Patent Application
20250214132
This application claims priority to Japanese Patent Application No. 2023-223399 filed on Dec. 28, 2023, incorporated herein by reference in its entirety.
The present disclosure relates to a method of manufacturing a core.
In Japanese Unexamined Patent Application Publication No. 2018-047493 (JP 2018-047493 A), a CS core method in which an inorganic material such as water glass is used as a binder is used for manufacturing a core.
In the CS core method, foundry sand utilized to manufacture a core is regenerated, and the sand that has been regenerated (regenerated sand) is reused to manufacture a core. Examples of a method of regenerating the foundry sand include a dry process and a wet process. The dry process is a method of removing a water glass component remaining on surfaces of foundry sand used to manufacture a core by performing heat treatment on the foundry sand and polishing based on vibration shock or the like. For example, Japanese Unexamined Patent Application Publication No. 2017-077566 (JP 2017-077566 A) discloses an example of the dry process. On the other hand, the wet process is a method of removing water glass from foundry sand used to manufacture a core by bringing the foundry sand into contact with a solvent such as water.
Japanese Unexamined Patent Application Publication No. 2020-089909 (JP 2020-089909 A) discloses a method of measuring bending strength of a test piece of a manufactured core. JP 2020-089909 A will be used to explain an embodiment, which will be described later.
According to the technologies of JP 2018-047493 A, JP 2017-077566 A, and JP 2020-089909 A, the dry process is a method of physically applying impact and friction to scrape off the water glass on the surfaces of the sand, and the existing methods thus have limitation in removing the water glass in the first place. If the polishing force is excessively strong, then cracking or the like may occur in sand bodies and may thereby cause a decrease in strength, the polishing force is thus limited, and efficiency of removing the water glass is insufficient. Therefore, a remaining binder is accumulated in regenerated sand through repeated sand regeneration. For example, the binder component absorbs moisture by the accumulation of the remaining binder, and a part of the component is dissolved in a secondary material when a core is manufactured by the CS core method, causing defects such as foaming inhibition and gas-defect. In addition, the strength of the core increases or decreases due to influences of the remaining binder.
On the other hand, since the wet process is a method of removing water glass by bringing the foundry sand into contact with a solvent such as water, the remaining binder in the regenerated sand is substantially completely removed, while insufficiency of the strength of the core manufactured by using the regenerated sand may occur.
In other words, the technologies according to JP 2018-047493 A and JP 2017-077566 A have a problem that it is not possible to reduce the remaining binder accumulated in the regenerated sand through the repeated sand regeneration, to secure the strength of the manufactured core, and to improve quality of the core.
In view of such a problem, an object of the present disclosure is to provide a method of manufacturing a core capable of reducing a remaining binder accumulated in regenerated sand through repeated sand regeneration, securing strength of a manufactured core, and improving quality of the core.
A method of manufacturing a core according to the present disclosure includes:
blending dry regenerated sand, wet regenerated sand, and new sand at predetermined ratios, the dry regenerated sand being sand obtained by regenerating, by a dry process, foundry sand used to manufacture a core, the wet regenerated sand being sand obtained by regenerating the foundry sand by a wet process; and
manufacturing a core from the blended sand,
and the ratios of the blending are 49 wt % to 95 wt % for the dry regenerated sand, 1 wt % to 49 wt % for the wet regenerated sand, and 1 wt % to 5 wt % for the new sand.
Also, the ratios of the blending are 69 wt % to 95 wt % for the dry regenerated sand, 1 wt % to 30 wt % for the wet regenerated sand, and 1 wt % to 5 wt % for the new sand in the method of manufacturing a core according to the present disclosure.
Moreover, the ratios of the blending are 79 wt % to 95 wt % for the dry regenerated sand, 1 wt % to 20 wt % for the wet regenerated sand, and 1 wt % to 5 wt % for the new sand in the method of manufacturing a core according to the present disclosure.
According to the present disclosure, it is possible to provide a method of manufacturing a core capable of reducing a remaining binder accumulated in regenerated sand through repeated sand regeneration, securing strength of a manufactured core, and improving quality of the core.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:
A method of manufacturing the core according to the first embodiment will be described with reference to
As shown in
Dry regenerated sand is sand in which foundry sand used for core production is regenerated by a dry process. In dry regenerated sand, the residual binder (residual water glass) is greater than 0 wt % and less than or equal to 4 wt %. In addition, the wet regenerated sand is sand in which the foundry sand used for manufacturing the core is regenerated by a wet process. In wet regenerated sand, the residual binder is less than 1 wt %. In addition, the new sand is a new sand, for example, sand containing aluminum oxide as a main component, instead of the foundry sand used in the production of the core being regenerated. New sand is sand blended to compensate for the amount of sand lost during the manufacturing process of the following cores.
The proportions of the abovementioned blends are preferably 49 wt % to 95 wt % dry regenerated sand, 1 wt % to 49 wt % wet regenerated sand and 1 wt % to 5 wt % new sand. The blending ratio is more preferably 69 wt % to 95 wt % of dry regenerated sand, 1 wt % to 30 wt % of wet regenerated sand, and 1 wt % to 5 wt % of new sand. The blending ratio is still more preferably 79 wt % to 95 wt % dry regenerated sand, 1 wt % to 20 wt % wet regenerated sand, and 1 wt % to 5 wt % new sand.
Further, in the above-described dry method, the dry method is a method of removing the water glass component remaining on the surface of the foundry sand by polishing the foundry sand used for manufacturing the core by heat treatment. Specifically, the dry method is disclosed in JP 2017-077566 A. For example, in the dry process, the foundry sand used in the production of the core is crushed until it becomes a granular material. The granules are heated at temperatures between 300° C. and 550° C. After the heating, the granules collide with each other, and the water glass is peeled off from the foundry sand. Air is blown onto the mixture of the peeled water glass and the foundry sand, and the foundry sand is separated and recovered as dry regenerated sand from the mixture by the difference in specific gravity between the water glass and the foundry sand.
Further, the wet method described above is a method of removing water glass from the dry regenerated sand or the foundry sand used in the production of the core by contacting the foundry sand with a solvent containing water. For example, in the wet process, dry regenerated sand having a residual binder of 1 wt % to 4 wt % is first prepared. The dry regenerated sand and 2000 g water of 1500 g are cleaned in a pressure vessel and the foundry sand is washed at 120° C. for 5 minutes. Thereafter, the washed foundry sand (hereinafter, washing sand) is drained. 1500 g cleaning sand is then rinsed with 2000 g water and recovered as wet regenerated sand.
After S101, sand obtained by blending dry regenerated sand, wet regenerated sand, and new sand at a predetermined ratio may be stored in a tank. In addition, if sand previously blended into the reservoir is stored, no S101 may be performed in the method of manufacturing the core.
Next, in S102, the blended sand (hereinafter, blended sand) is kneaded in a kneading kettle. In the kneading, 2 kg blended sand, 0.65 AI % (active ingredient %) water glass, 0.03 AI % surfactant, and 3.2 wt % water are mixed in a kneading kettle, and kneading is performed for 300 seconds.
Next, in S103, the kneaded blended sand (hereinafter, kneaded sand) is filled in the mold. The mold is filled 0.35 MPa a push-in pressure and with a press-in time of 30 seconds. The mold temperature of the mold is set to 260° C. by an electric heater or the like.
Next, in 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.
Next, with reference to
From the left side of the graph, the blending ratio of each test piece is: new sand 100 wt %, dry regenerated sand 100 wt %, wet regenerated sand 100 wt %, dry regenerated sand 95 wt % and new sand 5 wt %, new sand 1 wt % and wet regenerated sand 1 wt % (dry regenerated sand 98 wt %), new sand 1 wt % and wet regenerated sand 4 wt % (dry regenerated sand 95 wt %), new sand 1 wt % and wet regenerated sand 6 wt % (dry regenerated sand 93 wt %), new sand 1 wt % and wet regenerated sand 12 wt % (dry regenerated sand 87 wt %), new sand 1 wt % and wet regenerated sand 20 wt % (dry regenerated sand 79 wt %), new sand 1 wt % and wet regenerated sand 30 wt % (dry regenerated sand 69 wt %), and new sand 1 wt % and wet regenerated sand 49 wt % (dry regenerated sand 50 wt %). The above-mentioned blended sand of the new sand 5 wt % and the dry regenerated sand 95 wt % is also called the current sand, and represents the regenerated sand used in the production of the core currently used.
A test method for measuring the bending strength is disclosed in JP 2020-089909 A. Here, the flexural strength is a value indicating the strength to bending. The bending strength is measured by a bending strength tester for the mold, in which each test piece is set in the bending strength tester for the mold.
Evaluation of the bending strength of each test piece is as follows. When the flexural strength is 20.0 [kgf/cm2] to 50.0 [kgf/cm2], the test piece of the core is considered to be “good”. When the flexural strength is more than 31.0 [kgf/cm2], the test piece of the core is regarded as “excellent”. When the bending strength is more than the current 95% line of sand (indicated by the dashed-dotted line in
The flexural strength was evaluated as “good” in the test pieces of new sand 1 wt % and wet regenerated sand 1 wt %, test pieces of new sand 1 wt % and wet regenerated sand 4 wt %, test pieces of new sand 1 wt % and wet regenerated sand 6 wt %, test pieces of new sand 1 wt % and wet regenerated sand 12 wt %, test pieces of new sand 1 wt % and wet regenerated sand 20 wt %, test pieces of new sand 1 wt % and wet regenerated sand 30 wt %, and test pieces of new sand 1 wt % and wet regenerated sand 49 wt %, because the flexural strength is 20.0 [kgf/cm2] to 50.0 [kgf/cm2]. Therefore, it was verified that the core produced with the blending ratio of new sand 1 wt % and wet regenerated sand 1 wt % to 49 wt % can be expected to have the bending strength.
In addition, the flexural strength was evaluated as “excellent” in the test pieces of the new sand 1 wt % and the wet regenerated sand 1 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 4 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 6 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 12 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 20 wt %, and the test pieces of the new sand 1 wt % and the wet regenerated sand 30 wt %, because the flexural strength is 31.0 [kgf/cm2] or more. Therefore, it was verified that the core produced with the blending ratio of the new sand 1 wt % and the wet regenerated sand 1 wt % to 30 wt % can expect bending strength more.
In addition, in the test pieces of the new sand 1 wt % and the wet regenerated sand 1 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 4 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 6 wt %, the test pieces of the new sand 1 wt % and the wet regenerated sand 12 wt %, and the test pieces of the new sand 1 wt % and the wet regenerated sand 20 wt %, the flexural strength was more than the current sand 95% line (indicated by the dashed-dotted line in
As described above, in the method of manufacturing a core according to the first embodiment, the dry regenerated sand, the wet regenerated sand, and the new sand are blended at a predetermined ratio, and the core is manufactured from the blended sand. The blending ratio is preferably from 49 wt % to 95 wt % dry regenerated sand, from 1 wt % to 49 wt % wet regenerated sand and from 1 wt % to 5 wt % new sand. The blending ratio is more preferably 69 wt % to 95 wt % of dry regenerated sand, 1 wt % to 30 wt % of wet regenerated sand, and 1 wt % to 5 wt % of new sand. The blending ratio is still more preferably 79 wt % to 95 wt % dry regenerated sand, 1 wt % to 20 wt % wet regenerated sand, and 1 wt % to 5 wt % new sand.
Here, when only dry regenerated sand is used for core production, residual binder accumulates in the regenerated sand by repeated sand regeneration. On the other hand, in the case where only the wet regenerated sand is used for the production of the core, the residual binder in the regeneration sand is almost completely removed, but the strength of the core produced by using the regeneration sand is insufficient.
In the method of manufacturing a core according to the first embodiment, the strength of the core to be manufactured can be ensured by blending the dry regenerated sand in addition to the wet regenerated sand so that the ratio of the blend is set. Further, in the method of manufacturing a core, it is possible to reduce the residual binder accumulated in the regenerated sand by repeated sand regeneration (in other words, in the repeated sand regeneration, the binder amount of the regenerated sand can be brought close to a constant). Therefore, in the method of manufacturing a core, by reducing the residual binder accumulated in the regenerated sand by repeated sand regeneration, it is possible to reduce the possibility of occurrence of defects such as foaming inhibition and gas defects due to accumulation of residual binder. Further, it is possible to reduce the possibility that the strength of the core increases or decreases due to the influence of the residual binder. In addition, in the method of manufacturing the core, the quality of the core can be improved. In the method of manufacturing a core, for example, wrinkles and clogging defects of the core are reduced, and therefore, the surface of the coarse material (e.g., engine) becomes clean. Further, since the core does not lose the pressure of the aluminum hot water, blistering failure of the coarse material is reduced.
The present disclosure is not limited to the above embodiments, and can be appropriately modified without departing from the spirit thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-223399 | Dec 2023 | JP | national |
