ASTM B361 / ASME SB-361 Aluminum and Aluminum-Alloy Pipe Fittings Specification
ASTM B361 aluminum pipe fitting
ASTM B361 is the principal ASTM specification for factory-made wrought aluminum and aluminum-alloy welding fittings.
It covers aluminum fittings manufactured under controlled factory conditions rather than field-made piping components. The standard applies to butt-welding and socket-end parts, including elbows, return bends and other fitting configurations manufactured to referenced dimensional standards.
Typical products supplied for aluminum piping systems include:
- 45-degree elbows
- 90-degree long-radius elbows
- 90-degree short-radius elbows
- 180-degree return bends
- Equal tees
- Reducing tees
- Concentric reducers
- Eccentric reducers
- Pipe caps
- Socket-end fittings
- Custom fabricated fittings
The exact fitting type, aluminum alloy, temper, dimensions and testing requirements must be verified against the edition stated in the purchase order.
ASTM B361 Specification at a Glance
| Item | Description |
|---|---|
| Standard designation | ASTM B361 |
| ASME designation | ASME SB-361 |
| Official scope | Factory-made wrought aluminum and aluminum-alloy welding fittings |
| Connection types | Butt-welding and applicable socket-end connections |
| Typical products | Elbows, return bends, tees, reducers, caps and custom fittings |
| Raw-material forms | Rod, bar, forging, sheet, plate, seamless pipe and seamless tube |
| Manufacturing methods | Forming, pressing, bending, extrusion, rolling and fusion welding |
| Dimensional references | ASME B16.9 and other applicable fitting standards |
| Main controls | Alloy, temper, manufacturing, dimensions, workmanship and testing |
| Typical applications | Marine, cryogenic, chemical, industrial gas and lightweight piping |
What Does ASTM B361 Cover?
ASTM B361 covers completed wrought aluminum welding fittings manufactured in a factory.
The term “wrought” distinguishes these products from cast fittings. A wrought fitting is produced from a processed material form such as pipe, tube, plate, bar or forging and is subsequently formed, machined or welded into the required fitting shape.
The specification distinguishes factory-made products from fittings fabricated or modified at the installation site.
ASTM B361 specifically identifies butt-welding and socket-end components such as:
- 45° elbows
- 90° short-radius elbows
- 180° return bends
- Other fitting configurations made to referenced dimensional standards
Commercially supplied tees, reducers and caps may also be ordered where their alloy, temper, construction and dimensional requirements comply with the applicable specification and approved drawing.
ASTM B361 vs ASME SB-361
ASTM B361 and ASME SB-361 are related specifications, but the designations are not automatically interchangeable.
ASTM B361
ASTM B361 is published by ASTM International for general industrial procurement.
It establishes requirements relating to:
- Aluminum alloy and temper
- Permitted raw-material forms
- Manufacturing processes
- Mechanical properties
- Dimensions and tolerances
- Testing
- Workmanship
- Marking and certification
ASME SB-361
ASME SB-361 is the corresponding nonferrous material specification adopted within ASME BPVC Section II, Part B.
ASME Section II, Part B uses SB designations for nonferrous material specifications and establishes requirements covering chemical and mechanical properties, manufacturing and testing. (美国机械工程师学会)
ASME SB-361 is normally specified when fittings are intended for equipment or piping constructed under an applicable ASME Code.
ASTM and ASME Comparison
| Requirement | ASTM B361 | ASME SB-361 |
|---|---|---|
| Publishing organization | ASTM International | ASME |
| Specification family | ASTM nonferrous product specification | ASME BPVC Section II, Part B |
| Typical use | General industrial procurement | ASME Code construction |
| Designation | B361 | SB-361 |
| Applicable edition | Purchase-order edition | Adopted ASME Code edition |
| Automatic equivalence | Not assumed | Not assumed |
| Certification | ASTM specification compliance | Applicable ASME edition compliance |
A supplier should not change a certificate from ASTM B361 to ASME SB-361 without verifying compliance with the applicable ASME Code edition.
ASTM B361 Is a Fitting Standard
ASTM B361 covers completed aluminum welding fittings. It is not a specification for ordinary aluminum pipe, plate or extruded profiles.
| Standard | Product covered | Role in an aluminum piping order |
|---|---|---|
| ASTM B361 / ASME SB-361 | Factory-made aluminum welding fittings | Finished fitting specification |
| ASTM B241 / ASME SB-241 | Seamless pipe and seamless extruded tube | Possible raw pipe material |
| ASTM B221 / ASME SB-221 | Extruded bars, profiles and tubes | Possible extruded raw material |
| ASTM B209 / ASME SB-209 | Aluminum sheet and plate | Plate or sheet raw material |
| ASTM B247 / ASME SB-247 | Aluminum forgings and rolled rings | Forged starting material |
| ASME B16.9 | Butt-welding fitting dimensions | Dimensions, tolerances and marking |
| ASME B16.52 | Forged nonferrous socket-weld and threaded fittings | Forged aluminum fitting standard |
A technically complete order normally combines several requirements.
For example:
ASTM B361 Aluminum Alloy 5083-O, 90° Long Radius Butt Weld Elbow, dimensions to ASME B16.9, OD 168 mm × WT 10 mm.
In this description:
- ASTM B361 controls the finished aluminum fitting.
- 5083-O identifies the alloy and temper.
- ASME B16.9 establishes the fitting dimensional pattern.
- OD 168 × WT 10 mm defines the connecting pipe dimensions.
ASME B16.9 and ASTM B361
ASME B16.9 covers overall dimensions, tolerances, ratings, testing and marking for factory-made wrought butt-welding fittings from NPS 1/2 through NPS 48.
ASTM B361 and ASME B16.9 perform different functions.
| Requirement | ASTM B361 | ASME B16.9 |
|---|---|---|
| Aluminum alloy | Primary requirement | Not the principal purpose |
| Temper | Controlled | Not the principal purpose |
| Starting material | Controlled | Not the principal purpose |
| Manufacturing process | Controlled | General fitting requirements |
| Mechanical properties | Controlled | Not a material specification |
| Center-to-end dimensions | Referenced | Primary requirement |
| Dimensional tolerances | Referenced | Primary requirement |
| Fitting angle and radius | Referenced | Primary requirement |
| Marking | Included | Included |
| Material certification | Product specification basis | Insufficient by itself |
The description:
ASME B16.9 Aluminum Elbow
is incomplete because it does not identify the aluminum alloy, temper or finished-fitting material specification.
A better description is:
ASTM B361 Aluminum Alloy 5083-O Butt Weld Elbow, dimensions to ASME B16.9.
Socket-Weld Aluminum Fittings
ASTM B361 includes applicable socket-end welding fittings. However, current projects should also consider ASME B16.52 when forged aluminum socket-weld or threaded fittings are required.
ASME B16.52 covers ratings, dimensions, tolerances, marking and material requirements for forged fittings made from titanium, titanium alloys, aluminum and aluminum alloys, with socket-welding or threaded ends.
The applicable standard should therefore be selected according to the fitting construction.
| Product construction | Recommended specification framework |
|---|---|
| Wrought aluminum butt-weld fitting | ASTM B361 / ASME SB-361 plus ASME B16.9 |
| Wrought socket-end welding fitting | ASTM B361 / ASME SB-361 and applicable dimensional requirements |
| Forged aluminum socket-weld fitting | ASME B16.52 and specified material standard |
| Forged aluminum threaded fitting | ASME B16.52 and specified thread standard |
| Nonstandard fabricated fitting | Approved drawing plus project material and welding requirements |
Permitted Raw Materials
ASTM B361 permits fittings to be manufactured from approved wrought aluminum material forms.
These may include:
- Rod
- Bar
- Forging
- Sheet
- Plate
- Seamless pipe
- Seamless tube
Each starting material must comply with the applicable requirements for its alloy, temper and product form. (ASTM Store)
Why the Starting Material Matters
The same aluminum alloy can have different properties depending on whether it is supplied as:
- Annealed pipe
- Extruded tube
- Rolled plate
- Forged stock
- Strain-hardened sheet
- Heat-treated bar
A complete specification should identify:
Alloy + temper + raw-material form + raw-material standard + finished-fitting standard
For example:
Aluminum Alloy 5083-O seamless pipe to ASTM B241, formed into a 90° long-radius elbow complying with the applicable requirements of ASTM B361.
Aluminum Alloys and Tempers
Common commercial inquiries for aluminum fittings may include:
- Aluminum 1060
- Aluminum 1100
- Aluminum 3003
- Aluminum 5083
- Aluminum 5086
- Aluminum 6061
The exact alloy and temper must be checked against the specified ASTM or ASME edition before compliance is confirmed.
Alloy and Temper Must Be Stated Together
The following descriptions are incomplete:
- Aluminum elbow
- 5083 reducer
- 6061 tee
More complete descriptions include:
- 5083-O aluminum butt weld elbow
- 5086-H112 aluminum reducer
- 6061-T6 aluminum socket-weld fitting
The selected temper affects:
- Formability
- Strength
- Elongation
- Corrosion performance
- Welding behavior
- Finished-fitting properties
Temper Changes During Manufacturing
Forming and welding may change the original material condition.
For example:
- 5083-O is suitable for extensive forming.
- 5083-H112 is commonly associated with shaped or extruded products.
- 5083-H116 and H321 are marine-service tempers requiring controlled product conditions.
- 6061-T6 may experience local strength reduction in the weld heat-affected zone.
A completed fitting should be certified according to its actual finished condition rather than automatically inheriting every property listed on the starting-material certificate.
Manufacturing Methods
ASTM B361 fittings may be manufactured by one process or a combination of processes.
Typical operations include:
- Pressing
- Bending
- Rolling
- Extrusion
- Piercing
- Upsetting
- Forming
- Fusion welding
- Machining
- Dimensional correction
Formed Aluminum Fittings
Formed fittings are generally manufactured through the following steps:
- Raw-material verification
- Cutting or blank preparation
- Cold or controlled warm forming
- Dimensional correction
- End preparation
- Surface cleaning
- Inspection and testing
- Product marking
Products commonly made by forming include:
- Elbows
- Return bends
- Reducers
- Caps
Fabricated Aluminum Fittings
Large-diameter or nonstandard components may require welded fabrication.
Typical fabricated fittings include:
- Large equal tees
- Reducing tees
- Large-diameter reducers
- Segmental elbows
- Crosses
- Transition fittings
- Drawing-specific branches
Where fusion welding is used, the purchase order should define:
- Welding code
- Welding Procedure Specification
- Procedure qualification
- Welder qualification
- Filler metal
- Nondestructive examination
- Joint acceptance criteria
- Heat-treatment requirements
- Documentation requirements
ASTM B361 is a product specification and does not replace the construction code governing the completed piping system.
Dimensions and Wall Thickness
The fitting must be dimensionally compatible with the connecting pipe and project piping class.
Important dimensions include:
- Nominal pipe size
- Actual outside diameter
- Nominal wall thickness
- Minimum finished wall thickness
- Center-to-end dimension
- Elbow angle
- Elbow radius
- Run and branch dimensions
- End preparation
- Internal mismatch
- Ovality
Schedule Descriptions
Descriptions such as Schedule 40 may be used where the mating pipe follows a recognized schedule system.
However, “Schedule 40” alone may be insufficient for aluminum piping because some projects use metric or customized aluminum pipe dimensions.
A better specification states both the schedule and actual dimensions:
NPS 4, Schedule 40, OD 114.3 mm × WT 6.02 mm.
For nonstandard aluminum piping, always state:
Outside diameter × wall thickness.
Forming Thinning
Wall thickness may decrease during elbow or reducer forming.
The purchase order should therefore clarify:
- Nominal starting wall
- Minimum finished wall
- Permitted thinning
- Measurement locations
- Acceptance tolerance
- Corrosion allowance
Inspection and Testing
Inspection requirements should be selected according to the alloy, fitting construction, application and governing code.
| Inspection or test | Purpose |
|---|---|
| Material certificate review | Verify alloy, temper and raw-material specification |
| Visual inspection | Check workmanship and surface condition |
| Dimensional inspection | Verify angle, radius, dimensions and tolerances |
| Chemical analysis | Confirm aluminum alloy composition |
| Tensile testing | Verify applicable mechanical properties |
| Wall-thickness measurement | Check thinning after forming |
| Dye penetrant examination | Detect surface-breaking discontinuities |
| Radiographic examination | Examine applicable fusion-welded seams |
| Positive material identification | Support alloy verification |
| Hydrostatic testing | Verify pressure integrity where required |
| Pneumatic leak testing | Check leakage under an approved procedure |
| Third-party inspection | Independent inspection and document review |
ASTM B361 includes mechanical and hydrostatic-testing provisions. The exact test method, sampling frequency and requirement for individual fitting testing must be determined from the ordered edition and purchase specification.
Marking and Traceability
Typical fitting markings may include:
- Manufacturer identification
- ASTM B361 or ASME SB-361
- Aluminum alloy
- Temper
- Fitting type
- Nominal size
- Outside diameter
- Wall thickness
- Elbow angle
- Long radius or short radius
- Heat or lot number
- Purchase-order number
- Drawing number
Thin-wall fittings may require ink marking, tagging or low-stress marking rather than deep stamping.
How to Specify ASTM B361 Aluminum Fittings
A complete inquiry should include the following information.
Product Type
- Elbow
- Tee
- Reducer
- Return bend
- Cap
- Socket-end fitting
- Custom fitting
Material
- Aluminum alloy
- UNS or EN designation
- Temper
- ASTM B361 or ASME SB-361
- Raw-material standard, where required
Dimensions
- Nominal pipe size
- Actual outside diameter
- Wall thickness
- Elbow angle
- Long radius or short radius
- Run and branch size
- Center-to-end dimensions
- Minimum finished wall thickness
Technical Requirements
- Dimensional standard
- Seamless, formed or welded construction
- Welding requirements
- NDE method and percentage
- Hydrostatic testing
- Surface finish
- Cleaning requirements
- Material traceability
- Inspection certificate
- Third-party inspection
Example: 5083 Aluminum Elbow
ASTM B361 Aluminum Alloy 5083-O, 90° Long Radius Butt Weld Elbow, dimensions to ASME B16.9, OD 168 mm × WT 10 mm, with material certificate and dimensional inspection report.
Example: 5083 Aluminum Reducer
ASTM B361 Aluminum Alloy 5083-O Concentric Reducer, OD 219 mm × 168 mm, matching wall thickness 12 mm × 10 mm, manufactured to approved dimensions with minimum finished wall thickness specified.
Example: ASME Code Fitting
ASME SB-361 Aluminum Alloy Welding Fitting, alloy and temper as specified, manufactured and certified to the ASME BPVC edition stated in the purchase order.
Applications of ASTM B361 Aluminum Fittings
ASTM B361 and ASME SB-361 fittings may be used in:
- Shipbuilding piping
- Marine auxiliary systems
- Offshore equipment
- Air-separation plants
- Industrial gas equipment
- Cryogenic piping
- LNG-related equipment
- Chemical-processing systems
- Heat exchangers
- Low-temperature equipment
- Transport tanks
- Lightweight process piping
- Aluminum pipe spools
Final material selection must consider:
- Process fluid
- Design pressure
- Design temperature
- Corrosion conditions
- Galvanic compatibility
- Fatigue loads
- Welding condition
- Governing design code
Compliance with ASTM B361 alone does not establish suitability for every pressure, temperature or corrosion environment.
Frequently Asked Questions
What is ASTM B361?
ASTM B361 is the specification for factory-made wrought aluminum and aluminum-alloy welding fittings.
It covers butt-welding and applicable socket-end fittings manufactured from approved wrought aluminum material forms.
Is ASTM B361 a pipe standard?
No.
ASTM B361 is a finished fitting specification. Aluminum seamless pipe and seamless extruded tube are commonly covered by ASTM B241.
What is ASME SB-361?
ASME SB-361 is the corresponding nonferrous material specification adopted within ASME BPVC Section II, Part B.
It is normally required when the fitting forms part of an applicable ASME Code construction.
What is the difference between ASTM B361 and ASME B16.9?
ASTM B361 controls the aluminum alloy, temper, manufacturing and material requirements of the fitting.
ASME B16.9 primarily controls the dimensions, dimensional tolerances, testing and marking of butt-welding fittings.
The two standards may be specified together.
Does ASTM B361 cover aluminum elbows?
Yes.
Its scope includes factory-made aluminum welding fittings such as 45° elbows, 90° short-radius elbows and 180° return bends.
Does ASTM B361 cover aluminum tees and reducers?
Tees, reducers and other configurations may be supplied where their material, construction and dimensional requirements comply with the applicable specification and approved design.
The exact scope should be verified against the ordered edition.
Can ASTM B361 fittings be fusion welded?
Yes.
Fusion welding may be used as part of the manufacturing process, subject to the applicable product requirements, welding procedures and inspection requirements.
Does ASTM B361 cover 5083 aluminum fittings?
5083 fittings may be ordered under ASTM B361 where the specified alloy, temper, raw material and finished-fitting condition comply with the applicable edition.
The description “5083 fitting” alone is not sufficient.
Can ASTM B361 fittings use ASME B16.9 dimensions?
Yes.
ASME B16.9 is commonly used as the dimensional standard for applicable ASTM B361 butt-welding fittings.
Which standard covers forged aluminum socket-weld fittings?
ASME B16.52 covers forged nonferrous socket-weld and threaded fittings made from aluminum, aluminum alloys, titanium and titanium alloys.
Are ASTM B361 fittings hydrostatically tested?
ASTM B361 contains hydrostatic-testing requirements.
The exact testing obligation, pressure, sampling and acceptance criteria must follow the ordered standard edition and purchase specification.
ASTM B361 Aluminum Pipe Fittings Manufacturer
We manufacture and supply ASTM B361 and ASME SB-361 aluminum alloy pipe fittings for marine, cryogenic, industrial gas, chemical-processing and lightweight piping projects.
Our product range includes:
- Aluminum long-radius elbows
- Aluminum short-radius elbows
- Aluminum return bends
- Equal tees
- Reducing tees
- Concentric reducers
- Eccentric reducers
- Aluminum pipe caps
- Socket-end fittings
- Customized aluminum fittings
- Prefabricated aluminum pipe spools
Available materials include project-specified aluminum alloys and tempers, subject to technical review and the applicable standard edition.
Each inquiry is reviewed to confirm:
- Alloy and temper
- Product type
- Raw-material form
- Outside diameter
- Wall thickness
- Dimensional standard
- Manufacturing method
- Testing requirements
- Documentation
- Delivery requirements
