Refractory product
Provided is a refractory product which is not impregnated with pitch or the like, wherein it has higher corrosion-erosion resistance and thermal shock resistance as compared to a refractory product subjected to pitch or the like-impregnation treatment. The refractory product which is not impregnated with tar or pitch is characterized in that, in terms of values of physical properties of a sample of the refractory product as measured after heat-treating the sample in a non-oxidizing atmosphere at 1200° C.: an apparent porosity is 7% or less; a total void volume of pores having a pore diameter of 1 μm or less is 80% or more of an integrated void volume of pores of the entire sample of the refractory product; and a gas permeability is 50×10 −17 m 2 or less.
1. A refractory product which is not impregnated with tar or pitch, wherein in terms of values of physical properties of a sample of the refractory product as measured after heat-treating the sample in a non-oxidizing atmosphere at 1200° C.,
an apparent porosity is 7% or less;
a total void volume of pores having a pore diameter of 1 μm or less is 80% or more of an integrated void volume of pores of the entire sample of the refractory product; and
a gas permeability is 50×10 −17 m 2 or less.
2. The refractory product as claimed in claim 1 , which is formed as a sliding nozzle plate, wherein a Weibull modulus (shape index) obtained from a three-point bending test of a sample cut out of a portion of the sliding nozzle plate other than a boss portion of the sliding nozzle plate is 15 or more.
3. The refractory product as claimed in claim 1 , which is formed as a sliding nozzle plate, wherein, in a result of a three-point bending test of the sample of the refractory product, a value of an average strength ratio derived from dividing an average bending strength obtained from a boss portion of the sliding nozzle plate by an average bending strength obtained from a portion of the sliding nozzle plate other than the boss portion is 0.9 or more.
4. The refractory product as claimed in claim 1 , which is produced by a process comprising kneading, shaping and heat treatment, wherein:
with respect to 100% by volume of a total amount of raw material particles except for carbonaceous particles (except for carbon compound particles) and organic particles in a mixture to be subjected to the shaping (said raw material particles will hereinafter be referred to as “inorganic raw material particles”), a ratio (Vf/Vr) of a percent by volume Vf of a total amount of a part of the inorganic raw material particles having a particle size of 45 μm or less to a percent by volume Vr of a total amount of a part of the inorganic raw material particles having a particle size of 1 mm or more is 1.0 to 1.6, and a sum (Vf+Vr) of the percent by volume Vf and the percent by volume Vr is 50% by volume to 80% by volume; and
a covering layer comprising a fine powder having a particle size of 45 μm or less together with an organic resin is formed on each surface of at least the part of the inorganic raw material particles having a particle size of 1 mm or more.
5. The refractory product as claimed in claim 4 , wherein the mixture to be subjected to the shaping contains, with respect to 100% by mass of the entirety mixture:
one selected from the chemical components consisting of Al 2 O 3 , SiO 2 , MgO and ZrO 2 in an amount of 84% by mass to 97% by mass, or two or more selected from the chemical components consisting of Al 2 O 3 , SiO 2 , MgO, ZrO 2 , Cr 2 O 3 and CaO, or one or more compounds or solid solutions of the two or more chemical components, in a total amount of 84% by mass to 97% by mass;
one or more carbide components selected from SiC and B 4 C in a total amount of less than 4% by mass (including zero);
one or more selected from the group consisting of Al, Si and Mg as metals in a total amount of 1% by mass to less than 7% by mass; and
a carbon component in an amount of 1% by mass to less than 4% by mass.
6. The refractory product as claimed in claim 1 , which is a sliding nozzle used for continuous casting of steel, or a nozzle installed on an upstream or downstream side of the sliding nozzle to form a molten steel-passing path.