When industrial piping systems operate in sub-zero environments—such as liquefied natural gas (LNG) plants, refrigeration units, or arctic oil and gas pipelines—standard carbon steel fittings like ASTM A234 WPB fall short. Under severe cold, ordinary carbon steel can suffer from catastrophic brittle fracture
This is where ASTM A420 Grade WPL6 comes in. Engineered specifically for low-temperature service down to -50°F (-46°C), WPL6 fittings form the backbone of safe, reliable cryogenic and sub-zero fluid transportation.
What does the grades WPL6 mean?
W: Wrought or weldable carbon steel fitting.
P: Pertains to pressure piping.
L: Low-temperature service.
6: Refers to the matching base material grade, corresponding to ASTM A333 Grade 6 (seamless pipe) or ASTM A516 Grade 60/70 (plates for welded construction)
Unlike standard high-temperature or ambient carbon steel fittings, every batch of A420 WPL6 fittings must undergo rigorous Charpy V-Notch (CVN) impact testing at -46°C to verify that the material retains exceptional notch toughness and ductility under extreme cold.
Technical Specifications & Standards
To ensure complete compliance with international pressure vessel and piping codes, WPL6 fittings are manufactured strictly according to recognized dimensional and material standards:
| Parameter | Specification Detail |
| Applicable Standards | ASTM A420 / A420M |
| Dimensional Standards | ASME B16.9 (Butt-weld), ASME B16.11 (Socket-weld/Threaded), MSS SP-75 |
| Matching Pipe Grade | ASTM A333 Grade 6 (Seamless/Welded) |
| Matching Flange Grade | ASTM A350 LF2 Class 1 |
| Impact Test Temperature | -50°F (-46°C) |
| Minimum Yield Strength | 35 ksi [240 MPa] |
| Tensile Strength Range | 60–85 ksi [415–585 MPa] |
The chemical composition
To maintain low-temperature notch toughness and weldability, the chemistry restricts carbon while balancing manganese and silicon for grain refinement.
| Element | Composition Limit (%) |
| Carbon (C) | 0.30 max |
| Manganese (Mn) | 0.50 – 1.35 |
| Phosphorus (P) | 0.035 max |
| Sulfur (S) | 0.040 max |
| Silicon (Si) | 0.15 – 0.40 |
| Nickel (Ni) | 0.40 max |
| Chromium (Cr) | 0.30 max |
| Molybdenum (Mo) | 0.12 max |
| Copper (Cu) | 0.40 max |
| Vanadium (V) | 0.08 max |
Mechanical Properties
WPL6 fittings must meet strict tensile and yield parameters under room-temperature testing standards:
| Property | Metric (MPa) | Imperial (ksi) |
| Tensile Strength | 415 – 585 MPa | 60 – 85 ksi (up to 95 ksi max) |
| Yield Strength (min) | 240 MPa min | 35 ksi min |
| Elongation (Longitudinal) | 30% min | 30% min |
| Elongation (Transverse) | 16.5% min | 16.5% min |
If you are in need, send us email by sales@hysteelpipefitting.com(For urgent inquiries, reach our WhatsApp Customer Support: +86 15028741153).
We,Hebei Haiyuan Pipe Fitting Co., Ltd. maintain a complete set of compliance and qualification systems required for pipe fitting and flange procurement. The company holds ISO 9001 Quality Management System certification, ISO 14001 Environmental Management System certification, ISO 45001 Occupational Health and Safety Management System certification, and Bureau Veritas Quality System certification. In addition, it possesses a Special Equipment Production License covering pressure pipeline components such as seamless pipe fittings (B1, B2), forged fittings, and steel forged flanges.
Regarding export compliance and material standards, Haiyuan holds PED 2014/68/EU Material Approval and provides EN 10204:2004 3.1 material certificates for common materials like WPB. The company is registered for Foreign Trade Operations and exports products globally to Europe, the United States, Japan, Russia, the Middle East, and other international markets.
Our product portfolio covers carbon steel, stainless steel, alloy steel, and other materials, with sizing specifications ranging from DN15 to DN2800. Main products include slip-on flanges, weld neck flanges, high-pressure flanges, elbows, tees, crosses, reducers, caps, bend pipes, pipe supports and hangers, anti-corrosion/insulated pipe fittings, and complete pipeline assemblies.
Products comply with major national and international standards including GB, ASME,EN, DIN, and JIS. Tailored engineering and customized pipe fitting solutions are also available based on specific project needs.
Also if you are looking to optimize your supply chain with high quality piping components, send us email by sales@hysteelpipefitting.com(For urgent inquiries, reach our WhatsApp Customer Support: +86 15028741153).