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KR-102963561-B1 - METHOD OF MANUFACTURING GRAIN-ORIENTED ELECTRICAL STEEL SHEET

KR102963561B1KR 102963561 B1KR102963561 B1KR 102963561B1KR-102963561-B1

Abstract

A method for manufacturing an oriented electrical steel sheet that exhibits superior magnetic properties compared to conventional technology by actively utilizing inhibitors and highly controlling the texture of the primary recrystallized sheet. Directional electronic method comprising: heating a steel slab to a temperature exceeding the γ-phase precipitation temperature and below 1380°C; performing rough rolling at a temperature above (temperature where the γ-phase fraction is maximum - 20°C) and including at least two passes of rolling with an introduced true deformation εt of 0.50 or more; performing finish rolling at a rolling end temperature of 900°C or higher to produce a hot-rolled plate; cooling the hot-rolled plate for at least one second at a cooling rate of 70°C/s or higher within 2 seconds after the end of finish rolling; coiling at a coiling temperature of 600°C or lower; performing hot-rolled plate annealing at a cracking temperature between 1000°C and (1150–2.5Y)°C, where the recrystallization rate of the center layer of the hot-rolled plate thickness after coiling is Y(%); and subsequently performing cold rolling, primary recrystallization annealing, and secondary recrystallization annealing. Method for manufacturing steel plates.

Inventors

  • 다카조 시게히로
  • 야마구치 히로이

Assignees

  • 제이에프이 스틸 가부시키가이샤

Dates

Publication Date
20260511
Application Date
20220302
Priority Date
20210304

Claims (9)

  1. C: 0.005∼0.085 mass%, Si: 2.00∼4.50 mass%, Mn: 0.03∼1.00 mass%, sol. Al: 0.008 mass% or more and less than 0.030 mass% and N: 0.004–0.009 mass% or less Contains, additionally, A steel slab having a composition in which at least one of S: 0.0005~0.02 mass% and Se: 0.0005~0.02 mass% is contained, and the remainder is Fe and unavoidable impurities, is heated to a temperature above the γ-phase precipitation temperature and below 1380°C, and Next, for the above steel slab, rough rolling is performed at a temperature of (temperature at which the γ-phase fraction is maximum - 20°C) or higher, including at least two passes of rolling with an introduced plate thickness true strain εt of 0.50 or higher, to produce a rough rolled plate, and Next, the above rough rolled plate is subjected to finish rolling at a rolling end temperature of 900℃ or higher to produce a hot rolled plate, and Subsequently, within 2 seconds after the end of the finishing rolling, cooling is performed on the hot-rolled plate for at least 1 second at a cooling rate of 70℃/s or higher, and The above hot-rolled plate after cooling is wound at a winding temperature of 600℃ or lower, and Next, the hot-rolled plate after coiling is subjected to hot-rolled plate annealing, wherein the recrystallization rate Y of the central layer of the plate thickness of the hot-rolled plate after coiling is 10% or more and cracks for 60 seconds or more at a cracking temperature of 1000℃ or higher and (1150－2.5Y)℃ or lower, thereby becoming a hot-rolled annealed plate. Subsequently, the above hot-rolled annealed plate is subjected to cold rolling with a reduction rate of 88% or more and 91% or less to form a cold-rolled plate having a final plate thickness, and Next, the above cold-rolled plate is subjected to primary recrystallization annealing to become a primary recrystallization annealed plate, and A method for manufacturing a oriented electrical steel sheet, wherein a second recrystallization annealing is performed on the first recrystallization annealing plate to obtain an oriented electrical steel sheet. Here, the plate thickness true strain εt is calculated using the following formula (1). ε t ＝－ln(plate thickness after rolling / plate thickness before rolling)… (1)
  2. In paragraph 1, The above component composition is additionally, Sb: 0.005∼0.500mass％, Sn: 0.005∼0.500mass％, Ni: 0.01∼1.50 mass%, Cr: 0.005∼0.50 mass%, Cu: 0.03∼0.50 mass%, P: 0.005∼0.500mass％, As: 0.0005∼0.050mass％, Bi: 0.005∼0.500mass％, Mo: 0.005∼0.100mass％, B: 0.0002∼0.0025 mass%, Te: 0.0005∼0.0100mass％, Zr: 0.001∼0.010 mass%, Nb: 0.001∼0.010 mass%, V: 0.001∼0.010 mass% and A method for manufacturing a oriented electrical steel sheet containing one or two types selected from the group consisting of Ta: 0.001 to 0.010 mass%.
  3. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet, wherein the above rough rolling includes one or more passes of rolling at a temperature between (temperature at which the γ-phase fraction is maximum - 20°C) and (temperature at which the γ-phase fraction is maximum + 50°C).
  4. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet, wherein the number of passes of the above-mentioned rough rolling is a total of 4 or more passes.
  5. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet, wherein cooling is performed on the hot-rolled sheet after the above crack, such that the first average cooling rate v1 from the crack temperature to 800℃ is less than 40℃/s, and the second average cooling rate v2 from 800℃ to 650℃ is greater than or equal to v1 .
  6. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet having a recrystallization rate Y of 18% or more.
  7. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet, wherein the above recrystallization rate Y is 20% or more, and skin pass rolling with an elongation rate of 0.05% or more is performed after the end of the finish rolling and before the annealing of the hot-rolled sheet.
  8. In paragraph 1 or 2, A method for manufacturing a oriented electrical steel sheet in which the magnetic flux density B8 in the rolling direction of the oriented electrical steel sheet is 1.940T or higher.
  9. delete

Description

Method of Manufacturing Grain-Oriented Electrical Steel Sheet The present disclosure relates to a method for manufacturing a oriented electrical steel sheet. Grained electrical steel sheets are primarily used as materials for the iron core inside transformers. To improve the energy efficiency of transformers, it is required to reduce iron loss in grained electrical steel sheets. Methods for reducing iron loss in grained electrical steel sheets include increasing the specific resistance of the steel sheet, increasing film tension, and reducing the thickness, as well as methods by surface processing of the steel sheet and methods by sharpening the crystal orientation of the crystal grain to the {110}<001> orientation (hereinafter referred to as the Goss orientation). As an indicator of magnetic properties, iron loss W 17/50 per kg of steel sheet is used when magnetized to 1.7 T with an alternating magnetic field of 50 Hz, and in particular, magnetic flux density B 8 at a magnetic field strength of 800 A/m is mainly used as an indicator of the sharpening of the crystal orientation toward the {110}<001> orientation (hereinafter referred to as Goss orientation). To increase the concentration of Goss orientations, it is important to provide a difference in grain boundary mobility so that only sharp Goss orientation grains grow preferentially, that is, to form the texture of the primary recrystallized sheet into a predetermined structure, and to suppress the growth of recrystallized grains other than Goss orientations by using a precipitate called an inhibitor. As for technologies utilizing this inhibitor, for example, a method using AlN and MnS is disclosed in Patent Document 1, and a method using MnS and MnSe is disclosed in Patent Document 2, and both have been commercialized industrially. It is desirable to disperse these inhibitors uniformly and finely within the steel. Therefore, in the method of using inhibitors, it is common practice to perform the slab at a high temperature of 1300°C or higher before hot rolling to solution the inhibitor components, and then to precipitate them finely in subsequent processes. For example, in Patent Document 3, Al is added to the steel, and after hot rolling, the hot-rolled sheet is annealed at 750 to 1200°C, and then rapidly cooled to precipitate fine AlN, thereby obtaining a very high magnetic flux density. On the other hand, a method for manufacturing oriented electrical steel sheets that does not rely on inhibitors (inhibitor-less method) is also being considered. The inhibitor-less method is characterized by using steel of higher purity to induce secondary recrystallization by controlling the crystal texture. In this method, since heating the slab at high temperatures to solution the inhibitor component is unnecessary, it is possible to manufacture oriented electrical steel sheets at a low cost. For example, Patent Document 3 shows that by having a large number of grains with {554}<225> orientation and {411]<148> orientation in the primary recrystallization structure, the accumulation of Goss orientation after secondary recrystallization increases, and the magnetic flux density increases. (Form for carrying out the invention) First, we will explain the experiment that led to the development of the present invention. First, the inventors carefully observed the crystal structure of a hot-rolled sheet to verify whether it is effective to coarsen the crystal grain size before cold rolling in order to form a desirable texture in the primary recrystallized sheet of a oriented electrical steel sheet in order to improve magnetic properties. Experiment 1 A steel material (C: 0.060 mass%, Si: 3.40 mass%, Mn: 0.06 mass%, sol. Al: 0.014 mass%, N: 0.007 mass%, S: 0.020 mass%, Sb: 0.035 mass%) consisting of the remainder being Fe and unavoidable impurities was melted to form a steel slab, and then the steel slab was heated to 1310°C. Subsequently, rough rolling was performed on the steel slab, consisting of one-pass rolling at 1200°C with a plate thickness true strain εt 0.6, one-pass rolling at 1150°C with a plate thickness true strain εt 0.4, and one-pass rolling at 1100°C with a plate thickness true strain εt 0.4, to produce a rough rolled plate. Next, the rough-rolled plate was finished by rolling at a finishing temperature of 1050°C and finished rolling was performed to produce a hot-rolled plate with a thickness of 2.2 mm. Next, 1 second after the finish rolling was completed, cooling was performed for 5 seconds at a cooling rate of 80°C/s, and then coiled at a coiling temperature of 520°C. Next, the hot-rolled plate was annealed by cooling at 1100°C for 90 seconds, then air cooling from 600 to 450°C for 2 minutes, and then water cooling to 100°C to produce a hot-rolled annealed plate. Next, the hot-rolled annealed plate was cold-rolled at a reduction rate of 90% to produce a cold-rolled plate with a final thickness of 0.22 mm. After that, by a known method, a first recrystal