Oil Pipeline Steel according to API and EN standards

Author:

Piotr Sompoliński

Date added:

19.08.2026 year

Pipelines are one of the most efficient ways to transport natural gas and crude oil. The operating pressure of the world’s largest oil pipelines can reach 10 MPa. Over the years, pipeline diameters and operating pressures have increased to improve transport efficiency. This requires either thicker pipe walls or steel with a higher yield strength. However, when material, transportation and welding costs are taken into account, using a higher-grade steel is often more economical than increasing wall thickness. For example, replacing X70 steel with X80 steel can reduce the required pipe wall thickness by 12.5%.

Pipelines used to transport oil and gas from sour reservoirs must be made from steel that is resistant to hydrogen-induced cracking.

Pipeline steels according to API and EN standards

The most important standards for pipeline steels were developed by the API (American Petroleum Institute), and the European EN 10208 standards are based on their work. In both systems, steel grades are primarily designated according to their minimum yield strength. The American system uses pounds per square inch (ksi), while the European system uses megapascals (MPa).

Under the API designation system, X60 steel has a minimum yield strength of 60 ksi, equivalent to 413.7 MPa. In the European system, L415 steel has a minimum yield strength of 415 MPa. Based on this property and using the conversion 1 ksi = 6.895 MPa, the approximate European equivalents of American pipeline steel grades are:

X60 — L415NB
X65 — L450MB / L450QB
X70 — L485MB
X80 — L555MB / L555QB

Many different steel grades with slightly different chemical compositions can meet the requirements for X65, X70 and other pipeline steel grades. The table below presents examples of pipeline steel compositions that comply with American and European standards.

Standard	Steel Grade
	Chemical Composition %
	Fe:	C:	Mn:	Si:	P:	S:	Ni:	Mo:	Cu:	Nb:	V:	Ti:	Other:	Yield Strength:
API 5L	X65
	Reszta	0.02	1.59	0.14	0.018	0.003	-	-	-	0.04	-	0.017	B:0.001	> 65 ksi
	X65
	Reszta	0.03	0.61	0.16	0.016	0.003	0.17	-	-	0.05	-	0.016	B:0.001	> 65 ksi
	X65
	Reszta	0.06	1.35	-	0.025	0.005	0.25	-	0.33	0.04	0.07	-	-	> 65 ksi
	X70
	Reszta	0.03	1.91	0.14	0.018	0.003	-	-	-	0.05	-	0.018	B:0.001	> 70 ksi
	X70
	Reszta	0.08	1.6	-	-	-	-	-	-	0.04	0.07	-	-	> 70 ksi
	X80
	Reszta	0.07	1.65	-	-	0.002	-	0.22	-	0.05	0.075	-	-	> 80 ksi
	X80
	Reszta	0.02	1.95	0.26	0.022	0.003	0.38	0.31	-	0.04	-	0.019	B:0.001	> 80 ksi
	X80
	Reszta	0.08	1.5	0.1	-	-	-	-	-	0.052	0.076	-	-	> 80 ksi
	X80
	Reszta	0.036	1.6	0.1	-	-	0.35	0.29	-	0.064	-	-	-	> 80 ksi
	X80
	Reszta	0.07	1.86	0.27	0.015	0.001	-	0.15	-	0.04	-	0.023	-	> 80 ksi
	X100
	Reszta	0.07	1.90	0.20	-	-	0.20	0.30	0.20	0.005	-	0.015	-	> 100 ksi
EN 10253	L415MB / 1.8972
	Reszta	<0.21	<1.6	<0.45	<0.025	<0.02	<0.3	-	<0.25	Nb<0.05; V<0.15; Ti<0.04; V+Nb+Ti<0.15			Al:0.015-0.06	> 415 MPa
	L450MB / 1.8975
	Reszta	<0.16	<1.6	<0.45	<0.025	<0.02	<0.3	<0.1	<0.25	Nb<0.05; V<0.1; Ti<0.06; V+Nb+Ti<0.15			Al:0.015-0.06	> 450 MPa
	L485MB / 1.8977
	Reszta	<0.16	<1.7	<0.45	<0.025	<0.02	<0.3	<0.35	<0.25	Nb<0.06; V<0.1; Ti<0.06; V+Nb+Ti<0.15			Al:0.015-0.06	> 485 MPa
	L555MB / 1.8978
	Reszta	<0.16	<1.8	<0.45	<0.025	<0.02	<0.6	<0.35	<0.25	Nb<0.06; V<0.1; Ti<0.06; V+Nb+Ti<0.15			Al:0.015-0.06	> 555 MPa

The boron-containing steel grades listed in the table have a bainitic microstructure. During their production, the reheating temperature is between 1000 and 1150°C, while fine TiN particles inhibit grain growth. The finishing temperature is approximately 700°C. X60 steels generally have a ferrite-pearlite microstructure. Grain refinement strengthening is achieved through controlled rolling and the addition of niobium. X65 and X70 steels often also contain vanadium, which provides precipitation strengthening. X80 and X100 steels are produced using small additions of nickel and molybdenum. Higher strength is achieved through accelerated cooling after rolling to form bainite or martensite.

API 5L Designations

Types and size ranges:

SMLS — seamless pipes; used where higher material integrity and uniformity are required.
- sizes: NPS 1/2″ to 36″ / DN 15 to DN 900
ERW — Electric Resistance Welded pipes; cost-effective and widely used for gas pipelines and gathering lines.
- sizes: NPS 2″ to 26″ / DN 50 to DN 650
SAW — Submerged Arc Welded pipes; used for large-diameter transmission pipelines.
- sizes: NPS 20″ to 60″ / DN 500 to DN 1500

The ANSI / API 5L standard specifies requirements for two product specification levels: PSL 1 and PSL 2. For material use in a sour service application, refer to Annex H; for offshore service application, refer to Annex J.

EN Designations and Standards

The designation system for pipeline steels under EN 10208-1 and EN 10208-2 is as follows:

L + minimum yield strength (210–555) + designation (G / M / N / Q) + requirement class (A / B)

In addition to the Lxxx designation, grades are also identified using the 1.xxxx material number system.

EN 10208-1 covers pipeline steels with requirement class A. Examples include:

L210GA / 1.0319
L235GA / 1.0458
L245GA / 1.0459
L290GA / 1.0483
L360GA / 1.0499

EN 10208-2 covers pipeline steels with requirement class B. Examples include:

L245MB / 1.0418
L245NB / 1.0457
L290NB / 1.0484
L360MB / 1.0578
L360NB / 1.0582
L360QB / 1.8948
L415MB / 1.8973
L415NB / 1.8972
L415QB / 1.8952
L485QB / 1.8955
L485MB / 1.8977
L555QB / 1.8957
L555MB / 1.8978

Post author

Piotr Sompoliński

CSO Virgamet

p.sompolinski@virgamet.pl

+48 793 726 124

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