What type of flame is recommended for brazing copper to copper connections?

For brazing copper to copper connections, a neutral flame is the recommended choice. This type of flame is characterized by a balanced ratio of oxygen and acetylene, allowing for efficient heat application without introducing any additional elements that could adversely affect the joint.

Using a neutral flame during brazing ensures that the copper base metals are heated evenly and adequately to the required temperature for the filler material to flow and bond properly without oxidizing the surfaces. The neutral flame minimizes the risk of oxidation of the metal surfaces, which is crucial because oxidation can prevent the brazing filler from adhering properly and create weak points in the joint.

A carburizing flame, which has an excess of acetylene, can introduce carbon into the joint, possibly causing brittleness. An oxidizing flame has an excess of oxygen and could lead to oxidation of the copper, which is detrimental for creating a strong, durable bond. A reducing flame is less commonly used in copper brazing and may lead to similar issues as the carburizing flame, potentially compromising the integrity of the connection. Therefore, the neutral flame is the most suitable for achieving quality brazed joints in copper work.