When arc welding is used to weld butt joints, it is usually determined whether to reserve a gap, the size of the gap, and the form of the groove according to the thickness of the welded plate. When other conditions are constant, the larger the size of the groove or gap, the smaller the reinforcement of the welded seam, which is equivalent to the decrease of the weld position, and the fusion ratio decreases at this time. Therefore, leaving a gap or beveling can be used to control the size of the reinforcement and adjust the fusion ratio. Compared with opening the groove without leaving a gap, the heat dissipation conditions of the two are somewhat different. Generally speaking, the crystallization conditions of the groove are more favorable.

When the welding wire is tilted forward, the effect of the arc force on the metal in the molten pool is weakened, the liquid metal layer at the bottom of the molten pool becomes thicker, the penetration depth decreases, the depth of the arc diving into the butt welding flange decreases, and the moving range of the arc spot expands. The melt width increases and the reinforcement height decreases. The smaller the wire forward angle α is, the more obvious this effect is. The opposite is true when the wire is tilted back. When electrode arc welding is used, the electric back tilt method is mostly used, and the inclination angle α is between 65° and 80°.