MIG WELDING

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MIG WELDING

• MILBANK WELDING CLASS

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I CAN

• I can compare the MIG welding process to Shielded
  Metal Arc Welding
• I can describe the correct operating procedure of
  MIG welding.
• I can demonstrate the correct method of the MIG
  machine operation.

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MIG WELDING PROCESS
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MIG Welding

• Gas Metal Arc Welding (GMAW) is frequently
  referred to as MIG welding. MIG welding is a
  commonly used high deposition rate welding
  process. Wire is continuously fed from a spool.
  MIG welding is therefore referred to as a
  semiautomatic welding process.
• MIG Welding Benefits All position capability
  Higher deposition rates than SMAW Less
  operator skill required Long welds can be made
  without starts and stops Minimal post weld
  cleaning is required

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Wire Welder

• Industry Standardsused to make beads automatic
  and identical to each
• Uses a spool of copper wire to weld with.
• More automatic
• Produces no slag
• FluxArgon/Carbon dioxide
• When weldingshould sound like bacon frying.
• Keep nozzle and tip clean. Use nozzle dip.
• Turn on flow gage1st Thing.
• Keep wire hose straight.

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What is GMAW?

• Gas Metal Arc Welding (GMAW) is often known as
  Metal Inert Gas (MIG) or Metal Active Gas (MAG)
• GMAW is an arc welding process that uses a
  continuous solid wire electrode for the filler
  metal and a shielding gas to protect the weld
  zone.
• The molten puddle is shielded by an external
  shielding gas
• ARGON/CO2 MIX
• CO2

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Principles of the GMAW Process

• The Gas Metal Arc Welding process is one in which
  an arc is established when a continuously fed
  solid wire consumable electrode makes contact
  with the work piece.
• The molten puddle is shielded by an external
  shielding gas.
• An operator may push or pull the welding gun
  depending on the mode of metal transfer and
  whether the desired result is increased
  penetration or a smoother weld appearance.
• Little to no slag is deposited on the weld

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MIG PROCESS
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GUN MOVEMENTS
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GUN DIRECTION
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GMAW - ADVANTAGES

• The main one being that quality welds with high
  deposition can be made in a variety of metals and
  alloys. This is due to the fact that the
  shielding gas protects the metal from
  contamination.
• A variety of material types can be welded
• A variety of thickness can be GMAW welded due to
  the fact that a broad range of amperages and
  voltages can be used.
• GMAW is also clean, with little to no slag and
  spatter. Therefore, efficiency levels are high
  (93-98),

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GMAW - Limitations

• Due to the fact that a shielding gas is needed,
  GMAW welding is less portable than those
  self-contained processes
• The gas bottles, hoses and regulators may be
  cumbersome
• The shielding gas is also susceptible to winds
  and drafts.
• NO GASPITTS THE BEADS

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SHORT CIRCUIT TRANSFER

• Welding wire actually short circuiting
  (touching) the base metal between 90-200 times
  per second.
• With short circuit transfer, wire feed speed,
  voltages and deposition rates are usually lower
  than other types of metal transfer.
• Very versatile allowing the welder to weld on
  thin or thick metals in any position.
• Sounds like BACON FRYING.

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ARC LENGTH

• The desired arc length is set by voltage on the
  power source and is also dependent upon
  electrical stickout.
• A CC system (i.e. Pulse) compensates for
  variations in the contact tip-to-work distance,
  which readily occur during welding by
  automatically (adaptive control) supplying
  increased and decreased amperages to maintain the
  desired arc length.
• The desired arc length is set by controlling
  amperage with a term called Trim and is
  independent of electrical stickout due to the
  adaptive control of these types of machines.
• Wire feeders feed the electrode wire from a spool
  and push it through the gun cable and the gun.
  Constant speed wire feeders obtain their voltage
  to run from a control or interconnecting cable to
  the power source.

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INTERNAL PARTS

• The wire feeder consists of a wire spool holder
  with a drag brake, an electric motor that drives
  either one or two sets of opposing drive rolls
  and various controls.
• The wire feeder usually contains the shielding
  gas connections and gas control solenoid, and the
  cooling water flow control solenoid if a
  water-cooled gun is being used.
• The wire feeder uses motor driven opposing drive
  rolls to grip and advance the wire.
• The welding gun is used to introduce the
  electrode and shielding gas to the weld zone and
  to transmit electrical power to the electrode.
• Different types of welding guns have been
  designed to provide maximum efficiency regardless
  of the application.
• These range from heavy-duty guns for high
  current, high production work to lightweight guns
  for low current or out of position welding.
• GMAW guns support and guide the wire electrode
  and provide the electrical contact between it and
  the welding machine electrode lead.

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WELDING GUN

• Guns also contain the trigger to start and stop
  the wire feed, welding current from the power
  source and the shielding gas flow.
• The contact tip guides the wire electrode through
  the center of the nozzle and makes electrical
  connection with the electrode cable.
• Contact tip must be matched to the wire size and
  must be replaced when it wears out from wire
  friction and electrical erosion.
• Shielding gas protects the electrode and weld
  from contamination.
• Shielding gas is directed around the electrode
  end and the weld zone by the nozzle of the gun.
• Shielding gases are supplied in bulk as liquids
  or as gases in pressurized cylinders of various
  sizes.
• A flow meter is required to control the flow of
  shielding gas to the gun at a preset flow rate.

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BASICSGAGES

• A typical flow meter consists of a preset
  pressure regulator with cylinder pressure gauge
  and cylinder valve stem, metering needle valve
  and flow rate gauge.
• The metering valve is used to adjust the gas flow
  to the gun nozzle.
• The flow gauge shows the gas flow rate in cubic
  feet per hour or liters per second.
• Multi-gas gauges have different scales for gases
  of different densities.
• A gas hose is required from the regulator/flow
  meter to the gas solenoid on the wire feeder.
• One of the benefits of this welding process is
  that the filler metal is supplied in continuous
  lengths of wire wound on spools of various sizes.
• Spools can be as small as 4 inches OD and
  weighing as little as 1 pound. Spools weighing up
  to 44 pounds, coils weighing up to 60 pounds and
  bulk packages that are 300 lb-1000 lb on reels
  and drums are available. Bulk packaging is ideal
  for anyone using a lot of wire and can be sold as
  a cost reduction based upon less changeover time.
• The type of consumable wire electrode selected
  depends upon the base metal.

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Flow Gage
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Wire WelderMAKE SURE TO TURN ON FLOW GAGES!!

• Millermatic 35
• Set heat 16 (Turn Pull)
• Set wire speed
• Usually around 50
• Adjust heat and speed as needed.

• Blue Hobart
• Determine type of metal and position
• Lift cover and determine welder preset selection
  for heat and speed.
• Adjust machine
• Fine adjustment wire speed and heat to individual
  needs.

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WELDING WITHOUT GAS
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Wire Welder Problems

• 1. Make sure your turn on the flow gages.
• Setting to around 2530
• 2. Make sure your hoses are straight
• 3. Popping NoiseAdjust wire speed down.
• 4. Check wire tips
• 5. Dip wire tips into nozzle lubricant
• 6. Make sure you have good penetration.
• Internet Site http//www.lincolnelectric.com/kno
  wledge/articles/content/gmaw.asp

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