CN110769952A

CN110769952A - Die casting furnace system with ultrasonic unit for improving molten metal quality

Info

Publication number: CN110769952A
Application number: CN201880040112.6A
Authority: CN
Inventors: 兰迪·S·贝亚尔斯
Original assignee: Magna International Inc
Current assignee: Magna International Inc
Priority date: 2017-06-16
Filing date: 2018-06-15
Publication date: 2020-02-07
Also published as: EP3638438A1; US20200094315A1; EP3638438B1; EP3638438A4; WO2018232201A1

Abstract

A die casting furnace system includes a die casting holding furnace unit defining a cavity for holding molten metal. A dosing unit is disposed inside the cavity and defines a dosing region disposed in fluid communication with the cavity for receiving molten material during pressurization of the cavity. The cavity of the die-casting holding furnace unit has a first storage capacity, and the batching region of the batching unit has a second storage capacity smaller than the first storage capacity. An ultrasonic unit is operatively coupled with the limited-sized dosing region and is configured to introduce vibrations into the received molten material to facilitate removal of gas from the received molten material. The use of an ultrasonic unit to treat a dosing area of limited size results in improved metal cleanliness and accuracy not achieved by prior art systems.

Description

Die casting furnace system with ultrasonic unit for improving molten metal quality

Cross Reference to Related Applications

This PCT international patent application claims the benefit of U.S. provisional patent application serial No.62/520,940 entitled "Die Casting batch furnace With Ultrasonic Degassing System For improving Aluminum Molten metal" filed on 6/16/2017, the entire disclosure of which is considered part of the disclosure of the present application and is incorporated herein by reference.

Background

Technical Field

The present disclosure relates generally to systems and methods for improving the quality of molten metal in a die casting holding furnace unit.

Prior Art

This section provides background information related to the present disclosure that is not necessarily prior art.

A conventional batch furnace is a closed holding furnace with a nozzle for delivering direct metal (e.g., liquid metal or molten metal) into a cold chamber die casting machine. Conventional batch ovens are designed such that the entire oven must be pressurized for each cycle of the machine. When the metal level in the batching furnace is pressurized, all the metal in the batching furnace physically moves upwards. After the shot, the batch furnace was depressurized and the metal returned to the lowest level. This type of oscillation may produce scum, sludge, oxides, etc. In addition, existing batching furnaces use a porous plug at the bottom of the batching unit to degas or remove hydrogen from the metal (e.g., aluminum). The successful introduction of a rotary degassing unit into a pressurized batching furnace has not been achieved, since this would lead to problems with regard to the gas tightness of the batching furnace itself, as well as the introduction of turbulence, such as dross, oxides, etc. Attempts have been made to use ultrasonic degassing for small holding furnaces; however, the metal volume in conventional batch furnaces is too large to effectively perform ultrasonic degassing vibrations/fluctuations.

Disclosure of Invention

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of the features, aspects, and objects of the disclosure.

A die casting furnace system includes a die casting holding furnace unit defining a cavity for holding molten metal. The die cast furnace system also includes a dosing unit disposed or positioned inside the cavity and defining a dosing region disposed in fluid communication with the cavity for receiving molten material during pressurization of the cavity. An ultrasonic unit is operatively coupled to the dosing region and is configured to introduce vibrations into the received molten material to assist in removing gas from the received molten material prior to the molten material moving into the die casting machine.

By using a die casting furnace system with a small batching unit arranged inside the die casting holding furnace unit, the ultrasonic unit operates on an optimal volume of molten metal (e.g. aluminum) to achieve as high a metal quality as possible directly before the molten metal is introduced into the die casting machine. The system also achieves an optimal combination of metal cleanliness and accuracy in the die casting furnace system by using a combination of an ultrasonic unit and a dosing unit arranged in the cavity of the die casting furnace unit. Thus, the ultrasonic unit provides a large increase in the quality of the molten metal. Indeed, as will be explained in more detail below, the amount of dross and/or hydrogen is reduced by more than five times compared to argon (Ar) rotary degassing and other systems. Thus, the combination of a dosing unit of limited size in combination with an ultrasonic unit advantageously provides a treated molten metal with lower hydrogen content, higher density, lower void count and higher tensile properties relative to prior art systems.

These and other objects, features and advantages of the present invention will become more apparent from the following description.

Drawings

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional side view showing a die-cast holding furnace system including a dosing unit during a refill cycle;

FIG. 2 is a cross-sectional side view of a die-cast holding furnace system showing the batching cycle;

FIG. 3A is a cross-sectional side view of the die cast holding furnace system showing the ultrasonic unit operably coupled with the dosing unit;

FIG. 3B is an enlarged view of a portion of FIG. 3A showing a probe of the ultrasonic unit positioned within the molten metal in the dosing unit for introducing a degasser and generating cavitation bubbles;

FIG. 4 is a cross-sectional side view of the die cast holding furnace system showing the automated grain refinement unit operably coupled with the dosing unit;

FIG. 5A is a cross-sectional side view of a die-cast holding furnace system showing an automatic feed unit for a Metal Matrix Composite (MMC) operably coupled with an ultrasonic unit; and

FIG. 5B is an enlarged view of a portion of FIG. 5A showing the probe of the ultrasonic unit positioned within the molten metal for introducing the degassing agent and the ceramic particles received from the automatic feed unit.

Detailed Description

Referring to the drawings, wherein like reference numbers refer to corresponding parts throughout the several views, there is generally shown in fig. 1-5 a die cast holding furnace system 100 known as a dual chamber furnace. The die casting holding furnace system 100 includes a die casting holding furnace unit 102, the die casting holding furnace unit 102 defining a cavity 103, the cavity 103 having a first storage capacity for holding molten metal or molten material 104. The molten metal 104 may include aluminum, an Al-Si-Mg alloy (300 series aluminum), or other metals or alloys. The furnace unit 102 is a closed holding furnace having a runner system leading to a die casting machine shot sleeve 106 for dispensing molten metal 106 from the die casting holding furnace unit 102 through the shot sleeve 104 to a die casting machine 108.

A dosing unit 110 is arranged or positioned inside the cavity 103, and the dosing unit 110 defines a dosing region 112, the dosing region 112 being arranged in fluid communication with the cavity 103 for receiving the molten metal 104 during a refilling cycle. For example, fig. 1 shows the die-casting holding furnace system 100 during the refilling cycle, in which a pressure of, for example, 60 millibar (mbar) is reduced or removed from the pressure being applied to the dosing region 112, thereby causing the dosing region 112 to be filled with molten metal 104. In other words, during the refill cycle, the positive pressure inside the die cast furnace unit 102 raises the level of the molten metal 104 inside the batching unit 110 until the molten metal 104 reaches a particular level or range of levels. As shown in the figure, the dosing region 112 defined by the dosing unit 110 has a second storage capacity that is smaller than the first storage capacity of the cavity 103 of the die cast furnace unit 102. As will be explained in more detail below, this smaller or limited size of the dosing region 112 compared to the cavity 103 of the die casting furnace unit 102 allows for optimized handling of the molten metal 104 received during the refilling cycle before it is introduced into the die casting machine 108.

As further shown in fig. 1, the dosing region 112 has an inlet 113 and an outlet 114, the inlet 113 being arranged in fluid communication with the cavity 103 for receiving the molten metal 104 from the die casting furnace unit 102, the outlet 114 being arranged in fluid communication with the shot sleeve 106. A check valve 115, such as a one-way ball valve, is disposed in the inlet 113 for allowing the molten metal 104 to pass through the inlet 113 during a refilling cycle while preventing the molten metal 104 from returning to the cavity 103 when received within the dosing zone 112.

Fig. 2 shows the die-cast holding furnace system 100 during a batching cycle. The dosing cycle begins with a positive pressure generated inside the dosing unit 110, such as another application of 60mbar as described above, causing the check valve 115 to close and the molten metal 104 to be discharged through the shot sleeve 106 and into the die casting machine 108. When a specific amount of molten metal 104 is delivered into die casting machine 108, the dosing process is terminated by reducing or relieving the pressure applied to dosing unit 110. The specific amount of molten metal 104 may be a predetermined amount. When the dosing cycle is complete, the level of molten metal 104 in the dosing unit 110 is at a lower level than the level of molten metal 104 before the dosing cycle begins. After the batching cycle is complete, the die cast holding furnace system 100 is ready to begin a refill cycle. As shown in fig. 1, the refill cycle runs until the level of molten metal 104 within the batch area 112 returns to a specified level again, and the die cast holding furnace system 100 is ready to begin another batch cycle.

As best shown in fig. 3A, the die cast holding furnace system 100 includes an ultrasonic unit 116, the ultrasonic unit 116 being operatively coupled with the dosing unit 112, and the ultrasonic unit 116 being configured to introduce vibrations into the molten metal 104 received within the dosing area 112 after a refill cycle. As will be explained in greater detail below, the ultrasonic unit 116 facilitates the removal of gas from the received molten metal 104 before the received molten metal 104 is dispensed into the shot sleeve 106. The ultrasonic unit 116 includes a probe 117 attached to the holding furnace unit 102 and extending downward to be positioned within the molten metal 104 disposed or received in the batching region 112. The probe 117 is configured to generate vibrations and additionally provide a degasser 118 within the dosing region 112, the degasser 118 to interact with the molten metal 104 prior to the molten metal 104 moving into the diecasting machine 108. The degasser 118 is used to remove gases, such as hydrogen, from the molten metal 104 to provide purging of the molten metal 104 entering the diecast machine 108. As previously described, the batching area 110 has a defined or limited storage capacity that is smaller than the cavity 103 of the holding furnace unit 102. Thus, the ultrasonic unit 114 in combination with this limited storage capacity of the dosing region 112 provides improved purification of the molten metal 104 because the ultrasonic unit only processes the molten metal 104 disposed within the dosing unit 110, and thus the ultrasonic unit is more suitably sized to effectively and efficiently degas the molten metal 104.

As best shown in fig. 3B, the degassing agent includes both carrier gas 120 and cavitation bubbles 122 introduced into the molten metal 104 by the probe 117. The cavitation bubbles 122 may transport gas through the cavitation bubbles 122 as they move throughout the molten metal 104, including reaching the surface of the molten metal 104. However, without any assistance, the cavitation bubbles 122 may collapse before reaching the surface. Thus, the carrier gas 120 may be used to transport the cavitation bubbles 122 and dissolved gases throughout the molten metal 104. The high intensity ultrasonic vibrations generated from the probe 117 of the ultrasonic unit 114 cause bubbles of the carrier gas 120 to burst and generate a large amount of cavitation bubbles 122. Carrier gas 120 bubbles may remain in molten metal 104 because the carrier gas 120 bubbles do not dissolve in the molten metal 104. As the carrier gas 120 moves throughout the molten metal 104, the carrier gas 120 collects the cavitation bubbles 122 containing dissolved gas and transports the cavitation bubbles 122 uniformly throughout the molten metal 104, thereby improving the degassing efficiency. In addition, the ultrasonic vibration also creates smaller degasser bubbles, which allows for greater surface area while degassing the molten metal 104. After the ultrasonic unit 116 operates on the molten metal 104, the molten metal 104 moves through the die casting machine shot sleeve 106, toward the die casting machine 108, and into the die casting machine 108.

In order to produce high quality aluminum alloy products, precise control of the cast structure is required. An effective method to provide a fine and uniform as-cast grain structure is to add a grain refiner 128, such as a nucleating agent, to the molten metal 104 to control crystal formation during solidification. As best shown in FIG. 4, the die cast holding furnace system 100 includes an automatic grain refinement unit 130, the automatic grain refinement unit 130 operatively coupled with the dosing region 112 to introduce a grain refiner 128 into the received molten metal 104 in (b). The grain refining unit 130 includes a wire rod 132, the wire rod 132 positioned in the batching unit 110 to introduce the grain refiner 128 as the molten metal 104 refills the batching region 112. This step is performed between Die Casting Machine (DCM) cycles. The grain refining unit 130 adds grain refiner 128 into the dosing region 110 for direct contact with the molten metal 104. The grain refiner 128 may be a chemical added to the molten metal 104 or alloy to control grain growth, such as SiO₂Or TiB₂。

As best shown in fig. 5A, the die cast holding furnace system 100 includes an automated Metal Matrix Composite (MMC) feed unit 134, the automated Metal Matrix Composite (MMC) feed unit 134 operably coupled with the ultrasonic unit 116, and the automated Metal Matrix Composite (MMC) feed unit 134 configured to provide ceramic particles 136 to the ultrasonic unit 116. As best shown in fig. 5B, the ultrasonic unit 116 then releases both the degassing agent 118 and the ceramic particles 136 into the molten metal 104 via the probe 117. The ceramic particles 136 are fed directly into the ultrasonic waves for uniform distribution throughout the molten metal 104. The ceramic particles 136 may comprise SiC, B₄C. Nano alumina (Al)₂O₃) Decorating aluminium or SiO₂Ceramic composite materials or other suitable materials.

The ultrasonic assistance provided by the automated MMC feeding unit 134 includes an electromagnetic pump 138 for both Lorentz (Lorentz) force agitation and Joule (Joule) heating. As shown in fig. 5A, an electromagnetic pump 138 applies an alternating magnetic field (single or multi-phase) to a conductor to induce a current in the conductor, where the magnetic field acts as a non-invasive stirring device and passes the current through the conductor to generate heat. In other words, the electromagnetic pump 138 is a pump that uses electromagnetic action to move the molten metal 104 (i.e., liquid metal or any electrically conductive liquid). As the molten metal 104 moves into the magnetic field, an electrical current is passed through the molten metal 104, thereby creating an electromagnetic force that moves the molten metal 104 along with the degasser 118 and the ceramic particles 136. This prevents ceramic particles 136 from precipitating in the uniform distribution of molten Al before reaching diecasting machine 108.

As mentioned above, the ultrasonic vibrations with degassing agent provided by the ultrasonic unit 116 in combination with the limited storage capacity of the dosing zone 112 achieve a large increase in the melt quality of the metal. For example, as established by table 1 below, this combination results in a more than five-fold reduction in dross volume as compared to argon rotary degassing. This combination also provides a reduction in the amount of hydrogen compared to other systems.

In more detail, Table 1 is a comparison of various properties of 250kg of degassed Al-Si-Mg alloys after using different degassing methods for the Al-Si-Mg alloys. For example, using ultrasonic degassing on 250kg of Al-Si-Mg alloy yields 0.17cm³Molecular hydrogen content of 2.706g/cm³Density of 1 to 2, and a tensile property of Unified Threading Standard (UTS) of 245MPa (force per unit area) and 5.1% El (elongation). The use of ultrasonic degassing is a more advantageous process compared to other degassing processes, because the use of ultrasonic degassing results in lower hydrogen content, higher density, lower number of pores and higher tensile properties.

TABLE 1

In one embodiment, such as SiO₂Is introduced into the molten metal 104 via the dosing unit 110. Grain refiner SiO₂Compared with the commonly used TiB₂Master alloys are cheap and more effective in grain refinement. Referring to tables 2 to 5, SiC and/or B₄The C-ceramic composite is added in small doses until the material becomes an in-situ MMC. The composite material may have increased strength and modulus. However, the composite may have a lower ductility.

Table 2 is a comparison of the density characteristics of in situ MMC when ceramic composites are added in small doses. For example, as the amount of ceramic composite increases, the density of the MMC increases (i.e., 2.65g/cm without ever adding ceramic composite)³To 2.82g/cm in the case where the ceramic composite material constitutes 15% of the MMC³)。

TABLE 2

Table 3 is a comparison of the hardness properties of the in-situ MMC when the ceramic composite is added in small doses. For example, as the amount of ceramic composite material increases, the hardness of the MMC increases (i.e., from 62HBW without the addition of ceramic composite material to 72HBW with the ceramic composite material comprising 15% of the MMC).

TABLE 3

Table 4 is a comparison of the tensile modulus properties of the in situ MMC when the ceramic composite was added in small doses. For example, as the amount of ceramic composite increases, the tensile modulus of the MMC increases (i.e., from 75GPa without the addition of ceramic composite to 125.25GPa where the ceramic composite constitutes 15% of the MMC).

TABLE 4

Table 5 is a comparison of tensile properties of the in situ MMC when the ceramic composite was added in small doses. For example, as the amount of ceramic composite increases, the force per unit area of the MMC increases (i.e., from 205UTS without the addition of ceramic composite to 260UTS with the ceramic composite constituting 15% of the MMC), while the elongation of the MMC decreases (i.e., from 15% El with the addition of no ceramic composite to 13% El with the ceramic composite constituting 15% of the MMC).

TABLE 5

The die cast holding furnace system 100 with the combination of the dosing unit 110 and the ultrasonic unit 116 as described in this disclosure has various beneficial results. One beneficial result is an ultra-pure molten metal 104, such as molten aluminum. Another benefit is that the die cast holding furnace system 100 has a dosing accuracy within +/-1%. Furthermore, the dosing is accurate where the dosing region 112 is both refilled with molten metal 104 and pressurized at the same time. This is in contrast to conventional systems which have problems with pressurization of the system due to proportional valves becoming confused during refilling, furnace metal levels changing, etc. Another benefit is better temperature control of the batch metal.

Still another benefit is that the die casting holding furnace system 100 allows for small additions of grain refiner 128, such as TiB₂And/or SiO₂Is added directly to the molten metal 104 so as to form a uniform distribution due to the ultrasonic waves. The die cast holding furnace system 100 also allows a small addition of ceramic particles 136 to be added directly to the molten metal 104, resulting in a uniform distribution due to the ultrasonic waves, which results in an in situ MMC material.

The foregoing description of embodiments has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment even if not specifically shown or described. The various elements or features of a particular embodiment may also be varied in a number of ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A die casting furnace system comprising:

a die-casting holding furnace unit defining a cavity for holding molten metal;

a dosing unit disposed within the cavity and defining a dosing region disposed in fluid communication with the cavity for receiving molten material during pressurization of the cavity; and

an ultrasonic unit operatively coupled with the dosing region and configured to introduce vibrations in the received molten material to facilitate removal of gas from the received molten material.

2. The die casting furnace system of claim 1, wherein the ultrasonic unit comprises a probe extending into the compounding area to establish the operative coupling between the ultrasonic unit and the compounding area and additionally introduce a degasser into the received molten material.

3. The die casting furnace system of claim 2, wherein the cavity of the die casting holding furnace unit has a first storage capacity and the dosing region of the dosing unit has a second storage capacity that is less than the first storage capacity.

4. The die casting furnace system of claim 3, wherein said dosing region has an inlet arranged in fluid communication with said cavity for receiving said molten material from said die casting holding furnace unit and an outlet arranged in fluid communication with a shot sleeve for dispensing said molten material from said dosing unit and into a die casting machine after treatment by said degasser.

5. The die cast furnace system of claim 4, wherein the degasser comprises a carrier gas and the probe is configured to generate ultrasonic vibrations for rupturing the carrier gas and introducing a plurality of cavitation bubbles into the received molten material.

6. The die cast furnace system of claim 5, further comprising an automatic grain refinement unit operably coupled with the batching region to introduce grain refiner into the received molten material.

7. The die cast furnace system of claim 6, wherein the automatic grain refinement unit includes a wire rod positioned within the batching region to establish the operable coupling between the automatic grain refinement unit and the batching region.

8. The die casting furnace system of claim 7, wherein the grain refiner comprises SiO₂Or TiB₂At least one of (a).

9. The die casting furnace system of claim 5, further comprising:

an automated metal matrix composite dosing unit operatively coupled with the ultrasonic unit and configured to provide ceramic particles to the ultrasonic unit; and is

The probe is configured to introduce the ceramic particles into the received molten material along with the carrier gas and the cavitation bubbles.

10. The die cast furnace unit of claim 9, wherein said ceramic particles comprise SiC, B₄C or nano alumina (Al)₂O₃) Decorating at least one of the aluminum.

11. The die casting furnace unit of claim 9 further comprising a solenoid pump operatively coupled with said shot sleeve for moving the molten material dispensed from said outlet of said dosing region through said shot sleeve and preventing said ceramic particles from settling out of the dispensed molten material prior to reaching said die casting machine.

12. The die-casting furnace unit of claim 11, wherein the electromagnetic pump is configured to generate both Lorentz (Lorentz) force agitation and Joule (Joule) heating of the dispensed molten material.

13. The die cast furnace unit of claim 4, wherein the inlet of the dosing region includes a check valve for allowing the molten material to pass through the inlet during the pressurization of the cavity of the die cast holding furnace unit and for preventing the molten material from returning to the cavity when received within the dosing region.

14. The die-casting furnace unit according to claim 1, wherein the die-casting holding furnace unit is a closed holding furnace.

15. The die cast furnace unit according to claim 2, wherein the probe is fastened to the die cast holding furnace unit and extends down into the batching area.