Welding MCQ Quiz in मल्याळम - Objective Question with Answer for Welding - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Spot welding is an example of resistance welding.

TYPES OF WELDING:

1. Resistance Welding

I.Spot welding

II.Projection welding

III. Seam welding

IV. Resistance butt welding

V. High-frequency resistance welding

2. Arc welding

I. Carbon arc welding

II. Metal arc welding

III. Hydrogen arc welding

IV. TIG (Tungsten Inert Gas welding)

V. MIG (Metal Inert Gas)

VI. Plasma arc welding

3. Radiant Energy Welding processes

I. Electron beam welding

II. Laser beam welding

4. Thermo-chemical welding processes

I. Thermit welding

II. Atomic hydrogen welding

5. Gas Welding

I. Air-acetylene welding

II. Oxy-acetylene welding

III. Oxy-hydrogen welding

VI. Pressure gas welding

Plastic or Non fusion welding: In this welding, the pieces of metal to be joined are heated to a plastic state and then forced together by external pressure. This procedure is used in forge welding, resistance welding, thermit welding and gas welding.

Fusion or Non pressure welding: In the fusion welding, the material at the joint is heated to a molten state and allowed to solidify. This includes gas welding, arc welding etc.

Electric welding accessories required to carry out proper welding operation are:

• Electric welding power sets
• Electrode holder to hold the electrodes
• Face screen,Hand Screen with coloured glass
• Chipping hammers to remove sag from a molten weld
• Wire brush to clean the weld
• Earth clamp and protective clothing (apron, gloves, etc.)

Types of welding:

1.) Ultrasonic welding:

• Ultrasonic welding is a solid-state welding process in which the joining of materials (metals and plastics) occur without melting.
• In this type of welding, high-frequency mechanical vibrations are transferred to the parts to be joined, which causes sliding of one part over another.

2.) Laser beam welding:

• Laser Beam Welding is a fusion welding process in which two metal pieces are joined together by the use of a laser.
• The laser beams are focused on the cavity between the two metal pieces to be joined.
• The laser beams have enough energy and when it strikes the metal pieces produce heat that melts the material from the two metal pieces and fills the cavity.
• After cooling a strong weld is formed between the two pieces.

3.) Electron beam welding:

• Electron-beam welding is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined.
• The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact.

4.) Inert gas metal arc welding:

• Metal Inert Gas (MIG) welding is an arc welding process that uses a continuous solid wire electrode heated and fed into the weld pool from a welding gun.
• The inert gas options include argon, argon + hydrogen, and argon/ helium. 
•  Helium is generally added to increase the heat input, which increases the welding speed.

Explanation:

• It is utilized to join the metal pieces end to end.
• In this technique, the parts to be welded, usually bars and rods of the same cross-sectional area, are clamped edge to edge in copper jaws of the welding machine which acts as electrode clamps.
• One of the electrodes is fixed and the other is movable.
• The two ends of the workpieces are butted together ina solid contact so that their contact surface forms a locality of high electric resistance, while current flows to heat the joint quickly.
• At the point/surface of contact, the pressure applied upsets or forges the parts together.
• This process is suitable for welding non-ferrous materials in the shape of formed parts, tubes, bars, and rods.
• The voltage required is 2-8 V and the current required ranges from 50 A to several hundred amperes depending upon material and the area to be welded at a time

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The correct answer is option 1):(TIG (Tungsten Inert Gas) welding)

Concept:

Arc welding

• Arc welding is the most commonly used welding type.
• It uses the heat-produced electric arc to weld metals together
• The arc occurs from the base material to the electrode, the welding rod or wire, and melts the metal. Then the welder can fuse the molten metal and craft it into a weld. 

The different types of arc welding is 

1. Shielded metal arc welding 

2. Gas metal arc welding

3. Flux-cored arc welding

4. Gas Tungsten Arc Welding (TIG welding)

5. Carbon arc welding

6. Submerged arc welding

7. Electroslag welding

       8. Drawn Arc (DA) stud welding

Gas Tungsten Arc Welding (TIG welding)

This method uses a non-consumable tungsten electrode and constant current power source to create a plasma arc between metals and can be conducted with or without filler material. Inert shielding gas protects the weld area and electrode from the atmosphere.

TIG welding can be difficult to learn and technically demanding. It requires more operator control than similar processes, but there are both manual and automatic methods available.

The process produces high-quality, clean, and strong welds but can be time-consuming. It’s primarily suitable for welding thin materials and non-ferrous metals but isn’t ideal for thicker metal joints.

Additional Information

Arc welding uses an electric arc to generate heat and join together two metals. The power supplied to the electric arc can be alternating current (AC) or direct current (DC). AC arc welders are often inexpensive while DC arc welders offer a smoother arc that works better on thin materials, however they are more expensive.

All arc welding processes use an electric arc to weld and have at least the following:

An electrode
An electrode cable
A work cable and clamp
Power supply
Metals to join

 The welding arc during the process of any type of arc welding will be around 3500°C. 

During the arc welding process, the welder works with two types of metal.

Parent Material: This is the metal parts that are joined together during the welding process. 

Consumables Material: This is the additional materials that are heated up in the arc and deposited over the joints to create a stronger bond. 

In a basic arc welding process, the power supply is switched on, and the electrode is brought near the base material. Then, intense heat is generated to produce the electric arc. The heat then melts the base metal, electrode core and flux coating. The flux coating then provides a shielding environment to weld. The molten metal is deposited between the two metal work pieces to join them together. Once this solidifies, it forms a strong bond between the two materials. Then, the metal work pieces are left to cool down. 

Spot welding means the joining of two metal sheets and fusing them together between electrode tips at suitably spaced intervals by means of heavy electric current passed through the electrodes.

The electrodes are made up of copper or copper alloy and are water cooled.

The Correct answer is Option 4.

Key Points In AC (alternating current) welding, transformers play a crucial role in adjusting the voltage levels to facilitate the welding process. The specific type of transformer commonly used in AC welding is the step-down transformer.

Function of a Transformer in AC Welding:

Welding typically requires a lower voltage but a higher current to generate the necessary heat for melting and fusing metals. The transformer helps in achieving this by transforming the voltage from the power source to the desired levels for welding.
Step-Down Transformer:

A step-down transformer is designed to decrease the voltage from the primary winding (connected to the power source) to the secondary winding (connected to the welding electrode or workpiece). This reduction in voltage is necessary to provide the high current required for welding.

Components of a Step-Down Transformer:

Primary Winding: Connected to the power source, the primary winding receives alternating current (AC) from the power supply. The AC causes a magnetic field to form around the primary winding.
Secondary Winding: Linked to the welding electrode or workpiece, the secondary winding receives the transformed voltage. As the magnetic field induces a current in the secondary winding, it results in a change in voltage suitable for welding applications.
Voltage Transformation: The primary-to-secondary winding ratio determines the transformation of voltage. In a step-down transformer, the number of turns in the secondary winding is less than that in the primary winding, resulting in a reduced voltage at the secondary winding.
Importance of High Current in Welding: High current is essential in welding to generate heat for melting metals and creating a strong, durable weld. The step-down transformer allows for the adjustment of voltage to achieve the necessary current levels for effective welding.
AC Welding Process: In AC welding, the alternating current from the step-down transformer creates an oscillating flow of current. This constant change in direction helps prevent the accumulation of excessive heat at the electrode, contributing to a more stable welding process.

In conclusion, the step-down transformer is a critical component in AC welding, as it enables the transformation of voltage to provide the required high current for effective and efficient welding. The design of the transformer ensures that the welding process achieves the desired heat levels without compromising safety or the integrity of the weld.

The correct answer is (option 4) i.e. Projection welding

Explanation:

Electric resistance welding refers to a group of welding processes that produces coalescence of faying surfaces where heat to form the weld is generated by the electrical resistance of material combined with the time and the force used to hold the materials together during welding. Different types of resistance welding are

1. Resistance spot welding

2. Resistance seam welding

3. Projection welding

4. Upset welding

5. Flash welding

6. Percussion welding

Forge welding is a type of solid-state welding.

Projection welding is a multi-spot welding process.

Spot welding process:

In resistance spot welding, two or more sheets of metal are held between electrodes through which welding current is supplied for a definite time and also force is exerted on workpieces.

Projection welding:

Projections are little projected raised points which offer resistance during the passage of current and thus generate heat at those points. These projections collapse under heated conditions and pressure leading to the welding of two parts on cooling.

Projection welding involves the joining of parts by a resistance welding process which closely resembles spot welding. Projection welding may be carried out with one projection or more than one projection simultaneously.

In resistance welding very high‐current (up to 100, 000 A) and very low‐voltage (0.5 to 10 V) is used.

Resistance Welding:

Processes in which welding heat is produced by the resistance offered to the passage of electric current through the two metal pieces being welded.

These processes differ from the fusion processes in the sense that no extra metal is added to the joint using a filler wire or electrode.

According to Joule’s law, the heat produced (H) electrically is given by,

H = I²Rt J

Here, R is the contact resistance between the two metals being welded together.

Advantages:

• Heat is localized where required
• Welding action is rapid
• No filler material is needed
• Requires comparatively lesser skill
• Is suitable for large quantity production
• Both similar and dissimilar metals can be welded
• The parent metal is not harmed
• Difficult shapes and sections can be welded.
   

Note: The only disadvantages are concerning a high initial as well as maintenance cost.

Arc Welding Machines:

Arc welding is never done directly from the supply mains, special welding machines are used which provided currents of various characteristics.

The use of such machines is essential for the following reasons:

• To convert AC supply into DC supply when DC welding is desired.
• To reduce the high supply voltage to a safer and suitable voltage for welding purposes.
• To provide the high current necessary for arc welding without drawing a correspondingly high current from the supply mains.
• To provide suitable voltage/current relationships necessary for arc welding at minimum cost.
   

There are two general types of arc welding machines:
(a) DC welding machines
(i) motor-generator set
(ii) a.c. transformers with rectifiers

(b) AC welding machines