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Guidelines To
Gas Metal Arc Welding
(GMAW)
WARNING
ARC WELDING can be hazardous.
This document contains general information about the topics discussed herein. This document is
not an application manual and does not contain a complete statement of all factors pertaining to
those topics.
This installation, operation, and maintenance of arc welding equipment and the employment of
procedures described in this document should be conducted only by qualified persons in
accordance with applicable codes, safe practices, and manufacturer's instructions.
Always be certain that work areas are clean and safe and that proper ventilation is used. Misuse
of equipment, and failure to observe applicable codes and safe practices, can result in serious
personal injury and property damage.
PRINTED IN USA
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Summary of Contents for Miller Electric GMAW
- Page 1 Guidelines To Gas Metal Arc Welding (GMAW) WARNING ARC WELDING can be hazardous. This document contains general information about the topics discussed herein. This document is not an application manual and does not contain a complete statement of all factors pertaining to those topics.
- Page 2 WARNING ELECTRIC SHOCK can kill. • Always wear dry insulating gloves. • Insulate yourself from work and ground. • Do not touch live electrical parts. • Keep all panels and covers securely in place. FUMES AND GASES can be hazardous to your health. •...
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Page 3: Gas Metal Arc Welding (Gmaw)
1. Gas Metal Arc Welding (GMAW) Regulator/ Welding Flowmeter Power Source 115V/24V Contactor Wire Feeder Shielding Work Electrode Lead Work Lead ST-800 357-A Figure 1. Typical GMAW Process Connections 154 557 Page 2... - Page 4 Select Voltage Set voltage midway between high/low voltage. Wire speed (amperage) con- trols weld penetration. (wire speed = burn-off rate) Voltage controls height and width of weld bead. ST-800 354 Figure 2. Typical GMAW Process Control Settings 154 557 Page 3...
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Page 5: Fillet Welds
NOTE Welding wire is energized when gun trigger is pressed. Before lowering helmet and pressing trigger, be sure wire is no more than 1/2 in (13 mm) past end of nozzle, and tip of wire is positioned correctly on seam. Hold Gun And Control Gun Trigger Workpiece... - Page 6 NOTE Weld bead shape depends on gun angle, direction of travel, electrode extension (stickout), travel speed, thickness of base metal, wire feed speed (weld current), and voltage. ° Push ° Perpendicular Drag GUN ANGLES AND WELD BEAD PROFILES Short Normal Long ELECTRODE EXTENSIONS (STICKOUT) Short...
- Page 7 NOTE Normally, a single stringer bead is satisfactory for most narrow groove weld joints; however, for wide groove weld joints or bridging across gaps, a weave bead or multiple stringer beads works better. Stringer Bead – Steady Move- ment Along Seam Weave Bead –...
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Page 8: Welding Troubleshooting
Fine Spatter Uniform Bead Moderate Crater During Welding Weld a new bead or layer for each 1/8 in (3.2 mm) thickness in metals being welded. No Overlap Good Penetration Into Base Metal S-0052-B Figure 7. Good Weld Bead Characteristics 2. Welding Troubleshooting Table 1. - Page 9 Table 2. Porosity Porosity – small cavities or holes re- sulting from gas pockets in weld metal. S-0635 Possible Causes Corrective Actions Inadequate shielding gas Check for proper gas flow rate. coverage. Remove spatter from gun nozzle. Check gas hoses for leaks. Eliminate drafts near welding arc.
- Page 10 Table 3. Incomplete Fusion Incomplete Fusion – failure of weld metal to fuse completely with base metal or a preceeding weld bead. S-0637 Possible Causes Corrective Actions Workpiece dirty. Remove all grease, oil, moisture, rust, paint, undercoating, and dirt from work surface before welding. Insufficient heat input.
- Page 11 Possible Causes Corrective Actions Improper weld technique. Maintain normal gun angle of 0 to 15 degrees to achieve maxi- mum penetration. Keep arc on leading edge of weld puddle. Be sure welding wire extends not more than 1/2 in (13 mm) be- yond nozzle.
- Page 12 Increase travel speed. Weld in small segments and allow cooling between welds. 3. Common GMAW Shielding Gases This is a general chart for common gases and where they are used. Many differ- ent combinations (mixtures) of shielding gases have been developed over the years.
- Page 13 NOTES 154 557 Page 12...
- Page 14 Fillet Fillet Short Circuiting Stainless Steel Spray Arc Aluminum Positions Short Circuiting All Positions Aluminum Globular Transfer 90% HE + 7-1/2% AR + 2-1/2% CO Heavy Thicknesses Also for GMAW-P, All Positions Single Pass Welding Only 154 557 Page 13...
- Page 15 Argon + 25% Argon + Argon + Helium Tri-Mix 50% CO Helium Flat & Flat & Horizontal Horizontal Fillet Fillet All Positions All Positions All Positions All Positions All Positions All Positions All Positions 154 557 Page 14...
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