JP6728550B2 - Method for removing mold remaining in casting - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for removing a mold that remains and adheres to a casting from a casting cast using the casting mold.

Casting is performed by pouring a molten metal into a mold and cooling the molten metal to solidify it. Here, the mold is manufactured by combining foundry sand such as silica sand with a binder to form a predetermined shape. Then, when the molten metal is cast into the mold for casting, the high temperature of the molten metal acts on the mold, so that the binder is thermally decomposed by the action of this high temperature, and the binding force by the binder decreases. Therefore, when a shock is applied to the mold after casting, the mold collapses so that the molding sand that has been bound with the binder falls apart, and the molded product can be taken out of the mold. ..

In the mold, there are organic binders and inorganic binders as the above binders, and thermosetting resins such as phenolic resins and sugars such as starch and sugar are mainly used as the organic binders. Here, since sugar has a low thermal decomposition temperature, it is used as a binder for a mold used for casting a metal at a relatively low temperature. Further, since the sugar has such a low thermal decomposition temperature, it is easily thermally decomposed by the action of high temperature when pouring the molten metal, the mold easily collapses and the foundry sand falls apart. Therefore, it is easy to remove the foundry sand from the casting.

On the other hand, a thermosetting resin such as phenol resin is widely used as a binder of a mold in the shell molding method or the like. Since the thermosetting resin has higher heat resistance than saccharides, the strength of the mold can be maintained even when casting a metal having a relatively high temperature. However, since the thermosetting resin has a high thermal decomposition temperature, it may not be easily thermally decomposed even when the high temperature of the molten metal acts when pouring the molten metal. For this reason, even if the mold is broken after casting, most or part of the mold may remain attached to the cast product without being broken by the binding force of the binder. Especially when the mold is a core, it is difficult to remove the core from the casting because the core is inside the casting.

Therefore, various methods for removing the mold from the casting have been conventionally proposed, for example, as disclosed in Patent Document 1 and Patent Document 2.

JP, 2010-64082, A JP2012-139718A

As a method of removing the mold from the cast, as seen in the above-mentioned Patent Documents 1 and 2, the method of applying a shock or vibration to the cast to collapse the mold is the main one. However, in the state where the thermal decomposition of the binder of the mold is insufficient and the mold remains in the casting without being collapsed, the casting of the mold that remains and adheres to the casting even if some shock or vibration is applied. It is difficult to break the sand apart. In particular, when casting is performed with a mold manufactured using a binder having a high bond strength such as a thermosetting resin, even if a large shock or vibration is applied to the cast product, the mold remaining in the mold is destroyed and removed. It was difficult to do.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of removing a mold that can easily disintegrate and remove the mold that remains and adheres to the casting. ..

The method of removing the mold remaining in the casting according to the present invention, when the mold obtained by casting using a mold formed by binding the molding sand with an organic binder is released from the mold, casting A method of removing a mold remaining adhered to an object, characterized by removing the mold adhered to a casting after performing a process of further activating and carbonizing an organic binder of the mold adhered to a cast To do.

When the organic binder of the mold attached to the casting is carbonized, the organic binder becomes a carbide with a porous structure and its strength decreases, and when the carbide of the organic binder is further activated, the porous fine structure further develops and becomes fine. The cracks are generated, the strength of the carbide of the organic binder is further reduced, and the organic binder of the mold remaining and adhering to the casting becomes extremely brittle. As a result, the foundry sand of the mold that remains and adheres to the casting easily collapses and falls apart, and the mold that remains and adheres to the casting can be easily removed.

Further, the present invention is characterized in that the casting to which the mold is attached is placed in an activating gas atmosphere, and the casting is heat-treated under the condition of carbonizing the organic binder of the mold and further activating the carbide of the organic binder. It is a thing.

When the casting with the mold attached is heated in an activation gas atmosphere, the activation gas permeates between the particles of the casting sand of the casting mold attached to the casting, efficiently after carbonizing the organic binder binding the casting sand. It can be activated and can easily bring the organic binder into a brittle state.

Further, the present invention is characterized in that after the organic binder of the mold attached to the cast is carbonized and further activated, the mold attached to the cast is collapsed by applying an external force.

Even after the organic binder is carbonized and activated as described above, the mold attached to the casting often retains its outer shape, but since the carbide of the organic binder is in a very brittle state, It is easily collapsed by applying a small amount of force, and can be easily removed from the casting in a state where the foundry sand is disintegrated into pieces.

Further, the present invention is characterized in that a gas selected from steam, carbon dioxide, oxygen, and a mixed gas of two or more kinds of these is used as the activating gas.

By using these as the activation gas, the activation can be performed with high efficiency. In particular, since water vapor has high latent heat and sensible heat, it can efficiently heat the organic binder of the mold attached to the casting, and can carbonize and activate the organic binder in a short time. ..

Further, in the present invention, the steam is a superheated steam.

The superheated steam is a high-temperature dry steam, which can heat the organic binder of the mold attached to the casting with higher efficiency, can carbonize the organic binder in a short time, and can activate it.

Further, in the present invention, the organic binder of the template is a thermosetting resin.

The thermosetting resin has high heat resistance and may not be thermally decomposed by the heat of the molten metal, but the thermosetting resin is easy to carbonize and activate and can easily be made into a brittle carbide. Even if is a thermosetting resin, the mold attached to the casting can be easily removed.

Further, in the present invention, the template is a core.

The core is often left inside the casting after casting, but the activating gas enters the inside of the casting through the opening and acts on the core, binding the molding sand of the core. The organic binder can be efficiently activated after being carbonized, and even the core remaining inside the casting can be easily removed.

According to the present invention, when the organic binder of the mold attached to the casting is carbonized, the organic binder becomes a carbide of a porous structure, and further activation of this carbide develops a porous fine structure, and the organic binder has strength. Is a very small carbide, the organic binder of the mold can be in a very brittle state, the mold that remains and adheres to the casting easily disintegrates, and the casting sand of the mold is broken up It can be easily removed from the casting in the state.

It is a schematic front view which shows an example of the apparatus used in this invention. It is a schematic front view which shows another example of the apparatus used in this invention. It is a figure which shows the casting mold used in an Example, (a) is front sectional drawing, (b) is a top view.

Embodiments of the present invention will be described below.

The present invention can be applied without particular limitation as long as it is a cast product cast using a mold having an organic binder having carbon as a molecular skeleton as a binder (binder). The organic binder is also not particularly limited as long as it is a thermosetting resin, a thermoplastic resin, a saccharide or the like that is used in the production of a mold. Even when using an organic binder having a high carbonization yield, even if the carbonization yield is high, such as a thermosetting resin such as a phenol resin or a furan resin, a template is obtained by carbonization and activation. Will be easy to collapse.

There is also no particular limitation on the molding sand that forms the mold, and it is commonly used for molds such as silica sand, mountain sand, alumina sand, olivine sand, chromite sand, zircon sand, mullite sand, reclaimed sand, and other artificial sand. Can be exemplified.

In addition, the mold produced by using the foundry sand and the organic binder can be used without limitation regardless of what method is used. For example, a mold obtained by kneading foundry sand and an organic binder in a wet state, filling the mixture with a molding die and heating the mixture can be used. Alternatively, by kneading the foundry sand and the organic binder to prepare a so-called resin coated sand in which the surface of the foundry sand is coated with a solid organic binder, the resin coated sand is filled in a hot mold and the temperature of the mold is set. Use a mold obtained by heating with a mold or a mold obtained by filling resin mold in the resin coated sand, ventilating steam into the mold, and heating the resin coated sand in the mold with steam. You can also do it.

Casting can be performed by pouring a molten metal, which is a molten metal, into a mold and cooling the molten metal to solidify it. Since the high temperature of the molten metal acts on the mold when pouring the molten metal into the mold, the organic binder of the mold is thermally decomposed at this high temperature, and the strength of the organic binder that binds the foundry sand decreases. Therefore, when a shock is applied or vibration is applied, the mold collapses so that the foundry sand is scattered, and the cast product can be taken out from the mold.

At this time, if the thermal decomposition of the organic binder during casting is not sufficient due to the temperature of the molten metal and the heat resistance of the organic binder, the entire mold will not collapse and a part or most of the mold will remain in the casting. Sometimes. The mold remaining in the casting is the one in which the molding sand is in the state of being bound by the organic binder and is attached to the casting with the organic binder, and the mold thus remaining and attached to the casting is the casting It is difficult to remove easily even if a shock or vibration is applied to the.

In view of this, the present invention is to perform a process of carbonizing the organic binder of the mold remaining and adhering to the casting and further activating it in the casting in which the mold remains and the molding sand adheres. In the present invention, it is preferable to use an activating gas for activating the carbide, and steam is particularly preferable among the activating gases. And when performing a process using steam as an activating gas, the carbonization activating device A as shown in FIG. 1 can be used, for example.

The carbonization activation processor A of FIG. 1 is formed by including a heat treatment container 1 and a steam generator 10. In the heat treatment container 1, an inlet 3 through which water vapor is blown into the container 1 is provided at the bottom, and the container 1 is provided. An exhaust port 4 for discharging the water vapor therein is provided in the upper part. By closing the opening 5 on the front surface of the heat treatment container 1 with the door 6, the inside of the heat treatment container 1 is sealed except for the inlet 3 and the exhaust port 4, and a sealed space is formed in the heat treatment container 1. It has become so. A steam generator 10 is connected to the inlet 3 via a valve 12. The steam generator 10 is formed by including a boiler, and can heat water in the boiler to generate steam (saturated steam) and send it out. By connecting a superheater to this boiler, the steam generated by the boiler can be further heated by the superheater and sent out from the steam generator 10 as superheated steam.

Then, the door 6 is opened to set a mold to which a part of the mold remains and adheres in the heat treatment container 1, and after the door 6 is closed, the valve 12 is opened and steam is aerated in the heat treatment container 1. Steam acts on the remaining and adhered mold, and the organic binder of the mold can be heated with steam. Since steam has high latent heat and sensible heat, the organic binder can be instantly heated to a high temperature in a short time. In addition to the steam acting on the mold attached to the exposed surface of the casting, the steam also enters the inside of the casting through the opening, so the steam also acts on the casting inside the casting. And since the water vapor passes between the particles of the foundry sand and penetrates into the mold, it is possible to uniformly heat the remaining mold, bond the foundry sand and adhere the foundry sand to the foundry. The organic binder can be heated with steam.

Here, as described above, the inside of the heat treatment container 1 is a steam atmosphere in which air (oxygen) is excluded, and in such a non-oxygen atmosphere, by heating the organic binder of the foundry sand adhered to the casting with steam, The organic binder can be carbonized. When the organic binder becomes a carbide, it has a porous structure, so that the strength is reduced and the carbide of the organic binder becomes brittle.

Then, after carbonizing the organic binder, by further supplying steam to the heat treatment container 1 to continue aeration, the carbide of the organic binder is further subjected to the action of steam to activate the carbide. That is, the steam reacts with the carbon of the carbide as an activating gas to further develop the porous microstructure formed in the carbide and activate the carbide. When the carbides are activated in this way, a porous structure develops, the strength of the carbides of the organic binder becomes low, and the organic binder becomes brittle. For this reason, the mold remaining and attached to the casting is likely to collapse, and when impact or vibration is applied to the casting, the casting mold easily collapses, and the casting sand of the casting mold becomes disjointed, It can be removed from the casting.

Even after the organic binder is carbonized and activated as described above, the mold attached to the casting often retains its outer shape. In this case, the attached mold may not collapse even if shock or vibration is applied to the cast, so by directly applying an external force to the mold by poking this mold with a jig such as a rod, The sand breaks apart and the mold can be easily collapsed.

In the carbonization activation processor A of FIG. 2, the heat treatment container 1 is provided with a heating means 8. The heating means 8 may be anything as long as it can self-heat due to combustion or electric resistance to raise the temperature in the heat treatment container 1, and for example, a gas burner, an electric heater or the like can be used. In this case, the temperature of the atmosphere in the heat treatment container 1 can be set to a temperature higher than the temperature of water vapor by heating with the heating means 8, and carbonization and activation treatments can be performed in a high temperature atmosphere in a short time. Can be done.

The conditions of the heat treatment with steam in the heat treatment container 1 of each of the above-mentioned embodiments are not particularly limited and vary depending on the type of the organic binder and the like, but generally, for carbonizing the organic binder and further activating the carbide. The heating temperature is preferably about 200° C. or higher, more preferably 300° C. or higher, even more preferably 400° C. or higher. Carbonization of the organic binder and activation of the carbide are carried out continuously or simultaneously in a series of steps in which steam is continuously supplied to the heat treatment container 1 and aerated, and carbonization and activation with high production efficiency. Is something that can be done. Further, the time required for heat-treating the organic binder varies depending on the temperature of water vapor, the type of organic binder, the size of the casting, the degree of activation, etc., but is generally set to about 0.1 to 40 hours. In particular, it is preferably 0.5 hours or more in order to perform the activation sufficiently. For example, when a thermosetting resin such as phenol resin or furan resin is used as the organic binder, the temperature of steam is set to 300 to 900° C., and the time for ventilating the steam in the heat treatment container 1 is set to the range of 0.1 to 30 hours. It is preferable that the time is 0.5 hours or more for sufficient activation.

As the steam, not only saturated steam but also superheated steam can be used as described above. Superheated steam is steam in a completely gaseous state in which saturated steam is further heated to a temperature equal to or higher than the boiling point, and is dry steam at 100° C. or higher. Since the superheated steam can raise the temperature to about 900° C., the organic binder can be heat-treated at a high temperature, and the activation heat-treatment time can be shortened.

Although steam is used as the activating gas in the above embodiment, various kinds of activating gas other than water vapor can be used, such as carbon dioxide, oxygen, or water vapor, carbon dioxide, Examples of the mixed gas include two or more kinds selected from oxygen. When an activating gas other than water vapor is used, the heat treatment container 1 provided with the heating means 8 as shown in FIG. That is, the temperature in the heat treatment container 1 is set by the heating means 8 to the condition for carbonizing and activating the organic binder, the activation gas is supplied from the inlet 3 into the heat treatment container 1, and the activation gas in the heat treatment device 1 is exhausted. By evacuating from the port 4 and ventilating the activation gas so that the inside of the heat treatment container 1 becomes an activation gas atmosphere, carbonization and activation treatment can be performed.

In the present invention, the binder used in the mold is not particularly limited as long as it is an organic binder that can be carbonized by heating. Here, when the organic binder is a thermosetting resin, the thermosetting resin has high heat resistance and may be difficult to be thermally decomposed by the heat of the molten metal, but the heat treatment easily carbonizes the thermosetting resin. Can be further activated, and the organic binder can be made brittle. Therefore, even if the organic binder is such a thermosetting resin, the remaining mold can be easily removed from the casting, and the present invention is effective even when the organic binder is a thermosetting resin. Is. Further, even if the organic binder is a thermosetting resin having a high carbonization yield such as a phenol resin or a furan resin, it can be easily carbonized by a heat treatment with steam. It is possible to obtain a high effect.

Further, as described above, the activating gas such as water vapor not only acts on the mold attached to the exposed surface of the casting, but the activating gas such as water vapor also opens into the inside of the casting not exposed on the surface of the casting. Since it enters from the inside, the activating gas such as water vapor also acts on the mold adhered inside the casting to carbonize the organic binder of this mold inside the casting to further activate it. Here, when the mold is a core, the core is difficult to completely remove because it is left inside the casting, but in the present invention, even if the core remains attached inside the casting, steam By heat-treating in an atmosphere of an activating gas, the organic binder in the core can be easily carbonized, and the organic binder can be activated more easily, and the organic binder can be made brittle. Therefore, after treating with an activating gas such as water vapor, a jig such as a rod is inserted into the inside of the casting and the remaining core is pierced to apply a force directly to break the core sand into pieces. In this state, the core can be removed from the cast, and by applying the present invention, the core remaining inside the cast can be easily removed.

Next, the present invention will be specifically described with reference to examples.

(Resin coated sand No1 and No2)
30 kg of flattery silica sand heated to 135° C. was charged into a whirl mixer, phenol resin was added in an amount shown in Table 1, kneaded for 30 seconds, and then hexamethylenetetramine dissolved or dispersed in 450 g of water as needed. 120 g was added and kneaded until the lump of sand grains collapsed. Then, 30 g of calcium stearate as a lubricant was added and kneaded for 30 seconds, and the mixture was discharged from a whirl mixer, cooled by aeration, and then coated with solid phenol resin at a coating amount of 3.0% by mass with respect to silica sand. Resin coated sand No. 1 and No. 2 coated with were obtained.

The fusion points of the phenolic resin on the surfaces of the resin coated sands No1 and No2 prepared as described above were measured according to JACT test method C-1 "fusion point test method". The results are shown in Table 1.

Further, a molding die capable of molding a test piece having a width of 23 mm, a length of 70 mm, and a thickness of 23 mm is heated to 240±5° C., and resin coated sand Nos. 1 and 2 are blown into the molding die at an air pressure of a gauge pressure of 0.1 MPa. The test piece was obtained by filling in with, and demolding after 60 seconds. The bending strength of this test piece was measured according to JACT test method SM-1. The results are shown in Table 1.

(Example 1, Comparative Example 1)
A molding die capable of molding a test piece having a width of 40 mm, a height of 40 mm, and a length of 180 mm is heated to 240±5° C., and resin coated sand No. 1 is blown into the molding die at an air pressure of 0.1 MPa to fill the mold. After 120 seconds, the mold was removed to obtain a test piece for a disintegration test. This test piece was wrapped in aluminum foil in three layers.

Then, using the carbonization activation processor A shown in FIG. 2, the test piece was placed in the heat treatment container 1 having an inner dimension of 400 mm in width, 400 mm in depth, and 400 mm in height, and the gauge pressure generated by the boiler was 0.3 MPa and the temperature was 143° C. The saturated steam of Nomura Gikko Co., Ltd. was heated to 500° C. by a superheater “Model GE100”, and the heated superheated steam was blown into the heated steam. It was set to °C. The phenol resin of the test piece was carbonized by holding this state for 20 minutes. The carbonized test piece was taken out from the heat treatment container 1 and naturally cooled, and then a part of the test piece was used to measure the bending strength according to JACT test method SM-1 and observe the appearance. The results are shown in Table 2.

Next, the remaining test piece taken out was halved, the aluminum foil was peeled off on one side, and the other side was wrapped in the aluminum foil and placed again in the heat treatment container 1 under the same 650° C. conditions as above. The processing was performed while holding for the time shown in. After performing this treatment, it was naturally cooled, the bending strength was measured according to JACT test method SM-1, and the appearance was observed.

Here, one test piece from which the aluminum foil was peeled off, and one test piece from which the aluminum foil was peeled off, of the other test pieces that were still wrapped in the aluminum foil, were activated by heat treatment with steam. The bending strength and the appearance are shown in Table 2 using this as Example 1. The test piece wrapped with the other aluminum foil did not proceed with activation even if it was heat-treated with steam. Therefore, Table 2 shows the bending strength and the appearance as Comparative Example 1.

(Example 2, Comparative Example 2)
Same as above except that resin coated sand No. 2 was used.

In Table 2, Examples 1 and 2 are obtained by carbonizing and activating test pieces prepared assuming a mold, and Comparative Examples 1 and 2 are obtained by carbonizing test pieces. Then, in Examples 1 and 2, it is confirmed that the carbonization and activation treatment significantly reduce the bending strength with the treatment time, and the test piece becomes brittle and disintegrates.

Here, if the bending strength is about 2.0 MPa or less, the brittleness is such that it is easily disintegrated by an external force of pushing with a finger, so in Example 1, carbonization for 20 minutes, activation for 60 minutes, and Example 2 Then, it is confirmed that the mold can be easily disintegrated and removed from the casting by the treatment of carbonization for 20 minutes and activation for 60 minutes.

(Example 3)
Using resin coated sand No. 1, a mold composed of the main mold 15 and the core 16 shown in FIG. 3 was produced. The outer shape of the main mold 15 is a cylindrical shape having a diameter of 10 cm and a height of 10 cm, and a concave portion 17 having an inner diameter of 6 cm and a depth of 7 cm is formed, and a hole 18 having a diameter of 2 cm and a depth of 1 cm is provided at the center thereof. .. The core 16 has a cylindrical shape with a diameter of 2 cm and a height of 8 cm. Each of the main mold 15 and the core 16 was molded by blowing resin-coated sand No. 2 into a molding die heated to 240±5° C. by air pressure of 0.1 MPa gauge pressure, and removing the mold after 60 seconds. Is.

Then, after setting the core 16 in the main mold 15 as shown in FIG. 3, a molten aluminum alloy at 800° C. is poured into the concave portion 17 of the main mold 15 and allowed to cool naturally, and the casting in the main mold 15 is performed. Casting was performed by allowing 19 to cool to room temperature. The high temperature of the molten aluminum alloy acts on the main mold 15 and the core 16, and the part of the main mold 15 and the core 16 in contact with the casting 19 is carbonized and becomes black, but the other parts remain in the original color. Met. After casting in this way, when the main mold 15 and the core 16 were hit with a mallet to give an impact, 20 to 30% of the main mold 15 remained attached to the surface of the cast product without collapsing. Further, 60 to 70% of the core 16 did not collapse and remained attached to the inside of the casting 17.

Next, using the steam heat treatment apparatus A shown in FIG. 2, the casting 19 remaining with the main mold 15 and the core 16 attached thereto is set in the heat treatment container 1, and the gauge pressure generated by the boiler is set to 0. The superheated steam prepared by heating saturated steam having a temperature of 143° C. of 3 MPa to 500° C. by a superheater “Model GE100” manufactured by Nomura Gikko Co., Ltd. is blown in, and at the same time, the heating means 8 composed of an electric heater is operated to heat-treat the vessel. The temperature in 1 was set to 650°C. Then, by maintaining this state for 90 minutes, the main mold 15 and the core 16 were heated with steam.

After that, when taken out of the heat treatment container 1 and cooled to room temperature, and hitting the main mold 15 with a mallet, the main mold 15 collapsed into disintegrated sand grains and fell off from the surface of the casting 19. Also, after the core 16 was hit with a mallet to give an impact, and a metal rod was inserted and stirred, the core 16 collapsed into disintegrated sand grains, which could be taken out from the casting 19.

1 Heat Treatment Container 2 Inlet 3 Exhaust 10 Steam Generator 15 Mold 16 Mold 19 Casting

Claims (7)

When removing from the mold the casting obtained by casting using a mold formed by combining the molding sand with an organic binder, a method of removing the remaining mold attached to the casting, A method for removing a mold remaining in a casting, comprising: carbonizing an organic binder of the mold attached to the casting and further activating the organic binder, and then removing the mold attached to the casting. The cast product to which the mold is attached is placed in an activating gas atmosphere, and the cast product is heat-treated under a condition of carbonizing the organic binder of the mold and further activating the carbide of the organic binder. Method for removing the mold remaining in the casting. The cast product according to claim 1 or 2, wherein after the organic binder of the mold attached to the cast product is carbonized and further activated, the mold attached to the cast product is collapsed by applying an external force. Method for removing the remaining mold in the mold. The method for removing a mold remaining in a casting according to claim 2 or 3, wherein a gas selected from water vapor, carbon dioxide, oxygen, and a mixed gas of two or more kinds of these is used as the activation gas. The method for removing a mold remaining in a casting according to claim 4, wherein the steam is superheated steam. The method for removing a mold remaining in a casting according to any one of claims 1 to 5, wherein the organic binder of the mold is a thermosetting resin. The method for removing a mold remaining in a casting according to any one of claims 1 to 6, wherein the mold is a core.

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