US3289257A - Continuous casting mold having ribs - Google Patents

Description

Dec. 6, 1966 J. H. RICHARDS 3,289,257

CONTINUOUS CASTING MOLD HAVING RIBS Filed Jan. 29, 1964 4 sheets-sheet 1 JOHN H.R|cHARDs BY ATTORNEY Dec. 6, 1966 J. H. RICHARDS CONTINUOUS CASTING MOLD HAVING RIBS 4 Sheets-Sheet 2 Filed Jan. 29, 1964 INVENTOR.

H R I C HARDS J 0H N ATTORNEY Dec. 6, 1966 J. H. RICHARDS 3,289,257

CONTINUOUS CASTING MOLD HAVING RIBS Filed Jan. 29, 1964 4 Sheets-Sheet 3 Fig@ CGOLI NG WATER COOLING 4? WATER COOLING WATER OUT WATER T IN INVENTOR.

JOHN H.R|cHAROs BY 5MM/26% ATTORNEY Dec 6, 1966 J.H,R1HARDS 3,289,257

CONTINUOUS CASTING MOLD HAVING RIBS BY M2M@ ATTORNEY United States Patent O 3,289,257 CONTINUOUS CASTENG MlLD HAVING RIBS John H. Richards, Penn Hills Township, Allegheny County, Pa., assigner to United States Steel Corporation, a corporation of Delaware Filed lian. 29, 1964, Ser. No. 340,875 4 Claims. (Cl. 22-57.2)

This invention relates to molds for the continuous casting of metals and more particularly to a novel mold for the formati-on of castings having less segregation of impurities than conventional castings.

The continuous casting mold in general use is an upright open-ended tubular structure having substantially vertical walls, open at its upper end `tor the introduction of molten metal and open at its lower end for the dischauge of a metal casting which is at least partially solidified, The mold is water cooled. The cross-sectional shape of the mold is approximately the same as that desired in the casting, yand is frequently rectangular.

In addition to a mold, conventional continuo-us casting :apparatus ralso in-cludes cooling rneans comprising a plurality of water sprays located below the mold for directing cooling water lagainst the casting, guide means comprising a plurality of guide rolls located between the water sprays `for guiding the casting as it moves downwardly through the cooling zone, and motor driven pinch rolls located below the guide rolls and cooling mea-ns :for control-ling the rate of descent of the casting.

The lower end of the rno'ld is closed by a suitable closure member, usually a starter bar, prior to the pouring of molten metal into the mold. Molten metal is then poured into the mold. A skin of metal adjacent the upper end of the starter bar 'and the side walls of the mold solidies while the starter bar is still in place in the lower end of the mold. When the molten metal has reached a predetermined level in the mold, the starter bar with the partially solidified casting attached thereto is lowered under the control of the pinch rolls. The interior of the casting progressively solidies as the casting, supported yby the starter bar, descends below the mold through the cooling zone. After `the starter bar has descended below the pinch rolls, it is detached from the casting. This can |be done in any desired manner, as for example by cutting the casting a short distance above the starter bar. The starter bar is then lowered and removed from the casting apparatus. The casting may be subjected to such further treatment as desired, as for example rolling, longitudinal grooving and cutting along the grooves to form billets.

One presently known mold is a rectangular mold, having a pair of opposed substantial-ly parallel and substantially vertical side w-alls and Ia plair of opposed suI stantially parallel `and substantially vertical end walls. A rectangular casting is formed in this type of mold. The common practice is to provide 1a slight taper from top to bottom of the mold, so that opposed mold w-alls are substantially but not absolutely vertical. However the mold walls can be absolutely vertical if desired.

The principal advantage of a rectangular casting is that such a casting is more easily guided as it descends below the mold than a casting of any other shape. Cylindrical guide rolls can be used; specially shaped rolls are not required. Where the casting has a thickness relatively small compared to its width, it is usually necessary to provide only two sets of guide rolls bearing against opposite faces of the casting. Where the casting is of greater thickness, two sets of edge rolls, each bearing against the two edges of the casting, may be necessary in Iaddition to the face rolls.

A disadvantage of la rectangular mold is the tendency for impurities in the casting to become concentrated near the center. Solidiiication in a continuously formed casting starts along the exterior surfaces of the casting while the casting is still in the mold, and then proceeds inwardly Ias the casting descends below the mold and is cooled. When yan alloy such as steel is being cast, impurities and -alloying constituents which have lower melting points than that of the principal constituent remain preferentially in the liquid phase. Thus as freezing continues, these impurities and aloying constituents tend to migrate toward the center of the casting, which is the last portion to freeze. This establishes a high concentration of impurities Iand alloying constituents at the center of the casting when it is completely solidiiied. In the case of a rectangular casting, this zone of irnpurities is la small zone which is seen as a thin black center line running in the longitudinal direction of the casting when the casting is out into billets. This results in a non-uniform casting, the center portion of which has properties differing from those of the rest of the casting.

An object of this invention is to provide a mold which forms a casting having substantially less segregation and impurities than in the conventional rectangular casting and yet is easily guided similarly to the rectangular casting.

Another object of this invention is to provide a mold which forms a grooved casting which can be cut readily along the grooves in subsequent operations.

These and other objects will be lapparent from the description which follows, in which:

FIG. l is a horizontal sectional view of the apparatus of this invention;

FIG. 2 is a front elevational View of the mold of this invention;

FIG. 3 is a vertical sectional view on a lange scale taken lalong line 3-3 of FIG. 1;

FIG. 4 is a schematic view of a continuous casting apparatus which includes Ia mold according to this invention and a processing line including rolls for further grooving the casting and a saw for cutting the casting along the grooves thereof; and

FIG. 5 is a sectional view of a pair of opposed grooving rolls of the apparatus shown in FIG. 4.

Referring now to FIGS. l to 3 and especially to FIG. l of the drawing, 1t) indicates generally an upright openended continuous casting mold which is open at its upper end for receiving molten metal and at its lower end for the discharge of a partially solidified metal casting. Mold 10 has a pair of opposed side walls 12 and a pair of opposed end walls 14, which lare made of a highly conductive metal or alloy, preferably copper. These side walls 12 and end walls 14 dene therebetween a mol-d cavity 15 in which :a casting is formed and in which initial solidication takes place at the perimeter of the casting. The opposed side walls 12 may be absolutely vertical and parallel, but it is preferred practice to pr-ovide side walls which slope at a small :angle to the vertical, so that the opposed side walls 12 are slightly closer together at the bottom of the mold than at the top. Tapering of the mold walls in this manner is known and does not constitute a part of this invention. lEnd walls 14 may ybe similarly tapered.

Each of the side walls 12 and each of the end walls 14 has a plurality of ver-tical cooling water channels 16 therein. These channels lmay -be machined by known techniques. The ydead ends of channels 16 at the bottoms of walls 12 and 14 are closed by -screw-thneade-d plugs 1S. Lateral passages 20, which lmay be either level or sloped las shown in FIG. 3, provide connections from -channels 16 to water headers not shown. The water headers may be of conventional construction.

An important novel feature of the present invention is the provision of 1a plurality of spaced apart inwardly extending ribs 22 on side walls 12. These may be secured to side walls 12 by 4screws 24. Each of these ribs 22 is symmetrical about a vertical plane which is at right angles to the longitudinal axis of the casting. lEach of the ribs 22 has a pair of walls 26 which :are disposed at an acute angle with respect to each other. Each of these walls 26 intersects the adjacent mold side wall 12 `at an obtuse tangle. The two w-alls 26 of each rib 22 do not intersect; instead :a rounded forward edge 28 connects these two walls. Each rib 22 has a vertical cooling channel 30 extending from the bottom of the rib uipwardly to a point near the top of the rib. The lower end of each channel 30 terminates in an internally screw-threaded bore 32 which is of slightly langer diameter than the channel itself. This internally screw-threaded bore 32 receives an externally screw-threaded fitting 34. Fitting 34 has, in concentric relationship, an externally screw-threaded portion 36 at .its upper end for enga-ging the internally screw-threaded portion 32 of -rib 22, a bore 33 which is coaxial with channel 30 and of approximately the same diameter, and a thin metal pipe itl which -is of smaller diameter than bore 3S and which extends fa substantial distance int-o channel 30 when fitting 34 is threadedly secured to ribs 22 as shown in FIG. 3. An annular passageway 42 is formed between pipe 40 on the inside and channel 30 and bore 3S on the outside. Fitting 34 also has a pair of lateral passageways 44 and 46 which are open at one end and in communication with the interior of pipe 40 and the annular passageway 42 Irespectively at the other end. The iopen ends of passaigeways 44 and 46 are internally screw-threaded to receive water pipes or hoses 47 `and 4S. Cooling water is supplied through passageway 44 and pipe 40, and returns through the annular passageway 42 and lateral passageway 46.

The copper .side walls 12 and end walls 14 are backed up by a steel back-up structure 49. This structure comprises a plurality of panels 50, one -for each of the walls `12 and 14 reinforced by both vertical and horizontal aniges or webs 52. This steel back-up structure 49 may be joined to the copper side and end walls 12 and 14 respectively by any ydesired means, such as bolts 53 (shown in FIG. 2). A plurality of Water inlet manifolds 54 and water outlet manifolds 55 convey cooling water to and from the mold 10. Preferably each panel 50 has an inlet manifold 54 secured to the lower por-tion thereof and an outlet mani-fold S secured to `the -upper portion thereof. The manifolds may be secured by conventional means such `as welding. Lateral passages 56 in the steel back-up structure and passages in copper walls 12 and 14 provide communication between channels 16 and manifolds 54 and 55. A fplurality of sealing ring such -as conventional O-rings 58, provide `for sealing engagement between the copper side land end walls 12 and 14 in the steel back-up structure 49.

Four spacer plates 60, preferably made of copper, separate t-he face of each side wall 12 and end w-all 14 from the edge of the adjacent wall 14 and .side wall 12. These spacer plates 60 extend from the exterior of the mold to one corner of the mold cavity. Preferably the inner ends of plate i60 `are beveled so that the :mold cavity has beveled corners rather than square corners.

The distance between the two end walls 14 is preferably at least labout three times the distance between the side wall 12. Thus `castings Kformed in the instant mold have a width lat least three times the thickness. In a preferred embodiment, the distance between the end walls 14 is from :about ve to six times the distance between side walls 12.

The opposed ribs 22 preferably lie directly opposite each other. The forward edges 28 of ribs 22 preferably extend inwardly a distance not less than 1/6 and not more than :about 1/3 the distance between side walls 12,

so that the dista-nce between the yforward edges 28 of two opposed ribs 22 is :at least about i but not more than about 2/3 the distance between .side walls 12. The distance between the center planes of successive ribs 22 is preferably approximately equal to the distance between side walls 12, but may be somewhat greater or somewhat less. The distance between the last pair of ribs on each side wall 12 `and the adjacent end wall 14 is likewise approximately equal to the distance between side walls 12. A preferred mold according to this invention has a distance of 27 inches at the top `and 26% inches -at the bottom between side walls 12, a distance of 5 inches between end walls 14 with four ribs on each side, each extending inwardly a distance of about 31/32 of an inch from the adjacent si-de wall, so that the distance between the opposed ribs is 31/16 inches. Successive ribs are spaced in this embodiment :at a distance of 51/2 inches. The distance between the pair of ribs nearest each end wall and the adjacent end wall is approximately 51A inches. It is understood that this embodiment is given merely by way of illustration of a preferred embodiment, and is in no sense limitative of the invention.

The continuous casting of metals in a mold according to this invention will now be described with reference to FIG. 4. A starter bar is inserted into the lower end of mold 10, and then molten metal is poured from `a conventional bottom pour ladle '70 into the mold. The metal adjacent the mold walls and immediately above the starter bar solidies. The solidified metal immediately above the starter bar becomes attached to the bar. Preferably the upper end of the starter bar is provided with a structure which will grip the solidified lower end of the casting in interlocking engagement. When the mold 10 has been substantially lled, the starter bar and the casting attached thereto are lowered. The casting has a rectangular cross section With grooves formed by ribs 22. This casting and the starter bar are guided by means of conventional guide rolls 72 as they descend vertically below the mold. Simultaneously the surface of the casting is cooled by means of a plurality of water sprays 74, which are located between adjacent guide rolls 72. The rate of descent of the starter bar and casting are controlled by pinch rolls 76. The starter bar and attached casting descend vertically until the upper end of the starter bar is below pinch rolls '76. Then the casting is cut a short distance above the upper end of the starter bar by one or more cutting torches 78, or the starter bar is otherwise disconnected from the casting. After the starter bar has been severed from the casting, the starter bar is lowered vertically, independently of the casting, which continues to descend at the same rate as before severance, and then the starter bar is lowered to the horizontal position by tilting basket 80.

After the starter bar -and casting have been separated, the casting may be brought straight down, and cut into sections by means of cutting torch'78, and each section then transferred separately from the vertical to the horizontal direction by means of the tilting basket St) in the same manner as the starter bar.' Alternatively, after cutting of the casting from the starter bar by torch 7S, the casting may be bent from its vertical direction of travel by bending rolls 82, guided by a curved frame 84, and straightened when it has reached a horizontal path by straightening rolls 86.

After the casting has reached a horizontal path, it may be reheated in furnace 87, rolled, grooved, and cut according to conventional rolling mill operations. Thus the casting may travel in a horizontal path over conveyor 88 through sizing rolls 90 in order to reduce the casting to the desired thickness. This causes the grooves in the casting to flatten out somewhat but not to disappear entirely. After sizing, the casting may be grooved in groov ing roll 92. Preferably grooving is along the lines of the grooves which were formed in the casting by molding, so that the grooving operation deepens the existing grooves to a point which makes subsequent cutting easy without forming any new grooves.

Referring now to FIG. 5, the grooving rolls 92 are shown in cross section. These grooving rolls may be conventional grooving rolls as known in the art, and have a plurality of lands 93 equal to the number of grooves in the casting. The lands 93 are so spaced that they are aligned exactly with the grooves in the casting. Thus lands 93 on grooving roll 92 are somewhat closer together than the ribs 22 in mold 10, because considerable shrinkage of the casting takes place due to solidilication and cooling between the time it is formed in the mold and the time Vit passes through grooving rolls 92. Grooving rolls 92 are driven by a conventional motor equipped with speed control means.

After the casting has been grooved by grooving rolls 92, it is slit along the grooves by means of a saw 94 and then parted into billets.

Castings formed in the mold of this invention have a much more nearly uniform distribution of impurities than do castings formed in conventional rectangular-molds. The dark Zone of impurities, which lappears as a dark center line in a cross-sectional cut of a conventional rectangular casting, is not present in castings formed in the instant mold. The water-cooled ribs in the present mold alter the solidification pattern so that solidication in the zone lying between two opposed grooves is complete while a substantial volume of molten metal remains elsewhere in the mold. This has the effect of distributing impurities throughout large areas of the casting instead of concentrating the impurities in a lthin lengthwise extending zone in the center of the casting.

While this invention has been described with reference to a specific embodiment thereof, it is understood that Variations may be made within the skill of the art without departing from this invention.

What is claimed is:

1. An open-ended tubular continuous casting mold of generally rectangular cross section comprising a pair of opposed substantially parallel and substantially vertical side walls and a pair of opposed substantially parallel and substantially vertical end walls defining a mold cavity therebetween, the distance between said end walls being substantially greater than the distance between said side walls, said side walls comprising flat wall surfaces and a plurality of spaced apart vertically extending ribs projecting inwardly from said surfaces, each of said ribs having a vertical cooling water channel therein.

2. A mold according to claim 1 wherein the distance between said end walls is at least three times the distance between said side walls.

3. A mold according to claim 1 wherein the distance between said end walls is at least three times the distance between said side walls, and the distance between successive ribs is approximately equal to the distance between said side walls.

4. Continuous casting apparatus comprising an openended tubular continuous casting mold of generally rectangular cross section comprising a pair of opposed substantially parallel and substantially vertical side walls and a pair of opposed substantially parallel and substantially vertical end walls defining a mold cavity therebetween, the distance between said end walls being substantially greater than the distance between said side walls, said side walls comprising flat wall surfaces and a plurality of spaced apart vertically extending ribsl projecting inwardly from said surfaces, each of said ribs having a vertical cooling water channel therein, and a plurality -of grooving rolls for further grooving said casting along the lines of the grooves formed by said ribs in the mold.

References Cited by the Examiner UNITED STATES PATENTS 9/ 1937 Gatlimann 249-174 X 9/1964 Boehm.

Claims (1)

1. ON OPEN-ENDED TUBULAR CONTINUOUS CASTING MOLD OF GENERALLY RECTANGULAR CROSS SECTION COMPRISING A PAIR OF OPPOSED SUBSTANTIALLY PARALLEL AND SUBSTANTIALLY VERTICAL SIDE WALLS AND A PAIR OF OPPOSED SUBSTANTIALLY PARALLEL AND SUBSTANTIALLY VERTICAL END WALLS DEFINING A MOLD CAVITY THEREBETWEEN, THE DISTANCE BETWEEN SAID END WALLS BEING SUBSTANTIALLY GREATER THAN THE DISTANCE BETWEEN SAID SIDE WALLS, SAID SIDE WALLS COMPRISING FLAT WALL SURFACES AND A PLURALITY OF SPACED APART VERTICALLY EXTENDING RIBS PROJECTING INWARDLY FROM SAID SURFACRS, EACH OF SAID RIBS HAVING A VERTICAL COOLING WATER CHANNEL THEREIN.

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