"Don't skimp on weld quality": interview with a structural engineer on the safety of metal structures

Weld quality is one of the least noticeable but most critical factors in the durability of any metal structure. However, this is exactly where builders often try to save money. We asked Oleksandr Marchenko, a structural engineer at a metallurgical company with 15 years of experience, why this is dangerous, what mistakes contractors make, and how to properly monitor installation.

Why welding quality is more important than metal thickness?

— Mr. Marchenko, why is the issue of weld quality so critical?

Oleksandr Marchenko:

"A weld is the weakest point of a structure. Even if you use high-quality metal, an improperly made weld can negate all engineering calculations. Welding changes the structure of the metal, its strength, and corrosion resistance. In 90% of the metal structure accidents I've seen, the reason was the same: poor-quality execution of joints, which contradicts DSTU EN ISO 5817 standards that clearly define quality levels for defects.

Engineer's tip: The weldability of metal directly depends on its chemical composition. For example, when you order hollow sections or steel sheets, it is important that the carbon content does not exceed the norm (according to DSTU EN 10025), otherwise microcracks will occur in the weld zone. I always advise checking quality certificates for compliance of steel with standards."

Typical ways of "dangerous savings" during installation

— What do contractors usually try to save on?

Oleksandr: There are several critical mistakes, each of which can lead to destruction:

• Cheap consumables. Using electrodes that do not match the steel grade.


• Low qualification. Refusing certified welders in favor of "cheap labor".


• Ignoring surface preparation. Welding over rust or paint guarantees lack of fusion and pores.


• Violation of geometry. Reducing the length or leg of the weld contrary to the drawings.

Important comment: "This is especially critical for high-load structures. If an I-beam or a massive U-channel are welded 'hastily', the weld will simply burst under load. Saving on 10 centimeters of welding leads to deformation of the entire building frame, which violates the requirements of DSTU 2766 (GOST 23118) regarding general technical conditions for metal structures."

Consequences: from corrosion to collapse

— What real risks does such saving pose to the customer?

Oleksandr: The consequences do not appear immediately, but they are always fatal:

• Cracking of the weld under wind or snow loads.


• Intergranular corrosion, which begins exactly at the place of metal overheating.


• Deflections and distortions that make further operation of the building impossible.

How to recognize a defect: 5 signs for a non-specialist

— How can an ordinary customer understand that the work is poorly done?

Oleksandr: According to DSTU EN ISO 17637 (visual inspection), pay attention to these points:

1. Uneven weld: A ragged pattern indicates low qualification.


2. Undercuts and overlaps: The metal around the weld should not be "burnt".


3. Craters: Unfilled depressions at the end of the weld are future crack centers.


4. Inconsistency with the drawing: The weld is thinner or shorter than projected.


5. Dirt: Presence of slag that was not removed after welding.

"Also pay attention to geometry. For example, if a frame is being welded where steel angles are used, any distortion due to an incorrect thermal regime of the weld will make further installation impossible. High-quality rolled metal has a smooth surface, which significantly facilitates the welder's work."

Mandatory quality control methods

— What control do you consider mandatory for critical objects?

For structures falling under consequence classes CC2 and CC3, I recommend:

• Visual and Measurable Inspection (VIC): Basic inspection of every meter of the weld.


• Ultrasonic Testing (UT): According to DSTU EN ISO 17640, to detect internal lack of fusion.


• Penetrant Testing: To find microcracks on the surface.

Advice to customers: how not to become a victim of circumstances

— What would you advise people planning construction now?

1. Demand technical maps (WPS). This is a document specifying how and with what to weld a specific node.


2. Check metal certificates. Do not buy rolled metal without documents.


3. Do not allow "tack welding". If the project calls for a continuous weld, it must be continuous.

Conclusion: "The reliability of a structure begins with the choice of the right materials. By using certified steel pipes and other rolled metal from trusted suppliers, such as UTMK, you minimize risks at the procurement stage. Good welding is not an expense, but an investment in safety for 50–70 years."

List of standards for quality checking:

• DSTU EN ISO 17637 — Visual inspection of welds.


• DSTU EN ISO 5817 — Quality levels for welding defects.


• DSTU 2766 / GOST 23118 — Steel construction structures.


• DSTU EN ISO 17640 — Ultrasonic testing of welded joints.