Stainless Steel 904L Flanges Manufacturer & Supplier - USA Piping Solution

When industrial processes push materials to their limits, particularly in corrosive environments, Stainless Steel 904L Flanges emerge as a truly robust solution. At USA Piping Solution, we specialize in manufacturing and supplying these high-performance UNS N08904 Flange products globally. Engineered to excel where standard grades falter, our 904L flanges provide the reliability needed for critical connections involving acids, chlorides, and elevated temperatures. With a comprehensive inventory, deep technical know-how, and an unwavering commitment to quality, USA Piping Solution ensures you get the right flange, whether standard or custom, for lasting performance.

What are Stainless Steel 904L Flanges?

At their core, Stainless Steel 904L Flanges are vital connecting pieces, skillfully forged or machined from a specialized high-alloy austenitic stainless steel. You'll often see it referenced by designations like Werkstoff No. 1.4539 or UNS N08904. What truly sets Grade 904L apart is its remarkable resistance to corrosion, especially when facing aggressive substances. This resilience comes down to its carefully engineered chemistry.

Think of it as a strategic blend:

• High Nickel (23-28%) & Chromium (19-23%): These form the backbone of its corrosion defense and austenitic structure.
• Significant Molybdenum (4-5%): This is key for fighting off pitting and crevice corrosion, particularly in environments laced with chlorides (like seawater or certain industrial process streams). It significantly boosts the Pitting Resistance Equivalent Number (PREN), often pushing it above 35.
• Added Copper (1.0-2.0%): This gives 904L a distinct advantage against reducing acids, most notably sulfuric acid, where many other stainless steels struggle. It also performs admirably in phosphoric acid services.
• Low Carbon (≤ 0.020%): Keeping carbon content minimal helps prevent issues like sensitization during welding, preserving corrosion resistance around the weld zones.

This unique combination delivers tangible benefits:

1. Exceptional Acid Resistance: Tackles aggressive reducing acids where others fail.
2. Superior Localized Corrosion Defense: Stands strong against pitting and crevice attacks in chloride-rich settings.
3. Enhanced Stress Corrosion Cracking (SCC) Resistance: The high nickel content offers better protection against SCC compared to standard 300-series grades, vital in warm chloride solutions.
4. Workable & Weldable: Despite its high alloy content, SS 904L can be welded using common techniques (matching filler is best) and formed, though it does require more force due to higher work-hardening rates.
5. Non-Magnetic Nature: As typical for austenitic steels, it remains non-magnetic when annealed.

In essence, Stainless Steel 904L Flanges provide a secure and durable joining method for piping systems facing conditions too harsh for common grades like 316L, ensuring long-term integrity in critical industrial processes.

Types of Stainless Steel 904L Flanges

USA Piping Solution understands that different applications require different connection methods. That's why we offer a full spectrum of Stainless Steel 904L Flanges, each suited for specific needs:

Slip-On Flanges

As the name suggests, SS 904L Slip-On Flanges slide onto the pipe end. They are secured by two fillet welds – one inside, one outside at the hub. Their appeal often lies in a lower upfront cost and simpler alignment during installation. However, keep in mind their pressure-holding capacity is generally less than that of a Weld Neck flange. They are a common sight in lower-pressure lines and less critical systems where extreme stress isn't the primary challenge. We supply them with Raised Face (RF) or Flat Face (FF) finishes.

Weld Neck Flanges

Instantly recognizable by their long, tapered hub, 904L Weld Neck Flanges (often called WNRF) are designed for a direct butt-weld connection to the pipe. This creates an integral structure offering outstanding strength and stress distribution. They are the go-to choice for demanding situations involving high pressure, high temperature, significant stress, or conditions with temperature/pressure fluctuations. Because the flange bore matches the pipe's internal diameter, flow is smoother, minimizing turbulence and potential erosion. Essential for critical service in chemical plants and the oil & gas sector.

Blind Flanges

Think of a 904L Blind Flange as a solid metal plate, drilled only for bolts. Its purpose is simple but crucial: to securely seal the end of a pipe run, a valve port, or a pressure vessel opening. This allows safe isolation for maintenance, inspection, or future system tie-ins. Since they bear the full brunt of system pressure and bolting forces without a central opening, their robust construction is vital. USA Piping Solution provides these essential sealing components across various pressure classes and facings (RF, FF, RTJ).

Threaded Flanges

Stainless Steel 904L Threaded Flanges (or screwed flanges) have internal threads that mate with external pipe threads. They offer a connection solution where welding isn't feasible or permitted – perhaps in highly flammable zones or for simpler utility lines. Installation doesn't require welding, but their use is generally restricted to lower-pressure systems. They aren't typically recommended where significant temperature changes or high mechanical loads occur, as the threads can become a potential leak path under stress.

Lap Joint & Socket Weld Flanges

• Lap Joint Flanges (LJF): These work as a two-part system. The flange itself slips over the pipe but isn't welded to it. Instead, a separate 904L 'Stub End' fitting is butt-welded to the pipe. The Lap Joint flange then bears against the back of the stub end collar. The key benefit? The flange can rotate freely, making bolt hole alignment much easier, especially helpful in large or awkward piping layouts. They are frequently used where systems need regular dismantling, usually in moderate-to-low pressure service.
• Socket Weld Flanges (SWF): Primarily used for smaller pipe sizes in high-pressure lines, these flanges have a recessed area (the socket) where the pipe end sits. A fillet weld around the hub secures the pipe. This design provides a relatively smooth internal bore compared to threaded options. While offering good strength, SS 904L Socket Weld Flanges can potentially trap corrosive media in the small gap at the socket's base if not perfectly installed, which requires consideration in certain aggressive environments.

Beyond these common types, USA Piping Solution can also source specialized 904L flanges like Orifice, Spectacle Blind, Long Weld Neck (LWN), and fully custom designs to meet unique project specifications.

Stainless Steel 904L Flange Specifications

Ensuring flanges fit correctly, perform safely, and meet regulatory demands hinges on adhering to established standards. USA Piping Solution supplies Stainless Steel 904L Flanges manufactured and rigorously tested against key international specifications:

ASTM B649 / ASME SB649 vs. ASTM A182 F904L

It's helpful to clarify these common specifications:

• ASTM B649 / ASME SB649: This standard primarily defines the requirements for UNS N08904 Plate, Sheet, and Strip. Flanges can indeed be cut from plate meeting this spec, often referred to as "plate flanges." These are generally suitable for less demanding, lower-pressure services. Querying for ASTM B649 904L Flanges often refers to these plate-derived types.
• ASTM A182 / ASME SA182 F904L: This is the definitive specification for forged Stainless Steel 904L flanges, along with fittings, valves, and other pressure components designed for elevated temperature and pressure service. The forging process typically yields a superior grain structure and enhanced mechanical strength compared to flanges cut directly from plate.

USA Piping Solution provides both types, but for applications demanding maximum integrity, forged flanges meeting ASTM A182 F904L are generally recommended and more commonly supplied.

ANSI, DIN, EN, BS Standards

Dimensional consistency is crucial for interchangeability and proper installation. Our SS 904L flanges are manufactured to comply with globally recognized dimensional and pressure-temperature standards:

• ASME B16.5: The cornerstone standard for Pipe Flanges and Flanged Fittings from NPS ½ up to NPS 24, covering pressure classes 150 through 2500. We supply ANSI B16.5 904L Flange products meeting all requirements of this standard.
• ASME B16.47 Series A & B: Addresses larger diameter flanges (NPS 26 to NPS 60). Series A generally results in thicker, heavier flanges compared to Series B for the same size and pressure class.
• ASME B16.36: Specific requirements for Orifice Flanges used in flow measurement.
• ASME B16.48: Covers steel Line Blanks like Spectacle Blinds and Paddle Blanks/Spacers.
• EN 1092-1: The primary European standard for flanges (using PN designations for pressure).
• DIN Standards: Respected German standards (e.g., DIN 2527 Blind Flanges).
• BS Standards: Relevant British standards (e.g., BS 4504).

We ensure every flange aligns with the specified standard regarding dimensions, tolerances, facing finish (RF, FF, RTJ), and required markings.

Chemical Composition and Mechanical Properties

The reliable performance of SS 904L flanges is a direct result of their precise chemical balance and the mechanical strength derived from it.

Chemical Composition (Typical)

Here’s a look at the target chemical composition for ASTM A182 F904L / UNS N08904 (weight %):

Element	Content (%)	Notes
Carbon (C)	≤ 0.020	Minimizes weld sensitization
Manganese (Mn)	≤ 2.00
Silicon (Si)	≤ 1.00
Phosphorus (P)	≤ 0.045	Limit impurity
Sulfur (S)	≤ 0.035	Limit impurity
Chromium (Cr)	19.0 - 23.0	Key for passive film formation (corrosion res.)
Nickel (Ni)	23.0 - 28.0	Enhances toughness, SCC resistance, acid res.
Molybdenum (Mo)	4.0 - 5.0	Boosts pitting/crevice corrosion resistance
Copper (Cu)	1.0 - 2.0	Critical for resisting reducing acids
Nitrogen (N)	≤ 0.10	Can enhance pitting resistance & strength
Iron (Fe)	Balance	Base element

Note: Based on ASTM A182 ranges.

Mechanical Properties

Here are typical mechanical properties for annealed Stainless Steel 904L (ASTM A182 F904L) at ambient temperature:

Property	Minimum Value (ASTM A182)	Typical Range	Significance
Tensile Strength	490 MPa (71 ksi)	520 - 650 MPa	Overall strength
Yield Strength (0.2% Offset)	220 MPa (32 ksi)	240 - 300 MPa	Stress required for permanent deformation
Elongation (in 50mm or 2")	35 %	40 - 50 %	Ductility / Ability to deform without fracture
Hardness (Brinell)	-	~ 150 HB	Resistance to indentation
Hardness (Rockwell B)	-	70 - 90 HRB (Typical)	Alternative hardness measure

Surface Finish and Pressure Ratings

Achieving a leak-tight seal relies heavily on the flange face finish and its interaction with the gasket. We supply SS 904L Flanges with finishes appropriate for the application:

• Stock Finish: The common, versatile machined finish suitable for many gasket types in general service.
• Serrated Finish (Concentric or Spiral): These machined grooves (like fine phonograph records) bite into softer gaskets, creating a more secure seal. Very common on Raised Face (RF) flanges.
• Smooth Finish: Required for certain metallic or filled gaskets that need uniform contact pressure without grooves.
• Ring Type Joint (RTJ) Finish: A precision-machined groove designed specifically for a solid metal ring gasket. This provides an extremely reliable, high-integrity metal-to-metal seal, essential for high-pressure and high-temperature critical services.
• Pressure Ratings (like Class 150 or PN16) indicate the maximum pressure a flange can safely handle at a specified temperature, according to the governing standard (e.g., ASME B16.5). Selecting the correct pressure rating for your system's operating conditions is paramount for safety and performance.

Certifications and Quality Assurance

At USA Piping Solution, quality isn't just a buzzword; it underpins everything we supply. Our Stainless Steel 904L Flanges come with the assurance of rigorous quality checks and complete documentation:

• Material Test Certificates (MTC): We furnish MTCs compliant with EN 10204 3.1 as standard, detailing the exact chemical analysis, mechanical test results, and heat treatment for the material used. If required, EN 10204 3.2 certification (with third-party inspector witnessing) can be arranged.
• Material Verification: We conduct 100% Positive Material Identification (PMI) using calibrated XRF or OES equipment to confirm the 904L grade and composition before shipment.
• Standards Compliance: We strictly manufacture and inspect flanges to meet all dimensional, tolerance, material, and testing requirements of the specified ASTM, ASME, EN, or other standards.
• Full Traceability: From the original metal melt to the finished flange, complete traceability is maintained via heat numbers marked on each part and cross-referenced in the documentation.
• Additional Testing: We readily facilitate supplementary testing based on client needs, such as NACE MR0175/ISO 15156 testing for sour service suitability, corrosion tests (e.g., ASTM A262), UT, DP, or RT examinations.
• Inspection Ready: We always welcome inspections by our clients or their designated third-party agencies (like TUV, DNV, BV, SGS).

This commitment ensures you receive reliable, fully traceable, and certified ASTM A182 F904L (forged) or plate-derived (from ASTM B649) flanges you can trust.

Why Choose USA Piping Solution for SS 904L Flanges?

Partnering with USA Piping Solution for your Stainless Steel 904L Flanges brings tangible benefits to your project:

• Deep Alloy Knowledge: We possess extensive experience supplying high-nickel alloys like 904L for critical applications worldwide.
• Uncompromising Quality: Our rigorous quality systems and thorough certification processes provide peace of mind.
• Ready Availability: We stock a wide array of standard UNS N08904 Flange types and sizes, enabling faster turnaround times.
• Global Logistics: Our established network ensures efficient and timely delivery to your site, wherever it may be.
• Expert Technical Support: Our team understands the materials and standards, ready to help you navigate specifications and select the right product.
• Custom Solutions: We have the capability to source or manage the production of non-standard flanges tailored to your unique requirements.
• Real Value: Through strong mill partnerships and efficient operations, we offer competitive pricing without ever sacrificing quality.
• Dedicated Service: We focus on understanding your project needs and providing responsive, dependable support.

Choose USA Piping Solution when you need reliable 904L Weld Neck Flange, SS 904L Slip-On Flange, 904L Blind Flange, or any other 904L flange configuration.

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Complementing our flange offerings, USA Piping Solution is also your source for other essential components in Stainless Steel 904L

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