Evolution of Inclusions in Physically Simulated Heat-Affected Zones of a Weld Metal Used with a 500 MPa Offshore Steel

Abstract:

Non-metallic inclusions in weld metals often have a role inducing the formation of acicular ferrite, which is known to improve the toughness and other properties of the weld metal. The ability of the inclusions to promote the acicular ferrite formation depends on various factors such as chemical composition, morphology and size of the inclusions. In multipass welding, additional thermal cycles affect the inclusions in the pre-existing weld passes, potentially causing compositional and morphological changes in the inclusions. These changes may influence the inclusions’ ability to promote the formation of acicular ferrite. In the current study, the thermal cycles of multipass welding were produced on a single pass weld by physical simulation. Coarse-grained heat-affected zones (CGHAZ-W) in weld metal were simulated using three different cooling times from 800 °C to 500 °C (t_8/5). Inclusions in the heat-affected zones of the weld were analyzed using field emission scanning electron microscope equipped with energy dispersive spectroscope (FESEM-EDS), after which they were classified according to their chemical composition. The results showed that the inclusion content in the weld metal was affected by the thermal cycles. In the CGHAZ-W simulation the number of Mn-bearing inclusions increased compared to the unaffected single-pass weld metal. Increasing cooling time was observed to increase the area fraction of MnS in CGHAZ-W. The increase of these inclusions was expected to affect the microstructure by increasing the acicular ferrite fraction.

• Periodical: Key Engineering Materials (Volume 1040)
• Pages: 47-53
• DOI: https://doi.org/10.4028/p-KPi3DF
• Online since: January 2026
• Authors: Henri Tervo*, Marcell Gáspár, Judit Kovács, Vahid Javaheri, Johannes Sainio, Tuomas Alatarvas, Jukka Kömi, Antti Kaijalainen
• Keywords: Acicular Ferrite, HAZ, Inclusions, Offshore Steel, Welding

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