WO2022138002A1 - 鋼の連続鋳造方法 - Google Patents
鋼の連続鋳造方法 Download PDFInfo
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- WO2022138002A1 WO2022138002A1 PCT/JP2021/043677 JP2021043677W WO2022138002A1 WO 2022138002 A1 WO2022138002 A1 WO 2022138002A1 JP 2021043677 W JP2021043677 W JP 2021043677W WO 2022138002 A1 WO2022138002 A1 WO 2022138002A1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 115
- 239000010959 steel Substances 0.000 title claims abstract description 115
- 238000009749 continuous casting Methods 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005266 casting Methods 0.000 claims abstract description 28
- 238000003756 stirring Methods 0.000 claims abstract description 19
- 238000005452 bending Methods 0.000 claims description 13
- 238000007711 solidification Methods 0.000 claims description 13
- 230000008023 solidification Effects 0.000 claims description 13
- 230000004907 flux Effects 0.000 claims description 12
- 238000005336 cracking Methods 0.000 abstract description 5
- 239000007788 liquid Substances 0.000 abstract 2
- 230000001939 inductive effect Effects 0.000 abstract 1
- 238000007654 immersion Methods 0.000 description 15
- 230000005499 meniscus Effects 0.000 description 8
- 230000007547 defect Effects 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 238000013019 agitation Methods 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000012935 Averaging Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 238000005422 blasting Methods 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000002500 effect on skin Effects 0.000 description 1
- 238000005206 flow analysis Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 230000008685 targeting Effects 0.000 description 1
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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
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
-
- 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
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
-
- 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
- B22D11/041—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds for vertical casting
-
- 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
-
- 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
- B22D11/18—Controlling or regulating processes or operations for pouring
-
- 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
- B22D11/18—Controlling or regulating processes or operations for pouring
- B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level
- B22D11/186—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by using electric, magnetic, sonic or ultrasonic means
Definitions
- the present invention relates to a continuous casting method for steel in which slab slabs are continuously cast by a vertical non-solidification bending type continuous casting machine.
- the present invention relates to a continuous casting method for steel to be continuously cast.
- Steel sheets for boilers, low-alloy steel sheets for pressure vessels, high-strength steel sheets for offshore structures and industrial machinery, etc. have a thickness exceeding 100 mm and are used as important members (high-quality extra-thick steel sheets). be.
- high-quality extra-thick steel sheets internal quality may be a problem in terms of usage performance.
- a manufacturing method was adopted in which a high-quality extra-thick steel sheet was manufactured by rolling or forging, thereby improving the internal quality of the high-quality extra-thick steel sheet.
- Patent Document 1 discloses a method of continuously casting an extra-thick slab slab having a thickness of 400 mm or more by applying electromagnetic agitation to the molten steel in a mold to give a swirling flow velocity to the molten steel in the vicinity of the meniscus. According to Patent Document 1, by giving a swirling flow velocity to the molten steel in the vicinity of the meniscus, it is possible to prevent the skin of the meniscus and suppress the growth of the solidified shell in the vicinity of the meniscus, and the temperature of the molten steel in the meniscus in the mold described above. It is said that it can solve the problems caused by the deterioration.
- Patent Document 2 describes a dipping nozzle as a method for continuously casting an extra-thick slab slab having a slab thickness of 380 mm or more at a slab drawing speed of 0.2 m / min or less using a vertical continuous casting machine. Continuous casting by installing in the center of the slab thickness, continuous casting with the degree of superheat to the liquidus temperature of the tundish in-mold steel set to 10 to 50 ° C, and in-mold molten steel using in-mold electromagnetic stirring. Is disclosed to be continuously cast while stirring.
- Patent Document 2 a large number of equiaxed crystal nuclei are generated in the molten steel by the above continuous casting method, and the grain size of the equiaxed crystals generated in the center of the extra-thick slab slab is miniaturized to generate zaku. It is said that this can improve the toughness of steel sheet products. Further, Patent Document 2 also discloses that continuous casting while stirring molten steel in a mold using electromagnetic stirring in the mold enhances the effect of reducing the particle size of equiaxed crystals.
- Patent Document 1 shows only an example in which the slab drawing speed is 0.25 m / min when the thickness of the extra-thick slab slab is 400 mm, and the conditions of electromagnetic stirring in the mold are meniscus. It is only described that electromagnetic stirring is performed so that the swirling flow velocity of the molten steel in the vicinity is 0.2 to 0.4 m / s.
- Patent Document 2 uses a vertical continuous casting machine, and the vertical continuous casting machine has a slower slab drawing speed than the vertical unsolidified bending type continuous casting machine due to the length of the continuous casting equipment. Therefore, when the thickness of the extra-thick slab slab is 380 mm, only an example in which the slab drawing speed is 0.15 to 0.16 m / min is shown. Further, the conditions of electromagnetic agitation in the mold at that time are not described.
- the steel grades that are the target of extra-thick slab slabs include steel grades such as sub-molded steel in which surface cracks are likely to occur on the surface of the slab. Is likely to occur, and the risk of surface cracking of extra-thick slab slabs is significantly increased.
- the internal quality has been mainly considered in the past, but as the slab drawing speed of extra-thick slab slabs increases, the casting conditions are set in consideration of preventing surface cracking. Is needed.
- the present invention has been made in view of the above circumstances, and an object thereof is to continuously cast even an extra-thick slab slab at a higher speed by using a vertical non-solidification bending type continuous casting machine. It is to provide a continuous casting method of steel which ensures the internal quality of the slab slab and at the same time prevents surface cracking.
- the gist of the present invention for solving the above problems is as follows.
- An alternating current moving magnetic field that moves in the width direction of the mold is applied to the molten steel in the mold by an electromagnetic stirring device in the mold to induce a swirling flow in the molten steel, and continuous casting is performed while stirring the molten steel.
- U 2 ⁇ f ............ (1)
- U is the traveling speed (m / s) of the AC moving magnetic field
- ⁇ is the distance between the magnetic poles of the coil of the electromagnetic agitator in the mold (m)
- f is the coil of the electromagnetic agitator in the mold.
- the frequency (Hz) of the applied current is the traveling speed (m / s) of the AC moving magnetic field.
- the average flow velocity of the molten steel at the solidification interface of the slab slab at a position 50 mm below the molten steel surface in the mold in the casting direction is 0.08 to 0.3 m / s, from the above [1] to the above [6].
- the method for continuous casting of steel according to any one of.
- the internal quality is good even for extremely thick slab slabs by appropriately determining the conditions of electromagnetic stirring in the mold. It is possible to continuously cast slab slabs without surface cracks under casting conditions with a higher slab drawing speed.
- FIG. 1 is a diagram showing an example of numerical calculation results, and is a result of investigating the influence of the frequency of the current applied to the coil on the temperature distribution of the molten steel in the mold.
- the method for continuous casting of steel according to the present invention is a method for continuously casting slab slabs with a vertical unsolidified bending type continuous casting machine, which has a pair of long sides of a mold and a pair of short sides of a mold.
- a pair of magnetic poles facing each other across the long side of the mold are arranged on the back surface of the pair of long sides of the mold for continuous casting that forms a rectangular internal space between the long side and the short side of the mold.
- This magnetic pole is installed in a range in the mold width direction that covers the maximum width of slab slabs continuously cast by a vertical unsolidified bending type continuous casting machine.
- an AC moving magnetic field in which the moving direction of the magnetic field is the mold width direction is generated, an AC moving magnetic field is applied to the molten steel in the mold, a swirling flow is induced in the molten steel in the mold, and the molten steel in the mold is removed. Continuous casting is performed while stirring.
- the molten steel in the mold When an AC moving magnetic field is applied to the molten steel in the mold, the molten steel in the mold within the range where the AC moving magnetic field acts moves in the moving direction of the AC moving magnetic field along the solidification interface on the long side of the slab.
- the moving directions of the AC moving magnetic fields applied from the pair of magnetic poles facing each other across the pair of mold long sides to the opposite directions, the molten steel near the solidification interface of the opposing slab long sides is opposite to the mold width direction. Since it moves in the direction, a swirling flow of molten steel swirling in the mold width direction is induced in the mold.
- a stirring flow of the molten steel having a flow velocity component that rotates in the horizontal direction is formed in the molten steel in the mold.
- the moving direction of the AC moving magnetic field As long as the moving directions of the AC moving magnetic fields applied from the pair of magnetic poles are opposite to each other, even if the moving direction of the magnetic field when viewed from directly above the mold is in the clockwise direction. Also, it may be in the counterclockwise direction. The effect is the same whether in the clockwise or counterclockwise direction.
- An AC moving magnetic field in the same moving direction is applied from the same back magnetic pole with respect to the long side of the mold.
- the "vertical unsolidified bending type continuous casting machine” means that the range of the mold and the lower part of the mold is vertical, that is, vertical (vertical part), and the lower part of the vertical part is curved in an arc shape (curved part). After that, it is a continuous casting machine that pulls out slabs in the horizontal direction (horizontal part). That is, it is a continuous casting machine that pulls out the slab from the vertical portion to the curved portion in a state where the unsolidified phase exists inside the slab.
- the present inventors have an extremely thick slab having a thickness of 400 mm to 500 mm and a slab width of 1900 mm to 2450 mm in a continuous casting method in which the flow of molten steel in a mold is controlled by using an AC moving magnetic field as described above.
- a survey was conducted on the flow status of molten steel in the mold when slab slabs were continuously cast.
- the "extremely thick slab slab” is a slab slab having a thickness of 360 mm or more.
- the width of the extra-thick slab slab is usually about 1000 mm or more, but when targeting high-quality extra-thick steel sheets, it is desirable to increase the mass per unit length of the extra-thick slab slab. In this case, the slab width is 1600 mm or more.
- the flow velocity distribution of the molten steel in the mold was repeatedly obtained by changing the combination of the slab drawing speed and the application conditions of the AC moving magnetic field, mainly by numerical calculation.
- the conditions for the immersion nozzle for injecting molten steel into the mold from the tundish are two rectangular holes with a width of 65 mm and a length of 75 mm, and the discharge angle of the discharge holes is downward from the horizontal direction.
- the temperature was 15 to 25 ° and the immersion depth was 200 mm.
- the "immersion depth of the immersion nozzle” is the length (distance) from the meniscus to the upper end of the discharge hole of the immersion nozzle.
- the slab drawing speed is 0.3 m / s by performing continuous casting under the condition that the traveling speed of the AC moving magnetic field calculated by the following equation (1) satisfies 0.20 to 1.50 m / s. It has been found that high-quality extra-thick slab slabs with few defects can be obtained even under casting conditions of min or more.
- U 2 ⁇ f ............ (1)
- U is the traveling speed (m / s) of the AC moving magnetic field
- ⁇ is the distance between the magnetic poles of the coil of the electromagnetic agitator in the mold (m)
- f is the coil of the electromagnetic agitator in the mold.
- the frequency (Hz) of the applied current is the traveling speed (m / s) of the AC moving magnetic field.
- the distance between the magnetic poles (pole pitch) ⁇ of the coil of the in-mold electromagnetic agitator cannot be changed, and once the equipment of the in-mold electromagnetic agitator is installed, it is fixed at a constant value. Therefore, in order to control the traveling speed of the AC moving magnetic field calculated by the above equation (1) in the range of 0.20 to 1.50 m / s, between the magnetic poles of the coils of the installed electromagnetic agitator in the mold. The frequency of the current applied to the coil is adjusted according to the distance ⁇ .
- the frequency of the current applied to the coil is set within the range of 0.143 Hz to 1.071 Hz, so that the progress of the AC moving magnetic field calculated by Eq. (1)
- the speed U is 0.20 to 1.50 m / s. That is, when the distance between the magnetic poles of the coil is 700 mm and the frequency of the current applied to the coil is in the range of 0.2 to 1.0 Hz, the traveling speed U of the AC moving magnetic field calculated by Eq. (1) is. It is in the range of 0.20 to 1.50 m / s.
- the traveling speed of the AC moving magnetic field calculated by the equation (1) is less than 0.20 m / s, the traveling speed of the AC moving magnetic field is too slow to control the flow of the molten steel in the mold.
- the traveling speed of the AC moving magnetic field calculated by Eq. (1) exceeds 1.50 m / s, the horizontal swirling flow induced in the molten steel by the AC moving magnetic field is limited to the vicinity of the inner surface of the mold (center of mold thickness). A swirling flow is unlikely to be induced in the molten steel in the vicinity), and as a result, the distribution of the molten steel temperature on the molten steel surface in the mold becomes remarkable.
- the temperature of the molten steel near the inner surface of the mold is lower than the temperature of the molten steel near the center of the mold thickness, and the temperature difference of the molten steel at the molten steel surface in the mold becomes large, which adversely affects the quality of the slab slab. .. This is because the larger the frequency of the current applied to the coil of the electromagnetic stirrer in the mold, the more difficult it is for the AC moving magnetic field to permeate toward the center of the mold thickness due to the skin effect.
- FIG. 1 shows an example of numerical calculation results.
- FIG. 1 shows a position 2.5 mm away from the surface of the long side of the mold when continuously casting an extra-thick slab slab having a slab thickness of 460 mm and a slab width of 2400 mm at a slab drawing speed of 0.6 m / min. This is the result of investigating the influence of the frequency of the current applied to the coil on the molten steel temperature distribution in.
- the distance between the magnetic poles of the coils ⁇ is 700 mm.
- the traveling speed of the AC moving magnetic field calculated by Eq. (1) is 4.6 m / s, which does not satisfy the scope of the present invention.
- the difference between the maximum value and the minimum value of the molten steel temperature is 2.0 ° C.
- a portion having a low molten steel temperature is formed in the vicinity of the short side of the mold. This is because the swirling flow due to the AC moving magnetic field does not reach the center of the mold thickness where the immersion nozzle, which is the source of the hot molten steel, exists, and only the relatively low temperature molten steel near the inner surface of the mold swirls due to the AC moving magnetic field. It is considered to indicate that.
- the traveling speed of the moving magnetic field calculated by Eq. (1) is 0.49 m / s, which satisfies the scope of the present invention.
- the difference between the maximum value and the minimum value of the molten steel temperature is 1.6 ° C., and the temperature difference is smaller than when a current having a frequency of 3.3 Hz is applied to the coil. It can be seen that the temperature distribution of the molten steel in the mold approaches more evenly.
- there is no low temperature part recognized when the frequency of the current applied to the coil is 3.3 Hz, and most of the mold width direction is when the frequency of the current applied to the coil is 0.35 Hz.
- the molten steel temperature is high in. This is considered to indicate that the high temperature molten steel supplied from the immersion nozzle is supplied to the entire inside of the mold as a result of the swirling flow due to the AC moving magnetic field reaching the center of the mold thickness. As a result, in continuous casting of extra-thick slabs, non-uniformity of initial solidification in the mold is less likely to occur even if the slab drawing speed is increased, and the risk of surface cracking of extra-thick slab slabs can be reduced.
- the position in the mold height direction is the center position in the height direction of the coil of the electromagnetic stirrer in the mold, and the position in the mold thickness direction is 15 mm from the inner surface of the long side of the mold toward the center of the mold thickness.
- the effective value of the component in the mold thickness direction of the magnetic flux density of the AC moving magnetic field is 0.008 T or more as an average value in the mold width direction. If the magnetic flux density satisfying the above conditions can be secured at this position, a suitable in-mold molten steel flow can be realized by the swirling flow induced in the molten steel by the AC moving magnetic field. Further, the stronger the magnetic flux density of the AC moving magnetic field, the easier it is to induce a swirling flow in the molten steel, so that it is not necessary to set an upper limit of the magnetic flux density.
- the effective value of the component in the mold thickness direction of the magnetic flux density of the AC moving magnetic field is 0.030 T or less in the average value in the mold width direction.
- the average flow velocity of the molten steel at the solidification interface of the slab slab at a position 50 mm below the molten steel surface in the mold in the casting direction is 0.08 to 0.3 m / s.
- the average flow velocity of the molten steel at the solidification interface of the slab slab at a position 50 mm below the molten steel surface in the mold is slower than 0.08 m / s, non-metal inclusions suspended in the molten steel will form a solidified shell. It becomes easier to be caught in the slab, and the risk of defects in the slab slab increases.
- the average flow velocity of the molten steel at the solidification interface of the slab slab at a position 50 mm below the molten steel surface in the mold exceeds 0.3 m / s, the molten steel flow collides with the solidified shell at high speed and the solidified shell. Redissolves, creating a risk of breakout during continuous casting.
- the present inventors performed numerical calculations by adding conditions to the range where the thickness of the slab is 360 mm or more and 540 mm or less, and confirmed the following tendency.
- the steel continuous casting method according to the present invention can more preferably enjoy the effect when the thickness of the continuously cast slab slab is 360 mm or more and 540 mm or less.
- the thickness of the slab slab is less than 360 mm, the slab slab is thin, so that the stirring effect acts on the entire molten steel in the mold even if the swirling flow induced in the molten steel by the AC moving magnetic field is only near the inner surface of the mold.
- the effect obtained by applying is small.
- the thickness of the slab slab exceeds 540 mm, it is necessary to increase the size of the in-mold electromagnetic agitator in order to allow the AC moving magnetic field to penetrate to the vicinity of the center in the mold thickness direction, and the equipment cost of the in-mold electromagnetic agitator.
- the thickness of the continuously cast slab slab is 400 mm or more and 500 mm or less.
- the present invention is a continuous casting operation in which the slab drawing speed is 0.3 to 0.8 m / min when the thickness of the slab slab to be continuously cast is an extra-thick slab slab of 360 mm or more and 540 mm or less. When applied to, the effect is more pronounced, which is preferable.
- INDUSTRIAL APPLICABILITY According to the present invention, in continuous casting of extra-thick slab slabs, high-speed casting with a slab drawing speed of 0.3 m / min or more, which was difficult to achieve with a conventional vertical continuous casting machine, becomes possible.
- the conditions of electromagnetic stirring in the mold are preferably set to obtain an extra-thick slab slab.
- the present invention was applied to continuous casting at a slab drawing speed of 0.8 m / min.
- the immersion nozzle used is a two-hole type immersion nozzle having rectangular discharge holes of 65 mm in width and 75 mm in length on the left and right sides of the immersion nozzle, and the discharge angle (angle with respect to the horizontal direction) of the discharge holes is downward 15
- the degree was set to °
- the immersion depth was set to 200 mm.
- the magnetic flux distance ⁇ of the coil of the electromagnetic stirrer in the mold used is 700 mm, and in this electromagnetic stirrer in the mold, the position in the height direction of the mold is the center position in the height direction of the coil of the electromagnetic stirrer in the mold.
- the effective value of the component in the mold thickness direction of the magnetic flux density of the AC moving magnetic field was 0.008 T on average in the mold width direction. ..
- the internal quality and surface quality of the manufactured extra-thick slab slabs were investigated.
- internal quality central segregation, zaku and internal cracks were investigated by hydrochloric acid corrosion test of polished slab cross section and sulfur print.
- surface quality after removing the oxide film on the surface of the slab by shot blasting, vertical cracks, horizontal cracks and inclusion of inclusions on the surface of the slab were investigated by a penetration test.
- Example 1 of the present invention no defects occurred in both the internal quality and the surface quality of the extra-thick slab slab. On the other hand, in Comparative Example 1, central segregation and zaku occurred. In Comparative Example 2, the internal quality was sound, but vertical cracks were generated on the surface of the slab.
- the present invention was applied to continuous casting at a slab drawing speed of 0.6 m / min.
- the immersion nozzle used is a two-hole type immersion nozzle having rectangular discharge holes of 65 mm in width and 75 mm in length on the left and right sides of the immersion nozzle, and the discharge angle (angle with respect to the horizontal direction) of the discharge holes is downward 15
- the degree was set to °
- the immersion depth was set to 200 mm.
- the magnetic flux distance ⁇ of the coil of the electromagnetic stirrer in the mold used is 700 mm, and in this electromagnetic stirrer in the mold, the position in the height direction of the mold is the center position in the height direction of the coil of the electromagnetic stirrer in the mold.
- the effective value of the component in the mold thickness direction of the magnetic flux density of the AC moving magnetic field was 0.008 T on average in the mold width direction. ..
- the internal quality and surface quality of the manufactured extra-thick slab slabs were investigated.
- internal quality central segregation, zaku and internal cracks were investigated by hydrochloric acid corrosion test of polished slab cross section and sulfur print.
- surface quality after removing the oxide film on the surface of the slab by shot blasting, vertical cracks, horizontal cracks and inclusion of inclusions on the surface of the slab were investigated by a penetration test.
- Example 2 of the present invention no defects occurred in both the internal quality and the surface quality of the extra-thick slab slab.
- Comparative Example 3 although the internal quality was sound, inclusions were involved on the surface of the slab.
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Abstract
Description
鋳型内電磁撹拌装置により鋳型内の溶鋼に鋳型幅方向に移動する交流移動磁場を印加して、前記溶鋼に旋回流を誘起し、前記溶鋼を撹拌しつつ連続鋳造を行なうにあたり、
下記の(1)式で算出される前記交流移動磁場の進行速度が0.20~1.50m/sである、鋼の連続鋳造方法。
U=2τf………(1)
(1)式において、Uは、交流移動磁場の進行速度(m/s)、τは、鋳型内電磁撹拌装置のコイルの磁極間距離(m)、fは、鋳型内電磁撹拌装置のコイルに印加される電流の周波数(Hz)である。
(1)式において、Uは、交流移動磁場の進行速度(m/s)、τは、鋳型内電磁撹拌装置のコイルの磁極間距離(m)、fは、鋳型内電磁撹拌装置のコイルに印加される電流の周波数(Hz)である。
Claims (7)
- 垂直未凝固曲げ型連続鋳造機を用いて、スラブ鋳片を連続鋳造する鋼の連続鋳造方法であって、
鋳型内電磁撹拌装置により鋳型内の溶鋼に鋳型幅方向に移動する交流移動磁場を印加して、前記溶鋼に旋回流を誘起し、前記溶鋼を撹拌しつつ連続鋳造を行なうにあたり、
下記の(1)式で算出される前記交流移動磁場の進行速度が0.20~1.50m/sである、鋼の連続鋳造方法。
U=2τf………(1)
(1)式において、Uは、交流移動磁場の進行速度(m/s)、τは、鋳型内電磁撹拌装置のコイルの磁極間距離(m)、fは、鋳型内電磁撹拌装置のコイルに印加される電流の周波数(Hz)である。 - 前記鋳型内電磁撹拌装置のコイルに印加される電流の周波数が0.2~1.0Hzである、請求項1に記載の鋼の連続鋳造方法。
- 鋳型高さ方向位置が、前記鋳型内電磁撹拌装置のコイルの高さ方向の中心位置で、鋳型厚み方向位置が、鋳型長辺の内面から15mmの位置の鋳型内において、前記交流移動磁場の磁束密度の鋳型厚み方向成分の実効値が、鋳型幅方向の平均値で0.008T以上である、請求項1または請求項2に記載の鋼の連続鋳造方法。
- 連続鋳造されるスラブ鋳片の厚みが360mm以上540mm以下である、請求項1から請求項3のいずれか1項に記載の鋼の連続鋳造方法。
- 連続鋳造されるスラブ鋳片の厚みが400mm以上500mm以下である、請求項1から請求項3のいずれか1項に記載の鋼の連続鋳造方法。
- 鋳片引き抜き速度が0.3~0.8m/minである、請求項4または請求項5に記載の鋼の連続鋳造方法。
- 鋳型内溶鋼湯面から鋳造方向50mm下方の位置でのスラブ鋳片の凝固界面における溶鋼の平均流速が0.08~0.3m/sである、請求項1から請求項6のいずれか1項に記載の鋼の連続鋳造方法。
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JPH11277197A (ja) | 1998-03-26 | 1999-10-12 | Nippon Steel Corp | 大断面鋳片の連続鋳造方法 |
JP2000015413A (ja) * | 1998-06-30 | 2000-01-18 | Nkk Corp | 厚鋼板用大断面鋳片の連続鋳造方法 |
JP2007229736A (ja) | 2006-02-28 | 2007-09-13 | Nippon Steel Corp | 厚鋼板用大断面鋳片の垂直型連続鋳造方法 |
JP2018103198A (ja) * | 2016-12-22 | 2018-07-05 | 株式会社神戸製鋼所 | 連続鋳造方法 |
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JPH11277197A (ja) | 1998-03-26 | 1999-10-12 | Nippon Steel Corp | 大断面鋳片の連続鋳造方法 |
JP2000015413A (ja) * | 1998-06-30 | 2000-01-18 | Nkk Corp | 厚鋼板用大断面鋳片の連続鋳造方法 |
JP2007229736A (ja) | 2006-02-28 | 2007-09-13 | Nippon Steel Corp | 厚鋼板用大断面鋳片の垂直型連続鋳造方法 |
JP2018103198A (ja) * | 2016-12-22 | 2018-07-05 | 株式会社神戸製鋼所 | 連続鋳造方法 |
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