Se lavori sul petrolio e sul gas cinesi, infrastrutture comunali, o progetti industriali che necessitano di un rapporto costo-efficacia, reliable pipeline steel that meets China’s national standards for low-to-medium pressure applications—GB L245 pipeline steel is an ideal choice. Come qualità principale nel GB/T cinese 9711 standard (per tubi longitudinali in acciaio saldati ad arco sommerso e senza saldatura), suo 245 MPa minimum yield strength balances performance and affordability, making it a staple in domestic pipeline projects. Questa guida analizza le sue proprietà principali, applicazioni del mondo reale, processo di produzione, 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 Composizione chimica
GB L245 adheres to strict GB/T 9711 standard, with composition tailored for China’s pipeline construction needs (per esempio., compatibility with domestic welding processes and soil conditions). Di seguito è riportata la sua tipica composizione chimica:
| Elemento | Simbolo | Gamma di contenuti (%) | Key Role |
|---|---|---|---|
| Carbonio (C) | C | ≤ 0.22 | Enhances strength; kept low to preservesaldabilità (critical for long-distance domestic pipelines) |
| Manganese (Mn) | Mn | 0.90 – 1.60 | Aumentaresistenza alla trazione Eduttilità without compromising toughness |
| Silicio (E) | E | 0.10 – 0.40 | Aiuta la disossidazione durante la produzione dell'acciaio; supports structural integrity in humid Chinese regions |
| Fosforo (P) | P | ≤ 0.030 | Minimized to prevent brittle fracture in cold northern China winters |
| Zolfo (S) | S | ≤ 0.030 | Controlled to avoid corrosion and weld defects (per esempio., porosità) in coastal areas |
| Cromo (Cr) | Cr | ≤ 0.30 | Trace element; improves mild corrosion resistance in China’s acidic soil (per esempio., southern regions) |
| Nichel (In) | In | ≤ 0.30 | Trace element; enhances low-temperatureimpact toughness (for northeast China’s -30 °C winters) |
| Vanadium (V) | V | ≤ 0.08 | Trace element; refines grain structure for uniform strength in high-pressure sections |
| Molibdeno (Mo) | Mo | ≤ 0.10 | Trace element; no significant impact on standard domestic pipeline performance |
| Rame (Cu) | Cu | ≤ 0.30 | Trace element; adds resistance to atmospheric corrosion for above-ground pipelines in industrial zones |
1.2 Proprietà fisiche
These properties determine how GB L245 performs during installation and operation in China’s diverse environments:
- Densità: 7.85 g/cm³ (consistent with carbon-manganese steels, simplifying weight calculations for domestic infrastructure projects)
- Punto di fusione: 1,420 – 1,460 °C (2,588 – 2,660 °F)—compatible with China’s mainstream welding processes (ME, SAW)
- Conducibilità termica: 45.0 Con/(m·K) A 20 °C—ensures even heat distribution during welding, reducing residual stress in temperature-fluctuating regions (per esempio., central China)
- Coefficiente di dilatazione termica: 11.6 × 10⁻⁶/°C (20 – 100 °C)—minimizes pipeline expansion/contraction in China’s seasonal shifts (per esempio., winter freezes to summer heatwaves)
- Proprietà magnetiche: Ferromagnetico (attira i magneti)—enables non-destructive testing (NDT) like magnetic particle inspection, widely used in Chinese quality control.
1.3 Proprietà meccaniche
GB L245’s mechanical performance meets China’s low-to-medium pressure pipeline demands. Below are typical values (per GB/T 9711):
| Proprietà | Metodo di misurazione | Valore tipico | GB Standard Minimum Requirement |
|---|---|---|---|
| Durezza (Rockwell) | HRB | 70 – 85 HRB | N / A (controlled to avoid brittleness) |
| Durezza (Vickers) | alta tensione | 140 – 170 alta tensione | N / A |
| Resistenza alla trazione | MPa | 375 – 510 MPa | 375 MPa |
| Forza di snervamento | MPa | 245 – 320 MPa | 245 MPa |
| Allungamento | % (In 50 mm) | 22 – 28% | 22% |
| Resistenza all'impatto | J (A 0 °C) | ≥ 35 J | ≥ 27 J (for general service, per GB/T 9711) |
| Fatigue Limit | MPa (rotating beam) | 170 – 210 MPa | N / A (tested per domestic project pressure cycles) |
1.4 Altre proprietà
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 (per esempio., west-east gas transmission branches) senza rompersi.
- Formabilità: Good—easily bent into pipes of various diameters (from 2” to 48”) for urban water networks and rural gas lines.
- Resistenza alla corrosione: Moderate—resists freshwater and mild soil corrosion; for coastal areas (per esempio., Guangdong, Zhejiang), it requires coatings (per esempio., 3PE) to fight saltwater damage.
- Duttilità: High—can absorb minor pressure spikes (per esempio., 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 (per esempio., Sichuan Basin) or regional transmission networks.
- Transmission Pipelines: Natural gas branch pipelines for Chinese cities (per esempio., Chengdu, Wuhan)—its saldabilità 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 (per esempio., Dalian, Ningbo)—handling light hydrocarbons like propane or butane.
- Industrial Gas Pipelines: Pipelines for industrial nitrogen, ossigeno, or compressed air—used in China’s manufacturing hubs (per esempio., Guangdong, Jiangsu).
- Construction and Infrastructure: Temporary pipelines for Chinese construction sites (per esempio., water for high-speed rail projects) or mining operations (per esempio., coal slurry in Shanxi).
- Offshore Platforms: Shallow-water (≤ 100 metri) 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. Ecco il processo tipico:
- Produzione dell'acciaio:
- GB L245 is made using an Forno ad arco elettrico (EAF) (common in China for scrap recycling, aligning with national sustainability goals) O Fornace ad ossigeno basico (BOF). The process focuses on precise control of carbon (≤ 0.22%) and manganese (0.90–1.60%) to meet GB/T 9711.
- Rotolamento:
- The steel is Laminato a caldo (1,100 – 1,200 °C) into slabs (per tubi saldati) or billets (per tubi senza saldatura). Hot rolling refines the grain structure, enhancing tenacità for China’s climate diversity.
- 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 (per esempio., Sinopec refineries).
- Welded Pipes: Hot-rolled steel coils are bent into a cylinder and welded via Submerged Arc Welding (SAW) (large diameters) O Electric Resistance Welding (ERW) (small diameters). Used for municipal water/gas pipelines to reduce costs.
- Trattamento termico:
- 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.
- Temperamento: Opzionale (for high-demand projects)—reheating to 550 – 650 °C to reduce residual stress from welding.
- Lavorazione & Finitura:
- Pipes are cut to length, and ends are beveled or threaded for easy joining. Rettifica smooths welds to prevent flow restrictions, per Chinese pipeline standards.
- Trattamento superficiale:
- Rivestimento: 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+ anni.
- Zincatura: For coastal or humid areas—meeting GB/T 9799 per la protezione dalla corrosione.
- Cement Mortar Lining: For water pipelines—preventing rust and reducing friction, per GB/T 17457.
- Pittura: For above-ground pipelines—using China’s environmental standard low-VOC paints to meet national emission regulations.
- Rivestimento: Most GB L245 pipes get Chinese-standard anti-corrosion treatments:
- Controllo qualità:
Chinese standards mandate rigorous testing for GB L245:- Chemical Analysis: Verify alloy content via spectrometry (per GB/T 223).
- Mechanical Testing: Trazione, impatto, 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. Casi di studio: GB L245 in Action
Real Chinese projects demonstrate GB L245’s reliability.
Caso di studio 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"diametro, 3PE-coated) for their cost-effectiveness andsaldabilità. The pipeline was installed in 5 mesi (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.
Caso di studio 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"diametro, cement mortar-lined) for theirresistenza alla corrosione 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? La tabella seguente lo scompone:
| Materiale | Similarities to GB L245 | Differenze chiave | Ideale per |
|---|---|---|---|
| API 5L X42 | Medium-pressure pipeline steel | API standard (NOI.); similar yield strength (290 MPa); slightly higher tensile strength | Global oil/gas projects; interchangeable with GB L245 for most medium-pressure uses |
| EN L245 | European pipeline steel | EN standard; nearly identical composition; compatible with GB L245 in Sino-European joint projects | European or joint-venture projects in China |
| GB L290 | Chinese pipeline steel | Higher yield strength (290 MPa); più costoso | Chinese medium-to-high pressure gas pipelines |
| API 5L X52 | High-pressure pipeline steel | Higher yield strength (359 MPa); API standard; pricier | Global high-pressure oil/gas pipelines |
| Acciaio inossidabile (GB 06Cr19Ni10) | Pipeline use | Eccellente resistenza alla corrosione; 3× more expensive | Chinese chemical or coastal water pipelines |
| Plastica (HDPE, GB/T 13663) | Low-pressure pipeline use | Leggero, resistente alla corrosione; forza inferiore | Chinese residential water/sewage lines (≤ 100 psi) |
Yigu Technology’s Perspective on GB L245
Alla tecnologia Yigu, GB L245 is our top recommendation for Chinese low-to-medium pressure projects—water, gas, e industriale. 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, zinco, or cement coatings, tailored to Chinese regions (per esempio., 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
- Is GB L245 interchangeable with API 5L X42 in global projects?
Yes—for most medium-pressure applications (fino a 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. - 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. - What coating is best for GB L245 in China’s coastal areas (per esempio., Guangdong)?
3PE (3-Layer Polyethylene) rivestimento (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.