Study On Microstructure Of Fe-6.5%Si Steel And AZ31 Magnesium Alloy In Rolling Process With Heated Roller

Such as silicon steel,titanium alloy,magnesium alloy and high strength steel are widely applied in the aviation and aerospace,electronics,medical instruments,chemical engineering.Due to a series of problems such as large deformation resistance,seriously working-hardening and difficult plastic deformation,which restrict the rolling parameter of the strip and deep study and application of the products.However,it is the key factor that the roller is preheated to maintain the deformation temperature to improve plastic ability of the alloy strip in rolling process.In this study,the typical difficult-to-deform alloy is chosen as research object,the rolling experiment and microstructure and properties analysis are taken to study and explore regularity of microstructure change of Fe-6.5%Si and AZ31 alloy in the wide range deformation temperature in rolling process with heated roller.The main contents and conclusions are as follows:1.Fe-6.5%Si steel was rolled of single compression deformation in the temperature of 300??600 ? and strain rate of 0.05 s-1?5 s-1.Due to obvious work-hardening,the flow stress increases with the increment of strain rate and the reduction of temperature.When the flow stress reaches the peak stress,because of work-hardening rate is almost closed to softening rate,the flow stress enters the stable state.An equation of Fe-6.5%Si steel in the work-hardening stage is constructed by non-linear regression and linear fitting.Described the establishment as follow:?=(2674.54-2.06T)·?0.07541?-0.021exp(711/T)2.By analyzing the curve of the deformation temperature of 800 ??1100 ? and strain rate of heat flow stress 0.01 s-1?1 s-1 condition,it can be known that the material has dynamic recrystallization and peak flow stress obviously increase with increasing of the strain rate with reduction of the deformation temperature.Using Arrhenius equation model deduced Fe-6.5%Si steel peak stress constitutive relation,when the peak flow stress,A material structure factor is 2.16 ×10-14s-1,stress factor a is 0.013591 Mpa-1,stress exponent n is 2.495333,and deformation activation energy Q is 342.199 KJ/mol.3.Analysis on microstructure of Fe-6.5%Si steel in warm rolling and annealing process at the roller preheating temperature of 300?,it can be found that grains of Fe-6.5%Si in warm rolling changed obviously.With the increase of temperature,deformation mechanism changes from twinning to recrystallization.Continue to increasing temperature,recrystallization grains grow up.There are recrystallization grains after annealing and grain size is slightly different.Because of large deformation resistance and poor thermal conductivity of the Fe-6.5%Si steel,thus the ratio of single reduction is limited in the warm rolling with heated roller.4.In the condition of conventional rolling,the temperature of the strip reduced too fast after the strip comes out of the furnace,so that microstructure exists twinning in the rolling process.The annealing microstructure is static recrystallization grain after single rolling pass and grain size is fine and uniform.With the increase of rolling pass,annealing microstructure appears incomplete grain and fine recrystallization grains mixed large grains and exists twinning,which is due to inhomogeneity of the temperature and deformation.Therefore,interpass annealing leads to recrystallization grain significantly grow up and is unhelpful for the grain to refine.5.In order to control heterogeneity of deformation and weakening of grain refining,using inductive heating technology to achieve stability of the temperature in the rolling process and study the regularity of microstructure change at different roller surface temperature and different heating conditions.When temperature of the roller surface reduces,grains exist obvious twinning.Above 250? of the roll temperature,it can be found that microstructure occurs significantly dynamic recrystallization.With the increase of the temperature of roll surface,dynamic recrystallization is more sufficient.When the temperature is 300?,the grains are almost equiaxed grains and the average grain size of 1 ?m?2 ?m,and grains refinement is very obvious.Therefore,heated roller can not only realize the large amount of reduction and can effectively refine grains.