Threaded Flange Carbon Steel — Factory Direct Supplier | Huaxia-Steel

Huaxia-Steel supplies carbon steel threaded flanges manufactured from ASTM A105 forgings, fully threaded to ASME B1.20.1 NPT and machined to ASME B16.5 dimensions. Threaded flanges attach to pipe without welding — a torch, a wrench and thread sealant are all that’s needed — making them the standard choice for utility lines, small-bore connections, galvanized piping and any installation where hot work is prohibited or impractical. We stock Class 150 and 300 in common sizes and machine other classes and special dimensions to order, with EN 10204 3.1 mill certificates and factory-direct export pricing.

Product Overview

A threaded flange (TH flange) is a flat or raised-face flange with an internal NPT taper thread that screws onto the matching pipe thread. The joint is sealed by the thread interference plus sealant or PTFE tape; no welding is involved. Compared with socket weld and slip-on flanges, threaded flanges trade some pressure capability and fire safety for zero hot work — which is exactly what many maintenance crews and low-pressure systems need.

• Material: ASTM A105 (room-temp carbon steel), A350 LF2 (low-temperature), A694 F42–F70 (high-yield pipeline service) on request.
• Size range: NPS 1/2″ – 24″ (DN15–DN600).
• Pressure class: ASME Class 150, 300, 600 (other classes to order).
• Thread: NPT per ASME B1.20.1; BSPT/BS21 and DIN 2999/ISO 7 available for export markets.
• Facing: raised face (RF, 1/16″ for Class 150/300); flat face for mating cast-iron equipment.
• Standard: ASME B16.5 dimensions and tolerances; threaded flanges above NPS 24 fall outside B16.5 — contact us for B16.47 options or special machining.

Specifications & Dimensions (Class 150, ASME B16.5)

NPS	Flange OD (in)	Thickness (in)	RF Dia (in)	Bolts × Size	Bolt Circle (in)	Threads (TPI)
1/2	3.50	0.44	1.38	4 × 1/2″	2.38	14
1	4.25	0.50	1.88	4 × 1/2″	3.12	11½
2	6.00	0.69	3.00	4 × 5/8″	4.75	11½
4	9.00	0.88	5.00	8 × 5/8″	7.50	8
6	11.00	0.94	7.00	8 × 3/4″	9.50	8
8	13.50	1.06	8.50	8 × 3/4″	11.75	8
12	19.00	1.19	12.75	12 × 7/8″	16.00	8
16	21.25	1.25	15.25	12 × 7/8″	18.75	8

Class 300 dimensions (thicker flange, 12-bolt patterns at larger NPS) and full dimension tables for all sizes are available on request — we supply the complete table set with every quotation.

Available Grades & Equivalents

Grade	Standard	Service
A105	ASTM A105/A105M	-29 °C to +425 °C general carbon steel service
A350 LF2 CL1	ASTM A350	Down to -46 °C impact-tested service
A694 F52	ASTM A694	High-yield flanges for API 5L pipeline systems
PN16/PN40 equivalents	EN 1092-1, P250GH	European-spec threaded flanges (with parallel thread options)

Manufacturing Standards & Process

1. Forging: A105 bars/forgings forged and normalized (or as-rolled with hardnes limits) per the material spec.
2. Machining: OD, thickness, raised face and bore machined to B16.5; facing finish 125–500 AARH serrated.
3. Threading: NPT taper threads cut or rolled to ASME B1.20.1, gauged with L1 and L2 plug gauges — every flange, not samples.
4. Marking: per MSS SP-25 — grade, NPS, class, B16.5, heat number and our brand; laser or stamp marking.
5. Inspection: hardness (≤187 HB for A105), dimensional and thread gauge reports with each lot; PMI and MPI available.

Applications

• Utility and instrument connections where welding is not allowed (paint shops, tank farms, refineries under hot-work restrictions).
• Galvanized and coated pipe systems — welding would destroy the coating.
• Temporary or reusable piping: spools, rental equipment, dredging lines that are dismantled and reassembled.
• Small-bore branches and drains on large pipe, low-pressure air, water and steam-condensate service.

Pressure/temperature limits: threaded joints are recommended for moderate service. Per ASME B31.3 and industry practice, avoid threaded flanges above ~Class 300 equivalent pressure, above 200 °C steam, or in severe cyclic and vibration service. For those conditions, weld neck or socket weld flanges are the correct choice.

Quality Assurance

• Every flange threaded and gauged; thread gauge reports (L1/L2) supplied on request.
• EN 10204 3.1 MTC with heat-number traceability on every shipment.
• Hardness testing per A105 (187 HB max), sampled per lot.
• Dimensional inspection to ASME B16.5 Table 12 tolerances, including bolt-circle straddling.
• Third-party inspection (SGS, BV, TUV, Lloyd’s) welcome; we coordinate at cost.

Packaging & Shipping

Flanges are thread-protected (plastic caps or tape on the threaded bore), packed in seaworthy plywood or steel pallets, each bundle strapped and marked with size/class/heat. Containerized shipment for small lots; loose or breakbulk for large-diameter orders. Typical lead time: stocked Class 150/300 in 7–15 days; machined-to-order in 3–5 weeks. We ship FOB, CFR, CIF and DAP from Tianjin, Shanghai, Qingdao or Ningbo.

Why Buy Threaded Flanges from Huaxia-Steel

• Factory direct: forging, machining and threading under one roof — no trading markup.
• Full gauge inspection of threads, the number-one rejection point on low-cost imports.
• Mixed-size container loading: combine Class 150/300 threaded, weld neck and blind flanges in one order.
• Documentation package: MTC, dimensional report, gauge report, packing list and photos before shipment.

Get a threaded flange quote today. Send us your size list (NPS, class, facing) to [email protected] or use the inquiry form — factory pricing and delivery schedule within 24 hours.