JP5778550B2 - Mold manufacturing method - Google Patents

Description

  The present invention relates to a method of forming a mold in a hollow when manufacturing a mold using a binder coated sand.

  As one method for producing a mold using a binder coated sand (so-called resin coated sand) prepared by mixing a binder with a refractory aggregate, the binder is placed in a mold heated to a high temperature. There is a method in which a coated sand is injected and filled, and the binder of the binder coated sand is heated and cured by the heat of the mold, and the refractory aggregate is bonded with the binder to mold the mold.

  When the binder coated sand filled in the mold is heated by the heat of the mold to mold the mold, the mold is filled, and then the mold is turned upside down, A hollow mold has been conventionally formed by discharging uncured binder coated sand out of the binder coated sand filled in (see, for example, Patent Documents 1 and 2). ).

  In the mold formed using the binder coated sand, for example, in the case of a shell mold, especially when the mold is a core, the mold should be hollow in order to reduce the occurrence of defects due to the gas generated during casting. In view of the fact that expensive binder-coated sand (resin-coated sand) can be saved, a hollow mold is desirable.

  An example of a method for producing such a hollow mold is shown in FIG. An injection port 3 is formed on the upper surface of the mold 1 and the mold 1 is heated to a high temperature by a built-in electric heater or the like. First, the binder-coated sand 2 is injected from the injection port 3, and the binder-coated sand 2 is filled into the mold 1 as shown in FIG. The binder coated sand 2 filled in the mold 1 is heated by the heat of the mold 1, and curing proceeds from the portion of the binder coated sand 2 in contact with the inner surface of the mold 1. Therefore, when the binder of the binder coated sand 2 in contact with the inner surface of the mold 1 has been cured, the binder of the binder coated sand 2 inside is uncured. When the mold 1 is turned upside down as shown in FIG. 5B and the injection port 3 is turned downward, the uncured binder coated sand 2 is discharged from the injection port 3 and the curing proceeds. Since the binder-coated sand 2 is solidified in layers, the layer of the binder-coated sand 2 in contact with the inner periphery of the mold 1 remains in the mold 1.

  Next, as shown in FIG. 5 (c), the mold 1 is returned to its original state and left for a predetermined time to heat the binder-coated sand 2 left in layers in the mold 1 with the heat of the mold 1. Then, the curing of the binder coated sand 2 is advanced. Of the binder coated sand 2 in the mold 1, it is necessary to invert the mold 1 as described above while the binder coated sand 2 in the center is uncured, so that the mold 1 is discharged. The binder in the layer of the binder coated sand 2 in contact with the inner circumference of the binder has not yet completely cured, and is in a semi-cured or gelled stage or in a state where the binder is thermally melted. Therefore, even after the uncured binder coated sand 2 is discharged from the mold 1, the binder coated sand 2 in the mold 1 is heated by the heat of the mold 1 by leaving it for a predetermined time. It is necessary to cure the binder in the layer of the binder coated sand 2 to be completely cured.

  Thus, by completely curing the binder in the layer of the binder coated sand 2 in the mold 1, a hollow mold A as shown in FIG. 5 (e) can be molded. The hollow mold A can be obtained by opening the mold 1 and removing the mold.

JP-A-6-339747 JP 2004-141930 A

  As described above, after the uncured binder coated sand 2 is discharged, the binder coated sand 2 remaining in a layered form in contact with the inner surface of the mold 1 is heated by the heat of the mold 1 to be completely cured. However, with the heat transferred from the mold 1 to the binder coated sand 2, the heating rate of the binder coated sand 2 is slow, and the binder cannot be completely cured in a short time.

  In the state where the binder of the binder coated sand 2 is not sufficiently cured, since the binding force by the binder is small, the layer of the binder coated sand 2 formed in the mold 1 has low strength. . For this reason, when it takes time for the binder to completely cure, as shown in FIG. 5 (d), in the layer of the binder-coated sand 2 in the mold 1, the vertical or downward portion is located. There is a risk of so-called peel back. That is, in the part of the binder-coated sand 2 that is in contact with the cavity 6, the heat of the mold 1 directly acts, so that the curing progresses and is in close contact with the inner surface of the cavity 6. The part of the binder coated sand 2 is in a softened state due to insufficient curing, and if it takes time for the part in the softened state to harden sufficiently, in a vertical or downward position where there is no support, Peelback occurs in which the softened portion is delaminated by its own weight.

  Accordingly, a peeling part 25 as shown in FIG. 5 (f) is generated in the mold A which is hollowly formed in the mold 1, and the peeling part 25 is dropped into the mold A as shown in FIG. 5 (g). Sometimes. When such a peel-back failure occurs, the thickness of the mold A becomes thinner than the assumed thickness at the part where the delamination occurs. Therefore, when casting is performed using this mold A, there is a possibility that the delamination may occur due to the thermal shock of the molten metal poured or the weight of the molten metal, and cracks may occur in the thinned portion, and the molten metal flows into the mold A and solidifies. For example, a defect is likely to occur in the casting.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a mold manufacturing method capable of molding a mold without causing defects such as peelback. .

  In the mold manufacturing method according to the present invention, the binder coated sand 2 is filled in the mold 1, and the curing of the binder coated sand 2 in contact with the mold 1 by the heat of the mold 1 is advanced. Thereafter, the uncured binder-coated sand 2 is discharged from the mold 1, and then steam is blown into the mold 1 to heat the binder-coated sand 2 in the mold 1 with water vapor. The binder coated sand 2 is further cured.

  In this way, after discharging the uncured binder coated sand 2 from the mold 1, the steam is blown into the mold 1, so that the binder coated sand 2 is rapidly brought about by condensation latent heat and sensible heat of water vapor. The binder can be cured in a short time, and before the delamination occurs due to its own weight in the layer of the binder coated sand 2 in the mold 1, The mold A can be cured without causing defects such as peel back.

  In the present invention, the injection port 3 is formed on the upper portion of the mold 1, the binder coated sand 2 is filled into the mold 1 from the injection port 3, and the portion of the mold 1 that is in contact with the mold 1 is heated. After the curing of the binder coated sand 2 is advanced, the molding die 1 is turned upside down to discharge the uncured binder coated sand 2 from the injection port.

  According to this method, the uncured binder-coated sand 2 can be discharged using the injection port 3 into which the binder-coated sand 2 has been injected by inverting the mold 1. There is no need to form the mold 1 in a complicated structure.

  Further, in the present invention, after the mold 1 is turned upside down and the binder-coated sand 2 is discharged as described above, the mold 1 is further turned upside down and water vapor is blown into the mold 1 from the inlet 3. It is characterized by.

  According to this method, water vapor can be blown using the inlet 3 for injecting and discharging the binder coated sand 2, and it is not necessary to form the mold 1 in a complicated structure. Is.

  Further, in the present invention, a discharge port 4 is formed in the lower part of the mold 1 provided with the injection port 3, the binder coated sand 2 is filled into the mold 1 from the injection port 3, and molding is performed by the heat of the mold 1. After the hardening of the binder coated sand 2 in contact with the mold 1, the discharge port 4 is opened and the uncured binder coated sand 2 is discharged.

  According to this method, it is possible to discharge the uncured binder-coated sand 2 from the discharge port 4 at the bottom of the mold 1 without having to turn the mold 1 upside down. There is no need to provide a mechanism for reversing.

  Further, the present invention fills the molding die 1 with the binder coated sand 2 in a state in which the discharge port 4 is closed with the plug 21 having a lower thermal conductivity than the mold 1 and opens the discharge port 4 by removing the plug 21. In this case, the uncured binder coated sand 2 is discharged.

  By closing the discharge port 4 with the plug 21 having a low thermal conductivity in this way, the conduction of heat to the binder coated sand 2 in the portion facing the discharge port 4 can be suppressed so that curing does not proceed. It is possible to prevent the discharge port 4 from being blocked by the hardened binder coated sand 2 and not being able to discharge the uncured binder coated sand 2.

  The present invention is characterized in that superheated steam is used as the steam.

  Superheated steam is high-temperature dry air, and it is less likely that condensed water is excessively generated from water vapor in the mold 1, and the temperature rise rate of the binder-coated sand 2 in the mold 1 is further increased. In addition, it is possible to reduce the moisture contained in the mold.

  In the present invention, the binder coated sand 2 is filled in the mold 1, and the curing of the portion of the binder coated sand 2 in contact with the mold 1 with the heat of the mold 1 is allowed to proceed. Then, the uncured binder coated sand 2 is discharged, and then the binder coated sand 2 is heated by blowing steam into the mold 1 and heating the binder coated sand 2 in the mold 1 with water vapor. The curing is further advanced. And after discharging the uncured binder coated sand 2 from the mold 1 in this way, by blowing water vapor into the mold 1, the binder coated sand 2 is formed by the condensation latent heat and sensible heat of the water vapor. The binder can be rapidly heated and the binder can be cured in a short time, and before the delamination occurs due to its own weight in the layer of the binder coated sand 2 in the mold 1. The agent can be cured, and the hollow mold A can be molded without causing defects such as peelback.

An example of embodiment of this invention is shown, (a) (b) (c) (d) is a schematic sectional drawing of each process, (e) is a schematic sectional drawing of a casting_mold | template. It shows another example of the embodiment of the present invention, (a) (b) (c) (d) is a schematic sectional view of each step, (e) is a schematic sectional view of the mold. It shows another example of the embodiment of the present invention, (a) (b) (c) (d) is a schematic sectional view of each step, (e) is a schematic sectional view of the mold. The other embodiment of this invention is shown, (a) (b) is sectional drawing. It shows a conventional example, (a) (b) (c) (d) is a schematic cross-sectional view of each step, (e) (f) (g) is a schematic cross-sectional view of the mold.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of an embodiment of the present invention. As shown in FIG. 1 (a), the mold 1 is provided with a cavity 6 inside and an injection port 3 communicating with the cavity 6 on the upper surface. Is formed. The mold 1 is composed of a pair of molds 1a and 1b, and a groove for forming an air vent 7 is provided on at least one facing surface of the molds 1a and 1b. The air vent 7 does not allow the binder-coated sand 2 to pass therethrough, but is formed to a size that allows gas such as water vapor to pass easily. The mold 1 can be formed by clamping the pair of molds 1a and 1b so as to match.

  The mold 1 is provided with heat generating means such as an embedded electric heater so that it can be heated to a high temperature. The heating temperature of the mold 1 is set according to the type of binder of the binder coated sand 2 and is usually about 200 to 350 ° C.

  On the other hand, the binder coated sand 2 is also called resin coated sand (RCS), and is formed by coating the surface of the refractory aggregate with the binder by mixing the refractory aggregate with the binder. Is. In the present invention, the refractory aggregate is not particularly limited, but examples include dredged sand, mountain sand, alumina sand, olivine sand, chromite sand, zircon sand, mullite sand, reclaimed sand, and other artificial sand. In addition to using these alone, it is also possible to use a mixture of plural types.

  The binder is not particularly limited as long as it is used for a binder-coated sand (resin-coated sand) for a mold, but a thermosetting resin is generally used. .

  Examples of thermosetting resins include phenolic resins such as resol type, novolak type, and benzylic ether type, epoxy resins, furan resins, isocyanate compounds, amine polyol resins, polyether polyol resins, and the like. It can be used by adding an isocyanate compound, an organic ester, hexamethylenetetramine, etc. as a curing agent and a tertiary amine, a pyridine derivative, an organic sulfonic acid, etc. as a curing catalyst, and making it thermosetting. . These may be used alone or in combination of two or more.

  When a phenol resin is used as the binder, the phenol resin can be prepared by reacting phenols and formaldehyde in the presence of a reaction catalyst.

  Here, the phenols mean phenol and phenol derivatives. For example, in addition to phenol, trifunctional compounds such as m-cresol, resorcinol, 3,5-xylenol, bisphenol A, dihydroxydiphenylmethane, etc. Tetrafunctional, bifunctional such as o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4 or 2,6-xylenol An o- or p-substituted phenol can be mentioned, and a halogenated phenol substituted with chlorine or bromine can also be used. Of course, one type can be selected and used, or a plurality of types can be mixed and used.

  As formaldehydes, formalin, which is in the form of an aqueous solution, is optimal, but forms such as paraformaldehyde, acetaldehyde, benzaldehyde, trioxane, and tetraoxane can also be used. It can also be used by replacing with furyl alcohol.

  The blending ratio of the above phenols and formaldehyde is preferably set so that the molar ratio of phenols to formaldehyde is in the range of 1: 0.6 to 1: 3.5.

  When preparing a novolak-type phenolic resin, the reaction catalyst is an inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid, or an organic acid such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid or xylenesulfonic acid, and zinc acetate. Etc. can be used. Moreover, when preparing a resol type phenol resin, an alkaline earth metal oxide or hydroxide can be used, and aliphatic dimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, diethylenetriamine, dicyandiamide and the like can be used. Primary amine, secondary amine, tertiary amine, aliphatic amines having aromatic rings such as N, N-dimethylbenzylamine, aromatic amines such as aniline and 1,5-naphthalenediamine, ammonia, hexamethylenetetramine, etc. In addition, other divalent metal naphthenic acids, divalent metal hydroxides, and the like can also be used.

  Moreover, when using a phenol resin as mentioned above as a binder, in order to accelerate hardening rate, it is made to contain 1-60 mass% of polyhydric phenol chosen from a dihydric phenol and a trihydric phenol in a phenol resin. Also good.

  Here, the dihydric phenol is not particularly limited, but catechol (melting point 105 ° C.), alkyl catechol, hydroquinone (melting point 170.3 ° C.), resorcin (melting point 110 ° C.), alkyl resorcin, 4-hexyl resorcin. (Chemical formula (1)). The trihydric phenol is not particularly limited, and examples thereof include pyrogallol (melting point 133 ° C.), phloroglucin (melting point 219 ° C .: chemical formula (2)) and the like. These divalent or trivalent polyhydric phenols can be used alone or in combination of two or more.

  The phenol resin binder may be in a state in which a polyhydric phenol selected from dihydric phenol and trihydric phenol reacts and binds in the phenol resin, and the phenolic resin contains dihydric phenol and trihydric phenol. The polyhydric phenol selected from may be mixed in a state where it does not react. In addition, some of the polyhydric phenols selected from dihydric phenols and trihydric phenols are reacted and bound in the phenolic resin, and other polyhydric phenols selected from dihydric phenols and trihydric phenols It may be mixed without reacting with the phenol resin.

  In preparing a phenol resin binder by reacting and binding a polyhydric phenol selected from dihydric phenol and trihydric phenol into a phenol resin, monohydric phenols and aldehydes are added as described above. When synthesizing a phenol resin by reacting in the presence of a catalyst, it can be carried out by adding and reacting a polyhydric phenol selected from dihydric phenol and trihydric phenol.

  At this time, by adding polyhydric phenol from the initial stage of the reaction in which monohydric phenols and aldehydes are reacted, monohydric phenols and polyhydric phenols are reacted with aldehydes, respectively. A phenol resin binder composition in which a monovalent phenol is bound and taken in can be prepared.

  Alternatively, by adding a polyhydric phenol in the course of synthesizing a phenol resin by reacting a monohydric phenol with an aldehyde, a part of the polyhydric phenol is reacted with the aldehyde, A phenol resin binder can be prepared in a state in which a part of the polyhydric phenol is bound and incorporated, and another part of the polyhydric phenol is mixed without reacting with the phenol resin.

  Furthermore, after completing the synthesis of the phenol resin by reacting monohydric phenols and aldehydes, add the polyphenol before taking out the phenol resin from the reaction system, and melt-mix the phenol resin and polyhydric phenol. Thus, a phenol resin binder in a state in which polyphenol is mixed with the phenol resin can be obtained.

  In this phenol resin binder in which a polyphenol is contained in a phenol resin, the content of the polyphenol in the phenol resin is set in a range of 1 to 60% by mass. The content of the polyhydric phenol is more preferably in the range of 3 to 60% by mass, particularly preferably 5 to 30% by mass. The effect of shortening the curing time of the phenol resin binder by reducing the gelation time due to the high reactivity of the polyhydric phenol by containing the polyhydric phenol in the phenol resin when the polyphenol content is low Can't get enough. Conversely, if the content of polyhydric phenol is too large, it becomes difficult to control the gelation reaction, and the curing time becomes too fast, which may cause a problem in workability.

  The gel time of this phenol resin binder containing divalent or trivalent phenol in the phenol resin is preferably 100 seconds or less at a measurement temperature of 130 ° C., more preferably 80 seconds or less. preferable. If the gelation time is longer than this, the effect of shortening the curing time of the phenol resin binder cannot be sufficiently obtained. The lower limit of the gelation time is not particularly set, but from the viewpoint of workability, the gelation time is preferably 10 seconds or more. This gelation time is a numerical value measured according to JACT test method RS-5. Here, in JACT test method RS-5, the measurement temperature is set to 150 ° C., but the phenol resin binder used in the present invention has a short gel time, and when measured at a temperature of 150 ° C., the gel time is short. Therefore, measurement is difficult, the measurement results are likely to vary, and it is difficult to confirm the difference in gelation time. Therefore, the measurement temperature is set to a low temperature of 130 ° C.

  Then, by adding a binder to the particles of the refractory aggregate and mixing them, the surface of the refractory aggregate can be coated with the binder to obtain the binder coated sand 2 used in the present invention. It is.

  The amount of the binder to be coated on the refractory aggregate differs depending on the components and applications, and cannot be specified unconditionally. The range is generally preferred, and the lubricant is generally preferably set to a range of 0.02 to 0.15 parts by mass in terms of solid content. Examples of a method for coating the surface of the refractory aggregate with a binder include a hot coat method, a cold coat method, a semi-hot coat method, and a powder solvent method.

  In the hot coating method, a solid binder is added to and mixed with a refractory aggregate heated to 110 to 180 ° C., and the solid binder is melted by heating with the refractory aggregate. In this method, the surface of the refractory aggregate is wetted and coated, and then cooled with the mixture kept, thereby obtaining a granular free-flowing binder coated sand. Alternatively, a fire-resistant aggregate heated to 110 to 180 ° C. is coated with a binder that is dissolved or dispersed in a solvent such as water, and the solvent is evaporated to obtain a binder-coated sand. is there.

  In the cold coating method, the binder is dispersed or dissolved in a solvent such as water or methanol to form a liquid, which is added to and mixed with the refractory aggregate particles, and the solvent is volatilized to coat the binder. This is how to get sand.

  In the semi-hot coating method, a binder dispersed or dissolved in the above-mentioned solvent is added to and mixed with refractory aggregate particles heated to 50 to 90 ° C., and the solvent is volatilized. How to get.

  In the powder solvent method, a solid binder is pulverized, this pulverized binder is added to the refractory aggregate particles, and a solvent such as water or methanol is added and mixed to volatilize the solvent. To obtain a binder coated sand.

  In any of the above methods, the surface of the refractory aggregate can be coated with a solid coating layer at room temperature (30 ° C.) to obtain a granular free-flowing binder coated sand. In this case, the hot coating method is preferable. In addition, when mixing the binder with the refractory aggregate as described above, various coupling agents such as a curing agent and a silane coupling agent for making the refractory aggregate and the binder compatible with each other, Moreover, carbonaceous materials, such as graphite, can also be mix | blended.

  When the binder coated sand 2 prepared as described above is injected into the mold 1, the binder coated sand 2 is supplied to the sand supply head 9. Then, the nozzle 10 of the sand supply head 9 is connected to the inlet 3 of the mold 1 as shown in FIG. 1B, and high-pressure air is supplied to the sand supply head 9 from the air pipe 11 connected to the sand supply head 9. Thus, the binder coated sand 2 can be injected into the cavity 2 of the mold 1 from the nozzle 10 through the injection port 3 with this air pressure. The air blown into the cavity 6 together with the binder coated sand 2 is discharged from the air vent 7, and the cavity 6 can be filled with the binder coated sand 2.

  In this way, when the cavity 6 of the mold 1 is filled with the binder coated sand 2 and a predetermined time elapses, the high temperature of the mold 1 is transferred to the binder coated sand 2, and the caking in the mold 1 is performed. The agent coated sand 2 is heated, and the binder of the binder coated sand 2 is cured. The binder coated sand 2 filled in the mold 1 is first heated by being transferred to the portion in contact with the inner surface of the cavity 6, so that the binder of the binder coated sand 2 is cured. The progress starts at the portion in contact with the inner surface of the cavity 6, and the curing of the binder in the central binder coated sand 2 away from the inner surface of the cavity 6 starts slowly.

  Accordingly, among the binder coated sand 2 in the cavity 6, the curing of the binder coated sand 2 in contact with the inner surface of the cavity 6 is proceeding, but the binder coated sand in the center portion. The binder of No. 2 is rotated 180 ° by rotating the mold 1 up and down as shown in FIG. Thus, when the mold 1 is turned upside down so that the injection port 3 faces downward, the binder coated sand 2 in which the binder is uncured out of the binder coated sand 2 in the cavity 6 is scattered particles. As there is, it is discharged from the inlet 3. On the other hand, since the curing of the binder coated sand 2 in contact with the inner surface of the cavity 6 is proceeding, the particles are bonded by the melting and curing of the binder, and the layer of the binder coated sand 2 is formed. Are integrated as one. Accordingly, the binder coated sand 2 layer in contact with the inner surface of the cavity 6 remains in the mold 1 in a hollow shape.

  Here, the time until the mold 1 is turned upside down in order to discharge the uncured binder coated sand 2 after filling the binder 1 with the binder coated sand 2 is the binder. Although it is adjusted according to the kind of binder of the coated sand 2, the temperature of the mold 1, the thickness of the layer of the binder coated sand 2 left in the mold 1, etc., About 60 seconds is preferable. If the time until the mold 1 is reversed is short, the thickness of the binder-coated sand 2 remaining in the mold 1 becomes thin, and the thickness of the mold to be molded becomes thin, causing a problem in strength. . On the contrary, if the time until the mold 1 is inverted is long, the amount of the uncured binder coated sand 2 discharged becomes small, and the effect obtained by forming the mold in a hollow state becomes insufficient.

  In addition, since the heat | fever of the shaping | molding die 1 does not act easily on the part facing the injection inlet 3 among the binder coated sand 2 which contact | connects the cavity 6, hardening of the binder coated sand 2 of this part does not advance easily. . For this reason, the injection port 3 is not blocked by the binder coated sand 2 which has been cured, and the uncured binder coated sand 2 can be discharged from the injection port 3 without any trouble as described above. Is.

  However, the binder coated sand 2 in the vicinity of the injection port 3 is also cured, for example, when the time from filling the binder coated sand 2 into the mold 1 to extending the mold 1 upside down is increased. Then, the injection port 3 may be blocked by the binder coated sand 2 that has been cured. At this time, even if the mold 1 is turned upside down, the uncured binder coated sand 2 cannot be discharged. Therefore, at this time, after filling the molding die 1 with the binder coated sand 2, as shown in FIG. 4 (a), a plug 15 having a length deeper than the inlet 3 is inserted into the inlet 3, What is necessary is just to insert the front-end | tip part of the stopper 15 in the binder coating sand 2. FIG. The plug 15 is preferably formed of a heat-resistant material that can withstand the temperature of the mold 1 and has a heat insulation property lower than that of the mold 1. For example, the plug 15 is formed of heat-resistant rubber or the like. can do. By inserting the plug 15 having a high heat insulating property in this way, it is possible to prevent the heat of the mold 1 from being transferred to the binder coated sand 2 in the portion facing the injection port 3. It is possible to prevent the injection port 3 from being blocked by the hardening of the binder coated sand 2 in the facing portion. Therefore, the uncured binder coated sand 2 can be discharged from the injection port 3 without hindrance by removing the plug 15 from the injection port 3 immediately before reversing the molding die 1 and inverting the molding die 1. Is.

  After discharging the uncured binder coated sand 2 as described above, in the layer of the binder coated sand 2 left in contact with the inner surface of the cavity 6, the binder has not sufficiently cured. Since the semi-curing or gelation stage or the binder is in the state of being melted by heat, the binder-coated sand 2 layer in the mold 1 is heated to further promote the curing of the binder. Need to be completely cured. In the present invention, the heating for further hardening of the binder coated sand 2 is performed by steam.

  That is, the uncured binder-coated sand 2 is discharged as described above, and the layer of the binder-coated sand 2 that is in contact with the inner surface of the cavity 6 is left in the mold 1 in a hollow shape. The mold 1 is turned upside down again so that the injection port 3 faces upward, and the nozzle 18 of the water vapor supply head 17 is connected to the injection port 3 as shown in FIG. A steam hose 19 is connected to the steam supply head 17, and steam is supplied from the steam hose 19 to the steam supply head 17, and steam is blown into the cavity 6 of the mold 1 from the nozzle 18 through the inlet 3. It is something that can be done. The water vapor blown into the mold 1 is exhausted from the air vent 7 after passing through the layer of the binder-coated sand 2 on the inner periphery of the cavity 6. The layer of the binder coated sand 2 is bonded and hardened by the binder, but the binder is not completely cured, and many gaps are formed between the particles of the refractory aggregate. Is easily exhausted from the air vent 7 through the gaps between the aggregate particles.

  Then, when steam is blown into the mold 1 as described above, the steam contacts the surface of the binder-coated sand 2, so that the steam condenses latent heat and sensible heat to the binder-coated sand 2. However, since water vapor has high latent heat and sensible heat, the temperature of the binder coated sand 2 can be rapidly increased by the latent heat transferred when the water vapor condenses. Further, since the condensed water generated in the mold 1 by the condensation of water vapor is evaporated by heating with the water vapor blown into the mold 1 after that, the temperature in the mold 1 is rapidly increased to near the temperature of the water vapor. The binder coated sand 2 can be rapidly heated at this temperature. In particular, since water vapor is heated by directly contacting each particle of the binder-coated sand 2, the binder-coated sand 2 can be heated to a high temperature almost instantaneously.

  In this way, the mold A is molded by blowing steam into the mold 1 and heating the layer of the binder-coated sand 2 on the inner periphery of the cavity 6 to advance the curing of the binder and completely cure it. A hollow mold A as shown in FIG. 1 (e) can be obtained by opening the mold 1 and separating the molds 1a and 1b.

  Here, by rapidly heating the layer of the binder coated sand 2 in the mold 1 with water vapor, the binder of the binder coated sand 2 can be cured in a short time, The time required to completely cure the layer of the binder-coated sand 2 varies depending on the temperature of the water vapor, the flow rate of blowing into the mold 1, the thickness of the layer of the binder-coated sand 2 in the mold 1, and the like. However, it is usually a short time of about 3 to 40 seconds. The binder-coated sand 2 layer in the mold 1 has a low bonding strength and low strength due to insufficient curing of the binder. Before the delamination due to its own weight, as shown in FIG. 5 (d), the binder can be sufficiently cured in a short time without causing a peel-back failure. A hollow mold A can be formed.

  In the present invention, saturated steam can be used as it is, but it is preferable to use superheated steam. Superheated steam is water vapor in a complete gas state that is further heated to saturated boiling water to a temperature equal to or higher than the boiling point, and is dry steam at 100 ° C. or higher. The superheated steam obtained by heating the saturated steam may be one that is expanded at a constant pressure without increasing the pressure, or may be pressurized steam that is increased without increasing the pressure. The temperature of the superheated steam blown into the mold 1 is not particularly limited, and the temperature of the superheated steam can be increased to about 900 ° C., so that the temperature is set between 100 and 900 ° C. as necessary. That's fine.

  When the hollow mold A is formed as described above, an opening a as shown in FIG. 1 (e) is formed in the mold A as a hole after the uncured binder coated sand 2 is discharged. The mold A is mainly used as a core or the like at the time of casting. If the opening a does not hinder the casting operation, the mold A having the opening a can be used as it is. On the other hand, when the opening a becomes an obstacle to the casting operation, a lid formed separately using the binder coated sand 2 is used, and the lid is inserted into the opening a to be bonded, or a refractory aggregate is used. The opening a may be blocked by filling the opening a with a molding material kneaded with a liquid binder and heat-curing it.

  FIG. 2 shows another embodiment. In the embodiment of FIG. 1, the injection port 3 is formed as a small port in the mold 1, but in FIG. 2, the injection port 3 is formed with a large opening. It is. That is, as shown in FIG. 2A, the injection port 3 is provided with a large opening on the lower surface of the mold 1, and the cavity 6 in the mold 1 is entirely opened by the injection port 3. An air vent 7 is formed between the molds 1a and 1b.

  Then, the mold 1 is turned upside down so that the injection port 3 faces upward. In this state, the binder coated sand 2 is filled into the cavity 6 of the mold 1 as shown in FIG. Since the injection port 3 has a large opening, it is not necessary to inject the binder-coated sand 2 by air pressure using the sand supply head 9 as shown in FIG. 1B, and the binder-coated sand 2 is poured. The cavity 6 can be filled with the binder coated sand 2 by work or the like.

  In this way, the cavity 6 of the mold 1 is filled with the binder coated sand 2, and a predetermined time elapses. The high temperature of the mold 1 is transferred to the binder coated sand 2, and comes into contact with the inner surface of the cavity 6. When the portion of the binder-coated sand 2 has progressed, the mold 1 is turned upside down and the injection port 3 faces downward. When the mold 1 is turned upside down, the binder-coated sand 2 in which the binder is uncured among the binder-coated sand 2 in the cavity 6 is discrete particles. Discharged. On the other hand, since the curing of the binder coated sand 2 in contact with the inner surface of the cavity 6 is proceeding, the particles are bonded by the melting and curing of the binder, and the layer of the binder coated sand 2 is formed. Are integrated as one. Accordingly, as shown in FIG. 2C, the binder-coated sand 2 layer in contact with the inner surface of the cavity 6 remains in the mold 1 in a hollow shape. The time from when the binder coated sand 2 is filled in the mold 1 to when the mold 1 is turned upside down is preferably about 5 to 60 seconds as in the embodiment of FIG.

  Next, after discharging the uncured binder coated sand 2 as described above and leaving the layer of the binder coated sand 2 in contact with the inner surface of the cavity 6 in the hollow mold 1, The mold 1 is turned upside down again, the injection port 3 is directed upward, and water vapor is blown into the mold 1. The steam can be blown using the steam supply head 17 in the same manner as in FIG. 1 (d). However, since the injection port 3 is wide open, as shown in FIG. It is desirable to use the one provided with the cover piece 24 extending greatly, and the nozzle 18 is connected to the injection port 3 in a state where the injection port 3 is covered with the cover piece 24 and the injection port 3 is sealed. Then, water vapor is blown into the cavity 6 of the mold 1 from the nozzle 18 through the inlet 3. The water vapor blown into the mold 1 is exhausted from the air vent 7 after passing through the layer of the binder-coated sand 2 on the inner periphery of the cavity 6.

  In this way, the mold A is molded by blowing steam into the mold 1 and heating the layer of the binder-coated sand 2 on the inner periphery of the cavity 6 to advance the curing of the binder and completely cure it. A hollow mold A as shown in FIG. 2 (e) can be obtained by opening the mold 1 and separating the molds 1a and 1b.

  Here, by rapidly heating the layer of the binder coated sand 2 in the mold 1 with water vapor, the binder of the binder coated sand 2 can be cured in a short time, The time required to completely cure the binder coated sand 2 layer is usually a short time of about 3 to 40 seconds, as in the case of FIG. When the mold is molded with the mold 1 having the cavity 6 as shown in FIG. 2, the vertical direction of the cavity 6 in the layer of the binder coated sand 2 remaining in the mold 1 as shown in FIG. Peeling is likely to occur at locations that are attached to a flat surface, but before such delamination occurs, the binder can be completely cured in a short time by steam heating, and peel back The hollow mold A can be formed without causing defects.

  Next, the embodiment of FIG. 3 will be described. In this embodiment, an injection port 3 provided at the upper part and a discharge port 4 provided at the lower part are used as the molding die 1, and the injection port 3 is formed on the upper surface of the molding die 1 as shown in FIG. And a discharge port 4 on the lower surface. An air vent 7 is formed between the molds 1a and 1b.

  Before the binder-coated sand 2 is injected into the mold 1, the outlet 21 is plugged and the outlet 4 is closed with the stopper 21. The plug 21 is preferably formed of a heat-resistant material that can withstand the temperature of the mold 1 and has a heat insulation property lower than that of the mold 1. For example, the plug 21 is formed of heat-resistant rubber or the like. can do.

  Then, the nozzle 10 of the sand supply head 9 is connected to the injection port 3 of the mold 1 as shown in FIG. 3B, and high-pressure air is supplied to the sand supply head 9 from the air pipe 11 connected to the sand supply head 9. Thus, the binder coated sand 2 can be injected into the cavity 2 of the mold 1 from the nozzle 10 through the injection port 3 with this air pressure. The air blown into the cavity 6 together with the binder coated sand 2 is discharged from the air vent 7, and the cavity 6 can be filled with the binder coated sand 2. Since the discharge port 4 at the lower end of the mold 1 is closed by the plug 21, the binder coated sand 2 does not leak from the discharge port 4.

  In this way, the cavity 6 of the mold 1 is filled with the binder coated sand 2, and a predetermined time elapses. The high temperature of the mold 1 is transferred to the binder coated sand 2, and comes into contact with the inner surface of the cavity 6. When the portion of the binder-coated sand 2 has progressed, the stopper 21 is removed from the outlet 4 on the lower surface of the mold 1 to open the outlet 4. The time from filling the binder coated sand 2 into the mold 1 until the plug 21 is removed and the outlet 4 is opened is the time until the mold 1 in the embodiment of FIG. 1 is turned upside down. Similarly, about 10 to 60 seconds are preferable.

  When the plug 21 is thus pulled out and the discharge port 4 is opened, the binder coated sand 2 in which the binder is uncured out of the binder coated sand 2 in the cavity 6 is discharged from the discharge port 4. . On the other hand, since the binder of the binder coated sand 2 in contact with the inner surface of the cavity 6 is cured, the particles are bound by the binder and are solidified as a layer of the binder coated sand 2. . Therefore, as shown in FIG. 3C, the binder-coated sand 2 layer in contact with the inner surface of the cavity 6 remains in the mold 1 in a hollow shape.

  Here, since a plug 21 having a heat insulating property lower in thermal conductivity than the mold 1 is inserted into the discharge port 4, a portion of the binder coated sand 2 in contact with the cavity 6 that faces the discharge port 4. In this case, the heat of the mold 1 is difficult to act, and the curing of the binder coated sand 2 in the portion facing the discharge port 4 is difficult to proceed. Therefore, the discharge port 4 is not blocked by the binder-coated sand 2 that has been hardened, and the uncured binder-coated sand 2 is discharged without any trouble by opening the discharge port 4 by removing the plug 21. Is something that can be done.

  However, the binder coated sand 2 in the vicinity of the discharge port 4 is also cured, for example, when the time from filling the binder coated sand 2 into the mold 1 to removing the plug 21 and discharging is increased. In some cases, the discharge port 4 may be blocked by the binder coated sand 2 which has proceeded with the curing. Therefore, at this time, as shown in FIG. 4 (b), when the plug 21 is formed with a length deeper than the discharge port 4 and the plug 21 is inserted into the discharge port 4, the tip of the plug 21 comes from the inner surface of the cavity 6. It is better to protrude inward. If it does in this way, it can suppress that the heat | fever of the shaping | molding die 1 is heat-transferred to the binder coated sand 2 of the part which opposes the discharge port 4, and the binder coated sand of the part which opposes the discharge port 4 It is possible to prevent the curing of No. 2 from proceeding and closing the outlet 4. Therefore, the uncured binder coated sand 2 can be discharged from the discharge port 4 without any trouble by removing the plug 21 from the discharge port 4 and opening it.

  As described above, the uncured binder-coated sand 2 is discharged from the cavity 6 of the mold 1 so that the layer of the binder-coated sand 2 that is in contact with the inner surface of the cavity 6 has a hollow shape. 3D, the nozzle 18 of the water vapor supply head 17 is connected to the inlet 3 on the upper surface of the mold 1 as shown in FIG. 3D, and water vapor is supplied from the nozzle 18 through the inlet 3 to the cavity 6 of the mold 1. Blow in. At this time, a plug 22 may be inserted into the outlet 4 so as to prevent the water vapor from coming out of the outlet 4 in a short circuit. The water vapor thus blown into the mold 1 passes through the layer of the binder-coated sand 2 on the inner periphery of the cavity 6 and is then exhausted from the air vent 7.

  In this way, the mold A is molded by blowing steam into the mold 1 and heating the layer of the binder-coated sand 2 on the inner periphery of the cavity 6 to advance the curing of the binder and completely cure it. A hollow mold A as shown in FIG. 3E can be obtained by opening the mold 1 and separating the molds 1a and 1b.

  Here, by rapidly heating the layer of the binder coated sand 2 in the mold 1 with water vapor, the binder of the binder coated sand 2 can be cured in a short time, The time required to completely cure the binder coated sand 2 layer is usually a short time of about 3 to 40 seconds, as in the case of FIG. Then, the binder is completely cured in a short time before delamination occurs due to its own weight as shown in FIG. 5 (d) in the vertical or downward portion of the binder coated sand 2 layer. Therefore, the hollow mold A can be formed without causing a peel-back failure.

  In the embodiment of FIG. 3, the uncured binder coated sand 2 can be discharged from the discharge port 4 provided on the lower surface of the mold 1. Therefore, when discharging the uncured binder coated sand 2 from the mold 1, it is not necessary to turn the mold 1 upside down, and it is not necessary to provide a mechanism for turning the mold 1 upside down. Is.

  In this embodiment, the hollow mold A is provided with openings a and b at the inlet 3 and the outlet 4. The mold A is mainly used as a core or the like during casting. However, if the openings a and b do not hinder the casting operation, the mold A having the openings a and b can be used as it is. . On the other hand, when the openings a and b are obstructed in the casting operation, a lid material separately formed using the binder coated sand 2 is used, and the lid material is inserted into the openings a and b and bonded. Alternatively, the openings a and b may be closed by filling the openings a and b with a molding material obtained by kneading the refractory aggregate with a liquid binder and heating and curing them.

  Next, the present invention will be specifically described with reference to examples.

Example 1
As the mold 1, a mold having a spherical cavity 6 having an inner diameter of 100 mm and an injection port 3 having a diameter of 10 mm provided on the upper surface was used (see FIG. 1A). The mold 1 was used after being heated to 250 ° C. with a built-in electric heater.

  On the other hand, 30 kg of flattery sand heated to 145 ° C. is placed in a whirl mixer, 540 g of resol type phenolic resin (“LT-15” manufactured by Lignite Co., Ltd.) is added thereto, kneaded for 30 seconds, and then 450 g of water is added. Added and kneaded thoroughly. Subsequently, 30 g of calcium stearate was further added and kneaded for 30 seconds, followed by aeration to obtain a binder-coated sand 2 having 1.8% by mass of a phenol resin having a fusion point of 108 ° C. as a binder. It was.

  First, a sand supply head 9 is connected to the injection port 3 of the mold 1 and the binder-coated sand 2 is blown from the injection port 3 into the mold 1 with an air pressure of a gauge pressure of 0.1 MPa (see FIG. 1 (b)).

  Next, after 15 seconds had elapsed from the completion of filling the binder coated sand 2 into the mold 1, the mold 1 was turned upside down, and the uncured binder coated sand 2 was discharged from the inlet 3 ( (Refer FIG.1 (c)).

  Thereafter, the mold 1 is immediately turned upside down to return to its original state, the steam supply head 17 is connected to the inlet 3 of the mold 1, and the gauge pressure generated by the boiler is 0.4 MPa, and the temperature is saturated at 143 ° C. Supplying superheated steam at 350 ° C. and a gauge pressure of 0.45 MPa at a flow rate of 60 kg / h, prepared by heating the steam with a superheated steam generator (“GE-100” manufactured by Nomura Engineering Co., Ltd.) This superheated steam was blown into the mold 1 (see FIG. 1 (d)).

  After blowing the superheated steam for 15 seconds, the mold 1 was immediately opened, and the molded mold A was taken out (see FIG. 1 (e)). This mold A was formed into a hollow sphere having a thickness of about 10 mm. The mold A was a perfect sphere with a diameter of 100 mm, which was the same as the shape of the cavity 6, and no deformation such as delamination was observed inside.

(Comparative Example 1)
In the same manner as in Example 1 above, the binder-coated sand 2 was injected into the mold 1 (see FIG. 1B), and the mold 1 was turned upside down to transfer the binder-coated sand 2 from the mold 1 to the mold 1. Was discharged (see FIG. 1 (c)). Thereafter, the mold 1 was again inverted so that the injection port 3 faced upward and left in this state for 40 seconds.

  Next, the mold 1 was opened, and the molded mold A was taken out. This mold A was formed into a hollow sphere. The mold A had a diameter of 100 mm, which was the same as the shape of the cavity 6. However, the mold A had a double layer deformation due to delamination in the upper part, and had a peel back defect as shown in FIG. 5 (f). Met.

(Example 2)
As the mold 1, a mold having a spherical cavity 6 with an inner diameter of 100 mm, an inlet 3 having a diameter of 10 mm on the upper surface, and an outlet 4 having a diameter of 10 mm on the lower surface was used (FIG. 3A). reference). The mold 1 was used after being heated to 250 ° C. with a built-in electric heater.

  First, a heat-resistant rubber plug 21 is inserted into the discharge port 4 and closed, and a sand supply head 9 is connected to the injection port 3 of the mold 1, and the binder coated sand 2 is fed from the injection port 3 to a gauge pressure of 0. The mold 1 was blown and filled with an air pressure of 1 MPa (see FIG. 3B).

  Next, after 10 seconds have passed since the filling of the binder coated sand 2 into the mold 1 is completed, the plug 21 of the discharge port 4 is removed, and the uncured binder coated sand 2 is discharged from the discharge port 4. (See FIG. 3C).

  Immediately after the discharge of the uncured binder coated sand 2 is completed, a heat-resistant rubber plug 22 is immediately inserted into the discharge port 4, and the water vapor supply head 17 is connected to the injection port 3 of the mold 1 and is generated by a boiler. Prepared by heating saturated steam at a gauge pressure of 0.4 MPa and a temperature of 143 ° C. with a superheated steam generator (“GE-100” manufactured by Nomura Engineering Co., Ltd.), at 350 ° C. and a gauge pressure of 0.45 MPa. Was supplied at a flow rate of 60 kg / h, and this superheated steam was blown into the mold 1 (see FIG. 3D).

  After blowing the superheated steam for 15 seconds, the mold 1 was immediately opened, and the molded mold A was taken out (see FIG. 3 (e)). This mold A was formed into a hollow sphere having a thickness of about 10 mm. The mold A was a perfect sphere with a diameter of 100 mm, which was the same as the shape of the cavity 6, and no deformation such as delamination was observed inside.

(Comparative Example 2)
In the same manner as in Example 2 above, the binder-coated sand 2 was injected into the mold 1 from the inlet 3 (see FIG. 3B), the plug 21 was pulled out, and the binder-coated sand from the outlet 4 was discharged. 2 was discharged (see FIG. 3C). And it was left for 40 seconds in this state.

  Next, the mold 1 was opened, and the molded mold A was taken out. This mold A was formed into a hollow sphere. The mold A had a diameter of 100 mm, which was the same as the shape of the cavity 6. However, the mold A had a double layer deformation due to delamination in the upper part, and had a peel back defect as shown in FIG. 5 (f). Met.

DESCRIPTION OF SYMBOLS 1 Mold 2 Binder coated sand 3 Inlet 4 Outlet 6 Cavity 7 Air vent 9 Sand supply head 17 Water vapor supply head 21 Plug A Mold

Claims (6)

  After filling the mold with the binder coated sand and curing the binder coated sand in the part contacting the mold with the heat of the mold, the uncured binder coated sand is removed from the mold. A mold manufacturing method characterized in that the curing of the binder-coated sand is further progressed by discharging the steam into the mold and then heating the binder-coated sand in the mold with the steam. .   After forming the injection port on the upper part of the mold, filling the binder coated sand into the mold from the injection port, and proceeding with the curing of the binder coated sand in the part contacting the mold with the heat of the mold 2. The method for producing a mold according to claim 1, wherein the mold is turned upside down to discharge the uncured binder coated sand from the inlet.   3. The method for producing a mold according to claim 2, wherein after the mold is turned upside down and the binder coated sand is discharged, the mold is further turned upside down and water vapor is blown into the mold from the inlet. .   A discharge port is formed in the lower part of the mold provided with the inlet, and the binder-coated sand is filled into the mold from the injection port, and the binder-coated sand is cured at the part contacting the mold with the heat of the mold. 2. The method for producing a mold according to claim 1, wherein after proceeding, the discharge port is opened to discharge the uncured binder coated sand.   Uncapped binder coated sand by filling the mold with binder coated sand with the plug having a lower thermal conductivity than the mold, filling the mold with the binder coated sand, and opening the outlet by removing the stopper. The method for producing a mold according to claim 4, wherein the mold is discharged.   The method for producing a mold according to any one of claims 1 to 5, wherein superheated steam is used as the steam.

Images