Effect of arc welding on microstructure and mechanical properties of S960 MC to S960 QT ultra-high strength steel dissimilar joints
Ayub, Haseeb (2026)
Diplomityö
2026
School of Energy Systems, Konetekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2026051545603
https://urn.fi/URN:NBN:fi-fe2026051545603
Tiivistelmä
The use of ultra-high strength steels (UHSS) has been speeding up in heavy machinery, crane production, transportation, load-bearing construction and other areas due to the demand for light weight and high-performance structural components. This work specifically focuses on the industrial problem of joining dissimilar S960 grade steels (S960MC and S960QT), which are commonly required to be joined together in engineered assemblies to achieve the desired structural properties and to minimise cost and weight.
In this thesis, the effect of robotic gas metal arc welding (GMAW) on the evolution of microstructure and properties of these dissimilar joints were studied. The study characteristically identifies a formation of coarse grains in heat-affected zone (HAZ) of the 6 mm and 8 mm plates in both plate thickness sizes.
Experimental results indicate that the S960QT side is more sensitive to the effect of thermal cycles, as the hardness decreases to about 230-260 HV. Tensile testing showed that the 6 mm joints had an ultimate tensile strength (UTS) of 952 MPa, whereas the 8 mm joints had lower UTS value of 823 MPa, probably because they had higher heat input and lower cooling rates. The results are important for the upgradation of industrial welding standards and design guidelines to high strength structural applications.
In this thesis, the effect of robotic gas metal arc welding (GMAW) on the evolution of microstructure and properties of these dissimilar joints were studied. The study characteristically identifies a formation of coarse grains in heat-affected zone (HAZ) of the 6 mm and 8 mm plates in both plate thickness sizes.
Experimental results indicate that the S960QT side is more sensitive to the effect of thermal cycles, as the hardness decreases to about 230-260 HV. Tensile testing showed that the 6 mm joints had an ultimate tensile strength (UTS) of 952 MPa, whereas the 8 mm joints had lower UTS value of 823 MPa, probably because they had higher heat input and lower cooling rates. The results are important for the upgradation of industrial welding standards and design guidelines to high strength structural applications.