How to Brazing Aluminum – A Technical Guide

Aluminum brazing has become prevalent in the manufacturing industry, repair shops, automotive industry, or even at the homes of our DIY guys and hobbyists.

Most manufacturers and repair companies are using all-aluminum or mostly aluminum components for the repair of holes, cracks, rivets, leaks, threads, broken ears. This is also to quickly cast aluminum or iron and fabricate aluminum easily, thus repairing the broken part and sometimes making it stronger than new.

This is because aluminum brazing alloys carry an all-aluminum structure with good destruction resistance and great strength. Aluminum brazing is very doable even for beginners. You don’t have to be called a professional to braze aluminum professionally.

To do so, let’s first take a good look at the brazing process itself and understand how it actually works.

What is aluminum brazing?

Aluminum brazing is a popular metal joining process in which the base metal is not melted but joined through heating up aluminum brazing rods or fillers.

Once it reaches the melting point, you can use it to either attach metal pieces together or fill in cracks, holes, and gaps present in any given object.

After that, as the temperature of the molten aluminum falls, it starts to solidify and settle, thus completing the aluminum brazing process.

MORE: What is Brazing?

What are the methods of aluminum brazing?

  • Torch brazing is obtained by heating the parts to be brazed with an oxyfuel gas torch or propane torches. This uses a chemically aggressive combination of chlorides and fluorides called flux that melts at a temp just below the filler metal. Very thin or very fine structures can be really difficult to braze because of the inability to evenly heat the parts. Brazing filler metal may be pre-placed at the joint or fed from handheld filler metal. Cleaning and fluxing are sometimes needed.
  • Dip brazing aluminum is done in a large amount of molten salt bath containing the flux held in a ceramic pot at dip brazing temperature by direct resistance heating. The filler metal is poured around the braze joint, and the part is dipped into the bath. This method is often applied for projects that require multiple joints.
  • Flux less vacuum brazing: this does not include the critical post braze cleaning phase that must support brazing when the flux is included. Aluminum brazing flux is corrosive and could cause breakage if it’s not thoroughly cleaned out. Flux removal is done by soaking and rinsing in water or by chemical cleaning.
  • Furnace brazing: this type of method is performed in gas, oil, or electrically heated furnaces. Temperature must be regulated within 5ºF (2.8ºC) and is vital to secure consistent results. Continuous circulation of the furnace atmosphere is desirable since it reduces brazing time and results in more equal heating. Products of combustion in the furnace can be damaging to brazing and satisfactory quality of brazed assemblies in the heat treatable alloys.
Aluminum brazing use to repair cracks, holes, leaks, rivets, broken ears, threads, or fabricate aluminum, cast aluminum, and cast iron quickly, easily, and stronger than new. It’s not hard at all.

Equipment’s needed

  • Base metal pieces: this is basically the two pieces of metal that you will connect or the metal surfaces that needs to be repaired.
  • Brazing metal rod: A brazing rod is a tool that is used to fabricate two pieces of metal together during the brazing process. This is basically the same thing as the traditional welding rod, but it is made specifically for brazing that’s opposite to the alternative.
  • Propane torch: A propane torch is basically used for the application of flame or heat which uses propane, a hydrocarbon gas, for its fuel.
  • Auto darkening welding helmet: A welding helmet, also known as “hood,” is one of the most necessary pieces of PPE that any welder must have. A good helmet protects the eyes and skin not only from severe sparks, but also from potentially vision-damaging ultraviolet and infrared rays emitted by the arc.
  • Welding gloves: Welding gloves are personal protective equipment (PPE) that protects your hands from the hazards of welding. These gloves allow digit articulation while protecting you from electrical shock, extreme heat, and ultraviolet and infrared radiation, and also provide abrasion resistance and enhanced grip.
  • Welding apron: Welding aprons cover the front of the worker’s torso to the knee or lower to protect workers from burns and injuries caused by flying sparks and debris encountered while welding. This apron is worn over your work clothes and has adjustable neck and waist straps for a secure fit.

How to Brazing Aluminum?

Knowing how to braze aluminum can be a useful skill for anyone who is faced with a variety of at-home repairs. Brazing aluminum is a quick and inexpensive option for repairing leaks, cracks, or holes in aluminum and is often found in air-conditioning repairs.

When compared to welding equipment, aluminum brazing equipment is inexpensive, portable, and does not require high amounts of voltage.

  1. Wear non-flammable clothing, gloves, and safety goggles before you begin the brazing process.
  2. Clean all dirt, oil, paint, or other residue from the area to be repaired by aluminum brazing. Use a degreasing solvent to get rid of oil and grease. Depending on the size of the repaired area, you may need to sandblast the area or use an emery cloth, grinding wheel, or file.
  3. Clamp or support the piece to be brazed.
  4. Use a brush to apply the flux appropriate to the temperatures and the metal. An all-purpose flux covers a wide range of temperatures and is beneficial to have on hand for general purpose brazing. Add flux by dipping the filler rod into the flux. You may also use flux-coated rods to eliminate this step. The flux-coated rods apply the flux during the aluminum brazing process.
  5. Heat the repaired area with a propane or acetylene torch until the aluminum shows an orange bloom. This happens when the metal gets very hot. Once you apply a flux, it should change colors or turn clear throughout.
  6. Apply the filler metal by running a brazing rod along the crack or the joint. The heat of the metal will melt the filler into the area needing the repair. Move the flame of the torch on and off as needed to melt the rod.
  7. Remove the flux after the filler material has solidified by dipping the part or pouring hot water on the repair. The flux will flake off. If it does not come off, use a wire brush to gently scrub the brazed area while wet or still in the hot water.
  8. Polish the area with an emery cloth after the metal has cooled completely.
  9. Coat the area with a rust-resistant coating if you are not immediately finished with the area.

Why choose brazing over other methods?

Braze welding is a fast and strong joining process that requires only heat and pressure to weld two pieces of metal together.

It is typically used for connecting pipes, tubes, castings, plates, or other heavy sheet metal where the joint must remain visible. The process can be applied to both ferrous and non-ferrous metals but is easier on non-ferrous metals (easy burning).

The process brings together the advantages of brazing/soldering with those of arc welding such as quickly completing most joints in one step without a need for preheating.

Brazing aluminum uses rods made up of copper with small amounts of zinc added; this helps prevent oxidation during the process.

Brazing aluminum is easy to learn how to do but you have to take safety precautions. If you go into this project with the right mindset and confidence then anyone can how to braze aluminum.

Common ways to used brazed aluminum joints in everyday life

Brazed aluminum joints are often used in larger projects where a high level of mechanical loading is expected. This includes projects like bridges, ships, railroad cars, and even some sporting equipment like tennis rackets and hockey sticks.

Brazed aluminum joints are also used in smaller projects such as the ones mentioned above; they can be seen how to braze aluminum in everyday life and when taken care of properly, how to join aluminum is long-lasting.

Risks to brazing aluminum

Using how to braze aluminum is a risky process in itself. Brazing aluminum can cause safety hazards for those that are not using it properly.

If you’re using how to braze aluminum and the metal becomes too hot, you could burn yourself. If the joint is not thoroughly coated with how to brazed aluminum and flux, then the brazed aluminum may not take hold and the brazed aluminum will be unsuccessful.

Since how to braze aluminum can only be used on non-ferrous metals, it cannot be used on any ferrous metal or steel – this means that how braze aluminum cannot be used on either type of material.

If aluminum brazing is not done correctly, the aluminum may become distorted or even severely damaged.

Brazing aluminum will remove material and make how join aluminum weaker than how it was originally; this makes how to brazed aluminum a cosmetic solution only that can be used for aesthetic purposes. If you use how to join aluminum in an area where mechanical force must be applied, then how to brazed aluminum will likely fail when tested

How do I prevent these risks?

The best way how to avoid risk while using how to brazed aluminum is with proper safety precautions. It’s important how to maintain a safe workspace, have the right tools, and know what you’re doing before starting any aluminum brazing project.

Advantages of Aluminum Brazing

Aluminum brazing offers many advantages over welding and other types of metalworking. Here are some of the benefits of aluminum brazing in comparison to welding:

  • Low cost: There are many supplies needed in welding, such as shielding gas, filler wire, and electricity, that aren’t necessary for aluminum torch brazing. This ultimately leads to a much cheaper metalworking experience since the cost of shielding gases like argon and helium are not cheap as far as supplies go.
  • Easy use: Unlike TIG welding rigs, which can be somewhat challenging for metalworkers to get a feel for since they involve manipulating a molten weld pool, torch brazing is a relatively uncomplicated process. This makes it an excellent entry-level metalworking skill in comparison to MIG or TIG welding.
  • Safe practice: While aluminum brazing still involves high heat that can lead to a burn, aluminum brazing with a gas torch does not require working with high-voltage electricity. This can make it a fantastic method for metalworkers who aren’t comfortable manipulating voltage on a TIG torch.
  • Works on multiple alloys: Aluminum brazing works on any alloy of aluminum or cast aluminum, making it a useful technique choice for many different kinds of aluminum-based projects.
  • Smooth, good-looking joint: Unlike welding (which can leave a splattered or uneven welding seam if performed by a novice welder), brazing is generally easier to handle and results in a more even bond with less pitting or bumps.
  • Quick repair: Aluminum brazing is a much faster metal-joining technique than TIG welding and other forms of welding. Since it has equivalent strength to these other metalworking skills, this makes aluminum brazing a good option for metalworking jobs that must be performed fast or as part of an assembly line.