Penetration　behavior　of　slags　with　two　different　kinds　of　chemical　compositions　into　magnesia　refractory brick　was　studied　at 1550℃ by　crucible　test．Secondly，microstructure　of　slag　penetrated　magnesia　refractory brick　was　examined．In　the　penetration　process　of　calcium　aluminosilicate　slag　without　MgO，MgO　grains react　with　the　slag，resulting　in　the　formation　of　spinel　at　the　interface　between　MgO　grains　and　slag． On　the　other　hand，in　the　penetration　process　of　calcium　aluminosilicate　slag　in　which　spinel　was　supersaturated，the　slag　caused　heterogeneous　nucleation，resulting　in　the　formation　of　spinel　on　MgO　grains．lt　has　been　clarified　that　these　different　types　of　reactions　between　MgO　and　slags　influence　greatly　on　the　behavior　of　slag　Penetration．

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The penetration of molten silver into porous refractories was observed directly using a high temperature X-ray radiographic apparatus. Experimental phenomena were analyzed using equations derived from a capillary model. Measured data, such as surface tension, density and sessile drop contact angle of molten silver on an A12O3 plate were obtained under the same conditions as the penetration experiments Molten silver penetrates rapidly into porous refractories and reaches a maximum penetration height in a short time. The penetration height then remains almost constant. Molten silver penetrates unevenly into porous refractories due to the uneven pore size distribution. The minimum external pressure under which molten silver can penetrate into porous refractories, that is the critical pressure, depends on the structure of the porous refractories. Below the critical pressure, molten silver cannot penetrate into porous refractories. Above the critical pressure, the maximum penetration height of molten silver increases linearly with increasing external pressure. Experimental and theoretical investigations on the penetration height were performed in relation to factors such as external pressure, pore structure and pore radius in the refractory and surface tension, density and contact angle of molten silver with the refractory. The penetration of molten metal into a porous refractory can be suppressed by the following : increasing the contact angle of molten metal with the refractory, making the pores smaller than a certain pore radius and a more uniform and sharper pore size distribution. The latter can be obtained by adjusting the constituents and particles size distribution of the raw materials.

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