Abstract
AbstractThe mechanism of inclusions precipitation of the E690 offshore platform steel, with and without addition of yttrium, was studied using the thermodynamic calculation method. The results show that in the E690 steel in the absence of yttrium, the MnS inclusions were precipitated in the liquid phase at the solidification front. By adding the yttrium, MnS inclusions were replaced by spindle and spherical yttrium-containing oxide and sulfide complex inclusions, and the precipitation sequence of yttrium-containing inclusions in the liquid steel was Y2O3, Y2O2S, and YS. However, Y2S3 inclusions cannot be precipitated in the liquid steel under the experimental conditions. It was also found that Al2O3 inclusions can be formed in the liquid steel with and without addition of yttrium. The thermodynamic calculation results are in accordance with the experimental results.
Highlights
The scientific exploration and exploitation of the ocean resources is proceeding at a greatly accelerated rate [1]
Al2O3 inclusions can be precipitated in the steel without the addition of yttrium, and MnS inclusions adhere to the surface of the Al2O3 inclusions
The MnS inclusions extend along the rolling direction, resulting in the Al2O3 inclusions embedded in the MnS inclusions
Summary
The scientific exploration and exploitation of the ocean resources is proceeding at a greatly accelerated rate [1]. Several investigations have been carried out to control the inclusions in steel, and the main control methods include the elimination and the modification of inclusions. Extensive research has been carried out on the influence of the RE elements lanthanum and cerium on the microstructures and mechanical properties of various test steels [28,29,30]. Yttrium, another reactive element, exhibits some similarities with lanthanum and cerium and displays its own favorable characteristics [31]. The mechanism of inclusions precipitation was clarified by thermodynamic calculation
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