Tuesday, December 17, 2013

Brazing Copper: A Comprehensive Guide and Overview

Brazing copper is a process where metal is joined by a filler metal. It is heated above a melting point and distributed between two or more parts. The filler metal is generally slightly above its melting temperature and is protected by a suitable atmosphere. It flows over the base metal—also known as a wetting—and is cooled in order to keep the pieces working together.

Brazing is very similar to soldering. Soldering is a process where two or more metal items are joined together by melting and flowing a filler metal—known as a solder—into the joint, with the filler metal having a lower melting point than the contiguous metal.

The one main difference between brazing copper and soldering is its temperature. When it comes to brazing, the filler metal temperature is higher.

What is important to know about brazing? 

Well, for one thing, obtaining high-quality brazed joints requires parts to be closely fitted. The base metals must be clean and oxide-free. One of the most important parts of brazing is the joint clearance.
What are the recommended joint clearances for brazing?

For brazing, the recommended joint clearances are 0.03 to 0.08 mm, or 0.0012 to 0.0031 in. This is for the best capillary action and joint strength.

What is capillary action?

Capillary action is the ability of a liquid to flow in narrow spaces, without the assistance or opposition of gravity.

What can cause faulty joints?

Faulty joints can be caused by a myriad of various reasons, including improper joint preparation prior to brazing, lack of proper support, improper heat control and distribution, inadequate amount of filler metal applied, and sudden shock cooling.

What are some common types of brazing?

When it comes to brazing copper, some companies specialize in furnace type and some by using the resistance method.  When brazing copper or any precious metals, the brazing of the copper or other metal to each other can be tricky and is a critical part of the process.  Depending on the method of brazing the copper, this will determine whether the copper and other metal are held in place by jigs or by pressure, at least until the brazing is complete. This is common for use when brazing copper to a more expensive metal such as silver alloy for use in making electrical contacts. This allows for electrical contacts to meet the important precious metal content requirement while brazing the copper to the contact material allows for the remaining part of the contact’s design to be formed as needed
Which industries typically implement the use of copper brazing? 

Quite a few, but some of the most common include the plumbing industry, automotive industry, and the HVAC (heating ventilation and air conditioning) industry.

Brazing copper is one of the most common methods of joining copper tubes and fittings. When brazing copper, it is important to braze the assembly to at least 800° F. However, it is important to use a filler metal that will melt above 800° F, but will be below the melting point of the metals to be joined.

John Bowie works in the HVAC industry where he frequently works with metal joining processes. He is quite familiar with brazing copper as a part of his occupation. On the side, John Bowie enjoys writing about HVAC and technical-related topics to inform others.

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