JPH07232233A - Method reconditioning molding sand - Google Patents

Abstract

PURPOSE:To smoothly execute the work of the casting process by adding and blending the replenishing material in a prescribed amount so as to make the measured stirring load value at a desired value. CONSTITUTION:The returned molding sand which is used as the sand mold is blended with the replenishing material such as water and reconditioned by using a blending device provided with a blending tank and a stirring machine. When the stirring of the molding sand of the prescribed amount which is charged in the blending tank is completed, the stirring load value to be added in the stirring machine is measured. Then, the replenishing material in the desired amount is added in the blending tank and blended so that the measured stirring load value may be the desired value. The load current value of an electric driven motor of the stirring machine is measured. This constitution enables the reconditioning work of the returned molding sand without any skilled person.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reclaiming foundry sand, and more specifically, for reclaiming foundry sand that is used by kneading a return foundry sand used in a foundry sand mold with a replenishing material such as water by a kneader. Regarding the method.

[0002]

2. Description of the Related Art Foundry sand used for foundry sand mold contains water and clay in order to form a sand mold having appropriate strength and packing density. The molding sand can have an appropriate fluidity due to the water content and the clay content. Most of the water content and the clay content in the foundry sand disappear by evaporation or combustion when the molten metal is poured into the formed sand mold and cast. As described above, the foundry sand in which much of the water content and clay content contained has disappeared has lost appropriate fluidity, and cannot form a sand mold having appropriate strength and packing density, and as it is. It cannot be used for casting. For this reason, when the molding sand is recycled, it is necessary to add a supplemental material such as water or clay to the returned molding sand in order to reuse the molding sand that has been conventionally used for casting (hereinafter, also referred to as return molding sand). After that, the kneading and kneading are performed to give an appropriate fluidity to the return molding sand.

[0003]

When the amount of such a supplementary material added is appropriate, the sand mold formed by the reclaimed molding sand can have appropriate strength and packing density because it can impart appropriate fluidity to the reclaimed molding sand. Can have. However, the average fluidity of the returned foundry sand, which is the basis for determining the replenishment amount of the required replenishment material, is often based on the intuition cultivated by skilled workers over many years. For this reason, when a skilled worker is absent, it is impossible to determine the amount of supplementary material to be added, and it is impossible to regenerate the return molding sand, which may hinder other casting operations. Further, for example, the water content, which is a measurable component, can be measured using a water content meter. However, the moisture values measured by inserting the moisture meter back into the foundry sand are extremely variable and it is difficult to determine the average value. For this reason,
An excess or deficiency of the addition amount of the replenishment material is likely to occur, and it may not be possible to impart an appropriate fluidity amount to the reclaimed molding sand. Since the sand mold formed by using the reclaimed molding sand that does not have such an appropriate fluidity amount is inferior in strength and packing density, the quality of the finally obtained cast product is deteriorated.

Therefore, an object of the present invention is to grasp the average fluidity of return molding sand without resorting to the intuition of a skilled worker,
An object of the present invention is to provide a method for regenerating foundry sand to which an appropriate amount of supplementary material can be added.

[0005]

Means for Solving the Problems The inventors of the present invention have been studying in order to achieve the above-mentioned object. It was found that a good sand mold can be formed when the stirring load value of the reclaimed molding sand obtained by adding a supplement to the return molding sand shows a predetermined value, which is not constant by the return molding sand, and the present invention has been reached. . That is, the present invention, when the reclaimed molding sand used in the molding sand mold and a replenishing material such as water are kneaded and regenerated by a kneading device equipped with a kneading tank and a stirrer, they are placed in the kneading tank. When the stirring of the fixed amount of return molding sand is completed, the stirring load value applied to the stirrer is measured, and then, the predetermined stirring load value is set in the kneading tank so that the measured stirring load value becomes a desired value. A method for reclaiming foundry sand is characterized by adding and kneading. In the present invention having such a configuration, the stirring load value can be easily measured by measuring the load current value of the electric drive motor of the stirrer as the stirring load value.

[0006]

In general, the stirring load value applied to the stirrer is
The agitation load value of the agitation product having poor fluidity increases and the agitation load value of the agitation product having a high fluidity decreases, depending on the fluidity of the agitation product to be agitated. Therefore, the fluidity of the agitated product can be grasped by measuring the agitation load value. Therefore, as in the present invention, by measuring the stirring load value of the return molding sand, it is possible to objectively grasp the average degree of fluidity of the return molding sand, the stirring load value of the optimum state. The addition amount of the supplementary material can be determined so that the stirring load value of the molding sand having fluidity is obtained.
Further, whether or not the amount of the supplementary material added is appropriate can be determined by kneading the supplementary material and the return molding sand and then measuring the stirring load value of the regenerated molding sand. As described above, according to the present invention, it is possible to determine the addition amount of the supplementary material based on the objectively grasped average fluidity of the return molding sand, and the fluidity of the reclaimed molding sand. Since the quality can be judged, even an unskilled person can perform the operation of reclaiming the returned foundry sand.

[0007]

SUMMARY OF THE INVENTION In the present invention, first, it is important to put a predetermined amount of return molding sand into a kneading tank of a kneading device and stir to measure the stirring load value applied to the stirrer. Here, the kneading tank for introducing the return molding sand, that the inside contacting the molding sand is resin-coated with a resin or resin sheet having good wear resistance such as ultra-high density polyethylene resin, the molding sand is It can be prevented from adhering to the wall surface of the kneading tank, and an accurate stirring load value can be measured. Further, as the stirrer, a stirrer provided with a stirring blade that stirs the return molding sand can be used to easily grasp the correlation between the fluidity of the return molding sand and the stirring load value. Further, by adopting a fluid drive motor such as a hydraulic pressure or an electric drive motor as a drive means of the agitator, the agitation load value can be easily measured by measuring a fluid pressure such as a hydraulic pressure applied to the drive motor or a load current value. Can be measured. In particular, it is preferable to use an electric drive motor as the driving means of the stirrer in view of the ease of measuring the stirring load value and the simplification of the equipment. The amount of the return molding sand to be added to the kneading tank is the amount to be added to the kneading tank at one time in the normal regenerating operation, so that the optimum amount of supplementary material is added for each regenerating operation. be able to.

A method of measuring the stirring load value required to stir the return molding sand that has been put into the kneading tank in a predetermined amount will be described with reference to FIG. The stirring load value curve shown in FIG. 1 is a measurement of the load current value applied to the electric drive motor of the stirrer. In FIG. 1, 10 is a load current value when the stirrer is under no-load operation, 20 is a load current value when a predetermined amount of return molding sand is completely charged into the stirring tank, and 30 is charged into the stirring tank. The load current values when the stirring of a predetermined amount of return molding sand is completed are shown respectively. In the present invention, the completion of the stirring of the return molding sand can be confirmed by the fact that the load current value becomes substantially flat in FIG. 1, and the load current value at this time is the stirring of the molding sand. The load current value at that time is 30.

The load current value 30 is at least 1 when the load current value becomes substantially flat.
It is preferable to measure about 0 times and use the average value. Further, the load current value 30 changes depending on the adjustment of the stirrer, the input amount of the return molding sand, and the like. Therefore, when the stirrer is adjusted, data that can convert the amount of change in the load current value 30 due to the adjustment of the stirrer is collected, and the measured load current value 30 of the return molding sand is converted. It is preferable. The load current value 30 of the return foundry sand measured in this manner [Fig.
(A), FIG. 3 (a)] is compared with the load current value 30 ′ of the molding sand having the fluidity in the optimum state [FIG. 2 (b), FIG. 3 (b)], the load of the return molding sand The current value 30 is shown in FIG.
There are cases where it is low as shown in FIG. 3A or high as shown in FIG.

When the load current value 30 of the return molding sand is lower than the load current value 30 'of the molding sand having the fluidity in the optimum state [FIG. 2 (a)], the molding sand having the fluidity in the optimum state is used. Compared with the above, the water content or the clay content is small and the fluidity is excessive. Such a sand mold formed from foundry sand having a load current value of 30 shown in FIG. 2A has low strength. By the way, when casting sand is recycled,
Since a fixed amount of clay is regularly added to the clay component, a large change in the clay content in the circulating molding sand is unlikely to occur. For this reason, it is preferable to use water, which is easy to handle and is most likely to evaporate and disappear during casting, as a supplementary material. Moreover, the clay content is insufficient and the load current value 30 is low.
Even in the case of (a)], by adding water as a supplement and kneading, it is possible to impart suitable fluidity to the reclaimed molding sand as shown in FIG. 2 (b).

On the other hand, when the load current value 30 of the return molding sand is higher than the load current value 30 'of the molding sand having the fluidity in the optimum state [FIG. 3 (a)], the fluidity in the optimum state is obtained. This is a case where the water content or the clay content is excessive and the fluidity is poor as compared with foundry sand. In such a sand mold formed of foundry sand exhibiting the load current value 30 shown in FIG. 3 (a), the filling density of the foundry sand becomes low and the sand mold wall surface becomes rough, resulting in poor casting surface of the obtained foundry product. . In such a case, by adding a molding sand having a low water content or a clay content as a replenishing material and kneading, it is possible to impart suitable fluidity to the reclaimed molding sand as shown in FIG. 3 (b). In this case, since the amount of foundry sand to be kneaded increases, it is necessary to correct the load current value 30 of the foundry sand.

As described above, for comparison with the load current value 30 of the return molding sand, it is necessary to measure the load current value 30 'of the molding sand having the fluidity in the optimum state in advance. At this time, the load current value 30 'of the molding sand in the optimum state is measured in advance for each type in order to change the degree of fluidity required for the molding sand depending on the type of sand mold to be formed. It is also preferable to simultaneously measure the relationship between the amount of molding sand and the load current value 30 'so that the load current value 30' due to an increase or decrease in the amount of molding sand can be corrected. Furthermore, when repairing the stirring blade of the stirrer, the drive motor, etc., the load current value 3
Since 0'changes, it is preferable to measure the load current value 30 'again.

If the load current value 30 when the stirring of the return molding sand is completed is found, it is compared with the load current value 30 'of the molding sand suitable for the sand mold to be formed to determine the supply amount of the replenishing material. . The replenishment material of the determined replenishment amount is the load current value 3
In order to measure 0, the entire amount may be added to the kneading tank into which the return molding sand has been charged, but it is preferable to charge the kneading tank in a plurality of divided portions (preferably in two divided portions). At this time, the load current value 30 is measured every time a part of the replenishment material is charged and kneaded.
0 is the load current value 3 of the foundry sand having the fluidity in the optimum state
It can approach 0 '.

Although the operator can perform the reclaiming work of the return molding sand, the reclaiming work of the reclaiming molding sand can be automated by using the computer. In this case, the load current value 30 of the foundry sand can be measured by the computer, and the load current value 30
The number of measurements can be increased, and the more averaged load current value 30 can be measured. Further, if the load current value 30 'of the molding sand having the optimum fluidity for each type of sand mold and the relationship between the addition amount of the supplementary material and the load current value 30 of the molding sand are input to the computer, It is possible to estimate the replenishment amount of the replenishment material with respect to the measured load current value 30 of the return foundry sand. In addition, the estimated amount of replenishment material
It is also possible to knead by automatically adding to the return molding sand according to the instruction of the computer.

According to the method for reclaiming foundry sand of the present invention described above, it is possible to obtain foundry sand having a load current value close to the load current value of the foundry sand, which has fluidity in the optimum state, and is suitable. A sand mold with strength and good packing density can be obtained. Therefore, it is possible to finally obtain a cast product of good quality.

[0016]

【Example】

Example 1 An agitator driven by an electric drive motor provided with agitating blades is installed in a kneading tank of a kneading device whose inner wall is coated with ultra-high density polyethylene resin.
While driving the stirrer of the kneading device, 400 kg of molding sand was returned to the kneading tank and kneading was performed for 3 minutes. At this time, when the load current value of the electric drive motor became substantially flat, the load current value was measured assuming that the stirring of the foundry sand was completed. After the load current value was measured about 10 times, the averaged measured value was 28A. On the other hand, as the molding sand for the sand mold to be molded, the molding sand having the optimum fluidity has a load current value of 38A. The load current value of the return molding sand measured in this way is 1 more than the optimum load current value of the molding sand.
Since it is as low as 0 A, the amount of water added as a replenisher is estimated to be 16 kg based on past data.

Next, when half of the estimated 16 kg of water was added to the kneading tank while driving the stirrer and kneaded, the load current value became higher than that before the addition of water, but the optimum fluidity was still obtained. Since it is lower than the load current value of the foundry sand with, the remaining water was added. As a result, the load current value of the foundry sand was substantially equal to the load current value of the foundry sand having the optimum fluidity, and thus kneading was completed. After that, using the obtained reclaimed molding sand, when molding a sand mold,
It had appropriate strength and packing density, and the finally obtained cast product was also of good quality exhibiting a good casting surface.

Example 2 The load current value of the return foundry sand measured in the same manner as in Example 1 was 40A. This value is about 2 A higher than 38 A which is the load current value of the casting sand having optimum fluidity as the casting sand for the sand mold to be molded. Therefore, the moisture content as a supplementary material is 1% based on past data.
The amount of dry foundry sand added was estimated to be 50 kg. Next, when half of 50 kg of the dry foundry sand was added to the kneading tank while driving the stirrer and kneaded, the load current value became lower than before the addition of the dry foundry sand,
The remaining dry foundry sand was added because it is higher than the load current value of foundry sand that still has optimum fluidity. As a result, the load current value of the foundry sand was substantially equal to the load current value of the foundry sand having the optimum fluidity, and thus kneading was completed. After that, using the obtained reclaimed molding sand, when molding a sand mold, it has a suitable strength and packing density, the finally obtained casting also has a good quality showing a good casting surface. It was the one.

[0019]

According to the present invention, since the average fluidity of the return molding sand can be objectively grasped, the addition amount of the replenisher can be estimated even by an unskilled person. Regarding the fluidity of the reclaimed molding sand, it is possible to objectively grasp the average fluidity, so it is necessary for the expert to judge whether or not the reclaimed molding sand having the target fluidity of the molding sand was obtained. Can be done easily without resorting to. For this reason, the operation of reclaiming the foundry sand can be performed even without an expert, and the operation of the casting process can be smoothly carried out.

[Brief description of drawings]

FIG. 1 is a graph showing a stirring load curve applied to an electric drive motor of a stirrer.

FIG. 2 is a graph showing an example of a stirring load curve of return molding sand and an example of a stirring load curve of molding sand having optimum fluidity.

FIG. 3 is a graph showing a stirring load curve different from the stirring load curve of the return foundry sand shown in FIG. 2 and an example of a stirring load curve of foundry sand having optimum fluidity.

[Explanation of symbols]

10 Load current value when the stirrer is operated without load 20 Load current value when a predetermined amount of return molding sand is completely added to the stirring tank 30 Load current value when stirring of the return molding sand is completed 30 'Optimal Current value of foundry sand with excellent fluidity

Claims (2)

[Claims] 1. A predetermined amount put in a kneading tank when kneading a reclaimed molding sand used for a sand mold of a casting and a replenishing material such as water by a kneading device equipped with a kneading tank and a stirrer for regeneration. When the stirring of the return molding sand is completed, the stirring load value applied to the stirrer is measured, and then a predetermined amount of supplementary material is added to the kneading tank so that the measured stirring load value becomes a desired value. A method for reclaiming foundry sand, characterized by mixing and kneading. 2. The method for reclaiming foundry sand according to claim 1, wherein a load current value of an electric drive motor of the stirrer is measured as the stirring load value.