Aluminum Brazing, Aluminum Dip Brazing Services
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Our company offers aluminum fabrication services, such as aluminum brazing, and aluminum dip brazing. Our services range from design, engineering and prototyping, to full production runs. We serve all industries, and we pride ourselves with quality design, manufacturing and tooling, and low costs. Contact us Today for a Free Evaluation of your Prints and Specs .

Brazing is a group of welding processes which produce coalescence of materials by heating them in the presence of a filler metal having a liquidus above 840 F (450C) and below the solidus of the base metal. The filler metal (aluminum) is distributed between the closely fitted faying surfaces of the joint by capillary action. Brazing is used in all industries, for applications such as leaktight joints, tubing joints, engine nozzles; joining electrical wire, cables and bus bars; and producing tanks, vats and piping.

Brazing of aluminum alloys was made possible by the development of fluxes that disrupt the oxide film on aluminum without harming the underlying metal and filler metals (aluminum alloys) that have suitable melting ranges and other desirable properties, such as corrosion and mechanical resistance.

The aluminum-base filler metals used for brazing aluminum alloys have liquidus temperatures much closer to the solidus temperature of the base metal than those for brazing most other metals. The non-heat treatable wrought aluminum alloys, such as the 1xxx, 3xxx, and 5xxx (low-magnesium) series, have been brazed successfully. Alloys that contain higher magnesium contents are more difficult to braze by the usual flux methods because of poor wetting and excessive penetration by the filler metal. Filler metals that melt below the solidus temperatures of most commercial, non-heat treatable wrought alloys are available.

The most commonly brazed heat-treatable wrought alloys are those of 6xxx series. The 2xxx and 7xxx series of aluminum alloys have low melting points and therefore are not normally brazeable. Alloys that have solidus temperatures above 595^oC are easily brazed with commercially binary aluminum-silicon filler metals. Higher-strength, lower-melting-points alloys can be brazed with proper attention to filler metal selection and temperature control, but the brazing cycle must be short to minimize penetration by the molten filler metal.

Sand and permanent mold casting alloys with high solidus temperatures are brazeable. Commercial filler metals for brazing aluminum are aluminum-silicon alloys containing 7 to 12 wt% Si. Brazing fillers with lower melting points are attained, with some sacrifice in resistance to corrosion, by adding copper and zinc. Filler metals for vacuum brazing of aluminum usually contain magnesium.

Most filler metals are used for any of the common brazing processes and methods. Two alloys, 4004 and 4104, have been developed exclusively for use in fluxless vacuum brazing.

Aluminum Dip Brazing

The dip brazing process allows simultaneous joining of multiple joints with varying material thicknesses. The resultant joints are leak-tight and EMI shielded. As the parts are uniformly heated with minimum fixturing, only minor distortion results. This minor distortion is easily managed with proper tolerancing and design of components.

The parts are cleaned of excess oxides. Parts are then assembled with the proper filler metal applied. The form of filler alloy varies to suit the type of joint. We utilize our in-house Photo Chemical Etching process to make our brazing shims. The precision achieved with this process yields excellent control over excess filler metal flow. Parts are placed onto stainless steel fixtures or baskets. The fixtured assembly is heated to 1050°F in a pre-heat furnace and then immersed in a bath of molten salt that contains a flux. The molten flux (1100°F) serves a multi-purpose role: providing heat transfer, supporting the assembly, and of course, fluxing the joints. Immersion time required will vary, but generally is less than two minutes. During the course of this cycle, filler metal will melt and flow to all joints through a capillary action. The assembly is removed from the bath, cooled, and cleaned; ready for further processing.

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