API 5L X46 is a carbon steel line pipe grade used in the transportation of oil, gas, and other fluids in the pipeline industry. The API 5L designation comes from the American Petroleum Institute specification, and X46 indicates a minimum yield strength of 46,000 psi, or approximately 317 MPa. The same grade is designated L360 under ISO 3183, where the number expresses the minimum yield strength in megapascals. X46 is selected for service where the strength of X42 is marginal and the higher cost of X52 or X60 is not justified.
Grade Designation and Strength
The X number in API 5L grades states the minimum yield strength in thousands of pounds per square inch. X46 therefore requires a minimum yield strength of 46 ksi, 317 MPa, and a minimum tensile strength of 60 ksi, 414 MPa. These values are the same for PSL 1 and PSL 2; the two product specification levels differ in chemistry, toughness, and testing requirements rather than in base strength.
PSL 1 vs PSL 2
PSL 1 is the standard quality level with controlled chemistry, standard mechanical testing including tensile, hardness, and flattening tests, and no mandatory Charpy impact testing. It is suitable for general service pipelines where high toughness is not critical. PSL 2 applies tighter chemical limits, maximum carbon equivalent values to guarantee weldability, mandatory Charpy V-notch impact testing with minimum absorbed energy values, and additional non-destructive examination of the seam. PSL 2 is specified for offshore, arctic, high-pressure, and sour service lines.
Chemical Composition
X46 is a low-carbon manganese steel. Typical PSL 1 maximums are carbon 0.26 percent, manganese 1.30 percent, sulfur 0.030 percent, and phosphorus 0.030 percent. PSL 2 tightens these to about 0.24 percent carbon, 1.20 percent manganese, 0.025 percent phosphorus, and 0.015 percent sulfur, with carbon equivalent limits such as CE IIW of 0.43 maximum or CE Pcm of 0.25 maximum depending on thickness. The controlled chemistry keeps field welding straightforward and reduces the risk of hard zones.
| Element, max % | PSL 1 | PSL 2 |
|---|---|---|
| Carbon | 0.26 | 0.24 |
| Manganese | 1.30 | 1.20 |
| Phosphorus | 0.030 | 0.025 |
| Sulfur | 0.030 | 0.015 |
| Carbon equivalent | Not specified | CE IIW 0.43 max |
Mechanical Properties
| Property | PSL 1 | PSL 2 |
|---|---|---|
| Minimum yield strength | 46 ksi (317 MPa) | 46 ksi (317 MPa) |
| Minimum tensile strength | 60 ksi (414 MPa) | 60 ksi (414 MPa) |
| Elongation | Per standard formula | Per standard formula |
| Charpy V-notch impact | Not mandatory | Mandatory |
| Hardness test | Not mandatory | Required for sour service |
Sizes and Manufacturing Routes
X46 pipe is produced in a wide size range, from small diameters such as 2.375 inches to large diameters above 42 inches. Wall thickness is ordered by schedule, such as SCH 40 or SCH 80, or by a specified decimal thickness. Lengths are supplied as single, double, or triple random, or cut to length. Manufacturing routes include seamless pipe for smaller sizes, ERW electric resistance welded pipe for medium diameters, and LSAW or SSAW submerged arc welded pipe for large diameters and thick walls. All routes must satisfy the same grade and PSL requirements.
Common Applications
X46 is used in gathering lines that move crude oil or natural gas from the wellhead to processing facilities, transmission pipelines for long-distance transport, distribution networks that deliver gas to industrial and residential users, refinery and petrochemical plant process piping, and water or produced-water handling lines. It is occasionally used for structural columns and piling in marine environments, although structural tubing standards are the primary choice for such duty.
Advantages and Limitations
The main advantages of X46 are the strength increase over X42 without a large cost jump, wide availability, and good weldability when chemistry is controlled, especially in PSL 2. The limitation is that compared with X65, X70, or X80, X46 is not suitable for very high pressure or deep-water service where wall thickness and weight become critical. Like all carbon steel, it requires external coating, such as fusion bonded epoxy or three-layer polyethylene, and cathodic protection when buried or submerged.
How to Order X46 Pipe
Specify the standard and grade, for example API 5L X46 or ISO 3183 L360; the product specification level; the manufacturing process; outside diameter, wall thickness, and length; pipe end preparation; and any supplementary requirements such as impact test temperature, sour service controls, or third-party inspection. Confirming PSL at enquiry stage is essential because it changes chemistry, testing, and cost.
FAQ
What is the yield strength of API 5L X46?
X46 has a minimum yield strength of 46,000 psi, or 317 MPa, and a minimum tensile strength of 60,000 psi, or 414 MPa.
Is X46 the same as L360?
Yes. ISO 3183 uses the L designation with strength in MPa, so X46 is L360 in ISO 3183 terms.
What is the difference between X46 and X42?
X46 offers 317 MPa minimum yield versus 290 MPa for X42, giving roughly 9 percent more strength with a modest cost increase. Chemistry and welding behavior are similar.
When should X46 be ordered as PSL 2?
PSL 2 is required for offshore, arctic, high-pressure, and sour service projects, where mandatory Charpy toughness, carbon equivalent control, and additional non-destructive testing are needed.
Can X46 pipe be used for water pipelines?
Yes. X46 is commonly used for water and produced-water transmission lines where its strength allows a thinner wall than Grade B for the same operating pressure.
