I. Carbon Steel Flanges
Characteristics: Carbon content 0.05%–1.3%, iron-based; high strength, low cost, but weak corrosion resistance.
Common Grades:
- China: Q235, 20#, 35#, 45#
- USA: A105, A350 LF2, A182 F1
Applications:
- Non-corrosive media (water, air, steam) in plumbing/heating systems;
- Low-to-medium pressure/temperature (≤350°C);
- Cost-sensitive municipal/industrial pipelines.
II. Stainless Steel Flanges
Characteristics: Chromium (Cr) ≥10.5%, forms passivation layer; excellent corrosion/heat resistance.
Common Grades & Types:
- Austenitic Stainless Steel
- 304 (06Cr19Ni10): General use; resistant to atmosphere/weak acids.
- 316 (06Cr17Ni12Mo2): Molybdenum-enhanced; withstands chlorides (seawater).
- 316L (022Cr17Ni12Mo2): Low-carbon; anti-intergranular corrosion (food/pharma).
- 310S (06Cr25Ni20): Heat-resistant (≤1200°C; boilers).
- Ferritic Stainless Steel:
- 430 (10Cr17): Economical; limited corrosion resistance (kitchen equipment).
- Martensitic Stainless Steel:
- 410 (12Cr13): High strength; mechanical parts (valve flanges).
Applications:
- Chemical corrosive media (acids/alkalis);
- Sanitary pipelines (316L/304L);
- High-temp steam/cryogenic liquids (310S/304L).
III. Alloy Steel Flanges
Characteristics: Alloyed with Mo/Cr/V; enhanced strength/heat/corrosion resistance.
Common Grades:
- China: 15CrMo, 12Cr1MoV
- USA: A182 F11, F22, F91
Applications:
- High-pressure/high-temp systems (power plants; ≤550°C);
- Hydrogen-resistant pipelines (oil refineries);
- High-strength chemical equipment.
IV. Cast Iron Flanges
Characteristics: High carbon (2%–4%); low cost, brittle, low strength.
Common Types:
- Gray Iron (HT200/HT250): Low-pressure systems.
- Ductile Iron (QT400-15/QT500-7): Higher strength/impact resistance.
Applications:
- Low-pressure water/sewage pipelines;
- Irrigation/firefighting systems.
V. Copper & Copper Alloy Flanges
Characteristics: Excellent thermal conductivity/seawater resistance; high cost.
Common Grades:
- Red Copper (T2/T3), Brass (H62/H68), Bronze (QSn6.5-0.1)
Applications:
- Seawater desalination/ship pipelines;
- Heat exchangers/AC refrigeration;
- Electrical conductivity systems.
VI. Aluminum Alloy Flanges
Characteristics: Lightweight (1/3 steel density); atmospheric corrosion resistance.
Common Grades: 6061, 6063 (heat-treatable alloys)
Applications:
- Aerospace/shipbuilding (weight reduction);
- Food-grade equipment (anodized surface);
- Low-pressure non-corrosive gas (compressed air).
VII. Non-Metallic Flanges
Characteristics: Extreme corrosion resistance/insulation; low strength/heat tolerance.
Common Types:
- Plastic: PP, PVC, PTFE.
- Rubber: NBR, EPDM.
- Composite: Steel-lined PTFE/rubber.
Applications:
- Strong acids/alkalis (sulfuric/hydrofluoric acid);
- Pharma/food industry (PTFE non-toxicity);
- High-corrosion environments (electroplating).
VIII. Special Alloy Flanges
Characteristics: Extreme conditions; ultra-high cost.
Common Materials:
- Titanium Alloys (TA2/TC4): Seawater/chloride resistance (submarines).
- Hastelloy (C-276/B-3): Strong acids/high-pressure (petrochemicals).
- Monel (Monel 400): Hydrofluoric acid resistance (fluorochemicals).
Applications:
- Offshore/nuclear/aerospace engineering;
- Extreme R&D equipment.
