JPS6132276B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the production of basic melt cast refractories having predominant crystalline phases of periclase and magnesium-spinel. The main crystals are often associated with a small amount of silicate phase. Examples of this type of refractory are U.S. Patent No. 3,198,643 and British Patent No.
It is described in specification No. 965850. Small solid lumps, particles, granules, powder, small pieces, fragments, etc. (hereinafter generally referred to as "grogu")
is incorporated into the cast molten refractory raw material to control the natural formation of a relatively large shrinkage cavity during the solidification of the molten raw material, and also to suppress the various problems associated therewith, generally forming a dense core. Its role is to provide melt-casting products with several parts. An example of embodying the above concept to create various fused cast refractory compositions is provided in U.S. Patent No. 1,728,350;
No. 1878870, No. 2154153, No. 3233994, No. 3662058,
Specification No. 3763302, British Patent No. 392364,
“Refractries” (written by F.H. Norton, 4th edition)
1968, McGraw-Hill Book Co., New York, p. 189). An exception to this purpose is described in GB 1344650. That is, it is described that when magnesia particles are blended into a raw material for a cast molten refractory, the thermal shock resistance of an apparently dense molten cast refractory having the main crystal phases of periclase and calcium chromite is improved. In the case of basic fused cast refractories having periclase and magnesium-spinel predominant crystalline phases, the blended grog was usually a cullet of the same basic fused cast refractory. (See U.S. Pat. No. 3,763,302 and "Refractries", supra). This latter product usually forms a significantly denser center, and many of them
They are also known to exhibit one or two unique disadvantageous properties. One of these disadvantageous properties is that from about 1340°C
In the temperature range of 1500° C., especially at working temperatures of the latter temperature, the flexural rupture strength (modulus of rupture or “MOR”) of this kind of melt-cast refractories is limited. Another disadvantageous property is the formation of shells in these products. This tendency to form a shell is particularly strong when casting molten refractory raw material produced in a melting furnace that operates at or near the maximum capacity in order to obtain a volumetric outflow of molten refractory raw material per unit time. . A shell is a unique structural condition that grows into a fused cast refractory product as it solidifies. This shell is located at a relatively short distance below the casting surface of the molten cast product formed adjacent to the surface of the casting recess and substantially extends substantially parallel to the surface of the void or cavity. or at least result from semi-continuous layer formation. Such a void layer forms a relatively thin casting surface (ie, a "skin" portion) that overlies substantially away from the body of the melt-cast product. These parts, referred to as "shells", are easily separated from the cast product during removal from the mold and/or during subsequent processing, or
It will peel off easily. Products with this “shell” are
It is not normally commercially available, and the only option is to scrap it so that it can be reused as grain when making bricks by recombining the molten grains, or as grog in the melt casting process. The present invention solves the above-mentioned thermal modulus of rupture (MOR) limit and "shell" problem basically by combining (by weight) 45-78% MgO, 0-30% Cr ₂ O ₃ , 0
~35% _Al2O3 , 0-17% FeO+ _{Fe2O3 at} least 82% _MgO + _Cr2O3 + _{Al2O3 + FeO} +
Fe ₂ O ₃ , 1-8% SiO ₂ , 0-2% CaO + BaO
The finding that a basic melt-cast refractory consisting of the main crystalline phases of periclase and magnesium-spinel with an analytical composition consisting of +SrO, 0-10% TiO ₂ and 0-3% F can be substantially solved. It is based on Usually SiO ₂ is 5% or less. The method we found to solve these problems is that the loss on ignition (LOI) at 1000℃ is approximately
All or part of the grog added to the melt (lower than the molten grog) is less than 0.5% by weight and the SiO ₂ content is before, during and after pouring the melt into the mold. an unmelted (i.e., never melted) inorganic oxide of suitable particle size at least approximately equal to the SiO ₂ content of the cast refractory-forming melt as a not insignificant amount); and
It is used in the form of particles with a balanced particle size distribution (in place of conventional molten grog). This non-melting inorganic oxide generally consists of a refractory oxide having a melting point of 1300°C or higher, and is usually
It is an oxide component used in basic melt cast refractories. The particle size and amount of unmelted grog particles are
at least a partial melting of the added grog particles by the casting melt and penetration by the casting melt into the particles and resolidification of the particles with the casting melt, thereby causing solidification; grain size and quantity sufficient to form a continuously agglomerated crystalline structure throughout the cast (approximately 70% by weight of the refractory).
amount). In this case, the separated grog particles and their residues (if any) are present in the solidified casting to such an extent that they cannot be optically confirmed. In a preferred embodiment of the invention, the amount of grog particles (unfused or fused) added is
It is 20% by weight or more. Typically, for a particle size range that passes through a sieve with a sieve opening of about 25 mm (preferably 13.5 mm) but does not pass through a sieve with a sieve opening of about 0.5 mm, and for cast refractories, about 2.5 to 70 wt. % (preferably 5 to 50% by weight) of unmelted grog particles. The amount of grog particles blended is
If it is greater than about 35% by weight of the cast refractory, at least this 35% by weight or more is SiO ₂ (e.g., silica sand and/or olivine, chromite, etc.).
It is made of bauxite (a part of other grog materials made of SiO ₂ ). Therefore, in the case of the present invention, a large amount of grog can be blended. The present invention relates to an improvement in the process for producing the above-described basic fused cast refractories, in which the above-mentioned improved process (i.e., at least about 1340 to 1500
a process that substantially increases the modulus of rupture (MOR) in the temperature range of It is something that This type of conventional method generally involves producing a melt of refractory raw material and injecting this melt into a mold to fill the mold with the melt, while before, during, and after pouring the melt. The method includes the step of adding grog particles to a melt and solidifying the melt at least partially in a mold into a self-retaining cast shape that substantially conforms to the internal surface shape of the mold. Example 1 In this example, for the production of basic melt-cast refractories,
This figure shows an example using the present invention. In this basic melt-cast refractory, the magnesium-spinel phase basically consists mainly of Mg, Fe, Cr and Al.
The periclase phase is a composite solid solution consisting of oxides of FeO, and the periclase phase contains some FeO (a small amount of other oxides may be mixed in) in the solid solution. Analytically speaking, this refractory is basically
(by weight) 53-59% MgO, 16-24% _{Cr2O3 ,}
9-13% FeO+ _{Fe2O3 ,} 6-15% _{Al2O3 ,} 1
~3% _SiO2 , 0.4-1.5% CaO, 2% or less
It consists of TiO ₂ and a F component of 1% or less.
A typical average analytical composition is (by weight) 55%
MgO _, 19.6% _Cr2O3 , 11.0% FeO, 7.5%
_Al2O3 , 2.0% _SiO2 , 0.9% _CaO , 16% _TiO2
and 0.3% F component. According to the present invention, suitable inorganic refractory raw materials and their particle sizes when blending unfused grog or other grog are listed in Table 1, together with representative known examples of fused scrap grog of the above-mentioned fused cast refractory compositions. Describe it. Typically, these inorganic refractory raw materials are in a substantially dry, low loss on ignition (LOI) or calcined state (LOI).
(approximately 0.5% by weight or less). The reason for this is to avoid the adverse effects caused by substantial amounts of volatiles (water vapor, CO2 _, etc.), such as acceleration of shell formation and undesirable increase in porosity. However, the loss on ignition (LOI) of the entire grog mixture
is less than about 0.5% by weight, the loss on ignition is substantially greater, but otherwise suitable materials may be mixed in small amounts. These materials have typical analytical compositions (% by weight) as shown in Table 2.

【table】

[Table] Table 3 shows preferred grogs obtained from the above-mentioned refractory raw materials, the raw materials in each grog are expressed in weight ratio, and the amount of each grog blended is expressed in weight percent of the cast refractories. be. These grog formulations typically incorporate a substantially uniform proportion of grog particles into the melt injection stream during injection of the molten refractory material into an existing billet casting mold lined with graphite. This is done by adding small amounts at a time.

【table】

[Table] Ru chromite
Magnesai 42.5 32.5 25 0
to

Claims (1)

[Claims] 1. Main crystal phases of periclase and magnesium-spinel, basically 45-78% (by weight)
MgO, 0-30% _{Cr2O3 ,} 0-35% _{Al2O3 ,}
0-17% FeO+Fe ₂ O ₃ , 82% or less MgO+
Cr ₂ O ₃ + Al ₂ O ₃ + FeO + Fe ₂ O ₃ , 1-8%
SiO ₂ , 0-2% CaO + BaO + SrO, 0-10%
In producing basic melt-cast refractories with an analytical composition consisting of TiO ₂ and 0-3% F,
making the refractory melt and pouring the melt into a mold cavity to fill the mold cavity with casting melt, while before pouring the melt into the mold cavity; During and/or after entry, grog particles are added to the melt to bring the casting melt into a self-retaining shape that substantially conforms to the inner surface shape of the mold cavity. In a method of at least partial solidification in-house, the modulus of rupture (MOR) is substantially increased in the temperature range of at least about 1340°C to 1500°C, and at least half of the compounded grout is heated to 1000°C.
Loss on ignition (LOI) is 0.5% by weight or less,
Formation of shells in refractories can be prevented by supplying unmelted inorganic oxide particles with a SiO ₂ content ratio that is at least the same as or higher than the SiO ₂ content ratio of the melt for forming cast refractories. the amount of grog particles added does not exceed 70% by weight of the cast refractory;
The particle size also provides for at least partial melting of the grog particles by the casting melt and penetration by the casting melt into the particles and resolidification of the particles with the casting melt. , whereby the grain size is sufficient to form a continuously agglomerated crystalline structure throughout the solidified casting; further, within the solidified casting, the grog particles and their remnants are: Optically, it cannot be clearly confirmed individually, and if the amount of grog particles added exceeds 35% by weight of the cast refractory, at least the excess portion is characterized by consisting of SiO ₂ , a method for producing basic melt-cast refractories. 2. The particle size of the grog particles is such that it passes through a 25 mm sieve and remains on a 0.5 mm sieve, and the amount thereof is 2.5 to 70% by weight of the cast refractory. The manufacturing method described in Section 1. 3 The non-melting grog particles are silica sand, olivine,
The method according to claim 1, which is zircon sand, magnesia, chromite, bauxite, alumina, ilmenite, mill scale, or a mixture thereof. 4. The magnesium-spinel phase is basically a composite solid solution mainly consisting of oxides of Mg, Fe, Cr and Al, the periclase phase contains FeO in the solid solution, and the refractory is
(by weight) 53-59% MgO, 16-24%
Cr ₂ O ₃ , 9-13% FeO + Fe ₂ O ₃ , 6-15%
_{Al2O3 ,} 1-3% _SiO2 , 0.4-1.5% CaO, 2
% or less TiO ₂ and 1% or less F. 5. The manufacturing method according to claim 1, wherein all of the grog are non-melting particles. 6. The method according to claim 2, wherein the amount of grog particles is 5 to 50% by weight of the cast refractory. 7. Process according to claim 1, in which grog particles are added to the melt injection stream. 8. The manufacturing method according to claim 3, wherein the grog particles are a mixture of chromite and magnesia. 9. The manufacturing method according to claim 3, wherein the grog particles are a mixture of silica sand and olivine. 10. The manufacturing method according to claim 3, wherein the grog particles are chromite. 11. The manufacturing method according to claim 3, wherein the grog particles are a mixture of silica sand and chromite. 12 The magnesium-spinel phase is basically a composite solid solution mainly consisting of oxides of Mg, Fe, Cr and Al, the periclase phase contains FeO in the solid solution, and the refractory has
(by weight) 60-75% MgO, 12-18%
Cr ₂ O ₃ , 7-11% FeO + Fe ₂ O ₃ , 4-10%
_{Al2O3 ,} 1-3% _SiO2 , 0.4-1.5% CaO, 2
% or less TiO ₂ and 1% or less F. 13 The magnesium-spinel phase is magnesium aluminate, and the refractory comprises (by weight) 65-69% MgO, _29-34 % _Al2O3 , 1% or less CaO, and 1% or less SiO. 2. The manufacturing method according to claim 1, having an analytical composition consisting of ₂ . 14. The manufacturing method according to claim 1, wherein the amount of grog particles is 20% by weight or more of the cast refractory.