L245 in the Line Pipe Grade Family
L245 is the lowest strength grade of the L series used for line pipe in ISO 3183 and GB/T 9711, with a specified minimum yield strength of 245 MPa. It is the metric equivalent of API 5L Grade B, and because it combines moderate strength with excellent ductility and weldability it remains the workhorse grade for oil, gas and water transmission at low to medium pressure.
The letter L identifies a line pipe grade and the number is the minimum yield strength in MPa, so L245, L290 and L360 are grades of increasing strength in the same table. Pipe made to this grade is supplied as welded pipe produced by electric resistance or high frequency welding, or as seamless pipe where a seamless product is required by the design.
Grade Equivalence and Product Specification Levels
| System | Designation | Minimum yield strength | Minimum tensile strength |
|---|---|---|---|
| ISO 3183 and GB/T 9711 | L245 | 245 MPa | 415 MPa |
| API 5L imperial table | Grade B | 35 000 psi | 60 000 psi |
PSL 1 grade L245 satisfies basic chemistry and tensile requirements. PSL 2 offers the same strength level with tighter control: carbon, phosphorus and sulphur are restricted, carbon equivalent limits apply, and Charpy V-notch impact testing becomes mandatory. Within PSL 2 the delivery condition is indicated by a suffix letter, with L245N normalized, L245Q quenched and tempered, and L245M thermomechanically rolled or formed.
Chemical Composition and Mechanical Properties
| Element | PSL 1 limit, mass percent | PSL 2 limit, mass percent |
|---|---|---|
| Carbon | 0.28 maximum, seamless; 0.26 maximum, welded | 0.24 maximum |
| Manganese | 1.20 maximum | 1.20 maximum |
| Phosphorus | 0.030 maximum | 0.025 maximum |
| Sulphur | 0.030 maximum | 0.015 maximum |
| Property | PSL 1 L245 or Grade B | PSL 2 L245N, L245Q, L245M |
|---|---|---|
| Yield strength | 245 MPa minimum | 245 to 440 MPa |
| Tensile strength | 415 MPa minimum | 415 to 760 MPa |
Yield strength is determined by the 0.5 % total extension under load method. The low carbon and manganese content of the grade keeps the carbon equivalent low, which is the reason L245 can be welded in the field with simple procedures and without preheating in normal ambient conditions.
Sizes, Manufacture and Finishing
L245 line pipe is produced as ERW or HFW welded pipe and as seamless pipe, with outside diameters from about 20 mm to 610 mm and wall thicknesses from about 0.4 mm to 25 mm depending on the process. Standard lengths are random or fixed up to 12 m, and the pipe is supplied with plain ends, beveled ends, or threaded ends protected by caps.
Surface condition: bare or black, with anti-rust oil, varnish, or a painted finish in colours to order.
Coatings: galvanized, polyethylene or PVC coating, and three layer polyethylene or fusion bonded epoxy for buried service.
Inspection: chemical analysis of the heat, tensile testing, flattening and bend tests, hydrostatic testing, and ultrasonic or eddy current testing of the weld seam.
Applications
The grade is used for water supply and distribution mains, gas distribution networks, low pressure oil and gas gathering lines, irrigation and slurry lines, and process piping in plants. Outside the pipeline sector, L245 pipe is also bought as a certified structural tube for machine frames, agricultural equipment, greenhouse structures, scaffolding and furniture because the grade offers a known yield strength, documented toughness and good formability at a competitive price.
FAQ
Q: What is L245 equivalent to?
L245 in ISO 3183 and GB/T 9711 is the metric equivalent of API 5L Grade B, both having a specified minimum yield strength of 245 MPa, which is 35 000 psi.
Q: What are the minimum mechanical properties of L245?
A minimum yield strength of 245 MPa and a minimum tensile strength of 415 MPa apply to the PSL 1 grade. PSL 2 restricts the yield strength to a range of 245 to 440 MPa and the tensile strength to 415 to 760 MPa.
Q: What is the difference between L245N, L245Q and L245M?
The suffix gives the delivery condition of the PSL 2 grade: N for normalized or normalizing rolled, Q for quenched and tempered, and M for thermomechanically rolled or formed.
Q: How is L245 line pipe manufactured?
It is produced as electric resistance welded or high frequency welded pipe from coil, and as seamless pipe by hot piercing and rolling, in outside diameters from about 20 mm to 610 mm and wall thicknesses from about 0.4 mm to 25 mm.
Q: Which end finishes and coatings are available?
Plain, beveled or threaded ends with caps are standard, and the pipe can be supplied bare, oiled or painted, or with galvanized, polyethylene, three layer polyethylene or fusion bonded epoxy coating for buried and corrosive service.
Q: Why is L245 easy to weld?
Its low carbon and manganese content keeps the carbon equivalent low, so it can be welded with conventional procedures at ambient temperature without preheat and with a low risk of cold cracking.
