Title of Invention

A METHOD OF NON-INTRUSIVE DETECTION OF LIQUID METAL/ALLOY STIRRING

Abstract

The present invention relates to a device for non-intrusive detection of liquid metal/alloys stirring, said device comprises (a) linear electromagnetic stirrer(s) to generate electromagnetic forces; (b) a crucible in core of the electromagnetic stirrer(s), closed at one end by a dummy block; and (c) a standard calibrated load cell attached underneath the dummy block to continuously monitor the weight change of the stirring melt; and a non-intrusive method of detecting liquid metal/alloys stirring, said method comprising steps of (a) introducing liquid metal/alloys in a crucible; (b) applying electromagnetic force to the crucible for stirring the liquid metal/alloys; and (c) continuously monitoring weight of the stirring melt with a load cell, wherein stirring stops as the metal/alloy solidifies as reflected by stability in the weight by load cell.

Full Text

FIELD OF THE INVENTION: The present invention relates to detection of liquid metal stirring during casting with an electromagnetic stirrer. It provides for a device and a method for non-intrusive detection of liquid metal/alloys stirring. BACKGROUND AND PRIOR ART: During electromagnetic stirring of liquid metals and alloys undergoing solidification, the solid fraction progressively increases. Stirring .will stop once the solid fraction reaches a critical value, usually known as the coherency point. It is useful to detect experimentally when this coherency point is reached and stirring stops. Detection of stirring by conventional flow visualization methods do not work for liquid metals and alloys as the medium is opaque. Other methods such as insertion of thermocouples or periodic sampling are intrusive in nature. However, the present invention relates to a device and a method for detection of stirring of liquid metal in presence of electromagnetic forces which is completely non-intrusive. Eddy currents are induced in all metals when subjected to an external magnetic field. By Fleming's left hand rule, the induced eddy current along with the magnetic field produces a net mechanical force known as Lorentz force. The equations for the calculation of the Lorentz force is mathematically represented below: J is the current density A/m2 μis the permeability of the metal H/m μ is the conductivity The mechanical forces given by the vector cross products are as follows: Fz = JBr Fr = JBz F0 = O If the metal is in liquid state then the above forces result in stirring of the metal. Theoretically, from the above equations it can be seen that the fluid velocity (or stirring) changes the resultant Lorentz force. In the case of a linear electromagnetic stirrer, the net Lorentz force is in the vertical direction (i.e. along the axis of the stirrer, as shown in figure 1). This net Lorentz force in the vertical direction can be measured by weighing the metal (in solid or liquid state) with a suitable weighing instrument. It is observed that the weight change in liquid metal is different from that measured in a solid metal under identical conditions. Hence, by measuring the weight change, one can predict whether the metal is stirring or not. OBJECTS OF THE INVENTION; The main object of the present invention is to obtain a device for non-intrusive detection of liquid metal/alloys stirring. Another main object of the present invention is to obtain a device for non-intrusive detection of liquid metal/alloys stirring using electromagnetic stirrer. Yet another object of the present invention is to obtain a device for regular production of castings Still another object of the present invention is to obtain a non-intrusive method of detecting liquid metal/alloys stirring. Still another object of the present invention is to obtain a non-intrusive method for regular production of castings. STATEMENT OF THE INVENTION: The present invention relates to a device for non-intrusive detection of liquid metal/alloys stirring, said device comprises (a) linear electromagnetic stirrer(s) to generate electromagnetic forces; (b) a crucible in core of the electromagnetic stirrer(s), closed at one end by a dummy block; and (c) a standard calibrated load cell attached underneath the dummy block to continuously monitor the weight change of the stirring melt; and a non-intrusive method of detecting liquid metal/alloys stirring, said method comprising steps of (a) introducing liquid metal/alloys in a crucible; (b) applying electromagnetic force to the crucible for stirring the liquid metal/alloys; and (c) continuously monitoring weight of the stirring melt with a load cell, wherein stirring stops as the metal/alloy solidifies as reflected by stability in the weight by load cell. DETAILED DESCRIPTION OF THE INVENTION: The present invention relates to a device for non-intrusive detection of liquid metal/alloys stirring, said device comprises: a) linear electromagnetic stirrer(s) to generate electromagnetic forces; b) a crucible in core of the electromagnetic stirrer(s), closed at one end by a dummy block; and c) a standard calibrated load cell attached underneath the dummy block to continuously monitor the weight change of the stirring melt. In another embodiment of the present invention, the crucible is made of electrically non¬conducting material. In still another embodiment of the present invention, the crucible alongwith the dummyblock is freely suspended onto the load cell. In still another embodiment of the present invention, the crucible or the dummyblock does not touch the sides of the electromagnetic stirrer(s). In still another embodiment of the present invention, the load cell generates electrical output which is calibrated, amplified and connected to a digital readout. In still another embodiment of the present invention, the linear electromagnetic stirrer is provided with alternating current. In still another embodiment of the present invention, the force generated by the linear electromagnetic stirrer is Lorentz force, which is along the axis of the electromagnetic stirrer. In still another embodiment of the present invention, the device is suitable for regular production of castings. The present invention also relates to a non-intrusive method of detecting liquid metal/alloys stirring, said method comprising steps of: a) introducing liquid metal/alloys in a crucible; b) applying electromagnetic force to the crucible for stirring the liquid metal/alloys; and c) continuously monitoring weight of the stirring melt with a load cell, wherein stirring stops as the metal/alloy solidifies as reflected by stability in the weight by load cell. In still another embodiment of the present invention, the crucible is made of electrically non-conducting material. In still another embodiment of the present invention, the crucible is freely suspended onto the load cell. In still another embodiment of the present invention, the load cell generates electrical output which is calibrated, amplified and connected to a digital readout. In still another embodiment of the present invention, the method is suitable for regular production of castings. In still another embodiment of the present invention, the alloy is preferably a metallic alloy. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS: Fig la: shows the block diagram of the experimental setup of the invention. Fig lb: shows the schematic diagram of the experimental setup of the invention. Fig 2: is a plot showing variation of Lorentz force with current in solid and liquid states In another embodiment, the present invention relates to a device and a method for detection of stirring of liquid metal in presence of electromagnetic forces which is completely non-intrusive. As against the existing methods, the present method is completely non intrusive or location specific. The technique is applicable for casting processes involving electromagnetic stirring. Scientific Principle of the present invention: Eddy currents are induced in all metals when subjected to an external magnetic field. By Fleming's left hand rule, the induced eddy current along with the magnetic field produces a net mechanical force known as Lorentz force. The equations for the calculation of the Lorentz force is mathematically represented below: If the metal is in liquid state then the above forces result in stirring of the metal. Theoretically, from the above equations it can be seen that the fluid velocity (or stirring) changes the resultant Lorentz force. In the case of a linear electromagnetic stirrer, the net Lorentz force is in the vertical direction (i.e. along the axis of the stirrer, as shown in figl). This net Lorentz force in the vertical direction can be measured by weighing the metal (in solid or liquid state) with a suitable weighing instrument. It is observed that the weight change in liquid metal is different from that measured in a solid metal under identical conditions. Hence, by measuring the weight change, one can predict whether the metal is stirring or not. The invention is further elaborated with the help of following examples. However, these examples should not be construed to limit the scope of invention. Example 1: The linear electromagnetic stirrer is powered by a 3-phase alternating supply, to generate the required forces. There is a crucible made of electrically non-conducting material placed in the core of a linear electromagnetic stirrer. The crucible is closed at one end by a dummy block. A standard calibrated load cell (strain guage rosette) is attached underneath the dummy block. Care is taken to see that the crucible or the dummy block does not touch the sides of the electromagnetic stirrer. For accurate reading the crucible along with the dummy block should be freely suspended on the load cell. The electrical output from the load cell is calibrated, amplified and connected to a digital readout. Example 2: The liquid metal is introduced into the crucible at a specified temperature. The metal starts stirring due to the action of electromagnetic forces. The intensity of stirring depends on the strength of the imposed magnetic field. The load cell continuously monitors the "weight" of the stirring melt under the action of electromagnetic forces. The metal is cooled by a suitable cooling arrangement. As the metal solidifies it is observed that there is an appreciable change in the weight of the metal measured by the load cell (fig 2). When there is no more weight change recorded by the load cell, it is concluded that stirring has stopped. Alloy used: INDALLOY 117 Composition: 44.7Bi-8.3Sn-22.6Pb-19.1In-5.3Cd Melting temperature = 47°C = 320 K Frequency of current: 50 Hz. AC input voltage= 8 V when the current fed = 200A Transformer: Primary (input) = 225 V Secondary (output) = 18V Weighing balance used: Explorer Pro series (Max: 32 Kg Accuracy of 0.1 g) (Ohaus make) Example 4: Variation in the Lorentz force with current in solid and liquid states FULL LIQUID - FOR ALL MOLD POSITIONS - LEVITATION MODE FOR DIFFERENT COIL POSITIONS OF THE MOLD LEVITATION MODE WEIGHT OF MOLD WITOUT METAL IN GRAMS 1070 WEIGHT OF METAL IN GRAMS 3430 BARE WEIGHT IN G 4500 WHEN THE MOLD ENDS AFTER THE 6 TH COIL Technical value of the invention: a) The present technique is a direct on-line measurement, which can be used as a process control/monitoring parameter. There is no scope for human error associated with this technique. No specialized or skilled manpower will be required. b) The technique can be incorporated in any existing casting process in presence of electromagnetic stirring, with only minor modifications. c) The instrumentation is simple, cost effective and standard. d) The method is non intrusive, and hence, can be used in regular production of castings. We claim: 1. A device for non-intrusive detection of liquid metal/alloys stirring, said device comprises: a) linear electromagnetic stirrer(s) to generate electromagnetic forces; b) a crucible in core of the electromagnetic stirrer(s), closed at one end by a dummy block; and c) a standard calibrated load cell attached underneath the dummy block to continuously monitor the weight change of the stirring melt. 2. The device as claimed in claim 1, wherein the crucible is made of electrically non-conducting material. 3. The device as claimed in claim 1, wherein the crucible alongwith the dummyblock is freely suspended onto the load cell. 4. The device as claimed in claim 1, wherein the crucible or the dummyblock does not touch the sides of the electromagnetic stirrer(s). 5. The device as claimed in claim 1, wherein the load cell generates electrical output which is calibrated, amplified and connected to a digital readout. 6. The device as claimed in claim 1, wherein the linear electromagnetic stirrer is provided with alternating current. 7. The device as claimed in claim 1, wherein the force generated by the linear electromagnetic stirrer is Lorentz force, which is along the axis of the electromagnetic stirrer. 8. The device as claimed in claim 1, wherein the device is suitable for regular production of castings. 9. A non-intrusive method of detecting liquid metal/alloys stirring, said method comprising steps of: a) introducing liquid metal/alloys in a crucible; b) applying electromagnetic force to the crucible for stirring the liquid metal/alloys; c) continuously monitoring weight of the stirring melt with a load cell, wherein stirring stops as the metal/alloy solidifies as reflected by stability in the weight by load cell. 10. The non-intrusive method as claimed in claim 10, wherein the crucible is made of electrically non-conducting material. 11. The non-intrusive method as claimed in claim 10, wherein the crucible is freely suspended onto the load cell. 12. The non-intrusive method as claimed in claim 10, wherein the load cell generates electrical output which is calibrated, amplified and connected to a digital readout. 13. The non-intrusive method as claimed in claim 10, wherein the method is suitable for regular production of castings. 14. The device and the method as herein described with reference to examples and figures.

Documents:

1074-CHE-2007 AMENDED PAGES OF SPECIFICATION 03-02-2012.pdf

1074-CHE-2007 AMENDED PAGES OF SPECIFICATION 23-11-2011.pdf

1074-CHE-2007 AMENDED CLAIMS 03-02-2012.pdf

1074-CHE-2007 AMENDED CLAIMS 23-11-2011.pdf

1074-CHE-2007 CORRESPONDENCE OTHERS 25-01-2012.pdf

1074-CHE-2007 EXAMINATION REPORT REPLY RECEIVED 23-11-2011.pdf

1074-CHE-2007 FORM-1 23-11-2011.pdf

1074-CHE-2007 FORM-13 23-11-2011.pdf

1074-CHE-2007 FORM-13-1 23-11-2011.pdf

1074-CHE-2007 POWER OF ATTORNEY 23-11-2011.pdf

1074-CHE-2007 CORRESPONDENCE OTHERS 03-02-2012.pdf

1074-CHE-2007 CORRESPONDENCE OTHERS 18-01-2012.pdf

1074-CHE-2007 CORRESPONDENCE OTHERS.pdf

1074-CHE-2007 CORRESPONDENCE PO.pdf

1074-CHE-2007 FORM-18.pdf

1074-CHE-2007 POWER OF ATTORNEY 22-09-2010.pdf

1074-che-2007-abstract.pdf

1074-che-2007-claims.pdf

1074-che-2007-correspondnece-others.pdf

1074-che-2007-description(complete).pdf

1074-che-2007-drawings.pdf

1074-che-2007-form 1.pdf

1074-che-2007-form 3.pdf

1074-che-2007-form 5.pdf