JP2000197955A - Injection-molding method for metallic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection-molding method, with which the necessary molten metal fluidity can surely be obtd. in the suitable injection-molding condition without excessively raisin the temp. of a mold, in case of molding a metallic member with a semi-molten injection-molding method. SOLUTION: In the injection-molding method for metallic member by injection-filling the molten metal into a molding cavity in the mold from an injection nozzle in the semi-molten state so as to obtain the molded product, the injecting molding is executed by setting so that a product (Fs×ds) of a solid phase ratio (Fs [%]) of the molten metal in the semi-molten state and an average solid phase diameter (ds [μm]) becomes <=4000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method of a metal member for obtaining a molded product by injecting a molten metal such as a light metal in a semi-molten state having a melting point lower than its melting point from an injection nozzle into a molding cavity of a molding die. .

[0002]

2. Description of the Related Art For example, light metals such as magnesium (hereinafter, appropriately denoted by its element symbol Mg) and its alloy or aluminum (hereinafter, appropriately denoted by its element symbol: Al) and its alloy are used as materials. As a method of manufacturing a metal member, a so-called semi-molten product is obtained by injection-filling a molten metal in a semi-molten state (essentially less than the melting point) from an injection nozzle into a molding cavity of a mold. Injection molding methods are conventionally known (for example,
Japanese Patent Publication No. 15620/1990).

[0003] The semi-solid injection molding method is relatively clean (clean) in terms of working environment and higher in safety than the casting method such as a die casting method, and has high precision in quality. It is known as a process capable of obtaining a homogeneous light metal molded product. In addition, since the temperature of the molten metal (hereinafter, also referred to as “molten metal” even if it is in a semi-molten state rather than a completely molten state) is low, so-called “burr”
This is suitable for high-speed and / or high-pressure injection, which is advantageous in improving productivity.

[0004]

However, in the case of the above-mentioned semi-solid injection molding method, the temperature of the molten metal is lower than that of the so-called cold chamber type die casting method. Also, the supply portion (injection nozzle) for supplying to the nozzle is usually set so that the inner diameter is reduced by narrowing the tip. For this reason, as the volume of the molding cavity increases, it becomes more difficult to uniformly fill the molten metal throughout the cavity, and this is generally disadvantageous particularly when a large-sized molded product having a certain size or more is manufactured.

[0005] In the present specification, (over a certain level)
"Large molded product" means that the maximum value (Da) when the diameter (D) of the circle circumscribing the projected view of the molded product is the maximum value (Da) is 300 [mm]. (Millimeters) or more. " If the size of the molded product is smaller than this, the molding condition is adjusted by appropriately 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. Although it is relatively easy to inject the molten metal uniformly over the entire cavity to obtain a sound molded product (that is, a high-quality molded product having few defects and predetermined mechanical properties), the size of the molded product is relatively easy. Is more than the above, it is generally difficult to stably obtain a sound molded product only by adjusting the temperature conditions, the injection conditions, and the like.

In the case of the semi-molten injection molding method, the molten metal of the injection nozzle is provided between the end of one (one shot) injection from the injection nozzle and the next (next shot) injection. The molten metal in the supply path is cooled, and a solidified portion (a so-called cold plug) or a high solid phase portion having a high solid phase ratio is generated at the nozzle tip side. And at the time of the injection of the next shot,
When the molten metal is injected and filled with the cold plug and the high solid phase portion included, local unevenness in the material structure of the molded product (that is, the solid phase ratio is lower than that of the surrounding portion) Portion that is higher than a certain level), and the mechanical properties thereof are greatly impaired.

[0007] In this specification, the term "solid phase" refers to "a portion which is not melted and remains in a solid state when the molten metal is in a semi-molten state". Refers to "a part which is completely melted and is in a liquid state". By observing the solidified structure of the molded article after injection, the “solid phase” is referred to as a “part that has been maintained in a solid state without being melted in a semi-molten molten metal state”. It was completely melted and in a liquid state. ''
The liquid phase part can be easily identified. When the molded article is referred to as a “solid phase”, it refers to “a part that was maintained in a solid state without being melted in a semi-molten molten metal (solid phase)”. Further, in the present specification, the “solid phase ratio” refers to “the ratio of the solid phase to the entire molten metal (solid phase + liquid phase) in the metal melt in a semi-molten state”. By observing, the ratio (area ratio) of the portion that was the “solid phase” to the entire observation region can be obtained numerically.

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

For this reason, for example, Japanese Patent Application Laid-Open No. 9-38758
As shown in the publication, a concave portion (a so-called plug catcher) is provided in a portion facing an injection nozzle of a molding die, and when the molten metal is injected from the injection nozzle into the molding die, the injection is mainly performed. The cold plug and the high solid phase portion existing on the tip side of the nozzle are captured and stored in the plug catcher, so that the material due to the mixing of the cold plug and the high solid phase portion in the molded product of the next shot is obtained. It is conceivable to prevent the occurrence of local unevenness on the tissue. However, even in this case, the effect of preventing the cold plug and / or the high solid phase portion from being mixed has a large difference depending on how the size and the like of the plug catcher are set.

Further, when the molded product has a thick portion having a larger thickness than the surrounding portion, a so-called "shrinkage" occurs when the molten metal solidifies in the partially thick portion. Therefore, there is a problem that a defect of a shrinkage cavity easily occurs in the obtained molded article.

In the semi-solid injection molding method, it is very important to ensure 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 molded product" of a certain size or more, as described above, it is difficult to uniformly inject and fill the molten metal throughout the molding cavity. This has a direct effect on the quality of the product.

The fluidity of the molten metal can be increased by, for example, increasing the temperature of the mold (mold temperature). However, even if the fluidity of the molten metal is ensured only by adjusting the mold temperature, a good molded product can be obtained. It is generally difficult to get. That is, when the fluidity of the molten metal is ensured by increasing the mold temperature, there is a problem in terms of production efficiency that the molding cycle time is generally increased because solidification of the molten metal takes much longer time. If the value is too high, there is a fear that inconveniences such as an increase in “burrs” or an increase in the tendency of the molten metal to leak from the mating surface of the molding die may occur.

It is considered that the fluidity of a molten metal in a semi-molten state is greatly affected by the solid fraction of the molten metal. This solid fraction is obtained as a result of incorporating various injection molding conditions including temperature conditions such as a cylinder temperature and / or a mold temperature of an injection molding machine, as apparent from the above definition. Therefore, if the quality of the fluidity 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 is possible to reliably obtain a required molten metal fluidity under suitable injection molding conditions without excessively increasing the mold temperature.

However, when the relationship between only the solid fraction and the flow length is actually examined, as shown in the graph of FIG. 14, the solid fraction changes (changes between about 2-45 [%]). The change in the flow length [m] (meter) in the case of being made was extremely irregular, and no significant correlation was observed between the two.

The present invention has been made in view of the above-mentioned problems in molding a metal member by a semi-solid injection molding method, and is intended to provide a required molten metal flow under suitable injection molding conditions without excessively increasing the mold temperature. Properties can be reliably obtained, and the incorporation of a cold plug and / or a high solid phase portion into a molded product can be more effectively prevented, and furthermore, the occurrence of shrinkage cavities in a thick portion can be effectively prevented. The purpose is to be.

[0016]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above technical problems, and as a result, have considered not only the solid phase ratio of the molten metal in the semi-molten state but also the average solid phase diameter. By using the index as a combination of the two (specifically, using the product multiplied by the two as an index), a high correlation is obtained between the index and the fluidity (flow length) of the molten metal. In addition, it has been found that by devising the setting of the depth and diameter of the plug catcher, it is possible to more reliably obtain a high effect of 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" refers to "the average value of the diameters of equivalent circles of portions of a semi-molten metal that are not melted and remain in a solid state". . This “average solid phase diameter” is obtained by observing the solidification structure of the molded article after injection, and calculating the “average of the equivalent circle diameter of the portion of the semi-molten metal that was not melted and maintained in the solid state. Value can be measured.

Therefore, the method of injection molding a metal member according to the invention of claim 1 of the present application (hereinafter referred to as the first invention) is a method of injection filling a molten metal in a semi-molten state from an injection nozzle into a molding cavity of a molding die. A method of injection molding a metal member to obtain a molded product, wherein the product of the solid phase ratio (Fs [%]) of the molten metal in the semi-molten state and the average solid phase diameter (ds [μm]) is obtained. Fs × ds) is set to be 4000 or less, and injection molding is performed.

The reason why the upper limit of the product (Fs × ds) of the solid phase ratio Fs and the average solid phase diameter ds is set to 4000 is that if 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 invention according to claim 2 of the present application (hereinafter referred to as “the invention”)
According to the second aspect, in the first aspect, the molded product is formed by projecting the diameter (D) of a circle circumscribing the projected view to the maximum value (Da). D
a) is not less than 300 [mm] (millimeter).

Here, 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, it does not correspond to the "large molded article" in the present application). In this case, the molten metal is uniformly injected over the entire molding cavity by appropriately 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. Although it is relatively easy to obtain a sound molded product (that is, a high-quality molded product having few defects and having predetermined mechanical properties) by filling, the maximum value Da of the circumscribed circle of the molded product is 300. In the case of [mm] or more (that is, in the case of “a large-sized molded product” in the present application), it is generally difficult to stably obtain a healthy molded product only by adjusting the temperature conditions and the injection conditions. by.

Further, the invention according to claim 3 of the present application (hereinafter referred to as "the invention")
According to a third aspect of the present invention, in the first or second aspect, a concave portion having a predetermined diameter (φ) and a predetermined depth (h) is formed at a portion facing the injection nozzle of the molding die. Injection molding is performed by setting the ratio (h / φ) of the depth (h) to the diameter (φ) to be 0.5 or more.

Here, the reason why 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 is that the value of this ratio (h / φ) Is 0.
In the range of less than 5, the cold plug and / or the high solid phase portion cannot be effectively captured and stored by the plug catcher, and the inclusion of these causes the solid structure ratio in the molded article to be particularly high as compared with other materials. This is because a uniform portion occurs.

Further, the invention according to claim 4 of the present application.
(Hereinafter, referred to as a fourth invention) is a method according to any one of the first to third inventions, wherein the molded article has a thick portion having a greater thickness than a surrounding portion, and the molding cavity has A thick-walled molding portion corresponding to the thick-walled portion is provided, and after injecting and filling the molten metal into a molding cavity, before solidifying the molten metal, partially pressurizing the thick-walled molding portion. It is a characteristic.

Further, the invention according to claim 5 of the present application.
(Hereinafter referred to as a fifth invention) is characterized in that, in any one of the first to fourth inventions, a light metal melt is used as the metal melt.

[0026]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding apparatus for performing injection molding of a metal member according to the present embodiment. As shown in the figure, the injection molding apparatus 1 is a so-called screw type, which has a nozzle 4 at a tip end and a heater 4 arranged on the outer periphery.
, A screw 6 rotatably supported in the molding machine main body 5 connected to the cylinder 2 and the cylinder 2, and a rotation driving device that includes, for example, a motor mechanism and a reduction mechanism, and drives the screw 6 to rotate. 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 main body 5. Although not specifically shown, a high-speed injection mechanism for advancing the screw 6 toward the nozzle 3 is provided in the molding machine main body 5. This high-speed injection mechanism advances the screw 6 at a predetermined timing,
When the screw 6 retreats by a preset distance, it is detected that the rotation of the screw 6 is stopped and the retreat operation is also stopped at the same time.

In the injection molding apparatus 1, the position of the inner passage of the nozzle 3 and the runner 12 connected to the molding cavity 11 are set so as to communicate with each other. Used. The raw material charged into the hopper 8 and stored therein is measured in a predetermined amount by a feeder 9 and supplied into the molding machine main body 5.
Is fed into the heated cylinder 2 by the rotation of.
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, a metal melt in a semi-molten state lower than the melting point of the raw material is obtained by such a process.

As the molten metal in the semi-molten state thus obtained is pushed out of the screw 6, the screw 6 moves backward by the pressure. As another method, the screw may be forcibly retracted at a desired speed. When the screw 6 retreats by a preset distance, the high-speed injection mechanism (not shown) in the molding machine main body 5 detects this and stops the rotation of the screw 6 and at the same time stops the retreat operation. The measurement of the raw material may be performed by setting the retreat distance of the screw 6.

Then, the screw 6 that has stopped rotating and is in the retracted position is advanced by a high-speed injection mechanism (not shown) and is pushed out by a predetermined force, so that the molten metal in a semi-molten state enters the mold 10 from the nozzle 3. Be injected. That is, the molten metal is injected and filled into the molding cavity 11 from the nozzle 3 through the runner portion 12. In the present embodiment, a magnesium (Δg) alloy, which is a kind of light metal, is used as a raw material, and is supplied to the hopper 8 of the injection molding apparatus 1 in the form of, for example, chip-shaped pellets. An inert gas (for example, argon gas) is more preferably provided in a 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 molding a metal member by the semi-solid injection molding method, it is possible to reliably obtain the required molten metal fluidity under suitable injection molding conditions without excessively increasing the mold temperature. In order to make it possible to prevent the cold plug and / or the high solid phase portion from being mixed into the molded product more effectively, it is also effective to reduce the occurrence of shrinkage cavities in the thick portion. Various tests were conducted in order to prevent this. 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 performed to examine the fluidity of a molten metal in a semi-molten state will be described.
2 and 3 are explanatory views schematically showing a molding cavity in a test die which is a part of a test device for examining a flow length of a molten metal in semi-solid injection molding. As shown in this figure, the molding cavities 21 used in this test were used.
Is formed by folding a passage having a predetermined cross-sectional shape (a rectangular cross-sectional shape having a thickness of 3 millimeters (mm) and a width of 20 millimeters (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,
The molten metal is injected into the molding cavity 21, and when the molten metal reaches at least from the cavity entrance 21a to the vertex 21p of the first U-shaped curve, the obtained molded product is surrounded by a circle 23 circumscribing the projection. The maximum value Da when projected so that the diameter becomes the maximum value Da is 3
It is a thing of 00 [mm] (mm) or more, that is, a “large-sized molded product” referred to in the present application.

A so-called plug catcher 22 is provided at the mold portion immediately adjacent to the cavity inlet 21a. As will be described in detail later, the plug catcher 22 is a concave portion provided at 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 housed therein. By providing such a plug catcher 22, it is possible to prevent local unevenness in the material structure due to the inclusion of the cold plug and / or the high solid phase portion in the molded product.

Then, an injection nozzle is set at a position facing the plug catcher 22, and the molten metal in a semi-molten state is injected, whereby the molten metal is formed into a passage-shaped molding cavity 21 by a length corresponding to its fluidity. Will be filled. Therefore, after the molten metal is solidified, the fluidity of the injected molten metal is compared by comparing the length of the metal-filled portion of the molding cavity 21 (ie, the length of the injection-molded body). Pass / fail can be evaluated.

In this test 1, taking into account not only the solid fraction of the molten metal in the semi-molten state but also the average solid phase diameter, an index combining the two (specifically, the “product” multiplied by both) and the metal The relationship between the fluidity (fluid length) of the molten metal was examined. During this test, the mold temperature was kept at 200 ° C. If the mold temperature is at this level, there is no danger that burrs will be excessive or the molten metal will easily leak from the mold mating surface. And the molding cycle time is not excessively long.

The test results are as shown in the graph of FIG. 12. For each of the alloys A and B, the solid phase ratio (Fs [%]) of the molten metal in the semi-molten state and the average solid phase diameter (Fs [%]) were obtained. It has been found that there is a high correlation between the product (ds [μm]) (Fs × ds) and the flow length of the molten metal.
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 an injection-molded molded body. Also, for any of the materials, a graph (Fs × ds) of the product of the solid phase ratio (Fs [%]) and the average solid phase diameter (ds [μm]) is set on the horizontal axis, and the flow length is set on the vertical axis. 12), a so-called inflection point appears. When the product (Fs × ds) is equal to or less than a certain value (4000 or less), a relatively long flow length (a flow length of about 1 m or more) can be stably secured. The product (Fs × ds) is 4
When it exceeds 000, it was found that the drop in the flow length became remarkable. In addition, if the flow length is about 1 m or more, a sound molded product can be obtained without any trouble as long as it has a certain size, even when molding the "large molded product" referred to in the present application. The above-described test for examining the relationship between only the solid fraction and the flow length (see FIG. 14) was performed using a sample alloy B at a mold temperature of 200 ° C. using the same test apparatus as in the first test. Things.

As described above, taking into account not only the solid phase ratio Fs of the molten metal in the semi-molten state but also the average solid phase diameter Fd, the index is a combination of both (specifically, the product (Fs × Fd) ”as an index), it was found that a high correlation was obtained between this index and the fluidity (flow length) of the molten metal. Then, this index (Fs × F
By setting the suitable condition range using d), it is possible to reliably obtain the required molten metal fluidity under suitable injection molding conditions without excessively increasing the mold temperature. That is, by performing injection molding while setting the product (Fs × ds) of the solid phase ratio Fs and the average solid phase diameter ds to be 4000 or less, required fluidity (flow length of about 1 m or more) is obtained. It can be secured stably. In addition, if the flow length is about 1 m or more, even when molding the “large molded article” referred to in the present application,
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 ratio Fs of the molten metal in the semi-molten state and the average solid phase diameter ds is not more than a predetermined value (4000 or less according to the present test) is, for example, as follows. This is performed as follows. That is, for a certain material, using a certain injection molding apparatus, 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 are variously adjusted and adjusted. Molding is performed, the solidified structure of each molded product obtained by injection molding is observed, and the product (Fs × ds) of the solid 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 so that the product (Fs × ds) of the solid phase ratio Fs and the average solid phase diameter ds is equal to or less than a predetermined value. This makes it possible to set conditions for performing injection molding on the material using the injection molding apparatus. If the material and / or the injection molding device is different, it is only necessary to collect data again and set conditions.

<Test 2> Next, Test 2 performed to examine the relationship between the depth and the diameter of a so-called plug catcher for mixing a cold plug and / or a high solid phase portion into a molded article will be described. FIG. 4 and FIG. 5 show an example in which a so-called “flesh” is attached to a molded work Kw that has been injection-molded using the above-described injection molding apparatus 1, that is, a plate-shaped molded work Kw. A 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. FIG. FIG. 6 is an enlarged sectional explanatory view showing 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 molten metal in a semi-molten state remains in the internal passage 3H of the nozzle 3, but the remaining molten metal is cooled down with the passage of time, and as can be clearly understood from FIG. Part of it solidifies by the next cycle (next shot) (solidification part: so-called cold plugМ)
p) or a high solid phase portion Δs having a high solid phase ratio. Since this cooling usually occurs from the nozzle tip side where the temperature is low,
In the internal passage 3H of the nozzle 3, a solidified portion {p (cold plug)} and a high solid phase portion {s} are arranged in order from the tip side, followed by a molten metal in a semi-molten state with a normal solid fraction. become.

In the present test, a plug catcher is used to effectively prevent the injection and filling of the molten metal with the cold plug {p and / or the high solid phase portion} s included during the injection in the next cycle. Injection molding is performed by changing the value of the ratio (h / φ) of the depth h to the diameter φ of Jp,
Regarding the molded workpieces Kw obtained respectively, different portions (solid portion ratio measurement portions W1 and W1 in FIGS. 4 and 5)
The solid fraction in 2) was examined and compared.

The test results are as shown in the graph of FIG. 13. In the solid fraction measurement section W1 almost connected to the runner section Jr, even if the value of the ratio (h / φ) is low (h / φ = 0.2
Although the solid phase ratio is sufficiently low (about 5%) and is kept constant, the ratio (h / φ) is low in the solid phase ratio measurement unit W2 farthest from the runner Jr. Ba (h /
At φ = about 0.2 or less, the solid fraction is very high (about 25).
% Or more), and a slight change in the value of the ratio (h / φ) greatly changes the solid phase ratio. And this ratio (h /
When the value of (φ) is 0.5 or more, the solid fraction is also sufficiently low (about 5 mm) even in the solid fraction measuring section W2 farthest from the runner Jr.
%) And constant with respect to a change in the value of the ratio (h / φ).

This is because the value of the ratio (h / φ) of the depth h of the plug catcher Jp to the diameter φ of the plug catcher Jp is set to 0.5 or more so that 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 melted metal over time and, more preferably, the high solid phase portion に s, as shown by the broken line in FIG. By being reliably captured and stored, the molding work Kw
It is considered that this is because mixing into the inside 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 has been confirmed that the incorporation of a non-uniform portion on the material structure, which has a particularly high solid phase ratio in the molded product as compared with the others, can be prevented.

<Test 3> Next, Test 3 relating to a method for effectively preventing the occurrence of shrinkage cavities in thick portions will be described. FIGS. 8 to 10 show a molded workpiece Sw which is injection-molded using the above-described injection molding apparatus 1 and which has a so-called “flesh” as it is, that is, a molded article having a concave cross section and a predetermined thickness (thickness 5 mm). A runner corresponding portion Sr and a gate portion Q corresponding to the three runner portions Qr of the cavity Q formed by the mold R (the mold R1 + the mold R2) shown in FIG.
It is explanatory drawing which shows the compact S with the gate corresponding part Sg corresponding to g and the plug catcher corresponding part Sp corresponding to the plug catcher Qp connected. 8 shows a longitudinal section, FIG. 9 shows a front side, and FIG. 10 shows a back side. In each drawing, the unit of the number representing the dimension is millimeter ([mm]).

The molded workpiece Sw is, for example, a frame body of a seat, and has a rectangular shape with a length of 300 [mm] and a width of 400 [mm] in a front view. Corresponds to. When such a large molded product is injection molded, the runner portion Qr and the molding cavity Qw are connected via the gate portion Qg having a small opening (passage area), so that the molten metal filled in the molding cavity Qw is formed. Therefore, even if the volume of the molding cavity Qw is larger than a certain level, the inside of the molding cavity Qw can be uniformly filled with the molten metal.

The molded workpiece Sw is provided with a thick portion St (thickness 10 mm) which is thicker than a surrounding portion (thickness 5 mm) on a part of the back surface thereof. In the mold R, a pressing pin Pn for partial pressing is arranged at a position corresponding to the thick portion St of the molding cavity Qw, and the pressing pin Pn is arranged outside the mold R. The cylinder device Cy moves forward and backward. still,
The cylinder device Cy is electrically connected to a control unit (not shown) of the injection molding device 1 and moves the pressure pin Pn at a predetermined timing in accordance with a control signal from the control unit. ing.

The pressure pin Pn is connected to the molding cavity Qw
After the molten metal is injected and filled in the inside, the thick portion St is partially pressed with a predetermined pressure during the period from the start of solidification to the end thereof, thereby increasing the thickness. Department St
The purpose of the present invention is to prevent the occurrence of shrinkage cavities due to coagulation in the inside. In this test, the effect of preventing shrinkage cavities was examined by comparing the density of the thick portion St of the formed workpiece Sw between the case where the pressure pin Pn was operated and the case where partial pressurization was performed and the case where partial pressurization was not performed. Was. The density was measured not only at the portion P2 corresponding to the thick portion St, but also at the other three points P1, P3, and P4, as indicated by hatching in FIG. Table 2 shows the measurement results.

[0049]

[Table 2]

As can be seen from Table 2, when no partial pressure is applied, the density at the point P2 is lower than the density at the other three points, and the shrinkage cavities are liable to occur in the thick portion St. Was confirmed. Then, the thick portion St (measurement site P2
Point), the density of the portion is greatly increased in any of the alloy A and the alloy B, and the partial pressure by the pressing pin Pn is applied to the thick portion St. It was confirmed that it was extremely effective in preventing shrinkage nests from occurring.

Although the above embodiment is mainly concerned with the case where a "large molded product" is injection-molded, the present invention is not limited to such a "large molded product". The present invention can also be effectively applied to injection molding of a small-sized molded product. In the above embodiment,
Although the case where the Δg alloy is used as the injection material has been described, the present invention can be effectively applied to a case where another kind of metal (particularly, light metal) is used as the material. As described above, the present invention is not limited to the above embodiments, and it goes without saying that various changes or design improvements can be made without departing from the spirit of the present invention.

[0052]

According to the first aspect of the present invention, when forming a metal member by the semi-solid 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 is taken into consideration.
By using an index that combines the two (specifically, using the “product” as the index multiplied by both), a high correlation can be obtained between this index and the fluidity (flow length) of the molten metal. it can. Then, by setting a suitable condition range using this index (solid fraction × average solid diameter), the required molten metal fluidity can be ensured under suitable injection molding conditions without excessively increasing the mold temperature. Can be obtained. 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, required fluidity can be stably secured.

According to the second aspect of the present invention, basically the same effects as those of the first aspect can be obtained. In particular, for a "large molded product", that is, a molded product whose maximum value Da is 300 [mm] or more when the diameter D of a circle circumscribing the projected view is the maximum value Da, without any problem. A sound molded product can be obtained by injection molding.

Further, according to the third aspect of the present invention, basically the same effects as those of the first or second aspect can be obtained. In addition, a concave portion (plug catcher) having a predetermined diameter φ and a depth h is provided at a portion facing the injection nozzle of the molding die, and the ratio (h / φ) of the depth h of the plug catcher to the diameter φ is provided. Is set to 0.5 or more, the cold plug and / or the high solid phase portion can be effectively captured and stored by the plug catcher. In particular, it is possible to prevent the occurrence of a non-uniform portion on a high material structure.

Further, according to the fourth invention of the present application,
Basically, the same effect as any one of the first to third inventions can be obtained. In particular, since the molten metal is injected and filled into the molding cavity and before the molten metal is solidified, the thick molded part is partially pressurized. With regard to (1), the occurrence of defects due to shrinkage cavities can be effectively prevented.

Further, according to the fifth invention of the present application,
When performing semi-solid injection molding of a metal member using a molten metal of a light metal, the same effect as any one of the first to fourth inventions can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional explanatory view showing a schematic configuration of an injection molding apparatus 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.

FIG. 3 is an explanatory sectional view taken along line Y3-Y3 in FIG. 2;

FIG. 4 is an explanatory front view of a molded body according to Test 2.

FIG. 5 is an explanatory sectional view taken along line Y5-Y5 in FIG. 4;

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

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

8 is an explanatory longitudinal sectional view of a molded body according to Test 3, which is an explanatory sectional view taken along line Y8-Y8 in FIG. 9;

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

FIG. 10 is an explanatory rear view of a molded body according to Test 3.

FIG. 11 is an explanatory longitudinal sectional view of a mold apparatus 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 phase 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 a test result of a conventional test and showing a relationship between only a solid fraction and a flow length.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Injection molding apparatus 3 ... Nozzle 10, J ... Die 11 and 21 ... Molding cavity 23 ... Circumscribed circle Cy ... (Pressing) cylinder device Pn ... Pressing pin St ... Thick part Sw ... Molded workpiece

Claims (5)

[Claims] 1. A method for injection molding a metal member in which 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 molten metal in the semi-molten state is provided. Wherein the product (Fs × ds) of the solid phase ratio (Fs [%]) and the average solid phase diameter (ds [μm]) is set to be 4000 or less and the injection molding is performed. Injection molding method. 2. The molded product has a maximum value (Da) of 300 [mm] (millimeter) when projected so that the diameter (D) of a circle circumscribing the projected view becomes a maximum value (Da). The injection molding method for a metal member according to claim 1, wherein: 3. A concave portion having a predetermined diameter (φ) and a depth (h) is formed at a portion of the mold opposite to the injection nozzle, and the ratio of the depth (h) of the concave portion to the diameter (φ) is defined. (H
/ Φ) is set to be 0.5 or more, and the injection molding is performed. 4. The molded product has a thick portion having a thickness greater than that of a surrounding portion, and a thick molded portion corresponding to the thick portion is provided in the molding cavity. 4. The metal member according to any one of claims 1 to 3, wherein after thickening the molten metal into the molding cavity and before solidifying the molten metal, the thick molded portion is partially pressurized. Injection molding method. 5. The injection molding method of a metal member according to claim 1, wherein a light metal melt is used as the metal melt.