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BTEB Welding Exam practice questions

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Question 1Welding Technology (BTEB vocational/short-course curriculum)

In manual metal arc welding, what is the primary function of the electrode coating?

  1. It cools the weld bead rapidly to increase hardness
  2. It conducts the welding current from the holder into the workpiece
  3. It provides the mechanical strength of the finished joint
  4. It shields the molten weld pool from atmospheric contamination and stabilises the arc Correct answer.

Explanation

The coating burns to produce shielding gases and slag that protect the molten metal from oxygen and nitrogen in the air, and it also contains arc-stabilising and alloying ingredients. The core wire, not the coating, carries the current and supplies filler metal.

Question 2Welding Technology (BTEB vocational/short-course curriculum)

Which welding process uses a continuous bare wire fed through a torch with shielding gas supplied separately?

  1. Gas metal arc welding Correct answer.
  2. Manual metal arc welding
  3. Oxy-acetylene welding
  4. Resistance spot welding

Explanation

Gas metal arc welding feeds a continuous consumable wire electrode and relies on an externally supplied shielding gas such as CO2 or an argon mixture. The other listed processes use a coated stick, a fuel-gas flame, or pressure and current without filler wire.

Question 3Welding Technology (BTEB vocational/short-course curriculum)

What is the standard included angle of a single-V butt joint preparation in typical plate welding practice?

  1. 120 degrees
  2. 60 degrees Correct answer.
  3. 10 to 15 degrees
  4. 30 degrees

Explanation

A single-V groove is normally prepared with an included angle of about 60 degrees, which gives the electrode or torch enough access to the root while limiting filler metal consumption. Angles far below this cause lack of fusion, and very wide angles waste metal and increase distortion.

Question 4Welding Technology (BTEB vocational/short-course curriculum)

A welder must join two thin sheets of low-carbon steel with minimum distortion. Which edge preparation is most suitable?

  1. Single-U groove
  2. Square edge with a small root gap Correct answer.
  3. Single-J groove
  4. Double-V groove

Explanation

Thin sheet does not need bevelling because full penetration can be achieved with a square edge and a small gap, which keeps heat input and distortion low. U, V and J grooves are used on thicker material where the root would otherwise be inaccessible.

Question 5Welding Technology (BTEB vocational/short-course curriculum)

Why is the electrode held at a slight backhand or drag angle during vertical-up welding?

  1. To keep the molten pool from running ahead of the arc Correct answer.
  2. To increase deposition rate to the maximum
  3. To avoid the need for a root gap
  4. To reduce the shielding gas requirement

Explanation

In vertical-up welding gravity pulls the pool downward, so a slight upward drag angle and controlled weave keep the molten metal behind the arc and prevent it from overrunning the root. Deposition rate and gas demand are not the reason for the angle.

Question 6Welding Technology (BTEB vocational/short-course curriculum)

Which defect is most likely when the welding current is set too low for the electrode size being used?

  1. Lack of fusion at the side walls Correct answer.
  2. Undercut at the toe
  3. Excessive spatter
  4. Burn-through at the root

Explanation

Low current produces a cold, sluggish arc that does not melt the side walls of the joint, so the filler metal sits on top without fusing. Excessive spatter, undercut and burn-through are all associated with current that is too high.

Question 7Welding Technology (BTEB vocational/short-course curriculum)

What is the main purpose of preheating a thick low-alloy steel component before welding?

  1. To slow the cooling rate and reduce the risk of hydrogen cracking Correct answer.
  2. To increase the tensile strength of the weld metal
  3. To reduce the amount of filler metal required
  4. To remove the need for post-weld heat treatment

Explanation

Preheating raises the base metal temperature so heat drains away more slowly after welding, which allows hydrogen to escape and produces a softer, less crack-sensitive microstructure. It does not increase weld strength or reduce filler consumption.

Question 8Welding Technology (BTEB vocational/short-course curriculum)

Which gas is commonly used as the fuel gas with oxygen in a gas welding torch?

  1. Nitrogen
  2. Argon
  3. Carbon dioxide
  4. Acetylene Correct answer.

Explanation

Acetylene burned with oxygen produces the hottest common fuel-gas flame, reaching roughly 3200 degrees Celsius, which makes it the standard choice for oxy-acetylene welding. Argon and carbon dioxide are shielding gases, and nitrogen is not a practical fuel gas.

Question 9Welding Technology (BTEB vocational/short-course curriculum)

A neutral oxy-acetylene flame is adjusted so that the two gas streams are supplied in the ratio that produces which visible feature?

  1. No visible inner cone at all
  2. A short green outer envelope
  3. A long feathery white inner cone
  4. A sharply defined inner cone with no feather Correct answer.

Explanation

A neutral flame shows a well-defined, rounded inner cone with no white feather beyond it, indicating roughly equal volumes of oxygen and acetylene. An excess of either gas produces a carburising feather or a sharp oxidising hiss.

Question 10Welding Technology (BTEB vocational/short-course curriculum)

What does the number 6013 in an electrode classification such as E6013 indicate about minimum tensile strength?

  1. 60,000 psi Correct answer.
  2. 6,013 psi
  3. 6,000 psi
  4. 600 psi

Explanation

In the E6013 designation the first two digits give the minimum tensile strength of the deposited weld metal in thousands of pounds per square inch, so 60 means 60,000 psi. The third digit indicates welding position and the fourth indicates coating type and current.

Question 11Welding Technology (BTEB vocational/short-course curriculum)

In the AWS electrode designation E7018, what does the digit 8 primarily indicate?

  1. The coating is high in cellulose
  2. The electrode is a low-hydrogen type with iron powder in the coating Correct answer.
  3. The minimum yield strength is 8,000 psi
  4. The electrode may be used only in the flat position

Explanation

The final digit of the E7018 designation identifies a low-hydrogen, iron-powder electrode with a basic lime coating, used for higher-quality work on steels sensitive to hydrogen cracking. Position capability is given by the third digit, and strength by the first two.

Question 12Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the most important safety precaution before striking an arc in a confined space?

  1. Ensuring adequate ventilation and a means of rescue Correct answer.
  2. Wearing a leather apron
  3. Selecting a larger electrode
  4. Increasing the welding current

Explanation

Confined spaces accumulate shielding gases, fumes and oxygen deficiency, so forced ventilation and a standby person with rescue equipment are essential before entry. Personal protective clothing alone does not address the atmospheric hazard.

Question 13Welding Technology (BTEB vocational/short-course curriculum)

What type of radiation is the main hazard to the eyes and skin of welders, and which filter lens protects against it?

  1. Microwave radiation, blocked by a plastic visor
  2. Radio waves, blocked by a metal shield
  3. Alpha radiation, blocked by a cotton glove
  4. Infrared and ultraviolet radiation, blocked by a dark filter lens Correct answer.

Explanation

The arc emits intense ultraviolet and infrared radiation that can cause arc eye and skin burns, and a properly shaded filter lens of the correct shade number is required. Ordinary visors or gloves do not provide the necessary protection.

Question 14Welding Technology (BTEB vocational/short-course curriculum)

Which type of current is generally preferred for welding thin sheet with the gas tungsten arc process?

  1. Pulsed direct current electrode positive
  2. Alternating current Correct answer.
  3. Direct current electrode negative
  4. Direct current electrode positive

Explanation

Alternating current combines good penetration on the electrode-negative half cycle with the cleaning action of the electrode-positive half cycle, which helps break up the oxide film on aluminium and magnesium sheet. Straight polarity gives deep penetration but no cleaning action.

Question 15Welding Technology (BTEB vocational/short-course curriculum)

A welder is joining aluminium with gas tungsten arc welding and notices a dull, grey, poorly fused bead. Which change is most likely to correct the problem?

  1. Reduce the shielding gas flow to zero
  2. Increase the tungsten electrode diameter and use direct current electrode negative
  3. Use a shorter arc and a smaller nozzle
  4. Switch to alternating current to obtain oxide cleaning Correct answer.

Explanation

Aluminium forms a refractory oxide that must be broken up during welding, and alternating current provides the electrode-positive half cycle that does this cleaning. Direct current electrode negative alone leaves the oxide intact and produces poor fusion.

Question 16Welding Technology (BTEB vocational/short-course curriculum)

What is the purpose of a backing bar or backing strip in a single-V butt weld?

  1. To replace the need for a root gap
  2. To increase the welding current
  3. To cool the weld rapidly
  4. To support the molten root and prevent burn-through Correct answer.

Explanation

A backing bar supports the molten pool at the root so that full penetration can be achieved without the metal falling through, and it also helps control root bead shape. It does not change the current setting or eliminate the need for proper fit-up.

Question 17Welding Technology (BTEB vocational/short-course curriculum)

Which type of weld joint is formed when two members are laid edge to edge in the same plane and welded along the seam?

  1. Corner joint
  2. Tee joint
  3. Butt joint Correct answer.
  4. Lap joint

Explanation

A butt joint places the two edges in the same plane and the weld is made along the abutting edges, often with a groove preparation. Lap, tee and corner joints involve overlapping, perpendicular or angled members.

Question 18Welding Technology (BTEB vocational/short-course curriculum)

What is the effect of increasing the welding current while keeping all other variables constant in manual metal arc welding?

  1. The slag becomes easier to remove but the bead is unchanged
  2. Penetration increases and the bead becomes wider Correct answer.
  3. The arc becomes more stable but penetration is unchanged
  4. Penetration decreases and the bead becomes narrower

Explanation

Higher current increases heat input and arc force, so the arc digs deeper into the base metal and deposits more metal, producing deeper penetration and a wider, taller bead. Too much current risks undercut and burn-through.

Question 19Welding Technology (BTEB vocational/short-course curriculum)

Which welding position is designated as 3G in the AWS classification system?

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

Explanation

In the AWS position numbering, 1G is flat, 2G is horizontal, 3G is vertical and 4G is overhead for groove welds. The letter G indicates a groove weld, and the number gives the axis orientation.

Question 20Welding Technology (BTEB vocational/short-course curriculum)

A welder notices a long, straight crack running along the centre of a weld bead shortly after welding. Which cause is most likely?

  1. A tungsten inclusion in the weld
  2. Excessive travel speed with a short arc
  3. Insufficient shielding gas flow
  4. High sulphur and phosphorus content combined with deep penetration and high restraint Correct answer.

Explanation

Centre-line solidification cracking occurs when low-melting impurities such as sulphur and phosphorus segregate at the centre of the bead, and deep, narrow penetration with high restraint makes it worse. The remedy is to control sulphur and phosphorus and adjust the bead shape.

Question 21Welding Technology (BTEB vocational/short-course curriculum)

What is the primary purpose of post-weld heat treatment of a welded pressure vessel?

  1. To relieve residual stresses and temper the heat-affected zone Correct answer.
  2. To increase the carbon content of the weld
  3. To remove the need for non-destructive testing
  4. To increase the hardness of the heat-affected zone

Explanation

Post-weld heat treatment raises the component to a controlled temperature and holds it so that residual stresses relax and the hardened heat-affected zone tempers, improving toughness and dimensional stability. It does not add carbon or replace inspection.

Question 22Welding Technology (BTEB vocational/short-course curriculum)

Which non-destructive test method is most suitable for detecting internal volumetric defects such as porosity and slag inclusions in a thick butt weld?

  1. Visual inspection
  2. Magnetic particle testing
  3. Dye penetrant testing
  4. Radiographic testing Correct answer.

Explanation

Radiography passes penetrating radiation through the weld and records density differences on film or a detector, so internal voids and inclusions show as darker or lighter areas. Penetrant and magnetic particle methods detect only surface or near-surface discontinuities.

Question 23Welding Technology (BTEB vocational/short-course curriculum)

What does the term duty cycle mean for a welding power source rated at 60 percent at 200 amperes?

  1. The machine can weld for 6 minutes out of every 10 at 200 amperes without overheating Correct answer.
  2. The machine delivers 60 percent of 200 amperes as its maximum output
  3. The machine requires 60 percent of the input voltage as a reserve
  4. The machine can weld continuously at 200 amperes without stopping

Explanation

Duty cycle is the proportion of a ten-minute period during which the power source can operate at its rated current without exceeding its temperature limit. A 60 percent rating at 200 amperes therefore allows six minutes of welding followed by four minutes of cooling.

Question 24Welding Technology (BTEB vocational/short-course curriculum)

Which type of power source characteristic gives a nearly constant current output and is preferred for manual metal arc welding?

  1. Constant-voltage characteristic
  2. Drooping characteristic Correct answer.
  3. Flat characteristic
  4. Rising characteristic

Explanation

A drooping characteristic gives a steep voltage-current curve so that arc length changes cause only small current changes, which stabilises the arc when the welder's hand moves. Flat or constant-voltage characteristics are used for continuous wire processes.

Question 25Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the correct way to extinguish an oxy-acetylene torch when finishing a weld?

  1. Leave both valves open and shut off the regulators
  2. Close the acetylene valve first, then the oxygen valve Correct answer.
  3. Close the oxygen valve first, then the acetylene valve
  4. Close both valves at exactly the same moment

Explanation

The acetylene valve is closed first and then the oxygen valve, which prevents a carbon-rich soot deposit in the tip and avoids a pop or flashback. Closing oxygen first can leave an acetylene-rich mixture that burns back into the torch.

Question 26Welding Technology (BTEB vocational/short-course curriculum)

Which electrode coating type is designed to give a low-hydrogen weld deposit and must be stored in a heated holding oven after opening?

  1. Oxidising
  2. Basic (low-hydrogen) Correct answer.
  3. Rutile
  4. Cellulosic

Explanation

Basic coatings are formulated with calcium carbonate and calcium fluoride so the arc atmosphere is low in hydrogen, which greatly reduces the risk of hydrogen-assisted cold cracking in restrained joints. Because the coating is hygroscopic, moisture picked up from the air destroys this benefit, so electrodes are baked and then kept in a heated holding oven until used.

Question 27Welding Technology (BTEB vocational/short-course curriculum)

In a single-V butt weld, what is the primary reason for including a root gap between the two plates?

  1. To reduce the amount of filler metal required
  2. To allow complete through-thickness fusion at the root Correct answer.
  3. To make the joint easier to tack weld
  4. To prevent angular distortion of the assembly

Explanation

A root gap provides space so the arc and molten pool can reach the full thickness at the bottom of the V, allowing the root pass to fuse both plate faces and penetrate fully. Without a gap the root tends to be unfused or to contain incomplete penetration.

Question 28Welding Technology (BTEB vocational/short-course curriculum)

Which shielding gas mixture is most commonly used for gas metal arc welding of carbon steel in the short-circuiting transfer mode to improve arc stability?

  1. Argon with 2 percent oxygen
  2. Pure oxygen
  3. Pure helium
  4. Argon with 15 to 25 percent carbon dioxide Correct answer.

Explanation

Adding carbon dioxide to argon raises the arc energy and stabilises short-circuiting transfer on carbon steel while keeping the cost reasonable. The CO2 also helps control the bead profile and reduces spatter compared with pure CO2.

Question 29Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the correct order of operations for lighting and adjusting an oxy-acetylene welding torch?

  1. Open the acetylene valve, open the oxygen valve, then light the mixture
  2. Open the acetylene valve, light the gas, then open the oxygen valve and adjust the flame Correct answer.
  3. Open the oxygen valve, light the gas, then open the acetylene valve
  4. Open both valves fully, then light the mixture

Explanation

The acetylene is opened slightly and lit first so a smoky, soot-free carburising flame is obtained, then oxygen is gradually added until the desired neutral flame is reached. Lighting a pre-mixed oxy-acetylene stream can cause a pop or flashback because the mixture is already explosive.

Question 30Welding Technology (BTEB vocational/short-course curriculum)

A welder is using the shielded metal arc process and the arc keeps extinguishing and sticking to the workpiece. Which adjustment is most appropriate?

  1. Increase the arc length and reduce current
  2. Reduce the current and increase travel speed
  3. Change to a larger diameter electrode at the same current
  4. Increase the current within the electrode manufacturer's range Correct answer.

Explanation

Stubbing and arc extinction in manual metal arc welding are typical signs of insufficient current for the electrode size, so the pool does not stay molten and the electrode freezes to the plate. Raising the current within the recommended range restores a stable arc and proper fusion.

Question 31Welding Technology (BTEB vocational/short-course curriculum)

Which type of weld is produced when weld metal is deposited into a hole or slot cut through one member of a lap joint?

  1. Plug weld Correct answer.
  2. Seam weld
  3. Groove weld
  4. Fillet weld

Explanation

A plug weld is made by filling a circular hole in the upper plate so the weld metal fuses to the lower plate, joining the two members. It is a common substitute for spot welds in lap joints.

Question 32Welding Technology (BTEB vocational/short-course curriculum)

What is the main function of the flux coating on a covered electrode in manual metal arc welding?

  1. To act as a permanent backing for the root pass
  2. To cool the weld pool rapidly after deposition
  3. To generate shielding gas and form a protective slag over the weld pool Correct answer.
  4. To increase the electrical conductivity of the core wire

Explanation

As the coating burns, it decomposes to release shielding gases and forms a slag that floats on the pool, protecting the solidifying metal from atmospheric oxygen and nitrogen. The coating also stabilises the arc and can add alloying elements.

Question 33Welding Technology (BTEB vocational/short-course curriculum)

In resistance spot welding of two steel sheets, which combination of parameters mainly controls the size of the weld nugget?

  1. Arc voltage and travel speed
  2. Electrode force and welding current Correct answer.
  3. Shielding gas flow rate
  4. Flux composition and polarity

Explanation

The nugget forms from resistance heating at the interface, so the current determines the heat generated and the electrode force controls the contact resistance and contains the molten metal. Together they set the nugget diameter and penetration.

Question 34Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the correct procedure for storing gas cylinders at a welding station?

  1. Store them inside a closed cupboard next to the welding machine
  2. Keep them upright, secured against falling, and separated by type Correct answer.
  3. Store oxygen and acetylene cylinders close together for convenience
  4. Lay them horizontally so they cannot topple

Explanation

Cylinders must be kept upright and chained or otherwise restrained so they cannot fall and shear the valve. Fuel gas and oxygen cylinders are segregated to prevent a leak from feeding a fire, and they are kept away from heat and ignition sources.

Question 35Welding Technology (BTEB vocational/short-course curriculum)

Which non-destructive method is best suited to detecting surface-breaking cracks in a ferromagnetic steel weld using a magnetic field and fine iron particles?

  1. Dye penetrant testing
  2. Radiographic testing
  3. Magnetic particle testing Correct answer.
  4. Ultrasonic testing

Explanation

Magnetic particle inspection magnetises the part, and a surface or near-surface crack distorts the field so particles collect at the leakage, giving a visible indication. It is fast and sensitive for surface defects in ferromagnetic materials.

Question 36Welding Technology (BTEB vocational/short-course curriculum)

A welder is welding 6 mm aluminium plate with gas tungsten arc welding using direct current electrode negative and finds penetration is poor. What is the most appropriate change?

  1. Switch to alternating current with a balance control Correct answer.
  2. Use a smaller tungsten electrode without changing current
  3. Increase travel speed significantly
  4. Reduce the shielding gas flow to zero

Explanation

Aluminium forms a tenacious oxide that melts at a much higher temperature than the metal, so some electrode-positive half-cycle is needed to break it up. Alternating current with an adjustable balance gives cleaning action on the positive half and penetration on the negative half.

Question 37Welding Technology (BTEB vocational/short-course curriculum)

Which statement correctly describes the difference between forehand and backhand techniques in oxy-acetylene welding?

  1. Forehand requires no filler rod, while backhand always requires a filler rod
  2. Forehand is used only on vertical joints, while backhand is used only on flat joints
  3. Forehand uses a carburising flame, while backhand uses an oxidising flame
  4. Forehand progresses with the torch pointing away from the completed weld, while backhand points the torch toward the completed weld Correct answer.

Explanation

In the forehand technique the torch moves left to right with the tip leading, so the flame points in the direction of travel and preheats the unwelded metal. In the backhand technique the torch points back over the finished bead, giving deeper penetration and a narrower weld on thicker plate.

Question 38Welding Technology (BTEB vocational/short-course curriculum)

Which of the following best explains why a weld may show undercut along the edges of a fillet?

  1. Using a dry electrode
  2. Insufficient current causing lack of fusion
  3. Too much shielding gas flow
  4. Excessive current or too long an arc melting the base metal without filler to replace it Correct answer.

Explanation

Undercut is a groove melted into the base metal at the weld toe that is not filled by filler metal. It is typically caused by too high a current, an excessively long arc, or incorrect electrode angle, all of which melt the parent metal faster than the pool can fill it.

Question 39Welding Technology (BTEB vocational/short-course curriculum)

What is the significance of the American Welding Society electrode position suffix such as the 2 in E7018-2 or the designation 1G, 2G, 3G in welder qualification?

  1. It states the maximum heat input in kilojoules per millimetre
  2. It specifies the minimum preheat temperature in degrees Fahrenheit
  3. It indicates the welding position in which the electrode or procedure is qualified Correct answer.
  4. It gives the diameter of the electrode in millimetres

Explanation

Position designations such as 1G, 2G and 3G describe the test position: flat, horizontal and vertical respectively. Electrode suffixes and procedure qualification records use these codes to show which positions the welder or consumable is approved for.

Question 40Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the main reason for using a weaving motion when depositing a vertical-up weld?

  1. To increase the travel speed beyond the normal range
  2. To reduce the number of passes needed on a thick joint
  3. To control the molten pool so it does not run ahead of the arc and to ensure fusion at both side walls Correct answer.
  4. To avoid the need for any root gap

Explanation

In vertical-up welding gravity pulls the pool downward, so a controlled weave lets each puddle freeze before the arc returns, giving a stacked bead and wetting into both side walls. The pause at each side ensures fusion and prevents the pool from sagging.

Question 41Welding Technology (BTEB vocational/short-course curriculum)

Which of the following tests is a destructive test used to assess the toughness of a welded joint by striking a notched specimen with a swinging hammer?

  1. Macro-etch examination
  2. Charpy V-notch impact test Correct answer.
  3. Bend test
  4. Brinell hardness test

Explanation

The Charpy test measures the energy absorbed when a notched specimen is broken by a single blow from a pendulum, giving a direct indication of notch toughness. It is widely specified for weld procedure qualification on steels that must resist brittle fracture.

Question 42Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the most appropriate action if a welder receives an electric shock from the electrode holder but is not seriously injured?

  1. Switch off the machine and have the equipment inspected before further use Correct answer.
  2. Increase the open-circuit voltage
  3. Continue welding after changing gloves
  4. Reverse the polarity and resume welding

Explanation

A shock indicates a fault such as damaged insulation, a faulty holder, or a poor earth connection, so the equipment must be isolated and inspected by a competent person before use. Continuing work would expose the welder to a second, possibly fatal, shock.

Question 43Welding Technology (BTEB vocational/short-course curriculum)

Which of the following describes the correct technique for striking an arc with a covered electrode?

  1. Hold the electrode 10 mm above the plate before switching on
  2. Press the electrode firmly into the plate and hold it there
  3. Strike the arc on the earth clamp
  4. Scratch the electrode tip lightly on the work like a match and lift to the arc length Correct answer.

Explanation

A light scratching motion transfers metal and ionises the gap so the arc initiates, after which the electrode is lifted to the correct arc length. This avoids the electrode freezing to the plate, which happens if it is pressed and held.

Question 44Welding Technology (BTEB vocational/short-course curriculum)

Which of the following best explains why hydrogen can cause cracking in the heat-affected zone of a high-strength steel weld?

  1. Hydrogen increases the carbon content of the weld metal
  2. Hydrogen reacts with iron to form a low-melting compound at the grain boundaries
  3. Hydrogen diffuses into the stressed region and reduces the ductility needed to accommodate shrinkage strains Correct answer.
  4. Hydrogen raises the austenitising temperature so the zone stays soft

Explanation

Hydrogen absorbed from moisture or organic contamination diffuses into the hard, highly stressed heat-affected zone and embrittles it, so the residual shrinkage stress causes delayed cracking. Control relies on low-hydrogen consumables, preheat, and controlled cooling.

Question 45Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the correct way to check for a leak on an oxy-acetylene regulator connection?

  1. Spray the joint with water and watch for a flame
  2. Hold a lit match near the joint
  3. Apply a soap solution and look for bubbles Correct answer.
  4. Listen for a hissing sound only

Explanation

A soap or leak-detection solution applied to the joint produces bubbles where gas escapes, giving a safe and reliable indication. Flames or sparks must never be used because the escaping gas is flammable.

Question 46Welding Technology (BTEB vocational/short-course curriculum)

A welded butt joint in a thick section shows a crack that follows the centreline of the weld metal and appears during solidification. Which cause is most likely?

  1. Excessive sulphur and phosphorus in the weld metal Correct answer.
  2. Too much preheat applied to the joint
  3. An excessively short arc length
  4. Insufficient travel speed

Explanation

Solidification, or hot, cracking occurs when low-melting impurities such as sulphur and phosphorus form films at the grain boundaries that cannot accommodate shrinkage strains. The remedy is to use clean, low-impurity consumables and to control the weld bead shape.

Question 47Welding Technology (BTEB vocational/short-course curriculum)

Which of the following best describes the purpose of the root pass in a multi-pass butt weld?

  1. To establish fusion at the joint root and form the foundation for subsequent passes Correct answer.
  2. To act as a cushion that prevents later passes from penetrating
  3. To provide the full strength of the joint on its own
  4. To remove slag from the joint preparation

Explanation

The root pass must fuse both plate faces at the bottom of the preparation and produce a sound base for the fill and cap passes. If the root is defective, later passes cannot repair it because they do not reach the same depth.

Question 48Welding Technology (BTEB vocational/short-course curriculum)

Which of the following is the main reason for using a copper backing bar behind a root pass on a thin stainless steel sheet?

  1. To increase the arc voltage
  2. To add alloying elements to the root
  3. To magnetise the joint
  4. To support the molten pool and dissipate heat so the root does not burn through Correct answer.

Explanation

Copper has high thermal conductivity, so a copper backing bar draws heat away from the root and supports the pool, preventing burn-through and giving a smooth root surface. It may also be grooved and supplied with inert gas to protect the root from oxidation.

Question 49Welding Technology (BTEB vocational/short-course curriculum)

Which of the following statements about the welding symbol with a fillet weld on the arrow side is correct?

  1. The triangle is replaced by a circle at the junction
  2. The triangle is placed above the reference line
  3. The triangle is placed on both sides of the reference line
  4. The triangle is placed below the reference line Correct answer.

Explanation

On a standard welding symbol the reference line separates the two sides, and a fillet triangle drawn below it means the weld is on the arrow side of the joint. A triangle above the line would mean the other side.

Question 50Welding Technology (BTEB vocational/short-course curriculum)

A welder is preparing to weld a galvanised steel bracket. Which precaution is most important to control the hazard?

  1. Increase the welding current to burn through the coating faster
  2. Wear a respirator and provide local exhaust ventilation to remove zinc oxide fume Correct answer.
  3. Use a carburising flame to consume the zinc
  4. Weld without a helmet to see the coating burn away

Explanation

Welding galvanised steel vaporises zinc and produces zinc oxide fume that can cause metal fume fever, so local exhaust ventilation and suitable respiratory protection are essential. The coating should also be removed from the weld zone before welding where practicable.