This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Soldering and Brazing”.
1. The liquid temperature of the filler metal used in brazing is _________
a) 150oC
b) 427oC
c) 723oC
d) 1000oC
View Answer
Explanation: Brazing is defined as the joining of two metal pieces by using a filler metal. The liquid temperature of the filler metal is above 427oC and below the solidus of the base metal.
2. Copper and aluminum can be joined by brazing when _________ alloy is used.
a) Copper-zinc
b) Aluminum-silicon
c) Copper-tellurium
d) Aluminum-zinc
View Answer
Explanation: Most metals and alloys such as carbon steels, cast iron, stainless and alloy steels, brass, and others can be brazed. Aluminum and copper can also be joined if an aluminum-silicon alloy is used as the brazing filler metal.
3. Which of the following filler metals is used in the electrical industry?
a) BAG-1
b) BAG-3
c) BAG-5
d) BAG-6
View Answer
Explanation: Silver brazing filler alloys are used for joining most ferrous and non-ferrous metals except aluminum and magnesium. BAG-5 filler metal is composed of 44-46% Ag, 29-31% Cu, 23-27% Zn, and 0.15% of other elements. It is mostly used in the electrical industry.
4. Nickel filler metals are heat resistant up to ________ in short time service.
a) 610oC
b) 982oC
c) 1204oC
d) 1666oC
View Answer
Explanation: Nickel filler metals are used for their corrosion and heat resistance properties up to 982oC for continuous service and 1204oC for short time service. These are used primarily on AISI 300 and 400 series stainless steels and nickel and cobalt base alloys.
5. Which of the following filler metals is used for carbide tip brazing?
a) BAG-1
b) BAG-4
c) BAG-8
d) BAG-18
View Answer
Explanation: BAG-4 filler metal is used for carbide tip brazing and is composed of 39-41% Ag, 29-31% Cu, 26-30% Zn, 1.5-2.5% Ni, and 0.15% of other elements. BAG-1 freely flows into low and narrow capillary joints. BAG-8 filler metal is used in a controlled atmosphere or vacuum brazing, whereas BAG-18 is used for brazing of ferrous and non-ferrous alloys without flux.
6. Tin-zinc solders are used for joining __________
a) Aluminum
b) Zinc
c) Copper
d) Glass
View Answer
Explanation: Tin-zinc solders contain a varying composition of tin and zinc, each with a solidus temperature of 199. These solders are used for joining aluminum. Aluminum can also be joined using zinc-aluminum solders.
7. What is the solidus temperature of tin-lead solders?
a) 183
b) 297
c) 444
d) 604
View Answer
Explanation: Tin-lead solders constitute the largest portion of all solders in use. They possess good corrosion resistance to most media and can be used to join most metals. Except for the 5/95% Sn/Pb solders, all solders of this type have a solidus temperature of 183.
8. Addition of ___________ increases the mechanical properties of a tin-lead solder.
a) Bismuth
b) Tellurium
c) Antimony
d) Molybdenum
View Answer
Explanation: Addition of antimony up to 60% of the tin content increases the mechanical properties of the solder. However, this results in a slight impairment of the soldering characteristics. Of the various solders of this type, the composition of Pb is the highest, whereas that of antimony is lowest.
9. Aluminum can be joined to another aluminum with the use of ________ solder.
a) Lead-silver
b) Indium-tin
c) Cadmium-silver
d) Fusible alloy
View Answer
Explanation: Cadmium-silver solders are used for joining aluminum to itself or to other metals. It is composed of 95% cadmium and 5% silver. Due to high cadmium content, improper use of this solder may lead to health hazards.
10. __________ solders are used for glass-to-glass and glass-to-metal soldering.
a) Lead-silver
b) Tin-zinc
c) Cadmium-zinc
d) Indium-tin
View Answer
Explanation: A 50% indium and 50% tin solder is used for glass-to-metal and glass-to-glass soldering. Cadmium-zinc and Tin-zinc solders are used for soldering and joining aluminum. Lead-zinc solders are used for soldering of copper and its alloys.
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