Carbon Steel Flanges
Comprehensive guide to carbon steel flange materials. ASTM A105, A350 LF2, A516, and A694 specifications with detailed technical properties and industrial applications.
Carbon Steel Material Grades
Primary carbon steel specifications used for industrial flanges and pressure components.
ASTM A105
Carbon Steel Forgings
Temperature Range:
-20°F to 650°F
Pressure Rating:
Up to 2500 Class
Yield Strength:
≥36,000 PSI
Primary Use:
General industrial piping, standard service
Typical Composition:
C: 0.35% max, Mn: 0.60-1.05%, Si: 0.10-0.35%
ASTM A350 LF2
Low-Temperature Carbon Steel
Temperature Range:
-320°F to 100°F
Pressure Rating:
Full pressure ratings
Yield Strength:
≥36,000 PSI
Primary Use:
Cryogenic, LNG, low-temperature service
Typical Composition:
C: ≤0.20%, Mn: 0.60-1.35%, Ni: 0.40% max (optional)
ASTM A516 Gr.70
Pressure Vessel Plate Steel
Temperature Range:
-20°F to 650°F
Pressure Rating:
Pressure vessel service
Yield Strength:
≥38,000 PSI
Primary Use:
Pressure vessel plates, equipment bodies
Typical Composition:
C: 0.31% max, Mn: 0.80-1.10%, Si: 0.15-0.30%
ASTM A694 F65
High-Strength Carbon Steel
Temperature Range:
-20°F to 600°F
Pressure Rating:
High-pressure applications
Yield Strength:
≥65,000 PSI
Primary Use:
Sour service, high-pressure systems
Typical Composition:
C: 0.26% max, Mn: 0.85-1.15%, Si: ≤0.30%
Mechanical Properties
Comparison of key mechanical properties for primary carbon steel grades.
| Property | ASTM A105 | ASTM A350 LF2 | ASTM A516 Gr.70 |
|---|---|---|---|
| Tensile Strength | 70,000-95,000 PSI | 70,000-95,000 PSI | 70,000-90,000 PSI |
| Yield Strength | ≥36,000 PSI | ≥36,000 PSI | ≥38,000 PSI |
| Elongation | ≥24% (2") | ≥24% (2") | ≥21% (2") |
| Hardness (Max) | ~197 HV (187 HBW max) | ~197 HV (197 HBW max) | ~197 HV |
Pressure-Temperature Ratings
ASME B16.5 pressure ratings decrease with temperature. Maximum working pressure is temperature-dependent.
Pressure-temperature derating varies by material group. Refer to ASME B16.5 Table 2-1.1 (Group 1.1 for A105 carbon steel) for the certified values at each temperature. Call (281) 484-8325 for project-specific P-T verification.
Understanding Pressure Derating
As temperature increases, the material loses strength. ASME standards provide derating curves showing the maximum working pressure at each temperature. Always verify the appropriate pressure rating for your operating temperature using official ASME derating tables.
Example: A Class 300 flange rated for 740 PSI at 100°F can only be rated at ~550 PSI when operating at 600°F.
Industrial Applications
Carbon steel flanges serve diverse industrial applications requiring cost-effective, reliable solutions.
Oil & Gas
Pipelines, processing plants, wellhead equipment, manifolds
Power Generation
Steam systems, cooling water lines, boiler feed systems
Chemical Processing
Process piping, reactor connections, distillation equipment
Water Treatment
Water utility systems, treatment plants, distribution mains
HVAC & Building
Steam distribution, chilled water, heating systems
Manufacturing
General industrial piping, compressed air, utility lines
Carbon Steel Advantages
Cost Effectiveness
Carbon steel is the most economical material choice for industrial applications with moderate temperature and pressure requirements.
- ✓ Lower material cost vs stainless/alloy
- ✓ Standard production processes
- ✓ Wide supplier availability
- ✓ Best value for general service
Proven Performance
Decades of industrial experience demonstrate carbon steel reliability for standard applications.
- ✓ Well-understood material behavior
- ✓ Extensive code coverage
- ✓ Predictable maintenance requirements
- ✓ Industry-standard specifications
Wide Temperature Range
Carbon steel performs well from low-temperature cryogenic to elevated temperature service.
- ✓ A350 LF2 for cryogenic (-320°F)
- ✓ Standard A105 to 650°F
- ✓ Suitable for wide operating ranges
- ✓ Versatile material selection
Key Considerations
Important factors when specifying carbon steel flanges for your application.
Corrosion Protection
Carbon steel requires corrosion protection in corrosive or outdoor environments. Painting and coatings extend service life.
- • Epoxy coating for external protection
- • Passivation not sufficient for carbon steel
- • Consider stainless for water service
Pressure Derating
Always verify pressure rating at your operating temperature. Maximum rated pressure applies only at reference temperature.
- • Use ASME derating tables
- • Temperature significantly affects rating
- • Consult design specification
Cryogenic Service
For temperatures below -20°F, use ASTM A350 LF2 which maintains toughness at low temperatures.
- • A105 becomes brittle below -20°F
- • A350 LF2 impact tested to -50°F
- • Required for LNG and cryogenic service
Sour Service
Sour service applications require NACE MR0175 compliance. A694 can be specified with NACE testing for sour service. Consult your project spec for material qualification requirements.
- • API 6A specification compliance
- • Lower hardness limits control
- • Special material testing required
Related Materials & Resources
Stainless Steel
When carbon steel corrosion protection becomes impractical, consider stainless steel alternatives.
Learn More →Alloy Steel
For elevated temperature service above 650°F, alloy steel materials provide enhanced strength.
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