferrite was lower. Therefore, the strength of tested steels were lower and the results of drop weight tear test were not satisfied the demand.