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AC/OX CUTTING/WELDING/BRAZING A good brazed or soldered joint depends on: 1. Correct mating of the surfaces to be joined. Whether the joint is to be made by capillary brazing, soldering or braze welding depends on the type of joint and strength required.

Reducing flame.

Slight surplus of Acetylene.

2. It is essential that the surfaces to be joined are clean. Keep in mind that brazing and soldering are surface bonds.

3. Correct preheating. The workpiece must be preheated to a temperature equal to the melting point of the filler metal.

4. Correct flux, and no overheating.

Soft soldering

The principal difference between soldering and brazing is the working temperature of the filler material used. In soldering the working temperature of the filler alloy is always below 400 °C. The filler alloy is normally basen on tin (Sn).

Soft soldering is commonly used in electrical connections, and in joints where a leak-tight connection is required.

Compared with brazing soldering gives a weaker joint. The solders alloyed with silver will normally have the best mechanical strength.

AC/OX soldering is done with a soft, slightly carburizing (reducing) flame. The parts must be heated evenly so that the entire soldering area reaches soldering temperature at the same time. Be careful not to overheat. This may destroy the bonding properties of the solder.

Heat indirectly when using a welding torch for soldering.

Brazing

The term brazing is used when the melting point of the filler material is above 400 °C and below the melting point of the material in the workpiece. With correct joint preparation and brazing technique it is possible to obtain joints with high mechanical strength, and tensile strength of up to 490 Mpa is fully possible with a high quality general purpose brazing alloy like e.g. AG-60. The general term brazing covers two different application methods; capillary brazing and what is often called braze welding.

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