54 557 C 2012−04 Processes MIG (GMAW) Welding Guidelines For Gas Metal Arc Welding (GMAW) Visit our website at www.MillerWelds.
TABLE OF CONTENTS SECTION 1 − SAFETY PRECAUTIONS - READ BEFORE USING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1. Symbol Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2. Arc Welding Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3.
SECTION 1 − SAFETY PRECAUTIONS - READ BEFORE USING som 2011−10 7 Protect yourself and others from injury — read, follow, and save these important safety precautions and operating instructions. 1-1. Symbol Usage DANGER! − Indicates a hazardous situation which, if not avoided, will result in death or serious injury. The possible hazards are shown in the adjoining symbols or explained in the text. Indicates a hazardous situation which, if not avoided, could result in death or serious injury.
FUMES AND GASES can be hazardous. Welding produces fumes and gases. Breathing these fumes and gases can be hazardous to your health. D Keep your head out of the fumes. Do not breathe the fumes. D If inside, ventilate the area and/or use local forced ventilation at the arc to remove welding fumes and gases. D If ventilation is poor, wear an approved air-supplied respirator.
1-3. Additional Symbols For Installation, Operation, And Maintenance FIRE OR EXPLOSION hazard. BATTERY EXPLOSION can injure. D Do not install or place unit on, over, or near combustible surfaces. D Do not install unit near flammables. D Do not overload building wiring − be sure power supply system is properly sized, rated, and protected to handle this unit. D Do not use welder to charge batteries or jump start vehicles unless it has a battery charging feature designed for this purpose.
1-4. California Proposition 65 Warnings Welding or cutting equipment produces fumes or gases which contain chemicals known to the State of California to cause birth defects and, in some cases, cancer. (California Health & Safety Code Section 25249.5 et seq.) This product contains chemicals, including lead, known to the state of California to cause cancer, birth defects, or other reproductive harm. Wash hands after use. 1-5.
SECTION 2 − GAS METAL ARC WELDING (GMAW) Gas Metal Arc Welding (GMAW) is a welding process which joins metals by heating the metals to their melting point with an electric arc. The arc is between a continuous, consumable electrode wire and the metal being welded. The arc is shielded from contaminants in the atmosphere by a shielding gas. GMAW can be done in three different ways: S Semiautomatic Welding - equipment controls only the electrode wire feeding. Movement of welding gun is controlled by hand.
2-1.
2-2. Typical GMAW Semiautomatic Setup With Voltage-Sensing Feeder 1 Constant Current (CC-DC) Or Constant Voltage (CV) Welding Power Source 2 Weld Cable To Feeder 3 Ground Cable To Workpiece 4 Workpiece 5 Voltage-Sensing Clamp 6 Welding Gun 7 Gun Trigger Receptacle 8 Voltage-Sensing Wire Feeder 9 Gas Hose 10 Shielding Gas Cylinder 1 10 2 9 8 3 7 4 5 6 Ref.
2-3. Typical GMAW Process Control Settings . These settings are guidelines only. Material and wire type, joint design, fit−up, position, shielding gas, etc. affect settings. Test welds to be sure they comply to specifications. 1 1 1/8 or .125 in. Convert Material Thickness to Amperage (A) (.001 in. = 1 ampere) .125 = 125 A . Material thickness determines weld parameters. 2 2 3 Select Wire Size Wire Size Amperage Range .030 in. .035 in. .045 in.
2-4. Holding And Positioning Welding Gun . 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. 1 3 2 1 Hold Gun And Control Gun Trigger 2 Workpiece 3 Work Clamp 4 Electrode Extension (Stickout) 1/4 To 1/2 in.
2-5. Conditions That Affect Weld Bead Shape . 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.
2-6. Gun Movement During Welding . Normally, a single stringer bead 1 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. 2 1 Stringer Bead − Steady Movement Along Seam 2 Weave Bead − Side To Side Movement Along Seam 3 Weave Patterns Use weave patterns to cover a wide area in one pass of the electrode. 3 S-0054-A 2-7.
2-8. Good Weld Bead Characteristics 1 2 4 3 1 Fine Spatter Or No Spatter 2 Uniform Bead 3 Moderate Crater During Welding 4 No Overlap 5 Good Penetration Into Base Metal 5 S-0052-B 2-9. Common GMAW Shielding Gases This is a general chart for common gases and where they are used. Many different combinations (mixtures) of shielding gases have been developed over the years.
SECTION 3 − MODES OF GMAW TRANSFER . GMAW transfer mode is determined by variables such as shielding gas type, arc voltage, arc current, diameter of electrode and wire feed speed. 3-1. Short Circuit Transfer 1 Short Circuit Transfer Short circuit transfer refers to the welding wire actually “short circuiting” (touching) the base metal between 90 - 200 times per second.
3-2. Globular Transfer 1 Globular Transfer Globular transfer refers to the state of transfer between short-circuiting and spray arc transfer. Large globs of wire are expelled off the end of the electrode wire and enter the weld puddle. 1 Globular transfer can result when welding parameters such as voltage, amperage and wire feed speed are somewhat higher than the settings for short circuit transfer.
SECTION 4 − GMAW WELDING TROUBLESHOOTING 4-1. Excessive Spatter Excessive Spatter − scattering of molten metal particles that cool to solid form near weld bead. Possible Causes Corrective Actions Wire feed speed too high. Select lower wire feed speed. Voltage too high. Select lower voltage range. Electrode extension (stickout) too long. Use shorter electrode extension (stickout). Workpiece dirty.
4-3. Incomplete Fusion Incomplete Fusion − failure of weld metal to fuse completely with base metal or a preceeding weld bead. Possible Causes Corrective Actions Workpiece dirty. Remove all grease, oil, moisture, rust, paint, coatings, and dirt from work surface before welding. Insufficient heat input. Select higher voltage range and/or adjust wire feed speed. Improper welding technique. Place stringer bead in proper location(s) at joint during welding.
4-6. Burn Through Burn-Through − weld metal melting completely through base metal resulting in holes where no metal remains. Possible Causes Corrective Actions Excessive heat input. Select lower voltage range and reduce wire feed speed. Increase and/or maintain steady travel speed. 4-7. Waviness Of Bead Waviness Of Bead − weld metal that is not parallel and does not cover joint formed by base metal. Possible Causes Corrective Actions Unsteady hand. Support hand on solid surface or use two hands.
Miller Electric Mfg. Co. An Illinois Tool Works Company 1635 West Spencer Street Appleton, WI 54914 USA International Headquarters−USA USA Phone: 920-735-4505 Auto-Attended USA & Canada FAX: 920-735-4134 International FAX: 920-735-4125 For International Locations Visit www.MillerWelds.com ORIGINAL INSTRUCTIONS − PRINTED IN USA 2012 Miller Electric Mfg. Co.
