US2839290A

US2839290A - Soaking pits

Info

Publication number: US2839290A
Application number: US402492A
Authority: US
Inventors: Quentin M Bloom
Original assignee: Selas Corp of America
Current assignee: Selas Corp of America
Priority date: 1954-01-06
Filing date: 1954-01-06
Publication date: 1958-06-17
Anticipated expiration: 1975-06-17

Description

O. M. BLOOM SOAKING FITS June 17, 1958 6 Sheets-Sheet 1 Filed Jan. 6, 1954 INVENTO R QUENTIN M. BLOOM XNI ATTORNEY 6 Sheets-Sheet 3 Q. M. BLOOM SOAKING PITS June 17, 1958 Filed Jan 6, 1954 INVENTOR QUENTIN M. BLOOM ATTORNEY Q. M. BLOOM June 17, 1958 SOAKING FITS 6 Sheets-Sheet 4 Filed Jan. 6, 1954 INVENTOR uarrrm M. BLOOM ATTORNEY June 17, 1958 Q. M. BLOOM 2,839,290

' SOAKING PITS Filed Jan, 6, 1954 6 Sheets-Sheet 5 m m 11 m m m to k (u m a 2 0 3 I ,1

.ai I

\0 (UP m mm QUENTIN M. BLOOM zwxm,

ATTORNEY k 6 Sheets-Sheet 6 INVEN TOR QUENTml M, BLOOM BYX fi ATTORNEY O. M. BLOOM SOAKING PITS June 17, 1958 Filed Jan. 6, 1954 Unite assgzae SOAKING rrrs Application January 6, 1954, Serial No. 462,492

6 Claims. (Cl. 266-) The present invention relates to the construction of furnaces of the type commonly referred to as soaking pits which are in common use in steel mills for the purpose of heating ingots to a desirably uniform steel rolling temperature which varies with operating conditions. Soaking pits now in use in this country are customarily deep chambers, or underground furnaces of square or rectangular sections with top openings normally closed by removable covers. A typical modern soaking pit for heating blooming mill ingots is large enough to hold from eight to sixteen ingots each in an upright position. Each such ingot may be about six feet tall and is substantially square or rectangular in cross section, with one side about twenty-three inches long at its lower end. Each ingot is customarily tapered, being somewhat smaller at its upper end than at its lower end. Usually each ingot inserted in a steel mill soaking pit, is a hot steel casting, the inner portion of which may still be molten when the ingot is inserted in a soaking pit. Cold ingots are ordinarily put into soaking pits only in starting a rolling mill into operation following a shut down so that no hot ingots are then available. in normal operation, a hot ingot inserted in a soaking pit needs to be subjected to a suitable and suitably uniform temperature for several hours. The soaking period is substantially longer .for ingots which are cold when put into the soaking pit. The heating of ingots in soaking pits has long been generally recognized as highly ineflicient, although the heating provisions usually include regenerators or recuperators external to the soaking pits.

A general object of the present invention is to provide a soaking pit which is more efficient than the soaking pits heretofore in use, and is characterized by the transfer of heat to the opposite sides of each ingot being soaked, by radiation from the adjacent side walls of the soaking pit. To this end, the side walls of the soaking pits are advantageously provided with burners comprising open ended combustion chambers in the form of circular cavities in the side Walls of the pits and comprising a separate burner pipe or conduit coaxial with and extending into each cavity from the outerportion of the furnace wall, and discharging a combustible mixture of fluid fuel and air which burns alongside the cavity wall in the general manner disclosed in the Furczyk Patent 2,561,793 of July 24, 1951.

A further and practically important object of the present invention is to make effective use of individual soaking pits each having relatively small ingot holding capacity. instead of using a soaking pit large enough to simultaneously hold eight or more ingots distributed in different horizontal directions, I ordinarily use a soaking ,pit only large enough to hold a single short horizontal row of ingots. In practice there may well be three ingots in each row, with the ingots in each row receiving radiant heat directly from the uprising heating walls adjacent the elongated sides of the rows.

Such reduction in the size of the soaking pits employed Zfififi Patented June 17, 1958 radiant heating walls, contributes to increased efiiciency by reducing the soaking pit cooling action which is an inevitable result of the heat loss occurring when the upper end of the soaking pit is periodically opened, as is necessary, for the removal of ingots ready for rolling, and for their replacement by ingots to be heated. The rate at which heated ingots are withdrawn from each soaking pit, ordinarily depends upon the operating characteristics of the associated rolling mill. If, as may well be the case, three ingots are advantageously withdrawn at one time, each ingot after being inserted in a soaking pit is necessarily subjected only to a single cooling and scaling action prior to its passage to the rolling mill. .If ingots are withdrawn three at a time from a soaking pit holding twelve ingots, for example, on the average, each ingot willnecessarily be exposed to at least four separate cooling and scaling actions prior to its passage to the rolling mill.

In the use of the presentinvention, a separate cover structure is provided for each soaking pit with the re sult that the weight of each individual cover is much smaller than the weight of the cover for the larger soaking pits heretofore used. The reduction in the weight of a cover means a reduction in the amount of power required for the removal and replacement of the cover, and some reduction, also, in the time required to remove and replace a cover. In practice, a plurality of covers may be moved out of and back into their normal positions along a single pair of track rails.

The replacement of a single large soaking pit by a plurality of smaller soaking pits makes it practically feasible to effect closer control of the heating operation of. the individual soaking pits with the practical advantage in some cases of reducing the time required for heating the individual ingots, and with the desirable result that the average time required for heating an ingot is reduced and in consequence a reduction in the number of ingots necessarily being heated at any one time to supply the heated ingots required in a mill plant of given size.

A further object of the invention is to provide soaking pits with floors which can be readily removed for repair or replacement without work on or contact with other portions of the pits. The ability to remove and replace the floor of a soaking pit Without disturbing the rest of the soaking pit structure is practically important, since in normal operation the floor of a soaking pit is subjected to more need for repairs and reconstruction than all of the remaining portions of the pit structure.

A further and important object of the invention is to provide a soaking pit structure in which the roof or cover closing the upper end of a soaking pit or pits is suspended from overhead supporting means at all times. Such suspension avoids the warping or flexing of the cover, and resultant cracking of the cover refractories, heretofore experienced when the pit cover is normally supported on the vertical pit walls, but is suspended from an overhead structure when the cover is moved to open up the soaking pit for the removal and insertion of ingots.

The various features of novelty which characterize my invention'ar'e pointed out with particularity in the claims annexed to and forming apart of this specification. ever, its advantages, and specific objects attained with its used, reference should be had tothe accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of the invention. Ofthe drawingsz. V 1

Fig. 1 is a diagrammatic plan viewof an ingot heating and preheating structure;

Fig. '2 is a partial section on the line 22 of. Fig. 1; Fig. 3 is alpartial section on the line '33 of Fig. 1; Figs. 4 and 5 are sections taken'on' a portion of the line 2F-2, and on the line 33 of Fig.1, respectively, showing soaking pit floor portions on larger scale and in.

greater detail than they .are shown in Figs. 2 and 3,

respectively; I

Fig.6 is a diagrammatic plan view of asoaking pit furnace cover; p I 1 Fig. 7 is an elevation in section on' the broken line 77 of Fig. 6;

Fig. 8 is a section on the line 8-8 of Fig. 7;.

Fig. 9 is a diagrammatic elevation of means for sup plying fluid fuel and combustion air to the burners of an individual soaking pit; and

Fig. 10 is an end elevation partly in section through a soaking pit, and illustrating bottom wall hoisting apparatus.

The soaking pit structure .1 shown diagrammatically in Fig. l, compriscs'four main soaking pit chambers 2,

3, 4 and 5, and two preheating pit chambers 6 and 7. In the particular'constructionshown, three vertical ingots 8 are arranged'side by-side in a straight row in each of the pits 2,. 3, 4, 5, 6 and 7. The pit 3 is arranged in end-to-end relation with the pit 2, and the

pits

4 and 5 are arranged in end-to-end'relation with one another, and are respectively alongside the pits 2 and 3, but are spaced away from'the latter. Each of the pits has vertical refractory walls 9 at its sides and ends and each side wall of each of the

pits

2, 3, 4' and 5 is formed with a plurality of burners 10. Eachburner locomprises a wall cavity open to the pitch amber and a separate pipe 11 which opens into the cavity, and normally discharges a mixture of air and fluid fuel therein. Ordinarily, the fuel will. be gas, and it is noted by wayof illustration and example that the burners may be constructed and arranged in the general manner shown in the Sisto and Milos application, Serial -No. 362,293, filed June 17, 1953. The manner in which air and fuel is supplied to the burners 10'ofeach of thepits 2-5, is illustrated diagrammatically in Fig. 7 9, and 115' hereinafter described. The preheating pits. 6 and. 7 are generally similar in shape to, and are alongside the

ingot heater pits

4 and 5.

Channels 12 formed in the masonry walls alongside the soaking and preheating pits, and including portions below the level of the botom walls-of the chambers 2 to 7, pass the gaseous products of combustion formed in the

pit chambers

2, 3,4 and 5, intothe preheating pit chambers 6 and 7 and thence to the chimney 13, as indicated by the arrows 14 shown in Fig. l. i

The lower end of each of the pits 2 to 7 is normally closed by a removable'bottom wall or floor 15. In accordance with the present invention, each pit floor is readily replaceable; 'As shown in Figs. 4 and 5, the floor of the pit z comprises refractory material 16 directly supported by metal plates 17 and a metallic rimfram'e 18. The plates 17' and frame 18 are attached to and supported by metallic channelbars or beams 19 which normally rest on the beams 19a of a metallic sub-structure. The rim frame 18 is shown-as of angle bar cross section with its horizontal flanges extending inward from anouter vertical base flange, ,ZThe Ffloor member is slightly shorter and narrower than the soaking'pitzin which it is mounted. Each side and end of the frame 18 is spaced away from an adjacent. vertical wall of the cor- For a better understanding of the invention, howresponding pit, and, as shown, is directly supported by a 'subjacent channel bar or beam20l 'Each'such' beam 20 is alongside a beam or channel bar 20a beneath the adja cent pit Wall.

The space between theadjacent beams or bars 20 and 20a is closed by horizontally elongated bricks 21. Each beam 20 and the adjacent beam 20a are provided with

brackets

22 and 23. The side-by-

side brackets

22 and 23 support the bricks 21, or analogous refractory members. Those members support a mass of refractory filling material 24, which normally consists mainly of slag and scale, and which extends upward to a level adjacent the top of refractory floor material 16. When it becomes necessary to open or replace a floor member 15, the associated bricks 21 are broken and the slag, scale and other material above the bricks are permitted to -flow down into the space below the beams 19a; The ability to readily make the pit floors accessible for replacement or repairs is of substantial practical importance, par-. ticularly as the floors of furnace pits are customarily rebuilt at relatively frequent intervals primarily. because of undesirable changes in the composition of the floors due largely to' scale deposits. After the bricks 21 associated with the bottom wall 15 have been broken away, the bottomjwall may be lifted verticallyout of the corresponding soaking pit for repairs or replacement.

As is diagrammatically illustrated in Fig. l0,the bottom wall in the soaking pit 2 is shown in engagement with hoisting apparatus. Thatxapparatus includes a cable depending from an overhead crane or analogous hoisting element, andtong elements 71 having their upper ends secured to the lower end of the cable 70 and each having a lower portion passing downward 1 between adjacent channel bars 20 and 20a, and having itsho'ok end 73 extending beneath and engaging the underside of the bottom member 15. The isoaking pit 2a shown in Fig. 10 may be identical in structure to the pitsfshown in Figs'. l, 2, 3, 4 and 5, but some of the structural details shown in the last mentioned figures are omitted in Fig 10.

As shown in Figsi4 andS, each ingot 8 in a pit cham ber may well be supported on four tubular'water cooled pins 25 which extend vertically through the floor struc- 1 ture and to a'level a few inches above the top ofthe refractory body portion 16 of the floor. H Each pin 25 The upper end of'each of the soaking and preheating pits is provided with a separate readily removablecover 30. In accordance with the present invention, each cover comprises an upper crane-like supporting structure 31.

having a platform-like body with spaced apart

wheels

32 and 33, respectively adjacent each of two opposed edges of the structure 31. As shown, the two wheels 32 "are driving wheels connected by an axle 34 and the two wheels 33 are idler wheels connected to a separate axle 35 mounted in the structure" 31; The driving wheel axle 34 is connected by speed reducing gearing to a'driving motor 36 mounted on the stru cture 31. The motor'36 mounted oneach member 31 is arranged to move the latter, along track rails 37 supported by thesoaking pit structure 1 between its soaking pit closing position, and

a position at one side of said closing position.

As shown in Fig. l, the cover supporting members 31 associated with the

soaking'pits

2, 4 and 6 are movable along the. same pair of track rails 37 transverse to the length of the opposite ends of each of said

pits

2,4 and 6, and each platform structure 31 and the cover suscalled a parking position. As shown, there is sparking space 38 at the right of each of the

pits

2, 3, 4, .5 and 6. The covers for the pits 3 and .5 run on a second pair of rails 37 parallel to the first mentioned rails 37. A parking position 38' is provided for the cover 30 which normally closes the upper end of the pit 7. The last mentioned cover has its

wheels

32 and 33 arranged to run on track rails 37.at right angles to the rails 37. The contemplated spacial requirements of the structure 1 shown in Fig. 1 make it desirable to have the rails 37' at right angles to the rails 37. As will be apparent, whether one or more pairs of track rails are transverse to the long or short side of the associated pit may depend on conditions.

Each cover member 30 is suspended from the corresponding supporting member 31 for up and down movement between a lower position in which the cover 3% extends into and closes the upper end of the corresponding soaking pit, and an upper position in which the cover 30 is above the top wall of 'the soaking pit structure and will not interfere with the movement of the member 31 horizontally along the corresponding track rails 37 or 37'. As shown, each cover member 34 is suspended from the corresponding supporting member 31 by bell crank levers 39. As shown, there are four levers 39, each pivotally connected intermediate its ends to the structure 31 by a corresponding pivot 39a. The lower end of each lever 39 is connected tothe cover 30 by a link 3%. The latter has its upper end pivotally connected to the lever and having its lower end connected to the cover 30 by a removable pin 3%.

The upper end of each lever 39 is connected by a pivot 39c to a separate link 4% The links 40 connected to the two levers 39 adjacent the left end of the member 31, have their second ends connected to aligned crank pins 42 rigidly connected to and laterally displaced toward the left end of the member 31 as seen in Figs. 6 and 7 from a crank shaft 41 parallel to the track rails 37. The links 4-0 connected to the two levers 39 adjacent the right hand end of the member 31, as seen in Figs. 6 and 7, are connected to crank pins 422 rigidly connected to the crank shaft 41 angularly displaced 180 from the crank pins 42. The crank shaft 41 is arranged for rotation through speed reducing gearing by a second motor 43 mounted on the member 31.

As shown, each cover is provided with 21 depending flange 44 along the sides and ends of the structure and normally extends into a sand seal 55, thus providing an effective seal against air or gas leakage into or out of the corresponding soaking pit. Each cover member 3i includes a mass of bricks or other refractory material of poor heat conductivity suspended from metallic framework beam port'cns d6 of the cover member 36. Since the weight of the cover 3% is supported at all times by the structure 31, the movement of the cover into and away from its normal closed position does not tend to flex or strain the cover structure, as it would if the cover were supported in its closed position by the walls of the corresponding pit and were suspended from the member 3i when moved upward away from its normal position.

In accordance with the present invention, provisions are advantageously made for a separately regulated supply of fuel fiuid and combustion air to each of the

main heating pits

2, 3, 4 and 5, so that the rate at which heat is supplied to each of those pits may be independently adjusted. Such regulation is especially desirable during operating periods in which the rates at which ingots are supplied to and withdrawn from the

pits

2, 3, 4 and fluctuate. Ordinarily, when the normal operation is thus upset, the rate at which the combustible fuel mixture is supplied to the burners in one main soaking pit should be varied relative to the rate at which the mixture is supplied to the burners in one or more other main soaking pits. in the particular construction illustrated, each of the two side Walls of each of the pits 2, 3, d and 5 has sixv burners 10 directly facing the adjacent side of each ingot in the pit, and the six burners are-located at four difierent levels, one burner at each of two upper levels and two burners at each of two lower levels. The fuel and air mixture supplied to each burner may be mixed at each burner, as is done in the apparatus disclosed in said Furczyk Patent 2,561,793.

As is shown diagrammatically in Fig. 9, the fuel and combustion air may be separately passed to the burners 10 of each of the soaking pits 2, 3, 4 and 5 through piping of the character diagrammatically illustrated in Fig. 9. in that figure, fuel gas is supplied under pressure to the inlet side of a throttling valve 50 located at a level above the soaking pits 8. The valve 50 passes gas at a regulated rate into the upper end of a pipe 51 which extends down through the soaking pit structure into a tunnel 52 below the channel 12, and then passes into an uprising gas pipe 53. The latter is connected to a horizontal manifold 54 which has four

vertical branches

55, 56, 57 and 58 at the outer side of one side wall of the pit 2. Those four branch pipes are distributed longitudinally of the pit 2 and of the three ingots 8 therein so that the branch 55 may supply gas to four burner pipes it associated with the ingot 3 adjacent the left end of the pit 2. As shown, two of those four burner pipes 11 are located at difierent upper levels and the other two burners are located at different lower levels. The branch 56 supplies fuel gas to two burner pipes 11 at different lower levels and alongside the lower portions of each of the two adjacent ingots, and supplies fuel gas to one upper burner pipe 11 associated with the central ingot in the pit 2. The branch pipe 57 supplies fuel gas to burner pipes 11 at different lower levels associated with each of the two ingots adjacent the right ended the chamber 2, and supplies fuel gas to one of the two upper level burner pipes alongside the central ingot. The pipe 53 supplies gas to four. burner pipes 11 at different levels alongside the ingot 8 adjacent the right end of the pit 2.

An air compressor 68 above the soaking pits and draw ing air from the atmosphere, supplies air under suitable pressure to the upper end of a pipe 61 which is substantially larger in cross section than the pipe 51. The pipe 61 extends down into the tunnel 52 where it is connected to an uprising pipe 53 supplying air to a manifold 64 alongside the manifold 54 and provided with four

branch pipes

65, 66, 67 and 68. Each of the

manifold branch pipes

65, 66, 6'7 and 68 may be arranged to supply combustion air to the burner pipes 11 which receive fuel gas from the corresponding fuel

gas branch pipes

55, 56, 5? and 58, respectively. The valve 50 and blower associated with the soaking pit 2., may advantageously supply gas and air, respectively, to manifolds and branch pipes and burner pipes 11 in the side wall of the pit 2 which is in juxta-position to the side wall shown in Fig. 9. Y

The mixture of fluid fuel and air passed to the burners is advantageously proportioned so that all of the gas is burned and so that the amount of excess air is relatively small in amount. With the fuel and air so proportioned, it is not difficult to regulate the fuel and air supply as required to vary the combustion rate and thereby the temperature in the

pits

2, 3, 4 and 5, while at the same time heating the dished refractory ourner wall surfaces to incandescence, and thus maintain a relatively high ratio of the radiant heating effect to the convection heating effect.

As has been made apparent, the invention is characterized in particular by the relative ease with which each bottom wall 15 may be removed for repair or replacement. The vertical extent of the piers 19b is suflicient to permit a workman to move around in the space beneath the beams 19a. Thus the bricks 21 may be readily broken and removed, and subsequently replaced after the repaired or replacement bottom wall is put in place on the beams Furthermore, each bottom wall may be soaking pit is out'of regular operation.

The means for the continuous suspension of the soaking pit cover member 30 in normal operation, not only avoids -"the risk of objectionable distortion of the cover member but-facilitates the separation from the supporting structure 31 of a damaged cover member and the subsequent 31 may be attached to the latter by the replacement of the pins 3%.

While in accordance with the provisions of statutes,

I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the forms of the apparatus disclosed Without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without. a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A soaking pit structure comprising a plurality of side by side soaking pits each proportioned .to receive a single short row of spaced apart vertical ingots with each pit having a refractory side wall close to each side of said row and an end wall close to each end of said row, each of said side walls being provided with a plurality of fluid fuel burners directed toward each of the ingots between them and spaced over an area of said Walls substantially equal to the area of the ingots and the configuration'of the ingots and operative to pass a large portion of the heat generated by the burners in the form'of radiant heat without flame impingement to the sides of ingots between and facing said side walls.

2 A soaking pit structure comprising a plurality of side by side soaking pits each proportioned to receive a single short row of spaced apart vertical ingots with each pit'having a refractorysidewall close to each side of said row and an end wall close to each end of said row, a plurality of fluid fuel burners in the portions of each of said side walls immediately adjacent the sides of each of said'ingots and spaced over an area of said walls substantially, equal to the area of the ingots and the con: figuration of .the ingots .and directed toward them, said burnersbeing operative to pass a large portion of the heatgenerated to the ingots in the form of radiant heat and without flame impingement, a removable cover normally-closing the upper end of each pit and means for passing gaseous products of combustion away from the soaking pit.

3. A- soaking pit structure comprising vertical walls surrounding a soaking pit chamber, a removable cover normally closing the upper end ofsaid chamber, means for passing heating gases into and out of said chamber,

1 fi t pqfi r ml m b h n s pp i walls, a second supporting structure beneath said chamher and having itsouter'edge displaced inwardly from said'w'alls, a destructible third bottom wall supporting structure bridging the gap betweensaid ifiISt and said second supporting structures, and refractory material supported by said secondand third supporting structures and forming th'e pit bottom walL-whereby s aid'sec ond supporting structure may be moved upward through said pit chamber when said cover is removed'and said destructible supporting structure is broken. I i

4. A soaking pit structure comprising vertical valls surrounding a soaking pit chambena removable cover normally closing'the'upper end' of said chambergmeans for passing heating gases into andout of said chamber, a first supporting structure beneath and supporting said walls, a second supporting structure directly beneath said chamber. and having its: outer edge displaced inwardly from said walls, bricks forming a destructible bridge forming a third bottom wall supporting structure extending between said first and second supporting structures, and refractory'material supported by said bridge and second supporting structure and forming the pit bottom wall, whereby said bottom Wall may be removed through said chamber for repair. or reconstruction upon breaking said destructible bridge. 1

5. A soaking pit structure as specified in claim 4, in

' which said first and second supporting structures comprise metallic parts forming abutments supporting the opposite ends of the bricks forming said bridge.

6. In a furnace, the combination of a supporting frame, vertically extending furnace walls outlining it furnace chamber on said frame, a furnace floor slightly smaller in area than said chamber resting on said frame within the confines of said walls, shelf means on said walls and extending inwardly from said walls toward said floor, additional shelf means on said floor and extending outwardly toward said walls, a plurality of re' movable bricks resting on said shelf means to bridge the gap between said walls-and floor, removable refractory material on said bricks to seal the space between said floor and walls, a removable roof for saidchamber, and means to support saidroof above said walls in gas tight relation therewith.