Abstract
Improving the mechanical performance of low-carbon offshore steel is of great significance in shipbuilding applications. In this paper, a new Cu-Cr microalloyed offshore structural steel (FH36) was developed based on EH36. The microstructure, mechanical properties, and fatigue crack propagation properties of rolled plates of FH36, EH36, and normalizing rolled EH36 plates (EH36N) manufactured by a thermo-mechanical control process (TMCP) were analyzed and compared (to simplify, the two rolled specimens are signified by FH36T and EH36T, respectively). FH36T showed an obvious advantage in elongation with the value of 29%, 52.2% higher than the EH36T plates. The normalizing process led to a relatively lower yield stress (338 MPa), but substantially increased the elongation (33%) and lessened the yield ratio from 0.77 to 0.67. Electron back-scattered diffraction (EBSD) analysis showed that SFs of the deformation texture of FH36T and EH36N along the transverse direction (TD) and normal direction (ND) were much higher than those of the EH36T plate, which enhanced the lateral movement ability in the width and thickness direction, enhancing the ductility. Moreover, FH36 plates showed a better fatigue crack propagation resistance than rolled EH36 plates. The formation of the jagged shape grain boundaries is believed to induce a decrease of effective stress intensity factor during the fatigue crack propagation process.
Highlights
Accepted: 17 November 2021In recent years, many strategies have been under development for large-scale, lightweight, environmentally friendly ocean vessels with deep ocean accessibility
This paper developed new kind of offshore structural steel rolled plate product, FH36T, based on micro-adding Cu and Cr elements, and compared the microstructure and mechanical performance of EH36T (EH36 rolled plates prepared by thermo-mechanical control process (TMCP)) and EH36N
The addition of Cu-Cr elements significantly improved the ductility, which increased by 52.2% compared to EH36T, and both yield strength and ultimate strength were enhanced slightly with the values of 438 MPa and 553 MPa, respectively
Summary
Accepted: 17 November 2021In recent years, many strategies have been under development for large-scale, lightweight, environmentally friendly ocean vessels with deep ocean accessibility. Especially large ocean-going ships, are often confronted with strong winds and waves during their navigation. This often exposes the hull to complex stress conditions due to the huge impact forces and periodic alternating loads from different directions. To ensure the safety and work-reliability of ocean vessels, major steel manufacturers are only focusing on improving the coupling performance of strength, ductility, and fatigue resistance of offshore structural steels [1,2]. As a typical low carbon bearing high strength offshore steel, EH36 possesses various advantages which make it widely used in the marine industry, such as high strength, comprehensive performance, and the ability to reduce the dead weight of the hull. EH36 is a kind of microalloyed low carbon steel with Mn as the main alloying element
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