| T4003belongs to low chromium ferritic stainless steel. Compared with the carbon steel and weathering steel, it has excellent corrosion resistance; Compared with the austenitic stainless steel and high chromium ferritic stainless steel, it has a very low cost. This makes it an economical stainless steel. For railway freight cars, the use of such kind of stainless steel wagon body can significantly reduce the weight of the vehicle, increase the loading capacity, save energy, reduce the maintenance costs and will have a long term and considerable economic benefits. However, there are some problems such as the large brittle tendency and intergranular corrosion sensitivity, the poor welding ability and welding coarse grain of the heat affected zone (HAZ), etc. Because of the existence problems, it is limited in the production and use. Therefore, it is necessary to conduct a further research about T4003.The main contents of this paper are as below:The microstructure and performances of T4003ferritic stainless steel with different repair times were studied through the conventional mechanical tests such as tensile, bending, impact, hardness and microstructure analysis. The fatigue performances of T4003ferritic stainless steel were studied by the pulsating tensile fatigue tests. The results of the tests were compared and analyzed within the welded joints without repair welding, welded joints of once and twice repair welding and the welded joints without repair welding (without controlling the interpass temperature).The results show that:there’s little effect of once and twice repair welding on the tensile, bending and impact properties. The microstructure of base metal is blocky ferrite and the grains extending along the rolling direction, the microstructure of welding seam is hybrid organization of austenite and8-ferrite, the microstructure of HAZ is ferrite and coarse grain martensite. Base material with different welding repair times has the same hardness. The hardness of the welding seam is almost similar. The effect of repair welding on the hardness of HAZ is not obvious. Along with the increase of welding repair times, fatigue strength of butt joints without the weld reinforcement has been significantly reduced:median fatigue strength of the welded joints of once repairing welding was reduced by about5.0MPa comparing to the welded joints without repair welding while the welded joints of twice repairing welding was reduced by about25.3MPa. Fatigue strength of butt joints without controlling the interpass temperature is more distinct (reduced about37.5MPa). Therefore, twice repair welding of T4003ferritic stainless steel welded joints is feasible. However, in order to obtain the excellent performance, it has to reduce the number of repair welding times, use small welding energy and strictly control interpass temperature during welding process. |
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