Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – With means to discharge molten material
Reexamination Certificate
1999-02-03
2001-04-17
King, Roy (Department: 1742)
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
With means to discharge molten material
C266S241000, C222S590000, C222S593000
Reexamination Certificate
active
06217825
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for splashing and/or teeming of liquid metals, in particular steel, through a discharge in the wall or in the bottom of a metallurgical vessel, wherein the discharge is electromagnetically coupled to the electromagnetic field of at least one fluid-cooled inductor. The inductor and the discharge are disposed at least partially in the wall or in the bottom of the metallurgical vessel. Following splashing, the electric power of the inductor or the inductors, if appropriate, is changeable.
Such process for an inductor is disclosed in De 44 28 297 A1 in a free-running nozzle. In DE 41 36 066 A1 a discharge device for a metallurgical vessel is described, in which a cooled inductor is disposed outside of the bottom of a vessel. In DE-A-24 33 582 an arrangement for the production of cast parts is disclosed, wherein several inductors, disposed one next to the other and switchable independently of one another, are provided and which are cooled either with water or with air. DE-AS 1 049 547 discloses an arrangement for the electrically controlled teeming of metals. Below, and thus outside, of the bottom of a metallurgical vessel three coils are disposed as inductors laterally of a discharge. The coils are intended to generate in the steel column an alternating traveling field advancing from below toward the top, through which in the steel column, i.e. the outflowing melt, an upwardly directed force component is generated, which, depending on the field strength, can decelerate or cancel the outflowing of the liquid steel. The metal column, rigid at the beginning of casting, can be inductively melted by the alternating field. In the technical work “Metallurgie des Stranggie&bgr;ens”, {metallurgy of continuous casting}, Editor: K. Schwerdtfeger, Publisher: Stahl-Eisen, Dusseldorf, 1992, pp. 449, electromagnetic agitation during continuous casting and associated inductors are explained. Agitators are always disposed within the region of the strand-forming chill or, in the direction of flow of the strand, behind it. A regulation and closing device for a metallurgical vessel with a rotor and a stator (pipe-in-pipe closing system) is described in DE 195 00 012 A1. Depending on the selection of the material for the rotor, either the rotor itself or the melt flowing through it is coupled to the electromagnetic field of an inductor.
In the case of horizontal continuous casting machines, the pouring discharge or pouring discharges mount into a side wall of the melt vessel. The pouring discharge or pouring discharges is/are flanged onto a chill such that the melt flows horizontally through the pouring discharge, or the pouring discharges, into the chill. According to prior art, the pouring discharges before splashing are heated with a gas burner in order to prevent the freezing of the melt already during splashing. Carrying out this preheating is problematic since it cannot be maintained during the preparatory mounting processes and thus the temperature of the pouring discharge decreases, leading to the pouring discharge being frozen closed during splashing. In the case of horizontal continuous casting machines, by necessity a specific temperature gradient is set up in the liquid metal in a distributor. In the liquid metal flowing through the pouring discharges, this leads to so-called temperature streaks or “black strips” and thus to a quality of reduction the cast strand.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a process of the above type for the improvement of splashing and/or teeming. It is furthermore an object of the invention to provide a refractory discharge suitable for this purpose and a suitable arrangement or assembly incorporating such discharge.
According to the invention the above objects are achieved by provision of an air-cooled inductor for use according to the invention in the bottom or the wall of a metallurgical vessel. Through the inductive heating of a discharge during splashing it is attained that during splashing the discharge or the pouring discharge does not receive thermal shock fractures and that the metal melt entering it does not freeze and even, in case an interruption occurs in casting, does not freeze or metal frozen in it melts again. The heating of the discharge or of the pouring discharge by means of at least one inductor is made possible by use therefor at least partially of a material capable of being coupled to the electromagnetic field of the inductor. The pouring discharge of an inductively coupling material can also entirely or partially comprise in its passage an inner layer of a non-inductively coupling, wear-resistant material which is heated by thermal conduction and/or heat radiation. When using a pouring discharge of a non-coupling material, it is encompassed by a susceptor coupled to the electromagnetic field which outputs to the pouring discharge thermal energy through thermal conduction and/or heat radiation.
After splashing, thus for teeming, the frequency of the electromagnetic field of the inductor or of the inductors can be adjusted in such a way that the field penetrates the pouring discharge and, if appropriate, also the susceptor and now also couples electromagnetically at least the outer layer of the liquid metal itself to the field. Thus, a temperature effect of the steel flowing through the pouring discharge becomes more effective. If appropriate, the liquid metal strand in the region of the discharge is coupled to a further electromagnetic filed which does not primarily serve for heating but rather has different functions, for example, an agitating function. It is thus coupled for the purpose of splashing, as long as no liquid metal flows through the discharge, to it alone and does so with optimum power and frequency for an adjustment in time of the desired temperature of the discharge. For teeming, the frequency and, if necessary, also the power of the inductor is adjusted such that the liquid metal flowing through the discharge is also exposed to the electromagnetic field. The power can normally be reduced until the customary temperature losses in the discharge system are compensated. However, it is also possible, in particular toward the end of teeming, to avoid freezing of liquid metal in the pouring discharge. Thereby, the discharge and/or the liquid metal flowing through the discharge, is inductively heated by means of the inductor, for the purpose of which the power of the inductor is successively increased. The potentially existing necessity of power matching depends on the inducting thermal energy, desired for reasons of process engineering, for heating or the desired movement in the steel flowing through the discharge for the purpose of making the temperature uniform.
As indicated earlier, spatially changeable magnetic fields can be generated in the liquid metal, and lead to motion in the liquid metal flowing through the pouring discharge. Such magnetic fields are realized as rotary and/or linear traveling fields which generate in the liquid metal in the discharge an agitation effect, similar to that described in the earlier cited technical work, resulting in the temperature in the throughflow cross section of the liquid metal becoming uniform such that temperature streaks do not occur in the steel during its entrance into the chill. Thereby, “black stripes” are avoided, leading to a quality improvement of the strand. The frequencies and/or powers required for this purpose differ from those of heating inductors.
The process solves not only preheating problems or cooling problems existing before the melt outflow, but also temperature problems existing in the through-flowing melt itself. The process can readily be carried out since for this purpose only the electromagnetic field of the inductor or of the inductors, in particular only is frequency and power, must be adjusted accordingly. The process can be used especially advantageously in a horizontal continuous casting machine. However, it can also be used in other installation
Bruckner Raimund
Grimm Daniel
Dider Werke AG
King Roy
McGuthry-Banks Tina
Wenderoth , Lind & Ponack, L.L.P.
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