US3437129A - Apparatus for continuously casting elongated metal bodies - Google Patents

Description

J. T. BLACK, JR

APPARATUS FOR CONTINUOUSLY CASTING ELONGATED METAL BODIES April 8, 1969 Sheet of 4 Original Filed March 1, 1965 Wm 1 Y m [4 M 8 7M M r "H s A m M April 8, 1969 J. T. BLACK, JR

APPARATUS FOR CONTINUOUSLY CASTING ELONGATED METAL BODIES Z of 4 Sheet Original Filed March 1, 1965 JAMES 7TBL4 /f J ATTORNZ-"YS April 8, 1969 J. 'r. BLACK, JR

APPARATUS FOR CONTINUOUSLY CASTING ELONGATED METAL BODIES Original Filed March 1, 1965 1 N VEN TOR. Jfi MES I suck, A

ATTORNEYS Sheet 4 of 4 April 8, 1969 J. T. BLACK, JR

I APPARATUS FOR cou'rmuousm CASTING ELONGATED METAL BODIES Original Filed March 1, 1965 e 7 2 1 we 5 8 f E 3 a 4 flu M: E .7 F

ATTORNFYSV United States Patent US. Cl. 164-282 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus restoring to a moving length of metal having a solidified outer skin and a molten interior the desired right angle cross sectional shape. Rollers engage corners of the length of metal as it comes from a mold with the rollers being held spaced from each other to define a confining passageway of fixed dimensions for the length of metal.

Reference to related application This is a division of my copending application Ser. No. 436,033, filed Mar. 1,, 1965, now Patent No. 3,303,943.

Background of the invention This invention relates to apparatus for continuously casting elongated metal bodies and has particular reference to such apparatus for assuring the delivery of accurately cross sectioned castings.

In this art the basic apparatus for continuously casting elongated bodies, strands, or billets of steel or the like is presently well developed and is in commercial use. By way of example, the continuous casting of steel in 20 ton heats in 4" x 4" square continuous lengths is typically illustrative of such apparatus. Briefly, such apparatus includes the use of a vertically reciprocable water-cooled, open-ended, sleeve-like mold into the open upper end of 'which the molten metal is poured during the continuous casting operation. The casting, after becoming solidified on its outer surface, namely, after developing an outer solidified skin capable of retaining the inner, still molten core, is continuously removed from the open bottom end of the sleeve-like mold at a rate correlative to the rate at which metal is poured into the mold. It has been found that such castings, while still in the mold and probably due to unequal cooling therein, tend to assume a cross sectional shape different from the cross sectional shape of the mold. For example, if a square cross sectioned casting is desired the mold used is square in cross section. However, while in the mold, the casting, still molten in its interior, will assume, for instance, a rhomboidal shape in cross section. Thus, it heretofore has been necessary to run the still white-hot, molten interior casting through a series of rollers, called in the art a roller apron. Such roller apron has consisted of a plurality of groups of rollers, four to a group, the individual ones of which contact the flat sides of the casting. This roller apron has been located with the topmost group of the rollers thereof as close to the bottom of the mold as practical, and the entire apron has been mounted to reciprocate with the mold. In a typical installation this apron may be on the order of four feet long and embody as many as eighty separate rollers. Since these rollers must be mounted in bearings, in turn mounted on framework, there is uneven contraction and expansion of the assembly, resulting in an uneven or variable cross sectional path for the casting formed by the rollers of the apron. Further, since the casting must be cooled by water sprays in the area of such roller apron, its presence has hindered even and proper application of the cooling water to the moving casting. Since a large portion of such cooling water strikes various parts and surfaces of the roller apron rolls and frame local cooling thereof is unavoidable, thereby further distorting the overall passageway for the casting defined by such roller apron. Still further, since the elongated cast body from these machines is delivered downwardly from the mold, the presence of the elongated roller apron requires that the building housing the machine be on the order of some four feet higher than would be required if the roller apron could be eliminated. Occasionally, due to the lack of developing a proper skin thickness for the casting, such casting breaks through, spilling the molten metal from the interior to the outside. When this happens above or within the roller apron spillage of such metal causes a considerable amount of difficulty, requires the machine to be shut down and the spilled metal cleaned by hand from the roller apron.

In view of all the foregoing the prime object of my invention is to provide apparatus for handling the continuously moving cast body or strand from a continuous casting machine which assures the delivery therefrom of a casting having the desired cross sectional shape, while at the same time eliminating as such the heretofore used roller apron.

My invention is characterized in one essential by my discovery that when casting bodies of, for instance, right angle parallelogram cross section, such cross sectional shape may be assured in the finished product by exerting compressive forces on the casting just as it leaves the mold, in the areas of at least two opposite corners thereof, which forces embody major components which converge toward the cross sectional geometrical center of the casting.

My invention is further characterized by the application of the aforementioned forces at different points along a selected length of the casting as it moves away from the mold, as for instance, by reciprocating the points of application of the forces longitudinally of the casting.

Another object and feature of my invention is to eliminate the heretofore used roller apron having cylindrical rollers engaging the fiat sides of the moving casting and to use instead a single set of four double conical rollers, opposed pairs of which are disposed to engage the casting in the corner areas thereof, thereby to realign or restore the cross sectional configuration of the casting to that of a substantially true right angle parallelogram.

Another object is to mount the aforesaid rollers directly beneath the discharge end of the mold, preferably on the mold or its supporting structure, so that as the mold reciprocates the rollers likewise reciprocate, thus to apply the realigning forces along a length of the moving casting, resulting in the entire length delivered from the casting machine having been trued up or brought back to the desired cross sectional shape.

A still further object is to fixedly mount the rollers relative to the mold opening in position to hold the lower part of the casting centered in the mold, thus to decrease wear on the lower portion of the mold due to excessive friction which occurs when the mold rcciprocates rela tive to such off-center casting.

Apparatus illustrating the constructional features of my invention is shown in the accompanying drawings forming a part hereof, in which:

FIG. 1 is a fragmental, diagrammatic elevational view, partly in section, of portions of a continuous casting machine having my invention applied thereto;

FIG. 2 is an enlarged side elevational view of the reciprocating mold and surrounding water box of a con- 3 tinuous casting machine, partly in section, certain parts being omitted for the sake of clarity;

FIG. 3 is an enlarged detail sectional view taken generally along line IIIIII of FIG. 2 and looking upwardly beneath the bottom of the mold;

FIG. 4 is a diagrammatic vertical sectional view of the mold and showing the formation of the continuous casting therein; and,

FIGS. 5, 6, 7 and 8 are detail sectional views taken respectively along the lines V-V, VIVI, VIIVII and VIII-VIII of FIG. 4, FIG. 8 being enlarged.

Referring now to the drawings for a better understanding of my invention and more particularly to FIG. 1, I show diagrammatically a continuous casting machine into which molten steel or the like is being poured from a ladle indicated at 10. The molten steel or other molten metal pours through a tundish 11. From the tundish the molten iron pours into a vertically elongated, reciprocable, sleeve-like mold indicated generally by the numeral 12. For the purpose of interrupting the flow of metal from the tundish to the mold 12 there is a swingable lander 13, it being understood that the tundish also is mounted to be swung in a horizontal plane into and out of operative position.

The vertically disposed sleeve-like mold is adapted to be reciprocated up and down by means of a rock bar 14 having one end pivotally connected to cross members 16 which in turn are connected to the bottom of the mold by vertically extending member \17. Suitable mechanism for rocking the bar 14 about its pivot point 14a may be in the form of a vertically reciprocating member 18 driven by a motor indicated at 19.

Immediately beneath the mold is a series of sprays indicated at 21 which are adapted to spray cooling water onto the strand or casting C as it emerges from the mold. A further cooling of the casting is provided by additional water sprays 22. Beneath the sprays 22 the casting C passes between the pinch roll mechanism indicated generally at 23. Without further amplification the purpose of the pinch roll section 23 is to control the movement of the casting C from the mold and its delivery downwardly out of the machine and at a rate correlative to the rate of pouring.

At 24 I show what is called a bender, this being generally a roller mounted on a pivoted arm and pushed outwardly by a cylinder 26 into contact with a side of the casting. This changes the direction of the casting from the vertical position generally toward the horizontal position, in curved fashion as indicated. From the bender 24 the casting passes continuously to a set of supporting rollers 27. From the rollers 27 the casting passes to a set of straightening rolls, not shown, and thence to a cutting mechanism, likewise not shown, where the casting is cut into the desired length for rolling or the like.

The apparatus so far described is old in the art. Heretofore, in the area of the sprays 21 is where the aforementioned vertically elongated roller apron has been placed. As heretofore constructed the apron has been moved up and down with the mold 12 by means of the rock bar 14 and the drive means 19.

My invention comprises the placing, directly beneath the mold, of a set of at least two and preferably four double conical rollers each of which is indicated generally by the numeral 28. Preferably, the rollers 28 are mounted for free rotation on shafts 29 which in turn are supported in bearings mounted in members 31. See FIGS. 2 and 3.

The members 31 in turn may be directly secured to the lower flange structure 32 of a water box 33 which surrounds the mold 12 proper. It will be understood that the water box, along with the mold, is vertically reciprocated. Further, cooling water is admitted through a conduit 34 into the box, surrounding the mold, and the hot water is withdrawn at 36.

It will be particularly noted that each of the rollers 28 is so mounted that the minor diameter portions 28a thereof of opposed pairs lie along lines passing diagonally through the casting or strand of metal. In the instance shown I represent the casting of a length of metal of right angle parallelogram cross section. However, my invention is useful in casting various shapes. Additional water sprays in the form of nozzles 37 are provided to spray water just over the tops of the rollers 28, that is, in position to contact all four corners of the casting just as it emerges from the mold 12.

It will also be seen that the rollers 28 are rigidly or fixedly mounted in centered relation to the vertically projected opening of the mold. Being thus centered, the rollers guide the lower end of the casting holding it centered relative to the mold, or at least tending to do so, thereby decreasing the frictional engagement between casting and mold. In actual practice mold wear is materially reduced by this arrangement.

In order to obtain the advantages of my invention I locate the opposed pairs of rollers 28 with their minor diameters spaced a few thousandths of an inch less than the diagonal dimensions of the mold 12. For instance, in casting a 4" x 4" section of steel minor diameters of the rollers 28 would be set, for instance, .032 inch closer together than the diagonal dimension of the mold.

Referring now more particularly to FIGS. 4 to 8 inclusive it has been found that when molten steel is poured into a mold of the type employed in continuous casting machines, there are places within the mold where the casting actually shrinks away from the walls of the mold. For instance, in the area indicated by the numeral 38 in FIG. 4 the casting, moving continuously downwardly in the direction of arrow 39, has shrunk away from the mold as indicated. See also FIG. 6. This shrinkage may occur on all four sides of the mold and in some instances only on opposite sides, or even in some instances on a single side. By the time the casting has progressed downwardly through the mold to approximately the point indicated by the section line VIIVII, it will be found that it has, more often than not, pulled away at opposite corners as indicated at 40, thereby assuming a somewhat rhomboidal shape. It is this rhomboidal shape of the casting which the previously used roller apron was supposed to correct and which my improved apparatus does correct. It will be understood, of course, that while in the mold the casting has a molten interior C and that this molten center remains in the casting for a considerable length of time. The entire body does not ordinarily solidify until it has completed its passage through the lowermost water sprays 22.

It will be seen that as the casting progresses downwardly from the lowermost end of the mold 12 it passes between the rollers 28, while still containing the molten core C. As stated, these rollers are so set as to provide a path slightly less across the corners of the casting than the same dimension taken across the corners of the mold. Therefore, as the pinch roll system pulls the casting downwardly a certain amount of pressure is applied to the casting by the pair of rolls 28 which contact the acute corners thereof. Thus, as the rhomboidal shaped casting approaches the rollers 28 it is gradually trued-up or reshaped to true right-angle parallelogram form. This action is accomplished by the rollers due to their setting and the cross-sectional misalignment of the casting. Pressure is thereby exerted on the acute angle corners of the casting in a direction such that the principal components of such pressure, indicated by the lines 41, converge toward the geometrical cross sectional center of the casting. By the time the casting passes downwardly through the rolls 28 its shape is brought back to that desired and the outer skin S has thickened enough for the casting to be selfcontaining. Upon passing through the lower water sprays 22, it is solidified and becomes a self-sustaining, stable body.

It will be noted that the rollers 28 are not driven except by a frictional contact with the moving casting C. Ob-

viously, at all points outwardly along the surfaces of the double conical rollers 28 from their minor diameters, there is some slippage between the surface of the casting and the larger diameter portions of the rollers, assuming, of course, that the rollers are engaging the casting directly at the corners. While theoretically it would appear that this slipping may have a deleterious effect upon the functioning of these rolls, in actual practice I have found that such is not true. While I may be mistaken in this, I attribute this fact to the presence of scale on the sides of the casting which permits the larger diameter segments of the rollers readily to slip relative to the surfaces of the casting.

From the foregoing it will be seen that I have provided improved apparatus for realigning or retruing the cross sectional configuration of castings as they emerge from the molds of continuous casting machines.

In view of the fixed setting of the rollers 28 relative to the mold opening there is some tendency actually to pre- -vent the casting from getting out of shape. At all events,

whether my invention prevents cross-sectional misalignment or corrects such defect after it occurs, castings made thereby are accurately shaped to the degree required in practice.

In actual practice, it has been found that the major number of 'break-throughs of the molten metal through the skin of the partially solidified casting occurs at points just removed from the corners of the casting, at about the points marked X in FIG. 8. Sometimes such breaks occur directly at the corners. With rollers 28 installed as indicated, I have found that I have reduced the number of break-throughs of the molten center, when casting the same type metal, in the same size castings, and in fact in the same machine, by as much as 500%, over the number encountered with the use of the prior roller apron. Furthermore, since the roller apron has been removed, the operator of the machine now has a substantially unrestricted view of the casting as it emerges from the mold. In practice, with my invention when the operator spots a break-through, he is enabled to slow down the rate of discharge of the casting from the machine, and in a large majority of the instances where break-throughs normally would have occurred, this procedure makes them sel-fhealing. That is to say, in view of the fact that the casting, where it is apt to break through, is now visible because I have eliminated the roller apron, the operator is enabled to discover and cure many break-throughs Without interrupting the heat or shutting down the machine due to that cause.

Another advantage of my invention lies in the fact that by removing the roller apron I am enabled to cool the casting by the water sprays 21 much more evenly and accurately and with less water. Further, I have found that by truing up the cross sectional configuration of the casting by the single group of rollers 28 I eliminate the subsequent reintroduction of errors in cross sectional configuration which have been occasioned by misalignment of the heretofore used roller apron. As will be readily apparent, such an elongated set of rolls, mounted on frames, being unevenly heated and cooled, have resulted in a distorted confining path for the casting. Therefore, and in actual practice I have found that castings produced by my improved process and apparatus are much more uniform in cross sectional configuration than those produced with the aforesaid roller apron.

As previously mentioned, my invention also permits the entire continuous casting machine to be lowered by some four feet. When it is realized that the entire building structure for supporting and housing one of these machines may be on the order of 110 feet high, this saving will be appreciated.

Viewing FIG. 8, it will be apparent that the resultant components of the forces indicated by the lines 41 which are exerted on the castings by the rollers 28 produce an entirely different action on the casting in realigning it over what is produced by four rollers, operating along the flat sides of the casting. In the latter instance it will be seen that the only forces of such sets of four flat rollers 'which meet at the center are the minor components of such pressure of opposite roll pairs which happen to act through the center. Furthermore, with sets of rolls arranged to engage the fiat sides of the casting warping of the supporting frame often causes the rolls to engage the flat side at only one end. In such cases it will be seen that the forces tending to realign the casting are more or less randomly applied thereto so that not only grater forces must be applied if the rollers engage the flat sides, but also the control of these forces is more difiicult and less sure than with my improved apparatus. Thus, by bringing a rhomboidal shaped casting back to that of a substantially true right-angle parallelogram by pressing the same inwardly along the acute angle corners, I achieve the realignment with a fewer number of rollers, do so in a more certain and accurate way and eliminate the likelihood of redeforming the casting by the action of subsequent sets of rolls. While it is true that there are other components of inwardly directed forces which are normal to the engaging surfaces of the rolls 28, other than those indicated at 41, nevertheless the major component of the forces exerted on the casting to realign it are directed diagonally of the casting as illustrated in FIG. 8.

While I have shown and described my invention in connection with casting right angle parallelogram castings, it will be apparent to those skilled in the art that the principles thereof have utility in casting other shapes such as rounds, or other shapes having intersecting outer surfaces.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. For use with a continuous casting machine from the mold of which is continuously delivered a moving metal body of right angle parallelogram cross section having a solidified outer skin and a molten interior which tends to change in cross sectional shape,

(a) means to restore to the moving body of material the desired right angle cross sectional shape comprising double conical rollers mounted adjacent the discharge end of the mold and rotatably engaging corner areas of the moving body of material, said rollers being fixedly spaced in opposed pairs with their minor radii lying at the ends of lines connecting opposite corners of the metal 'body, whereby at least some pressure is exerted by at least a pair of the rollers on the metal along said lines.

2. Apparatus as defined in claim 1 in which the rollers are mounted as a group on the mold and in which there is means to reciprocate the mold and hence the rollers relative to the longitudinal axis of the moving body of metal.

References Cited UNITED STATES PATENTS 494,659 4/1893 Very 164-283 X 2,284,703 6/1942 Welblund et al. 164-282 X 2,527,545 10/1950 Goss 164-283 X 2,814,843 12/1957 Savage et al. 164-82 3,040,396 6/1962 Hudson 164-282 X FOREIGN PATENTS 1,353,998 1/1964 France.

I. SPENCER OVERHOLSER, Primary Examiner. R. SPENCER ANNEAR, Assistant Examiner.

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