JP2000312958A - Method and device for pressurizing die cast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably charge a molten metal into a mold by making the molten metal into a cylindrical shape, stabilizing it hydrodynamically, performing a temperature standization and an equal distribution of pressure, supplement- supplying the molten metal volume during/after fulfilling of a die cast mold, and forming a casting product under supplemental compression pressure. SOLUTION: The molten metal introduced in a metal pouring chamber 3 through an adsorbing pipe 2 from a molten metal container 1 is made into a cylindrical shape, and the molten metal is accelerated along the metal pouring chamber 3. Preferably, the metal pouring chamber 3 is equipped with a back pressure piston 9 and a compression piston 10 for compressing the metal being crystallized in a die cast mold 5. By slide of a metal pouring piston 8, the molten metal is stabilized and temperature of the molten metal is also evened. The molten metal piston 8 moves forwards to the back pressure piston 9. The molten metal piston 8 acts on unstable molten metal at a constant driving force, pushes the molten metal at the front, presses the metal, so as to make the molten metal into a cylindrical shape and stabilize the metal hydrodynamically. The molten metal is activated in a crystallizing process by pressure rising due to pressing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a casting of an aluminum alloy and a magnesium alloy,
Specifically, vacuum is applied from the beginning of the casting process to a horizontal pouring chamber equipped with a pouring piston, and the molten metal introduced into the pouring chamber is cooled so as to be in a semi-solid state and stirred by an electromagnetic field. Also, the present invention relates to a press die casting method and apparatus which are configured to accelerate the molten metal to flow into the mold and pressurize the molten metal before reaching or at the latest when reaching the gate of the mold.

[0002]

2. Description of the Related Art In the above-described pressure die casting, basically, a pouring chamber can be arranged horizontally or vertically. In this arrangement, however, the molten metal in front of a pouring port of a mold can be formed. Each flow characteristic has its own advantages and disadvantages.

A particular feature that can be considered typical of pressurized die casting processes with horizontal pouring chambers is the formation of a hydrodynamically unstable melt flow that fills the die casting mold at very high speeds. is there. The filling process in this case is equivalent to injection rather than flow. As a result, air and oxygen are trapped in the casting, which causes cracking inside the casting and blistering on the casting surface.

In fact, in all cases, the cast metal is
It only fills a part of the horizontal cylindrical pouring chamber and the cast metal forms a movable non-cylindrical geometry. Its one side is limited by the pouring piston,
The other side has no geometrically limited dimensional restrictions,
Free in the flow direction. As a result, the predetermined constant hydrodynamic force acting on the unstable contact surface between the pouring piston and the melt flow is not evenly distributed on the other side surface, Hydrodynamic stagnation in front of the gate causes movement of the molten metal which impedes the outflow.
Hydrodynamic processes that are not stabilized at this stage do not reach stability at the next stage, and the vortex created at the outflow cross-section scatters further in the next operating phase, during which the already generated turbulent melt flow Hits the wall of the movable mold half at the speed of the compression piston. At this time, the inflow speed increases due to the decrease in the cross-sectional area.

[0005] EP 0733421 A1 discloses that laminar inflow during filling of a molten metal into a die casting mold is converted into a metal suspension by cooling the molten metal having a temperature slightly higher than the liquidus temperature in a pouring chamber. And then heated and then pressed and pushed into the mold space. In order to maintain the required mold filling time (5 to 100 ms) in die casting,
Laminar flow conditions are not sufficient. The above-mentioned prior art does not suggest whether and how flow velocity averaging can be performed in the pouring chamber. Thus, there is turbulence in the flow along the pouring chamber, which creates a vortex in the area of the pedestal and causes a metal stagnation. The molten metal collides with the wall of the movable mold half and flows into the die casting mold as a free-dispersing jet. Improvements in quality, for example by additional compression into a casting that is already crystallizing, are not possible with this known configuration. Therefore,
The practical use of this known method is limited and it is not possible to produce an improved end product.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems in pressurized die casting, and an object of the present invention is to provide a die casting die using a flow of molten metal which is stabilized hydrodynamically. It is an object of the present invention to provide a pressure die casting method and apparatus which allows the filling of the casting and the crystallization of the casting to be carried out under additional compression pressure without splattering the incoming jet.

[0007]

According to a first aspect of the present invention, there is provided a pressure die casting method for producing a casting under a vacuum, wherein a horizontal casting method is used. A pressurized die casting method comprising a hot-water chamber and a pouring piston, wherein the molten metal is accelerated before entering the mold, and is pressurized before or at the latest when the molten metal reaches the gate of the mold. The incoming melt was cylindricalized prior to said acceleration, and its shape was maintained until hydrodynamic stabilization, temperature averaging and uniform pressure distribution of the melt were achieved, and b) the die casting mold was filled. Later or while the die casting mold is being filled, the crystallizing metal in the mold is additionally supplied with a melt volume specially formed for it, and c) the solidification of the casting is reduced to a certain additional compression pressure. Characterized by what is done below That.

Further, a pressure die casting apparatus according to the present invention is an apparatus for carrying out the pressure die casting method according to claim 1, wherein the pressure die casting method has a special configuration of a pouring chamber having a T-member structure. It is realized by. In other words, in order to accelerate the molten metal along the pouring chamber, the pouring piston and the counter pressure piston are arranged opposite to each other in the pouring chamber, and the molten metal is melted in the mold in the mold. The compression piston is arranged in a vertical passage in order to compress supply.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are listed below. (1) In the pressure die casting method according to the first aspect, the molten metal is formed into a cylindrical shape before acceleration, and the molten metal is in a compressed state between the pouring piston and the back pressure piston. The method of claim 1, wherein: (2) In the pressure die-casting method according to claim 1 or (1), the hydrodynamic stabilization and temperature averaging of the cylindrical molten metal are performed by introducing a cooling powder into the molten metal. The metal suspension produced in the chamber is activated and held under pressure until accelerated.

(3) In the pressure die casting method according to any one of (1) and (2), the molten metal is accelerated in a direction of a pressure drop between a back pressure piston surface and a free surface of the molten metal. However, beginning after the rapid retraction of the counter pressure piston to the gate, the counter pressure piston having a concave elliptical cross section at the end is stopped at the gate, thereby forming the gate section. (4) In the pressure die-casting method according to any one of (1) to (3), the molten metal which has already been accelerated and only the hydrodynamic pressure acts can be die-cast by sliding a pouring piston. Introduced into the mold, the pouring piston is connected to the counterpressure piston, whereby a small cylindrical residual melt is formed in the space between the end faces of the pouring piston and the counterpressure piston.

(5) In the pressure die-casting method according to any one of (1) to (4), the cylindrical residual molten metal is disposed below the gate, and the axis of the residual molten metal is , And have a common axis with the gate. (7) In the pressure die-casting method according to any one of (1) to (5), the residual molten metal is pushed into the die-casting chamber through a gate using a compression piston. The solidified casting is pre-pressed by the end face of the compression piston at the gate, where the gate and the compression piston are arranged on one common axis.

(9) In the pressure die casting apparatus according to the second aspect, the pouring chamber has a T-shaped configuration, and does not end in front of the gate, and the pouring piston and the counter pressure piston are arranged to face each other. While the compression piston is located in a vertical passage. (10) In the pressure die-casting apparatus according to claim 2 or (9), the end faces of the pouring piston and the back pressure piston are formed into an elliptical concave surface and have the same cross-section that can be replaced left and right. .

The construction of the pouring piston, the back pressure piston and the compression piston according to the present invention has a significant meaning.
It determines the advantages of the most important technical methods. One of the advantages is that the melt in the pouring chamber is first made cylindrical by the sliding of the opposing pouring piston and the counter pressure piston, so that the piston and the melt flow An even pressure distribution at the contact surface is obtained. In addition, an elastic liquid wave is generated in the compressed cylindrical molten metal. These elastic liquid waves promote the formation of spherical primary crystals at an early stage, that is, in the pouring chamber. Furthermore, in the method according to the invention, it is possible to form, from an unstable melt stream, a metal suspension with hydrodynamically stable and suitably adjustable flow properties. The improvement and retention of the flow effect is achieved by the introduction of a metal cooling powder.

[0014] The crystallization conditions that occur in the pouring chamber are such that the morphology of the structure does not depend mainly on the heat dissipation by the walls of the pouring chamber, but the molten metal is brought into a semi-solid state in a short time and the crystallization rate is increased. Is to rely on new solid extrinsic crystal nuclei. This leads to the simultaneous and uniform formation of a solid phase in the entire melt volume, which makes the temperature of the metal suspension uniform.

During porosity formation in the casting, the increase in external pressure in the confined melt plays an extremely important role. The reason is that at this stage there is a basis for the production of non-porous castings. Pores generated from the nucleation process can be stably present in the melt only when the difference between the gas pressure and the melt pressure is greater than the capillary pressure due to the surface tension of the melt. Therefore, the melt pressure is increased to prevent pore nucleation during solidification. The process according to the invention is carried out in the pouring chamber with a compressed melt volume. The pressure created in the metal suspension is the sum of the existing dynamic pressure and the internal static pressure. This pressure makes nucleation of pores almost impossible and creates crystallization conditions which greatly increase the density value of the final product.

During the use of the piston during special molten metal processing,
The process of hydrodynamic stabilization, temperature averaging and uniform pressure distribution over the entire cylindrical melt volume is simultaneously started in the confined and compressed melt. However, according to the present invention, the melt acceleration following this stabilization phase is not affected by the hydrodynamic pressure of the pouring piston, but rather results from the hydrodynamic back pressure caused by the use of a counter pressure piston. This is related to the special configuration of the pouring chamber, and it is important that the back pressure piston is retracted to the gate, that is, to a position where the gate is released. The rapid piston sliding causes a pressure drop at the free contact surface of the cylindrical melt and the melt tends to flow into the freed pouring chamber space. The temperature-averaged and hydrodynamically stabilized melt is moved in the direction of the sprue by a counter pressure piston. This movement, by virtue of its frontal movement, allows an inflow method which can be called laminar flow for filling taking place from the gate side. This step plays a very important role in filling the casting path with a vortex-free melt jet.

In a further preferred form of the method according to the invention, the opposing or end faces of the pouring piston and the counter-pressure piston are formed so that they have an elliptical concave surface and have an equal cross-section which can be exchanged from side to side. Such a cross section forms a cylinder with two spherical portions each in the intermediate space. Hereinafter, the form of the compressed melt volume is referred to as a cylinder or a cylindrical volume.

The special piston structure offers other technical advantages. That is, during a brief pressure drop due to the retraction of the back pressure piston, the pressure is averaged out by the pouring piston slide. The die casting mold is filled with the next molten part while receiving the hydrodynamic pressure of the pouring piston acceleration. The sliding of the pouring piston is terminated by a connection to the counterpressure piston in the sprue area. Accordingly, a small cylindrical molten metal is formed which is arranged below the gate and above the compression piston. In the compressed state, the cylindrical melt, the gate and the compression piston have a common axis. As a result, an additional molten metal is formed near the die casting mold and the gate. This additional melt can be additionally supplied to the already crystallizing casting before its final solidification.

By pressing the molten metal, the casting being crystallized is further compressed using a compression piston. In order to achieve the above technical operation, a compression piston is integrated in the vertical part of the pouring chamber of the T configuration so as to be able to perform vertical sliding in the direction of the sprue. Based on this configuration and by accelerating the compression piston to the die casting mold, the molten metal formed between the pouring piston and the back pressure piston is compressed into the mold by a corresponding hydrodynamic force.

An essential structural condition for this is that the diameter of the end face of the compression piston must correspond to the inner diameter of the cylindrical profile formed by the pouring piston and the counterpressure piston. This not only avoids inflow scattering, but also reduces metal loss because no metal remains at the gate. In addition, appropriate additional compression is applied to the solidifying casting.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages, features and details of the invention will be explained by means of a preferred embodiment with reference to the drawings. Note that this embodiment shows a preferred embodiment of the present invention, and the present invention is not limited to this embodiment.

FIG. 1 schematically shows a pressure die casting machine. FIG. 1 shows a pouring room 3 (hereinafter, referred to as a pouring room) formed in a T shape by using a suction pipe 2. The contacted molten metal container 1 is shown. The pouring chamber 3 is provided with a die casting mold 5 composed of a movable half 6 and a fixed half 7 through a gate 4.
Has been contacted. In a horizontal area of the pouring chamber 3, a pouring piston 8 and a back pressure piston 9 are arranged, while a compression piston 10 is arranged in a vertical passage. The suction pipe 2 and the pouring chamber 3 are equipped with a powder metering device 11 and an electromagnetic stirring unit 12 arranged annularly around the pouring chamber 3.

The practical application of the present invention will be described with reference to FIGS. The molten metal 13 or a predetermined volume of the molten metal is introduced from the molten metal container 1 into the pouring chamber 3 through the suction pipe 2. In this process, the molten metal is mixed with the cooling powder in the suction pipe 2 by the powder metering device 11 (FIG. 2). The incorporation of the powder causes a cooling effect, which avoids the superheated and supercooled areas of the melt, averages the crystallization process and ultimately improves the uniformity of the casting.

The cooled melt is introduced into the pouring chamber 3 in front of the pouring piston 8 occupying the position P8-1, and after a short time already begins to produce primary crystals, preferably having a round shape. Before the molten metal enters the pouring chamber 3, the position of the back pressure piston 9 changes. The back pressure piston 9 slides along the pouring chamber 3 to leave its initial position P9-1, and moves to the position P9-
Occupy 2. Thus, a space that is geometrically limited is formed in the pouring chamber 3. This space contains the molten metal that is confined between the pouring piston and the back pressure piston and does not contact the gate 4 (FIG. 2).

In the conventional method, the melt flow, when flowing into the pouring chamber 3, exhibits a very pronounced hydrodynamic instability that occurs during the pressure rise, but according to the invention, according to the invention, the pouring piston 8 Sliding not only stabilizes the melt but also equalizes the temperature of the melt. Pouring piston 8 moves forward toward counter pressure piston 9 and occupies position p8-2. The pouring piston 8 acts on the unstable molten metal with a constant driving force, pushes the molten metal forward, and presses the molten metal (FIG. 3). As a result, the following advantages are obtained. The melt has a cylindrical shape. The melt is hydrodynamically stabilized. The crystallization process of the molten metal is activated by the pressure increase due to the pressing.

During the above activation, an elastic pressure wave is generated in the molten metal, causing fluctuations in density and energy, thereby promoting the crystallization process. However, as a prerequisite, it is necessary that a cylinder of the solid-liquid melt is formed in the pouring chamber 3 and a uniform pressure distribution is achieved.

The averaging of the molten metal temperature is performed by electromagnetic stirring. For this purpose, the annular stirring unit 12 is
Are arranged around. The electromagnetic stirring produces a circular motion in the melt already cooled by the cooling powder, resulting in an average of the temperature of the cylindrical melt and a round (spherical) shape
The crystallization conditions for crystal formation are promoted.

In the next stage, the back pressure piston 9 is moved to the position P9.
-2 retreats to the position P9-1. Thereby, the gate 4 is opened (FIG. 4). After the sliding of the back pressure piston 8 stops, the back pressure piston contour end is adjacent to the sprue contour end. This metal suspension, which has already been temperature-averaged and hydrodynamically stabilized, is pushed into the free space and is turned at the counterpressure piston 9 into the sprue 4. Therefore, as a result, the following advantages are obtained. The pressure and temperature conditions in the melt moved axially are uniform. The flow of the melt that is hydrodynamically stabilized can reach the gate 4 without causing the impact of the steady free jet on the vertical wall of the movable half and without the jet being scattered. The casting path and the gate are filled with a layered melt.

The short-term pressure drop due to the retraction of the piston 9 is compensated in the next stage by the sliding of the pouring piston 10 (FIG. 5). The change in position of the pouring piston 8 from P8-2 to P8-3 ends before the gate 4. The movement of the piston 8 at this time is connected to the back pressure piston 9. The metal suspension fills the casting channel and the sprue and is pressed into the die casting mold 5 by hydrodynamic piston action. Since the end face of the pouring piston 8 has an elliptical concave cross section just like the back pressure piston 9, a small cylindrical molten metal region is formed in the intermediate space. This melt zone is in an elasto-plastic state just below the gate 4 and just above the compression piston 10. The cylindrical molten zone (reservoir) can be used to additionally supply a casting that is already crystallizing. In the last operating step, which can be referred to as additional compression of the end product, a vertical sliding of the compression piston 10 in the direction of the sprue is performed, thereby ending the die casting process.

The compression piston 10 has its initial position P10
Away from -1, the cylindrical metal part is pushed above the gate 4 to reach a new position P10-2 (FIG. 6). This provides an additional supply of molten metal to the already crystallized casting. The solidified casting is pressed by the end face of the compression piston 10 at the gate.

FIG. 7 shows an important form of the deformation region of the metal inflow according to the present invention (φM: diameter of the cylindrical molten metal, φK: contour formed by the end faces of the pouring piston and the back pressure piston. Diameter). The contoured configuration allows for vortex-free filling of the die casting mold, additional feeding and additional compression of the final product. This configuration can further significantly reduce metal loss (reduction of casting residue).

[0032]

The first tests of the method according to the invention have clearly confirmed the following: The spatially limited pouring chamber, the arrangement of the T-shaped pistons and the closed piston (head) surface improve the metal inflow conditions and provide a hydrodynamically stabilized die casting with the melt flow. The filling of the mold is performed and the crystallization of the casting can be performed under additional compression pressure without splattering the incoming jet.

In the manufactured casting, a uniform and fine structure can be obtained. Typical casting defects, such as dispersed shrinkage bubbles, cavities and porous non-densified structures, are reduced by the additional supply of molten metal and additional compression pressure to the casting being crystallized and produced by the method according to the invention. The density of the cast product is increased by a factor of five.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a T-shaped vacuum die casting machine according to the present invention including a pouring chamber, a pouring piston, a counter pressure piston, and a compression piston.

FIG. 2 is a cross-sectional view showing a position of a piston when a molten metal is filled in a pouring chamber.

FIG. 3 is a cross-sectional view showing piston positions when the molten metal is in a cylindrical and compressed state.

FIG. 4 is a cross-sectional view showing a piston position when a generated metal suspension flows into a die casting mold under hydrodynamic pressure.

FIG. 5 is a cross-sectional view showing a piston position when a cylindrical molten metal (storage portion) is arranged below a gate.

FIG. 6 is a cross-sectional view showing a piston position when additional supply and additional compression of molten metal to a casting being crystallized are performed.

FIG. 7 is a cross section of the filled mold hollow space after the filling process is completed.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Molten container 2 Suction pipe 3 Pouring room 4 Gate 5 Die casting mold 6 Movable half mold 7 Fixed half mold 8 Pouring piston 9 Reverse pressure piston 10 Compression piston 11 Powder metering device 12 Electromagnetic stirring unit 13 Molten metal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Gerhard Pereshka Germany 63825 Wester Grunde Geisbergstrasse 13

Claims (2)

[Claims] 1. A pressure die-casting method for producing a casting under vacuum, comprising a horizontal pouring chamber and a pouring piston, wherein the molten metal is accelerated before entering the mold, and In a press-die casting method in which the molten metal is pressurized before reaching or at the latest at the time of the gate, a) prior to said acceleration, the melt is cylindricalized and hydrodynamically stabilized in that state;
Averaging of temperature and equal distribution of pressure in the volume of the cylinder; b) the metal being crystallized in the mold after or while the mold is being filled; Pressure die-casting method, characterized in that an additional supply of the specially formed melt volume is provided therefor; and c) the casting is formed under a specific additional compression pressure. 2. An apparatus for performing the pressure die casting method according to claim 1, wherein the molten metal is formed into a cylindrical shape, the molten metal is accelerated along a pouring chamber, and crystallization in a die casting mold is performed. Pressurizing die casting apparatus characterized in that the pouring chamber is provided with a back pressure piston and a compression piston for compressing the metal being formed.