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Certified Robotic Arc Welding (CRAW) practice questions

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Question 1Weld Equipment Setup

When setting up a GMAW (MIG) welding station, what is the primary function of the shielding gas in the process?

  1. It provides the electrical path between the nozzle and the workpiece
  2. It increases the deposition rate by preheating the filler wire
  3. It prevents atmospheric contamination of the molten weld pool Correct answer.
  4. It cools the contact tip to extend its service life

Explanation

Shielding gas displaces ambient air around the arc and molten pool, preventing nitrogen and oxygen from causing porosity and embrittlement. It does not carry current, preheat wire, or cool the tip. Correct gas selection and flow rate are foundational setup decisions in GMAW.

Question 2Weld Equipment Setup

In a GTAW (TIG) setup, which component is responsible for transferring welding current to the electrode while allowing the electrode to be adjusted?

  1. The torch switch
  2. The gas lens screen
  3. The collet body and collet Correct answer.
  4. The ceramic cup

Explanation

The collet grips the tungsten electrode and the collet body threads into the torch head, together conducting current from the torch body to the electrode. The ceramic cup shields gas flow, the gas lens screens and stabilizes it, and the switch controls arc start. These are distinct setup parts with separate functions.

Question 3Weld Equipment Setup

A welder is preparing a SMAW (stick) station and notices the electrode holder jaws are loose and the insulation on the stinger cable is cracked. What is the correct setup action?

  1. Wrap the cracked section with electrical tape and continue
  2. Increase the amperage setting to compensate for poor contact
  3. Swap the electrode to a smaller diameter and proceed
  4. Replace or repair the holder and cable before welding begins Correct answer.

Explanation

Damaged insulation and loose jaws present shock and arc-strike hazards and degrade current transfer, so the affected components must be repaired or replaced before use. Taping over cracked insulation or compensating with amperage does not address the safety defect. Equipment condition checks are part of every proper station setup.

Question 4Weld Equipment Setup

What is the standard purpose of the flowmeter on a shielding gas regulator during setup?

  1. To detect the presence of moisture in the gas line
  2. To indicate the rate of gas delivered to the torch in cubic feet per hour or liters per minute Correct answer.
  3. To regulate the welding current output of the machine
  4. To measure the pressure remaining in the cylinder

Explanation

A flowmeter displays the volumetric gas flow delivered to the torch, typically in CFH or L/min, which the welder sets to match the process and joint. Cylinder pressure is shown by the high-pressure gauge on a regulator, not the flowmeter. Current output and moisture detection are handled by other devices.

Question 5Weld Equipment Setup

Which polarity setup is typical for DCEP (electrode positive) in GMAW, and what does it accomplish?

  1. Alternating current between electrode and workpiece to reduce spatter
  2. Electrode connected to negative and workpiece to positive, concentrating heat at the electrode
  3. Both electrode and workpiece connected to positive for balanced heat
  4. Electrode connected to positive and workpiece to negative, concentrating heat at the workpiece for deeper penetration Correct answer.

Explanation

In DCEP the electrode is positive and the workpiece negative, which places more heat in the workpiece and gives good penetration, the common configuration for GMAW. DCEN reverses this and puts more heat in the electrode. AC and dual-positive arrangements are not standard GMAW setups.

Question 6Weld Equipment Setup

A welder is setting up a FCAW station and must select the correct wire feed drive rolls. What should the drive roll groove profile match?

  1. The shielding gas flow rate
  2. The workpiece thickness only
  3. The wire diameter and wire type, such as a knurled roll for flux-cored wire Correct answer.
  4. The duty cycle of the power source

Explanation

Drive rolls must match the filler wire diameter and construction; flux-cored wires typically use knurled or V-groove rolls that grip without crushing the sheath, while solid wires use smooth V or U grooves. Gas flow, plate thickness, and duty cycle do not determine groove profile. Mismatched rolls cause feed problems and wire deformation.

Question 7Weld Equipment Setup

When setting up a GTAW torch with a gas lens, how does this compare with a standard collet body setup?

  1. The gas lens requires a smaller diameter tungsten electrode
  2. The gas lens provides smoother, more laminar shielding gas flow and allows a longer electrode extension Correct answer.
  3. The gas lens increases welding current capacity by conducting heat away faster
  4. The gas lens eliminates the need for a ceramic cup

Explanation

A gas lens uses a series of fine screens to straighten the gas stream, producing more laminar flow that permits greater electrode stickout and better coverage. It does not increase current capacity or remove the need for a cup. Tungsten selection is independent of the lens.

Question 8Weld Equipment Setup

A GMAW power source is being set up for short-circuit transfer on thin sheet. Which parameter combination best supports this mode?

  1. High wire feed speed with very high voltage and long stickout
  2. Lower voltage and lower wire feed speed with a short arc length Correct answer.
  3. High voltage and high wire feed speed with a long arc length
  4. Maximum voltage with minimum wire feed speed

Explanation

Short-circuit transfer requires voltage and wire feed speed in a range that keeps the arc short so the wire repeatedly contacts the pool. Excess voltage lengthens the arc and pushes the process into globular or spray transfer. High wire speed with high voltage does not define short-circuiting and can cause burn-through on thin sheet.

Question 9Weld Equipment Setup

During setup of a plasma cutting table, what is the purpose of establishing the correct standoff distance between the torch and the workpiece?

  1. To eliminate the need for a swirl ring
  2. To increase the gas pressure inside the torch body
  3. To maintain arc stability and cut quality consistent with the consumable and cut chart Correct answer.
  4. To maximize the electrical resistance of the cutting circuit

Explanation

Manufacturer cut charts specify a standoff that balances arc stability, kerf quality, and consumable life. Too much or too little standoff degrades the cut and shortens consumable life. Standoff does not change circuit resistance, torch gas pressure, or the function of the swirl ring.

Question 10Weld Equipment Setup

A welder is connecting a water-cooled GTAW torch. Which setup practice protects the torch from overheating?

  1. Use the torch only in AC mode to avoid heat buildup
  2. Run the torch dry at low amperage to test the arc first
  3. Verify coolant flow and connections before striking an arc Correct answer.
  4. Cap the coolant return line to increase pressure

Explanation

Water-cooled torches depend on continuous coolant circulation; confirming flow and secure connections before welding prevents overheating and torch damage. Running dry defeats the cooling system, capping the return line blocks circulation, and AC mode does not substitute for coolant flow.

Question 11Weld Equipment Setup

Which factor most directly determines the appropriate shielding gas flow rate when setting up a GMAW station?

  1. The thickness of the workpiece cable
  2. The color of the ground clamp
  3. The nozzle size, joint configuration, and whether welding is indoors or in drafty conditions Correct answer.
  4. The age of the power source

Explanation

Flow rate must be sufficient to shield the pool given nozzle diameter, joint geometry, and exposure to drafts, which can blow the gas away. Cable thickness, clamp color, and machine age do not influence gas coverage. Excessive flow can also cause turbulence that draws in air.

Question 12Weld Equipment Setup

When preparing a SAW (submerged arc) setup, what is the role of the flux delivery and recovery system?

  1. It blankets the arc and weld zone with granular flux and recovers unused flux for reuse Correct answer.
  2. It provides the electrical ground path
  3. It cools the weld immediately after solidification
  4. It supplies shielding gas to the arc

Explanation

Submerged arc welding relies on a layer of granular flux that covers the arc, protecting the molten metal and contributing to the slag and alloying. The system delivers flux ahead of the arc and recovers unused flux. SAW does not use shielding gas, and flux is not a ground path or a cooling medium.

Question 13Weld Equipment Setup

A welder sets up a GMAW machine and finds the wire birdnests at the drive rolls. Which setup adjustment is most appropriate to address this?

  1. Reduce drive roll tension and check that the liner and contact tip match the wire size Correct answer.
  2. Increase the spool brake tension significantly
  3. Switch to a larger contact tip bore than the wire diameter
  4. Increase drive roll tension to the maximum setting

Explanation

Birdnesting often results from excessive drive roll tension, a mismatched or clogged liner, or a contact tip that is too small, causing the wire to buckle at the rolls. Reducing tension and verifying liner and tip compatibility addresses the root cause. Increasing tension or brake drag worsens the problem, and an oversized tip causes poor contact.

Question 14Weld Equipment Setup

In a GTAW setup on aluminum using AC, what is the purpose of the balance (waveform) control?

  1. To determine the filler wire diameter
  2. To control the travel speed of the torch
  3. To adjust the proportion of cleaning (electrode positive) versus penetration (electrode negative) half-cycles Correct answer.
  4. To set the shielding gas flow rate

Explanation

On AC, the electrode-positive half-cycle provides cathodic cleaning of the oxide layer while the electrode-negative half-cycle provides penetration and limits tungsten heating. The balance control shifts the proportion between them. It does not set gas flow, travel speed, or filler diameter.

Question 15Weld Equipment Setup

A welder is setting up a resistance spot welding machine. Which setup parameter most directly controls the amount of heat generated at the weld nugget?

  1. The electrode cooling water temperature alone
  2. The welding current and its duration through the workpiece resistance Correct answer.
  3. The clamping force applied by the fixture table
  4. The color of the electrode caps

Explanation

Resistance welding heat follows the relationship of current squared times resistance times time, so current magnitude and weld duration are the dominant controllable heat inputs. Cooling water and fixture clamping are secondary, and cap color is irrelevant. Electrode force affects contact resistance and quality but does not by itself define heat input.

Question 16Weld Equipment Setup

An engineer is configuring a synergic GMAW power source. What does the synergic control do when the operator changes wire feed speed?

  1. It automatically adjusts voltage and other parameters along a programmed curve for the selected wire and gas Correct answer.
  2. It disables the gas solenoid to save shielding gas
  3. It switches the process to SMAW automatically
  4. It locks the voltage so it cannot be changed at all

Explanation

Synergic (one-knob) control ties voltage and related parameters to wire feed speed along a characteristic curve programmed for the chosen wire type, diameter, and gas, simplifying setup. It does not lock voltage entirely, change processes, or disable gas flow. Operators can still trim the arc.

Question 17Welding Processes

In the AWS A3.0 welding vocabulary, which term describes the entire group of joining processes that produces coalescence by heating materials to a suitable temperature with or without the application of pressure, with or without filler metal?

  1. Adhesive bonding
  2. Soldering
  3. Brazing
  4. Welding Correct answer.

Explanation

AWS A3.0 defines welding broadly as a materials-joining process that produces coalescence by heating to suitable temperature, with or without pressure, and with or without filler metal. Brazing and soldering are defined separately by filler-metal melting temperature below the base metal. Adhesive bonding involves no metallic coalescence at all.

Question 18Welding Processes

Which arc welding process feeds a continuous solid wire electrode that is consumed in the arc and is shielded entirely by an externally supplied gas with no flux core?

  1. FCAW
  2. SMAW
  3. SAW
  4. GMAW Correct answer.

Explanation

Gas metal arc welding uses a continuous solid consumable wire and depends on an external shielding gas supplied through the torch. FCAW uses a tubular wire containing flux, and SAW uses granular flux instead of gas. SMAW uses a covered stick electrode, not a continuous wire.

Question 19Welding Processes

A welder is using the short-circuiting transfer mode on thin sheet steel. Which characteristic best distinguishes this mode from spray transfer?

  1. The electrode never touches the weld pool and metal transfers as a fine axial spray.
  2. Metal transfers only during repeated electrical short circuits at relatively low current. Correct answer.
  3. The arc is buried beneath a layer of granular flux.
  4. Transfer occurs only when the electrode is negative.

Explanation

Short-circuiting transfer cycles between arc and short circuit many times per second, depositing metal at low heat input suitable for thin sections. Spray transfer requires higher current and transfers fine droplets axially without contact. The other options describe SAW or incorrect polarity claims.

Question 20Welding Processes

Which welding process characteristically uses granular flux piled over the joint so the arc is completely hidden from the operator?

  1. Gas tungsten arc welding
  2. Submerged arc welding Correct answer.
  3. Oxyfuel gas welding
  4. Shielded metal arc welding

Explanation

Submerged arc welding blankets the joint in granular flux that melts to form a slag shield and hides the arc. GTAW uses a tungsten electrode with inert gas and a visible arc. SMAW uses a covered electrode but the arc remains visible, and oxyfuel welding uses a gas flame.

Question 21Welding Processes

Which type of power source output is required for gas tungsten arc welding of aluminum to break up the surface oxide and provide cleaning action?

  1. Alternating current Correct answer.
  2. Direct current electrode negative only
  3. Constant current with pulsed direct current electrode negative only
  4. Direct current electrode positive only

Explanation

Alternating current alternates between electrode-positive and electrode-negative half cycles. The electrode-positive portion provides cathodic cleaning that breaks up aluminum oxide, while the electrode-negative portion limits tungsten heating. Straight DCEN gives penetration but little cleaning, and DCEP overheats the tungsten.

Question 22Welding Processes

In shielded metal arc welding, what is the primary function of the electrode covering?

  1. It generates shielding gas and slag to protect the weld from contamination. Correct answer.
  2. It acts as a heat sink to cool the joint.
  3. It provides the structural strength of the completed weld.
  4. It conducts the welding current to the base metal.

Explanation

The flux covering decomposes to produce shielding gas and forms slag that protects the solidifying weld from atmospheric contamination. It also stabilizes the arc and can add alloying elements. Current is carried by the metal core, and weld strength comes from the deposited metal.

Question 23Welding Processes

Which AWS filler metal classification prefix identifies a covered electrode intended for shielded metal arc welding of carbon steel?

  1. R
  2. ER
  3. E Correct answer.
  4. F

Explanation

In AWS filler metal designations, the prefix E on a covered electrode such as E7018 indicates an arc welding electrode. The ER prefix denotes a solid wire or rod used in processes such as GMAW or GTAW. F and R prefixes do not designate covered electrodes.

Question 24Welding Processes

Which welding position is designated by the letter F in AWS position nomenclature?

  1. Horizontal
  2. Overhead
  3. Flat Correct answer.
  4. Vertical

Explanation

AWS position letters are 1 for flat, 2 for horizontal, 3 for vertical, and 4 for overhead, with the letter F denoting a fillet weld. A designation such as 1F therefore means a flat-position fillet weld. The other letters do not correspond to those positions.

Question 25Welding Processes

A fabricator must join 25 mm thick low-carbon steel plate in a single pass with high deposition efficiency and no edge preparation on the root. Which process is best suited for this application?

  1. Gas tungsten arc welding
  2. Oxyfuel gas welding
  3. Submerged arc welding Correct answer.
  4. Shielded metal arc welding

Explanation

Submerged arc welding delivers very high deposition rates and deep penetration, making it well suited to thick plate in a single pass. GTAW and SMAW are limited in deposition rate for such thickness, and oxyfuel welding is slow and suited to thin material. SAW also tolerates minimal joint preparation because of its deep penetration.

Question 26Welding Processes

An operator notices the GMAW arc wandering and the weld bead becoming irregular with poor penetration on aluminum. Which action most directly addresses the likely cause?

  1. Reduce the wire feed speed to lower current.
  2. Switch from electrode-positive to electrode-negative polarity.
  3. Increase the shielding gas flow to 40 L/min regardless of conditions.
  4. Replace the contact tip and check the wire feed for erratic delivery. Correct answer.

Explanation

Erratic arc and irregular bead in GMAW frequently result from a worn contact tip or inconsistent wire feed, which destabilizes current transfer. Replacing the tip and checking the feed restores steady deposition. Excess gas flow can cause turbulence, and polarity or current changes do not fix mechanical feed problems.

Question 27Welding Processes

A welder is instructed to use a 7018 electrode but the electrodes have been left exposed to humid air for several days. What is the correct action before welding?

  1. Switch to DCEN and weld without drying.
  2. Bake them in a holding oven at the manufacturer's recommended temperature before use. Correct answer.
  3. Dip them in water to soften the flux.
  4. Use them as-is because the flux is waterproof.

Explanation

Low-hydrogen electrodes such as E7018 absorb moisture, which can cause hydrogen-induced cracking. They must be stored and, if exposed, baked at the manufacturer's recommended temperature to restore low-hydrogen condition. Using them wet or altering polarity does not remove the moisture hazard.

Question 28Welding Processes

In gas tungsten arc welding, which condition most likely causes tungsten electrode contamination and arc instability?

  1. Using too small a tungsten diameter for the current
  2. Using a properly sharpened electrode
  3. Using pure argon shielding gas
  4. Touching the tungsten to the weld pool Correct answer.

Explanation

Dipping the tungsten into the molten pool transfers metal to the electrode tip, disrupting electron emission and destabilizing the arc. Oversized current for the diameter can also melt the tip, but the direct contact described is the classic contamination cause. Proper shielding gas and sharpening support stable operation.

Question 29Welding Processes

Which type of joint is formed when two members are placed at approximately right angles and welded along the intersection of their surfaces?

  1. Butt joint
  2. T-joint Correct answer.
  3. Lap joint
  4. Corner joint

Explanation

A T-joint occurs when one member is set at right angles to the surface of another and welded at the intersection, often with a fillet weld. Butt joints align members end to end, lap joints overlap surfaces, and corner joints meet at an edge.

Question 30Welding Processes

A weld symbol shows a fillet weld with the triangle on the reference line below the line and a dimension of 6 mm. What does the placement below the line indicate?

  1. The weld is made on the other side of the joint.
  2. The weld is made on both sides.
  3. The weld is a full-penetration groove weld.
  4. The weld is made on the arrow side of the joint. Correct answer.

Explanation

In AWS welding symbols, a fillet triangle below the reference line indicates the arrow side of the joint. A symbol above the line indicates the other side. Symbols on both sides indicate welds on both sides, and a groove weld symbol is not a triangle.

Question 31Welding Processes

Which shielding gas mixture is commonly used for GMAW spray transfer on carbon steel to improve arc stability and penetration?

  1. Argon with 1 to 5 percent oxygen Correct answer.
  2. Argon with 25 percent nitrogen
  3. Pure helium
  4. Pure carbon dioxide

Explanation

Argon-rich mixtures with small oxygen or CO2 additions stabilize the arc and support spray transfer on carbon steel. Pure helium is used for special applications, pure CO2 supports only short-circuiting or globular transfer, and nitrogen is not a standard shielding addition for steel.

Question 32Welding Processes

A welder observes porosity concentrated at the start of a GMAW bead. Which cause is most likely?

  1. Too large a contact tip
  2. Excessive travel speed at the end of the weld
  3. Insufficient preflow or a gas surge at the start of the weld Correct answer.
  4. Excessive wire feed speed

Explanation

Porosity at the start often results from inadequate shielding gas coverage while the gas line purges or from a surge of flow. Setting proper preflow and using a gas flow regulator corrects this. Travel speed at the end and contact tip size do not explain start-of-bead porosity.

Question 33Welding Processes

Which destructive test is specifically designed to evaluate the soundness of a weld by bending a specimen so the weld root is in tension?

  1. Nick break test
  2. Face bend test
  3. Root bend test Correct answer.
  4. Macroetch test

Explanation

A root bend test places the weld root in tension to reveal lack of penetration or root defects. A face bend test puts the weld face in tension, a nick break test fractures a notched section to expose internal defects, and a macroetch reveals the cross-sectional structure.

Question 34Welding Processes

A welding procedure specifies a preheat of 150 °C for thick high-carbon steel. What is the primary purpose of this preheat?

  1. To improve the appearance of the weld bead
  2. To slow the cooling rate and reduce the risk of hydrogen-assisted cracking Correct answer.
  3. To remove the need for postweld heat treatment
  4. To increase the deposition rate of the electrode

Explanation

Preheating slows cooling after welding, which reduces the formation of hard martensite and allows hydrogen to diffuse out, lowering cracking risk in crack-sensitive steels. It does not raise deposition rate or substitute for postweld heat treatment. Bead appearance is not the purpose.

Question 35Welding Processes

Which welding process is most appropriate for joining thin stainless steel sheet where minimal distortion and high-quality appearance are required?

  1. Electroslag welding
  2. Oxyfuel gas welding
  3. Gas tungsten arc welding Correct answer.
  4. Submerged arc welding

Explanation

GTAW offers precise heat control and clean, high-quality welds with low distortion, making it well suited to thin stainless sheet. Oxyfuel welding causes wide heat input and distortion, while SAW and electroslag welding are for thick sections.

Question 36Welding Processes

In FCAW, what is the difference between self-shielded and gas-shielded wire?

  1. Gas-shielded wire contains no flux.
  2. Self-shielded wire relies on flux ingredients to generate shielding, while gas-shielded wire needs an external gas supply. Correct answer.
  3. Self-shielded wire requires an external gas cylinder, while gas-shielded wire does not.
  4. Self-shielded wire can only be used with AC current.

Explanation

Self-shielded flux-cored wire generates its own shielding gas and slag from the flux core, allowing use in windy field conditions without a gas cylinder. Gas-shielded wire requires an external shielding gas supply. Both are tubular flux-containing wires, and current type is not the distinguishing factor.

Question 37Welding Processes

A weld exhibits undercut along the toes of a fillet weld. Which combination of factors most likely contributes to this defect?

  1. Excessive shielding gas flow
  2. Excessive current and improper travel angle Correct answer.
  3. Insufficient current and too slow travel
  4. Using a smaller electrode than specified

Explanation

Undercut results when the arc melts the base metal at the weld toe faster than filler metal fills it, commonly from excessive current, poor travel angle, or excessive travel speed. Insufficient current tends to cause lack of fusion rather than undercut, and gas flow does not directly cause undercut.

Question 38Welding Processes

A procedure qualification test uses a groove weld on 10 mm plate to qualify a procedure for production plate from 5 mm to 20 mm. Under AWS qualification rules, which range is generally supported by that test coupon thickness?

  1. Only 10 mm exactly
  2. From 5 mm to 10 mm only
  3. From 1.5 mm to 20 mm Correct answer.
  4. From 10 mm to 20 mm only

Explanation

AWS procedure qualification generally allows a qualified thickness range based on the test coupon, with a minimum around 1.5 mm and a maximum of twice the coupon thickness for the upper bound. A 10 mm coupon therefore supports roughly 1.5 mm to 20 mm. The other ranges either exclude thinner material or fail to use the permitted upper limit.

Question 39Welding Processes

During GTAW of aluminum, an operator switches from AC to DCEN to increase penetration but finds the weld now shows heavy oxide inclusions. What is the best explanation?

  1. DCEN reverses the shielding gas composition.
  2. DCEN concentrates heat on the tungsten and cleans the oxide.
  3. DCEN increases shielding gas flow and causes oxidation.
  4. DCEN removes the electrode-positive cleaning half cycle, so surface oxide is not broken up. Correct answer.

Explanation

Cathodic cleaning of aluminum oxide occurs during the electrode-positive portion of an AC cycle. Switching to DCEN eliminates that half cycle, so oxide is not removed and can become entrapped, even though penetration increases. DCEN does not clean oxide, and polarity does not change gas flow or composition.

Question 40Welding Processes

A fabricator must weld a pressure vessel in the 6G position with full joint penetration and radiographic acceptance. Which combination of process and technique is most appropriate?

  1. GTAW root with SMAW fill and cap using qualified procedures and welders Correct answer.
  2. Short-circuiting GMAW on 20 mm plate in one pass
  3. SAW in the vertical position
  4. Oxyfuel welding with a single pass

Explanation

Critical pressure vessel joints commonly use a GTAW root for clean full penetration followed by SMAW fill and cap, all executed under qualified procedures and welder performance qualification. Oxyfuel welding cannot achieve the required penetration, short-circuiting GMAW is unsuitable for thick plate in one pass, and SAW is not a vertical-position process.

Question 41Welding Processes

A weld made with E7018 exhibits a small amount of porosity distributed throughout the bead. Which factor is least likely to explain this result?

  1. Damp electrode covering
  2. High sulfur base metal
  3. Properly cleaned joint surfaces Correct answer.
  4. Excessive arc length

Explanation

Clean joint surfaces remove the contaminants that cause porosity, so proper cleaning is the least likely explanation for porosity. Damp covering, excessive arc length, and high sulfur in the base metal can all introduce gas or disrupt the weld pool. Porosity requires a source of gas or contamination, which clean surfaces do not provide.

Question 42Welding Processes

In AWS filler metal classification, what does the 'E' prefix in a designation such as E6010 or E7018 indicate?

  1. The electrode is a flux-cored wire for submerged arc welding.
  2. The electrode is a bare solid wire for gas metal arc welding.
  3. The electrode is intended for electroslag welding.
  4. The electrode is a covered electrode for shielded metal arc welding. Correct answer.

Explanation

The 'E' prefix in AWS electrode classifications stands for 'electrode' and specifically denotes a covered electrode used in shielded metal arc welding (SMAW). This prefix is part of the standard AWS A5 series for mild steel covered electrodes, where the following digits indicate tensile strength, position, coating, and current type. Other processes use different prefixes, such as 'ER' for bare rods/wires or 'F' for flux-cored wires.

Question 43Welding Processes

When welding low-carbon steel with the gas metal arc welding (GMAW) process in the spray transfer mode, which shielding gas composition is most typical to achieve a stable, high-current arc with good penetration?

  1. 100% carbon dioxide (CO2)
  2. 98% argon + 2% oxygen Correct answer.
  3. 75% argon + 25% CO2
  4. 90% helium + 7.5% argon + 2.5% CO2

Explanation

Spray transfer in GMAW requires a shielding gas with high argon content to provide the necessary ionization potential and stable axial spray. A mixture of 98% argon and 2% oxygen is commonly used for low-carbon steel because the oxygen improves arc stability and weld bead wetting without excessive oxidation. Higher CO2 levels promote short-circuiting or globular transfer and are not suitable for true spray transfer.

Question 44Welding Processes

A welder is using the gas tungsten arc welding (GTAW) process on aluminum and notices that the tungsten electrode becomes contaminated and the arc becomes unstable. Which condition is the most likely cause?

  1. The welding current is set to AC (alternating current) with high frequency.
  2. The tungsten electrode is extended too far beyond the gas nozzle. Correct answer.
  3. The welding current is set to DCEN (direct current electrode negative).
  4. The shielding gas flow rate is set too high.

Explanation

In GTAW, the tungsten electrode must be shielded by the inert gas flowing from the nozzle. If the electrode is extended too far beyond the nozzle, the gas coverage is lost, allowing atmospheric contamination that oxidizes the tungsten and destabilizes the arc. Proper electrode extension is typically 3 to 6 mm (1/8 to 1/4 in) beyond the nozzle for most applications.

Question 45Welding Processes

A fabricator must weld a thick section of low-carbon steel using the flux-cored arc welding (FCAW) process. The procedure specifies a semi-automatic operation with a shielding gas. Which statement correctly describes a characteristic of gas-shielded FCAW compared to self-shielded FCAW?

  1. Self-shielded FCAW is preferred for outdoor use because it does not require a shielding gas, while gas-shielded FCAW is limited to indoor applications.
  2. Gas-shielded FCAW requires a separate shielding gas supply and typically produces lower deposition rates than self-shielded FCAW.
  3. Gas-shielded FCAW generally provides better weld metal toughness and is more commonly used for welding thicker sections than self-shielded FCAW. Correct answer.
  4. Gas-shielded FCAW uses a flux-cored wire that contains gas-forming ingredients and does not require an external gas supply.

Explanation

Gas-shielded FCAW uses an external shielding gas (often CO2 or argon-CO2 mixtures) in addition to the flux core, which improves arc stability and weld metal quality. It typically yields better toughness and is often used for thicker sections and higher-quality welds compared to self-shielded FCAW, which relies solely on the flux for shielding and is more susceptible to porosity in thick sections. Self-shielded FCAW is indeed suitable for outdoor use, but gas-shielded FCAW is not strictly limited to indoor applications; however, the key differentiator is the better toughness and thicker-section capability of gas-shielded FCAW.

Question 46Welding Processes

A welding procedure specification (WPS) for shielded metal arc welding (SMAW) of a pressure vessel requires a minimum preheat of 150 °C for a 25 mm thick low-carbon steel joint. The welder measures the base metal temperature and finds it is 100 °C. According to AWS D1.1 structural welding code, what is the most appropriate action?

  1. Reduce the welding current to decrease heat input and prevent cracking.
  2. Use a lower hydrogen electrode to compensate for the lower preheat.
  3. Proceed with welding because the ambient temperature is above 0 °C.
  4. Apply additional preheat to raise the base metal temperature to at least 150 °C before welding. Correct answer.

Explanation

AWS D1.1 and most welding codes require that the specified preheat temperature be maintained before and during welding. If the base metal temperature is below the WPS minimum, the welder must apply additional preheat to meet the requirement. Welding at a lower temperature could lead to hydrogen-assisted cracking and violates the qualified procedure.

Question 47Weld Examination

Under AWS D1.1, what is the primary purpose of performing visual examination on a completed weld before any other NDT method is applied?

  1. To replace radiographic testing when the weld is fully penetrated
  2. To determine the exact chemical composition of the filler metal used
  3. To measure the ultimate tensile strength of the deposited weld metal
  4. To verify weld appearance, dimensions, and surface discontinuity acceptance before subsurface testing Correct answer.

Explanation

Visual examination is required by AWS D1.1 to be completed and documented before other NDT methods are applied, and it screens for surface discontinuities, dimensional conformance, and appearance acceptance criteria. It cannot measure tensile strength, chemistry, or substitute for volumetric inspection of internal soundness.

Question 48Weld Examination

A CWI is asked to select the correct nondestructive method for detecting lack of fusion located entirely beneath the weld surface in a butt joint. Which method is best suited?

  1. Visual examination
  2. Liquid penetrant testing
  3. Ultrasonic testing Correct answer.
  4. Magnetic particle testing

Explanation

Ultrasonic testing transmits sound through the weld volume and detects planar internal discontinuities such as lack of fusion, lack of penetration, and internal cracks. Surface methods cannot reliably detect defects that do not reach the surface.

Question 49Weld Examination

When magnetic particle testing is performed on a weld using the yoke technique, which condition is essential for the test to be effective?

  1. The surface must be nonmagnetic to allow flux flow
  2. The magnetic field must be oriented approximately perpendicular to the discontinuity Correct answer.
  3. The part must be heated above the Curie temperature
  4. The weld must be polished to a mirror finish

Explanation

Magnetic particle testing relies on flux leakage, which is strongest when the magnetic field lines are oriented roughly perpendicular to the long axis of the discontinuity. A field parallel to the defect produces little leakage and the indication may be missed.

Question 50Weld Examination

A radiograph of a groove weld shows a dark, elongated indication aligned with the weld axis near the root. Which discontinuity is most consistent with this appearance?

  1. Porosity
  2. Slag inclusion
  3. Lack of penetration Correct answer.
  4. Undercut

Explanation

Lack of penetration appears on a radiograph as a dark, straight, elongated indication running along the weld centerline at the root, because the unfused root region offers less radiation absorption. Its axial alignment and root location distinguish it from rounded porosity or scattered slag.