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:

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).

Worked Example — WPS for S355J2 Butt Weld

Problem: Prepare a Welding Procedure Specification for a full-penetration butt weld in S355J2 plate, 20 mm thick, welded in flat position (PA) using MAG process in a shop environment. Project requires EXC2 execution class per EN 1090-2. Structure located in Central Europe with minimum service temperature of -15°C.

Step 1 — Select Filler Metal per EN ISO 2560-A: Base metal S355J2 (fy = 355 MPa, fu = 470 MPa minimum). For matching strength and -20°C toughness, select:

Step 2 — Determine Preheat per EN 1011-2: CEV for S355J2 at 20 mm ≈ 0.40. Per EN 1011-2 Annex C, for CEV < 0.42 and t ≤ 30 mm, no preheat is required at ambient ≥ 5°C. Interpass temperature: 150°C-250°C per EN 1090-2 Table 16.

Step 3 — Joint Preparation per EN ISO 9692-1: Single-V groove with 60° included angle, root gap 2 mm, root face 1.5 mm. Backing bar not required (access to back side for back gouging).

Step 4 — Welding Parameters: Process: 135 (MAG). Current: 240-280 A. Voltage: 26-28 V. Travel speed: 350-400 mm/min. Wire feed rate: 7-8 m/min. Heat input: Q = 0.8 × 27 × 260 / (375/60) = 0.8 × 7020 / 6.25 = 0.90 kJ/mm — well within the 1.5-2.5 kJ/mm recommended range for S355 per EN 1011-2.

Step 5 — WPS Documentation per EN ISO 15609-1: Record all parameters in WPS document including: base material (S355J2 per EN 10025-2), thickness range (15-30 mm qualified), welding position (PA), filler metal classification, preheat/interpass temperatures, electrical parameters, travel speed range, heat input range, and post-weld treatment (none required for this application).

Step 6 — WPQR Qualification per EN ISO 15614-1: For EXC2, the WPS must be supported by a WPQR. Test plate: 20 mm S355J2, butt weld. Required tests: 2 tensile (EN ISO 6892-1), 4 bend (EN ISO 5173), 1 Charpy set at -20°C (EN ISO 9016), 1 hardness survey (EN ISO 9015-1), 1 macrograph (EN ISO 17639). All tests must meet acceptance criteria for Level C per EN ISO 5817.

Result: WPS qualified for S355J2, thickness range 10-40 mm, flat position, MAG process, EN 1090-2 EXC2.

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

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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