The microstructure of welding seam is affected by cooling rates.The microstructure of welds consists of dendritic structure near melted line and equiaxed grain at the centerline of welding seam.

• 冷却速度对显微组织的形成影响明显，在靠母材的焊缝两侧，焊缝的显微组织为树枝晶，而焊缝的中心为等轴晶；