US2030199A - Mold extension for ingot molds - Google Patents

Description

Feb. 11, 1936. w. M. CHARMAN 2,030,199

MOI-JD EXTENSION FOR INGOT MOI-IDS Filed May as, 1952 2' Sheets-Sheet 1 Ame-Mme.- MzmeMWm/v ArraeuErs Feb. 11, 1936. w. M. CHARMAN 2,030,199

MOLD EXTENSION FOR INGOT MOLDS Filed May 23, '1932 2 Sheets-Sheet 2 Mzrze/Ifmemw Armewsrs Patented Feb. 11, 1936 UNITED STATES PATENT OFFICE 2,030,199 MOLD EXTENSION FOB INGOT MOLDS Walter M. Char-man, Cleveland Heights, Ohio Application May 23, 1932, Serial No. 613,006

2 Claims. (01. 22-147) This invention relates to mold extensions for ingot molds.

Open or rimmed steel and semi-killed steel are terms applied to steels which are not fully de- 5 oxidized. As a result of the carbon monoxide and other gases contained within such steels, they do not remain quiet after being teemed into the mold, but are subject to considerable agitation. As a result of this agitation the tendency 10 to form pipe around the axial line of the ingot is absent except at the upper end of the ingot for a short distance downwardly from the top. Cooling takes places at the surface of the ingot very rapidly and the bubbles of gas which form there 15 do not have time to work their way out of the heavy viscous liquid into the more fluid liquid nearer the center of the mass. As a consequence these bubbles are trapped a short distance beneath the surface and result in what are termed 20 blow-holes. These blow-holes do not always weld up completely when the ingot is rolled into blooms, but in certain classes of materials where a high strength-weight ratio is not essential, imperfections due to blow-holes are not serious un- 25 less the blow-holes run out at the surface of the ingot permitting oxidation. In addition to the sub-cutaneous blow-holes just mentioned there may be a second set of blow-holes located further inward toward the axis of the ingot and extend- 30 ing practically its entire length. The metal surrounding such blow-holes is little subject to oxidation, however, and hence such blow-holes cause no great amount of damage.

It has been common to produce rimmed steel 35 or open steel in big end down molds, partly because the top of the ingot contains segregation and some shallow piping frequently, and is otherwise unusable and must be cropped off, and if the cross-sectional area is large, as it would be in a big end up mold, a given depth of cropping will remove a greater weight of metal, and of course it is economical and necessary to preserve as much metal as possible.

The common practice, as stated above, of pro- 45 ducing rimmed steel or semi-killed steel in big end down molds has been due principally to the fact that the advantages of producing these steels in big end up molds have not been ap-- preciated, while the difliculty of getting such in- 50 guts out of the molds has also been a factor. In.

furnish a convenient means for enabling the 55 ingot to be grasped by handling tongs, Further.

more, until quite recently the steels produced in big end down molds were of a quality good enough to satisfy the requirements of the trade. Now however, under the existing conditions of present day steel fabricators requirements, the steel comnames are having greater dlfiiculties every day in marketing rimmed steel produced in the old manner. It is the purpose of my invention to provide economical means and methods for the production in big end up molds of rimmed or open steel and of semi-killed steel. The slightly increased cost in the production of big end up ingots of these steels by my method over the cost of big end down ingots is quite trivial, when the manifold advantages, including increased yield and improved quality, are considered.

In a big end down mold the metal does not rim in as well as in a big end up mold, and blowholes occur nearer to the surfaces of big end down ingots than where the same steel is cast in big end up molds, due to the fact that the contained gases can more easily escape during the rimming and solidification of the ingots, and due to the progressive freezing of the ingot from the bottom upward. However, the latter disadvantage is generally considered to be overcome by the advantage of cropping at the small end of the ingot. Furthermore, the stripping of an ingot from a big end up mold presents practical difiiculties owing to the fact that, thereis no upwardly projecting part of the ingot which may be grasped by tongs or the like. In ingots made from fully deoxidized steel or killed steel this difliculty is not encountered, because such ingots are poured in molds provided with hot tops, which are used in order to maintain a supply of molten metal available to flow down and fill the pipes or shrinkage cavities which form around the axis of the ingot. When the metal in the hot top finally hardens it constitutes an extension of the 40 ingot projecting above the mold, and is available as a projection which may be grasped by a crane in the stripping operation.

One of the objects of the present invention is the provision of apparatus for making rimming or semi-killed steel ingots with a relatively thick skin and with blow-holes positioned well beneath the surface, which shall result in an ingot having a small upper end to be cropped, and which shall provide an upper extension for the ingot adapted to be grasped by a handling crane, characterized by the fact that provision is made for releasing the extension should internal pres sure exceed a predetermined amount.

Other objects and features of novelty will appear as I proceed with the description of those embodiments of the invention which, for the pur-- poses of the present application, I have illustrated in the accompanying drawings, in which Figure l is a vertical central sectional view of a mold and mold extension with an ingot therein.

Fig. 2 is a vertical sectional view of one form of mold extension in position upon an ingot mold.

Fig. 3 is a bottom plan view of the same.

Fig. 4 is a view similar to Fig. 2 but showing a different form of mold extension.

Fig. 5 is a vertical sectional view of a big end down mold embodying certain features of the invention.

Fig. 6 is a top plan view of the same, showing means for locking the mold cap in place.

Fig. 7 is a detailed side view of a hOld-rdOWIl. employed in this form of the invention. I

Fig. 8 is a view partly in section upon the line 8-8 of Fig. 7, and

Figs. 9 to 12 inclusive are diagrammatic illustrations of successive steps in the rolling out of an ingot made in accordance with my new method of casting, showing how the formation 01 fishtailing with consequent loss of steel is avoided.

In the drawings I have shown atill an ingot mold of the big end up type, that is one in which the ingot cavity tapers toward the lower end. While in some of its aspects the invention is not necessarily limited to the use of a big end up mold, one of that character is preferred for-reasons which will presently appear.

Big end up molds have seldom been used for open or rimming steel for two reasons, first because the removal of the ingots from the molds is diflicult, and second because the discard metal at the top of the ingot which must be cropped off is at the point of largest cross-sectional area of the ingot and therefore involves the loss of more metal than when the big end of the ingot is down. I propose to overcome both of these difficulties by necking in the upper end of the ingot, so that a projection is formed which may be grasped by tongs when the ingot is to be stripped from the mold, and so that the segregation occurs within the necked-in portion of the ingot, thereby reducing considerably the mass of the metal removed by cropping. Since the solidification of the ingot takes place from the outside inwardly, there is also less danger of trapping gases within the lower part of the ingot when In order to neck in the upper portion of the ingot as above stated, I employ a mold extension which may take different forms. Some of these forms are illustrated in the drawings. These extensions may be and preferably are rather heavy. They may or may not be tied down to the mold.

In Fig. 1 the extension is numbered II. It fits upon the top of the mold and has a lip I 2 ex tending downwardly into the mold and fitting closely against the inner wall of the same. The wall of the extension is made thick so as to give it considerable weight and therefore enable it by the action of gravity to resist the tendency of the ingot to grow, but instead of making the extension heavy, or in addition to making it heavy, I may employ hold-downs for this purpose. As 11- lustrated in Fig. 1 the extension H may be provided at suitable intervals, as for instance at every or point, with pairs of cars or projections l3 between "which may be pivotally mounted hold-down hooks M, the lower ends of which are adapted to take under shoulders IS on the mold Ill. The detailed construction of these hold-downs will be referred to again, in connection with the description of Figs. '7 and 8, where similar hooks are shown in inverted relation. Just outside the depending lip I2 01 the extension I provide a shoulder l6 which is preferably machined to receive a gasket I], see'Fig. 5, interposed between the mold and the extension for the purpose of preventing the flow of molten metal outwardly between the mold and extension when the extension is locked down in place.

" In connection with this form of the invention I have shown a mold cap l8. This cap may be held against upward movement by a locking bar l9 taking under overhanging retainers "embedded or cast into the extension ll The particular character of this cap retaining means is illustrated somewhat more in detail in Fig. 6.

In the form of the apparatus shown in Figs.

2 and 3 the mold extension comprises a metal casing 26 having an internal ledge 21 at its lower end extending entirely around the casing. The casing has an internal wall which is preferably vertical. preferably made of metal, are mounted within the casing and are preferably so fitted together as to require no fastenings. This is accomplished by inclining the edges of the members 28 and 29 towards each other at the top, and by beveling the side edges along planes through the axis-of the extension. Hence the facing members 28 and 29 when assembled in the casing are wedged in place and cannot be dislodged without inverting the casing. Spacing blocks 30 may be secured to the casing opposite the members 28 if desired, in which case the latter members are assembled first and the members 28 inserted later in a lengthwise direction from the top of the casing. The members 28 and 29 are of course supported by the ledge 21. Between the casing 26 and the facing members 28 and 29 a space is provided, through which air may circulate, entering through holes 3| in the casing near the lower end thereof and leaving through holes 32 in the upper flanges of the facing members. By this means the casing is protected more or less from the heat of theingot, and its life accordingly lengthened.

The lower end of the extension is of a size and form which permits it to extend into the mold, a

where it is adapted to be supported by means of wooden blocks 33 which are engaged by trunnion bosses on the sides of the casing.

In order to close the space surrounding the extension within the mold walls and to provide means to dam the flow of molten metal upwardly through this space I may provide a relatively thin metal strip 34 extending in one or more pieces all the way around the mold extension. This strip is somewhat flexible in order that it may engage the inclined mold wall regardless of the distance to which the extension may be caused to enter the mold. Other means for damming the flow of metal may be employed however without departing from the spirit of the invention in its I broader aspects.

Below the lower end of the casing 26 and below the lower ends of the facing members 28 and 29 I mount a bottom facing which consists preferably of a one-piece ring 35 of metal, refractory A series of facing members 28 and 29,

- material, or other heat resisting substance. The

upper outer edge of the ring may be rabbeted to receive the strip 34, which is thus gripped between the rlng 35 and the lower end of the casing. The ring 35 may be supported .in various ways, but I prefer to suspend it against the casing by means of spring clamps 36 having short angular ends adapted to be mounted in holes made in the outer surfaces of the casing and having their opposite extremities formed to'spring into small notches in the inner surface of the ring 33. The strips 34 are notched at the proper places to receive these clamps and enable the latter to lie close against the outer surfaces of the casing and ring. When the clamps are snapped into position the ring 35 is held in place securely. However, the clamps 35 are designed to fall after theingot I is poured, when the mold extension is strippedfrom the ingot, if the ingot and ring tend to stick together. In that event the ring remains on the ingot, and a new one is mounted on the extension before the next heat is poured.

In Fig. 4 a mold extension 31 is employed which is somewhat similar to that of Fig. l, but instead of resting upon the top of the mold it is designed to extend down into the mold in which position it is supported by means ofwooden blocks 33 in the manner referred to in connection with Figs. 2 and 3. v In this form of the invention also a metal strip 39 is employed to dam the flow of molten metal upwardly around theoutside of the mold extension. It consists in this case of one or a plurality of sheet metal pieces of angle section so as to fit around the lower corner of the extension, each piece having an upper flange adapted. to wipe against the mold wall as the extension is lowered into the mold. These strips 39 may be removably supported by means of spring clamps 40 which are arranged more or less reversely to the clips 35 of Fig. 2, that is to say, they have angular ends 400 fitting into substantially vertical holes in the extension 31 and knuckles 30b at their opposite extremities adapted to snap into sockets formed in the exterior wallof the extension. In connection with this modification of the invention, I have illustrated means, such as a steel strap 4 I, for preventing the extension 31 from rising above a predetermined point when the ingot grows due to the formation of gas bubbles. This strap, or its equivalent, ex tends across the top of the extension and downwardly on either side thereof, being secured at its lower ends either to the mold or to the stool upon which the mold is supported. In the latter event, a heavy pressure may be exerted upon the ingot in its formation stage, that is after the blocks 38 have been removed, by exerting a lifting effort upon the mold 10 through any suitable mechanism.

As previously stated, I prefer to employ the invention in connection with big end up molds, but it is also applicable to big end down molds, and is illustrated in connection with a mold of that character in Figs. 5 to 8 inclusive of the drawings, where the mold, shown at 5|, is open at its lower end and mounted upon a mold stool v52. The latter is provided with pairs of upstanding ears 53, which are perforated to receive frangible pins 54 having tapered portions 55 intermediate their ends. Each of these pins is adapted to be projected through the round perforations in'the ears 53 and through a somewhat elongated opening 56 in a hold-down hook 51, which is adapted to take over projecting shoulders 58 on the sides of the mold ii. The driving of the tapered portion of pin 54 into the opening 55 serves to pull the hook 51 taut against the sholuder 53 The hold-down hooks of Fig. 1 are similarly constructed and similarly operated.

An extension 53, similar in form and function to the extension ll of Fig. 1, is mounted on the upper end of the mold. It has a depending lip l2 and agasket ll, similar to the corresponding parts in Fig. 1. The extension is intended to be positively locked to the mold, and to that end the mold may be provided with pairs of ears 60. Between the ears of each pair there is pivoted an eye bolt ii that is adapted to be swung up through a slot in a lug 5,2 projecting outwardly from the extension 39. When the bolts are in the latter position their nuts 53 may be tightened down. of course it will be apparent that holddowns with frangible pins similar to those used at the bottom of this mold or at .the top of the mold in Fig. 1 might be employed instead of the bolts 5|, if desired, or the bolts 5i themselves may be so designed as to fail at a predetermined strain.

In this form of the invention, as well as in that shown in Fig. 1,- I may employ a mold cap I8,

4 As previously stated, the solidification of the metal along the walls of the mold is quite rapid, and the gases formed in this portion of the ingot while the metal there is still viscous have difllculty in working their way out into the'more fluid metal at the interior. In the prior methods of casting rimming or semi-killed'steel into ingots, many of these gas bubbles are trapped close to the surface of the ingot and form large blowholes grouped to closely resemble a honeycomb, and in many instances these honeycomb areas of theingot make their presence known by means of small pin holes in the outer surfaces of the ingot. Such honeycombing runs inwardly sometimes anywhere from a depth of two to three inches, there being only a very thin paper-like wall between adjacent blow-holes. Of course the contained gas has escaped through the pin holes in the thin outer surface and has permitted the surfaces of the-blow-holes to become oxidized,

preoludingany welding of the blow-holes together upon being crushed during the rolling or forging .of the ingots. This would cause defects in semi-finished steel, such as for example sheet bar, billets or the like, and therefore necessitates the rejection and-scrapping of the whole ingot. Of course this difliculty would extend, where one ingot was bad, to' all like ingots, and many times this would necessitate therejection of whole heats of. steel, which may represent anywhere from ten to seventy-five ingots in present day steel plant practice.

One of the important features of my invention is the reduction or practical elim nation of blowholes near the skin of the ingot. which result I accomplish by causing forces evolved in the formation of the ingot to exert pressure upon the 1 metal along the walls of the mold, thereby forcing' gases out of that metal tow'ard the-center of the ingot. The blow-holes occurring in an ingot cast by my-method are therefore deepseated, do not oxidize, and cause little if any harm- The pressure necessary to accomplish this highly desirable result is engendered in the ingot 'itself when the latter begins to .grow, tending to lift the mold extension. Such pressure works against the action of gravity upon the relatively heavy mold extension or against the tie-downs for the mold extension, or against both of these means taken together.

When an ingot has been cast in either a big end up or a big end down mold, represented generally by the disclosures in Figs. 1 and 5, the ingot gradually rims in, and when it has. cooled to the proper extent, the cap it is placed inside the mold extension M or 59, as the case may be, and looked down by the locking bar US. If the gas pressure evolved within the ingot, either before or after the placing of the mold cap in position, should become excessive, there would be danger of the mold or the exmnsion bursting and permitting hot metal to be thrown about. In my construction however this is prevented by the use of the frangible pins Ed in the hold-downs, which are so designed as to fail at a predetermined strain well below the maximum strain which the remainder of the apparatus can safely carry.

I In the use of apparatus such as is disclosed in Figs. 2 and 3 and in Fig. 4, the metal is poured while the extensions are supported upon the blocks 88 or 38, as the case may be. When the metal begins to solidify these blocks are knocked out and the extensions are permitted to float upon the ingot.

When an ingot has been cast in accordance with the method herein described, and stripped from the mold, it may have a form somewhat as shown in Fig. 9, the neck portion 42 containing all oi the unusable part or the metal, except a small portion at the lower extremity of the ingot. The next step is the formation of the ingot into a bloom or a forging. In the former case this is accomplished by giving it numerous passes between rolls to reduce the cross-section and increase the length, while in the latter case, it is accomplished. by forging the ingot under presses or hammers into a forging having proper dimensions for rolling into the semi-finished product. When an ingot produced by the old conventional method is thus rolled, the reduction takes place throughout the length of the ingot, and some good metal is rolled out over the piping and segregation area, producing what is known in the art as fish-tailing". All of such metal must be cropped off before the bloom can be used. It will be readily seen that this method now in general use entails a considerable percentage of loss in yield of sound steel from the ingot, and the larger the ingot, the more pron ounced is this loss, especially where the ingots are reduced to relatively small sections or blooms.

Where the unusable metal is carried into the neck 42 however, as in my method, the mils 43 and 44 which are used for the first few passes do not touch the neck 42. Fig. 10 indicates the condition a little later in the rolling process, showing that the rolls have reduced the cross-section of the ingot somewhat and increased its length, but practically all of this reduction and lengthening has taken place-below the neck 42, which is still practically unaffected by the rolls 45 and 46. Fig. 11 shows a further reduction and lengthening without materially affecting the neck, the movement of metal being nearly all away from the neck, and the rolls 41 and 48 still spaced further apart than the diameter of the smaller portion of the neck. In Fig. 12 the bloom is shown completed by rolls 48 and 50, and the neck 42 is rolled down to smaller section and greater length, and whatever small quantity of fishtail is present is included entirely within the necked in portion 42, which must be cropped of! for remelting.

From the above description, it is now readily apparent that one of the outstanding features of my invention is the prevention of the formation of blow-holes and imperfections near the surfaces of open or rimmed and semi-killed ingots by means of pressure exerted at the right times and places during the transition of ingots from the molten to the solid state, so as to force the foreign materials from the outer portions of the ingot inwardly and to facilitate the escape of the entrapped gases into the more fluid portionof the ingot, and thus facilitate their escape out through the upper extremity of the ingot, enabling the producer of big end up ingots to receive and retain. the full benefit of increased yield, due to much less necessary bottom cropping oi the ingot, and through the constricting of the unusable portion at the upper end of the ingot into a smaller mass, referred to herein as the neckedin portion, thus relieving the manufacturer of having to forfeit the advantage gained by increased yield atthe bottom of his ingot, to greater loss in yield in the necessary cropping of the upper portion of the ingot, as he would otherwise have to do.

The invention also permits the easy extraction of the big end up ingot from the mold, which would otherwise have had to be accomplished through the turning of the ingot mold upside down to drop the ingot out, or else through some expensive means of pushing the ingot up from the bottom of the mold in such manner as might be necessary in order to permit the grasping of the ingot by some suitable crane tongs. This also permits of the entire elimination of what is commonly known as the stripper crane, a very elaborate mechanism which is generally installed and housed, at great expense, since the ingot may be removed directly from the big end up molds in one operation by soaking pit cranes and placed directly in the soaking pitwhere they receive their uniform heating prior to rolling, which is of course necessary in any event.

In my method heavy fish-tailing is largely eliminated with consequent saving in yield and scrap loss. This new method, because of the superior quality of the rimmed or semi-killed steel that may be produced by its employment, permits the use of such steels for purposes for which killed steel only was formerly considered suitable. Killed steel necessitates the use in its production of expensive deoxidizers, such as aluminum, silicon, manganese or the like. Furthermore, the presence of these deoxidizers is objectionable in steels used for some purposes, where they must be subjected to deep drawing for instance. Hence steel produced by my method is not only less costly, but actually superior to killed steel for some purposes.

It has been quite generally known for a number of years that killed steel ingots produced in big end up molds are far superior in quality, as regards soundness and surface, to those produced in 7 big end down molds, and with the advent of my method, it is now possible for manufacturers to have only one type of equipment where they formerly had to have two types and all the attendant handling and control apparatus, since the molds which I prefer to use in my method are the molds quite generally now in use for the production of killed steel ingots only.

Having thus described my invention, I claim:

1. In apparatus for casting undeoxidlzed or semi-deoxidized steel ingots, an ingot mold, a heat dissipating mold extension adapted to be temporarily supported upon the upper end of the mold during the teeming and solidifying of the metal, and frangible means for tying the extension to the mold to prevent upward movement, said frangible means being adapted to fail at a predetermined internal mold pressure less than bursting pressure, said mold extension having an average internal cross-sectional area less than that of the upper end oi the mold, and having a lower end wall engaging the metal of the ingot adjacent the inner wall 01' the mold, whereby the extension has the capacity to resist the tendency of the ingot to grow at the rim.

2. In apparatus for casting undeoxidized or semi-deoxidized steel ingots, an ingot mold, a heat dissipating mold extension adapted to be temporarily supported upon the upper end of the mold during the teeming and solidifying of the metal, frangible means for tying the extension to the mold to prevent upward movement, said frangible means being adapted to fail at a predetermined internal mold pressure less than bursting pressure, said mold extension having an average internal cross-sectional area less than that 01' the upper end of the mold, and having a lower end wall engaging the metal of the ingot adjacent the inner wall of the mold, whereby the extension has the capacity to resist the tendency of the ingot to grow at the rim, a mold cap, and releasable means carried by the extension for holding the cap in the extension.

WALTER M. CHARMAN.

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