1.
Molten metal in a brazing process flows due to ______.
Correct Answer
D. Capillary action
Explanation
In a brazing process, molten metal flows due to capillary action. Capillary action is the ability of a liquid to flow in narrow spaces against the force of gravity. When a brazing filler metal is heated, it becomes molten and is drawn into the joint by capillary action. The surface tension of the liquid metal creates a meniscus that pulls the molten metal into the narrow gaps between the joint surfaces. This allows for a strong and uniform bond to be formed between the parts being brazed.
2.
Solders in soldering shall have a temperature _________.
Correct Answer
A. Below 450°C
Explanation
Soldering is a process that involves melting a metal alloy called solder to join two or more metal components together. The temperature at which solder melts is typically below 450°C. Therefore, it is necessary for the soldering temperature to be below 450°C to ensure that the solder melts and forms a strong bond between the metal components. Temperatures above 450°C may damage the components or result in poor solder joints.
3.
What is the maximum temperature that liquids can be when soldering joints?
Correct Answer
B. 250 degrees
Explanation
The maximum temperature that liquids can be when soldering joints is 250 degrees. This temperature is typically used for soldering as it allows the solder to melt and flow properly without causing damage to the components or the solder joint. Temperatures higher than 250 degrees can potentially lead to overheating, which can result in the degradation or failure of the solder joint. Therefore, it is important to ensure that the temperature is controlled and kept within the safe range during soldering operations.
4.
The purpose of applying flux in soldering and brazing is primarily to ______.
Correct Answer
D. Dissolve oxides
Explanation
The purpose of applying flux in soldering and brazing is primarily to dissolve oxides. Oxides can form on the surface of the metal during the heating process, which can prevent proper bonding between the solder or brazing material and the metal. Flux helps to remove these oxides by chemically reacting with them, allowing for better wetting and adhesion of the solder or brazing material. This ensures a strong and reliable bond between the metals being joined.
5.
Which of the following is NOT the purpose of flux in brazing?
Correct Answer
B. Increasing the weight of brazed joint
Explanation
Flux in brazing serves several purposes, including promoting wetting properties, chemically cleaning the metal, and shielding from the atmosphere. However, increasing the weight of the brazed joint is not one of its purposes. The weight of the joint is determined by the materials being brazed and the brazing process itself, not by the flux used.
6.
Soft solder consists of
Correct Answer
D. Lead and tin
Explanation
Soft solder consists of lead and tin. This is because lead and tin have low melting points, making them suitable for joining materials together by melting the solder and allowing it to solidify. The combination of lead and tin creates a strong bond between the materials being soldered.
7.
Solder is an alloy of
Correct Answer
B. Tin and lead
Explanation
Solder is an alloy used to join metals together. It is typically made by combining different metals to create a material with a lower melting point than the metals being joined. In this case, the correct answer is tin and lead. Tin and lead are commonly used in solder because they have compatible melting points and create a strong bond when melted and solidified.
8.
An oxidizing process of coating aluminum and magnesium particles is called ________
Correct Answer
A. Anodizing
Explanation
Anodizing is the correct answer because it is a process of coating aluminum and magnesium particles with an oxide layer. This process involves immersing the metal in an electrolyte bath and applying an electric current to create a controlled oxidation reaction. The resulting oxide layer provides enhanced corrosion resistance, increased durability, and can also be dyed or painted for aesthetic purposes. Parkerising, galvanizing, and sheardizing are different processes used for coating metals but are not specifically related to aluminum and magnesium particles.
9.
Which of the following is not true about brazing?
Correct Answer
B. It causes metallurgical damage by pHase transformation
Explanation
Brazing does not cause metallurgical damage by phase transformation. Brazing is a joining process that uses a filler material with a lower melting point than the parent materials being joined. The filler material is melted and flows into the gap between the parent materials through capillary action. It then solidifies and forms a strong bond between the parent materials without causing any metallurgical damage.
10.
The soldering process is carried out in the temperature range.
Correct Answer
C. 180 – 250°C
Explanation
The correct answer is 180 - 250°C. Soldering is a process that involves melting a filler metal and using it to join two or more metal components. The temperature range of 180 - 250°C is commonly used for soldering because it allows the filler metal to melt and flow properly without damaging the components being soldered. Temperatures below this range may not provide enough heat to melt the solder, while temperatures above this range can cause overheating and potential damage to the components.