EP0776716A1 - Procede de coulee en continu de pieces minces - Google Patents

Procede de coulee en continu de pieces minces Download PDF

Info

Publication number
EP0776716A1
EP0776716A1 EP96918856A EP96918856A EP0776716A1 EP 0776716 A1 EP0776716 A1 EP 0776716A1 EP 96918856 A EP96918856 A EP 96918856A EP 96918856 A EP96918856 A EP 96918856A EP 0776716 A1 EP0776716 A1 EP 0776716A1
Authority
EP
European Patent Office
Prior art keywords
slab
thickness
casting speed
casting
roll reduction
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.)
Withdrawn
Application number
EP96918856A
Other languages
German (de)
English (en)
Other versions
EP0776716A4 (fr
Inventor
Takashi Kanazawa
Sei Hiraki
Seiji Kumakura
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 Corp
Original Assignee
Sumitomo Metal Industries 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 Sumitomo Metal Industries Ltd filed Critical Sumitomo Metal Industries Ltd
Publication of EP0776716A1 publication Critical patent/EP0776716A1/fr
Publication of EP0776716A4 publication Critical patent/EP0776716A4/fr
Withdrawn legal-status Critical Current

Links

Images

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
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • 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

Definitions

  • an immersion nozzle must employ a rather thin refractory wall compared with conventional ones. Breaking of the immersion nozzle due to corrosive damage to the refractory easily occurs. Thus, since the service life of the nozzle is short, the number of strands which can be cast simultaneously is at most 3. In this respect, continuous casting of 7 or 8 strands is possible for conventional processes. Since the number of strands is limited, therefore, it is critical how to reduce the unstable area in order to increase the yield of the product.
  • An object, therefore, of the present invention is to provide a process for continuously casting thin slabs and carrying out squeeze reduction of the slabs, in which the roll reduction force can be released during casting so as to change the thickness of the slab while preventing formation of internal defects.
  • Another object of the present invention is to provide a process for continuously casting thin slabs and carrying out squeeze reduction of the slabs, in which the roll reduction force can be released to decrease the length of an unstable area of the slab to be as short as possible and to change the thickness of the slab during casting while preventing formation of internal defects.
  • the changing in the casting speed be started at the same time or prior to the time when the changing point of the cast slab passes the roll reduction finishing area.
  • Fig. 4 is a longitudinal side view of the shape of a cast slab during process in which the roll reduction force is released in accordance with the present invention.
  • Fig. 1 is a schematic illustration of the structure of a continuous casting machine (hereunder referred to merely as “machine”) which is preferably used for carrying out the process of the present invention.
  • Mold 1 measures about 90 - 150 mm in thickness and about 1000 - 1800 mm in width. Cast slabs having these dimensions are reduced to a thickness of about 30 - 70 mm by squeeze reduction.
  • the solidifying front moves downstream from the roll reduction finishing area within the roll reduction zone, and the slab swells due to bulging, causing possible marked deterioration in internal quality of the slab, such as formation of internal cracking and a degradation in central segregation.
  • the release of the roll reduction force not be carried out immediately after the changing point of the thin slab passes the roll reduction zone, but that the release of the roll reduction force be carried out after or at the same time that the casting speed is lowered to a speed at which the thin slab after roll reduction can be completely solidified within the squeeze reduction zone.
  • this process of releasing the roll reduction force it is possible to produce cast slabs which are free of deterioration of internal quality even in a transitional area during the thickness changing period so that continuous casting can be continued efficiently without a reduction in yield.
  • the casting of a slab 100 mm thick is started and continued at a given casting speed of 4.0 m/min, and squeeze reduction is carried out to reduce the thickness of the slab to 50 mm. It is assumed that it is necessary to change the thickness of the slab from 50 mm to 100 mm because of a requirement from a production schedule for example.
  • a shift of operating conditions at this time is started when the changing point of the slab passes the roll reduction finishing area of the squeeze reduction zone. Namely, the casting speed is continuously reduced to 2.0 m/min, and simultaneously the roll reduction force is also continuously released.
  • the target casting speed mentioned above is equal to or lower than the casting speed at which a cast slab having a target thickness, 100 mm in this example, is completely solidified within the roll reduction zone.
  • the casting speed can be varied depending on a target thickness of the slab.
  • the solidified front moves upstream or downstream of the roll reduction zone depending on a lowering of the casting speed and on a release of the roll reduction force, so long as the solidifying front is essentially located upstream of the roll reduction finishing area within the squeeze reduction zone, the casting speed as well as the rate of releasing the roll reduction force are not limited to any specific ones.
  • the rate of decreasing the casting speed is not limited to a specific level, and it is preferable that the casting speed be lowered as quickly as the machine permits from the viewpoint of avoiding the occurrence of unstable states as completely as possible.
  • the length "a" means the length of time required to reduce the casting speed to a target speed.
  • the casting speed After the casting speed is lowered to a given casting speed, the casting is continued at the given casting speed. On the other hand, during this period of time, the release of the roll reduction force is also continued. After the roll reduction force is reduced to a target level, i.e., after a target thickness of the cast slab is achieved, then the casting speed begins to return to the normal casting speed.
  • the length "b" up to this point of time means the length of time required for the solidifying front located upstream from the roll reduction finishing area of the roll reduction zone to return to the roll reduction finishing zone.
  • the solidifying front which is once moved upstream of the roll reduction finishing area due to a reduction in the casting speed continues moving gradually to downstream of the roll reduction finishing area as the thickness of the slab increases.
  • the solidifying front returns to the roll reduction finishing area after time b elapses. After this point of time, the casting speed can be increased by adjusting cooling conditions while the solidifying front is kept at this position.
  • the solidifying front may be situated upstream of the roll reduction finishing area after the elapse of time b, and the solidifying front may be returned to the roll reduction finishing area by increasing the casting speed.
  • the point of time at which the thickness of a slab is required to be changed to 100 mm under usual conditions due to the requirements of a production schedule is determined on the basis of the roll reduction finishing area.
  • the time required to reduce the casting speed from 4.0 m/min to 2.0 m/min is determined.
  • the casting speed can be lowered to 2.0 m/min in 1 minute, and at least one minute is necessary to reduce the casting speed from 4.0 m/min to 2.0 m/min. Three minutes are necessary for the casting speed to return to a given stable casting speed before the changing point of the slab passes the roll reduction finishing area which is located 6 m downstream from the meniscus in the mold.
  • the casting speed may start to be lowered from the point 4 minutes upstream from the point of time or location when or where the changing point of the slab passes the roll reduction finishing area.
  • a stable casting speed is changed to a casting speed lower than the speed at which a thin slab is completely solidified within the squeeze reduction zone.
  • the above-mentioned casting speed is one at which the thickness of the solidified shell is 50 mm at the point of the roll reduction finishing area.
  • a preferred casting speed is determined depending on the thickness of the mold and the length of the squeeze reduction zone. In general, a preferred casting speed is in the range of 1.0 - 2.0 m/min.
  • the rate at which the casting speed is changed i.e., an acceleration or deceleration rate preferably is in the range of 1.0 - 4.0 m/min 2 .
  • a cast slab having an unsolidified portion in the slab was subjected to squeeze reduction to reduce the thickness to 50 mm.
  • the roll reduction zone was located in an area 3 m long between the first segment and the fifth segment in the roller apron zone of the machine.
  • the roll reduction finishing area was located 4 m down from the molten steel meniscus in the mold.
  • the roll reduction was carried out at a uniform reduction rate with a reduction of 10 mm for each of the segments.
  • Fig. 3 is a graph showing a variation in the casting speed and slab thickness with respect to elapse of the casting period. As is apparent from the graph, increase in the slab thickness, i.e., opening of the roll gaps at the point of the roll reduction finishing area proceeded continuously.
  • Figs. 4 and 5 illustrate shapes of unstable areas of cast slabs which were obtained by the thickness restoring operations of an example of the present invention and a comparative example, respectively.
  • the direction of the arrow indicates the direction of drawing of a cast slab, i.e., the casting direction.
  • the resulting cast slabs were cut and examined on their cross sections. Cast slabs from the first strand to which the process of the present invention was applied were free from internal defects even in a transition area where the slab thickness was increased gradually. Further rolling following the continuous casting was carried out successfully, resulting in a coil having good quality. On the other hand, the cast slabs obtained from the second strand to which an immediate release of the roll reduction force was applied, as shown in Fig. 6, suffered from internal cracking and breaking into two pieces in the barrel-like swollen portion of the slab. Regarding central segregation, heavy normal and inverse segregation was found in scattered places, resulting in troubles such as formation of internal defects at the time of subsequent rolling.
  • Example 1 was repeated, and low carbon, Al-killed steel having the steel composition shown in Table 2 was cast at a normal casting speed of 5.0 m/min. In this example, too, the casting speed at which a cast slab was completely solidified before it passed the roll reduction finishing area was 1.3 m/min for a slab thickness of 100 mm.
  • Fig. 7 shows a comparison of the internal quality of the resulting cast slabs of the example of the present invention and the comparative example.
  • the code number on the Y-axis is a numerical indication of inner quality of the resulting slabs based on the following definition. Code Number Porosity area/10 cm 2 of horizontal area 0 0 % 1 0 - 10% 2 10 - 30% 3 30 - 50% 4 50 - 70% 5 70% or more
  • Example 1 was repeated, and medium carbon, Al-killed steel having the steel composition shown in Table 1 was cast at a normal casting speed of 5.0 m/min.
  • the casting speed was varied to 1.3, 2.0, and 3.0 m/min by adjusting the deceleration rate at the beginning of restoration of the thickness.
  • the casting speed at which a cast slab was completely solidified before it passed the roll reduction finishing area was 1.3 m/min.
  • the thickness of the cast slab was successively changed from 100 mm to 50 mm and then to 100 mm.
  • the resulting cast slabs were free from internal cracking, and a degradation in the central segregation was not found.
  • the solidified shell thickness was 40 mm and 33 mm, respectively, in the roll reduction finishing area, and an unsolidified portion remained when the slab passed the roll reduction finishing area.
  • the unstable portion of the slab swelled like a barrel upon release of the roll reduction force.
  • the slab there were occurrence of internal cracking, degradation in central segregation, and an increase in porosity, resulting in a reduction in the yield when the casting speed was 2.0 or 3.0 m/min at the time of release of the roll reduction force.
  • the present invention during operation of continuous casting, it is possible to change the thickness of cast slabs, without a degradation in surface conditions and inner quality, and a variety of sizes of slabs can be produced efficiently with a high yield.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Metal Rolling (AREA)
EP96918856A 1995-06-22 1996-06-20 Procede de coulee en continu de pieces minces Withdrawn EP0776716A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP156394/95 1995-06-22
JP15639495 1995-06-22
PCT/JP1996/001701 WO1997000748A1 (fr) 1995-06-22 1996-06-20 Procede de coulee en continu de pieces minces

Publications (2)

Publication Number Publication Date
EP0776716A1 true EP0776716A1 (fr) 1997-06-04
EP0776716A4 EP0776716A4 (fr) 1999-06-30

Family

ID=15626785

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96918856A Withdrawn EP0776716A4 (fr) 1995-06-22 1996-06-20 Procede de coulee en continu de pieces minces

Country Status (4)

Country Link
EP (1) EP0776716A4 (fr)
KR (1) KR100227594B1 (fr)
CN (1) CN1048203C (fr)
WO (1) WO1997000748A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19933635A1 (de) * 1999-07-17 2001-01-18 Sms Demag Ag Verfahren und Vorrichtung zur Formatdickenänderung des Gußstranges einer Stranggießanlage im kontinuierlichen Gießbetrieb
KR100518327B1 (ko) * 2002-12-23 2005-10-04 주식회사 포스코 쌍롤형 박판 주조장치에서의 초기 주조된 박판의 인발방법
CN103192043B (zh) * 2013-04-07 2016-01-20 昆明理工大学 一种抑制铸锭中心裂纹产生的方法
US10076783B2 (en) * 2014-05-14 2018-09-18 Nippon Steel & Sumitomo Metal Corporation Method for continuous-casting slab

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4436328A1 (de) * 1993-10-14 1995-04-20 Voest Alpine Ind Anlagen Verfahren und Anlage zum Stranggießen

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5422777B2 (fr) * 1973-09-17 1979-08-09
JPS53102224A (en) * 1977-02-18 1978-09-06 Ishikawajima Harima Heavy Ind Drawing off method and apparatus for continuous casted segment
JPS5813454A (ja) * 1981-07-13 1983-01-25 Nippon Steel Corp 連続鋳造における鋳片厚みの制御方法およびその装置
JPH01271047A (ja) * 1988-04-20 1989-10-30 Sumitomo Metal Ind Ltd 連続鋳造機における軽圧下方法
US5110533A (en) * 1990-11-07 1992-05-05 Milad Limited Partnership Method for the use of gas assistance in the molding of plastic articles to enhance surface quality

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4436328A1 (de) * 1993-10-14 1995-04-20 Voest Alpine Ind Anlagen Verfahren und Anlage zum Stranggießen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO9700748A1 *

Also Published As

Publication number Publication date
EP0776716A4 (fr) 1999-06-30
CN1156980A (zh) 1997-08-13
CN1048203C (zh) 2000-01-12
WO1997000748A1 (fr) 1997-01-09
KR970704535A (ko) 1997-09-06
KR100227594B1 (ko) 1999-11-01

Similar Documents

Publication Publication Date Title
EP0804981B1 (fr) Procede de coulage continu et appareil s'y rapportant
US3974559A (en) Continuous casting process
JP3018078B2 (ja) 鋼の連続鋳造装置
EP0776716A1 (fr) Procede de coulee en continu de pieces minces
CN111659863A (zh) 用于钢坯或初轧坯的连铸设备的改装
JP3186631B2 (ja) 連続鋳造における一定速引抜鋳込終了方法
US7025118B2 (en) Method and device for continuously casting ingots, slabs or thin slabs
JP5018441B2 (ja) 連続鋳造における鋳込終了後の鋳片の引抜方法
CN109909302B (zh) 一种连铸机扇形段出口处的铸坯铸轧方法
KR20000077170A (ko) 연속적인 주물을 제조하는 방법 및 장치
JP3111954B2 (ja) 連続鋳造方法
JP2961893B2 (ja) 薄鋳片の連続鋳造方法
JPS6216722B2 (fr)
JP3452799B2 (ja) 連続鋳造ガイドロール装置および連続鋳造方法
JPH08257715A (ja) 連続鋳造方法
JP3314036B2 (ja) 連続鋳造方法および連続鋳造装置
JPH0390263A (ja) 連続鋳造方法
JPH0663715A (ja) 連鋳鋳片の凝固末期軽圧下法
JPS6127151A (ja) 連続鋳造方法及び直送圧延方法
JP3395387B2 (ja) 広幅薄鋳片の連続鋳造法
JP3063533B2 (ja) 広幅薄鋳片の連続鋳造方法
JPH091292A (ja) 薄鋳片の連続鋳造方法
JP3498586B2 (ja) 連続鋳造方法
JP3124466B2 (ja) 鋼の連続鋳造装置および連続鋳造方法
JPH08257714A (ja) 連続鋳造装置

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT DE IT

17P Request for examination filed

Effective date: 19970630

A4 Supplementary search report drawn up and despatched

Effective date: 19990517

AK Designated contracting states

Kind code of ref document: A4

Designated state(s): AT DE IT

RIC1 Information provided on ipc code assigned before grant

Free format text: 6B 22D 11/20 A, 6B 22D 11/12 B

17Q First examination report despatched

Effective date: 19991210

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Withdrawal date: 20010924