Only materials listed in the ASME B16.5 materials groups, and capable of withstanding the specified pressure at the corresponding temperature, may be legally and compliantly used to manufacture ASME B16.5 flanges.
ASME B16.5 itself is a dimensional and pressure‐rating standard, not a material chemical composition standard.
The materials used for flanges must come from the ASTM/ASME forging material specifications referenced by ASME B16.5 (such as ASTM A105, A182 F304/316, A350 LF2, etc.), and must comply with the pressure–temperature rating requirements defined for their respective material groups in the standard, in order to qualify as compliant ASME B16.5 flanges for engineering design and installation.
Materials must meet pressure–temperature ratings
ASME B16.5 contains an entire set of tables (such as Table 2-1.X) that list the allowable working pressure based on material group + pressure class + temperature.
A conceptual example (values for illustration only):
- Material Group: Carbon steel (e.g., A105)
- Class: 300 flange
- Temperature and Maximum Allowable Pressure:
- 100°C → 51 bar
- 200°C → 45 bar
- 300°C → 38 bar
The higher the temperature, the lower the allowable pressure—this is the purpose of the Pressure-Temperature Ratings tables.
The material must belong to an ASME B16.5 materials groups
ASME B16.5 classifies materials into several Material Groups, for example:
- Group 1.1: A105, A350 LF2 carbon steels
- Group 2.2: F304/F316 stainless steels
- Group 3.x: Alloy steels
- ……
Each material group has its corresponding Pressure-Temperature Ratings table.
If a certain material is not listed in these groups, it is not officially recognized by B16.5 for manufacturing B16.5 flanges.
When selecting a material, its allowable pressure at the service temperature must be adequate
During design/selection, you must ensure:
Design Pressure ≤ Allowable Pressure at service temperature
Example:
- Material: ASTM A105
- Flange rating: Class 300
- Service temperature: 200°C
- Design pressure: 35 bar
If the ASME B16.5 table shows that for this material group, Class, and temperature, the allowable pressure is 40 bar, then it is acceptable.
If the table shows 30 bar, then the combination is unsafe / non-compliant. You must either:
- Use a higher class, or
- Change material, or
- Reduce design pressure.
ASME B16.5 Materials Groups
Group 1 Carbon Steel & Alloy Steel
| Material Group No. | Nominal Designation | Pressure-Temperature Rating Table | Forgings | Castings | Plates |
| 1.1 | C-Si | 2-1.1 | A105 | A216 Gr. WCB | A515 Gr. 70 |
| C-Mn-Si | A350 Gr. LF2 | … | A516 Gr. 70, A537 Cl. 1 | ||
| C-Mn-Si-V | A350 Gr. LF6 Cl. 1 | … | … | ||
| 3½Ni | A350 Gr. LF3 | … | … | ||
| 1.2 | C-Mn-Si | 2-1.2 | … | A216 Gr. WCC | … |
| C-Mn-Si-V | A350 Gr. LF6 Cl. 2 | A352 Gr. LCC, LC2, LC3 | … | ||
| 3½Ni | … | A352 Gr. LC3 | A203 Gr. E | ||
| 1.3 | C-Si | 2-1.3 | … | A352 Gr. LCB | A515 Gr. 65 |
| 2½Ni | … | … | A203 Gr. A | ||
| C-½Mo | … | A217 Gr. WC1 | A204 Gr. B | ||
| 1.4 | C-Si | 2-1.4 | … | … | A515 Gr. 60 |
| C-Mn-Si | A350 Gr. LF1 Cl. 1 | … | A516 Gr. 60 | ||
| 1.5 | C-½Mo | 2-1.5 | A182 Gr. F1 | … | A204 Gr. B |
| 1.7 | Ni-Cr-½Mo | 2-1.7 | A182 Gr. F2 | A217 Gr. WC4 | … |
| ¾Ni-¾Cr-1Mo | … | A217 Gr. WC6 | … | ||
| 1.9 | 1¼Cr-½Mo | 2-1.9 | A182 Gr. F11 Cl. 2 | … | A387 Gr. 11 Cl. 2 |
| 1.1 | 2¼Cr-1Mo | 2-1.10 | A182 Gr. F22 Cl. 3 | A217 Gr. WC9 | A387 Gr. 22 Cl. 2 |
| 1.11 | C-½Mo | 2-1.11 | … | … | A204 Gr. C |
| 1.13 | 5Cr-½Mo | 2-1.13 | A182 Gr. F5a | A217 Gr. C5 | … |
| 1.14 | 9Cr-1Mo-V | 2-1.14 | A182 Gr. F91 Type 1 | A217 Gr. C12A | A387 Gr. 91 Cl. 2 |
| 1.17 | 1Cr-½Mo | 2-1.17 | A182 Gr. F12 Cl. 2 | A217 Gr. C12 | … |
| 1.18 | 9Cr-2W-V | 2-1.18 | A182 Gr. F92 | … | … |
Group 2 Stainless Steel & Duplex Stainless Steel
| Material Group No. | Nominal Designation | Pressure-Temperature Rating Table | Forgings | Castings | Plates |
| 2.1 | 18Cr-8Ni | 2-2.1 | A182 Gr. F304 | A351 Gr. CF3 | A240 Gr. 304 |
| 18Cr–8Ni18Cr-8Ni | A182 Gr. F304H | A351 Gr. CF8 | A240 Gr. 304H | ||
| 2.2 | 16Cr-12Ni-2Mo | 2-2.2 | A182 Gr.F316 | A351 Gr.CF3M | A240 Gr.316 |
| 16Cr-12Ni-2Mo | A182 Gr.F316H | A351 Gr.CF8M | A240 Gr.316H | ||
| 18Cr-13Ni-3Mo | A182 Gr.F317 | … | A240 Gr.317 | ||
| 19Cr-10Ni-3Mo | … | A351 Gr.CG8M | … | ||
| 2.3 | 18Cr-8Ni | 2-2.3 | A182 Gr.F304L | … | A240 Gr.304L |
| 16Cr-12Ni-2Mo | A182 Gr.F316L | … | A240 Gr.316L | ||
| 18Cr-13Ni-3Mo | A182 Gr.F317L | … | … | ||
| 2.4 | 18Cr-10Ni-Ti | 2-2.4 | A182 Gr.F321 | … | A240 Gr.321 |
| 18Cr-10Ni-Ti | A182 Gr.F321H | … | A240 Gr.321H | ||
| 2.5 | 18Cr-10Ni-Cb | 2-2.5 | A182 Gr. F347 | … | A240 Gr. 347 |
| 18Cr-10Ni-Cb | A182 Gr. F347H | … | A240 Gr. 347H | ||
| 18Cr-10Ni-Cb | A182 Gr. F348 | … | A240 Gr. 348 | ||
| 18Cr-10Ni-Cb | A182 Gr. F348H | … | A240 Gr. 348H | ||
| 2.6 | 23Cr-12Ni | 2-2.6 | … | … | A240 Gr. 309H |
| 2.7 | 25Cr-20Ni | 2-2.7 | A182 Gr. F310 | … | A240 Gr. 310H |
| 2.8 | 20Cr-18Ni-6Mo | 2-2.8 | A182 Gr. F44 | A351 Gr. CK3MCuN | A240 Gr. S31254 |
| 22Cr-5Ni-3Mo-N | 2-2.8 | A182 Gr. F51 | – | A240 Gr. S31803 | |
| 25Cr-7Ni-4Mo-N | 2-2.8 | A182 Gr. F53 | – | A240 Gr. 32750 | |
| 24Cr-10Ni-4Mo-V | 2-2.8 | … | A995 Gr. CEBMN | … | |
| 25Cr-5Ni-2Mo-3Cu-N | 2-2.8 | … | A995 Gr. CD4MCuN | … | |
| 25Cr-7Ni-3.5Mo-W-Cb | 2-2.8 | … | A995 Gr. CD3MWCuN | … | |
| 25Cr-7.5Ni-3.5Mo-N-Cu-W | 2-2.8 | A182 Gr. F55 | … | A240 Gr. S32760 | |
| 2.9 | 23Cr-12Ni | 2-2.9 | … | … | A240 Gr. 309S |
| 25Cr-12Ni | 2-2.9 | … | … | A240 Gr. 310S | |
| 2.1 | 25Cr-12Ni | 2-2.10 | … | A351 Gr. CH8 | … |
| 25Cr-12Ni | 2-2.10 | … | A351 Gr. CH20 | … | |
| 2.11 | 18Cr-10Ni-Cb | 2-2.11 | … | A351 Gr. CF8C | … |
| 2.12 | 25Cr-20Ni | 2-2.12 | … | A351 Gr. CK20 | … |
Group 3 High Alloy Steel
| Material Group No. | Nominal Designation | Pressure-Temperature Rating Table | Forgings | Castings | Plates |
| 3.1 | 35Ni-35Fe-20Cr-Cb | 2-3.1 | A182 Gr.N08020 | … | A182 Gr.N08020 |
| 3.2 | 99.0Ni | 2-3.2 | B564 Gr.N02200 | … | B162 Gr.N02200 |
| 3.3 | 99.0Ni-Low C | 2-3.3 | … | … | B162 Gr.NO2201 |
| 3.4 | 67Ni-30Cu | 2-3.4 | B564 Gr.N04400 | … | B127 Gr.N04400 |
| 3.5 | 72Ni-15Cr-8Fe | 2-3.5 | B564 Gr.N06600 | … | B168 Gr.N06600 |
| 3.6 | 33Ni-42Fe-21Cr | 2-3.6 | A182 Gr.N08800 | … | A182 Gr.N08800 |
| 3.7 | 65Ni-28Mo-2Fe | 2-3.7 | B462 Gr.N10665 | … | B333 Gr.N10665 |
| 64Ni-29.5Mo-2Cr-2Fe-Mn-W | B462 Gr.N10675 | … | B333 Gr.N10675 | ||
| 3.8 | 54Ni-16Mo-15Cr | 2-3.8 | B462 Gr.N10276 | … | B575 Gr.N10276 |
| 60Ni-22Cr-9Mo-3.5Cb | B564 Gr.N06625 | … | B443 Gr.N06625 | ||
| 62Ni-28Mo-5Fe | … | … | B333 Gr.N10001 | ||
| 70Ni-16Mo-7Cr-5Fe | … | … | B434 Gr.N10003 | ||
| 61Ni-16Mo-16Cr | … | … | B575 Gr.N06455 | ||
| 42Ni-21.5Cr-3Mo-2.3Cu | B564 Gr.N08825 | … | B424 Gr.N08825 | ||
| 55Ni-21Cr-13.5Mo | B462 Gr.N06022 | … | B575 Gr.N06022 | ||
| 55Ni-23Cr-16Mo-1.6Cu | B462 Gr.N06200 | … | B575 Gr.N06200 | ||
| 3.9 | 47Ni-22Cr-9Mo-I8Fe | 2-3.9 | B572 Gr.N06002 | … | B435 Gr.N06002 |
| 21Ni-30Fe-22Cr-18Co-3Mo-3W | B572 Gr.R30556 | … | B435 Gr.R30556 | ||
| 3.10 | 25Ni-47Fe-21Cr-5Mo | 2-3.10 | … | … | B599 Gr.N08700 |
| 3.11 | 44Fe-25Ni-21Cr-Mo | 2-3.11 | A182 Gr.N08904 | … | A240 Gr.N08904 |
| 3.12 | 26Ni-43Fe-22Cr-5Mo | 2-3.12 | … | … | B620 Gr.N08320 |
| 47Ni-22Cr-20Fe-7Mo | … | … | B582 Gr.N06985 | ||
| 46Fe-24Ni-21Cr-6Mo-Cu-N | A182 Gr.N08367 | A351 Gr.CN3MN | B688 Gr.N08367 | ||
| 46Fe-24Ni-21Cr-6Mo-Cu-N | B462 Gr.N08367 | A351 Gr.CN3MN | B688 Gr.N08367 | ||
| 3.13 | 49Ni-25Cr-18Fe-6Mo | 2-3.13 | … | … | B582 Gr.N06975 |
| Ni-Fe-Cr-Mo-Cu-Low C | B564 Gr.N08031 | … | B625 Gr.N08031 | ||
| 3.14 | 47Ni–22Cr–19Fe–6Mo | 2-3.14 | … | … | B582 Gr. N06007 |
| 40Ni–29Cr–15Fe–5Mo | B462 Gr. N06030 | … | B582 Gr. N06030 | ||
| 58Ni–33Cr–8Mo | B462 Gr. N06035 | … | B575 Gr. N06035 | ||
| 3.15 | 42Ni–42Fe–21Cr | 2-3.15 | A182 Gr. N08810 | … | A240 Gr. N08810 |
| 42Ni–42Fe–21Cr | B564 Gr. N08810 | … | B409 Gr. N08810 | ||
| 3.16 | 35Ni–19Cr–1¼Si | 2-3.16 | B511 Gr. N08330 | … | B536 Gr. N08330 |
| 3.17 | 29Ni–20.5Cr–3.5Cu–2.5Mo | 2-3.17 | … | A351 Gr. CN7M | … |
| 3.19 | 57Ni–22Cr–14W–2Mo–La | 2-3.19 | B564 Gr. N06230 | … | B435 Gr. N06230 |
Conclusion
The selection of materials for ASME B16.5 flanges is governed not by chemistry alone, but by strict compliance with the standard’s defined Material Groups and their corresponding pressure–temperature rating tables. Only materials explicitly listed in ASME B16.5 and capable of sustaining the required design pressure at the operating temperature are legally acceptable for flange manufacturing and engineering application.
During design and procurement, engineers must verify that the chosen material, pressure class, and service temperature combination meets the allowable limits specified in the standard. Any deviation—such as using an unlisted material or exceeding allowable pressure—results in a non-compliant, unsafe configuration.
By adhering to the material group classifications and pressure–temperature ratings, engineers ensure that ASME B16.5 flanges deliver reliable, predictable performance across a wide range of process conditions and industry applications.
