Presentation on theme: "Work to be welded is connected to one side of an electric circuit (the ground cable). A metal electrode is connected to the other side (the electrode."— Presentation transcript:
Work to be welded is connected to one side of an electric circuit (the ground cable). A metal electrode is connected to the other side (the electrode cable). These two parts of the circuit are brought together and then separated slightly. The electric current jumps the gap and causes a continuous spark called an arc. The high temperature of this arc melts the metal to be welded, forming a molten puddle. The electrode also melts and adds metal to the puddle. As the arc is moved, the metal solidifies. **The melting action is controlled by changing the 1) amount of electric current that flows across the arc and 2) the size of the electrode. **
Alternating Current: reverses direction 120 times per second Direct Current: flows in same direction at all times *We will always use DC+ current.* DC+ sets the metal piece is negative; electrode is positive. DC+ is more stable and every electrode can be used!
-Usually has a steel core, which is covered with a coating that shields the arc to keep harmful oxygen and nitrogen in the atmosphere away from the weld. AWS (American Welding Society) E-60131= all positions (2= flat/horizontal;3=deep groove) E=Electrode3= indicates operating characteristics (polarity,coating, etc.) 60 = gives minimum tensile strength in thousands psi (60,000)
Right-handed welders see better welding L to R; while left-handed welders should weld R to L. 4 Things that Affect the Results of Arc Welding: 1.) current setting (or amperage) 2.) length of arc (or arc voltage) 3.) rate of travel 4.) angle of electrode *General rule of thumb: current setting (amps) should be equal to the diameter of the electrode (core rod) in thousandths of an inch EX: 1/8” electrode =.125” and operates well at 125 +/- 10 (115-135) 5/32”electrode =.156” and operates well at 150+/-10 (140-160)
*Arc length increases as arc voltages increases.* Ex: arc 3/16” long requires 3x the voltage of a 1/16” arc *Arc length should be slightly less than diameter of electrode being used.* *Use the sound of the arc to guide you: sound should be sharp, energetic crackle.* *Electrode must be fed downward at a constant rate to keep the right arc length!* *Rate of travel of the arc changes with the thickness of the metal being welded, amount of current, and shape/size of weld (bead) wanted.* *Arc length and arc travel should be such that the puddle of molten metal is about twice the diameter of the rod used.*
On flat pieces, electrode should make an angle of 90 degrees with the work. In other than flat work, good results are obtained if the rod splits whatever angle is being welded. (Ex: 90 degree angle weld; electrode should be tilted at a 45 degree angle for best results.)