Methods for recycling foundry sand

Abstract

To provide a method for recycling foundry sand that can suppress the decrease in core strength after remanufacturing. [Solution] The method for regenerating foundry sand according to the present invention comprises a preparation step S1 for preparing foundry sand to which a binder has been fixed; a washing step S2 for washing the foundry sand prepared in the preparation step S1; a polishing step S3 for polishing the foundry sand washed in the washing step S2; and a rinsing step S4 for rinsing the foundry sand polished in the polishing step S3.

Description

Technical Field

[0001] The present invention relates to a method for recycling foundry sand.

Background Art

[0002] A method of recovering and recycling foundry sand from cores used in casting is known. Patent Document 1 discloses a cleaning method capable of efficiently removing a binder from foundry sand to which the binder is adhered.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The cores remanufactured using the foundry sand recycled by the method described in Patent Document 1 sometimes had inferior strength compared to the cores manufactured using new foundry sand. As a result of intensive studies by the present inventor, it was found that after eluting the binder, minute irregularities occurred on the surface of the foundry sand, and these irregularities caused a decrease in the strength of the cores.

[0005] The present invention has been made in view of such circumstances, and provides a method for recycling foundry sand capable of suppressing a decrease in the strength of cores after remanufacture.

Means for Solving the Problems

[0006] The method for recycling foundry sand according to the present invention includes a preparation step of preparing foundry sand to which a binder is adhered, a cleaning step of cleaning the foundry sand prepared in the preparation step, a polishing step of polishing the foundry sand cleaned in the cleaning step, and a rinsing step of rinsing the foundry sand polished in the polishing step.

Effects of the Invention

[0007] The present invention provides a method for recycling foundry sand that can suppress the decrease in core strength after remanufacturing. [Brief explanation of the drawing]

[0008] [Figure 1] This is a flowchart of the method for recycling foundry sand according to this embodiment. [Figure 2] This graph shows the flexural strength of cores manufactured using new sand, recycled sand from the example, and recycled sand from the comparative example. [Modes for carrying out the invention]

[0009] The following describes specific embodiments to which the present invention is applied, with reference to the drawings. However, the present invention is not limited to the following embodiments. The present invention is not limited to the embodiments described below, and can be modified as appropriate without departing from the spirit of the invention. For clarity, the following descriptions and drawings have been simplified as appropriate. Furthermore, in this disclosure, the "~" indicating a numerical range includes the values ​​before and after it as the lower and upper limits.

[0010] Figure 1 is a flowchart of the method for recycling foundry sand according to this embodiment. As shown in Figure 1, the method for recycling foundry sand according to this embodiment comprises steps S1 to S4.

[0011] Step S1 is a preparation step to prepare foundry sand to which a binder has been fixed. The binder is a substance that adheres the foundry sand together when manufacturing the core, and an example of this is a water-soluble binder such as water glass. In the preparation step, foundry sand to which the binder has been fixed can be obtained, for example, by crushing the core.

[0012] Step S2 is a washing step in which the foundry sand prepared in the preparation step is washed. In the washing step, the solvent that dissolves the binder is mixed with the foundry sand and stirred to remove the binder that has adhered to the foundry sand. If the binder is water-soluble, water can be used as the solvent. In particular, if the binder is water glass, it is preferable to use water at 70-100°C from the viewpoint of removal efficiency. Alternatively, water at 100-120°C may be used under conditions of pressurization to a pressure higher than the saturated water vapor pressure. By raising the water temperature to 70°C or higher, the binder can be dissolved quickly, and the washing time can be shortened.

[0013] Step S3 is a polishing step in which the foundry sand that was cleaned in the washing step is polished. In the polishing step, the foundry sand is polished by rubbing its surface. The method of polishing is not particularly limited, but for example, one method is to polish the foundry sand by rubbing it against itself, and a method of rubbing the foundry sand while stirring it in contact with a solvent such as water is particularly preferred. By bringing it into contact with a solvent, the efficiency of rubbing the foundry sand can be improved. In addition, by using water as a solvent in particular, water-soluble binders can be removed efficiently.

[0014] In step S3, when the foundry sand is stirred while in contact with the solvent to cause friction between the foundry sand particles, the amount of solvent is preferably 4 to 20% by mass of the foundry sand after the washing process. By setting the amount of solvent to 4% by mass or more of the foundry sand, the entire foundry sand can easily come into contact with the solvent, thereby increasing the stirring efficiency. Alternatively, by setting the amount of solvent to 20% by mass or less of the foundry sand, the dispersion of the foundry sand in the solvent can be suppressed, and the frequency of friction between the foundry sand particles can be increased.

[0015] Furthermore, when stirring the foundry sand in water in step S3 to rub the sand particles against each other, the stirring speed is preferably 1 to 12 m / second. By setting the stirring speed to 12 m / second or less, the impact on the foundry sand can be reduced, and damage to the foundry sand can be suppressed. Also, by setting the stirring speed to 1 m / second or more, the polishing time can be shortened. When the stirring speed is 1 m / second or more, the polishing time can be 5 to 10 minutes.

[0016] Step S4 is a rinsing process for rinsing the cast sand polished in the polishing process. In the rinsing process, by rinsing the cast sand with clean water, fine dirt remaining on the surface of the cast sand is removed. The rinsing method is not particularly limited, but it is preferable to rinse with a larger amount of water than the amount of the solvent used in the polishing process.

[0017] The cast sand regenerated by the method including the above steps S1 to S4 has the binder removed in the cleaning process and the surface irregularities reduced and smoothed in the polishing process, so it can be suitably used for the production of cores.

[0018] In the above example, the method of performing steps S1 to S4 in order was described. However, the polishing process (step S3) and the rinsing process (step S4) may be performed in the reverse order. In this case, in the rinsing process, fine binders and the like remaining in the cast sand in the cleaning process can be removed, so the polishing efficiency can be improved.

[0019] Also, the method for regenerating cast sand according to the present invention may include a drying process (not shown) for drying the cast sand rinsed in the rinsing process after step S4. By drying, the cast sand can be made easier to handle.

[0020] Furthermore, the method for regenerating cast sand according to the present invention may include a new sand mixing process (not shown) for mixing new sand with the dried cast sand after the above drying process.

Example

[0021] Next, an example using the method for regenerating cast sand of the present invention will be described. (Example 1) First, used cores were crushed to prepare casting sand with a binder adhered thereto. Next, the casting sand was washed with water at 120°C under 0.15 MPa for 5 minutes. Next, with water equivalent to 17% by mass of the washed casting sand contained therein, the casting sand was stirred at a speed of 1 m / s for 5 minutes to polish the casting sand. Then, the casting sand was rinsed with clean water, drained, and dried. This was used as the recycled sand of the example. (Comparative Example) In the above procedure, recycled sand was produced by omitting only the polishing step, and this was used as the recycled sand of the comparative example.

[0022] (Strength Experiment) Cores of the same shape were manufactured using new sand, the recycled sand of the example, and the recycled sand of the comparative example, and the flexural strength was measured by a three-point bending test. The measurement results are shown in Figure 2. As shown in Figure 2, the cores manufactured with the recycled sand of the comparative example had a flexural strength inferior to that of the cores manufactured with new sand. On the other hand, the cores manufactured with the recycled sand of the example had a flexural strength comparable to that of the cores manufactured with new sand.

Claims

1. The preparation process involves preparing the foundry sand to which the binder has been fixed, A washing step for washing the foundry sand prepared in the preparation step, A polishing step in which the foundry sand cleaned in the cleaning step is polished, The process includes a rinsing step for rinsing the foundry sand polished in the polishing step, Methods for recycling foundry sand.

2. The polishing process involves polishing the foundry sand by stirring it in contact with a solvent and rubbing the foundry sand particles against each other. A method for recycling foundry sand according to claim 1.

3. The amount of the solvent is 4 to 20% by mass of the foundry sand after the washing process. The method for recycling foundry sand according to claim 2.

4. The solvent is water. The method for recycling foundry sand according to claim 2.

5. The stirring speed in the polishing process is 1 to 12 m / second. A method for recycling foundry sand according to any one of claims 2 to 4.

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