PPT METALS

• According to Chang (2010), the use and refinement of metals date back to early human history. Archaeologists discovered that first millennium humans in Sri Lanka used monsoon winds to run smelting furnaces for high-carbon steel.
• Ancient Tools

  
• Occurrence of Metals

  Metals - Mostly come from minerals

  Minerals - Naturally occurring substance with a range of chemical composition

  Ore - deposit that allows economical recovery of a desired metal

  Occurrence of Metals
• Metallurgy - Science of separating metals from their ores and alloys
• Alloy - Solid solution of two or more metals or with nonmetals
• Steps in Recovery of Metals

  1. Preparation of the Ore
  2. Production of Metals
• Gangue - Waste materials, usually made of clay and silicate
• Flotation - Method of separating gangue from minerals
• Ferromagnets - Metals strongly attracted to magnets
• Amalgam - Alloy of mercury with another metal
• Mercury - Forms amalgams with various metals used to extract them from ore
• 2. Production of Metals Because metals in their combined forms always have positive oxidation numbers, production of free metals is a reduction process
• Standard Reduction Potential Where the purity of a metal obtained from reduction depends on
• Standard Reduction Potential of Some Metals

  
• Pyrometallurgy

  Procedures carried out at high temperatures

  Involves most major metallurgical processes

  Reduction may be accomplished either chemically or electrolytically
• Chemical Reduction

  Using a more electropositive metal as a reducing agent to separate less electropositive metals from a compound

  
• Chemical Reduction

  Sometimes molecular hydrogen is used as a reducing agent, such as preparation of tungsten in lightbulbs

  
• Electrolytic Reduction

  is suitable for very electropositive metals, such as sodium, magnesium, and aluminum.
• Electrolytic Reduction

  The process is usually carried out on the

  anhydrous molten oxide or halide of the metal:

  
• The Metallurgy of Iron Iron exists in various minerals.

  Common ores include:

  -iron pyrite (FeS₂),

  -siderite (FeCO₃),

  -hematite (Fe₂O₃), and

  -magnetite (Fe₃O₄)
• hematite and magnetite are particularly suitable for the extraction of iron.
• The metallurgical processing of iron involves the chemical reduction of the minerals by carbon (in the form of coke) in a blast furnace.
• The oxygen gas reacts with the carbon in the coke to form mostly carbon monoxide and some carbon dioxide.
• These reactions are highly exothermic, and as the hot CO and CO₂ gases rise, they react with the iron oxides in different temperature zones.
• Key Steps

  
• The limestone decomposes in the furnace

  
• Calcium Oxide

  
• The mixture of calcium silicate and calcium aluminate that remains molten at the furnace temperature is known as slag.
• Pig iron is the initial product of iron extraction, characterized by high impurities.

  Composition:

  • Up to 5% Carbon
  • Impurities: Silicon, Phosphorus, Manganese, Sulfur
  • Carbon and Sulfur primarily sourced from coke
  • Characteristics:
  • -Granular and brittle
  • -Relatively low melting point (1180°C)
  • Due to its casting ability, often referred to as cast
  • iron.
• Steelmaking - Steel manufacturing is one of the most important

  metal industries.

  Annual Consumption in the U.S.: Exceeds 100 million tons.
• Steel

  • An alloy of iron containing 0.03 to 1.4% carbon.
  • Includes various other alloying elements.
  • Mechanical Properties:
  • Properties depend on chemical composition and heat treatment.

  Iron Production

  -Primarily a reduction Process

  Steel Production

  -An oxidation process
• Basic Oxygen Process

  • Most common method for steel production today.
  • High efficiency with a cycle time of about 20 minutes for each large-scale conversion.
• Molten iron from the blast furnace is poured into an upright cylindrical vessel.
• Pressurized oxygen gas is introduced via a water-cooled tube
• Basic Oxygen Process

  Impurities react with oxygen to form oxides.

  Oxides react with fluxes (e.g., CaO, SiO₂) to create slag.

  Output: Produces molten
• The type of flux chosen depends on the specific

  composition of the iron.

  If the main impurities are silicon and phosphorus, a

  basic flux such as CaO is added to the iron:

  
• If manganese is the main impurity, then an acidic flux such as SiO₂ is needed to form the slag:

  
• Basic Oxygen Process

  
• Basic Oxygen Process

  
• Tempering

  Heating steel to a specific temperature for a short

  period, followed by rapid cooling.

  Purpose:

  -To adjust the ratio of carbon present