Patent Application
20180178271
The present application claims priority under 35 U.S.C.§ 119 to Korean Patent Application No. 10-2016-0178205, filed on Dec. 23, 2016, the entire contents of which is incorporated herein for all purposes by this reference in its entirety.
The present invention relates to a saltcore for die-casting with aluminum and a manufacturing method thereof, and more particularly, to a saltcore and a manufacturing method thereof capable of reducing shrinkage while satisfying strength during casting by including at least one cation of K+, Na+ and Mg2+ and at least one anion of and CO32−.
A casting process uses the flow of a liquid and is a kind of material processing method of putting a molten metal material into a prepared mold and filling and coagulating the mold, and various methods have been used according to a shape and an injection method of the mold.
Such a casting process has an advantage of forming a complex shape by using a meltable material in only one step. The casting process consists of a mold manufacturing process, a melting process, an injection process, a mold separation process, and the like. In the mold manufacturing process, the mold needs to have a shape and a size appropriate for a desired casting so as to be manufactured and have a proper margin for shrinkage of a solidifying material. In the melting process, the metal is heated at the appropriate temperature to form a liquid, and then a hydrogen gas furnace in the molten metal needs to be removed. The injection process needs to be designed to prevent the solidification shrinkage during solidification while minimizing generation of eddy current during injection. Thereafter, the mold is separated, and after separation, the casting process is finished through the processes of cutting, washing, heating and inspecting an injection port and a spout hole.
On the other hand, a shape (material) inserted into the mold to form the internal shape of the casting is called a core. The core is used for manufacturing a hollow product and the core needs to have sufficient mechanical strength to withstand heat and pressure of the molten metal and maintain the shape during casting, and simultaneously, needs to be relatively easily broken or dissolved into other materials to be easily removed from the cast article after die-casting.
Sand or thermosetting resin is generally used as a material of such a core. In the case of method of using the sand, that is, a sand core, the sand forms the core with a binder, and after casting a desired structure around the core, the binder and the sand that support the core are removed. In the case of a method using the thermosetting resin, a foam is used as a material of the core. However, methods using the sand or the thermosetting resin have been pointed out to cause environmental problems. Furthermore, in the case of the sand core, there is a problem that the sand core may not be realized when a reverse gradient shape exists in the cast article. In order to solve the problems, the material of the core used for casting is made of salt, but in the case where a saltcore in the related art is used for aluminum casting, there is a problem in that the strength to withstand the impact of molten aluminum is insufficient or the shape of the cast article is deformed due to shrinkage of the saltcore during casting.
In order to solve the above-mentioned problems, the present invention proposes a saltcore for aluminum casting capable of reducing the shrinkage while maintaining the strength of the saltcore in the aluminum casting process, and a manufacturing method thereof.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Various aspects of the present invention are directed to providin a saltcore for casting with aluminum capable of reducing shrinkage of the saltcore while satisfying strength (providing desired strength) during casting with aluminum.
Various aspects of the present invention are directed to providin a manufacturing method of the saltcore for casting with aluminum capable of reducing manufacturing costs by reducing the defect rate while improving the dimensional accuracy of the manufactured aluminum cast article. Also, manufacturing costs are reduced by the reduced strinkage of the saltcore.
Technical objects desired to be achieved in an exemplary embodiment of the present invention are not limited to the aforementioned technical objects, and other technical objects not described above will be apparent to those skilled in the art from the disclosure of the present invention.
An exemplary embodiment of the present invention are directed to providing a saltcore for casting with aluminum including at least one cation of K+, Na+ and Mg2+ and at least one anion of Cl− and CO32−.
The K+ may be 35 to 40 mol %, the Na+ may be 110 to 130 mol %, and the Mg2+ may be more than 0 mol % and less than 1 mol %, the may be more than 35 mol % and less than 42 mol %, and the CO32− may be 55 to 65 mol %.
The K+ or Mg2+ may be bonded to the Cl−, and the Na+ may be bonded to the CO32−.
The KCl may be 35 to 40 mol %, the Na2CO3 may be 55 to 65 mol %, and the MgCl2 may be more than 0 mol % and less than 1 mol %.
Another exemplary embodiment of the present invention are directed to providing a saltcore for casting with aluminum including at least one cation of K+ and Na+, at least one anion of Cl− and CO32−, and dolomite.
The K+ may be 35 to 40 mol % or the Na+ may be 110 to 130 mol %, and the Cl− may be 35 to 40 mol % or the CO32− may be 55 to 65 mol %, and the dolomite may be more than 0 wt % and less than 1 wt % with respect to the total weight.
The K+ may be bonded to the Cl−, and the Na+ may be bonded to the CO32−.
The KCl may be 35 to 40 mol %, the Na2CO3 may be 55 to 65 mol %, and the dolomite may be more than 0 wt % and less than 1 wt % with respect to the entire weight.
Yet another exemplary embodiment of the present invention are directed to providing a method for manufacturing a saltcore for casting with aluminum including: a mixing step of mixing and forming a mixture containing components of the saltcore for casting with aluminum; a melting step of forming a molten salt by melting the mixture containing components of the saltcore; a heating step of heating the molten salt by a caster; and an injecting step of injecting the heated molten salt into the mold by the caster.
In the melting step, the molten salt may be molten by using an electric furnace.
The temperature of the melting step may be 700 to 800° C.
The caster in the heating step may be a low-pressure caster or a high-pressure caster.
According to the saltcore for casting with aluminum of the present invention, it is possible to provide a saltcore for casting with aluminum which reduces shrinkage of the saltcore while satisfying the strength when casting aluminum.
According to the method for manufacturing the saltcore for casting with aluminum of the present invention, it is possible to provide a saltcore for casting with aluminum which reduces manufacturing costs by reducing a defect rate while improving the dimensional accuracy of an aluminum cast article, by applying the saltcore for casting with aluminum reducing shrinkage.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.
In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.
Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.
An aspect of the present invention relates to a manufacturing method for a saltcore for casting with aluminum.
Generally, a manufacturing method which is the most widely used among methods for manufacturing an aluminum component for a vehicle is a high-pressure casting method. The high-pressure casting method has an advantage of shortening a manufacturing time and improving productivity by injecting molten aluminum into a mold at high pressure. Specifically, as compared with a gravity casting method and a low-pressure casting method in the related art, the high-pressure casting method has high productivity because a cycle time of producing the cast article is about 10% to largely reduce the cost.
When the sand core 11 is used in the high-pressure casting process, there is a problem in that when the cast article is manufactured, molten aluminum 1 that is injected into the mold is collapsed without withstanding the high pressure. Accordingly, the present invention provides a core for casting with aluminum in which a cast article may be easily removed after being manufactured while withstanding the pressure of molten aluminum injected into a mold in the high-pressure casting process.
In order to manufacture a high-strength core for solving the problems of the related art, a variety of salts have been used as materials used for the core.
In detail, the saltcore for casting with aluminum of the present invention relates to a saltcore which applies a method in which one or more various salts are mixed and melted, the molten salt is injected and solidified into the mold used for manufacturing the core so as not to be collapsed at pressure generated when injecting the molted aluminum in the high-pressure casting process, and after the aluminum cast article is cast, the cast article is removed by high-pressure water, that is, water jet.
To overcome disadvantages of the gravity casting method, a high pressure casting method is applied to the present invention. However, since there is a problem in that the sand core used in the related art does not withstand the pressure generated when casing the molten aluminum in the high pressure casting method, in an exemplary embodiment of the present invention, a saltcore other than the sand core is applied to the high-pressure casting method.
Manufacturing of the component by a high-pressure casting method using the saltcore of the present invention is constituted by the following two steps. That is, the manufacturing is constituted by manufacturing the saltcore as a first step and manufacturing a component by a high-speed high-pressure casting method using the saltcore as a second step.
When describing the manufacturing of the saltcore as the first step in detail,
In more detail, after the mixing step (S101) of forming the mixture by uniformly mixing a salt containing components of the saltcore for casting with aluminum to be described below, that is, an industrial salt having a high melting point, the melting step (S103) of melting the salt is performed at about 700 to 800° C. which is a melting point or more of the salt by using the electric furnace. However, the means of melting the salt is not limited to the electric furnace and various means for melting the salt may be applied. After the melting step (S103), the heating step (S105) of heating the molten salt by the low-pressure caster or the high-pressure caster is performed. Thereafter, the injecting step (S107) of injecting the molten salt into the mold at a high speed and a high pressure with the low-pressure caster or the high-pressure caster in which the molten salt is heated is performed. When the molten salt is solidified, the saltcore for casting with aluminum of the present invention is formed.
When describing the manufacturing step of the component by the high-speed and high-pressure casting method applying the saltcore as the second step in detail,
In more detail, the molten aluminum is formed by melting aluminum at about 700° C. which is the melting point or more of aluminum. Thereafter, the saltcore manufactured in the first step is inserted and mounted into the mold for casting the aluminum cast article. Thereafter, the molten aluminum is heated in the high-pressure caster and then the molten aluminum is injected into the mold by the high-pressure caster. Thereafter, when the molten aluminum injected into the mold is solidified to form the aluminum cast article including the saltcore, the saltcore is removed using the high-pressure water jet to complete the cast article.
Meanwhile, another aspect of the present invention relates to a saltcore for casting with aluminum. In order to solve the problems of the above-described related art, the present invention provides a saltcore for casting with aluminum including at least one cation selected from K+, Na+ and Mg2+ and at least one anion selected from Cl− and CO32−. Further, the K+ is about 35 to 40 mol % (e.g., about 35 mol %, 36, 37, 38, 39, or about 40 mol %), the Na+ is about 110 to 130 mol % (e.g., about 110 mol %, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, or about 130 mol %), and the Mg2+ is about more than 0 mol % and less than 1 mol % (e.g, about more than 0 mol %, about 0.1 mol %, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or about less than 1 mol %), the Cl− is about more than 35 mol % and less than 42 mol % (e.g., about more than 35 mol %, about 36 mol %, 37, 38, 39, 40, 41, or about less than 42 mol %), the CO32− may be about 55 and 65 mol % (e.g., about 55 mol %, 56, 57, 58, 59, 60, 61, 62, 63, 64, or about 65 mol %), and the K+ or Mg2+ may be bonded to the Cl−, and the Na+ may be bonded to the CO32−. Furthermore, the KCL may be about 35 to 40 mol % (e.g., about 35 mol %, 36, 37, 38, 39, or about 40 mol %), the Na2CO3 may be about 55 to 65 mol % (e.g., about 55 mol %, 56, 57, 58, 59, 60, 61, 62, 63, 64, or about 65 mol %), and the MgCl2 may be about more than 0 mol % and less than 1 mol % (e.g, about more than 0 mol %, about 0.1 mol %, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or about less than 1 mol %).
In order to solve the above-described related art, the present invention provides a saltcore for casting with aluminum including at least one cation of K+, Na+ and Mg2+, at least one anion of Cl− and CO32−, and dolomite. Furthermore, the K+ is about 35 to 40 mol % (e.g., about 35 mol %, 36, 37, 38, 39, or about 40 mol %) or the Na+ is about 110 to 130 mol % (e.g., about 110 mol %, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, or about 130 mol %), and the Cl− is about 35 to 40 mol % (e.g., about 35 mol %, 36, 37, 38, 39, or about 40 mol %) or the CO32− is about 55 to 65 mol % (e.g., about 55 mol %, 56, 57, 58, 59, 60, 61, 62, 63, 64, or about 65 mol %), and the dolomite may be about more than 0 wt % and less than 1 wt % (e.g., about more than 0 wt %, about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or about less than 1 wt %) with respect to the entire weight, and the K+ may be bonded to the Cl−, and the Na+ may be bonded to the CO32−. Further, the KCl may be about 35 to 40 mol % (e.g., about 35 mol %, 36, 37, 38, 39, or about 40 mol %), the Na2CO3 may be about 55 to 65 mol % (e.g., about 55 mol %, 56, 57, 58, 59, 60, 61, 62, 63, 64, or about 65 mol %), and the dolomite may be about more than 0 wt % and less than 1 wt % (e.g., about more than 0 wt %, about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or about less than 1 wt %) with respect to the total weight.
Meanwhile, in the related art, there are problems in that the saltcore is broken by the injection pressure of the molten aluminum during the high-pressure casting and the aluminum caste article is deformed by excessive shrinkage in the process of solidifying the molten aluminum. Therefore, the saltcore for casting with aluminum of the present invention not only improves the strength but also reduces the shrinkage of the saltcore, thereby reducing the occurrence of deformation of the aluminum cast article.
The sand core in the related art has the strength of about 3 to 5 MPa and has a problem that the sand core may not withstand the pressure at which the molten metal is injected during high-pressure casting. Therefore, in order to withstand the pressure at which the molten metal is injected during high-pressure casting, the strength of at least about 15 MPa needs to be satisfied. In addition, the shrinkage of the saltcore is required to be about 1.2% or less, which is similar to the shrinkage of aluminum because the cast article to be cast by inserting the saltcore uses aluminum.
As a result, in order to develop the saltcore satisfying the conditions, a method for evaluating the strength and the shrinkage of the saltcore will be described. When describing a method of measuring the strength of the saltcore in detail,
When describing the method of measuring the shrinkage of the saltcore in detail,
Solidification shrinkage (%)=Vinner space of saltcore specimen for measuring shrinkage/Vsaltcore specimen for measuring shrinkage [Equation 1]
Equation 1 illustrates a solidification shrinkage (micro shrinkage) and corresponds to a value obtained by dividing a cavity of the inner space of the saltcore specimen for measuring the shrinkage by a cavity of the saltcore specimen for measuring the shrinkage. More particularly, the solidification shrinkage corresponds to an index capable of verifying a difference in shrinkage according to a difference of the saltcore, which is obtained by dividing a cavity generated when the inner space of the saltcore specimen is shrunk is divided by the cavity of the entire mold. That is, the solidification shrinkage may be referred to as a kind of inner shrinkage.
Shrinkage (%)=(Vsaltcore specimen for measuring shrinkage−Vsalt)/Vsaltcore specimen for measuring shrinkage [Equation 2]
Equation 2 is a value obtained by dividing a difference value between the cavity of the saltcore specimen for measuring the shrinkage and a cavity of the salt by the cavity of the saltcore specimen for measuring the shrinkage and corresponds to a shrinkage. Equation 2 corresponds to an index representing whether a dimension of the mold coincides with a dimension of the saltcore and in order to apply the saltcore of the present invention, in addition to the inner shrinkage, that is, the solidification shrinkage, consistency of an outer dimension of the saltcore also corresponds to an important factor. In addition to the inner shrinkage of Equation 1, consistency of the outer dimensions of the mold and the saltcore corresponds to an important factor for the purpose of not shrinking during casting of the saltcore. Accordingly, the shrinkage (micro shrinkage) is used as a criterion for comparing the shrinkages of the salt cores of the related art and the present invention.
Therefore, the strengths and shrinkages in Comparative Example as the related art and Example as the present invention are measured according to the method and the criteria for evaluating the strength and the shrinkage of the saltcore.
Hereinafter, the present invention will be described in more detail through Examples. These Examples are just to exemplify the present invention, and it is apparent to those skilled in the art that it is interpreted that the scope of the present invention is not limited to these Examples.
Table 1 is a table illustrating components in Comparative Examples as the related art. The Comparative Examples 1 and 2 correspond to a saltcore containing only NaCl and Na2CO3 and have different composition ratios. The Comparative Examples 3 and 4 correspond to a saltcore containing only KCl and Na2CO3 and have different composition ratios. The Comparative Examples 5 and 6 correspond to a saltcore containing only NaCl, KCl and Na2CO3 and have different composition ratios. The Comparative Examples 7 and 8 correspond to a saltcore containing only NaCl and CaCl2 and have different composition ratios. The Comparative Examples 9 and 10 correspond to a saltcore containing only KCl and CaCl2 and have different composition ratios. The Comparative Examples 11 to 16 correspond to a saltcore containing only Na2CO3 and CaCl2 and have different composition ratios. The Comparative Examples 17 and 18 correspond to a saltcore containing KCl, Na2CO3 and dolomite and have different composition ratios and the composition ratios of the dolomite are 1 wt % and 5 wt % with respect to the entire weight of the saltcore.
Table 2 is a table illustrating a composition of the saltcore including the dolomite in the saltcore for casting with aluminum of the present invention. Particularly, the Examples 1 to 3 correspond to a saltcore containing KCl, Na2CO3,and dolomite and have different composition ratios and the composition ratios of the dolomite are 0.1 wt %, 0.3 wt % and 0.5 wt % with respect to the entire weight of the saltcore, respectively.
Table 3 is a table illustrating a composition of a saltcore including MgCl2 in the saltcore for casting with aluminum of the present invention. Particularly, the Examples 4 to 6 correspond to the saltcore containing KCl, Na2CO3, and MgCl2 and have different composition ratios and MgCl2 includes 0.1 mol %, 0.3 mol % and 0.5 mol %, respectively.
Table 4 illustrates the strengths and the shrinkages in Comparative Examples and Examples. In order to apply a high-pressure casting method in the saltcore for casting with aluminum of the present invention, the strength of the saltcore needs to satisfy about 15 MPa or more. Furthermore, in order to perform high-pressure casting using molten aluminum, in order to prevent deformation due to a difference between shrinkage of aluminum and shrinkage of the saltcore, the shrinkage needs to have a value of about 1.2% or less similar to the shrinkage of aluminum.
When describing the Example and the Comparative Example in detail, in the case of preparing the saltcore with a composition in Comparative Examples 7 to 16, there is a problem in that cracks are generated in the saltcore specimen for measuring the strength and the saltcore specimen may not serve as the saltcore and the strength cannot be measured.
It can be seen that the shrinkages of Comparative Examples 1 to 6 and Comparative Examples 17 to 21 exceed 1.2% and do not satisfy the shrinkage of the saltcore of the present invention. Further, in the Comparative Examples 4, 19 and 20, it can be seen that minimum strengths are smaller than 15 MPa and do not satisfy the strength of the saltcore of the present invention.
More particularly, the strengths and the shrinkages of the Examples and the Comparative Examples are illustrated in graphs in
As a result, as illustrated in
Particularly, when describing the components related to the shrinkage of the saltcore of the present invention in detail, the amount corresponding to more than about 0 wt % and less than 1 wt % of dolomite, which is a compound having magnesium-based oxide or calcium-based oxide as a main component, with respect to the entire weight of the saltcore or more than 0 mol % and less than 1 mol % of MgCl2 was added and then a test result is as follows.
The dolomite and MgCl2serve to compensate for the shrinkage of the saltcore generated when the molten aluminum is solidified by forming micro bubbles in the saltcore by adding the dolomite and MgCl2, and the effect of the micro bubbles increases to 1 wt % of the dolomite or 1 mol % of MgCl2 according to an added amount. If the added amount is more than 1 wt % of the dolomite or 1 mol % or more of MgCl2, micro bubbles in the saltcore are excessively generated, and the shrinkage of 1.2% is not satisfied by the expansion of the saltcore due to the excessive bubble effect.
There is an advantage of obtaining effects of reducing cost and weight when gravity casting using a sand core in the related art is changed to a high-pressure casting method using a saltcore for casting with aluminum of the present invention. Specifically, it is required that the thickness of the cast article is at least 4 mm or more so as to manufacture an aluminum cast article by the gravity casting method, but when the high-pressure casting method using the saltcore for casting with aluminum of the present invention is applied, the thickness of the aluminum cast article may be prepared with 2 mm or less, and it is possible to obtain an effect of reducing a weight by about 5 to 8%.
In the case of applying the gravity casting method as the related art, a cycle time for producing a single cast article is about 600 seconds, but in the case of applying the high-pressure casting method using the saltcore for casting with aluminum of the present invention, the cycle time is reduced to about 60 seconds which is a level of 1/10 of the related art, and thus the cost is reduced by about 10 to 15%.
In detail,
In detail,
In the case where NaCl is included instead of KCl among components of the saltcore for casting with aluminum according to an exemplary embodiment of the present invention, problems will be described. After preparing Comparative Examples 22 to 24, which are three saltcores containing KCl as a component of the saltcore, the strengths were measured.
After preparing Comparative Examples 25 to 28, which are four saltcores containing NaCl as a component of the saltcore, the strengths were measured.
In the case of applying the saltcore for casting with aluminum of the present invention, a reverse gradient (undercut) shape can reduce weight and cost by using a high-pressure casting method. In more detail, the aluminum cast article including the reverse gradient shape has advantages of reducing a weight by about 10% of the weight of the cast article in the related art, reducing the thickness and the weight, and forming the shape applied to an actual component, by changing the gravity casting method or the low-pressure casting method in the related art to the high-pressure casting method to which the saltcore for casting with aluminum of the present invention is applied. Further, in the gravity casting method in the related art, about 600 seconds are required for producing the cast article, but according to an exemplary embodiment of the present invention, about 60 seconds are required and thus the cycle time is reduced and the cost is reduced by about 10 to 15%.
According to the saltcore for casting with aluminum of the present invention, applicable components can be diversified. More particularly,
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2016-0178205 | Dec 2016 | KR | national |
