Fe, <0.08% C, 17-19% Cr, 9-12% Ni, <2% Mn, <1% Si, 0.3-0.7% Ti, <0.045% P, <0.03% S
Grade 321 and 347 include the basic austenitic 18/8 steel (Grade 304) stabilised by Titanium (321) or Niobium (347) additions. These grades are widely-used because they are not responsive to intergranular corrosion after heating inside the carbide precipitation selection of 425-850°C. Grade 321 is the products selection for applications from the temperature range up to about 900°C, combining high strength, resistance to scaling and phase stability with effectiveness against subsequent aqueous corrosion.
Grade 347 is merely occasionally utilized as parent plate material.
These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.
Typical compositional ranges for grade 321 stainless steel is given in table 1.
Table 1. Composition ranges for 321 grade stainless steel
Typical mechanical properties for grade 321 stainless steels are given in table 2.
Table 2. Mechanical properties of 321 grade stainless steel
Typical physical properties for annealed grade 321 stainless steels are given in table 3.
Table 3. Physical properties of 321 grade stainless steel in the annealed condition
Grade Specification Comparison
Approximate grade comparisons for 321 stainless steels are given in table 4.
Table 4. Grade specifications for 321 grade stainless steel
Possible Alternative Grades
Possible alternative grades to grade 321 stainless steels are given in table 5.
Table 5. Possible alternative grades to 321 grade stainless steel
Equivalent to Grade 304 in the annealed condition, and superior if a weldment in these grades has not been post-weld annealed or if the application involves service in the 425-900°C range. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C.
Good oxidation resistance in intermittent service to 900°C and in continuous service to 925°C.
These grades perform well in the 425-900°C range, and particularly where subsequent aqueous corrosive conditions are present. 321H has higher hot strength, and is particularly suitable for high temperature structural applications.
Solution Treatment (Annealing) - heat to 950-1120°C and cool rapidly for maximum corrosion resistance.
Stabilising - heat to 870-900°C for 1 hour per 25mm of thickness and air cool. Stabilisation is recommended for most severe service conditions (above 425°C) and particularly for material annealed at the upper side of the annealing temperature range.
Stress Relief - Heat to 700°C for 1 to 2 hours and air cool.
These grades cannot be hardened by thermal treatment.
Excellent weldability by all standard fusion methods, both with and without filler metals.
AS 1554.6 pre-qualifies welding of 321 and 347 with Grade 347 rods or electrodes; high silicon version of 347 is also pre-qualified for welding of 321.
Typical applications include:
• Aircraft exhaust manifolds
• Expansion joints
• Furnace parts
• Heating element tubing
• Heat Exchangers
• Woven or welded screens for high temperature mineral processing
• Stainless steel 321 blind flange for Natural gas and Oil pipeline
Tel No：+86-18267732328 / Email:[email protected]
Address：Longwan District, Wenzhou, Zhejiang Province, China.
Copyright Notice © www.yaang.com Yaang Pipe Industry Co., Limited All rights reserved.
Yaang Pipe Industry Co., Ltd. is an international supplier of piping solutions for flange, butt welding fittings, socket welding fittings and threaded fittings. Our products are widely used in different industrial fields, including oil and gas, chemical industry, petrochemical industry, power plant, pulp and paper industry, environmental and water conservancy engineering, engineering projects, etc.