本論文研究SN490B結構用鋼，經GMAW銲接後，銲道橫截面之硬度變化、熱影響區之衝擊韌性及銲道、熱影響區、母材的顯微組織及織構。
實驗結果顯示，粗晶粒熱影響區的硬度最高但衝擊韌性低，破裂面呈現劈裂；顯微組織在銲道以晶界肥粒鐵PF（G）、肥粒鐵側板FS（SP）及針狀肥粒鐵AF為主，粗晶粒熱影響區以上變韌鐵UB為主；在多重銲道中，前銲道組織會受後續銲道再熱影響再結晶而使晶粒細化；母材在{110}的極圖上呈現較弱的{110}纖維織構，低溫退火區無特定織構且晶向也沒有集中在特定方位上。再熱細晶粒區的晶粒成長方向呈現隨機且均勻分佈。在ND的晶向分佈圖中，粗晶粒熱影響區的晶粒在[101]至[112]之間的晶向成長較快，熔合區得晶粒則偏向[001]，銲道區的晶粒則偏向[111]，從{110}的極圖上粗晶粒熱影響區及銲道區整體上呈現{001}、{112}及{111}的混合織構。

The microstructure and texture of SN490B construction steel GMAW weldment was studied.
As a result, the hardness of GCHAZ was highest and the impact toughness was lowest than that of other. The fracture surface of impact specimen was cleavage. The microstructure of weld metal was consisted of grain boundary ferrite PF(G), ferrite side plate FS(SP) and acicular ferrite AF. The microstructure of GCHAZ was upper bainite FS(UB). The grain of GCHAZ and weld metal had been finer due to the effect of the following welding. The {110} pole figure of base metal has weak {110} fiber texture and the texture of the temper zone and the reheated grain-refined zone were random. The grain was easily to growth with crystal orientation between [101] and [112] for GCHAZ, [001] for fusion zone and [111] for weldment shown on orientation map of ND. The {110} pole figure of GCHAZ and weldment has {001}, {112} and {111} mixed texture。

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