Mechanical Properties of Materials: Ferrous Metals & Testing
Mechanical Properties of Materials
Elasticity
The ability of a material to regain its original form after the deforming force is removed.
Plasticity
The ability of a material to retain its new shape after being deformed.
Ductility
The ability of a material to be stretched into threads or wires.
Malleability
The ability of a material to be spread into thin sheets.
Hardness
The resistance a material offers to being scratched or penetrated by another material (wear resistance).
Fragility
The tendency of a material to shatter upon impact.
Toughness
The resistance a material offers when subjected to slow strain.
Fatigue
The deformation of a material subjected to varying loads over a period of time or number of cycles.
Machinability
The ease with which a material can be cut or shaped by removing chips.
Castability
The ability of a molten material to fill a mold completely.
Resilience
The ability of a material to resist shocks or sudden impacts.
Physical Forces on Materials
Tension
A force that tends to elongate an object, acting perpendicular to the surface.
Compression
A force that tends to shorten an object, acting perpendicular to the surface.
Flexion (Bending)
A force that is parallel to the surface and tends to bend the object.
Cutting (Shear)
A force that acts across the surface, causing it to break.
Torque (Torsion)
A force that tends to twist an object.
Buckling
Similar to compression, but occurs in objects with a small cross-section and great length.
Types of Material Tests
Tensile Test
Slowly stretching a standard length and section of material to analyze its behavior until it breaks.
Fatigue Test
Spinning a standardized cylinder of the material rapidly while applying a deforming force. The speed at which it revolves before breaking is called the fatigue limit.
Hardness Testing
Applying a force with a diamond or steel ball on the material and measuring the indentation left behind.
Charpy Impact Test
Determining the energy required to break a specimen of material by impact, using a pendulum with a velocity of 5-7 m/s.
Ferrous Metals
Ferrous metals are those containing iron as their primary component. The main iron ore deposits are located in Rio Doce (Brazil), Cerro Bolivar (Venezuela), and MIFERMA (Mauritania). The largest producers are Russia, Australia, and the USA.
Types of Iron Ore
- Magnetite (75% purity)
- Hematite (70% purity)
- Limonite (60% purity)
- Siderite (50% purity)
Steel and Ferrous Product Production
Blast Furnace Raw Materials
The blast furnace is charged with:
- 60% Iron Ore: Pre-treated to separate the useful ore from the waste material (gangue).
- 30% Coal Coke: Artificially produced from coal to improve combustion and chemical reactions.
- 10% Flux: Composed of limestone, its function is to react with the remaining gangue to form slag.
Blast Furnace Operation
The materials are loaded into the furnace, and the temperature is increased to 1650°C. The flux reacts with the ore to form slag, which floats on the iron. The slag and pig iron are separated through designated outlets.
The pig iron then passes through an LD converter to be formed into steel ingots. Hot air is extracted around the furnace.
Converter Operation
The converter is tilted, and flux (and sometimes cast iron scrap) is added. It is then set upright, and a lance is lowered to inject oxygen into the molten metal. The impurities are burned off. The furnace is tilted again, and the slag floating on the steel is poured off. Alloys and carbon are then added to the steel.