CN111356778A - Method for recovering machining waste - Google Patents

Abstract

A method is provided that includes providing a quantity of a metal contaminated with a contaminant that includes a quantity of carbon; configuring the vacuum induction furnace to operate according to a set of operating parameters selected based on a characteristic of the contaminant, the set of operating parameters including at least one of pressure, atmosphere composition, casting temperature, or holding time; charging the amount of metal into a vacuum induction furnace; and operating the vacuum induction furnace to melt the quantity of metal in accordance with the set of operating parameters to remove at least some contaminants from the quantity of metal to provide an output metal having a carbon concentration less than or equal to the carbon concentration in the as-cast metal.

Description

Method for recycling machining waste

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is an International (PCT) patent application that relates to and claims the benefit of commonly owned, co-pending U.S. Provisional Patent Application No. 62/588,752, filed November 20, 2017, entitled "METHODS FOR RECOVERING ALUMINUM-LITHIUM SCRAP," The contents of which are incorporated herein by reference in their entirety.

technical field

The present invention relates to a method for cleaning and recycling machining scrap, such as aluminum-lithium ("AlLi") alloy scrap, for reuse.

Background technique

When virgin metal alloys (eg, in the form of extrudates or sheets) are to be machined to produce finished parts, they are coated with a water-soluble lubricant to facilitate the machining process. In some embodiments, the water-soluble lubricant contains one or more organic compounds (ie, carbon-containing compounds) dissolved in water. The result of the machining process is a finished product and a certain amount of scrap. In some cases, the finished product may use only about 10% of the raw material, and the remaining raw material may become machining waste that is still contaminated with water-soluble lubricants. Machining waste is commercially valuable and suitable for reuse, but cannot be reused until water-soluble lubricants have been removed from it.

SUMMARY OF THE INVENTION

In one embodiment, a method includes providing an amount of metal contaminated with a contaminant including an amount of carbon; configuring a vacuum induction furnace to operate according to a set of operating parameters, the set of Operating parameters are selected based on characteristics of the contaminant, the set of operating parameters including at least one of pressure, atmosphere composition, pouring temperature, or holding time; charging the vacuum induction furnace with the amount of metal; and according to the one The set of operating parameters operates the vacuum induction furnace to melt the quantity of metal to remove at least some contaminants from the quantity of metal to provide an output metal with a carbon concentration lower than or equal to the carbon concentration in the as-cast metal.

In some embodiments, the amount of metal comprises an amount of machining waste. In some embodiments, the method further includes the step of compacting the amount of metal into a monolithic metal prior to charging the amount of metal into the vacuum induction furnace.

In some embodiments, the set of operating parameters includes a hold time, and the hold time is between 0 minutes and 60 minutes. In some embodiments, the set of operating parameters includes pressure, and the pressure is between 1 micron and 300 microns. In some embodiments, the set of operating parameters includes an atmosphere composition. In some embodiments, the atmosphere composition includes an inert gas atmosphere. In some embodiments, the set of operating parameters includes a pouring temperature, and the pouring temperature is between 700°C and 770°C.

In some embodiments, the at least one contaminant includes sodium and lubricants. In some embodiments, the set of operating parameters includes pressure, pour temperature and hold time, the pressure is between 1 micron and 300 microns, the temperature is between 700°C and 755°C, and the hold time is between 30 minutes and 90 minutes. between.

In some embodiments, the amount of metal comprises one of a 2000-series aluminum alloy, a 5000-series aluminum alloy, a 6000-series aluminum alloy, a 7000-series aluminum alloy, or an 8000-series aluminum alloy. In some embodiments, the amount of metal comprises an aluminum-lithium alloy.

In some embodiments, the amount of metal is also contaminated with an amount of sodium. In some embodiments, the operating parameters include temperature and hold time, and the temperature and hold time are selected to provide a residual sodium concentration below the target concentration. In some embodiments, the target concentration is 6 parts per million.

In some embodiments, the contaminants comprise lubricants. In some embodiments, the operating parameters include a pour temperature of about 700°C and substantially no hold time. In some embodiments, the operating parameters include a pressure of about 300 microns. In some embodiments, the operating parameters include an argon atmosphere and a pressure of about 1 atmosphere.

Description of drawings

FIG. 1 is a flowchart depicting the steps of a method according to an exemplary embodiment; and

Figure 2 is a schematic illustration of a vacuum induction furnace that may be used in conjunction with exemplary embodiments.

Detailed ways

The invention may be further described with reference to the included drawings, wherein like structures are designated by like reference numerals throughout the several views. The accompanying drawings constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. Additionally, any measurements, specifications and the like shown in the figures are intended to be illustrative and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. The drawings shown are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

Among those benefits and improvements that have been disclosed, other objects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the various forms of the invention. Additionally, each example given in connection with various embodiments of the present invention is intended to be illustrative and not limiting.

Throughout the specification and claims, unless the context clearly dictates otherwise, the following terms take the meanings explicitly associated herein. As used herein, the phrases "in one embodiment" and "in some embodiments" do not necessarily refer to the same embodiment (although they may be). Additionally, as used herein, the phrases "in another embodiment" and "in some other embodiments" do not necessarily refer to different embodiments (although they may be). Accordingly, as described below, various embodiments of the present invention may be readily combined without departing from the scope or spirit of the present invention.

Also, as used herein, the term "or" is an inclusive "or" operator and is equivalent to the term "and/or" unless the context clearly dictates otherwise. Unless the context clearly dictates otherwise, the term "based on" is not exclusive and is permitted to be based on other factors not described. Further, throughout this specification, the meanings of "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

In some embodiments, the exemplary invention relates to a method of recycling machining waste to make it suitable for reuse. In some embodiments, exemplary inventions relate to a method of melting, cleaning and purifying machining waste to make it suitable for reuse. FIG. 1 shows a flow diagram of a method 100 according to an exemplary embodiment. In step 110, an amount of machining waste is provided. In some embodiments, the machining scrap comprises aluminum. In some embodiments, the machining waste contains lithium. In some embodiments, the machining waste includes aluminum and lithium. In some embodiments, the machining scrap comprises 2000-series aluminum alloys (ie, copper-based aluminum alloys). In some embodiments, the machining scrap comprises a 7000-series aluminum alloy (ie, a zinc-based aluminum alloy). In some embodiments, the machining scrap comprises one or more of alloys AA2050, AA2055, AA2060, AA2090, AA2091, AA2094, AA2095, AA2097, AA2098, AA2099, AA2195, AA2196, AA2197, AA2198, AA2199, AA2297, and AA2397 species, these alloys are named by the Aluminum Association of America. In some embodiments, the machining waste is coated with a lubricant. In some embodiments, the lubricant includes sodium. In some embodiments, the machining waste is not coated with a lubricant. In some embodiments, the machining scrap comprises a lithium-free aluminum alloy. In some embodiments, the machining waste has a bulk density between 20 and 50 pounds per cubic foot.

In step 120, at least a portion of the machining waste is compressed into a monolith. In some embodiments, the blocks are of the type commonly referred to as "disks." In some embodiments, the machining waste is bundled. In some embodiments, the machining waste contains solids. In some embodiments, the block has a mass of about 80 kilograms. In some embodiments, the block has a weight of about 1,500 pounds. In some embodiments, the block has a weight between 3,000 pounds and 6,000 pounds. In some embodiments, an amount of machined waste (eg, in an amount as described above) is selected for further processing, but is not compressed into pieces. In some embodiments, the discs are broken into smaller pieces prior to further processing. In some embodiments, omitting the step of forming the disc or instead breaking the disc into smaller pieces will provide an increase in the lubricant-coated surface area exposed during subsequent steps of the method 100 . It will be apparent to those skilled in the art that this step can be repeated as needed based on the amount of machining waste provided in step 110 .

In step 130, a vacuum induction furnace is provided. In some embodiments, the vacuum induction furnace is a vacuum induction degassing casting furnace. Figure 2 shows an exemplary vacuum induction furnace. In some embodiments, the vacuum induction furnace includes an enclosed vacuum chamber. In some embodiments, the vacuum induction furnace includes a vacuum pump configured to remove gas (eg, air, argon, vaporized lubricant) from the vacuum chamber. In some embodiments, the vacuum pump is configured to provide a configurable pressure level within the vacuum chamber. In some embodiments, the vacuum pump is configured to provide a pressure level within the vacuum chamber between 1 micron (ie, a pressure unit equal to 1/1000 of a millimeter of mercury) to 1 atmosphere. In some embodiments, the vacuum induction furnace includes an argon gas supply configured to selectively introduce argon gas into the vacuum chamber. In some embodiments, the vacuum induction chamber includes a vent. In some embodiments, the vacuum induction furnace includes an induction furnace within a vacuum chamber. In some embodiments, the induction furnace is configured to heat the contents of the container to a selected temperature for a selected period of time. In some embodiments, the vacuum induction furnace includes a mold within a vacuum chamber. In some embodiments, the vacuum induction furnace is configured to be operable to pour the contents of the container (eg, molten) into the mold at a selected time (eg, after the contents of the container have been heated for a selected period of time). machining waste).

Returning to Figure 1, in step 140, the vacuum induction furnace is configured to operate according to a given set of parameters. In some embodiments, parameters are selected to clean, melt, and cast aluminum-lithium machining waste while minimizing oxidation losses, maximizing alloy retention (especially maximizing lithium retention), and removing contaminants (eg, lubrication) as necessary agent) and minimize cycle time. In some embodiments, the parameter includes a target temperature. In some embodiments, the parameters include the heating rate to reach the target temperature. In some embodiments, the heating is performed at a controlled rate to ensure that moisture is not trapped below the level of the molten metal. In some embodiments, the parameters are selected based on the properties of the machined waste. In some embodiments, the parameters are selected based on whether the machining waste is coated with a lubricant. In some embodiments, the parameters are selected based on whether the machining waste contains contaminants (eg, sodium, calcium, potassium, etc.). In some embodiments, the vacuum induction furnace is configured to provide a vacuum. In some embodiments, the vacuum induction furnace is configured to provide an argon atmosphere. In some embodiments in which the vacuum induction furnace is to be configured to melt scrap without lubricant (eg, scrap resulting from dry dry machining), the vacuum induction furnace is configured to provide an argon atmosphere at or about atmospheric pressure, to provide about A temperature of 730°C and no hold time is provided after the temperature has been reached. In some embodiments in which the vacuum induction furnace is to be configured to melt scrap with lubricants but no contaminants (eg, sodium, calcium, potassium, etc.), the vacuum induction furnace is configured to provide (a) a vacuum of about 300 microns or (b) An argon atmosphere at or about atmospheric pressure, providing a temperature of about 700°C and no hold time after the temperature has been reached. In some embodiments where the vacuum induction furnace is to be configured to melt scrap with lubricants and contaminants (eg, sodium, calcium, potassium, etc.), the vacuum induction furnace is configured to provide a vacuum of about 300 microns, to provide a vacuum of about 700°C to temperature between about 755°C and a hold time of one hour. It will be apparent to those skilled in the art that the above-described configurations are exemplary only and other optimized configurations may be determined based on the characteristics of the particular batch of machining scrap at hand, based on the general characteristics of the machining scrap stream in progress, and the like.

Continuing with the description of step 140 of the exemplary method 100, the range of values for various parameters of the vacuum induction furnace will be described below. It will be apparent to those skilled in the art that all ranges described herein are inclusive (ie, a range between 100°C and 200°C includes values between 100°C and 200°C and all values therebetween). In some embodiments, the parameters include the internal atmosphere of the vacuum induction furnace (eg, the atmosphere within the vacuum chamber of the vacuum induction furnace). In some embodiments, the internal atmosphere includes a pressure level. In some embodiments, the pressure level is expressed in microns. In some embodiments, the pressure level is 1 micron. In some embodiments, the pressure level is 100 microns. In some embodiments, the pressure level is 200 microns. In some embodiments, the pressure level is 300 microns. In some embodiments, the pressure level is between 1 micron and 100 microns. In some embodiments, the vacuum level is between 1 micron and 200 microns. In some embodiments, the pressure level is between 1 micron and 300 microns. In some embodiments, the pressure level is between 100 microns and 200 microns. In some embodiments, the pressure level is between 100 microns and 300 microns. In some embodiments, the pressure level is between 200 microns and 300 microns. In some embodiments, pressure levels are expressed in millibars. In some embodiments, the pressure level is 0.001 mbar. In some embodiments, the pressure level is 0.132 mbar. In some embodiments, the pressure level is 0.263 mbar. In some embodiments, the pressure level is 0.4 mbar. In some embodiments, the pressure level is between 0.001 mbar and 0.132 mbar. In some embodiments, the pressure level is between 0.001 mbar and 0.263 mbar. In some embodiments, the pressure level is between 0.001 mbar and 0.4 mbar. In some embodiments, the pressure level is between 0.132 mbar and 0.263 mbar. In some embodiments, the pressure level is between 0.132 mbar and 0.4 mbar. In some embodiments, the pressure level is between 0.263 mbar and 0.4 mbar. In some embodiments, the pressure level is about 1,000 microns. In some embodiments, the pressure level is between 900 microns and 1,000 microns. In some embodiments, the pressure level is about 1 atmosphere. In some embodiments, the internal atmosphere includes an inert gas atmosphere. In some embodiments, the internal atmosphere includes an argon atmosphere. In some embodiments, the vacuum induction furnace is configured to generate a vacuum (eg, a vacuum of 100 microns) and then fill the internal atmosphere with argon. In some embodiments, the vacuum induction furnace is configured to generate a vacuum (eg, a 100 micron vacuum) and then fill the interior atmosphere with argon at a pressure level of about 1 atmosphere.

Continuing with the description of step 140 of the exemplary method 100, in some embodiments, the parameters include pouring temperature. In some embodiments, the pouring temperature is 700°C. In some embodiments, the pouring temperature is 710°C. In some embodiments, the pouring temperature is 720°C. In some embodiments, the pouring temperature is 730°C. In some embodiments, the pouring temperature is 740°C. In some embodiments, the pouring temperature is 750°C. In some embodiments, the pouring temperature is 755°C. In some embodiments, the pouring temperature is 760°C. In some embodiments, the pouring temperature is 768°C. In some embodiments, the pouring temperature is 770°C. In some embodiments, the casting temperature is between 700°C and 710°C. In some embodiments, the pouring temperature is between 700°C and 720°C. In some embodiments, the pouring temperature is between 700°C and 730°C. In some embodiments, the pouring temperature is between 700°C and 740°C. In some embodiments, the pouring temperature is between 700°C and 750°C. In some embodiments, the pouring temperature is between 700°C and 760°C. In some embodiments, the pouring temperature is between 700°C and 770°C. In some embodiments, the pouring temperature is between 710°C and 720°C. In some embodiments, the pouring temperature is between 710°C and 730°C. In some embodiments, the pouring temperature is between 710°C and 740°C. In some embodiments, the pouring temperature is between 710°C and 750°C. In some embodiments, the pouring temperature is between 710°C and 760°C. In some embodiments, the pouring temperature is between 710°C and 770°C. In some embodiments, the pouring temperature is between 720°C and 730°C. In some embodiments, the pouring temperature is between 720°C and 740°C. In some embodiments, the pouring temperature is between 720°C and 750°C. In some embodiments, the pouring temperature is between 720°C and 760°C. In some embodiments, the pouring temperature is between 720°C and 770°C. In some embodiments, the pouring temperature is between 730°C and 740°C. In some embodiments, the pouring temperature is between 730°C and 750°C. In some embodiments, the pouring temperature is between 730°C and 760°C. In some embodiments, the pouring temperature is between 730°C and 770°C. In some embodiments, the pouring temperature is between 740°C and 750°C. In some embodiments, the pouring temperature is between 740°C and 760°C. In some embodiments, the pouring temperature is between 740°C and 770°C. In some embodiments, the pouring temperature is between 750°C and 760°C. In some embodiments, the pouring temperature is between 750°C and 770°C. In some embodiments, the pouring temperature is between 760°C and 770°C.

Continuing with the description of step 140 of the exemplary method 100, in some embodiments, the parameters include hold time (ie, the time period for which the material received in the vacuum induction furnace is maintained at the target temperature and pressure after the target temperature and pressure have been reached) . In some embodiments, the hold time is 0 minutes. In some embodiments, the hold time is 30 minutes. In some embodiments, the hold time is 60 minutes. In some embodiments, the hold time is 90 minutes. In some embodiments, the hold time is between 0 minutes and 30 minutes. In some embodiments, the hold time is between 30 minutes and 60 minutes. In some embodiments, the hold time is between 60 minutes and 90 minutes. In some embodiments, the hold time is between 0 minutes and 60 minutes. In some embodiments, the hold time is between 30 minutes and 90 minutes. In some embodiments, the hold time is between 0 minutes and 90 minutes.

Continuing to look at Figure 1, in step 150, the block formed in step 120 from the machining scrap is placed in a vacuum induction furnace. In step 160, the vacuum induction furnace is operated to heat the machining waste. In some embodiments, heating is performed as configured in step 140 . Lubricants are removed from machining waste during the heating process under selected conditions. In some embodiments, the lubricant is vaporized and carried away from the machining waste in a vacuum stream. In some embodiments, the lubricant is collected from the vacuum stream for subsequent use and/or disposal. In some embodiments, a small amount of lubricant condenses on the interior surfaces of the vacuum chamber. In some embodiments, the lubricant is vaporized and oxidized.

In some embodiments, the heating step includes heating to vaporize the lubricant. In some embodiments, the step of heating to vaporize the lubricant includes maintaining the machining waste at a selected temperature and in a selected ambient composition for a time sufficient to vaporize the lubricant. In some embodiments, the time is about one hour. In some embodiments, the selected environment is a moderate vacuum pressure (eg, between 0.001 mbar and 30 mbar) and the temperature is above the boiling point of the lubricant at the selected pressure but below the solid state of the machining waste The temperature of the phase point (eg, about 660°C). In some embodiments, the temperature is below the boiling point of the lubricant at standard temperature and pressure (which is, for example, 370°C).

In some embodiments, the environment is an argon atmosphere at about one atmosphere at a temperature above the boiling point of the lubricant (which is, for example, 370°C at standard temperature and pressure) but below the solid phase point of the machining waste (eg, about 660°C).

In some embodiments, the heating step includes heating to vaporize and oxidize the lubricant. In some embodiments, the step of heating to vaporize and oxidize the lubricant includes maintaining the machining waste at a selected temperature and in a selected ambient composition for a time sufficient to vaporize the lubricant. In some embodiments, the time is about one hour. In some embodiments, the selected environment is a low vacuum pressure (eg, between 30 mbar and 1000 mbar), an air environment, and the temperature is above the boiling point of the lubricant at the selected pressure but below machining The temperature of the solid point of the waste (eg, about 660°C). In some embodiments, the temperature is below the boiling point of the lubricant at standard temperature and pressure (which is, for example, 370°C).

In some embodiments, the environment is an argon/air environment. In some embodiments, the argon/air environment contains between 0% and 100% argon, with the balance being air. In some embodiments, the temperature is a temperature above the boiling point of the lubricant (eg, 370°C at standard temperature and pressure) but below the solid phase point of the machining waste (eg, about 660°C).

In some embodiments, the environment is an air environment at or about atmospheric pressure, and the temperature is above the boiling point of the lubricant (at standard temperature and pressure, which is, for example, 370°C) but below the solid phase point of the machining waste (eg, about 660°C).

Continuing to look at FIG. 1, in step 170, a vacuum induction furnace is operated to melt machining scrap. In some embodiments, this step includes maintaining the atmospheric conditions (eg, pressure, atmosphere composition) used in step 160 . In some embodiments, this step includes changing atmospheric conditions. In some embodiments, this step includes continuing to heat the machining waste (eg, from a temperature at which the lubricant is vaporized and/or oxidized, as discussed above in connection with step 160 ) until the machining waste reaches its solid phase point.

In some embodiments, the melting step includes melting to vaporize and/or oxidize the lubricant during the melting step. In some embodiments, the step of melting to vaporize and/or oxidize the lubricant includes melting at a predetermined ambient composition. In some embodiments, the environment is a low vacuum (eg, between 30 mbar and 1000 mbar), an air environment and the temperature is at or above the solid phase point of the machining waste (eg, about 660°C). In some embodiments, the environment is an argon/air environment at or about one atmosphere of pressure and the temperature is at or above the solid phase point of the machining waste (eg, about 660°C). In some embodiments, the environment is an air environment at or about one atmosphere of pressure and the temperature is at or above the solid phase point of the machining waste (eg, about 660°C).

Continuing to look at Figure 1, in step 180, after the machining waste is completely liquid, the temperature is raised to a level selected during step 140 and held at this selected level for a selected hold time. When the molten scrap is maintained at this temperature, any contaminants (eg, sodium, calcium, potassium, etc.) are vaporized and carried away from the molten scrap in the vacuum flow. In some embodiments, contaminants, if any, are collected from the vacuum stream for subsequent use and/or disposal.

Continuing to look at Figure 1, in step 190, molten machining scrap is poured as desired (eg, into a mold, fed to an ingot caster, etc.). It will be apparent to those skilled in the art that steps 150 to 190 may be repeated as needed based on the amount of machining waste on hand. After step 190, the method 100 is complete.

In some embodiments, the material produced by operation of the vacuum induction furnace as described above has been cleaned of substantially all of the lubricant originally applied to it. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains substantially no residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 200 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 190 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 180 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 170 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 160 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 150 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 140 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 130 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 120 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 110 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains 100 parts per million or less of residual carbon. In some embodiments, the material produced by the operation of the vacuum induction furnace contains an amount of residual carbon that is equal to or lower than the amount of residual carbon in the as-cast aluminum alloy.

In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains substantially no residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 25 parts per million or less of residual sodium. In some embodiments, the material produced by operation of the vacuum induction furnace as described above contains 24 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 23 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 22 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 21 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 20 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 19 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 18 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 17 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 16 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 15 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 14 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 13 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 12 parts per million or less of residual sodium. In some embodiments, the material produced by operation of the vacuum induction furnace as described above contains 11 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 10 parts per million or less of residual sodium. In some embodiments, the material produced by operation of the vacuum induction furnace as described above contains 9 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 8 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 7 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 6 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 5 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 4 parts per million or less of residual sodium. In some embodiments, the material produced by operation of the vacuum induction furnace as described above contains 3 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 2 parts per million or less of residual sodium. In some embodiments, the material produced by the operation of the vacuum induction furnace as described above contains 1 part per million or less of residual sodium.

In some embodiments, the above process is performed in the absence of flux (ie, flux-free). In some embodiments, the material produced by operation of the vacuum induction furnace retains substantially all of the lithium contained therein. In some embodiments, the material produced by operation of the vacuum induction furnace retains substantially all of the alloying material contained therein prior to melting in the vacuum induction furnace. In some embodiments, little or no oxidation occurs.

In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 0% and 0.4% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 0.4% and 0.8% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 0.8% and 1.2% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 1.2% and 1.6% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 1.6% and 2.0% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 2.0% and 2.4% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace contains between 2.4% and 2.7% lithium. In some embodiments, the material produced by the operation of the vacuum induction furnace is suitable for repeated commercial use.

Exemplary embodiments described herein have been described in particular in conjunction with techniques for melting and cleaning AlLi machining waste contaminated with sodium and/or lubricants. However, it will be apparent to those skilled in the art that the principles embodied by the exemplary embodiments are equally applicable to the melting and cleaning of any other metal. It will also be apparent to those skilled in the art that the principles embodied by the exemplary embodiments are equally applicable to metals contaminated with any other type of high vapor pressure contaminant.

While various embodiments of the present invention have been described, it is to be understood that these embodiments are illustrative only and non-limiting, and that various modifications may be apparent to those skilled in the art. Still further, unless the context clearly dictates otherwise, the various steps may be performed in any desired order and any applicable steps may be added and/or eliminated.

Claims (19)

1. A method comprising: providing an amount of metal contaminated with a contaminant including an amount of carbon; Configuring the vacuum induction furnace to operate according to a set of operating parameters selected based on characteristics of the contaminant, the set of operating parameters including at least one of pressure, atmosphere composition, pouring temperature, or holding time ; charging the vacuum induction furnace with the amount of metal; and The vacuum induction furnace is operated according to the set of operating parameters to melt the quantity of metal to remove at least some of the contaminants from the quantity of metal to provide a carbon concentration lower than or equal to the carbon concentration in the as-cast metal the output metal. 2. The method of claim 1, wherein the amount of metal comprises an amount of machining waste. 3. The method according to any one of claims 1-2, further comprising the step of: The quantity of metal is compacted into a monolithic metal prior to charging the quantity of metal into the vacuum induction furnace. 4. The method of any of claims 1-3, wherein the set of operating parameters includes a hold time, and wherein the hold time is between 0 minutes and 60 minutes. 5. The method of any of claims 1-4, wherein the set of operating parameters includes pressure, and wherein the pressure is between 1 micron and 300 microns. 6. The method of any of claims 1-5, wherein the set of operating parameters includes an atmosphere composition. 7. The method of claim 6, wherein the atmosphere composition comprises an inert gas atmosphere. 8. The method of any of claims 1-7, wherein the set of operating parameters includes a pouring temperature, and wherein the pouring temperature is between 700°C and 770°C. 9. The method of any of claims 1-8, wherein the at least one contaminant comprises sodium and a lubricant. 10. The method of claim 9, wherein the set of operating parameters includes pressure, pouring temperature, and holding time, wherein the pressure is between 1 micron and 300 microns, and wherein the temperature is between 700°C and 755°C , and wherein the holding time is between 30 minutes and 90 minutes. 11. The method of any one of claims 1-10, wherein the amount of metal comprises a 2000-series aluminum alloy, a 5000-series aluminum alloy, a 6000-series aluminum alloy, a 7000-series aluminum alloy, or an 8000-series aluminum alloy One of a series of aluminum alloys. 12. The method of any of claims 1-11, wherein the amount of metal comprises an aluminum-lithium alloy. 13. The method of any of claims 1-12, wherein the amount of metal is also contaminated with an amount of sodium. 14. The method of claim 13, wherein the operating parameters include temperature and hold time, and wherein the temperature and hold time are selected to provide a residual sodium concentration below a target concentration. 15. The method of claim 14, wherein the target concentration is 6 parts per million. 16. The method of any of claims 1-15, wherein the contaminant comprises a lubricant. 17. The method of claim 16, wherein the operating parameters include a pour temperature of about 700°C and substantially no hold time. 18. The method of claim 17, wherein the operating parameter comprises a pressure of about 300 microns. 19. The method of claim 17, wherein the operating parameters include an argon atmosphere and a pressure of about 1 atmosphere.

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