JP2008149372A - Die for material molding, material molding method and material molding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die in which the change in the temperature of the surface in a cavity for material molding is reduced as possible, further, a suitable temperature distribution is obtained therein, and a sound produce in which a defect in gas involvement or the like is reduced can be economically produced, and to provide a working method and a device utilizing the same. <P>SOLUTION: A phase changing substance 2 absorbing latent heat in the vicinity of a temperature to which it is desirably held constant, and dissolved is arranged at a position close to the surface 1a of a cavity, and the phase changing substance is cooled, and heat is released to the outside of the die. If required, a flow passage 3 is further provided between the phase changing substance and the cavity 1, after a workpiece is packed into the cavity 1, water, heat resistant oil or the like are made to flow through the flow passage, and it is cooled to a product discharging temperature. If required, a phase changing substance with a different melting point is dispersedly arranged in the die, and a suitable temperature distribution is produced in the workpiece. By utilizing the die, the workpiece is inserted into the cavity at a low velocity in which air involvement or the like do not occur. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a processing method in which a heated workpiece material such as casting, die casting, injection molding, forging, and powder metallurgy is inserted into a mold and molded.

  There are various processing methods such as casting, die casting, injection molding, forging, powder metallurgy, and the like, in which a heated workpiece material is poured into a mold or press-fitted into the mold. In these molding processes, appropriately controlling or adjusting the mold temperature is extremely important for economical production of sound products. For example, if the mold temperature is too low, the temperature of the material to be processed decreases too much, making it difficult to fill the mold, and excessive power is required. If the mold temperature is too high, seizure occurs. Further, when the mold temperature change is large, the service life is shortened.

  Conventional mold temperature control is performed by flowing water or oil through a flow path provided in the mold, and in some cases, a heater is installed in the mold. The temperature of the mold is adjusted by the balance between the heat inflow transmitted to the heat and the heat outflow due to cooling. Therefore, although it is good when the production speed is controlled to be constant, in practice, it is not constant due to various factors, and it is difficult to maintain the optimum state. Further, the conventional method has the following problems.

  For example, in the case of die casting of an Al alloy, in the conventional method as described above, it is not easy to inject and mold the molten metal at a cavity surface temperature of about 400 ° C. or higher in order to prevent poor hot water and gas entrainment. This is because the temperature is too low in water cooling, and it takes too much time to heat the mold before injection, and if the cooling is too weak, the mold temperature increases too much and seizure occurs. If there is a fluid that can be used at 300 ° C. or higher, it can be easily maintained at a higher temperature than in the case of water cooling. Therefore, in a normal die casting, the mold temperature is set to about 250 ° C. or less, and in order to prevent defects in the hot water run, the molten metal is injected at a high pressure of about 60 MPa or more and at a high speed of several tens of m / s, and the cavity is filled in a short time. Yes. However, when the molten metal flow rate is increased, the molten metal entrains the air in the cavity and the generated gas and becomes a defect. In addition, a high-pressure, large-capacity hydraulic device is required, and the device is also enlarged. In order to prevent this entrainment defect, the cavities are made high vacuum, the ultra-high speed injection to make the entrained bubbles finer, etc., but the equipment becomes larger and the maintenance cost increases, which becomes a problem ing.

  In low pressure casting, the pouring gate part becomes a feeder, so the mold temperature is controlled so that directional solidification is achieved, where solidification proceeds toward the pouring gate. If the temperature is too low, it is not easy to recover in a short time, and again it is not easy to maintain the optimum temperature.

  In resin injection molding or the like, the mold temperature can be controlled by the conventional method because the temperature is not high as described above, but it is desired to control the mold temperature more reliably and at low cost. In addition, it is desired to control the mold temperature at low cost in forging and powder metallurgy.

  Mold that can reduce the temperature change of the cavity surface for material molding as much as possible, realize an appropriate temperature distribution in the mold, and economically produce a sound product with few entrapment defects such as gas, etc. and processing using it Provide methods and equipment.

  A phase change material that absorbs and dissolves latent heat near the temperature to be maintained is disposed near the cavity surface. If necessary, the phase change material is cooled with water, oil, air or the like to release heat out of the mold. If necessary, a cooling flow path is provided between the phase change material and the cavity, and after the material to be processed fills the cavity, water or heat-resistant oil is poured into the flow path to take out the product. Cool to temperature. Further, if necessary, phase change materials having different melting points are dispersed in the mold to generate an appropriate temperature distribution in the mold. As the phase change material, a pure metal or an alloy is mainly used when the holding temperature is about 200 ° C. or higher, and a non-metallic material used as a latent heat storage material is mainly used when the holding temperature is about 200 ° C. or lower. Using such a mold, the material to be processed is inserted into the cavity at a low speed that does not involve air or the like. The mold includes all components such as a main mold and a core.

  First, the principle of the invention will be described with reference to FIG. FIG. 2 shows the temperature distribution with respect to the distance from the cavity surface when the phase change material is arranged in the vicinity of the cavity of the mold for molding the material. When the work material fills the cavity, the mold temperature rises due to the heat energy of the work material. After a certain time (after 4 s in FIG. 2), the heat energy is transferred to the phase change material, and the phase change material absorbs latent heat and dissolves, so that the temperature of the phase change material becomes substantially constant near the melting point ( The temperature of the dissolved and liquid phase rises, but convection occurs, resulting in a substantially uniform temperature distribution). As time passes (after 6 s in FIG. 2), the temperature of the material to be processed decreases and the mold temperature also decreases. On the other hand, one end of the phase change material (on the opposite side of the cavity) is cooled (natural convection or heat transfer to the mold may be sufficient without forced cooling), but the phase change material accumulates. Since the solidified latent heat is released, the temperature becomes substantially constant until solidification is completed. Therefore, if the initial temperature of the mold is set near the melting point of the phase change material (but below the melting point), the workpiece material heated while maintaining the temperature near the cavity at a temperature around the melting point of the phase change material. The mold can be filled and taken out as a product. Since the mold temperature rises until the heat of the material to be processed reaches the phase change substance, the temperature change is smaller as the phase change substance is placed closer to the cavity surface.

  By utilizing the above principle, the following various effects can be obtained. For example, FIG. 1 is an example of die casting of an Al alloy and using industrial pure Zn as the phase change material. Industrial pure Zn absorbs and melts about 100 kJ / kg of latent heat of fusion at about 410 ° C., so that the temperature in the vicinity of the cavity can be easily maintained at about 400 ° C. as described above. If the mold temperature can be maintained at a high temperature of about 400 ° C., the solidification time becomes longer. Therefore, it is not necessary to inject the molten metal at a high pressure and a high speed, and it is possible to fill the cavity at a low speed without involving air or gas. That is, the plunger speed can be 0.5 m / s or less, the molten metal speed in the mold can be several m / s or less (for example, 5 m / s or less), and the molten metal injection pressure can be 60 MPa or less (Non-patent Document 1). In order to shorten the product removal time by speeding up the cooling, a cooling flow path is provided between the phase change material and the cavity surface, and the phase change material is dissolved to some extent and then cooled until the removal time. It ’s fine. Even if such cooling is applied, the temperature of the phase change material does not decrease until the latent heat is released, so that the temperature inside the mold does not easily decrease, and the mold temperature is increased when the work material is inserted in the next cycle. Saving time and energy.

  FIG. 3 shows three phase change materials having different melting points, a phase change material 2a having the lowest melting point at a position farthest from the gate, a phase change material 2b having a slightly higher melting point in the middle, and a portion close to the gate 8. The phase change material 2c having a higher melting point is arranged so that solidification proceeds in one direction from the front end of the product toward the gate 8. This principle can also be applied to low pressure casting. In addition, if directional solidification can be achieved, products with no shrinkage can be obtained even if the applied pressure is small. Therefore, even in the case of die casting, molten metal injection can be performed by electric servo motor drive instead of hydraulic drive, miniaturizing the equipment and saving energy. Is possible. In addition, even a resin injection molding can provide a sound product with low shrinkage and less shrinkage.

  If the mold temperature can be kept high, the cavity can be filled at low speed, reducing the heat and impact load on the mold, producing a product with high dimensional accuracy, and extending the mold life (if the temperature is below a certain level, Is greatly related to fluctuations in temperature distribution). Further, since the melting point of the phase change material is low, it is easy to cast the flow path in the phase change material as a metallic pipe or the like, and the cost is lower than the flow path forming process by the conventional cutting process. Furthermore, cooling can be performed even in places where cutting is difficult, and there is no danger of cracks occurring in the water-cooled flow path, leakage of cooling water, and explosion due to reaction with the molten metal. If the product removal cycle is somewhat long, heat is released through the mold even if the phase change material is enclosed in the vicinity of the cavity without water cooling. For example, in places where water cooling does not easily occur, such as an extrusion pin. Can also be used.

  Even when the thermal shock to the mold, such as resin injection molding, is small, it is desirable to keep the mold temperature constant in order to manufacture a product with high dimensional accuracy because the thermal expansion error can be reduced. Also in this case, the temperature can be adjusted more easily by using the phase change material than in the conventional case.

In forging, powder, and gold, if the mold temperature is kept constant to some extent, the workability of the material to be processed increases, and the mold can be processed with a lower load, and the mold life is extended. In addition, it is possible to serve as a heat treatment that needs to be maintained at a constant temperature in the mold, which helps to reduce costs.
Non-Patent Document 1 2006 Japan Die Casting Conference Proceedings, (2006.11), p. 121 Japan Die Casting Association

FIG. 1 is a side view of a mold in Example 1, and phase change substances 2 are arranged at four positions within 2 mm to 50 mm from the cavity surface 1a. A flow path 4 is provided in each phase change material, and in a steady state, the heat energy transmitted from the work material to the mold is released from the mold at a substantially constant heat removal rate. If it takes too much time for the cavity surface temperature to drop to a predetermined temperature before product removal, the phase change material is dissolved to some extent, and then water or heat resistant oil is added to the flow path 3 installed near the cavity surface. To increase the cooling rate. If the temperature of the cavity surface drops too much after taking out the product, the cavity surface is heated by radiation or high temperature gas. In some cases, the mold temperature can be raised by flowing a high-temperature fluid through the flow paths 3 and 4 at the start of molding.
Furthermore, when manufacturing thin products of Al alloy or Mg alloy with a thickness of 1 or 2 mm or less by die casting, for example, industrial pure Zn is used as the phase change material, and the cavity surface temperature is set to about 400 ° C. Injection is performed at a speed of 5 m / s or less instead of the conventional several tens of m / s or more. For this reason, the molten metal may be injected not by a conventional hydraulic drive but by an electric servo motor drive.
In addition, the dimension and arrangement position of the phase change substance are between 2 and 400 mm from the cavity surface in consideration of the material, dimensions, and shape of the material to be processed, the insertion / removal cycle into the cavity, the material of the mold, the allowable life, etc. Place it in the appropriate range.

  FIG. 3 shows a phase change material 2a having a low melting point near the cavity farthest from the gate 8, a phase change material 2b having a slightly high melting point in the middle, and a phase change material having a high melting point near the gate. The material is inserted by the plunger tip 7 with the temperature distribution in the mold by arranging 2c. Instead of using the plunger tip 7, the molten metal may be pushed up by gas pressure and inserted into the cavity. Further, the plunger tip may be driven by an electric servo motor instead of hydraulic pressure.

FIG. 4 shows a third embodiment in which the phase change substances are collected in one place, and the convection resistance in the dissolved phase change substance is reduced to generate more intense convection so that the temperature is more constant.
When the support 9 is insufficient for fixing and supporting the flow path 4, it is desirable to perform cooling so that the flow path 4 and a part of the mold are always connected in solid phase.

As the phase change substance, an appropriate one is selected in consideration of the melting point, latent heat, cost, reaction with the mold, etc. If a melting point of about 200 ° C. or higher is required, IA, IIA, IVBVIII, IB, IIB, IIIA, IVA, VA, VIA pure metal or industrial pure metal, or an alloy having an appropriate melting point by combining two or more elements included in the above group use. In the case of similar melting points, an alloy or pure metal (which may be a low-cost industrial pure metal) having a large latent heat and a small difference between the liquidus temperature and the solidus temperature is selected. When the melting point is about 200 ° C. or lower, a low melting point alloy may be used, but it can be selected in the same manner as described above from organic and inorganic substances that are used or candidates as latent heat storage materials. The location of the phase change material is appropriately determined in consideration of the thermophysical value, dimensions, production cycle, etc. of the product to be molded, but it is better to be close to the cavity surface as long as there is no problem with the mold strength . In addition, since many of the above phase change substances expand when dissolved, it is better to provide an appropriate space around the phase change substance in advance so that the expansion volume can be absorbed.
Moreover, as a type | mold, a ceramic type | mold and a sand type | mold other than a metal can also be utilized. However, in the case of a sand mold or the like where the dissolved phase change material flows out, it is necessary to store the phase change material in a metal case.

  It can be used for casting, die casting, injection molding, forging, molding of powder and gold.

1 is a side view of Example 1. FIG. It is a figure which shows the temperature change in the cavity vicinity, and the temperature distribution in a type | mold. It is a figure which shows the side view of Example 2, and the temperature distribution in a type | mold. 6 is a side view of Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cavity 1a Cavity surface 2, 2a, 2b, 2c Phase change material 3 Flow path 4 Flow path 5, 5 'Die 6 Extrusion pin 7 Plunger tip 8 Gate 9 Pipe support

Claims (7)

  In a processing method in which a heated workpiece material is inserted into a mold and molded, a phase change material that absorbs and dissolves latent heat when the temperature exceeds a certain temperature is placed in the mold, and the temperature of the mold is adjusted. Molds (including cores) for molding materials and molding methods   A mold for molding a material and a molding method, wherein the temperature of the mold is adjusted by dispersing and arranging phase change substances having different melting points in the mold according to claim 1   3. A mold for molding a material and a molding method, wherein a flow path for flowing a fluid is provided in the phase change substance according to claim 1 and temperature of the mold is adjusted.   4. A mold for molding a material and a molding process, characterized in that a flow path for cooling or heating is provided between the phase change material according to claim 1 and the cavity surface of the mold to adjust the temperature of the mold. Law   The phase change material according to any one of claims 1 to 4, wherein the element is a pure metal having a melting point of 900 ° C or lower and belonging to the group IA, IIA, IVBVIII, IB, IIB, IIIA, IVA, VA, VIA in the periodic table of elements. Alternatively, an industrial pure metal, or an alloy having a melting point of 900 ° C. or lower using a combination of two or more elements included in the above group and a mold for forming a material, and using this mold Characteristic molding process As the phase change material according to any one of claims 1 to 4, KNO ₃ / LiNO ₃ / NaNO ₃ , MgCl ₂ .6H ₂ O, Al ₂ (SO ₄ ) ₃ .10H ₂ O, NH ₄ Al (SO ₄ ) ₂ 12H ₂ O, KAl (SO ₄ ) ₂ · 12H ₂ O, Mg (NO ₃ ) ₂ · 6H ₂ O, Sr (OH) ₂ · 8H ₂ O, LiNO ₃ / NH ₄ NO ₃ / NH ₄ Cl, Ba (OH) ₂ · 8H ₂ O, Mg (NO ₃ ) ₂ · 6H ₂ O / Al (NO ₃ ) ₃ · 9H ₂ O, Mg (NO ₃ ) ₂ · 6H ₂ O / MgCl ₂ · 6H ₂ O, NaCH ₃ COO 3H ₂ O and other salts, silicides, paraffin, sodium acetate, high-density polyethylene, esters, fatty acids and materials having a melting point of 500 ° C. or less Use Forming method, characterized in that   7. A material molding apparatus using the material molding die according to claim 1.

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