The temperature of the molten pool directly affects the welding quality, the temperature of the molten pool is high, the molten metal is large, the molten metal is good, and it is easy to fuse, but when it is too high, the molten metal is easy to flow down, the back of the single-sided welding is easy to burn through, forming a welding tumor, and the forming is difficult to control, and the joint is plastic and bending is easy to crack.
When the temperature of molten pool is low, the molten pool is small, the molten iron is dark, the fluidity is poor, and the defects such as non-penetration welding, non-fusion and slag inclusion are easy to occur.
The temperature of molten pool is closely related to welding current, electrode diameter, electrode Angle, arc burning time, etc. The following measures are taken to control the temperature of molten pool according to relevant factors.

1. Welding current and electrode diameter
The welding current and electrode diameter are selected according to the weld space position and welding level. In opening welding, the welding current and electrode diameter are larger, and the vertical and horizontal position are smaller.
For example, the sealing base of 12mm flat butt welding uses φ3.2mm electrode, welding current: 80-85A, filling, covering layer uses φ4.0mm electrode, welding current: 165-175A, reasonable selection of welding current and electrode diameter, easy to control the temperature of the weld pool, is the basis of weld forming.

2, transport method
The temperature of the circular groove groove weld pool is higher than that of the crescent groove groove, and the temperature of the crescent groove groove is higher than that of the serrated groove groove. In the bottom layer of the 12mm flat welding seal, the serrated groove groove is adopted, and the swing amplitude and the stop on both sides of the groove are used to effectively control the temperature of the weld pool, so that the size of the weld hole is basically the same, and the probability of no welding bump and burning through at the root of the groove is reduced. The lack of penetration has been improved, so that it is no longer difficult to form both sides of single-side welding in flat welding.

3, electrode Angle
When the Angle between the electrode and the welding direction is 90 degrees, the arc is concentrated, the molten pool temperature is high, the Angle is small, the arc is dispersed, and the molten pool temperature is low, such as the bottom of the 12mm flat welding seal, the electrode Angle is 50-70 degrees, so that the molten pool temperature is reduced, and the welding bump or high on the back is avoided.
For example, after changing the electrode at the bottom of the 12mm plate vertical welding seal, the electrode Angle of 90-95 degrees is used in the joint, so that the temperature of the weld pool is rapidly increased, the weld hole can be opened smoothly, the back is formed smoothly, and the phenomenon of the concave joint point is effectively controlled.

4, arc burning time
In the practice teaching of horizontal and vertical fixed welding of φ57×3.5 pipes, the arc breaking method is used to weld, and when the bottom layer is welded, the arc breaking frequency and arc burning time directly affect the temperature of the molten pool. Because the pipe wall is thin, the arc heat bearing capacity is limited, and if the arc breaking frequency is slowed down to reduce the temperature of the molten pool, shrinkage holes are easy to occur.
Therefore, the arc burning time can only be used to control the temperature of the molten pool, if the temperature of the molten pool is too high, the molten hole is large, the arc burning time can be reduced, and the molten pool temperature can be reduced, at this time, the molten hole becomes smaller, the forming height inside the pipe is moderate, and the welding seam inside the pipe can be avoided.