JP2006070348A - High strength magnetic steel sheet, its production method and working method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably produce a high strength magnetic steel sheet having high strength satisfying the tensile strength Ts of ≥600 MPa and having wear resistance, and further having excellent magnetic properties in magnetic flux density and core loss on-line while maintaining its cold rolling properties, annealing operability or the like comparable to those of ordinary magnetic steel sheets. <P>SOLUTION: The high strength magnetic steel sheet comprises, by mass, ≤0.060% C, 0.2 to 3.5% Si, 0.05 to 3.0% Mn, ≤0.30% P, ≤0.040% S, ≤2.50% Al and ≤0.020% N, and comprises 0.1 to 8.0% Cu or 0.03 to 8.0% Nb as well, and in which a worked structure remains at the inside. In its production method, strain is applied thereto in a final working stage, and thereafter, heat treatment dissipating the worked structure is not performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-strength electrical steel sheet, particularly a high-strength non-oriented electrical steel sheet, and is excellent in low iron loss for high-speed rotating machines, high magnetic material with high magnetic flux density and high wear resistance for electromagnetic switches. The present invention relates to a magnetic material and a manufacturing method thereof.

  Conventionally, laminated electromagnetic steel sheets have been used for rotor (rotor) materials. Recently, in applications where high-speed rotation or an increase in rotor diameter is required, the centrifugal force applied to the rotor is reduced. The possibility of exceeding the strength has come out. In addition, there are many motors with a structure that incorporates magnets in the rotor, and even if the rotation speed is not so high, the load applied to the rotor material itself during rotation of the rotor is large, and the strength of the material is also in terms of fatigue strength Is becoming a problem.

  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 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 and Patent Document 2, it is proposed to use a slab having a high Si content and further containing one or more solid solution strengthening components such as Mn, Ni, Mo, and Cr. However, there is a risk that sheet breakage may occur frequently during rolling, and there is room for improvement such as a decrease in productivity and a decrease in yield, and since it contains a large amount of Ni, Mo, and Cr, it is extremely It becomes an expensive material.

  Furthermore, Patent Document 3 discloses that a high-strength non-oriented steel sheet is produced from a molten steel containing 2.5% or more of Si by a rapid solidification method. Patent Document 4 discloses improving rolling properties by wrapping 2.5% or more of high Si steel with 2.0% or less of low Si steel. Since all of these proposals have a special process, they cannot be manufactured with ordinary electromagnetic steel sheet manufacturing equipment, and are considered difficult to produce industrially.

JP-A-1-162748 JP-A-61-84360 JP-A-61-87848 JP-A-8-41601

  As described above, many proposals have been made for high-strength electrical steel sheets, but it has been necessary to achieve stable industrial production using ordinary electrical steel sheet manufacturing equipment while ensuring necessary magnetic properties. The fact is that it is not. Under such circumstances, the present inventor has filed a patent application in Japanese Patent Application No. 2003-347084 for a high-strength electrical steel sheet in which a processed structure remains in the steel sheet.

  One method of leaving the processed structure is to perform annealing after cold rolling at a low temperature at which recrystallization does not occur completely, but it is premised that general electrical steel sheets are recrystallized. In order to perform annealing at a low temperature, it is necessary to switch the furnace temperature, and since the temperature difference from a general material is relatively large, it takes time to adjust the temperature, which may be an obstacle to production.

  Also, depending on the annealing atmosphere, unburned atmospheric gas is generated at such a halfway temperature, and if this leaks from the furnace, it may impair the safety of the worker who sucked it, or in the worst case, it will explode in the furnace. The fear of doing it cannot be denied. For this reason, a problem has been raised as to how the processed structure can remain in the high-strength electrical steel sheet using the processed structure at the time of annealing at the same high temperature as that of a general material.

The present invention has a high tensile strength (TS) of 600 MPa or more, wear resistance, and magnetic flux density (B ₅₀ ) and iron loss when used in a high frequency magnetic field such as a motor rotating at high speed. The purpose of the present invention is to stably manufacture a high-strength non-oriented electrical steel sheet having excellent magnetic properties, such as cold rolling property and annealing workability, on-line stably.

The present invention has been made to solve the above-mentioned problems, and the means thereof is as follows.
1) A processed structure is present in the steel sheet structure to increase the strength by strengthening dislocations.
2) In order to prevent the annealing temperature after cold rolling from becoming too low, the recrystallization temperature of the steel sheet is increased so that the processed structure remains even if annealing is performed at a temperature similar to that of a normal steel sheet.
3) In order to further raise the recrystallization temperature, fine precipitates are formed in the steel by a thermal history until the recrystallization is completed.
4) Control so that elements and precipitates used for delaying recrystallization do not impair magnetic properties.

  The specific gist of the technical means in the present invention is as follows.

  (1) By mass%, C: 0.060% or less, Si: 0.2 to 3.5%, Mn: 0.05 to 3.0%, P: 0.30% or less, S: 0.040 %: Al: 2.50% or less, Cu: 0.1-8.0%, N: 0.020% or less, the balance is Fe and inevitable impurities, and the work structure is inside the steel plate. A high-strength electrical steel sheet that remains.

  (2) By mass%, C: 0.060% 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, Nb: 0.03 to 8.0%, N: 0.020% or less, the balance being Fe and unavoidable impurities, and a processed structure inside the steel plate A high-strength electrical steel sheet that remains.

  (3) By mass%, C: 0.060% 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, Cu: 0.1-8.0%, Nb: 0.03-8.0%, N: 0.020% or less, the balance Fe and inevitable impurities A high-strength electrical steel sheet characterized by comprising a processed structure remaining inside the steel sheet.

  (4) The high-strength electrical steel sheet according to (1) or (3), wherein the steel sheet contains a metal phase mainly composed of Cu.

  (5) The high-strength electrical steel sheet according to (2) or (3), wherein the metal element inside the steel sheet mainly contains Nb carbide or nitride.

  (6) Steel component is 1% by mass or more of Ti: 1.0% or less, B: 0.010% or less, Ni: 5.0% or less, Cr: 15.0% or less. The high-strength electrical steel sheet according to any one of (1) to (5), wherein the high-strength electrical steel sheet is contained.

  (7) It is characterized by containing 0.5% or less in total of one or more of Mo, W, Sn, Sb, Mg, Ca, Ce, and Co in a steel component by mass% (1 ) To (6) The high strength electrical steel sheet according to any one of the items.

  (8) The high-strength electrical steel sheet according to any one of (1) to (7), wherein a processed structure existing inside the steel sheet is 1% or more in terms of an area ratio in cross-sectional observation.

(9) The high-strength electrical steel sheet according to any one of (1) to (8), wherein an average dislocation density in a processed structure inside the steel sheet is 1 exp13 / m ² or more.

  (10) When manufacturing the steel sheet according to any one of items (1) to (9), in the final cold working step, after giving the work that the tensile strength is increased by 50 MPa or more, the tensile strength before and after the heat treatment The manufacturing method of the high intensity | strength electrical steel sheet characterized by not performing the heat processing which the fall allowance becomes 600 Mpa or more.

  (11) The method for producing a high-strength electrical steel sheet according to (10), wherein a strain of 5% or more is imparted in the final cold working step.

  (12) The method for producing a high-strength electrical steel sheet according to (10) or (11), wherein the heat treatment after the final cold working is not performed such that the heat treatment is maintained at 1000 ° C. or higher for 30 seconds or longer. .

  (13) The production of the high strength electrical steel sheet according to (10) or (11), wherein the heat treatment after the final cold working is performed for 30 seconds or more in a temperature range not exceeding 950 ° C. Method.

  (14) After the high-strength electrical steel sheet according to any one of (1) to (9) is processed as a part, it is not subjected to heat treatment that causes the processed structure in the steel sheet to disappear. Processing method of electrical steel sheet.

  According to the present invention, a high-strength electrical steel sheet that is hard and excellent in magnetic properties can be stably manufactured. That is, the present invention can obtain the intended strength even if the additive element used for solid solution strengthening and precipitation strengthening is relatively low, so that the cold rolling property is improved and the productivity of the cold rolling process is improved. At the same time, since annealing within the normal operating range is possible, the workability of the annealing process is also improved. In addition, by performing re-cold rolling after annealing, it becomes possible to easily produce an ultrathin material that has been difficult to manufacture.

  As a result, strength, fatigue strength, and wear resistance can be ensured. Therefore, high-speed rotating motors, motors incorporating magnets in rotors, and electromagnetic switch materials can be made more efficient, smaller, and have a longer life. Achieved.

  The present inventors have conducted various experiments and studies in order to achieve the above object. That is, the present invention is C: 0.060% or less, Si: 0.5-3.5%, 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, and further containing Cu: 0.1-8.0% or Nb: 0.05-8.0% Electrolysis even under normal manufacturing process conditions by delaying recrystallization during annealing after cold rolling with a metal phase consisting of solute Cu or solute Nb and fine Cu formed in the steel sheet or Nb charcoal / nitride By leaving and generating a processed structure in the steel sheet, an electrical steel sheet having high productivity and high strength and excellent magnetic properties is obtained without causing troubles such as workability.

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

  Since C deteriorates the magnetic characteristics, it is set to 0.060% or less. From the standpoint of increasing strength, particularly increasing yield stress, improving warm strength and creep strength, and improving fatigue properties in warm conditions, and in the case of Nb-containing steels, NbC also has the effect of delaying recrystallization. Therefore, it is preferably 0.0031 to 0.0301%, more preferably 0.0051 to 0.0221%, still more preferably 0.0071 to 0.0181%, and still more preferably 0.0081 to 0.0151%. .

  When the above-mentioned effects by C are not particularly regarded as important, higher C is contained from the viewpoint of deoxidation efficiency until the slab stage, and C may be reduced by decarburization annealing after forming the coil. Is possible. When the content is reduced to about 0.010% or less, it is advantageous to reduce the amount of C by degassing equipment at the molten steel stage from the viewpoint of manufacturing cost. In particular, if it is 0.0020% or less, the effect of reducing iron loss is remarkable, and in the steel of the present invention that does not require non-metallic precipitates such as carbides for high strength, the strength can be increased even if it is 0.0015% or less. It is possible, and even if it is 0.0010% or less, sufficient strength can be increased.

  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%. Preferably it is 1.0% or more, More preferably, it is 1.5% or more, More preferably, it is 2.0% or more, More preferably, you may be 2.5% or more. Generally, when used under a high-frequency magnetic field, the loss due to eddy current increases. However, in the steel of the present invention containing a processed structure, it is effective to increase the Si content particularly in order to suppress this eddy current loss. However, if it exceeds 3.5%, the steel is embrittled and further the magnetic flux density of the product is lowered, so the content is made 3.5% or less. 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 may be positively added to increase the strength of the steel, but is not particularly required for this purpose in the steel of the present invention that utilizes a fine metal phase as the main means for increasing the strength. Although it adds for the purpose of reducing a core loss by raising a specific resistance and reducing an eddy current loss, since excessive addition reduces a magnetic flux density, it is made 0.05 to 3.0%. 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 easily binds to Cu, which is an essential element in the steel of the present invention, affects the formation behavior of a metal phase mainly composed of Cu, which is important in the present invention, and may lower the strengthening efficiency. Moreover, since the produced sulfide may deteriorate the magnetic properties, particularly the iron loss, the S content is preferably as low as possible, and is limited to 0.0040% or less. 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. Since SiN deoxidized steel with an Al content of about 0.005% or less does not produce AlN, it also has an effect of reducing iron loss. On the contrary, it can be actively added to promote the coarsening of AlN and the iron loss can be reduced by increasing the specific resistance. However, if it exceeds 2.50%, embrittlement becomes a problem. To do.

  Cu is an important element in the present invention. It is used not only as solid solution Cu but also to form a metal phase mainly composed of Cu in the steel sheet (hereinafter referred to as “Cu metal phase” in this specification) and delay recrystallization of the steel sheet. In addition, the fine Cu metal phase has the effect of increasing the strength within a range that does not adversely affect the magnetic properties. This range is limited to 0.1 to 8.0%. Preferably it is 0.8 to 4.0%.

  When the content of Cu is low, the recrystallization delay effect is reduced, and the heat treatment conditions for obtaining the recrystallization delay effect are limited to a narrow range, and the degree of freedom in management of production conditions and production adjustment is reduced. On the other hand, if the Cu content is excessively high, the influence on the magnetic properties is increased, and the iron loss is particularly increased. In particular, Cu existing as a solid solution Cu exceeding the solid solubility limit in steel is less efficient than the Cu metal phase in the recrystallization delay effect, and the influence on the deterioration of magnetic properties is also increased. Excessive Cu also forms a relatively coarse Cu metal phase at a high temperature during hot rolling, for example, and forms a metal phase in an unfavorable stage. Or adversely affect the magnetic properties. A particularly preferable range is 1.0 to 2.9%. More preferably, it is 1.3-2.4%, More preferably, it is 1.5-2.0%.

  Nb, like Cu, is an important element in the present invention. It is used not only as solute Nb but also to form mainly Nb charcoal / nitrides (hereinafter referred to as “Nb precipitates” in the present specification) in the steel sheet and delay the recrystallization of the steel sheet. In addition, the fine Nb precipitate has the effect of increasing the strength within a range that does not adversely affect the magnetic properties. This range is limited to 0.05 to 8.0%. Preferably it is 0.08 to 2.0%.

  When the Nb content is low, the recrystallization delay effect is reduced and the heat treatment conditions for obtaining the recrystallization delay effect are limited to a narrow range, and the degree of freedom in management of production conditions and production adjustment is reduced. On the other hand, when the content of Nb is excessively high, the influence on the magnetic properties is increased, and the iron loss is particularly increased. In particular, Nb existing as a solid solution Nb exceeding the solid solubility limit in steel is not preferable because it has a larger influence on magnetic property deterioration than Cu. Although depending on the C and N contents, excessive Nb forms excessive Nb precipitates in the steel depending on the thermal history and delays recrystallization, but is more likely to be a cause of deterioration of magnetic characteristics than Cu metal phase. Further, for example, when a relatively coarse Nb precipitate is formed at a high temperature during hot rolling or the like, not only the recrystallization delay effect is reduced, but also the adverse effect on the magnetic properties may be increased. A particularly preferable range is 0.1 to 1.5%. More preferably, it is 0.12-1.0%, More preferably, it is 0.15-0.8%.

  N, like C, degrades the magnetic properties, so it is set to 0.040% or less. Si deoxidized steel with an Al content of about 0.005% or less increases strength like C, especially increases yield stress, improves warm strength and creep strength, improves warm fatigue properties, and contains Nb. In the case of steel, it has an effect of delaying recrystallization by NbN, and is an effective element from the viewpoint of texture improvement. From this viewpoint, preferably 0.0031 to 0.0301%, more preferably 0.0051 to 0.0221%, more preferably 0.0071 to 0.0181%, and still more preferably 0.0081 to 0.0151%. It is.

  When Al is about 0.010% or more, it is possible to form a fine AlN by adding a large amount of N to enhance the recrystallization delay effect, but in the Cu metal phase which is the main mechanism of the present invention. In comparison, the recrystallization delay efficiency is poor and the adverse effect on the magnetic properties is relatively large, so there is no need to add it. In Al deoxidized steel, it should be 0.0040% or less. The lower the steel of the present invention which does not expect the strength increase and recrystallization delay effect due to nitride, the lower the content, 0.0027% or less is preferable. The effect of suppressing deterioration of characteristics due to AlN in steel is remarkable, more preferably 0.0022%, and further preferably 0.0015% or less.

  In addition, most of the elements used to increase the strength of conventional high-strength electrical steel sheets are not only problematic in terms of the cost of addition, but also have a detrimental effect on magnetic properties. Absent. Moreover, it has the effect of delaying recrystallization similarly to Cu and Nb characteristic of the steel of the present invention, but the efficiency is not good. In the case of intentionally adding, one or more of Ti, B, Ni, and Cr are added in consideration of recrystallization delay effect, strengthening effect, cost increase and magnetic property deterioration. Ti: 1.0% or less, B: 0.010% or less, Ni: 5.0% or less, Cr: 15.0% or less.

  Ti is an element that forms fine precipitates such as carbides, nitrides or sulfides in the steel sheet and is effective in increasing the strength. However, compared with Nb, the effect is small, but iron loss is degraded. The tendency is strong. Further, when a partially recrystallized structure is used in the annealing process after cold rolling, it has a strong effect of promoting accumulation in the {111} orientation, which is disadvantageous for improving the magnetic flux density. . Therefore, the upper limit is set to 1.0%. Preferably it is 0.50% or less, more preferably 0.30% or less, and good iron loss can be obtained by setting it to 0.0050% or less, which is inevitably mixed without any addition.

  B is bent at the crystal grain boundary and has the effect of suppressing embrittlement due to the P grain boundary deflection. The addition for this purpose is not important. Rather, it is added for the purpose of delaying the recrystallization due to the influence of the solid solution B on the recrystallization temperature. If it exceeds 0.010%, the material is significantly brittle, so the upper limit is made 0.010%.

  Ni is known to be effective in preventing surface roughness (Cu hege) during hot rolling with Cu, which is a very important element in the steel of the present invention, and may be actively added for this purpose. it can. In addition, it is an element that is often used in high-strength electrical steel sheets because it has a relatively small adverse effect on magnetic properties and is also effective in increasing strength. Moreover, although it is effective also in improving corrosion resistance, it is preferable to set the upper limit to 5.0% in consideration of the adverse effect on the addition cost and magnetic properties.

  Cr is an element added for improving the corrosion resistance and improving the magnetic characteristics in the high frequency range. However, the upper limit is preferably made 15.0% in consideration of the adverse effect on the addition cost and the magnetic characteristics.

  Moreover, about the other trace element, in addition to the quantity contained inevitably from an ore or a scrap, even if it adds for a well-known various objective, the effect of this invention is not impaired at all. In addition, there are elements that form at least fine carbides, sulfides, nitrides, oxides, etc., and have a considerable recrystallization delay effect, but these fine precipitates have a great adverse effect on magnetic properties, Further, in the steel of the present invention, a sufficient recrystallization delay effect can be obtained by Cu or Nb, so that it is not necessary to add these elements. The inevitable content of these trace elements is usually about 0.005% or less for each element, but may be added to about 0.01% or more for various purposes not described in this specification. Is possible. Also in this case, in consideration of cost and magnetic characteristics, one or more of Mo, W, Sn, Sb, Mg, Ca, Ce, and Co are made 0.5% or less in total.

  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 or a continuous casting process in which the production of a ribbon by the rapid solidification method or the hot rolling process is omitted.

  In the present invention, it is necessary to form a special structure called “processed structure” in the steel sheet in the present invention. The “processed structure” in the present invention is distinguished from a “recrystallized structure” that occupies almost the entire amount of steel sheet with a normal electromagnetic steel sheet. Generally, it refers to a structure in which the strain accumulated in the steel sheet due to cold rolling or the like has not sufficiently disappeared. More specifically, in the process of annealing a cold-rolled steel sheet, a structure that is deformed by cold rolling and contains high-density dislocations is a structure having a low dislocation density generated by holding at a high temperature in the annealing process (“recrystallized structure”). The region that is not engulfed by this “recrystallized structure” is defined as “processed structure”. This processed structure generally has a low dislocation density due to so-called recovery during annealing, but it is not as low as the recrystallized structure, and the strain distribution is `` processed structure '' and `` recrystallized structure ''. The situation is uneven. The “processed structure” can also be obtained by further processing the recrystallized structure. In this case, uniform strain remains in the tissue as a whole. In the present invention, this processed structure is utilized to increase the intended strength.

  The steel plate targeted by the present invention has a tensile strength of 600 MPa or more. If the steel sheet has a lower tensile strength than this, it is strengthened mainly by solid solution elements such as ordinary Si and Mn, and even in steel sheets that are completely occupied by a recrystallized structure, the productivity deteriorates so much. This is because it is possible to manufacture without using the material, and the material is significantly superior in terms of magnetic properties. The present invention is limited to high-strength materials that cannot be manufactured without deteriorating productivity, with the usual solid solution strengthening as a main component. In order to enjoy the merits of the present invention to a greater extent, it should preferably be applied to a steel plate of 650 MPa or more, more preferably 700 MPa or more, more preferably 800 MPa or more, and has been produced at all. It is possible to manufacture a steel plate of 900 MPa or higher, and even a steel plate of 1000 MPa or higher, which has not been imagined in the past, can be manufactured with high productivity.

  This processed structure is assumed to be 1% or more in terms of the area ratio in the cross-sectional structure observation of the steel sheet. In the present invention, the cross-sectional structure observation is performed in a cross section in which one side of the cross section is the steel plate rolling direction and the other side is the steel plate thickness direction. Uses chemicals such as Nital, which are performed on ordinary steel plates, and uses a method of revealing the structure by etching. However, the method is not particularly limited to the observation method, and any technique that can distinguish the recrystallized structure and the processed structure is acceptable. .

  When the area ratio of the processed structure is 1% or less, the effect of increasing the strength is reduced. When the processed structure is substantially 0%, it is a normal steel plate itself, and controlling within the range of 0 to 1% makes the temperature control of annealing very strict for the effect of increasing the strength is small. Needed and not realistic. In practice, the area ratio of the processed structure is controlled so as to obtain the required strength level, but preferably 5% or more, more preferably 10% or more, more preferably 20% or more, more preferably 30% or more, Preferably it is 50% or more, more preferably 70% or more. There is no problem even if the processed structure is 100% in which substantially no recrystallized structure is observed. In this case, the state is a so-called full-hard state in which annealing is not performed at all, or a state of a recovery structure in which annealing is performed but before recrystallization starts.

  The structure is adjusted according to the required strength and magnetic properties, but this adjustment can be made according to steel composition, hot rolling history, cold rolling rate, annealing temperature, annealing time, heating rate, cooling rate, etc. A person skilled in the art can carry out this without any problems after several trials. Alternatively, it is possible to form a processed structure by imparting strain to a steel sheet that has been annealed to occupy the entire amount of the recrystallized structure by recold rolling or the like. In this case, since strain is generally applied uniformly macroscopically, the entire amount of the tissue becomes a processed structure, which corresponds to 100% of the processed structure. In this case, the strength and magnetic properties are controlled by the amount of processing in consideration of the steel composition, heat history, characteristics, etc. before processing, but those skilled in the art can also perform this without any problems by several trials. Is.

  When a new processed structure is formed by re-cold rolling, etc., if the processing amount is low, it may be difficult to clearly show the presence of the processed structure by the above-described structure observation method, but it is a guideline that sufficiently obtains the effects of the invention. As (crystal grain size in the plate thickness direction) / (crystal grain size in the rolling direction) in cross-sectional structure observation may be used, and this value is set to 0.9 or less. If it is 0.8 or less, the effect of increasing the strength is clearly obtained, preferably 0.7 or less, more preferably 0.6 or less, more preferably 0.5 or less, and further preferably 0.3 or less. . However, it should be noted that if this value becomes excessively low, the magnetic characteristics will deteriorate significantly.

The effect of the “processed structure” described above can also be evaluated by the dislocation density in the “processed structure”. The average dislocation density in the processed structure is 1 exp13 / m ² or more, more preferably 3 exp13 / m ² or more, more preferably 1 exp14 / m ² or more, and further preferably 3 exp14 / m ² or more. This dislocation density is measured by a transmission electron microscope or the like. In an ordinary electrical steel sheet in which the total amount of the steel sheet is a recrystallized structure, the average dislocation density is about 1 exp12 / m ² or less, and therefore, the difference is set to 10 times or more as a sufficient difference for sorting the processed structures.

  The processed structure as described above is left in the final product by optimally controlling a processing process such as cold rolling for forming the processed structure and an annealing process for eliminating the processed structure.

  Assuming that the processed structure that has existed in a considerable amount at a certain point in the manufacturing process is not subjected to heat treatment at all, or is left in the final product without completely disappearing in the subsequent process, the processing process for forming the processed structure is The applied strain amount must be 5% or more, or the amount of increase in the tensile strength of the material due to the processing step must be 50 MPa or more. Further, in the heat treatment step, the reduction in tensile strength of the material due to the heat treatment does not exceed 600 MPa, or it is necessary not to hold at 1000 ° C. or higher for 30 seconds or longer.

  If the amount of strain applied is less than 5%, the magnetic property is greatly deteriorated for a small increase in strength, and no merit can be obtained. The amount of strain is preferably 10% or more, more preferably 20% or more, more preferably 30% or more, more preferably 50% or more. 70 degree of cold rolling performed after normal rolling and before annealing in a normal electromagnetic steel sheet. It is possible to obtain the maximum merit of the present invention from the viewpoint of increasing the strength by performing cold rolling of at least%.

  Similarly, no merit can be obtained in processing where the increase in tensile strength is lower than 50 MPa. Preferably it is 100 MPa or more, More preferably, it is 200 MPa or more, More preferably, it is 300 MPa or more, More preferably, it is 400 MPa or more.

  The above processing is usually performed by cold rolling, but it is not necessary to stick to this as long as the amount of strain or material change is within the rules of the present invention, warm rolling, hot rolling to such an extent that the work structure is not lost. Furthermore, any method such as tensile deformation by applying tension, bending deformation by a leveler, shot blasting, forging, etc. may be used. Rather, since the dislocation structure is changed to a preferable one for the present invention described later by the method of imparting strain, further improvement in characteristics can be achieved.

  If the heat treatment process following processing is a complete recrystallized structure, it is not possible to obtain the advantage of high strength due to the remaining processed structure, which is a feature of the present invention. Shall not exceed 600 MPa. Preferably, it does not exceed 500 MPa, but if it is a so-called full hard without any annealing, the magnetic properties are inferior to those subjected to annealing although it is a recovery region, so that heat treatment is performed to a certain extent even in a low temperature region. Softening is preferable from the viewpoint of balance between strength and magnetic characteristics. From this point of view, the reduction in tensile strength due to annealing is preferably 100 to 400 MPa, more preferably 150 to 300 MPa, so that high strength and good magnetic properties can be maintained.

  Moreover, as a heat history at this time, it is preferable not to hold | maintain at 1000 degreeC or more for 30 seconds or more, and even if it is this invention steel which suppresses recrystallization by Cu or Nb if it exceeds this, it is the characteristics of this invention. The merit of high strength is lost. Preferably, the temperature does not exceed 950 ° C., and more preferably does not exceed 900 ° C. However, annealing at a temperature significantly different from that of a normal electromagnetic steel sheet requires a significant change in the furnace temperature. As described above, there is a case where not only the performance is deteriorated but also the safety is caused by the generation of unburned gas. In the present invention, since it is one of the objects to solve these problems caused by cryogenic annealing, the lower limit of the annealing temperature is set. From this viewpoint, it is preferably 550 ° C. or higher, more preferably 600 ° C. or higher, more preferably 650 ° C. or higher, more preferably 700 ° C. or higher. An invention steel having a completely recovered structure that does not recrystallize at all even at a temperature of about 750 to 800 ° C. at which the material is annealed can be obtained.

  An annealing time of at least 30 seconds is necessary to exert the effect of annealing. Since the time until complete recrystallization becomes longer as the temperature becomes lower, it becomes easier to adjust the disappearance amount of the processed structure by the annealing time. The preferred annealing time depends on the components and the manufacturing history up to the heat treatment and cannot be clearly specified, but the standard is within 5 minutes at 950 ° C, within 1 hour at 850 ° C, and 5 at 800 ° C. Within 700 hours, it is about 10 hours at 700 ° C. A person skilled in the art can find out the conditions under which the effects of the invention can be enjoyed without any problems after several trials.

  In addition, normal recrystallization annealing or annealing at a lower temperature is performed to make a complete recrystallization structure or partial recrystallization or recovery structure like a normal steel sheet, and then re-cold rolling to leave the processed structure in the final product. It is also possible to make it. As for the processing conditions in this case, the amount of strain to be applied is 5% or more, or the amount of increase in the tensile strength of the material due to the processing step is 50 MPa or more as described above. The preferable range is also the same. In this way, when the material softened to some extent in the annealing process is further hardened by re-cooling, the material can be easily thinned, and the productivity of the ultra-thin electrical steel sheet, which was conventionally difficult to manufacture, is also improved. . Such an ultra-thin electromagnetic steel sheet according to the present invention can suppress eddy current loss particularly when used under a high-frequency magnetic field, and thus has an advantage of being effective in reducing iron loss.

  At present, there are electrical steel sheets, so-called semi-process electrical steel sheets, which have been subjected to skin pass rolling of about 1 to 20% on steel sheets subjected to recrystallization annealing as in the method of the present invention and are shipped as products. This is because a skin-passed plate is shipped as a product, processed as a motor part by a motor manufacturer, and then annealed under conditions that cause sufficient recrystallization to cause strain-induced grain growth. A means for obtaining a recrystallized structure and improving magnetic properties is sometimes referred to as a skin pass method, but in this method, the processed structure is not left at the time of use as a member.

  The present invention is essentially different from the steel plate and method, and basically no heat treatment is performed after being processed as a part of an electrical device. Even when any heat treatment is performed for adhesion or surface control of a steel plate, the processed structure defined in the present invention is not lost, and the present invention is limited to those that remain within the definition of the present invention. This is because when the processed structure disappears or deviates from the specified range of the present invention, the strength of the steel sheet required in the situation where it is used as an actual motor will be insufficient. The standard of the temperature of this heat processing is the same as the temperature conditions in the above-mentioned steel plate annealing process. Optimal conditions are those with the cooperation of those skilled in the art of manufacturing steel sheets, or those who are ordinary electrical equipment manufacturers without cooperation can find the conditions that can enjoy the effects of the invention without any problems after several trials. It is possible.

  Strictly speaking, in order to use various members in ordinary electromagnetic steel sheets, processing such as shearing and caulking is performed by a manufacturer or the like, so that a considerable amount of distortion introduced into the steel sheets remains, and the characteristics of the members are reduced. It is known to affect. Such strains enter only the processed portion of the steel sheet, and unlike the strain that consciously remains on the entire surface of the steel sheet in the present invention, it hardly contributes to increasing the strength of the entire member.

  The reason why good magnetic properties can be maintained even if the processed structure remains in the material as in the present invention is not clear, but is considered as follows. Conventionally, the processed structure is not considered as a means for increasing the strength of the material because it greatly deteriorates the magnetic properties, and the increase in the strength has been performed by crystal grain refinement, solid solution strengthening, precipitation strengthening and the like. However, the demand for higher strength of materials is increasing, and conventional strength enhancement means have to step into the area of conditions that significantly deteriorates magnetic properties. If we look at the means for strengthening using the processed structure again, it seems to be one aspect that it is no longer a disadvantageous method.

  Conventionally, the influence of the processed structure has been studied only in the range where the material is cold worked and the amount of strain is relatively small. Under such conditions, the dislocation structure in the material is relatively uniform, and it is expected that a relatively stable dislocation arrangement such as a so-called cell structure or a recovery structure has not been formed. In this amount of processing, it was not attractive at all as a means of increasing the strength, and in such a dislocation structure, the dislocation only became an obstacle to the domain wall movement and the deterioration of the magnetic properties was remarkable and was not put into practical use. I think that the.

  On the other hand, dislocations form a relatively stable cell structure when a relatively high strain amount of cold working is performed as in the present invention, or in a processed structure recovered by annealing. The size of the cell is usually less than 1 μm in diameter and is about 0.1 μm, and the cell boundary is formed by dislocations, except that the crystal orientation difference between adjacent cells is small. It has a similar structure, and can be regarded as a kind of ultrafine crystal grains, and is considered to be less likely to be an obstacle to domain wall movement. Further, such ultrafine crystal grains have high strength and have a certain degree of ductility when processing is necessary. Considering the balance between strength and magnetism, the ultrafine crystal grains are considered to be sufficiently practical.

  In addition, in the steel of the present invention in which a processed structure exists, addition of Si, Mn, Al, Cr, Ni, etc. is not necessary in applications where the iron loss is used in a high-frequency magnetic field where the contribution of eddy current loss is particularly large. The development of dislocation strengthened steels based on electrical steel sheets has become important in so-called ordinary steels for processing used in automobiles and containers, because they are important and have a great influence on dislocation behavior such as work hardening behavior and recrystallization behavior. It has a completely different meaning.

  Next, the Cu metal phase or Nb precipitate that may be characteristically present in the present invention will be described. In the present invention, the Cu metal phase or the Nb precipitate has an effect of suppressing recrystallization during annealing after cold rolling, so that it can be actively used in the present invention. In some cases, the magnetic properties may be deteriorated as compared with solute Nb. When using a Cu metal phase or Nb precipitate, it must be present in the steel by the end of this recrystallization at the latest. It can be formed by controlling the heat history before cold rolling, or can be formed by a heating process before recrystallization is completed during annealing after cold rolling.

  In the present invention, the thermal history for precisely controlling the form of the precipitate is not particularly limited. In the thermal history for controlling recrystallization defined in the present invention, depending on the steel components, A Cu metal phase or Nb precipitate is generated and contributes effectively. The precipitation behavior of these Cu metal phases or Nb precipitates is not significantly different from the generally known knowledge, and those skilled in the art having ordinary skill level will have an appropriate range after several trials. Can be controlled.

The present inventor has already filed a technology for forming a Cu metal phase in a magnetic steel sheet to increase the strength. However, combining the Cu metal phase with this application impairs the effects of the present invention. It is not a thing. Although it does not specifically limit, the diameter of the Cu metal phase or Nb precipitate which exists in this invention steel is about 0.20 micrometer or less. Beyond this, the efficiency of recrystallization delay is reduced, and not only a large amount of metal phase is required, but also the adverse effect on the magnetic properties is increased. Similarly, although not particularly limited, the number density of the Cu metal phase or Nb precipitate is limited in the range that can be taken in relation to the content of Cu, Nb or C and the size of the precipitated phase, but 20 / μm ³ That's about it.

  The effect of the present invention can be applied to a non-oriented or directional electrical steel sheet because it does not depend on the manufacturing process, regardless of the presence and type of a surface film usually formed on the surface of the electrical steel sheet. In particular, the steel according to the present invention can impart characteristics that are greatly different from those of steel sheets having a conventional recrystallization structure in the in-plane anisotropy of characteristics. Looking at the magnetic flux density, the characteristics in the 45 ° direction (D direction) from the coil rolling direction are higher than the characteristics in the rolling direction (L direction) or the coil width direction (C direction) in the fully hard state as cold rolled. It has become. In most cases of electrical steel sheets having a normal recrystallized structure, the characteristics in the D direction are lower than those in the L or C direction. By controlling to the crystallization stage, it is possible to easily obtain a steel sheet having almost no in-plane anisotropy. The fact that there is almost no in-plane anisotropy is a steel sheet having a feature that can exhibit very favorable characteristics depending on applications such as a rotating machine.

  The use is not particularly limited, and it is applicable to all uses where strength and magnetic properties are required in addition to the use of a rotor of a motor used in home appliances or automobiles.

Product plates were produced from steel pieces having a thickness of 200 mm having the components shown in Table 1 under the production conditions shown in Tables 2 and 3 (continued in Table 2). Some materials were heat-treated (user annealed) assuming heat treatment at the motor manufacturer. These characteristics were evaluated in mechanical properties, and 55mm angle iron loss W _10/400 and the magnetic flux density B ₂₅ by SST test by JIS5 No. specimen. For both the mechanical characteristics and the magnetic characteristics, the average value was determined by the following formula for the rolling direction of the coil, the 45 ° direction, and the direction perpendicular thereto.
X = (X ₀ + 2 × X ₄₅ + X ₉₀ ) / 4
Here, X ₀ , X ₄₅ , and X ₉₀ are characteristics of the coil rolling direction, 45 ° direction, and its perpendicular direction.

  The results are shown in Tables 2 and 3. As is apparent from the results, the material produced under the conditions of the present invention is hard and has excellent magnetic properties.

  The example of No. 10 is an example of developed steel as a steel plate, but is a case where recrystallization has completely occurred by heat treatment equivalent to a motor manufacturer assuming use as a member. In applications where such usage is assumed, care must be taken because the characteristics for achieving the purpose of increasing strength, which is important in the present invention, are lost.

Claims (14)

  In mass%, C: 0.060% or less, Si: 0.2 to 3.5%, Mn: 0.05 to 3.0%, P: 0.30% or less, S: 0.040% or less, Al: 2.50% or less, Cu: 0.1-8.0%, N: 0.020% or less, the balance is Fe and inevitable impurities, and the processed structure remains inside the steel plate. High strength electrical steel sheet characterized by   In mass%, C: 0.060% or less, Si: 0.2 to 3.5%, Mn: 0.05 to 3.0%, P: 0.30% or less, S: 0.040% or less, Al: 2.50% or less, Nb: 0.03 to 8.0%, N: 0.020% or less, the balance is Fe and unavoidable impurities, and the processed structure remains inside the steel plate. High strength electrical steel sheet characterized by   In mass%, C: 0.060% or less, Si: 0.2 to 3.5%, Mn: 0.05 to 3.0%, P: 0.30% or less, S: 0.040% or less, Al: 2.50% or less, Cu: 0.1-8.0%, Nb: 0.03-8.0%, N: 0.020% or less, the balance Fe and unavoidable impurities, A high-strength electrical steel sheet characterized in that a processed structure remains in the steel sheet.   The high-strength electrical steel sheet according to claim 1 or 3, wherein the steel sheet contains a metal phase mainly composed of Cu.   4. The high-strength electrical steel sheet according to claim 2, wherein the metal element inside the steel sheet mainly contains Nb carbide or nitride.   The steel component further contains one or more of Ti: 1.0% or less, B: 0.010% or less, Ni: 5.0% or less, Cr: 15.0% or less in terms of mass%. A high-strength electrical steel sheet according to any one of claims 1 to 5.   The steel component further contains at least 0.5% in total of one or more of Mo, W, Sn, Sb, Mg, Ca, Ce, and Co in mass%. The high-strength electrical steel sheet according to any one of the above.   The high-strength electrical steel sheet according to any one of claims 1 to 7, wherein a processed structure existing inside the steel sheet is 1% or more in terms of an area ratio in cross-sectional observation. The high-strength electrical steel sheet according to any one of claims 1 to 8, wherein an average dislocation density in a processed structure inside the steel sheet is 1 exp13 / m ² or more.   In producing the steel sheet according to any one of claims 1 to 9, after the processing of increasing the tensile strength by 50 MPa or more in the final cold working step, the allowance for reducing the tensile strength before and after the heat treatment is 600 MPa. The manufacturing method of the high intensity | strength electrical steel sheet characterized by not performing the heat processing which becomes the above.   The method for producing a high-strength electrical steel sheet according to claim 10, wherein a strain of 5% or more is applied in the final cold working step.   The method for producing a high-strength electrical steel sheet according to claim 10 or 11, wherein the heat treatment after the final cold working is not performed such that the heat treatment is maintained at 1000 ° C or higher for 30 seconds or longer.   The method for producing a high-strength electrical steel sheet according to claim 10 or 11, wherein the heat treatment after the final cold working is performed for 30 seconds or more in a temperature range not exceeding 950 ° C.   A method for processing a high-strength electrical steel sheet, characterized in that after the high-strength electrical steel sheet according to any one of claims 1 to 9 is processed as a part, no heat treatment is performed so that the processed structure in the steel sheet disappears. .