Chapter 15 GMAW and FCAW Flashcards
GMAW is a welding process in which metals are joined by heating them with a welding arc between a ________________ and ____________
Continuous consumable electrode and the base metal
GMAW is MIG welding. MIG stands for ______________. However, since not all gases used in GMAW are _______, MIG is an inaccurate term.
Metal inert gas
inert
GMAW uses _______ as an electrode. A welding arc is struck between ____ and ___.
wire
electrode and base metal
Why is the electrode used in GMAW known as consummable?
Because the electrode is melted and becomes part of the weld.
What is a metal cored electrode?
They are used for GMAW. They have a carbon steel sheath. The core contains iron powder and other metal alloy powders
Direct current electrode positive (DCEP) is also called ______________________ which is typically used for GMAW.
Direct current reverse polarity (DCRP)
A ____________ power source is used for GMAW and FCAW.
constant voltage
On a constant voltage power source, the welder sets the required voltage and required __________.
wire feed speed
The wire feed speed is directly related to ______________
welding current
A constant voltage welding machine maintains a constant voltage by altering the ______________
current
What does the designation FCAW-S mean?
It is for flux cored arc welding self-shielded process which does not require any additional shielding gas.
Self-shielding electrodes produce their own ____________
shielding gas
An electrode used for FCAW-S has materials in the flux to remove more ______ and _____ from the weld than are removed with FCAW-G electrodes.
Oxygen and nitrogen
Short circuiting transfer is also called _____. It uses a low welding current and ________.
Short arc
voltage
In short arc welding, a small diameter electrode of _______ is used.
0.030”-0.045” (0.8 mm - 1.2 mm)
The ________ transfer method adds the least amount of heat to the base metal of any transfer method.
short circuiting
Which transfer method is used to join thin sheets of metal and out-of-position welding for welding parts that have large gaps?
Short circuiting transfer is used because it adds the least amount of heat to the base metal
Why would the end of an electrode explode?
The end of an electrode explodes if the welding machine increases the welding current too fast
What is inductance?
it is an electrical means of controlling the rate of current change in a circuit.
In a welding machine __________ controls how fast the welding machine increases the welding current.
inductance
The inductance should be _________ if the end of the electrode appears to explode and creates a lot of spatter.
increased
Increasing the inductance ________ the rate of current increase
slows
Globular transfer uses slightly __________ voltage and current settings that those used for short circuiting transfer.
higher
In globular transfer, the arc melts the end of the electrode and the base metal. The size of the molten metal __________ or ball on the end of the electrode increases until it is larger than ______________.
Globule
the diameter of the electrode
In globular transfer, the globule continues to grow in size until _____________
the globule falls off the electrode due to its own weight
Which type of transfer requires higher voltage and current settings?
Spray transfer requires higher voltage and current settings than globular transfer.
In ____________ transfer, hundreds of small droplets are formed every second at the middle of the electrode end. They travel at a high rate of speed directly _______________.
spray
into the weld
In __________ transfer, good penetration is obtained with very little spatter and the weld pool is ____________
Spray
very fluid
Which position is spray transfer primarily used for?
flat position or on horizontal fillet welds
Metal that is ________ or thicker can be welded using the spray transfer process
1/8” (3.2 mm)
Which type of shielding gas should be used for spray transfer?
A mixture containing at least 90% argon
_____________ electrodes produce an excellent weld bead when used with spray transfer.
metal cored
Why does a metal cored electrode produce such an excellent weld bead when used with spray transfer?
The current produces a broad, cone-shaped arc. The spray droplets do not form in the centre of the electrode, they form around the outside of the electrode.
When would you choose a solid electrode instead of a metal cored electrode for spray transfer?
When you need to bridge a wider gap in the weld joint because solid electrodes will create a slightly wider weld pool.
The same power supply can be used for both GMAW and FCAW. Both processes require constant _________________.
voltage or constant potential power supply
What can supply the constant voltage power for GMAW and FCAW?
A transformer-rectifier
an inverter
or an engine driven generator
Can GMAW and GTAW use the same power supply?
No, GMAW needs a constant voltage power supply, GTAW needs a constant current power supply.
Which types of power supply are needed for GMAW, FCAW, SMAW and GTAW?
GMAW and FCAW need constant voltage
SMAW and GTAW need constant current
A constant voltage power supply maintains a constant arc voltage and arc length, even though_____________________________
the welder may not maintain a constant distance from the welding gun to the base metal.
A welding machine for _______ or _______ is considered to be self-adjusting, since it makes adjustments automatically. Those changes are made very quickly to compensate for any changes that the welder makes.
GMAW and FCAW
What happens when the welding gun is moved closer to the base metal while welding?
The arc length shortens and the voltage decreases. The power supply instantly increases the current so the electrode melts faster which in turn increases the arc length. When the electrode burns back to the original arc length and arc voltage, the current returns to its original setting.
If the welding gun is _________the base metal, both the arc length and the voltage increases. The power supply instantly reduces the current.
pulled away from the base metal
___________ is the most common shielding gas for GMAW. It is used to weld almost all types of metals.
Argon
What can be added to the shielding gas argon for GMAW?
Carbon dioxide, oxygen or helium
What happens when argon is used in spray transfer?
The weld has a very deep penetration in the centre. with very little spatter. The edges, however, are undercut. Oxygen or carbon dioxide is added to eliminate this undercutting.
What is a common shielding gas mixture for GMAW?
Argon with 1%-5% oxygen or Argon with 3%-50% carbon dioxide
What shielding gas is required in GMAW for spray transfer?
At least 90% argon
Metal cored GMAW electrodes require at least _____ % argon combined with _____________
75% with carbon dioxide
______________ is commonly used as a shielding gas for FCAW. It provides ____________ transfer of the electrode.
Carbon dioxide
globular
Why is CO2 used?
It is inexpensive and creates a weld with deep penetration.
A common gas mixture for FCAW is _____% Ar and ____% CO2 which allows metal transfer that approaches ___________ transfer.
75%
25%
spray
A water cooled gun has two hoses and a cable assembly. One hose which is usually blue, carries the water ___________. The other hose, which is usually red, carries the water _____________.
To the gun (blue)
From the gun (red)
The cable assembly carries which three things?
electricity, electrode and shielding gas
What is the gas nozzle used for?
To direct shielding gas to the weld area
The cable assembly through which the electrode wire travels has a liner in it. This liner gradually becomes worn and needs to be replaced occasionally. What is the purpose of this liner?
To keep the electrode traveling smoothly through the cable. It is generally a flexible tube made of coiled wire.
For welding with soft electrodes, such as aluminum, a _________ liner is used
teflon
Shielding gases used for GMAW are primarily argon and carbon dioxide. Mixtures of these gases, along with ______ and _____ may also be used.
oxygen and helium
_______ gases do not combine with the weld metal.
Inert
Carbon dioxide (CO2) and oxygen (O2) are active gases. What are active gases?
Gases that react or combine with the weld metal. If CO2 or O2 enters the weld, the weld becomes oxidized.
Carbon dioxide (CO2) and oxygen (O2) are active gases. What are active gases?
Gases that react or combine with the weld metal. If CO2 or O2 enters the weld, the weld becomes oxidized.
What is the difference between a typical welding gun for FCAW-G and FCAW-S?
There is no nozzle on the FCAW-S gun
In welding guns that are commonly used for _________ electrodes and __________ diameter electrodes, the wire feeder pushed the electrode through the gun.
Steel
Large
Electrode wire may bend and jam the machine if _______________________
The welding takes place a long distance from the wire feeder or if a small, soft electrode such as aluminum is used.
What is a pull-type gun?
A gun that has a motor that pulls the wire through the cable and prevents the electrode from being bent. Often a wire feeder pushes the electrode while the welding gun pulls it. This is a push-pull system.
When is a pull-type gun used?
To prevent a jam when welding takes place a long distance form the wire feeder or if a small, soft electrode is used.
