Soldering and Brazing MCQ Quiz - Objective Question with Answer for Soldering and Brazing - Download Free PDF

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.

Explanation:

Flux in Soldering

• Soldering is a fundamental process in manufacturing and electronics where two or more metal surfaces are joined by melting and flowing a filler metal (solder) into the joint. The process requires clean and oxide-free metal surfaces to ensure a strong bond. This is where flux plays a critical role.
• Flux is a chemical cleaning agent used in soldering to prepare the surfaces to be joined. Its primary function is to remove oxides and other impurities from the metal surfaces, ensuring they are clean and conducive to forming a strong bond. Oxides are naturally formed when metals are exposed to air, and they can hinder the wetting and bonding of the solder to the metal surface. Flux also prevents re-oxidation during the heating process, enabling a smooth and effective soldering operation.

Explanation:

Both brazing and soldering are the metal joining processes in which parent metal does not melt but only filler metal melts filling the joint with capillary action.

Brazing:

• If the filler metal is having a melting temperature more than 420°C but lower than the melting temperature of components then it is termed as a process of brazing or hard soldering.

Soldering:

• If the melting temperature of filler metal is lower than 420°C and lower than the melting point of the material of components then it is known as soldering or soft soldering.

Concept:

Soldering:

• Soldering is a metal joining process where two or more similar or dissimilar metals are joined together by melting a filler metal (solder) that has a lower melting point than the base metals. The base metals are not melted. Instead, the molten solder flows between the surfaces due to capillary action and solidifies to form a strong electrical and mechanical bond. It is commonly used in electronic circuits, plumbing, and metalworks.

Key Characteristics:

• Temperature: Below 450°C
• Filler Material: Usually a tin-lead or tin-silver alloy
• Used For: Joining wires, electronic components, small pipes

Explanation:

Torch Brazing

Definition: Torch brazing is a process of joining two or more metals by melting and flowing a filler metal into the joint, which has a lower melting point than the base metals being joined. The heat required for this process is generated by burning a mixture of gases, commonly oxy-acetylene.

Correct Option Analysis:

In torch brazing, heat is produced by burning a mixture of oxy-acetylene gas. This is the most commonly used gas mixture in torch brazing due to its high flame temperature, which can reach up to 3,160°C (5,720°F). The high temperature allows for rapid heating of the base metals and efficient melting of the filler metal. Oxy-acetylene is preferred because it provides a concentrated and controllable flame, which is essential for achieving precise and strong joints in various metalworking applications.

Working Principle: In torch brazing, the oxy-acetylene torch is used to heat the joint area of the base metals. The intense heat generated by the combustion of acetylene in the presence of oxygen melts the filler metal, which is then drawn into the joint by capillary action. The filler metal flows into the joint and solidifies upon cooling, creating a strong bond between the base metals.

Advantages:

• High flame temperature allows for efficient heating and quick brazing cycles.
• Precise control over the flame, making it suitable for delicate and intricate work.
• Versatile and can be used with a wide range of metals and filler materials.

Disadvantages:

• Requires proper handling and safety precautions due to the high temperatures and flammable gases involved.
• May not be suitable for very large or thick metal parts due to the limited heat output of the torch.

Applications: Torch brazing is widely used in various industries, including automotive, aerospace, plumbing, and HVAC. It is commonly employed for joining pipes, tubes, and small metal parts, as well as for repair and maintenance work.

Analysis of Other Options:

Option 2: Oxy-neon gas

Oxy-neon gas is not a practical or commonly used gas mixture for torch brazing. Neon is an inert gas and does not support combustion. Therefore, it cannot generate the high temperatures required for brazing. This makes oxy-neon an unsuitable choice for producing the necessary heat for the brazing process.

Option 3: Oxy-nitrogen gas

Oxy-nitrogen gas is also not used for torch brazing. Nitrogen, like neon, is an inert gas and does not support combustion. Using nitrogen in combination with oxygen would not produce the necessary heat for brazing. Hence, oxy-nitrogen gas is not a viable option for this application.

Option 4: Oxy-hydrogen gas

Oxy-hydrogen gas can be used for torch brazing, and it is indeed employed in some specific applications. The flame temperature of oxy-hydrogen can reach up to 2,800°C (5,072°F), which is lower than that of oxy-acetylene. While oxy-hydrogen can be effective for certain brazing tasks, it is less commonly used compared to oxy-acetylene due to its lower flame temperature and different combustion characteristics.

Conclusion:

The correct answer is option 1, oxy-acetylene gas, as it provides the highest flame temperature and precise control needed for efficient and effective torch brazing. The other options, including oxy-neon, oxy-nitrogen, and oxy-hydrogen gases, are either impractical or less commonly used for this specific application.

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

Concept: 

Cementation: There are three types of cementation process for protecting metal surfaces.

• Sherardizing (Zinc coating)
• Calorizing (Aluminium coating)
• Chromizing (Chromium coating)

Anodizing: 

• Anodizing is to provide a decorative and corrosion-resistant coating on aluminium and its alloys only.
• A thin coating of oxide on aluminium can protect the surface from corrosion.
• Aluminium is ideally suited to anodizing, although other non-ferrous metals such as magnesium and titanium also can be anodized.

Parkerising 

• It is a process used for making thin phosphate coating on steel.

Galvanizing: 

• It is a process of giving a protective coating of zinc on iron sheets and components to protect the surface from corrosion.
• It is the process of coating zinc by hot- dipping.

Concept:

• Soldering is a brazing type of operation where the filler metal has a melting temperature below 450°C.
• In soldering, the strength of the filler metal is low.
• Soldering is used for a neat leak‐proof joint or a low resistance electrical joint. Soldering is not suitable for high‐temperature applications.
• During soldering the joint area should be clean and closely fitted to avoid cracks.
• Binding wires are used to support the joints are usually made of soft iron.
• The most commonly used material is stainless steel.
• Another advantage to using stainless wire is that it doesn’t end up accidentally soldered to the workpiece.

The correct answer is Tin and lead.

Explanation:

The correct answer is Option 3 i.e. Sn and Pb

• Electrical solder is an alloy of tin (Sn) and lead (Pb).
• Tin-Lead solder is the largest single group and the most widely used of soldering alloys.
• Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint.
• The filler metal has a relatively low melting point.
• A solder is a fusible metal alloy with a melting point or melting range of 90 to 450°C.
• The solder is melted in the process of soldering to join metallic surfaces.
• It is especially useful in electronics and plumbing.

Explanation:

In brazing two metal items are joined together using a filler metal that flows to the joint by capillary action. The melting point of filler metal is lower than that of adjoining metal

Brazing uses higher temperatures than soldering for a process and involves the parts to be closely fitted.

Explanation:

• Soldering is the process by which metallic materials are joined with the help of another liquified metal (solder)
• Soldering can be classed as soft soldering and hard soldering.
• The process of joining metals using tin-lead solders which melt below 420°C is known as soft soldering
• The process of joining metals using hard solders consisting of copper, zinc, cadmium and silver which melt above 600° is known as hard soldering
• The eutectic alloy of tin-lead solder is a mixture of 63% tin and 37% lead. 63/37 solder melts at 183°C

Explanation:

• Soldering is the process by which metallic materials are joined with the help of another liquified metal (solder)
• Soldering can be classed as soft soldering and hard soldering.
• The process of joining metals using tin-lead solders which melt below 420°C is known as soft soldering
• The process of joining metals using hard solders consisting of copper, zinc, cadmium and silver which melt above 600° is known as hard soldering
• The eutectic alloy of tin-lead solder is a mixture of 63% tin and 37% lead. 63/37 solder melts at 183°C

Explanation:

• Ceramic tools are fixed to the tool using the brazing process. Ceramic tools normally have higher tool life than carbide tools.
• Cutting tools play a vital role in the efficiency and reliability of manufacturing processes. Super abrasive materials containing diamond and or/cubic boron nitride provide enhanced machining performance over conventional materials and are widely used as tool inserts.
• Due to the high material cost of super abrasives, fabrication techniques have been developed and optimized to reduce the number of super abrasives in the insert.
• The super abrasive tip is attached to a corner or edge of the insert body by a brazing process. Brazing provides enough binding force to withstand the cutting forces and heat and is a convenient method to attach small abrasive tips.

• In brazing two metal items are joined together using a filler metal which flows to the joint by capillary action. The melting point of filler metal is lower than that of adjoining metal
• Brazing uses higher temperatures than soldering for a process and involves the parts to be closely fitted.
• In welding, the workpieces are also melted but in brazing, they are not.

Explanation:

• Electrical solder is an alloy of tin (Sn) and lead (Pb).
• Tin-Lead solders is the largest single group and the most widely used of the soldering alloys.
• Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint.
• The filler metal has a relatively low melting point.
• A solder is a fusible metal alloy with a melting point or melting range of 90 to 450°C.
• The solder is melted in the process of soldering to join metallic surfaces.
• It is especially useful in electronics and plumbing.

Explanation:

Both brazing and soldering are the metal joining processes in which parent metal does not melt but only filler metal melts filling the joint with capillary action.

Brazing:

• If the filler metal is having a melting temperature more than 420°C but lower than the melting temperature of components, then it is termed as a process of brazing or hard soldering.

Soldering:

• If the melting temperature of filler metal is lower than 420°C and lower than the melting point of the material of components then it is known as soldering or soft soldering.