Evaluation of different alloying concepts to trace non-metallic inclusions by adding rare earths on a laboratory scale

Abstract

Different alloying concepts to trace deoxidation products, mainly aluminium oxides, using rare earth elements (REEs), were tested on the laboratory scale by melting trials with a high-frequency remelting furnace. Lanthanum and Cerium, which belong to the group of light REEs, were used for these experiments. The formed multiphase inclusions were characterized by scanning electron microscopy with energy dispersive spectroscopy. Concerning the higher atomic numbers of REEs, traced non-metallic inclusions (NMIs) seem brighter than the steel matrix compared to deoxidation products. REE-traced aluminium oxides showed a primarily heterogeneous and almost globular morphology. The mean equivalent circle diameter of REE-containing NMIs is for all trials similar and is about 2 µm. The experimental results pointed out that the recovery rates of the various alloying concepts differ only slightly. In contrast, the values mainly depend on the surface-tovolume ratio and the amount of oxygen in the melt.

Optimization of the Two‐ and Three‐Dimensional Characterization of Rare Earth‐Traced Deoxidation Products

“…The ternary systems in Figure 9 show the different distributions of RE-containing Al-oxides of the cross-sections and filters from automated SEM/EDS measurements of each sample. The compositions of the majority of the NMIs in cross-section samples were in the range of complex REAl 11 O 18 inclusions (19.2 wt% RE, 41.0 wt% Al, and 39.8 wt% O), similar to the distribution described in Thiele et al [32] In addition, accumulations of several inclusions were detected in all samples; these had similar compositions to that of the complex REAlO 3 (65.0 wt% RE, 12.6 wt% Al, and 22.4 wt%). Particularly for Sample 6, many inclusions were found with compositions similar to that of the complex REAlO 3 .…”

“…In Samples 2, 4, and 6, REs were wrapped in Al foil, and in Sample 5, ferrocerium was used as an alloying element. The influence of the alloying concepts on the output of REs has previously been discussed by Thiele et al [32] The composition in terms of REs varies across the six samples, depending on the various alloying concepts and furnaces used.…”

“…Besides Al, either La or Ce was additionally alloyed; hence, the deoxidation products, Al 2 O 3 NMIs, were traced using these elements. A detailed description and a schematic illustration of the single states of the samples’ production in an HFR furnace could be found in Thiele et al [ 32 ]…”

“…In Samples 2, 4, and 6, REs were wrapped in Al foil, and in Sample 5, ferrocerium was used as an alloying element. The influence of the alloying concepts on the output of REs has previously been discussed by Thiele et al [ 32 ]…”

“…Besides Al, either La or Ce was additionally alloyed; hence, the deoxidation products, Al 2 O 3 NMIs, were traced using these elements. A detailed description and a schematic illustration of the single states of the samples' production in an HFR furnace could be found in Thiele et al [32] The production route differs for Sample 6. This sample was produced in a resistance-heated Tammann-type furnace (Ruhrstrat HRTK 32-Sond.)…”