# Aerospace Materials and Processes Questions and Answers – Steel and its Alloys-2

This set of Aerospace Materials and Processes Interview Questions and Answers for Experienced people focuses on “Steel and its Alloys-2”.

1. The density of stainless steel is __________
a) 4.5 gm. Per c.c
b) 6.8 gm. Per c.c
c) 2.8 gm. Per c.c
d) 7.92 gm. Per c.c

Explanation: Density is the ratio of mass to volume of a substance or object. The density of stainless steel is around 7.92 gm. Per c.c. 4.5 gm. Per c.c is the density of titanium and 2.8 gm. Per c.c is the density of aluminium.

2. The atomic number of stainless steels is _________
a) 13
b) 22
c) 26
d) 3

Explanation: The atomic number indicated the number of protons in the nucleus of an atom. The atomic number of stainless steels is twenty-six. The atomic number of aluminium is thirteen and that of titanium is twenty-two.

3. The atomic weight of stainless steel is __________
a) 60
b) 26.97
c) 55.84
d) 47.9

Explanation: The atomic weight or atomic mass of stainless steel is typically 55.84. This is because while steel or stainless steel is not an element, it consists primarily of iron. Hence, its atomic mass is considered 55.84 u.

4. ___________ steel is required when high hardness is desired and ductility is not crucial.
a) High-carbon steel
b) Low-carbon steel
c) Medium-carbon steel
d) Wrought iron

Explanation: Different types of steel, or steel that differs in its components and concentration of carbon show different properties. High-carbon steel is required when ductility is not crucial but hardness is important.

5. Manganese has a property known as penetration ____________
a) softness
b) hardness
c) medium
d) ductility

Explanation: Manganese has a property commonly known as penetration hardness. This is when the manganese is subjected to heat treatment of large sections and hardness penetrates to the core instead of being limited to the surface.

6. The amount of carbon present in high carbon steel is __________
a) 0.10% to 0.30%
b) 2.2% to 4.5%
c) 0.70% to 2.2%
d) 12% to 13%

Explanation: The amount of carbon present in steel differs. They are classified as high carbon steels, low carbon steels, medium carbon steels and wrought iron and cast iron. High carbon steel has 0.70% to 2.2% of carbon.

7. Tungsten steels exhibit a property called “red hardness”.
a) True
b) False

Explanation: The above statement is correct. “Red hardness” of tungsten steels is an advantageous property. It means that this tungsten chromium steel used in tools when heated to dull redness tends to keep its cutting edge.

8. Medium carbon steels are preferred when both ___________ strength and __________ is necessary.
a) no, brittle nature
b) good, brittle nature
c) no, ductility
d) good, ductility

Explanation: Steels that contain different levels of carbon exhibit different properties and each type is used for specific applications. Medium carbon steels are used when both good strength and ductility are necessary.

9. __________ element is responsible for “cold shortness”.
a) Manganese
b) Carbon
c) Phosphorus
d) Sulphur

Explanation: The element phosphorus is the cause of the phenomenon “cold shortness” or brittleness. This happens when metal is cold. Phosphorus is an undesirable element in steels. It should not be present in more than 0.05% in quantity.

10. Chromium has a __________ melting point.
a) Low
b) High
c) Medium
d) Average

Explanation: Chromium is an element that has a high melting point. It is a hard grey metal. It is a desirable element as it gives strength, magnetic quality, wear resistance, hardness and corrosion resistance.

11. Molybdenum decreases the ___________ of material.
a) elastic limit
b) grain size
c) homogeneity
d) impact value

Explanation: Molybdenum is a very productive element in steel. It decreases the grain size. It also increases the homogeneity, elastic limit and impact value. Steels containing molybdenum also exhibit an increase in air-hardening properties.

12. Tools that are made of tungsten-chromium contain _____ of tungsten.
a) 2% to 4%
b) 5% to 10%
c) 20% to 25%
d) 14% to 18%

Explanation: Tungsten steels typically have no use in direct components of an aircraft. But, tungsten chromium steels are utilized in making tools. These steels contain 14% to 18% of tungsten and 2% to 4% chromium.

13. Vanadium alloys do not have a trace of chromium in them.
a) True
b) False

Explanation: The above statement is incorrect. Vanadium alloys are used in very small quantities. It is very expensive. Vanadium alloys or specifically the frequently used chrome-vanadium steel generally possess around 1% chromium. They have high strength.

Sanfoundry Global Education & Learning Series – Aerospace Materials and Processes.

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