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Alloy 321 1.4541 (UNS N32100) is a stabilized stainless steel pipe which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperature in the chromium carbide precipitation range from 800 to 1500°F (427 to 816°C). Alloy 321 stainless steel tubing is stabilized against chromium carbide formation by the addition of titanium.
Alloy 321 stainless steel tube is also advantageous for high temperature service because of its good mechanical properties. Alloy 321 stainless steel pipe offers higher creep and stress rupture properties than Alloy 304 and, particularly, Alloy 304L, which might also be considered for exposures where sensitization and intergranular corrosion are concerns.
321 is a titanium-stabilised version of 304, used in particular applications within the sensitizing temperature range. Its resistance to sensitization, coupled with its higher strength at high temperature makes it suitable in application where 304 will become sensitized, or where 304L has insufficient hot strength. It is not subject to weld decay intergranular corrosion when exposed to mildly corrosive environments. However, welded 321 must never be used in highly oxidising environments as it is liable to 'Knife-line' attack. However, 321 is a much better option in operating temperature environments in excess of 500° C and therefore has its own merits.
General Properties
Chemical Composition
Resistance to Corrosion
Physical Properties
Mechanical Properties
Heat Treatment
Fabrication
Elevated Temperature Oxidation Resistance
Oxidation Behavior of Type 321 Stainless Steel Tube
Physical Properties of 321/321H Alloys in the Annealed Condition at -20°F to +100°F
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Tensile Strength |
Yield Strength |
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| Alloy |
UNS |
Spec |
psi |
MPa |
ksi |
psi |
MPa |
ksi |
Elongation in 2 inches (min.) % |
Grain Size Req. |
Maximum Harndess |
Modulus of Elasticity (x106 psi) |
Mean Coefficient of Thermal Expansion (IN./IN./°F x 10-6) |
Thermal Conductivity (BTU-in/ft2-h-°F) |
| 321 |
S32100 |
— |
75,000 |
515 |
— |
30,000 |
205 |
— |
35 |
— |
— |
29.0 |
9.2 |
— |
| 321H |
S32109 |
— |
75,000 |
515 |
— |
30,000 |
205 |
— |
35 |
7 or coarser |
— |
29.0 |
9.2 |
— |
Composition 321/321H stainless steel tube
| Grade |
321 |
321H |
| UNS Designation |
S32100 |
S32109 |
| Carbon (C) Max. |
0.08 |
0.04–0.10 |
| Manganese (Mn) Max. |
2.00 |
2.00 |
| Phosphorous (P) Max. |
0.04 |
0.04 |
| Sulphur (S) Max. |
0.03 |
0.03 |
| Silicon (Si) Max. |
0.75 |
0.75 |
| Chromium (Cr) |
17.0–20.0 |
17.0–20.0 |
| Nickel (Ni) |
9.0–12.0 |
9.0–12.0 |
| Molybdenum (Mo) |
— |
— |
| Nitrogen (N) |
0.1 Max. |
0.1 Max. |
| Iron (Fe) |
Bal. |
Bal. |
| Other Elements |
Ti=5(C) to 0.70% |
Ti=4(C) to 0.60% |
321/321H Product Range
| Alloy |
UNS Designation |
Werkstoff NR. |
Specifications* |
| 321 |
S32100 |
1.4541 |
A269, A/SA249, A/SA312 |
| 321H |
S32109 |
— |
A/SA249, A/SA312 |
*Note: The specifications noted including ASTM, ASME, or other applicable authorities are correct at the time of publication. Other specifications may apply for use of these materials in different applications.
Typical Properties in the Annealed Condition
The properties quoted in this publication are typical of mill products. Unless otherwise indicated they should not be regarded as guaranteed minimum values for specification purposes.
1. Mechanical Properties at Room Temperature
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Typical |
Minimum |
| Tensile Strength, MPa |
580 |
515 |
| Proof Stress (0.2 % offset), MPa |
280 |
205 |
| Elongation (Percent in Lo = 5.65 So) |
60 |
40 |
| Hardness (Brinell) |
163 |
- |
| Endurance (fatigue) limit, MPa |
260 |
- |
2. Properties at Elevated Temperatures
Short Time Elevated Temperature Tensile Strength
| Temperature, oC |
600 |
650 |
700 |
750 |
800 |
850 |
| Tensile Strength, MPa |
390 |
329 |
280 |
230 |
190 |
140 |
Creep data
Stress to develop a creep rate of 1% in the indicated time at the indicated temperature.
| Time |
Temperature oC |
550 |
600 |
650 |
700 |
800 |
| 10 000 h |
Stress MPa |
180 |
100 |
70 |
40 |
10 |
| 100 000 h |
Stress MPa |
120 |
80 |
50 |
25 |
5 |
Creep Rupture Stress
| Time |
Temperature oC |
500 |
600 |
650 |
700 |
800 |
| 1 000 h |
Stress MPa |
270 |
180 |
140 |
70 |
30 |
| 10 000 h |
Stress MPa |
240 |
130 |
90 |
50 |
10 |
| 100 000 h |
Stress MPa |
200 |
90 |
50 |
15 |
5 |
Recommended Maximum Service Temperature
(Oxidising Conditions)
Continuous Service 950oC
Intermittent Service 870oC
Thermal Processing
1. Annealing Heat from 1050 to 1150oC and cool in air. This ensures maximum ductility of the steel.
2. Stress Relieving 321 can be stress-relief annealed within the sensitization temperature range
450-800oC without carbide precipitation occurring, thus avoiding the possibility of intergranular corrosion.
3. Hot working
Initial forging and pressing temperature: 1150 - 1250oC
Finishing temperature: 950oC
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