JP6142953B1 - Casting method and a pair of molds - Google Patents

Abstract

Provided is a technique capable of realizing a sufficiently low cooling rate and prevention of deterioration of a mold without increasing the thickness of a sand layer. In a casting method of casting a product using a pair of molds 100, 100 that form a pouring space V between molds by matching the molds, first, a pouring surface region 11 that forms the pouring space V is provided. A pair of molds 100, 100 in which the pouring surface region 11 of the mold 1 having a surface is covered with the sand layer 2 is prepared (preparation process), and the pair of molds 100, 100 are mold-matched (mold matching process) ( Step S101). And a molten metal is inject | poured into the pouring space V (pouring process) (step S103). Before or after the pouring step, a gap Q is formed between the mold 1 and the sand layer 2 (gap forming step) (step S102). Then, after the pouring step and the gap forming step, the mold 1 is completely separated from the sand layer 2 (separation step) (step S104). [Selection] Figure 4

Description

  The present invention relates to a technique for casting a product using a pair of molds that form a pouring space between the molds by matching the molds.

  As a casting method, a pair of molds are partly aligned on a parting surface, and a liquid metal (molten metal) is poured (pouring) into a pouring space (a space having a product shape) formed between them. It is well known that the molten metal in the pouring space is naturally cooled and solidified in a state, and after the molten metal has solidified, both molds are separated and the shaped product is taken out.

  In this casting method, depending on the type of metal, the temperature profile when the molten metal solidifies greatly affects the state of the finished product. For example, in the case of cast iron that is most commonly used, if the cooling rate of the molten metal is too fast, the resulting product will be hard and brittle. In order to avoid this, the cooling rate of the molten metal must be sufficiently small.

  In order to reduce the cooling rate of the molten metal, it is preferable that the mold is formed of a material having a low thermal conductivity. As molds, metal molds and sand molds formed using sand (cast sand) are well known, but sand molds are preferable to molds in order to reduce the cooling rate of the molten metal. It can be said.

  However, the sand mold needs to be newly formed every time it is cast, and sand processing equipment is required to circulate and use the foundry sand, and the working environment is poor. Further, since it is difficult to control the cooling of the injected molten metal, there is a problem that it takes a long time for cooling and the working efficiency is poor.

  Thus, for example, Patent Document 1 describes a mold in which a sand coating layer (sand layer) is formed on the product cavity surface of a metal base. When this mold is used, the molten metal is not in contact with a metal base, but is in contact with a sand layer having a lower thermal conductivity. Therefore, compared to a normal mold in which the entire mold is made of metal, The cooling rate can be reduced. On the other hand, since the main part of the mold is formed of a metal that can be used repeatedly, the sand layer can be formed efficiently in a short time compared to a normal sand mold in which the entire mold is formed of sand. The amount of sand required for casting is less.

JP 2004-1024

According to the mold of Patent Document 1, since the thickness of the sand layer covering the molten metal is thin, the cooling rate cannot be sufficiently reduced, and in many cases, it is still hard and brittle compared to products manufactured with conventional sand molds. There is. In addition, since the sand layer is thin and its heat insulating effect is weak, the metal base is greatly damaged by the molten metal. Therefore, there is a problem that the number of times the mother body can be used repeatedly is reduced.
On the other hand, if the thickness of the sand layer is increased in order to enhance the heat insulation effect, the amount of sand required for one casting increases and the time required for forming the sand layer also increases.

  The problem to be solved by the present invention is to provide a technique capable of realizing a sufficiently low cooling rate and prevention of deterioration of the mold without increasing the thickness of the sand layer.

The present invention made to solve the above problems
A casting method for casting a product using a pair of molds that form a pouring space between the molds,
a) a preparation step of preparing a pair of molds in which the pouring surface area of the mold having the pouring surface area forming the pouring space is covered with a sand layer;
b) a mold matching step of matching the pair of molds;
c) a pouring step of injecting molten metal into the pouring space after the mold matching step;
d) a gap forming step of forming a gap between the mold and the sand layer before or after the pouring step;
e) a separation step of completely separating the mold from the sand layer after the pouring step and the gap formation step;
Is provided.

  By forming a gap between the mold and the sand layer covering the pouring surface area, an air layer is formed between the pouring surface area and the sand layer. Since air has a lower thermal conductivity than sand, this layer of air acts as a main heat insulating layer between the molten metal injected into the pouring space and the mold in the pouring step. Therefore, even if the sand layer is thin, the cooling rate of the molten metal can be made sufficiently small, and the mold can be prevented from being damaged by the heat of the molten metal. That is, a sufficiently low cooling rate and prevention of mold deterioration can be realized without increasing the thickness of the sand layer.

The size of the gap formed in the gap forming step (the thickness of the air layer) may be 0.1 mm or more in order to obtain the heat insulation effect. However, when this gap becomes excessively large, it becomes necessary to increase the thickness of the sand layer so that the molten metal poured into the pouring space can be reliably and independently held only by the sand layer. If this gap is 3 mm or less, even if an unforeseen situation where the pouring space cannot be held only by the sand layer occurs, the mold can be closed immediately and the pouring space can be closed. It is not necessary to increase the thickness of the sand layer in preparation for the situation.
Further, in the gap forming step, it is sufficient that a gap is formed between at least a part of the sand layer and the mold, and the gap does not necessarily have to be formed between the entire sand layer and the mold.
Further, the thickness of the sand layer in the pair of molds used here can be 10 mm or less, and particularly preferably about 2 mm.

  In the above casting method, if the gap forming step is performed before the pouring step, the cooling rate of the molten metal can be suppressed to a sufficiently small value from the start of pouring until the molten metal is solidified after being injected. The cooling profile can be particularly preferred. Moreover, according to this structure, since it can fully avoid that a metal mold | die receives a thermal damage by a molten metal, deterioration of a metal mold | die can fully be suppressed.

  On the other hand, in the above casting method, if the gap forming step is performed after the pouring step, no gap is formed between the sand layer and the mold while the molten metal is poured, and the sand layer is backed up by the mold. Since it is in a state, it is possible to avoid such a situation that the injected molten metal leaks from the pouring space, or the sand layer is damaged by an impact when the molten metal is injected.

In addition, when performing a clearance gap formation process after a pouring process, it is preferable to prescribe | regulate the timing which performs the said clearance gap formation process according to the timing when the state of the molten metal inject | poured into the pouring space changes.
For example, when the molten metal is a cast iron molten metal, the gap forming step may be performed at the timing when the graphite expansion ends. In this case, since the sand layer is backed up by the mold while the graphite expansion is occurring, it is possible to expect the effect of suppressing shrinkage nest generation due to the graphite expansion.
Further, for example, the gap forming step may be performed before the molten metal reaches the primary crystal temperature. In this case, since the molten metal can be kept at a sufficiently low cooling rate from the stage where the molten metal is in a liquid state, the cooling profile from when the molten metal is injected until solidified can be made sufficiently favorable.
Further, for example, the gap forming step may be performed after the molten metal reaches the primary crystal temperature and before reaching the eutectic temperature, or after the molten metal reaches the eutectic temperature and reaches the A1 transformation point. You may go before.

The present invention is also directed to a pair of molds used for casting products. The pair of molds is
A pair of molds that form a pouring space between the molds by matching the molds,
A mold having a pouring surface region forming the pouring space;
A sand layer covering the pouring surface area;
A pin member provided so as to be able to appear and retract with respect to the pouring surface area;
Equipped with a,
When the pair of molds are aligned with each other, the two molds are moved relative to each other in a direction away from each other, and the pin member protrudes from the pouring surface area. A gap is formed in the gap.

According to this configuration, in a state in which the pair of molds are matched with each other, the pin member provided on the mold is pushed in the direction protruding from the pouring surface region, is brought into contact with the sand layer, and is pressed against the sand layer. The sand layer can be supported in a matched state. From this state, by moving the pair of molds relative to each other in a direction away from each other with respect to the plurality of pin members, a gap can be formed between the sand layer and the mold in the mold-matched state. it can.

  According to the present invention, an air layer is formed between the pouring surface area and the sand layer by forming a gap between the mold and the sand layer covering the pouring surface area. Since air has a lower thermal conductivity than sand, this layer of air acts as a main heat insulating layer between the molten metal injected into the pouring space and the mold. Therefore, even if the sand layer is thin, the cooling rate of the molten metal can be made sufficiently small, and the mold can be prevented from being damaged by the heat of the molten metal. That is, a sufficiently low cooling rate and prevention of mold deterioration can be realized without increasing the thickness of the sand layer.

The figure which shows typically a pair of casting_mold | template which concerns on embodiment. The figure which shows typically the state in which the pair of casting_mold | templates matched type | mold, and the state in which the clearance gap was formed between the metal mold | die and the sand layer. The figure for demonstrating the manufacturing method of a pair of casting_mold | template. The figure for demonstrating the method of casting a product using a pair of casting_mold | template. The figure which shows the cooling curve of a molten metal typically. The figure which shows the temperature change of a metal mold | die typically. The figure for demonstrating another method of casting a product using a pair of casting_mold | template.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

<1. Mold configuration>
The configuration of the pair of molds according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a side sectional view schematically showing a pair of molds 100, 100. FIG. 2 is a side cross-sectional view schematically showing a state in which the pair of molds 100 and 100 are matched with each other and a state in which a gap is formed between the mold 1 and the sand layer 2.

  The pair of molds 100 and 100 are arranged opposite to each other to form a pouring space V between them, and each mold 100 is composed of a mold 1 and a thin sand layer formed thereon. 2 and a plurality of pin members 3 provided on the mold 1.

  The mold 1 is made of metal (specifically, for example, cast iron), and has a surface region (a pouring surface region) 11 for forming a pouring space V and a parting surface 12 connected to the main surface 10 side. Is formed. The pouring surface region 11 has a shape that is slightly larger than the outer shape of the product while imitating the outer shape of the product. Further, a part of the pouring surface area 11 forms a pouring gate for pouring the molten metal into the pouring space V. On the other hand, the parting surface 12 is formed so as to surround the pouring surface region 11 and has a flat shape.

The sand layer 2 is formed by firing sand (that is, cast sand, for example, resin-coated sand) (a specific forming method will be described later).
The sand layer 2 covers the pouring surface area 11. The portion of the sand layer 2 covering the pouring surface region 11 has a surface simulating the outer shape of the product. The sand layer 2 may further cover at least a part of the parting surface 12 of the mold 1 as well as the pouring surface region 11. In the illustrated example, the sand layer 2 is formed so as to cover the entire parting surface 12. However, the sand layer 2 does not necessarily have to cover the parting surface 12 and may be formed to cover only the pouring surface region 11.
The thickness of the sand layer 2 can be 10 mm or less, and particularly preferably about 2 mm.

The plurality of pin members 3 are members for forming gaps between the mold 1 and the sand layer 2. Each pin member 3 is, for example, an elongated rod-like member, and is inserted through a pin insertion hole 13 formed in the mold 1.
The pin insertion hole 13 has an inner diameter slightly larger than the outer diameter of the pin member 3, and opens at one end to the main surface 10 side of the mold 1 (that is, the pouring surface region 11 or the parting surface 12). It extends linearly and opens at the other end on the back surface of the mold 1 (surface opposite to the main surface 10). The mold 1 has the same number of pin insertion holes 13 as the pin members 3. The plurality of pin insertion holes 13 are preferably laid out uniformly with respect to the mold 1.
Each of the plurality of pin members 3 is inserted into one of the plurality of pin insertion holes 13 and arranged so that one end thereof coincides with (is flush with) the pouring surface region 11 or the parting surface 12. In the state, they are connected to each other via the connecting member 30 at the other end (that is, on the back side of the mold 1). In this configuration, the tip of each pin member 3 is moved with respect to the pouring surface region 11 or the parting surface 12 by moving the connecting member 30 in a direction to approach or separate from the back surface of the mold 1. Can be infested synchronously.

  When a pair of molds 100 having such a configuration are matched (left side in FIG. 2), a pouring space V is formed between them. The pouring space V is a space surrounded by the sand layer 2 and surrounded by the mold 1 (that is, a space doubled by the sand layer 2 and the mold 1). In this state, the plurality of pin members 3 are pressed in the direction protruding from the pouring surface area 11 or the parting surface 12 and brought into contact with and pressed against the sand layer 2, whereby the pair of sand layers 2 are matched with each other (That is, a state in which the peripheral edges are in close contact with each other). Then, from this state, the plurality of pin members 3 are fixed, and only the pair of molds 1 are moved relative to each other in a direction away from each other, whereby the sand layer 2 (that is, the sand layer in a matched state). A gap Q can be formed between 2) and the mold 1.

<2. Manufacturing method of mold 100, 100>
An example of a method for manufacturing the molds 100 will be described with reference to FIG. 3 in addition to FIGS. FIG. 3 is a diagram for explaining the method.

Step S1: First, a pair of molds 1 and a casting target product model 7 are prepared. As described above, the pouring surface region 11 and the parting surface 12 connected thereto are formed on the main surface 10 of the mold 1. The die 1 is formed with a plurality of pin insertion holes 13 (not shown in FIG. 3) that penetrate from the main surface 10 side to the back side, and the pin member 3 is inserted into each pin insertion hole 13. Yes.
The model 7 includes a thin flat plate portion 71. Shape portions (product shape portions) 72 and 73 simulating the product shape are formed on the main surfaces of the thin plate portion 71. Further, the model 7 has a built-in heater.

Step S2: Next, a pair of molds 1 are arranged opposite to each other with the parting surface 12 sandwiched between the models 7. Here, a plurality of rod-like protrusions 711 are provided on the model 7 (preferably, the thin plate portion 71 of the model 7) at intervals, and the protrusions 711 allow the mold 1 and the model 7 to be connected to each other. A gap 20 is formed between them.
What is necessary is just to prescribe | regulate the magnitude | size (specifically the separation distance between the pouring surface area | region 11 and the product shape parts 72 and 73 of the model 7) of this clearance gap 20 according to the thickness of the sand layer 2 to form. For example, when it is desired to form the sand layer 2 having a thickness of 2 mm, the size of the gap 20 may be about 2 mm. The size of the gap 20 can be adjusted by the size of the protrusion 711.
The gap 20 may extend between the parting surface 12 and the thin plate portion 71 of the model 7. In this case, the dimension between the parting surface 12 and the thin plate portion 71 is preferably about 0.3 mm. When the gap 20 extends between the parting surface 12 and the thin plate portion 71, the sand layer 2 that covers not only the pouring surface area 11 but also the parting surface 12 is formed. However, the parting surface 12 and the thin plate portion 71 may be in contact with each other without any gap, and in this case, the sand layer 2 that covers only the pouring surface region 11 is formed.
Note that a flange portion 712 projecting outward is formed on the entire side surface of the thin plate portion 71 (however, excluding a portion of the upper side surface and a portion of the lower side surface), and the flange portion 712 is a mold. By abutting on the outer peripheral surface of 1, the gap 20 becomes a closed space while forming openings on the top and bottom.

Step S3: Next, the gap 80 between the mold 1 and the model 7 is filled with sand 80. The sand 80 used here is foundry sand, specifically, aggregates (for example, dredged sand, mountain sand, alumina sand, olivine sand, chromite sand, zircon sand, mullite sand, artificial sand, hollow particles ( Specifically, for example, hollow ceramic particles), etc. are coated with a thermosetting resin such as a phenol-based resin, which is a so-called “resin coated sand (RCS)”. By using hollow particles as the aggregate, the sand layer 2 can be a heat insulating layer having a high heat insulating effect.
When filling the gap 80 with the sand 80, specifically, the sand supply cup 81 is set in the upper opening of the gap 20 and the suction device 82 is set in the lower opening. Then, a suction pressure is formed by the suction device 82 in the lower opening while supplying the sand 80 from the sand supply cup 81 toward the gap 20 through the upper opening. As a result, the sand 80 is filled into the gap 20. However, the method of filling the gap 80 with the sand 80 is not limited to this, and may be performed by, for example, a blow method (blow method).

  Step S4: When the sand 80 is filled in the entire gap 20, the sand 80 filled in the gap 20 is subsequently heated using a heater or the like built in the model 7. Then, the sand 80 filled in the gap 20 adheres to the mold 1 by the thermosetting reaction and is baked. As a result, a sand layer 2 covering the mold 1 is formed. When the size of the gap 20 is 2 mm, the thickness of the formed sand layer 2 is about 2 mm. In addition, when the gap 20 extends between the parting surface 12 and the model 7, the sand layer 2 that covers not only the pouring surface region 11 but also the parting surface 12 is formed.

  Step S5: Next, each mold 1 (that is, the mold 1 on which the sand layer 2 is formed) is completely separated from the model 7. Thus, a pair of molds 100, 100 are obtained.

<3. Manufacturing method of product 9>
Next, a method of casting a product (cast product) 9 using a pair of molds 100, 100 will be described with reference to FIG. FIG. 4 is a diagram for explaining the method.

  Step S101: First, for example, a pair of molds 100, 100 manufactured by the above manufacturing method is prepared (preparation process), and the molds are matched (mold matching process). Specifically, the molds 1 are arranged to face each other via the parting surface 12, and a pouring space V is formed between the pair of molds 100, 100. At this time, the plurality of pin members 3 are pushed in a direction protruding from the pouring surface region 11 or the parting surface 12 and brought into contact with and pressed against the sand layer 2 so that the pair of sand layers 2 are matched with each other. To support. As described above, since the pouring surface region 11 of each mold 1 is covered with the sand layer 2, the pouring space V is a space surrounded by the sand layer 2 and the mold 1.

Step S102: Next, a gap Q is formed between the mold 1 and the sand layer 2 (gap forming step). Specifically, for example, as described above, a plurality of pin members 3 (that is, a plurality of support pins 3 that support a pair of sand layers 2 in a matched state) are fixed to each other while a pair of them are fixed. A gap Q is formed between the sand layer 2 (that is, the sand layer 2 in a mold-matched state) and the mold 1 by relatively moving only the mold 1 away from each other. The gap Q only needs to be formed between at least a part of the sand layer 2 and the mold 1, and the gap Q is not necessarily formed between the entire sand layer 2 and the mold 1. For example, the gap Q is not formed between the surface of the sand layer 2 (surface on the mold 1 side) 201 parallel to the support pins 3 and the mold 1 in the second stage of FIG. A sufficient heat insulating effect can be obtained by the gap Q provided at the location. Of course, only such a surface 201 of the sand layer 2 is tapered (the surface on the molten metal 90 side is left as it is), and when the mold 1 is separated, there is also a gap between the surface 201 and the mold 1. May be provided.
However, the size of the gap Q formed here (the thickness of the air layer) may be 0.1 mm or more in order to obtain a heat insulating effect described later. However, if the gap Q becomes excessively large, it is necessary to increase the thickness of the sand layer 2 so that the molten metal 90 poured into the pouring space V can be held independently and reliably only by the sand layer 2. If this gap Q is 3 mm or less, even if an unexpected situation occurs in which the pouring space V cannot be held only by the sand layer 2, the mold 1 can be closed immediately and the pouring space V can be closed. It is not necessary to increase the thickness of the sand layer 2 in preparation for such an unexpected situation.

  Step S103: Next, molten metal (for example, cast iron melt) 90 is poured into the pouring space V through the pouring gate (pouring step). Here, the molten metal 90 contacts the sand layer 2 formed of sand having a relatively low thermal conductivity. Further, here, since the gap Q is formed between the sand layer 2 and the mold 1, an air layer is formed between the mold 1 and the sand layer 2. Since air has a lower thermal conductivity than sand, this layer of air acts as a main heat insulating layer between the molten metal 90 injected into the pouring space V and the mold 1 in the pouring step. Therefore, even if the thickness of the sand layer 2 is thin, the cooling rate of the molten metal 90 can be made sufficiently small, and the mold 1 is sufficiently suppressed from being damaged by the heat of the molten metal 90. In the description of this specification, the “molten metal 90” is not limited to the liquid state, but also refers to the one after it has solidified.

  FIG. 5 schematically shows a cooling curve of the molten metal 90 (here, for example, a cooling curve of a molten cast iron having a carbon equivalent (CE) of 3.8 or more and 4.3 or less). Here, a cooling curve Op indicated by a solid line is a cooling curve when the gap Q is not formed. When the gap forming step is performed before the pouring step, the temperature of the molten metal 90 is lowered in the form indicated by the cooling curve Xp. That is, here, since the gap Q is formed before the pouring step, the cooling profile from the moment when the pouring is started to the cooling rate of the molten metal 90 is suppressed to a sufficiently small one, and the molten metal 90 is injected and solidified after being poured. Can be particularly preferred.

Further, FIG. 6 shows a profile of temperature change caused by pouring of the mold 1 (however, the mold 1 covered with the 2 mm sand layer 2) when the gap Q is not formed, and the gap before the pouring step. The profiles of the temperature change of the mold 1 when Q is formed are shown respectively. However, this temperature change profile is obtained when tin is used as the molten metal 90.
As shown in this figure, by forming the gap Q before the pouring step, the temperature change rate of the mold 1 (particularly, the temperature change rate at the moment of pouring) is reduced, and the mold 1 It can be seen that rapid temperature rise is suppressed. That is, it can be said that the formation of the gap Q before the pouring step effectively suppresses the mold 1 from being damaged by the heat of the molten metal 90.
It can also be seen from this figure that the larger the gap Q, the smaller the rate of temperature change of the mold 1 and the lower the maximum temperature reached. That is, it can be said that the greater the size of the gap Q, the smaller the thermal damage that the mold 1 receives.

  Step S104: When a predetermined time elapses from the pouring step, the molten metal 90 in the pouring space V is cooled to a predetermined temperature by natural cooling, and the molten metal 90 is solidified. Therefore, after the predetermined time has elapsed, the mold 1 is completely separated from the sand layer 2, and the solidified molten metal 90 (that is, the product 9) is demolded (separating step). In many cases, the sand layer 2 collapses and peels off from the product 9 during the demolding. After the remaining mold 1 is cleaned, it is used again as the mold 1 in step S1 (FIG. 3).

<5. Modification>
In said embodiment, the clearance gap formation process is performed before the pouring process. In this case, as described above, since the cooling rate of the molten metal 90 can be suppressed to a sufficiently small value from the moment of the start of pouring, the cooling profile from when the molten metal 90 is poured to solidification is particularly preferable. It is possible to sufficiently prevent the mold 1 from being thermally damaged by the molten metal 90 and sufficiently suppress the deterioration of the mold 1. On the other hand, in some cases, the order of the pouring step and the gap forming step may be reversed.

In this case, as shown in FIG. 7, after forming the gap Q after the step S101, the molten metal 90 is poured into the pouring space V through the pouring gate (pouring step) (step S102a).
Here, since the pouring surface area 11 of the mold 1 is covered with the sand layer 2, the molten metal 90 comes into contact with the sand layer 2 formed of sand having a relatively low thermal conductivity. Therefore, the cooling rate of the molten metal 90 during pouring can be reduced to some extent. Further, since the mold 1 is not in direct contact with the molten metal 90, the mold 1 is also prevented from being damaged by the heat of the molten metal 90 during pouring.
In particular, here, no gap Q is formed between the sand layer 2 and the mold 1 while the molten metal 90 is being injected, and the sand layer 2 is backed up by the mold 1 and thus injected. It is possible to avoid such a situation that the molten metal 90 leaks from the pouring space V, or the sand layer 2 is damaged by an impact when the molten metal 90 is injected.

  Then, after the pouring step, a gap Q is formed between the mold 1 and the sand layer 2 (gap forming step) (step S103a). Specifically, for example, as described above, the gap Q is formed between the sand layer 2 and the mold 1 by relatively moving only the pair of molds 1 in a direction away from each other with respect to the plurality of pin members 3. . As described above, a gap Q is formed between the sand layer 2 and the mold 1, whereby an air layer is formed between the mold 1 and the sand layer 2. Thereby, the cooling rate of the molten metal 90 after the gap Q is formed can be made sufficiently small, and the mold 1 can be prevented from being damaged by the heat of the molten metal 90.

  When the gap forming step is executed after the pouring step as in this modification, the timing at which the gap forming step is executed (that is, the timing at which the gap Q is formed) is the state of the molten metal 90 injected into the pouring space V. It is preferable to define in accordance with the changing timing.

  For example, when the molten metal 90 is a cast iron molten metal, the molten metal 90 immediately after being poured into the molten metal space V is liquid (time zone A shown in FIG. 5), and the temperature at which it is cooled (primary crystal temperature). : Here, after reaching about 1200 ° C., the liquid and austenite coexist (time zone B shown in FIG. 5). After reaching a certain temperature (eutectic temperature: here about 1153 ° C.), austenite and graphite coexist (time zone C shown in FIG. 5). Further, after reaching a certain temperature (A1 transformation point: about 738 ° C. here), graphite and ferrite coexist (time zone D shown in FIG. 5).

The gap forming step may be performed before the molten metal 90 reaches the primary crystal temperature (time zone A). In this case, as indicated by the cooling curve Ap, since the molten metal 90 can be suppressed to a sufficiently low cooling rate from the liquid state, the cooling profile from when the molten metal 90 is injected until solidified. Can be made sufficiently preferable.
Further, for example, the gap forming step may be performed after the molten metal 90 reaches the primary crystal temperature and before the eutectic temperature is reached (time zone B). In this case, as indicated by the cooling curve Bp, the cooling rate of the molten metal 90 can be suppressed to a sufficiently small value before the molten metal 90 reaches the eutectic temperature.
Further, for example, the gap forming step may be performed after the molten metal 90 reaches the eutectic temperature and before reaching the A1 transformation point (time zone C). In this case, as indicated by the cooling curve Cp, the cooling rate of the molten metal 90 can be suppressed to a sufficiently small value before the molten metal 90 reaches the A1 transformation point.
Further, for example, since the molten metal 90 expands while graphite is precipitated (graphite expansion), the gap forming step may be performed at the timing when the graphite expansion ends. In this case, since the sand layer 2 is backed up by the mold 1 while the graphite expansion is occurring, the effect of suppressing shrinkage cavities due to the graphite expansion can be expected.

DESCRIPTION OF SYMBOLS 100 ... Mold 1 ... Mold 10 ... Main surface 11 ... Pouring surface area | region 12 ... Parting surface 13 ... Pin insertion hole 2 ... Sand layer 3 ... Pin member 30 ... Connecting member 7 ... Model 71 ... Thin plate flat plate part 711 ... Protrusion 712 ... Flange 72 ... Product shape part 80 ... Sand 81 ... Sand supply cup 82 ... Suction device 9 ... Product 90 ... Molten metal Q ... Gap V ... Pouring space

Claims (4)

A casting method for casting a product using a pair of molds that form a pouring space between the molds,
a) a preparation step of preparing a pair of molds in which the pouring surface area of the mold having the pouring surface area forming the pouring space is covered with a sand layer;
b) a mold matching step of matching the pair of molds;
c) a pouring step of injecting molten metal into the pouring space after the mold matching step;
d) a gap forming step of forming a gap between the mold and the sand layer before or after the pouring step;
e) a separation step of completely separating the mold from the sand layer after the pouring step and the gap formation step;
A casting method. The casting method according to claim 1,
Performing the gap forming step before the pouring step,
Casting method. The casting method according to claim 1,
Performing the gap forming step after the pouring step,
Casting method. A pair of molds that form a pouring space between the molds by matching the molds,
A mold having a pouring surface region forming the pouring space;
A sand layer covering the pouring surface area;
A pin member provided so as to be able to appear and retract with respect to the pouring surface area;
Equipped with a,
When the pair of molds are aligned with each other, the two molds are moved relative to each other in a direction away from each other, and the pin member protrudes from the pouring surface area. Configured to form a gap in the
A pair of molds.

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