1. Characteristics of welding direction and angle
1.1 Basic concepts
For gas metal arc welding, when the operator holds the welding gun with his right hand, it is welded from right to left.
The nozzle of the welding gun has an obtuse angle (> 90°) with the welding direction, which is called left welding method; Welding from left to right, with an acute angle (<90°) between the welding gun nozzle and the welding direction, is called right welding method.
If the operator holds the welding gun with his left hand, the welding direction is just the opposite.
Figure 1 shows the schematic diagram of the left welding method and right welding method.
Fig. 1 Schematic diagram of left welding method and right welding method
The angle between the axis of the welding gun and the surface of the weldment is the working angle;
In the plane where the axis of the welding gun and the welding direction are located, the angle between the axis of the welding gun and the straight line perpendicular to the welding direction is the walking angle.
Fig. 2 (a) shows the working angle and traveling angle of the fillet weld, and Figure 2 (b) shows the working angle and traveling angle of the butt weld.
(a) Working angle and traveling angle of fillet weld (T-joint)
(b) Working angle and traveling angle of butt weld (butt joint)
Fig. 2 Schematic diagram of working angle and walking angle
Generally, the working angle of fillet weld is 45°, and that of butt weld is 90 °;
According to the different welding directions, the walking angle can be divided into rake angle and caster angle.
When welding in the right direction, it is called caster angle, and when welding in the left direction, it is called rake angle.
1.2 Effect on weld formation
When the welding direction and angle are different, the action mode of arc and weldment is different.
Most of the arc acts directly on the weldment during right welding, while most of the arc acts on the liquid molten pool during left welding.
Therefore, under the same welding current, arc voltage and welding speed, the weld width and penetration are different.
Fig. 3 is the schematic diagram of welding direction and angle and its influence on weld formation.
(a) Schematic diagram of influence of butt weld welding direction and travel angle on weld formation
(b) Schematic diagram of influence of fillet weld welding direction and travel angle on weld formation
Fig. 3 Schematic diagram of welding direction and angle and its influence on weld formation
In addition to the influence on the weld formation, the welding direction and walking angle also have a certain influence on the observation effect of the welder’s weld pool, the size of spatter and the effect of gas protection.
During left-hand welding, the operator shall observe the welding arc and welding pool from one side of the welding arc at a 45°～70°angle, which is easy to observe the melting of the protruding end of the welding wire and the change of the weld pool;
When welding in the right direction, the welding gun blocks the operator’s line of sight and is difficult to operate.
Fig. 4 is a schematic diagram of the operator’s viewing angle of left welding (flat welding position).
Fig. 4 Perspective of left welding (flat welding position) operator
At the same time, when the travel angle is large, the air is easy to be drawn into the weld and form pores.
In order to prevent pores, the downward travel angle is usually 10°～15°.
In addition, the welding direction also has the characteristics of large left welding spatter and small right welding spatter.
2. Application of welding direction and angle
Since the welding direction and angle have an important impact on weld formation, spatter size, gas protection effect, etc., in the actual welding production, according to different technical requirements and actual conditions, left welding and right welding also have different application occasions.
See the attached table for the practical application of typical welding directions.
Table – Practical application of welding direction
|Application||Right welding method||Left welding method|
|Flat welding||sheet||Not suitable, because large penetration is easy to burn through||Suitable, because the baking depth is shallow and the weld is flat.|
|plate||Suitable, because it can ensure good fusion||Not suitable, because of the shallow penetration, the penetration cannot be guaranteed.|
|Transverse welding||Single pass welding||Not suitable because narrow and deep welds tend to form convex welds||Suitable, because it is easy to obtain wide and flat welds.|
|Multi pass welding||Suitable for backing welding and filling welding||Suitable for cover welding|
|Vertical upward welding||arbitrarily||unsuited||fit|
|Vertical downward welding||arbitrarily||fit||unsuited|
3.1 The left welding method has the characteristics of shallow penetration and wide weld bead, which is suitable for thin plate welding;
The right welding method has the characteristics of large penetration and narrow weld bead, which is suitable for medium and heavy plate welding.
3.2 The walking angle is small, which has the characteristics of large melting depth and good molten pool protection effect;
When the travel angle is large, it has the characteristics of small penetration and poor weld pool protection effect.
When the travel angle is 10°～15°, the weld pool protection effect is good.