Method for producing mold powder

Abstract

To reduce the viscosity of slurry in the production of mold powder using a mineral beneficiated by flotation as a raw material.SOLUTION: A method for producing mold powder includes a first step of heating a mineral beneficiated by flotation at 160°C or higher, a second step of mixing the mineral heated in the first step with other raw materials and a dispersion medium to obtain slurry, and a third step of spray-granulating the slurry to obtain mold powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a mold powder. [Background technology]

[0002] Various minerals are used as raw materials for mold powder, which is used in continuous casting of steel. Minerals mined from mines contain many impurities. Therefore, it is necessary to select high-purity minerals from the minerals mined from mines in order to use them as raw materials for mold powder.

[0003] Methods for beneficiating minerals include manual sorting and flotation. As described in Patent Document 1, manual sorting is a method of visually sorting minerals. On the other hand, flotation is a method of separating minerals that float in a liquid from minerals that settle. Flotation is a more efficient method of beneficiating minerals than manual sorting, and flotation-treated minerals are cheaper than manual sorted minerals, so flotation-treated minerals are advantageous in terms of reducing the manufacturing costs of mold powder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-030146 Summary of the Invention [Problem to be solved by the invention]

[0005] Hollow granular molding powder is produced by spray granulating a slurry obtained by mixing raw materials with a dispersant such as water. When minerals beneficiated by flotation are used as raw materials, it is difficult to produce a slurry in which the raw materials are uniformly dispersed, as described in Patent Document 1. In particular, according to the inventors' investigations, when minerals beneficiated by flotation are used, the viscosity of the slurry increases, causing the problem of not being able to spray properly.

[0006] The present invention has been made in view of the above circumstances, and has an object to reduce the viscosity of a slurry in the production of mold powder using minerals that have been beneficiated by flotation as raw materials. [Means for solving the problem]

[0007] The present inventors have discovered that in the production of mold powder using minerals beneficiated by flotation, the viscosity of the slurry increases if the minerals beneficiated by flotation are used as is, whereas the viscosity of the slurry can be reduced by heating the minerals beneficiated by flotation to 160°C or higher before use. The present inventors speculate that heating the minerals reduces the amount of collector adhering to the surfaces of the minerals, which results in the minerals being uniformly dispersed in the dispersion medium, thereby reducing the viscosity of the slurry.

[0008] The present invention includes the following aspects. [1] A method for producing mold powder, comprising: a first step of heating ore separated by flotation at 160°C or higher; a second step of mixing the heated ore with other raw materials and a dispersant to obtain a slurry; and a third step of spray-granulating the slurry to obtain mold powder. [2] The manufacturing method according to [1], wherein the mineral is fluorite. [3] The manufacturing method according to [1] or [2], wherein the mineral is heated to 180°C or higher in the first step. [Effects of the Invention]

[0009] According to the present invention, in the production of mold powder using minerals that have been beneficiated by flotation as raw materials, it is possible to reduce the viscosity of the slurry. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0011] One embodiment of the present invention is a method for producing mold powder, comprising a first step of heating a mineral that has been separated by flotation at 160°C or higher, a second step of mixing the mineral heated in the first step with other raw materials and a dispersant to obtain a slurry, and a third step of spray-granulating the slurry to obtain mold powder.

[0012] The mineral used in the first step may be a mineral that has been beneficiated by a known flotation method. Specifically, for example, the mined mineral is crushed, mixed with a collector and water, and foam is generated by stirring or blowing air into the mixture, and the mineral that floats with the foam is collected, thereby enabling the beneficiation of the target mineral. The mineral used in the first step may also be purchased commercially.

[0013] Examples of collectors used in flotation include fatty acids such as oleic acid (boiling point: 360°C), linoleic acid (boiling point: 229°C), and α-linolenic acid (boiling point: 230°C). The collector may be attached to the surface of the mineral that has been beneficiated by flotation.

[0014] In the first step, the viscosity of the slurry can be reduced by heating the mineral separated by flotation to 160°C or higher. The temperature to which the mineral is heated may be 170°C or higher. From the viewpoint of suppressing the generation of bubbles on the surface of the slurry when the mineral is mixed (stirred) with other raw materials to obtain a slurry in the second step described below, the temperature to which the mineral is heated may preferably be 180°C or higher, 190°C or higher, 200°C or higher, 250°C or higher, or 300°C or higher. The temperature to which the mineral is heated may be 500°C or lower, 450°C or lower, or 400°C or lower.

[0015] In the first step, the time for heating the mineral may be 1 hour or more, 2 hours or more, or 2.5 hours or more, and may be 6 hours or less, 5 hours or less, or 4 hours or less. The heating in the first step may be carried out in an air atmosphere.

[0016] The mineral beneficiated by flotation may be at least one selected from the group consisting of fluorite, zircon, flaky graphite, magnesium carbonate, strontium carbonate, rutile, and spodumene, and is preferably fluorite.

[0017] The purity of the mineral concentrated by flotation may be 90% by mass or more, 91% by mass or more, 92% by mass or more, 93% by mass or more, 94% by mass or more, 95% by mass or more, or 96% by mass or more. Note that the purity of the mineral refers to the content of the main component based on the total amount of the mineral.

[0018] Fluorite is a mineral whose main component is CaF2. The CaF2 content in the fluorite (fluorite purity) may be 90 mass% or more, 91 mass% or more, 92 mass% or more, 93 mass% or more, 94 mass% or more, 95 mass% or more, or 96 mass% or more based on the total amount of fluorite. Examples of impurities in fluorite include SiO2, Fe2O3, Al2O3, KO, S, and PO5.

[0019] In the second step, the mineral heated in the first step is mixed with other raw materials and a dispersing medium to obtain a slurry. The content of the flotation mineral may be 6% by mass or more, 8% by mass or more, 10% by mass or more, or 12% by mass or more, based on the total solids content. The content of the flotation mineral may be 40% by mass or less, 38% by mass or less, or 36% by mass or less, based on the total solids content.

[0020] Other raw materials include a base material raw material, an SiO2 raw material, a flux raw material, a carbonaceous raw material, an organic binder, etc. The base material raw material may be, for example, a premelt base material raw material, specifically, raw materials produced through a heat melting process, such as blast furnace slag and converter slag produced in the ironmaking and steelmaking processes, electric furnace slag produced in electric furnaces and cupolas, yellow phosphorus slag, wollastonite, and synthetic calcium silicate. The SiO2 raw material may be glass powder, silica powder, etc. The flux raw material may be, for example, a metal oxide such as manganese dioxide, a fluoride such as sodium fluoride, or a carbonate such as lithium carbonate or sodium carbonate. The carbonaceous raw material may be carbon black. The organic binder may be, for example, dextrin or a cellulose-based polymer compound.

[0021] The total content of the other raw materials may be 60% by mass or more, 62% by mass or more, or 64% by mass or more, and may be 94% by mass or less, 92% by mass or less, 90% by mass or less, or 88% by mass or less, based on the total solid content.

[0022] The dispersion medium may be, for example, water (pure water). The content of the dispersion medium may be, for example, 15% by mass or more, 20% by mass or more, or 25% by mass or more, and 45% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total amount of the slurry.

[0023] The solid content of the slurry may be 55% by mass or more, 60% by mass or more, or 65% by mass or more, based on the total amount of the slurry, and 85% by mass or less, 80% by mass or less, or 75% by mass or less, based on the total amount of the slurry.

[0024] In the third step, the slurry obtained in the second step is spray granulated to obtain a molding powder. Specifically, the slurry obtained in the second step is spray granulated using a spray or the like, and then dried to volatilize the dispersion medium and obtain a molding powder in the form of hollow granules.

[0025] The chemical composition of the mold powder obtained as described above 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%, ZrO2: 0-5 mass%, MnO: 0-5 mass%, Na2O + Li2O + MgO + SrO: 0-30 mass% (all mass % based on the total amount of mold powder) [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 Fluorite powder (product name: fluorite, CaF2 purity: 97% by mass or more) was used, which had been subjected to flotation using a collector containing oleic acid. This fluorite powder was heated at 400°C for 3 hours. The heated fluorite powder was then mixed with other raw materials (blast furnace slag, wollastonite, glass powder, silica powder, etc.) to obtain 700 g of solids. This solids and 300 g of water were placed in a plastic container (cylindrical, diameter: 75 mm, height: 160 mm) and stirred for 30 minutes to obtain a slurry with a solids content of 70% by mass relative to the total slurry volume.

[0028] (Examples 2 to 7 and Comparative Examples 1 and 2) A slurry was obtained in the same manner as in Example 1, except that the heating temperature of the fluorite powder was changed from 400° C. to the temperatures shown in Table 1.

[0029] (Comparative Example 3) A slurry was obtained in the same manner as in Example 1, except that the fluorite powder was used without heating.

[0030] [Measurement of slurry viscosity and evaluation of foaming] Immediately after the 30 minutes of stirring, the viscosity of each slurry of the Examples and Comparative Examples was measured using a viscometer (product name "VISCOTESTER VT-04", manufactured by Rion Co., Ltd.). Note that any viscometer can be used, and is not limited to the above viscometer, as long as it can relatively evaluate the difference in viscosity (high or low viscosity) between the slurries of the Examples and Comparative Examples. The results are shown in Table 1. The surface of the slurry after stirring was visually inspected, and the presence or absence of bubbles on the surface of the slurry was judged according to the following criteria. The results are shown in Table 1. A: No foaming B: Foaming was confirmed in less than 50% of the area of ​​the slurry surface. C: Foaming was observed in 50% or more but less than 80% of the surface area of ​​the slurry. D: Foaming of 80% or more of the slurry surface area was confirmed.

[0031] [Table 1]

[0032] When the slurries of Examples 1 to 7 were spray granulated, hollow granular mold powders were obtained.

Claims

1. A first step of heating the mineral concentrated by flotation at 160°C or higher; a second step of mixing the mineral heated in the first step with other raw materials and a dispersion medium to obtain a slurry; a third step of spray-granulating the slurry to obtain a molding powder; A method for producing a mold powder comprising:

2. The method of claim 1 , wherein the mineral is fluorite.

3. The manufacturing method according to claim 1 or 2, wherein the mineral is heated to 180°C or higher in the first step.

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