Iron+&+Steel+(ChatLog)

Iron & Steel

Iron:  a ductile, malleable, silver-white metallic element, scarcely known in a pure condition, but much used in its crude or impure carbon-containing forms for making tools, implements, machinery. Cast iron:  Is the first metal that could be substituted for traditional structural materials, was used in bridge building as early as 1779. Because cast iron has much more compressive than tensile strength it was largely replaced in the late 19th century by steel, which is more uniformly strong, elastic, and workable, and its high resistance in all stresses (tension, compression and bending) can be closely calculated. Steel:  Any of various modified forms ofiron, artificially produced, having acarbon content less than that of pig iron and more than that of wrought iron, and having qualities of hardness, elasticity, and strength varying according to composition and heat treatment. If the first industrial age was one of iron and steam, the second industrial age, which began in about 1880, could be called one of steel and electricity. Steel structural members are rolled in a variety of shapes, the commonest of which are plates, angles, I beams, and U-shaped channels. These members may be joined by steel bolts or rivets, and the development of welding in the 20th century made it possible to produced fused joints with less labor and material.

__Wood: __ Cost: Low Weight: Low Strengths: Cheap, lightweight, moderately strong in compression and tension. Weaknesses: rots, swells and burns easily. Applications: Bridges, houses, two-to three-story buildings, roller coasters

__Plastic: __ Cost: High Weight: Low <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: Flexible, lightweight, long-lasting, strong in compression and tension. <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: expensive. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Umbrellas, inflatable roofs over sports arenas.

__<span style="font-family: Tahoma,Geneva,sans-serif;">Aluminium: __ Cost:High <span style="font-family: Tahoma,Geneva,sans-serif;">Weight: Low <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: lightweight, doesn't rust, strong in compression and tension. <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Expensive. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Airplane wings, boats, cars, skyscraper "skin"

__<span style="font-family: Tahoma,Geneva,sans-serif;">Brick: __ Cost:Low <span style="font-family: Tahoma,Geneva,sans-serif;">Weight: Medium <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: Cheap, strong in compression <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Heavy, week in tension. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: walls of early skyscrapers and tunnels, domes

__<span style="font-family: Tahoma,Geneva,sans-serif;">Concrete: __ <span style="font-family: Tahoma,Geneva,sans-serif;">Cost:Low <span style="font-family: Tahoma,Geneva,sans-serif;">Weight: Medium <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: Cheap, fireproof and weatherproof, molds to any shape, strong in compression. <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Cracks with temperature changes, weak in tension. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Early arch bridges and domes

__<span style="font-family: Tahoma,Geneva,sans-serif;">Reinforced Concrete: __ Cost:Medium W<span style="font-family: Tahoma,Geneva,sans-serif;">eight: Medium <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: Low cost, fireproof and weatherproof, molds to any shape, strong in compression. <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Can crack as it cools and hardens. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Bridges, dams, domes, beams and columns in skyscrapers.

__<span style="font-family: Tahoma,Geneva,sans-serif;">Cast Iron: __ C<span style="font-family: Tahoma,Geneva,sans-serif;">ost:High <span style="font-family: Tahoma,Geneva,sans-serif;">Weight: Heavy <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: Molds to any shape, strong in compression. <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Weaker than steel in tension, breaks without warning. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Arch bridges, cannons, historic domes

__<span style="font-family: Tahoma,Geneva,sans-serif;">Steel: __ <span style="font-family: Tahoma,Geneva,sans-serif;">Cost:High <span style="font-family: Tahoma,Geneva,sans-serif;">Weight: Heavy <span style="font-family: Tahoma,Geneva,sans-serif;">Strengths: One of strongest materials used in construction, strong in compression and tension <span style="font-family: Tahoma,Geneva,sans-serif;">Weaknesses: Rusts, loses strength in extremely high temperatures. <span style="font-family: Tahoma,Geneva,sans-serif;">Applications: Cables in suspension bridges, trusses, beams and columns in skyscrapers, roller coasters

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<span style="font-family: Tahoma,Geneva,sans-serif;">Homework: <span style="font-family: Tahoma,Geneva,sans-serif;"> The materials that we used to construct our city are very important. We need to know how they act in different moments, for example when you **squeeze** a **brick** this will break. Those material need special care, for example **steel** lose the **strength** in extremely high temperatures and the **reinforced concrete** can **crack** as it cools and hardens. So is very important knowing where we can use these materials. <span style="background-color: #ffffff; color: #444444; display: block; font-family: 'Segoe UI','Lucida Grande',Arial; text-align: left; vertical-align: baseline;"> <span style="background-color: #ffffff; color: #444444; display: block; font-family: 'Segoe UI','Lucida Grande',Arial; text-align: left; vertical-align: baseline;">