US2941266A

US2941266A - Continuous casting process and apparatus

Info

Publication number: US2941266A
Application number: US645085A
Authority: US
Inventors: Ostermeyer Gunter; Wittmoser Adalbert; Kaufmann Robert
Original assignee: Eisenwerke Gelsenkirchen AG
Current assignee: Eisenwerke Gelsenkirchen AG
Priority date: 1956-03-15
Filing date: 1957-03-11
Publication date: 1960-06-21
Anticipated expiration: 1977-06-21
Also published as: CH348242A; NL212789A; FR1169042A; BE553248A; NL104710C; DE1070787B

Description

June 21, 1960 G. OSTERMEYER El AL 2,941,266

CONTINUOUS CASTING PROCESS AND APPARATUS Filed March 11, 1957 9 Sheets-Sheet 1 l5 fl 4 {i 15 7.9

Invenfor-S? June 21, 1960 Filed March 11, 1957 G. OSTERMEYER EI'AL CONTINUOUS CASTING PROCESS AND APPARATUS I]: HH M H 9 Sheets-Sheet 2 Inventors 0 June 21, 1960 G. OSTERMEYER ETAL 2,941,266

CONTINUOUS CASTING PROCESS AND APPARATUS Filed March 11, 1957 9 Sheets$heet 3 A 7 June 21, 1960 G, OSTERMEYER ETAL 2,941,266

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commuous CASTING PROCESS AND APPARATUS Filed March 11, 1957 9 Sheets-Sheet a jm emor'a M 0% WWW W/TW 'MdM June 21, 1960 G. OSTERMEYER ETAL 2,941,256

CONTINUOUS CASTING PROCESS AND APPARATUS Filed March 11, 1957 9 Sheets-Sheet 7 CONTINUOUS CASTING PROCESS AND APPARATUS Filed March 11, 1957 .9 Sheets-Sheet 8 June 21, 1960 a. OSTERMEYER ETAL. 2,941,266

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United States Patent CONTINUOUS CASTING PROCESS AND APPARATUS Giinter Ostermeyer, Ditzingen, near Stuttgart, and Adalbert Wittmoser and Robert Kaufmann, Gelsenkirchen, Germany, assignors to Eisenwerke Gelsenkirchen Aktiengesellscliaft, Gelsenkirchen, Germany Filed Mar. 11, 1957, Ser. No. 645,085

Claims priority, application Germany Mar. 15, 1956 9 Claims. (Cl. 22-573) The present invention relates to a process and ap-- paratus for continuously casting articles.

More particularly, the present invention relates to a process and apparatus for continuously casting'elongated hollow tubular articles which have at one end a trans verse dimension greater than the transverse dimension of the remainder of the article. y

In the art of continuous casting 'ofelongated hollow articles such as pipes and the like, special problems arise in the casting of articles of this type which are provided at one end With a larger transverse dimension'than the transverse dimension of the remainder of the article. For example, it is necessary with many types of pipes to cast at one end thereof either an outwardly extending annular flange or the interior diameter of one end of the hollow pipe must be larger than the internal diameter of the remainder of the pipe. On the one hand, it is necessary for the tubular article being cast to be moved downwardly with respect to an inner core member as soon as the inner surface of the cast article hardens sufficiently to hold the molten metal in the interior of the cast material, since otherwise the material of the cast article will shrink onto the inner core member to prevent sliding of the cast article with respect to the core member and to give rise to faulty castings which may be considered only as waste material. On the other hand, the thicker lower end portion of such a cast article as well as the weight of the molten material over the lower portion of the cast article requires a fairly long time for the lower end portion of the cast article to harden sufficiently to permit movement of the cast article with respect to the mold parts. These conflicting requirements render the molding of articles of this type very inconvenient and difficult to carry out properly.

One of the objects of the present invention is to provide a process and apparatus according to which it is possible to continuously cast articles of the above type in an efficient, convenient manner.

Another object of the present invention is toprovide a process and apparatus which make it possibleto cast articles of the above type in a simple Way and with a relatively simple apparatus.

A further object of the present invention is to provide a process and apparatus capable of accomplishing the above objects and at the same time capable of maintaining the best possible pouring operations.

With the above objects in view, the present invention mainly consists of a process for continuously casting an elongated hollow article having at one end a transverse dimension greater than the transverse dimension of the remainder of the article, this process including the step of maintaining the surface level of a material poured into .an annular space between an inner core member and an outer mold member at a substantially constant elevation with respect to the inner core member while lowering the outer mold member with respect to the inner core member 7 lowering means cooperates with the ring and mold mem-,

i with additional objects and advantages thereof, will be ble ring limits the bottom of the annular space and en-- gags the core member and the mold member, and a her for lowering the ring and mold member until the mold member reaches a normal position with respect tothe core member at which the transverse dimension of the cast article located beyond the end thereof of relative- 1y large transverse dimension is formed between .the outer:

mold member and the inner core member.

' The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a fragmentary, partly diagrammatic sectional, elevational view of an apparatus according to the present invention capable of carrying out the process of the present invention, the parts being shown in Fig. l in the position which they take at the beginning of the casting process just before the lowering of the outer mold member;

Fig. 2 shows the structure of Fig. 1 after the outer mold member has reached its lowest position;

Fig. 3 shows a still later stage in the process illustrated in Figs. 1 and 2;

Fig. 4 is a partly fragmentary, diagrammatic sectional, elevational view of another embodiment of an apparatus according to the present invention adapted to perform a process according to the invention for making a different type of article, the parts being shown in Fig. 4 at the position which they take at the start of the process;

Fig. 5 shows the structure of Fig. 4 at a later stage in the process;

Fig. 6 is a partly diagrammatic, fragmentary, sectional, elevational view of still another embodiment of an apparatus according to the present invention, the parts being shown in Fig. 6 in the position whichthey take at the start of the process;

Fig. 7 illustrates a later stage in the process carried out with the apparatus of Fig. 6, Fig. 7 showing how the cast article moves downwardly with respect to the outer mold;

Fig. 8 shows a still further stage in the process where the outer mold has moved downwardly to its lowermost position; and

Fig. 9 shows a stage of the illustrated in Fig. 8.

According to the embodiment of the invention which is illustrated in Figs.1-3, a stationary pouring platform 1 is formed with an opening which is bridged by a framework 2 which carries a rigid hollow tubular member 3 which in turn carries at its lower end an inner core member 4. With this construction the inner core member 4, which has a vertical axis, remains stationary. .The core member 4 is of a frusto-conical configuration and diminishes in cross section toward its bottom end.

The bottom portion of the member 3 which is located above the core member 4 carries and turnably supports 'a sleeve which is fixed to members extending radially outwardly from the sleeve, these members fixedly carrying at their outer ends an annular channel 5 whichis supplied process subsequent to that Patented Juneau 1.960

Wifli t moltn m al .a d which. ha t bQt Wall formed with suitable openings through which the molten metal falls. The molten metal flows from a suitable ladle or the like along a pair of channels @which are supported hya structure not shown in thedrawing; and these chanchannel about the axis of the core member 4. The

hollow tubular member 3'is divided in its interior by a partition which directs cooling water downwardly into the hollow core member 4 and upwardly away from the core member 4, and the cooling water is supplied to the hollow member 3 by a conduit 8 and is carried away from the hollow member 3 by a conduit 9. These conduits may be in the form of stationary pipes since elements '1-4 remain stationary.

The apparatus also includes an outer mold member 10 which is coaxial with the core member 4 andwhich is hollow and water cooled, suitable bafllcs. being located within the mold member 10 for directing the cooling liquid therethrough. The mold member 10 includes an upper portion 11 which has an inner diameter whichcooperates with the core member 4 to provide the cast article with its normal thickness and diameter. The lower part 12 of the outer mold member 10 is of a larger diameter than the upper portion 11 and has a length which gives to the cast article the desired larger transverse dimension of one end thereof. Also, the portion 12 extends through the desired axial distance. I

The outer mold member 10 rests upon an outwardly extending flange 14 of a vertically movable ring 13 which is carried by a tubular carrying body 15, the, latter being in turn carried by a vertically movable table 16 which is moved up and down in any suitable known way with a structure not shown in the drawings. At the beginning of the casting process (Fig. 1) the upper portion of the ring 13 closes the bottom end of the annular space defined between the inner core member 4 and the outer mold member 10, and the inner periphery of the ring 13 has a sealed sliding engagement with the outer face of the core member 4 at a part of the latter located just beneath an upper zone thereof, and the ring 13 also has a fluidtight engagement with the outer mold member 10.

At the beginning of the process of the invention the outer mold member 10 is raised to such an elevation that the top end of the core member 4 as well as the channel 5 located over the core member 4 are Within a lower or intermediate portion of the mold member 10 which surrounds the core member '4, as is evident from Fig. 1.

After the pouring of the molten material has started so that the surface level 17 of the molten material has reached the elevation shown in Fig. 1, the table 16 is lowered so that the ring .13 and mold member 10 also move downwardly, and the elevation of the surface level 17 of the molten material is maintained substantially constant and at the same part of the core member 4.

During this downward movement of elements 10'and 13, the workpiece 18 (Fig. 2) hardens-while the workpiece 18 slides downwardly along the core member 4 andwhile the workpiece 18 remains stationary with respect to the outer mold member 10. Because of the frusto conical configuration of the core member 4, the hardening workpiece can shrink without resistance at its solidified inner surface, while the outer thicker end portion of the work-. piece is still surrounded and retained within the outer mold member 10 during the initial part of the downward movement of the latter and the ring 13.

After a certain periodof' time'flle. bottom face Qfihe 4 outer mold member 10 engages a stop ring 19 which is adjustably carried (in any suitable way) by the pouring platform 1 in the opening thereof through which the ring member 13 passes and into which the mold member 10 extends. For example, the ring .19 may be threadedly connected to the platform 1 in this opening thereof. Upon engagement of the bottom face of the mold member 10 with the stop ring 19, the downward movement of the mold member 10 terminates, and Fig. 2 shows the position which the parts take at this point in the process.

At this time the outer mold member 10 has reached its normal position with respect to the core member 4, and at this normal position the workpiece 18 will have elements 1% and 4 form the part thereof of lesser transverse dimension which is located beyond the bottom end portion of the workpiece 18, as viewed in Fig. 2. The further stages of the continuous casting process are carried out while the outer mold member 1% remains stationary, as is evident from Fig. .3. The cooling water may be fed to the interior of the outer mold member 10 through telescoped tubing 20 and may be carried away from the interior of the hollow outer mold member 10 by the telescoped tubing 21, as is also shown diagrammatically in Figs. 1'3.

According to the embodiment of the invention as shown in Figs. 4 and 5, a water cooled hollow outer mold member 22 is provided at its lower end with a configuration which will give the workpiece-the desired increase in diameter at one end portion thereof. The embodiment of Figs. 4 and 5 includes a hollow inner core member 23 which its water cooled and which is carried by a member 24 which is substantially identical with the element 3 described above. This element 24 is supported in the same way as the element 3, and the hollow member 24 serves in the same way as element 3 to lead the cooling water to and from the core member 23. The lowering means which includes the table 25 carries a hollow support member 26 which in turn carries the vertically movable ring 27 provided with an annular projection 28 which extends in a fiuidtight manner into the interior of the bottom end portion of the hollow mold member 22. Furthermore, the ring 27 is fixed at its inner periphery to an upwardly extending tubular member which cooperates with the upper face of the ring 27 to support an inner movable core member 29, this member 29 moving vertically with the ring 27. A stop 32 which may have its elevation adjusted in any known way is carried by the pouring platform. Except for the above features, the embodiment of Figs. 4 and 5 is the same as that of Figs. 1-3.

Before the beginning of the casting process with the embodiment of Figs. 4 and 5, the ring 27 is raised with a respect to the core member '23 to an elevation which places the top end of the core member 29 just below the upper zone of the core member 23 at which the surface level 30 of the molten material is maintained during the continuous casting process.

After .the molten material has been poured into the apparatus shown in Fig. 4 and the surface level 30 of the molten material is at the elevation shown in Fig. 4, the molten material being poured from a channel 31 identical with the channel 5, the table 2.5 is lowered together with the support 26 as well as the ring 27 and the outer mold member 22, while the liquid level 30 is maintained at a substantially constant elevation, and at this time the pouringofthe'portion of the workpiece of normal cross sectiontakesplace. During this downward movement. of the outer mold member together with the ring 27, the inner surface of the workpiece shifts downwardly with respect to the inner core member 23, and the downward movement of

elements

22 and 27 commences immediately after the moltenmaterial has reached the surface level shown in Fig. 4, so that the solidifying workpiece-can shrink without resistance.

Arte: the outer mold member 22 has been lowered to extent which the surface level of the molten material in the outer mold member 22 at an elevation with respect to the latter which is normal tor the continuous casting process, the downward movement of this mold member is stopped by the stop ring 32, so that during the continuous downward movement of the table 25 only the ring 27 with the

portions

28 and 29 earned thereby continue to move downwardly.

In the example illustrated in Figs. 4 and 5 the mner core member 29 is made of a material which simply breaks up during the inner shrinking of the work material. However, where an inner mold member similar to member 29 is made of metal, and in this case the inner surface of the .cast article would not be threaded as shown in Figs. 4 and 5 but would instead be smooth, then such a core member must be moved downwardly out of the workpiece with a separate unillustrated mechanism as soon as the inner surface of the workpiece hardens sufficiently and before any shrinking takes place, so that in this way a metal core member will not be gripped by the shr1nking workpiece, as for instance it is described in U.S. patent application No. 404,679, now Patent No. 2,829,407.

According to the embodiment of the invention which is shown in Figs. 6-9, wherein only the most important parts are designated with reference characters, the parts take the position shown in Fig. 6 atthe beginning of the casting process, and it will be noted that in this position the outer mold member 33 is elevated to a relatively high elevation with respect to the inner member 34. The

vertically movable ring, together with thetubular carrying body (not shown in the drawing) closes the bottom of the annular space defined. between the outer mold member 33 and the inner core member 34.

The vertically movable table 38 is connected to a hyd'raulic cylinder 39. The piston rod of this cylinder, in

turn, is connected to the vertically movable ring 35,v

able table 38 and which can unimpededly move between the stop dogs 42. 1

After the thicker bottom portion of the workpiece 36 is poured and the surface level 37 of the molten material has reached its normal elevation with respect to the inner core member 34, in accordance with the present invention after the outer portions of the thicker bottom end of the workpiece 36 have solidified, at first the ring 35 alone is lowered by means of the cylinder 39 and the piston rod 40. As is shown in Fig. 7, that lowering can continue until the thicker end of the workpiece 36 has moved out of the part of the outer mold member 33 which controls the shape of this end of the workpiece, the outer mold member 33 remaining stationary at this time.

Then, whilst the piston 40 in the cylinder 39 remains stationary the vertically movable table 38 moves downwards simultaneously with the vertically movable ring 35, and the outer mold member 33 together with the workpiece 36, which is now building up. That lowering continues until the upper portion of the outer mold member with normal transverse dimension 33 reaches the normal elevation with respect to the surface 37 of the molten material, which is maintained at a substantially constant elevation, and the end of the downward movement of the outer mold member 33 is shown in Fig. 8. That downward movement of member 33 is limited by its resting on the stop dogs 42, so that the outer mold member33 is no longer in contact with the supports 41, as is shown in Fig. 8. the outer mold member 33 moves downwards need not correspond to the speed of the downward movement of the vertically movable ring 35 and that of the workpiece 36 which it carries. Thus, the speed of the downward movement of the mold 33, in accordance with the requirements; of a particular casting process, can be reduced. his an b bt n hatthe eed of w n t a Incidentally, the speed with which 38' and the outer mold member 33 'is for example'only half the speed of downward movement of the movable ring 35 with workpiece 36, it being understoodthat the piston 40 and the movable ring 35 additionally move towards the table 38 also at half speed.

As is shown in Fig. 9, during the continued downward movement of the vertically movable table 38 the mold' 33 maintains its lowermost elevation.

The following explanations are given in connection with the process featured in Figs. 6-9, and are typical of a casting operation under the present invention:

Ari elongated hollow piece of gray iron was cast, having a length of 2150 mm., an internal diameter of 750 mm., the external diameter of the upper portion of the, workpiece with normal transverse dimension being 930 mm. and the outwardly extending flange cast thereto having an-outside diameter of 1000 mm. and a thickness of mm. The temperature of the molten metal, when being poured, was 1320" C. When a period of 2 minutes from the commencement of the pouring had elasped the surface of molten iron had reached the level 37 shown in Fig. 6. As from that moment the vertically movable ring was being lowered by means of the cylinder 39 and the piston 40 at a speed of 120 mm. per minute. After, a *fiurther minute the vertically movable table 38 wasv moved downwards at a speed of 120 mm. per minute, so that both the vertically movable ring 35 and the outer mold member 33 moved downwards at a speed of 120 mm. per minute. When a further minute had elapsed,-

cooling water put through the cooling system was 1500 litres per minute, and the time required for the complete casting process was 19 /2 minutes.

In all oft-he above described embodiments it is important that relative movement between the workpiece and inner core member take place during the solidifying of the workpiece. Also, a part of the casting process may be carried out in such a way that the workpiece remains during part of the process stationary with respect to the outer mold member.

It will be noted that by maintaining the surface level of the molten material substantially constant during the entire process and at all times at a predetermined part of the inner core member, the hardening characteristics of the workpiece remain substantially constant and the workpiece cannot shrink onto the inner core member. Furthermore, with the process and apparatus of the invention the work material at the enlarged bottom end of the workpiece is stressed to the smallest possible degree and remains for only a short period of time in engagement with the outer mold member so that the danger of cooling the" work'material at too great a rate with the undesirable properties resulting from such cooling are avoided. Thus, with the process and apparatus of the invention it cannot happen that the bottom end portion of the workpiece remains in engagement with the cooled outer mold member for a length of time sufficient to carry away so much heat that flaws such as the formation of cracks or the like take place. Also, in the 'case of cast iron, the workpiece willnot have at its outer surface an extremely hard zone which makes further machining of the workpiece difiicult.

It will be noted that with the above-described structure the outer mold member is; made of one, piecej A1- thouglrlthisconstruction is preferred, it isnot absolutely". essentiahand. the upper portion ofthe outer mold mem-s beriwhichlisiofl normal cross section may be made separateofromthe lowerportion of the mold member which: has the enlarged cross sectioni- It-is possible to make this lower enlarged portion of the outer mold member in the form of a member integral with the vertically movable.

ring, for example, andof course with such a construction'the upper part of the outer mold memberflwould move downwardly-with the ring through the desired dis-' takesplace with respect to the inner core member, while a part ofthe process may include practically no relative movement between the outer mold member and the workpiece because of the lowering of the outer mold member with the workpiecetso that this part of the process is similar to stationary casting with respect to the outer mold member.

mold member also.

' dtis also possible to maintain the outer mold member stationary at all times. and instead of moving theouter mold: member downwardly, it is possible to provide an arrangement where the inner core member moves up wardly together with the annular channel from which themetal pours into the annular space between the inner core member and theou'ter mold member, and with such an arrangement'the surface level of the molten material moves upwardly with the inner core member and remains stationary with respect thereto. With such an arrangement, after the upward movement of the inner core member has stopped, thenormal continuous casting process follows;

It is' also possible to use the process of the invention in an arrangement where'a conventional continuous casting takes place at the beginning of the process and where the features of the invention are then used to provide a workpiece with a thicker wall portion which extends through'a desired axial length along the workpiece.

It should be noted that if the molten material is poured into the annular space between an inner core member and an. outer mold-member which initially have a position such as that shown in Fig. 2, for example, then during the time that the surface level of the molten material rises to the desired elevation there is a great danger of thenlow er portion of the material hardening sufficiently to shrink tightly ontoth'e inner core member. With the process of the invention the work material starts to move downwardly along the inner core member immediately'after the work material firstengages the core member, sothat the work material does not remain in engagement with the core member while the surface level of the work material rises. Because of the tapering of the core member and because of the continuous downward movement of the work material with respect to the core member thework material can shrink without any danger of seizing the core member.

It will'be understood that each of the elements described above, or two or more together, may also find a useful: application in other types of continuous casting processes differing from the types described above.

While the invention has been illustrated and described as embodied in a process for continuously casting articles having at least one enlarged end,'it is not intended to be limited tothe details'shown, since various modifications and structural changes may be made without departing in any way-from the spirit bf-the'present invention.

Without further-analysis, the foregoing will so fully re- Of'course, after the outer mold. member-has stopped movingdownwardly the continuous J castingprocess takes place with respect to the outer veal the gist of the present invention that others can by applyingkcurrent knowledge readily adapt'i't forvarioi s" application without omitting features that, from the" standpoint-of -prior art, fairly constitute essential characteristics. of the generieor specific aspects of this invention :and, therefore, such adaptations shouldandare intended to he comprehended within the meaning and range of equivalence of the following claims. a

' What is claimed as new and desired to be secured by Letter'sPatentis'f 1; In a process for continuously casting an elongated hollowbody having at one endof-dirnension larger than attire remainder of said body, -the step of pouring a molten material into an annular space between an inner coreiand' anou-ter mold member while maintaining the surface of the molten material in'said space at a substantially constant elevation slightly below the top surface of sa-id' core member andwhile changing the elevation of the surface level of the molten material with respect to the outer mold member only in a direction which places the surface of the molten material in said space in contact with'a part of the inner surface of the outer mold member higher than a part of said inner surface previously in engagement with thesurface of the molten material.

2.. In a process for continuously casting an elongated hollow body having at the end portion of the'hollow body which is cast first a larger transverse dimension than at the remainder of said body, the steps of pouring molten material which solidifies upon cooling into an annular spacedefined between an inner core member and an outer moldmember and limited at its bottom by a substantially vertically movable ring; maintaining the inner core member stationary and the surface level of the molten material substantially stationary with respect to the inner core member while'simultaneously moving said ring and outer mold member onlyin downward direction relative to said core member to .move the solidified portion of the material relative to the inner core member so as to prevent shrinkage of the solidified material onto the core member;-

stopping the lowering of said outer mold member after the-latter has reached an'elevation with respect to said core member which provides the hollow body with a solidified portion of smaller transverse dimension beyond said end portion thereof, while continuing the lowering ofsaid ring.

3. In' a process for continuously casting an elongated hollow body having at its end portion which is cast first a transverse direction greater than the transverse direction ofthe remainder of the hollow body, the steps of starting the process'by pouring molten material capable of solidifyingupon cooling into an annular space-defined between an inner core member and an outer mold member and limited at its bottom by a substantially vertically movable ring, while maintaining the inner core member stationary and'moving the outer mold member together with the ring only in downward direction relative to said core member and while raising the surface level of the molten material to a predetermined normal part of the core member and thenmaintaini'ng the surface level substantially at the elevation of said predetermined part of said core member; and then stopping the lowering of said outer mold memher after it reaches an elevation with respect to said inner core" member which provides the hollow body with a solidifiedportion of lesser transverse dimension located beyond'saidend'portion thereof, while continuing to lower saidringr 4. In a hollow body continuous casting process which includes. in part -the lowering of an outer mold member with respect to an inner core member, the step of startingthe process by positioning the outer mold member and the innercore member at relative elevations which locate the inner core member within the outer mold member at an elevation with respect to said outer mold member which islbwer than an elevation of said core member in which the top 1 of said ou-ter mold member is substantially 9 flush with the top surface of said core member by an amount substantially equal to the extent through which the outer mold member is lowered during the casting process.

-5. In a continuous casting apparatus, in combination, an inner stationary core member; an outer mold member coaxial with said core member and having a bottom end portion substantially beneath the top of said outer mold member, said bottom end portion surrounding an upper portion of said core member and defining an annular space therewith; a ring closing the bottom of said annular space, said ring surrounding and engaging said core member and also engaging said bottom end portion of said mold member; and means for lowering said ring and outer mold member with respect to said core member from a position in which said ring is located at a part of said core member just beneath the part thereof where the liquid level of the molten material is maintained during the continuous casting.

6. In a continuous casting apparatus, in combination, an inner stationary core member; an outer mold member coaxial with said core member and having a portion substantially beneath the top of said outer mold member surrounding an upper portion of said core member and defining an annular space therewith; a mold ring closing the bottom of said annular space, said mold ring surrounding and engaging said core member and also engaging a lower part of said outer mold member so that said mold member rests on said ring; means operatively connected to said mold ring for lowering said mold ring and said outer mold member resting thereon with respect to said core member from a position in which said ring is located at the part of said core member just beneath the part thereof where the liquid level of the mold material is maintained during the continuous casting; and a stop ring located beneath said mold member for engaging and stopping the downward movement thereof while said mold ring continues to move downwardly.

7. In an apparatus as recited in claim 6, said outer mold member having a lower portion of a larger diameter than the remainder of said mold member above said lower portion thereof and said stop ring being located at an elevation which stops the lowering of said outer mold member when a part of the inner surface of said mold member above said lower portion thereof is located at the elevation of a part of said inner core member at which the surface level of the molten material is maintained during the continuous casting.

8. In an apparatus for continuously casting an elongated hollow article, in combination, an inner stationary core member having a substantially vertical axis; an outer mold member coaxial with and surrounding said core member and defining an annular space therewith, said mold member having a lower end portion of a larger interior diameter than the remainder of said mold member; a ring surrounding and slidably engaging said core member and engaging the bottom end of said mold member so as to support said mold member; means for lowering said ring and said mold member supported thereon with respect to said core member along the axis of the latter; and stop means located in the path ofdownward movement of said mold member for limiting the downward movement thereof while permitting further downward movement of said ring.

9. In an apparatus as recited in claim 8, said ring having a tubular member fixed to its inner periphery and surrounding said inner core member, said tubular member extending from the top face of said ring upwardly along said core member; and a second core member engaging the outer face of said tubular member and the upper face of said ring for defining the inner surface of a cast article at an end portion of the latter which is carried by said ring during the casting process.

References Cited in the file of this patent UNITED STATES PATENTS 2,130,202 Tama Sept. 13, 1938 2,367,123 Hopkins Jan. 9, 1945 FOREIGN PATENTS 179,615 Australia Sept. 25, 1954 877,940 Germany May 28, 1953