For brazing copper, brass, low-nickel alloys, Monel, medium and high carbon steels. Hydrogen (AWS type 7): Strong deoxidizer, highly thermally conductive. Can be used for copper brazing and annealing steel. May cause hydrogen embrittlement to some alloys. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium and high carbon steels and chromium alloys, cobalt alloys, tungsten alloys, and carbides. Inorganic vapors (various volatile fluorides, AWS type 8): Special purpose. Can be mixed with atmospheres AWS 1–5 to replace flux. Used for silver-brazing of brasses. Noble gas (usually argon, AWS type 9): Non-oxidizing, more expensive than nitrogen. Inert. Parts must be very clean, gas must be pure. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium and high carbon steels chromium alloys, titanium, zirconium, hafnium. Noble gas+hydrogen (AWS type 9A) Vacuum: Requires evacuating the work chamber. Expensive. Unsuitable (or requires special care) for metals with high vapor pressure, e.g. silver, zinc, phosphorus, cadmium, and manganese. Used for highest-quality joints, for e.g. aerospace applications. Common techniques Torch brazing Torch brazing is by far the most common method of mechanized brazing in use. It is best used in small production volumes or in specialized operations, and in some countries, it accounts for a majority of the brazing taking place. There are three main categories of torch brazing in use: manual, machine, and automatic torch brazing. Manual torch brazing is a procedure where the heat is applied using a gas flame placed on or near the joint being brazed. The torch can either be hand held or held in a fixed position depending on whether the operation is completely manual or has some level of automation. Manual brazing is most commonly used on small production volumes or in applications where the part size or configuration makes other brazing methods impossible. The main drawback is the high labor cost associated with the method as well as the operator skill required to obtain quality brazed joints. The use of flux or self-fluxing material is required to prevent oxidation. Torch brazing of copper can be done without the use of flux if it is brazed with a torch using oxygen and hydrogen gas, rather than oxygen and other flammable gases. Machine torch brazing is commonly used where a repetitive braze operation is being carried out. This method is a mix of