JP5086906B2 - Green sand mold apparatus and green sand mold making method - Google Patents

Description

  The present invention relates to a green sand mold apparatus and a green sand mold making method based on green sand containing an inorganic binder.

Conventionally, a sand mold forming method is known in which a first layer is formed with a curable mold (CO2 mold or furan mold) having high self-hardening property or gas curing property, and a second layer as a backing is formed with a fresh sand mold. (Patent Document 1). The second layer is formed by projecting green sand onto the back surface side of the first layer with an impeller. Fresh sand contains bentonite (inorganic binder).
Japanese Patent Laid-Open No. 2-155534

  The curable mold described above is formed of a CO2 mold or a furan mold. In recent years, when CO2 reduction is sought, it is preferable to avoid CO2. For environmental measures, it is preferable to avoid furan molds using furan resin.

  The present invention has been made in view of the above circumstances, and while adopting the green sand mold, the volume of the green sand mold is small, and the amount of green sand used by the green sand mold is small, Accordingly, it is an object of the present invention to provide a green sand mold apparatus and a green sand mold making method in which the kneading cost for mixing green sand is reduced.

(1) A fresh sand mold apparatus according to aspect 1 includes: (i) a fresh sand mold formed by pressing an aggregate of fresh sand containing an inorganic binder, and having a casting cavity on a surface thereof; A casting frame that accommodates a sand mold, and (iii) the fresh sand mold in the casting frame that is disposed in a space portion on the back side facing the surface of the fresh sand mold in the space in the casting frame. And a back-up material that does not contain the inorganic binder or that the inorganic binder is 1/5 or less of the blending ratio of the inorganic binder in the raw sand. The backup material is an aggregate of particles and contains water as a binder .

  Green sand is sand containing an inorganic binder and moisture. Typical examples of the inorganic binder are bentonite (montmorillonite clay), kibushi clay, and refractory clay (kaolinite). According to this invention, the back surface side is backed up and reinforced by the backup material among the fresh sand molds arranged in the casting frame. For this reason, the thickness of the green sand mold can be reduced and the volume thereof can be reduced, so that the amount of green sand used by the green sand mold can be reduced. Therefore, the kneading cost for kneading raw sand is reduced. Furthermore, since the backup material does not contain the inorganic binder or the content of the inorganic binder is small, compared with the case where the portion corresponding to the backup material is also formed by the green sand mold, Sometimes the gas permeability in the backup material is increased. For this reason, it can contribute to suppression of the gas defect of cast iron.

(2) The green sand mold making method according to aspect 2 includes (i) green sand containing an inorganic binder, and the inorganic binder does not contain the inorganic binder or the inorganic binder in the green sand. A step of preparing a backup material having a blending ratio of 1/5 or less of the binder; and (ii) an aggregate of the raw sand in a state where a model for forming a casting cavity is disposed in the casting frame. (Iii) After that, in a state where the model and the aggregate of fresh sand face each other, (iii) the inside of the cast frame from the side facing away from the model Forming a green sand mold in the casting frame by pressing and compressing the aggregate of green sand with a pressure body; and (iv) after that, among the green sand molds in the casting frame, By inserting the backup material on the side facing away from the model, the fresh sand mold Out look including a reinforcing process for reinforcing the model or the side that said casting cavity and facing away, the backup material is an aggregate of particles, characterized in that it comprises water as binder.

  Green sand is sand containing an inorganic binder and moisture. Typical examples of the inorganic binder are bentonite (montmorillonite clay), kibushi clay, and refractory clay (kaolinite). According to the present invention, the back surface side of the green sand mold disposed in the casting frame is backed up and reinforced by the backup material by the reinforcing step. For this reason, the thickness of the green sand mold can be reduced and the volume thereof can be reduced, so that the amount of green sand used by the green sand mold can be reduced. Therefore, the kneading cost for kneading raw sand is reduced. Furthermore, since the backup material does not contain the inorganic binder or the content of the inorganic binder is small, compared with the case where the portion corresponding to the backup material is also formed by the green sand mold, Sometimes the gas permeability in the backup material is increased. For this reason, it can contribute to suppression of the gas defect of cast iron.

  According to the present invention, the following preferred embodiments are mentioned.

  -The backup material can be an aggregate of particles. Examples of the particles include sand particles, waste sand particles, ceramic particles, and metal spheres.

  -Raw sand preferably contains no organic binder (furan resin or the like), but may contain it in some cases. Preferably, the backup material does not contain the inorganic binder, or even if it contains it, it is 1/5 or less or 1/10 or less of the blending ratio of the inorganic binder in the green sand mold. Since this backup material has higher fluidity than raw sand, it is possible to increase the loading efficiency when loaded into a casting frame.

  Preferably, the backup material is an aggregate of particles and contains water as a binder. Water acts as a binder and can enhance the bonding between the particles of the backup material. For this reason, the backup property with respect to a green sand mold can be improved. Moisture is preferable in terms of environment compared to organic binders because it does not cause excessive discharge of harmful emissions.

  -Preferably, the particle size of the particle | grains of a backup material is larger than the particle size of the sand particle which comprises a fresh sand mold. In this case, the gas permeability in the backup material is increased when the molten metal is poured. For this reason, it can contribute to suppression of the gas defect of cast iron. In some cases, the particle size of the backup material particles can be smaller than the particle size of the sand particles constituting the green sand mold. In this case, the loading density of the backup material is increased and the backup performance for the green sand mold is improved. The particle size may be an average particle size. The average particle diameter may be a median diameter or a simple average diameter. The particle diameter can be measured with an optical microscope or a magnifier.

  -Preferably, the thickness of the green sand mold may be such that the inorganic binder is damaged (burned) by the heat of the molten metal during pouring. In this case, the thickness of the green sand mold is reduced.

  -Cracks occur in the green sand mold due to the molten metal pressure during pouring and often develop. In this case, the dimensional accuracy of cast iron may be reduced. Therefore, the green sand mold is preferably set to a thickness that forms a condensed water layer formed by condensation of water vapor generated during pouring in the green sand mold. Since the condensed water layer is rich in moisture, it has the effect of suppressing further development of cracks generated in the green sand mold. For this reason, if the thickness of the green sand mold is set so that a condensed water layer is formed inside the green sand mold, even if cracks occur in the green sand mold, the effect of suppressing the progress of cracks Can be expected.

  In some cases, the thickness of the green sand mold is set so that a condensed water layer formed by condensation of water vapor generated during pouring is not formed inside the green sand mold but inside the backup material. It can also be left.

  -Preferably, the pressurization body is divided | segmented into the some division | segmentation pressurization body which can be driven mutually independently. In this case, the position and / or stroke of the pressurizing body can be made variable according to the area of the green sand mold, the pressurization allowance can be adjusted, and the mold strength can be adjusted accordingly.

  -Preferably, the moisture content of the backup material is adjusted according to the structure of cast iron and / or graphite. By adjusting the water content of the backup material, the cooling rate of the molten metal and cast iron can be adjusted, and the cast iron structure and / or graphite can be adjusted. Even if the moisture content of the backup material is adjusted, the strength of the green sand mold itself is not significantly affected, so that the strength of the green sand mold is maintained. When the backup material not containing water is 100 parts by mass, the water can be adjusted, for example, in the range of 0 to 20 parts by mass and in the range of 0 to 10 parts by mass. However, it is not limited to this.

  Preferably, in the reinforcing step, the loading rate of the backup material can be increased by applying pressure and / or vibration to the backup material in a state where the green sand mold and the model are facing each other. In this case, the back-up property for the green sand mold can be improved.

  -Depending on the case, green sand can contain a thermosetting resin, for example. In this case, preferably, in the modeling step, the thermosetting resin is thermally cured by pressurizing and compressing the aggregate of fresh sand in the casting frame and irradiating the aggregate of fresh sand with microwaves. Performed by irradiation operation.

  According to the present invention, the back surface side of the green sand mold in the casting frame is backed up by the backup material. For this reason, the thickness of the green sand mold can be reduced, the volume thereof can be reduced, and the amount of green sand used by the green sand mold can be reduced, thereby reducing the kneading cost for kneading the green sand. Further, since the backup material does not contain an inorganic binder or the content of the inorganic binder is small, the connectivity between particles of the backup material is low, and the gas permeability of the backup material is good. For this reason, compared with the case where the part corresponded to a backup material is also formed with the fresh sand mold, the gas permeability in a backup material can be improved at the time of molten metal pouring, and the gas defect of cast iron can be suppressed.

(Embodiment 1)
A first embodiment embodying the present invention will be described with reference to FIGS. First, the molding of the lower raw sand mold apparatus 1d will be described. First, a lower model 5d capable of forming a lower casting cavity is prepared. The lower model 5d includes a lower surface plate 50d that covers the first opening 301 of the lower casting frame 3d having a square frame shape formed of metal or hard resin, and a lower model held by the lower surface plate 50d. Part 51d. The mold surface 53d of the lower model portion 51d has a shape that becomes the lower casting cavity 20d.

  As shown in FIG. 1, an aggregate 70 of fresh sand 7 containing an inorganic binder is covered with the lower casting frame while covering the first opening 301 of the lower casting frame 3 d with the lower surface plate 50 d of the lower model 5 d. Insert into the 3d space. Thereby, the aggregate 70 of the required amount of fresh sand 7 is disposed in the space of the lower casting frame 3d. As a result, the mold surface 53d of the lower model 5d and the aggregate 70 of the fresh sand 7 face each other in the lower casting frame 3d. In this state, the lower pressurizing body mode operation unit is disposed above the aggregate 70 of the fresh sand 7.

  The raw sand 7 contains moisture and an inorganic binder (bentonite) and also contains a regulator. Examples of the regulator include carbonaceous material (coal dust sand) and starch. When the sand particles of green sand 7 are 100 parts by mass, the water content can be 2 to 5 parts by mass, and the inorganic binder (bentonite) can be 6 to 10 parts by mass. However, it is not limited to this.

  The lower pressure member 6d is a hydraulic or pneumatic lower cylinder portion having a lower piston 60d that can be fitted into the second opening 302 of the lower casting frame 3d and a rod 61d that moves the lower piston 60d forward and backward. 62d (lower drive source). The lower cylinder portion 62d is driven to extend the rod 61d, the lower piston 60d is advanced in the forward direction (arrow Y1 direction, downward), and the aggregate 70 of fresh sand 7 is pressurized and compressed in the thickness direction. . Thus, the lower raw sand mold 2d (see FIG. 2) is formed.

  Thereafter, the lower cylinder portion 62d is driven in the opposite direction to contract the rod 61d, the lower piston 60d is retracted in the backward direction (arrow Y2 direction, upward), and the lower piston 60d is detached from the lower casting frame 3d. Let

  Thereafter, an assembly of the lower backup sand 4d (backup material) is loaded on the side of the lower raw sand mold 2d facing away from the lower model 5d (lower casting cavity 20d) in the lower casting frame 3d. To do. In this case, the lower backup sand 4d may be dropped and loaded by gravity, or the lower backup sand 4d may be projected and loaded by the centrifugal force of the impeller. Or you may apply a vibration to the lower side casting form 3d suitably.

  As a result, the side of the lower raw sand mold 2d that faces away from the lower model 5d (lower casting cavity 20d) is reinforced with the lower backup sand 4d (see FIG. 2). The lower backup sand 4d does not contain an inorganic binder, or is a sand particle with a blending ratio of the inorganic binder smaller than that of raw sand 7, and thus has high fluidity and high loadability. Here, when the sand particles of the lower backup sand 4d are 100 parts by mass, the water content can be 1 to 3 parts by mass, and the inorganic binder (bentonite) can be 0 to 1 part by mass. However, it is not limited to this. Further, a support surface plate 25d is placed on the lower casting frame 3d. The support surface plate 25d can function as a weight with respect to the lower backup sand 4d, and can further enhance the backup performance.

  FIG. 2 shows the manufactured lower raw sand mold apparatus 1d. As shown in FIG. 2, the lower fresh sand mold apparatus 1d includes a lower fresh sand mold 2d formed by pressurizing an aggregate 70 of fresh sand 7 containing an inorganic binder, and a lower fresh sand mold 2d. 3d, and lower back-up sand 4d loaded in the lower cast frame 3d. A lower model portion 51d is disposed on the surface 201 of the lower raw sand mold 2d. The back surface 202 of the lower raw sand mold 2d faces away from the lower model portion 51d (lower casting cavity 20d).

  The lower backup sand 4d is disposed in a space portion on the back surface 202 side of the lower raw sand mold 2d in the space in the lower casting frame 3d, and the lower raw sand mold in the lower casting mold 3d. The back surface 202 side of 2d is backed up and reinforced. Further, a support surface plate 25d that can also function as a weight is detachably mounted on the lower backup sand 4d to enhance the reinforcement. Since the lower model portion 51d is released from the lower raw sand mold 2d at an appropriate time, the space occupied by the lower model portion 51d is the lower casting cavity 20d (see FIG. 4). It is formed in the green sand mold apparatus 1d. Here, the back surface 202 of the lower raw sand mold 2d is backed up and reinforced by the lower backup sand 4d. For this reason, since the thickness and volume of the lower green sand mold 2d can be reduced, the amount of green sand 7 used by the lower green sand mold 2d can be reduced. Therefore, the kneading cost for kneading raw sand 7 is reduced. The minimum thickness of the lower backup sand 4d layer is indicated by pd.

  Next, the upper fresh sand mold apparatus 1u will be described with reference to FIG. The upper fresh sand mold apparatus 1u is basically manufactured in the same procedure as the lower fresh sand mold apparatus 1d. The produced upper fresh sand mold apparatus 1u has basically the same structure as the lower fresh sand mold apparatus 1d, and is formed by pressing an aggregate 70 of fresh sand 7 containing an inorganic binder. It has a sand mold 2u, an upper casting frame 3u having a square frame shape for accommodating the upper raw sand casting mold 2u, and upper backup sand 4u (backup material) loaded in the upper casting mold 3u. As shown in FIG. 3, the upper model 5u has an upper surface plate 50u and an upper model part 51u.

  An upper model portion 51u is disposed on the surface 201 of the upper fresh sand mold 2u. The back surface 202 of the upper fresh sand mold 2u faces away from the upper model portion 51u.

  The upper backup sand 4u is disposed in a space portion on the back surface 202 side of the upper green sand mold 2u in the upper casting frame 3u, and backs up and reinforces the back surface 202 side of the upper green sand mold 2u. Yes. Thus, the back surface 202 side of the upper fresh sand mold 2u is backed up and reinforced by the upper backup sand 4u. For this reason, since the thickness and volume of the upper fresh sand mold 2u can be reduced, the amount of fresh sand 7 used by the upper fresh sand mold 2u can be reduced. Therefore, the kneading cost for kneading raw sand 7 is reduced. A support surface plate 25u that can also function as a weight is placed on the upper backup sand 4u to further enhance the backup performance. Here, when the sand particles of the upper backup sand 4u are 100 parts by mass, the water content can be 1 to 3 parts by mass, and the inorganic binder (bentonite) can be 0 to 1 part by mass. However, it is not limited to this.

  At an appropriate time, the upper model 5u is released from the upper raw sand mold 2u, and an upper casting cavity 20u (see FIG. 4) is obtained. The upper model 5u is formed by an upper surface plate 50u and an upper model part 51u. The minimum wall thickness of the upper backup sand 4u layer is denoted by pu.

  As shown in FIG. 4, the upper fresh sand mold apparatus 1u is assembled on the upper side, and the lower fresh sand mold apparatus 1d is assembled on the lower side, whereby the fresh sand mold apparatus 1 is formed. In this case, the lower fresh sand mold apparatus 1d is turned upside down. At the time of upside down, the fall of the lower backup sand 4d due to gravity is suppressed by the support surface plate 25d.

  The upper casting cavity 20u and the lower casting cavity 20d are integrated to form the casting cavity 20. As shown in FIG. 5, when the molten M of cast iron is poured into the casting cavity 20, and the molten M is solidified, the cast iron M1 is formed. Here, the lower backup sand 4d and the upper backup sand 4u basically do not contain or contain a binder. Furthermore, there is less moisture than fresh sand 7. For this reason, the gas permeability of the lower backup sand 4d and the upper backup sand 4u is enhanced. Therefore, at the time of pouring, the gas releasing property for releasing the gas in the casting cavity 20 is enhanced, which can contribute to the reduction of gas defects in the cast iron M1. Furthermore, when the size of the sand particles of the lower backup sand 4d and the upper backup sand 4u is larger than the size of the sand particles of the raw sand 7, the gas permeability is further enhanced.

  Moreover, in taking out the cast iron M1 in the mold releasing step, it is preferable to turn the upper fresh sand mold apparatus 1u upside down as shown in FIG. In this case, the upper backup sand 4u is lowered and removed in the direction of the arrow D1 by gravity unless it is burned. Furthermore, as shown in FIG. 7, if the supporting surface plate 25d of the lower raw sand mold apparatus 1d is removed, the lower backup sand 4d is lowered and removed by gravity in the direction of arrow D2 unless it is seized. Here, the lower backup sand 4d and the upper backup sand 4u basically do not contain or contain a binder. For this reason, the lower backup sand 4d and the upper backup sand 4u have high disintegration and fluidity at the time of mold release, and the mold releasing process is facilitated. In particular, the lower back-up sand 4d and the upper back-up sand 4u have a low moisture content, and when they are in a dry state, high disintegration and fluidity can be obtained, and the mold release process becomes easier.

  Further, even when the lower raw sand mold 2d is collapsed together with the lower backup sand 4d in the mold releasing step, the lower raw sand mold 2d is agglomerated, but the lower backup sand 4d has high fluidity. Therefore, if vibration is applied, separation of both becomes easy. The same applies to the upper fresh sand mold 2u.

  As described above, according to this embodiment, although the thickness of the lower raw sand mold 2d disposed in the lower casting frame 3d is thin, the lower raw sand mold 2d is lower in the lower casting mold 3d. Backed up by side backup sand 4d and reinforced. For this reason, since the volume of the lower green sand mold 2d can be reduced, the amount of green sand 7 used by the lower green sand mold 2d can be reduced. Therefore, the kneading cost for kneading raw sand 7 is reduced. Similarly, although the thickness of the upper fresh sand mold 2u arranged in the upper casting frame 3u is thin, the upper fresh sand mold 2u is backed up and reinforced by the upper backup sand 4u in the upper casting mold 3u. For this reason, since the volume of the upper fresh sand mold 2u can be reduced, the amount of fresh sand 7 used by the upper fresh sand mold 2u can be reduced. Therefore, the kneading cost for kneading raw sand 7 is reduced. The regeneration process for regenerating the fresh sand 7 affected by the hot molten metal M is also reduced.

  According to this embodiment, when molding the lower raw sand mold 2d, the raw sand 7 is pressurized at a portion corresponding to the lower raw sand mold 2d having a reduced thickness. Therefore, the pressurization efficiency can be made higher than that of the prior art. Similarly, when molding the upper fresh sand mold 2u, the fresh sand 7 is pressurized at a portion corresponding to the upper fresh sand mold 2u having a reduced thickness. Therefore, the pressurization efficiency can be made higher than that of the prior art. For this reason, the pressure strength of the lower fresh sand mold 2d and the upper fresh sand mold 2u can be increased, the density of the lower fresh sand mold 2d and the upper fresh sand mold 2u can be increased, and the lower side The dimensional accuracy and casting surface of the green sand mold 2d and the upper green sand mold 2u can be improved.

  When molten metal is poured into the casting cavity 20, the lower fresh sand mold 2d and the upper fresh sand mold 2u are likely to be displaced away from each other by the molten metal pressure. In this case, since the lower backup sand 4d and the upper backup sand 4u act as resistors against the displacement, the displacement described above is suppressed, and the dimensional accuracy of the cast iron is maintained well.

  According to this embodiment, if the minimum wall thickness pu (see FIG. 3) of the upper backup sand 4u and the minimum wall thickness pd (see FIG. 2) of the lower backup sand 4d are increased, the upper backup sand 4u and the lower backup sand 4u. It can be expected that the amount of sand 4d used will increase and the cooling rate of the molten metal and cast iron in the casting cavity 20 (the temperature passing through the A1 transformation point during cooling) will slow down. Further, if the minimum wall thicknesses pu and pd are reduced, the amount of use of the upper backup sand 4u and the lower backup sand 4d is reduced, and the cooling rate of the molten metal and cast iron in the casting cavity 20 can be promoted. The upper backup sand 4u and the lower backup sand 4d can be in a dry state.

  By adjusting the wall thickness pu and wall thickness pd as described above, the metal structure (ferrite ratio, pearlite ratio) and graphite morphology (graphite grain number, graphite size) of the cast iron M1 can be adjusted. When the cooling rate of the molten metal M and the cast iron M1 in the casting cavity 20 is high (the A1 transformation point passage temperature during cooling), the ferrite rate is decreased and the pearlite rate is increased. Furthermore, the number of graphite grains can be increased and the graphite size can be reduced. On the other hand, when the cooling rate of the molten metal M and the cast iron M1 is slow, the ferrite rate is increased and the pearlite rate is decreased. Furthermore, the number of graphite grains can be reduced and the graphite size can be increased.

(Embodiment 2)
FIG. 8 shows the test results representing the relationship between the green sand temperature and the effective binder residual rate. The effective binder remaining ratio means the ratio of the effective inorganic binder remaining after pouring. As can be understood from FIG. 8, in order to increase the effective binder residual ratio, it is preferable to maintain the green sand temperature at 500 ° C. or lower, particularly 400 ° C. or lower. FIG. 9 shows test results representing the relationship between the elapsed time from the start of pouring and the mold sand temperature. The mold sand temperature was measured when the distance from the molten metal contact surface was 5 mm, 10 mm, 20 mm, or 40 mm. As shown in FIG. 9, the mold sand temperature gradually increases with the elapsed time. The shorter the distance from the molten metal contact surface, the faster the mold sand temperature rise rate. If the distance from the molten metal contact surface is 40 millimeters, the temperature rise of the mold sand temperature at the distance is suppressed to about 100 ° C.

  By the way, before pouring, the upper fresh sand mold 2u and the lower fresh sand mold 2d have moisture. For this reason, when molten metal is poured into the casting cavity 20, the moisture contained in the upper fresh sand mold 2u and the lower fresh sand mold 2d is vaporized by the heat of the molten metal and cast iron in the casting cavity 20, and the water vapor is An attempt is made to evaporate to the opposite side of the cast iron in the casting cavity 20. Here, when the mold sand temperature exceeds 100 ° C., it is considered that the moisture is vaporized. If the mold sand temperature is around 100 ° C., the vaporized water vapor is condensed to form water, and the condensed water layer 200 is formed inside the upper fresh sand mold 2u and the lower fresh sand mold 2d. Here, in the upper fresh sand mold 2u and the lower fresh sand mold 2d, cracks may occur during the pouring due to the molten metal pressure or the like, and may develop. If the crack progresses greatly, there is a risk that the dimensional accuracy of the cast iron will decrease.

  Therefore, according to the present embodiment, as schematically shown in FIG. 10, the wall thickness tu of the upper fresh sand mold 2u is a meat that can form a condensed water layer 200 generated during pouring in the upper fresh sand mold 2u. The thickness is set. Similarly, the wall thickness td of the lower raw sand mold 2d is set to a thickness capable of forming the condensed water layer 200 generated during pouring in the lower raw sand mold 2d.

  Therefore, even if a crack occurs in the lower fresh sand mold 2d and the upper fresh sand mold 2u, the condensed water layer 200 described above has abundant moisture and has a low mold rigidity, and therefore suppresses further progress of the crack. Has an effect. For this reason, if the lower fresh sand mold 2d and the upper fresh sand mold 2u are set to a thickness that can include the condensed water layer 200, an effect of suppressing the progress of the crack can be obtained even if a crack occurs. Here, it is estimated that the condensed water layer 200 is formed when the mold sand temperature is in the range of 90 to 100 ° C. Accordingly, the wall thickness tu of the upper fresh sand mold 2u and the wall thickness td of the lower fresh sand mold 2d are preferably about 10 to 40 millimeters. However, it is not limited to this. With this thickness, the condensed water layer 200 having an effect of suppressing crack propagation can be formed inside the lower fresh sand mold 2d and the upper fresh sand mold 2u. In addition, it is preferable that the particle size of the sand particles constituting the lower backup sand 4d and the upper backup sand 4u is larger than the particle size of the sand particles constituting the raw sand 7 in order to improve the gas releasing property.

(Embodiment 3)
The present embodiment has basically the same configuration and operational effects as the first and second embodiments. However, unlike Embodiment 2, the wall thickness tu of the upper fresh sand mold 2u is set to a size that does not form the condensed water layer 200 generated during pouring in the upper fresh sand mold 2u. Similarly, the wall thickness td of the lower raw sand mold 2d is set to a size such that the condensed water layer 200 generated during pouring is not formed inside the lower raw sand mold 2d. The aforementioned condensed water layer is formed inside the upper backup sand 4u and the lower backup sand 4d. At the time of pouring, the water content of the upper backup sand 4u is small, and when the upper backup sand 4u is 100 parts by mass, the water is 2 parts by mass or less, preferably 1 part by mass or less. Thus, the upper backup sand 4u is dry. The same applies to the lower backup sand 4d. Thus, the upper backup sand 4u and the lower backup sand 4d having a high degree of dryness not only ensure high gas release properties but also have an action of suppressing the progress of cracks.

(Embodiment 4)
11 and 12 show a fourth embodiment. The present embodiment has basically the same configuration and operational effects as the first embodiment. Hereinafter, a description will be given centering on differences from the first embodiment. FIG. 11 shows the lower pressurizing body 6d facing the aggregate 70 of fresh sand 7. The lower pressure body 6d is formed of a plurality of lower divided pressure bodies 600d that can be driven independently of each other. As shown in FIG. 11, each of the lower divided pressurizing bodies 600d includes a lower piston 60d and a hydraulic or pneumatic lower cylinder portion 62d (drive source) that moves the lower piston 60d forward and backward via a rod 61d. ) And are formed. Since the lower divided pressurizing bodies 600d can be driven independently of each other, the aggregate 70 of fresh sand 7 can be compressed for each region. Therefore, the movement stroke of the lower piston 60d of the lower divided drive body 600d may be increased in a region where the strength is particularly required in the lower raw sand mold 2d.

  On the other hand, in the region where the strength is not so required, the movement stroke of the lower piston 60d of the lower divided drive body 600d may be reduced. Here, since each lower cylinder part 62d is held by the common base part 620d, when the common base part 620d comes close to the lower casting frame 3d, each lower cylinder part 62d together with each lower piston 60d. It is possible to approach the lower casting frame 3d.

  FIG. 12 shows the upper pressurizing body 6 u facing the aggregate 70 of fresh sand 7. The upper pressure body 6u is formed of a plurality of upper divided pressure bodies 600u that can be driven independently of each other. Each of the upper divided pressurizing bodies 600u is formed by an upper piston 60u and a hydraulic or pneumatic upper cylinder portion 62u (drive source) that moves the upper piston 60u forward and backward through a rod 61u. Since the upper divided pressure bodies 600u can be driven independently from each other, the aggregate 70 of the fresh sand 7 can be individually compressed. Therefore, in the upper fresh sand mold 2u, in the region where the strength is particularly required, the moving stroke of the upper piston 60u may be increased.

  On the other hand, the movement stroke of the upper piston 60u may be reduced in the region where the strength is not so required. Here, since each upper cylinder part 62u is hold | maintained at the common base part 620u, if the common base part 620u approaches with respect to the upper casting frame 3u, each upper cylinder part 62u will be set to upper casting frame 3u with each upper piston 60u. Can approach.

(Embodiment 5)
Since this embodiment basically has the same configuration and the same function and effect as those of Embodiments 1 to 4, FIGS. 1 to 12 are applied mutatis mutandis. Hereinafter, a description will be given centering on differences from the first to fourth embodiments. FIG. 13 shows the temperature change in the process of pouring the molten metal into the casting cavity 20 to solidify and further cool it. As shown in FIG. 13, the temperature of the cast iron after pouring gradually decreases. Here, if the moisture content in the lower backup sand 4d and the upper backup sand 4u is adjusted, the cooling rate (A1 transformation point passing temperature) of the molten metal and cast iron in the casting cavity 20 can be adjusted. This is because the latent heat when water is steamed is large.

  In order to increase the ferrite rate in the cast iron structure, it is preferable to reduce the cooling rate of the cast iron. Therefore, it is preferable to relatively reduce the amount of water in the lower backup sand 4d and the upper backup sand 4u. For example, the moisture content of the raw sand 7 can be reduced to a dry state to increase the heat retention. On the other hand, in order to increase the pearlite rate in the cast iron structure, it is preferable to increase the cooling rate of the cast iron. Therefore, it is preferable to relatively increase the amount of water in the lower backup sand 4d and the upper backup sand 4u. For example, it is possible to increase the water content of the raw sand 7 and increase the cooling rate of the molten metal and cast iron with the heat of vaporization of water.

  For this reason, according to the present embodiment, the cast iron structure is obtained by adjusting the water content in the lower backup sand 4d and the upper backup sand 4u while ensuring the moldability of the lower fresh sand mold 2d and the upper fresh sand mold 2u. It is possible to adjust the ferrite ratio and / or the pearlite ratio. The number and / or size of graphite particles per unit area can be adjusted. In general, as the ferrite rate increases, the ductility of the cast iron improves, and as the pearlite rate increases, the strength of the cast iron increases. In general, the strength of cast iron increases as the size of graphite decreases, and the vibration damping capacity of cast iron increases as the size of graphite increases.

  According to this embodiment, even if the moisture content of the lower backup sand 4d is adjusted, basically, the strength of the lower raw sand mold 3d itself is not affected. Furthermore, the backup capability by the lower backup sand 4d is basically not affected. Similarly, the same applies to the upper backup sand 4u. For this reason, the moisture adjustment in the lower backup sand 4d and the upper backup sand 4u can be widened from the dry state to the wet state, and the width of the cast iron structure adjustment and the graphite adjustment can be widened.

  According to this embodiment, it is preferable to increase the sensitivity that moisture in the lower backup sand 4d and the upper backup sand 4u affects the cooling rate of cast iron. Accordingly, the wall thickness td of the lower raw sand mold 2d and the wall thickness tu of the upper raw sand mold 2u can be reduced to 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less. However, it is not limited to this.

(Embodiment 6)
Since this embodiment basically has the same configuration and the same operation and effect as those of the first to fourth embodiments, FIGS. Hereinafter, a description will be given centering on differences from the first and second embodiments. As described above, the temperature of the cast iron after pouring gradually decreases. If the moisture content in the lower backup sand 4d and the upper backup sand 4u is adjusted, the cooling rate of the cast iron can be adjusted. This is because the latent heat when water is steamed is large.

  In the case of spheroidal graphite cast iron, it is preferable to reduce the cooling rate of cast iron in order to reduce the number of graphite per unit area in the cast iron structure. Therefore, it is preferable to relatively reduce the amount of water in the lower backup sand 4d and the upper backup sand 4u. In order to increase the number of graphite per unit area in the cast iron structure, it is preferable to increase the cooling rate of the cast iron. Therefore, the amount of water in the lower backup sand 4d and the upper backup sand 4u can be relatively increased. For this reason, the graphite per unit area of the cast iron structure is adjusted by adjusting the water content in the lower backup sand 4d and the upper backup sand 4u while ensuring the moldability of the lower fresh sand mold 2d and the upper fresh sand mold 2u. The number can be adjusted. In general, as the number of graphite increases, the graphite size decreases. As the number of graphite decreases, the graphite size increases. It is possible to increase the sensitivity that moisture in the lower backup sand 4d and the upper backup sand 4u affects the cooling rate of the cast iron. Therefore, the wall thickness td of the lower raw sand mold 2d and the wall thickness tu of the upper raw sand mold 2u can be reduced to 50 mm or less, 40 mm or less, or 30 mm or less. However, it is not limited to this.

  According to the present embodiment, as described above, even if the moisture content of the lower backup sand 4d is adjusted, basically, the strength of the lower raw sand mold 3d itself is not affected. Similarly, even if the moisture content of the upper backup sand 4u is adjusted, basically, the strength of the upper fresh sand mold 3u itself is not affected. For this reason, the width of moisture adjustment in the lower backup sand 4d and the upper backup sand 4u can be widened, and the width of structure adjustment and graphite adjustment can be widened.

(Embodiment 7)
FIG. 14 shows a seventh embodiment. This embodiment has basically the same configuration and the same operation and effect as the first embodiment. A description will be given centering on differences from the first embodiment. First, similarly to the above-described embodiments, the lower raw sand mold 2d is formed in the lower casting frame 3d. Thereafter, the lower back-up sand 4d is charged by gravity or a centrifugal impeller. Thereafter, the lower surface plate 25d is fitted into the opening 302 of the lower casting frame 3d, and the support surface plate 25d is placed on the lower backup sand 4d. In this state, the lower back-up sand 4d is pressed in the thickness direction of the lower raw sand mold 2d by the lower pressure body 6d (other pressure bodies may be used). It is preferable to vibrate the lower back-up sand 4d by vibrating the lower casting frame 3d before pressurization or simultaneously with pressurization, thereby increasing the loading rate of the lower back-up sand 4d.

  At the time of pressurization, as shown in FIG. 14, the lower model part 51d exists so as to face the lower raw sand mold 2d. For this reason, the profile shape of the lower raw sand mold 2d is favorably maintained without collapsing. According to this embodiment, the loading density of the lower backup sand 4d can be increased, and the reinforcing effect can be further enhanced. Therefore, it is possible to contribute to reducing the thickness of the lower raw sand mold 2d and reducing the amount of the lower backup sand 4d used. Furthermore, by adjusting the pressure applied to pressurize the lower backup sand 4d, the loading density of the lower backup sand 4d can be adjusted, and as a result, the gas release property of the lower backup sand 4d can be adjusted. The upper fresh sand mold 2u is formed in the same procedure.

(Embodiment 8)
15 and 16 show the eighth embodiment. This embodiment has basically the same configuration and the same operation and effect as the first embodiment. A description will be given centering on differences from the first embodiment. The raw sand 7W includes a thermosetting resin that can be thermoset, an inorganic binder (bentonite), and water. For example, when the raw sand 7W is 100 parts by mass, 0.01-20 parts by mass of the thermosetting resin, 5-10 parts by mass of the inorganic binder, and 3-30 parts by mass of water are blended. The thermosetting resin is exemplified by a phenol resin or an epoxy resin. The phenol resin may be a resol type or a novolac type.

  In the microwave irradiation apparatus 200, before irradiating the microwave 215, the green sand 7W is pressure-formed by the lower pressurizing body 6d, and the lower green sand mold 2d is formed in the lower casting frame 3d. Thereafter, the lower raw sand mold 2d is irradiated with the microwave 215 from the microwave irradiator 210 of the microwave irradiation apparatus 200 for a predetermined time (for example, 5 seconds to 600 seconds). As a result, the water contained in the surface layer of the lower raw sand mold 2d is heated by the irradiation of the microwave 215 and becomes high temperature. For this reason, the thermosetting resin contained in the surface layer of the lower raw sand mold 2d is thermoset. As a result, a lower green sand mold 2d having a hardened surface layer 20m is formed.

  Here, the microwave is preferably a radio wave having a wavelength of 100 cm to 0.3 mm, 30 cm to 0.3 mm, and a frequency of 0.3 GHz to 1 THz, 1 GHz to 1 THz (1000 GHz). The wavelength of the microwave may be any wavelength that allows dielectric heating of water. Thereafter, as shown in FIG. 16, the lower back sand 4d can be loaded on the back surface 202 side of the lower fresh sand mold 2d to manufacture the lower fresh sand mold apparatus 1d. Although not shown, the upper fresh sand mold apparatus 1u can be formed in the same manner.

  Note that after forming the lower fresh sand mold 2d outside the microwave irradiation apparatus 200, the lower fresh sand mold 2d may be accommodated in the microwave irradiation apparatus 200 and irradiated with the microwave 215. .

  The lower casting frame 3d and the lower model 5d described above can be formed of a material that can transmit microwaves, such as wood, glass material, ceramic material, and resin material. Wood is particularly preferable. Since the lower raw sand mold 2d irradiated with the microwave has the hardened surface layer 20m, it is reinforced. Therefore, the lower green sand mold 2d can be thinned, and the amount of green sand 7W used can be saved. The upper fresh sand mold can be formed by the same procedure.

(Embodiment 9)
The present embodiment basically has the same configuration and the same function and effect as the above-described first to eighth embodiments. However, the particle size (average particle size) of the sand particles of the lower backup sand 4d and the upper backup sand 4u is smaller than the particle size (average particle size) of the sand particles constituting the raw sand 7 and 7W. For this reason, although the gas release properties of the lower backup sand 4d and the upper backup sand 4u are lowered, the loading density is increased, and the backup performance can be enhanced to enhance the reinforcing effect.

(Embodiment 10)
The present embodiment basically has the same configuration and the same function and effect as the above-described first to eighth embodiments. However, the particle size (average particle size) of the sand particles of the lower backup sand 4d and the upper backup sand 4u is approximately the same as the particle size (average particle size) of the sand particles constituting the raw sand 7 and 7W. .

(Other)
The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within a range not departing from the gist. Since each embodiment is merely an example, a configuration peculiar to a certain embodiment may be combined with another embodiment.

  The present invention can be used for producing cast iron such as flake graphite cast iron, spheroidal graphite cast iron, worm-like graphite cast iron, eutectic graphite cast iron, alloy cast iron and the like.

It is sectional drawing which shows the process in which a lower raw sand mold apparatus is manufactured. It is sectional drawing which shows a lower raw sand mold apparatus. It is sectional drawing which shows an upper fresh sand mold apparatus. It is sectional drawing which shows the fresh sand mold apparatus which assembled | attached the upper fresh sand mold apparatus and the lower fresh sand mold apparatus. It is sectional drawing which shows the state which shape | molds cast iron by the casting cavity of a fresh sand mold apparatus. It is a sectional view showing the state where the upper back sand is discharged by turning the upper fresh sand mold device upside down. It is sectional drawing which shows the state which is discharging | emitting lower backup sand from a lower raw sand mold apparatus. It is a graph which shows the relationship between green sand temperature and an effective binder residual rate. It is a graph which shows the relationship between elapsed time and mold sand temperature. It is sectional drawing which shows a condensed water layer. It is sectional drawing which shows the process in connection with Embodiment 4 and manufacturing a lower side raw sand mold apparatus. It is sectional drawing which shows the process in connection with Embodiment 4 and manufacturing an upper fresh sand mold apparatus. It is a graph which concerns on Embodiment 5 and shows the cooling temperature of the cast iron in a casting cavity. It is sectional drawing which shows the process in connection with Embodiment 7 and manufacturing a lower raw sand mold apparatus. It is sectional drawing which shows the process in connection with Embodiment 8 and manufacturing a lower raw sand mold apparatus. It is sectional drawing which concerns on Embodiment 8 and shows a lower side fresh sand mold apparatus.

Explanation of symbols

  1d is lower green sand mold device, 1u is upper green sand mold device, 2d is lower green sand mold, 2u is upper green sand mold, 3d is lower casting frame, 3u is upper casting frame, 4d is lower backup Sand (backup material), 4u is upper backup sand (backup material), 5d is a lower model, and 5u is an upper model.

Claims (8)

(I) a green sand mold formed by pressing an aggregate of green sand containing an inorganic binder and having a casting cavity on the surface;
(Ii) a casting frame that accommodates the green sand mold;
(Iii) It is disposed in a space portion on the back surface side facing away from the surface of the green sand mold in the space in the cast frame, and the back surface side of the green sand mold in the cast frame is backed up. And a backup material that does not contain the inorganic binder or the inorganic binder is 1/5 or less of the blending ratio of the inorganic binder in the raw sand , A fresh sand mold apparatus which is an aggregate of particles and contains water as a binder . 2. The raw sand mold apparatus according to claim 1 , wherein the particle size of the particles constituting the backup material is larger than the particle size of the sand particles constituting the green sand mold. 3. The fresh sand mold according to claim 1 , wherein the fresh sand mold is set to a thickness that forms a condensed water layer formed by condensation of water vapor generated during pouring in the fresh sand mold. Green sand mold equipment to do. 3. The thickness of the green sand mold according to claim 1 or 2 , wherein the green sand mold is formed inside the backup material without forming a condensed water layer formed by condensation of water vapor generated during pouring in the green sand mold. A fresh sand mold device characterized by being set to. (I) Raw sand containing an inorganic binder and a backup in which the inorganic binder is not contained or the inorganic binder is 1/5 or less of the blending ratio of the inorganic binder in the raw sand. Preparing the material,
(Ii) a loading step of loading the green sand aggregate into the space of the casting frame in a state where a model for forming the casting cavity is disposed in the casting frame;
(Iii) After that, in a state where the model and the aggregate of fresh sand face each other, the aggregate of fresh sand in the casting frame is compressed with a pressure body from the side facing away from the model. A molding process for molding the green sand mold in the casting frame,
(Iv) After that, by inserting the backup material on the side of the green sand mold facing away from the model in the casting frame, the model or the casting cavity and the back of the green sand mold look contains a reinforcing step of reinforcing the side of the backup material is an aggregate of particles, green sand mold formation method which comprises water as binder. 6. The green sand mold making method according to claim 5 , wherein the pressure body is divided into a plurality of divided pressure bodies that can be driven independently of each other. 7. The green sand mold making method according to claim 5 , wherein the water content of the backup material is adjusted according to the structure of cast iron and / or graphite formed by the green sand mold. In one of Claims 5-7 , in the said reinforcement | strengthening process, in the state which the said fresh sand mold and the said model are facing, loading of the said backup material is performed by applying a pressurizing force and / or a vibration to the said backup material. A green sand mold making method characterized by increasing the rate.

Images