The Research On Corrosion And Mechanical Properties Of 301L Stainless Steel For Rail Vehicles

301L austenitic stainless steel has excellent corrosion resistance,cold forming processability and better comprehensive mechanical properties,so it’s widely used as body materials for rail vehicles.In order to meeting the requirements of lightweight,cost-saving and service life extension,optimizing the chemical composition of cold-rolled 301L stainless steel from the perspective of alloying,studying the influence of main alloying elements on its mechanical properties,and evaluating the surface corrosion resistance of 301L stainless steel is of great significance in actual production.In this paper,the influence of the three main alloying elements of Ni,N and Mn on the microstructure and mechanical properties of 301L stainless steel was studied by the aluminothermic method,and the electrochemical performance and salt spray corrosion resistance and stress corrosion resistance of 301L stainless steels of three strength grades of DLT（Deadline Tensile Strength）,ST（Special Tensile Strength）and HT（High Tensile Strength）in NaCl corrosion medium were further evaluated,which could provide a certain technical reference for the application and promotion of stainless steel.The effects of different contents of Ni,N and Mn on the microstructure and tensile properties of cold-rolled 301L stainless steels were studied.The results show that with the increase of Ni content,the elongation of stainless steel increases,but the tensile strength decreases;the increase of N content reduces the martensite content of the cold-rolled lath first and then increases,and when the N content is moderate,301L stainless steels have both high strength and ductility;and the influence of Mn on the structure and mechanical properties of 301L stainless steels tend to be consistent with Ni;when Ni content is 6.75%,N content is 0.10%,and Mn content is 1.42%,301L stainless steel has good comprehensive mechanical properties.Studying the corrosion resistance of DLT,ST and HT strength grade stainless steels in the corrosive media of different NaCl concentrations by the electrochemical method.The results show that with the increase of the strength grade,the martensite content increases,the self-corrosion potential E_corrof DLT,ST and HT stainless steels shift negatively,and the corrosion current density I_corrincrease sequentially.With the increase of the strength grade,the corrosion tendency increases and the corrosion rate is accelerated.The results of EIS show that the improvement of the strength level reduces the resistance of the passivation film and the charge transfer resistance,and the corrosion resistance of stainless steel decreases with the increase of the NaCl concentration.The corrosion resistance of three strength grades of 301L stainless steels under the condition of neutral salt spray test were studied.The results show that the three strength grades of stainless steels have a higher corrosion tendency and a faster corrosion rate in the initial stage of corrosion,but as time goes by,the corrosion rate gradually decreases and then tends to stop.The corrosion product layer is mainly Fe oxides and a small amount of Cr and Ni oxides,and corrosion is easy to nucleate at the MnS inclusions.Studying the corrosion resistance of three strength grades of 301L stainless steels under constant deformation stress corrosion test conditions,the results show that HT stainless steel has higher stress corrosion resistance,DLT and ST stainless steels have higher stress corrosion sensitivity,and the corrosion is mainly concentrated in U-shaped tips and cold bends with a higher degree of deformation.The corrosion products are needle-like（Fe,Cr,Ni）_mO_n,and they are gathered into a layer to cover the surface of the material.As the concentration of the NaCl solution increases,the stress corrosion sensitivity of the three strength grades of stainless steels increase.