US2001879A - Ingot mold - Google Patents

Description

May 21, 1935. E. J. KAUFFMAN INGOT MOLD Filed July 25, 1932 ATTORNEYS Patented May 21, 1935 PATENT OFFICE INGOT MOLD I Edmund J. Kaufiman, Girard, Ohio, asalgnor to Valley Mould & Iron Corporation, Hubbard,

Ohio, a corporation of New York Application July 23, 1932, Serial No. 624,202

6 Claims.

with the shape of the vertical cross-section of the matrix of a vertical ingot mold whereby the formation of surface defects in ingots such as mold skin cracks, bleed-out scabs and the like are avoided.

When an ingot of steel is cast in a vertical ingot mold of the type common in the art, a mold skin forms when the hot molten steel touches the cold matrix wall of the mold. The interior of the mass of the ingot is molten and the heat of the molten mass is dissipated through the mold skin to the mold walls and the surrounding atmosphere. When an ingot mold is filled with molten steel, the mold skin extends the full length of the matrix of the mold and the bottom of the ingot freezes first because this is formed from the steel which was first poured, and also the stool on which the mold sets and the bottom side walls of the mold have a greater capacity for heat absorption than does the upper part of the mold. Steel shrinks upon freezing, and, therefore, the mold skin which is frozen steel tends to shrink. The weight-of the molten steel in the center of the ingot produces a ferro-static pressure tending to force the mold skin into contact with the matrix walls until the mold skin has developed sufficient strength so that it tends to shrink away from the matrix walls. The bottom part of the ingot cooling more rapidly than the middle zone, the skin of the ing-ct in the lower zone tends to shrink more rapidly both circumferentially and vertically than the skin at the middle zone of the ingot. Since the middle zone of the ingot is hot and the skin is tightly pressed against the matrix side wall w ile the mold skin at the bottom part of the ingo has separated slightly from the matrix side wall, there is a tendency of this shrinkage to lift the bottom of the ingot from the bottom of the mold or stool. As this shrinkage continues, a heavy stress is localized on the thin mold skin adjacent the lower part of the hot middle zone of the ingot. Since this middle zone skin is hot, and, therefore, of relatively low tensile strength, it frequently happens that the mold skin just below the hot middle zone is cracked. It is not unusual for these cracks to open up into the liquid core which runs out of the cracks to meet the matrix side wall and usually, the zone in which the cracks occur has shrunken away from the matrix side wall sufficiently to permit enough molten steel to run out to form a button which quickly chills and freezes against the mold side wall. scabs. The buttons act as wedges to tightly wedge this portion of the ingot to the side wall of the" mold and cause the ingot to tend to hang in the mold so that as further stresses occur during shrinkage, other cracks form at or below the but.- tons. The cracks just described have a general horizontal direction. The surfaces of the metal in these cracks quickly oxidize so that these surfaces will not weld together in subsequent treatment of the ingot and thus produce serious defects in the finished products.

The present invention overcomes the difficulties of the known prior art by providing a vertical contour to the matrix of the mold of such shape as to permit the hot upper portion of a top poured ingot to settle down on the colder bottom portion of the ingot and to prevent the ingot from hanging in the mold and thereby obviating the cracks referred to, which are sometimes known as hanger cracks.

These buttons are known as fbleed-ou The present invention may be embodied in an ingot mold in which the larger cross-sectional areas of the mold are of substantially a narrow taper, and the matrix side walls of the mold in the smaller cross-sectional areas taper at a much sharper angle. The same effect may be obtained by a non-uniformly curved vertical contour whereby the inward curve in the larger portion of the mold matrix tapers but slightly from a vertical line or plane whereas in the smaller portion of the matrix, the vertical contour curves at a more rapid rate, and departs more widely from a vertical plane or line.

In the preferred form of mold embodying the present invention, when the ingot is cast the hot zone of the ingot being in that part of the contour of the matrix having the inwardly tapered side walls which overhang the lower part of the ingot, the hot part of the ingot is prevented from hanging in the mold and is permitted to settle down on the lower portion of the ingot which is held within the lower part of the matrix. In this way, the vertical shrinkage of the mold skinonthe ingot does not tend to lift the bottom of the ingot from the stool. Since the hot portion of the ingot is located in the sharp taper part of the mold, vertical longitudinal stresses tend to pull the mold skin downward in the hot zone and away from the matrix side walls. The tendency of the hot zone of the ingot to bind or hang in the mold is thereby entirely obviated, and consequently, the strain on the mold skin is avoided because the stresses which produce this strain are not present. The upper taper of the matrix is 1 not in the limiting sense.

sufficiently slight, however, to support the hot mold skin against rupture by the ferro-static head of the molten steel and at the same time obviate the skin from sticking to' the mold side wall and hanging the ingot in the mold.

It is realized that the present invention may be carried Out by structures other than those specifically disclosed herewith, and, therefore, the disclosure is to be understood as illustrative and In orderto illustrate the invention, the taper of the matrix side walls is shown in the drawing as being exaggerated somewhat beyond what is preferable in actual practice.

Fig. 1 illustrates a vertical cross-section of an ingot mold of the big-end-down type according to the present invention when the vertical taper of the matrix side walls is illustrated-on substantially straight lines.

Fig. 2 illustrates a vertical cross-section of an ingot mold according to Fig. 1 wherein the vertical taper of the side walls is illustrated as a differential curve which approximates a parabolic curve.

Fig. 3 is a vertical cross-section through another form of ingot mold of the big-end-down type embodying the present invention.

Fig. 4 shows a cross-section on line 5-5, Fig. 1.

Referring to the drawing and more especially to Fig. l, which illustrates the preferred embodiment of the present invention, the ingot mold I is seated on a stool 2. Vertical lines A--A and 3-3 have been drawn perpendicular to the surface 4 on the stool 2 with these vertical lines passing through the corner formed by the lower matrix side walls 5 and the surface 4 of the stool.

The lower matrix side walls 5 are of a slight taper inward relative to the vertical lines AA and BB, preferably not to exceed one inch taper in seventy in length, which slight taper extends upwardly to below the middle of the hot zone, for example, to the point 6 of the mold. From the point 6 of the mold to the mouth 1 of the mold, the side walls 8 are inclined at a substantially greater taper relative to the vertical lines AA and BB, preferably substantially more than one inch taper in seventy of length. In other words, the overhang of the matrix wall portions 8 relative to-the interior of the matrix is substantially greater than the overhang or projection of the matrix walls 5 relative to the surface 4 on the stool. Where an ingotis cast in a mold of the character shown in Fig. 1, the mold skin in the portion 8 of the matrix mold walls having a sharper taper, tends to pull away from the mold wall when the ingot shrinks longitudinally and this portion of the ingot tends to settle down upon that portion of the ingot in the part of the mold having the narrow tapered matrix side walls 5. In view of the fact that the place 6 of the matrix side wall where the narrow taper joins with the increased taper is located adjacent the lower portion 01 the normal hot zone, preferably about one-third the vertical height of the mold, there is no tendency of an ingot cast in the mold to hang in the mold. Also, the narrow taper at the bottom of the mold prevents secondary piping in the bottom of the ingot, and furthermore, supports the mold skin on the ingot against rupture due to ferro-static head of molten steel on the interior of the ingot.

Fig. 2 illustrates a slightly different embodiment of the invention wherein the stool 2 is identically the same as the stool in Fig. 1 and the vertical lines A-A and 3-3 bear the same 879 relation to the mold and stool as in Fig. 1. In

Fig. 2, the matrix side wall of the mold comprises a diiierential curve approaching a portion of a parabolic curve, which curve departs but slightly from the vertical lines A--A and 3-3 up to the point 9 which corresponds to the point 6 on the mold in Fig. 1. From the point 9 to the mouth I of the mold in Fig. 2, the matrix side wall curve swings inwardly at a relatively rapid rate as compared to the curve between the point 9 and the top surface 4 of the stool 2. The result of casting an ingot in the mold shown in Fig. 2 is substantially the same as that of an ingot cast in the mold illustrated in Fig. 1, in that over the portion of the ingot between the point 8 and the mouth I of the mold, the mold skin tends to pull away from the matrix side wall when the ingot shrinks longitudinally so that the upper portion. of the ingot instead of hanging in the mold tends to settle down upon the lower portion of the ingot resting on the stool. This point 8 in Fig. 2 is located adjacent the lower hot, zone of the mold and preferably about one-third the height of the mold from the stool 2.

Referring now to Fig. 3 which embodies a further form of the present invention, substantially the lower two-thirds portion of the mold I is substantially the same as the lower part of the mold illustrated in Fig. 1, in that the lower portion of the matrix 5 is a narrow taper for substantially one-third of the vertical height of the mold, while the middle zone 8 is of an increased taper substantially the same as that in Fig. 1. The upper third ill of the mold about the point II is again of narrow taper preferably of substantially the same degree as the narrow taper 5 in the bottom of the mold.

The ingot in a top poured mold may be divided roughly into three zones, each of which may be roughly said to comprise about one-third of the height of the mold. As the upper two-thirds portion of the ingot is hotter than the lower portion, the ferro-static head in this portion of the ingot due to the molten interior tends to force the mold skin against the matrix side walls, especially in the lower portion of the middle zone wherein the hanging or sticking of the ingot is more likely to occur. Consequently, an ingot cast in the mold of the type shown in Fig. 3 tends to settle down in the mold as the ingot cools and shrinks longitudinally, because of the lack of tendency for the ingot to stick in the hot zones. The side wals ill of the matrix in the upper zone may be of narrow taper because this portion of the skin will stretch and also because the ferrostatic head in this zone is slight, whereas in the zone comprising the middle portion of the vertical cross-section of the ingot wherein the ferrostatic head is greater, the side walls are provided with a substantial taper so that the vertical shrinkage and gravitational forces will cause the mold skin to settle downwardly as the vertical shrinkage occurs. The type of ingot cast in a mold in accordance with the disclosure in Fig. 3 has a slight increase in weight over the type of ingot cast in the molds illustrated in Figs. 1 and 2, and for some purposes is slightly better adapted; for rolling in that the bite of the rolls does not increase as rapidly as in the ingots cast in Figs. 1 and 2. The general principle, however, is the same in all of the molds illustrated herewith so far as prevention of surface defects is concerned.

The tapers herein referred to may correspond to those with which one skilled in the art is familiar, but as a matter of example, the taper in the lower part of the mold may be such that this part of the mold is substantially straight or preferably with a taper not to exceed one inch in seventy, whereas the taper in the middle zone of the mold substantially exceeds one inch in seventy of length. The term taper used in the claims has reference to the deviation of the matrix side wall surface from vertical lines substantially at right angles to the base of the mold.

Fig. illustrates a cross-section taken on line 5-5 of Fig. 1 and represents in general outline a horizontal cross-section of a similar part of all the molds herein disclosed. The comers 20 of the molds are preferably of lesser thickness than the mid portions 2| thereof and preferably the mold walls are thicker at the bottom of the mold than at the top thereof. The outside surfaces of the mold side walls are preferably generated on straight lines so that a vertical cross-section through a mold shows the outside surfaces of the molds as being straight lines 22.

It is to be understood that in a multi-sided matrix, it is not necessary that all sides of the matrix may be in accordance with the present illustrated configuration because in molds having a long rectangular horizontal cross-section to the matrix, such as molds known in the art as plate molds, the difficulties which the present invention is intended to overcome does not occur so strongly on all side walls. It is, therefore, sufficient in accordance with the present invention that the side walls which tend to produce the hanging of the ingot in the mold shall be in accordance with the disclosure herewith, whereas the other side walls may be of such taper as is) convenient or desired.

It is to be understood, however, that the present invention is concerned primarily with vertical or longitudinal shrinkage of the ingot, and, therefore, is applicable to ingots of various shaped cross-section.

From the foregoing, it will be observed that the present invention is concerned with providing a vertical contour to the mold matrix in such manner as to permit the ingot to settle down in the mold and thereby avoid hanging or sticking of portions of the ingot in the mold which heretofore in the art has resulted in surface defects due to cracks in the mold skin.

What I claim is:--

1. An ingot mold for steel ingots comprising a body member of cast iron having a matrix therein with opposed side walls of said matrix in the middle zone of said mold being tapered in excess of the taper in the lower zone of said matrix and with the upper zone of said matrix having a taper of lesser degree than the middle zone thereof.

2. A big-end-down mold for casting ingots having a substantially rectangular longitudinal cross section comprising a mold member having a matrix therein with the cross section of the matrix being larger at the bottom end than at the top end and with the cross-sectional area of the top end of the matrix being in excess of onehalf the area of the cross-section of the bottom of the matrix, matrix side walls having a narrow inward taper substantially one-third the vertical height of the matrix from the bottom end, and having an increased gradual inward taper above the said one-third vertical height of the matrix.

3. A big-end-down ingot mold for casting ingots having a substantially rectangular longitudinal cross-section, comprising a mold body member with a matrix therein with the bottom end thereof being larger than the upper end, the vertical contour of said matrix having opposed side walls provided with a narrow inward tapered portion adjacent the bottom end thereof and an increased gradual taper extending from above the narrow tapered portion to the upper end of the matrix.

4. A big-end-down ingot mold for steel ingots having a substantially rectangular longitudinal cross-section comprising a body portion of heat absorbing material having an inwardly tapered matrix therein, the largest cross-section of the matrix being adjacent the bottom of the mold, the lower substantially one-third portion of the matrix having a narrow inward taper not to exceed one inch in seventy, the matrix side walls for substantially the upper two-thirds of said matrix having an increased gradual inward taper substantially in excess of the narrow taper.

5. A big-end-down ingot mold for casting steel ingots. having a substantially rectangular longitudinal cross-section, comprising an integral body portion of heat absorbing material having a differential inwardly tapered matrix therein, the bottom portion of the matrix having a slight inward taper, and a vertical cross-section of said matrix comprising opposed side walls with the middle vertical portion thereof having an inward taper in excess of the inward taper in the bottom portion of the matrix.

6. A big-end-down ingot mold of substantially rectangular cross-section and having a vertical matrix with the vertical cross-section thereof being curved gradually and tapering inwardly from the bottom to the top of the matrix, the vertical side walls of the matrix comprising in cross-section gradually curved surfaces approximating the curvatures of parabolic curves and with the bottom end of the matrix being of larger cross-sectional area than the top end thereof.

EDMUND J. KAUFFMAN.

Images