Welding applications and applied welding technology
This domain asks how the generic rules are applied under sector specifications and to difficult materials - pressure, structural, pipeline, rail, stainless and aluminium.
Core rules
- Structural steel: EN 1090-2 execution classes EXC1–EXC4. EXC3 and above require WPQR to ISO 15614-1, welders to ISO 9606-1, and a defined NDT extent tied to the class.
- Pressure: PED 2014/68/EU leads to EN 13445 or ASME BPVC IX; impact testing and PWHT follow material group and thickness.
- Duplex stainless: heat input typically 0.5–2.5 kJ/mm, interpass ≤ 150 °C, ferrite 35–65 %, no PWHT.
- Aluminium: remove oxide mechanically just before welding; AC TIG or pulsed MIG; expect porosity unless filler and surface are dry.
- Dissimilar joints: choose filler for the higher-alloy or lower-strength side; nickel-based filler for carbon steel to stainless.
Worked example
A 2205 duplex WPS states 3.2 kJ/mm, interpass 200 °C and PWHT at 550 °C. Three defects, each metallurgical: heat input above the usual 2.5 kJ/mm ceiling promotes sigma phase and nitrides; 200 °C interpass embrittles and unbalances the ferrite; 550 °C sits in the 475 °C embrittlement range. Reject the procedure and rewrite it with ≤ 2.5 kJ/mm, ≤ 150 °C and no PWHT.
Traps
Applying carbon-steel PWHT practice to duplex or austenitic grades; assuming a welder qualified in one process is qualified in another; treating EN 1090-2 NDT percentages as negotiable rather than class-driven.