Study On Effect Of Asymmetric Hot Rolling Process On Microstructure And Mechanical Property Of Vessel Steel

The goal of improving strength and toughness simultaneously is always pursued by science researcher who devoted into steel.Especially,obtaining fine grain is one of the most practical methods of improving strength and toughness simultaneously. Severe plastic deformation(SPD) and thermo-mechanical control process(TMCP) are major ways of obtaining fine grain.Shear deformation of asymmetric rolling technology is one method of SPD.And asymmetric rolling is also put into practice. So, asymmetric rolling combines SPD and TMCP. Furthermore,it has the advantages of obtaining fine grain of metal material,decreasing rolling pressure and increasing pass reduction rate. Given those,asymmetric rolling technology is applied to steel material of12Cr1MoVR vessel steel to study on the effect of asymmetric hot rolling process on microstructure and mechanical properties of steel material,aiming at providing parameters of theoretic research and practical application. Some conclusions are following:(1)The difference of microstructure along the whole height of hot rolling tested steel12CrlMoVR is investigated with symmetric monotonic rolling and asymmetric monotonic rolling of mismatch1.2.The average grain size of asymmetric monotonic rolling with five different position along the height faster roller side,1/4h to faster roller side,center,1/4h to slower roller side, slower roller side are more and more larger from the surface to center. The position of min grain size is faster roller side. With similar process parameter, the difference of average grain size of symmetric monotonic rolling is tiny.Beside, grain size of asymmetric rolling is smaller than symmetric rolling in the same position.(2)The effect of shear deformation on shear bond and precipitation morphology is studied.Compared to symmetric rolling, shear bond is found in tested steel of asymmetric rolling.Its grain size in some area is coarser than other area.The VC precipitation distribution of symmetric monotonic rolling is parallel to each other with some particle being coarse. However, the asymmetric mono tonic rolling is complex.Several patterns is found.Some of VC precipitation is parallel to each other.Some of them precipitation is similar to interphase precipitation.The form of random precipitation is also discovered.(3)The law of reversal asymmetric rolling on grain size of tested steel is investigated.The trend of grain size of reversal asymmetric rolling is familiar to monotonic asymmetric rolling.However, effect of reversal asymmetric rolling is smaller monotonic asymmetric rolling. The grain size of reversal symmetric rolling is homogeneous.The difference of fracture mechanism and mechanical properties between asymmetric rolling and sym rolling is studied. Impact energy of monotonic asymmetric rolling is higher than monotonic symmetric.The fracture mechanism of monotonic asymmetric rolling is ductile fracture,while,the one of monotonic symmetric rolling is formed of brittle and ductile fracture.The fracture mechanism of reversal asymmetric rolling and reversal symmetric rolling is ductile fracture.However,the trend of ductile fracture in reversal symmetric is discovered. The strength of monotonic asymmetric rolling is smaller than monotonic symmetric rolling.The strength of reversal asymmetric rolling is larger than reversal symmetric rolling.