Metals

Question 1

Describe tbe ways in which metals can be strengthened

Answer 1

Alloying: Adding small amounts of element(s) to base metal ,increases the strength of the metal. E.g. Adding nickel to steel to create stainless steel

Cold working: it include methods rolling,bending and forming It process whereby the metal is subjected to plastic deformation at low temperatures.This process increases the dislocation density,thus causing metal to be harder and stronger

Heat treatment: Process like annealing,tempering,and queching can refine grain structure , reduce internal stress and improve strength, hardness and toughness

Controlling of grain size: The grain boundaries are discontinuities in the atomic structure, thus they have different orientations on either side of the boundary,Thus the dislocation is stuck in first grain.Hence other dislocations will pile up behind,thus exerting a force, hence internal strength is improved in that way.

Question 2

Advantages of cold rolling over hot rolling

Answer 2

-cold rolling produces smother and uniform surface finish than hot rolling,which can help to improve the appearance and quality of the final product.

Cold rolling allows for tigher dimensional tolerances (accurate dimensions)than hot rolling which is inconsistent

Cold rolling can increase the strength and hardness of metal

Reduced risk of surface cracking compared to hot rolling

Question 3

How does the carbon content affect the physical properties of the steel?

Answer 3

Hardness: increasing the amount of carbon content in steel will increase the hardness of the steel. Thus,low carbon content steel have low hardness

Strength: carbon contributes to the strength of the steel.forming solid solution with iron. As the carbon content increases, the steel becomes stronger and yield strength

Ductility
Ductility refers to a material’s ability to deform without fracture.Therefore, low carbon-content steel has greater ductility.Thus, increasing the carbon content will decrease the ductility of the steel.thus it tends to be brittle

Weldability
Increasing the carbon-content in the steel,thus it is more difficult to weld due increased likelihood to cracking.Thus weld ability is decreased
Machineability:
Higher carbon content steel are more difficult to machine ,low carbon steel are more easier to machine with due to their low hardness

Question 4

How can the corrosion resistance of stainless steel be increased?

Answer 4

Using alloying elements such as nickel or chromium thus adding these content of these elements will increase resistance to corrosion.
Surface perservation helps to create protective oxide layer on the suface to remove contaminants such as iron particles that may compromise the steel’s corrosion resistance.
Proper cleaning and maintenance

Question 5

What effect does tempering have on queched/hardned steel?

Answer 5

Reduction of hardness and brittleness: hardened steel is often brittle,thus after tempering,the hardness and brittleness of steel are reduced as it is allowed to undergo a controlled softening process.

Improvement in toughness and ductility:Tempering improves the toughness and ductility of the steel by relieving the internal stresses and reducing the brittleness

Reduction of residual stresses: tempering helps to relieve internal stress which helps the steel to be less prone to sudden fracture