What is Brazing? Process and Uses

What is Brazing and How to Braze Metal

Brazing has been used throughout history as a metal-joining process recognized for its long-term durability, strong joints, and ability to effectively join various materials. This popular confluence of metalworking artistry and engineering know-how is ideal for manufacturing professionals, hobbyists, and everyday users seeking exceptional strength in their constructions. In this blog post, we will take an in depth look at the brazing process, detailing methods, material choices, technique variations and practical uses across numerous industries. So without further ado – Let us explore what makes brazing so special!

What is Brazing?

Brazing is a metal-joining process that involves melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from welding in that the workpieces are not melted.

Brazing differs from soldering in that it uses a higher temperature and much closer-fitting parts than soldering.

Capillary action causes the filler metal to flow into the gap between close-fitting parts during brazing. The filler metal is heated to slightly above its melting (liquidus) temperature while being shielded by an appropriate atmosphere, usually a flux.

It is then cooled after flowing over the base metal (a process known as wetting) to join the workpieces together. Combining metals of the same or different alloys with significant strength is a significant advantage of brazing.

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Brazing Rods Materials

  • Copper, brass, and Bronze: Copper Phosphorous Brazing & Welding Rods
  • Steel, stainless steel, nickel alloys, copper alloys, cast iron, tungsten carbide: Nickel Silver Brazing & Welding Rods
  • Cast iron, galvanized, nickel, steel, malleable iron: Bronze Brazing & Welding Rods
  • Aluminum: Bernzomatic AL3 Aluminum Brazing & Welding Rods

How to Braze Metal?

Brazing is a metal (but also ceramic) joining process in which molten filler metal (the braze alloy) flows into the joint.

Step-by-Step Instructions

  • Scuff the metal’s surface with a wire brush or emery cloth. Then, using soapy water or a degreaser, clean the surfaces.
  • Place the metal in the desired location. In most cases, an overlapped joint is stronger and easier to braze together than a gapped joint. Clamps can be used to hold the pieces in place if necessary.
  • Heat the joint where the two pieces of metal will come together until it glows.
  • Apply the brazing rod to the joint while heating the metal surfaces. For large areas, heat portions of the joint to temperature and then move to the next adjacent area.
  • After brazing, use a wire brush to clean the brazed surface to remove any oxidation or residue.

The melting point of the filler metal is above 450°C but always lower than the melting temperature of the parts to be joined, distinguishing the process from welding, which uses high temperatures to melt the base metals together.

While heated slightly above the melting point, the filler metal is shielded by a suitable atmosphere, which is frequently a flux. The molten filler metal cools to join the workpieces together, forming a strong bond between similar or dissimilar metals.

The brazing process can be performed in a variety of atmospheres, including air, combusted fuel gas, ammonia, nitrogen, hydrogen, noble gases, inorganic vapours, and vacuum, with a variety of heating sources such as a torch, furnace, and induction coil.

Welding vs Brazing

The AWS classifies brazing as a liquid-solid phase bonding process. The filler metal is melted when liquid and the base material or materials are not melted when solid.

Brazing, unlike welding, does not involve the workpieces being melted. The primary distinction between brazing and arc welding is the source of heat. Brazing uses a torch, furnace, induction, dipped, or resistance as heat sources at temperatures above 840°F (450°C), whereas arc welding uses electricity as a heat source at temperatures around 10,000°F.

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