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Steel

Steel is an alloy of iron and carbon

  • high elastic modulus, yield strength, fracture strength
  • carbon content of steel is between 0.02% and 2.14% by weight

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The ductility and elongation of the pure iron state decrease upon the addition of carbon

Steel Grades

SAE steel grades system is a standard alloy numbering system

  • Formerly, Society of Automotive Engineers

Major classifications of steel

SAE Designation Steel Type
1xxx Carbon steels
2xxx Nickel steels
3xxx Nickel-chromium steels
4xxx Molybdenum steels
5xxx Chromium steels
6xxx Chromium-vanadium steels
7xxx Tungsten steels
8xxx Nickel-chromium-molybdenum steels
9xxx Silicon-manganese steels

Cast Iron

  • higher than 2.1% carbon content are known as cast iron
  • cast iron is not malleable even when hot
  • can be formed by casting as it has a lower melting point than steel

Wrought iron

  • iron alloy with a very low carbon content (less than 0.05%)
  • 1008 hot rolled strip steel usually used to form wrought products
    • low-carbon, non-alloy steel
    • standard shapes of metal, such as sheets, rods, plates, and bars that are later worked into a unique form
    • high thermal conductivity
    • low-carbon steel that yields excellent weldability
    • low electrical conductivity
    • low tensile strength
    • High ductility makes AISI 1008 steel great for screw machining

Carbon Steel (mild steel)

  • carbon content from about 0.05 up to 2.1 percent by weight.

Mild Steel

  • contains approximately 0.05–0.30% carbon
    • most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications
    • making it malleable and ductile
    • relatively low tensile strength, but it is cheap and easy to form
  • surface hardness can be increased with carburization
  • the density of mild steel is approximately 7.85 g/cm3 (7,850 kg/m3; 0.284 lb/cu in)
  • the Young's modulus is 200 GPa (29×106 psi)

Stainless steels

  • typically contain 18% chromium
  • exhibit improved corrosion and oxidation resistance

Alloys

Common alloying elements include:

  • manganese
  • nickel
  • chromium
  • molybdenum
  • boron
  • titanium
  • vanadium
  • tungsten
  • cobalt
  • niobium

Additional elements, most frequently considered undesirable:

  • phosphorus
  • sulphur
  • silicon
  • traces of oxygen, nitrogen, and copper

Citations

  • https://en.wikipedia.org/wiki/Steel