Aluminum brazing process

Aluminum welding method:


Almost all kinds of welding methods can be used to weld aluminum and aluminum alloy, but the adaptability of aluminum and aluminum alloy to various welding methods is different, and each welding method has its own application situation.


Gas welding and shielded metal arc welding have the advantages of simple equipment and convenient operation. Gas welding can be used for repair welding of aluminum sheet and castings with low welding quality requirements.


Electrode arc welding can be used for repair welding of aluminum alloy castings. Inert gas welding (TIG or MIG) is the most widely used welding method for aluminum and aluminum alloy.


The aluminum and aluminum alloy sheet can adopt the tungsten electrode alternating current argon arc welding or the tungsten electrode pulse argon arc welding. Tungsten helium arc welding, argon helium mixed tungsten arc welding, gas metal arc welding and pulse metal arc welding can be used for aluminum and aluminum alloy thick plate.


GMAW and pulsed GMAW are widely used (argon or argon / helium mixture)


Preparation before welding


1. Cleaning before welding: when welding aluminum and aluminum alloy, the oxide film and oil stain on the welding junction and the surface of welding wire shall be strictly removed before welding;

1) The chemical cleaning has high efficiency and stable quality. It is suitable for cleaning welding wire and workpieces with small size and mass production. Two methods can be used: immersion and scrubbing.

Organic solvents such as acetone, gasoline, kerosene and other organic solvents can be used to remove oil on the surface. Alkaline washing of 5% – 10% NaOH solution at 40 ℃~ 70 ℃ for 3min-7min (pure aluminum time is slightly longer but not more than 20min), and then wash with flowing water, and then acid wash with 30% HNO3 solution from room temperature to 60 ℃ for 1min-3min, wash with flowing water, air dry or low-temperature drying.

brazing furnace flux


2) Mechanical cleaning: mechanical cleaning is often used when the size of the workpiece is large, the production cycle is long, and there is contamination after multi-layer welding or chemical cleaning. Firstly, wipe the surface with acetone, gasoline and other organic solvents to remove oil, and then directly use copper wire brush or stainless steel wire brush with diameter of 0.15mm-0.2mm until metallic luster is exposed.

Generally, it is not suitable to use grinding wheel or ordinary sandpaper for grinding, so as to avoid the defects such as slag inclusion caused by sand particles remaining on the metal surface and entering the molten pool during welding. In addition, scraper and file can also be used to clean the surface to be welded.

After cleaning, if the storage time is too long (such as more than 24h), it should be re treated.

2. Backing plate: the strength of aluminum alloy is very low at high temperature, and the flow property of liquid aluminum is good, and the weld metal is easy to collapse during welding. In order to ensure full penetration without collapse, backing plates are often used to support the molten pool and nearby metals.

The base plate can be graphite plate, stainless steel plate, carbon steel plate, copper plate or copper bar, etc. An arc-shaped groove is opened on the surface of the backing plate to ensure the forming of the welding seam on the reverse side. It is also possible to weld on both sides without backing plate, but it is required to be skilled in welding operation or take advanced technological measures such as strict automatic feedback control of arc welding energy.

brazing furnace

3. Preheating before welding: generally, thin and small aluminum parts do not need preheating. Preheating before welding can be carried out when the thickness is between 10 mm and 15 mm. According to different types of aluminum alloy, the preheating temperature can be 100 ℃ – 200 ℃, which can be heated by oxygen acetylene flame, electric furnace or blowtorch. Preheating can reduce the deformation and porosity of weldments. Wholesale manufacturer of aluminum alloy after welding

1) Cleaning after welding, the residual flux and welding slag left in and near the weld after welding will damage the passivation film on the aluminum surface, and sometimes corrode the aluminum parts, so it should be cleaned up. Workpieces with simple shape and general requirements can be cleaned by hot water washing or steam blowing.

Aluminum parts with high requirements and complex shapes should be washed with a bristle brush in hot water, then soaked in chromic anhydride solution or potassium dichromate solution with concentration of 2% – 3% at 60 ℃ – 80 ℃ for 5min to 10min, and then washed and washed in hot water, dried in oven, or dried with hot air, or dried naturally.

2) Postweld heat treatment aluminum vessels generally do not require heat treatment after welding.

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