| Apparatus for producing a molten seal in a continuous casting furnace -> Monitor Keywords |
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  Apparatus for producing a molten seal in a continuous casting furnaceRelated Patent Categories: Metal Founding, Means Providing Inert Or Reducing Atmosphere, In Continuous Casting ApparatusThe Patent Description & Claims data below is from USPTO Patent Application 20080060783. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of U.S. patent application Ser. No. 10/989,563, filed on Nov. 16, 2004; the disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Technical Field [0003] The invention relates generally to the continuous casting of metals. More particularly, the invention relates to the protection of reactionary metals from reacting with the atmosphere when molten or at elevated temperatures. Specifically, the invention relates to using a molten material such as liquid glass to form a barrier to prevent the atmosphere from entering the melting chamber of a continuous casting furnace and to coat a metal cast formed from such metals to protect the metal cast from the atmosphere. [0004] 2. Background Information [0005] Hearth melting processes, Electron Beam Cold Hearth Refining (EBCHR) and Plasma Arc Cold Hearth Refining (PACHR), were originally developed to improve the quality of titanium alloys used for jet engine rotating components. Quality improvements in the field are primarily related to the removal of detrimental particles such as high density inclusions (HDI) and hard alpha particles. Recent applications for both EBCHR and PACHR are more focused on cost reduction considerations. Some ways to effect cost reduction are increasing the flexible use of various forms of input materials, creating a single-step melting process (conventional melting of titanium, for instance, requires two or three melting steps) and facilitating higher product yield. [0006] Titanium and other metals are highly reactive and therefore must be melted in a vacuum or in an inert atmosphere. In electron beam cold hearth refining (EBCHR), a high vacuum is maintained in the furnace melting and casting chambers in order to allow the electron beam guns to operate. In plasma arc cold hearth refining (PACHR), the plasma arc torches use an inert gas such as helium or argon (typically helium) to produce plasma and therefore the atmosphere in the furnace consists primarily of a partial or positive pressure of the gas used by the plasma torches. In either case, contamination of the furnace chamber with oxygen or nitrogen, which react with molten titanium, may cause hard alpha defects in the cast titanium. [0007] In order to permit extraction of the cast from the furnace with minimal interruption to the casting process and no contamination of the melting chamber with oxygen and nitrogen or other gases, current furnaces utilize a withdrawal chamber. During the casting process the lengthening cast moves out of the bottom of the mold through an isolation gate valve and into the withdrawal chamber. When the desired or maximum cast length is reached it is completely withdrawn out of the mold through the gate valve and into the withdrawal chamber. Then, the gate valve is closed to isolate the withdrawal chamber from the furnace melt chamber, the withdrawal chamber is moved from under the furnace and the cast is removed. [0008] Although functional, such furnaces have several limitations. First, the maximum cast length is limited to the length of the withdrawal chamber. In addition, casting must be stopped during the process of removing a cast from the furnace. Thus, such furnaces allow continuous melting operations but do not allow continuous casting. Furthermore, the top of the cast will normally contain shrinkage cavities (pipe) that form when the cast cools. Controlled cooling of the cast top, known as a "hot top", can reduce these cavities, but the hot top is a time-consuming process which reduces productivity. The top portion of the cast containing shrinkage or pipe cavities is unusable material which thus leads to a yield loss. Moreover, there is an additional yield loss due to the dovetail at the bottom of the cast that attaches to the withdrawal ram. [0009] The present invention eliminates or substantially reduces these problems with a sealing apparatus which permits continuous casting of the titanium, superalloys, refractory metals, and other reactive metals whereby the cast in the form of an ingot, bar, slab or the like can move from the interior of a continuous casting furnace to the exterior without allowing the introduction of air or other external atmosphere into the furnace chamber. BRIEF SUMMARY OF THE INVENTION [0010] The present invention provides a casting furnace for manufacturing a metal cast, the furnace comprising: an interior chamber having a sidewall; a passage wall having an inner periphery which defines a passage extending through the sidewall of the interior chamber for communicating with the interior chamber and with atmosphere external to the interior chamber; a circumferential space within the passage; a metal cast pathway extending from the interior chamber through the passage and adapted for moving the metal cast from the interior chamber to the external atmosphere; a source of solid particulate coating material; a heat source for melting the particulate coating material to form molten coating material within the circumferential space; and a dispenser for dispensing the solid particulate coating material in a solid state from the source directly into the circumferential space adjacent the pathway. [0011] The present invention also provides a casting furnace for manufacturing a metal cast, the furnace comprising: an interior chamber having a sidewall; a passage wall having an inner periphery which defines a passage extending through the sidewall of the interior chamber for communicating with the interior chamber and with atmosphere external to the interior chamber; a metal cast pathway extending from the interior chamber through the passage and adapted for moving the metal cast from the interior chamber to the external atmosphere; a molten bath bounding the pathway along at least a portion of the passage and adapted to prevent the external atmosphere from entering the interior chamber; a source of particulate coating material; a dispenser for dispensing the particulate coating material in a solid state from the source to adjacent the molten bath; and a heat source adjacent the molten bath for melting the particulate coating material to form molten coating material for the molten bath. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0012] FIG. 1 is a sectional view of the seal of the present invention in use with a continuous casting furnace. [0013] FIG. 2 is similar to FIG. 1 and shows an initial stage of forming an ingot with molten material flowing from the melting/refining hearth into the mold and being heated by heat sources over each of the hearth and mold. [0014] FIG. 3 is similar to FIG. 2 and shows a further stage of formation of the ingot as the ingot is lowered on a lift and into the seal area. [0015] FIG. 4 is similar to FIG. 3 and shows a further stage of formation of the ingot and formation of the glass coating on the ingot. [0016] FIG. 5 is an enlarged, view of the encircled portion of FIG. 4 and shows particulate glass entering the liquid glass reservoir and the formation of the glass coating. [0017] FIG. 6 is a sectional view of the ingot after being removed from the melting chamber of the furnace showing the glass coating on the outer surface of the ingot. [0018] FIG. 7 is a sectional view taken on line 7-7 of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION [0019] The seal of the present invention is indicated generally at 10 in FIGS. 1-5 in use with a continuous casting furnace 12. Furnace 12 includes a chamber wall 14 which encloses a melting chamber 16 within which seal 10 is disposed. Within melting chamber 16, furnace 12 further includes a melting/refining hearth 18 in fluid communication with a mold 20 having a substantially cylindrical sidewall 22 with a substantially cylindrical inner surface 24 defining a mold cavity 26 therewithin. Heat sources 28 and 30 are disposed respectively above melting/refining hearth 18 and mold 20 for heating and melting reactionary metals such as titanium and superalloys. Heat sources 28 and 30 are preferably plasma torches although other suitable heat sources such as induction and resistance heaters may be used. Continue reading... Full patent description for Apparatus for producing a molten seal in a continuous casting furnace Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Apparatus for producing a molten seal in a continuous casting furnace patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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