JP3369993B2 - Injection molding method for metal members - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection molding a metal member, in which a molten metal such as a light metal is injected in a semi-molten state below its melting point from an injection nozzle into a molding cavity of a molding die to obtain a molded product. .

[0002]

2. Description of the Related Art For example, light metals such as magnesium (hereinafter appropriately referred to as its element symbol Mg) and its alloys or aluminum (hereinafter appropriately referred to as its element symbol Al) and its alloys are used as materials. As a method for producing a metal member, a so-called semi-molten metal is obtained by injection-filling a molten metal in a semi-molten state (basically below its melting point) from an injection nozzle into a molding cavity of a molding die. Injection molding methods are conventionally known (for example,
(See Japanese Patent Publication No. 15620/1990).

This semi-molten injection molding method is relatively clean in terms of working environment and safer than the casting method such as die casting method, and is highly accurate in terms of quality. It is known as a process capable of obtaining a homogeneous light metal molded product. Further, since the molten metal temperature (hereinafter, referred to as “molten metal” even in a semi-molten state, not in a completely molten state) is so-called “burr”.
It is also suitable for injection at high speed and / or high pressure, and is advantageous in improving productivity.

[0004]

However, in the case of the above-mentioned semi-molten injection molding method, the temperature of the molten metal is lower as described above and the molten metal is kept in the molding die as compared with the so-called cold chamber type die casting method. As for the supply portion (injection nozzle) for supplying to (1), the inner diameter is usually set smaller by narrowing the tip end portion. Therefore, as the volume of the molding cavity increases, it becomes more difficult to uniformly fill the molten metal throughout the cavity, which is generally disadvantageous when a large-sized molded article having a certain size or more is manufactured.

In the present specification, (above a certain level)
"Large-sized molded product" means "the maximum value (Da) when projected so that the diameter (D) of the circle circumscribing the projection of the molded product becomes the maximum value (Da) is 300 [mm]. (Mm) or more ”. If the size of the molded product is smaller than this, adjust the temperature conditions such as the cylinder temperature of the molding machine and the mold temperature (mold temperature), and the injection conditions such as injection pressure and injection speed. It is relatively easy to uniformly inject the molten metal over the entire cavity to obtain a sound molded product (that is, a high-quality molded product with few defects and predetermined mechanical properties), but the size of the molded product If the above is above the above range, it is generally difficult to stably obtain a sound molded product only by adjusting the temperature condition and the injection condition.

Further, in the case of the semi-melt injection molding method, the melt of the injection nozzle is melted after one injection (one shot) from the injection nozzle to the next (next shot) injection. The molten metal in the supply path is cooled, and a solidified portion (so-called cold plug) or a high solid phase portion having a high solid phase ratio is generated on the nozzle tip side. And at the shot of the next shot,
If the molten metal is injected and filled with the cold plug and the high solid phase portion included, a locally non-uniform portion (that is, the solid fraction is higher than the surrounding portion) in the material structure of the molded product. Therefore, there is a problem in that the mechanical properties are greatly impaired.

In the present specification, the term "solid phase" means "a portion where the molten metal is in a semi-molten state and remains in a solid state without being melted", and is also referred to as "liquid phase". Means "a part that is completely melted into a liquid state". By observing the solidification structure of the molded product after injection, the above "solid phase" is defined as "a part that remains in a solid state without being melted in a semi-molten metal melt state", It was completely melted into a liquid state. ''
The liquid phase portion can be easily identified. When the term "solid phase" is used for a molded article, it means "a portion that was in a semi-molten molten metal state but was not melted but remained in a solid state (was a solid phase)". In the present specification, the term "solid phase ratio" refers to "a ratio of the solid phase to the entire molten metal (solid phase + liquid phase) in the metal melt in a semi-molten state", which is a solidification structure of a molded product after injection. By observing, the ratio (area ratio) of the portion that was the “solid phase” to the entire observation region can be numerically obtained.

Further, in the present specification, the "semi-molten state" of the molten metal as the raw material to be injected is basically "melted with the solid state raw material (solid phase) to become a liquid state". A state in which the raw material (liquid phase) coexists ", and is usually a state obtained by heating the raw material below its melting point. However, the case where the temperature of the molten metal is substantially the melting point or just above the melting point and the solid fraction is substantially equal to 0 (zero)% is also included in this “semi-molten state”.
Even when the molten metal itself has such a solid phase ratio of substantially 0%, considering the actual injection molding process, as described above, a so-called cold plug or solid phase is provided in the molten metal supply path of the injection nozzle. Since a high solid phase portion with a high rate is generated, the molten metal actually injected into the molding cavity inevitably contains the solid phase portion.

Therefore, for example, Japanese Unexamined Patent Publication No. 9-38758
As disclosed in Japanese Patent Publication No. JP-A-2003-242242, a recess (so-called plug catcher) is provided in a portion of the mold facing the injection nozzle, and when the molten metal is injected from the injection nozzle into the mold, the injection is mainly performed. By allowing the cold plug and high solid phase portion existing on the tip side of the nozzle to be captured and stored in the plug catcher, the material obtained by mixing the cold plug and high solid phase portion in the molded product of the next shot It is considered to prevent the occurrence of local nonuniformity in the organization. However, even in this case, the effect of preventing the inclusion of the cold plug and / or the high solid phase portion greatly differs depending on how the size of the plug catcher is set.

Further, when the molded product has a thick portion having a larger thickness than the surrounding portion, a so-called "shrinkage" occurs at the solidification of the molten metal in the thick portion having a partially large volume. Therefore, there is a problem that a shrinkage cavity defect is likely to occur in the obtained molded product.

By the way, in the semi-molten injection molding method, it is very important to secure the fluidity of the molten metal in order to perform good injection molding and obtain a sound molded product. In particular, when injection-molding a "large-sized molded product" of a certain size or more, it is difficult to uniformly inject and fill the molten metal throughout the molding cavity as described above. It will directly affect the quality of the product.

The fluidity of the molten metal can be increased, for example, by raising the temperature of the molding die (mold temperature). However, even if the fluidity of the molten metal is secured only by adjusting the mold temperature, a good molded product can be obtained. It's generally hard to get. In other words, when the fluidity of the molten metal is secured by increasing the mold temperature, there is a problem in production efficiency that the solidification of the molten metal generally takes a longer time, resulting in a longer molding cycle time. If the temperature is raised too high, "burrs" may increase, or the molten metal may easily leak from the mating surface of the molding die.

It is considered that the solid fraction of the molten metal has a great effect on the fluidity of the molten metal in the semi-molten state. As is clear from the above definition, this solid phase ratio is obtained as a result of incorporating various injection molding conditions including temperature conditions such as the cylinder temperature and / or the mold temperature of the injection molding machine. Therefore, if the flowability of the molten metal can be evaluated based on the magnitude of the solid phase ratio, a very simple and highly practical index can be obtained. And
By setting a suitable condition range using such an index, it becomes possible to reliably obtain the required melt fluidity under suitable injection molding conditions without raising the mold temperature excessively.

However, actually, when the relationship between only the solid phase ratio and the flow length is examined, the solid phase ratio changes (changes between about 2 to 45 [%]) as shown in the graph of FIG. The change of the flow length [m] (meter) in the case of making it is extremely irregular, and no significant correlation was observed between the two.

The present invention has been made in view of the above problems in molding a metal member by a semi-molten injection molding method, and the required molten metal flow under suitable injection molding conditions without excessively raising the mold temperature. Of the cold plug and / or the high solid phase portion can be more effectively prevented from being mixed into the molded product, and the occurrence of shrinkage cavities in the thick wall portion can be effectively prevented. The purpose is to do so.

[0016]

The inventor of the present invention has conducted extensive studies in view of the above technical problems, and as a result, considers not only the solid fraction of the metal melt in the semi-molten state but also the average solid diameter. , By using an index that is a combination of both (specifically, the “product” that is the product of the two is used as an index), a high correlation can be obtained between this index and the fluidity (flow length) of the molten metal. It has also been found that by devising the setting of the depth and diameter of the plug catcher, a high effect can be obtained more reliably in preventing the cold plug and / or the high solid phase portion from being mixed into the molded product.

In the present specification, the term "average solid phase diameter" means "the average diameter of the equivalent circle of the portion of the molten metal which is in a semi-molten state and is maintained in the solid state without being melted". . By observing the solidification structure of the molded product after injection, this "average solid-phase diameter" is "the average diameter of the equivalent circles of the part that was maintained in the solid state without being melted in the semi-molten metal melt state. It can be measured as "value".

Therefore, in the injection molding method for a metal member according to the invention of claim 1 (hereinafter referred to as the first invention) of the present application, the molten metal is injected and filled from the injection nozzle into the molding cavity of the molding die in a semi-molten state. In the injection molding method of a metal member, a molded product is obtained by projecting so that the diameter (D) of the circle circumscribing the projection becomes the maximum value (Da). The maximum value (Da) is 300 [mm]
(Mm) or more, and the solid phase ratio (Fs [%]) and the average solid phase diameter (ds [μ
m]) is set so that the product (Fs × ds) is 4000 or less, and injection molding is performed.

Here, the upper limit of the product (Fs × ds) of the solid phase fraction Fs and the average solid phase diameter ds is set to 4000 because when the product (Fs × ds) of both falls below this value, the metal This is because the degree of decrease in the fluidity of the molten metal increases and it becomes difficult to stably secure the required fluidity. Further, the lower limit of the maximum value Da of the circumscribed circle is set to 300 [mm] when the maximum value Da is less than this value (that is, when it does not correspond to the “large molded product” in the present application). By adjusting the temperature conditions such as the cylinder temperature of the molding machine and the temperature of the molding die (mold temperature) and the injection conditions such as the injection pressure and the injection speed, it is possible to uniformly inject and fill the molten metal over the entire molding cavity for soundness. It is relatively easy to obtain a good molded product (that is, a high quality molded product with few defects and predetermined mechanical properties), but the maximum value Da of the circumscribed circle of the molded product is Da.
When the value is 300 [mm] or more (that is, when it corresponds to the “large-sized molded product” referred to in the present application), it is generally possible to stably obtain a healthy molded product only by adjusting the temperature conditions and injection conditions. It's difficult.

[0020]

[0021]

The invention according to claim 2 of the present application (hereinafter,
According to a second invention), in the first invention, a predetermined diameter (φ) is provided in a portion of the molding die facing the injection nozzle.
And a recess having a depth (h) is formed, and injection molding is performed by setting the ratio (h / φ) of the depth (h) of the recess to the diameter (φ) to be 0.5 or more. It is characterized by.

Here, the lower limit of the ratio (h / φ) of the depth h of the recess (that is, the so-called plug catcher) to the diameter φ is set to 0.5 because the value of this ratio (h / φ). Is 0.
If the range is less than 5, the cold plug and / or the high solid phase portion cannot be effectively captured / stored by the plug catcher, and due to these inclusions, the solid phase ratio in the molded product is particularly high compared with other materials, and the structural defects of the material are not high. This is because a uniform portion is generated.

The invention according to claim 3 of the present application (hereinafter,
(Third invention) corresponds to the thick portion in the molding cavity, wherein the molded product has a thick portion having a larger thickness than a surrounding portion in the first or second invention. A thick formed part is provided, and after the molten metal is injected and filled into the forming cavity, the thick formed part is partially pressurized before solidification of the molten metal.

The invention according to claim 4 of the present application
(Hereinafter, referred to as a fourth invention) is characterized in that, in any one of the first to third inventions, a molten metal of light metal is used as the molten metal.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding device for injection molding a metal member according to this embodiment. As shown in this figure, the injection molding apparatus 1 is of a so-called screw type, and has a heater 4 arranged at the outer periphery having a nozzle 3 at the tip.
2, a cylinder 2 and a screw 6 rotatably supported in the molding machine main body 5 connected to the cylinder 2, and a rotary drive device for rotating the screw 6 including, for example, a motor mechanism and a reduction mechanism. 7, a hopper 8 into which the raw material is charged and stored, and a feeder 9 for measuring the raw material in the hopper 8 and feeding it into the molding machine body 5. Although not specifically shown, a high-speed injection mechanism for advancing the screw 6 to the nozzle 3 side is provided in the molding machine body 5. This high-speed injection mechanism advances the screw 6 at a predetermined timing and
When the screw 6 retracts by a preset distance, it is detected and the rotation of the screw 6 is stopped, and at the same time, the retracting operation is also stopped.

The injection molding apparatus 1 is set such that the internal passage of the nozzle 3 and the runner portion 12 connected to the molding cavity 11 communicate with each other, and the tip side of the cylinder 2 is connected to the mold 10. Used. The raw material charged into the hopper 8 and stored therein is measured by a feeder 9 in a predetermined amount and supplied into the molding machine main body 5, and the screw 6
Is fed into the heated cylinder 2.
The fed raw material is heated to a predetermined temperature while being sufficiently stirred and kneaded by the rotation of the screw 6 inside the cylinder 2. In the present embodiment, by such a process, a metal melt in a semi-molten state below the melting point of the raw material is obtained.

As the semi-molten metal melt thus obtained is pushed forward of the screw 6, the screw 6 moves backward by its pressure. As another method, the screw may be forcibly retracted at a desired speed. When the screw 6 retracts by a preset distance, the high-speed injection mechanism (not shown) in the molding machine body 5 detects it and stops the rotation of the screw 6, and at the same time, the retracting operation is also stopped. The raw material may be measured by setting the retreat distance of the screw 6.

Then, the screw 6 which has stopped rotating and is in the retracted position is advanced by a high-speed injection mechanism (not shown) and pushed out with a predetermined force, whereby the metal melt in a semi-molten state is injected from the nozzle 3 into the mold 10. Is ejected. That is, the molten metal is injected and filled from the nozzle 3 into the molding cavity 11 via the runner portion 12. In this embodiment, a magnesium (Mg) alloy, which is a kind of light metal, is used as a raw material, and this is supplied to the hopper 8 of the injection molding apparatus 1 in the form of, for example, swarf-like pellets. More preferably, an inert gas (for example, argon gas) is provided in the passage leading from the hopper 8 into the molding machine body 5.
To prevent the oxidation reaction of the raw material (Mg alloy pellets).

Further, in the present embodiment, when the metal member is molded by the semi-molten injection molding method, it is possible to surely obtain the required melt fluidity under suitable injection molding conditions without excessively raising the mold temperature. In order to be able to do so, and to more effectively prevent the inclusion of cold plugs and / or high solid phase parts in the molded product, the occurrence of shrinkage cavities in thick parts is also effective. Various tests were carried out in order to prevent the above. These tests were performed using two types of Mg alloys (alloy A and alloy B) shown in Table 1 below as raw materials.

[0031]

[Table 1]

<Test 1> First, Test 1 which was carried out to examine the fluidity of the metal melt in a semi-molten state will be described.
2 and 3 are explanatory views schematically showing a molding cavity in a test mold, which is a part of a testing apparatus for investigating the flow length of a molten metal in semi-molten injection molding. As shown in this figure, the molding cavity 21 used in this test
Is formed by folding back a passage having a predetermined cross-sectional shape (a rectangular cross-sectional shape having a thickness of 3 mm (mm) and a width of 20 mm (mm): see FIG. 3) in a U-shape at a predetermined pitch Lp. The maximum width Lw of this U-shaped part is 3
It is set to 00 millimeters (mm). Therefore,
When the molten metal is injected into the molding cavity 21 and reaches at least the apex 21p of the first U-shaped curve from the cavity inlet portion 21a, the obtained molded product has a circle 23 circumscribing its projection. The maximum value Da when projected such that the diameter becomes the maximum value Da is 3
It is more than 00 [mm] (millimeter), that is, a “large-sized molded product” referred to in the present application.

A so-called plug catcher 22 is provided in the mold part immediately near the cavity inlet part 21a. As will be described later in detail, the plug catcher 22 is a concave portion provided in a portion facing the injection nozzle of the mold, and is mainly used when the molten metal is injected from the injection nozzle into the mold. A so-called cold plug and / or a high solid phase portion existing on the tip side is accommodated. By providing such a plug catcher 22, it is possible to prevent the occurrence of local nonuniformity in the material structure due to mixing of the cold plug and / or the high solid phase portion in the molded product.

Then, by setting an injection nozzle at a portion facing the plug catcher 22 and injecting a semi-molten metal melt, the metal melt has a passage-shaped molding cavity 21 for a length corresponding to its fluidity. Will be filled. Therefore, after the molten metal is solidified, the length of the metal-filled portion of the molding cavity 21 (that is, the length of the injection-molded body) is compared to determine the fluidity of the injected molten metal. The quality can be evaluated.

In this test 1, not only the solid phase ratio of the molten metal in the semi-molten state but also the average solid phase diameter are taken into consideration, and an index (specifically, "product" obtained by multiplying both) and metal The relationship between the fluidity (fluid length) of the molten metal was investigated. The mold temperature was kept at 200 ° C. during this test. If the mold temperature is around this level, there is no risk of problems such as excessive burrs or the tendency of the molten metal to leak from the mold mating surface, and the time required for the molten metal to solidify. Also, the molding cycle time will not be excessively lengthened due to excessive load.

The test results are shown in the graph of FIG. 12, and the solid phase ratio (Fs [%]) and the average solid phase diameter (Fs [%]) of the metal melt in the semi-molten state are shown for both alloy A and alloy B It was found that there is a high correlation between the product of ds [μm]) (Fs × ds) and the flow length of the metal melt.
In this test, the solid phase ratio (Fs [%]) and the average solid phase diameter (ds [μm]) are numerical values obtained by observing and measuring the solidified structure of the injection-molded molded product. In addition, for all materials, a graph in which the product (Fs × ds) of the solid phase ratio (Fs [%]) and the average solid phase diameter (ds [μm]) is the horizontal axis and the flow length is the vertical axis (Fig. 12), a so-called inflection point appears, and when the product (Fs × ds) is below a certain value (4000 or less), a relatively long flow length (flow length of about 1 m or more) can be stably secured, The product (Fs × ds) is 4
It has been found that when it exceeds 000, the flow length is significantly reduced. In addition, if the flow length is about 1 m or more, even when the “large-sized molded product” referred to in the present application is molded, if it has a certain size, a sound molded product can be obtained without trouble. The test for investigating the relationship between only the solid fraction and the flow length (see FIG. 14) was performed using the sample alloy B under the condition that the mold temperature was 200 ° C. and the same test apparatus as in the main test 1. It is a thing.

From the above, not only the solid phase ratio Fs of the molten metal in the semi-molten state but also the average solid phase diameter Fd are taken into consideration and used as a combined index (specifically, the product (Fs XFd) "as an index), it was found that a high correlation can be obtained between this index and the fluidity (flow length) of the molten metal. And this index (Fs × F
By setting a suitable condition range using d), it becomes possible to reliably obtain the required melt fluidity under suitable injection molding conditions without raising the mold temperature excessively. That is, by setting the product (Fs × ds) of the solid phase ratio Fs and the average solid phase diameter ds to be 4000 or less, injection molding is performed to obtain the required fluidity (fluid length is about 1 m or more). It can be secured stably. In addition, if the flow length is about 1 m or more,
With a certain size, a sound molded product can be obtained without any trouble.

The setting such that the product (Fs × ds) of the solid phase fraction Fs of the molten metal in the semi-molten state and the average solid phase diameter ds (Fs × ds) is equal to or less than a predetermined value (4000 or less according to this test) is, for example, Do the following: That is, using a certain injection molding device for a certain material, various conditions such as the cylinder temperature of the molding machine and the temperature of the molding die (mold temperature) and the injection conditions such as the injection pressure and the injection speed are changed and adjusted. Molding is performed, the solidified structure of the molded product obtained by each injection molding is observed, and the product (Fs × ds) of the solid phase fraction Fs and the average solid phase diameter ds is measured to collect data. Then, based on this data, temperature conditions and injection conditions may be selected such that the product (Fs × ds) of the solid phase fraction Fs and the average solid phase diameter ds becomes a predetermined value or less. Accordingly, it is possible to set conditions for performing injection molding on the material using the injection molding apparatus. When the material and / or the injection molding apparatus are different, the data may be collected again and the condition may be set.

<Test 2> Next, a test 2 carried out for investigating the relationship between the depth and diameter of a so-called plug catcher with respect to the inclusion of the cold plug and / or the high solid phase portion in the molded product will be described. 4 and 5 show a molded work Kw injection-molded using the injection molding apparatus 1 with a so-called "flesh" attached, that is, a plate-shaped molded work Kw, and the metal shown in FIG. The molded body K in which the runner corresponding portion Kr corresponding to the runner portion Jr of the mold J, the gate corresponding portion Kg corresponding to the gate portion (not shown), and the plug catcher corresponding portion Kp corresponding to the plug catcher Jp are still connected is shown. FIG. 6 is an enlarged cross-sectional explanatory view of the nozzle 3 provided at the tip of the cylinder 2 of the injection molding apparatus 1.

When the injection of one shot is completed, the semi-molten metal melt remains in the inner passage 3H of the nozzle 3, but the remaining metal melt is cooled with the passage of time, and as can be seen from FIG. 6, By the next cycle (next shot), part of it solidifies (solidification part: so-called cold plug М
p) or high solid phase Мs with a high solid fraction. Since this cooling usually occurs from the nozzle tip side where the temperature is low,
Inside the inner passage 3H of the nozzle 3, a solidification part Мp (cold plug) and a high solid phase part Мs are arranged in order from the tip side, followed by a semi-molten metal melt Мm with a normal solid fraction. become.

In this test, at the time of injection in the next cycle, it is possible to effectively prevent injection filling of the molten metal with the cold plug Мp and / or the high solid phase portion Мs included, so that the plug catcher can be effectively prevented. Injection molding is performed by changing various values of the ratio (h / φ) of the depth h of Jp to the diameter φ,
Different portions (solid fraction measurement portions W1 and W in FIGS. 4 and 5) of the molded work Kw obtained in each case.
The solid fraction in 2) was investigated and compared.

The test results are shown in the graph of FIG. 13, and in the solid fraction measuring portion W1 which is almost connected to the runner portion Jr, the ratio (h / φ) is low (h / φ =). 0.2
The solid fraction is sufficiently low (about 5% or less) and kept constant, but the ratio (h / φ) is low in the solid fraction measuring unit W2 farthest from the runner Jr. If (h /
The solid fraction is very high (about φ = 0.2 or less) (about 25)
% Or more), and moreover, the solid fraction changes significantly with a slight change in the value of the ratio (h / φ). And this ratio (h /
When the value of φ is 0.5 or more, even in the solid fraction measuring portion W2 farthest from the runner portion Jr, the solid fraction is sufficiently low (about 5).
%) And becomes constant with respect to changes in the value of the ratio (h / φ).

This is because by setting the value of the ratio (h / φ) of the depth h of the plug catcher Jp to the diameter φ to be 0.5 or more, it remains in the internal passage 3H of the nozzle 3 in the previous shot at the time of injection molding. The cold plug Мp generated by cooling the molten metal that has been cooled with time, and more preferably, the high solid phase portion Мs, in addition to this, are placed in the plug catcher Jp as shown by the broken line in FIG. By being reliably captured and stored, the molded work Kw
It is considered that this is because entry into the interior is effectively prevented.

From the above, the depth h of the plug catcher Jp
By setting the value of the ratio (h / φ) to the diameter φ of 0.5 or more, the cold plug Мp and / or the high solid phase portion Мs can be effectively captured and stored by the plug catcher Jp. It was confirmed that it is possible to prevent the occurrence of a non-uniform portion on the material structure having a particularly high solid fraction in the molded product due to mixing.

<Test 3> Next, Test 3 relating to a method for effectively preventing the occurrence of shrinkage cavities in a thick portion will be described. FIG. 8 to FIG. 10 show a molding work Sw injection-molded by using the above-mentioned injection molding device 1 with a so-called “flesh” attached, that is, molding with a predetermined thickness (thickness 5 mm) having a concave cross-section. A runner corresponding portion Sr corresponding to a runner portion Qr branched into three cavities Q formed by a die R (die R1 + die R2) shown in FIG.
It is explanatory drawing which shows the molded object S with the gate corresponding part Sg corresponding to g, and the plug catcher corresponding part Sp corresponding to the plug catcher Qp still connected. FIG. 8 shows the vertical cross section, FIG. 9 shows the front, and FIG. 10 shows the back. In each drawing, the unit of the numerical value indicating the dimension is millimeter ([mm]).

The above-mentioned molded work Sw is, for example, a frame body of a seat, and has a rectangular shape of 300 [mm] in length and 400 [mm] in width in a front view. Corresponds to. When such a large-sized molded product is injection-molded, the molten metal filled in the molding cavity Qw by connecting each runner portion Qr and the molding cavity Qw through the gate portion Qg having a narrow frontage (passage area). It is possible to increase the flow rate of the molten metal, and thereby, even when the volume of the molding cavity Qw is large to some extent or more, the molten metal can be uniformly filled therein.

A thick portion St (thickness 10 mm) having a larger thickness than the surrounding portion (thickness 5 mm) is provided on a part of the back surface of the molded work Sw. Then, in the mold R, a pressure pin Pn for partial pressure is arranged at a portion corresponding to the thick portion St of the molding cavity Qw, and the pressure pin Pn is arranged outside the mold R. It can be moved back and forth by the cylinder device Cy. still,
The cylinder device Cy is electrically connected to a control unit (not shown) of the injection molding device 1 and moves the pressurizing pin Pn forward and backward at a predetermined timing according to a control signal from the control unit. ing.

The pressure pin Pn has a molding cavity Qw.
After the molten metal is injected and filled into the inside, the thick portion St is partially pressed with a predetermined pressure between the start and the end of solidification, whereby the thick portion St is thickened. Department St
It prevents the generation of shrinkage cavities associated with solidification inside. In this test, the effect of preventing shrinkage cavities was examined by comparing the densities of the thick portions St of the molded work Sw with and without the partial pressure applied by operating the pressure pin Pn. It was The density measurement was performed not only on the portion P2 corresponding to the thick portion St, but also on the other three points P1, P3, and P4, as indicated by hatching in FIG. The measurement results are shown in Table 2.

[0049]

[Table 2]

As can be seen from Table 2, the density at point P2 is lower than that at the other three points when partial pressure is not applied, and shrinkage cavities are likely to occur in the thick portion St. Was confirmed. Then, the thick portion St (measurement site P2
By performing partial pressure on the point A), the density of the alloy A and alloy B materials is significantly increased, and the partial pressure by the pressure pin Pn is increased by the thick portion St. It was confirmed that it was extremely effective in preventing the shrinkage cavities from occurring.

Although the above-mentioned embodiment is for the case where the Мg alloy is used as the injection material, the present invention is also effective when other kinds of metals (especially light metals) are used for the material. Can be applied to. As described above, it is needless to say that the present invention is not limited to the above embodiments, and various changes and design improvements can be made without departing from the gist of the present invention.

[0052]

According to the first invention of the present application, the "large molded product", that is, the maximum value Da when projected so that the diameter D of the circle circumscribing the projection is the maximum value Da. When a metal member of a molded product having a diameter of 300 [mm] or more is molded by a semi-molten injection molding method, not only the solid phase ratio of the molten metal in the semi-molten state but also the average solid phase diameter are taken into consideration, and both are combined. By using the index (specifically, the “product” obtained by multiplying the two by using the index), a high correlation can be obtained between this index and the fluidity (flow length) of the molten metal. By setting a suitable condition range using this index (solid fraction x average solid diameter), the required melt fluidity can be ensured under suitable injection molding conditions without excessively raising the mold temperature. It will be possible to obtain. That is, by performing injection molding while setting the product of the solid phase ratio and the average solid phase diameter to be 4000 or less, the required fluidity can be stably ensured, particularly for "large-sized molded products". Therefore, it is possible to perform injection molding without any trouble and obtain a sound molded product.

[0053]

According to the second invention of the present application, basically, the same effect as that of the first invention can be obtained. Moreover, a recess (plug catcher) having a predetermined diameter φ and a depth h is provided at a portion of the molding die facing the injection nozzle, and the ratio of the depth h of the plug catcher to the diameter φ (h / φ). Since the value of was set to 0.5 or more, the cold plug and / or the high solid phase part can be effectively captured and stored by the plug catcher, and by mixing these, the solid phase ratio in the molded product is higher than that of other parts. It is possible to prevent particularly high unevenness of the material structure from occurring.

Further, according to the third invention of the present application, basically, the same effect as that of the first or second invention can be obtained. Particularly, after the molten metal is injected into the molding cavity and before the molten metal is solidified, the thick-walled molded part is partially pressurized, so that the "thinning" is likely to occur during solidification. With respect to, it is possible to effectively prevent the occurrence of defects due to shrinkage cavities.

Further, according to the fourth invention of the present application,
In the case of semi-melt injection molding of a metal member using a molten metal of a light metal, the same effect as that of any one of the first to third inventions can be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding device according to an embodiment of the present invention.

FIG. 2 is an explanatory view schematically showing a molding cavity of a test mold of Test 1.

3 is a cross-sectional explanatory view taken along the line Y3-Y3 of FIG.

FIG. 4 is a front view illustrating a molded body according to Test 2.

5 is an explanatory cross-sectional view taken along the line Y5-Y5 of FIG.

FIG. 6 is an explanatory longitudinal sectional view showing an enlarged tip portion of a nozzle of the injection molding apparatus.

FIG. 7 is an explanatory longitudinal sectional view showing a main part of a mold and a nozzle tip part according to test 2.

8 is a vertical cross-sectional explanatory view of the molded body according to Test 3, and is a cross-sectional explanatory view taken along the line Y8-Y8 of FIG. 9.

9 is a front explanatory view of a molded body according to Test 3. FIG.

FIG. 10 is a rear view illustrating a molded body according to Test 3.

FIG. 11 is a vertical cross-sectional explanatory view of a mold device according to test 3.

FIG. 12 is a graph showing the test result of Test 1 and showing the relationship between the product of the solid fraction and the average solid diameter and the flow length.

FIG. 13 is a graph showing the test result of Test 2 and showing the relationship between the ratio of the depth of the plug catcher to the diameter and the solid fraction.

FIG. 14 is a graph showing the test results of the conventional test and showing the relationship between only the solid fraction and the flow length.

[Explanation of symbols] 1 ... Injection molding equipment 3 ... Nozzle 10, J ... Mold 11, 21 ... Molding cavity 23 ... circumscribed circle Cy ... (for pressurizing) cylinder device Pn ... Pressurizing pin St ... Thick part Sw ... Molding work

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B22D 17/00 B22D 17/22 B22D 17/30

Claims (4)

(57) [Claims] 1. An injection molding method for a metal member, wherein a molten metal is injected in a semi-molten state from an injection nozzle into a molding cavity of a molding die to obtain a molded product, wherein the molded product is a projection thereof. The maximum value (Da) when projected so that the diameter (D) of the circle circumscribing the figure becomes the maximum value (Da) is 300 [mm] (millimeter) or more, and the semi-molten metal A metal member characterized by performing injection molding by setting the product (Fs × ds) of the solid phase ratio (Fs [%]) of the molten metal and the average solid phase diameter (ds [μm]) to be 4000 or less. Injection molding method. 2. A recess having a predetermined diameter (φ) and a depth (h) is formed at a portion of the molding die facing the injection nozzle, and a ratio of the depth (h) of the recess to the diameter (φ) is formed. (H
/ Φ) is set to 0.5 or more and injection molding is performed, and the injection molding method for a metal member according to claim 1. 3. The molded product has a thick portion having a thickness larger than that of a surrounding portion, and a thick molding portion corresponding to the thick portion is provided in the molding cavity. 3. The injection molding method for a metal member according to claim 1, wherein the thick-walled molding portion is partially pressed after the metal is injected into the molding cavity and before the molten metal is solidified. 4. The injection molding method for a metal member according to claim 1, wherein a molten metal of light metal is used as the molten metal.