Grade X52
API 5L X52 · API 5L
Grade X52 (API 5L X52) is a pipeline steel (Carbon-Manganese family) to API 5L. It has a specified 0.2 % proof stress of 359 MPa and a typical tensile strength of about 455 MPa, with a uniform elongation of 21 %. Nominal carbon content is around 0.26 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 465 MPa above it. A plain-carbon steel: economical and predictable, strengthened by carbon content and heat treatment rather than alloying.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 21.0% · conservative analysis limit ½εu = 10.5%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitymoderate
Medium carbon (~0.26%) — preheat and hydrogen-controlled consumables advisable, especially in thicker sections.
Machinabilitygood
Machines well, particularly in the normalised or pre-tempered condition.
Corrosion resistancepoor
No inherent corrosion resistance — protect by paint, galvanising or plating in exposed use.
Hardenabilitylow
Limited hardenability at low carbon — surface hardening is possible but through-hardening is not.
Toughnessmoderate
Adequate toughness for general use at ambient temperature.
Indicative ratings derived from composition and family — engineering guidance, not specification values.
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 80.8 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.0 | ×10⁻⁶/°C |
| Thermal conductivity | 48 | W/(m·K) |
| Specific heat | 470 | J/(kg·K) |
| Magnetic | Yes |
Typical values for carbon-manganese steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Typical composition per API 5L — confirm PSL1/PSL2 and sour-service limits against the standard.
Available forms
Common applications
- Oil and gas transmission line pipe
- Water and slurry pipelines
- Structural and pressure piping
History
API 5L is the global line-pipe standard. Its grades trace the rise of micro-alloyed, controlled-rolled steels that let cross-country oil and gas pipelines run at ever-higher pressures with the weldability and toughness needed for field girth welding. The “X” number is the minimum yield in ksi (X52 ≈ 359 MPa).
- 1928API 5L first published for line pipe
- 1970Micro-alloyed (Nb/V) controlled-rolled steels lift pipeline strength
- 2000PSL2 formalises tighter chemistry, toughness and NDE
This profile is generated from the grade's core data and family. Composition is decoded from the designation where its naming system defines it; physical properties are family-typical and ratings are indicative. Confirm critical values against the governing standard or the mill certificate. Equivalents, historical designations and hand-written expert notes are added per grade over time.