Arc Welding Positions

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Travel Speed Figure 7-15.—Work angle. Figure 7-16.—Travel angle. Electrode Angle The  angle  at  which  you  hold  the  electrode  greatly affects the shape of the weld bead which is very impor- tant in fillet and deep groove welding. The electrode angle  consists  of  two  positions:  work  angle  and  travel angle. Work angle is the angle from the horizontal measured at right angles to the direction of welding (fig, 7-15).  Travel  angle  is  the  angle  in  the  direction  of welding and may vary from 5 to 30 degrees, depending on  the  welder’s  choice  and  conditions  (fig.  7-16). Work  angle  is  especially  important  in  multiple-pass fillet  welding.  Normally,  a  small  variance  of  the  work angle will not affect the appearance or quality of a weld; however,  when  undercuts  occur  in  the  vertical  section of a fillet weld, the angle of the arc should be lowered and the electrode directed more toward the vertical section. Travel speed is the rate at which the electrode travels along a weld seam. The maximum speed of welding depends on the skill of the operator, the position of the weld, the type of electrode, and the required joint pene- tration. Normally, when the travel speed is too fast, the molten pool cools too quickly, locking in impurities and causing the weld bead to be narrow with pointed ripples, as shown in figure 7-12, view D. On the other hand, if the travel speed is too slow, the metal deposit piles up excessively and the weld is high and wide, as shown in figure 7-12, view E. In most cases, the limiting factor is the highest speed that produces a satisfactory surface appearance of a normal weld, as shown in figure 7-12, view A. Breaking the Arc The most commonly used method to break the arc is to hold the electrode stationary until the crater is filled and  then  slowly  withdraw  the  electrode.  This  method reduces  the  possibilities  of  crater  cracks. Reestablishing the Arc When it becomes necessary to reestablish the arc (as in a long weld that requires the use of more than one electrode),  the  crater  must  first  be  cleaned  before  strik- ing the arc. Strike the tip of the new electrode at the forward (cold) end of the crater and establish an arc. Move the arc backward over the crater, and then move forward  again  and  continue  the  weld.  This  procedure fills the crater and prevents porosity and slag inclusions. Peening Peening  is  a  procedure  that  involves  lightly  ham- mering a weld as it cools. This process aids in relieving built-up stresses and preventing surface cracking in the joint area; however, peening should be done with care because excess hammering can work harden and in- crease stresses in the weld. This condition leads to weld embrittlement  and  early  failure.  Some  welds  are  cov- ered by specific codes that prohibit peening so you should  check  the  weld  specification  before  peening. ARC WELDING POSITIONS The types of welds, joints, and welding positions used in manual-shielded metal arc welding are very similar to those used in oxygas welding. Naturally, the techniques are somewhat different because of the equip- ment  involved  is  different. 7-12

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