[go: up one dir, main page]

WO2024262308A1 - Procédé de fabrication de brame - Google Patents

Procédé de fabrication de brame Download PDF

Info

Publication number
WO2024262308A1
WO2024262308A1 PCT/JP2024/020427 JP2024020427W WO2024262308A1 WO 2024262308 A1 WO2024262308 A1 WO 2024262308A1 JP 2024020427 W JP2024020427 W JP 2024020427W WO 2024262308 A1 WO2024262308 A1 WO 2024262308A1
Authority
WO
WIPO (PCT)
Prior art keywords
slab
reduction
thickness
gradient
soft
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.)
Pending
Application number
PCT/JP2024/020427
Other languages
English (en)
Japanese (ja)
Inventor
圭吾 外石
則親 荒牧
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.)
JFE Steel Corp
Original Assignee
JFE Steel Corp
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 Steel Corp filed Critical JFE Steel Corp
Priority to JP2024552781A priority Critical patent/JP7597281B1/ja
Publication of WO2024262308A1 publication Critical patent/WO2024262308A1/fr
Anticipated expiration legal-status Critical
Pending 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
    • 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
    • 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
    • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
    • 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
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould

Definitions

  • the present invention relates to a method for producing a slab having a thickness of 350 mm or more and a width-to-thickness ratio of 1.6 to 7.2, using a continuous casting machine.
  • molten steel solidifies by cooling to become a slab.
  • the slab is drawn out in the casting direction.
  • the unsolidified molten steel also called the unsolidified layer, flows in the direction of drawing the slab as it solidifies and shrinks, creating a so-called suction flow.
  • solute elements such as carbon (C), phosphorus (P), sulfur (S), and manganese (Mn) are concentrated. When these solute elements flow to the center of the slab and solidify, so-called central segregation occurs.
  • Central segregation deteriorates the quality of steel products, especially thick steel plates.
  • thick steel plates are used as line pipe materials for transporting oil and natural gas. If central segregation is present in these line pipe materials, there is a risk that hydrogen-induced cracking will occur starting from the central segregation due to the action of sour gas.
  • Steel is produced by rolling slabs produced in a continuous casting process. Conventionally, efforts have been made to reduce central segregation of slabs from the continuous casting process to the rolling process.
  • a method known as a method for improving central segregation in slabs is the soft reduction method at the end of solidification, in which a slab with an unsolidified layer is reduced inside a continuous casting machine.
  • the soft reduction method at the end of solidification is a method for producing slabs by gradually reducing the slab during continuous casting using reduction rolls located near the position where the slab has completed solidification.
  • the soft reduction method at the end of solidification is performed at a reduction speed equivalent to the amount of solidification shrinkage.
  • Patent Document 1 discloses that in a continuous casting method in which soft reduction is applied to a cast slab, the reduction amount per unit time in the section in which soft reduction is applied is specified.
  • the reduction amount is specified based on the surface temperature of the cast slab at the start of reduction and the thickness of the unsolidified layer of the cast slab at the reduction position.
  • Patent Documents 2 and 3 disclose that in a continuous casting method in which a bloom slab is continuously cast while being pressed down by multiple roll pairs, the reduction speed is increased according to the solid fraction at the center of the slab's thickness.
  • reduction is performed in the range from the point at which the solid fraction at the center of the slab's thickness reaches a temperature equivalent to 0.1 to 0.3 to the point at which the temperature reaches the limit of solid fraction flow.
  • Patent Document 4 discloses that in continuous casting of steel, in which a slab is continuously cast while being subjected to a rolling reduction, the rolling reduction conditions are adjusted based on information on the cross-sectional shape perpendicular to the longitudinal direction of the slab and information on the shape of the unsolidified portion in that cross-section.
  • Patent Documents 1 to 4 can produce slabs of appropriate quality, and further improvements are needed in the manufacturing method of slabs using continuous casting machines.
  • the present invention was made in consideration of the above circumstances, and aims to provide a method for manufacturing slabs using a thickness continuous casting machine that can produce slabs of appropriate quality regardless of the size of the slab.
  • the present invention has the following features:
  • a method for producing a slab having a thickness of 350 mm or more and a width-to-thickness ratio of 1.6 to 7.2, using a continuous casting machine comprising: a soft reduction region setting step of setting a soft reduction region including a start point for soft reduction of the slab in the continuous casting machine and an end point for soft reduction to end, based on a condition of cooling water for cooling the slab in the continuous casting machine, a withdrawal speed of the slab, and a solid phase ratio of the slab calculated using a composition of the slab; a reduction gradient setting step of setting a reduction gradient in the soft reduction region based on a thickness of the slab, a width of the slab, and a withdrawal speed of the slab; a secondary cooling intensity setting step of setting a first strength section as a section in which secondary cooling is performed in the soft reduction region, and a second strength section in which the secondary cooling is performed at an intensity stronger than that of the first strength section, based on the solid phase fraction of the slab; a continuous casting process in which continuous casting is performed using the
  • V is the slab withdrawal speed (m/min).
  • ⁇ is the thickness coefficient (-).
  • Z is the reduction gradient (mm/m).
  • D is the slab thickness (mm) just below the mold.
  • Do is the standard slab thickness (mm) just below the mold.
  • W1 is the water density (L/m 2 /min).
  • ⁇ and ⁇ are coefficients determined by the width W2 (mm) of the slab 11.
  • Rt is the total reduction amount of the slab (mm)
  • D is the thickness of the slab just below the mold (mm)
  • Do is the standard thickness of the slab just below the mold (mm)
  • ⁇ is the thickness coefficient (-).
  • the method for producing slabs using the continuous casting machine of the present invention makes it possible to obtain slabs of appropriate quality regardless of the size of the slab.
  • FIG. 1 is a side view showing an overall configuration of a continuous casting machine.
  • FIG. FIG. 2 is a flow chart showing the process steps of a method for producing a slab.
  • the inventors have found through experience that in continuous casting, in which a soft reduction is applied to a slab to cast it, the optimal reduction speed in the range in which a reduction force is applied to the slab (hereinafter also referred to as the "soft reduction zone”) varies depending on the thickness of the slab.
  • the thickness of the slab is set based on the thickness of the steel product after rolling and the reduction ratio during rolling required by the steel product specifications. Therefore, the thickness of the slab is set, for example, according to the specifications of the steel product. If a slab of the set thickness has never been cast using the soft reduction method, it is necessary to set a new reduction rate for soft reduction appropriate for the thickness of the slab.
  • the reduction rate during soft reduction can be determined, for example, by casting experiments using an actual machine with several levels of reduction gradient set. Setting the reduction rate requires a great deal of time and money. There is a demand for a simple method of determining the reduction gradient during soft reduction.
  • roll reduction gradient refers to the amount of change in the gap between opposing rolls (hereinafter also referred to as “roll gap”) when the roll gap is set to gradually narrower toward the downstream side in the casting direction.
  • the roll reduction gradient is usually expressed as the amount of change in roll gap per meter (mm/m).
  • the roll reduction gradient (mm/m) multiplied by the slab withdrawal speed (m/min) equals the roll reduction speed (mm/min).
  • Patent Document 1 continuous casting is performed with a focus on the thickness of the unsolidified layer of the slab as an index for effectively implementing soft reduction.
  • Patent Document 1 focuses on this focus based on the knowledge that the more reduction is performed downstream in the casting direction, i.e., the thinner the unsolidified layer of the slab, the smaller the proportion of the reduction amount set by the reduction rolls that is transmitted to the solid-liquid interface of the slab (hereinafter also referred to as "reduction efficiency").
  • Patent Documents 2 and 3 tests were conducted on three types of slabs with thickness x width of 300 mm x 500 mm, 162 mm x 162 mm, and 380 mm x 560 mm.
  • Patent Documents 2 and 3 both relate to soft reduction casting of bloom slabs. Bloom slabs have a smaller ratio of width to thickness (width/thickness) in a cross section perpendicular to the drawing direction than slab slabs. For this reason, the soft reduction efficiency of bloom slabs at the end of solidification is lower than that of slab slabs. When casting bloom slabs, the reduction amount is set to be larger as the solidification end is approached. In the bloom slab examples of Patent Documents 2 and 3, the reduction amount is about 2 to 3 times larger than that of the slab slab example of Patent Document 1. There is a problem in that these reduction conditions cannot be applied to soft reduction of slab slabs.
  • Patent Documents 1 to 3 the reduction gradient of the light reduction zone is changed along the drawing direction of casting. For this reason, in these examples, the setting of the roll gap of the slab support rolls is complicated, and there is a problem that the structure of the equipment is complicated in order to realize this in an actual machine.
  • the target is a bloom slab
  • the rolling conditions are set based on information about the cross-sectional shape perpendicular to the longitudinal direction of the slab, i.e., the width and thickness of the slab.
  • the reduction conditions are set using the ratio of the width to the thickness of the slab and the ratio of the width to the thickness of the unsolidified portion of the slab, and the reduction conditions are not set using the thickness of the slab itself.
  • the shape of the molten layer of the slab may become flattened in the vertical direction depending on the cooling ratio of the top and bottom surfaces of the slab in the continuous casting machine. Also, the shape of the molten layer of the slab may become flattened in the horizontal direction depending on the cooling ratio of the left and right surfaces of the slab. There is a risk that the molten layer of the slab may become flattened in both directions, rather than just one or the other.
  • Patent Document 4 aims to enable optimal soft reduction even when both types of flattening occur.
  • Patent Document 4 which is based on the premise that the unsolidified layer will flatten in the left-right and up-down directions, there is a problem in that it cannot effectively prevent center segregation in slab slabs.
  • FIG. 1 shows a side view of a continuous casting machine.
  • the continuous casting machine 100 has a vessel-shaped tundish 20 for storing molten steel 10 supplied from a ladle (not shown).
  • An immersion nozzle 21 for discharging the stored molten steel 10 is installed at the bottom of the tundish 20.
  • the tundish 20 is also provided with a sliding nozzle 22 for adjusting the flow rate of the molten steel 10.
  • the continuous casting machine 100 has a mold 30 that cools the molten steel 10 discharged from the tundish 20.
  • the mold 30 is formed in a cylindrical shape with openings at the top and bottom and a cavity that contains the molten steel 10.
  • the cavity is composed of a pair of plate-shaped long sides arranged opposite each other, and a pair of plate-shaped short sides arranged opposite each other in a direction perpendicular to the opposing surfaces of the long sides.
  • the molten steel 10 that flows in from the opening at the top is cooled in the cavity of the mold 30 to form the outer shell of the cast piece 11.
  • the cast piece 11 is pulled out from an opening formed below the mold 30.
  • the cooling of the molten steel 10 that takes place in the mold 30 is also called primary cooling.
  • the cast piece 11 is a slab cast piece.
  • the cast piece 11 has an unsolidified layer 11a and a solidified shell 11b that surrounds the unsolidified layer 11a.
  • the solidified shell 11b is the outer shell of the cast piece 11 that is formed when the molten steel 10 is cooled in the mold 30.
  • the thickness of the slab 11 is 350 mm or more.
  • the thickness of the slab 11 is, for example, 350 to 600 mm.
  • a thicker slab 11 is preferable because it allows for a higher reduction ratio.
  • the thickness of the slab 11 can be set by the length of the short side of the opening formed below the mold 30.
  • the frequency of occurrence of center segregation tends to increase.
  • the slab manufacturing method of the present invention it is possible to prevent the occurrence of center segregation in slabs 11 that are 350 mm or more in thickness and have a width-to-thickness ratio of 1.6 to 7.2.
  • the thickness of the slab 11 600 mm or less By making the thickness of the slab 11 600 mm or less, the structure in the center can be refined. In addition, in the vertical bending type continuous casting machine 100, it becomes possible to appropriately bend and straighten the slab 11.
  • the ratio of width to thickness (width/thickness) of the slab 11 is, for example, 1.6 to 7.2.
  • the width of the slab 11 can be set by the length of the long side of the opening formed below the mold 30. By setting the ratio of width to thickness to 1.6 to 7.2, it is possible to prevent insufficient or excessive reduction.
  • the continuous casting machine 100 has a slab support roll 40 that is provided below the mold 30.
  • the slab support roll 40 is composed of a support roll 41, a guide roll 42, and a pinch roll 43.
  • the support rolls 41 are cylindrical and arranged in pairs to sandwich the front and back surfaces of the slab 11. Multiple support rolls 41 are arranged in a row toward the downstream of the casting direction.
  • the guide rolls 42 are cylindrical and are arranged next to the support rolls 41.
  • the guide rolls 42 are arranged in pairs to sandwich the front and back surfaces of the cast piece 11.
  • Multiple guide rolls 42 are arranged in a row toward the downstream of the casting direction.
  • the pinch rolls 43 are cylindrical and are arranged following the guide rolls 42.
  • the pinch rolls 43 are arranged in pairs to sandwich the front and back surfaces of the cast piece 11.
  • Multiple pinch rolls 43 are arranged in a row toward the downstream of the casting direction.
  • the cast piece 11 in which the solidified shell 11b has been formed in the mold 30 is secondary-cooled with cooling water.
  • spray nozzles (not shown) are arranged between adjacent cast piece support rolls 40 (support roll 41, guide roll 42, pinch roll 43).
  • the section in which the spray nozzles that spray secondary cooling water are arranged is also referred to as the secondary cooling zone.
  • the spray nozzles that can be used include water spray nozzles and air mist spray nozzles.
  • the cast piece 11 is cooled by cooling water sprayed from a spray nozzle while moving in the casting direction in the secondary cooling zone.
  • the cooling water used for secondary cooling is also called secondary cooling water.
  • a soft reduction area (hereinafter also referred to as the soft reduction zone) 44 is provided in which pressure is applied in the thickness direction of the slab 11.
  • the soft reduction zone 44 the support rolls 41, guide rolls 42, and pinch rolls 43, which are arranged in pairs facing each other, are arranged so that the distance between them gradually narrows.
  • an amount of reduction equivalent to the amount of solidification shrinkage is applied to the slab 11.
  • the distance between the paired support rolls 41, guide rolls 42, and pinch rolls 43 is also called the roll gap.
  • the roll gap is adjusted to set the reduction gradient.
  • the reduction gradient is adjusted, for example, by the roll opening narrowing amount (mm/m) per meter in the casting direction.
  • the reduction speed (mm/min) in the light reduction zone 44 is obtained by multiplying the reduction gradient (mm/m) by the withdrawal speed (m/min) of the slab 11.
  • the soft reduction zone 44 is composed of two roll segments 45 arranged consecutively in the casting direction.
  • Each roll segment 45 is composed of three pairs of cast piece support rolls 40.
  • the number of roll segments 45 constituting the soft reduction zone 44 is not particularly limited, and may be one or more.
  • the number of slab support rolls 40 constituting each roll segment 45 is not particularly limited, and may be two or more pairs of slab support rolls 40.
  • the continuous casting machine 100 has a transport roll 50 that is provided following the strand support roll 40.
  • the continuous casting machine 100 also has a strand cutter 60 that is provided above the transport roll 50.
  • the strand cutter 60 operates at a predetermined timing to cut the strand 11 to a predetermined length.
  • the solidification of the slab 11 progresses to the inside and is completed at the solidification completion position 13 in the light reduction zone 44. Once solidification is completed, the slab 11 is cut by the slab cutter 60.
  • Figure 2 shows a side view of a roll segment 45 of a continuous casting machine.
  • Figure 3 shows a front view of a roll segment 45 of a continuous casting machine.
  • Figures 2 and 3 show an example in which one roll segment 45 is made up of three pairs of cast piece support rolls 40.
  • the roll segment 45 has a pair of rectangular plate-shaped frames 46, 47 arranged opposite each other in the vertical direction.
  • a number of roll chocks 48 are provided on the opposing surfaces of the pair of frames 46, 47.
  • the cast piece support roll 40 is supported by the roll chocks 48.
  • the pair of frames 46, 47 are supported by tie rods 49 provided at their four corners.
  • a pair of tie rods 49 are provided on both sides on the upstream side in the casting direction.
  • a pair of tie rods 49 are also provided on both sides on the downstream side in the casting direction.
  • Each tie rod 49 is provided with a worm jack WJ.
  • the worm jack WJ is connected to a motor MT.
  • the distance between the frames 46, 47 can be adjusted by operating the worm jack WJ with the motor MT.
  • the rolling gradient can be adjusted by adjusting the distance between the opposing slab support rolls 40.
  • the distance between the opposing slab support rolls 40 is a value that corresponds to the distance between the frames 46, 47. Therefore, the rolling gradient can be adjusted by adjusting the distance between the frames 46, 47.
  • the amount of movement of the frame 46 corresponds to the amount of movement of the worm jack WJ. Therefore, by recording in advance the amount that corresponds to the amount of movement of the worm jack WJ, the rolling gradient of the roll segment 45 can be set according to the amount of movement of the worm jack WJ.
  • the adjustment of the reduction gradient should be performed under conditions where no load from the slab 11 acts on the slab support rolls 40.
  • An example of such a condition is when there is no slab 11 on the roll segment 45.
  • Figure 4 is a flow diagram showing the method for producing a cast piece 11 using the continuous casting machine 100.
  • a soft reduction zone setting process (step S01) is performed in the continuous casting machine 100 to set a soft reduction zone 44 that includes the start point where soft reduction is performed on the cast piece 11 and the end point where the soft reduction ends.
  • step S01 the start point of the soft reduction and the end point at which the soft reduction ends are set based on the conditions of the cooling water used to cool the slab 11, the withdrawal speed of the slab 11, and the solid fraction of the slab 11, which is calculated using the composition of the slab 11.
  • the start point of the soft reduction zone 44 should be set before the position where the solid fraction in the center of the thickness direction of the slab 11 corresponds to 0.1.
  • the center of the thickness direction of the slab 11 can be, for example, within a range of 15 mm from the center of the thickness direction of the slab 11.
  • the end point where the soft reduction ends should be set at the position where the solid fraction in the center of the thickness direction of the slab 11 reaches the flow limit solid fraction.
  • the solid fraction is defined as 0 before solidification begins and 1.0 when solidification is complete. Therefore, the position where the solid fraction at the center of the thickness direction of the slab 11 in the continuous casting machine 100 is 1.0 corresponds to the position where solidification is completed.
  • the solid fraction can be determined using the conditions of the cooling water used to cool the slab 11, the drawing speed of the slab 11, and the composition of the slab 11.
  • the solid fraction at the center can be estimated based on the results of determining the temperature distribution of the slab 11 using a two-dimensional solidification heat transfer calculation.
  • the solid fraction at the center in the thickness direction of the slab 11 can be determined using a value estimated from the surface temperature of the slab 11.
  • the limit of the solid fraction flow is said to be 0.7 to 0.8. It is recommended to reduce the slab 11 in the soft reduction zone 44 until the solid fraction at the center in the thickness direction of the slab 11 reaches 0.7 to 0.8.
  • the unsolidified layer 11a does not move, and the effect of the soft reduction is weakened. For this reason, it is preferable to stop the soft reduction at the flow limit solid fraction.
  • the strength of the slab 11 will be greater than when the solid fraction is less than the flow limit solid fraction. This means that a large reaction force will be generated during the light reduction, and there is a risk that the slab 11 will not be reduced properly.
  • a reduction gradient setting process (step S02) is performed to set the reduction gradient in the soft reduction zone 44 based on the thickness of the slab 11, the width of the slab 11, and the withdrawal speed of the slab 11.
  • the rolling efficiency tends to decrease as the thickness of the solidified shell 11b increases.
  • the soft reduction conditions can be determined as follows.
  • the soft reduction conditions should be set as follows: the thickness of the slab 11, the reduction gradient of the soft reduction zone 44, the withdrawal speed of the slab 11, and the secondary cooling conditions.
  • the thickness of the slab 11, the reduction gradient of the soft reduction zone 44, and the withdrawal speed of the slab 11 are set to satisfy the relationships in the following equations (1) and (2).
  • the secondary cooling conditions are set to satisfy the following equation (3).
  • V is the slab withdrawal speed (m/min).
  • ⁇ is the thickness coefficient (-).
  • Z is the reduction gradient (mm/m).
  • D is the slab thickness just below the mold (mm).
  • Do is the slab reference thickness just below the mold (mm).
  • W1 is the water density (L/m 2 /min).
  • ⁇ and ⁇ are coefficients determined by the slab width W2 (mm).
  • ⁇ and ⁇ are expressed as follows depending on the range of the width W2 of the slab 11.
  • ⁇ 1.58
  • the above formulas (1) to (4) can be found as follows. First, to find formula (1), it is advisable to find the optimal range of the reduction gradient in the light reduction zone 44 when continuously casting a slab 11 with a thickness of 350 mm. The optimal range of the reduction gradient can be found, for example, by casting experiments using an actual machine.
  • the correction value can be found, for example, by a numerical simulation of the deformation of the slab 11 during soft reduction.
  • the numerical simulation can be performed for a thickness of the slab 11 in the range of 150 to 600 mm. From the simulation results, the relationship between the thickness of the slab 11 and the reduction efficiency was found, and a thickness coefficient ⁇ was calculated as a correction value.
  • the coefficients in equation (2) for calculating the thickness coefficient ⁇ were obtained as a linear approximation of the thickness of the slab 11.
  • the value of the thickness coefficient ⁇ becomes smaller as the thickness D of the slab 11 increases. This indicates that the rolling efficiency decreases as the thickness D of the slab increases.
  • the standard thickness Do of the slab 11 directly below the mold is the thickness of the slab 11 at which the thickness coefficient ⁇ in equation (2) is 1.
  • the standard thickness Do is 187 mm.
  • the rolling efficiency will change from the rolling efficiency of the standard thickness.
  • the change in rolling efficiency that accompanies the change in thickness of the cast piece 11 can be adjusted by adjusting the rolling gradient.
  • the reduction efficiency of the slab 11 can be made appropriate. This prevents center segregation and porosity in the slab 11, and also prevents inverse V segregation and internal cracks in the slab 11 due to excessive reduction.
  • the width of the slab 11 cast by the continuous casting machine 100 is a wide range, from 1000 to 2500 mm. Therefore, the thickness coefficient ⁇ was calculated for the entire range of slabs, where the thickness of the slab 11 is 350 to 600 mm, the width is 1000 to 2500 mm, and the ratio of width to thickness (width/thickness) is 1.6 to 7.2.
  • the main resistance to rolling during soft reduction in the soft reduction zone 44 is the part of the short side of the slab 11 where solidification has been completed.
  • the absolute value of the length of this part in the width direction of the slab 11 is approximately the same regardless of the width of the slab 11, provided that the thickness of the slab 11 is the same.
  • the rolling resistance is small due to the presence of the unsolidified layer. This rolling resistance is negligibly small compared to the areas where solidification is complete at both ends of the short sides of the cast slab 11.
  • a 1600 mm wide cast piece 11 has a larger proportion of the width of the portion of the short side where solidification has been completed than a 2100 mm wide cast piece 11. Therefore, the rolling resistance of a 1600 mm wide cast piece 11 is greater than that of a 2100 mm wide cast piece 11.
  • the reaction force due to the reduction resistance may exceed the set stress of the disc spring.
  • the roll gap may be widened during the light reduction, and the actual reduction gradient may be smaller than the set reduction gradient.
  • the thickness of the solidified shell 11b and the solid phase ratio at the center of the thickness direction of the slab 11 are calculated in advance using two-dimensional heat transfer solidification calculations, etc.
  • the amount of secondary cooling water or the withdrawal speed of the slab 11 is adjusted so that the solid fraction in the center of the slab 11 in the thickness direction when it enters the soft reduction zone 44 is 0.1 or less, and the solid fraction in the center of the slab 11 in the thickness direction when it leaves the soft reduction zone 44 is equal to or greater than the flow limit solid fraction.
  • a total reduction amount setting step (step S03) is performed to set a total reduction amount of the slab 11.
  • the total reduction amount (Rt) of the slab 11 and the thickness of the slab 11 are set within a range that satisfies the relationship of the following formula (4).
  • Rt is the total reduction amount of the slab (mm).
  • a secondary cooling strength setting process (step S04) is performed in which a first strength section and a second strength section in which secondary cooling is performed at a strength stronger than that of the first strength section are set as sections in which secondary cooling is performed in the light reduction zone 44 region based on the solid phase ratio of the cast slab 11.
  • the thickness of the slab 11 is 350 mm or more, the temperature gradient in the center of the slab 11 increases, the solidification structure becomes coarse, and central segregation may worsen. As a result, the effect of soft reduction alone is insufficient to improve the internal quality.
  • the first strength section can be set, for example, from the start of the soft reduction zone 44 until the solid fraction in the center of the slab 11 in the thickness direction reaches 0.2.
  • the second strength section can be set, for example, as a section in which the solid fraction at the center in the thickness direction of the slab 11 is from 0.2 to 0.8.
  • cooling is preferably performed at a water flow rate of, for example, 10 (L/ m2 /min) or more. By cooling the slab 11 at such a water flow rate, it is possible to refine the solidified structure.
  • step S05 the continuous casting process (step S05) is performed, in which continuous casting is performed using the soft reduction region, reduction gradient, first strength section, and second strength section set in each of the above steps S01 to S04.
  • the method for producing cast slabs of the present invention makes it possible to obtain cast slabs of appropriate quality regardless of the size of the slab.
  • the optimal reduction conditions can be easily determined. In other words, it is possible to prevent the occurrence of center segregation due to insufficient reduction and internal cracks due to excessive reduction. This makes it possible to quickly respond to the demands for manufacturing steel products with diverse specifications without the significant time and expense required for conducting actual machine experiments with multiple levels.
  • the slabs of Examples 1 to 9 and Comparative Examples 1 to 9 were cast using a continuous casting machine, and the degree of central segregation, the presence or absence of porosity, and the presence or absence of internal cracks were confirmed.
  • the slabs of Examples 1 to 9 and Comparative Examples 1 to 9 were made from low-carbon aluminum-killed steel.
  • the slabs of Examples 1 to 9 and Comparative Examples 1 to 9 were produced with thicknesses of 350 mm, 400 mm, and 450 mm, and a width of 2000 mm.
  • the casting conditions for the slabs of Examples 1 to 9 and Comparative Examples 1 to 9 are shown in Table 1.
  • the continuous casting machine used in the tests was the same as the continuous casting machine 100 shown in Figure 1.
  • the central segregation degree of the slab used in the test evaluation was measured by the following method. In a cross section perpendicular to the slab's drawing direction, the carbon concentration was analyzed at equal intervals along the thickness direction of the slab, and the maximum value in the thickness direction was taken as Cmax. The carbon concentration analyzed in the molten steel taken from the tundish during casting was taken as C0, and Cmax/C0 was taken as the central segregation degree. The closer the central segregation degree is to 1.0, the less central segregation the slab has. In this invention, a slab with a central segregation degree of 1.10 or more was determined to have a poor degree of central segregation.
  • the presence or absence of porosity and internal cracks in the slab was determined by microscopic observation near the center of the slab thickness in a cross section perpendicular to the slab's drawing direction.
  • the drawing speed of each cast piece was set so that the solid fraction at the center of the cast piece in the thickness direction in the light reduction zone was between 0.1 and the flow limit solid fraction.
  • the reduction gradient and the secondary cooling water flow density were set to satisfy the above formulas (1), (2), and (3).
  • the reduction gradient was set to a value below the lower limit of the optimal range of the reduction gradient determined by formulas (1) and (2).
  • the reduction gradient was set to a value above the upper limit of the optimal range of the reduction gradient determined by formulas (1) and (2).
  • the total reduction amount (Rt) was set to a value above the upper limit value of formula (4).
  • the secondary cooling water flow rate (W1) in the second strength section was set to a value below the lower limit value of formula (3).
  • the optimal range of the reduction gradient in Comparative Example 1, as determined by formulas (1) and (2), is 0.1 to 4.1 mm/m.
  • the reduction gradient is set to 0.05 mm/m.
  • the reduction gradient was insufficient, and the center segregation degree exceeded 1.100.
  • porosity was also observed inside the cast piece.
  • Comparative Examples 4 and 7 the reduction gradient was insufficient, and the center segregation degree exceeded 1.100.
  • the optimal range of the reduction gradient for Comparative Example 2 is 0.1 to 3.5 mm/m.
  • the reduction gradient is set to 5 mm/m. Internal cracks occurred in the slab of Comparative Example 2. For this reason, it is believed that the total reduction amount for Comparative Example 2 was excessive.
  • Comparative examples 5 and 8 had an excessive reduction gradient, with central segregation exceeding 1.100. Internal cracks occurred in the slab of comparative example 5. For this reason, it is believed that the total reduction amount in comparative examples 5 and 8 was excessive. Inverse V segregation, which appears in some parts when the reduction is excessive, was also confirmed in comparative examples 5 and 8.
  • Comparative Examples 3, 6, and 9 the central segregation exceeded 1.100. In Comparative Examples 3, 6, and 9, the solidification structure coarsened, and the degree of central segregation and porosity worsened compared to Invention Examples 1 to 9. This is thought to be because Comparative Examples 3, 6, and 9 had a lower cooling water density in the second strength range than Invention Examples 1 to 9.

Landscapes

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

Abstract

L'invention concerne un procédé de fabrication de brame au moyen duquel il est possible d'obtenir une brame de qualité appropriée. Dans ce procédé de fabrication de brame, une brame de taille prédéfinie est fabriquée à l'aide d'une machine de coulée continue. Le procédé de fabrication de brame comprend : une étape d'établissement de région de réduction de lumière pour établir une région de réduction de lumière comprenant un point de départ à partir duquel une brame est soumise à une réduction de lumière dans la machine de coulée continue et un point d'extrémité où la réduction de lumière se termine, sur la base des conditions concernant l'eau de refroidissement avec laquelle la brame est refroidie dans la machine de coulée continue, de la vitesse de retrait de la brame et d'un taux de phase solide de la brame obtenu à l'aide de la composition de la plaque ; une étape de réglage de gradient de réduction destinée à régler un gradient de réduction dans la région de réduction de lumière sur la base de l'épaisseur de la brame, de la largeur de la brame et de la vitesse de retrait de la brame ; une étape de réglage d'intensité de refroidissement secondaire pour régler, sur la base du taux de phase solide de la brame, une première section d'intensité en tant que section pour effectuer un refroidissement secondaire dans la région de réduction de lumière, et une seconde section d'intensité pour effectuer un refroidissement secondaire avec une intensité supérieure à celle de la première section d'intensité ; et une étape de coulée continue pour effectuer une coulée continue en utilisant la région de réduction de lumière, le gradient de réduction, la première section d'intensité et la seconde section d'intensité définis.
PCT/JP2024/020427 2023-06-20 2024-06-04 Procédé de fabrication de brame Pending WO2024262308A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2024552781A JP7597281B1 (ja) 2023-06-20 2024-06-04 鋳片の製造方法

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2023100473 2023-06-20
JP2023-100473 2023-06-20

Publications (1)

Publication Number Publication Date
WO2024262308A1 true WO2024262308A1 (fr) 2024-12-26

Family

ID=93935661

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2024/020427 Pending WO2024262308A1 (fr) 2023-06-20 2024-06-04 Procédé de fabrication de brame

Country Status (1)

Country Link
WO (1) WO2024262308A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004525767A (ja) * 2000-10-20 2004-08-26 エス・エム・エス・デマーク・アクチエンゲゼルシャフト 鋼材から成る鋳造ストランド、特に鋼塊サイズ又は粗形鋼サイズを有する鋳造ストランドを連続鋳造し、引き続き変形させるための方法及び装置
JP2015009264A (ja) * 2013-07-01 2015-01-19 Ｊｆｅスチール株式会社 鋼の連続鋳造方法
JP2019048322A (ja) * 2017-09-11 2019-03-28 新日鐵住金株式会社 連続鋳造機の２次冷却制御装置、連続鋳造機の２次冷却制御方法、およびプログラム
WO2020203715A1 (fr) * 2019-04-02 2020-10-08 Ｊｆｅスチール株式会社 Procédé de coulée continue d'acier

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004525767A (ja) * 2000-10-20 2004-08-26 エス・エム・エス・デマーク・アクチエンゲゼルシャフト 鋼材から成る鋳造ストランド、特に鋼塊サイズ又は粗形鋼サイズを有する鋳造ストランドを連続鋳造し、引き続き変形させるための方法及び装置
JP2015009264A (ja) * 2013-07-01 2015-01-19 Ｊｆｅスチール株式会社 鋼の連続鋳造方法
JP2019048322A (ja) * 2017-09-11 2019-03-28 新日鐵住金株式会社 連続鋳造機の２次冷却制御装置、連続鋳造機の２次冷却制御方法、およびプログラム
WO2020203715A1 (fr) * 2019-04-02 2020-10-08 Ｊｆｅスチール株式会社 Procédé de coulée continue d'acier

Similar Documents

Publication Publication Date Title
JP6115735B2 (ja) 鋼の連続鋳造方法
JP6384679B2 (ja) 熱延鋼板の製造方法
RU2678112C2 (ru) Способ непрерывного литья стали
JP3427794B2 (ja) 連続鋳造方法
JP5910577B2 (ja) 鋼の連続鋳造方法
JP3511973B2 (ja) 連続鋳造方法
JP7597281B1 (ja) 鋳片の製造方法
WO2024262308A1 (fr) Procédé de fabrication de brame
JPH08238550A (ja) 鋼の連続鋳造方法
US11471936B2 (en) Continuous casting method of steel
JP3111954B2 (ja) 連続鋳造方法
JP3275835B2 (ja) 連続鋳造方法および連続鋳造機
JP3356091B2 (ja) 薄鋳片の連続鋳造方法
JP3240978B2 (ja) 連続鋳造鋳片の製造方法
JP5195636B2 (ja) 連続鋳造鋳片の製造方法
JP7609290B2 (ja) 鋼の連続鋳造方法及び連続鋳造機
JP3876768B2 (ja) 連続鋳造方法
JP7679800B2 (ja) 鋼の連続鋳造方法
JP3994852B2 (ja) 垂直曲げ型連続鋳造機による連続鋳造方法およびそれにより製造される鋳片
JP3275828B2 (ja) 連続鋳造方法
JP3498586B2 (ja) 連続鋳造方法
JP3395674B2 (ja) 連続鋳造方法
JP3114679B2 (ja) 連続鋳造方法
JP3101785B2 (ja) 連続鋳造方法
JPH11309552A (ja) 連続鋳造丸鋳片の製造方法とその製造装置

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 2024552781

Country of ref document: JP

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 24825715

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2024825715

Country of ref document: EP

Effective date: 20251212