40th International Conference on Production Engineering of Serbia
ICPES 2025
Nis, Serbia, 18-19th september 2025
EFFECT OF THE MAXIMUM TEMPERATURE ON THE HARDNESS AT THE HEAT AFFECTED ZONE OF THREE DIFFERENT CARBON STEELS AFTER A SLOW COOLING
Nima Poursalimi, Juan Carlos Ferrero-Taberner, Lorenzo Solano-García, Norberto Feito-Sánchez, Miguel Ángel Pérez-Puig, Fidel Salas-Vicente
DOI: 10.46793/ICPES25.165P
The welding of carbon steels causes microstructural changes at the heat affected zone that modify the behaviour of the material during its in-service life. Usually these changes are associated with an increase in the hardness and a loss of tenacity that, despite being within an acceptable range, should be considered and predicted when the weld is part of a highly demanding application. Unfortunately, the common Continuous Cooling Transformation (CCT) diagrams employed for heat treatments are not always a reliable data source as the heat cycle in welding is different from that of a quench, with higher temperatures and no soaking time. This implies that hardness at the heat affected zone (HAZ) will not depend only on the cooling rate but also on the heating rate and the maximum temperature at each point of the HAZ, parameters that control the transformation of perlite to austenite and the homogenization of austenite. This paper studies the effect of the maximum temperature at each point of the HAZ on the hardness of three different steels (S355, C45 and S700MC) when a relatively slow cooling rate is assured. This has been done by heating different samples inside a furnace till the selected maximum temperatures are reached and immediately cooling them under an air flow. The results show that once a certain temperature is reached, a transition from low to high hardness takes place. This transition is related to grain coarsening and the end of the austenization process, although, when compared to an oil quench, other changes like the apparition of Widmanstätten microstructures are also present
Welding, steel, heat affected zone, hardening, overheating, CCT diagram, Widmanstätten
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