Heat-treatment of clad steel plate for application of hull structure

• Clad steel (EH40 base and super duplex stainless S32750 steel) was fabricated.
• Quenching and tempering (QT) and normalized heat treatment conditions were used.
• Heating conditions were optimized with lab-scale and verified with large clad steel plate.
• QT gave better mechanical strength and corrosion resistance than normalized heating.

Clad steel plate has good corrosion resistance and mechanical properties arising from the hot rolling of dissimilar metals, such as carbon steel and stainless steel. However, it is difficult to simultaneously achieve good corrosion resistance from the cladding metal (stainless steel) and good mechanical properties from the base metal (carbon steel) because the different steels display opposite behaviours during the heat treatment process. Proper material selection and heat-treatment conditions are necessary for fabricating clad steel plates for application in the hulls of ships. In this study, the optimal heat-treatment conditions for maximizing the corrosion resistance of the metal (S32750) and the mechanical properties of the base metal (EH40) were investigated on the laboratory scale. The quenching and tempering method employing water quenching after treatment at 1080 °C for 1 h/in and air cooling after treatment at 550 °C for ~1–2 h was more effective than normalized heat treatment. The characteristics of the fabricated clad steel plate were evaluated using the selected heat treatment conditions.