IMM Welding & Fabrication 1 — Questions and Answers
Question 1: Which welding process uses a consumable electrode covered with a flux coating?
- GMAW (MIG welding)
- SMAW (Stick welding) (Correct answer)
- GTAW (TIG welding)
- FCAW (Flux-Cored Arc Welding)
Correct answer: SMAW (Stick welding)
SMAW (Shielded Metal Arc Welding) uses a flux-coated stick electrode that melts to shield the weld pool from atmospheric contamination.
Question 2: What is the primary purpose of preheating steel before welding?
- To increase welding travel speed
- To reduce the risk of hydrogen-induced cracking (Correct answer)
- To improve the cosmetic appearance of the weld bead
- To lower the required amperage setting
Correct answer: To reduce the risk of hydrogen-induced cracking
Preheating slows the cooling rate and allows hydrogen to diffuse out of the weld zone, preventing hydrogen-induced (cold) cracking.
Question 3: Which shielding gas is standard for GTAW (TIG) welding of stainless steel?
- 100% CO2
- 75% Argon / 25% CO2
- 100% Argon (Correct answer)
- 100% Helium
Correct answer: 100% Argon
Pure argon is the standard shielding gas for TIG welding stainless steel because it is inert and provides excellent arc stability without oxidizing the material.
Question 4: What does 'duty cycle' mean when referring to welding equipment?
- The number of electrodes consumed per hour of operation
- The percentage of a 10-minute period a machine can weld at a rated output without overheating (Correct answer)
- The amperage required for a specific electrode diameter
- The frequency of scheduled preventive maintenance intervals
Correct answer: The percentage of a 10-minute period a machine can weld at a rated output without overheating
Duty cycle is the percentage of a 10-minute period that a welding machine can continuously operate at a given output level before it must cool down.
Question 5: Which weld defect is a groove melted into the base metal along the toe of the weld that is left unfilled by weld metal?
- Porosity
- Slag inclusion
- Undercut (Correct answer)
- Overlap
Correct answer: Undercut
Undercut is a groove eroded into the base metal along the weld toe, reducing the effective cross-sectional area and creating a stress concentration.
Question 6: What is the purpose of back purging with argon when TIG welding stainless steel pipe?
- To accelerate the cooling rate of the weld
- To prevent oxidation on the inside (root) surface of the weld (Correct answer)
- To increase penetration depth
- To reduce weld spatter
Correct answer: To prevent oxidation on the inside (root) surface of the weld
Back purging introduces argon to the pipe interior to exclude oxygen, preventing oxidation ('sugaring') on the root surface that would compromise corrosion resistance.
Question 7: What is the correct polarity when welding with an E7018 low-hydrogen electrode?
- AC (Alternating Current)
- DCEN (Direct Current Electrode Negative)
- DCEP (Direct Current Electrode Positive) (Correct answer)
- High-frequency AC
Correct answer: DCEP (Direct Current Electrode Positive)
E7018 electrodes require DCEP (reverse polarity), which concentrates heat at the electrode tip for proper flux melting and provides a stable, smooth arc.
IMM Welding & Fabrication 1
Which welding process uses a consumable electrode covered with a flux coating?