Brazing aluminum alloy brazing

Aluminum and aluminum alloys can connect a large variety of soldering processes. share brazing or brazing and soldering or soldering. In English, for these types of solder used a variety of terms - brazing and soldering, respectively.

Solid include solders with melting points liquidus, ie the melting end, higher 450 ° C, and also below the temperature solidus, that is, the onset of melting, base metal. Soldering differs from brazing solder melting point - solders melt below the temperature 450 ° C.

Unlike brazing welding

Brazing differs from welding in order, that when there is no significant base metal submelting. Thus, brazing temperature is between the fusion temperature and soft soldering alloys. Moreover, brazed aluminum structures typically are between welded and brazed soft solders also strength, and corrosion resistance.

a flux, the liquidus temperature and the solidus

Brazing aluminum alloy brazing was made possible thanks to the development of flux, which destroy the oxide film, without damaging the underlying metal and solder, which are also aluminum alloys.

(Cm. also Fluxes for aluminum melting)

Solders based on aluminum, used for brazing aluminum alloys, have liquidus temperatures much closer to the temperature solidus base metal, than in most other brazing metals. For this reason, soldering brazing, strict temperature control. soldering temperature should be about 40 ° C below the temperature solidus base metal. In some cases, the precise temperature control and the short brazing cycle, This difference may be even 5 ° C. Most aluminum alloy brazing solder at temperatures from 560 by 615 ° C.

Aluminum alloys for brazing

Uncultivated thermally deformable alloys, are soldered best, are alloys of the series 1xxx and 3xxx, as well as the 5xxx series alloys with low magnesium content. Alloys with higher content of magnesium soldered difficult.

Usually well-soldered heat of hardening alloys 6xxx series, for example, 6063 and 6061. Aluminum alloys 2xxx and 7xxx series have low melting temperature and therefore it is difficult to solder, except such as a relatively low-alloy 7004 and 7005.

Because casting of aluminum alloys is well soldered alloys 356.0, 357.0, 359.0, 443.0, 710.0, 711.0 and 712.0.

Brazing of aluminum brazing product is typically limited thickness not exceeding 0,4 mm. However, when soldering by dipping and vacuum brazing without flux thickness of the product can reach 0,03 mm.

Industrial solid solders

Industrial solid solders for soldering aluminum and aluminum alloys contain from 7 by 12 % silicon. Lowering the melting point obtained - at some loss in corrosion resistance - by the addition of copper and zinc. Solid solders are aluminum wrought alloy series 4xxx. The most famous of them are welding alloys 4343, 4047 and 4145.

Selection brazing

When brazing with the use of burner commonly used solder liquidus temperature as low as possible from the base metal solidus temperature. Since in this case the temperature control is difficult, melting the large temperature difference will reduce the likelihood of accidental parent metal submelting.

(Cm. The melting point of aluminum alloys)

When it is desired to obtain a tight brazed seam selected solder short melting interval - the minimum difference in temperature between liquidus and solidus. for instance, alloy 4047 It is the interval between the temperatures of the solid and liquid states of all 5,5 ° C. This solder is almost eutectic and quickly turns from a liquid to a solid and strongly reduces soldering time, it is often very beneficial effect on the quality of the soldered seam. This solder is particularly suitable for thin solder joints.

Source: Aluminum andAluminumAlloys, ASM International, 1996