Weld Neck Flange Carbon Steel — Factory Direct Supplier | Huaxia-Steel
A carbon steel weld neck flange features a long, tapered hub that transitions smoothly into the pipe via a full-penetration butt weld. This design provides the highest strength and fatigue resistance of any flange type, making weld neck flanges the preferred choice for high-pressure, high-temperature, and cyclic-loading applications. Huaxia-Steel manufactures carbon steel weld neck flanges to ASME B16.5, ASME B16.47, EN 1092-1, and JIS B2220 standards in sizes from 1/2″ to 48″ and pressure classes from 150 to 2500.
The distinguishing feature of a weld neck flange is its tapered hub, which reduces stress concentration at the weld joint and provides excellent load transfer between the flange and pipe. This makes it ideal for services involving thermal cycling, vibration, bending moments, and high pressure—conditions where slip-on or socket weld flanges would fail prematurely. Weld neck flanges are the standard for refinery, petrochemical, power plant, and subsea applications.
Product Overview
Carbon steel weld neck flanges from Huaxia-Steel are forged from certified billets and precision-machined to exacting tolerances. The long neck allows the flange to be butt-welded directly to the pipe, creating a continuous, uniform structure that handles stress as effectively as the pipe itself. They are the most reliable flange type for critical service.
Specifications & Dimensions
Typical dimensions for ASME B16.5 carbon steel weld neck flanges (raised face):
| Nominal Size | Class 150 OD (mm) | Hub Length (mm) | Class 300 OD (mm) | Hub Length (mm) | Pipe OD Match |
|---|---|---|---|---|---|
| 1/2″ (DN15) | 89 | 64 | 95 | 70 | 21.3 |
| 1″ (DN25) | 108 | 70 | 117 | 76 | 33.4 |
| 2″ (DN50) | 152 | 92 | 165 | 108 | 60.3 |
| 4″ (DN100) | 229 | 111 | 254 | 140 | 114.3 |
| 6″ (DN150) | 279 | 124 | 318 | 159 | 168.3 |
| 8″ (DN200) | 343 | 140 | 381 | 190 | 219.1 |
| 12″ (DN300) | 483 | 168 | 559 | 248 | 323.9 |
The weld neck hub outside diameter matches the pipe outside diameter, enabling a full-penetration butt weld per ASME B31.3 or B31.1.
Weight Reference (Approximate)
| Size | Class 150 (kg) | Class 300 (kg) | Class 600 (kg) |
|---|---|---|---|
| 2″ (DN50) | 3.0 | 5.0 | 7.5 |
| 4″ (DN100) | 7.5 | 13.5 | 22.0 |
| 6″ (DN150) | 13.5 | 27.0 | 45.0 |
| 8″ (DN200) | 21.0 | 44.0 | 72.0 |
Available Carbon Steel Grades
| Grade | Standard | Yield (min MPa) | Tensile (min MPa) | Service Temp | Application |
|---|---|---|---|---|---|
| A105 | ASTM A105 | 250 | 485 | -29°C to 425°C | Standard high-pressure |
| A350 LF2 | ASTM A350 | 250 | 485 | -46°C to 425°C | Low-temperature |
| A516 Gr.70 | ASTM A516 | 260 | 485 | -46°C to 425°C | Pressure vessel |
| A694 F52 | ASTM A694 | 360 | 490 | -29°C to 232°C | High-yield pipelines |
| S235JR | EN 10025 | 235 | 360 | Ambient | European structural |
For sour service (H2S environments), we offer A350 LF2 with NACE MR0175/ISO 15156 compliance and hardness control below 187 HB.
Manufacturing Standards
Our carbon steel weld neck flanges conform to:
- ASME B16.5 — Pipe flanges and flanged fittings (NPS 1/2 to 24)
- ASME B16.47 — Large diameter flanges (NPS 26 to 60, Series A & B)
- EN 1092-1 — European flange standard (Type 11 weld neck)
- JIS B2220 — Japanese flange standard (5K to 20K)
- ASTM A105 / A350 / A694 — Carbon steel forging material specs
- API 6A / 17D — Wellhead and subsea flange references
Why Choose Weld Neck Over Other Types
| Factor | Weld Neck | Slip-On | Socket Weld |
|---|---|---|---|
| Stress at weld | Lowest | Higher | Medium |
| Fatigue resistance | Excellent | Poor | Fair |
| High-pressure rating | Yes (to 2500) | Limited | Limited (to 3000 psi) |
| Thermal cycling | Handles well | Prone to failure | Moderate |
| Cost | Highest | Low | Medium |
Applications
Carbon steel weld neck flanges are specified for the most demanding services:
- Refineries and petrochemical plants — high-pressure process lines
- Power generation — boiler, steam, and turbine piping
- Offshore and subsea — risers, manifolds, wellhead connections
- Pipelines — high-pressure transmission and gathering lines
- Pressure vessels — nozzles and shell connections
- Cryogenic facilities — LNG with A350 LF2 low-temp grade
- Heat exchangers — where thermal cycling is severe
Quality Assurance
Every weld neck flange is subjected to comprehensive QC:
Packaging & Shipping
- Anti-rust oil on machined faces and hub bore
- Individual VCI wrapping or bubble protection
- Seaworthy wooden cases or pallets with steel strapping
- Clear marking: size, rating, grade, heat number, standard
- Lead time: 20–35 days for standard; expedited available
We export worldwide under FOB, CIF, CFR, DAP terms with full documentation: commercial invoice, packing list, certificate of origin, MTC (EN 10204 3.1/3.2), and inspection reports.
Why Choose Huaxia-Steel
- Factory-direct pricing with no distributor markup
- Forged flanges with full UT/MT inspection
- Complete size and class coverage in stock or fast production
- Certified materials with EN 10204 3.1/3.2 documentation
- MOQ from 1 ton, mixed orders accepted
- Third-party inspection support (SGS/BV/TÜV)
- Reliable global shipping with complete export paperwork
Request a quote for carbon steel weld neck flanges. Contact Huaxia-Steel with your required size, class, facing type, grade, and quantity. Our technical team will respond within 24 hours with a competitive offer and documentation support.
