Question

Select the correct statement from the following.

• A. The strength of brazed joint is lower than soldered joint and welded joint.
• B. The strength of brazed joint is higher than soldered joint and welded joint.
• C. The strength of brazed joint is lower than soldered joint but higher than welded joint.
• D. The strength of brazed joint is higher than soldered joint but lower than welded joint.

Hint:

Joint strength hierarchy: welded joints (strongest)>brazed joints>soldered joints (weakest), based on the bonding mechanism and filler material properties.

Answer 1

The Correct Option is D

Step 1: Understand the joining processes.
Soldering: A process where two metals are joined using a filler metal (solder) with a low melting point (typically below 450°C). The bond is primarily mechanical and relies on the adhesion of the solder to the base metals, resulting in relatively low strength.
Brazing: A process where two metals are joined using a filler metal with a higher melting point than solder (above 450°C but below the melting point of the base metals). The filler metal flows into the joint by capillary action, creating a stronger metallurgical bond than soldering.
Welding: A process where the base metals are melted and fused together, often with a filler material. This creates a very strong metallurgical bond, as the joint is essentially a continuation of the base metal.
Step 2: Compare the strength of the joints.
Soldered joints: These are the weakest because the bond is primarily mechanical, and the low-melting-point solder (e.g., tin-lead alloys) has limited strength. Soldered joints are typically used for electrical connections or low-stress applications.
Brazed joints: These are stronger than soldered joints because the filler metal (e.g., brass, silver alloys) has a higher melting point and forms a better metallurgical bond with the base metals. Brazed joints are used in applications requiring moderate strength, such as plumbing or bicycle frames.
Welded joints: These are the strongest because the base metals are melted and fused, creating a joint that can be as strong as the parent material (depending on the welding process and quality). Welded joints are used in high-strength applications, such as structural steel or pressure vessels. Step 3: Establish the strength hierarchy.
Welded joints are typically the strongest due to the fusion of the base metals.
Brazed joints are stronger than soldered joints due to the higher strength of the filler metal and better bonding.
Soldered joints are the weakest due to the low strength of the solder and the nature of the bond.
Therefore, the strength hierarchy is: welded joint \(>\) brazed joint \(>\) soldered joint.
Step 4: Evaluate the options.
(1) The strength of brazed joint is lower than soldered joint and welded joint: Incorrect, as brazed joints are stronger than soldered joints. Incorrect.
(2) The strength of brazed joint is higher than soldered joint and welded joint: Incorrect, as brazed joints are weaker than welded joints. Incorrect.
(3) The strength of brazed joint is lower than soldered joint but higher than welded joint: Incorrect, as brazed joints are stronger than soldered joints and weaker than welded joints. Incorrect.
(4) The strength of brazed joint is higher than soldered joint but lower than welded joint: Matches the established hierarchy. Correct. Step 5: Select the correct answer.
The strength of a brazed joint is higher than a soldered joint but lower than a welded joint, matching option (4).