Welding aluminium using the MIG procedure, a certain knowledge of the metal and its mechanical characteristics is required, in order to prepare it in the best possible way for the process and obtain a high quality result. Let’s find out what you need to know and how to weld aluminium flush.
Aluminium welding: mechanical characteristics
For a correct welding of aluminium it is necessary to know the characteristics of this metal: light and resistant, it has a high thermal and electrical conductivity, melting at a temperature of about 660°C.
During the welding process it reacts strongly with oxygen creating an oxide film, very problematic because it is very hard and has a very high melting point (over 2000°C).
The most suitable welding procedures are TIG, braze welding and MIG, the latter is preferred because of the gas layer protecting and preventing the formation of oxide.
Aluminum alloys, currently on the market, offer a wide range of different characteristics. The classification system has 4 digits and 9 classes, divided according to the main alloy elements:
- Aluminum (1000 series): it is pure metal with a minimum of 99%
- Copper (2000 series): more resistant to high temperatures
- Manganese (3000 series): with high mechanical resistance
- Silicon (4000 series): more fluid and with a low expansion coefficient
- Magnesium (5000 series): more resistant to corrosion
- Zinc (series 7000): increased strength and hardness
Preparation for continuous wire aluminum welding
The continuous wire welding of aluminium begins with the preparation of the material. The first step is the cleaning step, the purpose of which is to remove the surface oxide film and all low melting impurities. Brushes with stainless steel bristles (pre-treated with a degreaser), solvents or other suitable stains are recommended for this purpose.
As we have said in the previous paragraph, this layer compromises the regular course of the welding process, as it has a much higher melting temperature than the metal itself.
Subsequently we move on to preheating the base material: the high thermal conductivity of aluminium can cause the pieces to deform or break through the welding joint. For some thicknesses, therefore, it is better to carry out preheating and avoid certain risks.
The last step before welding aluminium is the choice of gas, which commonly falls on pure argon or on mixtures of argon and helium.
How to weld aluminium with MIG
Once the metal has been prepared, it is time to weld the aluminium using the MIG process.
The high thermal conductivity requires the use of higher currents compared to other metals, as well as a faster pass speed. Being slow risks breaking through the base material.
Too high a speed, however, can cause some defects such as gluing, no melting or even porosity.
Aluminium has many positive characteristics and, for this reason, is used in various processes. It requires experience and accuracy, but the results are of the highest quality.
