ASTM A420 WPL6 Low Temperature Pipe Fittings
ASTM A420 Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service
ASTM A420 Pipe fittings Covers wrought carbon steel and alloy steel butt-welding fittings, including elbows, tees, reducers, and caps.
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Designed for low-temperature applications.
Applicable to fittings made from seamless and welded pipe or plate.
WPL6 Material Grade
- WPL6 stands for:
- W: Wrought
- P: Pressure
- L6: Low-temperature grade 6 carbon steel
ASTM A420 WPL6 pipe fittings are fully compatible with ASTM A333 grade pipe and ASTM A350 LF2 flanges.
These 3 materials are designed for low-temperature service, and they are often used together in cryogenic and cold service pipeline systems.
Typical Low-Temperature Piping Assembly:
- Pipe: ASTM A333 Gr. 6 Seamless Pipes
- Fittings: ASTM A420 WPL6 (elbows, tees, reducers)
- Flanges: ASTM A350 LF2 Cl.1 (weld neck, slip-on, blind, etc.)
Other Material Grades in ASTM A420
The specification includes several grades such as:
- Grade WPL6 – Most commonly used for low-temperature carbon steel.
- Grade WPL9
- Grade WPL3
- Grade WPL8 – For nickel alloy steels.
1. ASTM A420 Scope
This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction, covered by the latest revision of ASME B16.9, ASME B16.11, MSS SP-79, MSS SP-83, MSS SP-95, and MSS SP-97. Fittings differing from these ASME and MSS standards shall be furnished in accordance with Supplementary Requirement S58 of Specification A960/A960M. These fittings are for use in pressure piping and pressure vessel service at low temperatures.
2. Referenced Documents
In addition to those Referenced Documents listed in Specification A960/A960M, the following list of standards apply to this specification.
- A350/A350M Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components
- A370 Test Methods and Definitions for Mechanical Testing of Steel Products
- A960/A960M Specification for Common Requirements for Wrought Steel Piping Fittings
- A1058 Test Methods for Mechanical Testing of Steel Products—Metric
- ASME B16.9 Factory-Made Wrought Steel Butt-Welding Fittings⁴
- ASME B16.11 Forged Steel Fittings, Socket-Welding Threaded⁴
ASME Boiler and Pressure Vessel Code:⁴ - Section VIII Division 1, Pressure Vessels⁴
- MSS SP-25 Standard Marking System for Valves, Fittings, Flanges, and Unions⁵
- MSS SP-79 Socket Welding Reducer Inserts⁵
- MSS SP-83 Steel Pipe Unions, Socket-Welding and Threaded⁵
- MSS SP-95 Swage(d) Nipples and Bull Plugs⁵
- MSS SP-97 Integrally Reinforced Forged Branch Outlet Fittings—Socket Welding, Threaded and Buttwelding Ends
- SNT-TC-1A Recommended Practice for Nondestructive Testing Personnel Qualification and Certification⁶
3. General Requirements
Product furnished to this specification shall conform to the requirements of Specification A960/A960M, including any supplementary requirements that are indicated in the purchase order.
4. Material
The starting material for fittings shall be fully killed steel, consisting of forgings, bars, plates, sheet, and seamless or fusion welded tubular products with filler metal added and shall conform to the chemical requirements in Table 1. The steels shall be made using recognized melting practices necessary to produce steels that shall meet the impact requirements of this specification.
5. Manufacture
For welded fittings,
The radiography of welds shall be done either prior to or after forming at option of manufacturer. Personnel performing NDE examinations shall be qualified in accordance with SNT-TC-1A.
The welded joints of the fittings shall be finished in accordance with the requirements of Paragraph UW-35 (a) of Section VIII, Division 1 of ASME Boiler and Pressure Vessel Code.
For Seamless fittings
All butt-weld tees manufactured by cold-forming methods shall be liquid penetrant or magnetic particle examined by the methods specified in Supplementary Requirement S52 or S53 of Specification A960/A960M..
6. ASTM A420 WPL3 WPL6 Heat Treatment
All fittings shall be furnished in the normalized, normalized and tempered, annealed, or quenched and tempered condition. All welding shall be completed prior to the austenitizing heat treatment.
7. ASTM A420 Chemical Composition
The steel shall conform to requirements of chemical composition for the respective material prescribed in below table
| Grade | C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Nb | V |
|---|---|---|---|---|---|---|---|---|---|---|---|
| WPL6 | 0.30 | 0.50 – 1.35 | 0.035 | 0.040 | 0.15 – 0.40 | 0.40 | 0.30 | 0.12 | 0.40 | 0.02 | 0.08 |
| WPL9 | 0.20 | 0.40 – 1.06 | 0.030 | 0.030 | … | 1.60 – 2.24 | … | … | 0.75 – 1.25 | … | … |
| WPL3 | 0.20 | 0.31 – 0.64 | 0.05 | 0.05 | 0.13 – 0.37 | 3.2 – 3.8 | … | … | … | … | … |
| WPL8 | 0.13 | 0.90 | 0.030 | 0.030 | 0.13 – 0.37 | 8.4 – 9.6 | … | … | … | … | … |
Note 1: All requirements are maximum unless otherwise indicated.
Note 2: Where an ellipsis (…) appears in this table, there is no requirement.
A: When fittings are of welded construction, the symbols above shall be supplemented by the letter “W”.
B: By agreement, the limit for niobium may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
C: Fittings made from plate or forgings may have 0.90 % max manganese.
D: Fittings made from plate may have 0.98 % max manganese.
E: Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.
8. ASTM A420 Tensile Properties
The tensile properties of the fittings material shall conform to the requirements for the applicable grade of material as listed in below table
| Requirement | Grade – WPL6 | Grade – WPL9 | Grade – WPL3 | Grade – WPL8 |
|---|---|---|---|---|
| Tensile strength, min ksi [MPa] | 60 [415] – 95 [655] | 63 [435] – 88 [610] | 65 [450] – 90 [620] | 100 [690] – 125 [865] |
| Yield strength, min ksi [MPa] | 35 [240] | 46 [315] | 35 [240] | 75 [515] |
| Elongation Requirements – Standard round specimen, or small proportional specimen, min % in 4D – Longitudinal | 22 | 20 | 22 | 16 |
| Elongation Requirements – Standard round specimen, or small proportional specimen, min % in 4D – Transverse | 12 | … | 14 | … |
| Elongation Requirements – Strip specimen for wall thickness ⅝ in. [7.94 mm] and over, and for all small sizes tested in full section; min % in 2 in. or 50 mm – Longitudinal | 30 | 28 | 30 | 22 |
| Elongation Requirements – Strip specimen for wall thickness ⅝ in. [7.94 mm] and over, and for all small sizes tested in full section; min % in 2 in. or 50 mm – Transverse | 17 | 18 | 20 | … |
| Elongation Requirements – Formula for calculating minimum elongation for strip specimens thinner than ⅝ in. [7.94 mm]; min % in 2 in. or 50 mm (½ – in. [12.7 – mm] wide specimen) – Longitudinal (t = actual thickness in inches) | 48t + 15 | 48t + 13 | 48t + 15 | 40t + 9.5 |
| Elongation Requirements – Formula for calculating minimum elongation for strip specimens thinner than ⅝ in. [7.94 mm]; min % in 2 in. or 50 mm (½ – in. [12.7 – mm] wide specimen) – Transverse (t = actual thickness in inches) | 32t + 6.5 | 32t + 8 | 32t + 10 | … |
| Elongation Requirements – Formula for calculating minimum elongation for strip specimens thinner than ⅝ in. [7.94 mm]; min % in 2 in. or 50 mm (½ – in. [12.7 – mm] wide specimen) – Longitudinal (t = actual thickness in mm) | 1.9t + 15 | 1.9t + 13 | 1.9t + 15 | 1.57t + 9.5 |
| Elongation Requirements – Formula for calculating minimum elongation for strip specimens thinner than ⅝ in. [7.94 mm]; min % in 2 in. or 50 mm (½ – in. [12.7 – mm] wide specimen) – Transverse (t = actual thickness in mm) | 1.26t + 6.5 | 1.26t + 8 | 1.26t + 10 | … |
Note 1: Where an ellipsis (…) appears in this table, there is no requirement.
A: Requirements for equivalent wall thickness expressed in inches and mm may differ from each other.编辑分享
9. ASTM A420 WPL6 Impact Test Properties
The Charpy V-Notch (CVN) impact requirements for ASTM A420 Grade WPL6 WPL9,WPL3 are critical because this material is used in low-temperature service.
Charpy Impact Requirements for WPL6, WPL9, and WPL3ᴬ
| Size of Specimen (mm) | Charpy V – Notch Impact Value Required for Acceptance (Average of Three Specimens) | Minimum Charpy V – Notch Impact Value Without Requiring Retest (One Specimen Only of a Set) | ||
|---|---|---|---|---|
| ft·lbf | J | ft·lbf | J | |
| 10 by 10.0 | 13 | 18 | 10 | 14 |
| 10 by 7.5 | 10 | 14 | 8 | 11 |
| 10 by 5.0 | 7 | 9 | 5 | 7 |
| 10 by 2.5 | 4 | 5 | 3 | 4 |
ᴬStraight – line interpolation for intermediate values is permitted.
Charpy Impact Requirements for WPL8
| Size of Specimen (mm) | Charpy V – Notch Impact Value Required for Acceptance (Average of Specimens) | Minimum Charpy V – Notch Impact Value Without Requiring Retest (One Specimen Only of a Set) | ||
|---|---|---|---|---|
| ft·lbf | J | ft·lbf | J | |
| 10 by 10.0 | 25 | 34 | 20 | 27 |
| 10 by 7.5 | 21 | 29 | 17 | 23 |
| 10 by 5.0 | 17 | 23 | 14 | 19 |
| 10 by 2.5 | 8 | 11 | 6 | 8 |
ASTM A420 material Impact Test Temperature
| Grade | Impact Test Temperature, °F [°C] |
|---|---|
| WPL6 | – 50 [ – 45] |
| WPL9 | – 100 [ – 75] |
| WPL3 | – 150 [ – 100] |
| WPL8 | – 320 [ – 195] |
10,ASTM A420 WPL6 Pipe fittings product type and Dimensions
Butt-welding fittings and butt-welding short-radius elbows and returns purchased in accordance with this specification shall conform to the dimensions and tolerances given in the latest revision of ASME B16.9 or MSS SP-95
| Fitting Type | Description |
|---|---|
| Elbows | 45°, 90°, 180°; long or short radius |
| Reducers | Concentric and eccentric |
| Tees | Equal and reducing |
| Caps | End closures for pipes |
| Crosses | Four-way connections (less common) |
11. Surface Finish, Appearance, and Corrosion Protection
The requirements of Specification A960/A960M apply.
12.Marking Requirements of ASTM A420 WPL6
Fittings must be marked with:
- Manufacturer’s name or trademark
- Grade WPL6
- Heat number or traceability info
- Size and schedule
- ASTM A420 marking