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Quality Policy



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Tips
PRACTICAL TIPS FOR WELDING ALUMINUM
PRACTICAL TIPS FOR WELDING ALUMINUM

1) For heat treated alloys:
-select the alloy that will be least affected by the weld thermal cycle.
-design assemblies so that weld joints are located in places less subject to stress
-use as short a weld cycle as possible

2) Aluminum - copper alloys (2XXX series) are highly susceptible to burn through. To minimize the risks, pass through the solidification range quickly.

3) If the base metal temperature exceeds 350ºC, recrystallization of the cold worked zone occurs causing a lowering of mechanical strength.

4) When welding, annealing may occur, thereby undoing all the effects of previous heat treatments.

5) Tendency to hot cracking is greater when the weld metal contains from 0.5 to 1.5% silicon and/or 0.5 to 2.5% magnesium.

6) Aluminum – magnesium alloys (6XXX series) have the highest resistance to atmospheric corrosion. However, that are anodic with respect to several non-heat-treated alloys and can corrode when welded to the latter.

7) Using filler metal containing silicon (4043) when welding an alloy of a type other than aluminum – silicon produces blackening of the weld during the post weld anodizing treatment.

8) Careful joint preparation ensures good penetration and strong mechanical properties (see OPERATIONAL WELDABILITY, page )

9) In order to retain heat, when brazing or arc-welding Aluminum, put fire bricks or asbestos sheets under the work piece.

10) Preheat large sections uniformly. The temperature of acetylene-oxygen flame reaches the range of 5700ºF even if the flame adjustment is reducing (excess acetylene). The melting point of aluminum us only 1220ºF.

11) Keep work piece at pre-heat temperature during the welding or brazing process.

12) Remove flux residues after welding or brazing by means of brushing with warm water or flux removing solutions.

13) When arc-welding aluminum it is well to remember that the melt-off rate of the electrode, due to the tremendous temperature of the arc (4000ºC) and low melting temperature of the aluminum core wire (650ºC) is exceptionally high. To achieve an even arc-length it is important therefore to feed the electrode rapidly.

14) When brazing aluminum take into account that the oxide-film which forms and covers aluminum instantly, melts at 1650ºC. The underlying aluminum melts much sooner at 660ºC. A chemical (flux 4) is used to dissolve the high melting oxides and to prevent formation of new oxides during the brazing operation.