US3544094A - Metallurgical walking beam furnace - Google Patents

Description

United States Patent inventor Ruediger Knack Neuss, Germany App1.No. -719,990 Filed April 9, 1968 Patented Dec. 1, 1970 Assignee Koppers-Wistra-Ol'enbau G.m.h.l'l.

Dusseldorf, Germany Priority April 15, 1967 Germany No.K62025 METALLURGICAL WALKING BEAM FURNACE 2 Claims, 4 Drawing Figs.

2,017,024 10/1935 Cochran etal. 3,450,394 6/1969 Wilde etal ABSTRACT: A walking beam metallurgical furnace wherein the walking beams are separated from stationary beams by narrow vertical gaps having upper portions of lesser and lower portions of greater width. Each beam comprises two superimposed hollow internally cooled elongated metallic carriers which are immediately adjacent to the respective gap and are welded to each other, and a row of work-engaging plates which are mounted on the uppermost carriers of the respective beams so as to be held against tilting and/or lengthwise displacement. The walking beams move at a lesser speed during engagement with and during disengagement from the workpieces, and at a greater speed during movement with reference to the workpieces.

' Sheet JNVEN TOR HIS A TTORNEY.

Patented Dec. '1, 1910 Pafehted .1, 1970 Sheet br 3 Fig. 4

JNVENTOR RUDIGER K NAAK L L/{CQIC Jfav HIS AITORNEY.

METALLURGICAL WALKING BEAM FURNACE CROSS-REFERENCE TO RELATED APPLICATION The furnace of the present invention constitutes an improvement over and a further development of the furnace disclosed in the copending application Ser. No. 700,630, now US. Pat. No. 3,480,264 filed on Jan. 25, 1968 by Wilhelm Krause and assigned to the same assignee.

BACKGROUND OF THE INVENTION The present invention relates to metallurgical furnaces in general, and more particularly to improvements in walking beam metallurgical furnaces. Walking beam furnaces are employed for transport of ingots, slabs, rods, bars or like bulky metallic workpieces through a heating chamber. The walking beams of such furnaces are movable up and down as well as forwardly and backwards to transport workpieces stepwise from the inlet toward and through the outlet of the heating chamber. Conventional walking beam furnaces are over firing furnaces, i.e. the workpieces are heated from above but not from below. This is due to the fact that the stationary beams and the motion transmitting devices for the walking beams occupy too much room in the lower zone of the heating chamber. Absence of underfiring often presents serious problems, particularly when the workpieces are bulky, because the material of the workpieces is heated unevenly which leads to excessive thermal stresses.

There are two presently preferred classes of furnaces which are used for continuous transportation of metallic workpieces through a heating chamber. The so-called pusher type furnaces employ tails along which the workpieces are pushed through the heating chamber whereby the workpieces are heated from above and preferably also from below. A drawback of such pusher type furnaces is that the heating chamber cannot be readily evacuated. Thus, when the operation of the furnace is interrupted, some workpieces normally dwell in the interior of the heating chamber which is undesirable for a number of reasons. Furthermore, the surfaces of workpieces are likely to be scratched or otherwise damaged during sliding movement along the rails and along the grate in the interior of the heating chamber. This is particularly undesirable when the furnace is employed for treatment of expensive and highly sensitive metallic workpieces.

The other class of furnaces embraces the aforediscussed walking beams furnaces. Such furnaces can be readily evacuated and their walking beams are much less likely to damage the workpieces because the workpieces need not slide along the stationary beams. Moreover, a walking beam furnace can transport exceptionally long and bulky workpieces without damage to such workpieces in contrast to pusher type furnaces wherein a preceding workpiece is pushed through the heating chamber by the next-following workpiece or workpieces which often results in a pileup of workpieces in the interior of the chamber and causes undesirable overheating. Therefore, walking beam furnaces are often preferred over pusher type furnaces, particularly for treatment of expensive, elongated and sensitive metallic workpieces. Their sole serious drawback is that the workpieces cannot be properly heated from below for reasons which were discussed above. This applies especially to earlier types of walking beam furnaces wherein the stationary beams and the walking beams provide a substantially continuous supporting surface for the workpieces with minimal clearances between the stationary beams and walking beams.

Recent types of walking beam furnaces comprise two or more narrow stationary beams which extend lengthwise through the heating chamber and an equal number of narrow walking beams each of which is adjacent to a stationary beam. Such furnaces permit limited heating of workpieces from below, namely, through the space between the stationary beams insofar the propagation of heat is not impeded by the walking beams. The spaces cannot be made too wide because, in order to be sufficiently versatile, the furnace must be designed for transport of relatively short workpieces which travel sideways and must be properly supported by at least two stationary beams and at least two walking beams. The width of such spaces is further reduced by jackets of insulating material which are provided around stationary and walking beams. In other words, the heating chamber must accommodate at least four bulky heat-insulating jackets which prevent effective heating of workpieces from below. The situation is aggravated in relatively small walking beam furnaces wherein the ratio of the area occupied by insulating material to the overall area of the heating chamber is small because the thickness of insulation depends on the temperatures which prevail in the chamber, not on the dimensions of parts which must be protected from heat.

SUMMARY OF THE INVENTION It is an object of my invention to provide a novel and improved walking beam furnace wherein the ratio of space occupied by the insulation for stationary and walking beams to the area enclosed by the heating chamber is much more satisfactory than in heretofore known walking beam furnaces.

Another object of the invention is to provide improved stationary and walking beams for use in a furnace of the just outlined character.

A further object of the invention is to provide a novel drive for the walking beams and to operate the drive in such a way that the workpieces are not scratched during transfer from stationary beams onto walking beams or vice verse.

An additional object of the invention is to provide a walking beam furnace wherein the workpieces can be properly heated from above as well as from below.

The improved furnace comprises a heating chamber having an inlet and an outlet, a plurality of elongated stationary holders or beams provided in the chamber and extending between the inlet and the outlet to support at intervals metallic workpieces which are fed through the inlet and advance intermittently toward and through the outlet, and a plurality of elongated walking beams or conveyors, each closely adjacent to one of the holders and each movable between raised and lowered positions as well as toward and away from the outlet to lift workpieces off the holders during movement to raised position, to transport the thus lifted workpieces during movement toward the outlet in the raised position thereof, to deposit the workpieces on the holders during movement to lowered position, and to thereupon move away from the outlet in the lowered position thereof. Each holder defines with the corresponding conveyor a very narrow substantially vertical gap for descending scale and each holder and each conveyor comprises a jacket of heat-insulating material. Such jackets are open at the respective gaps and they enclose internally cooled elongated carriers of metallic material which are provided in each of the beams and support rows of work-engaging portions against lengthwise and/or lateral movement.

The conveyors are preferably movable at a lesser speed during engagement with and during disengagement from the workpieces, and at a higher speed when they move with reference to the workpieces.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved furnace itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a transverse vertical sectional view of a metallurgical walking beam furnace which embodies one form of my invention, the section being taken in the direction of arrows as seen from the line H of FIG. 2;

FIG. 2 is a fragmentary longitudinal vertical sectional view of the furnace as seen in the direction of arrows from the line II-ll of FIG. 1;

FIG. 3 is a fragmentary top plan view of a detail as seen in the direction of arrows from the line III-Ill of FIG. 1; and

FIG. 4 is a perspective view of a work-engaging plate which can be utilized in the furnace of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS sideways, as indicated by arrow A, i.e. from the inlet 1a,

through the interior of the chamber 1, and toward and through the outlet lb. The chamber 1 accommodates two stationary parallel horizontal supporting units or beams 2 which extend across the interior of the chamber and through and beyond the inlet la and outlet lb. For convenience, the stationary units or beams 2 will be called holders. Each of these holders 2 is associated with a mobile supporting unit or walking beam 3 (hereinafter called conveyor). The purpose of the conveyors 3 is to intermittently advance the workpieces 8 in the direction indicated by arrow A. To this end, the conveyors 3 are movable up and down between raised and lowered positions as indicated by arrows B and C, as well as forwardly and backwards between advanced and retracted positions as indicated by arrows D and E. In order to transport the workpieces 8 by a step, the conveyors 3 are moved upwardly (arrow B) in their retracted positions to thereby lift the workpieces 8 off the holders 2, thereupon forwardly (arrow D) in their raised positions to advance all of the workpieces 8 by a step of predetermined length, thereupon downwardly (arrow C) to deposit the workpieces 8 on the holders 2, and then in rearward direction (arrow E) in their lowered positions to return to retractedposrtions prior to the start of a fresh cycle. The same operation is repeated as often as necessary in order to transport a batch or a continuous succession of workpieces 8 through'the chamber l where the workpieces are heated from above and-from below. workpieces are placed onto the holders 2 at a loading station which is outwardly adjacent to the inlet la.

Each holder 2 and each conveyor 3 comprises two preferably horizontal superimposed elongated tubular metallic carriers 4 of rectangular cross-sectional outline, and the carriers are cooled internally by circulating water or by other suitable cooling fluid. The purpose of carriers 4 is to take up all bending and compressive stresses which are due to'the weight of workpieces 8 and to the weight of other parts of the respective holder or conveyor. It will be noted that each holder 2 is substantially mirror symmetrical with reference to the adjoining conveyor 3. The carriers 4 are welded to each other and the upper carrier 4 of each holder 2 supports a row 5 of platelike work-engaging portions 5a whose height exceeds the height of platelike work-engaging portions 5 on the upper carrier of the adjacent conveyor 3. Thus, when the carriers 4 of the conveyors 3 are located at the same level as the carriers of the holder 2 (FIG. 1) the portions 5a of the holders 2 extend above and beyond the portions 5 of the conveyors 3 and support the workpieces 8 from below. The width of the portions 5, 5a is the same as that of the carriers 4. The top parts of the portions 5, 5a are solid and their lower parts are provided with recesses 5', 5a to accommodate upwardly extending tubular projections or connectors 6, 6a which are welded to the adjacent upper carriers 4. The bottom faces of the work-engaging portions 5, 5a rest on the adjoining carriers 4. The connectors 6, 6a are preferably of square or other polygonal outline and fit snugly into the complementary recesses 5', 5a in the undersides of the portions 5, 5a to hold the latter against tilting and/or lengthwise displacement with reference to the carriers 4. This is shown in FIG. 3. If desired, the projections 6, 6a can be coupled to the work-engaging portions by means of bolts, pins or like fasteners 7, 7a (indicated in FIG. 3 by broken lines) to prevent lifting of portions 5, 5a above and 0 ,gap l0. The- numerals 11a, 11 respectively denote insulating jackets which surround the holders 2 and conveyors 3 but permit passage of scale through the gaps10. The side faces of the carriers 4 areimmediately adjacent to such gaps. It will be noted that the width of gaps 10 is greater in the regions between the carriers 4. but is less in the regions between the work-engaging portions 5, 5a. This is due to the provision of ledges ;9. Scale which'penetrates into a gap 10 can readily descend by gravity as soon as it advances beyond the ledges 9. The height of the ledges'9 preferably exceeds the distance by which the portions 5 extend above and beyond the portions 5a when the conveyors 3 reach their upper end positions.

The holders 2 are mountedon internally cooled upright columns 12 .which are rigid with or extend downwardly beyond the bottomwall 1d of the chamberl and include shells or envelopes 13 of heat-insulating material. The shells 13 accommodate hollow metallic frames 14 for the carriers 4 of the respective holder 2 and reciprocable and vertically movable frames 15 for the carriers 4 of the conveyors '3. The interior of each frame 15 is preferably cooled by circulating water or other fluid coolant. The shells 13.defrne internal compartments which accommodate the fixed frames 14 and the movable frames 15. The. displacing assembly 1541 for moving the frames 15 up and down as well as forwardly and backwards may be constructed and assembled in a number of ways and the exact design of such assembly forms no part of the present invention. For example, the frames 15 may be moved up and down by hydraulic jacks 15A and may be moved forwardly and backwards by double-acting hydraulic cylinder and piston assemblies 158 which are pivoted to the columns 12 and to the respective conveyors 3. The assembly 15a for moving the conveyors 3 is indicated in FIGS. 1 and 2 at a level below the bottom wall 'Id of the chamber 1. This assembly moves the conveyors 3 by way of the hollow frames 15. The compartments in the shells 13 are large enough to accommodate sturdy frames 14, 15 and to permit requisite movements of frames 15 in order to raise and lower the conveyors 3 as well as to move them forwardly and backwards. The speed at which the conveyors 3 move forwardly and backwards, as well as upwardly and downwardly can be changed by adjustable valves which regulate the'flow of a pressure medium to and from the cylinders of jacks 15A and assemblies 153.

The gaps 10 may accommodate strips, rails or like inserts 17 of wear-resistant material which take up pressures when a conveyor 3 happens to move toward the associated holder 2. Such inserts 17 may be provided on the carriers 4 of the ho]- ders 2 and/or on the carriers of the conveyors 3. The cooled portions of the holders 2 and/or conveyors 3 may be further provided with rails or like guides 18 which prevent a reduction of gaps 10 below a minimum width..The guides 18 may be affixed vto the carriers 4 of the holders 2 and/or to the carriers of the conveyors 3. Also, the guides v18 may be embedded in the material of the jackets 11 and/or lla. The inserts and guides 18 further serve to reinforce the beams.

The work-engaging portions 5 and 5a may be replaced by portions of inverted U-shaped outline (FIG. 4). Each such below and when they are about to deposit the workpieces on the portions 5a of the holders 2 during movement toward their lower end positions. This enables the conveyors 3 to lift the workpieces gently and to deposit them gently back onto the holders 2. The speed at which the conveyors 3 move to their lower end positions subsequent to deposition of workpieces on the holders 2 and the speed at which the conveyors move in directions indicated by arrows D and E can be much higher.

An important advantage of my walking beam furnace is that the holders 2 and conveyor 3 are not completely encased in insulating material. For example, and assuming that the jackets 11, 11a for the carriers 4 were replaced by jackets which would also extend into the spaces between the carriers 4 of a holder and the carriers 4 of the adjoining conveyor, and as suming further that the thickness of those portions of the jackets which would extend into the spaces between the carriers would equal the thickness of a carrier, the width of each holder and of each conveyor would be increased by 50 percent at the expense of under firing. In a pusher type furnace with two stationary rails which are completely encased in insu-' lating material, the space available for under firing is not much greater than in my furnace. Thus, and assuming that the unit width of a rail equals the thickness .of insulation, the total width of a rail with insulation at both sides then equals three units whereas the combined width of a conveyor 3 and a holder 2 in my furnace is four units if the width of a carrier 4 equals one unit. Since the width of gaps is small, the quantity of heat which can penetrate between the carriers 4 of a holder 2 and the carriers of the adjoining conveyor 3 is negligible and can be tolerated in view of the fact that the combined width of a holder and the adjoining conveyor is reduced by approximately 50 percent with resulting improvement in under firing.

It was found that carriers 4 of rectangular or square crosssectional outline are particularly suited for use in the furnace of my invention. The width of a rectangular carrier with satisfactory moments of inertia and resistance is relatively small so that this, too, contributes to a reduction of the width of a holder or conveyor with improved under firing of work-- pieces during travel through the heating chamber.

As stated before, the width'of the work-engaging portions 5 and Sapreferably equals the width of the carriers 4. This is of particular importance at the upper ends of such portions, i.e., at those ends which come in contact with hot workpieces because such upper ends are heated to elevated temperatures with resulting decreases in their resistance to deformation under the weight of workpieces. On the other hand, the lower ends of portions 5, 5a should be in small-area contact with the upper carriers 4 to prevent uncontrolled cooling of workpieces and excessive heat exchange with the carriers. The portions 5, 5a preferably consist of highly heatand pressure-resistant material and, since they do not extend laterally beyond the carriers 4, they do not interfere with heating of the workpieces from below. Additional improvements in heating action from below are due to the fact that the portions 5 are shorter than the portions 5a, i.e., that the workpieces can be heated from below in the regions above the portions 5 when the conveyors 3 dwell in their lower end positions. Though the heat insulating action of portions 5 is less satisfactory than that of the portions 5a, this is of no consequence because the portions 5 are in short-lasting contact with the workpieces.

Iclairn:

l. A walking beam metallurgical furnace, comprising a heating chamber having an inlet and an outlet; a plurality of elongated stationary holders provided in said chamber and extending between saidinlet and said outlet to support at intervals metallic workpieces which are fed through said inlet and advance intermittently toward and through said outlet; a plurality of elongated conveyors, each closely adjacent to one of said holders and each movable between raised and lowered positions as well as toward and away from said outlet to lift workpieces off said holders during movement to raised position, to transport the thus lifted workpieces during movement toward said outlet 1n the raised position thereof, to deposit the workpieces on the holders during movement to lowered position, and to thereupon move away from said outlet in the lowered position thereof, each of said conveyors defining with the adjoining holder a narrow substantially vertical gap and each of said holders and each of said conveyors having a jacket of heat-insulating material; and wear-resistant inserts in said gaps to take up pressure when a conveyor approaches the respective holder.

2. A walking beam metallurgical furnace, comprising a heating chamber having an inlet and an outlet; a plurality of elongated stationary holders provided in said chamber and extending between said inlet and said outlet to support at intervals metallic workpieces which are fed through said inlet and advance intermittently toward and through said outlet; a plurality of elongated conveyors, each closely adjacent to one of said holders and each movable between raised and lowered positions as well as toward and away from said outlet to lift workpieces off said holders during movement to raised position, to transport the thus lifted workpieces during movement toward said outlet in the raised position thereof, to deposit the workpieces on the holders during movement to lowered position, and to thereupon move away from said outlet in the lowered position thereof, each of said conveyors defining with the adjoining holder a narrow substantially vertical gap and each of said holders and each of said conveyors having a jacket of heat-insulating material; and a stack of superimposed elongated hollow internally cooled carriers of rectangular cross-sectional outline forming part of each of said conveyors and each of said holders, the carriers of said stacks being welded to each other and the uppermost carrier of each stack supporting a row of wearand heat-resistant work-engaging portions, the height of work-engaging portions in said conveyors being less than the height of work-engaging portions of said conveyors being spaced from workpieces in the lowered positions of said conveyors.

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