KR20140044928A - Process for producing grain-oriented electromagnetic steel sheet with excellent core loss characteristics - Google Patents

Abstract

As mass%, C: 0.001-0.10%, Si: 1.0-5.0%, Mn: 0.01-0.5%, sol.Al: 0.003-0.050%, N: 0.0010-0.020%, 1 type chosen from S and Se, or 2 types: When the steel slab containing 0.005-0.040% in total is hot-rolled, cold-rolled, primary recrystallization annealing, finish annealing, and manufactures a grain-oriented electrical steel plate, in the temperature rising process of the said primary recrystallization annealing The temperature increase rate S1 between T1 (° C): 500 + 2 × (NB-NA) and T2 (° C): 600 + 2 × (NB-NA) is 80 ° C / sec or more, and the temperature (T2) By making the average temperature increase rate S2 between -750 degreeC into 0.1 to 0.7 times of said S1, the grain-oriented electrical steel sheet with low iron loss is obtained over the whole product coil length. Here, in said formula, NA is N amount of precipitation after cold rolling, NB is N amount of precipitation after primary recrystallization annealing.

Description

PROCESS FOR PRODUCING GRAIN-ORIENTED ELECTROMAGNETIC STEEL SHEET WITH EXCELLENT CORE LOSS CHARACTERISTICS}

TECHNICAL FIELD This invention relates to the manufacturing method of a grain-oriented electrical steel plate, Specifically, It is related with the method of manufacturing the grain-oriented electrical steel sheet excellent in iron loss characteristic over the full length of a product coil.

A grain-oriented electrical steel sheet is a soft magnetic material whose crystal orientation is highly integrated in a goth orientation (# 110｝ <001>), and is mainly used as an iron core of a transformer or the like. To include grain-oriented electrical steel sheet for use in transformers, to reduce the no-load hand (energy loss), the iron loss represents the magnetic loss in sikyeoteul magnetization in a 50 ㎐ frequency to _{1.7 T W 17/50 (W} / kg) to a low demand do.

The iron loss of an electrical steel sheet is represented by the sum of the hysteresis loss which depends on crystal orientation, purity, etc., and the eddy current loss which depends on specific resistance, plate | board thickness, size of magnetic domain, etc. Therefore, as a method of reducing iron loss, a method of increasing the density of crystal orientations to improve magnetic flux density, a method of increasing the content of Si, which increases the electrical resistance, a method of reducing the sheet thickness of the steel sheet, and secondary recrystallized grains The method of refine | miniaturizing or subdividing a magnetic domain is known.

Among these, as a technique for refining secondary recrystallized grains, a method of rapid heating at the time of decarburization annealing or a method of rapidly heating immediately before decarburization annealing and improving a primary recrystallized texture is known. For example, Patent Document 1, the rolled steel sheet to a final thickness immediately prior to the annealing decarburization, PH ₂ O / PH ₂ is heated to above 700 ℃ temperature at a heating rate of at least 100 ℃ / sec in a 0.2 or less non-oxidizing atmosphere, By processing, furthermore, in Patent Literature 2, before decarburizing annealing the steel sheet rolled to the final plate thickness, rapid heating treatment is performed at 800 to 950 ° C at a heating rate of 100 ° C / sec or more at an atmospheric oxygen concentration of 500 ppm or less, and decarburization is performed. The temperature of the entire region of the annealing step is set to 775 to 840 ° C. lower than the temperature attained by rapid heating, and the subsequent rear region is subjected to decarburization annealing at 815 to 875 ° C. higher than all of the regions. It is disclosed that a very low iron loss grain-oriented electrical steel sheet is obtained. Moreover, in patent document 3 and patent document 4, the temperature range of at least 600 degreeC of the temperature rising step of a decarburization annealing process is heated to 800 degreeC or more at the temperature increase rate of 95 degreeC / s or more or 100 degreeC / s or more, and this temperature range The technique which obtains the electrical steel sheet excellent in the film | membrane characteristic and magnetic property by controlling the atmosphere of an appropriately is disclosed.

Japanese Laid-Open Patent Publication No. 07-062436 Japanese Patent Laid-Open No. 10-298653 Japanese Unexamined Patent Publication No. 2003-027194 Japanese Patent Application Laid-Open No. 2000-204450

Many of the above-mentioned prior arts uniquely determine the start temperature for rapid heating and define the attainment temperature for rapid heating at 700 ° C or higher, thereby improving primary recrystallized texture and miniaturizing secondary recrystallized grains. Doing. However, according to the studies of the inventors, by reliably applying the prior art, in many cases, secondary recrystallized grains can be refined and iron loss is improved, but depending on the precipitation state of the precipitate before rapid heating, secondary recrystallization It became clear that the behavior was not stable and the improvement effect could not be obtained over the entire length of the coil.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems with the prior art, and its object is to refine secondary recrystallized grains over the entire length of the product coil by stabilizing the secondary recrystallization behavior, thereby through the entire product coil. It is an object of the present invention to propose an advantageous method for producing a grain-oriented electrical steel sheet capable of having a low iron loss.

In order to solve the above problems, the inventors have studied from various viewpoints on the effect of the precipitation state of nitrogen (N) on the primary recrystallization behavior in the steel sheet in the rapid heating temperature range that is uniquely determined in the prior art. Was carried out. As a result, it turned out that the preferable rapid heating temperature range may change with the precipitation state (precipitation amount) of N in a steel plate. In general, solid solution N in the steel sheet is unevenly distributed on grain boundaries or dislocations, and solid solution N remaining in the steel sheet after cold rolling is precipitated in a subsequent temperature-heating process, but a large number of dislocations are unevenly distributed. It precipitates in the phase and suppresses the polygonalization of dislocations, and has the effect of delaying the recovery of the structure and the start of recrystallization. And it is because the said effect changes with the precipitation state (precipitation amount) of solid solution N.

Thus, the inventors have further studied, considering whether the refining of the secondary recrystallized grains can be stably achieved by accurately grasping and controlling the relationship between the recovery temperature range, the recrystallization temperature range, and the temperature increase rate. As a result, a relatively low temperature range where only the recovery proceeds is mainly set, i.e., as shown in Fig. 1, which sets the optimum temperature increase rate for each of the recovery temperature range and the recrystallization temperature range, respectively. A high temperature rise rate, and a relatively high temperature range where the recovery and recrystallization proceeds (hereinafter also referred to as a “high temperature range”). By setting the temperature raising rate, it was found that the refinement of the secondary recrystallized grain size can be achieved stably, and the present invention was developed.

That is, this invention is C: 0.001-0.10 mass%, Si: 1.0-5.0 mass%, Mn: 0.01-0.5 mass%, sol.Al: 0.003-0.050 mass%, N: 0.0010-0.020 mass%, S and 1 type or 2 types selected from Se: 0.005-0.40 mass% in total, and hot-rolled the steel slab which has the component composition which remainder consists of Fe and an unavoidable impurity, and after performing hot-rolled sheet annealing as needed, 1 Fabrication of a grain-oriented electrical steel sheet comprising a series of processes of cold rolling of the final sheet thickness by performing two or more cold rollings between the two or intermediate annealings, the first recrystallization annealing, the application of the annealing separator, and the final annealing. In the method, in the temperature raising process of the primary recrystallization annealing, the following formula (1);

T1 (° C): 500 + 2 x (NB-NA). (One)

Temperature (T1) calculated | required from, and following (2) Formula;

T2 (° C): 600 + 2 × (NB-NA). (2)

The temperature increase rate (S1) between temperature T2 calculated | required from is made into 80 degreeC / sec or more, and makes average temperature increase rate S2 between temperature (T2)-750 degreeC into 0.1 to 0.7 times of said S1. It is a manufacturing method of the grain-oriented electrical steel sheet characterized by the above-mentioned. In the formulas (1) and (2), NA is the amount of precipitate N after the final cold rolling (massppm), and NB is the amount of precipitation N after the primary recrystallization annealing (massppm).

The manufacturing method of the grain-oriented electrical steel sheet of this invention uses the total N content NB '(massppm) of steel slab instead of the precipitation N amount NB (massppm) after the said primary recrystallization annealing.

Moreover, in addition to the said component composition, the said steel slab in the manufacturing method of the grain-oriented electrical steel sheet of this invention further contains Cu: 0.01-0.2 mass%, Ni: 0.01-0.5 mass%, Cr: 0.01-0.5 mass% , Mo: 0.01-0.5 mass%, Sb: 0.01-0.1 mass%, Sn: 0.01-0.5 mass%, Bi: 0.001-0.1 mass%, P: 0.001-0.05 mass%, Ti: 0.005-0.02 mass%, and Nb : It characterized by containing 1 type (s) or 2 or more types chosen from 0.0005 to 0.0100 mass%.

According to the present invention, since the secondary recrystallized grain can be stably refined over the entire length of the product coil, it becomes possible to manufacture a low iron loss oriented electrical steel sheet with high yield.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the temperature rising pattern of this invention in primary recrystallization annealing compared with the temperature rising pattern of the prior art.

First, a high temperature rising rate is set for a relatively low temperature range (low temperature range) in which recovery is mainly performed, which is a basic technical idea of the present invention, and a relatively high temperature range (high temperature range) in which recovery and recrystallization proceeds. By setting the temperature increase rate lower than the low temperature region with respect to the above, it will be described to stably achieve refinement of the secondary recrystallized grains.

In order to optimize the secondary recrystallization behavior, control of the primary recrystallization aggregate structure is necessary. In particular, in order to refine the secondary recrystallized grains, the number of nuclei of the goth orientation (# 110 # <001>) in the primary recrystallized texture is important. In addition, in order to stably generate secondary recrystallization and not grow into coarse secondary recrystallized grains, a large number and a small number of '111' primary recrystallized structures infiltrated by goth orientation are largely related.

First, the reason for increasing the temperature increase rate of the low-temperature metropolitan area where only recovery progresses is demonstrated.

It is known that the nucleus of the said goth orientation # 110 '<001> exists in the deformation | transform band which generate | occur | produces in the # 111' fiber structure in which the strain energy of a rolled structure is easy to accumulate. This strain band is an area | region where strain energy accumulate | stored especially among # 111 'fiber tissue.

Here, when the temperature rising rate of the low temperature region in the primary recrystallization annealing is low, the strain band having a very high strain energy preferentially recovers, and the strain energy is relaxed, so that recrystallization of the goth azimuth nucleus is less likely to occur. On the other hand, when the temperature increase rate of the low temperature region is high, the deformation zone can be maintained at a high temperature while the strain energy is high, so that recrystallization of the goth bearing nucleus can be caused preferentially.

Next, the reason why the temperature increase rate is lower than the low temperature range and the temperature increase rate is limited to a specific range in the high temperature range following the low temperature range will be described.

In general, when there are too many [111] primary recrystallized structures that are easily encroached on the goth bearing (# 110 ｛<001>), the growth of secondary recrystallized grains (goth bearing grains) is promoted, so that the nucleus of the goth bearing is large. Even if it exists, there exists a possibility that one grain may coarsen before each grows. On the contrary, when there are too few # 111 # primary recrystallization structures, secondary recrystallization grains become difficult to grow and cause secondary recrystallization failure. Therefore, the # 111 # primary recrystallized structure needs to be controlled in an appropriate amount.

Herein, the '111' primary recrystallized structure is caused by recrystallization of the '111' fiber structure in the rolled structure. In addition, since the rolled aggregate is integrated in the # 111 'fiber structure, the phase of the primary recrystallized texture becomes the # 111' primary recrystallized structure unless a special heat treatment is performed. Moreover, although not as much as the deformation | transformation band which produces | generates the nucleus of a goth orientation, a # 111 'fiber structure has a high deformation energy compared with other surrounding structures. Therefore, it can be said that it is the crystal orientation which is easy to recrystallize following the goth orientation in the heat treatment condition which rapidly heats the low-temperature region which mainly recovers only.

After rapid heating of the low temperature region, by slowing down the temperature increase rate of the high temperature region, it is possible to promote recrystallization from the strain band holding the strain energy or the? 111? Fiber structure. If too slow, however, the nucleus of the goth defense will also increase somewhat, but the # 111 'primary recrystallized tissue, which is originally organized systematically, will increase excessively. As a result, the # 111 # primary recrystallized structure becomes excessive, and in the secondary recrystallization annealing, the goth azimuth grain is coarsened.

However, if a relatively high high temperature zone in which recovery and recrystallization proceed simultaneously is heated at the same high temperature rising rate as the low temperature zone, before the recrystallization of the goth orientation and the subsequent recrystallization of the? 111? Since the determination of all orientations also initiates primary recrystallization, it is randomized into an aggregate structure. As a result, the number of? 111? Primary recrystallization structures decreases, or secondary recrystallization itself does not occur.

Here, since the range of the low temperature range and the range of the high temperature range have a close relationship with the recovery temperature and the recrystallization temperature of the material, as described above, the polygonalization of the potential in the primary recrystallization annealing is suppressed. The precipitation state of the solid solution N having an effect of delaying the recovery of the structure and the start of recrystallization, specifically, changes depending on the amount of N precipitated in the primary recrystallization annealing. Therefore, it is necessary to change the temperature increase rate according to the precipitation N amount.

This invention is based on the said technical idea.

Next, the component composition of the steel slab used as the raw material of the grain-oriented electrical steel sheet of this invention is demonstrated.

C: 0.001 to 0.10 mass%

C is a component useful for generating goth azimuth grains, and in order to express such an action, it needs to contain 0.001 mass% or more. On the other hand, when C exceeds 0.10 mass%, there is a fear that decarburization is insufficient in decarburization annealing, resulting in deterioration of magnetic properties. Therefore, C is set in a range of 0.001 to 0.10 mass%. Preferably it is 0.005 to 0.08 mass%.

Si: 1.0 to 5.0 mass%

Si has the effect of raising the electrical resistance of steel and reducing iron loss, and in this invention, addition of at least 1.0 mass% is required. On the other hand, when it exceeds 5.0 mass%, cold rolling will become difficult. Therefore, the Si content is in the range of 1.0 to 5.0 mass%. Preferably it is the range of 2.0-4.5 mass%.

Mn: 0.01 to 0.5 mass%

Mn not only contributes effectively to the improvement of hot brittleness of the steel, and when S or Se is contained, it forms precipitates such as MnS and MnSe, and fulfills its function as an inhibitor. If the content of Mn is less than 0.01 mass%, the above effects are not sufficient, while addition of more than 0.5 mass% is not preferable because the slab heating temperature required for dissolving precipitates such as MnS and MnSe becomes very high. . Therefore, Mn is made into the range of 0.01-0.5 mass%. Preferably it is 0.01 to 0.3 mass%.

sol.Al: 0.003 to 0.050 mass%

Al is a useful component which forms AlN in steel, precipitates as a dispersed 2nd phase, and acts as an inhibitor. However, when content in sol.Al is less than 0.003 mass%, sufficient precipitation amount cannot be ensured and the said effect is not acquired. On the other hand, when it exceeds 0.050 mass% in sol.Al, the slab heating temperature required for solid solution of AlN will become very high, AlN will coarsen by the heat processing after hot rolling, and the function as an inhibitor will disappear. Therefore, Al is in the range of 0.003 to 0.050 mass% in sol.Al. Preferably it is 0.005 to 0.040 mass%.

N: 0.0010 to 0.020 mass%

N is a component necessary for forming AlN which is an inhibitor like Al. However, when the addition amount is less than 0.0010 mass%, precipitation of AlN is insufficient. On the other hand, when it exceeds 0.020 mass%, expansion etc. generate | occur | produce at the time of slab heating. Therefore, N is made into 0.0010 to 0.020 mass% of range. Preferably it is 0.0030 to 0.015 mass%.

S and Se: 0.005 to 0.040 mass% in total

S and Se are, in combination with Mn and Cu, MnS, MnSe, Cu _{2 - X} S, Cu _{2 -} to form an _X Se is precipitated as a dispersed second phase in the steel, the useful component which acts as an inhibitor. When the total addition amount of these S and Se is less than 0.005 mass%, the above-mentioned addition effect is not sufficiently obtained, while addition exceeding 0.040 mass% not only causes incomplete solid solution during slab heating but also causes the surface defect of the product. It can also be. Therefore, the amount of these elements added is in the range of 0.005 to 0.040 mass%, regardless of single addition or complex addition. Preferably it is 0.005 to 0.030 mass%.

In addition to the above-mentioned component composition, the grain-oriented electrical steel sheet of the present invention further contains 0.01 to 0.2 mass% of Cu, 0.01 to 0.5 mass% of Cr, 0.01 to 0.5 mass% of Cr, 0.01 to 0.5 mass% of Mo, and 0.01 to 0.5 mass% of Sb: 1 type selected from 0.01-0.1 mass%, Sn: 0.01-0.5 mass%, Bi: 0.001-0.1 mass%, P: 0.001-0.05-mass%, Ti: 0.005-0.02 mass%, and Nb: 0.0005-0.0100 mass% Or 2 or more types can be added. Cu, Ni, Cr, Mo, Sb, Sn, Bi, P, Ti, and Nb are elements that tend to segregate on grain boundaries or surfaces, or elements that form carbonitrides, and have a function as an auxiliary inhibitor. Therefore, by adding these elements, it is possible to further improve the magnetic properties. However, when the addition amount is not satisfied, the effect of suppressing coarsening of the primary recrystallized grains is not sufficiently obtained in the high temperature region of the secondary recrystallization process. On the other hand, when the said addition amount is exceeded, it will become easy to produce a secondary recrystallization defect and the appearance defect of a film. Therefore, when these elements are added, it is preferable to add them in the above range.

As mentioned above, the steel slab used as the raw material of the grain-oriented electrical steel sheet of this invention needs to contain 0.0010 mass% or more of N, and also contain nitride formation elements, such as Al which forms nitride and precipitates.

In addition, remainder other than the component mentioned above is Fe and an unavoidable impurity. However, as long as it is in the range which does not impair the effect of this invention, containing of other components is not rejected.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.

The manufacturing method of the grain-oriented electrical steel sheet of this invention hot-rolls the steel slab which has a component composition suitable for this invention mentioned above, and performs hot-rolled sheet annealing as needed, and then it is one or more times which puts an intermediate annealing in between. Cold rolling is performed to form a cold rolled sheet having a final sheet thickness, and is made up of a series of processes of primary recrystallization annealing, application of an annealing separator mainly containing MgO, Al ₂ O ₃ , and the like, followed by annealing.

Here, there is no restriction | limiting in particular except that it is necessary to adjust to satisfy the component composition suitable for this invention, The manufacturing method of the said steel slab can use a well-known manufacturing method normally. Moreover, since the temperature of reheating before hot rolling of a steel slab needs to fully solidify an inhibitor component, it is preferable to set it as 1300 degreeC or more.

In addition, the hot rolling conditions, the hot rolled sheet annealing conditions to be carried out as necessary, and two or more cold rolling conditions sandwiched between one or an intermediate annealing as cold rolled sheets of final sheet thickness, There is no restriction | limiting in particular. Moreover, in the said cold rolling, you may employ | adopt an interpass aging and a warm rolling suitably. Hereinafter, the manufacturing conditions after cold rolling are demonstrated.

The primary recrystallization annealing after cold rolling stably realizes miniaturization of the secondary recrystallized grains, and in order to increase the ratio of the region of low iron loss in the coil, the low-temperature region in which the recovery mainly proceeds, In addition to the recovery, it is necessary to appropriately control the rate of temperature rise in the high temperature zone where the primary recrystallization proceeds. Specifically, the temperature increase rate in the low temperature range is set to 80 ° C / sec or more higher than that of a conventional primary recrystallization annealing, and the temperature increase rate in the high temperature range is 0.1 to 0.7 of the temperature increase rate in the low temperature range. By setting it to the range of times, the iron loss reduction effect can be obtained stably.

Here, the temperature range of the low temperature zone and the high temperature zone in the temperature raising process is determined based on the precipitation state of N in the steel sheet. The solid solution N present after cold rolling is localized on the grain boundary or dislocation, and forms nitride in the temperature rising process of the primary recrystallization annealing and fine precipitates on the dislocation, thereby limiting the displacement of the dislocation and suppressing polygonization. That is, there is an effect of delaying recovery of the rolled structure and recrystallization. Therefore, it is thought that the amount of N precipitated by primary recrystallization annealing greatly influences recovery or recrystallization.

Under such a thought, the inventors measured the precipitation N amount NA (massppm) in the steel sheet after the final cold rolling and the precipitation N amount NB (massppm) in the steel sheet after the primary recrystallization annealing, and their difference (NB-NA) (massppm) ) Is assumed to be the amount of N newly precipitated by primary recrystallization annealing, and many experiments are repeated in order to investigate the relationship between this (NB-NA) and the temperature raising conditions (heating rate, temperature range) at which good magnetic properties are obtained. It was. As a result, it was found that appropriate temperature raising conditions according to (NB-NA) as shown below exist.

First, in the low temperature range, the following formula (1);

T1 (° C): 500 + 2 x (NB-NA). (One)

Temperature (T1) calculated | required from, and following (2) Formula;

T2 (° C): 600 + 2 × (NB-NA). (2)

It turned out that it is necessary to make temperature increase rate S1 between temperature T2 calculated | required from 80 degreeC / sec or more.

The above formulas (1) and (2) indicate that when the amount of N precipitated in the primary recrystallization annealing increases, recovery or recrystallization is delayed, so that the temperature range of the low temperature region becomes high.

Moreover, when the temperature increase rate S1 of this temperature range is slower than 80 degreeC / sec, recovery will generate | occur | produce in the deformation | transformation zone which the nucleus of goth azimuth | 110｝ <001> will generate | occur | produce, and preferential recrystallization of a goth azimuth nucleus will not arise. Since the number of Goss bearing nuclei cannot be increased, the secondary recrystallized grains cannot be refined.

In addition, in this invention, since the temperature increase rate in this low temperature range is only 80 degreeC / sec or more, you may make an average temperature increase rate 80 degreeC / sec or more from the temperature below T1.

Next, the high temperature range where recrystallization advances with recovery is made into the temperature range of said T2 (= 600 + 2 (NB-NA))-750 degreeC, and the temperature increase rate S2 between them is a low temperature range It is preferable to set it as the range of 0.1-0.7 times of the temperature increase rate (S1) of.

Here, the lower limit temperature of the high temperature range is the upper limit temperature (T2) of the low temperature range, and only the specific crystal orientation (goth orientation) corresponds to the temperature at which the specific crystal orientation (goth orientation) starts recrystallization by heating at the temperature increase rate (S1). do. In addition, an upper limit temperature is 750 degreeC which is the temperature at which most crystals are recrystallized.

Moreover, since the temperature increase rate S2 of a high temperature range has a relation with S1, since the temperature increase rate of a low temperature range is high, it can be made into the state which suppressed the recovery of the goth orientation which wants to recrystallize preferentially, This is because even if the residence time of the high temperature zone is short, the recrystallization of the goth orientation can be promoted, and the optimum temperature rise rate of the high temperature zone is also increased accordingly according to the temperature increase rate S1 of the low temperature zone.

However, when the temperature increase rate S2 of the high temperature region is too high, even the recrystallization of the tissue to be recrystallized preferentially is suppressed, so that all orientations cause recrystallization and the recrystallized aggregate structure is randomized. In order to cause secondary recrystallization failure, it is preferable to limit the temperature increase rate of S2 to 0.7 times or less of S1. On the contrary, when the temperature increase rate S2 of this high-temperature region becomes too slow, it is preferable to set it to 0.1 times or more of S1 since the? 111｝ primary recrystallized structure increases and the micronized effect of the secondary particles is not obtained. . Preferable S2 is 0.2 to 0.6 times the range of S1.

In addition, the present invention is based on the premise that N, which is unevenly distributed on the dislocations introduced by cold rolling, forms a nitride on the dislocations and precipitates as it is by primary recrystallization annealing. Therefore, the present invention cannot be applied when the nitriding treatment of increasing the N content in steel by primary recrystallization annealing is performed.

In general, primary recrystallization annealing is often performed in combination with decarburization annealing, and in the present invention, primary recrystallization annealing also serves as decarburization annealing. In this case, the decarburization annealing under the oxidation of the atmosphere PH ₂ O / PH ₂ of 0.1 or more wet hydrogen atmosphere, it is preferred to heat treatment with a suitable temperature elevation rate to the invention. In addition, when there are restrictions on the annealing equipment, heat treatment by the temperature range and the temperature increase rate suitable for the present invention may be performed in a non-oxidizing atmosphere, followed by decarburization annealing.

The steel sheet subjected to primary recrystallization annealing as described above is then subjected to finish annealing to cause secondary recrystallization after applying an annealing separator to the steel sheet surface as appropriate. As the annealing separator, for example, in the case of forming a forsterite film, MgO is used as a main component, and TiO ₂ or the like is added as necessary, and in the case of not forming a forsterite film, SiO ₂ and Al ₂ O ₃ as the main component can be used.

The finished annealed steel sheet is then removed from the unreacted annealing separator on the surface of the steel sheet, and then coated with an insulating coating on the surface of the steel sheet as necessary, or a flattened annealing for shape correction is made into a product sheet. . In addition, there is no restriction | limiting in particular about the kind of the said insulating film, In order to reduce iron loss further, it is preferable to use the tension coating which gives a tensile tension to the steel plate surface, for example, Unexamined-Japanese-Patent No. 50-A The insulation coating which baked the coating liquid containing the phosphate-chromic acid-colloidal silica described in 79442, Unexamined-Japanese-Patent No. 48-39338, etc. can be used preferably. In addition, when using the thing which does not form a forsterite film in the annealing separator mentioned above, the surface of the steel plate after finish annealing is apply | coated the water slurry which has MgO as a main component again, and annealing which forms a forsterite film is performed. After that, the insulating coating may be formed. Moreover, in order to reduce iron loss further, the well-known magnetic domain subdividing process which performs a plasma jet, a laser irradiation, and an electron beam irradiation in linear form, or gives a linear deformation with a projection roll to the steel plate after finishing annealing, You may also

In this way, according to the manufacturing method of this invention, since the secondary recrystallization structure can be refine | miniaturized stably over the whole length of a product coil, a grain-oriented electrical steel sheet with low iron loss can be manufactured with high yield.

Example 1

C: 0.06 mass%, Si: 3.3 mass%, Mn: 0.08 mass%, S: 0.023 mass%, sol.Al: 0.03 mass%, N: 0.008 mass%, Cu: 0.2 mass% and Sb: 0.02 mass% The steel slab contained was heated to 1430 ° C. for 30 minutes, and then hot rolled to form a hot rolled sheet having a thickness of 2.2 mm, and subjected to hot rolled sheet annealing at 1000 ° C. for 1 minute, followed by cold rolling to a medium thickness of 1.5 mm. It was made into a cold rolled sheet, and the intermediate annealing was performed. In addition, this intermediate annealing is a condition of promoting the precipitation of N at a cooling rate of 30 deg. C / sec after heating to 1100 deg. C, and a cooling rate of 100 deg. C / sec after heating to 1150 deg. It was carried out at two levels of conditions. Thereafter, further cold rolling was performed to obtain a final cold rolled sheet having a plate thickness of 0.23 mm.

100 mm x 300 mm test piece was extract | collected from the center part of the longitudinal direction and the width direction of each obtained cold rolled coil, and the primary recrystallization which combined primary recrystallization and decarburization was performed in the laboratory. In addition, as shown in Table 1, the primary recrystallization annealing is heated by varying the heating rate between 300 ° C and 800 ° C in various ways as shown in Table 1, and then maintained at 840 ° C for 2 minutes to decarburize. Proceeded. At this time, PH ₂ O / PH ₂ in the atmosphere was 0.3.

In addition, the test piece collected from the cold rolled sheet was electrolyzed using 10 mass% AA-based electrolyte solution (acetylacetone), and the amount of precipitated N in the cold rolled sheet was quantified from the residue remaining after filtration and extraction. The value was made into precipitation N amount NA of a cold rolled sheet. In addition, about the steel plate after primary recrystallization annealing, the amount of precipitation N was similarly quantified, and this value was made into the amount of precipitation N after primary recrystallization annealing, and the difference (NB-NA) of said NB and NA is 1 It was set as N amount which precipitated newly by car recrystallization annealing.

Subsequently, 50 pieces of test pieces subjected to the primary recrystallization annealing (decarburization annealing) were produced for each of the heating conditions, and each annealing separator was prepared by adding 10 mass% of TiO ₂ to MgO as a main component on the surface of these test pieces. Was dried in the form of a water slurry, and subjected to finish annealing to recrystallize secondary, followed by coating and baking an phosphate-based insulating tension coating.

In this way the measurement for both the 50 sheets of test pieces of the respective heating conditions obtained, the iron loss W _17/50 to the end plate and the magnetic tester was obtained a mean value and a standard deviation. Moreover, after the iron loss measurement, the coating was pickled and removed from the test piece, the secondary recrystallized grain diameter in the range of 300 mm length was measured by the line segment method, and the average value of 50 sheets was calculated | required and the result was put together in Table 1. From this result, it turns out that the steel plate which heated up the primary recrystallization annealing on conditions suitable for this invention has a small secondary recrystallization particle size, the iron loss characteristic is favorable, and the deviation is also reduced.

Example 2

The steel slab having the component compositions shown in Tables 2 and 3 was hot rolled after heating at 1400 ° C. for 20 minutes to form a hot rolled sheet having a plate thickness of 2.0 mm, and then cold rolled at 1000 ° C. for 1 minute. To an intermediate cold rolled sheet having a thickness of 1.5 mm, followed by intermediate annealing at 1100 ° C. for 2 minutes, followed by cold rolling to a final cold rolled sheet having a thickness of 0.23 mm. It was formed and subjected to magnetic domain segmentation treatment.

Then, in a non-oxidizing atmosphere, and Table 2 and then heated up at a heating rate shown in Table 3 750 ℃, 750 ~ average rate of temperature rise up to 840 ℃: and heated to 10 ℃ / sec, thereafter, PH ₂ O / PH ₂ Primary recrystallization annealing was carried out in the atmosphere of = 0.3 for 2 minutes and decarburized. Subsequently, an annealing separator comprising MgO as a main component and 10 mass% of TiO ₂ added to the surface of the steel sheet after the primary recrystallization was mixed with water to form a slurry, coated and dried, wound on a coil, and finished annealing. After implementation, planarization annealing for the purpose of application baking of the phosphate-based insulating tension coating and planarization of the steel strip was performed to obtain a product plate.

In addition, in this manufacturing process, the precipitation N amount NA of the steel plate after cold rolling and the precipitation N amount NB of the steel plate after primary recrystallization were calculated | required by analyzing the test piece collected from the coil longitudinal direction edge part and the width direction center part.

In this way each product at a predetermined interval from the longitudinal direction of the coil, Epstein test piece becomes equal to or greater than 500 g mass 30 obtained by the set minute (分) collected, and core loss over a coil in full length W _17/50 is measured, the coil full length and the worst value of the iron loss, the iron loss W _17/50 is the ratio of the total length of the product coil 0.80 W / ㎏ or less part of in in: obtaining the (Achievement%), which was given the results are shown in Table 2.

From Table 2, in the invention example heating to conditions suitable for the present invention, the iron loss W _{17 /} worst value of ₅₀ is also good, and also the iron loss W _17/50 ratio in the coil is not more than 0.80 W / ㎏ (Achievement) with the high It can be seen that.

In addition, as in the present embodiment, in the case where N in steel is not actively increased (not nitriding) during primary recrystallization, after primary recrystallization annealing, it may be considered that all the N content in the steel slab is precipitated. Therefore, in actual operation phase, if the precipitation N amount after cold rolling (before primary recrystallization annealing) turns out, it can set an appropriate temperature increase rate pattern. Moreover, if manufacturing conditions, such as an annealing pattern before final cold rolling, are constant, it is also possible to estimate also the precipitation N amount in the steel plate after cold rolling based on prior preliminary irradiation.

Industrial availability

The technique of the present invention can be applied to improving the texture of aggregates of non-oriented electrical steel sheets or to improving the texture of thin steel sheets.

Claims (3)

C: 0.001-0.10 mass%,
Si: 1.0-5.0 mass%,
Mn: 0.01-0.5 mass%,
sol.Al: 0.003-0.050 mass%,
N: 0.0010 to 0.020 mass%,
One or two selected from S and Se: hot-rolled steel slab containing a total composition of 0.005 to 0.040 mass%, the balance having a component composition consisting of Fe and unavoidable impurities, and then hot-rolled sheet annealing as necessary. Oriented electrical steel sheet consisting of a series of processes of cold rolling of the final sheet thickness by performing one or more cold rolling between one or intermediate annealing, primary recrystallization annealing, applying an annealing separator, and finishing annealing. In the manufacturing method of
In the temperature raising process of the said primary recrystallization annealing, the temperature increase rate S1 between temperature T1 calculated | required from following formula (1) and temperature T2 calculated | required from following formula (2) is 80 degreeC / sec or more. The average temperature increase rate (S2) between temperature (T2)-750 degreeC shall be 0.1-0.7 times of said S1, The manufacturing method of the grain-oriented electrical steel sheet characterized by the above-mentioned.
T1 (° C): 500 + 2 x (NB-NA). (One)
T2 (° C): 600 + 2 × (NB-NA). (2)
Where NA is the amount of precipitation N after the final cold rolling (massppm)
NB: Precipitation N amount after primary recrystallization annealing (massppm) The method according to claim 1,
The total N content NB '(massppm) of a steel slab is used instead of the precipitation N amount NB (massppm) after the said primary recrystallization annealing, The manufacturing method of the grain-oriented electrical steel sheet characterized by the above-mentioned. 3. The method according to claim 1 or 2,
The steel slab is, in addition to the above-described component composition, in addition to Cu: 0.01 to 0.2 mass%, Ni: 0.01 to 0.5 mass%, Cr: 0.01 to 0.5 mass%, Mo: 0.01 to 0.5 mass%, Sb: 0.01 to 0.1 1 type or 2 types selected from mass%, Sn: 0.01-0.5 mass%, Bi: 0.001-0.1 mass%, P: 0.001-0.05 mass%, Ti: 0.005-0.02 mass%, and Nb: 0.0005-0.0100 mass% The manufacturing method of the grain-oriented electrical steel sheet containing the above.

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