JPH06122065A - Chemical removal method for molding material and device therefor - Google Patents

Abstract

PURPOSE:To enhance the effect of removing molding materials by immersing castings into an aq. alkaline soln. kept at a temp. above b.p. under an atm. pressure in a hermetic vessel. CONSTITUTION:The castings are immersed into the aq. alkaline soln. 2 in the hermetic vessel 1 and the vessel is closed with a cap 6. The aq. alkaline soln. is heated to boil by a heating element 3. Steam is cooled and condensed by a steam cooling means 4 and is returned into the vessel 1. The aq. alkaline soln. 2 is smaller in surface tension and viscosity than a molten alkali and, therefore, penetrates and diffuses deep into core parts and stop holes, thereby accelerating the dissolution of casting molds and core materials. The effect of physically peeling the molding materials is added by the volumetric expansion of intermittent boiling. The effect of removing the molding materials is high with casting molds consisting of alumina and zircon refractories as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a part of a molding material that is accompanied by a core such as a core enclosed in a cast product portion or sand attached to the cast product after casting the cast product by precision casting. And a device used therefor.

[0002]

2. Description of the Related Art Generally, a mold for precision casting is mainly made of a silicic refractory material. As a method for removing the refractory material adhered to the casting product after the molten metal is cast and solidified in the mold. Generally, a method of removing the shape by a physical treatment such as a blast treatment after performing mold separation due to vibration or the like is used. Blasting generally requires a lot of man-hours,
In addition, there are those that cannot be applied with the blast treatment due to requirements such as the surface quality of products, and those that have complicated shapes or cores that are difficult to remove by the blast treatment. Casting products that cannot be blasted are treated with caustic soda at 400 to 500 ° C.
A molten alkali dipping method is used in which a mold material such as a core material is dissolved and removed by immersing in a melt that is heated and melted. Further, Japanese Patent Publication No. 51-39626 proposes a method of improving the treatment efficiency by performing the primary sand removal with an alkaline aqueous solution and then using the molten alkali method as described above for the detailed sand removal. .

[0003]

However, in the conventional molten alkali dipping method, although sand removal (mold removal) is relatively easy with sand containing a large amount of silicic acid, it is difficult to use a fire resistant alkali-resistant material such as zircon or alumina. For objects, it is very difficult to remove sand, and the process efficiency is low and, in some cases, casting is difficult for mold removal of products with non-penetrating holes, that is, blind holes and castings with complicated shapes. The product surface is corroded. In addition, since this method handles caustic soda, which is a deleterious substance, in a high-temperature molten state, it is feared that the working environment will be deteriorated and the human body and equipment will be adversely affected. Therefore, improvement of the working environment has been strongly demanded from the past. Further, the molten alkali dipping method is not applied in the case of cast products of copper or copper alloys because corrosion of the cast product surface is considered, and sand removal was performed by blast treatment or the like. There are the above-mentioned drawbacks such as a large number of man-hours required for sand removal, and some restrictions on applied products. It is an object of the present invention to provide a method for chemically removing a template material which is effective for an alkali resistant refractory material such as alumina and zircon and a copper alloy material, and which reduces the number of steps, and an apparatus optimal for the method.

[0004]

In order to solve the above problems, the present invention immerses a cast product in an alkaline aqueous solution, heats it in a closed container, and pressurizes it to improve the ability to remove sand and copper alloy. The inventors have found that it can be applied to, and completed the present invention.

That is, the present invention is characterized in that a cast product with a part of a mold material is immersed in an alkaline aqueous solution such as caustic soda or caustic potash, which is kept at a boiling point or higher under atmospheric pressure in a closed container. This is a method of chemically removing the template material. In the present invention, it is desirable to boil the alkaline aqueous solution particularly intermittently by heating the aqueous solution and condensing the generated steam by cooling. Further, the second invention of the present application is a chemical removal of the template material comprising a container with a lid capable of blocking atmospheric pressure, heating means for heating the alkaline aqueous solution contained therein, and cooling means for cooling and condensing the generated water vapor. It is a device.

[0006]

The method invention of the present application focuses on the dissolving action of the alkaline aqueous solution with respect to the colloidal silica component used as the binder in the mold material, and prevents boiling by using a closed container to raise the temperature of the alkaline aqueous solution. This enhances this dissolving action. Due to this effect, for example, 1.5 kg for a 30 wt% caustic soda solution
At a saturation temperature (boiling temperature) of f / cm ² or higher, or at a saturation temperature of 1.3 kgf / cm ² or higher in the case of 40 wt% with the same aqueous solution, 100% of the deposits of the molds associated with the castings are obtained.
% Can be removed. Further, since the alkaline aqueous solution used in the present invention has smaller surface tension and viscosity than molten alkali, it permeates and diffuses into the core portion and the inner part of the blind hole to promote dissolution of the template and core material. Further, when the aqueous solution is boiled as a preferred embodiment of the present invention, it is likely that the sound wave vibration caused by boiling causes the boiling to be intermittent, that is, the water vapor coexisting with the solution is heated after the aqueous solution is heated to a high temperature. By repeating the cycle of cooling or discharging to reduce the pressure in the container and boiling the aqueous solution, the action of removing the template material is promoted. The effect of this intermittent boiling is that the effect of physically exfoliating the mold material is added due to the volume expansion when the alkaline aqueous solution that permeates the interface between the mold material and the cast metal vaporizes at that portion.
The intermittent boiling mentioned above, especially for the core and blind holes,
Supplying a fresh alkaline aqueous solution to the inner part and effectively peeling action by physical pressure due to generation of a large amount of water vapor of the alkaline aqueous solution in the part. The method of the present invention is an effective means when applied to cast products of copper materials and copper alloys because it does not corrode the surface. The apparatus of the present invention is configured to effectively perform the above intermittent boiling. In this configuration, as the heating means, it is effective to use electric heating provided inside or outside the liquid level of the container or indirect heating by steam. On the other hand, by providing a vapor cooling means such as a pipe or a fin that allows cooling water to flow through at a portion above the liquid level in the container, it is expected that the vapor containing the vaporized alkali is condensed and the pressure in the container is reduced. This means is effective as a means for depressurizing the inside of the container without releasing the water vapor in the container to the outside and deteriorating the environment. Condensed water generated as a result of cooling returns to the container, and the concentration of the aqueous solution in the container can be kept constant. This heating and cooling is
It is recommended that this order be repeated once or alternately.

[0007]

EXAMPLES The present invention will be described below based on examples.

(Example 1) A casting obtained by casting SCM415 in a precision casting mold fired using colloidal silica as a binder composed of silica content of 50% and the balance of zircon and alumina, and subjecting the cast product to vibration-induced mold separation. It was used as a test material. Treatment liquid is 10, 20, 30, 40, 50
An aqueous solution of caustic soda with a different concentration of wt% was soaked, and the container was left open to atmospheric pressure (10 kgf / cm ² ) after immersing a specified amount of the test material, and the internal pressure was obtained by covering the container with the atmosphere. 1.2, 1.3, 1.5, 2.0, 3.0, 5.
Heating was controlled so that the temperature was maintained at 0, 8.0, and kgf / cm ^2, and the samples were immersed and held for 1 hour for comparison. The weight ratio of the mold material removed by this treatment to the average value of the amount of the mold material adhered to the test material with the molds left unmolded was obtained and evaluated.
The results are shown in Table 1.

[0009]

[Table 1]

From the table, it can be seen that at a constant temperature, the higher the holding pressure (higher temperature), the higher the removal weight ratio, that is, the effect of the present invention is great. Further, it can be seen that when the pressure is constant, the higher the concentration, the higher the removal weight ratio.
In the case of this example, a pressure of 1.3 (without boiling)
If it is more than kgf / cm ² and the concentration is more than 30wt%, the template is almost completely eluted and removed, and it is 30wt% at 1.3kgf / cm ^2.
Only in such a case, a good cast product could be obtained by using a simple sandblasting treatment together thereafter.

(Example 2) Using the same mold material as in Example 1, a casting having a complicated shape having a blind hole, which was cast by SUS304, was used as a test material and immersed in an aqueous 30 wt% caustic potash solution. The internal pressure is 2.0kgf / cm ^{2 in the same} manner as
It was heated as the pressure was increased to. Cooling water was passed through the cooling coil in the upper part of the pressurizing tank shown in FIG. 1 for 3 minutes, and then heated so that the original pressure was increased in 2 minutes, and the water was repeatedly passed and held for 1 hour. As a result, the mold material was completely eluted and removed including the blind holes. However, about 30% by weight is obtained for 1 hour after keeping the internal pressure at 2.0 kgf / cm ^2.
Mold sand remained. In addition, when sand is removed with molten caustic soda, strong oxide scale adheres,
According to the present invention, since the temperature was low and the concentration was low, the adhesion of oxide scale was not observed.

(Example 3) Using the same mold material as in Example 1, a cast product obtained by casting HBSC2 (high-strength brass casting type 2) was used as a test material. When this is subjected to sand removal treatment with molten caustic soda, an oxide scale layer is recognized at a depth of about 1 mm from the surface layer, and the surface skin becomes rough. However, when the treatment liquid and conditions of Example 2 are used, good results are obtained. A cast product having a surface skin could be obtained.

Next, an embodiment of the device of the present invention will be described. FIG. 1 is a half sectional elevation view of an embodiment of the apparatus of the present invention manufactured for small precision castings. In the closed container 1, the heating element 3 is attached to the outer peripheral surface below the liquid surface of the alkaline aqueous solution 2, and the heat insulating layer 8 is provided. The closed container 1
Is provided with a lid and a lid opening / closing device 5 so that the lid 6 can be airtightly held in the closed container 1. Inside the center of the lid 6, there is provided a steam cooling means 4 which is a flexible pipe for feeding and discharging cooling water through pipes 4 ′ and 4 ″.
When the lid 6 is opened, the vapor cooling means does not hinder loading and discharging of the object to be treated in the closed container 1, and while the lid is closed, the vapor cooling means is located in the water vapor retention portion on the liquid surface. Only
It is positioned to cool and condense. Reference numeral 7 is an air relief valve. The heating and cooling are controlled by turning on / off the heating element and supplying cooling water by a temperature controller provided in the closed container 1. The object to be processed is housed in a dedicated basket, and the basket is operated by a hoist or the like. Reference numeral 9 is a platform which is a work floor.

[0014]

As described above, the method invention of the present invention has a high effect of removing the mold material not only for the silica-based mold but also for the mold made of alumina or zircon-based refractory, and particularly for the core and the inner part of the blind hole. However, low man-hour processing is possible. At the same time, it has the effect of improving the processing environment. Also,
It can be applied to copper alloys, which was not possible with conventional alkaline aqueous solutions, and it is extremely effective in the mass production finishing process of precision castings without the formation of oxide scale. In addition, the apparatus of the present application is particularly configured to effectively perform intermittent boiling among the method inventions of the present application, and since the closed container itself is provided with heating and steam cooling means, indoor environment pollution due to steam release is caused. In addition, the entire apparatus can be made compact.

[Brief description of drawings]

FIG. 1 is an elevational view showing an embodiment of a device of the present invention as a half sectional view.

[Explanation of symbols]

 1 Airtight container 2 Alkaline aqueous solution 3 Heating element 4 Steam cooling means 4'pipe 4 ″ pipe 5 Lid opening / closing device 6 Lid 7 Air release valve 8 Heat insulation layer 9 Platform

Claims (3)

[Claims] 1. A method for chemically removing a casting material, which comprises immersing a cast product with a portion of the casting material in an aqueous alkaline solution which is kept at a temperature of at least the boiling point under atmospheric pressure in a closed container. 2. The method for chemically removing a template material according to claim 1, wherein the alkaline aqueous solution is boiled by reducing the pressurizing pressure. 3. A container for accommodating an alkaline aqueous solution in which a product to be treated is immersed so as to be shielded from the atmosphere, a heating means provided in the container for heating the aqueous solution, and a portion above the liquid surface in the container. A chemical removing device for a casting material, comprising a vapor cooling means provided with a cooling means for circulating cooling water.