Materials & grades
API 5L X65 / L450 line pipe (PSL1 and PSL2)
API 5L X65 (ISO 3183 L450) is a line pipe grade with a minimum yield strength of 450 MPa (65.3 ksi). It is supplied as PSL1 or PSL2 pipe for high-pressure oil and gas transmission lines, including long-distance and offshore pipelines. PSL2 adds a yield ceiling, tighter chemistry and mandatory impact testing; PSL2 comes only as Q (seamless or welded) or M (welded).
Names by standard
What it is called in each region
| Region | System | Designation | Norma | Match |
|---|---|---|---|---|
| USA | API 5L (PSL1 name) | X65Grade name used for PSL1 pipe. The number is the minimum yield strength in ksi, rounded (65.3 ksi = 450 MPa). | API Spec 5L, 46th edition | Same material |
| API 5L (PSL2 designation) | X65Q / X65MPSL2 names add a delivery-condition letter. Sour-service and offshore pipe add S or O, for example X65QS. | API Spec 5L, 46th edition | Same material | |
| API 5L / ISO 3183 (metric name) | L450Metric grade name; the number is the minimum yield strength in MPa. X65 and L450 are the same steel grade. | API Spec 5L, 46th edition | Same material | |
| UK | BS EN ISO 3183 | L450Q / L450MThe UK adopts the European edition of ISO 3183; grade names are the metric names with a delivery-condition letter. | BS EN ISO 3183 | Same material |
| BS EN 10208-2 (legacy) | L450MBWithdrawn; replaced by BS EN ISO 3183. Class B pipe, thermomechanical, welded. | BS EN 10208-2 | Equivalent | |
| EU | EN ISO 3183 name | L450Q / L450MCurrent European line pipe standard, the CEN adoption of ISO 3183. | EN ISO 3183 | Same material |
| EN 10208-2 name (legacy) | L450MBSuperseded by EN ISO 3183 (withdrawn around 2012). Thermomechanical, welded. Minimum yield matches; limits on yield maximum, tensile and chemistry differ from API 5L PSL2. | EN 10208-2 | Equivalent | |
| EN 10027-2 number (EN 10208-2) | 1.8975Material number of L450MB. | EN 10208-2 | Equivalent | |
| EN 10208-2 name (legacy) | L450QBSuperseded by EN ISO 3183 (withdrawn around 2012). Quenched and tempered. Minimum yield matches; limits on yield maximum, tensile and chemistry differ from API 5L PSL2. | EN 10208-2 | Equivalent | |
| EN 10027-2 number (EN 10208-2) | 1.8952Material number of L450QB. | EN 10208-2 | Equivalent | |
| India | API 5L (ordered directly) | X65Indian pipe makers and pipeline owners order and certify to API 5L or ISO 3183 directly. IS 3589 covers pipe for water and sewage, not line pipe grades; the Indian adoption of ISO 3183 is listed below. | API Spec 5L | Same material |
| IS/ISO 3183:2019 | L450Identical adoption of ISO 3183:2019 under single numbering (BIS second revision). It supersedes IS/ISO 3183:2012 and the earlier IS/ISO 3183:2007, both withdrawn; the 2007 edition amalgamated IS 1978 (line pipe) and IS 1979 (high test line pipe). | IS/ISO 3183:2019 | Equivalent | |
| Japan | API 5L / ISO 3183 (used directly) | X65 / L450Japan has no separate line pipe grade system. Mills and operators use API 5L and ISO 3183. JIS G 3454 (STPG) and G 3455 (STS) are pressure-piping standards, not equivalents. | API Spec 5L / ISO 3183 | Same material |
On equivalence
- X65 and L450 are the same grade under two naming conventions: the X number is the minimum yield strength in ksi, the L number is the same strength in MPa.
- EN ISO 3183 uses the L450 names with a delivery-condition letter. The older European standard EN 10208-2 named the class B equivalents L450MB, L450QB; it was withdrawn around 2012 and those grades are equivalents, not identical specifications (yield maximum, tensile and chemistry differ).
- Old DIN 17172 names exist for this grade, but the sources found disagree on the pairing, so none is listed here.
- India has no separate grade names for API line pipe. BIS publishes ISO 3183 unchanged as IS/ISO 3183:2019, so the L-grade names apply there; IS 1978 and IS 1979 were amalgamated into IS/ISO 3183:2007, since withdrawn and superseded. IS 3589 covers pipe for water and sewage. In practice Indian projects specify API 5L or ISO 3183.
- Japan uses API 5L and ISO 3183 directly. JIS G 3454 (STPG) and JIS G 3455 (STS) are piping standards with different grades and scope; they are not line pipe equivalents.
- Source tables disagree on small points. Older API editions converted ksi to MPa (65 ksi = 448 MPa); the 46th edition uses the rounded metric minimum (450 MPa). Some published tables still show the older figures.
Chemical composition
Composition limits, mass %
| Element | X65 / L450 PSL1, seamless, up to 25 mm wallUSA · API Spec 5L, 46th edition (PSL1) | X65 / L450 PSL1, welded, up to 25 mm wallUSA · API Spec 5L, 46th edition (PSL1) | L450Q / X65Q (seamless and welded), up to 25 mm wallUSA · API Spec 5L, 46th edition (PSL2) | L450M / X65M (welded only), up to 25 mm wallUSA · API Spec 5L, 46th edition (PSL2) |
|---|---|---|---|---|
| C | ≤0.28 | ≤0.26 | ≤0.18 | ≤0.12 |
| Si | — | — | ≤0.45 | ≤0.45 |
| Mn | ≤1.40 | ≤1.45 | ≤1.70 | ≤1.60 |
| P | ≤0.030 | ≤0.030 | ≤0.025 | ≤0.025 |
| S | ≤0.030 | ≤0.030 | ≤0.015 | ≤0.015 |
| Cr | ≤0.50 | ≤0.50 | — | ≤0.50 |
| Ni | ≤0.50 | ≤0.50 | — | ≤0.50 |
| Mo | ≤0.15 | ≤0.15 | — | ≤0.50 |
| Cu | ≤0.50 | ≤0.50 | — | ≤0.50 |
| B | — | — | — | ≤0.001 |
| Nb+V+Ti | ≤0.15 unless otherwise agreed | ≤0.15 unless otherwise agreed | ≤0.15 | ≤0.15 |
| CE | not specified | not specified | — | — |
| CEIIW | — | — | ≤0.43 (C >0.12) | ≤0.43 (C >0.12) |
| CEPcm | — | — | ≤0.25 (C ≤0.12) | ≤0.25 (C ≤0.12) |
Mechanical properties
Strength and hardness
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| PSL1, X65 / L450, pipe bodySpecified minimums only; no maximum yield or tensile; elongation depends on size by formulaAPI Spec 5L, 46th edition; minimums confirmed for PSL2 by Mannesmann | ≥535 MPa≥77.6 ksi | ≥450 MPa≥65.3 ksi | — | — |
| PSL2, X65Q / X65M, pipe bodySpecified minimum and maximum; yield-to-tensile ratio ≤0.93; Charpy V-notch test required; elongation depends on size by formulaAPI Spec 5L, 46th edition as listed by Mannesmann (Salzgitter) | 535–760 MPa77.6–110.2 ksi | 450–600 MPa65.3–87.0 ksi | — | — |
In practice
Behaviour, heat treatment and uses
Characteristics
- Minimum yield 450 MPa (65.3 ksi) and minimum tensile 535 MPa (77.6 ksi) apply to both PSL levels; PSL2 also caps yield at 600 MPa and tensile at 760 MPa.
- PSL2 limits the yield-to-tensile ratio to 0.93, which keeps some strain-hardening capacity in the pipe.
- PSL2 requires Charpy V-notch impact testing; PSL1 does not. Minimum energy and test temperature depend on grade, size and the purchase order.
- Weldability is controlled in PSL2 by a carbon-equivalent limit: CE (IIW) ≤0.43 when carbon is above 0.12 %, CE (Pcm) ≤0.25 when carbon is 0.12 % or below. PSL1 sets no carbon-equivalent limit.
- There is no normalized PSL2 version of X65: the grade is made as Q (quenched and tempered) or M (thermomechanically rolled), with low carbon for field weldability.
- Sour-service (S) and offshore (O) variants are PSL2 only and add hardness and chemistry limits.
- The edition behind these values is the 46th (2018). API published a 47th edition in 2026 that revises chemical element ranges among other items; confirm limits against the edition on your purchase order.
Heat treatment
- Delivery condition is part of the PSL2 grade name: R as rolled, N normalized (or normalizing formed), Q quenched and tempered, M thermomechanical rolled or formed.
- PSL1 names carry no condition letter; PSL1 pipe is delivered in a condition set by the standard for the process or agreed with the buyer.
- Seamless pipe in the higher grades is usually quenched and tempered; large-diameter welded pipe in the higher grades is usually made from thermomechanically rolled plate or coil.
- Field welding procedures should be qualified for the actual carbon equivalent; preheat depends on wall thickness and CE, not on the grade name alone.
Usos habituales
- Long-distance oil and gas transmission lines
- Offshore and subsea pipelines in PSL2 offshore (O) or sour (S) form
- Higher-pressure systems where wall thickness is to be reduced
Pipe and tube steels
Similar grades compared
| Grado | C % | Mn % | Cr % | Ni % | Tensile, first listed condition |
|---|---|---|---|---|---|
| API 5L X65 / L450 | ≤0.28 | ≤1.40 | ≤0.50 | ≤0.50 | ≥535 MPa |
| API 5L X42 / L290 | ≤0.28 | ≤1.30 | ≤0.50 | ≤0.50 | ≥415 MPa |
| API 5L X52 / L360 | ≤0.28 | ≤1.40 | ≤0.50 | ≤0.50 | ≥460 MPa |
| API 5L X60 / L415 | ≤0.28 | ≤1.40 | ≤0.50 | ≤0.50 | ≥520 MPa |
| API 5L X70 / L485 | ≤0.28 | ≤1.40 | ≤0.50 | ≤0.50 | ≥570 MPa |
| A53 Grade B | ≤0.30 | ≤1.20 | ≤0.40 | ≤0.40 | ≥415 MPa |
| A106 Grade B | ≤0.30 | 0.29–1.06 | ≤0.40 | ≤0.40 | ≥415 MPa |
| A500 Grade B / C | ≤0.26 | ≤1.35 | — | — | ≥400 MPa |
| IS Yst 310 | ≤0.26 | ≤1.35 | — | — | ≥330 MPa |
| S355J2H | ≤0.23 | ≤1.35 | — | — | 470–630 MPa |
Composition from the US standard where one exists, otherwise the first standard listed on each grade's page. Strength conditions differ between grades; open a grade for its full table.
Preguntas resueltas
Common questions
What is the difference between X65 and X70?
X70 has a higher minimum yield (485 MPa against 450 MPa) and tensile (570 MPa against 535 MPa). Both PSL2 grades cap tensile at 760 MPa and yield-to-tensile ratio at 0.93, and both are made only as Q or M in PSL2.
Why does X65 have no N grade in PSL2?
API 5L defines PSL2 normalized grades only up to X60 (L415N). X65 and above are quenched and tempered (Q) or thermomechanically rolled (M), which reach the strength at lower carbon.
What is the equivalent of API 5L X65 in EN ISO 3183?
L450, with Q or M for PSL2 (L450Q, L450M). The withdrawn EN 10208-2 grades were L450MB (1.8975) and L450QB (1.8952).
What do X65QS and X65QO mean?
Q is quenched and tempered. The second letter marks the purchase variant: S for pipe ordered for sour service and O for pipe ordered for offshore service. Both are PSL2 only and add stricter hardness and chemistry limits.
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Related references
References
Sources
- API Specification 5L, 46th edition (announcement and effective date) — Edition the values on this page follow.
- API announces 47th edition of API Specification 5L (2026) — Newer edition; the standard's own tables were not available to check.
- Mannesmann (Salzgitter): L450M / X65M, API 5L PSL 2 grade data — Composition maxima, yield and tensile limits.
- Nippon Steel: Steel tube and pipe catalog (applicable specifications, sour and offshore grades) — Lists API 5L grades B to X100, ISO 3183, and QS/QO grades; lists JIS G 3454 and G 3455 as separate pressure-piping standards.
- Arvedi: steels for large diameter pipelines (API 5L and EN 10208-2) — PSL1 minimum yield and tensile strength for X42 and X52; EN 10208-2 material numbers.
- BIS: IS/ISO 3183:2007, Petroleum and natural gas industries, steel pipe for pipeline transportation systems (withdrawn) — Identical adoption of ISO 3183 that amalgamated IS 1978 and IS 1979.
- METI (Japan): list of applicable standards naming ISO 3183 (API 5L) as the line pipe standard — Lists JIS G 3454, G 3455 and G 3456 as piping standards and ISO 3183 (API 5L) separately as line pipe.
- Genorma: EN 10208-2:2009 (withdrawn) — Withdrawn; replaced by EN ISO 3183.
- Bühlmann Group: steel line pipe product table (EN 10208-2 material numbers) — EN 10208-2 grade names and material numbers.
- Tubing China: chemical composition for API 5L PSL 2 pipes — PSL2 chemical limits by grade and delivery condition; cross-checked against Mannesmann for the grades it lists.
- Tubing China: chemical composition for API 5L PSL 1 pipes — PSL1 carbon and manganese limits for seamless and welded pipe.
- ProjectMaterials: API 5L PSL1 vs PSL2 — Differences between the two product specification levels.
- Total Materia: API Grade X52 PSL 1 and PSL 2 (cross-references, API 5L 2004 values) — Older-edition values and the L 360 GA, StE 360.7 cross-references.
- Valve World Americas: API publishes 47th edition of line pipe standards — Lists the topics changed in the 47th edition, including chemical element ranges.
- API announces 47th edition of API Specification 5L (news release, 2 June 2026) — Confirms the 47th edition was published in June 2026 and lists chemical element ranges among the updated topics; gives no values.
- BIS: IS/ISO 3183:2019, Petroleum and natural gas industries, steel pipe for pipeline transportation systems (second revision) — Latest Indian adoption of ISO 3183 listed by BIS; identical under single numbering; supersedes IS/ISO 3183:2012.
- BIS: IS/ISO 3183:2012 (first revision, withdrawn, superseded by IS/ISO 3183:2019) — Shows the chain 2007, 2012, 2019.
- Krakatau POSCO: plate for pipeline, API 5L 45th edition table — Independent mill table: PSL2 yield and tensile ranges, yield-to-tensile 0.93, and M-grade chemistry.
- Salzgitter Flachstahl: hot-rolled coils for large-diameter pipes (EN 10208-2 and API 5L grade correspondence) — Independent mill table: PSL2 N and M chemistry, including X60N carbon equivalent as agreed.
- Mannesmann (Salzgitter): L450 / X65, API 5L PSL 1 grade data — PSL1 welded C 0.26 and Mn 1.45 maxima; minimum yield and tensile.
Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.