Effect of annealing temperature on microstructure and properties of cold-rolled multiphase steel
Taking cold-rolled high-strength duplex steel for automobiles as the research object,the effect of annealing temperature on the microstructure and properties of duplex steel for automobiles has been studied by SEM,EBSD,XRD,and uniaxial tensile testing methods.The results show that the microstructures of experimental steel after annealing at different temperatures and air cooling are all ferrite,martensite,and bainite.The higher the annealing temperature,the more martensite and bainite content,and the less ferrite content.The yield strength and tensile strength of the test steel show a trend of first increasing and then decreasing with the increase of annealing temperature,while the elongation is the opposite.The XRD analysis results indicate that after annealing at different temperatures,all austenite in the test steel undergoes transformation,and no residual austenite exists when air cooled to room temperature.When the annealing temperature is 850 ℃,the experimental steel obtains the best mechanical properties,with a tensile strength of 990 MPa,a yield strength of 818 MPa,an elongation of 23.3％,and a strength plastic product of 23.07 GPa·％.
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