All 120 456A Practice Questions & Answers

Grinding produces sparks and flying metal particles. A face shield worn over safety glasses provides full-face protection; gloves, a helmet, or hearing protection alone leave the eyes and face exposed.

Atmospheric testing with a calibrated gas monitor must occur before entry to detect flammable gas, oxygen deficiency, or toxic vapours.

WHMIS (Workplace Hazardous Materials Information System) is Canada's national hazard communication standard for hazardous products.

SMAW at 150–200 A requires a shade 10–11 lens to protect against the intense UV and infrared radiation of the welding arc. Using a lower shade (e.g., shade 8) would allow damaging UV/IR through and cause arc eye (photokeratitis) and retinal damage — symptoms appear hours after exposure. A shade 14 is unnecessarily dark (typically used for plasma cutting) and would make it difficult to see the weld pool. Shade selection increases with amperage: low-amperage SMAW (≤75A) may use shade 8–9; 150–200A uses 10–11; above 300A typically requires shade 12+. Always check CSA Z94.3 or the lens manufacturer's table for the correct shade by process and amperage.

Stainless steel contains chromium. Welding it produces Cr(VI) fumes, which are carcinogenic and regulated under OHS.

CSA regulations require oxygen and fuel gas cylinders to be stored at least 6 m apart or separated by a 1.5 m high fire-resistant wall.

Damaged insulation creates electrocution and fire hazard. Equipment must be repaired or replaced before use.

ANSI Z49.1 (Safety in Welding and Cutting) and OSHA 1910.252(c)(2) specify a minimum of 2,000 cfm (approximately 57 m³/min) of fresh air per welder for mild steel welding to dilute and remove welding fumes. This mechanical ventilation requirement applies when the space is less than 10,000 cubic feet per welder, the ceiling height is less than 16 feet, or the area is partitioned so cross-ventilation is obstructed. This is a general ventilation threshold — local exhaust ventilation (LEV/fume extraction gun) is preferred as it captures fumes at source and requires less total airflow. Wrong answers: 500 cfm is far too low for safe dilution; 10,000 cfm is appropriate for confined spaces or heavy-fume processes, not typical workshop SMAW. When welding coated, galvanized, or stainless steel, local exhaust is mandatory regardless of general ventilation levels because toxic fumes (zinc oxide, hexavalent chromium) exceed threshold limit values even with 2,000 cfm dilution.

Class C fires are electrical fires. CO₂ or dry chemical extinguishers are non-conductive and appropriate for electrical fires; water-type (Class A) extinguishers conduct electricity.

Argon and CO₂ are heavier than air and can accumulate at floor level in low-lying areas, displacing oxygen and causing asphyxiation.

Hot work permits authorize welding, cutting, or grinding in areas with combustible materials or fire hazards, ensuring fire watch and precautions.

Containers must be thoroughly purged, cleaned, and gas-tested to below 10% LEL before any hot work — explosive residues can remain after airing.

Cable must handle the amperage and duty cycle of the welding process without overheating. Undersized cable creates excessive resistance, heat, and fire hazard.

Welding screens protect nearby workers and bystanders from arc flash (UV/IR radiation), which can cause arc eye (photokeratitis) and skin burns.

Acetylene has an LEL of 2.5% and an UEL of 81% in air, making it one of the most flammable industrial gases.

OFC works by preheating steel to kindling temperature (~870°C/1600°F), then directing a high-pressure oxygen jet at the preheated metal to oxidize (burn) it rapidly.

A neutral flame has a 1:1 oxygen-to-acetylene ratio, producing a sharp bright inner cone with no feather — suitable for most welding.

A carburizing (reducing) flame has excess acetylene, creating a low-oxygen atmosphere that prevents oxidation of aluminum, nickel alloys, and high-carbon steel.

An oxidizing flame has excess oxygen, producing a shorter, more pointed inner cone with a hissing sound — used for brazing brass/bronze.

Acetylene is opened and ignited first (producing a smoky flame), then oxygen is added to produce the desired flame type. This prevents a backfire from oxygen pressure.

Flashback occurs when the flame burns back into the hoses or torch body, causing a hissing/squealing sound. It can cause hose fires or cylinder explosions.

Acetylene becomes unstable and can decompose explosively above 103 kPa (15 psi) gauge for distribution, but safe working pressure at the torch is limited to 103 kPa. Cylinder withdrawal rate must not exceed 1/7 of cylinder capacity per hour.

The kerf is the width of material removed during cutting. A narrower kerf means less material waste and more precise cuts.

When travel speed is too fast, the oxygen jet cannot cut through the full thickness vertically, causing the cut to lag behind and produce curved drag lines.

OFC relies on oxidation, so it cannot cut stainless steel, aluminum, or other non-ferrous metals. Plasma arc cutting uses a high-temperature ionized gas jet and works on any conductive metal.

Increasing tip-to-work distance reduces heat intensity at the workpiece, potentially insufficient for proper preheat and causing poor cutting or failure to cut.

Oxygen under high pressure can cause oil and grease to ignite spontaneously (oxygen-enriched combustion). This can cause violent fires or explosions.

E7018 classification: E=electrode; 70=minimum 70,000 psi (480 MPa) tensile strength; 1=usable in all positions (flat, horizontal, vertical-up, overhead); 8=low-hydrogen potassium flux coating, usable on DCEP or AC. The ‘8’ suffix (low-hydrogen) is the critical Red Seal exam point: E7018 requires electrodes to be stored in a rod oven at 120–150°C and used within 4 hours of removal to prevent moisture absorption — hydrogen in the weld causes hydrogen-induced cracking. Wrong answers confuse E6010 (DCEP only, deep penetration, no oven needed) with E7018, or misread ‘1’ (all-position) as ‘1G’ flat-only. E7018 is the go-to code for structural steel where hydrogen cracking is a risk.

E6010 has a high-cellulosic sodium coating that produces a forceful, deep-penetrating arc. It requires DCEP and is ideal for root passes on pipe and dirty/rusty steel.

E6013 (rutile-coated) produces a soft arc, light spatter, easy slag removal, and shallow penetration — making it ideal for thin sheet metal where burn-through is the primary risk. Wrong answers: E6010 and E6011 have deep penetration and forceful arc (designed for root passes and pipe), which would easily burn through thin material. E7018 (low-hydrogen) is excellent for structural work but requires an oven and produces a broader bead; it is not the preferred choice for light gauge sheet. E6013’s easy restriking and smooth bead also make it a good learning electrode, but its low penetration means it’s NOT suitable for code-quality root passes or high-strength joints where full fusion is required.

Arc blow occurs when stray magnetic fields deflect the DC arc from its intended path, causing inconsistent penetration, spatter, and porosity. It is most common with DC welding near the end of a joint.

Vertical-up welding requires a weave or whip-and-pause technique at 10–15% reduced amperage to allow the weld pool to solidify against gravity.

When the arc is suddenly extinguished, the weld pool shrinks rapidly. If the crater is not filled, tensile stresses from contraction cause a star-shaped crater crack.

The hot pass is applied immediately after the root pass at higher amperage to fuse and burn out slag inclusions, increase penetration, and tie in the root pass edges.

Slag inclusions occur when slag from a previous pass is not fully removed, or when poor electrode manipulation traps slag under the weld metal.

HIC (cold cracking) occurs when hydrogen from the electrode diffuses into the HAZ and combines with residual stress and microstructure to cause delayed cracking. Cellulosic (E6010/E6011) electrodes produce the most hydrogen.

Low-hydrogen electrodes absorb moisture rapidly. Storage in a rod oven at 120–150°C prevents moisture pickup and keeps hydrogen content low (<5 mL/100g).

DCEP (reverse polarity): electrode is connected to the positive terminal, work to negative. Produces deeper penetration and is used with E6010, E7018.

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Higher CE means greater hardenability of the base metal, requiring preheat to slow cooling and reduce HIC risk.

Undercut is a groove melted into the base metal along the weld toe, caused by excessive heat (high amperage or long arc) or an improper electrode angle.

Preheat slows the cooling rate of the HAZ, reducing hardness and the risk of hydrogen-induced cracking, especially in high-carbon or low-alloy steels.

Interpass temperature is the maximum temperature allowed in the weld joint between passes. Exceeding it can cause grain growth, reduced toughness, and metallurgical changes.

Back-step welding deposits short weld segments in the opposite direction to the overall travel. Each segment starts where the previous segment ended, reducing overall heat buildup and distortion.

Work angle is the electrode angle measured from the workpiece surface, in the plane perpendicular to the weld axis (from the joint axis). Travel angle is the tilt in the direction of travel.

PWHT (stress relief) reduces residual stresses from welding, improves toughness, and reduces the risk of stress corrosion cracking. It is required by many welding codes for thick or high-strength steel.

Porosity is gas pockets (voids) trapped in the solidifying weld metal. Caused by moisture, rust, oil, or paint contamination, or moisture in the electrode coating.

The guided bend test bends a weld specimen around a mandrel to reveal cracks, porosity, and incomplete fusion, especially in the root area. Required by most qualification codes.

A WPS specifies the welding variables used for production welding of a joint. A PQR documents the actual test results (mechanical testing) that demonstrate the WPS produces a sound weld.

A stringer bead is a narrow, straight pass with no side-to-side weaving motion. It provides better mechanical properties (especially toughness) than a wide weave bead.

Longer arc length increases arc voltage and heat, but also exposes the molten weld pool to atmospheric contamination, causing porosity and spatter. Proper arc length equals electrode diameter.

Per CSA W47.1 / AWS D1.1, qualifying in 3G (vertical) on plate also qualifies 1G (flat) and 2G (horizontal). 4G (overhead) is a separate qualification.

The four GMAW transfer modes: (1) Short-circuit transfer — lowest voltage (14–19V), wire periodically touches the puddle, suitable for thin gauge and out-of-position, but risk of cold lap/incomplete fusion at heavy thickness; (2) Globular transfer — large irregular drops transfer erratically, high spatter, generally not a preferred mode in production; (3) Spray transfer — above the spray transition current, metal transfers as fine axial droplets, high quality and deposition rate, but restricted to flat/horizontal positions only and requires minimum material thickness; (4) Pulsed spray — background current below spray transition + peak pulse current above it, achieves spray transfer quality at lower average heat input, allowing out-of-position use. Red Seal key point: spray transfer cannot be used out-of-position (gravity causes puddle to sag); pulsed spray solves this.

C25 (75% Ar / 25% CO₂) is the most widely used mixture for mild steel GMAW. It provides a stable arc, good penetration, and lower spatter than 100% CO₂.

100% argon is used for GMAW of aluminum. CO₂ and oxygen-containing mixes would oxidize aluminum, causing excessive porosity.

Burn-back occurs when the wire electrode burns back and fuses to the contact tip, stopping the weld. Caused by low wire feed speed relative to voltage.

Inductance controls the rate of current rise when the wire short-circuits to the weld pool. This smoother current rise causes the droplet to transfer more gently, reducing spatter.

Spray transfer requires voltage typically in the range of 26–40V combined with current above the spray transition threshold (which varies by wire diameter and shielding gas — for 0.9mm wire with Ar/CO₂ 75/25, roughly 200–250A). Below this transition, metal transfers in globular mode regardless of voltage. The spray transition is lowered (easier to achieve) with higher argon content in the shielding gas — which is why 100% CO₂ cannot achieve true spray transfer (CO₂ elevates the transition to beyond practical current levels). Wrong answers: low voltage (14–19V) produces short-circuit transfer, not spray; medium voltage (19–22V) is the globular range. For Red Seal: if a question shows 100% CO₂ + high voltage, the answer is globular — not spray.

CTWD (Contact Tip to Work Distance) is the distance from the contact tip to the workpiece. It affects electrical stickout and therefore current/deposition rate.

GMAW uses a constant voltage (CV) power source. Wire feed speed determines the melt-off rate, which in turn controls welding current. Higher WFS = higher amperage.

Cold lap occurs when the weld metal flows over the base metal without achieving fusion. Caused by insufficient amperage, low voltage, or excessive travel speed that prevents proper melting.

P-GMAW alternates between a high peak current (spray transfer) and a low background current. Each peak transfers one droplet. This achieves spray-quality deposits at lower average heat input, enabling out-of-position welding.

ER5356 (5% magnesium) is used for welding 5000-series aluminum alloys (magnesium-based). ER4043 (4.5% silicon) is preferred for 6000-series.

The liner (conduit liner) guides the wire electrode from the drive rolls through the torch body to the contact tip, preventing kinking and ensuring smooth wire feed.

Porosity in GMAW results from atmospheric contamination of the molten weld pool. Causes include shielding gas contamination, insufficient gas flow, gas leaks, drafts disrupting coverage, or moisture/rust on the base metal.

Silicon (Si) and manganese (Mn) are deoxidizers. ER70S-6's higher Si/Mn content scavenges oxygen from the weld pool, improving weld quality on slightly rusty or dirty base metal and giving better wetting.

Birdnesting is a wire tangle between the drive rolls and the contact tip (typically at the rolls or in the torch liner) that stops wire feeding. Caused by excessive backpressure, kinked liner, or wrong drive roll tension.

GMAW uses a CV (constant voltage) power source. This maintains a relatively stable arc length — if arc length changes, current self-adjusts to maintain the preset voltage.

CO₂ dissociates at arc temperatures, releasing carbon that can be absorbed into the stainless weld metal, reducing chromium carbide precipitation resistance (sensitization).

Push (forehand): torch angles away from the weld pool in the travel direction — lower penetration, flatter bead, better visibility. Pull (backhand/drag): torch angles toward the weld pool — deeper penetration, higher crown.

Proper balance of voltage, WFS, and an adequate inductance setting minimizes spatter. C25 gas produces less spatter than 100% CO₂.

Spray transfer requires an argon-rich gas (at least ~80% Ar). With 98Ar/2O₂, 0.9 mm ER70S-6 transitions from globular to spray at roughly 165 A; with 90Ar/10CO₂ the transition rises to about 200 A. With C25 (75/25) true axial spray cannot be achieved — the high CO₂ content disrupts the arc column.

Longer CTWD increases electrical stickout (the wire resistance between the tip and arc). This preheats the wire, reducing the current needed to melt it — decreasing amperage and penetration.

Irregular wire feed causes the arc to stutter and pop. Causes include a kinked liner, contaminated wire, worn or mis-grooved drive rolls, or wire drive tension issues.

GMAW solid wire uses DCEP (direct current electrode positive / reverse polarity). This produces deeper penetration and stable spray transfer.

Globular transfer occurs at intermediate voltages between short circuit and spray thresholds. Large irregular droplets — bigger than the wire diameter — form and fall into the pool, causing significant spatter. Generally avoided in production.

Anti-spatter spray is applied to nozzles and workpiece surfaces to prevent spatter from adhering and bonding. It reduces nozzle cleaning frequency and cleanup time.

GTAW = Gas Tungsten Arc Welding. A non-consumable tungsten electrode produces the arc; filler metal is added separately or the weld is autogenous (no filler).

AWS A5.12 colour coding: Pure tungsten (EWP) = Green. Used with AC for aluminum and magnesium welding.

DCEN (electrode negative) is used for GTAW on steel, stainless, and titanium. It concentrates heat in the workpiece (2/3 of heat at anode = work), providing deep penetration and a cooler tungsten.

Aluminum has a tenacious oxide layer (Al₂O₃, melting point 2050°C) that prevents fusion. During the electrode positive (DCEP) half of AC, electrons flow from the work to the electrode, breaking up the oxide — this is cathodic cleaning.

Back purging floods the inside of the pipe with argon (or other inert gas) to protect the weld root from oxidation and "sugaring" of the stainless steel root by atmospheric oxygen.

Tungsten contamination occurs when the electrode tip contacts the molten weld pool, embedding tungsten particles (inclusions) in the weld. These are hard, brittle inclusions that cause failures.

HF start initiates the arc via a high-frequency spark across the gap between the electrode and workpiece — no contact required. This prevents tungsten contamination and electrode tip damage.

Helium has higher thermal conductivity and ionization potential than argon, producing a hotter arc with deeper, wider penetration. However, argon provides better arc stability, easier starting, and lower cost.

An autogenous weld uses heat from the arc alone to fuse the base metal edges together, without adding any filler wire — base metal only. Used for thin materials where joint fit-up allows complete fusion.

"Walking the cup" means bracing the ceramic nozzle against the pipe and using a rocking or rolling motion to move the torch. This provides a stable torch angle and consistent arc length for pipe welding.

Pulsed GTAW alternates between a high peak current (fusion/penetration) and low background current (cooling), controlling heat input and pool size. This reduces average heat input, enabling welding of thin materials and out-of-position joints with better control.

For DCEN GTAW (steel, stainless, titanium), the tungsten is ground to a tapered point. For AC GTAW (aluminum), a rounded ball forms naturally at the tip.

Grinding tungsten longitudinally (along its length) creates consistent grain structure at the tip, producing a stable, symmetric arc. Circumferential grinding can cause arc wander.

Black soot indicates atmospheric contamination of the weld — insufficient shielding gas flow, leaks in the gas line, draft conditions, or contaminated shielding gas.

ER308L is used for welding Type 304 and Type 308 austenitic stainless steel. The "L" denotes low carbon (<0.03%), which reduces carbide precipitation (sensitization) risk.

Post-flow continues shielding gas after the arc extinguishes, protecting the hot tungsten electrode and solidifying weld metal from oxidation as they cool.

Balance control on AC GTAW adjusts the proportion of the positive (DCEP) and negative (DCEN) half-cycles. More DCEP = more cleaning action (shallower, wider bead). More DCEN = more penetration, less cleaning.

P91 (9% Cr, 1% Mo) creep-resistant steel requires matching filler metal ER90S-B9 (or equivalent). Standard carbon steel or stainless filler would produce mismatched mechanical properties.

A gas lens replaces the standard collet body. Its porous metal mesh screen produces a smooth, laminar (non-turbulent) flow of shielding gas, extending coverage and enabling longer electrode stickout.

"Sugaring" is a rough, oxidized surface on the weld root caused by atmospheric oxygen reacting with chromium in the hot metal, forming chromium oxides (Cr₂O₃) and depleting the corrosion-resistant chromium from the surface.

FCAW-S (self-shielded) generates its own shielding from the flux core, allowing outdoor welding without gas cylinders. FCAW-G (gas-shielded) requires external CO₂ or Ar/CO₂ shielding gas.

FCAW-G typically uses DCEP (electrode positive), similar to GMAW solid wire. Some FCAW-S wires use DCEN — always check the manufacturer's specification.

FCAW (especially FCAW-G) provides higher deposition rates than solid wire GMAW, with flux-assisted penetration and slag support giving better out-of-position capabilities.

FCAW uses a drag (backhand/pull) technique with a 10–15° angle from perpendicular in the travel direction. Drag technique promotes slag following behind the arc.

FCAW flux-cored wire uses longer electrical stickout (19–38 mm) than GMAW solid wire due to the larger wire diameter and flux core. The longer stickout preheats the wire, increasing deposition efficiency.

FCAW-S generates its own shielding gases and slag from the flux core, so it does not rely on external gas coverage that wind could blow away. Wind disperses external shielding gas (FCAW-G), causing porosity.

E71T-1 is a rutile-type flux-cored wire used with CO₂ or Ar/CO₂ shielding gas. It produces a fluid, easily removed slag and is suitable for all-position welding.

E71T-1 classification: E=electrode; 7=70,000 psi (480 MPa) minimum tensile strength; 1=all-position (the ‘1’ after the T confirms flat/horizontal/vertical-up/overhead capability); T=tubular wire (flux-cored); -1=usability designator specifying suitability for CO₂ or Ar/CO₂ shielding gas, DCEP polarity, and fluid fast-freezing slag. Common exam trap: E71T-11 (no external shielding gas — self-shielded FCAW) vs E71T-1 (requires external gas — FCAW-G). Self-shielded FCAW-S cannot be used for most structural work per CSA W59/AWS D1.1 without engineering approval. Wrong answers often confuse the ‘1’ position digit with the flux type, or confuse T (tubular) with S (solid wire in GMAW nomenclature). Always check -G (gas-shielded) vs -S (self-shielded) designator on the wire classification.

Low arc voltage relative to wire feed speed causes an unstable arc and excessive spatter in FCAW-G. Proper voltage-WFS balance is critical. Also, 100% CO₂ produces more spatter than Ar/CO₂ mixes.

Slag from previous FCAW passes must be completely removed before depositing the next pass. Trapped slag creates slag inclusions in subsequent passes — a type of non-metallic inclusion defect.

Dual-shield FCAW (FCAW-G) uses flux inside the wire core AND external shielding gas for superior weld quality. This produces high-quality, low-hydrogen welds with excellent mechanical properties — common in structural and offshore applications.

Excessive stickout in FCAW preheats too much wire before the arc, reducing the current needed to melt it — decreasing penetration and increasing the risk of insufficient fusion and incomplete penetration.

The HAZ is the region of base metal adjacent to the fusion zone that has not melted but experienced temperatures high enough to alter its microstructure and properties (grain growth, hardening).

AWS A2.4 welding symbols communicate weld type, size, length, location, and finishing requirements on engineering drawings without written notes. Key elements: the reference line is horizontal — symbol below the line = arrow side weld; symbol above = other side weld; both sides = weld both sides. The tail contains welding process or specification reference. Common Red Seal exam traps: a flag on the reference line = field weld; a filled circle at the arrow-reference line junction = weld all around; finish symbols (G=grind flush, C=chipping, M=machining) follow the weld size. Wrong answers confuse ‘arrow side’ with ‘front of the part’ — arrow side means the side the arrow touches, regardless of orientation. Symbols are read left-to-right along the reference line; length and pitch follow size.

Martensite forms when austenite is cooled very rapidly (quenched). It is extremely hard and brittle, has high residual stress, and is highly susceptible to hydrogen-induced cracking (HIC).

The Charpy test strikes a notched specimen with a pendulum and measures the energy absorbed before fracture (in joules). It evaluates toughness at specified temperatures, critical for pressure vessels and low-temperature service.

Distortion is dimensional change in the welded assembly resulting from non-uniform thermal expansion and contraction during welding. Metal expands when heated and contracts during cooling — if constrained or uneven, the assembly warps or bows.

RT (X-ray/gamma) and UT (ultrasound) detect subsurface volumetric defects (cracks, porosity, inclusions). VT and PT only find surface defects. MT finds near-surface defects in ferromagnetic materials.

Preheat slows the cooling rate of the weld and HAZ. Slower cooling reduces the formation of hard martensite, lowers residual stress and HAZ hardness, and allows hydrogen to diffuse out before HIC cracking can occur.

When austenitic stainless (e.g., 304) is held in the 425–870°C sensitization range, carbon combines with chromium to form Cr₂₃C₆ at grain boundaries, depleting the surrounding area of corrosion-protective chromium and reducing corrosion resistance.

A groove weld occupies a groove or gap prepared in the base metal (butt joint). A fillet weld is a triangular cross-section weld joining surfaces at approximately 90° (T-joint, lap joint, corner joint).

The leg of a fillet weld is the distance from the root of the joint to the toe of the weld, measured along the fusion face. For an equal-leg fillet, both legs are the same length.

A CJP groove weld's metal penetrates and fuses through the complete joint thickness. A PJP groove weld's metal extends through only a portion of the joint thickness. CJP is stronger and required for critical applications.

Per CSA W47.1, a welder's qualification expires if they have not welded in the applicable process, position, or material group within the preceding 6 months — requiring re-qualification to maintain it.