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Seven Elements In Aluminium Welding Preparation
Dec 07, 2016

Groove processing

Thickness in the following 3mm not Groove of butt weld, just at the back seam 0.5~1mm point, so that gas emissions and avoid the back Groove. The back chamfer effect on weld, aluminum alloy thick-plate Groove angle greater than steel. General 55 ° single bevel Groove, using bilateral Groove 35 ° Groove on each side. So that's up to improve, at the same time reduce the risk of incomplete fusion flaw produced. For t-joint of thick plate HV or HY joints, requiring fill slopes outside, plus a fillet weld, make the weld size s is smaller than the plate thickness t.

Cleaning prior to welding work
Preparations for welding takes the most clean, otherwise the corrosion resistance ability, and porosity. Welding of aluminum alloy and welding steel habits completely differentiated. Welded steel has been used tools, used when welding is strictly prohibited. Oxide film of the trimming area and other impurities as possible using a stainless steel brush or clean with acetone. Cannot use wheel polishing, wheel polishing would only make the fusion welding of oxide film surface, without actually removing it. And if you use a hard grinding wheels, of impurities into the weld, leading to hot cracking. In addition, Al2O3 films in a very short period of time and are regenerated and stacked, in order to make the film as little impact on weld, cleaned up immediately after welding.

Preheating and interpass temperature control
With thickness more than 8mm welding of thick plates, must be preheated before welding, preheat temperature is between 80 ℃, interpass temperature controlled between 60 ¡æ ~100 ¡æ. Preheating temperature is too high, apart from the work environment, also could have an impact on performance of aluminum alloy, there joints soften, poor weld appearance shape and so on. Interpass temperature too high will make aluminum welding hot cracking risk.

Rational selection of parameters
Physicochemical properties of aluminum alloys and steels thus far, according to the welding characteristics of aluminum alloy to test and determine the welding parameters. Coefficient of heat conductivity of the aluminum itself (about 4 times the steel), fast heat dissipation. Therefore, under the same welding speed, the heat input when welding aluminum to be larger than the amount of heat input when welding steel 2~4 times. If heat input is not enough, prone to insufficient penetration even incomplete fusion of the problem, particularly in the weld start position.

Wire feed speed to be adjusted higher
Wire feed speed is closely related to the specification parameters such as current, voltage, and match each other. When the welding current is increased, wire feed speed should be increased accordingly.

Selection of welding speed
For thin plate welding, in order to avoid overheating, generally use small welding current and welding speed for thick plate welding, welder and weld fusion full gas escapes, using slower large welding current and welding speed.

Torch angle selection
In the direction of welding, welding torch angle is 90 ° around, too large and too small will cause weld defects. Torch angle too much resulting in inadequate gas porosity; angle is too small or has the potential to bring the liquid aluminium to front of the arc, arc not directly on the resulting incomplete fusion weld.