Research On Microstructural And Property Of GF08Al Narrow Strip With Ultra-fast Cooling And Annealing Process

In recent years, production of hot rolled narrow strip steel is growing fastly which makes narrow strip steel market competes fiercely, at the same time, quality of the narrow steel that the customers require is much more increasing, so the major critical issue that the steel companies are faced is how to yield stable, low-cost products which satisfy the market’s needs. Because of the important role of controlled cooling on the processing properties,mechanical properties, physical properties for the finished steel, it is more and more important to promote and applicate ultra-fast cooling technology on narrow strip steel production line. This research studies the regularity that ultra-fast cooling and annealing processes using on GF08A1narrow steel affect on the organizational performance, and its main contents and results are as follows:(1) Through the thermal simulation experiments, the high temperature deformation behavior and continuous cooling transformation behavior of the experimental steels have been studied and obtained true stress-true strain curve and static CCT curves of the experimental steels. The experimental steel stress exponent is4.73on regression, dynamic recrystallization activation energy is295.82kJ/mol, constructing a deformation resistance mathematical model of the experimental steels through a comprehensive analysis of the influence of deformation resistance on different deformation conditions, analyzing the transformation regularity of supercooled austenite of the experimental steels under different cooling conditions.(2) Through the process simulation experiments, the variation regularity of the experimental steel microstructure and hardness in different deformation temperatures, coiling temperatures and cooling rates on the simulator have been studied. Low deformation temperature makes structure refinement, but not lower than the deformation temperature of850℃, when the coiling temperature is low, the organization ferrite grain size is reduced, but when the temperature is too low, there will be tissue temperature phase transformation structure, which will deteriorate the uniformity, the coiling temperature should be selected between600℃-700℃, the faster cooling rate can refine the organization, and improve strength. (3) Based on the results of thermal simulation experiments, we have conducted the hot-rolled experiments in the laboratory, comparatively analysed the regular effects of different finishing temperature, coiling temperature and cooling rate on microstructure and mechanical properties of hot-rolled steels, resulted this experiment for the optimal parameters window:the finishing temperature controlled at870℃-890℃, the coiling temperature is620℃-640℃, the cooling rate is50℃/s-60℃/s, the experimental steels can get better mechanical properties.(4)Through designing cold-rolled annealing process for experimental steels, we have studied the regular effects of annealing temperature and annealing time on cold-rolled annealed sheet structure, properties and texture, with the extension of the annealing temperature and the annealing time, the construction refines, strength decreases, the elongation ratio of plastic strain shows a tendency to rise, and the texture component of{111} enhances, the texture components of{001} weakens, thereby improving the deep-draw and forming performance of the experimental steel improves.