EN10219 Cold Formed Structural Hollow Sections - Clarification on Welding Process
It's crucial to begin with a key clarification: EN10219 primarily covers cold-formed structural hollow sections. While the longitudinal seam of these sections is indeed welded, the primary welding process specified in the standard is High-Frequency Welding (HFW) for circular sections and similar methods for square/rectangular sections, not Submerged Arc Welding (SAW).
However, LSAW pipes can be manufactured to the material and testing requirements of EN10219, especially for thicker walls or specific project specifications. In this context, it is a "cold-formed, LSAW pipe to EN10219."
1. Standard Scope: EN10219-1 & EN10219-2
Part 1: EN10219-1: Technical delivery conditions.
Part 2: EN10219-2: Tolerances, dimensions, and sectional properties for square, rectangular, and circular hollow sections made from cold-formed welded steel.
Key Manufacturing Difference from EN10210:
EN10210: Hot-finished (formed and possibly welded at high temperature, often normalized).
EN10219: Cold-formed (formed at ambient temperature from strip or plate, then welded). This affects tolerances, residual stresses, and available sizes.
2. Steel Grades & Mechanical Properties
The standard defines steel grades based on minimum yield strength and impact toughness. The grades are similar but not identical to EN10210.
Table 1: Common Steel Grades and Mechanical Properties (EN10219-1)
| Steel Grade | Minimum Yield Strength (ReH) MPa | Tensile Strength (Rm) MPa | Minimum Elongation (A₅) % | Impact Toughness (KV) | Typical Process |
|---|---|---|---|---|---|
| S235JRH | 235 | 360 - 510 | 21 | 27 J at +20°C | Cold formed, HFW |
| S275J0H | 275 | 410 - 560 | 20 | 27 J at 0°C | Cold formed, HFW |
| S275J2H | 275 | 410 - 560 | 20 | 27 J at -20°C | Cold formed, HFW |
| S355J0H | 355 | 470 - 630 | 20 | 27 J at 0°C | Cold formed, HFW |
| S355J2H | 355 | 470 - 630 | 20 | 27 J at -20°C | Cold formed, HFW |
| S355K2H | 355 | 470 - 630 | 20 | 40 J at -20°C | Cold formed, HFW |
| S460NH/NLH* | 460 | 550 - 720 | 17 | 40 J at -20°C / -50°C | Often LSAW+Normalized |
Notes:
J0, J2, K2: Designate impact energy and test temperature (+20°C, 0°C, -20°C).
H: Denotes "Hollow Section".
*Grades like S460NH/NLH: To achieve these higher strengths with good toughness after cold-forming, the manufacturing route often involves using a normalized plate, forming, and then using LSAW for the longitudinal seam, followed by potential post-weld heat treatment. This is where LSAW fits into the EN10219 scope.
3. Dimensions & Tolerances for Circular Hollow Sections (CHS)
Cold-forming allows for tighter dimensional tolerances compared to hot-finished products.
Table 2: Size Range and Tolerances for Cold-Formed CHS (Extract)
| Outside Diameter (D) mm | Typical Wall Thickness (t) Range mm | Tolerance on Diameter (at any cross-section) | Tolerance on Wall Thickness |
|---|---|---|---|
| 21.3 - 168.3 | 1.0 - 8.0 | ± 0.5 mm (D ≤ 40mm) to ± 0.75% of D | Typically ± 10% of nominal 't' |
| > 168.3 - 457 | 2.0 - 12.5 | ± 0.75% of D | Typically ± 10% of nominal 't' |
| > 457 - 1200* | 4.0 - 16.0+ | ± 0.75% of D or as agreed | Typically ± 10% or as agreed |
*Note: Sizes above ~457mm are less common for classic cold-forming and may involve a hybrid LSAW approach.*
4. Manufacturing Route for an "EN10219 LSAW Pipe"
For larger diameters/thicker walls, the process would be:
Material: Cold-formed from normalized steel plate (e.g., EN10025 S460NL).
Forming: Plate is cold-formed (e.g., via a UOE process) into a cylinder.
Welding: The longitudinal seam is welded using Submerged Arc Welding (SAW) for superior weld quality and penetration on thick material.
Post-Weld Treatment: The weld area may be normalized or the entire pipe stress-relieved to restore properties.
Testing: It is then tested and inspected as per EN10219-1 requirements.
5. Key Comparison: EN10210 LSAW vs. EN10219 LSAW
| Feature | EN10210 (Typical LSAW) | EN10219 (Cold-Formed + possible LSAW) |
|---|---|---|
| Primary Process | Hot-finished, Normalized | Cold-formed |
| Typical Seam Weld | Submerged Arc Welding (SAW) | High-Frequency Welding (HFW) or SAW |
| Surface Quality | Mill scale, rougher | Smoother, better surface finish |
| Tolerances | Standard (wider) | Tighter (especially on diameter/ovality) |
| Residual Stress | Lower (due to hot-finish/normalizing) | Higher (due to cold-forming) |
| Common Grades | S355J2H, S355NH | S355J2H, S355K2H, S460NH |
Conclusion
While EN10219 is fundamentally a standard for cold-formed welded hollow sections, the use of Longitudinal Submerged Arc Welding (LSAW) is a valid and sometimes specified manufacturing method within its framework, particularly for:
Higher strength grades (S460 and above).
Applications requiring verified weld integrity on thicker walls.
Projects specifying cold-formed tolerances but SAW weld quality.
Therefore, you can have an "LSAW Pipe manufactured to EN10219" which combines the dimensional precision of cold-forming with the robust weld quality of the submerged arc process.
