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International Welding Engineer (IWE) Exam Questions and Answers
- According to ISO 2553, what does the symbol “a” represent in a fillet weld symbol?
- a) Leg length
- b) Throat thickness
- c) Weld length
- d) Penetration depth
- Answer: b) Throat thickness
- Explanation: ISO 2553 defines “a” as the nominal throat thickness for fillet welds, critical for strength calculations.
- Which ISO standard specifies requirements for welding quality management systems?
- a) ISO 9001
- b) ISO 3834
- c) ISO 5817
- d) ISO 15614
- Answer: b) ISO 3834
- Explanation: ISO 3834 outlines quality requirements for fusion welding, ensuring consistent weld quality.
- In GTAW welding, what is the primary function of the inert gas?
- a) Stabilize arc
- b) Protect weld pool from oxidation
- c) Increase penetration
- d) Reduce heat input
- Answer: b) Protect weld pool from oxidation
- Explanation: Inert gases like argon shield the weld pool from atmospheric contamination.
- What is the main advantage of pulsed current in GMAW?
- a) Higher deposition rate
- b) Reduced heat input
- c) Better arc stability
- d) Lower cost
- Answer: b) Reduced heat input
- Explanation: Pulsed GMAW minimizes heat input, reducing distortion in thin materials.
- According to ISO 5817, which quality level has the most stringent weld imperfection requirements?
- a) Level D
- b) Level C
- c) Level B
- d) Level A
- Answer: c) Level B
- Explanation: ISO 5817 defines Level B as the most stringent for weld imperfections.
- What is the purpose of a backing strip in welding?
- a) Increase welding speed
- b) Support root pass
- c) Reduce distortion
- d) Improve weld appearance
- Answer: b) Support root pass
- Explanation: Backing strips support the root pass, preventing burn-through in groove welds.
- Which element primarily improves corrosion resistance in stainless steel?
- a) Carbon
- b) Manganese
- c) Chromium
- d) Nickel
- Answer: c) Chromium
- Explanation: Chromium forms a passive oxide layer, enhancing corrosion resistance.
- In ultrasonic testing (UT), what does ‘DAC’ stand for?
- a) Distance Amplitude Correction
- b) Digital Amplitude Control
- c) Defect Assessment Curve
- d) Dynamic Angle Calibration
- Answer: a) Distance Amplitude Correction
- Explanation: DAC adjusts for signal amplitude variation with distance in UT.
- According to ISO 9606-1, what is the validity period of a welder’s qualification?
- a) 1 year
- b) 2 years
- c) 3 years
- d) 5 years
- Answer: b) 2 years
- Explanation: ISO 9606-1 specifies a 2-year validity, extendable with verification.
- What is the primary heat generation mechanism in laser beam welding?
- a) Electrical resistance
- b) Friction
- c) Photon absorption
- d) Chemical reaction
- Answer: c) Photon absorption
- Explanation: Laser energy is absorbed by the material, generating heat.
- Which process is most suitable for welding thin aluminum sheets?
- a) SMAW
- b) GMAW
- c) GTAW
- d) SAW
- Answer: c) GTAW
- Explanation: GTAW offers precise control for thin aluminum, minimizing burn-through.
- In ISO 6520-1, which group number corresponds to cracks?
- a) 100
- b) 200
- c) 300
- d) 400
- Answer: a) 100
- Explanation: ISO 6520-1 classifies cracks under group 100.
- What is the main purpose of preheating before welding?
- a) Increase welding speed
- b) Reduce hydrogen-induced cracking
- c) Improve weld appearance
- d) Decrease heat input
- Answer: b) Reduce hydrogen-induced cracking
- Explanation: Preheating slows cooling, reducing crack risk in high-CE steels.
- Which standard guides welding procedure qualification?
- a) ISO 9001
- b) ISO 3834
- c) ISO 15614
- d) ISO 5817
- Answer: c) ISO 15614
- Explanation: ISO 15614 specifies procedure qualification requirements.
- In GMAW, what does ‘short-circuiting transfer’ mean?
- a) Wire touches weld pool
- b) Reduces spatter
- c) Welds thick plates
- d) Controls heat input
- Answer: a) Wire touches weld pool
- Explanation: Short-circuiting involves wire contacting the pool, transferring metal.
- Typical frequency range for UT in welds?
- a) 0.5 to 1 MHz
- b) 1 to 5 MHz
- c) 5 to 10 MHz
- d) 10 to 20 MHz
- Answer: b) 1 to 5 MHz
- Explanation: 1–5 MHz is standard for weld inspection in UT.
- How is a staggered intermittent fillet weld represented in ISO 2553?
- a) Single line
- b) Parallel lines
- c) Zigzag line
- d) Dashed line
- Answer: c) Zigzag line
- Explanation: ISO 2553 uses a zigzag line for staggered welds.
- Which is NOT a welding joint type?
- a) Butt joint
- b) Lap joint
- c) T-joint
- d) Slip joint
- Answer: d) Slip joint
- Explanation: Slip joint is not a recognized welding joint type.
- Primary function of flux in SAW?
- a) Provide shielding gas
- b) Stabilize arc
- c) Remove impurities
- d) Increase deposition
- Answer: c) Remove impurities
- Explanation: Flux cleans the weld pool in SAW.
- In RT, ‘IQI’ stands for?
- a) Image Quality Indicator
- b) Internal Quality Inspection
- c) Incident Quantum Intensity
- d) Integrated Quality Index
- Answer: a) Image Quality Indicator
- Explanation: IQI assesses radiographic image quality.
- Standard for welding personnel qualification?
- a) ISO 9001
- b) ISO 3834
- c) ISO 9606
- d) ISO 15614
- Answer: c) ISO 9606
- Explanation: ISO 9606 governs welder qualification.
- Main advantage of electron beam welding?
- a) Low cost
- b) High penetration depth
- c) Portability
- d) Material versatility
- Answer: b) High penetration depth
- Explanation: EBW achieves deep penetration in a vacuum.
- ‘HAZ’ stands for?
- a) Heat Affected Zone
- b) High Alloy Zone
- c) Hardness Assessment Zone
- d) Hydrogen Absorption Zone
- Answer: a) Heat Affected Zone
- Explanation: HAZ is the area altered by welding heat.
- Stainless steel most prone to sensitization?
- a) Austenitic
- b) Ferritic
- c) Martensitic
- d) Duplex
- Answer: a) Austenitic
- Explanation: Austenitic steels risk chromium carbide precipitation.
- Purpose of root gap in butt weld?
- a) Allow shrinkage
- b) Ensure full penetration
- c) Reduce heat input
- d) Improve appearance
- Answer: b) Ensure full penetration
- Explanation: Root gap aids weld penetration.
- ISO 3834 part for elementary quality requirements?
- a) Part 2
- b) Part 3
- c) Part 4
- d) Part 5
- Answer: c) Part 4
- Explanation: Part 4 covers basic quality needs.
- Current for subsurface defects in MT?
- a) AC
- b) DC
- c) Both
- d) Pulsed
- Answer: b) DC
- Explanation: DC penetrates deeper for subsurface detection.
- Reason for low-hydrogen electrodes?
- a) Reduce spatter
- b) Prevent hydrogen-induced cracking
- c) Increase deposition
- d) Improve stability
- Answer: b) Prevent hydrogen-induced cracking
- Explanation: Low-hydrogen electrodes minimize crack risk.
- Process with continuous wire and external gas?
- a) SMAW
- b) GMAW
- c) GTAW
- d) SAW
- Answer: b) GMAW
- Explanation: GMAW uses wire and shielding gas.
- Thickness qualification range for 10 mm test piece in ISO 15614-1?
- a) 5 mm to 20 mm
- b) 3 mm to 20 mm
- c) 10 mm to 20 mm
- d) 5 mm to 40 mm
- Answer: a) 5 mm to 20 mm
- Explanation: ISO 15614-1 specifies 0.5t to 2t for t ≤ 12 mm.
- AC advantage over DC in GTAW for aluminum?
- a) Better penetration
- b) Cleaning action on oxide layer
- c) Lower cost
- d) Higher deposition
- Answer: b) Cleaning action on oxide layer
- Explanation: AC removes oxide during welding.
- Solid-state welding process?
- a) GMAW
- b) GTAW
- c) Friction stir welding
- d) SAW
- Answer: c) Friction stir welding
- Explanation: FSW joins without melting.
- Arrow side in weld symbols indicates?
- a) Side where weld is made
- b) Opposite side
- c) Welding direction
- d) Weld type
- Answer: a) Side where weld is made
- Explanation: Arrow side is where welding occurs.
- Heat input range for GMAW spray transfer?
- a) <1 kJ/mm
- b) 1 to 2 kJ/mm
- c) 2 to 3 kJ/mm
- d) >3 kJ/mm
- Answer: b) 1 to 2 kJ/mm
- Explanation: Typical for spray transfer in GMAW.
- Standard for wire electrodes in GMAW of carbon steels?
- a) ISO 14341
- b) ISO 2560
- c) ISO 18275
- d) ISO 14171
- Answer: a) ISO 14341
- Explanation: ISO 14341 classifies GMAW wires.
- Primary cause of solidification cracking?
- a) High cooling rate
- b) Low ductility in weld metal
- c) Excessive restraint
- d) High hydrogen
- Answer: b) Low ductility in weld metal
- Explanation: Low ductility causes cracks during solidification.
- ‘PQR’ stands for?
- a) Procedure Qualification Record
- b) Process Quality Requirement
- c) Product Quality Report
- d) Personnel Qualification Record
- Answer: a) Procedure Qualification Record
- Explanation: PQR documents procedure qualification.
- Defect with gas pockets in weld metal?
- a) Slag inclusion
- b) Porosity
- c) Lack of fusion
- d) Undercut
- Answer: b) Porosity
- Explanation: Porosity is gas entrapment in welds.
- Frequency range in MT?
- a) 50 Hz to 60 Hz
- b) 100 Hz to 1 kHz
- c) 1 kHz to 10 kHz
- d) 10 kHz to 100 kHz
- Answer: a) 50 Hz to 60 Hz
- Explanation: Standard for AC MT.
- Parameters controlling heat in friction welding?
- a) Rotational speed
- b) Axial force
- c) Time
- d) All of the above
- Answer: d) All of the above
- Explanation: All contribute to heat generation.
- Standard for visual inspection of welds?
- a) ISO 17637
- b) ISO 17640
- c) ISO 17638
- d) ISO 17639
- Answer: a) ISO 17637
- Explanation: ISO 17637 governs visual inspection.
- Purpose of chill bar in welding?
- a) Increase cooling rate
- b) Reduce distortion
- c) Support weld pool
- d) Improve appearance
- Answer: a) Increase cooling rate
- Explanation: Chill bars accelerate cooling.
- Requirement to prevent oxidation in EBW?
- a) Shielding gas
- b) Vacuum environment
- c) Flux
- d) Water cooling
- Answer: b) Vacuum environment
- Explanation: EBW requires a vacuum to avoid oxidation.
- Factor NOT affecting weldability?
- a) Composition
- b) Thickness
- c) Joint design
- d) Welder’s skill
- Answer: d) Welder’s skill
- Explanation: Weldability is material-specific.
- Arc voltage range in GMAW?
- a) 10-15 V
- b) 15-25 V
- c) 25-35 V
- d) 35-45 V
- Answer: b) 15-25 V
- Explanation: Typical for GMAW.
- ‘Dilution’ in welding?
- a) Mixing of filler and base metal
- b) Reduced strength
- c) Decreased heat input
- d) Increased speed
- Answer: a) Mixing of filler and base metal
- Explanation: Dilution is filler-base metal mixing.
- Standards for aluminum welding?
- a) ISO 9606-2
- b) ISO 15614-2
- c) Both a and b
- d) Neither
- Answer: c) Both a and b
- Explanation: Cover welder and procedure qualification.
- Advantage of pulsed GTAW?
- a) Higher deposition
- b) Better heat input control
- c) Lower cost
- d) Easier learning
- Answer: b) Better heat input control
- Explanation: Pulsed GTAW controls heat precisely.
- ‘Arc blow’ is?
- a) Arc extinguishing
- b) Arc deflection by magnetic fields
- c) Excessive spatter
- d) Unstable arc length
- Answer: b) Arc deflection by magnetic fields
- Explanation: Magnetic fields cause arc deviation.
- Joint with plates at right angles?
- a) Butt joint
- b) Lap joint
- c) T-joint
- d) Corner joint
- Answer: c) T-joint
- Explanation: T-joint forms a right angle.
Descriptive Questions Answers
- WPS vs. PQR (ISO 15614-1):
- WPS: A Welding Procedure Specification outlines detailed instructions for executing a weld, including welding process, base and filler materials, joint design, preheat, interpass temperatures, welding technique, and post-weld heat treatment (PWHT). It ensures consistent weld quality and is based on the validated results of the PQR.
- PQR: A Procedure Qualification Record documents the actual parameters used during a qualification test weld, along with results from mechanical tests (e.g., tensile, bend, impact) and non-destructive testing (NDT). It verifies that the WPS produces welds meeting required standards, serving as evidence of procedure qualification.
- Steps to Qualify a Welder for GTAW Welding of Stainless Steel Pipes (ISO 9606-1):
- Select Test Piece: Choose a representative stainless steel pipe test piece (e.g., 316L, specific diameter and thickness) matching production conditions, including joint type and welding position (e.g., 6G for pipe welding).
- Prepare Test Piece: Machine or grind the pipe ends to the specified joint configuration (e.g., V-groove, root gap), ensuring cleanliness to avoid contamination.
- Perform Weld: The welder executes the weld under supervision, adhering to a qualified WPS, using GTAW with appropriate filler (e.g., ER316L) and shielding gas (e.g., argon).
- Non-Destructive Testing (NDT): Conduct visual inspection per ISO 17637, followed by NDT like radiographic testing (RT) or dye penetrant testing (PT) to check for surface and internal defects.
- Destructive Testing: If NDT is acceptable, perform destructive tests, typically including two face bend and two root bend tests, or side bend tests for thicker pipes, plus macro-examination to assess weld integrity.
- Evaluation and Certification: Compare test results against ISO 9606-1 acceptance criteria (e.g., no cracks >1.5 mm). If passed, issue a qualification certificate specifying the range of validity (material group, thickness, position).
- Calculate CE and Discuss Weldability:
- Composition: C=0.18%, Mn=1.2%, Cr=0.5%, Mo=0.2%, Ni=0.3%, Cu=0.1%.
- IIW Formula: CE = C + Mn/6 + {Cr + Mo + V}/5 + \{Ni + Cu}/15
- Calculation: 0.547
- Weldability: A CE of ~0.55 indicates moderate weldability. Steels with CE between 0.4–0.6 may require preheating (e.g., 100–150°C for 15 mm thickness, low hydrogen) to slow cooling and prevent hydrogen-induced cracking, per EN 1011-2. Careful control of welding parameters and PWHT may also be needed for thicker sections or high-restraint joints.
- Factors Influencing Shielding Gas Choice in GMAW for Carbon Steel:
- Penetration: CO₂ provides deeper penetration due to higher arc energy, suitable for thicker sections, while argon-rich mixtures (e.g., 75% Ar/25% CO₂) offer shallower penetration for thinner materials.
- Spatter Control: Higher argon content reduces spatter, improving weld cleanliness and reducing post-weld cleanup.
- Weld Bead Appearance: Argon-rich gases produce smoother, flatter beads, enhancing aesthetics and reducing grinding needs.
- Cost: CO₂ is less expensive but may increase spatter-related costs; argon mixtures are costlier but improve quality.
- Metal Transfer Mode: Spray transfer requires higher argon (e.g., 80% Ar/20% CO₂), while short-circuiting works with CO₂ or mixed gases, affecting weld quality and speed.
- Causes and Prevention of Porosity in Welds:
- Causes: Porosity results from gas entrapment due to contamination (oil, grease, moisture on base metal or filler), inadequate shielding gas flow, incorrect welding parameters (e.g., high voltage), or turbulent gas flow.
- Prevention: Clean base metal with solvents or grinding, ensure proper gas flow (15–20 L/min), use dry consumables stored per manufacturer guidelines, optimize voltage and current, and maintain consistent torch angle to avoid turbulence.
- Heat Input Concept and Effect on HAZ:
- Concept: Heat input (HI) measures energy transferred to the weld, calculated as: HI = {V x I x 60} / {S x1000} kJ/mm, where V is voltage, I is current, and S is welding speed (mm/min).
- Effect on HAZ: Higher HI increases HAZ width and grain size, potentially reducing toughness but improving ductility. Lower HI results in a narrower HAZ with finer grains, enhancing strength but risking cracks if too low. Per EN 1011-2, HI control is critical for material properties.
- Magnetic Particle Testing (MT) Process and Application:
- Process: MT detects surface and near-surface defects in ferromagnetic materials. The part is magnetized (using AC for surface, DC for subsurface), magnetic particles are applied (dry or wet suspension), and indications are observed under UV or white light.
- Application: Used for welds in carbon steels, detecting cracks, seams, and laps. ISO 17638 specifies MT procedures, ensuring reliable defect identification.
- Purpose of PWHT and When Required:
- Purpose: PWHT relieves residual stresses, improves ductility, reduces HAZ hardness, and enhances toughness, preventing issues like stress corrosion cracking.
- When Required: Required for high-carbon or alloy steels, thick sections, or critical applications (e.g., pressure vessels), as specified in ISO 15614-1, EN 13445, or project requirements, particularly when CE > 0.4 or restraint is high.
- Comparison of UT and RT for Weld Inspection:
- UT: Uses ultrasonic waves to detect internal defects (cracks, inclusions). Advantages: portable, no radiation, detects planar defects. Limitations: operator skill-dependent, requires surface preparation.
- RT: Uses X-rays/gamma rays for imaging. Advantages: permanent record, detects volumetric defects. Limitations: radiation hazards, requires two-sided access, less sensitive to planar defects. ISO 17636 (RT) and ISO 17640 (UT) guide procedures.
- Difference Between CJP and PJP Welds:
- CJP (Complete Joint Penetration): Weld penetrates the entire joint thickness, providing maximum strength, used in critical applications like bridges or pressure vessels where full load transfer is needed.
- PJP (Partial Joint Penetration): Weld penetrates only part of the thickness, suitable for non-critical joints (e.g., brackets) where design allows reduced strength, per ISO 2553.
- Importance of Preheating HSLA Steels:
- Preheating reduces cooling rates, preventing brittle martensite formation in the HAZ, thus minimizing hydrogen-induced cracking risks. For HSLA steels (e.g., S355), EN 1011-2 recommends preheat based on CE, thickness, and hydrogen content, typically 100–200°C for CE > 0.4.
- Role of Flux in SAW:
- Flux in SAW shields the weld pool from atmospheric gases, removes impurities (oxides, slag), stabilizes the arc, and influences bead shape and mechanical properties. ISO 14174 classifies fluxes, ensuring compatibility with wire and base metal.
- Key Parameters in Laser Beam Welding:
- Laser Power: Controls penetration depth.
- Welding Speed: Affects heat input and bead width.
- Focus Position: Determines beam intensity and weld quality.
- Shielding Gas: Prevents oxidation (e.g., helium or argon). ISO 13919-1 specifies quality levels for laser welds.
- Weldability Concept:
- Weldability is the ease of producing defect-free welds, influenced by material composition, microstructure, and properties. Good weldability (e.g., low-carbon steel) allows easy welding; poor weldability (e.g., cast iron) requires special techniques due to high carbon or brittleness.
- Significance of IIW CE Formula:
- The IIW formula CE = C + Mn/6 + {Cr + Mo + V}/5 + \{Ni + Cu}/15, quantifies steel weldability, predicting cracking risk. Higher CE indicates greater hardenability, requiring preheating or PWHT, per EN 1011-2.
- Friction Stir Welding (FSW) Process and Advantages:
- Process: FSW is a solid-state process where a rotating tool generates frictional heat, plasticizing material without melting, joining metals like aluminum.
- Advantages: No solidification defects, low distortion, suitable for dissimilar materials, high joint strength, per ISO 25239.
- Visual Inspection Requirements (ISO 17637):
- Inspect welds for surface imperfections (cracks, porosity, undercut) using adequate lighting (≥350 lux), magnification if needed, and comparison against ISO 5817 acceptance criteria. Tools like gauges ensure dimensional accuracy.
- Interpreting Weld Symbol (ISO 2553):
- For a fillet weld with 6 mm leg length: Symbol is a triangle on the reference line, with “z6” indicating leg length. Arrow side placement shows weld location; additional notations (e.g., intermittent) specify pattern.
- Importance of Interpass Temperature:
- Interpass temperature controls cooling rates between weld passes, affecting microstructure and properties. Too high causes grain growth, reducing strength; too low risks cracking