The Behaviour of Selenium Impurities During the Addition of Se‐Containing Manganese to Steel Melt

Abstract

Manganese is an important alloy addition for alloy steels. It is normally added to steel melts as ferromanganese. However, for the adjustment of melt composition, manganese metal is used as a trimming addition since it has lower levels of impurities than ferromanganese. The manganese used for this purpose is obtained from the electrolytic processing route wherein selenium-containing additives are added to the electrolyte bath to improve the current efficiency. This practice introduces selenium to the manganese metal. Given that selenium and its compounds are potentially toxic and damaging to the work place and environment, effluents have to be treated in a controlled manner. In order to determine how selenium typically distributes between molten steel, slag and gas phases, a laboratory-scale experimental study was carried out to evaluate the deportment of selenium following the addition of selenium containing manganese to the steel melt. Contaminated commercial manganese metal, as well as Mn-AI-Se spiked briquettes with different selenium contents were added to steel melts at 1600 "O. Selenium recovery to the solidified steel samples varied from 16% to 75%, depending on selenium levels of additions. Owing to the high vapour pressure of selenium, significant amounts of the selenium added to the melt evaporated, reacting with air to form selenium dioxide. SEM analysis of the solidified steel samples revealed that the selenium was largely present as manganese selenide (MnSe) in the form of spherical inclusions within the iron matrix. A thermodynamic assessment on the potential formation of possible selenium compounds within the steel melt suggests that the most stable selenium compound under the test conditions is MnSe, in accord with experiments.

Hot Workability of as-Cast High Manganese-High Carbon Steels

“…The hot ductility curve of stainless steel 1.4301 (18%Cr-8.7%Ni) tested using a constant cooling rate of 3 K/s from the melting to the test temperature and the same strain rate [13] is also shown for comparison. The ZDT and ZST of the steel 1.4301 are about MnS and MnSe [14] are stable compounds. MnS and MnSe form unlimited solutions in the solid and liquid states in the MnS-MnSe phase diagram [16].…”

“…Selenium in the steel could come from the Mn metal used as manganese source. It has been reported that selenium-containing additives are commonly added to the electrolyte as seleneous acid in order to improve the production efficiency of the electrolytic manganese metal [14]. The manganese produced in this process can become significantly contaminated with Se (e.g.…”

Conventional and Tailored Mn-Bearing Alloying Agents for the Production of High Manganese Steels

“…Selenium originates from the aqueous winning electrolysis and largely evaporates during alloying of steel melts thus causing potential environmental and working place hazards in elemental or compound form. [2] Hydrogen, also resulting from the aqueous electrolysis, is a critical impurity, which many high manganese steel grades are sensitive to. Its content is lowered by effusion annealing of EMM.…”

“…Electrolytic manganese metal (“EMM”) features the highest chemical purity, apart from selenium and hydrogen in some EMM grades. Selenium originates from the aqueous winning electrolysis and largely evaporates during alloying of steel melts thus causing potential environmental and working place hazards in elemental or compound form . Hydrogen, also resulting from the aqueous electrolysis, is a critical impurity, which many high manganese steel grades are sensitive to.…”

Influence of Selenium on the Internal Oxidation of Fe–Si–Al–C Alloy

“…Selenium can be introduced into the melts in the steel processing route, normally as impurity in the manganese metal. 9) About some positive effects of the selenium on the texture formation and the magnetic properties of the nonoriented electrical steels have already been reported. It is likely that the growth of the grains with soft magnetic orientations near the plane (001) is to be enhanced.…”