JP2017127883A - Mold and method of manufacturing mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold that is formed by binder jetting and applicable to a large casting and allows precision casting, and a method of manufacturing the mold.SOLUTION: An additive manufacturing mold 1 as an example of a mold of the present invention comprises a main mold 2 and a core 3. The main mold 2 has therein a space with the same shape as the outer shape of a valve box 4 for a globe valve, and is formed by combining a plurality of partial main molds 5. The main mold 2 has a structure divided in the height direction into a sprue runner side region part 6 formed with sprues and sprue runners, a product side upper region part 7, and a product side lower region part 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mold and a method for producing the mold. More specifically, the present invention relates to a mold that can be formed by a powder fixed lamination method, can be applied to a large casting, and can cast a high-precision casting, and a mold manufacturing method.

  For a long time, mass production using a metal material has been performed by casting using a mold. There are several methods for casting depending on the usage of the mold, the type of mold, the method of fixing the aggregate, and the like.

  In recent years, with the widespread use of 3D modeling machines, mold manufacturing methods using this equipment have attracted attention. In this method, a mold material mixed with a binder for binding mold sand and mold sand is laminated and cured one layer at a time by applying a binder solution with an inkjet head. Yes.

  In the powder fixing lamination method, a casting mold can be directly manufactured without manufacturing a wooden mold or a mold as a casting mold, so that it is possible to expect a reduction in manufacturing time and cost of the casting. It is also suitable for use in producing small quantities of various shaped castings.

  Further, in the production of a mold by the powder fixing lamination method, it is possible to form a mold with high dimensional accuracy as compared with the production of a mold using a conventional wooden pattern. Further, it is not necessary to form a draft required when taking out the wooden mold or the like from the mold, and the mold material can be reduced.

  As described above, in the powder fixing lamination method, as in the case of conventional casting, foundry sand that becomes an aggregate and a binder are used as a raw material for a mold. The binding agent binds foundry sands and has a property of being cured by moisture or heat. The foundry sand and the binder need to have heat resistance capable of stably forming the shape of the casting even when the casting material is poured.

  However, there are currently limited types of mold materials used in the powder-fixing lamination method including those on the market, and the mold material cannot cope with the melting point temperature of the metal material of the casting, resulting in defects. is there. Thus, for example, Patent Document 1 proposes a modeling material that can be poured even with a high-melting-point metal having a melting point exceeding 1,000 ° C.

  As described above, in the production of a mold by the powder fixed lamination method, attempts have been made to diversify the types of metals that can be poured and to improve the quality of castings by improving the mold material.

JP 2010-110802 A

  However, in the production of molds by the powder fixing lamination method, there is also a problem with the size of a model that can be manufactured, and the size of the mold depends on the maximum modeling size of the 3D modeling machine to be used. It has become. That is, in a highly versatile model, a modeled object having a length of about 20 cm is generally the limit of the size that can be manufactured in one layered modeling.

  Therefore, a large mold having a length of more than 1 m could not be manufactured by one layered modeling. In addition, a model that can manufacture a 1 m square shaped object with high accuracy has a very expensive apparatus, and is not easily introduced at a manufacturing site.

  There is also a risk that the shape stability and the strength of the mold will be insufficient when a large mold is formed. In addition, it is necessary to ensure accuracy in the quality of the casting, such as the smoothness of the casting surface of the casting manufactured with a large mold.

  The present invention has been devised in view of the above points, and provides a mold and a mold manufacturing method that can be applied to a large-sized casting that is formed by a powder fixing lamination method and that can cast a high-precision casting. For the purpose.

  In order to achieve the above object, in the mold of the present invention, a first partial mold that can be fitted to an adjacent member and members adjacent to a region that does not contact the molten metal are arranged with a predetermined interval. The columnar member, the crosspiece member that connects the adjacent columnar members, and the reinforcing portion that is located at the intersection of the columnar member and the crosspiece member and covers the intersection, and is fitted to the adjacent member The first partial mold and the second partial mold are made of foundry sand, and the first partial mold can be fitted with the second partial mold. It has become something.

  Here, the first partial mold that can be fitted to the adjacent member constitutes the mold including the first partial mold. Further, since the first partial mold can be fitted to the adjacent member, it can be combined with the adjacent first partial mold or the second partial mold. The first partial mold here includes a partial mold that does not have a structure such as a columnar member, a crosspiece member, and a reinforcing portion, as the second partial mold described later has.

  In addition, the second partial mold includes a columnar member in which members adjacent to a region not in contact with the molten metal are arranged with a predetermined interval, a crosspiece member that connects the adjacent columnar members, a columnar member, and a crosspiece. By having a reinforcing part located at the intersection of the members and covering the intersection, the mold material necessary for forming the second partial mold can be reduced while ensuring the stability of the shape of the second partial mold. Can do. In addition, solidification can be promoted by forcing cooling from the side of the region not in contact with the molten metal to promote solidification, and solidification defects can be reduced. In addition, the second partial mold is, for example, in a portion of the entire mold that needs to be degassed on the back surface of the cavity portion into which the molten metal flows, or a portion that needs cooling by convection or radiation of the gas on the back surface of the cavity portion. It is possible to use it. Such a part needs to be efficiently vented and cooled, and is a part that is desired to be formed as thin as possible in the mold, and is a place where the strength to maintain the shape of the mold is likely to be insufficient by making the part thin.

  In addition, the second partial mold that can be fitted to the adjacent member constitutes the mold including the second partial mold. Further, since the second partial mold can be fitted to the adjacent member, it can be combined with the adjacent first partial mold or second partial mold.

  In addition, since the first partial mold can be fitted to the second partial mold, a mold can be formed by combining the first partial mold and the second partial mold. Here, the mold of the present invention includes not only the first partial mold and the second partial mold, but also the first partial mold and the second partial mold. The mold may be formed by combining three or more partial molds.

  Further, when the foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold are different in type of foundry sand, the type of foundry sand is made different for each partial mold constituting the mold. It becomes possible. That is, for example, each partial mold can be formed mainly with natural foundry sand in one partial mold and mainly with artificial foundry sand in another partial mold. Moreover, it is possible to use foundry sand having excellent thermal conductivity or foundry sand having different bending strength depending on the part of the shape of the mold. In addition, the kind of foundry sand can also be varied between the first partial molds or between the second partial molds.

  In addition, when the foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold have different particle sizes of the foundry sand, the particle size of the foundry sand is determined for each partial mold constituting the mold. Can be changed. That is, for example, the first partial mold and the second partial mold have the same type of foundry sand as the main component, but the particle size of the foundry sand constituting the first partial mold is large, and the second part The particle size of the foundry sand constituting the mold can be made smaller. Further, the particle size of the foundry sand can be changed to make the particle size different. In addition, the particle size of foundry sand can also be varied between the first partial molds or between the second partial molds.

  Further, the foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold constitute a mold when the contents of the binder or additive contained in the foundry sand are different. The content of the binder or additive contained in the foundry sand can be changed for each partial mold. That is, for example, the first partial mold and the second partial mold are mainly composed of the same type of foundry sand, but the content of additives in the foundry sand constituting the first partial mold, and the second The additive content of the foundry sand constituting the partial mold can be changed and employed. In addition, content of the binder or additive contained in foundry sand can also differ between 1st partial mold | types or 2nd partial mold | types.

  Further, at least part of the cavity portion into which the molten metal of the second partial mold flows is formed so as to penetrate the second partial mold, and unbound foundry sand forming the second partial mold is accommodated therein. In the case where the vent portion is provided, the gas generated from the mold at the time of casting can be easily vented, and the gas defect to the casting can be hardly caused. That is, it is possible to suppress the leakage of the molten metal with the foundry sand while allowing the gas to escape from the perforated region. The undecided foundry sand here refers to foundry sand that is not subjected to a binder that initiates hardening with a binder during the lamination of the powder-fixing lamination method, and is disposed in an uncured state in a penetrating area. Will be.

  The first fitting portion and the second fitting portion have a recess formed in a joining region between adjacent members, and a connecting member that fits the recess and connects the adjacent members. In such a case, it is possible to further stabilize the structure in which the partial molds are combined. For example, it is possible to provide a concave portion on the surface of adjacent partial molds to be joined, and to use a separate member fitted in the concave portion as a connecting member.

  The first partial mold or the second partial mold is a combination of a partial mold for casting including a region where a casting is formed and a partial mold for a molten metal including a region where a gate and a drain are formed. Therefore, it becomes easy to process into a shape suitable for each application. For example, if it is a partial mold for runners, parts other than the area where the molten metal flows are unnecessary, so it is easy to process into a partial mold that has been processed into the minimum required shape and reduced mold material. Become.

  Moreover, when the core connected with at least one part of the 1st partial type | mold or the 2nd partial type | mold is provided, the flash produced in a casting_mold | template can be reduced. That is, conventionally, a cast-in beam is formed between the core and the upper mold or the lower mold as the main mold, but the cast-in can be reduced because the partial mold and the core are connected.

  The first partial mold and the second partial mold are aggregates composed of first particles and second particles having a particle size 1.5 to 2 times the particle size of the first particles. Between the particles in a mixed state of the mold material when the aggregate material is formed by binding the aggregates together and the binder having a particle size smaller than the particle size of the first particles. As a result, the surface smoothness of the mold can be further improved. Moreover, the density of the mold material at the time of lamination becomes high, and the strength of the mold can be further increased. In addition, the particle diameter of a particle here means an average particle diameter, and includes the dispersion | variation at the time of particle manufacture. Moreover, strength means the bending strength measured by a bending test, and the details of the test will be described later.

  On the other hand, in the case of the second particle having a particle size of less than 1.5 times the particle size of the first particle, the second particle approaches the first particle. As a result, the density of the mixed state is lowered, and the bending strength is not sufficiently improved. In addition, since the particle size is small, the particles are easily lost during the lamination, and it is difficult to improve the smoothness of the mold surface. Further, in the case of the second particles having a particle size exceeding twice the particle size of the first particles, gaps between the particles of the second particles are likely to occur, and the density of the mixed state is lowered, and the resistance is reduced. The bending strength is not improved sufficiently. Further, surface irregularities between the second particles are likely to occur, and it becomes difficult to improve the smoothness of the mold surface.

  In addition, when the ratio of the weight ratio of the second particles based on the aggregate amount based on the weight ratio of the first particles based on the aggregate amount is within the range of 1.5 to 3.0, Furthermore, the bending strength of the mold can be improved.

  Here, when the ratio of the weight ratio based on the total amount of the second particles to the weight ratio based on the total amount of the first particles is less than 1.5, it is difficult to ensure the smoothness of the mold surface. It becomes. In addition, when the ratio of the weight ratio of the second particles based on the total amount of the first particles to the weight ratio of the second particles exceeds 3.0, the bending strength of the mold is insufficient. It becomes.

In order to achieve the above object, the mold manufacturing method according to the present invention includes a first partial mold that can be fitted to an adjacent member, and a member adjacent to a region that does not contact the molten metal having a predetermined interval. A columnar member disposed in a row, a crosspiece member that connects the adjacent columnar members, a reinforcing member that is located at the intersection of the columnar member and the crosspiece member, and covers the intersection. Forming a member to be fitted and a second partial mold that can be fitted by additive fabrication using a powder fixed lamination method;
A step of fitting adjacent members together to form a mold by combining at least the first partial mold and the second partial mold.

  Here, the first partial mold that can be fitted to the adjacent member constitutes the mold including the first partial mold. Further, since the first partial mold can be fitted to the adjacent member, it can be combined with the adjacent first partial mold or the second partial mold. The first partial mold here includes a partial mold that does not have a structure such as a columnar member, a crosspiece member, and a reinforcing portion, as the second partial mold described later has.

  In addition, the second partial mold includes a columnar member in which members adjacent to a region not in contact with the molten metal are arranged with a predetermined interval, a crosspiece member that connects the adjacent columnar members, a columnar member, and a crosspiece. By having a reinforcing part located at the intersection of the members and covering the intersection, the mold material necessary for forming the second partial mold can be reduced while ensuring the stability of the shape of the second partial mold. Can do. In addition, solidification can be promoted by forcing cooling from the side of the region not in contact with the molten metal to promote solidification, and solidification defects can be reduced. In addition, the second partial mold is, for example, in a portion of the entire mold that needs to be degassed on the back surface of the cavity portion into which the molten metal flows, or a portion that needs cooling by convection or radiation of the gas on the back surface of the cavity portion. It is possible to use it. Such a part needs to be efficiently vented and cooled, and is a part that is desired to be formed as thin as possible in the mold, and is a place where the strength to maintain the shape of the mold is likely to be insufficient by making the part thin.

  In addition, the second partial mold that can be fitted to the adjacent member constitutes the mold including the second partial mold. Further, since the second partial mold can be fitted to the adjacent member, it can be combined with the adjacent first partial mold or second partial mold.

  Further, by combining the adjacent members and forming the mold by combining at least the first partial mold and the second partial mold, the mold is formed by combining the first partial mold and the second partial mold. It can be formed. Here, in the mold manufacturing method of the present invention, not only the first partial mold and the second partial mold are combined to form one mold but also the first partial mold and the second partial mold. It may be a mold formed by combining three or more partial molds including the mold.

  As the contents of the present invention, means for solving the problems described below are also considered.

  In order to achieve the above object, the mold of the present invention has a fitting portion that can be fitted to an adjacent member, and is formed by combining partial molds formed by layered molding by a powder fixing lamination method. .

  Here, since the mold is formed by combining partial molds formed by the layered modeling by the powder fixed lamination method, a large mold can be obtained. That is, a plurality of partial molds can be used to form a single large mold. In addition, the partial mold | type here means what further divided | segmented the upper mold | type, lower mold | type, and core which are used by the conventional casting. The large mold means a mold that cannot be produced in the shape of the entire mold by one layered modeling process, although it depends on the maximum modeling size that can be manufactured by a three-dimensional molding machine.

  Moreover, the combination work of partial molds can be facilitated by a partial mold having a fitting portion that can be fitted to an adjacent member. Moreover, the structure which combined partial type | molds can be stabilized.

  In addition, when the partial mold is formed by combining a partial mold for casting including a region where a casting is formed and a partial mold for a molten metal including a region where a gate and a runner are formed, each use It will be easy to process into a shape that matches. For example, if it is a partial mold for runners, parts other than the area where the molten metal flows are unnecessary, so it is easy to process into a partial mold that has been processed into the minimum required shape and reduced mold material. Become.

  In addition, in the case where the fitting portion is a concavo-convex portion that can be fitted to each other and is formed in a joining region between adjacent partial molds, a structure in which the partial molds are combined can be further stabilized. . For example, it can be fitted in a shape such as a joint that combines the concavities and convexities of the surfaces to be joined, or a tenon joint that combines a concave part and a convex part provided in a part of the partial mold.

  Moreover, when the fitting part has the recessed part formed in the joining area | region of adjacent partial mold | types, and the connection member which fits a recessed part and connects adjacent members, it combined partial mold | dies. It becomes possible to further stabilize the structure. For example, it is possible to provide a concave portion on the surface of adjacent partial molds to be joined, and to use a separate member fitted in the concave portion as a connecting member.

  In addition, when a columnar member in which adjacent members are arranged with a predetermined interval and a crosspiece member that connects the adjacent columnar members are formed in a region that does not come into contact with the partial molten metal, The mold material necessary for forming the partial mold can be reduced while ensuring the stability of the shape of the partial mold. Also, solidification can be promoted by forcibly cooling by blowing air from the side of the region not in contact with the partial molten metal, and solidification defects can be reduced.

  In addition, in the case of including a vent portion that is formed through the partial mold in at least a part of the cavity portion into which the molten metal of the partial mold flows, and in which unbound foundry sand that forms the partial mold is accommodated, The gas generated from the mold during casting can be easily vented, and gas defects in the casting can be prevented. That is, it is possible to suppress the leakage of the molten metal with the foundry sand while allowing the gas to escape from the perforated region. The undecided foundry sand here refers to foundry sand that is not subjected to a binder that initiates hardening with a binder during the lamination of the powder-fixing lamination method, and is disposed in an uncured state in a penetrating area. Will be.

  Further, when a core connected to at least a part of the partial mold is provided, it is possible to reduce the flashing generated in the mold. That is, conventionally, a cast-in beam is formed between the core and the upper mold or the lower mold as the main mold, but the cast-in can be reduced because the partial mold and the core are connected.

  Further, the partial mold is formed of an additive manufacturing material including an aggregate composed of first particles and second particles having a particle size 1.5 to 2 times the particle size of the first particles. In this case, the gaps between the particles and the surface irregularities in the mixed state of the mold material are reduced, and the smoothness of the mold surface can be further improved. Moreover, the density of the mold material at the time of lamination becomes high, and the strength of the mold can be further increased. In addition, the particle diameter of a particle here means an average particle diameter, and includes the dispersion | variation at the time of particle manufacture. Moreover, strength means the bending strength measured by a bending test, and the details of the test will be described later.

  On the other hand, in the case of the second particle having a particle size of less than 1.5 times the particle size of the first particle, the second particle approaches the first particle. As a result, the density of the mixed state is lowered, and the bending strength is not sufficiently improved. In addition, since the particle size is small, the particles are easily lost during the lamination, and it is difficult to improve the smoothness of the mold surface. Further, in the case of the second particles having a particle size exceeding twice the particle size of the first particles, gaps between the particles of the second particles are likely to occur, and the density of the mixed state is lowered, and the resistance is reduced. The bending strength is not improved sufficiently. Further, surface irregularities between the second particles are likely to occur, and it becomes difficult to improve the smoothness of the mold surface.

  Further, when the ratio of the weight ratio based on the total amount of the second particles to the weight ratio based on the total amount of the first particles is in the range of 1.5 to 3.0, the resistance of the mold is further increased. Folding strength can be improved.

  Here, when the ratio of the weight ratio based on the total amount of the second particles to the weight ratio based on the total amount of the first particles is less than 1.5, it is difficult to ensure the smoothness of the mold surface. It becomes. In addition, when the ratio of the weight ratio of the second particles based on the total amount of the first particles to the weight ratio of the second particles exceeds 3.0, the bending strength of the mold is insufficient. It becomes.

  In addition, when the weight ratio of the binder based on the total amount is 33%, the bending strength of the mold can be further improved. Moreover, the smoothness of the casting surface can be further enhanced.

The mold according to the present invention is formed by a powder fixing lamination method, and can be applied to a large-sized casting and can cast a high-precision casting.
In addition, the mold manufacturing method according to the present invention is a method that is formed by a powder fixed lamination method, can be applied to a large casting, and can cast a highly accurate casting.

It is the schematic which shows the structure of a main mold | type and a core. It is the schematic which shows the valve part for the ball-shaped valve manufactured from a casting_mold | template, the product part based on a casting plan, a gate, and a rise. It is the schematic (a) of the detailed structure of the state which has arrange | positioned the core to the main type | mold, and the schematic (b) which shows the tenon joint of a core. It is the perspective view (a), front view (b), and side view (c) which show the support structure of a casting_mold | template. It is the schematic (a) of the casting_mold | template which does not provide a support structure, and the schematic (b) of the casting_mold | template provided with the support structure. It is the schematic which shows the vent part of a casting_mold | template, and its partial enlarged view. Schematic diagram (a) showing a mold in which the upper mold and the lower mold are not integrated with the core, (b) schematic diagram showing a mold in which the upper mold and the core are integrated, and the lower mold and the core are integrated. It is the schematic (c) which shows a casting_mold | template. It is a figure which shows the result of the bending strength test done with respect to the plate-shaped test piece of Examples 1-6 and Comparative Example 1. FIG. It is the photograph (a) which shows the surface state of the casting_mold | template in the test piece of Example 4, and the photograph (b) which shows the surface state of casting_mold | template in the test piece of the comparative example 1. It is a figure which shows the result of the bending strength test done with respect to the plate-shaped test piece of Examples 7-11. It is a figure which shows the result of a coagulation test. It is a figure which shows the result of the bending strength test done with respect to the plate-shaped test piece of Examples 17-21 (1-5) and the comparative example 2. FIG. It is the photograph (a) which shows the surface state of the casting_mold | template in the test piece of Example 19, and the photograph (b) which shows the surface state of casting_mold | template in the test piece of Comparative Example 2.

Hereinafter, embodiments of the present invention will be described for understanding of the present invention.
FIG. 1 is a schematic view showing the structure of the main mold and the core. FIG. 2 is a schematic view showing a product portion, a gate and a rise based on a valve box for a ball valve manufactured from a mold and a casting method. FIG. 3 is a schematic diagram (a) of the detailed structure in which the core is arranged in the main mold and a schematic diagram (b) showing the tenon joint of the core.

  Hereinafter, an additive manufacturing mold 1 that is an example of a mold to which the present invention is applied will be described.

  As shown in FIG. 1, the additive manufacturing mold 1 includes a main mold 2 and a core 3. The additive manufacturing mold 1 is a mold used when casting a valve box 4 for a valve having a shape shown on the left side of FIG. The main mold 2 is a mold having a length (symbol L in FIG. 1) of 800 mm.

  The main mold 2 has a space having the same shape as the outer shape of the valve box 4 for the ball valve inside, and is formed by combining a plurality of partial main molds 5. The main mold 2 has a structure divided in the height direction into a runner side region portion 6 on which a gate and a runner are formed, a product side upper region portion 7 and a product side lower region portion 8. Reference numerals 9 and 10 indicate division positions of the main mold 2 in the height direction.

  Further, the partial main molds 5 adjacent to each other in the width direction of the main mold 2 are combined by a joint 11. The region where the molten metal does not flow in the portion of the joint 11 is fixed by a member such as a bolt nut or a clamp (not shown). A detailed division structure will be described later.

  As shown in FIG. 1, the core 3 is formed by combining members of an upper core 12, an intermediate core 13, and a lower core 14. The core 3 is accommodated in the internal space of the main mold 2 and forms a cavity of the valve box 4 for the ball valve. Further, the upper core 12 and the intermediate core 13, and the intermediate core 13 and the lower core 14 are combined with a tenon joint and fixed with a member such as a bolt nut or a clamp. The detailed structure of the tenon joint will be described later.

  The main mold 2 and the core 3 have a thinned shape, and portions that are not used for casting are cut away, and only a mold material necessary for securing the shape is used.

  When casting is performed using the main mold 2 and the core 3, a valve valve box 4 having a shape shown on the left side of FIG. 2 can be manufactured. Further, on the right side of FIG. 2, the product portion 15 that becomes the valve box for the valve at the time of casting, and the formation positions of the gate 50 and the rise 16 are shown.

  Here, the mold to which the present invention is applied does not necessarily need to be composed of the main mold 2 and the core 3. For example, there may be a mold in which only the main mold is formed by a plurality of partial main molds without using a core, or only the upper mold or the lower mold of the main molds is formed by a plurality of partial main molds.

  Further, the length of the main mold 2 is not necessarily limited to 800 mm, and the object to be modeled does not have to be a valve valve box. By forming the size of an object to be manufactured and a plurality of partial main molds necessary for the object, it is possible to form a main mold having a length of 1000 mm or more, for example.

  Further, the position at which the main mold 2 and the core 3 are divided is not particularly limited, and it is possible to appropriately change the design into a shape that allows easy combination and handling of members. However, the main mold 2 has a structure divided into a runner side region portion 6 on which a gate and a runner are formed, a product side upper region portion 7 and a product side lower region portion 8, so that each It becomes easy to process into a shape that suits the application.

  That is, it is preferable that the main mold 2 has a structure that can be divided into a runner side region and a product side region. For example, the area on the runner side requires less mold material than the area on the product side, and forming only the shape of the area on the runner side increases the formation efficiency of the main mold. Can do.

  In addition, it is not always necessary to have a structure in which adjacent partial main molds and core members are combined by joining or tenon joining. However, from the point that the combined structure becomes a stable structure, it is preferable that adjacent partial main molds and core members are combined by a joint or a tenon joint. From the same point of view, it is possible to adopt a structure in which concave portions are provided in both areas to be joined and combined by using actual members that fit into the combined concave portions.

  FIG. 3A shows a more detailed divided structure of the main mold 2 and the core 3. The main mold 2 is formed by a plurality of partial main molds 5. Further, as described above, the core 3 is formed by three members, that is, the upper core 12, the intermediate core 13, and the lower core 14.

  Each of the partial main mold 5, the upper core 12, the intermediate core 13 and the lower core 14 is manufactured by a three-dimensional modeling machine capable of manufacturing a general modeling-compatible size object having a length of about 20 mm. It has become.

  Looking more closely at each partial main mold 5, reference numerals 17 and 18 are raised parts, reference numeral 19 is a spout, reference numerals 20 and 21 are intermediate main molds, and reference numerals 22 and 23 are lower main molds. . Further, the rising portion 17 and the rising portion 18 are portions that form the rising 16 shown in the right side of FIG.

  FIG. 3B shows the detailed structure of the core 3. The upper core 12 has a convex portion 42 at the lower portion and a concave portion 43 at the upper portion of the intermediate core 13. Further, a recess (not shown) is formed in the lower part of the intermediate core, and a convex part 44 is formed in the upper part of the lower core 14.

  Each opposing concavo-convex part is a tenon joint part of the core 3, and the core 3 becomes a stable structure by being combined at this part.

  Thus, by subdividing one main mold, it is possible to form a large mold with high accuracy. Each member is formed by inputting three-dimensional data of a desired shape for the additive manufacturing apparatus.

  In the mold to which the present invention is applied, a structure as described below with reference to FIGS. 4 to 7 can be adopted.

  FIG. 4 shows a mold in which a region opposite to the cavity portion of the mold is thinned and a support structure using a columnar member is provided.

  The mold 24 shown in FIG. 4 has a support structure 26 formed in a region opposite to the cavity portion 25 into which the molten metal flows. The support structure 26 includes a column portion 27 that is disposed substantially in parallel with a predetermined interval, and a crosspiece member 28 that connects adjacent column portions 27 to each other.

  In addition, a portion where the column portion 27 and the crosspiece member 28 intersect with each other is formed with a spherical portion 29 having a larger volume than each member, and has a structure that reinforces the intersection. FIG. 4B shows a front view of the mold 24 viewed from the region opposite to the cavity portion 25, and FIG. 4C shows a view of the mold 24 viewed from the side.

  FIG. 5A shows a mold 30 without the support structure 26, and FIG. 5B shows a mold 24 having the support structure 26 described above. Compared with the mold 30, the mold 24 can greatly reduce the mold material forming the mold by thinning a region opposite to the cavity portion.

  Moreover, the casting_mold | template 24 can ensure the intensity | strength of a casting_mold | template by having the support structure 26. FIG. Further, since the mold 24 is thinned, the casting material can be forcibly cooled after pouring, for example, by applying air to the cavity portion 25 from a region opposite to the cavity portion. As a result, solidification is promoted and the occurrence of solidification defects due to the cooling rate can be reduced.

  In the mold to which the present invention is applied, a partial mold (second partial mold) having a support structure 26 such as the mold 24 and a partial mold (first partial mold) not having the support structure 26 are combined. It is possible to construct one template.

  Moreover, in a large mold constructed with a plurality of partial molds, for example, in the entire mold, it is necessary to degas the back of the cavity part into which the molten metal flows, or due to the convection and radiation of the gas on the back of the cavity part. It is conceivable to arrange a partial mold having a support structure 26 such as the above-described mold 24 at a place where cooling is necessary. Further, a partial mold that does not have the support structure 26 is disposed at a location where strength is required in the mold.

  By setting it as the casting_mold | template of such a structure, the efficiency which can maintain the intensity | strength can be improved for the location which needs to degas and cool efficiently. Moreover, it becomes easy to ensure the strength of the entire mold by disposing a partial mold without a support structure at a location where strength is required. That is, it is possible to form a mold in which both a partial mold having a support structure and a partial mold without a support structure are combined and arranged at appropriate positions.

  FIG. 6 shows a structure in which a vent for venting gas is provided in the cavity of the mold.

  The mold 31 shown in FIG. 6 has a plurality of vent portions 33 in the cavity portion 32. As shown in the enlarged view portion of FIG. 6, the vent portion 33 is formed by collecting a large number of through holes 34 having a diameter of about 5 mm.

  The through hole 34 penetrates the mold 31 from the cavity part toward the back side thereof. Further, foundry sand (not shown) serving as a mold material of the mold 31 is accommodated in the through hole 34. The foundry sand is one that is not sprayed with a binder that initiates curing when the mold 31 is layered.

  Since the foundry sand is in an unbound state, even if it is accommodated in the through-hole 34, a certain level of air permeability can be maintained, and gas generated from the mold during casting can be released. As a result, gas defects are less likely to occur in the casting.

  Further, since the foundry sand is accommodated, the molten metal can be prevented from leaking to the outside through the through hole 34. By providing the vent portion 33 in the mold in this way, the structure can promote gas venting during casting.

  Here, the diameter of the through hole 34 is not necessarily set to about 5 mm, and can be appropriately selected depending on the type of the mold material and the shape of the mold. However, if the diameter of the through-hole is too large, molten metal leaks, and therefore it is preferable to select a size that does not easily cause unbound foundry sand to fall off.

  FIG. 7 illustrates a structure in which the core is connected to a part of the main mold and integrated.

  FIG. 7A shows a structure in which the core 35 is not connected to either the upper die 36 or the lower die 37 constituting the main die. Here, FIG. 7B shows a main mold 38 in which the core and the upper mold are connected and integrated, and a lower mold 39 that is paired with the main mold 38.

  In the mold shown in FIG. 7A, a gap exists between the core 35 and the upper mold 36, and a flash is generated in the gap portion. On the other hand, the main mold 38 shown in FIG. 7 (b) has a structure in which the gap between the core and the upper mold is not formed, and the occurrence of cast-in can be reduced.

  FIG. 7C shows a main mold 40 in which the core and the lower mold are connected and integrated, and an upper mold 41 paired with the main mold 40. Similarly to the main mold 38, the main mold 40 has a structure in which no gap is generated between the core and the lower mold, and the occurrence of casting can be reduced.

  Subsequently, an example of a mold material used for manufacturing the additive manufacturing mold 1 will be described. The mold material described below is merely an example, and the mold material to which the present invention is applied is not limited thereto.

  The mold material of the layered molding mold 1 includes a first alumina sand and a second alumina sand which are aggregates (casting sand), and an alumina cement which is a binder.

The first alumina sand and the second alumina sand 2 are white dielectric alumina made of aluminum oxide (Al ₂ O ₃ ) having a purity of 99% or more, and both have heat resistance of 1,500 ° C. or more. . The first alumina sand is composed of particles having a center particle diameter of 45 to 53 μm. The second alumina sand is composed of particles having a central particle size of 75 to 106 μm.

Alumina cement is a powdery precursor containing 72.5% aluminum oxide (Al ₂ O ₃ ) and 25.8% calcium oxide (CaO) in a weight ratio based on the total amount of alumina cement. Alumina cement is composed of particles having an average particle size of 4.5 μm and has heat resistance of 1,730 ° C. or higher.

  The alumina cement is hardened by binding the mixed first alumina sand and second alumina sand by being sprayed with a binder solution from an inkjet print head during additive manufacturing. As the binder solution, an aqueous solution containing 1% or less of 2-pyrrolidone is used.

Further, the mold material is provided with lithium carbonate (Li ₂ CO ₃ ) as an auxiliary agent for increasing the curing rate of the binder.

  The mold material has a composition in which the weight ratio based on the total amount includes the first alumina sand: 44%, the second alumina sand: 22%, the alumina cement: 33%, and the lithium carbonate: 1%.

  Here, the ratio of the weight ratio on the basis of the total amount of the first alumina sand to the weight ratio on the basis of the total amount of the second alumina sand is 2.0, but this value is not necessarily required. However, from the viewpoint of improving the bending strength of the mold and increasing the smoothness of the mold surface, the ratio of the weight ratio is preferably in the range of 1.5 to 3.0, and more preferably 2.0. It is even more preferable.

  Moreover, the weight ratio on the basis of the total amount of alumina cement is not necessarily 33%. However, from the viewpoint of improving the mold bending strength and enhancing the smoothness of the mold surface, the weight ratio of the alumina cement based on the total amount is preferably set to 33%.

Also, the mold material, as an adjunct to accelerate the curing rate of the binder, it is preferred to add lithium carbonate (Li 2 _{CO 3).} In addition, by increasing the amount of lithium carbonate added, the initial time at which curing begins is shortened and the curing rate is increased, but the amount of lithium carbonate can be appropriately selected in consideration of the amount of other components. preferable. In addition, the bending strength of the mold is improved by adding lithium carbonate.

  Subsequently, still another example of the mold material used for manufacturing the additive manufacturing mold 1 will be described. The mold material described below is merely an example, and the mold material to which the present invention is applied is not limited thereto.

  The mold material of the layered molding mold 1 includes a first alumina sand and a second alumina sand which are aggregates (casting sand), and an alumina cement which is a binder.

The first alumina sand and the second alumina sand 2 are white dielectric alumina made of aluminum oxide (Al ₂ O ₃ ) having a purity of 99% or more, and both have heat resistance of 1,500 ° C. or more. . The first alumina sand is composed of particles having a center particle diameter of 20 to 25 μm. The second alumina sand is composed of particles having a central particle size of 45 to 53 μm.

Alumina cement is a powdery precursor containing 72.5% aluminum oxide (Al ₂ O ₃ ) and 25.8% calcium oxide (CaO) in a weight ratio based on the total amount of alumina cement. Alumina cement is composed of particles having an average particle size of 4.5 μm and has heat resistance of 1,730 ° C. or higher.

  The alumina cement is hardened by binding the mixed first alumina sand and second alumina sand by being sprayed with a binder solution from an inkjet print head during additive manufacturing. As the binder solution, an aqueous solution containing 1% or less of 2-pyrrolidone is used.

Further, the mold material is provided with lithium carbonate (Li ₂ CO ₃ ) as an auxiliary agent for increasing the curing rate of the binder.

  The mold material has a composition in which the weight ratio based on the total amount includes 66% of aggregate, 33% of alumina cement, and 1% of lithium carbonate. Moreover, it has a composition containing 35% of the first alumina sand and 65% of the second alumina sand on the basis of the amount of the aggregate.

  Here, the ratio of the weight ratio of the first alumina sand aggregate on the basis of the amount of aggregate on the basis of the amount of aggregate of the second alumina sand is 1.68. There is no need to become. However, the ratio of the weight ratio on the basis of the amount of aggregate is preferably in the range of 1.50 to 2.33 from the viewpoint of improving the bending strength of the mold and increasing the smoothness of the mold surface. Furthermore, it is still more preferable to become 1.68.

  Moreover, although the casting sand which comprises an aggregate is comprised only with the 1st alumina sand and the 2nd alumina sand, the structure of an aggregate is not limited to this. The first alumina sand and the second alumina sand are the main components of the aggregate, and sand having a center particle size in a range sandwiched between the center particle sizes of both alumina sands is blended as the third component. Is also possible. For example, you may make the component of 3rd foundry sand contain several% on the basis of the quantity of aggregate.

  Moreover, the weight ratio on the basis of the total amount of alumina cement is not necessarily 33%. However, from the viewpoint of improving the mold bending strength and enhancing the smoothness of the mold surface, the weight ratio of the alumina cement based on the total amount is preferably set to 33%.

Also, the mold material, as an adjunct to accelerate the curing rate of the binder, it is preferred to add lithium carbonate (Li 2 _{CO 3).} In addition, by increasing the amount of lithium carbonate added, the initial time at which curing begins is shortened and the curing rate is increased, but the amount of lithium carbonate can be appropriately selected in consideration of the amount of other components. preferable. In addition, the bending strength of the mold is improved by adding lithium carbonate.

  Here, at least a first particle made of aluminum oxide having a particle size in the range of 20 to 25 μm, and a second particle made of aluminum oxide having a particle size in the range of 45 to 53 μm, The bending strength of the mold can be sufficiently improved by the aggregate composed of the above. Moreover, the smoothness of the casting surface can be sufficiently improved. The particle size of “20 to 25 μm” of the first particles and the particle size of “45 to 53 μm” of the second particles are the same as those in the “JIS Z 2601-1993 foundry sand test method”. This is specified on the basis of the particle size of the foundry sand screened based on the sand particle size test method (Appendix 2) (Reference Material 1). The sieves used in the particle size test method are those specified in “JIS Z 8801 (test sieves) (reference material 2)”.

More specifically, the second particle is a JIS Z 8801 sieve mesh that uses 53 μm and 45 μm in an overlapping manner, passes through the 53 μm sieve, and remains on the 45 μm sieve. In addition, the first particle is a JIS Z 8801 sieve mesh that is used by overlapping 25 μm and 20 μm, passes through the 25 μm sieve, and remains on the 20 μm sieve. In addition, as a sieving machine, use the low-tap type sieving machine described in JIS Z 2601-1993 Foundry Sand Testing Method (Appendix 2) and install the sieve on the sieving machine. I am testing. The determination of the particle size of the foundry sand as described above is very commonly performed in the casting field. This is because the casting grain size technology of the casting technology series published in March 2002 published by the General Materials Center, which is generally used as a material in the field of casting, regarding the particle size of the foundry sand (2nd edition) ”on page 536 to page 538,“ 1.1.2 Particle size test method ”(http://www.sokeizai.or.jp/japanese/publish/shuppan.html) (reference material 3) And “Testing Methods for Molds and Mold Materials”, “Grinding Sand Grain Size Testing Method (Page 1)” (https://unit.aist.go.jp/cpiad/ci/techno_kw/ mono-kyohon_pdf / technote023.pdf) (reference material 4) is also clear from the fact that JIS Z 2601-1993 (Appendix 2) and JIS Z 8801 are adopted.
For reference, the above-mentioned “Copy of JIS Z 2601-1993 Foundry Sand Grain Size Testing Method (Appendix 2)” in JIS Z 8801 is referred to as JIS Z 8801. JIS Standard Sieve Table (Excerpt) ”as Reference Material 2,“ Casting Technology Series Issued March 2002, Mold Production Technology (2nd Edition) pp. 536 to 538 ”as Reference Material 3 and“ "Test method for mold and mold material (1st page)" is published as Reference Material 4. In addition, about the 1st particle | grains comprised by the aluminum oxide whose particle size is in the range of 45-53 micrometers mentioned above, and the 2nd particle | grains comprised by the aluminum oxide whose particle diameter is in the range of 75-106 micrometers. Similarly, the particle diameter is defined.

  Here, the casting sand of the mold to which the present invention is applied is not necessarily limited to the above-mentioned alumina sand. For example, conventionally used silica sand, olivine sand, chromite sand, zircon sand, ceramic artificial sand and the like can also be used.

  In addition, the partial molds constituting the mold to which the present invention is applied are not necessarily formed of the same foundry sand, and the type of the foundry sand can be varied for each partial mold. For example, one partial mold may be formed from the alumina sand described above, and another partial mold combined therewith may be formed from olivine sand. In this case, it is possible to manufacture by changing the foundry sand material when forming the partial mold by additive manufacturing.

  Moreover, in the casting_mold | template to which this invention is applied, the particle size of the foundry sand which comprises each partial type | mold can also be varied. For example, a certain partial mold may be composed of foundry sand having a large particle size as a main component, and another partial mold may be composed of foundry sand having a small particle size as a main component.

  Moreover, in the casting_mold | template to which this invention is applied, content of the binder or additive contained in the foundry sand which comprises each partial type | mold can also be varied. For example, the two partial molds are composed of the same type of foundry sand as the main component, but one side contains 1% lithium carbonate as an additive and the other contains 5% lithium carbonate. The content of the additive can also be changed. Similarly, the content of the binder can be changed depending on the partial mold.

  Hereinafter, the flow from the production of the layered molding mold 1 to the production of the valve box 4 for the bead valve will be described.

(Preparation of 3D CAD data)
First, 3D CAD data of the shape of the valve box 4 for a ball valve to be manufactured was produced. In the production of 3D CAD data, 3D CAD data of the layered mold 1 reflecting the casting system and the like was produced based on the casting casting method.

  Further, the 3D CAD data of the layered molding mold 1 is divided in accordance with the modeling area size of the layered modeling apparatus (three-dimensional modeling machine) to be used, and data corresponding to the shapes of the partial main mold 5 and each core component member is produced. did. Here, the shape of the joint or tenon is also reflected.

(Preparation of mold material)
The mold material described above was prepared. The first alumina sand and second alumina sand, which are aggregates, and alumina cement and lithium carbonate were mixed to obtain a mold material.

(Laminated modeling process)
The 3D CAD data corresponding to the shape of each member was converted into a data format that can be used by the additive manufacturing apparatus, and input to the additive manufacturing apparatus software. Also, various materials and print heads necessary for modeling were replenished to the apparatus and attached.

  The additive manufacturing apparatus used an apparatus having the following performance. Modeling frame dimensions: 508 mm × 381 mm × 229 mm, height direction modeling speed: 5-15 mm / hr, minimum stacking pitch: 0.1 mm. A sand mold having a desired shape was layered from various modeling materials, and after the modeling was completed, excess mold material was removed, and the model was taken out of the apparatus.

(Preparation of pouring hot water)
The main mold 2 and the core 3 were formed by connecting and combining the sand molds that were divided and shaped. The joints and tenon joints were combined and fixed with bolts or clamps. A core 3 was set inside the main mold 2 to obtain a layered molding mold 1. The coating agent was applied to the layered mold 1 and dried at a temperature of 200 ° C.

(Pouring hot water)
The molten metal was poured into the additive manufacturing mold 1 manufactured in the above process, and cast. A ball valve box 4 shown on the left side of FIG. 2 was manufactured by solidifying by natural cooling or partial forced cooling, separating the mold, removing the mold, and finishing.

  The additive manufacturing mold, which is an example of the mold to which the present invention described above is applied, manufactures a member obtained by further dividing the main mold and the core by the additive manufacturing process, so that a large mold can be manufactured. It has become. In addition, the mold can be directly manufactured, and the manufacturing period for manufacturing the casting can be greatly shortened.

  In the layered molding mold, each member obtained by dividing the main mold and the core has sufficient bending strength. Moreover, it has a support structure and a connection structure that can maintain the shape even if the mold material is reduced.

  In addition, defects that affect the quality of the casting such as solidification defects and gas defects during cooling hardly occur, and the casting is highly accurate. Moreover, it is a casting excellent in smoothness of the casting surface.

As described above, the mold to which the present invention is applied is formed by the powder fixed lamination method, and can be applied to a large casting and can cast a high-precision casting.
The mold manufacturing method to which the present invention is applied is formed by a powder fixed lamination method, and is applicable to a large casting and capable of casting a highly accurate casting.

  Examples relating to the mold material of the present invention will be described below.

[First embodiment]
(1) Chemical composition of test piece First, among the mold materials described above, the first alumina sand (having a center particle size in the range of 45 to 53 μm) and the second alumina sand (having a center particle size of 75) which are aggregates. Examples 106 and Comparative Example 1 were prepared by adjusting the mold material components so that the first alumina sand and the second alumina sand had the blending ratio shown in Table 1 on the basis of the total amount of aggregate. It was. The mold materials of Examples 1 to 6 and Comparative Example 1 are mixed with 33% alumina cement and 1% lithium carbonate based on the total amount of the mold material. In Examples 1 to 6 and Comparative Example 1, a plate-shaped test piece having a size of 10 mm (W) × 20 mm (t) × 75 mm was formed using an additive manufacturing apparatus. In addition, the numerical value of the 1st step | paragraph and the 2nd step | paragraph of the following Table 1 shows the weight ratio (%) on the basis of the total amount of aggregate among mold material powder. Table 2 shows the chemical components of the alumina cement.

(2) Folding strength test and smoothness of mold FIG. 8 is a diagram showing the results of bending strength tests performed on the plate-like test pieces of Examples 1 to 6 and Comparative Example 1. In FIG. 8, the vertical axis represents the bending strength (MPa), and the horizontal axis represents the weight ratio (%) of the first alumina sand based on the total amount of aggregate.
In order to investigate the bending strength of each test piece prepared with the above composition, a bending strength test was performed. Using a foundry sand strength tester, the test piece was supported at a fulcrum distance of 50 mm (L), a load was applied to the center of the test piece, and the breaking load (P) when the test piece was broken was determined. The bending strength (MPa) in this test was calculated by the following formula (1) using the breaking load of the test piece.
Bending strength (MPa) = 1.5 × LP / 100 Wt ² Formula (1)
L: distance between fulcrums (50 mm), P: breaking load (kgf), W: width of test piece (10 mm), t: thickness of test piece (20 mm)
Further, the roughness of the surface of each test piece was visually observed to confirm the smoothness of the mold surface.

In all of Examples 1 to 6, the bending strength was a numerical value of 1.4 MPa or more. Particularly, in Examples 2 to 4, the bending strength was a numerical value of 1.7 MPa or more, and in Example 4, a high numerical value of 2.0 MPa was shown. Further, the smoothness of the mold surface was good in Examples 3 to 6. Moreover, in Examples 1-2, the improvement was seen a little compared with the smoothness with which the surface of the comparative example 1 was rough.
For reference, a photograph showing the surface state of the mold in the test piece of Example 4 is shown in FIG. 9A, and a photograph showing the surface state of the mold in the test piece of Comparative Example 1 is shown in FIG. 9B.

A test was conducted on the relationship between the amount of binder in the mold material, the bending strength of the mold, and the smoothness of the mold surface.
(3) Chemical composition of test piece Example 7 was prepared by adjusting the mold material components so that the above-mentioned mold material had a blending ratio shown in Table 3 based on the total amount of the mold material alumina cement as a binder. It was set to ~ 11. In addition, the mold materials of Examples 7 to 11 are blended so that the first alumina sand and the second alumina sand are 50% based on the total amount of aggregate. Moreover, 1% of lithium carbonate is blended based on the total amount of the mold material. Examples 7 to 11 were plate-shaped test pieces having a size of 10 mm (W) × 20 mm (t) × 70 mm using an additive manufacturing apparatus. In addition, the numerical value of the following Table 3 shows the weight ratio (%) on the basis of the total amount of aggregate among mold material powders. The alumina cement used here has chemical components shown in Table 2.

(4) Folding strength test and mold smoothness The bending strength test and confirmation of the smoothness of the mold were performed by the same method as (2) described above. In addition, the bending strength test produced the test piece about each Example, and tested it.
FIG. 10 is a diagram showing the results of bending strength tests performed on the plate-like test pieces of Examples 7 to 11. In FIG. 10, the vertical axis indicates the bending strength (MPa), and the horizontal axis indicates the weight ratio (%) of the alumina cement based on the total amount of the mold material.

  Each of Examples 7 to 11 had a bending strength of 1.0 MPa or more. Further, the smoothness of the mold surface was good in Examples 7 and 8.

Subsequently, the relationship between the blending amount of lithium carbonate in the mold material and the curing rate of the mold material was tested.
(5) Chemical component of the sample Lithium carbonate is an auxiliary agent that accelerates the curing rate by the binder. Here, as the sample, the sample components were adjusted so that lithium carbonate had a blending ratio shown in Table 4 on the basis of the total amount of the sample, and Examples 12 to 16 were obtained. In addition, the samples of Examples 12 to 16 are blended with 292.5 g of the second alumina sand, 157.5 g of alumina cement, and 67.5 g of the binder solution. In addition, the numerical value of the following Table 4 shows the weight ratio (%) on the basis of the whole quantity of the sample.

(6) Coagulation test of sample FIG. 11 is a diagram showing the results of the coagulation test performed on the samples of Examples 12 to 16. In FIG. 11, the vertical axis indicates the distance (mm) between the bottom surface of the slurry and the tip of the first needle in the coagulation tester, and the horizontal axis indicates the elapsed time (min) from the start of measurement.
In order to investigate the solidification time of the mold material for each sample prepared with the above composition, a test was conducted according to the setting test described in JIS R5201-1977 “Physical Test Method for Cement”. Add lithium carbonate (1% to 10%) to the second alumina sand and alumina cement, stir, add binder solution, knead for 1 minute, and then use sample coagulation tester (Vicat needle device) and sample slurry. The distance at the tip of the needle was measured. The measurement was carried out every minute until the distance between the bottom surface of the sample slurry and the tip of the starting needle reached 40 mm three times. In FIG. 11, reference numeral 45 indicates the twelfth embodiment, reference numeral 46 indicates the thirteenth embodiment, reference numeral 47 indicates the fourteenth embodiment, reference numeral 48 indicates the fifteenth embodiment, and reference numeral 49 indicates the sixteenth embodiment.

  In Examples 12-16, the increase in the hardening rate of the casting | molding material was confirmed with the increase in the compounding quantity of lithium carbonate. Moreover, with the increase in the blending amount of lithium carbonate, the initial time until curing began was shortened.

[Second Embodiment]
(7) Chemical composition of test piece First, among the above-described mold materials, the first alumina sand and the second alumina sand, which are aggregates, are the first alumina sand (having a center particle size of the aggregate based on the total amount of aggregate). 20 to 25 μm) and the second alumina sand (with a center particle diameter in the range of 45 to 53 μm) were adjusted so that the blending ratios shown in Table 5 were adjusted, and Examples 17 to 21 and It was set as Comparative Example 2. Further, the mold materials of Examples 17 to 21 and Comparative Example 2 are blended with 33% alumina cement and 1% lithium carbonate based on the total amount of the mold material. In Examples 17 to 21 and Comparative Example 2, a plate-shaped test piece having a size of 10 mm (W) × 20 mm (t) × 75 mm was formed using an additive manufacturing apparatus. In addition, the numerical value of the 1st step | paragraph and the 2nd step | paragraph of the following Table 5 shows the weight ratio (%) on the basis of the total amount of aggregate among mold material powder.

(8) Folding Strength Test and Mold Smoothness FIG. 12 is a diagram showing the results of bending strength tests performed on the plate-like test pieces of Examples 17 to 5 and Comparative Example 2. In FIG. 12, the vertical axis represents the bending strength (MPa), and the horizontal axis represents the weight ratio (%) of the first alumina sand based on the total amount of aggregate.
In order to investigate the bending strength of each test piece prepared with the above composition, a bending strength test was performed. Using a foundry sand strength tester, the test piece was supported at a fulcrum distance of 50 mm (L), a load was applied to the center of the test piece, and the breaking load (P) when the test piece was broken was determined. The bending strength (MPa) in this test was calculated by the following formula (1) using the breaking load of the test piece.
Bending strength (MPa) = 1.5 × LP / 100 Wt ² Formula (1)
L: distance between fulcrums (50 mm), P: breaking load (kgf), W: width of test piece (10 mm), t: thickness of test piece (20 mm)
Further, the roughness of the surface of each test piece was visually observed to confirm the smoothness of the mold surface.

In Examples 17 to 21, the bending strength was a numerical value of 1.6 MPa or more. Particularly, in Examples 18 to 20, the bending strength was a numerical value of 1.75 MPa or more, and in Example 19, a high numerical value of 1.9 MPa was shown. Further, the smoothness of the mold surface was good in Examples 17 to 20. Further, in Examples 17 and 21, a slight improvement was seen compared to the rough smoothness of the surface of Comparative Example 2.
For reference, a photograph showing the surface state of the mold in the test piece of Example 19 is shown in FIG. 13A, and a photograph showing the surface state of the mold in the test piece of Comparative Example 2 is shown in FIG. 13B.

The relationship between the amount of binder in the mold material and the smoothness of the mold surface was tested.
(9) Chemical component of test piece Example 22 was prepared by adjusting the mold material component so that alumina cement as a binder was 33% based on the total amount of the mold material among the mold materials described above. The mold material of Example 22 is blended so that the first alumina sand and the second alumina sand are 50% based on the total amount of aggregate. Moreover, 1% of lithium carbonate is blended based on the total amount of the mold material. In Example 22, a plate-shaped test piece having a size of 10 mm (W) × 20 mm (t) × 70 mm was formed using an additive manufacturing apparatus. The alumina cement used here has chemical components shown in Table 2.

(10) Smoothness of mold The smoothness of the mold was confirmed by the same method as in (8) described above.

  The smoothness of the surface of the mold of Example 22 was good.

DESCRIPTION OF SYMBOLS 1 additive manufacturing mold 2 main mold 3 core 4 valve box for ball-shaped valve 5 partial main mold 6 runner side area part 7 product side upper area part 8 product side lower area part 9 height direction of main mold Dividing position 10 Dividing position of main mold in the height direction 11 Joint 12 Upper core 13 Intermediate core 14 Lower core 15 Product part 16 Up 17 Up part 18 Up part 19 Mouth part 20 Intermediate main type 21 Intermediate main type 22 Lower main mold 23 Lower main mold 24 Mold 25 Cavity part 26 Support structure 27 Column part 28 Beam member 29 Spherical part 30 Mold 31 Mold 32 Cavity part 33 Vent part 34 Through hole 35 Core 36 Upper mold 37 Lower mold 38 Main mold 39 Lower mold 40 Main mold 41 Upper mold 42 Convex part 43 Concave part 44 Convex part 45 Results of coagulation test corresponding to Example 12 46 Results of coagulation test corresponding to Example 13 47 Example 14 Corresponding coagulation tests results 48 Example 15 of the corresponding clotting tests results 49 Example 16 of the corresponding clotting test results 50 sprue

Claims (10)

A first partial mold that can be fitted with an adjacent member;
Positioned at the intersection of the columnar member and the beam member, the columnar member arranged with a predetermined interval between the members adjacent to the region not in contact with the molten metal, the beam member connecting the columnar members adjacent to each other And a reinforcing part that covers the intersection, and a second partial mold that can be fitted to an adjacent member.
The first partial mold and the second partial mold are made of foundry sand, and the first partial mold can be fitted with the second partial mold. The mold according to claim 1, wherein the foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold have different types of foundry sand. The casting mold according to claim 1 or 2, wherein the foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold have different particle sizes of the foundry sand. The foundry sand constituting the first partial mold and the foundry sand constituting the second partial mold have different contents of the binder or additive contained in the foundry sand. The mold according to claim 3. An unbound foundry sand that is formed through the second partial mold in at least a part of the cavity portion into which the molten metal of the second partial mold flows is accommodated in the second partial mold. The mold according to claim 1, claim 2, claim 3, or claim 4. The first fitting portion and the second fitting portion have a recess formed in a joining region between adjacent members, and a connecting member that fits the recess and connects adjacent members. The mold according to claim 1, claim 2, claim 3, claim 4 or claim 5. The core according to claim 1, 2, 3, 4, 5, or 6, comprising a core connected to at least a part of the first partial mold or the second partial mold. Mold. The first partial mold and the second partial mold are bones composed of first particles and second particles having a particle size 1.5 to 2 times the particle size of the first particles. The material according to claim 1, claim 2, or claim 2, comprising a material and a binder for binding the aggregates to each other and a binder having a particle size smaller than that of the first particles. The mold according to claim 3, claim 4, claim 5, claim 6 or claim 7. The ratio of the weight ratio of the second particles based on the aggregate amount to the weight ratio of the first particles based on the aggregate amount is within a range of 1.5 to 3.0. The mold described. A first partial mold that can be fitted to an adjacent member, a columnar member in which members adjacent to a region that does not contact the molten metal are arranged at a predetermined interval, and a bar that connects the adjacent columnar members to each other. Laminating a member and a second partial mold that is positioned at the intersection of the columnar member and the crosspiece member and that covers the intersection, and that can be fitted to an adjacent member by a powder fixing lamination method Forming by modeling,
A method for manufacturing a mold, comprising: a step of fitting adjacent members together to form a mold by combining at least the first partial mold and the second partial mold.