US2884671A - Foundry apparatus - Google Patents

Description

y 5, 1959 v E. A. WALCHER, sR., ETAL 2,884,671

FOUNDRY APPARATUS Flled reb. 18, 1957 2 Sheets-Sheet 1 INVENTORS EDWIN A. WALCHER SR. LUTHER A. KLEBER ROY A. GEZELIUS ATTOR Y May 5, 1959 E. A. WALCHER, SR ET AL FOUNDRY APPARATUS 2 Sheets-Sheet 2 Filed Feb. 18, 1957 R s M R m S HB M EI LLL KE 1w 2 A.E A N MWY DUO ELR Y B ATT NEY United States Patent 6 FOUNDRY APPARATUS Edwin A. Walcher, Sr., Chicago, Ill., Luther A. Kleber,

Maryland Heights, Mo., andRoy A. Gezelius, Wallingford, Pa'., assignors to General Steel Castings Corporation, Granite City, 111., a corporation of Delaware Application February 18, M57, Serial No. 640,776 4 Claims. (Cl. 22-177) The invention relates to: foundry apparatus and consists particularly in molds. provided with means for the controlled circulation of cooling media.

In the production of large volume castings, such as, for example, iron and steel rolls for rolling mills, or ingots, the density and physical characteristics of castings can be improved'by acceleratingthe rate of cooling, and properly controlling the accelerated rate.

In rolls it is desirable that the wearing surface be chilled to a substantial depth in order to permit the initial dressing down of the roll from its original diameter and still present a hard, defect-free wearing surface. If the depth. of the chilled portion is insufficient, the roll is frequently unsuitable for mill use upon being dressed down, dueto the presence of segregation lines, softness, and lack. of. density in the zone immediately beneath the chilled rim. portion.

In the case.of.ingots,.the hardness of the surface is not important, but it is: importantv that the ingot be free from internal defects, and this can be achieved by accelerating the rate of cooling and controlling it in such a manner that the lower portions of the ingots are cooled most rapidly withthe rate of cooling declining uniformly upwardly from the bottom of the ingot.

In the conventional roll. mold consisting of sand rammed into a steel flask, the chilling action, as the molten metal comes into contact with the relatively cool mold wall, causes the formationof a thin skin on the casting metal. This action is caused by the rapid conduction-of heat from the relatively hot molten metal to the relatively cool mold wall. As additional molten metal is introduced into the mold, through the usual tangential gate near the bottom of the mold, it swirls upwardly within the thin skin. As this occurs, heat is transferred from the casting metal to the mold, which initially expands inwardly, because its outer surface is relatively cool, until the mold Walls are uniformly heated throughout by conduction from the casting metal. Heat is thereafter removed from the outer'surface of the flask by transference into the ambient atmosphere. Further expansion of the mold is outward, with the result that an air space forms between the outer surface of the casting and the inner surface of the mold. Since air is a relatively poor conductor, effective conduction of heat from the casting metal to the mold walls then ceases. Because the mold becomes heated very rapidly, the chilling action is at bestof'very short duration, terminating when the inner surface of the mold approaches the temperature of the outer surface of the. casting, or when the insulating air space formsbetween the mold wall and casting surface.

It is evident from the foregoing that it is desirable to accelerate the'rate of cooling, and to provide means for accurately controlling therate of cooling of large volume castingsand ingots;

One method of' achieving an' accelerated rate of cooling in casting rolls has been to use chill rings or blocks conforming in shape to the passes or plain cylindrical portions of the roll surface. These elements are embedded in the sand and the extent or depth of chilling action is dependent on the size of the chill rings. This method is very satisfactory up to a point, but of course only permits limited extensionof the period available for chilling action.

Ina second'method sand is: not used, the metal Wall 2,884,511 Patented May 5, 1959 of the flask being indirect engagement with the casting metal. Because the insulating effect of sand is eliminated the cooling rate of the rim portion of the roll casting is accelerated, resulting in a somewhat deeper chilled portion than is possible with the methods described above in which sand molds are used. This method cannot be used in the production of pass rolls because of the substantial contraction of the roll longitudinally with consequent downward movement towards its seat during cooling which would be resisted by the portions of the mold forming the passes. A further disadvantage of this method is that the depth of the primary crystalline structure is limited to two or three inches, which of course limits the depth to which the roll may be dressed down.

Another more positive method of accelerating the cooling action has been to spray water on the outside of the molds. Because of the inability to accurately control the rate of chilling and to maintain a uniform rate, this method has not been atall satisfactory. As a result of observing the inadequacy ofithismethod but realizing at the same time the 'substantial'advantage of Water cooling over previous methods, it has beenrecognized that water cooling would result in improved'rolls if it could be properly controlled.

Various means. havebeen used to achieve improved control. All of these. have involved the circulation of water around the mold;

In one form, helices of Water=circulating pipes surround the outer wall of the metal mold. In this form the use ofatsand or oth'erirefractory lining is precluded because due: to the necessary'thi-ckness of the flask, if a sand lining were. used muchof th'echilling action derived from the water would be lost: because of the distance be tween the exterior cooling coils and the inside of the flask coupled withthe insulating effect of the sand.

The patented artdiscloses another form of water chill, in which the pass chill portionsare-integral with the metal mold. In this design, the. placement of the cooling coils in the pass portions of the'moldi wall would present'a serious problem in casting the. mold, and'the mold wouldv not function satisfactorily for any other than very small rolls due to the fact that the necessary shrinkage. longitudinally of'the roll due to contraction of the metal in cooling would be interfere'd'with by the'inward projections on the chill wall'at the pass locations.

In the most satisfactory formifor water chillingof rolls heretofore known, involving the use of a cage of longitudinally extending equally-spaced rectangular section water pipes embeddedv in the sand wall of the mold, there are several disadvantages. Thecage is a complex structure of many parts, and: is easily damaged during the molding and strippingoperations; even the storage and handling of such a. complex structure becomes a substantial problem. The danger ofleaks. due to the numerous joints between the longitudinal pipes and the annular water-circulating manifolds in great. Moreover, it is difficult'to maintain. accurate spacing of the pipes, with the resultant non-uniformity of chilling action. Because ofthe insulating properties: of the sand surrounding the pipes, chillingaction'is not completely uniform, the resulting roll surface between the pipe locations being of less density than'that adjacent'to the pipe locations. Where pass chill rings are used in connection with this chilling apparatus they are normally positioned with their backs against the outer surfaceof thepipes forming the cage, and because of imperfections inherent in the formation of the pipe cages, engagement between the chill rings and the pipe surfaces is not uniform, with the result that the conduction of heat from. the chill rings into. the pipes-is far from uniform.

Accordingly it.isan. object of. the invention to provide a mold for rolls, ingots, and other. castings where density and freedom from defects are of prime importance, in which a more uniform and directional chilling action with resultant superior solidification pattern in the casting is achievable than in any molds presently in use.

Another object is to provide apparatus of this type in which the chilling action can be accurately controlled so as to attain the desired solidification pattern and structure in the final casting.

A further object is to circulate chilling media through the mold wall in such a way as to achieve more uniform cooling than has been achieved by prior art apparatus.

An additional object is to provide mold components which can be assembled to form molds of different lengths and with any desired combination of water cooled and solid wall portions and which are adaptable either for plain body rolls or any types of pass rolls as well as other castings of substantial section.

We achieve these and additional objects by means of a basic unit consisting of a metal flask including within its wall at any desired depth from the inside surface of the wall a series of equally spaced longitudinally extending pipes of round, square, rectangular, or any other desired cross section, connected at their ends by annular manifolds. These flasks are preferably of relatively short length so that they may be combined to provide any desired length roll body, and are semi-cylindrical to facilitate diflerent mold ramming methods, the placement within the flasks of chill rings for pass rolls, and removal of castings after solidification. Preferably a sand lining will be used although it will be understood that they may be used without sand. This type of flask presents a substantial advantage over those known in the art and referred to above in that, due to the equal and relatively close spacing of the water passages at a uniform depth from the inner wall of the flask, and the very high conductivity of the metal flask throughout its wall structure, the conduction of heat from the inner surface of the flask into the pipes will be substantially uniform throughout the inner surface of the flask. Be-' cause of this, the surface of any rolls formed in molds composed of flasks of this type will be of uniform density. Each flask has its own independent water circulating system, thus eliminating the danger of leaks at joints between adjacent flasks and increasing the flexibility of arrangement of the flasks, as well as permitting improved and accurate control of the rate of chilling in the various flasks making up a mold. For example, if it is desired to chill one portion of a roll or other object being cast at a more rapid rate than other portions, the rate of flow of the cooling media in the various flasks can be varied as desired either by valving or varying the pipe sizes leading to the flask and due to the arrangement of the water passages and metal-to-metal joints between adjacent flasks, the temperature gradient, or transition from flask to flask will be gradual and even rather than abrupt. It is contemplated that other cooling media than water may be used where the circumstances indicate this would be advisable.

The above objects and advantages as well as others more detailed will be evident from the following description and accompanying drawings in which:

Figure 1 is a vertical sectional view of a roll mold embodying the invention.

Figure 2 is a horizontal sectional view along the line 22 of Figure 1.

Figure 3 is a fragmentary vertical sectional view of the upper flange and adjacent wall portion of the fluid cooled chill flask shown in Figures 1 and 2.

Figure 4 is a horizontal sectional view of a similar mold arranged for casting pass rolls.

Figure 5 is a vertical sectional view along the line 5-5 of Figure 4.

Figure 6 is a plan view of a modified form of the pass chill ring segments shown in Figures 4 and 5.

Figure 7 is a side view of another modification of pass chill ring segments.

Referring to the drawings, the numeral 1 refers generally to a cope flask comprising a series of ring portions 3, 4, and 5 secured together by the usual flask clamps (not shown). Each ring portion consists of two semicylindrical halves bolted together. The lower flange of flask 5 is secured to the upper flange of a flask 6 which in turn is secured at its lower end to a similar flask 6. Flasks 6 constitute the chills for the body of a roll. At the lower end of the second flask 6, it is clamped in the usual manner to the drag flasks also of semi-cylindrical design generally indicated at 7 and comprising rings 8 and 9, ring 9 being formed with the usual gate portion 10. The flasks 1, 6, 7 rest on a steel base plate 11 and is lined with foundry sand 12 or other refractory material, which forms the inner surface of the mold.

In the cope flask 1, the upper end is enlarged as at 13 to form the head of the roll and narrowed as at 14 to form the upper neck portion. At the neck portion, a series of longitudinally spaced quarter section chill rings 16 are embedded in the sand for providing the desired mild chilling action and temperature gradient on the roll neck portion. Slightly below the lower-most ring 16 the mold cavity is widened as at 18 to form the body of the roll. It is in this area that the effect of chilling action is most critical, and for this reason, flasks 6 are provided with means for forced circulation through their wall structure of a cooling medium which may be water or other cooling media, such as sodium gas, ammonia, or molten tin.

Flasks 6 are each semi-cylindrical as can best be seen in Figure 2 and are formed with a series of equally spaced cylindrical passages 20 extending substantially throughout their length and spaced uniformly from the inner surface of the flask wall. At their upper and lower ends passages 20 are connected by semi-annular manifold passages 21 and 22, the location of passages 21 and 22 being as near the ends of the flask as possible. As best seen in Figure 3, passage 21 is formed by milling a shallow semi-annular groove in the end of the flask and welding a thin cover plate over it, the upper part of the groove being wider to permit recessing and seating the cover plate so that its upper surface is flush with the end of the flask. Passage 22 is formed similarly. Passage 22 communicates with the outer surface of the flask 6 by means of a water inlet passageway 24 through the lower flange which is adapted to be connected with a source of water or other cooling fluid, and a passage 25 in the upper flange communicating with passage 21 functions as an outlet for water introduced to the flask through passage 24 and circulated through passages 22, 20 and 21. Each of the flasks 6 is similarly constructed, and it will be understood that the rate of flow, and accordingly the rate of cooling, of each of the flasks may be varied as desired by external means thus meeting previously determined chilling requirements. In the portion of the mold circumscribed by flask 6 it will be noted that the depth of the sand or other molding material is very shallow, preferably in the order of inch or less. This is desirable in order to minimize the insulating effect of the sand or other mold lining, but it will be understood that the thickness may be varied, as desired in accordance with the required surface condition of the mold upon first molten metal contact and the desired rate of subsequent chilling. It will also be evident that due to the positioning of the water circulating passages uniformly from the inner wall of the mold and uniformly from each other, and due to the superior conductivity of the flask wall metal the rate at which heat is conducted from the casting metal through the sand and into the cooling medium within the passageways 20, 21, 22 will be substantially uniform throughout the interior surface of the mold.

Below the lower end of the lower flask 6 the mold cavity is narrowed as at 26 and chill blocks 28 whose surface corresponds in shape to the inner surface of the mold are embedded in the sand to form and chill the lower neck portion of the roll. By positioning chill blocks 28 close to the lower water passages 22 in the adjacent flask 6 a temperature gradient without abrupt change is established between flask 6 and chill blocks 28.

It will be seen from the foregoing that the arrangement of the chills in a mold of this type can be varied as desired. For example any number of water-cooled flasks 6 might be used, dependent upon the length of the roll body, or solid wall chill flasks could he interspersed between the water-cooled flasks. As pointed out above, due to the independent fluid-circulating systems of each of the flasks the rates of cooling may be varied from flask to flask, and, because of the proximity of the water passages to the flask ends, and the metal-to-metal contact between adjacent flask ends, there will be no abrupt line of demarcation in the rate of cooling from flask to flask.

In making swept out pass rolls, it has been the usual practice to use chill rings, or segments, inserted in the mold at the pass locations. This practice is followed in connection with the above mentioned water-cooled mold having a pipe cage embedded in its sand wall, the back of the rings being placed in contact with the inner surface of the square water pipes. This was a substantial improvement over the prior art, but because of the difliculty of obtaining and maintaining uniform contact between the chill rings and each of the pipes, transfer of heat from the chill rings to the pipes is not uniform throughout the surface of the chill rings, with resultant variation in density and hardness of the passes.

The casting of swept out pass rolls is facilitated and the quality of the rolls improved by the use of our watercooled flasks in combination with chill rings for the passes, as seen in Figures 4 and 5. In the preferred form, we use quarter-section chill rings 27 of slightly smaller diameter than the inner wall of the flask, and provide a thin layer of sand between the chill rings and the flask wall. Because there is no direct metal-to-metal contact between part of the chill rings and the water-cooled structure and sand insulation between other portions of the chill rings and the water-cooled structure, as in prior art apparatus, the conduction of heat from the rings into the uniformly-cooled flask is uniform throughout. Moreover, the interposition of sand between the rings and the flask wall accommodates expansion of the rings and permits axial movement of the roll within the mold during cooling. It will be understood, of course, that completely uniform and more rapid heat transfer can be achieved by placing accurately machined rings in direct engagement with the flask wall. Expansion of the rings, and axial movement of the roll during cooling can then be accommodated by loosening the bolts connecting the semi-cylindrical halves of the flasks.

Further variation in the rate of chilling of the passes is permitted by using chill ring segments of the type shown in Figure 6 in which the back of each of the segments 27a is formed with a plurality of radial ribs 29a. Since the rate of heat transfer to the flask will be slower in the spaces between the ribs than at the rib locations, due to the greater thickness of the sand or other insulation in these spaces, the rate of chilling of the passes will be proportional to the ratio of the circumferential surfaces of the ribs to the corresponding surfaces intermediate the ribs. In Figure 7, a similar ring 27b is provided with circumferential ribs 29b for the same purpose as the radial ribs of Figure 6.

It will be understood that the details of the apparatus may be varied from the forms shown without departing from the spirit of the invention, and the exclusive use of those modifications coming within the scope of the appended claims is contemplated.

What is claimed is:

1. A mold including a flask having a peripheral metal wall, a fluid circulating system disposed between the inner and outer surfaces of said wall and communicating only with the exterior of said flask, said fluid circulating system including a plurality of passages uniformly spaced from each other and from the inner surface of said wall, and solid metal elements having a first surface conforming to indentations in objects to be cast within said mold and a second surface generally conforming to a portion of the inner surface of said wall, said metal elements being positioned in said flask with their second surfaces selectively spaced a uniform distance inwardly of the flask from the inner surface of the said wall, and refractory material between said spaced surfaces whereby the conduction of heat from the casting metal to the flask may be substantially uniform throughout the area of the depressed surface portions of said cast object but may be varied by varying the spacing between the second surfaces of said elements and the inner surface of said wall.

2. A mold according to claim 1 in which the surfaces of said metal elements adjacent to the flask wall are formed with uniformly spaced alternate raised and depressed portions, the spacing of the raised and depressed portions being varied in accordance with the desired rate of heat transfer from said elements to said flask.

3. A mold for casting rolls comprising a drag flask and a cope flask each including a lining of refractory material shaped to form a mold for the lower and upper neck portions, respectively, of a roll, an intermediate flask secured at one end to said drag flask and at the other end to said cope flask and forming a mold for the body of a roll, said intermediate flask comprising a plurality of metal wall sections separable from each other along an axial plane, each of said sections containing within its wall structure an independent fluid circulating system comprising a plurality of communicating passages, said passages being uniformly spaced from each other and from the inner surface of said wall structure substantially throughout the area of the inner surface of said wall structure, means for circulating coolant through said passages, a portion of said passages being in close proximity with end surfaces of said sections, chill blocks having surfaces corresponding generally to the lower neck portion of the roll embedded in the lining of said drag flask and having another surface in proximate relation with an end surface of the adjacent intermediate flask section whereby a temperature gradient without abrupt change is established between said intermediate flask and the chill blocks, a plurality of pass chill ring segments arranged within said intermediate flask, said segments being similar in contour to the inner surface of said intermediate flask whereby to permit them to be uniformly spaced from the inner surface of said intermediate flask to provide uniform heat transfer thereto, and a layer of refractory material in the spaces between said segments and the inner surface of said intermediate flask.

4. In a mold for casting rolls, pass chill ring segments according to claim 3, said ring segments having their surfaces adapted to be positioned adjacent the inner wall surface of said intermediate flask formed with uniformly spaced alternate raised and depressed portions, the spacing of the raised and depressed portions being varied in accordance with the desired rate of heat transfer from said segments to said intermediate flask.

References Cited in the file of this patent UNITED STATES PATENTS 990,710 Crook Apr. 25, 1911 1,776,355 Eppensteiner Sept. 23, 1930 2,104,906 Mueller et al Jan. 11, 1938 2,377,731 Walcher June 5, 1945 2,501,663 Cordes Mar. 28, 1950 2,693,624 Corneil Nov. 9, 1954 FOREIGN PATENTS 963,803 France Ian. 18, 1950

Images