Specialty GMAW/MIG Welding 4th year Flashcards
What is GMAW?
Gas metal arc welding
List some possible electrical shock hazards when MIG welding.
not having gloves and shoes in a dry and good condition, welding on a wet surface or wet weather condition, not checking electrical connections and insulation on the welding gun and cables are in good condition.
Eyes should be protected from what when welding?
electric arc
The face and body should be protected, why?
Radiation reflected from shiny surfaces can cause sunburn to the skin, the reflected light can become a concern when work is done inside tanks.
Should ear plugs be worn?
yes
What protective clothing is preferred?
dark-coloured tightly woven denim clothing is preferred.
Is ventilation mandatory?
yes, adequate ventilation is mandatory for all GMAW operations.
Extreme caution should be taken when welding metals that contain zinc, why?
Fumes from these metals can be toxic, you should use adequate ventilation.
Should the valves be closed and protective caps be installed when handling cylinders?
Yes, when returning cylinders you should ensure that valves are closed.
What are three metal transfer methods?
Short-circuit transfer
Globular transfer
Spray arc transfer
The welding of sheet metal uses which of the three methods?
Short-circuit transfer
The globular transfer is generally avoided why?
Due to spatter problems and poor weld metal appearance.
The spray mode of metal transfer is used for joining materials_____and greater in thickness.
2.4 mm
When the wire speed is increased the_______are increased.
currents
What will happen if the voltage is too high or the wire is too low?
the wire will burn back,feed,make contact, burn back, feed, make contact ans so forth.
What will happen if the voltage is too low or the wire speed is too high?
you will get stubbing ( which is where the wire in not burning off at a fast rate and is actually striking the bottom of the weld pool.
After setting the machine recommendations
( charts) what must be done to insure good set-up conditions are achieved?
play around with it to make sure that if the wire seems to be burning off, losing the arc, advancing, re-establishing the arc and burning off again, you are definitely running too high voltage or too low a wire speed.
What are the benefits of flux cored welding?
-All position capability
-leaves a good quality weld metal deposit
higher deposition rates than shielded metal arc welding.
-low operator skill required
-metallurgical benefits that can be gained from a flux
Each type of shielding gas can affect the weld characteristics in what way?
each have a specific effect on the arc characteristics, the depth of fusion, the weld bead profile, the weld speed, the cleaning action and the mode of metal transfer,
What is the primary purpose of shielding gas?
to prevent the molten weld metal from absorbing elements such as oxygen and nitrogen from atmospheric air.
List some items that should be considered when selecting shielding gas.
base metal type and thickness
welding process
joint design and positioning
type of metal transfer
Argon has a high or low thermal conductivity?
low
helium has a high or low thermal conductivity?
high
Can argon cause suffocation?
yes
carbon dioxide can act as an asphyxia. True or False?
true
Co2 is the cheapest gas available. True or false?
true
When oxygen is added to shielding gas it can help with the puddle fluidity. True or false?
true
Hydrogen is the lightest know element and highly combustible. True or false?
true
Nitrogen is considered inert. True or false?
true
Nitrogen is flammable. True or false?
false
C-25( argon-carbon dioxide) is characterized by____?
a stable arc, good puddle control and little spatter.
What is the current and polarity for GMAW of stainless steel?
DCEP
What is the correct traverse and longitudinal gun angles?
For GMAW welding, the gun angle is typically held at a 15-30 degree angle to the workpiece for both traverse and longitudinal welds. A slight drag angle is also commonly used, which means that the gun is pulled in the direction of travel. This angle helps reduce spatter and allows for proper gas coverage.
Which gas is preferred for welding stainless steel?
helium
Must the material be cleaned before welding?
yes
Stainless steel has a high or low thermal conductivity?
low
Stainless steel has a high thermal expansion rate. True or false?
yes
What is the ore of aluminum?
bauxite
What are some advantages of GMAW on aluminum?
enables aluminum welding to be done at high speeds in all positions,less distortion and deep penetration.
Aluminum has a high or low thermal conductivity?
high
What is the melting point of aluminum?
The melting point of aluminum is 660.32°C (1220.58°F).
What precautions should be taken when dealing with the highly reflective materials?
eye and skin protection
Does aluminum develop an oxide?
yes
Aluminum coefficient of expansion is how much greater than steel?
twice as much
Higher heat is needed when welding aluminum, why?
Due to its high thermal’s conductivity,aluminum requires a heat input 4 times more rapid than mild steel to raise its temperature to melting point. This requires the the use of an intense heat source for successful welding.
GMAW enables aluminum welding to be done at high speeds. True or false?
True
What gas is normally used to weld aluminum?
Aragon
What is the current and polarity use for welding GMAW aluminum?
DCEP
Name two types of wire feeders used for welding aluminum?
Push type, pull type
Dirty materials will cause what problems to the welds?
Porosity
A lack of shielding gas will cause what problems to the welds?
Porosity, incomplete fusion, weld splatter.
What is the correct traverse gun angle for a lap seam?
45 degrees
How far should the electrode stick out?
Between 0.5-1.5 inches
What is stubbing?
The proccess of accidentally striking the electrodes or wire against the base metal.
What are the correct gas flow settings?
For GMAW, the recommended gas flow rate typically ranges from 20 to 50 cfh, depending on the type of gas being used and the welding application. A lower flow rate is typically used for welding thinner materials, while a higher flow rate is used for thicker materials or for welding in a windy environment.
How is the electrode sized?
The diameter of the electrode is typically measured if fraction of an inch or millimeters.
Where should the contact tip be placed?
The contact tip should be placed as close as possible to the workpiece without making contact with it.
Sketch the symbol to a fillet weld?
