All 125 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. Ventilation, an attendant posted outside and personal protective equipment are all required as well, but the test result is what tells you whether entry — and hot work inside — is permitted at all, so the test comes first.

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

CSA W117.2, Safety in welding, cutting and allied processes, is the Canadian welding safety standard, and CCOHS reproduces sample rows of its arc-welding shade table. The shade is selected by welding process, electrode (wire) diameter and operating current, and every row carries two numbers: a minimum shade and a suggested shade. CCOHS prints the rule in capitals: ALWAYS use suggested shade numbers instead of minimum shade numbers. A 4.8 mm electrode at 200 A falls in the SMAW row for 4 to 6.4 mm electrodes at 160 to 250 A, which reads minimum shade 10, suggested shade 12, so shade 12 is the filter to fit. Shade 10 is the trap: it is a real figure for this very row, but it is the floor the filter may not drop below, not the shade the welder is told to work behind, and the two columns are not interchangeable. Shade 8 is the minimum for the lighter SMAW row (2.5 to 4 mm electrodes at 60 to 160 A) and sits below this joint's floor altogether. Shade 14 is the suggested shade for the heavier row (electrodes over 6.4 mm at 250 to 550 A); the higher the number, the darker the filter and the less light passes through, so at 200 A it is darker than the table calls for and makes the weld zone harder to see. In Canada the helmet itself is a CSA Z94.3 Class 3 protector, and provincial regulation makes that approval mandatory: Alberta's OHS Code s. 229, for example, requires eye protection approved to CSA Z94.3 and appropriate to the work and the hazard, and s. 231 forbids arc welding where another worker could be exposed to the arc unless that worker has suitable eye protection or is behind a screen. CCOHS adds that anyone directly observing the arc should use the same shade as the welder, and that gas welding goggles, sunglasses or smoked plastic must never stand in for a proper welding filter.

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.

In Canada welding ventilation is an exposure-limit duty, not a fixed airflow number. Provincial regulation makes CSA W117.2 (Safety in welding, cutting, and allied processes) mandatory and then requires capture at source: British Columbia's OHS Regulation section 12.112 requires welding, cutting and similar processes to be carried out according to CSA W117.2, and section 12.114 requires effective local exhaust ventilation at any fixed work station to minimize worker exposure to harmful air contaminants. The test of adequacy is whether fume and gas stay below the occupational exposure limits for the metals and coatings involved — use the edition of W117.2 and the exposure limits your province adopts. The 2,000 cfm per welder figure offered here is American, not Canadian: OSHA 1910.252 sets that rate where the space is less than 10,000 cubic feet per welder or the ceiling is less than 16 feet, and it has no force here. The 1,000 cfm variant simply invents a Canadian version of that same US ceiling-height trigger. The idea that ventilation only matters above some current is false — fume is produced at every setting, and there is no amperage below which ventilation stops being required. The one Canadian airflow figure worth memorizing comes from the Canadian Centre for Occupational Health and Safety: a moveable exhaust hood should provide an air velocity of at least 100 ft/min (0.5 m/s) across the welding arc, placed as close to the work as practical. Local exhaust is mandatory regardless of general airflow when welding coated, galvanized or stainless material, where zinc oxide and hexavalent chromium exceed exposure limits even in a well-ventilated shop. AWS D1.1 and CSA W59 are fabrication codes and set no ventilation requirement.

A fire in energized electrical equipment is a Class C fire, so the extinguisher must carry a Class C rating. A dry chemical agent does not conduct, so it can be discharged onto live equipment without putting the operator into the current path. Water-type and foam agents both conduct electricity and must never be used on energized equipment, and a dry powder unit is formulated for burning metals such as magnesium or titanium, not for electrical gear. Where it can be done safely, de-energize the circuit first — once the power is off the fire is classified by whatever is actually burning.

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, and they set out the precautions — including a trained fire watch kept in place during the work and for at least 60 minutes after it ends.

Containers must be thoroughly cleaned, purged, and then gas-tested and certified free of flammable vapour before any hot work — explosive residues can remain long after airing, soaked into scale, seams and sludge. Where a residual reading is tolerated at all, the hot-work limit is far tighter than the limit for cold work: Ontario's confined space guideline permits cold work under 10% LEL but hot work only under 5% LEL, and British Columbia requires flammable gases and vapours to be held below 20% of the LEL. A rinse, or a day with the lid off, proves nothing.

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.

IHSA shows that two slings lifting 1,000 lb put 500 lb on each leg only when the legs hang at 90 degrees. The force on each leg goes up as the angle drops. At 30 degrees, each leg carries about 1,000 lb, the full weight of the load. 500 lb is the answer for vertical legs, which a weak candidate gets by simply splitting the load in half. 707 lb is IHSA's figure for a 45 degree angle. 2,000 lb doubles the load and overstates the tension. For this reason IHSA says to keep sling angles above 45 degrees whenever possible and calls any angle below 30 degrees extremely hazardous.

The speed marked on a wheel or attachment is the fastest it can safely spin. CCOHS says to check that this marked speed is equal to or greater than the grinder's maximum speed, and never to use a wheel rated below the grinder's RPM. A wheel spun faster than its rating can break apart. Choosing a lower-rated wheel "for a margin" gets it backwards: the grinder would overspeed the wheel. Half the grinder's rating is still too low. A guard is required too, but it does not make an under-rated wheel safe to use.

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.

An oxidizing flame has excess oxygen, producing a shorter, more pointed inner cone with a hissing sound — used for welding brass and bronze, and a slightly oxidizing flame for torch brazing steel and cast iron.

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.

Free acetylene gas is chemically unstable and can decompose explosively on its own, without any oxygen present, once its pressure climbs too high — so the fuel regulator is never set above 103 kPa (15 psi) gauge. Note what this limit applies to: it is the delivery pressure the regulator feeds to the torch, not the cylinder pressure. A full acetylene cylinder reads far higher, roughly 1700 kPa (250 psi), and that is safe only because the acetylene inside is dissolved in acetone held in a porous filler rather than existing as free gas. For the same reason the withdrawal rate is limited, commonly to about one-seventh of cylinder capacity per hour, so that acetone is not dragged out with the gas.

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. Travel that is too slow does the opposite: the top edge melts and rounds and slag clings underneath, but the cut face stays square, so no drag develops. Excessive cutting oxygen pressure gives a wide, rough, gouged kerf rather than drag, and oversized preheat flames melt and round the top edge.

Oxy-fuel cutting works by rapid oxidation of iron, so it is confined to carbon and low-alloy steel. It cannot cut stainless steel — stainless is ferrous, but its chromium forms a refractory oxide that will not burn away — and it cannot cut aluminum or the other non-ferrous metals. Plasma arc cutting melts the metal with a high-temperature ionized gas jet and blows it out of the kerf, so it handles stainless, aluminum and copper readily. Plasma does need an electrically conductive workpiece with the work lead clamped to it, so it offers nothing on materials that do not conduct. Galvanized steel cuts perfectly well with oxy-fuel, and on heavy carbon steel plate oxy-fuel remains the practical choice, since plasma capacity falls away as thickness climbs.

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.

In manual CAC-A, travel speed controls gouge depth: the faster you travel, the shallower the gouge, and a slower travel speed produces a deeper one. Speeding up does the opposite and leaves the groove even shallower. Pulling the electrode back is wrong. Once the arc is struck you hold a short arc and keep moving fast enough to keep up with the metal removal. If the gap opens too far, the arc goes out. The air jet does not set depth. It blows the molten metal and slag out, and it should point along the gouge. Aiming it at one side only changes which edge the slag sticks to. Electrode diameter sets the groove width, and a groove deeper than about 1-1/2 times the electrode diameter has to be made in more than one pass.

A pilot arc forms when the torch fires but the plasma arc is not yet in contact with the workpiece. For the cutting arc to transfer, the workpiece has to be part of the circuit through the work clamp and work lead. A clamp sitting on paint, rust or coatings has no good metal-to-metal contact, so the arc cannot transfer. The manufacturer's fix is to clean the clamp contact area down to bare metal and check the clamp for damage. Stainless steel conducts electricity, and air plasma is rated for stainless, mild steel and aluminum, so the grade of steel is not the problem. Dragging the tip with shielded consumables is the recommended hand-cutting method, and it keeps the torch close to the work, which helps the arc transfer. A plate that is too thick still lets the arc transfer. It just does not cut all the way through.

E7018 classification: E=electrode; 70=minimum tensile strength of 70,000 psi, written as 490 MPa in the metric tables of AWS A5.1 and CSA W48; 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. On Canadian work under CSA W47.1/W59 you will see this same electrode written E4918 per CSA W48, the Canadian filler-metal standard — same electrode, metric strength designation. Boxes sold in Canada are dual-marked, for example AWS A5.1 E7018-1 H4R / CSA W48 E4918-1-H4.

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.

A slag inclusion is solidified flux trapped inside the deposit. It gets there when slag from an earlier pass is left in the joint and welded over, or when a poor travel angle rolls the slag ahead of the arc so the puddle runs on top of it. Chipping, wire brushing and grinding each pass clean, and keeping the electrode angled so the slag stays behind the arc, are the controls. The other conditions produce different defects: too long an arc gives spatter and porosity, a damp coating gives porosity and hydrogen-induced cracking, and insufficient preheat gives cracking or lack of fusion — none of them leaves flux buried in 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 keeps the coating dry, and a dry coating is what keeps diffusible hydrogen out of the weld metal — moisture picked up by the flux is the source of the hydrogen behind hydrogen-induced (cold) cracking and porosity.

DCEP (reverse polarity) means the electrode is connected to the positive terminal and the work to the negative terminal. In SMAW this is the deeper-penetrating polarity, and it is what E6010 and E7018 are run on. Do not carry that rule across to GTAW: the tungsten there is not consumed, and DCEN is the polarity that concentrates the heat in the work and gives the deeper penetration. The rule about which polarity penetrates belongs to the process, not to the letters.

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 direction opposite to the overall travel. Each new segment is started ahead of the last one, in the overall direction of progression, and welded back to the point where the previous segment began, so heat is spread along the joint instead of being driven continuously in one direction. That reduces 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.

A plate groove test welded vertically also covers the flat and horizontal positions, because vertical work demands more puddle control than either of them. It does not reach overhead: that is the separate 4G plate test, so a shop needing every plate groove position tests both. Assuming one plate test covers everything is the common error — it is 6G pipe, welded on a fixed 45 degree axis, that is the all-encompassing groove qualification. Read the extent of a qualification off the standard you were tested to rather than off habit: in Canada, welders working for a company certified to CSA W47.1 are qualified by the Canadian Welding Bureau, which requires that all welders, welding operators and tack welders employed by the company be tested for the processes and positions of welding they use in production.

The four GMAW transfer modes: (1) Short-circuit transfer — the lowest arc voltage of the four, the wire periodically touches the puddle and extinguishes the arc, suitable for thin gauge and out-of-position, but a cold lap and incomplete fusion risk at heavy thickness; (2) Globular transfer — a longer arc carrying drops larger than the wire diameter, transferring erratically with 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 and horizontal positions and requiring an argon-rich gas; (4) Pulsed spray — a background current below the spray transition and a peak pulse current above it, which gives spray-type droplet transfer at a lower average current and heat input. Red Seal key point: spray transfer cannot be used out of position because gravity makes the puddle sag, and pulsed spray is what solves that.

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.

Rank the modes by arc length and you rank them by voltage. Short circuit sits at the bottom: the arc is so short that the wire dips into the puddle and extinguishes the arc many times a second. Globular sits in the middle, with a longer arc carrying drops larger than the wire diameter across it. True axial spray sits at the top, because the arc has to be long enough and hot enough to pinch the wire tip into a fine stream of droplets smaller than the wire. Pulsed spray is the trap here: its peak current does climb above the spray transition, but the whole point of pulsing is to get spray-type droplet transfer at a lower average voltage and current, which is exactly what lets it run out of position. Voltage alone is not enough either — true spray also needs an argon-rich shielding gas, and a CO₂-rich gas will not give axial spray at any voltage setting.

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.

Aluminum wire has far less column strength than steel wire of the same diameter — push on it and it behaves more like cooked spaghetti than like a rod. Down a long liner it buckles and piles up at the drive rolls instead of feeding, and it abrades badly against a steel liner on the way. The cure is to shorten the push: a spool gun carries a small spool at the gun itself, and a push-pull gun adds a motor at the gun that pulls the wire while the feeder pushes it. Around that go a nylon or polymer liner, U-groove rolls that cradle the soft wire instead of biting into it, and the straightest, shortest gun run the work allows. Note what does not change — a spool gun draws its shielding gas from the same cylinder as any other GMAW gun, aluminum still needs 100% argon, and solid aluminum wire still runs DCEP like other solid wire.

ER5356 is a magnesium-bearing filler (about 5% magnesium) and is the standard choice for the magnesium-bearing 5000-series, including 5083. ER4043 is a silicon-bearing filler (about 5% silicon) meant for the 6000-series; on high-magnesium 5xxx alloys such as 5083, 5086 and 5456 its silicon combines with the magnesium in the base metal to form brittle magnesium silicide, so it is kept off those alloys. Low-magnesium 5052 is the exception where 4043 is accepted. ER308L is a stainless steel filler and ER70S-6 a carbon steel filler; neither belongs on aluminum.

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.

Shielding works because the gas leaves the nozzle as a smooth column that pushes the air off the puddle and holds it off. Past a certain flow that column breaks up: turbulent gas mixes with what is around it instead of displacing it, so the stream itself starts drawing room air into the arc, and the oxygen and nitrogen it brings leave the bead porous. Opening the flowmeter is therefore one of the more expensive wrong reflexes in the shop — it burns gas and makes the defect worse at the same time. Set the flow to what the procedure calls for and hunt the real fault: a cut or leaking gas hose, a loose fitting drawing air on the suction side, a nozzle packed with spatter, a fan or an open door blowing across the joint, mill scale, rust, oil or paint left on the plate, or a stickout so long that the arc has crept out from under the nozzle.

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 is an active gas, not an inert one. In the arc it dissociates, and some of that carbon transfers into the molten pool, raising the carbon content of the weld metal. As the weld cools through roughly 425-870 °C (800-1600 °F) that carbon combines with chromium at the grain boundaries to form chromium carbides (Cr23C6). Chromium tied up in carbides is no longer available to maintain the passive film, so the metal beside the boundaries is chromium-depleted and the weld is sensitized: it loses corrosion resistance and becomes prone to intergranular attack. Avoiding exactly that is what a low-carbon L grade such as 304L is bought for, so shielding it with 100% CO₂ defeats the purpose of both the base metal and the filler. Established practice on austenitic stainless keeps CO₂ to roughly 3% for L grades and about 5% for other austenitic grades for this reason, so 100% is around thirty times that, on top of heavy chromium and silicon oxidation and a dark, scaled bead. Correct practice is argon with about 1-3% CO₂ for spray and pulsed spray, or a helium-rich trimix such as 90% He / 7.5% Ar / 2.5% CO₂ for short-circuit work on thin material.

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.

The feed path controls how smoothly the wire reaches the arc. Worn or wrongly grooved drive rolls, incorrect drive tension, a kinked or clogged liner, a worn contact tip or a tangled spool make the wire arrive in surges, so the arc lengthens and shortens, pops, and burns back. The other faults leave the feed alone and show themselves differently: low shielding gas flow shows up as porosity, too slow a travel speed as excessive buildup and cold lap, and a wrong work angle as undercut and poor bead placement. Check the feed system first — liner condition and length, drive roll size and groove type for the wire being run, drive tension, and the contact tip.

GMAW solid wire uses DCEP (direct current electrode positive, also called reverse polarity). On a consumable electrode this is the polarity that gives deeper penetration, and it is what stable spray transfer requires. Flux-cored wire is where polarity actually varies: most self-shielded wires are classified for DCEN, so the habit of assuming DCEP for everything that comes off a spool will eventually cost a welder a run of porous, poorly fused weld.

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 A5.12M/A5.12 (a modified adoption of ISO 6848) colour coding: pure tungsten, classification EWP, is Green. EWP is unalloyed tungsten, 99.5% minimum, with no oxide addition. It is used with alternating current for welding aluminum and magnesium, where it holds a clean balled end. The other three colours in this question belong to different electrodes: Grey is 2% ceriated (EWCe-2), Red is 2% thoriated (EWTh-2), and Gold is 1.5% lanthanated (EWLa-1.5). One change catches people out on the exam and in the rod drawer: the 2009 edition of A5.12 moved EWCe-2 from orange to grey, and grey is no longer the EWG code. Older charts and older stock still show orange for ceriated, so trust the current colour band, not the wall chart.

Gas tungsten arc welding on carbon steel, stainless steel and titanium is run on DCEN - direct current, electrode negative, what the shop floor calls straight polarity. AWS states it plainly: for carbon steel, stainless steel and many alloys, GTAW typically uses DCEN, which concentrates heat in the workpiece and provides good penetration, and it keeps the tungsten relatively cool. That second part is the reason the choice is not negotiable in the way it might be with a consumable electrode. The tungsten is not meant to be consumed, and the polarity that drives heat into the work is also the polarity that spares the electrode; set the machine the other way and the heat goes into the tungsten instead of the joint, so the electrode runs far hotter and erodes while the weld goes shallow. Aluminum is the exception to the DCEN habit and is welded on AC. And keep the polarity-and-penetration rule scoped to the process rather than to the letters: with a consumable electrode, as in SMAW or GMAW, DCEP is the deeper-penetrating polarity, while with a non-consumable tungsten it is DCEN. The filler rod does not enter into it - polarity is set by the process and the base metal, not by which rod is in your hand.

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 swings the welding current between a higher peak level and a lower background level at a set frequency, and AWS describes the division of labour in one sentence: the peak current provides penetration and fusion, while the background current lets the puddle cool slightly without extinguishing the arc. Both halves of that sentence carry weight. The background level is deliberately too low to go on melting the joint, which is what allows the pool to begin freezing between pulses and keeps average heat input down - the reason pulsing suits thin sections, heat-sensitive alloys and out-of-position work, where a steady pool would sag or burn through. But it is not switched off either: take the current to nothing and the arc goes out and has to be re-established, so the background level is set low enough to let the puddle cool and high enough to keep the arc alive. Melting and penetration are the peak current's job, not the background's, which is the most common way this gets remembered backwards. Two other things do not happen at the background level. On DC the polarity does not change with the pulse - the electrode stays negative through both the peak and the background, and alternating between electrode negative and electrode positive is a polarity setting, a separate control from pulse level. And pulsing the current is not pulsing a wire feed; the filler, wherever it comes from, is a separate matter from what the current is doing.

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, so it can be run outdoors and in wind without gas cylinders. FCAW-G (gas-shielded) needs external CO₂ or an argon/CO₂ mix on top of the core, which is why the shop floor calls it dual-shield — the arc is protected twice over, by the gases the core generates and by the gas coming out of the nozzle. Wind is the practical consequence of the difference: a breeze that would strip the nozzle gas off an FCAW-G weld and leave it porous does not touch a self-shielded arc, so FCAW-G outdoors needs a windbreak or an enclosure.

Gas-shielded flux-cored wire is run on DCEP, direct current electrode positive, the same polarity as GMAW solid wire. AWS A5.20/A5.20M:2005 Table 2, Electrode Usability Requirements, defines the term in a footnote as direct current electrode positive, or reverse polarity, and its polarity column is where the word "typically" in the question comes from. The gas-shielded usability designators are 1, 2, 5, 9 and 12. Designators 1, 2, 9 and 12, which include the widely used E71T-1, are listed for DCEP, and the annex describes the T-1 wires as designed for single and multiple pass welding using DCEP. Designator 5 is the exception: the flat-and-horizontal E70T-5C and E70T-5M electrodes are listed DCEP, but the all-position E71T-5C and E71T-5M electrodes are listed "DCEP or DCEN", with a footnote that some of them are recommended for DCEN to improve out-of-position welding and that the manufacturer should be consulted. Self-shielded wire is where polarity really varies: designators 3, 4 and 6 are DCEP, while 7, 8, 10, 11, 13 and 14, the majority and the common E71T-8 and E71T-11 among them, are DCEN. So a gas-shielded wire is set up electrode positive unless its classification or the manufacturer's data sheet says otherwise, and the leads are never left where the last spool had them: wrong polarity on a flux-cored wire shows up as an erratic arc, heavy spatter, porosity and poor fusion. The polarity column of that table carries only DCEP, DCEN, or "not specified" for the G classifications, so AC is not a classified polarity for any carbon steel flux-cored designator. Nor does any designator tie polarity to where the work is done: indoors or outdoors decides between gas-shielded and self-shielded wire, not between electrode positive and electrode negative.

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. It is not chosen for cleanliness: flux-cored wire leaves a slag that must be chipped off between passes and it generates more welding fume than solid wire, so fume extraction matters more, not less.

Travel angle is the tilt of the gun along the weld axis, measured from perpendicular to the work; work angle is the separate measurement taken across the joint, and the two are not the same setting. Flat and horizontal FCAW is run with a drag (backhand, pull) travel angle: the gun is tilted back against the direction of travel, so the arc stays on the leading edge of the puddle and the molten slag is left behind the arc. AWS Welding Digest's FCAW troubleshooting guidance is to maintain a steady 10 to 20 degree drag angle. A push (forehand) angle floats the slag ahead of the arc, where the advancing weld metal rolls over it and traps it as a slag inclusion. Tipping the gun to something near 45 degrees takes the nozzle so far off the joint that gas coverage on gas-shielded wire and puddle control both suffer, and holding the gun square to the plate leaves the welder no control at all over where the slag sits.

Flux-cored wire is normally run at a longer contact-tip-to-work distance (CTWD) than solid wire, and the reason is in the core. The wire becomes electrically live the moment it touches the inside of the contact tip, so every millimetre between the tip and the arc is being resistance-heated. Lincoln Electric's flux-cored welding guide gives the normal CTWD for flux-cored electrodes as 3/4 to 1 in. (20 to 25 mm) and calls that much longer than the roughly 10 mm average it quotes for short-circuit GMAW with solid wire. The extra length buys a split second more of resistance heating, and that is what lets the core ingredients fully react and protect the arc. Run the distance too short and the core may be incompletely activated, which can show up as gas marks or porosity on and in the weld. Run it too long without changing the wire feed speed and the arc goes unstable, spatter rises and penetration drops. The same guide separates the two measurements a welding document may quote: CTWD is contact tip to work, electrical stickout (ESO) is contact tip to the top of the arc, and ESO is generally about 6 mm shorter than CTWD, so the comparison holds whichever figure a procedure prints. Both flux-cored families run the normal band; what differs is the ceiling. Gas-shielded wire is held to roughly 30 mm because that is about as far as the nozzle gas still covers the arc, while self-shielded wire needs no gas coverage and can be run at 75 to 100 mm with insulated guides for extended-stickout, high-deposition work. Gas-shielded datasheets confirm the band: Lincoln's UltraCore 71A85 procedures are all written at 25 mm CTWD, and ESAB's Dual Shield 7100 Ultra sheet runs tip-to-work from about 10 mm for the smallest wire at the lowest current up to about 32 mm for 1.6 mm wire at high current, so the exact figure rises with diameter and current and must be taken from the wire datasheet, which is what the Red Seal standard requires. The other three answers carry real misconceptions. More stickout does not draw more current: on a constant-voltage machine the wire feed speed sets the current, and lengthening the CTWD at a fixed feed speed lowers it, because the preheated wire needs less current to melt. Shortening the distance to spare the tubular wire is backwards, since a short CTWD is what starves the core of heating time. And a constant-voltage machine holding arc length does not make the distance irrelevant; it is precisely because the machine holds voltage that a change in stickout shows up as a change in current and penetration.

H8 is the optional diffusible-hydrogen designator. It records a measured property of the weld deposit: test welds made with the wire gave no more than 8 millilitres of diffusible hydrogen per 100 grams of deposited weld metal. It is not a description of the flux and it is not a time limit. The Lincoln Electric UltraCore 71C datasheet shows how it reads on a real product sold in Canada: the wire is classified AWS E71T-1C-H8 and E71T-9C-H8 (a T-9 wire meets every requirement of a T-1 wire and adds a tougher impact test), and on the CWB/CSA W48 line of the same conformance list it is E491T-9 H8, the 49 being the 490 MPa metric strength level and the T-9 matching the AWS T-9 classification. Its deposit table lists the diffusible hydrogen requirement as 8.0 mL/100 g maximum against typical results of 4 to 7. Hobart's flux-cored selection guide puts the principle in one line: the optional H4 and H8 designators added to an AWS classification show the maximum allowable diffusible hydrogen the filler metal provides, and lower is better. The CWB Group's article on hydrogen testing of consumables gives the scale: 16 mL/100 g of deposited metal is the ceiling for a consumable to be called low hydrogen, which earns H16, and manufacturers now test to the tighter H8, H4 and H2 grades; the deposit is welded, quenched, analysed by gas chromatography and the results averaged, and, in the article's own example, 8 mL/100 g of deposited metal is given the designator H8. The number matters on thick or higher-strength steel, where hydrogen in the deposit is the driver of hydrogen-induced cold cracking; a lower-hydrogen wire can in some applications reduce the preheat needed. It also matters when matching wire to the WPDS: a classification only guarantees its own maximum, so an H8 spool does not give what a WPDS calling for H4 requires. The traps: the 8 has nothing to do with the final 8 in E7018, which names the low-hydrogen basic coating on an SMAW rod, whereas an E71T-1 wire has a rutile slag; there is no hour count in the designator, since keeping spools sealed and cutting back exposed wraps is a storage practice and the four-hour exposure limit belongs to E7018 rods, not to an H8 marking; and the figure is measured in the weld deposit, not as parts per million of hydrogen in the steel strip the wire is made from.

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.

Read E71T-1 one character at a time. E is electrode. 7 is the minimum tensile strength, 70 000 psi. Do not convert that number yourself: AWS publishes a separate metric classification, and in it the same wire is E491T-1, where 49 stands for 490 MPa. AWS A5.20/A5.20M:2005 Table 1 requires 70–95 ksi for the E7XT-1 classifications and Table 1M requires 490–670 MPa for E49XT-1, and the specification states that the two systems 'are not equivalent, each system must be used independently of the other.' The 1 that sits ahead of the T is the position digit and means all-position. T means the wire is tubular, that is flux-cored, as opposed to a solid GMAW wire. The -1 that follows the T is the usability designator: it identifies a rutile-type, fast-freezing slag system run on DCEP with CO₂ or an argon/CO₂ mix as the shielding gas. The two 1s in the designation therefore carry different meanings, and it is the trailing one that describes gas and polarity. Also keep the shielding split straight: E71T-1 requires an external shielding gas (FCAW-G), while a self-shielded wire such as E71T-11 or E71T-8 generates its own shielding from the core (FCAW-S) and runs with no gas bottle at all.

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.

Solid wire is a stiff rod, and a smooth V-groove roll squeezing it firmly feeds it without trouble. Flux-cored wire is not a rod at all — it is a thin steel strip folded into a tube around granular flux — so the same grip flattens it. A crushed wire drags in the liner, feeds unevenly and changes how much flux is reaching the arc, which shows up as wandering arc length and inconsistent slag coverage. What tubular wire needs is more bite and less squeeze: knurled (serrated) rolls of the size marked for the wire, with the tension set to the least that will feed without slipping. Set the tension by feel, not by habit — back it off until the wire slips, then bring it up just past that point. Slipping shows as a stuttering, popping arc; crushing shows as flux dust in the liner and a wire that looks oval where it left the rolls.

These are worm tracks, also called gas tracks: shallow tunnels or grooves in the surface of the bead, hidden under the slag until it comes off. The flux core generates gas as it burns, and most of that gas escapes up through the puddle. When the slag blanket freezes over the top before the last of it is out, the gas is trapped at the interface and leaves its path printed along the crown. That makes worm tracks a surface signature, quite unlike the fine scattered voids through the body of the bead that come from a damp consumable. Too long an arc is the usual reason — it gives the core more gas to shed and less time in which to shed it — and wire that has picked up moisture adds to the gas load, so shorten the arc, slow down enough to let the puddle degas, and use wire that has been stored dry. The other three answers name real flux-cored defects with different signatures: undercut is a groove in the base metal at the toe, a slag inclusion is non-metallic material buried inside the deposit, and an arc strike is a mark outside the weld itself.

Flux-cored wire is hygroscopic, and the core is open to the air along the seam of the tube. Left unwrapped in an unheated shop, the flux takes up moisture, which dissociates in the arc into hydrogen and oxygen and shows up as fine scattered porosity through the bead. On higher-strength steel the same moisture is a hydrogen source and a cracking risk, not just a cosmetic problem. The fix is to cut back and discard the wraps that were exposed, then store spools sealed with desiccant, or in a dry heated cabinet once opened, and to discard wire that has rusted or discoloured. Note what the scenario rules out: nobody touched the machine, so a setting cannot have changed. Gas flow that is too high genuinely does cause porosity, by making the stream turbulent enough to pull air into the shielding envelope — but it would have done so on Friday too. A worn contact tip shows as an erratic arc, poor current pickup and burnback rather than uniform scattered porosity, and travel speed changes bead shape and fusion rather than filling a sound bead with gas holes.

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, Standard Symbols for Welding, Brazing, and Nondestructive Examination, is the welding-symbol reference used on Canadian drawings. On structural work it reaches you through CSA W59, Welded steel construction, the Canadian structural welding standard, which adopts the AWS A2.4 symbols together with additional conventions of its own — so a Canadian shop drawing is read to AWS A2.4 alongside CSA W59. Welding symbols communicate weld type, size, length, location and finishing requirements on engineering drawings without written notes. Key elements: the reference line is horizontal — a symbol below the line means an arrow side weld, a symbol above means an other side weld, and symbols on both sides mean weld both sides. The tail carries the welding process or a specification reference, but the symbol does not name the shielding gas and it never names a machine. Common Red Seal exam traps: a solid flag (pennant) at the junction of the arrow and the reference line means field weld, while a circle at that same junction means weld all around — two different symbols in the same place, so do not read the flag as the circle; and the size is placed to the left of the weld symbol with length and pitch to its right, while contour and finish symbols (G = grinding, C = chipping, M = machining) are placed beyond the weld symbol, the finish symbol sitting outside the contour symbol away from the reference line. Wrong answers confuse 'arrow side' with 'front of the part' — arrow side means the side of the joint the arrow touches, whatever the orientation of the part.

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 (internal) defects such as cracks, porosity and inclusions. VT and PT only find surface defects. MT finds surface and near-surface defects in ferromagnetic materials.

Almost every weld contains some discontinuity. A discontinuity only becomes a defect when it falls outside the acceptance criteria of the code or job specification the work is being performed to, so the same undercut can be acceptable on one job and rejectable on another. The Red Seal Occupational Standard makes this the welder's call to determine acceptability according to job specifications and codes, and to keep records of what was found. Repairability does not change the accept or reject decision, and inspection aids such as magnifying lenses and mirrors are normal visual-inspection tools, not the dividing line.

When austenitic stainless (e.g., 304) is held in the 425–870 °C (800–1600 °F) 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, but PJP groove welds are not limited to non-critical work: the design drawings and the governing welding standard specify where CJP is required, and a PJP weld is sized by its design throat.

Per CSA W47.1 (administered by the CWB), a welder's qualification is subject to revocation if the welder has not been engaged in the applicable process for a period of 3 months or more — requiring re-qualification. Do not confuse this with the 6-month continuity period used by AWS D1.1 in the United States.

Two numbers joined by a hyphen to the right of a fillet weld symbol mark an intermittent fillet weld. The first number is the length of each weld segment and the second is the pitch. Pitch is measured centre to centre from one segment to the next. It is not the clear space between them. So 3-12 means 3 in welds at 12 in centres, and the unwelded length between segments is the pitch minus the segment length: 12 − 3 = 9 in. Answering 12 in treats the pitch as the clear gap, which is the classic print-reading mistake. That reading would put the segments at 15 in centres, which is where the 15 in answer comes from, since it adds the segment length to the pitch. The 6 in answer has no basis in the notation. It is just half the pitch.

In the standard welding symbol system (AWS A2.4), the joint is the basis of reference: the arrow side is the side of the joint the arrow points to, and the other side is the opposite side. A weld symbol placed below the reference line calls for the weld on the arrow side. The other side is wrong because that weld would be shown by a symbol placed above the line. Both sides is wrong because that needs weld symbols above and below the line. Leaving it to the welder is wrong because the symbol's position fixes the location, and that is the whole point of the symbol. Arrow side means the side the arrow touches, not the front or top of the part as drawn.