Problems in Welding Process of the Flange and Flange Blank
With the continuous development of the stamp flange blank, the flange processing technology has also developed rapidly. However, the flange has many physical and chemical properties, such as a strong oxidizing nature, a low melting point, fast heat conduction, a large coefficient of linear expansion, large latent heat of fusion. Therefore, the following common problems will easily occur if the welding method is used.
In the process of solidification and rapid cooling of the flange weld pool, there is no time for hydrogen to escape, and hydrogen blowholes are easily to be formed. The important sources of hydrogen in the flange weld include moisture in arc column atmosphere, welding materials of the flange and moisture adsorbed by an oxide film on the surface of parent metal. Thus, the sources of hydrogen should be strictly controlled to prevent the formation of blow holes.
In the process of flange welding, a large amount of heat can be quickly conducted to the inside of the base metal. Therefore, during the welding of aluminum and aluminum alloys, in addition to the heat consumed in the pool of molten metal, more heat is consumed in other parts of the metal. This useless energy consumption is more significant than that of steel welding. In order to obtain high-quality welded joints, energy with energy concentration and high power should be adopted as far as possible, and sometimes technological measures can be used, for instance, preheating.
Before welding, the flange should be cleaned strictly by chemical or mechanical methods to remove the oxide film on its surface. In TIG welding, the AC power supply is selected and the oxide film is removed by cathode cleaning. In gas welding, flux used for removing the oxide film is used. In thickness welding, the welding heat can be increased.
Shrinkage cavities, shrinkage porosity, hot crack and high internal stress are easy to occur when the flange weld pool solidifies. The measures of adjusting welding wire composition and welding process can be used to prevent hot crack in flange production. When the silicon content in the flange is 0.5%, hot cracking is easy to happen. With the increase of the silicon content, the crystallization temperature range of the flange becomes small; the fluidity is significantly improved; the shrinkage decreases; the hot tearing tendency decreases accordingly. In the light of the production experience, when the silicon content is 5% to 6%, there is no hot crack, and the SAlSi welding wire (Silicon content is 4.5% to 6%.) will have better crack resistance.
In the process of solidification and rapid cooling of the flange weld pool, there is no time for hydrogen to escape, and hydrogen blowholes are easily to be formed. The important sources of hydrogen in the flange weld include moisture in arc column atmosphere, welding materials of the flange and moisture adsorbed by an oxide film on the surface of parent metal. Thus, the sources of hydrogen should be strictly controlled to prevent the formation of blow holes.
In the process of flange welding, a large amount of heat can be quickly conducted to the inside of the base metal. Therefore, during the welding of aluminum and aluminum alloys, in addition to the heat consumed in the pool of molten metal, more heat is consumed in other parts of the metal. This useless energy consumption is more significant than that of steel welding. In order to obtain high-quality welded joints, energy with energy concentration and high power should be adopted as far as possible, and sometimes technological measures can be used, for instance, preheating.
Before welding, the flange should be cleaned strictly by chemical or mechanical methods to remove the oxide film on its surface. In TIG welding, the AC power supply is selected and the oxide film is removed by cathode cleaning. In gas welding, flux used for removing the oxide film is used. In thickness welding, the welding heat can be increased.
Shrinkage cavities, shrinkage porosity, hot crack and high internal stress are easy to occur when the flange weld pool solidifies. The measures of adjusting welding wire composition and welding process can be used to prevent hot crack in flange production. When the silicon content in the flange is 0.5%, hot cracking is easy to happen. With the increase of the silicon content, the crystallization temperature range of the flange becomes small; the fluidity is significantly improved; the shrinkage decreases; the hot tearing tendency decreases accordingly. In the light of the production experience, when the silicon content is 5% to 6%, there is no hot crack, and the SAlSi welding wire (Silicon content is 4.5% to 6%.) will have better crack resistance.
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