Stainless Steel 904L Flanges

Stainless Steel 904L Flanges are pipe connection components manufactured from UNS N08904, a high-alloy austenitic stainless steel containing molybdenum (4–5%), copper (1–2%), and nickel (23–28%). The copper addition specifically enhances resistance to reducing acid environments, such as sulphuric acid, phosphoric acid, and acetic acid, where standard 316L corrodes rapidly. Stainless Steel 904L Flanges are specified when both pitting resistance and acid corrosion resistance are required at the same flanged joint.

These flanges are available across all standard face types, pressure classes, and flange forms to ASTM A182 F904L. They perform reliably in aggressive chemical, marine, and desalination environments without supplementary coatings. Their very low carbon content (0.02% max) ensures no sensitisation in the welded condition, making them a practical choice for systems that cannot accommodate post-weld heat treatment.

Price of Stainless Steel 904L Flanges

The pricing for Stainless Steel 904L flanges depends on the high nickel and molybdenum content, market fluctuations, required pressure ratings, and specific dimensions for severe acid-resistant applications.

Price Per Unit / Kg

The Indian market pricing for Stainless Steel 904L Flanges is Rs. 900/- to Rs. 2800/- per kilogram. International pricing follows LME nickel and molybdenum prices closely, and 904L has far higher alloy content than normal austenitic grades.

Factors Affecting Price

High nickel (23–28%) and molybdenum (4–5%) contents are the main cost drivers. Final cost will be based on pressure class, size, facing type, and ASTM A182 F904L certification. Buy Verified Stainless Steel 904L Flanges suppliers with complete MTC documents at a justifiable premium over non-certified stock.

Types of Stainless Steel 904L Flanges

Select from a specialised inventory of high-performance 904L components, specifically engineered for superior corrosion resistance in acidic and severe chemical processing environments.

Stainless Steel 904L Weld Neck Flanges (WN)
Stainless Steel 904L Slip-On Flanges (SO)
Stainless Steel 904L Blind Flanges (BL)
Stainless Steel 904L Socket Weld Flanges (SW)
Stainless Steel 904L Threaded Flanges (TH)
Stainless Steel 904L Lap Joint Flanges (LJ)
Stainless Steel 904L Long Weld Neck Flanges (LWN)
Stainless Steel 904L Orifice Flanges
Stainless Steel 904L Reducing Flanges
Stainless Steel 904L Spectacle Blind Flanges
Stainless Steel 904L Ring Type Joint (RTJ) Flanges

Specifications of Stainless Steel 904L Flanges

The specifications of Stainless Steel 904L Flanges, including size, standard, and pressure class, are listed in the table below.

Parameter	Verified Details
Manufacturing Standards	ASTM A182 / ASME B16.5 / EN1092-1
Standard Size Range	1/2" to 48" NB standard
Pressure Class / Rating	Class 150 to 2500 / PN6–PN64
Material Grades	SS 904L / UNS N08904
Flange Face Type	RF, FF, RTJ, T&G
Common Flange Types	Weldneck, Slip-on, Blind, Socket
Production Technique	Forged or plate machined
Surface Finish	Smooth or serrated finish

Chemical Properties of Stainless Steel 904L Flanges

The chemical composition of Stainless Steel 904L Flanges, including their proportions, is listed in the table below.

Grade	C	Mn	Si	P	S	Cr	Mo	Ni	N	Cu
904L Min	—	—	—	—	—	19.0	4.0	23.0	—	1.0
904L Max	0.02	2.0	1.0	0.045	0.035	23.0	5.0	28.0	0.10	2.0

Mechanical Properties of Stainless Steel 904L Flanges

Below you can see the mechanical properties of Stainless Steel 904L Flanges, such as tensile strength, yield strength, and elongation.

Property	Value
Tensile Strength	490 MPa min
Yield Strength (0.2% Offset)	220 MPa min
Elongation (% in 50 mm)	35% min
Hardness (Brinell)	200 HB max

Physical Properties of Stainless Steel 904L Flanges

The physical properties of Stainless Steel 904L Flanges are listed in the table below, along with density and thermal conductivity.

Grade	Density (kg/m³)	Elastic Modulus (GPa)	Mean Co-eff of Thermal Expansion (µm/m/°C) 0–100°C	Thermal Conductivity (W/m.K) at 100°C	Specific Heat (J/kg.K)	Elec Resistivity (nΩ.m)
904L	8000	190	15.0	12.0	450	900

Dimension Chart of Stainless Steel 904L Flanges

Review the following dimension chart for SS 904L RTJ flanges to ensure compatibility across various international standards, including ANSI, AS, and ISO.

Standard	Class / Rating	Diameter (mm)	Bolt Circle (mm)	Number of Bolts	Bolt Size	Bolt Hole (mm)
ANSI B16.5	Class 150	89	60	4	1/2"	16
ANSI B16.5	Class 300	95	67	4	1/2"	16
ANSI B16.5	Class 600	95	67	4	1/2"	16
ANSI B16.5	Class 900	121	83	4	3/4"	22
AS 4087	PN14	95	67	4	M12	14
AS 2129	Table C / D / E	95	67	4	1/2"	14
AS 2129	Table H / J	114	83	4	5/8"	17
ISO 7005 (DIN)	PN6	80	55	4	M10	11
ISO 7005 (DIN)	PN10 / 16	95	65	4	M12	14
ISO 7005 (DIN)	PN20	90	60.5	4	M14	16
ISO 7005 (DIN)	PN25 / 40	95	65

Dimensions per ASME B16.5 Class 150. Confirm dimensions for other pressure classes with your supplier.

Size Chart of Stainless Steel 904L Flanges

Please refer to the following size chart of SS 904L Flanges given below in the table, useful for the procurement and getting proper material as required.

NPS	OD	Thickness	Hub Diameter	Fillet Radius	Socket Depth
1/2"	3.50	0.44	1.19	0.125	0.38
3/4"	3.88	0.50	1.50	0.125	0.44
1"	4.25	0.56	1.94	0.125	0.50
1-1/4"	4.62	0.62	2.31	0.187	0.56
1-1/2"	5.00	0.69	2.56	0.25	0.62
2"	6.00	0.75	3.06	0.312	0.69
2-1/2"	7.00	0.88	3.56

Pressure Rating Chart of Stainless Steel 904L Flanges

Review the pressure-temperature limits for Grade 904L flanges to ensure safe operation within high-corrosion and high-pressure process environments.

Pressure Class	–29 to 38°C	100°C	200°C	300°C
Class 150	15.9	13.3	11.2	9.7
Class 300	41.4	34.8	29.2	25.4
Class 600	82.7	69.6	58.3	50.8
Class 900	124.1	104.4	87.5	76.2
Class 1500	206.8	174.0	145.8	127.0
Class 2500	344.7	290.0	243.0

Pressure ratings per ASME B16.5 for Group 2.10 (UNS N08904). Always verify with the relevant ASME table for your exact service temperature.

Key Features of Stainless Steel 904L Flanges

Understand the specialised corrosion resistance and critical industrial deployments for this high-alloy austenitic grade.

Intergranular Corrosion Resistance
Acid Resistance
Chloride Resistance
Non-Magnetic
Crack Resistance
Weld Readiness
Standard Facings
Code Compliance

Applications of Stainless Steel 904L Flanges

Explore the severe chemical and marine environments where Grade 904L is the primary choice for structural integrity.

Chemical Plants
Oil/Gas Pipework
Desalination Systems
Pharmaceutical Piping
Pulp/Paper Equipment
Flue Scrubbing
Heat Exchangers
Food Processing
Offshore Piping

How to Choose the Right Stainless Steel 904L Flanges Supplier?

Please consider the following points before placing an order for the materials for your project, as these points will help you plan best for it.

Supplier Selection Criteria

Verify that the supplier provides mill test certificates with full heat and lot traceability confirming UNS N08904 composition. Check copper and nickel values on the MTC 904L, which is regularly confused with 317L or 316L by unverified suppliers, and the absence of copper immediately identifies an incorrect grade. Always request EN 10204 3.1 as a minimum; EN 10204 3.2 is advisable for pressure vessels and ASME-coded systems.

Technical Considerations

Confirm flange standard and pressure class before ordering. ASME B16.5 covers up to 24" NB; ASME B16.47 covers 26" and above. Verify the facing type matches your gasket and mating flange. For ASME pressure systems, ensure material is certified to ASTM A182 F904L, not generic "904L plate" or bar-converted stock, which may not meet forging qualification requirements.

Quality & Certification Check

Best Stainless Steel 904L flange suppliers are ISO 9001:2015 certified and have third-party inspection by SGS, BV, TUV, or Lloyds. Please confirm that EN 1092-1 documentation is available for PED-compliant European projects. Check that heat treatment records are included with each package of documentation. Flanges must be provided in the solution annealed state.

Procurement Tips for Bulk Orders

Consolidate flange types, sizes, and pressure classes with one specialist 904L supplier to simplify MTC management and improve pricing. For ongoing procurement, a vendor-qualified supplier reduces repeated quality checks. For first-time purchases, request MTCs from two to three sources to validate UNS N08904 chemistry and benchmark current market pricing.