Understanding Steel Alloys, Cast Iron, and Metal Properties

Steel Alloys and Carbon Content

Steel is an alloy of iron and carbon. Carbon steels are classified by their carbon content:

• Low Carbon Steels: 0.06% to 0.25% carbon (soft or sweet steels).
• Medium Carbon Steels: 0.25% to 0.50% carbon (semi-hard or semi-soft steels).
• High Carbon Steels: 0.50% to 1.67% carbon (hard or extra-hard steels).

Alloy Steels

Alloy steels contain less than 1% carbon and include additional chemical elements. Types include:

• Cobalt, chromium, sulfur, molybdenum, lead, silicon, vanadium, and tungsten steels.

Stainless Steel

Stainless steel offers high hardness and resistance to oxidation and wear. It is classified by its nickel and chromium content:

• Ferritic Stainless Steel: Contains between 10% and 18% chromium.
• Martensitic and Austenitic Stainless Steel.

Cast Iron

Cast iron is an alloy of iron and carbon with a carbon content between 1.67% and 6.67%.

Types of Cast Iron

• White Cast Iron: Carbon ratio of 1.7% to 2.5%, forming pearlite and cementite.
• Gray Cast Iron: 2.5% to 4% carbon.
• Malleable or Ferritic Cast Iron: Derived from white cast iron (1.67% to 2.5% carbon), treated to reduce hardness and fragility.

Non-Ferrous Metals

• Light Metals: Aluminum, magnesium, titanium, and their alloys.
• Heavy Metals: Copper, brass, bronze, zinc, tungsten, chromium, tin, lead, and anti-friction materials.
• Sintered Metals: High-performance materials.

Physical and Mechanical Properties of Metals

Physical Properties

• Dilatability: The property of increasing in volume when heated.
• Fusibility: The ability to change from a solid to a liquid state at a specific melting point.

Mechanical Properties

• Hardness: Resistance of a body to being penetrated or scratched by others.
• Elasticity: The ability of a metal to recover its original shape or volume after deforming forces are removed. The elastic limit is the maximum force applied before deformations become permanent.