EP4286072A1 - Inorganic coated sand - Google Patents

Inorganic coated sand Download PDF

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Publication number
EP4286072A1
EP4286072A1 EP22745685.2A EP22745685A EP4286072A1 EP 4286072 A1 EP4286072 A1 EP 4286072A1 EP 22745685 A EP22745685 A EP 22745685A EP 4286072 A1 EP4286072 A1 EP 4286072A1
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EP
European Patent Office
Prior art keywords
mass
parts
inorganic
inorganic binder
coated sand
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Pending
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EP22745685.2A
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German (de)
French (fr)
Inventor
Hiroaki Aonuma
Keisuke Nakane
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Kao Corp
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Kao Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
    • B22C1/186—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents contaming ammonium or metal silicates, silica sols
    • B22C1/188—Alkali metal silicates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B22C1/10—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for influencing the hardening tendency of the mould material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents

Definitions

  • the present invention relates to inorganic coated sand.
  • the mold obtained by using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate to mold the desired shape is known.
  • Patent Document 1 Japanese Unexamined Patent Publication No.2014-117740
  • Patent Document 2 Pamphlet of International Publication No. WO2015/194550
  • Patent Document 1 a production method related to a dry coated sand having normal temperature fluidity which is made by blending a specific water glass aqueous solution as a binder with a heated refractory aggregate and evaporating moisture to form a coating layer of the binder on the surface of the refractory aggregate is described.
  • Patent Document 2 a production method for a casting mold, in which a molding material mixture containing at least a refractory aggregate, a binder including a water glass as an essential component, and a carbonate and/or a borate is filled and held within a forming mold heated to a specific temperature, and thus the molding material mixture is cured.
  • the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, in which the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • FIG. 1 A cross-sectional view for explaining a measurement method for deformation of the casting mold in Examples.
  • the present invention provides a method for reducing deformation of a casting mold during casting in the casting mold prepared using an inorganic coated sand.
  • the present invention provides an inorganic coated sand that reduces deformation of the casting mold occurring during casting.
  • the present inventors found that in a casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the deformation of the casting mold during casting can be reduced by containing zinc oxide or magnesium oxide in the inorganic binder layer.
  • the present invention it is possible to provide a method for reducing deformation of a casting mold during casting in a casting mold prepared using an inorganic coated sand.
  • the method for reducing deformation of the casting mold during casting is a method in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of zinc oxide and magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder, specifically with respect to 100 parts by mass of the solid content of the inorganic binder.
  • the reason why the effect of reducing the deformation of the casting mold is exhibited is not clear, but it is considered as follows.
  • the inorganic binder contains alkali silicate or alkali metasilicate as an example
  • by containing a specific amount of zinc oxide or magnesium oxide in the inorganic binder layer of the inorganic coated sand to, for example, form a salt of zinc oxide or magnesium oxide with alkali metal ions of alkali silicate or alkali metasilicate alkali metal ions that inhibit cross-linking of silicate chains is released to outside of the system to promote cross-linking of silicate chains and to consolidate the silicate network.
  • the softening point of the inorganic binder rises, and it is thought that deformation due to the softening of the inorganic binder is less likely to occur even in a case where the casting mold is exposed to the heat of the molten metal.
  • the inorganic coated sand has a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate.
  • the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide.
  • the total content of zinc oxide and magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder, specifically with respect to 100 parts by mass of the solid content of the inorganic binder.
  • the inorganic coated sand is specifically composed of inorganic coated sand particle groups
  • the refractory aggregate is specifically composed of refractory aggregate particle groups.
  • the inorganic coated sand is preferably spherical from the viewpoint of improving the fluidity and further improving the fillability into the molding die.
  • the spherical inorganic coated sand means that the inorganic coated sand has a round shape like a ball.
  • the sphericity of the inorganic coated sand is preferably 0.75 or more, more preferably 0.80 or more, and still more preferably 0.82 or more from the viewpoint of improving fluidity, casting mold quality, and casting mold strength, and from the viewpoint of ease of molding the casting mold.
  • the upper limit of the sphericity is specifically 1 or less.
  • the sphericity of the inorganic coated sand can be determined by performing image analysis of a particle image (photograph) obtained by an optical microscope or a digital scope (for example, VH-8000 manufactured by KEYENCE CORPORATION) to obtain the particle projected sectional area of particles and the perimeter of the cross section, then to calculate [the circumferential length of a perfect circle (mm) having the same area as the particle projected sectional area (mm 2 )]/[the perimeter of the particle projected cross section (mm)] for each of any 50 particles, and averaging these values.
  • a particle image photograph
  • a digital scope for example, VH-8000 manufactured by KEYENCE CORPORATION
  • the average particle diameter of the inorganic coated sand is preferably 0.05 mm or more and more preferably 0.1 mm or more from the viewpoint of improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold.
  • the average particle diameter of the inorganic coated sand is preferably 2 mm or less, more preferably 1 mm or less, and still more preferably 0.5 mm or less from the viewpoint improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold.
  • the average particle diameter of the inorganic coated sand and the later-described refractory aggregate may be specifically measured by the following method.
  • the diameter (mm) is measured, while in a case where the sphericity ⁇ 1, the major axis diameter (mm) and minor axis diameter (mm) of the randomly oriented particle are measured to obtain (major axis diameter + minor axis diameter)/2.
  • the obtained values are averaged to obtain the average particle diameter (mm).
  • the major axis diameter and minor axis diameter are defined as follows.
  • the width of the particle at which the distance between the parallel lines is the smallest is referred to as the minor axis diameter
  • the length of a particle between two parallel lines perpendicular to the parallel lines is referred to as the major axis diameter.
  • the major axis diameter and minor axis diameter of the particles are obtained by taking an image (photograph) of the particles with an optical microscope or a digital scope (for example, VH-8000 manufactured by KEYENCE CORPORATION) and analyzing the obtained image.
  • Examples of materials for the refractory aggregate include one or more selected from the group consisting of natural sand and artificial sand.
  • natural sand examples include one or two or more selected from the group consisting of silica sand containing quartz as a main component, chromite sand, zircon sand, olivine sand, and alumina sand.
  • artificial sand examples include one or two or more selected from the group consisting of synthetic mullite sand, SiO 2 -based casting sand containing SiO 2 as a main component, Al 2 O 3 -based casting sand containing Al 2 O 3 as a main component, SiO 2 /Al 2 O 3 -based casting sand, SiO 2 /MgO-based casting sand, SiO 2 /Al 2 O 3 /ZrO 2 -based casting sand, SiO 2 /Al 2 O 3 /Fe 2 O 3 -based casting sand, and slag-derived casting sand.
  • the main component means the most abundant component among the components contained in sand.
  • the artificial sand is not casting sand produced from nature, but casting sand obtained by artificially preparing a metal oxide component and melting or sintering.
  • recovered sand obtained by recovering used refractory aggregates and recycled sand obtained by subjecting recovered sand to recycling treatment may also be used.
  • the refractory aggregate is preferably in the form of particles from the viewpoint of improving the fluidity of the inorganic coated sand and further improving the fillability into the molding die.
  • the average particle diameter of the refractory aggregate is preferably 0.05 mm or more and more preferably 0.1 mm or more from the viewpoint of improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold.
  • the used amount of the inorganic binder layer can be reduced during the production of the casting mold and thus the inorganic coated sand is more easily recycled.
  • the average particle diameter of the refractory aggregate is preferably 2 mm or less, more preferably 1 mm or less, and still more preferably 0.5 mm or less from the viewpoint improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold.
  • the inorganic binder layer specifically contains an inorganic binder and one or more selected from zinc oxide and magnesium oxide.
  • the inorganic binder layer is specifically a coating layer formed on the surface of the refractory aggregate.
  • the inorganic binder layer may be, for example, a layer coated with a mixture of an inorganic binder and one or more selected from zinc oxide and magnesium oxide; a layer further coated with one or more selected from zinc oxide and magnesium oxide on the layer coated with the inorganic binder; or a layer further coated with one or more compounds selected from zinc oxide and magnesium oxide on the layer coated with a mixture of the inorganic binder and one or more compounds selected from zinc oxide and magnesium oxide.
  • the content of the inorganic binder layer in the inorganic coated sand is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more, even still more preferably 1.0% by mass or more, and especially preferably 1.5% by mass or more with respect to the whole components excluding water in the inorganic coated sand.
  • the content of the inorganic binder layer in the inorganic coated sand is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less, even still more preferably 4.5% by mass or less, and yet even still more preferably 4% by mass or less with respect to the whole components excluding water in the inorganic coated sand.
  • the content of the inorganic binder layer refers to the content excluding water contained in the inorganic binder layer.
  • the content is calculated in terms of sodium metasilicate.
  • the content of the inorganic binder layer in the inorganic coated sand is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, still more preferably 0.5 parts by mass or more, even still more preferably 1 part by mass or more, and especially preferably 1.5 parts by mass or more with respect to 100 parts by mass of the refractory aggregate.
  • the content of the inorganic binder layer in the inorganic coated sand is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 6 parts by mass or less, even still more preferably 4.5 parts by mass or less, and yet even still more preferably 4 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
  • the inorganic binder contains, for example, a silicic acid compound, and preferably at least one selected from sodium silicate and sodium metasilicate.
  • the inorganic binder may further contain a compound in which a water-soluble silicic acid compound other than the above is contained as a main component.
  • silicic acid compound other than sodium silicate and sodium metasilicate include potassium silicate, potassium metasilicate, lithium silicate, and ammonium silicate.
  • sodium silicate examples include one or two or more selected from the group consisting of sodium silicates Nos. 1 to 5.
  • sodium silicate is classified into Nos. 1 to 5 according to the molar ratio of SiO 2 /Na 2 O, and sodium silicates Nos. 1 to 3 are prescribed in JIS-K-1408.
  • the molar ratio of SiO 2 /Na 2 O in each sodium silicate is as follows.
  • the molar ratio of SiO 2 /Na 2 O may be adjusted to a desired degree.
  • Sodium silicate is preferably at least one selected from No. 1 water glass and No. 3 water glass.
  • Sodium metasilicate is preferably a hydrate from the viewpoint of improving the productivity of the inorganic coated sand and the viewpoint of improving the productivity of the casting mold.
  • the sodium metasilicate hydrate is preferably at least one selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate, and more preferably sodium metasilicate nonahydrate.
  • the content of the inorganic binder in the inorganic binder layer is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and even still more preferably 40% by mass or more with respect to the whole inorganic binder layer.
  • the content of the inorganic binder in the inorganic binder layer is preferably 94% by mass or less and more preferably 93% by mass or less with respect to the whole inorganic binder layer.
  • the content of the inorganic binder in the inorganic binder layer refers to the content of the inorganic binder excluding moisture with respect to the whole components excluding water in the inorganic binder layer.
  • the total content of sodium silicate and sodium metasilicate in the inorganic binder is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, even still more preferably 98% by mass or more, and yet even still more preferably substantially 100% by mass.
  • the term "substantially” means that unintentionally contained components, for example, components other than sodium silicate and sodium metasilicate contained in sodium silicate and sodium metasilicate which are raw materials, may be contained.
  • the total content of sodium silicate and sodium metasilicate in the inorganic binder refers to the total content of sodium silicate and sodium metasilicate with respect to whole components excluding water in the inorganic binder.
  • the content of the inorganic binder in the inorganic coated sand is preferably 0.03 parts by mass or more, more preferably 0.1 parts by mass or more, still more preferably 0.5 parts by mass or more, even still more preferably 0.8 parts by mass or more, and especially preferably 1 part by mass or more with respect to 100 parts by mass of the refractory aggregate.
  • the content of the inorganic binder in the inorganic coated sand is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and even still more preferably 2 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
  • the properties of zinc oxide (ZnO) and magnesium oxide (MgO) are preferably fine particles from the viewpoint of enhancing reactivity with the inorganic binder.
  • the average particle diameters of zinc oxide and magnesium oxide are preferably 100 um or less, more preferably 50 um or less, still more preferably 30 um or less, even still more preferably 20 um or less, and yet even still more preferably 15 um or less.
  • the average particle diameters of zinc oxide and magnesium oxide is preferably 0.1 um or more, more preferably 0.3 um or more, still more preferably 0.5 um or more, and even still more preferably 1 um or more.
  • the average particle diameters of zinc oxide and magnesium oxide may be performed using the following measurement method.
  • the average particle diameter is 50% volume cumulative particle diameter measured using a laser diffraction particle size distribution measuring device LA-960V2 (manufactured by HORIBA, Ltd.). Analysis conditions are as follows.
  • the total content of zinc oxide and magnesium oxide in the inorganic binder layer is preferably 2% by mass or more and more preferably 3% by mass or more with respect to whole components excluding water in the inorganic binder layer.
  • the total content of zinc oxide and magnesium oxide in the inorganic binder layer is preferably 45% by mass or less, more preferably 40% by mass or less, and still more preferably 35% by mass or less with respect to the whole components excluding water in the inorganic binder layer.
  • the total content of zinc oxide and magnesium oxide with respect to 100 parts by mass of the inorganic binder is preferably 6 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, even still more preferably 15 parts by mass or more, and especially preferably 20 parts by mass or more.
  • the total content of zinc oxide and magnesium oxide with respect to 100 parts by mass of the inorganic binder is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 55 parts by mass or less, and even still more preferably 50 parts by mass or less.
  • the inorganic binder layer may contain various additives as necessary.
  • additives include moisturizing agents, moisture resistance improvers, coupling agents that strengthen the bond between the refractory aggregate and the inorganic binder, lubricants, surfactants, releasing agents.
  • moisturizing agents include polyhydric alcohols, water-soluble polymers, hydrocarbons, sugars, proteins, and inorganic compounds other than those mentioned above.
  • moisture resistance improvers include metal oxides (excluding zinc oxide and magnesium oxide), carbonates, borates, sulfates, phosphates.
  • lubricants include waxes; fatty acid amides; alkylene fatty acid amides; stearic acid; stearyl alcohol; metal stearates such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate; monoglyceride stearate; stearyl stearate; hydrogenated oil.
  • releasing agents include paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, vermiculite, fluorine-based releasing agent, and silicone-based releasing agent.
  • the inorganic coated sand may further contain inorganic fine particles excluding zinc oxide and magnesium oxide.
  • the inorganic fine particles preferably form part of the inorganic binder layer.
  • the inorganic binder layer preferably further contains inorganic fine particles at least one of on the layer and in the layer, and more preferably further contains inorganic fine particles on the layer.
  • the inorganic fine particles may be contained both on the inorganic binder layer and in the inorganic binder layer.
  • the particles of the inorganic coated sand are more firmly bound to each other through the inorganic fine particles, and as a result, the strength of the obtained casting mold can be further improved.
  • the inorganic fine particles on the inorganic binder layer may be partially embedded in the inorganic binder layer.
  • inorganic fine particles include, but are not limited to, silica particles and silicon particles. From the viewpoint of improving the strength of the casting mold, silica particles are preferable, and from the viewpoint of having a large specific surface area and being highly reactive with sodium silicate and sodium metasilicate, amorphous silica particles are more preferable. These inorganic fine particles may be used singly or may be used in combination of two or more.
  • the inorganic coated sand may further contain amorphous silica particles.
  • Amorphous silica particles preferably form part of the inorganic binder layer.
  • the amorphous degree of the amorphous silica particles is preferably 80% or more, more preferably 90% or more, still more preferably 93% or more, even still more preferably 95% or more, and especially preferably 98% or more.
  • the upper limit of the amorphous degree of the amorphous silica particles is not limited, but is, for example, 100% or less, may be 99.8% or less, and also may be 99% or less.
  • the amorphous degree of amorphous silica particles may be obtained by the X-ray diffraction method shown below.
  • Amorphous silica particles are pulverized in a mortar and pressed against an X-ray glass holder of a powder X-ray diffractometer for measurement.
  • the average particle diameter d 50 in the weight-based particle size distribution of amorphous silica particles by a laser diffraction scattering particle size distribution measurement method is preferably 0.1 um or more and more preferably 0.3 um or more. Further, from the viewpoint of improving the strength of the casting mold, the above-described average particle diameter d 50 of the amorphous silica particles is preferably 2.0 um or less, more preferably 1.0 um or less, still more preferably 0.8 um or less, and even still more preferably 0.6 um or less.
  • the average particle diameter d 50 in the weight-based particle size distribution of the amorphous silica particles by the laser diffraction scattering particle size distribution measurement method may be obtained, for example, by dissolving the inorganic binder layer in water to remove it from the inorganic coated sand, collecting the amorphous silica particles, and then measuring the particle size of the obtained amorphous silica particles by a laser diffraction scattering particle size distribution measurement method.
  • the average particle diameter d 50 in the weight-based particle size distribution of the amorphous silica particles by the laser diffraction scattering particle size distribution measurement method may also be obtained by measuring the particle size of the amorphous silica particles as a raw material by the laser diffraction scattering particle size distribution measurement method.
  • the average particle diameter of the amorphous silica particles obtained from the observation image of the scanning electron microscope is preferably 0.1 um or more and more preferably 0.3 um or more.
  • the average particle diameter of the amorphous silica particles obtained from the observation image of the scanning electron microscope is preferably 2.0 um or less, more preferably 1.0 um or less, still more preferably 0.8 um or less, and even still more preferably 0.6 um or less.
  • Random particle sorting may be performed as a pretreatment. For example, after determining the inorganic binder layer and the amorphous silica particles based on the elements, 100 arbitrary amorphous silica particles are selected, their particle diameters are measured, and the average particle diameter of 80 amorphous silica particles excluding a total of 20 amorphous silica particles of 10 particles counted from the maximum particle diameter and 10 particles counted from the minimum particle diameter may be the average particle diameter of the amorphous silica particles.
  • the content of the amorphous silica particles in the inorganic binder layer is specifically 0% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, and still more preferably 30% by mass or more with respect to the whole components excluding water in the inorganic binder layer.
  • the content of the amorphous silica particles in the inorganic binder layer is preferably 55% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less with respect to the whole components excluding water in the inorganic binder layer.
  • the content of the amorphous silica particles is specifically 0 parts by mass or more, preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and even still more preferably 60 parts by mass or more with respect to 100 parts by mass of the inorganic binder.
  • the content of the amorphous silica particles is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, still more preferably 100 parts by mass or less, even still more preferably 90 parts by mass or less, and yet even still more preferably 80 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the inorganic binder.
  • the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, still more preferably 150 parts by mass or less, and even still more preferably 140 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • the content of water in the inorganic binder layer contained in the inorganic coated sand may be adjusted according to the type of inorganic binder.
  • the content of water in the inorganic binder layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of sodium silicate.
  • the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 55 parts by mass or less and more preferably 50 parts by mass or less with respect to 100 parts by mass of sodium silicate.
  • the content of water in the inorganic binder layer is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, still more preferably 90 parts by mass or more, and even still more preferably 110 parts by mass or more with respect to 100 parts by mass of sodium metasilicate, and from the viewpoint of improving fluidity and further improving the fillability into the molding die, the content of water in the inorganic binder layer is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, still more preferably 150 parts by mass or less, and even still more preferably 140 parts by mass or less with respect to 100 parts by mass of sodium metasilicate.
  • the content of water is 74 parts by mass with respect to 100 parts by mass of sodium metasilicate, and in a case where it is only sodium metasilicate nonahydrate, the content of water is 133 parts by mass with respect to 100 parts by mass of sodium metasilicate.
  • the method for producing the inorganic coated sand may be selected, for example, according to the type of inorganic binder.
  • a dry inorganic coated sand having normal temperature fluidity can be obtained by, for example, kneading or mixing a water glass aqueous solution as the inorganic binder with the heated refractory aggregate, together with additives as necessary to blend uniformly, coating the surface of the refractory aggregate with the water glass aqueous solution, and allowing the moisture in the water glass aqueous solution to being evaporated.
  • a dry inorganic coated sand can be obtained by a production method including, for example, mixing the refractory aggregate and the sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate to obtain a mixture; and cooling the mixture to a temperature less than the melting point of the sodium metasilicate hydrate.
  • the inorganic binder layer can be crystallized, thus an inorganic coated sand having excellent fluidity can be obtained as compared with the conventional production method.
  • a dehydration step is not needed, and the production method for the inorganic coated sand can be simplified.
  • the surface of the refractory aggregate is coated with the fluidized sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate.
  • Examples of the method of mixing the refractory aggregate and the sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate include a method of adding the sodium metasilicate hydrate to a refractory aggregate heated to a temperature not less than the melting point of the sodium metasilicate hydrate and mixing the refractory aggregate and the sodium metasilicate hydrate while melting the sodium metasilicate hydrate; and a method of adding the heat-melted sodium metasilicate hydrate to the refractory aggregate and mixing them.
  • the method of adding the heat-melted sodium metasilicate hydrate to the refractory aggregate and mixing them is preferable.
  • the obtaining the mixture does not include intentionally adding water.
  • Mixing conditions such as stirring speed and treatment time when the refractory aggregate and sodium metasilicate hydrate are mixed may be appropriately determined according to the treatment amount of the mixture.
  • the fluidity of the sodium metasilicate hydrate is reduced by cooling the mixture obtained in the obtaining the mixture to a temperature less than the melting point of the sodium metasilicate hydrate, the sodium metasilicate hydrate is fixed on the surface of the refractory aggregate, and the sodium metasilicate hydrate layer, that is, the inorganic binder layer is formed.
  • inorganic coated sand there are no restrictions on the method of adding zinc oxide or magnesium oxide, for example, after the refractory aggregate is coated with the inorganic binder, optionally the amorphous silica particles and the above-described other additives, one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives may be coated.
  • the refractory aggregate may be coated together with the inorganic binder and one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives.
  • the refractory aggregate may be coated together with the inorganic binder and one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives, one or more selected from zinc oxide and magnesium oxide, or optionally amorphous silica particles and other additives may be coated.
  • the refractory aggregate is coated with an inorganic binder and then is coated with one or more selected from zinc oxide and magnesium oxide.
  • Zinc oxide or magnesium oxide in solid form or in aqueous dispersion can be mixed with the refractory aggregate, the inorganic binder, and the like.
  • zinc oxide or magnesium oxide may be added all at once, or may be added in a plurality of times.
  • the inorganic coated sand in the present embodiment may be obtained.
  • the obtained inorganic coated sand can be used singly or in combination with other known refractory aggregates or other additives to mold desired casting molds.
  • the casting mold is made by using the inorganic coated sand in the present embodiment described above.
  • the molding method for the casting mold include a molding method using a heated molding die, and a molding method in which water vapor is further passed through the heated molding die and then hot air is passed through the heated molding die.
  • the inorganic binder layer contains sodium metasilicate hydrate
  • a method of molding by filling a heated molding die with inorganic coated sand is preferable.
  • the inorganic binder layer contains sodium silicate
  • the inorganic binder layer contains sodium metasilicate hydrate
  • the inorganic coated sand is first filled into the molding die that provides the desired casting mold.
  • the molding die is preferably heated in advance to keep it warm before filling with the inorganic coated sand.
  • the heating temperature at this time is preferably 100°C or more, and more preferably 150°C or more, and is also preferably 300°C or less and more preferably 250°C or less.
  • the molding die After filling with the inorganic coated sand, the molding die is heated without passage of water vapor to cure the inorganic coated sand.
  • the inorganic binder layer contains sodium metasilicate hydrate
  • the inorganic coated sand can be cured without using adding water to the inorganic coated sand and kneading, or passing water vapor, and thus the equipment or the like for passing water vapor is unnecessary.
  • the heating temperature is preferably 100°C or more, and more preferably 150°C or more, and is also preferably 300°C or less and more preferably 250°C or less.
  • the heating time is preferably 30 seconds or more and more preferably 60 seconds or more, and is also preferably 600 seconds or less.
  • the inorganic binder layer contains sodium silicate
  • water is added to the inorganic coated sand and the inorganic coated sand is kneaded, and then filled into a heated molding die.
  • water vapor is passed through
  • water vapor is blown in after the inorganic coated sand is filled into the molding die that provides the desired casting mold.
  • the passage of water vapor wets the filled phase of the inorganic coated sand to be in a wet state.
  • hot air is passed through the molding die heated to 90°C to 200°C to dry and cure the inorganic coated sand.
  • the inorganic coated sand in the present embodiment may also be used in the laminate molding method.
  • the present invention further discloses a method for reducing deformation of a casting mold, and an inorganic coated sand described below.
  • Mikawa Silica Sand R6 (100 parts by mass) was added to a stirrer as a refractory aggregate. Next, sodium metasilicate nonahydrate (4.00 parts by mass) melted by heating to 80°C was added to the stirrer and kneaded for 4 minutes, and then amorphous silica fine particles (1.20 parts by mass) were added thereto and kneaded for 2 minutes. Then, zinc oxide or magnesium oxide in the amount shown in Table 1 was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 1 to 4. Table 1 shows a blending composition of the inorganic coated sand.
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate.
  • No. 1 50 water glass (4.00 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed.
  • zinc oxide or magnesium oxide (the amount shown in Table 2) was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 5 to 12.
  • Table 2 shows a blending composition of the inorganic coated sand.
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 3 water glass (4.00 parts by mass) and zinc oxide or magnesium oxide (0.41 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed and to obtain the inorganic coated sands of Examples 14 and 16. Table 3 shows a blending composition of the inorganic coated sand.
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 3 water glass (4.00 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed. Furthermore, zinc oxide or magnesium oxide (0.41 parts by mass) was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 15 and 17.
  • the inorganic coated sand of Comparative Example 1 was obtained in the same manner as in Examples 1 to 4, except that neither zinc oxide nor magnesium oxide was added.
  • Table 1 shows a blending composition of the inorganic coated sand.
  • the inorganic coated sand of Comparative Example 2 was obtained in the same manner as in Examples 5 to 12, except that neither zinc oxide nor magnesium oxide was added.
  • Table 2 shows a blending composition of the inorganic coated sand.
  • the inorganic coated sand of Comparative Example 3 was obtained in the same manner as in Example 13, except that zinc oxide was not added.
  • Table 2 shows a blending composition of the inorganic coated sand.
  • the inorganic coated sand of Comparative Example 4 was obtained in the same manner as in Examples 14 to 17, except that neither zinc oxide nor magnesium oxide was added.
  • Table 3 shows a blending composition of the inorganic coated sand.
  • a 22.3 ⁇ 22.3 ⁇ 180 mm test piece (5-cavity) mold was heated to 180°C.
  • the inorganic coated sand of each example using a CSR-43 blow molding machine, the inorganic coated sand was filled into the test piece mold at a blow pressure of 0.3 MPa. Then, the inorganic coated sand was allowed to stand for 150 seconds in the molding die to cure it, and a casting mold test piece was obtained.
  • Fig. 1(a) and Fig. 1(b) are cross-sectional views for explaining a measurement method for deformation of the casting mold.
  • the casting mold test piece of each example obtained by the above-described method was left in a thermostatic chamber at 25°C/55 %RH for 1 hour, and then cut into a plate-shaped test piece 10 of 5 ⁇ 22.3 ⁇ 90 mm.
  • Metal pedestals 11a and 11b (13 mm ⁇ 13 mm, height of 13 mm) were arranged on an iron plate of appropriate size such that the distance between the centers was 90 mm, and a plate-shaped test piece 10 was placed on it such that the edges of the plate-shaped test piece 10 were positioned at the centers of the pedestals, respectively ( Fig. 1(a) ).
  • a weight 13 (4.7 g) was placed on the center of the plate-shaped test piece 10. Then, the iron plate on which the plate-shaped test piece 10 was placed was heated in a muffle furnace heated under the conditions described later. After a predetermined time had elapsed, the plate-shaped test piece 10 was taken out from the muffle furnace and allowed to stand for 1 hour to cool. Then, the deformation amount of the plate-shaped test piece 10 was measured. The deformation amount was defined as the maximum vertical distance from the straight line connecting both ends of the plate-shaped test piece 10 to the curved portion ( Fig. 1(b) ).
  • the heating conditions were 500°C and 10 minutes for all of Examples 1 to 17 and Comparative Examples 1 to 4.

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Abstract

A method for reducing deformation of a casting mold during casting, in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.

Description

    TECHNICAL FIELD
  • The present invention relates to inorganic coated sand.
    • BACKGROUND ART
  • As a casting mold used for casting a casting, for example, the mold obtained by using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate to mold the desired shape is known.
  • Techniques related to such an inorganic coated sand include those described in Japanese Unexamined Patent Publication No.2014-117740 (Patent Document 1) and Pamphlet of International Publication No. WO2015/194550 (Patent Document 2).
  • In Patent Document 1, a production method related to a dry coated sand having normal temperature fluidity which is made by blending a specific water glass aqueous solution as a binder with a heated refractory aggregate and evaporating moisture to form a coating layer of the binder on the surface of the refractory aggregate is described.
  • In Patent Document 2, a production method for a casting mold, in which a molding material mixture containing at least a refractory aggregate, a binder including a water glass as an essential component, and a carbonate and/or a borate is filled and held within a forming mold heated to a specific temperature, and thus the molding material mixture is cured.
    • SUMMARY OF THE INVENTION
  • According to the present invention, there is provided a method for reducing deformation of a casting mold during casting , in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • According to the present invention, there is provided an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, in which the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • [Fig. 1] A cross-sectional view for explaining a measurement method for deformation of the casting mold in Examples.
    • DESCRIPTION OF EMBODIMENTS
  • According to the studies of the present inventors, it was newly found that with conventional inorganic coated sand, for example, in a case where a casting mold having a complicated and thin shape is manufactured, the casting mold is deformed by being exposed to high-temperature molten metal during casting, and there is room for improving the dimensional accuracy.
  • The present invention provides a method for reducing deformation of a casting mold during casting in the casting mold prepared using an inorganic coated sand. In addition, the present invention provides an inorganic coated sand that reduces deformation of the casting mold occurring during casting.
  • The present inventors found that in a casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the deformation of the casting mold during casting can be reduced by containing zinc oxide or magnesium oxide in the inorganic binder layer.
  • According to the present invention, it is possible to provide a method for reducing deformation of a casting mold during casting in a casting mold prepared using an inorganic coated sand. In addition, according to the present invention, it is possible to provide an inorganic coated sand that reduces deformation of the casting mold during casting.
  • Hereinafter, the embodiments of the present invention will be described. In addition, in this specification, "A to B" indicating a numerical range represents a range of A or more and B or less, unless otherwise specified, and includes values at both ends. Furthermore, the configurations and elements described in each embodiment may be combined appropriately as long as the effects of the invention are not impaired.
    • <Method for reducing deformation of casting mold during casting>
  • In the present embodiment, the method for reducing deformation of the casting mold during casting is a method in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of zinc oxide and magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder, specifically with respect to 100 parts by mass of the solid content of the inorganic binder.
    • (Mechanism of deformation reduction)
  • In the present embodiment, the reason why the effect of reducing the deformation of the casting mold is exhibited is not clear, but it is considered as follows. Taking a configuration in which the inorganic binder contains alkali silicate or alkali metasilicate as an example, specifically, by containing a specific amount of zinc oxide or magnesium oxide in the inorganic binder layer of the inorganic coated sand to, for example, form a salt of zinc oxide or magnesium oxide with alkali metal ions of alkali silicate or alkali metasilicate, alkali metal ions that inhibit cross-linking of silicate chains is released to outside of the system to promote cross-linking of silicate chains and to consolidate the silicate network. As a result, the softening point of the inorganic binder rises, and it is thought that deformation due to the softening of the inorganic binder is less likely to occur even in a case where the casting mold is exposed to the heat of the molten metal.
  • Hereinafter, the production method for the inorganic coated sand and the casting mold will be described in more detail.
    • <Inorganic coated sand>
  • The inorganic coated sand has a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate. The inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide. The total content of zinc oxide and magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder, specifically with respect to 100 parts by mass of the solid content of the inorganic binder.
  • The inorganic coated sand is specifically composed of inorganic coated sand particle groups, and the refractory aggregate is specifically composed of refractory aggregate particle groups.
  • The inorganic coated sand is preferably spherical from the viewpoint of improving the fluidity and further improving the fillability into the molding die. Here, the spherical inorganic coated sand means that the inorganic coated sand has a round shape like a ball.
  • More specifically, the sphericity of the inorganic coated sand is preferably 0.75 or more, more preferably 0.80 or more, and still more preferably 0.82 or more from the viewpoint of improving fluidity, casting mold quality, and casting mold strength, and from the viewpoint of ease of molding the casting mold. In addition, the upper limit of the sphericity is specifically 1 or less.
  • Here, the sphericity of the inorganic coated sand can be determined by performing image analysis of a particle image (photograph) obtained by an optical microscope or a digital scope (for example, VH-8000 manufactured by KEYENCE CORPORATION) to obtain the particle projected sectional area of particles and the perimeter of the cross section, then to calculate [the circumferential length of a perfect circle (mm) having the same area as the particle projected sectional area (mm2)]/[the perimeter of the particle projected cross section (mm)] for each of any 50 particles, and averaging these values.
  • The average particle diameter of the inorganic coated sand is preferably 0.05 mm or more and more preferably 0.1 mm or more from the viewpoint of improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold. In addition, it is also preferable that in a case where the average particle diameter of the inorganic coated sand is not less than the above-described lower limit, the used amount of the inorganic binder layer can be reduced during the production of the casting mold and thus the inorganic coated sand is more easily recycled.
  • The average particle diameter of the inorganic coated sand is preferably 2 mm or less, more preferably 1 mm or less, and still more preferably 0.5 mm or less from the viewpoint improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold. In addition, it is also preferable that in a case where the average particle diameter of the inorganic coated sand is not more than the above-described upper limit, the porosity is reduced during the production of the casting mold and thus the strength of the casting mold can be increased.
  • In the present embodiment, the average particle diameter of the inorganic coated sand and the later-described refractory aggregate may be specifically measured by the following method.
    • (Measurement method for average particle diameter)
  • For each of arbitrary 100 particles, in a case where the sphericity from the particle projected cross section of the particle = 1, the diameter (mm) is measured, while in a case where the sphericity < 1, the major axis diameter (mm) and minor axis diameter (mm) of the randomly oriented particle are measured to obtain (major axis diameter + minor axis diameter)/2. The obtained values are averaged to obtain the average particle diameter (mm). The major axis diameter and minor axis diameter are defined as follows. In a case where a particle is stabilized on a plane and the image of the particle projected onto the plane is sandwiched between two parallel lines, the width of the particle at which the distance between the parallel lines is the smallest is referred to as the minor axis diameter, while the length of a particle between two parallel lines perpendicular to the parallel lines is referred to as the major axis diameter.
  • The major axis diameter and minor axis diameter of the particles are obtained by taking an image (photograph) of the particles with an optical microscope or a digital scope (for example, VH-8000 manufactured by KEYENCE CORPORATION) and analyzing the obtained image.
    • (Refractory aggregate)
  • Examples of materials for the refractory aggregate include one or more selected from the group consisting of natural sand and artificial sand.
  • Examples of natural sand include one or two or more selected from the group consisting of silica sand containing quartz as a main component, chromite sand, zircon sand, olivine sand, and alumina sand.
  • Examples of artificial sand include one or two or more selected from the group consisting of synthetic mullite sand, SiO2-based casting sand containing SiO2 as a main component, Al2O3-based casting sand containing Al2O3 as a main component, SiO2/Al2O3-based casting sand, SiO2/MgO-based casting sand, SiO2/Al2O3/ZrO2-based casting sand, SiO2/Al2O3/Fe2O3-based casting sand, and slag-derived casting sand. Here, the main component means the most abundant component among the components contained in sand.
  • The artificial sand is not casting sand produced from nature, but casting sand obtained by artificially preparing a metal oxide component and melting or sintering. In addition, recovered sand obtained by recovering used refractory aggregates and recycled sand obtained by subjecting recovered sand to recycling treatment may also be used.
  • The refractory aggregate is preferably in the form of particles from the viewpoint of improving the fluidity of the inorganic coated sand and further improving the fillability into the molding die.
  • In addition, the average particle diameter of the refractory aggregate is preferably 0.05 mm or more and more preferably 0.1 mm or more from the viewpoint of improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold. In addition, it is also preferable that in a case where the average particle diameter of the refractory aggregate is not less than the above-described lower limit, the used amount of the inorganic binder layer can be reduced during the production of the casting mold and thus the inorganic coated sand is more easily recycled.
  • The average particle diameter of the refractory aggregate is preferably 2 mm or less, more preferably 1 mm or less, and still more preferably 0.5 mm or less from the viewpoint improving casting mold quality and casting mold strength and from the viewpoint of ease of molding the casting mold. In addition, it is also preferable that in a case where the average particle diameter of the refractory aggregate is not more than the above-described upper limit, the porosity is reduced during the production of the casting mold and thus the strength of the casting mold can be increased.
    • (Inorganic binder layer)
  • The inorganic binder layer specifically contains an inorganic binder and one or more selected from zinc oxide and magnesium oxide.
  • The inorganic binder layer is specifically a coating layer formed on the surface of the refractory aggregate. The inorganic binder layer may be, for example, a layer coated with a mixture of an inorganic binder and one or more selected from zinc oxide and magnesium oxide; a layer further coated with one or more selected from zinc oxide and magnesium oxide on the layer coated with the inorganic binder; or a layer further coated with one or more compounds selected from zinc oxide and magnesium oxide on the layer coated with a mixture of the inorganic binder and one or more compounds selected from zinc oxide and magnesium oxide.
  • From the viewpoint of improving the strength of the casting mold, the content of the inorganic binder layer in the inorganic coated sand is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more, even still more preferably 1.0% by mass or more, and especially preferably 1.5% by mass or more with respect to the whole components excluding water in the inorganic coated sand.
  • In addition, from the viewpoint of improving the fillability into the molding die and the viewpoint of improving the strength of the casting mold, the content of the inorganic binder layer in the inorganic coated sand is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less, even still more preferably 4.5% by mass or less, and yet even still more preferably 4% by mass or less with respect to the whole components excluding water in the inorganic coated sand.
  • Here, the content of the inorganic binder layer refers to the content excluding water contained in the inorganic binder layer. For example, in a case where the sodium metasilicate hydrate described later is used as an inorganic binder, the content is calculated in terms of sodium metasilicate.
  • From the viewpoint of improving the strength of the casting mold, the content of the inorganic binder layer in the inorganic coated sand is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, still more preferably 0.5 parts by mass or more, even still more preferably 1 part by mass or more, and especially preferably 1.5 parts by mass or more with respect to 100 parts by mass of the refractory aggregate.
  • In addition, from the viewpoint of improving the fillability into the molding die and the viewpoint of improving the strength of the casting mold, the content of the inorganic binder layer in the inorganic coated sand is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 6 parts by mass or less, even still more preferably 4.5 parts by mass or less, and yet even still more preferably 4 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
  • Next, the components contained in the inorganic binder layer will be explained.
    • (Inorganic binder)
  • In the present embodiment, from the viewpoint of excellent productivity and the viewpoint of availability, the inorganic binder contains, for example, a silicic acid compound, and preferably at least one selected from sodium silicate and sodium metasilicate.
  • In addition, the inorganic binder may further contain a compound in which a water-soluble silicic acid compound other than the above is contained as a main component. Specific examples of silicic acid compound other than sodium silicate and sodium metasilicate include potassium silicate, potassium metasilicate, lithium silicate, and ammonium silicate.
  • Specific examples of sodium silicate include one or two or more selected from the group consisting of sodium silicates Nos. 1 to 5. Here, sodium silicate is classified into Nos. 1 to 5 according to the molar ratio of SiO2/Na2O, and sodium silicates Nos. 1 to 3 are prescribed in JIS-K-1408. Specifically, the molar ratio of SiO2/Na2O in each sodium silicate is as follows.
  • Sodium silicate No. 1: molar ratio of SiO2/Na2O = 2.0 to 2.3
  • Sodium silicate No. 2: molar ratio of SiO2/Na2O = 2.4 to 2.6
  • Sodium silicate No. 3: molar ratio of SiO2/Na2O = 2.8 to 3.3
  • Sodium silicate No. 4: molar ratio of SiO2/Na2O = 3.3 to 3.5
  • Sodium silicate No. 5: molar ratio of SiO2/Na2O = 3.6 to 3.8
  • In addition, by mixing two or more sodium silicates, the molar ratio of SiO2/Na2O may be adjusted to a desired degree.
  • Sodium silicate is preferably at least one selected from No. 1 water glass and No. 3 water glass.
  • Sodium metasilicate is preferably a hydrate from the viewpoint of improving the productivity of the inorganic coated sand and the viewpoint of improving the productivity of the casting mold.
  • From the above viewpoint, the sodium metasilicate hydrate is preferably at least one selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate, and more preferably sodium metasilicate nonahydrate.
  • From the viewpoint of improving the strength of the casting mold and the viewpoint of improving the surface shape of the casting mold, the content of the inorganic binder in the inorganic binder layer is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and even still more preferably 40% by mass or more with respect to the whole inorganic binder layer.
  • In addition, from the viewpoint of reducing deformation of the casting mold at high temperature, the content of the inorganic binder in the inorganic binder layer is preferably 94% by mass or less and more preferably 93% by mass or less with respect to the whole inorganic binder layer.
  • Here, the content of the inorganic binder in the inorganic binder layer refers to the content of the inorganic binder excluding moisture with respect to the whole components excluding water in the inorganic binder layer.
  • From the viewpoint of improving the strength of the casting mold, the viewpoint of excellent productivity, and the viewpoint of availability, the total content of sodium silicate and sodium metasilicate in the inorganic binder is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, even still more preferably 98% by mass or more, and yet even still more preferably substantially 100% by mass. Here, the term "substantially" means that unintentionally contained components, for example, components other than sodium silicate and sodium metasilicate contained in sodium silicate and sodium metasilicate which are raw materials, may be contained.
  • The total content of sodium silicate and sodium metasilicate in the inorganic binder refers to the total content of sodium silicate and sodium metasilicate with respect to whole components excluding water in the inorganic binder.
  • In addition, from the viewpoint of improving the strength of the casting mold and the viewpoint of improving the surface shape of the casting mold, the content of the inorganic binder in the inorganic coated sand is preferably 0.03 parts by mass or more, more preferably 0.1 parts by mass or more, still more preferably 0.5 parts by mass or more, even still more preferably 0.8 parts by mass or more, and especially preferably 1 part by mass or more with respect to 100 parts by mass of the refractory aggregate.
  • In addition, from the viewpoint of improving the fillability into the molding die, the content of the inorganic binder in the inorganic coated sand is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and even still more preferably 2 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
    • (Zinc oxide, magnesium oxide)
  • The properties of zinc oxide (ZnO) and magnesium oxide (MgO) are preferably fine particles from the viewpoint of enhancing reactivity with the inorganic binder.
  • From the viewpoint of enhancing reactivity with the inorganic binder, the average particle diameters of zinc oxide and magnesium oxide are preferably 100 um or less, more preferably 50 um or less, still more preferably 30 um or less, even still more preferably 20 um or less, and yet even still more preferably 15 um or less.
  • In addition, from the viewpoint of ease of handling and the viewpoint of availability, the average particle diameters of zinc oxide and magnesium oxide is preferably 0.1 um or more, more preferably 0.3 um or more, still more preferably 0.5 um or more, and even still more preferably 1 um or more.
  • Specifically, the average particle diameters of zinc oxide and magnesium oxide may be performed using the following measurement method.
    • (Measurement method for average particle diameter)
  • The average particle diameter is 50% volume cumulative particle diameter measured using a laser diffraction particle size distribution measuring device LA-960V2 (manufactured by HORIBA, Ltd.). Analysis conditions are as follows.
    • ·Measurement method: flow method
    • ·Dispersion medium: water
    • ·Dispersion method: stirring, built-in ultrasonic wave for 3 minutes
    • ·Sample concentration: 2 mg/100 mL
    • ·Refractive index: refractive index of each oxide (zinc oxide: 2.00, magnesium oxide: 1.76)
  • From the viewpoint of reducing deformation of the casting mold at high temperature, the total content of zinc oxide and magnesium oxide in the inorganic binder layer is preferably 2% by mass or more and more preferably 3% by mass or more with respect to whole components excluding water in the inorganic binder layer.
  • In addition, from the viewpoint of improving the strength of the casting mold, the total content of zinc oxide and magnesium oxide in the inorganic binder layer is preferably 45% by mass or less, more preferably 40% by mass or less, and still more preferably 35% by mass or less with respect to the whole components excluding water in the inorganic binder layer.
  • From the viewpoint of reducing deformation of the casting mold at high temperature, the total content of zinc oxide and magnesium oxide with respect to 100 parts by mass of the inorganic binder is preferably 6 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, even still more preferably 15 parts by mass or more, and especially preferably 20 parts by mass or more.
  • In addition, from the viewpoint of improving the strength of the casting mold, and from the viewpoint reducing dust scattering in a case of adding zinc oxide and magnesium oxide after the refractory aggregate is coated with an inorganic binder (external addition) in the production of inorganic coated sand, the total content of zinc oxide and magnesium oxide with respect to 100 parts by mass of the inorganic binder is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 55 parts by mass or less, and even still more preferably 50 parts by mass or less.
    • (Other additives)
  • In addition to the components described above, the inorganic binder layer may contain various additives as necessary. Examples of other additives include moisturizing agents, moisture resistance improvers, coupling agents that strengthen the bond between the refractory aggregate and the inorganic binder, lubricants, surfactants, releasing agents.
  • Among these, examples of moisturizing agents include polyhydric alcohols, water-soluble polymers, hydrocarbons, sugars, proteins, and inorganic compounds other than those mentioned above.
  • Examples of moisture resistance improvers include metal oxides (excluding zinc oxide and magnesium oxide), carbonates, borates, sulfates, phosphates.
  • Examples of lubricants include waxes; fatty acid amides; alkylene fatty acid amides; stearic acid; stearyl alcohol; metal stearates such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate; monoglyceride stearate; stearyl stearate; hydrogenated oil.
  • Examples of releasing agents include paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, vermiculite, fluorine-based releasing agent, and silicone-based releasing agent.
    • (Inorganic fine particles)
  • In the present embodiment, the inorganic coated sand may further contain inorganic fine particles excluding zinc oxide and magnesium oxide. The inorganic fine particles preferably form part of the inorganic binder layer. In this case, the inorganic binder layer preferably further contains inorganic fine particles at least one of on the layer and in the layer, and more preferably further contains inorganic fine particles on the layer. The inorganic fine particles may be contained both on the inorganic binder layer and in the inorganic binder layer.
  • Consequently, the particles of the inorganic coated sand are more firmly bound to each other through the inorganic fine particles, and as a result, the strength of the obtained casting mold can be further improved.
  • Here, the inorganic fine particles on the inorganic binder layer may be partially embedded in the inorganic binder layer.
  • Examples of inorganic fine particles include, but are not limited to, silica particles and silicon particles. From the viewpoint of improving the strength of the casting mold, silica particles are preferable, and from the viewpoint of having a large specific surface area and being highly reactive with sodium silicate and sodium metasilicate, amorphous silica particles are more preferable. These inorganic fine particles may be used singly or may be used in combination of two or more.
    • (Amorphous silica particles)
  • In the present embodiment, the inorganic coated sand may further contain amorphous silica particles. Amorphous silica particles preferably form part of the inorganic binder layer.
  • From the viewpoint that the particles of the inorganic coated sand are more firmly bound to each other through the amorphous silica particles, the amorphous degree of the amorphous silica particles is preferably 80% or more, more preferably 90% or more, still more preferably 93% or more, even still more preferably 95% or more, and especially preferably 98% or more. The upper limit of the amorphous degree of the amorphous silica particles is not limited, but is, for example, 100% or less, may be 99.8% or less, and also may be 99% or less.
  • The amorphous degree of amorphous silica particles may be obtained by the X-ray diffraction method shown below.
    • (X-ray diffraction method)
  • Amorphous silica particles are pulverized in a mortar and pressed against an X-ray glass holder of a powder X-ray diffractometer for measurement. As the powder X-ray diffractometer, Multiplex (light source of CuKα ray, tube voltage of 40 kV, tube current of 40 mA) manufactured by Rigaku Corporation is used, and the measurement is performed at scanning interval of 0.01° and scanning speed of 2°/min in the range of 20 = 5° to 90° with slits DS of 1, SS of 1, and RS of 0.3 mm. In the range of 20 = 10° to 50°, a straight line that connects the X-ray intensities on the low angle side and the high angle side is drawn, the area under the straight line is used as the background, and the crystallinity is obtained using the software attached to the instrument and is subtracted from 100 to obtain the amorphous degree. Specifically, for the area above the background, the amorphous peak (halo) and each crystalline component are separated by curve fitting, each area is obtained, and the amorphous degree (%) is calculated by the following formula. Amorphous degree % = Halo area / Crystalline component area + Halo area × 100
    Figure imgb0001
  • From the viewpoint of improving the strength of the casting mold and the viewpoint of improving handling property, the average particle diameter d50 in the weight-based particle size distribution of amorphous silica particles by a laser diffraction scattering particle size distribution measurement method is preferably 0.1 um or more and more preferably 0.3 um or more. Further, from the viewpoint of improving the strength of the casting mold, the above-described average particle diameter d50 of the amorphous silica particles is preferably 2.0 um or less, more preferably 1.0 um or less, still more preferably 0.8 um or less, and even still more preferably 0.6 um or less.
  • Here, the average particle diameter d50 in the weight-based particle size distribution of the amorphous silica particles by the laser diffraction scattering particle size distribution measurement method may be obtained, for example, by dissolving the inorganic binder layer in water to remove it from the inorganic coated sand, collecting the amorphous silica particles, and then measuring the particle size of the obtained amorphous silica particles by a laser diffraction scattering particle size distribution measurement method.
  • In addition, the average particle diameter d50 in the weight-based particle size distribution of the amorphous silica particles by the laser diffraction scattering particle size distribution measurement method may also be obtained by measuring the particle size of the amorphous silica particles as a raw material by the laser diffraction scattering particle size distribution measurement method.
  • In addition, from the viewpoint of improving the strength of the casting mold per unit mass and improving handling property, the average particle diameter of the amorphous silica particles obtained from the observation image of the scanning electron microscope is preferably 0.1 um or more and more preferably 0.3 um or more. In addition, from the viewpoint of improving the strength of the casting mold per unit mass, the average particle diameter of the amorphous silica particles obtained from the observation image of the scanning electron microscope is preferably 2.0 um or less, more preferably 1.0 um or less, still more preferably 0.8 um or less, and even still more preferably 0.6 um or less.
  • Here, as the average particle diameter of the amorphous silica particles obtained from the observation image of the scanning electron microscope, various image analysis techniques can be used. Random particle sorting may be performed as a pretreatment. For example, after determining the inorganic binder layer and the amorphous silica particles based on the elements, 100 arbitrary amorphous silica particles are selected, their particle diameters are measured, and the average particle diameter of 80 amorphous silica particles excluding a total of 20 amorphous silica particles of 10 particles counted from the maximum particle diameter and 10 particles counted from the minimum particle diameter may be the average particle diameter of the amorphous silica particles.
  • From the viewpoint of improving the strength of the casting mold, the content of the amorphous silica particles in the inorganic binder layer is specifically 0% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, and still more preferably 30% by mass or more with respect to the whole components excluding water in the inorganic binder layer.
  • In addition, from the viewpoint of improving the surface shape of the casting mold and the viewpoint of reducing dust scattering, the content of the amorphous silica particles in the inorganic binder layer is preferably 55% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less with respect to the whole components excluding water in the inorganic binder layer.
  • Furthermore, from the viewpoint of improving the strength of the casting mold, the content of the amorphous silica particles is specifically 0 parts by mass or more, preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and even still more preferably 60 parts by mass or more with respect to 100 parts by mass of the inorganic binder.
  • In addition, from the viewpoint of improving the surface shape of the casting mold and the viewpoint of reducing dust scattering, the content of the amorphous silica particles is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, still more preferably 100 parts by mass or less, even still more preferably 90 parts by mass or less, and yet even still more preferably 80 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • From the viewpoint of obtaining a high-strength casting mold, the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the inorganic binder.
  • In addition, from the viewpoint of fillability into the molding die and the viewpoint of obtaining the high-strength casting mold, the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, still more preferably 150 parts by mass or less, and even still more preferably 140 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
  • The content of water in the inorganic binder layer contained in the inorganic coated sand may be adjusted according to the type of inorganic binder.
  • In a case where the inorganic binder is sodium silicate, from the viewpoint of obtaining the high-strength casting mold, the content of water in the inorganic binder layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of sodium silicate.
  • In addition, from the viewpoint of fillability into the molding die and the viewpoint of obtaining the high-strength casting mold, the content of water in the inorganic binder layer contained in the inorganic coated sand is preferably 55 parts by mass or less and more preferably 50 parts by mass or less with respect to 100 parts by mass of sodium silicate.
  • In a case where the inorganic binder is sodium metasilicate, from the viewpoint of obtaining the high-strength casting mold and the viewpoint of easy production of the casting mold, the content of water in the inorganic binder layer is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, still more preferably 90 parts by mass or more, and even still more preferably 110 parts by mass or more with respect to 100 parts by mass of sodium metasilicate, and from the viewpoint of improving fluidity and further improving the fillability into the molding die, the content of water in the inorganic binder layer is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, still more preferably 150 parts by mass or less, and even still more preferably 140 parts by mass or less with respect to 100 parts by mass of sodium metasilicate.
  • For example, in a case where the inorganic binder constituting the inorganic binder layer is only sodium metasilicate pentahydrate, the content of water is 74 parts by mass with respect to 100 parts by mass of sodium metasilicate, and in a case where it is only sodium metasilicate nonahydrate, the content of water is 133 parts by mass with respect to 100 parts by mass of sodium metasilicate.
    • <Method for producing inorganic coated sand>
  • The method for producing the inorganic coated sand may be selected, for example, according to the type of inorganic binder.
  • In a case where the inorganic binder contains sodium silicate, a dry inorganic coated sand having normal temperature fluidity can be obtained by, for example, kneading or mixing a water glass aqueous solution as the inorganic binder with the heated refractory aggregate, together with additives as necessary to blend uniformly, coating the surface of the refractory aggregate with the water glass aqueous solution, and allowing the moisture in the water glass aqueous solution to being evaporated.
  • In a case where the inorganic binder contains sodium metasilicate hydrate, a dry inorganic coated sand can be obtained by a production method including, for example, mixing the refractory aggregate and the sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate to obtain a mixture; and cooling the mixture to a temperature less than the melting point of the sodium metasilicate hydrate.
  • According to such production method, the inorganic binder layer can be crystallized, thus an inorganic coated sand having excellent fluidity can be obtained as compared with the conventional production method. In addition, since it is not necessary to use an aqueous solution of sodium metasilicate hydrate, a dehydration step is not needed, and the production method for the inorganic coated sand can be simplified.
  • Specifically, in the obtaining the mixture, the surface of the refractory aggregate is coated with the fluidized sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate.
  • Examples of the method of mixing the refractory aggregate and the sodium metasilicate hydrate at a temperature not less than the melting point of the sodium metasilicate hydrate include a method of adding the sodium metasilicate hydrate to a refractory aggregate heated to a temperature not less than the melting point of the sodium metasilicate hydrate and mixing the refractory aggregate and the sodium metasilicate hydrate while melting the sodium metasilicate hydrate; and a method of adding the heat-melted sodium metasilicate hydrate to the refractory aggregate and mixing them.
  • Among these, from the viewpoint of shortening the coating time, the method of adding the heat-melted sodium metasilicate hydrate to the refractory aggregate and mixing them is preferable.
  • From the same viewpoint, it is preferable to mix the sodium metasilicate hydrate without making it into an aqueous solution in advance in the obtaining the mixture. It is also preferable that the obtaining the mixture does not include intentionally adding water.
  • Mixing conditions such as stirring speed and treatment time when the refractory aggregate and sodium metasilicate hydrate are mixed may be appropriately determined according to the treatment amount of the mixture.
  • In the cooling the mixture, the fluidity of the sodium metasilicate hydrate is reduced by cooling the mixture obtained in the obtaining the mixture to a temperature less than the melting point of the sodium metasilicate hydrate, the sodium metasilicate hydrate is fixed on the surface of the refractory aggregate, and the sodium metasilicate hydrate layer, that is, the inorganic binder layer is formed.
  • In addition, in the production of inorganic coated sand, there are no restrictions on the method of adding zinc oxide or magnesium oxide, for example, after the refractory aggregate is coated with the inorganic binder, optionally the amorphous silica particles and the above-described other additives, one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives may be coated.
  • Alternatively, the refractory aggregate may be coated together with the inorganic binder and one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives.
  • Alternatively, after the refractory aggregate may be coated together with the inorganic binder and one or more selected from zinc oxide and magnesium oxide, optionally amorphous silica particles and other additives, one or more selected from zinc oxide and magnesium oxide, or optionally amorphous silica particles and other additives may be coated.
  • From the viewpoint of reducing deformation of the casting mold, it is preferable that the refractory aggregate is coated with an inorganic binder and then is coated with one or more selected from zinc oxide and magnesium oxide.
  • Zinc oxide or magnesium oxide in solid form or in aqueous dispersion can be mixed with the refractory aggregate, the inorganic binder, and the like.
  • In addition, zinc oxide or magnesium oxide may be added all at once, or may be added in a plurality of times.
  • By the above method, the inorganic coated sand in the present embodiment may be obtained.
  • In addition, the obtained inorganic coated sand can be used singly or in combination with other known refractory aggregates or other additives to mold desired casting molds.
    • <Casting mold>
  • In the present embodiment, the casting mold is made by using the inorganic coated sand in the present embodiment described above. Examples of the molding method for the casting mold include a molding method using a heated molding die, and a molding method in which water vapor is further passed through the heated molding die and then hot air is passed through the heated molding die.
  • In a case where the inorganic binder layer contains sodium metasilicate hydrate, a method of molding by filling a heated molding die with inorganic coated sand is preferable. In a case where the inorganic binder layer contains sodium silicate, a method of adding water to the inorganic coated sand, kneading it, and then filling it into a heated molding die for molding, or a method in which the inorganic coated sand is filled into a heated molding die, water vapor is then passed through the heated molding die, and then hot air is further passed through the heated molding die, is preferable.
  • In a case where the inorganic binder layer contains sodium metasilicate hydrate, in the molding method using a heated molding die, for example, the inorganic coated sand is first filled into the molding die that provides the desired casting mold.
  • Here, from the viewpoint of improving productivity of the casting mold, the molding die is preferably heated in advance to keep it warm before filling with the inorganic coated sand. From the viewpoint of improving productivity of the casting mold and from the viewpoint of improving the strength of the casting mold, the heating temperature at this time is preferably 100°C or more, and more preferably 150°C or more, and is also preferably 300°C or less and more preferably 250°C or less.
  • After filling with the inorganic coated sand, the molding die is heated without passage of water vapor to cure the inorganic coated sand. In a case where the inorganic binder layer contains sodium metasilicate hydrate, the inorganic coated sand can be cured without using adding water to the inorganic coated sand and kneading, or passing water vapor, and thus the equipment or the like for passing water vapor is unnecessary.
  • From the viewpoint of improving productivity of the casting mold and the viewpoint of improving the strength of the casting mold, the heating temperature is preferably 100°C or more, and more preferably 150°C or more, and is also preferably 300°C or less and more preferably 250°C or less. In addition, from the viewpoint of obtaining the stable strength of the casting mold, the heating time is preferably 30 seconds or more and more preferably 60 seconds or more, and is also preferably 600 seconds or less.
  • In addition, in a case where the inorganic binder layer contains sodium silicate, water is added to the inorganic coated sand and the inorganic coated sand is kneaded, and then filled into a heated molding die. In addition, in the molding method in which water vapor is passed through, for example, water vapor is blown in after the inorganic coated sand is filled into the molding die that provides the desired casting mold. The passage of water vapor wets the filled phase of the inorganic coated sand to be in a wet state. Then, hot air is passed through the molding die heated to 90°C to 200°C to dry and cure the inorganic coated sand.
  • In addition, the inorganic coated sand in the present embodiment may also be used in the laminate molding method.
  • In relation to the above-described embodiments, the present invention further discloses a method for reducing deformation of a casting mold, and an inorganic coated sand described below.
    • <1>
      A method for reducing deformation of a casting mold during casting, in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <2>
      The method for reducing deformation of a casting mold during casting according to <1>,
      • in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide,
      • the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder,
      • the inorganic binder contains at least one selected from the group consisting of sodium silicate and sodium metasilicate in a total amount of 80% by mass or more of sodium silicate and sodium metasilicate, and
      • the content of the inorganic binder layer is 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the refractory aggregate in the inorganic coated sand.
    • <3>
      The method for reducing deformation of a casting mold during casting according to <1> or <2>,
      • in which in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide,
      • the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the inorganic binder,
      • the inorganic binder contains at least one selected from the group consisting of sodium silicate and sodium metasilicate in a total amount of 98% by mass or more of sodium silicate and sodium metasilicate, and
      • the content of the inorganic binder layer is 1 part by mass or more and 4.5 parts by mass or less with respect to 100 parts by mass of the refractory aggregate in the inorganic coated sand.
    • <4> The method for reducing deformation of the casting mold during casting according to any of <1> to <3>, in which the inorganic coated sand has an average particle diameter of 0.05 mm or more and 2 mm or less.
    • <5> The method for reducing deformation of the casting mold during casting according to any of <1> to <4>, in which the refractory aggregate has an average particle diameter of 0.05 mm or more and 2 mm or less.
    • <6> The method for reducing deformation of the casting mold during casting according to any of <1> to <5>, in which the content of the inorganic binder layer in the inorganic coated sand is 1.0% by mass or more and 4.5% by mass or less.
    • <7> The method for reducing deformation of the casting mold during casting according to any of <1> to <6>, in which the content of the inorganic binder in the inorganic binder layer is 35% by mass or more and 94% by mass or less.
    • <8> The method for reducing deformation of the casting mold during casting according to any of <1> to <7>, in which the total content of sodium silicate and sodium metasilicate in the inorganic binder is substantially 100% by mass.
    • <9> The method for reducing deformation of the casting mold during casting according to any of <1> to <8>, in which the content of the inorganic binder in the inorganic coated sand is 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
    • <10> The method for reducing deformation of the casting mold during casting according to any of <1> to <9>, in which the zinc oxide and magnesium oxide have an average particle diameter of 0.5 um or more and 30 um or less.
    • <11> The method for reducing deformation of the casting mold during casting according to any of <1> to <10>, in which the total content of zinc oxide and magnesium oxide in the inorganic binder layer is 2% by mass or more and 40% by mass or less.
    • <12> The method for reducing deformation of the casting mold during casting according to any of <1> to <11>, in which the total content of the zinc oxide and the magnesium oxide is 20 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <13> The method for reducing deformation of the casting mold during casting according to any of <1> to <12>, in which the content of water in the inorganic binder layer is 20 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <14> An inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate,
      • in which the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and
      • the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <15> The inorganic coated sand according to <14>,
      • which is an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate,
      • in which the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide,
      • the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the inorganic binder,
      • the inorganic binder contains at least one selected from the group consisting of sodium silicate and sodium metasilicate in a total amount of 80% by mass or more of sodium silicate and sodium metasilicate, and
      • the content of the inorganic binder layer in the inorganic coated sand is 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
    • <16> The inorganic coated sand according to <14> or <15>,
      • which is an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate,
      • in which the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide,
      • the total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the inorganic binder,
      • the inorganic binder contains at least one selected from the group consisting of sodium silicate and sodium metasilicate in a total amount of 98% by mass or more of sodium silicate and sodium metasilicate, and
      • the content of the inorganic binder layer in the inorganic coated sand is 1 part by mass or more and 4.5 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
    • <17> The inorganic coated sand according to any of <14> to <16> in which the inorganic coated sand has an average particle diameter of 0.05 mm or more and 2 mm or less.
    • <18> The inorganic coated sand according to any of <14> to <17> in which the refractory aggregate has an average particle diameter of 0.05 mm or more and 2 mm or less.
    • <19> The inorganic coated sand according to any of <14> to <18> in which the content of the inorganic binder layer in the inorganic coated sand is 1.0% by mass or more and 4.5% by mass or less.
    • <20> The inorganic coated sand according to any of <14> to <19> in which the content of the inorganic binder in the inorganic binder layer is 35% by mass or more and 94% by mass or less.
    • <21> The inorganic coated sand according to any of <14> to <20> in which the total content of sodium silicate and sodium metasilicate in the inorganic binder is substantially 100% by mass.
    • <22> The inorganic coated sand according to any of <14> to <21> in which the content of the inorganic binder in the inorganic coated sand is 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
    • <23> The inorganic coated sand according to any of <14> to <22> in which the zinc oxide and magnesium oxide have an average particle diameter of 0.5 um or more and 30 um or less.
    • <24> The inorganic coated sand according to any of <14> to <23> in which the total content of zinc oxide and magnesium oxide in the inorganic binder layer is 2% by mass or more and 40% by mass or less.
    • <25> The inorganic coated sand according to any of <14> to <24> in which the total content of the zinc oxide and the magnesium oxide is 20 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <26> The inorganic coated sand according to any of <14> to <25> in which the content of water in the inorganic binder layer is 20 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <27> The inorganic coated sand according to any of <14> to <26> in which the inorganic coated sand contains amorphous silica particles, and the content of the amorphous silica particles is 50 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the inorganic binder.
    • <28> The inorganic coated sand according to <27> in which the content of the amorphous silica particles in the inorganic binder layer is 20% by mass or more and 45% by mass or less.
    • <29> The inorganic coated sand according to <27> or <28> in which the amorphous silica particles have the amorphous degree of 90% or more and an average particle diameter of 0.1 um or more and 2.0 um or less.
    • <30> A method for producing the inorganic coated sand according to any of <14> to <29>, including coating a refractory aggregate with an inorganic binder, and coating the refractory aggregate coated with the inorganic binder with at least one selected from zinc oxide and magnesium oxide.
    Examples
  • Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these.
  • First, the raw materials used in the following examples are shown.
    • (Raw materials used for producing inorganic coated sand)
    • ·Refractory aggregate
      • Mikawa Silica Sand R6 (manufactured by Mikawakeiseki Co., Ltd., average particle diameter: 200 um)
      • Lunamos MS #60 (artificial sand for casting, manufactured by Kao Quaker, average particle diameter: 200 µm)
    • ·Inorganic binder
      • Sodium metasilicate nonahydrate (Na2SiO3·9H2O) (manufactured by NIPPON CHEMICAL INDUSTRIAL CO.,LTD.)
      • No. 1 50 water glass (SiO2/Na2O = 2.1) (manufactured by FUJI CHEMICAL Co., Ltd., 45% by mass aqueous solution)
      • No. 3 water glass (SiO2/Na2O = 3.1) (manufactured by FUJI CHEMICAL Co., Ltd.: 40% by mass aqueous solution)
    • ·Amorphous silica fine particles
      Denka fused silica SFP-20M (average particle diameter d50: 0.4 um, amorphous degree: 99.5% or more) (manufactured by Denka Company Limited)
    • ·Zinc oxide (ZnO)
      Zinc oxide: manufactured by Fujifilm Wako Pure Chemical Corporation, powdery, average particle diameter of 1.37 um
    • ·Magnesium oxide (MgO)
      Magnesium oxide: manufactured by Fujifilm Wako Pure Chemical Corporation, powdery, average particle diameter of 12.2 um
    <Examples 1 to 4>
  • Mikawa Silica Sand R6 (100 parts by mass) was added to a stirrer as a refractory aggregate. Next, sodium metasilicate nonahydrate (4.00 parts by mass) melted by heating to 80°C was added to the stirrer and kneaded for 4 minutes, and then amorphous silica fine particles (1.20 parts by mass) were added thereto and kneaded for 2 minutes. Then, zinc oxide or magnesium oxide in the amount shown in Table 1 was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 1 to 4. Table 1 shows a blending composition of the inorganic coated sand.
    • <Examples 5 to 12>
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 1 50 water glass (4.00 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed. Furthermore, zinc oxide or magnesium oxide (the amount shown in Table 2) was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 5 to 12. Table 2 shows a blending composition of the inorganic coated sand.
    • <Example 13>
  • Lunamos MS #60 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 1 50 water glass (2.00 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed. Furthermore, zinc oxide (0.19 parts by mass) was added thereto and kneaded for 2 minutes to obtain an inorganic coated sand of Example 13. Table 2 shows a blending composition of the inorganic coated sand.
    • <Examples 14 and 16>
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 3 water glass (4.00 parts by mass) and zinc oxide or magnesium oxide (0.41 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed and to obtain the inorganic coated sands of Examples 14 and 16. Table 3 shows a blending composition of the inorganic coated sand.
    • <Examples 15 and 17>
  • Mikawa Silica Sand R6 (100 parts by mass) heated to about 120°C was added to a stirrer as a refractory aggregate. Next, No. 3 water glass (4.00 parts by mass) was put into a stirrer and kneaded to evaporate moisture, and stirred for about 3 minutes until the sand grain lumps collapsed. Furthermore, zinc oxide or magnesium oxide (0.41 parts by mass) was added thereto and kneaded for 2 minutes to obtain inorganic coated sands of Examples 15 and 17.
    • <Comparative Example 1>
  • The inorganic coated sand of Comparative Example 1 was obtained in the same manner as in Examples 1 to 4, except that neither zinc oxide nor magnesium oxide was added. Table 1 shows a blending composition of the inorganic coated sand.
    • <Comparative Example 2>
  • The inorganic coated sand of Comparative Example 2 was obtained in the same manner as in Examples 5 to 12, except that neither zinc oxide nor magnesium oxide was added. Table 2 shows a blending composition of the inorganic coated sand.
    • <Comparative Example 3>
  • The inorganic coated sand of Comparative Example 3 was obtained in the same manner as in Example 13, except that zinc oxide was not added. Table 2 shows a blending composition of the inorganic coated sand.
    • <Comparative Example 4>
  • The inorganic coated sand of Comparative Example 4 was obtained in the same manner as in Examples 14 to 17, except that neither zinc oxide nor magnesium oxide was added. Table 3 shows a blending composition of the inorganic coated sand.
    • (Evaluation method)
  • Using the inorganic coated sand obtained in each example, a casting mold was produced by the following method, and its deformation was evaluated. The evaluation results are shown together with each table.
    • (Preparation of casting mold) <Examples 1 to 4, Comparative Example 1>
  • A 22.3 × 22.3 × 180 mm test piece (5-cavity) mold was heated to 180°C. For the inorganic coated sand of each example, using a CSR-43 blow molding machine, the inorganic coated sand was filled into the test piece mold at a blow pressure of 0.3 MPa. Then, the inorganic coated sand was allowed to stand for 150 seconds in the molding die to cure it, and a casting mold test piece was obtained.
    • <Examples 5 to 17, Comparative Examples 2 to 4>
  • Water (2 parts by mass) was added to the inorganic coated sand (100 parts by mass) in advance and kneaded for 2 minutes, then the inorganic coated sand was filled into the molding die with the same operation as Examples 1 to 4 and Comparative Example 1 to obtain the casting mold test piece.
    • (Deformation of casting mold)
  • Fig. 1(a) and Fig. 1(b) are cross-sectional views for explaining a measurement method for deformation of the casting mold. The casting mold test piece of each example obtained by the above-described method was left in a thermostatic chamber at 25°C/55 %RH for 1 hour, and then cut into a plate-shaped test piece 10 of 5 × 22.3 × 90 mm. Metal pedestals 11a and 11b (13 mm × 13 mm, height of 13 mm) were arranged on an iron plate of appropriate size such that the distance between the centers was 90 mm, and a plate-shaped test piece 10 was placed on it such that the edges of the plate-shaped test piece 10 were positioned at the centers of the pedestals, respectively (Fig. 1(a)). Furthermore, a weight 13 (4.7 g) was placed on the center of the plate-shaped test piece 10. Then, the iron plate on which the plate-shaped test piece 10 was placed was heated in a muffle furnace heated under the conditions described later. After a predetermined time had elapsed, the plate-shaped test piece 10 was taken out from the muffle furnace and allowed to stand for 1 hour to cool. Then, the deformation amount of the plate-shaped test piece 10 was measured. The deformation amount was defined as the maximum vertical distance from the straight line connecting both ends of the plate-shaped test piece 10 to the curved portion (Fig. 1(b)).
  • The heating conditions were 500°C and 10 minutes for all of Examples 1 to 17 and Comparative Examples 1 to 4.
    • [Table 1]
  • Table1
    Inorganic coated sand Content of ZnO and MgO in inorganic binder layer (% by mass) Content of ZnO and MgO with respect to 100 parts by mass of solid content of inorganic binder (parts by mass) Deformation of test piece (mm) 500°C/10 min
    Refractory aggregate Inorganic binder layer
    Inorganic binder Metal oxide Amorphous silica
    Type Parts by mass Type Parts by mass Sodium metasilicate (parts by mass) Type Parts by mass Parts by mass
    Example 1 Mikawa Silica Sand R6 100 Sodium metasilicate nonahvdrate 4.00 1.71 ZnO 0.80 1.20 21.5 46.8 4
    Example 2 Mikawa Silica Sand R6 100 Sodium metasilicate nonahvdrate 4.00 1.71 ZnO 0.40 1.20 12.1 23.4 6
    Example 3 Mikawa Silica Sand R6 100 Sodium metasilicate nonahvdrate 4.00 1.71 ZnO 0.12 1.20 4.0 7.0 9
    Example 4 Mikawa Silica Sand R6 100 Sodium metasilicate nonahvdrate 4.00 1.71 MgO 0.40 1.20 12.1 23.4 9
    Comparative Example 1 Mikawa Silica Sand R6 100 Sodium metasilicate nonahvdrate 4.00 1.71 - 0.00 1.20 0 0 14
    • [Table 2]
  • Table 2
    Inorganic coated sand Content of ZnO and MgO in inorganic binder layer (% by mass) Content of ZnO and MgO with respect to 100 parts by mass of solid content of inorganic binder (parts by mass) Deformation of test piece (mm) 500°C/10 min
    Refractory aggregate Inorganic binder layer
    Inorganic binder Metal oxide
    Type Parts by mass Type Parts by mass Solid content (parts by mass) Type Parts by mass
    Example 5 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 ZnO 0.82 31.3 45.6 4
    Example 6 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 ZnO 0.37 17.1 20.6 8
    Example 7 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 ZnO 0.21 10.4 11.7 10
    Example 8 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 ZnO 0.14 7.2 7.8 12
    Example 9 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1. 80 MgO 0.82 31.3 45.6 6
    Example 10 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 MgO 0.37 17.1 20.6 8
    Example 11 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 MgO 0.21 10.4 11.7 10
    Example 12 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 MgO 0.14 7.2 7.8 12
    Example 13 Lunamos #60 100 No. 1 50 water glass 2.00 0.90 ZnO 0.19 17.4 21.1 7
    Comparative Example 2 Mikawa Silica Sand R6 100 No. 1 50 water glass 4.00 1.80 - 0.00 0 0 14
    Comparative Example 3 Lunamos #60 100 No. 1 50 water glass 2.00 0.90 - 0.00 0 0 16
    • [Table 3]
  • Table 3
    Inorganic coated sand Content of ZnO and MgO in inorganic binder layer (% by mass) Content of ZnO and MgO with respect to 100 parts by mass of solid content of inorganic binder (parts by mass) Deformation of test piece (mm) 500°C/10 min
    Refractory aggregate Inorganic binder layer
    Inorganic binder Metal oxide
    Type Parts by mass Type Parts by mass Solid content (parts by mass) Type Parts by mass Method of adding
    Example 14 Mikawa Silica Sand R6 100 No. 3 water glass 4.00 1.60 ZnO 0.41 Internal addition 20.4 25.6 5
    Example 15 Mikawa Silica Sand R6 100 No. 3 water glass 4.00 1.60 ZnO 0.41 External addition 20.4 25.6 4
    Example 16 Mikawa Silica Sand R6 100 No. 3 water glass 4.00 1.60 MgO 0.41 Internal addition 20.4 25.6 5
    Example 17 Mikawa Silica Sand R6 100 No. 3 water glass 4.00 1.60 MgO 0.41 External addition 20.4 25.6 4
    Comparative Example 4 Mikawa Silica Sand R6 100 No. 3 water glass 4.00 1.60 - 0.00 - 0 0 7
  • From Tables 1 to 3, by comparing between Examples 1 to 4 and Comparative Example 1, between Examples 5 to 12 and Comparative Example 2, between Example 13 and Comparative Example 3, and between Examples 14 to 17 and Comparative Example 4, each of Examples was superior to Comparative examples in the effect of reducing deformation of the casting mold.
    • REFERENCE SIGNS LIST
    • 10 Plate-shaped test piece
    • 11a, 11b Pedestal
    • 13 Weight

Claims (6)

  1. A method for reducing deformation of a casting mold during casting,
    wherein in the casting mold prepared using an inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on a surface of the refractory aggregate, the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and
    a total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of an inorganic binder.
  2. The method for reducing deformation of a casting mold according to claim 1,
    wherein a content of the inorganic binder layer in the inorganic coated sand is 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
  3. The method for reducing deformation of a casting mold according to claim 1 or 2,
    wherein the inorganic binder contains at least one selected from sodium silicate and sodium metasilicate.
  4. An inorganic coated sand comprising:
    a refractory aggregate; and
    an inorganic binder layer formed on a surface of the refractory aggregate,
    wherein the inorganic binder layer contains one or more selected from zinc oxide and magnesium oxide, and
    a total content of the zinc oxide and the magnesium oxide is 6 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of an inorganic binder.
  5. The inorganic coated sand according to claim 4,
    wherein a content of the inorganic binder layer in the inorganic coated sand is 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the refractory aggregate.
  6. The inorganic coated sand according to claim 4 or 5,
    wherein the inorganic binder contains at least one selected from sodium silicate and sodium metasilicate.
EP22745685.2A 2021-01-29 2022-01-19 Inorganic coated sand Pending EP4286072A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS342257B1 (en) * 1957-05-10 1959-04-09
US3923525A (en) * 1973-04-17 1975-12-02 Ashland Oil Inc Foundry compositions
JP4209286B2 (en) * 2003-08-19 2009-01-14 トヨタ自動車株式会社 High-strength water-soluble core and method for producing the same
DE102004042535B4 (en) * 2004-09-02 2019-05-29 Ask Chemicals Gmbh Molding material mixture for the production of casting molds for metal processing, process and use
JP5986498B2 (en) 2012-12-19 2016-09-06 旭有機材株式会社 Coated sand manufacturing method and mold manufacturing method
EP3159073B1 (en) 2014-06-20 2023-04-05 Asahi Yukizai Corporation Mold manufacturing method and mold

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