ITMC Welding Fundamentals 5 — Questions and Answers
Question 1: What is the purpose of a backing strip (backing bar) used during butt joint welding?
- To preheat the joint before welding
- To support the root pass and prevent burn-through on the first pass (Correct answer)
- To provide additional filler metal to the joint
- To act as a heat sink to prevent distortion
Correct answer: To support the root pass and prevent burn-through on the first pass
A backing strip supports the molten weld pool on the root pass of a butt joint, preventing burn-through and helping achieve complete joint penetration.
Question 2: What is interpass temperature in multi-pass welding?
- The preheat applied before the first pass
- The maximum temperature of the weld zone between successive passes (Correct answer)
- The PWHT temperature applied after all passes
- The temperature of the filler wire as it enters the arc
Correct answer: The maximum temperature of the weld zone between successive passes
Interpass temperature is the temperature of the weld joint measured before each subsequent pass is deposited, and must be controlled to avoid excessive heat buildup or unacceptable microstructural changes.
Question 3: Which FCAW variant does NOT require an external shielding gas supply?
- FCAW-G (gas-shielded flux-cored)
- FCAW-S (self-shielded flux-cored) (Correct answer)
- Dual-shield FCAW
- Metal-cored wire welding
Correct answer: FCAW-S (self-shielded flux-cored)
FCAW-S (self-shielded) electrodes contain flux compounds in the core that generate their own shielding gases and slag when burned, eliminating the need for external gas.
Question 4: A fillet weld callout reads '3/8' on the welding symbol. What does this dimension represent?
- The weld length in inches
- The leg size of the fillet weld (Correct answer)
- The throat size of the fillet weld
- The gap between the plates
Correct answer: The leg size of the fillet weld
The number to the left of the fillet weld symbol represents the leg size of the fillet weld, which is the distance from the root to the toe along each face.
Question 5: What hazard is specifically associated with welding on galvanized (zinc-coated) steel?
- Carbon monoxide poisoning
- Metal fume fever from zinc oxide fumes (Correct answer)
- Ozone overexposure only
- Nitrogen dioxide toxicity
Correct answer: Metal fume fever from zinc oxide fumes
Heating galvanized steel releases zinc oxide fumes that cause metal fume fever, a flu-like illness with chills, fever, and muscle aches.
Question 6: In GTAW, what is the result of using too large a tungsten electrode diameter for the amperage being used?
- Arc wander and difficulty maintaining arc stability (Correct answer)
- Tungsten melting and contaminating the weld pool
- Excessive penetration into the base metal
- Shielding gas flow becomes turbulent
Correct answer: Arc wander and difficulty maintaining arc stability
An oversized tungsten electrode for the given amperage produces a diffuse, unstable arc that is difficult to direct, reducing weld quality and control.
Question 7: What is the definition of 'heat input' in welding and why is it important?
- The preheat temperature applied; important for preventing distortion
- The energy per unit length of weld calculated from voltage, amperage, and travel speed; affects microstructure and mechanical properties (Correct answer)
- The total power consumed by the welding machine; important for energy cost
- The temperature of the shielding gas; affects arc stability
Correct answer: The energy per unit length of weld calculated from voltage, amperage, and travel speed; affects microstructure and mechanical properties
Heat input (kJ/mm or kJ/in) = (Volts × Amps × 60) / (Travel Speed in/min × 1000), and controlling it is critical to managing grain growth, HAZ toughness, and distortion.
ITMC Welding Fundamentals 5
What is the purpose of a backing strip (backing bar) used during butt joint welding?