Classifications

• • 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
  • 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
  • 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-rolled annealed steel sheet, a manufacturing method thereof, and a manufacturing method of a non-oriented electrical steel sheet.
• HEVs hybrid electric vehicles
• EVs electric vehicles driven solely by electric motors
• FCEVs fuel cell electric vehicles
• HEVs high-frequency range
• Non-oriented electrical steel sheets are often used as the iron core material for these motors. To achieve high motor efficiency, there is a strong demand for these steel sheets to have low iron loss in the high-frequency range.
• non-oriented electrical steel sheets have been designed to have low iron loss by adding alloying elements such as Si and Al to increase resistivity, or by reducing eddy current loss through thinning the sheet thickness.
• alloying elements such as Si and Al
• adding large amounts of alloying elements reduces the ductility and toughness of the steel sheet, resulting in frequent fractures during the cold rolling process.
• Patent Document 1 discloses a method for manufacturing non-oriented electrical steel sheets with high magnetic flux density, which prevents cracking during cold rolling by cold-rolling rapidly solidified cast pieces at 180°C to 350°C.
• a more preferable solution to the problem for the hot-rolled annealed sheet according to the present invention is that the ratio Rc of recrystallized structure in the sheet width center portion Xc is 80% or more, and/or the ratio Re of recrystallized structure at the steel sheet position Xe is in the range of 5% to 95%.
• the method for producing a hot-rolled annealed sheet according to the present invention is as follows: (a) In the hot-rolled sheet annealing step, at least one of the following (1) to (4) is satisfied: (b) When a hot-rolled sheet having a sheet width W in the range of 900 mm or more and 1100 mm or less is subjected to the hot-rolled sheet annealing process, a heat suppression region is provided in a range from 20 mm or more in the sheet width direction from the edge of the sheet width to 0.250 ⁇ W or less in the sheet width direction from the edge of the sheet width, This would be a more preferable solution to the problem.
• the holding temperature T1 of the width center portion Xc of the hot-rolled sheet is set to 900 ° C.
• the holding time t1 at the holding temperature T1 of the width center portion Xc of the hot-rolled sheet is set to a range of 2 seconds to 120 seconds
• the maximum temperature T2 at the steel plate position Xe is set in the range of 750 ° C. or more and 1000 ° C. or less; and (4) The time t2 during which the temperature is equal to or higher than the maximum temperature T2 -50°C is set to a range of 5 seconds to 20 seconds.
• Pb 0.0001% or more and 0.0020% or less
• Pb is an element that has the effect of increasing the strength of the steel sheet and can be added as needed. To obtain this effect, the Pb content should be 0.0001% or more. However, if the Pb content exceeds 0.0020%, fine precipitates will form in the steel sheet, increasing iron loss. Therefore, it is preferable to set the upper limit of the Pb content to 0.0020%.
• J group one or two elements selected from Ga: 0.0005% to 0.0300% and Ge: 0.0005% to 0.0300% Ga: 0.0005% to 0.0300% Ga is an element that improves the texture of the steel sheet and increases the magnetic flux density, and can be added as needed. To achieve this effect, the Ga content should be 0.0005% or more. However, adding a large amount of Ga saturates the effect and increases the alloy cost, so it is preferable to set the upper limit of the Ga content to 0.0300%.
• Ge 0.0005% or more and 0.0300% or less Ge is an element that has the effect of improving the texture of the steel sheet and increasing the magnetic flux density, and can be added as needed. To obtain such effects, the Ge content should be 0.0005% or more. However, if a large amount of Ge is added, the effect saturates and the alloy cost increases, so it is preferable to set the upper limit of the Ge content to 0.0300%.
• recrystallization refers to the generation and growth of crystal grains with extremely low dislocation density by holding the material at high temperature.
• the recrystallized structure and the non-recrystallized structure can be distinguished by observation with an optical microscope.
• the ratio Re/Rc of the recrystallized structure ratio Re at a position Xe 10 mm away from the outermost edge in the width direction of the sheet to the recrystallized structure ratio Rc at the center Xc of the sheet width is 0.95 or less>
• the work-hardening rate at the width edge is lower than that at the width center, which causes stress to act to reduce tension at the width edge during rolling. This significantly suppresses the initiation of cracks at the steel sheet edge, thereby reducing fractures and edge cracks. That is, by setting the ratio Re/Rc (the recrystallized structure ratio Re at the width center Xc of the hot-rolled annealed sheet, Rc, to the recrystallized structure ratio Re at the position Xe 10 mm away from the width edge in the width direction) to 0.95 or less, a hot-rolled annealed sheet can be obtained that sufficiently suppresses fractures and edge cracks during cold rolling.
• the ratio is preferably 0.8 or less, and more preferably 0.7 or less. There is no particular need to set a lower limit, but it is usually 0.05 or more in a hot-rolled and annealed sheet produced using the method described below.
• the hot-rolled annealed sheet of this embodiment controls the ratio of the recrystallized structure ratio Rc in the sheet width center to the recrystallized structure ratio Re at the steel sheet position Xe on the sheet width edge side, and the effects of the present invention are not limited by the value of the recrystallized structure ratio at the sheet width center itself.
• there is a suitable range for the recrystallized structure ratio at the sheet width center and the effects of the present invention are even more pronounced when it is within that range.
• the recrystallized structure ratio at the sheet width center Xc is 80% or more, the magnetic properties of the final product are less likely to deteriorate.
• the recrystallized structure ratio Rc at the sheet width center Xc is 80% or more.
• the hot-rolled annealed steel sheet of this embodiment controls the ratio of the recrystallized structure ratio Rc at the width center to the recrystallized structure ratio Re at the width edge of the steel sheet at position Xe.
• the effects of the present invention are not limited by the value of the recrystallized structure ratio at position Xe itself. However, there is a preferred range for the recrystallized structure ratio at position Xe, and the effects of the present invention are more pronounced when the ratio is within that range.
• the hot-rolled annealed steel sheet according to the present embodiment is obtained by successively hot-rolling and hot-rolled annealing a steel material having the above-described chemical composition.
• any commonly known method may be used.
• the steel material is not particularly limited as long as it has the above-mentioned component composition.
• the method for producing the steel material and the method for adjusting the composition are not particularly limited, and known methods for producing the steel material using a converter or an electric furnace, a vacuum degassing device, or other devices and methods can be used. From the viewpoint of productivity and other factors, it is preferable to produce a slab (steel material) by continuous casting after the production. On the other hand, a slab or thin slab may also be produced by known casting methods such as ingot making-blooming rolling or thin slab continuous casting.
• the hot-rolled sheet annealing process is a process in which the temperature rise rate Vc at the widthwise center portion Xc is 1.0°C/s or more higher than the temperature rise rate Ve at the steel sheet position Xe.
• the holding temperature T1 is 900°C or higher.
• the holding time t1 at the holding temperature T1 is in the range of 2 seconds to 120 seconds.
• the maximum temperature T2 at the steel sheet position Xe is in the range of 750°C to 1000°C.
• the time t2 during which the steel sheet temperature at position Xe is equal to or higher than the maximum temperature T2 -50°C is set to a range of 5 seconds to 20 seconds.
• a heating suppression region is provided in a range from 20 mm or more in the sheet width direction from the outermost edge of the sheet width to 0.250 ⁇ W or less in the sheet width direction from the outermost edge of the sheet width.
• a pickling process is usually carried out.
• the pickling process There are no particular restrictions on the pickling process, as long as it is a process that can pickle the steel sheet to the extent that it can be cold-rolled after pickling; for example, a conventional pickling process using hydrochloric acid or sulfuric acid can be applied.
• This pickling process may be carried out continuously in the same line as the hot-rolled sheet annealing process, or it may be carried out in a separate line.
• the hot-rolled sheet annealed in this invention includes both a state that has not been pickled (black skin) and a state that has been pickled (white skin).
• the heating rate when heating the sheet width center Xc from room temperature to the holding temperature T1 is defined as Vc. Furthermore, the heating rate when the steel sheet position Xe, 10 mm away from the outermost edge in the sheet width direction, reaches the maximum temperature T2 from room temperature is defined as Ve. Vc-Ve is limited to 1.0°C/s.
• Vc-Ve ⁇ 1.0°C/s the difference in the proportion of recrystallized structure between the sheet width center and the sheet width edge becomes small, and the ratio Re/Rc of the proportion Rc of recrystallized structure at the sheet width center to the proportion Re of recrystallized structure at the sheet width edge cannot be set to 0.95 or less.
• Vc-Ve ⁇ 3°C/s and more preferably, Vc-Ve ⁇ 5°C/s.
• ⁇ Holding temperature T1 at width center Xc is 900°C or higher>>
• the holding temperature T1 of the sheet width center portion Xc is preferably 900°C or higher.
• the ratio Rc of the recrystallized structure in the sheet width center portion Xc can be set to 80% or higher.
• T1 is higher than 1100°C
• the sheet width edge portion may be heated by heat conduction, and the ratio of the recrystallized structure in the sheet width edge portion may become excessively high. Therefore, it is preferable to control the holding temperature T1 of the sheet width center portion Xc to 900°C or higher and 1100°C or lower.
• the holding time t1 at the holding temperature T1 of the sheet width center portion Xc is set to 2 seconds or more and 120 seconds or less>>
• the holding time t1 at the holding temperature T1 of the sheet width center Xc is preferably 2 seconds or more and 120 seconds or less. If t1 is 120 seconds or less, the ratio Re/Rc of the recrystallized structure ratio between the sheet width center and the sheet width edge can be set to 0.95 or less, which is preferable because it improves cold rolling properties.
• the holding time t1 at the holding temperature T1 of the sheet width center Xc is preferably 2 seconds or more and 120 seconds or less.
• ⁇ Maximum temperature T2 at steel plate position Xe is set in the range of 750°C or higher and 1000°C or lower>>
• the maximum temperature T2 at the steel sheet position Xe which is 10 mm away from the outermost edge of the hot-rolled sheet in the width direction, is preferably set to 750°C or higher and 1000°C or lower.
• the maximum temperature T2 is 750°C or higher, recrystallization at the steel sheet position Xe is sufficient, and the recrystallized structure ratio Re satisfies 5% or higher.
• the maximum reached temperature T2 is 1000°C or lower, the recrystallized structure ratio Re satisfies 95% or lower.
• the time t2 during which the steel plate temperature at the position Xe is equal to or higher than the maximum temperature T2 -50°C is set to a range of 5 seconds to 20 seconds>>
• the time t2 during which the steel sheet position Xe is at or above the maximum temperature T2 -50°C is in the range of 5 seconds to 20 seconds.
• t2 is the sum of the time to heat the steel sheet to the maximum temperature T2 and the time to cool it from the maximum temperature T2 .
• the following methods can be used to provide a heat suppression region that intentionally changes the temperature in the sheet width direction: (a) preventing overheating by weakening burner heating only at the edge, (b) preventing overheating by applying an edge cover, (c) applying a temperature rise prevention material with low emissivity that can suppress radiant heating, and (d) preventing temperature rise by removing black scale only at the edge. Any method that can intentionally change the temperature is acceptable and does not limit the scope of the invention.
• a heat suppression region in a range of 20 mm or more in the sheet width direction from the outermost edge of the sheet. If the heat suppression region is in a range of 20 mm or more from the outermost edge of the sheet width, the temperature at the steel sheet position Xe, 10 mm from the outermost edge, is less likely to rise due to thermal conduction of the steel sheet. Therefore, the temperature rise rate Vc at the sheet width center Xc can be made 1.0°C/s or more higher than the temperature rise rate Ve at the steel sheet position Xe.
• the heat suppression region when a hot-rolled sheet having a sheet width W in the range of 900 mm to 1100 mm is subjected to the above-mentioned hot-rolled sheet annealing process, it is preferable to provide the heat suppression region in a range from the outermost width portion to 0.250 ⁇ W or less in the sheet width direction. Within this range, the proportion of recrystallized structures in the entire steel sheet is sufficient, and deterioration of magnetic properties can be suppressed. Therefore, preferably, the heat suppression region is set to a range of 20 mm or more in the sheet width direction from the outermost width portion.
• the heat suppression region is set to a range from the outermost width portion to 0.250 ⁇ W or less in the sheet width direction.
• the pickling process is a process of pickling the hot-rolled annealed sheet after the hot-rolled sheet annealing process.
• the pickling process is not particularly limited as long as it is a process that can pickle the steel sheet after pickling to an extent that cold rolling can be performed, and for example, a conventional pickling process using hydrochloric acid or sulfuric acid can be applied.
• this pickling process may be performed continuously in the same line as the hot-rolled sheet annealing process, or may be performed in a separate line.
• An example of a commonly used cold rolling process is a cold rolling process in which a pickled sheet is rolled using a five-stand tandem mill under conditions of a total reduction of 80% or more but less than 95% to produce a cold-rolled sheet of the specified dimensions and shape.
• the number of stands may be four or less, or six or more.
• An example of a commonly used annealing process is a finish annealing process in which cold-rolled sheet is heated to a temperature of 800°C or higher and 1200°C or lower in a non-oxidizing atmosphere, held at that temperature for 5 to 60 seconds, and then cooled.
• Tables 3-1 and 3-2 show that all hot-rolled and annealed sheets according to the present invention have excellent cold rolling properties, and furthermore, cold-rolled and annealed sheets obtained by cold-rolling and annealing the hot-rolled and annealed sheets according to the present invention also have excellent magnetic properties.

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• 2024
  • 2024-10-28 JP JP2025506134A patent/JPWO2025169547A1/ja active Pending
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