EN 1090-2 Welding Procedure — WPS per European Structural Fabrication
Complete guide to welding procedure requirements per EN 1090-2:2018. Welding Procedure Specification (WPS), Welding Procedure Qualification Record (WPQR), preheat and interpass temperatures, heat input control, electrode selection for S235, S275, and S355 structural steels.
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Welding Procedure Specification — EN 1090-2 Clause 7
Every fabrication weld must be covered by a Welding Procedure Specification (WPS) per EN ISO 15609-1. The WPS documents:
| WPS Parameter | Required Information |
|---|---|
| Base materials | Steel grade, thickness range, product form |
| Filler metal | Electrode type, diameter, classification (EN ISO) |
| Joint preparation | Bevel angles, root gap, root face |
| Welding position | PA, PB, PC, PD, PE, PF, PG per EN ISO 6947 |
| Welding process | 135 (MAG), 111 (SMAW), 121 (SAW), 141 (TIG) |
| Preheat temperature | Minimum preheat, interpass temperature range |
| Welding parameters | Current, voltage, travel speed, heat input |
| Post-weld heat treatment | Temperature, holding time, cooling rate |
Welding Procedure Qualification Record
The WPQR (EN ISO 15614-1) qualifies the WPS through destructive testing:
| Test | Standard | Acceptance Criterion |
|---|---|---|
| Tensile test | EN ISO 6892-1 | ≥ specified minimum f_u of base metal |
| Bend test (side/face/root) | EN ISO 5173 | No defect > 3 mm after bending |
| Charpy V-notch impact | EN ISO 9016 | ≥ 27 J at specified temperature |
| Hardness survey | EN ISO 9015-1 | ≤ 380 HV10 (S355, no PWHT) |
| Macroscopic examination | EN ISO 17639 | Full fusion, no cracks, acceptable porosity |
For EXC2, the WPQR range of qualification covers:
- Thickness: 0.5× to 2× the qualified thickness
- Diameter: 0.5× to 2× the qualified pipe diameter
- Heat input: ±25% of qualified range
Preheat and Interpass Temperatures
Minimum Preheat for Structural Steels
| Steel Grade | t ≤ 20 mm | 20 < t ≤ 40 mm | 40 < t ≤ 60 mm | t > 60 mm |
|---|---|---|---|---|
| S235JR | None | None | 50°C | 75°C |
| S275JR | None | None | 50°C | 100°C |
| S355JR | None | 50°C | 75°C | 125°C |
| S355J2 | None | 50°C | 100°C | 150°C |
| S460 | 50°C | 100°C | 125°C | 175°C |
Conditions: Low-hydrogen process (HD ≤ 5 mL/100g), ambient ≥ 5°C. Increase preheat by 50°C for cellulosic electrodes or high restraint.
Interpass Temperature Limits
| Steel Grade | Maximum Interpass Temperature |
|---|---|
| S235JR | 250°C |
| S275JR | 250°C |
| S355JR | 250°C (300°C for fine grain) |
| S460 | 250°C |
Electrode Selection — EN ISO 2560-A
Matching Electrodes for Structural Steels
| Base Metal | Electrode Class (MAG) | Electrode Class (SMAW) | Minimum f_u |
|---|---|---|---|
| S235JR | G 42 0 M21 | E 42 0 RR 12 | 420 MPa |
| S275JR | G 42 0 M21 | E 42 0 RR 12 | 420 MPa |
| S355JR | G 46 4 M21 | E 46 0 RR 12 | 460 MPa |
| S355J2 | G 46 5 M21 | E 46 5 B 42 | 460 MPa |
| S355K2 | G 50 6 M21 | E 50 6 B 42 | 500 MPa |
The electrode designation follows EN ISO 2560-A: "G" for gas-shielded, numbers indicate minimum yield (e.g., 42 = 420 MPa), final number indicates Charpy temperature (0 = 0°C, 4 = -40°C).
Heat Input Control
Excessive heat input reduces strength and toughness. Maximum heat input per EN 1011-2:
| Process | Max Heat Input (kJ/mm) for S355 | Travel Speed (mm/min) for 1.2 mm wire |
|---|---|---|
| MAG (135) | 1.5-2.5 | 250-450 |
| SMAW (111) | 1.5-2.0 | 150-250 |
| SAW (121) | 3.0-5.0 | 400-800 |
Heat input calculation: Q = η × U × I / v × 1000
Where η = 0.8 (MAG), 0.7 (SMAW), 1.0 (SAW); U = voltage (V); I = current (A); v = travel speed (mm/s).
Workmanship Requirements — EN 1090-2 Clause 7.5
| Requirement | Acceptance Criterion |
|---|---|
| Welding sequence | Minimize distortion, balanced welding around neutral axis |
| Back gouging | Required for double-sided welds to sound metal before welding second side |
| Tack welds | Must be made by qualified welders, incorporated into final weld |
| Splices | Minimum overlap 15 mm, staggered in multi-run welds |
| Cleanliness | Remove slag between passes, grind start/stop positions |
| Heat straightening | Permitted if temperature ≤ 600°C for S355 |
Frequently Asked Questions
What preheat is required for welding S355JR 25 mm plate?
For S355JR plate 25 mm thick (20 < t ≤ 40 mm), EN 1011-2 recommends a minimum preheat of 50°C using low-hydrogen MAG welding. Increase to 75°C for highly restrained joints or ambient temperature below 5°C. The interpass temperature must not exceed 250°C.
What is the difference between WPS and WPQR?
A Welding Procedure Specification (WPS) is the document that specifies how welding is to be performed (parameters, materials, positions). The Welding Procedure Qualification Record (WPQR) is the evidence that the WPS produces acceptable welds — verified through destructive testing (tensile, bend, Charpy, hardness) per EN ISO 15614-1. The WPQR qualifies the WPS for production use.
Related Pages
- Weld Inspection — EN 1090-2 NDT requirements
- Weld Capacity — Fillet weld design per EN 1993-1-8
- Weld Symbols — EN 22553 weld symbols
- European Steel Chemical Composition — CEV and weldability
- All European References
Educational reference only. Welding procedure per EN 1090-2:2018 and EN 1011-2:2001. Verify WPS and WPQR comply with project specification and applicable National Annex. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification.
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