Braze aluminum

Brazing aluminum is more demanding and expensive than brazing other metals. There are also differences in the solders used and the burners. Below we describe the brazing of aluminum for you.

The properties of aluminum must be taken into account

The brazing of aluminum differs significantly by certain properties of aluminum:

  • low melting point
  • no tempering color when heating
  • high thermal conductivity
  • Oxidation layer with high thermal resistance
  • rapid new formation of a new oxide layer

The melting temperature of aluminum

Aluminum is exceptional over most other metals. Depending on the aluminum alloy, the melting point is between 580 and 680 degrees Celsius, in part and depending on the alloy, it can also reach up to 500 degrees Celsius.

The occasion color

While the brazing of other metals mainly uses silver solders, those for aluminum brazing mainly consist of silicon. An important aspect of brazing aluminum is the fact that the light metal does not show tempering color.

With other metals, the temperature range and thus the correct temperature range for brazing can be easily determined based on the changing tempering color. This is so far decide that the melting point begins depending on the alloy from 500 degrees, the brazing itself but only from 450 degrees Celsius is possible.

Removing the oxide layer

Therefore, the optimum temperature for brazing can only be determined from the flux and the solder, which melts in the correct temperature range. The flux must not be forgotten and must be explicitly suitable for aluminum. Because aluminum has an oxide layer on the surface.

However, the melting temperature of this oxidation layer is between 1,500 and well over 2,000 degrees Celsius, ie significantly above the melting temperatures of aluminum. If the oxide layer can not be removed, aluminum can not be joined.

It does not do any good to remove the oxidation layer by sole pickling from the aluminum or grinding. Because a new oxidation layer forms within a few minutes.

Effects of high thermal conductivity

Another fundamental property, which is often ignored when brazing aluminum, is the thermal conductivity of aluminum, which is up to 1.5 times higher than that of steels. Therefore, the temperature is quickly dissipated, especially for large workpieces. Also, two differently sized aluminum workpieces to be joined must be heated to different intensities.

Pay attention to a well-sized burner

The larger workpiece must be preheated much more intense. The mistake, which is generally made frequently, is the use of an undersized, so too small burner. The right temperature for brazing is very difficult to achieve with a torch that is too small, as it will dissipate so quickly.

High quality brazing of aluminum means to go into the material

If you consider these features when brazing aluminum, the texture becomes high quality. Of course, experience and a sense of brazing aluminum are also needed.

Tips & Tricks

Of course, we also show you in the house journal how to solder aluminum or solder it conventionally.

Video Board: How To Easily Join Together Aluminum Plates & Repair Aluminum Parts