Millwright Certification Welding and Cutting Processes 1 — Questions and Answers
Question 1: Which welding process uses a non-consumable tungsten electrode and a separate filler rod?
- SMAW (Stick welding)
- GTAW (TIG welding) (Correct answer)
- FCAW (Flux-cored arc welding)
- SAW (Submerged arc welding)
Correct answer: GTAW (TIG welding)
GTAW (TIG) uses a non-consumable tungsten electrode to create the arc while filler metal is added manually with a separate rod, making it ideal for precise, high-quality welds on thin or critical materials.
Question 2: What is the correct sequence for shutting down an oxy-acetylene torch at the end of a job?
- Close the oxygen valve first, then the acetylene valve, then bleed the lines
- Close the acetylene valve first, then the oxygen valve, then bleed the lines (Correct answer)
- Close both valves simultaneously, then bleed the lines
- Bleed the lines first, then close both cylinder valves together
Correct answer: Close the acetylene valve first, then the oxygen valve, then bleed the lines
Closing acetylene first extinguishes the flame safely and prevents a backfire or soot deposit in the tip. Oxygen is then closed, and lines are bled to relieve pressure and prevent hose deterioration.
Question 3: In SMAW (stick) welding, what is the purpose of the flux coating on the electrode?
- To increase the electrical conductivity of the rod
- To add carbon to the weld pool for hardness
- To shield the weld pool from atmospheric contamination and form slag (Correct answer)
- To preheat the base metal ahead of the arc
Correct answer: To shield the weld pool from atmospheric contamination and form slag
The flux coating burns and vaporizes to produce a shielding gas cloud around the arc and molten pool, keeping out oxygen and nitrogen. It also forms a slag layer over the bead that protects the weld as it cools.
Question 4: A millwright notices porosity in a completed weld bead. What is the most likely cause?
- Excessive preheat temperature
- Contamination or moisture in the weld zone (Correct answer)
- Too slow a travel speed
- Electrode diameter too large for the joint
Correct answer: Contamination or moisture in the weld zone
Porosity (gas pockets trapped in the solidified weld) is almost always caused by contaminants such as oil, moisture, rust, or paint releasing gases into the molten pool faster than they can escape before solidification.
Question 5: When cutting with a plasma arc system, what material conducts the return current path back to the power supply?
- The plasma gas stream
- The work clamp (ground) attached to the workpiece (Correct answer)
- The torch body and hose assembly
- The ionized shielding air around the arc
Correct answer: The work clamp (ground) attached to the workpiece
The work clamp completes the electrical circuit. Current flows from the power supply through the torch electrode, through the plasma arc into the workpiece, and returns via the work clamp cable. Without a solid work connection the arc will not transfer.
Question 6: What type of flame is used when oxy-acetylene welding most steel and iron?
- Oxidizing flame (excess oxygen)
- Carburizing flame (excess acetylene)
- Neutral flame (balanced oxygen and acetylene) (Correct answer)
- Reducing flame (pure acetylene only)
Correct answer: Neutral flame (balanced oxygen and acetylene)
A neutral flame has equal volumes of oxygen and acetylene, producing a clean, balanced combustion that neither adds carbon to nor removes carbon from the base metal. It is the standard flame for welding most ferrous metals.
Millwright Certification Welding and Cutting Processes 1
Which welding process uses a non-consumable tungsten electrode and a separate filler rod?