US3907023A

US3907023A - Process for starting an operation to continuously cast metal rod

Info

Publication number: US3907023A
Application number: US381965A
Authority: US
Inventors: Larry D Frus
Original assignee: Stoody Co
Current assignee: Stoody Co
Priority date: 1973-07-23
Filing date: 1973-07-23
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

A starting process is disclosed for a system in which molten metal flows from a reservoir into a cooled forming die from which externally-solidified incremental lengths of metal are drawn to produce a continuous integral shape, e.g. rod. A starter length of hollow material is positioned in the forming die to receive the initial flow, which develops a tapered liquid-solid interface with the starter length. Externally-solidified incremental sections may then be drawn or cast.

Description

'United States Patent [191 Frus [ 1 Sept. 23, 1975 I PROCESS FOR STARTING AN OPERATION TO CONTINUOUSLY CAST METAL ROD [75] Inventor: Larry D. Frus, Whittier, Calif.

[73] Assignee: Stoody Company, Santa Fe Springs,

Calif.

[22] Filed: July 23, 1973 [21] Appl. No.: 381,965

6,602,207 9/1966 Netherlands 164/83 Primary ExaminerJ. Howard Flint, Jr.

Assistant Examiner-Gus T. Hampilos Attorney, Agent, or FirmNilsson, Robbins, Bissell, Dalgarn & Berliner [57] ABSTRACT A starting process is disclosed for a system in which molten metal flows from a reservoir into a cooled forming die from which externally-solidified incremental lengths of metal are drawn to produce a continuous integral shape, e.g. rod. A starter length of hollow material is positioned in the forming die to receive the initial flow, which develops a tapered liquid-solid interface with the starter length. Externally-solidified incremental sections may then be drawn or cast.

10 Claims, 4 Drawing Figures VGA/TUE PUMP PROCESS FOR STARTING AN OPERATION TO CONTINUOUSLY CAST METAL ROD BACKGROUND AND SUMMARY OF THE INVENTION In general, difficulties encountered in continuouscasting processes include starting problems in addition to various production failures as by the billet freezing in'thc mold, breaking off, or the contents of the mold becoming molten, to result in an external flow of metal. In spite of such failures, continuous-casting processes have attained a relatively advanced state with regard to certain metals, e.g. aluminum and copper. However, efforts to continuously cast certain other metals (for example high'tcmperature metals) particularly in lengths of relatively-small sectional size, have contin' ued to present significant problems. One promising process has been developed wherein the rod or billet being cast is drawn in a reciprocating motion pattern to be developed as incremental sections. However, considerable difficulties have been experienced in starting the process in view of the various critical states that are involved. I

In general, the present invention is directed to a process for initiating a continuous casting operation. Specifically, the system of the present invention involves the use of a hollow or tubular seed or starting rod for accomplishing the critical starting condition that can be perpetuated to continuously cast. Additionally, the starting rod, or the like, isconditioncd as by an airstream to avoid such problems as condensation.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which constitute a part of this specification, an exemplary embodiment exhibiting various objectives and features hereof is set forth, specifically:

FIG. I is a diagrammatic view of a casting system for use in accordance with the present invention; and

FIG. 2 constitutes a series of fragmentary sectional views through the die portion of the system of FIG. 1 which are illustrative of the process of the present invention.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT As required, a detailed illustrative embodiment of the invention is disclosed herein which is representative of the best mode within the purview of present knowledge for that purpose. The embodiment exemplifies the invention which may, of course, be constructed in accordance with other forms and steps, some of which may be radically different from those disclosed herein. However, the specific structural and process details disclosed are representative and provide a basis for the claims which define the scope of the present invention.

Reference will be made initially to FIG. I, for a consideration of a continuous casting process to which the present invention is applicable. There is shown a fur nace F for providing molten metal to a cooled die structure D. In the operation of the system, molten metal entering the die structure D is externally solidified (adjacent the die walls) so that it may be drawn in a rod form from the die structure D by a withdrawal roller mecha nism R. A drive unit U actuates the roller mechanism R in a manner so that the billet or rod B (or other de sired linear casting) is drawn from the die structure D in an intermittent-motion pattern. That is, a length of rod B which has been externally solidified in the die structure D is drawn in what might be termed a forward drawing or withdrawal stroke. Then following each withdrawal stroke, the roller mechanism R is actuated by the unit U to accomplish a reverse movement or abbreviated return stroke of the rod B to compensate for shrinkage resulting from solidification of the metal and to preserve the rod B integral so as to accomplish a continuous shape. The motion pattern of the rod B is critical and is one of the elements of accomplishing the desired integral product.

Considering the structure of FIG. 1 in somewhat greater detail, the furnace F contains a mass 12 of molten metal for supplying the desired continuous rod B. Specifically, the mass 12 is contained in a crucible 14 of refractory material which is somewhat upright and defines a bottom outlet passage 16 from which molten metal flows to develop the rod B. An induction coil 18 is provided about the crucible I4 and is connected, as well known in the art, to an electrical power source 20. of course, an external housing, as well known in the art, may be provided for the furnace F outside of the coil 18.

Molten metal flowing from the reservoir mass 12 through the passage 16 is received in a generallycylindrical casting cavity 22 of the die structure D. The cavity 22 is generally coextensive with the passage 16. As illustrated, the cavity 22 is concentric within a hollow annulus 24 through which coolant 26, e.g. water, is circulated. Specifically, an intake duct 28 receives coolant from a source (not shown) which coolant cir culates through the annulus 24 and exhausts through an outlet duct 30. Recognizing that a variety of specific arrangements and materials may be employed, in one embodiment the annulus 24 has been formed of an alloy that is primarily copper. Accordingly, hightemperature capabilities exist along with good heattransfer characteristics.

As indicated above, it is to be understood that the rod B is drawn in a continuous integral form section-bysection from the die structure D by engagement with a roller mechanism R including a pair of

pinch rollers

34 and 36. Of course, the

rollers

34 and 36 may be variously supported for rotation and in that regard, the roller 34 is driven while the roller 36 functions as a backup of idler. The roller 34 is connected (as indicated by a dashed line 38) to the drive unit U for accomplishing the desired reciprocating motion pattern. That is, the unit U actuates the roller 34 to draw a lengthof the rod B from the die structure D during a drawing stroke, then moves the rod B in a lesser reverse or return stroke to preserve integrity with the liquid phase and compensate for the shrinkage in the metal resulting from solidification.

In view of the above pertinent considerations, the system of the present invention may now be best understood by describing the sequence of the method. Accordingly, assume initially that the molten mass 12 has not yet been placed in the crucible I4 (functioning as in a holding furnace) or, alternatively, that in an alternate structure a gate (not shown) is closed, inhibiting the flow of molten metal through the passage 16.

Prior to the passage of molten metal into the casting cavity 22 (FIG. 2a) and in accordance herewith, a seed section or hollow elongated starting rod 40 is positioned in the die structure as illustrated. The rod 40, as indicated is an elongated member of uniform cross section and ideally comprises a composition that is compatible to that of the molten mass 12. That is, the two compositions (e.g. cobaltnickel alloy and stainless steel) should have good weld bond characteristics to effectively join together. One end 42 of the hollow rod 40 is positioned to lie well within the casting cavity 22 as illustrated. The passage 44 (through the rod 40) extends to an opposed end 46 which is received in a venturipump 48. A radial bore 50 is provided contiguous to the end 42 of the rod 40 in the cavity 22. A stream of air is drawn through the passage 44 (arrow 51) to avoid condensation of moisture in the die structure D and the tube 40, and to preheat these elements (die structure D and seed tube 40).

When the molten mass 12 (FIG. 1) attains the desired casting temperature, flow is initiated into the cavity 22 (FIG. 2a). At that time, molten metal enters the passage 44 (substantially cooler) and a liquid-solid interface is developed, resulting in a configuration that simulates a stage in the casting process, deemed to be somewhat as illustrated in FIG. 2b. Certain of the molten metal flowing into the passage 44 solidifies and is welded to the starter rod 40 while the rod also provides an' initial artificial metal skin 55 or solid exterior. It is also noteworthy that as the molten metal enters the starter rod 40, gases are permitted to escape through the bore 50 then serving as a venting port rather than as during the preliminary period when the function was to prevent condensation from taking place inside the die and reducing the temperature of the rod 40.

Considering the subsequent operation of the system,

a reoccurring cycle is performed to develop incremental lengths of the continuous integral rod B. Specifically, from the condition depicted in FIG. 2b, a length or incremental section 52 of externally-solidified metal is drawn from the casting cavity 22. Of course, the length 52 may vary in specific instances; however, it is generally less than the length of the casting cavity 22. The drawing stroke is indicated by an arrow 54 and is accomplished by the reciprocaldrive unit U (FIG, 1) and the coacting

pinch rollers

34 and 36. 7 At the conclusion of the drive stroke, a newly-formed incremental section 52 of the rod has been drawn from the casting cavity 22. Thereafter, the return stroke occurs during which the section 52 is moved in a reverse direction as indicated by an arrow 58 (FIG. which motion compensates for the shrinkage of solidification within the metal.

Although some fine-adjustment deviations may be desirable, the relationship of the drawing stroke to the return stroke is somewhat in the ratio of the volume of material drawn during a stroke, to the volume of the shrinkage for that volume of material upon solidification. Gcnerally, the cross section of the rod B may be considered to be substantially uniform. Consequently, the volume of the incremental section 52 provided dur' ing each drawing stroke is related to the length of the stroke. Accordingly, the length of the return stroke is generally adjusted to coincide to the volumetric change of the casting metal attendant solidification.

It may, therefore, be seen that the seed" tube or rod 40 as employed herein is effective to initiate a process which becomes continuous in the sense that lengths of metal are produced increment-by-increment, passing as a continuous length from a die structure. Of course, various specific techniques may be involved; however, the steps of the present invention are described above and afford a basis for the claims as set forth below.

What is claimed is:

1. A starting process for the continuous casting of a solid rod of metal, wherein a stream of molten metal is flowed into a casting cavity to be cooled therein for horizontal movement in an externally-solidified, continuous-length form through a passage from said casting cavity, comprising:

placing a hollow section of solid metal horizontally disposed in said passage from said casting cavity; releasing said stream of molten metal to provide an initial flow of said molten metal to enter said hollow section and become welded thereto; and

moving said hollow section of metal to withdraw out of said passage from said cavity along with metal from said stream, to begin said process for the continuous casting of a rod of solid metal.

2. A starting process according to claim I wherein said hollow section comprises an elongated member of substantially-uniform cross section.

3. A starting process according to claim 1 wherein said stream of molten metal and said section of solid metal are of compatible compositions.

4. A starting process according to claim I wherein said molten metal and said section of solid metal are of compositions having weld bond characteristics to join each other,

5. A starting process according to claim I further including the step of forcefully passing an airstream through a portion of said hollow section contiguous to said cavity and moving away from said casting cavity.

6. A starting process according to claim I wherein said hollow section of solid metal comprises an elongated hollow tubc defining a vent passage therethrough.

7. A starting process according to claim 6 wherein said vent passage includes a radial bore defined in said tube.

8; A starting process according to claim 7 wherein said hollow tube and said molten metal are compatible in that effective weld bonds exist therebetween.

9. A starting process according to claim 8 wherein said metal is moved from said casting cavity in discrete steps.

10. A starting process according to claim 1 wherein said metal is moved from said casting cavity in discrete steps.

Claims

1. A starting process for the continuous casting of a solid rod of metal, wherein a stream of molten metal is flowed into a casting cavity to be cooled therein for horizontal movement in an externally-solidified, continuous-length form through a passage from said casting cavity, comprising: placing a hollow section of solid metal horizontally disposed in said passage from said casting cavity; releasing said stream of molten metal to provide an initial flow of said molten metal to enter said hollow section aNd become welded thereto; and moving said hollow section of metal to withdraw out of said passage from said cavity along with metal from said stream, to begin said process for the continuous casting of a rod of solid metal.

2. A starting process according to claim 1 wherein said hollow section comprises an elongated member of substantially-uniform cross section.

4. A starting process according to claim 1 wherein said molten metal and said section of solid metal are of compositions having weld bond characteristics to join each other.

5. A starting process according to claim 1 further including the step of forcefully passing an airstream through a portion of said hollow section contiguous to said cavity and moving away from said casting cavity.

6. A starting process according to claim 1 wherein said hollow section of solid metal comprises an elongated hollow tube defining a vent passage therethrough.

8. A starting process according to claim 7 wherein said hollow tube and said molten metal are compatible in that effective weld bonds exist therebetween.