Method for producing core

Abstract

To provide a method for producing a core, capable of: reducing a residual binder accumulated in reclaimed sand by repeated sand reclamation; and ensuring strength of the produced core and improving quality of the core.SOLUTION: A method according to the present disclosure for producing a core includes the steps of: blending, at a predetermined ratio, a dry reclaimed sand obtained by reclaiming molding sand having been used for core production through a dry method, a wet reclaimed sand obtained by reclaiming the molding sand through a wet method, and a new sand; and producing a core from the blended sand. The blending ratio is 49 to 95 wt.% of the dry reclaimed sand, 1 to 49 wt.% of the wet reclaimed sand, and 1 to 5 wt.% of the new sand.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing neutrons.

Background Art

[0002] In Patent Document 1, when manufacturing neutrons, the CS core method that uses an inorganic material such as water glass as a binder is used.

[0003] In the CS core method, the casting sand used for manufacturing neutrons is recycled, and the recycled sand (reclaimed sand) is reused for manufacturing other neutrons. There are a dry method and a wet method for the method of recycling casting sand. The dry method is a method of removing the water glass component remaining on the surface of the casting sand by heat-treating the casting sand used for manufacturing neutrons and polishing by vibration shock or the like. For example, Patent Document 2 discloses an example of the dry method. On the other hand, the wet method is a method of removing water glass from the casting sand by bringing the casting sand used for manufacturing neutrons into contact with a solvent such as water.

[0004] Patent Document 3 discloses a method for measuring the flexural strength of a manufactured neutron test piece. Patent Document 3 will be used in the description of the embodiments described later.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the technologies according to Patent Documents 1 to 3, in the dry method, since the water glass on the sand surface is physically removed by applying impact and friction, there is a fundamental limit in removing the water glass with the existing method. If the polishing force is too strong, cracks or the like may occur in the sand body, which may also cause a decrease in strength, so there are limitations, and the removal efficiency of the water glass is insufficient. Therefore, residual binders accumulate in the recycled sand by repeated sand recycling. For example, due to the accumulation of the residual binder, this binder component absorbs moisture, and during the production of cores by the CS core method, a part of the components dissolves into the auxiliary materials, causing defects such as foam inhibition and gas defects. Also, due to the influence of the residual binder, the strength of the cores increases or decreases.

[0007] On the other hand, in the wet method, since it is a method of removing water glass by bringing the foundry sand into contact with a solvent such as water, the residual binder in the recycled sand is almost completely removed, but insufficient strength of the cores produced using the recycled sand occurs.

[0008] That is, in the technologies according to Patent Documents 1 and 2, there has been a problem that it is impossible to reduce the residual binder accumulated in the recycled sand by repeated sand recycling, ensure the strength of the cores to be produced, and improve the quality of the cores.

[0009] In view of such problems, the present disclosure provides a method for manufacturing cores that can reduce the residual binder accumulated in the recycled sand by repeated sand recycling, ensure the strength of the cores to be produced, and improve the quality of the cores.

Means for Solving the Problems

[0010] The method for manufacturing cores of the present disclosure includes a step of blending dry recycled sand, which is sand obtained by recycling foundry sand used in the production of cores by the dry method, wet recycled sand, which is sand obtained by recycling the foundry sand by the wet method, and new sand at a predetermined ratio, and a step of manufacturing cores from the blended sand, and the blending ratio is such that the dry recycled sand is 49 to 95 wt%, the wet recycled sand is 1 to 49 wt%, and the new sand is 1 to 5 wt%.

[0011] In addition, in the method for manufacturing cores of the present disclosure, the blending ratio is such that the dry recycled sand is 69 to 95 wt%, the wet recycled sand is 1 to 30 wt%, and the new sand is 1 to 5 wt%.

[0012] In addition, in the method for manufacturing cores of the present disclosure, the blending ratio is such that the dry recycled sand is 79 to 95 wt%, the wet recycled sand is 1 to 20 wt%, and the new sand is 1 to 5 wt%.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to provide a method for manufacturing cores that can reduce the residual binder accumulated in the recycled sand by repeated sand recycling, ensure the strength of the manufactured cores, and improve the quality of the cores.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0015] (First Embodiment) Using FIG. 1, the method for manufacturing cores according to the first embodiment will be described.

[0016] FIG. 1 is a flowchart showing an example of a method for manufacturing cores according to the first embodiment. As shown in FIG. 1, first, in step S101, dry recycled sand, wet recycled sand, and new sand are blended in a mixer at a predetermined ratio.

[0017] Dry recycled sand is sand obtained by recycling casting sand used in the production of cores by the dry method. In dry recycled sand, the residual binder (residual water glass) is greater than 0 wt% and less than or equal to 4 wt%. Wet recycled sand is sand obtained by recycling casting sand used in the production of cores by the wet method. In wet recycled sand, the residual binder is less than 1 wt%. New sand is not recycled casting sand used in the production of cores, but rather new sand, such as sand mainly composed of aluminum oxide. New sand is sand blended to make up for the amount of sand lost in the following core production process.

[0018] The blending ratio described above is preferably 49 - 95 wt% dry recycled sand, 1 - 49 wt% wet recycled sand, and 1 - 5 wt% new sand. More preferably, the blending ratio is 69 - 95 wt% dry recycled sand, 1 - 30 wt% wet recycled sand, and 1 - 5 wt% new sand. Even more preferably, the blending ratio is 79 - 95 wt% dry recycled sand, 1 - 20 wt% wet recycled sand, and 1 - 5 wt% new sand.

[0019] Also, the dry method described above is a method of removing the water glass component remaining on the surface of the casting sand by heat-treating and polishing the casting sand used in the production of cores. Specifically, the dry method is disclosed in Patent Document 2. For example, in the dry method, the casting sand used in the production of cores is crushed until it becomes granular. The granular material is heated at a temperature of 300°C to 550°C. The heated granular materials are made to collide with each other, and the water glass is peeled off from the casting sand. Air is blown onto the mixture of the peeled water glass and the casting sand, and the casting sand is separated and recovered as dry recycled sand from the mixture due to the specific gravity difference between the water glass and the casting sand.

[0020] Further, the above wet method is a method of removing water glass from the foundry sand by bringing the dry regenerated sand or the foundry sand used in the production of cores into contact with a solvent containing water. For example, in the wet method, first, runner dry regenerated sand with a residual binder of 1 to 4 wt% is prepared. 1500 g of the dry regenerated sand and 2000 g of water are placed in an autoclave, and the foundry sand is washed at 120°C for 5 minutes. Thereafter, the washed foundry sand (hereinafter, washed sand) is drained. Then, 1500 g of the washed sand is rinsed with 2000 g of water and recovered as wet regenerated sand.

[0021] Note that after step S101, sand in which dry regenerated sand, wet regenerated sand, and new sand are blended at a predetermined ratio may be stored in a tank. Further, when sand previously blended is stored in the tank, in the method for manufacturing the present core, step S101 may not be executed.

[0022] Next, in step S102, the blended sand (hereinafter, blended sand) is kneaded in a kneading kettle. In the kneading, 2 kg of the blended sand, 0.65 AI% (Active ingredient%) of water glass, 0.03 AI% of a surfactant, and 3.2 wt% of water are placed in the kneading kettle, and kneading is performed for 300 seconds.

[0023] Next, in step S103, the kneaded blended sand (hereinafter, kneaded sand) is filled into a mold. The filling into the mold is performed at a pushing pressure of 0.35 MPa and a pressing time of 30 seconds. The mold temperature of the mold is set to 260°C by an electric heater or the like. Next, in step S104, the kneaded sand filled in the mold is fired. The firing is performed at a mold temperature of 260°C and a firing time of 60 seconds.

[0024] Subsequently, with reference to FIG. 2, verification results of suitable blending ratios of dry regenerated sand, wet regenerated sand, and new sand in the method for manufacturing a core according to the first embodiment will be described.

[0025] Figure 2 is a graph showing the measurement test results of the flexural strength of test pieces of each neutron manufactured at different blend ratios by the neutron manufacturing method according to the first embodiment. The horizontal axis of the graph indicates the blend ratio of each test piece. The vertical axis of the graph indicates the measurement results of the flexural strength [kgf / cm2] of each test piece.

[0026] The blend ratios for each test piece are, from the left side of the graph, 100 wt% new sand, 100 wt% dry recycled sand, 100 wt% wet recycled sand, 95 wt% dry recycled sand and 5 wt% new sand, 1 wt% new sand and 1 wt% wet recycled sand (98 wt% dry recycled sand), 1 wt% new sand and 4 wt% wet recycled sand (95 wt% dry recycled sand), 1 wt% new sand and 6 wt% wet recycled sand (93 wt% dry recycled sand), 1 wt% new sand and 12 wt% wet recycled sand (87 wt% dry recycled sand), 1 wt% new sand and 20 wt% wet recycled sand (79 wt% dry recycled sand), 1 wt% new sand and 30 wt% wet recycled sand (69 wt% dry recycled sand), and 1 wt% new sand and 49 wt% wet recycled sand (50 wt% dry recycled sand). The blended sand of 5 wt% new sand and 95 wt% dry recycled sand described above is also called current sand and represents the recycled sand currently used in the manufacture of neutrons.

[0027] The measurement test method for flexural strength is disclosed in Patent Document 3. Here, the flexural strength is a value indicating the strength against bending. The flexural strength is measured by a mold flexural strength tester with each test piece set in the mold flexural strength tester.

[0028] The evaluation of the flexural strength of each test piece is as follows. If the flexural strength is 20.0 to 50.0 [kgf / cm2], the neutron test piece is rated "good". If the flexural strength is further 31.0 [kgf / cm2] or more, the neutron test piece is rated "excellent". If the flexural strength is further above the current sand 95% line (indicated by the dashed-dotted line in Figure 2), the neutron test piece is rated "best". This threshold value is set at the 95% line when the flexural strength of the current sand is taken as 100% because it can be said that the flexural strength is equivalent when the strength is ±5% based on 5 wt% new sand and 95 wt% dry recycled sand (current sand).

[0029] For specimens with 1 wt% of new sand and 1 wt% of wet recycled sand, specimens with 1 wt% of new sand and 4 wt% of wet recycled sand, specimens with 1 wt% of new sand and 6 wt% of wet recycled sand, specimens with 1 wt% of new sand and 12 wt% of wet recycled sand, specimens with 1 wt% of new sand and 20 wt% of wet recycled sand, specimens with 1 wt% of new sand and 30 wt% of wet recycled sand, and specimens with 1 wt% of new sand and 49 wt% of wet recycled sand, since the flexural strength is 20.0 - 50.0 [kgf / cm2], the evaluation of the flexural strength was "good". Therefore, it was verified that the cores manufactured with a blend ratio of 1 wt% of new sand and 1 - 49 wt% of wet recycled sand can be expected to have flexural strength.

[0030] Also, for specimens with 1 wt% of new sand and 1 wt% of wet recycled sand, specimens with 1 wt% of new sand and 4 wt% of wet recycled sand, specimens with 1 wt% of new sand and 6 wt% of wet recycled sand, specimens with 1 wt% of new sand and 12 wt% of wet recycled sand, specimens with 1 wt% of new sand and 20 wt% of wet recycled sand, and specimens with 1 wt% of new sand and 30 wt% of wet recycled sand, since the flexural strength is further 31.0 [kgf / cm2] or more, the evaluation of the flexural strength was "excellent". Therefore, it was verified that the cores manufactured with a blend ratio of 1 wt% of new sand and 1 - 30 wt% of wet recycled sand can be more expected to have flexural strength.

[0031] Also, for specimens with 1 wt% of new sand and 1 wt% of wet recycled sand, specimens with 1 wt% of new sand and 4 wt% of wet recycled sand, specimens with 1 wt% of new sand and 6 wt% of wet recycled sand, specimens with 1 wt% of new sand and 12 wt% of wet recycled sand, and specimens with 1 wt% of new sand and 20 wt% of wet recycled sand, since the flexural strength is further above the 95% line of the current sand (indicated by the dashed line in Figure 2), the evaluation of the flexural strength was "the best". Therefore, it was verified that the cores manufactured with a blend ratio of 1 wt% of new sand and 1 - 20 wt% of wet recycled sand can be more expected to have flexural strength.

[0032] As described above, in the method for manufacturing cores according to the first embodiment, dry recycled sand, wet recycled sand, and new sand are blended at a predetermined ratio, and cores are manufactured from the blended sand. The blending ratio is preferably 49 to 95 wt% of dry recycled sand, 1 to 49 wt% of wet recycled sand, and 1 to 5 wt% of new sand. More preferably, the blending ratio is 69 to 95 wt% of dry recycled sand, 1 to 30 wt% of wet recycled sand, and 1 to 5 wt% of new sand. Even more preferably, the blending ratio is 79 to 95 wt% of dry recycled sand, 1 to 20 wt% of wet recycled sand, and 1 to 5 wt% of new sand.

[0033] Here, when only dry recycled sand is used for manufacturing cores, residual binders accumulate in the recycled sand due to repeated sand recycling. On the other hand, when only wet recycled sand is used for manufacturing cores, the residual binders in the recycled sand are almost completely removed, but insufficient strength of the cores manufactured using the recycled sand occurs.

[0034] In the method for manufacturing cores according to the first embodiment, in addition to wet recycled sand, dry recycled sand is blended to obtain the above-described blending ratio, thereby ensuring the strength of the manufactured cores. Also, in this method for manufacturing cores, it is possible to reduce the residual binders that accumulate in the recycled sand due to repeated sand recycling (in other words, in repeated sand recycling, the amount of binder in the recycled sand can be made closer to a constant value). Therefore, in this method for manufacturing cores, by reducing the residual binders that accumulate in the recycled sand due to repeated sand recycling, it is possible to reduce the possibility of defects such as foaming inhibition and gas defects caused by the accumulation of residual binders. Also, it is possible to reduce the possibility that the strength of the cores increases or decreases due to the influence of the residual binders. Further, in this method for manufacturing cores, the quality of the cores can be improved. In this method for manufacturing cores, for example, wrinkles and clogging defects of the cores are reduced, so the surface of the rough material (e.g., engine) becomes cleaner. Also, since the cores are not deformed under the pressure of molten aluminum, the swelling defects of the rough material are reduced.

[0035] Note that the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the gist thereof.

Claims

1. A step of blending dry recycled sand, which is sand obtained by recycling casting sand used in the production of neutrons by a dry method, wet recycled sand, which is sand obtained by recycling the casting sand by a wet method, and new sand at a predetermined ratio; A step of producing neutrons from the blended sand, and comprising: The blending ratio is: The dry recycled sand is 49 to 95 wt%, the wet recycled sand is 1 to 49 wt%, and the new sand is 1 to 5 wt%. A method for producing neutrons.

2. The blending ratio is: The dry recycled sand is 69 to 95 wt%, the wet recycled sand is 1 to 30 wt%, and the new sand is 1 to 5 wt%. The method for producing neutrons according to Claim 1.

3. The blending ratio is: The dry recycled sand is 79 to 95 wt%, the wet recycled sand is 1 to 20 wt%, and the new sand is 1 to 5 wt%. The method for producing neutrons according to Claim 2.

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