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
|
Density (kg/m3)
|
Elastic Modulus (GPa)
|
Mean Coefficient of Thermal Expansion (μm/m/°C)
|
Thermal Conductivity (W/m.K)
|
Specific Heat 0-100°C (J/kg.K)
|
Electrical Resistivity (nΩ.m)
|
0-100°C
|
0-315°C
|
0-538°C
|
at 100°C
|
at 500°C
|
321
|
8027
|
193
|
16.6
|
17.2
|
18.6
|
16.1
|
22.2
|
500
|
720
|
Grade Specification Comparison
Approximate grade comparisons for 321 stainless steels are given in table 4.
Table 4. Grade specifications for 321 grade stainless steel
Grade
|
UNS No
|
Old British
|
Euro norm
|
Gb
|
Japanese JIS
|
BS
|
En
|
No
|
Name
|
321
|
S32100
|
321S31
|
58B, 58C
|
1.4541
|
X6CrNiTi18-10
|
0Cr18Ni11Ti
|
SUS 321
|
321H
|
S32109
|
321S51
|
-
|
1.4878
|
X10CrNiTi18-10
|
1Cr18Ni9Ti
|
SUS 321H
|
347
|
S34700
|
347S31
|
58G
|
1.4550
|
X6CrNiNb18-10
|
1Cr18Ni11Nb
|
SUS 347
|
These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.
|
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
Grade
|
Why it might be chosen instead of 321
|
304L
|
The requirement is for resistance to intergranular corrosion, not for high temperature strength
|
3CR12
|
Only mild "high temperature" environment is present… up to about 600°C.
|
304H
|
Only mild "high temperature" environment is present… up to about 800°C.
|
310
|
The temperature of the operating environment is up to about 1100°C - too high for 321 or 321H.
|
S30815
(253MA)
|
The temperature of the operating environment is up to about 1150°C- too high for 321 or 321H.
|
Corrosion Resistance
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.
Heat Resistance
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.
Heat Treatment
Solution Treatment (Annealing) - heat to 950-1120°C and cool rapidly for maximum corrosion resistance.
Stabilizing - heat to 870-900°C for 1 hour per 25mm of thickness and air cool. Stabilization 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.
Welding
Excellent weld ability 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.