MODULE 2.2 - STEEL 1

MODULE 2.2 - STEEL

1. Difference Between Metal and Steel

• Metal

  • Refers to a class of chemical elements characterized by:

    • Luster

    • Malleability

    • Ductility

    • Electrical conductivity

• Steel

  • A specific type of metal primarily composed of iron and carbon.

2. Types of Metals

A. Ferrous Metals

• Contain iron as their primary constituent

  • Characteristics: magnetic, strong, durable, conductive

  • Examples:

    1. Iron

    • Malleable, ductile, silver-white metallic element; precursor to pig iron and steel.

    2. Wrought Iron

    • Soft, low-carbon form of iron, readily forged; used for decorative purposes.

    3. Cast Iron

    • Hard, brittle, non-malleable iron-based alloy; used in engine blocks, pipes, cookware.

    4. Steel

    • Alloy of iron and carbon; strong, versatile, and affordable.

B. Non-Ferrous Metals

• Metals with minimal to no iron content; non-magnetic

  • Examples:

    1. Alloy

    • Metal made by combining two or more metallic elements for enhanced strength or corrosion resistance.

    2. Mercury

    • Liquid at room temperature; unique among non-ferrous metals.

    3. Aluminum

    • Ductile, malleable; resistant to corrosion; widely used in secondary building elements and alloys.

    • ACP: Aluminum Cladding Panel

    • Anodizing: Process of thickening the oxide coating on aluminum for corrosion resistance.

    4. Copper

    • Excellent for electrical wiring and piping; very good corrosion resistance.

    5. Brass

    • Alloy of copper and zinc; golden color, corrosion resistant; used in hardware and plumbing.

    6. Bronze

    • Alloy of copper, tin, and aluminum; strong, historically significant; develops a green patina over time.

    7. Lead

    • Heavy, malleable; used for flashing, sound isolation, and radiation shielding; toxic when disturbed.

    8. Zinc

    • Low strength; mainly used for galvanizing to prevent rust.

    9. Tin

    • Soft, low tensile strength; often used to coat steel to prevent corrosion.

3. Steel Construction Introduction

A. Advantages

• Combines high strength, stiffness, and elasticity

• 100x stronger than concrete in resisting tensile stresses

• Precise and predictable in performance

• Lightweight relative to strength

• Suitable for rapid construction of repetitive structures

B. Disadvantages

• Corrodes in certain environments

• Strength may decrease in severe fires

4. Brief History of Steel Construction

A. Early Use

• Ancient civilizations used wrought and cast iron for structural applications.

B. Industrial Revolution

• Bessemer Process (1850s) allowed for mass production of steel by removing impurities from iron ore.

C. Development of Structural Steel

• Gustave Eiffel's construction of the Eiffel Tower in 1889 demonstrated steel's potential in large structures.

• Cast and wrought iron used increasingly for framing in the 19th century, but with limitations.

• The introduction of the Bessemer process made inexpensive steel widely available.

D. Key Steelmaking Methods

1. Bessemer Process

   • Air blown into molten iron vessel to eliminate impurities.

2. Open-Hearth Method

   • Melting pig iron with scrap steel in large ovens for better quality steel.

E. Landmark Construction

• Skyscrapers developed with steel frame construction, exemplified by the Empire State Building.

5. Modern Applications of Steel

• Continues to be preferred for high-rise buildings and large projects.

  • Example: Home Insurance Company Building, first steel framed building (1895).

  • Ingalls Building: first reinforced concrete skyscraper (1903).

6. Properties of Steel

• Composition:

  • Alloy of iron with less than 2% carbon.

  • Strength and ductility determined by carbon content.

• Key Properties:

  1. Strength: High tensile strength; resistant to breaking under stress.

  2. Durability: Wear, degradation, and corrosion resistant.

  3. Versatility: Easily shaped and fabricated.

  4. Malleability: Can be shaped without breaking; ideal for manufacturing.

  5. Ductility: Significant deformation before rupturing.

  6. Weldability: Can be joined using various welding techniques for complex structures.

  7. Thermal Conductivity: Efficient heat transfer.

  8. Electrical Conductivity: Good, suitable for applications needing strength and durability.

  9. Recyclability: Can be melted and reused without losing properties.

• Carbon Steel:

  • Unalloyed steel with controlled residual elements; higher carbon = stronger, less ductile.

• Alloy Steel:

  • Carbon steel with added elements for specific properties.

• Weathering Steel:

  • High strength, low alloy; develops rust-like appearance for protection.

• Tungsten Steel:

  • Alloy with high tungsten content for added hardness.

• Stainless Steel:

  • Corrosion-resistant alloy containing at least 10.5% chromium.

• Galvanized Iron:

  • Iron/steel coated with zinc to prevent rust; zinc acts as a sacrificial layer.

7. Galvanization Methods

1. Hot-Dip Galvanization:

   • Steel immersed in molten zinc for thick coating.

2. Electro-Galvanization:

   • Thin zinc layer applied through electrolysis, less durable but smoother finish.

8. Process of Converting Iron Ore to Steel

A. Raw Materials

• Iron Ore, Limestone, Coal

B. Smelting Process

1. Blast Furnace:

   • For smelting iron from ore; combustion enhanced by air blast.

2. Coke:

   • Solid coal residue used as fuel.

3. Slag:

   • Remaining vitrified material after smelting.

4. Molten Iron:

   • Drawn off for processing into steel.

9. Steel Production Methods

• Basic Oxygen Process: Most common for converting iron to steel.

• Electric Arc Furnaces: For structural steel production from scrap.

10. Steel Shapes

1. W Shape:

   • Wide flange; used for beams and columns.

   • Ex: W8x18 (8 inches depth, 18 lbs/ft).

2. I-beam:

   • Less efficient than W-shape; known as S-shape.

   • Ex: S18x70 (I-beam shape, dimensions).

3. C-Shape:

   • Common type for building support.

4. L Shapes:

   • Versatile, for various structural applications.

5. HSS:

   • Hollow Structural Sections, in various shapes.

6. Structural Bars:

   • Used for railings, accents, and fences.

7. Zee Bar:

   • Used commonly for window frames, construction, and furniture.