API 5L Grade X65 is a specification that defines the requirements for line pipe used in the oil and natural gas industries for the transportation of fluids such as oil, gas, and water. The "X" in X65 denotes a pipeline grade, and "65" refers to the minimum yield strength of 65,000 psi. Here are the key aspects of the API 5L Grade X65 specification:

1. Material Composition:

Carbon (C): 0.12% maximum

Manganese (Mn): 1.40% maximum

Phosphorus (P): 0.025% maximum

Sulfur (S): 0.015% maximum

Silicon (Si): 0.45% maximum

Other elements: Small amounts of Ni, Cr, Mo, Cu, V, Nb, and Ti may be present as required.

2. Mechanical Properties:

Yield Strength: Minimum 450 MPa (65,000 psi)

Tensile Strength: 535 MPa (77,000 psi) minimum, up to 760 MPa (110,000 psi)

Elongation: Depends on the size and form of the pipe, but typically around 21% for most sizes.

3. Product Specification Levels (PSL):

PSL 1: Basic level of requirements, including chemical composition and mechanical properties.

PSL 2: Higher level of requirements with stricter controls on chemical composition, notch toughness, and non-destructive testing. This level is typically used in more demanding applications.

4. Manufacturing Process:

Pipes can be seamless or welded.

The pipes are typically manufactured through processes like electric resistance welding (ERW), submerged arc welding (SAW), or high-frequency welding (HFW) for welded pipes.

For seamless pipes, processes such as extrusion, drawing, and forging are used.

5. Applications:

Transportation of Oil and Gas: X65 pipes are used in pipelines transporting natural gas, crude oil, and refined petroleum products.

Offshore and Onshore Pipeline Projects: The material is suitable for both onshore and offshore applications due to its high strength and toughness.

High-Pressure Applications: X65 is often used in environments that require resistance to high pressures.

6. Heat Treatment:

Pipes may undergo heat treatment such as quenching and tempering or normalizing to achieve the required mechanical properties.

For PSL2 pipes, heat treatment is often required to ensure the toughness and strength needed for specific applications.

7. Testing Requirements:

Tensile Testing: To verify the mechanical properties such as yield and tensile strength.

Impact Testing: Usually required for PSL2 to ensure notch toughness, especially for low-temperature service.

Non-Destructive Testing (NDT): Includes ultrasonic testing and radiographic testing to detect internal flaws.

Summary:

API 5L Grade X65 is a high-strength pipeline steel grade used in the transportation of oil, gas, and water. It is available in both PSL1 and PSL2 specifications, with PSL2 having stricter requirements. This material is known for its high yield strength, good weldability, and resistance to harsh environments, making it suitable for demanding pipeline applications.