GB/T 9711.1 L245 is a very common and widely used material specification for manufacturing Spiral Submerged Arc Welded (SSAW) steel pipes [citation:3, citation:7]. This combination is a standard product offered by numerous Chinese and global manufacturers for oil and gas transmission, water pipelines, and general structural applications under the Chinese national standard for pipeline transportation systems [citation:2, citation:6].
The designation "GB/T 9711.1 L245 Spiral Submerged Arc Pipe" combines a widely-used pipeline steel grade (L245) with the standard PSL1 quality level, produced using the economical spiral welding process for large-diameter applications [citation:5, citation:8].
📋 Key Specifications for GB/T 9711.1 L245 SSAW Pipe
The table below summarizes the primary specifications for this product, based on comprehensive industry data [citation:1, citation:2, citation:5, citation:6, citation:8, citation:10].
| Attribute | Description |
|---|---|
| Standard | GB/T 9711.1: "Petroleum and natural gas industries - Steel pipe for pipelines - Technical delivery conditions - Part 1: Pipes of requirement class A" [citation:2, citation:9]. |
| Quality Level | Class A (PSL1 equivalent) : The standard quality level with basic requirements (no mandatory impact testing, standard chemistry limits, minimum strength only specified) [citation:1, citation:4]. |
| Steel Grade | L245: A commonly used carbon steel grade. The "L" stands for "Line pipe," and "245" indicates the minimum yield strength in MPa [citation:2, citation:8]. |
| International Equivalent | API 5L Grade B (L245) [citation:5, citation:8]. |
| Manufacturing Process | Spiral Submerged Arc Welding (SSAW/HSAW) : Formed from hot-rolled steel coil, with the weld seam running continuously in a spiral along the pipe's length. Welded using double-sided automatic submerged arc welding [citation:3, citation:10]. |
| Chemical Composition (max %) [citation:5, citation:8] | Carbon (C): 0.26% max Manganese (Mn): 1.20% max Phosphorus (P): 0.030% max Sulfur (S): 0.030% max Niobium+V+Ti: ≤ 0.15% total (when micro-alloyed) |
| Mechanical Properties (min) [citation:8, citation:10] | Yield Strength: 245 MPa (35,500 psi) Tensile Strength: 415 MPa (60,200 psi) Elongation: Varies by wall thickness |
| Typical Size Range [citation:2, citation:3, citation:5] | Outside Diameter: 219 mm to 4064 mm (approx. 8" to 160") Wall Thickness: 3.2 mm to 50 mm (common range 5-25 mm) Length: 3 m to 18 m standard; up to 50 m available for specific applications |
| Key Testing Requirements [citation:2, citation:10] | Chemical analysis; tensile test; flattening test; bend test; hydrostatic test (each pipe); non-destructive testing (ultrasonic or X-ray of weld seam - standard practice). Impact testing is not required for Class A (PSL1 equivalent) [citation:1, citation:4]. |
| Common Applications [citation:3, citation:7, citation:8] | Medium-pressure oil and gas transmission pipelines; natural gas gathering lines; water transmission mains; general utility piping; structural applications; piling foundations; irrigation systems. |
| Certification | Mill Test Certificate typically to EN 10204 Type 3.1 or equivalent, with full test results and traceability records [citation:2, citation:6]. |
📊 GB/T 9711.1 Grade Comparison
L245 is a very common strength grade in the GB/T 9711.1 specification. The table below shows its position relative to other grades [citation:1, citation:4, citation:9]:
| Grade | Minimum Yield Strength (MPa) | Equivalent API 5L Grade | Typical Application |
|---|---|---|---|
| L175 | 175 | A | Very low-pressure gathering, drainage |
| L210 | 210 | A | Low-pressure water, gas, general service |
| L245 | 245 | B | General pipeline service - MOST COMMON |
| L290 | 290 | X42 | Medium-pressure transmission |
| L320 | 320 | X46 | Medium-pressure transmission |
| L360 | 360 | X52 | General transmission |
| L390 | 390 | X56 | Higher-pressure transmission |
| L415 | 415 | X60 | High-pressure transmission |
| L450 | 450 | X65 | High-pressure, offshore |
| L485 | 485 | X70 | Long-distance high-pressure |
| L555 | 555 | X80 | Ultra-high-pressure trunk lines |
📏 Dimensional Specifications
GB/T 9711.1 specifies the following typical tolerances for SSAW pipes [citation:2, citation:5, citation:8]:
| Parameter | Tolerance |
|---|---|
| Outside Diameter | ±0.75% of specified diameter (varies by size) |
| Wall Thickness | +15.0%, -12.5% of nominal |
| Straightness | ≤ 0.1% of total length |
| Length | +100mm / -0mm (for fixed lengths) |
Standard Diameter Range: 219mm to 4064mm (8" to 160") [citation:2, citation:3, citation:5]
🔍 Key Points to Understand
What "GB/T 9711.1 L245" Means: This is the Chinese national standard for pipeline steel pipes with basic quality requirements. L245 is the most common strength grade, with minimum yield strength of 245 MPa. It is directly equivalent to API 5L Grade B (L245) in international specifications [citation:5, citation:8].
Class A (PSL1) Quality Level: GB/T 9711.1 represents the A-level quality requirements, similar to API 5L PSL1 [citation:1, citation:4]. Key characteristics include:
Chemistry: Standard limits (C ≤ 0.26%, Mn ≤ 1.20%, S/P ≤ 0.030%)
Strength: Only minimum yield and tensile strengths are specified
Impact Testing: Not required by the standard
Typical Use: Suitable for general pipeline service where enhanced toughness and tighter controls are not necessary
L245 vs. Higher Grades: L245 offers excellent balance of strength, weldability, and cost. It is the most common choice for medium-pressure pipelines, water mains, and general utility applications, offering approximately 17% higher strength than L210 (245 MPa vs. 210 MPa) .
SSAW Advantages for L245: The spiral welding process offers specific benefits for large-diameter pipes [citation:3, citation:5, citation:10]:
Large Diameter Capability: Can economically produce pipes up to 160" diameter
Cost Efficiency: 20-30% lower cost than LSAW for very large diameters
Long Lengths: Up to 50m lengths reduce field welding requirements
Diameter Flexibility: Same steel coil can produce various diameters by adjusting the spiral angle
🔧 Manufacturing Process for GB/T 9711.1 L245 SSAW Pipe
The manufacturing process follows standard SSAW production methods [citation:2, citation:3, citation:5, citation:10]:
Raw Material Preparation: Hot-rolled steel coils meeting GB/T 9711.1 L245 chemistry requirements are leveled, inspected, and edge-milled .
Spiral Forming: The steel strip is continuously formed into a cylindrical shape at a specific helix angle (typically 50-70°) at room temperature .
Submerged Arc Welding: Double-sided automatic submerged arc welding (inside and outside) creates the spiral seam with full penetration .
Non-Destructive Testing: 100% ultrasonic or X-ray inspection of the weld seam is standard practice .
Hydrostatic Testing: Each pipe individually tested to verify pressure integrity .
Mechanical Testing: Tensile tests, flattening tests, and bend tests to verify properties .
End Finishing: Ends prepared (plain or beveled per ASME B16.25) for field welding .
Coating: Optional external coatings (FBE, 3LPE, coal tar epoxy, etc.) and internal linings as required [citation:5, citation:8].
🏭 Applications
GB/T 9711.1 L245 SSAW pipes are widely used in [citation:3, citation:7, citation:8]:
| Application | Description |
|---|---|
| Medium-Pressure Oil and Gas Transmission | Pipelines for crude oil, natural gas, and refined products |
| Natural Gas Gathering Lines | Connecting wells to processing facilities |
| Water Transmission Mains | Large-diameter municipal and industrial water pipelines |
| General Utility Piping | Industrial water lines, cooling water systems, fire water mains |
| Structural Applications | Piling, bridge supports, construction projects |
| Irrigation Systems | Large-scale agricultural water transport |
📝 Important Considerations
Standard Version: GB/T 9711.1 has been updated over the years (1997, 2011, 2017 versions). When ordering, specify the required version year (e.g., GB/T 9711.1-2017) to ensure compliance with current requirements [citation:7, citation:9].
PSL1 vs. PSL2: GB/T 9711.1 (Class A) is equivalent to API 5L PSL1. For applications requiring enhanced toughness, tighter chemistry controls, or sour service capability, specify GB/T 9711.2 (Class B/PSL2) instead [citation:1, citation:4].
Impact Testing: GB/T 9711.1 does not require Charpy impact testing by the standard . If low-temperature service is anticipated, consider specifying impact testing as a supplementary requirement.
Cost-Effectiveness: L245 offers the best value for most medium-pressure pipeline applications. It is the most commonly used grade in the GB/T 9711.1 family .
International Equivalents: L245 is directly equivalent to :
API 5L Grade B (L245)
ISO 3183 L245
Complete Specification: When ordering, specify [citation:2, citation:5, citation:8]:
GB/T 9711.1, Grade L245, SSAW (spiral welded), Size (OD x WT), Length, End Finish
Standard version: [e.g., GB/T 9711.1-2017]
Coating requirements: [e.g., bare, FBE, 3LPE]
Any supplementary requirements (impact testing if needed)
📝 Summary
GB/T 9711.1 L245 Spiral Submerged Arc Welded pipes are the standard, most commonly used product for large-diameter pipeline applications under the Chinese national standard for petroleum and natural gas industries [citation:3, citation:5, citation:7, citation:8]. With minimum yield strength of 245 MPa (35,500 psi) – equivalent to API 5L Grade B – these pipes offer an excellent balance of strength, weldability, and cost for medium-pressure oil and gas transmission, water mains, and general utility applications [citation:5, citation:8].
Available in diameters from 219mm to over 4000mm with wall thicknesses to 50mm and lengths up to 50m, these pipes are produced using the cost-effective SSAW manufacturing process while meeting the rigorous requirements of the GB/T 9711.1 specification [citation:2, citation:3, citation:5].
GB/T 9711.1 Class A (PSL1 equivalent) is suitable for general pipeline service in temperate climates where enhanced toughness and tighter controls are not necessary. L245 is the most commonly used grade for a wide range of applications, directly equivalent to API 5L Grade B .
For applications requiring guaranteed low-temperature toughness, tighter chemistry controls, or sour service capability, consider upgrading to GB/T 9711.2 (Class B/PSL2) with higher grades as needed [citation:1, citation:4].
When ordering, ensure you clearly indicate the complete standard with version year, grade L245, manufacturing process (SSAW), required dimensions, and any coating or supplementary requirements based on your specific application [citation:2, citation:5, citation:8].
