Evaluation of High Strength Cast Steel Welded Joints Suitable to Mooring Components

Abstract

This work investigates the performance of high strength cast steel welded joints to confirm their feasibility for application in mooring components. Three welded joints, with ultimate tensile strength in the range of 700 to 900 MPa, were obtained by the shielded metal arc welding process, the most applied in repair operation. After welding, a post welding heat treatment was performed to relieve the residual stresses. The results obtained in tension, impact Charpy-V, and hardness tests, at different positions of the heat affected zone were compared with equivalent welded joints performed with rolled steels currently applied in mooring chain links. These results showed that cast steels can obtain results equivalent to the rolled steels. Furthermore, the composition of cast steels for more stringent requirements (UTS > 860 MPa) is adjusted with higher nickel contents, while rolled and forged steels show increased C, Cr, and Mo contents. As a consequence, a refined microstructure with excellent impact toughness was obtained. Thus, these steels present a high potential to be used in this application contributing to reduce manufacturing costs.

Key-words:
Cast steel; Welded joint; Mechanical properties; Mooring components