I-CAR Welding Techniques and Processes 1 — Questions and Answers
Question 1: Which welding process is most commonly specified by vehicle manufacturers for structural collision repair?
- Oxyacetylene welding
- Squeeze-type resistance spot welding (STRSW) (Correct answer)
- TIG welding
- Flux-core arc welding
Correct answer: Squeeze-type resistance spot welding (STRSW)
Squeeze-type resistance spot welding (STRSW) is the OEM-preferred process because it most closely replicates the factory spot welds used in vehicle assembly.
Question 2: When performing MIG plug welds as a substitute for factory spot welds, what drill bit size is typically used to prepare the plug weld hole?
- 1/4 inch (6 mm)
- 3/8 inch (9.5 mm)
- 8 mm (5/16 inch) (Correct answer)
- 1/2 inch (12 mm)
Correct answer: 8 mm (5/16 inch)
An 8 mm (5/16 inch) hole is the standard size for MIG plug welds to ensure adequate weld nugget size matching factory spot welds.
Question 3: What is the primary reason oxyacetylene welding is generally prohibited on modern high-strength steel (HSS) structural components?
- It produces too much slag
- The heat-affected zone is too large and degrades HSS properties (Correct answer)
- It cannot achieve proper penetration
- Acetylene gas is not hot enough
Correct answer: The heat-affected zone is too large and degrades HSS properties
Oxyacetylene welding creates an excessively large heat-affected zone that anneals and destroys the strength properties of high-strength steel.
Question 4: In MIG (GMAW) welding for collision repair, which shielding gas mixture is most widely recommended?
- 100% argon
- 100% CO2
- 75% argon / 25% CO2 (Correct answer)
- 50% argon / 50% helium
Correct answer: 75% argon / 25% CO2
A 75% argon / 25% CO2 mixture provides the optimal balance of arc stability, penetration, and spatter control for automotive steel welding.
Question 5: What does the term 'heat-affected zone' (HAZ) refer to in welding?
- The area where the weld bead is deposited
- The region of base metal that was not melted but had its properties altered by welding heat (Correct answer)
- The zone where the shielding gas is active
- The discolored area on the surface of the weld bead
Correct answer: The region of base metal that was not melted but had its properties altered by welding heat
The HAZ is the area of base metal adjacent to the weld that was not melted but experienced temperatures high enough to change its microstructure and mechanical properties.
Question 6: When welding ultra-high-strength steel (UHSS), why must weld wire selection match the base metal strength?
- To prevent the wire from melting too quickly
- To ensure the weld joint meets or exceeds the base metal's tensile strength (Correct answer)
- To reduce the cost of the repair
- To improve arc starting characteristics
Correct answer: To ensure the weld joint meets or exceeds the base metal's tensile strength
Using weld wire matched to UHSS base metal strength ensures the completed joint meets the original design tensile requirements for structural integrity.
Question 7: Which personal protective equipment (PPE) is specifically required to protect a welder's eyes from UV and IR radiation?
- Safety glasses with side shields
- A welding helmet with the appropriate shade lens (Correct answer)
- A full face shield only
- UV-blocking sunglasses
Correct answer: A welding helmet with the appropriate shade lens
A welding helmet with an appropriate shade number (typically shade 10–13 for MIG) is required to protect eyes from the intense UV and IR radiation produced by the welding arc.
I-CAR Welding Techniques and Processes 1
Which welding process is most commonly specified by vehicle manufacturers for structural collision repair?