Carbon Steel Socket Weld Flange — Factory Direct Supplier | Huaxia-Steel
Carbon steel socket weld flanges (SW flanges) are the preferred connection for small-bore, high-pressure piping in chemical, petrochemical, oil & gas, power and refinery service. Unlike slip-on or weld neck flanges, the socket weld flange is engaged by a fillet weld around the OD of the pipe — making it ideal for Class 600 and above systems up to 2" NPS where butt welding a small pipe is impractical. Huaxia Steel manufactures SW flanges in ASTM A105 / A105N forged carbon steel, in sizes 1/2" to 24" and ASME pressure classes 150 to 2500.
1. Product Overview
- Strong, leak-tight joint for high-pressure small-bore piping
- Reduced weld preparation compared to butt welding (no 37.5° bevel required)
- Self-aligning engagement — pipe rests in the socket for accurate fit-up
- Suitable for Class 600 and above systems up to 2" NPS
- Compatible with ASME B16.5 pipe schedule 40 and 80 bore
Socket weld flanges are not recommended for services with severe thermal cycling, crevice corrosion risk, or where the system must be drained and re-entered frequently. The crevice between pipe OD and socket bore can collect process fluids and corrosion products.
2. Material Grades
| Grade | Standard | Typical Application |
|---|---|---|
| ASTM A105 | Forged carbon steel for piping components | General process piping, ambient and elevated temperature |
| ASTM A105N | A105 normalised (grain refined) | Low-temperature service down to −29°C (−20°F) |
| ASTM A350 LF2 | Low-temperature carbon steel | Cryogenic service down to −46°C (−50°F) |
| ASTM A694 F42 / F46 / F52 | High-strength carbon steel | High-pressure transmission piping |
For sour service (NACE MR0175), specify A105 with supplementary requirement S9 (hardness ≤ 22 HRC, sulphur ≤ 0.015%).
3. Standard Size Range and Pressure Class
Huaxia Steel socket weld flanges are produced per ASME B16.5 in the following size and class combinations:
| Pressure Class | Size Range (NPS) | Manufacturing Standard |
|---|---|---|
| Class 150 | 1/2" – 24" | ASME B16.5 |
| Class 300 | 1/2" – 24" | ASME B16.5 |
| Class 600 | 1/2" – 24" | ASME B16.5 |
| Class 900 | 1/2" – 24" | ASME B16.5 |
| Class 1500 | 1/2" – 24" | ASME B16.5 |
| Class 2500 | 1/2" – 12" | ASME B16.5 |
Note: Socket weld flanges are most commonly used in NPS 1/2" to 2" where butt welding of small pipe is impractical. Above 2" NPS, weld neck flanges are typically preferred. Above 24" NPS, ASME B16.47 series A or B flanges apply.
4. Dimensional Standards
All SW flanges conform to ASME B16.5 dimensional tolerances. Key parameters:
- Outside diameter (OD): per ASME B16.5 Table 2
- Bore diameter (socket ID): matches pipe schedule 40 / 80 bore + 0.79 mm / − 0.00 mm tolerance
- Socket depth: per ASME B16.5 § 6.4 (typically 9.5 mm for NPS ≤ 3", deeper for larger)
- Hub length: per ASME B16.5
- Bolt circle, number and diameter of bolt holes: per ASME B16.5 Table 2
- Flange thickness: per ASME B16.5 Table 2
5. Facing Types
| Type | Description | Typical Application |
|---|---|---|
| Raised Face (RF) | 1.6 mm (1/16") or 3.2 mm (1/8") raised face with serrated finish (125–250 RMS) | Standard for Class 150 & 300; default for most service |
| Flat Face (FF) | No raise; flat sealing face | Used with cast iron flanges or where flat gasket is required |
| Ring Type Joint (RTJ) | RTJ groove per ASME B16.5 | High-pressure Class 600 and above |
| Male & Female (M&F) | Matching tongue-and-groove facing | Self-aligning high-pressure service |
| Tongue & Groove (T&G) | Similar to M&F, different geometry | High-pressure service |
The most common facing for carbon steel SW flanges is Raised Face (RF) with 1.6 mm (1/16") or 3.2 mm (1/8") height and a 125–250 micro-inch (AARH) serrated finish. Spiral-wound or compressed non-asbestos gaskets are typically used with RF flanges.
6. Chemical Composition (ASTM A105)
7. Mechanical Properties (ASTM A105)
| Property | ASTM A105 Requirement |
|---|---|
| Tensile strength, min | 70 ksi (485 MPa) |
| Yield strength, min | 36 ksi (250 MPa) |
| Elongation in 2 in. (50 mm), min | 22% |
| Reduction of area, min | 30% |
| Hardness, max | 187 HB |
8. Common Applications
- Small-bore chemical and petrochemical process piping (1/2" to 2" NPS)
- Steam systems up to Class 1500
- High-pressure hydraulic and instrument piping
- Refinery and gas plant auxiliary systems
- Power plant boiler feedwater and condensate lines
- Offshore platform small-bore hydraulic and control piping
- Pharmaceutical and food-grade piping (with proper gasket and surface finish)
11. Packaging and Shipping
Flanges are individually wrapped in plastic or kraft paper, then packed in fumigated wooden crates or plywood boxes. Each crate is strapped with steel bands, labelled with flange size, class, material, heat number and MTC number. Socket bore is protected with plastic caps or wooden plugs to prevent damage in transit. Small crates can be loaded into 20’ containers; large flanges are loaded on pallets or flat racks.
Standard lead time: 20–40 days for standard size and class; 40–65 days for non-standard combinations. Sample lot of 5–20 pieces available for trial orders.
Need carbon steel socket weld flanges for a high-pressure small-bore piping project? Huaxia Steel manufactures A105 / A105N SW flanges in Class 150–2500, NPS 1/2"–24", with RF / FF / RTJ facing and EN 10204 3.1 certificate. Email [email protected] with your size, pressure class, material grade, facing, quantity and delivery port, and we will respond with a quotation within 24 hours.
10. Quality Assurance and Inspection
Each lot of socket weld flanges is supplied with EN 10204 Type 3.1 mill certificate including:
- Heat number and forging traceability
- Chemical composition (heat + product analysis)
- Tensile test, yield strength, elongation, reduction of area
- Hardness test (HB) — per batch
- Charpy V-notch test (if specified — mandatory for A350 LF2)
- Dimensional inspection report (OD, ID, thickness, bolt circle, facing)
- Visual and surface finish inspection
- 100% magnetic particle examination (per ASME B16.5 for higher classes)
For critical service, third-party witnessed inspection by SGS, BV, TUV or ABS can be arranged. PMI (Positive Material Identification) and hydrostatic testing are available on request.
11. Packaging and Shipping
Flanges are individually wrapped in plastic or kraft paper, then packed in fumigated wooden crates or plywood boxes. Each crate is strapped with steel bands, labelled with flange size, class, material, heat number and MTC number. Socket bore is protected with plastic caps or wooden plugs to prevent damage in transit. Small crates can be loaded into 20’ containers; large flanges are loaded on pallets or flat racks.
Standard lead time: 20–40 days for standard size and class; 40–65 days for non-standard combinations. Sample lot of 5–20 pieces available for trial orders.
Need carbon steel socket weld flanges for a high-pressure small-bore piping project? Huaxia Steel manufactures A105 / A105N SW flanges in Class 150–2500, NPS 1/2"–24", with RF / FF / RTJ facing and EN 10204 3.1 certificate. Email [email protected] with your size, pressure class, material grade, facing, quantity and delivery port, and we will respond with a quotation within 24 hours.
10. Quality Assurance and Inspection
Each lot of socket weld flanges is supplied with EN 10204 Type 3.1 mill certificate including:
- Heat number and forging traceability
- Chemical composition (heat + product analysis)
- Tensile test, yield strength, elongation, reduction of area
- Hardness test (HB) — per batch
- Charpy V-notch test (if specified — mandatory for A350 LF2)
- Dimensional inspection report (OD, ID, thickness, bolt circle, facing)
- Visual and surface finish inspection
- 100% magnetic particle examination (per ASME B16.5 for higher classes)
For critical service, third-party witnessed inspection by SGS, BV, TUV or ABS can be arranged. PMI (Positive Material Identification) and hydrostatic testing are available on request.
11. Packaging and Shipping
Flanges are individually wrapped in plastic or kraft paper, then packed in fumigated wooden crates or plywood boxes. Each crate is strapped with steel bands, labelled with flange size, class, material, heat number and MTC number. Socket bore is protected with plastic caps or wooden plugs to prevent damage in transit. Small crates can be loaded into 20’ containers; large flanges are loaded on pallets or flat racks.
Standard lead time: 20–40 days for standard size and class; 40–65 days for non-standard combinations. Sample lot of 5–20 pieces available for trial orders.
Need carbon steel socket weld flanges for a high-pressure small-bore piping project? Huaxia Steel manufactures A105 / A105N SW flanges in Class 150–2500, NPS 1/2"–24", with RF / FF / RTJ facing and EN 10204 3.1 certificate. Email [email protected] with your size, pressure class, material grade, facing, quantity and delivery port, and we will respond with a quotation within 24 hours.
9. Manufacturing Standards
- ASME B16.5 — Pipe Flanges and Flanged Fittings (NPS 1/2 through NPS 24)
- ASME B16.47 — Large Diameter Steel Flanges (NPS 26 and above)
- ASTM A105 / A105N — Forged carbon steel for piping components
- ASTM A350 LF2 — Low-temperature carbon steel
- EN 1092-1 — Flanges and their joints (PN designation)
- MSS SP-97 — Forged carbon steel branch outlet fittings (for socket weld outlets)
10. Quality Assurance and Inspection
Each lot of socket weld flanges is supplied with EN 10204 Type 3.1 mill certificate including:
- Heat number and forging traceability
- Chemical composition (heat + product analysis)
- Tensile test, yield strength, elongation, reduction of area
- Hardness test (HB) — per batch
- Charpy V-notch test (if specified — mandatory for A350 LF2)
- Dimensional inspection report (OD, ID, thickness, bolt circle, facing)
- Visual and surface finish inspection
- 100% magnetic particle examination (per ASME B16.5 for higher classes)
For critical service, third-party witnessed inspection by SGS, BV, TUV or ABS can be arranged. PMI (Positive Material Identification) and hydrostatic testing are available on request.
11. Packaging and Shipping
Flanges are individually wrapped in plastic or kraft paper, then packed in fumigated wooden crates or plywood boxes. Each crate is strapped with steel bands, labelled with flange size, class, material, heat number and MTC number. Socket bore is protected with plastic caps or wooden plugs to prevent damage in transit. Small crates can be loaded into 20’ containers; large flanges are loaded on pallets or flat racks.
Standard lead time: 20–40 days for standard size and class; 40–65 days for non-standard combinations. Sample lot of 5–20 pieces available for trial orders.
Need carbon steel socket weld flanges for a high-pressure small-bore piping project? Huaxia Steel manufactures A105 / A105N SW flanges in Class 150–2500, NPS 1/2"–24", with RF / FF / RTJ facing and EN 10204 3.1 certificate. Email [email protected] with your size, pressure class, material grade, facing, quantity and delivery port, and we will respond with a quotation within 24 hours.
