Development of high impact toughness offshore engineering steel by yttrium-based rare earth addition

ABSTRACT

The effect of yttrium-based rare earth on the inclusions and impact toughness of EH36 offshore engineering steel were investigated by scanning electron microscopy, electron backscattered diffraction and electron probe x-ray microanalysis techniques. It was found that impact toughness and isotropy of EH36 were enhanced significantly by rare earth addition. The longitudinal and transverse impact toughness at −60°C were increased by 33.5% and 113.7%, respectively. Moreover, the differences between the longitudinal and transverse textures decrease significantly with the addition of rare earth, the low-temperature impact property isotropy increased by 61.1%. Meanwhile, rare earth can modify elongated irregular MnS inclusions into small spherical regular RE-inclusions. Most of the RE-inclusions are within 3μm in diameter, which account for 97.84% of total inclusions. With the addition of rare earth in EH36 offshore engineering steel, the average effective grain size was reduced by 9.7%.

KEYWORDS:

• Offshore engineering steel
• EH36 steel
• yttrium-based rare earth
• inclusions
• impact toughness
• grain size

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (grant numbers 51974139 and 51664021), and the Major Science and Technology Research and Development Special Project of Jiangxi Province (grant number 20194ABC28011).