Materials

• Work hardening: the material is worked under its recrystallisation temperature, atoms begin to slip as the metal deforms. This is further done through the dislocations in a material
• Work hardening process 


  Where easier/harder is related to the pressure

  
• It begins to get harder to deform the metal as dislocations get jammed up in grain boundaries and other dislocations
• The more compact a material's grain structure is, the more strength is has
• Heat treatment for steel includes,

  • Annealing
  • Process annealing
  • Normalising
  • Spheroidising
  • Tempering
• Stress strain diagram

  
• Iron is Bcc in room temperature, however, turns into FCC when heated and BCC again when heated more.
• When the grain structure of a material is more compact, it means that it is stronger.
• alpha iron - ferrite, means that it is pure iron, which is soft and ductile.
• Cementite is iron with >0.83% carbon content, making is brittle and hard.
• Eutectoid point: 0.83% carbon content in iron.
• Steel is constituent of mainly iron and carbon, however, it may be highly alloyed, or lightly alloyed to favor some properties.
• Pearlite: purely occurs at the eutectoid point.
• Wrought iron is iron which is forged from raw materials found, and has weak points of slag which are darker in colour under a miscroscope
• Grey Cast Iron contains graphite flakes, while White Cast Iron contains carbide inclusions.
• Cast Iron is iron with >2% carbon content
• Some low alloying materials of steel

  • Silicon
  • Nickel
  • Tungsten
  • Molybdenum
  • Vanadium
  • Copper
  • Boron
  • Manganese
  • Sulfide
  • Chromium
• Silicon


  • Good for high grade structural steel, similar enhacing properties to nickel
• Nickel


  • Toughness, temperature resistivity, at 15-20% good corrosion resistance
• Tungsten


  • Improves temperature stability
• Molybdenum


  • Hardenability and increased strength at 0.3%
• Vanadium


  • Elastic strength and temperature stability
• Copper


  • Corrosion resistance, sacrificing surface quality and hot working behavior
• Boron


  • Good for hardenability (at 0.001%-0.003%), effects reduce as carbon content increases
• Manganese


  • Increased hardenability, strengthens the ferrite phase
• Sulfide


  • Brittle, better machining properties
• Chromium


  • Improve wear resistance
• Cast irons:

  • Grey cast irons
  • White cast irons
  • High duty cast irons
  • Malleable cast irons
• Grey cats iron feature a high level of silicone content, thus, they can either be found as pearlitic or ferritic. This means that it has graphite flakes. The bigger the graphite flakes, the lesser cementite it will have. Such iron is good in compressive strength, however, bad in tensile strength
• The more graphite in Grey cast iron, the lesser the strength of the material
• Steel is used over iron due to higher tensile strength (and compressive strength, mainly tensile though)
• Cast irons are irons with carbon content >2%
• When a cast iron has silicon added, it becomes ferritic. The more the silicon, the lesser cementite properties
• White cast iron is hard and brittle, similar properties to cementite, due to its low silicon contents.
• White cast iron is good for sliding parts
• For high duty cast iron, magnesium or cerium is added (usually to grey cast iron) to ensure that the graphite is in spheroidal shape. This is done to increase strength, the new name is called spheroidal graphite.
• Types of steels (with carbon content):

  1. Dead mild - 0.05-0.15
  2. Mild - 0.15-0.30
  3. Medium - 0.30-0.60
  4. High - 0.60-0.90
  5. Tool - 0.90-1.4
• Pig iron is raw iron molted into blocks