US984970A - Furnace for metallurgical purposes. - Google Patents

Description

W. RODENHAUSER. FURNACE FOR METALLURGICAL PURPOSES.

PPLIGATION FILED NOV.3,1908.

Patented Feb. 21, 1911 2 SHEETS-SHEET 1.

W. RODENHAUSER. FURNACE FOR METALLURGICAL PURPOSES, APPLICATION FILED NOV. 3, 1908.

984,970. Patented Feb. 21, 1911.

2 SHEETS-SHEET 2.

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UNI ED STATES PATENT OFFICE.

WILHELM nonENHAUsna, OFIVGLKLIINGEN, GEIQMANY, ASSIGNOR TO THE eaoNnAL IUELLIN COMPANY, LIMITED, 012* LoNnoN, ENGLAND.

FURNACE FOR METALLURGICAL PURPOSES.

Specification of Letters Patent.

Patented Feb. 21, 1911.

Application filed November 3, 1908. Serial No. 460,956.

, ing is a specification.

This invention relates. to 3 furnaces for metallurgical purposes, the chief object being to provide an improved furnace in which \7 the material to be treated can be more uniformly heated than in furnaces of the kind now in use.

Metallurgical furnaces hitherto employed are defective owing to the uneven (llStI'lblltion of the heat that is imparted to the material to be melted. In electricarc furnaces, for example, the charge in the melting cham her is very irregularly heated, because the electric current in passing from one electrode to the other creates an electric are which acts directly upon a portion of the furnace of the charge only, the remainder of the charge being only heated indirectly by conduction from the portion that is directly exposed to the source of heat. This is true not only of the electric arc furnace in the narrow sense, that is to say of a furnace in which an electric arc passes between the oppositely placed extremities of two electrodes presenting the form of rods and located above the material to be melted, but also applies to electric furnaces of the kind in which an electric current passes into-the charge by way of a rod electrode, then crosses, in the form of an are, a narrow air gap between the electrode and a layer of slag, and after passing through the slag, or slag and metal, leavesthe furnace by way of another air gap and electrode (Heroult furnace), or by way of a plate inserted in the bottom of the furnace. Even in this latter form of furnace, the current that, afterpassing the air gap, flows through the material undertreatment, is, quite apart from the \Vhen it is further considered that the more or less coarse material stacked in the furnace at the beginning of the melting operation constitutes a bad conductor of heat, it will be readily understood that the melting of the portions of the material located near to the electric arc or to the electrodes will take place much sooner than the melting of those parts which arelocated at a greater distance; a considerable period of time will therefore elapse before the whole of the material has become sufficiently fluid, and during this time much heat is lost by radiation and conduction. For this reason the thermic efficiency of these furnaces must be low. The vigorous heating of the material almost exclusively at the surface as above referred to presents the further defect that the material is not thoroughly mixed. The top layer of the material. upon which the electric are directly acts is always much hotter and therefore specifically lighter than the lower layers which, practically speaking, are only heated by conduction, A circulatory movement of the maafter the melting has been completely effected. The material withdrawn from the furnace must therefore be mixed and rendered homogeneous by a special operation, or the furnace must be adapted to be tilted so that the material may be displaced by rocking the furnace while the melting operation is in progress. Both of these methods of mixing the molten material and rendering it homogeneous are of course inconvenient and expensive in practice.

The same defects, which as described above are inherent in the electric arc furnaces heretofore used, also occur in flame or reverberatory furnaces such as Martin furnaces, in which the heatin of the material is effected by the action of urnace gases passing over it; for it will be readily understood that in this case also only the upper parts of the material are directly heated. Moreover owing to the irregular heating of the various parts of the material much time and utilizable heat are lost, and for the reasons already stated no circulatory movement of the material takes place. A consideration of these defects has led to the present invention which resides in the fact that metallurgical furnaces of the kind above referred to are provided, in addition to the are,-

- suitable places.

flame or other source of heat acting upon the surface of the charge, with a second or auxiliary source of heat of an electrical nature which renders it possible to positively heat the lower part of the charge, and there by effect a circulatorymovement of the same and a more uniform distribution of heat than in the prior arrangements above referred to.

In order that the said invention may be clearly understood and readily carried into effect, I will proceed to describe the same more fully with reference to the accompanying drawings which show several types of furnaces to which my invention is applied.

Figure l is a vertical section, and Fig. 2 a sectional plan on the lin 22 of Fig. 1 showing my invention applied to an electrio-arc furnace. Fig. 3 is a sectional plan of a modified form of furnace, rectangular in plan. Fig. 4: is a vertical section and Fig. 5 a horizontal section onthe line 55 of Fig. 4: illustrating a furnace with two electrodes suspended vertically above the charge in the melting chamber, a small air gap bein provided between the end face of each of the electrodes and the surface of the charge, so that two arcs in series are formed across the two air gaps when the electric current passes. Fig. 6 is a vertical section, and Fig. 7 a horizontal section on the line 7-7 of Fig. 6 illustrating a modified form of the furnace shown in Figs. 4 and 5, in which only one electrode is placed above the charge in the melting chamber, the other electrode, which may be a water cooled steel plate, being built or let into the bottom of the chamber.

In each of these figures, A A represent the terminal plates of the electrodes by means of which the second source of heat is introduced into the furnace in accordance with this invention.

B represents the furnace walls, and C the refractory lining.

E andE are the electrodes between which the electric arc is struck.

The electrodes, by which the second source of heat is introduced, are built inside the furnace wall B below the surface of the charge and directly in contact therewith at These electrodes may consist of two main parts; one part b is a platelike layer of refractory material which is a conductor of electricity at high temperatures only, but .which for the pur ose of rendering it a sufficiently good cont uctor even in a cold state is mixed with a carbonaceous binding medium, say tar or powdered carbon; the other part a is a metal plate equal in superficial area to the plate-like layer of refractory material I) and embedded between this material and the furnace wall 13. The electrode terminals A, A are attached to or form part of these metal plates a, on the l l l r l i l l l 'cesses or channels of dovetail or similar cross-section, with the object of preventing the layer of refractory material from becoming detached from the metal plate and also of increasing the area for the transmission of the current. The current serving to feed these electrodes may be taken, in the case of electric arc furnaces, from the same source of current as that which serves to feed the are. If a transformer is used, the arrangement may be such that its secondary Winding is subdivided so that only a part of the winding, which may consist of thick wire or bars, serves to supply the current for feeding the electrodes which are let into the furnace wall at the lower part of the furnace. The remaining windings which may consist of fine wires or rods, and the secondary windings as a whole, serve for the generation of a current of appropriate voltage for feeding the electric are.

In the case of flame or reverberatory furnaces, such as Martin furnaces, the above described method of heating the lower parts of the metal bath by heat derived from electrical resistance may be employedat any time to assist in the heating of the charge by the hot gases without incurring injury to the electrodes by the action of the hot gases upon them. It may be found advantageous to apply this method of heating to converters for the manufacture of steel, thereby enabling the temperature of the molten mass in the converter to be increased during the blowing operations or the bath to be heated and thereby drive out any objectionable gases that may, be formed.

In all constructions the electrode plates are arranged inside the furnace walls in such a manner that the current conducted to the plates is obliged to flow through the lower part of the material that is being melted. By suitably regulating this current, the heating of the material can be rendered thoroughly uniform.

What I claim and desire to secure by Letters Patent of the United States is 1. A furnace for melting metal, comprising a melting chamber in which the charge is contained, electric means for heating the surface of the charge and independent electric means below the surface of the charge for leading an electric current to the body of the latter whereby a substantially uniform heat may be' maintained in all portions thereof, substantially as described.

2. A furnace for melting metals, comprising a melting chamber in which the charge is contained, means for heating the surface of the charge, and electric conductors forming portion of the lining of the melting chamber below the surface of the charge for leading an electric current to the body of the latter,

whereby a substantially uniform heat may be maintained in all portions thereof, substantially as described.

3. A furnace for melting metals, comprising a melting chamber in which the charge is contained, electric arcing means for heating' the surface of the charge and electric conductors forming portion of the wall of the chamber below the surface of the charge,

for leading a current to the body of the latter, whereby a substantially uniform heat may be maintained in all portions thereof, substantially as described.

4. A furnace for meltmg metals, comprising a melting chamber in which the charge is maintained, means for heating the surface of the charge, in combination with electric conductors forming portion of the wall of the chamber below the surface of the charge for leading a current to the body of the latter whereby a substantially uniform heat may be maintained in all portions thereof, substantially as described.

In testimony whereof I aflix my signature in presence of two witnesses.

Witnesses LoUIs VANDORN, H. STELZER.

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