Discovery and identification of arsenic removal products from molten steel by adding rare earth

The use of scrap steel is bound to increase significantly in the following decades to reduce carbon emissions. However, the enrichment of residual elements in steel production has become a severe problem in recycling scrap steel. Arsenic compounds formed in La-added molten steel were investigated by simulation and experiments, and two of them were identified for the first time. The arsenic compounds turned out to be mainly La-S-As, La-As, and LaAsO4. The crystallographic system of La-S-As was certified cubic with a lattice constant of 0.6060 nm. La-S-As can be considered a solid solution resulting from randomly replacing S atoms of LaS with As, and its chemical formula was proved to be La4S3As. The La -As binary compound was identified as cubic with a lattice constant of 0.6162 nm, and its chemical formula was determined as LaAs. La4S3As started to form in molten steel and aggregated to generate large clusters that floated up mostly. It provides a new strategy for reducing residual elements represented by arsenic in molten steel. LaAsO4 and LaAs were initially generated during solidification and preferred to precipitate at grain boundaries. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The use of scrap steel is expected to increase in order to reduce carbon emissions. However, the enrichment of residual elements in steel production during recycling has become a problem. This study investigates the formation of arsenic compounds in La-added molten steel, identifying two compounds - La-S-As and La-As - for the first time. These compounds mainly consist of La-S-As, La-As, and LaAsO4, with La4S3As identified as a solid solution resulting from the replacement of S atoms with As in LaS. La4S3As started to form in molten steel and aggregated to generate large clusters that floated up mostly, providing a new strategy for reducing residual elements in molten steel represented by arsenic.