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* Steels & Properties
* Heat Treatment


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TYPICAL VACUUM HEAT TREATMENT PROCESSES

Processes available for vacuum heat treatment

  • Gas or oil quenching - normal hardening
  • Carburising / nitrocarburising - case hardening
  • Stabilization, normalizing, stress-relieving
  • Bright annealing / tempering - stainless steels, molds, maraging steels
  • Structural hardening of superalloys & Beryllium copper alloys
  • Hardening of martensitic stainless steels
  • Regeneration, out-gassing, solutionising of Titanium & its alloys
  • Solutionising and aging of magnesium alloys
  • Magnetic annealing of magnetic materials, e.g. FeNi, Permalloy
  • Bright aging / precipitation hardening - Beryllium copper
  • Brazing - copper, silver, nickel, carbide, etc.
  • Sintering

A typical hardening procedure for SS 304

  •  Pump down to 1 micron or less
  •  Heat at a rate of 17ºC (30ºF)/ min. to 650ºC (1200ºF)
  •  Hold at temperature for 15 min.
  •  Heat at a rate of 17ºC (30ºF)/ min. to 870ºC (1600ºF)
  •  Hold temperature for 15 min.
  •  Heat at a rate of 17ºC (30ºF)/ min. to 1050ºC (1975ºF)
  •  Hold at temperature for 1 h
  • Force-cool to 65ºC (150ºF)

A typical hardening procedure for air-hardening tool steels

  •  Pump down to 1 micron or less
  •  Heat at a rate of 20ºC (35ºF)/ min. to 650ºC (1200ºF)
  •  Hold at temperature for 45 min.
  •  Heat at a rate of 20ºC (35ºF)/ min. to 815ºC (1500ºF)
  •  Hold at temperature for 30 min.
  •  Heat at a rate of 20ºC (35ºF)/ min. to 1030ºC (1880ºF)
  • Hold at  temperature for 1 h
  • Force cool to 65ºC (150ºF)

A typical annealing procedure for steels

  • Pump down to 1 micron or less
  • Heat at a rate of 17ºC (30ºF)/ min. to 650ºC (1200ºF)
  • Hold at temperature for 30 min.
  • Heat at a rate of 17ºC (30ºF)/ min. to 870ºC (1600ºF)
  • Hold at temperature for 30 min.
  • Heat at a rate of 11ºC (20ºF)/ min. to 1150ºC (2100ºF)
  • Hold at temperature for 1 h.
  • Vacuum cool to 870ºC (1600ºF) at a rate of 22ºC (40ºF)/ h
  • Backfill with argon and force-cool to 65ºC (150ºF)

A typical brazing procedure for Ni-based brazing filler alloys

  • Pump down to 1 micron or less
  • Heat at a rate of 17ºC (30ºF)/ min. to 650ºC (1200ºF)
  • Hold at temperature for 20 min.
  • Heat at a rate of 17ºC (30ºF)/ min. to 845ºC (1550ºF)
  • Hold at temperature for 30 min.
  • Heat at a rate of 11ºC (20ºF)/ min. to 1085ºC (1985ºF)
  • Hold at temperature for 15 min.
  • Force cool to 65ºC (150ºF)

A typical hardening procedure for M2 steels

  • Load the work into a cold furnace, in baskets or fixtures, and position the workload thermocouples
  • Pump down chamber to 1 micron or less. (If the furnace is not diffusion-pump-equipped, pressure will be 10 to 20 microns)
  • Heat to 780 to 845ºC (1450 to 1550ºF) at the rate of 17ºC (30ºF)/ min., which allows the material to heat slowly through transition
  • Hold at temperature for 10 to 15 min. (Add 5 min. for every inch over 3 in. of cross section)
  • Heat to 1095ºC (2000ºF) at the rate of 17ºC (30ºF)/ min.
  • Hold temperature for 10 to 15 min.
  • Heat to 1205ºC (2200ºF) at the rate of 17ºC (30ºF)/ min.
  • Hold at temperature for 5 mins.
  • Rapidly backfill chamber with the quenching gas and circulate from the hot zone to heat exchanger
  • Cool to 120ºC (250ºF), as indicated by workload thermocouples
  • Equalize furnace pressure and room pressure and remove load.
 
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