JPS627664A - Limy refractories - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a calcareous refractory that can be used as a refractory that has heat insulating properties and can absorb steel inclusions for use in various industrial furnaces for steel manufacturing.

[Conventional technology] Calcareous refractories have the following characteristics: Melting point is as high as 2600℃; Stable under high temperature vacuum; Has desulfurization and dephosphorization ability.

For this reason, various studies have been conducted on various refractories. However, the rate of digestion due to the hydration reaction between CaO and water is extremely fast, which poses a problem in the production and use of lime refractories, and currently they are not used.

In order to prevent this CaO digestion, various efforts have been made to stabilize lime clinker.

That is, Fe2O,, A I 203, Cr2O,
3, T i O2, S i O2, P, O3, MgOl
A method of stabilizing by mixing oxides such as MnO2, a method of stabilizing with fluorides such as CaF2 and LiF, a method of increasing the size of CaO crystals by high temperature firing or melting and delaying digestion, or molten CaO
Methods include blowing off limestone to rapidly cool it and stabilizing it, and methods such as adsorbing C○2 gas on the surface of calcined lime clinker and forming a film of calcium carbonate to prevent digestion, but none of these methods work. It has not yet reached the point of preventing the digestion of CaO. Digestion of CaO becomes a problem when storing lime talinker in large quantities, pulverizing the grain, or mixing wires, as well as in the raw corner after brick molding or in the low-temperature firing zone during firing, and this becomes a major obstacle in the production of lime refractories. ing.

[Problems to be Solved by the Invention] Examples of calcareous refractories that do not require consideration of the problem of CaO digestion as described above include refractories using limestone described below. For example, Japanese Patent Application Laid-open No. 5
No. 5-51763 discloses a calcareous refractory made by adding silicate or phosphate to limestone or dolomite. Furthermore, Japanese Patent Application Laid-Open No. 54-20016 proposes a spray material in which a binder is added to an aggregate consisting of 95 to 40 parts by weight of magnesia and 5 to 60 parts by weight of limestone. Also in this case, sodium silicate or sodium phosphate is used. Also, the 21st edition of Ceramic Data Book 1980
Pages 1 to 218 describe bricks made by adding CaCl□ to limestone and firing, or bricks made by adding CaCl* to limestone and hot pressing at high temperatures. The above-mentioned Japanese Patent Application Publication No. 55-51763 and Japanese Patent Application Publication No. 54-2001
Since all of Publications No. 6 use silicate or phosphate, the purity of lime is lowered, which is not desirable from the viewpoint of dephosphorization of molten steel, reduction in desulfurization ability, or contamination of molten steel.

Furthermore, the fired bricks made of limestone with CaCl2 added thereto described in the ceramic data book have low raw corner strength at the raw corner stage before firing, and have the disadvantage that corner chips and cracks are likely to occur, resulting in poor yield. Furthermore, bricks made by adding CaCl2 to limestone and hot pressing at a high temperature have a problem in that although the bricks are strong because they are pressed at a temperature of 500 to 800 DEG C., the productivity is extremely low. When using a refractory made of limestone with Ca CI
It may produce raw horns. This tendency is particularly pronounced for large bricks. Further, when used as a monolithic refractory, the viscosity and strength during construction are insufficient, sufficient filling properties cannot be obtained, and the construction strength is insufficient, causing problems such as falling off and peeling.

[Means for solving the problems] The present invention provides limestone, dolomite, or both.
Aggregate consisting of 100 fUt parts and 0 to 80 parts by weight of magnesia clinker, alkali metal halogenated compounds, alkaline earth metal halogenated compounds, halogenated compounds of group Ⅰ metals of the periodic table, alkali metal carbonates, and alkali metal aluminates. 0.1 to 20 parts by weight of one or more inorganic binders selected from the group consisting of salts and 0.005 to 2 parts by weight of a water-soluble organic resin having a pH of 6 or more as an organic binder.
To provide a calcareous refractory containing 0 parts by weight.

[Function] The limestone or dolomite used in the present invention is not particularly limited, and may be limestone that is normally used as a raw material for lime for steelmaking or dolomite that is used as dolomite clinker for refractories. Generally, the particle size of limestone or dolomite that is normally used for refractories can be applied.

Halogenated compounds of alkali metals, alkaline earth metals, and group Ⅰ metals of the periodic table, as well as alkali metal carbonates and alkali metal aluminates, which are added as inorganic binders, suppress the firing shrinkage of limestone or dolomite, and It is possible to obtain hot volumetric stability of refractories using dolostone. Compounds that can produce similar effects include alkali metal silicates, phosphates, borates, sulfates, and nitrates, which contain Si, P
, B, S, and N are not preferred because they may contaminate the steel. Alkali metal hydroxides also have similar effects, but are not preferred in terms of work since they are strongly alkaline.

Even if additives other than the above-mentioned compounds are added, limestone,
Even with only dolomite, the firing shrinkage is as large as 10 to 25%, and the stability of hot volume, which is an important characteristic when used as a refractory, is lacking.

Halogenated compounds include fluoride, chloride, bromide,
Iodide can be used. Among various halogenated compounds, compounds with alkali metals, alkaline earth metals, and metals of group Ⅰ of the periodic table are preferred. If a strongly acidic compound is used, it is not preferable because it causes an acid-base reaction with limestone and dolomite, generates CO2 gas, and causes cracking and collapse. In addition, boron halogenated compounds that have an adverse effect on steel are not preferred. Even if the halogenated compound is poorly soluble in water, it can suppress the shrinkage of limestone or dolomite. Therefore, examples of halogenated compounds include fluorides such as lithium fluoride, potassium fluoride, sodium fluoride, calcium fluoride, and magnesium fluoride; lithium chloride;
Chlorides such as potassium chloride, sodium chloride, calcium chloride, magnesium chloride, barium chloride, and aluminum chloride can be used. Since both alkali metal carbonates and alkali metal aluminates are alkaline and do not react with limestone, they do not pose the problem of halogenated compounds. Examples of alkali metal carbonates and alkali metal aluminates include lithium carbonate and carbonate. Potassium, sodium aluminate, potassium aluminate, lithium aluminate, etc. can be used.

The amount of the inorganic binder added is preferably 0.1 to 20 parts by weight,
If it is less than 0.1 part by weight, it is not preferable because the desired bonding strength cannot be obtained and the shrinkage suppressing effect does not work sufficiently. Furthermore, if the amount exceeds 20 parts by weight, the corrosion resistance will be poor, and even if more than 20 parts by weight is added, the resulting addition effect will not be obtained, which is not preferable. Two or more of the above-mentioned inorganic binders can be used in combination.

Merely adding an inorganic binder to limestone and dolomite or limestone, dolomite and magnesia has the disadvantage of insufficient plasticity and low bonding strength. Therefore, when used as a monolithic refractory, the workability is poor, the filling properties are insufficient, and the refractories are likely to fall off, peel, etc. Furthermore, when used as a shaped refractory, the strength of the horn is low and the strength after drying is also insufficient, resulting in chipping and cracking of the horn during handling, transportation, furnace construction, etc. In particular, the larger the size, the more this tendency becomes a problem.

Usually, clay is used to develop plasticity or strength, but clays are not preferred because they promote sintering and reduce the activity of CaO. Therefore, organic binders are added that provide plasticity and strength and do not affect the activity of CaO. It is important that the organic binder is water soluble so that the aqueous solution dissolves the inorganic binder and creates a stable solution, yet does not react with the limestone or dolomite. Therefore, it is preferable that the organic binder has a pH of 6 or more, which is in the weakly acidic to alkaline range. Examples of the organic binder include sodium polyacrylate, emulsion of acrylic copolymer resin, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, sodium ligninsulfonate, sodium alginate, and the like. However, even with these organic binders, for example, sodium polyacrylate is a salt of monovalent ions and only causes a decrease in viscosity, but salts of divalent ions cause coagulation, so care must be taken when using them. There is a need. Also, carboxymethylcellulose is A+
In the presence of 3+ or Ba'+, precipitation occurs, and as a result, the clay or slurry of the calcareous refractory of the present invention loses its plasticity or lacks strength. Therefore, the selection of the organic binder depends on the inorganic binder used. It needs to change. The amount of the organic binder added is preferably 0.005 to 20 parts by weight,
If it is less than 0.005 parts by weight, the strength will be low, and if it exceeds 20 parts by weight, the strength will be extremely low after the organic resin is burned during preheating or firing, which is not preferable.

The concentration of the aqueous solution of the organic binder varies depending on the type of organic binder, the amount added, the formability of the clay, the strength after drying, etc.
．． A concentration of 1 to 50% can be used.

Limestone, dolomite, or both are used as aggregates, but when used in molten steel, there is no problem with corrosion resistance, but the parts that come into contact with slag have poor corrosion resistance, so limestone is used to provide this corrosion resistance. Alternatively, it is necessary to replace dolostone with magnesia clinker. The amount of magnesia blended is preferably 0 to 80 parts by weight per 20 to 100 parts by weight of limestone, dolomite, or both.

If the amount of magnesia added exceeds 80 parts by weight, it is not preferable because the ability of the steel to absorb inclusions decreases.

The calcareous refractory of the present invention is easily calcinable, and if it cannot be preheated at the place of use, or if preheating is possible but the COa gas in limestone or dolostone cannot be sufficiently dissociated, it can be fired at a temperature of 1000°C or higher. It can also be used after baking.

As mentioned above, the calcareous refractories of the present invention produced in this way can be used for monolithic refractories such as stamp materials, coating materials, castables, unfired bricks, fired bricks, board refractories, etc., and can be used for purposes other than iron making. Can also be used in cement glass kilns.

[Example] The calcareous refractory of the present invention will be further explained with reference to Examples below.

Unfired bricks and stamp materials made of the calcareous large-sized material of the present invention and comparative fired bricks and stamp materials were manufactured using the compounding ratios shown in Table 1 below.

Table 1 also shows cow horn strength and dry strength (110°C, 24°C).
time), as well as the shrinkage rate and apparent porosity after firing at 1500°C for 2 hours.

The test was conducted using large-sized unfired bricks and stamp materials (the unfired bricks were 500 to 700 mm x 60n+n+, and the stamp material was molded into a frame of 200 mm x 30 mm).

Note that the pH of the 43% solution of the acrylic polymer resin emulsion used as the organic binder in this example is 7.2, and the pH of the 2% solution of methyl cellulose is 7.0.
Moreover, 9H of a 2% solution of polyvinyl alcohol was 6.5.

The unfired bricks of the present invention have high purity and do not have any corner chips or cracks when handled, but the comparative products cracked in the center and had many corner chips.

The workability of the stamp material is also very good, and comparison products are difficult to install, do not have sufficient strength, and often crack from the center.
It turned out that there was no strength.

; The above-mentioned products I and (2) of the present invention were tested as 35-ton, tank-push weir bricks from Company A. The comparison product could not be used for testing due to breakage during handling and transportation.
A comparison was made between Chamotte brick weirs and inclusions. After the weir bricks were installed, they were preheated at 1200°C for 2 hours and received, but no problems occurred. In order to compare the products of the present invention and chamotte bricks, inclusions in the steel were compared. Table 2 below shows a comparison when the total amount of A1□03, S and oxygen in the mold on the chamotte brick side is set to 1.

First λ−j! As mentioned above, the calcareous refractory of the present invention exhibits excellent strength, which allows it to be used as large unburned bricks or monolithic refractories, and has excellent porosity and inclusion absorption ability. Obtained.

[Effects of the Invention] The following effects can be obtained by the present invention: (1) Good workability when used as a monolithic refractory; (2) High bullhorn strength and strength after drying when used as a brick; Very few corner chips or cracks occur when the bricks are transported; (3) When used as unfired products or when producing fired bricks, there is no need to worry about digestion during the firing stage; (4) Productivity is improved. Good; (5) Preheating or firing at 1000°C or higher produces active CaO, which can absorb inclusions such as molten steel, S, and P; (6) After decarboxylation, the apparent porosity is approximately 60%. , exhibits excellent high-temperature insulation properties.

Claims (1)

[Claims] Aggregate consisting of 20 to 100 parts by weight of limestone or dolomite or both and 0 to 80 parts by weight of magnesia clinker, an alkali metal halide compound, an alkaline earth metal halide compound, a halogenated compound of Group III metal of the periodic table , 0.1 to 20 parts by weight of one or more inorganic binders selected from the group consisting of alkali metal carbonates and alkali metal aluminates, and pH as an organic binder.
A calcareous refractory containing 0.005 to 20 parts by weight of a water-soluble organic resin having 6 or more.