How well do you really understand MIG welding? Here are some questions (and answers) to test your knowledge!

1.) In the GMAW process, what is the primary source of deoxidizers and alloying elements that contribute to the purity and mechanical properties of the weld metal?

A. The wire
B. The shielding gas
C. The mode of transfer
D. The weld parameters

The answer is A. The wire is mostly responsible for the deoxidizing that occurs in the weld puddle. Although the shielding gas can play a role, it isn’t the primary source of the elements that help purify the weld metal.

2.) What is the purpose of copper coating on MIG wires?

A. To prevent rust
B. To increase contact tip life
C. To assure good electrical conductivity
D. All the above

If you chose D, you are correct. Cu-coated wire contributes to rust inhibition, increasing tip life and assuring good electrical conductivity.

3.) What elements are most commonly added to GMAW wires as deoxidizers?

A. Molybdenum and Copper
B. Nickel and Molybdenum
C. Manganese and Silicon
D. Silicon and Chromium

The correct answer is C, Manganese and Silicon. These two elements purify the weld metal. They can be assisted with a higher CO2 level in the shielding gas.

4.) Rust is a source of:

A. Silicon
B. Oxygen
C. Manganese
D. Nickel

The answer is B, oxygen, which isn’t a desirable element in weld metal. The higher the oxygen level, typically the lower the impact values. When welding over rust using the GMAW process the arc is much more violent compared to welding on clean material. This is the result of the increased impurities in the puddle. If the level of oxides and/or rust is excessive, porosity will occur.

5.) In GMAW, using 100% CO2 shielding gas produces:

A. less spatter and concave welds
B. more spatter and convex welds
C. more spatter and flatter welds

The correct answer is B, more spatter and a tendency towards a convex weld bead profile.

6.) What type of power supply is commonly used for general GMAW welding?

A. Constant Current
B. Constant Voltage
C. Pulse
D. Syncrowave

The answer is B, constant voltage, also referred to as constant potential. Although the use of pulse equipment is increasing, pulse is typically used in more demanding applications where spatter, distortion and/or fume reduction is needed or out-of-position capabilities are necessary.

7.) As the percentage of CO2 in the shielding gas increases, the amount of alloy recovered in the weld metal:

A. increases
B. decreases
C. stays the same

The correct answer is B. CO2 is in the shielding gas reacts with the puddle and is broken down into carbon monoxide and free oxygen. The oxygen reacts with the elements transferring across the arc. With higher percentages of CO2, the reaction with the elements in the arc increases, resulting in a lower level of these elements in the weld metal.

8.) What does the “D” indicate on a wire classified as an ER 80S-D2?

A. Downhand use only
B. 0.5% Molybdenum
C. No preheating required
D. 1% Molybdenum

The answer is B, 0.5% molybdenum. This wire can be used for welding the chrome/moly types when post weld heat treatment will not be used.

9.) What limitation exists for use of GMAW-Spray transfer?

A. Position of welding
B. Polarity
C. Mechanical Properties
D. Higher Diffusable Hydrogen

The correct answer is A. When using spray transfer, overhead welding is very difficult and vertical-up welding is not possible.

10.) Cold Lap can occur with:

A. Short circuit transfer
B. Globular transfer
C. Spray transfer
D. All of the above

D is the correct answer. All modes of transfer can generate cold lap if improper technique is used.

11.) For Globular transfer in GMAW, what shielding gas is used?

A. 75% Argon, 25% CO2
B. 100% CO2
C. 92% Argon, 8% CO2
D. 85% Argon, 15% CO2

The answer is B, 100% CO2. Usually reserved for non-critical welds where appearance isn’t a factor, the Globular mode of transfer is used very little today.

12.) What is the major reason for using a Modified Spray?

A. Increased travel speed
B. Higher Deposition efficiency
C. Uses less shielding gas
D. Better mechanical properties

The correct answer is A. In applications where speed is the primary objective, an Argon mix shielding gas is used with lower voltage in an effort to increase travel speeds.

13.) Generally, what is the minimum Argon percentage required to achieve a “true” spray transfer?

A. 75%
B. 70%
C. 80%
D. 90%

The answer is C, 80%. Although a spray can be achieved with around 78% Argon, we generally say a “true” spray requires 80%.

14.) What is the major advantage of GMAW over SMAW?

A. Higher Deposition
B. Simplicity of equipment
C. Portability
D. Versatility

The answer is A, higher deposition. SMAW generally produces around 4-9 lbs./hr. deposition for a 3/16” electrode. A 1/16” MIG wire can easily deposit more than 9 lbs./hr. with an efficiency of more than 90%, while the GMAW process usually has an efficiency of 60% when stub length is considered.

15.) What limits the short circuit current?

A. Inductance
B. Slope
C. Wire Feed Speed
D. Voltage

The correct answer is B, Slope, usually noted in terms of volts per 100 amps. By limiting the short circuit current, spatter is reduced.

16.) Why would you use the GMAW Pulse-Spray mode of transfer?

A. Increased deposition rate over spray
B. All position capability
C. Uses less shielding gas
D. Higher current levels

The correct answer is B, all-position capability. Pulse is also used to lower fume and distortion.