The brazing of aluminum can be carried out by chemical and physical methods.
Release time:
2022-12-12
【Summary Description】 The following chemical and physical methods can only be used for brazing aluminum. The master-slave order of the aluminum brazing method is FB → VB → NB, and the physical reduction method VB and VAW do not require flux coating. The disadvantage of the VB method is that the reduction is not thorough enough, leaving a part of the oxide, and then strengthening the magnesium added to the aluminum in the vacuum with the reduction reaction decomposition, so that it is corrosion resistant. In addition, the medium gas of the VAW method requires the use of nitrogen with a dew point of -70°C and an oxygen content of 6-8ppm, which is difficult to achieve. And after the metal surface treatment must be carried out before painting. The other is a chemical reduction method. The biggest difference between FB method and NB method lies in the different types of flux. The FB method uses a chloride flux (ZnCl2,LiCl2) base, which not only corrodes the base material (substrate) but also causes environmental pollution and other public hazards. Therefore, subsequent cleaning operations are essential. And the surface treatment must be carried out before painting. Compared with the NB method, fluoride flux (KAlF4) is used, no cleaning is required after brazing, the corrosion resistance is strong, and no surface treatment is required during coating. Although the flux will contaminate the equipment like the FB method, the corrosion of the equipment itself is less than that of chloride (furnace age FB = 1/2 year, NB = 5-6 years). However, only the fluorine (F) in the flux reacts with the magnesium (Mg) in the base metal material (base metal) to affect the brazing quality, so the Mg content in the base metal should be below 1%. Another disadvantage is the problem of flux residue. But this method has many advantages, so NB furnace is still the mainstream in brazed heat exchanger.
The following chemical and physical methods can only be used for brazing aluminum.
The master-slave order of the aluminum brazing method is FB → VB → NB, and the physical reduction method VB and VAW do not require flux coating. The disadvantage of the VB method is that the reduction is not thorough enough, leaving a part of the oxide, and then strengthening the magnesium added to the aluminum in the vacuum with the reduction reaction decomposition, so that it is corrosion resistant. In addition, the medium gas of the VAW method requires the use of nitrogen with a dew point of -70°C and an oxygen content of 6-8ppm, which is difficult to achieve. And after the metal surface treatment must be carried out before painting.
The other is a chemical reduction method. The biggest difference between FB method and NB method lies in the different types of flux. The FB method uses a chloride flux (ZnCl2,LiCl2) base, which not only corrodes the base material (substrate) but also causes environmental pollution and other public hazards. Therefore, subsequent cleaning operations are essential. And the surface treatment must be carried out before painting. Compared with the NB method, fluoride flux (KAlF4) is used, no cleaning is required after brazing, the corrosion resistance is strong, and no surface treatment is required during coating. Although the flux will contaminate the equipment like the FB method, the corrosion of the equipment itself is less than that of chloride (furnace age FB = 1/2 year, NB = 5-6 years). However, only the fluorine (F) in the flux reacts with the magnesium (Mg) in the base metal material (base metal) to affect the brazing quality, so the Mg content in the base metal should be below 1%. Another disadvantage is the problem of flux residue. But this method has many advantages, so NB furnace is still the mainstream in brazed heat exchanger.
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