![]() Flux can also be applied using brazing rods with a coating of flux, or a flux core. Flux can be applied in any number of forms including flux paste, liquid, powder or pre-made brazing pastes that combine flux with filler metal powder. The flux also serves the purpose of cleaning any contamination left on the brazing surfaces. Nitrogen), a flux such as borax is required to prevent oxides from forming while the metal is heated. Unless brazing operations are contained within an inert or reducing atmosphere environment (i.e. This is not always the case, however, since in some non-production settings, time and cost are secondary to other joint attributes (e.g., strength, appearance). In general, however, most production processes are selected to minimize brazing time and associated costs. The effect of time on the brazed joint primarily affects the extent to which these effects are present. In some cases, a worker may select a higher temperature to accommodate other factors in the design (e.g., to allow use of a different filler metal, or to control metallurgical effects, or to sufficiently remove surface contamination). Maximize the life of any fixtures or jigs used.Minimize filler metal/base metal interaction.Minimize any heat effects on the assembly.The best temperature is usually selected to: However, several factors influence the joint designer's temperature selection. In general, the brazing temperature selected must be above the melting point of the filler metal. As the temperature of the braze alloy is increased, the alloying and wetting action of the filler metal increases as well. ![]() ![]() Īnother consideration is the effect of temperature and time on the quality of brazed joints. In the case of mechanical cleaning it is important to maintain the proper surface roughness, as wetting on a rough surface occurs much more readily than on a smooth surface of the same geometry. The two main methods for cleaning parts, prior to brazing, are chemical cleaning and abrasive or mechanical cleaning. Cleanliness of the brazing surfaces is also important, as any contamination can cause poor wetting (flow). In most cases, joint clearances of 0.03 to 0.08 mm (0.0012 to 0.0031 in) are recommended for the best capillary action and joint strength in some brazing operations, however, it is not uncommon to have joint clearances around 0.6 mm (0.024 in). High-quality brazed joints require that parts be closely fitted with base metal surfaces exceptionally clean and free of oxides. ![]()
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