JP2018178197A - Nonoriented electromagnetic steel sheet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented electromagnetic steel sheet excellent in magnetic property and capable of preventing sagging during die-stamping.SOLUTION: The nonoriented electromagnetic steel sheet has a chemical composition containing, by mass%, C:0.001 to 0.005%, Si:2.0 to 5.0%, Mn:0.1 to 1.5%, P:0.02% or less, S:0.005% or less, Al:0.001 to 2.0%, N:0.001 to 0.005%, and the balance Fe with impurities. Integration degree of a {111}<112> orientation at a t/10 depth position from a surface of the nonoriented electromagnetic steel sheet, I(s) is 6.0 or more and integration degree of a {100}<012> orientation at a t/2 depth position from a surface of the nonoriented electromagnetic steel sheet, I(c) is 4.0 or more, when sheet thickness of the nonoriented electromagnetic steel sheet is defined as t.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing the same.

  Non-oriented electrical steel sheets are used as the material of the iron core of electrical equipment. In these electric devices, high energy efficiency, downsizing and high output are required. Therefore, low core loss and high magnetic density are required for non-oriented electrical steel sheets used as iron cores of electrical equipment.

Conventionally, in order to reduce the iron loss of non-oriented electrical steel sheets, the following technology is employed.
・ Si and Al etc. are contained in the non-oriented electrical steel sheet.
・ Control the grain size of non-oriented electrical steel sheet.
・ Reduce the thickness of non-oriented electrical steel sheets.

  On the other hand, in order to increase the magnetic density of non-oriented electrical steel sheets, control of texture is used. In texture control, the degree of integration of crystal planes including easy magnetization axes is increased in the steel plate plane. Specifically, the accumulation on the {111} plane not including the easy magnetization axis in the steel sheet plane is suppressed, and the accumulation on the {110} plane and the {100} plane including the easy magnetization axis is increased.

  In order to increase accumulation on {110} plane and {100} plane including easy magnetization axis, crystal rotation accompanying rolling deformation in hot rolling process and cold rolling process is controlled. In addition, in non-oriented electrical steel sheets, so-called "warm rolling" may be carried out, in particular, in which the temperature of cold rolling is carried out at a temperature higher than normal temperature (room temperature, about 25 ° C).

  In the manufacture of a non-oriented electrical steel sheet, in order to improve the magnetic properties, techniques for performing warm rolling after hot rolling are proposed in Patent Documents 1 to 5.

In the method of manufacturing a non-oriented electrical steel sheet disclosed in Patent Document 1, the Al content of the non-oriented electrical steel sheet is set to 0.02% or less by mass. In the final cold rolling step, at least one pass excluding the final pass is warm rolling at 100 to 300 ° C. Furthermore, the final pass is rolled at 100 ° C. or less at 10 to 30%. Patent Document 1 describes that this improves the iron loss W _15/50 of the non-oriented electrical steel sheet.

  In the method of manufacturing a non-oriented electrical steel sheet disclosed in Patent Document 2, Cu: 0.2% or more and 4.0% or less, Ni: 0.5% or more and 5.0% or less by mass% For the steel material, warm rolling at a rolling temperature of 100 to 300 ° C. or more is performed in one or more passes in the final cold rolling step, and the cumulative rolling reduction of warm rolling at that time is 45% or more. Patent Document 2 describes that a non-oriented electrical steel sheet excellent in the balance between strength and iron loss can be manufactured.

In the method of manufacturing a non-oriented electrical steel sheet disclosed in Patent Document 3, the hot rolling finish temperature is set to 700 ° C. or higher, which is _lower than the A _r3 transformation point. After descaling the produced hot-rolled steel sheet, the total strain applied in cold rolling is converted to logarithmic strain, and 50% or more of it is rolled at a warm temperature of 100 ° C. to 400 ° C., Finish annealing is performed at 700 ° C. to 950 ° C. for 3 minutes or less. Patent Document 3 describes that a non-oriented electrical steel sheet having excellent magnetic properties can be manufactured by this.

  In warm rolling implemented by patent documents 1-3, rolling temperature is higher than cold rolling. Therefore, the crystal orientation may change due to a change in the sliding behavior of dislocations in the steel. It is considered that the interaction between the element contained in the steel and the dislocation depends on the temperature, and this temperature dependency changes the crystal orientation.

Patent Document 4 and Patent Document 5 propose techniques for controlling warm rolling conditions by paying attention to the interaction between such elements and dislocations. In the electromagnetic steel sheet manufacturing method disclosed in Patent Document 4, a steel having a solid solution (C + N) of 10 ppm or more is rolled at a reduction ratio of 20% or more in a temperature range of 200 to 500 ° C., and then recrystallization annealing is performed And develop the (110) [001] orientation component of the texture. In the method of manufacturing a non-oriented electrical steel sheet disclosed in Patent Document 5, P, S and Se in steel are suppressed to be P + 100 × S + 300 × Se ≦ 0.5, and hot-rolled sheet annealing is performed using Ac ₃ Do it in the temperature range above the point.

  On the other hand, non-oriented electrical steel sheets are processed into iron cores for motors by punching or the like. Therefore, "punching processability" is also required of the non-oriented electrical steel sheet. In particular, it is required to suppress the occurrence of "sagging" which is an inclined surface formed when a non-oriented electrical steel sheet is pushed into a die by a punching punch. That is, it is required to suppress the occurrence of sagging at the time of punching.

  The technique regarding the improvement of punching processability including suppression of generation | occurrence | production of such dripping is proposed by patent documents 6-13.

  In the non-oriented electrical steel sheets disclosed in Patent Document 6 and Patent Document 7, the punching property is enhanced by controlling the hardness and the yield stress. In the non-oriented electrical steel sheet disclosed in Patent Document 8, the crystal grain size of the ferrite phase is controlled to enhance the processability. In the techniques proposed in Patent Documents 6 to 8, the mechanical properties of the non-oriented electrical steel sheet are controlled to enhance the punching processability.

  In the non-oriented electrical steel sheet disclosed in Patent Document 9, the strength in the {011} <100> direction is controlled within a predetermined range, and in Patent Document 10, the influence of grain boundary strength is examined. Further, in the method of manufacturing a non-oriented electrical steel sheet disclosed in Patent Document 11, warm rolling improves punching workability in consideration of the influence of grain size control and crystal orientation control (magnetic flux density) on the occurrence of sagging. Is stated to be effective. In the non-oriented electrical steel sheets disclosed in Patent Documents 12 and 13, the punching processability is improved by adjusting the hardness and chemical composition of the surface layer of the steel sheet.

  Further, among the magnetic characteristics, particularly with regard to high frequency characteristics, it is shown in Patent Documents 14 to 17 that special consideration is required for texture including the {111} orientation of the surface layer.

Patent No. 3888033 JP, 2005-120431, A Patent 2870818 gazette JP-A-58-84924 Unexamined-Japanese-Patent No. 2006-104530 Japanese Patent Application Publication No. 2005-60737 JP, 2005-105407, A JP, 2014-122405, A JP 2012-36474 A Unexamined-Japanese-Patent No. 2014-40622 JP 2003-243214 A Unexamined-Japanese-Patent No. 2-156091 JP-A-4-173940 JP-A-7-150310 JP-A-8-134606 JP 2001-158948 A International Publication No. 2016/148010

  In the above-mentioned patent documents, proposals have been made to suppress the magnetic properties and the punching processability, particularly the sag. However, improvement of magnetic properties and punching processability by other methods is also required.

  An object of the present invention is to provide a non-oriented electrical steel sheet which is excellent in magnetic properties and can suppress the occurrence of sagging at the time of punching.

  In the non-oriented electrical steel sheet according to the present invention, the chemical composition is, in mass%, C: 0.001 to 0.005%, Si: 2.0 to 5.0%, Mn: 0.1 to 1.5% , P: 0.02% or less, S: 0.005% or less, Al: 0.001 to 2.0%, and N: 0.001 to 0.005%, the balance being from Fe and impurities Become. When the thickness of a non-oriented electrical steel sheet is defined as t, the degree of integration I (s) of {111} <112> orientation at the t / 10 depth position from the surface of the non-oriented electrical steel sheet is 6.0 or more And the degree of integration I (c) of {100} <012> orientation at the t / 2 depth position from the surface of the non-oriented electrical steel sheet is 4.0 or more.

In the method of manufacturing a non-oriented electrical steel sheet according to the present invention, a hot rolling process for producing a hot rolled steel sheet by performing hot rolling on a material having the above-described chemical composition and 400 for a hot rolled steel sheet Warm rolling is performed in at least the first pass rolling using a rolling stand having a pair of work rolls having a diameter of 1000 mm, and warm rolling or cold rolling is performed in the second and subsequent passes. It comprises a finish rolling step of manufacturing a thin steel plate having a thickness of 0.10 to 0.50 mm, and a finish annealing step of performing finish annealing on the thin steel plate. In the finish rolling step, when the rolling temperature is T (° C.), the strain rate is ε dot (s ⁻¹ ), and the rolling reduction is r (%) in the first pass rolling, formulas (1) to (5) Warm rolling is performed on the hot-rolled steel sheet under the conditions satisfying 3). Then, the cumulative rolling reduction in the finish rolling step is set to 75 to 95%.

  The non-oriented electrical steel sheet according to the present invention is excellent in magnetic properties and can suppress the occurrence of sagging during punching.

FIG. 1 shows the degree of integration I (s) of {111} <112> orientation in the surface layer and {100} <012> orientation in the thickness center layer in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention. It is a figure which shows the relationship between accumulation degree I (c) of this, and the amount of dripping (micrometer). FIG. 2 shows the degree of integration I (s) of {111} <112> orientation in the surface layer and {100} <012> orientation in the thickness center layer in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention Is a diagram showing the relationship between the degree of integration I (c) of the magnetic flux density and the magnetic flux density B ₅₀ (T). FIG. 3 shows an initial strain rate (s ⁻¹ ) and an initial rolling temperature (° C.) in the first pass warm rolling in the manufacturing process of the non-oriented electrical steel sheet of the chemical composition of the present invention It is a figure which shows the relationship with s). FIG. 4 is a schematic view for explaining the sag measurement test of the example.

  Hereinafter, the present invention will be described in detail.

  The present inventors conducted investigations and studies on a non-oriented electrical steel sheet having excellent magnetic properties and suppressing the occurrence of sagging during punching. As a result, the following findings were obtained.

  When the thickness of a non-oriented electrical steel sheet is defined as t, the integration degree I (s) of {111} <112> orientation at a depth position t / 10 (hereinafter referred to as surface layer) from the rolling surface is 6.0. In the above, punching is performed by setting the degree of integration I (c) of {100} <012> orientation at a position t / 2 deep from the rolling surface (hereinafter referred to as thickness center layer) to 4.0 or more. The occurrence of sagging at the time can be further suppressed.

  FIG. 1 shows the degree of integration I (s) of {111} <112> orientation in the surface layer and {100} <012> orientation in the thickness center layer in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention. It is a figure which shows the relationship between accumulation degree I (c) of, and the amount of dripping.

  Referring to FIG. 1, when the degree of integration I (c) of {100} <012> orientation in the thickness central layer is less than 4.0 (× mark in FIG. 1), {111} <in the surface layer Even if the degree of integration I (s) of the 112> orientation changes, the amount of sag does not change so much. On the other hand, when the degree of integration I (c) of {100} <012> orientation in the thickness center layer is 4.0 or more (○ in FIG. 1), the integration of {111} <112> orientation in the surface layer As the degree I (s) increases, the amount of sagging decreases. Then, when the degree of integration I (s) becomes 6.0 or more, the amount of sagging becomes 15.0 μm or less, and the occurrence of sagging at the time of punching can be remarkably suppressed.

The influence on the magnetic characteristics is small when the degree of integration I (s) of the {111} <112> direction in the surface layer changes. FIG. 2 shows the degree of integration I (s) of {111} <112> orientation in the surface, the degree of integration I (c) of {100} <012> orientation in the thickness center layer, and the magnetic flux density B ₅₀ ( It is a figure which shows the relationship with T). As shown in FIG. 2, although the magnetic flux density B ₅₀ increases with the increase in the degree of integration I (c) of the {100} <012> orientation in the thickness central layer, the {111} <112> in the surface layer It is hardly affected by the change in direction density I (s).

  From the above, when the thickness of the non-oriented electrical steel sheet is defined as t, the degree of integration I (s) of {111} <112> orientation in the surface layer is 6.0 or more, and in the thickness central layer When the degree of integration I (c) in the {100} <012> orientation is 4.0 or more, generation of sagging during punching can be suppressed while maintaining the magnetic characteristics.

  By defining the texture of the surface layer and the texture of the thickness center layer as described above, the mechanism by which the occurrence of sagging is significantly suppressed is not clear, but the following may be considered.

  Heretofore, it has been known that a crystal orientation such as {011} orientation is effective for suppressing the occurrence of sagging (see, for example, Patent Document 9). Patent Literatures 6 and 12 disclose techniques for improving punching processability focusing on the mechanical characteristics of the surface layer.

  However, the present invention suppresses the occurrence of sagging from an approach different from these conventional findings. In the steel plate of the chemical composition of the present invention, in the {111} <112> direction, the rigidity is much higher than the {011} direction in which the sagging suppressing effect is already known. On the other hand, the rigidity is very low in the {100} <012> orientation.

  Unlike the behavior in the plastic deformation region such as hardness and yield ratio, the rigidity is basically a factor that governs the deformation in the elastic deformation region. On the other hand, sag is a phenomenon that extends to the plastic deformation region in principle. However, the amount of deformation of the steel sheet at the time of occurrence of sagging is very small, and in particular, in a region from the shear surface to the inside of the steel sheet, it remains substantially elastic deformation. Therefore, the sag is influenced not only by the deformation in the plastic deformation area but also in the elastic deformation area.

  In the non-oriented electrical steel sheet of the present invention, in the surface layer, the degree of integration of the {111} <112> direction is enhanced, and in the thickness central layer, the degree of integration of the {100} <012> direction is enhanced. That is, in the non-oriented electrical steel sheet of the present invention, the surface layer has high rigidity and the thickness central layer has low rigidity. By realizing this combination, the return of elastic deformation when the deformation stress in the plastic deformation region is unloaded, such as a so-called spring back, is increased. As a result, it is considered that the occurrence of sagging is significantly suppressed.

  The integration degree I (s) of {111} <112> orientation in the surface layer is 6.0 or more, and the integration degree I (c) of {100} <012> orientation in the thickness center layer is 4.0 If it is set as the above, as shown in FIG. 1, generation | occurrence | production of the dripping at the time of stamping can be suppressed notably.

Incidentally, as shown in FIG. 2, when the degree of integration I (c) of {100} <012> orientation in the thickness central layer is 4.0 or more, the magnetic flux density B ₅₀ is 1.65 T or more, which is excellent. Magnetic properties can also be obtained.

  In addition, it is effective to make the average crystal grain of the non-oriented electrical steel sheet finer in order to suppress the occurrence of sagging. In the chemical composition of the present invention, setting the preferred average crystal grain size to 50 μm or less is more effective in suppressing the occurrence of sagging.

The inventors examined an example of a manufacturing method for realizing the above-described texture of the surface layer and the thickness center layer. As a result, when producing a non-oriented electrical steel sheet by rolling a hot rolled steel sheet, warm rolling is performed in at least the first pass rolling, and warm rolling or cold rolling is performed in the second and subsequent passes. Conduct (finish rolling process). Furthermore, in warm rolling in the first pass, when the rolling temperature is T (° C.), the strain rate is ε dot (s ⁻¹ ), and the rolling reduction is r (%), formulas (1) to (3) It has been found that the non-oriented electrical steel sheet having the above-described texture can be manufactured by carrying out rolling under the conditions satisfying the above and making the cumulative rolling reduction in the finish rolling step 75 to 95%.

  The non-oriented electrical steel sheet of the present invention completed based on the above findings has a chemical composition of, in mass%, C: 0.001 to 0.005%, Si: 2.0 to 5.0%, Mn: 0.1 to 1.5%, P: 0.02% or less, S: 0.005% or less, Al: 0.001 to 2.0%, and N: 0.001 to 0.005% And the remaining part consists of Fe and impurities, and when the thickness of the non-oriented electrical steel sheet is defined as t, the accumulation of {111} <112> orientations at a depth of t / 10 from the surface of the non-oriented electrical steel sheet Degree I (s) is 6.0 or more, and the integration degree I (c) of {100} <012> orientation at a depth of t / 2 from the surface of the non-oriented electrical steel sheet is 4.0 or more .

The above chemical composition further includes one or two selected from the group consisting of Ti: 0.01% or less, V: 0.01% or less, and Nb: 0.01% or less, instead of part of Fe. It may contain more than species. In this case, the chemical composition satisfies the formula (A).

  The above chemical composition is, in place of a part of Fe, Sn: 0.2% or less, Cu: 0.1% or less, Ni: 0.1% or less, Cr: 0.2% or less, and B: 0 It may contain one or more selected from the group consisting of .001% or less.

In the method of manufacturing a non-oriented electrical steel sheet according to the present invention, a hot rolling process for producing a hot rolled steel sheet by performing hot rolling on a material having the above-described chemical composition and 400 for a hot rolled steel sheet Warm rolling is performed in at least the first pass rolling using a rolling stand having a pair of work rolls having a diameter of 1000 mm, and warm rolling or cold rolling is performed in the second and subsequent passes. It comprises a finish rolling step of manufacturing a thin steel plate having a thickness of 0.10 to 0.50 mm, and a finish annealing step of performing finish annealing on the thin steel plate. In the finish rolling step, when the rolling temperature is T (° C.), the strain rate is ε dot (s ⁻¹ ), and the rolling reduction is r (%) in the first pass rolling, formulas (1) to (5) Warm rolling is performed on the hot-rolled steel sheet under the conditions satisfying 3). Then, the cumulative rolling reduction in the finish rolling step is set to 75 to 95%.

  In the cold rolling, for example, the rolling temperature is set to 150 ° C. or less.

  In the finish rolling step, a tandem rolling mill may be used, each having a pair of work rolls and including a plurality of rolling stands arranged in a row. In this case, warm rolling is performed at the rolling stand that performs the first pass rolling, and rolling at the second and subsequent passes is performed cold at the rolling stand arranged downstream of the rolling stand that performs the first pass rolling. It is carried out by rolling.

  In the finish annealing step, the highest temperature may be 800 to 900 ° C.

  Hereinafter, the non-oriented electrical steel sheet according to the present invention will be described in detail.

[Chemical composition]
The chemical composition of the non-oriented electrical steel sheet according to the present invention contains the following elements. In addition, "%" in the chemical composition of a non-oriented electrical steel sheet means mass% unless otherwise noted.

C: 0.001 to 0.005%
Carbon (C) is present as solid solution C in the steel and improves the texture due to dynamic strain aging during warm rolling. This increases the magnetic flux density of the non-oriented electrical steel sheet. If the C content is less than 0.001%, this effect can not be obtained. On the other hand, if the C content exceeds 0.005%, fine carbides are precipitated in the steel and the magnetic properties are degraded. Therefore, the C content is 0.001 to 0.005%. The lower limit of the C content is preferably 0.0015%, more preferably 0.002%. The upper limit of the C content is preferably 0.004%, more preferably 0.003%.

Si: 2.0 to 5.0%
Silicon (Si) increases the specific resistance of the steel plate and reduces the eddy current loss. Si further reduces the hysteresis loss. If the Si content is less than 2.0%, the above effect can not be obtained. In addition, if the Si content is less than 2.0%, phase transformation may occur during finish annealing, and the effects of the present invention may be impaired. On the other hand, if the Si content exceeds 5.0%, the rollability in warm rolling described later and the punching processability of the non-oriented electrical steel sheet decrease. Therefore, the Si content is 2.0 to 5.0%. The preferable lower limit of the Si content is 2.5%, and more preferably 3.0%. The upper limit of the Si content is preferably 4.5%, more preferably 4.0%.

Mn: 0.1 to 1.5%
Manganese (Mn) increases the resistivity of the steel. Mn further coarsens sulfides and renders them harmless. If the Mn content is less than 0.1%, these effects can not be obtained. On the other hand, if the Mn content exceeds 1.5%, the magnetic flux density of the steel decreases. Furthermore, phase transformation occurs during annealing, and the effect of the present invention is lost. Therefore, the Mn content is 0.1 to 1.5%. The preferable lower limit of the Mn content is 0.2%, more preferably 0.5%. The upper limit of the Mn content is preferably 1.2%, more preferably 1.0%.

P: 0.02% or less Phosphorus (P) is an impurity. P lowers the workability of the steel and can cause cracking in the steel sheet during cold rolling. Therefore, the P content is 0.02% or less. The P content is preferably as low as possible. The lower limit of the P content is not particularly limited. From the viewpoint of cost and productivity of dephosphorization, a preferable lower limit of P content is 0.01%.

S: 0.005% or less Sulfur (S) is an impurity. S generates MnS to increase iron loss. Therefore, the S content is 0.005% or less. The S content is preferably as low as possible. The lower limit of the S content is not particularly limited. From the viewpoint of the cost and productivity of desulfurization, the preferable lower limit of the S content is 0.001%.

Al: 0.001 to 2.0%
Aluminum (Al) deoxidizes the steel. Al further coarsens nitrides to render them harmless. Al, like Si, further increases the specific resistance of steel and reduces core loss. Since Al further suppresses phase transformation, the effect of the present invention can be obtained by not performing phase transformation. If the Al content is less than 0.001%, these effects can not be obtained. On the other hand, if the Al content exceeds 2.0%, the efficiency of pickling decreases, and furthermore, the hysteresis loss increases. Therefore, the Al content is 0.001 to 2.0%. The preferable lower limit of the Al content is 0.01%, and more preferably 0.1%. The preferred upper limit of the Al content is 1.5%, more preferably 1.2%.

N: 0.001 to 0.005%
Nitrogen (N), like C, is present as solid solution N in the steel, and improves texture by dynamic strain aging during warm rolling. This increases the magnetic flux density of the non-oriented electrical steel sheet. If the N content is less than 0.001%, this effect can not be obtained. On the other hand, if the N content exceeds 0.005%, fine AlN precipitates and the magnetic properties deteriorate. Therefore, the N content is 0.001 to 0.005%. The preferred lower limit of the N content is 0.0015%, and more preferably 0.002%. The upper limit of the N content is preferably 0.004%, more preferably 0.003%.

  The balance of the chemical composition of the non-oriented electrical steel sheet according to the present invention consists of Fe and impurities. Here, when the non-oriented electrical steel sheet is manufactured industrially, the impurities are mixed from ore as a raw material, scrap, or manufacturing environment. The content of these impurities is acceptable as long as the non-oriented electrical steel sheet of the present embodiment is not adversely affected.

[Arbitrary element]
The chemical composition of the non-oriented electrical steel sheet of the present invention may further contain one or more selected from the group consisting of Ti, V and Nb instead of part of Fe. When these elements are contained, the chemical composition satisfies the formula (A).
Here, the content (mass%) of the element in the non-oriented electrical steel sheet is substituted for the element symbol in the formula (A).

Ti: 0.01% or less V: 0.01% or less Nb: 0.01% or less Titanium (Ti), vanadium (V) and niobium (Nb) are optional elements. These elements form carbonitrides to fix C and N. If these carbonitrides exist before cold rolling, dynamic strain aging due to solid solution C and solid solution N can not be obtained. The Ti content is 0.01% or less, the V content is 0.01% or less, the Nb content is 0.01% or less, and the total content of Ti, V and Nb satisfies the formula (A). For example, dynamic strain aging by solid solution C and solid solution N can be used. In the present specification, when the Ti content is 0.004% or less, the Ti content is interpreted as the impurity level. Similarly, when the V content is 0.004% or less, the V content is interpreted as the impurity level. When the Nb content is 0.004% or less, the Nb content is interpreted as the impurity level.

  The chemical composition of the non-oriented electrical steel sheet of the present invention may further contain one or more selected from the group consisting of Sn, Cu, Ni, Cr and B in place of part of Fe. .

Sn: 0.2% or less Tin (Sn) is an optional element and may not be contained. When contained, Sn improves the texture of the steel sheet and increases the magnetic flux density. Sn further suppresses nitriding at the time of finish annealing and suppresses deterioration of the magnetic properties. On the other hand, if the Sn content exceeds 0.2%, the workability of the steel sheet may be reduced to cause cracks in the steel sheet during cold rolling. Therefore, the Sn content is 0.2% or less. The preferred lower limit of the Sn content is 0.01%, and more preferably 0.02%. The preferable upper limit of the Sn content is 0.15%, and more preferably 0.1%.

Cu: 0.1% or less Copper (Cu) is an optional element and may not be contained. If excessively contained, Cu lowers the saturation magnetic flux density, lowering the magnetic flux density B _50. Cu further forms CuS and degrades iron loss. Furthermore, when Cu is contained together with Ni, an internal oxide layer is easily formed on the surface of the steel sheet, and as a result, high frequency iron loss is deteriorated. Therefore, the Cu content is 0.1% or less. The lower limit of the Cu content is not particularly limited, but is preferably 0.01% or more from the viewpoint of being mixed from iron scrap.

Ni: 0.1% or less Nickel (Ni) is an optional element and may not be contained. When it is contained, Ni increases the magnetic flux density B ₅₀ and further enhances the steel plate strength. However, if the Ni content is too high, the raw material cost becomes high. When Ni is further contained together with Cu, an internal oxide layer is easily formed on the surface of the steel sheet, and as a result, high frequency iron loss is deteriorated. Therefore, the Ni content is 0.1% or less. The lower limit value of the Ni content is not particularly limited, but is preferably 0.01% or more from the viewpoint of the magnetic flux density B ₅₀ and the steel plate strength.

Cr: 0.2% or less Chromium (Cr) is an optional element and may not be contained. If excessively contained, Cr lowers the saturation magnetic flux density, thereby decreasing the magnetic flux density B _50. Therefore, the Cr content is 0.2% or less. The lower limit of the Cr content is not particularly limited, but is preferably 0.01% or more from the viewpoint of being mixed from iron scrap.

B: 0.001% or less Boron (B) is an optional element and may not be contained. If excessively contained, B lowers the saturation magnetic flux density, thereby decreasing the magnetic flux density B _50. Therefore, the B content is 0.001% or less. The lower limit value of the B content is not particularly limited, but is preferably 0.0001% or more from the viewpoint of being mixed from iron scrap.

[Group organization]
When the thickness of the non-oriented electrical steel sheet of the present invention is defined as t (mm), the texture of the non-oriented electrical steel sheet has the following (feature A) and (feature B).
(I) In the texture at the t / 10 depth position (surface layer) from the steel sheet surface, the integration degree I (s) of the {111} <112> orientation is 6.0 or more.
(II) In the texture at the t / 2 depth position (plate thickness central layer) from the steel sheet surface, the degree of integration I (c) of {100} <012> orientation is 4.0 or more.

[I: About surface textures]
If the degree of integration I (s) of {111} <112> orientation in the surface layer is high, the rigidity of the surface layer of the non-oriented electrical steel sheet is increased. As a result, generation of sagging at the time of punching can be suppressed by the combination with the texture in the thickness center layer described later. If the degree of integration I (s) is 6.0 or more, this effect is effectively obtained. The lower limit of the degree of accumulation I (s) is preferably 7.0, more preferably 8.0.

  The {111} <112> orientation is generally an undesirable orientation for magnetic properties. Therefore, if I (s) becomes excessively high, the adverse effect on the magnetic properties is also concerned. However, as will be described later, the magnetic properties can be complemented by accumulation of {100} <012> orientation, which is preferable for the magnetic properties, to the thickness central layer. Therefore, in the present invention, the upper limit of I (s) is not particularly limited. In view of the fact that the steel of the present invention is based on the basic composition and manufacturing conditions of a general non-oriented electrical steel sheet, the upper limit is naturally suppressed to about 20.0 or less.

[II: Texture of central thickness layer]
The {100} <012> orientation enhances the magnetic properties. The {100} <012> orientation in the thickness center layer further suppresses the occurrence of sagging during punching due to the interaction with the {111} <112> orientation described above. If the degree of integration I (c) of {100} <012> orientation is 4.0 or more, this effect is effectively obtained. The lower limit of the degree of accumulation I (c) is preferably 4.5, more preferably 5.0.

  The {100} <012> orientation is also generally the preferred orientation for magnetic properties. Therefore, it is not necessary to set a rule for raising I (c). Even in the state (single crystal) in which the thickness central layer is completely filled with crystal grains of {100} <012> orientation, the effects of the invention do not disappear.

[Combination of surface texture and thickness center layer texture]
The {111} <112> orientation defined in the present invention has a much higher rigidity than the {011} orientation, for which the sagging suppressing effect is already known. On the other hand, the {100} <012> orientation has a very low rigidity. In the non-oriented electrical steel sheet of the present invention, in the surface layer, the degree of integration of the {111} <112> orientation is enhanced, and in the inner layer, the degree of integration of the {100} <012> orientation is enhanced. That is, in the non-oriented electrical steel sheet of the present invention, the surface layer is made to have high rigidity and the inner layer is made to have low rigidity. Thereby, return of elastic deformation at the time of unloading of the deformation stress in a plastic deformation area | region like what is called spring back becomes large. As a result, it is considered that the occurrence of sagging is significantly suppressed.

[Method of measuring I (s) and I (c)]
I (s) and I (c) can be measured by the following method. The non-oriented electrical steel sheet is cut at a cross section perpendicular to the rolling direction, and a plurality of rough sample pieces having a thickness t are collected. Chemical polishing is performed on the rough sample piece to prepare a test piece for I (s) measurement in which the plate thickness is reduced by t / 10 from the surface. In addition, chemical polishing is performed on the rough test specimen to prepare a test specimen for measurement of I (c) whose thickness is reduced by t / 2 from the surface.

The pole figure of the {200}, {110}, and {211} planes is measured by the X-ray diffractometer for the produced I (s) measurement test piece, and the orientation distribution function ODF (Orientation Determination function) is measured. Function) is created. The {111} <112> orientation indicates an integration degree of == 30 ° from φ ₁ = 55 ° of the φ ₂ = 45 ° cross section in the ODF.

Similarly, the pole figure of the {200}, {110}, and {211} planes is measured using the X-ray diffractometer for the I (c) measurement test piece, and the crystal orientation distribution function ODF is created. Do. The {100} <012> orientation indicates the integration degree of φ ₁ = 20 ° and = 0 = 0 ° of the φ ₂ = 45 ° cross section.

[About average grain size]
In the present invention, the average grain size is not particularly limited. Preferably, the average grain size of the non-oriented electrical steel sheet of the present invention is 50 μm or less. In a non-oriented electrical steel sheet, the crystal orientation can be controlled completely independently of the crystal grain size. However, if the chemical composition is fixed, for example, when crystal grains are grown by increasing the heat treatment temperature, it is also a fact that a specific orientation develops continuously. Assuming this, in the surface layer of the steel sheet of the present invention, the {111} orientation is easily corroded in the {100} orientation along with the grain growth. When the average grain size becomes coarse, the {111} orientation is corroded to the {100} orientation, and the degree of integration I (s) of the {111} <112> orientation decreases. Therefore, the degree of integration I (s) may be reduced, and the effects of the present invention may be impaired. Set 50 μm as the upper limit of the grain size to avoid this. The upper limit of the average crystal grain size is preferably 35 μm, more preferably 20 μm. However, as described above, even if the average crystal grain size exceeds 50 μm, if the degree of accumulation I (s) is 6.0 or more and the degree of accumulation I (c) is 4.0 or more, occurrence of sagging is It can be suppressed.

  The average grain size of the non-oriented electrical steel sheet can be measured by the following method. The metal structure in the cross section in the longitudinal direction and the thickness direction is photographed at about 100 times to obtain a photographic image. A line is drawn in the longitudinal direction with respect to the obtained photographic image, the number of intersections of grain boundaries is counted, and the length of the line in the longitudinal direction may be divided by the number of intersections.

[Method of manufacturing non-oriented electrical steel sheet]
An example of the manufacturing method of the non-oriented electrical steel sheet of the present invention will be described. The method for producing a non-oriented electrical steel sheet according to the present invention comprises warm rolling the step of hot rolling a slab to produce a hot rolled steel sheet (hot rolling step) and at least first pass rolling, 2 In warm rolling or cold rolling by rolling after the pass, and further, warm rolling in the first pass is performed under specific conditions to produce a thin steel plate (finish rolling step); And a step of performing finish annealing to recrystallize (finish annealing step). Each step will be described in detail below.

[Hot rolling process]
In the hot rolling step, the slab is hot rolled to produce a hot rolled steel sheet. The slab has the chemical composition described above. The slabs are manufactured in a known manner. For example, a molten metal having the above-described chemical composition is used to produce a slab by a continuous casting method. The melt having the above-described chemical composition may be used to produce an ingot by the ingot method, and the ingot may be rolled to produce a slab. Slab rolling may be performed on a slab manufactured by a continuous casting method.

  Hot rolling is performed on the prepared slab. The various conditions in hot rolling are not specifically limited. The slab heating temperature at the time of hot rolling is not particularly limited. Preferably, the slab heating temperature is 1000 ° C. to 1300 ° C. from the viewpoint of cost and hot rollability. A further preferable lower limit of the slab heating temperature is 1050 ° C. A further preferable upper limit of the slab heating temperature is 1250 ° C.

  In the manufacturing method of the present invention, hot-rolled sheet annealing may or may not be performed on the hot-rolled steel sheet. When hot-rolled sheet annealing is performed, for example, the finishing temperature is 700 ° C. to 950 ° C., and the winding temperature is 750 ° C. or less. When hot-rolled sheet annealing is not performed, the finishing temperature is 850 to 900 ° C., and the winding temperature is 850 ° C. or less.

  When hot-rolled sheet annealing is performed, for example, the maximum temperature reached is 950 to 1050 ° C., and the holding time is 1 to 180 seconds. Hot-rolled sheet annealing is performed, for example, by a continuous annealing furnace. If the maximum ultimate temperature and the holding time are within the above ranges, the load on the equipment can be suppressed and productivity can also be enhanced. Furthermore, the magnetic properties of the non-oriented electrical steel sheet are also enhanced.

[Finish rolling process]
In the finish rolling step, at least the first pass rolling in warm rolling is performed on the hot-rolled steel sheet manufactured by the hot rolling step. And rolling after 2nd pass is implemented by warm rolling or cold rolling, and a thin steel plate is manufactured. Here, "pass" means that a steel plate passes through one rolling stand which has a pair of work rolls, and receives pressure.

  In the finish rolling step, tandem rolling may be performed using a tandem rolling mill including a plurality of rolling stands arranged in a row (each rolling stand has a pair of work rolls) to perform a plurality of passes. A plurality of passes may be performed by performing reverse rolling with a Sendzimir rolling mill or the like having a pair of work rolls. From the viewpoint of productivity, it is preferable to carry out a plurality of rolling passes using a tandem rolling mill.

  When the cold rolling process is performed, heat treatment may be performed on the steel plate during the cold rolling. That is, in the cold rolling step in the present invention, a plurality of passes may be performed by sandwiching the heat treatment halfway.

  Hereinafter, the conditions in the finish rolling process will be described.

[Cumulative rolling reduction in finish rolling process]
The cumulative rolling reduction in the finish rolling step is 75 to 95%. The cumulative rolling reduction (%) is defined as follows.
Cumulative rolling reduction = (1-Thickness of thin steel sheet after final pass of finish rolling process / thickness of hot rolled steel sheet before warm rolling in 1st pass) × 100

  The cumulative rolling reduction is defined based on the constraints on the product thickness and the point of increasing the degree of integration of the {100} orientation. For example, when the thickness of the heat-rolled steel plate is 2.0 mm and the final thickness of the non-oriented electrical steel plate is 0.10 to 0.50 mm, the cumulative rolling reduction is 75 to 95%. Furthermore, as described above, in order to increase the degree of integration of the {100} <012> orientation at the center of the plate thickness, it is preferable that the cumulative rolling reduction be high. From the above viewpoints, the cumulative rolling reduction in the finish rolling step in the present invention is 75 to 95%. The preferable lower limit of the cumulative rolling reduction is 85%. The preferred upper limit of the cumulative rolling reduction is 92.5%.

[First pass warm rolling process]
As described above, the first pass rolling on the heat-rolled steel plate is performed by warm rolling. The conditions for warm rolling in the first pass are as follows.

[Diameter of work roll of rolling stand which carries out warm rolling in the first pass]
The diameter of the work roll of the rolling stand that carries out warm rolling is a factor that affects the amount of shear deformation at the surface of the steel sheet. If the work roll diameter of the initial rolling stand is too large, the accumulation of strain accompanied by shear deformation in the vicinity of the grain boundary of the rolled material in the surface layer of the steel sheet becomes insufficient. In this case, the occurrence of the {111} <112> orientation is not sufficiently promoted, and the degree of integration I (s) becomes less than 6.0. On the other hand, if the work roll diameter of the initial rolling stand is too small, the shear deformation extends to the thickness center layer. In this case, in the thickness central layer, the occurrence of the {100} <012> orientation becomes insufficient, and the degree of integration I (c) becomes less than 4.0. When the work roll diameter of the initial rolling stand is 400 to 1000 mm, the generation of the {111} <112> orientation of the surface layer is promoted, provided that the equations (1) to (3) described later are satisfied. The generation of {100} <012> orientation of the thickness center layer can also be promoted. As a result, the accumulation I (s) becomes 6.0 or more, and the accumulation I (c) becomes 4.0 or more. The preferred upper limit of the work roll diameter of the initial rolling stand is 600 mm.

[Regarding Formula (1) to Formula (3)]
In warm rolling in the first pass, rolling is further performed under the conditions satisfying formulas (1) to (3).
Here, T (° C.) is the rolling temperature at the first pass rolling (unit: ° C., hereinafter referred to as initial rolling temperature), and more specifically, the rolling stand entry side where the first pass rolling is performed Steel plate temperature in ° C. The ε dot (epsilon dot) is a strain rate (the unit is s ^-1 , hereinafter referred to as an initial strain rate) of the first pass rolling. r is the rolling reduction of the first pass rolling (unit:%, hereinafter, referred to as initial rolling reduction).

  That is, in the first pass rolling in the finish rolling step, warm rolling is performed at an initial strain rate satisfying the formula (2), an initial reduction ratio satisfying the formula (3), and a rolling temperature satisfying the formula (1) .

[About formula (1)]
The initial rolling temperature T is a factor that controls the degree of occurrence of dynamic strain aging. The occurrence of the dynamic strain aging increases the accumulation of strain in the vicinity of grain boundaries in the steel sheet during rolling. In particular, when dynamic strain aging occurs in the presence of a shear deformation component in the vicinity of the surface layer, generation of {111} orientation in the surface layer is promoted in subsequent recrystallization annealing.

  If the initial rolling temperature T (° C.) does not satisfy the equations (1) to (3), strain is less likely to be accumulated near grain boundaries in the surface layer of the steel sheet. Therefore, generation of {111} orientation in the surface layer is not promoted, and I (s) becomes less than 6.0.

FIG. 3 shows the initial strain rate (s ⁻¹ ) and the initial rolling temperature (° C.) in the first pass warm rolling in the manufacturing process of the non-oriented electrical steel sheet of the chemical composition of the present invention, and the degree of integration I (s Is a diagram showing the relationship between In FIG. 3, as an example, the initial rolling reduction is 30% (satisfying equation (3)). Therefore, the left side of equation (1) is T = 2223.2 × (ε dot) ^0.1159 , and the right side of equation (1) is T = 149.0 × (ε dot) ^0.09648 .

Referring to FIG. 3, when the initial strain rate is 10 to 1000 (s ⁻¹ ), the initial rolling temperature is a curve of T = 223.2 × (ε dot) ^0.1159 and T = 149.0 × (ε dot) If it is between the curve of ^0.09648, the degree of integration I (s) becomes 6.0 or more. Then, if the initial rolling temperature is above the curve of T = 223.2 × (ε dot) ^0.1159 or ^below the curve of T = 149.0 × (ε dot) ^0.09648 , the degree of integration I (s) is It will be less than 6.0.

[About formula (2)]
The initial strain rate ε dot, in conjunction with the initial rolling temperature T, is a factor that affects the occurrence of dynamic strain aging. The initial strain rate ε dot is also a factor that controls the frequency of occurrence of an inhomogeneously deformed structure due to the sliding deformation of the crystal. If the initial strain rate ε dot is high, the dislocation moving speed can not follow deformation, and nonuniform deformation such as a deformation zone occurs. Such nonuniform deformation strongly affects the deformation behavior of the thickness central layer which is unlikely to cause shear deformation and deformation is simple, and promotes the generation of {100} orientation in the thickness central layer in the subsequent recrystallization annealing. Do.

If the initial strain rate ε dot is less than 10 s ⁻¹ , uneven deformation in the thickness central layer is not sufficient, and I (c) is less than 4.0. On the other hand, when the initial strain rate ε dot exceeds 1000 s ⁻¹ , the influence of the nonuniform deformation also increases in the surface layer of the steel plate. In this case, since the {100} <012> orientation also increases in the surface layer, I (s) becomes less than 6.0. If the initial strain rate ε dot satisfies the equation (2), the thickness central layer is promoted while promoting the generation of the {111} <112> orientation of the surface layer on the condition that the equation (1) and the equation (3) are satisfied. It can also promote the occurrence of {100} <012> orientation of. As a result, I (s) becomes 6.0 or more and I (c) becomes 4.0 or more. The preferred lower limit of the initial strain rate ε dot is 10 s ⁻¹ . The preferred upper limit of the initial strain rate ε dot is 100 s ⁻¹ .

[Formula (3)]
The initial rolling reduction r, in conjunction with the initial rolling temperature T, is a factor that affects the occurrence of dynamic strain aging. The initial rolling reduction r is also a factor that controls the frequency of occurrence of an inhomogeneously deformed structure due to the sliding deformation of the crystal.

  The initial rolling reduction r particularly affects the degree of shear deformation applied to the surface layer of the steel sheet. Therefore, the distribution of the {111} <112> orientation in the surface layer of the steel sheet and the {100} <012> orientation in the thickness central layer is determined by the combination of the initial draft r and the diameter of the work roll described above.

  If the initial rolling reduction r is less than 10%, the uneven deformation in the thickness center layer of the steel plate becomes insufficient, and the generation of the {100} <012> orientation is not sufficiently promoted. On the other hand, if the initial rolling reduction r exceeds 50%, the influence of the nonuniform deformation also increases on the surface layer of the steel sheet. In this case, since the {100} <012> orientation also increases in the surface layer, I (s) becomes less than 6.0. If the initial draft r satisfies the equation (3), the generation of the {111} <112> orientation of the surface is promoted while the condition of the equation (1) and the equation (2) is satisfied. The generation of {100} <012> orientation can also be promoted. As a result, I (s) becomes 6.0 or more and I (c) becomes 4.0 or more. The upper limit of the initial draft r is preferably 30%, more preferably 20%.

[About pass schedule]
From the viewpoint of improving the magnetic properties of the non-oriented electrical steel sheet, by performing warm rolling from at least the first pass rolling, the frequency of occurrence of nonuniform deformation such as a deformation zone can be sufficiently high, and as a result, plate Recrystallization in the {100} <012> orientation can be maximized in the thick central layer. Since the plate thickness is thin in rolling after the second pass (rolling on a rolling stand placed downstream of the initial rolling stand), a sufficient rolling shape ratio (roll contact arc length / average plate thickness) It is difficult to take. For this reason, it is difficult to set the deformation state required for the present invention, and significant improvement of the effects of the present invention can not be expected. Further, in the latter stage of the rolling process, regardless of the deformation state to which the present invention is focused, it is necessary to reduce the rolling shape ratio in order to secure the plate thickness accuracy of the final product. In addition, there is also an aspect that cold rolling in which sufficient lubrication is possible from the viewpoint of plate thickness accuracy is advantageous.

  In the present invention, when warm rolling or cold rolling is performed with such a small rolling shape ratio, the deformation state necessary for the present invention introduced in the first pass partially disappears, and the steel sheet after recrystallization The accumulation of {111} <112> orientations formed in the surface layer is reduced, which also inhibits the effects of the invention. Therefore, in the present invention, the manufacturing method is defined under the conditions of the first pass rolling. However, it goes without saying that warm rolling after the second pass is not excluded unless the invention effect is completely lost.

  Further, also from the viewpoint of avoiding brittle fracture, it is advantageous to use warm rolling for the first pass rolling with a high rolling shape ratio.

  Furthermore, from the viewpoint of avoiding over-tension failure, when the rolling reduction per pass is increased or when the strain rate per pass is increased, the rolling load may increase and the tension may become too large. In this case, the steel plate during rolling may break. As a result of the investigation, excessive tension is likely to occur at the outlet side of the rolling stand (initial rolling stand) where the first pass rolling is performed and at the outlet side of the rolling stand where the second pass rolling is performed. Performing warm rolling in the first pass rolling is also advantageous in order to suppress excess tension being applied to the steel sheet.

  From the viewpoint of the work rolls used for warm rolling, the roll life by warm rolling is lower than the roll life by cold rolling. In warm rolling, work rolls are more easily worn than cold rolling, and tempering occurs. In the present invention, the rolling rate can be increased by setting only the first pass to warm rolling.

  For the above reasons, it is a preferable embodiment of the present invention to use warm rolling as the former stage including the first pass of rolling and cold rolling as the latter stage. In the latter stage cold rolling, the rolling temperature (the steel plate temperature) is 150 ° C. or less. As a result, while improving the magnetic characteristics, it is possible to reduce the thickness variation and to avoid the concern that the preferred working texture state formed in the first pass warm rolling may be destroyed.

  In the case of using a tandem rolling mill, warm rolling is performed at a rolling stand for performing at least first pass rolling, and a rolling stand arranged downstream of the rolling stand, and warm rolling is performed at the rolling stand. Cold rolling may be performed at one or more rolling stands located downstream.

[Control of rolling temperature]
The hot rolled steel sheet is heated for warm rolling in the previous stage including the first pass of rolling. As a heating method in the warm rolling process, a known heating method can be applied, including electromagnetic induction heating, electric current heating, heater heating, heating in an atmosphere gas, and the like.

  When applying cold rolling in order to obtain the above merits in post-warm rolling after warm rolling, contact with a cooling roll or the like, cooling gas, etc., before warm-rolling and before a pass to be cold-rolled, or cooling gas The steel plate may be cooled to a required temperature by a known method such as spraying.

[Finish annealing process]
The cold rolled steel sheet manufactured by carrying out the finish rolling process is subjected to finish annealing to manufacture a non-oriented electrical steel sheet. In the finish annealing, the cold rolled steel sheet finished to the final thickness is annealed and recrystallized.

  The maximum reaching temperature and the holding time of the finish annealing are not particularly limited as long as the average grain size of the non-oriented electrical steel sheet after finish annealing is 50 μm or less. The highest reaching temperature and the holding time are appropriately set according to the chemical composition of the non-oriented electrical steel sheet, the conditions of the hot rolling process and the finish rolling process. The setting of the maximum attainable temperature and the retention time is easy for those skilled in the art. For example, the highest reach | attainment temperature in finish annealing is 800-900 degreeC. In addition, the retention time at the highest temperature (that is, the retention time at 800 to 900 ° C.) is 20 to 90 seconds. Heat treatment and structure observation are performed using sample cold-rolled steel plates rolled by the same chemical composition, the same hot rolling process conditions, and the same finish rolling process conditions, and the conditions of the finish rolling annealing (maximum achieved temperature and retention in advance) Time) may be determined. In this case, more appropriate conditions for reducing the average crystal grain size to 50 μm or less can be determined.

[Other process]
In the manufacturing method described above, the coating step may be performed after the finish annealing step. In the coating step, an insulating coating is applied to the surface of the non-oriented electrical steel sheet after finish annealing. The type of insulating coating is not particularly limited. The insulating coating may be an organic component or an inorganic component. The insulating coating may contain an organic component and an inorganic component. The inorganic component is, for example, a dichromic acid-boric acid type, a phosphoric acid type, a silica type or the like. The organic component is, for example, a general acrylic resin, acrylic styrene resin, acrylic silicon resin, silicon resin, polyester resin, epoxy resin, or fluorine resin. In consideration of paintability, preferred resins are emulsion type resins. An insulating coating may be provided which exhibits adhesive ability by heating and / or pressing. The insulating coating having adhesion is, for example, acrylic resin, phenol resin, epoxy resin, melamine resin.

  By the above manufacturing process, the non-oriented electrical steel sheet according to the present invention can be manufactured. The non-oriented electrical steel sheet of the present invention is excellent in magnetic properties. Furthermore, the occurrence of sagging in punching can be suppressed.

  Hereinafter, the present invention will be specifically described by way of examples.

  Hot rolling was performed on slag (slabs) having a chemical composition shown in Table 1 to produce a hot-rolled steel plate having a thickness of 2.0 mm. "-" In Table 1 shows that content of the corresponding element was less than the detection limit.

  With respect to the hot-rolled steel sheet, hot-rolled sheet annealing was carried out soaking at 1000 ° C for one minute. Thereafter, using a tandem rolling mill in which five rolling stands were arranged in a row, rolling under the first pass was carried out by warm rolling under the conditions shown in Table 2. Furthermore, the 2nd-5th pass rolling was implemented by cold rolling at 100 degrees C or less, and the thin steel plate of 0.25 mm of plate | board thickness was manufactured. The cumulative pressure at the finish rolling step was 86%. The steel sheet after finish rolling was held at the finish annealing temperature (maximum ultimate temperature) shown in Table 2 for 14 seconds. A non-oriented electrical steel sheet was manufactured by the above manufacturing process.

In addition, T1 in Table 2 was made into the left side of Formula (1), and T2 was made into the right side of Formula (1). Specifically, T1 and T2 were as follows.
The following evaluation test was implemented with respect to the non-oriented electrical steel sheet manufactured by the above process.

[Measurement of density I (s), I (c)]
I (s) and I (c) can be measured by the following method. The non-oriented electrical steel sheet was cut at a cross section perpendicular to the rolling direction, and a plurality of rough sample pieces having a thickness t were collected. Chemical polishing was performed on the rough sample pieces to prepare test pieces for I (s) measurement in which the plate thickness was reduced by t / 10 from the surface. In addition, chemical polishing was performed on the rough test specimen to prepare a test specimen for I (c) measurement in which the thickness of the plate was reduced by t / 2 from the surface.

  The pole figure of the {200}, {110}, and {211} planes is measured by the X-ray diffractometer for the produced I (s) measurement test piece, and the orientation distribution function ODF (Orientation Determination function) is measured. Function) was determined, and the degree of integration I (s) was determined. Similarly, the pole figure of the {200}, {110}, and {211} planes is measured using the X-ray diffractometer for the I (c) measurement test piece, and the crystal orientation distribution function ODF is created. And the accumulation degree I (c) was determined.

[Measurement of average grain size]
A sample including a cross section in the thickness direction of the rolling direction on the surface was taken at a depth of t / 2 from the surface of the non-oriented electrical steel sheet. After mechanically polishing the surface of the collected sample (the cross section in the plate thickness direction of the rolling direction), etching was performed with a nital solution. The structure was observed with a 100 × optical microscope, and the average crystal grain size was determined by the above-mentioned method (cutting method).

[Magnetic property evaluation test]
Relative to the non-oriented electrical steel sheet of each test number, the 55mm angle magnetic measurement test, the magnetic flux density was measured _{B 50} in 5000A / m. The magnetic flux density B ₅₀ is obtained as an average of L direction (rolling direction) and C direction (the direction perpendicular to the rolling direction).

[Dropage measurement test]
Punching was performed on the manufactured non-oriented electrical steel sheet. The non-oriented electrical steel sheet was cut so as to have a cross section parallel to the punching direction and perpendicular to the punching blade. And the edge part of the nondirectional electromagnetic steel plate was embedded in resin among the cut surfaces, and it grind | polished. The edge of the non-oriented electrical steel sheet after polishing was photographed with an optical microscope to generate a photographic image. Using the photographic image, the amount of sagging formed at the end of the steel plate by punching was measured. FIG. 4 is a schematic view of a photographic image of an end of a steel plate in a sag measurement test. Referring to FIG. 4, the steel plate end portion 100 is formed with a sagging portion 101, a sheared surface 102, a fractured surface 103, and a burr 104 in order from the punching direction PU. The sag amount D101 of the sag portion 101 is measured at any five steel plate end portions after punching. The average of the measured dripping amount D101 was defined as the dripping amount.

[result]
The evaluation results are shown in Table 2. Referring to Table 2, in the test numbers 1 to 11, 17, 20 to 22, 34 and 35, the chemical composition was appropriate, and the production conditions were also appropriate. Therefore, the integration degree I (s) was 6.0 or more, and the integration degree I (c) was 4.0 or more. As a result, the amount of sagging was as small as 15 μm or less, and the occurrence of sagging during punching could be sufficiently suppressed. Further, the magnetic flux density _{B 50} of not less than 1.65 T, was obtained excellent magnetic properties.

On the other hand, in the test numbers 12 to 15, the initial strain rate was too low. Therefore, the degree of integration I (c) was less than 4.0. As a result, the magnetic flux density B ₅₀ was less than 1.65 T, and the magnetic properties were low. In Test No. 15, since the initial rolling temperature was too high, the degree of integration I (s) was less than 6.0, and the amount of sagging exceeded 15 μm.

In the test numbers 16 and 19, the initial rolling temperature was too low. Therefore, the degree of integration I (s) and the degree of integration I (c) were too low. As a result, the magnetic flux density B ₅₀ was less than 1.65 T, and the magnetic properties were low. Furthermore, the amount of dripping exceeded 15 μm.

  In the test numbers 18 and 23, the initial rolling temperature was too high. Therefore, the degree of accumulation I (s) was less than 6.0, and the amount of sag exceeded 15 μm.

In the test numbers 24 to 28, the initial strain rate was too fast. Therefore, the degree of accumulation I (s) was less than 6.0, and the amount of sag exceeded 15 μm. In Test No. 24, the initial rolling temperature was too low. Therefore, the degree of integration I (c) was low, the degree of integration I (c) was less than 4.0, and the magnetic flux density B ₅₀ was as low as less than 1.65T.

In Test No. 29, the initial rolling reduction was too low. Therefore, the degree of integration I (c) was less than 4.0, and the magnetic flux density B ₅₀ was as low as less than 1.65T.

  In the test number 30, the initial rolling reduction was too high. Therefore, the degree of accumulation I (s) was less than 6.0, and the amount of sag exceeded 15 μm.

In Test No. 31, the work roll diameter was too small. Therefore, the degree of integration I (c) was less than 4.0, and the magnetic flux density B ₅₀ was as low as less than 1.65T.

  In Test No. 32, the work roll diameter was too large. Therefore, the degree of accumulation I (s) was less than 6.0, and the amount of sag exceeded 15 μm.

In Test No. 33, the finish annealing temperature (maximum achieved temperature) at the finish annealing was too low. Therefore, the degree of integration I (c) was less than 4.0, and the magnetic flux density B ₅₀ was as low as less than 1.65T.

  In Test No. 36, the finish annealing temperature (maximum achieved temperature) during finish annealing was too high. The degree of accumulation I (s) was less than 6.0, and the amount of sag exceeded 15 μm.

  In mass%, Si: 3.3%, Al: 1.0%, Mn: 0.7%, P: 0.01%, C: 0.003%, N: 0.002%, S: 0. Hot rolling was performed on a slag (slab) containing 0005% and the balance being Fe and an impurity element to obtain a hot-rolled steel plate having a thickness of 2.0 mm. Hot-rolled sheet annealing was performed on this hot-rolled steel sheet, which was heated at 1000 ° C. for one minute.

After hot-rolled sheet annealing, the finish rolling process was performed using a tandem rolling mill in which five rolling stands were arranged in a line. Specifically, in the first pass rolling, the initial strain rate was 31 s ⁻¹ and the initial rolling reduction was 30%. The cumulative rolling reduction in the finish rolling step was 85%. The rolling temperature at each stand from the first pass to the fifth pass was as shown in Table 3. The steel sheet after finish rolling was held at a finish annealing temperature (maximum achieved temperature) of 850 ° C. for 14 seconds. A non-oriented electrical steel sheet was manufactured by the above manufacturing process.

  In addition, about the plate | board thickness fluctuation | variation in the steel plate of each test number, the plate | board thickness of a total of 16 places was measured by 4 places * 4 places in length direction in board width direction at 50 mm intervals. Then, half of the difference between the maximum value and the minimum value of the measured plate thickness was defined as the plate thickness fluctuation (mm). The average of 16 measured points was defined as the average plate thickness (mm).

  For the non-oriented electrical steel sheet of each test number, determine the degree of integration I (s), the degree of integration I (c), the magnetic flux density B 50 (T), and the amount of sag (μm) in the same manner as in Example 1. The

[result]
The results are shown in Table 3. In Test Nos. 1 to 4, the chemical composition was appropriate, and the production conditions were also appropriate. Therefore, the integration degree I (s) was 6.0 or more, and the integration degree I (c) was 4.0 or more. As a result, the amount of sagging was as small as 15 μm or less, and the occurrence of sagging during punching could be sufficiently suppressed. Further, the magnetic flux density _{B 50} of not less than 1.65 T, was obtained excellent magnetic properties.

On the other hand, in the test numbers 6 to 13, the initial rolling temperature in the first pass was too low to satisfy the formula (1). Therefore, the degree of integration I (s) and the degree of integration I (c) were too low. As a result, the magnetic flux density B ₅₀ was less than 1.65 T, and the magnetic properties were low. Furthermore, the amount of dripping exceeded 15 μm.

  Moreover, the rolling temperature of the 2nd-5th pass is 150 degreeC or more, and the test numbers 7-13 included warm rolling. Therefore, compared with the test number 6 of all in cold rolling, the plate thickness fluctuation range became large. Furthermore, the plate thickness fluctuation range became larger than the test numbers 1 to 6 warm-rolled at 300 ° C. in the first pass.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these examples. It is obvious that those skilled in the art can conceive of various modifications or alterations within the scope of the idea described in the claims, and they are naturally within the technical scope of the present invention. It is understood that.

Claims (7)

Non-oriented electrical steel sheet,
The chemical composition is
In mass%,
C: 0.001 to 0.005%,
Si: 2.0 to 5.0%,
Mn: 0.1 to 1.5%,
P: 0.02% or less,
S: 0.005% or less,
Al: 0.001 to 2.0%, and
N: 0.001 to 0.005%,
Contains
The balance consists of Fe and impurities,
When the thickness of the non-oriented electrical steel sheet is defined as t,
An integration degree I (s) of {111} <112> orientation at a depth of t / 10 from the surface of the non-oriented electrical steel sheet is 6.0 or more,
A non-oriented electrical steel sheet having a degree of integration I (c) of {100} <012> orientation at a depth of t / 2 from the surface of the non-oriented electrical steel sheet is 4.0 or more. The non-oriented electrical steel sheet according to claim 1, wherein
The chemical composition is further substituted for part of Fe,
Ti: 0.01% or less,
V: 0.01% or less, and
Nb: contains one or more selected from the group consisting of 0.01% or less,
The non-oriented electrical steel sheet, wherein the chemical composition satisfies the formula (A).
The non-oriented electrical steel sheet according to claim 1 or 2, wherein
The chemical composition is further substituted for part of Fe,
Sn: 0.2% or less,
Cu: 0.1% or less
Ni: 0.1% or less Cr: 0.2% or less, and
B: Non-oriented electrical steel sheet containing one or more selected from the group consisting of 0.001% or less. The hot rolling process which hot-rolls with respect to the raw material which has a chemical composition in any one of Claims 1-3, and manufactures a hot rolled sheet steel,
The hot rolling is performed in at least the first pass rolling using a rolling stand having a pair of work rolls having a diameter of 400 to 1000 mm on the heat-rolled steel plate, and the warm rolling is performed in the second and subsequent passes. A finish rolling step of performing rolling or cold rolling to produce a thin steel plate having a thickness of 0.10 to 0.50 mm;
And a finish annealing step of performing finish annealing on the thin steel plate,
In the finish rolling process,
In the first-pass rolling, when the rolling temperature is T (° C.), the strain rate is ε dot (s ⁻¹ ), and the rolling reduction is r (%), formulas (1) to (3) are satisfied. Warm rolling is performed on the hot rolled steel sheet under the conditions;
The manufacturing method of a non-oriented electrical steel sheet which makes a cumulative rolling reduction in the above-mentioned finish rolling process 75 to 95%.
A method of manufacturing a non-oriented electrical steel sheet according to claim 4,
In the cold rolling,
The manufacturing method of the non-oriented electrical steel sheet which makes the said rolling temperature 150 degrees C or less. A method of manufacturing a non-oriented electrical steel sheet according to claim 4 or claim 5,
In the finish rolling process,
Using a tandem rolling mill, each having a pair of work rolls, comprising a plurality of rolling stands arranged in a row,
The warm rolling is performed at the rolling stand which carries out at least the first pass rolling, or at the rolling stand and a rolling stand arranged downstream thereof.
The manufacturing method of a non-oriented electrical steel sheet implemented by cold rolling with the rolling stand arranged downstream of the said rolling stand which implements the said warm rolling. A method of manufacturing a non-oriented electrical steel sheet according to any one of claims 4 to 6,
In the finish annealing step,
The manufacturing method of a non-oriented electrical steel sheet which makes the highest achieving temperature 800-900 ° C.