Study On Deformation Behavior And Strain Rate Sensitivity Of The Cold-rolling Austenitic Stainless Steel In Different Directions

With high nitrogen metastable 301L cold-rolling series steel is the main material on creating rail vehicles,which is the applied austenitic stainless steels with the lowest stacking fault energy and stability in engineering, currently.Because it can produce strain-induced martensite strengthening phase by means of plastic deformation, and therefore it has a strong work-hardening capacity. At present, the domestic cold-rolling stainless steel sheet has been put into use,but owing to the lack of basic research,there are many of difficulties be solved urgently during use, such as plastic molding difficult, poor molding quality and so on. In this paper,selecting the increasing levels of three hardening strength domestic cold-rolling plate 301L-DLT, 301L-ST and 301L-MT for study.Different direction and different strain rate uniaxial tension and deep drawing forming tests are to research the properties of the plastic molding for different levels sheets,and investigate the feasible method of improving the performance.The results show as followed:with the increasing levels of hardening strength plate,the disparity of the yield strength between the plate and the rolling direction, perpendicular and 45°angle is larger. The same plate with different direction different to the yield strength, the largest is the rolling direction, and perpendicular to the direction is the smallest, and 45°angle is the middle. The strain-induced martensite of the plate for the different direction is different also. The least amount of martensitic is rolling direction,leading its worden-hardening rate to be the lowest; while the highest martensite hardening capacity and worden-hardening rate is vertical direction. Along with the increasing of the angle,the plastic strain ratio r of the different hardening strength grade sheet decreases.The higher hardening intensity level,the biger the plastic strain ratio r and plane anisotropy△r is.So it causes sheet anisotropy and the difficulty of forming increasing,and molding performance degradating. Higher strength grade sheet can be adjusted to position of the forming sheet so that it can improve the forming quality. The strain rate sensitivity of the 301L cold-rolling series steel increases with the hardening intensity level decreasing; 301L-DLT has the maximum strain rate sensitivity,and 301L-MT's sensitivity is the minimum. So the properties of plastic molding for lower strength grade lumber can be improved by reducing the strain rate.The deep-drawing samples of the three hardening strength sheet appear lugs in rolling direction and the vertical direction;and the higher hardening strength level, the more obvious the lug is.When the rate of dieing speeds up, the plane strain zone expands,which will increase the occurrence of plastic instability. The results show that by adjusting the plate position and reducing the strain rate to improve the quality of sheet metal forming is feadsible.