Mechanical properties of Steel

Question 1

Define stress and its formula.

Answer 1

Force per unit area.

Stress= Load/Area

Question 2

Define strain and its formula.

Answer 2

Deformation per unit length.

Strain= deformation/original length

Question 3

What happens after the yield point?

Answer 3

The material begins permanent/plastic deformation.

Question 4

What is plastic deformation?

Answer 4

Where a material will not return to its original shape; it has been permanently deformed.

Question 5

What is elastic deformation?

Answer 5

Where a material will return to it original shape after deformation; it has not been permanently deformed.

Question 6

What does isotropic mean?

Answer 6

The mechanical properties are the same in all directions.

Question 7

What is the longitudinal axis?

Answer 7

The direction that the load is applied.

Question 8

What is the lateral axis?

Answer 8

The direction perpendicular to direction of the applied force.

Question 9

Define Poisson’s ratio and its formula.

Answer 9

The ratio between lateral strain and longitudinal strain

v = -e lateral/e longitudinal

Question 10

Why is there a negative sign in front of -e lateral?

Answer 10

Lateral strain is measured as a negative number. To make it positive it must be multiplied by -1.

Question 11

Where can Poisson’s ratio ONLY be applied?

Answer 11

When a material is deforming elastically and it is isotropic (same mechanical properties in all directions).

Question 12

What is steel?

Answer 12

An alloy of iron and carbon.

Question 13

What is the chemical symbol for iron and what is its atomic number?

Answer 13

Fe, 26

Question 14

How is pure iron hardened and strengthened?

Answer 14

By removing impurities.

Question 15

What is coke and how is it made?

Answer 15

A solid fuel made by heating coal in the absence of air.

Question 16

How is Iron made?

Answer 16

Hot air, of around 1,000 degrees Celsius, is blasted into a furnace filled with iron ore, coke, limestone and sinter.
The coke reaches temperatures of over 2,000 degrees Celsius and this heat creates molten iron.
The limestone combines with impurities to form slag which is less dense than the molten iron, therefore it floats on top of the molten and can be removed.
Slag can then be used in cement and road building industries.
The molten metal is then ‘tapped’ from the bottom of the furnace and moved by rail to the steel plant to convert to steel.

Question 17

Explain the refining process.

Answer 17

Impurities are reduced in an oxygen furnace.

Question 18

Explain the casting process.

Answer 18

Liquid steel is sufficiently cooled and formed into semi- finished products such as:
Billets
Bloom
Slabs

Question 19

What is hot-rolling and why is it done?

Answer 19

Hot rolling is the process of heating the semi-finished products at 1200 degrees Celsius to make the metal malleable.
It is done to then roll the metal into finished products such as: plates, rails, structural sections, rods etc.

Question 20

What are the final mechanical properties of steel influenced by?

Answer 20

The rolling process, finishing temperature, cooling rate, heat treatment, Carbon content, and alloying elements.

Question 21

What effect does a high Carbon content in steel have?

Answer 21

Higher hardness, yield, and tensile strength of steel.

Lower ductility and toughness.