Recrystallization And Precipitation During Finishing Rolling Of High Nb-Ti Non-oriented Silicon Steel For New Energy Vehicle

High Nb-Ti non-oriented silicon steel for new energy vehicles requires high magnetic induction,low iron loss and high strength requirements.By adding Nb and Ti elements to the traditional non-oriented silicon steel composition system,the strength of the materials used in the electric motors of new energy vehicles can be improved to meet the requirements of the materials used.However,the existence of Nb and Ti elements in the experimental steel and their influence on the structure and recrystallization behavior are not yet known.In the production process of non-oriented silicon steel,the hot rolling process is an important step in the production process.The heating process,recrystallization law and precipitation behavior will all affect the hot rolled structure.Due to the heredity of the structure,the structure and properties of the finished product are affected.Studying the heating process and the relationship between precipitation and recrystallization in hot rolling,and analyzing the effects of Nb and Ti elements have important guiding significance for the development of a new composition system of non-oriented silicon steel for new energy vehicles.The results show that when the heating temperature is 1200?and the holding time is 40min,the grain size is about 1 mm and the microstructure uniformity is good.The solid solution content of Nb is 96.58%and that of Ti is 86.28%.The amount of undissolved second phase is less.The large particles are mainly on the grain boundary and the small particles are in the grain.In single pass deformation,the deformation resistance decreases with the increase of deformation temperature.At each deformation temperature,the deformation resistance increases slightly when the deformation rate increases from 0.5 s^-1to 1 s^-1.When the deformation rate increases from 1 s^-1to 5 s^-1at 900?,the deformation resistance increases about 25MPa.Combined with EBSD analysis,it is considered that dynamic recrystallization does not occur in each process.When the deformation amount is 31%,the softening rate changes from 45%to 41%at900?and holding time from 1 s to 100 s.When the deformation temperature is 1000?and the holding time is from 1 s to 100 s,the softening rate increases from 53%to 68%.When the deformation is 50%,the softening rate decreases from 68%to 57%at 900?for 10s to 100s,and it is in the partial recrystallization zone.When the deformation temperature is 1000?,the complete static recrystallization occurs under each holding time.When the holding time is from10s to 100s,the softening rate increases from 85%to 99%.The results of rolling test show that when the deformation temperature is 1000?,the deformation amount is 31%,and the holding time is increased from 10s to 100s,the precipitation amount of Nb does not change obviously,but the precipitation amount of Ti increases by 2.45%.When the deformation temperature is 1000?,the deformation amount is50%,and the holding time is increased from 10s to 100s,the precipitation amount of Nb increases by 1.67%,and the precipitation amount of Ti decreases slightly.When the deformation temperature is 900?,the deformation amount is 31%,and the holding time is increased from 10s to 100s,the precipitation amount of Nb and Ti increases by 2.95%and1.45%,respectively;When the deformation temperature is 900?,the deformation amount is50%,and the holding time is increased from 10s to 100s,the precipitation amount of Nb and Ti increases by 1.06%and 3.40%,respectively.The results show that the precipitation rates of Nb and Ti are increased at 900?compared with those before rolling.The precipitation rates of Nb and Ti are 1.17%and 1.15%respectively at 31%deformation for 10s.When the deformation is 50%,the precipitation rates of Nb and Ti are 4.66%and 4.53%respectively.It can be seen that the precipitation rates of Nb and Ti increase with the increase of deformation.When the holding time is 100s,the precipitation rates of Nb and Ti are 4.12%and 2.60%respectively when the deformation is 31%,and 5.72%and 7.93%respectively when the deformation is 50%.With the increase of deformation,the precipitation rate of Nb increases slightly,and the precipitation rate of Ti increases significantly.When the deformation temperature is 1000?and the deformation amount is 31%,the morphology of precipitates is elliptical.With the decrease of deformation temperature and the extension of holding time,the degree of deformation increases.The morphology of precipitates tends to be long strip,and the size decreases from 400 nm to 200 nm.The amount of precipitates increases,mainly distributed on or near the grain boundary.