Engineering Materials MCQ Questions & Answers | Mechanical Engineering

Properties of gray cast iron,
• It has good machinability
• It has good resistance to galling and wear
• It has good ductility

Malleable iron is obtained by the heat treatment of white iron so the hard iron carbide structure of ledeburite is converted to a matrix of ferrite or pearlite and graphite is precipitated within the iron.
This form of graphite is sometimes referred to as tempered carbon.

There are several properties about cast iron is listed below:
• It has three to five times more compression strength compared to steel
• It has good machinability (gray cast iron)
• It has excellent anti-vibration (or damping) properties hence it is used to make machine frames
• It has good Sensibility
• It has excellent resistance to wear
• It has constant Mechanical properties between 20 to 350 degree Celsius
• It has very low notch sensitivity
• It has Low stress concentration
• It bears Low cost
• It is Durability
• It has Resistance to deformation

Nickel and chromium in steel help in Providing corrosion resistance and Providing high strength at elevated temperatures and Raising the elastic limit

Malleable iron is obtained by the heat treatment of white iron so the hard iron carbide structure of ledeburite is converted to a matrix of ferrite or pearlite and graphite is precipitated within the iron.
This form of graphite is sometimes referred to as tempered carbon.

Beryllium bronze is a copper-base alloy containing beryllium.
Beryllium bronze has high yield point and high fatigue limit.

the gamma iron (γ) is a face-centered cubic (FCC).

The alpha iron (α) is a body-centered cubic (BCC).

The maximum internal diameter of a blast furnace is about 9m

Correct Answer: B: Amount of carbon it contains

Here's why:

* Hardness Explained: Hardness is a material's resistance to permanent deformation, like scratching or indentation.

* Role of Carbon in Steel: Steel is primarily iron (Fe) with added carbon (C). The amount of carbon significantly impacts its hardness.

* Carbon and Hardness Relationship: Generally, increasing the carbon content in steel increases its hardness and strength. Carbon atoms interfere with the movement of iron atoms, making it more difficult to deform the steel.

* Why other options are less accurate:
* A: Amount of cementite it contains: Cementite (Fe3C) is a compound of iron and carbon. While it contributes to hardness, the *amount of carbon* present is the more direct factor.
* C: Contents of alloying elements: Alloying elements (like chromium, nickel, etc.) can definitely affect hardness, but the *primary* influence is from carbon.
* D: Method of manufacture of steel: Manufacturing methods (like heat treatment) can alter the microstructure and hardness of steel, but they don't fundamentally change its inherent hardness potential, which is set by the carbon content.