JP5061964B2 - Pressure casting mold and temperature control method thereof - Google Patents

Description

  The present invention relates to a pressure casting mold and a temperature control method thereof.

  In the die-casting method, in order to suppress the shrinkage defect of the cast product generated during the solidification process, the pressure of the molten metal is often increased using a pressurizing means such as an injection plunger or a local squeeze. However, increasing the pressure leads to an increase in the size and cost of equipment and molds, and thus there is a need for a technique for suppressing shrinkage defects without increasing the pressure. As a result, directional solidification is known in which a casting is sequentially solidified from a tip portion or a tip portion far from the gate to the gate. Patent Documents 1 and 2 describe a technique for cooling or heating a mold or a mold in order to realize this directional solidification.

  Patent Document 1 describes a cooling method for a low-pressure casting mold, in which a plurality of temperature sensors are installed along a direction in which directional solidification proceeds, and a specific part of the mold is formed. A plurality of mold cooling means are installed outside, and the mold cooling means is selectively operated to perform feedback control so that the detected temperature of each temperature sensor has a predetermined temperature gradient.

  Patent Document 2 describes a directional solidification method for precision casting. This method is provided with heaters in three upper, middle, and lower regions of a substantially cylindrical mold having a top formed with a gate. By setting the temperature of each heater to, for example, 1300 ° C., 1000 ° C., and 800 ° C. from the top, directional solidification from the bottom to the top is promoted.

JP 2000-61610 A Japanese Patent Application Laid-Open No. 11-57984

  Any of the methods described in Patent Documents 1 and 2 can actively apply a temperature distribution or a temperature gradient to a mold (die), but particularly when the thickness of a casting is drastically changed. It is considered difficult to set the temperature distribution of the casting mold, which is a continuum, to a desired distribution that realizes directional solidification.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a mold and a mold temperature control method for promoting directional solidification in a pressure casting method.

  The present invention provides a mold and a mold temperature control method described in each of the claims as technical means for achieving the above object.

  The invention described in claim 1 is a pressure casting mold (1), at least one heating means (14) and / or cooling means (15) disposed in the mold (1). And at least one heat insulating layer (17) that at least partially defines a region of the mold in which the heating means (14) and / or the cooling means (15) are disposed.

  By providing the heat insulating layer (17) on the mold (1), the heat transfer between the regions of the mold defined by the heat insulating layer (17) is suppressed, and as a result, more to each region of the mold. Thermally independent temperature control is possible. Thus, it becomes possible to increase the gradient of the temperature change of the mold, and it is possible to set an appropriate mold temperature even for a casting in which directional solidification is difficult to proceed, for example, a casting having a sudden change in thickness. Become.

  According to a second aspect of the present invention, the pressure casting mold (1) according to the first aspect includes a plurality of mold elements (Dtn, Dbn) that can be divided along the heat insulating layer (17). It is characterized by. By dividing the mold in this way, it is possible to increase the degree of freedom of arrangement of the heat insulating layer (17).

  The thermal insulation layer (17) may be formed from a layer of air or a layer of ceramic material.

  The invention according to claim 5 is characterized in that at least one heating means (14) and / or cooling means (15), heating means (14) and / or cooling arranged in the pressure casting mold (1). A method for controlling the temperature of the pressure casting mold (1) comprising at least one heat insulating layer (17) at least partially dividing a region of the mold in which the means (15) is disposed. 17) virtually dividing the mold (1) into a plurality of mold elements (Dtn, Dbn) by a virtual mold dividing surface (21) extending including the plurality of mold elements (Dtn, Dbn). For each of the at least one heating means (14) so as to achieve a step of setting the mold element temperature (Tdn) for realizing directional solidification and the set mold element temperature (Tdn). ) And / or the amount of heat generated and / or the amount of heat absorbed by the cooling means (15). It is characterized in that it comprises the steps of: section, the.

  Since the virtually divided mold elements (Dtn, Dbn) correspond to the area of the mold in which the heating means (14) and / or the cooling means (15) are arranged and actually partitioned by the heat insulating layer. The temperature of each mold element (Dtn, Dbn) can be easily adjusted, and the temperature change gradient between adjacent mold elements can be increased.

According to a sixth aspect of the present invention, in the temperature control method according to the fifth aspect, the step of setting the mold element temperature (Tdn) includes: casting (10) formed by the mold (1), Virtually dividing into a plurality of casting elements (Cn) by a virtual casting dividing surface (20) continuous with the virtual mold dividing surface (21), and for each of the plurality of casting elements (Cn), Predicting a temperature (Tcn), setting a solidification time (tn) for realizing directional solidification for each of the plurality of casting elements (Cn), and a plurality of casting elements (Cn) For each of the steps of calculating the amount of heat removal (Qn) required for solidification, and for each of the plurality of mold elements (Dtn, Dbn) in contact with the plurality of casting elements (Cn), Determine mold element temperature (Tdn) It is characterized by being comprised of the steps.
(Tcn−Tdn) · kn = Qn / tn
However, kn in the above formula is a coefficient obtained by multiplying the heat transfer area (Sn) between each casting element (Cn) and the mold element (Dtn, Dbn) by the heat transfer coefficient of the molten metal.

  As a result, the amount of heat removed from each casting element can be determined from the volume, heat transfer area, and temperature of each casting element, so that each mold element temperature for realizing directional solidification can be determined with higher accuracy. It becomes possible.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  The term “pressure casting method” used in the present specification includes a die casting method in which a molten metal pressure is high (MPa order) and a molten metal injection speed is high (m / sec order), a high pressure low speed squeeze casting method, and a low pressure casting. The law is included.

  The mold 1 according to the first embodiment of the present invention will be described with reference to FIG. 1 which is a schematic cross-sectional view showing the right half of the central axis Ax of the mold 1. The mold 1 includes an upper mold 2 that constitutes a movable mold and a lower mold 3 that constitutes a fixed mold. The upper die 2 is fixed to the upper mounting plate 6 via the upper heat insulating plate 4 and the receiving block 5, and the lower die 3 is fixed to the lower mounting plate 7. An extrusion pin 9 held by an extrusion plate 8 disposed above the upper die 2 passes through the upper die 2. The casting 10 cast by the mold 1 is represented by the hatched region in FIG. 1 corresponding to the cavity 11 formed by combining the upper mold 2 and the lower mold 3, and has a generally bottomed cylindrical shape. And has a protrusion 12 extending downward from the center of the bottom of the cylinder, and a gate 13 is provided at the lower end of the protrusion 12. Further, the dividing surface Ps between the upper mold 2 and the lower mold 3 is provided at the same level as the tip surface of the casting 10 that is farthest from the gate 13. Moreover, the material of the metal mold | die 1 of this embodiment is alloy tool steel, and the material of the casting 10 is an aluminum alloy.

  The upper die 2 is embedded with four heaters 14 schematically represented by rectangles in FIG. 1 as heating means for heating it and three cooling water pipes 15 as cooling means for cooling. The lower mold 3 has eight heaters 14 and one cooling water pipe 15 embedded therein. The heater 14 is disposed in each part of the mold 1 other than the tip part of the casting 10 farthest from the gate 13, and the cooling water pipe 15 is embedded in the part of the mold 1 in contact with the tip part. 1 uses a ring-shaped sheathed heater, but a plate-shaped ceramic heater can also be used. The heater output varies depending on the insertion position (from 0.1 KW to 2 KW), and the gap between the heater insertion portions is filled with a highly heat conductive filler. On the other hand, as the cooling means 15 in FIG. 1, water is used as a refrigerant, but instead, a refrigerant such as air or CO2 gas may be used. Also, means (mist, dry ice grains) for removing the heat of vaporization and cooling can be used.

  A large number of gaps 16 formed by elongated rectangular holes are formed between the heaters 14 embedded in the mold 1 and between the cooling water pipe 15 and the heater 14 in the mold 1. The gap 16 is formed inside the respective edges of the upper mold 2 and the lower mold 3, and the mold 1 is arranged so as to sandwich the heater 14 or the cooling water pipe 15 or the heater 14 or the cooling water pipe 15 is disposed. Are arranged so as to at least partially divide the region. The gap 16 is provided in order to use the air therein as the heat insulation layer 17, and the heat insulation layer 17 of the air allows the gap 16 to be adjacent to a certain region of the mold 1 where the heater 14 is disposed. The movement of heat between the heater 14 and the other area of the mold 1 in which the cooling water pipe 15 is disposed is suppressed. As a result, it is possible to adjust the temperature more independently for each region of the mold 1 at least partially partitioned by the heat insulating layer 17. Thus, the gradient of the temperature change of the mold 1 can be increased, and an appropriate mold temperature can be set even for the casting 10 in which the directional solidification is difficult to proceed, for example, the suddenly changing portion of the wall thickness exists. It becomes possible. By the way, in this embodiment, although the said gap | interval 16 contains air, in order to improve the heat insulation effect, you may make the said gap | interval 16 into a sealed space and make it a vacuum.

In the present embodiment, the lower mold 3 is integrated, but the upper mold 2 is divided into _five mold elements Dt _{1 to} Dt 5 by a plurality of dividing surfaces 18 in order to form the gap 16. The upper die 2 is formed by cutting the concave portion for forming the gap 16 along the dividing surface 18 of each mold element Dtn and then integrally joining the mold elements Dtn with a plurality of connection bolts (not shown). Produced.

  Each heater 14 is connected to a controller (not shown) disposed outside the mold 1 by an electric cable (not shown) so that the amount of generated heat can be individually adjusted by operating the controller. It is configured. Each cooling water pipe 15 forms a circulation path and is connected to a heat exchanger (not shown) outside the mold 1. Each cooling water pipe 15 is provided with a valve (not shown), and the amount of cooling water can be adjusted by operating this valve. The temperature of the cooling water can be adjusted by a temperature control circuit.

Next, the metal mold | die of 2nd Embodiment is shown in FIG. In the mold 1, also the lower mold 3 is divided into a plurality of divided surfaces 19 by nine of the mold element Db ₁ Db ₉ along the heat insulating layer 17, the divided nine mold elements Dbn was the Are connected to each other by a plurality of bolts (not shown).

  Next, a third embodiment will be described below with reference to FIG. The mold of this embodiment has substantially the same configuration as the mold of the second embodiment, but the heat insulating layer 17 represented by a thick line in FIG. 3 is configured by a ceramic plate. The difference is that the heat insulating layer 17 of the ceramic plate extends to reach the cavity 11 to form a part of the cavity 11. In FIG. 3, the ceramic plates constituting one heat insulating layer 17 are expressed so as to be continuous and integrated, but are actually divided at the bent portions. In FIG. 3, the heat insulating layer 17 extending in the vertical direction in the upper mold 2 shows a longitudinal section of a ceramic pipe material. However, the heat insulating layer 17 equivalent to the pipe material may be formed by combining arc-shaped members having a central angle of 90 degrees obtained by dividing the pipe material into, for example, four parts for the purpose of absorbing dimensional errors. In this embodiment, silicon nitride is used as the ceramic material, but other ceramic materials such as alumina may be used.

  In the third embodiment, a large number of heaters 14 are arranged as a whole and the upper mold 2 and the lower mold 3 are divided as a whole. For example, a heater is provided only in a part of the upper mold and / or the lower mold. It is possible to divide the nesting from the main mold part by forming the part of the mold where the heater is arranged as a nesting and providing a heat insulating layer around the nesting. is there. Such a structure is suitable, for example, when there is a partial thin portion in the casting, and it is possible to extend the solidification time of the thin portion by disposing a heater corresponding to the thin portion.

  Next, a mold temperature control method according to a fourth embodiment of the present invention will be described below. The mold temperature control method according to this embodiment is implemented using the mold according to any of the first to third embodiments described above. The method of this embodiment is the third method shown in FIG. It demonstrates as what is implemented using the metal mold | die of embodiment.

The procedure of the mold temperature control method according to the fourth embodiment will be described below.
First, the lower mold 3 and the upper mold 2 are virtually divided into a plurality of mold elements Dtn and Dbn by the virtual mold dividing surface 21. At this time, the virtual mold dividing surface 21 virtually divides the mold 1 so as to extend along the heat insulating layer 17 and the actual mold dividing surfaces 18 and 19. Therefore, the virtually divided mold elements Dtn and Dbn in the embodiment of FIG. 3 substantially match the actual mold elements Dtn and Dbn. In the case of the lower mold 3 of the mold 1 of the first embodiment, the virtual mold dividing surface 21 extends along the heat insulating layer 17 to the edges of the cavity 11 and the lower mold 3.

  Next, a mold element temperature Tdn for realizing directional solidification is set for each mold element Dtn, Dbn. This mold element temperature Tdn is the temperature of the surface forming the cavity of each mold element Dtn, Dbn, and is determined in consideration of the distance from the gate 13 and the thickness of the casting.

  Next, the amount of heat generated by the heater 14 is adjusted by a controller (not shown) and the amount of flowing water in the cooling water pipe 15 is adjusted by a valve (not shown) so as to achieve each set mold element temperature Tdn. In addition, as a method for confirming the temperature of each part of the mold, for example, a method of confirming the temperature by attaching a temperature sensor to the surface of each part of the mold forming the cavity 11 or embedding the temperature sensor in the mold. The former method can be carried out as part of the mold condition determination test before operating the mold, and the latter method can confirm the mold temperature immediately after the molten metal is injected.

  Next, a mold temperature control method according to the fifth embodiment will be described with reference to FIG. Reference is also made to FIG. 4, which schematically shows the temperature of each part of the casting 10 and the amount of heat released. The mold temperature control method according to the fifth embodiment is different from the method according to the fourth embodiment in that the mold element temperature Tdn is set according to the following procedure. This is the same as the embodiment.

In the setting procedure of the mold element temperature Tdn in the method according to the fifth embodiment, first, the casting 10 is virtually divided into a plurality of casting elements Cn by the virtual casting dividing surface 20 represented by a dotted line in FIG. At this time, the virtual casting dividing surface 20 is continuous with the virtual mold dividing surface 21 and thus the mold dividing surfaces 18 and 19. In FIG. 3, it is virtually divided into _eight casting elements C _{1 to} C ₈ .

Next, a solidification time tn for realizing directional solidification is determined for each casting element Cn. The solidification time tn is determined on the condition that directional solidification is realized while considering productivity. Therefore, the casting is usually set so that the tip end portion is the shortest and the gate portion is the longest. That is, when the solidification time tn of the casting element Cn is t ₁ , t ₂ , t ₃ ... T ₈ from the tip side, it is t ₁ <t ₂ <t ₃ <..... <t It is set to satisfy ₈ .

  Next, the molten metal temperature Tcn is predicted for each of the casting elements Cn. The temperature Tcn of the molten metal can be obtained by using a three-dimensional casting CAE system such as “ADSTEFAN” (registered trademark), for example.

Next, for each of the casting elements Cn, the amount of heat released, that is, the amount of heat removed Qn required for solidification is calculated. Heat removal amount Qn of the casting element Cn is each casting element Cn, weight Wn, the solidus temperature of the melt metal Ts, the specific heat of the molten metal Cp, and the latent heat of solidification and Q _L, be determined by the formula Can do.
Qn = Wn (Cp · (Tcn−Ts) + Q _L )
The heat removal amount Qn is represented by three or two waveform arrows from the casting element Cn to the mold elements Dtn and Dbn in FIG. Since heat removal amount to Q ₁ from the casting element C ₁ is in contact with three sides in the mold Q _1a, Q _1b, represented by three waveforms arrow Q _1c, dissipation heat amount Q ₂ of the casting element C ₂ is Since it is in contact with the mold on two sides, it is represented by two waveform arrows Q _2a and Q _2b .

Next, for each of the mold elements Dtn and Dbn in contact with each casting element Cn, the mold element temperature Tdn is obtained by solving the following equation.
(Tcn−Tdn) · kn = Qn / tn
Here, the symbol kn in the above equation is a coefficient obtained by multiplying the contact area (heat transfer area) Sn between each casting element Cn and the mold elements Dtn and Dbn by the heat transfer coefficient of the molten aluminum. Further, when solving the above equation, it is assumed that the mold temperatures Tdn of the plurality of heat transfer surfaces related to one casting element Cn are equal.

Next, a mold according to a sixth embodiment of the present invention will be described below with reference to FIG. FIG. 5 is a schematic cross-sectional view showing the main part of the lower mold 3 and the cavity 11 on the right side of the center axis of the mold. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, and has a ceramic plate as the heat insulating layer 17 between the mold elements Dbn. The mold element Dbn includes a heating means 14 or a cooling means 15. However, in FIG. 5, the material of the divided mold element Dbn of the lower mold 3 is used in combination with alloys having different thermal conductivities (for example, alloy tool steel, copper, heavy alloy). By using a material having high thermal conductivity for the mold element Db ₁ on the side of the sluice and using a material having low thermal conductivity for the mold element Db ₅ on the side of the sluice, it is inclined from the sluice toward the sluice. Mold temperature distribution can be set.

Next, the metal mold | die of 7th Embodiment is demonstrated below, referring FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but the thickness of the divided mold element Dbn of the lower mold 3 in FIG. The mold element Db ₁ is the thickest, and the mold element Db ₄ on the gate side is the thinnest. In this way, by changing the plate thickness stepwise from the hot water tip to the gate, the heat capacity of each mold element Dbn partitioned by the heat insulating layer 17 changes in an inclined manner, and the mold temperature distribution in an inclined manner. Can be set.

  Next, a mold according to an eighth embodiment will be described below with reference to FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but the thickness of the heat insulating layer 17 between the divided mold elements Dbn of the lower mold 3 in FIG. The hot water side is thin and the gate side is thick. Thus, by changing the thickness of the heat insulation layer 17 stepwise from the molten metal tip to the gate, the temperature gap between the mold elements changes in an inclined manner, and the mold element temperature becomes closer to the molten metal side. Since the mold element temperature is maintained at a higher temperature as the temperature approaches a lower temperature and closer to the gate, the mold temperature distribution can be set in a slanting manner.

  Next, a ninth embodiment will be described below with reference to FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but in FIG. 8, the heater 14 as a heating means to be inserted into the divided mold element of the lower mold 3. The pouring side is located farther from the casting or cavity 11 and the pouring side is located closer to the casting. Thus, by changing the position where the heating means 14 (heater) is disposed from the tip to the gate, that is, the distance of the heater from the casting, the temperature on the side of the gate can be maintained at a constant high temperature. The mold temperature distribution can be set to be inclined from the hot water side to the gate side. In addition to this embodiment, the mold temperature distribution can be more easily set to be inclined by gradually increasing the amount of heat generated by the heating means (heater output) from the hot water side to the gate side. Is possible.

  Next, a mold according to a tenth embodiment will be described below with reference to FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but insertion of the cooling means 15 to be inserted into the divided mold element Dbn of the lower mold 3 in FIG. The position is arranged close to the casting or cavity 11 on the side of the molten metal, and located far from the casting. In this way, by gradually changing the distance from the casting to the position where cooling is arranged from the pouring point toward the pouring gate, the mold temperature distribution can be set to be inclined from the pouring side toward the pouring side. it can. Further, in addition to the present embodiment, the amount of water in the cooling means 15 is reduced stepwise from the hot water side to the gate side, or the water temperature of the cooling means 15 is increased stepwise from the hot water side to the gate side. By doing so, it is also possible to make it easier to set the mold temperature distribution in a more inclined manner.

  Next, the metal mold | die of 11th Embodiment is demonstrated below, referring FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but the heating means 14 in contact with the divided mold element Dbn of the lower mold 3 in FIG. 10 is movable. It arrange | positions in a state and is arranged in multiple numbers toward the gate side from the hot water side. By separating the heating means 14 from the mold element in order from the tip to the gate, the mold temperature distribution can be set to be inclined from the tip side to the gate side. In addition to this embodiment, the mold temperature distribution can be more easily set to be inclined by gradually increasing the amount of heat generated by the heating means (heater output) from the hot water side to the gate side. Is possible.

  Next, a mold according to a twelfth embodiment will be described below with reference to FIG. The mold of this embodiment has substantially the same configuration as the mold of the third embodiment, but in FIG. 11, a position separated by a certain distance from the divided mold element Dbn of the lower mold 3. The cooling means 15 is arranged in a movable state, and a plurality of cooling means 15 are arranged from the hot water side to the gate side. By bringing the cooling means 15 into contact with the mold elements in order from the tip to the gate, the mold temperature distribution can be set to be inclined from the tip side to the gate side. Further, in addition to the present embodiment, the amount of water in the cooling means 15 is reduced stepwise from the hot water side to the gate side, or the water temperature of the cooling means 15 is increased stepwise from the hot water side to the gate side. By doing so, it is also possible to make it easier to set the mold temperature distribution in a more inclined manner.

It is a typical sectional view of a metallic mold by a 1st embodiment. It is typical sectional drawing of the metal mold | die by 2nd Embodiment. It is a typical sectional view of a metallic mold by a 3rd embodiment. It is a figure which represents typically the temperature and the amount of heat removal of each part of a casting and a metal mold | die. It is a typical sectional view of a metallic mold by a 6th embodiment. It is typical sectional drawing of the metal mold | die by 7th Embodiment. It is typical sectional drawing of the metal mold | die by 8th Embodiment. It is typical sectional drawing of the metal mold | die by 9th Embodiment. It is typical sectional drawing of the metal mold | die by 10th Embodiment. It is a typical sectional view of a metallic mold by an 11th embodiment. It is a typical sectional view of a metallic mold by a 12th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold 2 Upper mold 3 Lower mold 14 Heating means 15 Cooling means 17 Heat insulation layer 20 Virtual cast parting surface 21 Virtual mold parting surface Cn Casting element Dtn Mold element Dbn Mold element

Claims (1)

A pressure casting mold (1),
At least one heating means (14) and / or cooling means (15) disposed in the mold (1);
At least one heat insulating layer (17) that at least partially defines a region of the mold in which the heating means (14) and / or the cooling means (15) are disposed ;
A plurality of mold elements (Dtn, Dbn) that can be divided along the heat insulating layer (17),
The thermal insulation layer (17) is formed from a layer of ceramic material;
The mold for pressure casting, wherein the plurality of mold elements have different thicknesses, and a mold element closer to the gate of the mold for pressure casting has a thinner thickness ( 1).

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