Processing of Low-Carbon Cast Steels for Offshore Structural Applications

Abstract

Cast steels with carbon contents of approximately 0.05%, 0.1%, and 0.2% (low-carbon steels) were processed. The investigated steels were first cast. Fully lath martensite was obtained after austenitization and water quenching of the cast steels. The mechanical properties of ∼0.05% carbon steel did not significantly change after tempering at 500°C, 540°C, and 580°C. The strength of ∼0.1% carbon content steel decreased after tempering for 2 h to 3 h at 580°C, and then stabilized at longer tempering times of 6 h. The ductility remained almost constant through the processes. The Charpy impact energy increased when the tempering time was increased from 2 h to 4 h, but decreased remarkably after tempering for 6 h. By increasing the tempering temperature from 450°C to 550°C, the ductility of the ∼0.2% carbon content steel increased, followed by a drop at 600°C. The strength of this steel was the highest at 450°C, but decreased and stabilized at tempering temperatures of 500°C to 600°C. The Charpy impact energy increased monotonically and reached its highest value at 600°C. Finally, the applicability of the investigated cast steels for offshore structures was assessed in detail.

Keywords:

• Carbon
• Low
• Offshore
• Steel
• Structure