JPH0428474A - Method for treating salt - Google Patents

Abstract

PURPOSE:To improve the operation efficiency of salt treatment and to prevent reaction product from sticking to a bathtub by changing the reaction product stored in salt liquid efficiently into sludge so that interrution is avoided as possible during salt treatment and taking it out of the bathtub. CONSTITUTION:The temperature of the salt liquid 14 is lowered in a range between the salt treatment temperature to remove the reaction of an attachment attaching to a material 18 to be treated and the solidifying temperature of the salt liquid 14 to retain the Brownian movement of the salt liquid 14. Therefore, the molecules of reaction product floating in the salt liquid stick to each other, the sedimentation of the reaction product is quickened by its weight and changed into sludge in a short time. Consequently, when the reaction product is solidified like water-glass, it is changed into sludge before it is solidified and can be taken out of the bathtub.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an operating method for salt treatment (salt bath treatment) carried out to remove mold material, etc. that adheres to castings after casting in investment casting methods, etc. In particular, it relates to an industrially advantageous method for removing reaction products generated and accumulated in a salt bath mainly consisting of molten caustic soda while avoiding interruption of the salt treatment as much as possible. .

(Background Art) Conventionally, for example, in investment casting, etc., after the casting has cooled down, there are
When removing mold material formed from refractories, a salt treatment is performed in which a vine made of molten caustic soda is immersed in a bath and reacted with silicon dioxide (SiO2), a component of the mold material, to remove it. .

By the way, in such a treatment, the reaction product of the deposits such as mold material and caustic soda gradually settles in the salt solution and settles in the bathtub. It is necessary to take it out of the tank by some means.

Therefore, in such salt treatment, if the reaction product has a slow settling rate and is suspended in the liquid for a long period of time, as the salt treatment is repeated, the reaction product may fall into the liquid. It was inevitable that the salt solution would gradually accumulate and the cleanliness of the salt solution would gradually decrease. As a result, there was a problem in that the rate of removal of deposits decreased significantly at an early stage, causing a decrease in the efficiency of salt treatment, and as a result, operational efficiency deteriorated.

Therefore, conventionally, 1. Sodium chloride etc. are added,
Attempts have been made to attach negative ions to the reaction product to cause it to settle, or to mix surfactants to speed up the precipitation, but these efforts have not been sufficiently effective.

In addition, when removing mold materials made of refractory materials from castings, silicon dioxide (Sin) and caustic soda (N
aOH), water glass (Na, 0
-nsioz) is generated, and in addition to the above-mentioned problem of lowering the cleanliness of the salt solution, the water glass solidifies while floating in the bath and firmly adheres to the inner surface of the bathtub, making it impossible to remove by regular scooping. There was a problem that could not be resolved. In order to remove such stuck substances, a situation arises in which the salt treatment has to be stopped, further reducing operational efficiency.

(Problem to be solved) The present invention has been made against the background of the above-mentioned circumstances, and the object to be solved is to prevent the salt treatment from being interrupted as much as possible, and to By efficiently turning the reaction products accumulated in the bath into sludge in a short time and removing it from the bath, the liquid is regenerated and its cleanliness is maintained over a long period of time, thereby increasing the operational efficiency of salt treatment. In particular, the purpose is to prevent reaction products from sticking inside the bathtub.

(Solution Means) In order to solve this problem, in the present invention, an object to be treated such as a casting is immersed in a salt solution mainly consisting of molten caustic soda, so that it adheres to the surface of the object to be treated. When removing deposits such as mold materials by reaction, the salt solution in which the reaction products generated by the above treatment have accumulated is taken out from the salt treatment tank and led to a separate tank, and the temperature of the salt solution is increased in the separate tank. In order to reduce the treatment temperature to a region where the salt solution does not solidify, the reaction products present in the salt solution are separated by sedimentation as sludge, and then the resulting supernatant salt solution is returned to the salt treatment tank. This is the summary.

Further, in the present invention, when the object to be treated is immersed in a salt solution and the deposits thereon are removed by reaction, a plurality of salt treatment tanks filled with the salt solution are provided, and the plurality of salt treatment tanks are provided. In a part of the treatment tank, the salt treatment is carried out, while in the remaining salt treatment tank, which accommodates the salt solution in which the reaction products generated by the treatment have accumulated, the temperature of the salt solution is lowered from the treatment temperature. The gist thereof is to carry out an operation in which the reaction products present in the salt solution are sedimented and separated as sludge by lowering the salt solution in a non-coagulating region.

(Function/Effect) In short, the present invention changes the temperature of the salt solution from the salt treatment temperature at which the reaction removes the deposits adhering to the object to be treated.
By lowering the temperature in a range where the salt solution does not solidify and stagnating the Brownian motion of the salt solution, the molecules of the reaction products floating in the salt solution adhere to each other, and their weight causes the reaction products to This speeds up the sedimentation of the sludge and turns it into sludge in a short period of time.

Therefore, even if the reaction product solidifies like water glass, it can be turned into sludge and taken out of the tank before it solidifies, and the sludge may stick to the inner surface of the bathtub and cannot be taken out. Fear is gone.

In addition, by providing the oak that performs such a liquid temperature lowering operation separately from the salt treatment tank, the cooling rate can be effectively increased by transferring the salt liquid between the two tanks, and the liquid temperature lowering operation can be carried out. The required time can be shortened, and the interruption time of the salting process accompanying this operation can be advantageously shortened. In addition, in such a salt treatment method, if the salt solution in which the reaction products have been accumulated is transferred to a separate tank and then the clean salt solution is introduced to the salt treatment tank and the salt treatment is continued, the salt treatment can be carried out. This makes it possible to almost completely avoid interruptions.

In addition, when multiple salt treatment tanks are installed and some of them are used for salt treatment and the remaining tanks are used to lower the liquid temperature, the salt treatment is interrupted by performing the salt liquid regeneration operation. There is no such thing.

Therefore, in the present invention, the cleanliness of the salt solution can be restored and a high salt processing capacity can be maintained while avoiding interruption of the salt processing as much as possible, which greatly improves operational efficiency compared to the conventional method. The result was an improvement.

(Example) Hereinafter, the present invention will be clarified more specifically based on the drawings.

In FIG. 1, reference numeral 10 denotes a salt treatment apparatus to which the method of the present invention is applied, and a salt treatment tank 12 is filled with a salt solution 14 mainly made of molten caustic soda, and the temperature of the salt solution 14 is kept constant. A heater 16 is installed in the tank to maintain the temperature. The temperature of the salt solution 14 is usually set at 4, because the higher the solution temperature, the higher the salt treatment efficiency.
Although it is heated to 50°C or higher, it is more preferable to heat it to about 500 to 550°C, and under the heating, the workpiece 8 is immersed in accordance with a known procedure, and the surface of the workpiece 8 is immersed. Adhering mold materials and the like are removed by reaction.

As such salt treatment is repeated, reaction products between deposits and caustic soda gradually accumulate in the salt solution, resulting in a decline in salt treatment capacity (specifically, Although it depends on conditions such as the temperature of the salt solution, in general, if a reaction product of around 4% in terms of heavy duty ratio accumulates in the salt solution, the salt treatment capacity will decrease significantly. Reaction products are removed by lowering the temperature of the liquid.

Here, in the method of the present invention, the salt solution 14 is taken out from the salt treatment tank 12 and guided to the cooling tank 20. The specific method of transferring the salt is not particularly limited, and in addition to forcibly transferring it using a pump, etc., the cooling tank 20 is installed at a lower position than the salt treatment tank 12, as shown in FIG. Then, the salt can be introduced from the bottom of the salt treatment tank 12 through the transfer pipe 22.

The salt liquid 14 led to the cooling tank 20 is allowed to cool naturally, and as the temperature decreases, reaction products are precipitated. As a result, the sludge 24 settles at the bottom of the cooling tank 2o, but the salt liquid 14 is deposited at the bottom of the cooling tank 2o.
2 to a separate cooling tank 20 for cooling, the cooling can be done effectively and the time required for the entire liquid temperature lowering operation can be advantageously shortened.

In the present invention, the lowering temperature is set within a temperature range in which the salt solution does not solidify;
It is possible to set the temperature up to about 330°C. However, the wider the temperature drop, the longer it takes to cool down and re-heat, which reduces operational efficiency. , temperature drop, and other conditions are determined.

Incidentally, 50 kg of 100% molten caustic soda (salt solution) heated to 540°C is mixed with 50 kg of refractory (mold material).
After adding 0 g of the salt solution and reacting for 1 hour, the temperature of the salt solution was lowered and the change in sludge 1 that settled as the temperature was lowered was measured, and the results shown in FIG. 2 were obtained. As is clear from Fig. 2, 89% of the total settled sludge 1 settles when the temperature drops to 460''C, and the rate of increase in sludge thereafter is low.
In such a case, in consideration of operational efficiency, it is preferable to lower the temperature to at least 460°.

The precipitated sludge 24 is taken out from the cooling tank 20 by various known methods, while the supernatant liquid 26 is returned to the treatment tank 12 through the reflux pipe 28 and heated. - The temperature is raised again by the heater 16,
It is then subjected to salt treatment again.

As for the timing to start raising the temperature, it is possible to maintain the predetermined lowering temperature for a certain period of time to advance the settling of the sludge 24, and then start raising the temperature. If the temperature of the sludge 14 is still low and the sedimentation rate of the sludge 24 is high, it is also possible to advance the sedimentation of the sludge 24 while increasing the temperature.

In this way, the present invention 1. ．． By lowering the temperature of the salt solution in the following manner, the reaction products are precipitated in large quantities in a short period of time, and the salt solution can be purified. (7) In that case, the liquid for cleaning can be moved to a tank separate from the salt treatment tank to effectively lower the temperature and advantageously shorten the time required for such cleaning operations. From a certain point, interruptions in salt processing are avoided as much as possible.

Next, another embodiment of the present invention will be described based on FIGS. 1 and 3. 5. In order to simplify the explanation, the same members as those used in the salt processing apparatus 10 are given the same reference numerals.

In this salt processing apparatus 30, a first salt processing tank 32 and a second salt processing tank 34 are installed as a pair of two tanks, and a heater 16 is installed in each of them, and a salt liquid 14 is installed. is fulfilled.

In the first salt treatment tank 32, the heating tank 16
As a result, the temperature of the salt solution 14 is maintained at about 500 to 550"C, and the object 18 to be treated is immersed in the salt solution 14, and the salt solution 14 is subjected to the treatment. In the second salt treatment tank 34, the heating by the heater 16 is stopped and natural cooling is performed, whereby the temperature of the salt solution 14 is lowered and the sludge 24 is cooled down.
is precipitated and separated from supernatant 2G.

So, from this state, the second salt treatment? ! ! When the sludge 24 is taken out from the second salt treatment tank 34, the temperature of the second salt treatment tank 34 is raised so that the salt treatment can be carried out. In the salt treatment tank 32, the heater 1
6 is turned off and natural cooling begins.

That is, in the salt treatment device [30], while the temperature is lowered in one salt tank in which reaction products are accumulated, the salt treatment is carried out in the other keyaki tank filled with highly clean salt solution 14. The efficiency of salt treatment is always high from the viewpoint of ■.

Since the salt treatment is not interrupted, the operational efficiency is extremely high. 1. It goes without saying that the present invention is not subject to any restrictions, and the present invention is subject to various changes, writing pressures, improvements, etc. based on the knowledge of those skilled in the art, without departing from the spirit of the present invention. It should be understood that it is possible to add
A device may be used to actively lower the temperature. In addition, in the salt treatment apparatus 10, while the temperature of the salt liquid 14 in which reaction products have been accumulated is lowered in the cooling tank 20, the salt treatment is continued in the salt treatment tank 12 using a clean salt liquid. For example, interruption of the salt treatment can be avoided and more efficient operation can be achieved.6Furthermore, although the salt treatment apparatus 30 has two salt treatment tanks, it may be configured to have three or more tanks as appropriate. Of course, it is good to do so.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an outline of a salt processing apparatus to which the method of the present invention is applied. In addition, FIG. 2 is a graph showing an example of the relationship between the salt liquid temperature and the amount of sludge sedimentation.
The figure is an explanatory diagram showing an outline of another example device to which the method of the present invention is applied. 10.30: Salt treatment device 12: Salt treatment tank 14: Salt solution 16: Heater 18: Object to be treated 20: Cooling tank 24: Sludge 26: Supernatant liquid 32: First salt treatment tank 34: Second Salt treatment tank

Claims (2)

[Claims] (1) When an object to be treated, such as a cast article, is immersed in a salt solution mainly consisting of molten caustic soda to react and remove deposits such as mold material adhering to the surface of the object to be treated, it is possible to remove the deposits caused by the above treatment. The salt solution in which the reaction products have accumulated is taken out from the salt treatment tank and introduced into a separate tank, and in the separate tank, the temperature of the salt solution is lowered from the treatment temperature to a region where the salt solution does not solidify. 1. A salt treatment method, which comprises separating the reaction products present in the salt solution by sedimentation as sludge, and then returning the obtained supernatant salt solution to the salt treatment tank. (2) When an object to be treated, such as a casting, is immersed in a salt solution mainly consisting of molten caustic soda to react and remove deposits such as mold material adhering to the surface of the object, the salt solution is A plurality of filled salt treatment tanks are provided, and the salt treatment is carried out in some of the plurality of salt treatment tanks, while the remaining salt treatment tank accommodates a salt liquid in which reaction products generated by the treatment have accumulated. Salt treatment is characterized by carrying out an operation in which reaction products present in the salt solution are sedimented and separated as sludge by lowering the temperature of the salt solution from the treatment temperature in a region where the salt solution does not solidify. Method.