CA2404560A1 - Systems for detecting and measuring inclusions - Google Patents
Systems for detecting and measuring inclusions Download PDFInfo
- Publication number
- CA2404560A1 CA2404560A1 CA002404560A CA2404560A CA2404560A1 CA 2404560 A1 CA2404560 A1 CA 2404560A1 CA 002404560 A CA002404560 A CA 002404560A CA 2404560 A CA2404560 A CA 2404560A CA 2404560 A1 CA2404560 A1 CA 2404560A1
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- inclusions
- particles
- gas
- fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000001514 detection method Methods 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 41
- 238000005259 measurement Methods 0.000 claims abstract description 33
- 230000003287 optical effect Effects 0.000 claims abstract description 12
- 239000002245 particle Substances 0.000 claims description 55
- 229910052751 metal Inorganic materials 0.000 claims description 32
- 239000002184 metal Substances 0.000 claims description 32
- 239000007788 liquid Substances 0.000 claims description 27
- 239000007789 gas Substances 0.000 claims description 21
- 239000012530 fluid Substances 0.000 claims description 19
- 238000009826 distribution Methods 0.000 claims description 17
- 238000000926 separation method Methods 0.000 claims description 16
- 229910052782 aluminium Inorganic materials 0.000 claims description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 15
- 230000003750 conditioning effect Effects 0.000 claims description 11
- 230000005012 migration Effects 0.000 claims description 8
- 238000013508 migration Methods 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 238000003384 imaging method Methods 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000007254 oxidation reaction Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 239000010453 quartz Substances 0.000 claims description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 239000004020 conductor Substances 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 230000004044 response Effects 0.000 claims description 2
- 229910052711 selenium Inorganic materials 0.000 claims description 2
- 239000011669 selenium Substances 0.000 claims description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 2
- 229910052721 tungsten Inorganic materials 0.000 claims description 2
- 239000010937 tungsten Substances 0.000 claims description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims 1
- 239000000460 chlorine Substances 0.000 claims 1
- 229910052801 chlorine Inorganic materials 0.000 claims 1
- 238000003331 infrared imaging Methods 0.000 claims 1
- 229910001338 liquidmetal Inorganic materials 0.000 abstract description 29
- 239000000155 melt Substances 0.000 description 28
- 150000002739 metals Chemical class 0.000 description 12
- 238000012545 processing Methods 0.000 description 12
- 238000007689 inspection Methods 0.000 description 5
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- 229910052733 gallium Inorganic materials 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 230000001143 conditioned effect Effects 0.000 description 3
- 239000000356 contaminant Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- 241001424392 Lucia limbaria Species 0.000 description 2
- 241001275902 Parabramis pekinensis Species 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004512 die casting Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- SBYXRAKIOMOBFF-UHFFFAOYSA-N copper tungsten Chemical compound [Cu].[W] SBYXRAKIOMOBFF-UHFFFAOYSA-N 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000013500 data storage Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011344 liquid material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000012056 semi-solid material Substances 0.000 description 1
- 229910052566 spinel group Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/42—Constructional features of converters
- C21C5/46—Details or accessories
- C21C5/4673—Measuring and sampling devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C1/00—Magnetic separation
- B03C1/32—Magnetic separation acting on the medium containing the substance being separated, e.g. magneto-gravimetric-, magnetohydrostatic-, or magnetohydrodynamic separation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
- G01N33/205—Metals in liquid state, e.g. molten metals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Pathology (AREA)
- Immunology (AREA)
- General Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- Metallurgy (AREA)
- Food Science & Technology (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Fluid Mechanics (AREA)
- Medicinal Chemistry (AREA)
- Investigating And Analyzing Materials By Characteristic Methods (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
- Dispersion Chemistry (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Sampling And Sample Adjustment (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The present invention relates to systems of methods of detecting and measuri ng inclusions in liquid metals. More particularly, non-metallic inclusions havi ng a conductivity level different from the liquid metal melt are forced to migrate and are collected on a measurement surface using electromagnetic Lorentz forces. The inclusions and their concentrations are detected at the measurement surface using either an electrostatic detection system or an optical detection system.
Description
SYSTEMS FOR DETECTING AND MEASURING INCLUSIONS
This is a Continuation-in-Part Application of U.S. Application No.
09/700,975 filed on November 21, 2000 which is a U.S. National Phase Application of PCT/LTS00/08668 filed on March 31, 2000.
BACKGROUND OF THE INVENTION
Due to the increasing demand for high quality metals, the purification of molten metals is becoming increasingly crucial. As a result, methods for the detection, measurement, separation and removal of inclusions from molten metals are desirable. W particular, the aluminum casting industry is in need of a reliable, fast, and economical detection system that enables furnace operators to conduct fine metal cleaning operations, and thus prevent small defects in the finished products.
A typical aluminum melt, for example, contains a large number of small non-metallic inclusions, less than or equal to SO~.m in size. These include particles of oxides (AIz03), spinels (MgAIz04), and carbides (SiC, AI4C3), with a higher melting point. Inclusions in alloys can impair the mechanical properties of articles made therefrom, are also detrimental to surface finish and maclunability, increase internal porosity in the castings, as well as increase corrosion. Non-metallic inclusions act as stress-raisers, and can cause premature failure of a component.
The assessment of the level of inclusions present in the melt is one of the key parameters which needs to be measured in molten metal processing. The existing detection techniques include pressure filter test, acoustic emission detection, and electric resistivity Coulter counter. The first two methods mainly rely upon a qualitative distinction between heavily contaminated melts and a clean melt.
The Coulter counter method evaluates both concentration and size distribution of inclusions larger than 15-20~,m for a small probe. However, this method is quite expensive and can only detect the effective size of an inclusion.
SUMMARY OF THE INVENTION
The present invention relates to a system for detecting and measuring non-metallic inclusions in molten metals. The methods for measuring inclusions in molten metals of the present invention include the steps of forcing the migration of the contaminant particles or inclusions onto a measurement region or surface using electromagnetic Lorentz forces, for example, detecting the particles in the measurement region and determining particle size and concentration at the measurement surface.
Electromagnetic force mechanisms have been investigated and used for purposes of separation and removal of contaminants in liquid metals. However, the cleaung systems relying on electromagnetic forces are not very effective because a very low force density is typically generated in a large liquid metal melt volume which needs to be cleaned, resulting in a slow relative particle motion. In the present invention electromagnetic forces are used to detect and measure non-metallic inclusions in a liquid metal. A detector system uses a small inspection volume, thus allowing for the generation of large force densities. The present invention may also be used to separate inclusions from metals such as aluminum utilizing the basis of high electromagnetic force density in chamlels having small volumes.
In particular, a preferred embodiment utilizes permanent magnets and a direct current ~(DC) source to generate electromagnetic forces. In addition, the methods for the detection of inclusions utilize electrostatic detection of the particle concentration at the measurement region or surface through a mufti-pin measurement configuration. Further, conditioning of the surface is required to overcome the surface tension forces that are responsible for preventing the inclusions from penetrating through the melt surface. By conditioning the surface, the particles penetrate the surface in order to be detected. The methods of conditioning the surface to enable particle detection can comprise a mechanical system or an acoustical vibration system or a combination of these two systems. A
mechanical system can use, for example, a roller, to continuously stretch out the surface layer of the melt. An acoustical vibration system involves the shaking of the liquid melt surface at a particular resonance frequency, for example 10-40Hz depending on the geometric size of the inspection volume, using an alternating current (AC) superimposed over the DC current flowing through the melt. The surface vibrations stimulate particle motion. Alternatively, a stream of a gas, or mixtures of gases, can be directed over the surface of the melt. Gas pressures in the cavity above the melt can be between 2=3 atmospheres, for example, to condition the surface. The gas flow can be used to delay oxidation and/or reduce surface tension on the melt surface. This serves to increase migration rates of inclusions to the surface region of the melt. Depending upon the direction and rate of flow, one or more gas inlets and outlets to the cavity above the melt can be used to control conditions on the surface region of interest. Inert gases such as helium or argon can be used, or active fluids such as chlorine gas can be used with or replace the inert gas which can also serve to loosen bonds at the surface to further improve particle migrations and detection. These gases can also improve the contrast in the heat signature of surface region components.
In another preferred embodiment of the present invention, the detection system is an optical system which features a solid state imaging device such as a charge-coupled-device (CCD). The CCD based detector system facilitates the electronic recording of the particles distributed over the surface aperture.
Once the particles are collected on the measurement surface or free melt surface by the application of electromagnetic Lorentz forces, low-frequency acoustic vibrations are initiated to enable the migration of the particles through the metal melt.
Recording of the particle size and distribution is performed with the CCD camera in conjunction with optical magiufication of the region of interest using a lens system.
The CCD camera may be coupled to an image acquisition system, which in turn may be coupled to a processor such as a microcontroller or personal computer having an electronic memory for data storage. The systems can be programmed with software modules to perform image processing on the collected image data and determine quantitative values including particle size and distribution. This processed data can be used to control flow rates and separation rates of the system.
In another preferred embodiment of the invention, detectors or detector systems sensitive in the range of wavelengths from 500-1200 rim are used to count inclusions. By detecting in the visible, near infrared and infrared regions of the electromagnetic spectrum, subsurface particles can be detected as well.
Commercially available detectors, such as amorphous selenium, can be used with a quartz window to image surface and subsurface particles at video frame rates.
Yet another embodiment of the present invention uses only an AC power source to induce electromagnetic forces in the melt and thereby cause movement of the melt and consequent positioning of inclusions for measurement. The detection system can be used in conjunction with a system for the separation of inclusions from the melt and provide real-time feedback control of the processing operation.
The systems of the present invention provide for the quantitative measurement of small inclusions, and can determine particle shape. Further, the systems of the present invention can distinguish between a single particle and a cluster of particles, and can distinguish between gas bubbles and solid particles.
There are several applications of the systems of the present invention including but not limited to the detection of inclusions in molten metals and the separation of inclusions from molten metals such as aluminum, ferrous materials, brasses and copper based alloys. Tn addition, the systems of the present invention may be utilized in semi-solid processing or die casting to homogenize segregated interdendritic liquid as well as breaking up dendritic networks.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A is a schematic illustration of a system to provide liquid metal utilizing the system for detecting and measuring inclusions in accordance with the present invention.
Figure 1B is a schematic illustration of the system of the present invention being utilized as a separation system described in Figure 1A.
Figure 1 C is a flow chart describing the details of a molten metal processing system incorporating the system for detecting and measuring inclusions in accordance with the present invention.
Figure 2A is a schematic illustration of an embodiment of the system to measure inclusions in molten metals in accordance with the present invention.
Figure 2B is a schematic diagram of a preferred embodiment of the detection system to detect and measure inclusions in molten metals in accordance with the present invention.
Figure 2C illustrates the top view of the container apparatus shown in Figure 2A.
Figure 2D illustrates a cross-sectional view of the container apparatus taken along lines 2D-2D of Figure 2C.
Figure 2E illustrates a cross-sectional view of the container assembly taken along lines 2E-2E of Figure 2C.
Figure 2F is a schematic diagram of another preferred embodiment of the detection system in accordance with the system of the present invention.
Figure 3A is a schematic illustration of another preferred embodiment of the system in accordance with the present invention.
Figure 3B is a detailed schematic illustration of the sensor element shown in Figure 3A.
Figure 4 is a schematic illustration of another preferred embodiment of the invention.
Figures SA-SE illustrate examples of the magnetic field and Lorentz force distribution in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to systems and methods to detect and measure inclusions in liquid metals. Further embodiments involve the processing of liquid or semi-solid materials.
The systems and methods to detect and measure inclusions in liquid metals use electromagnetic forces to force the migration of the contaminant particles to a detection and measurement surface. The invention is predicated on the fact that the included particles have a different electric conductivity level than that of the liquid melt and as such are treated as being non-conducting as compared to the liquid melt.
Thus, upon the application of a direct current (DC) throughout the melt with current density j and an imposed perpendicular magnetic flux density B, the Lorentz force density in the melt is f = j x B, where the force density, current density and magnetic flux density are vector quantities and the force density is the vector cross product of the current density and the magnetic flux density. The Lorentz force is induced in the metal but not in the non-conducting inclusions since no current can propagate through them. As a reaction to this electromagnetic force (Newton's third law), the inclusions are equally forced in the opposite direction. The corresponding reaction force density fa on the non-conducting inclusions fa = -f is known as Archimedes electromagnetic force. Archimedes electromagnetic force is well suited for detection purposes since a detector uses a small inspection volume, where extremely large force densities can be obtained with corresponding rapid particle motion.
Refernng now to the drawings, Figure 1A is a schematic illustration of a preferred method to provide liquid metal incorporating the system for detecting and measuring inclusions in accordance with the present invention. The particular sequence of steps describes the use of the system of the present invention in a system which provides liquid metal free of non-metallic inclusions. The metal is melted either in a reverbatory furnace or in an electrically heated furnace.
Alternatively, the metal may be induction melted. The system comprises a sensor element 110 which consists of a container 112 into which flows a liquid metal having inclusions per step 114. The liquid metal flows out of the metal per step 116 after the sensing and detection of the included particles has occurred. Electrodes 11 ~ are integrated with the container 112 to provide a voltage drop in the container. An electromagnetic force is induced in the container which acts on the liquid metal and not on the included particles. The electromagnetic force can be generated by applying power supplied by the power supply 120, to the container. A DC current in combination with the permanent magnet system 124 can create the required electromagnetic force. Alternatively, the electromagnetic force can be generated by applying a high AC current also supplied by the power supply 120, whose self induced magnetic field eliminates the need for the permanent magnet system 124.
The inclusions which are non-conducting as compared to the liquid metal rise toward a measurement region wluch is the free melt surface. Since the melt is not transparent in the visual domain the measurement region needs to be conditioned so as to force the inclusions to break through the melt surface which has a metal oxide layer disposed on it. To overcome the surface tension forces which retain the particles below the free melt surface, the measurement region may be conditioned mechanically per step 128, or by an acoustic conditioning system 132 or alternatively by a combination of the two.
The included particles are then detected by a detection system 136. The detection system may be an electrostatic measurement system or an image detection system.
The results of the detection system are then recorded and particle size and concentration are computed in the processor 140. The results of the processing step 140 maybe displayed on a display 144 and used to monitor the size and concentration of inclusions. A particle separation system 148 is coupled to the computer to remove the detected inclusions to provide liquid metal free of inclusions.
Figure 1B is a schematic illustration of the use of the present invention as a separation or cleaning system. A container 152 of liquid metal having inclusions feeds into a separation system 154. The separation system consists of small channels 156 for the liquid metal to flow into. The particles are separated in a separation zone 158 in each channel 156 by applying a high electromagnetic force density to the liquid metal in each channel. The resultant liquid metal that is _g_ collected from the separation system 154 in a container 160 is substantially free of inclusions. Each zone 158 or channel 156 can have a detector system as shown in Figure 1A to provide monitoring of each channel.
Figure 1 C schematically illustrates further details of the utility of the present invention in a molten metal processing system 162 that supplies liquid metal, having reduced concentrations of larger inclusions or is substantially free of inclusions, for casting and other applications. The particular sequence of steps describes the system to provide inclusion free metal. Liquid metal in step 164 is degassed per step 166 to remove gaseous hydrogen, for example. The liquid metal then flows through a filtration system per step 168 to remove inclusions as part of a typical molten metal processing system. The resultant liquid metal is then used in a casting process per step 170. A certain small volume of the filtered liquid metal is fed into the detection and measurement system in accordance with the present invention per step 172.
Step 172 senses inclusions and determines particle size and distribution. The sensor data is then translated into an actual distribution for the molten metal per step 174.
The actual distribution of inclusions is then compared with a desired distribution per step 176. The desired, ideal distribution computed per a model such as predicted in step 178, is stored electronically in a memory and retrieved to perform the comparison per step 176. If the actual distribution of the inclusions is within an acceptable range of the desired distribution, no corrective action is taken.
However, if the actual distribution of the inclusions is not within an acceptable range of the desired distribution then corrective action is initiated per the process model and control laws of step 180. The control variables listed in step 182, for example, filter life and size, the operations of the degassing unit and the charge of the melt are then recalculated and changes are programmed into the processing system. As a result of changes made to the control variables, the process model is updated per step 184.
Figure 2A, is a schematic illustration of a preferred embodiment of the system to detect and measure inclusions which can be used to perform the methods of the present invention. A container 210, which for example is made of ceramic, is filled with the liquid melt 212, for example liquid gallium. The liquid melt 212 is subjected to both an electric as well as a magnetic field.
The resulting electromagnetic Lorentz force density is created by two permanent magnets 214 having a range of 0.3 Tesla to 0.6 Tesla acid a DC
current having a range of 100 A to 150A supplied by a DC power supply 216. Other embodiments can employ current in a range of 50 to 2000A depending upon the particular application. Commercial systems will preferably have currents in the range of 200-2000A to improve flow rates. The magnetic field is nearly homogeneous in between the two electrodes 224. The system may be conF'igured so that the melt continuously flows through the container 210 and the inclusions are collected on a region 220 of the free melt surface. If the flow cross-section is 0.5 by 1 cm, then the current density j is 2.4x106A/m2 based on a total current of 120A.
Accordingly, the Lorentz force density is 7.2 x 105 N/m3 if the flux density is 0.3 Tesla. Flow rates of the melt are preferably in the range of 50-200 ml per minute.
This is more than thirty (30) times the gravitation force density acting on the molten metal such as aluminum. Simultaneously, this is more than sixty (60) times the gravitation Archimedes force on spinet inclusions (p=3600 kg/m3) in molten aluminum. These considerations underscore the fact that electromagnetic treatment is quite effective if the cross-sectional area for the metal flow is sufficiently small.
Coupled to both sides of the container 210 are electrodes 224. The electrodes may, for example, be made. of copper tungsten, graphite, aluminum or other conductive materials. The electrodes provide the DC current flow which in combination with the magnetic field is responsible for the electromagnetic Lorentz force. In addition, the current flow encounters an electric resistance due to the presence of the liquid metal. As a consequence, a voltage drop is created between the electrodes which in turn can be measured through the placement of small copper point electrodes in contact with the free melt surface. Variations in the voltage drop between the adjustment point electrodes permit the detection of particles that migrated to the surface in response to the Lorentz force. The electrodes are selected depending upon the materials in the fluid metal that will either be stable under the operating condition or that deteriorate at known rates.
Non-conducting particles experience uniform longitudinal motion with constant velocity and, simultaneously, transverse motion, rising toward the free melt surface or region 220 with a given velocity. Even for inclusions of 10~,m in diameter, the rise velocity is sufficient to enable inclusion collection on a region of the free melt surface within a reasonable time duration. Since the melt is not transparent in the visual domain of the electromagnetic spectrum, inclusion escape on the free melt surface plays a decisive role. The main mechanism that prevents escape is surface tension. The Archimedes electromagnetic force is much smaller than the surface tension force, for all possible particle sizes. Thus, an additional treatment of the melt surface is necessary.
The surface is conditioned mechanically, by continuously stretching out the surface layer of the melt, for example by a rotating cylinder such as a ceramic roller 228. The roller drags the surface layer away from the detection region. This process makes the melt surface appear as if it is being "stretched" with new particles continuously appearing. Another method for conditioning the melt surface is acoustically vibrating the liquid melt surface in the range of 10-40Hz depending on the geometric size of the inspection volume. This can be accomplished through an AC power amplifier supply 232 in the range between 500-800W, and an AC signal generator 234 providing an AC current. An additional periodic Lorentz force component appears in the transverse direction, which produces surface vibrations.
Such vibrations stimulate particle escape. Methods for providing oscillations of liquid metal by electromagnetic Lorentz forces are described in "Resonant oscillations of a liquid metal column driven by electromagnetic Lorentz force sources", by Sergey Makarov, Reinhold Ludwig and Diran Apelian, J. Acoust.
Soc.
Am., Vol 105, No. 4, April 1999, which is incorporated herein by reference.
Methods described in the aforementioned reference publication can be used with the systems described herein to provide acoustic vibrations for conditioning the free melt surface.
Both methods for conditioning the surface have their advantages and disadvantages. Mechanical stretching implies moving sensor components, for example rollers, whereas acoustic vibration reduces the quality of the optical image formation. A combination of the two methods may be used to offset the disadvantages of the individual methods.
Based on an exemplary cylindrical volume, a current strength of 150A (DC
current) supplied through two electrodes to a measurement container of 20 mm in length and 5 mm in radius creates an average radial force density of 100 kN/m3.
This is sufficient to force 75% of the inclusions with an average 40 micron effective diameter to the surface, amounting to an inspection speed of 88 ml/min.
In a preferred embodiment illustrated in Figure 2B, the detection system in accordance with the present invention is an optical detection system which may include optical magnification of the region of interest using a lens system 252, for example a microscope, a CCD camera 256 and a display 260. In addition, the CCD
camera may be coupled to a frame grabber 262 which in tum is coupled to a processor 264. The optical detection method predicts non-conducting and low-conducting inclusions of an average diameter in the range of 5 to 50 microns in molten aluminum.
Figures 2C, 2D and 2E provide further details regarding the container assembly and the mechanical conditioning system described in Figures 1 and 2A.
The roller stretches the free melt surface and in doing so disrupts the metal oxide layer that forms on the surface, which then enables the escape of the particles to the surface which allows for detection of the particles. The action of the mechanical roller tends to move a layer of the melt on top of the roller, potentially allowing for the separation of the included particles in the top layer into a baffle 270 shown in Figure 2D.
Figure 2F illustrates another embodiment of the detection system of the present invention. Once the particles reach the surface, this embodiment of the present invention uses an electrostatic measurement device 280 having voltage recording pins 282 in the range of 10 to 100 pins, deployed over the free melt surface to measure a differential voltage distribution which subsequently can be compared to a baseline distribution of pure molten aluminum. The pins may be small copper point electrodes in contact with the free melt surface. If the probe spacing is on the order of 0.3 mm using laser drilling, the approximate calculations indicate that the expected differential potential distribution exceeds 4 to 5 ~,V, well above the background noise. This detection system predicts nonconducting and low-conducting inclusions of an average diameter in the range of 20 to 100 microns in molten aluminum.
Referring to Figure 3A, another preferred embodiment of the system to detect and measure inclusions in liquid metal includes a sensing element 310 consisting of three columns or sections which are placed in a container 314 filled with a liquid metal 316. The columns may be made from ceramic or a refractory material. An AC power supply 318 supplying a current in the range of SODA to 1000A is coupled to the electrodes 320 which are integrated with the sensing element 310.
The optical or infrared detection system 322 includes optical magnification of the region of interest using a lens system 328, a CCD or infrared camera 330, an image acquisition system 334 coupled to a processor 336, and a display 338. A
long focal length objective lens 328 with a magnification in the range of 1000 to 2000 is coupled to the CCD. The CCD based detector system facilitates the electronic recording of the particles distributed over the surface aperture. Low-frequency acoustic vibrations can be initiated through alternating Lorentz force using a modulating AC signal generator in conjunction with an AC power amplifier as previously described. Low-frequency acoustic vibration in the frequency range of 10-40 Hz break-up the surface layer (an oxide film plus surface tension forces) of the liquid melt, to allow the escape of the inclusions from the melt to facilitate detection.
The sensing element has a self cleaning feature due to the angular relationship between the columns. A tilt angle 350 in the range of 2-5°
allows the liquid melt to flow out of the sensing element 310 once the element is removed from the melt.
An inert gas supply 340 provides an inert carrier gas to remove any gaseous impurities to maintain a clean interface for the quartz window 324.
No permanent magnets are required for the embodiment as discussed with respect to Figure 3A. Referring to Figure 3B, which provides further details of the sensing element 310 illustrated in Figure 3A, a sufficiently strong self induced average magnetic-field in the range of 0.05 Tesla to 0.1 Tesla is initiated by the 60Hz AC current of 50-2000 Amperes, and preferably 1000-2000 Amperes, when applied to the container. The total power applied is in the range of 2-3 kW.
Although the self induced magnetic field is weaker than the field provided by the embodiment having the permanent magnet system, the significantly higher current density as a result of the lugher AC current is responsible for a strong electromagnetic Lorentz force density. It also may be possible to replace the power supply by a transformer. Additionally, another embodiment of the system of the present invention may use a removable sensor or sensing element made of tungsten as opposed to ceramic.
The advantage of the embodiment as illustrated by Figures 3A and 3B, is the creation of a self induced magnetic field which eliminates the use of permanent magnets. Permanent magnets require an external cooling system which does not need to be provided for by the system described with respect to Figures 3A and 3B.
In addition, a DC power supply which is typically move expensive and cumbersome to handle than an AC power supply, is not required to operate the system as disclosed with respect to Figures 3A and 3B. Further, the embodiment illustrated by Figures 3A and 3B eliminates the need for an external pump. W stead, the embodiment relies on a self pumping mechanism to assure continuous melt flow through the measurement region.
Figure 4 illustrates another preferred embodiment of the invention wherein the gas flow inlet 340 is controlled by a valve that can be connected at 344 to a system controller. A gas flow outlet 360 can also be fluidly coupled to the cavity 362 above the metal fluid in the chamber 364 through which the metal fluid flows.
Alternatively, one or more inlets 370 can be positioned about the quartz window 324 through which a region of interest 352 can be viewed. The metal fluid is forced upwards in opposition to a gravitational force through channel 400.
The metal fluid can be directed through the chamber 364 and a plurality of outlets. The flow through the outlets 380, 390 can be directed downstream for a further processing such as a separation system. The gas flow system operates to control surface characteristics such as oxidation rate, bonding properties, contrast and migration rate of particles in the region of interest 352.
Figures SA-SE illustrate examples of the magnetic field and force density characteristics. For a container having a current I of 1000A, for example, as shown in Figure SA, the magnetic field strength in a one centimeter square cross section is shown in Figure SB and the field orientation is shown in Figure SC. The resulting Lorentz force density and orientation are illustrated in Figures SD and SE
respectively.
The following table illustrates the ratio of the magnitude of the force acting on the fluid to the gravitational force in four cases having different total currents directed through the fluid. The metals in these particular examples are aluminum and gallium..
Parameters Case Case Case 3 Case Total current, 1000 700 300 120 A
d, mm 5 5 5 5 la, mm 10 10 10 10 Current density, 2* 10' 1.4* 6* 106 2.4%106 A/m2 10' Bx(0, +h/2), Tesla-0.048 -0.034 -0.014 -0.0058 By(0, +l2/2,0), +0.045 +0.032 +0.014 +0.0054 Tesla fy + j Bx (0,+hl2),-9.6*105-4.7*105-8.6*~104-1.4*104 N/m3 fx + j Bx (0,+hl2),+ 9.1 - 4.4* - 8.2* -1.3 N/m3 * 105 105 104 * 104 Aluminum: flfg 41 20 3.7 0.6 Aluminum: f /fg 39 19 3.5 0.5 Gallium: f~/fg 17 8 1.5 0.24 Gallium: f /fg 16 7.7 1.4 0.23 The system of the present invention can be used to detect and measure inclusions in molten metal. Further application of the present invention is in the separation of inclusions from molten metals such as aluminum, ferrous, brasses and copper alloys. In addition, the systems of the present invention may be utilized in semi-solid processing or die casting to homogenize segregated interdendritic liquid as well as breaking up dendritic networks.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
This is a Continuation-in-Part Application of U.S. Application No.
09/700,975 filed on November 21, 2000 which is a U.S. National Phase Application of PCT/LTS00/08668 filed on March 31, 2000.
BACKGROUND OF THE INVENTION
Due to the increasing demand for high quality metals, the purification of molten metals is becoming increasingly crucial. As a result, methods for the detection, measurement, separation and removal of inclusions from molten metals are desirable. W particular, the aluminum casting industry is in need of a reliable, fast, and economical detection system that enables furnace operators to conduct fine metal cleaning operations, and thus prevent small defects in the finished products.
A typical aluminum melt, for example, contains a large number of small non-metallic inclusions, less than or equal to SO~.m in size. These include particles of oxides (AIz03), spinels (MgAIz04), and carbides (SiC, AI4C3), with a higher melting point. Inclusions in alloys can impair the mechanical properties of articles made therefrom, are also detrimental to surface finish and maclunability, increase internal porosity in the castings, as well as increase corrosion. Non-metallic inclusions act as stress-raisers, and can cause premature failure of a component.
The assessment of the level of inclusions present in the melt is one of the key parameters which needs to be measured in molten metal processing. The existing detection techniques include pressure filter test, acoustic emission detection, and electric resistivity Coulter counter. The first two methods mainly rely upon a qualitative distinction between heavily contaminated melts and a clean melt.
The Coulter counter method evaluates both concentration and size distribution of inclusions larger than 15-20~,m for a small probe. However, this method is quite expensive and can only detect the effective size of an inclusion.
SUMMARY OF THE INVENTION
The present invention relates to a system for detecting and measuring non-metallic inclusions in molten metals. The methods for measuring inclusions in molten metals of the present invention include the steps of forcing the migration of the contaminant particles or inclusions onto a measurement region or surface using electromagnetic Lorentz forces, for example, detecting the particles in the measurement region and determining particle size and concentration at the measurement surface.
Electromagnetic force mechanisms have been investigated and used for purposes of separation and removal of contaminants in liquid metals. However, the cleaung systems relying on electromagnetic forces are not very effective because a very low force density is typically generated in a large liquid metal melt volume which needs to be cleaned, resulting in a slow relative particle motion. In the present invention electromagnetic forces are used to detect and measure non-metallic inclusions in a liquid metal. A detector system uses a small inspection volume, thus allowing for the generation of large force densities. The present invention may also be used to separate inclusions from metals such as aluminum utilizing the basis of high electromagnetic force density in chamlels having small volumes.
In particular, a preferred embodiment utilizes permanent magnets and a direct current ~(DC) source to generate electromagnetic forces. In addition, the methods for the detection of inclusions utilize electrostatic detection of the particle concentration at the measurement region or surface through a mufti-pin measurement configuration. Further, conditioning of the surface is required to overcome the surface tension forces that are responsible for preventing the inclusions from penetrating through the melt surface. By conditioning the surface, the particles penetrate the surface in order to be detected. The methods of conditioning the surface to enable particle detection can comprise a mechanical system or an acoustical vibration system or a combination of these two systems. A
mechanical system can use, for example, a roller, to continuously stretch out the surface layer of the melt. An acoustical vibration system involves the shaking of the liquid melt surface at a particular resonance frequency, for example 10-40Hz depending on the geometric size of the inspection volume, using an alternating current (AC) superimposed over the DC current flowing through the melt. The surface vibrations stimulate particle motion. Alternatively, a stream of a gas, or mixtures of gases, can be directed over the surface of the melt. Gas pressures in the cavity above the melt can be between 2=3 atmospheres, for example, to condition the surface. The gas flow can be used to delay oxidation and/or reduce surface tension on the melt surface. This serves to increase migration rates of inclusions to the surface region of the melt. Depending upon the direction and rate of flow, one or more gas inlets and outlets to the cavity above the melt can be used to control conditions on the surface region of interest. Inert gases such as helium or argon can be used, or active fluids such as chlorine gas can be used with or replace the inert gas which can also serve to loosen bonds at the surface to further improve particle migrations and detection. These gases can also improve the contrast in the heat signature of surface region components.
In another preferred embodiment of the present invention, the detection system is an optical system which features a solid state imaging device such as a charge-coupled-device (CCD). The CCD based detector system facilitates the electronic recording of the particles distributed over the surface aperture.
Once the particles are collected on the measurement surface or free melt surface by the application of electromagnetic Lorentz forces, low-frequency acoustic vibrations are initiated to enable the migration of the particles through the metal melt.
Recording of the particle size and distribution is performed with the CCD camera in conjunction with optical magiufication of the region of interest using a lens system.
The CCD camera may be coupled to an image acquisition system, which in turn may be coupled to a processor such as a microcontroller or personal computer having an electronic memory for data storage. The systems can be programmed with software modules to perform image processing on the collected image data and determine quantitative values including particle size and distribution. This processed data can be used to control flow rates and separation rates of the system.
In another preferred embodiment of the invention, detectors or detector systems sensitive in the range of wavelengths from 500-1200 rim are used to count inclusions. By detecting in the visible, near infrared and infrared regions of the electromagnetic spectrum, subsurface particles can be detected as well.
Commercially available detectors, such as amorphous selenium, can be used with a quartz window to image surface and subsurface particles at video frame rates.
Yet another embodiment of the present invention uses only an AC power source to induce electromagnetic forces in the melt and thereby cause movement of the melt and consequent positioning of inclusions for measurement. The detection system can be used in conjunction with a system for the separation of inclusions from the melt and provide real-time feedback control of the processing operation.
The systems of the present invention provide for the quantitative measurement of small inclusions, and can determine particle shape. Further, the systems of the present invention can distinguish between a single particle and a cluster of particles, and can distinguish between gas bubbles and solid particles.
There are several applications of the systems of the present invention including but not limited to the detection of inclusions in molten metals and the separation of inclusions from molten metals such as aluminum, ferrous materials, brasses and copper based alloys. Tn addition, the systems of the present invention may be utilized in semi-solid processing or die casting to homogenize segregated interdendritic liquid as well as breaking up dendritic networks.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A is a schematic illustration of a system to provide liquid metal utilizing the system for detecting and measuring inclusions in accordance with the present invention.
Figure 1B is a schematic illustration of the system of the present invention being utilized as a separation system described in Figure 1A.
Figure 1 C is a flow chart describing the details of a molten metal processing system incorporating the system for detecting and measuring inclusions in accordance with the present invention.
Figure 2A is a schematic illustration of an embodiment of the system to measure inclusions in molten metals in accordance with the present invention.
Figure 2B is a schematic diagram of a preferred embodiment of the detection system to detect and measure inclusions in molten metals in accordance with the present invention.
Figure 2C illustrates the top view of the container apparatus shown in Figure 2A.
Figure 2D illustrates a cross-sectional view of the container apparatus taken along lines 2D-2D of Figure 2C.
Figure 2E illustrates a cross-sectional view of the container assembly taken along lines 2E-2E of Figure 2C.
Figure 2F is a schematic diagram of another preferred embodiment of the detection system in accordance with the system of the present invention.
Figure 3A is a schematic illustration of another preferred embodiment of the system in accordance with the present invention.
Figure 3B is a detailed schematic illustration of the sensor element shown in Figure 3A.
Figure 4 is a schematic illustration of another preferred embodiment of the invention.
Figures SA-SE illustrate examples of the magnetic field and Lorentz force distribution in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to systems and methods to detect and measure inclusions in liquid metals. Further embodiments involve the processing of liquid or semi-solid materials.
The systems and methods to detect and measure inclusions in liquid metals use electromagnetic forces to force the migration of the contaminant particles to a detection and measurement surface. The invention is predicated on the fact that the included particles have a different electric conductivity level than that of the liquid melt and as such are treated as being non-conducting as compared to the liquid melt.
Thus, upon the application of a direct current (DC) throughout the melt with current density j and an imposed perpendicular magnetic flux density B, the Lorentz force density in the melt is f = j x B, where the force density, current density and magnetic flux density are vector quantities and the force density is the vector cross product of the current density and the magnetic flux density. The Lorentz force is induced in the metal but not in the non-conducting inclusions since no current can propagate through them. As a reaction to this electromagnetic force (Newton's third law), the inclusions are equally forced in the opposite direction. The corresponding reaction force density fa on the non-conducting inclusions fa = -f is known as Archimedes electromagnetic force. Archimedes electromagnetic force is well suited for detection purposes since a detector uses a small inspection volume, where extremely large force densities can be obtained with corresponding rapid particle motion.
Refernng now to the drawings, Figure 1A is a schematic illustration of a preferred method to provide liquid metal incorporating the system for detecting and measuring inclusions in accordance with the present invention. The particular sequence of steps describes the use of the system of the present invention in a system which provides liquid metal free of non-metallic inclusions. The metal is melted either in a reverbatory furnace or in an electrically heated furnace.
Alternatively, the metal may be induction melted. The system comprises a sensor element 110 which consists of a container 112 into which flows a liquid metal having inclusions per step 114. The liquid metal flows out of the metal per step 116 after the sensing and detection of the included particles has occurred. Electrodes 11 ~ are integrated with the container 112 to provide a voltage drop in the container. An electromagnetic force is induced in the container which acts on the liquid metal and not on the included particles. The electromagnetic force can be generated by applying power supplied by the power supply 120, to the container. A DC current in combination with the permanent magnet system 124 can create the required electromagnetic force. Alternatively, the electromagnetic force can be generated by applying a high AC current also supplied by the power supply 120, whose self induced magnetic field eliminates the need for the permanent magnet system 124.
The inclusions which are non-conducting as compared to the liquid metal rise toward a measurement region wluch is the free melt surface. Since the melt is not transparent in the visual domain the measurement region needs to be conditioned so as to force the inclusions to break through the melt surface which has a metal oxide layer disposed on it. To overcome the surface tension forces which retain the particles below the free melt surface, the measurement region may be conditioned mechanically per step 128, or by an acoustic conditioning system 132 or alternatively by a combination of the two.
The included particles are then detected by a detection system 136. The detection system may be an electrostatic measurement system or an image detection system.
The results of the detection system are then recorded and particle size and concentration are computed in the processor 140. The results of the processing step 140 maybe displayed on a display 144 and used to monitor the size and concentration of inclusions. A particle separation system 148 is coupled to the computer to remove the detected inclusions to provide liquid metal free of inclusions.
Figure 1B is a schematic illustration of the use of the present invention as a separation or cleaning system. A container 152 of liquid metal having inclusions feeds into a separation system 154. The separation system consists of small channels 156 for the liquid metal to flow into. The particles are separated in a separation zone 158 in each channel 156 by applying a high electromagnetic force density to the liquid metal in each channel. The resultant liquid metal that is _g_ collected from the separation system 154 in a container 160 is substantially free of inclusions. Each zone 158 or channel 156 can have a detector system as shown in Figure 1A to provide monitoring of each channel.
Figure 1 C schematically illustrates further details of the utility of the present invention in a molten metal processing system 162 that supplies liquid metal, having reduced concentrations of larger inclusions or is substantially free of inclusions, for casting and other applications. The particular sequence of steps describes the system to provide inclusion free metal. Liquid metal in step 164 is degassed per step 166 to remove gaseous hydrogen, for example. The liquid metal then flows through a filtration system per step 168 to remove inclusions as part of a typical molten metal processing system. The resultant liquid metal is then used in a casting process per step 170. A certain small volume of the filtered liquid metal is fed into the detection and measurement system in accordance with the present invention per step 172.
Step 172 senses inclusions and determines particle size and distribution. The sensor data is then translated into an actual distribution for the molten metal per step 174.
The actual distribution of inclusions is then compared with a desired distribution per step 176. The desired, ideal distribution computed per a model such as predicted in step 178, is stored electronically in a memory and retrieved to perform the comparison per step 176. If the actual distribution of the inclusions is within an acceptable range of the desired distribution, no corrective action is taken.
However, if the actual distribution of the inclusions is not within an acceptable range of the desired distribution then corrective action is initiated per the process model and control laws of step 180. The control variables listed in step 182, for example, filter life and size, the operations of the degassing unit and the charge of the melt are then recalculated and changes are programmed into the processing system. As a result of changes made to the control variables, the process model is updated per step 184.
Figure 2A, is a schematic illustration of a preferred embodiment of the system to detect and measure inclusions which can be used to perform the methods of the present invention. A container 210, which for example is made of ceramic, is filled with the liquid melt 212, for example liquid gallium. The liquid melt 212 is subjected to both an electric as well as a magnetic field.
The resulting electromagnetic Lorentz force density is created by two permanent magnets 214 having a range of 0.3 Tesla to 0.6 Tesla acid a DC
current having a range of 100 A to 150A supplied by a DC power supply 216. Other embodiments can employ current in a range of 50 to 2000A depending upon the particular application. Commercial systems will preferably have currents in the range of 200-2000A to improve flow rates. The magnetic field is nearly homogeneous in between the two electrodes 224. The system may be conF'igured so that the melt continuously flows through the container 210 and the inclusions are collected on a region 220 of the free melt surface. If the flow cross-section is 0.5 by 1 cm, then the current density j is 2.4x106A/m2 based on a total current of 120A.
Accordingly, the Lorentz force density is 7.2 x 105 N/m3 if the flux density is 0.3 Tesla. Flow rates of the melt are preferably in the range of 50-200 ml per minute.
This is more than thirty (30) times the gravitation force density acting on the molten metal such as aluminum. Simultaneously, this is more than sixty (60) times the gravitation Archimedes force on spinet inclusions (p=3600 kg/m3) in molten aluminum. These considerations underscore the fact that electromagnetic treatment is quite effective if the cross-sectional area for the metal flow is sufficiently small.
Coupled to both sides of the container 210 are electrodes 224. The electrodes may, for example, be made. of copper tungsten, graphite, aluminum or other conductive materials. The electrodes provide the DC current flow which in combination with the magnetic field is responsible for the electromagnetic Lorentz force. In addition, the current flow encounters an electric resistance due to the presence of the liquid metal. As a consequence, a voltage drop is created between the electrodes which in turn can be measured through the placement of small copper point electrodes in contact with the free melt surface. Variations in the voltage drop between the adjustment point electrodes permit the detection of particles that migrated to the surface in response to the Lorentz force. The electrodes are selected depending upon the materials in the fluid metal that will either be stable under the operating condition or that deteriorate at known rates.
Non-conducting particles experience uniform longitudinal motion with constant velocity and, simultaneously, transverse motion, rising toward the free melt surface or region 220 with a given velocity. Even for inclusions of 10~,m in diameter, the rise velocity is sufficient to enable inclusion collection on a region of the free melt surface within a reasonable time duration. Since the melt is not transparent in the visual domain of the electromagnetic spectrum, inclusion escape on the free melt surface plays a decisive role. The main mechanism that prevents escape is surface tension. The Archimedes electromagnetic force is much smaller than the surface tension force, for all possible particle sizes. Thus, an additional treatment of the melt surface is necessary.
The surface is conditioned mechanically, by continuously stretching out the surface layer of the melt, for example by a rotating cylinder such as a ceramic roller 228. The roller drags the surface layer away from the detection region. This process makes the melt surface appear as if it is being "stretched" with new particles continuously appearing. Another method for conditioning the melt surface is acoustically vibrating the liquid melt surface in the range of 10-40Hz depending on the geometric size of the inspection volume. This can be accomplished through an AC power amplifier supply 232 in the range between 500-800W, and an AC signal generator 234 providing an AC current. An additional periodic Lorentz force component appears in the transverse direction, which produces surface vibrations.
Such vibrations stimulate particle escape. Methods for providing oscillations of liquid metal by electromagnetic Lorentz forces are described in "Resonant oscillations of a liquid metal column driven by electromagnetic Lorentz force sources", by Sergey Makarov, Reinhold Ludwig and Diran Apelian, J. Acoust.
Soc.
Am., Vol 105, No. 4, April 1999, which is incorporated herein by reference.
Methods described in the aforementioned reference publication can be used with the systems described herein to provide acoustic vibrations for conditioning the free melt surface.
Both methods for conditioning the surface have their advantages and disadvantages. Mechanical stretching implies moving sensor components, for example rollers, whereas acoustic vibration reduces the quality of the optical image formation. A combination of the two methods may be used to offset the disadvantages of the individual methods.
Based on an exemplary cylindrical volume, a current strength of 150A (DC
current) supplied through two electrodes to a measurement container of 20 mm in length and 5 mm in radius creates an average radial force density of 100 kN/m3.
This is sufficient to force 75% of the inclusions with an average 40 micron effective diameter to the surface, amounting to an inspection speed of 88 ml/min.
In a preferred embodiment illustrated in Figure 2B, the detection system in accordance with the present invention is an optical detection system which may include optical magnification of the region of interest using a lens system 252, for example a microscope, a CCD camera 256 and a display 260. In addition, the CCD
camera may be coupled to a frame grabber 262 which in tum is coupled to a processor 264. The optical detection method predicts non-conducting and low-conducting inclusions of an average diameter in the range of 5 to 50 microns in molten aluminum.
Figures 2C, 2D and 2E provide further details regarding the container assembly and the mechanical conditioning system described in Figures 1 and 2A.
The roller stretches the free melt surface and in doing so disrupts the metal oxide layer that forms on the surface, which then enables the escape of the particles to the surface which allows for detection of the particles. The action of the mechanical roller tends to move a layer of the melt on top of the roller, potentially allowing for the separation of the included particles in the top layer into a baffle 270 shown in Figure 2D.
Figure 2F illustrates another embodiment of the detection system of the present invention. Once the particles reach the surface, this embodiment of the present invention uses an electrostatic measurement device 280 having voltage recording pins 282 in the range of 10 to 100 pins, deployed over the free melt surface to measure a differential voltage distribution which subsequently can be compared to a baseline distribution of pure molten aluminum. The pins may be small copper point electrodes in contact with the free melt surface. If the probe spacing is on the order of 0.3 mm using laser drilling, the approximate calculations indicate that the expected differential potential distribution exceeds 4 to 5 ~,V, well above the background noise. This detection system predicts nonconducting and low-conducting inclusions of an average diameter in the range of 20 to 100 microns in molten aluminum.
Referring to Figure 3A, another preferred embodiment of the system to detect and measure inclusions in liquid metal includes a sensing element 310 consisting of three columns or sections which are placed in a container 314 filled with a liquid metal 316. The columns may be made from ceramic or a refractory material. An AC power supply 318 supplying a current in the range of SODA to 1000A is coupled to the electrodes 320 which are integrated with the sensing element 310.
The optical or infrared detection system 322 includes optical magnification of the region of interest using a lens system 328, a CCD or infrared camera 330, an image acquisition system 334 coupled to a processor 336, and a display 338. A
long focal length objective lens 328 with a magnification in the range of 1000 to 2000 is coupled to the CCD. The CCD based detector system facilitates the electronic recording of the particles distributed over the surface aperture. Low-frequency acoustic vibrations can be initiated through alternating Lorentz force using a modulating AC signal generator in conjunction with an AC power amplifier as previously described. Low-frequency acoustic vibration in the frequency range of 10-40 Hz break-up the surface layer (an oxide film plus surface tension forces) of the liquid melt, to allow the escape of the inclusions from the melt to facilitate detection.
The sensing element has a self cleaning feature due to the angular relationship between the columns. A tilt angle 350 in the range of 2-5°
allows the liquid melt to flow out of the sensing element 310 once the element is removed from the melt.
An inert gas supply 340 provides an inert carrier gas to remove any gaseous impurities to maintain a clean interface for the quartz window 324.
No permanent magnets are required for the embodiment as discussed with respect to Figure 3A. Referring to Figure 3B, which provides further details of the sensing element 310 illustrated in Figure 3A, a sufficiently strong self induced average magnetic-field in the range of 0.05 Tesla to 0.1 Tesla is initiated by the 60Hz AC current of 50-2000 Amperes, and preferably 1000-2000 Amperes, when applied to the container. The total power applied is in the range of 2-3 kW.
Although the self induced magnetic field is weaker than the field provided by the embodiment having the permanent magnet system, the significantly higher current density as a result of the lugher AC current is responsible for a strong electromagnetic Lorentz force density. It also may be possible to replace the power supply by a transformer. Additionally, another embodiment of the system of the present invention may use a removable sensor or sensing element made of tungsten as opposed to ceramic.
The advantage of the embodiment as illustrated by Figures 3A and 3B, is the creation of a self induced magnetic field which eliminates the use of permanent magnets. Permanent magnets require an external cooling system which does not need to be provided for by the system described with respect to Figures 3A and 3B.
In addition, a DC power supply which is typically move expensive and cumbersome to handle than an AC power supply, is not required to operate the system as disclosed with respect to Figures 3A and 3B. Further, the embodiment illustrated by Figures 3A and 3B eliminates the need for an external pump. W stead, the embodiment relies on a self pumping mechanism to assure continuous melt flow through the measurement region.
Figure 4 illustrates another preferred embodiment of the invention wherein the gas flow inlet 340 is controlled by a valve that can be connected at 344 to a system controller. A gas flow outlet 360 can also be fluidly coupled to the cavity 362 above the metal fluid in the chamber 364 through which the metal fluid flows.
Alternatively, one or more inlets 370 can be positioned about the quartz window 324 through which a region of interest 352 can be viewed. The metal fluid is forced upwards in opposition to a gravitational force through channel 400.
The metal fluid can be directed through the chamber 364 and a plurality of outlets. The flow through the outlets 380, 390 can be directed downstream for a further processing such as a separation system. The gas flow system operates to control surface characteristics such as oxidation rate, bonding properties, contrast and migration rate of particles in the region of interest 352.
Figures SA-SE illustrate examples of the magnetic field and force density characteristics. For a container having a current I of 1000A, for example, as shown in Figure SA, the magnetic field strength in a one centimeter square cross section is shown in Figure SB and the field orientation is shown in Figure SC. The resulting Lorentz force density and orientation are illustrated in Figures SD and SE
respectively.
The following table illustrates the ratio of the magnitude of the force acting on the fluid to the gravitational force in four cases having different total currents directed through the fluid. The metals in these particular examples are aluminum and gallium..
Parameters Case Case Case 3 Case Total current, 1000 700 300 120 A
d, mm 5 5 5 5 la, mm 10 10 10 10 Current density, 2* 10' 1.4* 6* 106 2.4%106 A/m2 10' Bx(0, +h/2), Tesla-0.048 -0.034 -0.014 -0.0058 By(0, +l2/2,0), +0.045 +0.032 +0.014 +0.0054 Tesla fy + j Bx (0,+hl2),-9.6*105-4.7*105-8.6*~104-1.4*104 N/m3 fx + j Bx (0,+hl2),+ 9.1 - 4.4* - 8.2* -1.3 N/m3 * 105 105 104 * 104 Aluminum: flfg 41 20 3.7 0.6 Aluminum: f /fg 39 19 3.5 0.5 Gallium: f~/fg 17 8 1.5 0.24 Gallium: f /fg 16 7.7 1.4 0.23 The system of the present invention can be used to detect and measure inclusions in molten metal. Further application of the present invention is in the separation of inclusions from molten metals such as aluminum, ferrous, brasses and copper alloys. In addition, the systems of the present invention may be utilized in semi-solid processing or die casting to homogenize segregated interdendritic liquid as well as breaking up dendritic networks.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (40)
1. A method for detecting and measuring inclusions in a fluid comprising the steps:
forcing the migration of particles in a fluid conductor to a measurement region; and detecting the particles in the measurement region.
forcing the migration of particles in a fluid conductor to a measurement region; and detecting the particles in the measurement region.
2. The method of Claim 1 wherein the step of forcing the migration of the particles comprises applying an electromagnetic Lorentz force to the fluid.
3. The method of Claim 2 wherein the electromagnetic Lorentz force is applied using a plurality of permanent magnets and a direct current (DC) source.
4. The method of Claim 2 wherein the electromagnetic Lorentz force is applied using an alternating current (AC) source.
5. The method of Claim 1 further comprising conditioning the measurement region to move the particles within the measurement region.
6. The method of Claim 5 wherein the conditioning of the measurement region further comprises applying a mechanical force to a surface of the region.
7. The method of Claim 5 wherein the conditioning of the measurement region is comprises vibrating the region.
8. The method of Claim 1, wherein the step of detecting the particles uses an electrostatic measurement.
9. The method of Claim 1 wherein the step of detecting the particles uses an image detection system that detects the particles.
10. The method of Claim 1 further comprising flowing a fluid material over a surface of the fluid to alter a surface characteristic.
11. The method of Claim 10 further comprising flowing a gas across the measurement surface.
12. The method of Claim 1 wherein the step of flowing a gas further comprises flowing a gas selected from the group comprising helium, argon and chlorine.
13. The method of Claim 11 further comprising flowing a gas mixture over the measurement surface.
14. The method of Claim 10 further comprising flowing a gas over the surface to increase a particle flow rate in the measurement region.
15. The method of Claim 1 further comprising providing a detective that detects light in a range of wavelengths from 500nm to 1200nm.
16. The method of Claim 15 further comprising providing a solid state infrared detector.
17. The method of Claim 1 further comprising providing an amorphous selenium detector.
18. The method of Claim 10 wherein the step of altering a surface characteristic can comprise altering an oxidation rate at the fluid surface, reducing surface tension at the fluid surface, increasing contrast between particles in the fluid and the fluid, or increasing flow rate of particles through a region of interest.
19. The method of Claim 1 further characteristic comprises comprising controlling separation reducing an oxidation rate of particles from the fluid at the fluid surface.
20. Apparatus for measuring inclusions in a conductive liquid comprising:
a conductive liquid source;
an electrode device positioned relative to the liquid that provides a current path in the liquid;
a current source connected to said electrode device; and a detection device that detects material in the liquid.
a conductive liquid source;
an electrode device positioned relative to the liquid that provides a current path in the liquid;
a current source connected to said electrode device; and a detection device that detects material in the liquid.
21. The apparatus of Claim 20 wherein the current generator is a direct current (DC) source.
22. The apparatus of Claim 20 wherein the current generator is an alternating current (AC) source.
23. The apparatus of Claim 20 further comprising a plurality of permanent magnets to a create magnetic field.
24. The apparatus of Claim 20 wherein the detection device is an electrostatic device system.
25. The apparatus of Claim 20 wherein the electrostatic device further comprises a plurality electrodes contacting a measurement surface to detect changes in voltage as inclusions flow through the measurement surface between said electrodes.
26. The apparatus of Claim 20 wherein the detection device is an optical detection system.
27. The apparatus of Claim 20 wherein the detection system further comprises, an optical magnifier to magnify the measurement surface and a solid-state imaging device.
28. The apparatus of Claim 20 wherein the detection system is coupled to a display.
29. The apparatus of Claim 20 further comprising an image processor and a system controller.
30. The apparatus of Claim 20 further comprising a magnetic field source that applies a force to the liquid to move the liquid against a gravitational force.
31. The apparatus of Claim 20 wherein the electrode device comprises a plurality of graphite, tungsten, aluminum or copper electrodes.
32. The apparatus of Claim 20 wherein the detection device comprises an infrared imaging detector.
33. The apparatus of Claim 20 comprising a flow container including a metal liquid source inlet and an outlet.
34. The apparatus of Claim 20 further comprising a gas source coupled to a housing such that a gas can flow across a surface region of the liquid.
35. The apparatus of Claim 20 further comprising an inclusion separator.
36. The apparatus of Claim 34 wherein the gas comprises an inert gas or an active gas.
37. The apparatus of Claim 20 further comprising a memory and an image processor that measures particle size and distribution in the liquid.
38. The apparatus of Claim 20 a gas flow controller to control gas flow in a chamber above the liquid and quartz window.
39. Apparatus for measuring inclusions in a liquid comprising:
a source of a liquid having inclusions;
an electrode system positioned to provide a current path in the liquid;
a current source connected to said electrodes; and an imaging device to sense inclusions in the liquid.
a source of a liquid having inclusions;
an electrode system positioned to provide a current path in the liquid;
a current source connected to said electrodes; and an imaging device to sense inclusions in the liquid.
40. The apparatus of Claim 39 further comprising an optical system that optically couples a surface of the liquid to the imaging device and a system controller that controls process parameters in response to detected images.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
USPCT/US00/08668 | 2000-03-31 | ||
USPCT/US00/08668 | 2000-03-31 | ||
US70097500A | 2000-11-21 | 2000-11-21 | |
US09/700,975 | 2000-11-21 | ||
PCT/US2001/010371 WO2001075183A2 (en) | 2000-03-31 | 2001-03-30 | System for detecting inclusions in molten metals |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2404560A1 true CA2404560A1 (en) | 2001-10-11 |
Family
ID=26680179
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002404560A Abandoned CA2404560A1 (en) | 2000-03-31 | 2001-03-30 | Systems for detecting and measuring inclusions |
Country Status (10)
Country | Link |
---|---|
EP (1) | EP1268866A2 (en) |
JP (1) | JP2003535316A (en) |
KR (1) | KR20020095199A (en) |
CN (1) | CN1427898A (en) |
AU (1) | AU2001251167A1 (en) |
BR (1) | BR0107533A (en) |
CA (1) | CA2404560A1 (en) |
MX (1) | MXPA02009593A (en) |
NO (1) | NO20024613L (en) |
RU (1) | RU2002128920A (en) |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8505397B2 (en) * | 2010-09-30 | 2013-08-13 | GM Global Technology Operations LLC | Methods of characterizing aluminum oxides |
EP2906927B1 (en) * | 2012-10-15 | 2021-08-04 | ABB Inc. | Liquid metal cleanliness analyzer |
CN103123329B (en) * | 2012-12-31 | 2015-07-29 | 上海大学 | The method for quick of non-metallic inclusion and device for fast detecting in metal |
CN103245711B (en) * | 2013-04-18 | 2016-10-05 | 沈阳理工大学 | Aluminum liquid non-metallic inclusion online soft sensor device and method based on neutral net |
FI125886B (en) * | 2014-01-29 | 2016-03-31 | Ilkka Jaakkola | ARRANGEMENTS FOR ELIMINATING ELECTRICITY LEADING PARTICLES |
CN104007170B (en) * | 2014-05-19 | 2016-10-05 | 中国科学院大学 | The method measuring molten metal degree of purity by condition conversion based on electromagnetic principle |
CN105108093B (en) * | 2015-09-02 | 2017-03-08 | 青岛理工大学 | The physical simulating method of the non-metallic inclusion characteristics of motion in continuous cast mold under stirring the action of a magnetic field |
US9651469B1 (en) * | 2016-01-27 | 2017-05-16 | General Electric Company | Electrostatic particle sensor |
CN105499142B (en) * | 2016-01-27 | 2017-06-20 | 东北大学 | A kind of resultant field spiral chute metal bead piece-rate system and method |
CN106018448B (en) * | 2016-05-16 | 2019-01-08 | 横店集团东磁股份有限公司 | Miscellaneous phase content appraisal procedure in a kind of LaFeSi base magnetic refrigerating material |
CN106017993B (en) * | 2016-05-17 | 2019-11-26 | 沈阳理工大学 | Metal bath sampling equipment |
CN107119192B (en) * | 2017-04-17 | 2019-02-22 | 上海大学 | The method and device of electromagnetism vortex driving force purifying molten metal |
CN108043586A (en) * | 2017-12-21 | 2018-05-18 | 西安欧中材料科技有限公司 | A kind of method of nonmetal inclusion content in detection metal powder |
KR102309284B1 (en) | 2018-08-03 | 2021-10-06 | 주식회사 엘지에너지솔루션 | Method of measument for undissolved solutes in polymer solution |
CN110068483A (en) * | 2019-05-27 | 2019-07-30 | 邯郸百世创联电子科技有限公司 | A kind of environmental monitoring Urban Underground sewage detection sampler |
CN110412489B (en) * | 2019-07-29 | 2020-08-14 | 大连理工大学 | Estimation method for internal composite magnetic field of permanent magnet coupler |
-
2001
- 2001-03-30 CA CA002404560A patent/CA2404560A1/en not_active Abandoned
- 2001-03-30 MX MXPA02009593A patent/MXPA02009593A/en unknown
- 2001-03-30 EP EP01924518A patent/EP1268866A2/en not_active Withdrawn
- 2001-03-30 RU RU2002128920/02A patent/RU2002128920A/en not_active Application Discontinuation
- 2001-03-30 AU AU2001251167A patent/AU2001251167A1/en not_active Abandoned
- 2001-03-30 BR BR0107533-0A patent/BR0107533A/en not_active IP Right Cessation
- 2001-03-30 JP JP2001573055A patent/JP2003535316A/en active Pending
- 2001-03-30 CN CN01808824A patent/CN1427898A/en active Pending
- 2001-03-30 KR KR1020027012866A patent/KR20020095199A/en not_active Application Discontinuation
-
2002
- 2002-09-26 NO NO20024613A patent/NO20024613L/en not_active Application Discontinuation
Also Published As
Publication number | Publication date |
---|---|
KR20020095199A (en) | 2002-12-20 |
RU2002128920A (en) | 2004-04-20 |
MXPA02009593A (en) | 2004-05-14 |
NO20024613D0 (en) | 2002-09-26 |
CN1427898A (en) | 2003-07-02 |
JP2003535316A (en) | 2003-11-25 |
NO20024613L (en) | 2002-11-27 |
EP1268866A2 (en) | 2003-01-02 |
BR0107533A (en) | 2003-06-10 |
AU2001251167A1 (en) | 2001-10-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2404560A1 (en) | Systems for detecting and measuring inclusions | |
US6693443B2 (en) | Systems for detecting and measuring inclusions | |
CN103123329B (en) | The method for quick of non-metallic inclusion and device for fast detecting in metal | |
Samarian et al. | Self-excited vertical oscillations in an rf-discharge dusty plasma | |
US6590200B1 (en) | Systems for detecting measuring inclusions | |
US20160288211A1 (en) | Multi-metal particle generator and method | |
CN108183632A (en) | A kind of method that form to electromagnetic suspension liquid metal is regulated and controled | |
Zhang et al. | Effect of external longitudinal magnetic field on arc plasma characteristics and droplet transfer during laser-MIG hybrid welding | |
WO2001075183A2 (en) | System for detecting inclusions in molten metals | |
Grants et al. | Contactless magnetic excitation of acoustic cavitation in liquid metals | |
Tam et al. | Weld pool impedance for pool geometry measurement: stationary and nonstationary pools | |
Bardin et al. | Investigating transport of dust particles in plasmas | |
US5621751A (en) | Controlling electrode gap during vacuum arc remelting at low melting current | |
Cibula | Investigation into the spatio-temporal properties of arcs in vacuum arc remelting furnaces | |
KR100897764B1 (en) | Molten Metal Inclusion Sensor Probes | |
Sun et al. | A new method for refinement of Ti-6Al-4 V prior-β grain structure in the alternating magnetic field assisted narrow gap gas tungsten arc welding (AMF-GTAW) via filler wire oscillation | |
Zanner et al. | Behavior of sustained high-current arcs on molten alloy electrodes during vacuum consumable arc remelting | |
King et al. | Control of the distribution of vacuum arcs within vacuum arc remelting with externally applied magnetic fields | |
Kuo et al. | Particle Chromatography | |
Badowski et al. | Measurement of non-metallic inclusions in the size range of 10–20μm by LiMCA | |
Zheng et al. | A novel control approach for the droplet detachment in rapid prototyping by 3D welding | |
De Sliva | Process developments in electrochemical arc machining | |
Madigan | Control of gas metal arc welding using arc light sensing | |
Chiriac et al. | On the measurement of surface tension for liquid FeSiB glass-forming alloys by sessile drop method | |
JPH08259380A (en) | Growing method for silicon crystal |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FZDE | Dead |