Which type of flame is used when performing torch brazing or silver soldering?

The neutral flame is the correct choice for torch brazing or silver soldering because it provides a balanced mixture of fuel gas and oxygen, resulting in a flame that has no excess of either component. This produces a clean and controlled heat that is ideal for joining metals without introducing contaminants or unwanted effects. The neutral flame helps maintain the integrity of the base metals being joined and prevents oxidation, which is crucial for achieving strong and durable joints in brazing and soldering processes.

In contrast, an oxidizing flame contains too much oxygen, which can lead to the oxidation of the materials being worked on and compromise the effectiveness of the joint. A carburizing flame, sometimes called a reducing flame, has an excess of fuel gas, which could alter the properties of the base metals and may introduce carbon into the joint, weakening it. Therefore, the neutral flame is the optimal choice for these types of metal joining techniques.