METHOD AND APPARATUS FOR REDUCING BUBBLES OR GAS POCKETS IN A METAL INGOT USING A CONTINUOUS CASTING MOLD
A method and apparatus are provided to cast a metal ingot using a continuous casting mold so that the ingot is essentially free of gas pockets which otherwise would result from gas bubbles being entrapped in the mushy zone and solid portion of the ingot during formation, wherein such bubbles may be caused by pouring molten metal into a molten liquid portion of the forming ingot and by impingement of a plasma plume of a plasma torch on the upper surface of the molten liquid portion.
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1. Technical Field
The invention relates generally to furnaces for melting metals. More particularly, the invention relates to a continuous casting furnace and method for eliminating or reducing gas bubbles or pockets within an ingot.
2. Background Information
One of the problems in the continuous casting of metal ingots is the formation or entrapment of bubbles or gas pockets in the ingot. As discussed in greater detail further below, such bubbles or gas pockets may be caused by the pouring of molten material into the molten metal within the continuous casting mold or by the impingement of the plume of a plasma torch along the top surface of molten material in the mold.
SUMMARYIn one aspect, the invention may provide a method comprising the steps of: providing a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers and a plurality of electrically nonconductive high temperature insulation pieces; withdrawing a metal ingot from the mold wherein the ingot comprises a solid portion, a mushy zone on top of the solid portion and a liquid portion on top of the mushy zone; producing gas bubbles in the liquid portion by at least one of (a) pouring molten metal into the liquid portion and (b) heating the liquid portion with a plasma plume of a plasma torch; and heating the liquid portion with an induction coil adjacent the mold whereby the liquid portion comprises a liquid metal head and a bubble zone such that the liquid metal head is on top of the mushy zone and essentially free of gas bubbles, and the bubble zone is on top of the liquid metal head and comprises gas bubbles.
In another aspect, the invention may provide a method comprising the steps of: providing a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers having respective tops and a plurality of electrically non-conductive high temperature insulation pieces; withdrawing a metal ingot from the mold; pouring molten metal into the mold atop the ingot; preventing the pouring molten metal from contacting the tops of the fingers with a top member disposed directly above and adjacent the fingers; and heating a portion of the ingot within the mold with an induction coil adjacent the mold.
In another aspect, the invention may provide an apparatus comprising: a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers having respective tops and a plurality of electrically non-conductive high temperature insulation pieces; a top member disposed directly above and adjacent the tops of the fingers and adapted to prevent pouring molten metal from contacting the tops of the fingers; and an induction coil adjacent the mold.
Preferred embodiments of the invention, illustrative of the best mode in which Applicant contemplates applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims.
Similar numbers refer to similar parts throughout the drawings.
DETAILED DESCRIPTIONWith reference to
A sample embodiment of the present furnace is shown generally at 1 in
Feed mechanism 8 may be any type of feed mechanism, such as a conveyor, a vibratory feeder or other feed mechanism known in the art for feeding solid metal into a melting cavity 32 of hearth 6. Hearth 6 may further include an overflow or pouring lip 34 along one side to allow molten metal to move from cavity 32 through overflow or lip 34 into the top of mold 4. Hearth torch 10 is positioned above melting cavity 32 in order to heat metal within cavity 32, while mold torch 12 is likewise positioned above mold 4 in order to heat metal within mold 4. Induction coil 4 may circumscribe mold 4, as described in greater detail further below. Top member 16 is an annular member which is positioned directly above and adjacent the top of mold 4.
With primary reference to
Each finger 60 thus has a bottom 64 such that the bottoms 64 serve as the bottom of upper section 56 and the top of lower section 54. Each finger 64 is thus rigidly secured at its bottom 64 to the top of lower section 54 and extends upwardly or is cantilevered upwardly therefrom. Each finger 60 may be substantially vertical and include an inner surface 66, an outer surface 68, and a pair of opposed side surfaces 70 and 72 which extend radially outwardly from axis X from inner surface 66 to outer surface 68. Inner surfaces 66 of fingers 60 form the great majority of wider upper cavity portion 48 and an upper portion of narrower lower cavity portion 46. For each adjacent pair of fingers 60, the side surface 70 of one of the pair and the side surface 72 of the other finger of the pair are typically vertical, parallel and closely adjacent one another and define therebetween a slot or gap 74 extending from bottom 64 to top 62 and from inner surface 66 to outer surface 68.
Side wall 36 further includes a refractory insulation piece 76 within each gap 74 extending from adjacent bottom 64 to adjacent top 62 such that opposed sides of each piece 76 respectively abut the side surface 70 and side surface 72 which defines a given gap 74. The inner surface of each piece 76 may be substantially flush with the inner surfaces 66 of the adjacent pair of fingers which define the gap in which piece 76 is disposed. Likewise, the outer surface of each piece 76 may be generally flush with the outer surface 68 of the pair of fingers 60 defining the gap 74 in which the given piece 76 is disposed. Each insulation piece 76 may be formed of mica or any other suitable high temperature insulation material which is electrically non-conductive. Fingers 60 and pieces 76 have upper segments which define upper cavity portion 48 and lower segments which define an upper part of lower cavity portion 46. Each pair of surfaces 70 and 72 which define a given gap are not directly in electrical contact with one another although all of fingers 60 are in electrical communication with one another via their physical and electrical contact with lower section 54 of metal portion 52. Thus, mold 4 includes in alternating fashioning a plurality of electrically conductive upwardly extending fingers 60 and a plurality of upwardly extending electrically non-conductive high temperature insulation pieces 76. The sample mold 4 includes 16 fingers 60 although this number may vary depending on the specific desired characteristics. The top of induction coil 14 may be adjacent the tops 62 of fingers 60, the tops of pieces 76 and the top of mold 4, while the bottom of induction coil 14 may be adjacent the bottoms 64 of fingers 60 and the bottoms of pieces 76.
A plurality of substantially vertical finger passages 78 are formed in metal portion 52 each having a closed top end 80 and a bottom entrance opening 82 which communicates with annular cavity 58. Each finger passage 78 extends upwardly into a given finger 60 and thus extends from the bottom of the given finger 60 to adjacent and below the top 62 thereof. A hollow ring 84 is disposed in annular cavity 58 and thereby circumscribes a lower portion of lower cavity portion 46. Ring 84 defines an annular passage 85. A plurality of fluid tubes 86 are connected to and extend upwardly from the top of ring 84 and respectively into finger passages 78. Each fluid tube 86 may be substantially vertical and define a substantially vertically passage 88 having a top entrance opening 90 adjacent and below closed top end 80 and a bottom entrance opening 92 which communicates with annular passage 85. Lower section 54 defines a fluid or water inlet 94 which is in fluid communication with annular cavity 85, and a fluid or water outlet 96 which is in fluid communication with annular cavity 58. Fluid feed and return lines 98 and 100 are respectively connected to inlet 94 and outlet 96 at one end and at another end to a water source or other cooling fluid source 102.
Top member 16 (
Wall 104, which is formed of an electrically conductive material such as copper or another metal, forms a nearly continuous ring except adjacent circumferential ends 122 and 124 thereof (
The operation of the sample furnace is now described with primary reference to
Molten metal 2 is then poured through passage 116 of top member 16 into passage 40 of mold 4 on top of the top of lift 18 or on a starter stub within mold 4. Top member 16 is configured to prevent molten metal which is being poured from hearth 6 into mold 4 from contacting the top 62 of fingers 60 and the top of mold 4, including the top of the insulation pieces 76. Induction coil 14 is electrically powered in order to inductively heat the molten metal within mold 4 while water or another cooling liquid is moved from source 102 through the induction coil 14, the water cooling system of mold 4 and top member 16 to cool induction coil 14, mold 4 and top member 16. More particularly and with reference to
As previously described with reference to the prior art example of
The sample method and apparatus thus provide a way to produce ingots with a continuous casting mold wherein the ingots are free of or essentially free of gas pockets formed therein as a result of bubbles caused by the pouring of molten metal into the mold and/or the bubbles formed by the plasma plume of a plasma torch impinging on the upper surface of the molten metal within the mold. The sample method and apparatus thus provide the ability to provide substantially improved ingots.
In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the description and illustration of the preferred embodiment of the invention are an example and the invention is not limited to the exact details shown or described.
Claims
1. A method comprising the steps of:
- providing a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers and a plurality of electrically nonconductive high temperature insulation pieces;
- withdrawing a metal ingot from the mold wherein the ingot comprises a solid portion, a mushy zone on top of the solid portion and a liquid portion on top of the mushy zone;
- producing gas bubbles in the liquid portion by at least one of (a) pouring molten metal into the liquid portion and (b) heating the liquid portion with a plasma plume of a plasma torch; and
- heating the liquid portion with an induction coil adjacent the mold whereby the liquid portion comprises a liquid metal head and a bubble zone such that the liquid metal head is on top of the mushy zone and essentially free of gas bubbles, and the bubble zone is on top of the liquid metal head and comprises gas bubbles.
2. The method of claim 1 further comprising the step of heating the liquid portion with a plasma plume of a plasma torch.
3. The method of claim 1 further comprising the step of pouring molten metal into the liquid portion.
4. The method of claim 3 wherein the step of pouring comprises pouring molten metal into the liquid portion from a hearth; wherein the hearth and mold are within an inert gas atmosphere.
5. The method of claim 4 further comprising the step of heating the liquid portion with a plasma plume of a plasma torch.
6. The method of claim 3 further comprising the step of preventing the pouring molten metal from contacting the tops of the fingers with a top member disposed directly above and adjacent the fingers.
7. The method of claim 1 further comprising the step of pouring molten material into the mold through a pouring passage defined by an annular top member disposed directly above and adjacent the fingers.
8. The method of claim 7 wherein the top member has a top surface, a bottom surface, an outer perimeter, and an inner perimeter which defines the pouring passage; and a gap is formed in the top member extending from the top surface to the bottom surface and from the outer perimeter to the inner perimeter.
9. The method of claim 8 further comprising an electrically non-conductive material in the gap.
10. The method of claim 7 further comprising the step of cooling the top member by moving a cooling liquid through a cooling passage formed in the top member.
11. The method of claim 7 wherein the top member entirely covers the tops of the fingers so that the tops of the fingers are not visible as viewed from above.
12. The method of claim 1 wherein the mold has a sidewall having an inner perimeter which defines a mold cavity in which the liquid portion is disposed; the inner perimeter defines a wider upper cavity portion and a narrower lower cavity portion and includes a step which extends inwardly from the wider upper cavity portion to the narrower lower cavity portion.
13. The method of claim 12 wherein the step angles inwardly and downwardly from the wider upper cavity portion to the narrower lower cavity portion.
14. The method of claim 12 wherein the fingers comprise respective upper segments which define the wider upper cavity portion and respective lower segments which define at least a portion the narrower lower cavity portion.
15. The method of claim 14 wherein the sidewall has a lower section; and the fingers are cantilevered upwardly from the lower section.
16. The method of claim 1 wherein the induction coil circumscribes the mold.
17. The method of claim 16 wherein the fingers have respective bottoms; and the induction coil has a bottom adjacent the bottoms of the fingers.
18. The method of claim 17 wherein the fingers have respective tops; and the induction coil has a top adjacent the tops of the fingers.
19. A method comprising the steps of:
- providing a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers having respective tops and a plurality of electrically non-conductive high temperature insulation pieces;
- withdrawing a metal ingot from the mold;
- pouring molten metal into the mold atop the ingot;
- preventing the pouring molten metal from contacting the tops of the fingers with a top member disposed directly above and adjacent the fingers; and
- heating a portion of the ingot within the mold with an induction coil adjacent the mold.
20. An apparatus comprising:
- a segmented continuous casting mold comprising in alternating fashion a plurality of electrically conductive upwardly extending fingers having respective tops and a plurality of electrically non-conductive high temperature insulation pieces;
- a top member disposed directly above and adjacent the tops of the fingers and adapted to prevent pouring molten metal from contacting the tops of the fingers; and
- an induction coil adjacent the mold.
Type: Application
Filed: May 2, 2013
Publication Date: Nov 6, 2014
Applicant: RTI International Metals, Inc. (Niles, OH)
Inventors: Michael P. Jacques (Canton, OH), Kuang-O Yu (Highland Heights, OH)
Application Number: 13/875,689
International Classification: B22D 11/041 (20060101); B22D 11/10 (20060101);