Products Features
High strength matched with good toughness (core advantage)
The core advantage of API 5L X65 lies in its excellent balance between high strength and toughness. Thanks to a low-carbon micro-alloyed design (with carbon content typically ≤ 0.18%) and TMCP controlled rolling and cooling process, X65 maintains good low-temperature impact toughness while ensuring a minimum yield strength of 450 MPa and a minimum tensile strength of 535 MPa. Its yield strength is approximately 1.55 times that of X42 (290 MPa), making it suitable for higher pressure transmission applications.
|
Performance indicators |
PSL1 Requirements |
PSL2 Requirements |
|
Minimum Yield Strength (MPa) |
450 |
450 |
|
Maximum Yield Strength (MPa) |
- |
600 |
|
Minimum Tensile Strength (MPa) |
535 |
535 |
|
Maximum Tensile Strength (MPa) |
- |
760 |
|
Yield ratio |
- |
Usually ≤ 0.93 |
|
Elongation |
≥ 22% |
≥ 22% |
Note: PSL2 imposes limits on both maximum yield strength and maximum tensile strength (with upper limits of 600 MPa and 760 MPa respectively), ensuring the material has sufficient plastic deformation capacity and a higher safety margin to avoid brittle failure risks caused by an excessively high yield-to-tensile ratio.
Excellent welding performance (core requirement for pipeline steel)
The low carbon equivalent design of API 5L X65 ensures excellent welding performance, which is a core requirement for large-scale construction of pipeline steels. Grade PSL2 requires a carbon equivalent (CEIIW) ≤ 0.43 and Pcm ≤ 0.25, ensuring good toughness and resistance to cold cracking in the heat-affected zone under field welding conditions.
Key Welding Points:
• Low CE value:
Effectively reduces the tendency of the welding heat-affected zone to harden and lowers the risk of cold cracks
• Low-harmful-element content:
Strict control of P and S content (S ≤ 0.005%) to ensure the purity of the weld and base material
• Suitable for various welding methods:
butt welding of seamless steel pipes, submerged arc welding of spiral/straight seam welded pipes, etc., with good field ring welding performance
For PSL1 grade, the upper limit of carbon content is relatively wide (≤ 0.28%), and preheating of 100-150°C is recommended during welding. For PSL2 grade, the carbon content requirement is stricter (≤ 0.16-0.18%), resulting in better weldability and typically no special preheating or only lower preheating temperature is needed.
Good low-temperature toughness and resistance to brittle fracture
The API 5L X65 PSL2 grade requires Charpy V-notch impact testing to ensure the material's resistance to brittle fracture under low-temperature service conditions. The fine-grained microstructure obtained through the TMCP process significantly enhances the material's low-temperature toughness, enabling X65 line pipe steel to be reliably applied in cold regions and environments with large seasonal temperature variations.
Typical impact toughness index (PSL2):
• Test temperature: -30°C or lower (as per user requirements)
• Minimum impact energy: ≥ 42 J (average) / ≥ 36 J (individual value)
• The impact energy of X65 is typically above 75-100 J
Good corrosion resistance and environmental adaptability
API 5L X65 exhibits good resistance to uniform corrosion in normal atmospheric, fresh water, soil, and oil and gas media. For acidic service environments (containing H₂S), API 5L PSL2 Appendix J provides supplementary requirements for sour-resistant pipes (X65MS / L450MS), including lower sulfur content (≤ 0.002%), hardness control (≤ 250 HV), and strict verification of HIC/SSC resistance performance.
For marine environments, the X65 Q/T grade, after tempering, exhibits superior low-temperature toughness and resistance to brittle fracture, making it suitable for offshore platform structural pipes and subsea pipelines. When used in sour service conditions, the PSL2 standard imposes stricter requirements on chemical composition, hardness, and hydrogen-induced cracking (HIC) resistance.
Good cold bending and processing performance
API 5L X65 has a lower carbon content and a moderate yield-to-tensile ratio (PSL2 requirement ≤ 0.93), which gives it good cold bending formability. It is suitable for cold-bent pipe production and can be used to manufacture hot-bent elbows through hot bending processes. It also exhibits good shearing, blanking, and roll forming properties in coil and plate conditions. Its work hardening characteristics help improve strength after cold bending.
Technical Specifications
Chemical Composition(API Spec 5L / ISO 3183)
|
Element |
PSL1 Seamless Tube |
PSL1 Welded Pipe |
PSL2 |
Note |
|
C |
≤ 0.28% |
≤ 0.26% |
≤ 0.16-0.18% |
Low-carbon design to ensure weldability and low-temperature toughness |
|
Mn |
≤ 1.30% |
≤ 1.30% |
≤ 1.10-1.70% |
Solid solution strengthening, improve strength |
|
P |
≤ 0.030% |
≤ 0.030% |
≤ 0.025% |
Harmful elements, strictly controlled |
|
S |
≤ 0.030% |
≤ 0.030% |
≤ 0.005-0.015% |
Harmful elements, strictly controlled to ensure low-temperature toughness |
|
Si |
≤ 0.45% |
≤ 0.45% |
≤ 0.45-0.50% |
Deoxidizer, improve strength |
|
V |
≤ 0.05% |
≤ 0.05% |
≤ 0.10% |
Microalloying elements, precipitation strengthening |
|
Nb |
≤ 0.05% |
≤ 0.05% |
≤ 0.05% |
Microalloying elements, controlled rolling for fine grain |
|
Ti |
≤ 0.04% |
≤ 0.04% |
≤ 0.02-0.04% |
Microalloying elements, precipitation strengthening |
|
Cr |
- |
- |
≤ 0.50% |
Improve hardenability and corrosion resistance |
|
Mo |
- |
- |
≤ 0.20% |
Improve hardenability and temper stability |
|
Ni |
- |
- |
≤ 0.20% |
Improve low-temperature toughness |
|
Cu |
- |
- |
≤ 0.20% |
Improve atmospheric corrosion resistance |
|
CEIIW |
- |
- |
≤ 0.43% |
Carbon equivalent, controlling weldability |
|
Pcm |
- |
- |
≤ 0.25% |
Crack Sensitivity Index |
|
Fe |
Remaining quantity(≈ 97%) |
Remaining quantity(≈ 97%) |
Remaining quantity(≈ 97%) |
Matrix element |
Physical Properties
|
Property |
Value/Range |
Test Conditions |
|
Density |
≈ 7.85 g/cm³ |
Room Temperature (20°C) |
|
Melting Point |
≈ 1420-1460°C |
--- |
|
Elastic modulus |
≈ 207 GPa |
Room Temperature |
|
Thermal Conductivity |
≈ 50 W/(m·K) |
Room Temperature |
|
Coefficient of Thermal Expansion (20-100°C) |
≈ 12.0 × 10⁻⁶ /K |
--- |
|
Poisson's ratio |
≈ 0.28 |
Room Temperature |
Mechanical Properties (Typical Value)
|
Performance |
PSL1 |
PSL2 |
Implementation standards |
|
Minimum Yield Strength |
450 MPa |
450 MPa |
API Spec 5L / ISO 3183 |
|
Maximum Yield Strength |
- |
600 MPa |
API Spec 5L / ISO 3183 |
|
Minimum Tensile Strength |
535 MPa |
535 MPa |
API Spec 5L / ISO 3183 |
|
Maximum Tensile Strength |
- |
760 MPa |
API Spec 5L / ISO 3183 |
|
Elongation |
≥ 22% |
≥ 22% |
API Spec 5L |
Note: The 'X65' in API 5L X65 refers to the minimum yield strength of 65,000 psi (approximately 450 MPa), with the number representing the unit of kilopounds per square inch (ksi). The strength level of X65 is approximately 1.55 times that of X42 (290 MPa). The actual yield strength of the pipe material typically ranges between 470-550 MPa, and the tensile strength ranges between 550-650 MPa.
Applicable Media
1. Natural gas, crude oil, and refined oil: High-pressure long-distance main transmission lines
2. Water and slurries: Long-distance water pipelines, slurry transportation
3. Chemical media: High-pressure fluid pipelines in chemical plants
4. Urban gas: Urban high-pressure gas distribution networks
5. Structural pipes: Building structures, offshore platform jacket (non-corrosive environments)
6. General corrosive environments: Conventional soil, atmosphere, freshwater
Note: API 5L X65 is not suitable for high-temperature, high-pressure, strongly acidic media (such as hot concentrated hydrochloric acid and hydrofluoric acid). In acidic oil and gas environments containing H₂S, special grade materials specified in Appendix J of API 5L PSL2 (acid-resistant pipes X65MS / L450MS) should be selected, with additional control over sulfur content (≤ 0.002%), hardness (≤ 250 HV), and HIC resistance performance.
Product Form and Manufacturing Process
Seamless steel pipe (Seamless)
Process: Hot Rolling Piercing + Extension Rolling
Diameter Range: 21.3 - 1067 mm (1/2" - 42")
Wall thickness range: 2 - 150 mm
Features: Seamless, high pressure-bearing capacity, suitable for high-pressure oil and gas mainlines
Typical applications: high-pressure fluid transportation, oil and gas wellhead gathering and transmission pipelines
Straight Seam High-Frequency Resistance Welded Pipe (ERW)
Process: Hot-rolled coil → Cold bending forming → High-frequency resistance welding
Outer Diameter Range: Typically ≤ 610 mm (24")
Wall thickness range: Typically ≤ 20 mm
Features: High dimensional accuracy, high production efficiency, and significant cost advantages
Typical applications: medium and low-pressure oil and gas branch lines, urban gas pipelines, and structural pipes
Welding Heat Input Control: High-frequency welding at ≥ 100 kHz (PSL2 requirement) to ensure stable weld quality
Spiral Submerged Arc Welded Pipe (SSAW)
Process: Hot-rolled coil → Spiral forming → Dual-sided submerged arc welding
Outer Diameter Range: Typically 219 - 2500 mm
Wall thickness range: 6 - 25 mm
Features: The large diameter offers significant advantages, allowing steel strips of the same width to produce various diameters. The stress of spiral welds is only 75-90% of that of straight seams, enabling them to withstand higher pressures. Theoretically, they can be continuously produced in unlimited lengths.
Typical applications: large-diameter water/gas transmission pipelines, offshore engineering jacket
Straight Seam Submerged Arc Welded Pipe (LSAW)
Process: Steel Plate → JCOE Forming / UOE Forming → Dual-Sided Submerged Arc Welding
Outer Diameter Range: 406 - 1620 mm (16" - 64")
Wall thickness range: 6 - 50 mm
Features: Short welds, low welding material consumption, wide range of outer diameter and wall thickness
Typical applications: high-pressure long-distance transmission pipelines, submarine pipelines, oil and gas gathering and transportation mainlines
Applicable Standards and Delivery Condition
Standard:API Spec 5L,ISO 3183,GB/T 9711
Product Specification Level: PSL1 (Basic Level), PSL2 (Enhanced Level)
Delivery Condition: Hot-rolled, Controlled Rolling (TMCP), Normalized, Normalized Rolling, Heat Treatment (Quenching + Tempering), etc.
End Processing: Flat Ends, Beveled Ends, Threaded Ends, Special Fitting Ends
Certificate: When complying with PSL2 requirements, a compliance certificate (SR15.1 mandatory) must be provided, and full-process traceability must be implemented (SR15.2 mandatory).
Treatment Regime and Welding Key Points
The final performance of API 5L X65 depends on the TMCP controlled rolling and controlled cooling process or quenching and tempering (Q&T) treatment:
1. Controlled Rolling and Controlled Cooling (TMCP, used to obtain a fine-grained microstructure and optimal mechanical properties):
Heat to 1100-1200°C for rough rolling, then perform controlled rolling with large reduction in the 850-950°C finishing temperature range (rolling in the non-recrystallization zone), followed by controlled cooling within 600-800°C. This results in a uniform and fine ferrite + pearlite microstructure (grain size typically ≥ 9), ensuring a balanced combination of strength and toughness. For sour service line pipes, TMCP is the preferred process route to avoid the precipitation of harmful phases.
2. Quenching and Tempering (Q&T, for X65Q grade, to achieve superior overall performance):
For X65Q in the PSL2 grade, quenching and tempering treatment is required: heat to 900-940°C for quenching, followed by tempering within the range of 530-630°C. The quenching and tempering treatment can further refine the grain structure, improve HIC resistance and organizational uniformity. The lower the tempering temperature (e.g., 530°C), the higher the strength; the higher the tempering temperature (e.g., 630°C), the better the toughness.
3. Post-weld Heat Treatment (if required):
If stress relief is required after pipe ring weld welding, post-weld heat treatment at 550-650°C for 1-2 hours can be performed. Post-weld heat treatment should pay attention to controlling the heating and cooling rates to avoid affecting the microstructure and properties of the base material. Studies have shown that post-weld stress-relief heat treatment at 600°C can effectively reduce residual stresses and improve toughness.
Important Reminder:
In conventional oil and gas transmission environments without H₂S, stress relief heat treatment is typically not required after welding.
For pipelines in an acidic environment (containing H₂S), strict compliance with Appendix J of API 5L PSL2 is required to prevent excessive hardness (≤ 250 HV) caused by improper post-weld heat treatment.
During welding, strict control of heat input (recommended 0.5-2.5 kJ/mm) and interpass temperature (typically ≤ 100°C) is required to prevent grain coarsening in the heat-affected zone and excessive hardness.
API 5L X65 (L450) is suitable for high-pressure oil and gas long-distance transmission pipelines, marine pipelines, and high-strength structural pipe applications. It is recommended for use in the following areas:
Application Fields
-
Long-distance main transmission lines for oil and natural gas
● High-pressure long-distance oil and gas transmission main pipelines
● Submarine pipelines, marine risers
● Large gas field gathering and transmission mainlines, natural gas trunk pipeline network -
Urban high-pressure gas pipeline network
● Urban high-pressure natural gas transmission and distribution main pipeline network
● High-pressure gas regulation station inlet and outlet main pipelines -
Water Conveyance and Irrigation Engineering
● Long-distance high-pressure water transmission main pipeline
● Large-scale water conservancy project supporting pipelines -
Chemical Engineering and Industrial High-Pressure Piping
● High-pressure process pipelines in chemical plants
● Power Station High-Pressure Circulating Water Pipe -
Structural Tubing (High Strength)
● Offshore Platform Jacket (High-Strength Section)
● Pipes for large bridge pile foundations
● High-rise building steel structure support pipes
● Offshore wind power foundation structural pipe
Delivery and Customization
We offer flexible and reliable supply chain solutions to ensure you receive API 5L X65 line pipe that perfectly matches your project requirements.
|
Form |
 Seamless Steel
Pipe |
 Straight Seam Resistance
Welded Pipe (ERW) |
 Spiral Submerged Arc
Welded Pipe (SSAW) |
 Straight Seam Submerged
Arc Welded Pipe (LSAW) |
|---|---|---|---|---|
|
Conventional Range |
Outer Diameter: 21.3 - 1067 mm; Wall Thickness: 2 - 150 mm |
Outer Diameter: 21.3 - 610 mm; Wall Thickness: 2 - 20 mm |
Outer Diameter: 219 - 2500 mm; Wall Thickness: 6 - 25 mm |
Outer Diameter: 406 - 1620 mm; Wall Thickness: 6 - 50 mm |
|
Customization Capability |
Hot-rolled seamless pipes, fixed-length cutting, bevel machining, pipe end threads, special heat treatment conditions |
High-frequency straight-seam welded pipes, fixed-length cutting, bevel processing, galvanization/plastic coating treatment |
Large-diameter spiral welded pipes, fixed-length cutting, bevel processing, anti-corrosion coating (FBE/3PE) |
JCOE/UOE forming, length cutting, bevel machining, special pipe end treatment |
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FAQ
Q: What are the main advantages of API 5L X65?
Q: What is the difference between API 5L X65 PSL1 and PSL2? How to choose?
Q: What are the differences between API 5L X42, X52, X65, and X70? How to choose among them?
Q: What is the maximum operating temperature for API 5L X65?
Q: What is the welding performance of API 5L X65?
Q: What is the corrosion resistance of API 5L X65?
Q: Can API 5L X65 replace ASTM A53 or X42?
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