US1904664A - Lining a furnace by freezing - Google Patents

Description

April 18, 1933 H. NEUHAUSS LINING A FURNACE BY FREEZING Filed sept. 14, 1929 than through the @aten/ted Apr., ld. lg3d HEINRICH NHAUSS, F'DUSSELDORF, GEEW Emili@ A FURNACE BY FREEZXNG' Application tiled September la, 1929.

My invention relates to methods and apparatus for melting charges ina completely neutral lining and in a furnace in which the heat is communicated to the metal otherwise lining against which the charges rest. I

My invention is suitable for use in other electrical furnaces than in induction furnaces but finds its highest development not only in induction furnaces but in furnaces of this type in which the inductor surrounds an electrically inducting charge and is artificially cooled. y

One purpose of my. invention is to rapidly cool the outer part of an electrically conducting furnace charge heated through the action of a primary coil surrounding the charge so that4 the molten interior partof the charge will be protected by a chilled outer layer.

further purpose is to provide protection for a molten charge by inefficient furnace operation, freezing the outer part of the charge or freezing a slag around the walls of the crucible to form a protective lining which may be of a dierent material than, or of the same material as that which is being melted.

A lfurther purpose is control the extent of freezing of a protective. lining within a furnace by the heat conductivity and the amount of artificial cooling of the exterior covering about the lining.

Further purposes will appear in the specication and in the claims.

My invention relates to the process involved and also to apparatus by which the process may be carried outu ln the drawing I have preferred to illustrate one main form only of an invention which obviously may appear in various forms, selecting a form which is practical, effective and fully operative and which at the same time Well illustrates the principles involved.

Figure 1 is a diagrammatic view showing an old form of furnace.

Figure 2 is a diagrammatic view corresponding generally to Figure l, but showing matter illustrative of one embodiment of my invention.

Figure 3 is a diagrammatic view correcurrent.

Serial No., 893,669.

spending generally with Figure Il and with y a liquid charge in place.

Figurc l is a diagrammatic. view corre-- sponding generally with lig. 3 but with additional cooling coils in the furnace base.

ln the drawing similar numerala indicate like parts.

ln Figure l l show an oldtype of furnace in which the Crucible 5 is formed of any usual material such as magnesia and in which the Crucible is heat insulated along the outside by a powdered filling such as magnesia poivder 6, between it and a limiting electrically insulating shield 7 by which a high frequency coil 8 is protected and by which the powder is held in place.

ln this old. form of furnace the entire charge is melted up to the side walls of the furnace and, assuming uniform conductivity, the conditions of coupling will cause most of the current to be generated in the outer layer of the charge adjoining the crucible.

lt has been the practice in the past to heat vinsulate the Crucible as much as possible and the water cooling of the coil with or with- -out multiple paths of flow through the turns of the coil has been for the purpose of protecting the coil and not with any thought of cooling the outer part of the charge.

The cooling of the inductor coil is beneficial not only in protecting against actual injury to the coil by the heat generated Within it and such heat as has inevitably reached it from the charge by conduction and radiation but has kept the resistance of the coil down to advantage, though it has been needed muchless with high frequency current than would be the case with lower frequency There has been little advantage, however, from refrigeration of the coil-cooling content as the additional advantage of reduced resistance is small.

Vith my invention additional cooling of the coil becomes edective through the better heat conductivity of the Crucible or filling, or both, to more easily and effectively produce and control the effect of the freezing within the Crucible.

My invention contemplates selectively chilling the outer part of the charge, which (ill) both can be changed. In the illustration I have preferred to secure it by the use of a filling materialwhich is thinner or is a comparatively good heat conductor as compared with' magnesia powder very generally used.

My method and apparatus are eifective to maintain any otherwise fusible lining as a coating upon the interior walls of the crucible by Cooling and to maintain a predetermined lining thickness by this means whether the lining be of the same material as the charge or not.

In Figures 2 and 3 a Crucible 5', coil 8, and restraining and insulating shield 7 are shown as in Figure 1, but a thin layer of filling ma- -f terial9 is used such as'substantially pure chromium ore, which is reasonably heat conductive with the result that with whatever means of coil cooling is used the outer part of the furnace is chilled, chilling the crucible sufficiently to freeze an outer part ofa charge within the furnace. This frozen insulating material may be a special slag intended for this purpose only and within which after it is frozen the Charge may be placed, as in Figure 2 where an acid slag 10 is shown, or it may be the same material as the charge itself, as in Figure 3 where the insulating material comprises a frozen layer 11 holding a molten charge 12 of a highermelting oxide for example.

Instead of a chromium ore powder any other material may be used which is reasonably but not excessively heat conducting, and which is not a conductor of electricity.

It will be evident that in the case of Figure 2, for example, the Crucible could be filled with a molten charge of the character desired for the lining-independently of the ultimate Charge of the furnace-and that a predetermined depth of this molten charge can be frozen within the Crucible, the balance of the charge being then poured out if the ultimatecharge is intended to be different.

The Charge from which an outer layer is to be frozen need not be initially molten but can be wholly melted within the Crucible with subseqent freezing of the outside layer through the control offered by artificial cooling of the inductor coil, the melting being effected with less or with no artificial cooling and the artificial cooling being then applied to the desired extent in order to effect and control the freezing.

In order tc increase the control over the thickness of the lining I show in Figure Il cooling coils 8 about the bottom of the fur nace through these coils will not ordinarily be required as 4any desired cooling of the base of the furnace can so easily be effected by various ways of cooling the base upon which the furnace rests.

The inductor coil 8 shown is the same in all forms and is arranged for liquid cooling through pipes 13, 14 and 15, of which 13 and 15 may be inlet and 14 outlet or the reverse, if multiple flow of cooling fluid be desired. The cooling coil 8 hasfluid supply and outlet pipes. 13', 15', 14.

The alternating current is supplied from the source 16 through leads 17 and 18 and power factor correction is provided by capacity 19.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain part or all o f the benefits of my invention without Copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I Claim as new and desire to secure by Letters Patent ist- 1. The method of forming and maintaining a lining in a pool surrounding induction furnace having a Container and a surrounding refractory, while operating the furnace which consists in chilling a molten content against the wall of the furnace and in maintaining it in solid form by continuously artificially cooling the content from the exterior of the furnace through the container while inducing current in a charge within the lining.

2. The method of maintaining a predetermined lining thickness within a pool surrounding induction furnace holding a molten charge, which consists in artificially coolin the exterior of the furnace sufficiently to chil a limited depth of material next to the furnace wall within the furnace while inducing current in the charge within the lining.

3. The method of lining an induction furnace of the pool-surrounding inductor coil type, which consists in artificially chilling a layer of material against the interior of the furnace and in maintaining it in chilled condition while inducing current in a charge within the lining.

4. The method of lining an induction furnace of the pool-surrounding inductor coil type and at the same time operating the furnace, which consists in artificially chilling a layer of material different from that of the intended charge against the interior of the furnace and in maintaining it in chilled condition while inducing current in the charge within the lining.

5. The method of lining an induction furnace of the pool-surrounding inductor coil type, which consists in artificially chilling 4a incassa layer of material constituting a part of the intended charge against the interior of the furnace and in maintaining it in chilled condition while inducing current in the charge within the lining.

6. The method of building up and maintaining a lining for an induction electric furnace, which consists in lining the furnace with a material free from injurious edect upon the charge and molten at the normal temperature to Which the charge is to be raised, in melting the material by inducing electrical current. within it and in freezing the lining material by artificially conducting heat from the exterior of the furnace while inducing current in the charge within the lining so as to maintain the lining at a temperature below the temperature to which the charge is to be raised, providing a noninetallic heat insulator about the crucible and a non-metallic heat conductor by which the heat is conveyed from the furnace.

7.. The method of maintaining a predetermined lining thickness Within a refractory furnace Crucible which consists in melting a lining material within the furnace by electric current induced within it, in cooling the lining material to a temperature below its melting point and below the temperature of the charge to chill sufficient depth of material to act as a lining, conducting the heat away from the crucible by non-metallic partially insulating material and in maintaining the lining material in chilled condition While melting the charge within the furnace by passage of alternating, current about the charge.

8. The method of forming a lining within an induction furnace of the pool surrounding type having a non-metallic refractory container, a finely divided refractory outside of it and an inductor coil surrounding the refractory, which consists in melting a material suitable for the lining within the Crucible by electrical current induced within it, increasing heat loss of the exterior of the lining material melted by selection of a heat conducting refractory to chill a lining covering fthe interior of the crucible while inductively maintaining the body of cooling the oxide to maintain its temperature below the softening point and in main- Jtaining molten metal in contact with the lining.

ll. The method of operating a furnace, which consists in fusing a refractory oxide, in spreading that oxide as a lining in the furnace, in cooling the oxide to solidify it in place as a lining, in continuously artiically cooling the oxide to maintain its temperature below the softening point and in passing alternating current around the furnace outside of the lining to inductively heat the metal within the lining.

12. A solidified-in-place metallic oxide lining, containing a molten metallic charge within' that lining and means forcontinuously artificially cooling the lining to prevent melting out of the lining by heat from the charge.

HEINRICH NEUHAUSS.

the material within the furnace molten to y be poured out to leave the lining or to constitute the charge.

9. An electric induction furnace, a furnace body, a fusible chilled lining therein, a refractory highly heat conductive couering about the body and a cooling coil about the covering comprising a high frequency inductor of an electric furnace in heat transfer with the covering.

10. The method of operating a furnace, which consists in fusing a refractory oxide, in spreading that oxide as a lining in the furnace, in cooling the oxide to solidify it in place as a lining, in continuously artificially

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