WO2025115662A1 - 熱間圧延方法、熱延コイルの製造方法及び方向性電磁鋼板の製造方法 - Google Patents

熱間圧延方法、熱延コイルの製造方法及び方向性電磁鋼板の製造方法 Download PDF

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WO2025115662A1
WO2025115662A1 PCT/JP2024/040734 JP2024040734W WO2025115662A1 WO 2025115662 A1 WO2025115662 A1 WO 2025115662A1 JP 2024040734 W JP2024040734 W JP 2024040734W WO 2025115662 A1 WO2025115662 A1 WO 2025115662A1
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slab
less
hot
hot rolling
temperature
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French (fr)
Japanese (ja)
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之啓 新垣
遼太 久保村
知義 小笠原
祐介 下山
邦 山田
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JFE Steel Corp
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JFE Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite 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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a hot rolling method, a method for manufacturing hot rolled coils, and a method for manufacturing grain-oriented electrical steel sheets.
  • Grain-oriented electrical steel sheets are usually produced by using a precipitate called an inhibitor to cause secondary recrystallization of Goss-oriented ( ⁇ 110 ⁇ 001>) grains during final annealing.
  • an inhibitor to cause secondary recrystallization of Goss-oriented ( ⁇ 110 ⁇ 001>) grains during final annealing.
  • Japanese Patent Publication No. 40-15644 discloses a method using AlN and MnS as inhibitors
  • Japanese Patent Publication No. 51-13469 discloses a method using MnS and MnSe as inhibitors, both of which have been put into practical use industrially.
  • These methods using inhibitors are useful for stably developing secondary recrystallized grains, but because the precipitates must be finely dispersed, it is necessary to heat the slab before hot rolling at a high temperature of 1300°C or higher.
  • high temperature heating of slabs not only increases the equipment costs, but also increases the amount of scale generated during hot rolling, resulting in reduced yields and complicated maintenance of the equipment.
  • inhibitor-less methods manufacturing techniques that do not use inhibitors as mentioned above (inhibitor-less methods) have also been proposed.
  • a technique has been proposed that uses more highly purified steel without containing inhibitor-forming components in the slab, and induces secondary recrystallization by controlling the texture (texture) (Patent Document 1).
  • the present invention advantageously solves the above problems, and aims to provide a hot rolling method that appropriately controls the slab heating conditions before hot rolling to improve the shape of the slab before hot rolling, thereby improving the shape of the hot rolled coil, and a manufacturing method for hot rolled coils and grain-oriented electrical steel sheets that includes a step of hot rolling a slab using this hot rolling method.
  • the present inventors conducted a detailed investigation into the hot rolling conditions of hot-rolled coils in which shape defects actually occurred, and found that shape defects occurred at the longitudinal ends of the hot-rolled coils in the following cases.
  • the maximum temperature reached by the slab during slab heating before hot rolling is 1200°C or higher, and the slab has a chemical composition such that the gamma phase fraction at the maximum temperature is 10 mol% or less.
  • the edge of the slab lifted by the extractor is deformed and sinks.
  • the slab temperature can be obtained by passing a slab with a thermocouple attached through a heating furnace and recording the temperature change of the slab at each position in the heating furnace in advance.
  • Thermocouples can be attached, for example, to a total of six positions at the center of the slab in the longitudinal direction and at both longitudinal ends, the surface and the center in the thickness direction, and the average value of the six measured values at each position in the heating furnace can be used as the temperature of the slab at that position. If the slab temperature is actually measured in the heating furnace, that value may be used.
  • the ⁇ phase ratio can be calculated using the thermodynamic software Thermo-calc ver. 2019b (database TCFE7) manufactured by Thermo-Calc Software AB.
  • the conventional method for controlling slab heating is as follows.
  • one of the purposes of slab heating in general steel is to lower the deformation resistance of the steel by heating the slab to a high temperature, and to enable hot rolling at a large reduction to obtain hot rolled coils.
  • the object of control is the temperature of the slab at the time of extraction from the heating furnace, and it is not necessary to make it higher than the temperature of the slab at the time of extraction before that. Therefore, it is common to gradually increase the temperature of the slab in the heating furnace and control it so that it reaches its maximum temperature at the time of extraction.
  • FIG. 1 is a schematic diagram showing the state in which the edge of a high-temperature slab lifted by a four-jaw extractor is deformed and sinks downward due to its own weight.
  • Creep deformation occurring at high temperatures is particularly likely to occur in the ⁇ (ferrite) phase, while the rate of deformation of the ⁇ (austenite) phase is slow, so creep deformation in which the slab ends sink during extraction is likely to occur when steel with a low ⁇ -phase ratio is extracted.
  • the amount of slab sinking deformation is also related to the placement of the extractor claws 2 and the slab 1.
  • the overhang length L 1 the length from the extractor claw 2 (slab support part) located at the closest slab end to the end of the slab 1 is taken as the overhang length L 1 , for example, in the case of a slab with a width of 0.9 to 1.2 m, a thickness of 170 to 240 mm, and a total length in the longitudinal direction of 5 to 15 m, it has been found that deformation is likely to occur when the overhang length L 1 exceeds 1.2 m. In Figure 1, deformation in which the slab ends sink (sinking width L 2 ) occurs at both ends.
  • electrical steel sheets usually contain a high concentration of Si in order to improve the final magnetic properties.
  • Si stabilizes the ⁇ phase and reduces the ⁇ phase ratio when heated at high temperatures.
  • C Another element that greatly affects the ⁇ phase ratio is C, which has the effect of improving the hot-rolled structure and the texture during primary recrystallization, so there is an appropriate amount of C from the perspective of improving the final magnetic properties. Therefore, it is difficult to adopt a method of significantly changing the composition of electrical steel sheets that have already been manufactured in a process and increasing the ⁇ phase ratio at high temperatures.
  • the maximum temperature that a slab can reach during slab heating is usually set to dissolve trace amounts of impurity elements and precipitate-forming elements and homogenize the slab.
  • lowering the maximum temperature is not necessarily an option, but it is possible to lower the temperature of the slab when it is removed from the heating furnace. If the cause of the poor shape of the longitudinal ends of the hot-rolled coil is the poor shape of the slab ends that occurs during removal, there is a high possibility that the shape can be improved by lowering the temperature when the slab is removed from the heating furnace, where deformation occurs.
  • the inventors therefore took advantage of the fact that in actual systems, when elements that have been dissolved and homogenized once re-precipitate, there exists a supersaturated temperature range in which precipitation does not proceed even if the temperature is lowered below the precipitation temperature calculated by thermodynamic equilibrium calculations, etc., and came up with a method of once heating the slab to achieve homogenization by heating it to a high temperature, and then lowering the temperature to a range in which no re-precipitation of impurities or precipitate-forming elements occurs and the slab remains homogenous, thereby suppressing deformation of the slab when it is lifted and transported by the extractor during extraction.
  • a hot rolling method in which a slab is heated in a heating furnace and then hot rolled, The slab temperature is set to T1 (unit: °C), which is the maximum temperature reached by the slab in the heating furnace, at least 10 minutes before the slab is extracted from the heating furnace, and the slab temperature at the time of extraction from the heating furnace is set to T2 (unit: °C); Where: T1 ⁇ 1200; T2 ⁇ T1 ⁇ 20 and The slab has a composition in which the ⁇ phase ratio at T 1 (unit: °C) is 10 mol % or less.
  • Hot rolling method is a composition in which the ⁇ phase ratio at T 1 (unit: °C) is 10 mol % or less.
  • the method includes two consecutive hot rolling passes, each pass being performed in a temperature range of 1030 ° C. to 1150 ° C., with a reduction rate of 50% or less, a strain rate of 15 s -1 or more, and a time between passes of 15 s or more;
  • the slab has, by mass%, C: 0.03% or more and 0.08% or less; Si: 2.0% or more and 8.0% or less, Mn: 0.005% or more and 3.0% or less, Al: less than 0.0100%, 0: 0.0060% or less, A steel slab having a composition containing N: 0.0060% or less and S + 0.405 ⁇ Se: 0.0060% or less, with the balance being Fe and unavoidable impurities.
  • the hot rolling method according to [1] or [2].
  • the slab further comprises, in mass %, Ni: 0.005% or more and 1.50% or less, Sn: 0.01% or more and 0.50% or less, Sb: 0.005% or more and 0.50% or less, Cu: 0.01% or more and 0.50% or less, Mo: 0.01% or more and 0.50% or less, P: 0.0050% or more and 0.50% or less, Cr: 0.01% or more and 1.50% or less, Nb: 0.0005% or more and 0.0200% or less, Ti: 0.0005% or more and 0.0200% or less, B: 0.0005% or more and 0.0200% or less, Contains one or more selected from the group consisting of Te: 0.0005% or more and 0.0200% or less and Bi: 0.0005% or more and 0.0200% or less, The hot rolling method according to [3].
  • a method for producing a hot-rolled coil comprising hot-rolling a slab by any one of the hot rolling methods according to [1] to [4] to obtain a hot-rolled coil.
  • a method for producing a grain-oriented electrical steel sheet comprising hot rolling a slab by any one of the hot rolling methods [1] to [4], annealing the resulting hot-rolled sheet, subjecting the sheet to one or more cold rolling steps with intermediate annealing therebetween, and then subjecting the sheet to primary recrystallization annealing and final finish annealing.
  • the shape of the slab end portion before hot rolling is improved, and the shape of the longitudinal end portion of the obtained hot rolled coil is improved, and thus the threading of the grain-oriented electrical steel sheet in the manufacturing process after the hot rolling process can be made more stable.
  • grain-oriented electrical steel sheet can be manufactured much more easily than before.
  • a method for producing a hot-rolled coil and a grain-oriented electrical steel sheet which includes a step of hot-rolling a slab by this hot rolling method.
  • the present invention is a hot rolling method in which a slab is heated in a heating furnace and then hot rolled, in which the slab temperature is made to reach T1 (unit: °C; hereinafter omitted), which is the maximum temperature the slab will reach in the heating furnace, at least 10 minutes before being removed from the heating furnace, and the slab temperature at the time of removal from the heating furnace is T2 (unit: °C; hereinafter omitted).
  • T1 and T2 satisfy the following formulas (1) and (2).
  • the time from when the slab is charged into the heating furnace until when it is extracted is usually 120 minutes or more and 300 minutes or less.
  • the conveying speed of the slab in the heating furnace is usually constant.
  • a slab having a composition in which the ⁇ -phase ratio at T1 is 10 mol% or less is used.
  • a slab having a composition in which the ⁇ -phase ratio is 5 mol% or less is used, a greater effect can be obtained.
  • the lower limit of the ⁇ -phase ratio is not particularly limited, and it can be applied to the case of 0 mol%.
  • composition of the slab preferably satisfies the following.
  • percentages used for the composition are by mass unless otherwise specified.
  • C 0.03% or more and 0.08% or less C has the effect of improving the texture during hot rolling and primary recrystallization, so it is preferable to set the C content to 0.03% or more from the viewpoint of improving the final magnetic properties.
  • the C content exceeds 0.08%, it becomes difficult to reduce the C content to 50 ppm or less at which magnetic aging does not occur even if decarburization annealing is performed. From this point of view, it is preferable to limit C to 0.08% or less.
  • Si 2.0% to 8.0% Si is a useful element that improves iron loss by increasing electrical resistance. In order to obtain good magnetic properties, it is preferable to contain Si at 2.0% or more, more preferably 2.8% or more. On the other hand, Si is also an element that increases the brittleness of steel, and in order to reduce the risk of breakage during threading and suppress deterioration of cold rolling properties, it is preferable to limit Si to 8.0% or less, more preferably 4.5% or less.
  • Mn 0.005% or more and 3.0% or less
  • Mn is a useful element from the viewpoint of improving hot workability and controlling the formation of oxide film during primary recrystallization. From this viewpoint, Mn is preferably contained at 0.005% or more, more preferably 0.01% or more. On the other hand, from the viewpoint of avoiding deterioration of magnetic properties due to deterioration of primary recrystallization texture, Mn is preferably limited to 3.0% or less, more preferably 0.5% or less.
  • N less than 0.0100%
  • O 0.0060% or less
  • S + 0.405 ⁇ Se 0.0060% or less
  • Al is excessive, it may be difficult to obtain a secondary recrystallized structure due to the effect of texture inhibition, so it is preferable to limit Al to less than 0.0100%, and more preferably to 0.0800% or less.
  • the N content is preferably limited to 0.0060% or less, and more preferably 0.0040% or less.
  • the O forms oxides and inhibits deterioration of the magnetic properties of the final sheet product, so it is preferable to limit the O content to 0.0060% or less, and more preferably to 0.0030% or less.
  • the total amount of S and Se multiplied by 0.405 is preferably limited to 0.0060% or less, and more preferably 0.0040% or less.
  • Al, N, O, S and Se are inhibitor components.
  • Ni 0.005% or more and 1.50% or less
  • Sn 0.01% or more and 0.50% or less
  • Sb 0.005% or more and 0.50% or less
  • Cu 0.01% or more and 0.50% or less
  • Mo 0.01% or more and 0.50% or less
  • P 0.0050% or more and 0.50% or less
  • Cr 0.01% or more and 1.50% or less
  • Nb 0.0005% or more and 0.0200% or less
  • Ti 0.0005% or more and 0.0200% or less
  • B 0.0005% or more and 0.0200% or less
  • Te 0.0005% to 0.0200%
  • Bi 0.0005% to 0.0200%
  • Ni is a useful element that improves the structure of hot-rolled coils and enhances their magnetic properties. To fully obtain this effect, when Ni is included, it is preferable that the Ni content be 0.005% or more. On the other hand, if there is an excess of Ni, the secondary recrystallization becomes unstable and the magnetic properties deteriorate, so it is preferable that the Ni content be 1.50% or less.
  • Sn, Sb, Cu, Mo, P, Cr, B and Bi are grain boundary segregation elements that can improve various properties, but if they are present in excess, they can inhibit the development of secondary recrystallized grains. For this reason, when these elements are included, the amounts should be within the above ranges.
  • Nb, Ti and Te are precipitate-forming elements that can improve various properties, but if present in excess they can make secondary recrystallization unstable. For this reason, if these elements are included, the amounts should be within the above ranges.
  • the slab used in the method of the present invention preferably has a composition containing the above essential components and optional components, with the remainder being Fe and unavoidable impurities.
  • the slabs used in the method of the present invention can be produced by refining molten steel adjusted to the desired composition by known methods such as using a converter or electric furnace, and then vacuum processing, if necessary, and then using the usual ingot-making method or continuous casting method. Also, thin cast pieces with a thickness of 100 mm or less can be directly produced by direct casting to be used as slabs.
  • the slab used in the method of the present invention has a composition in which the gamma phase ratio is 10 mol% or less at T1 , which is the maximum temperature reached by the slab in the heating furnace.
  • the gamma phase ratio can be calculated using the thermodynamic software Thermo-calc ver.2019b (database TCFE7) manufactured by Thermo-Calc Software AB. After adjusting the composition of the slab, the above-mentioned thermodynamic software Thermo-calc ver.2019b (database TCFE7) can be used to set the maximum temperature T1 at which trace elements are dissolved uniformly or do not precipitate coarsely and unnecessarily exhibit an inhibition effect.
  • the ⁇ phase ratio at T1 is similarly calculated and confirmed to be 10 mol% or less.
  • a maximum temperature T1 that the slab will reach in the heating furnace may be set, and the composition may be adjusted so that the ⁇ phase rate at T1 is 10 mol % or less.
  • the maximum temperature T1 is the maximum temperature that the slab reaches in the heating furnace and satisfies the above formula (1). That is, T1 is a temperature of 1200°C or higher. If the temperature is 1200°C or higher, the slab can be easily homogenized. From the viewpoint of suppressing creep deformation, T1 can be preferably 1300°C or lower, and is preferably 1260°C or lower.
  • the slab temperature is allowed to reach T1 at least 10 minutes before extraction from the heating furnace, preferably between 30 minutes and 15 minutes before extraction.
  • the slab temperature T2 at the time of extraction from the heating furnace satisfies the above formula (2) in order to suppress creep deformation. That is, T2 is set to a temperature T2 that is 20°C or more lower than T1 .
  • T2 is preferably a temperature 20 to 80°C lower than T1 .
  • T2 is preferably 1200° C. or less in order to suppress creep deformation, and is preferably 1120° C. or more in order to suppress reprecipitation of precipitates.
  • the method of the present invention is advantageous when the length from the extractor claw at the end supporting the slab to the end of the slab (overhang length) is relatively large (for example, when the length exceeds 1.2 m for a slab with a width of 0.9 to 1.2 m, a thickness of 200 to 240 mm, and a total length in the longitudinal direction of 5 to 15 m).
  • the method of the present invention is even more advantageous when the overhang length is 1.5 m or more and 4.0 m or less.
  • the slabs used in the method of the present invention are not limited to the above shapes (width, thickness, total length).
  • the slab composition has a ⁇ -phase ratio of more than 10 mol% at the maximum temperature T1 or is heated in a range where the maximum temperature is less than 1200°C, the amount of deformation when the slab is lifted by the extractor during extraction is not so large. Even when the heat pattern of the present invention is applied to these conditions, it is possible to expect an effect of improving the shape defects of the slab end, but the degree of effect is relatively small.
  • heating furnaces increase the fuel utilization efficiency during heating by gradually heating the slab up to the desired maximum temperature, so that in the range where the shape defects of the slab are not a major problem, it is not rational from the viewpoint of energy efficiency to actively use the heat pattern of the present invention.
  • the temperature inside the furnace is the temperature of the atmospheric gas inside the furnace, and can be measured with a sensor such as a thermocouple. If multiple sensors are installed inside the furnace, such as above, below, left and right of the slab, the temperature can be the average of the measured values of each sensor. Instead of sensor measurement, control may be performed based on the calculated value of the slab temperature.
  • the heating furnace since the slab itself carries heat, in order to create a large temperature difference within the furnace, it is advantageous for the heating furnace to have different burners for different locations within the furnace, a furnace wall structure that suppresses radiant heat, a mechanism for controlling atmospheric gas convection, etc., and conventional heating furnaces can be improved as appropriate.
  • the length from the extractor claws to the end of the slab when extracting the slab does not have to be the same at both ends.
  • the overhang length at one end is relatively large (e.g., more than 1.2 m for a slab that is 0.9-1.2 m wide, 200-240 mm thick, and 5-15 m long) and the overhang length at the other end is relatively small (e.g., 1.2 m or less for a slab that is 0.9-1.2 m wide, 200-240 mm thick, and 5-15 m long).
  • the furnace temperature on the side with the relatively large overhang length may be actively lowered, and the slab temperature at that end only may be 20°C or more lower than the maximum temperature reached.
  • the slab extracted through the above-mentioned slab heating process has homogenized steel and achieves minimal sinking of the overhanging part of the extractor (the end of the slab) during extraction.
  • the slab is then hot rolled, which is relatively easy because sinking and poor shape at the ends of the slab is prevented.
  • the hot rolling step in the method of the present invention at least two consecutive passes of rolling from the slab stage to the sheet bar stage can be carried out in a temperature range of 1030°C to 1150°C. From the viewpoint of improving the shape of the longitudinal end portions of the hot rolled coil, it is preferable that the time between two successive passes is 15 s or more, the rolling reduction of each pass is 50% or less, and the strain rate is 15 s ⁇ 1 or more.
  • the method of the present invention uses a slab in which the gamma phase ratio is 10 mol% or less at T1 , which is the maximum temperature reached in the heating furnace, and the gamma phase ratio is usually maximum in the temperature range of 1030°C to 1150°C.
  • austenite has a higher deformation resistance than ferrite and is less likely to deform when reduced. Therefore, the reduction ratio of each pass is limited to 50% or less. From the viewpoint of homogenizing the structure of the hot rolled coil, the reduction ratio is preferably 15% or more, and more preferably 20% or more.
  • the time between passes is preferably 15 s or more, since dislocations formed once by deformation are recovered or disappear by recrystallization, and rolling can be performed without excessively increasing deformation resistance.
  • the time between passes is preferably 120 s or less, since it suppresses the formation of precipitates nucleated by dislocations generated during deformation.
  • the strain rate is preferably 15 s -1 or more because this makes it easier to improve the shape of the longitudinal end portions of the hot rolled coil, and is preferably 50 s -1 or less.
  • the strain rate ⁇ can be calculated using the following Ekelund equation.
  • vR is the roll peripheral speed (mm/s)
  • R' is the roll radius (mm)
  • h1 is the roll entry side plate thickness (mm)
  • r is the rolling reduction rate (%).
  • the roll peripheral speed is preferably 4000 mm/s or more and 8000 mm/s or less, since this allows the speed at which the slab enters the roll to be controlled within an appropriate range and the slab to be held in place by friction with the roll at an earlier stage.
  • the roll radius is preferably 700 mm or more and 1300 mm or less, since the load can be easily controlled within an appropriate range.
  • the longitudinal ends of a hot-rolled coil have greater thickness fluctuations (maximum thickness minus minimum thickness) than the steady-state portion including the center, but the method of the present invention can suppress thickness fluctuations at the longitudinal ends of the hot-rolled coil.
  • the widthwise thickness fluctuation range in the 1-2% range can be controlled to 1.5 times or less the widthwise thickness fluctuation range in the 20-21% range.
  • the widthwise thickness fluctuation range in the 1-2% range is preferably 1.5 times or less the widthwise thickness fluctuation range in the 20-21% range.
  • the present invention also relates to a method for producing grain-oriented electrical steel sheet, which comprises hot rolling a slab by the hot rolling method of the present invention, annealing the resulting hot-rolled sheet, cold rolling once or at least twice with intermediate annealing in between, and then optionally decarburizing annealing, followed by final annealing.
  • the hot-rolled sheet has an improved shape at the longitudinal end, which makes it possible to suppress meandering and breakage during the cold rolling process.
  • hot-rolled sheet annealing It is essential that hot-rolled sheet annealing be performed at 1150°C or lower. If the hot-rolled sheet annealing temperature exceeds 1150°C, the inhibitor-forming components that are inevitably mixed in will dissolve and will re-precipitate unevenly during cooling, making it difficult to achieve a regular-grained primary recrystallization structure and inhibiting the development of secondary recrystallization. Furthermore, if the hot-rolled sheet annealing temperature exceeds 1150°C, the grain size after hot-rolled sheet annealing will become too coarse, which is detrimental to achieving an appropriate primary recrystallization structure. From the viewpoint of promoting recrystallization, it is preferable to perform hot-rolled sheet annealing at 900°C or higher.
  • the sheet After hot-rolled sheet annealing, the sheet is cold-rolled once or twice or more with intermediate annealing in between.
  • Cold rolling is performed at a rolling temperature of 80°C to 150°C, with the temperature between rolling passes being raised to 100°C to 300°C, and aging treatment is performed once or twice or more times, which is effective in developing the Goss structure.
  • decarburization annealing is performed as necessary to reduce the C content to 50 mass ppm or less, at which point magnetic aging does not occur, and preferably to 30 mass ppm or less.
  • primary recrystallization annealing is performed.
  • the purpose of this primary recrystallization annealing is to perform primary recrystallization of the cold-rolled sheet having a rolled structure, adjust the primary recrystallized grain size to an optimal size for secondary recrystallization, and decarburize the carbon contained in the steel by making the annealing atmosphere a wet hydrogen nitrogen or wet hydrogen argon atmosphere, and at the same time, form an oxide film on the surface by the above-mentioned oxidizing atmosphere. For this reason, it is preferable to perform the primary recrystallization annealing at 750°C or higher and 900°C or lower by introducing a dew point in an H2 mixed atmosphere.
  • the temperature rise of the primary recrystallization annealing it is preferable to set the temperature rise rate between 550°C and 680°C to 200°C/s or higher, since this can further enhance the texture improvement effect.
  • a technique of increasing the Si content by siliconizing after decarburization annealing may be used in combination.
  • a forsterite film may be formed using an annealing separator mainly composed of MgO.
  • the formation of the forsterite film can be further promoted by adding an appropriate amount of Ti oxide or Sr compound to the separator.
  • the addition of an auxiliary agent that promotes the uniform formation of the forsterite film is advantageous for improving the peeling characteristics.
  • the formation of the film may be suppressed by using any annealing separator such as Al2O3 .
  • the final annealing must be performed at 800°C or higher to induce secondary recrystallization, but the heating rate up to 800°C can be any condition since it does not significantly affect the magnetic properties.
  • the annealing atmosphere can be any of N2 , Ar, or H2 , or a mixed gas containing two or more of these.
  • the temperature can be kept isothermal near the secondary recrystallization temperature, but this is not essential since the same effect can be obtained by slowing down the heating rate.
  • the precipitation of trace elements in the final product leads to deterioration of the magnetic properties, so the maximum annealing temperature is set to 1100°C or higher to purify the elements.
  • an insulating coating can be applied and baked on the surface of the steel sheet.
  • any known insulating coating can be used.
  • a preferred method is to apply a coating liquid containing phosphate, chromate, and colloidal silica, as described in JP-A-50-79442 and JP-A-48-39338, to the steel sheet and bake it at about 800°C.
  • the steel sheet can be shaped by flattening annealing.
  • Flattening annealing can also be combined with the baking process of the insulating coating.
  • Example 1 A steel slab (width 1m, thickness 180mm, total length 8m in the longitudinal direction) containing 3.2-3.4% Si, 0.035-0.055% C, 0.07% Mn, 0.0050-0.0080% Al, less than 0.0060% N, O, S + 0.405 ⁇ Se, and the remainder being Fe and unavoidable impurities, and not containing inhibitor components, was heated using a heating furnace having a structure in which the overhang length of the slab end is 1.3m when the slab is supported by an extractor (extraction device) used during extraction from the heating furnace, according to the heating pattern shown in Table 1.
  • the time required from the time the maximum temperature (maximum reached temperature) in the furnace was reached to the start of extraction is recorded as 0 minutes when the timing of the start of extraction and the time of the maximum temperature were coincident.
  • the third and fourth passes of the four-pass rough rolling were performed under the conditions shown in Table 1.
  • the diameter of the rolls of the rolling mill was 800 mm, and the roll peripheral speed was controlled so as to obtain the strain rate shown in Table 1.
  • the sheet was subjected to finish hot rolling in a temperature range of 850 to 950°C with multiple passes to finish the sheet to a thickness of 2.2 mm.
  • Example 2 A steel slab containing the components shown in Table 2 with the balance being Fe and unavoidable impurities, and having a calculated gamma phase rate of 10 mol% or less over the entire temperature range, was hot rolled under the conditions also shown in Table 2 using a heating furnace having a structure in which the overhang length of the slab end is 1.3 m when the slab is supported by an extractor (extraction device) used for extracting from the heating furnace.
  • Two hot-rolled coils were produced under the same conditions, and one of the coils was used to evaluate the shape of the longitudinal end portion in the same manner as in Example 1.
  • the hot-rolled coils that were not sampled were annealed at 1020°C to confirm whether they would traverse and meander for 20mm or more when passing through. After that, they were first cold-rolled to 1.7mm at 100°C in a reverse mill, then intermediate annealed at 900°C for 1 minute, and then second reverse cold-rolled again, with coiling aging treatment at 200°C in between to a thickness of 0.22mm.
  • Example 3 A steel slab containing the components shown in Table 3 with the balance being Fe and unavoidable impurities, and having a calculated gamma phase rate of 10 mol% or less over the entire temperature range, was hot rolled under the conditions also shown in Table 3 using a heating furnace having a structure in which the overhang length of the slab end is 1.3 m when the slab is supported by an extractor (extraction device) used for extracting from the heating furnace. Two hot-rolled coils were produced under the same conditions, and one of the coils was used to evaluate the shape of the longitudinal end portion in the same manner as in Example 1. The hot-rolled coils from which no samples were taken were checked for meandering in the same manner as in Example 2, and the magnetic properties were also checked. The results are shown in Table 3.
  • the invention example improves manufacturing stability and provides good magnetic properties.
  • the hot rolling method of the present invention improves the shape of the slab ends before hot rolling, thereby improving the shape of the longitudinal ends of the resulting hot-rolled coil, which in turn makes the threading of grain-oriented electrical steel sheet more stable in the manufacturing process after the hot rolling process, making it possible to manufacture grain-oriented electrical steel sheet much easier than before.
  • the present invention can also provide a method for manufacturing grain-oriented electrical steel sheet that includes a step of hot rolling a slab using this hot rolling method, as well as a hot-rolled coil having a good shaped slab.

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PCT/JP2024/040734 2023-11-29 2024-11-15 熱間圧延方法、熱延コイルの製造方法及び方向性電磁鋼板の製造方法 Pending WO2025115662A1 (ja)

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4015644B1 (https=) 1963-04-05 1965-07-21
JPS4839338A (https=) 1971-09-27 1973-06-09
JPS5079442A (https=) 1973-11-17 1975-06-27
JPS5113469B2 (https=) 1972-10-13 1976-04-28
JPS60114518A (ja) * 1983-11-24 1985-06-21 Kawasaki Steel Corp 一方向性けい素鋼板の製造方法
JPH03115528A (ja) * 1989-09-29 1991-05-16 Kawasaki Steel Corp 磁気特性の均一な一方向性けい素鋼板の製造方法
JP2000129356A (ja) 1998-10-28 2000-05-09 Kawasaki Steel Corp 方向性電磁鋼板の製造方法
JP2004506093A (ja) * 2000-08-09 2004-02-26 ティッセンクルップ　アッチアイ　スペチアリ　テルニ　ソシエタ　ペル　アチオニ 方向性電磁鋼帯の製造におけるインヒビター分散の調整方法
CN114854966A (zh) * 2022-04-12 2022-08-05 湖南华菱涟钢特种新材料有限公司 电工钢及其制备方法和制品
WO2022250112A1 (ja) * 2021-05-28 2022-12-01 Ｊｆｅスチール株式会社 方向性電磁鋼板の製造方法

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4015644B1 (https=) 1963-04-05 1965-07-21
JPS4839338A (https=) 1971-09-27 1973-06-09
JPS5113469B2 (https=) 1972-10-13 1976-04-28
JPS5079442A (https=) 1973-11-17 1975-06-27
JPS60114518A (ja) * 1983-11-24 1985-06-21 Kawasaki Steel Corp 一方向性けい素鋼板の製造方法
JPH03115528A (ja) * 1989-09-29 1991-05-16 Kawasaki Steel Corp 磁気特性の均一な一方向性けい素鋼板の製造方法
JP2000129356A (ja) 1998-10-28 2000-05-09 Kawasaki Steel Corp 方向性電磁鋼板の製造方法
JP2004506093A (ja) * 2000-08-09 2004-02-26 ティッセンクルップ　アッチアイ　スペチアリ　テルニ　ソシエタ　ペル　アチオニ 方向性電磁鋼帯の製造におけるインヒビター分散の調整方法
WO2022250112A1 (ja) * 2021-05-28 2022-12-01 Ｊｆｅスチール株式会社 方向性電磁鋼板の製造方法
CN114854966A (zh) * 2022-04-12 2022-08-05 湖南华菱涟钢特种新材料有限公司 电工钢及其制备方法和制品

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