Cold-rolled State Twip Steel Recrystallization Behavior Research

As a steel of expandable tube,TWIP steel in the underground temperature field will occur recovery and recrystallization behavior. This thesis is specific to systematic research the recovery and recrystallization theoretical issues of the independent development of effective anti-acid corrosion10Mn24Cr5A12Ni2MoSi TWIP steel.The TWIP steel of cold rolling reduction rate of30%was annealed between100and750℃temperature range interval of50℃.Using electronic tensile testing machine, OM, SEM and electrochemical workstation, the mechanical properties, the microstructure and electrochemical properties of the TWIP steels were observed and tested. The internal changes of TWIP steel in recovery process were analysised by positron annihilation. The recrystallization kinetics were also analysised. At the same time, the mechanical properties and microstructure of TWIP steel at the cold rolling reduction rate of10%,20%and30%were researched in the Warm deformation.After annealed at different temperatures, TWIP steel had some results by performance testing.Elongation was no big up and down from room temperature to500℃, increased at550℃.Tensile strength first decreased and then increased, declined at550℃. By microstructure, the grains did not significantly change from room temperature to550℃,annealed at600℃the grain within the organization uniform small grains,small grains increased after annealed at650℃, the grain at700℃re-grew and appeared the second grew at750℃. Hardness declined at550℃. It was obtained that the TWIP Steel recrystallization appered at550℃and completed at about700℃. The electrochemical property of annealed TWIP steels changed with increasing temperature. corrosion potential didn’t change, the corrosion current decreased, the corrosion resistance becomed better.The positron annihilation study obtained the defects reduced with the increasing temperature in the process of recovery at100-600℃.The most of vacany disappeared at300℃. The recrystallization activation energy of TWIP steel calculated by JMAK formula was approximately351.25KJ/mol.In warm deformation process, the TWIP steel of cold rolling reduction rate of10%and20%appeared strengthening effect by dynamic strain aging. The mechanical properties TWIP steel at depressed rate of30%were affected by dynamic recovery. A lot of bending deformation twins appeared in warm deformation process.