Material Properties, Classification, and Processing

Posted on Dec 20, 2024 in Technology

Classification of Materials

Materials can be broadly classified into three categories:

  • Natural materials: Those found in nature.
  • Artificial materials: Those made from natural materials found in nature but have not undergone prior processing.
  • Synthetic materials: Man-made from artificial materials.

Material Properties

Sensory Properties

These properties relate to how a material interacts with our senses. For instance, garments made from natural products are often more pleasant to the touch, while synthetic fibers may be less satisfactory. Other factors include odor, brilliance, and texture color.

Optical Properties

These refer to the reaction of a material when light shines on it. Materials can be:

  • Opaque: Do not allow light to pass through.
  • Translucent: Allow light to penetrate but not clearly.
  • Transparent: Allow light to pass through clearly.

Thermal Properties

These describe the behavior of a material to heat. For example, metals are good conductors of heat.

Magnetic Properties

These refer to the ability of a ferrous metal to be attracted by a magnet.

Chemical Properties

These relate to a material’s resistance to oxidation and corrosion. For example, steel and its alloys are rather easily oxidized in contact with moisture.

Mechanical Properties

  • Elasticity: The ability of a material to recover its shape once 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.
  • Malleability: The ability of a material to be spread into sheets without breaking.
  • Hardness: Resistance to scratching or penetration by another body.
  • Fragility: The opposite of resilience; the material shatters when a force is applied.
  • Toughness: Resistance to breakage when subjected to slow strain.
  • Fatigue: Deformation of a material subjected to varying loads below the breaking point over time.
  • Machinability: Ease with which a body can be cut by material removal.
  • Acrimony: Increased hardness, brittleness, and resistance in certain metals due to cold deformation.
  • Castability: Ability of a molten material to fill a mold.
  • Resilience: Resistance to shocks or sudden forces.

Physical Effort

  • Drive: The force tends to elongate the object and acts perpendicularly to the surface.
  • Compression: The force tends to narrow the object, acting perpendicularly to the surface.
  • Flexion: The force is parallel to the attachment surface, tending to bend the object.
  • Torque: The force tends to twist the object, with forces parallel to the attachment surface.
  • Cutting: The force is parallel to the surface and breaks through it.
  • Buckling: Similar to compression but occurs in subjects with a small cross-section and great length.

Material Tests

  • Tensile test: Slowly stretching a standardized specimen to analyze the material until it breaks.
  • Fatigue test: A rapidly spinning cylinder of standardized material is deformed due to force; the number of revolutions before failure is the fatigue limit.
  • Hardness test: Applying a given force with a diamond or steel ball to analyze the indentation left.
  • Charpy impact test: Determining the energy needed to break a standard specimen with an impact.

Material Types (Exhaustion)

  • Renewable materials: Rational use will not cause depletion (e.g., wood, paper, linen).
  • Nonrenewable materials: Found within the Earth; once used, they are depleted if not recycled (e.g., copper, aluminum, iron).

Waste Types

  • Inert waste: Presents no risk to the environment or humans (e.g., rubble, gravel, ceramics).
  • Toxic waste: Flammable, corrosive, or toxic substances that pose health hazards (solid, liquid, and gas).

Waste Operations

These include reduction at source, treatment (physico-chemical-biological), incineration, and landfill.

Raw Material of Blast Furnace

  • Iron ore: Crushed and ground to separate the ore from the gangue before being introduced into the furnace.
  • Coking coal: Artificially created from coal.
  • Flux: Composed of limestone, it reacts chemically with the gangue and lowers its melting point.

Operation of Blast Furnace

Once ignited, a blast furnace runs continuously until repair is needed. The load descends from the top, increasing in temperature until it reaches the bosh (around 1650°C), where the ore turns into iron droplets that collect in the crucible. Slag is removed every 2 hours through a tap hole. Most pig iron is converted into steel using an LD converter.

Conversion of Pig Iron to Steel

Impurities are removed from pig iron using a converter.

Raw materials used by the converter: Pig iron, scrap metal, flux.

Furnace converter features: Firebrick interior, 300-ton steel capacity, 1 batch per production cycle.

Steel Production from Scrap

This process involves flexible cables, an electric transformer, electrode arms, electrode clamping with hydraulic arms, a smoke extraction system, and a chilled rocker structure.

Classification of Ferrous Materials

  • Iron: 0.01-0.03% carbon
  • Steel: 0.03-1.76% carbon
  • Cast iron: 1.76-6.67% carbon
  • Graphite: More than 6.67% carbon

Steel Commercial Presentations

  • Sheets: Rolled sheets measuring between 1x2m and 3x3m.
  • Bars: If the bar section is round and smaller than 5mm in diameter, it is called wire. Very thin, long plates are called strapping.
  • Profiles: Hollow sections with lengths varying between 5 and 12m.

Features of Non-Ferrous Metals

Tin

  1. Very bright color.
  2. Malleable and soft at room temperature, but fragile and brittle when hot.
  3. Decomposes below -18°C (tin disease).
  4. Produces a”tin cr” sound when bent.
  5. Alloys: Bronze (copper + tin) and solder.

Copper

  1. Very ductile and malleable.
  2. High electrical and thermal conductivity.

Zinc

  1. Highly resistant to oxidation and corrosion in air and water, but not to acids and salts.
  2. Highest thermal expansion coefficient among metals.
  3. Brittle at room temperature but very malleable between 100 and 150°C.

Lead

  1. Very pliable and soft.
  2. Greyish-white color when freshly cut, brilliant. Rusts easily.
  3. Highly resistant to hydrochloric and sulfuric acids.
  4. Applications:
    • Pure state: Lead oxide, pipes, battery coating.
    • Alloy: Soft solder and lead-based solder.

Aluminum

  1. Very light and stainless in the air due to a thin protective aluminum oxide film.
  2. Good conductor of electricity and heat.
  3. Very malleable and ductile.

Titanium

  1. Silvery-white metal, resists oxidation and corrosion better than stainless steel.
  2. Mechanical properties similar or superior to steel, maintained up to 400°C.

Magnesium

  1. Flammable in liquid or powder form.
  2. White color similar to silver.
  3. Stronger than aluminum. Used in aeronautics.

Plastics and Polymers

Polymers are synthetic materials obtained through chemical reactions, with additives added to improve properties. Key features include resistance to corrosion, chemicals, heat, sound, and aesthetic presence.

Types of Plastic

Thermoplastics, Thermosets, Elastomers.

Families of Plastics

PC (polycarbonate), PVC (polyvinyl chloride), PP (polypropylene), PE (polyethylene), PMMA (polymethyl methacrylate), PS (polystyrene), ABS (acrylonitrile butadiene styrene), PF, UF, MF, EP, PUR.