US3908744A - Method of continuously casting wide slabs, in particular slabs wider than 1000 mm - Google Patents

Method of continuously casting wide slabs, in particular slabs wider than 1000 mm Download PDF

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Publication number
US3908744A
US3908744A US387371A US38737173A US3908744A US 3908744 A US3908744 A US 3908744A US 387371 A US387371 A US 387371A US 38737173 A US38737173 A US 38737173A US 3908744 A US3908744 A US 3908744A
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liquid core
cast
segregated
core
slabs
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US387371A
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English (en)
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Thorwald Fastner
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Voestalpine AG
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Voestalpine AG
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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
    • B22D11/10—Supplying or treating molten metal

Definitions

  • the invention relates to a method of continuously casting wide slabs, in particular slabs wider than 1000 mm, in particular from steels tending to segregate by using a vertical, preferably straight, water-cooled mold, into which the steel is allowed to flow and from which the cast strand having a liquid core and a solidified skin layer is withdrawn.
  • Segregations in the core of cast strands are known to occur, because various elements, such as C, Mn and S, have a higher solubility in liquid steel than in solidified steel. These elements are therefore being enriched in the remaining melt during solidification. In zones where the steel solidifies last, as, e.g., in the core of continuously cast strands, therefore substantially higher contents of these elements can be found than in the surface zone.
  • Segre gations cause a deterioration in quality of rolled products made from cast strands; i.e., segregated sheets show lower elongationand notch-impact values. Their ductility is also deteriorated by the segregations.
  • a particular aim of the invention consists in being able to produce steels without cracks on-a high-capacity continuous casting plant, without having to keep the casting temperature within narrow limits and without having to apply a too heavy secondary cooling.
  • the invention consists in that the velocity of the casting stream penetrating into the liquid core in vertical direction is kept at a value in dependence on the length of the liquid core, which value is higher than a lower limit value lying within the range of 60 to l cm/sec, represented by curve C of FIG. 2 of the drawings, as subsequently explained.
  • it is suitable to use refractory casting tubes known per se, immersing below the casting level in the continuous casting mold and being open at their lower end, in order to enable the freely emerging casting stream to penetrate as deep as possible into the liquid core of the strand.
  • This steel is commonly killed with Si and Al, the Sicontent lying approx. at 0.3 and the Al-content below 0.1
  • the P- and S-contents should be as low as possible; they lie at approx. 0.020
  • various alloy elements such as Nb, V, Cr, Ni, Ti and Mo may be added at an amount of up to 2
  • the composition (casting analysis) of various melts is given which have been produced by the method of the invention, wherein no quality diminishing influence in sheets or plates made from these cast strands has been found.
  • these steels are cast in continuous casting plants having a vertical, straight mold, followed by a vertical, straight guiding path, after which the strand can be gradually bent into the horizontal.
  • the strand skin at the lower side of the strand might be too strongly eroded by the vertically penetrating casting stream. As a consequence, cracks and steel-breakthroughs might occur. Principally, it is also possible to allow the steel to flow freely falling into the continuous casting mold. For avoiding the occurrence of non-metallic inclusions,
  • the hardness determined in the segregated core zone exceeds the hardness of the nonsegregated surface zone by maximumly 3O It is to be observed that the method of this invention is not suited for any strand cross section, but can only be used for casting slabs having a width of at least 1000 mm. This width is necessary in order to achieve a marked compensation flow by the stream penetrating deeply into the liquid core, which would not be possible in narrow slabs or billets. It has been found that the decrease of segregation, achieved by the present invention, does not involve any disadvantages as to quality. In particular, no cracks on the slab surface'and no strand breakthroughs occurred.
  • the deoxidation products are present substantially in the form of manganese-silicates, which are liquid during casting, coagulate rapidly and are precipitated to a large degree already in the pouring ladle or in the tundish. Only a small portion gets into the continuous casting mold and, on account of this, the kind and intensity of the flow in the liquid core have no considerable influence as to the inclusion content of the strand.
  • FIG. 1 is a vertical section of the upper part of a continuous casting plant which is particularly advantageous for carrying out the method of the invention.
  • FIG. 2 illustrates the relationship between the velocity of exit v of the casting stream from the casting tube, respectively the relationship between the velocity of penetration of the casting stream into the liquid core of the strand, and the core length L.
  • FIG. 3 is a diagram which illustrates the correlation between the increase in hardness as a consequence of the segregations in the strand core and the casting temperature.
  • FIG. 4 shows a segregated test piece, taken from the center of the strand, in which the increase in hardness in the segregation zone is determined in comparison with the increase in hardness in the non-segregated zone.
  • a tundish is denoted with 1, from which the liquid steel 2 is conveyed vertically in direction of the arrow through a refractory casting tube 3 into a straight, vertical water-cooled mold 4.
  • the velocity of exit v of the liquid steel from the casting tube 3 is regulated by a liftable and lowerable refractory stopper 5.
  • 6 and 7 denote horizontal planes through the casting level in the mold 4, 'and through the lower edge of the casting tube 3, respectively.
  • the casting tube 3 immerses several cm below the casting level covered with casting powder, so that the steel cannot get into touch with the atmosphere.
  • 8 denotes the liquid core of the cast strand having a solidified skin layer 9, the cast strand being continuously supported and guided by the rollers 10, 11 and 12.
  • the rollers form, together with the straight mold, a vertical, straight strand guiding of 2 to 3 m length, followed by a bending device formed by the rollers 11 and a circular arc-shaped strand guiding device formed by the rollers 12.
  • a straightening device (not illustrated) and a degree for drawing out the cast strand running out horizontally are provided.
  • the lowest point of the liquid pool 13 may reach as far as the end of the circular arc-shaped strand guiding depending upon the casting velocity and the type of plant.
  • the velocity v of the casting stream 14, freely leaving the casting tube 3 and penetrating into the liquid core 8, respectively measured within the plane 7 is adjusted in such a way that the depth effect becomes greater as the liquid core length L increases.
  • FIG. 2 is a diagram, in which, on the abscissa, the core length L in m is plotted and, on the ordinate, the velocity of exit v of the casting stream from the casting tube 3 in cm/sec.
  • 16 and 17 limiting lines are denoted, within which the invention is applied advantageously.
  • the velocity of exit v is to lie within these limiting lines 16, 17, above the lower limiting curve C, i.e., in the range B, indicated by hatched lines, whose upper limit is defined approx. by the curved line 18. Therefore with a core length L of 8 m, the velocity of exit v is to amount to at least 60 cm/sec.
  • FIG. 3 illustrates a correlation between casting temperature and segregation.
  • the casting temperature in C measured in the tundish 1 is plotted and on the ordinate, the increase in hardness in the segregated zone of the cast slab is plotted in of the hardness of the non-segregated zone.
  • the casting temperature in a type of steel preferred according to the invention lies within the limiting lines 19, 20, i.e., between 15 10 and 1530C.
  • this steel is cast under normal conditions i.e., at a velocity v lying in field A of FIG. 2, an increase in hardness in the segregated part of the slab occurs, which lies within a field "A', limited by the lines 21, 22.
  • the casting temperature strongly influences the segregation intensity, if one works with velocities of exit v of the stream lying in the field A.
  • the influence of the casting temperature upon the segregation is considerably lower: the lines 23, 24 run considerably flatter than the lines 21, 22 and the field B lies below the limit line D.
  • the casting temperature would always have to lie below 1515C, so as surely not to exceed an increase in hardness of 30%. In practice, however, this is hardly possible.
  • test piece is cut out of the cast strand, as illustrated in FIG. 4.
  • the test piece is cut from the range of the longitudinal axis 25 of the slab, i.e., at approx, half the length of the strand (the vertical axis through the strand center is denoted with 26).
  • the test piece suitably has a width 27 of 200 mm and a thickness which corresponds to the strand thickness d.
  • Its cross-sectional area 28 is ground and deep-etched with hydrochloric acid, whereby in the core zone 29 segregations 30 become visible. These segregations 30 illustrated slightly exaggerated appear dark and are clearly set off against the structure of the rest of the cross section.
  • C-contents in the cast strand are determined which lie up to I00 above the value of the casting analysis.
  • Mncontents, higher by up to 30 and S-contents, higher by up to 50 are detected there.
  • the increased C- content in the segregated zone is also to be regarded as the reason for the occurrence of dark spots after the deep-etching.
  • Segregated zones have a higher pearlite content than non-segregated ones, and a structure with a higher pearlite content behaves differently during t etching than a structure with a lower pearlite content.
  • the hardness of the steel is greater there than in the remaining casting material. Therefore the hardness increase in the segregated zone of these steels can be regarded as a good indicator for the intensity of the segregation.
  • the hardness is tested through the segregated zones 30 along a'line 31 after abrading the surface 28 at the measuring points 32, which are arranged at distances of lO'mm each.
  • the line 31 is led parallel in relation to line 29, so that the largest partpossible of itslongitudinal extension lies in segregated zones 30.
  • the line 31 may, but need not coincide with the line 29.
  • the" Vickers hardness test (HV 5) may be applied, wherein the mean value of all measuring points 32 is compared with EXAMPLE 1
  • HV 5 Vickers hardness test
  • the size of the mold was 1600 X 225 mm, and the withdrawal speed of the strand was 0.6 m/min. From this, a casting output of 1.55 t/min. results.
  • the liquid core length L may be calculated from the following relationships: I
  • L a r respectively d denotes the strand thickness in mm
  • c is the solidification factor, inserted with 27 mm/min
  • t denotes the solidification time in min
  • a stands for the withdrawal speed of the strand in mm/min.
  • the liquid core length L was calculated to measure 10.4 m.
  • the temperature of the steel (casting temperature) measured in the tundish l was 1530C.
  • a minimum velocity of exit of the steel from the casting tube 3 of 68 cm/sec is necessary in order to avoid disturbing segregations. Therefore a casting tube was used, being open at its lower end and having a lumen of mm. From the relationship casting output (in em /sec) equals the product of cross section of casting tube. (in cm and velocity of exit v (in cm/sec), the velocity of exit v was calculated to be 127 cm/sec in I this example (point 34 in FIG. 2).
  • the improvement comprising that the stream of molten steel vertically penetrates into the liquid core and is, in dependence upon the length (L) of the liquid core, cast at a velocity (v) kept at a value higher than a lower limit value that increases with increasing length of the liquid core and that lies within 60 to 110 cm/sec for lengths (L) of from 8 to 15 m, the range of lower limit values being represented by curve C in FIG. 2.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
US387371A 1972-08-10 1973-08-10 Method of continuously casting wide slabs, in particular slabs wider than 1000 mm Expired - Lifetime US3908744A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT691072A AT323919B (de) 1972-08-10 1972-08-10 Verfahren zum kontinuierlichen giessen von breiten, insbesondere über 1000 mm breiten brammen

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US (1) US3908744A (it)
JP (1) JPS537128B2 (it)
AT (1) AT323919B (it)
BE (1) BE803408A (it)
BR (1) BR7306109D0 (it)
CA (1) CA1003618A (it)
CH (1) CH562071A5 (it)
DE (1) DE2340291B2 (it)
ES (1) ES417694A1 (it)
FR (1) FR2327834A1 (it)
GB (1) GB1438826A (it)
IT (1) IT990361B (it)
SE (1) SE384331B (it)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4043382A (en) * 1975-01-13 1977-08-23 Nippon Kokan Kabushiki Kaisha Method and apparatus for continuously casting steel
US4064925A (en) * 1975-02-25 1977-12-27 Vereinigte Osterreichische Eisen- Und Stahlwerke-Alpine Montan Aktiengesellschaft Continuous casting method and apparatus
CN108436049A (zh) * 2018-02-08 2018-08-24 中国科学院金属研究所 一种控制大尺寸连铸坯中v偏析的方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54142053A (en) * 1978-04-27 1979-11-05 Kouji Matsuda Electronic relay
JPS586444U (ja) * 1981-07-03 1983-01-17 富士通テン株式会社 入出力絶縁形直流信号伝送回路
GB9013199D0 (en) * 1990-06-13 1990-08-01 Alcan Int Ltd Apparatus and process for direct chill casting of metal ingots

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2218171A (en) * 1936-09-15 1940-10-15 Junghans Siegfried Apparatus for continuous casting processes
US2458236A (en) * 1944-12-07 1949-01-04 Scovill Manufacturing Co Continuous pouring furnace
US3465811A (en) * 1965-11-15 1969-09-09 Est Aciers Fins Plants for the continuous casting of steel
US3536122A (en) * 1966-09-23 1970-10-27 Concast Ag Method of producing steel bars by continuous casting
US3804147A (en) * 1971-03-30 1974-04-16 Etudes De Centrifugation Continuous rotary method of casting metal utilizing a magnetic field

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2218171A (en) * 1936-09-15 1940-10-15 Junghans Siegfried Apparatus for continuous casting processes
US2458236A (en) * 1944-12-07 1949-01-04 Scovill Manufacturing Co Continuous pouring furnace
US3465811A (en) * 1965-11-15 1969-09-09 Est Aciers Fins Plants for the continuous casting of steel
US3536122A (en) * 1966-09-23 1970-10-27 Concast Ag Method of producing steel bars by continuous casting
US3804147A (en) * 1971-03-30 1974-04-16 Etudes De Centrifugation Continuous rotary method of casting metal utilizing a magnetic field

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4043382A (en) * 1975-01-13 1977-08-23 Nippon Kokan Kabushiki Kaisha Method and apparatus for continuously casting steel
US4064925A (en) * 1975-02-25 1977-12-27 Vereinigte Osterreichische Eisen- Und Stahlwerke-Alpine Montan Aktiengesellschaft Continuous casting method and apparatus
CN108436049A (zh) * 2018-02-08 2018-08-24 中国科学院金属研究所 一种控制大尺寸连铸坯中v偏析的方法
CN108436049B (zh) * 2018-02-08 2019-11-01 中国科学院金属研究所 一种控制大尺寸连铸坯中v偏析的方法

Also Published As

Publication number Publication date
FR2327834B1 (it) 1978-04-14
FR2327834A1 (fr) 1977-05-13
JPS4953531A (it) 1974-05-24
BE803408A (fr) 1973-12-03
SE384331B (sv) 1976-05-03
CH562071A5 (it) 1975-05-30
CA1003618A (en) 1977-01-18
DE2340291A1 (de) 1974-02-21
IT990361B (it) 1975-06-20
BR7306109D0 (pt) 1974-06-27
JPS537128B2 (it) 1978-03-15
DE2340291B2 (de) 1975-08-28
ES417694A1 (es) 1976-06-16
AT323919B (de) 1975-08-11
GB1438826A (en) 1976-06-09

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