In the atomic - hydrogen arc-welding process , an ac-arc is maintained between the two non-consumable tungsten electrodes while a stream of hydrogen gas under a pressure of about 0.5 kgf / cm2 (50 kN / m2) is passed through the arc and around the electrodes.
When hydrogen molecule is broken down into atomic form, the atom become very active and have a great tendency to recombining to form molecular hydrogen. This is exactly what happens in the atomic-hydrogen process. As the molecules of hydrogen pass through the electric arc, they are changed into the atomic state and thus absorb a considerable amount of energy. But when the atoms the hydrogen recombine into molecules just outside the arc a large amount of heat is liberated. This extra heat, added to the intense heat of the arc itself, produces a temperature of the order of 4000*C, as compared to 2000*C produced by the combination of the normal hydrogen and oxygen . The heat is used in making fusion welds. When additional metal is required, filler rods are melted into the joint.
One of the other principal benefits of this process is that the hydrogen excludes all oxygen and other gases which might combine with the molten metal to form oxides and other impurities. It also removes oxides from the surface of the wok. Thus, it is capable of producing smooth, uniform, strong and ductile welds.
This process of welding is employed in welding alloy steel. It is successfully applied for welding stainless steel. Most non ferrous metals can also be successfully welded.
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