JP5712863B2 - Method for producing non-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet and a method for producing the same. More specifically, the present invention is suitable for use in iron cores of high-efficiency motors mainly used in high-speed rotation areas such as compressor motors such as air conditioners and refrigerators, drive motors and generators such as electric vehicles and hybrid vehicles. The present invention relates to a non-oriented electrical steel sheet.

  Due to the need to reduce greenhouse gases, products with low energy consumption are rapidly spreading in the fields of automobiles, home appliances, and the like. For example, in the automobile field, there are low fuel consumption vehicles such as hybrid vehicles having a drive system in which a gasoline engine and a motor are combined, and motor-driven electric vehicles. In the field of home appliances, there are high-efficiency air conditioners, refrigerators and the like that consume less electricity annually. The technology common to these is the motor, and it is important to improve the motor efficiency. To increase the efficiency of the motor, iron loss reduction and magnetic flux density improvement of the non-oriented electrical steel sheet, which is the core material, are performed. Is required. Since motor drive motors and home appliance compressor motors such as those described above are frequently used in high-speed rotation regions, non-oriented electrical steel sheets with low iron loss under high-frequency conditions are suitable as the iron core material. .

As a means for reducing iron loss, a means for increasing the content of an alloy element having an action of increasing specific resistance such as Si or Al is generally used. However, there arises a problem that the magnetic flux density is deteriorated due to an increase in the alloy content and a problem that the steel sheet is hardened and the breaking rate in cold rolling is increased.
As a means for suppressing breakage in cold rolling as described above, warm rolling is generally used. For example, Patent Document 1 discloses that a transition temperature in an impact test of a hot-rolled sheet annealed sheet, that is, a transition temperature of a steel sheet before cold rolling is 60 ° C. or less.

Further, as means for reducing iron loss, means for adding Sn has also been proposed (see Patent Document 2).
On the other hand, as means for improving the magnetic flux density, means for adding P or Sb has been proposed (see Patent Documents 3 to 4).

JP 2007-247047 A JP-A-55-158252 JP 2005-200756 A Japanese Patent Laid-Open No. 59-100197

The invention disclosed in Patent Document 3 enables high-frequency iron loss reduction by further increasing the amount of alloying elements by improving the magnetic flux density. It is a very excellent invention that contributes to efficiency. Further, according to the inventions disclosed in Patent Document 2 and Patent Document 4, the magnetic characteristics are improved.
However, due to the recent demand for higher motor efficiency, a means for improving the magnetic flux density that can further reduce the high-frequency iron loss is required.

  Further, as described above, warm rolling is generally used as a means for suppressing breakage in cold rolling. However, since warm rolling requires special equipment, it is inferior in terms of cost. Moreover, the impact test of the hot-rolled sheet annealing plate evaluated in Patent Document 1 is a Charpy impact test, and the strain rate of this Charpy impact test is about 500 to 1000 / s, which is the strain rate in rolling. It is far from 100 / s and is not appropriate as an evaluation method of cold rolling property. Furthermore, in Patent Document 1, the upper limit of the transition temperature is set to 60 ° C. because the steel plate temperature of 70 ° C. can be secured in the manufacturing processes of pickling, cold rolling, and finish annealing that may cause breakage. Although described, heating equipment such as a heater is required to increase the steel sheet temperature to 70 ° C. or higher, which increases the manufacturing cost.

  The present invention has been made in view of the above circumstances, and the problem is suitable for use in iron cores of compressor motors such as air conditioners and refrigerators, drive motors such as electric vehicles and hybrid vehicles, and high efficiency motors such as generators. Another object is to provide a non-oriented electrical steel sheet having excellent magnetic properties and productivity.

  In order to solve the above-mentioned problems, the present inventors have newly paid attention not only to the influence of P, Sn, and Sb on magnetic characteristics, but also to the influence of interactions with other elements on the magnetic characteristics. A new idea of further improving the magnetic characteristics by using, has been intensively studied. As a result, the following new findings were obtained.

(A) After containing S in a very small amount, by regulating the upper limit of the total content of S, As, Nb, Ti, V, Zr and N, the effect of improving the magnetic flux density by adding P, Sn, and Sb Is effectively enhanced.
(B) As the amount of alloy elements such as Si, Al, Mn, and P increases, the breaking rate in cold rolling increases. As a result of detailed investigations on breaking in cold rolling, 1 to 3 passes of cold rolling It is roughly divided into two types: a break that occurs in the first pass of the eye and a break that occurs in the second pass after the fourth pass of cold rolling.
(C) Breakage occurring in the preceding pass is likely to occur at the start of rolling at a strain rate of about 10 to 30 / s.
(D) In order to appropriately evaluate such cold rollability, it is necessary to test under conditions close to the strain rate in actual rolling. In the V block method specified in JIS Z 2248: 2006, Instead of “applying a press fitting to the center of the test piece and gradually applying a test force to bend it into the specified shape”, “the press fitting in the center of the test piece from the specified height with respect to the test piece. By carrying out the test of “falling down and bending into a specified shape”, it becomes possible to easily perform a test for imparting a strain rate in actual rolling, and it is possible to appropriately evaluate the cold rolling property. .
(E) In the test of (d) above, if the height of the metal clamp with respect to the test piece when falling is 1.2 m, the bending angle is 90 ° and the inner radius is 5 mm, the strain rate is 10-30 / s, and the risk of breakage occurring in the previous pass can be accurately evaluated. By setting the breakage rate under such test conditions to 40% or less, the breakage occurring in the previous pass is effectively prevented. Can be prevented.
(F) By subjecting the hot-rolled steel sheet to be subjected to cold rolling to predetermined hot-rolled sheet annealing, the breaking rate can be reliably reduced to 40% or less.
(G) A steel sheet containing 0.025% or more in total of P, Sn, and Sb is most likely to break when cold-rolling a steel sheet that has been reduced by about 32 to 33%. For this reason, the fracture | rupture at the time of cold rolling can be prevented effectively by setting the reduction rate of cold rolling so that such conditions may be avoided.
(H) The fracture occurring in the subsequent pass is mainly caused by fine damage existing on the edge and surface of the steel sheet used for cold rolling. In order to suppress such damage, the finishing temperature, the winding temperature and the plate It is effective to perform hot rolling using the thickness as a predetermined condition.

The present invention is based on these new findings, and the gist thereof is as follows.
That is, the present invention relates to mass%, Si: 4.0% or less, sol. Al: 4.0% or less, Mn: 4.0% or less, P: 0.1% or less, Sn: 0.1% or less, Sb: 0.1% or less, S: 0.0005% or more and 0.0050 % Or less, C: 0.0050% or less, As: 0.0050% or less, Nb: 0.0030% or less, Ti: 0.0030% or less, V: 0.0030% or less, Zr: 0.0030% or less And N: 0.0050% or less, with the balance being Fe and impurities, having a chemical composition satisfying the following formulas (1) to (3), and a plate thickness of 0.10 mm to 0.35 mm And an iron loss W _10/800 [W / kg] and a plate thickness t [mm] when having a steel structure with an average crystal grain size of 60 μm or more and 180 μm or less, and magnetized at a frequency of 800 Hz and a magnetic flux density of 1.0 T, Provides a non-oriented electrical steel sheet characterized by satisfying the following formula (4): .
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
P + Sn + Sb ≧ 0.025 (2)
S + As + Nb + Ti + V + Zr + N ≦ 0.018 (3)
W _10/800 ≦ 100 × t + 15 (4)
(Here, each element symbol in the formulas (1) to (3) indicates the content (unit: mass%) of each element in the steel.)

  In the above invention, the chemical composition is in mass%, instead of a part of the Fe, from the group consisting of Cr: 0.2% or less, Cu: 0.2% or less, and Ni: 0.2% or less. One or two or more selected may be contained.

  Moreover, in the said invention, the said chemical composition replaces a part of said Fe, and is the group which consists of Ca: 0.01% or less, Mg: 0.01% or less, and REM: 0.01% or less by the mass%. 1 type (s) or 2 or more types selected from may be contained.

  Furthermore, in the said invention, it replaces with a part of said Fe, and the said chemical composition may contain B: 0.01% or less by the mass%.

Moreover, this invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A), (B1), (C), and (D).
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B1) The hot-rolled steel sheet obtained by the hot-rolling rolling process is subjected to hot-rolled sheet annealing that is held in a temperature range of 750 ° C. or higher for 1 hour or more and 50 hours or less, and the fracture rate in the following falling weight bending test is 40. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing [falling weight bending test]
In the V-block method specified in JIS Z 2248: 2006, instead of “applying a metal fitting to the center of the test piece and gradually bending it to the specified shape by applying a test force,” “in the center of the test piece The test piece is a test in which the metal clamp is dropped from a height of 1.2 m and bent into a specified shape, and the bending angle is 90 ° and the inner radius is 5 mm.

Furthermore, this invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A), (B2), (C), and (D).
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B2) The hot-rolled steel sheet obtained by the hot-rolling rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. or higher for 1 second or more and 600 seconds or less. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing [falling weight bending test]
In the V-block method specified in JIS Z 2248: 2006, instead of “applying a metal fitting to the center of the test piece and gradually bending it to the specified shape by applying a test force,” “in the center of the test piece The test piece is a test in which the metal clamp is dropped from a height of 1.2 m and bent into a specified shape, and the bending angle is 90 ° and the inner radius is 5 mm.

  Here, the “breakage rate” is the number ratio of the number of test pieces in which breakage occurs to the number of test pieces subjected to the falling weight bending test.

Moreover, this invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A), (B3), (C), and (D).
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B3) Hot-rolled steel sheet obtained by the hot-rolled rolling process is subjected to hot-rolled sheet annealing that is held in a temperature range of 750 ° C. or higher and 850 ° C. or lower for 1 hour or more and 50 hours or less to form a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing

Furthermore, this invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A), (B4), (C), and (D).
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B4) Hot-rolled steel sheet obtained by the above hot-rolled rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. to 1150 ° C. for 1 second to 600 seconds to obtain a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing

  The non-oriented electrical steel sheet according to the present invention can be expected to improve motor efficiency. Moreover, since the manufacturing method of the non-oriented electrical steel sheet which concerns on this invention does not require special equipment, it is excellent also in terms of manufacturing cost.

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

A. Non-oriented electrical steel sheet First, each structure in the non-oriented electrical steel sheet of the present invention will be described.

1. Chemical composition First, the reasons for limiting the chemical composition of the steel sheet will be described. “%” Indicating the content of each element means “mass%” unless otherwise specified.

Si, sol. Al and Mn are effective elements for increasing the specific resistance of the steel sheet and reducing iron loss. Therefore, the following formula (1) is satisfied. Especially, it is preferable that the following formula (1-1) is satisfied, and it is more preferable that the following formula (1-2) is satisfied.
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
Si + sol. Al + 0.5 × Mn ≧ 2.5 (1-1)
Si + sol. Al + 0.5 × Mn ≧ 3.0 (1-2)
(Here, each element symbol in the formula indicates the content (unit: mass%) of each element in the steel.)
On the other hand, when these elements are contained excessively, the steel sheet is hardened and the breaking rate in cold rolling increases. Therefore, the Si content is 4.0% or less, and the sol. The Al content is 4.0% or less, and the Mn content is 4.0% or less. Preferably, the Si content is 3.5% or less. The Al content is 3.0% or less, and the Mn content is 3.0% or less. More preferably, the Si content is 3.0% or less. The Al content is 2.0% or less, and the Mn content is 2.0% or less.
From the viewpoint of grain growth during annealing, sol. The Al content is preferably 0.03% or less or 0.1% or more, and the Mn content is preferably 0.10% or more. sol. The Al content is more preferably 0.01% or less or 0.2% or more, and the Mn content is further preferably 0.15% or more.

P, Sn, and Sb have the effect of improving the texture by improving the texture. Therefore, the following formula (2) is satisfied. Especially, it is preferable that the following formula (2-1) is satisfied, and it is more preferable that the following formula (2-2) is satisfied.
P + Sn + Sb ≧ 0.025 (2)
P + Sn + Sb ≧ 0.030 (2-1)
P + Sn + Sb ≧ 0.035 (2-2)
(Here, each element symbol in the formula indicates the content (unit: mass%) of each element in the steel.)
On the other hand, when these elements are contained excessively, the breaking rate in cold rolling increases. Therefore, the P content is 0.1% or less, the Sn content is 0.1% or less, and the Sb content is 0.1% or less. Preferably, the P content is 0.05% or less, the Sn content is 0.05% or less, and the Sb content is 0.05% or less.

  S is an element that is generally contained in steel as an impurity, and combines with Mn in steel to form fine MnS, which inhibits the growth of crystal grains during annealing and deteriorates magnetic properties. Conventionally, this element has been required to reduce its content. However, as a result of the above-described studies by the present inventors, after adding a small amount of S, by regulating the upper limit of the total content of S, As, Nb, Ti, V, Zr and N, P, Sn It has been clarified for the first time that the effect of improving the magnetic flux density by adding Sb can be effectively enhanced. Therefore, the S content is set to 0.0005% or more. Preferably it is 0.0010% or more, More preferably, it is 0.0015% or more. On the other hand, when the S content is excessive, the deterioration of the magnetic properties becomes remarkable due to the inhibition of crystal grain growth during annealing. Therefore, the S content is 0.0050% or less. Preferably it is 0.0040% or less, More preferably, it is 0.0035% or less.

  C is an element that is contained as an impurity and deteriorates magnetic properties. For this reason, C content shall be 0.0050% or less. Preferably, it is 0.0040% or less.

  As, Nb, Ti, V, and Zr are contained as impurities and are elements that deteriorate the magnetic properties. Therefore, As content is 0.0050% or less, Nb content is 0.0030% or less, Ti content is 0.0030% or less, V content is 0.0030% or less, Zr content is 0.0030%. The following. Preferably, the As content is 0.0040% or less, the Nb content is 0.0020% or less, the Ti content is 0.0020% or less, the V content is 0.0020% or less, and the Zr content is 0.0020. % Or less.

  N is an element that is contained as an impurity and combines with Al to form fine inclusions, which inhibits the growth of crystal grains during annealing and deteriorates magnetic properties. Therefore, the N content is 0.0050% or less. Preferably it is 0.0040% or less, More preferably, it is 0.0030% or less.

It has been conventionally known that iron loss is reduced by reducing the contents of impurity elements S, As, Nb, Ti, V, Zr and N. However, as a result of the above-described studies by the present inventors, after adding a small amount of S, by regulating the upper limit of the total content of S, As, Nb, Ti, V, Zr and N, P, Sn It has been clarified for the first time that the effect of improving the magnetic flux density by adding Sb can be effectively enhanced. Accordingly, the total content of S, As, Nb, Ti, V, Zr and N shall satisfy the following formula (3). Especially, it is preferable that the following formula (3-1) is satisfied, and it is more preferable that the following formula (3-2) is satisfied.
S + As + Nb + Ti + V + Zr + N ≦ 0.018 (3)
S + As + Nb + Ti + V + Zr + N ≦ 0.016 (3-1)
S + As + Nb + Ti + V + Zr + N ≦ 0.014 (3-2)
(Here, each element symbol in the formula indicates the content (unit: mass%) of each element in the steel.)

  Cr, Cu, and Ni have the effect | action which raises the specific resistance of a steel plate and reduces an iron loss. Therefore, you may contain 1 type, or 2 or more types of these elements. However, even if the content of any element exceeds 0.2%, the effect of the above action is saturated and disadvantageous in cost. Therefore, the Cr content is 0.2% or less, the Cu content is 0.2% or less, and the Ni content is 0.2% or less. Preferably, the Cr content is 0.15% or less, the Cu content is 0.15% or less, and the Ni content is 0.15% or less. In order to more reliably obtain the effect of the above action, the content of any element is preferably 0.02% or more.

  Ca, Mg, and REM are effective elements for controlling the form of inclusions, and have an action of promoting the growth of crystal grains. Therefore, you may contain 1 type, or 2 or more types of these elements. However, even if the content of any element exceeds 0.01%, the effect of the above action is saturated and disadvantageous in cost. Therefore, the Ca content is 0.01% or less, the Mg content is 0.01% or less, and the REM content is 0.01% or less. Preferably, the Ca content is 0.005% or less, the Mg content is 0.005% or less, and the REM content is 0.005% or less. In order to more reliably obtain the effect of the above action, the content of any element is preferably 0.0001% or more. More preferably, the content of any element is 0.0003% or more.

  B has the effect of detoxifying the negative effects of N described above. Therefore, B may be contained. However, even if the B content exceeds 0.01%, the effect by the above action is saturated and disadvantageous in cost. Therefore, the B content is 0.01% or less. Preferably, it is 0.005% or less. In order to more reliably obtain the effect of the above action, the B content is preferably 0.0001% or more, and more preferably 0.0003% or more.

2. Average crystal grain size If the crystal grain size is too large or too small, the iron loss deteriorates. Therefore, the average crystal grain size is 60 μm or more and 180 μm or less.
The average crystal grain size may be the average value of the crystal grain sizes measured by the cutting method in the plate thickness direction and the rolling direction in the longitudinal sectional structure photograph. An optical micrograph can be used as the longitudinal cross-sectional structure photograph. For example, a photograph taken at a magnification of 50 times or 100 times may be used.

3. Thickness To improve the efficiency of compressor motors such as air conditioners and refrigerators, drive motors and generators such as electric vehicles and hybrid vehicles, non-oriented electrical steel sheets, which are core materials, have low iron loss in the high frequency range. Is desirable. Since the iron loss is reduced as the plate thickness is reduced, the plate thickness is set to 0.35 mm or less. Preferably it is 0.33 mm or less, More preferably, it is 0.30 mm or less. On the other hand, excessive thinning significantly reduces the productivity of steel plates and motors. Therefore, the plate thickness is 0.10 mm or more. Preferably it is 0.15 mm or more, More preferably, it is 0.20 mm or more.

4). Magnetic properties As a core material for a motor used in a high-speed rotation range, a non-oriented electrical steel sheet having a low iron loss in a high-frequency range is preferable. On the other hand, as described above, the iron loss has a correlation with the plate thickness. Therefore, the iron loss W _10/800 [W / kg] and the plate thickness t [mm] when magnetized at a frequency of 800 Hz and a magnetic flux density of 1.0 T satisfy the following formula (4). Especially, it is preferable that the following formula (4-1) is satisfied.
W _10/800 ≦ 100 × t + 15 (4)
W _10/800 ≦ 100 × t + 13 (4-1)

B. Next, a method for producing a non-oriented electrical steel sheet according to the present invention will be described.
The manufacturing method of the non-oriented electrical steel sheet of the present invention has four embodiments. In the following, each embodiment will be described separately.

1. 1st embodiment The manufacturing method of the non-oriented electrical steel sheet of this embodiment has the following process (A), (B1), (C), and (D), It is characterized by the above-mentioned.
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B1) The hot-rolled steel sheet obtained by the hot-rolling rolling process is subjected to hot-rolled sheet annealing that is held in a temperature range of 750 ° C. or higher for 1 hour or more and 50 hours or less, and the fracture rate in the following falling weight bending test is 40. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing [falling weight bending test]
In the V-block method specified in JIS Z 2248: 2006, instead of “applying a metal fitting to the center of the test piece and gradually bending it to the specified shape by applying a test force,” “in the center of the test piece The test piece is a test in which the metal clamp is dropped from a height of 1.2 m and bent into a specified shape, and the bending angle is 90 ° and the inner radius is 5 mm.

  Hereinafter, each process in the manufacturing method of the non-oriented electrical steel sheet according to the present invention will be described.

(1) Hot rolling process The finishing temperature in a hot rolling process shall be 700 degreeC or more, and coiling temperature shall be 300 degreeC or more. If the finishing temperature is lower than the above range or the winding temperature is lower than the above range, minute damage is introduced to the steel sheet surface during hot rolling or winding, and fracture occurs in the latter pass of cold rolling. There is a case. Preferably, the finishing temperature is 750 ° C. or higher, and the winding temperature is 350 ° C. or higher. The upper limit of the finishing temperature and the coiling temperature need not be specified from the viewpoint of cold rollability, but the finishing temperature is preferably 1000 ° C. or less from the viewpoint of suppressing the yield reduction due to scale loss. The taking temperature is preferably 800 ° C. or lower.

  The thickness of the hot-rolled steel sheet is 1.4 mm or more and 3.5 mm or less. When the thickness of the hot-rolled steel sheet is less than the above range, the manufacturing cost of the hot rolling process increases. Preferably it is 1.6 mm or more. On the other hand, when the thickness of the hot-rolled steel sheet exceeds the above range, the cold rolling process takes a long time, and the manufacturing cost increases. Preferably it is 3.0 mm or less, More preferably, it is 2.5 mm or less.

(2) Hot-rolled sheet annealing step The hot-rolled sheet annealing temperature is 750 ° C or higher. If the hot-rolled sheet annealing temperature is less than the above range, the promotion of recrystallization is insufficient and it is difficult to obtain excellent magnetic properties.
On the other hand, when the hot-rolled sheet annealing temperature is excessively high, the fracture rate according to the falling weight bending test increases, and fracture may occur in the previous pass of cold rolling. Therefore, it is preferable to set the hot-rolled sheet annealing temperature to 850 ° C. or less.
In addition, even if the hot-rolled sheet annealing time is high, if the fracture rate by the falling weight bending test is 40% or less, it is possible to effectively prevent the fracture in the first pass of cold rolling.

  The hot-rolled sheet annealing time is 1 hour or more and 50 hours or less. When the hot-rolled sheet annealing time is less than the above range, recrystallization is not sufficiently promoted, and excellent magnetic properties may not be obtained. In addition, when the hot-rolled sheet annealing time is in the above range, the hot-rolled sheet annealing is performed by box annealing. However, if the hot-rolled sheet annealing time exceeds the above range, the productivity is lowered and the manufacturing cost increases. .

  The fracture rate of the hot-rolled annealed plate by the falling weight bending test is set to 40% or less. If the breaking rate exceeds the above range, the breaking may occur in the first pass of cold rolling. If the breaking rate is within the above range, it is possible to effectively prevent the breaking in the first pass of cold rolling even if the hot-rolled sheet annealing temperature is high as described above. The breaking rate is preferably 30% or less.

Other conditions in the hot-rolled sheet annealing step are not particularly specified.
Moreover, you may perform pickling before or after hot-rolled sheet annealing.

(3) Cold rolling step P, Sn, and Sb are contained in a total amount of 0.025% or more, and are generated when cold rolling a steel sheet in which the contents of P, Sn, and Sb are all 0.1% or less. As a result of investigating the fracture in detail, it was found that the fracture is most likely to occur when the steel sheet that has been reduced by 32 to 33% is cold-rolled. Specifically, when the rolling reduction in the first pass was 32 to 33%, the fracture occurred in the second pass, and when the total rolling reduction after the second pass was 32 to 33%, the fracture occurred in the third pass. The reason for this is not clear, but is presumed to be as follows.
That is, when the structure of the steel sheet after rolling was examined in detail, the result that the processed structure introduced into the steel sheet that had been reduced by 32 to 33% was the most uneven was obtained. From this fact, the reason why the steel sheet having a rolling reduction of about 32 to 33% is most likely to break when cold-rolled is that stress is concentrated during cold-rolling due to the presence of a non-uniform work structure. It is guessed.
Therefore, by setting the cold rolling reduction ratio so as to avoid such a condition, it is possible to effectively prevent breakage during cold rolling. Specifically, by adopting a pass schedule that sets the rolling reduction of the first pass to 10% to 30% and the total rolling reduction after the second pass is 35% to 60%, avoiding breakage in the previous pass. it can. Here, the lower limit of the rolling reduction in the first pass is from the viewpoint of productivity, the upper limit is from the viewpoint of suppressing breakage in the rolling of the first pass, and the lower limit of the total rolling reduction after the second pass is a viewpoint of avoiding the above-described conditions. Therefore, the upper limit is defined from the viewpoint of equipment load. Preferably, the rolling reduction in the first pass is 15% to 28%, and the total rolling reduction after the second pass is 38% to 55%. More preferably, the rolling reduction in the first pass is 15% or more and 25% or less, and the total rolling reduction after the second pass is 40% or more and 55% or less.

In the cold rolling step, the finished sheet thickness may be obtained by one cold rolling, or the finished sheet thickness may be obtained by two cold rollings sandwiching the intermediate annealing.
In the latter case, two cold rollings only need to satisfy the above conditions, and the intermediate annealing conditions may satisfy the same conditions as the hot rolled sheet annealing conditions.

  The thinner the cold-rolled steel sheet is, the more iron loss is reduced. Preferably it is 0.33 mm or less, More preferably, it is 0.30 mm or less. On the other hand, excessively thinning significantly reduces the productivity of steel plates and motors, so the plate thickness is 0.10 mm or more. Preferably it is 0.15 mm or more, More preferably, it is 0.20 mm or more.

  Other conditions in the cold rolling process are not particularly defined.

(4) Finish annealing process The conditions in the finish annealing process are not particularly specified, but the annealing temperature is preferably 900 ° C. or more from the viewpoint of promoting sufficient grain growth and ensuring excellent magnetic properties. The annealing time is preferably 1 second or longer. On the other hand, the annealing temperature is preferably 1180 ° C. or less, and the annealing time is preferably 300 seconds or less, from the viewpoint of load on equipment and manufacturing cost.

2. 2nd embodiment The manufacturing method of the non-oriented electrical steel sheet of this embodiment has the following process (A), (B2), (C), and (D), It is characterized by the above-mentioned.
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B2) The hot-rolled steel sheet obtained by the hot-rolling step is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. or higher for 1 second or more and 600 seconds or less, and the breaking rate in the falling weight bending test is 40. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing

  In addition, since it is the same as that of the said 1st embodiment about a hot rolling process, a cold rolling process, and a finish annealing process, description here is abbreviate | omitted. Hereinafter, the other process in the manufacturing method of the non-oriented electrical steel sheet of this embodiment is demonstrated.

(Hot rolled sheet annealing process)
The hot-rolled sheet annealing temperature is 850 ° C. or higher. If the hot-rolled sheet annealing temperature is less than the above range, the promotion of recrystallization is insufficient and it is difficult to obtain excellent magnetic properties.
On the other hand, when the hot-rolled sheet annealing temperature is excessively high, the fracture rate according to the falling weight bending test increases, and fracture may occur in the previous pass of cold rolling. Therefore, it is preferable to set the hot-rolled sheet annealing temperature to 1150 ° C. or less.
In addition, even if the hot-rolled sheet annealing time is high, if the fracture rate by the falling weight bending test is 40% or less, it is possible to effectively prevent the fracture in the first pass of cold rolling.

  The hot-rolled sheet annealing time is 1 second to 600 seconds. When the hot-rolled sheet annealing time is less than the above range, recrystallization is not sufficiently promoted, and excellent magnetic properties may not be obtained. Also, when the hot-rolled sheet annealing time is in the above range, it is normal to perform hot-rolled sheet annealing by continuous annealing, so if the hot-rolled sheet annealing time exceeds the above range, the equipment becomes longer and the productivity is increased. Cause a decline.

  The fracture rate of the hot-rolled annealed plate by the falling weight bending test is set to 40% or less. If the breaking rate exceeds the above range, the breaking may occur in the first pass of cold rolling. If the breaking rate is within the above range, it is possible to effectively prevent the breaking in the first pass of cold rolling even if the hot-rolled sheet annealing temperature is high as described above. The breaking rate is preferably 30% or less.

Other conditions in the hot-rolled sheet annealing step are not particularly specified.
Moreover, you may perform pickling before or after hot-rolled sheet annealing.

3. 3rd embodiment The manufacturing method of the non-oriented electrical steel sheet of this embodiment has the following process (A), (B3), (C), and (D), It is characterized by the above-mentioned.
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B3) Hot-rolled steel sheet obtained by the hot-rolled rolling process is subjected to hot-rolled sheet annealing that is held in a temperature range of 750 ° C. or higher and 850 ° C. or lower for 1 hour or more and 50 hours or less to form a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing

  In addition, since it is the same as that of the said 1st embodiment about a hot rolling process, a cold rolling process, and a finish annealing process, description here is abbreviate | omitted. Hereinafter, the other process in the manufacturing method of the non-oriented electrical steel sheet of this embodiment is demonstrated.

(Hot rolled sheet annealing process)
The hot-rolled sheet annealing temperature is 750 ° C. or higher and 850 ° C. or lower. If the hot-rolled sheet annealing temperature is less than the above range, the promotion of recrystallization is insufficient and it is difficult to obtain excellent magnetic properties. On the other hand, when the hot-rolled sheet annealing temperature exceeds the above range, the fracture rate by the drop weight bending test becomes high, and fracture may occur in the previous pass of cold rolling.

  The hot-rolled sheet annealing time and other conditions are the same as those in the first embodiment, and a description thereof is omitted here.

4). Fourth Embodiment A method for producing a non-oriented electrical steel sheet according to this embodiment includes the following steps (A), (B4), (C), and (D).
(A) The slab having the above-described chemical composition is subjected to hot rolling at a finishing temperature of 700 ° C. or higher and a winding temperature of 300 ° C. or higher to obtain a hot rolled steel plate having a thickness of 1.4 mm to 3.5 mm. Hot rolling process;
(B4) Hot-rolled steel sheet obtained by the above hot-rolled rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. to 1150 ° C. for 1 second to 600 seconds to obtain a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the reduction ratio of the first pass is 10% or more and 30% or less, and the total reduction ratio of the first pass and the second pass is 35% or more and 60%. A cold rolling step for forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process. Finish annealing process for finishing annealing

  In addition, since it is the same as that of the said 1st embodiment about a hot rolling process, a cold rolling process, and a finish annealing process, description here is abbreviate | omitted. Hereinafter, the other process in the manufacturing method of the non-oriented electrical steel sheet of this embodiment is demonstrated.

(Hot rolled sheet annealing process)
The hot-rolled sheet annealing temperature is 850 ° C. or higher and 1150 ° C. or lower. If the hot-rolled sheet annealing temperature is less than the above range, the promotion of recrystallization is insufficient and it is difficult to obtain excellent magnetic properties. On the other hand, when the hot-rolled sheet annealing temperature exceeds the above range, the fracture rate by the drop weight bending test becomes high, and fracture may occur in the previous pass of cold rolling.

  The hot-rolled sheet annealing time and other conditions are the same as those in the second embodiment, and a description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

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

[Example 1]
A slab having the chemical composition shown in Table 1 below was hot rolled at a finishing temperature of 850 ° C. and a coiling temperature of 600 ° C. to obtain a hot-rolled steel plate having a thickness of 2.0 mm, and pickled. These pickled steel sheets were subjected to hot-rolled sheet annealing held at 950 ° C. for 60 to 120 seconds to make the average crystal grain size uniform at 100 μm. These annealed sheets were cold-rolled with a reduction ratio of 25% for the first pass and a total reduction ratio of 2% after the second pass being 45% to obtain cold-rolled steel sheets having a finished sheet thickness of 0.30 mm. These cold-rolled steel sheets were subjected to finish annealing that was maintained at a temperature of 1030 ° C. for 30 seconds to obtain non-oriented electrical steel sheets having an average crystal grain size of 89 to 129 μm.

For these non-oriented electrical steel sheets, the iron loss W _10/800 when magnetized at a frequency of 800 Hz and a magnetic flux density of 1.0 _T and the magnetic flux density B ₅₀ when magnetized at a magnetizing force of 5000 A / m were measured.
Steel plate No. 1 to 20 is 100 × t + 15 = 45 in the above formula (4).
Here, the steel plate No. 1 is a reference material P, Sn, Sb is hardly added, the B ₅₀ and the steel sheet No. The difference ΔB ₅₀ between 2 and 20 B ₅₀ was calculated, and the magnitude of the B ₅₀ improvement effect due to the addition of P, Sn, and Sb was evaluated. This means that the greater the ΔB ₅₀ is, the greater the effect of improving B ₅₀ by the addition of P, Sn, and Sb. Further, since ΔB ₅₀ increases as the P, Sn, and Sb content increases, X is calculated from the following equation (5) in consideration of this point, and X is set to 0 or more as a target characteristic.
X = ΔB ₅₀ −0.4 × (P + Sn + Sb−0.01) (5)

Moreover, the falling weight bending test was performed on the steel sheet after the hot-rolled sheet annealing to measure the fracture rate (n = 20).
Table 2 shows the rupture rate and magnetic properties in the falling weight bending test.

Steel plate No. No. 13 had a low S content. No. 14 had a low P + Sn + Sb content. No. 15 had a high Nb and Zr content. Since No. 16 had a high As content, the effect of improving B ₅₀ by adding desired P, Sn, and Sb could not be obtained. Steel plate No. No. 17 had a high Ti, V, N content and S + As + Nb + Ti + V + Zr + N content. No. 18 had a high S + As + Nb + Ti + V + Zr + N content. No. 19 had a high S content. Since No. 10 had high Nb and Ti contents, it was not possible to obtain the effect of improving B ₅₀ by addition of desired P, Sn, and Sb, and part of the desired iron loss could not be obtained. .
Steel plate No. As shown in 5 to 12, even if Ca, REM, Mg, Cu, Ni, Cr, and B were contained, the magnetic properties were not adversely affected as long as they were within a predetermined range.

[Example 2]
A slab having a chemical composition shown in Table 3 below was hot rolled into a steel sheet having a thickness of 1.7 mm by hot rolling at a finishing temperature of 650 to 850 ° C. and a winding temperature of 280 to 600 ° C. These hot-rolled steel sheets are subjected to continuous annealing-type hot-rolled sheet annealing that is held at a temperature range of 950 to 1200 ° C. for 30 to 300 seconds, and then pickled or held at a temperature of 800 ° C. for 20 hours after pickling. Box-type hot-rolled sheet annealing was performed. These annealed sheets are cold-rolled so that the rolling reduction in the first pass is 20 to 32%, the temperature of the steel plate at the start of the second pass is 30 to 60 ° C., and the total rolling reduction after 2 passes is 33 to 45%. Thus, a cold-rolled steel sheet having a finished sheet thickness of 0.25 mm was obtained. At this time, a part was broken. The cold-rolled steel sheet that did not break was subjected to finish annealing that was held at 980 ° C. for 60 seconds to obtain a non-oriented electrical steel sheet having an average crystal grain size of 85 to 92 μm.

The iron loss W _10/800 and the magnetic flux density B ₅₀ of these non-oriented electrical steel sheets were measured.
Steel plate No. 21 to 26 are 100 × t + 15 = 40 in the above-described formula (4).
Here, P, Sn, and Sb are hardly added to the composition B, and only the P, Sn, and Sb contents are different from the composition A, and the improvement effect of B ₅₀ by P, Sn, and Sb is calculated. It corresponds to the reference material. Using the composition B, the steel plate No. 21 to 26 were manufactured under the same manufacturing conditions, and used as reference materials. B _{50 of} each reference material and steel plate No. The difference ΔB ₅₀ between 21 and 26 and B ₅₀ was calculated. Further, X is calculated from the above formula (5), and the target characteristic is that X is 0 or more.

Moreover, the falling weight bending test was performed on the steel sheet after the hot-rolled sheet annealing at room temperature to measure the fracture rate (n = 20).
The production conditions and measurement results are shown together in Table 4.

  Steel plate No. Since No. 21 was hot rolling conditions outside a predetermined range, it broke in the latter pass of cold rolling. Steel plate No. Since No. 22 had a high hot-rolled sheet annealing temperature, the fracture rate in the drop weight bending test increased, and fracture occurred in the first pass of cold rolling. Steel plate No. Nos. 23 and 24 were broken because the cold rolling conditions were outside the predetermined range.

Claims (7)

A method for producing a non-oriented electrical steel sheet comprising the following steps (A), (B1), (C) and (D):
(A) By mass%, Si: 4.0% or less, sol. Al: 4.0% or less, Mn: 4.0% or less, P: 0.1% or less, Sn: 0.1% or less, Sb: 0.1% or less, S: 0.0005% or more and 0.0050 % Or less, C: 0.0050% or less, As: 0.0050% or less, Nb: 0.0030% or less, Ti: 0.0030% or less, V: 0.0030% or less, Zr: 0.0030% or less And N: 0.0050% or less, with the balance consisting of Fe and impurities, and having a chemical composition satisfying the following formulas (1) to (3) , finishing temperature: 700 ° C. or more and winding temperature : Hot rolling step of hot rolling at 300 ° C. or higher to obtain a hot rolled steel sheet having a thickness of 1.4 mm to 3.5 mm;
(B1) The hot-rolled steel sheet obtained by the hot rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 750 ° C. or higher for 1 hour or more and 50 hours or less. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the rolling reduction ratio of the first pass is 10% to 30%, and the total rolling reduction ratio of the first pass and the second pass is 35% to 60%. A cold rolling step of forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process Finish annealing process that performs finish annealing.
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
P + Sn + Sb ≧ 0.025 (2)
S + As + Nb + Ti + V + Zr + N ≦ 0.018 (3)
(Here, each element symbol in the formulas (1) to (3) indicates the content (unit: mass%) of each element in the steel.)
[Falling weight bending test]
In the V-block method specified in JIS Z 2248: 2006, instead of “applying a metal fitting to the center of the test piece and gradually bending it to the specified shape by applying a test force,” “in the center of the test piece The test piece is a test in which the metal clamp is dropped from a height of 1.2 m and bent into a specified shape, and the bending angle is 90 ° and the inner radius is 5 mm.   The chemical composition is one type selected from the group consisting of Cr: 0.2% or less, Cu: 0.2% or less, and Ni: 0.2% or less in mass% instead of a part of the Fe. Or it contains 2 or more types, The manufacturing method of the non-oriented electrical steel sheet according to claim 1 characterized by things.   The chemical composition is one type selected from the group consisting of Ca: 0.01% or less, Mg: 0.01% or less, and REM: 0.01% or less in mass%, instead of a part of the Fe. Or the 2 or more types are contained, The manufacturing method of the non-oriented electrical steel sheet of Claim 1 or Claim 2 characterized by the above-mentioned.   The non-directional property according to any one of claims 1 to 3, wherein the chemical composition contains B: 0.01% or less in mass% instead of a part of the Fe. A method for producing electrical steel sheets. A method for producing a non-oriented electrical steel sheet comprising the following steps (A), (B2), (C) and (D):
(A) A slab having the chemical composition according to any one of claims 1 to 4 is subjected to hot rolling at a finishing temperature of 700 ° C or higher and a winding temperature of 300 ° C or higher to obtain a sheet thickness of 1. A hot rolling step for producing a hot rolled steel sheet of 4 mm to 3.5 mm;
(B2) The hot-rolled steel sheet obtained by the hot-rolling rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. or higher for 1 second or more and 600 seconds or less. % Of hot-rolled sheet annealing process,
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the rolling reduction ratio of the first pass is 10% to 30%, and the total rolling reduction ratio of the first pass and the second pass is 35% to 60%. A cold rolling step of forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process Finish annealing process that performs finish annealing.
[Falling weight bending test]
In the V-block method specified in JIS Z 2248: 2006, instead of “applying a metal fitting to the center of the test piece and gradually bending it to the specified shape by applying a test force,” “in the center of the test piece The test piece is a test in which the metal clamp is dropped from a height of 1.2 m and bent into a specified shape, and the bending angle is 90 ° and the inner radius is 5 mm. A method for producing a non-oriented electrical steel sheet comprising the following steps (A), (B3), (C) and (D):
(A) A slab having the chemical composition according to any one of claims 1 to 4 is subjected to hot rolling at a finishing temperature of 700 ° C or higher and a winding temperature of 300 ° C or higher to obtain a sheet thickness of 1. A hot rolling step for producing a hot rolled steel sheet of 4 mm to 3.5 mm;
(B3) Hot-rolled steel sheet obtained by the hot-rolled rolling process is subjected to hot-rolled sheet annealing that is maintained in a temperature range of 750 ° C. or higher and 850 ° C. or lower for 1 hour or more and 50 hours or less to form a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the rolling reduction ratio of the first pass is 10% to 30%, and the total rolling reduction ratio of the first pass and the second pass is 35% to 60%. A cold rolling step of forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process Finish annealing process that performs finish annealing. A method for producing a non-oriented electrical steel sheet comprising the following steps (A), (B4), (C) and (D):
(A) A slab having the chemical composition according to any one of claims 1 to 4 is subjected to hot rolling at a finishing temperature of 700 ° C or higher and a winding temperature of 300 ° C or higher to obtain a sheet thickness of 1. A hot rolling step for producing a hot rolled steel sheet of 4 mm to 3.5 mm;
(B4) Hot-rolled steel sheet obtained by the hot-rolled rolling process is subjected to hot-rolled sheet annealing that is held at a temperature range of 850 ° C. to 1150 ° C. for 1 second to 600 seconds to obtain a hot-rolled annealed sheet. Plate annealing process;
(C) To the hot-rolled annealed sheet obtained by the hot-rolled sheet annealing step, the rolling reduction ratio of the first pass is 10% to 30%, and the total rolling reduction ratio of the first pass and the second pass is 35% to 60%. A cold rolling step of forming a cold rolled steel sheet having a thickness of 0.10 mm to 0.35 mm by performing multi-pass cold rolling; and (D) a cold rolled steel sheet obtained by the cold rolling process Finish annealing process that performs finish annealing.