A pulverulent insulating and purifying covering (3) for the surface of liquid metal (2) contained in a metallurgical receptacle (1), comprises a layer (4) which includes at least one metallic oxide of basic character, capable of reacting with oxide inclusions contained in the liquid metal. This layer (4) covers a first layer (5) in direct contact with the liquid metal and including also at least one such metallic oxide and additionally a flux (6) in a quantity sufficient to render fluid this first layer (5) under the influence of the heat of the liquid metal (2). The metallic oxide is selected from the group consisting of lime, magnesia, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, dolomite and a mixture thereof. Each layer (4, 5) includes a mixture of lime and magnesia. The first layer (5) in contact with the liquid metal (2) includes a substantial amount up to 30% by weight of flux, while layer (4) which covers the first layer (5) is substantially free from flux. There is added, either continuously or periodically, to the first layer (5) flux sufficient to maintain the first layer in a fluid condition under the influence of the heat of the liquid metal (2). This can be done by feeding the flux through a conduit which opens below the lower surface of the second layer (4), for example by introducing the flux into a casting tube (9) through which the liquid metal (2) has been introduced into the metallurgical receptacle (1) , or by introducing the flux through both layers ( 4, 5) and into the liquid metal so that the flux rises to the underside of the first layer (5).
Relatively resilient flux encasings for solder preforms are obtained when a mixture of 5 to 30 wt. % potassium silicate having a molar ratio of K.sub.2 O:SiO.sub.2 ranging from 1:2.5 to 1:4.5, 0.5 to 10 wt. % concentrated phosphoric acid, 0.1 to 5 wt. % boric acid and 0 to 10 wt. % finely divided silicon dioxide, with the remainder water, is used as the binder.
A process for continuously casting steel wherein liquid steel is teemed from a ladle through a shroud into the pour box section of a tundish and poured from the tundish through one or more outlets remote from the pour box, and wherein the surface of the steel in the tundish is covered with a first flux in the area of the pour box and with a second flux in the remaining areas of the tundish. The flux used in the pour box area has a higher melting temperature than the flux used in the remaining areas. Preferably all fluxes used are basic fluxes containing CaO and Al.sub.2 O.sub.3.
The tundish flux composition of the invention employs solid recycled ladle metallurgy furnace (LMF) slag as a fluidizing and refining base ingredient in a mixture of raw materials. The preferred recycled LMF slag material comprises about 35% to about 65% CaO, about 10% to about 35% Al.sub.2 O.sub.3, about 1% to about 10% SiO.sub.2, about 3% to about 15% MgO, about 0.3% to about 10% FeO, about 0.1% to about 5% MnO, about 0.1% to about 0.15% P.sub.2 O.sub.5, and about 0.1% to about 0.5% S. The tundish flux composition comprises from about 10% to about 80% of recycled LMF slag with the balance being raw materials selected from a calcium oxide source, a fluorine source, a magnesium oxide source, a carbon source, a silica source, a sodium source, a potassium source, and mixtures of these raw materials.
The tundish flux composition of the invention employs solid recycled ladle metallurgy furnace (LMF) slag as a fluidizing and refining base ingredient in a mixture of raw materials. The preferred recycled LMF slag material comprises about 35% to about 65% CaO, about 10% to about 35% Al.sub.2 O.sub.3, about 1% to about 10% SiO.sub.2, about 3% to about 15% MgO, about 0.3% to about 10% FeO, about 0.1% to about 5% MnO, about 0.1% to about 0.15% P.sub.2 O.sub.5, and about 0.1% to about 0.5% S. The tundish flux composition comprises from about 10% to about 80% of recycled LMF slag with the balance being raw materials selected from a calcium oxide source, a fluorine source, a magnesium oxide source, a carbon source, a silica source, a sodium source, a potassium source, and mixtures of these raw materials.
