US2767448A

US2767448A - Continuous casting mold

Info

Publication number: US2767448A
Application number: US296004A
Authority: US
Inventors: Harter Isaac; Jr Isaac Harter; Temple W Ratcliffe
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1952-06-27
Filing date: 1952-06-27
Publication date: 1956-10-23
Anticipated expiration: 1973-10-23

Description

Oct. 23, 1956 l. HARTER ET AL CONTINUOUS CASTING MOLD Filed June 2'?,` 1952 2 Shets-Sheet 1 FIG.2

INVENTORS fama .5L/@Mer BY dmac Harecf IIIII LLM.

um ATTORNEY Oct. 23, 1956 l. HARTER ETAL CONTINUOUS CASTING MOLD 2 Sheets-Sheet 2 Filed June 2'?, 1952 Q/ l/ LQ@ W M F i?? RIZ r. E mffwm mymfa 0 V ./,mw mc A mw@ www n Y c United States Patent CONTINUOUS CASTING MOLD Isaac Harter, Isaac Harter, Jr., and Temple W. Ratcliffe,

Beaver, Pa., assignors to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application June 27, 1952, Serial No. 296,004 3 Claims. (Cl. 225l7.2)

The present invention relates to the construction of molds for the continuous casting of metals, and more particularly to the construction of iluid cooled molds for continuous casting where the major axis of the mold cross-section is at least several times the minor'axis dimen-sion.

As disclosed in U. S. Patent 2,590,311, molds constructed for the continuous casting of high melting temperature metals and alloys are subjected to high cooling rates to attain commercial rates of casting production. Such high cooling rates are obtained by the use of large volumes of water passed in turbulent, high velocity flow in contact with the exterior surfaces of the mold. Advantageou'sly,v the mold liner or molding tube is constructed of a high heat conductivity metal and of a desirable thickness for a high rate of heat flow therethrough between the metal being cast and the cooling water. To fulfill constructional requirements for heat transfer conditions and desired cross-sectional shapes the molds are frequently structurally weak and deform in operation so as to seriously interfere with the good quality of the cast product and sometimes lead to interruptions in the casting Operations. v

In accordance with the invention an open ended molding tube of the desired elongated cross-sectionaly shape is provided with a plurality of parallel longitudinal flow passageways along the exterior surfaces of an intermediate longitudinal portion of the molding tube. The molding tube or liner is secured lto aV supporting structure which not only defines the outer wall of the longitudinal ilow passageways intermediate the length of the tube but provides a structure capable of avoiding inward or outward distortion or" the molding tube as may be caused by the pressure of the metal being cast within the mold or by cooling water pressure. Additionally the upper portion of the molding tube is strengthened by an internal sleeve insert depending from the top of the mold.

The various features of novelty which characterize our invention are pointed out with particularity inV the-claims annexed to and forming a part of this specification.` For a better understanding of the invention, its Operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described an embodiment of the invention.

Of the drawings: A

Fig. 1 is an elevation', partly in section, of a casting mold constructed in accordance with the invention;

Fig. 2 is a partial plan view of the mold shown in Fig. 1

Fig. 3 is a cross-section taken on the line 3-3' of Fig. l;

Fig. 4 is a cross-section of an alternate 'casting mold shape;

Fig. 5 is an enlarged elevation of 'aportrionmofithe apparatus shown in Fig. 1; and

Fig. 6 is a horizontal section of portion of'an alterl` nate mold construction.

ICC

In general, the mold construction illustrated in the drawings is applicable to any mold cross-section shape, but is particularly useful in the continuous casting of metal ingots having a cross-sectional length several times its width.

As shown in Figs. l and 3, the mold assembly includes an upright molding tube or liner 10 of elongated cross-section with the exterior surface having a major portion of its length cooled by a high velocity flow of cooling water. The intermediate portion of the liner 10 is circumferentially provided with a substantially uniformly spaced series of longitudinally extending spacers or ribs 11 which engage and are attached to a surrounding skirt or support structure 12. The water How channels 13a dened by the exterior of the liner 10 and the interior surface of the structure 12 between the ribs 11 receives water from a distributing chamber 13 at their upper ends and ends at a position 14 spaced from the lower end of the mold liner 10.

As hereinafter described, the liner 10 is constructed in two complementary halves longitudinally joined along the major axis of the cross-section shape. In the intermediate length portion of the liner the complementary halves are held together by clamping means forming part of the support structure 12, while in the upper end portion associated with the distributing chamber 13 and below the position 14 the mold liner halves are joined by silver solder.

Referring particularly to Figs. l and 2, the chamber 13 includes a top plate 15 having a central opening 16 therein formed to embrace and to form a fluid tight connection with the upper end portion of the liner 10 and having a circular exterior edge machined with a lip 17 to t an annular plate 18. The

plates

15 and 13 are bolted together by a series of circumferentially spaced stud bolts 20 to form a fluid tight seal therebetween. As shown, the plate 13 is grooved to accommodate the upper end of a cylindrical wall 21 secured in position by a series of bolts 22 extended through lugs 23 on the wall 21 and the outer circumferential portion of the plate 18. The lower end of the cylindrical wall 21 is tted into a groove formed in the upper surface of a lower annular plate 24 which is not only bolted to the cylindrical wall as shown for the connection between the plate 18 and the wall 21, but it is also attached to a member 25 by a circumferentially spaced series of stud bolts 26.

The distributing chamber 13 is provided with four eircumferentially equally spaced water inlet fittings 31 positioned in the lower portion of the cylindrical wall 21.. A cylindrical baille plate 32 is disposed in an upright position radially spaced between the inlet fittings 31 and the converging entrance 27 and projects upwardly from the lower wall of the chamber to a position spaced below the plate 15. A greater or lesser number of water inlet openings may be provided for the chamber 13, depending upon the size of the chamber and the volume of cooling water flow thereto. The corners in the upper portion of the chamber are provided with circumferentially faced

filler pieces

15 and 21 supported on the plate 15 and wall 21, respectively, to streamline the water ow. over the bafe 32 and into the converging entrance 27.

The member 25 is of L-shaped cross-section with one leg of the member forming the lower wall of the chamber 13 and a circular outer edge, while the other leg 28 is upright and cooperates with the external surface of the liner 10 to dene a downwardly converging entrance 27 -to the upper end of the channels 13a. The horizontal spacing between the inner surface of the leg 2S and the exterior surface ofthe liner 10 is substantially uniform throughout its circumferential extent for a well-distribu- 3 ted ow of cooling water to each of the channels 13a. For ease of construction and assembly, the member 25 is constructed in complementary halves divided along the minor axis of the shape and with adjoining portions bolted together through upstanding flanges 30.

The structural members 12 are provided with bars 33 through which a series of stud bolts 34 extend to secure the members 12 to the leg 2S of the member 25 and thus to the distributing chamber 13. While the liner is supported throughout its intermediate length by the structural members 12, the upper portion of the liner 1t? is not in contact with or supported by any structural part of the distributing chamber between the top plate and the upper end of the members 12. A sleeve 35, preferably of cast iron or steel is inserted into the upper end of the molding tube or liner 1d to strengthen the liner and to thereby avoid distortion of the liner as caused by the pressure of cooling water within the chamber 13. As shown in Figs. 1 and 2, the sleeve is formed with an external surface substantially conforming with the internal surface of the liner 10. A flange 36 formed at the upper end of the sleeve provides a shoulder 37 intended to abut the upper end of the liner 1G and an end portion of the plate 15 when the sleeve is inserted in the molding tube. The lower end of the sleeve is chamfered and extends downwardly within the liner for a major length of the unsupported upper portion thereof.

Due to the ditliculty in obtaining a uniform fit between the facing surfaces of the cast sleeve and the mold liner lil,l a series of longitudinally and circumferentially spaced horizontally adjustable spacers or blocks 33 are inserted in recesses formed in the surface of the sleeve 35. The blocks 38 are moved by means of socket-headed screws 39 threaded through the wall of the sleeve. This construction is shown in Fig. 5 where the` gap between the sleeve 35 and the liner 1i) is exaggerated for illustrative purposes.

The structural support means for a molding tube having `a rectangular cross-sectional shape with rounded corners is illustrated in Fig. 3. As shown, the intermediate length of the mold liner is formed of two longitudinally divided complementary halves, with the longitudinal ends of each half provided with integral, outwardly extending flanges 4t) and `41 which are machined and clamped in abutting relationship by transverse end bolts 42 acting through

end blocks

43 and 44, and

side plates

45 and 46. The sideplates are longitudinally grooved to accommodate the outer edge surfaces of the ribs 11, with the lateral relationship between the

plates

45 and 46 with the adjoining halves of the liner 10 maintained by machine bolts 4'7 threaded into correspondingly threaded holes in the ribs 11. Adjacent to the rounded corners of the liner 1G the

plates

45 and 46 and the

blocks

43 and 44 are longitudinally recessed to receive corner pieces 48 which are also secured to the plates 45 and 46- by machine bolts 56' and 51, respectively. The corner pieces 48 are generally of right triangular cross-section with one side machined to a curvature similar to the adjacent exterior surface of the liner and to form a substantially uniform thickness of the water flow passageway. Machine bclts 52 are threaded into the end blocks 43` and 44 to maintain the positional relationship between

plates

45 and 46 and the blocks.

In the construction described the skirt construction strengthens the liner 1G so that the liner does notdeform during normal operation of the casting unit. The beam strength of the `liner segments between adjacent ribs 11 is suiiicient to withstand the pressures exerted thereon, `and the strength and rigidity of the

plates

45 and 46 is sutlcient to resist movement from pressures exerted by cooling water flow through the passages 13a or by the weight of metal within the mold.

The mold cross-section shown in Fig. 4 `illustrates va shape wherein the mold liner 5,5 is formed yfrom metal tubing with the internal surface thereof continuously con ycave and having a curved surface of changing radius. The liner 55 is surrounded by a skirt 56 of similar shape which. is uniformly radially spaced from the liner by a circumferential series of ribs 57 extending longitudinally of the mold liner and integral therewith. The liner and skirt are joined by machine screws 58 threaded into the ribs, so that any forces tending to distort or deflect the liner 55 is not only resisted by the liner but also by the skirt `56. The beam strength of the liner segments between adjaeent ribs 57 is suii'icient to withstand the pres sui-es imposed thereon under the usual operating conditions of continuous casting.

In the embodiments of the invention shown in Figs. 3 and 4, the intermediate portion of the molding tube is bolted to the supporting skirt. Alternately, the spaced relationship between liner and skirt can be attained by means other than a bolted attachment. For example, a dovetail connection can be usedfor this purpose, as shown in Fig. 6. As shown, the molding tube 60 is provided with ribs 61 having diverging walls fitted into correspondingly slotted recesses 62 formed in the skirt member 6,3. With this construction, any movement of the mold liner in a horizontal direction is restrained by the structural support provided by the skirt through the ribs 61.

In the continuous casting of high melting temperature metals, such as steel, molten metal is delivered to the upper end of the molding tube and an embryo casting having a frozen shell and a molten core is withdrawn from the lower end thereof. The metal is cooled within the mold by heat exchange through the walls of the molding tube, with the stream of cooling water `passed at high velocities along the exterior surface of the molding tube. In the embodiment of this invention shown in Figs. 1, 2 and 3, the molten metal level maintained in the mold liner 10 is maintained `at a level below the lower end of the sleeve 35. A frozen shell or skin is almost immediately formed around the molten metal against the interior surface of the cooled molding tube. As the shell or skin thickens with progressive cooling of the metal, the shell acquires sufficient strength to contract thereby losing direct contact with the mold wall. Ordinarily, it is believed the shell laterally expands and contracts during the withdrawal of the embryo casting along the wall of the mold. This is caused by the high heat transfer to the mold wall while the casting is in contact therewith, i. e., the rate of heat transfer from the periphery of the casting to the cooling water is greater than the heat transfer from the core to the periphery of the casting. With shrinkage of the shell from the mold wall and the reduction of heat transfer to the mold wall and the cooling water, the rate of heat transfer from the molten core to the shell becomes the greater thereby reheating the shell until. it expands to contact with the mold wall and the rate of heat transfer to the cooling water again increases to repeat the process of lateral expansion and contraction of the embryo casting within the mold.

During the periods of time the `casting is not in contact with the cooling surface of the mold, the pressure of the cooling water flow on the exterior of the molding tube tends to distort the walls toward the `axis of the mold. The construction described not only provides a structural reinforcement for the tube liner against inward movement of ,the liner walls but `also avoids movement of the liner wall outwardly away from the axis of the mold as may occur by reason of the molten metal pressure within the mold.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form of the invention, and its mode of construction now known to us, those skilled in the art will understand4 that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

We claim:

1. A lluid cooled mold comprising an elongated tube, a plurality of longitudinally extending external ribs substantially equally spaced circumferentially of said elongated tube and continuously extending between spaced positions adjacent the opposite ends of said tube, structural support means longitudinally coextensive with said ribs and surrounding said liner, means for attaching said liner to said structural support means and said ribs to define a plurality of parallel flow passageways of substantially equal cross-section area, and walls connected with said structural support means to deline a cooling liquid distributing chamber enclosing one end portion of said tube and cooperating with the external surface of said elongated tube to define a circumferentially unobstructed converging entrance of substantially uniform Width iopening to said parallel passageways.

2. A fluid cooled mold comprising an upright elongated tube of substantially uniform cross-section, a plurality of external ribs attached to and substantially equally spaced circumferentially of said elongated tube and c-ontinuously extending axially of said tube between spaced positions adjacent the opposite ends or said tube, structural support means coextensive with said ribs and surrounding said liner, means for attaching said ribs to said structural support means to define a plurality of parallel tlow passageways of substantially equal cross-section area extending axially of the exterior surface of said tube, and walls connected with said structural support means to define a cooling liquid distributing chamber enclosing the upper end portion of said tube and cooperating with the external surface of said elongated tube to define a circumferentially unobstructed converging entrance of substantially uniform width opening downwardly to said parallel ow passageways.

3. A fluid cooled mold comprising an upright elongated tube, a plurality of outwardly projecting ribs substantially equally spaced circumferentially of said elongated tube and continuously extending axially of said tube between spaced positions adjacent the opposite ends of said tube, structural support means coextensive with said ribs and surrounding said liner, means for attaching said liner to said structural support means and said ribs to define a plurality of parallel flow passageways of substantially equal cross-section area, walls connected with said structural support means to define a cooling liquid distributing chamber enclosing the upper end portion of said tube and cooperating with the external surface of said elongated tube to define a circumferentially unobstructed converging entrance or" substantially uniform width opening downwardly to said parallel passageways, and an internal sleeve of substantially uniform crosssection projecting downwardly from the upper end of said elongated tube to a position spaced above said structural support means to strengthen said tube in the vicinity of said distributing chamber.

References Cited in the le of this patent UNITED STATES PATENTS 550,089 Armand et al Nov. 19, 1895 894,410 Trotz July 28, 1908 1,895,135 Rohn Jan. 24, 1933 1,936,280 Williams Nov. 21, 1933 2,079,644 Williams May 11, 1937 2,187,720 Williams Jan. 23, 1940 2,424,640 Spooner July 29, 1947 2,479,191 Williams et al Aug. 16, 1949 2,590,311 Harter et al Mar. 25, 1952 FOREIGN PATENTS 906,415 France May 14, 1945