ForMatter/Processes/treatment/Heat Treatment of Steel
proc_heat_treatment_steel

Heat Treatment of Steel

treatment · quench and temper, annealing, normalizing, case hardening, carburizing

Steel is heated, held, and cooled in controlled ways to change how hard or soft it is. Quench it fast for hardness, temper it for toughness, anneal it slow for softness. The reason a screwdriver can be hard at the tip and tough enough not to snap.

Thermal cycling that transforms steel's microstructure. Austenitize above the upper critical temperature (~723 °C+, alloy-dependent), then control cooling: rapid quench (water, oil, or polymer) → martensite (hard, brittle); slow cool → ferrite-pearlite (soft, ductile). Temper martensite at 150–650 °C to trade hardness for toughness. Case hardening (carburizing, nitriding) hardens only the surface layer.

Scale & Tolerance

  • scale (mm)1 – 5000
  • tolerance (mm)0.1
  • skillintermediate to advanced — chemistry- and grade-specific recipes
  • costmoderate per batch; capital cost moderate to high

Equipment

  • school_shopyes — torch-heat for spot work; small kilns and quench tanks for instructional pieces
  • professionalsalt-bath, atmosphere, and vacuum furnaces
  • industrialcontinuous belt furnaces, induction-hardening cells

Environmental

  • energy_usehigh (furnace heat)
  • waste_streamspent quench oil (regulated), salt-bath salts, scale
  • consumablesquench oil, atmosphere gas, salts

Citations