WO2023095637A1 - 無方向性電磁鋼板用熱延鋼板の製造方法および無方向性電磁鋼板の製造方法 - Google Patents
無方向性電磁鋼板用熱延鋼板の製造方法および無方向性電磁鋼板の製造方法 Download PDFInfo
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- WO2023095637A1 WO2023095637A1 PCT/JP2022/041981 JP2022041981W WO2023095637A1 WO 2023095637 A1 WO2023095637 A1 WO 2023095637A1 JP 2022041981 W JP2022041981 W JP 2022041981W WO 2023095637 A1 WO2023095637 A1 WO 2023095637A1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 175
- 239000010959 steel Substances 0.000 title claims abstract description 175
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 41
- 238000005096 rolling process Methods 0.000 claims abstract description 179
- 238000000034 method Methods 0.000 claims abstract description 58
- 238000005098 hot rolling Methods 0.000 claims abstract description 43
- 238000009749 continuous casting Methods 0.000 claims abstract description 24
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 229910000565 Non-oriented electrical steel Inorganic materials 0.000 claims description 56
- 238000000137 annealing Methods 0.000 claims description 45
- 239000010960 cold rolled steel Substances 0.000 claims description 22
- 238000005097 cold rolling Methods 0.000 claims description 18
- 239000000126 substance Substances 0.000 claims description 8
- 238000003303 reheating Methods 0.000 abstract description 21
- 229910045601 alloy Inorganic materials 0.000 abstract description 3
- 239000000956 alloy Substances 0.000 abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 57
- 206010037660 Pyrexia Diseases 0.000 description 47
- 230000000694 effects Effects 0.000 description 31
- 229910052742 iron Inorganic materials 0.000 description 24
- 238000010438 heat treatment Methods 0.000 description 23
- 238000001556 precipitation Methods 0.000 description 19
- 230000001965 increasing effect Effects 0.000 description 14
- 239000002244 precipitate Substances 0.000 description 14
- 238000001953 recrystallisation Methods 0.000 description 14
- 239000012535 impurity Substances 0.000 description 12
- 230000002708 enhancing effect Effects 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 230000006698 induction Effects 0.000 description 11
- 238000005259 measurement Methods 0.000 description 9
- 238000002474 experimental method Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- 229910052761 rare earth metal Inorganic materials 0.000 description 7
- 150000002910 rare earth metals Chemical class 0.000 description 7
- 229910052717 sulfur Inorganic materials 0.000 description 7
- 229910052804 chromium Inorganic materials 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 6
- 238000005520 cutting process Methods 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 229910052698 phosphorus Inorganic materials 0.000 description 6
- 229920006395 saturated elastomer Polymers 0.000 description 6
- 238000009413 insulation Methods 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 150000003568 thioethers Chemical class 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000001737 promoting effect Effects 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 229910001208 Crucible steel Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000011162 core material Substances 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
Images
Classifications
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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
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/147—Alloys characterised by their composition
Definitions
- the present invention relates to a method for manufacturing hot-rolled steel sheets for non-oriented electrical steel sheets and a method for manufacturing non-oriented electrical steel sheets.
- a non-oriented electrical steel sheet is a material used for the iron cores of motors and generators.
- CO2 reduction there is a strong demand for higher efficiency of electrical equipment, and further reduction in iron loss is required for non-oriented electrical steel sheets, which are iron core materials.
- a method of manufacturing a non-oriented electrical steel sheet using a steel slab (thin slab) that is thinner than before has been proposed.
- a thin slab is manufactured using a continuous casting machine called a thin slab caster, and then the thin slab is subjected to rolling.
- the load in both hot rolling and cold rolling can be reduced.
- energy costs can be greatly reduced because slab reheating is omitted by directly connecting a continuous casting machine (thin slab caster) and a hot rolling mill.
- Patent Document 1 discloses a technique of hot-rolling a thin slab with a thickness of 20-100 mm to form a hot-rolled steel strip with a thickness of 1.0-4 mm.
- Patent Document 2 discloses a technique of hot rolling a thin slab with a thickness of 30 to 140 mm to form a hot rolled steel strip with a thickness of 0.7 to 4.5 mm.
- JP 2010-047785 A Japanese Patent Application Laid-Open No. 2002-206114
- An object of the present invention is to solve the above problems.
- the purpose is to suppress
- the present invention has been completed based on the above findings, and the gist thereof is as follows.
- a method for producing a hot-rolled steel sheet for a non-oriented electrical steel sheet comprising: A method for producing a hot-rolled steel sheet for non-oriented electrical steel sheet, wherein the hot-rolling step is performed under conditions satisfying (1) and (2) below.
- the chemical composition of the steel slab is, in mass%, C: 0.005% or less, Cr: 3.0% or less, Ni: 2.0% or less, Cu: 2.0% or less, P: 0.2% or less, S: 0.0050% or less, N: 0.0050% or less, O: 0.0050% or less, Ti: 0.0040% or less, Sn: 0.20% or less, Sb: 0.20% or less, Mo: 0.10% or less, Ca: 0.01% or less, REM: 0.05% or less, 5.
- the heat for non-oriented electrical steel sheet according to any one of 1 to 4 above, further containing at least one selected from the group consisting of Mg: 0.01% or less and Zn: 0.01% or less.
- a method for manufacturing a rolled steel sheet is, in mass%, C: 0.005% or less, Cr: 3.0% or less, Ni: 2.0% or less, Cu: 2.0% or less, P: 0.2% or less, S: 0.0050% or less, N: 0.0050% or less, O
- a thin non-oriented electrical steel sheet with a large alloy content can be produced at low cost without causing ridging.
- 4 is a graph showing the correlation between the total content (% by mass) of Al and Mn in a steel slab and the arithmetic mean waviness Wa ( ⁇ m) in the width direction of a non-oriented electrical steel sheet.
- 5 is a graph showing the correlation between the heat retention temperature (° C.) and heat retention time (seconds) in the heat retention step and the arithmetic mean waviness Wa ( ⁇ m) in the width direction of the non-oriented electrical steel sheet.
- 4 is a graph showing the correlation between the total rolling reduction (%) in rough rolling, the total rolling reduction (%) in finish rolling, and the arithmetic mean waviness Wa ( ⁇ m).
- Reheat rolling After removing the steel slab from the vacuum melting furnace, the entire steel slab was allowed to cool to room temperature in the atmosphere. Next, the steel slab was inserted into an electric furnace and reheated at 1100° C. for 30 minutes, after which the steel slab was removed from the electric furnace and inserted into a hot rolling mill.
- the steel slab in the hot rolling, is roughly rolled to a plate thickness of 15 mm, then reheated to 1100 ° C. by an induction heating device, and then finish rolled to a plate thickness of 1.5 mm. Steel plate.
- the obtained hot-rolled steel sheet was subjected to hot-rolled steel annealing at 1000°C for 40 seconds, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.3 mm.
- the cold-rolled steel sheet was subjected to finish annealing at 980° C. for 20 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa of the surface of the non-oriented electrical steel sheet was measured.
- a stylus type surface roughness meter was used, and the arithmetic mean waviness Wa was calculated from the waviness curve obtained by measuring the steel sheet surface in the width direction with a measurement length of 16 mm.
- Fig. 1 shows the relationship between the total content (% by mass) of Al and Mn in the steel slab used and the measured Wa ( ⁇ m).
- [Al] is the Al content of the steel slab
- [Mn] is the Mn content of the steel slab
- [Al] + [Mn] is the total content of Al and Mn in the steel slab. write.
- Example 2 The present inventors presumed that fine precipitates such as MnS and AlN precipitated in direct rolling, and that these fine precipitates prevented recrystallization during hot-rolled sheet annealing. Therefore, it was decided that the precipitating process should be performed before the hot rolling process to precipitate and grow the precipitates to reduce the fine precipitates.
- the steel slab was taken out from the electric furnace, inserted into a hot rolling mill, and hot rolled.
- the steel slab is roughly rolled to a thickness of 10 mm, then reheated to 1100° C. by an induction heating apparatus, and then finish rolled to a thickness of 1.2 mm to obtain a hot rolled steel sheet.
- the obtained hot-rolled steel sheet was subjected to hot-rolled steel annealing at 1000°C for 40 seconds, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.3 mm.
- the cold-rolled steel sheet was subjected to finish annealing at 980° C. for 20 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa on the surface of the obtained non-oriented electrical steel sheet was measured by the same procedure as in Experiment 1 above.
- Fig. 2 shows the relationship between the heat retention temperature and heat retention time in the heat retention process and the arithmetic mean waviness Wa.
- the heat retention time was less than 60 seconds, ridging occurred at any heat retention temperature.
- the heat retention time was 60 seconds or more, ridging was suppressed within the heat retention temperature range of 1100°C or higher and 1300°C or lower.
- a steel slab with a thickness of 160 mm was melted in a vacuum melting furnace. While maintaining the surface temperature of the steel slab at 800° C. or higher, the steel slab was transported and inserted into an electric furnace, where it was heat-treated at 1150° C. for 300 seconds. After that, the steel slab was taken out from the electric furnace, inserted into a hot rolling mill, and hot rolled.
- the steel slab was subjected to rough rolling, reheat treatment, and finish rolling in order to obtain a hot-rolled steel sheet with a thickness of 0.6 mm, 1.0 mm, or 1.8 mm.
- the total rolling reduction in the rough rolling was 70.0 to 98.0%, and the total rolling reduction in the finish rolling was 43.8 to 98.8%.
- the reheating treatment was performed using an induction heating apparatus, and the sheet bar (steel after rough rolling) was heated to 1100°C.
- the obtained hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000°C for 25 seconds, and then cold-rolled at a cold-rolling reduction of 80% to obtain a cold-rolled steel sheet.
- the cold-rolled steel sheet was subjected to finish annealing at 980° C. for 20 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa on the surface of the obtained non-oriented electrical steel sheet was measured by the same procedure as in Experiment 1 above.
- Fig. 3 shows the relationship between the total rolling reduction in rough rolling, the total rolling reduction in finish rolling, and the arithmetic mean waviness Wa.
- the three lines in FIG. 3 respectively correspond to the results at the delivery side thickness in the finish rolling (final thickness in the hot rolling process): 0.6 mm, 1.0 mm and 1.8 mm. Also, the numerical value attached to each point is the total rolling reduction (%) in the finish rolling.
- the heat retention temperature is 1100 ° C. or more and 1300 ° C. or less, and the heat retention time is It was found that the ridging can be suppressed by performing the heat-retaining treatment for 60 seconds or more and setting the total rolling reduction ratio in each of the rough rolling and the finish rolling to 80% or more.
- the total rolling reduction in rough rolling the amount of dislocations in the sheet bar increases, the rolled structure of the sheet bar is refined, and the grain boundary density increases. These dislocations and grain boundaries serve as precipitation sites for MnS and AlN that were not precipitated by the heat treatment, and promote the precipitation. Furthermore, by increasing the total rolling reduction in the finish rolling, the hot-rolled structure becomes finer, and the grain boundary density that becomes the recrystallization site increases.
- Si 2.0-5.0%
- Si is an element that has the effect of increasing the specific resistance of the steel sheet and reducing iron loss.
- the Si content is set to 2.0% or more.
- the Si content is made 5.0% or less.
- the Si content is preferably 2.5% or more, more preferably 2.8% or more.
- the Si content is preferably 4.5% or less, more preferably 4.0% or less.
- Al 3.0% or less
- Al is an element that has the effect of increasing the specific resistance of the steel sheet and reducing iron loss. However, if the Al content exceeds 3.0%, rolling becomes difficult. Therefore, the Al content is set to 3.0% or less. From the viewpoint of improving castability, the Al content is preferably 1.5% or less.
- the lower limit of the Al content is not limited, but from the viewpoint of the balance between iron loss and manufacturability, the Al content is preferably 0.2% or more, more preferably 0.3% or more. It is preferably 0.5% or more, and more preferably 0.5% or more.
- Mn 3.0% or less
- Mn is an element that has the effect of increasing the specific resistance of the steel sheet and further reducing iron loss.
- the Mn content is set to 3.0% or less.
- the lower limit of the Mn content is not limited, but from the viewpoint of further suppressing the precipitation of fine MnS, it is preferably 0.20% or more.
- Total content of Al and Mn 0.40% or more
- the total content of Al and Mn should be 0.40% or more, preferably 1.00% or more, and more preferably 1.50% or more.
- the upper limit of the total content of Al and Mn is not particularly limited. However, since the Al content is 3.0% or less and the Mn content is 3.0% or less as described above, the maximum total content of Al and Mn is 6.00%.
- the steel slab is Si: 2.0% or more and 5.0% or less, Al: 3.0% or less, Mn: 3.0% or less,
- the balance consists of Fe and unavoidable impurities, It may have a component composition in which the total content of Al and Mn is 0.40% or more.
- the chemical composition of the steel slab may further optionally contain at least one of the following elements.
- C 0.005% or less C contained in a non-oriented electrical steel sheet is a harmful element that forms carbides, causes magnetic aging, and deteriorates iron loss characteristics. Therefore, when the steel slab contains C, the C content is made 0.005% or less, preferably 0.004% or less.
- the lower limit of the C content is not particularly limited, but from the viewpoint of suppressing the decarburization cost in the refining process, the C content is preferably 0.0001% or more.
- Cr 3.0% or less Cr is an element that has the effect of increasing the resistivity of the steel sheet and reducing iron loss. However, if the Cr content exceeds 3.0%, carbide precipitates and the iron loss rather increases. Therefore, when Cr is added, the Cr content is made 3.0% or less. From the viewpoint of magnetic properties, the Cr content is preferably 1.5% or less. On the other hand, the lower limit of the Cr content is not limited, but from the viewpoint of enhancing the effect of adding Cr, the Cr content is preferably 0.001% or more, more preferably 0.005% or more. , more preferably 0.01% or more.
- Ni 2.0% or less
- Ni is an element that has the effect of improving the magnetic flux density of the steel sheet.
- Ni is an expensive element, and if the Ni content exceeds 2.0%, the cost becomes very high. Therefore, when Ni is added, the Ni content is set to 2.0% or less. From the viewpoint of the balance between magnetic properties and cost, the Ni content is preferably 0.5% or less.
- the lower limit of the Ni content is not limited, but from the viewpoint of enhancing the effect of Ni addition, the Ni content is preferably 0.001% or more, more preferably 0.005% or more. , more preferably 0.01% or more.
- Cu 2.0% or less
- Cu is an element that has the effect of improving the magnetic flux density of the steel sheet.
- the Cu content exceeds 2.0%, it causes hot shortness and causes surface defects. Therefore, when Cu is added, the Cu content is set to 2.0% or less. From the viewpoint of the balance between magnetic properties and cost, the Cu content is preferably 0.5% or less.
- the lower limit of the Cu content is not limited, but from the viewpoint of enhancing the effect of adding Cu, the Cu content is preferably 0.005% or more, more preferably 0.01% or more. , more preferably 0.05% or more.
- P 0.2% or less
- P is an element used for strength adjustment of the steel sheet.
- the P content should be 0.2% or less.
- the P content is preferably 0.1% or less.
- the lower limit of the P content is not limited, but from the viewpoint of increasing the effect of adding P, the P content is preferably 0.001% or more, more preferably 0.005% or more. , more preferably 0.01% or more.
- S 0.0050% or less
- S is an element that forms sulfide and increases iron loss. Therefore, when S is contained, the S content should be 0.0050% or less, preferably 0.0020% or less, more preferably 0.0010% or less.
- the lower limit of the S content is not limited, and may be 0%.
- S is an element inevitably mixed into steel as an impurity, and excessive reduction causes an increase in manufacturing costs. Therefore, from the viewpoint of cost, the S content is preferably 0.0001% or more, more preferably 0.0005% or more.
- N 0.0050% or less
- N is an element that forms nitrides and increases iron loss. Therefore, when N is contained, the N content is made 0.0050% or less, preferably 0.0030% or less, more preferably 0.0020% or less.
- the lower limit of the N content is not limited, and may be 0%.
- N is an element that is inevitably mixed into steel as an impurity, and excessive reduction causes an increase in manufacturing costs. Therefore, from the viewpoint of cost, the N content is preferably 0.0001% or more, more preferably 0.0005% or more.
- O 0.0050% or less
- O is an element that forms an oxide and increases iron loss. Therefore, when O is contained, the O content should be 0.0050% or less, preferably 0.0020% or less, and more preferably 0.0010% or less.
- the lower limit of the O content is not limited, and may be 0%.
- O is an element that is inevitably mixed into steel as an impurity, and excessive reduction causes an increase in manufacturing costs. Therefore, from the viewpoint of cost, the O content is preferably 0.0005% or more, more preferably 0.001% or more.
- Ti is an element that forms carbonitrides and increases iron loss. Therefore, when Ti is contained, the Ti content should be 0.0040% or less, preferably 0.0020% or less, and more preferably 0.0010% or less. On the other hand, from the viewpoint of iron loss, the lower the Ti content, the better. Therefore, the lower limit of the Ti content is not limited, and may be 0%. However, Ti is an element that is inevitably mixed into steel as an impurity, and excessive reduction causes an increase in manufacturing costs. Therefore, from the viewpoint of cost, the Ti content is preferably 0.0001% or more, more preferably 0.0005% or more.
- Sn 0.20% or less
- Sn is an element that suppresses nitridation and oxidation of the surface layer and has the effect of reducing iron loss. However, the effect saturates even if it is added in excess of 0.20%, so when Sn is added, the Sn content is made 0.20% or less, preferably 0.10% or less. On the other hand, from the viewpoint of enhancing the above effect, the Sn content is preferably 0.005% or more.
- Sb 0.20% or less
- Sb is an element that has the effect of suppressing nitridation and oxidation of the surface layer and reducing iron loss. However, the effect saturates even if it is added in excess of 0.20%, so when Sb is added, the Sb content is made 0.20% or less, preferably 0.10% or less. On the other hand, from the viewpoint of enhancing the above effects, the Sb content is preferably 0.005 or more.
- Mo 0.10% or less
- Mo is an element that has the effect of suppressing nitridation and oxidation of the surface layer and reducing iron loss. However, adding more than 0.10% rather increases the core loss. Therefore, when Mo is added, the Mo content should be 0.10% or less, preferably 0.05% or less. On the other hand, from the viewpoint of enhancing the above effects, it is preferable to set the Mo content to 0.001% or more.
- Ca 0.01% or less Ca is an element that suppresses the formation of fine oxides and sulfides and reduces iron loss. However, even if it is added in excess of 0.01%, the effect is saturated. Therefore, when Ca is added, the Ca content should be 0.01% or less, preferably 0.006% or less. On the other hand, from the viewpoint of enhancing the effect, the Ca content is preferably 0.001% or more.
- REM 0.05% or less REM (rare earth metal) is an element that suppresses the formation of fine sulfides and reduces iron loss. However, even if it is added in excess of 0.05%, the effect is saturated. Therefore, when REM is added, the REM content should be 0.10% or less, preferably 0.03% or less. On the other hand, from the viewpoint of enhancing the above effects, the REM content is preferably 0.005% or more.
- Mg 0.01% or less Mg is an element that suppresses the formation of fine sulfides and reduces iron loss. However, even if it is added in excess of 0.01%, the effect is saturated. Therefore, when Mg is added, the Mg content should be 0.10% or less, preferably 0.006% or less. On the other hand, from the viewpoint of enhancing the effect, the Mg content is preferably 0.001% or more.
- Zn 0.01% or less
- Zn is an element that suppresses the formation of fine oxides and sulfides and reduces iron loss. However, even if it is added in excess of 0.01%, the effect is saturated. Therefore, when Zn is added, the Zn content should be 0.01% or less, preferably 0.005% or less. On the other hand, from the viewpoint of enhancing the above effects, the Zn content is preferably 0.001 or more.
- a method for producing a hot-rolled steel sheet for a non-oriented electrical steel sheet includes a continuous casting step of producing a steel slab by a continuous casting method, and a conveying step of conveying the steel slab to the furnace, a heat retaining step of retaining the steel slab in the furnace under conditions of a heat retention temperature of 1100 ° C. or more and 1300 ° C. or less and a heat retention time of 60 seconds or more, and rough rolling and reheating of the steel slab , and a hot rolling step in which finish rolling is sequentially performed to form a hot rolled steel sheet.
- a continuous casting step of producing a steel slab by a continuous casting method
- a conveying step of conveying the steel slab to the furnace
- a heat retaining step of retaining the steel slab in the furnace under conditions of a heat retention temperature of 1100 ° C. or more and 1300 ° C. or less and a heat retention time of 60 seconds or more
- rough rolling and reheating of the steel slab and a hot rolling step in which
- a steel slab having the above-described composition is manufactured by a continuous casting method (continuous casting process).
- a method for continuous casting is not particularly limited, and a conventional method can be used.
- a method for adjusting the components of molten steel used for continuous casting is also not particularly limited, and any method can be used.
- a converter, an electric furnace, a vacuum degassing device, and other devices and methods can be used to adjust the composition of the molten steel.
- Steel slab thickness 50-200mm
- a steel slab having a thickness of 50 mm or more and 200 mm or less is manufactured. If the thickness of the steel slab is less than 50 mm, a sufficient rolling reduction in rough rolling and finish rolling in the hot rolling process cannot be obtained, and recrystallization in hot-rolled sheet annealing is inhibited. Therefore, the thickness of the steel slab shall be 50 mm or more. From the viewpoint of suppressing a decrease in slab temperature between the continuous casting process and the heat retention process, it is preferable to set the thickness of the steel slab to 100 mm or more. Furthermore, from the viewpoint of ensuring a sufficient rolling reduction in rough rolling and finish rolling, it is more preferable to set the thickness of the steel slab to 140 mm or more. On the other hand, if the thickness of the steel slab exceeds 200 mm, the rolling load in the hot rolling process increases, leading to an increase in the length of the rolling equipment and the equipment cost. Therefore, the thickness of the steel slab shall be 200 mm or less.
- the steel slab manufactured in the continuous casting process is conveyed to a furnace used for thermal insulation (conveyance process).
- the transporting step it is important to transport while maintaining the surface temperature of the steel slab at 800° C. or higher.
- the steel slab is conveyed so that the surface temperature of the steel slab does not drop below 800° C. from the time it is produced in the continuous casting process until it reaches the furnace.
- the surface temperature of the steel slab is less than 800°C, the energy required for reheating the steel slab increases, and the effect of energy saving cannot be obtained.
- the method for suppressing the surface temperature drop of the steel slab in the transport process is not particularly limited, but for example, the surface temperature drop can be suppressed by increasing the casting speed or increasing the slab thickness.
- the steel slab may be cut and then transported to the furnace.
- Heat Retention Step the steel slab is heated in the furnace at a heat retention temperature of 1100° C. or higher and 1300° C. or lower for a heat retention time of 60 seconds or longer (heat retention step).
- heat retention step By promoting the precipitation and coarsening of MnS and AlN by heat-retaining treatment, recrystallization is promoted in the hot-rolled sheet annealing process when manufacturing a non-oriented electrical steel sheet.
- Heat retention temperature 1100-1300°C If the heat retention temperature is lower than 1100° C., coarsening of precipitates is not promoted, and fine precipitates remain in the slab. As a result, recrystallization in hot-rolled sheet annealing is inhibited, and ridging is likely to occur. Therefore, the heat retention temperature is set to 1100° C. or higher, preferably 1150° C. or higher. On the other hand, if the heat retention temperature is higher than 1300° C., precipitation of precipitates does not progress, and fine precipitation of MnS and AlN occurs during hot rolling after heat retention. As a result, recrystallization in hot-rolled sheet annealing is inhibited, and ridging is likely to occur. Therefore, the heat retention temperature is set to 1300° C. or lower, preferably 1250° C. or lower.
- Heat retention time 60 s or more If the heat retention time is less than 60 s, precipitation and coarsening of MnS and AlN do not proceed, and thus ridging is likely to occur. Therefore, the heat retention time is set to 60 s or longer, preferably 300 s or longer. On the other hand, the upper limit of the heat retention time is not particularly limited, but if it exceeds 3600 seconds, the effect is saturated and the construction cost of the facility increases. Therefore, the retention time is preferably 3600 s or less, more preferably 2400 s or less, and even more preferably 2000 s or less.
- a heating method in the heat insulating treatment is not particularly limited, and any method such as induction heating, gas furnace, electric furnace, or the like can be used.
- any method such as induction heating, gas furnace, electric furnace, or the like can be used.
- gas furnace when a gas furnace is used, scale is generated on the surface of the steel sheet by the combustion gas. Therefore, from the viewpoint of suppressing scale formation and CO 2 emission, it is preferable to use induction heating or an electric furnace, which are heating methods using electric energy.
- the electric furnace is suitable for continuously heating the steel slab for a long time, and the construction cost is low. Therefore, it is more preferable to use an electric furnace for the thermal insulation.
- Hot rolling step the steel slab is subjected to rough rolling, reheat treatment, and finish rolling in order to form a hot rolled steel sheet (hot rolling step).
- hot rolling step it is important to carry out the hot rolling step under conditions satisfying the following (1) and (2).
- Total rolling reduction in rough rolling 80% or more If the total rolling reduction in rough rolling is less than 80%, the promotion of precipitation of MnS and AlN due to the introduction of dislocations is insufficient, and the subsequent reheating treatment causes precipitates to coarsen. do not have. Also, the grain boundary density after hot rolling is not sufficiently refined. As a result, recrystallization is not promoted in hot-rolled sheet annealing for producing non-oriented electrical steel sheets, and ridging tends to occur. Therefore, the total reduction in rough rolling is set to 80% or more, preferably 88% or more, and more preferably 91% or more.
- the total rolling reduction of rough rolling is the rolling reduction calculated from the thickness before the start of rough rolling (thickness of steel slab) and the thickness after completion of rough rolling (thickness at delivery side).
- the number of passes of the rough rolling is not particularly limited, and may be any number of passes of 1 or more.
- Total rolling reduction in finish rolling 80% or more If the total rolling reduction in finish rolling is less than 80%, the grain boundary density after hot rolling will not be sufficiently refined, so recrystallization in hot rolled sheet annealing will occur. is not promoted, and ridging tends to occur. Therefore, the total reduction in finish rolling is set to 80% or more, preferably 88% or more, and more preferably 91% or more. In particular, when the total rolling reduction in finish rolling is 91% or more, the grain boundary density after hot rolling increases significantly, and the number of dislocations remaining in the steel sheet after hot rolling also increases significantly. . As a result, recrystallization is more likely to occur during hot-rolled sheet annealing, and ridging can be more effectively suppressed.
- the total reduction ratio of finish rolling is a reduction ratio calculated from the thickness before the start of finish rolling and the thickness after completion of finish rolling (delivery side thickness).
- the number of passes in the finish rolling is not particularly limited, and may be an arbitrary number of passes greater than or equal to one.
- the total rolling reduction in rough rolling is preferably larger than the total rolling reduction in finish rolling.
- the limitation of the rolling reduction in the present invention is for solving the problem of ridging peculiar to direct rolling, and is based on a novel idea that is completely different from the control of the rolling reduction in conventional reheat rolling. It was made.
- Reheating is performed between the above rough rolling and finish rolling. It is necessary to carry out the reheating treatment in order to coarsen the precipitates finely precipitated in rough rolling and suppress ridging. Further, by performing the reheating treatment, the temperature of the material can be raised to lower the deformation resistance during finish rolling.
- the heating temperature in the reheating treatment is not particularly limited, but is preferably 950°C or higher, more preferably 1050°C or higher.
- the upper limit of the heating temperature is not particularly limited, but if the heating temperature is excessively high, the effect is saturated and the energy efficiency is lowered. Therefore, the heating temperature in the reheating treatment is preferably 1300° C. or lower, more preferably 1200° C. or lower.
- the heating method in the reheating treatment is not particularly limited, and any method such as induction heating, gas furnace, electric furnace, etc. can be used.
- the delivery side thickness (the thickness of the finally obtained hot-rolled steel sheet) in the finish rolling is not particularly limited, and may be any thickness. However, if the delivery-side plate thickness is less than 0.4 mm, the total length of the steel plate becomes excessively long, resulting in a decrease in productivity. Therefore, from the viewpoint of productivity, it is preferable to set the delivery side plate thickness in the finish rolling to 0.4 mm or more. On the other hand, if the delivery side plate thickness exceeds 2.0 mm, the cold rolling load increases. Therefore, from the viewpoint of reducing the load in cold rolling, it is preferable to set the delivery side plate thickness in finish rolling to 2.0 mm or less. From the viewpoint of reducing the cold rolling load even when the final thickness after cold rolling is thin, it is more preferable to set the delivery side thickness to 1.5 mm or less.
- a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises a hot-rolled steel sheet manufacturing step of manufacturing a hot-rolled steel sheet by the manufacturing method described above, and a hot-rolled sheet annealing step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing. and a cold-rolling step of cold-rolling the hot-rolled steel sheet to form a cold-rolled steel sheet, and a finish annealing step of subjecting the cold-rolled steel sheet to finish annealing.
- the steps of hot-rolled sheet annealing, cold rolling, and finish annealing are not particularly limited, and can be carried out according to conventional methods.
- pickling after the hot-rolled sheet annealing and prior to the cold rolling. It is also preferable to form an insulating coating on the surface of the obtained non-oriented electrical steel sheet after the finish annealing.
- the pickling and formation of the insulating coating are not particularly limited, either, and can be carried out according to conventional methods.
- Example 1 C: 0.002%, Si: 3.2%, Al: 0.60%, Mn: 0.50%, S: 0.0010%, N: 0.0015%, O: 0.0010%, Cr : 0.02%, Ni: 0.01%, Cu: 0.02%, P: 0.01%, and Ti: 0.001%, and the balance is Fe and unavoidable impurities.
- 60 mm thick steel slabs were produced by continuous casting. Without cutting the steel slab, the surface temperature of the slab was maintained at 800° C. or higher and conveyed to a tunnel electric furnace, where heat-retaining treatment was performed in the electric furnace. The heat retention temperature and heat retention time in the heat retention treatment were as shown in Table 1. For comparison, some examples were not subjected to thermal insulation.
- the steel slab was subjected to hot rolling consisting of 3 passes of rough rolling, reheat treatment, and 4 passes of finish rolling under the conditions shown in Table 1 to obtain hot rolled steel sheets.
- reheating treatment the slab immediately after rough rolling was heated by an induction heating method.
- reheating treatment was omitted in some examples.
- the hot-rolled steel sheet after finish rolling was continuously wound into a coil to form a hot-rolled coil, and the hot-rolled coil was subjected to hot-rolled sheet annealing at 1030°C for 40 seconds to obtain a hot-rolled annealed sheet.
- the hot-rolled and annealed sheet was cold-rolled at a rolling reduction of 85% to obtain a cold-rolled steel sheet.
- the cold-rolled steel sheet was subjected to finish annealing at 1000° C. for 15 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa of the surface of the non-oriented electrical steel sheet was measured.
- a stylus type surface roughness meter was used, and the arithmetic mean waviness Wa was calculated from the waviness curve obtained by measuring the steel sheet surface in the width direction with a measurement length of 16 mm. The measurement results are also shown in Table 1.
- Example 2 C: 0.002%, Si: 3.0%, Al: 1.3%, Mn: 0.40%, S: 0.0005%, N: 0.0015%, O: 0.0010%, Cr : 0.10%, Ni: 0.15%, Cu: 0.18%, P: 0.02%, and Ti: 0.0015%, and the balance is Fe and unavoidable impurities.
- 160 mm thick steel slabs were produced by continuous casting. Without cutting the steel slab, the surface temperature of the slab was maintained at 800° C. or higher, and the steel slab was conveyed to a tunnel-type gas furnace, and heat-retaining treatment was performed in the gas furnace. The heat retention temperature and heat retention time in the heat retention treatment were as shown in Table 2. For comparison, some examples were not subjected to thermal insulation.
- the steel slab was subjected to hot rolling consisting of 4 passes of rough rolling, reheat treatment, and 5 passes of finish rolling under the conditions shown in Table 2 to obtain hot rolled steel sheets.
- reheating treatment the slab immediately after rough rolling was heated by an induction heating method.
- reheating treatment was omitted in some examples.
- the hot-rolled steel sheet after finish rolling was continuously wound into a coil to form a hot-rolled coil, and the hot-rolled coil was subjected to hot-rolled sheet annealing at 1020°C for 30 seconds to obtain a hot-rolled annealed sheet.
- the hot-rolled and annealed sheet was cold-rolled at a rolling reduction of 85% to obtain a cold-rolled steel sheet.
- the cold-rolled steel sheet was subjected to finish annealing at 1000° C. for 15 seconds to obtain a non-oriented electrical steel sheet.
- Example 3 C: 0.002%, Si: 3.4%, Al: 0.3%, Mn: 0.60%, S: 0.0008%, N: 0.010%, O: 0.0010%, Cr : 0.015%, Ni: 0.015%, Cu: 0.03%, P: 0.015%, and Ti: 0.0015%, and the balance is Fe and unavoidable impurities.
- a steel slab with a thickness of 190 mm was produced by continuous casting. Without cutting the steel slab, the surface temperature of the slab was maintained at 800° C. or higher, and the steel slab was conveyed to a tunnel-type gas furnace, and heat-retaining treatment was performed in the gas furnace. The heat retention temperature and heat retention time in the heat retention treatment were as shown in Table 3. For comparison, some examples were not subjected to thermal insulation.
- the steel slab was subjected to hot rolling consisting of 4 passes of rough rolling, reheat treatment, and 5 passes of finish rolling under the conditions shown in Table 3 to obtain hot rolled steel sheets.
- reheating treatment the slab immediately after rough rolling was heated by an induction heating method.
- reheating treatment was omitted in some examples.
- the hot-rolled steel sheet after finish rolling was continuously wound into a coil to form a hot-rolled coil, and the hot-rolled coil was subjected to hot-rolled sheet annealing at 1050°C for 20 seconds to obtain a hot-rolled annealed sheet.
- the hot-rolled and annealed sheet was cold-rolled at a rolling reduction of 85% to obtain a cold-rolled steel sheet.
- the cold-rolled steel sheet was subjected to finish annealing at 1000° C. for 15 seconds to obtain a non-oriented electrical steel sheet.
- Example 4 A steel slab having a thickness of 150 mm and having the chemical composition shown in Tables 4 to 6 was produced by a continuous casting method. Without cutting the steel slab, the surface temperature of the slab was maintained at 800° C. or higher, and the steel slab was conveyed to a tunnel-type gas furnace, and heat-retaining treatment was performed in the gas furnace. The heat retention temperature in the heat retention treatment was set to 1150° C., and the heat retention time was set to 1500 seconds.
- the steel slab was subjected to hot rolling consisting of 4 passes of rough rolling, reheat treatment, and 5 passes of finish rolling to obtain a hot rolled steel sheet.
- the total rolling reduction in the rough rolling was 90%, and the total rolling reduction in the finish rolling was 93.3%.
- the slab immediately after rough rolling was heated to 1100° C. by an induction heating method.
- the hot-rolled steel sheet after finish rolling was continuously wound into a coil to form a hot-rolled coil, and the hot-rolled coil was subjected to hot-rolled sheet annealing at 1050°C for 20 seconds to obtain a hot-rolled annealed sheet.
- the hot-rolled and annealed steel sheet was cold-rolled at a rolling reduction of 80% to obtain a cold-rolled steel sheet having a thickness of 0.20 mm.
- the cold-rolled steel sheet was subjected to finish annealing at 1000° C. for 20 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa of the surface of the non-oriented electrical steel sheet was measured in the same manner as in Example 1 above. The measurement results are also shown in Tables 4-6.
- Example 5 Steel slabs having a thickness of 150 mm and having chemical compositions shown in Tables 7-9 were produced by continuous casting. Without cutting the steel slab, the surface temperature of the slab was maintained at 800° C. or higher, and the steel slab was conveyed to a tunnel-type gas furnace, and heat-retaining treatment was performed in the gas furnace. The heat retention temperature in the heat retention treatment was 1150° C., and the heat retention time was 500 seconds.
- the steel slab was subjected to hot rolling consisting of 4 passes of rough rolling, reheat treatment, and 5 passes of finish rolling to obtain a hot rolled steel sheet.
- the total rolling reduction in the rough rolling was 92%, and the total rolling reduction in the finish rolling was 91.7%.
- the slab immediately after rough rolling was heated to 1100° C. by an induction heating method.
- the hot-rolled steel sheet after finish rolling was continuously wound into a coil to form a hot-rolled coil, and the hot-rolled coil was subjected to hot-rolled sheet annealing at 1050°C for 20 seconds to obtain a hot-rolled annealed sheet.
- the hot-rolled and annealed steel sheet was cold-rolled at a rolling reduction of 80% to obtain a cold-rolled steel sheet having a thickness of 0.20 mm.
- the cold-rolled steel sheet was subjected to finish annealing at 1000° C. for 20 seconds to obtain a non-oriented electrical steel sheet.
- the arithmetic mean waviness Wa of the surface of the non-oriented electrical steel sheet was measured in the same manner as in Example 1 above. The measurement results are also shown in Tables 4-6.
Abstract
Description
Si:2.0%以上5.0%以下、
Al:3.0%以下、および
Mn:3.0%以下を含有し、
AlとMnの合計含有量が0.40%以上である成分組成を有し、
厚みが50mm以上200mm以下である鋼スラブを連続鋳造法により製造する連続鋳造工程と、
前記鋼スラブの表面温度を800℃以上に維持したまま炉に搬送する搬送工程と、
前記炉において前記鋼スラブを保熱温度1100℃以上1300℃以下、保熱時間60s以上の条件で保熱する保熱工程と、
前記鋼スラブに粗圧延、再加熱処理、および仕上圧延を順次施して熱延鋼板とする熱延工程と、を含む無方向性電磁鋼板用熱延鋼板の製造方法であって、
前記熱延工程が下記(1)および(2)を満たす条件で行われる、無方向性電磁鋼板用熱延鋼板の製造方法。
(1)前記粗圧延の総圧下率:80%以上
(2)前記仕上圧延の総圧下率:80%以上
(1’)前記粗圧延の総圧下率:88%以上
(2’)前記仕上圧延の総圧下率:88%以上
C :0.005%以下、
Cr:3.0%以下、
Ni:2.0%以下、
Cu:2.0%以下、
P :0.2%以下、
S :0.0050%以下、
N :0.0050%以下、
O :0.0050%以下、
Ti:0.0040%以下、
Sn:0.20%以下、
Sb:0.20%以下、
Mo:0.10%以下、
Ca:0.01%以下、
REM:0.05%以下、
Mg:0.01%以下、および
Zn:0.01%以下からなる群より選択される少なくとも1つをさらに含有する、上記1~4のいずれか一項に記載の無方向性電磁鋼板用熱延鋼板の製造方法。
前記熱延鋼板に熱延板焼鈍を施す熱延板焼鈍工程と、
前記熱延鋼板に冷間圧延を施して冷延鋼板とする冷延工程と、
前記冷延鋼板に仕上焼鈍を施す仕上焼鈍工程と、を含む無方向性電磁鋼板の製造方法。
C:0.002%、Si:3.0%、Al:0.05~2.0%、Mn:0.05~1.0%、Cr:0.01%、Ni:0.01%、Cu:0.01%、P:0.01%、N:0.003%、S:0.002%、O:0.001%、およびTi:0.001%を含有し、残部Feおよび不可避的不純物からなる成分組成を有する、厚さ160mmの鋼スラブを真空溶解炉で溶製した。その後、得られた鋼スラブを以下の2つの方法のいずれかで熱間圧延した。
前記鋼スラブを真空溶解炉から取り出したのち、該鋼スラブ全体を室温まで大気中で放冷した。次いで、該鋼スラブを電気炉に挿入し、1100℃、30分間の再加熱処理を行ったのち、電気炉から前記鋼スラブを取り出して熱間圧延機に挿入した。
前記鋼スラブを真空溶解炉から取り出したのち、表面温度が900℃以下とならないように熱間圧延機に挿入した。
本発明者らは、直送圧延では、MnSやAlNなどの析出物が微細に析出し、それら微細な析出物が熱延板焼鈍における再結晶を妨げていると推定した。そこで、熱間圧延工程の前に保熱処理を行って析出物を析出・成長させ、微細な析出物を低減することとし、そのために必要な条件について検討した。
次に、本発明者らは、直送圧延における粗熱延と仕上熱延の圧下率の配分について検討するために、以下の実験を行った。
本発明において、鋼スラブの成分組成の限定理由について説明する。
Siは鋼板の固有抵抗を上げ、鉄損を低減する効果を有する元素である。前記効果を得るために、Si含有量を2.0%以上とする。一方、Si含有量が5.0%を超えると圧延が困難となるため、Si含有量は5.0%以下とする。固有抵抗と加工性のバランスの観点からは、Si含有量を2.5%以上とすることが好ましく、2.8%以上とすることがより好ましい。同様の理由から、Si含有量は4.5%以下とすることが好ましく、4.0%以下とすることがより好ましい。
Alは鋼板の固有抵抗を上げ、鉄損を低減する効果を有する元素である。しかし、Al含有量が3.0%を超えると圧延が困難となる。そのため、Al含有量は3.0%以下とする。鋳造性を良好とするという観点からは、Al含有量を1.5%以下とすることが好ましい。一方、Al含有量の下限については限定されないが、鉄損と製造性のバランスの観点からは、Al含有量が0.2%以上であることが好ましく、0.3%以上であることがより好ましく、0.5%以上であることがさらに好ましい。
Mnは鋼板の固有抵抗を上げ、鉄損をさらに低減する効果を有する元素である。しかし、Mn含有量が3.0%を超えるとスラブ割れが生じるなど、操業性が悪化する。そのため、Mn含有量は3.0%以下とする。微細なMnSの析出を抑制するという観点からは、Mn含有量を1.5%以下とすることがより好ましい。一方、Mn含有量の下限は限定されないが、微細なMnSの析出をさらに抑制するという観点からは、0.20%以上とすることが好ましい。
AlとMnの合計含有量が0.40%未満になると、析出物の析出温度が低温化し、本発明の特徴である高温での保熱処理を適用すると、保熱処理で析出が進行せず、続く熱間圧延で微細に析出するためにリジングが発生してしまう。そのため,AlとMnの合計含有量は0.40%以上、好ましくは1.00%以上、より好ましくは1.50%以上とする。一方、AlとMnの合計含有量の上限については特に限定されない。しかし、上述したようにAl含有量が3.0%以下、Mn含有量が3.0%以下であることから、AlとMnの合計含有量は最大でも6.00%である。
Si:2.0%以上5.0%以下、
Al:3.0%以下、
Mn:3.0%以下を含有し、
残部Feおよび不可避的不純物からなり、
AlとMnの合計含有量が0.40%以上である成分組成を有していてもよい。
無方向性電磁鋼板に含まれるCは、炭化物を形成して磁気時効を起こし、鉄損特性を劣化させる有害元素である。そのため、鋼スラブにCが含まれる場合、C含有量を0.005%以下、好ましくは0.004%以下とする。一方、C含有量の下限は特に限定されないが、精錬工程での脱炭コストを抑制する観点から、C含有量を0.0001%以上とすることが好ましい。
Crは鋼板の固有抵抗を上げ、鉄損を低減する効果を有する元素である。しかし、Cr含有量が3.0%を超えると炭化物が析出し、鉄損がかえって高くなる。そのため、Crを添加する場合、Cr含有量を3.0%以下とする。磁気特性の観点からは、Cr含有量を1.5%以下とすることが好ましい。一方、Cr含有量の下限については限定されないが、Crの添加効果を高めるという観点からは、Cr含有量を0.001%以上とすることが好ましく、0.005%以上とすることがより好ましく、0.01%以上とすることがさらに好ましい。
Niは鋼板の磁束密度を向上させる効果を有する元素である。しかし、Niは高価な元素であり、Ni含有量が2.0%を超えると非常にコストが高くなる。そのため、Niを添加する場合、Ni含有量は2.0%以下とする。磁気特性とコストのバランスの観点からは、Ni含有量を0.5%以下とすることが好ましい。一方、Ni含有量の下限については限定されないが、Niの添加効果を高めるという観点からは、Ni含有量を0.001%以上とすることが好ましく、0.005%以上とすることがより好ましく、0.01%以上とすることがさらに好ましい。
Cuは鋼板の磁束密度を向上させる効果を有する元素である。しかし、Cu含有量が2.0%を超えると熱間脆性を引き起こし、表面欠陥の原因となる。そのため、Cuを添加する場合、Cu含有量を2.0%以下とする。磁気特性とコストのバランスの観点からは、Cu含有量を0.5%以下とすることが好ましい。一方、Cu含有量の下限については限定されないが、Cuの添加効果を高めるという観点からは、Cu含有量を0.005%以上とすることが好ましく、0.01%以上とすることがより好ましく、0.05%以上とすることがさらに好ましい。
Pは鋼板の強度調整に用いられる元素である。しかし、P含有量が0.2%を超えると鋼が脆くなり、冷間圧延が困難となる。そのため、Pを添加する場合、P含有量は0.2%以下とする。強度と脆性のバランスの観点からは、P含有量を0.1%以下とすることが好ましい。一方、P含有量の下限については限定されないが、Pの添加効果を高めるという観点からは、P含有量を0.001%以上とすることが好ましく、0.005%以上とすることがより好ましく、0.01%以上とすることがさらに好ましい。
Sは硫化物を形成し、鉄損を増加させる元素である。そのため、Sが含有される場合、S含有量を0.0050%以下、好ましくは0.0020%以下、より好ましくは0.0010%以下とする。一方、鉄損の観点からは、S含有量は低ければ低いほどよいため、S含有量の下限は限定されず、0%であってよい。しかし、Sは不純物として不可避的に鋼に混入する元素であり、過度の低減は製造コストの増加を招く。そのため、コストの観点からは、S含有量を0.0001%以上とすることが好ましく、0.0005%以上とすることがより好ましい。
Nは窒化物を形成し、鉄損を増加させる元素である。そのため、Nが含有される場合、N含有量を0.0050%以下、好ましくは0.0030%以下、より好ましくは0.0020%以下とする。一方、鉄損の観点からは、N含有量は低ければ低いほどよいため、N含有量の下限は限定されず、0%であってよい。しかし、Nは不純物として不可避的に鋼に混入する元素であり、過度の低減は製造コストの増加を招く。そのため、コストの観点からは、N含有量を0.0001%以上とすることが好ましく、0.0005%以上とすることがより好ましい。
Oは酸化物を形成し、鉄損を増加させる元素である。そのため、Oが含有される場合、O含有量を0.0050%以下、好ましくは0.0020%以下、より好ましくは0.0010%以下とする。一方、鉄損の観点からは、O含有量は低ければ低いほどよいため、O含有量の下限は限定されず、0%であってよい。しかし、Oは不純物として不可避的に鋼に混入する元素であり、過度の低減は製造コストの増加を招く。そのため、コストの観点からは、O含有量を0.0005%以上とすることが好ましく、0.001%以上とすることがより好ましい。
Tiは炭窒化物を形成し、鉄損を増加させる元素である。そのため、Tiが含有される場合、Ti含有量を0.0040%以下、好ましくは0.0020%以下、より好ましくは0.0010%以下とする。一方、鉄損の観点からは、Ti含有量は低ければ低いほどよいため、Ti含有量の下限は限定されず、0%であってよい。しかし、Tiは不純物として不可避的に鋼に混入する元素であり、過度の低減は製造コストの増加を招く。そのため、コストの観点からは、Ti含有量を0.0001%以上とすることが好ましく、0.0005%以上とすることがより好ましい。
Snは表層の窒化、酸化を抑制し、鉄損を低減する効果を有する元素である。しかし、0.20%を超えて添加しても効果が飽和するため、Snを添加する場合、Sn含有量を0.20%以下、好ましくは0.10%以下とする。一方、前記効果を高めるという観点からは、Sn含有量を0.005%以上とすることが好ましい。
Sbは表層の窒化、酸化を抑制し、鉄損を低減する効果を有する元素である。しかし、0.20%を超えて添加しても効果が飽和するため、Sbを添加する場合、Sb含有量を0.20%以下、好ましくは0.10%以下とする。一方、前記効果を高めるという観点からは、Sb含有量を0.005以上とすることが好ましい。
Moは表層の窒化、酸化を抑制し、鉄損を低減する効果を有する元素である。しかし、0.10%を超えて添加するとかえって鉄損が高くなる。そのため、Moを添加する場合、Mo含有量を0.10%以下、好ましくは0.05%以下とする。一方、前記効果を高めるという観点からは、Mo含有量を0.001%以上とすることが好ましい。
Caは微細な酸化物、硫化物の生成を抑制し、鉄損を低減させる元素である。しかし、0.01%を超えて添加しても効果が飽和する。そのため、Caを添加する場合、Ca含有量を0.01%以下、好ましくは0.006%以下とする。一方、前記効果を高めるという観点からは、Ca含有量を0.001%以上とすることが好ましい。
REM(希土類金属)は微細な硫化物の生成を抑制し、鉄損を低減させる元素である。しかし、0.05%を超えて添加しても効果が飽和する。そのため、REMを添加する場合、REM含有量を0.10%以下、好ましくは0.03%以下とする。一方、前記効果を高めるという観点からは、REM含有量を0.005%以上とすることが好ましい。
Mgは微細な硫化物の生成を抑制し、鉄損を低減させる元素である。しかし、0.01%を超えて添加しても効果が飽和する。そのため、Mgを添加する場合、Mg含有量を0.10%以下、好ましくは0.006%以下とする。一方、前記効果を高めるという観点からは、Mg含有量を0.001%以上とすることが好ましい。
Znは微細な酸化物、硫化物の生成を抑制し、鉄損を低減させる元素である。しかし、0.01%を超えて添加しても効果が飽和する。そのため、Znを添加する場合、Zn含有量を0.01%以下、好ましくは0.005%以下とする。一方、前記効果を高めるという観点からは、Zn含有量を0.001以上とすることが好ましい。
次に、上記成分組成を有する鋼スラブを用いて無方向性電磁鋼板用熱延鋼板を製造する際の製造条件について説明する。
まず、連続鋳造法により上述した成分組成を有する鋼スラブを製造する(連続鋳造工程)。連続鋳造を行う方法は特に限定されず、常法に従って行うことができる。連続鋳造に使用する溶鋼の成分調整方法についても特に限定されず、任意の方法で行うことができる。例えば、前記溶鋼の成分調整には、転炉、電炉、真空脱ガス装置、およびその他の装置と方法を用いることができる。
上記連続鋳造工程では、厚みが50mm以上200mm以下である鋼スラブを製造する。鋼スラブの厚みが50mm未満であると、熱延工程における粗圧延と仕上圧延の圧下率を十分にとることができず、熱延板焼鈍における再結晶が阻害される。そのため、鋼スラブの厚みを50mm以上とする。連続鋳造工程から保熱工程までの間におけるスラブ温度の低下を抑制するという観点からは、鋼スラブの厚みを100mm以上とすることが好ましい。さらに、粗圧延と仕上圧延において圧下率を十分に確保するという観点からは、鋼スラブの厚みを140mm以上とすることがより好ましい。一方、鋼スラブの厚みが200mmを超えると、熱延工程における圧延負荷が増大し、圧延設備の長大化をまねき設備コストが増大する。そのため、鋼スラブの厚みは200mm以下とする。
次に、上記連続鋳造工程で製造された鋼スラブを、保熱処理に用いる炉に搬送する(搬送工程)。前記搬送工程においては、鋼スラブの表面温度を800℃以上に維持したまま搬送を行うことが重要である。言い換えると、本発明では連続鋳造工程で製造されてから炉に到達するまでの間に、鋼スラブの表面温度が800℃未満にならないよう搬送を行う。鋼スラブの表面温度が800℃未満になると、該鋼スラブの再加熱に必要なエネルギーが増大し、省エネルギー化の効果が得られなくなる。
次いで、前記炉において前記鋼スラブを保熱温度1100℃以上1300℃以下、保熱時間60s以上の条件で保熱する(保熱工程)。保熱処理を行ってMnSやAlNの析出と粗大化を 促進することにより、無方向性電磁鋼板を製造する際の熱延板焼鈍工程における再結晶が促進される。
前記保熱温度が1100℃未満であると、析出物の粗大化が促進されず、微細なままスラブに残存する。そしてその結果、熱延板焼鈍における再結晶が阻害され、リジングが発生しやすくなる。そのため、保熱温度を1100℃以上、好ましくは1150℃以上とする。一方、保熱温度が1300℃より高いと、析出物の析出が進行しないため、保熱後の熱間圧延でMnSやAlNが微細析出する。そしてその結果、熱延板焼鈍における再結晶が阻害され、リジングが発生しやすくなる。そのため、保熱温度を1300℃以下、好ましくは1250℃以下とする。
また、保熱時間が60s未満であると、MnSやAlNの析出と粗大化が進行しないため、やはりリジングが発生しやすくなる。そのため、保熱時間は60s以上、好ましくは300s以上とする。一方、保熱時間の上限については特に限定されないが、3600sを超えると効果が飽和することに加え、設備の建設コストが増大する。そのため、前記保持時間は3600s以下とすることが好ましく、2400s以下とすることがより好ましく、2000s以下とすることがさらに好ましい。
次いで、前記鋼スラブに粗圧延、再加熱処理、および仕上圧延を順次施して熱延鋼板とする(熱延工程)。本発明では、下記(1)および(2)を満たす条件で前記熱延工程を実施することが重要である。
(1)粗圧延の総圧下率:80%以上
(2)仕上圧延の総圧下率:80%以上
粗圧延の総圧下率が80%未満であると、転位導入によるMnSやAlNの析出促進が不十分となり、続く再加熱処理での析出物粗大化が生じない。また、熱延後の粒界密度が十分に微細化されない。そしてその結果、無方向性電磁鋼板を製造する際の熱延板焼鈍において再結晶が促進されず、リジングが生じやすくなる。そのため、粗圧延の総圧下率は80%以上、好ましくは88%以上、より好ましくは91%以上とする。特に、粗圧延の総圧下率が91%であると、粗圧延後の加工組織の幅が極めて微細となり、MnSやAlNの析出サイトとなる粒界の板厚方向における密度が大幅に増加する。そしてその結果、MnSやAlNの析出を極めて効果的に促進することができる。ここで、粗圧延の総圧下率とは、粗圧延の開始前における板厚(鋼スラブの板厚)と、粗圧延終了後の板厚(出側板厚)から計算される圧下率である。なお、前記粗圧延のパス数はとくに限定されず、1以上の任意のパス数とすることができる。
また、仕上圧延の総圧下率が80%未満であると、熱延後の粒界密度が十分に微細化されないために、熱延板焼鈍にて再結晶が促進されずリジングが生じやすくなる。そのため、仕上圧延の総圧下率は80%以上、好ましくは88%以上、より好ましくは91%以上とする。特に、仕上圧延の総圧下率が91%以上であると、熱延後の粒界密度が大幅に増加することに加え、熱延後の鋼板への残留する転位の数も大幅に相加する。そしてその結果、熱延板焼鈍での再結晶がさらに生じやすくなり、リジングをさらに効果的に抑制することができる。なお、ここで、仕上圧延の総圧下率とは、仕上圧延の開始前における板厚と、仕上圧延終了後の板厚(出側板厚)から計算される圧下率である。なお、前記仕上圧延のパス数はとくに限定されず、1以上の任意のパス数とすることができる。
本発明の一実施形態における無方向性電磁鋼板の製造方法は、上記製造方法により熱延鋼板を製造する熱延鋼板製造工程と、前記熱延鋼板に熱延板焼鈍を施す熱延板焼鈍工程と、前記熱延鋼板に冷間圧延を施して冷延鋼板とする冷間圧延工程と、前記冷延鋼板に仕上焼鈍を施す仕上焼鈍工程とを含む。
C:0.002%、Si:3.2%、Al:0.60%、Mn:0.50%、S:0.0010%、N:0.0015%、O:0.0010%、Cr:0.02%、Ni:0.01%、Cu:0.02%、P:0.01%、およびTi:0.001%を含有し、残部Feおよび不可避的不純物からなる成分組成を有する、厚さ60mmの鋼スラブを連続鋳造法で製造した。前記鋼スラブを切断することなく、該スラブの表面温度を800℃以上に維持したままトンネル式の電気炉に搬送し、前記電気炉で保熱処理を行った。前記保熱処理における保熱温度と保熱時間は表1に示したとおりとした。なお、比較のため、一部の実施例では保熱処理を行わなかった。
C:0.002%、Si:3.0%、Al:1.3%、Mn:0.40%、S:0.0005%、N:0.0015%、O:0.0010%、Cr:0.10%、Ni:0.15%、Cu:0.18%、P:0.02%、およびTi:0.0015%を含有し、残部Feおよび不可避的不純物からなる成分組成を有する、厚さ160mmの鋼スラブを連続鋳造法で製造した。前記鋼スラブを切断することなく、該スラブの表面温度を800℃以上に維持したままトンネル式のガス炉に搬送し、前記ガス炉で保熱処理を行った。前記保熱処理における保熱温度と保熱時間は表2に示したとおりとした。なお、比較のため、一部の実施例では保熱処理を行わなかった。
C:0.002%、Si:3.4%、Al:0.3%、Mn:0.60%、S:0.0008%、N:0.010%、O:0.0010%、Cr:0.015%、Ni:0.015%、Cu:0.03%、P:0.015%、およびTi:0.0015%を含有し、残部Feおよび不可避的不純物からなる成分組成を有する、厚さ190mmの鋼スラブを連続鋳造法で製造した。前記鋼スラブを切断することなく、該スラブの表面温度を800℃以上に維持したままトンネル式のガス炉に搬送し、前記ガス炉で保熱処理を行った。前記保熱処理における保熱温度と保熱時間は表3に示したとおりとした。なお、比較のため、一部の実施例では保熱処理を行わなかった。
表4~6に示した成分組成を有する、厚さ150mmの鋼スラブを連続鋳造法で製造した。前記鋼スラブを切断することなく、該スラブの表面温度を800℃以上に維持したままトンネル式のガス炉に搬送し、前記ガス炉で保熱処理を行った。前記保熱処理における保熱温度は1150℃、保熱時間は1500秒とした。
表7~9に示した成分組成を有する、厚さ150mmの鋼スラブを連続鋳造法で製造した。前記鋼スラブを切断することなく、該スラブの表面温度を800℃以上に維持したままトンネル式のガス炉に搬送し、前記ガス炉で保熱処理を行った。前記保熱処理における保熱温度は1150℃、保熱時間は500秒とした。
Claims (6)
- 質量%で、
Si:2.0%以上5.0%以下、
Al:3.0%以下、および
Mn:3.0%以下を含有し、
AlとMnの合計含有量が0.40%以上である成分組成を有し、
厚みが50mm以上200mm以下である鋼スラブを連続鋳造法により製造する連続鋳造工程と、
前記鋼スラブの表面温度を800℃以上に維持したまま炉に搬送する搬送工程と、
前記炉において前記鋼スラブを保熱温度1100℃以上1300℃以下、保熱時間60s以上の条件で保熱する保熱工程と、
前記鋼スラブに粗圧延、再加熱処理、および仕上圧延を順次施して熱延鋼板とする熱延工程と、を含む無方向性電磁鋼板用熱延鋼板の製造方法であって、
前記熱延工程が下記(1)および(2)を満たす条件で行われる、無方向性電磁鋼板用熱延鋼板の製造方法。
(1)前記粗圧延の総圧下率:80%以上
(2)前記仕上圧延の総圧下率:80%以上 - 前記仕上圧延における出側板厚を0.4mm以上2.0mm以下とする、請求項1に記載の無方向性電磁鋼板用熱延鋼板の製造方法。
- 前記熱延工程が下記(1’)および(2’)の少なくとも一方を満たす条件で行われる、請求項1または2に記載の無方向性電磁鋼板用熱延鋼板の製造方法。
(1’)前記粗圧延の総圧下率:88%以上
(2’)前記仕上圧延の総圧下率:88%以上 - 前記粗圧延の総圧下率が前記仕上圧延の総圧下率より大きい、請求項1~3のいずれか一項に記載の無方向性電磁鋼板用熱延鋼板の製造方法。
- 前記鋼スラブの成分組成が、質量%で、
C :0.005%以下、
Cr:3.0%以下、
Ni:2.0%以下、
Cu:2.0%以下、
P :0.2%以下、
S :0.0050%以下、
N :0.0050%以下、
O :0.0050%以下、
Ti:0.0040%以下、
Sn:0.20%以下、
Sb:0.20%以下、
Mo:0.10%以下、
Ca:0.01%以下、
REM:0.05%以下、
Mg:0.01%以下、および
Zn:0.01%以下からなる群より選択される少なくとも1つをさらに含有する、請求項1~4のいずれか一項に記載の無方向性電磁鋼板用熱延鋼板の製造方法。 - 請求項1~5のいずれか一項に記載の無方向性電磁鋼板用熱延鋼板の製造方法により熱延鋼板を製造する熱延鋼板製造工程と、
前記熱延鋼板に熱延板焼鈍を施す熱延板焼鈍工程と、
前記熱延鋼板に冷間圧延を施して冷延鋼板とする冷延工程と、
前記冷延鋼板に仕上焼鈍を施す仕上焼鈍工程と、を含む無方向性電磁鋼板の製造方法。
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JPH1161256A (ja) * | 1997-08-08 | 1999-03-05 | Nkk Corp | 表面性状が優れ且つ鉄損の低い無方向性電磁鋼板の製造方法 |
JP2007516345A (ja) * | 2003-05-14 | 2007-06-21 | エイケイ・スティール・プロパティーズ・インコーポレイテッド | 無方向性電磁鋼ストリップの改善された製造方法 |
KR20200065141A (ko) * | 2018-11-29 | 2020-06-09 | 주식회사 포스코 | 낮은 철손 및 우수한 표면품질을 갖는 무방향성 전기강판 및 그 제조방법 |
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