JP2001287012A - Method and apparatus for forming injection-formed material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a forming method for an injection-formed material so as to restrain the occurrence of internal defect (particularly, gas defect) in the case of injection-forming molten light metal in the semi-molten state at a temperature less than the melting point or the molten state at a temperature equal to or just above the melting point. SOLUTION: The flowing-in speed of the molten light metal into a cavity 12 is regulated to 1-30 m/s. The ratio Sq/Sw of the cross sectional area Sq in a gate part 13 and the maximum cross sectional area Sw of the cavity 12 in almost perpendicular direction to the molten metal flowing-in direction, is regulated to >=0.2 or >=0.8. As the other way, the ratio Pmax/Pmin of the pressure Pmax for pulling out a plug and the minimum value Pmin of the pressure acted to the molten light metal in the flowing-in process of the molten light metal into the cavity 12, is regulated to <=1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for molding an injection molded material.

[0002]

2. Description of the Related Art Casting is one of the most common methods for producing metal moldings. In such a casting method, the cycle time is short and the cost is low, so that the die casting method is particularly often applied to the production of automobile parts made of light metals such as aluminum and magnesium. However, the die casting method is a method in which a mist of molten metal is injected into a mold at a high speed to perform molding, and a large amount of air or the like is involved in the molding process. There is a disadvantage in that a large number of them cannot be obtained because they contain a large number.

Further, there is a forging method as another method for producing a metal molded material. In the forging method, a metal material such as a billet is set in a mold, and the metal material is hit into the mold to form a predetermined shape. Since a lattice defect (strain) is introduced into the molded product, the casting method is used. Thus, it is possible to obtain a molded article having higher strength than that of the above. However, in the forging method, the metal material is processed by raising the temperature to a high temperature. Further, since it is necessary to repeatedly apply a hit until the metal material has a predetermined shape, the processing efficiency is low. There is a disadvantage that a large number of molds are required and the cost is high.

In view of such circumstances, there is a casting and forging method configured to extract only the advantages of the casting method and the forging method, and there is a practical example of aluminum. Specifically, in the casting forging method, a forging material similar to a final molded product is manufactured by a casting method, and the forging material is processed by the forging method to finish the final shape. According to this method, a forging material close to the final product is manufactured in the casting process, and the finish forging can be simplified to only one process. A molded article can be obtained.

[0005] Incidentally, if internal defects such as gas defects and shrinkage cavities are present in the forged material before forging, the strength of the final product is reduced and the variation in the strength is increased. Accordingly, it is not appropriate to apply a material that generates a large amount of internal defects (particularly gas defects) in a forged material such as a die casting method as a casting process of the casting forging method, even though it is advantageous in terms of cost.

In this regard, Japanese Patent Application Laid-Open No. H11-10480 discloses
No. 0 discloses that an injection molding method having the same cost advantage as a die casting method is applied as a casting process.
% Of a solid / liquid phase coexisting in a semi-molten state or a molten state at a temperature just above the melting point, and then performing injection molding to produce a forged material excellent in forgeability. ing.

[0007]

However, even when the injection molding method is applied as a casting step in the casting forging method, the entrainment of air in the process of flowing the molten metal into the cavity is inevitable. If the number increases, a high-strength molded product cannot be obtained even by forging a molded forging material, and the advantages of the casting forging method cannot be utilized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to injection-mold a light metal melt in a semi-molten state below the melting point or in a molten state from the melting point to just above the melting point. An object of the present invention is to provide a method for molding an injection-molded material in which the occurrence of internal defects (particularly, gas defects) is suppressed.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to an injection molding method having the same cost advantage as a die casting method, by filling a light metal melt into a cavity in a state close to a relatively low-speed laminar flow. To prevent the occurrence of internal defects (gas defects and the like) in the injection molded material.

Specifically, the invention of the present application relates to a method for molding an injection-molded material by injection-molding a light metal melt in a semi-molten state below the melting point or in a molten state from the melting point to just above the melting point. The flow rate of the light metal melt into the cavity for forming the molten metal is 1 to 30 m / s.

According to the above construction, the molten light metal is a fluid having a high viscosity in a semi-molten state below the melting point or in a molten state from the melting point to just above the melting point.
Since the molten metal flows into the cavity at a velocity of 0 m / s, the molten metal flows into the cavity in a laminar flow or a state close to the laminar flow, and the entrainment of air due to the turbulent flow of the molten metal is effectively suppressed. A sound injection molded material with few internal defects (particularly gas defects) is molded. Specifically, it is possible to mold an injection molded material having a relative density of 95% or more.
Relative density is the percentage of the actual density of the injection molding material relative to the theoretical density of the injection molding material assuming that there are no internal defects.

Here, the reason why the inflow speed is set to 30 m / s or less is that if the speed is higher than 30 m / s, the molten metal becomes turbulent, and many internal defects are generated due to the entrainment of air in the injection molded material. Because. From such a viewpoint, it is preferable that the inflow velocity is 10 m / s or less, and in that case, an injection molded material having a relative density of 96% or more can be obtained. The reason why the inflow speed is set to 1 m / s or more is 1 m / s
If it is slower than s, the molten metal solidifies before it spreads over the entire cavity, resulting in poor filling.

[0013] The light metal refers to a low-density metal or alloy such as aluminum or magnesium, and specifically includes AZ91D standardized by ASTM.

[0014] The semi-molten state refers to a state in which a portion where the light metal as a raw material remains in a solid state and a portion where the light metal is melted to a liquid state coexist. This is a state obtained by heating to.

Another invention of the present application is a method for molding an injection-molded material in which a molten light metal is injection-molded in a semi-molten state lower than a melting point or in a molten state from a melting point to a temperature just above the melting point. The ratio Sg / Sw of the cross-sectional area Sg of the gate portion, which is the inflow port of the light metal melt, to the maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the melt inflow direction is 0.2 or more. It is characterized by the following.

According to the above configuration, the cross-sectional area S of the gate portion
Since g is relatively large with respect to the maximum cross-sectional area Sw of the cavity, the entanglement of air due to the turbulence of the molten metal flowing into the cavity after passing through the gate portion is effectively suppressed, and A sound injection molded material with few defects (especially gas defects) is formed.

Here, the reason why Sg / Sw is set to 0.2 or more is that if the value of Sg / Sw is smaller than 0.2, the molten metal is released from the narrow gate portion to the wide cavity, so that a turbulent state occurs, and the injection molding material is formed. This is because many internal defects are generated due to air entrapment. The relative density of the injection-molded material can be increased by increasing the ratio. However, when the ratio is 0.8 or more, the relative density of the injection-molded material can be maintained at a substantially high level. Note that this ratio is 1.0
If the cross-sectional area Sg of the gate portion is larger than the maximum cross-sectional area Sw of the cavity, no technical inconvenience occurs, but an excess molded body is generated in the gate portion, and the yield is poor. Problem arises.

Further, the cavity is defined as
The space for molding the injection molding material as a product
For example, the same applies to the case where the throttle portion of the molten metal flow path in the gate portion is not provided and the gate portion does not substantially exist. In this case, the flow path of the molten metal communicating with the cavity ( The boundary between the runner and the cavity is the gate.

[0019] Such a configuration has a cross-sectional area Sg of a gate portion which is an inflow port of a molten metal into a cavity of a mold mounted on an injection molding apparatus, and a maximum size of the cavity in a direction substantially perpendicular to a molten metal inflow direction. Ratio Sg to cross-sectional area Sw
This is achieved by setting / Sw to be 0.2 or more (preferably 0.8 or more).

In the case where Sg / Sw is set to 0.8 or more, a branch portion formed so that the molten metal is divided into a plurality of flow passages in a runner portion forming a supply passage of the molten metal to the cavity of the mold. Is preferably provided. When the gate portion is provided widely as in the case where Sg / Sw is 0.8 or more, no problem occurs in a semi-molten state molten metal having a large amount of solid components, but a semi-molten state or a molten state having a small amount of solid components is not produced. If the flow viscosity is low, such as molten metal, the molten metal will flow along the walls forming the cavity, the air in the cavity will be trapped, and a hollow part (casting defect) will occur in the molded injection molded material. There is. However, according to the above configuration, the flow of the molten metal flowing into the cavity is slightly disturbed at the branch portion, and the molten metal is filled in order from the gate portion, and the occurrence of such a hollow portion (casting defect) is prevented. Becomes Further, as means having the same effect, a constricted portion may be provided in the runner portion so that the cross-sectional area in a direction substantially perpendicular to the flow direction of the molten metal is smaller than that of the upstream portion and the downstream portion.

The above-described invention of the present application and other inventions of the present application may of course be configured independently, or may be configured to combine both.

Another invention of the present application is a method for molding an injection-molded material in which a light metal melt is injection-molded in a semi-molten state lower than a melting point or in a molten state from a melting point to a temperature just above the melting point. While the light metal melt used for the injection molding is stored in the cylinder front part of the injection molding apparatus, the light metal melt is connected to a plug provided in the cylinder front part and connected to a cavity for molding the injection molding material. A pressure Pmax acting on the light metal melt accumulated in the front portion of the cylinder to push and remove the cold plug formed by solidifying the light metal melt to close the plug so that it does not flow out during the injection molding.
And a minimum value Pm of the pressure applied to the light metal melt in the process of flowing the light metal melt into the cavity.
ax / Pmin is set to 10 or less.

In the injection molding method, the molten metal is injected when a predetermined amount of molten metal has accumulated in the front part of the cylinder. Until that time, the molten metal flows out of the nozzle provided in the front part of the cylinder. Need to be prevented. Therefore, while the molten metal is stored in the front part of the cylinder, the nozzle temperature is lowered and the nozzle is closed by a cold plug formed by solidification of the molten metal. When the molten metal is injected, pressure is applied to the collected molten metal. Then, the cold plug is pushed out and removed, and the molten metal is injected into the cavity of the mold. At this time, if the pressure applied to the molten metal to remove the cold plug (plug release pressure) is large, the molten metal flows into the cavity in a turbulent state immediately after the cold plug is released, and the air is entrained. Many internal defects occur in the material. However, according to the above configuration, the plug release pressure Pmax and the minimum pressure Pmi acting on the molten metal when the molten metal flows into the mold cavity are set.
Since the ratio Pmax / Pmin to n is set to 10 or less, it is possible to effectively prevent the occurrence of turbulent flow due to pressure fluctuation when the plug is pulled out, so that a sound injection-molded material with few internal defects (particularly gas defects) can be obtained. It will be molded.

Here, such a configuration is achieved by controlling the temperature of the plug, and requires cooling means such as circulating cooling water for lowering the temperature of the plug and heating means such as a heater for raising the temperature of the plug. In addition, since the nozzle comes into contact with the mold, heat is absorbed by the mold to lower the temperature, so that a heat insulating material or the like is desirably provided between the nozzle and the mold. It is even more preferable to use ceramics having a low density.

In each of the inventions of the present application, a light metal melt in a semi-molten state having a solid phase ratio of 10% or more, which is the volume percentage of the solid phase with respect to the volume sum of the solid phase and the liquid phase, is used. Is preferred. According to this configuration, the light metal melt becomes a fluid having a very high viscosity in a semi-molten state having a solid fraction of 10% or more, so that the flow of the melt into the cavity becomes a gentle laminar flow, and internal defects (particularly, gas defects) are caused. ), And a sound injection-molded material with little) is formed. Also,
Since the shrinkage that occurs when the melt solidifies is exclusively due to the shrinkage of the liquid phase, the amount of shrinkage when the melt solidifies is small, so that an injection molded material with good dimensional accuracy can be obtained and internal defects can be obtained. The number of shrinkage nests is reduced.

Here, the solid phase refers to a portion where the molten metal is in a semi-molten state and remains in a solid state without being melted, and the liquid phase is completely melted to be in a liquid state. The part that does. The solid phase is formed as a portion that has been maintained in a solid state without being melted in a semi-molten molten state, and the liquid phase is formed as a portion that has been completely melted and has been in a liquid state in a semi-molten molten state. By observing the pseudo-solid structure of the injection-molded material, each can be easily identified. Further, the solid phase ratio can be obtained numerically as an area ratio of the solid phase portion to the entire observation region, that is, a volume ratio, by observing the surface structure of the formed injection molded material.

The injection-molded material manufactured by each invention of the present application can be used as a material for plastic working such as forging. Like a non-closed forging process in which the forging space formed by the forging die is not completely closed, and at least a part of the forging material can be freely plastically deformed without being restricted by the forging die. In such a case, it is difficult to sufficiently crush internal defects in the forging process,
The injection-molded material manufactured according to the invention of the present application has very few internal defects, and can sufficiently crush internal defects even in non-closed plastic working such as non-closed forging. Of course, internal defects can be sufficiently crushed even if closed plastic working such as closed forging is performed.

In addition, since the injection-molded material manufactured by each invention of the present application has very few internal defects,
It can be used as it is as a primary product.

[0029]

According to the invention of the present application, a light metal melt is a fluid having a high viscosity in a semi-molten state below the melting point or in a molten state from the melting point to just above the melting point.
Flow into the cavity at a speed of ~ 30 m / s,
The molten metal is filled into the cavity in a laminar or near laminar flow form, and the entrainment of air due to the turbulent flow of the molten metal is effectively suppressed. Injection molding material can be molded.

According to another aspect of the present invention, since the cross-sectional area Sg of the gate portion is provided to be relatively large with respect to the maximum cross-sectional area Sw of the cavity, the molten metal flowing into the cavity passes through the gate. Entrainment of air due to the turbulent state is effectively suppressed, and a sound injection molded material having few internal defects (particularly, gas defects) can be formed.

According to another invention of the present application, the ratio Pmax / Pmin of the plug release pressure Pmax to the minimum pressure Pmin acting on the molten metal when the molten metal flows into the mold cavity.
Is set to 10 or less, whereby the occurrence of turbulent flow due to pressure fluctuation at the time of plug removal can be effectively prevented, so that a sound injection-molded material having few internal defects (particularly gas defects) can be formed. .

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Injection Molding Apparatus) FIG. 1 shows an injection molding apparatus 1 for molding a light metal injection molded material (forged material) according to this embodiment.

The injection molding apparatus 1 includes a main body 2, a screw 3 rotatably supported by the main body 2,
A rotary drive unit 4 for rotating the screw 3 disposed on the back of the cylinder 5, a cylinder 5 fixed to the main body 2 so as to surround the screw 3, and a predetermined pitch in the longitudinal direction on the outer periphery of the cylinder 5 Heater 6 arranged
And a hopper 7 into which the light metal raw material is charged and stored, a feeder 8 for measuring the light metal raw material in the hopper 7 and supplying the light metal raw material into the injection molding apparatus 1, and a mold 9 mounted on the tip of the cylinder 5. I have.

The body 3 has a screw 3 and a cylinder 5
An injection mechanism for advancing in the longitudinal direction is provided.
When the retreat distance of the screw 3 which retreats due to the pressure of the light metal melt sent forward becomes predetermined, the injection mechanism detects this and stops the rotation of the screw 3 and the retreat operation. Screw 3 at timing
Is advanced to inject the molten metal. The forward speed of the screw 3 is controllable, and
Flow rate of the molten metal into the cavity 12 of 1 to 30 m / s
Is controlled so as to fall within the range of.

A nozzle 10 is provided at the tip of the cylinder 5, and the molten metal stirred and kneaded in the cylinder 5 is injected into the cavity 12 through the nozzle 10. The injection of the molten metal into the cavity 12 is performed when a predetermined amount of the molten metal has accumulated in the front part of the cylinder 5. Therefore, it is necessary to prevent the molten metal from flowing out of the nozzle 10 until that time. Therefore, while the molten metal is stored in the front portion of the cylinder 5, the nozzle 10
When the molten metal is solidified, the nozzle 10 is closed by a cold plug formed by solidification of the molten metal. When the molten metal is injected, the temperature of the nozzle 10 is raised by a nozzle heater to melt the interface of the cold plug with the nozzle 10. The temperature of the nozzle 10 is controlled so that the molten metal is easily pushed out of the mold 9 side when the molten metal is injected. By this temperature control, it is possible to freely control the pressure (easiness of detaching the cold plug) applied to the molten metal, which is necessary for pushing out and removing the cold plug. In the injection molding apparatus 1, a pressure Pmax acting on the molten metal when the cold plug is extruded and removed, and a steady pressure Pmin acting on the molten metal when flowing the molten metal into the cavity 12 (this steady pressure becomes a minimum pressure). Is configured such that the ratio Pmax / Pmin of the above is 10 or less. In order to prevent the temperature of the nozzle 10 from being lowered by being absorbed by the mold 9, a heat insulating material is provided between the nozzle 10 and the mold 9, and the nozzle 10 is formed of ceramic.

The heater 6 provided on the outer periphery of the cylinder 5
Is divided into a plurality of zones so that the temperature increases as the cylinder 5 moves forward along the longitudinal direction, and the temperature is increased while the light metal material is conveyed forward in the cylinder 5 by the screw 3. In addition, the molten metal is controlled so as to be in a semi-molten state having a melting point lower than the melting point or a molten state at a melting point or just above the melting point at the front portion of the cylinder 5.

The hopper 7, the feeder 8, the cylinder 5, and the passage connecting them are filled with an inert gas (for example, Ar gas) to prevent oxidation of the light metal.

The mold 9 has a runner 11 for guiding the molten metal injected from the nozzle 10. The runner part 1
1 is formed in an L-shape which extends straight from the nozzle 10 of the cylinder 5 and then rises vertically, and a plug receiving portion 11a for receiving a cold plug detached from the nozzle 10 is provided at a corner thereof. ing. As shown in FIG. 2, the mold 9 includes a cavity 12 for forming a plate-shaped product having a width of 100 mm, a length of 170 mm, and a thickness of 10 mm, which communicates with the runner portion 11. Gate section 13 which forms a boundary with 11
And an overflow section 14 provided at a position away from the gate section 13 of the cavity 12 and for accommodating gas in the cavity 12 replaced by the molten metal.

The gap between the cavity 12 and the runner section 11 is formed to be 10 mm, and the gap between the gate section 13 is 2 mm.
(In FIG. 2, the gate portion 13 is formed).
Is 2 mm). Here, the gap of the gate portion 13 is 2 to
10 mm, the cross-sectional area Sg of the gate portion is 200
～1000Mm ² becomes, since the horizontal cross-sectional area Sw of the cavity 12 is 1000 mm ^2, Sg / Sw 0.2
-1.0. Here, Sg / Sw = 1.0 means that the cross-sectional area of the gate portion 13 is equal to the cross-sectional area of the cavity 12, and the gate portion 13 has no protrusion serving as a narrow portion of the molten metal flow path. Means And this Sg /
By setting Sw in the range of 0.2 to 1.0, the flow rate of the molten metal into the cavity 12 can be controlled. The control can also be performed by a combination with the forward speed of the screw 3. (Injection Molding Method) Next, an injection molding method for light metal using the above-described injection molding apparatus 1 will be described.

First, a chip-shaped light metal (eg, Mg-A
1 alloy) as a raw material into the hopper 7 of the injection molding apparatus 1. The supplied light metal chips are measured in a predetermined amount by the feeder 8 and supplied into the injection molding apparatus 1.

Next, the light metal chips are fed into the heated cylinder 5 by the rotation of the screw 3 and heated to a predetermined temperature while being sufficiently stirred and kneaded by the rotation of the screw 3 inside the cylinder 5. As a result, the light metal tip has a solid fraction of 10% below the melting point.
The light metal melt in the above semi-molten state is obtained.

The molten metal thus obtained is pushed forward by the screw 3 and stored in the front part of the cylinder 5, and the screw 3 retreats due to the pressure of the collected molten metal. At this time, the temperature of the plug provided in the cylinder 5 is lowered, so that the plug is closed by a cold plug formed by solidifying a part of the molten metal, and the molten metal flows out of the cylinder 5 through the plug. To prevent

When the screw 3 retreats by a predetermined distance, the injection mechanism of the main body 2 detects this and stops the rotation and retreat operation of the screw 3. At this time, the molten metal for one shot is stored in the front part of the cylinder 5.

By raising the temperature of the nozzle 10 with the nozzle heater, the interface of the cold plug with the nozzle 10 is melted, and the screw 3 is advanced by the injection mechanism to apply the pressure Pmax to the molten metal. The cold plug is pushed out to the mold 9 side and removed, and the molten metal injected from the nozzle 10 flows into the cavity 12 at a steady pressure Pmin (this steady pressure becomes the minimum pressure). At this time, control is performed so that Pmax / Pmin becomes 10 or less. This control is performed by the nozzle 10 when the molten metal is injected.
This is achieved by controlling the temperature of Further, control is performed so that the inflow speed of the molten metal into the cavity 12 is 1 to 30 m / s (preferably 10 m / s or less). In this control, the forward speed of the screw 3 is set within an appropriate range, or the ratio Sg / Sw of the sectional area Sg of the gate portion 13 of the mold 9 to the sectional area Sw of the cavity 12 is set to 0.2 to 1. 0
Or a combination thereof. The removed cold plug is held by the plug receiving portion 11a of the runner portion 11.

Finally, after the molten metal has solidified, the mold 9 is opened, and the formed injection molded material is taken out.

The removed injection-molded material is subjected to forging as a forged material, and then subjected to a heat treatment such as T6.

According to the method of manufacturing an injection-molded material having the above structure, the molten light metal is a semi-molten liquid having a high viscosity in a semi-molten state below the melting point, and the molten metal flows into the cavity 12 at a speed of 1 to 30 m / s. Therefore, the molten metal flows into the cavity 12 in a laminar flow or a state close to the laminar flow,
Since the entrainment of air due to the turbulence of the molten metal is effectively suppressed, a sound injection-molded material having few internal defects (particularly, gas defects) is formed.

Further, since the cross-sectional area Sg of the gate portion 13 is provided to be relatively large with respect to the maximum cross-sectional area Sw of the cavity 12, the molten metal flowing into the cavity 12 becomes turbulent after passing through the gate. As a result, the entrainment of air is effectively suppressed.

Further, the ratio Pmax / Pmin between the plug release pressure Pmax and the minimum pressure Pmin that acts on the molten metal when the molten metal flows into the cavity 12 is set to 10 or less, so that turbulent flow is generated due to pressure fluctuation when the plug is removed. Can be effectively prevented.

Then, as a light metal melt in a semi-molten state,
Since a solid phase ratio of 10% or more is used, the flow of the molten metal into the cavity 12 becomes a gentle laminar flow. In addition, the amount of shrinkage when the molten metal solidifies becomes small, so that an injection molded material having good dimensional accuracy can be obtained, and shrinkage cavities forming internal defects are reduced.

Further, the injection-molded material manufactured in the present embodiment has extremely few internal defects, and can sufficiently crush internal defects even in non-closed plastic working such as non-closed forging. (Other Embodiments) In the above embodiment, the light metal tip is heated so as to be in a semi-molten state having a solid fraction of 10% or more, but may be heated to a melting state from a melting point to a temperature just above the melting point.

When Sg / Sw is set at 0.8 or more, as shown in FIG.
A mold C provided with a branch portion 11b such as a partition between the two may be used so that the molten metal colliding with the branch portion 11b branches and flows into the cavity 12 from the gate portions 13 on both sides. When the gate portion 13 is provided widely, in the case where the flow viscosity is low, such as a molten metal in a semi-molten state or a molten state having a small solid component, the molten metal flows along the wall surface forming the cavity 12, Cavity 12
The inside air is trapped, and a hollow part (casting defect) may occur in the formed injection molded material. However,
By providing such a branch portion 11b, the flow of the molten metal flowing into the cavity 12 is slightly disturbed in the branch portion 11b, and the molten metal is filled in order from the gate portion 13, so that such a hollow portion (casting defect) is generated. Will be prevented.

Also, as shown in FIG. 4, the same effect can be obtained in a mold D in which a branch portion 11b formed in a substantially triangular shape is provided in a liner portion.

Further, as shown in FIG.
In addition, the constricted portion 1 is formed so that the cross-sectional area in a direction substantially perpendicular to the flow direction of the molten metal is narrower than the upstream portion and the downstream portion.
The same effect can be obtained also in the mold E provided with 1c.

In this embodiment, the molten metal flows from the single liner portion 11 into the cavity 12. However, the present invention is not limited to this. The molten metal flows into the cavity 12 from a plurality of liners. You may make it do.

In this embodiment, the injection molded material is provided as a forging material for forging, but may be used as it is as a primary product.

[0057]

EXAMPLES (Test Evaluation 1) A test evaluation was performed on the relationship between the relative density of an injection-molded injection-molded material and the strength of a forged material obtained by forging an injection-molded material (forged material). <Test Evaluation Method> Using an injection molding apparatus (model: JLM-450E, manufactured by Nippon Steel Works Co., Ltd.) with a mold clamping force of 4.4 × 10 ⁶ N equipped with the mold A having the configuration shown in FIG.
100 mm wide and 170 mm long from alloy A whose composition is shown in Table 1.
A metal plate-like injection molded material having a thickness of 10 mm and a thickness of 10 mm was injection molded under various conditions. At this time, the temperature of the molten metal was controlled so that the solid phase ratio of the molded injection molded material was 10%, and the solid phase ratio was confirmed by image analysis of the surface of the molded injection molded material. Here, the alloy A is AZ91D according to the ASTM standard.

Next, from the upper part (overflow part side) and lower part (gate part side) of each injection molded material, FIG.
As shown in Table 1, a total of six square plates each having a side of 33 mm were cut out, and the densities of the square plates were measured by Archimedes' method and averaged. The average value of the density was divided by the theoretical density considered to be measured when the same shape was completely filled with the alloy A, and the result was multiplied by 100 to obtain a relative density. That is, 1
The difference between 00 and the relative density is the internal defect rate.

Further, a block-shaped forging material having a width of 10 mm, a length of 35 mm and a thickness of 21 mm as shown in FIG. 7A is cut out from each injection-molded material, and is constrained in the width direction. As shown in FIG. 7B, forging was performed from a thickness of 21 mm to a half of 10.5 mm to obtain a forged material (forging rate: 50%). Then, a heat treatment of T6 (a heat treatment at 410 ° C. for 16 hours as a solution treatment) followed by a aging treatment at 170 ° C. for 16 hours.
Heat-treated for a period of time and air-cooled), and then a tensile test was performed on each forged material.

[0060]

[Table 1]

<Test Evaluation Results> FIG. 8 shows the relationship between the relative density of each molded injection molded material and the tensile strength of the forged material after forging. According to the figure, it is understood that when the relative density of the injection-molded material becomes 95% or less, the tensile strength of the forged material is greatly reduced. This means that even if forging is performed, a high-strength forged material cannot be obtained unless a material with small internal defects (a material with a high relative density) is used as the injection-molded material. It is. (Test Evaluation 2) Test evaluation was performed on the relationship between the flow rate of the molten metal into the cavity during injection molding and the relative density of the injection-molded material. <Test evaluation method> As a mold for molding a metal plate-like injection molded material having the same shape as the test evaluation 1, the cross-sectional area Sg of the gate portion, which is the inlet of the molten metal into the cavity, and the cross-sectional area Sw of the cavity. A with the ratio Sg / Sw of 0.2
(See FIG. 2) and a mold B having the same configuration as the mold A except that Sg / Sw was set to 1.0.

Next, for each of the mold A and the mold B, the screw speed was varied by three levels, and a metal plate-like injection molded material having the same shape as that of the test evaluation 1 was injection-molded with the alloy A. At this time, the inflow speed of the molten metal was measured at the gate portion in the case of the mold A, and in the portion of the mold B where the flow path diameter was large in the runner portion. Further, the temperature of the molten metal was controlled so that the solid phase ratio of the molded injection-molded material was 0 to 5%, and the solid phase ratio was confirmed by image analysis of the surface of the molded injection-molded material.

Then, similarly to the test evaluation 1, the density of each molded injection-molded material was measured, and the relative density was calculated. <Test Evaluation Results> FIG. 9 shows the relationship between the melt inflow rate into the cavity and the relative density of the injection molded material. According to the figure, it can be seen that when the flow rate of the molten metal into the cavity exceeds 30 m / s, the relative density of the injection-molded material rapidly decreases. This is because when the inflow speed increases, the inflow of the molten metal into the cavity becomes a turbulent state, and air is entrained, so that many internal defects occur in the injection molded material. Conceivable. When the inflow velocity of the molten metal is 10 m / s or less, the relative density becomes 95 even at a low solid phase ratio.
It can be seen that more than 100% of the injection molded material can be injection molded. However, the molten metal inflow speed is 1 m /
Below s, the molten metal did not reach the entire cavity, resulting in poor filling. (Test Evaluation 3) Test evaluation was performed on the relationship between the solid phase ratio and the relative density of the injection-molded injection-molded material. <Test Evaluation Method> The temperature of the molten metal was varied, that is, the solid phase ratio was varied, and a metal plate-like injection molded material having the same shape as that of the test evaluation 1 was injection-molded with the alloy A. Here, the mold B used in Test Evaluation 2 was used. The flow rate of the molten metal into the cavity was 10 m / s. Further, the solid phase ratio was confirmed by image analysis of the surface of the injection molded material.

Then, as in the test evaluation 1, the density of each injection-molded material was measured, and the relative density was calculated. <Test Evaluation Results> FIG. 10 shows the relationship between the solid fraction and the relative density of the injection molded material. According to the figure, it can be seen that a higher relative density can be obtained by injection molding with a molten metal in a semi-molten state. Specifically, it can be confirmed that a high relative density can be stably obtained when the solid phase ratio is 10% or more. This is considered to be because the molten metal in a semi-molten state having a solid fraction of 10% or more is a fluid having a very high viscosity, and the molten metal flows into the cavity in a gentle laminar flow. Further, even when the solid phase ratio is 10% or more, the relative density is not improved and does not become 100%. This is considered to be because shrinkage cavities are necessarily generated in the injection molded material. (Test Evaluation 4) A test evaluation was performed on the relationship between Sg / Sw and the relative density of the injection molded material. <Test Evaluation Method> Sg / Sw was varied by 5 levels, and a metal plate-like injection molded material having the same shape as that of Test Evaluation 1 was injection-molded with alloy A. Here, the molten metal inflow speed into the cavity was 20 m / s. Further, the temperature of the molten metal was controlled so that the solid phase ratio of the molded injection-molded material was 0 to 5%, and the solid phase ratio was confirmed by image analysis of the surface of the molded injection-molded material.

Then, as in Test Evaluation 1, the density of each molded injection-molded material was measured, and the relative density was calculated. <Test Evaluation Results> FIG. 11 shows the relationship between Sg / Sw and the relative density of the injection molded material. According to FIG.
It can be seen that when the value is smaller than 2, the decrease in the relative density of the injection molded material increases. Further, it can be seen that when Sg / Sw is 0.8 or more, the relative density of the injection-molded material can be maintained at a substantially high level. (Test evaluation 5) A test evaluation was made on the relationship between the ratio Pmax / Pmin of the plug release pressure Pmax and the minimum value Pmin of the pressure applied to the molten metal in the process of flowing the molten metal into the cavity, and the relative density of the injection molded material. Was. <Test evaluation method> Pmax / Pmin was changed by 5 levels by changing the temperature of the nozzle during injection molding, and an alloy B having the composition shown in Table 1 was used to form a metal plate-like injection molded material having the same shape as Test Evaluation 1. Injection molded. Here, the mold B used in Test Evaluation 2 was used. The flow rate of the molten metal into the cavity was 20 m / s. Further, the temperature of the molten metal was controlled so that the solid phase ratio of the formed injection molded material was 0 to 5%, and the solid phase ratio was confirmed by image analysis of the surface of the formed injection molded material. <Test Evaluation Results> FIG. 12 shows the relationship between Pmax / Pmin and the relative density of the injection molded material. According to the figure, Pmax / Pm
It can be confirmed that the relative density of the injection molded material decreases as in increases. Specifically, if Pmax / Pmin is larger than 10, the relative density will be lower than 90%. This is because if Pmax is larger than Pmin, the molten metal will flow into the cavity in a turbulent state immediately after the cold plug comes off, and air will be trapped,
This is considered to be because the molded injection-molded material has many internal defects.

That is, as shown in FIG. 13 (a), when the temperature of the nozzle is low, the pressure acting on the molten metal increases until the cold plug comes off (Pmax), and when the cold plug comes off, the pressure drops at once. To a steady state (Pmi
n). Then, the injection speed of the molten metal shows a temporary peak after the cold plug comes off, and thereafter changes to increase toward a predetermined value. Therefore, in this case, the flow rate of the molten metal rapidly changes up and down, so that the flow of the molten metal becomes turbulent, entrains air, and flows into the cavity. On the other hand, as shown in FIG. 13 (b), when the temperature of the nozzle is high, the pressure acting on the molten metal changes constantly because the cold plug easily comes off the nozzle. Then, the injection speed of the molten metal changes so as to gradually increase. Accordingly, in this case, the flow velocity of the molten metal does not fluctuate rapidly up and down, and the flow of the molten metal flows into the cavity as a laminar flow. (Test Evaluation 6) Test evaluation was performed on the relationship between the difference in the shape of the runner portion of the mold and the casting defect generated in the formed injection molded material. <Test evaluation method> Die C used in Test Evaluation 2 and Die C having the same configuration as Die B except that a branch portion serving as a partition between the runner portion and the cavity was provided as shown in FIG. And FIG.
As shown in FIG. 5, a mold D having the same configuration as the mold B except that a branch portion having a substantially triangular shape is provided in the runner portion, and a mold B having a constricted portion in the runner portion as shown in FIG. A mold E having the same configuration was prepared.

Using the respective molds, a metal plate-like injection molding material having the same shape as that of the test evaluation 1 was injection-molded with the alloy B. Here, the molten metal inflow speed into the cavity is 20 m / s
And Further, the solid phase ratio of the molded injection molded material is 0 to 5%.
The temperature of the molten metal was controlled so that the solid phase ratio was confirmed by image analysis of the molded product. That is, as the molten metal to be injection molded, one having a low solid phase ratio and a low flow viscosity in a semi-molten state was used.

Then, the cross section on the gate side of each injection molded material was observed. <Test Evaluation Results> FIGS. 14A to 14D show molds B to E.
Each shows a cross-sectional photograph of a gate side of a metal plate-shaped injection molded material molded in the above.

As shown in FIG. 14A, a hollow portion (a casting defect) can be observed in the cross section of the injection-molded material formed using the mold B. This is considered to be caused by the flow of the molten metal along the wall surface forming the cavity, thereby trapping air in the cavity. On the other hand, as shown in FIGS.
Such a hollow portion is not observed in an injection molded material molded by using the method. This is considered to be because the flow of the molten metal was slightly disturbed at the branch portion or the constricted portion in the runner portion, and the molten metal was filled in order from the gate portion.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an injection molding apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an internal configuration of a mold (mold A) of the injection molding apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing an internal configuration of a mold C;

FIG. 4 is a diagram showing an internal configuration of a mold D.

FIG. 5 is a diagram showing an internal configuration of a mold E;

FIG. 6 is an explanatory plan view related to sampling of a density measurement sample from a plate-like injection molded material.

FIG. 7 is a perspective view of a forged material cut out of an injection-molded material before and after forging.

FIG. 8 is a graph showing a relationship between a relative density of an injection molded material and a tensile strength of a forged material.

FIG. 9 is a graph showing a relationship between a molten metal inflow speed and a relative density of an injection molded material.

FIG. 10 is a graph showing the relationship between the solid fraction of the molten metal and the relative density of the injection molded material.

FIG. 11 is a graph showing the relationship between Sg / Sw and the relative density of an injection molded material.

FIG. 12 is a graph showing the relationship between Pmax / Pmin and the relative density of an injection molded material.

FIG. 13 is a graph schematically showing changes over time in pressure and injection speed acting on the molten metal.

FIG. 14 is a cross-sectional observation photograph of an injection-molded material molded using dies B to E.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Main body part 3 Screw 4 Rotation drive part 5 Cylinder 6 Heater 7 Hopper 8 Feeder 9 Mold 10 Nozzle 11 Runner part 11a Plug receiving part 11b Branch part 11c Neck part 12 Cavity 13 Gate part 14 Overflow part

Claims (12)

[Claims] 1. A method for molding an injection-molded material, wherein a light metal melt is injection-molded in a semi-molten state lower than a melting point or in a molten state from a melting point to a temperature just above the melting point. A method for molding an injection-molded material, wherein the inflow speed of a light metal melt is 1 to 30 m / s. 2. The method according to claim 1, wherein the inflow velocity is 10 m / s or less. 3. A method for molding an injection-molded material in which a molten light metal is injection-molded in a semi-molten state lower than a melting point or in a molten state from a melting point to a temperature just above the melting point, the method comprising: The ratio Sg / Sw of the cross-sectional area Sg of the gate portion, which is the inlet of the light metal melt, to the maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the inflow direction of the melt is 0.2 or more. Molding method for injection molding material. 4. A method for molding an injection-molded material, wherein a light metal melt is injection-molded in a semi-molten state below a melting point or in a molten state from a melting point to a temperature just above the melting point, the method comprising: The ratio Sg / Sw of the cross-sectional area Sg of the gate portion, which is the inlet of the light metal melt, to the maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the inflow direction of the melt is 0.8 or more. Molding method for injection molding material. 5. A method for molding an injection-molded material for injection-molding a light metal melt in a semi-molten state lower than a melting point or in a molten state from a melting point to a temperature just above the melting point, the method comprising: While the light metal melt used for the injection molding is being stored, the nozzle is provided so that the light metal melt does not flow out of a nozzle provided at the front of the cylinder and connected to a cavity for molding the injection molded material. A plug release pressure Pmax acting on the light metal melt accumulated in the front portion of the cylinder to extrude and remove the cold plug formed by solidifying the light metal melt to close the nozzle during the injection molding, and to the cavity. The ratio Pmax / Pmin to the minimum value Pmin of the pressure applied to the light metal melt in the inflow process of the light metal melt is set to 10 or less. Molding method of injection molding material to symptoms. 6. A method for molding an injection molding material in which a light metal melt is injection-molded in a semi-molten state below a melting point or in a molten state from a melting point to a temperature just above the melting point, the method comprising: The inflow speed of the light metal melt is set to 1 to 30 m / s, and the cross-sectional area S of the gate portion, which is the inlet of the light metal melt, into the cavity.
A method of molding an injection-molded material, wherein a ratio Sg / Sw of g to a maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the melt inflow direction is 0.8 or more. 7. The light metal melt in the semi-molten state has a solid phase ratio of 10% or more, which is a volume percentage of the solid phase with respect to the volume sum of the solid phase and the liquid phase. The method for molding an injection molded material according to any one of the above. 8. The method for molding an injection molded material according to claim 1, wherein the injection molded material is used as a material for plastic working. 9. An injection molding apparatus used for injection molding a light metal melt in a semi-molten state below the melting point or in a molten state from the melting point to just above the melting point. The ratio Sg / Sw of the cross-sectional area Sg of the gate portion, which is the inlet of the light metal melt, to the maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the melt inflow direction is 0.2 or more. An injection molding apparatus characterized by the above-mentioned. 10. A light metal melt is in a semi-molten state below its melting point,
Or an injection molding apparatus used for injection molding in a molten state from a melting point to a temperature just above the melting point, wherein a cross-sectional area Sg of a gate portion which is an inflow port of the light metal melt into a cavity for molding the injection molded material. And a ratio Sg / Sw of the maximum cross-sectional area Sw of the cavity in a direction substantially perpendicular to the inflow direction of the molten metal is 0.8 or more. 11. A runner portion communicating with the cavity and forming a supply passage of the light metal melt to the cavity,
The injection molding apparatus according to claim 10, further comprising a branch portion formed so that the light metal melt is divided into a plurality of flow paths. 12. A runner portion communicating with the cavity and forming a supply passage of the light metal melt to the cavity,
The injection molding apparatus according to claim 10, further comprising a constricted portion formed so that a cross-sectional area in a direction substantially perpendicular to a flowing direction of the light metal melt is narrower than an upstream portion and a downstream portion.