However, compared to laser cutting and laser marking, laser soldering has a relatively shorter development history and is more technically challenging. Among the issues affecting the spot welding quality of laser soldering machines, this has become a major concern for customers when purchasing laser soldering equipment. Zichen Laser believes the main factors include welding current and energizing time, electrode pressure, and current shunting.
1. Welding Current and Energizing Time. Based on the magnitude of the welding current and the duration of the energizing time, spot welding can be divided into two types: hard parameters and soft parameters. A hard parameter applies a large current for a short time, offering advantages such as high productivity, long electrode life, and minimal workpiece deformation, making it suitable for welding metals with good thermal conductivity. A soft parameter applies a smaller current for a longer time, resulting in lower productivity and is suitable for welding metals with a tendency to harden.
2. Electrode pressure: During spot welding, the pressure applied to the workpiece by the electrode is called electrode pressure. The electrode pressure should be selected appropriately. When the pressure is high, it can eliminate shrinkage porosity and shrinkage cavities that may occur during the solidification of the weld nugget, but it will reduce the resistance and current density, resulting in insufficient heating of the workpiece, a smaller weld nugget diameter, and a decrease in weld strength.
The magnitude of the electrode pressure can be selected based on the following factors:
(1) Material of the weldment. The higher the high-temperature strength of the material, the greater the electrode pressure required. Therefore, when welding stainless steel and heat-resistant steel, a higher electrode pressure should be selected than when welding low-carbon steel.
(2) Welding parameters. The more stringent the welding specifications, the greater the electrode pressure.
3. Current shunting: During spot welding, the current flowing outside the main welding circuit is called current shunting. Current shunting reduces the current flowing through the welding area, resulting in insufficient heating, a significant decrease in weld strength, and a negative impact on welding quality.
The main factors affecting the degree of diversion are as follows:
(1) Weld thickness and weld spacing. As the weld spacing increases, the shunt resistance increases and the shunt degree decreases. When a conventional weld spacing of 30-50 mm is used, the shunt current accounts for 25%-40% of the total current, and the shunt degree decreases as the weld thickness decreases.
(2) Surface condition of the weldment. When there are oxides or dirt on the surface of the weldment, the contact resistance between the two weldments increases, the current through the welding area decreases, that is, the degree of current shunting increases, and the workpiece can be pickled, sandblasted or ground.
