ISO 15614-1 — Welding Procedure Qualification (WPQR) Complete Guide
Introduction
ISO 15614-1 is the standard that defines how to qualify a welding procedure for steels and nickel alloys. While the WPS (Welding Procedure Specification) describes *how* to weld, ISO 15614-1 describes *how to prove* that the procedure works — through testing a test piece welded under the same conditions.
The result is the WPQR (Welding Procedure Qualification Record), the document certifying that the procedure has been tested and approved. Without a WPQR, the WPS has no validity in regulated welded construction (EN 1090, EN 13480, EN 13445, etc.).
Source: ISO 15614-1:2017 — Specification and qualification of welding procedures for metallic materials — Welding procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys.
Scope
ISO 15614-1 applies to:
- Arc welding (processes 111, 114, 131, 135, 136, 138, 141, 15)
- Gas welding (process 311)
- Steels and nickel alloys
It does not cover aluminium (see ISO 15614-2), copper (ISO 15614-6), or maintenance/repair welding under special conditions.
Essential variables
Essential variables are parameters that, if changed beyond the permitted limits, require a new qualification. The following table summarises the main ones:
| Variable | Typical limits |
|---|---|
| Welding process | Each process requires separate qualification (e.g. 135 does not qualify 136) |
| Joint type | Butt joint qualifies butt; fillet joint qualifies fillet |
| Material group | Per ISO/TR 15608 (e.g. Group 1.1 carbon steels, Group 8.1 austenitic stainless) |
| Base material thickness | Range defined in Table 5 (e.g. 12mm test piece qualifies 3–24mm) |
| Welding position | Each position (PA, PB, PC, PF, etc.) must be qualified |
| Preheat | Reduction >50°C requires requalification |
| PWHT | Addition or removal of PWHT requires requalification |
| Current type | Change from DC to AC (or reverse) requires requalification |
| Shielding gas | Change of gas group (e.g. M21 to C1) requires requalification |
| Filler material | Change of consumable classification requires requalification |
| Number of passes | Change from multipass to single-pass requires requalification |
| Heat input | If outside the ±25% range of the value recorded in the WPQR |
Test piece preparation
The test piece must be welded under the exact conditions of the preliminary WPS (pWPS). Critical points:
- Base material representative of the group/subgroup (ISO/TR 15608)
- Minimum dimensions per Table 1 of the standard (e.g. for butt weld in plate, minimum 300mm weld length)
- Welder qualified per ISO 9606-1 (procedure qualification does not replace welder qualification)
- All parameters recorded during execution: current, voltage, travel speed, gas flow rate, interpass temperature
- The test piece must be identified and traceable
Required tests
After welding, the test piece undergoes destructive and non-destructive testing. The following table shows typical tests for a butt joint in plate:
| Test | Test standard | Typical quantity |
|---|---|---|
| Visual examination (VT) | ISO 17637 | 100% of weld |
| Radiography (RT) or Ultrasonics (UT) | ISO 17636 / ISO 17640 | 100% of weld |
| Transverse bend test (face and root) | ISO 5173 | 2 face + 2 root |
| Transverse tensile test | ISO 4136 | 2 specimens |
| Charpy impact test (if required) | ISO 9016 | 2 sets (WM + HAZ) |
| Macro and micrography | ISO 17639 | 1 section |
| Hardness test (if required) | ISO 9015-1 | 1 indentation line (HV10) |
For fillet joints, testing is simplified: visual examination, macrography, and if required, fracture test.
Acceptance criteria
- Visual examination and RT/UT: quality level B per ISO 5817 (except imperfections 501, 502, 503, 5214 — level C)
- Transverse tensile: strength ≥ minimum specified value for the base material
- Bend test: no open cracks >3mm in any direction after 180° bend (former diameter per thickness)
- Charpy impact: average value ≥ requirement of the applicable construction standard
- Hardness: maximum values per ISO 15614-1 Table 4 (e.g. Group 1 carbon steels — maximum 380 HV10)
- Macrography: sound weld, no visible macroscopic defects
Qualification range — Thickness
The test piece thickness defines the qualified thickness range. Simplified general rule:
| Test piece thickness (t) | Qualified range |
|---|---|
| t ≤ 3 mm | t to 2×t |
| 3 < t ≤ 12 mm | 3 mm to 2×t |
| 12 < t ≤ 100 mm | 0.5×t to 2×t (max 2×t or 150mm) |
| t > 100 mm | ≥ 0.5×t |
Note: For wider qualification, weld a test piece at an intermediate thickness (e.g. 12mm qualifies 3 to 24mm).
Validity and requalification
- The WPQR has no expiry date — it is valid indefinitely as long as conditions remain unchanged
- If the company changes any essential variable outside the permitted limits, a new WPQR is required
- The company must keep records (WPQR + WPS + test results) available for audit
Difference between ISO 15614-1 and ISO 9606-1
| Aspect | ISO 15614-1 | ISO 9606-1 |
|---|---|---|
| What it qualifies | The procedure (WPS → WPQR) | The welder (personal certificate) |
| Who welds the test piece | Any qualified welder | The welder being qualified |
| Validity | Indefinite | 3 years (with 6-monthly prolongation) |
| Typical tests | RT/UT + tensile + bend + Charpy + macro + hardness | RT/UT + bend or fracture |
| Result | WPQR | Welder certificate |
Both are required: the company needs valid WPS/WPQR AND qualified welders to execute the WPS.
Sources and references
- ISO 15614-1:2017 — Specification and qualification of welding procedures for metallic materials
- ISO/TR 15608:2017 — Welding — Guidelines for a metallic materials grouping system
- ISO 15607:2019 — Specification and qualification of welding procedures for metallic materials — General rules
- ISO 9606-1:2012 — Qualification testing of welders — Fusion welding — Part 1: Steels
- ISO 5817:2014 — Welding — Fusion-welded joints in steel, nickel, titanium and their alloys — Quality levels