Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
  • B22D1/002—Treatment with gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
  • B22D1/002—Treatment with gases
  • B22D1/005—Injection assemblies therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
  • B22D21/04—Casting aluminium or magnesium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/02—Making non-ferrous alloys by melting
  • C22C1/026—Alloys based on aluminium

Definitions

• the present exemplary embodiment relates to a method and apparatus for improving the quality of aluminum, more particularly, to the treatment of molten aluminum with a gas prior to casting and solidification. It finds particular application in conjunction with casting of aluminum pieces and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
• molten metals When many molten metals are used for casting and similar processes, they must be subjected to a preliminary treatment to remove unwanted components that may adversely affect the physical or chemical properties of the resulting cast product.
• molten aluminum is extremely reactive, therefore, when it comes into contact with moist air or wet tools, the water decomposes to release hydrogen in the melt. Hydrogen solubility decreases rapidly as the metal freezes during casting, causing the hydrogen to leave the solution. Casting problems such as twisting and flaking in thin section extrusions and blisters on cast products can result.
• Degassing molten aluminum is generally accomplished by using a purge (inert) gas, typically introduced into the melt by a rotary degassing unit. This process of removing hydrogen is often referred to as “metal degassing”.
• In-line degassing systems are often installed between a holding furnace and a casting station.
• a standard degassing system involves the injection of an inert gas utilizing one or more injectors or injection devices, such as spinning rotor devices.
• the injector would typically introduce the inert gas, such as Argon, into the molten metal in the form of bubbles that the injector may sheer and disperse into the molten metal in order to saturate the molten metal with the inert gas.
• Many degassing systems function automatically and without much attention by the operator. This has led to inefficient purge gas usage and expenses relating to other downstream in-line processes, such as filtration.
• An in-line degassing apparatus and process for in-line aluminum treatment is disclosed in U.S. Patent No. 8,025,712, the disclosure of which is herein incorporated by reference.
• the present invention relates to methods and apparatus for monitoring and reducing undesirable impurities in molten metals.
• the following description will be directed to the treating of aluminum although other molten metal systems may benefit using the system of the present disclosure.
• a method for treating molten aluminum as it passes between a melting furnace and a casting apparatus includes monitoring the hydrogen concentration in the molten aluminum and calculating the quantity of inert gas required to achieve a target hydrogen concentration in the molten aluminum. The method further includes automatically adjusting the quantity of inert gas injected into the molten aluminum based on the above calculation.
• the degasser automatically adjusts the inert gas concentration output from the degasser and rotor speed to maintain a constant hydrogen level as the molten aluminum enters the casting apparatus.
• an analyzer is used to monitor the incoming and outgoing hydrogen levels in the molten metal and signals the degasser to make adjustments accordingly during the casting process.
• monitoring of the hydrogen concentration is continuous.
• the monitoring of the inert gas concentration is continuous.
• the hydrogen concentration and the inert gas concentration are measured.
• monitoring of the hydrogen concentration and/or the inert gas concentration occurs periodically.
• a method of measuring the gas content of molten metal using a gas measurement system comprising monitoring the hydrogen concentration contained in the molten metal and correlating the inert gas concentration usage with the hydrogen concentration contained in the molten metal, wherein a degasser unit automatically adjusts the degasser unit’s output to maintain a substantially constant hydrogen content level in the molten metal be cast in real-time.
• substantially constant means a variation of hydrogen concentration over the cast of less than 10%, or less than 5% or less than 1%.
• the hydrogen concentration is measured continuously by an analyzing unit.
• the analyzing unit can also continuously measures the inert gas.
• the inert gas is argon, however other inert gases, such as nitrogen, may be used.
• the apparatus comprises a degassing station that includes a first sensor for measuring hydrogen concentration in molten metal and a second sensor for measuring inert gas concentration.
• the first sensor for measuring hydrogen concentration in molten metal and the second sensor for measuring inert gas concentration is the same sensing device.
• the first sensor and the second sensor are the same sensor and measures the hydrogen concentration and the inert gas concentration at the same time.
• Other aspects of the apparatus include a control unit (e.g. a programmable logic controller “PLC”) for receiving the gas concentration measurement.
• PLC programmable logic controller
• control unit correlates the hydrogen concentration within the molten metal with the inert gas concentration within the molten metal and/or being introduced to the degassing unit. In other embodiments, the control unit balances the inert gas concentration with the correlated hydrogen concentration to maintain a constant outlet hydrogen content.
• Sensor devices in accordance with embodiments of this invention may be in contact with molten metals such as aluminum or, for example, as disclosed in U.S. Patent 6,216,525, which is incorporated herein by reference.
• Analyzing devices in accordance with embodiments of this invention may be in contact with molten metals such as aluminum or, for example, as disclosed in U.S. Patent 4,907,440, which is incorporated herein by reference.
• the degassing unit is an in-line degassing system.
• the in-line degassing system may be located between the holding furnace and the casting station.
• United States patents referring to such systems include the following: U.S. Pat. No. 9,127,332 for Molten Aluminum Refining and Gas Dispersion System; U.S. Pat. No. 5,198,180, for a Gas Dispersion Apparatus with a Rotor and Stator for Molten Aluminum Refining; U.S. Pat. No. 5,846,481, for a Molten Aluminum Refining Apparatus; U.S. Pat. No. 3,743,263, for an Apparatus for Refining Molten Aluminum; and U.S. Pat. No. 4,203,581 , for an Apparatus for Refining Molten Aluminum; all of which are hereby incorporated by this reference.
• FIGURE 1 illustrates a process flow of an exemplary degassing method to the embodiments of the disclosure
• FIGURE 2 illustrates a schematic diagram of an exemplary degassing apparatus according to the embodiments of the disclosure
• FIGURE 3a is a front view of a representation aluminum cast illustrating effects of hydrogen concentration
• FIGURE 3b is a view of the aluminum cast of Fig. 3a;
• FIGURE 3c is a graphic displaying the hydrogen concentration level contained in the aluminum cast of Fig. 3b.
• FIGURE 3d is a front view of the hydrogen concentration contained in an aluminum cast with a graphic displaying the hydrogen concentration level.
• FIGURE 4 is a perspective view of a representation in-line metal treatment system; and with baffles and a rotary dispenser in accordance with the prior art;
• FIGURE 5 is a perspective cutaway view of a prior art degassing rotor.
• kits or devices or methods as “consisting of’ and “consisting essentially of’ the enumerated components/steps, which allows the presence of only the named components/steps, and excludes other components/steps.
• a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified.
• the modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.”
• the term “about” may refer to plus or minus 10% of the indicated number.
• upper and lower are relative to each other in location, i.e. an upper component is located at a higher elevation than a lower component.
• Examples 1 and 2 demonstrate that hydrogen concentration of aluminum leaving a furnace is typically the highest at the beginning of the process and will gradually decrease during casting.
• a degasser is set to one-fixed- parameter, the hydrogen concentration after the degasser will also follow the same path as the inlet hydrogen, and hydrogen removal efficiency will remain around the same level.
• This approach creates a solid, slab, or billet with a different concentration of hydrogen depending on the furnace outlet and the preset parameters of the degasser.
• a degasser is set to one-fixed-parameter, most of the time it is set to highest metal flow, most humid season, hard to remove alloy. As a consequence, casting operations almost universally over treat molten aluminum.
• Examples 3-6 display data collected from two separate casts without changing the parameter on the degasser. ALSCAN tests were performed respectively on two separate dates. Examples 3 and 4 are test results taken on day 1. Examples 5 and 6 are test results taken on day 3. The only change that occurred was the incoming metal temperature and the metal level in the launders. This process makes the incoming metal hydrogen content levels occasionally go higher than expected. However, even though incoming hydrogen content levels could be lower, in both cases, it was observed that hydrogen levels decrease in time.
• FIGURE 1 illustrates a process flow of an exemplary degassing method.
• Process 100 shows a method for treating molten aluminum as it passes between a melting furnace and a casting apparatus.
• the method 100 includes monitoring the hydrogen concentration in the molten aluminum 102 and monitoring the inert gas concentration in the molten aluminum 104.
• the process 100 further includes correlating the gas concentration usage with the hydrogen concentration 106.
• a degasser is used at the degassing station 202 and the degasser includes a controller to automatically adjust the inert gas concentration output from the degasser 106 to maintain a constant hydrogen level as the molten aluminum enters a casting apparatus.
• FIGURE 2 illustrates a schematic diagram of an exemplary degassing apparatus.
• the apparatus 200 includes a degassing station 202.
• the degassing station 202 includes a first sensor for measuring hydrogen concentration in molten metal 204a, and an optional second sensor for measuring inert gas concentration 204b.
• the information is sent to a control unit 212.
• the control unit 212 is configured for receiving the inert gas concentration measurement 206.
• the control unit 212 correlates the hydrogen concentration within the molten metal with the inert gas concentration within the molten metal.
• the control unit 212 balances the inert gas concentration with the correlated hydrogen concentration 208 to maintain a constant outlet hydrogen content level.
• the control unit 212 is configured to automatically adjust the hydrogen output 210 based on the inert gas concentration.
• the lower part of the refinement vessel is generally referred to as the tub assembly 301.
• the tub assembly 301 is a two stage refining vessel wherein the aluminum or other molten metal is introduced into the first refinement stage or first refinement compartment of the vessel through metal inlet 302.
• the metal flows to the second refinement compartment, where it is further refined before exiting through the metal outlet 303.
• the design of the refinement vessel is such that the inlet and outlet for the metal can be reversed to accommodate the particulars of the facility in which it is used, i.e. the metal inlet 302 can be used as an outlet and the metal outlet 303 can be used as an inlet.
• the first refinement compartment then becomes the second and visa versa.
• the trough transfers the molten material from a furnace, configured to melt the aluminum material into the molten metal alloy, to a casting mechanism to form the molten material into a desired shape.
• the dome lid assembly 305 can be securely and sealably attached to the upper outer surface of the containment vessel tub assembly 301 by numerous different known means.
• the dome lid body 306 has four outer walls, a lid body front wall 306a, two lid body side walls 306b and a lid body rear wall (not shown), in addition to the lid body roof 306d.
• FIG. 4 illustrates how the lid body front wall 6a and the two lid body side walls 306b are inwardly sloping.
• the front access door 307a comprises a substantial area on the dome lid front wall 306a and can consequently be very heavy. In order to more easily open the front access door 307a. A hydraulic cylinder assembly 8 is provided.
• the side access doors 307b are smaller than the front access door 307a and much more easily handled by workmen and handles 309 are therefore provided to open the side access doors 307b, without the need for mechanical assistance.
• lid body roof 306d Mounted on the lid body roof 306d are two rotary gas dispersion devices 312, one for each refining compartment or stage.
• FIG. 5 is a perspective cutaway view of one embodiment of a molten metal refining gas dispersing device 660 contemplated by this invention.
• FIG. 6 illustrates an injector which in this embodiment includes stator 662, rotor shaft 661 , passageway between the stator 662 and the rotor shaft 661 through which gas 664 is passed through.
• Spinning rotor 667 includes blades 670 (or vanes) with space or distance 671 there-between.
• Gas bubbles 677 which include gases are released as indicated by arrows 669 and 673 into the molten aluminum for dispersion.
• FIG. 6 also illustrates a central passageway 666 (or conduit) through which gas and flux are introduced as indicated by arrow 663 from an external source 678, which is being injected or pumped into central passageway 666.
• FIG. 3 also shows gas passageway 659 between stator 662 and rotor shaft 661 , and through which gas is introduced into the injector 660 or molten metal refining system (preferably molten aluminum). While typically flux may be provided in powder or other solid form and mixed with gas to inject it into the molten metal, there may also be applications such as future applications wherein a flux in liquid or gaseous form is utilized.
• the rotor shaft 661 is rotatably positioned within the internal cavity within stator 662 such that it may be driving by a motor or other drive within the stator 662 cavity.
• the rotor shaft 661 is operably attached to the spinning rotor 667 such that the nozzle rotates with the rotor shaft 661.
• a gas passageway is also provided between the internal cavity surface of the stator 662 and the outer surface of the rotor shaft 661 such that gasses 664 may pass through the passageway before being discharged between the bottom of the stator 662 and the top of the spinning rotor 667.
• the gas is discharged and preferably sheared between the top of the spinning rotor 667 and the bottom of the stator 662, and the vanes 670 of the spinning rotor 667 contribute to the sheering of the gas bubbles 677 and dispersion thereof within the molten metal surrounding the spinning rotor 667.
• the stator 662 may be smooth, include vanes 670, or include any one of a number of different surfaces and configurations on the outer surface thereof, with no one in particular being required to practice this invention.
• FIG. 6 also illustrates where the outer surface of the rotor shaft 661 interacts with the interior surface of the stator 662, with that intersection identified as item 679, which may also be referred to as gap 679.
• the area of that intersection 679 may be referred to as a bushing, a bearing, or using other terms, and there may in some embodiments be a two to four one-thousandths of an inch clearance between the two components. It is typically desirable to maintain a certain pressure of gas in that gap 679 so that molten metal does not enter the gap 679 at the lower end near the rotating rotor 667. It is typically desirable to maintain a certain pressure of gas below that gap 679 so that molten metal does not enter the gap 679 at the lower end near the rotating rotor 667.
• the gas and flux flow rates will depend on the metal flow rate, the impurities in the incoming metal in a given application, and the desired quality of the output metal.
• the gas may range flow up to five cfm (eight Nm3/h), with a typical range being in the two to four and one-half cfm (three to seven Nm3/h).
• the flux material in typical application may utilize up to twenty g/m or higher.
• the flow rates given herein are per nozzle and are given as examples and not to limit the invention in any way as it is not dependent on any particular range or set of parameters in the metal processing system.
• a preferred gas used in combination with this invention in a given embodiment is argon, nitrogen, or others may also be utilized.
• a preferred flux material in a given embodiment may be a eutectic mixture of magnesium chloride and potassium chloride (which is commonly known by trademarks ProMag and Zendox).

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 2023
  • 2023-02-16 WO PCT/US2023/013233 patent/WO2023158747A1/en not_active Ceased
  • 2023-02-16 CN CN202380022354.3A patent/CN118973740A/zh active Pending
  • 2023-02-16 EP EP23756883.7A patent/EP4479205A4/de active Pending
  • 2023-02-16 US US18/838,976 patent/US20250178076A1/en active Pending
  • 2023-02-16 CA CA3251253A patent/CA3251253A1/en active Pending
  • 2023-02-16 KR KR1020247030622A patent/KR20240150478A/ko active Pending
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• 2024
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