UNS S35000 / SUS 633 Precipitation Hardening Stainless Steel Corrosion Resistance

UNS S35000 (AM 350, SUS 633) semi-products for high vacuum systems and variety of vales for oceaneering

1 PRODUCT

UNS S35000 (AM 350, SUS 633) semi-products for high vacuum systems and variety of vales for oceaneering.

UNS S35000 is available in product forms as plate, sheet, strip, pipe, tube, bar (round, flat, hexagon, square, shapes), wire (profile, round, flat, square), forgings, etc.

2 EQUIVALENT DESIGNATION

AM 350 (Type 633), AISI 350, Grade 350, SUS 633(JIS), ATI AM 350®, CarTech® 350 Alloy (Pyromet alloy 350)

3 APPLICATION

S35000 is generally used in applications under 1000 °F where a combination of strength and good corrosion resistance are required.

S35000 has been available for many years and has found application in a variety of aerospace applications and especially in edge welded bellows applications that require high strength. Non-aerospace applications include use in precision seals, in couplings for semiconductor processing equipment, and in high vacuum systems, bellows, industrial cutters, knives and a variety of vales and gas turbine compressor componets such as blades, discs, rotors and shafts, and similar parts where high strength was required at room and intermediate temperatures.

4 OVERVIEW

S35000 is a chromium-nickel-molybdenum precipitation hardening semi-austenitic stainless steel used for applications requiring high strength and excellent weldability along with corrosion resistance. It brings together the strength of heat treatable martensitic grades with the corrosion resistance of some of the chromium nickel austenitic grades.

S35000 precipitation hardening stainless steel may be formed in a soft austenitic condition and hardened to a high strength level by low temperature heat treatments. The low temperature allows minimum distortion compared to conventional quench and temper hardening processes.

5 CHEMICAL COMPOSITION (wt%):

6 PHYSICAL PROPERTY

Melting range: 2500-2550°F

Density:

Annealed: 7920 kg/m³(0.286 lb/in³)

Condition SCT 850: 7810 kg/m³(0.282 lb/in³)

Condition DA: 7670 kg/m³(0.277 lb/in³)

Thermal conductivity

Mean coefficient of thermal expansion

7 MECHANICAL PROPERTIES

Typical mechanical properties in annealed condition:

Ultimate Tensile Strength: 200 KSI max (1380 MPa max)

Yield Strength: (0.2% offset) 85 KSI max (585 MPa max)

Elongation:

8% min: gauges < 0.010 inches

12% min: gauges > 0.010 inches

Hardness: Rc 30 max

Typical mechanical properties in heat treated Typical 850°F

Ultimate Tensile Strength: 185 KSI min (1275 MPa min)

Yield Strength: (0.2% offset) 145 KSI min (1000 MPa min)

Elongation:

2% min: gauges 0.0005 - 0.0015 inches

4% min: > 0.0015 - 0.002 inches

6% min: > 0.002 - 0.010 inches

8% min: > 0.010 inches

Typical mechanical properties in heat treated Typical 1000°F

Ultimate Tensile Strength: 165 KSI min (1140 MPa min)

Yield Strength: (0.2% offset) 150 KSI min (1035 MPa min)

Elongation:

2% min: gauges 0.0005 -.0 0015 inches

4% min: WWS- 0.002 inches

6% min: > 0.002 - 0.010 inches

8% min: > 0.010 inches

8 CORROSION RESISTANCE

S35000 has corrosion resistance superior to that of other quench-hardenable martensitic stainless steels. It has shown good corrosion resistance in ordinary atmospheres and numerous other mild chemical environments. Material in the double-aged or equalized condition is susceptible to intergranular corrosion because of the precipitation of chromium carbides. When the alloy is hardened by treatments employing sub-zero cooling as in the following paragraph, it is not subject to intergranular attack.

The treatment for optimum stress-corrosion resistance of S35000 is as follows: Heat to 1850/1950°F (1010/1066°C), cool rapidly to room temperature, sub-zero cool 3 hours at -100°F (-73°C); reheat to 1700/1750°F (927/954°C) about 90 minutes per inch (25.4 mm) of thickness, cool rapidly to room temperature, sub-zero cool 3 hours at -100°F (-73°C), then temper 3 hours at 1000°F (538°C).

For optimum corrosion resistance, surfaces must be free of scale, lubricants, foreign particles, and coatings applied for drawing and heading. After fabrication of parts, cleaning and / or passivation should be considered.

9 HEAT TREATMENT

Annealing

Heat to 1850/1950°F (1010/1066°C), cool rapidly to room temperature.

Hardening

S35000 can be hardened by either sub-zero cooling and tempering (SCT) or double aging (DA). Sub-zero cooling and tempering will result in higher strength than double aging. "Conditioning" of the alloy by rapid cooling from 1710°F (932°C) ±25°F is required before the SCT treatment, and is not required but is recommended before double aging. It is further recommended that following an anneal at 1850/1950°F (1010/1066°C), S35000 be cooled to -100°F (-73°C) for at least 3 hours before hardening.

Double aging

Hold for 3 hours at 1350-1400°F (732-760°C), air cool to room temperature; heat to 825-875°F (440-468°C), hold 2-3 hours, air cool.

10 WORKING INSTRUCTION

Hot working

S35000 is readily hot worked. It is worked from a maximum temperature of 2150°F (1177°C). The use of temperatures above 2150°F (1177°C) will cause an increase in the amount of ferrite. Finishing temperature should be in the range of 1700-1800°F (927-982°C) to prevent grain coarsening on subsequent heat treatment and promote homogeneous precipitation of carbides.

Cold working

In the annealed condition, S35000 is essentially austenitic and has forming characteristics similar to those of the AISI 300 series stainless steels. It has a higher rate of work hardening and cold forming will cause martensite formation in proportion to the amount of deformation. If capacity is limited or deformation is severe, heating the material to 300°F (149°C) or above will minimize work hardening. In the hardened condition, S35000 has sufficient ductility for limited forming or straightening operations.

Machinability

Successfully machining S35000 requires the same practices used for other stainless steels, such as rigid tool and work supports, slower speeds, positive cuts, absence of dwelling or glazing, and adequate coolant. In the annealed condition, the alloy is soft and gummy and has a high work-hardening rate. Machining S35000 in the annealed condition is consequently not recommended. Best machinability is obtained in the equalized and over tempered condition. Finishing operations may be performed in this condition if proper allowances are made for growth during subsequent hardening treatments. If extreme dimensional accuracy is necessary, finish machining should be done in the hardened condition.

11 STANDARD SPECIFICATION

ASTM A693 / ASME SA693

Precipitation Hardening Stainless and Heat-Resisting Steel Plate Sheet and Strip

AMS 5548

Steel Corrosion and Heat-Resistant Sheet and Strip 16.5Cr - 4.5Ni - 2.9Mo - 0.10N 1850 to 1975 °F (1010 to 1079 °C) Annealed (UNS S35000)

AMS 5745

Steel, Corrosion and Heat-Resistant, Bars and Forgings 16.5Cr - 4.5Ni - 2.9Mo - 0.1 0N Equalized and Over-Tempered (UNS S35000)

MIL S-8840

12 COMPETITIVE ADVANTAGE

(1) More than 50 years experience of research and develop in high temperature alloy, corrosion resistance alloy, precision alloy, refractory alloy, rare metal and precious metal material and products.
(2) 6 state key laboratories and calibration center.
(3) Patented technologies.

(4) Ultra-purity smelting process: VIM + IG-ESR + VAR

(5) Excellent high performance.

13 BUSINESS TERM