Glass-to-metal seal formation of lithium tungstate. Due to its low thermal expansion coefficient, matched to glass, tungsten is frequently used for glass-metal bonds. Tungsten forms satisfying bonds with glasses with similar thermal expansion coefficient such as high-borosilicate glass. The surface of both the metal and glass should be smooth, without scratches. Tungsten has the lowest expansion coefficient of metals and the highest melting point. 304 Stainless steel forms bonds with glass via an intermediate layer of chromium(III) oxide and iron(III) oxide. Further reactions of chromium, forming chromium silicide dendrites, are possible. The thermal expansion coefficient of steel is however fairly different from
Flux melting Flux melting In igneous petrology, flux melting occurs when water and other volatile components are added to hot solid rock. In engineering and metallurgy, flux is a substance, such as salt, that produces a low melting point mixture with a metal oxide. In the same way, the addition of water and other volatile compounds to rocks composed of silicate minerals lowers the melting temperature of those rocks. In subduction zones, the ultramafic rock of the upper mantle is melted by the addition of volatiles from the down-going plate. The subducting slab of oceanic crust carries water and other volatiles into