US1819705A - Ingot mold - Google Patents

Description

Aug. 18, 1931. E. GATHMANN led Feb. 5,

Patented Aug. 18, 1931 UNITED. STATES EMIL GATHMANN, OF BALTIMORE, MARYLAND meow mom) Application filed February 5, 1931. Serial No. 513,751.

This invention relates to ingotmolds and ingots cast therein and more particularly to the vertical sectional contours of molds and ingots of the big-end-up kind. I l

As is now well known, the best steel ingots are produced in big-end-up molds. The superior quality of such ingots is chiefly due to the. manner in which the ingot cast in such a mold cools and solidifies. Due to the fact that the cross section of the molten ingot body is relatively small at the bottom and progressively increases from the bottom to the top thereof, the extraction of heat from the molten ingotmetal is most rapid at the bottom and progressively decreases towardthe top, the upper part of the ingot being the last to solidify. In this way a reservoir of molten metal is always present above the solidifying portion of the ingot and the formation of a shrinkage cavity or pipe in the ingot, which necessarily occurs due to.

the shrinkage in the volume of the metal from the liquid to the solid state, is confined to 'the uppermost part of the solidified ingot, thus reducing to a'minimum the amount of the ingot that must be cropped to assure of soundness in bloom or billet.

In obtaining interior soundness thru a differential horizontal cross section or big-endup contour, hanging of the ingot at the upper part of the mold frequently occurs, causing tears in the ingot surface. It will be understood that when an ingot mold is teemed, the inner wallportions, being first heated, will expand and move inwardly, thus tending to grip and bind the ingot. This gripping action is desirable, since. while it lasts heat is quickly abstracted from the entire outer surface of the ingot and a relative- 1y thick initial skin is formed. It frequently happens, however, that when the mold is heated throughout and releases the ingot, as it were, the lower portion of the ingot has cooled and contracted to such a degree that r it pulls away from the top portion and tears the ingot skin, causing what is known as a hanging ingot. In the rolling or other working of such an ingot, these tears are opened and extended, resulting in an inferior finished product.

In U. S. Letters Patent previously granted to me, particularly No. 983,357 of February 7, 1911 and No. 1,643,241 of September 20, 1927, I have shown and described ingot molds in whichthe walls of the chamber are provided with a differential taper i. e. the top portion of the chamber is tapered to a lesser degree than the lower body portion or is substantially straight.v Altho these contours proved quite eflicient in decreasing surface defects due to ingot hanging, as well as allowing of fewer initial mill passes than a uniform taper ingot, .I have now determined thru numerous tests that the rollin mill advantages of the differential taper lngot can be maintained and hanging ingots entirely eliminated thru the employment of substantially straight upper mold chamber walls if certain definite relative dimensions are maintained.

The accompanying drawings illustrate diagrammatically in a specific form a mold and ingot contour having the desired characteristics.

Figure 1 is a vertical sectional view of a mold embodying the invention, and

Figure 2 is a perspective view of an ingot cast in the mold shown in Figure 1.

The mold M shown in Figure 1 is formed with a chamber defined by mold walls W, each ofwhich walls includes a lower necked-in portion 10', an intermediate body portion "w which merges with the adjacent necked-in portion and which tapers upwardly and outwardly to a plane wm below the mold top, and a substantially vertical wall portion 'w which extends upward from the plane w-a: to the mold top. The bottom of the mold is provided with an opening 0 closed by a combined plug and bottom protector plate P, such as is illustrated and described in my U. s. Patent No. 1,419,454 of June 13, 1922. Preferably the horizontal area of the mold chamber at the top'b of the-tapered intermediate'wall portions is about 20% greater than the horizontal area of the chamber at the bottom a of the intermediate wall portions, since this relation effects the most efficient cooling of the .ingotrmetal from the bottom progressively to the top thereof. The width or maximum cross section b of the mold chamber at the top thereof is the same as or substantially the same as the width b at the plane a:w. The dimension d indicates the top width of a mold chamber of the kind defined by mold walls which taper from the bottom all the way to the mold top, such for example as the walls of the mold shown in my Patent No. 1,419,454 referred to above; but it is to be understood that in molds constructed in accordance with the present invention, the mold chamber width is constant or substantially constant above a plane located somewhat below the top of the mold, such as the plane w-w.

As stated in my Patent No. 1,643,241 before referred to, it is important that the substantially straight upper portion be of a specific length as compared with the length of the tapered body portion. I have recently determined, however, that the best practice is dependent upon the ratio of the length of the said substantially straight portion to the minimum cross section at the top of the mold chamber.

In accordance with the present invention, the length Z of the substantially vertical walls w is less than seven-eighths of the cross section b of the upper part of the mold chamber, and is greater than about five-eighths of the said cross section b. It is particularly important that the length Z of the walls be not greater than seven-eighths of the cross section 6, because if the walls w are longer than seven-eighths b, the progressive cooling and solidification from the bottom to the top of the ingot is not attained and some shrinkage cavitles will consequently occur throughout the body portion of the ingot. Ingots of improved quality have been produced in molds in which the length of the substantially vertical walls varies from five-eighths to seven-eighths of the cross section of the upper portion of the mold chamber, but, as indi cated'from the results obtained in the production of many thousands of ingots, the best results are obtained when the length of the vertical or'substantially vertical walls is about two-thirds of the upper chamber cross section b. Preferably the length l of the tapered wall portion 'w is not over about three and one-half times as great as the width a of the mold chamber at the bottom of the sides W-W of the ingot mold, with the exception that the vertically-extending upper side portions 8 of the ingot are somewhat less in length thanthe corresponding mold wall portions 10 The length h of the sub- 7o stantially vertical or straight portion of the ingotsides is preferably between one-third and two-thirds of the cross section b, and the best results have been obtained when the length of these sides is about five-eighths of the cross section b.

It isto be understood that various other horizontal contours of mold chamber and ingot section may be employed than those illustrated. lVhen the mold chamber and ingothorizontal cross sections are of oblong contour, as for example the type illustrated in my U. S. Patent No. 1,7 67,174 of June 24, 1930, the length of the vertical walls Z of the mold chamber must be proportionate to the minimum cross sectional dimension of the mold chamber at the top section 'b. For example, in a mold chamber having a 24 x 48" top cross sectional dimension, the length of the substantially vertical upper walls must not exceed seven-eighths of the smaller or 24 section. The upper vertical dimension will, therefore, not exceed 21".

An ingotproduced in a mold having the prescribed approximate proportions will be entirely free of horizontal shrinkage tears. This initial freedom of the ingot from surface defects allows of the working of the ingot, in either mill or forge, into a superior quality bloom or billet.

I claim:

In a metallic mold of the big-end-up type, an ingot-forming chamber the lower and intermediate portions of which are defined by upwardly diverging walls and the top portion of which is defined by substantially parallel walls, the vertical length of said parallel walls being greater than five-eighths but less than seven-eighths of the minimum' cross section of the chamber at the top of the mold.

In testmony whereof, I have hereunto subscribed my name.

EMIL GATHMANN.

walls 10 while the vertical length l of the necked-in portion w is about one-fourth the width of a.

The ingot I shown in Figure 2 is of a contour corresponding to that of the mold chamber, with the exception that in practice it is customary when not using a shrinkhead casing, or so-called hot top, to pour the ingot short of the top of the mold chamber so that the ingot produced is usually not quite as long as the mold chamber. .-Thus the ingot I includes sides S corresponding to the

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