US 3510345 A
Description (OCR text may contain errors)
P. R. MARCHANT M y .7 APPARATUS AND METHOD FOR AUTOMATICALLY CONTROLLING THE MOLTEN METAL BATH LEVEL IN A METALLURGICAL PROCESS Filed Nov. 1.196?
.5 TP A EM w v, M nx A TTO/PNEV United States Patent APPARATUS AND METHOD FOR AUTOMAT- ICALLY CONTROLLING THE MOLTEN METAL BATH LEVEL IN A METALLURGI- CAL PROCESS Peter R. Marchant, San Francisco, Calif., assignor to General Electric Company, a corporation of New York Filed Nov. 1, 1967, Ser. No. 679,696 Int. Cl. C23c 1/00 US. Cl. 117114 2 Claims ABSTRACT OF THE DISCLOSURE In the dip-forming process for accreting metal onto a core member passed through a crucible containing a molten bath of metal, a melt of molten metal is continuously supplied to the crucible from a holding chamber. An inverted pressure bell is disposed in the holding chamber, and gas is introduced into the enclosed portion of the bell for exerting pressure on the surface of the molten metal within the bell. A liquid level sensing means is immersed in the molten metal, and gas is continuously introduced through the liquid level sensing means whereby a back pressure is established in the sensing means which is correlated with the level of molten metal in the holding chamber.
The dip-forming process, such as used in casting metal, is now well known in the art. According to this process, an elongated body such as a metal rod is typically pretreated by passing it through a straightener, and a surface cleaning apparatus, and then through a vacuum entrance chamber arranged in the wall of a crucible which contains a bath of molten material. The elongated core or body is passed through the molten bath, which bath may have been the same chemical composition as that of the core or a different composition. The molten material in the crucible accretes or deposits upon the outer surface of the core thereby increasing its cross-sectional area appreciably. After emerging from the crucible, the resulting cast member is cooled as by. a water spray from one or more jet nozzles at least sufiiciently so that the cast member can be rolled or worked. From there, the cast member may be passed through a suitable roll mechanism where it is reduced in cross-sectional area and then passed to a suitable receiving means such as a take-up reel.
It is essential for the successful operation of the dipforming process that the depth of molten metal in the crucible be controlled accurately. If the bath of molten metal is too shallow relative to the core size and speed, full accretion will not occur and output therefore will be lost. On the other hand, if the bath is excessively deep, re-melting of the cast body will occur which results also in reduced output.
This invention has therefore as among its objects to provide a means and method for accurately controlling the bath depth of molten metal which eliminates wide fluctuations in bath depth.
Other objects and advantages of the invention will best be understood by referring to the following detailed specification, and to the accompanying FIG. 1 illustrating in elevation a preferred embodiment of the invention, with the control mechanism being illustrated schematically.
In general, the apparatus of this invention employed in a dip-forming process, in which molten metal is accreted to a core passed through a crucible containing the molten metal, includes a holding chamber disposed adjacent the crucible and in communication therewith. The holding chamber, which contains a supply of molten metal, is provided with suitable means for adjusting or regulating the level of molten metal, such as an inverted displace- 3,510,345 Patented May 5, 1970 ment bell, or a graphite block as disclosed in United States Pat. No. 3,060,053 to Carreker et al. and assigned to the assignee of this application. Gas is continuously introduced through a liquid level sensing device immersed in the molten metal, whereby the back pressure estab lished in the device is correlated with the level of molten metal in the holding chamber. The level regulating means is adjusted in response to the back pressure thereby regulating the bath level within the holding chamber and, in turn, within the crucible.
Although the invention is described hereinbelow with reference to dip-forming a copper rod, it is understood that the invention is applicable to other metals.
Referring to the drawing, core rod 10, such as a copper rod, is supplied to a drawing apparatus 12 located adjacent a suitable shaving apparatus 14 which shaves a thin layer of metal from the periphery of the rod to remove the oxide coating and other surface contaminants therefrom. If desired, other cleaning means such as chemical cleaning means may be utilized for removing the oxide coating and cleaning the surface of the rod. The rod is passed through a suitable drive means, including capstan 15 and drive rolls 16 contained in housing 18, and from there into tube 20. Members 12, 14, 18, and 20 are sealed and interconnected by a suitable passageway, and tube 20 has connected thereto exhaust tube 22 and evacuating pump 24 to maintain a vacuum in the passageway. Entry port member or nozzle 26 is mounted in the upper end of tube 20 and extends into crucible 28 which is maintained at the desired elevated temperature by suitable heating means such as electric induction heater 30. Core rod 10 is fed through nozzle 26 and into crucible 28 where the rod comes into contact with the molten copper which accretes to the rod.
Molten copper is supplied to crucible 28 from a suitable melting furnace indicated generally by the numeral 32, which is heated by a plurality of silicon carbide electric radiant heaters 34. Cathode copper plates 35, or other suitable feed material of low oxygen content, is supplied to the furnace 32 by any suitable means such as a mechanical drive means (not shown). Desirably the furnace is provided with a sloping or inclined section 36 and an integral horizontal section 38. The cathode copper plates are charged to section 36 of the furnace through a flapper-type door (not shown), and melted gradually on the incline as they pass to the horizontal section 38 where a pool of molten metal collects. The molten metal flows by displacement over a weir 40 into a holding chamber 42 of the furnace described hereinbelow in greater detail. It is desirable that an inert or reducing atmosphere be maintained above the melt in the furnace as well as in the dip-forming crucible, which may be supplied through line 48 and line 49, respectively, from any suitable source (not shown). As the core rod passes through the molten bath of metal in the crucible, copper accretes progressively thereon thereby forming a rod of increased diameter with molten metal substantially bonded to the core rod.
An elongated tube 52 extends upwardly from crucible 28, and the resulting cast rod having copper accreted thereto is passed out of the crucible to the extension tube. The cast rod emerging from the crucible and extension tube is at a relatively high temperature and is cooled somewhat by cooling means 54, such as a water spray nozzle, before the rod is passed through direction changing rolls 56. From there the cast rod is directed to a suitable rolling mill and coiling apparatus (not shown) and to a storage area as desired.
Passageway or conduit 58 establishes communication between the holding chamber 42 and the crucible 28, and molten metal will flow from the holding chamber to crucible when the level of molten metal in the holding chamber adjacent the inlet 60 of the communicating passageway 58 is above the level of the passageway. An inverted pressure bell or displacement bell 62 is disposed within the holding chamber in order to selectively adjust the level of molten metal in the holding chamber, described hereinbelow in greater detail. The side walls of the bell are at least partially immersed below the level of molten metal contained in the holding chamber, and desirably the bottom edge of the bell is spaced from the bottom surface of the holding chamber so as to enable molten metal to flow into the enclosed portion of the bell. The top portion of the pressure bell has a cylindrical extension 64 which projects upwardly through the upper wall of the holding chamber 42. The cylindrical extension 64 is sealed at'the top, and a first pipe 66 is mounted therein for conducting gas from a source (not shown) through a pressure control valve 68 and into the enclosed portion of the bell for applying pressure on the surface of the molten metal contained therein. A second pipe 7 having valve 71 is mounted in the top of the extension 64 for exhausting the gas from within the bell for relieving the pressure on the surface of the molten metal contained therein.
During the dip-forming operation, the molten metal contained in the crucible and holding chamber decreases. In accordance with the present invention, the level of molten metal is continuously measured by a liquid level sensing device. For this purpose, a sensing device 72, composed of a material substantially inert to the molten metal, is immersed in the bath, preferably in the holding chamber as shown in the drawings, but alternatively may be disposed in the dip-forming crucible. The sensing device is a substantially cylindrical member composed of molybdenum or other suitable material and provided with a longitudinal bore opening at the bottom thereof such that upon immersion in the coating bath, communication is established between the longitudinal bore and the; interior of the crucible below the level of molten metal. In this manner, a gas, which is desirably inert to the molten metal, is introduced to the molten bath from a source not shown through line 74 to sensing device 72, and bubbles to the surface of the bath. The rate of flow of gas introduced to the molten bath is automatically controlled at a constant value by pressure regulator or valve 76 and flow control meter 78, both of which are incorporated in line 74. Suitable gases, which may be used in either the sensing device or the displacement bell, in clude the inert or reducing gases, for example, nitrogen, argon, carbon dioxide, natural gas, etc.
When gas is introduced to the molten bath, the back pressure, or level indicating pressure, in the sensing device is measured. This pressure is a measure of the fluid level above the outlet of sensing device. This back pressure actuates differential pressure transducer 80. The power output from the transducer is supplied to control valve 68 via line 82 which automatically regulates the gas pressure inside the inverted displacement bell above the molten metal. It will be observed that the pressure within the enclosed portion of the bell regulates the level of molten metal in the holding chamber and, in turn, the level in the crucible. This control substantially eliminates wide fluctuations in bath depth thereby rendering the process more efiicient and providing a more uniform product.
The present invention is particularly useful in the dip forming process for casting copper on a copper core rod. It should be understood however, that the process is also applicable for use in casting dissimilar metals, such as copper or steel.
1. In an apparatus for the continuous casting of metal which includes the steps of continuously passing an elongated core member through a bath of molten metal contained in a crucible thereby accreting metal to said core member, the improvement comprising:
(a) a furnace for melting feedstock having an integrally arranged holding chamber disposed adjacent said crucible for containing a supply of molten metal; I
(b) communication means opening to said holding chamber and said crucible for establishing communication therebetween;
(c) an inverted pressure bell disposed in said holding chamber spaced from the bottom surface thereof and having its side walls at least partially immersed below the level of molten metal contained in said holding chamber, and including means for introducing gas into the enclosed portion of said bell for applying pressure on the surface of molten metal contained therein;
(d) a liquid level sensing means immersed in the molten metal;
(e) means for continuously introducing gas substantially inert to the molten metal through said liquid level sensing means whereby a back pressure is established in said sensing means which is correlated with the level of molten metal contained in said holding chamber; and
(f) means responsive to said back pressure for actuating the pressure within the enclosed portion of said bell thereby controlling the level of molten metal in said holding chamber.
2. In a method for the continuous casting of metal Which includes the steps of continuously passing an elongated core member through a bath of molten metal contained in a cruible thereby accreting metal to said core member, the improvement comprising:
(a) continuously supplying molten metal to said crucible from a holding chamber arranged adjacent said crucible and in communication therewith;
(b) continuously introducing a gas into the enclosed portion of an inverted pressure bell disposed in said holding chamber and having its side walls at least partially immersed below the level of molten metal contained in said holding chamber thereby applying pressure on the surface of molten metal contained therein;
(c) continuously introducing gas substantially inert to the molten metal through a liquid level sensing means immersed in the molten metal whereby a back pressure is established in said sensing means which is correlated with the level of molten metal contained in said holding chamber; and
(d) continuously adjusting the pressure within the enclosed portion of said bell in response to said back pressure thereby controlling the level of molten metal in said holding chamber.
References Cited UNITED STATES PATENTS 310,994 1/1885 Farmer 164-275 867,659 10/1907 Hoopes et a1 164-275 X 2,593,197 5/1952 Rough 65-346 X 2,664,852 1/ 1954 Chadsey 118-49 2,988,099 6/1961 Langhans 137-403 X 3,060,053 10/ 1962 Carreker et a1 164-86 X 3,104,678 9/1963 Cole 137-403 3,200,971 8/1965 Trethewey 137-403 X 3,384,150 5/1968 Newsome 164-337 X MORRIS KAPLAN, Primary Examiner US. Cl. X.R.