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Welding history

Classification of welding

Effect of welding speed

Welding defects

Types of welding joints

Welding position

Welding electrodes

Types of welding flame

Welding flux

Welding techniques

Welding symbol

Welding edge preparation

Advantages of welding joints

Thermal properties of metal

Welding safety

Types of welds

Brazing

Soldering

Welding flux

What is welding flux

When metals are heated in contact with atmosphere air, the oxygen of air which made oxide formation, which causes poor quality welding, low weld strength. In many cases make welding impossible. Due to this reason it is required to add a welding flux to the weld area. This being a substance capable of dissolving the oxide formation. The welding flux is lighter than the molten metal and thus the molten metal and flux together dissolved the oxide. These are floats on top as a slag, which may removed by chipping or filing or grinding after cooling it. During ordinary grade of mild steel welding it (welding flux) is not required and joint can be made successfully which is exceptional case in welding subject.

Nothing advantage is obtained when using more than the minimum amount of welding flux for good welding joint. An excessive amount of flux is wasteful and makes it more difficult to make a clean weld.

Welding flux composition


For the ferrous metal welding the flux should be borax, sodium silicate, sodium carbonate, sodium bicarbonate, it gives best result. The borax forms compounds with the iron oxide, when the carbonate is the cleanser and it promotes fluidity of the molten metal.


For removing the cuprous oxide during copper and its alloy welding which is very effective for the mixture of sodium and potassium borates, carbonates, chlorides, sulphates and boric acid.


For the welding of aluminum and its alloy, its flux should be chosen very carefully which must be capable of dealing with the oxide of aluminum known as alumina. During aluminum welding the alumina forms very easily and has an extremely high melting temperature which is near about 20000C. Generally aluminum welding fluxes used mixture of alkaline fluorides, chlorides and bi-sulphate. These mixture of fluxes melt at a temperature just bellow the melting point of aluminum and dissolved away the whole oxides.


For the magnesium alloy welding the same type of fluxes used for the aluminum.

Welding flux cleaning


In the practical field all the fluxes are chemically very effective therefore they are strongly corrosive. If it does not cleaning proper way it may be damage the valuable job or reduce the job life. It may be necessary to remove the fluxes from the weld repeatedly with a hot water or steam. Another way to removing the fluxes with pickling bath and do not keep any negligence with this cleaning. Any traces of fluxes left in or near the weld are possible sources of corrosion, which may caused failure the weld. Thus proper cleaning the flux which increased the job life.

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Welding flux