Figure 5-11. - Welding operation with backhand technique.
In oxygas welding of pipe, many tests have proved that fusion welded pipe joints, when properly made, are as strong as the pipe itself.
For success in oxygas welding of pipe, three essen- tial requirements must be met: there must be a convenient source of controlled heat available to produce rapid localized melting of the metal, the oxides present on the surface or edges of the joints must be removed, and a metal-to-metal union between the edges or surfaces to be joined must be made by means of molten metal.
One method used for welding steel and wrought iron pipe is known as FUSION WELDING. This method involves melting the pipe metal and adding metal from a rod of similar composition. The welding operation performed at the top of a joint in a horizontal pipe is shown diagrammatically in figure 5-11. This shows the BACKHAND welding technique. The rod and flame are moved alternately toward and away from each other, as shown in figure 5-12. Full strength oxygas welds can be made in any welding position.
The cohesiveness of the molten metal, the pressure of the flame, the support of the weld metal already deposited, and the manipulation of the rod all combine
Figure 5-12. - Flame and rod motion with backhand technique.
to keep the molten metal in the puddle from running or falling.
The soundness and strength of welds depend on the quality of the welding rod used. If you have any doubt about the quality of the rods or are not sure of the type to use, then it would be to your advantage to contact the manufacturer or one of his distributors. If the rod is supplied through the federal stock system, supply personnel should be able to look up the information based on the federal stock number of the rod.Continue Reading