Slurry and manufacturing method of mold powder

Abstract

To suppress an increase of the coefficient of viscosity of slurry containing blast furnace slag or portland cement, used in manufacturing mold powder, even when a temperature of agitation is 55-60°C.SOLUTION: Slurry contains at least one kind of material selected from a group consisting of blast furnace slag and portland cement, and at least one kind of binder selected from a group consisting of dextrin, lignin, and cane sugar, and is used fro manufacturing mold powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a slurry used in producing a molding powder and a method for producing the molding powder. [Background technology]

[0002] In continuous casting of steel, hollow granular mold powder is mainly used as the mold powder to be scattered on the molten metal surface in the mold. Hollow granular mold powder is generally obtained by spray granulation of a slurry containing raw materials for the mold powder. Portland cement, blast furnace slag, etc. are used as raw materials for the mold powder (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-294849 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the research of the present inventors, when blast furnace slag or Portland cement is used, stirring during the preparation of a slurry can significantly increase the viscosity of the slurry, which can cause problems such as the device used to stir the slurry not working properly. It has also been found that such an increase in the viscosity of the slurry is likely to occur when the temperature of the slurry during stirring reaches a high temperature of about 55 to 60°C. When preparing a slurry in the summer, the temperature of the slurry during stirring can reach about 55 to 60°C.

[0005] Therefore, one aspect of the present invention aims to suppress an increase in viscosity of a slurry containing blast furnace slag or Portland cement used in the production of molding powder, even when the temperature during stirring is about 55 to 60°C. [Means for solving the problem]

[0006] The present inventors have discovered that when a slurry containing blast furnace slag or Portland cement is used, the blast furnace slag or Portland cement can increase the viscosity of the slurry due to a hydration reaction, but that by adding at least one binder selected from the group consisting of dextrin, lignin, and sucrose to the slurry, the increase in viscosity of the slurry can be suppressed even when the temperature of the slurry during stirring is approximately 55 to 60°C.

[0007] The present invention includes the following aspects. [1] A slurry used in the production of molding powder, comprising at least one material selected from the group consisting of blast furnace slag and Portland cement, and at least one binder selected from the group consisting of dextrin, lignin, and sucrose. [2] The slurry according to [1], wherein the mass ratio of the content of the binder to the content of the material is 0.04 or more. [3] A method for producing a mold powder, comprising a step of spray-granulating a slurry to obtain a mold powder, wherein the slurry contains at least one material selected from the group consisting of blast furnace slag and Portland cement, and at least one binder selected from the group consisting of dextrin, lignin, and sucrose. [4] The manufacturing method according to [3], wherein the mass ratio of the content of the binder to the content of the material is 0.04 or more. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to suppress an increase in viscosity of a slurry containing blast furnace slag or Portland cement used in the production of molding powder, even when the temperature during stirring is about 55 to 60°C. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0010] One embodiment of the present invention is a slurry containing at least one material selected from the group consisting of blast furnace slag and Portland cement, and at least one binder selected from the group consisting of dextrin, lignin, and sucrose.

[0011] The content of at least one material selected from the group consisting of blast furnace slag and Portland cement may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more, and may be 98% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total solid content in the slurry. Note that the solid content refers to all components contained in the slurry excluding the dispersion medium.

[0012] Blast furnace slag may contain SiO2, CaO, Al2O3, Fe2O3, MgO, S, and MnO.

[0013] The contents of SiO2, CaO, Al2O3, Fe2O3, MgO, S, and MnO in the blast furnace slag may be as follows. SiO2: 30-37 mass%, CaO: 43-50 mass%, Al2O3: 8-14 mass%, T-Fe: 0-2 mass%, MgO: 0.5-15 mass%, S: 0-2 mass%, MnO: 0-2 mass% (all mass % based on the total amount of blast furnace slag)

[0014] Portland cement may contain SiO2, CaO, Al2O3, T-Fe (multiple iron oxides), MgO, and S.

[0015] The contents of SiO2, CaO, Al2O3, T-Fe, MgO, and S in Portland cement may be as follows. SiO2: 18-25 mass%, CaO: 60-70 mass%, Al2O3: 3-8 mass%, T-Fe: 0-5 mass%, MgO: 0-5 mass%, S: 0-5 mass% (all mass % based on the total amount of Portland cement)

[0016] The slurry may contain only one of blast furnace slag and Portland cement, or may contain both blast furnace slag and Portland cement.

[0017] From the viewpoint of further suppressing an increase in the viscosity of the slurry, the content of the binder may be 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more, based on the total amount of solids in the slurry, and 4% by mass or less, 3.9% by mass or less, 3.8% by mass or less, 3.7% by mass or less, 3.6% by mass or less, or 3.5% by mass or less, based on the total amount of solids in the slurry.

[0018] From the viewpoint of further suppressing an increase in slurry viscosity, the mass ratio of the binder content to the content of the at least one material selected from the group consisting of blast furnace slag and Portland cement may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, or 0.06 or more. The mass ratio of the binder content to the content of the at least one material selected from the group consisting of blast furnace slag and Portland cement may be 0.2 or less, 0.18 or less, 0.16 or less, or 0.14 or less.

[0019] The slurry may contain other ingredients, such as calcium silicate, fluorspar (calcium fluoride), alumina (aluminum oxide), and soda ash (sodium carbonate).

[0020] The dispersion medium may be, for example, water (pure water). The content of the dispersion medium may be, for example, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total amount of the slurry.

[0021] The slurry described above is used to produce mold powder (preferably hollow granular mold powder). Another embodiment of the present invention is a method for producing mold powder, comprising a step of obtaining mold powder from the above slurry. The above slurry is spray-granulated using a spray or the like, and then dried to volatilize the dispersion medium and obtain hollow granular mold powder. The spray-granulation and drying can be performed by known methods.

[0022] The above-mentioned manufacturing method may further include a step of mixing (stirring) at least one material selected from the group consisting of blast furnace slag and Portland cement, at least one binder selected from the group consisting of dextrin, lignin, and sucrose, and a dispersion medium to prepare a slurry.

[0023] The temperature of the slurry when it is prepared (stirred) may be 60°C or lower, 55°C or lower, or 50°C or lower. By setting the temperature of the slurry to 60°C or lower, an increase in the viscosity of the slurry can be further suppressed. In the slurry of this embodiment, even if the temperature reaches a relatively high temperature of about 55 to 60°C during preparation (stirring), an increase in viscosity is suppressed. The temperature of the slurry when it is prepared (stirred) may be 20°C or higher, 25°C or higher, or 30°C or higher.

[0024] In this manner, a mold powder is obtained. The chemical composition of the mold powder obtained is not particularly limited, but may be, for example, the following chemical composition. SiO2: 20-45 mass%, CaO: 15-55 mass%, Al2O3: 1-15 mass%, Fe2O3: 0-2 mass%, F: 0.5-30 mass%, C: 0.5-10 mass%, Zr2O: 0-5 mass%, Mn2O: 0-5 mass%, Na2O + Li2O + MgO + SrO: 0-30 mass% (all mass % based on the total amount of mold powder)

[0025] The mold powder may be, for example, in the form of hollow granules (hollow particles). This mold powder has excellent granular strength, so that even when the mold powder is transported by air from a storage location to a mold, powdering during transport is suppressed. Therefore, this mold powder exhibits the advantages of hollow granular mold powder (suppression of dust generation and thus maintenance of the working environment) and is suitable for use as a mold powder for continuous casting of steel. [Example]

[0026] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0027] Example 1 Blast furnace slag pulverized in a pulverizer was mixed with other raw materials such as dextrin as a binder, fluorite (calcium fluoride), and soda ash (sodium carbonate), and water was added to suspend the mixture to obtain a slurry. The blast furnace slag content was 50% by mass, the dextrin content was 3% by mass, and the other raw materials were 47% by mass, based on the total solid content. The solid concentration in the slurry was 68% by mass.

[0028] Examples 2 to 6 A slurry was obtained in the same manner as in Example 1, except that the content of dextrin relative to the total solid content was changed as shown in Table 1.

[0029] Example 7 A slurry was obtained in the same manner as in Example 4, except that lignin was used as the binder instead of dextrin.

[0030] Example 8 A slurry was obtained in the same manner as in Example 4, except that sucrose was used as the binder instead of dextrin.

[0031] (Comparative Example 1) A slurry was obtained in the same manner as in Example 1, except that no binder was used.

[0032] The slurries obtained in Examples 1 to 8 and Comparative Example 1 were stirred at approximately 55 to 60°C, and the viscosity of the slurries was measured every 30 minutes after the start of stirring. A viscometer, Viscotester VT-04F (Rion Corporation), combined with a No. 3 rotor was used for the viscosity measurements. The time from the start of stirring until the measured viscosity of the slurry reached 1300 mPa·s was evaluated as the arrival time. The longer the arrival time, the more suppressed the increase in viscosity of the slurry. The viscometer used is not limited to the above, as long as it can measure the increase in viscosity over time.

[0033] [Table 1]

[0034] (Reference experiment) The slurry used in Comparative Example 1 was evaluated for the time it took for the viscosity of the slurry to reach 1300 mPa·s in the same manner as above, except that the stirring temperature was changed to 50°C or 40°C. When the stirring temperature was approximately 55 to 60°C, the temperature reached the target in 150 minutes, as described above. However, when the stirring temperature was 50°C or 40°C, the viscosity of the slurry did not reach 1300 mPa·s even after 300 minutes (the viscosity of the slurry after 300 minutes was 450 mPa·s at 50°C and 310 mPa·s at 40°C). Thus, when the stirring temperature is relatively high, such as 55 to 60°C, the viscosity of the slurry is likely to increase. It is estimated that when the stirring temperature exceeds 60°C, the viscosity of the slurry becomes too high to be measured.

[0035] Example 9 A slurry was obtained in the same manner as in Example 1, except that the content of blast furnace slag was changed to 25 mass%, the content of dextrin was changed to 1.5 mass%, and the content of other raw materials was changed to 73.5 mass% relative to the total solid content.

[0036] (Examples 10 to 11) A slurry was obtained in the same manner as in Example 9, except that the content of dextrin relative to the total solid content was changed as shown in Table 2.

[0037] (Comparative Example 2) A slurry was obtained in the same manner as in Example 9, except that no binder was used.

[0038] Similarly, the time taken for the viscosity of the slurry to reach 1300 mPa·s was evaluated for each of the slurries obtained in Examples 9 to 11 and Comparative Example 2. The evaluation results are shown in Table 2.

[0039] [Table 2]

Claims

1. At least one material selected from the group consisting of blast furnace slag and Portland cement; and at least one binder selected from the group consisting of dextrin, lignin, and sucrose; Slurry used in the production of mold powder.

2. The slurry according to claim 1 , wherein a mass ratio of the content of the binder to the content of the material is 0.04 or more.

3. A method for producing a mold powder, comprising a step of spray-granulating a slurry to obtain a mold powder, The slurry At least one material selected from the group consisting of blast furnace slag and Portland cement; and at least one binder selected from the group consisting of dextrin, lignin, and sucrose.

4. The manufacturing method according to claim 3 , wherein a mass ratio of the content of the binder to the content of the material is 0.04 or more.

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