Patent Application
20240424551
The present disclosure relates to casting of vehicle components, more particularly, to a molten metal alloy filter device for casting of vehicle components.
Casting is a process that is characterized by flowing a molten metal alloy 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, particularly those of ultra-large cast components. Ultra-large cast components, also referred to as ultra-large castings, allow vehicles to be lighter and less complex to manufacture by replacing large numbers of stamped panels with a single piece ultra-large casting. These ultra-large castings are often referred to as mega-castings or giga-castings due to the huge size of the die casting machines used to make these castings. As a non-limiting example, a single piece ultra-large casting can have a width of at least 0.8 meter (m), a length of at least 1 m, and a height of at least 0.25 m.
In the automotive industry, molten casting aluminum alloys are normally subjected to a rotary degassing process before being injected into a die-casting mold. The rotary degassing process injects an inert gas, such as argon or nitrogen, into the molten metal casting aluminum alloys through a rotating graphite shaft in order to reduce contaminates such as hydrogen gas and aluminum oxides, both of which can cause porosity and other inclusions in the solidified castings.
Thus, while rotary degassing of molten casting alloys achieve their intended purpose, there is a continued need to further improve the quality of the molten alloys with respect to eliminating undesirable contaminates prior to introducing the molten alloys into the casting molds in the manufacturing of ultra-large cast vehicle components.
According to several aspects, a molten metal filter device is disclosed. The molten metal filter device includes a housing having an interior 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 disposed in the inlet channel. The inlet channel is configured to convey a molten metal into the chamber and the outlet channel is configured to direct the molten metal out of the chamber. The first filter includes a form factor occupying a cross-section of the inlet channel perpendicular to the direction of flow of the molten metal through the inlet channel. The first filter is operable to filter the molten metal to produce a filtered molten metal.
In an additional aspect of the present disclosure, the chamber is accessible to transfer a portion of the filtered molten metal from the chamber to a casting device.
In another aspect of the present disclosure, the molten filter device further include a nozzle operable to direct an inert gas flow into at least one of the inlet channel and the outlet channel to blanket the molten metal.
In another aspect of the present disclosure, a second filter element disposed in the inlet channel downstream of the first filter element.
In another aspect of the present disclosure, the outlet channel is immediately adjacent to the inlet channel and separated by a heat energy conductive partition wall.
In another aspect of the present disclosure, the outlet channel is configured to convey the molten metal in a direction counter-current to the direction of flow of the molten metal through the inlet channel.
In another aspect of the present disclosure, the molten metal filter device further includes at least one pump in fluid communication with at least one of the inlet channel and the outlet channel.
In another aspect of the present disclosure, the at least one pump includes an upstream pump in fluid communication with the holder and inlet channel, and a downstream pump in fluid communication with the outlet channel and the holder. The upstream pump is operable to draw the molten metal from the holder and pushes the molten metal through the inlet channel. The downstream pump is operable to draw the molten metal from the outlet channel and pushes the molten metal to the holder.
In another aspect of the present disclosure, the molten metal filter device further includes a hood covering at least one of the inlet channel and the outlet channel. The hood includes a removeable hatch to allow access to selectively remove the first filter element.
In another aspect of the present disclosure, the molten metal filter device further includes a heating element disposed within the hood and overhead at least one of the inlet channel and the outlet channel.
According to several aspects, a molten metal filter system is disclosed. The system includes, a holding tank operable to receive a molten metal; a filter device comprising a chamber, an inlet channel operable to receive the molten metal from the holding tank and convey the molten metal into the chamber, and an outlet channel operable to convey the molten metal out of the chamber and back into the holding tank; a pump operable to move the molten metal from the holding tank through the inlet channel; and a plurality of removeable filters disposed in series within the inlet channel. The plurality of removable filters are operable to remove inclusions above a determined diameter size from the molten metal.
In an additional aspect of the present disclosure, the outlet channel is in thermal communication with the inlet channel. The direction of flow of the molten metal through the outlet channel is counter-current to a direction of flow of the molten metal through the inlet channel.
In another aspect of the present disclosure, at least one of the plurality of removeable filters includes at least one of a zirconium silicate, zirconium oxide, and silicon carbide, and a pore size sufficient to remove particles size of about 20 microns and greater than 20 microns.
In another aspect of the present disclosure, the filter device includes at least one nozzle operable to direct an inert gas flow into at least one of the inlet channel and the outlet channel to blanket the molten metal.
In another aspect of the present disclosure, the chamber is accessible to transfer a filtered molten metal from the chamber to a casting device.
According to several aspects, a continuous flow molten metal filter system is closed. The system includes a filter device operable to filter a molten casting alloy to produce a filtered molten casting alloy and a casting device operable to receive the filtered molten casting alloy to form a solidified casting. The filter 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.
In an additional aspect of the present disclosure, the system further includes a pump operable to continuously recirculate the molten metal through inlet channel, chamber, and outlet chamber.
In another aspect of the present disclosure, the inlet channel is in thermal communication with the outlet channel. The direction of flow of the molten casting alloy in the outlet channel is counter-current to a direction of the flow of the molten casting alloy in the inlet channel.
In another aspect of the present disclosure, the filter device includes at least one nozzle operable to direct an inert gas flow into at least one of the inlet channel and the outlet channel to blanket the molten casting alloy.
In another aspect of the present disclosure, the chamber is accessible to transfer a filtered molten metal from the chamber to the casting device.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. The illustrated embodiments are disclosed with reference to the drawings, wherein like numerals indicate corresponding parts throughout the several drawings. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular features. The specific structural and functional details disclosed are not intended to be interpreted as limiting, but as a representative basis for teaching one skilled in the art as to how to practice the disclosed concepts.
In the non-limiting example shown, the holder 102 is configured to receive an unfiltered molten alloy 103 from a molten alloy source (not shown) and the second portion 105B of the filtered molten alloy from the filter device 200. A mixture of unfiltered molten alloy 103 and filtered molten alloy 105B is referred to as a partially filtered molten alloy 107. In one embodiment, the at least one transfer pump 104A, 104B includes only an upstream transfer pump 104A, also referred to as a first pump 104A, operable to draw the partially filtered molten alloy 107 from the holder 102 and pushes the partially filtered molten alloy 107 through the filter device 200. In another embodiment, the at least one transfer pump 104A, 104B includes only a downstream transfer pump 104B, also referred to as a second pump 104B, operable to draw the second portion 105B of filtered molten alloy from the filter device 200 and pushes the second portion 105B of filtered molten alloy to the holder 102 to be recirculated through the filter device 200. In yet another embodiment, the at least one transfer pump 104A, 104B includes both the upstream pump 104A and the downstream pump 104B. The upstream pump 104A coordinates with the downstream pump 104B to provide a consistent predetermined flowrate 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 filtered molten alloy out of the filter device 200.
A plurality of removable filter elements such as a first filter element 218A and a second filter element 218B are disposed in series within the inlet channel 206 to filter the molten alloy flowing through the inlet channel 206 to the chamber 210. The first and second filter elements 218A, 218B have a form factor adapted to fill a cross-sectional area (A) of the inlet channel 206 perpendicular to the direction of the molten alloy flow within the inlet channel 206. The interior surface 204 of the housing 202 may also define slots 219 to receive the filter elements 218A, 218B. The filter elements 218A, 218B may be manufactured of materials including, but not limited to, zirconium silicate, zirconium oxide, silicon carbide, and other materials capable of withstanding the temperature and flow of the molten alloy while filtering out contaminates above a predetermined diameter size.
For Aluminum-Silicon (Al—Si) casting alloys, it is desirable for the filter elements 218A, 218B to have a pore size such that of about 20 microns in diameter to remove undesirable contaminates larger than 20 microns such as slag dross, foam, and oxides from the molten alloy flow. Such contaminates may cause porosity and other undesirable inclusions in the solidified castings. Another benefit is that the filter elements 218A, 218B facilitate a homogenization of the alloying elements within the molten metal and turn turbulent flows into laminar flows by decelerating the molten metal flow as the molten metal moves through the filter device 200. This results in significantly smaller size contaminates entering into the die-casting device 300. The pores of the filter elements 218A, 218B may have predetermined shapes to increase the useful life of the filter elements 218A, 218B without plugging. The filter elements 218A, 218B may be manufactured by additive manufacturing such as three-dimensional (3-D) printing.
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 heat energy conductive partition wall 216. The inlet channel 206 is in thermal communication with the outlet channel 208, meaning that heat energy is transferred through the partition wall 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 holder 102 is in a direction counter-current to the flow of the molten metal flowing through the inlet channel 206 from the holder 102. The counter-current flow of the molten metal within the inlet channel 206 and outlet channel 208 enables a continuous molten metal flow through the filter elements 218A and 218B while minimizing temperature drop. The continuous counter-current flow extends the operating life of the filter elements 218A, 218B by preventing premature plugging of the filter elements 218A, 218B.
An access hatch 224 is provided in the cover 220 to allow for access to the plurality of filter elements 218A, 218B. The filter elements 218A, 218B may 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 blanket the surface 230 of the molten metal flow. The inert gas 228, also referred to as a cover gas, inhibits the formation of fresh oxides on the surface of the molten metal flow, where the molten metal is exposed to air.
Referring to
As a non-limiting example, the ultra-large casting 400 is manufacturable by casting an aluminum-silicon (Al—Si) based alloy using the system 100. The molten Al—Si alloy is filtered by the filter device 200 to remove any impurities, oxides, and other particles larger than about 20 microns to provide a homogenous casting alloy to the die-casting device 300. The device could be used to filter out particles as low as 5 microns for aluminum based alloy not containing silicon. The filtered molten metal 105A is injected by the plunger mechanism 308 through the shot sleeve system to fill the mold cavity 306 within a prescribed time and pressure. The molten metal is cooled to solidification in the mold 302 and ejected from the mold 302. The ejected solidified casting 400 is then machined to design dimensions and tolerances, and heat treated as necessary to desired specifications.
Ultra-large castings manufactured with a filtered casting alloy have ultra-low oxide content thus providing superior mechanical properties. An inclusion content less than 12 mm2/kg based on Porous Disk Filtration Analysis (PODFA) is considered to be ultra-low oxide content in the metal casting industry. The ultimate tensile strength, yield strength, percent elongation, and fatigue life are improved over the current casting alloy material properties used in computer-aided-design (CAD). Higher as-cast percent elongations may eliminate the need for heat treatment of some applications. Ultra-low oxide content improves fatigue properties and would permit more lightweighting of components, which improves vehicle mileage (range), reduces emissions, and reduces the material cost of the components.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the general sense of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.
