JP3948490B2 - Casting manufacturing method - Google Patents

Abstract

A casting process that employs a collapse-prone core is disclosed. The process includes the steps of mixing one or more kind of an aggregate granular material, one or more kind of a water-soluble binder, and water, to form a mixture of the aggregate granular material, and stirring the mixture to cause it to foam. Such a mixture prevents the generation of undesirable gases when molding a mold and pouring molten metal into the mold. The process also includes the steps of charging the foamed mixture into a molding space, evaporating the moisture within the charged mixture to harden the charged mixture to mold a mold with the hardened mixture, assembling at least one mold that is cast in the hardened mixture with the mating mold to form a completed mold, pouring molten metal into the completed mold, removing the completed mold from a cast article that is composed of the solidified molten metal during a process of cooling the cast article after the molten metal is solidified, and applying a heat treatment to the cast article.

Description

  The present invention relates to a casting manufacturing method, and more particularly to a casting manufacturing method using a mold that can be easily removed instead of a conventional shell mold process.

  As a conventional method for producing a light alloy casting, a shell mold process is known as described in, for example, Japanese Patent Laid-Open No. 5-261478. As the binder for the shell mold process, a binder containing a phenol-formaldehyde resin is employed. The sand covered with the binder is blown and filled into a heated mold, and the binder covered with the filled sand is cured by the heat of the mold.

  However, in such a shell mold process, since the core mold after pouring is relatively hard, a large impact force is applied to the core mold in order to collapse the core mold and remove it from the casting. A knockout process is required. In order to perform this knock-out process, it is necessary to sufficiently cool the casting before heat treatment of the casting. Moreover, even if a relatively large impact force of 1 Mpa or more is applied at 10 Hz or more for 10 seconds or more, only about 70 to 80% of the sand can be removed, so that the core mold remains after collapse during and after the heat treatment. Core sand and core lump remain in the casting. Therefore, removal of them again may be required. Furthermore, roasting is often required to regenerate the core mass removed from the casting.

  Further, in the shell mold process, volatile gas is generated when the binder is cured by heat of the mold. Such a volatile gas is accompanied by an unpleasant odor, and especially gases such as formaldehyde, phenol and ammonia have an adverse effect on the human body.

  Therefore, in place of the conventional shell mold process, there is a demand for a casting manufacturing method that facilitates removal of the mold and suppresses the generation of volatile gases.

  In the present specification, the “particulate aggregate” means one or more of quartz sand, zircon, sand, olivine sand, chromite sand, alumina sand, mullite sand, artificial sand and the like.

  In the present specification, “after the molten metal has solidified” means after the molten metal has solidified and hardened. This temperature varies depending on the process and the melt material.

  In the present specification, “during the cooling period of the casting” indicates a period during which the casting is cooled to a temperature lower than the temperature at which the casting is cooled to such an extent that the casting is not deformed even when the casting is taken out from the finished mold. For example, in the T6 treatment of an aluminum alloy, the casting is cooled to a temperature lower than the solution treatment temperature of about 520 ° C. but higher than the normal cooling temperature of 70 to 111 ° C., for example, 300 ° C. Show.

According to one aspect of the present invention, there is provided a method for manufacturing a casting, which is a method for manufacturing a casting,
Forming an aggregate mixture by mixing at least one particulate aggregate, at least one water-soluble binder, and water, and stirring the aggregate mixture to foam;
Filling the foamed aggregate mixture into the mold making space, evaporating moisture in the filled aggregate mixture to solidify the aggregate mixture, and molding the mold with the particulate aggregate; and
A process for producing a finished mold by combining the mold of the other party with the mold made of the particulate aggregate,
Pouring molten metal into the finished mold;
Removing the molding mold from the casting during a cooling period of the casting after the molten metal is solidified;
Heat-treating the casting.

  The molding mold made of the particulate aggregate is preferably a core mold. In this case, the counterpart mold (main mold) may be a mold or a sand mold.

  In the present specification, the “finished mold” means a mold that is composed of a combination of a main mold and at least one molding mold (core mold) made of particulate aggregate, and can pour molten metal. Accordingly, the components of the finished mold can include elements necessary for pouring in addition to the main mold and the core mold.

  The casting manufacturing method of the present invention may further include a step of collecting the particulate aggregate and a step of regenerating the collected particulate aggregate. It is preferable that the particulate aggregate recovered and regenerated is used again for mold making.

  According to one embodiment of the present invention, the step of recovering and regenerating the particulate aggregate is mechanical regeneration.

  The casting may be an aluminum alloy casting, a magnesium alloy casting, a copper alloy casting or the like.

The heat treatment may be T6 treatment or T7 treatment.

  According to one embodiment of the present invention, the step of removing the mold is a process of applying vibration to the mold. This includes, for example, applying an impact force of 1 Mpa or less to the mold at less than 30 Hz and less than 30 seconds in a time within 5 to 20 minutes after pouring.

A method for producing a casting provided by another aspect of the present invention includes a step of forming an aggregate mixture by mixing particulate aggregate, at least one water-soluble binder, and water;
The aggregate mixture is agitated and foamed, the foamed aggregate mixture is filled into the mold molding space, the moisture in the filled aggregate mixture is evaporated to solidify the aggregate mixture, and the core mold is molded. And a process of
Combining a core mold and a mold mold into a finished mold;
Pouring molten aluminum alloy into the finished mold;
Removing the core mold from the casting during the cooling period of the casting after the molten metal has solidified;
Heat-treating the aluminum alloy casting with T6 or T7.

The at least one water-soluble binder is at least one of polyvinyl alcohol and its derivative, or at least one of starch and its derivative.

Preferred form for carrying out the invention

  The process diagram of FIG. 1 schematically shows each process of the casting manufacturing method according to the present invention. First, the principle of the casting manufacturing method of the present invention will be described with reference to this process chart.

  In FIG. 1, first, at least one type of particulate aggregate, at least one type of water-soluble binder and water are mixed to form an aggregate mixture, which is then foamed by stirring (first ( Preparation) Step 1).

  Second, the foam mixture formed in the previous step is filled into a mold making space and solidified to form a mold made of particulate aggregate (second (molding) process) 2).

  Third, at least one or more molded molds (core molds) thus molded are combined with the counterpart mold (main mold) to produce a completed mold (third (assembly) step 3).

  Fourth, molten metal is poured into the finished mold (fourth (pouring) step 4).

  Fifth, during the cooling period of the casting after the molten metal has solidified, the core mold is removed from the casting and the die is removed (fifth (die cutting) step 5).

  Sixth, a finished product casting is manufactured by heat-treating the casting (sixth (heat treatment) step 6).

  Each step of FIG. 1 will be described in more detail.

  In the first (preparation) step 1, at least one of silica sand, zircon, sand, olivine sand, chromite sand, alumina sand, mullite sand, artificial sand and the like is used as the particulate aggregate.

  As the water-soluble binder, it is preferable to use a water-soluble binder at room temperature. Since a water-soluble binder having water solubility at room temperature can form an aggregate mixture without heating, the time and energy required to heat the binder and the particulate aggregate can be saved. This is an advantage of the present invention as opposed to coated sand production in a conventional shell mold process. The water-soluble binder used in the present invention is preferably water-soluble binder polyvinyl alcohol or a derivative thereof, starch or a derivative thereof, or both, but is not limited thereto. Since this water-soluble binder can be easily volatilized or decomposed, the core mold can be easily removed from the solidified casting of the molten metal in the subsequent fifth (die cutting) step 5. The water-soluble binder is preferably contained in an amount of 0.1 to 5.0 parts by weight with respect to the particulate aggregate.

  Such an at least one water-soluble binder, at least one particulate aggregate, and water are mixed to form an aggregate mixture. When this is foamed by stirring, the aggregate mixture becomes whipped cream.

  In the second (molding) step 2, when the aggregate mixture is solidified by evaporating the water in the aggregate mixture filled in the mold molding space, the aggregate is made of particulate aggregate due to foaming in the previous step. A hollow core mold (core mold) is formed. This hollow mold has a porosity of 3% to 60%. When the thickness of the hollow mold is, for example, about 40 mm, the water-soluble binder is aggregated by 50% or more in the mold surface layer between the mold surface and 10 mm depth. That is, in the hollow mold made of the foamed aggregate mixture, the bubbles contained in the aggregate mixture and the moisture contained in the binder are collected in the center of the mold, so by evaporating the moisture, The packing density of the aggregate is lowered.

  In the third (assembly) step 3, a completed mold can be configured by combining a main mold (an opponent mold) with at least one core mold made of particulate aggregate. The main mold may be a mold or a sand mold made of, for example, particulate aggregate. In this embodiment, a die is adopted as the main mold, and low pressure casting is applied. However, when a mold is used, the method of the present invention is not limited to low pressure casting but can be applied to other processes such as reverse pressure casting, die casting, and gravity mold casting.

  In the fourth (pouring) step 4, the molten metal material poured into the finished mold is an aluminum alloy in the present embodiment, but is not limited to this, and other light metal alloys or non-ferrous alloys (for example, magnesium alloys) Or a copper alloy). Instead of this, cast iron, cast steel, or an iron-based metal alloy may be used. However, when using an iron-based metal, it may be desirable to apply a coating material to the core mold.

  In the fifth (die cutting) step 5, the core mold is removed from the casting during the cooling period (period in which the casting is cooled to a temperature lower than the temperature at which the casting is cooled to such an extent that the casting is not deformed even if the casting is removed from the finished mold) Remove. Here, “in the cooling period” when the molten metal material in the fourth (pouring) step 4 is an aluminum alloy is lower than about 520 ° C., which is the solution treatment temperature in the T6 treatment of the aluminum alloy. This is a period in which the casting is cooled to a temperature higher than the cooling temperature of 70 to 111 ° C., for example, 300 ° C.

  In the case of an aluminum alloy, the heat treatment in the sixth (heat treatment) step 6 is T6 treatment, T7 treatment or other heat treatment.

  Molding step 2 for forming a core mold in preparation step 1 in which a particulate aggregate mixture containing a binder is kneaded and adjusted by using polyvinyl alcohol or a derivative thereof, or starch or a derivative thereof as a water-soluble binder. No unpleasant gas odor occurred.

  In addition, in the pouring step 4 in which the molten metal is poured into the molded core mold, even if the binder is heated by the heat of the molten metal, generation of unpleasant odor and undesired volatile gas from the core mold is recognized. I couldn't.

  As shown in FIG. 1, in the casting manufacturing method of the present invention, following the sixth (heat treatment) step 6, the following steps may be further added as necessary. That is, a recovery step 7 for recovering the core aggregate particulate aggregate (core sand) and core lump, a crushing step 8 for crushing the core lump, and mechanically regenerating the recovered particulate aggregate. This is a mechanical regeneration step 9. The particulate aggregate recovered and regenerated can be used again for the molding of the core mold.

  A specific embodiment of the casting manufacturing method of the present invention will be described with reference to the process diagram of FIG. However, the material names shown here are given for illustrative purposes and do not limit the present invention.

  In the first step (preparation step) 1 of the present embodiment, two types of aggregate mixtures A and B were obtained as follows.

Table 1 Aggregate mixture A
Particulate aggregate: 100 parts by weight of silica sand (flattery sand) Water-soluble binder: 0.8 parts by weight of polyvinyl alcohol (JP-05, Nippon Acetate / Poval) Crosslinker: Butanetetracarboxylic acid (Ricacid BT-W Shin Nippon) 0.2 parts by weight Rika) 100 parts by weight of the aggregate mixture having the composition shown in Table 1 and 6 parts by weight of water were mixed, stirred, kneaded and foamed to obtain a whipped cream-like aggregate mixture A.

Table 2 Aggregate mixture B
Particulate aggregate: 100 parts by weight of silica sand (Flatari-sand) Water-soluble binder: 0.2 parts by weight of polyvinyl alcohol (JL-05, manufactured by Nippon Acetate / Poval), starch (dextrin ND-S manufactured by Nissho Chemical Co., Ltd.) 0 part by weight, and 0.4 part by weight of citric acid (manufactured by Fuso Chemical) 100 parts by weight of a dry aggregate mixture having the composition shown in Table 2 and 6 parts by weight of water are mixed, stirred, kneaded and foamed. A whipped cream-like aggregate mixture B was obtained.

  In addition, in the preparation process 1 of this embodiment, the heating apparatus required in the process which manufactures the resin coated sand of the conventional shell mold process, and the deodorizing apparatus which removes the harmful gas which arises by the heating of a resin are unnecessary.

  Next, the two types of whipped cream-like aggregate mixtures A and B obtained in the preparation step 1 are placed in a cavity (not shown) of a mold for mold making (not shown) held at 250 ° C. Separately pressurize and hold for 1 minute to vaporize and solidify the moisture in the aggregate mixture, and then remove the core mold from the cavity of the mold for mold making (second (molding) step 2 ).

  As already described, this mold is assembled with another mold to form a completed mold (third (assembly) step 3). Here, in the assembly process 3 of the present embodiment, a core mold was incorporated into the main mold of the low pressure casting apparatus, a completed mold was manufactured, and pouring preparation was made.

Molten metal was poured into the finished mold (fourth (pouring) step 4). In this embodiment, a molten aluminum alloy casting AC4C (temperature: 720 ° C.) was poured from below using a low-pressure casting apparatus (not shown). Since the temperature of the molten metal at 720 ° C. volatilizes or decomposes the binder, it becomes easy to remove the core mold in the next step.

  During the cooling period of the casting after the molten metal solidified, the core mold was removed from the casting (fifth (die cutting) step 5). In the conventional shell mode process, in order to collapse and remove the core mold from the casting, it is necessary to apply a large impact force to the mold after the casting is sufficiently cooled. According to the method of the present invention, since the core mold having a high collapsibility is used, sufficient cooling and a large impact force thereafter required for removing the core mold from the casting are not required. Therefore, the core mold can be removed by a simple method, for example, a light vibration described below. In the mold removal step 5 of the present embodiment, the solidified molten metal was taken out as a casting about 10 minutes after pouring. Immediately thereafter, the core mold was completely removed by applying an impact force of 1 Mpa or less to the casting at a temperature of 350 ° C. by light vibration of 20 Hz for less than 20 seconds to remove sand. Also, according to experiments, in the die-cutting step 5, the core mold can be completely removed from the casting even when the sand is dropped to give an impact force of 1 Mpa or less at less than 30 Hz for less than 30 seconds within 5 to 20 minutes after pouring. It was.

  After removing the pouring gate of such a casting and removing the cast burr of the casting, this casting was heat-treated (sixth (heat treatment) step 6). The removal of the casting spout and cast burr is performed before the heat treatment of the casting in this embodiment, but may be performed after the heat treatment. Also in the present embodiment, following the sixth (heat treatment) step 6, a core sand collecting step 7, a crushing step 8, and a mechanical regeneration step 110 shown in FIG. 1 may be added.

  In the casting method using the mold mold, the particulate aggregate and the core lump are collected only from the core mold, so that the collected and regenerated particulate aggregate can be easily reused for mold making. it can.

  FIG. 2 (prior art) shown for comparison is a process diagram of a conventional casting manufacturing method using the shell mold process described in the above-mentioned Japanese Patent Application Laid-Open No. 5-261478.

  In the conventional method of FIG. 2, resin-coated sand is used. Usually, since the resin-coated sand is manufactured and sold by a vendor different from the casting manufacturer, the step (11) of manufacturing the resin-coated sand is performed at a location different from the casting manufacturing site. Therefore, even if the resin-coated sand is recovered and regenerated, it is difficult to reuse the resin-coated sand for molding a mold as opposed to the method of the present invention.

  According to the conventional method of FIG. 2, a casting manufacturer heats a commercially available resin-coated sand to form a core mold (12), assembles the molded core mold with other molds, and forms a finished mold. Manufacturing (13) and pouring the finished mold (14). Next, the core mold is removed by a sand dropping furnace (15), and the casting is sufficiently cooled (16). Then, the foundry sand is completely removed by a knockout process (17), and the casting is heat-treated (18). Furthermore, core sand containing core lump is recovered from the knockout process 17, the heat treatment process 18 and the subsequent processes (19). The collected core sand is subjected to core crushing 20, roasting 21, and mechanical regeneration 22 at a resin-coated sand manufacturing site that is usually a place different from the place where the collecting step 19 is performed. The

  In the casting manufacturing method of the present invention shown in FIG. 1, it is apparent that the number of steps is reduced as compared with the conventional method shown in FIG. For example, in the method of the present invention (FIG. 1), the fifth (mold removal) step 5 is easy to disintegrate the mold, and can be achieved by a simple step, for example, sand removal by light vibration. However, in the conventional method (FIG. 2) that makes it difficult to collapse the mold, the removal 15 by the sand dropping furnace, the sufficient cooling 16 of the casting, and the knockout process 17 are required for removing the mold. Further, the method of the present invention does not require roasting 21 in the recovery and regeneration of the conventional method.

  FIG. 3 is a graph showing the relationship between temperature and time in the fifth (template removal) step 5 and the sixth (heat treatment) step 6 of the embodiment of the present invention. For comparison, FIG. 4 (Prior Art) is a similar graph for the conventional process corresponding to the mold removal and heat treatment process in the method of the present invention.

  In the conventional method, as described above, after sufficient cooling of the casting (step 16 in FIG. 2), sand removal by the knockout step is performed (step 17 in FIG. 2), and then the temperature is raised again for the T6 treatment. Was. For this reason, as shown in FIG. 4, in addition to the time required for cooling, reheating time and energy for heat treatment are required.

  In the embodiment of the present invention shown in FIG. 3, after pouring at 720 ° C., the core mold is removed from the casting immediately after the molten metal is taken out in the mold removing step 5. Therefore, in order to remove the core mold, it is not necessary to apply a large impact after sufficiently cooling the cast product, and the solution treatment (heat treatment) can be started immediately. For this reason, since the time required for cooling can be shortened and the reheating time for heat treatment can be shortened, energy consumption can be saved and the number of processes can be reduced. The casting does not necessarily need to be cooled to 100 ° C, and an energy saving effect can be obtained even by cooling to 300 ° C.

  The above-described embodiments are merely illustrative of the present invention and are not intended to be limiting, and various modifications and variations will occur to those skilled in the art without departing from the scope and spirit of the appended claims. It is clear that

FIG. 1 is a process diagram of a casting manufacturing method according to the present invention. FIG. 2 is a process diagram of a conventional casting manufacturing method using a shell mold process. FIG. 3 is a graph showing the relationship between casting temperature and time in the mold removal and heat treatment steps of this embodiment. FIG. 4 corresponds to the process of FIG. 3 and is a graph similar to FIG. 3 showing the prior art process using the shell mold process.

Claims (15)

A method for manufacturing a casting,
Forming an aggregate mixture by mixing at least one particulate aggregate, at least one water-soluble binder, and water, and stirring the aggregate mixture to foam;
Filling the foamed aggregate mixture into the mold making space, evaporating moisture in the filled aggregate mixture to solidify the aggregate mixture, and molding the mold with the particulate aggregate; and
A step of producing a finished mold by combining a mold of the other party with respect to at least one molding mold formed of the particulate aggregate;
Pouring molten metal into the finished mold;
Removing the molding mold from the casting during a cooling period of the casting after the molten metal is solidified;
A method for producing a casting, including a step of heat-treating the casting. 2. The method according to claim 1, wherein at least one molding mold molded by the particulate aggregate is a core mold, and the counterpart mold is a main mold. 3. The method according to claim 2, wherein the main mold is a mold. The method according to claim 2, wherein the main mold is a sand mold. 5. The method according to claim 1, further comprising a step of collecting the particulate aggregate and a step of regenerating the collected particulate aggregate. 6. The method according to claim 5, wherein the recovered and regenerated particulate aggregate is used again for molding a mold. The method according to claim 5 or 6, wherein the step of recovering and regenerating the particulate aggregate is mechanical regeneration. 8. The method according to any one of claims 1 to 7, wherein the casting is an aluminum alloy casting or a magnesium alloy casting. 9. The method according to claim 8, wherein the heat treatment is T6 treatment or T7 treatment. 8. The method according to any one of claims 1 to 7, wherein the casting is a cast iron, cast steel, or iron metal alloy casting. 8. The method according to any one of claims 1 to 7, wherein the casting is a copper alloy casting. 12. The method according to any one of claims 1 to 11, wherein the step of removing the mold applies vibration to the mold. 13. The method according to claim 12, wherein applying vibration to the mold gives an impact force of 1 Mpa or less to the mold at less than 30 Hz for less than 30 seconds in a time within 5 minutes to 20 minutes after pouring. Including methods. A method for manufacturing a casting,
Forming an aggregate mixture by mixing at least one particulate aggregate, at least one water soluble binder, and water;
The aggregate mixture is agitated and foamed, the foamed aggregate mixture is filled into a mold molding space, the moisture in the filled aggregate mixture is evaporated to solidify the aggregate mixture, and the particulate aggregate Forming a core mold by
Combining at least one core mold and a mold mold into a finished mold;
Pouring a molten aluminum alloy into the finished mold;
Removing the core mold from the casting during a cooling period of the casting after the molten metal is solidified;
A method for producing a casting, including a step of heat-treating the aluminum alloy casting with T6 or T7. The method according to any one of claims 1 to 14, wherein the at least one water-soluble binder is at least one of polyvinyl alcohol and a derivative thereof.
Or the method which is at least one of starch and its derivative (s).

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