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BRAZING

Brazing is a joining method of same or dissimilar metals, without melting the base metals and by utilizing a filler metal (brazing alloy) which melts above 450°C. In the design, if work-pieces are place on top of the other, lapping each other or inserted one each other (i.e. well fitted), brazing alloy capillary flows through the joint by providing strong and leak-proof joint. This brazing method can be called as capillary brazing. If brazing is done by preparing V-, U-, X- groove on work-pieces, and by filling up this groove, the method can be called as braze welding. Except for joining, brazing process can also be applied for surfacing purposes.

In brazing process oxy-gas torches, furnace, induction, brazing gun, electrical resistance can be used for heating source. Depending on the joint design, application type and production rate, the most proper heating source can be chosen. industries, in which brazing is mostly used, are heating, cooling, air-conditioning systems, cycle, motorcycle, automotive, metal furniture and household appliances industries.

Brazing Alloys

Brazing alloys are standardized in DIN 8512, DIN 8513, AWS A5.8 and ISO 3677. In these standards alloys are classified with respect to chemical composition, type of filler metal and melting temperature range. More information about MAGMAWELD brazing alloys, are also given in product datasheets.

Surface Preparation for Brazing

Surface preparation is very important for quality of brazing. Surfaces shall be smooth, uniform, free-from oxydes, oil and grease. Sharp corners and edges have to be avoided. Surface preparation and cleaning can be made by mechanically or chemically. Cleaned surfaced shall be brazed as soon as possible, because oxidation occur on cleaned surface during waiting which needs re-cleaning the surfaces.

Brazing Fluxes

Chemical materials which is applied to surfaces to be brazed and also brazing alloy, is called as brazing fluxes. Fluxes get molten at 50-100°C below the melting temperature of brazing alloys and perform below functions during brazing.

Chemically dissolves oxides and remove from the surface surface oxidation during pre-heating for brazing, surface tension of molten brazing alloy to be able to wet the joints properly, some cases; decrease the cooling rate of the joint, the start of the brazing sequence by melting before brazing alloy. This property is important especially in Al-alloys which doesn’t exhibit color difference at higher temperatures.

It is important to not use less or excess flux during brazing. Because less flux causes to decrease brazing quality and insufficient joining and excess flux causes more flux residues. Depending on the flux type, residues can cause corrosion in the joint; they must be removed after brazing by washing with water, by mechanical brushing in hot water, by quenching the brazed part while they are still hot or picking solutions.