Carbon Steel Flanges
ASTM A105 and A350 LF2 Forged Flanges. Industry-standard material for general purpose and low-temperature applications from ambient to 800°F.
Carbon Steel: The Industry Standard
Carbon steel flanges are the most widely used flange material in the global industry, providing an optimal balance of mechanical properties, cost-effectiveness, and versatility. ASTM A105 carbon steel is the default material specification in most engineering codes and standards, including ASME B16.5, API 6D, and AWWA.
Our carbon steel flanges are forged from premium steel stock and heat-treated to ensure consistent mechanical properties. All flanges include full material traceability, mill test reports (MTR), and compliance with ASTM, ASME, and API standards.
Key Advantage: Carbon steel combines proven reliability, broad availability, competitive pricing, and excellent engineering support. Perfect for 95% of general industrial applications.
ASTM A105 - Carbon Steel Forgings
Standard specification for room temperature and elevated temperature service applications
Chemical Composition (%)
Element | Min(%) | Max(%) | Notes |
|---|---|---|---|
| Carbon (C) | - | 0.35 | Primary strengthening element |
| Manganese (Mn) | 0.60 | 1.05 | Improves strength and hardenability |
| Silicon (Si) | 0.10 | 0.35 | Enhances strength and deoxidation |
| Phosphorus (P) | - | 0.035 | Kept low for ductility |
| Sulfur (S) | - | 0.040 | Controlled for workability |
| Chromium (Cr) | - | 0.30 | Optional for enhanced hardenability |
| Molybdenum (Mo) | - | 0.12 | Optional for increased strength |
| Nickel (Ni) | - | 0.40 | Optional for toughness |
All values are weight percentages per ASTM A105 specification. The sum of Cu, Ni, Cr, Mo, and V shall not exceed 1.00%, and the sum of Cr and Mo shall not exceed 0.32%.
Mechanical Properties
Property | Value | ASTM Minimum | Notes |
|---|---|---|---|
| Tensile Strength | 70 - 100 ksi | 70 ksi (485 MPa) | Ultimate tensile strength requirement |
| Yield Strength (0.2% offset) | 36 ksi typical | 36 ksi (250 MPa) | Minimum proof strength |
| Reduction of Area | 30% | 30% | Cross-sectional reduction during tension test |
| Modulus of Elasticity | 30,000 ksi | - | Stiffness at room temperature |
| Poisson's Ratio | 0.27 - 0.30 | - | Lateral strain ratio |
All values are minimum unless noted. Properties verified by tensile testing and reduction of area testing per ASTM E8. Elongation measured in 2-inch gage length.
Temperature Service Range
Low Temperature Limit
ASTM A105 can be safely used down to -20°F in most applications. Below -20°F, the material becomes more brittle and impact testing is recommended. For temperatures below -20°F, use ASTM A350 LF2.
High Temperature Limit
ASTM A105 is suitable for continuous service up to 800°F. Above 800°F, material strength decreases significantly and alloy steels (F11, F22, F91) are recommended. Pressure derated above 600°F per ASME Section VIII.
Pressure Rating Derating
ASME B16.5 provides pressure vs. temperature derating tables. Always consult ASME tables for your exact conditions.
ASTM A350 LF2 - Low Temperature Forgings
Premium specification for cryogenic and low-temperature service down to -50°F
Chemical Composition (%)
Element | Min(%) | Max(%) | Notes |
|---|---|---|---|
| Carbon (C) | - | 0.30 | Lower max than A105 for improved toughness |
| Manganese (Mn) | 0.60 | 1.35 | Higher range than A105 for low-temperature toughness |
| Silicon (Si) | 0.15 | 0.30 | Deoxidation and strength |
| Phosphorus (P) | - | 0.035 | Controlled for ductility |
| Sulfur (S) | - | 0.040 | Controlled for workability |
| Chromium (Cr) | - | 0.30 | Optional, same limit as A105 |
| Nickel (Ni) | - | 0.40 | Optional for toughness |
| Molybdenum (Mo) | - | 0.12 | Optional for strength |
| Copper (Cu) | - | 0.40 | Optional |
| Niobium (Nb) | - | 0.02 | Trace element control |
Per ASTM A350 Class 1 (LF2). The sum of Cu, Ni, Cr, Mo, and V shall not exceed 1.00%. A350 LF2 requires Charpy V-notch impact testing at -50°F, which is the key differentiator from A105.
Mechanical Properties
Property | Value | ASTM Minimum | Notes |
|---|---|---|---|
| Tensile Strength | 70 - 95 ksi | 70 ksi (485 MPa) | Per ASTM A350 Class 1 |
| Yield Strength (0.2% offset) | 36 ksi typical | 36 ksi (250 MPa) | Per ASTM A350 Class 1 |
| Elongation in 2 inches | 22% minimum | 22% | Measured at room temperature |
| Reduction of Area | 30% minimum | 30% | Same requirement as A105 |
| Charpy Impact (-50°F) | 20 J (15 ft-lbs) minimum | 20 J | Mandatory for low-temperature qualification |
| Hardness | 197 HBW max | 197 HBW max | Per ASTM A350 |
| Service Temperature Limit | Down to -50°F | - | Rated for low-temperature service |
ASTM A350 LF2 requires Charpy V-notch impact testing at -50°F with a minimum of 15 ft-lbs. This ensures the material maintains toughness at cryogenic temperatures. Elongation and reduction of area are measured at room temperature.
Primary Applications
- • LNG (Liquified Natural Gas)
- • Liquid Nitrogen Service
- • Cryogenic Ethylene
- • Refrigeration Systems
- • Arctic Pipelines
- • Hydrogen Service
Why A350 LF2?
- ✓Proven toughness at extreme low temperatures
- ✓Mandatory Charpy impact testing for quality assurance
- ✓Meets API 579 and other cryogenic standards
- ✓Industry-standard for LNG facilities worldwide
- ✓Superior ductility prevents brittle fracture
A105 vs A350 LF2 Comparison
Feature | ASTM A105 | ASTM A350 LF2 |
|---|---|---|
| Carbon Content | 0.35% max | 0.30% max |
| Manganese Content | 0.60-1.05% | 0.60-1.35% |
| Nickel Content | Optional (max 0.40%) | Optional (max 0.40%) |
| Molybdenum Content | Optional (max 0.12%) | Optional (max 0.12%) |
| Phosphorus Maximum | 0.035% | 0.035% |
| Sulfur Maximum | 0.040% | 0.040% |
| Tensile Strength | 70 ksi min | 70-95 ksi |
| Yield Strength | 36 ksi min | 36 ksi min |
| Min Service Temp | -20°F (ambient) | -50°F (low-temperature) |
| Charpy Impact Testing | Not required | Required at -50°F |
| Primary Application | General purpose up to 800°F | Low-temperature service |
Selection Guidance
Use ASTM A105 if:
- • Service temperature is above -20°F
- • Operating up to 800°F
- • Cost is a primary consideration
- • General industrial/commercial applications
- • Standard pressure vessel service
Use ASTM A350 LF2 if:
- • Service temperature below -20°F
- • Cryogenic service (-50°F or higher)
- • LNG or cryogenic gas handling
- • Arctic/cold climate operation
- • Impact testing or charpy requirements
Temperature Service Guide
Temperature Range | Service Application | Recommended Material |
|---|---|---|
| -50°F to 0°F | Low-temperature (arctic, refrigeration) | ASTM A350 LF2 or ASTM A105 |
| 0°F to 70°F | Room temperature (standard conditions) | ASTM A105 (standard) |
| 70°F to 300°F | Moderate elevated (steam, hot water) | ASTM A105 (standard) |
| 300°F to 600°F | High temperature (steam piping) | ASTM A105 (standard) |
| 600°F to 800°F | Very high temperature (thermal service) | ASTM A105 (limit) |
| Above 800°F | Extreme temperature applications | Alloy Steel (F11, F22, F91) |
Temperature Selection Note: These are general guidelines. Specific temperature limits may vary based on: (1) ASME B16.5 pressure class, (2) system pressure, (3) fluid chemistry, (4) system design codes. Always consult applicable standards and engineering specifications for your exact application.
Protective Coating Options
Carbon steel flanges can be protected with various coatings for enhanced corrosion resistance in outdoor, marine, or potable water applications.
Bare (No Coating)
Standard
ASTM A105
Applications
Indoor, neutral environments
Service Life
Varies by environment
Cost Premium
Baseline
Hot-Dip Galvanized
Standard
ASTM A153
Applications
Outdoor, waterworks, moderate corrosion
Service Life
Extended outdoor service
Cost Premium
Contact for pricing
Zinc Plated
Standard
ASTM B633
Applications
Indoor light corrosion protection
Service Life
Light-duty protection
Cost Premium
Contact for pricing
Epoxy Coated (FBE)
Standard
AWWA C550
Applications
Potable water, waterworks
Service Life
Extended service in water applications
Cost Premium
Contact for pricing
Available Flange Types
Carbon steel is available in all ASME B16.5 flange types for maximum design flexibility:
Slip-On (SO)
Pipe passes through flange, requires fillet welds on both sides
Weld Neck (WN)
Long hub with taper, ideal for higher pressures and temperatures
Threaded (NPT)
Internal NPT threads, no welding required
Socket Weld (SW)
Socket for pipe insertion, fillet weld applied externally
Lap Joint (LJ)
Rotating on stub end, economical for frequent disconnection
Blind (BL)
No center hole, used to close off pipe ends
Common Applications
Water & Wastewater
- → Potable water systems
- → Wastewater treatment
- → Desalination plants
- → Water main connections
Oil & Gas
- → Onshore pipelines
- → Gathering systems
- → Crude oil transport
- → Natural gas piping
HVAC & Utilities
- → Steam distribution
- → Hot water lines
- → Chilled water systems
- → Compressed air
Chemical Processing
- → General chemical plants
- → Neutral fluid service
- → Temperature-controlled lines
- → Industrial piping
Power Generation
- → Low-pressure steam
- → Condensate piping
- → Circulating water
- → Auxiliary systems
Food & Beverage
- → Water lines
- → Process piping
- → Steam condensate
- → Utility connections
Frequently Asked Questions
Ready to Specify Carbon Steel Flanges?
Our engineering team can help you select the right grade (A105 or A350 LF2), flange type, and coating for your application. Get a quick quote or technical recommendation.