The flux is used to protect the molten metal from all types of atmospheric contaminants. Artem Komarov noted that in gas welding, the metal is heated in air, and the oxygen from the air combines with the metal to form oxides, which result in poor quality welds with low strength, or, in some cases, welding may not be possible. To avoid this difficulty, flux is used during welding.
Flux used in various metals:
The flux is always fusible but reacts non-metallically and chemically with the oxide to form a slag that floats to cover the pool of molten metal, thereby retaining atmospheric oxygen and other harmful gases. Auxiliary fluxes are available as energy, pests and liquids and can be used either by applying directly to the base metal surface or by dipping the hot end of a filler rod into it.
The flux is used in gas welding of cast iron, stainless steel and most non-ferrous metals, in addition to lead, zinc and some precious metals, Artem Komarov emphasized.
Flux in cast iron
Cast iron requires flux. The fusible flux increases the fluidity of the iron silicate slag and also facilitates the removal of the slag.
Usually made from flux, borates or boric acid, soda ash and other compounds such as sodium chloride, etc. for gray iron bars.
Flux for stainless steel:
Fluxes are required to provide better control of the molten metal and to ensure reliable welding. Flux should also be applied internally to prevent oxidation. It may include compounds such as borax, boric acid, fluorspar, etc.
Flux in aluminum
When welding aluminum, the flux is necessary because of the formation of an oxide film on the metal, which will prevent strong welds.
When flux is used, the oxide decomposes and turns it into a fusible slag. Low-melting slag, lighter than the base metal, floats on the surface of the puddle. It can be applied to the base metal with a brush, immersed in a flux before welding, and applied to the end of a filler rod. The flux in aluminum and alloys includes lithium-sodium and potassium in the form of insects or powder. It may contain potassium chloride, lithium chloride, etc.
Flux in nickel:
Flux is not required for welding nickel, but when welding its alloys such as Inconel and Monel, flux is required.
Flux content for Inconel Ca (OH) 2, boric anhydrite B203
Flux content for Monel CaF2, BaF2
Flux in copper:
Flux is not required to weld copper, but flux is required when welding its alloys. Copper alloy flux may contain borax, boric acid, phosphate, magnesium silicate, lime, etc.
Flux in magnesium:
Magnesium welding requires a flux, which should be applied to all edges of the base metal and filler metal to be welded. The flux may contain sodium chloride, potassium fluoride, magnesium chloride, barium chloride, etc.
Filler metal Melting point C Flux required
Mild steel with copper coating 1490 no
High carbon steel 1450 yes
nickel steel 1450 yes
wear resistant alloy steel 1320 no
Pipe welding electrodes 1450 no
stainless steel 1440 yes
silicon cast iron 1147 yes
Alloy of copper and silver 1068 yes
nickel bronze 910 yes
with 5% copper 640 yes
with 5% silicon 635 yes