This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Mold-Metal Reaction”.
1. With what does iron react to give out Ferrous Oxide?
a) Carbon dioxide
Explanation: Iron when reacts with Oxygen gas, it produces the compound, ferrous oxide. Ferrous oxide is an inorganic compound and possesses black colored appearance.
2. What is the chemical formula of fayalite?
Explanation: The chemical representation of the compound fayalite is given by FeOSiO2. Fayalite is also known by the name, iron chrysolite.
3. What is the chemical formula of silica?
4. Silica reacts with what to give out fayalite?
b) Iron Sulphate
c) Iron Oxide
d) Iron Carbide
Explanation: In the formation of the compound fayalite (FeOSiO2), Iron oxide reacts with silica to give out the compound fayalite or iron chrysolite.
5. What percent of magnesium is used in mold metal reactions?
a) More than 1%
b) More than 2%
c) More than 3%
d) More than 4%
Explanation: In the mold metal reactions, there is extremely less amount of magnesium used. Approximately more than 1% of magnesium is used in the reactions containing light alloys.
6. Which metal in aluminium alloy reacts with water to give out hydrogen filled pinholes?
Explanation: Magnesium which is present in small quantity inside the light alloy, when reacts with water, causes the formation of hydrogen filled pinholes.
7. What is the condition for mold metal reaction to take place?
a) Radiating contact between gas and metal
b) Direct contact between gas and metal
c) Radiating contact between gas and oxide film
d) Direct contact between gas and oxide film
Explanation: For mold – metal reaction to take place, the condition is that there has to be direct contact between the gas and the metal.
8. How can the pinholes be reduced?
c) Adding ozone
d) Adding calcium carbonate
Explanation: When pinholes are being produced more than necessary, the metal-mold reaction has to be deoxidized, which can cause the pinholes to reduce.
9. What is differential freezing?
a) Increase in oxygen concentration
b) Increase in nitrogen concentration
c) Increase in carbon concentration
d) Increase in hydrogen concentration
Explanation: When there is an increase in the hydrogen concentration of the metal – mold reaction, then that phenomena is called differential freezing.
10. In light alloys, metal – mold reaction can be suppressed by adding Helium.
Explanation: In light alloy, metal – bond reaction can be suppressed, but not by using Helium, but by using Boric acid and ammonium bi-fluoride.
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