Since the weld is started at the lowest position on the pipe, it is usually necessary for the welder to be in a kneeling or crouching position. Whether kneeling or crouching, he should be situated comfortably in order to avoid any unsteadiness in manipulating the welding electrode. Getting into a comfortable position, then, is the […]

The procedures given in this chapter are recommended for weld­ing the root bead on all heavy-wall pipe. In the following discussion 8-inch Schedule 60 mild steei pipe will be used as the example of welding in the 5G position. The actual outside diameter is 8.625 inches and the wall thickness is.406 inch. For welding this […]

The Root Bead The root bead is the foundation of a successful pipe weld and must be made as perfectly as possible. An illustration of a perfect root bead is shown in Fig. 5- І. Fig. 5-1. A. Top view of a perfect root bead; B. View of section through the root bead. Perhaps the […]

When the pipe nipples are tack welded in the 2G position, the weld is horizontal and it is necessary to use a slight whipping motion to control the molten metal in the puddle. The whipping motion, shown in Fig. 4-9, is a quick movement of the arc away from the puddle, in the direction of […]

The keyhole is an essential part in welding a root bead. It should be about iy3 times the diameter across the electrode coating in size. The keyhole helps to insure that the deposited bead will penetrate to the root as evidenced by the small crown at the back of the bead. This crown, Fig. 4-8, […]

Courte. vy of the Hobart Brothers Co. Fig. 4-4. Method of spacing two pipe nipples in preparation for tack welding (a); Correct alignment of pipe nipples in preparation for welding (b); and maximum allowable misalignment (c). To fit-up the pipe nipples, first determine the required width of the root opening. Next, find a piece of […]

The preparation of the pipe joint is an essentia! part of pipe welding, as the quality of the weld is affected by the care used in preparing the joint. Indeed, in many instances the failure of the pipe joint can be attributed to faulty joint preparation. The pipe welder must understand and then practice those […]

Fig. 3-5, Paths of heat flow found in some typical pipe weld joints. The distribution of heat in the weld zone is affected by the welding technique. While welding, the electrode and the arc are sometimes deliberately moved in and out of the puddle of molten metal, in a uniform pattern, to reduce the temperature […]

The intense heat of the arc increases the temperature of the metal beneath the arc, which therefore reaches the melting point very quickly. As soon as a temperature difference exists, the heat energy starts to flow out of the weld area and heats the surrounding metal. In welding, the welder must use skill to control […]

The objective of this chapter is to provide a review of shielded metal-arc welding technology. By learning the principles treated here, the welder will have a better understanding of how and why to make adjustments to the machine and in his welding technique. Basic Concept of Electric Arc Welding. In shielded metal-arc weld­ing, an electrical […]