How can the weldability of an old IPN beam be verified in the laboratory?

Home • Laboratoire d’expertise des matériaux BTP • Old IPN weldability

Assess the risk before making any welding decision

La Soudabilité en acier d’un ancien IPN ne peut pas être déduite d’un simple examen visuel ni d’une hypothèse sur l’âge de l’ouvrage.

Dans un projet de réhabilitation, de renforcement ou de réemploi acier diagnostic, un IPN ancien peut présenter une composition chimique hétérogène, des niveaux de carbone équivalent élevés, des défauts internes, des zones corrodées ou une microstructure défavorable au soudage. Ces paramètres influencent directement le risque de fissuration, la tenue de la zone affectée thermiquement et la conformité de l’assemblage futur. Chaque décision technique engage la responsabilité du professionnel : bureau d’études, maître d’ouvrage, entreprise travaux ou acteur du réemploi.

Identify the grade and equivalent carbon

The first step is to determine the steel composition using suitable elemental analysis, then estimate the equivalent carbon in steel. For old sections, the theoretical grade is often unknown or insufficiently documented; only laboratory characterization can secure the material assumption.

Combine chemical, micrographic and mechanical analysis

The diagnosis relies on complementary methods: composition analysis using elemental techniques, carbon and sulfur determination, metallographic observations under an optical microscope, hardness measurements, and SEM-EDX examinations to characterize the surface, inclusions or corrosion products. Depending on the project’s requirements, the laboratory may also compare several areas of the same section to detect material heterogeneity or localized deterioration likely to affect welding.

Secure the design, execution and compliance

Having the weldability of steel in an old IPN beam checked upstream helps reduce site risks, avoid costly rework and justify technical choices to stakeholders.

For the structural design office, it is a way to secure calculation assumptions and connection detailing.
For the project owner, it is a lever for controlling risk, safety and compliance.
For the contractor, it makes it possible to adapt the process, preheating, preparation or even отказаться from welding if the metallurgical condition requires it.

Have feasibility confirmed by a laboratory assessment

A specialized laboratory can establish a feasibility assessment based on objective measurements and observations. The approach combines metallurgical analysis for construction, composition determination, micrographic examination, hardness testing, search for corrosion-related alterations and, where needed, laboratory weldability testing. The goal is to identify welding limits, assess the level of risk and guide the decision: weld with precautions, adapt the procedure, limit the loads or exclude the element from structural reuse.

Examine the metallurgical and condition state of the component

Weldability also depends on the microstructure, the presence of inclusions, local heterogeneity, measured hardness and surface condition. Old corrosion, deposits, contamination or loss of thickness can degrade welding behavior. Tools such as optical microscopy, SEM-EDX, hardness measurement or surface chemical analysis make it possible to objectify these factors and avoid decisions based on assumptions.

Look for corrosion, deposits and surface defects

Lorsque l’IPN (ou poutre acier) provient d’un bâtiment existant, l’état de conservation doit être documenté. Des investigations de surface et de corrosion permettent d’identifier la nature des dépôts, l’origine probable d’une attaque, le degré d’oxydation et la compatibilité avec une opération de soudage ou de remise en état. Des techniques telles que MEB-EDX, ICP, XPS ou observations topographiques sont utiles pour distinguer une simple oxydation superficielle d’un endommagement plus critique pour la sécurité ou la durabilité.

Support a PEMD assessment and a reuse strategy

Within a PEMD assessment and reuse approach, laboratory analysis helps distinguish sections that can be recovered from those that should not be reintroduced into the structure. It provides objective evidence to decide between reuse, transformation, limited use or scrapping. This technical traceability is particularly useful in demanding rehabilitation projects where every decision engages the responsibility of those involved.

Provide the useful information and request expert advice

To start the study, it is recommended to provide the usage context, the profile dimensions, the known or presumed origin of the element, the exposure conditions, any corroded areas, the type of assembly planned, and the site constraints. The laboratory can then define an analysis program proportionate to the stakes: material characterization, corrosion testing, microstructural examination, hardness measurement, and an assessment of weldability. Request a quote, have the IPN beam analyzed, have the grade confirmed and contact an expert help you move forward on a solid technical basis.

Frequently asked questions

How can the weldability of an old IPN beam be verified in the laboratory before reuse or on-site modification?

To verify the weldability of an old IPN beam, its actual grade must be characterized, its chemical composition measured, the Ceq calculated, its microstructure observed, its hardness checked and any effects of corrosion or aging investigated. If necessary, the laboratory supplements this with surface examinations and targeted investigations into fracture or defects. This approach makes it possible to determine whether welding is feasible and what precautions must be imposed on the project.

Which parameters really determine the weldability of an old IPN-type steel section?

The key parameters are the actual chemical composition, the Ceq, the microstructure, hardness, the presence of inclusions or segregations, as well as the corrosion and surface condition. Together, they make it possible to assess the metallurgical risk associated with welding an old IPN beam.

What technical means does a laboratory use to diagnose an old IPN beam?

A laboratory generally uses chemical analysis, metallography, hardness measurement and surface examinations. When in doubt, it supplements these with investigations into corrosion, local defects or the origin of a failure in order to provide a technically supported feasibility opinion.

Why have this assessment carried out before starting a rehabilitation or reuse project?

The preliminary assessment makes it possible to make a documented decision before work begins, limit the risk of non-compliance, and secure a reuse strategy. It turns material uncertainty into actionable technical data for design and execution.

How can you quickly launch a feasibility study for an old weldable IPN beam?

To begin the study, you need to describe the project, provide a sample or arrange for sampling, then request an analysis program suited to the level of risk. The goal is to obtain a clear opinion on weldability and on the precautions to apply before any intervention.