How to Select the Right Flange Material for High-Temperature Service

Selecting the correct flange material for high-temperature service is one of the most critical decisions in piping design. Industries like Oil & Gas, Petrochemical, Power Generation, Boilers, Steam Plants, Chemical Processing, and Refineries operate at temperatures that can weaken metals, cause cracking, oxidation, scaling, gasket failure, and even pipeline explosions.

This guide explains, in simple engineer-friendly language:

Which flange materials can handle high temperature
Their temperature limits
Pros & cons
Best material for each application
Real-world selection chart

Let’s make this easy and practical.

What Happens to Flanges at High Temperature?

High temperature can cause:

Loss of strength
Thermal expansion
Oxidation & scaling
Creep (slow permanent deformation)
Gasket leakage
Bolt loosening
Fatigue cracking

Choosing the wrong material guarantees failure. Choosing the right one ensures years of safe performance.

Best Flange Materials for High-Temperature Service

A) Alloy Steel Flanges (Best for Steam, High Temp & Pressure)

Typical Grades for High Temperature:

ASTM A182 F1 (up to ~500°C)
ASTM A182 F5 (up to ~550°C)
ASTM A182 F9 (up to ~600°C)
ASTM A182 F11 (up to ~600°C)
ASTM A182 F22 (up to ~625°C)
ASTM A182 F91 (up to ~650°C)

Why Alloy Steel is Ideal:

Excellent strength at high temperature
Great resistance to creep
Handles pressure + temperature together
Standard choice in power plants

Best For:

Steam lines
Boiler piping
High-temperature chemical lines
Turbines
Heat exchangers

B) Stainless Steel Flanges (Best for Corrosion + Medium-High Temp)

Common Grades:

SS 304 / 304L
SS 316 / 316L
SS 321
SS 347

Temperature Limits:

SS 304/316 → ~425–870°C
SS 321 → ~870°C
SS 347 → ~870°C

Why Stainless Steel Works:

Excellent corrosion + moderate to high temperature resistance
No scaling at high temperature
SS 321 & 347 used for thermal cycling

Best For:

Heat exchangers
Chemical processing
Food & pharma reactors
Steam condensate systems

C) Nickel Alloy Flanges (Extreme Temperature + Extreme Corrosion)

Popular High-Temperature Nickel Alloys:

Inconel 600 (up to 1175°C)
Inconel 625 (up to 980°C)
Inconel 800 / 800H / 800HT (up to 1100°C)
Inconel 825
Hastelloy C276
Monel 400 / K500

Why Nickel Alloys Are the BEST:

Highest temperature resistance
Best oxidation resistance
Unmatched corrosion resistance
No creep, cracking, or embrittlement

Best For:

Furnaces
Heat-treat lines
High-temperature chemicals
Acidic & corrosive media
Offshore high-temperature use

D) Carbon Steel Flanges (Not for High Temp – But Important Note)

Temperature Limit: A105 flanges → max 425°C

Only suitable for low to medium temperature. Above 425°C → high risk of cracking.

Temperature-Wise Flange Material Selection Chart

Temperature Range	Best Flange Material
Up to 200°C	SS 304 / Carbon Steel
200–425°C	SS 316 / SS 304L / A105
425–550°C	Alloy Steel F5
550–600°C	Alloy Steel F9 / F11
600–625°C	Alloy Steel F22
625–700°C	Alloy Steel F91
700–980°C	Inconel 625
980–1175°C	Inconel 600 / Inconel 800H/HT

Media-Wise Material Selection Guide

Steam: Alloy Steel F11 / F22 / F91
Hydrocarbon: SS 316 / Inconel 825
High-Chloride: Duplex / Super Duplex
High Temperature + Corrosion: Inconel 600/800
Acidic Media: Hastelloy C276
Seawater: Monel 400 / Duplex
Thermal Cycling: SS 321 / SS 347

Industry-Wise Recommendations

Power Plants

Alloy Steel F22 / F91

Refineries

SS 316L / Inconel 825

Petrochemicals

Alloy Steel F11 / Nickel Alloys

Fertilizer Plants

SS 316L / Alloy Steel

Offshore Industry

Super Duplex / Inconel

Gasket Compatibility for High Temperature

Alloy Steel: Spiral Wound Gasket
Stainless Steel: Graphite Gasket
Inconel: Metal Jacketed / RTJ Gasket

Using the wrong gasket leads to high-temperature leakage.

Conclusion

Choosing the right flange material for high-temperature service is essential for safety, zero leakage, long service life, pressure stability, and corrosion resistance.

Use this simple formula:

🔥 Temperature High? → Alloy Steel
🔥 Temperature + Corrosion High? → Nickel Alloys
🔥 Corrosion High? → Stainless Steel or Duplex
🔥 Low Temperature? → Carbon Steel

Moksh Tubes supplies certified high-temperature flanges with full testing for safe, long-term performance.

FAQ's

Which flange is best for 600°C?

Alloy Steel F22 or F91.

Which material handles extreme heat above 1000°C?

Inconel 600 / Incoloy 800H/HT.

Which is better for steam lines?

Alloy Steel F11 / F22 / F91.

Do you provide RTJ high-temp flanges?

Yes — all sizes available