ASTM B564 UNS N08825 Weld Neck Flange | Alloy 825 ASME B16.5
ASTM B564 UNS N08825 flanges are forged nickel-iron-chromium-molybdenum-copper alloy flanges used in corrosive process piping systems. Alloy 825 combines good mechanical strength with resistance to chloride stress-corrosion cracking, reducing acids, oxidizing environments, pitting and crevice corrosion.
We manufacture and supply ASTM B564 / ASME SB-564 UNS N08825 weld neck, blind, slip-on and socket weld flanges to ASME B16.5, with RF and RTJ facing, EN 10204 3.1 certification and project-specific inspection.
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 |
| Flange Standard | ASME B16.5 |
| Flange Types | Weld Neck / Blind / Slip-On / Socket Weld / Threaded |
| Facing | RF / RTJ / FF as applicable |
| Pressure Classes | Class 150 / 300 / 400 / 600 / 900 / 1500 / 2500 |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is ASTM B564 UNS N08825?
ASTM B564 UNS N08825 is a forged nickel-alloy grade used for flanges and other pressure-containing forged components.
The alloy contains nickel, chromium, iron, molybdenum and copper, with titanium added for stabilization.
Its alloying system provides useful resistance to both oxidizing and reducing corrosive environments.
The principal material designations are:
| System | Designation |
|---|---|
| ASTM | B564 UNS N08825 |
| ASME | SB-564 UNS N08825 |
| UNS | N08825 |
| EN / W.Nr. | 2.4858 |
| Material | Alloy 825 |
ASTM B564 N08825 Chemical Composition
| Element | UNS N08825 |
|---|---|
| Nickel, Ni | 38.0–46.0% |
| Chromium, Cr | 19.5–23.5% |
| Iron, Fe | Balance |
| 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 | 1.0% max |
| Silicon, Si | 0.5% max |
| Aluminum, Al | 0.2% max |
| Phosphorus, P | 0.02% max |
| Sulfur, S | 0.03% max |
The combination of Ni-Cr-Mo-Cu is particularly important to the corrosion performance of UNS N08825.
Actual heat chemistry is reported on the Material Test Certificate.
Mechanical Properties
ASTM B564 UNS N08825 flanges are supplied to the mechanical-property requirements of the ordered material specification.
Important properties include:
- Tensile strength
- 0.2% yield strength
- Elongation
- Hardness where applicable
Actual mechanical test values are reported on the supplied Material Test Certificate.
For engineering design, the applicable ASTM B564 edition, ASME design code, pressure class and operating temperature should be used rather than relying only on typical material-property values.
Physical Properties
Typical physical properties of UNS N08825 include:
| Property | Typical Value |
|---|---|
| Density | Approx. 8.1 g/cm³ |
| Melting Range | Approx. 1370–1400°C |
Physical-property values are useful for engineering reference but are not substitutes for ASTM acceptance criteria.
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
- Mechanical properties
- Austenitic structure
- Stable material performance
Alloy 825 contains titanium, which contributes to stabilization against sensitization under suitable processing conditions.
Heat-treatment records can be supplied when required by the purchase specification.
Corrosion Resistance of UNS N08825
One of the main reasons for selecting Alloy 825 flanges is their resistance to a broad range of corrosive environments.
UNS N08825 provides useful resistance to:
- Chloride-ion stress-corrosion cracking
- Sulfuric acid environments
- Phosphoric acid environments
- Pitting corrosion
- Crevice corrosion
- Intergranular corrosion
- Many oxidizing environments
- Many reducing environments
The molybdenum content contributes to pitting and crevice-corrosion resistance, while copper improves resistance in several reducing acid environments.
Chromium contributes to resistance in oxidizing conditions.
Final material suitability should consider temperature, acid concentration, chlorides, contaminants, flow conditions and process chemistry.
ASTM B564 N08825 Weld Neck Flange
The weld neck flange is commonly selected for critical process piping because it uses a butt-welded connection and a tapered hub.
The tapered hub provides a gradual transition between the pipe and flange and helps distribute stresses generated by:
- Internal pressure
- Piping loads
- Thermal expansion
- Vibration
- Temperature cycling
Available configurations include:
WNRF – Weld Neck Raised Face
and
WNRTJ – Weld Neck Ring Type Joint
The flange bore can be machined according to the required 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 Flange | Butt-welded to pipe |
| Blind Flange | Closes a piping or equipment opening |
| Slip-On Flange | Pipe inserted and fillet welded |
| Socket Weld Flange | Socket connection for small-bore piping |
| Threaded Flange | Threaded connection where specified |
Available facing options can include:
- Raised Face – RF
- Ring Type Joint – RTJ
- Flat Face – FF where applicable
The required flange type, facing and bore should be specified in the purchase order.
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 |
The required pressure class should be selected according to the piping design conditions and applicable pressure-temperature rating.
Alloy 825 RTJ Flange
An RTJ flange uses a precision-machined ring groove and metallic ring gasket to form the flange seal.
RTJ facing is commonly specified for:
- High-pressure piping
- Refinery systems
- Chemical plants
- Oil and gas process systems
- High-pressure equipment connections
RTJ flanges should be ordered with the correct ring-groove configuration required by the applicable ASME flange standard.
Typical descriptions include:
N08825 WNRTJ Flange
and
N08825 Blind RTJ Flange
Alloy 825 vs Alloy 625 Flanges
Alloy 825 and Alloy 625 are both corrosion-resistant nickel alloys, but their compositions and application strengths differ.
| Item | Alloy 825 / N08825 | Alloy 625 / N06625 |
|---|---|---|
| Base System | Ni-Fe-Cr-Mo-Cu | Ni-Cr-Mo-Nb |
| Ni | 38–46% | 58% min |
| Mo | 2.5–3.5% | 8–10% |
| Cu | 1.5–3.0% | Low |
| Nb + Ta | Not major addition | 3.15–4.15% |
| Main Strength | Acid resistance and SCC resistance | Higher strength and aggressive chloride resistance |
| Typical Selection | Chemical / acid process service | Offshore / high-strength corrosive service |
Neither material is universally superior.
The correct choice depends on process chemistry, temperature, mechanical requirements and corrosion conditions.
Applications
ASTM B564 N08825 flanges are commonly used in:
- Chemical-processing plants
- Sulfuric acid systems
- Phosphoric acid systems
- Oil and gas processing
- Offshore piping
- Marine systems
- Pollution-control equipment
- Heat exchangers
- Pickling systems
- Process vessels
- Acid-production equipment
The alloy is particularly useful where a combination of acid resistance, chloride resistance and mechanical reliability is required.
Related UNS N08825 Piping Products
A complete N08825 piping system can include:
| Component | Typical Specification |
|---|---|
| Forged Flange | ASTM B564 UNS N08825 |
| Seamless Pipe | ASTM B423 UNS N08825 |
| Butt-Weld Fitting | ASTM B366 UNS N08825 |
| Plate / Sheet | ASTM B424 UNS N08825 |
ASTM B564 N08825 flanges can be supplied together with matching N08825 pipe, butt-weld fittings and plate 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
- Hardness testing when specified
- PT when required
- UT when specified
- RTJ groove dimensional inspection
- Third-party inspection
- Full heat-number traceability
Inspection requirements can be specified according to the material specification, 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.
Is Alloy 825 the same as UNS N08825?
Yes. UNS N08825 is the standardized material designation for Alloy 825.
The corresponding EN / Werkstoff material number is 2.4858.
What is the difference between Alloy 825 and Alloy 625 flanges?
Alloy 825 contains significant iron and copper and is particularly useful in several acid-processing environments, while Alloy 625 contains substantially more molybdenum and niobium and offers higher strength and stronger localized corrosion resistance in many aggressive environments.
Final selection depends on the actual service 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 pipe and fittings match ASTM B564 N08825 flanges?
A typical matching system includes:
ASTM B423 N08825 Pipe + ASTM B366 N08825 Butt-Weld Fittings + ASTM B564 N08825 Flanges
according to project requirements.
ASTM B564 N08825 Flange Manufacturer
We manufacture and supply ASTM B564 / ASME SB-564 UNS N08825 forged flanges for chemical, offshore, acid-processing and corrosion-resistant piping systems.
Available products include:
Weld Neck / WNRF / WNRTJ / Blind / Blind RTJ / Slip-On / Socket Weld 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 1:
ASTM B564 UNS N08825 WNRTJ Flange, NPS 3, SCH 40S, Class 900, ASME B16.5, EN 10204 3.1
Example 2:
ASTM B564 UNS N08825 Blind RTJ Flange, NPS 2, Class 900, ASME B16.5, EN 10204 3.1
