SMA490BW耐候钢接头组织及低温力学性能研究  

Study on Microstructure and Mechanical Properties of SMA490BW Weathering Steel Welded Joints at Low Temperature

作　　者：武永寿 张志毅 何永攀 陈辉[2] 李远星[2] 

机构地区：[1]中车青岛四方机车车辆股份有限公司,山东青岛266111 [2]西南交通大学材料科学与工程学院,四川成都610031

出　　处：《热加工工艺》2016年第13期51-54,共4页Hot Working Technology

摘　　要：主要研究了SMA490BW耐候钢MAG焊接接头组织,在0~40℃温度范围内对接头进行拉伸、冲击试验,在-40℃进行弯曲试验,检测接头低温力学性能,并对冲击断口进行了分析。结果表明,接头宏观形貌成型良好,未见裂纹和明显的夹渣等焊接缺陷;焊缝组织主要为先共析铁素体、针状铁素体和粒状贝氏体,焊缝层间区组织为细小等轴晶,层间过热区呈魏氏组织形貌,热影响区的过热区晶粒粗大,正火区为细小等轴晶,不完全重结晶区组织不均匀;在0^-40℃范围内,接头拉伸试样都断裂于母材,抗拉强度和屈服强度均随温度降低而提高,焊缝和母材冲击韧性随温度降低呈下降趋势,热影响区冲击韧性对温度敏感性较小且冲击韧性最好,焊缝冲击韧性最差;在-40℃时,母材断裂模式由韧窝转变为准解理断裂,焊缝为解理断裂,热影响区为韧窝断裂;接头在-40℃条件下弯曲性能良好,未出现裂纹等表面缺陷。Microstructure of SMA490BW weathering steel welded joints was researched. Tensile test and impact test for welded joints from 0℃ to -40℃ and bending test at -40℃ were carried out to investigate mechanical properties of welded joints at low temperature. Impact microscopic fracture of welded joints was also observed. The results show that macroscopic morphology of welded joints own good shape; cracks, visible inclusions and other weld defects are not found. Proeutectoid ferrite, acicular ferrite and granular bainite are primarily observed in the weld microstructure. Fine equiaxed grain is observed in the interlayer zone, while widmanstatten structure appears in the interlayer overheating zone. In the heat affected zone, coarse grains in the overheated zone and fine equiaxed grain in the normalized zone are observed, while in homogeneaus microstructure emerges in the incomplete recrystallized zone. In the temperature range of 0- -40℃, All the tensile specimens are broken at the base metal, and yield and tensile strength increases with the decreasing of the temperature. Impact toughness of weld and base material present a downward trend with the temperature decreasing. There is the best impact toughness in heat affected zone which is less sensitive to temperature. Impact toughness in the weld is the lowest. Fracture mode in base material transforms from dimple into quasi-cleavage fracture at -40℃. Fracture mode in the heat-affected zone is dimple fracture, while cleavage fracture is observed in the weld. Bending performance of welded joints is excellent at -40℃ ; cracks and other surface defects do not appear on the weld surface.

关 键 词：SMA490BW耐候钢 接头组织 低温力学性能 

分 类 号：TG407[金属学及工艺—焊接]