JP6855894B2 - Non-oriented electrical steel sheet and its manufacturing method - Google Patents

Description

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

Non-oriented electrical steel sheets are used as a material for iron cores of electrical equipment. These electric devices are required to have high energy efficiency, miniaturization and high output. Therefore, non-oriented electrical steel sheets used as iron cores of electrical equipment are required to have low iron loss and high magnetic density.

Conventionally, the following techniques have been adopted in order to reduce the iron loss of non-oriented electrical steel sheets.
-The non-oriented electrical steel sheet contains Si, Al, etc.
-Control the crystal grain size of non-oriented electrical steel sheets.
-Reduce the thickness of non-oriented electrical steel sheets.

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

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

Patent Documents 1 to 5 propose techniques for performing warm rolling after hot rolling in order to enhance magnetic properties in the production of non-oriented electrical steel sheets.

In the method for manufacturing non-oriented electrical steel sheets disclosed in Patent Document 1, the Al content of the non-oriented electrical steel sheets is 0.02% or less in mass%. Further, in the final cold rolling step, at least one pass excluding the final pass is warm rolled at 100 to 300 ° C. Further, the final pass is rolled at 100 ° C. or lower at 10 to 30%. It is described in Patent Document 1 that this improves _{the iron loss W 15/50} of the non-oriented electrical steel sheet.

The non-oriented electrical steel sheet manufacturing method disclosed in Patent Document 2 contains Cu: 0.2% or more and 4.0% or less, Ni: 0.5% or more, 5.0% or less in mass%. In the final cold rolling step, the steel material is subjected to one pass or more of warm rolling having a rolling temperature of 100 to 300 ° C. or higher, and the cumulative rolling reduction ratio of the warm rolling at that time is set to 45% or more. Patent Document 2 describes that this makes it possible to manufacture a non-oriented electrical steel sheet having an excellent balance between strength and iron loss.

In the method for manufacturing grain-oriented electrical steel sheets disclosed in Patent Document 3, the hot-rolled finishing temperature is set to 700 ° C. or higher, which is less than the _{Ar3 transformation point.} After descaling the manufactured hot-rolled steel sheet, the total strain applied in cold rolling is converted into logarithmic strain, and 50% or more of it is rolled at a 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 this makes it possible to manufacture a non-oriented electrical steel sheet having excellent magnetic properties.

In the warm rolling carried out in Patent Documents 1 to 3, the rolling temperature is higher than that in the cold rolling. Therefore, the crystal orientation may change due to the change in the slip behavior of dislocations in the steel. It is considered that the interaction between the elements contained in the steel and the dislocations depends on the temperature, and the crystal orientation changes due to this temperature dependence.

Patent Document 4 and Patent Document 5 have proposed techniques for controlling the conditions of warm rolling 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 in a temperature range of 200 to 500 ° C. at a rolling reduction of 20% or more, and then recrystallized and annealed. This is done to develop the (110) [001] orientation component of the texture. In the method for producing non-oriented electrical steel sheets disclosed in Patent Document 5, P, S and Se in the steel are suppressed so as to be P + 100 × S + 300 × Se ≦ 0.5, and hot-rolled sheet annealing is performed in Ac ₃ Perform in a temperature range above the point.

On the other hand, non-oriented electrical steel sheets are machined into iron cores for motors by punching or the like. Therefore, "perforated dimensional accuracy" is also required for non-oriented electrical steel sheets. In particular, it is required to suppress the difference between the maximum value and the minimum value of the outer diameter dimension of the core of the punching motor, which is formed when the non-oriented electrical steel sheet is pushed into the die by the punching punch. That is, it is required to suppress the generation of elastic strain during punching (promotion of introduction of plastic strain).

Patent Documents 6 to 8 propose techniques for improving punching workability, including improving punching dimensional accuracy.

In the non-oriented electrical steel sheet disclosed in Patent Document 6, Si and / or Al is controlled to 0.03% to 0.5% in total, and P is added in an amount of 0.10% to 0.26% to obtain an average grain size. Yield stress is increased by controlling the diameter to 30 to 80 μm, or controlling Si and / or Al to a total of more than 0.5% to 2.5% and adding 0.1 to 0.26% of P. The punching dimension accuracy is improved.

In the non-oriented electrical steel sheets disclosed in Patent Documents 7 and 8, ^{the product of the sheet thickness (mm) and the yield stress YP (N / m 2} ) is controlled to be 0.65 or more to improve the punching dimensional accuracy. ing. In the techniques proposed in Patent Documents 6 to 8, the yield stress of the non-oriented electrical steel sheet is increased to improve the punching dimensional accuracy.

Further, it is shown in Patent Documents 9 to 12 that it is necessary to give special consideration to the texture including the {111} orientation of the surface layer, particularly regarding the high frequency characteristic among the magnetic characteristics.

Japanese Patent No. 3888033 Japanese Unexamined Patent Publication No. 2005-120431 Japanese Patent No. 2870818 Japanese Unexamined Patent Publication No. 58-84924 Japanese Unexamined Patent Publication No. 2006-104530 International Publication No. 2003/002777 Japanese Unexamined Patent Publication No. 2003-197414 Japanese Unexamined Patent Publication No. 2004-152791 Japanese Unexamined Patent Publication No. 7-150310 Japanese Unexamined Patent Publication No. 8-134606 Japanese Unexamined Patent Publication No. 2001-158948 International Publication No. 2016/148010

In the above-mentioned patent documents, it is proposed to improve the magnetic characteristics and punching workability, particularly the punching dimensional accuracy. However, it is also required to improve the magnetic characteristics and punching dimensional accuracy by other methods.

An object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and capable of improving punching dimensional accuracy during punching.

The non-oriented electrical steel sheet according to the present invention has a chemical composition of mass%, C: 0.001 to 0.005%, Si: 0.5 to 2.0%, Mn: 0.1 to 1.5%. , P: less than 0.10%, S: 0.005% or less, Al: 0.001 to 2.0%, and N: 0.001 to 0.005%, and the balance is from Fe and impurities. And has a phase transformation. When defined as the thickness of the non-oriented electrical steel sheet and t, the degree of integration I (sa) of the {111} <112> orientation at the t / 10 depth position from the surface of the non-oriented electrical steel sheet is less than 6.0. The degree of integration I (cb) in the {100} <012> direction at a depth of t / 2 from the surface of the non-oriented electrical steel sheet is 4.0 or more, and t from the surface of the non-oriented electrical steel sheet. The ratio of the degree of integration I (sb) of the {100} <012> orientation at the / 10 depth position to the degree of integration I (cb) is 0.80 to 1.20.

The method for producing a non-directional electromagnetic steel sheet according to the present invention is the heat for producing a hot-rolled steel sheet _{at a finishing temperature of Ar 1 point (° C) to 1000 ° C by performing hot rolling on a material having the above-mentioned chemical composition.} In the inter-rolling process, the hot-rolled steel sheet is warm-rolled in at least the first pass, and warm-rolled or cold-rolled in the second and subsequent passes, and 0.10 to 0. It includes a finish rolling step for producing a thin steel sheet of .50 mm and a finish annealing step for performing finish annealing on the thin steel sheet. In the finish rolling process, in the first pass of rolling, the friction coefficient between the roll of the rolling stand and the hot-rolled steel sheet is set to more than 0.10 to 0.30, the rolling temperature is T (° C.), and the strain rate is epsilon dots (ε). When the dot) (s ^-1 ) and the reduction ratio are defined as r (%), warm rolling is performed on the hot-rolled steel sheet under the conditions satisfying the conditions (1) to (3). Then, the cumulative rolling reduction in the finish rolling process is set to 75 to 95%.

The non-oriented electrical steel sheet according to the present invention has excellent magnetic characteristics and can improve the punching dimensional accuracy at the time of punching.

FIG. 1 shows the degree of integration I (sa) of {111} <112> orientation on the surface layer and the degree of integration of {100} <012> orientation on the surface layer in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention. The relationship between the integration degree ratio RA = I (sb) / I (cb) to the integration degree I (cb) of the {100} <012> orientation in the central layer of the plate thickness of I (sb) and the punching dimensional accuracy is shown. It is a figure. FIG. 2 shows the degree of integration I (cb) of {100} <012> orientation in the central layer of thickness and RA = I (sb) / I (cb) in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention. ), It is a figure which shows the relationship with the magnetic flux density B _{50 (T).} FIG. 3 is a schematic diagram for explaining a linear expansion measurement test. ^{FIG. 4 shows the initial strain rate (s -1} ) and the initial rolling temperature (° C.) in the first pass of warm rolling in the manufacturing process of the non-oriented electrical steel sheet satisfying the chemical composition of the present invention, and the degree of integration I (integration degree I). It is a figure which shows the relationship with sa), I (cb) and RA = I (sb) / I (cb). FIG. 5 is a schematic view for explaining the punching dimensional difference measurement test in the embodiment.

Hereinafter, the present invention will be described in detail.

The present inventors have investigated and studied non-oriented electrical steel sheets having excellent magnetic properties and improving punching dimensional accuracy during punching. As a result, it was found that in the non-oriented electrical steel sheet having a chemical composition having a phase transformation, the punching dimensional accuracy is improved by satisfying the following requirements.

(I) When the thickness of the non-oriented electrical steel sheet having a phase transformation is defined as t, the degree of integration I in the {111} <112> orientation at the t / 10 depth position (hereinafter referred to as the surface layer) from the rolled surface. (Sa) is less than 6.0. Further, the accumulation degree I (sb) of the {100} <012> orientation on the surface layer is the accumulation of the {100} <012> orientation at the t / 2 depth position (hereinafter referred to as the plate thickness center layer) from the rolled surface. When the ratio to the degree I (cb) is defined as the degree of integration ratio RA = I (sb) / I (cb), the degree of integration ratio RA is 0.80 to 1.20. In this case, the punching dimensional accuracy at the time of punching can be improved.

FIG. 1 shows the degree of integration I (sa) in the {111} <112> orientation on the surface layer and the degree of integration ratio RA (= I (sb) / I (= I (sb) / I)) in the non-oriented electrical steel sheet satisfying the chemical composition of the present invention. It is a figure which shows the relationship between cb)) and the punching dimension difference (μm) which is an index of punching dimension accuracy. As will be described later, the smaller the punching dimension difference, the better the punching dimension accuracy.

With reference to FIG. 1, when the degree of integration I (sa) of the {111} <112> orientation on the surface layer is 6.0 or more (x mark in FIG. 1), even if the degree of integration ratio RA fluctuates, The punching dimension accuracy does not change much. On the other hand, when the degree of integration I (sa) of the {111} <112> orientation on the surface layer is less than 6.0 (marked with a circle in FIG. 1), the punching dimension difference becomes smaller as the degree of integration ratio RA increases. Then, in the range of the integration ratio RA of 0.8 to 1.2, the punching dimension difference is 10 μm or less. On the other hand, as the integration ratio RA increases from around 1.0, the punching dimensional accuracy increases.

In short, when the degree of integration I (sa) is less than 6.0, the punching dimension difference becomes a downwardly convex curve having an inflection point near the degree of integration RA = 1.0. When the integration ratio RA is in the range of 0.8 to 1.2, the punching dimension difference is 10 μm or less, and the punching dimension accuracy can be remarkably improved.

It should be noted that the influence on the magnetic characteristics when the integration ratio RA fluctuates is small. FIG. 2 shows the relationship between the degree of integration I (cb) of the {100} <012> orientation of the sheet thickness central layer and the magnetic flux density B _{50 (T) in the non-oriented electrical steel sheet having the chemical composition of the present invention.} It is a figure which shows. As shown in FIG. 2, the magnetic flux density B ₅₀ increases as the degree of integration I (cb) in the {100} <012> direction of the central layer of the plate thickness increases, but the degree of integration ratio RA (= I (sb)). It is hardly affected by fluctuations in / I (cb)). When the degree of integration I (cb) is 4.0 or more, the magnetic flux density B ₅₀ (T) is 1.80 or more, and excellent magnetic characteristics can be obtained.

Based on the above findings, in a non-oriented electrical steel sheet having a chemical composition having a phase transformation, when the plate thickness is defined as t, the degree of integration I (sa) of the {111} <112> orientation on the surface layer is 6. It is less than 0, the degree of integration I (cb) of the {100} <012> orientation in the central layer of the plate thickness is 4.0 or more, and the degree of integration ratio RA (= I (sb) / I (cb)) is If it is 0.80 to 1.20, the punching dimensional accuracy at the time of punching can be improved while maintaining the magnetic characteristics. Specifically, the chemical composition referred to here is, in mass%, C: 0.001 to 0.005%, Si: 0.5 to 2.0%, Mn: 0.1 to 1.5%, P. : Less than 0.10%, S: 0.005% or less, Al: 0.001 to 2.0%, and N: 0.001 to 0.005%, and the balance is a chemical consisting of Fe and impurities. Of the compositions, the composition is limited to a chemical composition having a phase transformation.

Here, in the present specification, the "chemical composition having a phase transformation" is a chemical composition in which two phases of a ferrite phase and an austenite phase coexist at 25 to 1200 ° C. or a temperature at which austenite is a single phase exists. Point to. The presence or absence of phase transformation is determined by the following coefficient of linear expansion measurement test. In the linear expansion coefficient measurement test, a round bar-shaped test piece having a diameter of 10 mm and a length of 20 mm is heated in an Ar atmosphere at 4 ° C./min in the range of 25 to 1200 ° C., and the linear expansion coefficient α is measured. FIG. 3 is a diagram showing the relationship between the temperature and the coefficient of linear expansion in the linear expansion measurement test. _{With reference to FIG. 3, when there is a temperature (Ac 1} point) in which the gradient dα / dT of the linear expansion coefficient α and the temperature T changes from positive to negative at 25 to 1200 ° C., in the test piece, from ferrite. It can be seen that the phase transformation to austenite started and the phase transformation occurred. Therefore, in the coefficient of linear expansion measurement test, if the gradient dα / dT changes from positive to negative, it is determined that the steel having the chemical composition has a phase transformation.

As described above, only for non-oriented electrical steel sheets having a chemical composition having a phase transformation, by defining the texture of the surface layer and the texture of the central layer of the plate thickness, the mechanism by which the punching dimensional accuracy is significantly improved is described. Although it is not clear, the following three factors can be considered.

The first factor is the difference in yield stress depending on the crystal orientation. The {111} orientation has a higher yield stress than the {100} orientation. Therefore, in the region near the shear plane during punching, the plastic deformation from the shear plane to the inside of the steel sheet is limited to a narrow region. As a result, the amount of elastic deformation during processing and during the unloading process after processing becomes large, and the punching dimensional accuracy tends to deteriorate. Especially on the surface layer, the texture of the hot-rolled steel sheet is {110} <001>. Therefore, if finish annealing is performed after cold rolling, the {111} <112> orientation is likely to develop, and the yield stress of the surface layer increases. As a result, the punching dimensional accuracy deteriorates.

The second factor is that if the textures of the surface layer and the central layer of the plate thickness are different, the ratio of the plastic deformation region fluctuates in the plate thickness direction, so that the punching dimensional accuracy deteriorates. In particular, the {100} orientation is easy to work harden. Therefore, the change in the degree of integration in the plate thickness direction strongly affects the punching dimensional accuracy.

The third factor is that the steel sheet having no phase transformation and the steel sheet having a phase transformation have different textures after hot rolling due to the phase transformation in the hot rolling process. In the steel sheet having no phase transformation, a texture having a high degree of integration in the {100} <012>, {411} <148>, and {110} <001> orientations can be obtained after hot rolling. On the other hand, in the steel sheet having a phase transformation, a texture having a high degree of integration in the {100} <011> and {110} <001> orientations can be obtained.

Due to the difference in texture after hot rolling, the slip deformation behavior in warm rolling changes. Therefore, at the time of recrystallization, the steel sheet having no phase transformation has a phase transformation, whereas the density distribution in the {100} <012> orientation becomes non-uniform in the thickness direction of the non-oriented electrical steel sheet. In the steel sheet, it is considered that the density distribution in the {100} <012> orientation becomes uniform in the thickness direction of the non-oriented electrical steel sheet.

In the non-oriented electrical steel sheet of the present invention, the degree of integration I (sa) of the {111} <112> orientation is weakened in the surface layer, and the difference in the degree of integration of the {100} <012> orientation between the surface layer and the central layer of the plate thickness is small. To do. That is, in the non-directional electromagnetic steel plate of the present invention, by realizing this combination, the return of elastic deformation when the deformation stress in the plastic deformation region such as so-called springback is unloaded becomes small. As a result, it is considered that the punching dimensional accuracy is remarkably improved.

The present inventors have examined an example of a manufacturing method that realizes the above-mentioned texture of the surface layer and the thickness center layer. As a result, when a hot-rolled steel sheet having a chemical composition having a phase transformation is rolled to produce a non-directional electromagnetic steel sheet, warm rolling is performed in at least the first pass of rolling, and warm rolling is performed in the second and subsequent passes. Perform inter-rolling or cold rolling (finish rolling process). Further, in the first pass of warm rolling, the friction coefficient between the roll of the rolling stand and the hot-rolled steel sheet which is a non-rolled material is set to more than 0.10 to 0.30, and the rolling temperature is set to T (° C.) and strain. When the speed is defined as ε dots (s ^-1 ) and the rolling reduction is defined as r (%), rolling is carried out under the conditions satisfying equations (1) to (3), and the cumulative rolling reduction in the finish rolling process. It has been found that a non-directional electromagnetic steel sheet having the above-mentioned texture can be produced by setting the value to 75 to 95%.

The non-oriented electrical steel sheet of the present invention completed based on the above findings has a chemical composition of C: 0.001 to 0.005%, Si: 0.5 to 2.0%, Mn: in mass%. Contains 0.1 to 1.5%, P: less than 0.10%, S: 0.005% or less, Al: 0.001 to 2.0%, and N: 0.001 to 0.005%. However, the balance is a chemical composition having a phase transformation among the chemical compositions composed of Fe and impurities, and when the thickness of the non-oriented electrical steel sheet is defined as t, t / 10 from the surface of the non-oriented electrical steel sheet. The degree of integration I (sa) of the {111} <112> orientation at the depth position is less than 6.0, and the degree of integration I (cb) of the {100} <012> orientation at the t/2 depth position from the surface. ) Is 4.0 or more, and the ratio of the degree of integration I (sb) of the {100} <112> orientation to the degree of integration I (cb) at the t / 10 depth position from the surface of the non-oriented electrical steel sheet is 0. It is .8 to 1.2.

The chemical composition is further selected from the group consisting of Ti: 0.01% or less, V: 0.01% or less, and Nb: 0.015% or less instead of a part of Fe. It may contain more than a seed. In this case, the chemical composition satisfies the formula (A).

Further, instead of a part of Fe, the above chemical composition has Sn: 0.2% or less, Cu: 0.1% or less, Ni: 0.1% or less, Cr: 0.2% or less, and B: It may contain one or more selected from the group consisting of 0.001% or less.

The method for producing a non-directional electromagnetic steel sheet according to the present invention is the heat for producing a hot-rolled steel sheet _{at a finishing temperature of Ar 1 point (° C) to 1000 ° C by performing hot rolling on a material having the above-mentioned chemical composition.} In the inter-rolling process, the hot-rolled steel sheet is warm-rolled in at least the first pass, and warm-rolled or cold-rolled in the second and subsequent passes, and 0.10 to 0. It is provided with a finish rolling step for producing a thin steel sheet having a plate thickness of .50 mm and a finish rolling step for performing finish rolling with a maximum reaching temperature of 800 ° C. to ₁ point for the thin steel sheet. In the finish rolling process, in the first pass rolling, the friction coefficient between the roll of the rolling stand for performing the first pass rolling and the hot-rolled steel sheet pair is set to more than 0.10 to 0.30, and the rolling temperature is set to T ( When the strain rate ^{is defined as ε dot (s -1} ) and the rolling reduction is defined as r (%), warm rolling is performed on the hot-rolled steel sheet under the conditions satisfying equations (1) to (3). To do. Then, the cumulative rolling reduction in the finish rolling process is set to 75 to 95%.

In the cold rolling, for example, the rolling temperature is set to less than 100 ° C.

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

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

[Chemical composition]
The chemical composition of non-oriented electrical steel sheets according to the present invention contains the following elements. Unless otherwise specified, "%" in the chemical composition of non-oriented electrical steel sheets means mass%.

C: 0.001 to 0.005%
Carbon (C) exists as a solid solution C in steel and improves the texture due to dynamic strain aging during warm rolling. As a result, the magnetic flux density of the non-oriented electrical steel sheet is increased. If the C content is less than 0.001%, this effect cannot 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 deteriorated. 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 preferred upper limit of the C content is 0.004%, more preferably 0.003%.

Si: 0.5-2.0%
Silicon (Si) increases the intrinsic resistance of the steel sheet and reduces eddy current loss. Si further reduces the hysteresis loss. If the Si content is less than 0.5%, these effects cannot be obtained. On the other hand, if the Si content exceeds 2.0%, there may be no phase transformation, and the effect of the present invention may not be obtained. Therefore, the Si content is 0.5 to 2.0%. The lower limit of the Si content is preferably 0.7%, more preferably 1.0%. The preferred upper limit of the Si content is 1.8%, more preferably 1.5%.

Mn: 0.1 to 1.5%
Manganese (Mn) increases the intrinsic resistance of steel and at the same time facilitates phase transformation. If the phase transformation does not occur, the effect of the present invention may not be obtained. Mn further coarsens and detoxifies sulfides. If the Mn content is less than 0.1%, these effects cannot be obtained. On the other hand, if the Mn content exceeds 1.5%, the magnetic flux density of the steel decreases. Therefore, the Mn content is 0.1 to 1.5%. This preferred lower limit of the Mn content is 0.2%, more preferably 0.5%. The preferred upper limit of the Mn content is 1.2%, more preferably 1.0%.

P: Less than 0.10% Phosphorus (P) is an impurity. P lowers the workability of the steel and can cause cracks in the steel sheet during cold rolling. Therefore, the P content is less than 0.10%. The P content is preferably as low as possible. The lower limit of the P content is not particularly limited. From the viewpoint of dephosphorization cost and productivity, the preferable lower limit of the P content is 0.01%.

S: 0.005% or less Sulfur (S) is an impurity. S produces MnS and increases 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 desulfurization cost and productivity, the preferable lower limit of the S content is 0.001%.

Al: 0.001 to 2.0%
Aluminum (Al) deoxidizes steel. Al further coarsens and detoxifies the nitride. Al also increases the intrinsic resistance of steel and reduces iron loss, similar to Si. If the Al content is less than 0.001%, these effects cannot be obtained. On the other hand, if the Al content exceeds 2.0%, the phase transformation may not occur, and the effect of the present invention may not be obtained. Therefore, the Al content is 0.001 to 2.0%. The lower limit of the Al content is preferably 0.01%, more preferably 0.1%. The preferred upper limit of the Al content is 1.0%, more preferably 0.5%.

N: 0.001 to 0.005%
Nitrogen (N), like C, exists as a solid solution N in steel and improves the texture due to dynamic strain aging during warm rolling. As a result, the magnetic flux density of the non-oriented electrical steel sheet is increased. If the N content is less than 0.001%, this effect cannot be obtained. On the other hand, if the N content exceeds 0.005%, fine AlN is precipitated and the magnetic characteristics are deteriorated. Therefore, the N content is 0.001 to 0.005%. The preferred lower limit of the N content is 0.0015%, more preferably 0.002%. The preferred upper limit of the N content is 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, the impurities are those mixed from ore, scrap, manufacturing environment, etc. as a raw material when the non-oriented electrical steel sheet is industrially manufactured. The content of these impurities is allowed as long as it does not adversely affect the non-oriented electrical steel sheet of the present embodiment. In the present specification, when the Ti content is 0.004% or less, the Ti content is interpreted as an impurity level. Similarly, if the V content is 0.004% or less, the V content is interpreted as an impurity level. If the Nb content is 0.004% or less, the Nb content is interpreted as an impurity level. That is, among the above impurities, the Ti content, V content and Nb content are as follows.
Ti: 0.004% or less,
V: 0.004% or less,
Nb: 0.004% or less

ここで、式（Ａ）中の元素記号には、無方向性電磁鋼板中のその元素の含有量（質量％）が代入される。 [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 a part of Fe. Furthermore, 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: 0.015% or less Titanium (Ti), vanadium (V) and niobium (Nb) are optional elements. These elements form carbonitrides to fix C and N. If these carbonitrides are present before cold rolling, dynamic strain aging due to solid solution C and solid solution N cannot be obtained. The Ti content is 0.01% or less, the V content is 0.01% or less, the Nb content is 0.015% or less, and the total content of Ti, V and Nb can satisfy the formula (A). For example, dynamic strain aging due to solid solution C and solid solution N can be suppressed.

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 instead of a 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 during finish annealing and suppresses deterioration of magnetic properties. On the other hand, if the Sn content exceeds 0.2%, the workability of the steel sheet is lowered, and cracks may occur in the steel sheet during cold rolling. Therefore, the Sn content is set to 0.2% or less. The preferred lower limit of the Sn content is 0.01%, more preferably 0.02%. The preferred upper limit of the Sn content is 0.15%, more preferably 0.1%.

Cu: 0.1% or less Copper (Cu) is an optional element and may not be contained. When excessively contained, Cu lowers the saturation magnetic flux density and lowers the magnetic flux density B ₅₀ . Cu further forms CuS and deteriorates iron loss. When Cu is further contained together with Ni, an internal oxide layer is likely to be 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 contained, Ni _{increases the magnetic flux density B 50} and further increases the strength of the steel sheet. However, if the Ni content is too high, the raw material cost will be high. When Ni is further contained together with Cu, an internal oxide layer is likely to be 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 of the Ni content is not particularly limited, but is preferably 0.01% or more from the viewpoint of _{the magnetic flux density B50 and the strength of the steel sheet.}

Cr: 0.2% or less Chromium (Cr) is an optional element and may not be contained. When excessively contained, Cr lowers the saturation magnetic flux density and lowers 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. When excessively contained, B lowers the saturation magnetic flux density and lowers the magnetic flux density B ₅₀ . Therefore, the B content is 0.001% or less. The lower limit of the B content is not particularly limited, but is preferably 0.0001% or more from the viewpoint of being mixed from iron scrap.

[Aggregate 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 surface of the steel sheet, the degree of integration I (sa) in the {111} <112> orientation is less than 6.0.
(II) The degree of integration I (cb) in the {100} <012> orientation is 4.0 or more in the texture at the t / 2 depth position (plate thickness center layer) from the surface of the steel sheet.
(III) Accumulation of {100} <012> orientations I (sb) at a depth of t / 10 from the surface of the steel sheet, and {100} <012> orientations at a depth of t / 2 from the surface. The ratio to the degree I (cb) (integration ratio RA = I (sb) / I (cb)) is 0.80 to 1.20.

[I: About the texture of the surface layer]
If the degree of integration I (sa) of the {111} <112> orientation on the surface layer is low, the yield stress of the surface layer of the non-oriented electrical steel sheet decreases, and the plastic deformation region expands from the sheared surface to the inside of the steel sheet. As a result, the punching dimensional accuracy at the time of punching can be improved by combining with the integration ratio RA described later. If the degree of integration I (sa) is less than 6.0, this effect can be effectively obtained. The preferred upper limit of the degree of integration I (sa) is 4.0, more preferably 2.0.

[II: About the texture of the central layer of plate thickness]
If the degree of integration I (cb) of the {100} <012> orientation in the central layer of the plate thickness is low, the magnetic flux density B ₅₀ of the non-oriented electrical steel sheet decreases. When the degree of integration I (cb) is 4.0 or more, the magnetic flux density is improved. The preferred upper limit of the degree of integration I (cb) is 4.5, more preferably 5.0.

[III: Concentration ratio RA of surface layer and central layer of plate thickness]
The integration ratio RA of the surface layer in the {100} <012> orientation and the thickness center layer improves the punching dimensional accuracy at the time of punching by the interaction with the above-mentioned {111} <112> orientation. When the integration ratio RA = I (sb) / I (cb) is 0.80 to 1.20, this effect can be effectively obtained. The preferred range of the integration ratio RA is 0.85 to 1.15, and more preferably 0.99 to 1.10.

[Measurement method of degree of integration]
I (sa), I (sb) and I (cb) can be measured by the following method. A non-oriented electrical steel sheet is cut with a cross section perpendicular to the rolling direction, and a plurality of coarse sample pieces having a plate thickness t are collected. The rough sample piece is chemically polished to prepare test pieces for measuring I (sa) and I (sb) whose plate thickness is reduced by t / 10 from the surface. Further, the rough test piece is chemically polished to prepare a test piece for I (cb) measurement in which the plate thickness is reduced by t / 2 from the surface.

For each of the produced test pieces for measurement, the pole diagrams of the {200} plane, the {110} plane, and the {211} plane are measured by an X-ray diffractometer, and the crystal orientation distribution function ODF (Orientation Determination Function) is obtained. create. Using the created ODF, the degree of integration I (sa), I (sb) and I (cb) are determined. The {111} <112> orientation _{indicates the degree of integration of φ 1} = 55 ° and Φ = 30 ° in the _{cross section of φ 2} = 45 ° in ODF. The {100} <012> orientation _{indicates the degree of integration of φ 2} = 45 ° cross section of φ ₁ = 20 ° and Φ = 0 ° in ODF.

[Manufacturing method of non-oriented electrical steel sheet]
An example of the method for manufacturing the non-oriented electrical steel sheet of the present invention will be described. In the method for producing a non-directional electromagnetic steel sheet of the present invention, a step of hot-rolling a slab to produce a hot-rolled steel sheet (hot-rolling step) and a step of warm-rolling at least in the first pass are performed. A process of manufacturing a thin steel sheet (finish rolling process) by performing warm rolling or cold rolling in the rolling after the first pass and then performing warm rolling in the first pass under specific conditions, and a thin steel sheet. On the other hand, it includes a step of performing finish rolling and recrystallizing (finish baking step). Hereinafter, each step will be described in detail.

[Hot rolling process]
In the hot rolling process, the slab is hot rolled to produce a hot-rolled steel sheet. The slab has the chemical composition described above. Slabs are manufactured by well-known methods. For example, a slab is produced by a continuous casting method using a molten metal having the above-mentioned chemical composition. An ingot may be produced by a lump formation method using a molten metal having the above-mentioned chemical composition, and the ingot may be block-rolled to produce a slab. Block rolling may be performed on the slab produced by the continuous casting method.

Hot rolling is performed on the prepared slab. The slab heating temperature during hot rolling is not particularly limited. From the viewpoint of cost and hot rollability, the slab heating temperature is preferably 1000 ° C. to 1300 ° C. A more preferable lower limit of the slab heating temperature is 1050 ° C. A more preferred upper limit of the slab heating temperature is 1250 ° C.

In the production method of the present invention, the finishing temperature in the hot rolling process is the temperature at which the transformation from the austenite single phase or the two phases of the ferrite phase and the austenite phase to the ferrite single phase is completed at Ar ₁ (° C.) or higher to 1000 ° C. is there. Here, the finishing temperature means the temperature of the steel sheet on the exit side of the rolling stand where the final rolling is performed in the hot rolling process.

If the lower limit of the finish rolling temperature is _{less than one} point (° C.) of Ar, a texture having a high degree of integration in the {100} <011> or {110} <001> orientation cannot be obtained in the hot-rolled texture. As a result, even if the manufacturing conditions of the subsequent process are appropriate, the degree of integration I (sa) of the {111} <112> orientation on the surface layer of the steel sheet after finish annealing is high, and the punching dimensional accuracy is low. Therefore, the lower limit of the finishing temperature is _{less than Ar 1} (° C.). On the other hand, the upper limit of the finishing temperature is 1000 ° C. from the viewpoint of operation. The winding temperature is not particularly limited, but is preferably 600 to 900 ° C. from the viewpoint of operation.

In the manufacturing method of the present invention, the hot-rolled sheet may or may not be annealed after the hot-rolling step and before the finish-rolling step. When hot-rolled sheet annealing is performed, for example, the maximum temperature reached is Ac ₁ point (° C.) or less (Ac ₁ point: the temperature at which ferrite begins to transform into austenite), and the holding time is 1 to 180 seconds. Hot-rolled sheet annealing is carried out, for example, in a continuous annealing furnace. If the maximum temperature reached and the holding time are within the above ranges, the load on the equipment can be suppressed and the productivity can be increased. Further, when the maximum temperature reached by hot-rolled sheet annealing is ₁ point or less, the crystal grain size before cold-rolling can be coarsened, and the magnetic characteristics of the non-oriented electrical steel sheet are also enhanced. On the other hand, when the hot-rolled plate annealing temperature _{exceeds one} point of Ac, the phase is transformed from a ferrite single phase to a two-phase region of a ferrite phase and an austenite phase, or to an austenite single phase, and the texture before cold rolling changes. As a result, even if the manufacturing conditions of the subsequent process are appropriate, the {100} <012> orientation integration degree (I (cb)) in the steel sheet center layer after finish annealing becomes low, and RA (= I (sb) / I (cb)) is not satisfied. As a result, the punching dimensional accuracy is lowered. Further, the magnetic characteristics may be deteriorated and the effect of the invention may not be obtained. Therefore, when the hot-rolled plate annealing step is carried out, the maximum temperature reached in the hot-rolled plate annealing is set to Ac ₁ point or less (° C.).

[Finish rolling process]
In the finish rolling step, at least the first pass of rolling is carried out by warm rolling on the hot-rolled steel sheet manufactured by the hot-rolling step. Then, the second and subsequent passes are rolled by warm rolling or cold rolling to produce a thin steel sheet. Here, the "pass" means that the steel sheet passes through one rolling stand having a pair of work rolls and receives rolling.

In the finish rolling process, tandem rolling may be performed using a tandem rolling machine including a plurality of rolling stands arranged in a row (each rolling stand has a pair of work rolls), and a plurality of passes may be performed. , Reverse rolling with a Zendimia rolling mill or the like having a pair of work rolls may be carried out to carry out a plurality of passes. 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 step is carried out, the steel sheet may be heat-treated during the cold rolling. That is, in the cold rolling step of the present invention, a plurality of passes may be carried out with a heat treatment in the middle.

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

The cumulative reduction rate is defined based on the restrictions on the product plate thickness and the point of increasing the degree of integration in the {100} direction. For example, when the thickness of the hot-rolled steel sheet is 2.0 mm and the final thickness of the non-oriented electrical steel sheet is 0.10 to 0.50 mm, the cumulative reduction rate is 75 to 95%. Further, as described above, in order to increase the degree of integration of the {100} <012> orientation in the central portion of the plate thickness, it is preferable that the cumulative reduction rate is high. From the above viewpoint, the cumulative rolling reduction in the finish rolling process in the present invention is 75 to 95%. The preferred lower limit of the cumulative reduction rate is 85%. The preferred upper limit of the cumulative reduction rate is 92.5%.

[Warm rolling process of the first pass]
As described above, the first pass of rolling on the hot-rolled steel sheet is performed by warm rolling. The conditions for warm rolling in the first pass are as follows.

[Friction coefficient μ in warm rolling in the first pass]
The friction coefficient μ between the roll of the rolling stand for warm rolling in the first pass and the hot-rolled steel sheet which is a non-rolled material is a factor that affects the amount of shear deformation in the surface layer of the steel sheet. If the friction coefficient is too low, the accumulation of strain accompanying shear deformation of the rolled material near the grain boundaries on the surface layer of the steel sheet becomes insufficient. In this case, the occurrence of the {111} <112> orientation is not sufficiently suppressed, and the degree of integration I (sa) becomes 6.0 or more. On the other hand, if the friction coefficient μ is too high, the shear deformation extends to the central layer of the plate thickness. In this case, the {100} <012> orientation is excessively generated in the central layer of the plate thickness as compared with the surface layer, and the integration ratio RA = I (sb) / I (cb) is less than 0.80. If the friction coefficient μ of the warm rolling in the first pass is more than 0.10 to 0.30, the surface layer {111} <112, provided that the following equations (1) to (3) are satisfied. > While suppressing the occurrence of orientation, the degree of integration of {100} <012> orientation between the surface layer and the thickness center layer can be made uniform. As a result, the degree of integration I (sa) becomes less than 6.0, and the degree of integration ratio RA becomes 0.80 to 1.20. The preferable range of the friction coefficient μ of the warm rolling in the first pass is 0.15 to 0.25.

ここで、Ｔ（℃）は１パス目の圧延での圧延温度（単位は℃、以下、初期圧延温度という）であり、より具体的には、１パス目の圧延を実施する圧延スタンド入側での鋼板温度（℃）である。εドット（イプシロンドット）は、１パス目の圧延のひずみ速度（単位はｓ^-1、以下、初期ひずみ速度という）である。ｒは、１パス目の圧延の圧下率（単位は％、以下、初期圧下率という）である。 [About equations (1) to (3)]
In the warm rolling of the first pass, rolling is further carried out under the conditions satisfying the equations (1) to (3).

Here, T (° C.) is the rolling temperature (unit: ° C., hereinafter referred to as initial rolling temperature) in the first pass of rolling, and more specifically, the side of the rolling stand where the first pass of rolling is performed. It is the steel plate temperature (° C) at. The ε dot (epsilon dot) is the strain rate of rolling in the first pass (unit: s ^-1 , hereinafter referred to as the initial strain rate). r is the rolling reduction rate of the first pass (unit:%, hereinafter referred to as the initial rolling reduction rate).

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

[About equation (1)]
The initial rolling temperature T is a factor that controls the degree of shear deformation in the vicinity of grain boundaries during rolling. In a steel sheet being rolled in an appropriate temperature range, the difference between the grain boundary strength and the intragranular strength becomes an appropriate situation, and the accumulation of shear strain in the vicinity of the grain boundary increases. Especially in the vicinity of the surface layer, when the shear component becomes a large deformation state in the vicinity of the grain boundary, the generation of the {111} orientation is suppressed in the subsequent recrystallization annealing.

If the initial rolling temperature T (° C.) does not satisfy the formulas (1) to (3), strain is less likely to be accumulated near the grain boundaries on the surface layer of the steel sheet. Therefore, the occurrence of the {111} orientation on the surface layer is not suppressed, and the degree of integration I (sa) is 6.0 or more.

^{FIG. 4 shows the initial strain rate (s -1} ) and the initial rolling temperature (° C.) in the first pass of warm rolling in the manufacturing process of the non-oriented electrical steel sheet satisfying the chemical composition of the present invention, and the degree of integration I (integration degree I). It is a figure which shows the relationship with sa), I (cb) and RA = I (sb) / I (cb). In FIG. 4, as an example, the initial reduction rate is set to 30% (satisfying the formula (3)). Therefore, the right side of the equation (1) is T = 149.0 × (ε dot) ^0.09648 .

With reference to FIG. 4, when the initial strain rate is 10 to 1000 (s ^-1 ) and the initial rolling temperature is equal to or less than the curve of T = 149.0 × (ε dots) ^0.09648 , the degree of integration I (sa) is It will be less than 6.0. If the initial rolling temperature is above the curve of T = 149.0 × (ε dots) ^0.09648 , the degree of integration I (sa) is 6.0 or more.

[About equation (2)]
The initial strain rate ε dots (epsilon dots) are factors that affect the shear deformation near the grain boundaries in relation to the initial rolling temperature T. The initial strain rate ε-dot is also a factor that controls the frequency of non-uniform deformation due to slip deformation of the crystal. If the initial strain rate ε dot becomes high, the moving speed of dislocations cannot follow the deformation, and non-uniform deformation such as a deformation band occurs. Such non-uniform deformation strongly affects the deformation behavior of the plate thickness center layer, which is less likely to cause shear deformation and is simple to deform, and promotes the generation of {100} orientation in the plate thickness center layer in the subsequent recrystallization annealing. To do.

If the initial strain rate ε dot is ^{less than 10s -1} , the non-uniform deformation in the plate thickness center layer is not sufficient, and the integration degree ratio RA (=) of the {100} <012> orientation of the surface layer and the plate thickness center layer I (sb) / I (cb)) is less than 0.80. On the other hand, if the initial strain rate ε dot ^{exceeds 1000 s -1} , the influence of non-uniform deformation becomes large even on the surface layer of the steel sheet. In this case, since the {100} <012> orientation also increases in the surface layer, the integration ratio RA becomes more than 1.20. If the initial strain rate ε dots satisfy the equation (2), the central layer of the plate thickness is suppressed while suppressing the occurrence of the {111} <112> orientation of the surface layer, provided that the equations (1) and (3) are satisfied. The generation of {100} <012> orientation can also be promoted. As a result, the integration ratio RA becomes 0.80 to 1.20. The preferred lower limit of the initial strain rate ε dot is 10s ^-1 . The preferred upper limit of the initial strain rate ε dots is 100s ^-1 .

[About equation (3)]
The initial rolling reduction r is a factor that affects the shear deformation near the grain boundaries in relation to the initial rolling temperature T. The initial reduction rate r is also a factor that controls the frequency of occurrence of non-uniformly deformed structures due to slip deformation of crystals.

The initial reduction rate 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 on the surface layer of the steel sheet and the {100} <012> orientation on the surface layer and the central layer of the plate thickness is determined by the combination of the initial reduction factor r and the above-mentioned friction coefficient μ.

If the initial reduction ratio r is less than 10%, the non-uniform deformation of the steel sheet in the plate thickness center layer becomes insufficient, and the generation of {100} <012> orientation is not sufficiently promoted. On the other hand, if the initial reduction rate r exceeds 50%, the influence of non-uniform deformation on the surface layer of the steel sheet becomes large. In this case, since the {100} <012> orientation also increases in the surface layer, the integration ratio RA becomes more than 1.20. If the initial reduction rate r satisfies the equation (3), the occurrence of the {111} <112> orientation of the surface layer is suppressed and the central layer of the plate thickness is satisfied, provided that the equations (1) and (2) are satisfied. The generation of {100} <012> orientation can also be promoted. As a result, the integration ratio RA becomes 0.80 to 1.20. The upper limit of the initial reduction rate r is preferably 30%, more preferably 20%.

[About pass schedule]
From the viewpoint of improving the magnetic properties of non-oriented electrical steel sheets, by performing warm rolling from at least the first pass rolling, the frequency of non-uniform deformation such as deformation bands can be sufficiently increased, and as a result, the plate The recrystallization of {100} <012> orientation can be maximized in the thick center layer, and the integration ratio RA can be controlled within the required range. Since the plate thickness is thin in the rolling after the second pass (rolling on the rolling stand located on the downstream side of the initial rolling stand), a sufficient rolling shape ratio (roll contact arc length / average plate thickness) should be obtained. Difficult to take. Therefore, it is difficult to obtain the deformed state required for the present invention, and a significant improvement in the effect of the invention cannot be expected. Further, in the latter stage of the rolling process, it is necessary to reduce the rolling shape ratio in order to ensure the plate thickness accuracy of the final product, regardless of the deformation state that the present invention pays attention to. Further, from the viewpoint of plate thickness accuracy, cold rolling, which enables sufficient lubrication, is advantageous.

In the present invention, when warm rolling or cold rolling is carried out with such a small rolling shape ratio, a part of the deformed state required for the present invention introduced in the first pass disappears, and the steel sheet after recrystallization The accumulation of {111} <112> orientations formed on the surface layer increases, which also hinders the effect of the invention. Therefore, in the present invention, the manufacturing method is defined under the condition of rolling in the first pass. However, it goes without saying that warm rolling after the second pass is not excluded unless the effect of the invention is completely lost.

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

Further, from the viewpoint of avoiding overtension fracture, when the rolling reduction rate per pass is increased or the strain rate per pass is increased, the rolling load may increase and the tension may become too large. In this case, the steel sheet being rolled may break. As a result of the investigation, excessive tension is likely to occur on the exit side of the rolling stand (initial rolling stand) for performing the first pass rolling and the exit side of the rolling stand for performing the second pass rolling. Performing warm rolling in the first pass of rolling is also convenient in order to prevent excessive tension from being applied to the steel sheet.

From the viewpoint of the work roll used for warm rolling, the roll life by warm rolling is lower than the roll life by cold rolling. This is because the work roll is more easily worn in the warm rolling than in the cold rolling, and tempering occurs. In the present invention, the roll basic unit can be increased by performing warm rolling only in the first pass.

For the above reasons, it is a preferred embodiment of the present invention that the first stage including the first pass of rolling is warm rolling and the second stage is cold rolling. In this case, in the cold rolling in the subsequent stage, the rolling temperature (steel plate temperature) is set to less than 100 ° C. As a result, it is possible to improve the magnetic properties, reduce the fluctuation in plate thickness, and avoid the concern that the processed structure state preferable for the present invention formed by the first pass of warm rolling is destroyed.

When using a tandem rolling mill, a rolling stand that performs rolling at least in the first pass, and a rolling stand that performs warm rolling at the rolling stand and a rolling stand arranged downstream of the rolling stand, and the rolling stand that performs warm rolling. Cold rolling may be carried out at one or more rolling stands arranged downstream.

[About rolling temperature control]
The hot-rolled steel sheet is heated for warm rolling in the pre-stage, including the first pass of rolling. As the heating method in the warm rolling step, known heating methods can be applied, including electromagnetic induction heating, energization heating, heater heating, heating in an atmospheric gas, and the like.

When applying cold rolling in order to obtain the above merits in the subsequent rolling after warm rolling, contact with a cooling roll or the like or cooling gas before the path of cold rolling after warm rolling. The steel sheet may be cooled to a required temperature by a known method such as spraying.

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

The maximum temperature reached and the holding time of finish annealing are limited to a range in which phase transformation does not occur during finish annealing and the average grain size of the non-oriented electrical steel sheet after finish annealing is 50 μm or less. The maximum temperature reached and the holding time at which phase transformation does not occur 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. Setting the maximum temperature reached and the holding time is easy for those skilled in the art. The maximum temperature reached in finish annealing is 800 ° C. to ₁ point of Ac ( ₁ point of Ac: the temperature at which ferrite begins to transform into austenite). The preferred upper limit of the maximum temperature reached is 900 ° C. The holding time at the maximum temperature reached is 20 to 90 seconds. Using sample cold-rolled steel sheets rolled under the same chemical composition, the same hot rolling process conditions, and the same finish rolling process conditions, heat treatment and microstructure observation are performed, and finish rolling annealing conditions (maximum temperature reached and retention) are performed in advance. Time) may be determined. In this case, more appropriate conditions can be determined so that the average crystal grain size is 50 μm or less. If the maximum temperature reached is less than 800 ° C., the integration ratio RA is less than 0.8, and the punching dimensional accuracy is lowered. On the other hand, when the maximum temperature reached _{exceeds one} point of Ac, I (cb) cannot be obtained, the magnetic flux density B ₅₀ becomes low, and the effect of the invention cannot be obtained.

[Other processes]
In the above-mentioned production method, a coating step may be carried out after the finish annealing step. In the coating process, 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, and the insulating coating may contain an organic component and an inorganic component. The inorganic component is, for example, dichromate-boric acid type, phosphoric acid type, silica type and the like. The organic component is, for example, a general acrylic-based, acrylic styrene-based, acrylic silicon-based, silicon-based, polyester-based, epoxy-based, or fluorine-based resin. Considering the coatability, the preferable resin is an emulsion type resin. An insulating coating that exhibits adhesiveness by heating and / or pressurizing may be applied. The adhesive coating having adhesive ability is, for example, an acrylic-based, phenol-based, epoxy-based, or melamine-based 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 has excellent magnetic properties. Further, it is possible to suppress the occurrence of sagging in the punching process.

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

Slabs (steel pieces) having the chemical compositions shown in Table 1 were produced. “-” In Table 1 indicates that the content was below the detection limit.

A sample having a diameter of 10 mm and a length of 20 mm was cut out from each slab. Then, the temperature was raised in the range of 25 to 1200 ° C. at 4 ° C./min in an Ar atmosphere, and the coefficient of linear expansion α was measured. The temperature at which the gradient dα / dT of the linear expansion coefficient α and the temperature T turned from positive to negative was judged to have started the phase transformation from the ferrite phase to the austenite phase, and was judged to be Ac ₁ point. Further, as shown in FIG. 3, the mixture was cooled at 4 ° C./min in the range of 1200 to 25 ° C., and the coefficient of linear expansion α at the time of lowering the temperature was measured. Then, it was determined that all the austenite phases were transformed into ferrite phases at the temperature at which the gradient dα / dT of the coefficient of linear expansion α and the temperature T changed from negative to positive, and that temperature was determined to be _{Ar 1.} Based on these results, the influence of manufacturing conditions after hot rolling was investigated.

The slab is heated to 1150 ° C. and hot-rolled to the finishing temperatures of 950 ° C., 900 ° C., 850 ° C. and 700 ° C. to a plate thickness of 2.0 mm and wound at 800 ° C. to obtain a hot-rolled steel sheet. Manufactured.

The hot-rolled steel sheet was annealed by soaking the hot-rolled steel sheet at 850 ° C., 950 ° C., and 1000 ° C. for 1 minute. Then, using a tandem rolling mill in which five rolling stands were arranged in a row, the first pass of rolling was carried out by warm rolling under the conditions shown in Table 2. Further, rolling in the 2nd to 5th passes was carried out by cold rolling at 100 ° C. or lower to produce a thin steel sheet having a plate thickness of 0.50 mm. The cumulative rolling reduction in the finish rolling process was 75%. The thin steel sheet after finish rolling was held at the finish annealing temperature (maximum temperature reached) shown in Table 1 for 14 seconds. A non-oriented electrical steel sheet was manufactured by the above manufacturing process.

以上の工程で製造された無方向性電磁鋼板に対して、次の評価を行った。 In addition, T1 in Table 2 was the left side of the equation (1), and T2 was the right side of the equation (1). Specifically, T2 is as follows.

The following evaluation was performed on the non-oriented electrical steel sheets manufactured by the above steps.

[Integration measurement test]
Based on the above-mentioned measurement method, the degree of integration I (sa) and the degree of integration I (sb) on the surface layer and the degree of integration I (cb) on the central layer of the plate thickness were determined.

[Magnetic characterization 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 was determined as an average value in the L direction (rolling direction) and the C direction (direction orthogonal to the rolling direction).

[Punching dimensional difference measurement test]
The punching test was carried out by the following method. Punching was performed using a 55 mm square die to prepare 55 mm × 55 mm test pieces shown in FIGS. 4 (A) and 4 (B). The clearance was 8% of the plate thickness.

As shown in FIG. 4 (A), the length of the square test piece in the rolling direction was measured at three points (L1 to L3). Specifically, with reference to FIG. 4A, the length of the test piece in the rolling direction at a position 5 mm in the width direction from the left side parallel to the rolling direction was defined as L1. Similarly, the length in the rolling direction at the center position in the width direction is defined as L2. The length in the rolling direction at a position 5 mm in the width direction from the right side parallel to the rolling direction was defined as L3.

Further, as shown in FIG. 4 (B), the length of the square shape in the width direction was measured at three points (C1 to C3). Specifically, with reference to FIG. 4B, the length in the width direction of the test piece at a position 5 mm in the rolling direction from the upper side parallel to the width direction was defined as C1. Similarly, the length in the width direction at the center position in the rolling direction was defined as C2. The length in the width direction at a position 5 mm in the rolling direction from the lower side parallel to the width direction was defined as C3.

The above-mentioned lengths L1 to L3 and lengths C1 to C3 were measured. The punching dimensional accuracy A (μm) defined by the following formula was evaluated.

[result]
The evaluation results are shown in Table 2. With reference to Table 2, in test numbers 2-11, 20, 26-28, 38, 39, 56 and 59, the chemical composition was appropriate and the production conditions were also appropriate. Therefore, the degree of integration I (sa) is less than 6.0, the degree of integration I (cb) is 4.0 or more, and the degree of integration ratio RA = I (sb) / I (cb) is 0.80-1. It was .20. As a result, the punching dimensional difference was as small as 10 μm or less, and the occurrence of dimensional variation during punching could be sufficiently suppressed. Further, the magnetic flux density B ₅₀ was 1.80 T or more, and excellent magnetic characteristics were obtained.

On the other hand, the Si content of Test No. 1 was too high. Therefore, the non-oriented electrical steel sheet of Test No. 1 did not undergo phase transformation. As a result, the degree of integration I (cb) was low, and the degree of integration ratio RA was also low. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Further, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test numbers 12 to 15, the initial strain rate was too low. Therefore, the integration ratio RA was less than 0.80. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy was low. In test number 15, since the initial rolling temperature T was also high, the degree of integration I (sa) was 6.0 or more, and the punching dimension difference exceeded 10 μm.

In test number 16, the initial rolling temperature T was too low and the friction coefficient μ was also low. Therefore, the degree of integration I (sa) was 6.0 or more, the degree of integration I (cb) was less than 4.0, and the degree of integration ratio RA was less than 0.80. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Further, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test number 17, the coefficient of friction μ was low. Therefore, the degree of integration I (sa) was 6.0 or more. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Furthermore, the degree of integration I (cb) was less than 4.0. Therefore, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test number 18, the initial rolling temperature T was too high and the friction coefficient μ was also low. Therefore, the degree of integration I (sa) was 6.0 or more, the degree of integration I (cb) was less than 4.0, and the degree of integration ratio RA was less than 0.80. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Furthermore, the degree of integration I (cb) was less than 4.0. Therefore, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test numbers 19 and 25, the initial rolling temperature T was too low. Therefore, the degree of integration I (cb) was less than 4.0, and the degree of integration ratio RA was less than 0.80. As a result, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test numbers 21 and 29, the initial rolling temperature T was too high. Therefore, the degree of integration I (sa) was 6.0 or more. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 22, the initial rolling temperature T was too low and the friction coefficient μ was too high. Therefore, the integration ratio RA was less than 0.80. As a result, as a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 23, the coefficient of friction μ was too high. Therefore, the integration ratio RA was less than 0.80. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 24, the initial rolling temperature T was too high and the friction coefficient μ was too high. Therefore, the degree of integration I (sa) was 6.0 or more, and the degree of integration ratio RA was less than 0.80. As a result, as a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 30, the initial rolling temperature T was too low and the initial strain rate was too high. Therefore, the degree of integration I (cb) was less than 4.0. As a result, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low. Furthermore, the integration ratio RA exceeded 1.20. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test numbers 31 to 33, the initial strain rate was too high. Therefore, the integration ratio RA exceeded 1.20. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 34, the initial rolling temperature T was too high. Therefore, the degree of integration I (sa) was 6.0 or more. Moreover, the strain rate was too high, and the integration ratio RA exceeded 1.20. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 35, the initial reduction rate r was too low. Therefore, the degree of integration I (cb) was less than 4.0. As a result, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In test number 36, the initial reduction rate r was too high. Therefore, the integration ratio RA exceeded 1.20. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 37, the maximum temperature reached during finish annealing was too low. Therefore, the degree of integration I (cb) was less than 4.0. As a result, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low. Furthermore, the integration ratio RA was less than 0.8. As a result, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test number 40, the maximum temperature reached during finish annealing was too high. As a result, the texture was changed by phase transformation, and the degree of integration I (cb) was less than 4.0. As a result, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In Test Nos. 41 to 48, the grain-oriented electrical steel sheets had a chemical composition in which the Si content was too high and did not undergo phase transformation. Therefore, the integration ratio RA was less than 0.80, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Further, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

In Test No. 49, steel having a P content exceeding the range specified in the present invention was produced by a conventional method. In test number 49, the punching dimensional accuracy was superior to that of the steel that did not satisfy the rolling conditions requested this time. However, in the example of the present invention, the magnetic flux density B ₅₀ was superior to the test number 49.

In test numbers 50 to 55, the range of each element was within the range specified in the present invention, but the chemical composition did not undergo phase transformation. Therefore, the degree of integration I (sa) exceeded 6.0. As a result, although the integration ratio RA was in the range of 0.80 to 1.20, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test numbers 57 and 58, the range of each element was within the range specified in the present invention, and although the chemical composition was phase-transformed, the finishing temperature in the hot rolling process _{was less than Ar 1} point (° C.). It was. Therefore, the degree of integration I (sa) exceeded 6.0. As a result, although the integration ratio RA was in the range of 0.80 to 1.20, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low.

In test numbers 60 and 61, the range of each element was within the range specified in the present invention, and although the chemical composition was phase-transformed, the maximum temperature reached in the hot-rolled plate annealing step _{exceeded Ac 1} point. Therefore, the degree of integration I (cb) was less than 4.0. As a result, the integration ratio RA was less than 0.80, the punching dimension difference exceeded 10 μm, and the punching dimension accuracy at the time of punching was low. Further, the magnetic flux density B ₅₀ was less than 1.80 T, and the magnetic characteristics were low.

A slab (steel piece) having the chemical composition of steel B shown in Table 1 was heated to 1150 ° C. and hot-rolled to a finishing temperature of 900 ° C. to obtain a plate thickness of 2.0 mm and 800. A hot-rolled steel sheet was manufactured by winding at ° C. The hot-rolled steel sheet was annealed by soaking the hot-rolled steel sheet at 850 ° C. for 1 minute.

After annealing the hot-rolled sheet, a finish rolling process was carried out using a tandem rolling mill in which five rolling stands were arranged in a row. Specifically, in the rolling of the first pass, the initial strain rate was set to 31s ^-1 , the initial reduction rate was set to 30%, and the friction coefficient μ was set to 0.2. The cumulative rolling reduction in the finish rolling process was 85%. The rolling temperatures at each stand from the 1st pass to the 5th pass are as shown in Table 3. The thin steel sheet after finish rolling was held at a finish annealing temperature (maximum ultimate temperature) of 850 ° C. for 14 seconds. A non-oriented electrical steel sheet was manufactured by the above manufacturing process.

Regarding the variation in the plate thickness of the steel plate of each test number, the plate thickness was measured at 4 locations in the plate width direction x 4 locations in the length direction at intervals of 50 mm, for a total of 16 locations. Then, 1/2 of the difference between the maximum value and the minimum value of the measured plate thickness was defined as the plate thickness variation (mm). The average of the 16 measured points was defined as the average plate thickness (mm).

For non-oriented electrical steel sheets of each test number, the degree of integration I (sa), the degree of integration I (sb), the degree of integration I (cb), and the magnetic flux density B ₅₀ (T) were applied in the same manner as in Example 1. , Punching dimensional accuracy (μm) was determined.

[result]
In Test Nos. 1 to 5, the results are shown in Table 3, and the chemical composition was appropriate and the production conditions were also appropriate. Therefore, the degree of integration I (sa) is less than 6.0, the degree of integration I (cb) is 4.0 or more, and the degree of integration ratio RA = I (sb) / I (cb) is 0.8 to 1. It was .2. As a result, the punching dimensional difference was as small as 10 μm or less, and excellent punching dimensional accuracy was obtained. The magnetic flux density B ₅₀ was 1.800 T or more, and excellent magnetic characteristics were obtained.

On the other hand, in test numbers 6 to 13, the initial rolling temperature of the first pass was too low and the formula (1) was not satisfied. Therefore, the degree of integration I (cb) was low. As a result, the magnetic flux density B ₅₀ was less than 1.800 T, and the magnetic characteristics were low. Further, since the integration ratio RA was less than 0.8, the punching dimensional accuracy exceeded 10 μm.

Further, test numbers 7 to 13 included warm rolling in which the rolling temperature was 100 ° C. or higher in any of the 2nd to 5th passes. Therefore, the plate thickness fluctuation range was larger than that of the cold rolling test number 6. Further, the plate thickness fluctuation range was larger than that in Test Nos. 1 to 5 in which the first pass was warm-rolled at 150 ° C.

Although suitable examples of the present invention have been described above, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the ideas described in the claims, which naturally belong to the technical scope of the present invention. It is understood as a thing.

Claims (7)

It is a non-oriented electrical steel sheet
The chemical composition is
By mass%
C: 0.001 to 0.005%,
Si: 0.5-2.0%,
Mn: 0.1 to 1.5%,
P: less than 0.10%,
S: 0.005% or less,
Al: 0.001 to 2.0% and
N: 0.001 to 0.005%,
The balance is a chemical composition having a phase transformation among the chemical compositions consisting of Fe and impurities.
When the thickness of the non-oriented electrical steel sheet is defined as t,
The degree of integration I (sa) of the {111} <112> orientation at the t / 10 depth position from the surface of the non-oriented electrical steel sheet is less than 6.0.
The degree of integration I (cb) of the {100} <012> orientation at the t / 2 depth position from the surface of the non-oriented electrical steel sheet is 4.0 or more.
The ratio of the degree of aggregation I (sb) in the {100} <012> orientation to the degree of integration I (cb) at the t / 10 depth position from the surface of the non-oriented electrical steel sheet is 0.8 to 1.2. There is a non-oriented electrical steel sheet. The non-oriented electrical steel sheet according to claim 1.
The chemical composition is further substituting for a portion of Fe.
Ti: 0.01% or less,
V: 0.01% or less and
Nb: Contains one or more selected from the group consisting of 0.015% or less,
A non-oriented electrical steel sheet having a chemical composition satisfying the formula (A).

The non-oriented electrical steel sheet according to claim 1 or 2.
The chemical composition is further substituting for a portion of Fe.
Sn: 0.2% or less,
Cu: 0.1% or less,
Ni: 0.1% or less,
Cr: 0.2% or less, and
B: 0.001% or less,
A non-oriented electrical steel sheet containing one or more selected from the group consisting of. A material having the chemical composition according to any one of claims 1 to 3 is hot-rolled to produce a hot-rolled steel sheet at _{a finishing temperature of Ar 1 point (° C.) to 1000 ° C.} Hot rolling process and
The hot-rolled steel sheet is subjected to warm rolling in at least the first pass, and warm or cold rolling in the second and subsequent passes, to form a 0.10 to 0.50 mm sheet. A finish rolling process for producing thick thin steel sheets,
The thin steel sheet is provided with a finish annealing step of performing finish annealing with a maximum temperature of 800 ° C. to _{1 point of Ac.}
In the finish rolling process,
In the first-pass rolling, the coefficient of friction between the roll of the rolling stand for performing the first-pass rolling and the hot-rolled steel sheet is set to more than 0.10 to 0.30.
When the rolling temperature is defined as T (° C.), the strain rate ^{is defined as ε dots (s -1} ), and the rolling reduction is defined as r (%), the hot-rolled steel sheet is subjected to the conditions satisfying equations (1) to (3). Warm rolling
The method for manufacturing a non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the cumulative rolling reduction in the finish rolling step is 75 to 95%.

The method for manufacturing a non-oriented electrical steel sheet according to claim 4.
In the cold rolling,
A method for manufacturing a non-oriented electrical steel sheet, wherein the rolling temperature is less than 100 ° C. The method for manufacturing a non-oriented electrical steel sheet according to claim 4 or 5.
In the finish rolling process,
Using a tandem rolling mill, each having a pair of work rolls and containing multiple rolling stands in a row.
The warm rolling is carried out at at least the rolling stand on which the first pass is rolled, or the rolling stand and the rolling stands arranged downstream thereof.
A method for producing a non-oriented electrical steel sheet, which is carried out by cold rolling at a rolling stand arranged downstream of the rolling stand where the warm rolling is carried out. The method for manufacturing a non-oriented electrical steel sheet according to any one of claims 4 to 6, further
A method for producing a non-directional electromagnetic steel plate, comprising a hot-rolled sheet annealing step of performing hot-rolled sheet annealing in which _{the maximum temperature reached is Ac 1} point ° C. or lower after the hot rolling step and before the finish rolling step.

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