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WIRE WELDING

for generating shielding gases and vapors and slag coverings. In essence, semiautomatic welding with flux-cored wires is equivalent to manual shielded metal-arc welding with an electrode several feet long instead of one of a few inches. By the press of the trigger completing the welding circuit, the operator activates the mechanism that feeds the wire to the arc. He uses a welding gun instead of an electrode holder, but it is correspondingly light in weight and easy to maneuver. The only difference being the weld metal of the electrode surrounding the shielding and fluxing chemicals, rather than being surrounded by them.

In the flux-core arc welding process, partial shielding is provided by vaporization of ingredients of the flux, which form a protective gas covering of the weld pool. When molten weld metal is transferred across the arc, it may not be completely covered by molten flux since the metal surrounds the flux, as both are heated. This means that some oxidation and nitrogen pickup may occur before the metal enters the weld pool. However, as opposed to the gas-shielded flux cored process, the self-shielded

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Knurled wire feeder rolls to be used

flux-cored process does not depend on gas shielding, it can operate satisfactorily outdoors where strong air currents are encountered. The self-shielded flux cored process is characterized by long wire extension beyond the contact tip (stickout). Extensions from 6 mm to 30 mm are used depending upon the application. Welding equipment for Gas Metal Arc Welding (GMAW) can in most cases also be used for Self Shielded Flux Cored Arc Welding with small modifications (wire feeder rolls should be knurled, insulation nozzle instead of gas nozzle etc.). Also note that selfshielded flux cored arc welding takes place with welding torch connected to minus (-) polarity.

Wires for self-shielded flux cored arc welding are available in standard sizes from 1 mm to 4 mm in mild steel and in some low alloy steel.