Joining MCQ Quiz - Objective Question with Answer for Joining - Download Free PDF

Last updated on Jul 22, 2025

Latest Joining MCQ Objective Questions

Joining Question 1:

In oxyacetylene gas welding, the temperature at the inner cone of neutral flame is around: 

  1. 3200°C
  2. 2600°C
  3. 2300°C
  4. 4000°C

Answer (Detailed Solution Below)

Option 1 : 3200°C

Joining Question 1 Detailed Solution

Explanation:

Joining or fabrication is the process of joining two similar or dissimilar metallic components.

Oxyacetylene Gas Welding:

  • Oxyacetylene gas welding involves a regulated supply of acetylene and oxygen into a welding torch which is ignited to generate heat. Gas welding, primarily meaning oxyacetylene gas welding, is the most suitable for welding aluminum and its alloys.

Basic Principle:

Oxyacetylene gas welding is based on the following chemical reaction between acetylene (C2H2) and oxygen (O2) mixed in equal volumes.

1 Volume of C2H2 contains 2.5 Volumes of  O2.

In 2.5 Volume of O21 volume of O2 is taken from the cylinder and 1.5 Volume of O2 is taken from the atmosphere.

The O2 cylinder is in Black colour.

Types of Flames:

  • Neutral Flame: 
    • ​​It has a Hissing sound. 
    • The inner cone temperature is 3200°c.
    • MS, CI, Low carbon steel, and medium carbon steels use neutral flame.
    • O2C2H2=1
  • Oxidizing Flame:
    • It has a Roaring sound.
    • The inner cone temperature is 3300°c.
    • W, Zn, Brass use Oxidizing flame.
    • O2C2H2=1.15 to 1.5.
  • Carburizing Flame:
    • It has no sound
    • The inner cone has 2900°c.
    • Nickel alloys and High carbon steels use carburizing flame.
    • O2C2H2=0.85 to 0.95

 

Joining Question 2:

In oxyacetylene welding, if acetylene is observed to be in excess, the flame is called as:

  1. reducing flame
  2. neutral flame
  3. originating flame
  4. oxidising flame

Answer (Detailed Solution Below)

Option 1 : reducing flame

Joining Question 2 Detailed Solution

Explanation:

Oxyacetylene Welding Flame Types

Oxyacetylene welding is a widely used welding technique that employs a flame produced by burning a mixture of oxygen and acetylene. The type of flame produced during welding depends on the ratio of oxygen to acetylene in the gas mixture. The three primary flame types are:

  1. Neutral Flame: This is produced when oxygen and acetylene are mixed in equal proportions. It is characterized by a well-defined inner cone and an outer envelope, and it is suitable for most welding applications as it does not alter the chemical composition of the metal being welded.
  2. Reducing Flame (Carburizing Flame): This is observed when acetylene is in excess in the gas mixture. It has a feather-like extension beyond the inner cone and is characterized by a lower temperature. This flame is used for welding metals like aluminum and for applications requiring the prevention of oxidation.
  3. Oxidizing Flame: This flame occurs when oxygen is in excess in the gas mixture. It has a shorter inner cone and produces a higher temperature. It is commonly used for welding metals like brass and for cutting operations.

Joining Question 3:

What is lack of penetration in welding defects?

  1. Failure of the filler metal to fuse with the parent metal
  2. Failure of the filler metal to penetrate into the root of the joint
  3. Cracks either in the weld metal or in the parent metal 
  4. Small holes throughout the weld metal

Answer (Detailed Solution Below)

Option 2 : Failure of the filler metal to penetrate into the root of the joint

Joining Question 3 Detailed Solution

Explanation:

Lack of Penetration in Welding Defects

  • Lack of penetration is a welding defect that occurs when the filler metal fails to completely penetrate into the root of the joint during the welding process. This defect is commonly encountered in welding operations and can significantly compromise the strength and integrity of the welded joint. It is critical to understand the causes, consequences, and preventive measures associated with this defect to ensure high-quality welds.
  • Lack of penetration refers to the incomplete fusion or inadequate penetration of the filler metal into the root area of the joint. The root of the joint is the narrowest and deepest part of the weld, where the two pieces of base metal meet. Proper penetration ensures the welded joint is strong and can withstand mechanical stresses.

Causes of Lack of Penetration:

  • Improper Welding Parameters: Using incorrect welding current, voltage, or travel speed can lead to insufficient heat generation, causing the filler metal to fail to penetrate into the root of the joint.
  • Incorrect Joint Design: A poorly designed joint, such as an excessively narrow or deep root, can make it challenging for the filler metal to reach the root area.
  • Insufficient Heat Input: Low heat input during welding can result in inadequate melting of the base metal, preventing the filler metal from penetrating properly.
  • Improper Electrode Angle: Incorrect positioning or angling of the welding electrode can lead to incomplete penetration in the weld joint.
  • Contaminated or Dirty Base Metal: Presence of impurities, grease, oil, or rust on the base metal can hinder the penetration of the filler metal into the root area.
  • Inadequate Root Opening: A root opening that is too narrow prevents the filler metal from flowing into the joint effectively.

Consequences of Lack of Penetration:

  • Reduced Joint Strength: The absence of adequate penetration results in weaker welds that are more prone to failure under mechanical stress.
  • Structural Instability: Welded components with lack of penetration defects may compromise the structural integrity of the assembly, especially in critical applications.
  • Crack Formation: Stress concentration at the root area can lead to the formation of cracks, further reducing the durability of the welded joint.
  • Potential for Failure: Components with lack of penetration defects are at a higher risk of sudden failure, especially under dynamic or cyclic loading conditions.

Prevention of Lack of Penetration:

  • Optimize Welding Parameters: Ensure proper selection of welding current, voltage, and travel speed to achieve sufficient heat input for complete penetration.
  • Improve Joint Design: Design the joint with an appropriate root opening and bevel angles to facilitate effective penetration.
  • Use Correct Electrode Angle: Position the welding electrode at the correct angle and maintain a consistent travel speed during welding.
  • Clean the Base Metal: Thoroughly clean the base metal to remove any contaminants, rust, grease, or oil before welding.
  • Perform Root Pass Welding: For thick joints, perform a root pass to ensure the filler metal penetrates deeply into the root area.
  • Conduct Visual and Non-Destructive Testing: Inspect the welded joint using visual inspection or non-destructive testing techniques to identify lack of penetration defects.

Joining Question 4:

Which of the following is generally used for melting metal in the metallic gun type of metal spraying process?

  1. Plasma torch 
  2. Compressed air
  3. Oxy acetylene flame
  4. Electric arc

Answer (Detailed Solution Below)

Option 3 : Oxy acetylene flame

Joining Question 4 Detailed Solution

Explanation:

Metallic gun type of metal spraying:

  • The metallic gun type of metal spraying process is a thermal spraying method where molten metal is applied to a surface to create a protective or decorative coating. The primary function of the process is to melt the metal feedstock and project it onto the target surface. Among the given options, the oxy-acetylene flame is generally used for melting metal in the metallic gun type of metal spraying process. This is due to its ability to achieve high temperatures, which are sufficient to melt most metals used in spraying applications.

Why Oxy-acetylene Flame is Used:

  • The oxy-acetylene flame is created by combining oxygen and acetylene gas in a specific ratio. When ignited, this mixture produces a high-temperature flame that can reach temperatures of up to 3,500°C (6,332°F). This temperature is adequate for melting metals like aluminum, zinc, and other alloys commonly used in thermal spraying.

Process Description:

In the metallic gun type of metal spraying process:

  • The metal feedstock (typically in the form of wire or powder) is fed into the spray gun.
  • An oxy-acetylene flame is used to melt the metal at the tip of the gun.
  • Compressed air or another gas is then used to propel the molten metal particles onto the surface being coated.
  • Upon impact, these particles solidify, forming a dense and adherent coating.

The oxy-acetylene flame provides a controlled and efficient heat source, ensuring that the metal is melted uniformly and sprayed effectively. This makes it the preferred choice for the metallic gun type of metal spraying process.

Applications:

The metallic gun type of metal spraying process using an oxy-acetylene flame is widely used in various industries, including:

  • Corrosion protection: Applying coatings of zinc or aluminum to steel structures to prevent rust.
  • Restoration: Repairing worn-out surfaces by adding layers of metal to restore dimensions.
  • Decorative purposes: Adding metallic coatings for aesthetic appeal.
  • Thermal insulation: Coating surfaces to improve thermal resistance.

Joining Question 5:

In the _____ method, a large amount of solder is melted in a tank that is closed. 

  1. soldering iron
  2. infrared soldering
  3. flame soldering
  4. dip soldering

Answer (Detailed Solution Below)

Option 4 : dip soldering

Joining Question 5 Detailed Solution

Explanation:

Dip Soldering:

  • Dip soldering is a soldering method in which a large amount of solder is melted in a tank or pot that is closed. Components or electronic assemblies are then dipped into the molten solder to create a solder joint. This method is commonly used in manufacturing processes for soldering through-hole components onto printed circuit boards (PCBs) and for other similar applications.
  • In dip soldering, the soldering process is achieved by immersing the component leads or the PCB into the molten solder. Flux is often applied beforehand to clean the surfaces and improve the wetting of the solder. As the component is removed from the molten solder, the solder adheres to the areas with proper flux and forms a strong joint after cooling and solidification. This method is especially suitable for large-scale production due to its efficiency and cost-effectiveness.

Steps in Dip Soldering:

  1. Preparation: The components or PCB are cleaned to remove any contaminants, and flux is applied to ensure proper solder adhesion.
  2. Heating: Solder is melted in a solder pot or tank, which is maintained at a consistent temperature to ensure uniform soldering results.
  3. Immersion: The component or PCB is dipped into the molten solder for a specific amount of time. The solder adheres to the exposed metal areas that have been treated with flux.
  4. Cooling: Once removed from the solder bath, the soldered assembly is allowed to cool, forming strong mechanical and electrical connections.

Top Joining MCQ Objective Questions

The distance from the joint root to the toe of the weld is called-

  1. Leg 
  2. Face
  3. Effective throat
  4. Actual throat

Answer (Detailed Solution Below)

Option 1 : Leg 

Joining Question 6 Detailed Solution

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Explanation:

Nomenclature of butt and fillet weld:

Throat thickness: The distance between the junction of metals and the midpoint on the line joining the two toes.

Leg length: The distance between the junction of the metals and the point where the weld metal touches the base metal ‘toe’.

The length of the leg is the distance from the root of the weld to the toe of the weld.

The theoretical throat is the perpendicular distance between the root of the weld and the hypotenuse joining the two ends of the length. It is the shortest distance from the root to the face.

RRB JE ME 29 14Q Welder 4 Hindi - Final.docx 5

Root: The parts to be joined that are nearest together.

Root gap: It is the distance between the parts to be joined.

Root face: The surface formed by squaring off the root edge of the fusion face to avoid a sharp edge at the root.

RRB JE ME 29 14Q Welder 4 Hindi - Final.docx 3

Reinforcement: Metal deposited on the surface of the parent metal or the excess metal over the line joining the two toes.

The toe of weld: The point where the weld face joins the parent metal.

Weld face: The surface of a weld seen from the side from which the weld was made.

Root penetration: It is the projection of the root run at the bottom of the joint.

RRB JE ME 29 14Q Welder 4 Hindi - Final.docx 4

The soldering process is carried out in the temperature range

  1. 15 – 60°C
  2. 70 – 150°C
  3. 180 – 250°C
  4. 300 – 500°C

Answer (Detailed Solution Below)

Option 3 : 180 – 250°C

Joining Question 7 Detailed Solution

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Explanation:

The soldering process is carried out generally in the temperature range of 180 – 250° C which is sufficient to melt the solder material. Most solders are alloys of lead and tin. Three commonly used alloys contain 60, 50, and 40% tin and all melt below 240°C.

In soldering, Solder Flux is used. Most commonly used soldering flux is as followed

  • Ammonium chloride or rosin for soldering tin
  • Hydrochloric acid and zinc chloride for soldering galvanized iron

The drawing representation shown in the figure given below for welding is used to represent-

SSC JE ME 5

  1. Field weld
  2. Weld all around
  3. Flush contour
  4. Chipping finish

Answer (Detailed Solution Below)

Option 2 : Weld all around

Joining Question 8 Detailed Solution

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Explanation:

Following table represents the weld symbols:

SSC JE ME 6

Grey iron is usually welded by

  1. Arc welding
  2. Gas welding
  3. TIG welding
  4. MIG welding

Answer (Detailed Solution Below)

Option 2 : Gas welding

Joining Question 9 Detailed Solution

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Explanation:

Grey cast iron is welded by gas welding.

In welding grey cast iron Neutral flame is used. Sometimes slightly oxidized flame can also be used for grey cast iron welding.

The grey iron castings are widely used for machine tool bodies, automotive cylinder blocks, heads, housings, fly‐wheels, pipes, and pipe fittings, and agricultural implements.

The grey cast iron is designated by the alphabet ‘FG’ followed by a figure indicating the minimum tensile strength in MPa or N/mm2. For example, ‘FG 150’ means grey cast iron with 150 MPa or N/mm2 as minimum tensile strength.

In submerged arc welding, the arc is struck between:

  1. Consumable coated electrode and work piece
  2. Non-consumable electrode and work piece
  3. Consumable bare electrode and work piece
  4. Tungsten electrodes and work piece

Answer (Detailed Solution Below)

Option 3 : Consumable bare electrode and work piece

Joining Question 10 Detailed Solution

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Explanation:

Submerged arc welding:

  • Submerged arc welding is an arc welding process in which heat is generated by an arc which is produced between bare consumable electrode wire and the work-piece.
  • The arc and the weld zone are completely covered under a blanket of granular, fusible flux which melts and provides protection to the weld pool from the atmospheric gases.
  • The molten flux surrounds the arc thus protecting arc from the atmospheric gases.
  • The molten flux flows down continuously and fresh flux melts around the arc.
  • The molten flux reacts with the molten metal forming slag and improves its properties and later floats on the molten/solidifying metal to protect it from atmospheric gas contamination and retards cooling rate.
  • A process of submerged arc welding is illustrated in Figure.

RRB JE ME 8 D4

Two plates, each of 6 mm thickness, are to be butt-welded. Consider the following processes and select the correct sequence in increasing order of size of the heat affected zone.

1. Arc welding

2. MIG welding

3. Laser beam welding

4. Submerged arc welding

  1. 1-4-2-3
  2. 3-4-2-1
  3. 4-3-2-1
  4. 3-2-4-1

Answer (Detailed Solution Below)

Option 4 : 3-2-4-1

Joining Question 11 Detailed Solution

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Heat Affected Zone (HAZ):  

  • The area of the base material of metal which is affected by the heat of the welding process. Melting of the base material does not occur here only microstructure is changed.
  • Heat affected zone may range from small to large depending on the rate of heat input. A process with low rates of heat input will result in a large HAZ.
  • The size of HAZ also increases as the speed of the welding process decreases.

 

SizeofHAZ1speedofwelding

So, order of welding processes in increasing speed is

Arc welding → Submerged Arc welding → MIG welding → Laser Beam welding

Therefore, the order of size of the heat affected zone in increasing sequence is

Laser Beam welding → MIG welding → Submerged Arc welding → Arc welding 

Important Points

Butt welding:  Joining of metal by its whole cross section side by side.

Open circuit voltage for arc welding is of the order of:-

  1. 18 - 40 volts
  2. 40 - 95 volts
  3. 100 - 125 volts
  4. 130 - 170 volts

Answer (Detailed Solution Below)

Option 2 : 40 - 95 volts

Joining Question 12 Detailed Solution

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Explanation:

  • The selection of an optimum value of OCV (Open circuit voltage) depends on the type of base metal, the composition of electrode coating, type of welding current and polarity, type of welding process etc.
  • It generally varies from 50 V - 100 V.

In a welding process, the welding parameters used are: welding current = 250 A, welding voltage = 25 V and welding traverse speed = 6 mm/s. Find welding power.

  1. 6.55 kW
  2. 65.5 kW
  3. 62.5 kW
  4. 6.25 kW

Answer (Detailed Solution Below)

Option 4 : 6.25 kW

Joining Question 13 Detailed Solution

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Concept:

Power in welding is given as

P = V × I

where V = voltage (V), I = current (A)

Calculation:

Given:

V = 25 V, I = 250 A

Power required is:

P = V × I

P = 25 × 250 = 6250 W = 6.25 kW

If there is no melting of the edges of the base metal at the root face or on the side face or between the weld runs, then it is -

  1. Lack of penetration
  2. Lack of fusion
  3. Burn through
  4. Excessive penetration

Answer (Detailed Solution Below)

Option 2 : Lack of fusion

Joining Question 14 Detailed Solution

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Explanation:

A fault is an imperfection in the weld which may result in failure of the welded joint while in service.

The following faults occur commonly in gas welding.

1. Undercut: A groove or channel formed in the parent metal at the toe of the weld is called undercut.

Cause: 

  • When the current setting is too high
  • When welding speed is too fast
  • By overheating of the job due to continuous heating
  • Due to faulty electrode motion
  • When electrode angle is wrong

undercut

2. Incomplete Penetration: Failure of the weld metal to reach the root of the joint is known as incomplete penetration.

Cause:

  • Too narrow edge penetration
  • Excessive welding speed
  • When the current setting is low
  • When a larger diameter electrode is used
  • Due to inadequate cleaning or gouging before depositing sealing run

lack of penetration

3. Porosity or blow-hole:  A group of pin-holes in a weld (porosity) or a larger hole in the weld (blow-hole) are caused by the gas being entrapped.

Cause:

  • Presence of contaminants on the job or electrode surface
  • Presence of high sulphur in the job or electrode material
  • Moisture trapped between joining surfaces
  • Freezing of weld at a faster rate

porosity   Blow holes

4. Spatters: An unintentional deposit of weld metal, in the shape of small globules on the job surface along the weld is known as spatters.

Cause:

  • A too high current setting
  • Use of moisture affected electrode
  • Wrong polarity
  • Use of a long arc
  • Arc-blows

spatter

5. Overlap: Metal flowing onto the surface of the base metal without fusing it.

Cause:

  • Improper welding technique
  • High welding current
  • By using large electrodes

overlap

6. Lack of fusion: If there is no melting of the edges of the base metal at the root face or on the side face or between the weld runs, then it is called lack of fusion.

Cause:

  • It occurs because of the low heat input
  • Incorrect electrode and torch angle
  • Low welding current
  • High welding speed

lack of fusion

The gases used in tungsten inert gas welding are

  1. helium and neon
  2. argon and helium
  3. ozone and neon
  4. None of these

Answer (Detailed Solution Below)

Option 2 : argon and helium

Joining Question 15 Detailed Solution

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Explanation:

TIG Welding: 

  • Tungsten Inert Gas (TIG) or Gas Tungsten Arc (GTA) welding is the arc welding process in which an arc is generated between a non-consumable tungsten electrode and workpiece.
  • The tungsten electrode and the weld pool are shielded by an inert gas normally argon and helium.
  • The principle of tungsten inert gas welding process is shown below

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