FILTER DEVICE FOR MOLTENED METAL FOR CASTING VEHICLE COMPONENTS

Abstract

A filtration system for molten aluminum metal comprising a receiving tank capable of receiving molten metal, a filter device for filtering the molten metal, a pump capable of continuously circulating the molten metal through the filter device, and a pouring device for receiving the filtered molten metal from the filter device. The filter device includes a chamber, an inlet channel capable of conveying the molten metal into the chamber, and an outlet channel capable of conveying unused filtered molten metal from the chamber back into the receiving tank. Removable filter elements are arranged in series in the inlet channel. The removable filter elements are designed to remove inclusions larger than a specified diameter from the molten metal.The filter device includes at least one nozzle capable of directing a stream of inert gas to cover the molten metal, and a heating element.

Description

INTRODUCTION

[0001] The present disclosure relates to the casting of vehicle components, in particular to a filter device for molten metal alloys for casting vehicle components.

[0002] Casting is a process in which a molten metal alloy flows into a mold cavity having a predetermined shape of a desired cast component. High-pressure die casting (HPDC) and low-pressure die casting (LPDC) processes are typically used in the automotive industry for casting vehicle components, especially very large cast components. Ultra-large cast components, also known as ultra-large castings, enable lighter and less complex vehicle manufacturing by replacing a large number of stamped body panels with a single, ultra-large casting. These ultra-large castings are often referred to as mega- or giga-castings due to the enormous size of the die-casting machines used to produce them.As a non-limiting example, a one-piece ultra-large casting may have a width of at least 0.8 meters (m), a length of at least 1 m, and a height of at least 0.25 m.

[0003] In the automotive industry, molten aluminum casting alloys typically undergo a rotary degassing process before being injected into a die. Rotary degassing involves injecting an inert gas such as argon or nitrogen into the molten aluminum casting alloys through a rotating graphite shaft to reduce impurities such as hydrogen gas and aluminum oxides, both of which can lead to porosity and other inclusions in the solidified castings.

[0004] Although rotary degassing of molten cast alloys serves its purpose, there is still a need to further improve the quality of the molten alloys with regard to the removal of unwanted impurities before the molten alloys are introduced into the casting molds in the production of ultra-large cast vehicle components. SUMMARY

[0005] According to several aspects, a molten metal filter device is disclosed. The molten metal filter device includes a housing having an inner surface defining an inlet channel, an outlet channel, and a chamber in fluid communication with the inlet channel and the outlet channel. A first filter element is disposed within the inlet channel. The inlet channel is configured to conduct molten metal into the chamber, and the outlet channel is configured to conduct the molten metal out of the chamber. The first filter includes a form factor that occupies a cross-section of the inlet channel perpendicular to the direction of flow of molten metal through the inlet channel. The first filter is operable to filter the molten metal to produce a filtered molten metal.

[0006] In another aspect of the present disclosure, the chamber is accessible to transfer a portion of the filtered molten metal from the chamber into a pouring device.

[0007] In another aspect of the present disclosure, the molten metal filtering apparatus further comprises a nozzle operable to direct a stream of inert gas into at least one of the inlet channel and the outlet channel to cover the molten metal.

[0008] In another aspect of the present disclosure, a second filter element is disposed downstream of the first filter element in the inlet passage.

[0009] In another aspect of the present disclosure, the outlet channel is immediately adjacent to the inlet channel and separated by a heat-conducting partition.

[0010] In another aspect of the present disclosure, the outlet channel is configured to convey the molten metal in a direction opposite to the direction of flow of the molten metal through the inlet channel.

[0011] In another aspect of the present disclosure, the molten metal filtering apparatus further comprises at least one pump in fluid communication with at least one of the inlet channel and the outlet channel.

[0012] In another aspect of the present disclosure, the at least one pump comprises an upstream pump in fluid communication with a receptacle and the inlet channel, and a downstream pump in fluid communication with the outlet channel and the receptacle. The upstream pump is operable to draw the molten metal from the receptacle and propel the molten metal through the inlet channel. The downstream pump is operable to draw the molten metal from the outlet channel and propel the molten metal to the receptacle.

[0013] In another aspect of the present disclosure, the molten metal filter device further comprises a hood covering at least one of the inlet channel and the outlet channel. The hood includes a removable door that provides access for selective removal of the first filter element.

[0014] In another aspect of the present disclosure, the molten metal filtering apparatus further comprises a heating element disposed within the hood and above at least one of the inlet channel and the outlet channel.

[0015] According to several aspects, a molten metal filtration system is disclosed. The system includes a receiving tank operable to receive molten metal; a filtration device including a chamber, an inlet channel operable to receive the molten metal from the receiving tank and direct the molten metal into the chamber, and an outlet channel operable to direct the molten metal from the chamber and back into the receiving tank; a pump operable to move the molten metal from the receiving tank through the inlet channel; and a plurality of removable filters arranged in series in the inlet channel. The plurality of removable filters are operable to remove inclusions above a certain diameter from the molten metal.

[0016] In another aspect of the present disclosure, the outlet channel is in thermal communication with the inlet channel. The flow direction of the molten metal through the outlet channel is opposite to the flow direction of the molten metal through the inlet channel.

[0017] In another aspect of the present disclosure, at least one of the plurality of removable filters comprises at least one of a zirconium silicate, zirconium oxide, and silicon carbide and a pore size sufficient to remove particles having a size of about 20 micrometers and greater than 20 micrometers.

[0018] In another aspect of the present disclosure, the filter device comprises at least one nozzle operable to direct a stream of inert gas into at least one of the inlet channel and the outlet channel to cover the molten metal.

[0019] In another aspect of the present disclosure, the chamber is accessible to transfer a filtered molten metal from the chamber into a pouring device.

[0020] According to several aspects, a continuous-flow molten metal filtration system is disclosed. The system includes a filtration device operable to filter a molten cast alloy to produce a filtered molten cast alloy, and a pouring device operable to receive the filtered molten cast alloy to form a solidified casting. The filtration device includes an inlet channel, a chamber downstream of the inlet channel, an outlet channel downstream of the chamber, and at least one removable filter disposed in the inlet channel.

[0021] In another aspect of the present disclosure, the system further comprises a pump operable to continuously circulate the molten metal through the inlet channel, the chamber, and the outlet chamber.

[0022] In another aspect of the present disclosure, the inlet channel is in thermal communication with the outlet channel. The flow direction of the molten cast alloy in the outlet channel is opposite to a flow direction of the molten cast alloy in the inlet channel.

[0023] In another aspect of the present disclosure, the filter device comprises at least one nozzle operable to direct a stream of inert gas into at least one of the inlet channel and the outlet channel to coat the molten cast alloy.

[0024] In another aspect of the present disclosure, the chamber is accessible to transfer a filtered molten metal from the chamber into the pouring apparatus.

[0025] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described in this specification are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Fig. 1 is a schematic representation of a casting system with a continuous circulation filter device; Fig. Figure 2A is a schematic plan view of the filter device in cross section; Fig. Figure 2B is a schematic cross-sectional elevation view of the filter device; Fig. 3 is a schematic representation of a casting device; and Fig. 4 is an illustration of an exemplary ultra-large casting of a body component for a vehicle. DETAILED DESCRIPTION

[0027] The following description is merely exemplary and is not intended to limit the present disclosure, application, or uses. The illustrated embodiments are disclosed with reference to the drawings, wherein like reference numerals designate corresponding parts throughout the several drawings. The figures are not necessarily to scale, and some features may be shown larger or smaller to show details of particular features. The specific structural and functional details disclosed are not to be considered limiting, but rather as a representative basis for teaching one skilled in the art to practice the disclosed concepts.

[0028] Fig. 1 is a schematic representation of a die casting system 100 with a continuous circulation filtration device 200 for molten metal alloy. The die casting system 100 includes a receiving vessel 102, the molten metal alloy filtration device 200, and a die casting device 300. For brevity, the die casting system 100 is also referred to as system 100, the receiving vessel 102 is also referred to as receptacle 102, and the molten metal alloy filtration device 200 is also referred to as filtration device 200. The system 100 further includes at least one transfer pump 104A, 104B operable to continuously circulate a molten metal alloy through the filtration device 200. The molten metal alloy is also referred to as molten metal or molten alloy.A first portion 105A of the filtered molten alloy from the filter device 200 is fed to the die casting device 300 and a remaining second portion 105B of the filtered molten alloy from the filter device 200 is transferred to the receptacle 102 to circulate through the filter device 200.

[0029] In the non-limiting example shown, the receptacle 102 is configured to receive an unfiltered molten alloy 103 from a molten alloy source (not shown) and the second portion 105B of filtered molten alloy from the filter device 200. A mixture of unfiltered molten alloy 103 and filtered molten alloy 105B is referred to as partially filtered molten alloy 107. In one embodiment, the at least one transfer pump 104A, 104B includes only one upstream transfer pump 104A, also referred to as a first pump 104A, operable to draw the partially filtered molten alloy 107 from the receptacle 102 and drive the partially filtered molten alloy 107 through the filter device 200.In another embodiment, the at least one transfer pump 104A, 104B comprises only a downstream transfer pump 104B, also referred to as a second pump 104B, which is operable to draw the second portion 105B of the filtered molten alloy from the filter device 200 and drive the second portion 105B of the filtered molten alloy to the receptacle 102 for circulation through the filter device 200. In yet another embodiment, the at least one transfer pump 104A, 104B comprises both the upstream pump 104A and the downstream pump 104B.The upstream pump 104A cooperates with the downstream pump 104B to provide a uniform, predetermined flow rate through the filter device 200 by balancing the flow of the partially filtered molten alloy 107 into the filter device 200 and the flow of the second portion 105B of the filtered molten alloy out of the filter device 200.

[0030] Fig. 2A is a schematic top view of the filter device 200 in cross-section. The filter device 200 includes a housing 202 having an inner surface 204 defining an inlet channel 206, an outlet channel 208, and a chamber 210 in fluid communication with both the inlet channel 206 and the outlet channel 208. The inlet channel 206 includes an inlet opening 212 for receiving a flow of molten metal from the receptacle 102. The outlet channel 208 includes an outlet opening 214 in fluid communication with the receptacle 102. The molten metal flows from the receptacle 102 through the inlet channel 206 into the chamber 210. From the chamber 210, the molten metal flows through the outlet channel 208 back into the receptacle 102 or from the chamber 210 into the die casting device 300.

[0031] A plurality of removable filter elements, such as a first filter element 218A and a second filter element 218B, are arranged in series in the inlet channel 206 to filter the molten alloy flowing through the inlet channel 206 into the chamber 210. The first and second filter elements 218A, 218B have a shape factor suitable to fill a cross-sectional area (A) of the inlet channel 206 perpendicular to the direction of flow of the molten alloy in the inlet channel 206. The inner surface 204 of the housing 202 may also define slots 219 for receiving the filter elements 218A, 218B. The filter elements 218A, 218B may be made of materials including, but not limited to, zirconium silicate, zirconium oxide, silicon carbide, and other materials that can withstand the temperature and flow of the molten alloy while filtering out contaminants above a predetermined diameter size.

[0032] For aluminum-silicon (Al-Si) casting alloys, it is desirable for the filter elements 218A, 218B to have a pore size of approximately 20 micrometers in diameter to remove unwanted contaminants larger than 20 micrometers, such as dross, foam, and oxides, from the molten alloy flow. Such contaminants can lead to porosity and other undesirable inclusions in the solidified castings. Another advantage is that the filter elements 218A, 218B facilitate homogenization of the alloying elements in the molten metal and convert turbulent flows into laminar flows by slowing the flow of molten metal as the molten metal moves through the filter device 200. This causes significantly smaller contaminants to enter the die casting device 300.The pores of the filter elements 218A, 218B may have predetermined shapes to increase the service life of the filter elements 218A, 218B without clogging. The filter elements 218A, 218B may be manufactured by additive manufacturing, such as three-dimensional (3D) printing.

[0033] In the non-limiting example shown, the inlet channel 206 is adjacent to the outlet channel 208 and is separated from the outlet channel 208 by a thermal energy-conducting partition 216. The inlet channel 206 is in thermal communication with the outlet channel 208, meaning that thermal energy is transferred through the partition 216 between the molten metal flowing through the inlet channel 206 and the outlet channel 208. The molten metal flowing through the outlet channel 208 back to the receptacle 102 flows in a direction opposite to the flow of molten metal flowing through the inlet channel 206 from the receptacle 102. The counterflow of molten metal in the inlet channel 206 and the outlet channel 208 allows for a continuous flow of molten metal through the filter elements 218A and 218B while minimizing the temperature drop.The continuous counterflow extends the service life of the filter elements 218A, 218B by preventing premature clogging of the filter elements 218A, 218B.

[0034] Fig. Figure 2B is a schematic cross-sectional side elevation view of the filter device 200. The chamber 210 is accessible for the continuous or batchwise discharge of filtered molten metal into the die casting device 300 via a ladle, plug rod, chute, or other known methods for withdrawing molten metal. The filter device 200 includes a cover 220 or hood 220 over the inlet channel 206 and the outlet channel 208 to minimize thermal energy loss of the molten metal. Overhead heating elements 222 are provided within the covered portion to maintain the temperature of the molten metal. Non-limiting examples of overhead heating elements 222 include radiators, gas-fired tubular heaters, and electrical resistance heating elements.A portion of the inner surface 204 of the filter device 200 may be lined with refractory materials 223 to minimize heat loss of the molten metal.

[0035] An access hatch 224 is provided in the cover 220 to allow access to the plurality of filter elements 218A, 218B. The filter elements 218A, 218B can be selectively removed and replaced through the access hatch 224. At least one nozzle 226 is disposed within the hood 220 and is configured to direct an inert gas 228, such as nitrogen or argon, into at least one of the inlet channel 206 and the outlet channel 208 to coat the surface 230 of the molten metal stream. The inert gas 228, also referred to as a shielding gas, prevents the formation of new oxides on the surface of the molten metal stream where the molten metal is exposed to air.

[0036] Fig. 3 is a schematic representation of the die casting apparatus 300. The die casting apparatus 300 includes a die casting mold 302 having an inner surface 304 defining a mold cavity 306. The mold cavity 306 is configured to receive the filtered molten metal from the chamber 210 of the filter apparatus 200 to form an ultra-large casting having a predetermined shape of the mold cavity 306. The die casting apparatus 300 also includes a piston mechanism 308 and / or a pouring mechanism 340 for transferring the molten metal into the shot chamber system 312 to direct the filtered molten metal into the mold cavity 306. The mold 302 is typically formed from two pieces 302a, 302b, one of which is a fixed piece 302a and the other of which is a movable piece 302b designed to allow the removal of the solidified casting.The smaller size and lower content of oxide particles in the filtered 105A alloy improves mechanical properties such as final tensile strength, yield strength, percent elongation, and fatigue life of the solidified casting. Increasing the percent elongation has the potential to eliminate heat treatment in some cast component applications. An extremely low oxide content increases the desired overall material properties. Although a die casting apparatus 300 is described, the die casting apparatus 300 may be any casting apparatus or mold capable of receiving a filtered 105A metal alloy to form solidified objects. Other objects include, but are not limited to, ingots, slabs, bars, and similar aluminum raw materials.Other casting processes include, but are not limited to, semi-permanent molding (SPM), sand casting, lost foam, and investment casting. The filter device 200 can be used for any casting process that utilizes molten aluminum.

[0037] With reference to Fig. 1-3, in one non-limiting example of the operation of the system 100, upon startup, an unfiltered molten metal 103 is introduced into the receptacle 102. The upstream pump 104A draws the unfiltered molten metal 103 from the receptacle 102 and forces the unfiltered molten metal 103 through the inlet channel 206 and the filters 218A and 218B to produce a filtered molten metal 105A. In a continuous or batch process, predetermined quantities of filtered molten metal 105A are transferred from the chamber 210 of the filter device 200 to the die casting device 300. The remaining portion of the filtered metal 105B flows through the chamber 210 and out of the filter device 200 through the outlet channel 208. The downstream pump 104B draws the unused filtered molten metal 105B from the chamber 210 and transfers the unused filtered molten metal 105B through the outlet channel 208 to the receiver 102.During steady-state operation, the molten metal in the receptacle 102 is continuously replenished with the unfiltered molten metal 103 in an amount equal to the amount of filtered molten metal 105A removed from the filter device 200, so that a mixture of filtered and unfiltered metal alloy 107 forms in the receptacle 102. The mixture of unfiltered and filtered molten metal 107 from the receptacle 102 is continuously circulated through the filter device 200 to provide the filtered molten metal 105A for the casting device.

[0038] Fig.4 is a non-limiting example of an ultra-large casting 400 for a vehicle that can be manufactured with the system 100. The ultra-large casting 400 shown is that of a structural floor body part of the vehicle's body. Other examples of structural ultra-large castings include, but are not limited to, body panels, battery trays, and other load-bearing components with varying cross-sectional thicknesses. The ultra-large casting 400 can be designed and manufactured for on-road vehicles such as cars, motorcycles, pickup trucks and trailers, sport utility vehicles (SUVs), and recreational vehicles (RVs), as well as for non-road vehicles such as watercraft, aircraft, and trucks.

[0039] As a non-limiting example, the ultra-large casting 400 may be produced by casting an aluminum-silicon (Al-Si)-based alloy with the system 100. The molten Al-Si alloy is filtered through the filter device 200 to remove impurities, oxides, and other particles larger than about 20 micrometers and provide a homogeneous casting alloy for the die casting device 300. The device can be used to filter particles down to 5 micrometers in size from aluminum-based alloys that do not contain silicon. The filtered molten metal 105A is injected by the piston mechanism 308 through the shot sleeve system to fill the mold cavity 306 within a prescribed time and pressure. The molten metal is cooled in the mold 302 until solidification and ejected from the mold 302.The ejected solidified casting 400 is then machined to the design dimensions and tolerances and, if necessary, heat treated to the desired specifications.

[0040] The ultra-large castings, produced with a filtered casting alloy, have an extremely low oxide content and therefore provide excellent mechanical properties. An inclusion content of less than 12 mm 2 / kg according to porous disk filtration analysis (PoDFA) is considered an extremely low oxide content in the metal casting industry. The ultimate tensile strength, yield strength, percent elongation, and fatigue life have been improved compared to current material properties of cast alloys used in computer-aided design (CAD). Higher percent elongations in the as-cast state can eliminate the need for heat treatment in some applications. An extremely low oxide content improves fatigue properties and allows for greater weight reduction of components, which increases mileage (range), reduces emissions, and lowers component material costs.

[0041] The description of the present disclosure is merely exemplary, and variations that do not depart from the general spirit of the present disclosure are intended to be included within the scope of the present disclosure. Such variations should not be construed as a departure from the spirit and scope of the present disclosure.

Claims

[1] A molten metal filter device comprising: a housing having an inner surface defining an inlet channel, an outlet channel, and a chamber in fluid communication with the inlet channel and the outlet channel; and a first filter element disposed in the inlet channel; wherein the inlet channel is configured to conduct a molten metal into the chamber, and the outlet channel is configured to conduct the molten metal out of the chamber; and wherein the first filter element comprises a form factor that occupies a cross-section of the inlet channel perpendicular to a flow direction of the molten metal through the inlet channel. [2] A molten metal filter apparatus according to claim 1, wherein the chamber is accessible to transfer a portion of the molten metal from the chamber into a pouring device. [3] The molten metal filtering apparatus of claim 1, further comprising a nozzle operable to direct a stream of inert gas into at least one of the inlet channel and the outlet channel to cover the molten metal. [4] The molten metal filter device according to claim 1, further comprising a second filter element disposed downstream of the first filter element in the inlet channel. [5] A molten metal filter device according to claim 1, wherein the outlet channel is immediately adjacent to the inlet channel and separated by a heat-conducting partition wall. [6] A molten metal filter device according to claim 5, wherein the outlet channel is operable to convey the molten metal in a direction opposite to the flow direction of the molten metal through the inlet channel. [7] The molten metal filter apparatus of claim 1, further comprising at least one pump in fluid communication with at least one of the inlet channel and the outlet channel. [8] A molten metal filter device according to claim 7, wherein the at least one pump comprises: an upstream pump in fluid communication with the inlet channel, the upstream pump being operable to drive the molten metal through the inlet channel; and a downstream pump in fluid communication with the outlet channel, the downstream pump operable to draw the molten metal from the outlet channel. [9] A molten metal filter device according to claim 1, further comprising: a hood covering at least one of the inlet channel and the outlet channel, the hood including a removable door providing access for selective removal of the first filter element. [10] The molten metal filter apparatus of claim 9, further comprising a heating element disposed within the hood and above at least one of the inlet channel and the outlet channel.

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