JP4239792B2 - Aluminum alloy for casting with high electrical resistivity - Google Patents

Description

  The present invention relates to an aluminum alloy for casting, and more particularly to an improvement in an aluminum alloy for casting used for a member such as a motor case or a motor housing that requires high electrical resistivity.

  Aluminum alloys have the characteristic of being lighter than iron-based materials, and therefore their range of use has been expanded by improving strength, heat resistance, wear resistance, and the like.

  For example, in automotive parts that are required to be lighter and thinner, aluminum alloys having optimal alloy components according to various manufacturing methods such as gravity casting, low pressure casting, and die casting have been developed. As an example of such an aluminum alloy, for example, in Patent Document 1 below, the flow of the molten metal and the temperature of the molten metal during casting are improved by adjusting the alloy element contained in the aluminum alloy to a predetermined value. An aluminum alloy for thin-wall casting that can produce a member is disclosed.

JP-A-06-212334

  By the way, in the automobile industry in which many aluminum alloy parts are employed, further improvement of the aluminum alloy and expansion of the application range are required due to the practical application of electric vehicles and hybrid vehicles in recent years.

  For example, a magnetic field is generated around the rotating motor due to leakage magnetic flux from the motor coil. The leakage magnetic flux is proportional to the number of rotations of the coil, and generates a strong magnetic field during high rotation. When a metal material such as an aluminum alloy is used in such a strong magnetic field, an eddy current (induced current) is generated, and the magnitude of the eddy current is inversely proportional to the electrical resistance of the material according to Ohm's law.

  On the other hand, output loss always occurs in the motor, and one of the losses is loss due to eddy current generated in the motor peripheral parts. When such an eddy current increases, for example, the temperature rises due to the generation of Joule heat, leading to a decrease in motor output.

  In order to reduce such motor output loss, it is necessary to suppress eddy currents generated in peripheral parts of the motor (for example, a motor case or a motor housing as a housing for a rotating electrical machine). Accordingly, there has been a demand for the development of an aluminum alloy with high electrical resistivity that can reduce motor output loss.

  Accordingly, an object of the present invention is to provide a new aluminum alloy having a castability and workability equivalent to or better than those of conventionally used aluminum alloys and having a high electric resistivity.

  The casting aluminum alloy with high electrical resistivity according to the present invention is Si: 10% to 12%, Mg: 4% to 6%, Mn: 0.5% to 3%, Cu: 4% to 6% by weight. %, The balance being made of Al and inevitable impurities.

  The casting aluminum alloy having a high electrical resistivity according to the present invention is characterized by having an electrical resistivity of 7 μΩ · cm to 10 μΩ · cm in an as-cast state.

  Further, the casting aluminum alloy having a high electrical resistivity according to the present invention is an alloy obtained by press-fitting a molten aluminum alloy having the above composition into a cavity of a mold by a die casting method, and without performing heat treatment. The electrical resistivity is 7 μΩ · cm to 10 μΩ · cm.

  The method for producing an aluminum alloy for casting with high electrical resistivity according to the present invention is such that a blank injection speed when a molten aluminum alloy having the above composition is press-fitted into a mold cavity by a die casting method is 1 at a low injection speed. 0.5 m / s or more, and 4.5 m / s or more at a high injection speed.

  Moreover, it is possible to manufacture the housing | casing housing | casing of a rotary electric machine by this manufacturing method.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in castability and workability, it can provide the aluminum alloy for casting with high electrical resistivity, without performing secondary processes, such as heat processing.

The aluminum alloy for casting according to the present invention contains, by weight, Si: 10% to 12%, Mg: 4% to 6%, Mn: 0.5% to 3%, Cu: 4% to 6%, balance is characterized in that it is either found configured Al and unavoidable impurities thereof. The aluminum alloy for casting having a high electric resistivity can be obtained by the function and effect exhibited by each alloy element having a limited composition range. Hereinafter, the action of each alloy element constituting the alloy of the present invention and the reason for limiting the composition range (% by weight) will be described.

About Si Si is an element that contributes to improvement of castability. In particular, in the case of casting by the die casting method, if there is no content of at least 10%, the castability is remarkably lowered. On the other hand, Si has a eutectic point with Al of 12%, and if the Si content exceeds 12%, Si will precipitate as a large crystal mass in the metal structure. Therefore, when the Si content is 12% or more, which is the eutectic point with Al, the castability is improved, but the workability is lowered. Therefore, the Si content is in the range of 10% to 12% in order to achieve both castability and workability.

Regarding Mg, Mg is one of the strengthening elements, and binds to Si and precipitates in the structure in the form of Mg ₂ Si. That is, Mg is an element that contributes to improvement in strength by age hardening by coexistence with Si. For example, in order to obtain strength required for a structural material such as a motor case or a motor housing, Mg needs to be at least 4% with respect to Si content of 10% to 12%. However, if Mg is added in an amount of 6% or more, the aluminum alloy is embrittled, so that the strength cannot be obtained even if it is added too much. Therefore, the content of Mg is set to a range of 4% to 6% which is optimal for improving the strength and preventing embrittlement.

About Mn Mn is an element that improves the ductility of an aluminum alloy by forming a compound with Fe. Specifically, it plays the role of agglomerating the Al—Si—Fe needle-like compound to prevent elongation reduction. The content is required to be at least 0.5%. However, if Mn is present in a large amount, the agglomerated Al—Si—Fe compound is coarsened or other metal compounds are formed, and the ductility is significantly reduced. These phenomena also cause a reduction in machinability. Furthermore, a large amount of Mn causes deterioration of corrosion resistance. Therefore, the upper limit was made 3% in order to maintain ductility, machinability, and corrosion resistance. Therefore, the range of 0.5% to 3% is appropriate for the Mn content.

Cu As with Mg , Cu is an element that contributes to the improvement of strength, and plays a role as a strengthening element over Mg by forming a compound with Al. However, if it is less than 4%, the effect of strengthening the strength is small, and if it exceeds 6%, the corrosion resistance is deteriorated. Therefore, the Cu content is in the range of 4% to 6% which is optimal for improving the strength and maintaining the corrosion resistance.

About Al Since Al is an element that contributes to weight reduction of automobile parts and the like, it is made the balance together with impurities and other necessary alloy elements.

  The casting aluminum alloy according to the present invention designed as described above can produce a target casting by a known casting method such as a gravity casting method, a low pressure casting method, a die casting method, or a squeeze method. .

  Examples of the aluminum alloy for casting according to the present invention will be specifically described below together with comparative examples.

Production of test material The test material used in this example was produced as follows. First, a test material blended with the alloy components shown in Table 1 is melted at a melting temperature of 750 ° C., and this molten metal is poured into a mold by a gravity casting method to produce a test casting. As the mold, a Lansley mold was used, and after casting, it was allowed to cool naturally to room temperature.

  In the comparative alloy, AC4C corresponding to JIS standard, and AC4C corresponding to JIS standard, Si alone was set to 12% of the same level as the present invention alloy, Mg alone was set to 5% same level as the present invention alloy, Only Mn was made 3% of the same level as that of the present invention alloy, and only Cu was made 5% of the same level as that of the present invention alloy. These comparative alloys are prepared for grasping the effect of each alloy element and more accurately grasping the effectiveness of the present invention alloy.

  The reason why the gravity casting method is adopted as the casting method is that it can be most easily performed, and it is difficult to think that the difference in the casting method affects the electric conductivity. In addition, the Lansley mold was adopted as the mold because the cooling rate after casting was increased by using a copper Lansley mold with high thermal conductivity, and the test was performed under conditions relatively close to casting by the die casting method. It depends on the consideration that the material can be made.

第１の実施例
第１の実施例では、本発明に係る鋳造用アルミニウム合金の電気抵抗率について検証する。

First Example In the first example, the electrical resistivity of the aluminum alloy for casting according to the present invention is verified.

  FIG. 1 is a diagram comparing the electrical resistivity measurement results of pure Al and aluminum alloys of the present invention alloy and the comparative alloy shown in Table 1.

  The electrical resistivity is measured by cutting a test piece from a predetermined position according to the JIS standard from an as-cast test (Lansley) casting produced by the above-described method, and using the DC four-terminal method for this test piece. The electrical resistivity used was measured.

  The reason why the direct current four-terminal method is used is to reduce the measurement error by eliminating the contact resistance between the measurement object and the measurement terminal as much as possible.

  As is apparent from the measurement results of the electrical resistivity shown in FIG. 1, the alloy of the present invention exhibited a high electrical resistivity of 10 μΩ · cm. This is an electric resistivity of about 5 times that of pure Al and about twice that of an aluminum casting material (AC4C) corresponding to JIS standards. In addition, comparative alloys in which only the alloy elements of Si, Mg, Mn, and Cu are equivalent to those of the present invention alloy are also confirmed to have a slight increase in electrical resistivity compared with the aluminum casting material (AC4C) equivalent to JIS standard. However, this time it did not reach the invention alloy. This indicates that the present invention alloy contains “Si: 10% to 12%, Mg: 4% to 6%, Mn: 0.5% to 3%, Cu: 4% to 6% by weight%”. This indicates that a high electrical resistivity can be realized.

Second Example In the second example, the influence of heat treatment on the electrical resistivity of the casting aluminum alloy according to the present invention is verified.

  FIG. 2 shows the present invention alloy and the comparative alloy shown in Table 1 in an as-cast (F) state without heat treatment, with annealing treatment (O), and with heat treatment called T6. It is the figure which compared the measurement result of the electrical resistivity about three types.

  The method for collecting the test piece in the as-cast state (F) is the same as the method shown in the first embodiment. From the test piece in the as-cast state (Lansley), the test piece is measured from a predetermined position according to the JIS standard. Was cut out.

  The test piece sampling method when annealing treatment (O) is performed is to maintain the as-cast test (Lansley) casting at a solution temperature of 530 ° C. for 5 hours, cool in the furnace, and bring the temperature to room temperature. Reduced. Thereafter, a test piece was cut out from a predetermined position according to the JIS standard.

  The test piece is sampled when heat treatment called T6 is performed. The as-cast test (Lansley) casting is maintained at a solution temperature of 540 ° C. for 5 hours, and then poured into water at a water temperature of 50 ° C. for water quenching. (WQ: water quenching) was performed, and when the test (Lansley) casting reached 50 ° C. which was the same as the water temperature, it was taken out of the water and allowed to cool to room temperature. Further, as an artificial aging treatment, a test (Landsley) casting was put into the furnace, the furnace temperature was maintained at 140 ° C. for 3.5 hours, and after releasing to the outside of the furnace, it was allowed to cool to room temperature. Thereafter, a test piece was cut out from a predetermined position according to the JIS standard.

  The electrical resistivity of each test piece collected as described above was measured by the direct current four-terminal method in the same manner as in the first example. As a result, as is clear from FIG. 2, it has been clarified that the electrical resistivity is decreased by performing the annealing (O) process or the T6 process. This indicates that the alloy of the present invention does not require heat treatment.

  In addition, it has been confirmed by experiments by the inventors that the electrical resistivity of the alloy of the present invention is 7 μΩ · cm to 10 μΩ · cm in an as-cast state.

  As is apparent from the embodiments and examples described above, in the casting aluminum alloy according to the present invention, the Si content is specified in the range of 10% to 12% (% by weight) that achieves both castability and workability. Therefore, both castability and workability are good. Moreover, the casting aluminum alloy according to the present invention can achieve a high electrical resistivity of 7 μΩ · cm to 10 μΩ · cm in an as-cast state without performing secondary processing such as heat treatment. Therefore, according to the present invention, the casting aluminum alloy can be applied to a structural material such as an automobile part, which can increase the electrical resistivity without impairing the castability and workability, and without performing heat treatment. Can be provided.

  In addition, as a method for producing an aluminum alloy for casting having a high electrical resistivity according to the present invention, for example, when a molten aluminum alloy having the composition described in the claims is pressed into a cavity of a mold by a die casting method, It is preferable that the blank shot injection speed is 1.5 m / s or more at a low injection speed and 4.5 m / s or more at a high injection speed. According to this manufacturing method, it is possible to manufacture a thin aluminum die cast product having a wall thickness of 2 to 20 mm. The thin-walled aluminum die-cast product thus obtained has a high electrical resistivity while maintaining the strength as a structural material, and is therefore suitable for use as a structural material such as an automobile motor case or motor housing. .

  The technical scope of the present invention is not limited to the scope described in the above embodiments and examples, and various changes or improvements can be added to the above embodiments or examples. In other words, the casting aluminum alloy according to the present invention may be any one as long as it has the chemical component composition described in the claims. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  Further, in the embodiment or the example described above, the casting aluminum alloy applied to a specific automobile part such as a motor case or a motor housing as a housing for a rotating electrical machine has been described as an example. It can be used for many products such as mission cases, flywheel housings, brackets, water-cooled cylinder blocks, and handles.

It is the figure which compared the measurement result of the electrical resistivity of the aluminum alloy in this invention alloy shown in Table 1, and a comparative alloy shown in Table 1. Regarding the present invention alloy and the comparative alloy shown in Table 1, there are three types of electricity: an as-cast (F) state without heat treatment, an annealing treatment (O), and a heat treatment called T6. It is the figure which compared the measurement result of the resistivity.

Claims (5)

  Si: 10% to 12% by weight, Mg: 4% to 6%, Mn: 0.5% to 3%, Cu: 4% to 6%, the balance being made of Al and inevitable impurities Aluminum alloy for casting with high electrical resistivity. In the aluminum alloy for casting with high electrical resistivity according to claim 1 ,
An aluminum alloy for casting having a high electrical resistivity, wherein the electrical resistivity is 7 μΩ · cm to 10 μΩ · cm in an as-cast state. An aluminum alloy obtained by press-fitting a molten aluminum alloy having the composition according to claim 1 into a cavity of a mold by a die casting method,
An aluminum alloy for casting having a high electrical resistivity, wherein the electrical resistivity is 7 μΩ · cm to 10 μΩ · cm without performing heat treatment. When the molten aluminum alloy having the composition according to claim 1 is press-fitted into a mold cavity by a die casting method, the idle injection speed is 1.5 m / s or more at a low injection speed and 4.5 m at a high injection speed. / S or more, The manufacturing method of the aluminum alloy for casting with high electrical resistivity characterized by the above-mentioned. The housing | casing housing | casing of the rotary electric machine manufactured by the manufacturing method of the aluminum alloy for casting with a high electrical resistivity of Claim 4 .

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