Flange Material Grades Guide
This guide brings together the common forging grades used for carbon steel, stainless steel, duplex and alloy steel flanges. It is written for maintenance engineers, project teams and buyers who need a quick way to compare minimum mechanical properties, chemistry ranges and typical service conditions before selecting a flange material.
Flange Material Families Overview
Most project specifications start by defining a material family. From there, you choose the exact ASTM / ASME grade based on pressure-temperature requirements, corrosion risk, operating environment and toughness targets. The cards below summarise how the main forging families are normally used in flange production.
Carbon Steel
ASTM A105 is the standard forging grade for general-purpose carbon steel flanges used in ambient-temperature pressure piping, utility service and many conventional industrial applications.
Low-Temperature Carbon Steel
ASTM A350 LF2 is selected where low-temperature toughness matters. It is commonly specified for colder operating conditions and projects requiring impact-tested forged flanges.
Austenitic Stainless Steel
ASTM A182 F304 / F304L and F316 / F316L are the standard forged grades for corrosion-resistant service in process plants, water systems, food handling and general industrial duty.
Duplex & Super Duplex Stainless Steel
Duplex grades combine high strength with improved chloride resistance. A182 F51 is widely used for offshore and seawater-related service, while F53 / F55 cover more aggressive conditions.
Cr-Mo Alloy Steel
Chrome-moly forging grades such as A182 F11 and F22 are used for elevated-temperature and higher-pressure duty in power generation, refining and hot hydrocarbon service.
Nickel Alloys & Specialty Grades
For strong acids, sour service, high temperature or demanding project specifications, nickel alloys and specialty forged materials can be supplied with project-specific test and documentation requirements.
Key Flange Forging Grades – Mechanical Reference
Values in the table are typical minimum room-temperature mechanical requirements taken from ASTM / ASME product specifications and commonly published manufacturer datasheets. Project specifications may call for additional testing, supplementary requirements or tighter limits.
| Grade | Material Family | UNS No. | Typical Forging Spec | Min. Tensile Strength | Min. Yield Strength | Typical Service |
|---|---|---|---|---|---|---|
| ASTM A105 | Carbon steel | K03504 | ASTM A105 / ASME SA105 | ≥ 485 MPa (70 ksi) | ≥ 250 MPa (36 ksi) | General-purpose forged flanges for ambient-temperature pressure piping. |
| ASTM A350 LF2 | Low-temperature carbon steel | K03011 | ASTM A350 / ASME SA350 | ≈ 485 MPa (70 ksi) min | ≈ 250 MPa (36 ksi) min | Low-temperature lines and vessels with impact testing to about −46 °C. |
| ASTM A182 F304 | Austenitic stainless steel | S30400 | ASTM A182 / ASME SA182 | ≥ 515 MPa (75 ksi) | ≥ 205 MPa (30 ksi) | Standard stainless flanges for water, food and mild chemical service. |
| ASTM A182 F304L | Austenitic stainless steel (low C) | S30403 | ASTM A182 / ASME SA182 | ≥ 485 MPa (~70 ksi) | ≥ 170 MPa (~25 ksi) | Improved weldability where lower carbon content is specified. |
| ASTM A182 F316 | Austenitic stainless steel (Mo-bearing) | S31600 | ASTM A182 / ASME SA182 | ≥ 515 MPa (75 ksi) | ≥ 205 MPa (30 ksi) | Better pitting resistance in chloride-containing media than 304. |
| ASTM A182 F316L | Austenitic stainless steel (Mo, low C) | S31603 | ASTM A182 / ASME SA182 | ≈ 485 MPa (~70 ksi) min | ≈ 170 MPa (~25 ksi) min | Critical welds, tanks and piping with stricter corrosion requirements. |
| ASTM A182 F51 (Duplex 2205) |
Duplex stainless steel | S31803 / S32205 | ASTM A182 / ASME SA182 F51 | ≥ 620 MPa (90 ksi) | ≥ 450 MPa (65 ksi) | High-strength flanges for seawater, offshore and chloride-rich service. |
| ASTM A182 F53 (Super Duplex 2507) |
Super duplex stainless steel | S32750 | ASTM A182 / ASME SA182 F53 | ≈ 800 MPa (≈ 116 ksi) min | ≈ 550 MPa (≈ 80 ksi) min | Very high PREN for aggressive seawater and offshore production systems. |
| ASTM A182 F11 | Cr-Mo alloy steel | K11597 | ASTM A182 / ASME SA182 F11 | ≥ 415 MPa (60 ksi) | ≥ 205 MPa (30 ksi) | High-temperature steam and hot hydrocarbon service. |
| ASTM A182 F22 | Cr-Mo alloy steel | K21590 | ASTM A182 / ASME SA182 F22 | ≥ 415 MPa (60 ksi) | ≥ 205 MPa (30 ksi) | Higher chromium-moly content for thicker sections and severe service. |
| Project-specific alloys | Nickel alloys / specials | On request | ASTM B564, others | Per grade | Per grade | Inconel, Hastelloy, super-austenitic and other specials can be produced to project specification with agreed test scope. |
Key Flange Material Grades & Properties
The table below compares the typical chemical composition ranges and minimum mechanical requirements for common forged flange grades. It is a practical reference for understanding why one material behaves differently from another in service.
| Grade | UNS No. | Key Chemical Composition (%) | Min. Tensile | Min. Yield | Typical Service |
|---|---|---|---|---|---|
| ASTM A105 | K03504 | C: ≤0.35 Mn: 0.60–1.05 Si: 0.10–0.35 | 70 ksi (485 MPa) | 36 ksi (250 MPa) | Standard carbon steel for ambient pressure piping. |
| ASTM A350 LF2 Class 1 |
K03011 | C: ≤0.30 Mn: 0.60–1.35 P/S: ≤0.035 / 0.040 | 70 ksi (485 MPa) | 36 ksi (250 MPa) | Low-temperature service (impact tested around −46 °C). |
| ASTM A182 F304 | S30400 | Cr: 18.0–20.0 Ni: 8.0–11.0 C: ≤0.08 | 75 ksi (515 MPa) | 30 ksi (205 MPa) | Basic stainless for water, air and mild chemical duty. |
| ASTM A182 F304L | S30403 | Cr: 18.0–20.0 Ni: 8.0–13.0 C: ≤0.030 | 70 ksi (485 MPa) | 25 ksi (170 MPa) | Improved weldability vs F304; reduces weld-affected corrosion. |
| ASTM A182 F316 | S31600 | Cr: 16.0–18.0 Ni: 10.0–14.0 Mo: 2.0–3.0 | 75 ksi (515 MPa) | 30 ksi (205 MPa) | Higher resistance to chlorides / pitting thanks to Mo. |
| ASTM A182 F316L | S31603 | Cr: 16.0–18.0 Ni: 10.0–14.0 Mo: 2.0–3.0 C: ≤0.030 | 70 ksi (485 MPa) | 25 ksi (170 MPa) | Preferred for corrosive systems where welding is unavoidable. |
| A182 F51 / F60 (Duplex 2205) |
S32205 | Cr: 22.0–23.0 Ni: 4.5–6.5 Mo: 3.0–3.5 N: 0.14–0.20 | 95 ksi (655 MPa) | 65 ksi (450 MPa) | High strength with excellent chloride stress-corrosion resistance. |
| A182 F53 (Super Duplex 2507) |
S32750 | Cr: 24.0–26.0 Ni: 6.0–8.0 Mo: 3.0–5.0 | 116 ksi (800 MPa) | 80 ksi (550 MPa) | Very aggressive seawater and offshore production systems. |
| ASTM A182 F11 Class 2 |
K11597 | Cr: 1.0–1.5 Mo: 0.44–0.65 C: 0.10–0.20 | 70 ksi (485 MPa) | 40 ksi (275 MPa) | High-temperature service such as boilers and steam lines. |
Practical Notes on Selecting a Flange Material
- Start from the design code and line class. Confirm pressure class, design temperature, corrosion allowance and any client-specific supplementary requirements before selecting a grade.
- Check toughness requirements early. Where low-temperature impact tests are specified, grades such as A350 LF2 are normally used instead of standard A105 forgings.
- Match corrosion resistance to the actual media. For chloride-bearing systems, 316L may be the entry point, while duplex or super duplex grades are selected where pitting or stress-corrosion cracking becomes a concern.
- Coordinate flange, pipe and fittings. Material selection should align with the connected piping system, especially in Cr-Mo and duplex service where mismatched materials can complicate fabrication and QA review.
- Use certified documentation for final approval. Before shipment, EN 10204 3.1 or 3.2 certificates, heat numbers, chemistry, mechanical tests and agreed NDE records should be reviewed by the QA team.
Frequently Asked Questions
These quick answers help buyers and engineers narrow down the right flange forging grade before issuing an enquiry or finalising a line class.