JPH08103848A - Adjusting method of kneading molding sand and device therefor - Google Patents

Abstract

PURPOSE: To reduce the cost for molding a green sand mold by adjusting the combining ratio of water to bentonite based on the water content and the temp. of high temp. sand. CONSTITUTION: High temp. recovered sand is sent from a hopper 2 and new sand is sent from a hopper 4 to a sand weigher 6. The water content in the recovered sand in the hopper 2 is measured with a water content sensor 13. The bentonite is transferred from a hopper 7 to a bentonite weigher 9 with a signal of an arithmetic controller 14, and its quantity is measured with a load cell 16. When the bentonite quantity reaches the calculated quantity, a screw conveyor 8 is stopped and the bentonite in the weigher 9 is supplied to a vacuum kneading vessel 1 through a pressure feeding tank 10 and the sand weigher 6. The water is supplied to the vacuum kneading vessel 1 from a water weigher 11 with a signal of the arithmetic controller 14. In such a way, the combining ratio of the water is adjusted and also, the combining ratio of the bentonite is adjusted. By this method, while keeping the strength of the green sand mold molded after vacuum-kneading, the consumption of the bentonite can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kneading adjusting method and a kneading adjusting device for molding sand using a vacuum kneading tank.

[0002]

2. Description of the Related Art A green molding line has a circulation system of kneading, molding, pouring, separating, and then kneading again by adding new sand if necessary, and reusing high temperature recovered sand. Therefore, the temperature of the foundry sand after kneading tends to rise, and in order to prevent this, conventionally, the recovered sand was cooled to about 40 ° C. before being subjected to kneading.

On the other hand, recently, a vacuum kneading tank has been partially introduced as sand processing equipment for a green molding line so that even high temperature sand of 40 to 70 ° C. can be cooled to a set temperature of 40 ° C. or less at once in the kneading tank. Became. This is high temperature sand, bentonite, and water in the vacuum kneading tank (water for keeping the casting sand after kneading at a predetermined water content, and water for cooling the high temperature sand).
And kneading while reducing the pressure in the kneading tank.
By reducing the pressure in the kneading tank, the boiling point of water is lowered, part of the added water (cooling water) evaporates, and the sand is cooled to the set temperature by the latent heat of vaporization generated at this time.

[0004]

By the way, the water contained in the foundry sand after kneading is divided into the adhered water adhering to the surface of the sand grains and the adsorbed water penetrating into the bentonite crystal layer, and the water permeating into the crystal layer evaporates. It is difficult to do and improves the water retention of the foundry sand. In the case of the molding sand kneaded in the vacuum kneading tank, the water retention is better than in the case of ordinary atmospheric pressure kneading, and the higher the temperature of the sand is, the more the water retention of the molding sand after kneading is improved. It is considered that this is because as the temperature of the sand becomes higher, the amount of cooling water increases, the amount of water vapor generated in the vacuum kneading tank increases, and the water easily penetrates into the bentonite crystal layer.

The adsorbed water that has penetrated into the bentonite crystal layer activates the bentonite to produce the green strength (coercive force).
It has the effect of increasing the strength of green mold while at the same time increasing the rising speed of. FIG. 2 is a graph showing the relationship between the coercive pressure and the water content of the green mold, which was produced by adding bentonite to the recovered sand of 25 ° C. and the recovered sand of 65 ° C. at the same mixing ratio and kneading in a vacuum kneading tank. The raw pressure using high temperature sand at ℃ has higher coercive force. For comparison, the figure also shows the coercive pressure of the green mold molded after kneading under atmospheric pressure.

Even when the above-mentioned vacuum kneading tank is used, the mixing ratio of bentonite to sand has been adjusted to be constant regardless of temperature, as in the case of kneading in the air. If attention is paid to the fact that the green mold strength is improved with the use of high-temperature sand, it should be possible to reduce the blending ratio of bentonite as a binder as long as the green mold strength is maintained at a predetermined value or more. is there. The present invention has been made based on the above findings, while maintaining the strength of the green mold (coercive pressure), by adjusting the blending ratio of bentonite based on the temperature of the sand, to suppress the amount of bentonite used The purpose is to reduce the cost of green molding.

[0007]

The method for adjusting the kneading of foundry sand according to the present invention is one in which high temperature sand and bentonite are put into a vacuum kneading tank, and water is added and kneading. And adjusting the mixing ratio of water to be added based on the temperature, and adjusting the mixing ratio of bentonite based on the temperature of the high-temperature sand. More specifically, the water to be added consists of added water for keeping the moisture value of the foundry sand after kneading constant and cooling water for lowering the temperature of the high temperature sand, and the mixing ratio of the cooling water is high temperature sand. It is characterized in that it is adjusted based on the temperature.

Further, a kneading adjusting device for foundry sand according to the present invention is a vacuum kneading tank, each supplying device for supplying high temperature sand, bentonite, and water to the vacuum kneading tank, and measuring the water content of the high temperature sand. Water content measuring means, temperature measuring means for measuring the temperature of high-temperature sand, and controlling the water supply device so as to receive water from the water content measuring means and the temperature measuring means and supply water at a predetermined mixing ratio. In addition, it is characterized by comprising control means for receiving the signal from the temperature measuring means and controlling the bentonite supply device so as to supply bentonite at a predetermined mixing ratio.

[0009]

As described above, when kneading in a vacuum kneading tank, the higher the temperature of the sand, the smaller the blending ratio of bentonite for obtaining the same green strength. Therefore, in the present invention,
For example, the relationship between the blending ratio of bentonite that can obtain a predetermined green strength and the temperature of sand is obtained in advance, and the temperature of the sand put into the vacuum kneading tank is measured each time, and the mixing ratio corresponding to that temperature is obtained. Add bentonite.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. 1 shows a kneading adjustment device for foundry sand in a green molding line, which measures a vacuum kneading tank 1, a recovered sand hopper 2, a vibration feeder 3, a new sand hopper 4, a screw conveyor 5, and recovered sand and new sand. Sand supply device including a sand measuring device 6 and the like, a bentonite hopper 7, a screw conveyor 8, a bentonite measuring device 9, and a pressure feeding tank 10.
A bentonite supply device including a water meter 11 and the like,
Temperature sensor 12 installed in the vacuum kneading tank 1, water content sensor 13 installed in the recovered sand hopper 2, and temperature sensor 12
And an arithmetic controller 14 that controls each of the above-mentioned supply devices based on signals from the water content sensor 13.
In addition, M shows the drive motor of each apparatus.

On the other hand, the mixing ratio of the cooling water in the added water is proportional to the specific heat of the sand, and the temperature of the supplied sand is equal to the set temperature of the vacuum kneading tank (the temperature of the sand after kneading, eg 40 ° C.). It is set to zero at the same time, and the higher the sand temperature, the higher the mixing ratio, and the mixing ratio of bentonite is
When the temperature of the supplied sand is the same as the set temperature, it takes a maximum value, and the higher the sand temperature is, the lower the mixing ratio is set, and both are preliminarily input to the arithmetic controller 14. When the temperature of the supplied sand is lower than the preset temperature, the blending ratio of the cooling water is set to zero and the blending ratio of bentonite is set to the blending ratio at the preset temperature.

The operation of this kneading adjusting device for foundry sand will be described in order. First, with the signal from the arithmetic controller 14,
The high temperature recovered sand is sent from the recovered sand hopper 2 to the sand meter 6 via the vibration feeder 3 and, if necessary, the new sand is sent from the new sand hopper 4 to the sand meter 6 via the screw conveyor 5, where the load cell 15 The weight is measured by and the measurement signal is input to the arithmetic controller 14 during weighing. When it reaches the predetermined weight, the arithmetic controller 14 gives a signal to stop the operation of the vibrating feeder 3 and the screw conveyor 5. The water content of the recovered sand is measured by the water content sensor 13 in the recovered sand hopper 2, and the measurement signal is input to the arithmetic controller 14.

Subsequently, the sand in the sand meter 6 is vacuum kneading tank 1
And is pre-kneaded in the vacuum kneading tank 1 under atmospheric pressure. The temperature of the sand at this time is measured by the temperature sensor 12,
The measurement signal is input to the arithmetic controller 14. The operation controller 14 calculates the mixing ratio of water required to keep the molding sand after kneading at a predetermined moisture value from the measured value of the water content of the recovered sand, and from the measured value of the temperature, the mixing ratio of the cooling water and the bentonite. Is calculated, and the total amount of water and the amount of bentonite actually required are calculated according to the weight of sand.

Next, the bentonite is sent from the bentonite hopper 7 through the screw conveyor 8 to the bentonite meter 9 by a signal from the arithmetic controller 14, where the amount of bentonite is measured by the load cell 16, and the measured signal is measured. In the meantime, it is input to the arithmetic controller. When the bentonite amount reaches the calculated value, the calculation controller 14 outputs a signal to stop the screw conveyor 8. Then, the bentonite in the bentonite meter 9 is transferred to the pressure feed tank 10 and is supplied to the vacuum kneading tank 1 via the sand meter 6 by air pressure feed. At the same time, water is supplied from the water meter 11 to the vacuum kneading tank 1 by a signal from the arithmetic controller 14.

After the sand, bentonite and water are supplied to the vacuum kneading tank 1, the pressure in the vacuum kneading tank 1 is reduced to vacuum kneading, and after kneading for a predetermined time, the pressure is returned to atmospheric pressure and the molding sand is sent to the molding machine. . In the above example, the relationship between the sand temperature and the blending ratio of bentonite was set, and the blending ratio of bentonite was directly obtained from the measured temperature of sand. Since the ratio of bentonite can be set lower when it becomes higher, the relationship between the ratio of cooling water and the ratio of bentonite is set, and this is input to the arithmetic controller. The blending ratio may be determined, and the blending ratio of bentonite may be determined from the blending ratio of cooling water.

[0016]

According to the present invention, it is possible to suppress the amount of bentonite used and reduce the cost of molding a green mold while maintaining the strength of the green mold molded after vacuum kneading.

[Brief description of drawings]

FIG. 1 is an explanatory view of a molding sand kneading adjusting device of an embodiment.

FIG. 2 is a diagram showing a relationship between a coercive pressure and a water content of a green mold produced after vacuum mixing.

Claims (3)

[Claims] 1. A method for kneading a molding sand in which high temperature sand and bentonite are put into a vacuum kneading tank and kneaded by adding water, wherein the mixing ratio of water to be added is based on the water content and temperature of the high temperature sand. A method for adjusting the kneading of foundry sand, which comprises adjusting the blending ratio of bentonite based on the temperature of high-temperature sand. 2. The added water comprises added water for keeping the moisture value of the foundry sand after kneading constant and cooling water for lowering the temperature of the high temperature sand, and the mixing ratio of the cooling water is high temperature sand. It adjusts based on the temperature of the said, The kneading | mixing adjustment method of the molding sand of Claim 1 characterized by the above-mentioned. 3. A vacuum kneading tank, supply devices for supplying high temperature sand, bentonite, and water to the vacuum kneading tank, water content measuring means for measuring the water content of the high temperature sand, and temperature of the high temperature sand. The water supply device is controlled so as to supply water at a predetermined mixing ratio by receiving signals from the temperature measuring means for measuring, the water content measuring means and the temperature measuring means, and at the same time receiving signals from the temperature measuring means. A kneading adjustment device for foundry sand, comprising control means for controlling the bentonite supply device so as to supply bentonite at a mixing ratio of.