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