WO2020235391A1 - Method for reproducing molding sand - Google Patents

Method for reproducing molding sand Download PDF

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Publication number
WO2020235391A1
WO2020235391A1 PCT/JP2020/018936 JP2020018936W WO2020235391A1 WO 2020235391 A1 WO2020235391 A1 WO 2020235391A1 JP 2020018936 W JP2020018936 W JP 2020018936W WO 2020235391 A1 WO2020235391 A1 WO 2020235391A1
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Prior art keywords
sand
particles
polishing
roasting
mold
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PCT/JP2020/018936
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French (fr)
Japanese (ja)
Inventor
浩 牧野
証一 村田
陽輔 高井
駿一 佐藤
勝太 堀
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伊藤忠セラテック株式会社
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Priority to JP2020130284A priority Critical patent/JP7487037B2/en
Publication of WO2020235391A1 publication Critical patent/WO2020235391A1/en

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose

Definitions

  • the present invention relates to a method for regenerating cast sand, and more particularly to a method capable of regenerating cast sand advantageously from a mold molded using an inorganic binder containing water glass as a main component.
  • the mold As one of the molds used for casting molten metal, it has been known that the mold is formed into a desired shape by using casting sand made of fire-resistant particles (aggregate) and a predetermined binder.
  • a binder (binder) for binding casting sand an organic binder mainly composed of resins such as phenol resin and furan resin, and an inorganic binder mainly composed of water glass, clay, etc. are used. ing.
  • 63-180340 states that old sand of casting sand containing a combustible binder (resin) is roasted in a fluidized roasting furnace. Therefore, a method has been clarified in which the combustible binder is burned and then regenerated by a mechanical method as needed.
  • Japanese Patent Laying-Open No. 2016-150368 describes a mold molded into a predetermined shape by using a mold binder-containing sand containing an aggregate and a binder derived from artificial sand and / or natural sand. A method of regenerating the mold waste sand generated after casting as raw material sand for the mold by roasting and then dry polishing has been clarified.
  • a novolak phenol resin is used as a binder and the mold is used. It has been clarified that by producing sand containing a binder for use (RCS) and subjecting it to a regeneration step, an effect of suppressing a reduction in the desired mold strength can be obtained.
  • Japanese Patent Application Laid-Open No. 2015-51446 a mold formed by using an inorganic binder such as sodium silicate is crushed after casting, and then mixed and stirred in water at 5 ° C to 70 ° C.
  • a method for regenerating the casting sand which comprises separating the inorganic binder adhering to the casting sand, and then recovering the casting sand from which the binder has been separated and heating and drying the casting sand, has been clarified, and further, Japanese Patent Application Laid-Open No. 2016-147287.
  • Japanese Patent No. 5401325 as a method for thermally regenerating the foundry sand, the used foundry sand to which water glass is attached is heat-treated at a temperature of at least 200 ° C., and the hydrochloric acid consumption of the foundry sand is reduced.
  • a method for carrying out such a heat treatment so as to reduce the amount to 10% has been clarified, but it is assumed that such a thermal regeneration treatment is repeatedly carried out.
  • the water glass firmly adhering to the foundry sand gradually accumulated, and when the heat treatment was performed so that the hydrochloric acid consumption was reduced to 10%, a large amount of water glass was found in the foundry sand. It is thought that it will remain.
  • the refractory particles used for molding the mold together with the predetermined binder are natural sand such as silica sand and the conventional regeneration method as described above is applied, in the roasting step, thermal cracking due to thermal expansion occurs.
  • the problem that the particles themselves are crushed will be caused, so it is practical for natural sand whose durability that can withstand the regeneration process cannot be recognized. It was extremely difficult to carry out such regeneration.
  • a mechanical regeneration method such as polishing is adopted for the regeneration of cast sand made of natural sand to which inorganic binders that cannot be easily burned and removed by roasting operation are adhered, pulverization of natural sand is caused. Therefore, it was extremely difficult to regenerate the cast sand from the mold using natural sand and an inorganic binder.
  • the present invention has been made in the context of such circumstances, and the problem to be solved thereof is that after casting a mold molded using an inorganic binder containing water glass as a main component. Therefore, it is an object of the present invention to provide a practical method for regenerating the foundry sand used for molding such a mold, and another problem is that a high mold strength is maintained even by repeated reclaiming treatment.
  • the purpose is to provide an effective method for regenerating foundry sand.
  • the present invention can be preferably carried out in various aspects as listed below, but each aspect described below can also be carried out in any combination. , Can be adopted. It should be noted that the aspects or technical features of the present invention are not limited to those described below, and can be recognized based on the invention idea that can be grasped from the description of the entire specification. Should be understood.
  • a method for regenerating the foundry sand from a mold formed by using an artificially produced foundry sand made of spherical fireproof particles and an inorganic binder mainly composed of water glass is used as (a). While crushing the used mold recovered from the casting process using the mold, the crushing step of separating and removing the fine powder generated there, and (b) sizing the crushed material taken out from the crushing step.
  • polishing surface polishing treatment is performed, Regeneration of cast sand characterized by having a polishing step of separating the crystallized water glass component on the sand surface and collecting and removing the separated crystallized water glass component with a dust collector.
  • the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces. It is characterized by having a pre-polishing process in which a part of the water glass component adhering to the sand surface is separated, and the separated water glass component is collected and removed by a dust collector.
  • the above-described embodiment characterized in that the sized sand used in the roasting step has fluidity in a fluidity test after hot treatment under the roasting treatment conditions.
  • the method for regenerating cast sand according to any one of (1) to (3).
  • Al 2 O 3 in which the artificially produced spherical refractory particles are 40% by weight or more.
  • such a mold is constructed from those used in the casting process of a mold molded by using an inorganic binder containing water glass as a main component.
  • artificially produced spherical fire-resistant particles are used as the casting sand instead of natural sand such as silica sand, and the used mold recovered from the casting process is crushed and sized. Then, the obtained sized sand is roasted to crystallize the water glass component adhering to the sand surface, and then the crystallized water glass component on the sand surface is separated and removed by mechanical polishing.
  • the particles of the foundry sand itself could be effectively prevented from being crushed and refined, and the water glass component adhering to the surface of the foundry sand could be advantageously removed. Even if the casting sand is repeatedly regenerated, it has become possible to maintain a high strength of the mold formed from the regenerated sand.
  • the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces and adhere to the sand surface.
  • a pre-polishing process that separates and removes part of the water glass component, and as artificially produced spherical fireproof particles, spherical firing artificially produced by the sintering method.
  • the forming particles the characteristics of the present invention can be exhibited even more advantageously, and in particular, such spherical sintered particles, particularly mullite or mullite corundum spherical sintered particles, can be used.
  • the mold strength of the regenerated sand that has been repeatedly regenerated can be made higher than the mold strength when the new sand is used, and the feature that the strength can be effectively maintained can be exhibited. ..
  • FIG. 5 is a process schematic diagram showing various regeneration methods applied to the pseudo-old sand of the refractory particles B and C in the second embodiment, respectively.
  • the mold to which the regeneration method according to the present invention is applied is molded by using casting sand and a binder in the same manner as in the conventional case.
  • the binder is water glass.
  • the casting sand is not natural sand such as silica sand, but artificially produced spherical fire-resistant particles, which regenerates the casting sand. It could be done in an advantageous way.
  • any known refractory artificial particles can be used as the target.
  • any known refractory artificial particles can be used as the target.
  • the spherical fire-resistant particles obtained by the sintering method have fine irregularities on the particle surface. Since the inorganic binder component enters there and gradually fills up, the mold strength is about the same as that of fresh sand, and even better than that, when it is repeatedly reused as recycled sand. Since it can be expressed, it will be preferably used.
  • the spherical artificial sand (aggregate) used in the present invention advantageously has a chemical composition of 40% by weight or more of Al 2 O 3 and 60% by weight or less of SiO 2. It is desirable to be.
  • the content of Al 2 O 3 is less than 40% by weight, in other words, when the content of SiO 2 exceeds 60% by weight, the thermal expansion of the refractory particles becomes large, which is peculiar to SiO 2. Anomalous expansion is evoked, and thus the problem of self-destruction is evoked in the process of regeneration according to the present invention.
  • refractory particles (aggregates) made of a mullite or mullite corundum material are preferably used in such a chemical composition.
  • the mullite-corundum quality means a state in which the crystal structure of mullite and the crystal structure of corundum coexist or are dispersed in the particles.
  • Al 2 O 3 is preferably contained in an amount of 50% by weight or more, more preferably 60% by weight or more in order to advantageously achieve the object of the present invention.
  • a ratio of about 90% by weight, preferably 80% by weight, and more preferably about 70% by weight is generally adopted.
  • SiO 2 is preferably contained in a proportion of 50% by weight or less, more preferably 40% by weight or less, and the lower limit thereof is generally 10% by weight, preferably 20% by weight, still more preferably about 30% by weight. The ratio of is adopted.
  • the chemical composition of Al 2 O 3 : 50 to 80% by weight and SiO 2 : 50 to 20% by weight is advantageously adopted, and further, Al 2 O 3 : 60 to 70% by weight and SiO 2 : 40 to 30% by weight are adopted.
  • the chemical composition of% will be more preferably adopted.
  • such a chemical composition can be easily measured using, for example, a general fluorescent X-ray analyzer.
  • the spherical artificial sand used in the present invention has an average particle size similar to that of the refractory particles conventionally used for molding a mold, and the average particle size is generally 0. It has a size of about 01 to 0.50 mm, preferably about 0.05 to 0.40 mm, and more preferably about 0.07 to 0.30 mm. If the average particle size of this artificial sand becomes too small, it will be difficult to handle it, and it will be difficult to regenerate the recovered sand. If the particle size becomes too large, the recovered sand will be regenerated. In addition to the problem of quality deterioration of cast products, it also causes the problem of deterioration.
  • the average particle size means the particle size (D 50 ) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method.
  • the artificial refractory particles used as such casting sand are composed of particles exhibiting a spherical shape, and the roundness thereof is generally preferably 0.70 or more, particularly 0.75 or more.
  • spherical refractory particles having a roundness of 0.80 or more will be advantageously used.
  • the roundness of the artificial refractory particles can be measured by a known method, and can be measured by, for example, a particle shape measuring device manufactured by Microtrac Bell Co., Ltd .: PartAnSI.
  • a particle shape measuring device manufactured by Microtrac Bell Co., Ltd .: PartAnSI.
  • Such a device is composed of a sample cell, a strobe LED and a high-sensitivity CCD camera, and its measurement principle is that water is circulated by a pump while a sample (fireproof particles) is charged to form a strobe LED light source and a CCD camera. Water mixed with sample particles passes through the sample cell arranged between and, and the projected area and maximum ferret diameter for each particle are obtained by image analysis of the projected image obtained at that time. Is.
  • sodium silicate which has been conventionally used as a binder or a binder in a composition for mold production, is preferably used. It will be used.
  • the casting sand and the inorganic binder as described above are mixed and kneaded according to a conventional method to form kneaded sand, and then the kneaded sand is used to mold a mold having a desired shape. Then, after casting a predetermined molten metal using the mold, the used mold recovered from the casting process is subjected to a predetermined regeneration treatment. A crushing step of obtaining crushed sand (crushed product) is carried out by crushing the used mold and separating and removing the fine powder generated therein.
  • the used mold is crushed in the crushing step by using a known crusher such as a jaw crusher, and the fine powder generated there is separated and removed by a dust collector or the like to obtain a crushed product.
  • the pyroclastic sand is taken out.
  • the fine powder to be separated and removed generally has an average particle size of about 10 ⁇ m or less.
  • the crushed sand thus obtained is subjected to a sizing (classification) operation using a sieve or the like in order to take out particles having a predetermined size, whereby the sizing sand having a predetermined particle size is taken out. It becomes.
  • the average particle diameter of the spherical refractory particles (new sand) used for molding the mold from the crushed sand which is the sizing object is 1/10 or less, preferably 1/7.
  • fine particles having an average particle diameter of more preferably one-fifth or less are removed.
  • the sizing sand taken out in the above-mentioned sizing step is generally effective as particles having a particle size of 5 mm or less, preferably 3 mm or less, which is equal to or larger than the particle size of spherical refractory particles (shinsuna).
  • the particle size of the spherical fireproof particles (new sand) is the particle size of each particle, but when such particles have a particle size distribution, practically, the average of the particles having such a particle size distribution.
  • a particle size of about 1/3 of the particle size, preferably about 1/2 of the particle size is adopted. Finer particles than spherical refractory particles (new sand) are fine powder generated when crushed and contain a large amount of active water glass components.
  • the sized sand having a predetermined particle size obtained through the crushing step and the sizing step as described above is subjected to a roasting treatment, a heat treatment, and a water glass adhering to the sand surface.
  • the components will be crystallized.
  • a fluidized bed furnace is generally used for this roasting process, and a method of applying a heat load while flowing sand in the furnace is adopted.
  • water glass which is the main component of the inorganic binder, exists in the water-containing form represented by Na 2 O, nSiO 2 , mH 2 O in the inorganic binder-coated sand used for molding the mold, and is present at the time of molding.
  • the roasting temperature in the roasting process the consuming ⁇ -Na 2 Si 2 O 5 is required to be equal to or higher than a temperature of generating is further heated at 800 ⁇ 870 °C, ⁇ -Na 2
  • the roasting temperature needs to be below that temperature because the melt of Si 2 O 5 and silicate will be formed. This is because when a melt is generated, poor fluidization or melt solidification may occur due to the presence of the melt during heating in a fluidized roasting furnace or a rotary kiln.
  • the roasting temperature adopted in the roasting treatment according to the present invention is generally 500 ° C. or higher, preferably 600 ° C. or higher, and the roasting treatment time is generally 10 minutes or longer, preferably 10 minutes or longer. Is used for more than 30 minutes, which inactivates the active water glass component remaining on the surface of the sized sand particles and kneads it with an inorganic binder when it is reused as recycled sand. It is possible to keep the pot life of the product (composition for molding) long.
  • the roasting temperature is less than 500 ° C. or the roasting treatment time is less than 10 minutes, a sufficient heat load is applied to inactivate the active water glass component adhering to the surface of the casting sand particles.
  • the sand in the roasting furnace becomes Generally, the roasting temperature is 800 ° C. or lower, preferably 750 ° C. or lower, and the roasting treatment time is generally 5 hours or less, preferably 5 hours or less, because fusion and fluidization defects are caused. Less than 3 hours will be adopted.
  • the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces.
  • a pre-polishing step of separating a part of the water glass component adhering to the sand surface and collecting and removing the separated water glass component with a dust collector is preferably adopted. ..
  • the sizing sand taken out in the sizing step is further subjected to the sizing action, and the isolation of the particles is promoted. Therefore, in the subsequent roasting step. Sufficient fluidity can be ensured, and heat load can be applied more efficiently.
  • the remaining water glass component prevents the sand (recovered sand) before regeneration from becoming particles of a desired size only by the crushing operation. Due to the accumulated water glass component, the particles are fixed to each other and a plurality of particles are integrated, and it is possible to obtain particles of a desired size by simply crushing (dissolving) the particles. This cannot be done, and as a result, problems such as insufficient heat transfer will occur in the subsequent roasting process. Therefore, the pre-polishing process as described above is adopted to crush the fixed particles, and further. It is desirable to partially remove the accumulated water glass component.
  • the surface polishing treatment is carried out by mechanically polishing the sized sand that has been subjected to the roasting treatment, and the crystallized water glass existing on the sand surface is performed. While the components are separated, a polishing step of collecting and removing the separated crystallized water glass components by a dust collector is carried out. In this polishing step, it is necessary to remove the water glass component adhering to the particle surface, which has been crystallized by the roasting (heating) treatment, and therefore, it is more than the mechanical polishing in the preliminary polishing step described above.
  • the fire-resistant particles used as casting sand need to have high crush resistance enough to withstand such mechanical polishing. Therefore, in the present invention, artificially produced spherical refractory particles are used as such refractory particles.
  • the mechanical polishing in the polishing step as described above can be carried out by using various known polishing devices together with the mechanical polishing in the preliminary polishing step described above.
  • the sized sand is brought into contact with the grindstone and its surface thereof.
  • a polishing device for polishing which is advantageous in that polishing is performed by supplying and contacting the peripheral surface of the cylindrical grindstone that is rotated around the axis with sized sand.
  • the method so as to be used will be preferably adopted.
  • 2016-413 can be used, and a commercially available sand fresher (Kiyota Casting Machine Co., Ltd.) can be used. In addition to this, polishing equipment called rotary reclamers, sand shiners, etc. can also be used. Further, although it is practically desirable that the mechanical polishing in the pre-polishing step and the mechanical polishing in the polishing step are performed by using the same polishing device, it is also possible to use different polishing devices. It is also possible to carry out each mechanical polishing.
  • the polishing action on the sized sand is considered to be mild in the pre-polishing step, while a heavy polishing action is added in the subsequent polishing step. Will be done.
  • the difference in the polishing action is realized by making the polishing time, the number of times of polishing, etc. different.
  • the mechanical polishing treatment time in the pre-polishing step may be shorter than the mechanical polishing treatment time in the subsequent polishing step.
  • the number of mechanical polishing treatments in the pre-polishing step is set to a small number, for example, one, while the number of mechanical polishing treatments in the subsequent polishing step is set to a larger number, for example, three times. Is possible.
  • fine powder of water glass component is generated by the mechanical polishing treatment, and such fine powder is prepared by the polishing treatment. It is separated from the grain sand, collected by a dust collector, and removed from the system. If fine powder is mixed in the sized sand that has been polished in the pre-polishing process, problems such as a decrease in fluidity and adhesion between the sands in the subsequent roasting process will occur. In addition, when the fine powder of the crystallized water glass component separated from the mechanically polished sized sand is mixed in the polishing step, the recycled sand obtained through such a polishing step is regenerated. This is because it becomes difficult to sufficiently realize characteristics such as mold strength at the time of use.
  • the foundry sand obtained through the crushing step, the sizing step, the pre-polishing step adopted as necessary, the roasting step, and the polishing step is regenerated.
  • the water glass component adhering to the surface thereof is effectively removed, and further, the effect of removing the water glass component adhering to the surface is advantageous even by repeated regeneration treatment of the casting sand.
  • the strength of the mold is effectively increased, and the recycling operation is repeated. It has become possible to maintain a high mold strength even in a mold using the regenerated sand obtained.
  • refractory particles A, B and C of various materials were prepared according to the known production methods shown in Table 1 below, respectively.
  • an inorganic binder containing water glass as a main component (Czech Republic: Geopol W11 manufactured by SAND TEAM) and a curing accelerator (Czech Republic: Geotek W303 manufactured by SAND TEAM) were added.
  • Three types of kneaded sand for molding were produced by mixing and kneading at the ratios shown in Table 2 below.
  • each of them is heat-treated at 150 ° C. for 1 hour to imitate the old sand (casting sand) recovered from the used mold.
  • each of the three types of pseudo-old sand obtained corresponding to the refractory particles A, B and C was crushed by a jaw crusher, and the fine powder generated at that time was removed by a dust collector.
  • the crushed product obtained by such a crushing operation is classified by a vibrating sieve to remove excessive particles and small particles, and has a particle size in the range of 105 ⁇ m to 2 mm3. Seed sized sand was removed.
  • the average particle size of the fine particles generated when crushed by the jaw crusher is 6.29 ⁇ m
  • the average particle size of the small particles removed by the vibrating sieve. was 43.1 ⁇ m.
  • These average particle diameters were obtained by measuring with a particle diameter distribution measuring device: MT3300EXII manufactured by Microtrac Bell Co., Ltd. From this, the fine particles removed by the dust collector are extremely fine, whereas the fine particles removed by the vibrating sieve are the particles broken by the above crushing operation or the water glass component adhering to the particle surface. However, it is recognized.
  • each of the three types of sized sand taken out was sequentially subjected to a roasting treatment (600 ° C. ⁇ 2 hours) and a mechanical polishing treatment (30 minutes), so that each sized sand was obtained.
  • a roasting treatment 600 ° C. ⁇ 2 hours
  • a mechanical polishing treatment (30 minutes)
  • the roasting process is carried out using a fluidized roasting furnace, while as a mechanical polishing process, 30 kg of pseudo old sand is transferred to a sand fresher (BR-305 manufactured by Kiyota Casting Machine Co., Ltd.), which is a polishing machine.
  • the grindstone (grinding stone diameter: 305 mm) is rotated at a high speed of 40 m / sec and brought into contact with the outer peripheral surface thereof, the pseudo old sand is polished and the water glass attached to the pseudo old sand is attached.
  • a dust collector Pulse jet dust collector manufactured by Amano Co., Ltd .: PiF-75U in which the removed inorganic binder-derived substance (fine powder) is connected to the sand fresher while separating and removing the substance derived from the inorganic binder mainly composed of ), A method of collecting dust at an air volume of 46 m 3 / min and removing it was adopted.
  • Example 2- Adopting the same conditions of crushing, sizing, roasting treatment and mechanical polishing treatment as in Example 1, various types of pseudo-old sand of the refractory particles B and C are shown in FIG. 1, respectively.
  • the regeneration operation was carried out according to the regeneration method of (1), and various recycled refractory particles were obtained.
  • the polishing treatment time is 10 minutes
  • the polishing treatment time after the roasting treatment is shorter than 30 minutes
  • a light polishing treatment is performed. Made to be implemented.
  • the regenerated refractory particles were respectively subjected to an inorganic binder (Geopol W11) containing water glass as a main component and a binder thereof in the composition shown in Table 3 below.
  • a curing accelerator (Geotek W303) is mixed and kneaded, and the obtained kneaded sand is further applied to a molding machine (KMTPZ1019 manufactured by Kiyota Casting Co., Ltd.) under the condition of air blow: 1.5 seconds / 0.4 MPa.
  • a molding machine KMTPZ1019 manufactured by Kiyota Casting Co., Ltd.
  • the obtained various test pieces were stored for 1 hour in an environment of temperature: 25 ° C. and humidity: 50% RH, respectively, and then using a vertical electric measuring instrument (MX2-2500N manufactured by Imada Co., Ltd.).
  • the bending strength was measured at a span of 150 mm and a descent speed of 5 mm / min, and the results are shown in Table 4 below.
  • the regenerated refractory particles (sand) obtained in the regenerating method (1) consisting of only polishing the sized sand are before being used for molding the mold. Although it exhibits a bending resistance equal to or higher than that of fresh sand, which is a refractory particle, since the active water glass component still remains on the particle surface, molding of kneaded sand after kneading sand and binder. It was judged to be impractical because the pot life, which is the possible time, was shortened.
  • the regenerated refractory particles obtained in the regeneration method (2) in which only the sizing sand is subjected to the roasting treatment and the regeneration method (3) in which the polishing treatment is followed by the roasting treatment Furthermore, the regenerated refractory particles obtained in the regeneration method (4), which consists of performing roasting treatment and polishing treatment without collecting dust or sizing when crushed, are more resistant than fresh sand. It only gave a test piece with low folding strength.
  • Example 3- The pseudo-old sands of the refractory particles B and C obtained in Example 1 were subjected to various regeneration treatments shown in Table 5 below, respectively, and the obtained recycled refractory particles were subjected to hot fluidity.
  • the test was carried out.
  • the hot fluidity test is carried out by leaving a refractory container containing each regenerated refractory particle in an electric furnace preheated to a predetermined temperature of 400 to 800 ° C. for a predetermined time of 10 to 60 minutes. , A predetermined heat treatment was performed.
  • the refractory container was taken out of the furnace, and immediately the refractory container was tilted to evaluate whether or not the regenerated refractory particles could be discharged from the refractory container. Then, the sand contained therein can be discharged only by tilting the fireproof container, which is evaluated as ⁇ , and the sand contained therein cannot be discharged only by tilting the fireproof container, but the fireproof container cannot be discharged. Those that could be discharged by hitting were evaluated as ⁇ , and those that could not discharge the contained sand from the refractory container were evaluated as ⁇ , and the results are shown in Table 5 below.
  • both the refractory particles B and C have poor hot fluidity from the heat treatment at 400 ° C. Is recognized.
  • the hot fluidity at 400 ° C. is improved, the hot fluidity from 500 ° C. is poor. Is recognized. This deterioration in hot fluidity also causes poor flow during the roasting process, indicating that sufficient roasting process cannot be performed. Therefore, the dust collection process causes fine particles. It is understood that sufficient hot fluidity cannot be exhibited only by removing the powder.
  • the size of the fine powder and fine particles that cause deterioration of hot fluidity is as follows:
  • the average particle diameter is about 6 ⁇ m in the crushing / dust collecting treatment, and the average particle in the sizing treatment.
  • the diameter is about 40 ⁇ m. Since all of them adversely affect hot fluidity, it is desirable to remove them as much as possible, and fine powders and fine particles having an average particle size of generally 20 ⁇ m or less, preferably 30 ⁇ m or less, and more preferably 45 ⁇ m or less. It is desirable to remove it.
  • Example 4- About the obtained kneaded sand after kneading sand and an inorganic binder with respect to the regenerated refractory particles obtained by the method (1) or (6) for regenerating the old sand of the refractory particles B and C in Example 2. , An evaluation test of the pot life, which is the time when the mold can be molded, was carried out. Here, in the evaluation test of the pot life, the regenerated refractory particles, the inorganic binder, and the curing accelerator are blended in the blending ratios shown in Table 3 above and kneaded, and then the obtained kneaded sand is mixed.
  • the refractory particles B and C can be filled with fresh sand and the regenerated refractory particles obtained by the regeneration method (6) even if the storage time is 2 hours. There is almost no change in comparison with the case where the usage time is 0 hours, and it is recognized that the usage time is sufficient.
  • the regenerated refractory particles obtained by the regenerating method (1) in which the regenerating treatment is performed only by the polishing treatment cannot form a test piece at a storage time of 1 hour, and therefore, the pot life is insufficient. Therefore, it is recognized that it is not practical as a reproduction method.
  • Example 5- Regeneration obtained by regenerating old sand of refractory particles B and C by the regeneration method (6) adopted in Example 2 and further repeatedly performing the same regeneration treatment on the obtained refractory particles.
  • a test piece was prepared in the same manner as in Example 2 for each number of times of regeneration, and the bending strength of the test piece was measured, and the results are shown in Table 7 below.
  • the refractory particles B are subjected to the regeneration treatment by the regeneration method (6) to develop a bending strength higher than that of the fresh sand, and then the repeated regeneration treatment is carried out.
  • the bending strength there is almost no change in the bending strength, and since it has sufficient bending strength, it is used for molds made using an inorganic binder containing water glass as the main component. It was judged that repeated use and regeneration are possible in the cast sand.
  • the refractory particles C have the same anti-folding strength as Shinsuna when the number of times of regeneration is 1, but the anti-folding strength is increased by increasing the number of times of regeneration to 2 or 3 times.
  • Example 6- The crushed sand or sized sand obtained by subjecting the old sand of the refractory particles B and C obtained in Example 1 to various regeneration treatments is roasted at a predetermined temperature up to 700 ° C. for 2 hours. After the treatment, the electric conductivity (mS / m) of each roasted sand was measured, and the results are shown in Table 8 below.
  • the electrical conductivity is such that 20 g of sand and 50 g of distilled water are stirred for 30 minutes using a stirrer and a stirrer, and then the supernatant is collected by decanting to obtain a multi-water quality manufactured by Toa DK Co., Ltd.
  • the higher the roasting temperature the lower the electrical conductivity of the regenerated refractory particles, regardless of the method of the regeneration treatment. It is recognized that the higher the temperature, the more inactivated the active water glass component remaining on the particle surface. Further, when the roasting temperature is changed from 400 ° C. to 500 ° C., the electric conductivity is remarkably lowered. Therefore, by adopting a roasting temperature of 500 ° C. or higher, the active water glass component is advantageously inactivated. It is acknowledged that it can be done. This is because Na 2 O and SiO 2 contained in the water glass react with each other to generate Na 2 Si 2 O 5 , and the temperature is 500 ° C. or higher in order to sufficiently inactivate the active water glass component. It can be said that the roasting temperature of is required.
  • the regeneration treatment is only crushing or only crushing / dust collection, as is clarified in Example 3, when the roasting temperature is 500 ° C. or higher, it is hot. It can be said that the roasting process at a temperature of 500 ° C. or higher is difficult because the fluidity decreases or is lost. Therefore, the refractory particles whose regeneration treatment is only crushing or crushing / dust collection are roasted by raising the roasting temperature to a temperature at which the active water glass component can be sufficiently inactivated. Therefore, in the regeneration method, the regenerated refractory particles (regenerated) obtained by the regenerating method in which the roasting process is immediately performed from the step of crushing or crushing / dust collection without performing the granulation in the regenerating process. The characteristics of sand) are not sufficient.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Abstract

Provided is an effective method for reproducing molding sand that has been used in the making of a mold using an inorganic binder containing a liquid glass as the main component thereof from the mold that has been casted.　In order to reproduce molding sand comprising artificial spherical refractory particles from a mold that is made using the molding sand and an inorganic binder containing a liquid glass as the main component thereof, the following steps are employed: a step of crushing the mold that has been used and simultaneously separating and removing a fine powder; a crushing/sizing step of sizing the ground product to obtain specific sized sand; a roasting step of subjecting the crushed/sized sand thus produced to a roasting treatment to cause the crystallization of a liquid glass component adhered to the surface of the sand; and a polishing step of mechanically polishing the crushed/sized sand that has been subjected to the roasting treatment to separate the crystallized liquid glass component on the surface of the sand, then collecting the crystallized liquid glass component thus separated using a dust collector and then removing the separated crystallized liquid glass component.

Description

鋳物砂の再生方法How to regenerate casting sand
　本発明は、鋳物砂の再生方法に係り、特に、水ガラスを主成分とする無機バインダを用いて造型された鋳型から、鋳物砂を有利に再生し得る方法に関するものである。 The present invention relates to a method for regenerating cast sand, and more particularly to a method capable of regenerating cast sand advantageously from a mold molded using an inorganic binder containing water glass as a main component.
　従来より、金属溶湯の鋳造に用いられる鋳型の一つとして、耐火粒子（骨材）からなる鋳物砂と所定のバインダとを用いて、目的とする形状に造型されてなるものが知られており、そこでは、鋳物砂を結合するための粘結剤（バインダ）として、フェノール樹脂、フラン樹脂等の樹脂を主体とする有機バインダや、水ガラス、粘土等を主体とする無機バインダが、用いられている。 Conventionally, as one of the molds used for casting molten metal, it has been known that the mold is formed into a desired shape by using casting sand made of fire-resistant particles (aggregate) and a predetermined binder. , There, as a binder (binder) for binding casting sand, an organic binder mainly composed of resins such as phenol resin and furan resin, and an inorganic binder mainly composed of water glass, clay, etc. are used. ing.
　ところで、上述の如き鋳型を用いた鋳造の分野においても、資源枯渇や産業廃棄物の規制等の問題から、一旦、鋳造に使用された鋳型を構成する鋳物砂を再生して、再度、鋳造に使用することで、廃棄される鋳物砂（廃砂）量を減少せしめることが検討されており、例えば、有機バインダである樹脂にて耐火粒子の表面を被覆してなる樹脂被覆砂（ＲＣＳ）を用いて得られた鋳型からの鋳物砂の再生方式として、特開昭６３－１８０３４０号公報には、可燃物粘結剤（樹脂）を含む鋳物砂の古砂を流動焙焼炉で焙焼して、かかる可燃物粘結剤を燃焼せしめた後、必要に応じて、機械的方法で再生処理する手法が、明らかにされている。また、特開２０１６－１５０３６８号公報には、人工砂及び／又は天然砂に由来する骨材や粘結剤を含む鋳型用粘結剤含有砂を用いて、所定の形状に造型された鋳型の鋳造後に生じる鋳型廃砂を焙焼した後、乾式磨鉱することにより、鋳型用原料砂として再生する方式が明らかにされ、その実施例では、粘結剤としてノボラック系フェノール樹脂を用いて、鋳型用粘結剤含有砂（ＲＣＳ）が製造され、そしてそれが再生工程に供されることにより、目的とする鋳型強度の低減の抑制効果が得られることが、明らかにされている。 By the way, even in the field of casting using a mold as described above, due to problems such as resource depletion and regulation of industrial waste, the casting sand that constitutes the mold used for casting is once recycled and then cast again. It has been studied to reduce the amount of foundry sand (waste sand) to be discarded by using it. For example, resin-coated sand (RCS) obtained by coating the surface of fire-resistant particles with a resin which is an organic binder is used. As a method for regenerating casting sand from a mold obtained by using this method, Japanese Patent Application Laid-Open No. 63-180340 states that old sand of casting sand containing a combustible binder (resin) is roasted in a fluidized roasting furnace. Therefore, a method has been clarified in which the combustible binder is burned and then regenerated by a mechanical method as needed. Further, Japanese Patent Laying-Open No. 2016-150368 describes a mold molded into a predetermined shape by using a mold binder-containing sand containing an aggregate and a binder derived from artificial sand and / or natural sand. A method of regenerating the mold waste sand generated after casting as raw material sand for the mold by roasting and then dry polishing has been clarified. In the embodiment, a novolak phenol resin is used as a binder and the mold is used. It has been clarified that by producing sand containing a binder for use (RCS) and subjecting it to a regeneration step, an effect of suppressing a reduction in the desired mold strength can be obtained.
　しかしながら、それら従来の再生方法にあっては、あくまでも、鋳物砂としての耐火粒子と共に、樹脂の如き有機バインダを用いて、造型された鋳型からの鋳物砂の再生処理において、その表面に付着している有機バインダ（樹脂）を、焙焼操作によって燃焼せしめることにより、その除去を図ることを前提としているに過ぎないものであって、そのような再生方式が、そのまま、燃焼せしめられることのない無機バインダを用いて、造型された鋳型からの鋳物砂の再生に適用され得るものでは、決してなかったのである。 However, in these conventional recycling methods, in the regeneration treatment of casting sand from a molded mold using an organic binder such as resin together with fire-resistant particles as casting sand, it adheres to the surface thereof. It is only premised on removing the organic binder (resin) that is present by burning it by a roasting operation, and such a regeneration method is an inorganic substance that is not burned as it is. It was never applicable to the regeneration of foundry sand from molded molds using binders.
　このため、特開２０１５－５１４４６号公報においては、ケイ酸ソーダの如き無機バインダを用いて造型された鋳型の鋳造後のものを粉砕した後、５℃乃至７０℃の水中において混合撹拌することにより、それに付着した無機バインダを分離せしめ、その後、バインダが分離された鋳物砂を回収して、加熱乾燥することからなる鋳物砂の再生処理方法が、明らかにされ、更に、特開２０１６－１４７２８７号公報においては、水ガラスを主体とするバインダにより被覆されている鋳物砂からなる鋳型を解砕した後、その解砕片に酸溶液を加えて、研磨を行なうことにより、鋳物砂を再生する方法が明らかにされているのであるが、そのような水中での混合撹拌処理や酸溶液を加えた研磨処理だけでは、鋳物砂（耐火粒子）の表面に強固に付着している無機バインダを剥離、除去せしめることは、容易ではなく、依然として、鋳物砂の表面には、無機バインダが少なからず残存し、その残存量が再生回数に比例して増大することにより、その再生鋳物砂を用いて得られる鋳型の物性に悪影響をもたらしている他、そこでは、水や酸溶液を用いた湿式処理が採用されるものであるところから、処理後の砂の洗浄や乾燥等の工程が増えることとなる実用上の問題も、内在しているのである。 Therefore, in Japanese Patent Application Laid-Open No. 2015-51446, a mold formed by using an inorganic binder such as sodium silicate is crushed after casting, and then mixed and stirred in water at 5 ° C to 70 ° C. A method for regenerating the casting sand, which comprises separating the inorganic binder adhering to the casting sand, and then recovering the casting sand from which the binder has been separated and heating and drying the casting sand, has been clarified, and further, Japanese Patent Application Laid-Open No. 2016-147287. In the publication, a method of regenerating casting sand by crushing a mold made of foundry sand coated with a binder mainly composed of water glass, adding an acid solution to the crushed pieces, and polishing the crushed pieces. Although it has been clarified, the inorganic binder firmly adhering to the surface of the casting sand (fireproof particles) is peeled off and removed only by such a mixing and stirring treatment in water or a polishing treatment with an acid solution. It is not easy to squeeze, and the inorganic binder remains on the surface of the foundry sand to a considerable extent, and the residual amount increases in proportion to the number of times of regeneration, so that the mold obtained by using the regenerated casting sand still remains. In addition to having an adverse effect on the physical properties of the stone, since wet treatment using water or an acid solution is adopted there, the number of steps such as washing and drying of the sand after the treatment will increase in practical use. The problem of is also inherent.
　また、特許第５４０１３２５号公報においては、鋳物砂の熱的再生の方法として、水ガラスの付着した使用済の鋳物砂を、少なくとも２００℃の温度にて加熱処理せしめ、鋳物砂の塩酸消費量が１０％となるまで減少するように、そのような加熱処理を実施するようにした手法が、明らかにされているのであるが、このような熱的再生処理が、繰り返し実施されることを想定した場合において、鋳物砂に強固に付着している水ガラスが次第に蓄積されるようになって、塩酸消費量が１０％まで減少するように加熱処理したところで、鋳物砂には、大量の水ガラスが残留するようになるものと考えられる。また、そこでは、砂粒にばらすための機械的処理が、前記した加熱処理の前又は後に実施されることも、明らかにされているのであるが、単に、砂粒にばらすだけでは、粒子表面に強固に付着している水ガラスを削り取ることが出来ないことは勿論のこと、機械的処理の前に熱処理を行なう場合と、機械的処理の後に熱処理を行なう場合とでは、得られる再生砂の性状が異なることとなるために、充分な鋳型性能を与える再生砂を得ることが困難であるという問題をも、内在している。 Further, in Japanese Patent No. 5401325, as a method for thermally regenerating the foundry sand, the used foundry sand to which water glass is attached is heat-treated at a temperature of at least 200 ° C., and the hydrochloric acid consumption of the foundry sand is reduced. A method for carrying out such a heat treatment so as to reduce the amount to 10% has been clarified, but it is assumed that such a thermal regeneration treatment is repeatedly carried out. In some cases, the water glass firmly adhering to the foundry sand gradually accumulated, and when the heat treatment was performed so that the hydrochloric acid consumption was reduced to 10%, a large amount of water glass was found in the foundry sand. It is thought that it will remain. It is also clarified that the mechanical treatment for separating into sand particles is carried out before or after the above-mentioned heat treatment, but simply disassembling into sand particles is strong on the particle surface. It goes without saying that the water glass adhering to the sand cannot be scraped off, and the properties of the regenerated sand obtained are different depending on whether the heat treatment is performed before the mechanical treatment or after the mechanical treatment. There is also an inherent problem that it is difficult to obtain recycled sand that gives sufficient mold performance because it is different.
　一方、所定のバインダと共に、鋳型の造型に用いられる耐火粒子が、珪砂の如き天然砂である場合において、上述の如き従来の再生方法を適用したとき、焙焼工程では、熱膨張による熱割れの問題が有り、また研磨工程においては、粒子自体が粉砕されてしまうという問題等が惹起されるようになるところから、再生工程に耐え得る耐久性が認められ得ない天然砂に対して、実用的な再生を行なうことは、極めて困難なことであったのである。特に、焙焼操作では容易に燃焼、除去され得ない無機バインダが固着した天然砂からなる鋳物砂の再生に、研磨の如き機械的再生方式を採用した場合には、天然砂の粉末化が惹起される恐れが高くなり、そのために、天然砂と無機バインダとを用いた鋳型からの鋳物砂の再生は、実用的に、極めて困難なことであったのである。 On the other hand, when the refractory particles used for molding the mold together with the predetermined binder are natural sand such as silica sand and the conventional regeneration method as described above is applied, in the roasting step, thermal cracking due to thermal expansion occurs. There is a problem, and in the polishing process, the problem that the particles themselves are crushed will be caused, so it is practical for natural sand whose durability that can withstand the regeneration process cannot be recognized. It was extremely difficult to carry out such regeneration. In particular, when a mechanical regeneration method such as polishing is adopted for the regeneration of cast sand made of natural sand to which inorganic binders that cannot be easily burned and removed by roasting operation are adhered, pulverization of natural sand is caused. Therefore, it was extremely difficult to regenerate the cast sand from the mold using natural sand and an inorganic binder.
特開昭６３－１８０３４０号公報Japanese Unexamined Patent Publication No. 63-180340 特開２０１６－１５０３６８号公報Japanese Unexamined Patent Publication No. 2016-150368 特開２０１５－５１４４６号公報JP-A-2015-51446 特開２０１６－１４７２８７号公報Japanese Unexamined Patent Publication No. 2016-147287 特許第５４０１３２５号公報Japanese Patent No. 5401325
　ここにおいて、本発明は、かかる事情を背景にして為されたものであって、その解決課題とするところは、水ガラスを主成分とする無機バインダを用いて造型された鋳型の鋳造後のものから、そのような鋳型の造型に用いられた鋳物砂の実用的な再生方法を提供することにあり、また、他の課題とするところは、繰り返しの再生処理によっても、高い鋳型強度を維持することの出来る、鋳物砂の有効な再生方法を提供することにある。 Here, the present invention has been made in the context of such circumstances, and the problem to be solved thereof is that after casting a mold molded using an inorganic binder containing water glass as a main component. Therefore, it is an object of the present invention to provide a practical method for regenerating the foundry sand used for molding such a mold, and another problem is that a high mold strength is maintained even by repeated reclaiming treatment. The purpose is to provide an effective method for regenerating foundry sand.
　そして、本発明は、上記した課題を解決するために、以下に列挙せる如き各種の態様において、好適に実施され得るものであるが、また、以下に記載の各態様は、任意の組み合わせにおいても、採用可能である。なお、本発明の態様乃至は技術的特徴は、以下に記載のものに何等限定されることなく、明細書全体の記載から把握され得る発明思想に基づいて、認識され得るものであることが、理解されるべきである。 Then, in order to solve the above-mentioned problems, the present invention can be preferably carried out in various aspects as listed below, but each aspect described below can also be carried out in any combination. , Can be adopted. It should be noted that the aspects or technical features of the present invention are not limited to those described below, and can be recognized based on the invention idea that can be grasped from the description of the entire specification. Should be understood.
（１）　人工的に製造された球状耐火粒子からなる鋳物砂と水ガラスを主成
　　　分とする無機バインダとを用いて造型された鋳型からの、前記鋳物砂
　　　の再生方法にして、（ａ）前記鋳型を用いた鋳造工程から回収される
　　　使用済鋳型を解砕する一方、そこで生じた微粉を分離、除去せしめる
　　　解砕工程と、（ｂ）かかる解砕工程より取り出された解砕物を整粒し
　　　て、前記耐火粒子の平均粒子径の１０分の１以下の平均粒子径を有す
　　　る微粒子を除去することにより、所定の整粒砂を得る整粒工程と、（
　　　ｃ）かくして得られた整粒砂を焙焼処理して、砂表面に付着する前記
　　　水ガラス成分を結晶化させる焙焼工程と、（ｄ）かかる焙焼処理の施
　　　された整粒砂を機械研磨することにより、表面研磨処理を実施して、
　　　砂表面の結晶化水ガラス成分を分離せしめる一方、その分離せしめた
　　　結晶化水ガラス成分を集塵装置にて捕集して、除去する研磨工程とを
　　　、有することを特徴とする鋳物砂の再生方法。
（２）　前記整粒工程と前記焙焼工程との間に、前記整粒砂を機械研磨して
　　　、かかる整粒砂中に存在する固着粒子を更に小さく解砕すると共に、
　　　砂表面に付着する水ガラス成分の一部を分離せしめる一方、その分離
　　　された水ガラス成分を集塵装置にて捕集して、除去する予備研磨工程
　　　を、更に有していることを特徴とする前記態様（１）に記載の鋳物砂
　　　の再生方法。
（３）　前記予備研磨工程における機械研磨処理時間が、前記研磨工程にお
　　　ける機械研磨処理時間よりも短い時間であることを特徴とする前記態
　　　様（２）に記載の鋳物砂の再生方法。
（４）　前記焙焼工程に供される整粒砂が、前記焙焼処理条件下での熱間処
　　　理後の流動性試験において、流動性を有していることを特徴とする前
　　　記態様（１）乃至前記態様（３）の何れか１つに記載の鋳物砂の再生
　　　方法。
（５）　前記整粒砂が、前記球状耐火粒子の粒径以上、５ｍｍ以下の粒径を
　　　有していることを特徴とする前記様態（１）乃至前記様態（４）の何
　　　れか１つに記載の鋳物砂の再生方法。
（６）　前記人工的に製造された球状耐火粒子が、４０重量％以上のＡｌ2Ｏ3
　　　と６０重量％以下のＳｉＯ2 を含む化学組成を有していることを特徴
　　　とする前記態様（１）乃至前記態様（５）の何れか１つに記載の鋳物
　　　砂の再生方法。
（７）　前記球状耐火粒子が、５０～８０重量％のＡｌ2Ｏ3と５０～２０重
　　　量％のＳｉＯ2 を含む化学組成を有していることを特徴とする前記態
　　　様（６）に記載の鋳物砂の再生方法。
（８）　前記人工的に製造された球状耐火粒子が、ムライト質又はムライト
　　　・コランダム質の球状粒子であることを特徴とする前記態様（１）乃
　　　至前記態様（７）の何れか１つに記載の鋳物砂の再生方法。
（９）　前記人工的に製造された球状耐火粒子が、焼結法によって人工的に
　　　製造された球状の焼結粒子であることを特徴とする前記態様（１）乃
　　　至前記態様（８）の何れか１つに記載の鋳物砂の再生方法。
（１０）　前記焙焼処理が、前記整粒砂をを流動せしめつつ、５００℃以上
　　　の温度で、少なくとも１０分間以上、加熱することにより、実施され
　　　ることを特徴とする前記態様（１）乃至前記態様（９）の何れか１つ
　　　に記載の鋳物砂の再生方法。
（１１）　前記機械研磨が、前記整粒砂を、軸回りに回転せしめられる円筒
　　　状砥石の周面に接触させることによって、実施されることを特徴とす
　　　る前記態様（１）乃至前記態様（１０）の何れか１つに記載の鋳物砂
　　　の再生方法。 (1) A method for regenerating the foundry sand from a mold formed by using an artificially produced foundry sand made of spherical fireproof particles and an inorganic binder mainly composed of water glass is used as (a). While crushing the used mold recovered from the casting process using the mold, the crushing step of separating and removing the fine powder generated there, and (b) sizing the crushed material taken out from the crushing step. Then, a sizing step of obtaining a predetermined sizing sand by removing fine particles having an average particle size of 1/10 or less of the average particle size of the fire-resistant particles, and (
c) The roasting step of roasting the sized sand thus obtained to crystallize the water glass component adhering to the sand surface, and (d) the sized sand subjected to the roasting treatment are machined. By polishing, surface polishing treatment is performed,
Regeneration of cast sand characterized by having a polishing step of separating the crystallized water glass component on the sand surface and collecting and removing the separated crystallized water glass component with a dust collector. Method.
(2) Between the sizing step and the roasting step, the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces.
It is characterized by having a pre-polishing process in which a part of the water glass component adhering to the sand surface is separated, and the separated water glass component is collected and removed by a dust collector. The method for regenerating cast sand according to the above aspect (1).
(3) The method for regenerating cast sand according to the above-mentioned mode (2), wherein the mechanical polishing treatment time in the preliminary polishing step is shorter than the mechanical polishing treatment time in the polishing step.
(4) The above-described embodiment characterized in that the sized sand used in the roasting step has fluidity in a fluidity test after hot treatment under the roasting treatment conditions. The method for regenerating cast sand according to any one of (1) to (3).
(5) One of the above-mentioned modes (1) to (4), wherein the sized sand has a particle size of 5 mm or less, which is equal to or larger than the particle size of the spherical refractory particles. The method for regenerating cast sand described in 1.
(6) Al 2 O 3 in which the artificially produced spherical refractory particles are 40% by weight or more.
The method for regenerating cast sand according to any one of the above-described aspects (1) to (5), which has a chemical composition containing 40% by weight or less of SiO 2 .
(7) The above-described state (6), wherein the spherical refractory particles have a chemical composition containing 50 to 80% by weight of Al 2 O 3 and 50 to 20% by weight of SiO 2. The method for regenerating cast sand according to the description.
(8) In any one of the above-described embodiments (1) and (7), wherein the artificially produced spherical refractory particles are mullite-quality or mullite-corundum-quality spherical particles. The method for regenerating cast sand according to the description.
(9) The aspect (1) of the above aspect (8), wherein the artificially produced spherical refractory particles are spherical sintered particles artificially produced by a sintering method. The method for regenerating cast sand according to any one of them.
(10) The aspect (1) to the above-described aspect (1), wherein the roasting treatment is carried out by heating the sized sand at a temperature of 500 ° C. or higher for at least 10 minutes or longer while flowing the sized sand. The method for regenerating cast sand according to any one of the above aspects (9).
(11) The aspect (1) to the aspect (11), wherein the mechanical polishing is carried out by bringing the sizing sand into contact with the peripheral surface of a cylindrical grindstone that is rotated about an axis. The method for regenerating cast sand according to any one of 10).
　このように、本発明に従う鋳物砂の再生方法にあっては、水ガラスを主成分とする無機バインダを用いて造型された鋳型の鋳造工程に供されたものから、そのような鋳型を構成する鋳物砂を再生するに際して、かかる鋳物砂として、珪砂の如き天然砂ではなく、人工的に製造された球状耐火粒子を用いると共に、鋳造工程から回収される使用済鋳型を解砕及び整粒し、そして、その得られた整粒砂を焙焼処理することにより、砂表面に付着する水ガラス成分を結晶化させた後、機械研磨により、砂表面の結晶化水ガラス成分を分離、除去せしめるようにしたことにより、鋳物砂の粒子自体が粉砕されて、微細化されるのを効果的に阻止しつつ、鋳物砂表面に付着する水ガラス成分を有利に除去せしめ得たのであり、これによって、鋳物砂が繰り返し再生されても、その再生砂から造型される鋳型の強度を高く維持することが、可能となったのである。 As described above, in the method for regenerating cast sand according to the present invention, such a mold is constructed from those used in the casting process of a mold molded by using an inorganic binder containing water glass as a main component. When regenerating casting sand, artificially produced spherical fire-resistant particles are used as the casting sand instead of natural sand such as silica sand, and the used mold recovered from the casting process is crushed and sized. Then, the obtained sized sand is roasted to crystallize the water glass component adhering to the sand surface, and then the crystallized water glass component on the sand surface is separated and removed by mechanical polishing. As a result, the particles of the foundry sand itself could be effectively prevented from being crushed and refined, and the water glass component adhering to the surface of the foundry sand could be advantageously removed. Even if the casting sand is repeatedly regenerated, it has become possible to maintain a high strength of the mold formed from the regenerated sand.
　しかも、本発明において、整粒工程と焙焼工程との間に、整粒砂を機械研磨して、かかる整粒砂中に存在する固着粒子を更に小さく解砕すると共に、砂表面に付着する水ガラス成分の一部を分離、除去せしめるようにした予備研磨工程を挿入することにより、更には、人工的に製造された球状耐火粒子として、焼結法によって人工的に製造された球状の焼結粒子を用いることにより、本発明の特徴は、より一層有利に発揮され得ることとなるのであり、特に、かかる球状の焼結粒子、中でも、ムライト質又はムライト・コランダム質の球状焼結粒子を用いることによって、繰り返し再生された再生砂の鋳型強度を、新砂を用いた場合における鋳型強度よりも高め、また、その強度を効果的に維持することが出来る特徴を発揮することが出来ることとなる。 Moreover, in the present invention, between the sizing step and the firing step, the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces and adhere to the sand surface. By inserting a pre-polishing process that separates and removes part of the water glass component, and as artificially produced spherical fireproof particles, spherical firing artificially produced by the sintering method. By using the forming particles, the characteristics of the present invention can be exhibited even more advantageously, and in particular, such spherical sintered particles, particularly mullite or mullite corundum spherical sintered particles, can be used. By using it, the mold strength of the regenerated sand that has been repeatedly regenerated can be made higher than the mold strength when the new sand is used, and the feature that the strength can be effectively maintained can be exhibited. ..
実施例２において、耐火粒子Ｂ及びＣの疑似古砂に対して、それぞれ、適用される各種再生方式を示す工程概略図である。FIG. 5 is a process schematic diagram showing various regeneration methods applied to the pseudo-old sand of the refractory particles B and C in the second embodiment, respectively.
　ところで、本発明に係る再生方法が適用される鋳型は、鋳物砂とバインダとを用いて、従来と同様にして、造型されたものであるが、そこにおいて、本発明では、バインダとして、水ガラスを主成分とする無機バインダが用いられる一方、鋳物砂としては、珪砂の如き天然砂ではなく、人工的に製造された球状耐火粒子を用いるようにしたのであり、これにより、鋳物砂の再生が有利に行なわれ得ることとなったのである。 By the way, the mold to which the regeneration method according to the present invention is applied is molded by using casting sand and a binder in the same manner as in the conventional case. In the present invention, the binder is water glass. While an inorganic binder containing the above as the main component is used, the casting sand is not natural sand such as silica sand, but artificially produced spherical fire-resistant particles, which regenerates the casting sand. It could be done in an advantageous way.
　そして、そのような本発明において、鋳物砂として用いられる、人工的に製造された球状耐火粒子は、球状のものであれば、公知の如何なる耐火性の人工粒子（骨材）をも、その対象とすることが出来る。具体的には、スプレードライ手法によって造粒された後に、ロータリーキルンで焼成して得られる焼結砂や、転動造粒法により造粒された後、ロータリーキルンで焼成して得られる焼結砂の他、高温で溶融して得られた溶融物をエアーで吹き飛ばして製造される溶融砂、火炎溶融法と呼ばれる方法で得られる溶融砂等があり、また材質的には、焼結ムライト、電融ムライトや焼結アルミナ、電融アルミナ等の材質のものを用いることが可能であるが、それらの中でも、焼結法によって得られる球状の耐火性粒子は、粒子表面に微細な凹凸が存在しており、そこに、無機バインダ成分が入り込み、徐々に埋まって行くようになるために、再生砂としての繰り返しての再利用に際して、鋳型強度が新砂と同程度、更にはそれよりも向上した値を発現し得るものであるところから、好適に用いられることとなる。 Then, in the present invention, as long as the artificially produced spherical refractory particles used as the casting sand are spherical, any known refractory artificial particles (aggregate) can be used as the target. Can be. Specifically, sintered sand obtained by firing with a rotary kiln after being granulated by a spray-drying method, or sintered sand obtained by firing with a rotary kiln after being granulated by a rolling granulation method. In addition, there are molten sand produced by blowing off the melt obtained by melting at a high temperature with air, molten sand obtained by a method called the flame melting method, etc., and the materials are sintered mullite and electric fusion. It is possible to use materials such as mullite, sintered alumina, and fused alumina, but among them, the spherical fire-resistant particles obtained by the sintering method have fine irregularities on the particle surface. Since the inorganic binder component enters there and gradually fills up, the mold strength is about the same as that of fresh sand, and even better than that, when it is repeatedly reused as recycled sand. Since it can be expressed, it will be preferably used.
　また、そのような本発明において用いられる球状の人工砂（骨材）は、有利には、４０重量％以上のＡｌ2Ｏ3と、６０重量％以下のＳｉＯ2 とからなる化学組成を有していることが、望ましい。ここで、かかるＡｌ2Ｏ3の含有量が４０重量％未満となると、換言すればＳｉＯ2 の含有量が６０重量％を超えるようになると、耐火粒子の熱膨張が大きくなって、ＳｉＯ2 特有の異常膨張が惹起され、そのため、本発明に従う再生処理の工程において、自己崩壊の問題が惹起されるようになる。特に、本発明にあっては、そのような化学組成において、ムライト質又はムライト・コランダム質の材質からなる耐火粒子（骨材）が、好適に用いられることとなる。なお、ここで、ムライト・コランダム質とは、粒子中にムライトの結晶構造とコランダムの結晶構造とが共存乃至は分散した状態のことを意味している。 Further, the spherical artificial sand (aggregate) used in the present invention advantageously has a chemical composition of 40% by weight or more of Al 2 O 3 and 60% by weight or less of SiO 2. It is desirable to be. Here, when the content of Al 2 O 3 is less than 40% by weight, in other words, when the content of SiO 2 exceeds 60% by weight, the thermal expansion of the refractory particles becomes large, which is peculiar to SiO 2. Anomalous expansion is evoked, and thus the problem of self-destruction is evoked in the process of regeneration according to the present invention. In particular, in the present invention, refractory particles (aggregates) made of a mullite or mullite corundum material are preferably used in such a chemical composition. Here, the mullite-corundum quality means a state in which the crystal structure of mullite and the crystal structure of corundum coexist or are dispersed in the particles.
　さらに、上述の如き耐火粒子の化学組成において、本発明の目的を有利に達成すべく、Ａｌ2Ｏ3は、好ましくは５０重量％以上、より好ましくは６０重量％以上の割合において含有せしめられ、その上限としては、一般に９０重量％、好ましくは８０重量％、より好ましくは７０重量％程度の割合が採用されることとなる。一方、ＳｉＯ2 は、好ましくは５０重量％以下、更に好ましくは４０重量％以下の割合において含有せしめられ、その下限としては、一般に１０重量％、好ましくは２０重量％、更に好ましくは３０重量％程度の割合が採用される。中でも、Ａｌ2Ｏ3：５０～８０重量％とＳｉＯ2 ：５０～２０重量％の化学組成が有利に採用され、更にはＡｌ2Ｏ3：６０～７０重量％とＳｉＯ2 ：４０～３０重量％の化学組成が、より一層好適に採用されることとなる。ここで、そのような化学組成は、例えば、一般的な蛍光Ｘ線分析装置を用いて、容易に測定することが可能である。 Further, in the chemical composition of the fire-resistant particles as described above, Al 2 O 3 is preferably contained in an amount of 50% by weight or more, more preferably 60% by weight or more in order to advantageously achieve the object of the present invention. As the upper limit thereof, a ratio of about 90% by weight, preferably 80% by weight, and more preferably about 70% by weight is generally adopted. On the other hand, SiO 2 is preferably contained in a proportion of 50% by weight or less, more preferably 40% by weight or less, and the lower limit thereof is generally 10% by weight, preferably 20% by weight, still more preferably about 30% by weight. The ratio of is adopted. Among them, the chemical composition of Al 2 O 3 : 50 to 80% by weight and SiO 2 : 50 to 20% by weight is advantageously adopted, and further, Al 2 O 3 : 60 to 70% by weight and SiO 2 : 40 to 30% by weight are adopted. The chemical composition of% will be more preferably adopted. Here, such a chemical composition can be easily measured using, for example, a general fluorescent X-ray analyzer.
　なお、かかる本発明において用いられる球状の人工砂は、従来から鋳型の造型に用いられてきている耐火粒子と同様な平均粒子径を有するものであって、一般に、その平均粒子径が、０．０１～０．５０ｍｍ程度、好ましくは０．０５～０．４０ｍｍ程度、より好ましくは０．０７～０．３０ｍｍ程度となる大きさを有するものである。この人工砂の平均粒子径が小さくなり過ぎると、その取り扱いが困難となり、回収砂の再生に困難を来たすようになる等の問題があり、また粒子径が大きくなり過ぎると、回収砂の再生上の問題に加えて、鋳造製品の品質低下の問題をも、惹起するようになる。ここで、平均粒子径は、レーザ回折・散乱法によって求められた粒度分布における積算値５０％での粒径（Ｄ50）を意味するものである。 The spherical artificial sand used in the present invention has an average particle size similar to that of the refractory particles conventionally used for molding a mold, and the average particle size is generally 0. It has a size of about 01 to 0.50 mm, preferably about 0.05 to 0.40 mm, and more preferably about 0.07 to 0.30 mm. If the average particle size of this artificial sand becomes too small, it will be difficult to handle it, and it will be difficult to regenerate the recovered sand. If the particle size becomes too large, the recovered sand will be regenerated. In addition to the problem of quality deterioration of cast products, it also causes the problem of deterioration. Here, the average particle size means the particle size (D 50 ) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method.
　また、そのような鋳物砂として用いられる人工の耐火粒子は、球状形状を呈する粒子として構成され、その真円度としては、一般に、０．７０以上であることが望ましく、中でも０．７５以上、特に０．８０以上の真円度を有する球状の耐火粒子が、有利に用いられることとなる。このような真円度を有する球状の耐火粒子を用いることにより、本発明に従う再生工程において、耐火粒子表面に付着する付着物の剥離、除去が有利に行なわれ得て、その再生工程の実用性が、より一層高められ得るのである。 Further, the artificial refractory particles used as such casting sand are composed of particles exhibiting a spherical shape, and the roundness thereof is generally preferably 0.70 or more, particularly 0.75 or more. In particular, spherical refractory particles having a roundness of 0.80 or more will be advantageously used. By using spherical refractory particles having such roundness, it is possible to advantageously perform peeling and removal of deposits adhering to the surface of the refractory particles in the regeneration step according to the present invention, and the practicality of the regeneration step. However, it can be further enhanced.
　ここで、人工耐火粒子の真円度は、公知の手法によって測定することが可能であり、例えば、マイクロトラック・ベル株式会社製の粒子形状測定装置：ＰａｒｔＡｎＳＩによって、測定することが出来る。かかる装置は、サンプルセル、ストロボＬＥＤ及び高感度ＣＣＤカメラから構成されており、その測定原理は、水をポンプにより循環させる一方、試料（耐火粒子）を投入することで、ストロボＬＥＤ光源とＣＣＤカメラとの間に配置されたサンプルセルを、試料粒子の混在する水が通過し、その際に得られる投影像を画像解析することにより、粒子毎の投影面積と最大フェレー径を求めることからなるものである。そして、その得られた最大フェレー径と投影面積の値から、下式：
　　真円度＝[４×投影面積（mm2）]/[π×{最大フェレー径(mm)}2]
により、粒子毎の真円度が算出される。具体的には、試料粒子を５０００個以上投入し、粒子毎の真円度を算出した後、それぞれ得られた真円度の合計値を測定粒子個数で平均することにより、真円度（平均値）が、それぞれ求められることとなる。 Here, the roundness of the artificial refractory particles can be measured by a known method, and can be measured by, for example, a particle shape measuring device manufactured by Microtrac Bell Co., Ltd .: PartAnSI. Such a device is composed of a sample cell, a strobe LED and a high-sensitivity CCD camera, and its measurement principle is that water is circulated by a pump while a sample (fireproof particles) is charged to form a strobe LED light source and a CCD camera. Water mixed with sample particles passes through the sample cell arranged between and, and the projected area and maximum ferret diameter for each particle are obtained by image analysis of the projected image obtained at that time. Is. Then, from the values of the maximum ferret diameter and projected area obtained, the following equation:
Roundness = [4 x projected area (mm 2 )] / [π x {maximum ferret diameter (mm)} 2 ]
Therefore, the roundness of each particle is calculated. Specifically, after inputting 5000 or more sample particles, calculating the roundness of each particle, and averaging the total value of the obtained roundness with the number of measured particles, the roundness (average). Value) will be calculated respectively.
　さらに、上記した鋳物砂と共に用いられる無機バインダの主成分となる水ガラスには、従来から、鋳型製造用組成物における粘結剤乃至は結合剤として用いられてきているケイ酸ソーダが、好適に用いられることとなる。なお、そのようなケイ酸ソーダは、一般式：Ｎａ2Ｏ・ｎＳｉＯ2（ｎ＝０．５～４．０）で表され、Ｎａ2ＯとＳｉＯ2とのモル比によって分類されて、一般に、ケイ酸ソーダ１号、２号、３号、４号等として呼称されるものがある。 Further, as the water glass which is the main component of the inorganic binder used together with the above-mentioned casting sand, sodium silicate, which has been conventionally used as a binder or a binder in a composition for mold production, is preferably used. It will be used. In addition, such sodium silicate is represented by the general formula: Na 2 O · nSiO 2 (n = 0.5 to 4.0), and is generally classified according to the molar ratio of Na 2 O and SiO 2. , Sodium silicate No. 1, No. 2, No. 3, No. 4, etc.
　そして、そのようなケイ酸ソーダに対して、鋳型造型用として公知の、各種の添加剤や、他の無機乃至は有機のバインダ、更には硬化剤乃至は硬化促進剤等が、必要に応じて添加、配合せしめられて、水ガラスを主成分とする無機バインダとして、鋳型の造型に用いられることとなるのである。なお、硬化剤や硬化促進剤は、無機バインダ中に、直接に、添加、配合せしめられる他、鋳型の造型工程において、鋳物砂と無機バインダとの混練砂（無機バインダ被覆砂）を成形型内に充填した後、成形型内に別途供給されて、無機バインダの硬化を行なう手法も、適宜に採用されることとなる。 Then, for such sodium silicate, various additives known for molding, other inorganic or organic binders, a curing agent, a curing accelerator, and the like can be added as needed. After being added and blended, it will be used for molding molds as an inorganic binder containing water glass as the main component. The curing agent and curing accelerator can be added and blended directly into the inorganic binder, and in the molding process of the mold, kneaded sand (inorganic binder-coated sand) of casting sand and the inorganic binder is formed in the molding mold. A method of curing the inorganic binder, which is separately supplied into the molding die after being filled in the mold, will also be appropriately adopted.
　本発明にあっては、上述の如き鋳物砂と無機バインダとを、常法に従って、配合・混練して、混練砂を形成した後、その混練砂を用いて、目的とする形状の鋳型を造型し、更にその鋳型を用いて、所定の金属溶湯を鋳造した後、その鋳造工程から回収される使用済の鋳型に対して、所定の再生処理を施すようにしたものであり、そこでは、先ず、かかる使用済鋳型を解砕する一方、そこで生じた微粉を分離、除去せしめることにより、解砕砂（解砕物）を得る解砕工程が実施される。 In the present invention, the casting sand and the inorganic binder as described above are mixed and kneaded according to a conventional method to form kneaded sand, and then the kneaded sand is used to mold a mold having a desired shape. Then, after casting a predetermined molten metal using the mold, the used mold recovered from the casting process is subjected to a predetermined regeneration treatment. A crushing step of obtaining crushed sand (crushed product) is carried out by crushing the used mold and separating and removing the fine powder generated therein.
　なお、かかる解砕工程における使用済鋳型の解砕は、ジョークラッシャーの如き公知の解砕機を用いて実施され、そして、そこで生じた微粉が、集塵機等によって分離、除去せしめられることにより、解砕物としての解砕砂が取り出されるのである。この分離、除去される微粉は、一般に、平均粒子径が１０μｍ以下程度のものである。 The used mold is crushed in the crushing step by using a known crusher such as a jaw crusher, and the fine powder generated there is separated and removed by a dust collector or the like to obtain a crushed product. The pyroclastic sand is taken out. The fine powder to be separated and removed generally has an average particle size of about 10 μm or less.
　また、かくして得られた解砕砂には、それから所定大きさの粒子を取り出すべく、篩等を用いた整粒（分級）操作が実施され、これによって、所定粒径の整粒砂が取り出されることとなる。この整粒操作を実施する工程において、整粒対象物である解砕砂から、鋳型の造型に用いられた球状耐火粒子（新砂）の平均粒子径の１０分の１以下、好ましくは７分の１以下、より好ましくは５分の１以下の平均粒子径を有する微粒子が除去されるのである。具体的には、そのような平均粒子径を有する微粒子を除去するために、球状耐火粒子の平均粒子径の５分の１以下、好ましくは３分の１以下、より好ましくは２分の１以下の目開きを有する篩を用いて、整粒操作が実施されることとなるのである。 Further, the crushed sand thus obtained is subjected to a sizing (classification) operation using a sieve or the like in order to take out particles having a predetermined size, whereby the sizing sand having a predetermined particle size is taken out. It becomes. In the step of carrying out this sizing operation, the average particle diameter of the spherical refractory particles (new sand) used for molding the mold from the crushed sand which is the sizing object is 1/10 or less, preferably 1/7. Hereinafter, fine particles having an average particle diameter of more preferably one-fifth or less are removed. Specifically, in order to remove fine particles having such an average particle size, one-fifth or less, preferably one-third or less, more preferably one-half or less of the average particle size of spherical refractory particles The sizing operation will be carried out using a sieve having the same size.
　そして、上記せる整粒工程において取り出される整粒砂は、一般に、球状耐火粒子（新砂）の粒径以上、５ｍｍ以下、望ましくは３ｍｍ以下の粒径の粒子として、取り出されるのが有効である。ここで、球状耐火粒子（新砂）の粒径とは、粒子個々の粒径であるが、そのような粒子が粒度分布を有する場合においては、実用的には、かかる粒度分布を有する粒子の平均粒子径の約１／３程度の粒径、好ましくは約１／２程度の粒径が採用されることとなる。なお、球状耐火粒子（新砂）よりも細粒のものは、解砕した際に発生する微粉であり、活性な水ガラス成分を多く含むものであるところから、後の焙焼処理工程において、熱負荷により、焙焼炉内で砂が固化する原因となるリスクを内在し、また整粒砂の粒度が、５ｍｍ以上となると、焙焼炉内において流動不良を惹起して、充分な熱負荷が伝わらなくなって、有効な焙焼処理を行ない難くなる問題を内在する。 Then, the sizing sand taken out in the above-mentioned sizing step is generally effective as particles having a particle size of 5 mm or less, preferably 3 mm or less, which is equal to or larger than the particle size of spherical refractory particles (shinsuna). Here, the particle size of the spherical fireproof particles (new sand) is the particle size of each particle, but when such particles have a particle size distribution, practically, the average of the particles having such a particle size distribution. A particle size of about 1/3 of the particle size, preferably about 1/2 of the particle size is adopted. Finer particles than spherical refractory particles (new sand) are fine powder generated when crushed and contain a large amount of active water glass components. Therefore, in the subsequent roasting process, due to heat load. , There is an inherent risk of causing sand to solidify in the roasting furnace, and if the particle size of the sized sand is 5 mm or more, it causes poor flow in the roasting furnace and a sufficient heat load cannot be transmitted. Therefore, there is an inherent problem that it becomes difficult to perform an effective roasting process.
　次いで、かくの如き解砕工程と整粒工程とを経て得られた、所定粒径の整粒砂には、焙焼処理が実施されて、加熱処理が施され、砂表面に付着する水ガラス成分が、結晶化せしめられることとなる。そして、この焙焼処理には、一般的に流動層炉が用いられて、炉内で砂を流動させながら、熱負荷をかける手法が、採用されることとなる。ところで、無機バインダの主成分である水ガラスは、鋳型の造型に供される無機バインダ被覆砂においては、Ｎａ2Ｏ・ｎＳｉＯ2・ｍＨ2Ｏ で表される含水形態において存在し、造型時の加熱による脱水反応で、Ｎａ2Ｏ・ｎＳｉＯ2・(ｍ－ｘ)Ｈ2Ｏ＋ｘＨ2Ｏ↑となり、この状態の水ガラスは、大気中の水分と容易に反応して、元の水ガラスであるＮａ2Ｏ・ｎＳｉＯ2・ｍＨ2Ｏ に戻る可逆反応を惹起するものであるが、水ガラスを更に加熱すると、５００～６００℃で、β－Ｎａ2Ｓｉ2Ｏ5 が生成するようになるのであって、その反応は、不可逆反応である。このため、焙焼処理における焙焼温度としては、かかるβ－Ｎａ2Ｓｉ2Ｏ5 が生成する温度以上とする必要があるが、更に加熱されると、８００～８７０℃で、α－Ｎａ2Ｓｉ2Ｏ5 とシリケートとの溶融物が生成するようになるところから、焙焼温度は、そのような温度以下にする必要がある。溶融物が生成すると、流動焙焼炉やロータリーキルンでの加熱時に、溶融物の存在により、流動化不良や溶融固化が惹起される恐れがあるからである。 Next, the sized sand having a predetermined particle size obtained through the crushing step and the sizing step as described above is subjected to a roasting treatment, a heat treatment, and a water glass adhering to the sand surface. The components will be crystallized. A fluidized bed furnace is generally used for this roasting process, and a method of applying a heat load while flowing sand in the furnace is adopted. By the way, water glass, which is the main component of the inorganic binder, exists in the water-containing form represented by Na 2 O, nSiO 2 , mH 2 O in the inorganic binder-coated sand used for molding the mold, and is present at the time of molding. By the dehydration reaction by heating, Na 2 O · nSiO 2 · (mx) H 2 O + xH 2 O ↑, and the water glass in this state easily reacts with the moisture in the atmosphere and is the original water glass. It induces a reversible reaction that returns to Na 2 O, nSiO 2 , mH 2 O, but when the water glass is further heated, β-Na 2 Si 2 O 5 is produced at 500 to 600 ° C. There, the reaction is an irreversible reaction. Therefore, as the roasting temperature in the roasting process, the consuming β-Na 2 Si 2 O 5 is required to be equal to or higher than a temperature of generating is further heated at 800 ~ 870 ℃, α-Na 2 The roasting temperature needs to be below that temperature because the melt of Si 2 O 5 and silicate will be formed. This is because when a melt is generated, poor fluidization or melt solidification may occur due to the presence of the melt during heating in a fluidized roasting furnace or a rotary kiln.
　従って、本発明に従う焙焼処理の際に採用される焙焼温度としては、一般に５００℃以上、望ましくは６００℃以上の温度が採用され、更に焙焼処理時間としては、一般に１０分間以上、望ましくは３０分間以上の時間が採用され、これによって、整粒砂粒子の表面に残留している活性な水ガラス成分を不活性化せしめて、再生砂として再度利用する際に、無機バインダとの混練物（鋳型造型用組成物）の可使時間を長く保つことが可能となるのである。なお、この焙焼温度が５００℃未満となったり、焙焼処理時間が１０分間未満となると、鋳物砂粒子表面に付着した活性な水ガラス成分を不活性化させるのに、充分な熱負荷をかけることが困難となり、再生砂として使用する際に、前記した可使時間が短くなって、鋳型の造型作業が困難となる問題を内在する。一方、かかる焙焼温度は高い程望ましく、更に焙焼処理時間は長い程望ましいものではあるが、そのような焙焼温度や時間が過剰に高く乃至は長くなると、焙焼炉内での砂の融着や流動化不良が惹起されるようになるところから、一般に、焙焼温度は８００℃以下、好ましくは７５０℃以下が採用され、また焙焼処理時間としては、一般に５時間以下、好ましくは３時間以下が、採用されることとなる。 Therefore, the roasting temperature adopted in the roasting treatment according to the present invention is generally 500 ° C. or higher, preferably 600 ° C. or higher, and the roasting treatment time is generally 10 minutes or longer, preferably 10 minutes or longer. Is used for more than 30 minutes, which inactivates the active water glass component remaining on the surface of the sized sand particles and kneads it with an inorganic binder when it is reused as recycled sand. It is possible to keep the pot life of the product (composition for molding) long. When the roasting temperature is less than 500 ° C. or the roasting treatment time is less than 10 minutes, a sufficient heat load is applied to inactivate the active water glass component adhering to the surface of the casting sand particles. There is an inherent problem that it becomes difficult to sprinkle, and when it is used as recycled sand, the above-mentioned pot life becomes short and the molding work of the mold becomes difficult. On the other hand, the higher the roasting temperature is, the more desirable it is, and the longer the roasting treatment time is, the more desirable it is. However, if the roasting temperature and time are excessively high or long, the sand in the roasting furnace becomes Generally, the roasting temperature is 800 ° C. or lower, preferably 750 ° C. or lower, and the roasting treatment time is generally 5 hours or less, preferably 5 hours or less, because fusion and fluidization defects are caused. Less than 3 hours will be adopted.
　ところで、本発明にあっては、前記した整粒工程と焙焼工程との間に、整粒砂を機械研磨して、かかる整粒砂中に存在する固着粒子を更に小さく解砕すると共に、砂表面に付着する水ガラス成分の一部を分離せしめる一方、その分離された水ガラス成分を、集塵装置にて捕集して、除去する予備研磨工程が、好適に採用されることとなる。この予備研磨工程の採用により、整粒工程において取り出された整粒砂には、更なる整粒作用が加わって、粒子の孤立化が進行せしめられることとなるところから、後の焙焼工程における流動性が充分に確保され得て、より効率よく熱負荷をかけることが可能となるのである。 By the way, in the present invention, between the sizing step and the roasting step described above, the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces. A pre-polishing step of separating a part of the water glass component adhering to the sand surface and collecting and removing the separated water glass component with a dust collector is preferably adopted. .. By adopting this pre-polishing step, the sizing sand taken out in the sizing step is further subjected to the sizing action, and the isolation of the particles is promoted. Therefore, in the subsequent roasting step. Sufficient fluidity can be ensured, and heat load can be applied more efficiently.
　特に、繰り返しの再生回数が増加するようになると、残存する水ガラス成分により、再生前の砂（回収砂）が、解砕操作だけでは、所望の大きさの粒子にならなくなるからであり、また蓄積された水ガラス成分により、粒子同士が固着して、複数の粒子が一体化するようになり、それを、単に、解砕する（解す）だけでは、所望の大きさの粒子を得ることが出来ず、そのために、後の焙焼工程において、熱が充分に伝わらなくなる等の問題を惹起するようになるところから、上述の如き予備研磨工程を採用して、固着粒子の解砕、更には蓄積される水ガラス成分の部分的な除去を図ることが、望ましいのである。 In particular, when the number of repeated regenerations increases, the remaining water glass component prevents the sand (recovered sand) before regeneration from becoming particles of a desired size only by the crushing operation. Due to the accumulated water glass component, the particles are fixed to each other and a plurality of particles are integrated, and it is possible to obtain particles of a desired size by simply crushing (dissolving) the particles. This cannot be done, and as a result, problems such as insufficient heat transfer will occur in the subsequent roasting process. Therefore, the pre-polishing process as described above is adopted to crush the fixed particles, and further. It is desirable to partially remove the accumulated water glass component.
　そして、本発明においては、前記した焙焼工程に続いて、焙焼処理の施された整粒砂を機械研磨することにより、表面研磨処理を実施して、砂表面に存在する結晶化水ガラス成分を分離せしめる一方、その分離せしめた結晶化水ガラス成分を集塵装置にて捕集して、除去する研磨工程が、実施されることとなるのである。なお、この研磨工程においては、焙焼（加熱）処理により結晶化せしめられた、粒子表面に付着する水ガラス成分を除去する必要があるところから、前記した予備研磨工程における機械研磨よりも、より重度な機械研磨処理が実施されることとなるが、鋳物砂として用いられている耐火粒子は、そのような機械研磨に耐えられる程の耐破砕性が高いものである必要がある。このため、本発明においては、そのような耐火粒子として、人工的に製造された球状耐火粒子が用いられているのである。 Then, in the present invention, following the roasting step described above, the surface polishing treatment is carried out by mechanically polishing the sized sand that has been subjected to the roasting treatment, and the crystallized water glass existing on the sand surface is performed. While the components are separated, a polishing step of collecting and removing the separated crystallized water glass components by a dust collector is carried out. In this polishing step, it is necessary to remove the water glass component adhering to the particle surface, which has been crystallized by the roasting (heating) treatment, and therefore, it is more than the mechanical polishing in the preliminary polishing step described above. Although severe mechanical polishing treatment will be carried out, the fire-resistant particles used as casting sand need to have high crush resistance enough to withstand such mechanical polishing. Therefore, in the present invention, artificially produced spherical refractory particles are used as such refractory particles.
　ここにおいて、かくの如き研磨工程における機械研磨は、前記した予備研磨工程における機械研磨と共に、公知の各種の研磨装置を用いて実施され得、例えば、整粒砂を砥石に接触させて、その表面を研磨するようにした研磨装置を用いることが出来、有利には、軸回りに回転せしめられる円筒状砥石の周面に対して、整粒砂を供給して、接触させることによって、研磨が行なわれるようにした方式が、好適に採用されることとなる。具体的には、特開２０１６－４１３号公報に開示の如き構造の、鋳物砂の機械再生装置を用いることが出来、また、市販品であるサンドフレッシャー（株式会社清田鋳機）を用いることが出来る他、ロータリーリクレマーやサンドシャイナー等と称される研磨装置も用いることが出来る。更に、それら予備研磨工程における機械研磨と、研磨工程における機械研磨とは、同様な研磨装置を用いて行なうことが、実用上からして望ましいものではあるが、また、異なる研磨装置を用いて、それぞれの機械研磨を実施することも、可能である。 Here, the mechanical polishing in the polishing step as described above can be carried out by using various known polishing devices together with the mechanical polishing in the preliminary polishing step described above. For example, the sized sand is brought into contact with the grindstone and its surface thereof. It is possible to use a polishing device for polishing, which is advantageous in that polishing is performed by supplying and contacting the peripheral surface of the cylindrical grindstone that is rotated around the axis with sized sand. The method so as to be used will be preferably adopted. Specifically, a mechanical reclaiming device for cast sand having a structure as disclosed in Japanese Patent Application Laid-Open No. 2016-413 can be used, and a commercially available sand fresher (Kiyota Casting Machine Co., Ltd.) can be used. In addition to this, polishing equipment called rotary reclamers, sand shiners, etc. can also be used. Further, although it is practically desirable that the mechanical polishing in the pre-polishing step and the mechanical polishing in the polishing step are performed by using the same polishing device, it is also possible to use different polishing devices. It is also possible to carry out each mechanical polishing.
　そして、本発明においては、予備研磨工程と研磨工程の目的の相違から、整粒砂に対する研磨作用が、予備研磨工程では軽度なものとされ、一方、後の研磨工程では重度な研磨作用が加えられることとなる。ここで、それら研磨作用の差異は、研磨時間や研磨回数等を異ならしめることによって実現され、例えば、予備研磨工程における機械研磨処理時間を、後の研磨工程における機械研磨処理時間よりも短くしたり、予備研磨工程における機械研磨処理回数を少ない回数、例えば１回とする一方、後の研磨工程における機械研磨処理回数を、それよりも多い複数回、例えば３回とすること等によって、実現することが可能である。後の研磨処理のみでは、鋳物砂（耐火粒子）表面に付着した活性な水ガラス成分を完全に剥離することは困難であるところから、焙焼工程の前に採用される予備研磨工程における機械研磨は、単に、後の焙焼工程における整粒砂の流動不良や炉内での固化を防ぎつつ、かかる活性な水ガラス成分の不活性化が有利に行なわれ得るようにすることを目的としているものであり、一方、後の研磨工程においては、活性な水ガラス成分を焙焼により結晶化させて、不活性化された水ガラス成分を、強研磨により完全に剥離せしめて、再生砂として再利用された際における鋳型強度が充分に高められ得るようにすることを目的としているのである。 In the present invention, due to the difference in purpose between the pre-polishing step and the polishing step, the polishing action on the sized sand is considered to be mild in the pre-polishing step, while a heavy polishing action is added in the subsequent polishing step. Will be done. Here, the difference in the polishing action is realized by making the polishing time, the number of times of polishing, etc. different. For example, the mechanical polishing treatment time in the pre-polishing step may be shorter than the mechanical polishing treatment time in the subsequent polishing step. , The number of mechanical polishing treatments in the pre-polishing step is set to a small number, for example, one, while the number of mechanical polishing treatments in the subsequent polishing step is set to a larger number, for example, three times. Is possible. Since it is difficult to completely remove the active water glass component adhering to the surface of the foundry sand (fireproof particles) only by the subsequent polishing process, mechanical polishing in the preliminary polishing process adopted before the roasting process is performed. Is merely intended to prevent the sizing sand from flowing poorly and solidifying in the furnace in the subsequent roasting process, while allowing such active water glass components to be advantageously inactivated. On the other hand, in the subsequent polishing process, the active water glass component is crystallized by roasting, and the inactivated water glass component is completely peeled off by strong polishing and regenerated as recycled sand. The purpose is to enable the mold strength to be sufficiently increased when it is used.
　なお、上記した予備研磨工程や研磨工程においては、機械研磨処理によって、微細な水ガラス成分の粉末が発生するようになるのであるが、そのような微細な粉末は、研磨処理の施された整粒砂から分離されて、集塵装置にて捕集され、系外に除去せしめられるようになっている。けだし、予備研磨工程において、研磨処理された整粒砂に微粉末が混在していると、後の焙焼工程における流動性の低下や砂同士の固着等の問題が惹起されるようになるからであり、また研磨工程において、機械研磨された整粒砂に、それより分離された結晶化水ガラス成分の微粉末が混在するようになると、そのような研磨工程を経て得られる再生砂の再利用時において、鋳型強度等の特性の充分な実現を図ることが困難となるからである。 In the pre-polishing step and the polishing step described above, fine powder of water glass component is generated by the mechanical polishing treatment, and such fine powder is prepared by the polishing treatment. It is separated from the grain sand, collected by a dust collector, and removed from the system. If fine powder is mixed in the sized sand that has been polished in the pre-polishing process, problems such as a decrease in fluidity and adhesion between the sands in the subsequent roasting process will occur. In addition, when the fine powder of the crystallized water glass component separated from the mechanically polished sized sand is mixed in the polishing step, the recycled sand obtained through such a polishing step is regenerated. This is because it becomes difficult to sufficiently realize characteristics such as mold strength at the time of use.
　かくの如くして、本発明に従って、解砕工程と、整粒工程と、必要に応じて採用される予備研磨工程と、焙焼工程と、研磨工程とを経て、得られた鋳物砂の再生砂にあっては、その表面に固着していた水ガラス成分が効果的に除去せしめられたものとなり、更に、鋳物砂の繰り返しの再生処理によっても、表面固着水ガラス成分の除去作用が、有利に実現され得ることとなるものであるところから、そのような再生砂を用いて、再度、造型して得られる鋳型においては、その強度が効果的に高められ、また、再生操作を繰り返し実施して得られる再生砂を用いた鋳型にあっても、その鋳型強度を高く維持することが可能となったのである。 In this way, according to the present invention, the foundry sand obtained through the crushing step, the sizing step, the pre-polishing step adopted as necessary, the roasting step, and the polishing step is regenerated. In the case of sand, the water glass component adhering to the surface thereof is effectively removed, and further, the effect of removing the water glass component adhering to the surface is advantageous even by repeated regeneration treatment of the casting sand. In the mold obtained by casting again using such recycled sand, the strength of the mold is effectively increased, and the recycling operation is repeated. It has become possible to maintain a high mold strength even in a mold using the regenerated sand obtained.
　以下に、本発明の代表的な実施例を示し、本発明を更に具体的に明らかにすることとするが、本発明が、そのような実施例の記載によって、何等の制約をも受けるものでないことは、言うまでもないところである。また、本発明には、以下の実施例の他にも、更には上記した具体的記述以外にも、本発明の趣旨を逸脱しない限りにおいて、当業者の知識に基づいて、種々なる変更、修正、改良等が加えられ得るものであることが、理解されるべきである。 Representative examples of the present invention will be shown below to clarify the present invention more concretely, but the present invention is not subject to any restrictions by the description of such examples. Needless to say. Further, in addition to the following examples, various modifications and modifications to the present invention are made based on the knowledge of those skilled in the art, as long as the gist of the present invention is not deviated from the specific description described above. It should be understood that improvements can be made.
－実施例１－
　鋳物砂として、各種材質の耐火粒子Ａ，Ｂ及びＣを、それぞれ、下記表１に示される公知の製造法に従って、準備した。 -Example 1-
As the casting sand, refractory particles A, B and C of various materials were prepared according to the known production methods shown in Table 1 below, respectively.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　次いで、それら耐火粒子Ａ～Ｃに対して、それぞれ、水ガラスを主成分とした無機バインダ（チェコ：ＳＡＮＤ　ＴＥＡＭ社製Ｇｅｏｐｏｌ　Ｗ１１）と硬化促進剤（チェコ：ＳＡＮＤ　ＴＥＡＭ社製Ｇｅｏｔｅｋ　Ｗ３０３）とを、下記表２に示される割合において配合せしめて、混練することにより、鋳型造型用の３種の混練砂を製造した。 Next, for each of the refractory particles A to C, an inorganic binder containing water glass as a main component (Czech Republic: Geopol W11 manufactured by SAND TEAM) and a curing accelerator (Czech Republic: Geotek W303 manufactured by SAND TEAM) were added. Three types of kneaded sand for molding were produced by mixing and kneading at the ratios shown in Table 2 below.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　かくして得られた３種の混練砂を用い、それらに対して、それぞれ、１５０℃×１時間の熱処理を施すことにより、使用済鋳型から回収される古砂（鋳物砂）に模した疑似古砂を、それぞれ、作製した。その後、耐火粒子Ａ，Ｂ及びＣに対応して得られた３種の疑似古砂を、それぞれ、ジョークラッシャーにて解砕する一方、その際に発生する微粉を、集塵機にて除去した。次いで、そのような解砕操作にて得られた解砕物を、振動篩にて分級することにより、過大な粒子や過小な粒子を除去して、１０５μｍ～２ｍｍの範囲内の粒子サイズを有する３種の整粒砂を取り出した。なお、耐火粒子Ｂにおいて、ジョークラッシャーにて解砕した際に発生する、集塵機にて除去した微粉の平均粒子径は６．２９μｍであり、また振動篩にて除去した過小な粒子の平均粒子径は、４３．１μｍであった。これらの平均粒子径は、マイクロトラック・ベル株式会社製の粒子径分布測定装置：ＭＴ３３００ＥＸIIにて測定して、得られたものである。このことから、集塵機で除去する微粉は著しく細かいのに対し、振動篩にて除去する微少な粒子は、上記解砕操作にて割れた粒子あるいは粒子表面に付着していた水ガラス成分であることが、認められる。 Using the three types of kneaded sand thus obtained, each of them is heat-treated at 150 ° C. for 1 hour to imitate the old sand (casting sand) recovered from the used mold. Were prepared respectively. After that, each of the three types of pseudo-old sand obtained corresponding to the refractory particles A, B and C was crushed by a jaw crusher, and the fine powder generated at that time was removed by a dust collector. Next, the crushed product obtained by such a crushing operation is classified by a vibrating sieve to remove excessive particles and small particles, and has a particle size in the range of 105 μm to 2 mm3. Seed sized sand was removed. In the refractory particles B, the average particle size of the fine particles generated when crushed by the jaw crusher is 6.29 μm, and the average particle size of the small particles removed by the vibrating sieve. Was 43.1 μm. These average particle diameters were obtained by measuring with a particle diameter distribution measuring device: MT3300EXII manufactured by Microtrac Bell Co., Ltd. From this, the fine particles removed by the dust collector are extremely fine, whereas the fine particles removed by the vibrating sieve are the particles broken by the above crushing operation or the water glass component adhering to the particle surface. However, it is recognized.
　その後、その取り出された３種の整粒砂に対して、それぞれ、焙焼処理（６００℃×２時間）と機械式研磨処理（３０分）とを順次実施することにより、それぞれの整粒砂の再生処理を行ない、３種の再生砂（耐火粒子）を得た。なお、焙焼処理は、流動焙焼炉を用いて実施する一方、機械式研磨処理としては、疑似古砂の３０ｋｇを、研磨機であるサンドフレッシャー（株式会社清田鋳機製ＢＲ－３０５）に投入して、砥石（砥石径：３０５ｍｍ）を周速４０ｍ／秒で高速回転させて、その外周面に接触せしめることによって、かかる疑似古砂を研磨して、疑似古砂に付着した、水ガラスを主体とする無機バインダ由来の物質を分離、除去せしめる一方、その除去した無機バインダ由来の物質（微粉末）を、かかるサンドフレッシャーに連結した集塵機（アマノ株式会社製パルスジェット集塵機：ＰｉＦ－７５Ｕ）により、風量：４６ｍ3 ／分にて集塵して、除去せしめる方式を採用した。 After that, each of the three types of sized sand taken out was sequentially subjected to a roasting treatment (600 ° C. × 2 hours) and a mechanical polishing treatment (30 minutes), so that each sized sand was obtained. Was regenerated to obtain three types of regenerated sand (refractory particles). The roasting process is carried out using a fluidized roasting furnace, while as a mechanical polishing process, 30 kg of pseudo old sand is transferred to a sand fresher (BR-305 manufactured by Kiyota Casting Machine Co., Ltd.), which is a polishing machine. By throwing in, the grindstone (grinding stone diameter: 305 mm) is rotated at a high speed of 40 m / sec and brought into contact with the outer peripheral surface thereof, the pseudo old sand is polished and the water glass attached to the pseudo old sand is attached. A dust collector (Pulse jet dust collector manufactured by Amano Co., Ltd .: PiF-75U) in which the removed inorganic binder-derived substance (fine powder) is connected to the sand fresher while separating and removing the substance derived from the inorganic binder mainly composed of ), A method of collecting dust at an air volume of 46 m 3 / min and removing it was adopted.
　その結果、耐火粒子Ｂ及びＣの疑似古砂からは、それぞれ、収率よく、再生砂を得ることが出来たが、耐火粒子Ａの疑似古砂に対する再生処理においては、機械式研磨処理にて、耐火粒子自体の粉砕が惹起されることが認められ、また焙焼処理では、熱膨張による熱割れにより、粉砕された微粉が著しく発生して、実用的な再生処理を実施することが困難であることが認められた。 As a result, recycled sand could be obtained in good yield from the pseudo-old sands of the refractory particles B and C, respectively. However, in the regeneration treatment of the pseudo-old sands of the refractory particles A, a mechanical polishing treatment was performed. It is recognized that the refractory particles themselves are crushed, and in the roasting process, crushed fine particles are remarkably generated due to thermal cracking due to thermal expansion, making it difficult to carry out a practical regeneration process. It was recognized that there was.
－実施例２－
　実施例１と同様な、解砕、整粒、焙焼処理及び機械式研磨処理の条件を採用して、前記耐火粒子Ｂ及びＣの疑似古砂に対して、それぞれ、図１に示される各種の再生方式に従って再生操作を実施し、各種の再生耐火粒子を得た。なお、再生方式（６）における焙焼処理前の予備研磨処理は、研磨処理時間を１０分間として、焙焼処理後の研磨処理の処理時間：３０分よりも短い時間として、軽度の研磨処理が実施されるようにした。 -Example 2-
Adopting the same conditions of crushing, sizing, roasting treatment and mechanical polishing treatment as in Example 1, various types of pseudo-old sand of the refractory particles B and C are shown in FIG. 1, respectively. The regeneration operation was carried out according to the regeneration method of (1), and various recycled refractory particles were obtained. In the pre-polishing treatment before the roasting treatment in the regeneration method (6), the polishing treatment time is 10 minutes, the polishing treatment time after the roasting treatment is shorter than 30 minutes, and a light polishing treatment is performed. Made to be implemented.
　次いで、かくして得られた各種の再生耐火粒子を用いて、それら再生耐火粒子に対して、それぞれ、下記表３に示される配合組成において、水ガラスを主成分とする無機バインダ（Ｇｅｏｐｏｌ　Ｗ１１）とその硬化促進剤（Ｇｅｏｔｅｋ　Ｗ３０３）とを配合せしめて混練し、更に、それら得られた混練砂を、造型機（株式会社清田鋳機製ＫＭＴＰＺ１０１９）に、エアーブロー：１．５秒／０．４ＭＰａの条件下で吹き込み、そして、金型温度：１５０℃、ガッシングエアー：１５０℃／０．３ＭＰａ／３０秒の条件下にて造型を行なうことにより、２２．４ｍｍ×２２．４ｍｍ×１７０ｍｍの大きさの各種試験片を作製した。 Then, using the various regenerated refractory particles thus obtained, the regenerated refractory particles were respectively subjected to an inorganic binder (Geopol W11) containing water glass as a main component and a binder thereof in the composition shown in Table 3 below. A curing accelerator (Geotek W303) is mixed and kneaded, and the obtained kneaded sand is further applied to a molding machine (KMTPZ1019 manufactured by Kiyota Casting Co., Ltd.) under the condition of air blow: 1.5 seconds / 0.4 MPa. By blowing under and molding under the conditions of mold temperature: 150 ° C. and gassing air: 150 ° C./0.3 MPa/30 seconds, the size of 22.4 mm × 22.4 mm × 170 mm. Various test pieces were prepared.
　その後、かかる得られた各種試験片について、それぞれ、温度：２５℃、湿度：５０％ＲＨの環境下で、１時間保管した後、縦型電動計測機（株式会社イマダ製ＭＸ２－２５００Ｎ）を用いて、スパン：１５０ｍｍ、降下速度：５ｍｍ／分にて抗折強度を測定し、その結果を、下記表４に示した。 After that, the obtained various test pieces were stored for 1 hour in an environment of temperature: 25 ° C. and humidity: 50% RH, respectively, and then using a vertical electric measuring instrument (MX2-2500N manufactured by Imada Co., Ltd.). The bending strength was measured at a span of 150 mm and a descent speed of 5 mm / min, and the results are shown in Table 4 below.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　かかる表４の結果から明らかなように、整粒砂に対して研磨処理のみを施すことからなる再生方式（１）において得られた再生耐火粒子（砂）は、鋳型の造型に用いられる前の耐火粒子である新砂と同等以上の抗折強度を発現しているが、粒子表面に活性な水ガラス成分が未だ残存するものであるところから、砂とバインダとを混練した後の混練砂の造型可能な時間である可使時間が短くなり、実用的ではないものと判断された。また、整粒砂に、焙焼処理のみを施すことからなる再生方式（２）や、研磨処理に続いて焙焼処理を施すことからなる再生方式（３）において得られた再生耐火粒子や、更に、解砕した際に、集塵や整粒を行なうことなく、焙焼処理及び研磨処理を施すことからなる再生方式（４）において得られた再生耐火粒子にあっては、新砂よりも抗折強度の低い試験片を与えるに過ぎないものであった。 As is clear from the results in Table 4, the regenerated refractory particles (sand) obtained in the regenerating method (1) consisting of only polishing the sized sand are before being used for molding the mold. Although it exhibits a bending resistance equal to or higher than that of fresh sand, which is a refractory particle, since the active water glass component still remains on the particle surface, molding of kneaded sand after kneading sand and binder. It was judged to be impractical because the pot life, which is the possible time, was shortened. Further, the regenerated refractory particles obtained in the regeneration method (2) in which only the sizing sand is subjected to the roasting treatment and the regeneration method (3) in which the polishing treatment is followed by the roasting treatment, Furthermore, the regenerated refractory particles obtained in the regeneration method (4), which consists of performing roasting treatment and polishing treatment without collecting dust or sizing when crushed, are more resistant than fresh sand. It only gave a test piece with low folding strength.
　これに対して、焙焼処理に先立って、集塵（微粉の除去）と整粒を実施した再生方式（５）や、更に焙焼処理に先立って、予備研磨処理（処理時間１０分）を採用した再生方式（６）において得られた再生耐火粒子は、何れも、新砂以上の抗折強度を有する試験片を与えるものであることが明らかとなり、それら再生方式が、鋳物砂の再生方法として有効であることが認められた。 On the other hand, prior to the roasting treatment, a regeneration method (5) in which dust collection (removal of fine particles) and sizing was performed, and a preliminary polishing treatment (treatment time: 10 minutes) prior to the roasting treatment. It was clarified that all the regenerated refractory particles obtained in the adopted reclaiming method (6) give test pieces having a bending strength higher than that of fresh sand, and these reclaiming methods are used as a method for regenerating casting sand. It was found to be effective.
－実施例３－
　実施例１において得られた耐火粒子Ｂ及びＣの疑似古砂に対して、それぞれ、下記表５に示される各種の再生処理を実施し、そしてその得られた再生耐火粒子について、熱間流動性試験を実施した。ここで、熱間流動性試験は、４００～８００℃の所定温度に予め加熱された電気炉に、各再生耐火粒子を収容した耐火容器を１０～６０分の所定時間の間、放置することにより、所定の熱処理を施した。そして、そのような熱処理が実施された後に、耐火容器を炉外に取り出し、直ちに、耐火容器を傾けて、かかる耐火容器から再生耐火粒子が排出可能であるか、どうか、を評価した。そして、耐火容器を傾けただけで、そこに収容されている砂が排出可能であったものを○と評価し、また、耐火容器を傾けただけでは収容砂は排出不可であるが、耐火容器を叩くことにより排出可能となったものを△と評価し、更に、耐火容器から収容砂が排出不可であったものを×と評価して、その結果を、下記表５に示した。 -Example 3-
The pseudo-old sands of the refractory particles B and C obtained in Example 1 were subjected to various regeneration treatments shown in Table 5 below, respectively, and the obtained recycled refractory particles were subjected to hot fluidity. The test was carried out. Here, the hot fluidity test is carried out by leaving a refractory container containing each regenerated refractory particle in an electric furnace preheated to a predetermined temperature of 400 to 800 ° C. for a predetermined time of 10 to 60 minutes. , A predetermined heat treatment was performed. Then, after such heat treatment was performed, the refractory container was taken out of the furnace, and immediately the refractory container was tilted to evaluate whether or not the regenerated refractory particles could be discharged from the refractory container. Then, the sand contained therein can be discharged only by tilting the fireproof container, which is evaluated as ○, and the sand contained therein cannot be discharged only by tilting the fireproof container, but the fireproof container cannot be discharged. Those that could be discharged by hitting were evaluated as Δ, and those that could not discharge the contained sand from the refractory container were evaluated as ×, and the results are shown in Table 5 below.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　かかる表５の結果から明らかなように、解砕処理のみが実施される再生処理の場合にあっては、耐火粒子Ｂ及びＣの何れもが、４００℃での熱処理から熱間流動性が悪いことが認められる。また、解砕・集塵処理が施される再生処理の場合にあっては、４００℃での熱間流動性には改善が見られたものの、５００℃からの熱間流動性は悪いことが認められる。この熱間流動性の悪化は、焙焼処理する際に、流動不良を起こす原因ともなり、充分な焙焼処理を施すことが出来ないことを示しており、このことから、集塵処理による微粉末除去だけでは、充分な熱間流動性を発揮することが出来ないことが理解される。これに対して、解砕・集塵処理と共に、整粒処理を実施することにより、複数の粒子が凝集した大きな複粒子や微小な粒子、更には解砕時に発生する割れた粒子、あるいは粒子表面に付着していた水ガラス成分を除去することが出来るところから、熱間流動性が改善され、加えて、そのような整粒処理を行なった整粒砂に対して、更に研磨処理（処理時間１０分）を施すことにより、加熱温度が８００℃となっても、充分な熱間流動性を発揮するものであることが認められた。熱間流動性を悪化させる原因となる微粉末及び微粒子サイズは、具体的には、耐火粒子Ｂにおいては、解砕・集塵処理では、平均粒子径が６μｍ程度、整粒処理では、平均粒子径は４０μｍ程度である。いずれも、熱間流動性に悪影響を及ぼすため、それらは、可能な限り除去することが望ましく、平均粒子径が、一般に２０μｍ以下、望ましくは３０μｍ以下、さらに望ましくは４５μｍ以下の微粉末及び微粒子を取り除くことが、望ましいのである。 As is clear from the results in Table 5, in the case of the regeneration treatment in which only the crushing treatment is carried out, both the refractory particles B and C have poor hot fluidity from the heat treatment at 400 ° C. Is recognized. Further, in the case of the regeneration treatment in which crushing and dust collection treatment is performed, although the hot fluidity at 400 ° C. is improved, the hot fluidity from 500 ° C. is poor. Is recognized. This deterioration in hot fluidity also causes poor flow during the roasting process, indicating that sufficient roasting process cannot be performed. Therefore, the dust collection process causes fine particles. It is understood that sufficient hot fluidity cannot be exhibited only by removing the powder. On the other hand, by performing the sizing treatment together with the crushing / dust collecting treatment, large double particles or fine particles in which a plurality of particles are aggregated, and the cracked particles generated during crushing, or the particle surface. Since the water glass component adhering to the sand can be removed, the hot fluidity is improved, and in addition, the sized sand that has undergone such sizing treatment is further polished (treatment time). It was confirmed that by applying (10 minutes), sufficient hot fluidity was exhibited even when the heating temperature was 800 ° C. Specifically, the size of the fine powder and fine particles that cause deterioration of hot fluidity is as follows: In the refractory particle B, the average particle diameter is about 6 μm in the crushing / dust collecting treatment, and the average particle in the sizing treatment. The diameter is about 40 μm. Since all of them adversely affect hot fluidity, it is desirable to remove them as much as possible, and fine powders and fine particles having an average particle size of generally 20 μm or less, preferably 30 μm or less, and more preferably 45 μm or less. It is desirable to remove it.
－実施例４－
　実施例２における耐火粒子Ｂ及びＣの古砂に対する再生方式（１）又は（６）により得られた再生耐火粒子に対して、砂と無機バインダとを混練した後、その得られた混練砂について、鋳型の造型が可能な時間である可使時間の評価試験を実施した。ここで、可使時間の評価試験は、再生耐火粒子と無機バインダ、硬化促進剤とを、前記表３に示した配合割合において配合して、混練せしめた後、その得られた混練砂を、温度：２５℃、湿度：５０％ＲＨの環境下において、所定時間（０～２時間）の間保管し、その後、実施例２に記載の方法にて、それぞれの試験片を造型した。そして、その得られた試験片の重量を測定し、その重量測定値と試験片の体積（２２．４ｍｍ×２２．４ｍｍ×１７０ｍｍ／１０００）とから、次式：
　　充填度（ｇ／ｃｍ3）＝[試験片重量（ｇ）]／[試験片体積（ｃｍ3）]
により、充填度を求めて、その結果を、下記表６に示した。 -Example 4-
About the obtained kneaded sand after kneading sand and an inorganic binder with respect to the regenerated refractory particles obtained by the method (1) or (6) for regenerating the old sand of the refractory particles B and C in Example 2. , An evaluation test of the pot life, which is the time when the mold can be molded, was carried out. Here, in the evaluation test of the pot life, the regenerated refractory particles, the inorganic binder, and the curing accelerator are blended in the blending ratios shown in Table 3 above and kneaded, and then the obtained kneaded sand is mixed. The test pieces were stored for a predetermined time (0 to 2 hours) in an environment of temperature: 25 ° C. and humidity: 50% RH, and then each test piece was molded by the method described in Example 2. Then, the weight of the obtained test piece is measured, and from the weight measurement value and the volume of the test piece (22.4 mm × 22.4 mm × 170 mm / 1000), the following equation:
Filling degree (g / cm 3 ) = [Test piece weight (g)] / [Test piece volume (cm 3 )]
The filling degree was obtained, and the results are shown in Table 6 below.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　かかる表６の結果から明らかなように、耐火粒子Ｂ及びＣにおいて、新砂と再生方式（６）にて得られた再生耐火粒子は、保管時間が２時間であっても、充填度は、可使時間が０時間である場合との比較において略変化がなく、充分な可使時間を有していることが認められる。一方、研磨処理のみにより再生処理を行なう再生方式（１）によって得られた再生耐火粒子は、保管時間：１時間において、試験片の造型が不可能となり、そのために、可使時間が不充分であって、再生方法としては実用的でないことが認められる。 As is clear from the results in Table 6, the refractory particles B and C can be filled with fresh sand and the regenerated refractory particles obtained by the regeneration method (6) even if the storage time is 2 hours. There is almost no change in comparison with the case where the usage time is 0 hours, and it is recognized that the usage time is sufficient. On the other hand, the regenerated refractory particles obtained by the regenerating method (1) in which the regenerating treatment is performed only by the polishing treatment cannot form a test piece at a storage time of 1 hour, and therefore, the pot life is insufficient. Therefore, it is recognized that it is not practical as a reproduction method.
－実施例５－
　実施例２において採用された再生方式（６）にて、耐火粒子Ｂ及びＣの古砂を再生処理して、得られた再生耐火粒子について、更に、繰り返し同じ再生処理を施して得られた再生耐火粒子について、再生回数毎に、実施例２と同様にして試験片を作製して、その試験片についての抗折強度を測定し、その結果を、下記表７に示した。 -Example 5-
Regeneration obtained by regenerating old sand of refractory particles B and C by the regeneration method (6) adopted in Example 2 and further repeatedly performing the same regeneration treatment on the obtained refractory particles. For the refractory particles, a test piece was prepared in the same manner as in Example 2 for each number of times of regeneration, and the bending strength of the test piece was measured, and the results are shown in Table 7 below.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
　かかる表７の結果から明らかなように、耐火粒子Ｂにあっては、再生方式（６）による再生処理を施すことで、新砂以上の抗折強度が発現され、その後、繰り返し再生処理を実施しても、その抗折強度の変化はほとんど認められず、充分な抗折強度を有しているものであるところから、水ガラスを主成分とする無機バインダを用いて作製される鋳型に使用される鋳物砂において、繰り返しの使用と再生が可能であると判断された。一方、耐火粒子Ｃにあっては、再生回数が１回の場合には、新砂と同等の抗折強度を有しているが、再生回数が２回、３回と増えることにより、抗折強度は低下傾向にあり、更に、再生回数が３回以上となると、抗折強度の変化は認められなかった。なお、再生処理後の粒子形状を観察するために、再生耐火粒子Ｃについての粒子形態を顕微鏡写真にて調べたところ、半球状の粒子形状を呈しており、機械式研磨処理によって、粒子自体が割れていることが認められた。 As is clear from the results in Table 7, the refractory particles B are subjected to the regeneration treatment by the regeneration method (6) to develop a bending strength higher than that of the fresh sand, and then the repeated regeneration treatment is carried out. However, there is almost no change in the bending strength, and since it has sufficient bending strength, it is used for molds made using an inorganic binder containing water glass as the main component. It was judged that repeated use and regeneration are possible in the cast sand. On the other hand, the refractory particles C have the same anti-folding strength as Shinsuna when the number of times of regeneration is 1, but the anti-folding strength is increased by increasing the number of times of regeneration to 2 or 3 times. Was on a downward trend, and when the number of regenerations was 3 or more, no change in the bending strength was observed. In order to observe the particle shape after the regeneration treatment, the particle morphology of the recycled refractory particles C was examined by a micrograph, and the particles themselves showed a hemispherical particle shape, and the particles themselves were subjected to the mechanical polishing treatment. It was found to be cracked.
－実施例６－
　実施例１において得られた耐火粒子Ｂ及びＣの古砂に対して、各種の再生処理を施して得られた解砕砂又は整粒砂について、７００℃までの所定温度で、２時間の焙焼処理を施した後、それぞれの焙焼処理砂の電気伝導度（ｍＳ／ｍ）を測定し、その結果を、下記表８に示した。なお、かかる電気伝導度は、砂２０ｇと蒸留水５０ｇとを、撹拌子とスターラーを用いて３０分間撹拌した後、デカンテーションにより、その上澄み液を採取して、東亜ディーケーケー株式会社製のマルチ水質計（ｐＨ／ＯＲＰ／イオン／電気伝導率／溶存酸素）ＭＭ－４３Ｘを用いて、かかる上澄み液の電気伝導度を測定する方法によって、求めた。ここで、そのような電気伝導度の値が低ければ低い程、再生耐火粒子の表面に残存している活性な水ガラス成分が少ないことを意味している。また、再生処理が解砕だけ又は解砕・集塵だけである耐火粒子Ｂ及びＣの焙焼温度として、６００℃又は７００℃を採用した場合にあっては、焙焼処理後の砂が固化し、塊状となったために、電気伝導度の有効な測定を行なうことが出来なかった。 -Example 6-
The crushed sand or sized sand obtained by subjecting the old sand of the refractory particles B and C obtained in Example 1 to various regeneration treatments is roasted at a predetermined temperature up to 700 ° C. for 2 hours. After the treatment, the electric conductivity (mS / m) of each roasted sand was measured, and the results are shown in Table 8 below. The electrical conductivity is such that 20 g of sand and 50 g of distilled water are stirred for 30 minutes using a stirrer and a stirrer, and then the supernatant is collected by decanting to obtain a multi-water quality manufactured by Toa DK Co., Ltd. It was determined by a method of measuring the electrical conductivity of such a supernatant using a meter (pH / ORP / ion / electrical conductivity / dissolved oxygen) MM-43X. Here, the lower the value of such electrical conductivity, the less active water glass component remains on the surface of the regenerated refractory particles. Further, when 600 ° C. or 700 ° C. is adopted as the roasting temperature of the refractory particles B and C whose regeneration treatment is only crushing or crushing / dust collection, the sand after the roasting treatment is solidified. However, because it became lumpy, it was not possible to effectively measure the electrical conductivity.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　かかる表８の結果から明らかなように、再生処理の方法の如何に関わらず、焙焼温度が高くなればなる程、再生耐火粒子の電気伝導度は低下しており、このことより、焙焼温度が高くなる程、粒子表面に残留している活性な水ガラス成分がより一層不活性化されていることが認められる。また、焙焼温度が４００℃から５００℃になると、著しく電気伝導度が低下することとなることにより、５００℃以上の焙焼温度の採用にて、活性な水ガラス成分が有利に不活性化され得ることとなることが認められるのである。これは、水ガラスに含まれるＮａ2Ｏ やＳｉＯ2 が反応して、Ｎａ2Ｓｉ2Ｏ5 が生成するためであり、活性な水ガラス成分を充分に不活性化させるには、５００℃以上の焙焼温度が必要であると言うことが出来る。 As is clear from the results in Table 8, the higher the roasting temperature, the lower the electrical conductivity of the regenerated refractory particles, regardless of the method of the regeneration treatment. It is recognized that the higher the temperature, the more inactivated the active water glass component remaining on the particle surface. Further, when the roasting temperature is changed from 400 ° C. to 500 ° C., the electric conductivity is remarkably lowered. Therefore, by adopting a roasting temperature of 500 ° C. or higher, the active water glass component is advantageously inactivated. It is acknowledged that it can be done. This is because Na 2 O and SiO 2 contained in the water glass react with each other to generate Na 2 Si 2 O 5 , and the temperature is 500 ° C. or higher in order to sufficiently inactivate the active water glass component. It can be said that the roasting temperature of is required.
　これに対して、再生処理が解砕のみ又は解砕・集塵のみである場合にあっては、実施例３で明らかにされているように、焙焼温度が５００℃以上となると、熱間流動性が低下乃至は喪失するようになるために、５００℃以上の温度での焙焼処理は困難であると言うことが出来る。このため、再生処理が解砕のみ又は解砕・集塵のみである耐火粒子を、活性な水ガラス成分が充分に不活性化せしめられる温度にまで、焙焼温度を上げて、焙焼処理することは出来ず、そのために、再生処理に際して、整粒を行なうことなく、解砕又は解砕・集塵の工程から、直ちに焙焼処理を行なう再生方式では、それによって得られる再生耐火粒子（再生砂）の特性が充分でないものとなるのである。 On the other hand, when the regeneration treatment is only crushing or only crushing / dust collection, as is clarified in Example 3, when the roasting temperature is 500 ° C. or higher, it is hot. It can be said that the roasting process at a temperature of 500 ° C. or higher is difficult because the fluidity decreases or is lost. Therefore, the refractory particles whose regeneration treatment is only crushing or crushing / dust collection are roasted by raising the roasting temperature to a temperature at which the active water glass component can be sufficiently inactivated. Therefore, in the regeneration method, the regenerated refractory particles (regenerated) obtained by the regenerating method in which the roasting process is immediately performed from the step of crushing or crushing / dust collection without performing the granulation in the regenerating process. The characteristics of sand) are not sufficient.

Claims (11)

  1. 　人工的に製造された球状耐火粒子からなる鋳物砂と水ガラスを主成分とする無機バインダとを用いて造型された鋳型からの、前記鋳物砂の再生方法にして、
    　前記鋳型を用いた鋳造工程から回収される使用済鋳型を解砕する一方、そこで生じた微粉を分離、除去せしめる解砕工程と、
    　かかる解砕工程より取り出された解砕物を整粒して、前記耐火粒子の平均粒子径の１０分の１以下の平均粒子径を有する微粒子を除去することにより、所定の整粒砂を得る整粒工程と、
    　かくして得られた整粒砂を焙焼処理して、砂表面に付着する前記水ガラス成分を結晶化させる焙焼工程と、
    　かかる焙焼処理の施された整粒砂を機械研磨することにより、表面研磨処理を実施して、砂表面の結晶化水ガラス成分を分離せしめる一方、その分離せしめた結晶化水ガラス成分を集塵装置にて捕集して、除去する研磨工程とを、
    有することを特徴とする鋳物砂の再生方法。     The method for regenerating the foundry sand from a mold formed by using an artificially produced foundry sand made of spherical refractory particles and an inorganic binder containing water glass as a main component is used.
    A crushing process in which the used mold recovered from the casting process using the mold is crushed, while the fine powder generated there is separated and removed.
    The crushed material taken out from the crushing step is sized to remove fine particles having an average particle size of 1/10 or less of the average particle size of the refractory particles, thereby obtaining a predetermined sized sand. Grain process and
    A roasting step in which the sized sand thus obtained is roasted to crystallize the water glass component adhering to the sand surface, and
    By mechanically polishing the sized sand that has undergone such roasting treatment, surface polishing treatment is performed to separate the crystallized water glass components on the sand surface, while collecting the separated crystallized water glass components. A polishing process that collects and removes with a dust device,
    A method for regenerating foundry sand, which comprises having.
  2. 　前記整粒工程と前記焙焼工程との間に、前記整粒砂を機械研磨して、かかる整粒砂中に存在する固着粒子を更に小さく解砕すると共に、砂表面に付着する水ガラス成分の一部を分離せしめる一方、その分離された水ガラス成分を集塵装置にて捕集して、除去する予備研磨工程を、更に有していることを特徴とする請求項１に記載の鋳物砂の再生方法。 Between the sizing step and the roasting step, the sizing sand is mechanically polished to further crush the fixed particles existing in the sizing sand into smaller pieces, and the water glass component adhering to the sand surface. The casting according to claim 1, further comprising a pre-polishing step of collecting and removing the separated water glass component with a dust collecting device while separating a part of the above. How to regenerate sand.
  3. 　前記予備研磨工程における機械研磨処理時間が、前記研磨工程における機械研磨処理時間よりも短い時間であることを特徴とする請求項２に記載の鋳物砂の再生方法。 The method for regenerating cast sand according to claim 2, wherein the mechanical polishing treatment time in the pre-polishing step is shorter than the mechanical polishing treatment time in the polishing step.
  4. 　前記焙焼工程に供される整粒砂が、前記焙焼処理条件下での熱間処理後の流動性試験において、流動性を有していることを特徴とする請求項１乃至請求項３の何れか１項に記載の鋳物砂の再生方法。 Claims 1 to 3 are characterized in that the sized sand used in the roasting step has fluidity in a fluidity test after hot treatment under the roasting treatment conditions. The method for regenerating cast sand according to any one of the above.
  5. 　前記整粒砂が、前記球状耐火粒子の粒径以上、５ｍｍ以下の粒径を有していることを特徴とする請求項１乃至請求項４の何れか１項に記載の鋳物砂の再生方法。 The method for regenerating cast sand according to any one of claims 1 to 4, wherein the sized sand has a particle size of 5 mm or more, which is equal to or larger than the particle size of the spherical refractory particles. ..
  6. 　前記人工的に製造された球状耐火粒子が、４０重量％以上のＡｌ2Ｏ3と６０重量％以下のＳｉＯ2 を含む化学組成を有していることを特徴とする請求項１乃至請求項５の何れか１項に記載の鋳物砂の再生方法。 Claims 1 to 5 are characterized in that the artificially produced spherical refractory particles have a chemical composition containing 40% by weight or more of Al 2 O 3 and 60% by weight or less of SiO 2. The method for regenerating cast sand according to any one of the above.
  7. 　前記球状耐火粒子が、５０～８０重量％のＡｌ2Ｏ3と５０～２０重量％のＳｉＯ2 を含む化学組成を有していることを特徴とする請求項６に記載の鋳物砂の再生方法。 The method for regenerating cast sand according to claim 6, wherein the spherical refractory particles have a chemical composition containing 50 to 80% by weight of Al 2 O 3 and 50 to 20% by weight of SiO 2. ..
  8. 　前記人工的に製造された球状耐火粒子が、ムライト質又はムライト・コランダム質の球状粒子であることを特徴とする請求項１乃至請求項７の何れか１項に記載の鋳物砂の再生方法。 The method for regenerating cast sand according to any one of claims 1 to 7, wherein the artificially produced spherical refractory particles are mullite or mullite corundum spherical particles.
  9. 　前記人工的に製造された球状耐火粒子が、焼結法によって人工的に製造された球状の焼結粒子であることを特徴とする請求項１乃至請求項８の何れか１項に記載の鋳物砂の再生方法。 The casting according to any one of claims 1 to 8, wherein the artificially produced spherical refractory particles are spherical sintered particles artificially produced by a sintering method. How to regenerate sand.
  10. 　前記焙焼処理が、前記整粒砂を流動せしめつつ、５００℃以上の温度で、少なくとも１０分間以上、加熱することにより、実施されることを特徴とする請求項１乃至請求項９の何れか１項に記載の鋳物砂の再生方法。 Any of claims 1 to 9, wherein the roasting treatment is carried out by heating the sized sand at a temperature of 500 ° C. or higher for at least 10 minutes or longer while flowing the sized sand. The method for regenerating cast sand according to item 1.
  11. 　前記機械研磨が、前記整粒砂を、軸回りに回転せしめられる円筒状砥石の周面に接触させることによって、実施されることを特徴とする請求項１乃至請求項１０の何れか１項に記載の鋳物砂の再生方法。 The method according to any one of claims 1 to 10, wherein the mechanical polishing is carried out by bringing the sized sand into contact with the peripheral surface of a cylindrical grindstone that is rotated about an axis. The method for regenerating cast sand according to the description.
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