#carbon_steel  steel whose characteristics are determined by the amount of carbon it contains
  supertype:  #steel  an alloy of iron with small amounts of carbon; widely used in construction; mechanical properties can be varied over a wide range
  subtype:  #drill_steel__drillsteel__drill_rod__drillrod  carbon steel used for rock drills and dowels
  subtype:  #eutectoid_steel__eutectoidsteel  a steel that contains 0.9% carbon (the eutectic point in the iron-carbon system); a carbon steel with 0.9% carbon is pure pearlite
  subtype:  #hyper-eutectoid_steel__hypereutectoidsteel  a steel that contains more than 0.9% carbon
  subtype:  #hypo-eutectoid_steel  a steel that contains less that 0.9% carbon

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