EP0663250B1 - Verfahren zum Stranggiessen von Stählen - Google Patents

Verfahren zum Stranggiessen von Stählen Download PDF

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Publication number
EP0663250B1
EP0663250B1 EP19950300052 EP95300052A EP0663250B1 EP 0663250 B1 EP0663250 B1 EP 0663250B1 EP 19950300052 EP19950300052 EP 19950300052 EP 95300052 A EP95300052 A EP 95300052A EP 0663250 B1 EP0663250 B1 EP 0663250B1
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EP
European Patent Office
Prior art keywords
cast piece
continuous casting
molten steel
cast
steels
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 - Lifetime
Application number
EP19950300052
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English (en)
French (fr)
Other versions
EP0663250A1 (de
Inventor
Kiyoshi Morii
Yoshio Inagaki
Shizunori Hayakawa
Hajime Takahashi
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.)
Daido Steel Co Ltd
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Daido Steel Co Ltd
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Publication date
Application filed by Daido Steel Co Ltd filed Critical Daido Steel Co Ltd
Publication of EP0663250A1 publication Critical patent/EP0663250A1/de
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    • 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
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling

Definitions

  • This invention relates to a continuous casting method applicable for steels such as bearing steels and spring steels according to the features as laid out in claim 1, which is based upon EP-A- 0 211 422.
  • the continuous casting process has remarkable advantages in the high yield rate and in the high productivity because a blooming process is not required, and is widely utilized as a casting method which is possible to continuously manufacture the final cast piece such as a slab, a bloom, a billet and so on directly from molten steel.
  • the segregation and the concentration phenomena of the chemical elements such as carbon in the center part of the cast piece is considered to be caused by the solidification of the molten steel proceeding toward the center part from the outer peripheral part of the cast piece, in particular, it is considered that flowing of the concentrated molten steel is produced by solidification shrinkage at the time a liquid phase remaining in the center part of the cast piece is finally solidified, and linked up with the concentrated segregation of carbon and the like.
  • the aforementioned soft reduction treatment is to prevent the flowing of the concentrated molten steel caused by the solidification shrinkage and to inhibit the segregation at the time of solidification by compressively deforming the unsolidified portion in the center of the cast piece at least an amount corresponding to the volume reduction at the time of solidification.
  • the soft reduction treatment is sometimes accompanied with a risk of generation of cracks at a front surface of the solidification according to magnitude of tensile stress produced by the deformation of unsolidified interface of the molten steel.
  • the cracks generated at the front surface of the solidification brings penetration into the cracks of the molten steel concentrated with carbon, sulfur, phosphorus and so on at the front surface of the solidification, and may be a defect harmful as much as center segregation in the finished products.
  • EP-A-0211422 discloses a continuous casting method wherein the thickness of a strand is continuously reduced in its unsolidified region (generally called a soft reduction treatment). The document further discloses casting the metal into a bloom having a rectangular cross section.
  • This invention is made in order to solve his kind of problem of the prior art.
  • the present invention provides a continuous casting method for steels comprising: pouring molten steel into a water cooled mould through an upper opening of the mould; solidifying the molten steel to form a cast piece in the mould and drawing continuously the cast piece through a lower opening of said mould at the same time, wherein said cast piece is subjected to soft reduction treatment with a flat part of a roll at a position of a solid phase ratio from 0.2 to 0.8 before the molten steel in the center part of the cast piece is completely solidified, and wherein said cast piece has a circular cross section, and the flat part of the roll forms a plane on a depressed surface of the cast piece.
  • the molten steel undergoes a change in state from perfect liquid phase A to perfect solid phase C through solid-liquid mixed phase B as shown in FIG.5.
  • the solid phrase ratio is defined as a weight ratio occupied by the solid phase on a cross section of the cast piece (the solid phase ratio 1 means the state of perfect solid phase).
  • the continuous casting method according to this invention is characterized by subjecting to the soft reduction treatment against the cast piece cast into a shape having a circular cross section with the flat part of the roll R at the position of the solid phase ratio from 0.2 to 0.8 in the solid-liquid mixed phase as shown in FIG.5.
  • the roll having the flat part means a roll possible to form a plane on the depressed surface of the cast piece with the circular cross section, and the roll is applicable without distinction of the shape so long as it is possible to form a plane on the contact surface of the cast piece.
  • the inventors carried out stress-strain analysis at the time of applying the soft reduction with the flat part of the roll R against a cast piece D having a circular cross section (350mm diameter) and a cast piece E having a square cross section (350mm square) shown in FIGS.3A and 3B through the finite element method using computer, and results were obtained as shown in FIG.4. Additionally, symbol F denotes the unsolidified portion, and symbol G denotes the completely solidified portion of the cast pieces D and E in FIGS. 3A and 3B.
  • the axis of abscissas shows a reduction ratio applied to the cast piece, and the axis of ordinates shows volume reduction of the unsolidified center portion with an index.
  • the reduction ratio means the decrease percentage of area on the cross section of the cast piece before and after the soft reduction.
  • This invention is made on basis of the above-mentioned findings, it is possible to prevent the cast piece from the segregation of carbon and the like at the same time of controlling the generation of the tensile stress in the cast piece in a low level and preventing the cast piece from the generation of cracks, therefore it is possible to improve the quality of the cast piece according to this invention.
  • This invention is especially effective when it is applied to steels containing carbon not lower than 0.5 %.
  • the continuous casting method according to this invention is especially characterized by performing the soft reduction at the position of the solid phase ratio from 0.2 to 0.8.
  • the soft reduction is applied on the cast piece at the position of the solid phase ratio from 0.2 to 0.8 for the reason that a liquid phase in the center portion of the cast piece loses its fluidity substantially and it is not possible to obtain the sufficient effect by the low reduction treatment even if the low reduction is applied on the cast piece at the position of solid phase ratio more than 0.8, and in contrast with this, the liquid phase occupied most of the cross section of the cast piece at the position of solid phase ratio less than 0.2 and it is not possible similarly to obtain the sufficient effect by the low reduction treatment owing to the excessive fluidity of the liquid phase.
  • the low reduction is performed for the purpose of preventing the cast piece from the cracks and the concentrated segregation of the chemical components such as carbon, phosphorus, sulfur and so on at the center portion of the cast piece.
  • the cast piece was subjected to the low reduction treatment with a reduction ratio of 2 % at a position of a solid phase ratio(fs) from 0.4 to 0.5 using a double roll disposed with two flat rolls on the upper and lower sides. Additionally, the roll is available so long as it has a flat part even a roll having a V-shaped recess partially.
  • Example 1 Steel including 0.6 % of carbon and specified as SUP 7 in JIS G 4801 (Spring Steels) was cast into a cast piece through the continuous casting process under the same condition as that of Example 1, and a graph on the upper side in FIG.2 was obtained as a result of analyzing the carbon content on the cross section of the obtained cast piece . Furthermore, there were not internal cracks at all. A graph on the lower side in FIG.2 shows a result of a cast piece obtained without applying the low reduction treatment.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)

Claims (3)

  1. Stranggußverfahren für Stahl, welches umfaßt:
    Gießen von Stahlschmelze in ein wassergekühltes Formwerkzeug durch eine obere Öffnung des Formwerkzeugs;
    Verfestigen der Stahlschmelze zur Bildung eines Gußstücks im Formwerkzeug und gleichzeitig kontinuierliches Ziehen des Gußstücks durch eine untere Öffnung des Formwerkzeugs, wobei das Gußstück einer Weichreduktionsbehandlung mit einem flachen Teil einer Walze an einer Stelle mit einem Festphasenverhältnis von 0,2 bis 0,8 unterworfen wird, bevor die Stahlschmelze im Mittelteil des Gußstücks vollständig verfestigt ist, dadurch gekennzeichnet, daß das Gußstück einen kreisförmigen Querschnitt besitzt und der flache Teil der Walze eine Ebene auf einer eingedrückten Fläche des Gußstücks bildet.
  2. Stranggußverfahren für Stähle nach Anspruch 1, bei welchem das Gußstück einer Weichreduktionsbehandlung mit einem Reduktionsverhältnis von 1,0 bis 3,0% unterworfen wird.
  3. Stranggußverfahren für Stähle nach Anspruch 2, bei welchem das Gußstück einer Weichreduktionsbehandlung mit einem Reduktionsverhältnis von 1,5 bis 2,5% unterworfen wird.
EP19950300052 1994-01-14 1995-01-05 Verfahren zum Stranggiessen von Stählen Expired - Lifetime EP0663250B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP15772/94 1994-01-14
JP01577294A JP3257224B2 (ja) 1994-01-14 1994-01-14 連続鋳造方法
JP1577294 1994-01-14

Publications (2)

Publication Number Publication Date
EP0663250A1 EP0663250A1 (de) 1995-07-19
EP0663250B1 true EP0663250B1 (de) 2001-05-23

Family

ID=11898106

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19950300052 Expired - Lifetime EP0663250B1 (de) 1994-01-14 1995-01-05 Verfahren zum Stranggiessen von Stählen

Country Status (3)

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EP (1) EP0663250B1 (de)
JP (1) JP3257224B2 (de)
DE (1) DE69520966T2 (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3367332B2 (ja) * 1996-05-15 2003-01-14 日本鋼管株式会社 難加工性継目無鋼管の製造方法
KR20000008005A (ko) * 1998-07-09 2000-02-07 이구택 슬라브의 중심결함이 저감되는 연속주조방법
CN101648212B (zh) * 2009-09-15 2011-08-31 邢台钢铁有限责任公司 预应力钢swrh82b大方坯连铸动态轻压下工艺
RU2678112C2 (ru) * 2014-12-24 2019-01-23 ДжФЕ СТИЛ КОРПОРЕЙШН Способ непрерывного литья стали
BR102015009492B1 (pt) * 2015-01-30 2021-05-04 Jfe Steel Corporation método de lingotamento contínuo de aço
CN108817338B (zh) * 2018-07-06 2020-01-24 青岛特殊钢铁有限公司 一种适用于高强弹簧扁钢的连铸连轧生产工艺

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4134440A (en) * 1974-09-16 1979-01-16 Nippon Kokan Kabushiki Kaisha Method of continuously casting steel
JPS5939225B2 (ja) * 1978-02-13 1984-09-21 日本鋼管株式会社 鋼の連続鋳造法
JPS60184455A (ja) * 1984-03-01 1985-09-19 Nippon Steel Corp 圧下を加える連鋳片の製造方法
US4687047A (en) * 1985-08-03 1987-08-18 Nippon Steel Corporation Continuous casting method
JPS635859A (ja) * 1986-06-25 1988-01-11 Nippon Steel Corp 高珪素鋼の連続鋳造方法
JPH01273658A (ja) * 1988-04-27 1989-11-01 Sumitomo Metal Ind Ltd 圧下を付与する鋼の連続鋳造方法
JP2964560B2 (ja) * 1989-08-16 1999-10-18 大同特殊鋼株式会社 垂直連続鋳造装置

Also Published As

Publication number Publication date
DE69520966D1 (de) 2001-06-28
JPH07204812A (ja) 1995-08-08
EP0663250A1 (de) 1995-07-19
DE69520966T2 (de) 2001-11-15
JP3257224B2 (ja) 2002-02-18

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