📄 PSL1 L450/X65 Pipeline Steel Plate (GB/T 21237-2018) – Technical Data Sheet
This standard specifies technical requirements for wide and heavy plates of 6mm~50mm thickness for petroleum and natural gas pipelines. L450/X65 (PSL1) is a high-strength pipeline steel offering superior performance for demanding oil and gas transmission applications requiring excellent strength, toughness, and weldability.
PSL1 L450/X65 pipeline steel plate conforms to GB/T 21237-2018, fully equivalent to API 5L Grade X65. It is designed for high-pressure oil and gas transmission lines, long-distance pipelines, offshore applications, and structural projects requiring higher strength. With controlled carbon content and optimized microalloying elements (Nb, V, Ti), X65 provides reliable strength (450MPa minimum yield) while maintaining good weldability and excellent low-temperature toughness, making it a preferred choice for demanding pipeline projects worldwide.
📌 Designation Rules (3.2.1 / 3.2.2)
🔹 Standard Naming (3.2.1)
Example: L415M
L — First letter of "Line" for pipeline
415 — Specified minimum yield strength (MPa)
M — Thermomechanical rolled condition
L450/X65: L450 = yield ≥450MPa, X65 = API 5L X65 grade (PSL1, hot-rolled/normalized/normalized-rolled)
🔸 API 5L Common Naming (3.2.2)
Example: X65
X — Line pipe identifier
65 — Minimum yield strength (ksi) = 65 × 6.895 ≈ 448 MPa (rounded to 450 MPa)
L450/X65 corresponds to API 5L Grade X65, yield ≥450MPa.
📘 Per Table 1, PSL1 hot-rolled/normalized state = L450/X65.
🧪 Chemical Composition (PSL1, ladle & product analysis)
| Grade | Cb (≤%) | Mnb (≤%) | P (≤%) | S (≤%) | V | Nb | Ti | Other restrictions |
|---|---|---|---|---|---|---|---|---|
| L450/X65 | 0.26* | 1.45* | 0.030 | 0.030 | —f | —f | —f | Cu≤0.50, Ni≤0.50, Cr≤0.50, Mo≤0.15 |
📋 Table 2 Notes:
a Copper max 0.50%; Nickel max 0.50%; Chromium max 0.50%; Molybdenum max 0.15%.
b For each 0.01% reduction in carbon below 0.26%, manganese may be increased by 0.05% above 1.45%, but max Mn ≤1.75% for L450/X65.
f Unless otherwise agreed, total Nb+V+Ti ≤0.15%.
g Unless otherwise specified, boron not intentionally added, residual B ≤0.001%.
* For L450/X65, the maximum carbon and manganese limits may be adjusted by agreement.
⚙️ Mechanical & Technological Properties (PSL1 Table 4)
| Steel grade | Rt0.5 (MPa) ≥ | Rm (MPa) ≥ | A50mmc (%) ≥ | 180° bend test | Specimen direction |
|---|---|---|---|---|---|
| L450/X65 | 450 | 535 | 17 | D=2a, no cracks | Transverse |
📋 Table 4 Notes:
a Tensile property range to be agreed between purchaser and supplier to ensure finished pipe compliance.
b Specimen direction transverse, to be stated in contract.
c Standard gauge length 50mm. Arbitration specimen: 50mm gauge length, 38mm width.
📐 Min elongation formula: A50mm=1940×S00.2/Rm0.9. Bend former diameter D=2a.
🔄 L450/X65 vs API 5L X65 – What's the Difference?
🇨🇳 GB/T 21237 L450/X65
- Standard: Chinese national standard GB/T 21237-2018 (PSL1)
- Yield strength: ≥450 MPa (65.3 ksi)
- Tensile strength: ≥535 MPa
- Carbon (max): 0.26% (adjustable)
- Manganese (max): 1.45% (adjustable up to 1.75%)
- Delivery condition: Hot-rolled, normalized, normalized-rolled
- Typical use: High-pressure oil & gas pipelines, long-distance transmission, offshore pipelines, arctic applications
🇺🇸 API 5L Grade X65
- Standard: API Spec 5L (PSL1 / PSL2)
- Yield strength: ≥448 MPa (65,000 psi)
- Tensile strength: ≥531 MPa (77,000 psi)
- Carbon (max): 0.26% (X65)
- Manganese (max): 1.45%
- Delivery condition: As-rolled, normalized, TMCP, Q&T
- Typical use: High-pressure oil/gas pipelines, sour service, offshore, arctic regions
💡 Bottom line: L450/X65 (GB/T 21237) is fully equivalent to API 5L Grade X65 in mechanical properties and chemical composition. The naming differs — "L" stands for "Line" in the Chinese standard, while API uses "X" — but material performance is identical. X65 is a high-strength pipeline grade widely used for long-distance high-pressure transmission, offshore pipelines, and arctic applications. For projects requiring API 5L X65 steel plates, L450/X65 from Chinese mills is a direct, cost-effective substitute trusted by engineers for demanding high-pressure pipeline applications worldwide.
📜 Supplementary Chemical Requirements (6.1.3 ~ 6.1.6)
✅ 6.1.3 Thickness > 25.0mm — Chemical composition may be agreed between supplier and purchaser for heavy plates up to 50mm.
✅ 6.1.4 Ladle analysis & CE — Supplier provides ladle analysis and carbon equivalent (CE); product analysis upon negotiation.
✅ 6.1.5 Intermediate grades — Intermediate grades between consecutive Table 2 grades may be supplied by agreement.
✅ 6.1.6 Other alloying elements — For L290/X42 and higher, other elements (Nb, V, Ti) may be added by agreement.
🏭 Smelting Method · Delivery Condition (6.3 & 6.4)
🔥 6.3 Smelting process
Oxygen converter or electric furnace. For PSL1 L450/X65 conventional smelting with controlled residuals.
📦 6.4 Delivery condition
Hot-rolled (R), normalized (N), normalized-rolled. L450/X65 typically delivered as hot-rolled or normalized. TMCP available by agreement.
📏 Dimensions & Other Technical Specifications
Dimensions (Clause 5): Per GB/T 709. Thickness 6mm~50mm. Trimmed/untrimmed edges. Tolerances per GB/T 709.
Grain size (6.6): Not mandatory for PSL1, reference No.7 or finer.
Non-metallic inclusions (6.7): PSL1 no mandatory limits, but clean steel practice required.
Banding (6.8): Not specified for PSL1; for reference only.
📋 Summary: Steel plate surfaces must be free from cracks, blisters, folds, inclusions, and visually detectable laminations. Defect removal permitted within tolerance limits, welding repair prohibited.
✅ 6.9.1 The steel plate surface shall be free from cracks, blisters, folds, bubbles, inclusions, and visually detectable laminations harmful to use. Removal allowed up to half thickness tolerance, maintaining min thickness.
✅ 6.9.2 Other local imperfections that do not affect use are permitted, provided minimum thickness is maintained.
✅ 6.9.3 For untrimmed edges, edge crack depth shall not exceed half width tolerance, min width maintained.
✅ 6.9.4 Upon agreement, defect depth and area may be measured per GB/T 14977.
✅ 6.9.5 Welding repair on steel plate surface is not permitted.
📋 Ordering content & Inspection rules
📑 Ordering content (Clause 4)
- Standard: GB/T 21237—2018
- Quality level: PSL1
- Grade: L450/X65
- Dimensions & thickness precision
- Delivery condition & edge condition
- Specimen direction (transverse)
- Application: gas/oil/fluid
🔬 Inspection rules
Batch: same grade, heat, thickness, rolling schedule. ≤60 tons per batch. Test methods: GB/T 228.1 (tensile), GB/T 232 (bend), GB/T 4336 (chemistry). Rounding per GB/T 8170.