Non-oriented electrical steel sheet and method for producing same

Abstract

Provided are a non-oriented electrical steel sheet having both good magnetic characteristics and punching workability, and a method for producing the same. A non-oriented electrical steel sheet having a component composition containing, in mass%, 0.0050% or less of C, 2.0-5.0% of Si, 0.2-1.8% of Mn, 0.020% or less of P, 0.0050% or less of S, 0.25-2.00% of Al, more than 0.0030% and 0.0150% or less of N, 0.0050% or less of O, 0.01-0.10% in total of one or both of Sn and Sb, with the remainder comprising Fe and unavoidable impurities, and having 10 or more AlN particles having a particle diameter of 0.8 [mu] m or more per 1 mm2 present in a sheet thickness cross-section in the rolling direction. Furthermore, a method for manufacturing a non-oriented electrical steel sheet in which, during the heating of a billet, the heating start temperature is set to 300 DEG C or higher, the heating temperature is set to 1100-1300 DEG C, the annealing temperature of a hot-rolled sheet is set to 800-950 DEG C, and the annealing temperature for final annealing is set to 850-1050 DEG C.

Description

Technical Field

[0001] The present invention relates to a non-oriented electrical steel sheet having excellent properties of a cut surface after punching and a method for producing the same. Background Art

[0002] In recent years, the demand for energy saving has increased, and high efficiency has been strongly required in electrical equipment. Therefore, there is a strong demand for improvement in iron loss characteristics for non-oriented electromagnetic steel sheets, which are widely used as core materials for electrical equipment. Therefore, iron loss has been improved by adding elements that increase resistivity, such as Si and Al, or by reducing the thickness of the sheet.

[0003] On the other hand, when non-oriented electromagnetic steel sheets are used as core materials for electric motors, the core is usually produced by cutting out steel sheets in the shape of the core from the electromagnetic steel sheets by punching and stacking them. However, this method has the problem of deterioration of the magnetic properties of the core due to the shape change of the cut surface after the punching process, such as strain introduced by the punching process, edge collapse and burrs.

[0004] Therefore, a lot of research has been conducted so far on measures to improve punching workability. For example, Patent Document 1 discloses a non-oriented electrical steel containing Si: 1.5% or less, Mn: 0.4% or more and 1.5% or less, sol.Al: 0.01% or more and 0.04% or less, Ti: 0.0015% or less, N: 0.0030% or less, S: 0.0010% or more and 0.0040% or less, B with a B / N ratio of 0.5 or more and 1.5 or less, the balance being Fe and unavoidable impurities, and 10% or more of the sulfides containing Mn being compositely precipitated with B precipitates in terms of number ratio. Moreover, in this technology, when the crystal grain size is 30 μm or less, both punching workability and magnetic properties are achieved.

[0005] In addition, Patent Document 2 discloses a non-oriented electromagnetic steel having excellent magnetic properties and punching workability, which has a steel composition containing, by mass%, C: 0.003% or less, Si: 1.0% or more and 3.0% or less, Al: 0.1% or more and 3.0% or less, Mn: 0.1% or more and 1.0% or less, the contents of Al and Si satisfy the relationship of 0.2≤Al / (Si+Al)≤0.6, and the balance is Fe and inevitable impurities, and the yield ratio represented by (yield strength / tensile strength) is 0.6 or more, and the Vickers hardness is 200 or less.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2005 / 100627

[0009] Patent Document 2: Japanese Patent Application Publication No. 2015-214758 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, the technology disclosed in the above-mentioned patent document 1 targets products with a Si content of 1.5% or less and low magnetic properties, and cannot be applied to products with a high Si content and high magnetic properties. In addition, the technology disclosed in the above-mentioned patent document 2 requires that the Vickers hardness of the product steel sheet be 200 or less, but since Si is an element that increases hardness, the Si content is limited. Therefore, in the above-mentioned prior art, there is a problem that good magnetic properties cannot be obtained.

[0012] Therefore, in view of the above problems in the conventional art, an object of the present invention is to provide a non-oriented electrical steel sheet having both good magnetic properties and punching workability, and to propose an advantageous production method thereof.

[0013] Methods used to solve problems

[0014] In order to solve the above problems, the inventors have repeatedly conducted in-depth studies on the influence of the composition of steel sheets, the manufacturing method, and the ratio of the shear plane to the fracture plane in the cut surface after punching on the magnetic properties. As a result, it was found that by increasing the content of N, which was previously believed to deteriorate the magnetic properties, the ratio of the shear plane in the cut surface after punching can be increased, and the deterioration of the magnetic properties can be suppressed, thereby developing the present invention.

[0015] The present invention based on the above findings is configured as follows.

[0016] [1] A non-oriented electrical steel sheet having a composition comprising, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 1.8%, P: 0.020% or less, S: 0.0050% or less, Al: 0.25 to 2.00%, N: more than 0.0030% and 0.0150% or less, O: 0.0050% or less, one or both of Sn and Sb: 0.01 to 0.10% in total, and the balance being Fe and inevitable impurities, wherein AlN particles having a particle size of 0.8 μm or more existing in a thickness section in a rolling direction are present in an amount of 1 mm 2 More than 10 hits.

[0017] [2] The non-oriented electrical steel sheet according to [1], wherein the steel sheet further contains at least one component of the following groups A to I in addition to the above component composition.

[0018] In terms of mass %,

[0019] Group A: one or more selected from Ca, Mg and REM: 0.0010-0.0080% in total;

[0020] Group B: one or more selected from Ti, Nb and V: 0.0005-0.0030% in total;

[0021] Group C: one or more selected from Cr, Mo, Cu and Ni: 0.005-0.40% in total;

[0022] Group D: one or more selected from Co, W and Ta: 0.0005-0.0200% in total;

[0023] Group E: B: 0.0003-0.0040%;

[0024] Group F: one or more selected from Ge and Ga: the total is 0.0005-0.0100%;

[0025] Group G: one or more selected from Zn and As: 0.001 to 0.010% in total;

[0026] ·Group I: Pb: 0.0001~0.0015%.

[0027] [3] The non-oriented electrical steel sheet according to [1] or [2], wherein a shear plane ratio in a cut surface of the steel sheet after punching is 60% or more.

[0028] Here, the shear plane ratio (%) refers to a value of (area of ​​shear plane) / (area of ​​shear plane+area of ​​fracture plane)×100.

[0029] [4] A method for producing a non-oriented electrical steel sheet, comprising the steps of: producing a steel sheet having a content of less than 0.0050% C, 2.0 to 5.0% Si, 0.2 to 1.8% Mn, 0.020% P, 0.0050% S, 0.25 to 2.00% Al, more than 0.0030% and less than 0.0150% N, 0.0050% O, 0.0010% or less of one or both of Sn and Sb, and the balance of Fe and inevitable impurities; The steel billets are heated and hot rolled to form hot rolled plates, the hot rolled plates are annealed, and then cold rolled once or twice or more with intermediate annealing to form cold rolled plates, and the cold rolled plates are finally annealed. In the method for manufacturing the non-oriented electromagnetic steel plate, during the heating of the steel billets, the heating start temperature is set to 300°C or more, and the heating temperature is set to 1100-1300°C, the annealing temperature of the hot rolled plates is set to 800-950°C, and the final annealing temperature of the cold rolled plates is set to 850-1050°C.

[0030] [5] The method for producing a non-oriented electrical steel sheet according to [4], wherein the steel slab further contains at least one component of the following groups A to I in addition to the above component composition.

[0031] In terms of mass %,

[0032] Group A: one or more selected from Ca, Mg and REM: 0.0010-0.0080% in total;

[0033] Group B: one or more selected from Ti, Nb and V: 0.0005-0.0030% in total;

[0034] Group C: one or more selected from Cr, Mo, Cu and Ni: 0.005-0.40% in total;

[0035] Group D: one or more selected from Co, W and Ta: 0.0005-0.0200% in total;

[0036] Group E: B: 0.0003-0.0040%;

[0037] Group F: one or more selected from Ge and Ga: the total is 0.0005-0.0100%;

[0038] Group G: one or more selected from Zn and As: 0.001 to 0.010% in total;

[0039] ·Group I: Pb: 0.0001~0.0015%.

[0040] Effects of the Invention

[0041] According to the present invention, a non-oriented electromagnetic steel sheet having both good magnetic properties and good punching workability can be manufactured, and thus a material suitable for manufacturing a motor using an iron core produced by punching can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the shearing processing end.

[0043] Figure 2 This is a graph showing the relationship between the number density of AlN particles and the shear plane ratio.

[0044] Figure 3 It is a graph showing the relationship between the shear plane ratio and the iron loss. DETAILED DESCRIPTION

[0045] The inventors of the present invention conceived that a non-oriented electrical steel sheet was punched to manufacture an electric motor, and conducted an experiment to investigate the influence of AlN precipitates on the properties of the cut surface after punching and the influence of the properties of the cut surface on the magnetic properties. Specifically, first, the N content in the raw material was changed in various ways, and test pieces with various changes in the size and number density of AlN precipitate particles in the steel sheet were prepared. Next, the following experiment was conducted to investigate the influence of the size and number density of AlN precipitates on the ratio of shear planes in the punched cut surface, and further investigate the influence of the ratio of shear planes on the magnetic properties.

[0046] Here, Figure 1 Schematic diagram of a punching cut surface S is shown in FIG. Generally, the punching cut surface S includes a shear drop 1 , a shear surface 2 , a fracture surface 3 , and a burr 4 .

[0047] The collapsed edge 1 is a region with small deformation from the upper surface of the steel plate with a plate thickness of t to the upper end of the shear surface 2. The burr 4 is a region protruding downward from the lower surface of the steel plate with a plate thickness of t. If the plate thickness is the same as that of a normal electromagnetic steel plate, it is sufficiently small compared to the shear surface and the fracture surface, and for this reason, it does not need to be considered when calculating the shear surface ratio.

[0048] Therefore, the ratio of the shear plane 2 is calculated from the ratio of the area of ​​the shear plane 2 to the total area of ​​the shear plane 2 and the area of ​​the fracture plane 3 .

[0049] A steel slab was prepared, which had a composition containing, by mass%, C: 0.0033%, Si: 2.8%, Mn: 0.30%, P: 0.010%, S: 0.003%, Al: 0.64%, Sn: 0.025% and O: 0.0013% as a base, and N was added in various amounts within the range of 0.0020 to 0.010%. Next, the steel slab was heated under the conditions of a heating start temperature of 500°C and a heating temperature of 1150°C, and hot rolled to produce a hot rolled sheet with a sheet thickness of 1.8 mm, and the hot rolled sheet was annealed at 930°C for 30 seconds. Next, the hot rolled annealed sheet was pickled, cold rolled to produce a cold rolled sheet with a final sheet thickness of 0.25 mm, and the cold rolled sheet was finally annealed at 980°C for 15 seconds to produce a non-oriented electrical steel sheet.

[0050] In order to evaluate the blanking workability and magnetic properties of the non-oriented electrical steel sheet thus obtained, a test piece of 280 mm in length and 30 mm in width was cut from the L direction (rolling direction) and C direction (direction perpendicular to the rolling direction) of the steel sheet by blanking with a gap of 5%. The iron loss W of the test piece was measured in accordance with JIS C 2550-1. 15 / 50 .

[0051] In addition, from the obtained non-oriented electrical steel sheet in the L direction and C direction, test pieces of 280 mm in length and 10 mm in width were cut by punching with a gap set to 5%. Then, the punched cut surface was observed with an optical microscope, and the ratio of the shear plane in the cut surface in the L direction and the C direction was measured, and the average value was calculated.

[0052] In addition, a test piece was cut out from the obtained non-oriented electrical steel sheet, and the test piece was ground. The thickness cross section in the rolling direction was observed using FE-SEM, and the thickness of each 1 mm 2 The number of AlN particles with a particle size of 0.8 μm or more was observed in the experiment. The reason for setting the particle size to 0.8 μm or more is that according to a previous investigation, the particle size that affects fracture is 0.8 μm or more.

[0053] Figure 2 Graph 3 shows the effect of the number of coarse AlN (grain size 0.8 μm or more) on the shear plane ratio. Figure 2 In the X-axis, AlN particles (pieces / mm 2 ) refers to AlN particles with a particle size of 0.8 μm or more. Figure 2 , coarse AlN reaches every 1mm 2 When there are 10 or more of them, the shear surface ratio is 60% or more. Figure 3 The effect of shear plane ratio on iron loss is shown in Figure 3When the shear surface ratio is above 60%, the iron loss is improved.

[0054] From the above results, it is known that the shear plane ratio in the cut surface S after punching is found as a new evaluation factor for the iron loss after punching, and that the deterioration of the iron loss caused by punching is suppressed by increasing the shear plane ratio as this evaluation factor. In addition, it was found that in order to increase the shear plane ratio, it is effective to increase the precipitated particles of coarse AlN with a particle size of 0.8 μm or more, and for this purpose, it is effective to increase the amount of N in the steel, and thus the present invention was developed.

[0055] <Non-oriented electrical steel sheet>

[0056] The non-oriented electrical steel sheet according to the present embodiment will be described.

[0057] First, the reasons for limiting the chemical composition of the non-oriented electrical steel sheet will be described. It should be noted that, unless otherwise specified, "%" for a component means "mass %".

[0058] C: 0.0050% or less

[0059] C is a harmful element that forms carbides and deteriorates iron loss. Therefore, the C content is set to 0.0050% or less. Preferably, the C content is 0.0035% or less, and more preferably, 0.0030% or less. It should be noted that the lower limit of the C content is not particularly specified, but from the perspective of reducing the decarburization cost in the steelmaking process, it is preferably 0.0003% or more.

[0060] Si: 2.0~5.0%

[0061] Si has the effect of increasing the resistivity of steel and reducing iron loss. In order to obtain this effect, the Si content is set to be greater than 2.0%. The preferred Si content is greater than 2.8%. In the case of being applied to high-grade materials that further require low iron loss, it is more preferably set to be greater than 3.0%. On the other hand, when the Si content exceeds 5.0%, the punching workability decreases and rolling becomes difficult. Therefore, the Si content is set to less than 5.0%. From the viewpoint of suppressing the reduction of magnetic flux density, the preferred Si content is less than 3.8%.

[0062] Mn: 0.2~1.8%

[0063] Mn is an element that is effective in reducing iron loss, just like Si. Therefore, the Mn content is set to be 0.2% or more. The Mn content is preferably 0.3% or more. On the other hand, when it exceeds 1.8%, the iron loss deteriorates due to the precipitation of fine Mn carbides. Therefore, the Mn content is set to be 1.8% or less.

[0064] P: 0.020% or less

[0065] P segregates at the grain boundaries and makes the steel sheet brittle, reducing blanking workability and rolling properties. Therefore, the P content is set to 0.020% or less. Preferably, the P content is 0.015% or less, and more preferably 0.010% or less. It should be noted that the lower limit of the P content is not particularly specified, but from the perspective of reducing the cost of low P in the steelmaking process, it is preferably 0.003% or more.

[0066] S: 0.0050% or less

[0067] S is a harmful element that impairs hot workability or forms fine sulfides to deteriorate iron loss. Therefore, the S content is set to 0.0050% or less. Preferably, the S content is 0.0030% or less. More preferably, it is less than 0.0020%.

[0068] Al: 0.25~2.00%

[0069] Al, like Si, has the effect of increasing the resistivity of the steel sheet and reducing the iron loss. In addition, in the present invention, it also has the effect of combining with N to form coarse AlN and dispersed in the steel, thereby improving the punching workability. Therefore, the Al content is set to be 0.25% or more. Preferably, the Al content is 0.6% or more. On the other hand, when Al is added excessively, a large amount of aluminum oxide is generated, the punching workability is reduced, and surface defects are induced. Therefore, the Al content is set to be less than 2.00%. Preferably, the Al content is 1.80% or less.

[0070] N: more than 0.0030% and less than 0.0150%

[0071] N has the effect of forming AlN and precipitating and dispersing in steel, thereby improving the punching workability. The larger the size of the AlN particles and the more the number, the more the above effect is improved. Therefore, the N content is set to be greater than 0.0030%. It should be noted that by making the size of the AlN particles larger and more dispersed, the punching workability is further improved. Therefore, it is preferred that the N content is greater than 0.0050%, and more preferably greater than 0.0080%. On the other hand, when N is added excessively, bubbles may be generated in the steel billet, reducing the manufacturability. In addition, the punching workability is reduced. Therefore, the N content is set to be less than 0.0150%.

[0072] O: 0.0050% or less

[0073] O forms oxides, inhibits the growth of crystal grains, and deteriorates iron loss. Therefore, the O content is set to 0.0050% or less. Preferably, the O content is 0.0030% or less.

[0074] One or both of Sn and Sb: 0.01 to 0.10% in total

[0075] Sn and Sb are elements effective in improving the texture and improving the magnetic properties. Therefore, the Sn content and the Sb content are set to 0.01% or more in total. On the other hand, even if one or both of Sn and Sb are added excessively, the above effect is saturated, so the Sn content and the Sb content are set to 0.10% or less in total in total.

[0076] In the non-oriented electrical steel sheet of the present invention, the balance other than the above components is Fe and inevitable impurities. In order to improve magnetic properties, it is preferred that the non-oriented electrical steel sheet further contains at least one component selected from the following groups A to I in addition to the component composition.

[0077] Group A: One or more selected from Ca, Mg and REM: 0.0010 to 0.0080% in total

[0078] Ca, Mg and REM have the effect of fixing S in the form of sulfide and improving iron loss. In addition, the sulfides of Ca, Mg and REM are generated at high temperatures compared to MnS, so the sulfide particles become coarse and have the effect of improving punching workability. Therefore, regarding the content of Ca, Mg and REM, it is preferred to set the total of one or more to 0.0010% or more. On the other hand, when the content of Ca, Mg and REM is excessive, inclusions are formed and manufacturability is reduced. Therefore, the content of Ca, Mg and REM is preferably set to less than 0.0080% in total of one or more. More preferably, the content of Ca, Mg and REM is less than 0.0050% in total of one or more.

[0079] Group B: One or more selected from Ti, Nb and V: 0.0005 to 0.0030% in total

[0080] Ti, Nb and V have the effect of forming precipitates and improving the punching workability by refining the structure and dispersing the precipitates. Therefore, the content of Ti, Nb and V is preferably set to 0.0005% or more in total. On the other hand, when the content of Ti, Nb and V is excessive, the growth of grains is significantly hindered, and the iron loss is deteriorated. Therefore, the content of Ti, Nb and V is preferably set to 0.0030% or less in total in total.

[0081] · Group C: one or more selected from Cr, Mo, Cu and Ni: 0.005 to 0.40% in total

[0082] Cr, Mo, Cu and Ni have the effect of increasing the resistivity of steel and improving iron loss. Therefore, the content of Cr, Mo, Cu and Ni is preferably set to 0.005% or more in total. On the other hand, when the content of Cr, Mo, Cu and Ni is excessive, the surface properties deteriorate. Therefore, the content of Cr, Mo, Cu and Ni is preferably set to 0.40% or less in total in total.

[0083] · Group D: One or more selected from Co, W and Ta: 0.0005 to 0.0200% in total

[0084] Co, W and Ta have the effect of forming precipitates and improving the punching workability by refining the structure and dispersing the precipitates. Therefore, the content of Co, W and Ta is preferably set to 0.0005% or more in total of one or more. It is further preferred that the content of Co, W and Ta is more than 0.0010% in total of one or more. On the other hand, when the content of Co, W and Ta is excessive, the growth of grains is significantly hindered and the iron loss is deteriorated. Therefore, the content of Co, W and Ta is preferably set to less than 0.0200% in total of one or more.

[0085] Group E: B: 0.0003~0.0040%

[0086] B has the effect of improving punching workability by making the structure finer. In order to obtain this effect, the B content is preferably set to 0.0003% or more. On the other hand, when the B content is excessive, not only the above effect is saturated, but also excessive boride is generated and iron loss is deteriorated. Therefore, the B content is preferably set to 0.0040% or less.

[0087] · Group F: One or more selected from Ge and Ga: 0.0005 to 0.0100% in total

[0088] Ge and Ga have the effect of improving iron loss by segregating on the surface and grain boundaries of the steel plate, inhibiting oxidation and nitridation during annealing. In order to obtain this effect, it is preferred to contain a total of 0.0005% or more of one or more selected from Ge and Ga. The content of Ge and Ga is more preferably 0.0008% or more. On the other hand, when the content of Ge and Ga is excessive, segregation becomes significant and blanking workability deteriorates. Therefore, the content of Ge and Ga is preferably set to 0.0100% or less.

[0089] · Group G: One or more selected from Zn and As: 0.001 to 0.010% in total

[0090] Zn and As have the effect of improving punching workability by making the structure finer. In order to obtain this effect, it is preferred that the total amount of one or more selected from Zn and As is set to 0.001% or more. On the other hand, when the content of Zn and As is excessive, the oxide is excessive and the iron loss is deteriorated. Therefore, the content of Zn and As is preferably set to 0.010% or less.

[0091] ·Group I: Pb: 0.0001~0.0015%

[0092] Pb has the effect of improving punching workability by making the structure finer. In order to obtain this effect, the Pb content is preferably set to 0.0001% or more. On the other hand, when the Pb content is excessive, the iron loss deteriorates due to the finely dispersed Pb particles, so the Pb content is preferably set to 0.0015% or less.

[0093] Next, the existence form of AlN particles existing in the non-oriented electrical steel sheet of the present embodiment will be described.

[0094] The number of AlN particles with a particle size of 0.8 μm or more present in the plate thickness cross section in the rolling direction is 1 mm 2 More than 10

[0095] The punching workability of steel sheets depends greatly on the dispersion state of AlN particles in the steel sheets. Specifically, when the particle size of AlN particles is small, there is no significant effect on the fracture behavior during punching. However, in the thickness section of the non-oriented electromagnetic steel sheet in the rolling direction, the dispersion state of AlN particles per 1 mm 2 If at least 10 AlN particles have a particle size of 0.8 μm or more, the ratio of shear planes in the cut surface after punching becomes high, and the punching workability is improved. Preferably, the AlN particles with a particle size of 0.8 μm or more are present per 1 mm 2 More than 18 per mm 2 More than 20. Preferably every 1mm 2 Less than 50.

[0096] If there are too many coarse AlN particles, the number density of the AlN particles decreases. Therefore, it is preferred that the number of AlN particles having a particle size of 0.8 μm or more and 6.0 μm or less be 1 mm 2 More than 10 hits.

[0097] Regarding the dispersion state of AlN, for example, the plate thickness cross-section in the rolling direction of the steel plate is observed using FE-SEM-EDX or FE-EPMA, the particle size is calculated from the square root of the product of the major axis and the minor axis of the AlN particles, and the number of AlN particles per unit area with a particle size of 0.8 μm or more is measured.

[0098] Next, the magnetic properties and punching workability of the non-oriented electrical steel sheet according to the present embodiment will be described.

[0099] Magnetic properties

[0100] The magnetic properties of the steel sheet after punching are evaluated. For example, in the case of a sheet thickness of 0.25 mm, if the iron loss W 15 / 50 When it is 2.40 W / kg or less, it is evaluated that the magnetic characteristics are good and it is effective for improving the efficiency of a motor or the like.

[0101] Punching processability

[0102] The blanking workability of the steel sheet is evaluated by the shear surface ratio in the cut surface S after blanking. When the shear surface ratio is 60% or more, good magnetic properties can be obtained even if the blanking state is maintained. Figure 1 , the shear plane ratio (%) refers to the value of (area of ​​shear plane 2) / (area of ​​shear plane 2+area of ​​fracture plane 3)×100.

[0103] It has been newly discovered that, in the cut surface S after punching, the shear plane 2 and the fracture plane 3 affect the punching workability, and that the proportion of the shear plane 2 in particular has a great influence, so the shear plane ratio is defined as described above.

[0104] The areas of the shear plane 2 and the fracture plane 3 are obtained by observing the cut surface S after the punching process using an optical microscope.

[0105] <Method for producing non-oriented electrical steel sheet>

[0106] Next, a method for producing a non-oriented electrical steel sheet according to the present embodiment will be described.

[0107] Billet

[0108] The composition of the steel billet used in the manufacture of the non-oriented electromagnetic steel sheet of the present embodiment is adjusted to the above-mentioned composition range. The smelting method of the steel can adopt a known refining process using a converter, an electric furnace, or a vacuum degassing device, etc., without particular limitation. In addition, the manufacturing method of the steel billet is preferably a continuous casting method, but an ingot-blowing rolling method or a thin slab continuous casting method can also be used. In addition, scrap iron and direct reduced iron can be used as raw materials.

[0109] Hot Rolling

[0110] Billet heating start temperature: 300°C or above, heating temperature: 1100-1300°C

[0111] Hot rolling is a process of reheating a steel billet having the above-mentioned composition to a specified temperature and then hot rolling it to obtain a hot-rolled plate of a specified thickness. However, if the steel billet after manufacturing is cooled to a low temperature below 300°C, the AlN in the steel billet will be excessively coarsened, and the number of AlN particles will decrease, and a sufficient number density will not be obtained in the finished plate. Therefore, it is necessary to use a heat shield or the like to keep the surface temperature of the steel billet above 300°C and to make the heating start temperature of the steel billet above 300°C. From the viewpoint of increasing the number density of AlN, the heating start temperature of the steel billet is preferably above 450°C, and more preferably above 550°C.

[0112] In addition, as mentioned above, the particle size of AlN in the steel billet before heating is large and the number of particles is small, so it is necessary to melt part of the AlN and make AlN in a properly dispersed state during hot rolling or in the process after hot rolling. Therefore, the heating temperature of the steel billet is set to be above 1100°C. In order to melt part of the AlN and sufficiently increase the number density of AlN, the heating temperature of the steel billet is preferably above 1150°C, and more preferably above 1220°C. On the other hand, when the heating temperature of the steel billet is too high, the re-melting of AlN proceeds excessively, and AlN precipitates finely during cooling after hot rolling, and large AlN particles cannot be obtained in the finished plate. Therefore, the heating temperature of the steel billet is set to be below 1300°C.

[0113] The holding time of the steel billet at the above-mentioned heating temperature is preferably 10 minutes or longer, and is more preferably 15 minutes or longer in order to make the temperature inside the steel billet more uniform.

[0114] In addition, hot rolling subsequent to heating of the steel slab may be performed under generally known conditions.

[0115] Furthermore, the coiling temperature of the hot-rolled steel sheet is preferably 500° C. or higher and 700° C. or lower.

[0116] Hot rolled sheet annealing

[0117] Annealing temperature of hot rolled plate: 800~950℃

[0118] Next, the hot-rolled steel plate is subjected to hot-rolled plate annealing to promote recrystallization and coarsening of the rolling structure of the hot-rolled plate, and to coarsen the AlN particles to an appropriate size in order to improve the punching workability. Therefore, the annealing temperature of the hot-rolled plate is set to above 800°C. The annealing temperature of the hot-rolled plate is preferably above 850°C. On the other hand, when the annealing temperature of the hot-rolled plate becomes too high, a part of the AlN melts and the number of coarse AlN decreases, and the punching workability decreases. Therefore, the annealing temperature of the hot-rolled plate is set to below 950°C. The annealing temperature of the hot-rolled plate is preferably below 930°C. It should be noted that the soaking time in the hot-rolled plate annealing is set to the time when the hot-rolled plate can be evenly heated, preferably 5 to 200s.

[0119] Pickling

[0120] Pickling is a process of removing scale from a hot-rolled steel sheet by pickling. The pickling conditions can be any conditions as long as the scale can be removed to a degree that allows cold rolling in the next step. For example, common pickling conditions using hydrochloric acid, sulfuric acid, etc. can be applied. It should be noted that in order to promote the removal of scale, the scale can be cracked by mechanical methods such as shot peening and light reduction rolling before or during pickling.

[0121] Cold Rolling

[0122] Cold rolling is a process of cold rolling the hot-rolled annealed sheet after pickling to obtain the plate thickness (final plate thickness) of the finished plate. There is no particular restriction on the cold rolling as long as the final plate thickness can be obtained. However, if the reduction rate in the cold rolling is too low, the strength of the steel plate after the final annealing may be greatly reduced, so the reduction rate in the cold rolling is preferably 50% or more, and more preferably 70% or more. In addition, the cold rolling is not limited to one time, and two or more cold rollings with intermediate annealing can be performed as needed. The intermediate annealing conditions in this case can be the commonly used conditions, and there are no particular restrictions.

[0123] Final annealing

[0124] Final annealing temperature: 850~1050℃

[0125] The final annealing of the cold-rolled sheet is a process of annealing the cold-rolled sheet made into the final sheet thickness by cold rolling to give the desired magnetic properties and strength properties. In order to make it recrystallize and fully eliminate the strain introduced in the cold rolling and obtain good magnetic properties, the final annealing temperature of the cold-rolled sheet is set to above 850°C. In order to obtain better magnetic properties, the final annealing temperature of the cold-rolled sheet is preferably set to above 880°C. On the other hand, when the final annealing temperature of the cold-rolled sheet is too high, the recrystallized structure becomes too coarse and the magnetic properties are reduced. Therefore, the final annealing temperature of the cold-rolled sheet is set to below 1050°C. The final annealing temperature of the cold-rolled sheet is preferably below 1030°C.

[0126] The steel sheet subjected to the final annealing is then coated with an insulating film as required to obtain a finished steel sheet. The insulating film may be inorganic, organic, or a mixture of inorganic and organic, and is not particularly limited.

[0127] Example

[0128] The steel having the composition shown in Table 1 was melted by a conventional refining process and then formed into a steel billet by continuous casting. Next, the steel billet was heated in a gas furnace at 1120°C for 45 minutes, and then hot rolled consisting of rough rolling and finish rolling to form a hot rolled plate with a plate thickness of 1.8 mm. The hot rolled plate was subjected to hot rolled plate annealing, pickling, and cold rolled to form a cold rolled plate with a final plate thickness of 0.25 mm, and the cold rolled plate was subjected to final annealing to form a finished plate. It should be noted that the conditions of the hot rolling, hot rolled plate annealing, and final annealing of the cold rolled plate are shown in Table 2.

[0129] Next, samples were cut out from the above-mentioned finished plates and subjected to the following evaluation tests.

[0130] [Magnetic properties]

[0131] Test pieces with a width of 30 mm and a length of 280 mm were cut from the above sample in the L direction (rolling direction) and the C direction (direction perpendicular to the rolling direction) by blanking with a gap set to 5%, and the iron loss W was measured in accordance with JIS C 2550-1. 15 / 50 .

[0132] [Blanking processability]

[0133] The cross section of the sample in the rolling direction was ground and observed using FE-SEM. The number of AlN particles with a particle size of 0.8 μm or more per 1 mm was measured by the above method. 2 The number of in .

[0134] In addition, test pieces of 280 mm in length and 10 mm in width were cut from the L and C directions of the above-mentioned samples by punching with a gap set to 5%, and the cut surfaces in the L and C directions were observed using an optical microscope, and the ratio of the sheared surfaces was measured to obtain the average values ​​in the L and C directions. As a result, a sheared surface ratio of more than 65% was regarded as excellent punching property and indicated by "◎", a sheared surface ratio of 60% or more and 65% or less was regarded as good punching property and indicated by "○", and a sheared surface ratio of less than 60% was regarded as poor punching property and indicated by "×".

[0135] The results of the above evaluation are shown in Table 2. According to the results, the number density of AlN particles with a particle size of 0.8 μm or more was 10 particles / mm. 2 The ratio of shear planes is 60% or more, and the iron loss is 2.40W / kg or less, which shows good magnetic properties. In addition, the number density of AlN particles with a particle size of 0.8μm or more is more than 18 / mm. 2 When the shear plane ratio is higher than 65%, the iron loss is less than 2.10W / kg, showing better magnetic properties.

[0136]

[0137]

[0138]

[0139]

[0140] Industrial Applicability

[0141] The technology of the present invention can also be applied to shearing of a plurality of stacked electromagnetic steel sheets.

[0142] Explanation of symbols

[0143] S: Shearing end

[0144] 1: Collapsed edge

[0145] 2: Clipping plane

[0146] 3: Fracture surface

[0147] 4: Burr

[0148] t: Plate thickness

Claims

1. A non-oriented electrical steel sheet having a composition comprising, by mass%, C: 0.0050% or less, Si: 2.0-5.0%, Mn: 0.2-1.8%, P: 0.020% or less, S: 0.0050% or less, Al: 0.25-2.00%, N: more than 0.0030% and 0.0150% or less, O: 0.0050% or less, one or both of Sn and Sb: 0.01-0.10% in total, and the balance being Fe and inevitable impurities, The number of AlN particles with a particle size of 0.8 μm or more present in the plate thickness cross section in the rolling direction is 1 mm 2 More than 10 hits.

2. The non-oriented electrical steel sheet according to claim 1, wherein: The steel plate further contains at least one component of the following groups A to I in addition to the above component composition. In terms of mass %, Group A: one or more selected from Ca, Mg and REM: 0.0010-0.0080% in total; Group B: one or more selected from Ti, Nb and V: 0.0005-0.0030% in total; Group C: one or more selected from Cr, Mo, Cu and Ni: 0.005-0.40% in total; Group D: one or more selected from Co, W and Ta: 0.0005-0.0200% in total; Group E: B: 0.0003-0.0040%; Group F: one or more selected from Ge and Ga: the total is 0.0005-0.0100%; Group G: one or more selected from Zn and As: 0.001 to 0.010% in total; ·Group I: Pb: 0.0001~0.0015%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein: The shear surface ratio of the cut surface of the steel plate after punching is 60% or more, Here, the shear plane ratio (%) refers to a value of (area of ​​shear plane) / (area of ​​shear plane+area of ​​fracture plane)×100.

4. A method for producing a non-oriented electrical steel sheet, comprising the steps of: heating a steel billet having a composition comprising, by mass%, C: 0.0050% or less, Si: 2.0-5.0%, Mn: 0.2-1.8%, P: 0.020% or less, S: 0.0050% or less, Al: 0.25-2.00%, N: greater than 0.0030% and 0.0150% or less, O: 0.0050% or less, one or both of Sn and Sb: 0.01-0.10% in total, and the balance being Fe and inevitable impurities, hot rolling to produce a hot-rolled sheet, annealing the hot-rolled sheet, and then cold rolling once or twice or more with intermediate annealing to produce a cold-rolled sheet, and finally annealing the cold-rolled sheet, The method for producing the non-oriented electrical steel sheet is characterized in that: In the heating of the steel billet, the heating start temperature is set to 300° C. or higher, and the heating temperature is set to 1100 to 1300° C., The annealing temperature of the hot rolled plate is set at 800-950°C. The final annealing temperature of the cold rolled sheet is set at 850-1050°C.

5. The method for producing a non-oriented electrical steel sheet according to claim 4, wherein: The steel slab further contains at least one component of the following groups A to I in addition to the above component composition. In terms of mass %, Group A: one or more selected from Ca, Mg and REM: 0.0010-0.0080% in total; Group B: one or more selected from Ti, Nb and V: 0.0005-0.0030% in total; Group C: one or more selected from Cr, Mo, Cu and Ni: 0.005-0.40% in total; Group D: one or more selected from Co, W and Ta: 0.0005-0.0200% in total; Group E: B: 0.0003-0.0040%; Group F: one or more selected from Ge and Ga: the total is 0.0005-0.0100%; Group G: one or more selected from Zn and As: 0.001 to 0.010% in total; ·Group I: Pb: 0.0001~0.0015%.

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