WO2023190645A1 - 熱延鋼帯の焼鈍方法 - Google Patents

熱延鋼帯の焼鈍方法 Download PDF

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WO2023190645A1
WO2023190645A1 PCT/JP2023/012737 JP2023012737W WO2023190645A1 WO 2023190645 A1 WO2023190645 A1 WO 2023190645A1 JP 2023012737 W JP2023012737 W JP 2023012737W WO 2023190645 A1 WO2023190645 A1 WO 2023190645A1
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steel strip
temperature
annealing
heating
hot
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PCT/JP2023/012737
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English (en)
French (fr)
Japanese (ja)
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弘和 小林
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Ｊｆｅスチール株式会社
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Priority to JP2023558798A priority Critical patent/JPWO2023190645A1/ja
Publication of WO2023190645A1 publication Critical patent/WO2023190645A1/ja

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/60—Continuous furnaces for strip or wire with induction heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/62—Continuous furnaces for strip or wire with direct resistance heating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon

Definitions

  • the present invention relates to a method of annealing a hot-rolled steel strip (hot-rolled steel strip) used in the production of electrical steel sheets.
  • annealing hot-rolled sheet annealing
  • electrical steel sheets containing 1.6 to 5.0 mass% Si before cold rolling the magnetic properties of the product sheet can be improved. It is known that the Goss orientation can be highly developed.
  • the above-mentioned hot-rolled sheet annealing is usually performed using continuous annealing equipment equipped with a heating zone, a soaking zone, and a cooling zone.
  • the annealing temperature in the above-mentioned hot-rolled sheet annealing greatly affects the magnetic properties of the product sheet, and it is necessary to control the steel sheet temperature to be constant and uniform over the entire length and width of the hot-rolled steel strip. Therefore, in the continuous annealing equipment described above, in order to control the heating temperature of the hot rolled steel strip to be annealed within a suitable range, the furnace temperature in the soaking zone is controlled to be constant.
  • hot-rolled steel strips are thick, the variation in thickness with respect to the rolled thickness is large, especially at the front and rear ends of the steel strip, so the heat capacity varies greatly even within the same steel strip. Therefore, hot-rolled steel strip has a greater effect on the furnace temperature of the annealing furnace than cold-rolled steel strip. It becomes difficult to heat the product to the desired soaking temperature.
  • Patent Document 1 states that in a furnace that heats a slab, the temperature may increase between a portion that contacts a bar-shaped skid that holds the slab (skid portion) and a portion that does not contact (non-skid portion). Disclosed. This indicates that the state of the precipitates and the solid solution state of the inhibitor change, and therefore the optimal heating conditions for obtaining good magnetic properties during annealing after hot rolling change.
  • Patent Document 2 discloses a technique for reducing the aging index of a steel sheet before final cold rolling in the production of grain-oriented electrical steel sheets by controlling the cooling rate during hot-rolled sheet annealing.
  • Patent Document 3 discloses a hot-rolled plate annealing technique for a Si-containing steel plate in which a steel strip is rapidly heated during hot-rolled plate annealing.
  • Patent Document 1 only discloses a heating method for a slab to eliminate variations in the magnetic properties of a product steel strip, but does not disclose a method for controlling the temperature of a steel sheet with high precision during hot-rolled sheet annealing. I haven't. Furthermore, although the technology of Patent Document 2 discloses improving the hot-rolled sheet structure of a grain-oriented electrical steel sheet by performing hot-rolled sheet annealing, the heating temperature of hot-rolled sheet annealing is controlled with high precision. There is no mention of the need to do so or the means to do so. Furthermore, the technology of Patent Document 3 uses rapid heating in hot-rolled sheet annealing as a means for improving descaling properties after annealing, and does not mention anything about increasing the precision of the heating temperature after rapid heating. .
  • the present invention aims to precisely control the annealing temperature of a steel strip to a temperature that is preferable for magnetic properties, thereby obtaining excellent magnetic properties over the entire length of the steel strip.
  • the purpose of this study is to propose an annealing method for hot-rolled steel strips that enables the following.
  • the inventors have made extensive studies to solve the above problems.
  • a continuous annealing facility having an annealing furnace consisting of a heating zone, a soaking zone, and a cooling zone
  • a rapid heating device is placed upstream of the soaking zone, a plate thickness gauge is placed upstream of the rapid heating device, and It is important to set the steel strip heating temperature of the above rapid heating device in consideration of the LSD value defined by the thickness of the steel strip measured with a plate thickness gauge and the threading speed of the steel strip during annealing.
  • the method of annealing a hot rolled steel strip for electrical steel sheets of the present invention is configured as follows. [1] A hot-rolled steel strip for electrical steel sheets obtained by heating and hot rolling a slab containing 1.6 to 5.0 mass% Si is placed in the order of heating zone, soaking zone, and cooling zone from the upstream side.
  • the temperature distribution information in the longitudinal direction of the slab in the slab heating or the temperature distribution information in the longitudinal direction of the steel strip in hot rolling is used to determine whether the temperature distribution in the annealing equipment is.
  • This is a method of annealing a hot rolled steel strip, in which a target annealing temperature in the longitudinal direction of the steel strip is determined, and heating conditions for the steel strip in the annealing equipment are set.
  • the heating conditions for the steel strip in the annealing equipment are such that a rapid heating device is placed upstream of the soaking zone, and a plate thickness gauge is placed upstream of the rapid heating device.
  • a rapid heating device is used to achieve the target annealing temperature.
  • This is a hot rolled steel strip annealing method that sets a steel strip heating temperature of .
  • LSD t ⁇ LS...(1)
  • t is the thickness (mm) of the steel strip
  • LS is the threading speed (m/min) of the steel strip.
  • the target annealing temperature in the longitudinal direction of the steel strip in the annealing is set using the in-furnace time during the slab heating in addition to the skid position information during the slab heating. This is a method of annealing a band.
  • the hot-rolled steel strip is annealed by feeding back furnace temperature information downstream from the rapid heating device to set the steel strip heating temperature of the rapid heating device. It's a method.
  • the present invention it is possible to control with high precision the temperature of the steel strip on the exit side of the heating belt, and furthermore the temperature of the steel strip on the exit side of the soaking zone, to a target annealing temperature favorable for magnetic properties, thereby improving the magnetic properties of product sheets. This greatly contributes to reducing the number of defects.
  • the present invention provides a steel strip length determined in consideration of the temperature distribution in the longitudinal direction of the slab during heating of the slab before hot rolling, or the temperature distribution in the longitudinal direction of the hot rolled steel strip during hot rolling.
  • the heating conditions of the annealing equipment are set so that the target annealing temperature in the horizontal direction (target soaking temperature) is achieved.
  • a rapid heating device is placed upstream of the soaking zone, a sheet thickness gauge is placed upstream of the rapid heating device, and the thickness of the steel strip measured with the sheet thickness meter and the steel being annealed are measured.
  • the heating temperature of the steel strip by the rapid heating device is set so as to achieve the target annealing temperature in consideration of the LSD value defined by the strip passing speed.
  • FIG. 1 is a schematic diagram showing an example of continuous annealing equipment used for annealing the hot rolled steel strip of the present invention. It is a schematic diagram which shows another example of the continuous annealing equipment used for annealing the hot-rolled steel strip of this invention.
  • FIG. 3 is a diagram illustrating the relationship between the slab heating temperature distribution and the target annealing temperature of the hot rolled steel strip, in which (a) shows the temperature distribution in the longitudinal direction of the slab during slab heating, and (b) shows the above (a). ) shows the target annealing temperature in the longitudinal direction of the hot-rolled steel strip determined by taking into account the temperature distribution.
  • the annealing equipment when annealing a hot-rolled steel strip for electrical steel sheets (hot-rolled sheet annealing) using an annealing equipment that includes a heating zone, a soaking zone, and a cooling zone in this order,
  • the annealing equipment is designed to achieve a target annealing temperature in the longitudinal direction of the steel strip that is preferable for magnetic properties determined from the temperature distribution in the longitudinal direction of the slab in slab heating or the temperature distribution in the longitudinal direction of the steel strip in hot rolling. Set the heating conditions.
  • a rapid heating device is disposed upstream of the soaking zone of the annealing equipment, and a plate thickness gauge is disposed upstream of the rapid heating device, and the steel measured with the plate thickness gauge is
  • the heating temperature of the steel strip by the rapid heating device is set so as to achieve the target annealing temperature, taking into consideration the LSD value defined by the strip thickness and the steel strip passing speed during annealing. It is.
  • Figure 1 shows the first half of a continuous annealing facility, which is used for annealing hot-rolled steel strips for electrical steel sheets of the present invention (hot-rolled sheet annealing) and is equipped with a heating zone, a soaking zone, and a cooling zone from the upstream side.
  • FIG. Usually, in the hot-rolled sheet annealing, the steel strip S is heated in a heating zone 3 so that the temperature of the steel strip on the exit side of the heating zone reaches a target soaking temperature, and then held at the soaking temperature for a predetermined time in a soaking zone 4. , and then cooled in a cooling zone (not shown).
  • the furnace temperature of the heating zone 3 and soaking zone 4 and the threading speed of the steel strip S are changed to the thickness of the steel plate and the threading speed from the viewpoint of maintaining the steel strip at a predetermined soaking temperature for a predetermined time. is held constant unless otherwise specified.
  • the temperature history of the slab is different between a portion of the slab that is in contact with the skid portion (skid portion) and a portion that is not in contact with the skid portion (non-skid portion). Therefore, the state of precipitates in the steel strip changes in the length direction during processes after hot rolling, which has a large effect on the recrystallization temperature, etc. Therefore, even if manufactured under the same conditions, the magnetic properties of the final product will change. Variations occur.
  • the influence of temperature variations in the longitudinal direction of the slab on the state of precipitates and recrystallization temperature in the hot rolled steel strip, and ultimately on the magnetic properties of the final product is reduced. Therefore, as shown in Figure 3, the target annealing temperature in the longitudinal direction of the steel strip during annealing (hot-rolled plate annealing) applied to the steel strip after hot rolling is adjusted according to the temperature distribution in the longitudinal direction of the slab during slab heating. By changing the temperature, the state of the precipitates and the recrystallization temperature are controlled to be uniform in the length direction of the steel strip.
  • the target annealing temperature in the longitudinal direction of the steel strip in the annealing equipment which is determined based on the temperature distribution in the longitudinal direction of the slab, has a different influence depending on the steel type and the type and amount of inhibitor, so it may affect the magnetic properties of the final product. It is desirable to set these after verifying the impact on Here, in setting the target annealing temperature through verification, it is preferable to use a method that processes large amounts of data, such as statistical processing, machine learning, and AI.
  • the policy for setting the target annealing temperature during annealing after hot rolling is that the solid solution of the inhibitor is likely to be insufficient in the parts of the slab where the heating temperature is low, and in the annealing after hot rolling, it is possible to Grains may grow. On the other hand, crystal grains are coarsened in areas where the heating temperature of the slab is high. Therefore, since a large amount of energy is required to grow crystals that are favorable for magnetic properties, the target annealing temperature is set high.
  • the effect of the slab heating temperature on the magnetic properties is alleviated to some extent, but if intermediate annealing is not performed, the temperature distribution in the longitudinal direction of the slab is It is more preferable to set the annealing temperature after rolling.
  • the information on the temperature distribution during heating of the slab may be obtained by numerical analysis from information such as the skid position, the furnace time, and the furnace temperature. This is because if the in-furnace time and skid position change, the temperature distribution of the slab during slab heating changes greatly in the thickness and longitudinal directions. Furthermore, when slab heating is performed by induction heating, it is preferable to perform numerical analysis in consideration of information on the arrangement of induction coils and power output.
  • the temperature distribution in the longitudinal direction of the slab it is also possible to use the temperature distribution in the longitudinal direction of the steel strip during rough rolling in hot rolling, which is the immediately subsequent step.
  • the surface temperature distribution in the longitudinal direction of the steel strip has the same tendency as the temperature distribution in the longitudinal direction of the slab during slab heating.
  • the surface temperature of the steel strip after rough rolling can be directly measured with a surface thermometer such as a radiation thermometer. At this time, in order to improve measurement accuracy, it is preferable to measure the surface temperature of the steel strip immediately after descaling to remove an oxide film formed on the surface of the steel strip.
  • FIG. 1 is a diagram showing the first half of a continuous annealing facility having an annealing furnace 1, which is used for annealing hot-rolled steel strips and has a heating zone 3, a soaking zone 4, and a cooling zone arranged from the upstream side.
  • a rapid heating device 2 is disposed upstream of a heating zone 3.
  • the rapid heating device 2 has a function of heating the steel strip to a target annealing temperature determined from the temperature distribution in the longitudinal direction of the slab in slab heating or the temperature distribution in the longitudinal direction of the steel strip in hot rolling. has.
  • the threading speed may be suddenly changed during annealing of the steel strip.
  • the furnace temperature must be adjusted. It is necessary to change the set temperature.
  • a sudden change in the set furnace temperature causes overshoot or hunting in not only the furnace temperature but also the steel strip temperature.
  • hot-rolled steel strip is thicker and has a larger heat capacity than cold-rolled steel strip, so it is not only difficult to follow changes in the furnace temperature of the heating zone, but also 3, it is difficult to heat the steel strip to the target temperature. Therefore, it is desirable to heat the heating zone 3 so that the temperature of the steel strip on the exit side of the heating zone always reaches a predetermined target temperature, regardless of variations in the thickness of the steel strip or the threading speed.
  • the ultimate purpose of hot-rolled sheet annealing is to perform heat treatment in the soaking zone 4 to maintain the steel strip S at a target annealing temperature (soaking temperature) for a predetermined period of time.
  • a target annealing temperature soaking temperature
  • the furnace temperature also changes, making it difficult to heat the hot rolled steel strip to the target soaking temperature.
  • the heating temperature of the steel strip S by the rapid heating device 2 is set higher as the LSD value of the hot rolled steel strip increases; The smaller the value, the lower the heating temperature by the rapid heating device 2 is set. More specifically, the thicker the steel strip is, including minute variations in the thickness of the steel strip, the steel strip temperature at the exit side of the rapid heating device, that is, the heating temperature by the rapid heating device 2, does not take into account LSD. Set the heating temperature higher than conventional heating temperature. On the other hand, the thinner the plate, the lower the steel strip temperature at the exit side of the rapid heating device, that is, the heating temperature by the rapid heating device 2, is set to be lower than the conventional heating temperature that does not take LSD into account.
  • the steel strip temperature at the exit side of the rapid heating device that is, the heating temperature by the rapid heating device 2
  • the steel strip temperature at the exit side of the rapid heating device that is, the heating temperature by the rapid heating device 2
  • the steel strip temperature at the exit side of the rapid heating device that is, the heating temperature by the rapid heating device 2
  • the heating temperature of the steel strip S in the rapid heating device 2 in consideration of the LSD value in this way, even if the thickness t of the hot rolled steel strip or the threading speed LS changes rapidly, the heating It becomes possible to suppress fluctuations in the steel strip temperature on the heating strip exit side without changing the furnace temperature setting in step 3. Furthermore, it becomes possible to suppress fluctuations in the furnace temperature in the soaking zone 4 and to control the temperature of the hot rolled steel strip to the target soaking temperature with high accuracy.
  • the rapid heating device 2 may be of any type as long as it can change the steel strip temperature with good responsiveness. Further, as a heating method for the steel strip S, any well-proven induction heating (solenoid method or transverse method), electrical heating, near-infrared heating, etc. can be suitably used.
  • the installation position of the rapid heating device 2 is the upstream side of the soaking zone 4, since the purpose of this device is to control the temperature of the steel strip on the exit side of the heating zone and, ultimately, the temperature of the steel strip on the exit side of the soaking furnace with high precision. do.
  • it may be placed on the upstream side of the heating zone, or as shown in FIG. do not have.
  • the heating zone 3 is divided into three stages from the upstream side into a front stage, a middle stage, and a rear stage. It is preferable to install it in the front or middle stage, avoiding the latter stage.
  • the heating capacity of the rapid heating device 2 is preferably as large as possible in order to cope with large variations in the thickness of the hot rolled steel strip and the strip passing speed.
  • the heating temperature for a steel strip with a thickness of about 2 mm should be changed by about ⁇ 20°C on the heating strip exit side, depending on the temperature range (position) where the rapid heating device is installed and the relationship between "temperature and specific heat" of the steel strip.
  • a heating capacity (amount of temperature increase) of approximately 50 to 100°C is sufficient to accommodate changes in plate thickness and plate threading speed.
  • the heating temperature of the steel strip S by the rapid heating device 2 is adjusted to achieve the set target annealing temperature (soaking temperature) using the LSD value, that is, (plate thickness x strip threading speed).
  • the LSD value that is, (plate thickness x strip threading speed).
  • the heat capacity of the steel strip changes in proportion to the width of the steel strip, so the amount of heat required to heat the steel strip and the amount of heat removed from the furnace body also change, which in turn changes the temperature of the steel strip on the exit side of the heating zone and the heating zone. This is because it also affects the furnace temperature in the soaking zone. In particular, when using annealing equipment that has a heating zone or soaking zone where the heat capacity of the furnace body is small and the furnace temperature is likely to change, it is desirable to set the heating temperature of the rapid heating device in consideration of the steel strip width.
  • the rapid heating device 2 when setting the heating temperature of the rapid heating device 2, it is preferable to take into consideration information on the furnace temperature of the heating zone 3 after the rapid heating device. .
  • the heating capacity of the rapid heating device 2 is small, when a large change occurs in the heat capacity of the steel strip due to a change in the thickness of the hot rolled steel strip, a change in the threading speed, or a change in LSD, the rapid heating device 2 Since there is a possibility that this method alone may not be sufficient, it is possible to intentionally change the furnace temperature setting of the heating zone 3. In such a case, the temperature of the steel strip at the exit side of the heating zone 3 can be further adjusted by feeding back the constantly changing furnace temperature information after the rapid heating device 2 and reflecting it in the heating temperature setting of the rapid heating device 2. It becomes possible to control with high precision.
  • ⁇ T temperature increase amount [°C]
  • ⁇ Stefan-Boltzmann constant (4.88 ⁇ 10 ⁇ 8 [kcal/m 2 ⁇ h ⁇ K 4 ])
  • ⁇ CG overall heat absorption rate
  • L heating length [m]
  • C p specific heat [kcal/kg°C]
  • ⁇ Density 7850 [kg/m 3 ]
  • V Threading speed [m/min]
  • t plate thickness [mm]
  • Tf Furnace temperature [°C]
  • T s Entry side steel plate temperature [°C] It is.
  • the temperature increase amount ⁇ T is adjusted by adjusting the entrance side steel plate temperature T s , that is, the steel plate heating temperature in the rapid heating device, taking into account the fluctuation of the furnace temperature T f , It becomes possible to control the temperature of the steel strip on the soaking input side.
  • the above-mentioned overall heat absorption rate ⁇ CG is an index representing the efficiency regarding the flow of heat throughout the furnace, and is determined based on the actual furnace temperature and plate temperature.
  • the temperature of the steel strip on the exit side of the heating belt In order to control the temperature of the steel strip on the exit side of the heating belt with even higher accuracy, in addition to the LSD, the steel strip width, and the furnace temperature of the heating zone after the rapid heating device, the temperature of the steel strip on the exit side of the heating belt, the uniform It is preferable that information on the furnace temperature in the tropics and the steel strip temperature on the outlet side of the soaking zone is also utilized for determining the steel strip heating temperature in the rapid heating device 2.
  • the hot-rolled steel strip for electrical steel sheets to which the present invention is directed preferably contains Si in a range of 1.6 to 5.0 mass%. Since Si is an element effective in increasing the specific resistance of steel and reducing iron loss, it is preferably contained in an amount of 1.6 mass% or more. However, when Si exceeds 5.0 mass%, not only the magnetic flux density decreases, but also the steel becomes brittle and cracks occur during cold rolling, resulting in a significant decrease in manufacturability. It is preferably in the range of 2.0 to 3.8 mass%.
  • the above-mentioned hot-rolled steel strip may further contain known inhibitor-forming components to induce secondary recrystallization, or may contain known additives to improve magnetic properties and mechanical properties. It may contain elements.
  • the hot rolled sheet annealing of the present invention as described above, over the entire length of the hot rolled steel strip in the longitudinal direction (rolling direction), variations in the thickness of the steel strip in the longitudinal direction and variations in the threading speed can be avoided.
  • heat treatment can be performed at an appropriate temperature that also corresponds to the temperature distribution in the longitudinal direction when heating the slab. Therefore, it is possible to obtain a product having excellent magnetic properties without secondary recrystallization defects or crystal orientation defects over the entire length of the steel strip.
  • a steel slab for electrical steel sheets containing 3.5 mass% Si (slab weight: 20 tons) is produced by a continuous casting method, heated to a temperature of 1200°C or higher, and then hot rolled to produce a hot rolled steel plate with a thickness of 2 mm. It was made into an obi.
  • the target annealing temperature (soaking temperature) and soaking time are set at 1050°C for 30 seconds. After the hot rolled sheet was annealed, it was descaled by pickling.
  • the temperature distribution in the longitudinal direction of the slab during slab heating or the steel strip during rough rolling during hot rolling was successively changed in the length direction of the steel strip, taking into consideration the temperature distribution in the length direction of the steel strip or skid position information during slab heating.
  • an induction heating device is used as the rapid heating device of the annealing equipment, and as shown in Table 1, for some steel strips, LSD (plate thickness x line speed) is used to obtain the target annealing temperature mentioned above. ) The heating temperature by the device was successively changed in the length direction of the steel strip.
  • the furnace temperature settings of the heating zone and soaking zone are kept constant, and the surface temperature of the steel strip is measured using a radiation thermometer on the exit side of the soaking zone.
  • the difference ⁇ T from the target annealing temperature determined in consideration of the temperature distribution was successively determined, and the maximum value ⁇ Tmax is shown in Table 1. Further, the target annealing temperature was set using equation (2) as the temperature at which the magnetic properties were most improved based on the past results of the hot rolled sheet annealing temperature and magnetic properties.
  • the pickled steel strip was cold-rolled to an intermediate thickness of 1.5 mm, and then the steel strip was divided into two in the length direction, and one half was intermediately annealed at 1100° C. for 20 seconds. After this, the other side was subjected to a second cold rolling without intermediate annealing to obtain a cold rolled steel strip with a final thickness of 0.23 mm.
  • the steel strip after the two-time cold rolling was subjected to decarburization annealing that also served as primary recrystallization annealing at a temperature of 840 ° C.
  • a final annealing consisting of a secondary recrystallization annealing and a purification treatment at a temperature of 1200° C. for 10 hours was performed.
  • the atmospheric gas for the final annealing was H 2 when the temperature was held at 1200° C. for purification treatment, and N 2 during other temperature increases (including secondary recrystallization annealing) and temperature decreases.
  • the steel strip after finish annealing obtained as described above was divided into 10 parts in the length direction, a test piece for measuring magnetic properties was taken from each divided section, and the magnetic flux density B8 was determined according to the Japanese Industrial Standards. Measurements were made in accordance with JISC2553, and the difference ⁇ B8 between the maximum value and the minimum value was taken as the variation in magnetic properties, and the results are shown in Table 1.
  • No. Steel strips Nos. 1 to 6 and 9 to 12 are able to control the difference between the steel strip temperature on the soaking zone exit side and the target annealing temperature considering the influence of slab heating temperature on magnetic properties to be small.
  • a grain-oriented electrical steel sheet with small variations in magnetic properties within the same steel strip was obtained.
  • the target annealing temperature for hot-rolled sheet annealing is determined by considering the skid position information during slab heating, but the LSD value is not taken into consideration when setting the heating temperature of the rapid heating device. No. In Nos.
  • hot-rolled plate annealing takes into consideration the temperature distribution in the longitudinal direction of the slab during slab heating, the temperature distribution in the longitudinal direction of the steel strip after rough rolling in hot rolling, or the skid position information during slab heating.
  • Steel strip No. 1 did not set a target annealing temperature and did not take the LSD value into account when setting the heating temperature of the rapid heating device.
  • Nos. 7 and 8 (conventional examples), the difference ⁇ T between the steel strip temperature on the exit side of the soaking zone with respect to the target annealing temperature is large, and the influence of temperature unevenness during slab heating on the magnetic properties cannot be eliminated.
  • the variation ⁇ B8 in the magnetic properties in the longitudinal direction within the steel strip was the largest.
  • the influence of the slab heating temperature distribution was reduced, and the variation in magnetic properties in the longitudinal direction of the steel strip was reduced.
  • the technology of the present invention can be applied not only to hot-rolled steel strips for electrical steel sheets, but also to all metal strips that need to be annealed in consideration of longitudinal fluctuations in slab heating temperature.

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PCT/JP2023/012737 2022-03-31 2023-03-29 熱延鋼帯の焼鈍方法 WO2023190645A1 (ja)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09118927A (ja) * 1995-10-27 1997-05-06 Nippon Steel Corp コイル内材質の均一性が良い冷延鋼板およびめっき鋼板とその製造方法
JP2003147440A (ja) * 2001-11-05 2003-05-21 Kawasaki Steel Corp 材質安定化システム
JP2011179035A (ja) * 2010-02-26 2011-09-15 Jfe Steel Corp 連続焼鈍炉の板温制御方法及び連続焼鈍炉
US20140175713A1 (en) * 2011-08-12 2014-06-26 Siemens Aktiengesellschaft Method for operating a continuous annealing line for the processing of a rolled good
JP2018066040A (ja) * 2016-10-19 2018-04-26 Ｊｆｅスチール株式会社 Ｓｉ含有熱延鋼板の熱延板焼鈍設備、熱延板焼鈍方法および脱スケール方法
WO2018074531A1 (ja) * 2016-10-18 2018-04-26 Ｊｆｅスチール株式会社 電磁鋼板製造用の熱延鋼板およびその製造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09118927A (ja) * 1995-10-27 1997-05-06 Nippon Steel Corp コイル内材質の均一性が良い冷延鋼板およびめっき鋼板とその製造方法
JP2003147440A (ja) * 2001-11-05 2003-05-21 Kawasaki Steel Corp 材質安定化システム
JP2011179035A (ja) * 2010-02-26 2011-09-15 Jfe Steel Corp 連続焼鈍炉の板温制御方法及び連続焼鈍炉
US20140175713A1 (en) * 2011-08-12 2014-06-26 Siemens Aktiengesellschaft Method for operating a continuous annealing line for the processing of a rolled good
WO2018074531A1 (ja) * 2016-10-18 2018-04-26 Ｊｆｅスチール株式会社 電磁鋼板製造用の熱延鋼板およびその製造方法
JP2018066040A (ja) * 2016-10-19 2018-04-26 Ｊｆｅスチール株式会社 Ｓｉ含有熱延鋼板の熱延板焼鈍設備、熱延板焼鈍方法および脱スケール方法

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