US1298035A - Method of teeming ingot-molds. - Google Patents

Description

E. GATHMANN.

METHOD 0F TEEMING INGOT MOLDS.

APPLxcATloN FILEDDEC. s, 191s.

Patented Mar. 25, 1919.

UNITED STATES PATEN noo EMIL GATHMANN, OF BALTIMORE, MARYLAND.

METHOD OF- TEEMING- INGOT-MOLDS.

Methods of Teeming Ingot-Molds, of which" the following is a. specification;

This invention relates to the casting of metal ingots or the like and particularly to the pouring or teeming of metallic ingot molds.

Heretofore the Common practice has been to teem a series of molds from a ladle of large size containing sufficient molten metal to fill a plurality of molds one after the otherand some attemptshave been made to fill two or more molds sin'iultaneously from the same ladle, but this latter method has not been successful inasmuch as often one mold was filled before the other or others owing to irregularities in the flow of metal through the passages leading from the ladle; therefore, the common practice is to lill the molds separately, the metal passing from the ladle through a valve-controlled nozzle in a large stream and with high velocity under the great hydraulic pressure of the large quantity of molten metal in the ladle. This stream of metal at first strikes the bottom of the mold chamber and often injures it and furthermore during the entire period of teeming the metal splashes violently causing it to mingle with air and to strike with great forceagainst the side walls of the mold chamber in such manner as to cut the mold walls and to cause the molten metal to weld to said walls and thus not only impede the proper shrinking of the ingot away from' said walls and also the easy stripping of the ingot from the molds but it often results in producing what are called cold Y shuts or scabs on the ingot which are serious defects that cannot be remedied by subsequent processes and often result in imperfeet products from the ingots.

It is also well known that during the teeming of a. mold the molten metal as it falls into the mold chamber is defiected and driven with considerable force against the side walls of the mold and a skin is formed on these walls above the level of the. more quiet metal in the mold. This skin is somewhat mushy or soft and often during the pouring of' the metal parts of it are out or broken away in an irregular manner leaving defects in the finished ingot. The difli- Speeication of Letters Patent.

Patented Mar. 25, 1919.

Applicationled December 6, 1918. Serial N o. 265,583.

culties above mentioned have long been recognized and attempts have been made to overcome them in various ways as by providing means for subdividing the stream of metal delivered by the ladle in such manner that the speed or momentum of the metal as it ent-ers the mold chamber will be reduced, the object Vbeing to reduce or prevent the formation of cold shuts or sca'bs and to otherwise remedy the difiiculties above mentioned. Mold teeming devicesof this class have, however, in all casesbeen inthe form of portable containers .whichwere interposed between the ladle proper and the top of the mold, the metal liowing freely from the nozzle of the ladle into the container which was provided with a plurality of openings through which the metal was delivered to the mold. In such cases the hydraulic pressure of the metal in the ladle was only used to force the metal through the outlet of the ladle, none of such pressure being utilized for forcing metal in a subdivided condition or with reduced velocity into the mold, therefore the speed of delivery was unduly .reduced and furthermore the metal was unduly cooled owing to the fact that it passed through an open air space between the nozzle and the perforated receptacle thereunder. In such cases also it was not possible to pass the molten metal uniformly through all of the openings or perforations in the receptacle and it was not ossible to regulate the flow of the metal tlirough said openings. Furthermore, owing to this irregularity in the flow of metal through the perforated receptacle the metalI often became thickened or mushy and some or all of the openings would be closed, therefore this method of pouring molds has never, so far as I am aware, been used, certainly its use has not been general.

According to my invention, I reduce the velocity without materially reducing the volume of metal discharged from the ladle into the moldand I utilize the hydraulic pressure of the mass of molten metal in the ladle to force the metal not only with sufficient velocity and with the required volume from the ladle but also to force it with reduced velocity and substantially the same volumeinto the mold chamber. In this way a much quieter pouring of the mold is effected without any loss of time. ably the solid stream of molten metal passing from'the ladle through the valve-con- Prefertrolled orifice is made to impinge upon a battling device arranged in a chamber which distributes or directs the molten metal with its high velocity thus modified to a series of discharge openings through which the metal passes in a plurality of relatively small streams each of which individually is of smaller cross section than that of the outlet opening of the ladle but which are collectively of greater cross section than said outlet opening. In this way the velocity or speed of the molten metal coming from the ladle is greatly reduced and vet the volume of metal passing from the ladle is not materially changed. Therefore the ladle can be emptied at the same speed as before but with the additional advantages above specified. Furthermore, the metal passing through the delivery openings is constantly under hydraulic pressure which insures the constant and unimpeded delivery of the metal, which has no chalice to cool or solidify in such manner as to delay the opera tion.

In carrying out my invention, I preferably employ a ladle or container of sufficient capacity to l'ill in succession a plu rality of molds and in the bottom of the ladle I provide an outlet opening controlled by a valve or stopper which may be of usual construction. The metal passes through the outlet opening in a relatively large stream but instead of passing directly into the mold as heretofore it enters what I call a distribution chamber of larger capacity than the outlet of the ladle and containing a battling device which receives the stream of molten metal, changes its velocity and deflects the metal or distributes it to a 'series of discharge openings through which the metal passes to the mold with reduced velocity but under hydraulic pressure and yet in such manner as to ,teem the mold in the required time without danger of the metal coolingor solidifying in the ladle before it is emptied. The metal is so delivered through the discharge openingsI that it enters the mold chamber in a much quieter manner than heretofore causing less boilingl or splashing and preventing the cutting or breaking of the mold walls or the .skin forming on the sides thereof and also preventing the wehling of metal to the niold walls which was` a serions defect in methods heretofore employed. Other featuresl of my invention will be hereinafter more fully described.

" In the accompanying drawings Figure 1 is a sectional view of a metallic ingot mold and a ladle forteeming the mold constructed in accordance with my invention.

Fig.

Fig. l.

Fi e'.

l2 shows a' section on the line 2 2 of A i, shows a section on the line 3 3 olI Fig. l.

upper portions than in their lower portions so that the formation of pipe in the ingot is reduced or eliminated in a manner now well known, but it will be understood that my invention may be applied to molds of other construction.

The ladle B is in gene-ral of well known construction except that. the devices applied to the outlet of the ladle are made in accordance with my invention. A s usual, the ladle comprises an outer casing or shell l) of metal and a lining Zi of refractory material, such as lire brick, and the ladle is provided wit-h ears b2 which may be engaged by suitable devices b3 for supporting the ladle and these devices may be connected with cranes or other mechanism for moving the ladle from place to place as desired. An opening fr is formed in the bott-om of the ladle and is preferably centrally located as indicate-d, and this opening' is controlled by a valve or stop-per B of well known construction which may be provided with any suitalble devices for operating it. The devices applied to the out-let opening constitute generally what may be termed a. nozzle. In liig. l this nozzle comprises av metallic easing D which may be detachably connected with the bottom of the ladle by bolts or other suitable devices d. This casing in-Y closes and supports a block E of refractory material. chanibered and provided .with passages for the mol-ten metal. The part Il projects into the opening and is suitably formed to provide a valve seat c for the valve or stopper B. Below the valve seat there is a passage of relatively large cross section through which 'the molten metal passes from the ladle and this may be termed the outlet of the ladle. Said passage f delivers to a chamber (l, the preferred form of which is clearly indicated in Fig. l Aot the drawings and is also indicated in otiher figures. This chamber I call the distribution chamber inasmuch as it divides the stream of .metal flowing through the. passage f and directs the metal .to a plurality of delivery openings g eac-h of which is of smaller cross section than the outlet opening f. lPreferably these passages g are arranged in an annular series and while each one is of less cross sectional area than the passage f collectively their cross sectional area is much greater; preferably about 50% or more greater. lVithin the distribution chamber is located a baliiing device H, formed from the block E which assists in distributing or directing the metal to the discharge .openings g and which also receives the full force or impact of the stream of metal passing from the ladle. and serves to reduce its velocity while at the same time defiecting the metal in the manner before specified. Y

Nhile the velocity of the metal passing through the outlet openings g is greatly reduced it is forced through the outlet openings by the great hydraulic. force or Ipressure of :the mass of metal in the ladle, this pressure being sufficient at all times lto deliver the metal with such speed as to prevent the cooling of the metal or the solidifying thereof before it. is discharged into the mold chamber. As before stated l prefeably divide the stream of 4metal passingl from the ladle into a yplurality of relatively small streams arranged in an annular series but it is not necessary that. said openings should be so arranged, and the number of such openings is not essential so far as some features of .my invention are concerned, it being important in th-is connection merely to so reduce the velocity of the metal passing from the ladle and before its entry into the mold chainlber that it shall not injure the walls of the mold or cut away or injure -t-he skin of the ingot during its process of formation. It is important, however, in this connection, for the reasons Abefore stated, that the metal shall be forced With reduced velocity by the hydraulic pressure of molten inet-al in the ladle and that the passage of a relatively large solid stream of molten metal from the ladle to the mold should be avoided. y

'I he passages for the metal from the ladle to the mold are preferably all formed in a single block E of refractory material, as illustrated in Fig. 1, and the Walls of these passages are so disposed as to avoid the formation of shoulders or corners which would unduly impede the flow of the metal through the nozzle. Preferably an annular series ot discharge openings are provided but these passages need not necessarily be arranged in an annular series and furthermore they ,may be merged and a Similar result obtained, 'l'. e. the single solid stream ot' metal will be so changed as to reduce the velocity .of the metal entering the mold and furthermore the force or impact ot' the metal will be reduced or distrilmted, resulting in a much quieter pouring opera-tion without any loss of time in filling the mold.

I preferably so proportion the cross sectional area of the passages or channels in the nozzle that the combined areas of the discharge openings are larger by approximately 5,0% or more than that part ot' the nozzle which connnunicates directly with the ladle. l may therefore use any desired number of discharge openings in the nozzle so long as they are of' such size when combined as to reduce the velocity of the metal passing through the nozzle without materially decreasing the volume of metal delivered during any period.

It will be observed by reference to Fig. l that the solid stream of metal passing through the opening f is enlarged into a substantially cylindrical or hollow body of metal entering the mold, and while several distinct streams of metal are included in this cylindrical body it is obvious that they may be merged and yet produce a satisfactory result because in either case the velocity of the metal entering the mold is reduced, the impact of metal on the metal in the mold is distributed and the violent disturbances heretofore encountered are avoided. Furthermore, the direct impact of the metal passiing from the ladle. is received by the baffling device in the distribution chamber. This serves also to reduce the. velocity of the metal and yet it doesl not impede ther volume of metal delivered by the nozzle.

The. size or cross sectional area of the intake passage in the nozzle is in present practice, as is well known, usually made as small as will, with the required factor of safety, drain the ladle of its molt-en liquid burden of metal within the time period necessary to teem or east a certain number of ingots.-y

Forexample, a ladle filled with a burden of 50 tons of steel should be fitted with a discharge opening of 2 inch diameter for filling each of ingot molds in succession with 2 tons of mol-ten steel; the' time of teeming or casting each individual ingot being approximately one minute, the actual pouring period is '25 minutes, the ladle or the molds being moved into teeming or casting position for each ingot made; one-fifth of a -ininute or collectively 5 minutes being taken for thus filling a group of 25 molds. By experiment it has Ibeen found that a ladle with a burden of 50 tons of molten liquid steel will retain the steel in its molten condition if placed inthe ladle at auitable temperature from the mel-ting furnace for a period of from 35 to 45 minutes. a factor of safety as to the time of' teeming or casting through a 2 inch nozzle from 5 to l() minutes is thus obtained. The importance ot' not unduly increasing the time offteeming or casting the burden of molten steel from aladle will thusl be understood from the example above explained. and it will also be understood that it iS impossible or improper to greatly decrease the volume or weight of metal teemed from the ladle within a specified time. A nozzle made in accordance with my invention is adapted to be firmly fixed or secured to the ladle while the latter 1s empty 4and reasonably cool. A new nozzle is required for every second to sixth heat of the molten metal carried by the ladle, the life of the nozzle depending considerably upon the grade of metal being cast, its temperature and other factors well known to those skilled in the art so that the nozzle as a whole, while adapted to lbe firmly secured to the ladle, is detach-ably connected therewith.

The ladle equipped with a nozzle made in accordance with my invention is operated in precisely the same way as those usually employed, the stopper B being made to control the delivery of the metal from the ladle. As the molten metal enters the mold that portion which comes in contact with the relatively cool inclosing mold walls and stool very rapidly frozen or solidified into a Semisolid or mushy condition forming what is termed the relatively thin skin 'of the ingot within which the inner body of the ingot later on solidifies or freezes. As the pouring operation continues and the interior of the ingot is formed the skin gradually thickens and becomes more solid and strong. The vertical walls or initial skin of the ingot grow as the ingot increases in height and although the-se walls are semi-solid they are extremelytender or in a mushy state due to the intense heat of the still liquid interior mass ofthe ingot. It is extremely imporant and well known to those skilled in the art that this skin of the ingot should not be disrupted or broken as such breaks of the mushy skin or semi-solid skin will not properly healer close and if breaks or cracks are once formed they usually remain as surface defects in otherwise sound, homogeneous in gots or in the finished produc-t.

I have found that one of the primary causes of such surface defects in ingots is due to the improper teeming from the ladle to the mold of a solid stream with high velocity which may in a great way be remedied by more quietly and gently delivering the liquid metal into the mold cavity than has heretofore been done.

It is known that liquid steel weighs approximately one-quarter pound per cubic inch, and the cross section of a two-inch stream of liquid steel passing from a two inch nozzle will thus weigh S14-ltimes l2 25 per foot of height or approxiniately l0 pounds. As the ladle is frequently filled with l0, 1Q or more feet depth of steel a pressure inthe nozzle from 100 to 125 pounds per stream area at the nozzle is common practice. As iron ingot molds are of considerable height, say from f3 toV 8 feet an additional weight of from (l0 to 8O pounds `is imparted to the descending column of the highly heated liquidv steel. The impact, of this mass of liquid steel is taken, first by the stool or bottom closure of the mold and second by the body of liquid steel which has already entered the mold and which forms the impacting cushion as the ingot grows or increases in size in the mold cavityv lic pressure caused therebyis brought under' control by my improvements in which I suitably proportion the discharge area of the nozzle to the area of the outlet passage from the ladle.

For example, if the outlet from the ladle has a cross section of two square inches and the delivery openings have a cross section of four square inches and assuming the velocity of stream flowing through the outlet of the ladle as l0 feet per second the same volume or amount in weight of metal will flow through the four square inch delivery openings at a velocity of 5 feet per second, provided of course the direction of the steam from the inlet to the nozzle is first diverted by means of a batiling device or by` means of a distribution chamber having a larger cross sectional area. The actual impact value of a 5 foot per second and a l0 foot per second stream is obviously as 5 squared is to l0 squared or as l is to l for the same volume or weight of the metal stream.

Fig. l indicates how the mushy skin is formed in the mold and this is incident to all casting operations of `the kind to which my invention relates. Where the velocity of the metal entering the mold is reduced in the manner before described, and especially where the solid stream is divided into a plurality of streams, as indicated inthe. drawings, the breaking down or injury to the skin is avoided or greatly reduced. As indicated in the drawings, where a plurality of streams are employed they are preferably so located as to be grouped around the longitudinal axis of the mold because a direct impact of even a relatively small streaiu would injure or break through the mushy walls or skins while the ingot is in process of formation. Direct impact or even dcfiected impact of a single large stream with the walls of the mold cavity either above or below the mushy skin of thc ingot during the process of ingot formation is also liable to cause serious defects in the walls of the ingot such as the formation of cold shuts or even actual welding of the ingot surface at various points to the mold walls thus preventing the ingot from freely shrinking during the cooling or solidication thereof and consequently causing tears or cracks in the surface of the skin of the ingot.

It will be observed that the discharge openings or passages g are arranged vertically and should be at least approximately vertical in order that the streams of metal entering the mold shall be delivered in a substantially vertical direction. were not so the metal Would strike against the sidewalls of the mold and defeat the objects of my invention, for the reasons hereinbefore explained. v

In the drawings, I have assumed t-hat the cross sec-tional area of the'passage f has a diameter of tWo inches, While the discharge openings g are each one inch in diameter so that the cross sectional area of the. resulting discharge opening is double that of the outlet opening f, but as before explained this relative arrangement is not essential but it is important that the area of discharge from the nozzle should be greater than the area of the entrance thereto.

My invention involves not only improvements'in the method of teeming molds but it also involves improvements in the apparatus therefor which are claimed in my application for Patent No. 265,582, tiled De- Cember 6, 1918.

I claim as my invention:

l. The method herein described of teeming an ingot mold from a ladle or container of molten metal, which consists in passing molten metal from the ladle With a definite volume and velocity and in delivering the metal to the mold under the hydraulic pressure of the metal in the ladle with the same volume but at reduced velocity in an approximately verti-cal direction to avoid -contact With the side Walls of the mold chamber.

2. The method herein described of teeming an ingot mold from a ladle containing` molten metal and provided with a delivery nozzle, ivhich consists in forcing the molten metal into the nozzle by the hydraulic pressure of the metal in the ladle and in delivering the metal in a substantially vertical direction under hydraulic pressure with reduced velocity but with equal volume from said nozzle to the mold.

3. The method herein described of teem- If this ing ingot molds, which consists in forcing proximately vertical direction from a ladle through a plurality of openings under reduced pressure into a single mold chamber.

4. The method herein described of teeming ingot molds from a ladle or container of molten metal from a delivery nozzle, which consists in passing molten metal from the ladle into the nozzle under the hydraulic pressure of the metal in the ladle, subdividing the stream of molten 4metal entering the nozzle into a plurality of streams and in causing said streams in such divided condition to pass directly and vertically from the nozzle to a mold chamber.

r5. The hereindescribed method of teeming an ingot mold from a ladle or container of molten metal, which consists in passing a volume of molten metal from the ladle under hydraulic pressure in a solid stream of relatively large cross sectional area and with a relatively high velocity and in delivering the metal to the, mold in an approximately vertical direction while still under hydraulic' pressure and- With the same volume but with a materially greater cross sectional area and therefore with a materially reduced velocity.

6. The hereindescribed method of teeming an ingot mold from a ladle or container of molten metal, which consists in passing a. volume of molten metal from the ladle under the hydraulic pressure of the metal in the ladle in a solid stream of relatively large cross sectional area and ivith a relatively high velocity and in delivering the metal to the mold While still under hydraulic pressure in substantially. the same volume but in a plurality of approximately vertical streams each of which is of materially smaller cross sectional area than the volume of the metal passing from the ladle,

but which collectively are of materially great-er cross sectional area in order to deliver the metal-to the mold at a materially reduced velocity.

In testimony whereof I have hereunto subscribed my name.

EMIL GATHMANN.

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