WO2021256243A1 - Procédé de coulée continue - Google Patents

Procédé de coulée continue Download PDF

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Publication number
WO2021256243A1
WO2021256243A1 PCT/JP2021/020838 JP2021020838W WO2021256243A1 WO 2021256243 A1 WO2021256243 A1 WO 2021256243A1 JP 2021020838 W JP2021020838 W JP 2021020838W WO 2021256243 A1 WO2021256243 A1 WO 2021256243A1
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WO
WIPO (PCT)
Prior art keywords
slab
continuous casting
mold
corner
steel
Prior art date
Application number
PCT/JP2021/020838
Other languages
English (en)
Japanese (ja)
Inventor
智也 小田垣
則親 荒牧
恭寛 重歳
義陽 大場
貴史 丸子
Original Assignee
Ｊｆｅスチール株式会社
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 Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to CN202180040196.5A priority Critical patent/CN115697587A/zh
Priority to KR1020227042643A priority patent/KR20230006903A/ko
Priority to JP2021545426A priority patent/JP6954514B1/ja
Priority to EP21824759.1A priority patent/EP4170054A4/fr
Publication of WO2021256243A1 publication Critical patent/WO2021256243A1/fr

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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
    • 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
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • 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
    • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

Definitions

  • the present invention relates to a continuous steel casting method that suppresses the occurrence of surface cracks in slabs in continuous casting.
  • the hot ductility of the alloy steel slab is significantly reduced at the temperature near the Ar 3 transformation point where the solidified structure is transformed from the austenite phase to the ferrite phase.
  • the surface temperature of the slab is controlled by secondary cooling to correct the temperature above the transformation point, or the solidified structure of the slab is controlled to a structure that is hard to crack. Is commonly done.
  • the spray pipe near the corner of the slab is generally closed and the spray width is cut without cooling.
  • Patent Document 1 As a method of controlling the solidification structure, for example, Patent Document 1, to start the secondary cooling of the slab immediately after withdrawal of the slab from the rectangular mold, once Ar 3 transformation of the surface temperature of the slab The time and slab surface to keep the slab surface temperature below the Ar 3 transformation point when cooling to a temperature below the point and then reheating to a temperature above the Ar 3 transformation point and then straightening the slab.
  • a technique has been disclosed in which the solidified structure from the surface of the slab to a depth of at least 2 mm is made into a mixed structure of ferrite and pearlite with an unclear austenite grain boundary by setting the minimum temperature at which the temperature reaches to an appropriate range. Is
  • the technique of spray width cutting is to stop the spray from the spray near the corner of the slab and prevent the corner temperature from dropping.
  • the width of the slabs is wide in response to various needs in recent years, there is a problem that a large amount of capital investment is required to properly spray the corners of the slabs of all sizes.
  • the corners of the slab are cooled from the two sides of the slab on the long side and the short side, so that supercooling is likely to occur.
  • the corner temperature is lowered by radiative cooling even if the cooling spray is not sprayed.
  • Patent Document 1 there is a concern about the influence of dripping water flowing along the slab after being sprayed onto the slab from the secondary cooling spray.
  • the dripping water affects the cooling of the slab surface, so that it may be difficult to quantitatively control the slab surface temperature, for example, by heat transfer calculation.
  • the present invention has been made in view of such circumstances, and an object of the present invention is to prevent surface cracks in a slab which has not been sufficiently eliminated by controlling the temperature of the slab by secondary cooling alone.
  • the purpose is to propose a continuous casting method that surely suppresses and produces high quality slabs without corner cracks in particular.
  • the inventors have found that surface cracking of a slab can be suppressed by suppressing a temperature drop at a corner of a slab during secondary cooling while using a mold having a casting space having an appropriate shape, and have conceived the present invention. ..
  • the continuous casting method of the present invention that advantageously solves the above problems is a method of continuously casting steel, using a mold in which the chamfered shape of the mold corner portion satisfies the following equation (1), and the slab corner portion. It is characterized in that the average secondary cooling water amount density from directly under the mold to the lower straightening is 20 to 60 L / (min ⁇ m 2). 0.09 ⁇ C / L ⁇ 0.20 ... (1)
  • C corner chamfer amount (mm)
  • L Short side length of slab (mm) Represents.
  • the component composition of the steel is C: 0.05 to 0.25% and Mn: 1.0 to 4.0% in mass%, and further Nb: A more preferable solution is to optionally have at least one selected from 0.01 to 0.1%, V: 0.01 to 0.1%, and Mo: 0.01 to 0.1%. It is thought that it can be.
  • the temperature of the corners of the slab is controlled by secondary cooling while using a mold in which a casting space having an appropriate shape is partitioned, so that corner cracking of the continuously cast slab is prevented and high quality is achieved. It will be possible to provide slabs.
  • the steel continuous casting method (steel piece manufacturing method) according to the embodiment of the present invention includes a step of casting while supporting the slabs drawn from the continuous casting mold by a plurality of pairs of rolls facing each other.
  • the molten steel is primarily cooled with a mold.
  • the slab is withdrawn from the mold at a predetermined drawing speed, and the slab is secondarily cooled while being supported by a plurality of pairs of rolls arranged in the casting direction to obtain a steel slab.
  • a mold in which a casting space having an appropriate shape is partitioned is used, and it is appropriate in the cooling zone from directly under the mold to the bending back straightening point (lower straightening). It is important to go through a proper cooling pattern.
  • the continuous casting machine used in the present embodiment is not particularly limited as long as it includes bending or bending back straightening from directly under the mold to carrying out the slab.
  • the inventors observed surface cracks in the slabs cast by the curved continuous casting machine. Surface cracks in the slab were concentrated in and near the top corners. This is because tensile stress is generated during bending back correction.
  • the upper surface side of the slab means the inside of the bending of the curved band of the curved continuous casting machine, that is, the long side surface side which is the upper surface of the horizontal band.
  • the cracks were etched, the cracks propagated along the old austenite grain boundaries, so it was considered that the cracks occurred in the temperature range where the ferrite transformation started from austenite (generally called the embrittlement temperature), and the secondary cooling conditions were set. Experiments with various changes were conducted.
  • the inventors focused on the shape of the slab. Since the conventional slab is rectangular and the corners are cooled from two surfaces, supercooling of the corners of the slab is likely to occur. We considered that changing the shape of the slab would change the cooling structure and suppress supercooling, and examined the appropriate slab shape by thermal stress analysis.
  • the slab has a chamfered shape with the four corners of the rectangular cross section orthogonal to the casting direction removed, resulting in supercooling at the slab corners and stress load. It was found that the stress can be reduced. Then, in order to make the four corners of the slab into a chamfered shape, casting using a mold in which the four corners (right-angled portions) of the casting space, which is rectangular like a mold having a rectangular cross section, is removed into a right-angled triangular shape to form a chamfered shape. It is important to do.
  • a mold having a casting space having such a chamfered shape is also referred to as a chamfer mold.
  • the chamfered portion 4 of the chamfer mold is shown in the top view of the chamfer mold of FIG.
  • the ratio of the right-angled triangle to the length a on the long side 2 side of the mold is the ratio b / a of the length b on the short side 3 side of the mold.
  • a thermal analysis was performed on the effect of this ratio b / a on the overcooling of the corners of the slab. The calculation result is shown in FIG.
  • this embodiment is suitable for application to steels having high embrittlement susceptibility to austenite to ferrite transformation.
  • the composition of steel has C: 0.05 to 0.25% and Mn: 1.0 to 4.0% in mass%, and further Nb: 0.01 to 0.1%, V. It can be suitably applied when one or more selected from: 0.01 to 0.1% and Mo: 0.01 to 0.1% are arbitrarily possessed.
  • the component composition is simply expressed as% in "mass%".
  • Mn 1.0 to 4.0% If the Mn content is less than 1.0%, MnS, which is an embrittlement factor, is unlikely to be generated, so that there is no problem. If it is 1.0% or more, the embrittlement sensitivity becomes high, but if it exceeds 4.0%, the product becomes too strong, which is not desirable. Therefore, it is preferable to apply this embodiment in the case of a steel composition having a high embrittlement sensitivity and a Mn content of 1.0 to 4.0%.
  • Nb 0.01 to 0.1%
  • V 0.01 to 0.1%
  • Mo 0.01 to 0.1%
  • Nb, V and Mo contribute to the improvement of steel strength.
  • the content of each element is less than 0.01%, it is difficult to form carbonitride which is an embrittlement factor, so that there is no problem.
  • it exceeds 0.1% the price of the alloy becomes high and the cost rises, and the performance becomes excessive more than necessary. Therefore, it is not desirable to add more than 0.1%.
  • Example 1 Using a curved continuous casting machine, in mass%, C: 0.18%, Si: 1.4%, Mn: 2.8%, P: 0.020% or less, S: 0.003% or less, And Ti: Steel having a predetermined composition containing 0.020% was cast.
  • the Ar 3 transformation point of this steel is 805 ° C.
  • the casting conditions were in the range of a casting thickness of 220 mm, a casting width of 1000 to 1600 mm, and a casting speed of 1.20 to 1.80 m / min.
  • the slab temperature when passing through the bent part (lower straightening) was confirmed by measuring with a thermocouple or a radiation thermometer.
  • the slab After casting, the slab is subjected to color check (dye penetrant inspection) after removing oxides on the slab surface by shot blasting in order to facilitate observation of cracks on the slab surface. The presence or absence of cracks in the corners was investigated. Then, the corner crack occurrence rate was evaluated by the number of corner cracked slabs / the number of surveyed slabs ⁇ 100%. For the investigation of internal cracks, a cross-sectional sample perpendicular to the casting direction of the slab was cut out, milled, and then macro-etched with warm hydrochloric acid. The presence or absence of internal cracks was investigated using macro-etched photographs.
  • Example 2 Next, in order to determine the relationship between the average secondary cooling water density applied to the corners of the slab until passing through the bent portion (lower straightening), corner cracks, and internal cracks, a test was conducted under the same steel grade and continuous casting conditions as in Example 1. Was carried out. The results are shown in Table 2.
  • the average secondary cooling water density is less than 20 L / (min ⁇ m 2 ) (test Nos. 10 and 11), so that the corner temperature becomes Ar 3 or more and the corner cracks. Can be seen to be reduced.
  • the thickness of the solidified shell near the corners is insufficient, causing internal cracking due to bulging. From this, it can be seen that it is not possible to suppress both corner cracking and internal cracking with a normal rectangular mold.
  • a chamfer mold test Nos. 17 to 23
  • Corner cracking could not be suppressed unless the density of the next cooling water was reduced to less than 20 L / (min ⁇ m 2 ), and internal cracking due to bulging could not be avoided.
  • the chamfer molds (test Nos. 24 to 31) of the present embodiment were applied, the point that internal cracks occurred at less than 20 L / (min ⁇ m 2 ) (test Nos. 24 and 25) was the same. ..
  • supercooling of the corners of the slab is suppressed in the average secondary cooling water density range (test No. 24 to 30) of 60 L / (min ⁇ m 2) or less, resulting in corner cracking. was able to prevent.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Continuous Casting (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

L'invention concerne un procédé de coulée continue permettant de supprimer de manière fiable une fissure de surface d'une brame coulée et, en particulier, de fabriquer une brame de haute qualité sans fissures de coin. Ce procédé de coulée continue est destiné à réaliser une coulée continue d'acier. Dans le procédé de coulée continue, un moule de coulée dans lequel une forme de chanfreinage d'une partie de coin de moule de coulée satisfait une relation de 0,09 ≤ C/L ≤ 0,20 (dans la formule, C représente une quantité de chanfreinage de coin (mm), L représente une longueur de côté court de brame de coulée (mm)) est utilisé et une densité moyenne de quantité d'eau de refroidissement secondaire à un redressement inférieur à partir d'une position directement sous le moule de coulée au niveau de la partie de coin de brame de coulée est établie à 20 à 60 L/ (min•m2). En particulier, il est préférable que l'acier ait une composition de constitution contenant, en % en masse, 0,05 à 0,25 % de C et 1,0 à 4,0 % de Mn et comprenant en outre éventuellement au moins un élément choisi parmi 0,01 à 0,1 % de Nb, 0,01 à 0,1 % de V et 0,01 à 0,1 % de Mo.
PCT/JP2021/020838 2020-06-18 2021-06-01 Procédé de coulée continue WO2021256243A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CN202180040196.5A CN115697587A (zh) 2020-06-18 2021-06-01 连续铸造方法
KR1020227042643A KR20230006903A (ko) 2020-06-18 2021-06-01 연속 주조 방법
JP2021545426A JP6954514B1 (ja) 2020-06-18 2021-06-01 連続鋳造方法
EP21824759.1A EP4170054A4 (fr) 2020-06-18 2021-06-01 Procédé de coulée continue

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2020-105178 2020-06-18
JP2020105178 2020-06-18

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WO2021256243A1 true WO2021256243A1 (fr) 2021-12-23

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002307149A (ja) 2001-04-11 2002-10-22 Sumitomo Metal Ind Ltd 連続鋳造方法
JP2007331000A (ja) * 2006-06-15 2007-12-27 Kobe Steel Ltd 連続鋳造用鋳型
JP2015503450A (ja) * 2011-12-27 2015-02-02 ポスコ 連続鋳造鋳型
JP2015128776A (ja) * 2014-01-06 2015-07-16 三島光産株式会社 連続鋳造用鋳型
JP2020066018A (ja) * 2018-10-23 2020-04-30 日本製鉄株式会社 連続鋳造用鋳型及び鋼の連続鋳造方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI270423B (en) * 2004-08-30 2007-01-11 Showa Denko Kk Method and apparatus for manufacturing metal material, metal material and metal workpiece

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002307149A (ja) 2001-04-11 2002-10-22 Sumitomo Metal Ind Ltd 連続鋳造方法
JP2007331000A (ja) * 2006-06-15 2007-12-27 Kobe Steel Ltd 連続鋳造用鋳型
JP2015503450A (ja) * 2011-12-27 2015-02-02 ポスコ 連続鋳造鋳型
JP2015128776A (ja) * 2014-01-06 2015-07-16 三島光産株式会社 連続鋳造用鋳型
JP2020066018A (ja) * 2018-10-23 2020-04-30 日本製鉄株式会社 連続鋳造用鋳型及び鋼の連続鋳造方法

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TWI784570B (zh) 2022-11-21

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