Mild Steel GMAW Flashcards
What is GMAW how does it work
Gas metal arc welding, Joins metal by heating them with a electric arc from a continuously fed metal filler
What is used in mig to prevent atmospheric contamination?
Shielding gas
What type of machine setting does GMAW use
Direct current, electrode positive
3 types of metal transfer
Short circuit, globular transfer, and spray transfer
What kind of welding contains a flux that generates shielding for field fabrication
FCAW flux core arc welding
3 types of wire drive systems
Push, pull, push and pull
Electrode holders and cable assemblies carry what? Also called what?
Welding current, shielding gas, control switch, and coolant also called guns
Main function of contact tube
Transfer electrical current to electrode and direct wire to weld zone
Directs shielding gas on to weld zone?
The nozzle
Main purpose of regulator
Reduce source pressure to working pressure
What controls the rate of flow of the shielding gas to gun nozzle
A gas solenoid valve
How are cylinders identified and stored
Clearly labeled with contents and whmis. They are to be stored outside or well ventilated area upright and secured.
What does a metal rupture disk do.
A safety device on cylinders that, if pressure becomes excessive, will burst, allowing a controlled release of gas
Flow rate for CO² and argon/ CO²
20 cfh
What can result if flow rate is to high or to low
If it is too low, there is a lack of gas coverage
If too high, there can be turbulence
Both lead to porosity
Another name for stickout
Electrode extenion or electrical stickout
Another name for electrode inclination what is it.
Work angle, the position of the electrode to the work piece in relation to the direction of travel
Two terms for the inclination when welding
Forehand (push angle)
Or backhand (pull angle)
Rate that welding moves in a direction. Measured in mms or ipm
Travel speed
Poor work lead connection can lead to what?
Unstable arc
What occurs when electrodes comes in contact with base metal and an erratic arc is produced
Stubbing
Another name for bird nesting? what can cause it.
Wire pile up, plugged or misaligned conduit liner
Sharp bends in cable assembly
Weld splatter plugs end of co tact tube
Electrode wire stubs and sticks to base metal
Wire welds to contact tip
5 basic joints in gmaw
Butt, lap, edge, corner, grooved
What type of joint uses fillet weld as there’s less need for weld metal penetration
Lap
Most common type of weld defect caused by reaction to atmosphere.
Porosity
What can happen if current is set to high and travel speed is to low
Burn through
Most serious weld defect that can lead to complete weld failure
Cracking
What is undercut
The melting away of the parent metal and failing to fill it back in with weld metal
What is porosity
Pockets of gas entrapped within weld metal
What is lack of fusion
Metals not melting together, no coalesce of metal.
What is lack of penetration
The failure to melt into the surface or root edges of a joint
What are whiskers
Lengths of unmelted electrode wires welded to and protruding from the root
What are inclusions, also known as?
Small pockets of non metallic elements entrapped in the weld zone. Wagon tracks or slag inclusions
What effect does changing wire speed have on amperage or voltage
Increased wire speed =Increased amperage, voltage not affected
What are the two different angles involved in welding regarding work angles
Work (transverse) and travel (
longitudinal)
What is used to indicate weld type on a blue print?
Welding symbols
What causes porosity
Contamination
What defect is GMAW specific
Whiskers
Most dangerous type of light ray emmited by welding
Infrared rays
Welding lenses will protect your eyes from ____ of harmful light ray
99%
3 types of clothing in order from best to order for welding protection
Leather, wool or tweed, cotton drills or denim
Recommended lense level for gmaw
9 to 13
Maximum safe working pressure of acetylene
15psi
Stubbing is when
Electrode comes in contact with base metal and fails to start an arc immediately. Also pushes gun or welding head away from base metal
What is the pinch effect
Molten metal is separated from the end of the filler with a squeezing force created by a magnetic field
3 power source machine types for gnaw, all three may produce what?
Motor driven generator, transformer rectifiers, and inverter. May produce either constant current (CC) or constant voltage (CV)
What is a push system
Wire is fed by a set of drive rolls located in wire feed unit itself
What is a pull system
Have drive rolls mount on the gun itself close to contact tip
What is the contact tip usually made of. How are they sized.
Copper or copper alloy. Wire size specific.
Purpose of cable assemblies.
Used to join power source to the gun
Can you transfer gas from one cylinder to another.
No use, only equipment and fittings designed for the gas delivery system
What do flow meters do and what are they calibrated to indicate.
L/min (liters per minute) or CFH cubic feet per hour
