Impact of the oxidation state of iron on the tensile strength of stone wool fibres

Stone wool samples of various chemical compositions and Fe 3+ /ΣFe ratios (=0.03―0.83) were produced using the cascade spinning method, and subsequently tested in uniaxial tension to obtain tensile strength data. The composition of the stone wool fibres resembled that of natural basalt. Stone wool fibres with the highest tensile strength were found in the most oxidised samples. An increase of the Fe 3+ /ΣFe ratio enhanced the tensile strength of the stone wool fibres when production conditions, e.g. total iron content, melting temperature and drawing atmosphere, were maintained constant. The Fe 3+ /ΣFe ratios of the stone wool fibres was controlled by the melting atmosphere and crucible materials. The origin of the increase in the tensile strength is discussed in terms of the relation of the oxidation state of iron both to melt homogeneity and to the glass structure.