WELDED NECK FLANGE
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 of the molten metal and to preheat the metal ahead of the weld. This technique is called "whipping.” When the puddle of molten metal is moved back and forth in a uniform manner across the weld joint, the heat in the area close to the weld is spread out; this technique is called “weaving.” It is used to spread the heat and to obtain a wider weld bead without maintaining an excessively large puddle of molten metal. Whipping and weaving will be treated in greater detail in later chapters.
In summary, the welder must analyze the weld joint and estimate the directions in which the heat will disperse. He can then adjust the current setting on the machine to provide an adequate amount of heat to maintain the molten puddle of metal and to obtain the desired welding speed. If the weld joint causes the heat to be withdrawn rapidly, the current setting is increased and possibly, the welding speed will have to be slowed down. On the other hand, if heat will not disperse readily from the weld joint, a lower current setting is used and it may be necessary to use the whipping technique.