KR20000035226A - Die casting method for manufacturing castings made of alloy with thixotropic property - Google Patents

Abstract

PURPOSE: A method is provided to fill metal suspension having uniform distribution in a casting chamber and to pressurize into a cavity of a die casting mold by treating a predetermined amount of molten material to semi-solid state. CONSTITUTION: In a die casting process using a die casting mold(14) arranged vertically, a space for receiving homogeneous thixotropic metal suspension is formed in a casting chamber by the downward displacement of a casting piston. A casting passage is closed by a dosing piston(7) and the suspension is pressurized by the movement of the casting piston in the casting chamber. The rotation of a magnetic field to the metal suspension is continued to the last step of the die casting process. The die casting mold is filled by the forward rotation of the thixotropic metal suspension.

Description

Die casting method for manufacturing castings made of alloy with thixotropic property

The present invention has a casting chamber with means for dosing a predetermined amount of melt, a casting piston and a die casting mold, which granulates primary crystals produced in the melt and cools the predetermined amount of melt, And a process for producing a casting from an alloy with thixotropic properties, by mixing in a press and in a semi-solidified state.

The casting properties are the result of relatively rapid crystallization processes in the melt. The crystallization process takes place between different known temperature intervals "liquid line-solid line" for each alloy. However, in this temperature section not only a crystalline "skeleton" is formed, but also in the formation of the crystalline structure of the casting, a process portion in which defects present in the molten metal are imprinted in the crystalline structure of the casting-a temperature section "superheat-liquid temperature "With-appears. The defect is detected as a casting error after solidification. First, gas porosity, microbubbles, separation and other physical-chemical and structural inhomogeneities are problematic. Thus, according to the crystallization theory, the influence of casting quality with respect to the selection and maintenance of crystallization conditions is only possible in the range of superheat-solidus temperature.

Given the manufacturing problems of qualitatively improved castings from the standpoint of not affecting the crystallization process in the range of temperatures given, any variation, damage or short-term process downtime will result in lower final results. From this, it appears that the selected crystallization conditions can only be observed for the crystallization of a certain amount of closed melt. This is important in the die casting process of alloys with thixotropic properties. Although the molding of the casting takes place in the temperature range "liquid line-solid line", such material is imprinted from a material that already has rheological properties and complete process specificity is maintained, which represents the actual potential of the material in forming the structure.

The aforementioned method is known from EP 0 733 421 A1. In this method, granulation of primary crystals produced in a predetermined amount of melt, processing by cooling and stirring of the cast tissue with thixotropy characteristics, molding by filling the die casting mold with the melt in a semi-solidified state This is done.

It is also known that the so-called semi-solidified state is the result of the treatment of the casting chamber melt filled with the casting spoon. In this case, the metal suspension in the casting chamber must be layered and flow into the die casting mold under pressure.

The gas uptake of the melt should be reduced.

However, the presented solutions are generally opposed to known theoretical and practical facts.

When the casting chamber is filled with the melt by the casting spoon, the falling liquid jet produces vortices, not laminar flow therein. Vortex first represents external cooling and then mixing. An important disadvantage of this method is that a continuous technical process step cannot be implemented for the same amount of melt as the casting spoon must be separated from the die casting mold in order for the casting chamber to be filled with the melt.

Firstly, the above-mentioned filling method of the casting chamber causes gas reception of the melt which appears as gas porosity in the casting.

Secondly, the suspension cannot be brought into the required homogeneous state, since the casting chamber is only divided according to the treatment mode.

Thirdly, the generation of a solid phase and its uniform distribution in the melt are not controlled. This is particularly important for the process and depends entirely on the intensity of heat release through the chamber walls only. After this heat exchange, primary crystals only occur in very thin melt regions in the wall and do not form throughout the melt.

The inhomogeneities already present as a result of the treatment process in the first stage may increase in other stages and may increase several times with laminar flow. The above-mentioned facts-depending on various casting errors-cause many returns, which are uneconomical.

It is an object of the present invention to provide a method in which a predetermined amount of melt is treated in a semi-solidified state, whereby it can be filled into the casting chamber as a metal suspension with a uniform distribution of solid phase and pressurized into the cavity of the die casting mold therefrom. will be.

1 is a cross-sectional view of a casting and dosing system and a processing chamber.

FIG. 2 is a cross-sectional view showing the position of the casting and dosing piston when the closed melt in the processing chamber is treated with a homogeneous, metal suspension. FIG.

3 is a cross-sectional view showing the position of the casting and dosing piston when the metal suspension is pressurized.

4 is a schematic representation of a method according to the present invention in which a processing chamber may be filled with a melt by vacuum.

* Description of the symbols for the main parts of the drawings *

2: melt line 3, 6: casting passage

4: processing chamber 5: casting chamber

7: dosing piston 8: casting piston

9: powder dosing device 10: magnetic field

13: metal suspension 14: mold

The object is that in the method described above according to the invention, the casting chamber is coupled to the die casting mold when dosing a predetermined amount of melt, the melt dosing is achieved by filling the processing chamber, and the processing chamber is melted. It is achieved by a method characterized in that it comprises a dosing piston and is connected via a line and a casting passage to a melt vessel and correspondingly to a casting chamber. Preferably, an amount of closed melt is processed in the processing chamber.

This results in the following advantages:

During the melt dosing and chamber filling, the gas chamber is excluded from the atmosphere because the casting chamber is not separated from the die casting mold.

The process chamber provides the possibility that an amount of closed melt is processed in the required manner, and that it can be obtained by uniform treatment and crystallization conditions for a predetermined amount of melt before pressurization.

The presence of a closed processing chamber allows for the best filling rate as needed.

성형 Forming the metal suspension to have a predetermined amount of solid phase, its uniform distribution in the metal matrix and granulated primary crystals is completed in the closed space of the chamber.

Another advantage of the process according to the invention is that the process of the metal suspension already starts in the melt line. For this purpose, cooling powder is introduced into the melt in this section. By heating and melting of the powder, the temperature of the melt drops and the temperature necessary for the subsequent process is obtained.

By the use of a rotating magnetic field, a predetermined amount of melt is mixed with the cooling powder in the melt line and the resulting metal suspension is stirred in the processing chamber and the casting chamber. Filling of the die casting mold is made by rotating metal suspension. The advantage of this technical design is that the metal suspension initially formed by rotation in a magnetic field is given general or physical-chemical and structural homogeneity, and its thixotropy properties can be guaranteed to the end of the process. Filling the die casting mold with the rotating metal suspension is important to obtain the casting as close to the final contour as possible by better mold filling.

The method according to the invention comprises a die casting process with four successive steps:

냉각 cooling of the melt by cooling powder and mixing in a rotating magnetic field;

충전 filling the process chamber with cooled melt, granulating the resulting primary crystals, forming a homogeneous metal suspension with thixotropic properties and rotating it;

Transfer the metal suspension from the processing chamber to the casting chamber.

가압 Pressure of rotating metal suspension.

By a particular embodiment, the formed homogeneous metal suspension is discharged from the processing chamber to the casting chamber by the dosing piston. The implementation of this step is accomplished by proper positioning of the dosing piston and the casting piston in the processing chamber and the casting chamber.

These steps and their technical transformations belong to important features of the method according to the invention.

The predetermined amount of melt can be varied by varying the dosing piston position in the processing chamber.

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

The die casting machine shown schematically in FIG. 1 is provided with a melt vessel 1. The melt vessel 1 is connected to the processing chamber 3 via the melt line 1 and the casting passage 3. The processing chamber 4 is mounted to the casting chamber 5 so that the casting passage 6 is formed between the processing chamber 4 and the casting chamber 5. The chamber shown is provided with a dosing piston 7 and a casting piston 8, respectively. The melt line 2 is provided with a powder dosing device 9 and an electromagnetic stirring device 10. The stirring device is arranged in a ring shape around the processing chamber and the casting chamber.

These are shown in FIG. 1.

The melt 11 flows from the melt chamber 1 into the melt line 2 by the rise of the stopper 12. In the melt line 2 the melt is cooled by cold powder. As shown, the powder is supplied by the powder dosing device 9. Due to the cooling action of the injected powder, the temperature of the melt lies within the liquidus temperature range. That is, the melt cooled in this manner “forms” primary crystals after a short time. Primary crystals are homogeneously distributed throughout the volume due to rotation and have a spherical crystalline shape. For mixing of these materials, a rotating magnetic field 10 is used on the melt line section. The rotating, treated melt flows into the processing chamber 4. The processing chamber 4 comprises a dosing piston 7 with a starting position P1-1. The casting passage 6 between the processing chamber and the casting chamber is simultaneously closed by the casting piston 8. When the processing chamber 4 is filled with a predetermined amount of melt, the dosing piston 7 provided with the casting passage 3 for the melt line 2 in the processing chamber 4 moves to position P1-2. By closing. The process continues in a closed chamber, or the melt that has already been cooled is rotated by the magnetic field 10 and is brought to the final state of the homogeneous metal suspension 13. The distinguishing features of these states are the uniform distribution of endogenous and exogenous crystalline shapes in the thixotropic metal matrix, and the absence of severe temperature fluctuations. Thus, the treatment chamber 4 is given a thixotropic suspension in a short period of time, its primary crystals are already granulated and the casting structure is refined. In this state it is discharged after the casting chamber 5 by the dosing piston 7 provided in the processing chamber 4, for which the casting piston 8 is brought to another position P2-2 so that the casting passage 6 ) Is opened. In the case of the die casting process in which the die casting mold 14 is vertically arranged, a space is formed in the casting chamber 5 to accommodate a homogeneous thixotropic metal suspension by the displacement of the casting piston downward. Then, as the casting passage 6 is closed by the dosing piston 7 (P1-3), the metal suspension is pressurized by the casting piston movement in the casting chamber 5. The rotational action of the magnetic field on the metal suspension continues to the end of the die casting process, causing the die casting mold to be filled by the forward rotational movement of the thixotropic metal suspension.

In another embodiment of the present invention, the processing chamber may be arranged such that castings are formed by horizontal placement of the die casting mold and the processing chamber is filled with melt by vacuum.

In the process according to the invention, the additional process chamber 4 significantly increases the functionality of the overall process, resulting in no casting errors such as gas emissions, bubbles, structural inhomogeneities, which is dependent on the isotropy of the thixotropic properties of the metal suspension. Is guaranteed only by

In the process according to the invention, a predetermined amount of melt is treated in a semi-solidified state so that it can be filled into the casting chamber as a metal suspension with a homogeneous distribution of solid phase and from there pressurized into the cavity of the die casting mold.

Claims (9)

Means for dosing a predetermined amount of melt, a casting chamber 5 with a casting piston 8 and a die casting mold 14, granulating the primary crystals produced in the melt and A method for producing a casting from an alloy with thixotropic properties in a manner that cools the melt, mixes it in the electromagnetic field 10 and presses it in a semi-solidified state, the casting chamber when dosing a predetermined amount of melt. (5) is coupled to the die casting mold 14, the melt dosing is by filling of the processing chamber 4, the processing chamber being melted through the melt line 2 and the casting passage 3 A die casting method, characterized in that it comprises a dosing piston (7) connected to the casting chamber (5) and to the vessel (1) and through the casting passage (6). The method according to claim 1, wherein an amount of the closed melt is processed in the processing chamber 4 or guided to a state of homogeneous metal suspension 13 having a homogeneous distribution of granulated primary crystals and solid phase. Die casting method, characterized in that. 2. The die according to claim 1, wherein the cooling of the predetermined amount of melt is effected by the cooling powder, for which a suitable amount of powder is introduced into the melt line 2 by means of the powder dosing device 9. Casting method. A homogeneous metal suspension (13) with thixotropic properties is carried out by means of a dosing piston (7) from the processing chamber (4) through the casting passage (6). 5) Die casting method characterized in that the conveyed. The metal suspension (13) according to any one of the preceding claims, wherein a predetermined amount of melt is mixed with the cooling powder in the melt line (2) by the use of a rotating magnetic field (10). The die, which is stirred in the processing chamber 4 and the casting chamber 5, is characterized in that the filling of the die casting mold 14 takes place in the forward rotational manner of the homogeneous thixotropic metal suspension 13-during pressurization. Casting method. The die casting method according to claim 1, wherein the entire die casting process consists of four successive steps comprising the following main operations: Cooling of the melt with cold powder and mixing in a rotating magnetic field 10; Filling the process chamber 4 with cooled melt, granulating the resulting primary crystals, forming a homogeneous metal suspension 13 having rotational and thixotropic properties; Transfer of the metal suspension 13 from the processing chamber 4 to the casting chamber 5; Pressurization of the metal suspension (13). The process according to any of the preceding claims, wherein the performance of the steps described above is effected by positioning of the dosing piston 7 and the casting piston 8 in the processing chamber 4 and the casting chamber 5. A die casting method characterized by the above-mentioned. Means for dosing a predetermined amount of melt from the melt vessel 1, and a casting chamber 5 with a casting piston 8 and a die casting mold 14 to granulate the primary crystals produced in the melt In a method for producing a casting from an alloy having thixotropic properties in such a way that it is quenched and cooled to a predetermined amount of melt, mixed in an electromagnetic field 10 and pressurized in a semi-solidified state, When dosing a predetermined amount of melt, the casting chamber 5 remains coupled to the die casting mold 14 and the dosing of the melt is made by filling the process chamber 4 and the process chamber 4 ) Comprises a dosing piston (7) and on the one hand is connected to the melt vessel (1) via a melt line (2) and a casting passage (3) and on the other hand a casting chamber (5) through a casting passage (6). ), The processing chamber 4 has a primary crystal granulated by a casting piston 8 moved in front of the casting passage 6 and a dosing piston 7 moved in front of the casting passage 3. Die casting method characterized in that it is closed until a homogeneous metal suspension is formed. Means for dosing a predetermined amount of melt from the melt vessel 1, a casting chamber 5 with a casting piston 8 and a die casting mold 14, created in the edge region during cooling of the melt. In a method for producing a casting from an alloy having thixotropic properties by granulating primary crystals and mixing in the electromagnetic field 10, Cooling of the predetermined amount of melt is effected by the cooling powder-starting at the center of the melt-and the process continues in the closed processing chamber 4 until the final state of the homogeneous metal suspension, at which time thixo Homogeneous distribution of exogenous and endogenous crystalline shapes within the tropic metal matrix, In order to obtain the isotropy of the thixotropic properties of the metal suspension in the casting, the metal suspension is characterized by mixing of aluminum powder under constant rotation, homogeneous distribution in the processing chamber, discharge from the processing chamber into the casting chamber and pressurized into the casting mold. Die casting method.