US2133329A - Method for heat treating furnace linings - Google Patents

Description

Oct. 13, 1933. w, E, MOORE ET AL 2,133,329

METHOD FOR HEAT TREATING FURNACE LININGS Filed Sept. 1, 1956 5 Sheets-Sheet 1 9 2 n mv M 2 3 m n m. m m 3 1.----. 3 m Hm 3 R mM r 1 m wAM/M t l1- 2 NM; i I: m NW. h S S G 5 N I v m ww w M m w m w w G I v 1 w m m M T S T w E m U. w W F F w i \v N M1 H ...?59 Fununm Huh 7 T F. I E M em 3 9 1 8 1 t c 0 Oct. 18,1938. w. E. MOORE ET AL METHOD FOR HEAT TREATING FURNACE LININGS 1936 5 Sheets-Sheet 3 7 Filed Sept. 1

S R O T N E V m mam Patented Oct. 18 1938 UNITED STATES PATENT OFFICE METHOD FOR HEAT LININ TREATING FURNACE Application September 1, 1936, Serial No. 98,918

. 2 Claims.

Our invention relates in general to refractory furnace linings and to the art of heat treating them, and more particularly to methods for burning in the refractory linings of furnaces and like structures and to a lining formed in situ.

Furnaces such as are used for melting, refining or treating metals, glass, or the like, or furnaces for boilers and the like are subject-to relatively high, temperatures and'are usually constructed with highly refractory linings. These linings are commonly made from flrebrick aggregates of silica or magnesite sand and the like, cemented or 5 bonded together by a binder, such as, for example, fireclay or hydrocarbons and similar substances. The fusing or maturing point of the binders employed is much lower than that of the refractory material from which the linings and particularly the bottoms are formed, and the use of such a binder impairs the effectiveness of the refractory material in direct proportion to the amount of binder used, as it renders the furnace linings more readily fusible at lower temperatures and more susceptible to disintegration. In the repairs of such furnaces, refractory substances with a bind ing material such as we mentioned, are usually employed and are subject to the same objections. It is also desirable that the lining have as dense and as homogeneous a surface as possible, so that the content of the furnace, such as molten metal, may not find its way into the body of the lining as the deterioration of the lining depends upon the extent of surface exposed to the corrosive action of the molten charge and the more porous the lining, the greater is the surface exposed. It is, therefore, a great advantage to fuse the lining of the furnace, particularly those parts which come into contact with highly v heated metals or highly heated or corrosive products of combustion and to fuse such portionswithout the use of binders or fluxes which will impair the resistance of the lining material to high temperatures and corrosion. I Heretofore, attempts have been made to burn in the bottoms of electric furnaces having highly refractory bottoms made from materials, such as magnesite, by means of the ordinary electric are which is generally set up to arc against a delta or T made of carbon electrodes placed across the bottom. While this plan may have some advantages for small furnaces, it becomes less practical as the size of the furnace increases and, even with small furnaces, it has heretofore been essential to reduce the melting temperature of a highly refractory material, such as magnesite, by adding to it a flux such as 8 to 10% of open hearth slag or silica, etc. The same difficulty applies to highly refractory bottoms and linings in open hearth furnaces and the like, as the heat is not available there from combustion of fuel to-burn in highly refractory bottoms. Even with such heat as is available, great damage resulting from.

the overheating thereof is usually done to the roof and other parts of the refractory lining of the furnace when burning in the bottom so that in open hearth furnaces the life of the refractory lining is still further sacrificed by fluxing it more liberally. The desirable condition, for example, in a metal melting furnace bottom and lining exposed to the action of molten metals and slag, is to have the inner layers thereof thoroughly fused together into a vitreous mass without the use of fluxes or binders. The heat resisting properties of the re- Y fractory material need not therefore be impaired by adulteration with fluxes, and We have found that such linings made according to our invention very successfully resist the dissolving action of slag and the boiling action of molten metal and like sources of lining deterioration.

The electric arc has a temperature sufiiciently highto melt any known refractory material if the are be concentrated or blown directly against the material. By means of our invention, we have provided a method and apparatus which utilizes the properties of the electric are for burning in or fusing the refractory linings, particularly the bottoms, banks or side walls, on all kinds of furnaces, electric, open hearth, or other kinds, but without overheating of other parts of the furnace structure. Furthermore, it is thus possible to provide a lining which is made from unfiuxed refractory material which may be formed in situ and fused to the shape of the furnace or like structure. The refractory material may be preformed, if desired, or a loose or granular material of any size particle may be employed, such as granular magnesite. Our device consists of a portable apparatus having supports for two electrodes of suitable material such as carbon or graphite in- .clinably mounted like a V with the arcing points nearest the bottom of the V. By means of this arrangement, the ,arc is blown or repelled vigorously by magnetic repulsion awe from the bottom of the V and may be directed against the material to be'fused or sintered in. The device is portableand is arranged for manipulation of the electrodes to different positions so that the arc may be brought to bear on practically any desired part of the furnace lining and thus fuse the refractory material progressively until the dewith a vitreous mass or to use the expression of the industry burned in. By our' invention, we provide a simple and convenient arrangement whereby an electric arc can be maintained between the electrodes of a; portable apparatus which can be readily manipulated so that the heat therefrom may be directed against any desired point.

In the accompanying drawings, illustrating present preferred embodiments of our invention, and in which like numerals are employed to designate like parts throughout the same;

Figure 1 is an elevation showing our device in position in a furnace;

Figure 2 is a view, partly in section, through one of the holders and to a larger scale than Figure 1;

Figure 3 is a view along the section IIL-III of Figure 2;

Figure 4 is a view along the section IV--IV of Figure 2; l

Figure 5 is a plan view of the electrode end of the apparatus.

Figure 6 is an elevation of the outer end of the control end of the apparatus;

Figures '7, 8, and 9 are detail views of the apparatus. p I

In the drawings, we have shown in Figure 1 aportable water-cooled electric torch T made according to our invention in position to burn in the bottom B of furnace F. It is to' be understood that the apparatus is suitable not only for burning in the refractory bottom but by proper manipulation other parts of the lining as well,

which are made of refractory material, may be treated.

The torch consists of two copper electrode holders l0, each mounted on an electrode carrying member or arm H. Each of the electrode arms H are slidably and rotatably mounted within a copper contact sleeve E2, to which a suitable terminal i 3 for the electric power supply is attached. Adjacent the holder end of the arms ii is a metal spacing member l4 having ends which embrace an insulated sleeve i5, each sleeve surrounding the arm H in such manner that each of the arms may be rotated within its associated sleeve. At the outer end of the electrode arms Ii, that is the end distant from the electrode holders. I0, suitable adjusting handl'es I6 are secured. By means of these handles, which are made of insulating material such as wood, fibre, or synthetic resin, etc., the electrode arms can be moved longitudinally and rotated, and the apparatus as a whole can be manipulated. Fixedly mounted on each electrode arm ll, between the handle l6 and contact sleeve I2 is a rock crank I. The cranks ii are swivelly connected by an insulating connecting link l8, preferably made of bakelite, fibre, or

other physically strong insulating material, so that when one arm is rotated in one direction, the other arm will move simultaneously in the opposite direction and in the same amount. The ends of arm I I adjacent the handles I 6 are rotatably secured together by'a spacing link IQ of insulating material. 1

The electrode arm II is preferably made from hollow copper tubing and is attached to the holder ID, in any suitable manner, as, for examp1e, by screw threading. The holder ID has an internal water passage therearound and to one end of this water passage a pipe 2| is attached.

This pipe is smaller in diameter than the inside of portions ,thus be passed through pipe 2| around passage 20 in holder t0, back through the annular space between the electrode arm and tube 2| and discharged through discharge connection-23.

Contact sleeves i2 are each mounted against movement within an insulating sleeve 25, which is received in a spacing member or support 26. The spacing member consists of an upper portion 27 and a lower portion 28, removably secured together. The ends of both of these portions are shaped to embrace and retain insulating sleeve in a predetermined position. A lifting hook 29 is secured to arm spacing member 26. The lower portion 28 has a rearwardly projecting horizontal arm 30 and a downwardly projecting bifurcated portion 3| which is pivotally secured by bolt 32 to the head 33 of a hollow screwthreaded upright or support 3 3, which is adjustably fastened tomovable truck 35.

Truck 35 has two front wheels 36 and a swivel wheel 3'! at the rear supporting a framework 38 through which the hollow upright 341 projects and is supported on the frame 38 by adjusting nut 39, which is in anti-friction engagement therewith. By manipulation of nut 39, the apparatus as a whole may be adjusted to the desired vertical position. A suitable counterweight may be placed, if necessary, on frame 38 to resist the turning movement due to the counterbalancede- 'Vice hereinafter to be-described.

In order to counterbalance the weight of the electrode-holders and electrodes so that the apparatus may be readily worked by man power, we provide a counterbalance device. This device consists of a balance arm' 4| having an upwardly inclined reduced end portion which is received in an opening 32 in supporting member 33. The

arm has various holes 33 along its length into any one of which, one end of a suitable spring 44 may be secured. The other end of spring 44 is fastened to hook member which, in turn, is

I I, and passes 4|, the other end in hook member 45, which, in

and by adjusting the connection 46, the proper counterbalancing force may be secured. In some installations, counterbalancing may be secured by means of suitably insulated counterweights (not shown) connected to arms H.

When placing the apparatus in position and at other times during the operation of the apparatus, it may be desirable to move the torch itself and the truck 35 as a unit. To prevent the torch .T from swingingin a horizontal plane with respect to the truck 35, we provide a lock member or latch 41 which is pivotally secured to the bifurcated portion 3| of spacing "member 26 so that when the torch is to be locked to truck 35,

- latch 41 will be in the position shown in Figures turn,-is secured in a suitable position to arm 30, i

framework 38. Secured to member 41 is a hook -groove 48 and thus permit the torch to freely swivel on the truck 35. In Figure 2, the latch locking engage-' 41 is shown in dotted lines out of meat.

The electrodes 50 of a suitable size and formed from a suitable material such as carbon or graphite, are secured in the electrode holder or clamp ill by any suitable means such as clamping wedges preferably made of copper, which are driven in from the upper side of the holder.

Operation of the apparatus A layer of refractory material is rammed in on the elementary bottom layers of the furnace lining which are usually of brick. The electrode end of .the'torch is projected through a door or other suitable opening into thefurnace and the water cooling circulation is established. An arc is then struck by rocking the arms I l by means of handle l6 until the tips of the electrodes 50 contact, after which they are rocked back slightly to draw the arc to the desired length, whereupon the free-burning arc is blown or projected against the lining at the desired point until the refractory lining is burned in or sintered. The

are is then moved from place to place on the lining until the desired area is burned in or sintered. Due to the construction of the torch.

the arms may be moved backwards or forward tilted and rotated, and the truck may be manipulated so that all the desired area of the furnace I lining may be processed.

It is also possible to disconnect the torch from the truck by removing bolt 32. The torch may then be suspended by means of hook from an overhead crane or the like, or from a convenient part of the structure to be treated, in which circumstances, the electrode end of the torch may ,be inserted into the furnace by first removing the roof or it may be introduced through any other convenient opening. In case the torch is suspended from a convenient support, the rock' cranks I! may be adjusted in position along the arms, so that sliding movement of the arms in the contact sleeves 2| is restricted. Many modern furnaces, especially electric furnaces, are of the tilting type'and have removable roofs and the overhead suspension of the torch is particularly applicable when treating such furnaces.

It will be observed that we have invented 'a flux free lining and a convenient and wholly satisfactory method and apparatus for heat treating the refractory lining of any type of furnace and which may be used for heat treating other refractory vessels, such as ladies, launders, spouts, etc., which require some kind of refractory lining. Linings so prepared and treated show pronounced economies and advantages in furnace operation. By our invention, not only can new linings be satisfactorily treated, but repairs can be expeditiously made to defective linings. Furthermore, the desirable refractory material may be burned in or fused without the use of fluxes, thus retaining unimpaired the maximum refractory and other desirable qualities of the lining.

While we have illustrated and described certain preferred embodiments of our invention, it will be understood that the invention is not limited thereto and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of our invention or the scope of the following claims.

We claim:

" e .1. The process of heat treating the refractory lining of a furnace or like structure, which consists in subjecting a limited area of said lining to the action of a mobile electric are blown against it and thereaftersubjecting other areas of the lining to the action of the electric arc

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