Qc. Horn et al., REACTIVE PHOSPHIDE INCLUSIONS IN COMMERCIAL FERROSILICON, Metallurgical and materials transactions. B, Process metallurgy and materials processing science, 29(2), 1998, pp. 325-329
Citations number
10
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
The goal of this work was to determine the origin of phosphine gas (PH
3), which has been reported to be generated from wet, commercial ferro
silicon alloys containing similar to 75 wt pet Si. Based on previous w
ork, it is suspected that PH3 evolves when phosphides present within t
he alloy react with atmospheric moisture or water. Reactive phosphides
have been identified in synthetic ferrosilicon alloys, which contain
higher amounts of phosphorus than are typically present in commercial
alloys. Therefore? reactive phosphides in commercial FeSi75 alloys are
expected to be important to the evolution of PH3 from these alloys. T
o identify the role of reactive phosphides in the evolution of PH3 fro
m commercial FeSi75 alloys, the microstructures of four commercial and
two synthetic FeSi75 ferrosilicon alloys were investigated. Reactive
phosphides were observed in each of the commercial alloys and characte
rized with respect to composition, morphology, and location within the
microstructure. The phosphides observed in all of the commercial allo
ys contained aluminum, calcium, and magnesium. The phosphides had incl
usion-like morphologies and were located on the silicon/zeta (high-tem
perature FeSi2) interfaces at microcracks. The microstructural feature
s observed support the hypothesis that atmospheric moisture penetrates
ferrosilicon, reacting with the phosphide inclusions to produce PH3.
A possible mechanism describing the spontaneous crumbling sometimes ob
served in ferrosilicon alloys is also presented.