Without doubt, the use of aluminum is increasing within the welding fabrication industry. Manufacturers are often adopting this material, either through innovation, or through pressure applied by their end users. Recently some aluminum welding problems have arisen during operation (as seen in the picture).
It warns us that we should pay more attention to the prevention for the defect of aluminum welding. There will show two major defects of aluminum welding and how to prevent components from them as follows.
Porosity: Porosity is a result of hydrogen gas becoming entrapped within solidifying aluminum during welding and leaving voids in the completed weld. Porosity can be divided into dense hole, needle hole, etc. The hydrogen can be from all aspects of welding area, such as the moisture from the arc column atmosphere, the moisture absorbed by welding material and parent metal surface oxidation film. Porosity has a great influence on the performance of the weld. It not only reduces the effective work of weld cross section to degrade the weld mechanical performance, but also destroy the density of weld joint, to cause leakage easily. Due to the formation of stress concentration in the edge of the hole, the plastic of weld joint will be down. Therefore for the important weldment, the air hole should be strictly controlled. There are some specific reasons for the causes of porosity.
- The argon gas purity is low, too many impurities or argon gas piping with water and argon gas pipeline leak.
- Welding wire or parent metal near the groove weld is not clean before welding, or is contaminated with dirt, moisture after cleaning up, etc.
- Argon arc welding with argon gas protection is unqualified, arc instability, arc is too long, tungsten electrode extended through long.
- Improper welding parameter selection, welding speed too fast or too slow.
- he humid surroundings, high wind speed.
For the above reasons, there are some preventive measures.
- Ensure the purity of protective gas.
- Keep welding wire and parent metal groove clean.
- Correct selection of welding parameter.
- Preheat before welding.
- Ensure that work environment is dry and install the windbreak device.
Cracking: This form of cracking in aluminum is typically caused by a combination of metallurgical weaknesses of the weld metal as it solidifies with transverse stress applied across the weld. Cracking is the most dangerous welding defect, seriously affects the performance and the safety reliability of the welding structure, and it’s also a major cause of many welding structure damage. There are the specific reasons.
