Recently, Haihao Group successfully completed the manufacturing and delivery of a full range of nickel alloy UNS N06625 (Inconel 625) pipe fittings and flanges for a high-specification offshore project. This batch included forged flanges, sockolets, couplings, swage nipples, and blind flanges. While all products shared the same base material – UNS N06625, the Mill Test Certificates (MTCs) showed two distinct ASTM specifications: ASTM B564 and ASTM B366.

So why do some items follow ASTM B564, while others are labeled under ASTM B366, even though they are all made from UNS N06625?

Let’s clarify the difference and explain why both standards are used in our supply.

MSS SP-97 Sockolet Nickel Alloy ASTM B366 UNS N06625

What Did Haihao Group Supply?

ASTM B366 UNS N06625 Products:

1 1/2″ x 24″ 3000# Sockolet, ASME B16.11, MSS SP-97

1 1/2″ x 16″ 3000# Sockolet, ASME B16.11, MSS SP-97

3/4″ 3000# Coupling SWE, ASME B16.11

1″ x 3/4″ SCH 40S Concentric Reducing Nipple (Swage Nipple), MSS SP-95

ASTM B564 UNS N06625 Products:

WN RF Flanges 150# (2″, 1 1/2″, 1″, 3/4″)

SWE RF Flanges 150# (1 1/2″, 1″, 3/4″)

Blind Flanges RF (150#, 300#, 600#) in sizes from 1/2″ to 3″

All flanges manufactured to ASME B16.5, with NACE MR-01-75 compliance

All components were tested, inspected, and delivered with full documentation, including MTCs, NACE compliance, and dimensional reports.

API 6A TYPE 6BX RTJ ASTM B564 UNS N06625 WN flanges

Why Two ASTM Standards for the Same Alloy?

Both ASTM B366 and ASTM B564 apply to UNS N06625, a corrosion-resistant nickel-chromium-molybdenum-niobium alloy commonly used in offshore, marine, and chemical service. However, the form and manufacturing process of the fittings determine which standard applies:

ASTM B366 UNS N06625

For Wrought Pipe Fittings

Standard Name: Standard Specification for Wrought Nickel Alloy Fittings

Applicable Products: Tees, elbows, reducers, nipples, swage nipples, sockolets, couplings

Form: Wrought or fabricated fittings (hot or cold formed, or welded)

Applications: Used in piping systems for welded or socket weld connections

Relevant Standards: ASME B16.9, ASME B16.11, MSS SP-97, MSS SP-95

In our supply, items like the Sockolets, Couplings, and Reducing Nipples fall under this category. These products require excellent weldability and pressure integrity in high-temperature, corrosive environments.

ASTM B564 UNS N06625

For Forged Flanges and Forged Fittings

Standard Name: Standard Specification for Nickel Alloy Forgings

Applicable Products: Flanges, forged outlet fittings, high-pressure forged components

Form: Forged and machined components

Applications: Ideal for flanged joints under high pressure and mechanical stress

Relevant Standards: ASME B16.5 (flanges), NACE MR0175 (sour service)

In our shipment, WN RF flanges, SWE flanges, and blind flanges were all manufactured in accordance with ASTM B564, offering high strength and excellent sealing performance for bolted flange joints.

Summary of Key Differences

Real-World Application: Offshore Systems

Haihao Group’s UNS N06625 components will be used in a high-salinity offshore environment, where corrosion resistance, fatigue strength, and compliance with NACE MR-01-75 are essential. Using ASTM B366 for the weldable components (Sockolets, nipples, couplings) ensures seamless integration into the pipeline. Meanwhile, ASTM B564 flanges provide secure, high-strength sealing in pressure-rated systems.

ASTM B366 MSS SP-95 NACE MR0175 ISO 15156 Swage Nipples

Why Choose Haihao Group for Inconel 625 Solutions?

40+ years of experience in alloy piping components

In-house forging, machining, and heat treatment facilities

Compliance with ASTM, ASME, MSS, and NACE standards

Custom fabrication and fast delivery for offshore and critical service projects

Need UNS N06625 fittings or flanges?
Whether you require forged flanges under ASTM B564 or socket weld pipe fittings under ASTM B366, Haihao Group delivers certified, high-quality components with full traceability and global compliance.

Contact us today for technical support, pricing, or custom inquiries. Email:sales@haihaogroup.com