MXPA99006008A - Electric furnace with insulated electrodes and process for producing molten metals - Google Patents

Abstract

An electric arc furnace (10) having a partially insulated electrode (37) produces molten metal (28) such as foundry iron from an iron source where little or no slag (30) is produced. The furnace (10) includes at least one insulated electrode (37) for immersing deep into the metal charge (26). An insulating coating can be a fibrous mat (48) wrapped around the electrode or a spray coating (72). In one embodiment, the electrode (156) has a coupling (172) at a first end (176) for coupling with an electrically conducting member (142) and a coupling (172) at the second end (178) for coupling with an adjacent electrode to form an electrode column. The coupling members (172) can be an internally threaded recess (166, 168) in the ends thereof. An externally threaded coupling member (172) can be threaded into the recesses (166, 168) of the electrodes (157) for coupling two or more electrodes (157) together.

Description

ELECTRIC OVEN WITH ISOLATED ELECTRODES AND PROCESS FOR THE PRODUCTION OF CASTED METALS Field of the Invention The present invention relates to isolated electrodes, to an electric furnace with an insulated electrode and to a process for producing molten metal, including cast iron, using an isolated electrode. More particularly, the invention is directed to an isolated electrode having an insulating material that surrounds and joins portions of the electrode.

Background to the Invention Metals, such as foundry iron, used to melt and obtain steel, are produced in the metal industry by a number of different processes. A process for producing cast iron uses a standard cupola type furnace. A variety of iron sources are fed into a vertical furnace well, powered by the combustion of the coke by an air jet. The filler added to the furnace generally contains a number of additives, such as ferrosilicon, to increase the silicon content of the iron and the materials that form the slag, such as limestone, to remove impurities, such as sulfur. The cupola-type furnace is a net silicon oxidizer, so that as much as 30 percent of the charged silicon is lost through oxidation and discharged into the slag. Typically, only 70 percent of the charged silicon available is present in the iron. Silicon is an essential element of cast iron and is typically added in the ferrosilicon form, since such silicon form can be easily combined with iron. The possibility of producing metals is dependent, in part, on the efficiency of the process used and the cost of the loading materials. The cost of slag iron and slag steel depends on several factors, including iron content, amounts of alloy constituents, desired and unwanted, present, and particle size. The use of light slag such as particles from drilling or turning in a cupola requires agglomeration or briquette formation, since the high volume of gases leaving the cupola, otherwise carries an unacceptably large percentage of the load from the oven. The cast iron is also produced with the electric induction furnace. A charge is heated and then the additives, which include silicon, coal and a material that forms the slag, are introduced to cover the iron. The charge of the iron is heated by eddy currents, which result from the electromagnetic induction of the alternating electric current flowing in the coil surrounding the charge. Silicon is typically added as ferrosilicon, and carbon is added in the form of a graphite material with low sulfur content. The resulting iron generally has a silicon content of about 1 to 3 percent and a carbon content of about 2 to 4 percent. Cast iron has been produced commercially in standard electric arc furnaces (EAF). The EAF typically consists of a refractory-lined container or hull, with a removable refractory roof, through which three electrodes, in a three-phase alternating current (AC) furnace, or an electrode in a direct current or continuous furnace (CD) are projected into the space above the load material, and the bath contained within the oven shell. For CD ovens, the return electrode is typically constructed at the bottom of the oven shell. The operation of the electric arc furnace typically involves loading the furnace by emptying the load buckets, which contain the slag and other materials, into the hull, closing the roof and then lowering the electrodes to make contact with the load and arch formation occurs. and the merger of the cargo. After melting, the slag layer is usually established for refining purposes, and additions of ferrosilicon and carbon are made until the composition reaches the desired point. The EAF has not been used extensively for the production of cast iron alloys, due to the relatively high production cost. This EAF has been limited in most by the economics of the production of cast irons of special alloys and steels. Cast iron is also produced by melting iron ore in a submerged electric arc furnace. The submerged arc furnaces have an advantage of directly melting the minerals together with the simultaneous carbothermal chemical reduction of the metal oxides by the carbonaceous reducing agents, such as coke and mineral coal. The electrodes are immersed in the charge and the slag layer is formed above the molten iron to allow efficient heat transfer between the arc and the charge materials. The electrical conductivity of the load must be controlled to allow simultaneous immersion of the electrodes deep inside the load, while avoiding excessive currents and overheating of the electrodes. An example of a submerged arc furnace for melting iron ore is described in U.S. Patent No. 4,613,363 to Weinert. The carbothermal reduction of minerals to produce iron requires large amounts of electrical energy, thus increasing production costs. The most widely used processes for producing cast iron (cupola and induction furnaces) require comparatively more expensive starting materials, and silicon carbide or ferrosilicon. These disadvantages have limited these prior processes to produce cast iron.

The electric arc furnace can be a cost effective method to produce molten metals. For example, U.S. Patent No. 5,588,982 to Hendrix discloses a process for efficiently producing cast iron in an electric arc furnace by melting the slag metal while reducing an oxide, such as silica. When producing molten metals from a highly conductive filler, the present electric arc furnaces are inherently inefficient, as a result of the construction of the electrode and particularly the cathode. The electrode is a non-insulated conductive bar of metal or metal alloy, graphite or carbon. The electrode is provided with threaded ends to connect several electrodes together and feed the electrodes in the electric arc furnace, during the fusion process. The arc is produced at the tip of the electrode, where the most efficient heating occurs. However, when the charge of the electric arc furnace is highly conductive, an open arc condition is created, which leads to inefficient heating. Arc furnaces have been used to melt the slag metal, as described in U.S. Patent No. 5,555,259 to Feuerstache. The furnace is formed with a central tube that surrounds the cathode, to prevent contact with the load. An arc is formed between the exposed end of the cathode and the metal bath, which is in contact with an anode to melt the charge. The lower end of the tube is tapered to feed the slag to the cathode. The tube that surrounds the cathode makes it possible for this cathode to be placed deep inside the bed of charge. This construction has the disadvantage of including a fixed, non-consumable water-cooled barrier between the electrode and the load. Therefore, the metal industry has a continuing need for an economical and efficient process to produce various metal alloys in an electric furnace.

SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide a method and apparatus for producing metal alloys in an electric furnace, particularly an electric arc furnace, using an isolated electrode, without reducing the voltage of this electrode. . Another object of the present invention is to provide an electrode for an electric furnace, particularly an electric arc furnace, which can be immersed deep within the charging material in the furnace, while operating at high voltages and substantially independent of the resistivity of the material Loading in the oven. Another object of the present invention is to provide an electric furnace, particularly an electrode of an electric arc furnace, which is covered, at least partially, with an electrically insulating material, to limit the surface area of the electrode in contact with the charging materials . Still another object of the present invention is to provide an electrode holder for connecting an isolated electrode to a power source. A further object of the present invention is to provide an electrode for an electric furnace, particularly an electric arc furnace, having a consumable insulating material, which surrounds at least a portion of the electrode. Another object of the present invention is to provide an efficient and economical process for producing molten metals and metal alloys, such as cast iron, using easily available and inexpensive fillers, such as slag metal, in an oven of electric arc. A further object of the present invention is to provide an efficient process for using slag iron or slag steel as the primary source of iron, to produce iron alloys. Still another object of the present invention is to provide an efficient process for melting slag iron, slag steel, direct reduced iron or hot iron into briquettes, in an electric furnace, particularly an electric arc furnace. A further object of the present invention is to provide a process for simultaneously refining metal compounds contained in the charge materials, as well as the additives contained in a consumable insulating material in an electrode, for melting a filler material to produce a molten metal. Another object of the present invention is to provide a process for producing iron alloys, such as cast iron, where substantially no slag is formed. A further object of the present invention is to provide a process for melting a source of iron or steel in an electric furnace, particularly an electric arc furnace, while refining or reducing a compound, to produce iron alloys. Another object of the invention is to provide a process for producing metal alloys from a primary source of metal, while reducing the oxides of silicon and the oxides of metals, such as copper, iron, magnesium, manganese, chromium, nickel, calcium. , aluminum, boron, zirconium, rare earth metals, and their mixtures, in an electric furnace, particularly an electric arc furnace. These and other objects of the present invention are basically achieved by the provision of an electrode for an electric furnace, comprising an electrically conductive core having a first end, a second end and a longitudinal middle section between the ends. In one embodiment, the first end of the conductive core has a first coupler member, for connecting to a power source, and the second end has a second coupler member, for coupling with a first coupler member of an adjacent electrode. An electrically insulating material surrounds and joins the middle section. The second end is free of the insulating material. These objects are furthermore achieved by the provision of an electrode assembly for an electric furnace, comprising an electrically conductive member, for connection to an electrical power source, and at least one electrode coupled to the electrically conductive member. The electrically conductive member has a first and a second end. The electrode has an electrically conductive core, with a first end, a second end and a longitudinal middle section between the ends. An electrically insulating material surrounds and joins the middle section. The first end of the electrode is coupled to the second end of the electrically conductive member.

These objects are also achieved by the provision of an electric oven, which comprises a container having a melting zone and an inlet for feeding a charge into the container. At least one electrode assembly is placed in the container. This electrode assembly includes an electrically conductive member, having a first and second ends, and at least one electrode, having an electrode core, with a first end coupled to the first member. An electrically insulating material surrounds and joins a portion of the electrode core. The electrode assembly has a lower end substantially free of the insulating material, which is placed in the fusion zone, and has a first end of an electrically conductive member, coupled to an electrical power source. At least one second electrode is placed in the container, to produce heat in the fusion zone with the electrode assembly. These objects are also achieved by a process of producing molten metal in an electric furnace, which comprises continuously feeding a charge in an electric furnace, to form a bed of charge. The furnace has at least one first electrode, with a lower end to cooperate with a second electrode. The first electrode may include an electrically conductive member, having first and second ends, wherein the first end is coupled to a movable mounting structure for raising and lowering the electrode relative to a loading bed in the furnace. The electrode has an electrode core, with a first and second ex emos, where the first end can be coupled, removably, to the electrically conductive member. An electrically insulating material covers a portion of the electrode core and isolates the electrode from the loading bed. The charge comprises at least one metal, metal compound, or mixtures thereof. The electrode assembly is submerged in the loading bed. Electric power is supplied to the electrodes to transport this electrical energy between them. The bed of charge is heated in the furnace by the electrical energy transported between the electrodes, to produce the molten metal. The process of the present invention is capable of using iron or cheap slag steel in the electric furnace, to produce iron alloys, such as cast iron, while controlling the carbon and silicon content and substantially in the absence of the iron. slag formation. A material containing silicon may be included in the charge or by the use of an isolated electrode. Silicon sources are reduced to silicon in the presence of a carbonaceous reducing agent, to increase and modify the silicon content of the metal alloy. The isolated electrode makes it possible for the electrode to be submerged deeper in the charge than an uninsulated electrode, without reducing the voltage or current. The carbonaceous reducing agent also supplies the coal for refining, and this carbon dissolves in the alloy of the molten metal. The objects are also achieved by supplying a process to produce cast iron, which comprises the steps of: feeding a charge inside a steel furnace, around its electrodes, this charge comprises a mixture of a source of silicon, an iron source , and a carbonaceous reducing agent, the iron source comprises ore, mill incrustations, DRI, HBI, slag iron or slag steel. At least one of the electrodes is partially surrounded with an insulating material to protect a portion of the electrode from the charging material. Electric power is supplied to the electrodes to generate an electric arc between them and to heat the charge by this electric arc between the electrodes, to melt the charge and reduce metal oxides and silica (which includes the insulating material), to produce the cast iron. This cast iron can have a silicon content of about 0.05 to 9.5 percent by weight and a carbon content of about 0.01 to 4.5 percent by weight. substantially in the absence of slag. The process can be continuous, continuously feeding the load. Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the accompanying drawings, discloses preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the drawings, which form part of this original description: Figure 1 is a side elevational view, in cross-section, of a submerged arc furnace, for use in a process in accordance with one embodiment of the present invention; Figure 2 is a side elevational view of an electrode coated with an insulating material, according to a second embodiment of the invention; Figure 3 is a side elevational view, in section, of an electric arc furnace, for use in a process according to an embodiment of the present invention; Figure 4 is a side elevational view, with separate parts, partially in section, of an electrode assembly covered with an insulating material, according to a first embodiment of the present invention, Figure 5 is a partial side elevation view , in section, of an isolated electrode member, according to a second embodiment of the present invention; and Figure 6 is a side elevation view of an isolated electrode member, according to a further embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an isolated electrode, an electric furnace (particularly an electric arc furnace), which has an electrode covered, at least partially, with electrical insulation. The invention is also directed to a process for producing molten metal, such as cast iron, with the use of the furnace. The insulation substantially covers the sides of the electrode, which leaves the tip exposed to conduct electrical energy and produce an arc in the furnace. The insulation makes it possible for the electrode to be submerged deeper in a bed of electrically conductive charge, at a given voltage and power input, compared to standard or conventional uninsulated electrodes. In embodiments of the present invention, the insulation covering the electrode may include a material that contains a compound not of metal or metal. An insulating material, particularly suitable, is a material containing silica. The insulation is gradually consumed together with the electrode, during use. This insulation serves as a source for an alloy material for the primary metal in the charge. The metal compound is reduced to the metal in the furnace, in the presence of a suitable reducing agent. This reducing agent can be, for example, a carbonaceous reducing agent. The insulation is preferably made of an inorganic material, such as silica or a metal oxide, which can be reduced in the furnace to supply an alloy metal or other component to the primary metal of the filler. The efficient production of the alloys of the charging materials, which are good conductors of electricity in an electric arc furnace, is achieved by the deep penetration of the electrode into the bed of charge. The penetration of the electrode improves the efficiency of the process, since the efficiency of the heat transfer from the electric arc is related to the depth of the arc below the surface of the load. The increased efficiency of heat transfer reduces the energy requirement, decreases refractory consumption, reduces electrode consumption, improves recovery efficiencies and produces higher yields. The present invention is further directed to processes for producing metals and metal alloys, with the use of an electric furnace, particularly a submerged arc furnace, having a protected or partially insulated electrode. The process of the present invention is particularly directed to producing molten metals including, for example, iron, cast iron, aluminum, aluminum alloys, steel, copper, copper alloys, magnesium, manganese, chromium, nickel, zinc, lead, cadmium, precious metals and the like. The process of the present invention is particularly suitable for producing cast irons as well as other molten metals. The process of the present invention comprises basically feeding a primary metal source, such as iron or slag steel, and carbonaceous materials, which serve both as a carbon source for iron and as a reducing agent, in an electric arc furnace. In embodiments of the present invention, a compound, such as silica or a silica source, can be added with the filler, as a source of an alloying material. In other embodiments, at least one of the electrodes of the electric furnace includes an insulator layer containing a compound, which can be reduced in the furnace, to supply an alloy matrix for mixing with the primary metal. The compound can be a metal compound, such as a metal oxide. The compound can also be an oxide, such as silica or materials containing silica, such as glass fiber. The metal oxide compound or material is refined by the electric arc to supply a source of metal or other alloy material to the charge. The heat produced by the electric arc or other electrical energy in the furnace reduces the alloy compound, in the presence of a carbonaceous reducing agent to the alloy material or other component, which is taken up by the primary metal together with the carbon of the alloys. reducing agents. In preferred embodiments, the process is carried out as a continuous process of simultaneously melting the primary metal sources and reducing the metal oxide sources, in the presence of the carbonaceous reducing agent.

As used herein, cast iron is used to define the resulting iron product having at least about 0.05 weight percent silicon and at least 0.01 weight percent carbon. The foundry iron class includes various iron compositions, which include, for example, sweet iron, gray iron, ductile iron, malleable iron and cast iron. The cast iron produced by the invention can be used directly without further processing, to produce the desired product, depending on the intended use of the iron. In other embodiments, the resulting cast iron can be further processed to modify the composition and nature of the iron to produce a steel. In embodiments of the invention for producing cast iron, this resulting cast iron contains about 0.05 to 12.0 percent silicon and about 0.01 to 4.5 percent carbon, with the remainder being iron and minor amounts of impurities, such as sulfur, phosphorus, manganese, aluminum, chromium, titanium and other metals. As used herein, the percentages are by weight, unless otherwise indicated. In preferred embodiments of the invention, the cast iron preferably comprises about 0.05 to 12.0 percent silicon and, more preferably, about 0.5 to 4.0 percent silicon and about 2.0 to 4.0 percent carbon. Typically, cast iron contains less than 3.0 percent silicon, around 2.0 percent to 4.0 percent carbon and less than about 1.0 percent sulfur, phosphorus, aluminum, manganese, chromium and other impurities. Preferably, the cast iron contains 0.10 weight percent or less of sulfur. In embodiments, the cast iron contains about 0.25 to 3.0 weight percent silicon. In other embodiments, the cast iron contains about 2.0 weight percent silicon. Referring to Figure 1, a suitable submerged arc furnace for carrying out the process of the present invention is illustrated. The submerged arc furnace 10 defines a container, which includes a bottom liner or crucible wall 12, side walls 14 and a roof or upper wall wall 16, for defining a melting and refining zone 18 and for collecting and remove dust, fumes and gases to a collection system. A loading opening 20 is provided in the roof 16 for feeding the charge or feedstock into the furnace 10, by conveyors or feeder jets (not shown). In an alternative, in the feed system, the loading materials are introduced by emptying the load directly on top of the existing load 26, using a mechanical hopper loading scheme, as is known in the art. One or more outlet branches 22 are included in the side wall 14 to remove the molten metal 28 from the melting zone 18. A slag molding 24 can also be included in the side wall 14 to remove the slag 30 from the area of fusion 18. The helmet of the furnace 10 can be cooled with a water film (not shown). A spray ring can be placed immediately below the roof flange of the side wall, whereby the water is collected in a trench at the bottom of the side walls 14. In embodiments of the invention, the roof or top wall can be split in its longitudinal dimension to allow the loading material to be fed to. any point in the oven.

Exhaust ducts 32 extend through the side wall 14 to collect and remove exhaust gases, such as combustion gases, dusts and fumes, emitted during the melting and refining phases of the process. The exhaust gases can be taken to a large bag to clean the gases before discharge to the atmosphere. The solids collected in the sack are recycled, processed or discarded in a conventional manner. The submerged arc furnace, illustrated in Figure 1, is a DC submerged arc furnace, having an anode 34 in the bottom wall 12 and a cathode 36, which extends through the roof 16. The anode 34 connects to a suitable DC power source by an electrical connection 38. Preferably, the anode 34 is placed below the cathode 36, as is known in the art. The cathode 36 extends through an opening 64 in the upper wall 16 in the melting zone 18 of the furnace 10. The cathode 36 has a nucleus of substantially cylindrical configuration, with the longitudinal dimension and is partially covered by an insulating layer 37. In the illustrated embodiment, the cathode 36 is wound in a spiral manner with a first fiberglass mat 40, which is fed from a supply roll 42 and forms a continuous first insulating layer 44 of glass fiber. A second fiberglass mat 46 is wound onto the first layer 44 in a spiral manner, opposite the first glass fiber mat 40, to form a second continuous layer 48 of glass fiber. The fiberglass mat 46 is supplied with a supply roll 50. Preferably, the fiberglass mats, 40 and 46, are wound in an overlap pattern to ensure full coverage of the cathode xn if it is in the furnace. However, the insulation can be formed on the electrode before being mounted in the furnace. In preferred embodiments, an adhesive 52 is applied to the cathode 36 to secure the fiberglass mats, 40, 46 in place. In the embodiment of Figure 1, the adhesive 52 is sprayed onto the cathode 36 by a suitable spray nozzle 54. In alternative embodiments, the adhesion can be applied to the cathode 36 and / or the fiberglass mats 40, 46 by any suitable method, such as paint, roller, dipping or extrusion. The fiberglass insulator layers 44 and 48 are wound around the cathode 36, so that the bottom or bottom end 56 of the cathode 36 is exposed. The insulator layers, 44, 48, cover a sufficient length of the cathode to effectively isolate the cathode from the charge materials and allow the cathode to be penetrated deep into the bed of charge, independent of the conductivity or resistivity of the charge bed . In the embodiment shown, the insulation covers a middle section around the circumference of the cathode body. In this manner, the tip of the electrode is exposed to produce the arc, while the remaining length of the electrode inside the furnace is electrically isolated from the charging materials. Fiberglass mats can be woven or non-woven, and are commercially available. In preferred embodiments, the thickness of the formed insulation layer 48 is from about 3.175 to 12.7 mm, but may be thicker or thinner, depending on the operating conditions of the furnace and the composition of the filler feed to the furnace. The adhesive is preferably one that will effectively bond the glass fiber or other insulating material to the cathode, during the use of the furnace, without interfering with the metal process or the furnace operation. The adhesive can be applied directly to the cathode surface, as shown in Figure 1, or applied to the fiberglass mat before or after the fiberglass mats are applied to the cathode. Alternatively, the fiberglass mat can be impregnated with an adhesive that can be activated by a solvent or by heat to melt the layers together. An upper end 58 of the cathode 36 is not covered by the insulation 37 to connect to a busbar 60 by a clamping device 62. This busbar is electrically connected to a source 61 of electrical power to supply power to the electrode. The busbar 60 is also coupled to a support assembly 63 for raising and lowering the electrode within the load 26 through an opening 64 in the ceiling 16 of the furnace 10. The electrodes can be, for example, graphite electrodes, pre-baked carbon electrodes, self-baked carbon or Soderberg electrodes, or metal electrodes, as is known in the art. The electrodes are preferably carbon electrodes of various shapes known in the art.

In the operation of the furnace 10, the charge is fed through the opening 20 into the furnace 10 and the cathode 36 is lowered into the loading bed 26 and above the anode 34. Electric current is applied to the electrodes 34 and 36 of the power source 61 for producing an arc 66 between the lower end 56 of the cathode 36 and the anode 34. The insulation layer 37 on the cathode protects this cathode 36 from the charge material, so the cathode 36 can be placed deep within of the loading bed 26, without adjusting the resistivity of the loading bed or the energy levels to the electrodes. During arc formation, the lower end 56 of the electrode 36 is gradually consumed, so that the position of the collecting bar 60 is adjusted to maintain the proper position of the cathode 36 in the loading bed 26. The lower end 68 of the fiberglass insulator layer 37 is exposed to intense heat from the arc at the cathode tip 36 and is also consumed to supply a source of silica to the filler. The resulting silica is then reduced to silicon, in the presence of a carbonaceous reducing agent, which is then combined with the primary metal of the filler. The thickness and silica content of the insulation layer is selected to supply the desired amount of silica to the filler. Referring to Figure 2, electrode 70, electrically conductive, in an alternative embodiment, includes an electrically and thermally insulating layer 72 formed by spraying an insulating material from a spray nozzle 74. The electrode 70 is similar to the cathode of Figure 1, having a lower end 76 extending beyond the insulator layer 72 and a bare upper end 78 for making the electrical connection to the electric power source of the furnace, a Similar to the embodiment of Figure 1. In further embodiments of the invention, the insulating layer 72 can be formed by dipping, painting, extrusion, fusion and other molding techniques, as is known in the art. The electrode 70 can be used as an anode or a cathode in a DC electric arc furnace or as an electrode in an AC electric arc furnace. In embodiments, about 15 cm to 91.44 cm from the lower end of the electrode assembly 36 is exposed beyond the insulating material. Preferably, the thickness of the insulation is sufficient to withstand the dielectric breakdown of the insulation during the operation of the furnace. Referring to Figure 3, an electric arc furnace suitable for carrying out one more embodiment of the present invention is illustrated. This electric arc furnace 110 is similar to the furnace of the embodiment of Figure 1 and includes a bottom or crucible wall liner 112, side walls 114 and a roof or upper wall enclosure 116, to define a melting and refining zone 118. A loading aperture 120 is provided in the ceiling 16 to feed the charge or feedstock directly to the top of the existing charge 126. Exit feelers 122 are included in the side wall 114 to remove the molten metal 128 from the fusion zone 118. A slag miter 124 can also be included in the side wall 114, to remove the slag 130 from the fusion zone 118. An exhaust duct 132 extends through the side wall 14 to collect and Remove the exhaust gases. The electric arc furnace, illustrated in Figure 3 is an electric arc furnace having an electrode 134 in the bottom wall 112, which serves as an anode and an electrode assembly 136, which extends through the roof 116 and which serves as a cathode. The anode 134 is connected to a suitable DC power source by an electrical connection 138. The electrode assembly 136 extends through an aperture 164 in the ceiling 116 within the melting zone 118 of the furnace 110. The assembly 136 The electrode has a cylindrical configuration, with a longitudinal dimension and is partially covered by a layer 140 of insulation. In the modality illustrated in Figures 3 and 4, the electrode assembly 136 includes an electrically conductive, cylindrical member, 142, which is secured to a busbar 144, electrically conducting, by a fastening member 146. This busbar 144 is connected to a source 148 of electrical power to supply electrical power to the electrode assembly 136. The busbar 144 is also coupled to a support assembly 150 for raising and lowering the electrode assembly 136 within the cargal26 through the aperture 164 in the ceiling 116. Referring to Figure 3, the electrically conductive member 142 has a substantially cylindrical configuration, with an upper end 152 for coupling with the bus bar 144, and a lower end 154 for coupling with an electrode 156. In the embodiment illustrated, the lower end 154 includes external threads 158, as shown in the Figure 4. The electrically conductive member 142 is made of a suitable metal, such as copper, copper alloys or other metals, to supply electrical power to electrode 156. In other embodiments, the electrically conductive member 142 is made of graphite, carbon or other electrically conductive materials. In the illustrated embodiment, the electrically conductive member is solid. In further embodiments, the upper end of the electrically conductive member is hollow. This upper end can be cooled by passing water or other refrigerants through the hollow portion of the electrically conductive member. The electrode 156, as shown in Figure 4, has a core 157 configured substantially cylindrically, having a longitudinal dimension with an upper end 160 and a lower end 162. The upper end 160 includes an internally threaded cavity 166, with a dimension for engaging the external threads 158 of the electrically conductive member 142. The lower end 162 includes a recessed portion 168, internally threaded, extending longitudinally. The core 157 of the electrode is typically made of graphite or carbon. In the illustrated embodiment, the core 157 is solid. An electrically insulating material, 170, surrounds the longitudinal middle section of the electrode core 157. Preferably, the insulating material 170 completely covers the sides of the electrode core 157, so when two or more of the electrodes 156 are coupled together, the insulating materials in each electrode 156 form a continuous insulating layer, as shown in Figure 3. A threaded coupler member 172, as shown in the embodiment of Figure 4, has a substantially cylindrical configuration, with continuous external threads 174, extending from a first end 176 to a second end 178. The coupling member 172 has a dimension for complementing the threaded cavities, 166 and 168, of the electrode 156. The external threads 174 of the coupling member 172 can be screwed into the cavities 166 and 168.

Referring to Figure 5, a further embodiment is illustrated, which includes a coupler member 180 having frustoconical end portions, 182 and 184, tapered. The end portions 182 and 184 have external threads, 186 and 188, respectively, for coupling with the electrodes 190. These electrodes "190 have an electrically conductive core 192 having a frusto-conical cavity 194 at each end, similar to the embodiment of Figure 5. The cavity 194 has threads 196 for coupling with the threads of the coupler member 180. In embodiments, the electrode assembly 136 can include two or more identical electrodes 156 coupled end-to-end together, as shown in the Figures. 3 and 4. The threaded coupler member 172 has a dimension to complement the internally threaded cavities 166 and 168, so a plurality of electrodes can be coupled together to obtain an electrode assembly of the desired length. The lower end .19.8 of the bottom electrode section of the electrode assembly 136 is without electrically insulating material, to produce an arc between the tip 200 of the lower end 198 and the counter-electrode in the furnace.

In further embodiments, a portion of the insulator material can be separated from the electrode to expose the tip 200 of the electrode. During use, the non-insulated tip 200 arcs with or otherwise transports the electrical energy to the counter-electrode in the furnace 110, to melt the charge. As the electrode 156 is consumed, during the fusion process, this electrode assembly 136 is lowered into the furnace to place the tip 200 of the electrode at the desired depth of charge. The electrode 156 can be removed from the electrically conductive member 142 and a new coupling member, attached to the internally threaded portion, 166, of the electrode .156, partially consumed. A new electrode is attached to the electrically conductive member. The resulting assembly is then attached to the electrically conductive member 142. In this manner, the entire electrode is consumed and it is not necessary to discard the remaining portions that are too short to be inserted into the loading materials. The insulating materials are preferably inorganic materials capable of electrically insulating the electrode from the filler material. In addition, the insulating material is preferably an inorganic material containing a compound that can be reduced or refined in the furnace to a metal or other component, to supply a metal or alloying component to the primary metal in the filler. The insulating material is typically a glass, ceramic or a mineral fiber material. Suitable materials include calcium silicate, diatomaceous earth, silica refractory clay, high alumina clay clays, calcium aluminate, zirconia, magnesite, dolomite, forsterite, chromium minerals, beryllium, lithium, and mixtures thereof. In further embodiments, the insulation material is selected from the group consisting of the oxides of aluminum, beryllium, boron, cobalt, chromium, nickel, magnesium, manganese, phosphorus, silicon, zirconium, thorium, rare earth metals, and mixtures thereof . The adhesive is preferably one that effectively binds the insulator material to the electrode during use of the furnace, without interfering with the metal process or the operation of the furnace. Alternatively, the insulating material can be impregnated with an adhesive, which can be activated by a solvent or heated to melt the layers together. The adhesive is generally an oven-type cement, such as sodium silicate or calcium aluminate cements. Other suitable adhesives include phosphorus oxides, pitch-based adhesives and tar-based adhesives. Other coating methods include, for example, normal spraying, such as plasma and flame spraying, melt coatings, such as electrophoretic coatings, electrostatic coatings and solgel type ceramic coatings. Alternatively, the insulation can be applied by surface modification, such as by electrolytic anodization. In a further embodiment, the insulation can be a pre-formed sleeve of suitable refractory material, which fits over the electrode core. The sleeve can be secured to the electrode in the desired position by adhesives, staples or other fasteners. In a further embodiment, shown in Figure 6, an electrode 202 has a core 204, electrically conductive. The core 204 of the electrode has an upper end with a cavity 206 of substantially cylindrical configuration, and a lower end with a projection 208 of substantially cylindrical configuration. The projection 208 has a dimension to fit tightly within the recess 206 of an adjacent electrode. A suitable adhesive, electrically conductive, can also be used to secure the electrodes together. The upper end of the electrode core 204 is coupled to an electrically conductive member, as in the embodiment of Figures 3 and 4. In further embodiments, other coupling members can be used to connect the electrodes together. In the embodiment shown in Figure 6, the core 204 of the electrode can be wound in a spiral manner with a first mat 210 of electrically insulating material, which is fed from a supply roll, to form a first continuous insulating layer. A second optional mat of insulating material may be wound on the first layer in a spiral manner, opposite the first mat, to form a second continuous layer. Preferably, the mats are wound in an overlapping pattern, to ensure complete coverage of the electrode core 204. In preferred embodiments, an adhesive is applied to the core 204 of the electrode, to secure the insulating mats in place. The adhesive can be sprayed onto the electrode by a suitable spray nozzle. In alternative embodiments, the adhesive may be applied to the electrode core 204 and / or the insulating mats by any suitable method, such as paint, roller, dip or extrusion. In other embodiments, the adhesive can be incorporated into the insulating mat. Referring to Figures 3 and 4, the insulator layer 170 covers a length of the electrode core 157 in sufficient form, to effectively isolate the electrode assembly 136 from the charging materials in the furnace 110 and allow the electrode assembly 136 penetrate deep into the bed of charge, regardless of the conductivity or resistivity of the bed of charge. In the embodiment shown, the insulation covers a middle section around the circumference of the electrode assembly 136. In this manner, the tip 200 of the electrode assembly 136 is exposed to produce the arc, while the remaining length of the electrode assembly 136 within of the furnace 110 is electrically insulated from the charging materials 126. The electrode core may be, for example, graphite, pre-baked charcoal, self-baked charcoal or Soderberg, made of metal or metal alloy, as is known from the art. The electrode cores are preferably graphite electrodes of various shapes known in the art. The operation of the furnace 110 is substantially similar to the operation of the furnace of Figure 1. The electrode assembly 136 is lowered into the loading bed 126 within the furnace, above the anode 134. The electrical current is supplied to the electrodes 134 and 136 to produce an arc between them. The insulator layer 170 in the electrode assembly 136 protects the electrode core 157 from the charge material 126, so this set of electrodes 136 can be placed deep within the load bed 126 without adjusting the resistivity of the load bed or the levels of power to the electrodes. As the lower end 162 of the electrode assembly 136 is gradually consumed, the position of the bus bar 144 is adjusted to maintain the proper position of the electrode assembly 136 in the bed of charge 126. The lower end of the insulator layer 170 is exposed to intense heat, to reduce the metal compound of the insulator material to the metal element, in the presence of a suitable reducing agent, which is then combined with the primary metal of the charge. The thickness and composition of the insulator layer is selected to supply the desired amount of alloy metals or other additives to the filler. Examples of suitable electric furnaces, particularly electric arc furnaces, are produced by Mannesmann Demag Huettentechnik AG of Duisburg, Germany (including the Confiare oven) and by Elkem Technology, Oslo, Norway The CD electric arc furnace typically has a single upper electrode immersed in the charge with a suitable return electrode (for example the anode) at the bottom of the container, as is known in the art. The furnace may be an AC electric arc furnace, a DC electric arc furnace, a submerged AC arc furnace or a DC submerged arc furnace. In further embodiments, an electric plasma arc furnace or an alternating current electric arc furnace, having at least two electrodes, can be used.

In a further embodiment, the furnace is an alternating current furnace, having three electrodes, which extend through the roof in the melting zone. The electrodes can be arranged in triangular or in line configurations. One or more of the electrodes may have an insulator layer in the same manner as the embodiments of Figures 1 to 6. The electrodes may be independently controlled to selectively adjust their vertical positions within the furnace, and to prevent overcurrents. These electrodes can be raised or lowered to vary the length of the arch, as is known in the art. The furnace is typically a three phase alternating current furnace, driven by a selectable voltage, of approximately 30 to 400 volts, with a maximum current of approximately 100,000 amperes per phase. The electric arc furnace provides the continuous production of molten metal, such as cast iron, allowing continuous feeding of the furnace with the filler material and deriving molten metal from the lower regions of the furnace. The process can be easily placed on a scale for high production regimes, while still controlling the production rate and the output composition of the metal. A suitable load carrier, hopper loading system, or loading tube, as known in the art, can be used to continuously supply the loading materials to the furnace. The production or production rate of the furnace is dependent on the power supplied to the furnace and the feeding regime of the kiln materials. The furnace can be designed to operate at a power level of approximately 1 megawatt to approximately 100 megawatts, depending on the construction of the furnace, the type of electrodes and the loading materials. In general, the electric arc furnace produces one ton of iron casting product with an electric power input of approximately 600 kilowatt-hours. Depending on the load materials, product characteristics and construction of the furnace, an AC electric arc furnace can produce cast iron at a rate of electric power input between about 500 to 1400 kilowatt-hours per ton of product.

The process of the invention can be carried out in an electric arc furnace using a level of charge and power so that the tips of the electrodes are embedded several feet (30.48 cm) into the bed of the face material in the furnace and within about one foot (30.48 cm) of the bath from the molten metal assembly. In this way, the arc zone narrows to the metal assembly or bath. The furnace is operated to maintain the bath temperature of molten alloy in the furnace between about 1149 to 1760 ° C. In preferred embodiments, the bath temperature is kept high enough to allow adequate overheating of the molten metal for easy derivation and handling or downstream processing. The tip of the electrode is immersed in the material and produces an arc near the molten metal bath, provides good heat transfer to the unprocessed material by radiation from the arc and molten metal, and by convection from the hot plasma gases and carbon monoxide gas, which is continuously generated by the chemical reduction of metal oxides and silica by carbon in the lower regions of the bed of charge. A DC submerged arc furnace is generally operated at a voltage of approximately 30 to 400 volts and at a maximum current of around 100, 000 amps per phase. A standard electric arc furnace includes a self-protection mechanism or control system, to automatically raise the electrode from the crucible to prevent excessive electrode currents, which can result when the conductivity of the fillers increases above a level predetermined. If the tip of the electrode remains too high, temperatures near the furnace crucible decrease and, if prolonged, may result in improper heating and melting of the metal and incomplete reduction of oxides, such as silica. It is important to have the height of the bed fed load so that the tip of the electrode can be placed to form the arc about 30.48 cm above the metal bath. The successful immersion or penetration of the electrode is achieved by providing the electrical insulator material along a substantial length of the upper electrode in an electric arc furnace. Since the majority of the electrode is electrically isolated from the charge materials, the tip of the electrode can be submerged in the charge deeper than with the uninsulated electrodes and thus achieve improved heating of the charge. This penetration of the deepest electrode is made possible by the configuration of the isolated electrode and results in better transfer of heat to the charge by the arc and the passage of the hot gases from the reaction product through the relatively deeper bed of charge, with the consumption of specific electrical power decreased consequently for the process. Achieving satisfactory immersion or penetration of the electrodes of an AC electric arc furnace in the furnace bed depends on several factors, including the specific electrical resistivity or conductivity of the charged materials, the selection and appropriate proportion of the materials in the maintenance with their specific electrical resistivity, their physical size, their distribution in the mixture and the operating voltage selected for the furnace. The operating voltage is selected to compensate for the relationship between the voltage, electrical current and resistance of the charging materials to achieve the deepest immersion of the electrodes in the load. The load bed resistance can be varied, varying the materials of load and the size of the materials to optimize the operation to obtain the penetration of the electrode deeper in the bed of load for a given operating voltage. The amount of electrical energy required per tonne of metal produced is highly dependent on the degree of oxidation or reduction of the metal materials charged, the amount of silica and other oxides required to achieve the desired composition or objective, the optimization of the submerged operation of the electrode, and the experience of the oven operator. For example, iron alloys containing approximately 0.5 to 4 percent carbon and approximately 0.25 to 2.5 percent silicon typically require around 500 to 650 kilowatt-hours per tonne of alloy produced. The higher percentages of silicon and the corresponding lower percentages of carbon require an increase of about 10 kilowatt-hours for highly non-oxidized iron sources for each additional increase of 0.1 percent in silicon above 2.5 percent silicon in the alloy. The raw material constituting the load to be fed to the arc furnace is preferably mixed before feeding. Alternatively, the different components of the load can be fed simultaneously from separate supplies in the furnace to a controlled rate and in the desired ratios. The composition of the resulting metal is dependent on the composition of the charge and the degree of chemical reduction that occurs in the furnace. In the production of cast iron, the fillers comprise an iron source, which includes slag iron or slag steel, a source of silicon and a carbonaceous reducing agent, as discussed above in greater detail. In general, silica is a primary source of silicon, which can be supplied with the charge, supplied by the consumption of the electrode and the silica-containing insulation, and their combinations. The melting of the iron and the reduction of the silica and the metal oxides, in the preferred embodiments, is substantially in the absence of an oxygen load or an oxidizing agent and in the absence of slag-forming materials. In other embodiments, the primary metal of the charge is aluminum, copper, magnesium, manganese, chromium, nickel, zinc, lead, cadmium, precious metals, such as gold and silver, and oxides and their alloys. The metal source can be slag metals or other metal sources. Slag iron and slag steel are available as commercial items, as is known in the metals industry. The market prices and grades of various types of iron and slag steel are regularly published in various industry publications, such as the American Metal Market. Iron and slag steel, as is known in the art, is graded according to the size and composition of metal particles. For example, one type of slag steel is defined as: "cast steel, 2 'max." Suitable sources of iron for use in the present invention include iron ores, mill incrustations, direct reduced iron (DRI), hot iron in briquettes (HBI), iron carbide, iron boring particles, turning shavings. Steel, fragmented steel cars, steel cans, and their mixtures. The composition of iron or slag steel will influence the composition of the resulting cast iron. Several sources or grades of slag iron can be mixed before feeding to the furnace, to supply the desired inlet and outlet compositions. The iron source generally comprises at least 50 percent slag, preferably 75 percent slag, and more preferably about 90 weight percent iron or slag steel. The iron source can be completely based on iron or slag steel. This iron or slag steel can be mixed with other iron or steel materials to increase or decrease the percentage of various alloy metals in the composition of the resulting cast iron. For example, direct reduced iron (DRI) and hot iron in briquettes (HBI), which typically contain about 90 percent iron, can be added to increase iron content in cast iron, thus diluting metals of alloy and reducing the percentage of unwanted metals. The amount and type of materials combined with iron and slag steel, is determined, in part, by the efficiency of the furnace in using its components and the relative cost of the load materials. For example, heavy steel slag, which is low in unwanted waste elements, is expensive in comparison to the auger particles of the cast iron or steel shavings of the lathe, so large amounts of heavy slag are usually not convenient from the economic point of view. For comparison, the steel shavings of the lathe, which are cheap compared to the heavy steel slag, usually contain high levels of undesirable residual elements. The use of the submerged arc furnace allows the use of very fine-sized slag materials, which, being less expensive than heavy slag, is an economic advantage in producing cast iron over other process methods. The particle size of the filler is important in obtaining the proper heating and melting of the slag, although there is no absolute limit. The slag metal has a size of 60 centimeters or less in any dimension. An adequate size of the slag metal is approximately 25 millimeters or less. In alternative modalities, the particle size of the slag metal is less than about 0.5 centimeters. The particle size of the charge is selected to be easily handled and loaded in the furnace and melted without bridging the electrodes or between the electrodes and the side walls of the furnace. The electric arc furnace, according to the preferred embodiments, is capable of handling a slag of small particle size smaller than 6.35 mm in its largest dimension. The particle size of iron or slag steel can vary from small fine particles or blasthole, to large pieces. The limit of the upper size is generally the face-to-face spacing between the electrodes in an AC submerged arc furnace or between the electrode and the refractory wall of the furnace in a dc submerged arc furnace, to avoid the formation of bridges Slag metals are highly conductive compared to minerals, so the electrode must be adequately isolated for an electric arc furnace or the conductivity and electrical resistivity of the charge must be selected and controlled to allow deep immersion of the electrodes. The electrical resistivity of the load can be modified by the selection of the particle size of the load and the type of materials. Reducing the particle size of the filler increases the resistivity of the charge. The most efficient particle size will depend on its inherent resistivity and the dependence of the permeability of the furnace charge to the passage of the exhaust gases on the particle size of the charged materials. In the production of cast iron, the filler material does not contain substantially mineral, although minor amounts of minerals can be added to modify the resistivity of the charge. Mill waste, highly oxidized, or resistive metal sources can also be used to modify the resistivity. The filler material may also include an amount of a silicon source, such as, for example, silica, silica or silicon dioxide sources, in a reducible form. Silica, and particularly quartzite, is the preferred silicon source. The silicon source can be any commercially available material, which can be refined or reduced to silicon in the electric arc, in the presence of a carbonaceous reducing agent, simultaneously with the melting of the primary metal source. Silicon is produced in a form that can be combined directly with the molten metal. In alternative modalities, the mineral containing silica, waste waste and sand, which has been washed to remove impurities, can be used. Typically, the filler is substantially absent from ferrosilicon or silicon carbide. In preferred embodiments, the silicon source contains at least 98 weight percent silica. The impurities are preferably removed to prevent the formation of the slag in the furnace, since the slag increases the energy demand to refine and melt the charge. Quartzite, used in the preferred embodiments as the primary silica source, is substantially free of clays and other foreign materials, such as metal oxides, which would contribute to the undesired formation of slag, as well as unwanted contamination of the material. cast iron resulting with traces of metal. Quartzite is generally a quartzite of a certain size, crushed or fragments of quartzite of high purity, containing at least 95 percent silica. The particle size of the silica source is determined by the particular dimensions of the furnace, the electrodes and the residence time of the fillers in the furnace, to ensure complete reduction to the silicon, in the presence of a reducing agent. Generally, quartzite has a particle size of 10 cm or less, although large kilns may use larger particles. The silica source preferably contains less than 0.5 weight percent aluminum, magnesium, zinc and titanium oxides. Some of these metals, such as zinc, can be oxidized and removed by the flow of air or oxygen through the furnace and removed in the bag. Other metal oxides are reduced in the furnace to the metal, which can be combined with the primary metal. The amount of the silicon source added to the furnace with the charge was determined by theoretical calculations of the desired silicon content of the resulting cast iron or other primary metal. The amount of the added silicon source is also based on the stoichiometric calculations, taking into account the calculated silica content of the filler metals and the calculated losses due to the predicted volatilization in the reduction of silica to elemental silicon. The silicon source can be added in the amount of about 0.01 to 20 percent by weight, based on the weight of the iron or slag steel. Typically, the silicon source is less than about 10 percent and preferably less than 5 percent by weight of the iron or slag steel, generally, about 90 percent or more of the available silicon is combined with the iron, while the remaining silicon is lost as fumes of silica and, if it is formed, it is like slag. Silicon recoveries are typically greater than 90 percent, experienced when alloys with 3% or less of silicon content are produced. The carbonaceous reducing agent can be any carbon source capable of reducing silica and other metal compounds in the furnace. Examples of carbonaceous reducing agents include, charcoal, mineral coal, coke, such as petroleum or bituminous coke, wood chips and their mixtures. Preferred carbonaceous materials have a high fixed carbon content and also have a low ash content, low moisture content, low levels of calcium oxide and aluminum oxide, and low levels of sulfur and phosphorus. The carbonaceous materials, in preferred embodiments, also have high reactivity and high electrical resistance. A preferred carbonaceous material for operations of the furnace, of submerged arc of AC is the chips of hard wood, free of bark, for example of oak. Wood chips provide a source of carbon to reduce silica to elemental silicon, as well as an element to reduce the electrical conductivity of the charge in the furnace, so that the electrodes can be immersed deep in the submerged arc furnace, to maintain the desired melting temperature of the slag and reduce the silica. The filler may contain about 5 to 40 weight percent of the carbonaceous reducing agents, based on the weight of the iron. Preferably, the filler contains at least 5 percent carbonaceous reducing agents based on the weight of the iron. The amount of the carbonaceous reducing agent added to the charge is determined by calculating the stoichiometric amount of the fixed carbon needed to reduce the metal compound to the metal, and the amount of free carbon needed to supply the desired carbon content in the resulting molten metal. The theoretical calculations are based on the content of the fixed carbon of the mineral coal, charcoal, coke, wood shavings or other carbonaceous reducing agent, according to the calculations, as it is known in the metallurgical industry. The amount, type and particle sizes of the carbonaceous reducing agent affect the resistivity of the filler material. For example, charcoal can be used in higher proportions to increase resistivity, since preferred vegetable carbons have a higher resistivity than coke or mineral coal. The process can be conducted in the complete absence of coke. The particle size of the carbonaceous reducing agent is selected according to the composition of the fillers, the reactivity and the resistivity or electrical conductivity of the filler composition. An adequate size of wood chips is usually around 15 cm or less, in the greater dimension. A suitable size for metallurgically grade coke is about 1.27 cm or less. The charcoal is around 5 cm or less while the charcoal is typically 15 cm or less in the longer dimension. In the production of cast iron, the filler composition preferably contains only minor amounts of impurities, such as sulfur, phosphorus, calcium, aluminum, chromium and zinc, to minimize slag formation and thus reduce energy consumption . The absence of slag makes it possible to preheat the charge material by heat from the molten metal. Excess slag formation also inhibits the flow of charge materials to the furnace heating zone and increases the likelihood of a load bridge in the furnace. In embodiments where the loading material contains high amounts of sulfur or other impurities, a slag-forming component may be added, when necessary. Suitable slag-forming components include limestone (calcium carbonate), lime (calcium oxide), or magnesia, although other slag-forming components, as known in the art, can be used. When necessary for efficient operation, lime with a particle size of less than 3 millimeters can be used. In embodiments, the process of producing cast iron is carried out in a direct current (DC) electric arc furnace, configured with an electrically insulating coating or sleeve that surrounds the upper electrode by much of the distance that the electrode extends. in the loading of the oven. The use of an AC or DC electric arc furnace, using the insulated electrode, facilitates deep penetration of the upper electrode into the charging materials and the close proximity of the electrode tip to the metal bath. The DC submerged arc furnace is capable of processing a wider range of sizes of filler materials, and may allow the removal of some load components, such as wood chips, which is usually required for satisfactory operation of the furnace. AC submerged arc, due to much stricter load conductivity requirements. The DC submerged arc furnace is an advantage for the process, because it allows operations at secondary voltages greater than an AC submerged arc furnace. This makes it possible to input more power into the CD oven when operating with the same electrode current as the AC submerged arc furnace. Another advantage of the DC submerged furnace for the process lies in its circular and cylindrical symmetry, which allows for more uniform material loading in the furnace, more even distribution of, and heating of, the charge by the arc and gaseous products of the reduction processes, and the more uniform descent of the load without bridge formation. In embodiments of the invention, the process of producing the cast iron is carried out in an electric arc furnace, in the absence of iron ore and coke, and generally produces a cast iron product having a temperature between about 1149 and 1760 ° C and less than about 0.1 weight percent slag, compared with 1 to 10 percent slag from conventional smelting iron processes, which use a submerged arc furnace. Typically, cast iron is produced substantially in the absence of the slag. Modes of the process of the invention are disclosed in the following non-limiting example.

EXAMPLE A simulated computer operation consists of feeding a mixture containing 908 kg of iron, 45.4 kg of wood chips, 38.56 kg of coal, 9.08 kg of coke and 34 kg of quartzite, charged in an AC submerged arc furnace , to an alloy production regime of 65,854 tons per hour. The energy input projected to the furnace was 50,000 kilowatts. The simulated slag iron load consists of 40 percent car steel in fragments, 15 percent remelting returns, 15 percent steel # 1 slag, 20 percent particles from the cast iron borehole , 5 percent tin plates / cans and 15 percent lathe shavings - low chrome. The charge mixture had a calculated alloy composition of 2.5 percent silicon, 3.85 percent carbon, 0.40 percent manganese, 0.10 percent chromium, 0.15 percent nickel, 0.15 percent copper, 0.01 percent of sulfur, 0.05 percent of phosphorus and 0.03 percent of tin, with the rest of iron, where the percentages are by weight. The resulting projected iron product, as derived from the furnace, had an iron content of 92.5 percent, a carbon content of 3.85 percent and a silicon content of 2.50 percent by weight, with the rest of the impurities. The calculated energy consumption was 650 kilowatt hours per ton of iron alloy. While various embodiments have been shown to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications may be made thereto, without departing from the scope of the invention, as defined in the appended claims.

Claims (23)

1. CLAIMS 1. An electrode for an electric arc furnace, this electrode comprises: an electrically conductive core, having a first end, a second end and a longitudinal middle section between the ends, this first end of the conductive core has a first member of coupling, for connection to a power source, and a second end, having a second coupling member for coupling with a first end of an adjacent electrode; And an electrically insulating material, which surrounds and joins the middle section, with the second end of the core being free of the insulating material, this electrically insulating material forms a substantially continuous insulating layer on the middle section and is consumable during arcing. in an electric arc furnace.
2. 2. The electrode of claim 1, wherein the insulating material is a fibrous mat, woven or nonwoven.
3. 3. The electrode of claim 2, wherein the insulating material is adhesively bonded to the electrically conductive member.
4. 4. The electrode of claim 1, wherein the insulating material includes an additive that improves the metal.
5. 5. The electrode of claim 1, wherein the insulating material has a thickness to resist dielectric failure of the insulating material during the operation of the furnace.
6. 6. The electrode of claim 1, wherein the insulating material is selected from the group consisting of glass, ceramics, mineral fibers, calcium silicate, diatomaceous earth, silica refractory clay, high aluminum diasporus clays, calcium aluminate, zirconia , magnesite, dolomite, forsterite, chromium minerals, beryllia, toria, alumina, rare earth metal oxides, and mixtures thereof.
7. 7. The electrode of claim 1, wherein the insulating material is selected from the group consisting of the oxides of aluminum, boron, cobalt, chromium, nickel, magnesium, manganese, phosphorus, silicon, zirconium, rare earth metals, and mixtures thereof .
8. 8. The electrode of claim 1, further comprising an electrically conductive member coupled to the first end of the electrically conductive core for connection to a power source.
9. 9. The electrode of claim 1, wherein the first coupler member is a portion threaded internally at the first end of the core; and the second coupling is a portion threaded internally at the second end of the core, where the electrode further comprises a threaded coupling member, for engaging internally threaded portions of the core.
10. 10. The electrode of claim 1, wherein the insulating material extends from the first end to the second end.
11. 11. An electric arc furnace, this furnace comprises: a container, having a melting zone and an inlet for feeding a charge into the container; at least one electrode assembly, placed in the container, this electrode assembly includes an electrically conductive member, having a first and second ends, and includes at least one electrode, having an electrode core with a first end coupled to the member conductor electrically and that has a material • electrically insulating, surrounding and joining a portion of the electrode core, which forms a substantially continuous insulation layer, this electrode assembly has a lower end substantially free of insulating material and placed in the fusion zone, the first end of the electrically conductive member is coupled to an electrical power source, the insulating layer is consumable during the formation of the arc in the container, to supply an insulating material to a molten metal, produced in the container; and at least one second electrode, placed in the container, to produce heat in the fusion zone with the electrode assembly.
12. 12. The electric arc furnace of claim 11, wherein the electrode assembly has a longitudinal middle section, extending between the first and second ends, the insulation material substantially covers the middle section and is spaced apart from the first and second ends of the electrode assembly. electrode set
13. 13. The electric arc furnace of claim 12, wherein the insulating material is a mineral fiber mat, woven or non-woven.
14. 14. The electric arc furnace of claim 13, wherein the insulating material is adhesively bonded to the first electrode.
15. 15. The electric arc furnace of claim 11, wherein the insulating material comprises the silica.
16. 16. The electric arc furnace of claim 11, wherein the furnace is a plasma arc furnace, direct current electric arc furnace, submerged direct current arc furnace, submerged alternating current arc furnace, or AC electric arc furnace.
17. 17. The electric arc furnace of claim 11, wherein the insulating material is selected from the group consisting of glass, ceramics, mineral fibers, calcium silicate, diatomaceous earth, silica refractory clay, high alumina clay clays, calcium aluminate , zirconia, magnesite, dolomite, forsterite, chromium minerals, beryllia, thoria, rare earth metal oxides, and mixtures thereof.
18. 18. The electric arc furnace of claim 11, wherein the insulating material is selected from the group consisting of oxides of aluminum, boron, cobalt, chromium, nickel, magnesium, manganese, phosphorus, silicon, zirconium, and mixtures thereof.
19. 19. The electric arc furnace of claim 11, wherein the insulating material has a thickness sufficient to withstand the dielectric failure of the insulating material during the operation of the furnace.
20. 20. The electric arc furnace of claim 11, wherein said at least one electrode core is removably coupled to the electrically conductive member.
21. The electric arc furnace of claim 11, comprising a plurality of electrode cores coupled together, wherein the second end of each electrode core is coupled to the first end of an adjacent electrode core.
22. 22. A process for producing molten metal in an electric furnace, this process comprises the steps of: feeding an electrically conductive charge in an electric arc furnace, with at least one first electrode, this at least one first electrode having a first end coupled to a movable assembly structure, for raising and lowering the electrode with respect to the loading bed in the furnace, and having a second end for cooperating with a second electrode, and an electrically insulating material, covering a portion of the first electrode and isolating the first electrode of the bed of charge, this charge comprises at least one metal compound or its mixtures; immersing this at least one first electrode in the bed of charge, at a depth independent of the conductivity of said charge; provide electrical power to the electrodes, to generate an electric arc between them; and heating the charge in the furnace by the electric arc between the electrodes, to produce the molten metal.
23. 23. The process of claim 22, wherein the furnace further comprises an electrically conductive member, having a first end coupled to the movable mounting structure and a second end coupled to the first end of this at least a first electrode.