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 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, corrosion and toughness requirements. The cards below summarise how the main forging families are normally used in flange production.
Carbon & Low-Temperature Carbon Steel
Standard choice for ambient service and low-temperature lines. Typical grades include ASTM A105 for general carbon steel and A350 LF2 for low-temperature service with Charpy impact testing.
Austenitic Stainless Steel
The workhorses for corrosion-resistant service. ASTM A182 F304/F304L and F316/F316L cover the common 300-series forged flange grades used in process plants, water treatment and general industrial service.
Duplex & Super Duplex Stainless Steel
Duplex grades combine higher strength with improved chloride stress-corrosion resistance. A182 F51 (2205) is widely used, while F53 / F55 serve more aggressive offshore and seawater conditions.
Cr-Mo Alloy Steel (High Temperature)
Chrome-moly grades are used for high-temperature and high-pressure service in power and refining. Common forging grades are A182 F11 and F22, matching P- and T-series pipe materials.
Nickel Alloys & Specialty Grades
For strong acids, sour service or high temperature, nickel alloys and special stainless grades may be specified. These are usually engineered project-by-project with full test 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 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 quick way to see 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 the required pressure class, design temperature and corrosion allowance before you choose a grade.
- Check toughness requirements. Where low-temperature impact tests are specified, grades like A350 LF2 or selected nickel steels are normally used instead of A105.
- Consider corrosion and media. For chlorides and seawater, 316L is usually a minimum; duplex F51 or super duplex grades are selected where stress-corrosion cracking is a risk.
- Match flanges to pipe and fittings. For example, A182 F11/F22 flanges are paired with corresponding P- and T-series Cr-Mo pipes in power and refining services.
- Rely on certified MTC/MTR. Before shipment Sunhyings can supply EN 10204 3.1 or 3.2 certificates with heat numbers, chemistry, mechanical tests and impact / NDE results so your QA team can verify compliance.