Certified Welder Heat Input and Distortion Control 1 — Questions and Answers
Question 1: What is the correct formula for calculating heat input in welding?
- (Amps × Volts × 60) / Travel Speed (in/min) (Correct answer)
- (Volts × Travel Speed) / Amps
- (Amps × Travel Speed) / Volts
- (Volts + Amps) × Travel Speed
Correct answer: (Amps × Volts × 60) / Travel Speed (in/min)
Heat input is calculated as (Amps × Volts × 60) / Travel Speed, expressed in joules per inch, representing total energy deposited per unit length.
Question 2: What effect does increasing travel speed have on heat input when amperage and voltage remain constant?
- Increases heat input
- Decreases heat input (Correct answer)
- Has no effect on heat input
- Doubles heat input
Correct answer: Decreases heat input
Increasing travel speed reduces the time the arc dwells over a given area, depositing less energy per inch and thereby decreasing heat input.
Question 3: Which type of distortion causes the ends of a welded plate to bow upward along its length?
- Angular distortion
- Transverse shrinkage
- Buckling
- Longitudinal bowing (camber) (Correct answer)
Correct answer: Longitudinal bowing (camber)
Longitudinal bowing (camber) causes the ends of a welded plate to curve upward due to differential shrinkage along the long axis of the weld.
Question 4: What is the primary purpose of preheating base metal before welding?
- To increase travel speed
- To reduce the risk of hydrogen-induced cracking by slowing the cooling rate (Correct answer)
- To increase arc voltage
- To improve electrode deposition rate
Correct answer: To reduce the risk of hydrogen-induced cracking by slowing the cooling rate
Preheating slows the cooling rate, allowing diffusible hydrogen to escape from the weld zone and reducing the risk of hydrogen-induced (cold) cracking.
Question 5: What does interpass temperature refer to in a multi-pass weld?
- The temperature of the electrode tip during welding
- The temperature of the weld bead before the next pass is deposited (Correct answer)
- The temperature of the shielding gas at the nozzle
- The temperature of the base metal before any welding begins
Correct answer: The temperature of the weld bead before the next pass is deposited
Interpass temperature is the temperature of the previously deposited weld bead or base metal adjacent to the weld before the next pass is applied, and must be kept within specified limits.
Question 6: High heat input in welding generally results in which of the following?
- A smaller heat affected zone and finer grain structure
- Reduced weld distortion
- A larger heat affected zone and coarser grain structure (Correct answer)
- Increased weld hardness
Correct answer: A larger heat affected zone and coarser grain structure
High heat input increases the size of the heat affected zone and promotes grain growth, producing a coarser microstructure that typically reduces notch toughness.
Question 7: When voltage and travel speed are held constant in GMAW, which parameter most directly controls heat input?
- Wire feed speed (which controls amperage) (Correct answer)
- Shielding gas flow rate
- Nozzle-to-work distance
- Electrode diameter
Correct answer: Wire feed speed (which controls amperage)
In GMAW, wire feed speed directly controls amperage; since heat input = (Amps × Volts × 60) / Travel Speed, changing amperage is the primary lever when the other two variables are fixed.
Certified Welder Heat Input and Distortion Control 1
What is the correct formula for calculating heat input in welding?