Interview question from GMAW process

Interview question from GMAW process

Interview question from GMAW process

What is GMAW Welding?
 GMAW Welding is an ARC welding process in which fusion is produced by heating the job along with an electric arc between the continuous filler metal electrode and the weld pool.

 How many types of metal transfer methods are used in GMAW process?
·         Dip Transfer
·         Spray Transfer
·         Pulsed Transfer
·         Synergic Pulsed Transfer
·         Globular Transfer
What are the variable parameters in GMAW Process?
·         Voltage
·         Wire feed speed
·         Gases
·         Inductance
What types of possible welding imperfections may occur in GMAW process?
·         Silica inclusions (On ferritic steels)
·         Lack of sidewall fusion
·         Porosity
·         Burn through
Give any five advantages of the GMAW process?
·         High Productivity
·         Easily automated (Robotics)
·         All positional
·         Wide material thickness range
·         Continuous electrode
Give any five disadvantages of the GMAW process?
·         Lack of fusion (Excessive inductance)
·         The small range of solid wires
·         Protection for site working
·         Complex equipment
·         High ozone levels
What is the current range for the following metals in GMAW process?
a) Carbon steel         b) Stainless steel         c) Aluminum

Arc current (Amps)
Electrode Día(mm)
Shielding gas
Flow rate of Shielding gas
Carbon Steels (Double V butt)
400 DCRP
6 to 12
Stainless Steel (Butt)
275-350 DCRP
Argon +1%O2
15 to20
Aluminum     (Square butt)
200-225 DCRP
1 -1.25

What is the different size of electrodes in the GMAW Process?
0.8mm,1.2mm,1.6mm, etc.
What type of materials can be welded by GMAW Process?
·         Carbon and low alloy steels
·         Stainless steels
·         Heat-resisting alloys
·         Aluminum and its alloys
·         Copper and its alloys (other than high zinc alloys)
·         Magnesium alloys
What are the various types of welding joints used in the GMAW Process?
·         Butt joint
·         Lap joint
·         T joint
·         Corner joint
·         Edge joint
Describe the GMAW Process Applications?
The GMAW process can be used for the welding of the following metals:
·         carbon,
·         silicon, and low alloy steels,
·         stainless steels
·          aluminum,
·         magnesium,
·         copper,
·         nickel and their alloys,
·         titanium, etc.
·         tool steels and dies.
·         For the manufacture of refrigerator parts.
·         Aircraft,
·         Automobile,
·         Pressure vessel,
·         Ship buildings.
What is the function of Shielding gases in GMAW Process?
The function of shielding gas in GMAW Process is to protect the molten metal and the electrode end from atmospheric contamination.
How many types of shielding gases are used in GMAW Process?

Shielding Gases
Metal to be welded

of Al, Mg, Cu, Ni, Ti  

Al, Mg, Cu   
Carbon dioxide

Mild steel   

Argon+(1-5 %) Oxygen

Al, low alloy and Carbon steels, stainless steels
Argon +CO2

Mild steel ,low alloy and stainless steel

Austenitic stainless steels 
Argon + Helium

Al, Cu, Ni

What are the function of solenoid valves and relays in GMAW Process?
solenoid valves and relays may be incorporated in the system to put on and off gas, water and wire feed mechanism.


What is the CO2 Welding process?
CO2 Is basically a Sami-automatic process, in which the arc length and the feeding of the electrode wire into the arc are automatically controlled.CO2 is used as an active gas (for shielding purpose) in this process.
What type of electrode should be used when co2 is used as shielding gas?
When using CO2 as the shielding gas the electrode wire must contain deoxidizer such as manganese and silicon that readily combine with the oxygen and prevent it from combining with the weld metal.
Describe the welding current range, different size of electrodes, and selection of electrodes upon the thickness of the base metals in CO2 Welding process?
Welding current range for various range of electrodes are as follows:
Electrode size(mm)
Current range (Amps)

Describe the thickness of the base metals, according to the current range, also choose the size of the electrode.
Workpiece thickness(mm)
8.0 and above
Wire diameter(mm)
1.6 and above

How many factors are responsible for selecting the welding’s current in the CO2 Welding process?
The welding current is selected according to:
·         Electrode size
·         Electrode feed speed
·         Type of metal transfer
·         Base metal thickness
Give any four advantages of the CO2 welding process?
·         Higher welding speed
·         Deep penetration with good weld bead
·         Good mechanical properties of the weld metal
·         Sound weld deposits which can be made consistently
What are the limitations of the CO2 welding process?

  • ·         Carbon dioxide is producing a rather harsh arc
  • ·         Excessive spatter unless a very short, uniform arc length is maintained
  • ·         High impact properties in the weld metal cannot be achieved.

Which of the following gases can be used as shielded gases in GMAW?
a- Carbon dioxide                               b-Argon –oxygen                                            
c-Argon-Carbon dioxide                    d-Argon
e-All of the above

e- All of the above

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