Brazing Copper to Copper: Joining Square Metal Tubing Made a Whole Lot Easier

Traditionally, joining one square metal tubing to another is achieved through two means: brazing and soldering. Brazing is the process of joining materials at an elevated temperature of between 1000 to 2300℉. It is a joining technique that, according to the American Welding Society, has been used since ancient times but has continued to play an important role in today’s society. Brazing copper results in higher joint strength for applications such as jewelry, kitchen cutlery, bathroom faucets and high temperature ceramics. The technique also delivers superior fatigue resistance for carrying loads such as pressure, thermal expansion or dead weight in automotive engines, jet aircraft engines and air conditioning systems.

When done right, brazing permanently joins base materials together whether they are dissimilar metals or of different thicknesses and surface areas. To make the process easier, here are some tricks you can apply to your project.

Make the Overlap Shorter

When joining tubing, the depth of insertion affects the strength of the joint and the ease with which they can be brazed. While it might make sense to think that more overlap is better, overlap of beyond twice the thickness of the thinner member does not actually increase the strength of the joint any further. It only makes brazing difficult. So, when fitting the tubes together, it is better to make the overlap shorter. This will ensure that there is reduced risk of trapping gas that may cause voids in the joint and the brazing rod does not melt too quickly.

Use Fittings and Joints

Maintaining the alignment of two copper tubes during brazing can be quite difficult. Fortunately, there are ways to make it easier, and one of them is using socket joints. Unlike butt joints, socket joints are self-aligning during assembly and brazing, which helps keep the depth insertion in control. Solder-joint fittings can also be used, but to achieve full strength in a brazed joint, the full depth of the joint fitting should not be used. Instead, brazers should only use solder-joint fittings with short cups or have a machine shop trim the excess off as needed.

Mind the Temperature

As a high temperature joining process, brazing exceeds the melting point of the base metals. Since copper begins to anneal or be changed from hard temper (rigid) to annealed temper (soft) at 700℉, brazers must keep a close eye on this aspect. When temper changes, an inherent loss in strength occurs simultaneously, so make sure that the material is heated at the right temperature and duration to retain the necessary strength. As a general rule, the higher the temperature, the less time it takes to change from hard temper to soft temper.

About Rotax Metals

With over 60 years in business, Rotax Metals is a renowned wholesale supplier of brass, bronze and copper products to many different industries. We offer an extensive catalog of products including tubes, sheets, extrusions, rods, channels, angles and coils, as well as more sizing options than our competitors. Whatever your needs are, we are confident that our team of knowledgeable sales professionals can assist you.

Sources:

Soldering and Brazing Explained, Copper.org

Brazing copper tubing, TheFabricator.com