Research Of Weldability And Neutral Salt Spray Corrosion Performance Of WHT1300HF High Strength Steel

It is forecasted that the amount of cars in China will be over 200 million in 2020 by the ministry of industry and information technology equipment industry division. In this case, the problems of energy and environment will become more prominent. Light-weight of car body can reduce energy consumption, emissions and pollution. The low-alloy high strength steel WHT1300 HF has high strength, good formability and weldability, it is an effective way of saving energy, reducing emission and ensuring the safety performance of vehicles. In addition,the market competition of automobile is more and more fierce. High salt content, moist sea air,acid rain will accelerate corrosion of the car, so the corrosion resistant quality has also become one of the focus of the auto market.Firstly, the WHT1300 HF high strength steel’s solid phase transformations in the processes of heating-up were observed in-situ by the laser scanning confocal microscope（LSCM）. The phase transformation process and transformation temperature from ferrite（α） to austenite（γ）, then to ferrite（δ） can be observed directly by CLSM.Secondly, Resistance spot welding is a high reliability, efficient and autom-atable connection method. It is one of the most widely used techniques in automobile production.The influence of the welding current, welding time and cooling time on tensile shear properties of the welded joint were analyzed. The result showed that the effect of three parameters on welded joints decreases in the sequence: welding current > welding time >cooling time. The microstructure of base metal is mainly ferrite and pearlite. The weld metal is lath martensite. The microstructure of HAZ is more complex, it mainly contains ferrite,pearlite and martensite. The failure modes of welded joint are button pull-out and interfacial fracture. The mechanical model of welded joint is established to analysis stress,the experimental result of critical nugget diameter is about 7.6mm, which is well coincided with theoretical calculation with a result of 7.53mmFinally, the corrosion resistance of two kinds of microstructure samples（（1） pearlite +ferrite,（2） martensite）of WHT1300 HF steel in the neutral salt spray environment was studied.The results showed that serious all-around corrosion happened to the samples after corrosion of 96 h. As the salt fog corrosion time extended, the trend of corrosion rate increases at first then decreases. The corrosion products are mainly α-Fe OOH, γ-Fe OOH and Fe₃O₄. In addition, it can obtain that the weight loss and corrosion rate of ferrite and pearlite is higher than martensite’s.