📄 PSL1 L360/X52 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. L360/X52 (PSL1) is a widely used medium-strength pipeline steel offering an excellent balance of strength, weldability, and toughness for oil and gas transmission lines.
PSL1 L360/X52 pipeline steel plate conforms to GB/T 21237-2018, fully equivalent to API 5L Grade X52. It is one of the most popular grades for long-distance oil and gas pipelines, water supply systems, and structural pipe applications. With optimized carbon content and controlled microalloying elements, X52 provides reliable strength (360MPa minimum yield) while maintaining excellent field weldability and formability, making it the industry standard choice for medium-to-high pressure 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
L360/X52: L360 = yield ≥360MPa, X52 = API 5L X52 grade (PSL1, hot-rolled/normalized/normalized-rolled)
🔸 API 5L Common Naming (3.2.2)
Example: X52
X — Line pipe identifier
52 — Minimum yield strength (ksi) = 52 × 6.895 ≈ 359 MPa (rounded to 360 MPa)
L360/X52 corresponds to API 5L Grade X52, yield ≥360MPa.
📘 Per Table 1, PSL1 hot-rolled/normalized state = L360/X52.
🧪 Chemical Composition (PSL1, ladle & product analysis)
| Grade | Cb (≤%) | Mnb (≤%) | P (≤%) | S (≤%) | V | Nb | Ti | Other restrictions |
|---|---|---|---|---|---|---|---|---|
| L360/X52 | 0.26 | 1.40 | 0.030 | 0.030 | c,d | c,d | c,d | 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 1.40%, but max Mn ≤1.65% for L360/X52.
c Unless otherwise agreed, total Nb+V ≤0.06%.
d Total Nb+V+Ti ≤0.15%.
e Unless otherwise specified, boron not intentionally added, residual B ≤0.001%.
⚙️ Mechanical & Technological Properties (PSL1 Table 4)
| Steel grade | Rt0.5 (MPa) ≥ | Rm (MPa) ≥ | A50mmc (%) ≥ | 180° bend test | Specimen direction |
|---|---|---|---|---|---|
| L360/X52 | 360 | 460 | 19 | 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.
🔄 L360/X52 vs API 5L X52 – What's the Difference?
🇨🇳 GB/T 21237 L360/X52
- Standard: Chinese national standard GB/T 21237-2018 (PSL1)
- Yield strength: ≥360 MPa (52.2 ksi)
- Tensile strength: ≥460 MPa
- Carbon (max): 0.26%
- Manganese (max): 1.40% (adjustable up to 1.65%)
- Delivery condition: Hot-rolled, normalized, normalized-rolled
- Typical use: Oil & gas pipelines, medium-to-high pressure transmission, structural pipes
🇺🇸 API 5L Grade X52
- Standard: API Spec 5L (PSL1 / PSL2)
- Yield strength: ≥359 MPa (52,000 psi)
- Tensile strength: ≥460 MPa (66,700 psi)
- Carbon (max): 0.26% (X52)
- Manganese (max): 1.40%
- Delivery condition: As-rolled, normalized, TMCP
- Typical use: Medium-to-high pressure oil/gas pipelines, cross-country transmission
💡 Bottom line: L360/X52 (GB/T 21237) is fully equivalent to API 5L Grade X52 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. X52 is one of the most widely used pipeline grades globally. For projects requiring API 5L X52 steel plates, L360/X52 from Chinese mills is a direct, cost-effective substitute trusted by engineers worldwide for medium-to-high pressure pipeline applications.
📜 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 L360/X52 conventional smelting with controlled residuals.
📦 6.4 Delivery condition
Hot-rolled (R), normalized (N), normalized-rolled. L360/X52 typically delivered as hot-rolled or normalized.
📏 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: L360/X52
- 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.