ASTM B564 UNS N08825 Weld Neck Flange | Alloy 825
ASTM B564 UNS N08825 flanges are forged nickel-iron-chromium-molybdenum-copper alloy flanges used for corrosion-resistant process piping and pressure equipment. Alloy 825 combines high nickel and chromium contents with molybdenum, copper and titanium to provide strong resistance to chloride stress-corrosion cracking, sulfuric and phosphoric acid environments, pitting, crevice corrosion and many oxidizing and reducing media.
We manufacture and supply ASTM B564 / ASME SB-564 UNS N08825 weld neck, blind, slip-on, socket weld and RTJ flanges to ASME B16.5, with EN 10204 3.1 certification and project-specific inspection when required.
ASTM B564 N08825 Flange Specification
| Item | Specification |
|---|---|
| Material Standard | ASTM B564 / ASME SB-564 |
| UNS | N08825 |
| Material | Alloy 825 |
| EN / W.Nr. | 2.4858 |
| Material Family | Nickel-Iron-Chromium-Molybdenum-Copper Alloy |
| Primary Flange Type | Weld Neck Flange |
| Other Flange Types | Blind / Slip-On / Socket Weld / Threaded / Orifice |
| Flange Standard | ASME B16.5 |
| Facing | RF / FF / RTJ as applicable |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is ASTM B564 UNS N08825?
ASTM B564 UNS N08825 is a nickel-iron-chromium-molybdenum-copper forging alloy used for corrosion-resistant flanges and other forged pressure components.also known as Incoloy 825
The alloy contains:
- Nickel for chloride stress-corrosion cracking resistance
- Chromium for resistance in oxidizing environments
- Molybdenum for pitting and crevice-corrosion resistance
- Copper for resistance in several reducing acid environments
- Titanium for stabilization
UNS N08825 is primarily selected for corrosive chemical and process environments, especially where sulfuric acid, phosphoric acid, chlorides and stress-corrosion cracking are important design considerations.
UNS N08825 / EN 2.4858 Designations
| System | Designation |
|---|---|
| ASTM | B564 UNS N08825 |
| ASME | SB-564 UNS N08825 |
| UNS | N08825 |
| EN / W.Nr. | 2.4858 |
| Material | Alloy 825 |
These designations identify corresponding material systems, while the applicable product standard and purchase specification should always be confirmed for the required component.
ASTM B564 N08825 Chemical Composition
| Element | UNS N08825 |
|---|---|
| Nickel, Ni | 38.0–46.0% |
| Chromium, Cr | 19.5–23.5% |
| Iron, Fe | 22.0% min / balance basis |
| Molybdenum, Mo | 2.5–3.5% |
| Copper, Cu | 1.5–3.0% |
| Titanium, Ti | 0.6–1.2% |
| Carbon, C | 0.05% max |
| Manganese, Mn | 1.00% max |
| Silicon, Si | 0.50% max |
| Sulfur, S | 0.03% max |
| Aluminum, Al | 0.20% max |
The Ni-Cr-Mo-Cu alloying system is the main reason for the broad corrosion resistance of UNS N08825.
Actual heat chemistry is reported on the Material Test Certificate.
ASTM B564 N08825 Mechanical Properties
Typical minimum room-temperature mechanical requirements include:
| Property | Minimum Requirement |
|---|---|
| Tensile Strength | 586 MPa / 85 ksi |
| Yield Strength | 241 MPa / 35 ksi |
| Elongation | 30% |
Actual test results are reported on the supplied MTC.
Mechanical acceptance criteria shall follow the ordered ASTM B564 edition and applicable product condition.
Heat Treatment of ASTM B564 N08825
ASTM B564 UNS N08825 forgings are supplied in the heat-treated condition required by the material specification.
Controlled annealing and cooling are important for maintaining:
- Corrosion resistance
- Ductility
- Mechanical properties
- Austenitic structure
- Stable material performance
Titanium contributes to stabilization and helps reduce susceptibility to intergranular corrosion under suitable processing and heat-treatment conditions.
Heat-treatment records can be supplied when required by the project specification.
Corrosion Resistance of UNS N08825 Flanges
One of the main reasons for selecting Alloy 825 flanges is their resistance to a wide range of corrosive environments.
Sulfuric Acid Resistance
The combination of nickel, molybdenum and copper provides useful resistance in many sulfuric acid environments.
Phosphoric Acid Resistance
UNS N08825 is widely used in equipment and piping exposed to phosphoric acid and related chemical-processing environments.
Chloride Stress-Corrosion Cracking
The relatively high nickel content provides strong resistance to chloride-ion-induced stress-corrosion cracking compared with many conventional stainless steels.
Pitting and Crevice Corrosion
Molybdenum improves resistance to localized corrosion, including:
- Pitting
- Crevice corrosion
- Chloride attack
Oxidizing and Reducing Environments
Chromium contributes to resistance in oxidizing environments, while molybdenum and copper improve performance in several reducing acid environments.
Final material suitability should consider temperature, chemical concentration, contaminants, flow conditions and process chemistry.
ASTM B564 N08825 Weld Neck Flange
The weld neck flange is commonly used in critical process piping because it has a long tapered hub and a butt-welded connection to the pipe.
This design provides gradual stress transfer between the pipe and flange and is suitable for systems exposed to:
- Internal pressure
- Thermal cycling
- Piping loads
- Vibration
- Corrosive process media
Available configurations include:
WNRF – Weld Neck Raised Face
WNRTJ – Weld Neck Ring Type Joint
The flange bore can be machined to match the specified pipe schedule or wall thickness.
A typical ordering description is:
ASTM B564 UNS N08825 WNRTJ Flange, NPS 3, SCH 40S, Class 900, ASME B16.5
Available Alloy 825 Flange Types
| Flange Type | Connection / Function |
|---|---|
| Weld Neck | Butt-welded to pipe |
| Blind | Closes a piping or equipment opening |
| Slip-On | Pipe inserted and fillet welded |
| Socket Weld | Socket connection for small-bore piping |
| Threaded | Threaded connection when specified |
| Orifice Flange | Used with flow-measurement systems when specified |
Available facing options include:
- Raised Face – RF
- Ring Type Joint – RTJ
- Flat Face – FF where applicable
The required flange type, bore, facing and pressure class should be clearly stated in the purchase specification.
ASME B16.5 Size & Pressure Classes
ASME B16.5 covers pipe flanges in the following standard size ranges:
| Pressure Class | Size Range |
|---|---|
| Class 150 | NPS 1/2–24 |
| Class 300 | NPS 1/2–24 |
| Class 400 | NPS 1/2–24 |
| Class 600 | NPS 1/2–24 |
| Class 900 | NPS 1/2–24 |
| Class 1500 | NPS 1/2–24 |
| Class 2500 | NPS 1/2–12 |
Pressure-temperature ratings depend on the applicable material group, design code and operating temperature.
Alloy 825 vs Alloy 625 Flanges
Alloy 825 and Alloy 625 are both corrosion-resistant nickel alloys but have different compositions and application strengths.
| Item | Alloy 825 / N08825 | Alloy 625 / N06625 |
|---|---|---|
| Base System | Ni-Fe-Cr-Mo-Cu | Ni-Cr-Mo-Nb |
| Ni | 38–46% | 58% min |
| Cr | 19.5–23.5% | 20–23% |
| Mo | 2.5–3.5% | 8–10% |
| Cu | 1.5–3.0% | Low |
| Nb + Ta | No major addition | 3.15–4.15% |
| Main Strength | Acid resistance and SCC resistance | Higher strength and aggressive chloride resistance |
| Typical Service | Chemical and acid-processing systems | Offshore and severe corrosive service |
Neither alloy is universally superior.
The correct material depends on process chemistry, corrosion environment, mechanical requirements and temperature.
Applications
ASTM B564 N08825 flanges are commonly used in:
- Chemical-processing plants
- Sulfuric acid systems
- Phosphoric acid systems
- Acid-production equipment
- Pickling systems
- Oil and gas processing
- Offshore piping
- Marine equipment
- Pollution-control systems
- Heat exchangers
- Process vessels
- Corrosion-resistant piping systems
UNS N08825 is particularly useful where a combination of acid resistance, chloride resistance and mechanical reliability is required.
Related UNS N08825 Products
A complete N08825 piping or equipment system can include:
| Product | Typical Specification |
|---|---|
| Round Bar | ASTM B425 UNS N08825 |
| Plate / Sheet | ASTM B424 UNS N08825 |
| Pipe | ASTM B423 UNS N08825 |
| Butt-Weld Fitting | ASTM B366 UNS N08825 |
| Forged Flange | ASTM B564 UNS N08825 |
ASTM B564 N08825 flanges can be supplied together with matching N08825 pipe, fittings, plate and bar according to project requirements.
Inspection & Certification
ASTM B564 N08825 flanges can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Heat chemical analysis
- Mechanical test results
- Heat-treatment records
- PMI
- Dimensional inspection
- Visual examination
- Flange-facing inspection
- RTJ groove inspection when applicable
- Hardness testing when specified
- PT when required
- UT when specified or applicable
- Third-party inspection
- Full heat-number traceability
Inspection requirements can be specified according to the material standard, flange standard and project ITP.
Frequently Asked Questions
What is ASTM B564 UNS N08825?
ASTM B564 UNS N08825 is a nickel-iron-chromium-molybdenum-copper forging alloy used for corrosion-resistant flanges and other forged pressure components.
What are the minimum mechanical properties of N08825 forgings?
Typical minimum room-temperature requirements include approximately 586 MPa tensile strength, 241 MPa yield strength and 30% elongation.
Actual mechanical test results are reported on the Material Test Certificate.
Why is Alloy 825 used in sulfuric acid service?
Nickel, molybdenum and copper provide Alloy 825 with useful resistance in many sulfuric acid environments.
Actual performance depends on acid concentration, temperature, contaminants and process conditions.
What size range does ASME B16.5 cover?
ASME B16.5 covers NPS 1/2–24 for Class 150 through Class 1500 and NPS 1/2–12 for Class 2500.
What is the difference between Alloy 825 and Alloy 625 flanges?
Alloy 825 is particularly useful in acid-processing and chloride stress-corrosion cracking environments, while Alloy 625 contains significantly more molybdenum and niobium and provides higher strength and stronger localized corrosion resistance in many aggressive environments.
Material selection should be based on actual service conditions.
ASTM B564 N08825 Flange Manufacturer
We manufacture and supply ASTM B564 / ASME SB-564 UNS N08825 forged flanges for chemical, acid-processing, offshore, oil and gas and corrosion-resistant piping systems.
Available products include:
Weld Neck / WNRF / WNRTJ / Blind / Blind RTJ / Slip-On / Socket Weld / Threaded Flanges
with ASME B16.5 dimensions, PMI, NDE and EN 10204 certification when required.
For quotation, please specify:
Material + Flange Type + NPS + Pipe Schedule/WT + Pressure Class + Facing + Standard + Quantity + Inspection Requirements
Example:
ASTM B564 UNS N08825 WNRTJ Flange, NPS 3, SCH 40S, Class 900, ASME B16.5, EN 10204 3.1
