| 摘要 |
<p>The invention concerns a fibre yarn comprising the following constituents, within the limits defined below, expressed in weight percentages: SiO2 54.5 to 58 %; Al2O3 12 to 15.5 %; SiO2 + Al2O3 70 to 73 %; CaO 17 to 25 %; MgO 0 to 5 %; RO = CaO + MgO 21 to 28 %; R2O = Na2O + K2O + Li2O up to 2 %; TiO2 less than 1 %; Fe2O3 less than 0.5 %; B2O3 up to 3 %; F2 less than 1 % and such that the ratio R1 = Al2O3/CaO is less than 0.7, and when SiO2 is more than 57 %, the boron proportion B2O3 is higher than 2 %.</p> |
