Formation Mechanism Of Recrystallization Texture Of Fine-grain High-strength IF Steel In Annealing Process

With the rapid development of automobile manufacturing industry of China,Lightweight automobiles is to become the inevitable trend of modern automobile development. The main way of lightweight is the thinning of the steel plate, but the safety performance of cars cannot be reduced at the same time. So the requirements on the strength and deep drawing performance of the automotive steel are higher and higher.In this paper, containing Nb fine-grain high-strength IF steel as the research object, the batch annealing experiments were completed in the laboratory.The microstructure of the experimental steel at different annealing temperatures and annealing time are analyzed by using metallographic analysis technology; Use EBSD, X ray diffraction and TEM complex to study the effect of different annealing conditions on the recrystallization texture formation mechanism and the second phase particle precipitation behavior influence on recrystallization texture formation.The research contents are as follows:1.With the increase of temperature, the grain of tested steel recrystallizates completely and the grain size tends to be uniform. But when continued to raise the temperature, the grain size coarsening is not obvious. And with the extension of holding time at the same high temperature, the grain size coarsens. Recrystallization activation energy is low at low temperature, that makes the recrystallization slow. The number of recrystallization grain is small at the same holding time.2.Through the experimental analysis and theoretical proof, recrystallization mechanism of tested steel is oriented nucleation and selective growth. And{111}<112> recrystallization grain is formed within the same orientation grain which is deformated in the way of "in situ" pattern. While {111}<110> new grain is formed on the {111} deformated grain boundary.3.The emergence rate of ΣCSL is related to grain size uniformity. The more uniform the grain size is, the bigger emergence rate will be. The grain size and uniformity are influenced by annealing temperature and holding time. With the increase of annealing temperature and holding time, The changing trend of emergence rate of ΣCSL grain boundary is the same, which is increasing first then decreasing.4.With the change of the annealing temperature and holding time, the changing trend of second phase particles is the same. With the increase of annealing temperature and holding time, the size of second phase particle becomes bigger, and number is decreased, the distribution of it changes from dispersion to sparse.5.The experimental results show that pinning effect of second phase particles mainly occurs in the process of grain growth. With the extension of holding time, the second phase particles gather and grow up, pinning force reduces, so the recrystallization grains grow up. Under different holding time, the changing tent ofrecrystallization grain size is significantly. The changing trend of recrystallization grain size under different annealing temperature is not obvious.6.The experimental results show that precipitation of second phase particles affect the crystal rotation., makes the {110}<110> and {112}<110> texture content reduced.