Transcript Gas Metal Arc Welding (GMAW)

Gas Metal Arc Welding (GMAW)
GMAW
• Gas Metal Arc Welding
• MIG ( Metal Inert Gas )
• MAG (Metal Active Gas)
• Wire Welding
Proper Attire
What is GMAW?
Gas Metal Arc Welding
• MIG - MAG Welding
– MIG = Metal Inert Gas
– MAG= Metal Active Gas
• Solid Wire with External
Shielding Gas
• DCEP (DC+) Polarity
ADVANTAGES:
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All Position Welding
Quality Welds
Little to No Slag
Low Spatter
Variety of Metals
Various Material
Thickness
• High Efficiency
• High Radiated Heat
LIMITATIONS:
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Cost
Portability
Outdoor Welding
Clean Base Material
Potential for Cold Lap
Potential for Undercut
High Radiated Heat
Identify Major Components
• Power Source, Wire Feeder, Shielding Gas,
Electrode Wire, Gun
Power Source
• Converts Primary ( Outside ) Power To
Secondary ( Useable ) Power
• DCEP Direct Current Electrode Positive /
Reverse Polarity
• DCEP = Lower spatter levels, Deeper
Penetration levels
Wire Feeder
• Delivers Wire To The Weld Pool At A Very
Constant Speed
• Wire Feeder starts gas flow, current, wire feed
• Wire Speed Is Measured In Inches Per Minute
Shielding Gas
• To Shields The Weld Pool Form Contaminants
That are In The Atmosphere
• Stabilize The Arc
• Helps Regulate Penetration
• Argon 75% - CO2 25% (C-25)
Mig GUN
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Trigger
Liner
Contact Tip
Diffuser
Nozzle
Electrode WIRE
ER70S-6
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ER = ELETRODE ROD
70,000 TENSILE STRENGTH
S = SOLID WIRE
6 = CHEMICAL COMPOSITION
• Wire Diameter Range (.025” - .125”)
• Copper coated vs. non-coated wire
Starting the Arc
Electrode Stick Out - ESO
Sheet ESO = 3/8 - 1/2 inch
Plate ESO = ¾ - 1 inch
Bead Initiation
Bead Manipulation
Travel Angle
Bead Termination
Modes of Metal Transfer
1. Short Circuiting (Short Arc)
2. Globular
3. Spray
The welding machine automatically selects mode of
transfer dependent upon settings & variables.
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Type/mix of shielding gas
Electrode diameter
Voltage
ESO
Short Circuiting
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Droplet Forms
Droplet Shorted
Metal Transfers
Fuse Forms
Arc Re-established
Low Cost
Deep Penetration
Less Spatter
More Fluid Weld Pool
Globular
• Arc Initiated
• Large Droplet Forms
• Projected into weld
pool
Globular
Advantages
• Deep Penetration
• High Deposition
• Low Cost Gas
Limitations
• Excessive Spatter
• Flat / Horizontal
Position Only
Spray
• Arc Initiated
• Point Forms on End of
Electrode Wire
• Numerous tiny Drops
Form the Weld Pool
• 100% Argon
Spray
Advantages
• Smooth Weld Bead
Limitations
• Potential Undercut
• Deep Penetration
• Higher Shielding Gas Cost
• High Deposition
• Flat / Horizontal Position Only
• Little to No Spatter
• High Radiated Heat
GMAW Process Parameters
Steel Material
Thickness
1/8”
3/16”
1/4”
5/16”
3/8”
.035” wire
Short-Arc Mode
Gas
Amps
Wire
75%ARSpeed
25%CO2
18-19
140-150
280-300
18-19
160-170
320-340
21-22
180-190
360-380
21-22
200-210
400-420
23-24
220-250
420-520
Volts
23-24
24-25
24-25
25-26
26-27
Determining IPM without readout
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Cut shielding gas
Pull trigger & count to 6
Measure length of wire
Multiply x 10
Wire Burnback
Wire welds itself to the tip
Possible Causes
Corrective Actions
* Drive Rolls in Poor Condition
* Excessive Welding Voltage
* Insufficient Electrical Stickout
*Tighten, Clean, or Replace Rolls
* Reduce Voltage
* Increase Contact Tip to Work
Piece Distance
* Clean or Replace Contact tip
* Remove Spatter
* Contact Tip in Poor Condition
* Spatter on Contact Tip
Burnthrough
Hole burns through base metal
Possible Causes
Corrective Actions
* Excessive Amperage
* Improper Travel Angle
*Travel Speed Too Low
* Insufficient Electrical Stickout
*Reduce Amperage
* Use a Push Angle
* Increase Travel Speed
* Increase Distance
Repairing Burn through
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Turn voltage slightly down
Extend ESO to ¾”
Small tack welds in a “star pattern”
Allow metals to cool sufficiently
Incomplete Penetration
• Toes should tie into metal
• 1/8 bead height max
Possible Causes
Corrective Actions
* Insufficient Amperage
* Improper Travel Angle
* Excessive Electrical Stickout
* Weld Joint Too Narrow
*Increase Amperage
* Use Less of a Drag angle
* Decrease Distance
* Increase joint opening
Lincoln V350 Setup - GMAW
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Plug ground wire into (-) Terminal
Plug Wire Feeder into (+) Terminal
Select CV-Wire mode
Hot start is not used
Set Arc Control to “-5”
-10= soft arc (for use with inert gases)
+10= crisp arc (for use with CO2)
(See Next Slide)