120103i GMAW on Aluminum Flashcards
GMAW on Mild Steel on Aluminum
Question: Up to what length of contact tip is best suited for GMAW with aluminum filler wires?
a) 25.4 mm (1”)
b) 50.8 mm (2”)
c) 76.2 mm (3”)
d) 101.6 mm (4”)
Answer: d) 101.6 mm (4”)
Explanation: Longer contact tips are more efficient for aluminum wires, as they provide better electrical transfer and minimize common issues like arcing and burnback.
Question: List three (3) advantages of using GMAW on aluminum.
Any three (3) of the following are correct.
a) high deposition rates compared to GTAW
b) can be used long distances from the power source
c) no flux or slag; no inclusions in the weld metal
d) clean up time is reduced or eliminated
e) may be used in all positions
f) works well on materials 3.2 mm (‘/s”) and up
g) works well for spot welding operations
Explanation: These advantages highlight GMAW’s efficiency, versatility, and cleanliness, especially its high deposition rates and suitability for various positions and distances.
Question: Which aluminum filler metal is not recommended for sustained high-temperature service?
Options:
a) 2319
b) 4145
c) 4043
d) 5356
Answer: d) 5356
Explanation: Filler metal 5356 is not recommended for high-temperature applications due to its properties under sustained heat, which may affect the integrity of the weld.
Question: What three (3) factors should you consider when setting GMAW welding parameters?
Answer: a) material thickness, b) alloy type, c) available equipment
Explanation: These factors ensure the welding parameters are appropriately set for effective welding, taking into account the specific characteristics of the material and equipment.
Question: What effect does stickout have on arc length with GMAW on aluminum?
Answer: Due to the high electrical conductivity of aluminum, the electrical stickout is not as critical as that required for steel. The resistance of the aluminum wire is almost the same for a long stickout as it is for a short stickout. Very little change in arc length is noticed with various stickout distances.
Explanation: Aluminum’s electrical properties reduce the impact of stickout length on arc stability, unlike with other metals like steel.
Question: After pre-cleaning aluminum, you should weld the joint:
Options:
a) with a copper backing bar to prevent oxide contamination
b) before it dries to prevent cracking
c) after age hardening has occurred
d) as soon as all liquids have evaporated from the joint area
Answer: d) as soon as all liquids have evaporated from the joint area
Explanation: Ensuring the joint area is dry prevents contamination and potential weld defects.
Question: What are the two most commonly used filler metals for GMAW on aluminum?
Options:
a) 2319 and 4145
b) 4145 and 5356
c) 4043 and 4047
d) 4043 and 5356
Answer: d) 4043 and 5356
Explanation: These filler metals are most commonly used due to their compatibility and performance with aluminum in GMAW processes.
Question: What precaution must you take when using heavy wire brushing or an abrasive grinding disc to remove a heavy oxide layer from aluminum?
Answer: Heavy brushing or abrasive discs tend to drive the aluminum oxides into the metal surface and entrap them. The result is possible contamination of the weld.
Question: What is the purpose of a light preheat on aluminum alloys?
Options:
a) to remove moisture
b) to reduce residual stresses after welding
c) easier arc starting
d) to remove surface oxides
Answer: a) to remove moisture
Explanation: A light preheat helps to eliminate moisture, which can cause porosity and other defects in the weld.
Question: What type of current do you use with GMAW for welding aluminum?
Options:
a) AC
b) DCEP
c) DCEN
d) AC with continuous high frequency
Answer: b) DCEP (Direct Current Electrode Positive)
Explanation: DCEP is used for its effectiveness in achieving good penetration and cleaning action during the welding of aluminum.
Question: What methods can you use to fill a crater?
Answer: A common method of filling the crater is to reverse travel direction for a short distance. Other techniques may use run-off tabs, breaking and restarting the arc, or the use of special current controls on the power source.
Explanation: These techniques are used to ensure that craters are adequately filled to prevent issues like cracking at the end of the weld.
Question: What electrode inclination is recommended for the welding of aluminum?
Options:
a) backhand (pulling) inclination
b) perpendicular to the workpiece
c) varying depending on the position
d) forehand (pushing) inclination
Answer: d) forehand (pushing) inclination
Explanation: The forehand inclination is recommended for better visibility and control of the weld pool in aluminum welding.
Question: Most shielding gases for GMAW on aluminum are:
Options:
a) inert gases
b) oxidizing gases
c) nitriding gases
d) ionized gases
Answer: a) inert gases
Explanation: Inert gases like argon and helium are commonly used for shielding in GMAW to prevent oxidation and contamination of the weld.
Question: The shielding gas most commonly used with GMAW on non-ferrous metals is:
Options:
a) carbon dioxide
b) nitrogen
c) helium
d) argon
Answer: d) argon
Explanation: Argon is preferred for its effectiveness in providing a stable arc, good cleaning action, and cost-efficiency in GMAW processes, especially with non-ferrous metals like aluminum.
Question: List four (4) causes of burnback.
Answer: Any four of the following are correct:
a) Wire feed speed too slow
b) Worn or dirty contact tube
c) Worn or dirty liner
d) Wrong polarity
e) Kinked electrode wire
f) Liner too long
g) Arcing inside the contact tube
Explanation: These factors can disrupt the consistent feed and electrical transfer to the wire, leading to burnback where the wire burns back to the contact tip.
