Search

EP-4737425-A1 - METHOD FOR MANUFACTURING UNFIRED BASIC BRICK

EP4737425A1EP 4737425 A1EP4737425 A1EP 4737425A1EP-4737425-A1

Abstract

Provided is an unfired basic brick manufacturing method using a binder capable of suppressing strength deterioration at 400 to 1000°C, without corrosion resistance deterioration caused by formation of a low-melting-point substance and concerns about dissolution of a binder component into molten steel, slaking of magnesia, and the like. The method comprises: adding water to a refractory raw material mixture that contains 0.2% by mass to 30% by mass of magnesia having a particle size of less than 75 µm, and 0.3% by mass to 2.5% by mass of silica having a particle size of less than 75 µm, with the remainder containing magnesia having a particle size of 75 µm or more, and at least one of spinel, alumina, and titania; and subjecting the resulting mixture to kneading, press-molding, and then heat treatment at a temperature of 60°C to 1000°C.

Inventors

  • KAWANO, Hayate

Assignees

  • Krosakiharima Corporation

Dates

Publication Date
20260506
Application Date
20240814

Claims (6)

  1. A method of manufacturing an unfired basic brick, the method comprising: adding water to a refractory raw material mixture that contains 0.2% by mass to 30% by mass of magnesia having a particle size of less than 75 µm, and 0.3% by mass to 2.5% by mass of silica having a particle size of less than 75 µm, with the remainder containing magnesia having a particle size of 75 µm or more, and at least one of spinel, alumina, and titania; and subjecting the resulting mixture to kneading, press-molding, and then heat treatment at a temperature of 60°C to 1000°C.
  2. The method as claimed in claim 1, wherein light-fired magnesia is used as the magnesia having a particle size of less than 75 µm, and silica flour is used as the silica having a particle size of less than 75 µm.
  3. The method as claimed in claim 1 or 2, wherein a content rate of the magnesia having a particle size of 75 µm or more, contained in the remainder of the refractory raw material mixture, is 50% by mass to 90% by mass, in terms of a proportion in 100% by mass of the refractory raw material mixture.
  4. The method as claimed in claim 3, wherein at least spinel is contained in the remainder of the refractory raw material mixture, wherein a content rate of the spinel is 5% by mass to 40% by mass, in terms of a proportion in 100% by mass of the refractory raw material mixture.
  5. The method as claimed in claim 3, wherein at least alumina is contained in the remainder of the refractory raw material mixture, wherein a content rate of the alumina is 1% by mass to 15% by mass, in terms of a proportion in 100% by mass of the refractory raw material mixture.
  6. The method as claimed in claim 3, wherein at least titania is contained in the remainder of the refractory raw material mixture, wherein a content rate of the titania is 1% by mass to 15% by mass, in terms of a proportion in 100% by mass of the refractory raw material mixture.

Description

TECHNICAL FIELD The present invention relates to a manufacturing method for an unfired basic brick which is used, in the iron and steel field or the like, as a lining material for molten metal containers or cement rotary kilns. BACKGROUND ART It is often the case that a magnesia-chrome brick having high corrosion resistance is used as a refractory lining material for molten metal containers or cement rotary kilns. However, since the magnesia-chrome brick contains a Cr2O3 component, there have been problems in terms of the environmental health because, after use, the brick can contain harmful hexavalent chromium. For this reason, a brick that does not contain Cr2O3 in its composition, for example, a so-called chrome-free basic brick, such as a magnesia-alumina based brick, a magnesia-spinel based brick, or a magnesia-titania-alumina based brick, is also used. However, since a commonly-used chrome-free basic brick is produced through firing at a high temperature of 1500°C or more, there are demerits such as CO2 emission and cost increases. In order to solve this problem, an unfired basic brick manufacturing method has also been studied. For example, Patent Document 1 and Patent Document 2 disclose a manufacturing method for a magnesia-alumina based unfired basic brick, and a manufacturing method for a magnesia-titania-alumina based unfired base brick, respectively. The Patent Documents 1 and 2 also describe that when an inorganic binder, such as phosphate, silicate, or alumina cement, is used as a binder in the above manufacturing methods, it can facilitate forming a ceramic bond under hot conditions to provide a strong microstructure. However, when phosphate is used as the binder, it is necessary to use the phosphate in the form of alkali metal phosphate, such as sodium phosphate, so as to prevent a rapid reaction with magnesia. In this case, the alkali metal phosphate reacts with magnesia to form a low-melting-point substance, leading to deterioration in corrosion resistance and failing to obtain sufficient durability. Further, since there is a concern about elution of the phosphorus component into molten steel, the use of phosphate is undesirable. When silicate is used as the binder, alkali metal silicate, such as sodium silicate, is also liable to form a low-melting-point substance, leading to deterioration in corrosion resistance. Further, such an alkaline binder causes an increase in the amount of hydroxyl groups to be supplied to magnesia, and consequently magnesium hydroxide is formed to make slaking (hydration) of the brick more likely to occur, leading to a possibility that cracks occur through storage or use over a long period of time. In order to minimize these harmful influences, it is also conceivable to suppress the amount of alkali metal phosphate or alkali metal silicate used. For example, in the manufacturing methods described in Patent Documents 1 and 2, 0.3 parts by weight of phosphate is used. In this case, however, there is a problem that sufficient strength cannot be obtained. Although there is also an alkali-free silicate binder such as silica sol, this binder is unpractical because when a brick is formed using this binder, the strength of the brick becomes insufficient. When alumina cement is used as the binder, it reacts with a CaO component in slag to form a low-melting-point substance, leading to deterioration in corrosion resistance and failing to obtain sufficient durability. Patent Document 3 discloses using a magnesium chloride aqueous solution as a binder for a magnesia-spinel based unfired basic brick. In this case, however, the binder component is decomposed in a temperature range of 400 to 1000°C, leading to a problem that strength deterioration and microstructural embrittlement are likely to occur. PRIOR ART DOCUMENTS [Patent Document] Patent Document 1: JP H08-143356 APatent Document 2: JP H08-310875 APatent Document 3: JP 4328053 B SUMMARY OF INVENTION [Technical Problem] The technical problem to be solved by the present invention is to provide an unfired basic brick manufacturing method using a binder capable of suppressing strength deterioration at 400 to 1000°C, without corrosion resistance deterioration due to formation of a low-melting-point substance, and concerns about dissolution of a binder component into molten steel, slaking of magnesia, and the like. [Solution to Technical Problem] The summary of the present invention is as follows. 1. A method of manufacturing an unfired basic brick, the method comprising: adding water to a refractory raw material mixture that contains 0.2% by mass to 30% by mass of magnesia having a particle size of less than 75 µm, and 0.3% by mass to 2.5% by mass of silica having a particle size of less than 75 µm, with the remainder containing magnesia having a particle size of 75 µm or more, and at least one of spinel, alumina, and titania; andsubjecting the resulting mixture to kneading, press-molding, and then heat treatment at a temp