WO2023248632A1 - 鋳片の連続鋳造設備及び鋳片の連続鋳造方法 - Google Patents

鋳片の連続鋳造設備及び鋳片の連続鋳造方法 Download PDF

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Publication number
WO2023248632A1
WO2023248632A1 PCT/JP2023/017363 JP2023017363W WO2023248632A1 WO 2023248632 A1 WO2023248632 A1 WO 2023248632A1 JP 2023017363 W JP2023017363 W JP 2023017363W WO 2023248632 A1 WO2023248632 A1 WO 2023248632A1
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Prior art keywords
slab
cooling water
cooling
spray
water injection
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Ceased
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PCT/JP2023/017363
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English (en)
French (fr)
Japanese (ja)
Inventor
佑介 野島
広和 杉原
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JFE Steel Corp
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JFE Steel Corp
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Publication date
Application filed by JFE Steel Corp filed Critical JFE Steel Corp
Priority to EP23826821.3A priority Critical patent/EP4501490A4/en
Priority to CN202380046709.2A priority patent/CN119365281A/zh
Priority to KR1020247040929A priority patent/KR20250009482A/ko
Priority to JP2023547099A priority patent/JPWO2023248632A1/ja
Publication of WO2023248632A1 publication Critical patent/WO2023248632A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • B22D11/12—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
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • 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
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling

Definitions

  • the present invention relates to continuous slab casting equipment and a continuous slab casting method.
  • molten steel injected into a mold is cooled, and the extracted slab is conveyed while being cooled at the exit side of the mold, thereby producing slabs continuously.
  • the slabs are then cut into predetermined lengths to produce rolling materials such as slabs, blooms, and billets.
  • the slab extracted from the mold has unsolidified molten steel inside. Unsolidified molten steel is solidified to the center by cooling at the exit side of the mold, but the properties and quality of the slab vary depending on the solidification rate. Therefore, cooling on the exit side of the mold (hereinafter referred to as secondary cooling) is a process that determines the characteristics and quality of the slab.
  • FIG. 1 is a graph showing the relationship between the surface temperature of a slab and each boiling state in the water cooling process of the slab.
  • the slab in the initial stage of water cooling, the slab is cooled in a film boiling state where there is a steam film between the slab and water.
  • the heat transfer coefficient which is an index of cooling capacity, is low, and the surface temperature of the slab decreases slowly.
  • the surface temperature of the slab reaches about 700°C, it becomes difficult to maintain a steam film between the water and the slab, and the slab is brought to a transition boiling point where water and the slab come into partial contact. cooled down.
  • the slab When water comes into contact with the slab, the water in contact with the slab evaporates and the flow of water near the slab becomes intense, causing a rapid increase in the heat transfer coefficient and a sudden drop in the surface temperature of the slab. do. Thereafter, the slab shifts to a nucleate boiling state where contact between the slab and water occurs regularly while maintaining a high heat transfer coefficient, and the surface temperature of the slab rapidly decreases to about the temperature of water.
  • a high-temperature object is cooled in a nucleate boiling state with high cooling capacity, large thermal stress is applied to the surface and inside of the object, increasing the risk of defects such as cracks. Therefore, in the secondary cooling of a continuous casting process in which the surface temperature of the slab is high, it is common to cool the slab in a film boiling state via a steam film between the slab and water.
  • Possible causes of the collapse of the film boiling state include a local increase in water density, retention of cooling water on the top surface of the slab, and collision of cooling water injected from adjacent sprays. Conventionally, attempts have been made to avoid the above causes and maintain the film boiling state in order to cast slabs of uniform quality across the entire width.
  • the local increase in water density has been dealt with by improving the tip of the nozzle that injects the cooling water and flattening the distribution of the cooling water injected onto the slab. Furthermore, it is also effective to suppress local concentration of cooling water by using a nozzle with a small aspect ratio of the spray injection surface and a large injection area.
  • the spray injection surface is rectangular, the ratio of the short side to the long side is called the aspect ratio, and when the spray injection surface is elliptical, the ratio of the short axis to the long axis is called the aspect ratio. Note that when the spray injection surface is square or circular, the aspect ratio is 1.
  • Patent Document 1 discloses a method of spraying a pair of rolls that support and convey the slab by injecting cooling water with the central axis of the spray inclined with respect to the central axis of the nozzle.
  • a technique has been disclosed that can efficiently discharge the cooling water that has accumulated during this period out of the zone and maintain a film boiling state.
  • Patent Document 2 discloses that cooling water is sprayed by tilting the long axis of the spray jet surface at an inclination angle ⁇ of 5° or more and less than 45° with respect to the width direction of the slab.
  • a technique has been disclosed that can avoid collisions of cooling water from adjacent sprays and maintain a film boiling state.
  • Patent Document 1 What is disclosed in Patent Document 1 is a technology aimed at preventing accumulated water from flowing down the downstream side of the vertical band and the curved band in continuous casting equipment having the vertical band and the curved band.
  • the technique disclosed in Patent Document 1 is insufficient to remove the cooling water that has accumulated on the slab in the horizontal zone where the surface layer temperature of the slab is low and the film boiling state is likely to collapse.
  • the cooling water is only injected upward so that it does not flow downstream, the water will stay between the roll pairs and the temperature deviation in the width direction will increase. Therefore, a technique is required for smoothly discharging the cooling water injected onto the slab outside the width of the slab even in the vertical zone and the curved zone.
  • the present invention has been made in view of the above-mentioned problems, and it is possible to suppress the collision of cooling water sprayed from spray nozzles adjacent to each other in the width direction of the slab, and to suppress the collapse of the film boiling state.
  • the purpose of the present invention is to provide casting equipment and a continuous casting method for slabs.
  • the means for solving the above problems are as follows.
  • [1] Continuous slab casting equipment equipped with cooling equipment for cooling slabs with water, the cooling equipment having two or more cooling water injection nozzles arranged in the width direction of the slab, A continuous casting facility for slabs, wherein the two or more cooling water injection nozzles are arranged so that the spray surfaces of cooling water injection nozzles adjacent to each other in the width direction of the pieces do not overlap.
  • the spray jetting surface of the cooling water jetting nozzle is rectangular or elliptical, and each of the two or more cooling water jetting nozzles is arranged within a range that satisfies the following formula (1), as described in [1].
  • Continuous casting equipment for slabs are described in [1].
  • L is the installation pitch (m) of the cooling water injection nozzle
  • ⁇ 1 is the angle (°) in the long side direction or long axis direction of the spray injection surface with respect to the width direction
  • t 1 is the length (m) of the short side or short axis of the spray injection surface.
  • L is the installation pitch (m) of the cooling water injection nozzles
  • ⁇ 2 is the angle (°) in one side direction of the spray injection surface with respect to the width direction
  • One side of is the side closest to the adjacent spray injection surface among the sides of the spray injection surface
  • t is the length (m) of the one side.
  • L is the installation pitch (m) of the cooling water injection nozzles
  • D is the diameter (m) of the spray injection surface.
  • a method for continuous casting of slabs which includes a cooling step of cooling the slab with water, in which cooling water is injected from two or more cooling water injection nozzles arranged in the width direction of the slab.
  • a continuous casting method for a slab wherein the two or more cooling water injection nozzles are arranged to cool the slab and so that the spray surfaces of cooling water injection nozzles adjacent to each other in the width direction of the slab do not overlap.
  • the spray jetting surface of the cooling water jetting nozzle is rectangular or elliptical, and each of the two or more cooling water jetting nozzles is arranged within a range that satisfies the following formula (1), as described in [8]. Continuous casting method for slabs.
  • L is the installation pitch (m) of the cooling water injection nozzle
  • ⁇ 1 is the angle (°) in the long side direction or long axis direction of the spray injection surface with respect to the width direction
  • t 1 is the length (m) of the short side or short axis of the spray injection surface.
  • L is the installation pitch (m) of the cooling water injection nozzles
  • ⁇ 2 is the angle (°) in one side direction of the spray injection surface with respect to the width direction
  • One side of is the side closest to the adjacent spray injection surface among the sides of the spray injection surface
  • t is the length (m) of the one side.
  • L is the installation pitch (m) of the cooling water injection nozzles
  • D is the diameter (m) of the spray injection surface.
  • collision of cooling water injected from spray nozzles adjacent in the width direction of the slab can be suppressed.
  • collapse of the film boiling state is suppressed during secondary cooling of the slab, the temperature deviation on the surface of the slab during cooling is reduced, and slabs with fewer defects can be continuously cast.
  • FIG. 1 is a graph showing the relationship between the surface temperature of a slab and each boiling state in a water cooling process of the slab.
  • FIG. 2 is a schematic cross-sectional view of continuous casting equipment for slabs, which is an embodiment of the present invention.
  • FIG. 3 is a diagram showing a spray jet surface on the slab S of the cooling water jetted from the cooling water jet nozzle.
  • FIG. 4 is a schematic diagram showing a configuration example of the control device 10.
  • FIG. 5 is a schematic partial cross-sectional view of continuous slab casting equipment having a draining roll.
  • FIG. 6 is a schematic partial cross-sectional view of continuous slab casting equipment having a purge nozzle.
  • FIG. 5 is a schematic partial cross-sectional view of continuous slab casting equipment having a draining roll.
  • FIG. 6 is a schematic partial cross-sectional view of continuous slab casting equipment having a purge nozzle.
  • FIG. 7 is a schematic partial cross-sectional view of continuous slab casting equipment having a draining roll and a purge nozzle.
  • FIG. 8 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • FIG. 9 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • FIG. 10 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • FIG. 2 is a schematic cross-sectional view of continuous slab casting equipment, which is an embodiment of the present invention.
  • Continuous slab casting equipment 1 which is an embodiment of the present invention, includes a mold 2 for cooling molten steel injected from a tundish (not shown) to form the outer shell shape of a slab, and
  • the main components include a cooling facility 3 that cools the cast slab, a thermometer 4 that measures the temperature of the slab at the exit side of the cooling facility 3, and a control device 10 that controls the operation of the cooling facility 3. .
  • the long side on the upper right side of the slab is referred to as 1
  • the short side on the front side of the paper is referred to as 2
  • the long side on the lower left side is referred to as 3.
  • the short side of the side is referred to as the 4th side.
  • the injected molten steel is cooled by the mold 2, solidifies from the contact surface between the molten steel and the mold 2 toward the inner layer, and forms an outer shell shape.
  • slab S molten steel in which an outer shell shape is formed, including a completely solidified state, will be referred to as slab S.
  • the slab S extracted from the mold 2 is cooled by the cooling equipment 3 while being supported and conveyed by slab support rolls 5 installed on the outlet side of the mold 2 .
  • the mold 2 a known mold may be used.
  • the cooling equipment 3 includes a water cooling device 31 that water-cools the slab S under predetermined cooling conditions.
  • the water cooling device 31 includes a slab support roll 5 that supports and conveys the slab S, and a cooling water injection nozzle 32.
  • the slab support rolls 5 are arranged in pairs on the first and third sides of the slab S at regular intervals in the casting direction. Between the slab support rolls 5 adjacent in the casting direction, two or more cooling water injection nozzles 32a on the first side and two or more cooling water injection nozzles 32c on the third side face each other with the slab S in between. They are arranged at a predetermined pitch in the casting direction. Cooling water W is injected from the cooling water injection nozzle 32 toward the slab S.
  • the slab S By feeding the slab S into the cooling equipment 3, the slab S is transported in the casting direction while being secondary cooled by the cooling water W injected from the cooling water injection nozzle 32.
  • a cooling section in which a pair of slab support rolls 5 in the casting direction is one unit will be referred to as a cooling zone, and the unit of the cooling section will be counted as a "zone.”
  • a total of 19 cooling zones are depicted in FIG. 2, the number of cooling zones is not limited to this, and the number may be greater or less than 19 zones.
  • the cooling equipment 3 is constituted by a curved band 7 that is water-cooled while being curved by the slab support roll 5, and a horizontal band 8 that water-cools the slab S that is curved by the slab support roll 5 and held in a horizontal position.
  • vertical bending type continuous casting equipment will be explained as an example, but it is not limited to vertical bending type continuous casting equipment, and includes vertical type continuous casting equipment having only the vertical band 6 in the cooling equipment 3, It is also applicable to curved continuous casting equipment having only the curved band 7 and horizontal band 8 and horizontal continuous casting equipment having only the horizontal band 8.
  • the operational parameters of the water cooling device 31 include the amount of cooling water W injected from the cooling water injection nozzle 32 (cooling water amount), the amount of compressed air (compressed air amount), and the conveyance speed of the slab S.
  • the larger the amount of cooling water the larger the cooling rate and temperature drop of the slab S can be.
  • the slower the conveyance speed of the slab S is, the larger the amount of temperature reduction of the slab S can be. Therefore, by controlling at least one of the transport speed and the amount of cooling water of the slab S, at least one of the surface cooling rate and the amount of temperature drop of the slab S can be controlled, and the slab S having a desired material can be cast.
  • the cooling capacity and the surface distribution of the cooling water W can be adjusted. Suitable conditions can be maintained by adjusting the amount of compressed air even in the face of aging deterioration of target characteristics and equipment or minute changes in nozzle arrangement.
  • the balance of the amount of cooling water for each cooling zone may be changed.
  • the cooling rate can be controlled according to the temperature range of the slab S.
  • the number of cooling zones to which cooling water is injected may be changed. By changing the number of cooling zones used, the amount of temperature drop in the slab S can be controlled while keeping the cooling rate the same.
  • the ratio between the amount of cooling water W injected from the cooling water injection nozzle 32a on the first side and the amount of the cooling water W injected from the cooling water injection nozzle 32c on the third side may be changed.
  • shape defects caused by the difference in temperature drop between the first and third sides of the slab S can be controlled.
  • the amount of cooling water may be changed depending on the components of the slab S. This is because the thermal conductivity changes depending on the components of the slab S, and the cooling state changes.
  • the amount of compressed air and the conveying speed of the slab S may also be changed.
  • the cooling capacity and the surface distribution of the cooling water W are controlled by changing the amount of compressed air, and the temperature history of the slab S is controlled by changing the conveyance speed of the slab S, thereby finely adjusting the cooling conditions.
  • the quality of the slab to be cast can be improved.
  • the operating parameters of the water cooling device 31 may be changed according to the progress of casting.
  • the tip and end of the slab S are likely to be cooled from their tip and end surfaces and become unsteady parts. Therefore, by finely adjusting the operating parameters of the water cooling device 31 for these parts, it is possible to contribute to ensuring quality over the entire length and across the entire width and improving yield at unsteady parts.
  • the operating parameters of the water cooling device 31 may be finely adjusted for the stationary portion excluding the tip and end portions according to the progress of casting. Even if the characteristics change in the longitudinal direction even in the stationary part due to component segregation of the slab S, a slab that is homogeneous over the entire length can be obtained by finely adjusting the operating parameters of the water cooling device 31.
  • the cooling rate can be varied depending on the material, operating conditions, and equipment status.
  • the surface cooling rate exceeds 100° C./sec, the surface layer often becomes martensitic and defects such as cracks occur on the slab surface. Therefore, the surface layer cooling rate is preferably 100° C./sec or less. Additionally, if the surface cooling rate is less than 0.3°C/sec, the cooling rate will be almost the same as air cooling, which will reduce production efficiency, and as the cooling rate decreases, segregation inside the slab will worsen. However, the quality of the slab also deteriorates. For this reason, it is preferable that the surface layer cooling rate is 0.3° C./sec or more.
  • the film boiling state always transitions to the nucleate boiling state. Therefore, the injection of cooling water W to the slab S should be stopped when the temperature of the front and back surfaces of the slab S is 500°C or higher, preferably 600°C or higher. Note that, after the cooling water W is injected, if the temperature of the front and back surfaces of the slab S becomes sufficiently high again due to internal regeneration, the cooling water W may be injected again. By increasing the cooling rate through re-injection, production efficiency can be increased and slab quality can be improved.
  • a nozzle that can uniformly spray a predetermined flow rate of cooling water as the cooling water injection nozzle 32.
  • a spray nozzle is used as the cooling water injection nozzle 32, but the nozzle is not limited to the spray nozzle, and other nozzles such as a slit-type nozzle, a multi-hole jet nozzle, a mist nozzle, and a fog nozzle may be used.
  • a one-fluid nozzle that injects only liquid (generally water) may be used, or a two-fluid nozzle that injects a mixed fluid of liquid (generally water) and gas (generally air) may be used. Good too.
  • the cooling water injection nozzle 32 is preferably a nozzle that can vary the amount of cooling water and compressed air depending on the target cooling rate.
  • FIG. 3 is a diagram showing a spray jet surface on the slab S of the cooling water jetted from the cooling water jet nozzle.
  • FIG. 3(a) is a diagram showing a rectangular spray jetting surface.
  • a cooling water injection nozzle 32 in which the spray injection surface on the slab S is rectangular, and the length of the short side is t 1 (m) and the length of the long side is t 2 (m). Due to the geometrical relationship, in order to avoid collisions in the long side direction of the spray jet surfaces, the cooling water jet nozzles 32 are arranged so that the spray jet surfaces of the cooling water jet nozzles 32 adjacent to each other in the width direction of the slab S do not overlap. need to be installed.
  • the installation pitch of the cooling water injection nozzles 32 adjacent to each other in the width direction of the slab S, the angle in the long side direction with respect to the width direction of the slab S, and the length of the short side of the spray injection surface are expressed by the following equation (1).
  • a cooling water injection nozzle 32 is installed within the range that satisfies the requirement. By installing the cooling water injection nozzle 32 within a range that satisfies the following formula (1), collisions in the long side direction of the cooling water W injected from the cooling water injection nozzles 32 adjacent to each other in the width direction of the slab S are suppressed. It is possible to suppress the collapse of the film boiling state.
  • L is the installation pitch (m) of the cooling water injection nozzles
  • ⁇ 1 is the angle (°) in the long side direction of the spray injection surface with respect to the slab width direction
  • t 1 is the spray injection This is the length (m) of the short side of the surface.
  • the aspect ratio of the injection surface is preferably 100 or less.
  • the aspect ratio of the spray injection surface is more preferably 50 or less, and even more preferably 30 or less.
  • the aspect ratio is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more.
  • the angle ⁇ 1 in the long side direction is less than 45° so that the cooling water W injected onto the slab S can be quickly discharged to the outside of the slab.
  • the angle ⁇ 1 in the long side direction becomes 45° or more
  • the velocity component in the conveying direction is greater than that in the slab width direction. This is not preferable because it increases the size. It is more preferable that the angle ⁇ 1 in the long side direction is 30° or less.
  • FIG. 3(b) is a diagram showing a square spray jetting surface.
  • the installation pitch of the cooling water injection nozzles 32 adjacent to each other in the width direction of the slab S, the angle in one side direction of the spray injection surface with respect to the width direction of the slab S, and the spray Collision of the cooling water can be suppressed by installing the cooling water injection nozzle 32 within a range where the length of one side of the injection surface satisfies the following formula (2).
  • L is the installation pitch (m) of the cooling water injection nozzles 32
  • ⁇ 2 is the angle (°) of the spray injection surface in one side direction with respect to the slab width direction
  • t is the spray This is the length (m) of one side of the injection surface.
  • one side of the spray ejection surface is the side closest to the adjacent spray ejection surface among the respective sides of the spray ejection surface. That is, in the spray ejection surface 20 in FIG. 3(b), one side direction is the direction of the side 21 closest to the adjacent spray ejection surface 22. Further, in the spray ejection surface 22, one side direction is the direction of one of the sides 23 and 24 closest to the adjacent spray ejection surfaces 20 and 25.
  • FIG. 3(c) is a diagram showing a circular spray jetting surface.
  • the installation pitch of the cooling water injection nozzles 32 adjacent to each other in the width direction of the slab S and the diameter of the spray injection surface must be within the range that satisfies the following formula (3).
  • L is the installation pitch (m) of the cooling water injection nozzles 32
  • D is the diameter (m) of the spray surface.
  • the degree of local concentration of cooling water can also be evaluated by the water flow density defined by flow rate/injection area. Since there is a positive correlation between the water volume density of the injected cooling water and the boiling transition temperature, the film boiling state can be maintained for a long time by lowering the water volume density.
  • the local water density of the cooling water in the continuous slab casting equipment 1 is preferably 1000 L/(m 2 ⁇ min) or less, and 800 L/(m 2 ⁇ min) or less, and even more preferably 600 L/(m 2 ⁇ min) or less.
  • the thermometer 4 may be a device that measures the surface temperature of the slab S by scanning the temperature in the width direction of the slab S, and is arranged one or more in the width direction of the slab S. It may also be a device that measures surface temperature. By measuring the surface temperature of the slab S cooled by the cooling equipment 3 using the thermometer 4, it can be confirmed whether the slab S is being cooled as expected.
  • thermometer 4 is installed on the outlet side of the cooling equipment 3 in FIG. It may be installed. At this time, a plurality of thermometers 4 may be arranged in parallel in the conveyance direction of the slab S to measure the temperature of the slab S in each cooling zone.
  • thermometer 4 may be installed on the entrance side of the cooling equipment 3 or the entrance side of the mold 2 to measure the initial temperature of the slab S and the injection temperature of molten steel. This is because the calculation accuracy of the cooling rate is improved by taking into account the temperature measurement results on the inlet side of the cooling equipment 3.
  • One or more thermometers 4 may be installed in the cooling equipment 3 to measure the temperature of the slab S during water cooling. By taking into account the temperature measurement results inside the cooling equipment 3, the calculation accuracy of the cooling rate is improved and the time history thereof can also be grasped.
  • the cooling rate during water cooling by performing heat transfer calculations and heat transfer simulations, and check whether the slab S is being cooled as expected. You may. Furthermore, it may be confirmed whether the slab S is uniformly cooled by measuring the in-plane temperature distribution of the slab S during or after water cooling. In addition, by measuring the in-plane temperature distribution of the slab S before water cooling, it may be confirmed whether the slab S is charged into the cooling equipment 3 with a uniform in-plane temperature distribution. Based on these calculation results, the operating parameters of the cooling equipment 3 and the operating conditions of the continuous slab casting equipment 1 may be changed.
  • FIG. 4 is a schematic diagram showing a configuration example of the control device 10.
  • the control device 10 is an information processing device such as a personal computer.
  • the control device 10 acquires, from the host computer 11, size information such as the molten steel temperature and the thickness of the slab S, as well as information regarding the target range of the cooling amount and the target range of the cooling rate necessary to obtain the desired material quality. .
  • the control device 10 calculates the operating conditions of the continuous slab casting equipment 1 to achieve the target cooling amount and target cooling rate, and determines the operating parameters of each device.
  • the control device 10 has a control section 12 and a storage section 13.
  • the control unit 12 is, for example, a CPU or the like, and causes the control unit 12 to function as the calculation unit 14 and the output unit 15 by executing a program read from the storage unit 13.
  • the storage unit 13 is, for example, an information recording medium such as an update-recordable flash memory, a built-in hard disk or a hard disk connected via a data communication terminal, a memory card, and a read/write device thereof.
  • the storage unit 13 records programs for the control unit 12 to execute various functions, data used by the programs, and the like.
  • the calculation unit 14 calculates the heat transfer based on the internal model, and determines the number of cooling zones, the amount of cooling water, the amount of compressed air, and the slab to be used so as to satisfy the target cooling amount and target cooling rate set as cooling conditions. Determine the transport speed of S.
  • the command values for the amount of cooling water, the amount of compressed air, and the conveyance speed of the slab S determined in this way are outputted from the output section 15 to the water cooling device 31.
  • the operating pressure and number of operating cooling water pumps, the operating pressure and number of operating air compressors, and the operating pressure and number of operating units of the cooling water injection nozzle 32 are determined. Commands for the number of headers provided on the upstream side, the opening degree of the flow rate regulating valve, and the rotational speed of the slab support roll 5 are generated, and the operating conditions of the water cooling device 31 are determined.
  • any or all of the number of cooling zones to be used, the amount of cooling water, the amount of compressed air, and the conveyance speed of the slab S are determined in advance using a table based on information such as the composition, size information, and target material of the slab S. , it may be sent to the water cooling device 31 as a command.
  • the slab S extracted from the mold 2 is supported by slab support rolls 5 installed on the exit side of the mold 2, and cooled by the cooling equipment 3 while being conveyed.
  • the number of zones, amount of cooling water, amount of compressed air, and conveyance speed to be used are calculated and set by the control device 10 according to the size of the slab S and the target characteristics of the slab S.
  • a description will be given assuming that the slab S is cooled by injecting water and air from all zones shown in FIG.
  • a predetermined amount of cooling water W and compressed air A are injected from 19 pairs of cooling water injection nozzles 32, and the slab support roll 5 is rotated at a predetermined speed. These parameters are set by the control device 10 and commanded to the cooling water injection nozzle 32 and the slab support roll 5 so that target slab characteristics can be obtained. By cooling the slab S with the cooling equipment 3, the slab S with desired characteristics can be cast. The slab S that has undergone this cooling process is subjected to a subsequent process.
  • FIG. 5 is a schematic partial cross-sectional view of continuous slab casting equipment having a draining roll.
  • a draining roll 33 may be installed on the outlet side of the water cooling device 31 of the continuous slab casting equipment 1 to cut off the cooling water W accumulated on the slab S.
  • the slab S is locally or entirely cooled by the cooling water W remaining on the slab S, and the desired cooling amount and furthermore, the desired properties cannot be obtained locally or entirely. can be suppressed.
  • the pressing force of the draining roll 33 against the slab S is preferably 4 tons or more.
  • the pressing force of the draining roll 33 against the slab S is more preferably 6 tons or more, and even more preferably 8 tons or more.
  • the pressing force of the draining roll 33 against the slab S is 20 tons or less.
  • a spring type such as a spring, or a mechanism capable of applying a constant pressing force such as pneumatic pressure or hydraulic pressure may be used.
  • a mechanism that can maintain a constant pressing force it is preferable to use a mechanism that can maintain a constant pressing force, and more preferably a mechanism that can change the pressing force in the longitudinal direction of the slab S.
  • the slab support roll 5 may also serve as a draining roll.
  • the pressing force of the slab support roll 5 in that case is not limited to the above range. This is because rolling down the slab S by the slab support roll 5 may result in a slab of higher quality.
  • FIG. 6 is a schematic partial cross-sectional view of continuous slab casting equipment having a purge nozzle.
  • a purge nozzle 34 may be disposed in place of the draining roll 33, and a draining purge 35 may be jetted to remove the cooling water W remaining on the slab S.
  • the drain purge 35 may be a liquid, a gas, or a mixed fluid thereof.
  • gas it is preferable to use gas as the drain purge 35. From the viewpoint of production costs, it is more preferable to use air as the drain purge 35.
  • FIG. 7 is a schematic partial cross-sectional view of continuous slab casting equipment having a draining roll and a purge nozzle.
  • a draining roll 33 and a purge nozzle 34 may be used together.
  • one or both of the draining roll 33 and the purge nozzle 34 may be disposed on the inlet side of the water cooling device 31 to cut off the cooling water W leaking from the water cooling device 31. This can prevent the temperature of the slab S fed into the cooling equipment 3 from decreasing and the cooling water W from flowing into another device (for example, the mold 2) located upstream of or around the cooling equipment 3. .
  • one or both of the draining roll 33 and the purge nozzle 34 may be arranged not only on the inlet and outlet sides of the water cooling device 31 but also on the inlet and outlet sides of each cooling zone to separate each cooling zone.
  • all the cooling water injection nozzles 32 included in the cooling equipment 3 do not have to satisfy the above formula (1), (2), or (3), and two or more cooling water injection nozzles adjacent to each other in the slab width direction It is sufficient that the injection nozzle 32 satisfies the above formula (1), (2), or (3).
  • collision of cooling water can be suppressed more than in continuous casting equipment for slabs that does not have any cooling water injection nozzle 32 that satisfies the above formulas (1), (2), or (3), and film boiling state is achieved. can suppress the collapse of
  • FIG. 8 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • the continuous slab casting equipment 40 is equipped with a cooling water injection nozzle 36 capable of injecting an amount of cooling water that changes the boiling state to a nucleate boiling state on both the inlet and outlet sides of the water cooling device 31.
  • the slab S is cooled using these materials according to the characteristics of the slab S.
  • the cooling water injection nozzle 36 may be provided on the inlet/output side of the water cooling device 31 to inject the amount of cooling water to change the boiling state to the nucleate boiling state.
  • the invention is not limited to this, and the cooling water injection nozzles 36 may be installed on either the input and output sides. Good too. Furthermore, the number of cooling zones in which the cooling water injection nozzles 36 are installed is as shown in FIG. However, the zone may be other than 3 zones.
  • FIG. 9 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • a cooling water injection nozzle 32 and a cooling water injection nozzle 36 capable of injecting an amount of cooling water that changes a boiling state to a nucleate boiling state are arranged in the same cooling zone.
  • the cooling water injection nozzle 32 and the cooling water injection nozzle 36 may be arranged in the same cooling zone, and by combining the cooling by the cooling water injection nozzle 32 and the cooling of the cooling water injection nozzle 36, even more various Cooling based on temperature history can be achieved.
  • FIG. 9 shows an example in which the cooling water injection nozzle 32 and the cooling water injection nozzle 36 are arranged in the same cooling zone in two zones. The zone is not limited to this, and may be other than two zones.
  • FIG. 10 is a schematic cross-sectional view showing another example of the continuous slab casting equipment according to the present embodiment.
  • a cooling water injection nozzle 37 that injects only the amount of water that changes the boiling state to the nucleate boiling state is arranged in a part of the cooling water injection nozzle in the water cooling device 31. has been done.
  • the cooling water injection nozzle 37 may be arranged in a part of the cooling water injection nozzles in the water cooling device 31. This is because if a portion other than the cooling water injection nozzle 37 is regarded as the water cooling device 31 and collision of cooling water can be suppressed in this portion, an effect of suppressing collapse of the film boiling state can be obtained.
  • cooling water injection nozzle 36 which can inject an amount of water that changes a boiling state to a nucleate boiling state, may be a one-fluid nozzle that injects only air or a one-fluid nozzle that injects only water, or a mixed fluid of water and air.
  • a two-fluid nozzle that injects may also be used.
  • the slab S extracted from the mold 2 is conveyed while being cooled and being compressed from the slab support rolls 5. This is because by pressing down the slab S, internal segregation is reduced and the quality of the slab is improved. Therefore, the method for continuous casting of slabs according to the present embodiment may be combined with the known slab rolling technique, thereby further improving the quality of the slabs produced. At this time, it is preferable that the operating parameters of the water cooling device 31 and the operating parameters related to the known slab reduction technique be coupled to each other.
  • the slab support rolls 5 are arranged on the 1st and 3rd sides of the slab S, but the invention is not limited to this. It may be placed on the second and fourth sides. By supporting and rolling down the second and fourth sides with rolls, it is possible to suppress expansion in the width direction that occurs due to rolling down from the slab support rolls 5 on the first and third sides.
  • a slab S continuously cast using the continuous slab casting equipment 1 shown in FIG. 2 is cooled by the cooling equipment 3 to produce a slab of rolling material.
  • the cooling equipment 3 is arranged downstream of the mold 2, and inside thereof there are 19 pairs of cooling water injection nozzles 32 constituting a water cooling device 31 and 20 pairs of slab supports.
  • a roll 5 is arranged.
  • the cooling water injection nozzle 32 has a structure in which a rectangular spray nozzle, a square spray nozzle, and a circular spray nozzle can be replaced, and they are replaced according to the casting conditions.
  • thermometer 4 was installed at a position 5 m away from the outlet side of the cooling equipment 3 on the downstream side, and the temperature distribution of the surface layer in the width direction of the slab S after passing through the cooling equipment 3 was measured.
  • the value obtained by subtracting the minimum value from the maximum value is evaluated as the temperature deviation value in the slab S, and if the temperature deviation value is less than 50 ° C The temperature deviation was considered to be a pass.
  • a slab manufactured by cutting the cast slab S was inspected in a post-process to check for minute cracks on the surface of the slab. Additionally, the number of segregated grains at the center of slab thickness was investigated.
  • the steel strip after hot and cold rolling of the slab was inspected to conduct a follow-up investigation to determine whether any defects were found in the steel strip after cold rolling. Furthermore, a heat transfer simulation was performed based on the temperature measurement results with the thermometer 4, and the surface cooling rate of the slab S was calculated.
  • the casting conditions and evaluation results for the slab S in this example are shown in Table 1 below. Note that in Table 1, the angle is ⁇ 1 for a rectangle, and ⁇ 2 for a square. Further, the length is t1 in the case of a rectangle, t in the case of a square, and the diameter D in the case of a circle.
  • the temperature deviation in the width direction was smaller when a rectangular spray nozzle was used than when a circular or square spray nozzle was used. This result is thought to be due to the fact that by using the rectangular spray nozzle, the cooling water W in the longitudinal direction with a high flow rate could be quickly discharged outside the width of the slab S.
  • the temperature deviation was the smallest when a spray nozzle with an aspect ratio of the spray ejection surface of 30 was used.
  • the aspect ratio is small, the drainage effect of the cooling water W is reduced, while when the aspect ratio is large, the cooling water W is locally concentrated and the temperature deviation becomes large. From this result, it was confirmed that there is an optimal value for the aspect ratio of the spray injection surface.
  • Invention examples 7-9 are casting examples in which rectangular, square, and circular spray nozzles are used, and the water density is increased.
  • Inventive Example 7-9 passed the test with a temperature deviation of less than 50°C, but several small cracks occurred on the slab surface. This microscopic crack is thought to be caused by the cooling rate being too high and the surface layer of the slab S becoming martensite. However, since the temperature deviation of Invention Examples 7-9 was acceptable, no defects were found in the steel strip after cold rolling, and the product could be shipped.
  • Invention examples 10-12 are casting examples in which a rectangular, square, or circular spray nozzle is used and the water density is lowered. Invention example 10-12 passed the test with a temperature deviation of less than 50°C, but the number of segregated grains at the center of the thickness of the slab increased. This increase in the number of segregated grains at the center of the slab thickness is thought to be because the cooling rate became too low and the temperature gradient inside the slab S became small. However, since the temperature deviation of Invention Examples 10-12 was acceptable, no defects were found in the steel strip after cold rolling, and the product could be shipped.
  • Comparative Example 1 is a casting example in which a flat spray nozzle was used and the spray angle was made small so that the above formula (1) was no longer satisfied.
  • the temperature deviation was 90° C., making it impossible to produce a homogeneous slab across the entire width, and defects occurred in the steel strip after rolling. For this reason, the steel strip manufactured from this slab could not be shipped. This is considered to be because the cooling water W injected from adjacent nozzles interfered with each other, causing the film boiling state to collapse in that area and improving the cooling capacity.
  • Comparative Example 2 is a casting example in which a rectangular spray nozzle was used and the spray angle was increased so that the above formula (1) was no longer satisfied.
  • the temperature deviation was 218° C., making it impossible to produce a homogeneous slab across the entire width, and defects occurred in the rolled steel strip. For this reason, the steel strip manufactured from this slab could not be shipped. This is because the cooling water W on the slab S could not be discharged outside the width of the slab S, and as the cooling water W remained on the slab S, the film boiling state locally transitioned to the nucleate boiling state. it is conceivable that.
  • Comparative Examples 3 and 4 are casting examples in which square or circular spray nozzles were used, and the nozzle installation pitch was shortened so that the above formula (2) or (3) was no longer satisfied.
  • the temperature deviation was 86° C. and 92° C., making it impossible to produce a homogeneous slab across the entire width, and defects occurred in the steel strip after cold rolling. For this reason, the steel strip manufactured from this slab could not be shipped. This is considered to be because the cooling water W injected from adjacent spray nozzles interfered with each other, and the cooling capacity was improved only in that part.

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PCT/JP2023/017363 2022-06-21 2023-05-09 鋳片の連続鋳造設備及び鋳片の連続鋳造方法 Ceased WO2023248632A1 (ja)

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EP23826821.3A EP4501490A4 (en) 2022-06-21 2023-05-09 CONTINUOUS CASTING OF CAST SLAB AND CONTINUOUS CASTING OF CAST SLAB PROCESS
CN202380046709.2A CN119365281A (zh) 2022-06-21 2023-05-09 铸片的连续铸造设备及铸片的连续铸造方法
KR1020247040929A KR20250009482A (ko) 2022-06-21 2023-05-09 주편의 연속 주조 설비 및 주편의 연속 주조 방법
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JP2009255127A (ja) 2008-04-17 2009-11-05 Jfe Steel Corp 連続鋳造鋳片の冷却方法及び冷却設備
JP2014050874A (ja) * 2012-09-10 2014-03-20 Nippon Steel & Sumitomo Metal 連続鋳造の二次冷却方法
JP2015217435A (ja) * 2014-05-21 2015-12-07 新日鐵住金株式会社 鋼の連続鋳造方法
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EP4501490A4 (en) 2025-07-09
EP4501490A1 (en) 2025-02-05

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