Dynamic Strain Aging And Microstructure Control Of Cr-Ti-B Micro-Carbon Steel With Ferrite Temperature Deformation

The advanced high-strength steel(AHSS)produced by the ferritic zone rolling technology improves its strength compared to the conventional austenitic zone rolled products,and the rolled plates produced by the ferrite zone rolling have better deep drawing performance.The deep-drawn properties of cold-rolled and annealed products obtained by further processing of the rolled sheet in the ferrite area will be further improved.However,the presence of solid C content during the warm rolling process results in a negative strain sensitivity coefficient and dynamic strain aging(DSA)in the stress-strain curve.Therefore,this paper takes Cr-Ti-B series micro carbon steel as the research object,using SEM,EBSD,TEM and other technical systems to study the influence of alloy elements and deformation processes on the behavior of DSA,revealing the formation rules and production mechanisms of DSA and the deformation process The evolution of organization and texture in China.This will further enrich the deep-drawing texture strengthening theory of micro-carbon steel to provide theoretical support for the lightweighting of AHSS.The main research of this study are as follows:(1)During the low-temperature deformation process of Cr-Ti-B series micro-carbon steel,sawtooth fluctuation and dynamic strain aging phenomenon(DSA)occur in the deformation temperature range of 300-450 ?.The reason for the DSA effect lies in the interaction of solute atoms and movable dislocations and the precipitation phase pinning dislocations,hindering the movement of dislocations.The addition of high content of Cr element will reduce the critical activation energy of sawtooth phenomenon,and promote the precipitation of carbides,so that the peak stress plateau can be smoothed and the temperature range of dynamic strain aging phenomenon appears.(2)The low-temperature rolling microstructure of Cr-Ti-B micro-carbon steel shows that there are intragranular shear bands in the low-temperature rolling samples,and the density of the shear bands reaches the maximum at 450 ?.The existence of dynamic strain aging at 250 ? and 350 ? inhibited the formation of shear bands.The addition of a high content of Cr element will refine the grains,promote the formation of carbides and lead to an increase in the density of the shear band.(3)Cr-Ti-B series micro-carbon steel has strong {111} and {110} textures and high distortion at 350 ?,450 ?,and 550 ? rolling temperatures.Among ? texture orientation density values,450 ? is similar to 550 ?,and both are higher than 350 ?;among ? texture orientation density values,the orientation density value of 450 ? is also the largest,followed by 350 ?,The orientation density value at 550 ? is the smallest.The addition of high content of Cr element suppresses the ? texture and ? texture at the rolling temperature of 350 ?,promotes the ? texture at 450 ? and 550 ?,and the ? at the rolling temperature of 450 ? and 550 ? The texture change is not obvious.