US2676011A - Construction for the tap holes of open-hearth furnaces - Google Patents

Description

April 20, 1954 F. H. LOFTUS ETAL 2,676,011

CONSTRUCTION FOR THE TAP HOLES OF OPEN-HEARTH FURNACES Filed Jan. 28, 1950 2 Sheets-Sheet 1 INVENTORS FRED A. LOFTUS MD BY VINCENT Q- noa uoue April 20, 1954 F. H. LOFTUS ET AL 2,676,011

CONSTRUCTION FOR THE TAP HOLES OF OPEN-HEARTH FURNACES Filed Jan. 28, 1950 2 Sheets-Sheet 2 INVENTOR FlED H. LOFIUS L BY VINCENT IL TEOGLIONE- Patented Apr. 20, 1954 CONSTRUCTION F OR THE TAP HOLES OF OPEN-HEARTH FURNACES Fred H. Loftus, Mount Lebanon, and Vincent R. Troglione, Wilkinsburg, Pa., assignors to Loftus Engineering Corporation, a corporation of Maryland Application January 28, 1950, Serial No. 141,024

6 Claims- 1 This invention relates to metallurgical furnaces, particularly to furnaces for melting and refining metal and metallic compositions, such furnaces as the open hearths employed in the production of steel. The invention consists in certain new and useful improvements in furnace construction at and below the outlet end of the tap hole of the furnace.

An. open hearth furnace consists of a chamber having a hearth, side walls, end walls and roof constructed of refractory material, supported and externally reinforced and tied by means of a steel framework. The hearth of the furnace is dished, providing a basin that sustains the charge of metal and ingredients required to produce a specified heat of steel. At the two ends of the furnace ports are provided, and during furnace operation fuel and air are admitted through the port at one end of the furnace, whereby flames and hot gases are projected across the hearth to supply the required heat to the furnace charge. The hot gases or products of combustion exit through the port at the opposite end of the furnace. From time to time the furnace is reversed; that is to say, the port which had been serving as the firing port becomes the outgo port, and the port which had been serving as the outgo port becomes the firing port. And so the operation of the furnace is continued, slag being flushed off and required materials added to the charge. After several hours of operation the metallic charge is reduced to desired analysis, whereupon the heat is tapped.

For purposes of tapping the metal, a hole opens laterally through the body of the furnace hearth, and this holecalled the tap hole-is normally closed and sealed by means of a stopper formed of refractory material. In order to tap a heat this stopper is opened or drilled through, and the molten metal flows outwardly from the hearth to an inclined spout leading from the outlet end of the tap hole to a ladle or other receptacle.

The inclined spout consists of a refractory.- lined chute, upon which the stream of molten metal emerging from the tap hole flows to the ladle. The spout is detachably joined to the furnace structure at the outlet end of the tap hole, and in the course of service the refractory lining of the spout becomes worn. For this reason one or more standby spouts are provided, whereby a spout whose lining has become worn in service may be readily removed and a new one substituted.

It has been found in the operation of open hearth furnaces that molten steel tends to escape in small quantities through the joint between the spout and the furnace structure at the outlet end of the tap hole. Furthermore, the refractory structure adjacent to the outlet end of the tap hole suffers under the extreme heat to which it is subjected, and frequently small avenues of escape develop, with the effect that, during the tapping of a heat, molten metal seeps downwardly and drips upon certain parts of the structural steelwork that supports the furnace. The molten metal, thus draining upon the steel-work, over a period of time cuts through the steel and weakens the basal structure of the furnace.

In the normal operation of an open hearth furnace it is necessary to make bottom after the tapping of each heat. Making bottom consists of filling in the holes or recesses worn in the hearth of the furnace by the erosive action of the molten metal. These holes or recesses are filled-in with particulate refractory material which, under the heat of the furnace, becomes fused into place, restoring the surface of the hearth to substantially normal contour. Sometimes the recesses appearing in the furnace hearth are located in such positions that all of the molten metal will not drain from the furnace when it is tapped. When this occurs the tapping spout is removed, and the residual pool of molten metal is blown by an air jet into the tap hole; sometimes the metal cannot be entirely removed in this way and it is necessary to form in the hearth a groove leading from the residual pool of metal to the upper end of the tap hole, whereby the residual metal may drain from the furnace. In either case the residual molten metal is caused to flow into the tap hole, whence it spills from the outer end of the tap hole and solidifies upon the parts of the furnace structure located therebelow, forming a solid scab of steelknown in the art as a monkey.

It will be understood that the residual metal thus removed from the furnace, while being sufficiently molten to run through the tap hole, does not have the temperature nor the heat content of the main body of molten steel which was tapped from the furnace, and it is for this reason that the residual metal solidifies quickly and forms a monkey. It is more practical to allow this metal to solidify on the furnace structure beneath the tap hole, as described, where it can be pulled away by means of the usual overhead crane, than to permit it to solidify in the spout. It is far more costly to remove solidified metal from the spout and make the spout repairs necessary than to remove a monkey from the furnace structure immediately below the tap hole outlet. However, the removal of monkeys is an objectionable incident to furnace operation, since the solidified metal sometimes freezes and anchors to the steel-work of the furnace body, requiring considerable time to effect its removalsometimes with injury to the furnace steel-work.

The major object of my invention is two-fold:

(1) To protect the steel-work of the furnace from the deleterious effects of molten metal that drains through the joint between the tap hole and the spout.

(2) To facilitate the removal of monkeys and to minimize damage to the furnace structure while so doing.

The invention will be understood upon reference to the accompanying drawings, in which Fig. 1 is a view of the central body portion of an open hearth furnace through which the tap hole opens, the view being fragmentary and illustrating the structure partly in side elevation and partly on the section planes indicated at 1-1 in Fig. 2;

Fig. 2 is a fragmentary sectional view of the furnace, as seen on a vertical plane extending through the axis of the tap hole, the section plane being indicated at II-II in Fig. l; and

Fig. 3 is a detailed view of the device in which our present invention is centered, the illustration being a horizontal section on the plane indicated at III-III in Fig. 2.

In view of the general description presented in the preamble of this specification, it is considered needless to illustrate and describe the complete structure of an open hearth furnace. The invention will be readily understood upon reference to the fragmentary illustrations presented.

Referring to the drawings, the reference numeral 2 indicates the refractory backwall and 3 the refractory hearth of an open hearth furnace of conventional construction. The furnace structure is borne upon and contained within a steel framework comprising horizontal hearth beams 5, overlaid with a pan 5 formed of heavy steel plate, upon which the insulation and refractory body of the furnace hearth is supported. The hearth beams 6 are supported on heavy concrete piers that are spaced from the opposite sides of the tap hole 4, which is located on the transverse center line of the furnace and extends through the refractory body of the furnace hearth. The concrete piers do not appear in the drawings, but may be conventional in arrangement and construction. An open hearth furnace of the construction specified herein is known in the art to be of pan-type construction.

The walls of the furnace (the conventional sloping backwall only being shown herein), are laterally supported and reinforced by means of buckstays 8 and cast steel or iron breast plates 9 and I2. The front and back buckstays are securely anchored at their lower ends to the front and back edges of the basal structure of t. e furnace, and at their upper ends the buckstays of the backwall are cross-connected to the upper ends of the buckstays of the front wall (not shown) of the furnace.

Extending outwardly and downwardly from the outlet end of the tap hole 4 is a, spout iii. This spout comprises a trough formed of cast ferrous metal, which is lined with refractory material II. The breast plate 12, through which the tap hole 4 opens, includes on each side of the outlet end of the tap hole an integral, vertically extending web or flange l3 which is notched at Hi. On each side of the spout a pin or boss I5 is integrally formed, and these pins or bosses are seated in the notches Hi, thereby removably securing the upper end of the spout to the furnace structure, with the refractory-lined trough of the spout joined, as at IS, with the outlet end of the tap hole 4. The lower end of the spout may be vertically supported in conventional manner, upon the usual platform or by means of an overhead hanger (not shown). As thus organized the spout may be readily removed and replaced as need be.

In open hearth furnaces as heretofore constructed, it is at the joint it where a seepage of molten metal develops during the repeated tapping of the furnace in operation. A fissure or crack opens downwardly through the refractory material installed at 20 beneath this joint, and, during each tapping of the furnace, molten metal drains through the fissure upon the steel pan 5 and hearth beams 6 below. The molten metal, thus draining and dripping downwardly, cuts through the steel pan and hearth beams below the joint 18. The furnace structure is thus wounded, and the wound is located at the middle of the span of the furnace-supporting beams between the piers, where a diminution in structural strength is particularly objectionable.

The removal of monkeys from the wounded furnace structure is not only rendered more difficult, but the damage to the structure is aggravated.

In the elimination of these objections, the furnace structure of this invention is fashioned to provide for the clear fall of the draining molten metal to the pit beneath the furnace, where it does no harm and can be removed when it is convenient to do so. The means embodied in the furnace structure to this end may be termed a base-protecting device.

More specifically, the two hearth beams ta, which in prior furnaces extend without interruption between the supporting piers, are discontinued for an interval beneath the outlet end of the tap hole, and means are provided for integrating the end of the beams at such interval, to afford a steelwork construction that is amply sturdy, while providing a vertical passage for an unobjectionable drainage of molten metal into the pit.

Such means consist in what is termed a splashplate, comprising a structural casting, preferably of iron or steel, of the approximately C-shape appearing in horizontal section in Fig. 3. The casting includes two side flanges or webs 22, between which inwardly extends a heavy web 22 of approximately semi-circular or C-shaped body substantially embraces a vertical line extending downwardly from the outlet end it of the tap hole as viewed in plan. This web 22 extends vertically in transverse or vertical section (see Fig. 2), and is provided with two sets of vertical reinforcing flanges 23 and 24, and two set of horizontal reinforcing flanges 25, 26 and 27. In Fig. 3 the ends of the two beams ta which are interrupted in extent beneath the outlet of the tap hole 4, have their medial webs 6b continued beyond the basal flanges 60 to receive in bolted union two steel angles 28. The adjacent hearth beam 6, whose extent is continuous beneath the furnace, carries two heavy transverse steel plates 28, to which the angles 28 at the ends of the beam 611 are welded. The plates 29 are spaced to receive snugly between them the structural casting 2 !-2:i, and such casting is securely assembled in the structure, by means of bolts 39 shown in Fig. 3. The plates 29 are in and of themselves a very sturdy structure, but they nonetheless are reinforced by mean of paired angles 3i, bolted to the vertical web of the adjacent hearth beam t. Over the ends of the discontinued beams 6a a heavy structural channel 32 is welded to the face of each plate 29, providing not only reinforcement for the plate, but a sturdy seat upon which the angle-reinforced ends of the beams 5a may bear, whereby all of the load on the beams need not be carried solely by the welded unions of such ends of the beams dc to the plates 29. In the case of large furnaces, or furnaces built with extra heavy steel-work, the plates 29 may be dispensed with, and the channels 32 may be united to the beam 6 (Fig. 3). The vertical webs of these channels may be bolted or welded to the ends of beams to and to the fianges 25 cf the structural casting 24-27.

referring particularly to Fig. 2, it will be noted that the arcuate web 22 of the structural casting carries at its upper and lower edges horizontal flanges 33 and 34 which are integrally united at their ends to the vertical webs 23. In the arcuate channel thu formed by and between the flanges 23, 33 and 34, and the arcuate web 22, a heavy lining or facing 35 of refractory brick is installed. This structure eliminates the objections alluded to, and affords reinforcement of the furnace steel-work, and many other advantages. It may be noted that the pan plate 5 of the furnace is out out above the structural casting 2i--2'I, so that metal draining from the joint iii and through the body 29 of refractory material may readily drop into the pit beneath the furnace. For purposes of supporting the refractory material 28 when it is initially installed, a small plate at is installed, as shown in Fig. 2. This plate may be readily renewed when it is desired to repair or replace the refractory material (20) beneath the outlet end of the tap hole.

It will be noted that the structural casting inserted, as illustrated and described, in the furnace structure is horizontally recessed or laterally inset beneath the outlet of the tap hole, to the end that any metal seeping from the joint [6, or draining from the outlet end of the tap hole when the spout It is removed for cleaning the hearth of the furnace while making bottom, has a clear fall to the pit beneath the furnace. Such small quantities of molten metal as may possibly adhere to the structure beneath the tap hole will soldify upon the refractory facing 35. If during a prolonged period of furnace operation a heavy scab of solid metal should build up upon the refractory facing or shield 35, it may readily be torn away by means of the usual overhead crane, possibly taking the refractory facing 35 with it. This presents no serious objection in operation, since the refractory facin can be readily renewed without unduly delaying furnace production.

While the invention has been described as it is particularly adapted to open hearth furnaces, it will be understood that the structure of the invention may be employed in other types of metal melting and refining equipment. It will further be understood that within the spirit of the invention defined in the appended claims, many variations and modifications are held in contemplation.

We claim:

1. In an open hearth furnace of pan-type construction, a furnace body having a dished hearth of refractory material laterally supported by breast plates and vertically supported upon a structural steel base comprising an assembly of steel hearth beams that extend longitudinally beneath the furnace body, a tap-hole for molten steel opening laterally through the hearth structure and terminating in an outlet located above such of said hearth beams as are positioned immediately below said breast plates, and piers spaced from the opposite sides of said tap-hole for the support of said structural steel base; the improvements herein described wherein the hearth beams located below said breast plates are of interrupted extent in the region below the outlet of said tap-hole, a splash-plate comprising a metal body incorporated in the steel base at said region of interruption in the extent of the hearth beams, the metal body of said splashplate having a recess which is of general 0 shape as viewed in a horizontal plane and extends inwardly beneath said breast plates into position vertically below said tap-hole outlet, to provide for the vertical drainage of molten steel leaking from said tap-hole outlet in the region of said interruption in the extent of the hearth beams.

2. In an open hearth furnace of pan-type construction, a furnace body having a dished hearth of refractory material laterally supported by breast plates and vertically supported upon a structural steel base comprising an assembly of steel hearth beams that extend longitudinally beneath the furnace body, a tap-hole for molten steel opening laterally through the hearth structure and terminating in an outlet located above such of said hearth beams as are positioned immediately below said breast plates, and piers spaced from the opposite sides of said tap-hole for the support of said structural steel base; the improvements herein described wherein the hearth beams located below said breast plates are of interrupted extent in the region below the outlet of said tap-hole, a splash-plate comprising a metal body incorporated in the steel base at said region of interruption in the extent of the hearth beams, the metal body of said splash-plate having a recess which is of general 0 shape as viewed in a horizontal plane and extend inwardly beneath said breast plates into position vertically below said tap-hole outlet, and a vertically disposed facing of refractory material extending along the edge of said recess in the splash-plate body, such refractory faced recess providing for the vertical drainage of molten steel leaking from said tap-hole outlet without prohibitive damage to said hearth beams while permitting the ready removal of a monkey of metal accumulating on the splash-plate body.

3. In an open hearth furnace of pan-type construction, a furnace body having a dished hearth of refractory material laterally supported by breast plates and vertically supported upon a structural steel base comprising an assembly of steel hearth beams that extend longitudinally beneath the furnace body, a tap-hole for molten steel opening laterally through the hearth structure and terminating in an outlet located above such of said hearth beams as are positioned immediately below said breast plates, a, tapping spout removably mounted at the outlet of said tap-hole in a joint located above said last mentioned hearth beams, and piers spaced from the opposite sides of said tap-hole for the support of the structural steel base; the improvements herein described wherein the hearth beams located below said breast plates are of interrupted extent in the region below said joint, a splashplate comprising a metal body incorporated in the steel base at said region of interruption in the extent of the hearth beams, the metal body of said splash-plate having a recess which is of general shape as viewed in a horizontal plane and extends inwardly beneath said breast plates into position vertically below said joint, to provide for the vertical drainage of molten steel leaking from said tap-hole outlet through said joint.

4. In an open hearth furnace of pan-type construction, a furnace body having a dished hearth of refractory material laterally supported by breast plates and vertically supported upon a structural steel base comprising an assembly of steel hearth beams that extend longitudinally beneath the furnace body, a tap-hole for molten steel opening laterally through the hearth structure and terminating in an outlet located above such of said hearth beams as are positioned immediately below said breast plates, a tapping spout removably mounted at the outlet of said tap-hole in a joint located above said last mentioned hearth beams, and piers spaced from the opposite sides of said tap-hole for the support of the structural steel base; the improvements herein described wherein the hearth beams located below said breast plates are of interrupted extent in the region below said joint,

through said joint without prohibitive damage to said hearth beams while permitting the ready removal of a monkey of metal accumulatin on the splash-plate body.

5. In an open hearth furnace the combination of a horizontal pan-type structural steel base portion of such furnace beneath an outlet end of a tap-hole thereof, a splash-plate comprising a vertically extending metal body of general 0- shape in horizontal section, and means for uniting said body in the furnace base portion be neath said tap-hole with said C-shaped body of the splash-plate positioned substantially to embrace a vertical line extending downwardly from said outlet end of the tap-hole and with the open side of the c directed outwardly from said base portion, said means comprising at back and closed side of the C a pair of vertical webs that extend rearwardly, one from each end of the metal body of the C, for rigid integration with the said horizontal structural steel base portion.

6. In a claim as in claim 5 wherein said splashplate carries upon the concave face of its vertically extending C-shaped body horizontal and vertical refractory-supporting members.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 100,003 Bessemer Feb. 22, 1870 439,924 Aiken Nov. 4, 1890 682,512 Wellman et a1. Sept. 10, 1901 1,149,203 Marshall Aug. 10, 1915 2,005,143 Hogg June 18, 1935 2,104,406 Sorensen et a1. Jan. 4, 1938 2,209,786 McCarroll et al. July 30, 1940 2,310,635 Hopkins Feb. 9, 1943 2,464,714 Petersen Mar. 15, 1949 2,490,382 Schueler Dec. 6, 1949 2,513,082 Dreyfus June 27, 1950

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