Porous refractory cast material, its use and production
A porous refractory cast material contains a closed refractory aggregate fraction having a minimum particle size and a maximum particle size; the ratio of maximum particle size to minimum particle size is 10:1 or less. This closed refractory aggregate fraction comprises all of the porous refractory cast material having a particle diameter greater than 0.1 mm. The porous refractory cast material also contains a binder phase containing refractory selected from calcium aluminate cement, alumina phosphate, hydratable alumina, colloidal silica and combinations thereof. Also disclosed is a metallurgical vessel with an interior lining incorporating the porous refractory cast material.
1. A metallurgical vessel comprising:
a wall;
and a porous refractory cast material consisting of:
85 to less than 95 wt. % of a closed refractory aggregate fraction having a minimum particle size and a maximum particle size, wherein the ratio of maximum particle size to minimum particle size is in the range of 2:1 to 5:1; and
more than 5 to 15 wt. % of a binder phase selected from a group consisting of refractory binder and the refractory binder in combination with an optional material, said refractory binder selected from a group consisting of: calcium aluminate cement, alumina phosphate, alumina formed from hydratable alumina, silica formed from colloidal silica and combinations thereof, wherein said optional material is selected from a group consisting of reactive alumina, calcined alumina, tabular alumina, fused alumina, carbon, silicon carbide, zirconium dioxide, magnesite, fume silica, chromium oxide, and combinations thereof;
wherein the closed refractory aggregate fraction comprises 100 wt. % of the material having a particle diameter greater than 0.1 mm, has a particle diameter of up to 20 mm, and consists of a material selected from the group consisting of alumina, magnesite, zirconia, calcium oxide, silica, spinel, calcium aluminates, mullite, olivine, forsterite, zircon, calcium silicate, alumina zirconia silicate, and combinations of these materials;
wherein the porous refractory has an open porosity in the range of greater than 30 to 60 vol. %; and
wherein the porous refractory cast material forms a liner on an interior surface of the wall and upon contacting molten metal retains tortuous porosity sufficient to constrain the molten metal, said liner attracting slag or impurities thereto thereby limiting oxidation of the molten metal.
2. The metallurgical vessel of claim 1 , wherein 100 wt % of the closed refractory aggregate fraction has a particle size with a diameter of at least 0.2 mm.
3. The metallurgical vessel of claim 1 , wherein the ratio between the size of the smallest particles of refractory aggregate and the largest particles in the binder phase is at least 10:1.
4. The metallurgical vessel of claim 1 , wherein the ratio between the size of the smallest particles of refractory aggregate and the largest particles in the binder phase is at least 2:1.
5. The metallurgical vessel of claim 1 , wherein 100 wt % of the binder phase consists of particles having a size of 100 microns or less.
6. A porous refractory cast material structure comprising:
a first layer comprising a first porous refractory cast material, the first porous refractory cast material consisting of:
85 to less than 95 wt. % of a first closed refractory aggregate fraction having a first minimum aggregate particle size and a first maximum aggregate particle size, wherein the ratio of first maximum aggregate particle size to first minimum aggregate particle size is in the range of 2:1 to 5:1; and
more than 5 to 15 wt. % of a first binder phase selected from a group consisting of a first refractory binder and the first refractory binder in combination with an optional material, the first refractory binder selected from a group consisting of: calcium aluminate cement, alumina phosphate, alumina formed from hydratable alumina, silica formed from colloidal silica and combinations thereof, wherein said optional material is selected from a group consisting of reactive alumina, calcined alumina, tabular alumina, fused alumina, carbon, silicon carbide, zirconium dioxide, magnesite, fume silica, chromium oxide and combinations thereof;
wherein the first closed refractory aggregate fraction comprises 100 wt. % of the material of the first layer having a particle diameter greater than 0.1 mm, has a particle diameter of up to 20 mm, and consists of a material selected from the group consisting of alumina, magnesite, zirconia, calcium oxide, silica, spinel, calcium aluminates, mullite, olivine, forsterite, zircon, calcium silicate, alumina zirconia silicate, and combinations of these materials, and having a first layer minimum aggregate particle size; and
a second layer comprising a second porous refractory cast material, the second porous refractory cast material consisting of:
85 to less than 95 wt. % of a second closed refractory aggregate fraction having a second minimum aggregate particle size and a second maximum aggregate particle size, wherein the ratio of second maximum aggregate particle size to second minimum aggregate particle size is 10:1 or less; and
more than 5 to 15 wt. % of a second binder phase selected from a group consisting of a second refractory binder and the second refractory binder in combination with an optional material, the second refractory binder selected from a group consisting of: calcium aluminate cement, alumina phosphate, alumina formed from hydratable alumina, silica formed from colloidal silica and combinations thereof, wherein said optional material is selected from a group consisting of reactive alumina, calcined alumina, tabular alumina, fused alumina, carbon, silicon carbide, zirconium dioxide, magnesite, fume silica, chromium oxide and combinations thereof;
wherein the second closed refractory aggregate fraction comprises 100 wt. % of the material having a particle diameter greater than 0.1 mm and consists of a material selected from the group consisting of alumina, magnesite, zirconia, calcium oxide, silica, spinel, calcium aluminates, mullite, olivine, forsterite, zircon, calcium silicate, alumina zirconia silicate, and combinations of these materials;
wherein the first minimum aggregate particle size is greater than the second aggregate maximum particle size; and
wherein the porous refractory material structure has an open porosity in the range of greater than 30 to 60 vol. %, forms a lining for a high-temperature metallurgical vessel, and, upon contacting molten metal, retains tortuous porosity sufficient to constrain the molten metal.
7. Process for the minimization of oxidation of a molten metal, comprising
a) transferring molten metal to a vessel having a lining structure comprising a porous refractory cast material according to claim 1 , and
b) transferring the molten metal out of the vessel.