Week 2: Properties and Uses of Metals in Ship Construction

  • 1. Elements and materials used in ship construction

    • Basic ship construction materials are similar to other construction projects and include iron, steel, aluminium, plastics, and related materials.

    • An element defined: the simplest form of matter that cannot be split into simpler substances by ordinary chemical or physical methods.

    • Element counts:

      • There are 118118 known elements.

      • Of these, 9292 are naturally occurring; the rest are artificially prepared.

    • Elements are classified based on properties into:

      • metals

      • non-metals

      • metalloids

      • Classification correlates with their placement in the periodic table.

    • Table 7.6.17.6.1: Characteristic properties of metallic and non-metallic elements

      • Metallic Elements:

      • Distinguishing luster (shine)

      • Malleable and ductile (as solids)

      • Conduct heat and electricity

      • Form cations in aqueous solution

      • Metallic oxides are basic, ionic

      • Nonmetallic Elements:

      • Non-lustrous, various colors

      • Nonmetallic oxides are acidic, covalent

      • Do not form cations in aqueous solution

    • Metals (with the exception of hydrogen) are elements that form positive ions by losing electrons during chemical reactions; they are electropositive with relatively low ionization energies.

    • General metallic characteristics include bright luster, hardness, ability to resonate sound, and excellent conduction of heat and electricity.

    • Metals are solids under normal conditions except for mercury (Hg).

    • Physical properties overview for metals:

      • Lustrous, malleable, ductile, good conductors of heat and electricity.

      • State at room temperature: typically solids; mercury is liquid at room temperature; gallium is liquid on hot days.

      • Luster: reflective and polishable surfaces (e.g., gold, silver, copper).

2. Mechanical properties and behavior of metals

  • Malleability:

    • Metals can be hammered into thin sheets (foils).

    • Related to the ability to plastically deform without cracking; malleability generally increases with temperature.

    • Hot working (e.g., forging, extrusion) leverages higher malleability to form complex ship components.

    • Example: a sugar-cube–sized piece of gold can be hammered into a sheet large enough to cover a football field.

  • Ductility:

    • The ability of a material to undergo plastic deformation under tensile stress before fracture.

    • Temperature dependence: generally, ductility decreases with rising temperature in some materials (note: in many metals ductility increases with temperature; the transcript notes a trend opposite to malleability, but the practical ship context often uses ductility at controlled temperatures).

    • Gold is extremely ductile; for ship construction, ductile materials such as tin, zinc, lead, copper, etc., are common.

    • Notch ductility: a related measure of toughness under localized stress concentrations; connected to the impact toughness of steel via impact testing.

    • Metals can be drawn into wires; example: 100extg100 ext{ g} of silver can be drawn into a thin wire about 200extm200 ext{ m} long.

  • Hardness:

    • Hardness describes resistance to plastic deformation, indentation, penetration, and scratching.

    • In engineering, steel hardness relates to surface wear resistance against friction from oil, steam, and water; higher hardness generally increases wear resistance but can hinder cutting/machining.

    • No single property defines hardness; several empirical hardness tests exist for steels.

  • Toughness and brittleness:

    • Toughness: a material’s ability to bend or deform through cycles without fracturing; requires many bending cycles before failure.

    • Brittleness: a material that fractures with little to no plastic deformation under bending or impact.

  • Valency:

    • Valency is the combining capacity of metals; it is the number of electrons a metal can lose to achieve a noble gas configuration.

    • Expression: the valency corresponds to the electrons lost to reach a stable electron arrangement.

  • Conduction (thermal and electrical):

    • Metals are good conductors of heat due to free electrons; non-metals and gases are typically poor conductors (insulators).

    • Free electrons enable efficient heat transfer; notable conductors are silver and copper (best for heat and electricity).

    • Poor conductors include lead; bismuth, mercury, and iron are also comparatively poorer conductors.

  • Density:

    • Metals generally have high densities; they are heavy.

    • Among elements, iridium and osmium have the highest densities; lithium has one of the lowest.

  • Melting and boiling points:

    • Metals typically have high melting and boiling points.

    • Tungsten has the highest melting and boiling points among common metals.

    • Mercury has the lowest melting point among the metals; sodium and potassium have low melting points as well.

3. Key definitions and implications for ship construction

  • Elemental definitions and properties:

    • An element is the simplest form of matter that cannot be split into simpler substances by ordinary chemical or physical methods.

    • Metals form positive ions by losing electrons; they are electropositive and have relatively low ionization energies.

  • Metal-oxide behavior:

    • Metallic oxides are basic and ionic; nonmetallic oxides are acidic and covalent.

  • Practical material selection considerations for ships:

    • Weight vs strength: high density materials add structural strength but increase weight.

    • Corrosion resistance: many ship components require corrosion resistance in seawater; steel is often protected with coatings, alloys, or sacrificial anodes.

    • Machinability: hardness affects ease of machining and fabrication on shipyards.

    • Thermal performance: high thermal conductivity aids heat dissipation in engines but may require insulation elsewhere.

    • Cost and availability: select metals that balance performance with cost and supply security.

  • Examples and memorable anecdotes:

    • Gold’s ductility: a practical showcase of extreme ductility by hammering a small gold block into an extensive sheet.

    • A 100 g piece of silver drawn into ~200 m of wire demonstrates substantial ductility and workability of metals.

4. Connections to shipbuilding fundamentals and real-world relevance

  • Materials commonality: iron, steel, aluminium, and plastics are widely used across ship structures, hulls, and components due to a balance of strength, weight, durability, and cost.

  • Material behavior under service conditions:

    • Interfaces with corrosion science, wear resistance, fatigue, and fracture mechanics in marine environments.

    • Temperature effects on malleability and ductility influence forming processes during fabrication and repair (e.g., forging, extrusion, welding strategies).

  • Cross-referencing core principles:

    • The electropositive nature of metals ties to electron transfer behavior in corrosion (anodic/cathodic processes) and galvanic corrosion considerations on ships.

    • Conduction properties underpin heat management in engines and heat exchangers, as well as electrical grounding and shielding strategies.

  • Practical engineering implications:

    • Hardness and toughness balance for structural components subject to impact and wear (e.g., propeller shafts, hull plating, fasteners).

    • Notch toughness and impact testing inform safe design against accidental loads and fatigue in cyclic sea stresses.

5. Etymology, ethics, and practical implications in marine contexts

  • Ethical and practical considerations include sustainable material sourcing, recycling of metals, and minimizing environmental impact from mining and processing.

  • Practical implications:

    • Material choice affects ship damage resilience, maintenance frequency, repair time, and overall lifecycle cost.

    • Corrosion protection strategies (coatings, cathodic protection) are essential for longevity in seawater.

    • Material compatibility and repairability influence maintenance planning for aging fleets.

6. Quick reference to notable numerical facts and concepts

  • Element count and natural occurrence:

    • Number of known elements: 118118

    • Naturally occurring elements: 9292

  • Examples illustrating properties:

    • Gold: extremely ductile; malleable; bright luster; excellent conductor.

    • Silver: among the best electrical and thermal conductors.

    • Copper: excellent conductor; widely used in electrical wiring and heat exchangers.

    • Tungsten: highest known melting/boiling point among common metals.

    • Mercury: unique as liquid at room temperature.

    • Sodium and potassium: low melting points (and reactivity) compared to many other metals.

  • Illustrative measures:

    • Drawability example: 100extg100 ext{ g} of silver can be drawn into a wire of length ≈ 200extm200 ext{ m}.

7. References cited in the material

  • Reference: https://chem.libretexts.org/Bookshelves/General_Chemistry/

  • Reference: https://www.brighthubengineering.com/naval-architecture/29400-mechanical-material-properties- required-in-ship-construction/