US2769218A - Continuous casting mold - Google Patents

Description

Nov. 6, 1956 l. HARTER ETAL 2,769,218

CONTINUOUS CASTING MOLD Filed Oct. 25, 1951 2 Sheets-Sheet l INVENTORS ATTORNEY Nov. 6, 1956 l. HARTER El'AL CONTINUOUS CASTING MOLD 2 Sheets-Sheet 2' Fileii Oct. 25, 1951 JsacJ/arer whirl INVENTOR ATTORNEY United States Patent 2,769,218 CONTINUOUS CASTING MOLD Isaac Harter, Isaac Harter, Jr., and Temple W. Ratclifife, Beaver, Pa., and Frank W. Armstrong, Jr., Barberton, Ohio, assignors, by mesne assignments, to The Babcock & Wilcox Company, Jersey City, N. J., a corporation of New Jersey Application October 25, 195:1, Serial No. 253,114

Claims. (Cl. 22-57.2)

The present invention relates to the construction of a mold for the continuous casting of metal.

In the continuous casting of metals, molten metal is delivered to the open upper end of a fluid cooled mold, the metal is cooled to form an embryo casting in the mold, with the casting withdrawn from the lower end of the mold. The solidification of the metal is accomplished within the mold by heat exchange with a cooling fluid, with the heat passing through the mold wall to a cooling fluid stream passing in contact with the exterior surface of the mold wall.

As disclosed and claimed in a co-pending application, Serial No. 10,956, the mold is constructed for high rates of heat exchange to the cooling fluid so as to attain commercial rates of casting production. This is accomplished by turbulent, high velocity water flow in contact with the mold surface, and the use of a sufficient volume of water to avoid a rise in the temperature of the cooling water above about or F.

Thin walled molds constructed of heat conductive materials are desirable for high rates of heat transfer between the metal being cast and the cooling water. However, adequate cooling water flow has a tendency to distort mold walls unless the mold has suflicient structural strength to withstand the pressure involved. Molds of circular cross section are inherently of high structural strength, but as pointed out in a co-pending application Serial No. 155,098, now abandoned, the castings produced in molds of circular cross-section are metallurgically unsound unless the casting rate is uneconomicallylow. The quality of casting produced can be improved by the use of molds having special cross-sectional shapes, such as disclosed in the said co-pending application. However, such special mold cross-section shapes are inherently low in structural strength and are subject to distortion under high pressure and turbulent cooling water flow velocities, particularly when such shapes have a cross-sectional area in excess of to square inches with a width to length ratio less than .50.

Attempts have heretofore been made to strengthen thin walled molds by the use of external ribs and by bolting the mold to exterior supports. These expedients have not been successful, due to obstructions in the cooling water flow path and the creation of inadequate cooling conditions at positions in the mold surface which have caused mold failures and poor castings. Such cons'tructions are expensive to construct and ditficult to assemble.

In accordance with the present invention an open ended molding tube of the desired cross-sectional shape is provided with a plurality of tubular water flow guides or channels which are secured to the exterior surface of the molding tube. The axes of the tubular guides are parallel to the longitudinal axis of the mold and each-is connected to a common source of cooling water supply for low pressure losses, good Water distribution circumferentially of the mold and effective mold cooling. The construction described is relatively simple and inexpen- "ice sive to construct, and strengthens a normally weak structural shape so that the cross-sectional area of the mold can be increased far beyond limits heretofore believed practical, and avoid serious distortion or deformation of the casting mold.

The various features of novelty which characterize our invention are pointed out with particularity in 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:

Fig. l is an elevation, in section, of a continuous casting mold constructed in accordance with the invention;

Fig. 2 is a plan, in section, ofthe mold shown in Fig. 1, taken on the line 22 of Fig. 1; and

Fig. 3 is a plan of a portion of the mold illustrating the mode of construction.

In the illustrated embodiment of the invention the continuouscasting mold assembly 10 includes an elongated sectional mold liner 11 of elongated cross-section, with a plurality of cooling water flow channelsor guide tubes 12 arranged in abutting relationship circumferentially of the exterior surface of the liner and having their axesparallel to the axis of the liner. While the cooling water flow passageways through the tubular guides are shown as. rectangular in cross-section, the cross-sectional shape may be round or square, or of any other desired shape. Itwill also be understood thetubular guides could be positioned along the interior surface of the mold liner 11. to thereby definetthesurface in'contact with the metal being cast.

As shown in Figs. 1 and 2, the sectional mold assembly 10 is formed from brass plate in complementary halves which are longitudinally bolted together to' define a continuous tube of elongated cross-section shape. Each of the water. flow guide tubes 12 is of rectangular section and is secured in contact with the mold from a lower position 13 upwardly spaced from the lower end 14 of the mold liner 11. At the upper end 15 of the mold liner, the tubes 12 are. bent away from the mold through an angle. of approximately Thereafter, the tubes are bent downwardly in: a pair of horizontally spaced rows 16 and 17, with alternate tubes forming each row. Each of the tubes in both rows are provided with a transition member 18 which-tapers from a circular inlet end portion. 20 to its discharge'end: portion 21 merging with and attached to the end of a tube 12. The transition element 18 isof suflicient length to provide tapering side walls having a slope approximating the slope of a ven turi approach. The dimension of -the end" portion 20 2Twhich is radially spacedfrom andencircles the mold liner 11'. The ends of'the nipples 23' insertedthrough manifold openings 26 areupset or belled on the inner side of the manifold to. formatight' fit therein. A plurality of. horizontally disposedwater inlet' ducts 2 8 are connected with the manifolds 27 for the admission of water at superatmospheric pressure and proper volume for substantially equal distribution of water to each of the water flow. guide tubes 12.

Oneof theilong sides of each of the guide tubes 12 isremoved'between-its lower endposition 13'andposition 30 downwardlyspaced from'the upper endiof the The open sided. portion: of the tube: faces the. exterior surfaceiofthegmold liner'll, and the.

mold liner 11.

- tubes 12. are. positioned with thefacing edge of the short sides 31 of the tubes abutting the liner wall in heat transfer relation therewith. The upper end portion of the mold liner 11 is machined to a depth equal to the removed thickness of the tube wall, so that when the guide tubes 12 are positioned against the liner, the water flow path is uninterrupted in its passage toward the outlet end of the tubes.

With the construction described the axes of the tubes 12 are parallel with the longitudinal axis of the mold liner 11, and the short side 31 of each tube abuts the short side of an adjacent tube at the surface of the liner 11. Thus a circumferential series of U-shaped water flow channels are formed along the exterior side of the mold liner. Any gap between the exterior portions of the short sides 31 of adjacent guide tubes 12 is filled with solder or the like to utilize the full compressive strength of the exterior walls of the guide tubes. The silver solder connection between the short sides 31 of the tubes and the mold liner is heat conductive, whereby the solid to liquid contact area of the multiple water flow channels is greater than the total exterior area of the mold liner wall.

In the illustrated embodiment of the invention both the mold liner 11 and the tubes 12 are of brass. Other materials can be used, such as copper or other relatively high heat transfer materials, and the mold and tubes need not necessarily be made of the same materials. However, we have found that brass is a particularly desirable material for the mold liner, since brass is essentially non-wetting under the fiuid cooling conditions of continuously casting ferrous alloys, and the material has a satisfactory structural strength and heat transfer coefiicient.

As shown in Figs. 1 and 2, the mold liner and guide tube assembly is enclosed by a sheet metal casing 35 which is spaced from the tubes 12 and is of rectangular cross-section shape. The casing is suitably reinforced at the top and bottom, and at the corners, by angle iron braces 36. A series of stud bolts 37 connect the casing 35 with the outer walls of the tubes 12. This is accomplished by silver soldering a series of metal blocks 38 to the exterior side of the tubes 12 and providing a series of threaded recesses 40 therein in alignment with bolt holes cut in the casing 35.

The casing 35 extends downwardly from the elevation of the upper end of the mold liner 11 to an intermediate position above the ends 13 of the water guide tubes 12. The space between the exterior surfaces of the tubes 12 and the casing 35 is filled with an initially plastic material 41, such as concrete, to assist in maintaining the mold assembly rigid and in proper relationship. An initially plastic refractory material 42 is installed above the mold and easing assembly to protect the upper and outward bend of the tubes 12 in their connection with the manifold 27. The material is formed with a converging inner surface 43 merging with the interior surface of the upper end of the mold liner 12 to provide an unobstructed opening into the mold for the entering molten metal stream. The connection between the casing 35 and the tubes 12, by means of the stud bolts 37, assists in strengthening the mold against inward distortion of the mold liner, while the filler concrete tends to prevent outward distortion of the mold liner.

In the manufacture and assembly of the mold 10 we prefer a segmental type of construction, as hereinafter described, since this construction is stronger and simpler to fabricate. However, it is possible to construct the mold 10 with a one-piece mold liner 11 which has been molded to the desired cross-section shape and thereafter to attach the cooling water flow guide tubes 12.

In the segmental construction and assembly of the mold, two plates 11a and 11b of the proper length and thickness are cut with a width greater than the developed dimension of one half the perimeter of the mold liner 11.- One end portion of each plate is machined to provide the recess 44. The tubes 12 are straightened and cut to the desired length, filled with a metal alloy material having a melting temperature less than that of the tube material, and machined to remove a measured length of one side of the tubular cross-section between the position 3% and 13. The machined length of the cut corresponds with the dimension between the lower shoulder of the recess 44 and the lower end position 13 of the guide tube passageway. A metal bar 45 is cut, to be installed the full length of the plate 11a, with a thickness equal to the thickness of a machined tube 12, and having a suitable width, greater than the width of a tube 12. Metal blocks 46 are also provided for mounting on the exterior of the tubes 12 at the side edges of the finished mold liner section 11a.

All of the metallic surfaces are sanded and cleaned where such surfaces are to be joined by silver solder. Thin sheets of silver solder, of the order of several thousandths of an inch in thickness, are interposed between the surfaces to be connected. The parts are clamped and bolted in the desired relationship, with the assembly mounted in a flask and heated to the desired temperature, in a protective atmosphere, to mature the silver solder.

After joining the parts, the tubes 12 are again filled with low temperature alloy metal and the tube and mold liner section is bent to the desired mold cross-section. Thereafter the side edges are machined to the dot-dash lines X and Y, and the necessary bolt holes drilled and tapped in the blocks 46 so that the two mold liner sections 11a and 1117 may be joined by bolts 47, as shown in Fig. 2. The inlet end portions of the tubes 12 are bent to the shape shown in Fig. l, to join the transition members 18. a

In the construction described, the mold assembly 10 is provided with a mold liner 11 of a thickness suitable for maximum structural strength consistent with good heat transfer. The channel type cooling water guide tubes 12 do not add metal thickness to the heat flow path through a major portion of the mold circumference, and provide stifiening flanges at spaced positions around the periphery of the mold. With silver solder used in the assembly of the parts, the heat flow path through the short side portions 31 of the tubes 12 provides means for additional heat flow to the short sides of the cooling water stream, so that in efiect the area of heat exchange to'the cooling water is greater than the total area of the mold wall outer surface. In selecting the size and thickness of the cooling water guide tubes 12 it is desirable to maintain the wall thickness of the short side 31 of the tubes not over one half the thickness of the mold liner 11.

Each guide tube 12 receives an equal portion of cooling water flow with a minimum flow resistance by reason of the transition member construction and the spaced connections with the manifold 27. Thus, the mold of the present assembly provides an eflicient cooling mechanism for a continuous casting mold, while providing a rigid construction capable of withstanding cooling water pressures without distortion. When assembled and constructed as described, the unit cost is low and maintenance costs are practically eliminated.

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 understand 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 mold assembly comprising an upright open ended 'rnold liner of substantially uniform cross-sectional shape and area throughout its extent, an inlet manifold for cooling fluid spaced from and encircling said mold liner, a plurality of abutting cooling fluid guide tubes extending throughout the upper portion of the external surface of said mold liner in heat exchange contact therewith to an open discharge position spaced from the lower end of said mold, and an upward extension of each of said tubes above said mold liner and connected with said inlet manifold.

2. A mold assembly comprising a vertically elongated open ended mold liner, said liner consisting of complementary sections longitudinally secured to define a liner tube, a cooling water distributing manifold horizontally spaced from and encircling said liner, a plurality of cooling water guide tubes extending vertically in side by side relationship throughout the upper portion of the exterior surface of said mold liner in heat exchange contact there with substantially throughout the length of said mold liner, and an upward extension of each of said tubes above said mold liner and connected with said inlet manifold.

3. A mold assembly comprising an open ended vertically elongated mold liner, a plurality of U-shaped cooling fluid flow channel means extending vertically in side by side abutting relationship along a major portion of the external surface of said mold liner, each of said flow channel means being of substantially equal cross-section and merging into a tube of rectangular section adjacent the upper portion of said mold liner with each of said tubes extending throughout the upper portion of and curving away from the upper end of said mold liner, a

cooling fluid manifold spaced from and encircling said mold liner and flow channel means, spaced rows of fittings of circular cross-section opening to said manifold, and transition section members connecting each of said circular fittings with one of said rectangular section guide tubes for substantially equally distributed flow of cooling fluid from said manifold through said fluid flow channel means.

4. A mold assembly comprising an open ended vertioally elongated mold liner, a separate cooling water manifold horizontally spaced from and encircling said liner, a row of cooling water flow guide tubes extending throughout the upper portion of the external surface of and in heat exchange relationship with said mold liner, means including an upward extension of said tubes above said mold liner and connecting the tubes with said manifold, each of said guide tubes being of rectangular cross-section and having an open side adjoining the exterior surface of the mold liner from a position downwardly spaced from the upper end of said mold liner to an open discharge upwardly spaced from the lower end of said mold liner, the upper end portion of said mold liner being of reduced thickness throughout its periphery substantially equal to the wall thickness of said guide tube.

5. A mold assembly comprising a vertically elongated mold liner, means defining a plurality of separate cooling fluid flow passageways of substantially equal cross-section externally in direct heat flow contact with said mold liner, a casing of metal plates spaced from and enclosing the upper portion of said mold and passageways, a cooling fluid manifold spaced from and encircling said casing, individual tubes extending throughout the upper portion of said mold and forming an upward extension of each .of said passageways defining means connected with said manifold, a plurality of tension resistant stub bolts for maintaining the positional relationship of said mold liner passageways and casings, and compression resistant filler means between said fluid flow defining means and said casing.

References Cited in the file of this patent UNITED STATES PATENTS 648,091 Trotz Apr. 24, 1900 653,133 Carpenter July 3, 1900 1,554,942 Angell et al Sept. 22, 1925 1,645,725 Vaughan Oct. 18, 1927 1,933,530 Meyers et a1 Oct. 31, 1933 1,988,425 Summey Jan. 15, 1935 2,054,635 Peirce Sept. 15, 1936 2,154,234 Eppensteiner Apr. 11, 1939 2,246,908 Webster June 24, 1941 2,295,041 Junghans Sept. 8, 1942 2,331,679 Hawkinson Oct. 12, 1943 2,428,657 Falk et a1 Oct. 7, 1947 2,479,191 Williams et al Aug. 16, 1949 2,518,055 Olsen et al Aug. 8, 1950 2,590,311 Harter et a1 Mar. 25, 1952 2,623,253 Harrison Dec. 30, 1952 2,631,343 Hunter Mar. 17, 1953 FOREIGN PATENTS 906,415 France May 14, 1945

Images