Analysis Of Microstructure Evolution During Cooling Of Hot Rolled Double-phase Steel Coil

With the development of all kinds of high-strength steel products and the continuous improvement of users’ requirements for shape quality,the problem of "regenerative" shape in the process of rewinding after rolling and coil cooling becomes more and more prominent which becomes one of the difficulties in the production control of all kinds of advanced high-strength steel.In rolling,the plate shape is good,but after unwinding,there will be partial or full-length billows,billows in the inner ring,billows in the outer ring,single side waves,transverse warping(C warping)and other defects.Laminar cooling,coil tension,cooling mode after coil and strip crown are all important factors affecting the mechanical properties of strip.Different cooling rates at different locations make the evolution of tissues inconsistent.The combined effect of the stress generated in the coiling process,the thermal stress and the microstructure stress generated in the cooling process will produce plastic deformation in the steel coil,which will change the shape of the plate after rolling.In order to explore this change rule,this paper analyzes and studies the temperature field,tissue evolution and tissue stress by combining with the data in the actual production.Firstly,the temperature field model is established according to the actual production environment and the finite difference method is used to solve the temperature field according to the heat transfer theory.The initial cooling conditions of steel coil are determined by theoretical analysis,and thermophysical parameters related to the material are determined by JMatPro software.Secondly,the phase equilibrium temperature and the starting temperature of the phase transition of each tissue were calculated,and the incubation period model and tissue evolution model under continuous cooling conditions were established by using the additive law and the additive law of the inverse formula according to the classical jiangbanyibin theory,and the computational parameters of the model were modified.Finally,to establish the mathematical model of organizational stress,in combination with the volume fraction of calculated according to elastic mechanics theory,according to the rate of change of volume gives a method of calculating tissue strain,according to the law of conservation of quality on tissue strain calculation formula of combined balance equation,physical equation,geometric equation on the calculation equation for organizational stress,organizational stress calculation model,calculation of circumferential stress and stress by the organization.To provide theoretical support for the "regeneration" of the plate type,improve the performance of the plate,improve the quality of the product.