Socket Weld Flange Carbon Steel — Factory Direct Supplier | Huaxia-Steel
Socket weld flanges are a widely used pipe connection component in high-pressure, small-bore piping systems. Featuring a recessed socket (counterbore) into which the pipe is inserted before fillet welding, socket weld flanges provide strong, leak-tight connections with excellent fatigue resistance. Huaxia-Steel manufactures carbon steel socket weld flanges to international standards for petrochemical, power generation, and industrial process piping systems.
Product Overview
A socket weld flange consists of a flat circular plate with a bolt-hole pattern and a raised face or flat face sealing surface. The bore features a counterbore (socket) machined to accept the pipe OD with a small clearance. The pipe is inserted into the socket until it bottoms against the shoulder, then withdrawn approximately 1.6mm (1/16″) to create an expansion gap, and fillet welded on the outside. This design eliminates the need for internal weld preparation and makes socket weld flanges particularly efficient for shop fabrication of small-bore piping.
The socket weld design offers several advantages over threaded flanges: it is not limited by thread strength at high pressures, it eliminates the risk of thread leakage, and it does not reduce the wall thickness of the connecting pipe. Compared to weld neck flanges, socket weld flanges are simpler and more economical for sizes NPS 4 (DN 100) and below.
Specifications & Dimensions
| Parameter | Standard |
|---|---|
| Size Range | NPS 1/2″ – 4″ (DN 15 – DN 100) |
| Pressure Class | Class 150, Class 300, Class 600, Class 900, Class 1500 |
| Facing Type | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Flange Face Finish | Smooth finish (Ra 3.2–6.3 μm), Serrated (stock finish), or smooth per specification |
| Bore | Per ASME B16.5 socket dimensions (pipe OD + clearance) |
| Socket Depth | Per ASME B16.5 / EN 1092-1 table values (varies by size and class) |
| Bolt Circle | Per class and size per applicable standard |
Standard dimensions for carbon steel socket weld flanges (ASME B16.5 Class 150):
| NPS | Pipe OD | Flange OD | Bolt Circle | # Bolts | Bolt Size | Flange Thickness | RF Height | Socket Depth (min) |
|---|---|---|---|---|---|---|---|---|
| 1/2″ | 21.3mm | 90mm | 60.3mm | 4 | 1/2″ | 9.6mm | 1.6mm | 10mm |
| 3/4″ | 26.7mm | 100mm | 69.9mm | 4 | 1/2″ | 11.2mm | 1.6mm | 11mm |
| 1″ | 33.4mm | 110mm | 79.4mm | 4 | 1/2″ | 12.7mm | 1.6mm | 13mm |
| 1-1/2″ | 48.3mm | 125mm | 98.4mm | 4 | 1/2″ | 14.3mm | 1.6mm | 14mm |
| 2″ | 60.3mm | 150mm | 120.7mm | 4 | 5/8″ | 15.9mm | 1.6mm | 16mm |
| 2-1/2″ | 73.0mm | 180mm | 139.7mm | 4 | 5/8″ | 17.5mm | 1.6mm | 17mm |
| 3″ | 88.9mm | 190mm | 152.4mm | 4 | 5/8″ | 19.1mm | 1.6mm | 19mm |
| 4″ | 114.3mm | 230mm | 190.5mm | 8 | 5/8″ | 22.3mm | 1.6mm | 21mm |
Available Steel Grades
| Grade | Standard | Chemical Requirements | Typical Pressure/Temp Rating |
|---|---|---|---|
| ASTM A105 | ASTM A105/A105M | C ≤0.35, Mn 0.60–1.05, P ≤0.035, S ≤0.040, Si 0.10–0.35, Cu ≤0.40 | Standard carbon steel forging for flanges; service from -29°C to 425°C |
| ASTM A105N | ASTM A105/A105M | Same as A105, normalized heat treatment | Normalized for improved toughness, service to -29°C |
| ASTM A350 LF2 | ASTM A350/A350M | C ≤0.30, Mn 0.60–1.35, impact tested at -46°C | Low-temperature carbon steel; service from -46°C to 425°C |
| ASTM A694 F52 | ASTM A694/A694M | C ≤0.26, high-strength, min yield 360 MPa | High-pressure pipeline flanges, transmission piping |
| C22.8 / P250GH | EN 10222-2 | C 0.16–0.22, Mn 0.60–1.20 | European pressure vessel standard, service to 400°C |
| 16Mn / Q345B | GB/T 1591 | C ≤0.20, Mn 1.00–1.60 | Chinese standard medium-strength flange material |
A105 is our standard carbon steel socket weld flange material and is suitable for most non-corrosive service applications from ambient to moderately elevated temperatures. For low-temperature service applications (-29°C to -46°C), we recommend ASTM A350 LF2 with Charpy impact testing.
Manufacturing Standards
Huaxia-Steel socket weld flanges are manufactured and tested to the following international standards:
Applications
Socket weld flanges in carbon steel are specified across a broad range of industrial piping systems:
- Oil and gas: Small-bore process piping, instrument connections, drain and vent lines, chemical injection quills, sample points. Class 600 and 900 flanges are common in refinery and gas processing applications. A105 material with NACE MR0175 compliance (H₂S service) available on request.
- Petrochemical: Utility piping (steam, condensate, cooling water, instrument air), process vent and drain connections, catalyst handling lines, heat exchanger piping. A105N normalized material preferred for process service above 200°C.
- Power generation: Boiler blowdown lines, steam tracing and drip legs, instrument and gauge connections, sampling lines, chemical feed piping. A105 material with supplementary requirements per ASME BPVC Section II.
- Chemical processing: General utility piping where carbon steel is chemically compatible. Small-bore process lines with manageable corrosion allowance. Note: socket weld flanges should not be used where crevice corrosion is a concern due to the gap at the base of the socket.
- Shipbuilding and marine: Fuel oil piping, lube oil lines, hydraulic piping, bilge and ballast lines (small bore), compressed air services. Hot-dip galvanizing available for topside marine exposure.
Quality Assurance
Our socket weld flange quality program includes the following inspection and testing:
Packaging & Shipping
- Small flanges (NPS 1/2″ – 2″): Packed in export-grade cartons with protective separators between flange faces. Maximum 25 kg per carton for manual handling.
- Medium flanges (NPS 2-1/2″ – 4″): Stacked with plywood or fiber separators to protect facing surfaces. Secured on export pallets with steel banding and wrapped in VCI film.
- Surface protection: Flange faces protected with rust preventive oil and plastic face covers. Threaded bolt holes fitted with plastic plugs.
- Documentation: Commercial invoice, packing list, certificate of origin (Form A / Form E / generic), material test certificates to EN 10204 Type 3.1, NDT reports (if ordered), hydrostatic test reports (if ordered).
Delivery times: 7–15 days for standard stock in A105 material; 25–40 days for non-stock sizes, special materials (A350 LF2), or large production quantities. Express air freight available for urgent requirements (3–7 days).
Request a Quotation
Contact Huaxia-Steel for carbon steel socket weld flanges. Specify: size (NPS or DN), pressure class (150/300/600/900/1500), facing type (RF/FF/RTJ), material grade (A105/A350 LF2/other), applicable standard (ASME B16.5/EN 1092-1/JIS B2220), and quantity. Our team will provide technical specification confirmation and competitive pricing within 24 hours.
