US2811759A

US2811759A - Copper cake mold

Info

Publication number: US2811759A
Application number: US534453A
Authority: US
Inventors: Calvin D Pearce
Original assignee: Int Smelting & Refining Co
Current assignee: International Smelting and Refining Co
Priority date: 1955-09-15
Filing date: 1955-09-15
Publication date: 1957-11-05
Anticipated expiration: 1974-11-05

Description

Nov. 5, 1957 c. D. PEARCE 2,311,759

COPPER CAKE MOLD Filed Sept. 15, 1955 FIG. 2

L. :5 FIG. I

I: Ii ii is INVENTOR. CALVIN 0. PEARCE T fM,W,mMf ?6 ATTO NEYS Unit This invention relates to molds for. use in the casting of copper, more especially large copper cakes.

It is the object of the invention to prolong, the useful 7 life of metal casting molds by minimizing cracking. of the molds: Briefly, this is accomplished; according to'the invention, by avoiding sharp angles in the mold walls, and by distributing"the'coolingd'ncts. so that the heating and cooling withrconsequent expansion. and contraction, is substantially uniform" in all directions, particularly in the vicinity of. the corners.

' [The mold in which copper cakes are cast. is preferably arranged in an upright position so that the longest dimension of the mold cavity is its'height (which. corresponds to the length of the copper cake cast therein). The upper end of the mold is open and serves as. an entrancev for the molten" copper. The practice of casting copper in molds so positioned and constructed, known as end-pouring, is preferred because it minimizes the. area of the. copper-air interface, and thereby concentrates surface imperfections and irregularities ata place one end of the rolled sheet) where they will be the least objectionable.

, Copper cake molds should be constructed so that the copper cakes cast therein can. be conveniently removed from the mold cavity. Such molds have been. constructed with thejmold cavity tapered in the direction. of its. height so that when the mold is turned over the cake cast. therein will fallout. However; the resulting taper ofthecake has been found highly undesirable. In order to avoid tapering of the mold" cavity; copper cake. molds have. been constructed with cooling water ducts distributed uniformly throughout the height and around the entire mold cavity.

construction permits rapid removal of heat and control of the rate of heat-transfer so that shrinkage of the copper cake can be. controlled in. order 'to permit easy removal of the copper cake from the mold. The bottom of the mold cavity is formed by a baseplate or door hinged to one of the sides of the mold. After casting a copper cake, the door is swung back and the cake falls out the bottom of the mold. v

Preferably, the sidewalls ofa water-cooled copper cake mold are formed by a monolithic block of'copper. A mold havingsid'es otherwise constructed as, for example, by welding together a plurality of pieces, is inferior because its susceptibility to failure at the joints due to the repeated heating. and cooling to which the mold is subjected during use. It is desirable that the mold be constructed of copper because of its high heat conductivity. When the side walls are formed by a monolithic block, the cavity maybe formed by forging, orthe mold may be cast around a core to form the cavity.

'Copper cakes. are rolled into sheet copper, and the production techniques used in the fabrication of products made from sheet copper have given rise to a demand for larger copper sheets, and therefore larger copper cakes from which sheet copper .is rolled. This demand. can most ecomomically be satisfied by supplying rolling mills with copper cakes of considerable length and width but which are not. unduly thick, for thereby the amount of 2 work which must be expended in rolling the cakeinto sheet: copper is decreased.

The production of larger copper cakes which are not unduly" thick requires larger copper cakemolds and, in particular, molds having cavities of greater height and length so: as to permit the casting of copper cakes of greater length and width, respectively, but relatively thin. Molds of the typeherein described, having cavities of, say, 5 to 6 /2 feet in height, 15 to 25 inches in length and 5 inches in width; have been used to cast copper cakes of the corresponding length, width and thickness, but they have not been economical because their economic success depends upon the mold life, i. e-., the number of castings. which can bemade beforethemoldmust be rejected. The life of the mold is determined chiefly by cracking, usually at or nea-r'cavity corners, and the extension of these cracks into the mold metal during heating and cooling. I I

It has previously been understood that inside corners are undesirable because they provide pockets where. mold dressing may accumulate to such an extent that it will not be evaporated to'dryness before the actual casting is commenced. lf evaporation occurs during casting the copper cake will become porous due to steam thus introduced into the molten copper; The small fillets, of inch radius or less, heretofore employed have been used to avoidthese corner pockets, but they have. had no appreciable elfect on the cracking.

Porosity by the evolution of steam also occurs when a crack extends through the mold metal to a cooling-water duct, usually the duct nearest the cavity corner at which the crack originates. Cracks are alsoundesirable because they give rise to a hazardous operation condition. 7 Thus, if a considerable quantity of water contained in the mold dressing is entrapped by molten copper, or if acrackextends into a cooling-Water duct While molten copper is being poured into the mold, an explosion may occur; Such cracks are otherwise undesirable because the molten copper finds it way into the cracks and solidifies there, making difiicul t the removal of the copper cake from the mold and producing ragged edges on the cast cake. Prior to thisir-rvention no means for substantially inhibiting the tendency towards corner-cracking in water-cooled molds has been known.

The present invention provides a large water-cooled copper cake mol'dof such construction that the tendency to cracking at or near the corners of the mold cavity in consequence of repeated heating and cooling of the mold is greatly inhibited. In fact, the new molds have a useful life of approximately three times the life of the best prior molds.

The mold of'this invention preferably comprises a monolithic block of tough pitch copper forming the side walls which, in turn, define a substantially rectangular mold cavity having inside plane surfaces. Other metals alloyed with the copper, or without copper, may be used. The block, if cast, may be cored undersize and thereafter machinedout to the required dimensions, including the fillets: later referred to. Ducts for the circulation of cooling water are provided at least in the long side walls of the mold. The mold of the invention is characterized in that the inside plane surface at the boundary of the mold cavity of each of the side walls is joined with the; corresponding inside plane surface of eachadjacent wallby a fillet of substantially greater radius than heretofore used, and in that the cooli-ng water ducts in each of the side Walls are disposed so as to avoid the excessive cooling at the corners of the mold heretofore experienced.

Although tbe fact of the improvement has been well established, the reason for the improved performance of molds constructedaccording to the invention is not def; initel-y known. However, it appears that the susceptibility of a mold to the development of corner cracks as a consequence of repeated heating and cooling is dependent in part on the relationship of the magnitude of the mold cavity length to the magnitude of its width. Where the ratio of length to width is substantially greater than unity, the rate of expansion and contraction varies considerably along the intersecting lines in the mold cross-section which bound the mold cavity or are parallel thereto. Such differing rates of expansion and contraction cause substantial stresses which may result in cracking of the mold at or near the cavity corners. This theory may be the explanation as to why considerable difficulty has heretofore been encountered in developing a mold not susceptible to corner cracking and which is adapted to casting large copper cakes which are not unduly thick, i. e., copper cakes having a thickness less than approximately one-third their width.

The invention will be better understood by consideration of the following description of a preferred embodiment as shown in the accompanying drawing, in which:

Fig. 1 is an elevation view of a mold according to the invention; and I Fig. 2 is an enlarged cross-section, taken along line 2-2 of Fig. 1.

Referring to Fig. 1 and Fig. 2, a mold 5 comprises a monolithic copper block 6 having a rectangular cavity 7 therein. The copper block 6 is about 6 feet in height, about 3 /2 feet long and about 2 feet wide, and forms the long side walls 8 and the short side walls (or ends) 9 of the mold. The inside plane surfaces 12 and 13 of the

mold walls

8 and 9, respectively, bound the mold cavity which is about 25 inches wide and 5 inches thick. The width of the cavity in all cases should be less than approximately one-third its length. The copper block comprising the mold may be cast so that the cavity is contained therein initially, or the cavity may be forged out of a solid casting. The cavity 7 extends all the way through the copper block 6. A base-plate door 15 of phosphorized copper is attached by hinges 16 to one of the short side walls 9. When closed, the door 15 serves as a bottom for the mold cavity. During casting, the door 15 is ,held closed by a bail 17, which spans the outside width of the mold and is pivoted at its ends 18 to the long side walls 8. The upper end of the cavity 7 serves as an entrance for the molten copper which may be poured in from a ladle 11.

The radius of the fillets 14 joining the intersecting plane surfaces which bound the mold cavity is preferably equal to the largest copper cake corner radius acceptable to copper cake purchasers. Accordingly, in the case of a mold cavity having a width of about 5 inches and a length of between three and six times as much, the fillet radius for each of the mold cavity corners should exceed inch. A radius of approximately one inch is satisfactory and is about as large as sheet-rolling mills will accept.

The long side walls 8 of the mold have

channels

19, 19a formed therein for the circulation of cooling water therethrough. The

channels

19, 19a are 1 inch diameter vertical holes and are disposed wholly between the lateral projections y-y of the inside plane surfaces 13 of the short side walls 9. The terminal channels 19a, which are nearest such lateral projections, should be spaced an appreciable distance therefrom. Thus, the shortest distance between such projections and channels 19a is about one inch, in the mentioned embodiment. In laying out the vertical channels, the terminal holes are drilled first, 1 inch or more from the projections y, y and then the required number of intermediate holes are distributed evenly within the space remaining. The number of vertical channels required depends on the heat to be dissipated, 10 to 16 being a suitable number for molds having dimensions of the order herein described.

When the ratio of thickness to width of the mold cavity is small, as in the mentioned example, no end cooling channels are usually required. This aspect of the invention is contrary to prior practice in which cooling ducts were uniformly spaced all around the cavity, including the ends and the quadrant areas a between the wall projections x, y and x, y. I have discovered that such distribution of ducts results in greater cooling of the end walls than of the side walls, thus causing uneven expansion and contraction, which is the primary cause of cracking of the mold. Hence, in all cases I omit cooling channels from the four quadrant areas a; and if the width of the mold (x-x') is such as to require end-cooling, the end channels 1% then provided should be spaced from the wall projections x, x at least as far as are the terminal channels 19a from projections y, y. In a mold for a 3000 lb. slab this was 1% inches. The optimum spacing between the inside face of the mold cavity and the vertical channels is not especially critical, and in the case of high conductivity metal such as copper it may be, say, 2 inches.

Cooling water is directed into

channels

19, 19a by the cold Water pipes 20, inlet manifolds 21 and horizontal passages 22, and is discharged from the tops of

channels

19, 19a into the hot water discharge pipe 24 through horizontal passages 23 and discharge manifolds 25.

Channels

19, 19a are made by drilling vertical holes through the copper block 6 and sealing the ends of these holes with plugs 26.

Horizontal passages

22 and 23 are then drilled into the side of the copper block to provide inlets and outlets, respectively, to the

channels

19, 19a. If channels 19b are used, similar passages (not shown) must be provided for them, and the manifolds can be extended across the short walls.

In using the mold of the invention, molten copper is poured from the ladle 11 into the mold cavity through the open upper end of the mold. Cooling water at the rate of about 250 G. P. M. enters the inlet manifold 21 at about F. and is equally distributed among

channels

19, 19a. The cooling water leaves the mold through the discharge manifolds 25 at about F.

After a copper cake has been cast, it may be removed with the aid of a slab dumper or elevator such as is described in copending U. S. patent application, Serial No. 265,126, new Patent No. 2,733,490, issued February 7, 1956, of Charles E. Yates and Calvin D. Pearce. To do so, the bail 17 is moved to an intermediate position so that the door 15 partially opens, whereupon the platform of the elevator such as described in the mentioned patent application, is slid under the bottom of the cake, between the cake and the partially open door. The bail 17 is then swung back beyond the hinge 16 permitting the door 15 to open fully. The cake is then moved away on the elevator. Movement of the bail and door can be controlled readily by hydraulic mechanisms well known in the art.

I claim:

A generally rectangular water-cooled mold suitable for casting large copper cakes comprising a monolithic metal block including, in horizontal cross-section, two long and two short vertical side walls which have inside plane surfaces bounding a generally rectangular mold cavity, the width of said cavity being less than one-third of its length, the thickness of said side walls being substantially the same entirely around the cavity, a displaceable bottom for said mold, a plurality of parallel cooling water channels extending vertically in both long side walls and symmetrically aligned in rows parallel to the two long opposite inside plane surfaces, inlet and outlet passageways formed in said long side walls for delivering cooling water to and withdrawing cooling water from said channels, said channels and said inlet and outlet passages being disposed entirely between the projections of the inside surfaces of the short walls, and the four quadrants defined by the projections of the inside surfaces of the two long walls and the two short walls being entirely free of any cooling channels.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Bossinger Aug. 12, 1913 Gathmann Ian. 2, 1923 Black Sept. 29, 1925 Krause July 5, 1927 Eppensteiner Dec. 23, 1930 6 Eppensteiner Ian. 17, 1933 Hazelett Oct. 27, 1936 Lindner June 29, 1934 Lindner Jan. 25, 1938 Gardner Mar. 23, 1954 Zeigler May 17, 1955