IMM Welding & Fabrication — Questions and Answers

Question 1: Which welding process uses a consumable electrode covered with a flux coating?

GMAW (MIG welding)
SMAW (Stick welding) (Correct answer)
GTAW (TIG welding)
FCAW (Flux-Cored Arc Welding)

Correct answer: SMAW (Stick welding)

SMAW (Shielded Metal Arc Welding) uses a flux-coated stick electrode that melts to shield the weld pool from atmospheric contamination.

Question 2: What is the primary purpose of preheating steel before welding?

To increase welding travel speed
To reduce the risk of hydrogen-induced cracking (Correct answer)
To improve the cosmetic appearance of the weld bead
To lower the required amperage setting

Correct answer: To reduce the risk of hydrogen-induced cracking

Preheating slows the cooling rate and allows hydrogen to diffuse out of the weld zone, preventing hydrogen-induced (cold) cracking.

Question 3: Which shielding gas is standard for GTAW (TIG) welding of stainless steel?

100% CO2
75% Argon / 25% CO2
100% Argon (Correct answer)
100% Helium

Correct answer: 100% Argon

Pure argon is the standard shielding gas for TIG welding stainless steel because it is inert and provides excellent arc stability without oxidizing the material.

Question 4: What does 'duty cycle' mean when referring to welding equipment?

The number of electrodes consumed per hour of operation
The percentage of a 10-minute period a machine can weld at a rated output without overheating (Correct answer)
The amperage required for a specific electrode diameter
The frequency of scheduled preventive maintenance intervals

Correct answer: The percentage of a 10-minute period a machine can weld at a rated output without overheating

Duty cycle is the percentage of a 10-minute period that a welding machine can continuously operate at a given output level before it must cool down.

Question 5: Which weld defect is a groove melted into the base metal along the toe of the weld that is left unfilled by weld metal?

Porosity
Slag inclusion
Undercut (Correct answer)
Overlap

Correct answer: Undercut

Undercut is a groove eroded into the base metal along the weld toe, reducing the effective cross-sectional area and creating a stress concentration.

Question 6: What is the purpose of back purging with argon when TIG welding stainless steel pipe?

To accelerate the cooling rate of the weld
To prevent oxidation on the inside (root) surface of the weld (Correct answer)
To increase penetration depth
To reduce weld spatter

Correct answer: To prevent oxidation on the inside (root) surface of the weld

Back purging introduces argon to the pipe interior to exclude oxygen, preventing oxidation ('sugaring') on the root surface that would compromise corrosion resistance.

Question 7: What is the correct polarity when welding with an E7018 low-hydrogen electrode?

AC (Alternating Current)
DCEN (Direct Current Electrode Negative)
DCEP (Direct Current Electrode Positive) (Correct answer)
High-frequency AC

Correct answer: DCEP (Direct Current Electrode Positive)

E7018 electrodes require DCEP (reverse polarity), which concentrates heat at the electrode tip for proper flux melting and provides a stable, smooth arc.

Question 8: In the electrode designation E7018, what does the number '70' represent?

Electrode diameter in thousandths of an inch
Minimum tensile strength of the deposited weld metal in ksi (Correct answer)
Recommended welding current in amperes
Percentage of iron powder in the flux coating

Correct answer: Minimum tensile strength of the deposited weld metal in ksi

The digits '70' in E7018 indicate a minimum tensile strength of 70,000 psi (70 ksi) for the weld deposit in the as-welded condition.

Question 9: What type of oxy-acetylene flame is used when welding cast iron?

Oxidizing flame
Neutral flame
Carburizing (reducing) flame (Correct answer)
Hydrogen flame

Correct answer: Carburizing (reducing) flame

A slightly carburizing flame is used for cast iron to add carbon to the weld zone and compensate for carbon burn-off during the welding process.

Question 10: What does FCAW stand for?

Full-Current Arc Welding
Flux-Coated Arc Welding
Flux-Cored Arc Welding (Correct answer)
Forge-Control Arc Welding

Correct answer: Flux-Cored Arc Welding

FCAW stands for Flux-Cored Arc Welding, which uses a tubular wire electrode with a flux-filled core to shield and protect the weld pool.

Question 11: What is the primary purpose of a backing bar (backing strip) placed behind a weld joint?

To preheat the base metal to welding temperature
To support the molten weld pool and ensure full root penetration on single-sided welds (Correct answer)
To regulate amperage fluctuations during welding
To prevent warping of thin sheet metal

Correct answer: To support the molten weld pool and ensure full root penetration on single-sided welds

A backing bar supports the molten root pass from below, allowing full-penetration welds to be made from one side without burn-through.

Question 12: What causes porosity in a completed weld?

Excessively slow travel speed during welding
Gas entrapped in the solidifying weld metal forming voids (Correct answer)
Amperage set too high for the electrode diameter
Improper groove angle on the joint preparation

Correct answer: Gas entrapped in the solidifying weld metal forming voids

Porosity occurs when gases such as hydrogen, nitrogen, or oxygen become trapped in the solidifying weld pool before they can escape, forming voids or bubbles.

Question 13: What travel angle is typically used with a drag technique during flat-position SMAW welding?

90° perpendicular to the base metal surface
45° to the direction of travel
10–15° from vertical in the direction of travel (Correct answer)
30° away from the direction of travel

Correct answer: 10–15° from vertical in the direction of travel

A 10–15° drag (travel) angle directs arc force slightly forward into the joint, improving penetration and bead shape in the flat position.

Question 14: Which weld joint configuration is formed when two pieces of metal are aligned end to end in the same plane?

T-joint
Lap joint
Butt joint (Correct answer)
Corner joint

Correct answer: Butt joint

A butt joint is created when two pieces of metal are placed edge to edge in the same plane and welded along their abutting edges.

Question 15: In the electrode classification E7018, what does the last digit '8' indicate?

The diameter of the electrode in sixteenths of an inch
The coating type and compatible current/polarity (Correct answer)
The minimum yield strength of the weld deposit
The number of weld passes required for full penetration

Correct answer: The coating type and compatible current/polarity

The last digit of an SMAW electrode classification designates the flux coating composition and specifies which current types and polarities are compatible.

Question 16: Which NDT method magnetizes ferromagnetic components and uses iron particles to reveal surface and near-surface discontinuities?

Ultrasonic testing (UT)
Radiographic testing (RT)
Magnetic particle testing (MT) (Correct answer)
Liquid penetrant testing (PT)

Correct answer: Magnetic particle testing (MT)

Magnetic particle testing (MT) induces a magnetic field in ferromagnetic material; particles accumulate at flux leakage points caused by surface or near-surface defects.

Question 17: What is the purpose of a weld test coupon?

To measure heat input in joules per inch during production welding
To qualify a welding procedure or certify a welder's proficiency (Correct answer)
To determine the correct electrode diameter for a given base metal thickness
To calibrate welding power source output

Correct answer: To qualify a welding procedure or certify a welder's proficiency

A weld coupon is a test piece used to qualify Welding Procedure Specifications (WPS) or to certify welders by evaluating weld quality and mechanical properties.

Question 18: What is the primary advantage of GTAW (TIG welding) compared to GMAW (MIG welding)?

Higher electrode deposition rate
Lower operator skill requirement
Superior weld quality and precise control, especially on thin materials and reactive alloys (Correct answer)
Better performance in outdoor or drafty environments

Correct answer: Superior weld quality and precise control, especially on thin materials and reactive alloys

GTAW provides a cleaner, more controllable arc with no spatter and independent control of heat and filler metal, making it ideal for thin sections, stainless steel, and aluminum.

Question 19: What are the primary goals of post-weld heat treatment (PWHT)?

To increase weld hardness and wear resistance
To relieve residual stresses and improve heat-affected zone toughness (Correct answer)
To remove surface oxidation and scale from the weld
To increase the carbon content of the weld deposit

Correct answer: To relieve residual stresses and improve heat-affected zone toughness

PWHT heats the welded assembly to a specified temperature and holds it there to reduce residual stresses, temper hard microstructures, and improve toughness and corrosion resistance.

Question 20: What is weld distortion, and which technique is commonly used to minimize it?

Arc instability from moisture; minimized by electrode pre-drying
Dimensional change from non-uniform heating and cooling; minimized by tacking, clamping, or back-step welding (Correct answer)
Electrode coating failure; minimized by proper storage conditions
Slag entrapment; minimized by increasing travel speed

Correct answer: Dimensional change from non-uniform heating and cooling; minimized by tacking, clamping, or back-step welding

Weld distortion is dimensional change caused by differential thermal expansion and contraction; it is controlled by pre-setting, clamping fixtures, balanced weld sequences, or back-step welding.

Question 21: Which weld joint type is formed when one piece of metal is welded perpendicular to the flat surface of another piece, forming a 90° angle?

Butt joint
Lap joint
T-joint (Correct answer)
Edge joint

Correct answer: T-joint

A T-joint is formed when one member is positioned perpendicular to the surface of another member, creating a 'T' shape that is welded with fillet welds on each side.

IMM Welding & Fabrication

Which welding process uses a consumable electrode covered with a flux coating?

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