JP2007269606A - Monolithic refractory forming material and monolithic refractory formed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monolithic refractory formed body which is excellent in both of thermal shock resistance and corrosion resistance and is also good in heat resistance, mechanical strength, heat insulating property, and mechanical processability, and to provide a forming material for the same. <P>SOLUTION: The monolithic refractory forming material contains alumina cement, diatomaceous earth or iron oxide, and other refractory materials. The monolithic refractory formed body is formed by adding water to the monolithic refractory forming material, kneading the resulting mixture and curing the kneaded material, and has a density of 1.0-2.5 g/cm<SP>3</SP>and a bending strength of 2-10 MPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a hydraulic molding material that is excellent in heat resistance, heat insulation, thermal shock resistance, corrosion resistance to molten metal, electrical insulation, machinability, and gives an amorphous refractory molded article suitable as a refractory material or heat insulation material. About. Further, the present invention provides a casting apparatus for casting a relatively low melting point metal having a melting point of 800 ° C. or less, such as aluminum, zinc, tin, lead, or an alloy thereof. The present invention relates to an indeterminate shaped refractory molded body used in a portion in contact with a molten metal of a low melting point metal.

  Casting refractories are widely used as lining materials for manufacturing, constructing or repairing members that come into contact with molten metal, such as firewood, molten metal holding furnaces, ladles, etc. Yes. Castable refractories are kneaded with an appropriate amount of water, then poured into a mold and cured, dried, baked, and free of water vapor and crystallization water so that no water vapor is generated during use, and fire resistance is good A lining material is formed.

  As a castable refractory for the lining of the casting apparatus as described above, alumina cement and wollastonite are conventionally used because they are difficult to wet with molten metal and have relatively good corrosion resistance (for example, Patent Document 1). reference).

JP-A-62-265151

  However, although conventional alumina cement and wollastonite castables have excellent corrosion resistance, they do not have sufficient resistance to stress generated during rapid heating or rapid cooling, so-called thermal shock resistance, and cracks and cracks occur. For this reason, it was necessary to frequently replace and repair. As a means to improve thermal shock resistance, attempts have been made to reduce the overall coefficient of thermal expansion by incorporating fused silica (amorphous silica) with a low coefficient of thermal expansion, but fused silica reacts very much with the molten metal. It was easy and the thermal shock resistance was improved, but the corrosion resistance was deteriorated.

  An object of the present invention is to provide an amorphous refractory molded article excellent in both thermal shock resistance and corrosion resistance, heat resistance, mechanical strength, heat insulation, and machinability, and a molding material thereof. is there.

In order to achieve the above object, the present invention provides the following amorphous refractory molding material and amorphous refractory molded article.
(1) An amorphous refractory molding material comprising alumina cement, diatomaceous earth or iron oxide, and other refractory materials.
(2) The amorphous refractory molding material as described in (1) above, comprising diatomaceous earth in a proportion of 2 to 30% by mass or iron oxide in a proportion of 0.1 to 10% by mass.
(3) The molding material for an irregular refractory according to the above (1) or (2), comprising 10 to 60% by mass of alumina cement and 10 to 88% by mass of other refractories.
(4) The other refractory material contains wollastonite (CaSiO ₃ ) in a proportion of 10 to 60% by mass of the total amount of the refractory material, according to any one of the above (1) to (3) The amorphous refractory molding material described.
(5) A molded product of a kneaded product obtained by adding water to the amorphous refractory molding material described in any one of (1) to (4) above, and having a density of 1.0 to 2 An amorphous refractory molded body having a bending strength of 2 to 10 MPa at 0.5 g / cm ³ .
(6) The amorphous refractory molded article according to the above (5), which is used in a portion that contacts a molten metal of a low melting point metal having a melting point of 800 ° C. or lower.

  The amorphous refractory molded body according to the present invention has excellent corrosion resistance, thermal shock resistance, heat insulation, machinability, and cracks even when used in locations where severe thermal shock occurs compared to conventional products. The occurrence of cracks and cracks is reduced, and the frequency of material replacement and repair is significantly lower than in the past. In addition, the cost of the material itself is almost the same as that of the conventional product. Therefore, in terms of the time required for replacement and repair and the cost of purchasing the compact, it is possible to cast a low-melting-point metal at a very low total cost compared to the conventional case.

  Hereinafter, the present invention will be described in detail.

  The amorphous refractory molding material (hereinafter referred to as “molding material”) of the present invention is a powder mixture containing alumina cement, diatomaceous earth or iron oxide, and other refractory materials.

There is no restriction | limiting in the kind of alumina cement, The thing conventionally used for a refractory etc. can be used. Among them, a high alumina cement in which the Al ₂ O ₃ component occupies 55% by mass or more is preferable because of the excellent appearance of the resulting heat-resistant molded article.

  There is no restriction | limiting also in the kind of diatomaceous earth, and what has been conventionally used for the coating wall material, a refractory, etc. can be used. Moreover, it is preferable that the average particle diameter of diatomaceous earth is 5-50 micrometers, and it is more preferable that it is 5-20 micrometers.

The iron oxide uses powder, but the average particle size is preferably 1 to 10 μm, and more preferably 2 to 6 μm. There is no particular limitation to the valence of iron _{oxide, FeO, Fe 2 O 3,} Fe 3 O 4 but may be mentioned, raw materials are stable trivalent _Fe 2 _{O 3} is preferably inexpensive.

As other refractory materials, since the present invention is intended for members that are in contact with a molten metal of a low melting point metal having a melting point of 800 ° C. or lower, such as aluminum, zinc, tin, lead, or alloys thereof, the melting point Use 800 degreeC or more. Specifically, oxide refractories such as silica, mullite, wollastonite (CaSiO ₃ ), zirconia, magnesia and zircon, nitride refractories such as boron nitride, silicon nitride, aluminum nitride and sialon, silicon carbide Carbide-based refractories such as graphite and carbon-based refractories such as graphite and graphite are mentioned, but it is preferable to include wollastonite in an amount of 10 to 60% by mass based on the total amount of other refractory materials. Moreover, it is preferable that the average particle diameter of other refractories is 0.5-20 micrometers, and it is more preferable that it is 3-7 micrometers.

  The compounding ratio of alumina cement, diatomaceous earth or iron oxide, and other refractory materials in the molding material is 10 to 60% by mass, preferably 20 to 50% by mass, more preferably 25 to 35% by mass for alumina cement. Diatomaceous earth is 2 to 30% by mass, preferably 6 to 15% by mass, and more preferably 8 to 10% by mass. Iron oxide is 0.1 to 10% by mass, preferably 0.1 to 5% by mass, and more preferably 0.5 to 2% by mass. The other refractory material is 10 to 88% by mass, preferably 40 to 80% by mass, and more preferably 50 to 70% by mass.

  Since alumina cement functions as a binder, if it is less than the lower limit, the mechanical strength of the resulting heat-resistant molded article may be adversely affected. Silicon earth or iron oxide has the effect of improving the thermal shock resistance and corrosion resistance, and if it is less than the lower limit, the effect of improving the thermal shock resistance and corrosion resistance of the resulting heat-resistant molded article may not be sufficient. In addition, when the content of diatomaceous earth increases, the thermal shock resistance tends to be inferior. Other refractory materials are responsible for the heat resistance and heat insulating properties of the resulting amorphous refractory molded body, so if the amount is less than the lower limit, the obtained amorphous refractory molded body exhibits the required heat resistance and heat insulating properties. There is a risk of not. In addition, when any component exceeds the above upper limit value, the content of other components is relatively reduced, and the indicated problem occurs.

  The molding material is mixed with water, and the resulting kneaded product is molded into a predetermined shape and cured to form an amorphous refractory molded body.

  In addition, for water, dispersants such as sodium hexametaphosphate, sodium tripolyphosphate, and sodium ultrapolyphosphate, curing accelerators such as lithium carbonate and calcium hydroxide, curing retarders such as boric acid and sodium fluorofluoride, or explosion An appropriate amount of organic fiber such as polypropylene fiber may be blended for the purpose of prevention.

  The mixing ratio of the molding material and water is not particularly limited as long as the shape can be maintained when the kneaded product is molded. However, it is preferable that water is 10 to 60 parts by mass with respect to 100 parts by mass of the molding material. The molding method is easy to pour into the mold and may be cured and cured in the mold. The curing conditions are not particularly limited, but for example, the curing is performed at 15 to 25 ° C. and a humidity of 50 to 95 RH for 24 hours or more.

  After forming into a predetermined shape, it is preferable to dry, and there is no particular limitation, but for example, it is performed at 100 to 120 ° C. for 24 hours or more. The amorphous refractory molded body may be fired to dehydrate the hydrated alumina cement in the molded body after drying, and is not particularly limited. Do time. Such firing is not necessarily required, and may be performed by heating applied during use.

  The amorphous refractory molded article of the present invention thus obtained is excellent in both thermal shock resistance and corrosion resistance, and also has good heat resistance, mechanical strength, heat insulation and machinability. Therefore, it is suitable as a lining material for a pouring box, a jar, a holding furnace or the like of a casting apparatus for casting a low melting point metal such as aluminum.

  EXAMPLES The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

(Test-1: Examples 1-7, Comparative Examples 1-2)
The kneaded material that has been sufficiently kneaded with the molding material shown in Table 1 and water in a planetary mixer is poured into a plate mold, cured under conditions of 20 ° C., 80% RH, 24 hours, and removed. The mold is dried at 105 ° C. for 24 hours, further heated to 700 ° C. at a heating rate of 200 ° C./hour, and kept at this temperature for 3 hours to perform dehydration of the alumina cement hydrate, A test specimen was prepared. Details of the materials are as follows. And the following physical-property evaluation was performed about each test body. The results are shown in Table 1.

(1) Measurement of linear change rate From a dimensional change between a molded body after curing, a molded body after drying, and a molded body after baking, the molded body after drying according to JIS R2554, and after baking The linear change rate of the molded body was measured.
(2) Measurement of density The density of the molded body after drying and the molded body after firing was measured according to JIS R2655.
(3) Measurement of bending strength and compressive strength The bending strength and compressive strength of the specimen were measured according to JIS R2553.
(4) Appearance evaluation The surface of the test specimen was visually observed to evaluate the presence or absence of cracks, cracks, and smoothness.
(5) Measurement of thermal expansion coefficient A test piece having a length of 20 mm, a width of 5 mm, and a thickness of 5 mm cut out from a specimen was measured at 5 ° C. in the air using a thermomechanical analyzer “TMA8310” manufactured by Rigaku Corporation. The temperature was increased from room temperature to 800 ° C. at a rate of / min, and the thermal expansion coefficient was measured.
(6) Spalling resistance test A test piece cut out from a specimen to a size of 114 mm x 65 mm x 230 mm was used, and a test was performed in accordance with JIS R2657. In the table, “◯” indicates that no crack was generated, and “Δ” indicates that several cracks occurred, and each was regarded as acceptable.
(7) Aluminum immersion test A test piece was cut out to a size of 160 mm × 40 mm × 40 mm from a specimen, and half of the length direction was immersed in a molten aluminum alloy (AC4C) maintained at 800 ° C. for 2 weeks. After being held, it was taken out, the immersed part was cut and the cross section was observed, and the eroded cross sectional area was measured. An erosion cross-sectional area of 10 mm ² or less was accepted, and “◯” was marked in the table.

  From Table 1, the thermal shock resistance and corrosion resistance are improved by blending diatomaceous earth. When the blending amount of diatomaceous earth is increased to 15 to 20% by mass, although low density and corrosion resistance are good, some cracks are generated in the spalling resistance test and the bending strength tends to be lowered. On the other hand, when the diatomaceous earth is reduced to 6 to 10% by mass, the density is slightly increased, but a balanced result is obtained in appearance, strength, corrosion resistance, and spalling resistance. Is the best.

(Test-2: Examples 8 to 11 and Comparative Examples 3 to 4)
Test specimens were prepared in the same manner as in Test-1 with the formulation shown in Table 2, and the same measurements and tests were performed. The results are shown in the same table.

  From Table 2, the thermal shock resistance and the corrosion resistance are improved by adding iron oxide.

Claims (6)

  An amorphous refractory molding material comprising alumina cement, diatomaceous earth or iron oxide, and other refractory materials.   The amorphous refractory molding material according to claim 1, comprising 2 to 30% by mass of diatomaceous earth or 0.1 to 10% by mass of iron oxide.   3. The molding material for an irregular refractory according to claim 1, comprising 10 to 60% by mass of alumina cement and 10 to 88% by mass of other refractories. The other refractory material contains wollastonite (CaSiO ₃ ) in a proportion of 10 to 60% by mass of the total amount of the refractory material, according to any one of claims 1 to 3. Molding material. A molded product of a kneaded product obtained by adding water to the amorphous refractory molding material according to any one of claims 1 to 4, and having a density of 1.0 to 2.5 g / cm ³ . An indeterminate refractory molded body having a bending strength of 2 to 10 MPa.   6. The amorphous refractory molded article according to claim 5, wherein the molded article is formed in contact with a molten metal of a low melting point metal having a melting point of 800 ° C. or lower.