It is known [1][2][3][4] that the life of a steel-teeming ladle lining is increased by replacement of slag by a heat-insulating packing. Laboratory investigations have been performed on the reaction of a number of heat-insulating materials with ladle refractories [5]. This article gives the results of the performance of heavy-duty steel-teeming ladles with use of certain heat-insulating packings.The tests were performed in 180-ton steel-teeming ladles of the Novolipetsk Metallurgical Factory. By means of a special device (or converter offtake), we restricted entry of slag into the ladle to a layer no thicker than 40-100 mm. The following heat-insulating packings were used: roasted vermiculite, schungisite gravel, blast-furnace slag, and crushed chamotte lightweight artifacts. The amount introduced ensured formation of a layer 100-150 mm thick.The melt formed on the metal surface during casting differs from the initial composition of the packing. It additionally contains residual steelmaking slag and secondary slag (supernatant products of steel refining, and components of the dissolved lining). The melt is saturated with oxides of silicon, calcium, aluminum, iron, manganese, and certain other oxides, depending on the brand of steel being cast. Thus even when we ensure that the packing has an inert composition, the melt contains some amount of the components which destroy chamotte and acid linings.We investigated the reaction of the packings with refractories both in individual smeltings and in complete ladle campaigns. In the first case (before sliding gates were adopted at the factory), we measured the wear of chamotte stopper pipes from the slag zone, where contact of the slag with the refractory is most prolonged. Table 1 lists the results of these measurements. After service, such pipes characteristically had the shape of a cone tapering downward, because the layer of inert packing was located at the melt surface.It will be seen from Table 1 that all the materials tested attack the refractory to a less extent than converter slag. The greater corrosiveness of blast-furnace slag is due to its high calcium oxide content. The refractoriness of crushed chamotte lightweight artifacts is higher than the temperature of liquid steel, therefore its components do not enter the melt at the metal surface; this induces fairly high wear of the lining.Petrographic investigations showed that fractures of stopper pipes after service exhibit a zonal structure with formation of a least altered zone, a working zone, and a zone of slag crust. Regardless of the type of packing, the structures of the first two zones are similar to that of theinitial material and consist of a cryptocrystalline mass with an overall refractive index N = 1.565 • 0.005. We also observe slightly altered quartz grains (1-2%); their peripheries exhibit thin fringes of metastable, outwardly structureless cristobalite.When vermiculite is used (specimen 1) the thickness of the working zone is 5-6 mm, for schungisite gravel (specimen 2) it is 10-12 mm, whereas ...
