Steel Structure Welding and Quality Control

Welding is one of the most critical processes in steel structure fabrication. A poorly executed weld can compromise the load-bearing capacity and safety of an entire structure. For this reason, steel structure welding is governed by strict European standards — primarily EN ISO 3834 and EN 1090-2. This article explains what these standards require, how quality control works, and what buyers of steel structures should know.

Why Is Weld Quality Critical in Steel Structures?

Welds in steel structures carry significant static and dynamic loads. Porosity, cracks, incomplete fusion, or incorrect cross-section in a weld can lead to premature structural failure — particularly in structures subject to fatigue loading such as bridges, crane runways, and industrial building frames. Under EN 1090-2, the execution class (EXC1–EXC4) is determined by the criticality of the structure and its service conditions.

EN ISO 3834 — Welding Quality Management System

EN ISO 3834 is the international standard establishing quality requirements for fusion welding. It is divided into three levels:

• EN ISO 3834-2 — Comprehensive quality requirements (high-consequence structures)
• EN ISO 3834-3 — Standard quality requirements (typical industrial structures)
• EN ISO 3834-4 — Elementary quality requirements (simple, low-consequence structures)

Steel Element OÜ operates in accordance with EN ISO 3834-2, ensuring the highest level of welding quality management. This includes certified welders (EN ISO 9606-1), qualified welding supervisors (IWI/EWI), and documented welding procedure specifications (WPS).

Welding Procedure Specifications (WPS) and Qualification Records (WPQR)

Every welding process must be documented in a Welding Procedure Specification (WPS). The WPS defines precisely: the welding process (MAG, MIG, TIG, manual metal arc), base material and filler material, current and voltage, travel speed, heat input, and welding position.

The WPS is based on a Welding Procedure Qualification Record (WPQR), which demonstrates that welding with the specified parameters produces a weld with the required mechanical properties. WPQR preparation involves a test weld and mechanical testing of the sample (tensile test, bend test, impact toughness test).

Welder Certification to EN ISO 9606-1

All Steel Element OÜ welders are certified in accordance with EN ISO 9606-1 (welding of steels). The certificate confirms the welder’s ability to work with a specific process, material group, and position. Certificates are renewed every two years, and ongoing competency is verified through continuous supervision.

Non-Destructive Testing (NDT) — What Is Tested and When?

EN 1090-2 requires weld inspection in accordance with the applicable execution class. NDT methods used:

• Visual Testing (VT) — all welds, always mandatory
• Magnetic Particle Testing (MT) — detection of near-surface defects in ferromagnetic materials
• Ultrasonic Testing (UT) — detection of internal defects in thick welds
• Penetrant Testing (PT) — detection of surface cracks in non-magnetic materials

At execution class EXC2, at least 10% of butt and T-joint welds are subject to NDT; at EXC3, 100% inspection is required.

What Should a Buyer Ask About Weld Quality?

When ordering steel structures, it is important to confirm that the manufacturer can provide: an EN ISO 3834 conformity certificate, welder certificates (EN ISO 9606-1), WPS documents, NDT inspection reports, and material certificates (EN 10204 3.1 or 3.2). These documents form part of the ISO 9001:2015 quality system output and guarantee the buyer receives a verified, compliant structure.

Steel Element OÜ supplies all required documentation with every order. Learn more about our production capabilities and services, or request a quote.