| With the rapid progress in the structural materials of vehicle, how to reduce vehicle's weight, reduce fuel consumption,control pollution of the environment and improve the driving safety factor has aroused great concern in many automotive industries. According to some official statistics, after reducing vehicle's weight for 1%, the use of fuel can reduce by 0.6～1.0%. Therefore, make the car lighter will be an important way to reduce fuel consumption (about 50%). Although in recent years, many kinds of materials have been used to decrease vehicle's weight, the proportion of iron and steel has been decreased to some extent. But the steel has its unique advantages as car materials. It will dominate the automotive industry in the following years. The proportion of steel in automotive materials is up to 70～80%.In order to reduce weight, a large number of high-strength steel has become a surely trend. As the strength of steel improved, its molding processing performance was worse. It is worthy doing research on the high-strength, high ductility steel to achieve lighter car in recent years, which greatly facilitated the manufacture of high strength steel and application of technical progress.TWIP (Twinning Induced Plasticity) steel is a kind of steel with high plasticity index (60～80%), high strength (600～800MPa) and high strain hardening rate. Its impact energy absorption is doubled the usual high strength steel. Therefore, it can greatly reduce the body weight, increase body resistance to impact capacity, reduce the deformation of the body plate, and finally increase the safety of vehicle operation.In this work, TWIP steel is investigated by using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical workstation system test equipment to investigate the characteristics of different shape and mechanical properties; by using salt spray corrosion test and stress corrosion test, the corrosion mechanisms were evaluated; Finally, micro-hardness analysis, organization observations were carried out to discussed the formation of banded structure in TWIP steel. Analysis the causes and elimination of banded structure. The main conclusions are as follows:1. As-annealed and as-deformed TWIP steel placed in 5% NaCl salt spray corrosion conditions for different time. After this experiment, the corrosion rate of the former is large, the corrosion product picked off seriously, while the latter was corroded lighter. As automobile steel, TWIP steel shows low corrosion resistance in NaCl salt spray. It should be taken measures to improve TWIP steel's surface. After being deformed, TWIP steel change its microstructure. The increase of twin density and quantities of coincidence site lattice in grain boundary lead to increase corrosion resistance of the material. Therefore, in the corrosion protection study of TWIP steel, surface treatment and processing deformation can be combined to improve the corrosion resistance.2. The SCC of TWIP will be accelerated with the increase concentration of NaCl. When the strain rate of TWIP steel is 1×10-5, it has more stress corrosion sensitivity. Different concentrations of NaCl solution on the TWIP steel SCC was significant. After SSRT tests, TWIP steel's tensile strength decreased with the increasing concentration of Cl-. The time required for fracture was shortened. 3. Banded structure was the result of the presence of Mn and S, MnS inclusions make the band structure more apparent. When the carbon content is low, austenite will be unstable.
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