CA1080425A - Coolant nozzle apparatus for twin-belt casting machine - Google Patents

Abstract

COOLANT NOZZLE APPARATUS FOR TWIN-BELT
CASTING MACHINE

ABSTRACT OF THE DISCLOSURE

Coolant nozzle apparatus for use in twin belt casting machines wherein the casting region is defined between opposed portions of a pair of revolving endless flexible casting belts and wherein the belts travel partially around respective nip rolls positioned upstream from the casting region with said nip rolls having deep circumferential grooves. The apparatus comprises curved coolant feed tubes which are curved to nest within the deep grooves and having nozzles at their ends with fingernail-like extenders attached to the ends of the respective tubes on the convex side of said tubes, said extenders projecting beyond the discharge ends of the respect-ive associated nozzles in position to intercept and spread out the coolant stream issuing from the nozzle, and the fingernail-like extenders tapering to a sharp straight edge toward which the spread out stream of coolant moves.

Description

~8~4z This application is a division of Canadian Patent Application No. 212,480 filed October 29, 1974 entitled TWIN-RF~,T
COl~rINUOUS CASTING METXOD AND APPARATUS.

DESCRIPTION

The present invention relates to continuous casting methods and apparatus Nherein thete~.~perature of the flexible casting belt in twi~-belt casting machines is controllably elevated prior to contact with the molten material being cast.

FIELD OF THE INVENTION

In twin-belt casting machines the material being castg 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 rollers naving 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 withdra~n through the portions of the two belts which are adjacent to the metal being cast.
This large a~,nount of heat is withdrawn by cooling the reverse surfaces of the belts by means of rapidly ving substantially continuous films of liquid coolant travelling along against these reverse surfaces.
Each of the two flexible casting belts ls revolved ~ound a belt carriage in a path defined by main rolls located in the carriage and arowld which the belt passes. In some twin-belt casting machines there are two main rolls at opposite ends of the carriage defining an oval path for the belt to travel. In other twin-belt casting machines there are three or more main rolls in each carriage def'ining the belt path.
In some twin-belt casting machine installations the upper and lower casting belts converge directly opposite 8~25 `
I !
,each other around opposed nip rolls to form the entrance to `the casting region, and the molten metal is fed in~o the machine through a pouring ~pout extending into the entrance.
I,This is o~ten called an "injection feeding" technique. In S ,other twin-belt casting machine installations the lower cast-'l 'ing belt is arranged to support a pool of molten metal adjacenlt ;~to the entrance between the upper and lower belts. This latter arrangement is called an "open pool" or "closed pool"
l'casting techni~ue, depending upon whether the surface of the molten pool i5 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. ~owever, as used herein, all ,,lof the various techniques for feeding molten metal into a l,twin-belt casting machine are intended to be included within ¦
Ithe descriptive phrase: '1open pool, closed pool, or injection 'feeding". -" The present invention can be employed to advan~agej ¦in any of these various twin-belt casting machines whether I,lusing two, three, or more main rolls in each carriage, and the invention can also be employed to advantage regardless of jwhether the molten metal is being fed into the machine by an 'open pool, closed pool, or injection feeding.
Il For further information about twin-belt casting ',,machines, the reader may refer to one or more of the following ~nited States patents in the name of Clarence W. Hazelett or R' William Hazelett and Richard Hazelett: 2,640,235; 2,904,860; 1 3,036,348; 3,041,686; 3,123,374; 3,142r873; 3,167,830; ', ,l,3,228,072; and 3,310,849.
I, .,, i ,~

_3_ v~zs : ~

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 insulative coat-ings were often applied to the front faces of the flexi~le me~al casting belts. It was these insulative coatings which were at the interface between the molten metal and the casting 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 counteract such distortion, as described and claimed in United States Patent No.
3,123,874.

:. . : , : , :, : , ~ . :~

8~4z~ . i ~i 1' The Inventlon The invention provides continuous casting methods and apparatus in which the temperature of the ~lexible cast-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 me~hods and ,apparatus, as explained in connection with the various illus-1ltrati~re embodiments of the invention which are described.
10 ¦1 In some embodiments of the invention, one or ¦ .
more banks of high intensity infra-red heaters may be direct-¦
~ed at close range against the front faces of the casting belts to elevate their temperature be~ore the belts come into con- j lltact with the molten metal. The banks of infra-red heaters may be arranged to heat the casting belts before they reach .
.the nip rolls at the entrance to the casting region or during travel of the belts around the nip rolls or bo:th before and ¦
,.during travel around the nip rolls. I
~ In other embodiments of the invention, ho~ fluid,¦
20 il such as steam, may be circulated within hollow nip rolls to .
¦lelevate the temperature of the casting belts before the belts~
come into contact with the molten metal or to control the change in temperature of the casting belts. .~
In further embodiments of the invention, the ..
~5 ¦Ihigh velocity liquid coolant may be directed onto ~he reversel.
¦surfaces of the-casting belts, so that this cooling effect /!
occurs only momentarily before or simultaneously wit~ the contact of the molten metal against the casting belts. I
~Special fingernail-like extensions are shown attached to liquid coolant nozzles nested within deep grooves in the nip rolls.
, '~ . .

i 5 10809~25 i' These ~ingernail extenders mask off the coolant streams from the reverse surface of the casting belt and !
spread out the coolant streams to form a sharply defined coolant layer. This sharply de~ined coolant layer enables the cooling action to be precisely started by application to the reverse surface of the casting belt very near to the ,point where the molten metal approaches the front surface of the casting belt. The cooling effect o~ the liquid I

llcoolant in conjunction with the nip roll may be controlled 'by insulating the deep grooves in the nip roll or by insulat-ing 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 ' to aid in elevating and controlling their temperature.

15 ii Mechanical and thermal sensors may be employed to sense any distortion in the casting belts near the entry to 'ilthe cas-ting region and to monitor the bel~ temperature-, and 'the elevation of the temperature of the casting belts ahead llof the casting region is controlled to optimize the casting ¦'~conditions as determined by these sensors.
¦I Various zones of heating may be provided, so that the temperature of the main central area of the casting l~belts is controllably elevated independently of the edge liportions of the belts and vice versa~ l !
~ A number of advantages and benefits as indicated !
hereinafter, are provided by employing the invention in twin-belt casting machines:

- 1. Casting belt distortion and transverse buck-ling along the casting region near and downstream from ~he 'lentry of the molten metal due to differential transverse ., I .
.. --6 . .

:

8~Z~ I

! thermal expansion is markedly reduced and often is completely ,overcome.

2. Thermal shock to the belt and to the insulat-¦
'ive coating on the belt due to contac~ of the molten metal at ¦'the entry to the casting region are mar~edly reduced because j the temperature of the insulative coating and belt are gradually elevated before contact with the molten metal ,occurs~ The operating lives of the belt and its coating are Ilthereby increased.
¦I, 3.Reduction in differential temperatures and resull_ ,ant reduction in belt stresses enhances belt life and operatinlg ,liconditions in the machine.
4. The belt coating may be dried or cured to 'achieve more consistent th ~alresitance or other desired ¦ ;
,characteristic such as absolute minimizing of moisture content ¦Ibefore contact with the molten metal. I
5. The provision of mechanical probes to sense ¦ i the belt shape and thermal probes to sense the temperature Iprofile enables overall precise control o the twin-belt cast ¦¦ ing operation to be obtained.
,1 6. By virtue of the minimization or elimination ¦¦of diferential or non-uniform thermal expansion and d~stortign !l or buckling effects, lighter or simpler or thinner or more ¦,durabla belt coatings with less insulating value (lower ~Ithermal resistance) can be utilized. These result in savingsl l~in belt fabrication time and material costs and also extend ¦
¦Ithe operating lives of belts and coatings to provide oper- ¦
ational savings.
il 7. Because coatings of less insulative value can ¦
j'be employed, the effective rate of cooling of the material Ii I , I
being cast is accelerated, and consequentl~ faster casting rates can be used in such cases, i.e. the tonnage output of 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 distor~ion, ,the thin cast shell which initially forms from the molten i metal adjacent to the belt is stabiliæed. Localized ~ariable ~,heat transfar rates are avoided because the casting belt doesl not distort but rather it remains stable in position against ¦
the thin ,~ast metal shell being formed. Thus, more uniform ¦ l, metallurgical properties can be attained, a more consistent ¦cast shape is provided, and more consistent surface appearanc~
l~is obtained over the top and bottom surfaces of the cast ~'product.
. More difficult or more critical alloys can be i~cast with greater commercial suitability in twin-belt limachines~
il 11. Thinner sectio~s of metal alloys of acceptable ~quality and sound structure are enabled ~o be cast in twin-helt machines employing the invention.
12. By minimizing or eliminating belt distortion !~land by controlling the temperature conditions a more uniform I!feed rate of molten metal into ~he casting machine can be ¦¦attained for all types of metal feeding, because the volume l the casting region remains more constant and ~he shrinkage of ¦
the metal being cast is more nearly constant.

~, I I

-8- , ~
I

4'~S 1 The various 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.

i, BRIEF DES ~

¦ FIG. 1 is an elevational view of the outboard ¦side o a continuous casti~g machine of the twin-belt type '.embodying the present invention;
¦I FIG~ 2 is an elevational view of the input end of the machine of FIGo l; .
¦' FIG. 3 is an enlarged partial sectional view ilshowing the entrance to the c~sting region in detail; .
I . FIGS~ 4 and 5 are sectional views taken along the l¦planes 4-4 and 5-5 in FIG. 3 and shown further enlarged; .
' FIG. 6 is a sectional and elevational view taken along the plane 6-6 in FIG. 7 showing the end of one of the Iwrap-around coolant nozzles with a fingernail extender for ,¦controlling and positioning the application of coolant; .
Il FIG. 7 is a side elevational view of this nozzle anc l~fingernail extender; I .
FIG. 8 is a perspective vie~ of a fle~ible casting ¦¦belt in the prior art; .
FIÇ. 8A is a diagrammatic plot of the belt tempera-llture profile along the longi~udinal section 8A-8A in FIG. 8; .
~! FIG. 8B is a diagrammatic plot of the belt tempera-ture profile along the transverse section 8B-8B in FIG. 8; ¦
! FIG. 9 is a perspective vie~ of a flexible casting ¦
belt being utilized with the present invention;
: ' 'i , 'i '.

_ 9 _ 10E~4Z~ I I

FIG. 9A is a diagrammatic plot of the belt tempera I
ture profile along the longitudinal section 9A-9A in FIG. 9; ', FIG. 10 is a sectional view of another type of i! i l twin-belt casting machine embodying the present invention;
l FIG. 11 is an enlarged elevational sectional view .,showing mechanical and thermal sensors associated with the ilower casting belt of a twin-belt casting machine embodying "the invention~ such as the machines shown in ~IG. 1 or FIG.
10; , o l! FIG. 12 is a sect.ional view showiny apparatus i'~or feeding hot ~luid, such as steam into a hollow nip roll ,~ of a t~in-belt casting machine, such as ~he machines shown . i in FIG. 1 or FIG. 10, for elevating and controlling the I :
Icasting belt temperature;
ll FIG. 13 is a partial sectional view illustrating ¦,the action of the curved coolant tubes nested between the l¦ridges of the nip roll of a prior art twin-belt casting ¦
,¦machine; . .
- FIG. 14 is a partial sectional view taken along ii the cur~ed line 14-14 in FIG. 3. FI~.. 14 is intended to be !
¦Icompared with FIG. 13, because FIG. 14 illustrates th~ ad-vantageous action of the fingernail extenders in cooperation !
¦¦with the curved coolant tubes ne~ted between the ridges . .
of the nip roll for controlling the application of the . ..
coolant to the belt;
FIG! 15A is a diagrammatic plot of the longitudina: .:
l,temperature profile of the casting belt in a machine embodyin~
- llthe invention. FIG. 15A shows a curve similar to the curve lishown in FIG. 9A;
. ,,, . I
i, - I

~" I'', ,.
,, .

l()~V4Z5 ' FIGS. 15B and 15C show other diayram~atic ,.plots of longitudinal temperature profiles o~ 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 diagramma-tic plot of the transversq temperature profile taken along the plane 16A-16A in FIG. 9 through the casting belt of a machine embodying the invention;
i, FIG5. 16B and 16C ~how other diagrammatic iplots of transverse temperature profiles taken along lplanes corresponding in position to 16A-16A in PIG. 9 in .
machines embodying the invention in which the edge portions of the belt are elevated in temperature.

DETAILED DESCRIPTION ¦ i Il In the continuous casting machine 10 shown in ~IFIGS. 1 and 2, the molten metal is introduced from a tundis~ ¦ ¦
12 located at the input end of the machine. The molten metal .
passes into ana is solidified in a casting region C definea ¦between -the spaced parallel surfaces of a pair of wide endless ¦¦flexible casting belts 14 and 160 In operation, these belts ¦I,are revolved around an upper and a lower belt carriage U and ..
. ¦ L, respectively. The two sides or ed~es of the casting .
region C are defined by a paix of laterally separated flexible endless side dams 18, which tr~vel between the upper and lower Icasting belts in the castin~ region and which revolve around - .... ... ......... .. ~
,' ~
il . .~
11 .
.. ~ i,, , . I

~- ' , .

,i . I
., I
'` I
`,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 ¦
lentrance to the casting region. Only o~e o~ the side dams ,18 and only one of the arcuate guides 20 can be seen in ~IFIG. 1.
Il In FIG. 2, the tundish 12, side dams 18 and 'arcuate guides 20 have been omitted for clarity-of I~illustration.
The carriage~ U and L of the upper and lower ¦belt are suppor~ed from the back 24 of the machine 10 mounted o~ a base 26~ The upper belt carriage U includes a pair of main rolls 28 and 30 located at the upstream and downstrea~
Iends of this carriage. Similarly, the lower belt carriage L !
l~includes a pair of main rolls 32 and 34 a~ its upstream iland downstream ends. ¦
In the machine 10, the downstream rolls 30 ¦and 34 serve to tension and to steer the respective belts j~n their cxrriages. The type o~ twin-belt machine shown in IFIGs. 1 and 2 is sometimes called a "t~70 roll" or "~wo ~pulley" machine oecause there are two main rolls on each of t~e ,~
. 1,, .
.' ' 1,1 . ,.
; !1i ,, , , ~:

:. ,, ..
j ; 1l , !
.. i li -12-~' , 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 '7nip" rolls.
m e 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 180 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 "front" face F.
The surface facing inwardly toward the main rolls is . .

~`~; - 13 -.`', .

~ .

;, .,, :, : , ~, .. . . ....

S
f, 1 ll l called the "reverse" or "back" face R of the belt. The belts are made of relatively thin sheet steel, and the front face I
often has a ~inely roughened texture produced by sand bla~tin~.
~A coating of thermal insulation material is often adhered to ~'this roughened surface.

l The reverse surfaces of each ~elt are cooled by - ¦Ihigh velocity layers of liquid coolant, u~ually wa~er, force-llfully propelled along these surfaces. An intense coolant llflow is employed usually amounting to t~ousands of gallons per minute to remove the large amount of heat being released I
'las the molten metal is solidifying. l i ¦i In order to initiate these high velocity layers 43 i l¦(FIG. 3) of coolant, the nip rolls 28 and 32 are formed with ¦¦multiple closely adjacent deep grooves 44 (as seen most clear-¦lly in FIGS. 3, 4 and 5) defining relatively narrow fins 4~ bet _ jilween neighboring grooves. A plurality of curved wrap-around ¦Icoo~ant tubes 48 and 52 having an oval cross section are ¦¦nested in the respective grooves of the nip rolls 28 and 32.
20 ¦IAS seen in FIG. l, large diameter header pipes 50 and 54 are ¦Irigidly secured to the respective coolant tubes 48 and 52 and ¦ifeed coolant into these curved tu~es. These curved tukes ¦48 and 52 have been formed essentially to the same radius as ¦the associated nippulley and are cantilevered from the large Irigid header pipes 50 a~d 54, respectively.
Near the entrance to the casting region, as shown in FIGS. 3, 4 and 5, the ends of the tubes 48 and 52 are ,~
I,formed into nozzles 56 positloned close to the reverse face I~R of each belt. These nozzles are aimed at small angles :~' ,1 . I
ii - j .
- ', I .

~ -14- !
'' ' ', ~approaching tangency toward the reverse belt ~ace R. The I .
~cross-sectional area of the nozzle bore is substantially less than the oval passages within the tukes 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-nail extensions 61 are shown more clearly in FIGS. 6 and 7~ 1 ,1 As shown in FIG. 3, the molten metal 55 from the ¦ .
~'.tundish 12, passes through an insulated spout 58 which is aimed directly into the entrance E to the casting region.
The end of this spout is shown projecting into the casting j .
¦entrance slightly beyond a line 60 joining the axes of the l~olls 28 and 32. In other words, the end of this spout 58 llis positioned just beyond the point of tangency of the kelts ; ¦!14 and 16 and their respective nip rolls 28 and 32. The l .
entry E of the casting region begins at the exit face o~ the ,Inozzle 58. The molten metal 55 initially comes into contact I , -¦,with the front faces of the casting belts at the entry E~ !
!I For further information about twin-belt casting . !Imachines, the reader may re~er to the United States patents ~.
¦listed in the introductory portion of the specification. . .

¦¦ Detailed Description and Analysis of Prior Art .
I . . - .
In a prior art twin-belt casting machine, belt ldistortion could occur under certain operating conditions : 'near the hot entrance to the casting region, as illustrated in FIG. 8. This distortion or transverse buckling, as in-¦I,dicated at 62, could occur momentarily or more or less conti-nuously, depending upon operating conditions, and was caused , - !
by restraint of the transverse thermal expandion of the casting belt near the hot entrance by cold ~raming on three ~sides 71, 72 and 73 of this buckling region. The ~ransverse buckling 62 (FIG. 8) was principally caused by the transverse S cold ~raming occurring in the region 71 ahead of the initial ' line 64 of contact of the molten metal wi~h the casting belt., The prior art prac~ice of applying insulative l coating on ~he ~ront bel~ face and of maintaining substantial I~longitudinal tension 63 across the full width of the belt did !minimize distortion over a majority of the casting region. I i Nevertheless, these prior art practices often did not elimi- I
l'nate transverse buckling at 62 in a region just downstream jlfrom the entrance E, as will be explained. I
lll In the prior art as shown in FIG. ~, the lower l i 15 il casting belt is indicated by 16' and the lower nip roll by 32t.
~¦The entrance region E extends transversely acxoss the belt ¦,approximately along the position of the line 64 of initial metal contact. The cold regions of the belt are shown by - lldotted shading. The full width of the belt as it wraps arou~d 20l~the nip roll 32' was cold. It was chilled by the nip roll ¦itself, which approached ambient temperature. Also, the ¦belt was chilled by the coolant streams 57 which struck the reverse surface R many inches ahead of the line of tangency ¦160 (FIGo 3~, ~or the fingernails 61 were absent in the prior -. ~5 11 art.
As shown in FIG. 13, in the prior art, twin-¦belt casting machines, the streams of coolant 57 from tke noz-zles 56 were applied directly to the reverse sur~ace R of 'he 'cas~i~g belt 16~. To assure that the coolant was adequat~ly ; 30spread out on the belt and was closely hugging against the I`, . I . .
il I ..

` 10~3114;~5 ~ j belt, the nozzle3 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 linto contact with the casting belt. The shaded areas 106 in FIG. 13 show ~he pattern of the coolant spreading out ~ag2inst ~he reverse belt surfaces, and this occurs a substan-tial distance and a substantial time before the contact line 64 o molten metal occurs. The coolant spread out in the I,channels between the respective narrow ridges 46 of the roll 10 l~2'. As a result of the substantial length of ~ravel of the ~
~coolant pattern 106 along the casting belt, the region of the ¦
belt 71 (FIG. 8B) ahead of the casting region was markedly l¦chilled by the coolant. Thus, the full width of the belt i¦as it approached the entrance E formed a first cold frame 71 II(FIG. 8). I A' ~I The initial cold condition of the belt is shown li ; ¦!in FIG. 8A by the low level of the longitudinal temperature ¦,profile curve 8I. After the belt passéd the entrance line ~l64 at E, the molten metal 55 came in contact w~th its front 1 face F. The temperature of the belt rapidly rose up after contact with the molten matal, as indicated by the upwardly ¦sloping profile 82. Soon the mean temperature of the main j¦central portion of the belt reached the elevated level, as indicated by the ele~ated pro~ile at 83.
¦,, The shaded edge portions ~2 and 73 indicate two more cold frames. These edge portions 72 and 73 project I,outwardly beyond the side dams, and they remained substantial-iily at ambient temperature along both edges of the casting -I I'region.

, ' ' I .
i~ I
, -17- ~ !

l: :
8~25 .

The temperature profile extending tra~sversely ~across the belt along the section 8B-8B is shown in FIG. 8B. .
. :The low level porti~ns 92 and 93 of this pro~ile indicate ~ .
' the ambient temperature of the two edge portions 72 and 73, 5 IlThe elevated central portion 94 shows the elevated mean temperature o the hot main central portion of the belt in the casting region.
~ Accordingly, the main central partion of the ¦Ibelt after passing the line 64 of initial metal contact o ! rapidly rose (as at 82) in temperature and correspondingly attemped to expand. The cold frame portions 71, 72 and 73 restrained this expansion. The edge framing 72 and 73 li . I
jlrestrained the longitudinal expansion somewhat, but this !~ edge framing was mostly overcome by the high longitudinal ¦¦tension 63 used in the prior art. The lead-in, or pxe-l entrance~ transverse, cold framing 71 imposed a severe res-; 'Itraint on the expanding belt, causing prior art distortion or transverse buckling 62 to occur just downstream from the initial metal contac~ line 64 at the entrance E. The amount¦
20 . ii of buckling 62 depended upon the operating conditions, but ~.
Ilgenerally it increased with the melting temperature of the ~¦metal 55 being cast. ~
. ¦ Also, the sudden rise in temperature 82 (FIG. 8A) . ' -¦ subjected the belt and its coating to thermal shock and :: 25 ¦differential expansion stresses.

1: !I Elevation of Casting Belt Temperature Before .
:i I Initial Contact with Molten Meta-l j, In order to overcome this problem of distortion 'lor transverse buckling closely downstream rom the entrance E¦
,dueto transverse restraint of this reg on's thermal expansion f 1'l . . ' . I

~ 39L2~ 1 ~

in accordance with the invention, the temperature of each casting belt is elevated ahead of the lin2 64 and the appli-cation of the coolant streams 57 to the reverse surface may be sharply defined and precisely controlled so ag to be applied to the belt at a line closely related to the line 64 ¦
, of initial metal contact with the belt. This control of the coolant will be explained in greater detail further belowJ
In order to elevate the temperature of the casting¦
libelts, as shown in FIGS. 1 and 2, a first bank 66 of multiplel radiant heaters 68 held by supports 67 is mounted to heat the¦
l'upper stretch of the upper belt during its return trip toward¦
¦l~he top of the nip roll 28 This fixst heater ~ank is mount-¦ I *
I,ed on the upper carriage structure U and is positioned to ¦,commence heating the upper belt 14 an appreciable distance ; - 15 .li ahead of the nip roll 28 for significant pre-heating (and ¦Itransverse expansion) to occur before the belt 14 encounters nip roll 28. In this embodiment, the intensive radiant pre-heating of the upper belt begins at a point approximately ~!e~uidistant bet~een the downstream pulley 30 and the nip pul-l~ley 28q ll Heaters 68 may be electrically energized or they Imay be fossil fuel fired, for example gas fired, of the so-I jcalled flameless radiant type. It is preferable to use elec-¦trical energy if it can be obtained economically because ~her ; 25 ¦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-~usted so that there are no tongues of flame issuing from the burner housing 68. ¦

, ,~ . . . .
Il ., i -?~-8~)4'~5 ~l ~he xadiant haaters 63 are capable of pr~viding in-¦¦tensive radiant energy and are positioned closely adjacent .and parallel to and uniormly spaced from the fron~ belt l¦surfacQ, and they include polished reflectors 69 extending I!across the width o the belt fox re~lectively directing as ~¦much of the available radiant energy toward the belt as !
possible. It has been found to ~e of advantage to mount all l I
l'heaters at a small spacing from ~he front face F of the belt. l ¦
¦¦For example, a small spacing of approximately one inch from Illthe front belt face F has been found ~o work to advantage with~
the reflectors 69 aimed at an angle of incidence perpendicular¦
Ito the belt face P.
¦¦ A second bank 76 of similar hea~ers 68 is similarl~ ¦
!!~ounted by means of an arcuate support 77 along a curved path ¦
¦¦nested about ~he nip pulley 68. This second radiant heater ¦Ibank 76 furth~r heats the belt 14 as it is travelling down ~ :
,around the nip roll 28.
¦ Similarly, for heating the lower stretch of the llower belt during its return trip toward the bottom of the nipl Iroll 32, there is a third bank 86 of similar radiant heaters 68 _ =¦mvunted by a support 87. This lower bank 86 is ~ositioned to begin heating the lower belt 16 an appreciable ~istance ahead of the nip roll 32 for signi~icant pre-heating (and trans~erse expansion~ to occur before the belt 1 6 encounters the nip roll 32. In this ernbodiment, the intensive adiant pre-heating of the lower belt begins at a point approxi-mately equidistant between the downstrearn roll 34 and the nip .
oll 32. A ~ourth bank 96 of similar heaters is mounted by ;~eans of an arcuate support 97 in curved relations~ip nested 1i , ' .1 ~ 20-2~ j I

about the nip roll 32. This fourth bank 96 further heats the lower belt 16 as it is travelling up axound the nip roll 32.
These heaters are connecte~ so that the four banks 66, 76, 86 and 96 can be independently con-trolled.
The first and third banks 66 and 86 are used to pre-heat the stretches of each belt before the belt begins to wrap j around the nip roll ~8 or 32. The second and fourth banks ¦
l 76 and 96 serve to further heat each belt while it is in i contact wi~h its nip roll. ¦
; i If more than sufficient pre-heating is being obtained for casting a particular product, then the numbex of heaters 68 for each belt may be reduced. Also, one of the banks 66 or 67, 86 or 96 for each belt may be energiæed ` 15 ',withou~ energizing the other bank. However, for most cases,¦
it is believed that it is preferable to utilize a relatively ~ !large number of heaters spaced over a relatively large seg-- lment of belt travel, as shown, so that the elevation in belt ¦Itemperatuxe is accomplishea relatively gradually to minimiza ¦
~Ithermal gradients and to minimize dif~erential expansion.
In addition, by vir~ue of the fact that the radiant heat is l,being applied to the front face F of each belt, it can be ¦lused to cure or dry any coating material applied to the belt.
l . ..
Zone Control of Belt Pre-~eating 25 Ij In the machine shown in FIGS D 1 and 2, the hea~ers 68 are all control}able 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 iof the casting region C. The secon~ and third zones (2~ an~
., .
, ~ .

z~ i t ., I

(3) span transversely across the respect.ive edge portions - ¦
l' ~ .of each belt outside of the casting region. The second and third zones of each heater are ganged together so that the ..two edge portions of each belt can be correspondingly and equally pre-heated independently of the amount of pre- .
heating being applied across the main central portion 1 of ' .
!
each belt.

Controlling.the.Coolant..Streams..~rom..t~e:Cu~ed Ii Nip Roll ~ubes to Aid Belt Pre-Heating _ ¦
1In order to.enhance the effect of the pre-heating `o~ each belt, the ingernail shields 61 ~FIG~. 6 and 7) may be employed. These shields 61 are attached by welding or .brazing at 98 and 99 to the nozzle 56 of each of the 'cur~ed coolant tubes 48 and 52. These fingernail ex~ensions ¦
ll 61 are generally rectangular in shape and they are sharply ` Itapered to a precise edge 100 extending sufficiently far down~
stream from the nozzles to form the coolant streams into ~layers before applying the coolant to the belt. In this machine, the flngernail exti~nsions project more than two iinches beyond the end of ~he nozzle 56. These.fingernail ..
shields 61 have a width just slightly less than the width llof the groove ~4, as shown in FIGS. 4 and 5. They provide ¦¦controlled and del~yed application of the coolant to the .
'I~reverse face R until the desired point, for example just ..
~limmediately before the belt tangent line 60 (FIG 3). In ,this illustrative emkiodiment, the coolant streams 57 ~o not ,contact the pre-heated belt until approximately one-half ,inch or less before the molten metal contacts the belt.
The action of these nozzle tube extensions 61 may ., I `
1,' - , I '.
,,,, !

- iOB0425 - be more fully understood rom a review of FIG. 14. Thecoolant streams 57 strike the extenders and spread out I I
laterally across them, as shown by the curved patterns 108.
A uniform layer of 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 con~act with the , reverse surface of the belt. The pattern which this coolant - forms in engaging the belt is shown by the shaded area 110 ,l in FIG. 14. It is noted that the line 109 where the coolanti initially contacts the belt is accurately de~ined as compared with the cur~es 106 ~FIG. 13). Accordingly, the well de~ine~
line 109 enables the coolant application to be accurately controlled and to be positioned close to the line of tangency 60, where the belt is separating from the ridges 46 on the , roll and also to be positioned close to the line 64 where the j, molten metal contacts the front face of the belt.
I As seen enlarged in FIG. 7, the inner surrace ,i 112 of the extenders 6~ 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 ar9 ¦ 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.
Il It is important that effective cooling action be 25 . Il present on the rear surface of the belt at or near the position 64 ~FIGSo 8 and 14) where the molten metal initiall~¦
I comes into contact with the front face of the belt.
I¦ When the extensions 61 are used, the noz21es 56 - i at the ends of the curved tubes 48 and 52 are enabled to be 'I positioned significantly farther downstream near the molten metal line 64 as compa~ed with the bare nozzles 56 o the li prior art, because of the increased control over the coolant "

il -23-Z~ ~, . stream pa~terns.
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 ¦
is formed into a stabilized layer, its application to the belt . 16 can be delayed until line 109 which is located only a . small distance before the line 64 at which the mol~en metal contacts. the belt. ¦ .

' A Number.of.Beneficial.. Efects.. o.Pre_ . Heating the Casting Belts ¦
The advantageous results of pre-heating the belts plus controlled and delayed applicatlon of liquid coolant to ~
lthe belts is shown in FIGS. 9 and 9A. The longitudinal I i " 15 llbelt temperature profile has a steady rise along the curve ¦
'101, so that substantially full operating temperature and full :~ llpre-expansion occurs in the pre-entrance region. As shown by.the arrows 104, the ull transverse pre-exapnsion has lloccurred before the casting belt reaches the tangency line at the entrance. ..
A very narrow cool transverse section 102 may be produced over the narrow band 110 (FIG, 14) where the coolant .
I¦contacts the belt before the molten metal contacts the belt.
¦However, this cooL transverse section 102 is 50 narrow that ~'lit does not have any significant restralning effect on the belt. The pre-heated, pre-expanded belt being stabilized by lying curved around the nip roll 32 completely dominates the ¦
narrow cool band 102. Very quickly the belt temperature .l 'rises ~ack up at 103 to its full operating temperatureD The !

,, . I .
~. - , ~ .
~ ~ ,i , .

34~5 ~ ~
.1 '. I

'beneficial effect is to eliminate or minimize to an insigni- l ficant level the tendency of the belt to distort or ~uckle. i Thermal shock to the belt and i~s coating are minimized and stresses due to differential thermal expansion are minimized.
Other beneficial effects and advantages are discussed elsewhere.

Pre-Heating of Casting Belts in T~in-Belt Machines Having More than Two Main Rolls in Each Carriage '`' The twin-belt casting machine 10A shown in FIG. 10 inc~udes more than two main rolls in each belt carriage U and L For clarity of illustration, only the input or upstream 'end of ~he machine is shown. There are nip rolls 28 and 3~ ' lhaving deep grooves 44 with narrow ridges 46 Belt-tensioning li rolls 200 and 202 serve to apply tension to the casting belts 14 and 16. Other main rolls ~not shown) are located at the Idownstream end of the machine.
! The molten metal feeds from a tundish 12A t~roug~
la spout 58 leaaing into the machine in an injection feeding i~l arrangement. For further information about twin~~elt cast-ing machines with injection eeding and having more than ~wo I
main rolls in each carriage, the reader may refer particularl~
llto Patents ~os. 3,167,830 and 3,310,849 among those listed in ¦¦the introduction. The first of these patents shows a "three-jroll" machine and the second shows a "four-roll" machineO
'¦ A bank 66A of infra-red heaters 68A mounted on a support frame 67A serves to heat the stretch of belt 14 between the main rolls 200 and 28. Additional heaters, such l'as shown at 68A', may begin heating the belt while it is stil~
,ltravelling around the roll 200 preceding the nip roll 28. !, iThese heaters 68A and 68A' are shown as being fossil fuel ,fired, in this example they are gas fired, and the~ are mount-i il, I ~ .
,i I ~
l -25-f ~` i, !
'ed to be spaced only a small distance from the front face of ,the belt 14, These heaters are of the flameless gas burning , .
,'type producing intensive infra-red radiation. If desired~
, , electrically energized heaters 68A may be used in lieu o~ . , 'fuel-fired ones.

, . The heater support 67A is pivoted at 204 to a ,~mounting frame 206 which is connected to the upper carriage U. A position adjustment mechanism 208 extend~ between the I
fixed mounting 206 and the pivoted heater support 67A. Thus, thé po~ition of the heaters 68A and 68A' can be s~t in accord ~ance with the position of belt 14 as determined by the adjust-.
able belt-tension roll 200. . ¦ .
, Another bank 86A o~ similar heaters 68A mounted ~
on a support frame 87A serves to heat the stretch of the belt¦
ill16.between rolls 202 and 32. The support-87A is pivoted at !
-',205 to a mounting 207 for the tundish 12A. An adjustment .
mechanism 209 extending between the fixed mounting 207 and . I
the pivoted heater support 87A serves to adlust the position i 'of the heaters 68A, in accordance crith the location of the . ..
''belt as determined by tensioning roll 202. The heaters 68A , .
l,on the frame 87A ex~end generally vertically and are trans-¦Iversely inclined to pro~ide uniform ovexlapping pre-heating . . ., ieffect on the bel~ 16. This mounting arrangement of the , ~lower heaters.is accommodating to the limited available space ~ilbetween the tundish mounting 207 and the lower carriage Lo : ' Insulating pads 210 and 211 are shown attached to the tundish ~mounting 207 to avoid over-heating of this mounting by the bank 86A of intensive infra-red heaters directed at the front ¦
Il'face of the belt 16.
l. The curved coolant`tubes 48 and 52 extending ' ! ' ¦¦from header conduits 50 and 54 and nested within the roll ¦
,~lgrooves 44 may be e~uipped with fingernail extenders 61 i 5 ,,, i, .
~ ' -26- 1 l ;. , .

~8~Z~i .
.. . I
I,~ , . ' .

similar to those described above I
Whereas the belts 14 and 16 in the machine 10 1 ¦
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 the machines and the differences in arrangement and mounting of the heaters 68 and 68A, the advantages ana effects of the belt pre-heating in the machine lOA ar~ sLmilar to those described above for the machine 10.
i', .
1 10 Additional ~ethods and Apparatus for Pre-Heating the Cast ng Belts- ¦
;~ ~ As shown in FIG 12, the casting belts can be pre-¦
i heated by heating the nip rolls 28 ~nd 32 in either t~e ,machine 10 or lOA. This pre-heating of the nip rolls can be Icarried out in conjunction with the use of the radiant heater~
68 or 68A, if desired. Alternatively, the heating of the nip rolls can be carried out without the use of the radiant heaters. It is preferred that the radiant heaters be I,utilized because they serve to heat the front face of the bel~
llwhich is the same surface as co~e~ in contact with the molten ~metal.
11 As shown in FIG. 12, hot heating fluid, such as ¦¦steam, is supplied through an insulated pipe 160 connected to lla passage 161 within a stationary gland member 162. This ''passage 161 communicates through an opening 164 with an axial Illpassage 165 in a rotating gland member 167. The passage 165 ,~is connected to a distribu~or pipe 166 extending axially ~through the hollow nip roll, such as roll 32 shown. The far ilend of the distributor pipe 166 is support~d by an annular l~shoulder 168, and there are a plurality of orifices 170 at ,, I
..

-27~

~V~2~

spaced points along the length of the distributor pipe 166. mese 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 portion 174 of the roll 32. The revolving gland member 167 ls 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. me 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 pro~ecting 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-heated~ if desired, directly into the nip roll grooves 44 beneath the reverse surfaces R of the casting belts. ~he manner in which this hot fluid is in~ected lnto the grooves 44 is to position conduits (not shown) near the header pipes 50 and 54 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 THE NIP RoTr~
While the fingernail extenders 61 mask off the coolant from the belt, it is to be noted fr~m Figure 14 that the coolant ~ - 28 -~S~34ZS

layers 108 may strike the side surfaces of the ridges 46 on the nip rolls, produclng a cooling action on the roll itsel~. Since the rlp rolls ha~e substa t~al arcs o~

, .:

- 28a -.
~, - ~ . .. : ., .. .. ;.. ~ :. . . . .

contact with the belts, this cooling effect is conducted into the belts.
In order to insulate the grooves 44 from 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 sho~m~ separate from the main body of the nip roll. These rings are then laounted onto the nip rolls with a layer of insulation material thermally isolating the rim portion of each ridge 46 from the remainder, of ~he nip roll.

Belt Pre-HIeating 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 therm21 sensors T (FIGS. 1, 9, 10 and 11) may j be installed.
.,, I
The mechanical sensors M include push rods 116 Ii(FIG. 11) mounted in bore holes 118, drilled into coolant applicator and scoop members 120. These coolant applicator and scoop members 120 are generally s~milar to those shown in I,United States Patent 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 bore 118' serves to~
i' I
support and guide the end 117 of the pro~e engaging the 3 reverse surface R of the casting belt 16. At the other end ¦
of the bore hole 118~ spaced away from the casting belt, there ~, i, 1 .

4;~5 1 , ~I . I .
'is a collar bushing 122 secured to the probe rod 116. This " collar bushing has a sleeve portion 124 extending in~o the .bore 118. These sleeve portions 124 provide a close slidingl fit for guiding the other end of the pro~e rod 116. The ' collar 122 acts as a stop to limit the amount of the tip end , 117 which can project from the members 120.
Spring means 126 urge the pro~s 116 toward the .belt, This spring means 126 is formed ~y a ~ilock of resilient . material, such as rubber, seated in a socket 128 in a mounting bracket 130~ attached to a coolant header conduit 132. An I
Ilelectro-mechanical transducer unit 134 is attached ~y screws ' '136 to the mounting bracket 130. This transducer 134 has a I
i' movable element 138 engaging the end of the probe rod 116. ¦
!ThUS, movement of the probe rod 116 produces a corresponding movement of the element 133.
jl Within each transducer unit 134 is means for converting the amount o~ displacement of the movable element 138 into a corresponding electrical signal. This means for ,~,converting mechanical movement into an electrical signal may I
I,utilize an electromagnetic or a piezo electric or a reluctance ¦,principie similar to the manner in which the motion o~ a l~phonograph needle is conver~ed into a corresponding electric I
¦signal. The particular mechanical-to-electrical transducing llmeans utilized in the units 134 is not being claimed and so ¦
jlit 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 the transducer 134 to generate an electrical signal as a function of the movement~ ' l,and this electrical signal is fed from the unit 134 through .an electrical cable connection V.
', j , ,j I
I

--30-- :

. ~8~3~2~
`. . I
, . l There is a fast moving film o~ coolant 43 1 . , (FIG. 3) travelling along the reverse surface~ of each of thel ..
~,belts 14 and 16 in FIG. 11. This coolant ~ilm is omitted ,~
from FIG. 11 for clarity of illustration. There are gutters ,140 provided for removal of the excess coolant as shown in FIG. 11, and their operation is described in detail in U.S.
,Patent No. 3,041,686, mentioned above.
1. The thermal probes T, as shown in FIG. 11, include a probe member 142 having a thermistox therein adapte~
"to engage t~e reverse surfac~ of the casting belt.. The , ,probe member 142 is movably mounted in the bore of a housing .144, and a spring member 146 seated in this bore urges the probe 142 against the reverse surface of the casting ~elt.
,iThe thermistor in the temperature probe'142 provides anelec- i ,.trical signal as a function of the temperature of the reversel i! ¦ .
l,surface of the belt. This electrical signal is fed from the¦ , .,respective thermal probes through electrical cables W. , I

. . A first thermal probe is positioned closely ad~

.liacent to the nip rolls, as seen in FrGS. 1 and 10. This I,first thermal probe Tl is shown in detail in FIG. 11. The first mechanical probe M has its probe rod 116A mounted at an angle in a support 19~. By virtue of being mounted at this ~langle, the tip 117A of'the probe 116~ engages the reverse ¦~surface of the casting belt rela~ively close to ~he line 64 ~YIIG,l4) ''at which the molten metal first contacts the casting belt. .' ,, As illustrated in FIGS. 1, g and 10, there are ',,thxee 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 prob~s positioned across the width " : .
., .

8~34~S I
i 1 ~of the casting belt. For example, FIG. 9 shows six rows of llthese mechanical and thermal probes T and M. The housings .
144 o the thermal sensors are shown mounted on support ~l llmembers 194 in the belt carriag~ which are secured ~o the con-,lduits 132 connected to a frame member 186. The support 196 ¦¦for the first mechanical sensor is shown connect2d to a framel .
member 194 by a diagonal brace 197. A curved shield plate 198 is positioned near the ridges 46 of the main roll. This i plate 198 shields the first ther~al se~sor Tl and the near~y Ifir~t mechani~al sensor Ml from any drops of coolant which l ¦may be carried by the ridges 46. The finned belt-guiding ¦
rollers, which are sometimes called belt back~up rolIers, are llshown at 192.

¦l . As diagrammatically illustrated in FIGS. 1 and ¦ 10, in order to provide automatic control of the pre-heating ¦ ¦
of the casting belts, the various electrical ca~les V and W I i ¦ from the mechanical probes M and thermal probes ~ are connectt ¦ed to a control circuit 150. These control circuits serve to I l, ¦¦control the energization of the banks of infra-red hea~ers 66l ¦
20 176, 86 and 96 and 66A and 86A... In addition, these control .
_ _J ¦circuits 150 may also control the relative energization of ..
the center zone 1 and the two end zones 2 and 3 (~IG. 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 described for the heaters 68 in the machine 10.
~'~ FIG. 11 shows the molten metal 55 and the ¦solidifying skins 212 of solidified metal gra~ually forming adjacent to the acing suraces of the respective belts 14 and , 16. It is to be understood that this represéntation of the llsolidifying shells 212 is for purposes of illustration and ¦lis not drawn to scale. The solidification rate in the cast- ¦

,. , !

ing zone C depends upon many factors, 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 Arran~ements 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 (Fig~re 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 f-lrst contacts the front ; face of the belt. When this ad~ustment 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 pro~ile with respect to the temperature pro~ile in the casting region.

~ - 33 -: . : -:, : : :. . .:

s 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 lQ5 is provided. The result of this temperat~e 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 reglon.

,~.
~.

'; :

.;

- 33a -i' I
FIG, 16A shows a transverse temperature profile ,i 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 ~of the belt near the casting region. If desired, as shown ~in FIG. 16B, the edge portions o~ the bel~ in the æones 2 and ¦
l3 tFIG. 2) and corresponding zones in FXG. 10 can be pre- ' 1 'heated to provide a transverse belt temperature profile, as l~ , ~lshown in FIG. 16B, in which the temperature profile 92B and '..93B of the belt adge portions is more nearly equal to the ~temperature profile 94 of the center poxtion 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 ''temperature as the center portions, some cooling of the edges 15 i,will occur as the belt moves along through the casting region.
.,~his edge cooling explains the profile shown in.FIG. 16B in .which the level of temperature in the edge portions 92B and ¦
.'g3B is somewhat lower than the central temperature profile 94.
If desired, as shown in FIG. 16C, a temperature ¦
~iovershoot can be provided in the heating of the edge portions ¦
¦'as shown by ~he temperature profile 92C.and 93C. This tem- ¦' l~perature overshoot compensates for the subsequent cooling of the belt ëdge portions as the belts travel along the casting region.
, 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) from the coolant, conduits 132 may be selectively temporarily blocked off by plug means, such as screw plugs inserted into the bores of 'these nozzles. The nozzles 214 are selectively blocked off ~080425i ! ~
I' with respect to the edge portions of the casting belt lying I i 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 profiles 92, 93 or 92B, 93B or 92C! 93C in FIGS. i 16A, B or C is minimized. In the region (zone 1~ corres-ponding with the main central portion of each belt passing adjacent to the casting region, the nozzles 214 remain open , to apply and propel the coolant along the reverse surface of l the casting belt. t If the distance between -the side dams 18 is increased for enlarging the width of the casting r~gion C l i to cast wider product, then corresponding ones of the nozzles 214 are unplugged to apply the coolant across the full width - 15 of the wider casting region, and vice versa. ~lso, if such a change in casting width is made, the zone control for the ~heaters 68 or 68A may be correspondingly adjusted.
i, , :
i~ The Methods and Apparatus of the Invention Can ~' Be Applied to Twin-Belt Machines of ~11 Types 1 Although FIGS. 1, 3 and 10 illustrate twin-belt casting machines in which the molten metal is supplied to thel ;
l,casting region by injeckion feeding, it is to be understood ¦Iby those skilled in the art that the methods and apparatus f the invention can be applied to twin-belt casting machines ¦¦ regardless of whether the feeding of-the molten metal is by open pool, closed pool or injection feedingO In the cases of an open pool or closed pool feeding, the nip roll for the low~r 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 2,904,86Q;
,.
.. . I

~8~ 5 .. .. i 13,036,348; 3,123,874; 3,142,873; 3,228,07Z; and FIGS. 14A, 14B, 14C, 14D and 14E of patent 3,167,830. The methods and apparatus of the invention are arranged accordingly.

Mean Bel~ Temperatures are Illus- ¦
trated and De-scribed --The various belt te~perature profile curves and ` associated description illustrate and describe the mean tem~
peratures of the belt as L-aken in a section through the thick l ness of the belt at any given location. It is to be under-10 ~Istood that there is a temperature gradient through the thick-, j ness of the belts as seen in FIGS. 3 and 11. The front faces , , F of the two belts adjacent to the molten metal 55 or the ¦
i'solidifying metal 212 in the casting region C are quite hot.
- ~ The rear faces R adjacent to the liquid coolant are much cooll 15 ll er. Thus, it is to be understood that the specification, draw-ings and clalms are speaking about mean belt temperatures;.
~' For example, in FIG, 15C, the temperature over- ¦
- ,~shoot 105 indicates that the mean belt temperature along the profile curve lOIC is elevated above the mean belt temperature 'along the profile curve 103.
il The temperature sensors T are sensing the temperature of the rear surface R. Because the temperature ,of the metal being cast is known, the mean belt temperatures can be estimated by using these sensors~
,l In the case of the regions of the belt approach-~ling the nip rolls, sensors T' ~FIGS. 1 and 10~ can ~e in- ¦
I istalled to engage the belt before it reaches the nip roll. I

I
1 j!
; ~!
., i ~ ' , . - I
l~ -36- j!

.

108~4Z5 , ~
Additional Methods ~or Insula-ting the Nip Rolls Il .
The insulati~g of the nip rolls is discussed in the-specification further above. Additional methods for 5insulating the nip rolls will now be discussed.
As will be understood from FIGS. 3 r 4 ~ 5 r 12 r 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- I
,sulating the nip rolls from the reverse surfaces o the belt ¦
,~is the machining of a narrow secondary groove, such as illustrated in FIGS. 4 and 5 at 216 into the perimeter 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 lS that these grooves 216 can be machined into the perimeter of I I
each ridge. ¦ ¦
These secondary grooves 216 significantly reduce ¦
the area of the perimeter of ridges 46 in contact with the reverse surfaces of the casting belts, and thus these narrow ~Isecondary grooves effectively provide thermal insulation 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 'by induction heat treating, to increase the wear resistance l~of these ridges. This hardening of the metal offsets the ,Ixeduction in area of the perimeter of the ridges with respect !
to wear resistance.
~1 In addit~on, a thermally insulative material, for ~
'example such as epoxy resin, can be inserted into these narro~i secondary grooves 216.
These narrow secondary grooves 216 can be arranged -37_ ~8~4~:S
to reduce ~he effective area of the periphery of ~he metal ridges 46 to one-half or less of the area thereo~ previously t in contact with the reverse surfaces o~ the belt. Thus, the '`conduction heat transfer at this interface between nip roll S and belt by this secondary grooving method can be cut down to one-half and less of that which would occur with the con-figuration of ridges previously used.
A durable thermally insula~ive material, for example such as epoxy resin or pol~urethane, can be held in 'the narrow secondary grooves 216 and project slightly beyond ~he perime~er of the 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 applied to the perimeter of each ridge 46, to prevent metal- ¦
,to-metal contact between the belt and ridges 46, such a layer is keyed into the seconcary grooves 216.

, Further As~ects of Controlling Belt Temperature , In connection with FIG. 12 it is discussed 'that the casting belts can be pre-heated by heating the nip ~rolls 28 and 320 Another way in which the heating of the I',nip rolls can be utilized and controlled to advantage is to ,Ireduce the flow of heat from the pre-heated be'lts into the nip rolls. The heaters 68 or'68A (FIG. 1 or 10~ elevate the ',¦temperatures of the belts, with the front faces becoming l'elevated to a higher temperature than the rear surfacesO
~,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.
In connection with FIG. 15C overshooting of the - ,elevation o~ mean belt temperatures is discussed. One ., ~desirable ob~ective in this overshooting method is to pre-heat the belts so that the temperatures 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 ii .
this interface is avoidedr whereby belt o?erating lie is '' ~extended.
It has already been discussed that the relative positions o 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 the position where the molten metal first contacts the front 15 ''face of the belt. In some case~ these components may be ~arranged so ~hat the molten metal inten~ionally does contact ~the front face of ths belt before the coolant contacts the 'reverse surface; however, there are critical limits to this ,.
''delayed coolant application. These limits on the amount of , ''delayed coolant application vary with the thickness of the ,metal in the belt and with the speed of movement of the belt, as shown in the following table which pertains to casting ,aluminum based metal. In this table "X thickness" means itimes the thicXness of the metal in the belt.

ll Belt Speed in Maximum Delay Distance Feet per Minute for Coolant APplication 6 X thickness 3 X thickness ,! .
Thus, for example, with a belt metal thickness ¦ ;

of 0.050 of an inch at a casting speed of 20 feet per minute '' I
, I

.

34~ ~
- the ma~imum dela~ d~stance for coolant application is 0.3 ;inch.
One reason wh~ it is an advantage to delay coolant application is that there are transient conditions occurring where the molten metal and coolant are initially 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 relatively quick response cooling effect.
,The delaying of the application of the coolant serves to 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 'in the casting region to enhance operation.
I , The above table applies to casting aluminum based metals. When casting metals having higher melting temperatures, such as copper or steel then the permissible ; 20 maximum delay is correspondingly reduced. When casting ii . I
- jmetals havi~g lower melting temperatures, then the permissible maximum delay is correspondingly increased.
1, In summary, depending upon the operating ! conditions, the coolant may be initially applied to the ¦ i 'ireverse surace of the casting belt within a range from a small distance before, to a small distance after, the position ~where the molten metal initially comes into contact with the ,1 1 !
1, :
i~' . .

i front ~ace o~ the respective casting bel~.
; 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 of the casting belt lying outside of the casting region. This is done to minimize cooling o~ the edge portions of the belts to preserv~
the pre-heated belt temperatures established ahead o~ the entrance to the casiting regiona The objective is to maintain Ithe temperatures of the edge portions of the belt at least I
''as 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 is to apply hot liquid of Icontrolled temperature to these edge portions while cold ¦
liquid coolant is being applied to the main central portions lof the belts in the casting region. The way in which this is ,~accomplished is to insert an insulated pipe line (not shown) ¦
into the coolant conduit 132 (FIG. 11). This insulated pipe ¦
I~is connected to insulated localized chambers (not shown) I,directly feeding the groups of nozzles 214 associated with ¦the two edge portions of the belt. This insulated pipe line ¦and localized chambers are arranged so that they do not lobstruct the flow of coolant to the remaining nozzles 214.
'IThe hot liquid used may be hot water.
il Since the coolant liquid and hot liquid are Itravelling longitudinally along the reverse surfaGe of the Ibelt at high velocity in a relatively thin layer, there is 'very little tendency for these different temperature liquids I to mix at their common boundary.

: 11l , i!
j ,; -41-, 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 temperature of the hot liquid to be appliea to the edge portions of the belts as described in the preceding paragraph.

Extendin~_Belt O~eratiny Life .~ , Another aspect of extending belt operating lie l I
will ~e discussed in connection with FIGS. 9, 9A and 14.
To provide background in~ormation for understanding this ~aspect, it is noted that in the prior art the casting belts, which are made of sheet steel, with insulative coating on the front face~ tend gradually to become stretched longitudinallyl during operation. This stretching occurs in the main centrall j 'casting region of the belt relati~e to its edge portions.
Thus, over a period of time the belt may become-very slightly ,baggy or slack in the main central region relative to the edge ,portlons. This stretching i5 caused by the thermal cycling llof the main central region plus the flexing thereof occurring llin passing around the main rolls. This slight bagging only L5 ¦occurs when the operating conditions are so severe that the I
Ithermal cycling and flexing cycling carry the belt metal into¦
jlits plastic deformation state as distinguished from the elastic deformation state. Whenever such slight bagging jbecomes undue in amount for the casting operations being 'i ' i ' !
~carried out, then the belt is removed and replaced.

.
,i . .
,, I

.,1 1 .

- lOE~5~Z5 . 'I
As shown in FIGS. 9, 9~ and 14, the initial application of the coolant to each belt can be arranged relative to the initial contact o~ the molten metal such that there is a narrow cool se~tion 102 extending transversely across the ~elt 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 la2 as may be desired. The thermal , I
expansion occurring adjacent to this narrow cool section 102 I j 'tends to stretch the metal of the belt in this narrow cool ,section laterally. Moreover, this lateral stretching l I
tendency occurs cont1nuously during operation and progres- I ¦
'sively for each incremental portion o the main central , ',region of the belt, i.e., it is occurring cyclically and "sequentially for each part of the main central reyion during ~,each revolution of the belt. The result is that this lateral stretching tendency compensates somewhat for the tendency of the belt to become baggy and thereby extends the belt oper-ating life.
' It is noted that the tendency of the belt to become ~baggy increases With higher belt operating temperatures in th~
casting regiondue to the combined efects of higher molten ~metal temperatures and the belt coating practices being llemployed. Advantageously, the pre-heating 104 is controlled l~and can be increased correspondingly to the higher belt operating temperatures. Thus the lateral stretching tendency appl;ed to this narrow cool section 102 can be increased in the case of higher belt operating temperatures to match and thereby to compensate for the increased i .: ,, li ' .~ , .

~8~34ZS

longitudinal stretching.
This lateral stretching can be considered as correctlve transverse stretching carrying the belt metal into the plastic deforma-tion state transversely to co~pensate for the belt metal being carried into the plastic deformation state longitudinally. m e 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.

_ 44 -

Claims

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

1. Coolant nozzle apparatus for use in twin-belt casting machines wherein the casting region is defined between opposed portions of a pair of revolving endless flexible casting belts and wherein the belts travel partially around respective nip rolls positioned upstream from the casting region with said nip rolls having deep circumferential grooves, said apparatus comprising:

curved coolant feed tubes which are curved to nest within the deep grooves and having nozzles at their ends with fingernail-like extenders attached to the ends of the respective tubes on the convex side of said tubes, said extenders projecting beyond the discharge ends of the respective associated nozzles in position to intercept and spread out the coolant stream issuing from the nozzle, and said fingernail-like extenders tapering to a sharp straight edge toward which the spread out stream of coolant moves.