CA1080424A - Heating apparatus for twin-belt casting machine - Google Patents

Abstract

HEATING APPARATUS FOR TWIN-BELT CASTING MACHINE
ABSTRACT OF THE DISCLOSURE

Heating apparatus for use in a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting belts and in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as it is being solidified.
The apparatus comprises a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting region, and the first and second support means aiming the banks of heaters to direct intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they enter the casting region, thereby to minimize the distortion of the casting belts after they begin carrying the molten metal between them in the casting region.

Description

This application is a division Or Canadian Patent Application No. 212,480 filed October 29, 1974 entitled TWIN-BELT
CONTINUOUS CASTING METHOD AND APPARATUS.

DESCRIPTION

The present invention relates to continuous casting methods and apparatus wherein thetemperature of the flexible casting belt in twin-belt casting machines is controllably eleva~ed prior to contact with the molten material being cast.

FIELD OF THE INVENTION

In twin-belt casting machines the material being cast, which is illustratively shown herein as molten metal~ is fed into a casting region between opposed portions of a pair of revolving flexible metal belts. The moving belts confine the molten metal between them and carry the molten metal along as it solidifies between them. Spaced l?ollers having narrow ridges support and drive the belts and also guide the belts as they move along through the casting region. The vast quantities of heat liberated by the molten metal as it solidifies are withdrawn through the portions of the two belts which are adjacent to the metal being cast.
This large amount of heat is withdrawn by cooling the reverse surfaces of the belts by means of rapidly moving substantially continuous films of liquid coolant travelling along against these reverse surfaces.
Each of the two flexible casking belts is revolved around a belt carriage in a path defined by main rolls located in the carriage and around which the belt passes. In some twin-belt casting machines there are two main rolls at opposite ends of the carriage defin~ng an ~` oval path for the belt to travel. In other twin-belt-casting machines there are three or more main rolls in each carriage defining the belt path.
In some twin-belt casting machine installations the upper and lower casting belts converge directly opposite !!
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each other around opposed nip rolls to form the entrance to the casting region, and the molten metal is fed into the machine through a pouring spout extending into the entrance. l ¦
',This is often called an "injection feeding" technique. In lother twin-belt casting machine installations the lower cast- I
-ing belt i5 arranged to support a pool of molten metal ad jace~t ~to the entrance between the upper and lower belts. This l!latter arrangement is called an "open pool" or "closed pool"
Icasting technique, depending upon whether the surface of the ,molten pool is open to the atmosphere or is closed over by a protective barrier to exclude the atmosphere, Variations of these molten metal feeding techniques are sometimes employed, such as a partially open pool. However, as used herein, all ,lof the various techniques for feeding molten metal into a ~,twin-belt casting machine are intended to be included within ~the descriptive phrase: "open pool, closed pool or injection I ,.
'feeding".
The-present invention can be employed to advantage~
'lin any of these varioUs twin-belt casting machines whether llusing two, three, or more main rolls in each carriage, and th~l inven~ion Can also be employed tv advantage regardless of . .;
,whether the molten metal is being fed into the machine by an ,'open pool, closed pool, or inj ection ~eeding.
! For further information about twin-belt casting 'llmachines, the reader may refer to one or more o the following !united States patents in the name of Clarence W. Hazelett or R
William Hazelett and Richard Hazelett: 2,640,235; 2,904,860; 1 . i ,3,036,348; 3,041,686; 3,123,874; 3,142,873; 3,167,830;
3,228,072; and 3,310,849.
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-3- ' Prior Art -,., ' .`
In the prior art, efforts were made to minimize the heating effects of the molten metal on the casting belts of twin-belt machines. The high velocity liquid coolant was applied to the reverse surfaces of the belts a relatively long time before the molten metal came in contact with their front faces. Also, the high velocity liquid coolant was applied to the reverse surfaces of the belts a relatively great distance ahead of the point where the molten metal came in contact with their front faces.
In addition, relatively thick insulatiye coat~
ings were often applied to the front faces~ of the flexible metal casting belts. It was these insulative coatings which w~ere at the interface between the molten metal and the c~stipg belts and served to reduce the rate of heat transfer from the molten metal into the belts.
Nevertheless, in the prior art, as the molten ` metal began to be carried along downstream with the belts near the entry to the casting region~ momentary or permanent belt distortion could occur due to buckling resulting from thermal expansion. Efforts were made in the prior art to minimize any such distortion by applying high tension forces to the belts, and one or more of the main rolls were sometimes contoured slightly as by reverse crowning to co~nteract ' such distortion, as described and claimed in United States Patent No.
3,123,874.
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2~ 1 ¦l The Invention The invention provides continuous casting methods !
and apparatus in which the temperature of the flexible cast- I .
' ing belts in twin-belt casting machines is controllably .elevated prior to contact with the material being cast, which.
is illustratively shown as molten metal. The casting belts may be elevated in temperature by various methods and I
,apparatus, as explained in connection with the various illus-l trati~rP embodiments of the invention which are described~ ~
11 In some embodime~ts of the invention, one or ~ .
more banks of high intensity infra-red hea~ers may be direct-¦
ed at close range against the front faces of the castiny belts to elevate their temperature before the belts come into con- I
tact with the molten metal. The bankY of infra-red heaters ¦ ;
llmay ~e arranged to heat the casting belts before they reach ¦.
¦lthe nip rolls at the entrance to the casting region or during : iltravel of the belts around the nip rolls or both before and during travel around the nip rolls.
~ In other embodiments of the invention, hot fluid,¦
~Isuch as steam, may be circulated within hollo~ nip rolls to .
elevate the temperature of the casting belts before the belts~
~ Icome into contact with the molten metal or to control the lichange in temperature of the casting belts. . .
Ij In further embodiments of ~he invention, the ..
¦Ihigh velocity liquid coolant may be directed onto the reversel.
¦surfaces of the casting belts, so that thls cooling effect occurs only momentarily before or simultaneously with the ~: l¦contact of the molten metal against the casting belts. I
~Special fingernail-like extensions are shown attached to liqu~d ,coolant nozzles nested within deep grooves in the nip rolls. I
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'i' ~L080 42L~ ¦ ' These fingernail extenders mask off ~he coolan~
streams ~rom the reverse surface of the casting belt and jspread out the coolant streams to form a sharply defined ¦
coolant layer. This sharply defined coolant layer enables the cooling action to be precisely started by application to ,'the reverse surface of the casting belt very near ~o the ,Ipoint'where the molten metal approaches the front sur~ace ~,of the castiny belt. The cooling effect of the liquid Illcoolant in conjunction with the nip roll may be controlled 10 ,~by insula~ing the deep grooves in the nip roll or by insulat-, ~ling the narrow ridges between these grooves.
, Hot fluid, such as steam, may be directed into 'the deep grooves of the nip roll beneath the casting belts I ' ¦,to aid in elevating and controlling their temperature. ,l "
,~ Mechanical and thermal sensors may be employed to '' I,sense any distortion in the casting belts near the entry to ~ithe casting region and to monitor the belt temperature and the elevation of the te~perature of the casting belts ahead ¦Iof the casting region is controlled to optimize the casting - 20 ¦llconditions as determined by these sensors. ~, Various zones of heating may be provided, so that the temperature of the main central area of the casting ¦
belts is controllably elevated independently of the edge portions of the belts and vice versa. l i I, A number of advantages and benefits, as indicated ~
Ihereinafter, are provided by employing the invention in twin- I
'l,belt casting machines: ¦
;, ' ~, 1. Casting belt distortion and transverse buck-,,ling along the casting region near and downstream from the I ;
. 30 ',entry of the molten metal due to differential transverse 1081)42~L j thermal expansion is markedly reduced and often i5 completely l'overcome.
- . 2. Thermal shock to the belt and to the insulat-~
ive coating on the belt due to contact of the molten metal at I the entry to he casting region are markedly reduced because the temperature of the insulative coating and bel~ are gradually elevated before contact with the molten metal ''occurs. The operating lives of the belt and its coating are¦
¦Ithereby increased.
, 3.Reduction in differential tempera~ures and result- .
,ant reduction in belt stresses enhances belt life and operating conditions in the machine. I I
¦¦ 4. The belt coating may be dried or cured ~o 'achieve more consistent thenm~l resitance or other desired .. 15 'characteristic such as absolute minimizing of moisture conten~
: ¦Ibefore contact with the molten metal.
! 5. The provision of mechanical probes to sense the belt shape and thermal probes to sense the temperature proile enables overall preci.se control of the twin-belt castl . ~j . .
¦¦ ing operation to be obtained. . .
,1 6. By virtue of the minimization or elimination.
I l¦of differential or non-uniorm thermal expansion and distortiln ¦or buckling effects, lighter or simpler or thinner or more ¦¦durable belt coatings with less insulating value (lower I!thermal resistance) can be utilized. These result in saving~
in belt fabrication time and material costs and also extend ¦
the operating lives of belts and coatings to provïde oper-! ational savings i 7. Because coatings of less insulative value can ¦
be employed, the effectlve rate of cooling of the material 1' . I :

-7- ' ~iL0i90424 being cast is accelerated, and consequently faster casting rates can be used in such cases, i.e. the tonnage output o~
the casting machine per hour can be increased. , , 8. The control of belt fLatness and thermal factors 'at the entry to the casting region and downstream from the ,entry enable improved metallurgical behavior to be achieved.

9. By minimizing or eliminating belt distortion, ~the thin cast shell which initially forms from the molten ' l~metal adjace~t to the belt lS stabilized. Localized variable ',heat transf2r rates are avoided because the cas~ing belt does not distort but rather it remains s~able in position against ,the thin cast metal shell being formed. Thus, more uniform metallurgical properties can be attained, a more consistent ~,icast shape is provided, and more consistent surface appearanc~ ¦
15' ~is obtained over the top and bottom surfaces of the cast I productO
10. More difficult or more critical alloys can be j'cast with greater commercial suitability in twin-belt ¦Imachines.
¦¦ 11, Thinner sections of metal alloys of acceptable ' ¦quality and sound structure are enabled to be cast in twin-belt machines employing the invention.
ll 12. By minimizing or eliminating belt distortion ¦land by controlling the temperature conditions a more uniform ¦
' 25 i!feed rate of molten metal into the casting machine can be ¦attained for all types of metal feeding, because the volume of the casting region remains more constant and the shrinkage of ,Ithe metal being cast is more nearly constant.
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The ~arious additional features, advantages and objects of the present invention will become more fully ¦
understood from a consideration of the following detailed 'description in conjunction with the accompanying drawings.

- BRIEF DESCR}PTIO~ OF THE DRAWINGS

.l FIG. 1 is an elevational view of the outboard llside of a continuous casting machine of the tw.in-belt type 'lembodying the present invention;
1~ FIG. 2 is an elevational view of the Lnput .
1~ ilend of the machine o~ FIG. l;
FIG. 3 is an enlarged partial sectional view ~ishowing the Pntrance to the c~sting region in detail; l .
~I FIGS.4 and 5 are sectional views taken along the - ¦Iplanes 4-4 and 5-5 in FIG. 3 and shown further enlarged; - .
¦l FIG. 6 is a sectional and elevational view taken along the plane 6-6 in FIG. 7 showing the end of one of the .
,wrap-around coolant nozzles with a fingernail extender for ,¦controlling and positioning the application of coolant, ¦! FIG. 7 is a side elevational view of this nozzle anc Ifingernail extender;
FIG. 8 is a perspective view of a flexible casting j ~-belt in the priox art; .
¦; FIG. 8A is a diagrammatic plot of the belt tempera- . .
¦iture profile along the longitudinal section 8A-8A in FIG. 8; .
1~ . FIG. 8B is a diagrammatic plot of the belt tempera-ture profile along the transverse section 8B-8B in FIG. 8;
1, FIG. 9 is a perspective vie~ of a flexible casting ¦.lbelt being utilized wi~h the present invention; ¦

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FIG. 9A is a diagrammatic plot of the belt temperal ture profile along the longitudinal section 9A-9~ in FIG. 9, ¦
FIG. 10 is a sectional view of another type of il I
~.twin-belt casting machine embodying the present invention; i 1 FIG. 11 is an enlarged elevational sectional view showing mechanical and thermal sensors associated with the lower casting belt of a ~win-belt casting machine embodying . the invention, such as the machines shown in FIG. 1 or FIG.

FIGo 12 is a sectional view showing apparatus ~or feeding hot ~luid, such as steam into a hollow nip roll of a ~in-belt casting machine, such as the machines Rhown . ¦
lin FIG. 1 or FIG. 10, for elevating and controlling the llcasting belt temperature;
li FIG. 13 is a partial sectional view illustrating .the action of the curved coolant t~bes nested between the llridges of the nip roll of a prior art twin-belt casting ,¦machine; . ¦
~¦ FIG. 14 is a partial sectional view taken along Ithe curved line 14-14 in FIG. 3. FIG.... 14 is intended to be ¦compared with FIG. 13, because FIG. 14 illustrate~ the ad-llvantageous action of the ingernail extenders in cooperation ¦¦with the curved coolant tubes nested between the ridges .
¦lof the nip roll for controlling the application of the ¦I coolant to the belt;
- 1~ FIG. 15A is a diagrammatic plot of the longitudina temperature profile of ~he casting belt in a machine embodyin~
ithe invention. FIG, 15A shows a curve similar to ~he curve shown in FIG. 9A;

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FIGS. 15B and 15C show other diagrammatic plots of longitudinal temperature profiles of casting belts, being taken along planes corresponding in position to 9A-9A
~in FIG. 9 in machines embodying the invention;
I, FIG. 16A is a diagrammatic plot of the transversq 'Itemperature profile taken along the plane 16A-16A in FIG. 9 through the casting belt of a machine embodying the invention;~
FIGS. 16B and 16C show other diagrammatic liplots of transverse temperature profiles taken along l,planes corresponding in position to 16A~16A in FIG. 9 in machines embodying the invention in which-the edge portions ,'of the belt are elevated in temperature~ ¦

DETAILED DESCRIPTION

Ij In the continuoaa casting machine 10 shown in I!FIGS. 1 and 2, the molten metal is introduced from a tundisn ¦12 located at the input end of the machine. The molten metal ~passes into and is solidified in a casting region C definéd i between the spaced parallel surfaces of a pair of wide endless l flexible casting belts 14 and 16. In operation, these belts 'are revolved around an upper and a lower ~elt carriage U and ~L, respectively. The two sides or edges of the casting Ilregion C are de~ined by a pair of laterally separated flexible - iiendless side dams 18, which travel be~ween the upper and lower Icasting belts in the casting region and which revolve around .
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the lower carriage L to complete their circuit of travel.
An arcuate guide 20 carrying multiple small pulley wheels 22 serves to guide each of the side dams as it moved into the 'entrance to the casting region. Only one of the side dams 18 and only one of the arcuate guides 20 can be seen in ~IG. 1. ~n FIG. 2, the tundish 12, side dams 18 and arcuate guides 20 have been omitted for clarity of lillustration.
' The carriages U and L of the upper and lower ¦-belt are supported from the back 24 of the machine 10 mounted ¦'on a base 26. The uppar belt carriage U includes a pair ¦lof main rolls 28 ~nd 30 located at the upstream and downstrea~
iiends of this carriage. Similarly, the lower belt carriage L
I,includes a pair o~ main rolls 32 and 34 at its upstream :; ' ',and downstream ends.

i, In the machine 10, the downstream rolls 30 I and 34 serve ko tension and to steer the respective belts I o~ their carriages. The type of twin-belt machine shown in FIGS. 1 and 2 is sometimes called a "two roll" or ~Itwo ~ pulley" machine because there are two main rolls on each o~ th e I~ , . .
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carriages. The upstream rolls 28 and 32 define the entrance or nip portion of the casting region and are used to drive the belts on the respective carriages. These rolls 28 and 32 are belt support means *and for convenience they will be referred to as the ~Inipl~ rolls.
The power mechanism 36 for driving the nip rolls is shown in Figure 2 with universal coupled drive shafts 38 and 40 extending from the `
power mechanism to the nip rolls. A pair of lift cylinders 42 acting through a lever system 45 serve to raise the whole upper carriage when it is desired to open up the casting region C or to change the thick-ness of the product to be cast.
As the upper casting belt 14 is revolved, it moves in an oval counterclockwise path as seen in Figure 1. This belt travels from the top of the downstream roll 30 to the left over to the top of the nip roll 28 and then curves 180 in passing down around the upper nip roll into the entrance to the casting region and moves toward the right along the castion region C to the bottom of the downstream roll 30 and then curves 180 in passing up around this downstream roll.
Similarly, as the lower casting belt 16 is revolved, it moves in an oval clockwise direction as seen in Figure 1. It curves 18~ in passing up around the lower nip roll 32 into the entrance to the casting region and again curves 180 in passing down around the down-stream roll 34 where it begins its return trip to the nip roll. ;~
The outer surface of each casting belt which faces ~
the casting region (see also Figure 3) is called the llfrontl' face F. -;
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The surface facing inwardly toward the main rolls is `~ ~
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,icalled the reverse or ~back~ face R Of the belt. The belts are made of relatively thin sheet steel~ and the ~ront face i of-ten has a finely roughened texture produced by sand blastin~.
A coating of thermal insulation material is o~ten adhered to ¦
5~this roughened surface.

The reverse surfaces o~ each belt are cooled by !
~high velocity laye.rs of liquid coolant, usually water, force-¦
llfully propelled along these surfaces. An intense coolant I~flow is employed usually amounting to thousands of gallons per minute to remove the large amount of heat being released ! AS the molten metal is solidi~yingO -In order to initiate these high velocity layers 43 ~(FIG. 3) of coolant, the nip rolls 28 and 32 are formed with ¦!multiple closely adjacent deep grooves 44 ~as seen most clear-¦¦ly in FIGS. 3, 4 and 5) defining relatively narr~w fins 4~ bet _ i ween neighboring grooves. A plurality of curved wrap-around .
ilcoolant tubes 48 and 52 having an oval cross section are !¦nested in the respective grooves of the nip rolls 28 and 32. ~.
~IAS seen in FI&. 1, large diameter header pipes 50 and 54 are I¦rigidly.secured to the respective coolant tubes 48 and 52 and 1 ¦Ifeed coolant into these curved tu~es. These curved tubes ~.
¦i48 and 52 have been formed essentially to the same radius as ~the associated nippulley and are cantilevered from the large , : 25 i~rigid header pipes 50 and 54, respectively. . .
i Near the entrance to the casting region, as shown in FIGS. 3j 4 and 5, the ends of the tubes 48 and 52 are Iformed into nozzles 56 positioned close to the reverse face ilR of each belt~ These nozzles are aimed at small angles :' il ' , I

approaching tangency toward the reverse belt face R. The I .
cross-sectional area of the nozzle ~ore is su~stantially ,'less than the oval passages within the tubes 48'and 52, so ,that each stream 57 of coolant issues from its nozzle 56 at .
~high velocity. The fingernail-like extensions 61, which are ¦
,attached to the nozzles 56, are novel and their purposes 'and functions will be descri~ed ~urther below. These finger-'lnail extensions 61 are shown more clearly in FIGS. 6 and 7.
As shown in FIG. 3, the molten matal 55 from the .
10 ~,tundish 12, passes through an insulated 5pout ~8 which is j 'aimed directly into the entrance E to the casting region. ¦
i'he end of this spout is shown projecting into the casting ¦
¦entrance slightly beyond a line 60 joining the axes of the ~
,~olls 28 and 32. In other words, the end of thi6 spout 58 .¦
15 liis positioned just beyond the point of tangency of the belts ~ ¦
h4 and 16 and their respective nip rolls 28 and 32. The entry E of the casting region begins at the exit face of the Ilinozzle 58. The.molten metal 55 initially comes into contact ¦,with the front faces of the casting belts at the entry E.
1! For further information about twin-belt casting ¦-achines, the reader may refer to the United States pate~ts ~, I¦listed in the introductory portion of the specification. ..
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etai,ied Description and Analys-is of Prior Art :

. I¦ . In a prior art twin-belt casting machine, belt lldistortion could occur under certain operating conditions . I

,near the hot entrance to the casting region, as illustrated i;in FIG. 8. This distortion or transverse ~uckling, as in-i! i ¦Idicated at 62, could occur momentarily or more or less conti- i nuously, depending upon operating conditions, and was caused 1081~4Z~ ~
by restrain-t of the transverse thermal expandion of the casting belt near the hot entrance by cold framing on three sides 71, 72 and 73 of this buckling region. The transverse ~bu~kling 62 (FIG. 8~ was principally caused by the transverse ,cold framing occurring in the region 71 ahead of the initial i Ililine 64 o~ contact o~ the molten metal with the casting belt.
,, The prior art practice of applying insulative coating on the front belt face and of maintaining substantial illongitudinal tension 63 across the full width of the belt did lQ . ¦l minimize distortion over a majority of the casting region.
¦,Nevertheless, these prior art practices often did no~ elimi-nate transverse buckling at 62 in a region just downstream from the entrance E, as will be explained.
ll In the prior art as shown in PIG. 8, the lower I i I,l casting belt is indicated by 16' and the lower nip roll by 321.
¦IThe entrance region E extends transversely across the belt ¦¦approximately along the position of the line 64 of initial l i ,Imetal contact. The cold regions of the belt are shown by lldotted shading. The full width of the beit as it wraps aro Id ¦¦the nip roll 32' was cold. It was chilled by the nip roll ¦itself, whlch approached ambient temperature. Also, the ! belt was chilled by the coolant streams 57 which struck the ¦Ireverse surface R many inches ahead of the line o tange~cy ~60 (FIG. 3), for the fingernails 61 were absent in the prior ~5 l¦art~
¦1 As shown in FIG. 13, in the prior art, twin-~belt casting machines, the streams of coolant 57 from the noz~
,zles 56 were applied directly to the reverse surface R_of the, ' casti~g ~elt 16 1 . To assure that the cool~nt was adequately ~spread out on ~he belt and was closely hugging against the I,~,' .
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;;belt, the nozzles 56, in the prior art, were positioned a substantial distance ahead of the line 64 at the entrance E
to the casting region C where the molten metal first came llinto contact with the casting belt. The shaded areas 106 in FIG. 13 show the pattern of the coolant spreading out 'against the reverse belt surfaces, and this occurs a substan-I `'tial distance and a substantial time before the contact line `64 of molten metal occurs. The coolant spread out in the ichannels between the respective narrow ridges 46 of the roll ll32'. As a result of the substantial length o~ travel of the coolant pattern 106 along the casting belt, the region of the ,belt 71 tFIG. 8B) ahead of the casting region was markedly l¦chilled by the coolant. Thus, the full width of the belt ias it approached the entrance E formed a first cold frame 71 Il(FIG. 8).
The initial cold condition of the belt is shawn ¦in FIG. 8A by the low level of the longitudinal temperature ,profile curve 81. After the belt passed th~ entra~c~ line '164 at E, the molten metal 55 came in contact with its front face F. The temperature of the belt rapidly rose up after contact with the molten metal, as indicated by the upwardly 'jsloping profile 82. Soon the mean temperature of the main '¦central portion of the belt reached the elevated level, as ¦indicated by the elevated profile at 83.
I The shaded edge portions 72 and 73 indicate two more cold frames. These edge portions 72 and 73 project outwardly beyond the side dams, and they remained substantial-~ly at ambient-temperature along both edges of the casting reglon, ,'i - ' I
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The temperature profile extending transversely across the belt along the section 8B-8B is shown in FIG. 8B.
The low level portions 92 and 93 of this pro~ile indicate ' the ambient temperature of the two edge portions 72 and 73.
IThe elevated central portion 94 shows the elevated mean 'temperature of the hot main central portion of the be7t in l the casting region.
I Accordingly, the main central portion of the l~ibelt after passing the line 64 of initial metal contact ~ rapidly rose (as at 82) m temperature and correspondingly attemped to expandO The cold frame portions 71, 72 and 73 - ,',restrained this expansion. The edge framing 72 and 73 restrained the longitudinal expansion somewhat, but this ~,edge framing was mostly overcome by the high longitudinal ¦
¦I tension 63 used in the prior art. The lead-in, or pre-l entrance, transverse, cold framing 71 imposed a severe res-traint on the expanding belt, causing prior art distortion or transverse buckling 62 to occur just downstream from the ilinitial metal contact line 64 at the entrance E. The amount 20 . 'll of buckling 62 depended upon the operating conditions, but ¦generally it increased with the melting temperature of the ¦metal 55 being cast.
¦¦ Also, the sudden rise in temperature 82 (F~G. 8A~
llsu~jected the belt and its coating to thermal shock and -¦¦ differential expansion stresses.
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Ele~ation of Casting Belt Temperature Before Initial Contact with Molten Metal ¦ ~ ;
~ In order to overcome this problem of distortion l ;
,lor transverse buckling closely downstream from the entrance E¦
dueto transverse restraint o~ th_s region's thermal expansion¦
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i 1 in accordance with the invention, the temper~ture of each casting bel~ is elevated ahead of the line 64 rmd the appli- I
'cation of the coolant stre,~ms 57 to the reverse surface may i ,be sharply defined and precisely controlled so as to be j applied to the belt at a lin~s closely related to the line 64 ¦
,~of initial metal contac-t with the belt. This control of the coolant will be explained in greater detail further below In order to elevate the temperature of the casting~
llbelts, as shown in FIGS. 1 and 2, a first ban~ ~6 of multiple Iradiant heaters 68 held by supports 67 is mounted to heat the upper stretch of the upper belt during its return trip toward the top of the nip roll 28. This first heater bank is mount-ed on the upper carriage structure U and is positioned to .
I,commence heating the upper belt 14 an appreciable dist~nce l'ahead of the nip roll 28 for significant pre~heating (and lltransverse expansion) to occur before the belt 14 encounters ,Inip roll 28. In this embodiment, t~e intensive radiant pre-,jheating of the upper belt begins at a point approximately 'lequidistant between the downstream pulley 30 and thè nip pul-¦~ley 28.
I Heaters 68 may be electrically energized or they llmay be fossil fuel fired, for example gas fired, of the so-called flameless radiant type. It is preferable to use elec-¦
l¦trical energy if it can be obtained economically because ther~
¦¦is no chance thereby of contaminating the coating on the front ! face of the belt. Flameless gas fired radiant heaters can ~be used satisfactorily if the fuel flow rate is carefully ad-justed so that there are no tongues of flame issuing from the burner housing 68.
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The radiant heaters 68 are capable o~ providing in- :
¦¦tensive radiant energy and are positioned closely adjacent and parallel to and uniformly spaced from the front belt l¦surface, and they include polished reflectors 69 extending lacross the width o~ the belt for reflectively directing as j Ilmuch of the available radiant energy toward the belt as ¦possible. It has been found to be of advantage ~o mount a}l ''heaters at a small spacing from the front face F of the belt.
¦¦For example, a small spacing of approximately one inch from ¦
llthe front belt face F has been found to work to advantage wit~
llthe reflectors 69 aimed at an angle of incidence perpendicular ¦,to the belt face F.
A second bank 76 of similar heaters 68 is similarl~ I
Imounted by means of an arcuate support 77 along a curved path ¦
~Inested about the nip pulley 68. This second radiant heater bank 76 further heats the belt 14 as it is travelling down around the nip roll 28. .
¦I Similarly, for heating the lower stretch of the lower belt during its return trip toward the bottom of the nipl, iroll 32, there is a third bank B6 of similar radiant heaters 68 = =¦mounted by a support 87. This lower bank 86 is ~ositioned to begin heating the lower belt 16 an appreciable distance ahead of the nip roll 32 or signi~icant pre-heating !(and transverse expansion~ to occur before the belt 1 6 I~encounters the nip roll 32. In this embodiment, the intensive radiant pre-heating of the lower belt begins at a point approxi-¦lately equidistant between the downstream roll 34 and the nip ioll 32. A fourth ban~ 96 of similar heaters is mounted by means of an aFcuate support 97 in curved relationship nested 1i 'l !
~ o ,labout the nip roll 32. This fourth bank 96 further heats the lower belt 16 as it is travelling up around the nip roll 32.
These heaters are connected so that the four banks 66, 76, 86 and 96 can be independently controlled. I
The first and third banks 66 and 86 are used to pre-heat the stretches of each belt before the belt begins to wrap around the nip roll ~8 or 32. The second and fourth banks ,~76 and 96 serve to further heat each belt while it is in contact with its nip roll. ¦
I~ more than sufficient pre-heating is being obtained for casting a particular product, then the number ~of heaters 68 for each belt may be reduced. Also, one of ithe banks 66 or 67, 86 or 96 for each belt may be energized 15 ll without energizing the other bank. Howevert for most cases,¦
it is believed that it is preferable to utilize a relatively ¦
Illarge number of heaters spaced over a relatively large seg- ¦
ilment o belt travel, as shown, so that the ele~ation in belt ' ¦,temperature is accomplished relatively gradually to minimize ¦
~Ithermal gradients and to minimize differential expansion.
IlIn addition, by vi~tue of the fact that the radiant heat is ¦,being appli~d to the front face F of each belt, it can be lused to cure or dry any coating material applied to the belt.

Il -Zone Control of Belt P e-H-ëating 1 In the machine sho~ in FIGS. 1 and 2, the heaters ,~'68 are all controllable with respect to three zones. The first zone 1 ~FIG. 2~ spans transversely across the main 'central portion of each belt for a width equal to the width ~
of the casting region C. The second and third zones (2~ an~

,' .. 1.

3V4~4 1 i ., I
i

(3) span transversely across the respective edge portions .i :of each belt outside of the casting region. The s.cond and third zones of each heater are ganged together so that th .~.two edge portions of each belt can ~e correspondingly and 'equally pre-heated independently of the amount of pre- 1 heating being applied acxoss the main central portion 1 of each belt. I
,, ` !
I,i Controlling.the.Coolant..St~eams..from..the Cur~ed I Wip Roll Tubes to Aid Belt Pre-Xea~Lng_ 1l In order to.enhance t~e effect of the pr~-heating of each belt, the fingernail shields 61 (FIG~. 6 a~d 7~ may be employed. These shields 61 are attached by welding or ibrazing at 98 and 99 to the nozzle 56 of each of the i~curved coolant tubes 48 and 52. These fingernail extensions ¦
`: ii I !
'161 are generally rectangular in shape and they are sharply ~tapered to a precise edge 100 extending sufficiently far down, stream from the nozzles to form the coolant streams into 'llayers before applying the coolant to the belt. In this Imachine, the fingernail extensions project more than two I i lihches beyond the end of the nozzle 56. These.fingernail t Ishields 61 have a width just slightly less than the width jlof the groove 44, a~ shown in FIGS. 4 and 5. They provide ¦¦controlled and delayed application of the coolant to the ¦

: ,'reverse face R until the desired point, for example just l¦immediately before the belt tangent line 60 (FIG. 3? . In ,~this illustrati~e embodiment, the coolant streams 57 do not ¦

- Icontact the pre-heated belt until approximately one-half iinch or less before the molten metal contacts the bel~
, The action of these nozzle tube extensions 61 may i . . .
~ ?-2~
be more fully understood from a review of FIG. 14. The coolant streams 57 strike the extenders and spread out I I
later~lly across them, as shown by the curved patterns 108.
A uniform layer o~ coolant is thereby formed before the travelling liquid reaches the edge 100 of these extenders.
The fast moving layer of coolant leaves the edge 100 and travels a short distance before coming in contact with the reverse surface of the belt. The pattern which this coolant forms in engaging the belt is shown by the shaded area 110 il in FIG. 14. It is noted that the line 109 where the coolantl initially contacts the belt is accurately de~ined as compared with the curVes 106 ~FIG. 13). AccordingIy, the well define~
line 109 enables the coolant application to be accurately 1 controlled and to be positioned close to the line of tangency i 60, where the belt i5 separating from the ridges 46 on the roll and also to be positioned close to the line 64 where th~
~I molten metal contacts the front face of the helt.
As seen enlarged in FIG. 7, the inner surface Il 112 of the extenders 61 is smooth and is tapered by grinding !
I to form a sharp edge 100. The outer surface 114 of the , extenders is curved in a gentle arc commensurate with the arc I¦ of the belt so that the tip 100 can be positioned closely ad~
¦¦ jacent to the surface of the casting belt, as shown in FIG.3.
I It is important that effective cooling action be I present on the rear surface of the belt at or near the position 64 (FIGS. 8 and 14~ where the molten metal initially comes into contact with the front face of the belt.
Il When the extensions 61 are used, the nozzles 56 Ii at the ends of the curved tubes 48 and 52 are enabled to be ~ positioned significantly farther downstream near the molten !~ metal line 64 as compared with the bare nozzles 56 of the Ii prior art, because of the increased control over the coolant ¦
., .
' Ii -23- 1 ., I,i stream patterns.
; Consequently, the fingernail extenders 61 serve the functions of spreading out the coolant to form a layer while at the same time preventing the coolant from prematurely engaging the belt. By virtue of the fact that the coolant j is formed into a stabilized layer, its application to the bel~
16 can be delayed until line 109 which is located only a small distance before the line 64 at which the molten metal contacts the belt~ ¦
. i A Number of Beneficial Efects o~ ~e- I
Heat ng the Casting Belts _ ¦
The advantageous results o~ pre-heating the belt~
plus controlled and de1ayed applicat.lon of liquid coolant to llthe belts is shown in FIGS, 9 and 9A~ The longitudinal ,ibelt temperature profile has a steady xise along the urve ¦
,~101, so that substantially ~ull operating temperature and full pre-expansion occurs in the pre-entrance region. As shown ~by the arrows 104, the full transverse pre-exapnsion has ! occurred before the casting belt reaches the tangency line at¦
,,the entrance.
A very narrow cool transverse section 102 may be¦
ilproduced over the narxow band 110 (FIG. 14) where the coolant¦
¦contacts the belt before the molten metal contacts the belt.
ilHowever, this cool transverse section 102 is so narrow that llit does not have any significant restraining effect on the ,Ibelt. The pre-heated, pre-expanded belt being stabilized by ,. I
lying curved around the nip roll 32 completely dominates the ¦
narrow cool band 102. Very quickly the belt temperature rises back up at 103 to its full operating temperature. The . I
;
.'1, , j .
., I , ' ' ' , `

l/ . I
beneficial e~fect is to eliminate or minimize ~o an insigni- , ficant level the tendency of the belt to distort or buckle. i Thermal shoc~ to the belt and its coating are minimi~ed and stresses due to differential thermal expansion are minimized.i Other beneficial effects an~ advantages are discussed ' elsewhere, Pre-Heating of Casting Belts in Twin-Belt Machines Ha~ing More than Two Main Rolls in Each Carriage _ _ ' ,, The twin-belt casting machine 10A shown in FIG. lq includes more than two main rolls in each belt carriage U andl L For clarity of illustration, only the input or upstream end of the machine is shown. There'are nip rolls 28 and 32 1 ¦

'having deep grooves 44 with narrow ridges 46. Belt-tensionin~
!' i ,rolls 200 and 202 serve to apply tension to the ca~ting'belts 14 and 16. Other main rolls ~not shown~ are located at the jldownstream end of the machine.
; ~ The molten metal feeds from a tundish 12A throug~
a spout 58 leading into the machine in an injection feeding ,'arrangement. For further information about twin-belt cast-ing machines with injection feeding and having more than two main rolls in each carriage, the reader may refer particularl~
to Patents Nos. 3,167,830 and 3,310,849 among those listed in¦
¦¦the introduction. The first of these patents shows a ~three ~¦roll" machine and the second shows a "four-roll" machine.

'1 A bank 66A of infra-red heaters 68A mounted on a support frame 67A serves to heat the stretch o~ belt 14 between the main rolls 200 and 28. Additional heaters, such I,as shown at 68A', may begin heating the belt while it is stil~

,travelling around the roll 200 preceding the nip roll 28.
Il . i ~These heaters 68A and 68A' are shown as being fossil fuel Ifired~ in this example they are gas fired, and the~ are mount i ; -25-8~Z~

'ed to be spaced only a s~all distance from the front face of ~he belt 14, These heaters are o the flameless gas burning .type producing intensive infra-red radiation. If desired, . ,electrically energized heaters 68A may be used in lieu o~ I
S ,,fuel-fired ones.

The heater support 67A is pivoted at 704 to a ~mounting ~rame ?~6 which is connected to t~e upper carriage ''U. A position adjustment mechanism 208 extends between the I

~,fixed mounting 206 and the pivoted heater support 67A. Thus,¦
the position of the heaters 68A and 68A' can be set in accord-, ! ance with the position of belt 14 as determined by t~e adjust-.
!' able belt-tension roll 200. . . ' I
,, Another bank 86A of similar heaters 68A mounted I ¦
lon a support frame 87A serves to heat the stretch of the belt¦
i'i16,between rolls 202 and 32. The support 87A is pivoted at ,205 to a mounting 207 for the tundish 12A. An adjustment jmechanism 209 extending between the fixed mounting 207 and . I , i ','the pivoted heater support 87A serves to adjust the position 'of the heaters 68A, in accordance with the location o~ the - ','belt as detexmined by tensioning roll 202. The heaters 68A
! on the ~rame 87A extend generally ~ertically and are trans-¦Iversely inclined to provide uniform overlapping pre-heating .
effect on the belt 16. This mounting arrangement of the Illower heaters.is accommodating to the limited available space , ., llbetween the tundish mounting 207 and the lower carriaye L. , :
,IlInsulating pads 210 and 211 are shown attached to the tundish mounting 207 to avoid over-heating of thi~ mounting by the ~,'bank 86A of intensive infra-red heaters directed at the ~ront ¦
!face of the belt 16.
1, The curved coolant tubes 48 and 52 extending . ¦ .
~from header conduits 50 and 54 and nested within the roll grooves 44 may be equipped with fingernail extenders 61 1 ~¦

similar to those described above.
Whereas the belts 14 and 16 in the machine lQ
travel approximately 180~ around the nip rolls 28 and 32, the belts in the machine lOA (FIG 10) travel approximately ' 90 around their nip rolls. In spite of this difference between ~he machines and the differences in arrangement and mounting of the heaters 68 and 68A, the advantages and effects, of the belt pre-heating in the machine lOA are sLmilar to l,those described above for the machine 10.

Additional Methods-and Appa~atus ~or ~ ¦

As shown in FIG. 12, the casting belts can be pre-jheated by heating the nip rolls 28 and 32 in either the ~machine 10 or lOA~ This pre-heating of the nip rolls can be ~'carried out in conjunction w-th the use of the radiant heaterc j 68 or 68A, if desired. Alternatively, the heating of the Inip rolls can be carried out without the use of the radiant heaters. It is pxe~erred that the radiant heaters be llutilized because they serve to heat the front face of the bell -l~which is the same surface as co~e~ in contact with the moltenl I
metal.
1i As shown in FIG. 12, hct heating fluid, such as ¦jsteam, is supplied through an insulated pipe 160 connected to 11 .
- lla passage 161 within a stationary gland member 16Z. This lpassage 161 communicates through an opening 164 with an axial ''passage 165 in a rotating gland mem~er 167. The passage 165 'lis connectea to a distributor pipe 166- extending axially through the hollow nip roll, such as roll 3~ shown. The far ,'end of the distri~utor pipe 166 is supported by an annular 'shoulder 168, and there are a plurality of orifices 170 at ; 'i ' I
,, , ;.
!

3V42~
.

spaced points along the length of the distributor pipe 166. These orifices 170 eject sprays 171 of the hot fluid directed against the inner surface of the hollow roll 32. ;
The spent fluid returns, as indicated by the arrows 172, through the annular space 173 within the hub por~ion 174 of the roll 32. The revolving gland member 167 is screwed at 175 into the hub 174 and has a plurality of radial passages 177 communicating with a channel 178 in a second stationary gland member 180 connected to a drain pipe 182. The hub 174 is supported by a bearing 184 in the - ~
carriage frame 186. Bearings 181 support the stationary gland 180 ;
on the rotating gland 167, and a pair of sliding seals 183 are located on either side of the channel 178. A bearing 187 supports the stationary gland 162 on the projecting end 163 of the rotating gland 167 with a sliding seal 188 between these glands.
Another method for pre-heating the casting belts is to ~ ;
. ~ . .
inject hot fluid, for example such as dry steam, which may be super- i;
heated, if desired, directly into the nip roll grooves 44 beneath .: :
the reverse surfaces R of the casting belts. The manner in which this hot fluid is injected into t~R grooves 44 is to position conduits (not shown) near the header pipes 50 and ~4 in the machine 10 or lOA.
Nozzles for the hot fluid (not shown) are connected to such conduits similar to the way in which the coolant tubes 48 and 52 are connected to the headers 50 and 54. These hot fluid nozzles are aimed into the spaces around the coolant tubes within the respective grooves 44, and the coolant tubes 48 and 52 are insulated from this hot fluid.

. .
INSULATING T~E NIP ROLLS
~ 1hile the fingernail extenders 61 mask off the coolant from the belt, it is to be noted from ~igure 14 that the coolant a- ~

~8a~z4 layers 108 may strike the side surfaces of the ridges 46 on the nip rolls, producing a cooling action on the roll itsel~. Since ;` :
the nip rolls have substantial arcs of .:
~ . ' . . .

:,.,. ,,'~
:.
` ~`'' , ', , ~,: ", ,,. '~'"' `'`; "" ~,.
' '~' .. . : ~.. .
... . .
~. :
''' ' ': ' .. ..
''"

!.
'~

", .`
'"` ' - 28a -,. :

`,. ~

lOB0424 contact with the belts, this cooling effect is conducted into the belts.
In order to insulate the gxooves 44 fxom the coolant, a thermal insulation coating 190 (FIGS, 4 and 5~ can be applied, as by painting or spraying, to cover the side walls and bottom of each groove 44.
Alternatively, the rim portions of the ridges 46¦
can be fabricated as rings ~not shown~ separate from the main ~ ¦
body of the nip roll. These rings are then ~Aounted onto the nip rolls with a layer of insulation material thermally isolating the rim portion of each ridge 46 from the remainder ~`of the nip roll.

Belt Pre-Heat:ing Control Methods and Apparatus .
~ In order to provide precise control over the ' pre-heating of the belt, and in order to sense whether any transverse buckling 62 (FIG. 8) is occurring, mechanical sensors M and thermal sensors T (FIGS. 1, 9, 10 and 11~ may be installed.
The mechanical sensors M incluae push rods 116 I (F~G. 11) mounted in bore holes 118, drilled into coolant applicator and scoop members 120. These coolant applicator and scoop members 120 are generally similar to those shown in United States Pate~t No. 3,041,686, mentioned in the intro-duction. The end 118' of each bore hole 118 near the belt is of reduced diameter for providing a close but loose slidinc fit with the probe rod 116. The reduced ~ore 118' serves to¦
support and guide the end 117 of the pro~e engaging the reverse surface R of the casting belt 16. At the other end I
of the bore hole 118, spaced away from the casting belt, there I

1 -29- ~

~ l is a collar bushing 122 secured to the probe rod 116. This collar bushing has a sleeve portion 124 extending into the bore 118. These sleeve portions 124 provide a close sliding I fit for guiding the other end of the probe rod 116. The ~ collar 122 acts as a stop to limit the amount of the tip end ,l,117 which can project from the mem~ers 120.
Spring means 126 urge the prob~s 116 toward the belt. This spring means 126 is formed ~y a block of resilient llmaterial, such as rubber, seated in a socket 128 n a mounting llibracket 130, attached to a coolant header conduit 132. An i electro-mechanical transducer unit 134 is attached b~ screws 136 to the mounting bracket 130. This transducer 134 has a ,movable element 138 engaging the end o~ the probe rod 116.
., . .
IlThus, movement of the probe rod lL6 produces a corresponding ',movement of the element 138.
'i Within each transducer unit 134 is means for "converting the amount of displacement of the movable element , Il I
138 into a corresponding electrical signal. This means for ,converting mechanical movement into an electrical signal may Ilutilize an electromagnetic or a piezo electric or a reluctanc ¦principle similar to the manner in which the motion o~ a ,phonograph needle i5 converted into a corresponding electric I
llsignal. The particular mechanical-to-electrical transducing ,¦means utilized in the units 134 is not being claimed and so ~,'it is not described in further detail.
Any buckling of the belt displaces the push rod ,116 causing a corresponding movement of the element 138.
,This motion of the element 138 causes ~he transducer 134 to ,generate an elec~rical signal as a function of the movementr 'land th-s electrical signal is fed from the unit 134 through an electrical cable connection V. I
i . i ' .

,., - ! -`~ , ,.

There is a fast moving ~ilm of coolant 43 ~
~(FIG~ 3~ travelling along the reverse surfaces of each of thej belts 14 and 16 in FIG. 11. This coolant film is omitted from FIG. 11 for clarity of illustration. There are gutters `140 provided for removal of the excess coolant as shown in j FIG. 11, and their operation is described in detail in U.S, I
Patent No. 3J041,686, mentioned above. I
The thermal probes T, as shown in FIG. 11, i include a probe member 142 having a thermistor therein adapte~
to engage the reverse sur~ace of ~he cas~ing belt. The r probe member 142 is movably mounted in the hore of a housing 144, and a spring memk,er 146 seated in this bore urges the probe 142 against the reverse surface of the casting k,elt.

, .
The thermistor in the temperature probe 142 provides anelec-trical signal as a function of the temperature of the reverse 'surface of the belt~ This electrical signal is fed from the ,'respective thermal probes through electrical ca~,les W.
A first thermal probe ls positioned closely ad- ¦
,jacent to the nip rolls~ as seen in FIGS. 1 and 10. This ! `
'~first thermal probe Tl is shown in detail in ~IG. 11. The first mechanical probe M has its probe rod lli,A mounted ~t an ,angle in a support 19~. By virtue of being mounted at this angle, the tip 117A of the probe 116A engages the reverse ¦,surface of the casting belt relatively close to the line 64 ~FIiG.14) Iat which the molten me~al first contacts the casting bel~. ¦
As illust~ated in FIGS~ 1, 9 and 10, there are three thermal probes T, indicated by dots in FIG. 9, and four¦
mechanical probes M, arranged in a row. There are a plurality of these rows of probes positioned across the width ', ' ' ~'.
--3 1-- i, ~, , .

~l `` i i 8~~Z~ I
1i i of the casting bslt. For example, FIG. 9 shows six rows of llthese mechanical and thermal probes ~ and M. The housings ¦144 of the thermal sensors are shown mounted on suppor~ I
members 194 in the belt carriage which are secured to the con-!lduits 132 connected to a frame member 186. The support 196 ¦¦for the first mechanical sensor is shown connect~d to a framel .
I member 194 by a diagonal brace 197. A curved shield pla~e 198 is positioned near the ridges 46 of the main roll. This ¦
plate 198 shields the first thermal sensor Tl and the nearby Ifirst mechanical sensor ~1 from any drops of coolant which ¦may be carried by the ridges 46. The finned belt-guiding ~
¦rollers, which are sometimes called belt ~ack-up rollers, arel sho~n at 192.
!`, . ¦ . As diagrammatically illustrated in FIGS, 1 and 10, in order to provlde automatic control of the pre-heating ¦ ¦
__ of the casting belts, ~he various electrical ~bles V and W
~from the mechanical probes M and thermal probes ~ are connect ¦¦ed to a control circuit 150. These control circuits serve to ¦Icontrol the energiza~ion of the banks of in~ra-red heaters 66!
176, 86 and 9~ and 66A and 86A... In addition, these control ¦
---~1 Icircuit5 15Q may also control the relative energization of . ' I ' .i the center zone 1 and the two end zones 2 and 3 (FIG. 2) of ¦
¦these heaters. ¦
It is to be understood that the heaters 68A of ¦
the machine lOA in FIG. 10 can be arranged for zone control . ¦ similar to that descri~ed for the heat,~rs 68 in the machine 10.
FIG. 11 shows the molten metal 55 and the solidifying skins 212 o~ solidiied metal gra~ually forming ¦
¦,adjacent to the facing surfaces of the respective belts 14 and 30 11 16. It is to be understood that this representation of the solidifying shells 212 is for purposes of illustration and is not drawn to scale. The solidiication rate in the cast-~, '"

ing zone C depends upon many ~actors, including the composition of the molten metal 55, speed of the machine, thickness of the casting being made, and so forth.
, Various Controlled Belt Pre-Heating Methods and Arrangements `

Various controlled belt pre-heating methods and arrangements can be employed as will be explained in connection with Figures 15A, B and C and Figures 16A, B and C. ;~
Figure 15A corresponds with Figure 9A and shows the method of pre-heating the casting belt in which there is a narrow region 102 of slight cooling produced by the narrow area of coolant 110 (Figure 14) which contacts the casting belt slightly before the molten metal.
:.:
If desired, the relative positions of the nozzles 56 and fingernail extenders 61 and the end of the spout 58, Figures 3 and 10, where the molten metal first contacts the belt, can be `~
:-:- ~
arranged so that the position 109 (Figure 14) where the controlled coolant first contacts the reverse side of the belt almost coincides with the line 64 where the molten metal first contacts the front ~;
; face of the belt. When this adjustment is achieved, the result is to provide a pre-heating pattern as shown in Figure 15B, in which the pre-heating temperature curve lOlB directly meets with the tem-perature curve 103 downstream from the entrance to the casting region.
In other words, Figure 15B shows an actual continuity of the pre-heating temperature profile with respect to the temperature profile in the casting region.
' ,:

. -If desired, the pre-heating of the casting belt can be carried out to a higher temperature lOlC, as shown in Figure 15C, in other words, a temperature overshoot 105 is provided. The result ':~
of this temperature overshoot is that the pre-expansion 104 (Figure 9) is greater and thereby tends to stretch the casting belt trans- , :
versely to assure that the belt is held flat at the entrance to the casting region.

''' `
'' :.
','`' '' '~ ' ` '~

' ", .

,, '' .
~ 33a ' ,.:

I
Z~ , FIG 16A shows a transverse tempera~ure profile curve 92, 93, 94 taken along the plane 16A-16A in FIG. 9.
The edge portions of the belt as shown at 92 and 93 are much cooler than the mean temperature 94 of the main central area 5 ~of the belt near the casting region. If desired, as shown in FIG. 16B, the edge portions of the belt in the zones 2 and I
l3 ~FIG. 2) and correspon~ing zones in FIG. 10 can be pre-heated to provide a transverse belt temperature profile, as shown in FIG. 16B, in which the temperature profile 92B and 1~ .93B of the belt edge portions is more nearly e~ual to the temperature profile g4 of the center portion of the belt. .
There is some loss of heat from the edge portions of the belt .such that when the edge portions are pre-heated to the same l , 'temperature as the center portions, some cooling of the edges I j 15 Iwill occur as the belt moves along through the casting region.
.This edge cooling explains the profile shown in.FIG. 16B in . .which the;level of temperature in the edge portions 92B and-- ..g3B is somewhat low~r than the central temperature profile 94.
If desired, as shown in FIG. 16C, a temperature iovershoot can be pravided in the heating of the edge portions ¦
¦'as shown by the temperature profile 92C.and 93C. This tem- .
Ii lperature overshoot compensates for the subsequent cooling of : ,Ithe belt ëdge portions as the belts travel along the casting llregion.

As a further step for heating up and maintaining : ~lthe temperature of the edge portions of the belts 14 and 16, .the coolant application nozzles 214 (FIG. 11~ ~rom the coolant . 'conduits 132 may be selectively temporarîly blocked off by ,: !
,plug means, such as screw plugs inserted into the bores of ~ i, ~ jthese nozzles. The nozzles 214 are selectively blocked off , il i,. i !l i i i - i with respect to the edge portions of the casting belt l~ing outside of the casting region, i.e. in the regions corres-ponding with zones 2 and 3 in FIG. 2, Thus, the cooling applied to edge portions of the belts associated with the s temperature pxofiles 92, 93 or 92B, 93B or 92C! 93C in FIGS.
l~A, B or C is minimized. In the region (zone l~ corres-ponding with the main central portion of each belt passing adjacent to the casting region, the nozzles 214 remain open l to apply and propel the coolant along the reverse surface of ¦
the casting belt~ ¦
If the distance between the side dams 18 is increased for enlarging the width of the casting region C
to cast wider product, then corresponding ones of the nozzles 214 are unplugged to apply the coolant across the full width .
of the wider casting region, and vice versa. Alsot if such l i a change in casting width is made, the zone control for the heaters 68 or 68A may be correspondingly adjusted.

i The Me~hods and Apparatus of the Invention Can !' Be Applied to Twin-Belt ~achines of All Types l Although FIGS. l, 3 and lO illustrate twin-~elt "casting machines in which the molten metal is supplied to the casting region by injection feeding, it is to be understood by those skilled in the art that the methods and apparatus f llthe invention can be applied to twin-~elt casting machines !lregardless of whether the fe~ding of the molten metal is by lopen pool, closed pool or injection feeding. In the cases of an open pool or closed pool feeding, the nip roll for the , lower casting belt may be located farther upstream than the nip roll for the upper belt. These relative possible posi-' tions of the nip rolls are shown in pat~nts 2,904,860;

..
., , j .
. .

.: `

iO81~4Z~ I

3,036,348; 3,123,874; 3,142,873; 3,228,072; and FIGS. 14A,i 14B, 14C, 14D ~nd 14E of patent 3,167,830. The me~hods and ~ apparatus of the invention are arranged accordingly.

Mean Belt Temperatures are Illus-trated and Described -; , . The various belt temperature pxo~ile curves and ¦
.associated description illustrate and describe the mean kem-~peratures of the belt as taXen in a section through the thick ~ness of ~he belt at any given location. I~ is to be under-stood that there is a temperature gradient through the thick-i .
ness of the belts as seen in FIGS~ 3 and 11. The front faces .
F of the two belts ad~acent to the molten metal 55 or the ~solidifying metal 212 in the casting region C are quite hot. I
.. The rear faces R adjacent to the liquid coolant are much coolf ¦er. Thus, it is to be understood that the specification, draw- I
.ings and claims are speaking about mean belt temperatures. I I
For example, in FIG. 15C, the temperature over ¦ i-shoot 105 indicates that the mean belt temperature along the ~profile curve lOlC is elevated above the mean belt temperature .along the profile curve 103.
ii The temperature sensors T are sensing the ¦
~temperature of the rear surface R. Because the temperature l,lof the metal being cast is known, the mean.belt temperatures l,can be estima~ed by using these sensors.
l, In the case of the regions of the belt approach-ing the nip rolls, sensors T' (FIGS. 1 and 10) can ~e in-stalled to engage the belt before it reaches the nip roll. I -~

~, , - , .

~ -36-- ~8~4 ; Additional Methods Eor Insulating the Nip Rolls The insulating of the nip rolls is discussed ' in the specification further above. Additional methods for insulating the nip rolls will no~ be discussed.
As will be understood from FIGS. 3, 4, 5, 12, 13 and 14, the ridges 46 on the nip rolls 28 and 32 are re-latively narrow and the intervening grooves 44 are much wider than these ridges. A method for effectively thermally in- , ,,sulating the nip rolls rom the reverse surfaces of the belt ¦
~is the machining of a narrow secondary groove, such as illustrated in FIGS. 4 and 5 at 216 into the perimetPr of eac~
ridge 46. Only one ridge is shown in FIGS. 4 and 5 with such a narrow secondary groove, and it is to be understood ¦ ;
'that these grooves 216 can be machined into the perimeter of I I
each ridge. ¦ ¦
These secondary grooves 216 significantly reduce ¦
I
the area of the perimeter of ridges 46 in contact with the reverse surfaces of the casting belts, and thus these narrow ' ,'secondary grooves effectively provlde therm~l insulation I,directly at the interface ~etween nip roll and belt., If desired, the perimeter of the ridges 46 con-taining these narrow secondary grooves can ~e hardened as I'by induction heat treating, to increase the wear resi~tance ¦ , ¦,of these ridges. This hardening of the metal offsets the I , reduction in area o the perimeter of the ridges with respectl I,to wear resistance.
In addit~on, a thermally insulative material,'for lexample such as epoxy resin, can be inserted into these narrow secondary grooves 216.
', ~
' , These narrow secondary ~rooves 216 can be arranged, .. . .

~8~4Z~
"
'to reduce the effective area of the periphery of the metal ridges 46 to one-half or less of the area thereof previously ~, in contact with the reverse surfaces of the belt. Thus, the ', ¦
'`conduction heat transer at this interface between nip roll and belt by this secondary grooving method can be cut down to one-half and less of that which would occur with the con- i jfiguration of ridges previously used.
; A durable thermally insulative material, for example such as epoxy resin or polyurethane, can be held in ''the narrow secondary grooves 216 and project slightly beyond the perimeter of ~he ridges 46 under operating conditions to prevent metal-to-metal contact between the belt and ridges 46. Where a thin layer of durable insulative material is i ' applied to the perimeter of each ridge 46, to prevent metal~
,,to-metal contact between the belt and ridges 46, such a layer ',lis keyed into the secondary grooves 216.
,. , .
Further Asnects of Controllina Belt Temperature ~ _ , I' , In connection with FIG. 12 it is discussed that the casting belts can be pre-heated by heating the nip 'rolls 28 and 32. Another way in which the heating of the nip rolls can be utilized and controlled to advantage is to ,,reduce the flow of heat from the pre-heated be'lts into the ,jnip rolls. The heaters 68 or 68A tFIG. 1 or 10) elevate the 'I,temperatures of the belts, with the front faces becoming ',elevated to a higher temperature than the rear surfaces.
~,',The heated nip rolls then serve to maintain the elevated temperature of the rear surfaces. In effect the heated nip rolls are serving to stabilize the tem~eratures of the previously heated belts. 'i ' In connection with FIG. 15C overshooting of the I -elevation of mean belt temperatures is discussed. One . I ' .
. I
~ -38- , ! I
desirable objective in this overshooting method is to pre-heat the belts so that the tem?eratures of the metal surfaces of the belts adjacent to the coatings on thelr front faces F becomes essentially the same ahead of the casting region as it is in the casting region. Thus, temperature conditions at the interface between the metal of the belt and the coat ;ing on the belt are stabilized, and thereby thermal shock at 'this interface is avoided, whereby belt operating life is extended.
' It has already been discussed that the relative positions of the nozzles 56 and the end of the spout 58 can be arranged so that the position where the coolant first contacts the reverse side of the belt almost coincides with I ¦
- `the position where the molten metal first contacts the front ''face of the belt. In some cases these components may be ; - arranged so that the molten metal intentionally does contact the front face of the belt before the coolant contacts the reverse surface; however, there are critical limits to this delayed coolant application. These limits on the amount of Idelayed coolant application vaxy with the thickness of the ; , I
i 'metal in the belt and with the speed of movement of the belt, as shown in the following table which pertains to casting ;alumlnum based metal. In this table "X thickness" means times the thickness of the metal in tha belt.

1 Belt Speed in Maximum Delay Distance I ' -Feet per Minute for Coolant Application ' i, 20 6 X thickness lO 3 X thickness Thus, for example, with a ~elt metal thickness of 0.050 of an inch at a casting speed of 20 feet per minute .
., ~

42~
- the maximum dela~ distance for coolant application is a. 3 inch.
One reason why it is an advantage to delay coolant application is that there are transient conditions occurring where the molten metal and coolant are ini-tially contacting opposite sides of the belt. The insulative coat-.ing on the belt tends to delay the moment when the heat from .the molten metal reaches the belt metal, i.e., it is a relatively slow response heating effect as compared to the lQ action of the coolant which is applied directly to the belt metal to produce a relativel~ quick response cooling effect. I
~The delaying of the application.o the coolant.serves to 1, compensate or the delay when the heat reaches the belt .metal. Thus, both heating and cooling effects are caused `.to commence at effectively the same moment on the belt metal i~in the castlng region to enhance operation.
, The above table applies to casting aluminum : 'Ibased metals. When casting metals having higher melting ¦
temperatures, such as copper or steel then the permissible .maximum delay is correspondingly reduc~d. When casting metals having lower melting temperatures, then the permissible maximum delay is correspondingly increased. ¦
In summary, depending upon the operating .¦
conditions, the coolant may be initially applied to the ¦
',reverse surface of the casting belt within a range from a ¦
~small distance before, to a small distance after, the positio ~
'where the molten metal initially comes into contact with the ¦

,1 1 .,i , ', ., , I

4Q- !

~80~2~
front face of the respective cas~ing belt.
In connection with FIG. 11 it is discussed that the coolant application nozzles 214 may be selectively blocked off with respect to the edge portions o~ the casting belt lying outside of the casting region. This is done to ~minimize cooling of the edge portions of the belts to preserve the pre-heated belt temperatures established ahead of the entrance to the casting region. The objective is to maintain lthe temperatures of the edge portions of the belt at least ' ias great as the temperatures in the belt across the full width in the casting region, A further method of preserving the pre-heat in the edge portions of the belts i5 to apply hot liquid of , controlled temperature to these edge portions while cold 15 lliquid coolant is being applied to the main central portions ¦
of the belts in the casting region. The way in which this is ' ilaccomplished is to insert an insulated pipe line (not shown) ¦
l,into the coolant conduit 132 (FIG. 11). This insulated pipe ¦
llis connected to insulated localized chambers (not shown) idirectly feeding the groups of nozzles 214 associated with ¦,the two edge portions of the belt D This insulated pipe line ¦¦and localized chambers are arranged so that they do not ~¦obstruct the flow of coolant to the remaining nozzles 214.
The hot liquid used may be hot water~
¦¦ Since the coolant liquid and hot liquid are travelling longitudinally along the reverse surface of the belt at high velocity in a relatively thin layer, there is very little tendency for these different temperature liquids to mix at their common boundary.

i -41-. . , ~ 8~3~2~
With respect to FIGS. 1 and 10, it is to be~
understood that the control circuits 150 can be used to control the temperature of the hot fluid fed into the line 160 (FIG. 12) for controlling the temperatures of the respective nip rolls 28 and 32 (FIGS. 1 and 10). Moreover, the control circuits 150can also be used to control the tempera~ure of the hot liquid to be applied to the edge portions of the belts as described in the preceding paragraphO

Extendiny Belt Operating Life Another aspect oX extending belt operating life will be discussed in connec~ion with FIGS. 9, 9A and 14.
To provide background information for understanding this ~aspect, it is noted that in the prior art the casting belts, which are made of sheet steel, with ins~lative coating on the front face, tend gradually to become stretched longitudinally ~during operation. This stretching occurs in the main central casting region of the belt relative to its edge portions.
,Thus, over a period of time the belt may become-very slightly ibaggy or slack in the main central region relative to the edge - ,portions. This stretching is caused by the thermal cycling jlof the main central region plus the flexing thereof occurring l¦in passing around the main rolls. This slight bagging only li¦ occurs when the operating conditions are so severe that the I
¦Ithermal cycling and flexing cycling carry the belt metal into¦
its plastic deformation state as distinguished from the elastic deformation state. Whenever such slight bagging Ibecomes undue in amount for the casting operations being carried out, then the belt is removed and replaced.

,i , I .

10804Z9~ i As shown in FIGS. 9, 9A and 14, the initial application of the coolant to each belt can be arranged !, relative to the initial contact of the molten metal such .
:that there is a narrow cool see*ion 102 extending transversely across the belt between the pre-heated expanded region 104 .and the ~asting region. The control of pre-heating and .
control of initial coolant application can be used to widen or narrow this section 102 as may be desired. The thermal .expansion occurring adjacent to this narrow cool section 102 j 'tends to stretch the metal of the belt in this narrow cool -section laterally. Moreover, this lateral stretching tendency occurs continuously during operation and progres- ¦
.sively for each incremantal portion of the main central .region of the belt, i.e., it is occurring cyclically and ,sequentially for each paxt o~ the main central region during ., .
each revolution of the belt. The result is that this lateral I.stretching tendency compensates somewhat for the tendency of ,the belt to become baggy and thereby extends the belt oper- i .ating life.
l . It is noted that the tendency of the belt to become I ' ,baggy increases With higher belt operating temperatures in the~
casting regiondue to the combined effeots of higher molten metal tempera ures and the belt coating practices being llemployed. Advantageously, the pre-heating 104 is controlled ¦
lland can be increased correspondingly to the higher belt ¦¦operating temperatures. Thus the lateral stretching !ItendencY applied to this narrow cool section 102 can be Il i increased in the case of higher belt operating temperatures to match and thereby to compensate for the increased !i l ' i i .

longitudinal stretching.
This lateral stretching can be considered as corrective transverse stretching carrying the belt metal into the plastic deforma-tion state transversely to compensate for the belt metal being carried into the plastic deformation state longitudinally. The corrective lateral stretching is correlated to the longitudinal stretching and ;
can be controlled by the pre-heating temperature applied to the belt and by varying the size of the cool section 102. As a result the tendency toward bagginess, if occurring, can be compensated to the extent desired to extend the belt operating life.

:, :

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting belts and in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as it is being solidified, the invention comprising:
a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting region, and said first and second support means aiming the banks of heaters to direct intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they enter the casting region, thereby to minimize the distortion of the casting belts after they begin carrying the molten metal between them in the casting region.

2. In a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting belts and in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as it is being solidified, the invention comprising:
a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting region, and said first and second support means aiming the banks of heaters to direct intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they enter the casting region, thereby to minimize the distortion of the casting belts after they begin carrying the molten metal between them in the casting region, a plurality of belt distortion sensors positioned to engage the reverse surfaces of the respective belts, as they travel through the casting region, said belt distortion sensors being arranged to provide electrical output signals as a function of the belt distortions being sensed, control means for said banks of heaters for controlling the amount of radiant heat energy being applied to the respective belts, and said control means being connected to said belt distortion sensors for controlling said banks of heaters as a function of the electri-cal output signals from said sensors.

3. In a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting belts and in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as it is being solidified, the invention comprising:

a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting regions, and said first and second support means aiming the banks of heaters to direct intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they enter the casting region, thereby to minimize the distortion of the casting belts after they being carrying the molten metal between them in the casting region, and zone control means for controlling the amount of radiant heat energy being applied to the front faces along the edge portions of the two revolving casting belts which will be travelling outside of the casting region independently of the amount of radiant heat energy being applied to the front faces along the main central portions of the two revolving casting belts which will be defining the casting region.

4. In a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting front faces of a pair of revolving endless flexible casting belts and wherein there are two nip rolls with the casting belts curving and travelling partially around the respective nip rolls as they move toward the casting region, in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as the metal is being cast, the invention comprising:

a plurality of banks of radiant heaters, arcuate support means mounting one bank of heaters in an arcuate configuration closely adjacent to the front face of one of the casting belts in a position where the belt is curving and travell-ing partially around its nip roll, other arcuate support means mounting another bank of heaters in an arcuate configuration closely adjacent to the front face of the other casting belts in a position where the belt is curving and travelling partially around its nip roll, and said arcuate support means aiming the banks of heaters for directing intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they reach the casting region, thereby to minimize the distortion of the casting belts when they begin carrying the molten metal between them in the casting region.

5. In a twin-belt casting machine, the invention as claimed in Claim 4, further comprising:
straight support means mounting another bank of heaters closely adjacent to the front face of one of the casting belts in a position where the belt is travelling in a straight stretch before reaching its nip roll, other straight support means mounting another bank of heaters in a plane configuration closely adjacent to the front face of the other casting belt in a position where the belt is travelling in a straight stretch before reaching its nip roll, said straight support means aiming said banks of heaters in a plane configuration for directing intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they reach the nip rolls, thereby to commence transverse expansion of the casting belts before they engage their respective nip rolls, and whereby said arcuate banks of heaters continue the pre-heating of the belts as the belts travel around the nip rolls.

6. In a twin belt casting machine, the invention as claimed in Claim 4, further comprising:
gland members having passages therein and being associated with each of said nip rolls, each of said nip rolls having passages therein com-municating with the passages in said gland members in sealed relationship therewith, and means for feeding hot fluid into said gland members to circulate the hot fluid in the passages of the nip rolls for heating the nip rolls to aid in pre-heating the casting belts before they reach the casting region.

7. In a twin belt casting machine, the invention as claimed in Claim 4, further comprising:
thermal insulation means in the nip rolls for insulating the nip rolls from the pre-heated casting belts

8. In a twin-belt casting machine, the invention as claimed in Claim 4, wherein the nip rolls have deep circumferential grooves forming narrow ridges engaging the reverse surfaces of the respective casting belts, said invention further comprising:
thermal insulation material insulating the rims of said narrow ridges from the remainder of the nip roll for insulating the nip rolls from the pre-heated belts,

9. In a twin-belt casting machine, the invention as claimed in Claim 4, wherein the nip rolls have deep circumferential grooves located beneath the reverse surfaces of the respective casting belts with curved coolant feed tubes nested within these deep grooves beneath the reverse surfaces of the casting belts and having nozzles at the ends of said tubes for directing streams of liquid coolant onto the reverse surfaces of the casting belts ahead of the position where the molten metal is initially brought into contact with the front faces of the casting belts, said invention further comprising:
fingernail-like members affixed to the nozzle ends of said tubes and positioned closely adjacent to the reverse surfaces of the belts, said fingernail-like members extending beyond said nozzles toward the casting region for masking off the streams of liquid coolant from the reverse surfaces of the casting belt, and said fingernail-like members terminating in a sharply defined edge for applying the liquid coolant to the reverse surfaces of the belt a small distance ahead of the position where the molten metal is initially brought into contact with the front faces of the casting belts.

10. In a twin-belt casting machine in which a casting region is defined between opposed portions of the front faces of a pair of revolving endless flexible casting belts and wherein there are two nip rolls with the casting belts curving and travelling partially around the respective nip rolls as they move toward the casting region, in which the molten metal to be cast is introduced into the casting region and comes into contact with the front faces of the respective belts to be carried along between the front faces of the belts as the metal is being cast and in which the nip rolls have deep circumferential grooves positioned beneath the reverse surfaces of the casting belts with curved coolant feed tubes nested within these grooves having nozzles at their ends for directing streams of the liquid coolant onto the reverse surfaces of the belts in advance of the position where the molten metal initially comes into contact with the front faces of the casting belts, the invention comprising:
a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting region, said support means aiming the banks of heaters for directing intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they reach the casting region, fingernail-like members mounted on the nozzle ends of said coolant feed tubes and fitting within said grooves and positioned closely adjacent to the reverse surfaces of said belts, said fingernail-like members extending toward the casting region and projecting beyond said nozzles for intercepting said streams of coolant to mask off the reverse surfaces of the belts from said coolant, and said fingernail-like members having straight edges on the ends thereof facing toward the casting region for applying the liquid coolant to the reverse surfaces of the belts along well defined lines located only a small distance in advance of the position where the molten metal initially comes into contact with the front faces of the casting belts, thereby to minimize the distortion of the casting belts when they begin carrying the molten metal between their front faces in the casting region.

11. In a twin-belt casting machine, the invention as claimed in 10, in which:
the surface of each of said fingernail-like members adjacent to the reverse surface of the belt is curved along an arch similar to the arc of the reverse surface, and the inner surface of each member is smooth with the member tapering to a sharp straight edge, said sharp straight edge being positioned closely adjacent to the reverse surface of the belt only a small distance in advance of the position where the molten metal initially comes into contact with the front face of the casting belt.

12. In a twin-belt casting machines, the invention as claimed in Claim 10, in which:
each fingernail-like member projects more than two inches beyond the end of the respective mozzle with wich the fingernail-like member is associated.

13. In a twin-belt casting machine in which a casting region is definedbetween opposed portions of the front faces of a pair of revolving endless flexible casting belts and in which the molten metal to be cast is introduced into the casting region to be carried along between the front faces of the belts as it is being solidified and wherein liquid coolant is applied to the reverse surfaces of the casting belts along the casting region and is also removed from the reverse surfaces by coolant applicator and scoop units, the invention comprising:
a plurality of banks of radiant heaters, first support means mounting one of the banks of heaters closely adjacent to the front face of one of the casting belts in a position located before the revolving belt enters the casting region, and second support means mounting another of the banks of heaters closely adjacent to the front face of the other casting belt in a position located before the revolving belt enters the casting region, and said first and second support means aiming the banks of heaters to direct intensive radiant energy onto the front faces of the respective belts at close range for pre-heating the belts before they enter the casting region, thereby to minimize the distortion of the casting belts after they being carrying the molten metal between them in the casting region, coolant applicator and scoop units having holes formed therein to extend toward the reverse surfaces of the casting belts, mechanical probes movably mounted in said holes having end portions projecting from said units adapted to engage the reverse surface of the nearby casting belt, resilient means for urging the ends of said probes toward the reverse surface of the belt, said probes being movable in response to distortion of the revolving casting belt, electro-mechanical transducer means associated with said mechanical probes for converting the movement of said probes into electrical signals as a function of the distortion of the casting belt, and control means for controlling said banks of heaters, said control means being connected to said transducer means for controlling said heaters as a function of belt distortion sensed by said probes and transducer means.