JP4341020B2 - Aluminum alloy casting manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing an aluminum alloy casting in which a molten aluminum alloy is cast into a mold, solidified, and then taken out, and then subjected to necessary treatment to obtain a product.

Conventionally, cast products of aluminum alloy castings such as cylinder heads, cylinder blocks, aluminum wheels, and valve bodies have to be heat-treated to obtain the required fatigue strength. For this reason, T5 defined in JIS standards after casting, A heat treatment such as T6 is applied. Further, when a core is required in the process of manufacturing an aluminum alloy casting, generally a sand core made by a shell mold method or a cold box method is used. In the casting process of the aluminum casting using this sand core, the cast product is released from the mold at about 500 ° C and once cooled to near normal temperature, then the gate and the hot water are cut and the core sand is hit. A solution treatment is performed in which the material is removed from the casting by applying vibrations such as, and then charged into a heat treatment furnace and heated again.
In such a process, there is a problem that a process of once cooling the cast product after casting is necessary, so that the heat retained in the cast product is wasted and processing equipment and time for cooling are required.

For this reason, the cooling process for sand removal of the cast product is abolished, and the “cast product manufacturing method” (Japanese Patent Laid-Open No. 6-210437), which aims to save energy and time in the heat treatment process, The energy-saving “aluminum alloy casting manufacturing method” in which the number of steps in the heat treatment stage is reduced by taking out the casting from the mold before the temperature does not drop below 350 ° C. and immediately keeping it in the holding furnace for a predetermined time. Japanese Patent Laid-Open No. 1-298139) has been proposed.

JP-A-6-210437 JP-A-1-298139

However, in the invention described in Japanese Patent Application Laid-Open No. 6-210437, the cooling step performed before the sand removal after the completion of casting can be made unnecessary. However, in order to remove the sand core, a sound wave is generated inside the heat treatment furnace. Therefore, the heat treatment furnace needs to have a sound wave function, so that the equipment efficiency is poor. Further, since the sand core is composed of an organic binder and an aggregate, combustion gas is generated during casting, which causes a casting defect.
Furthermore, some sand cores are collected after sand is dropped and reclaimed, and then used for core molding. However, the amount recycled is small and dedicated equipment and time are required for reclaim processing. There is also a drawback of being.

On the other hand, according to the casting method described in JP-A-1-298139, after the molten metal solidifies, the cast product is taken out of the mold before the casting temperature falls below 350 ° C., and immediately after taking out, it is placed in a holding furnace. The solution is kept at a solution treatment temperature for a certain period of time, and then immersed in water, thereby enabling an energy-saving manufacturing process in which the number of processes in the heat treatment stage is reduced, and in terms of strength compared to a cast product subjected to conventional T6 treatment. There is an effect that a cast product which is not inferior can be obtained.
In this method, since a water-soluble core is used, a vibration mechanism or the like for removing the core sand is not required, but the heat treatment furnace for the solution treatment is the same as the conventional air (gas) heating. Heating efficiency is poor because of the system. In addition, since most of the water-soluble core is removed and discarded every time it is molded, it is necessary to make a mold by supplementing newly consumed raw materials.
Furthermore, the core used in these documents cannot be used for die casting which is high pressure casting because of strength problems.

In order to achieve the above object, a method for producing an aluminum alloy casting according to the present invention includes an aluminum alloy casting in a mold in which a salt core having a melting point equal to or close to a temperature at which an aluminum alloy casting to be described later is taken out from the mold. The step of filling the molten metal and solidifying it into an aluminum alloy casting; taking out the aluminum alloy casting from the mold; and the same component as the salt core while the temperature of the aluminum alloy casting is in the range of 350 to 500 ° C. The aluminum alloy casting is solution-treated at the solution treatment temperature of the aluminum alloy casting by placing it in a salt bath using a molten salt of the salt as a heat medium and maintained at a temperature equal to or higher than the melting point of the salt core. While the salt core is eluted into the molten salt and the aluminum alloy casting from which the salt core has been removed is washed with a liquid to remove residual salt. With a step of performing quenching, then a step of tempering the aluminum alloy casting, minute and molten salt increased in the salt bath the salt core is eluted, the residual salt and washing the aluminum alloy casting And a step of using the molten salt obtained by concentrating the contained liquid for forming a new salt core. Thus, casting can be continued with almost no salt core consumed. Moreover, since the solution treatment is performed in a salt bath using a molten salt as a heat medium, the solution treatment can be performed in a short time with good heating efficiency.

  The method for producing an aluminum alloy casting according to the present invention is characterized in that the time for elution of the salt core into the salt bath is 10 to 30 minutes while solution-treating the aluminum alloy casting. Thereby, the solution treatment of the casting can be performed in a short time.

  The method for producing an aluminum alloy casting according to the present invention is characterized in that after the excess portion of the aluminum alloy casting taken out from the mold is removed, the aluminum alloy casting is put into a salt bath. Thus, the casting can be sized so as not to be bulky and can be put into the salt bath, so that the treatment is easy.

Moreover, the manufacturing method of the aluminum alloy casting in the present invention is characterized in that the liquid for cleaning the aluminum alloy casting is water or hot water. Thereby, the residual salt content can be easily removed.

Furthermore, in the method for producing an aluminum alloy casting according to the present invention, a molten aluminum alloy is filled in a mold having a salt core having a melting point of 190 to 220 ° C. by solidification by pressure die casting, and the aluminum alloy casting is obtained. And taking out the aluminum alloy casting from the mold, and using a molten salt of a salt of the same component as the salt core as a solvent, putting it in a salt bath maintained at a temperature of 220 to 250 ° C. A step of eluting the salt core into the molten salt, a step of removing residual salt by washing the cast aluminum alloy from which the salt core has been removed with a liquid, And a step of using the molten salt obtained by washing the aluminum alloy casting and the molten salt obtained by concentrating the liquid containing residual salt to form a new salt core. And features. Thereby, it becomes possible to produce a casting having a shape that could not be cast by the conventional pressure die casting method. Further, the salt core can be eluted into the molten salt without causing the casting product to bulge or break.

  In the method for producing an aluminum alloy casting by the pressure die casting method in the present invention, the melting point of the salt core is in the range of 190 to 220 ° C, and the temperature of the molten salt in the salt bath is maintained at 220 to 250 ° C. It is characterized by leaning. As a result, the salt core can be eluted into the molten salt without causing bulging or tearing of the cast product.

Further, the method for producing an aluminum alloy casting by the pressure die casting method in the present invention is characterized in that after the surplus portion in the aluminum alloy casting taken out from the mold is removed, the aluminum alloy casting is put into the salt bath. To do.

  As is apparent from the above description, the present invention provides a method for producing an aluminum alloy casting using a salt core. It is possible to realize an aluminum alloy casting manufacturing process that can be recycled with little core consumption. Further, the solution treatment can be performed in a shorter time compared to the conventional heating method using air (gas), and since a salt core is used, a gas causing a casting defect is not generated during combustion. Further, the use of the core makes it possible to produce a product having a shape that could not be produced by the conventional die casting method.

Hereinafter, the best mode for carrying out the present invention will be described. In the present invention, first, a molten aluminum alloy is filled in a mold and solidified to form an aluminum alloy casting (S1), and the salt core is eluted while solution treatment is performed on the aluminum alloy casting (S2). It is a method for producing an aluminum alloy casting by performing quenching and removal of residual salt at the same time (S3), followed by tempering (artificial aging treatment) (S4). Furthermore, the present invention secondly, the molten aluminum alloy is filled in a mold by a pressure die casting method (hereinafter “PDC”) and solidified (S10), and the formed aluminum alloy casting is melted in the molten salt. The salt core is eluted (S11), and then the residual salt content is removed by washing (S12). This is a method for producing an aluminum alloy casting (FIG. 2).

  The first invention is made by utilizing the solution treatment temperature (500 ° C.) of the aluminum alloy casting, the melting point of the salt core, and the temperature at which the casting is taken out from the mold. That is, the cast alloy's retained heat is wasted by putting it in a salt bath of molten salt that is a heat medium maintained at 500 ° C. while the aluminum alloy casting taken out of the mold is maintained at a temperature of 350 to 500 ° C. In this case, the solution treatment is efficiently performed, and the core is removed by dissolving the salt core in a molten salt maintained at a temperature equal to or higher than the melting point of the salt core. In addition, the molten salt in the salt bath is the same component as the salt in the salt core, so it can be dissolved in the molten salt to extract the increased amount of molten salt in the salt bath and produce a new salt core. Use it. The residual salt removed by washing with the liquid is concentrated and used as a molten salt for the production of new salt cores, so the salt core changes from solid to liquid (molten salt) and solidifies again. Since it becomes a salt core, the core is recycled with almost no waste. The melting point of the salt core is desirably the same as or higher than the take-off temperature of the aluminum alloy casting, but it is possible to cast even if it is slightly lower than the take-out temperature. However, if the melting point of the salt core is lower than the casting removal temperature, it is necessary to apply a coating to the salt core in order to prevent the baseboard from melting.

  According to the second invention of the present application, when an aluminum alloy casting is filled in a mold by PDC, the conventional core cannot be used because it has insufficient strength and cannot withstand casting (filling) pressure. Is made by paying attention to the fact that it is applicable to PDC because the bending strength is higher than that of the conventional core. When a cast product made of PDC is exposed to a high temperature above a certain level, bubbles that remain inside expand and a phenomenon called so-called blistering occurs that causes the product surface to swell or break. This heat treatment cannot be performed. Therefore, in the second invention for producing an aluminum alloy casting by PDC, as in the first invention, the solution treatment is simultaneously performed at the time of core dropping, or the residual salt content is removed together with quenching. However, it can be obtained by concentrating the molten salt increased by eluting the salt core into the molten salt of the same component as the salt core and removing the core, and the liquid from which the residual salt has been washed. Since the molten salt thus obtained is used for molding a new core, a casting process that hardly consumes the salt core can be realized as in the first invention.

Here, the “aluminum alloy casting” in the present invention means an alloy casting that contains copper (Cu), silicon (Si), magnesium (Mg) and the like as trace elements in addition to aluminum. “Salt core” means a core made of a stable salt that does not react with aluminum even at high temperatures. Specifically, it is a mixed salt of sodium nitrate, potassium nitrate, calcium nitrate, and sodium nitrite. Nitrate is preferred, but not limited thereto. In the present invention, the “molten salt” means a molten salt of the same component as the salt core used in the present invention. Furthermore, the “excess portion in the aluminum alloy casting” in the present invention means a portion that is necessary for casting of a pouring gate, a feeder, a weir, etc., but is not removed as a product by being removed in a post-treatment stage after casting. . The small flash of the casting surface is excluded from the surplus part here.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a flow diagram showing a series of manufacturing steps for an aluminum alloy casting.
An aluminum alloy made of aluminum, copper, silicon, or the like becomes a molten metal when a bulk metal is put into a melting furnace and heated to about 700 ° C., and the molten metal is appropriately transferred from the melting furnace to a holding furnace. The molten metal transferred to the holding furnace is conveyed by moving the holding furnace to the vicinity of the gravity casting apparatus or the low pressure casting apparatus. Then, a desired amount of molten metal is distributed to a hand-held furnace (insulating furnace) attached to the casting apparatus, and the molten metal is cast into the mold of the casting apparatus from the hand-held furnace. A predetermined shape of a salt core made by a core molding machine is arranged in a predetermined position in the mold, and the salt core is made of a mixed salt of sodium nitrate, potassium nitrate, calcium nitrate, and sodium nitrite. Is formed.

  Thereafter, the molten metal cast into the mold is cooled and solidified to form an aluminum alloy casting. Subsequently, the aluminum alloy casting with the salt core inside is taken out from the mold, and in a salt bath (salt bath) filled with molten salt as a heating medium while the temperature is in the range of 350 to 500 ° C. In Since the molten salt in the salt bath is maintained at 500 ° C., which is the solution treatment temperature of the aluminum alloy casting, the molten aluminum alloy casting is subjected to solution treatment and the salt core inside the aluminum alloy casting is It melts into the molten salt, so that the solution treatment and core dropping are performed in one step. At this time, since the temperature of the molten salt is 500 ° C., which is higher than the melting point of the salt core, the salt core is dissolved in a short time and absorbed as a part of the molten salt.

  The amount of the molten salt increases as the salt core dissolves into the molten salt, but this increased amount of molten salt is appropriately extracted from the salt bath and returned to the core molding machine to obtain a new one. It will be used for the molding of salt cores. In addition, the time required for the solution treatment was 1 to 2 hours in the conventional heating furnace method using air as a heat medium, but by performing the treatment in a salt bath using molten salt as a heat medium, The solution treatment time can be greatly reduced to 10 to 30 minutes. This is because air (gas), which is a heating medium of the heating furnace system, has a low heat transfer coefficient, so it is difficult to transfer heat to the inside of the aluminum alloy casting that is the heating target, especially to the center, but molten salt has a heat transfer coefficient. This is because it is easy to transfer heat because it is large, and the temperature of the casting can be increased uniformly even in a short time.

  It should be noted that before casting the aluminum alloy casting taken out from the mold into the salt bath, it is possible to remove the excess portion such as the gate, weir, and hot water of the casting in advance so that the casting is not bulky. This is preferable because the subsequent processing is easy to perform. In this case, the casting is removed at a high temperature where the casting is not solidified, so that the casting is likely to be deformed. If the excess part cannot be removed easily due to the ease of deformation, the product after tempering It will be removed in the finishing stage.

  The aluminum alloy casting that has undergone solution treatment and core dropping in the salt bath is taken out of the salt bath and quenched by quenching with water or warm water, and a small amount of salt core residue remains in the casting. Removed. Quenching and core dropping with water or hot water is performed by showering the casting with water or hot water, or by pouring the casting into a bathtub in which water or hot water circulates.

In this case, water having a temperature range of 15 to 25 ° C. can be applied. Moreover, what has a temperature range of 60-70 degreeC can be applied for warm water. Water is used when it is necessary to cause distortion in the aluminum alloy casting, and hot water is used when distortion is not caused in the casting, so that both are used properly.
As a liquid other than water and hot water for removing residual salt, for example, a liquid capable of dissolving a salt component in a salt core such as ethanol or acetone is applicable.

  The water or warm water containing the removed salt core residue is concentrated to a concentration of 90 to 95% by weight by a concentrator to form a concentrated salt water, which is transferred to a bath for evaporating the water of the concentrated salt water. . Therefore, the residual water in the concentrated salt water is evaporated to make only the molten salt and returned to the core molding machine to be used for molding a new salt core.

The cast aluminum alloy from which the residual salt core has been completely removed is put into a furnace for tempering, and is tempered (artificial aging treatment) for about several hours at an atmospheric temperature of 200 ° C. The aluminum alloy casting that has been tempered is taken out of the furnace and the cast burr is removed as a material finish, and then subjected to cutting, screw hole machining, and the like to obtain a final product. The removed surplus portion and cast burrs are recovered and compressed and granulated into a mass that is easy to be re-dissolved and reused. At this time, there is a possibility that non-metallic foreign matters such as salt core pieces are mixed in the collected surplus portion or cast flash, and it is necessary to remove such foreign matters and re-dissolve them. For this purpose, for example, it is possible to adopt a method in which only the aluminum alloy is compressed and granulated after separating the aluminum alloy and non-metallic foreign matter including salt with a separation device using electromagnetic force such as eddy current. it can.

A special die casting method (for example, a non-porous die casting method, a vacuum die casting method, etc.) of an aluminum alloy casting that can be heat-treated has been put into practical use due to recent advances in die casting technology. Therefore, in the present invention, the filling of the aluminum alloy casting into the mold can also be performed by such a special die casting method instead of the gravity casting method or the low pressure casting method. Similarly, since what was conventionally manufactured separately can be integrated by using a core, the production cost of the product can be reduced.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a flow diagram showing a series of manufacturing steps for an aluminum alloy casting by PDC.
The same procedure as in the previous embodiment is performed until the aluminum alloy is transported as a molten metal to the vicinity of the casting apparatus. The molten metal transported to the hand furnace is poured into a pouring port of a casting apparatus which is a die casting machine, and is filled into the mold at a high pressure by an injection cylinder. Similar to the first invention, a salt core of a predetermined shape made by a core molding machine is disposed at a predetermined position in the mold, and the salt core is sodium nitrate, potassium nitrate, calcium nitrate, It is formed from a mixed salt of sodium nitrite.

Thereafter, the molten metal cast into the mold is cooled and solidified to form an aluminum alloy casting. Subsequently, an aluminum alloy casting having a salt core therein is taken out from the mold and placed in a salt bath (salt bath) filled with molten salt. Since the temperature of the molten salt in the salt bath is maintained at a temperature (220 to 250 ° C.) higher than the melting point (190 to 220 ° C.) of the salt core, the salt core inside the cast aluminum alloy casting is melted. A core drop is performed by dissolving in salt.

In addition, when using a salt core which has a high melting point and does not elute at a temperature of 220 to 250 ° C., it is necessary to drop the core with water or hot water in order to prevent blisters of the cast product. Since the salt core is water-soluble, such treatment can be performed. Water in this case means water in the temperature range of 15 to 25 ° C., and hot water means water in the temperature range of 50 to 70 ° C. Although both are not used properly, warm water is more efficient in dropping the core than water. When the core is dropped with water or hot water, the casting is put into a bathtub in which water or hot water circulates, and the treatment is continued to remove residual salt. In addition, as the liquid other than water or hot water for performing core dropping, a liquid that can dissolve a salt component in a salt core such as ethanol or acetone is also applicable.

  The amount of the molten salt increases as the salt core dissolves into the molten salt in the salt bath. The molten salt corresponding to the increased amount is appropriately extracted from the salt bath, and is supplied to the core molding machine. By returning it, it will be used for making new salt cores. In addition, before the aluminum alloy casting taken out from the mold is put into the salt bath, it is better to remove excess portions such as the sprue and weir of the casting in advance, so that the casting does not become bulky. Is preferable because it is easy to perform. In this case, since the pouring gate is removed in a high temperature state where the casting is not solidified, the casting is likely to be deformed, and when the excess part cannot be removed easily due to this ease of deformation, the product in the subsequent process It will be removed in the finishing stage.

The aluminum alloy casting in which the core is dropped with molten salt in the salt bath is removed from the salt bath and washed with water or warm water to remove a small amount of salt core residue remaining in the casting. Removal of residual salt with water or hot water is performed by showering the casting with water or warm water, or by pouring the casting into a bathtub in which water or warm water circulates. Water in this case means water in the temperature range of 15 to 25 ° C., and hot water means water in the temperature range of 50 to 70 ° C. And although both are not used properly, the removal efficiency of residual salt is higher in warm water than in water.

  The water or warm water containing the removed salt core residue is concentrated to a concentration of 90 to 95% by weight by a concentrator to form a concentrated salt water, which is transferred to a bath for evaporating the water of the concentrated salt water. . Therefore, the residual water in the concentrated salt water is evaporated to make only the molten salt and returned to the core molding machine to be used for molding a new salt core.

The aluminum alloy casting from which the salt core has been completely removed is subjected to cutting, screw hole machining, and the like after the cast burr has been removed as a material finish to become the final product. The removed surplus portion and cast burrs are recovered, compressed and granulated into a mass that is easily re-dissolved, and then reused.
At this time, there is a possibility that non-metallic foreign matters such as salt core pieces are mixed in the collected surplus portion or cast flash, and it is necessary to remove such foreign matters and re-dissolve them. For this purpose, for example, it is possible to adopt a method in which only the aluminum alloy is compressed and granulated after separating the aluminum alloy and non-metallic foreign matter including salt with a separation device using electromagnetic force such as eddy current. The possible points are the same as in the previous embodiment of the present invention.

  According to the present invention, an aluminum alloy casting using a salt core is put into a salt bath using a molten salt of the same component as the salt core as a heat medium, and the salt core is added to the salt core while performing a solution treatment. Since it is a manufacturing method of an aluminum alloy casting that is eluted by the molten salt in the salt bath, it is possible to perform a solution treatment in a short time, and it is possible to recycle almost all the used salt cores. The availability is great.

It is process drawing which shows 1st embodiment of this invention. It is process drawing which shows 2nd embodiment of this invention. FIG. 3 is a process diagram showing one embodiment of the present invention. It is process drawing which shows another Example of this invention.

Explanation of symbols

S1 casting process S2 solution treatment and salt core elution process S3 residual salt removal and quenching process S4 tempering process S10 die casting process S11 salt core elution process S12 residual salt removal process

Claims (6)

A step of filling a molten aluminum alloy into a mold in which a salt core having a melting point equal to or close to the temperature at which an aluminum alloy cast to be described later is taken out from the mold is solidified to obtain an aluminum alloy cast; The casting is removed from the mold, and a molten salt of the same component as the salt core is used as a heat medium while the temperature of the aluminum alloy casting is in the range of 350 to 500 ° C. Elution of the salt core into the molten salt while the aluminum alloy casting is solution-treated at a solution treatment temperature of the aluminum alloy casting after being placed in a salt bath maintained at a temperature; and the salt core Removing the residual salt by washing the aluminum alloy casting from which the aluminum has been removed with a liquid and quenching the aluminum alloy casting, and then tempering the aluminum alloy casting The molten salt that has been dissolved into the salt bath by elution of the salt core and the molten salt obtained by concentrating the liquid containing residual salt by washing the aluminum alloy casting are newly added. A method for producing an aluminum alloy casting, comprising: a step for forming a salt core. It is a manufacturing method of the aluminum alloy casting of Claim 1, Comprising: Time to elute the said salt core in this salt bath is 10-30 minutes, while solution-treating the said aluminum alloy casting, It is characterized by the above-mentioned. A method for producing an aluminum alloy casting. It is a manufacturing method of the aluminum alloy casting in any one of Claim 1 or 2, Comprising: After removing the excess part in the said aluminum alloy casting taken out from the metal mold | die, throwing this aluminum alloy casting in a salt bath, A method for producing an aluminum alloy casting characterized by the above. It is a manufacturing method of the aluminum alloy casting in any one of Claims 1 thru | or 3, Comprising: The liquid which wash | cleans the said aluminum alloy casting is water or warm water, The manufacturing method of the aluminum alloy casting characterized by the above-mentioned. Filling a mold with a salt core having a melting point of 190 to 220 ° C. with a molten aluminum alloy by a pressure die casting method and solidifying it into an aluminum alloy casting; and said aluminum alloy casting from the mold Removing the molten salt of the same component as the salt core as a solvent, charging the salt core into a salt bath maintained at a temperature of 220 to 250 ° C., and eluting the salt core into the molten salt; The step of removing residual salt by washing the aluminum alloy casting from which the salt core has been removed with a liquid, the amount of molten salt eluted from the salt core and increased, and washing the aluminum alloy casting And a step of using the molten salt obtained by concentrating the liquid containing residual salt for forming a new salt core, and a method for producing an aluminum alloy casting. 6. The method for producing an aluminum alloy casting according to claim 5, wherein the aluminum alloy casting is poured into the salt bath after removing an excess portion in the aluminum alloy casting taken out from a mold. Manufacturing method of alloy castings.

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