This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Mold Materials”.
1. Which of the following properties must a material possess to be used in mold making?
a) High refractoriness
b) Chemical and thermal stability
c) High permeability
d) All of the mentioned
Explanation: A material must have all of the above properties so as to be a good mold making material.
2. Which of the following group of material type is used in mold making?
a) Metallic only
b) Non-Metallic only
c) Both metallic as well as non-metallic
d) Neither metallic nor non-metallic
Explanation: Both metallic as well as non-metallic materials are used for making molds.
3. Which of the following non-metallic material is not used in the synthesis of molds?
d) Valcanised rubber
Explanation: Valcanised rubber has a very low refractoriness, hence, using valcanised rubber for making molds can cause damage to the mold cavity or metallic structure so formed.
4. High refractoriness of a material refers to its __________
a) Slipperyness of the material
b) Chemical strength towards other material
c) Strength to withstand at high temperature
d) Ability to get dissolved in molten metal
Explanation: Refractoriness is the resistance to self deformation at high working temperatures. A material must possess such property in order to withstand the temperature of molten metal during casting.
5. Which of the following is a perfect composition of clay (Bentonite) used in moulding sand?
Explanation: Bentonite is one type of clay used in moulding sand as a binder. Its chemical formula is represented as Al2O3.2SiO2.2H2O.
6. Which of the following material is not used for mold making?
c) Mild steel
d) Alloy steel
Explanation: Zinc (Zn) has a very low melting point, making it non-dependable material to be used as the material for mold making.
7. Phosphorus is added to steel mold for which of the following reason?
a) It increases strength and hardness of steel
b) It increases refractoriness of steel
c) It increases porosity of steel
d) It increases finishing of steel
Explanation: Phosphorus has the ability to increase strength and hardness of steel material when added to it in the right compostion (2-4%).
8. Which of the following is a perfect composition for medium carbon steel?
a) Upto 0.3%
Explanation: The sequence of composition is in order from low carbon steel to high carbon steel till 1.7% carbon. Medium carbon steel belongs to a region of 0.3-0.6% carbon.
9. A form of cast iron in which free carbon is present in the form of nodules in the matrix of cementite and ferrite. This form of cast iron is ____________
a) Malleable iron
b) Pig iron
c) Wrought iron
d) None of these
Explanation: Malleable iron is one type of cast iron in which free carbon is present in the form of nodules in the matrix of cementite and ferrite.
10. Which of the following percent of carbon is correct for Eutectoid steel (at 723oC in Fe3-C diag)?
Explanation: At 723oC in Fe3C diagram the transformation change takes place. The carbon content at this point is 0.8% and is called as eutectoid steel.
11. Which of the following is not used as binders for mould materials?
Explanation: Backelite is a material which increases hardness beyond a limit which is acceptable for mold materials as well as its deformation takes place too early as plastic deformation. Hence, it is not used as a binder.
12. Which of the following is not used as an additive?
b) Coal dust
Explanation: Zinc is an alloying element and is not considered as additive.
Explanation: From the starting of martensite produced the hardness increases with % of carbon present in it but after a certain point this curve tends to remain constant for hardness value with increase in carbon content.
14. Nitriding process is used to increase surface hardness for which of the following materials?
a) Alloy steels
b) Low carbon steels
c) Medium carbon steels
d) High carbon steels
Explanation: Alloy steels ( due to low carbon content) can easily undergo nitriding process.
15. The famous iron pillar located near Qutab Minar in New Delhi is made up of which material?
a) Stainless steel
b) Malleable iron
c) Mild steel
d) Wrought iron
Explanation: Malleable iron is a raw kind of type of iron which was used in the making of Iron pillar.
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