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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。
In this paper, we mainly studied the microstructure of MAG welded joints of SMA490BW weathering steel. The joints were subjected to tensile and impact tests at 0 ~ 40 ℃. The bending test was carried out at -40 ℃. The mechanical properties at low temperature were measured and the impact fracture was analyzed. The results show that the macroscopic morphology of the joint is well-formed and no defects such as cracks and obvious slag inclusions are observed. The weld microstructure is mainly pro-eutectoid ferrite, acicular ferrite and granular bainite, The microstructure is fine equiaxed grains, Wiegand microstructure is observed in the overheated zone, the grains in the overheated zone in the heat affected zone are coarse, the equiaxed grains in the normalized zone are small and the microstructure is not uniform in the recrystallized zone; In the range of 40 ℃, the tensile specimens of the joints were all broken in the base metal, the tensile strength and yield strength of the joints were both decreased with the decrease of temperature, but the impact toughness of the weld and base metal decreased with the decrease of temperature. The impact toughness of heat- The sensitivity is less and the impact toughness is the best and the impact toughness of the weld is the worst. At -40 ℃, the fracture mode of the base metal changes from dimple to quasi-cleavage fracture, the weld is cleavage fracture and the heat affected zone is dimple Fracture; joint under the conditions of -40 ℃ bending performance is good, there is no surface defects such as cracks.