US3416777A

US3416777A - Zoned reheat furnace

Info

Publication number: US3416777A
Application number: US657976A
Authority: US
Inventors: Jr Frank Alexander
Original assignee: Morgan Construction Co
Current assignee: Siemens Industry Inc
Priority date: 1967-08-02
Filing date: 1967-08-02
Publication date: 1968-12-17
Anticipated expiration: 1985-12-17

Description

F. ALEXANDER, JR

ZONED REHEAT FURNACE Dec. 17, 19.68

2 Sheets-Sheet 1 Filed Aug.

mvENToR FRANK A. ALEXANDER,JR. BY

M ma@ 9 MAT, T O RNEXS Dec- 17, 1968 F. ALEXANDER, JR 3,416,777

ZONED REHEAT FURNACE Filed Aug. 2, 1967 2 Sheets-Sheet 2 i FIC-3.4 i fl 54/ i INVENTOR.

RANK A. ALEXANDER,JR. B

@LLM s# wd ATTORNEYS United States Patent O 3,416,777 ZNED REHEAT FURNACE Frank Alexander, Jr., West Boylston, Mass., assigner to Morgan Construction Company, Worcester, Mass., a corporation of Massachusetts Filed Aug. 2, 1967, Ser. No. 657,976 6 Claims. (Cl. 263-6) ABSTRACT F THE DISCLOSURE This invention relates to a furnace for reheating billets, blooms, or slabs (collectively referred to hereinafter as billets) prior to rolling in a rolling mill. The construction of the furnace makes it possible to heat each billet so that there is a controlled, substantial temperature gradient between the leading `and tail ends o-f the billet when it leaves the reheating furnace. The presence of the predetermined temperature gradient makes it possible to have a substantially uniform billet temperature at each roll stand for the entire length of the billet as it passes therethrough.

Background of the invention Reheating furnaces for heating a succession of billets prior to rolling the billet in the adjacent rolling mill are standard in the industry. In many mills it is acceptable practice to heat the billet throughout its length to the same or substantially the same temperature. For example, if the billet is to be rolled into rod, the required temperature might be 2l00 F. If the first pair of rolls to which the billet is fed is immediately adjacent the pushout door of the furnace, a uniform temperature of the billet is satisfactory because the temperature of each instantaneous part of the billet ias it passes through the first pai-r of rolls in the train will be substantially the same, namely 2l00 F. If this is the case, then the temperature of each instantaneous part of the rolled product, when passing through the last pair of finishing rolls, will likewise be the same but lower. Thus, with a uniform but decreasing temperature of the product at each of the roll stands throughout the rolling operation, the finished product will have correspondingly uniform metallurgical properties.

In some mill arrangements, however, it is not customary to have the first pair of rolls immediately ladjacent the the pushout door. Instead, the first pair of rolls may be a substantial distance from the reheating furnace, so that the pushed out billet will be completely out of the furnace before the leading end of the billet is engaged by the first pair of roughing rolls. lf it be assumed that the leading end of the billet enters the first pair of rolls at 2l00 F., then because of the time that must necessarily elapse before the tail end of the billet reaches the first pai-r of rolls, the temperature at the tail end may have dropped substantially, perhaps in the 4order of 100 F. In such case, it can be seen that the effective rolling temperature of each point in the length of the billet will be slightly below the temperature of that immediately preceding. The result is that the leading end of the billet, for example, might be rolled at a temperature of 2100a F. at the first pair of roughing rolls and l750 F. at the last pair of tinishing rolls, whereas the temperature at the tail end of the billet would be 2000" F. at the first pair of roughing rolls and 1650 F. at the last pair of finishing rolls. This being the case, the metallurgical qualities of the finished rod rolled at a changing temperature from one end to the other would obviously be non uniform.

The difficulty just referred to has, of course, been recognized and the desirability of heating the billet so as Patented Dec. 17, 1968 ice to present a temperature gradient has heretofore been appreciated. In the existing reheat furnace designs it is diflicult to develop a variable pattern of heat along the length of a billet. Normal practice has been to divide burners into groups across the width of a furnace and control the firing rate of each group. This will develop `differential heating to a minor degree. The limitation to the degree of differential heating is the effect of radiation and re-radi-ation from roof, walls, and hearth.

Summary Applicants invention is specifically directed to the particular construction of a re-heating furnace that makes it possible to impart to each billet prior to its being pushed out of the furnace to the rolls a temperat-ure gradient of any required degree. Experience will determine the gradient required so that the billet when rolled will present through all points of its length the same temperature at any given roll` stand. Thus, if it is desired that the temperature at the iinal finishing rolls should be 1900 F., the presence of the temperature gradient will result in a temperature of 1900 F. from the leading end to the tail end of the billet when each instantaneous part arrives at the finishing stand.

The furnace that achieves this result includes a novel arrangement of bafile walls located in spaced relation across the furnace width and running longitudinally in the furnace at right angles to the length of the billets. The baffle walls physically divide the furnace into zones and act to contain the heating radiations and re-radiations from the roof, walls, hearth and baffle walls in the -area where the heat pattern is required. By varying the nurn- -ber of baille walls, as many Zones may be provided as necessary to give the required temperature gradient. The gradient is developed sufficiently quickly that equalization of the temperature throughout the billet by conduction does not have time to occur before the billet is pushed out of the furnace.

Brief description of the drawings In the drawings, FIG. 1 is a vertical longitudinal cross section of a reheating furnace showing the depending bafiles at the high heat end of the furnace adjacent the pushout door.

FIG. 2 is a section taken on the line 2-2 -of FIG. 1 and drawn to an enlarged scale.

FIG. 3 is a fragmentary detail of a vertical section taken on the line 3-3 of FIG. l drawn to still further enlarged scale illustrating one construction of baffle.

FIG. 4 is a section on the line 4 4 of FIG. 3 showing details of the wall construction.

Description of the preferred embodiment Referring first to FIG. l, the numeral 2 indicates in general a reheating furnace of which the conventional billet receiving end at the right has been broken away. This furnace has a hearth, walls and ceiling indicated at 4, 6 and 8 Imade in conventional :manner of conventional materials. The billets 10 are pushed into the receiving end of the furnace to lie side by side and to be advanced toward the discharge end of the furnace by conventional pusher bars not shown. As the billets advance step by step and side by side through the furnace, they are gra-dually heated by a plurality of burners 12 located across the vertical intermediate Wall 14. By the time the billets have arrived under the low ceiling 16, they will have been heated uniformly from end to end and might be at a temperature in the order of l900 F. The billets then advance into the high temperature end of the furnace to be brought up to iinal temperature before being discharged through the pushout door 18.

The temperature gradient that is developed in each billet is achieved through the use of a plurality of the depending bailles 20 which are illustrated in detail in FIGS. 2, 3 and 4. Each of these bailles is identical with the others so that the description of one will suilice for all. While only two baiiles have been shown in FIG. 2, it will be understood that there may be three or four if it is found necessary to create a steeper temperature gradient. As shown in FIG. 2, it will be assumed that the end billet 10, fully heated, is to be pushed out through pushout door 22 through the use of conventional pusho'ut mechanism, not shown. The several burners in the nal zone are illustrated collectively at 24 in FIG. l and individually at 26, 28, 3), 32, 34, 36 and 38 in FIG. 2. Again the number and capacity of the burners and their location will be dictated by the temperature gradient required. Let us assume that each billet should have a temperature gradient when it leaves the furnace varying fro-m 2l00 F. at the leading end to 2300 F. at the tail end. To produce this result, the

burners

26 and 28 are set to produce a high temperature, the

burners

30, 32 and 34 an intermediate temperature, and the burners 36 and 38 a low temperature. The radiations from

burners

26 and 28, for example, reilect from the wall 40 and ceiling 42 and baille 20 to raise the temperature of billet 10 in Zone A to 2300 F. The burners in Zone B, 30, 32 and 34 will raise the temperature of the intermediate section of the billet to 2200 F., and the burners 36 and 38 in zone C will raise the temperature of the billet to 2100 F. It is obvious, of course, that if the billet were allowed to soak at these temperatures for a substantial period of time, the conductivity of the billet 10 would lessen the temperature gradient. However, by experimentation with the burner temperatures in the several zones, it has been found possible to create in each billet a substantial temperature gradient which will produce a uniform temperature of each instantaneous part of the work at each roll statnd as the work passes therethrough.

The suspended baille walls which serve to isolate suiliciently the different temperatures produced in each of the zones will now be described. It is to be understood, of course, that each baille may be made in any convenient way, but the form herein presented has been found relatively simple to install and easy to maintain.

Two longitudinal slots 44 are provided in the roof 44. These slots extend from the wall 6 to the low ceiling portion 16. Above the furnace are a suillcient number of crosswise extending beams 46 to which are attached longitudinally extending members 48 of suilicient strength to carry the load of the baille walls. In the form shown, there is a number 48 over each of the two openings 44. Depending from beams 48 are a plurality of U-shaped supporting rods S0 which carry one or more members 52 which in turn serve to support thereon refractory bricks 54. The two adjacent me-mbers 52, one above the other, are connected in any convenient manner as by an oval loop 56.

The members 52, as seen in FIG. 4, are in the shape of short sections of vertical I-bea-ms with their

flanges

53 and 55 acting as means for holding the inturned flanges S7 and 59 of the superimposed refractory members in aligned position in which the cooperating ribs and

grooves

61 and 63 interlock.

In assembling the baille Wall, the support rods 50 with the members S2 hanging therefrom are lowered down into the furnace a suillcient distance to permit the builder to place the individual refractory members 54 on the supports 52. The lowermost pie-shaped refractory members indicated at 58 are placed on the supports 52 rst, sliding downwardly to the bottom to meet and curve around in the manner shown. Then the horizontal members 60 are dropped in place, interlocking with the

members

52 and 4 with each other, thus to provide one unit of the baille Wall.

Each baille wall unit is indicated by the letter U as can be seen in FIG. l. As each unit is completed, it is pulled up in place against the underside of the ceiling 42, as shown in FIG. 3, by taking up on the nuts 62 acting on the threaded portion of the U-shaped support rods 50. Where the ceiling slopes as at 64, the 'upper surfaces of the adjacent refractory -units 54 are beveled so as to ilt snugly against this part of the underside of the ceiling.

In the foregoing manner, each baille unit is assembled and pulled up to final position. There is no requirement that the iit of the portion of the bailles within the slots 44 be of a precision character. They :merely need to t comfortably therewithin and pulled up tight enough to prevent the escape of furnace gases and attendant heat.

The vertical dimension of the battles may be varied to some degree. The greater the vertical dimension, the better the temperatures in zones A, B and C may be maintained Without interference from the diifering temperatures in the adjacent zones. On the other hand, baflles of greater vertical dimensions will cost somewhat more to install initially and to maintain thereafter.

With the principles of the invention now understood, it will be apparent that the requirement temperatures to be produced in each billet will have to be determined by a certain amount of experimentation with the burners. Once these zone temperatures and burner settings are determined, then billets with the required temperature gradient can be reproduced repeatedly to give the required uniform temperatures at all stands of the subsequent rolling operation. The present invention thus enables the rolling mill to produce a produce of capable of meeting the constantly increasing tolerances now required in the indlustry.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

I claim:

1. A reheating furnace having at the discharge end of the furnace a plurality of parallel spaced longitudinally extending baille walls that depend downwardly from the roof of the furnace to provide zoned heating areas that will be relatively immune from temperatures in adjacent zones, burners positioned in the end wall of the furnace in each Zone controllable as to temperature whereby the temperatures in each zone may be increased substantially from one side of the furnace to the other, and whereby the billets subjected to the progressively increasing temperatures in the zones will be heated so as to have a substantial temperature gradient therein extending increasingly from the leading end to the ail end of each billet and whereby each said billet so heated when pushed from the reheating furnace will incorporate such temperature gradient.

2. The furnace as set forth in claim 1 in which each said baille wall comprises a plurality of individual units arranged side by side thereby to produce a wall capable of isolating said temperature zones from each other.

3. 'I'he furnace as set forth in claim 1, in which the baille walls are constructed of a plurality of depending side by side units hanging from the ceiling and extending from the discharge end of the furnace to meet the sloping part of the ceiling that deilnes the limit of the high temperature part of the furnace.

4. The furnace as set forth n claim 1, in which the bottom of the baille walls are more or less on the same level as the burners in the end wall whereby the heat produced by the burners in each zone will lbe largely conilned therein to act on that portion of the billet therebelow to produce the required temperature gradient therein.

5. The furnace as set forth in claim 1, lin which each baille wall comprises a plurality of side by side substantially identical units made 'of a plurality of refractory members positioned one on the other, each unit being supported =by vertically movable means extending through the furnace ceiling permitting the unit to be lowered below the said ceiling far enough for initial assembly of the refractory members, and means for substantially closing all ceiling apertures above said baille walls when the walls are raised by said vertically movable means to final proper position.

6. The furnace set forth in claim 5, in which said vertically movable means comprises a depending rod hanging through said ceiling from a support thereabove, a member hanging from said -rod having vertically disposed means for receiving and holding thereon a plurality of vertically stacked refractory members whereby said refractory members after being assembled one on the other may be drawn upwardly by said -rod to rest against said ceiling.

References Cited UNITED STATES PATENTS JOHN J. CAMBY, Primaly Examiner.

U.S. C1. X.R. 263-36