US2221947A - Ingot mold - Google Patents

Description

Nov. 19, 1940. E, J. KAUFFMAN 2,221,947

I lll Patented Nov. 19, 1940 `UNITED STATES PATENT OFFICE INGOT MOLD Edmund J. Kauffman, Girard, Ohio, assignor to Valley Mould and Iron Corporation, Hubbard, Ohio, a corporation of New York Application October 1, 1938, Serial No. 232,820

4Claims.

ments in ingot molds and more particularly to lengthening the useful life of an ingot'mold. There is also a substantial improvement to the steel ingot.

The preferred form of the present invention comprises an ingot mold in which the side Walls of the matrix (either all orY a portion thereof) are provided with intersecting grooves which form intersecting beads or ribs on the surface of the ingot. These beads or ribs on the ingot are the iirst portions of the ingot to freezeI or solidify as the hot liquid steel cools.l The tensile strength of the steel increases as it cools from a liquid to a solid and, therefore, these ribs or beads having cooled before the intermediate ingot skin has.cooled, form lines of strength over Athe surface of the ingot. The eiect is much the same as if the hot skin of the ingot were supported by an enclosing wire mesn basket. The cooling of the beads or`ribs tends to pull these ribs from the side wall grooves of the mold due to shrinkage of the frozen steel. This pulling movement of the ribs also pulls away from the matrix face of the mold the ingot skin area comprising unit sections of the ingot surface bounded between the intersecting beads or ribs. This action separates the ingot skin from the side wall face of the mold. at a much earlier period in freezing of the ingot than where no beads are provided. In order that the present invention may be lmost eiective, it is desirable that the beads be suiciently close together to support the enclosed unit ingot skin areas Without'undue sagging of the units through the intermeshed beads or ribs so that as the beads or ribs shrink out of the grooves in the side wall of the mold, the intermediate hot skin on the ingot will be substantially separated from the side wall of the mold.

It is well recognized in the art that the maximum thermal effect of the molten steel on the mold occurs where the ingot remains for a substantial length of time in contact with the side walls of the mold, and that the transfer of heat from the hot steel to the mold is substantially decreased by even a very small air gap separating the ingot skin from the mold surface. The present invention, therefore, prevents the thermal shock to the mold which occurs where the surfaces of the ingot remain for a substantial period of time in contact with the surfaces of the mold. This thermal shock wherein the surface of the matrix of the mold is heated to a very high degree, results in cracks known in the art as re cracks. These cracks deepen and Widen during the normal use of the mold until ns of steel extend from the ingot into these cracks so -that when the ingot is stripped from the mold,

chunks of metal Vare torn away from the matrix face of the mold. Each subsequent use of the mold exaggerates these defects until the ingot is locked to the mold so that the ingot cannot be stripped from the mold. When this occurs, the useful life of the ingot mold is over.

It has been determined by a substantial use of the present invention in the steel art that ingot molds constructed in accordance with the disclosure herewith have a useful life that is very much greater than ingot molds made of the same material and under the same conditions but lacking the present invention. In the molds where .the present invention was used, the small areas on the mold surfaces, bounded by the intersecting grooves on the matrix Walls of the mold, were slightly re cracked after the mold had reached the normal mold life, but these re cracks did not proceed beyond the bounding grooves, thus isolating the fire cracks in smallareas so that the tendencies for large cracks to form was avoided. Furthermore, the size in width of the re cracks was greatly decreased. I believe this improved result to bedue largely to the air gap, formed at an early stage, between the'ingot skin and the mold matrix. There may be other reasons why the grooves in the side wall of the matrix tend to isolate the re cracks and perhaps another reason is that the grooves break the continuity of the surface of the matrix, whereby -iire cracks tend to terminate at the' boundary of the grooves. Whatever the reasons may be, the fact remains that molds utilizing the present invention have a greatly increased Other and further objects of the present inven- 'tlon will in part be obvious and will in, part be pointed out in the specication hereinafter following by reference to the drawings wherein like parts are designated by like characters.

Fig. l illustrates a cross-section through a mold embodying the present invention.

' life over-molds in which the present invention is not used.

Fig. 2 is a cross-section of fragments of the side walls of an ingot mold and. a. section of a portion of an ingot in accordance with the present invention.

Fig. 3 illustrates a fragment of the matrix face of an ingot mold bearing the preferred form of intersecting' grooves. p

Figs. 4, 5, 6, 7, and 8 are detail gures illustrating fragments of matrix side walls bearing modications ofthe arrangement of grooves for carrying out the present invention. i l

The present invention is useful in either bigend-up or big-end-down molds and, merely for illustration, a big-end-up mold is shown in Fig. 1. The mold i has the usual mold cavitybounded by matrix walls 2. These matrix walls may be covered in their entirety or only partially with diagonal grooves d as illustrated in Fig. l. Preferably, the molds in which the present invention is embodied, are the usual cast irontype of ingot molds in common use in the steel industry.

Fig. 2 illustrates fragments of the mold walls l provided with grooves 4. rlihis gure illustrates a fragment of an ingot 5 just prior to being stripped from the mold. The ribs 6 are shown as being substantially chilled and cold and the depth of the mold skin is indicated at 7. The remaining portion of the ingot usually is in a soft condition. It will be observed that the ribs 6 have been chilled to a substantial depth and, therefore, are of sumcient strength to support the intermediate mold skin 'i so that as the ribs 6 have shrunk away from the grooves 4,.the mold slnn 'l is carried from the surface face of the matrix 8 leaving an air gap 9, which is a very poor conduct'or of heat, so that the ingot tends to remain hot for a longer period of time, and the mold face does not heat so rapidly as where the ingot remains in contact with the mold matrix.

The depth of the grooves 4 is somewhat dependent upon the cross-sectional dimension of the mold in order to facilitate stripping of the ingot from the mold. Steel normally tends to shrink substantially 1.6% when molten steel freezes into a solid mass. This percentage, of course, varies with the temperature at which the calculation is made and it has been found by actual practice that grooves in the side wall of the mold having a depth varying from 1*; to %4 and with the base varying from 1,4 to 1% of an inch are entirely satisfactory for ingot molds having matrix openings ranging .from 10 inches square in horizontal cross-section, upward to 30 or 40 inches. The depth of the grooves for steel which shrinks 1.6% in lateral shrinkage preferably should not exceed one-one hundred and ftieth of the lateral dimension of the mold as measured directly in front of the groove. Since the ingot shrinks vertically as well as laterally, it is desirable that the side walls of the grooves 4 -in the mold be formed to permit the ribs 6 on the ingot to move out of the grooves 4 during shrinkage of the ingot while cooling and after the initial skin 'has set land been stretched according to my Patent 2,018,762, during the cooling thereof. To

this end, the preferred form of the invention comprises rounding or angular disposition, of the sides of each groove d. Angles varying from 25 to 35 (Fig. 2) have been found to be satisfactory.

In accordance with the preferred embodiment of the present invention, as it has been practiced in the art, it comprises providing on the matrix side walls of a mold (having a cross-section of twenty by twenty-two inches and a height of substantially sixty inches) intersecting grooves subagence? stantially three-sixteenths of an inch wide at the top and from three-sixty fourths to one-sixteenth of an inch deep. These grooves were separated substantially one and one-,half inches from center to center and were arranged in parallel diagonal directions to intersect at substantially 90 angles as shown in Fig. 3. The grooves il may also be arranged to intersect as shown in Fig. 4, Fig. 5, and Fig. 6. Improvement over the plain side Wall of the mold may be obtained by using vertical grooves d as illustrated in Fig. 6 or by using horizontal grooves fl as illustrated in Fig. 7. The horizontal grooves are preferred to the vertical grooves in that the horizontal grooves il shrink circumferentially around the ingot 5 and pull inwardly the ingot skin 'l between the grooves. The preferred embodiment, however, of the present invention is that disclosed in Figs. 1 and 2.

Aside from the improvement in mold wall life, thev present invention retains the advantages specied in my said prior Patent 2,018,762 plus a. further advantage which has to do withthe interior crystalline structure of the ingot. Heretofore in the art where the ingot skin tended to remain in contact with the side walls of the matrix and thereby rapidly dissipate the heat from the ingot,` there was a tendency of the upper end of the ingot chilling with such rapidity as to partially solidify and interfere with the feeding of molten steel from a hot top or sink head down into the interior of the ingot. The result of this was that some portions of the metal in the interior of the ingot below the cooled upper portion would show a condition known in the art as porosity because of the fact that fresh metal from the sink head or hot top had been cut oif from this portion of the ingot while the ingot was freezing dueto the restriction of the hot metal now because of chilling of the upper portion of the ingot. In the practicing of the present invention, it has been demonstrated that where the ingot skin is pulled awayfrom the side walls of the matrix by the chill ribs on the surface of the ingot, that the ingot does not lose heat as rapidly as heretofore in the art and that, therefore, the freezing is better graduated from the bottom of the ingot toward the top thereof which enables a hot top or sink head to feed hot metal downward into the ingot bocLv while the same is freezing and thereby avoid the condition of porosity and produce an ingot of sound steel. From the foregoing, it will appear that the present invention not only improves the mold itself, but also results in an improved. ingot.

Configurations such as small conical or pyvramidal recesses may be used in the place of grooves in the matrix faces providing the location of these recesses is such as to result in protuberances on the ingot surface of sufficient effect to sustain the intermediate ingot skin when shrinkage occurs. The depth of such recesses should be the saine as that above referred to relative to the depth of the groovesd in the side walls of the mold. These limiting' depths are such as will permit the ingot to bestripped from the mold without danger of interlocking the ingot with the mold after the ingot has cooled sufciently for stripping. The shrinkage of the ingot within the mold is such as to vpull the ribs, protuberances or other forms used, away from the mold matrix and when these members are proportioned in accordance with the dimensions previously specified, they will clear the side wall of the mold when the ingot is stripped.

While the present invention has been explained more especially with reference to ingot molds for use in casting steel ingots, it is to be understood that this explanation is merely for the purpose of illustration and that the invention is also applicable to the casting of ingots in other metals, as for example, copper, aluminum, alloys of various metals, or any other metallic ingot.

vWhat I claim is:

1. An ingot mold for steel ingots having a portion of the matrix wall providedwith a plurality of grooves adapted to producecomplemental ribs on the surface of an ingot cast in said mold, said grooves being preferably formed with the width of the mouths of said grooves being substantially four times the depth of said grooves, and with said grooves being spaced apart such distance as to support the initial ingot skin to separate the same from the matrix wall as the ribs separate from the grooves when the molten steel in the ingot is freezing.

2. An ingot mold for steel ingots having a portion of the matrix wall provided with a plurality of grooves adapted to produce complemental ribs on the surface of an ingot cast in said mold, said grooves being preferably formed with the width of the mouths of said grooves being substantially four times the depth of said grooves. the side walls of said grooves being inclined so that said grooves are substantially wedge shaped in crossection, and with said grooves being spaced a art such distance as to cause the'initial ingot sldn to separate from the matrix wall as the ribs separatefrom the grooves when the molten steel in the ingot' is freezing'. Y

3. An ingot mold for casting ingots having a portion of the matrix side walls provided with a plurality of intersecting grooves adapted to form intersecting ribs on ingots cast in said mold, the depth of said grooves being such as to permit the ribs formed thereby to be within the matrix side wall'plane when the ingot is frozen suiilcient to be stripped from the mold and the width ofl the mouths of said grooves being substantially four times the depth thereof, and said grooves being sufficiently close together to form chilled ribs on` the ingot that support and carry initial ingot skin unit areas away from the matrix side wall as the ribs move out of the grooves when the ingot shrinks during the freezing of the molten steel.

4. An ingot mold for casting ingots having a portion of the matrix side walls provided with a plurality of intersecting grooves adapted to form intersecting ribs on ingots east in said mold,

the depth Iof said grooves being one-one hundredout of the grooves when the ingot shrinks during the freezing oi' the molten steel.

' EDMUND J.

Images