What Does the Term EN 10025 LSAW Steel Pipe Mean?
EN 10025 is the European standard for hot rolled products of structural steels. It defines the chemical composition, mechanical properties and impact toughness of the steel plate, not of the finished pipe. When the market refers to an EN 10025 LSAW steel pipe, it means a longitudinally submerged arc welded pipe that has been manufactured from plate conforming to EN 10025.
This distinction matters in a purchase order. A complete pipe specification needs two documents: the material standard that fixes the plate grade, and a pipe manufacturing standard that fixes how the pipe is formed, welded, dimensioned and tested. Typical manufacturing standards used with EN 10025 plate include EN 10219-1 for cold formed welded structural hollow sections, EN 10217-1 for welded pressure tubes, and EN 10224 for non-alloy steel tube for water conveyance.
A correctly written order therefore reads as a pipe standard with a plate grade, for example longitudinally welded pipe manufactured from steel plate conforming to EN 10025 S355J2H, supplied to the dimensional and testing requirements of the pipe standard named in the enquiry.
EN 10025 Material Grades and Toughness Classes
EN 10025 grades are designated by minimum yield strength in MPa, with a suffix that defines the impact test temperature and the rolling condition:
| Grade | Minimum yield strength | Typical use |
|---|---|---|
| S235 | 235 MPa | General structural work, light columns |
| S275 | 275 MPa | Structural frames, pressure pipe plate |
| S355 | 355 MPa | Most widely used structural grade |
| S420 | 420 MPa | High strength structures, crane booms |
| S460 | 460 MPa | Heavy loaded members, offshore structures |
| Suffix | Meaning |
|---|---|
| JR | Impact tested at plus 20 degrees Celsius |
| J0 | Impact tested at 0 degrees Celsius |
| J2 | Impact tested at minus 20 degrees Celsius, common for general structures |
| K2 | Impact tested at minus 20 degrees Celsius for fine grain steel |
| N | Normalized rolled condition |
| NL | Normalized rolled, impact tested at minus 50 degrees Celsius |
| M | Thermo-mechanically rolled |
| ML | Thermo-mechanically rolled, impact tested at minus 50 degrees Celsius |
The delivery condition directly affects the pipe. Normalized plate gives a uniform ferrite and pearlite structure with predictable toughness after welding, while thermo-mechanically rolled plate reaches the same strength with lower carbon equivalent, which improves weldability at the expense of a more limited heating range during fabrication.
Manufacturing Route for LSAW Pipe
Longitudinally submerged arc welded pipe is produced from discrete plates rather than coils. The plate is edge-milled and crimped, then formed into a cylinder by the UOE route, in which the plate is pressed first into a U shape and then into an O shape before the seam is closed, or by the JCOE route, in which successive pressing steps form J, C and O profiles. After welding the pipe is mechanically expanded, which relieves forming stresses, improves roundness and increases dimensional accuracy.
The longitudinal seam is welded from the inside and outside with the submerged arc process, which uses a granular flux to shield the arc and produces deep penetration with a clean, uniform bead. Because the seam runs parallel to the pipe axis, it can be inspected along its full length, and ultrasonic or radiographic examination of the complete seam is standard practice for structural and pressure pipe alike.
Structural Applications
Building columns and supports in stadiums, airports and high-rise structures
Offshore platform jackets, piles, decks and transition pieces
Bridge piers, arches and heavy support structures
Foundation piling and retaining structures
Penstocks and water transmission mains where pressure duty is moderate
Heavy-duty equipment booms, frames and machine bases
Comparison with ASTM Based LSAW Pipe
| Feature | Pipe from EN 10025 plate | Pressure pipe standards |
|---|---|---|
| Governing concept | Material standard for the plate, pipe standard separate | Single comprehensive product standard |
| Primary design focus | Yield strength and impact toughness | Pressure containment at design temperature |
| Key testing | Charpy impact test on the plate material | Radiographic or ultrasonic testing of the weld plus hydrostatic test |
| Common grades | S235, S275, S355, S420, S460 | Grade B to X70 and equivalent classes |
| Typical use | Structural columns, piling, bridge piers | High pressure process piping, transmission lines |
The practical consequence is that a pipe ordered on an EN 10025 plate grade is optimised for load bearing rather than for internal pressure. If the line will operate at high pressure, a dedicated line pipe or pressure tube standard is specified instead, even when the strength level is similar.
Ordering and Inspection Points
An order should state the plate grade and its toughness suffix, the pipe manufacturing standard, outside diameter, wall thickness, length, end preparation, and the required testing regime. For structural pipe the essential tests are the plate impact test, dimensional verification, and weld examination; for pipe that also carries fluid, a hydrostatic test is added.
Carbon equivalent should be agreed in advance when the pipe will be welded on site, because it governs preheat requirements and the risk of cold cracking in thick sections. Surface condition, weld reinforcement height and the offset of plate edges are inspected against the pipe standard rather than the plate standard, since they relate to the finished hollow section.
FAQ
Q: Is EN 10025 a pipe standard?
No. EN 10025 defines hot rolled structural steel plate. It is used with a separate pipe manufacturing standard such as EN 10219-1, EN 10217-1 or EN 10224 when specifying a finished pipe.
Q: What does the J2 suffix mean?
The J2 suffix means the steel has been impact tested at minus 20 degrees Celsius, which qualifies it for structures that see low ambient temperatures.
Q: Which grade is most common for LSAW structural pipe?
S355 is the most widely ordered grade because it combines a high yield strength with good toughness and weldability at moderate cost.
Q: Can EN 10025 LSAW pipe carry internal pressure?
It can carry low to medium pressure where the design code permits, but for high pressure service a dedicated line pipe or pressure tube standard should be specified.
Q: What is the difference between normalized and thermo-mechanically rolled plate?
Normalized plate is reheated after rolling to refine the grain structure, while thermo-mechanically rolled plate achieves its properties through controlled rolling and cooling, giving a lower carbon equivalent and better weldability.
Q: How is the longitudinal weld inspected?
The full length of the seam is examined by ultrasonic or radiographic testing, and the pipe then passes a hydrostatic test when the end use requires pressure containment verification.
