6 proplems welding of ship aluminum

1. Oxidation
2. Pore
3. Large expansion coefficient
4. The connector is not waiting for strong
5. Fast thermal conductivity, high thermal capacity
6. When turning from solid state to liquid state, it is easy to cause welding collapse to form welding tumors

Welding aluminum alloy is a certain challenging project, because aluminum alloy has some unique physical and chemical characteristics, and there are many problems related to the welding process.

Oxidation

The combination of aluminum and oxygen is easy to generate alumina (Al2O3) film. The characteristics of this oxide film have a series of effects on welding.

• First of all, the melting point of the oxide film is quite high to 2050 ° C, while the melting point of aluminum alloy is only 660 ° C, which makes it difficult to melt the oxide film during welding.
• Secondly, the density of the oxide membrane is high, and oxide slag is easily formed in the weld, which affects the welding quality.
• In addition, the oxide film is low, and it is easy to transmit electrons, resulting in unstable welding arc.

Welding aluminum alloys need to take measures to deal with oxide films, such as proper protective gas, clean welding surface, etc.

Pore

The melting degree of hydrogen in aluminum increases with increased temperature, but the solubility of hydrogen is about 20 times compared to the liquid and coagulation point. Therefore, when aluminum alloy is cooled and solidified, a large amount of hydrogen is analyzed to form a pores. The pores have negative effects on the strength and sealing of the welded joint. In order to reduce the formation of pores, measures need to be taken during welding, such as using low hydrogen electrodes, controlling welding speed and welding parameters.

Large expansion coefficient

The expansion coefficient of aluminum is large, and the expansion volume during welding is about 2 times the steel, and the volume decrease in volume is about 5%during solidification. This leads to a large deformation during welding, especially for rigid components with large stress, which may cause cracks in welds, melting lines and thermal influence areas. In order to reduce welding deformation, preheating methods can be used, especially for thicker aluminum plates. Generally, preheating is needed when the thickness of the plate is greater than 10mm.

The connector is not waiting for strong

After welding, the mechanical properties of aluminum alloy joints have decreased more obvious, and there is a phenomenon of softening in the area of heat. Unlike the steel welding tank, welding aluminum alloys need to choose the welding method of centralized calories, correct welding materials, and a standardized welding process. This helps improve the strength and corrosion resistance of the welding joint.

Fast thermal conductivity, high thermal capacity

Aluminum alloy has high thermal conductivity and thermal capacity. Therefore, the welding method of centralized concentration is needed during welding to ensure that the welding area is uniform. For thicker aluminum plates, especially when the thickness of the plate is greater than or equal to 10mm, preheating may be required to reduce the thermal stress during the welding process.

When turning from solid state to liquid state, it is easy to cause welding collapse to form welding tumors

During the welding process of aluminum tube, in order to meet the requirements of single -sided welding double -sided formation, the weld must have an appropriate amount of collapse. Welders need to closely observe the melting pool during operation to ensure the temperature and liquidity during the welding process, so as to achieve the ideal weld shape and avoid the formation of welding tumors.

Welding aluminum alloy requires comprehensive consideration of the characteristics of the material and the problems that may be encountered during the welding process, and adopt appropriate welding methods, process and control measures to ensure the quality and performance of the welding joint.