US2310553A - Ingot mold - Google Patents

Description

b- 9, 19 3 w. w. SCHOFIELD ET AL 2,310,553

INGOT MGLD Filed March 12, 1942 BY (Ittor ne Patented Feb. 9, 1943 INGOT MOLD William W. Schofleld, Hubbard, Ohio, William Owen, Pittsburgh, Youngstown, Ohio and John Bidner.

Application March" 12, 1942, Serial No. 34,314

' 8 Claims. ((122-139) This invention relates to molds for casting metal, and, more particularly, is concerned with molds for casting steel ingots with the large end up. I

For many years in the steel industry substantially all ingots cast were produced in molds so shaped that the large end of the ingot was down. However, in more recentyears there has been a considerable swing to casting ingots with the large end up, and today the steel industry has changed over a considerable proportion of their equipment'so that about 30% of steel ingots are cast with the large end up which has certain advantages.

However, standard types of ingot molds for casting ingots with the large end up have a number of disadvantages. First, the big end up ingot mold is very apt to be top heavy and, can be easily upset in transit, for example, while being moved on ingot buggies from one department to another of a steel plant. Therefore, the general practice has been to cast the outside wall of the ingot mold perpendicular or to even slant the outside mold wall upwardly and inwardly whereby to provide a lower center of gravity and a larger base to prevent upsetting of the mold. All of this has increased the weight of the mold in relation to the weight of the ingot cast therein and has added considerably to the cost of the mold.

Second, it has long been thought essential to' ingot design to make the wall thickness of the ingot mold greater adjacent the-bottom of the mold cavity so that greater amounts of heat will be withdrawn from the lowerportion of the meet whereby the ingot will solidify from the bottom upwardly. The believed necessity to follow this standard practice in mold design and employ the practice in the construction of large end up ingot molds has resulted in a very heavy and a relatively expensive ingot moldin relation to the weight and size of the ingot cast. For example, it has been the usual practice in a large end up ingot mold to have a'ratio of mold wall area to ingot area near the bottom of the mold of over 1.50 to 1.00, and a ratio of mold wall area to ingot area near the top of the mold of less than 1.50 to 1.00.

Third, we have found that in employing large The attending difference in temperature of the mold wall parts and the associated difference in expansion of the parts resulted in severe stresses in the mold wall which caused horizontal or other cracking of the mold wall in use and'the early failure of the mold.

Fourth, we have found that the very heavy mold wall heretofore employed adjacent the botdisplacement flow, and by the conduction of themold wall itself.

Fifth, we believe that present types of big end up ingot molds have not been properly constructed so as to maintain all portions of the ingot mold at substantially the same temperature after the-casting of the ingot therein. Furthermore, proper attention has'not been paid in big end up ingot mold design so that the ingot mold will provide for the proper removal of heat from the cast ingot whereby solidification of the ingot will be progressively upwardly andwith a minimum of segregation or piping. I

It is the general object of our invention to avoid and overcome the foregoing and other ditficulties of prior art practices by the provision of an improved ingot mold for casting ingots with the large end up.

Another object of our invention is the provision of a large end up ingot mold having a materially increased life.

Another object of our invention i'sto provide a mold for casting steel ingots with the large end up, and with the mold weighing materially less than standard big end up ingot molds, and thereby costing appreciably less than such standard molds.

Another object of our invention is the provi-' sion of a large end up ingot mold wherein the mold wall thickness increases upwardly of the mold.

' Another object of our-invention is to provide improved means for increasing the stability against toppling of a large end up ingot mold,

In other words; our I with such means not adversely affecting the life.

of the ingot mold.

, Another object of our invention is the provision of a mold for casting steel ingots with the large end up. the mold having a wall thickness which decreases downwardly of the ingot mold, and having a mold to ingot ratio which is greater at the top of the mold than at the bottom.

Another object of our invention is to provide a large end up ingot mold having a' horizontal thickness of wall which increases upwardly of the ingot mold, and a mold to ingot ratio which is less at the top than at the bottom of the mold.

The foregoing and other objects of our invention are achievedby the provision of a mold for casting a steel ingot with the big-end up and characterized by having the mold wall thickness greatest at the large end of the ingot and of gradually decreasing thickness towards the small end of the ingot, and having a ratio oi mold wall area to ingot area at the top of the mold of between about .80 to 1.00 and about 1.50 to 1.00,

and a ratio of mold wall area at the bottom of.

the mold of between about 1.00 to 1.00 and about 1.50 to 1.00, and means connected to the bottom of the ingot mold and extending laterally a distance greater than the outside of the mold so as to provide good vertical stability for the mold, said means terminating at a point vertically below the straight sides of the ingot mold. In one specific embodiment of our invention the iatio of mold wall area to ingot area at the top of the mold is less than the ratio of the mold wall area to ingot area at the bottom of the mold.

For a better understanding of our invention reference should be had to the accompanying drawing wherein Fig. l is a side elevation of one particular embodiment of our invention; Fig. 2 is a side elevation of the mold shown in F ig. 1, but with Fig. 2 being taken 90 degrees in a horizontal plane from the elevation of Fig. 1; Fig. 3 is a top plan view of .the mold illustrated in Fig. l; and Fig. 4 is a bottom plan view of the mold of Fig. 1.

Referring to the drawing, the numeral It] indicates as a whole one embodiment of an ingot mold incorporating the principles of our invention. The ingot mold I is provided with a cavity l2 of slightly oblong shape inhorizontal cross section and having appropriately rounded corners, and with the horizontal dimensions of the cavity increasing gradually upwardly of the mold so that the ingot cast in the cavity has its large end up. The upwardly and outwardly diverging sides of the cavity l2 are substantially straight lines and the bottom of the cavity is .curved and terminates in the usual recess [4.

The outer surface of the mold I 0 substantially conforms to the inner surface, but is usually somewhat more circular in horizontal cross section whereby the mold wall thickness adjacent .the corners of the ingot cavity will be somewhat less than the mold wall thickness between the corners to facilitate a more uniform extraction of heat from the ingot. In any event, 65

and regardless of the exact cross sectional contour'of the ingot mold cavity and the outer surface of the ingot mold wall, the ingot mold wall thickness 'increases in horizontal thickness upwardly of the ingot mold. In other words, the thickness of the- 'mold wall is-greatest at the top of the mold and decreases uniformly downwardly of the mold, and the mold wall is thinnest at the bottom of the mold cavity.

The exact thickness of-the mold wall bears a definite relation with the area of the ingot. Specifically, the area of the mold wall at the top of the mold has a ratio with the ingot area at the top of the mold between about .80 to 1.00 and about 1.50 to 1.00. In other words, the area. of the mold wall at the top of the mold is between about .80 and 1.50 times the area of the ingot at the top of the mold. The ratio of mold wall area to ingot area at the bottom of the mold is between about 1.00 and about 1.50 to 1.00. The ratio of the mold wall area to ingot area at all points in the mold between the top and bottom of the cavity is substantially the same as or is progressively between the ratios of mold wall area to ingot area at the top and bottom of the mold.

Although broadly many of the advantages of our invention may be achieved when the mold to ingot ratios are within the limits stated in the preceding paragraph, we have found it advan tageous from a mold weight and expense standpoint to keep the area of the mold at the top between about .90 and about 1.20 times the area of the top of the ingot and to keep the area of .the mold at the bottom of the cavity between about 1.00 and about 1.20 times the area 01 the bottom of the ingot. The mold to ingot ratio in the remainder of the mold is kept substantially the same as or is progressively between the ratios of mold wall area to ingot area at the top and bottom of the mold. We have discovered that this can be done without efiecting the physical strength of the mold or its operating characteristics, and, in fact, when coupled with the remaining features of our invention gives the many advantages above and hereafter discussed.

The principles of our invention are intended tozinclude a big end up ingot mold having a ratio of mold wall area to ingot area at the top of the mold which is either greater 01' less than the ratio of mold wall area to ingot area at the bottom of the mold. Again, the ratio of mold wall area to ingot area may remain substantially constant over the entire mold height. In one preferred embodiment of our invention we provide an ingot mold in which the ratio of mold wall area to ingot area at the top of the mold is less than the ratio of mold wall area to ingot area at the bottom of the mold. Specifically, we ro vide a ratio of mold wall area to ingot area at the top of the mold of about .90 to 1.00 and a ratio of mold wall area to ingot area at the bottom of the mold of about 1.05to 1.00. A mold constructed in this manner has the advantage of a larger mold wall to ingot ratio at the bottom of the mold so that solidification of the cast metal in the mold proceeds from the bottom of the mold upwardly, and with the mold wall thickness at both the top and the bottom of the mold being kept to minimum requisites to provide adequate physical strength so that insulating characteristics of a relatively large body of metal in the mold are avoided, all as discussed above. Before leaving this embodiment of ouiiinvention it should be noted that the last above indicated ratios may be used without changing the fact that the thickness of the mold wallincreases progressively upwardly or the mold.

We have found that it is generally undesirable to decrease the mold wall area below that of the ingot area, i. e. a ratio of 1.00 to 1.00 because of lack of adequate strength in the ingot mold wall. Thus, the ratio given in the preceding paragraph may preferably comprise a ratio of mold wall area .to-ingot area at the top of the mold of about 1.00 to 1.00, and a ratio of, mold wall area to ingot area at the bottom of the mold of about 1.10 to 1.00. If the ratio of mold wall area to ingot area drops below 1.00 to 1.00 it is sometimes advisable to cast an integral band around the very top of the ingot mold which will give added strength and which will also serve as a narrow platform upon which the men handling the ingot mold hot-tops or otherwise working on the ingots or ingot molds, may walk.

In another embodiment we have made the ratio of mold wall area to ingot area at the top of the mold greater than the ratio of mold wall area to ingot area at the bottom of the r, of about 1.00 to 1.00 over the entire mold height but many of the advantages of the invention are retained if the ratio is constant over the entire vertical height of the mold and the mold wall area is between about 1.00 and about 1.20 times the ingot area.

An important part of our advance in the art is the provision of means associated-with and/or connected to and/or cast integrally on the bottom of the ingot mold to increase the vertical stability of the mold and prevent the mold from toppling over during handling, for example. when the ingot is moved on an ingot buggy from one department of a steel plant to another. The means for increasing verticalstability extend laterally beyond the sides of the ingot mold so as to provide a base of increased width on the ingot mold but the means do not extend above substantially the bottom of the mold cavity. We have found that when the means for increasing vertical stability are extended up on the side walls of the mold that they provide such additional masses of metal on the lower sides of the mold that certain of the prior art difliculties heretofore set forth cause an unequal expansion of the mold parts and premature failure thereof.

In the particular embodiment of the invention illustrated in the drawing the means for increasing vertical stability of the mold comprise a plurality of feet indicated by the numeral l6. Usually, we provide four feet [6 which are positioned at 90 degrees to each other and which are cast integral with the ingot mold I0 and of relatively narrow lateral width so that their weight, mass, and size is kept to a minimum. Two of the feet l6 may be formed as pull hooks to assist in stripping the ingot from the ingot mold iffound necessaryor desirable. It will be noted from the drawing that the feet I6 do not extend up on the straight sides of the mold or above substantially the bottom of the mold cavity l2 and hence have very little, if any, adverse effect upon the expansion and contraction of the mold l0 atevery vertical point therein adjacent the cavity l2.

Pull hooks [8 may be cast integrally with the together with the attendant initial ingot mold cost. For example, a 22 inch by 24 inch by 70 inch cavity mold of our invention weighingbut 9450 pounds replaces a prior art 22 inch by 24 inch by '70 inch cavity mold weighing 12,400 pounds.

Furthermore, we have found that our improved mold has a materially longer life than prior known types of ingot molds, andresults indicate that the additional life is from 25 to 50 per cent.

solidification of the cast ingot is improved, pouring times may be reduced, and segregation and piping difficulties are held to a minimum. The entire mold wall is maintained after casting at substantially the'same temperature so that uneven expansion of the mold and attendant horizontal or other cracking is largely eliminated. Our .improved mold possesses very 'satisfactory vertical stability, and because it. is of less weight requires less power to lift or otherwise handle.

While in accordance with the patent statutes we have specifically illustrated and described our invention, it should be particularly understood that we are not to be limited thereto or. thereby, but that the scope of our invention is defined in the appended claims.

top of the mold l0 and a pickup eye 20is-ordi- We claim:

-1. A mold having a cavity for casting a steel ingot with the big end up and characterized by having the mold wall thickness greatest at the large end of the ingot and of gradually decreasing thickness towards the small end of the ingot.

2. A mold for casting a'steel ingot with'the big end up and characterized by having the mold wall thickness greatest at the large end of the wall thickness greatest at the large end of the ingot and of gradually decreasing thickness towards the small end ofthe ingot, and having a ratio of mold wall area to ingot area at the top of the mold of about .90 to 1.00, and a ratio of mold wall area to ingot area at the bottom of the mold of about 1.05 to 1.00. a

4. A mold for casting an ingot with the big end up, said mold having a wall thickness greatest at the top of the mold cavity and of decreasing thickness downwardly of the mold, and having a ratio of mold wall area to ingot area below about 1.20 to 1.00 over the entire vertical height of the mold, and means connected to the bottom of the ingot mold and extending laterally in more than at least two directions a distance greater than the outside of the top of the mold so as to provide good vertical stability for the mold, said means terminating at a point vertically below substantially the bottom of the mold cavity.

5. A mold having a cavity for casting an ingot with the big end up, said -mold having a wall thickness greatest at the top of the mold cavity and of decreasing thickness downwardly of the mold, and having a ratio of mold wall area to ingot area below about 1.20 to 1.00 over the entire vertical height of the mold.

6. A mold for casting an ingot with the big end up, said mold having a wall thickness greatest at the top of the mold cavity and of gradually decreasing thickness downwardly of the mold, and having a ratio of mold wall area to ingot area below about 1.20 to 1.00 over the entire vertical height of the mold, the ratio of mold wall area to ingot area being substantially constant at every vertically spaced point in the mold.

7. *A mold for casting an ingot with the big end up, said mold having a wall thickness greatest at the top of the mold cavity and of gradually decreasing thickness downwardly of the mold, and having a ratio of mold wall area to ingot area below about 1.20 to 1.00 over the entire vertical height of the mold, the ratio of mold wall area to ingot area being progressively greater upward of the mold.

8. A mold ifor casting an ingot with the his end up, said mold having a wall thickness greatest at the top of the mold cavity and of gradually decreasing thickness downwardly of the

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