EP0363702B1 - Apparatus for continuous casting of metal strip - Google Patents

Apparatus for continuous casting of metal strip Download PDF

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Publication number
EP0363702B1
EP0363702B1 EP19890117471 EP89117471A EP0363702B1 EP 0363702 B1 EP0363702 B1 EP 0363702B1 EP 19890117471 EP19890117471 EP 19890117471 EP 89117471 A EP89117471 A EP 89117471A EP 0363702 B1 EP0363702 B1 EP 0363702B1
Authority
EP
European Patent Office
Prior art keywords
molten metal
pool
dams
pair
longitudinal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19890117471
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0363702A1 (en
Inventor
Takashi Yamauchi
Morihiro Hasegawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Nisshin Co Ltd
Original Assignee
Nisshin Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nisshin Steel Co Ltd filed Critical Nisshin Steel Co Ltd
Publication of EP0363702A1 publication Critical patent/EP0363702A1/en
Application granted granted Critical
Publication of EP0363702B1 publication Critical patent/EP0363702B1/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637—Accessories therefor
    • B22D11/064—Accessories therefor for supplying molten metal

Definitions

  • the present invention relates to an improvement in a twin roll continuous casting apparatus for continuously casting a metal strip directly from a molten metal such as a molten steel.
  • twin roll continuous casting apparatus in which a pair of internally cooled rolls having respectively horizontal axes and rotating in opposite direction to each other are disposed parallel to each other with an appropriate gap therebetween, a pool of molten metal is formed on the circumferential surfaces (the upper halves cylindrical surfaces in the axial directions) of the rolls above the gap and the molten metal is continuously cast into a metal strip through the gap while being cooled by the circumferential surfaces of the rotating rolls.
  • twin roll continuous apparatus applied to a case of continuous casting of steel to produce a steel strip directly from molten steel.
  • a pair of front and rear dams (referred to herein as “longitudinal dams") having their surfaces along the roll axes may be erected orthogonally to the side dams on the circumferential surfaces of the rolls so as to form a box-like pool for molten metal with the side dams and the longitudinal dams.
  • the box-like pool serves to prevent waves of molten metal in the pool from directly hitting the surfaces of the rolls, thereby preventing formation of wrinkles (called “molten metal wrinkles”) on the surfaces of the cast strip.
  • the molten metal stagnates at those comers of the pool, which are formed by the inside walls of the longitudinal dams and the surfaces of the rolls, where it is liable to be solidified forming so-called triple point shells on lower edges of the longitudinal dams, since it is cooled by both the longitudinal dams and rolls.
  • the triple point shells grow to a certain size, they drop from the longitudinal dams and are incorporated in surfaces of the strip being cast, causing defects of the product.
  • An object of the invention is to provide an improved twin roll continuous casting apparatus having a pair of longitudinal dams, which is capable of preventing formation of triple point shells and avoiding adverse affects of waves of molten metal, thereby ensuring a stable production of a strip of good quality.
  • An apparatus for continuously casting a metal strip comprises a pair of internally cooled rolls rotating in the opposite direction to each other and disposed parallel to each other with their axes held horizontal, and pairs of side dams and longitudinal dams for forming a pool of molten metal on the circumferential surfaces of the pair of rolls, said pair of side dams being disposed opposite to each other in a direction perpendicular to the roll axes with a space therebetween approximately corresponding to the width of a metal strip to be cast, said pair of longitudinal dams being disposed opposite to each other in a direction parallel to the roll axes, thereby continuously casting molten metal in the pool into a metal strip through a gap between the pair of rolls, wherein said pair of longitudinal dams are disposed with their bottom surfaces held slightly above the roll surfaces so that openings are formed between the bottom surfaces of the longitudinal dams and the roll surfaces and that during stationary running of the apparatus the openings are positioned at the level of the surface of molten metal in the pool, such that the metal partly fills said opening
  • the apparatus according to the invention further comprises a pouring device having an exhaling slit on the bottom for supplying molten metal through the slit to the pool which is disposed above the pool so that the slit is positioned above the surface of molten metal in the pool and extends parallel to the gap of rolls.
  • a pouring device having an exhaling slit on the bottom for supplying molten metal through the slit to the pool which is disposed above the pool so that the slit is positioned above the surface of molten metal in the pool and extends parallel to the gap of rolls.
  • reference numerals 1a, 1b designate a pair of internally cooled rolls rotating in the opposite direction to each other (the rotational directions of both rolls are shown by arrows) and opposed parallel to each other with their roll axes held horizontal.
  • Reference numerals 2a, 2b designate side dams slidably contacting respective side surfaces of the rolls, and 3a, 3b longitudinal dams disposed in parallel to the roll axes and perpendicularly to the side dams.
  • the bottom surfaces of the longitudinal dams and the surfaces of the rolls are substantially parallel to each other respectively with respective openings between them as described hereinafter in detail.
  • the respective longitudinal dams and the respective side dams contact each other so that leakage of molten metal be prevented.
  • the side dams may be of a type as disclosed in JP A 62-84,555 corresponding to US Patent No. 4,811,780, in which side dams are forcibly moved downwards while being abrasively worn by the rolls.
  • Fig. 1 depicts an example of the apparatus according to the invention, which is provided with a pouring device 4 for supplying molten metal to the pool defined by the longitudinal and side dams and the surfaces of the rolls.
  • Reference numeral 5 designates a surface level of molten metal in the pool, 6 a parent nozzle for supplying molten metal to the pouring device, and 7 a strip being cast.
  • Fig. 2 is a cross-sectional view of the apparatus of Fig. 1 taken along a plane perpendicular to the roll axes at the center of the rolls, showing the state of casting.
  • the pouring device is an intermediate vessel having an exhaling slit 8 on the bottom for supplying molten metal through the slit 8 to the pool, and is disposed above the pool so that the slit 8 is positioned above the surface 5 of molten metal in the pool and extends parallel to the gap of rolls.
  • the pouring device is located in position so that the direction in which the slit 8 extends is substantially in a plane which contains the narrowest gap 9 of the rolls 1a, 1b and is perpendicular to the surface 5 of molten metal.
  • the length of the slit 8 is preferably as close as possible to the length of the longitudinal dams (the distance between the side dams).
  • molten metal is continuously supplied through the parent nozzle 6 to the pouring device 4 at an appropriate rate to form a film flow of molten metal parallel to the inside surfaces of the longitudinal dams 3a, 3b, which falls through the slit 8 of the pouring device 4 in the pool at the central portion of the longitudinal dams (the position corresponding to the narrowest gap between the rolls 1a, 1b), thereby producing the strip 7 while maintaining the surface 5 of molten metal in the pool at a predetermined level.
  • Fig. 3 is an enlarged cross-sectional partial view of the longitudinal dam 3b and the surface of the roll 1b during stationary running of the apparatus. The same conditions symmetrically appear on the side of the longitudinal dam 3a, As shown in Fig. 3, the longitudinal dam 3 is disposed with the bottom surface 10 held slightly above the roll surface R so that an opening 11 is formed between the bottom surface 10 of the longitudinal dam 3 and the roll surface R and that during stationary running of the apparatus the opening 11 is positioned at a level of the surface 5 of molten metal in the pool.
  • the longitudinal dam 3 has an inside surface 12, an outside surface 13 and a predetermined thickness 14 therebetween
  • the bottom surface 10 within the range of the thickness 14 is formed a flat, preferably curved, surface corresponding the circumferential surface of the roll
  • the longitudinal dam 3 is disposed so that the level of the surface 5 of molten metal is positioned during stationary running of the apparatus between a level of an inside lower edge 15, defined by the inside surface 12 and the bottom surface 10, and a level of an outside lower edge 16, defined by the outside surface 13 and the bottom surface 10.
  • the apparatus is operated under such conditions that the surface 5 of molten metal in the pool is always positioned in the opening 11.
  • the longitudinal dam 3 is partly dipped in the pool with its inside lower edge 15 immersed in molten metal and stop waves on the surface of molten metal with its inside surface 12.
  • the outside lower edge 16 does not contact the molten metal entering the opening 11. If the clearance of the opening 11 is suitable, the molten metal in the opening 11 stationary forms a narrow round surface 17 which is uniform in the transverse direction (of the strip being cast) owing to a surface tension of the molten metal and the rotation of the roll 1.
  • the clearance of the opening 11 should preferably be from about 2 to 10 mm. If the clearance of the opening 11 is too small, the molten metal does not effectively enter the opening 11, and thus, the advantageous results of the invention cannot be enjoyed.
  • Figs. 4 and 5 show examples outside the scope of the invention.
  • the longitudinal dam 3 is erected on the circumferential surface R of the roll with the bottom surface of the dam slidably contacting the surface R, and the surface 5 of molten metal is positioned substantially above the above-mentioned slidable contact surface.
  • molten metal is liable to be solidified forming a so-called triple point shell 19 on the inside lower edge of the longitudinal dam, since it is cooled by both the longitudinal dam and roll.
  • the longitudinal dam 3 is disposed with a considerably large opening between its bottom surface and the roll surface, and so that the whole bottom surface of the dam 3 is submerged in the molten metal.
  • the casting is carried out under such conditions that the surface of molten metal goes beyond the outer lower edge 16 and reaches the circumferential surface of the roll outside the longitudinal dam 3.
  • the edge 20 of the surface of molten metal coming in contact with the circumferential surface of the roll does not become linear in the transverse direction of the strip (in the direction perpendicular to the plane of the figure) and looks something like side waves hitting something.
  • surface defects molten metal wrinkles
  • occurrence of such surface defects can be prevented, since a round edge 17 of the surface of molten metal, which is linear in the transverse direction of the strip, is formed in the opening 11 by the surface tension of molten metal.
  • Waves beating upon the inside surface 12 of the longitudinal dam 3 may be further minimized by providing the pouring device equipped with the exhaling slit 8 on the bottom in the manner as shown in Figs. 1 and 2, thereby eliminating or further reducing any surface defects caused by waving of the surface of molten metal in the pool.
  • the longitudinal dam in the manner as shown in Fig. 4 or 5.
  • the purpose of the invention is not achieved unless that position of the surface of molten metal which contact the roll surface is retained within the opening 11 formed between the bottom surface of the longitudinal dam and the roll surface.
  • the level of the surface 5 of molten metal in the pool is substantially the same as or slightly higher than the level of the round surface 17 of molten metal in the opening 11. An excessively high level of the surface 5 of molten metal in the pool should be avoided. It should also be avoided to immerse the longitudinal dam 3 so deeply that the molten metal may go beyond the longitudinal dam 3.
  • the surface 17 of molten metal in the opening 11 is vigorously renewed by the rotation of the roll and the viscosity of the molten metal; no triple point corners where molten metal tends to stagnate are formed in the pool; and cooling of molten metal in the vicinity of the inside lower edge 15 is reduced, since the longitudinal dam 3 is not cooled by the roll, and therefore, formation of the triple point solidified shells 19, as shown in Fig. 4, can be effectively prevented.
  • the longitudinal dams partly dam up a surface flow of molten metal in the pool, and pose a problem in that a solidified skin is likely formed on the surface of molten metal in the pool.
  • This problem is, however, effectively overcome by using the pouring device 4 equipped with the exhaling slit 8 on the bottom, thereby continuously supplying super heated molten metal over the whole width of the surface of molten metal in the pool.
  • the film flow of molten metal supplied by the pouring device 4 is uniform widthwise, thereby reducing localized rises of molten metal in the pool, and in turn further enhancing the widthwise uniformity of the surface 17 of molten metal in the opening 11.
  • the longitudinal dams in the apparatus according to the invention do not suffer from the problem, generally inherent in longitudinal dams, of formation of the solidified skin on the surface of molten metal in the pool, and are productive of the above-mentioned desirable results.
  • a suitable opening of the slit 8 is within the range of from about 2 to 7 mm.
  • the apparatus according to the invention makes it possible that the surface of molten metal may come in contact with the surfaces of the rolls while forming the transversely uniform contacting edges, by means of the prescribed longitudinal dams capable of preventing formation of triple point solidified shells, and therefore, the apparatus according to the invention is productive of metal strips having enhanced surface quality which are substantially free from molten metal wrinkles.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Manufacture And Refinement Of Metals (AREA)
EP19890117471 1988-09-30 1989-09-21 Apparatus for continuous casting of metal strip Expired EP0363702B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP243994/88 1988-09-30
JP24399488A JPH0761526B2 (ja) 1988-09-30 1988-09-30 薄板連鋳装置

Publications (2)

Publication Number Publication Date
EP0363702A1 EP0363702A1 (en) 1990-04-18
EP0363702B1 true EP0363702B1 (en) 1992-12-16

Family

ID=17112134

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890117471 Expired EP0363702B1 (en) 1988-09-30 1989-09-21 Apparatus for continuous casting of metal strip

Country Status (4)

Country Link
EP (1) EP0363702B1 (ja)
JP (1) JPH0761526B2 (ja)
DE (1) DE68903922T2 (ja)
ES (1) ES2036775T3 (ja)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AUPN545095A0 (en) * 1995-09-14 1995-10-12 Bhp Steel (Jla) Pty Limited Strip casting
CN115106494B (zh) * 2022-05-27 2023-08-18 燕山大学 一种螺旋槽管的柔性成型装置及方法

Also Published As

Publication number Publication date
DE68903922T2 (de) 1993-07-01
JPH0292440A (ja) 1990-04-03
ES2036775T3 (es) 1993-06-01
DE68903922D1 (de) 1993-01-28
JPH0761526B2 (ja) 1995-07-05
EP0363702A1 (en) 1990-04-18

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