US3157921A - Cooling molds for casting metal - Google Patents

Description

Nov. 24, 1964 c. B. PORTER COOLING Moms FOR CASTING METAL Filed May 23, 1963 2 Sheets-Sheet 1 .a l0, mm w l Il* l m Dm VO N lili M um WP. Wm LII l|..| lill l0.. W M nh 0 C U M (.Jn M M l\ O I i- 7 0, 7 -..4: M Illl ----\l\- f @kw.: 4 J 1TL i1! 1- |....I..

Nov. 24, 1964 c. B. PORTER 3,157,921

FiledMay 23, 1963 2 Sheets-Sheet 2 l 4. :jf-

/ //,.1\\\\\\\ yy/M United States Patent O 3,157,921 CGING MLDS FR CASTDIG METAL Carroll B. Porter, Metuchen, Nal., assigner to American Smelting and Reining Company, New York, NE., a corporation ol New .lersey Filed May 23, 1963, Ser.. No. 282,734 Claims. (Cl. 22-57.2)

The invention relates to molds for casting metal, and more particularly to an improved tube construction for cooling the mold.

The invention constitutes an improvement over the tube arrangement disclosed and claimed in' Patent 2,946,160 granted in the name of Richard Baier, lohn Stuart Smart, lr., and Albert l. Phillips, znthough not limited to the particular mold shown in the patent.

The Baier et al. patent discloses a calie mold for continuous casting. The mold comprises a graphite blocl; having a series of oversize ribbed cooling tubes fitted in drilled passages arranged around the oblong mold pocket. ln general, this mold has performed most satisfactorily, but after prolonged use under high operating temperatures, the heat transferring ability or" the cooling tubes becomes impaired. rlhe copper tubes become oxidized, particularly on the hot sides facing the mold cavity. The tubes also lose some of their natural temper; they relax their tight solid-to-solid film-free ht with the graphite block. rl`hese changes cause loss of heat conductivity across the interfa from graphite block to co-oling tube. This condition is aggravated by any misuse of the mold such as preheating the mold without turning on the cooling water prior to starting up .a casting operation.

Objects of the present invention are to overcome the above difficulties and to provide a generally superior tube construction, one that will maintain tight, solid-to-solid, film-free t between the tubes and the graphite block for long periods of time, and one in which the Contact pressure between tubes and block may be manually adjusted from time to time.

According to a preferred form of the invention, the holes around the mold pocket of the graphite block are provided with offset grooves. Disposed in the holes are silver tubes and disposed in the grooves are backer strips. The block has a series of transverse holes along the length of the tubes behind the hacker strips, in which are disposed screw-threaded adjustable studs. Helical springs are disposed between the studs and the blacker strips so that pressure may be placed against the cold sides of the tubes to press their hot sides against the sides of the holes adjacent the mold pocket.

Other objects and features of the invention will be more apparent from the following descrip-tion when considered with the accompanying drawings in which:

FIG. 1 is a fragmentary plan view of the end of a cake mold to which the invention lis applied;

HG. 2 is a fragmentary elevation of the mold of FiG. l, with supporting structure for the graphite block omitted;

FIG. 3 is a vertical section, taken on the line 3-3 of FIG. l, illustrating the new tube assembly in position in the mold;

FIG. 4 is a transverse section through the tube assembly and adjacentportions of the mold, taken on the line 4-4 of FIG. 2;

FGS. 5 ,and 6 are sections, corresponding to FIG. 4, but showing other positions the outer tube may assume relative to its hole under different operating conditions, and with tubes of different original sizes.

In the following description and in the claims, various details will be identified by specific names, for convenience, but they are intended to be as generic in their application as the art will permit.

3,l57,92l Patented Nov. 24, 19,64

rrlce Like reference characters denote like parts in the several igures of the drawings.

ln the accompanying drawings and description forming part of this specilication, certain specic disclosure of the invention is made for purposes oi explanation, but it will be undertsood that the details may be modied :in various respects without departure from the broad aspect of the invention.

Referring now to the drawings, and more panticularly to FIGS. l-4, the mold comprises two half-sections of massive graphite blocks 51, 51, clamped together and supported in a box-like metal structure having side plates 52 and bottom support 61B. The abutting surfaces 61 of the two blocks are machined to form a tight seal to prevent escape yof molten metal from the mold pocket 97.

The interior mold surface 96 forming the walls of the mold pocket 97 are machined to provide generally llat planar vertical surfaces. Arranged around the mold poele et are tube assemblies comprising outer tubes containing inner tubes 80. The outer tubes are closed by copper caps S3 silver-soldered thereto, and the entire mold is covered by top plates 4 (omitted in FIGS. 1 and 2).

Except for the construction and mounting of the cooling tubes, the mold of the present invention may be construoted and used in the same way as the mold described and claimed in the Baier et al. patent. Molten metal is poured intothe top of the mold pocket against the pocket walls 96, and the congealed oblong cake is removed from the bottom of thev mold. As in the patent, cooling water is supplied to the bottoms of the inner tubes 3@ in which it tlows upwardly and thence downwardly between the inner tubes and outer tubes 85, as indicated by the arrows shown in FIG. 3. The water then falls into collecting tank (not shown).

The graphite block 51 has a series of drilled :and roamed holes lll. Otfset from the holes ttl on the cold side remote from the pocket wall 96 tare oitset rectangular grooves 11 extending the length of the holes 1b.

Disposed in the holes l@ are a series of circular outer tubes 5 which preferably fit rather snugly in the holes when cold. However, the tightness of lit when cold is not too important for reasons discussed below. The inner tubes 8d are oval shaped and have a pair of top spacers 12 and a pair of bottom spacers 13 welded thereto. lt is suficient that the inner tubes 8th and spacers 12, 13 lit loosely in the outer tubes 85.

Disposed in the offset grooves 11 are backer strips 14 extending the length of the tubes 85 and resting on ledge 60 forming part of the box-like structure supporting the mold. Backer strips 14 have curved saddles 1S closely tilting the outer tubes S5. The hacker strips 14 t loosely in their grooves 11, so as to be freely movable under the urging of the backing springs 16. In this way the outer tubes 85 are elastically held in close contact with the hot sides ofthe bored holes 10 adjacent the mold pocket 96.

For maintaining pressure on the backer strips 14, a series of helical springs 16 and adjustable studs 17 are provided. In the form shown each tub-e 85 has four adjusting studs 17 and four springs 16. Each spring assembly uses a hole drilled through the graphite block 51, and also through plate 52 where necessary. Each hole comprises an inner bore 13 oi reduced diameter housing spring 16, and an outer threaded bore 19 of larger diameter receiving threaded stud 17. Stud 17 has a socket for an Allen-head wrench and a reduced pin 20 fitting inside the spring 16. The pressure of outer tubes 85 against the hot side of the tube holes lil is adjusted by turning the threaded studs 17.

The outer tubes 85 are preferably silver. They may be commercial silver 99.9% line, or sterling silver 92.5% silver, balance copper.' The studs 17, springs 15, and

3 backer strips 14 may be stainless steel. The inner tubes S and spacers 12, 13 may be copper.

In general, the above parts may be made of any metals having the necessary mechanical characteristics, and which will not harmfully corrode under operating conditions. Silver is preferred for the outer tubes because of its ability to resist harmful corrosion at the hot face where heat conductivity across the interface between tube and graphite is most important.

The size of the several parts is not especially critical so long as they perform their functions of providing elastic pressure and excellent heat transfer at the hot sides of the outer tubes. In a mold for casting a copper cake having a nominal cross section of about 41/2 or 5 inches by 25 inches, such as shown in the above Baier et al. patent, the outer tubes S5 may be about 20 inches long. The circular outer tube 85 may have an outside diameter of 1.000 inch and an inside diameter of 0.960 inch, providing a wall thickness of 0.020 inch.

The inner tubes Sti and spacing strips 12, 13 are sutilciently loose inside the outer tubes 85 that they play no part in enabling the outer tubes 85 to resist deforming pressure due to springs 16 or due to expansion of the outer tubes.

The outer tubes 85 have excellent elasticity, that is, ability to return to original shape when distorted and after the distorting pressure is removed The elasticity is maintained throughout the range of distorting strain or movement to which the tube is subjected. Expansion due to operating temperatures does not subject the tube to stresses above its elastic limit. This temper is maintained for prolonged periods of time and in spite of overheating.

Referring now to FIGS. 4-6, the tit of the outer tube 85 in the hole of the graphite block when cold and under operating conditions may be somewhat as illustrated in these figures, depending upon the original tit of the tube in the hole. These figures are based partly on theoretical considerations, and hence this explanation should not be interpreted in any limiting sense. Regardless of theory, the tube has performed most satisfactorily in actual practice. These figures serve to illustrate the ability of the outer tubes to maintain excellent heat transfer contact with the hole wall under operating conditions, regardless of original size of tube.

For example, if the outer tube fits snugly in its hole, or is only slightly undersize when cold, it may take a position somewhat as illustrated in FIG. 4 when cold, and when subjected to pressure of springs 16. As shown in FIG. 4, the cold side of the tube is spaced slightly from the cold side of the hole. As the tube expands with rise in temperature under operating conditions, it increases its area of contact with its hole, expanding to a position somewhat as illustrated in FIG. 5. The expansion of the tube also increases pressure of contact with the hole wall.

As a further example, if the tube is sufiiciently oversize when cold, it may occupy a position somewhat as illustrated in FIG. 5 when cold and subjected to the pressure of springs 16. As shown in FIG. 5, the tube contacts its hole on all sides. Upon rise in temperature under operating conditions, the tube may bulge or expand into groove 11, occupying a position somewhat as illustrated in FIG. 6. The expansion of the tube also increases pressure of contact with the hole wall.

In all cases, regardless of original tit, the Walls of the outer tubes are elastic and have sufiicient temper to exert pressure against the smooth surfaces of the holes to promote heat transfer therebetween. The tubes expand more than the graphite with temperature rise. The tubes main tain heat transfer Contact with the block. The baclrer and extra springs permit the walls of the tubes to move relative to the smooth surfaces of the holes and thus relieve fracturing pressure on the graphite block due to thermal expansion of the tubes.

In any event, the adjustable studs 17 provide a positive means, always under the control of the operator, to adjust pressure on the outer tubes 85 to maintain thc proper fluid-free, solid-to-solid contact between thc tubes and the hole walls.

Should the outer tubes lose part of their temper and take on a new set, due to overheating or for some other cause, the studs 17 may be screwed inwardly to further compress the springs 16 to press the hot sides of the tubes against the hot sides of the hole wall.

A further advantage of the invention is the greater leeway permitted in the original tit between outer tube and hole wall, permitting the tubes to fit comparatively loosely when installed in the graphite block, if desired. The silver tube has the advantage over a copper tube in that it is free from harmful corrosion at the hot face where it is most important to maintain heat llow. The circular tube shape and continuous support by mold wall and baci-:ing strip help prevent collapse of the `tubes under the pressure exerted by springs.

While certain novel features of the invention have been disclosed herein, and are pointed out in the annexed claims, it will be understood that, in accordance with the doctrine of equivalents, various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

I claim:

l. In a mold for casting metal, a graphite block having a mold pocket to receive molten metal, said block having walls with internal passages arranged around said mold pocket, said passages comprising holes of round cross section with offset longitudinal grooves, said grooves being located on the opposite sides of said holes from the mold pocket, tubes in said holes, backing strips in said grooves, means for yieldably urging said backing strips against said tubes and toward the mold pocket.

2. In the mold of claim 1, said backing strips having curved surfaces engaging the curved surfaces of said tubes.

3. In the mold of claim 1, said walls having a series of transverse bore holes, studs threaded in said transverse holes, and springs between said studs and backing strips.

4. In the mold of claim 1, inner tubes of oval cross section disposed within said first mentioned tubes, spacers at the shorter axes of said oval cross section, said pacers engaging the outer tubes at points adjacent the mold pocket and opposite therefrom.

5. In a mold for continuously casting metal, said mold comprising a body including a graphite block, said block having a mold pocket open at one end to receive molten metal and open at the other end to discharge the congealed casting, said block having internal passages arranged around said mold pocket, cooling tubes in said passages, backing strips in said passages disposed on the sides of said tubes remote from the mold pocket, auxiliary springs disposed between said body and said backing strips for urging said backing strips against said tubes to press said tubes against the walls of said passages adjacent the mold pocket.

Baier et al July 26, 1960 Rusterneyer et al, v Jan. 9, 1962

Claims (1)

1. 5. IN A MOLD FOR CONTINUOUSLY CASTING METAL, SAID MOLD COMPRISING A BODY INCLUDING A GRAPHITE BLOCK, SAID BLOCK HAVING A MOLD POCKET OPEN AT ONE END TO RECEIVE MOLTEN METAL AND OPEN AT THE OTHER END TO DISCHARGE THE CONGEALED CASTING, SAID BLOCK HAVING INTERNAL PASSAGES ARRANGED AROUND SAID MOLD POCKET, COOLING TUBES IN SAID PASSAGES, BACKING STRIPS IN SAID PASSAGES DISPOSED ON THE SIDES OF SAID TUBES REMOTE FROM THE MOLD POCKET, AUXILIARY SPRINGS DISPOSED BETWEEN SAID BODY AND SAID BACKING STRIPS FOR URGING SAID BACKING STRIPS AGAINST SAID TUBES TO PRESS SAID TUBES AGAINST THE WALLS OF SAID PASSAGES ADJACENT THE MOLD POCKET.

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