Am 350 Stainless Steel

UNS S35000 is a chromium-nickel-molybdenum stainless steel which can be hardnened by precipitation hardening and martensitic transformation. It can be used for gas turbine compressor components such as discs, blades, rotors, and shafts. And can also be used for similar parts where high strength is required at room and intermediate temperatures. Depending upon the heat treatment it can have martensitic structure with strengths comparable to those of martensitic steels and austenitic structure for best formability. It usually contains about 5 - 10% delta ferrite.

Am 350 Stainless Steel has superior corrosion resistance compared to other quench-hardenable martensitic stainless steels. It provides good corrosion resistance in ordinary atmospheres and various other mild chemical conditions. In the equalized environment or double-aged is susceptible to intergranular corrosion due to the chromium carbides precipitation. When it is hardened by treatments employing sub-zero cooling, it is not subject to intergranular attack. The treatment for optinum stress-corrosion resistance of it is as follows: Heat to 1850-1950 °F, cool rapidly to room temperature, sub-zero cool 3 hours at -100 °F reheat to 1700-1750 °F about 90 minutes per inch of thickness, cool rapidly to room temperature, sub-zero cool 3 hours at -100 °F, then temper 3 hours at 1000 °F. The surfaces must be free of scale and foreign particles and finished parts should be passivated for optimum corrosion resistance. Alloy 350 can be hardened by either sub-zero cooling or tempering or double aging. Tempering and sub-zero cooling will result in higher strength than double aging. "Conditioning" of it by rapid cooling from 1710 °F +/-25 °F is required before the SCT treatment, and is not required, but is suggested before double aging. It is further recommended that following an anneal at 1850/1950 ° F, it can be cooled to -100 °F  for at least 3 hours before hardening.

After conditioning Am 350 Stainless Steel Pipe at 1710 °F +/-25 °F for 90 minutes per inch of thickness, alloy 350 is held for a minimum of 3 hours at -100 °F, then tempered at either 850 °F or 1000 °F for a minimum of 3 hours. The 850 °F temper produces the highest strengths and hardnesses,and the 1000 °F temper produces improved toughness and stress corrosion properties. UNS S35000 Sheet can be readily hot worked. It is worked from a maximum temperature of 2150 °F. The use of temperature above 2150 °F will cause an increase in the amount of ferrite. Finishing temperature should be in the range of 1700-1800 °F to prevent grain coarsening on subsequent heat treatment and promote homogenous precipitation of carbides. In the annealed condition, Alloy 350 Stainless Steel material is essentially austenitic and has forming characteristics similar to those of the AISI 300 series stainless steels. It has a higher rate of cold forming and work hardening and will cause martensite formation in proportion to the amount of deformation. If capacity is limited or deformation is severe, heating the material to 300 ° for above will minimize work hardening. In hardened atmosphere it has sufficient ductility for limited forming or straightening operations.

Alloy 350 Pipe & Tube machining requires the same pratices used for other stainless steels, such as rigid tool and work suports, slower speeds, positive cuts, absence of dwelling or glazing, and adequate coolant. In the annealed condition, it is gummy and soft and has high work-hardening rate. In the annealed condition consequent machining not recommended. And best machinability can be obtained in the over tempered and equalized condition. In this condition finishing operations can be performed if proper allowances are made for growth while subsequent hardening treatments. Finish machining should be done in the hardened condition, if extreme dimensional accuracy is necessary.