JPH0976044A - Method for reclamation of molding sand and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of the reclaimed molding sand, and to suppress the amount of a binder by adjusting the degree of vacuum in a tank to increase the evaporation of water based on the temperature of the casting sand before kneading in vacuum relative to the target strength of the reclaimed sand. SOLUTION: The target strength of the reclaimed sand and the characteristics map are inputted to an operation controller 30 in advance. The operation controller 30 controls the amount of the secondary water to be fed by a water feeding device 10, the degree of vacuum in a vacuum mixer 1, and the amount of the caking agent to be added based on the temperature of the casting sand in the vacuum mixer 1 before the kneading in vacuum detected by an FK sensor 5. The degree of vacuum in a vacuum kneading tank is further increased to increase the evaporation amount of water. The amount of the finder may be reduced by the amount corresponding to the increase in the strength of the reclaimed casting sand, the strength of the reclaimed casting sand is kept to or above the prescribed value or above, the amount of the binder to be added is suppressed to reduce the molding cost, and at the same time, defective castings are reduced and the dimensional precision of the castings is improved.

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 an apparatus for reclaiming recovered foundry sand using a vacuum kneading tank.

[0002]

2. Description of the Related Art As is well known, in a green molding line for molding a green mold for casting, a molding sand is kneaded to mold a mold, and after casting is performed using this mold, it is used. The mold is separated to collect the foundry sand, and the recovered foundry sand (hereinafter simply referred to as "recovered sand") is used, or new sand is added if necessary, and kneading is performed again, and the molding of the next cycle is performed. Is performed. Foundry sand is regenerated and used many times through such a series of circulation cycles.

When the recovered sand is reclaimed and used, the recovered sand obtained by separating the mold after casting is kept at a considerably high temperature at the time of recovery, and is obtained by kneading it as it is. The temperature of the reclaimed sand will be too high.

Therefore, conventionally, water is added in proportion to the temperature of the recovered sand to cool it to a predetermined temperature (generally about 40 ° C. or lower), and the properties of the recovered sand are stabilized (Actual Kaihei 3-92545). issue).

By the way, in recent years, as a kneading tank used in a green molding line, the inside of the tank has a predetermined vacuum degree (74 HP).
A vacuum kneading tank, which can perform kneading while maintaining about a), is partially introduced and is being used.

By using this vacuum kneading tank, 40
It becomes possible to rapidly cool the recovered sand having a high temperature (eg, about 40 to 70 ° C.) exceeding 0 ° C. to a set temperature of 40 ° C. or less in the kneading tank.

[0007] That is, when kneading molding sand to form a green mold, usually, high-temperature recovered sand (adding new sand if necessary) is put into a kneading tank, and this is used as a binder for sand grains. The bentonite and the predetermined amount of water are added and kneading is carried out in the tank.However, when a vacuum kneading tank is used, the pressure in the tank is reduced to lower the boiling point of the water, thereby adding the added water. By evaporating a part (cooling water mentioned below) and depriving the latent heat of vaporization from the sand around the inside of the tank at this time, the sand in the tank can be cooled all at once to the set temperature.

When this vacuum kneading tank is used, the amount of water added to the tank is basically the same as that for kneading (moisturizing water) for keeping the water content of the foundry sand after kneading at a predetermined value. It is determined as the sum of cooling water (cooling water) for cooling the high temperature recovered sand during kneading. Of these, the amount that evaporates in the tank during kneading corresponds to the cooling water.

[0009]

When performing the above-described vacuum kneading, the amount of water added to the kneading tank is such that the quality of the sand (reclaimed sand) after kneading is ensured and the target sand strength, that is, ,
It is controlled so as to obtain the coercive force of the green mold made of recycled sand. It is generally known that there is a certain correlation between the water content of sand and the coercive pressure if the sand content is constant. Conventionally, after measuring the water content of the recovered sand, this correlation Based on the relationship, the amount of added water is controlled so that the water content of the reclaimed sand after kneading is constant.

By the way, the water contained in the foundry sand (reclaimed sand) after kneading can be divided into adhering water simply adhering to the surface of the sand grains and adsorbing water permeating into the bentonite crystal layer. Of these, the adsorbed water that has penetrated into the bentonite crystal layer is less likely to evaporate and improves the water retention of the foundry sand. Also,
It is considered that this adsorbed water activates bentonite, accelerates the sand strength, that is, the rise of the coercive pressure of the green mold, and increases the strength of the green mold itself.

FIG. 7 is a graph showing the results of examining the relationship between the water content of the reclaimed sand after kneading and the coercive pressure of the green mold, using the temperature of the recovered sand as a parameter. The case where the temperature of the recovered sand is 25 ° C. and the line B shows the case where the temperature is 25 ° C. In addition, this straight line A and straight line B
In and, all other test conditions such as the amount of bentonite added and the degree of vacuum at the time of kneading are set to be the same. As is clear from the graph of FIG. 7, when vacuum kneading is performed, even if the water content of the reclaimed sand is the same, the higher the temperature of the recovered sand, the higher the raw type coercive pressure. This is because the amount of cooling water to be added increases as the temperature of the recovered sand increases, so that the amount of water vapor generated in the vacuum kneading tank increases, the amount of adsorbed water that permeates the bentonite crystal layer increases, and the bentonite is activated. It is thought to be to proceed.

In other words, it can be said that the strength of the reclaimed sand increases as the amount of water vapor generated during the vacuum kneading increases, and if attention is paid to this fact, the strength of the reclaimed sand is maintained at a predetermined value or more. As far as possible, it should be possible to reduce the blending ratio of bentonite as a binder. It is apparent that the amount of water vapor generated during vacuum kneading increases as the degree of vacuum in the vacuum kneading tank increases.

Therefore, in the present invention, by paying attention to the correlation between the degree of vacuum in the vacuum kneading tank and the strength of the reclaimed sand, the reclaimed sand having a more stable quality can be obtained, and the strength of the reclaimed sand can be set to a predetermined value or more. The purpose is to suppress the amount of binder used while maintaining the value, and to reduce the cost of green molding.

[0014]

The invention according to claim 1 of the present application is a casting for reclaiming the recovered sand by introducing the recovered sand into a vacuum kneading tank, adding water and a binder and kneading. In the method of reclaiming sand, a target value of sand strength of reclaimed sand is set in advance, and the degree of vacuum in the tank is adjusted based on at least the temperature of the foundry sand in the tank before vacuum kneading with respect to the target value. It is characterized by.

If new sand is not added during kneading,
The above "casting sand in the tank before vacuum kneading" means "recovered sand" (the same applies hereinafter).

The invention according to claim 2 of the present application is the invention according to claim 1, characterized in that the amount of water added is adjusted based on at least the temperature of the foundry sand in the tank before vacuum kneading. To do.

Further, the invention according to claim 3 of the present application is as follows.
In the invention according to claim 1 or 2, the addition amount of the binder is adjusted based on at least the temperature of the molding sand in the tank before vacuum kneading.

Further, the invention according to claim 4 of the present application is
In the invention according to claim 3, the addition amount of the binder is reduced as the vacuum degree in the tank is higher.

The invention according to claim 5 of the present application is a reclaiming apparatus for foundry sand, comprising a vacuum kneading tank, and respective supplying means for supplying recovered sand, water and a binder to the vacuum kneading tank, respectively. , With temperature detection means for detecting the temperature of the foundry sand in the tank before vacuum kneading, and the relationship data between the amount of water vapor generated during vacuum kneading and the strength of reclaimed sand, and the recovery with the degree of vacuum in the tank as parameters The degree of vacuum in the tank is controlled based on the relational data between the temperature of the sand and the amount of cooling water added and the relational data between the temperature of the recovered sand and the amount of water vapor generated during vacuum kneading with the degree of vacuum in the tank as a parameter. It is characterized by comprising a control means.

According to a sixth aspect of the present invention, in the invention according to the fifth aspect, the control means sets the relational data between the temperature of the recovered sand and the amount of cooling water added with the degree of vacuum in the tank as a parameter. Based on the above, the amount of cooling water added is controlled.

Further, the invention according to claim 7 of the present application is
In the invention according to claim 5 or 6, the control means, based on the relational data between the amount of steam generated during vacuum kneading and the amount of binder added to the target value of the sand strength of the reclaimed sand,
It is characterized by controlling the addition amount of the binder.

[0022]

As described above, the greater the amount of water vapor generated during vacuum kneading, the more the binder (bentonite) is activated and the strength of the reclaimed sand, that is, the coercive pressure of the green mold molded after vacuum kneading, increases. It has been found that the amount of water vapor generated during vacuum kneading increases as the degree of vacuum in the vacuum kneading tank increases.

According to the inventions according to claims 1 and 5 of the present application, the target value of the sand strength of the recycled sand is set, and at least the temperature of the foundry sand in the vacuum kneading tank before vacuum kneading is set with respect to this target value. Since the degree of vacuum in the tank is adjusted based on the above, the degree of vacuum in the vacuum kneading tank is further increased (atmospheric pressure is higher than that in the conventional case in which the degree of vacuum in the tank is constant (for example, 74 HPa)). It can be lower) to increase water evaporation.

Therefore, as the strength of the reclaimed sand increases,
Since it is possible to reduce the necessary addition amount of the binder,
It is possible to suppress the amount of the binder used while maintaining the strength of the reclaimed sand at a value equal to or higher than a predetermined value, and to reduce the green molding cost.

Further, according to the inventions according to claims 2 and 6 of the present application, the amount of water added is further adjusted based on the temperature of the foundry sand in the vacuum kneading tank before vacuum kneading. The quality of the reclaimed sand can be made more stable than in the conventional case where the amount of added water is determined based on the relationship between the water content of the reclaimed sand and the sand strength. As a result, the coercive pressure of the green mold can be maintained more uniformly, which can contribute to reduction of defects during casting and improvement of dimensional accuracy of the cast product.

Further, according to the inventions according to claims 3 and 7 of the present application, the addition amount of the binder is adjusted based on the temperature of the molding sand in the tank before vacuum kneading.
Control becomes easy when the amount of the binder added is reduced in relation to the degree of vacuum in the tank during vacuum kneading.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view schematically showing an embodiment of a foundry sand recycling apparatus according to the present invention. This foundry sand recycling apparatus includes a vacuum mixer 1 and a weighing hopper 2 for introducing a predetermined amount of recovered sand, a binder (eg bentonite) as an additive, and fresh sand into the vacuum mixer 1 if necessary. And a water supply device 10 for supplying a predetermined amount of water to the vacuum mixer 1.

Although not shown in the drawings, the weighing hopper 2 is a collection station for separating a used mold after casting and collecting foundry sand, a bentonite feeder for supplying bentonite (binder) as an additive, and fresh sand. It is connected to a fresh sand supply station for supplying slag via a conveying means such as a conveyor device or a feeder device.

The water supply device 10 comprises a water meter 11 for measuring the amount of water to be supplied into the vacuum mixer 1 and a supply pump for pumping the water to be supplied from the condenser 13 side to the vacuum mixer 1 side through the supply line Ls. 12 and a circulation pump 14 for returning the water returned into the condenser 13 through the return line Lr to the condenser 13 after passing through the heat exchanger 15 connected to the cooling tower 16, and is substantially constant. Water maintained at temperature can be fed into the vacuum mixer 1.

Downstream of the water meter 11, primary and secondary water injection control valves 18 and 19 are provided. The primary water injection control valve 18 is for injecting warming water for kneading for maintaining the water content of the foundry sand (reclaimed sand) after kneading at a predetermined value into the vacuum mixer 1 as primary water, while The next water injection control valve 19 is for injecting the cooling water for cooling the high temperature recovered sand at the time of kneading into the vacuum mixer 1 as a secondary water injection. And the secondary water injection control valves 18 and 19.

The vacuum mixer 1 has a vacuum shut-off valve 2 on the way.
2 is connected to the vacuum duct 21. The vacuum duct 21 is connected to the vacuum pump 23 via the condenser 13. Also, the condenser 13 and the vacuum pump 2
A pressure switch 24 is provided in a pipe between the pressure control valve 3 and the pressure control valve 3, and a pressure control valve 25 is connected in parallel with the vacuum pump 23. As shown in FIG. 2, the pressure adjusting valve 25 is electrically connected to an arithmetic controller 30 that controls the operation of the regeneration device, and drives the vacuum pump 23 with the arithmetic controller 30 vacuum shutoff valve 22 open. Thus, the interior of the vacuum mixer 1 is evacuated through the vacuum duct 21, and the arithmetic controller 30 adjusts the degree of vacuum inside the vacuum mixer 1 through the pressure adjusting valve 25.

Further, the vacuum mixer 1 is connected to an atmosphere release valve 26 for introducing the atmosphere into the vacuum mixer 1. By opening the atmosphere release valve 26, the vacuum state in the vacuum mixer 1 can be almost instantly. It can be canceled.

Further, an FK sensor 5 for detecting the temperature and the water content of the sand (mainly recovered sand) charged in the vacuum mixer 1 is inserted in the vacuum mixer 1, and this FK sensor 5 is shown in FIG. As shown in FIG. 2, the arithmetic controller 3 is electrically connected to the arithmetic controller 30.
A detection signal is output for 0.

The operation controller 30 is mainly composed of, for example, a microcomputer, and in addition to the pressure adjusting valve 25 and the FK sensor 5, a load cell 11a in the water meter 11 and water injection control valves 18, 19 can send and receive signals. The detection signal of the load cell 11a is input to the arithmetic controller 30, and a control signal is output from the arithmetic controller 30 to the primary and secondary water injection control valves 18 and 19. There is.

A vacuum degree detection signal from the pressure switch 24 is input to the arithmetic controller 30, and the arithmetic controller 30 controls the opening / closing degree of the pressure adjusting valve 25 based on the vacuum degree detection signal to generate a vacuum. The degree of vacuum in the mixer 1 is adjusted. That is, when the pressure adjusting valve 25 is completely closed, the outside air is shut off and the degree of vacuum increases (atmospheric pressure decreases), and when the pressure adjusting valve 25 is opened, outside air is introduced and the degree of vacuum decreases ( The atmospheric pressure rises). .

Further, from the bentonite meter 31 provided in the bentonite supply device (not shown), a signal indicating the cut-out amount of bentonite as the binder supplied to the weighing hopper 2 is input to the arithmetic controller 30, and the arithmetic controller 30. The control signal is output to the drive motor 32 of the screw conveyor for cutting out the bentonite provided in the bentonite supply device.

Although not specifically shown, the arithmetic controller 30 may have, in addition to the above, a detection signal from the load cell of the weighing hopper 2, a detection signal of the water temperature of the supply line Ls of the water supply device 10, and the like. , Various signals are input, and, for example, valves such as the vacuum shutoff valve 22 and the atmosphere release valve 26, or the supply pump 12 and the vacuum pump 23.
Various control signals are respectively output to the pumps such as.

The operation of the foundry sand recycling apparatus having the above-mentioned structure will be described with reference to the time chart of FIG.

First, on the basis of a control signal from the arithmetic controller 30, a predetermined amount of high temperature recovered sand is conveyed and introduced into the weighing hopper 2 from the casting sand recovery station side (not shown). In addition, new sand (not shown) is transported and loaded from the new sand supply station as needed. Then, these are pre-kneaded in the vacuum mixer 1 under atmospheric pressure.

When this premixing is completed, the FK sensor 5
Measures the temperature and water content of the sand (mainly recovered sand) in the vacuum mixer 1 and outputs the detection signal to the arithmetic controller 30.
To enter.

A target value of the sand strength of the reclaimed sand and the characteristic maps shown in FIGS. 4, 5 and 6 are input in advance to the arithmetic controller 30.

The straight line A in the characteristic map of FIG. 4 represents the relationship between the strength of the reclaimed sand and the amount of water vapor during vacuum kneading.
The strength of reclaimed sand increases in proportion to the amount of water vapor during vacuum kneading. The straight line B represents the target value of the strength of the recycled sand. Also,
The straight line C represents the amount of bentonite added when the sand strength is kept at the target value with respect to the amount of water vapor during vacuum kneading, and the amount of bentonite added may be inversely proportional to the amount of water vapor during vacuum kneading. .

The characteristic map of FIG. 5 shows the relationship of the cooling water addition amount with respect to the temperature of the recovered sand, and the characteristic map of FIG. 6 shows the amount of water vapor during vacuum kneading with respect to the temperature of the recovered sand. . The straight line A in FIG. 5 and FIG. 6 indicates that the temperature of the sand after kneading is set to 40 ° C. and the boiling point of water is 40 ° C.
When the degree of vacuum is (74 HPa), the straight line B is
Set the sand temperature after kneading to 30 ° C and set the boiling point of water to 3
This is the case where the degree of vacuum is 0 ° C. (34 HPa). The characteristic maps of FIGS. 5 and 6 show that when the degree of vacuum is increased, the amount of cooling water added and the amount of water vapor increase even if the temperature of the recovered sand is the same, and the temperature of the sand after kneading is increased to 20 ° C., for example. If set, the amount of cooling water added and the amount of water vapor will further increase.

Therefore, the higher the degree of vacuum in the vacuum mixer 1 and the higher the temperature of the recovered sand, the more the amount of bentonite added can be reduced.

4 to 6 in accordance with the preset target value of the sand strength of the reclaimed sand and the temperature of the foundry sand before vacuum kneading detected by the FK sensor 5 in the arithmetic controller 30.
Using the characteristic value of, the degree of vacuum in the vacuum mixer 1 and the amount of bentonite added are set.

Further, in the arithmetic controller 30, the preset target value of the sand strength of the reclaimed sand and the temperature of the reclaimed sand (the lower the temperature of the reclaimed sand, the lower the die-resisting resistance and the less the defects during molding). , The water content of the reclaimed sand is set based on the temperature of the foundry sand in the vacuum mixer 1 before vacuum kneading detected by the FK sensor 5, and the set target water content and the FK sensor 5 are set. Based on the detected water content of the casting sand before vacuum kneading, calculate the amount of water to be added,
Further, a calculation is performed to distribute the amount of water to the primary water for kneading and the secondary water for cooling.

Then, the amount of primary water is determined based on this calculated value, a control signal is output to the primary water injection control valve 18 to open the valve 18, and a predetermined amount of primary water is introduced into the vacuum mixer 1. A signal from the arithmetic controller 30 drives the screw conveyor drive motor 32 for cutting bentonite, sends bentonite to the bentonite meter 31, and measures the bentonite cutting amount. When the bentonite cut-out amount reaches the set value, the drive motor 32 is stopped based on the control signal from the arithmetic controller 30, and the bentonite in the bentonite meter 31 is pneumatically fed through the measuring hopper 2 to the vacuum mixer. It is thrown into 1.

When the addition of sand, primary water and bentonite to the inside of the vacuum mixer 1 is completed, the gate valves and the like provided on each path leading to the inside of the vacuum mixer 1 are closed, and then the vacuum shutoff valve 22 is opened. And pressure control valve 25
Is closed and the vacuum pump 23 is driven, whereby the inside of the vacuum mixer 1 is evacuated. A signal indicating the degree of vacuum in the vacuum mixer 1 from the pressure switch 24 is input to the arithmetic controller 30, and when the degree of vacuum in the vacuum mixer 1 reaches the determined value (74 HPa or less), a control signal from the arithmetic controller 30 is output. Based on this, the opening degree of the pressure control valve 25 is adjusted while the vacuum pump 23 is operating, the degree of vacuum in the vacuum mixer 1 is maintained at the set value, and the vacuum kneading is started. The degree of vacuum is 74
The boiling point of water at HPa is 40 ° C. and is 34 HPa
The boiling point of water is 30 ° C.

Then, during the vacuum kneading (preferably in the first half of the vacuum kneading step), secondary water for cooling is added. That is, based on the control signal from the arithmetic controller 30, the secondary water injection control valve 19 is opened for a predetermined time, and a predetermined amount of secondary water is put into the vacuum mixer 1. As described above, by evaporating the secondary water, the sand in the vacuum mixer 1 is rapidly cooled to the set temperature.

When the vacuum kneading step is completed, the vacuum shutoff valve 22 is closed and the atmosphere release valve 26 is opened to bring the inside of the vacuum mixer 1 to the atmospheric pressure state. Then, each gate valve that is closed before the vacuum shutoff valve 22 is opened is opened, and kneading is performed for a predetermined time under atmospheric pressure.
When this atmospheric pressure kneading is completed, regenerated sand containing a preset amount of water and therefore having a preset sand strength is discharged from the discharge port 1a of the vacuum mixer 1,
It is again used for molding.

In this way, one cycle (180 seconds in the present embodiment) of reproduction processing is performed.

As described above, according to the present embodiment, the target value of the sand strength of the reclaimed sand and the characteristic maps of FIGS. 4 to 6 are input to the arithmetic controller 30 in advance, and the arithmetic controller 30 Based on the temperature of the foundry sand in the vacuum mixer 1 before vacuum kneading detected by the FK sensor 5, the secondary water into the vacuum mixer 1 by the water supply device 10 is adjusted so that the sand strength of the reclaimed sand reaches a target value. The amount of water supplied, the degree of vacuum in the vacuum mixer 1, and the amount of bentonite cut out are controlled. Therefore, with the degree of vacuum in the vacuum mixer 1 kept constant, based on the relationship between the water content of the reclaimed sand and the sand strength. The amount of water evaporated can be increased by increasing the degree of vacuum in the vacuum kneading tank (lowering the atmospheric pressure) as compared with the conventional method in which the amount of added water is determined.

Therefore, as the strength of the reclaimed sand increases,
Since it is possible to reduce the necessary addition amount of the binder,
It is possible to suppress the amount of the binder used while maintaining the strength of the reclaimed sand at a value equal to or higher than a predetermined value, and to reduce the green molding cost. Further, since the quality of the reclaimed sand can be made more stable, the coercive pressure of the green mold can be maintained more uniformly, which contributes to reduction of defects during casting and improvement of dimensional accuracy of cast products. be able to.

In the above-described embodiment,
The arithmetic controller 30 adjusts the degree of vacuum in the vacuum mixer 1 by controlling the opening degree of the pressure control valve 25. Instead of the pressure control valve 25, an inverter is attached to the vacuum pump 23, and By controlling the frequency by the arithmetic controller 30, the vacuum pump 2
The degree of vacuum in the vacuum mixer 1 may be adjusted by controlling the output of 3 itself.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing the overall configuration of a foundry sand reclamation apparatus according to an embodiment of the present invention.

2 is an explanatory diagram showing a water and binder supply control system and a vacuum degree control system in a vacuum mixer in the foundry sand reclamation apparatus of FIG. 1. FIG.

FIG. 3 is a time chart used to explain the operation of the foundry sand reclamation apparatus of FIG.

FIG. 4 is a characteristic map showing the relationship between the strength of reclaimed sand and the amount of bentonite added to the amount of water vapor during vacuum kneading.

FIG. 5 is a characteristic map showing the relationship between the temperature of the recovered sand and the amount of cooling water added with the degree of vacuum in the vacuum mixer as a parameter.

FIG. 6 is a characteristic map showing the amount of water vapor during vacuum kneading with respect to the temperature of the recovered sand with the degree of vacuum in the vacuum mixer as a parameter.

FIG. 7 is a graph showing the relationship between the water content of recycled sand and the coercive pressure of green mold.

[Explanation of symbols]

 1 Vacuum Mixer 5 FK Sensor 10 Water Supply Device 18 Primary Water Injection Control Valve 19 Secondary Water Injection Control Valve 23 Vacuum Pump 24 Pressure Switch 25 Pressure Control Valve 30 Arithmetic Controller 31 Bentonite Scale

Claims (7)

[Claims] 1. A method for reclaiming foundry sand by throwing recovered sand into a vacuum kneading tank and kneading by adding water and a binder, wherein a target value of sand strength of reclaimed sand is provided. Is set in advance, and the degree of vacuum in the tank is adjusted based on at least the temperature of the molding sand in the tank before vacuum kneading with respect to the target value. 2. The method for reclaiming foundry sand according to claim 1, wherein the amount of water added is adjusted based on at least the temperature of the foundry sand in the tank before vacuum kneading. 3. The method for reclaiming foundry sand according to claim 1, wherein the amount of the binder added is adjusted based on at least the temperature of the foundry sand in the tank before vacuum kneading. 4. The method for reclaiming foundry sand according to claim 3, wherein the amount of the binder added is reduced as the degree of vacuum in the tank increases. 5. A vacuum kneading tank, supply means for respectively supplying recovered sand, water and a binder to the vacuum kneading tank, and temperature detection for detecting the temperature of foundry sand in the tank before vacuum kneading. And the relationship between the amount of steam generated during vacuum kneading and the strength of reclaimed sand, the relationship between the temperature of the recovered sand and the amount of cooling water added as a parameter, and the vacuum in the tank. Based on the relational data between the temperature of the recovered sand and the amount of water vapor generated during vacuum kneading, the degree of which is a parameter,
A reclaiming device for foundry sand, comprising a control means for controlling the degree of vacuum in the tank. 6. The control means controls the added amount of cooling water based on the relational data between the temperature of the recovered sand and the added amount of cooling water with the degree of vacuum in the tank as a parameter. 5. The molding sand recycling apparatus of item 5. 7. The control means controls the addition amount of the binder based on the relational data between the amount of steam generated during vacuum kneading and the addition amount of the binder with respect to the target value of the sand strength of the reclaimed sand. 7. The apparatus for reclaiming foundry sand according to claim 5 or 6, wherein