📄 PSL1 L320/X46 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. L320/X46 (PSL1) is a medium-strength pipeline steel offering enhanced strength over X42 while maintaining excellent weldability and toughness for oil and gas transmission lines.
PSL1 L320/X46 pipeline steel plate conforms to GB/T 21237-2018, fully equivalent to API 5L Grade X46. It is widely used in oil and gas transmission pipelines, water supply systems, and structural pipe applications. With balanced carbon content and controlled microalloying elements, X46 provides improved strength while maintaining excellent field weldability and formability, making it a cost-effective choice for medium-pressure pipeline projects requiring higher performance than X42.
📌 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
L320/X46: L320 = yield ≥320MPa, X46 = API 5L X46 grade (PSL1, hot-rolled/normalized/normalized-rolled)
🔸 API 5L Common Naming (3.2.2)
Example: X46
X — Line pipe identifier
46 — Minimum yield strength (ksi) = 46 × 6.895 ≈ 317 MPa (rounded to 320 MPa)
L320/X46 corresponds to API 5L Grade X46, yield ≥320MPa.
📘 Per Table 1, PSL1 hot-rolled/normalized state = L320/X46.
🧪 Chemical Composition (PSL1, ladle & product analysis)
| Grade | Cb (≤%) | Mnb (≤%) | P (≤%) | S (≤%) | V | Nb | Ti | Other restrictions |
|---|---|---|---|---|---|---|---|---|
| L320/X46 | 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 L320/X46.
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 |
|---|---|---|---|---|---|
| L320/X46 | 320 | 435 | 20 | 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.
🔄 L320/X46 vs API 5L X46 – What's the Difference?
🇨🇳 GB/T 21237 L320/X46
- Standard: Chinese national standard GB/T 21237-2018 (PSL1)
- Yield strength: ≥320 MPa (46.4 ksi)
- Tensile strength: ≥435 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-pressure transmission, structural pipes
🇺🇸 API 5L Grade X46
- Standard: API Spec 5L (PSL1 / PSL2)
- Yield strength: ≥317 MPa (46,000 psi)
- Tensile strength: ≥435 MPa (63,100 psi)
- Carbon (max): 0.26% (X46)
- Manganese (max): 1.40%
- Delivery condition: As-rolled, normalized, TMCP
- Typical use: Medium-pressure oil/gas pipelines, cross-country transmission
💡 Bottom line: L320/X46 (GB/T 21237) is fully equivalent to API 5L Grade X46 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. For projects requiring API 5L X46 steel plates, L320/X46 from Chinese mills is a direct, cost-effective substitute. It delivers higher strength than X42 (320MPa minimum yield) while maintaining excellent weldability for medium-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 L320/X46 conventional smelting with controlled residuals.
📦 6.4 Delivery condition
Hot-rolled (R), normalized (N), normalized-rolled. L320/X46 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: L320/X46
- 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.