Physical Simulation of Heat-Affected Zones in a Weld Metal Used with 500 MPa Offshore Steel

Tervo, Henri and Gáspár, Marcell and Kovács, Judit and Kaijalainen, Antti and Javaheri, Vahid and Sainio, Johannes and Kömi, Jukka (2025) Physical Simulation of Heat-Affected Zones in a Weld Metal Used with 500 MPa Offshore Steel. In: The 65th SIMS Conference on Simulation and Modelling SIMS 2024, 2024.09.11-12, Oulu.

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Abstract

Offshore steels are engineered to have an outstanding combination of high strength and toughness to withstand extreme conditions needed in offshore and marine applications. Multiple welding passes may be needed when welding thick steel sections. In this case, microstructures of pre-existing passes are affected by the thermo-cycles caused by the subsequent passes. These heat-affected zones (HAZ) in the weld metal are less studied than the HAZs in the base metal next to the weld. HAZs after real welding process are relatively narrow and that way challenging to study and test reliably. Physical simulation provides an opportunity to produce different kinds of HAZs on sufficiently large area for various types of microstructural and mechanical properties characterization. Moreover, the effect of different welding methods and parameters can be easily studied by adjusting the simulation settings. Therefore, the aim of this study was to produce the coarse-grained (CGHAZ-W), intercritical (ICHAZ-W) and intercritically reheated heat-affected zones of the weld metal (ICCGHAZ-W) using physical simulation. Submerged arc welding (SAW) method was used to produce the original weld. HAZs with 2 different cooling times from 800 °C to 500 °C (t8/5 = 5 and 30 s) were simulated utilizing Gleeble 3500 thermomechanical simulator. Microstructures were characterized using a Zeiss Sigma field emission scanning electron microscope. The results indicated that the original weld metal contained acicular ferrite nucleated on oxide inclusions, and thermal cycles induced microstructural changes in the weld metal, with each simulation variant resulted in distinctive features. Microstructures obtained by the physical simulation were supported by the numerical simulation results carried out by JMatPro software.

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