US3536127A

US3536127A - Cooling system for continuous casting machine

Info

Publication number: US3536127A
Application number: US680254A
Authority: US
Inventors: Klaus Tafel
Original assignee: Schloemann AG
Current assignee: Schloemann AG
Priority date: 1966-11-03
Filing date: 1967-11-02
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27

Description

United States Patent Inventor Klaus Tafel I-Illden, Germany App1.No. 680,254 Filed Nov. 2, 1967 Patented Oct. 27, 1970 Assignee Schloemann Aktiengesellschaft Dusseldorf, Germany Priority Nov. 3, 1966 Germany 1,508,976

COOLING SYSTEM FOR CONTINUOUS CASTING MACHINE 6 Claims, 2 Drawing Figs.

134/122.134/199;164l89 Int.Cl 822d "/12 Field of Search 164/82, 89,

References Cited Primary Examiner-.1. Spencer Overholser Asristam ExaminerR. Spencer Annear Anumey-Sandoe, Neill, Schottler and Wikstrom ABSTRACT: Guide rollers for a casting emerging from a continuons casting mold are hollow and have spray nozzles in their circumferential surfaces. Coolant fed into the interior of each roller thus sprays out through the nozzles to cool the casting.

COOLING SYSTEM FOR CONTINUOUS CASTING MACHINE The invention relates to a cooling system for continuous casting machines in which the casting emerging from the mold is guided by rollers and cooled through nozzles to which a coolant is fed.

As is known, guide rollers disposed below the bottom of the mold on either side of the strand guide the casting coming from the mold into the machine sections following the mold and at the same time center it within the mold to prevent cross-sectional distortion due to differential local cooling conditions. Now the casting must also be cooled as it leaves the mold because at that point only its skin is solidified while its core is still liquid. Thus the skin of the casting is still deformable over this region, and the specific pinching pressure exerted by the guide rollers on the surface of the casting must therefore be kept relatively low. One way of accomplishing this is to provide a great many close-spaced guide rollers. in that case, however, there is not enough'room between the individual guide rollers to accommodate the coolant-fed nozzles, and effective cooling'cannot then be achieved.

One attempt at solving this problem consists in disposing directly at the lower end of the open ended mold platelike guide members which participate in the downstroke of the oscillating mold and in so doing are in close contact with the surface of the casting. During the upstroke the guide members come away from the casting surface-to be able to follow the ascending movement of the mold, laterally spaced therefrom. In the upper extreme position the guide members are then again pressed against the surface of the casting. These guide members may be cooled in any desired manner and thus serve to both guide and cool the continuous casting. As a result, however, the casting is cooled more intensively in the regions where the movements of the guide members overlap and is not guided during the upstroke.

The invention has as its object to improve cooling systems of the type described at the outset in such a way that on the one hand a minimum of pressure per unit area is exerted on the surface of the casting while more heat is abstracted therefrom by means of a coolant, and considerably more uniformly, than has hitherto been the case. In accordance with the invention, this is accomplished essentially by constructing the guide rollers hollow, by providing them with nozzles-distributed over their circumference, and by supplying them with a coolant through their ends. With this arrangement the spray nozzeles heretofore provided between the guide rollers may be dispensed with. This, in turn, makes it possible to dispose the guide rollers so as to begin directly at the bottom of the mold and to space them very closely. In this way, an enlarged contact area is obtained between the guide rollers and the surface of the casting, the pressure per unit area being correspondingly reduced with constant lateral forces. Deformation of the solidified skin of the casting is thus largely prevented, especially since the skin is thicker because of the improved cooling action. Moreover, this arrangement permits the guide rollers to be made considerably larger than heretofore, which also results in an increased contact area. By providing for improved strand guidance and cooling action, the invention further makes it possible to increase the casting speed and hence the capacity of the continuous casting machine, which is a factor particularly from the standpoint of its adaptation to a steelmaking shop preceding it.

The invention may be used to advantage both in continuous casting machines with curved molds and curved roller aprons and in continuous casting machines with vertical molds and associated vertical roller aprons. Also, the advantages offered by the invention will accrue both in the case of billet and of slab continuous casting machines.

The invention will now be described in greater detail with reference to the accompanying drawing, which is a diagrammatic representation of the novel cooling system.

FIG. 1 is an elevational sectional view of the apparatus of the invention.

FIG. 2 is a sectional view through one of the rolls.

The mold l is conventionally mounted in a mold table and is oscillated with the latter; It is supplied with coolant, in a manner not novel in itself, from either a recirculating or a once-through system. The level of metal 2 in the mold 1 is maintained by a constant flow of metal from a tundish while below the metal level 2 a skin forms in known manner whose thickness gradually increases under the influence of the coolant until the casting solidifies over its entire cross section some distance below the bottom of the mold. At the lower end of the mold l, the skin of the casting 3 thus is still relatively thin and easily deformed under the influence of the forces acting upon it, and intensive cooling is required to enable it to thicken sufficiently to develop adequate resistance to both external deforming forces and the internal'pressure of the liquid metal.

The guide rollers 5 begin directly at the botom end of the mold 1. They are spaced very closely especially at the beginning to support the solidified skin of the casting adequately without deforming it. As pointed out earlier, the

guide rollers 5 are hollow and are provided with nozzles 6.

Through these the coolant emerges in jets, as shown schematically, impinging upon the surface 4 of the casting uniformly and at high pressure. The coolant employed is preferably water at a pressure exceeding the vapor pressure of the steam envelope forming on the casting surface 4. Since the nozzles 6 are distributed over the entire circumference ofthe rollers and the latter follow the movement of the casting, the coolant is actually applied perfectly uniformly. in the gaps between two adjacent guide rollers the coolant jets strike the casting surface 4 obliquely while at the point of contact between a guide roller 5 and the casting surface 4 they strike the latter nearly perpendicularly. The cooling action will not be impaired by any accumulation of coolant which may occur in the space bounded by the lines of contact of two adjacent guide rollers 5 and the corresponding portion of the casting surface 4 because the emerging coolant jets 7 will act upon the casting even through the accumulation and displace the spent coolant outwardly.

The coolant supplied to the guide rollers may advantageously come from the same loop as the cooling medium for the mold 1. To minimize coolant losses and to prevent damage in the vicinity of the roller apron, a baffle plate 8 is provided on the side of the guide rollers 5 which is remote from the casting'surface. Said baffle plate may be constructed with a drain channel at its lower end, in a manner not shown in the drawing, through which the spent coolant is discharged continuously.

Since the casting surface 4 is often contaminated with lubricant residues, oxide films or other impurities adhering to it, and since the nozzles 6 come into direct contact with the casting surface as the guide rollers 5 turn, it is advisable to incorporate means adapted to prevent clogging of the nozzles 6. To this end, scraper brushes may be provided on the side of the guide rollers which is remote from the casting surface 4, with said brushes wiping against the guide rollers, and with the impurities so loosened being flushed into the drain channel along with the coolant. Or the guide rollers 5 and their nozzles 6 may be kept clean by means of scraper blades disposed at that point. Moreover, compressed air nozzles might be provided on the side of the guide rollers which is remote from the casting surface, either in combination with the aforesaid arrangements or independently, said nozzles being aimed at the circumference ofthe guide rollers, with the impurities on the surface of the guide rollers and on the nozzles then being blown off by blasts of compressed air.

In the arrangement shown diagrammatically, pressure-energy losses will occur because some of the coolant jets will impinge upon the baffle plate 8. To prevent the coolant from exiting on the side of the guide rollers which is remote from the casting surface 4 and the resultant pressure loss, the respective halves of the guide rollers 5 may be provided with semicircular shells in slightly spaced relation thereto. The longitudinal edges of these shells may then likewise be provided with scraper brushes, scraper blades, etc., in order to keep the nozzles 6 clean.

The simplest way of supplying-the guide rollersnwith coolant. preferably water. is to mount-them on hollowshafts-otf studs. seals being interposed where the latter. penetrate-the 1 two endsof therolle'rs, afndtheir inside portions being ori-" ficed. The coolant canfthen be iedlin through connections qz disposed at the outer shaft ends.

The novel guide ro l'ers 'mayjbe arrangedlin-unydesired V manner below" theinold: l. in a particularly advantageous arranger'nent they'are disposed so asto guide the casting J centered within the mold 1, Moreover. provision may be made for permit them to be adjusted to. h

varying their lateral spacing to different casting sizes;

Evenin cases where ;the guide rollers are disposed so as to oscillate with the mold the space saving made possible by h using them will permit them to be closely spaced in the" direction of the strand, in addition to being close-spaced radi-- 1 ally therefrom. In the event of a rupture of the skin,rth c arrangement offers further advantages with respect to aims-1 sembly since the rollers may be withdrawn from thetop'with' 1 =-20 The water consumption exceedsthat of conventional spray nozzles; But since the cooling action is more inte'nse'and more the mold." r

uniform, the water consumption may bereduced'bylimiting i the nozzled guide trailers to the section located dire'etly helow; themoldrather than placing them over the entire lengthof'th'e cooling apron.

I claim:

ga mold includingmeans for guiding and coo lingua .strand emerging from the mold comprising a plurality of id'tatably "for engaging and guiding the strand. said rollershaving holiowin- "te riors and spray nozzles 'openinghfromsaid hollow interiors l through the circumferential surfaceslof the rolls points dis tributed around said circumferences. and means for supplying supported guide rollers disposed" at the exit end of the liquid coolant to the-hollow interiors of the rollers to flow out lo through the noz zles and into contact with the strand.

2. The continuous casting machine of;claim l in which said guide rollers are mounted on hollow shafls having orifices opening from the hollow interiors of the shafts into the hollow interiors ofthe guide rollers and conduits connected to supply 5; The continuous castingrna'chine ofclaiin 4 in which the guide rollers are close together along-the direction offimove- "ment'ofthestrand. V

6. The continuous casting-machine of claim I including'a baffle plate at'the sides of the guide rollers away from said I. A continuous casting machine wherein a continuousstrand ofpartially solidified metal is cast by and emerges from r. strand.