JP2014155941A - Cast production method, cast and casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to produce a precise casting and facilitate reuse of casting sand.SOLUTION: The cast production method includes a mixing step in which sodium silicate and ρ-alumina are added to casting sand and mixed to form a mixed product, a cast producing mold installation step in which a cast producing mold having a shape along the outer shape of a cast is formed and installed, a filling step in which the cast producing mold is filled with the mixed product for compaction, a solidification step for solidifying the mixed product having filled the cast producing mold for compaction, and a removal step for removing the cast producing mold from the dried and solidified mixed product.

Description

  The present invention relates to a mold manufacturing method, a mold, and a casting method.

  When manufacturing a large casting, a sand mold may be used as a mold. In the casting method using a sand mold, a passenger compartment used for a steam turbine, a gas turbine, a compressor, or the like can be manufactured. Here, the passenger compartment is a container (also referred to as a casing) that contains a steam turbine, a gas turbine, or a main part of a compressor and confines steam or expansion gas.

  As a casting method using a sand mold, for example, a wooden mold is filled with foundry sand, subjected to high-temperature treatment at about 100 ° C. to form a sand mold, and the formed sand mold is melted at a high temperature of about 1200 to 1500 ° C. ) Is poured (casting), cooled to solidify the molten metal (casting molding), and then the sand mold is crushed and the solidified metal (casting) is taken out.

  Here, the sand mold is a mold made of foundry sand, and is formed by mixing a foundry sand with a binder and solidifying the foundry sand with the binder. In recent years, it has been proposed to use an inorganic material as a binder. For example, Patent Document 1 describes that a composite oxide sol made of silica and an inorganic oxide other than silica is added as a binder to a refractory material such as zircon sand or silica sand.

JP 05-277622 A

  Here, when an organic resin is used as the binder, the organic resin is thermally decomposed or burned by being heated by the metal poured at the time of casting, and gas is generated, causing a gas defect in the casting. On the other hand, by using the inorganic material described in Patent Document 1 as the binder, it is possible to suppress the generation of gas due to the binder, and it is possible to suppress the generation of gas when the molten metal is cast into the sand mold. .

  Here, since the sand mold is produced using a large amount of sand, it is desired that the sand mold can be recycled and reused from the viewpoints of economy, waste disposal, and the like. Therefore, in addition to durability as a sand mold, after manufacturing a casting, there is a demand for compatibility with ease of processing, specifically, brittleness (disintegration) so that it can be crushed and regenerated into sand. However, the mold using the binder described in Patent Document 1 has high strength even after casting, and may not be easily reused.

  An object of the present invention is to provide a mold manufacturing method, a mold, and a casting method capable of manufacturing a high-precision casting and facilitating reuse of foundry sand.

  In order to solve the above-described problems and achieve the object, the present invention is a mold manufacturing method used for manufacturing a casting, which is a kneaded product obtained by adding sodium silicate and ρ-alumina to a casting sand and mixing them. A kneading step for producing a mold, a mold manufacturing mold having a shape in accordance with the outer shape of the mold, and a mold manufacturing mold installation step for installing, and filling the mold manufacturing mold with the kneaded product and compacting A filling step, a solidification step for solidifying the compacted and kneaded product filled in the mold for mold production, and a removing step for removing the mold for mold production from the dried and solidified kneaded product. It is characterized by.

  In the kneading step, it is preferable to further add and mix sodium hydroxide to the foundry sand.

  In the kneading step, the amount of sodium silicate added to the foundry sand is 0.2 wt% or more and 0.6 wt% or less, and the amount of ρ-alumina added to the foundry sand is 0.5 wt%. % Or more and 1.0% by weight or less is preferable.

  The foundry sand is preferably mullite sand.

  In the solidification step, it is preferable that the kneaded product is dried while being heated to 100 ° C. or higher and 300 ° C. or lower to be solidified.

  In order to solve the above-described problems and achieve the object, the present invention is a mold used for manufacturing a casting, which is manufactured by the above-described manufacturing method.

  In order to solve the above-described problems and achieve the object, the present invention provides a casting method using the mold, the process of manufacturing the mold by the manufacturing method, and the injection process of injecting molten metal into the mold And a metal solidification step for solidifying the metal injected into the mold, and a removal step for taking out the solidified metal from the mold.

  In the injecting step, the molten metal is preferably injected into the mold at 1200 ° C. or higher.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to manufacture a highly accurate casting and reuse of foundry sand becomes easy.

FIG. 1 is a perspective view showing a schematic configuration of a mold according to the present embodiment. FIG. 2A is a YZ plane cross-sectional view showing a schematic configuration of the mold of the present embodiment. FIG. 2B is a ZX plane cross-sectional view showing a schematic configuration of the mold of the present embodiment. FIG. 3A is a schematic diagram showing the relationship between the foundry sand and the binder of the mold of this embodiment. FIG. 3B is a schematic diagram illustrating a schematic configuration of a mold binder of the present embodiment. FIG. 4 is a flowchart showing an example of the mold manufacturing method of the present embodiment. FIG. 5 is a diagram for explaining an example of the mold manufacturing method of the present embodiment. FIG. 6 is a diagram for explaining an example of the mold manufacturing method of the present embodiment. FIG. 7 is a flowchart showing an example of the casting method of the present embodiment. FIG. 8 is a diagram for explaining an example of the casting method of the present embodiment. FIG. 9 is a graph showing the compressive strength of the mold in Test Example 1. FIG. 10 is a graph showing the compressive strength of the mold in Test Example 2. FIG. 11 is a graph showing the compression strength of the mold in Test Example 3. FIG. 12 is a graph showing the compression strength of the mold in Test Example 4.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description. In addition, constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. In addition, the mold manufacturing method, the mold, and the casting method described below can be suitably applied to the manufacture of a casing (casing) such as a steam turbine, a gas turbine, and a compressor, but are not limited thereto.

  FIG. 1 is a perspective view showing a schematic configuration of a mold according to the present embodiment. FIG. 2A is a YZ plane cross-sectional view showing a schematic configuration of the mold of the present embodiment. FIG. 2B is a ZX plane cross-sectional view showing a schematic configuration of the mold of the present embodiment. A mold 10 shown in FIG. 1 has an upper mold 12 and a lower mold 14. As shown in FIGS. 2A and 2B, when the upper mold 12 and the lower mold 14 are overlapped with each other, the outer periphery side region between the lower surface 24 of the upper mold 12 and the upper surface 26 of the lower mold 14 is formed on the entire periphery of the mold 10. Contact. In the mold 10, a space 16 is formed between the lower surface 24 of the upper mold 12 and the upper surface 26 of the lower mold 14 in a state where the upper mold 12 and the lower mold 14 are overlapped. This space 16 has a shape corresponding to a casting to be formed, and becomes a casting forming region. The casting formation region is a region where a target casting is formed by pouring, filling, and hardening molten metal.

  The upper mold 12 is formed with a gate 20 and a plurality of air holes 22. The gate 20 and the plurality of air holes 22 are connected to the space 16. The space 16 is a closed space except for the portion connected to the gate 20 and the plurality of air holes 22.

  The mold 10 has the shape as described above, and a closed space 16 is formed except for the gate 20 and the plurality of air holes 22. In the present embodiment, the mold 10 has a shape in which the upper mold 12 and the lower mold 14 are overlapped, but the present invention is not limited to this. For example, the mold 10 may further include a core. The shape of the space of the mold 10 may be various shapes and sizes according to the shape of the target casting.

  Next, the mold 10 will be described in more detail with reference to FIGS. 3A and 3B. FIG. 3A is a schematic diagram showing the relationship between the foundry sand and the binder of the mold of this embodiment. FIG. 3B is a schematic diagram illustrating a schematic configuration of a mold binder of the present embodiment.

  The mold 10 is a so-called sand mold in which foundry sand is solidified to have a predetermined shape. Foundry sand is sand having fire resistance. As the foundry sand, conventionally known sand that can be used as sand forming a sand mold, such as silica sand, zircon sand, chromite sand, olivine sand, or mullite sand, can be used. Hereinafter, in the present embodiment, a case where mullite sand is used as the foundry sand will be described. Mullite sand is a highly fire-resistant particle.

  As shown in FIG. 3A, the mold 10 is solidified by connecting the foundry sand 30 using a binder 32. The casting mold 10 is solidified with a strength that allows the foundry sands 30 having a weak bonding force to be used as a casting mold by connecting the foundry sands 30 using a binder 32. The binder 32 is formed of a plurality of inorganic materials, and the foundry sand 30 and the foundry sand 30 are connected by the first connecting body 34 and the second connecting body 36. The 1st connection body 34 and the 2nd connection body 36 are examples which modeled the structure of the binder which connects sand particles.

Here, the 1st coupling body 34 is formed with the material formed by processing sodium silicate (silicate sodium), specifically, performing heat processing. The second coupling body 36 is formed of a material formed by treating ρ-alumina (Al ₂ O ₃ .nH ₂ O: ≈0.5), specifically, heat treating.

  ρ-alumina is a unique alumina among alumina and has a property of reacting with water and solidifying.

  Next, the manufacturing method of a casting_mold | template is demonstrated using FIGS. FIG. 4 is a flowchart showing an example of the mold manufacturing method of the present embodiment. The process shown in FIG. 4 may be executed fully automatically, or may be executed by an operator operating an apparatus that executes each process.

  First, a mold manufacturing method produces a kneaded material (step S12). In this embodiment, sodium silicate and ρ-alumina are added to and mixed with foundry sand to produce a kneaded product. Thereby, the kneaded material with which sodium silicate used as a binder and (rho) -alumina were mixed with casting sand is produced.

  Next, the mold manufacturing method performs the production and installation of a wooden mold (step S13). In the mold manufacturing method, a wooden pattern is produced according to the shape of the mold to be manufactured, and is set at a predetermined position. The wooden mold is a mold (mold for mold production) formed along the outer shape of the mold. The mold for mold production can be formed of various materials that can be used as a mold in the production of a sand mold. In the mold manufacturing method, the processes of step S12 and step S13 may be performed in parallel or in the reverse order.

  In the mold casting method, after the kneaded material is produced and the wooden mold is installed, the kneaded material produced by kneading is filled into the wooden mold and consolidated (step S14). Consolidation is an operation of filling a kneaded product to every corner of a wooden shape by applying a predetermined pressure. Here, the predetermined pressure is, for example, a pressure that is pressed by a human hand. Thereby, the kneaded material is filled in the space in the wooden mold.

  In the mold manufacturing method, after the kneaded material is filled in the mold, the kneaded material is solidified by drying (step S16). Here, the drying is preferably performed by heating to a predetermined temperature. In the case of heat drying, for example, the temperature is raised to about 120 ° C. by hot air drying.

  Here, in the kneaded product of the present embodiment, by drying, sodium silicate and ρ-alumina added to the foundry sand are connected to each other between the foundry sand and the foundry sand, so that the foundry sands are combined. The present inventors consider that it is solidified. Specifically, sodium silicate and ρ-alumina, which is a binder (binder) composition combined with water, are bonded to the foundry sand by water being evaporated by drying. The present inventors consider that the bonding is strengthened between the casting sands.

  Here, solidification of ρ-alumina proceeds by crystal conversion of the hydrate after the hydration reaction of the main component occurs, and combines the foundry sand and the foundry sand.

  In the mold manufacturing method, when the kneaded product in the wooden mold is solidified, the wooden mold is removed from the solidified kneaded product (step S18). The solidified kneaded product from which the wooden mold has been removed becomes at least a part of the mold. The mold manufacturing method manufactures a mold by producing each part included in the mold by the above-described processing.

  Next, the manufacturing method of the mold shown in FIG. 1 will be specifically described with reference to FIGS. 5 and 6 are diagrams for explaining an example of the mold manufacturing method of the present embodiment. Here, FIG. 5 shows an example of a mold manufacturing method for the upper mold 12 of the mold 10 described above. FIG. 6 shows an example of a mold manufacturing method for the lower mold 14 of the mold 10 described above.

  A method for manufacturing the upper mold 12 will be described with reference to FIG. In the manufacturing method of the upper mold, first, as shown in step S102, the wooden mold 52 is installed on the installation surface 50. The wooden mold 52 includes a wooden main body 54 and a frame portion 56 that covers the outer periphery of the wooden main body 54. The wooden main body 54 has a shape corresponding to the lower surface of the upper mold. The wooden main body 54 has a protrusion 54a at a position corresponding to the air hole of the upper mold. The frame portion 56 extends to a position higher than the upper end portion in the vertical direction (the portion where the kneaded material is filled) where the mold is provided. Next, in the method for manufacturing the upper mold, as shown in step S104, the kneaded material 60 is filled into the wooden mold 52 and consolidated. At this time, the kneaded material 60 is filled in a state in which the gate rod 58 is disposed in the region corresponding to the gate of the upper mold. In the upper mold manufacturing method, the filled kneaded product 60 is then dried and solidified, and the wooden mold 52 is removed, whereby the upper mold 12 is manufactured as shown in step S106. The upper mold 12 is mounted with the frame portion 56 as it is to hold the mold. A gate 20 and an air hole 22 as shown in the figure are formed.

  Next, a manufacturing method of the lower mold 14 will be described with reference to FIG. In the lower mold manufacturing method, first, as shown in step S112, the wooden mold 70 is installed. The wooden mold 70 includes a wooden main body 72 and a frame portion 74 that covers the outer periphery of the wooden main body 72. The wooden main body 72 has a shape corresponding to the upper surface of the lower mold. The frame portion 74 extends to a position higher than the upper end in the vertical direction (the portion where the kneaded material is filled) where the mold is provided. Next, in the lower mold manufacturing method, as shown in step S114, the kneaded material 80 is filled into the wooden mold 70 and consolidated. Thereafter, the lower mold 14 is manufactured by drying and solidifying the filled kneaded product 80 and removing the wooden mold 70 as shown in step S116.

  The mold 10 is manufactured by manufacturing the upper mold 12 and the lower mold 14 as shown in FIGS. 5 and 6 and combining the upper mold 12 and the lower mold 14.

  Next, the casting method will be described with reference to FIGS. FIG. 7 is a flowchart showing an example of the casting method of the present embodiment. FIG. 8 is a diagram for explaining an example of the casting method of the present embodiment. Here, the process shown in FIG. 7 may be executed fully automatically, or may be executed by an operator operating an apparatus that executes each process.

  First, the casting method of this embodiment produces a casting mold (step S60). Specifically, a mold is manufactured by the above-described mold manufacturing method. Specifically, as shown in step S122 of FIG. 8, the mold 10 is manufactured by combining the upper mold 12 and the lower mold 14. Here, the mold may be prepared in advance separately from the production of the casting, or may be produced every time the production of the casting is executed.

  Next, in the casting method, molten metal is injected into the mold (step S62). Specifically, as shown in step S <b> 124 of FIG. 8, molten metal 90 is injected from the gate 20 of the upper mold 12 into the space 16. The molten metal poured into the mold in the casting method of the present embodiment is also called a molten metal. The operation of pouring the molten metal into the mold is also called pouring. A series of processes in which a metal is melted at a high temperature and poured is called casting. Here, in the case of steel, the temperature of the molten metal at the time of casting is, for example, 1200 ° C. to 1500 ° C.

  In the casting method, the mold may be preheated before the molten metal is injected into the mold. For example, the mold is placed in a furnace (vacuum furnace, firing furnace) and heated to 800 ° C. or higher and 900 ° C. or lower. By performing preheating, it is possible to prevent the mold from being damaged when the molten metal is poured into the mold.

  In the casting method, when molten metal is injected into the mold, the molten metal poured into the mold is solidified (step S64). In the casting method, for example, the molten metal is solidified by cooling the mold by natural cooling or the like. As a result, as shown in step S126 of FIG. 8, the space 16 between the upper mold 12 and the lower mold 14 of the mold 10 can be filled with the solidified metal. Although the molten metal is solidified by natural cooling from the casting temperature to the environmental temperature, it may be cooled and solidified while controlling the temperature of the mold and the molten metal in the mold using a temperature adjusting device or the like. Good.

  Thereafter, the casting method takes out the solidified metal by crushing or crushing the mold from the mold (step S66). As shown in FIG. 8, the solidified metal 92 taken out from the mold becomes a casting 94. The removed casting is finished by appropriately performing surface and internal finishing as required.

  Here, the crushed or crushed mold can be reused as casting sand used for the mold by reprocessing. The regeneration treatment is to further pulverize the crushed or crushed mold into particles (sand particles), and to remove the binder (sodium silicate and ρ-alumina or their reaction products) adhering to the particles. It is the processing to make casting sand. For the regeneration process, a method of removing particles adhering to each other by rubbing particles with each other can be used.

  As mentioned above, this embodiment knead | mixes sodium silicate and ρ-alumina which are inorganic materials in foundry sand, throws the produced kneaded material into a wooden mold, and uses the sodium silicate and ρ-alumina as a binder. The casting sand put into the wooden mold is solidified to produce a mold.

  As described above, by using sodium silicate and ρ-alumina, which are inorganic materials, as a binder, it is possible to suppress the use of an organic material for the mold, and at the time of casting production, specifically casting, the mold It is possible to prevent gas from being generated and causing gas defects in the casting.

  Furthermore, this embodiment can reduce the mold strength after casting while increasing the mold strength before casting and during casting by using a binder in which sodium silicate and ρ-alumina are combined. Here, in this embodiment, before casting is before the molten metal is injected into the mold. During casting, the molten metal is being poured into the mold. After casting is after the molten metal injected into the mold has solidified. Since the mold strength before casting can be increased, the mold can be prevented from being deformed or damaged before the casting is manufactured using the manufactured mold. Further, the casting can also prevent the mold from being deformed or damaged by the pressure of the molten metal injected when the molten metal is injected into the mold. As a result, the production yield of the casting mold and the casting using the casting mold can be increased. Moreover, this embodiment can make it easy to take out the casting from the mold by lowering the mold strength after casting, that is, by increasing the mold collapse property after casting. Moreover, it can suppress that a casting is damaged with the force which grind | pulverizes a casting_mold | template at the time of taking out a casting. Furthermore, the energy required when the mold after the casting is taken out is pulverized into particles by the regeneration process can be reduced. Thereby, since the foundry sand used in large quantities for the production of the mold can be reused efficiently, the mold can be produced efficiently. Further, by reusing the foundry sand, it is possible to reduce the amount of waste generated during the production of the mold and the casting.

  Here, the above effect can be remarkably obtained when a molten metal at a high temperature, specifically, 1200 ° C. or higher is cast as a casting. That is, by using a binder in which sodium silicate and ρ-alumina are combined, the strength after casting can be made lower than when ρ-alumina is not used. More specifically, in the case of using sodium silicate without using ρ-alumina as a binder, after the casting process is performed, for example, once heated to a high temperature of 1200 ° C., the strength increases, and the It becomes difficult to take out the casting, and it becomes difficult to reuse the casting sand. On the other hand, the intensity | strength of the casting_mold | template after a casting process can be made low by using the binder which combined sodium silicate and (rho) -alumina. This is considered to be because the bonding strength becomes weak when ρ-alumina added together with sodium silicate is heated at a casting temperature, for example, 1200 ° C. or more and 1500 ° C. or less.

  Further, by using a binder in which sodium silicate and ρ-alumina are combined, the kneaded material can be solidified in a shorter time than when ρ-alumina is not used.

  Here, in this embodiment, the amount of sodium silicate added to the foundry sand is 0.2 wt% or more and 0.6 wt% or less, and the amount of ρ-alumina added to the foundry sand is 0.5 wt% or more. It is preferable to make it 1.0 wt% or less.

  By setting the addition amount of sodium silicate and ρ-alumina to the foundry sand within the above range, the mold strength before casting can be further increased, and the mold strength after casting can be further decreased. Thereby, the handleability (ease of processing) of the casting mold after the casting can be increased while maintaining the strength of the casting mold at the time of casting production. Moreover, the said effect can be acquired more suitably by making addition amount into a more preferable range and a more preferable range.

  Here, as for the manufacturing method of a casting, it is preferable to add sodium hydroxide to a kneaded material. By adding sodium hydroxide to the kneaded product, the fluidity of the kneaded product can be improved, and the strength before casting can be increased.

  As in the present embodiment, when the mold manufacturing mold is made of a wooden mold, the weight of the mold manufacturing mold can be reduced lightly and inexpensively. Thereby, even when it is set as the casting_mold | template for manufacturing a large sized casting (for example, turbine casing), manufacture of a casting_mold | template can be simplified. The mold solidification temperature in the case of producing a mold using a wooden mold is preferably a temperature of 100 ° C. or higher and 300 ° C. or lower. For example, a mold having a desired strength can be obtained by solidifying a sand mold by maintaining a mold solidification temperature of 100 ° C. or more and 300 ° C. or less for 4 hours. The mold manufacturing mold may be a metal mold or a ceramic ceramic mold. In addition, when using a ceramic mold or a mold, the temperature of the kneaded product can be raised to a higher temperature than that of the wooden mold, for example, about 200 ° C., and the drying and solidification steps can be performed in a shorter time. Can be executed.

Here, the mold preferably has a compressive strength before casting of 20 kgf / cm ² or more. As a result, it is possible to suitably suppress the deformation of the mold when removing the wooden pattern. Further, it is preferable that the mold has a compressive strength after casting of 30 kgf / cm ² or less, more preferably 10 kgf / cm ² or less. Thereby, when taking out the casting, the mold can be easily crushed or pulverized when the mold is regenerated. As described above, by using a binder in which sodium silicate and ρ-alumina are combined as described above, a mold that satisfies the above performance can be manufactured.

<Test example>
Hereinafter, the mold manufacturing method, the mold, and the casting method of this embodiment will be described using test examples. In the following test examples, mullite sand was used as foundry sand, a binder was added to mullite sand to prepare a kneaded product, and after filling and compacting a kneaded product prepared in a wooden mold of φ50 mm and height of 50 mm The mold was produced by placing in a dryer at 120 ° C. for 4 hours to dry and solidify, and then removing the wooden mold. The compression strength of the manufactured mold was measured as the compression strength after forced drying at 120 ° C. Thereafter, the compression strength of the mold after heat treatment at 1200 ° C. for 1 hour was measured as the compression strength after heat treatment at 1200 ° C. Here, the compression strength of the mold was measured by a compression tester. The measured compressive strength after forced drying at 120 ° C. can be regarded as the compressive strength of the mold before casting, and the compressive strength after heat treatment at 1200 ° C. can be regarded as the compressive strength of the mold after casting. Using the manufacturing method and the measuring method as described above, the material and amount used as the binder were variously changed and the test was performed.

(Test Example 1)
In Test Example 1, sodium silicate (50% by weight aqueous solution) was added to mullite sand and mixed, then ρ-alumina was added and further mixed to prepare a kneaded mixture. Molds were made with smelt. That is, in Test Example 1, a combination of sodium silicate and ρ-alumina was used as the binder. In Test Example 1, the amount of sodium silicate added to mullite sand was 0.6% by weight, and the amount of ρ-alumina added was 0.5% by weight. Further, as Comparative Example 1, a kneaded material in which only sodium silicate was added to mullite sand was produced, and a mold was produced. In the kneaded material of Comparative Example 1, the amount of sodium silicate added to mullite sand was 0.6% by weight.

The measurement results are shown in FIG. As shown in FIG. 9, in Test Example 1, the compressive strength after forced drying at 120 ° C. was 50 kgf / cm ² , and the compressive strength after heat treatment at 1200 ° C. was 27 kgf / cm ² . Thus, in Test Example 1, the compressive strength after 120 ° C. forced drying becomes 20 kgf / cm ² or more, and the compressive strength after 1200 ° C. heat treatment becomes 30 kgf / cm ² or less. Thereby, it is possible to increase the compressive strength of the mold before casting and to lower the compressive strength of the mold after casting, and to improve the handling property after mold manufacture while maintaining the strength as a mold. it can. In contrast, in Comparative Example 1, the compressive strength after forced drying at 120 ° C. was 72 kgf / cm ² , and the compressive strength after heat treatment at 1200 ° C. was 93 kgf / cm ² . For this reason, the handling property at the time of reprocessing the mold sand after the mold production is lowered.

  Moreover, the comparative example 1 which did not add (rho) -alumina was not enough dry state, and its handleability was bad by shape loss. On the other hand, in Test Example 1, solidification was promoted by a part of the aggregation of sodium silicate.

(Test Example 2)
0.1% by weight of sodium hydroxide (10% by weight aqueous solution) and 0.6% by weight sodium silicate (50% by weight aqueous solution) as in Test Example 1 were added to the same mullite sand as in Test Example 1. Then, the same ρ-alumina as in Test Example 1 was added and kneaded to prepare a kneaded product. That is, Test Example 2 used a combination of sodium silicate and ρ-alumina as a binder for a system containing sodium hydroxide. Further, as Comparative Example 2, a kneaded material obtained by adding only sodium silicate and sodium hydroxide to mullite sand was produced, and a mold was produced. In the kneaded material of Comparative Example 2, the amount of sodium silicate added to mullite sand was 0.6% by weight, and the amount of sodium hydroxide added was 0.1% by weight.

The measurement results are shown in FIG. As shown in FIG. 10, in Test Example 2, the compressive strength after forced drying at 120 ° C. was 52 kgf / cm ² , and the compressive strength after heat treatment at 1200 ° C. was 28 kgf / cm ² .

Thus, in Test Example 2, the compressive strength after 120 ° C. forced drying can be 20 kgf / cm ² or more, and the compressive strength after 1200 ° C. heat treatment can be suppressed to around 30 kgf / cm ² . Thereby, it is possible to increase the compressive strength of the mold before casting and to lower the compressive strength of the mold after casting, and to improve the handling property after mold manufacture while maintaining the strength as a mold. it can.

In contrast, in Comparative Example 2, the compressive strength after forced drying at 120 ° C. was 76 kgf / cm ² , and the compressive strength after heat treatment at 1200 ° C. was 96 kgf / cm ² . For this reason, the handling property at the time of reprocessing the mold sand after the mold production is lowered.

  Moreover, the comparative example 2 which has not added (rho) -alumina was not dry enough, and handling property was bad by shape loss. On the other hand, in Test Example 2, solidification was promoted due to partial aggregation of sodium silicate.

(Test Example 3)
For the same mullite sand as in Test Example 1, the amount of sodium silicate was changed, and the addition amount of ρ-alumina was fixed to 0.5% by weight to prepare various kneaded samples, and these were used. The compression strength of the produced mold was measured in the same manner as in Test Example 1.

  The measurement results are shown in FIG. As shown in FIG. 11, both the compressive strength after forced drying at 120 ° C. and the compressive strength after heat treatment at 1200 ° C. increased as the amount of sodium silicate added increased.

From the data shown in FIG. 11, it can be said that the addition amount of sodium silicate to mullite sand is preferably about 0.2 to 0.6% by weight in a system in which the addition amount of ρ-alumina is 0.5% by weight. In this range, the compressive strength after 120 ° C. forced drying becomes 20 kgf / cm ² or more, and the compressive strength after 1200 ° C. heat treatment becomes 30 kgf / cm ² or less. Therefore, the compressive strength of the mold before casting can be increased, and the compressive strength of the mold after casting can be decreased, and the handling properties after manufacturing the mold can be increased while maintaining the strength as a mold. .

(Test Example 4)
For the same mullite sand as in Test Example 1, the amount of sodium silicate was fixed at 0.5% by weight, and the amount of rho-alumina was changed to prepare various kneaded samples. The strength was measured in the same manner as in Test Example 1.

The measurement results are shown in FIG. As shown in FIG. 12, in the system in which the amount of sodium silicate added is 0.5% by weight, the amount of ρ-alumina added to mullite sand is preferably about 0.5 to 1.0% by weight. In this range, the compressive strength after 120 ° C. forced drying becomes 20 kgf / cm ² or more, and the compressive strength after 1200 ° C. heat treatment becomes 30 kgf / cm ² or less. Therefore, the compressive strength of the mold before casting can be increased, and the compressive strength of the mold after casting can be decreased, and the handling properties after manufacturing the mold can be increased while maintaining the strength as a mold. .

DESCRIPTION OF SYMBOLS 10 Mold 12 Upper mold 14 Lower mold 16 Space 20 Pouring gate 22 Air hole 24 Lower surface 26 Upper surface 30 Foundry sand 32 Binder 34 1st connection body 36 2nd connection body 50 Installation surface 52, 70 Wood type 54, 72 Wood main body 56, 74 Frame 60, 80 Kneaded product 90 Molten metal 92 Metal 94 Casting

Claims (8)

A mold manufacturing method used for manufacturing a casting,
A kneading step in which sodium silicate and ρ-alumina are added to the foundry sand and mixed to produce a kneaded product;
A mold manufacturing mold installation step for producing and installing a mold manufacturing mold having a shape along the outer shape of the mold; and
A filling step of filling the kneaded product into the mold for producing the mold and compacting the mold,
A solidification step of solidifying the kneaded product filled and consolidated in the mold for mold production;
And a removing step of removing the mold for producing the mold from the dried and solidified kneaded product.   In the kneading step, the amount of sodium silicate added to the foundry sand is 0.2 wt% or more and 0.6 wt% or less, and the amount of ρ-alumina added to the foundry sand is 0.5 wt% or more. The mold production method according to claim 1, wherein the mold production is 1.0% by weight or less.   3. The mold manufacturing method according to claim 1, wherein in the kneading step, sodium hydroxide is further added to and mixed with the foundry sand.   The mold manufacturing method according to claim 1, wherein the foundry sand is mullite sand.   3. The mold manufacturing method according to claim 1, wherein in the solidifying step, the kneaded product is dried while being heated to 100 ° C. or higher and 300 ° C. or lower to be solidified.   A mold manufactured by the mold manufacturing method according to any one of claims 1 to 5. A step of producing a mold by the method of producing a mold according to any one of claims 1 to 5,
An injection step of injecting molten metal into the mold;
A metal solidification step for solidifying the metal injected into the mold;
And a step of taking out the solidified metal from the mold.   The casting method according to claim 7, wherein in the injection step, the molten metal is injected into the mold at a temperature of 1200 ° C. or higher.

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