JP2016003371A - Non-oriented magnetic steel sheet having good entire circumferential magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-oriented magnetic steel sheet that is excellent in entire circumferential direction magnetic property and that is good in surface quality.SOLUTION: The non-oriented magnetic steel sheet has a steel content satisfying C: 0.0030% or less, Si: 2.0 to 3.0%, Al: 1.0 to 2.0%, Mn: 0.10 to 1.0%, and 3.5≤Si+Al≤4.75% and has a magnetic flux density (B50) in a direction forming 45° with respect to the rolling direction of the steel sheet of 0.83 or more of the saturation magnetic flux density Bs (=2.1561-0.0413[Si]-0.0198[Mn]-0.0604[Al]) of the steel sheet. The steel sheet is produced by subjecting the steel sheet to a hot-rolled steel strip annealing at 950 to 1050°C for 30 to 90 seconds to make the circle-equivalent crystal grain average diameter after the annealing of 100 μm or more and the cold-rolling ratio of 55 to 90%, and subjecting the steel sheet to a finish annealing at 950°C or more for 20 to 120 seconds.

Description

  The present invention relates to a non-oriented electrical steel sheet mainly used as an iron core of rotating electrical equipment, and particularly to an iron core material used in the field of highly efficient rotating equipment.

  In the field of transportation equipment in recent years, electrical steel sheets with excellent magnetic properties have attracted attention and are used as materials for electric drive equipment. In these equipment, in order to increase efficiency, the frequency is higher than that of commercial use. There is a need for a magnetic steel sheet that is improved in iron loss characteristics and has a high magnetic flux density that contributes to downsizing, in particular, a good electrical steel sheet in the entire circumferential direction.

Electrical steel sheets used for equipment in this field are produced metallurgically using primary recrystallization, and thus are included in the category of non-oriented electrical steel sheets and are mainly used as iron cores for rotating equipment. Its production is based on a circle, and it is desirable to produce it by integral punching in order to reduce the cost of drive equipment and improve productivity. In general, the magnetic properties within the rolled steel sheet surface are uniform and good in each direction. In other words, there is a strong demand for non-oriented electrical steel sheets having excellent magnetic properties in the entire circumferential direction.
However, in the current metallurgy, industrial production of such a cube texture ({100} <0vw>) with good magnetic properties cannot be realized.

  By the way, in view of the history of non-oriented electrical steel sheets, the production of cold-rolled non-oriented electrical steel sheets higher than 35A440 and 50A470 in Japanese Industrial Standards (JIS C 2552) is (x) magnetic properties in terms of metallurgy. (Y) Countermeasures against magnetic aging, (z) Countermeasures against ridging (surface properties), as the production structure changes from production of hot-rolled material by ingot casting-bundling rolling to production by continuous casting. It was the development of a method to do at cost.

Regarding the magnetic aging countermeasure of (y), at present, the ultra-low C melting technology necessary for suppression of magnetic aging has been established by the development of refining technology.
That is, to suppress magnetic aging, it is essential to reduce the C content of the final product. Either high C in the melting stage is reduced to extremely low C in the process up to the final product, or is extremely low C in the melting stage. In the initial stage of production of the cold-rolled non-oriented electrical steel sheet, since it was technically difficult to achieve extremely low C at the melting stage, it was decarburized in the intermediate annealing process or the final annealing process. At present, ultra-low C melting technology has been established with the development of refining technology.

However, other developments have the following problems.
The magnetic properties of the non-oriented electrical steel sheet (x) include magnetic flux density (B50) and iron loss, and both are required to be excellent.
Conventionally, magnetic properties are secured by adjusting the final annealing atmosphere, controlling the texture, ensuring good grain growth, and reducing domain wall pinning impurities. Specifically, they were bright final annealing, optimization of the cold rolling rate, (hot rolled steel strip) annealing, and reduction of impurity elements, respectively.
Further, the iron loss includes a reduction in hysteresis loss due to a reduction in plate thickness, a reduction in eddy current loss due to an increase in specific resistance, a reduction in impurities, a reduction in grain boundaries, and the like. However, the reduction of history loss due to texture improvement has reached its limit.
However, the evaluation of the magnetic properties of the non-oriented electrical steel sheet at the material stage was performed by adding the two directions of the rolling direction and the direction perpendicular to the rolling direction. And only in the direction perpendicular to it) and evaluation with actual electrical equipment (reflecting all directions of the material) may not match.

  In recent years, there has been a strong demand for punching of non-oriented electrical steel sheets in an integrated manner in order to further improve the characteristics of rotating equipment and further reduce costs. In this case, the non-oriented electrical steel sheet is required to have excellent all-around characteristics and good punchability. Conventionally, it was possible to obtain a non-oriented electrical steel sheet having uniform circumferential characteristics, but it had a random orientation in the rolled surface in the <111> direction, which was inferior in texture, and its absolute value characteristics were inferior. .

Furthermore, with an increase in demand for higher efficiency of electric motors, use in a higher frequency range has been promoted, and there has been a strong demand especially for electric motors used in transportation equipment.
In order to improve the iron loss at a higher frequency than before, in order to reduce the eddy current loss, in addition to reducing the thickness of the plate, addition of an element that contributes to increasing the specific resistance (the additive element is basically However, if the ratio of elements other than iron increases, the saturation magnetic flux density decreases, so the relationship between iron loss and magnetic flux density is in a trade-off relationship and faces technical difficulties. .
Thus, there has been a demand for providing a non-oriented electrical steel sheet that is superior in the all-round magnetic characteristics, which has not been conventionally obtained.

The ridging in (z) is caused by columnar crystals at the slab stage, and is a phenomenon in which grains in a specific direction behave like a single crystal and the structure is aligned. is there. Magnetic steel sheets must be avoided because they cause a decrease in the occupancy rate. This ridging occurs in a high-grade non-oriented electrical steel sheet having an α single phase structure without transformation.
In addition, ridging is also closely related to carbon (C). If C is high, a γ phase is present during casting, so the columnar crystal ratio is reduced and ridging does not occur. Since ingot casting was performed at the beginning when extremely low C was possible at the melting stage, there was an ingot forming (bundling) process, columnar crystals were destroyed, and no ridging was generated. After that, when the continuous casting is performed and the lump process is omitted, ridging is still a problem in the case of a high-grade non-oriented electrical steel sheet that becomes α single phase by extremely low C in melting.
Therefore, reduction of the columnar crystal ratio was attempted by applying electromagnetic stirring, and ridging was improved except in special cases (when the cold rolling rate is high, recrystallization in the hot rolled steel strip is insufficient, etc.). Yes.

Here, it describes about the prior art regarding this invention.
Patent Document 1 discloses a method of punching a non-oriented electrical steel sheet having excellent roundness of Si: 4% or less and Al: 2% or less. The manufacturing method and electromagnetic characteristics are specifically described. Is not mentioned. Moreover, the reason for the range containing Al is only defined by the addition cost.
Also, Patent Document 2 discloses a similar technique. In this case, the hot-rolled sheet annealing is a box shape.
Patent Document 3 discloses a non-oriented electrical steel sheet that is subjected to nitriding treatment and has different hardness in the thickness direction.
In Patent Document 4, Al is 0.2 to 3.0%, but the maximum is 0.60% in Examples, and no further mention is made regarding addition beyond that.

Japanese Patent Laid-Open No. 10-24333 JP 2001-059145 A JP 2008-031490 A JP 2009-291346 A JP-A-53-066816 Japanese Patent Publication No. 06-051889 JP 2008-260996 A

As a technique for producing a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, a method based on a double cold rolling method in which intermediate annealing is sandwiched in the middle is known. Patent Document 5 discloses such a method, but in this method, the annealing time is as short as 2 minutes and the example is very long as 5 minutes in terms of the temperature and time of intermediate annealing and finish annealing. Longer time means lower productivity and higher cost. Furthermore, the primary cold rolling rate is set to a fairly wide range of 20% or more, but in the low rolling rate region, the texture is the same as in the case where cold rolling is not performed, and the meaning of the primary cold rolling rate is Presumed to be absent.
That is, when α single-phase electrical steel sheet containing a large amount of Si and Al and having a small amount of C is cast by ordinary continuous casting and is produced by the double cold rolling method, it is said to be ridging when the primary cold rolling rate is low. Surface defects occur. This ridging occurs due to a high columnar crystal ratio, a low primary cold rolling rate, a high final cold rolling rate, incomplete recrystallization before cold rolling, a high tension during annealing, and the degree thereof becomes remarkable.
Further, in this method by cold rolling twice, the magnetic properties in the direction of 45 ° with respect to the rolling direction are not good, rather they are deteriorated, and the properties in the entire circumferential direction are also poor. The reason for this is the development of the so-called Goss orientation. Also, it is often avoided because there are two cold rolling and the cost increases.

  Therefore, the present invention is excellent in the magnetic properties in the entire circumferential direction and the surface properties in the method for producing the electrical steel sheet by one cold rolling without performing the cold rolling twice in order to reduce the cost. It aims at making it possible to obtain a non-oriented electrical steel sheet with favorable.

Of these, the inventors have made extensive studies on the texture control that requires the most metallurgical knowledge, and in the true sense that the magnetic properties are uniformly uniform in the entire circumferential direction, close to the cube texture. Of "Non-oriented electrical steel sheet".
The inventors diligently studied, and by adding a large amount of Al and optimizing the manufacturing process conditions, the texture control improves the magnetic flux density in the entire circumferential direction and can secure iron loss. It has been found that the ratio of the magnetic flux density (B50) in the direction of 45 ° to the saturation magnetic flux density Bs (T), which represents the magnetic properties in the entire circumferential direction of the steel sheet, can be a certain value or more.
That is, the texture succeeded in forming so-called split Goss ({101} <272> to {101} <010>) by adding a large amount of Al and optimizing the process conditions.
The recrystallized texture obtained by the cold rolling ratio of the present invention has split Goss ({101} <272> to {101} <010>) as the main orientation, and the all-around magnetic characteristics are improved.
Further, it has been found that there is no risk of ridging with respect to ridging by sufficiently recrystallizing before cold rolling, that is, by increasing the average particle size after hot-rolled sheet annealing to 100 μm or more.
The gist of the present invention is as follows.

[1] By mass%, C: 0.0030% or less, Si: 2.0 to 3.0%, Al: 1.0 to 2.0%, Mn: 0.10 to 1.0%, and 3 0.5 ≦ Si + Al ≦ 4.75%, consisting of the balance Fe and unavoidable impurities, and the magnetic flux density (B50) in the direction of 45 ° with the rolling direction of the steel plate is that of the steel plate represented by the following formula (1). A non-oriented electrical steel sheet having an excellent magnetic property in the entire circumferential direction, having a saturation magnetic flux density Bs (T) of 0.830 or more.
Bs = 2.1561−0.0413 [Si] −0.0198 [Mn] −0.0604 [Al] (1)
Here, the element with [] represents the content (% by mass) of each element.

[2] By mass%, C: 0.0030% or less, Si: 2.0 to 3.0%, Al: 1.0 to 2.0%, Mn: 0.10 to 1.0%, and 3 .5 ≦ Si + Al ≦ 4.75%, a steel slab consisting of the balance Fe and inevitable impurities is manufactured by a continuous casting method, then hot-rolled to the steel slab, and then hot-rolled steel strip annealed And performing a single cold rolling, finish annealing to produce a non-oriented electrical steel sheet, subjecting the hot rolled steel strip annealing to 950-1050 ° C. for 30-90 seconds, The circle-equivalent crystal grain average diameter after annealing is set to 100 μm or more, the rolling rate of the cold rolling is set to 55 to 90%, and then the finish annealing is performed at 950 ° C. or more for 20 to 120 seconds. A method for producing a non-oriented electrical steel sheet having excellent directional magnetic properties.

  By applying the present invention, an electrical steel sheet having excellent all-round magnetic properties and good surface properties can be produced at low cost. By using this electromagnetic steel sheet, it is possible to manufacture a rotating device with good efficiency.

  Hereinafter, the reasons for limiting the technical requirements characteristic of the non-oriented electrical steel sheet and the manufacturing method thereof according to the present invention will be sequentially described. In the following description, the content of each element is expressed by mass%, and the description of mass is omitted.

<Chemical composition of steel>
If C is more than 0.0030%, magnetic aging occurs, so 0.0030% or less. When C is contained in an amount exceeding 0.0030% to 0.005%, deterioration of magnetic properties (particularly iron loss) is not observed in the aging evaluation process for about 400 hours, but it exceeds 10,000 hours. Magnetic properties deteriorate with prolonged aging treatment. In particular, in a high-grade electrical steel sheet used for transportation equipment, the upper limit of C is set to 0.0030% in consideration of the point that the magnetic aging is required to be completely eliminated. If 0.0030% or less, magnetic aging does not occur, but iron loss is deteriorated as an impurity, so C is preferably 0.0015% or less.

C is made 0.0030% or less at the stage of slab during production.
If it exceeds 0.0030% at the slab stage, it must be decarburized to 0.0030% or less before the final product.
As a decarburization method, there is a method of performing hot-rolled sheet annealing or final annealing (finish annealing) in a humid atmosphere. However, decarburization in hot-rolled sheet annealing is very inefficient because the plate thickness is thick. is there. In addition, since decarburization in final annealing (finish annealing) is performed after pickling, in the case of a high alloy steel such as the present invention (a high Si and Al content has a strong affinity for oxygen), the surface is oxidized. The layer is formed thick, the high magnetic field characteristics of the final product are inferior, and more scum (dirt) is generated during cold rolling, so it should be avoided.
For this reason, in the manufacturing method of the present invention, the C amount in the melting stage is set to 0.0030% or less which does not particularly require decarburization in the intermediate process.

  Si is added to increase the specific resistance and improve the iron loss. If it is less than 2.0%, good iron loss cannot be obtained, and if it exceeds 3.0%, cold rolling becomes extremely difficult and it is not suitable for industrial production. A preferable range is 2.4 to 2.8%.

Al, like Si, is added to increase the specific resistance and improve iron loss. Furthermore, in the present invention, a great effect is exerted on the texture control, and if it exceeds 2.0%, the improvement of the magnetic properties in the circumferential direction due to the texture improvement effect is lowered and the cost is increased. When the content is less than 1.0%, the above effects are small, and when the content exceeds 2.0%, deterioration of castability and wear of the cold rolling roll become remarkable.
In the case of Al, the specific resistance is improved but the workability is secured rather than simply increasing the Si content. By the way, Patent Document 2 discloses, as already mentioned, that the hardness increases only with Si, and if a part of Si is replaced with Al, the specific resistance is secured and the remarkable increase in hardness is suppressed. However, the hot-rolled sheet annealing conditions are completely different, and the viewpoint of improving the texture is lacking. A preferable range is 1.5 to 1.9%.

  When Mn is less than 0.10%, workability is inferior, and when it is more than 1.0%, Mn- (O, S) -based inclusions are formed, grain growth is hindered, and iron loss is inferior. Further, when a large amount of Mn is contained, there is a pickup of C from ferromanganese alloy iron, and the value of C often exceeds 0.0030%, so that refining productivity is extremely inferior. 0.1 to 0.3%.

In order to improve the specific resistance, it is necessary to appropriately contain Si and Al, and in order to improve the cold rolling property, it is necessary to appropriately maintain the balance between the Si amount and the Al amount. Further, the total content of Si and Al (Si + Al) is set to 3.5% ≦ Si + Al ≦ 4.75%. From the viewpoint of magnetic properties, the upper limit of Si is set to 3.0% and the upper limit of Al is set to 2.0%. However, if these elements exceed 4.75% in total, workability deteriorates significantly, and cold rolling is performed. Becomes difficult and cannot be industrially produced.

Other elements other than those described above are as shown below.
Addition of Sn is not essential in the single cold rolling method as in the present invention. This is because Sn increases the Goss orientation texture, which is slightly different from the split goss of the present invention and does not contribute much to the improvement of the characteristics in the entire circumferential direction, which is the gist of the present invention. Usually, the content is about 0.01% as an inevitable impurity.
Although addition of B is also conceivable, since it is an α single phase in the component range of the present invention, B forms a fine precipitate with N and inhibits grain growth, so it is not added. Even when contained as an impurity, the content is preferably 0.0005% or less.

  In addition, N, S, Cu, Cr, Ni, Mo, Sb, P, W, O, Ti, Nb, As, Mg, Ca, Se, V, Bi, Zr, etc. may be contained as inevitable impurities. However, from the viewpoint of grain growth, it is preferable that these elements are as few as possible. However, in industrial production, their inclusion is allowed as follows from the viewpoint of cost and the like.

N binds to Al and Ti to form precipitates, so it is desirable that N be 0.0030% or less. For the same reason, S is preferably 0.003% or less.
Cu, Cr, Ni, and Mo are unavoidably contained in industrial production at about 0.02% or less. If it is this level, the magnetic characteristic will not deteriorate significantly.
Sb is not suitable for industrial production because it has the same texture effect as Sn but is toxic and inhibits the adhesion of the insulating coating. In industrial production, it is unavoidable to contain 0.01% or less.

If P is 0.04% or less, neither magnetic characteristics nor mechanical characteristics are deteriorated. For mechanical strength adjustment and the like, P may contain 0.04% at the upper limit. If it is that degree, there will be no influence in particular on the magnetic characteristic of this invention.
W and O are preferably 0.005% or less for securing magnetic properties (particularly iron loss). In the case of high alloy steel containing a large amount of Si and Al as in the present invention, O is 0.003% or less unless there is a special melting, and there is no inconvenience.
Furthermore, in the production of ordinary non-oriented electrical steel sheets, Ti, Nb, As, Mg, Ca, Se, V, Bi, and Zr are recognized as harmful elements, but each may be 0.003% or less. preferable.

<Magnetic properties of steel sheet>
The iron loss of an electrical steel sheet is composed of hysteresis loss and eddy current loss. Hysteresis loss depends largely on crystal orientation, impurity content, crystal grain size, internal strain, etc., and eddy current loss depends largely on plate thickness, specific resistance, and the like. The object of the present invention is to improve the crystal orientation and (extinguishment) as main factors in the plate thickness (0.65 to 0.20 mm) in the range of production in the past. Of course, it is necessary to contain Si and Al in order to improve the specific resistance, and to keep the balance between the Si amount and the Al amount appropriately in order to improve the cold rolling property.

<Relationship between the rolling direction of the steel strip and the magnetic flux density in the direction of 45 ° (45 ° direction B50) and the saturation magnetic flux density Bs>
As already mentioned, in non-oriented electrical steel sheets used in rotating machines, if the magnetic properties depend greatly on the direction relative to the rolling direction (the magnetic properties differ in the rolling direction), the magnetic properties as a whole are good. However, the flow of magnetic flux in the device core becomes non-uniform, and the performance as a device incorporating it becomes inferior.
For this reason, in addition to good absolute value characteristics, it is required to reduce the dependence of magnetic characteristics on the rolling direction. In the present invention, the magnetic flux density in the direction of 45 ° with respect to the rolling direction having the least magnetic properties (the magnetic flux density when excited with a magnetizing force of 5000 A / m in the direction of 45 ° with respect to the rolling direction, hereinafter referred to as “45 °. Focusing on the rolling direction dependency of the magnetic properties, the ratio of the 45 ° direction B50 to the saturation magnetic flux density Bs (T) of the steel sheet represented by the following formula (1) ( 45 ° direction B50 / Bs).
The upper limit of the value of this ratio should be as close as possible to 1, and the lower limit is 0.830. Preferably, it is 0.850.
Bs = 2.1561−0.0413 [Si] −0.0198 [Mn] −0.0604 [Al] (1)
Here, the element with [] represents the content (% by mass) of each element.
This equation (1) is based on Patent Document 7, but more precisely, the Mn content must be taken into consideration, and this equation in which the Mn term is added to the equation of Patent Document 7 is applied.

<Production conditions>
The non-oriented electrical steel sheet described above can be manufactured by the following manufacturing method.
(Slab casting)
Casting for obtaining a steel slab for a non-oriented electrical steel sheet having the above chemical components is a conventional continuous casting. In order to facilitate the heating of the slab, it is not impeded to apply the lump method to the continuous casting slab, but it should be avoided as much as possible because the cost increases as described above. Therefore, the block method is excluded from the present invention.

In the slab manufacturing, a slab having an initial thickness in the range of 150 mm to 300 mm, preferably in the range of 200 mm to 250 mm, is manufactured by a known continuous casting method. In continuous casting, for the purpose of reducing the columnar crystal ratio and reducing the generation of ridging, application of electromagnetic stirring, control operation of supercooling, and the like are performed, but this does not particularly hinder them.
Also, in recent years, as a supplement to normal continuous hot rolling, thin slab casting with a thickness of 30 mm to 100 mm and steel strip casting (strip caster) to obtain a direct steel strip have been put into practical use. Since a fine precipitation state of residual impurities such as AlN is formed, it is desirable to avoid application.

(Slab reheating)
The temperature condition during slab reheating prior to hot rolling is very important in the production of non-oriented electrical steel sheets. This is because it relates to the solid solution and precipitation of impurity elements. In order to prevent fine precipitation of the compound containing an impurity element after reheating, the slab reheating temperature is preferably 1150 ° C. or lower. Of course, if the absolute value of the content of S, N, etc., which are the main harmful elements, can be reduced, the slab heating temperature can be raised, but in that case, both of these contents should be 0.0005% or less. It is not realistic for industrial production because it is required to do so.

(Hot rolling)
The hot rolling conditions of the slab are basically low temperature extraction and high temperature rolling of the slab, but in the present invention, since the hot rolled steel strip is annealed, the coiling temperature does not need to be extremely high, rather, High temperature rolling is not preferable from the viewpoint of descaling property.
For this reason, it is preferable to apply conditions in which the inlet temperature in finish hot rolling is 900 ° C to 1000 ° C, the outlet temperature is 830 to 900 ° C, and the winding temperature is 600 ° C to 700 ° C.

(Hot rolled steel strip annealing)
In the present invention, it is essential to anneal the steel strip after hot rolling. It is also essential that the crystal grain size after annealing of the hot-rolled steel strip is 100 μm or more with an average diameter equivalent to a circle. If the crystal grain size is smaller than this, the {111} system increases in the texture, resulting in poor magnetic properties. Since recrystallization is sufficient when the thickness is 100 μm or more, the problem of ridging disappears. Preferably, it is 120 μm or more. The upper limit is not particularly specified, but 200 μm is the limit in consideration of the annealing cost.
In order to make the crystal grain size after annealing within the above range, the annealing temperature and time can be easily adjusted within the ranges described below by appropriately adjusting the thickness of the steel strip and the steel composition.

  The annealing temperature is in the range of 950 to 1050 ° C. When temperature is lower than 950 degreeC, annealing time will become long and cost will rise. On the other hand, when the temperature exceeds 1050 ° C., precipitates such as AlN and MnS are re-dissolved and finely precipitated after annealing, which hinders grain growth during finish annealing. A preferred temperature range is 970 ° C. to 1010 ° C. The annealing time is in the range of 30 to 90 seconds. If the time is shorter than 30 seconds, the grain growth is not sufficient, and even if it exceeds 90 seconds, there is no problem in quality, but the productivity of the annealing equipment is lowered and the cost is increased.

(Cold rolling)
The annealed hot-rolled steel strip is cold-rolled to obtain a cold-rolled steel strip having the final thickness. Due to the high Si and Al content of the steel strip, the problem of brittleness in cold rolling may occur. For this reason, it is desirable to perform cold rolling with a reverse (reversible) rolling mill. Of course, it can also be performed with a tandem (continuous) cold rolling mill, but care should be taken because production may be hindered by troubles such as breakage.

  The rolling rate of cold rolling is 55 to 90%. In the low cold rolling rate region where the cold rolling rate is less than 55%, the texture is inferior in magnetic properties because the {111} system is the main orientation. When the cold rolling rate exceeds 90%, the {111} system increases again, and the magnetic properties deteriorate. From the viewpoint of magnetic properties in the entire circumferential direction, a cold rolling rate of 60 to 80% is preferable, and more preferably 65% to 78%.

  In addition, since this invention is a manufacturing method by one cold rolling, what is called an intermediate annealing after the primary cold rolling of a 2 times cold rolling method becomes unnecessary.

(Finish annealing)
Continuous annealing is applied to finish annealing of cold rolled steel strip. The present invention is characterized by a shorter time than the prior art.
Finish annealing is greatly affected by time and temperature, and a higher temperature is better for shortening the annealing time, but the current state is defined by the specifications of continuous annealing furnace equipment, and 1075 ° C. is the maximum temperature. If the temperature is lower than 950 ° C. on the low temperature side, soaking for a long time is still necessary.
If the holding time of finish annealing is less than 20 seconds, the grain growth is not sufficient, and even if it exceeds 120 seconds, no further grain growth occurs, so the range is set to 20 to 120 seconds. Below 950 ° C., the grain growth is not sufficient, and the operation of continuous annealing at a temperature exceeding 1075 ° C. has not been technically established at present.
In order to improve the texture, Patent Document 6 proposes heating to a temperature of 750 to 1150 ° C. at a rate of 133 ° C./second or more. The present invention does not prevent the application of this technique.

(Insulation coating)
Since electromagnetic steel sheets are used by being laminated, an insulating coating is applied to the surface in order to ensure interlayer resistance. A material containing Cr has been applied in the past, but recently, a Cr-free coating has also been developed, and either one may be used.

<Example 1>
The molten molten steel having the components shown in Table 1 was cast by applying electromagnetic stirring to reduce ridging in an ordinary continuous casting machine to obtain a 250 mm thick slab, and after reheating the slab at 1150 ° C, Conventional continuous hot rolling was performed, and the coil was wound at a temperature of 650 ± 30 ° C. to obtain a hot-rolled steel strip having a thickness of 1.8 mm. Then, hot-rolled steel strip annealing was performed at 1000 ° C. for 90 seconds, pickled, and cold-rolled to 0.50 mm (rolling rate: 72.2%). Thereafter, a finish annealing was performed at 1025 ° C. for 30 seconds in an atmosphere of 30% hydrogen, the remaining nitrogen, and a dew point of −40 ° C.
Table 1 shows the measurement results of the magnetic properties of the non-oriented electrical steel sheet obtained. A non-oriented electrical steel sheet having a chemical composition that satisfies the requirements of the present invention and is manufactured under appropriate manufacturing conditions has a value of 45 ° B50 / Bs of 0.830 or more and excellent magnetic properties in the entire circumferential direction. It was confirmed that

<Example 2>
A slab is obtained from the molten steel of component A10 in Table 1 by a usual method, and hot-rolled steel strips of various thicknesses are obtained under the conditions of Example 1, and in addition to Example 1, further processed in the conditions of Table 2. did. Table 2 shows the measurement results of the magnetic properties of the non-oriented electrical steel sheets obtained and the results of ridging determination.
The iron loss was evaluated at 400 Hz, which has a higher frequency than before, and a magnetic flux density of 1.0T. In addition, ridging was determined by measuring in a direction perpendicular to the cold rolling direction (plate width direction) with a surface roughness meter according to JIS B 0601. For example, the determination is made by measuring 18 mm, excluding 1 mm at both ends, and using the roughness value (maximum value Zt of the height of the contour curve element). The determination criteria are as shown in Table 3 depending on experience.

It was confirmed that a non-oriented electrical steel sheet having a manufacturing condition that satisfies the requirements of the present invention can be manufactured without problems in manufacturing and having a 45 ° B50 / Bs value of 0.830 or more and excellent in magnetic properties. On the other hand, when the manufacturing conditions do not satisfy the requirements of the present invention, the magnetic properties are inferior or there are manufacturing problems.
b1 has a high hot-rolled steel strip annealing temperature, b8 has a low finish annealing temperature, b9 has a short finish annealing time, and the annealing conditions are not appropriate, so the grain growth is inferior and the iron loss is inferior. there were.
b2 has a low hot-rolled steel strip annealing temperature, b3 has a short hot-rolled steel strip annealing time, b5 has a low hot-rolled steel strip annealing temperature, the annealing conditions are not suitable, and the magnetic flux density ratio Was inferior.
b4 and b10 had a problem in manufacturing due to the long annealing time of the hot-rolled steel strip.
b6 and b7 had an inappropriate cold rolling rate, b6 had an excessively high cold rolling rate and a low magnetic flux density, and b7 had an inferior iron loss including a thick plate.

Claims (2)

In mass%, C: 0.0030% or less, Si: 2.0 to 3.0%, Al: 1.0 to 2.0%, Mn: 0.10 to 1.0%, and 3.5 ≦ The magnetic flux density (B50) satisfying Si + Al ≦ 4.75%, consisting of the balance Fe and inevitable impurities, and forming a direction of 45 ° with the rolling direction of the steel sheet is the saturation magnetic flux density of the steel sheet represented by the following formula (1). A non-oriented electrical steel sheet having excellent magnetic properties in the entire circumferential direction, having Bs (T) of 0.830 or more.
Bs = 2.1561−0.0413 [Si] −0.0198 [Mn] −0.0604 [Al] (1)
Here, the element with [] represents the content (% by mass) of each element.   In mass%, C: 0.0030% or less, Si: 2.0 to 3.0%, Al: 1.0 to 2.0%, Mn: 0.10 to 1.0%, and 3.5 ≦ A steel slab satisfying Si + Al ≦ 4.75% and comprising the balance Fe and inevitable impurities is manufactured by a continuous casting method, then hot-rolled to the steel slab, and then subjected to hot-rolled steel strip annealing, A method of producing a non-oriented electrical steel sheet by performing a single cold rolling and performing a finish annealing, wherein the hot rolling steel strip annealing is performed at 950 to 1050 ° C. for 30 to 90 seconds, and after the annealing An average magnetic grain diameter of 100 μm or more, a rolling ratio of the cold rolling of 55 to 90%, and then the finish annealing is performed at 950 ° C. or more for 20 to 120 seconds. A method for producing a non-oriented electrical steel sheet having excellent characteristics.