API 5L X42 is a carbon-manganese line pipe grade with a specified minimum yield strength of 42,000 psi (290 MPa). In ISO 3183 terminology, the corresponding grade designation is L290.
X42 is widely used for oil and gas gathering, transmission and utility pipeline applications where its strength, weldability and cost balance meet the project requirements. It can be supplied as seamless or welded line pipe and ordered to PSL 1 or PSL 2, depending on the project specification.
For buyers, however, "API 5L X42" is not a complete purchasing specification. The RFQ should also identify the PSL, manufacturing route, delivery condition, dimensions, testing requirements and applicable API 5L edition.
1. What Does API 5L X42 Mean?
The "X42" designation refers to the grade's specified minimum yield strength in ksi.
42 ksi ≈ 290 MPa
Therefore:
API 5L X42 = minimum specified yield strength of 42 ksi (290 MPa).
The ISO 3183 designation L290 corresponds to the same nominal strength level.
However, X42 and L290 should not simply be treated as interchangeable material certificates. The actual purchase requirement should state the governing standard, PSL, manufacturing route, delivery condition and testing requirements.
Basic X42 Mechanical Requirements
| Property | X42 |
|---|---|
| Minimum yield strength | 290 MPa (42,100 psi) |
| Minimum tensile strength | 415 MPa (60,200 psi) |
| Yield-to-tensile ratio | Subject to applicable API 5L requirements |
| Elongation | Calculated according to the applicable API 5L requirement |
For PSL 2 pipe, API 5L also places additional requirements on yield/tensile behavior, chemistry, carbon equivalent and impact toughness.
2. API 5L X42 Chemical Composition
The chemical composition of X42 depends on the PSL and delivery condition.
This is one area where a generic "X42 chemistry" table can be misleading. For example, in API 5L 46th Edition, PSL 1 X42 and PSL 2 X42 have different maximum limits, while PSL 2 X42R/X42N/X42Q/X42M also have different chemistry requirements.
X42 PSL 1 - Typical Limits for t ≤25 mm
| Element | Maximum, % |
| Carbon (C) | 0.28 |
| Manganese (Mn) | 1.30 |
| Phosphorus (P) | 0.030 |
| Sulfur (S) | 0.030 |
API 5L also contains provisions governing microalloying elements and residual elements. These limits should be checked against the applicable pipe type and the edition specified in the purchase order.
X42 PSL 2 - 46th Edition Reference Values
For pipe with wall thickness up to 25.0 mm, the 46th Edition lists the following basic X42 PSL 2 limits:
| Delivery condition | C max. | Si max. | Mn max. | P max. | S max. | Nb max. | V max. | Ti max. |
| X42R | 0.24% | 0.40% | 1.20% | 0.025% | 0.015% | 0.05% | 0.06% | 0.04% |
| X42N | 0.24% | 0.40% | 1.20% | 0.025% | 0.015% | 0.05% | 0.06% | 0.04% |
| X42Q | 0.18% | 0.45% | 1.40% | 0.025% | 0.015% | 0.05% | 0.05% | 0.04% |
| X42M* | 0.22% | 0.45% | 1.30% | 0.025% | 0.015% | 0.05% | 0.05% | 0.04% |
*X42M applies to welded pipe in the 46th Edition table.
The applicable carbon-equivalent limits for PSL 2 are also important:
CEIIW ≤ 0.43%
CEPcm ≤ 0.25%
These values are subject to the conditions and footnotes in the applicable API 5L table.
3. What Do X42R, X42N, X42Q and X42M Mean?
The suffix is important because it describes the delivery condition.
Typical API 5L PSL 2 designations include:
| Designation | Delivery condition |
| X42R | As-rolled |
| X42N | Normalized or normalized-formed |
| X42Q | Quenched and tempered |
| X42M | Thermomechanically rolled/formed |
The suffix should not be confused with the manufacturing route.
For example, an X42 pipe can be seamless or welded, while the applicable delivery condition depends on the product and API 5L requirements.
The 46th Edition tables include X42R, X42N and X42Q for the relevant product forms, while X42M is listed for welded pipe.
4. X42 Manufacturing Routes
API 5L covers both seamless and welded line pipe.
Seamless X42
Seamless pipe is produced without a longitudinal weld seam, typically through hot piercing and subsequent rolling or sizing.
It is commonly considered for:
Smaller diameters
Higher wall thicknesses
Applications where seamless construction is preferred by the project specification
HFW/ERW X42
High-frequency welded pipe is manufactured from steel strip or coil and formed into a pipe with a longitudinal high-frequency weld.
It can be attractive for:
Medium diameters
High-volume projects
Applications where welded line pipe is permitted by the specification
SAWL X42
SAWL means submerged arc welded longitudinally.
It is commonly used for large-diameter line pipe manufactured from plate.
SAWH X42
SAWH means submerged arc welded helically.
It is commonly used for large-diameter spiral line pipe.
Important Procurement Point
Do not assume that every X42 manufacturing route has the same availability, dimensional range or cost.
When requesting a quotation, state the required pipe type:
SMLS / HFW / SAWL / SAWH
rather than simply asking for "API 5L X42 pipe."
5. Where Is API 5L X42 Used?
X42 is used in a range of pipeline applications where its strength level and other material properties meet the design requirements.
Typical applications include:
Natural gas gathering pipelines
Oil gathering and transportation lines
Product pipelines
Water injection and utility pipelines
Industrial fluid pipelines
Selected transmission pipeline applications
However, it is not accurate to define X42 simply as a "medium-pressure pipe."
Pressure capability depends on OD, wall thickness, design code, design factor, operating temperature, corrosion allowance and other engineering parameters-not on the grade alone.
This is an important distinction for procurement.
6. Is API 5L X42 Suitable for Sour Service?
Not automatically.
X42 is not inherently a sour-service grade simply because it complies with API 5L.
Sour service introduces additional concerns such as:
Hydrogen sulfide exposure
Sulfide stress cracking (SSC)
Hydrogen-induced cracking (HIC)
Hardness
Chemical composition
Microstructure
Welding and heat treatment
Environmental conditions
If the pipeline will carry sour fluids, the purchase specification should clearly identify the required sour-service standard, testing and acceptance criteria.
Do not simply write:
API 5L X42 PSL 2
and assume that this makes the pipe suitable for H₂S service.
API's 2026 update to the 47th Edition specifically includes changes related to sour-service requirements, which makes the applicable edition even more important for current projects.
GNEE API 5L X42 Pipeline for Sale
Send us your grade, PSL, pipe type, OD × WT, quantity and project specification. We can review the requirements and provide available options, testing documentation and a quotation.
FAQ
Is API 5L X42 the same as L290?
X42 and L290 are corresponding grade designations at the same nominal yield-strength level: 290 MPa. However, the applicable standard, PSL, delivery condition and testing requirements still need to be specified. They should not be treated as interchangeable certificates without checking the complete purchase specification.
What is the minimum yield strength of X42?
The specified minimum yield strength is 290 MPa (42,100 psi).
What is the tensile strength of API 5L X42?
The specified minimum tensile strength is 415 MPa (60,200 psi). For PSL 2, the applicable API 5L requirements also define maximum tensile strength and other mechanical-property controls.
What is the difference between X42 PSL 1 and X42 PSL 2?
PSL 2 introduces additional requirements for chemical composition, carbon equivalent, mechanical properties, impact toughness and inspection compared with PSL 1.
The exact requirements should be checked against the API 5L edition stated in the purchase order.
Is X42 suitable for high-pressure pipelines?
X42 can be used in pipeline systems designed for the grade, but pressure rating cannot be determined from X42 alone.
The allowable operating pressure depends on pipe OD, wall thickness, design code, design factor, temperature, corrosion allowance and other engineering parameters.
Is X42 suitable for natural gas pipelines?
Yes. X42 is used in natural-gas pipeline and gathering applications where the grade, PSL, dimensions and service requirements meet the pipeline design.
Can X42 be used for sour service?
Not automatically. Sour-service pipe requires additional requirements related to H₂S exposure, cracking resistance, hardness, testing and other project-specific conditions.
What does X42N mean?
X42N is an API 5L PSL 2 designation indicating the applicable normalized or normalized-formed delivery condition.
The "N" does not describe whether the pipe is seamless or welded.
What does X42Q mean?
X42Q identifies the applicable quenched-and-tempered delivery condition for the relevant API 5L product form.
What does X42M mean?
X42M identifies the thermomechanically rolled/formed delivery condition and is listed for welded pipe in the API 5L 46th Edition requirements.
Technical Reference
API Specification 5L, Line Pipe
ISO 3183, Steel pipe for pipeline transportation systems
NACE MR0175 / ISO 15156, where sour-service requirements apply
GB/T 9711, where the Chinese standard is specified by the project
Standards note: API published the 47th Edition of API Specification 5L in June 2026. For new procurement, always state the required edition in the purchase order and verify the applicable chemical, mechanical, impact-testing and inspection requirements against the licensed standard.
