US479120A - Process of preventing segregation in large ingots - Google Patents

Description

(No Model.) 2 Sheets-Sheet l. W. R. HINSDALE.

PROCESS 0F PRBVENTING SBGREGATION 1N LARGE INGOTS. No. 479,120. Patented July 19, 1892.

Fig. 3.

""" NFO E Fig. 2

Fig. l

(No Model.) Y 2 sheets-sheet 2.

W. R. HINSDALE.

PROCESS 0F PRBVENTING SBGRBGATION IN LARGE INGoTs. No. 479,120. Patented July 19, 1892.

1H, l .1.1111111 N l'I' I. 11:11. '....wlf i., .1u!'151111111151111.

Attest. y Inventor.

UNITED- STATES PATENT OFFICE.

WILLIAM R. I-IINSDALE, OF NEWARK, NEW JERSEY.

PROCESS OF-PREEVENTING SEGREGATION IN LARGVEl INGAOTS.

SPECIFICATION forming part of Letters Patent No. 479,120, dated July 19, 1892. Application iiledvJuly 27, 1891. l Serial No. 400,821. (No specimens.)

T0 @ZZ whom t may concern.'

Be it known that I, WILLIAM R. HINSDALE, a citizen of the United States, residing at Newark, Essex county, New Jersey, have invented certain new and useful Improvements in the Process of Preventing Segregation inrLarge Ingots, fully described and represented in the following specification and theaccompan ying drawings, forming a part of the sanne.

In the manufacture of large steel ingots, as in those over sixteen or twenty inches in di# ameter, it has been found that a defect occurs which results from a certain action within the ingot during the coolingoperation and which is known assegregation. Thisinternalaction alters to a greater or less extent' the chemical constituency of a certain portion of the mass and destroys its homogenity. The so-called segregation7J consists in the concentration of a portion of the non-metallic constituents of the steel or the metalloids in a usuallypear-shaped mass at a point about one-third of the depth of the ingot from its top While the same is undergoing soliditication 'or crystallization. It has been found by the analysis of ingots so formed and constituted that this action is governed in a great degree by the differences in fusibility, affinity, and density of the constituents of the steel; and the cause of the segregation is said to consist in the crystalline force and surface tension of the steel in cooling, which tend toward differentiation and the overcoming of the diffusive force or tendency to uniformity. It is evident, therefore, that with steel of a given composition the time required for crystallization is an important factor, and practice has demonstrated it to be the chief factor involved in the process of segregation under existing conditions.

In practice it has been found that in the production of ingots of high-carbon steel the Variation between the proportion of carbon in the segregated mass and the mother meta or the steel composing the greater portion of the ingot was in many instances as high as ten or iifteen hundredths of one `.per cent. (10% or .15%) and in some extreme cases was as great as fifty-hundredths of one per cent., (.50%,) these variations in the proportion of carbon producing the well-known equivalent variations in the strength of the steel.` As subsequent working of the ingot found in an article made from such heterogeneous ingot, it is evident that the value of the whole ingot is correspondingly reduced, as the weakest point in such an article is a measure of the strength of the whole.

Abnormal breakage has often occurred in crank-shafts ofl marine engines and in similar members, in which the appearance of the fracture has indicated no structural defect in the steel composing thesame and for which no cause could be assigned; but the presence of segregation in the large ingots, from which such members were necessarily formed, and the composition of the segregated mass with its known effect upon the strength of the steel is, however, strong evidence that this defect in the ingot is the real cause of the fracture in such cases. In boiler and ship plates the accumulation of the metalloids is indicated by great hardness and brittleness, reducing the elasticity and tensile strength to such a degree 'as to render plates so affected utterly unfit for the purposes for which they were designed, and if such accumula' tion of metalloids is located in the center of such plates, where this condition is not likely to be detected in shearing and punching, it may lead to disastrous results. It will be seen that segregation therefore constitutes a serious defect in large steel ingots, and the desirability of avoiding the same is obvious. This lack of uniformity has been considered by some due to imperfect mixing of the constituents of the steel before pouring; but subsequent experiment has proved that this condition of the steel could not be remedied by mechanical mixing. It has also been proposed to hasten the cooling of the ingot by suitable means, so as to shorten the time required for crystallization sufficiently to prevent the separation and assemblage of the metalloids; but this remedy, While obviating to some extent the defect it was designed to avoid, was found to increase the volume of the pipe and the formation of blow-holes in its operation upon the chilled outer shell of the ingot, and thus failed to attain its pri- IOO mary object-that of producing a structurally and constitutionally perfect iiigot. In order to obviate this defect of segregation without affecting in any manner the other qualities of steel ingots, I have devised the following process, which operates upon the ingot in the portion where segregation is likely to occur:

Iii this process I fill a large mold to thetop with the molten steel and allow the walls ot' the ingot thus formed to crystallize. lVhile the central fluid portion is still fluid and before the chemical actions before referred to have taken place to any considerable or injurious extent in the ingot I pour an additional charge of steel from a point somewhat above the top of the ingot into the central fluid portion of the latter. This steel, plunging downward into the central fluid portion of the first-poured metal, interrupts the process of segregation, v which may have previously begun, and agitates and displaces the latter in its then chemically-unstable condition. This step not only removes that portion of the ingot in which segregation begins to take place apreciably at this stage in its crystalliztion, but furnishes in place of the molten metal thus removed an equivalent volume of the newly-poured metal, which, being of less quantity than the previously-crystal lized portion of the ingot, solidifies under the same conditions as the latter.

In practice it will be found that the point beyond which injurious segregation is likely to occur in the large ingot is reached when the steel has cooled sufficiently to crystallize inwardly about one-third the diameter of the mold, and it any tendency toward segregation is checked at this stage ot' solidification and the original condition of the remaining fluid steel is renewed the filial uniformity ofthe whole is assured.

To prevent the loss of the displaced metal,

' either of the following devices may be resorted to: A mold ot smaller diameter maybe placed upon the large mold, and the subsequent charge of' steel may he poured through this mold into the fluid center of the previouslypoured ingot, the overflow from the first ingot in the subsequent pouring being confined within such superposed uiold and permitted to solidify in conjunction with the first-poured metal. In lieu of the above means of retaining the displaced fluid metal the top of the larger mold may be provided with a lateral spout for directing the overflow into an additional niold or a ladle placed under the spout to receive it.

My improvement will be understood by refereiice to the annexed drawings, in which Figure 1 is a central vertical section of the large mold filled with fluid steel. Fig. 2 is a similar view of the same with a smaller mold placed thereon, illustrating the pouring of the subsequent charge and its physical effect upon the steel in the larger mold. Fig. 3 is a view similar to Fig. 2 of the original and superposed molds, but showing both filled with metal; and Fig. 4 is a plan of the same. Fig. 5 is a vertical elevation of a large mold provided with a spout for leading away the overflow from the second pouring. Fig. 6 is a seetional elevation similar to Fig. 3, but showing the smaller mold at one side of the largerwith the spout shown in Fig. 5 leading thereto; and Fig. 7 is a view similar to Fig. G, with the smaller mold replaced with a ladle to receive the displaced fluid steel.

In Figs. l to 4, inclusive, a is the larger mold, shown herein with the stand a and tapered upwardly, with a contracted mouth a2 at thetop. l) is a smaller mold of the ordinary tapered form, provided with the bottom flange b', Secured upon the mold ci. The flange b' is provided on opposite edges With slots c to receive the eyes e upon top of the mold a, through which are inserted keys d to fasten the molds together. A ladleZ is shown conventionally in Fig. 2 with a stream m2 of molten metal discharging through the mold Z1 into the fluid core ot' the steel m inthe original mold a.

The molten steel displaced from the lower mold into the superposed mold is by the abovedescribed method of operation disturbed before segregation has occurred therein to any considerable extent, and as the su perposed mold is of much smaller area than the original mold it is evident that the steel in this upper mold will solidify before the process of segregation can progress further to any injurious degree therein. When the upper mold becomes filled, the contents of both molds are permitted to cool and solidify in conjunction, and by making the smaller mold about the diameter of the core in the larger mold the steel in the two molds is perf'ectly united without any cold-shut, although the constitution of the casting in the smaller mold is somewhat different from that `in the larger. The smaller ingot is, however, readily eut from the larger one, which is then found of homogeneous constitution throughout.

The metalloids may appear in greater proportion in the smaller ingot; but owing to the admixture of new steel with that swept from the core beneath such proportion need not render the smaller ingot `useless for certain purposes, and the process thus corrects the tendency to segregation in the larger ingot without incurring any waste of steel whatever.

The smaller mold would be of dimensions in which segregation could not occur by reason of the rapid cooling, and the small ingot, as well as the large one, would thus be of homogeneous character, although slightly different in constitution from the larger or main ingot.

In Figs. 5 and G a spout s is shown applied to the top of the large mold a and provided with a clay lining s to protect the saine from the molten steel as it rims through the same. The smaller mold b is shown placed at the side of and slightly below the larger mold a to give ICO IIO

it a convenient position to receive the overow m3 from the larger mold during the second pouring of iiuid steel. The ladle Z is suspended a suitable distance above the larger mold a to give the steel poured therefrom the required head to penetrate the fluid core of the ingot m sufficiently to perform its function, as above described.

In Fig. 7 the construction and arrangements of the several part-s of the' apparatus are precisely the same as in Fig. 6, except that a ladle Z is substituted for the smaller mold b to catch the overflow m3.

It will thus be seen that the correction of the defect in the main in got is a wholly distinct matter from the mere preservation of the second charge of steel in the form of a smaller ingot, as the prevention of the segregation is possible Withoutthe use of a second or superposed mold and without retaining the second charge in any special receptacle or form.

A superposed mold is preferably employed only for convenience in utilizing the second charge in ingot form, which may be worked into any articles to which its constitution is adapted.

It has been foundin practice that the amount of segregation which takes place in molds less than twenty inches in diameter is inconsiderable, as the 'timev required for the crystallization of the steel is insufficient to permit an extensive separation of the metalloids therein from the mother metal; but in ingots of larger measurements this separation invariably occurs. It is therefore evident that in an ingot-mold thirty inches square the steel may be allowed to solidify in a shell of approximately ten inches thickness around the same, leaving the remaining molten core approximately ten inches diameter, as indicated by the dotted line m in Fig. 2 of the drawings, to be replaced, as above described.

I am aware that sink-heads have been applied to molds to hold a supply of metal to feed the internal shrinkage; but as such sinkheads are filled atthe same time as the mold the sink-head has no effect whatever in preventing segregation.

It is essential to the practice of my invention that the cooling of the ingot should precede the supplying of the second charge of steel in a considerable degree to fix positively the constitution of the mass of the ingot and to leave only an uncrystallized center, which when replaced with fresh steel is below the dimensions in which segregation can occur.

From the above description it will be seen that my process is intended especially for the production of ingots of large diameter and is wholly unsnited for making ingots of small dimensions.

Having thus set forth the nature of my invention, what I claim is- The method of casting ingots, which consists in, irst, filling the mold with a charge of fluid steel; second, pausing and allowing the ingot thus formed to partially cool, as described, and, third, pouring steel homogeneous with the first charge into the central iuid portion ofthe ingot, and thus displacing the same by a fresh supply of iuid steel, substantially as herein set forth.

In. testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

WILLIAM R. HINSDALE.

Witnesses:

GEo. C. MILLER, HENRY J. MILLER.

Images