Characteristics of Line Pipe

Pipeline Steel Pipe is a special steel pipe used to transport fluid media such as oil, natural gas, and water. It has the following core characteristics:

1. High strength
High yield strength and tensile strength: It needs to withstand high-pressure transportation (such as high-strength steel grades such as X70 and X80, with a yield strength of 490-550MPa or more).

Good toughness: It needs to resist brittle fracture in low-temperature environments (such as polar regions or deep sea), which is usually verified by Charpy impact tests.

2. Excellent corrosion resistance
Resistance to hydrogen sulfide (H₂S) corrosion: Acidic environments (such as sulfur-containing oil and gas fields) need to meet NACE MR0175 standards to prevent hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSCC).

Coating protection: 3PE (three-layer polyethylene), FBE (fusion-bonded epoxy powder) and other external anti-corrosion coatings, or linings with corrosion-resistant alloys are often used.

3. Excellent welding performance
Low carbon equivalent design: Ensure weldability by controlling carbon, sulfur and phosphorus content (such as CE≤0.43%) to avoid cracks in the heat-affected zone.

Matching welding process: Suitable for automated welding technologies such as submerged arc welding (SAW), high frequency welding (ERW) or laser welding.

4. Dimensional accuracy and geometric characteristics
Strict tolerance control: small deviation of outer diameter and wall thickness (such as API 5L standard requires wall thickness tolerance ±12.5%).

Roundness and straightness: Ensure the sealing and construction efficiency when the pipeline is docked.

5. Environmental adaptability
Low temperature toughness: Arctic pipelines must meet the impact toughness requirements below -60℃ (such as DWTT test).

Anti-deformation ability: Strain-Based Design is required in geological disaster areas (such as earthquakes and landslides).

6. Standard compliance
International standards: Common API 5L (American Petroleum Institute), ISO 3183, GB/T 9711 (Chinese national standard), etc.

Additional certification: such as DNV (Det Norske Veritas), ISO 9001 quality management system, etc.

7. Special demand characteristics
Fatigue resistance: Submarine pipelines need to withstand wave/current cyclic loads.

High deformation resistance: such as X80 HD2 (high deformation) steel grade, suitable for fault movement areas.

Typical application scenarios
Land long-distance pipelines: such as the West-East Gas Transmission Project (X80 steel grade).

Submarine pipelines: Double-sided anti-corrosion coating + concrete counterweight layer required.

Urban pipelines: Corrosion-resistant materials (such as TP316L stainless steel) or PE composite pipes.

The properties of line pipes need to be customized according to specific working conditions (pressure, medium, temperature, geological conditions, etc.), and performance balance can be achieved through composition optimization (such as adding Nb, V, Ti microalloying) and process control (such as TMCP thermomechanical rolling).