Weld aluminum

Contrary to popular opinion, aluminum is quite weldable. However, the properties of the light metal must be taken into special account. Below, we have created a guide for you, in which we discuss the different welding processes for aluminum welding.

Welding process for welding aluminum

Again and again it is to be heard that the welding of aluminum requires special welding equipment, aluminum is not weldable at all or only special welding procedures could be used. That is absolutely not the case. When welding aluminum, the following welding processes can all be used:

  • Autogenous welding
  • MIG welding
  • TIG welding
  • CMT welding
  • welding electrodes

Autogenous welding of aluminum

Autogenous welding is particularly interesting because aluminum has a high thermal conductivity. This is four times as high as steel. This means that - even when aluminum is being brazed - two differently sized aluminum workpieces that are to be welded together also heat differently.

The melting temperature of aluminum alloys

Therefore, it is customary to appropriately preheat the light metal in the case of aluminum autogenous welding. On the one hand, it is advantageous here that the melting point of aluminum is relatively low.

For pure aluminum, it is almost exactly 660 degrees Celsius. However, the melting point may vary and be between 580 and 680 degrees as most of the aluminum components are alloys. Depending on the alloy, the melting point is then different.

Difficulty heating - no tempering color

Here comes a major drawback in welding aluminum, which already shows effects during soldering: as you may know, steel discolors when you heat it - it achieves the so-called tempering color. Based on the tempering color, the optimum temperature for welding can be determined excellently.

Unfortunately, aluminum does not discolor on heating. Thus, it does not come to a tempering color, which makes it much more difficult to recognize the optimum welding temperature. Especially when autogenous welding of aluminum or in principle, if you need to preheat aluminum, experience in aluminum welding are very important here.

The MIG welding of aluminum

MIG welding is a very widespread welding technique. It is often referred to as MIG / MAG welding. This is related to the shielding gas and how it reacts. MIG welding is an inert shielding gas. Without dipping too deeply into the matter: during arc welding without gas, the melt would be exposed directly to the air.

As a result, however, immediately sets an oxidation and the slag changes in the properties. This process is prevented by the arc being enveloped by the protective gas at the welding point. This can lead to no reaction with the ambient air. Colloquially, this form of welding is therefore also referred to as inert gas welding. The current-carrying electrode burns off during MIG welding.

TIG welding of aluminum

TIG welding is also an inert shielding gas that is used. Wolfram plays a role here. In general, one of the biggest differences in TIG welding over MIG welding is that the power requirement is lower. As a result, even thin sheets can be welded much better. That is, burn through the sheets are much less often the case here.

Especially when it comes to MIG welding of very thin sheets, it is also strenuous for professionals to weld as far as possible without burning through the sheet. Therefore, the TIG welding process is often used on bodies. The blunt electrode does not burn down during TIG welding, the welding additive is additionally supplied manually or automatically (depending on the welding machine).

The CMT welding of aluminum

This is a welding process that is rarely found in home improvement. The welding wire runs backwards until it drips, then backwards in pushing direction. At the same time, the welding current is lowered again and again in this cycle. Since it is rather not used for home improvement, we do not want to dwell on it.

Electrode welding of aluminum

Electrode welding is probably the simplest form of electrical welding. With the devices a distinction is made between the most different versions of the inverter welding machine to the DC welding device. The electrode burns off here and is also current leader. Compared to the above-mentioned inert gas welding process, the electrode welding works without gas from the nozzle and thus without a gas cylinder.

But since welding in the air has disadvantages, this problem is solved differently in electrode welding. Here are the appropriate welding additives and flux in the electrode. Either sheathed or filled electrodes. In general, attention must be paid to the composition of the electrodes in all welding processes for aluminum as well as in the welding of other metals.

The electrodes for welding aluminum

According to the aluminum alloy to be welded, the corresponding alloy is also selected at the electrode. In the case of electrodes for aluminum welding, attention must be paid to the correct composition with alloys (silicates, magnesium, copper, etc.).

The oxide layer

If it is welding that does not contain any flux that dissolves the oxide layer, you will have to resort to other options here. You can grind the aluminum, but the oxidation layer forms immediately. In addition, there are also electrolyte solutions for signing aluminum to remove the oxide layer.

The significantly higher melting point of the oxide layer

The oxide layer must be removed because the melting point of the aluminum alloy will be between 580 and 680 degrees, but the melting point of the oxide layer will be around 2,050 degrees. That is, you can not conventionally melt the oxide layer. As a result, the proper connection of the materials is prevented and the structure is inferior. The oxide layer must therefore be removed imperatively. Incidentally, this also applies when soldering aluminum.

Tips & Tricks

In the house journal you will find numerous topics in the field of "aluminum processing". Here, we also show you how surface refinement, such as the chrome plating of aluminum, takes place.

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