结果表明：钢a和钢b冷轧低碳钢板焊接HAZ具有相同的显微组织特征，但铁素体晶粒大小不同。
The results obtained show the microstructure characteristics of the welded HAZ of the cold rolled low carbon sheets (steel a and b) are same, but the ferrite grain sizes are different.
此外，显微组织中网状、块状铁素体的存在以及螺纹表层脱碳使连接螺栓疲劳强度下降也是造成断裂的重要原因。
The existence of reticulation and mass shape ferrite, decarbonization at the screw thread surface layer which induced decline of fatigue strength of connecting bolt were also…
SS400的显微组织为铁素体、珠光体和少量的贝氏体。
The microstructures of super-steel SS400 were composed of ferrite, the pearlite and small amount of bainite.
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