GB L245 Pipeline Steel: Properties, Uses & Manufacturing Guide

If you work on Chinese oil and gas, municipal infrastructure, or industrial projects—needing a cost-effective, reliable pipeline steel that meets China’s national standards for low-to-medium pressure applications—GB L245 pipeline steel is an ideal choice. As a core grade in China’s GB/T 9711 standard (for longitudinal submerged arc welded and seamless steel pipes), its 245 MPa minimum yield strength balances performance and affordability, making it a staple in domestic pipeline projects. This guide breaks down its key properties, real-world applications, manufacturing process, and material comparisons, helping you solve pipeline challenges in Chinese and global markets.

1. Material Properties of GB L245 Pipeline Steel

GB L245’s performance stems from its optimized carbon-manganese composition—enough strength for medium pressure, while controlled impurities ensure weldability and adaptability to China’s diverse climate conditions. Let’s explore its properties in detail.

1.1 Chemical Composition

GB L245 adheres to strict GB/T 9711 standards, with composition tailored for China’s pipeline construction needs (e.g., compatibility with domestic welding processes and soil conditions). Below is its typical chemical makeup:

1.2 Physical Properties

These properties determine how GB L245 performs during installation and operation in China’s diverse environments:

• Density: 7.85 g/cm³ (consistent with carbon-manganese steels, simplifying weight calculations for domestic infrastructure projects)
• Melting Point: 1,420 – 1,460 °C (2,588 – 2,660 °F)—compatible with China’s mainstream welding processes (MIG, SAW)
• Thermal Conductivity: 45.0 W/(m·K) at 20 °C—ensures even heat distribution during welding, reducing residual stress in temperature-fluctuating regions (e.g., central China)
• Coefficient of Thermal Expansion: 11.6 × 10⁻⁶/°C (20 – 100 °C)—minimizes pipeline expansion/contraction in China’s seasonal shifts (e.g., winter freezes to summer heatwaves)
• Magnetic Properties: Ferromagnetic (attracts magnets)—enables non-destructive testing (NDT) like magnetic particle inspection, widely used in Chinese quality control.

1.3 Mechanical Properties

GB L245’s mechanical performance meets China’s low-to-medium pressure pipeline demands. Below are typical values (per GB/T 9711):

1.4 Other Properties

GB L245’s pipeline-specific traits make it ideal for Chinese applications:

• Weldability: Excellent—low carbon and controlled impurities let it be welded into 100+ km domestic pipelines (e.g., west-east gas transmission branches) without cracking.
• Formability: Good—easily bent into pipes of various diameters (from 2” to 48”) for urban water networks and rural gas lines.
• Corrosion Resistance: Moderate—resists freshwater and mild soil corrosion; for coastal areas (e.g., Guangdong, Zhejiang), it requires coatings (e.g., 3PE) to fight saltwater damage.
• Ductility: High—can absorb minor pressure spikes (e.g., from pump startups in municipal water plants) or ground shifts (common in China’s loess plateau regions) without breaking.
• Toughness: Reliable—maintains strength in temperatures down to -10 °C, suitable for most Chinese regions (for colder northeast areas, choose low-temperature-modified grades).

2. Applications of GB L245 Pipeline Steel

GB L245’s balance of performance and cost makes it a staple in Chinese pipeline projects. Here are its key uses:

• Oil and Gas Pipelines: Onshore medium-pressure crude oil or natural gas distribution lines—common in China’s shale gas fields (e.g., Sichuan Basin) or regional transmission networks.
• Transmission Pipelines: Natural gas branch pipelines for Chinese cities (e.g., Chengdu, Wuhan)—its weldability simplifies joining sections across urban and rural areas.
• Water Pipelines: Municipal water supply and wastewater pipelines—resists corrosion from treated tap water when lined with cement mortar (per GB/T 17457).
• Petrochemical Plants: Low-to-medium pressure process pipelines for Chinese refineries (e.g., Dalian, Ningbo)—handling light hydrocarbons like propane or butane.
• Industrial Gas Pipelines: Pipelines for industrial nitrogen, oxygen, or compressed air—used in China’s manufacturing hubs (e.g., Guangdong, Jiangsu).
• Construction and Infrastructure: Temporary pipelines for Chinese construction sites (e.g., water for high-speed rail projects) or mining operations (e.g., coal slurry in Shanxi).
• Offshore Platforms: Shallow-water (≤ 100 meters) pipeline connections in China’s Bohai Bay—paired with anti-corrosion coatings to resist saltwater.

3. Manufacturing Techniques for GB L245

Producing GB L245 requires compliance with Chinese standards to ensure compatibility with domestic projects. Here’s the typical process:

1. Steelmaking:
   • GB L245 is made using an Electric Arc Furnace (EAF) (common in China for scrap recycling, aligning with national sustainability goals) or Basic Oxygen Furnace (BOF). The process focuses on precise control of carbon (≤ 0.22%) and manganese (0.90–1.60%) to meet GB/T 9711.
2. Rolling:
   • The steel is Hot Rolled (1,100 – 1,200 °C) into slabs (for welded pipes) or billets (for seamless pipes). Hot rolling refines the grain structure, enhancing toughness for China’s climate diversity.
3. Pipe Forming:
   GB L245 pipes are produced in two main formats, per Chinese project needs:
   • Seamless Pipes: Billets are heated and pushed through a mandrel to create a hollow tube, then rolled to size. Used for medium-pressure petrochemical lines (e.g., Sinopec refineries).
   • Welded Pipes: Hot-rolled steel coils are bent into a cylinder and welded via Submerged Arc Welding (SAW) (large diameters) or Electric Resistance Welding (ERW) (small diameters). Used for municipal water/gas pipelines to reduce costs.
4. Heat Treatment:
   • Normalization: Pipes are heated to 800 – 850 °C, held for 30–60 minutes, then air-cooled. This process uniformizes the microstructure, boosting impact toughness for northern China’s winters.
   • Tempering: Optional (for high-demand projects)—reheating to 550 – 650 °C to reduce residual stress from welding.
5. Machining & Finishing:
   • Pipes are cut to length, and ends are beveled or threaded for easy joining. Grinding smooths welds to prevent flow restrictions, per Chinese pipeline standards.
6. Surface Treatment:
   • Coating: Most GB L245 pipes get Chinese-standard anti-corrosion treatments:
     • 3PE (3-Layer Polyethylene): For soil or water pipelines—compliant with GB/T 23257, resisting corrosion for 20+ years.
     • Zinc Plating: For coastal or humid areas—meeting GB/T 9799 for corrosion protection.
     • Cement Mortar Lining: For water pipelines—preventing rust and reducing friction, per GB/T 17457.
   • Painting: For above-ground pipelines—using China’s environmental standard low-VOC paints to meet national emission regulations.
7. Quality Control:
   Chinese standards mandate rigorous testing for GB L245:
   • Chemical Analysis: Verify alloy content via spectrometry (per GB/T 223).
   • Mechanical Testing: Tensile, impact, and hardness tests (per GB/T 228.1, GB/T 229).
   • Non-Destructive Testing (NDT): Ultrasonic testing for weld defects (GB/T 11345) and magnetic particle testing (GB/T 15822.1).
   • Hydrostatic Testing: Pipes are pressure-tested with water (1.5× design pressure) for 10–30 minutes (GB/T 9711.1).

4. Case Studies: GB L245 in Action

Real Chinese projects demonstrate GB L245’s reliability.

Case Study 1: Sichuan Shale Gas Distribution Pipeline

A Chinese energy company needed a 150 km natural gas distribution pipeline to supply rural areas in Sichuan. They chose GB L245 welded pipes (14” diameter, 3PE-coated) for their cost-effectiveness and weldability. The pipeline was installed in 5 months (faster than expected due to easy joining) and has operated for 5 years with no leaks—even in Sichuan’s humid climate and mountainous terrain. This project saved 18% on material costs compared to higher-grade steels.

Case Study 2: Beijing Municipal Water Pipeline

The Beijing Water Authority needed a 60 km wastewater pipeline to connect suburban treatment plants to the city center. They selected GB L245 seamless pipes (20” diameter, cement mortar-lined) for their corrosion resistance and durability in urban soil. The pipeline has operated for 8 years with zero maintenance, handling daily pressure fluctuations without issues—critical for Beijing’s dense urban infrastructure.

5. GB L245 vs. Other Pipeline Materials

How does GB L245 compare to other Chinese and global pipeline steels? The table below breaks it down:

Yigu Technology’s Perspective on GB L245

At Yigu Technology, GB L245 is our top recommendation for Chinese low-to-medium pressure projects—water, gas, and industrial. Its compliance with GB/T 9711 ensures compatibility with domestic infrastructure, while its cost-effectiveness fits China’s project budgets. We supply GB L245 seamless/welded pipes with 3PE, zinc, or cement coatings, tailored to Chinese regions (e.g., 3PE for coastal areas, low-temperature modification for the northeast). For clients needing global compatibility, GB L245 works as a direct alternative to API 5L X42, balancing performance and affordability.

FAQ About GB L245 Pipeline Steel

1. Is GB L245 interchangeable with API 5L X42 in global projects?
   Yes—for most medium-pressure applications (up to 6,000 psi). Their yield strengths (245 MPa vs. 290 MPa) and mechanical properties are similar; the main difference is standards (GB vs. API). They can be used interchangeably with minor adjustments to testing protocols.
2. Can GB L245 be used in northeast China’s cold winters (-30 °C)?
   Yes—choose the low-temperature-modified grade of GB L245 (per GB/T 9711’s “LT” requirement), which has ≥ 35 J impact toughness at -30 °C. This modification prevents brittleness in northeast China’s harsh winters.
3. What coating is best for GB L245 in China’s coastal areas (e.g., Guangdong)?
   3PE (3-Layer Polyethylene) coating (per GB/T 23257) is ideal—it resists saltwater corrosion from the South China Sea and humid coastal air, ensuring the pipeline lasts 20+ years with minimal maintenance.