1 July 2022

Alloying Elements in Steel

Alloying Elements in Steel

Alloying Elements used in Steel

1.) Manganese (Mn)

  • combines with sulfur to prevent brittleness
  • >1%                       – increases hardenability
  • 11% to 14%

–increases hardness

–good ductility

–high strain hardening capacity

–excellent wear resistance

  • Ideal for impact resisting tools

Sulfur (S)

  • Imparts brittleness
  • Improves machineability
  • Okay if combined with Mn
  • Some free-machining steels contain 0.08% to 0.15% S
  • Examples of S alloys:  –11xx – sulfurized (free-cutting)

Nickel (Ni)

  • Provides strength, stability and toughness, Examples of Ni alloys:

–30xx – Nickel (0.70%), chromium (0.70%)

–31xx – Nickel (1.25%), chromium (0.60%)

–32xx – Nickel (1.75%), chromium (1.00%)

–33XX – Nickel (3.50%), chromium (1.50%)

Chromium (Cr)

  • Usually < 2%
  • increase hardenability and strength
  • Offers corrosion resistance by forming stable oxide surface
  • typically used in combination with Ni and Mo

–30XX – Nickel (0.70%), chromium (0.70%)

–5xxx – chromium alloys

–6xxx – chromium-vanadium alloys

–41xxx – chromium-molybdenum alloys

Molybdenum (Mo)

  • Usually < 0.3%
  • increase hardenability and strength
  • Mo-carbides help increase creep resistance at elevated temps  –typical application is hot working tools

Vanadium (V)

  • Usually 0.03% to 0.25%
  • increase strength  –without loss of ductility

Tungsten (W)

  • helps to form stable carbides
  • increases hot hardness   –used in tool steels

Copper (Cu)

  • 0.10% to 0.50%
  • increase corrosion resistance
  • Reduced surface quality and hot-working ability
  • used in low carbon sheet steel and structural steels

Silicon (Si)

  • About 2%
  • increase strength without loss of ductility
  • enhances magnetic properties

Boron (B)

  • for low carbon steels, can drastically increase hardenability
  • improves machinability and cold forming capacity

Aluminum (Al)

  • deoxidizer
  • 0.95% to 1.30%
  • produce Al-nitrides during nitriding

Corrosion Resistant Steel

  • Stainless Steels (Corrosion-Resistant Steels) – contain at least 10.5% Chromium –trade name
  • AISI assigns a 3 digit number

–200 and 300 … Austenitic Stainless Steel

–400 … Ferritic or Martensitic Stainless Steel

–500 … Martensitic Stainless Steel

 

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