WG3013
Welding Guidelines
General |
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Nozzle | Contact | |
Shielding | Tip | |
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Gas | Flux | |
Slag | (Gasless | |
only) | ||
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Weld | Wire | |
Crater | Work Piece | |
Figure 9 - Weld Components | ||
This line of welding machines can utilize the Flux Cored Arc Welding (Gasless) process or the Gas Metal Arc Welding (MIG) process. The weld must be protected (shielded) from contaminates in the air while it is molten. The gasless process uses a tubular wire with a flux material inside. The flux creates a shielding gas when melted. The MIG process uses inert gas to shield the weld while molten.
When current is produced by a transformer (welding machine) and flows through the circuit to the weld wire, an arc is formed between the end of the weld wire and the work piece. This arc melts the wire and the work piece. The melted metal of the weld wire flows into the molten crater and forms a bond with the work piece as shown (Figure 9).
Arc Welding Basics
Five basic techniques affect weld quality. These are: wire selection, heat setting, weld angle, wire speed, and travel speed. An understanding of these techniques is necessary for effective welds.
HEAT SETTING
The correct heat involves the adjust- ment of the welding machine to the required setting. Heat or voltage is regulated by a switch on the welder. The heat setting used depends on the size (diameter) and type of wire, position of the weld, and the thickness of the work piece. Consult specif-
ications listed on the welder. It is suggested that the welder practice with scrap metal to adjust settings and compare welds with Figure 11.
WIRE TYPE AND SIZE
The correct choice of wire type involves a variety of factors, such as welding position, work piece material type, thickness and condition of surface to be welded. The American Welding Society, AWS, has set up certain requirements for each type of wire.
FLUX-CORE WIRE
E - 7 0 T - GS
Weld strength, times 10,000 psi
Welding positions (0 for flat or horizontal, 1 for any position)
Tubular flux core wire Flux type
AWS
SOLID WIRE
ER - 70 S - 6
Weld strength, times
1,000 psi Solid wire
Wire composition
WELD ANGLE
Weld angle is the angle at which the nozzle is held during the welding process. Using the correct angle ensures proper penetration and bead formation. As different welding positions and weld joints become necessary, nozzle angle becomes an increasingly important factor in obtaining a satisfactory weld. Weld angle involves two positions - travel angle and work angle.
Travel angle is the angle in the line of welding and may vary from 5º to 45º from the vertical, depending on welding conditions.
Work angle is the angle from hori-
zontal, measured at right angles to the line of welding. For most applications, a 45º travel angle and 45º work angle is sufficient. For specific applications, consult an arc welding handbook.
5º - 45º
WORK ANGLE
5º - 45º
TRAVEL ANGLE
Figure 10 - Weld Angle
WIRE SPEED
The wire speed is controlled by the knob on the front panel. The speed needs to be “tuned” to the rate at which the wire is being melted in the arc. Tuning is one of the most critical functions in wire feed welding. Tuning should be performed on a scrap piece of metal the same type and thickness as that to be welded. Begin welding with one hand “dragging” the gun nozzle across the scrap piece while adjusting the wire speed with the other hand. Too slow of speed will cause sputtering and the wire will burn up into the contact tip. Too fast a speed will also cause a sputtering sound and the wire will push into the plate before melting. A smooth buzzing sound indicates the wire speed is properly tuned. For aluminum, wire speed is typically set higher (7 - 9 speed range).
NOTE: Repeat the tuning procedure each time there is a change in heat setting, wire diameter or type, or work piece material type or thickness.
TRAVEL SPEED
The travel speed is the rate at which the torch is moved across the weld area. Factors such as diameter and type of weld wire, amperage, position, and
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