Porosity in welds is a common quality problem during robotic welding. The presence of porosity reduces weld strength and can even lead to cracks and fractures. The main reasons for porosity in robotic welds include the following:
1. Poor gas protection:
During welding, insufficient or uneven supply of shielding gas (such as argon, carbon dioxide, etc.) fails to effectively isolate oxygen, nitrogen, etc. from the air, resulting in gas mixing into the molten pool and forming pores.
2. Poor surface treatment of welding materials and base materials:
If the surface of the welding material or base material has impurities such as oil, rust, moisture, and oxide scale, these impurities will decompose and generate gas at the high temperature of welding, which will then enter the molten pool and form pores.
3. Inappropriate welding process parameters:
If the current, voltage, or welding speed is too high or too low, the molten pool will not be stirred sufficiently, and the gas will not be able to escape smoothly; or the shielding gas purging angle will be improper, affecting the gas shielding effect.
4. Inadequate weld design:
If the weld gap is too large, the molten metal has poor fluidity and the gas is not easy to escape; or if the weld shape is complex, the gas is not easy to escape from deep within the weld.
5. High humidity in the welding environment:
Moisture in the air decomposes into hydrogen at the high temperature of welding. Hydrogen has high solubility in the molten pool and cannot escape during the cooling process, forming pores.
The following measures can be taken to address porosity in robot welds:
1. Optimize gas protection:
● Ensure the protective gas has the required purity, appropriate flow rate, and proper distance between the nozzle and the weld to form a good gas curtain protection.
● Use appropriate gas composition and mixing ratio, such as using low-hydrogen or ultra-low-hydrogen welding electrodes and wires, to reduce the source of hydrogen.
2. Strict surface treatment:
● Thoroughly clean the surface of the welding material and base material before welding to remove impurities such as oil, rust, and moisture. Preheating treatment may be necessary.
● For environments where moisture may be present during welding, take drying measures, such as using a weld dryer or preheating the workpiece.
3. Adjust welding process parameters:
● Select appropriate current, voltage, and welding speed based on the welding material, base material, and welding position to ensure adequate stirring of the molten pool and sufficient gas escape time.
● Adjust the shielding gas purging angle to ensure that the gas evenly covers the weld.
4. Improve weld design:
● Control the weld gap within a reasonable range, avoiding it being too large or too small.
● For complex welds, methods such as segmented welding, pre-filled metal, or changing the welding sequence can be used to improve gas venting conditions.
5. Control the welding environment:
● Welding should be carried out in a dry, well-ventilated environment to avoid excessive humidity.
●For environments where humidity cannot be controlled, measures such as using desiccants and welding seam heating can be considered to reduce the impact of moisture.
6. Monitoring and Quality Control:
● Regularly check the performance of welding equipment, such as gas flow meters and welding torch nozzles, to ensure they are in good working order.
● Monitor the welding process in real time, such as by using a welding process monitoring system, to promptly detect and adjust abnormal parameters.
● Post-weld non-destructive testing (such as ultrasonic testing, radiographic testing, etc.) is performed to promptly identify and address welds containing porosity. By comprehensively applying the above measures, the generation of porosity in robotic welds can be effectively reduced, thus improving welding quality.
Porosity in robotic welds can be caused by various factors, including contamination of the welding material surface, insufficient gas shielding, improper control of welding current and voltage, and excessive welding speed. To address this issue, we need to take appropriate measures, such as using clean welding materials, selecting appropriate shielding gases and controlling their flow rates, setting suitable welding parameters, and adjusting the welding speed as needed. Only by addressing these multiple aspects simultaneously can we effectively prevent and resolve porosity in robotic welds and improve welding quality.
