KR101838174B1 - Method of fabricating diff cover and method of dicasting Al alloy - Google Patents

Abstract

The present invention relates to a method of performing aluminum alloy die casting with an injection weight of 5 kg or less by using a die casting apparatus having a mold clamping force of 350 ton or less in order to prevent die casting defects occurring during charging and solidification, The method comprising the steps of: preparing a molten metal; and diecasting the molten aluminum alloy, wherein the die casting step has a first section and a second section in which an injection speed is maintained constant, Wherein the injection speed of the first section is lower than the injection speed of the second section. The method of claim 1, wherein the injection speed of the first section is lower than the injection speed of the second section.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a deep cover and a die casting method of an aluminum alloy,

The present invention relates to a method of manufacturing a deep cover and a die casting method of an aluminum alloy, and more particularly, to a method of manufacturing a deep cover for an automobile and a die casting method of an aluminum alloy for casting.

Demand for lightweight automotive parts is increasing due to fuel efficiency and carbon dioxide emissions regulation. In response to this, researches to develop parts technology utilizing lightweight aluminum alloy have been actively conducted.

Related Prior Art Korean Patent Laid-Open Publication No. 2014-0122450 (published on October 20, 2014, entitled "Aluminum die casting die for automobile trunk liner manufacture") is available.

It is an object of the present invention to provide a method of manufacturing a dip cover and a die casting method of an aluminum alloy that can prevent die casting defects occurring during charging and solidification processes. However, these problems are exemplary and do not limit the scope of the present invention.

A method of manufacturing a deep cover according to one aspect of the present invention is provided. The method of manufacturing the deep cover is a method of manufacturing a diff cover made of an aluminum alloy having an injection weight of 5 kg or less by using a die casting apparatus having a mold clamping force of 350 tons or less, Preparing a molten metal of an aluminum alloy; And casting the molten aluminum alloy, wherein the aluminum alloy is an aluminum alloy for casting the ADC12, the die casting step has a first section and a second section in which the injection speed is kept constant, The injection speed of the first section has a range of 0.5 m / sec to 1.5 m / sec, the injection speed of the second section has a range of 2 m / sec to 3 m / sec, The distance is larger than the distance to be the first section.

There is provided a die casting method of an aluminum alloy according to another aspect of the present invention. The die casting method of the aluminum alloy is a die casting method of an aluminum alloy having an injection weight of 5 kg or less by using a die casting apparatus having a mold clamping force of 350 tons or less. The method includes preparing a molten aluminum alloy having a temperature range of 600 ° C. to 680 ° C. ; And casting the molten aluminum alloy, wherein the aluminum alloy is an aluminum alloy for casting the ADC12, the die casting step has a first section and a second section in which the injection speed is kept constant, The injection speed of the first section has a range of 0.5 m / sec to 1.5 m / sec, the injection speed of the second section has a range of 2 m / sec to 3 m / sec, The distance is larger than the distance to be the first section.

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According to some embodiments of the present invention as described above, it is possible to realize a method of manufacturing a deep cover and a die casting method of an aluminum alloy, which can prevent die casting defects occurring during charging and solidification processes. Of course, the scope of the present invention is not limited by these effects.

1 is a photograph showing a dip cover realized by a die casting method of an aluminum alloy according to an embodiment of the present invention.
2 is a graph illustrating a die casting method of an aluminum alloy according to an embodiment of the present invention.
Figs. 3 to 5 are photographs showing product shapes according to an experimental example of the present invention.
FIGS. 6 and 7 are graphs showing the results of the wear test according to the experimental example of the present invention.
8 to 9 are graphs showing yield strength, tensile strength and elongation according to Experimental Examples of the present invention.
10 is a photograph showing the microstructure according to the molten metal temperature and the injection speed according to the experimental example of the present invention.
Fig. 11 is a photograph actually comparing casting fluidity in a process of die-casting a molten aluminum alloy according to Example (a) and Comparative Example (b) of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of explanation.

Although the terms first, second, etc. are used herein to describe various sections, members, parts, regions, layers and / or sections, these sections, members, parts, regions, layers and / It should be understood that the present invention should not be construed as being limited thereto. These terms are only used to distinguish one section, element, component, region, layer or section from another region, layer or section.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention should not be construed as limited to the particular shapes of the regions shown herein, but should include, for example, changes in shape resulting from manufacturing.

Die casting is a precision casting method which obtains castings by injecting molten metal into a mold to perfectly match the required casting shape, and is advantageous in that it is dimensionally accurate, and is suitable for mass production and wide thickness products. However, there is a problem that the quality of the die casting deteriorates due to defects inevitably occurring during the charging and solidifying process.

It is known that when molding an automobile part having an injection weight of 5 kg or less in a die casting process, the molding force must be 500 ton or more in order to prevent the die casting defect in the charging and solidifying process, .

In the present invention, an automobile part having an injection weight of 5 kg or less, such as a deep cover, is manufactured at a molding force of 350 ton class to reduce manufacturing cost. The injection speed and the melt temperature are important factors for determining the quality of the aluminum alloy die casting product. However, since the desired injection conditions vary depending on the product type, it is necessary to limit the product type. In the embodiment of the present invention described below, a die casting method of an aluminum alloy mainly focusing on an automotive speed reducer cover (DIFF COVER) as an automobile part will be described.

1 is a photograph showing a dip cover realized by a die casting method of an aluminum alloy according to an embodiment of the present invention. Referring to FIG. 1, a Diff cover, also referred to as a Diff cover, is a part located between a reduction case and a motor in an electric vehicle. The deep cover has a purpose of being used in an electric driving motor and a speed reducer which are devices for generating a driving force and controlling a torque by electric energy supplied from the stack.

2 is a graph illustrating a die casting method of an aluminum alloy according to an embodiment of the present invention. An aluminum alloy die casting method according to an embodiment of the present invention is a method of performing an aluminum alloy die casting with an injection weight of 5 kg or less using a die casting apparatus having a mold clamping force of 350 tons or less, And diecasting the melt of the aluminum alloy.

Referring to FIG. 2, it can be seen that the die casting injection speed is realized in multiple stages when the position in the mold is taken as the horizontal axis from the injection region of the molten metal. The die casting step has a first section (I) and a second section (II) in which the injection speed is kept constant. In the die casting step, the first section I precedes the second section II.

Further, the injection speed of the second section II ranges from 2 m / sec to 3 m / sec. When the injection speed is slower than 2 m / sec, it is related to the solidification behavior of the molten metal. In the plunge part (referring to the part before the molten metal enters the mold in the die casting equipment), solidification of the alloy progresses, Which may cause problems in the shape of the product. Further, if the injection speed is lower than 2 m / sec, there is a possibility that the crystal grains of? -Al become coarse. As a result, if the crystal grains are coarsened by the Hall-petch type, a decrease in strength is expected. The present inventors experimentally confirmed the grain size according to the injection speed and proved this.

On the other hand, when the injection speed is faster than 3 m / sec, there is a flow phenomenon before the molten metal enters into the mold, and there is a possibility that the bubble is likely to be generated due to the defective product. In fact, the present inventors have found that when the injection speed is higher than 3 m / sec, Si of the needle is generated and the ductility of the material is lowered when Si is formed.

In the case of die casting, it is necessary to change the injection speed by the shape (including thickness and length) of the product, the equipment performance and structure, the mold design, the material composition and the strengthening phase (crystallization / precipitation) It is confirmed that the injection speed of the second section II is required to be in the range of 2 m / sec to 3 m / sec.

The injection speed of the first section I is lower than the injection speed of the second section II. For example, the injection speed of the first section I is in the range of 0.5 m / sec to 1.5 m / sec Lt; / RTI >

Table 1 shows the processing conditions of the die casting method of the aluminum alloy according to the embodiment of the present invention shown in FIG. 2, and Table 2 shows the processing conditions of the aluminum alloy die casting method according to the comparative example of the present invention.

Position (mm) 100 200 250 275 285 380 385 Injection speed (m / s) 0.1 0.2 1.0 1.0 2.5 2.5 1.5

Position (mm) 100 200 280 285 380 385 Injection speed (m / s) 0.1 0.2 0.3 2.5 2.5 1.5

Table 1 and Table 2 show that the die casting method of the aluminum alloy according to the comparative example of the present invention provides a section in which the injection speed is kept constant in a single number (Table 2), but the aluminum alloy according to the embodiment of the present invention The die casting method provides a plurality of sections in which the injection speed is kept constant (Table 1). The present inventors have found that the effect of preventing die-casting defects occurring during filling and solidifying is remarkably exhibited when the aluminum alloy die-casting process is performed according to an embodiment of the present invention in comparison with the comparative example.

Hereinafter, a method of manufacturing the deep cover using the die casting method of the aluminum alloy according to the technical idea of the present invention and various analysis results will be described. It should be understood, however, that the present invention is not limited to the following Examples, but is for the purpose of promoting understanding of the present invention.

Table 3 specifies conditions under which the experimental example of the present invention was performed.

Experiment Item Experimental equipment standard Condition Average output Die casting Toshiba DC 350J-MH - 2 - Component analysis Spark Emission Spectrometer 분광계 - Average after 5 measurements Wear test DRY SAND WHEEL ABRASION TEST MACHINE ASTM G65 B 10 min One measurement Tensile test Instron testing system equipped with Bluehill control software and a ± 10kN load cell  ASTM-E8 Sub 1 mm / min Except maximum / minimum after 5 measurements Organizational Analysis Nikon Eclipse MA 200 microscope - Keller's reagent, 10s -

In the die-casting process, the mold thickness is 375mm, gongta (stroke) is 405mm, the tip diameter of 70mm, thickness of 20mm biscuits, product thickness is 2.0mm, injection weight is 3kg, product weight is 1.50kg, the projection area of 400cm ^2, a gate Sectional area of 3.12 cm ² , the number of products is 1, and the casting pressure is 70 MPa. The injection speed was split as shown in Table 4.

Position (mm) 100 200 250 275 285 380 385 Injection speed (m / s) 0.1 0.2 1.0 1.0 2.0 2.0 1.5 Injection speed (m / s) 0.1 0.2 1.0 1.0 2.5 2.5 1.5 Injection speed (m / s) 0.1 0.2 1.0 1.0 3.0 3.0 1.5

Table 5 shows the results of the component analysis.

ingredient Cu Si Mg Zn Fe Mn Ni Al ADC12 1.5 to 3.5 9.6-12.0 0.3? 1.0? 1.3 ≤ 0.5? 0.5? Honey. Diff Average 1 2.18 10.77 0.23 0.30 0.68 0.257 0.02 Honey. Diff Average 2 2.12 11.70 0.43 0.89 0.96 0.30 - Honey.

Figs. 3 to 5 are photographs showing product shapes according to an experimental example of the present invention

Referring to Fig. 3, when the outer shape according to the temperature of the molten metal was observed, the unformed molding occurred at 560 ° C (see the red circle), and the unformed runner occurred at 580 ° C (see the red circle) It is predicted that there will be porosity. On the other hand, it can be confirmed that the appearance is good at 600 ° C.

Referring to FIG. 4, when the thickness of the biscuit according to the temperature of the molten metal was observed, it was confirmed that the thickness of the biscuit was different depending on the temperature, and it was confirmed that the lower the temperature of the molten metal, the less the tendency to form. Below 600 ℃, it is difficult to apply to actual products.

Referring to FIG. 5, in the case of a die casting product in which the melt temperature is 740 ° C., product shrinkage and denting phenomenon occur due to overheating of the melt (refer to a red square). .

6 to 7 are graphs showing results of wear tests according to the experimental example of the present invention.

Table 6 shows the abrasion amount according to various injection speeds when the temperature of the molten metal is 680 ° C. Referring to FIG. 6 and Table 6, it can be seen that the wear rate is the best at 2.0358g at an injection speed of 2.5m / s.

Injection speed Before the test After the test Wear amount 2.0 m / s 29.6708 27.4824 2.1884 2.5 m / s 28.9763 26.9405 2.0358 3.0m / s 29.6148 27.3783 2.2365

Table 7 shows the amount of wear according to various melt temperature conditions at an injection speed of 2.5 m / s. Referring to FIGS. 7 and 7, it can be seen that the wear amount is similar when the injection speed is 2.5 m / s and the molten metal temperature is 640 ° C., 680 ° C., and 720 ° C.

Melt temperature Before the test After the test Wear amount 720 ℃ 28.8646 26.8361 2.0284 680 ° C 28.9763 26.9405 2.0358 640 ° C 29.2853 27.2602 2.0251

Table 8 and Figs. 8 to 9 show the yield strength, tensile strength and elongation according to the experimental examples of the present invention. 8, the left side corresponds to the yield strength and the right side corresponds to the tensile strength. 8 to 9 relate to the third row at the top in Table 8 and correspond to the case of having the molten metal composition of the deep average 1 disclosed in Table 5. [ Table 8 relates to a row 1 at the bottom and corresponds to the case where the molten metal composition of the deep average of 2 disclosed in Table 5 is provided.

Melt temperature YS (MPa) UTS (MPa) EL (%) 640 占 폚 (dip average 1) 213 298 1.9 680 DEG C (dip average 1) 211 314 3.0 720 占 폚 (dip average 1) 168 333 3.2 720 DEG C (dip average 2) 166 278 3.7

In the case of having a molten metal composition having a dip average of 1 as shown in Table 5, the tensile strength is 300 MPa or less under the condition of the molten metal temperature of 640 캜, the tensile strength is 314 MPa and the yield strength is 211 MPa under the molten metal temperature of 680 캜, Is increased from 680 캜 to 720 캜, the tensile strength and elongation are increased but the elongation is decreased. The yield strength decreased to 168 MPa at the temperature of 720 ℃. It can be seen that the contrast elongation increases with the molten metal composition of the dip average 1 in the case of the molten metal composition having the dip average of 2 disclosed in Table 5. [

10 is a photograph showing the microstructure according to the melt temperature and the injection speed according to the experimental example of the present invention.

10, coarse? -Al was observed at 640 占 폚 and Si of the needle bed was confirmed. As the temperature increased from 640 占 폚 to 680 占 폚, refinement of? -Al grains was confirmed, Respectively. The Si of the needle was observed at 720 ℃, and the size of the needle Si was confirmed to be larger than 640 ℃. It was confirmed that the α-Al grains were refined at 2.5 m / s compared with the injection speed of 2.0 m / s. Si at the 3.0 m / s was observed at 2.0 m / s and 2.5 m / s, . According to the results, the most preferable microstructure was realized when the temperature of the molten metal was 680 ° C. and the injection speed was 2.5 m / s. In this case, the yield strength was 200 MPa, the tensile strength was 300 MPa, and the elongation was 3.0% or more Could.

Fig. 11 is a photograph actually comparing casting fluidity in a process of die-casting a molten aluminum alloy according to Example (a) and Comparative Example (b) of the present invention. FIG. 11 (a) is a cross-sectional view illustrating a first section and a second section in which the injection speed is kept constant in the die casting of the aluminum alloy having the temperature range of 600 ° C. to 720 ° C. according to the embodiment of the present invention , The injection speed of the second section is in the range of 2 m / sec to 3 m / sec, and the injection speed of the first section is lower than the injection speed of the second section Casting fluidity. On the contrary, FIG. 11 (b) shows casting fluidity in a general die casting process, not a multi-step injection. 11 (b), it can be seen that the movement distance of the molten metal is larger in the case of FIG. 11 (a), and the casting fluidity is further improved by the multi-stage injection process according to the conditions of the present invention.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (11)

A method of manufacturing a diff cover made of an aluminum alloy having an injection weight of 5 kg or less by using a die casting apparatus having a mold clamping force of 350 tons or less,
The method comprising: preparing a melt of an aluminum alloy having a temperature range of 600 ° C to 680 ° C; And
And die casting the molten aluminum alloy,
The aluminum alloy is an aluminum alloy for ADC12 casting,
Wherein the die casting step has a first section and a second section in which an injection speed is maintained constant,
The injection speed of the first section has a range of 0.5 m / sec to 1.5 m / sec, the injection speed of the second section has a range of 2 m / sec to 3 m /
Wherein a distance at which the second section is maintained is larger than a distance at which the first section is maintained,
A method of making a diff cover. delete The method according to claim 1,
Wherein in the diecasting step, the first section precedes the second section. delete delete delete A die casting method of an aluminum alloy having an injection weight of 5 kg or less by using a die casting apparatus having a mold clamping force of 350 tons or less,
The method comprising: preparing a melt of an aluminum alloy having a temperature range of 600 ° C to 680 ° C; And
And die casting the molten aluminum alloy,
The aluminum alloy is an aluminum alloy for ADC12 casting,
Wherein the die casting step has a first section and a second section in which an injection speed is maintained constant,
The injection speed of the first section has a range of 0.5 m / sec to 1.5 m / sec, the injection speed of the second section has a range of 2 m / sec to 3 m /
Wherein a distance at which the second section is maintained is larger than a distance at which the first section is maintained,
Die casting method of aluminum alloy. delete 8. The method of claim 7,
Wherein in the die casting step, the first section precedes the second section.


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