Materials Science: A Comprehensive Guide
Alloys, Fluxes, and Steelmaking
What are the alloys and fluxes in the oven?
Fluxes remove slag, while ferroalloys improve steel properties.
Why can’t converters be added with pig iron and fluxes at the beginning?
Ferroalloys and fluxes would be removed with the initial slag.
What is the hottest part of the blast furnace where iron ore melts?
The bosh.
How is steel produced?
By blast furnace, furnace refining, and electric oven.
Blast Furnace Operation
Iron ore, fluxes, and coke are introduced. As they descend, increasing temperature causes melting in the bosh. The molten iron and flux (forming slag) fall into the crucible. Slag is removed from the top, and pig iron from the bottom.
Coal Coke and Flux in the Blast Furnace
Coke provides heat for smelting and chemical reactions, supporting raw materials and allowing gas to pass upwards. Flux separates gangue from iron, allowing it to float and remain liquid.
Electric Oven Operation
Raw materials are added, and electricity heats the mixture to melting. Slag is removed, and ferroalloys are added to improve the steel before cooling.
Rolling Mills
Material passes between rollers rotating at the same speed but in opposite directions, creating thinner, elongated sheets. Hot rolling (around 1000°C) and cold rolling (room temperature) are used for sheet steel.
Cast Iron and Steel
Ordinary vs. Special Foundry Castings
Regular cast iron contains only carbon, while special castings use alloying elements.
Steel, Iron, Cast Iron, and Graphite
Steel has 0.03-1.76% carbon; iron, 0.01-0.03%; cast iron, 1.76-6.67%; and graphite has higher carbon levels.
Alloy vs. Non-Alloy Steel
Non-alloy steels have less than 1.60% alloying elements; alloy steels have more.
Non-Alloy Steel Classification
Steels are classified as supersoft, soft, semisoft, semi-hard, hard, and extra hard based on carbon content.
Steel Presentation
Steel is presented in various profiles: angle, IPN, tubular, square, T, and rectangular.
Recycling Ferrous Products
Recycling reduces water contamination, noise pollution, and landscape destruction.
Conventional Numerical Designation
Each steel is indicated by the letter F, a dash, and four digits:
- The first digit indicates application.
- The second digit indicates characteristics.
- The last two digits are qualifiers.
Non-Ferrous Metals
Lead Characteristics
Lead is pliable, soft, grayish-white, and easily oxidized, forming a protective carbonate layer.
Light Non-Ferrous Metals
Aluminum and Titanium
Aluminum Production
Bayer Method
Titanium Production
- Chlorination: Heating titanium minerals with carbon and chlorine produces titanium tetrachloride.
- Transformation: The tetrachloride is heated to 800°C with an inert gas and magnesium to form spongy titanium.
- Collection: The sponge is melted in an electric oven with a flux to produce pure titanium.
Major Magnesium Minerals
Carnallite, Dolomite, Magnesite
Magnesium Production
Electrolysis (less dense magnesium floats) or reduction in an oven with flux to remove oxygen.
Environmental Impact of Non-Ferrous Metal Extraction
Open-pit mining impacts habitats. Metal extraction causes heavy metal emissions (carcinogenic), gas and dust emissions, wastewater, and noise pollution.
Copper Production
Dry process for ores with >10% copper; wet process for <10%.
Metal Classification
Heavy metals (density ≥ 5 kg/dm³): tin, copper, zinc, etc. Light metals (2-5 kg/dm³): aluminum, titanium. Ultralight metals (<2 kg/dm³): magnesium, beryllium.
Tellurium (TE) Characteristics
Steel-gray, hard, bitter, highly resistant to corrosion and oxidation. Used in pure and chrome-plated forms.
Porous vs. Impermeable Materials
Porous materials (unvitrified) are permeable; impermeable materials are harder and vitrified.
Plaster Manufacturing
Calcium sulfate is calcined at 450°C for four hours, ground, and packaged. Water is added on-site.
Reinforced vs. Prestressed Concrete
Reinforced concrete has steel bars embedded in concrete. Prestressed concrete involves stretching steel bars before concrete setting.
Waterproof Ceramics
Common stoneware and fine stoneware are used in floors and walls. Porcelain is used in luxury items.
Cement Production
Limestone and clay are ground, heated (1300-1500°C), ground again, and mixed with gypsum.
Mortar and Concrete
Mortar is cement, sand, and water. Concrete adds aggregates.
Structural Materials
All materials discussed, valued for their mechanical properties.
Liquid Crystals
Used in flat-screen computers and televisions.
Wood Processing
Debarking: Removing bark. Parting: Cutting to length. Sawing: Cutting into boards or planks. Drying and Brushing: Improving appearance.
Wood Drying
Air drying to 15% humidity, followed by kiln drying, or direct kiln drying for increased strength and hardness.
Wood Classification and Uses
Softwood: packaging, boxes. Hardwood: instruments, boats, etc.
Papermaking
Wood is shredded, washed, and fibers are combined with glue or adhesive. Water is drained, and the paper is pressed and smoothed.
Paper vs. Cardboard
Density is the key difference.
Cork Production (Hulling)
Cork is removed from trees, air-dried, boiled, and cut.
Glass Production and Properties
Glass is made by fusing lime and sand. It’s hard, a good insulator, resistant to external agents, but fragile.
Polymers
Synthetic polymers with additives.
Plastic Characteristics
Shock resistance, corrosion resistance, sound insulation, electrical and thermal insulation, and aesthetics.
Basic Components of Plastics
- Basic materials (monomers): Used in chemical reactions.
- Additives: Enhance properties.
- Loads: Reduce costs and improve characteristics.
- Catalyst: Initiates and accelerates reactions.
Plastic Groups
- Thermoplastics: Remoldable after solidification.
- Thermosets: Cannot be remolded after solidification.
- Elastomers: Highly elastic.
Examples of Thermoplastics and Thermosets
Thermoplastics: PVC (pipes), PC (lenses), PS (packaging), PMMA (bathroom accessories), ABS (cabinets). Thermosets: PF (switches), UF (adhesives), MF (boards), EP (circuits), PUR (foam).
Plastic Processing Methods
Pressing: Molding under heat and pressure. Injection molding: Injecting molten plastic into a mold. Thermoforming: Heating plastic sheets and forming them with a mold. Extrusion blow molding: Extruding molten plastic into a mold and inflating it with air.
Plastic Compounds
Reinforced plastics (e.g., Kevlar in helmets, carbon fiber in car bodies).