TY - JOUR
T1 - Thermomechanical simulation of the heat-affected zones in welded ultra-high strength steels
T2 - Microstructure and mechanical properties
AU - Afkhami, Shahriar
AU - Javaheri, Vahid
AU - Amraei, Mohsen
AU - Skriko, Tuomas
AU - Piili, Heidi
AU - ZHAO, Xiao Lin
AU - Björk, Timo
N1 - Funding Information:
The authors wish to thank SSAB Europe Co. for providing the base materials used in this research. The help and support of Mr. Matti Koskimäki and Prof. Jari Larkiola for managing the experimental procedures, Mr. Juha Uusitalo in performing the Gleeble simulations, and Mr. Toni Väkiparta in conducting the SEM are highly appreciated. The authors also extend special thanks for the technical support provided by the staff members at the laboratories of LUT Steel Structures and Welding Technology. Vahid Javaheri would also like to thank Jenny and Antti Wihuri Foundation for the personal financial support.
Publisher Copyright:
© 2021 The Authors
PY - 2022/1
Y1 - 2022/1
N2 - Ultra-high strength steels (UHSS) have a determining role in construction and industry. Furthermore, welding as the primary joining process for steel has a similar role in promoting its applications. Therefore, welded UHSS have a vital role in related applications. However, due to their complex microstructures, these steels are more prone to harmful effects of welding heat input on the mechanical properties compared to mild steels. Thus, identifying the correlations between the microstructural transformations triggered by the heat input and the mechanical properties can lead to new insights and hindering the drawbacks. This study investigates the microstructures and mechanical properties of S960 (with a severe softening after welding) and S1100 (with a negligible decrease of the mechanical properties after welding) to understand the mechanisms behind the softening of welded UHSS. Microstructural analysis showed the formation of soft phases, e.g., ferrite and granular bainite, as the primary reason for the softening. Furthermore, tempered forms of martensite and bainite resulted in the simultaneous decrease of hardness and notch toughness. Finally, the applicabilities of two experimental approaches to predict hardness from microstructural constituents were evaluated for welded S960 and S1100 and proved to have relatively good reliability to detect their HAZ softened spots.
AB - Ultra-high strength steels (UHSS) have a determining role in construction and industry. Furthermore, welding as the primary joining process for steel has a similar role in promoting its applications. Therefore, welded UHSS have a vital role in related applications. However, due to their complex microstructures, these steels are more prone to harmful effects of welding heat input on the mechanical properties compared to mild steels. Thus, identifying the correlations between the microstructural transformations triggered by the heat input and the mechanical properties can lead to new insights and hindering the drawbacks. This study investigates the microstructures and mechanical properties of S960 (with a severe softening after welding) and S1100 (with a negligible decrease of the mechanical properties after welding) to understand the mechanisms behind the softening of welded UHSS. Microstructural analysis showed the formation of soft phases, e.g., ferrite and granular bainite, as the primary reason for the softening. Furthermore, tempered forms of martensite and bainite resulted in the simultaneous decrease of hardness and notch toughness. Finally, the applicabilities of two experimental approaches to predict hardness from microstructural constituents were evaluated for welded S960 and S1100 and proved to have relatively good reliability to detect their HAZ softened spots.
KW - Heat-affected zone
KW - Mechanical properties
KW - Microstructure
KW - Ultra-high strength steel
UR - http://www.scopus.com/inward/record.url?scp=85121968179&partnerID=8YFLogxK
U2 - 10.1016/j.matdes.2021.110336
DO - 10.1016/j.matdes.2021.110336
M3 - Journal article
AN - SCOPUS:85121968179
SN - 0264-1275
VL - 213
JO - Materials and Design
JF - Materials and Design
M1 - 110336
ER -