GB2188132A

GB2188132A - Slag retaining device for use in converters or ladles

Info

Publication number: GB2188132A
Application number: GB08606716A
Authority: GB
Inventors: Michael Donald Labate
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-03-19
Filing date: 1986-03-19
Publication date: 1987-09-23
Anticipated expiration: 2006-03-19
Also published as: GB8606716D0; DE3610449C2; GB2188132B; DE3610449A1

Abstract

A device for the separation of slag and its retention in a converter consists of a closure 10, 11 commonly called a dart, adapted to be placed either manually or automatically in the tap hole of the converter or ladle during tapping of molten metal therefrom. The device may have smooth exterior surfaces or may be externally ribbed enabling it to substantially close the tap hole and impart a swirling motion to the molten metal and slag therein. The device may be formed of material having a specific gravity lower than that of the metal in the converter or ladle, but higher than that of the slag. <IMAGE>

Description

SPECIFICATION Slag retaining device for use in converters, ladles, or the like This invention relates to a slag retaining device for use in tapping converters or hot metal ladles during the tapping of steel therefrom. The use of the device permits the tapping of steel free from slag.

Prior devices for blocking or minimizing slag carry over when tapping molten steel from a converter or ladle are known in the art and a typical disclosure of a device requiring manual placement is seen in Canadian Patent No. 822,607. An example of a prior artfloatable device may be seen in U.S. Patent 4,462,574, W. M. Keenan, and U.S. Patent 4,494,734, M.D. La Bate.

It is an object ofthe present invention to overcome the disadvantages of the above-mentioned prior art and to provide an improved automatically placed floatable device for minimizing slag carry over during tapping of molten metal from a converter or ladle and to provide a manually insertable device forming a closure having guide means and movable into the tap hole ofthe converter or ladle at a desired time to prevent molten slag from flowing therethrough. The device in its preferred form is combined with a cylindrical refractory sleeve positioned in the tap hole of the converter or ladle and forms circular valve seat for engagement with the slag retaining device and avoids the erosion of the material heretofore used in defining the tap hole which frequently resulted in an irregularly shaped tap hole and inability of a slag retaining device to properly seat therein.

The slag retaining device ofthe present invention is disclosed herein in two forms. The first of these is a manually insertable stopper body, commonly called a dart, which incorporates a depending guide member engageable in the tap hole and insures the accurate placement of the stopper body in closing relation to the tap hole. Alternate configurations of the stopper body increase the efficiency of the same with respect to its placement in and engagement with the tap hole particularly when the tap hole is defined by a cylindrical refractory member preformed and positioned in the refractory lining of the converter or ladle in registry with the tap hole therein.

Avariation of the form of the slag retaining device has a specific gravity lower than that of the steel, but higher than that of the slag therein in the converter or ladle and is automatically partially positioned in the tap hole where its configuration causestheswirling ofthe metal and the slag which may be visually observed and indicates that the slag is about to reach the tap hole whereupon the tapping of the converter or ladle may be terminated.

Description ofthe drawings Figure lisa vertical section through the manually insertable form of the slag retaining device; Figure 2 is a top plan view ofthe slag retaining device; Figure3is a side elevation with parts broken away showing the slag retaining device with annular grooves formed in its exterior surface; Figure 4 is a perspective view of an alternate form ofthe device seen in Figures 1 and 2whereinthe guide rod is eliminated; Figure 5is a perspective view of a further alternate form of the slag retaining device of Figure 4; Figure 6is a cross sectional view of a portion of a convertershowing a cylindrical refractorysleeve defining the tap hole therein with molten steel above the tap hole and molten slag thereon and the slag retaining device of Figure 1 positioned in the tap hole; and Figure 7is a cross sectional view of a portion of a ladleshowingthetap holethereinandacylindrical sleeve therein defining said tap hole with molten steel above the tap hole and molten slag thereon and the slag retaining device of Figure 4 engaged in the tap hole.

In the form ofthe invention seen in Figures 1,2 and 6 of the drawings, an upright, oval shaped body, which is cross sectionally circular, is preferably formed of upper and lower modified cone-shaped members 10 and 11 arranged in oppositely disposed relation to one another has its area of largest diameter 12 at its center, said area of largest diameter 12 being substantially greater than that of a tap hole in a converter or ladle in which it is to be placed.

The slag retaining device is shown assembled on a steel rod 13 with a portion of the rod 13 belowthe lower member 11 enclosed in sleeves 14 offireproof material such as a suitable refractory and including a cap 15 surrounding a fastener on the lower end ofthe rod 13. The rod 13extendsverticallythroughthe members 10 and 11 and upwardly and outwardly thereof and provides a portion of the slag retaining device that may be detachably engaged by a mechanical device used to position the slag retaining device in the tap hole.

In Figure 6 ofthe drawings, the slag retaining device is shown inthetap hole of a converter 16 in which a pool of molten metal Stopped buy a layerof molten slag S are illustrated. The tap hole in the converter 16 is defined by a refractory sleeve 17 which extends through the layer of insulating refractory 18 which lines the converter 16.

Those skilled in the art will observethattheslag retaining device with its smooth, modified, global shape is inserted into the converter or ladle before a vortex forms as the final portion of metal startsto drain out ofthe tap hole. Thetime may be calculated from the estimated tonage of metal contained in the converter or ladle and the size and the shape ofthe tap hole in relation to the contents. It is desirablethat the siag retaining device be introduced into the converterorladlewithin a calculated time of between cne to two minutes before the end ofthetap when all of the metal is drained from the furnace.

The preferred density of the slag retaining device for use in steel making is preferably between .12 to .22 Ibs. pew square inch. The material ofthe upper and lower members 10 and 11 is preferably substantially indissoluble in the molten metal and the slag and its density is such that it float at or near the surface of the molten steel M and atthejunction of the molten metal and the slag where its contoured modified global shape permits the molten steel to flow around the same and cause a bobbing action before finally seating in the tap hole where it stops the slag from flowing through the tap hole.

It will also be seen that the modified global shape of the slag retaining device when placed in the vortex formed by the molten metal above the tap hole will rotate several times before seating itself firmly. The rotation insures the desirable positioning ofthe slag retaining device in the tap hole which may be uneven or erroded which would otherwise tend to tiltthe slag retaining device and permit an undesired amountof slag to flow out ofthetap hole.

In orderto form the modified global-shaped body of the slag retaining device comprising the upper and lower body members 10 and 11, a suitable mix may comprise refractory cement 8 Ibs., fine iron ore concentrate 161bs., steel shot30 Ibs., stainlesssteel fibers 2 Ibs., and water from 3 Ibs. to 5 Ibs. This formula will produce a body having a density of from 0.15 to 0.17 Ibs./inch 3 although any density between that of the slag 0.10 Ibs./inch 3 and that of molten steel, about 0.25 Ibs./inch 3 is suitable.

It will occurto those skilled in the artthatthe shape of the exterior of the slag retaining device of Figures 1,2,4 and 6 ofthe drawings may be changed to increase its efficiency and one such modification is illustrated in Figure 3 of the drawings wherein the modified, global-shaped body of the slag retaining device is formed of upper and lower members 20 and 21 respectively, assembled on a steel rod 22, the members 20 and 21 provided with several annular grooves 23 spaced with respect to the area of widest diameter 24 ofthe device. A broken away section of the device is illustrated in Figure 3 of the drawings and the material of the device may be the same in the upper and lower members 20 and 21 or it may differ as to density so as to desirably control the floating relation of the device with respect to the molten metal and slag as hereinbefore described.The annulargrooves23assistinthefinal closing ofthe tap hole when the same moves in a bobbing action and/or rotates as it nears the same in the vortex of the metal flowing through the tap hole as defined by a refractory sleeve 17 which is illustrated in Figure 6 ofthe drawings and hereinbefore described. A further modification of the invention may be seen in Figures 5 and 7 ofthe drawings and in Figure 5upper and lower portions 26 and 27 respectively of a slag retaining device having a modified global shape with flat upper and lower ends 28 and 29 respectively is provided with circumferentially spaced substantially verticaliy positioned arcuate ribs 30 and grooves 31, the ribs 30 and grooves 31 being alternately arranged.The modified slag retaining device of Figure 5 may be used as illustrated, like that of Figure 4, by being positioned in the vortex of the metal flowing out of the tap hole in a convererorladle where itwill move in a bobbing and/or rotating motion as the level ofthe metal nears the tap hole so thatitwill seatinthetap hole and allow some metal toflowtherethrough creating a substantially increased swirling vortex in the metal and slag which will visually indicateto an operatortheproximityof the slag layer to the tap hole and enable the operator to move the converter or closethetap hole in a ladle to prevent the slag from entering the same.The modified forms of the invention are formed of the same material hereinbefore described and of the same or comparable densities to control their desired floating relation with respect to the metal and the slag thereon being control led with respectto preventing the entry of the slag into the tap hole.

One of the problems heretofore existing in tapping converters, hot metal ladles, and the like, is the irregular shape of the tap hole through which the hot metal flows. The refractory shape normally forming the tap hole in the prior art has been formed by placing a thin metal tube in the tap hole, the tube being of a slightly smaller diameter than the tap hole in the vessel and subsequently forming refractory clay in a putty-like consistency around the tube in the well which surrounds the tap hole as a result ofthe building up ofthe refractory lining in the vessel from refractory bricks and the like.

In the present disclosure, thetap hole in the refractory lining in the vessel is formed by a preshaped, prefired, cylindrical sleeve resembling a sewertilewhich is positioned in the vessel in registry with the tap hole therein and the refractory lining of the vessel formed directlythereabout.The preshaped, prefired, refractory sleeve is considerably more efficient in resisting erosion of hot metal flowing therethrough than the above described structures ofthe prior art and they are particularly useful in maintaining a circular configuration in which the slag retaining devices of the present invention may be seated manually or mechanically orfloated thereinto all as hereinbefore described.

In Figure 6 of the drawings the refractory sleeve is illustrated by the numeral 17 and the insulating refractory liner 18 which is usually refractory prefired bricks is shown directly abutting the refractory sleeve 17. Some refractory cement may be used in sealing the refractory bricks to one another and to the refractory sleeve 17 as will occur to those skilled in the art.

In Figure 7 ofthe drawings, the refractory sleeve is indicated by the reference numeral 32 and the insulating refractory lining 33 of the ladle 34 is usuallyformed of prefired refractory bricks which are laid up in abuttment with the refractory sleeve 32.

In Figure 7 of the drawings, the ladle 34 has a slide valve 35 positioned belowthe refractory sleeve 32 which can be used to control the flow of hot metal from the ladle as for example when the hot metal is being transferred into a tundish or like receptacle in communication with a continuous caster.

It will thus be seen that the substantially improved slag retaining device as illustrated and described herein in combination with the refractory sleeve defining the tap hole, substantially improves the function of the slag retaining device and in effect automatically shuts off the flow of molten steel through the tap hole before the slag layer reaches the same thus assuring that only clean steel free of slag (non-metallic inclusions) is delivered from the vessel.

Claims

1. The combination in a vessel for molten metal having a tap hole of a preformed cylindrical refractory sleeve registering with said tap hole and a preformed slag retaining deviceforselectively engaging said cylindrical refractory sleeve during the drawing off of metal from said vessel, said slag retaining device comprising a closure of a modified global shape of a size to effectively close said cylindrical refractory sleeve when engaged therein, said slag retaining device and said cylindrical refractory sleeve being formed of refractory materials resistant to dissolution in the molten metal and slag for a time sufficientto assure the lodgement of said slag retaining device in said cylindrical refractory sleeve and wherein said slag retaining device has a density of about .12 to about .22 Ibs. per cubic inch sothat twill floatin said molten metal and below said slag.

2. The combination setforth in claim 1 and wherein atleastone annular groove is formed in the outer surface of said slag retaining device.

3. The combination set forth in claim 1 and wherein a plurality of ribs of modified arcuate shape are formed substantially vertically on the outer surface of said slag retaining device and spaced circumferentia I Iy with respect to one another.

4. The combination setforth in claim 1 and wherein a plurality of grooves are formed in the outer surface of said slag retaining device substantially vertically thereof and circumferentially spaced with respect to one another.

5. The combination setforth in claim 1 and wherein a plurality of alternately spaced, substantiallyvertically positioned ribs and grooves areformed on and in the outersurface of said slag retaining device in circumferentially spaced arrangement with respect to one another.

6. Adevicefordefining a tap hole in a vessel for molten metal, said device comprising a preformed, cross sectionally circular refractory sleeve positioned in said vessel for molten metal and formed of refractory material resistantto dissolution in molten metal so as to retain its cylindrical shape for a time sufficient to receive a slag retaining device therein.

7. A slag retaining device, substantially as herein before described with reference to Figures 1, 2,3 and 6, with orwithoutthe modification of Figures 4 and 7 or Figure of the accompanying drawings.

7. Aslag retaining devicefora molten metal vessel, said slag retaining device comprising a preformed modified global shaped body of a height greaterthan its width and of a width greaterthan a tap hole in said vessel, said device being formed of refractory materials resistant to dissolution in said molten metal for a time sufficientto assure the lodgementofsaid device in said tap hole vessel.

8. A combination in a vessel for molten metal having a tap hole of a preformed cylindrical refractory sleeve registering with said tape hole and a preformed slag retaining deviceforselectively engaging said cylindrical refractory sleeve, substantially as hereinbefore described with reference to Figures 1,2,3 and 6, with orwithoutthe modifications of Figures 4 and 7 or FigureS ofthe accompanying drawings.

9. A devicefordefining atap hole in a vessel for molten metal, subtantially as herein before described with reference to Figure 6 or Figure 7 ofthe accompanying drawings.

10. Aslag retaining devicefora molten metal vessel, substantially as hereinbefore described with reference to Figures 1,2,3 and 6, with orwithoutthe modification of Figures 4 and 7 or Figure 5 ofthe accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 to 10 above have been deleted.

(b) New Claims 1 to 7 have been filed asfollows:-

1. Aslag retaining device for selectively engaging a tap hole in a vessel for molten metal during the drawing off of metal from said vessel, said slag retaining device comprising a closure of a modified global shape of a height greaterthan its width and of a width efficiently to close said tap hole when partially engaged therein, said slag retaining device being formed of refractory materials resistant to dissolution in the molten metal and slag for a time sufficienttoassurethe lodgement of said slag retaining device in said tap hole and wherein said slag retaining device has a density of about .12to about.22 Ibs. per cubic inch (3321.6 to 6089.6 Kg/m3) so that it will float in said molten metal and below said slag.

2. A device according to claim 1, wherein at least one annular groove is formed in the outersurfaceof said device.

3. A device according to claim 1, wherein a plurality of ribs of modified arcuate shape are formed substantially longitudinally on the outer surface of said device and spaced circumferentially with respect to one another.

4. A device according to claim 1, wherein a plurality of grooves are formed in the outer surface of said device substantially longitudinally thereof and circumferentially spaced with respect to one another.

5. A device according to claim 1, wherein a plurality of alternately spaced, substantially longitudinally positioned ribs and grooves are formed on and in the outer surface of said slag retaining device i n in circumferentially spaced arrangement with respect to one another.

6. A slag retaining device for a molten metal vessel having a tap hole, said slag retaining device comprising a preformed modified global shaped body of a height greater that its widdth and of a width greaterthan said tap hole in said vessel, said device being formed of refractory materials resistant to dissolution in said molten metal for a time sufficient to assure the lodgement of said device in said tap hole in said vessel.