JP4414727B2 - Magnetic steel sheet with excellent magnetic properties and deformation resistance and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electromagnetic steel sheet, particularly a non-oriented electrical steel sheet, and in addition to low iron loss and high magnetic flux density, deformation resistance, which is a problem in a rotating machine, especially deformation / breakage due to fatigue or creep, and further for an electromagnetic switch The present invention relates to a magnetic material having excellent wear resistance and a method for producing the same.

  Conventionally, the number of rotations required for rotating equipment is about 100,000 rpm at most, and laminated electromagnetic steel sheets have been used as rotor (rotor) materials. Recently, an ultra-high speed rotation of 20 to 300,000 rpm has been required, and the possibility that the electrical steel sheet is deformed by the centrifugal force applied to the rotor has come out. Furthermore, many motors have a structure in which a magnet is incorporated into a rotor, and the load applied to the rotor material itself during the rotation of the rotor is large. The deformation of the material at this time does not occur when the external force exceeds the material strength (yield stress) in the range of normal use conditions, but occurs when the external force is much lower than the yield stress of the material. The properties required for the material here are fatigue strength and creep strength. In general, since these characteristics have a correlation with the strength (yield stress) of the material, a high-strength material is often used as a countermeasure, but strictly speaking, it is not an optimal solution. Especially during the use of the material, the temperature of the member rises, so this influence must be taken into account.

  In addition, because the contact surface of the electromagnetic switch is worn as it is used, a magnetic material having excellent wear resistance as well as electromagnetic characteristics is desired. In such applications, generally, increasing the strength of the material is one countermeasure, but it goes without saying that the application of an optimal solution that takes into account the temperature rise of the material is preferable.

  In response to such needs, recently, non-oriented electrical steel sheets with high strength have been studied and several proposals have been made. For example, in Patent Document 1, the Si content is increased, and a solid solution strengthening component such as Mn, Ni, Mo, Cr or the like or one or more of precipitate forming elements for precipitation strengthening are contained in a large amount. Although it has been proposed to use slabs as raw materials, the risk of frequent plate breakage during rolling is extremely high, and strict management is required for low-speed plate passing, plate temperature and tension during rolling, etc. Decrease in production yield and yield, resulting in a significant increase in production cost. Moreover, since it contains a large amount of Ni, Mo, and Cr, it becomes an extremely expensive material. In addition, the magnetic properties, particularly the magnetic flux density, are inevitably lowered due to the addition of alloy elements. In particular, the segregation of elements added in large quantities and the uneven distribution of precipitates caused by the uneven temperature of steel during production cause a problem that the magnetic structure of the material becomes mixed and the magnetic properties deteriorate significantly. It has become.

  Under such circumstances, the present inventor has proposed various high-strength materials as shown in Patent Documents 2 and 3. These are very excellent compared to conventional high-strength materials, but due to the additive elements and the special manufacturing process, considerable deterioration in magnetic properties cannot be avoided compared to general electromagnetic steel sheets. Further, in these materials, no consideration is given to the effect of temperature rise during use, and it is not an optimal material depending on the application.

JP-A-1-162748 Japanese Patent Application No. 2003-347113 Japanese Patent Application No. 2003-347084

  In this way, many proposals have been made for high-strength electrical steel sheets, but the effects of temperature rise during material use are taken into account while ensuring magnetic properties equivalent to or better than general electromagnetic steel plates that do not limit strength properties. The actual situation is that the optimum characteristic control has been performed, and that it has not been industrially stably produced using ordinary electrical steel sheet production equipment.

  When the present invention is used as a member having a movable part, such as a motor or an electromagnetic switch, without significantly increasing the strength of the material, the magnetic flux to the member, current permeation, friction due to operation, or the like is considerable. When used as a part with increased temperature, it has excellent resistance to deformation and wear, especially against fatigue and creep, and excellent magnetic properties such as magnetic flux density and iron loss when used in a magnetic field. An object of the present invention is to stably produce an on-line electrical steel sheet having characteristics without changing from an ordinary electrical steel sheet, such as cold rollability.

The present invention has been made to solve the above-mentioned problems, and the gist thereof is as follows.
(1) By mass%, C: 0.080% or less, Si: 0.2-3.5%, Mn: 0.05-3.0%, P: 0.30% or less, S: 0.040 %, Al: 2.50% or less, N: 0.020% or less, consisting of the balance Fe and inevitable impurities, and the amount of solute C in the final product by the internal friction method : 0.0035% or more An electrical steel sheet having a thickness of 0.5 mm or less.
(2) Furthermore, the average diameter of the carbide mainly composed of Fe in the steel material characterized in that it is a 0.1 to 2 mu m (1) electrical steel sheet according.
(3) The electrical steel sheet according to (2), wherein the number density of carbides mainly composed of Fe in the steel material is 0.1 piece / μm ³ or less.
(4) The electrical steel sheet according to any one of (1) to (3), wherein the ratio of the grain size of the coarse grain part to the grain size of the fine grain part is 2 or less.
(5) Further, in the texture of the steel material, any one of (1) to (4), wherein the ratio of the maximum strength in the {110} plane and the maximum strength in the {111} plane is 2 or more The electrical steel sheet according to 1.
(6) Furthermore, in the texture of the steel material, any one of (1) to (5) is characterized in that the ratio of the maximum strength in the {100} plane and the maximum strength in the {111} plane is 2 or more. The electrical steel sheet according to 1.
(7) The electrical steel sheet according to any one of (1) to (6), wherein a value measured after the product is heated to 200 ° C. and cooled with water is used as the value of the solid solution C.
(8) In the method for producing a steel sheet according to any one of (1) to (7), the amount of solute C immediately before the cold rolling step with a cold rolling rate of 20% or more is 0.0005% or more. A method for producing an electromagnetic steel sheet.
(9) Of the method for producing a steel sheet according to (8), the cooling time from a temperature of 300 ° C. or higher to 200 ° C. or lower is set to 5 minutes or shorter in the heat treatment step before the cold rolling step with a cold rolling rate of 20% or higher. Then, cold rolling is started without raising to a temperature of 300 ° C. or higher.
(10) In the method for producing a steel sheet according to (8) or (9), the grain size of the steel sheet immediately before the cold rolling step with a cold rolling rate of 20% or more is 100 μm or more. Manufacturing method.
(11) Of the method for producing a steel sheet according to any one of (8) to (10), the heat treatment step at 700 ° C. or higher before the cold rolling step with a cold rolling rate of 20% or higher is from 1000 ° C. to 1200 ° C. A method for producing an electrical steel sheet, comprising performing a heat treatment for 5 seconds to 10 minutes, or 700 ° C to 999 ° C for 10 minutes to 30 hours, and then starting cold rolling.
(12) In the method for producing the steel sheet according to any one of (1) to (7), the C content is 0.005% or more in one stage of the production process, and decarburization is performed during the subsequent production process. A method for producing an electrical steel sheet, comprising:
(13) In the method for producing a steel sheet according to (12), the amount of solid solution C immediately before the cold rolling step with a cold rolling rate of 20% or more is 0.0005% or more, and the method for producing an electrical steel sheet .
(14) In the method for producing a steel sheet according to (12) or (13), the C content is 0.005% or more in a cold rolling step with a cold rolling rate of 20% or more, and then decarburization is performed. A method for producing an electromagnetic steel sheet.
(15) A method for producing an electrical steel sheet, wherein the amount of decrease in C due to decarburization is 0.002% or more of the steel sheet production method according to any one of (12) to (14).
(16) A method for producing an electrical steel sheet, wherein the amount of C after decarburization is 0.08% or less among the method for producing a steel sheet according to any one of (12) to (15).
(17) Of the method for producing a steel sheet according to any one of (12) to (16), decarburization is performed in a final heat treatment step involving recrystallization after cold rolling. Production method.
(18) Of the method for producing a steel plate according to any one of (12) to (17), decarburization is performed in a decarburizing atmosphere at a steel plate temperature of 500 ° C. or more and 10 minutes or less. Manufacturing method.
(19) Among the methods for producing the steel sheet according to any one of (8) to (18), the cooling time from the temperature of 300 ° C. or higher to 200 ° C. or lower is 5 in the final heat treatment step of heating to 300 ° C. or higher. A method for producing an electrical steel sheet characterized by being provided as a product without increasing the temperature to 300 ° C. or higher.

  As described above, according to the present invention, as a member having a movable part, such as a motor or an electromagnetic switch, as a component with a considerable temperature increase due to magnetic flux to the member, current transmission or friction accompanying operation, etc. When used, it improves the resistance to deformation and wear, especially against fatigue and creep, and has excellent magnetic properties such as magnetic flux density and iron loss when used in a magnetic field. A steel plate can be obtained. As a result, high-efficiency, miniaturization, long life, etc. of ultra-high-speed rotation motors, motors incorporating magnets in rotors, and electromagnetic switch materials are achieved.

  The present invention, C: 0.080% or less, Si: 0.5-3.5%, Mn: 0.05-3.0%, P: 0.30% or less, S: 0.040% or less, A steel material containing Al: 2.50% or less, N: 0.020% or less, by controlling the amount of C in the production process, particularly the amount of solid solution C and the amount of product C, particularly the amount of solid solution C An electromagnetic steel sheet having both magnetic properties and deformation resistance of a member is obtained.

  First, the component composition of the electrical steel sheet according to the present invention will be described.

  Since C deteriorates the magnetic characteristics, it is made 0.080% or less. As described later, in the present invention, since there is an object of improving magnetic properties by utilizing a large amount of C during production, higher C is contained in the middle of the production process, and finally C is obtained by decarburization. It is also possible to reduce. The amount of C in the final product is preferably 0.060% or less from the viewpoint of magnetic properties, more preferably 0.040% or less, further preferably 0.020% or less, more preferably 0.010%. Hereinafter, more preferably 0.005% or less, still more preferably 0.002% or less, and 0.001% or less. However, from the viewpoint of time required for decarburization and deformation resistance, it is preferably 0.0005% or more, more preferably 0.001% or more, further preferably 0.002% or more, and further preferably 0.005%. More preferably, the content is 0.010% or more, more preferably 0.020% or more, and further preferably 0.040% or more.

  Si increases the specific resistance of steel, reduces eddy currents, lowers iron loss, and increases tensile strength, but the effect is small when the amount added is less than 0.2%. If the Si content is increased, it is possible to greatly reduce the iron loss without significantly degrading the magnetic properties, and even if the C content is the same, it is possible to increase the solid solution C content which is an important requirement in the present invention. Therefore, it is preferably 1.0% or more, more preferably 1.5% or more, further preferably 2.0% or more, and further preferably 2.5% or more. However, if it exceeds 3.5%, the steel is embrittled and further the magnetic flux density of the product is greatly reduced. In order to further reduce the fear of embrittlement, it is preferably 3.2% or less, and if it is 2.8% or less, there is a balance with the amount of other elements, but there is almost no need to consider embrittlement.

  Mn is added for the purpose of reducing iron loss by increasing the strength of steel and reducing the eddy current loss by increasing the resistivity as well as Si and by promoting the grain growth by coarsening sulfides. Addition lowers the magnetic flux density and tends to segregate in the steel, causing mixed grains of the crystal structure in the product and degrading the magnetic properties, so 0.05 to 3.0%. Preferably they are 0.5%-2.5%, More preferably, they are 0.8%-2.0%.

  P is an element having a remarkable effect of increasing the tensile strength, but like the above Mn, it is not necessary to add it to the steel of the present invention. If it exceeds 0.3%, the embrittlement is severe and processing such as hot rolling and cold rolling on an industrial scale becomes difficult, so the upper limit is made 0.30%. Preferably it is 0.20% or less, More preferably, it is 0.15% or less.

  S is not particularly limited in the present invention, but since it may easily combine with Mn and Cu to form a sulfide and deteriorate magnetic characteristics, particularly iron loss, the S content is preferably as low as possible. It is limited to 0.0060% or less. Preferably it is 0.0040% or less, More preferably, it is 0.0030% or less, More preferably, it is 0.0020% or less, More preferably, it is 0.0010% or less.

  Al is usually added as a deoxidizing agent, but it is also possible to suppress the addition of Al and deoxidize with Si. In the Si deoxidized steel having an Al amount of about 0.005% or less, AlN is not generated, so that there is an effect of reducing iron loss. On the contrary, it can be actively added to promote coarsening of AlN and, like Si, can increase eddy current loss and reduce iron loss by increasing the specific resistance, but if it exceeds 3.0%, embrittlement is a problem. As the magnetic flux density decreases, the content is made 3.0% or less. Preferably it is 0.1 to 2.5%. More preferably, it is 0.5 to 2.0%.

  N is an element existing as an interstitial solid solution atom in steel as in C, and has the same effect as C. However, in magnetic steel sheets, it forms a precipitate with Si or Al, which is not a little added. Care must be taken because it may cause deterioration. Excessive addition causes a remarkable deterioration in magnetic properties, so it is limited to 0.020% or less. When Al is contained in an amount equal to or greater than N, it is preferably 0.015% or less, more preferably 0.010% or less, further preferably 0.005% or less, more preferably 0.003% or less, more preferably 0.002% or less, more preferably 0.001% or less.

In the present invention, the presence of C, particularly solute C, is important, and since the C content is higher than that of a normal electromagnetic steel sheet at least during one stage of the production process, the content of elements that form carbides in steel is It is necessary to pay attention. In particular, Nb, Ti, V, Zr, Mo, and W are relatively strong carbide-forming elements, so a large amount is not preferable. The carbides of these elements are fine and significantly deteriorate magnetic properties, particularly iron loss .

Moreover, about the other trace element, the quantity of the extent which is inevitably contained from an ore, a scrap, etc. does not impair the effect of this invention at all. The inevitable contents of these trace elements are usually about 0.005% or less for each element .

  A feature of the present invention is that the steel whose main component is adjusted in a molten state is solidified, and at least one stage of the manufacturing process including the product, more specifically, the C content, particularly the amount of solute C is higher than that of conventional steel at an appropriate period. By increasing it to a great extent, the deformation resistance of the material at the time of use, in particular, the deformation resistance during warming, is remarkably improved. In addition to the components described above, the final material according to the present invention has several characteristics. This feature is described below.

In the steel of the present invention, the solute C content is 0.0005% or more. In a normal electromagnetic steel sheet, C adversely affects magnetic properties, particularly magnetic aging, so that the amount of contained C itself is reduced. As a result, the amount of dissolved C is also very low. In the present invention, the amount of dissolved C is increased and utilized as useful for various materials, particularly deformation resistance. If the amount of dissolved C is less than this, the effect of the invention cannot be seen. Preferably it is 0.001% or more, More preferably, it is 0.002% or more, More preferably, it is 0.003% or more, More preferably, it is 0.004% or more, More preferably, it is 0.005% or more, More preferably, it is 0.007. % Or more, more preferably 0.009% or more, and further preferably 0.010% or more. The amount of C in the final product was defined as 0.0035% or more based on the examples. On the other hand, from the viewpoint of magnetic aging, it is preferably 0.050% or less, more preferably 0.030% or less.

  Further, considering the use situation of the present invention, it is easily assumed that depending on the use, not the amount of C in solution at room temperature but the amount of C in solution in the warm region becomes a problem. Therefore, in the present invention, more preferably, the amount of solute C measured after heating the product plate to 200 ° C. and cooling with water is defined as 0.0005% or more. Preferably it is 0.001% or more, More preferably, it is 0.002% or more, More preferably, it is 0.003% or more, More preferably, it is 0.004% or more, More preferably, it is 0.005% or more, More preferably, it is 0.007. % Or more, more preferably 0.009% or more, and further preferably 0.010% or more.

  Several methods for measuring the amount of solute C are known, but the internal friction method is used in the present invention.

Moreover, it has the characteristics also in the carbide | carbonized_material form in steel. What is important in the present invention is a carbide mainly composed of Fe and excludes carbides of Ti and Nb, which are generally known to be very stable in steel. In the present invention, the carbide mainly composed of Fe in the steel material has an average diameter of 0.1 μm or more or a number density of 0.1 / μm ³ or less. Although it depends on the C content, the magnetic properties deteriorate if the average diameter is less than this. The thickness is preferably 0.2 μm or more, more preferably 0.3 μm or more, and further preferably 0.5 μm or more. On the other hand, if it is too coarse, not only the magnetic properties are deteriorated, but also the deformation resistance, which is a feature of the steel of the present invention, is remarkably deteriorated. This is because deformation or destruction starts from coarse carbides. Preferably it is 2 micrometers or less, More preferably, it is 1 micrometer or less. On the other hand, if the number density of the carbide is too high, the magnetic properties are significantly deteriorated. Preferably it is 0.05 piece / micrometer < ³ > or less, More preferably, it is 0.02 piece / micrometer < ³ > or less, More preferably, it is 0.01 piece / micrometer < ³ > or less. The effect of the present invention is not lost even when almost all of the contained C is in a state other than carbides mainly composed of Fe, and particularly almost all of the C is solute C.

In the present invention, in the present invention, the extraction replica obtained by the SPEED method is basically observed with an electron microscope with EDX, but if the nitride is very fine and the extraction is not good, the transmission electron microscope is used. Any method such as thin film observation may be used. The determination of the composition is conducted by EDX, and the case where the non-metallic element mainly observed is C and the metallic element is Fe is defined as a carbide targeted by the present invention. The number density of carbides is that the total electric charge applied to the sample surface in the electrolysis process in the replica making process is consumed while the steel plate is electrolyzed as Fe divalent ions (Fe ²⁺ ), and the precipitates that remain as residues during electrolysis All calculated as supplemented on replica. For example, in replica production, if electrolysis is performed with an electric quantity of 50 C (Coulomb) / cm ^{2 on} the surface area of the sample, precipitates within a thickness of 18 μm from the sample surface will be observed on the replica. The method for calculating the number density is not particularly limited to the replica method as long as it is a reasonable method.

  One of the features of the steel of the present invention is that the crystal structure is very uniform. Although it is difficult to express this feature numerically, in the present invention, it is defined as follows. The mixed grain structure which deteriorates the magnetic characteristics which the present invention has a problem and further deteriorates the deformation resistance aimed by the present invention usually has a region where fine crystal grains are close to each other. In the present invention, since the crystal structure is quantified by observing the cross section of the steel sheet, the grain size that is directly observed depending on which position of the crystal grain appears on the cross section even if the steel sheet is composed of crystal grains having the same diameter. Produces a distribution. Further, even if there are coarse and fine grains in each crystal grain size, if they are uniformly distributed, the damage that is a problem in the present invention is unlikely to occur. In order to exclude such “mixed grains” that are not harmful to the present invention, in the present invention, in addition to a certain crystal grain in cross-sectional observation, a crystal grain adjacent to a certain crystal grain (first adjacent grain), and each first Of the grains adjacent to the neighboring grains, the area occupied by the crystal grains (second neighboring grains) excluding the first neighboring grains divided by the number is defined as the grain size of the region. The present invention is characterized in that the ratio of the particle size of the fine particle portion to the particle size of the coarse particle portion is 2 or less. Preferably it is 1.7 or less, More preferably, it is 1.5 or less, More preferably, it is 1.3 or less.

  One of the features of the present invention is that the crystal orientation that is usually difficult to develop is very strong. One is the {110} plane orientation, and the other is the {100} plane orientation. In particular, the present invention is characterized in that the development of these plane orientations is caused by the disappearance of the {111} plane orientation. In general, the development of the {111} orientation becomes remarkable in steels with reduced C, N and S concentrations, such as ordinary electromagnetic steel sheets. It is well known that this orientation is an undesirable orientation for improving magnetic properties, particularly magnetic flux density. On the other hand, it is well known that the {110} and {100} plane orientations, whose development is remarkable in the present invention, are preferable for improving the magnetic flux density. However, these directions cannot be controlled effectively. In the present invention, the weakening of the {111} plane orientation and the enhancement of the {110} or {100} plane orientation are effectively performed simultaneously. In the present invention, particular orientations in these orientations are weakened and strengthened, which appears as the peak intensity in each orientation. Therefore, in the present invention, the ratio between the maximum strength in the {110} plane and the maximum strength in the {111} plane or the ratio between the maximum strength in the {100} plane and the maximum strength in the {111} plane is 2 or more. Stipulate. Preferably it is 3 or more, More preferably, it is 5 or more, More preferably, it is 8 or more, More preferably, it is 10 or more.

  In the present invention, normally, the maximum intensity in the {110} plane is {110} <001>, the maximum intensity in the {111} plane is {111} <112>, and the maximum intensity in the {100} plane is {100} < 014> to {100} <012>. Whether {110} becomes stronger or {100} becomes stronger with the weakening of {111} is mainly influenced by the cold rolling rate. When the cold rolling rate is low, {110} is strong, and when the cold rolling rate is high, {100} is strong. Among these, the development of {100} is particularly noticeable at such a high rolling reduction that is not performed in the production of ordinary electrical steel sheets.

  When the {100} orientation develops, the in-plane anisotropy of the characteristics becomes very small, so it is very convenient in applications where the motor member is formed integrally. The preferred rolling reduction for developing the {100} orientation which is very advantageous for reducing the in-plane anisotropy is 85% or more, more preferably 88% or more, more preferably 90% or more, and more preferably 92% or more. It can be said that the development of the {100} <014> to {100} <012> orientations observed in such an ultra-high cold rolling rate region is a characteristic behavior in the steel of the present invention.

  It is not clear how the above-described features of the steel of the present invention have an effect on the improvement of the deformation resistance characteristically achieved by the steel of the present invention, but the following may be considered. . That is, the deformation to be suppressed in the present invention occurs at a considerably lower stress than the yield stress of the material as described above. Even with such a deformation, it is considered that the deformation is caused by the movement of dislocations in the material, but the moving speed is much lower than that of the normal deformation. In such a state, it is considered that the effect as an obstacle to the dislocation transfer of the solid solution element or fine precipitate that is usually used as a strengthening factor is reduced.

  In particular, when the temperature rises during use, it is considered that the dislocation absorbs the vacancies and moves upward, and overcomes the usual strengthening factor. In such a situation, it is considered that a solution such as solute C or solute N that moves following the movement of dislocation and always becomes an obstacle to the movement plays an important role. In addition, since solid solutions C and N are easy to move in steel, for example, when stress is concentrated depending on the shape of a member and deformation is preferentially advanced in a local region, the location is also the place. It seems that there is also an effect of suppressing local deformation more effectively by concentrating to a high concentration. Furthermore, carbides mainly composed of Fe not only hinder the movement of dislocations due to low stability in steel, but also increase the effect of releasing solid solution C on the dislocations entangled with carbides and hindering the movement. Seem.

  In addition, although the reason why the above-described characteristics appear in the particle size distribution and crystal orientation in the present invention is not clear, it is expected to be caused by the presence of solid solution C during the manufacturing process. Such characteristics of crystal structure or orientation change the movement behavior of dislocations during deformation under extremely low stress, which is a problem in the present invention, to form a structure in which dislocations are entangled, and to reduce concentration of deformation. This is considered to improve the deformation resistance. These features may or may not appear depending on the steel composition and the manufacturing method, but if there is even one feature, the effect of the present invention can be enjoyed, and if a plurality of features appear at the same time, the properties are additionally improved. Is.

  The steel containing the above components is melted in a converter in the same manner as a normal electromagnetic steel sheet, is made into a slab by continuous casting, and then manufactured by processes such as hot rolling, hot rolled sheet annealing, cold rolling, and finish annealing. The In addition to these steps, the formation of an insulating film and a decarburization step do not impair the effects of the present invention. Moreover, there is no problem even if it is manufactured not by a normal process but by a process such as a thin slab casting method that omits the manufacturing of a thin strip by a rapid solidification method and the hot rolling process.

  One of the features of the method for producing the steel of the present invention is that the amount of dissolved C is 0.0005% or more in one stage of the production process. If it is a normal process, it is heated to 700 ° C. or more and 1000 ° C. or more by hot rolling or annealing after cold rolling, and in such a state, it is natural that most of the contained C is usually dissolved. So this situation is excluded. What is defined by the present invention is the amount of solid solution C measured at a temperature of about room temperature during the manufacturing process. The process is preferably defined by the amount of dissolved C immediately before cold rolling. This is because a considerable portion of the effect of the present invention is brought about by the presence of solute C and cold rolling. The preferable amount of solute C at this time is 0.001% or more, more preferable amount of solute C is 0.002% or more, more preferable amount of solute C is 0.003% or more, and more preferable amount of solute C is 0. 0.005% or more, more preferably 0.01% or more, and further preferably 0.02% or more. Further, the cold rolling performed in this state requires 20% or more, preferably 40% or more, more preferably 60% or more, 80% or more, further 90% or more, and 95% or more. Is not detrimental.

  Thus, in order to control the amount of dissolved C immediately before cold rolling, the cooling conditions in the heat treatment immediately before cold rolling are important. The basic idea is to maintain the solid solution C increased by holding at a high temperature during the heat treatment to a temperature of about room temperature immediately before cold rolling by rapid cooling, thereby reducing the cooling time from 300 ° C. or higher to 200 ° C. or lower. It is preferable to start cold rolling without increasing the temperature to 300 ° C. or higher after that. Since the solid solution C increases as the temperature at which cooling starts is higher, it is preferably 400 ° C. or higher, more preferably 500 ° C. or higher, more preferably 600 ° C. or higher, more preferably 700 ° C. or higher. In addition, the shorter the time required for cooling, the more the solid solution C after cooling increases, so it is preferably 3 minutes or less, more preferably 1 minute or less, more preferably 30 seconds or less, depending on the plate thickness. The effect of this invention can be acquired more notably by setting it as 2 or less second or less. In addition, it is preferable not to maintain the temperature again after such heat treatment, and a temperature increase to 300 ° C. or higher should be avoided.

  In addition, the effect of the present invention is more apparent when the crystal grain size of the material to be cold rolled is coarser. The reason for this is not clear, but it is thought to be due to the effect of promoting the remaining of the solid solution C by reducing the abundance ratio of the grain boundaries that are likely to become precipitation sites of the solid solution C during cooling in the thermal history before cold rolling. Preferably, it is 100 μm or more, more preferably 200 μm or more, more preferably 300 μm or more, further preferably 400 μm or more, more preferably 500 μm or more, further preferably 700 μm or more, further preferably 1000 μm or more, and further preferably 1500 μm or more.

  Thus, in order to form coarse crystal grains before cold rolling, it is effective to perform heat treatment for a long time at a high temperature. For this purpose, some processing is performed at least at 700 ° C. or higher. Needless to say, the higher the temperature and the longer the time, the more convenient it is to obtain coarse crystal grains. In the present invention, the temperature is 1000 ° C. to 1200 ° C. for 5 seconds to 10 minutes, or 700 ° C. to 999 ° C. for 10 minutes or more. Limited to 30 hours or less. It is important to note that depending on the steel composition, transformation may occur in this temperature range, and the expected coarsening effect may not be obtained. A person skilled in the art can easily predict the possibility of transformation with empirical formulas, experiments, general-purpose calculation software, and the like. Note that this heat treatment is performed in the cooling process of the steel sheet after hot rolling, and further, by controlling the cooling conditions after this heat treatment, it is possible to obtain the effect of increasing the amount of solute C by the above-mentioned cooling. From the viewpoint of sex.

  One of the major points of the present invention is the utilization of C, particularly solute C, but the amount of C is different from the optimum range existing in the manufacturing process and the optimum range existing in the final product as described above. . That is, there are too many problems in the middle of the manufacturing process, and there is almost no problem, but in the final product, if there are too many from the viewpoint of magnetic aging or the like, there may be a problem. For this reason, adjusting the amount of C to an appropriate amount by adding a large amount of C in the course of the manufacturing process, particularly in the cold rolling process, and then decarburizing until the final product is obtained. Very preferred for the purpose. At this time, the amount of decrease in C due to decarburization is preferably 0.002% or more in view of the cost and effect required for decarburization. More preferably, it is 0.01% or more, More preferably, it is 0.02% or more, More preferably, it is 0.03% or more, More preferably, it is 0.04% or more, More preferably, it is 0.05% or more. Basically, the amount of C before decarburization is high, and the amount of C after decarburization is low, while enjoying the effects of the present invention relating to the production method, the magnetic aging of the final product is suppressed. There is a tendency to saturate in the C region where the effect of the C amount is high, the cost required for decarburization, and in the present invention, a considerable amount of C, particularly solid solution C, remains in the product plate, thereby improving deformation resistance. Excessive decarburization should be avoided because there is a purpose to achieve this. As a matter of course, the amount of C after decarburization that is the amount of C contained in the final product needs to be 0.08% or less.

  If this decarburization is a normal manufacturing process, it is preferable to carry out by the recrystallization annealing process after cold rolling from a viewpoint of productivity. The fact that this decarburization is performed after cold rolling is also because it is preferable that the amount of C is high in the cold rolling process as described above, but it is more productive to perform in a situation where the plate is thin in view of decarburization efficiency. This is preferable in terms of points. In the present invention, the thickness of the steel sheet is limited to 0.5 mm or less, but this is also in consideration of this decarburization efficiency. The thinner the plate, the shorter the decarburization possible, preferably the plate thickness is 0.35 mm or less, more preferably the plate thickness is 0.20 mm or less, more preferably the plate thickness is 0.15 mm or less, and further the plate thickness. If it is applied to a steel sheet of 0.10 mm or less, the targeted decarburization can be achieved without any decrease in productivity in the normal annealing process. Decarburization is usually performed by heat treatment of steel. What is necessary is just to hold | maintain in the high temperature atmosphere containing decarburization gas, such as water vapor | steam. In consideration of cost, efficiency, etc., it is preferable that the range be 500 ° C. or more and 10 minutes or less.

  Furthermore, in the present invention, the target deformation resistance can be improved by increasing the amount of dissolved C in the final product as described above. For this purpose, it is effective to control the cooling conditions for the final heat treatment of the steel sheet. In the present invention, in the final heat treatment step of heating to 300 ° C. or higher, the cooling time from 300 ° C. or higher to 200 ° C. or lower is set to 5 minutes or shorter, and then provided as a product without increasing the temperature to 300 ° C. or higher. And This is the same as the control of the amount of dissolved C immediately before the cold rolling described above, because the higher the temperature at which the cooling starts, the more the dissolved C increases, preferably 400 ° C. or higher, more preferably 500 ° C. or higher, More preferably, it is 600 degreeC or more, More preferably, it is 700 degreeC or more. In addition, the shorter the time required for cooling, the more the solid solution C after cooling increases, so preferably 3 minutes or less, more preferably 1 minute or less, more preferably 30 seconds or less, and the plate thickness is as thin as 0.5 mm or less. The cooling speed is possible, and the effect of the present invention can be obtained more remarkably by setting it to 5 seconds or less and 1 second or less by water cooling or the like. Further, it is preferable not to maintain the temperature again after such a heat treatment, and the temperature rise to 300 ° C. or higher should be avoided as in the heat treatment just before cold rolling.

  The technique of the present invention can also be applied to a case where a heat treatment at 300 ° C. or higher is performed for some purpose after the steel sheet is processed into a member. As such heat treatment, strain relief annealing (SRA), which improves the magnetic properties by removing the strain during processing and growing the crystal grains of the steel sheet, is well known and is often applied. Even in such a case, even if the uniform structure, unique texture, or morphological change formed in the present invention cannot be avoided, the effect of good magnetic properties and deformation resistance due to the carbide formed after heat treatment Can be enjoyed. In this heat treatment, however, it is needless to say that the amount of solid solution C is preferably controlled by controlling the cooling as described above, and in particular, the effect of improving the deformation resistance is sufficiently improved.

  As for the deformation resistance under low stress such as fatigue and creep as considered in the present invention, various findings are known for thick plates, steel pipes, thin plates and the like used in boilers and heat exchangers. However, the countermeasures there are mainly high alloying by addition of Cr and the like and dispersion of fine precipitates by addition of Ti, Nb, V, etc. From the viewpoint of magnetic properties and cost in the electromagnetic steel sheet to which the steel of the present invention is applied. It is not applicable. In addition, in the steel sheet, the carbide formation behavior and solid solubility limit of C in the steel are characteristically changed due to the large amount of Si, and fatigue resistance and creep resistance using C based on the steel sheet shown in the present invention. The development of wear-resistant steel has a completely different meaning from that of thick and thin plates. In general, a grain-oriented electrical steel sheet (GO) is known as an electrical steel sheet that has a high C content until the middle of the manufacturing process and then reduces the C content by decarburization. It uses the next recrystallization to form a unique texture, and it is manufactured without considering the use of solute C in the middle of the manufacturing process and the improvement of properties due to the solute C remaining in the final product. And is excluded from the present invention. Although the steel of the present invention has a texture similar to GO depending on the production conditions and may have strong in-plane anisotropy regarding the material, it is not described as a non-oriented electrical steel sheet (NO). In view of the manufacturing process and the like, it is basically classified as a non-oriented electrical steel sheet.

  In addition, the effect of this invention does not depend on the presence or absence and type of the surface film normally formed on the surface of the electrical steel sheet. In addition, the application is not particularly limited, and there is a possibility that deformation under low stress accompanying operation of a member may become a problem in addition to the use of a rotor of a motor used in home appliances or automobiles, and the magnetic characteristics are Applies to all required applications.

Steels A and B having the components shown in Table 1 were produced by slabs with a thickness of 250 mm by continuous casting. For steel A, elements other than C were the same as shown in Table 1, and based on this, a plurality of slabs were produced in which only the amount of C was varied. These amounts of C are shown in Table 2. These were hot rolled at a slab heating temperature of 1100 ° C. and a winding temperature of 650 ° C. to obtain a hot rolled plate having a thickness of 2.1 mm. Further, after heat treatment at 1000 ° C. for 30 seconds in a continuous annealing line, pickling and cold rolling to 0.5 mm were performed. All of these were annealed at 950 ° C. × 30 seconds, and the cooling rate at that time was variously changed. Table 2 shows the cooling time from 300 ° C to 200 ° C. Some materials were additionally heat treated at lower temperatures. In the additional heat treatment, the cooling time from 300 ° C. to 200 ° C. was 10 seconds. The product plate was obtained at room temperature and the amount of dissolved C after being heated to 200 ° C. and water-cooled by the internal friction method, and the magnetic flux density B ₅₀ and iron loss W _15/50 were measured by a 55 mm square SST test. The magnetic properties were measured in the direction of 0 °, 45 ° and 90 ° from the rolling direction.
(0 ° characteristic + 2 x 45 ° characteristic + 90 ° characteristic) / 4
The average value was obtained as an evaluation value.

  Deformation resistance is a fatigue test of uniaxial tension (sin wave, repetition rate 10Hz) at a maximum load of 0.8 times the yield stress at 200 ° C in a tensile specimen with a width of 25mm and a length of 45mm. And evaluated by the number of loads leading to breakage. Fatigue tests were performed for the rolling direction and the right angle of rolling, and the average values were used.

As is apparent from the results shown in Table 2, those having a solid solution C content within the range of the present invention exhibit excellent magnetic properties and deformation resistance.

Steels C and D having the components shown in Table 1 were produced by slabs having a thickness of 250 mm by continuous casting. These were hot-rolled at a slab heating temperature of 1150 ° C. and a coiling temperature of 600 ° C. to obtain hot-rolled plates having a plate thickness of 1.0 to 5.8 mm. All of these were further subjected to heat treatment at 1100 ° C. for 30 seconds in a continuous annealing line, and the cooling conditions at that time were changed. Table 3 shows the cooling time from 300 ° C to 200 ° C. Thereafter, pickling was performed, and all materials were cold-rolled to 0.35 mm. Since the thickness of the hot-rolled sheet is different, the cold rolling rate is also different, and the cold rolling rate of each plate is shown in Table 3. All the cold-rolled sheets thus obtained were annealed at 1000 ° C. for 20 seconds under the same conditions. The cross-sectional structure of the hot-rolled sheet immediately before cold rolling was observed and the amount of solute C was determined by the internal friction method. Table 3 shows the Hot plate particle size and Hot plate solid solution C. For the product plate, the magnetic flux density B ₁₀ and the iron loss W _10/400 were measured by a 55 mm square SST test together with cross-sectional observation and texture measurement. For texture, samples were processed from five positions (thickness 1/8, 1/4, 1/2, 3/4, 7/8) in the thickness direction, and the pole figure obtained by averaging these samples was calculated by the vector method. Three-dimensional analysis was performed, and the highest intensity in each plane orientation of {111}, {110}, and {100} was obtained. The magnetic properties were measured in the direction of 0 °, 45 ° and 90 ° from the rolling direction.
(0 ° characteristic + 2 x 45 ° characteristic + 90 ° characteristic) / 4
The average value was obtained as an evaluation value.

  In addition, the deformation resistance was evaluated by measuring the creep deformation at a constant load of 0.8 times the yield stress at 200 ° C. and taking the time to reach 2% deformation. The creep test was conducted for the rolling direction and the rolling right angle, and the average values were used.

  As is apparent from the results shown in Table 3, those having a particle size distribution or texture within the scope of the present invention exhibit excellent magnetic properties and deformation resistance.

A slab having a thickness of 250 mm was produced by continuous casting for steel E having the components shown in Table 1. For steel E, elements other than C were made identical as shown in Table 1, and based on this, a plurality of slabs were produced in which only the amount of C was varied. These C amounts are shown in Table 4. These were hot rolled at a slab heating temperature of 1050 ° C. and a winding temperature of 750 ° C. to obtain a hot rolled plate having a thickness of 2.1 mm. Then, it pickled and cold-rolled to 0.2 mm. All of these were recrystallized and annealed at 950 ° C. for 30 seconds, and subsequently decarburized by being kept in a high temperature and humid atmosphere. The degree of decarburization was variously adjusted by holding temperature and time. Such decarburization is routinely performed in the production of grain-oriented electrical steel sheets, and adjustment by the person skilled in the art has no problem. Table 4 shows the amount of C after decarburization and the amount of C decrease due to decarburization. In this heat treatment, the cooling time from 300 ° C. to 200 ° C. was kept constant at 10 seconds. For the product plate, the amount of dissolved C at 200 ° C. was determined by the internal friction method, and the magnetic flux density B ₅₀ and iron loss W _15/50 were measured by a 55 mm square SST test. The magnetic properties were measured in the direction of 0 °, 45 ° and 90 ° from the rolling direction.
(0 ° characteristic + 2 x 45 ° characteristic + 90 ° characteristic) / 4
The average value was obtained as an evaluation value.

Further, the deformation resistance was evaluated by the number of loads that led to fracture in the same fatigue test as in Example 1.
As is apparent from the results shown in Table 4, even when the amount of dissolved C at 200 ° C. is within the range of the present invention, it is possible to particularly improve the iron loss by performing appropriate decarburization.

About the steel F which shows a component in Table 1, the slab of thickness 250mm was manufactured by the continuous casting. This was hot rolled at a slab heating temperature of 1100 ° C. and a winding temperature of 650 ° C. to obtain a hot rolled plate having a plate thickness of 2.3 mm. Further, after heat treatment at 1000 ° C. for 30 seconds in a continuous annealing line, pickling and cold rolling to 0.2 mm were performed. All of these were recrystallized and annealed at 1000 ° C. for 20 seconds, and subsequently decarburized by being kept in a high temperature and humid atmosphere. The degree of decarburization was variously adjusted by holding temperature and time. Such decarburization is routinely performed in the production of grain-oriented electrical steel sheets, and adjustment by the person skilled in the art has no problem. Table 5 shows the amount of C after decarburization and the amount of C decrease due to decarburization. In this heat treatment, the cooling time from 300 ° C. to 200 ° C. was kept constant at 10 seconds. The texture of the product plate was determined in the same manner as in Example 2, and the magnetic flux density B ₁₀ and the iron loss W _10/400 were measured by a 55 mm square SST test. The magnetic properties were measured in the direction of 0 °, 45 ° and 90 ° from the rolling direction.
(0 ° characteristic + 2 x 45 ° characteristic + 90 ° characteristic) / 4
The average value was obtained as an evaluation value.

  The deformation resistance was evaluated by the deformation time in the same creep test as in Example 3.

  As is apparent from the results shown in Table 5, the texture is preferably changed by performing decarburization in the steel of the present invention, and in particular, further improvement in magnetic flux density is achieved, and deformation resistance is achieved by performing appropriate decarburization. It is also possible to improve the performance. This is considered to be a result of an increase in residual amount of solute C due to orientation selectivity in grain growth during decarburization annealing and disappearance of cementite accompanying decarburization.

Claims (19)

In mass%, C: 0.080% or less, Si: 0.2-3.5%, Mn: 0.05-3.0%, P: 0.30% or less, S: 0.040% or less, Al: 2.50% or less, N: 0.020% or less, consisting of the balance Fe and inevitable impurities, and the amount of solid solution C in the final product by the internal friction method : 0.0035% or more , An electrical steel sheet having a thickness of 0.5 mm or less. Furthermore, electromagnetic steel sheet according to claim 1, wherein the average diameter of the carbide mainly composed of Fe in the steel is 0.1 to 2 mu m. Furthermore, electromagnetic steel sheet according to claim 2, wherein the number density of carbides mainly composed of Fe in the steel is 0.1 or / [mu] m ³ or less. Furthermore , the ratio of the particle size of the coarse-grain part of a steel material and the particle size of a fine-grain part is 2 or less, The electrical steel sheet in any one of Claims 1-3 characterized by the above-mentioned . Furthermore, electromagnetic steel sheet according to any one of claims 1 to 4, wherein the ratio of the maximum intensity of the highest intensity and {111} plane of the {110} plane in the texture of the steel is 2 or more . Furthermore, electromagnetic steel sheet according to any one of claims 1 to 5, wherein the ratio of the maximum intensity of the highest intensity and {111} plane of the {100} plane in the texture of the steel is 2 or more . Wherein the value of the solute C, heating the product to 200 ° C., steel sheets electrodeposition according to any one of claims 1 to 6, characterized in that a value measured after water-cooling. A method of manufacturing a steel sheet according to any one of claims 1 to 7 electrodeposition you, wherein the amount of solute C immediately before between cold reduction ratio of 20% or more of cold rolling process is less than 0.0005% Manufacturing method of magnetic steel sheet. In the manufacturing method of the steel sheet according to claim 8 , the cooling time from the temperature of 300 ° C. or higher to 200 ° C. or lower is set to 5 minutes or less in the heat treatment step before the cold rolling step with a cold rolling rate of 20% or more, and thereafter 300 method of manufacturing features and to that electrical steel plate to start the cold rolling without ℃ increased to a temperature above. In the manufacturing method of the steel sheet according to claim 8 or 9, a manufacturing method of that electrical steel sheet to, wherein the crystal grain size of the steel sheet immediately before between cold reduction ratio of 20% or more cold rolling step is 100μm or more . In the manufacturing method of the steel sheet according to any one of claims 8 to 10, the cold rolling ratio of 20% or more cold rolling step prior 700 ° C. or more heat treatment steps, 10 minutes 5 seconds or more at 1000 ° C. to 1200 ° C. or less, or 700 ° C. 999 performs the following heat treatment above 10 minutes for 30 hours at ° C., the production method of the subsequent electrodeposition you characterized by initiating the cold-rolled steel sheets. A method of manufacturing a steel sheet according to any one of claims 1 to 7, the C content in the one time of the manufacturing process is 0.005% or more, to characterized in that middle decarburization subsequent manufacturing steps method of manufacturing that electrical steel plate. The method of manufacturing a steel sheet according to claim 12, the manufacturing method of that electrical steel sheet to, wherein the amount of solute C immediately before between cold reduction ratio of 20% or more cold rolling steps is 0.0005% or more. 14. The electrical steel sheet according to claim 12, wherein the C content is 0.005% or more in a cold rolling step with a cold rolling rate of 20% or more, and then decarburized. Manufacturing method. In the manufacturing method of the steel sheet according to any one of claims 12 to 14, the manufacturing method of to that electrical steel sheet, wherein a reduction of C by decarburization is 0.002% or more. In the manufacturing method of the steel sheet according to any one of claims 12-15, a manufacturing method of to that electrical steel sheet, wherein the C content after decarburization is less than 0.08%. In the manufacturing method of the steel sheet according to any one of claims 12 to 16, a manufacturing method of that electrical steel plate to characterized in that the decarburization is carried out in a final heat treatment step involving recrystallization after cold rolling. In the manufacturing method of the steel sheet according to any one of claims 12 to 17, decarburization temperature of the steel strip 500 ° C. or higher in a decarburizing atmosphere, the manufacturing method of that electrical steel plate to characterized by being performed in 10 minutes or less . In the method for producing a steel sheet according to any one of claims 8 to 18 , in the final heat treatment step of heating to 300 ° C or higher, the cooling time from 300 ° C or higher to 200 ° C or lower is set to 5 minutes or less, and thereafter method for producing that electrical steel plate to characterized in that it is provided as a product without increasing the 300 ° C. or higher.