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.