US2231985A - Reheating furnace - Google Patents

Description

Feb. 18, 1941;- s. BADLAM REHEATING FURNACE riginal Filed July 2. 193s 2 sheets-sham 1 3 I INVEgOR Feb. 18, 1941. s. BALAM REHEATING FURNACE originai Filed Jly 2, 1935 2 sheets-sheet 2 INVENTOR 511W Kw2/46M Patented Feb. 18, 1941 `UNITED .STATES REHEATING FURNACE Stephen Badlam, Rosslyn Farms Borough, Pa.

Original application July 2, 1935, Serial No. 29,480, now Patent No. 2,139,483, dated December 6, 1938. Divided and this application December 9, 1938, Serial No. 244,790

This invention relates to reheating furnaces A and is a division of an application filed by me on July 2, 1935, serially numbered 29,480, and patented December'G, 1938, as Patent No. 2,139,483.

An object of this invention is to produce a furnace for obtaining the differential heating of i successive length elements of a piece being rolled as set forth in said application.

A further object is to produce a relatively 10 short furnace by means of which comparatively long intermediate pieces may be reheated.

These, and other objects as will be made more apparent throughout the further description of' my invention, I attain by the apparatus described in the specication and illustrated inthe drawings accompanying and forming part of this application.

In the drawings:

Figure v1 is a. horizontal sectional view of a furnace embodying this invention and is taken along the lines I-I of Figures 2 and 3 with the loopers of Figure 2 in horizontal position;

Fig. 2 is a vertical sectional view along the lines II-lI of Figures 1 and 3 with the ioopers in lowered position:

Fig. 3 is a transverse sectional view along the line III-11'! of Figures 1 and 2;

Fig. 4 is a fragmentary plan view of -a struc- .tural detail included in the vfurnace illustrated in Figs. 1, 2 and 3: s

Fig. 5 is a fragmentary elevation; Fig. 6 a fragmentary side view and Fig. 'I is a fragmentary sectional view of the detail illustrated in as Fig.4. In Fig. 'l the looper is shown in lowered position.

one difficulty encountered in hot rolling metal to form thin fiat sections 'such as strip is due to a variation in the temperature between the front or leading end and the back or trailing end of` 40 the piece rolled, at the time each is subjected to the reducing forces.

It is apparent that; when a heated metal piece is subjected to the reducingaction of a roll pass,

the time at which the trailing end is subjected to 45 the reducing actionis later than the time ats which the leading end was subjected to the same reducing action, and that, due to the longer time during'which 'rit was exposed to the cooling iniluences, the trailing end will be subjected to '50 such reducing action at a lower temperature practice this difference will be substantially directly proportional to the length of the piece as it traverses the roll pass, and inversely as its thickness, and as the speed of the rolls. It is apparent that for a thick short piece this temperature differencel will be small in amount, and, for

all practical purposes negligible but for a long thin piece, and particularly at usual roll speeds it becomes a factor of major importance. It is furthermore apparent, that, when successive passes in the same direction are employed for the-hot reduction of a piece to a comparatively thin gage as for example in the rolling of strip, this action takes' place at each pass, and the ef- 15 fect iscumulative, as on leaving each pass'the rear end is not only slightly colder, but also slightlythicken than the front end.I In .practice these variations eiectively prevent the rolling of wide thin material in as long lengths as would otherwise be desirable.

My said applications sets forth a method for correcting these inequalities in the finished piece, by differentially heating the piece at an intermediate stage of the reduction in such manner that each .length element of the piece, from the hotter end to the cooler end, is subjected Ato an -elevated temperature for an increasing period of time, and such differential reheating is so regulated. in relation to the time of application of Vthe ensuing reducing forces that the temperature of each length element of the piece, at the time oi application of the last substantial reducing force, is such as to produce a finished piece of substantially uniform thickness and physical properties. 35

My improved furnace is preferably, although not necessarily, placed between the roughing train and the finishing train of a continuous mill and 4*has a double function. namely, to supply heat to the piece as it leaves the-last roughing 40 pass and enters the rst pass of the finishing train and also to so apply heat to the piece as to avoid the detrimental effects of temperature difference heretofore commented upon..

With the .furnace of this invention, the desired 45 heatinput to successive length elements of the piece is accomplished by employing a uniform distribution of temperature throughout the length of the heating chamber and by so controlling the delivery to and withdrawal from that chamber that the successive length elements of the piece are differentially heated so as' to produce an increase in temperature ofthe successive elements from the leading to the trailing end of the piece.

Since the piece is progressively heated from the leading to the trailing end each length element as it approaches the nal stand of the iinishing train is as hot as the preceding elements and vtherefore the trailing end of the piece arrives at such stand at substantially the same temperature that the leading end of the piece had when it arrived at that stand.

That is to say, the function of my reheating furnace is not only to supply heat to the previously heated piece as that piece' is delivered from the last pass of the roughing train and to the first pass of the finishing train, but to supply heat differentially along the piece so that all length elements thereof will be of substantially equal temperature as they are-acted upon by each of the finishing stands of the finishing train. It will, of course, be apparent that the leading end of the piece may be colder when it arrives at the last stand of the nishing train than when it arrived at the rst stand of said train due to the cooling effect occasioned by the' necessary lapse of time, but by means of my improved furnace I am able to so supply heat tol successive length elements of the piece while itis in my reheating furnace or is passing therethrough that each successive length element of the piece is of approximately the same temperature as every other length element thereof at the time it receives its last substantial amount of work, i. e., when it is acted upon by the ilnal stand of the ilinishing train.

My improved furnace is so constructed that I can deliver the piece thereinto from the last stand of the roughing train at a higher speed than the piece is withdrawn therefrom and delivered to the first stand of the finishing train. The furnace illustrated in the drawings may be employed in connection with rolling equipment, for instance a continuous mill, for carrying out the method disclosed in my said application.

Said furnace is adapted for the differential reheating of pieces having a greater length than the distance between the roll stand preceding it and that following it, thus materially saving door space.

'I'he furnace will preferably be located in line withthe roll stands making up the mill, and between the roughing and finishing trains so as to differentially heat the piece as it leaves the former and enters the latter. It is apparent that the roughing and finishing trains may each comprise several stands, or either or both may consist of a single stand in which one or more passes may be taken.

'I'he furnace includ a housing HI enclosing' a heating chamber H2 which extends above and below the plane generally defined by the pass line of the last stand of rolls AI ofthe roughing stand and the first stand of rolls A6 of the nishing stand. In its broader aspects, the furnace is of the tunnel type in that-it is provided at one end with an aperture H3 through which the piece delivered from stand A4 enters the furnace and it is provided with a similar aperture H4 at the other end through which the piece emerges as it moves toward stand A6 of the finishing train.

In order that the leading end of the. piece W issuing from stand A4 may beconveniently passed through the furnace and then presented to the first stand A8 of the finishing train, I employ what may be termed a conveyor table assembly vwhich is conveniently`formed by four dierent parts, each of which is movable. As illustrated. it consists of two oppositely disposed loopers ILl and L2 and a table proper which is formed in halves. TI and T2. Each half of the table proper is movable outwardly from the center line of the furnace heating chamber l. e., from the Work supporting position shown in Fig. 1 to a position out of the line of travel of a work piece or strip through the furnace'and each looper is movable from a horizontal position as shown in Figs. 1 and 6 to an inclined position as shown in Figs. 2 and 7. Thus, the parts described may either occupy positions such that they, in effect, substantially bridge the gap between the passes of the stands A4 and A6 and provide a substantially horizontal and uninterrupted conveying surface over which the leading endiof each piecefmay be guided from the entrance aperture H3 to the exit aperture H4 of the heating chamber; or the halves of the table proper may be retracted and the looper arms dropped to the inclined position thus permitting intermediate portions of each strip or work piece to fall below the ent'rance and exit plane of the chamber and loop within the lower portion of the chamber. It will be understood that one or both of the loopers may be omitted or the two loopers in themselves may be of sufficient length to bridge the gap, thus obviating the necessity for the table proper and all without affecting the operation of the furnace in effecting a dierential heating of the piece passing therethrough.

Each half Tl and T2 of the central portion of the table proper is carried by a separate movable frame which is more or less diagrammatically fil- 'lustrated as being fabricated from structural sections T3 and T4 and pipe sections T5 and T6, which latter may be protected against they heat of the furnace by causing water to flow through them. Each frame is mounted upon support rails,

T1 and T8, which extend transversely of the longitudinal center line of the furnace andare located wholly without the furnace chamber. The arrangement is such that each frame is movable along its supporting rails so as to move its corresponding table half TI, or T2, laterally to and from the position shown in Figures 1 and 3. Each frame is preferably provided with flanged wheels, T9, for facilitating this movement. Electric motors, MI I and M12, may be employed for actuating each frame, and reduction gearing DI I and DI2, and rack and pinions, TII and TIZ, may be employed betweeneach motor and its corresponding table half. As shown in Fig. 3, the inner, heat resisting wall of the furnace is provided with inwardly extending shoulders K which may aid in protecting the table halves, TI and T2, particularly when they are Ain their outermost positions, and not actively engaged in guiding the front end of the strip from stand A4, l

Each looper, LI or L2, consists essentially of a body or hub portion L8, and an integrally formed projecting arm, L4. The hub L3, 'is provided at each end with trunnions LU. adapted to -be supported in suitable bearings carried by pedestals.

'1.6, located on either side of the furnace. In

adapted to be pivotally connected to an actuating motor Q, Fig. 2, by means of a link, QI. The motor Q may be a solenoid, or a thrustor, or a pressure cylinder and its piston, in which case the link, QI would, in effect, constitute the piston rod. It may equally well be a rotating crank linkage.

The motivating means, Q, for each looper is adapted to move the arm L4 to and from a position in which the upper flat surface thereof is substantially horizontal, and as shown in Fig. 6,

or to and from the position shown in Figs. 2 and v 7. In the upper or horizontal position, the arm L4 of each looper cooperates with guide members, G5 and G6 which extend into the furnace and which constitute lateral guides for the piece moving into and from the heating chamber over the corresponding looper LI or L2. It will, of course, be apparent that all operating parts within the furnace, or exposed to the heat of the furnace are formed of heat resisting material, or are water cooled.

The operation of the heating chamber is as follows: As a piece W is delivered from the stand A4, it is guided by the delivery guides G4` of that stand onto the looper LI, which is then in 'elevated position with its arm L4, horizontal and cooperating with the guides G5. As the piece W enters the furnace, its leading end moves under the roller R2 and then continues its travel over the table proper, the halves Tl and T2 of which are in their innermost position, as shown in Fig. 3. The looper L2 is also .in the elevated position and thus is, in eiect, an extension of the l table proper, consequently the leading end continues over the arm L4 of the looper L2 and moves beneath the roller R2 of that looper. This movement of the strip is occasioned by the strip impelling means at the inlet end of the furnace, e. g., the reducing rolls of the stand A4, and continues until the leading end is engaged by the withdrawal means, e. g., the rolls of the scale breaker A5. When this occurs the loopers LI and L2 are dropped to the position shown in Fig. 2 and the table halves TI and T2, are withdrawn laterally from the center line of the furnace so that they no longer support the intermediate portion of the work piece W. Under such conditions the intermediate portion of the oncoming piece drops towards, or to, the bottom of the furnace chamber H2 and its further withdrawal -from the furnace is controlled by the gripping rolls on the exit side of the furnace, e. g., the rolls of scale breaker A5.

The roller-Ri of each looper LI and L2 is elevated as shown in Fig. '7, by the dropping of the looper arm, and these rollers, in connection with the rollers R2 of the loopers guide the strip into and as it moves out of the furnacewhen the loopers are lowered.

In this furnace-the rate of delivery of the piece W into the heating chamber exceeds the rate of withdrawal therefrom, consequently looping of the strip or work piece W will occur within the chamber and the form of the loop may be controlled by manipulating the looperY Ll, i. e., by raising and lowering the same so as to cause on-coming portions of the piece to overlap preceding portions.v

In this apparatus, the leading end of the work strip or piece W moves through the chamber at the entrance rate.. As soon as this end is engaged by the withdrawal means, e. g., by the' rolls of the scale breaker'A5,the rate .of Iwithdrawal of the piece is controlled by the rate at which the strip passes through these rolls. It will, therefore, beapparent that the intermediate length elements of the strip are retained in the furnace for a period of time which corresponds to the difference between the entranceand withdrawal rates, even though the entire piece is never located wholly within the furnace. As the trailing end of the piece is withdrawn from the furnace by the action of the gripping rolls at the exit end of the furnace, e. g., the rolls of scale breaker A5, the loopers are again raised,and the table is again moved inwardly so that its halves TI and T2, cooperate with the loopers to provide a continuous surface over which the leadingv end of the next succeeding piece W may move. that the looper Li may be elevated and the table halves Ti and T2 may be moved inwardly, i. e., to a strip supporting position, prior to the elevation of the looper L2 and for this reason a strip may be entering the furnace while the trailing end of the preceding piece is leaving it. The -rate of feeding pieces to the stand A4 however, must lbe so .timed asto avoid having the leading end of any piece 'overlap the trailing end of the preceding piece.

. The gripping rolls at the exit end of the furnace e. g., the rolls of scale breaker A5 should be so-located and all moving parts LI and L2, TI and T2, so manipulated. as to avoid forming excessive loops in the strip on the exit end of the furnace, and between the guiding roll R2 of the looper L2 and such gripping rolls. It is, of course, apparent that with this furnace the leading end, and a small but appreciablel portion of the strip immediately adjacent thereto will only be subjected 'to the direct heat of the furnace as they are propelled through the furnace at the speed Aoi? delivery from stand A4, but even so, the major portion, and in fact substantially all, of the strip will be differentially heated, as described, and the heat input into the piece, and each length element thereof may be so controlled by Vvarying the temperature of the furnace, the rate of delivery into, and the rate of withdrawal from the furnace, as to insure a predetermined heating of `eachA such element, such that all length elements of the piece arrive atthat an the length elements. are at substantiany Itis, of course,'apparent the same predetermined temperature at the time they are acted upon by the finishing stand, or by the final stand in which they receive substantial deformation. I am able to produce long lengths of flat material, in thin gages and -wide widths, which is uniform from end to end, from the standpoint of cross section, physical properties', and grain structure. and that I am able to A do this with a saving in power and a consequent Letters Patent is:

1. In a furnace for heating rolled material in long lengths, a heating chamber which is horizontally elongated but of materially less length than the lengths of material to be heated and having .horizontally aligned work passing apertures at opposite ends thereof, a work support at each end of the furnace, extending into said chamber through the adjacent work passing aperture and having a pivotal mounting outside of said chamber, and means locatedoutside of said chamber and operatively connected to said work supports for swinging the same to and from horizontal position.

2. In a furnace for heating rolled material in supporting means, and pivoted means extending v through saidapertures and cooperating with said horizontally movable support means in forming a substantially continuous work supportbetvs'reen said apertures.

3. In a furnace having work passing apertures at opposite ends thereof, pivotally mounted work support means extending into said chamber through said apertures, -workv supportmeans movable horizontally and in opposite directions throughopen'ings'in the sides of said chamber between said pivotally mounted work support means, andmeans for' moving said -pivotall'y mounted means to and from horizontal work supporting position.

4, In a heating furnace for wide thin material,

for heating rolled material in I long lengths, a heating chamber of materially less length than the material to be heated and ahousng enclosing a heating chamber and hav ing work passing apertures at opposite end thereof, work support means movable horizon tally into said chamber through openings in op posite sides thereof, and work supports pivotall mounted outside of said chamber and extend ing through said apertures to the interior there of.

- 5. In a furnace for heatingrolled strip mate rial Iat an intermediate stage of reduction, l housing enclosing a heating chamber and havin substantial depthbelow work passing aperture located at opposite ends thereof, work suppor means movable horizontally through openings l;

opposite sides of said chamberjside guides with in the chamber adjacent said apertures and Worf lsupport means pivotallj1 mounted 4outside of sail chamber and projecting l into the chambe through said apertures, and means outside o said chamber for moving said pivoted work sup port means to land from position in line with sai horizontally movable support means.

6. In a furnace for incrementally heating rolle strip material in its passage between -successiv stands of a rolling mill, a housing for said mil a heating chamber having work passing aperture at ,opposite ends thereof, with the distance be tween said apertures materially less than th length of the strip to be heated, hinged suppor means adjacent each such aperture and project ing therethrough into ,said chamber for support ing said strip in its passage from one apertu'r to the other; said chamber below thev plane o said apertures being of sumcient depth to permi looping of such strip and means for moving sai support means to a. position at which the stri STEPHEN BADLAM.

CERTIFICA'IEl OF CORRECTION.; Patent-No'. 2,251,985. Febraryl, 1914.1.

STEPHENv BADLAM.

It is herebly certifiedthat error a'ppearg in the lfnrinted specification of the above numbered partent requiring correction as follows: Page 5,4 first column? lines YO and Y1, for the words "work s-trip or? -Iead- ,--strip or work; and thai-. the Said Letters Patent should be read with this oorrec tion therein tht the/same may-co'\form to therecord of -the -ase. in 'the Patentlofie,

Signed andsealod this'25thday-oi `March, D.19b.1.

- Henry vanAz-sdal'e,

(Seal) 4 Ani-ting Commissioner of Petets.V

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