US3804584A

US3804584A - Pusher furnace

Info

Publication number: US3804584A
Application number: US00340006A
Authority: US
Inventors: G Herr
Original assignee: Koppers Wistra Ofenbau GmbH
Current assignee: Koppers Wistra Ofenbau GmbH; EOn Ruhrgas AG
Priority date: 1972-09-23
Filing date: 1973-03-12
Publication date: 1974-04-16
Anticipated expiration: 1991-04-16
Also published as: IT991415B; GB1390875A; JPS4965911A; DE2246772A1; FR2205183A5

Abstract

An elongated furnace for heat treatment of metallic workpieces which are pushed through the heated furnace chamber along guide means extending from an inlet at one end of the furnace chamber to an outlet at the other end thereof. The elongated guide means comprise metallic elements supported on and in direct contact with water-cooled pipes extending upwardly spaced from the bottom wall of the furnace from the inlet towards the outlet, and a ceramic hearth portion in the region of the outlet and having an upper guide face flush with upper faces of said metallic elements.

Description

United States Patent [191 Herr [ Apr. 16, 1974 PUSHER FURNACE [75] lnventor: Guenter Herr, Oberhausen, Germany [73] Assignee: 'Koppers-Wistra-Offenbau GmbH,

Dusseldorf, Germany 22 Filed: Mar. 12,1973

21 Appl.No.:.340,006

[30] Foreign Application Priority Data Sept. 23, 1972 Germany 2246772 [52] US. Cl....., 432/234,;432/128 [51] Int. Cl. F27b.9/14 [58] Field of Search 432/126-128, 432/233, 234, 227,230, 31, 207, 235

[5 6 I References Cited UNITED STATES PATENTS 3,637,198 1/19 72 Knaak 432/234 3,214,152 10/1965 Molz 432/235 3,081,073 3/1963 Conway 432/128 FOREIGN PATENTS OR APPLICATIONS 785,960

11/1957 Great Britain 432/233 Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firme-Michael S. Striker [57] ABSTRACT An elongated furnace for heat treatment of metallic workpieces which are pushed through the heated furnace chamber along guide means extending from an inlet at one end of the furnace chamber to an outlet at the other end thereof. The elongated guide means comprise metallic elements supported on and in direct contactwith water-cooled pipes extending upwardly spaced from the bottom wall of the furnace from the inlet towards the outlet, anda ceramic hearth portion in the region of the outlet and having an upper guide face flush with upper faces of said metallic elements.

10 Claims, Drawing Figures PUSHER FURNACE BACKGROUND OF THE INVENTION The present invention relates to elongated furnaces for heat treatment of metallic workpieces such as metal blocks, slabs or the like-in which the metallic worpieces are pushed in longitudinal direction through the furnace on guide rails mounted on metal pipes through which cooling water is circulated and in which the metallic workpieces, while being pushed along these guide rails, are heated from above and below.

Guide rail constructions for furnaces of the mentioned type are know in various construction forms. Thus, it has already been suggested to construct the guide rails at the inlet end of the furnace chamber as metallic wear strips which are welded onto upper portions of pipes through which cooling water is circulated, whereas in an intermediate region of the furnace the guide rails are constructed from metallic glide members which are without heat insulation loosely set onto the pipesand removably held thereon. In the region of the outlet ends of this known furnace, the guide rails are formed from metallic elements with pressureresistant heat-insulatin'g members sandwiched between the metallic elements and the water-cooled pipes, and in which the. heat-insulating' members and the heatresistant metallic'members are held on the pipes by metallic frames welded to the pipes.

Pusher furnaces with guide rail means of the abovementioned type have given satisfactory results especially with regard to the required uniform heating of the workpieces at very high temperatures. In certain cases, however, the use of the insolated'metallic guide members at the last part of the guidev rails means is not possible .or desirable for constructive or operative reasons. This is, for instance, the case when the pusher furnace has also a lateral discharge opening forpushing the heated workpieces in a direction transverse to the longitudinal axis of the guide rail means out of the furnace. Evidently, in this case, the danger exists that the metallic elements, which are supported by means of heat-insulating. members on the water-cooled pipes,

.may be damagedor even pushed off the water-cooled SUMMARY OF THE INVENTION It is an object of the present invention to provide an elongated pusher furnace for heat treatment of metallic workpieces in which the workpieces may be heated to a uniform temperature throughout.

It is an additional object of the present invention to provide a furnace of the aforementioned kind which is simple in construction so as to be'producable at reason-v able cost and soas to stand up under extended use, even if the workpieces are pushed out of the furnace in a direction transverse to the elongation of the latter.

. It is a further object of the invention to provide a furnace of the aforementioned kind which avoids the necessity of heat-insulated metallic guide elements at the outlet end of the furnace.

With these and other objects in view, which will become apparent as the description proceeds, the pusher furnace according to the present invention has an elongated furnace chamber comprising a first zone adjacent the furnace inlet, a second zone adjacent the furnace outlet and an intermediate zone between the first and the second zones. Elongated guide means extend longitudinally through the furnace and comprise elongated metallic water-cooled guide means extending longitudihearth portion in said second zone forming an upper I guide face flush with the upper faces of the metallic guide means. Heating means are provided in the furnace for heating the furnace chamber and the metallic workpieces pushedthereto.-

The elongated metallic guide means preferably comprise at'least two transversely spaced metal pipes extending longitudinally through the first and intermediate zones for circulation of cooling water therethrough, and'a metallic wearv strip is welded in the first zone to an upper portion of each pipe, wihereasa plurality of metallic slide members are mounted inflthe intermediate zoneof each of the pipes, while means for maintaining the slide member indirect contact with an upper portion of the respective pipe are provided to hold the slide members in contactwith respectivepipe removable therefrom. The heating means comprise burner means arranged for heating the' metallic workpieces from above and below while the latter are pushed along the metallic guide means and the burners are prefera bly arranged in such a manner so as to heat the workpieces as they are pushed along the guide means to a higher degree in the intermediate zones than in the first and the second zone.

The wear strips are preferably formed from chrome second zone permitting the workpieces to be pushed out of the furnace chamber in a direction transverse to the longitudinal direction thereof and this second outlet is preferably arranged in the furnace wall which is located laterally of the ceramic hearth portion.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional advantages and objects thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section through the furnace according to the present invention;

FIG. 2 is a partial transverse cross section taken along the line [I -II of FIG. 1, drawn to an enlarged scale; and I FIG. 3 is a partial transverse cross section taken along the line Ill-Ill of FIG. 1, likewise drawn to an enlarged scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 schematically illustrates in longitudinal cross section an elongated furnace 1, the walls of which define an elongated furnace chamber having an inlet la at the right end, as viewed in FIG. 1, and an outlet 1b at the left end. The interior of the furnace chamber may be considered as divided into three zones, that is a first zone in the region of the inlet la where the top wall of the furnace is slightly lower than in the remainder of the furnace, a second zone in the region of the outlet, that is towards the left of the downward depression in the top wall of the furnace, and an intermediate zone between the first and the second zone. Elongated guide means extend in longitudinal direction through the furnace chamber from the inlet la to the outlet lb along which metallic workpieces, not shown in the drawings, are to be pushed through the furnace in the direction indicated by the arrow A. The elongated guide means comprise in the first and the intermediate zone at least two transversely spaced metal pipes S,

only the front one is shown in FIG. 1, through which cooling water from a source not shown in the drawing may be circulated. Inthe first'zone a plurality of wear strips 11, as clearlyshown on an enlarged scale in FIG. 2, are welded to the upper portion of the cooling pipe 5 and these wear strips which may have preferably a square or rectangular cross section have an upper surface along which the metallic workpieces to be treated in the furnace are. pushed. In the intermediate zone a plurality of slide members 13 of a height greater than those of the wear strips are placed on the upper portions of the pipes 5 with the lower ends of the slide members 13 have to be flush, that is in one plane with the upper surfaces .of the wear strips 11. Since the slide members 13 are higher than the wear strips 11, the cross section of the pipes on which the slide members are removably supported is preferably reduced as compared to the cross section of the pipe portions which support the wear strips, as clearly shown in the figures of the drawing. The pipes 5 are supported spaced from the bottom wall of the furnace on longitudinally displaced frame members comprising upright pipes 7 and transversely arranged pipes 9. In the second zone, that is in the zone adjacent to the outlet 1b, the guide means comprise a ceramic hearth portion 17 having an upper face flush with the upper faces of the slide member 13 and the wear strips 11.

The interior of the furnace chamber is heated by a plurality'of burners 3, only schematically indicated in FIG. 1 by the center lines of the burners, and it will be seen that the burners are arranged in such a manner that workpieces, when pushed in longitudinal direction through the furnace, are heated to a higher degree in the intermediate zone than in the first and second zones. The height of the slide members 13 is chosen in such a mannner that the cooling of the slide members 13 by the water circulating through the pipes 5, even at the highest temperatures and the most unfavorable operating conditions, is great enough that the hottest portions of the slide members 13 will assume only a temperature in which the material from which the slide members 13 are formed will still have sufficient rigidity and load-bearing capacity.

The slide members 13 are preferably formed from high heat-resistant steel, for instance a cobalt steel alloy containing up to about 50 percent cobalt, whereas the wear strips 11 may be formed from chrome-nickel alloy steel.

When metallic workpieces to be heat treated in the furnace chamber are pushed in the direction of the arrow A therethrough, the bottom faces of these workpieces will be cooled along portions thereof in contact with the wear strips 11 or the slide members 13, so that these portions of the metallic workpieces will have a temperature smaller than the remainder thereof. To assure a uniform heat distribution throughout the whole workpieces, which is necessary for the further treatment of such workpieces, for instance during rolling of the same, the ceramic hearth portion 17 is provided in the second zone in which a temperature equalization throughout the workpieces will take place.

The furnace is preferably provided adjacent itsleft end, as viewed in FIG. 1, with a lateral opening 19 in the side wall of the furnace through which the heated workpieces may be pushed out of the furnace by a device not shown in the drawing.

The pusher furnace according to the present invention may be successfully used in all cases in which the above-described construction and operating conditions are present. The construction may also be used when existing furnaces, which have already a ceramic hearth portion at the outlet end, are to be rebuilt, while maintaining the ceramic hearth portion. I v i It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of pusher furnaces differing from the type described above.

While the invention has been illustrated and described as embodied in an elongated pusher furnace having a ceramic hearth portion at the outlet end of the furnace and elongated metallic water-cooled guide means extending longigudinally through the furnace from the inlet end to the ceramic. hearth portion, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A pusher furnace for heat treatment of metallic workpieces, said furnace having wall means including a bottom wall defining an elongated furnace chamber having an inlet at one end of said elongated furnace chamber and an outlet at the other end thereof, said furnace chamber comprising a first zone adjacent said inlet, a second zone adjacent said outlet and an intermediate zone between said first and said second zones; elongated guide means extending longitudinally through said furnace and comprising elongated metallic watercooled guide means extending only through said first and said intermediate zones spaced from said bottom wall and having upper faces along which metallic workpieces are to be pushed from said inlet towards said outlet, and a ceramic hearth portion in said second zone having an upper ceramic guide face flush with said upper faces of said metallic guide means; and heating means in said furnace for heating said furnace chamber and metallic workpieces pushed therethrough.

2; A furnace as defined inclaim 1, wherein said elongated metallic guide means comprise at least two transversely spaced metal pipes extending longitudinally through said first and said intermediate zones and arranged for circulation of cooling water therethrough, metallic wear strips welded in said first zone to an upper portion of each pipe and. a plurality of metallic slide membersmounted in said intermediate zone on each of said pipes, and means for main-taining said slide members in direct contact with an upper portion of the respective pipe.

3. A furnace as defined in claim 2, wherein said means for maintaining said slide members in direct contact with saidpipes comprisemetallic ribs welded to said pipes and projecting upwardly therefrom to opposite sides of of said slide members.

4. A furnace as defined in claim 2, and including support means supporting said pipes upwardly spaced from said bottom wall.

5. A furnace as defined in claim 4, wherein said heating means comprises burner means arranged for heating metallic workpieces pushed along said metallic guide means from above and below.

6. A furnace as defined in claim 2, wherein said wear strips are formed from a chrome-nickelalloy steel and said slide members from a high heat-resistant steel.

7. A furnace as defined in claim 6, wherein said slide members are formed from a cobalt steel alloy containing up to 50 percent cobalt.

8. A furnace as defined in claim 7, wherein said burn-,

ers are arranged to heat workpieces as they are pushed along said guide means to a higher degree in said intermediate zone than in said first and said second zones.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,804,584 Dated April 16 1974 Gue Inventoflg N ter H It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, item 175] "Guenter Herr" should read -Guenter Hepp Signed and sealed this 1st day of October 1974.

(SEAL) Attest: I

MCCOY 1M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM F o-1050 (10-69) USCOMM'DC cove-ps9 U.S, GOVERNMENT HUNTING OFFICE: 9 9 0

Claims

2. A furnace as defined in claim 1, wherein said elongated metallic guide means comprise at least two transversely spaced metal pipes extending longitudinally through said first and said intermediate zones and arranged for circulation of cooling water therethrough, metallic wear strips welded in said first zone to an upper portion of each pipe and a plurality of metallic slide members mounted in said intermediate zone on each of said pipes, and means for main-taining said slide members In direct contact with an upper portion of the respective pipe.

3. A furnace as defined in claim 2, wherein said means for maintaining said slide members in direct contact with said pipes comprise metallic ribs welded to said pipes and projecting upwardly therefrom to opposite sides of of said slide members.

6. A furnace as defined in claim 2, wherein said wear strips are formed from a chrome-nickel alloy steel and said slide members from a high heat-resistant steel.

8. A furnace as defined in claim 7, wherein said burners are arranged to heat workpieces as they are pushed along said guide means to a higher degree in said intermediate zone than in said first and said second zones.

9. A furnace as defined in claim 1, and including a second outlet in said second zone permitting the workpieces to be pushed out of said furnace chamber in a direction transverse to the longitudinal direction thereof, said second outlet being arranged in a portion of said wall means which is located laterally of said ceramic hearth portion.

10. A furnace as defined in claim 5, wherein said burner means are arranged for heating metallic workpieces pushed along said ceramic hearth portion only from above.