Comparison of Stainless Steel 321 and 321H Pipe Fittings
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Comparison of Stainless Steel 321 and 321H Fasteners
Both 321 and 321H stainless steel fasteners are titanium-stabilized austenitic stainless steels suitable for high-temperature environments, but the main difference lies in their carbon content: 321H has a higher carbon content (0.04-0.10%) than 321 (≤0.08%), which allows 321H to exhibit superior creep strength and high-temperature strength at temperatures above 1000°F (537°C) due to the formation of more stable carbides. Both also possess excellent weldability and corrosion resistance. Therefore, 321H is ideal for applications requiring higher temperature resistance, where 321 may not be sufficient.
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Gnee Steel is a renowned manufacturer of stainless steel 321 and 321H fasteners. We offer a comprehensive range of fastener products, covering almost all types and specifications. We conduct rigorous quality inspections on every piece of raw material to ensure the superior quality of our final products. We consistently adhere to international standards and quality specifications. Furthermore, we provide our customers with fast delivery services.
Due to their superior performance and impressive specifications, 321 and 321H stainless steel fasteners are in high demand. 321 stainless steel fasteners contain stabilizing titanium elements and belong to the austenitic stainless steel family. 321H alloy fasteners exhibit excellent intergranular corrosion resistance in environments exposed to chloride carbide precipitation, within a temperature range of 427°C to 816°C. They also easily resist general corrosion.
Stainless Steel 321/321H Chemical Composition
| Grade | C | Si | Ni | Mn | P | Cr | S | N | Ti |
|---|---|---|---|---|---|---|---|---|---|
| SS 321 | 0.08 max | 1.0 max | 9.00 – 12.00 | 2.0 max | 0.045 max | 17.00 – 19.00 | 0.030 max | 0.10 max | 5(C+N) – 0.70 max |
| SS 321H | 0.04-0.10 | 1 | 9-12 | 2 | 0.045 | 17-19 | 0.03 | 0.35 |
SS 321/321H Mechanical Properties
| Grade | Yield Strength 0.2% Proof (MPa) min | Tensile Strength (MPa) min | Elongation (% in 50 mm) min | Hardness | |
|---|---|---|---|---|---|
| Brinell (HB) max | Rockwell B (HR B) max | ||||
| 321 | 205 | 515 | 40 | 217 | 95 |
| 321H | 205 | 515 | 40 | 217 | 95 |
Stainless Steel 321/321H Equivalent Grades
| Grade | UNS No | Euronorm | British | Japanese JIS | Swedish SS | ||
|---|---|---|---|---|---|---|---|
| WNR | Name | BS | En | ||||
| 321 | S32100 | 1.4541 | X6CrNiTi18-10 | 321S31 | 58B, 58C | SUS 321 | 2337 |
| 321H | S32109 | 1.4878 | X10CrNiTi18-10 | 321S51 | – | SUS 321H | – |
Stainless Steel 321 vs 321H
| Property | Stainless Steel 321 | Stainless Steel 321H |
|---|---|---|
| Chemical Composition |
Carbon: ≤0.08% Chromium: 17-19% Nickel: 9-12% |
Carbon: 0.04-0.10% Chromium: 17-19% Nickel: 9-12% |
| Temperature range |
Up to 1000°F (540°C) |
Up to 1500°F (815°C) |
| Corrosion Resistance |
Good |
Improved in high-temperature environments |
| Heat Resistance |
Good |
Better |
| Strength |
Moderate |
Higher |
| Yield Strength |
207 MPa |
207-241 MPa |
| Tensile Strength |
517 MPa |
517-586 MPa |
| Welding |
Good |
Excellent |
| Applications |
General, chemical processing |
High-temperature applications |
SUS 321 Hex Bolt Size Chart
| Nominal size(D) | m10 | m14 | m12 | m16 | m24 | m20 | m30 | m42 | m48 | m36 | m56 | m72 | m64 | m90 | m80 | m100 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Body dia | D (MIN) | 9.78 | 13.73 | 11.73 | 15.73 | 23.67 | 19.67 | 29.67 | 41.38 | 47.38 | 35.61 | 55.26 | 71.26 | 63.26 | 89.13 | 79.26 | 99.13 |
| D (MAX) | 10 | 14 | 12 | 16 | 24 | 20 | 30 | 42 | 48 | 36 | 56 | 72 | 64 | 90 | 80 | 90 | |
| Head thickness | H (MIN) | 6.17 | 8.51 | 4.24 | 9.68 | 14.56 | 12.12 | 17.92 | 25.03 | 28.93 | 21.63 | 33.8 | 43.55 | 38.68 | 54.26 | 48.42 | 60.1 |
| H (MAX) | 6.63 | 9.09 | 7.76 | 10.32 | 15.44 | 12.88 | 19.48 | 26.97 | 31.07 | 23.38 | 36.2 | 46.45 | 41.32 | 57.74 | 51.58 | 63.9 | |
| Across the flats | F (MIN) | 15.73 | 20.67 | 17.73 | 23.67 | 35 | 29.16 | 45 | 62.9 | 72.6 | 53.8 | 82.2 | 101.4 | 91.8 | 125.5 | 111 | 140 |
| F (MAX) | 17 | 22 | 19 | 24 | 36 | 30 | 46 | 65 | 75 | 55 | 85 | 105 | 95 | 130 | 115 | 145 | |
| Across corners | C (MIN) | 17.77 | 23.35 | 20.03 | 26.75 | 39.55 | 32.95 | 50.85 | 71.71 | 82.76 | 60.79 | 93.71 | 115.6 | 104.65 | 143.07 | 126.54 | 159.6 |
| C (MAX) | 18.48 | 24.25 | 20.78 | 27.71 | 41.57 | 34.64 | 53.12 | 75.06 | 86.6 | 63.51 | 98.15 | 121.24 | 109.7 | 150.11 | 132.72 | 167.43 |
Stainless Steel 321H Threaded Rod Size Chart
| Dia (in) | 5/16 | 01/4 | 03/8 | 01/2 | 7/16 | 01/2 | 07/8 | 05/8 | 9/16 | 03/4 | 03/4 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| TPI (in) | 18 | 20 | 16 | 13 | 14 | 13 | 9 | 10 | 18 | 10 | 10 |
| Length (ft) | 6 | 3 | 10 | 3 | 12 | 10 | 12 | 12 | 3 | 3 | 6 |
| Dia (in) | 1 | 07/8 | 1 1/8 | 1 3/8 | 1 1/4 | 1 1/2 | 12 | 2 | 1 3/4 | 6 | |
| TPI (in) | 8 | 14 | 7 | 6 | 7 | 6 | 24 | 4.5 | 5 | 32 | |
| Length (ft) | 6 | 3 | 10 | 3 | 6 | 10 | 3 | 12 | 6 | 3 |
Inox 321 Stud Bolt Dimensions
| Nominal size dia D(inch) | 5/16 | 01/4 | 03/8 | 01/2 | 7/16 | 9/16 | 03/4 | 05/8 | 07/8 | 1 1/8 | 1 | 1 3/8 | 1 1/4 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tap end full thread length BM | Min. | 0.469 | 0.375 | 0.563 | 0.75 | 0.656 | 0.844 | 1.1.25 | 0.938 | 1.313 | 1.688 | 1.5 | 2.063 | 1.875 | |
| Max. | 0.44 | 0.35 | 0.532 | 0.708 | 0.62 | 0.802 | 1.075 | 0.892 | 1.258 | 1.625 | 1.438 | 2 | 1.813 | ||
| UNC & NC-5 | Thread | 0.498 | 0.4 | 0.594 | 0.792 | 0.692 | 0.896 | 1.175 | 0.983 | 1.368 | 1.75 | 1.562 | 2.125 | 1.938 | |
| Umax = 2P | UNF Thread | 0.111 | 0.1 | 0.125 | 0.154 | 0.143 | 0.167 | 0.2 | 0.182 | 0.222 | 0.286 | 0.25 | 0.333 | 0.286 | |
| 8UN Thread | 0.083 | 0.071 | 0.083 | 0.1 | 0.1 | 0.111 | 0.125 | 0.111 | 0.143 | 0.167 | 0.167 | 0.167 | 0.167 | ||
| L ≤ 10 | – | – | – | – | – | – | – | – | – | 0.25 | – | 0.25 | 0.25 | ||
| Minimum Nut End full Thread B min | 10 < L ≤ 16 | 0.875 | 0.75 | 1 | 1.25 | 1.125 | 1.375 | 1.75 | 1.5 | 2 | 2.5 | 2.25 | 3 | 2.75 | |
| L > 16 | 1.125 | 1 | 1.25 | 1.5 | 1.375 | 1.625 | 2 | 1.75 | 2.25 | 2.75 | 2.5 | 3.25 | 3 | ||
| 1.625 | 1.5 | 1.75 | 2 | 1.875 | 2.125 | 2.5 | 2.25 | 2.75 | 3.25 | 3 | 3.75 | 3.5 | |||
| Nominal size dia D(inch) | 1 5/8 | 1 1/2 | 1 3/4 | 2 | 1 7/8 | 2 1/4 | 2 3/4 | 2 1/2 | 3 | 3 1/2 | 3 1/4 | 4 | 3 3/4 | ||
| Tap end full thread length BM | Min. | 2.438 | 2.25 | 2.625 | 3 | 2.813 | 3.375 | 4.125 | 3.75 | 4.5 | 5.25 | 4.875 | 6 | 5.625 | |
| Max. | 2.375 | 2.188 | 2.563 | 2.925 | 2.75 | 3.3 | 4.05 | 3.675 | 4.425 | 5.15 | 4.775 | 5.9 | 5.525 | ||
| UNC & NC-5 | Thread | 2.5 | 2.313 | 2.688 | 3.075 | 2.875 | 3.45 | 4.2 | 3.825 | 4.575 | 5.35 | 4.975 | 6.1 | 5.725 | |
| Umax = 2P | UNF Thread | – | 0.333 | 0.4 | 0.444 | – | 0.444 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | |
| 8UN Thread | – | 0.167 | – | – | – | – | – | – | – | – | – | – | – | ||
| L ≤ 10 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | ||
| Minimum Nut End full Thread B min | 10 < L ≤ 16 | 3.5 | 3.25 | 3.75 | 4.25 | 4 | 4.75 | 5.75 | 5.25 | – | – | – | – | – | |
| L > 16 | 3.75 | 3.5 | 4 | 4.5 | 4.25 | 5 | 6 | 5.5 | 6.5 | 7.5 | 7 | 8.5 | 8 | ||
| 4.25 | 4 | 4.5 | 5 | 4.75 | 5.5 | 6.5 | 6 | 7 | 8 | 7.5 | 9 | 8.5 | |||
When to choose which material
If the application requires maximum strength and creep resistance at temperatures above 1000°F, such as in aircraft manifolds or high-temperature chemical processing equipment, choose 321H.
If the application environment is less demanding and only requires general high-temperature performance, choose 321, which offers excellent performance and good weldability at a lower cost.
Gnee Steel specializes in the production of a wide range of stainless steel products. Gnee Steel's product packaging includes: Steel Strapping: Pipes with an outer diameter of 3 inches or less are typically strapped together with polypropylene film to prevent rust during ocean shipping, and then secured with steel strapping. Wooden Cases/Crates: Pipes are typically packaged in wooden cases or crates to protect the pipes during transportation, especially those that are longer or have larger diameters. Seaworthy Export Packaging: Suppliers typically use standard seaworthy export packaging methods, which may include a variety of materials and techniques to protect the pipes during transportation. Tarpaulin Packaging: This prevents rain, seawater, and other external factors from penetrating the export crates during transportation. Gnee Steel specializes in the production and sale of alloy materials. Gnee Steel's products are widely used in the aerospace, chemical, power, automotive, and nuclear energy sectors, and we can provide customized alloy material solutions based on customer needs. For alloy material pricing or customized alloy material solutions, please contact us for a quote: ru@gneesteelgroup.com