JP6465049B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet.

  Electrical steel sheets are soft magnetic materials that are widely used as iron core materials for transformers and motors. Among them, grain-oriented electrical steel sheets are mainly used as iron core materials for large transformers because they exhibit excellent magnetic properties by highly accumulating crystal orientation in the {110} <001> orientation called the Goss orientation. ing. In order to reduce the energy loss that occurs when the transformer is excited, the grain-oriented electrical steel sheet is required to have a low loss that occurs in the steel sheet due to excitation, that is, iron loss.

  As a means for reducing the iron loss of a grain-oriented electrical steel sheet, a technique for reducing the eddy current loss of the steel sheet by making the secondary recrystallization grain size fine is known. For example, in Patent Document 1, by heating the decarburization annealing up to 700 ° C at an average of 30 ° C / s or more, Goss orientation grains in the primary recrystallization texture are increased, and secondary recrystallized grains are added. A technique for miniaturization is disclosed.

  As another means for reducing eddy current loss of a steel sheet, a magnetic domain refinement technique is known. For example, Patent Document 2 discloses a technique in which a resist is printed on a steel plate after the final cold rolling and etched to form grooves on the steel plate surface and subdivide the magnetic domain. Patent Document 3 discloses a technique for subdividing a magnetic domain by irradiating a grain-oriented electrical steel sheet with a laser and introducing a high dislocation density region in the steel sheet surface layer. Patent Document 4 discloses a technique for subdividing a magnetic domain by electron beam irradiation. Technology is disclosed.

  As another means for reducing the iron loss, a means for increasing the integration of the crystal orientation of the product in the Goss orientation and reducing the hysteresis loss is known. For that purpose, it is important to control the primary recrystallization texture of the product before finish annealing to an appropriate state. In the manufacture of grain-oriented electrical steel sheets, in general, only the grains having the Goss orientation among the primary recrystallized grains during the finish annealing cause secondary recrystallization that grows coarsely while eroding the surrounding grains. A steel plate highly accumulated in the orientation can be obtained. The {111} <112> and {411} <148> orientations are known as primary recrystallization textures that preferentially grow grains having Goss orientation during secondary recrystallization.

  As a means for sharpening the primary recrystallization texture in these directions, control of the final cold rolling reduction rate can be mentioned. For example, in Patent Document 5, by reducing the cold rolling reduction rate to 70% to 91%, recrystallization nucleation from the grain boundary is promoted during recrystallization annealing, which is suitable for the growth of Goss orientation {111 } Techniques for developing {111} // ND orientations containing <112> grains are disclosed. However, if only the cold rolling reduction ratio is set to a high pressure, only the {111} <112> orientation develops in the primary recrystallization texture, the {411} <148> orientation weakens, and both orientations are balanced. There existed a problem that there was a limit in improvement of magnetic flux density.

  In order to solve the above problem, in Patent Document 6, prior to any cold rolling excluding final cold rolling, heat treatment is performed at a temperature range of 500 ° C. to 750 ° C. for 10 minutes to 480 hours. By doing this, the carbide precipitated in layers in the pearlite, the second phase structure after hot rolling, is spheroidized, reducing the amount of non-uniform strain in the rolling process and reducing the grain size before the final cold rolling. By coarsening, it is possible to increase the frequency of {411} <148> orientation in the primary recrystallized texture and allow the {111} <112> and {411} <148> orientations to exist in a balanced manner. The technology to become is disclosed.

Japanese Patent Laid-Open No. 04-160114 Japanese Patent Publication No. 08-6140 Japanese Patent Publication No.57-2252 Japanese Patent Publication No. 06-072266 Japanese Patent No. 4123653 JP 2012-21229

  However, the heat treatment for spheroidizing the above-mentioned layered carbide (hereinafter referred to as spheroidizing treatment) needs to be performed for 10 minutes or longer, and when industrially carried out, the equipment becomes too long when a continuous annealing line is used. Therefore, batch annealing was necessary. Therefore, it takes time to heat and cool the coil, and the lead time is greatly increased, resulting in a problem that productivity is lowered.

  The present invention solves the above-mentioned problems and makes it possible to carry out the spheroidizing treatment in a short time in which continuous annealing is allowed, thereby preventing a decrease in productivity and a grain-oriented electrical steel sheet having excellent magnetic properties. It aims at providing the manufacturing method of.

  In order to solve the above-mentioned problems, the inventors have conducted intensive studies in order to shorten the spheroidizing treatment and enable the treatment by continuous annealing. As a result, it was found that the cooling process of the hot-rolled sheet annealing is rapidly cooled to control the form of the carbide precipitated in a layered manner, and the time for the carbide to be spheroidized by the subsequent heat treatment can be shortened.

First, an experiment that has led to the idea of the present invention will be described.
(Experiment 1)
After heating a steel slab containing C: 0.06%, Si: 3.1%, Mn: 0.1%, Al: 0.020%, N: 0.007%, Se: 0.01% in mass% at a temperature of 1400 ° C, The sheet was rolled to a thickness of 2.2 mm and subjected to hot-rolled sheet annealing at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was set in the range of 5 ° C./s to 200 ° C./s. Next, the hot-rolled sheet annealed steel sheet was heat-treated at 700 ° C. for 10 seconds to 3600 seconds. Then, after cold rolling to an intermediate thickness of 1.5 mm, intermediate annealing at 1100 ° C. × 80 s was performed, and final cold rolling was performed to a plate thickness of 0.23 mm. Thereafter, decarburization annealing at 850 ° C. × 120 s was performed, and after applying an annealing separator mainly composed of MgO, finish annealing was also performed which also served as purification annealing held at 1150 ° C. for 6 hours. The test piece after finish annealing thus obtained was measured for iron loss W _17/50 at a magnetic flux density of 1.7 T and an excitation frequency of 50 Hz in accordance with JIS C2550.

  FIG. 1 shows the measurement results of the magnetic properties of the test piece. By setting the cooling rate from 800 ° C to 400 ° C after hot-rolled sheet annealing to 20 ° C / s or more, even if the heat treatment time at 700 ° C after hot-rolled sheet annealing is shortened to 30s, the iron loss is 0.85W. Good magnetic properties of / kg or less can be obtained.

The reason why the time necessary for spheroidizing the layered carbide is reduced by making the cooling of the hot-rolled sheet annealing rapid is considered as follows. When the high-temperature steel on which austenite is precipitated is cooled, a pearlite phase precipitates at a point of A ₁ or less. Become. Therefore, compared with the case where the cooling rate is slow and the carbide layer is thick, dissolution and collapse of the layered carbide are promoted during the spheroidizing annealing, and thus it is considered that the spheroidization progressed in a short time. Alternatively, when the cooling rate is further increased, martensite precipitates instead of pearlite, and such a phase is unstable, and thus it is considered that spheroidization was promoted.

Next, the inventors examined the temperature at the time of applying the spheroidizing treatment.
(Experiment 2)
The same steel slab as used in Experiment 1 was heated at a temperature of 1400 ° C., and then hot rolled to a thickness of 2.2 mm and subjected to hot rolling at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was 10 ° C./s for some samples and 40 ° C./s for the remaining samples. Next, the hot-rolled sheet annealed steel sheet was heat-treated at a temperature in the range of 300 ° C to 900 ° C for 5 minutes. Then, after cold rolling to an intermediate thickness of 1.5 mm, an intermediate annealing of 1100 ° C. × 80 s was performed, and then final cold rolling was performed to a sheet thickness of 0.23 mm. Thereafter, decarburization annealing at 850 ° C. × 120 s was performed, and after applying an annealing separator mainly composed of MgO, finish annealing was also performed which also served as purification annealing held at 1150 ° C. for 6 hours. The test piece after finish annealing thus obtained was measured for iron loss W _17/50 at a magnetic flux density of 1.7 T and an excitation frequency of 50 Hz in accordance with JIS C2550.

  FIG. 2 shows the measurement results of the magnetic properties of the test piece. By setting the soaking temperature of the heat treatment in the range of 500 ° C. to 800 ° C., a good iron loss of 0.85 W / kg or less can be obtained.

The inventors consider the reason why it is necessary to set the soaking temperature in the range of 500 to 800 ° C. as follows. When the soaking temperature is less than 500 ° C., the spheroidization of the layered cementite does not proceed sufficiently, and when it exceeds 800 ° C., the austenitization of the pearlite structure proceeds by exceeding the A ₁ point of the steel. When cooled to ₁ point or less, the pearlite structure will precipitate again, so the grain size before the final cold rolling cannot be made coarse by cementite spheroidization, resulting in the primary recrystallization texture This is probably because the frequency of the {411} <148> orientation in the inside cannot be increased.

The present invention has been made based on the above findings.
That is, the gist configuration of the present invention is as follows.
(1) By mass%, C: 0.002% to 0.150%, Si: 2.5% to 6.0%, Mn: 0.01% to 0.80%, Al: 0.010% to 0.050%, N: 0.003% to 0.020% The following is also applied to steel slabs containing one or two elements selected from S: 0.002% to 0.030% and Se: 0.002% to 0.100%, with the balance being composed of Fe and inevitable impurities. Hot-rolled steel sheet is subjected to hot rolling, the hot-rolled steel sheet is subjected to hot-rolled sheet annealing, and the hot-rolled steel sheet after the hot-rolled sheet annealing is subjected to cold rolling at least twice including intermediate annealing. A steel sheet, subjected to decarburization annealing on the cold-rolled steel sheet, and a method for producing a grain-oriented electrical steel sheet that is subjected to finish annealing on the cold-rolled steel sheet after the decarburization annealing, wherein the hot-rolled sheet annealing is performed at 800 to 400 ° C The cooling rate up to 20 ° C / s or more, and after the hot-rolled sheet annealing and until the intermediate annealing after the first cold rolling, at a temperature of 500 ° C to 800 ° C for 30 seconds Method for producing a grain-oriented electrical steel sheet, wherein the heat treatment is less than the upper 600 seconds.

  (2) The above component composition is further in mass%, Cr: 0.01% to 0.50%, Cu: 0.01% to 0.50%, P: 0.005% to 0.500%, Ni: 0.01% to 1.50%, Sb: 0.005% to 0.500%, Sn: 0.005% to 0.500%, Mo: 0.005% to 0.100%, B: 0.0002% to 0.0025%, Nb: 0.0010% to 0.0100% and V: 0.001% or more The method for producing a grain-oriented electrical steel sheet according to (1) above, comprising one or more selected from 0.010% or less.

  (3) The method for producing a grain-oriented electrical steel sheet according to (1) or (2), wherein the decarburization annealing is performed at a heating rate from 500 ° C to 700 ° C of 80 ° C / s or more. .

  (4) The method for producing a grain-oriented electrical steel sheet according to any one of (1) to (3), wherein the cold-rolled steel sheet is subjected to a magnetic domain refinement process.

  (5) The method for producing a grain-oriented electrical steel sheet according to (4), wherein the magnetic domain subdividing treatment is performed by irradiating the cold-rolled steel sheet after the finish annealing with a continuous laser beam. .

  (6) The method for producing a grain-oriented electrical steel sheet according to (4), wherein the magnetic domain refinement process is performed by electron beam irradiation on the cold-rolled steel sheet after the finish annealing.

  According to the present invention, a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss can be produced without significantly reducing productivity.

It is a graph which shows the influence with respect to the iron loss of the soaking time of the heat processing after hot-rolled sheet annealing. It is a graph which shows the influence with respect to the iron loss of the soaking temperature of the heat processing after hot-rolled sheet annealing.

  Hereinafter, the manufacturing method of the grain-oriented electrical steel sheet by one Embodiment of this invention is demonstrated. First, the component composition of the steel material (slab) used for the material of the grain-oriented electrical steel sheet of the present invention will be described. In the present specification, “%” representing the content of each component element means “% by mass” unless otherwise specified.

C: 0.002% or more and 0.150% or less If C is less than 0.002%, the grain boundary strengthening effect due to C is lost, and cracks due to slabs occur, which hinders production. On the other hand, if it exceeds 0.150%, it becomes difficult to reduce C to 0.005% or less which does not cause time aging by decarburization annealing. Therefore, C is in the range of 0.002% to 0.150%. Preferably they are 0.01% or more and 0.150% or less.

Si: 2.5% to 6.0%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If the effect is less than 2.5%, it is not sufficient. On the other hand, if it exceeds 6.0%, the workability deteriorates and it becomes difficult to produce by rolling. Therefore, Si should be in the range of 2.5% to 6.0%. Preferably, it is 2.9% or more and 5.0% or less.

Mn: 0.01% or more and 0.80% or less
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.01%, the effect is not sufficiently obtained. On the other hand, if it exceeds 0.80%, the magnetic flux density of the product plate is lowered. Therefore, Mn is in the range of 0.01% to 0.80%. Preferably it is 0.02% or more and 0.50% or less of range.

Al: 0.010% to 0.050%, N: 0.003% to 0.020%
Both Al and N are necessary as inhibitor-forming elements, but if the amount is less than the above lower limit value, the inhibitor effect cannot be sufficiently obtained. On the other hand, if the upper limit value is exceeded, the solid solution temperature becomes high and the slab is reheated. Even if it is performed, it remains undissolved and deteriorates the magnetic properties. Therefore, Al ranges from 0.010% to 0.050%, and N ranges from 0.003% to 0.020%. Preferably, Al ranges from 0.015% to 0.035%, and N ranges from 0.005% to 0.015%.

One or two selected from S: 0.002% to 0.030% and Se: 0.002% to 0.100% S and Se both bind to Mn to form an inhibitor, but the content of each is lower than the above lower limit If the amount is less, the inhibitor effect cannot be sufficiently obtained. On the other hand, if the above upper limit is exceeded, the solid solution temperature becomes high, and even when the slab is reheated, it remains undissolved and deteriorates the magnetic properties. Let Preferably, the range is S: 0.004% to 0.015% and Se: 0.005% to 0.050%.

  The basic components in the present invention are as described above, and the balance is Fe and inevitable impurities. Examples of such unavoidable impurities include impurities inevitably mixed from raw materials, production facilities, and the like.

  The basic components of the present invention have been described above. However, in the present invention, the following elements can be appropriately contained as needed.

Cr: 0.01% to 0.50%
Cr is a useful element for improving productivity by stabilizing the formation of forsterite coating during finish annealing and reducing coating defects. However, if the content is less than 0.01%, the effect of stabilizing the film formation is poor, and if it exceeds 0.50%, the magnetic flux density deteriorates. Therefore, Cr is in the range of 0.01% to 0.50%. Preferably it is 0.05 to 0.40% of range.

Ni: 0.01% or more and 1.50% or less
Since Ni is an austenite-forming element, Ni is a useful element for improving the hot rolled sheet structure and improving magnetic properties by utilizing the austenite transformation. However, if the content is less than 0.01%, the effect of improving the magnetic properties is small. On the other hand, if the content exceeds 1.50%, the workability deteriorates and the plateability deteriorates, and secondary recrystallization becomes unstable. As a result, the magnetic properties deteriorate. Therefore, Ni is set in the range of 0.01% to 1.50%. Preferably it is 0.10% or more and 0.60% or less of range.

Sn: 0.005% to 0.500%, Sb: 0.005% to 0.500%, P: 0.005% to 0.500%, Cu: 0.01% to 0.50%, Mo: 0.005% to 0.100%
Sn, Sb, P, Cu and Mo are elements useful for improving magnetic properties. However, if the content is less than the lower limit of the above range, the effect of improving the magnetic properties is poor, while the content is When the upper limit of the above range is exceeded, secondary recrystallization becomes unstable and the magnetic properties deteriorate. Therefore, Sn: 0.005% to 0.500%, Sb: 0.005% to 0.500%, P: 0.005% to 0.500%, Cu: 0.01% to 0.50%, Mo: 0.005% to 0.100%, respectively Can be contained. Preferably, Sn: 0.01% to 0.10%, Sb: 0.01% to 0.10%, P: 0.01% to 0.10%, Cu: 0.05% to 0.3%, Mo: 0.01% to 0.05% is there.

B: 0.0002% or more and 0.0025% or less, Nb: 0.0010% or more and 0.0100% or less, V: 0.001% or more and 0.010% or less B, Nb, and V all precipitate as fine nitrides or carbides, thereby acting as inhibitors However, it is an element useful for improving the magnetic flux density. However, if the content is less than the lower limit of the above range, the effect of improving the magnetic properties is poor. On the other hand, if the content exceeds the above range, purification in finish annealing becomes difficult and iron loss deteriorates. . Therefore, B: 0.0002% or more and 0.0025% or less, Nb: 0.0010% or more and 0.0100% or less, and V: 0.001% or more and 0.010% or less, respectively. Preferably, B: 0.0002% to 0.0015%, Nb: 0.0010% to 0.0060%, and V: 0.001% to 0.0060%.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
A steel material (slab) may be produced by a conventional ingot-bundling rolling or continuous casting method after melting the steel having the above-described composition by a conventional refining process, or by direct casting. A thin cast piece having a thickness of 100 mm or less may be manufactured by the method. The slab is reheated to a temperature of about 1400 ° C. and subjected to hot rolling according to a conventional method.

  Next, hot-rolled sheet annealing is performed on the hot-rolled steel sheet obtained by hot rolling. The temperature of this hot-rolled sheet annealing is preferably in the range of 800 to 1150 ° C. in order to obtain good magnetic properties. If it is less than 800 ° C., the band structure formed by hot rolling remains, and it becomes difficult to obtain a primary recrystallized structure of sized particles, which inhibits the growth of secondary recrystallized grains. On the other hand, when the temperature exceeds 1150 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, so that it becomes difficult to obtain a primary recrystallized structure of sized particles.

  Further, as a feature of the present invention, in the cooling process of hot-rolled sheet annealing, a range of 800 ° C. to 400 ° C. needs to be a cooling rate of 20 ° C./s or more. When the cooling rate is slower than 20 ° C./s, the layer spacing of the layered carbides precipitated by pearlite transformation is not sufficiently refined, the time required for the spheroidizing treatment becomes long, and the treatment in the continuous annealing furnace becomes difficult, Productivity is greatly reduced. The cooling rate is preferably 40 ° C./s or more, more preferably 60 ° C./s or more. In order to obtain a pearlite structure or a martensite structure having a fine layer interval after hot-rolled sheet annealing, it is necessary that the rapid cooling start temperature is 800 ° C or higher and the rapid cooling stop temperature is 400 ° C or lower. When the rapid cooling start temperature is lower than 800 ° C., pearlite transformation occurs before the rapid cooling start, and when the rapid cooling stop temperature is higher than 400 ° C., the layer spacing of the pearlite structure cannot be sufficiently refined. The quenching start temperature may be higher than 800 ° C., but for example, as disclosed in JP-A-57-198214, 800 ° C. or more is used for the purpose of fine precipitation of inhibitors such as AlN and MnS. It may be slow cooling to an appropriate temperature, and rapid cooling at a temperature lower than 20 ° C./s. The quenching stop temperature may be 400 ° C. or less, and it is also effective to quench to near room temperature for the purpose of precipitation of martensite. The quenching stop temperature is preferably 300 ° C, more preferably 200 ° C.

Then, after hot-rolled sheet annealing, the final sheet thickness is obtained by cold rolling at least twice with intermediate annealing.
Here, as a feature of the present invention, between hot rolled sheet annealing and intermediate annealing after the first cold rolling, annealing at a temperature of 500 ° C. to 800 ° C. for 30 seconds to less than 600 seconds, a spherical shape The process is applied. The spheroidizing process spheroidizes the layered carbide in pearlite and coarsens the recrystallized grain size after intermediate annealing, increasing the {411} <148> orientation in the primary recrystallized texture, and increasing the product magnetic flux. The density is improved.

  If the temperature of the spheroidizing treatment is lower than 500 ° C., the spheroidization of the layered carbide does not proceed, and if it is higher than 800 ° C., the pearlite partially undergoes austenite transformation and the spheroidizing does not proceed. Therefore, the spheroidizing treatment temperature needs to be in the range of 500 to 800 ° C. Preferably, it is 600 to 760 ° C. The spheroidizing time is 30 seconds or more and less than 600 seconds. When the treatment time is shorter than 30 seconds, the spheroidization of the layered carbide does not proceed sufficiently. If the treatment time is 30 seconds or more, a long treatment may be performed, but annealing for 600 seconds or more can obtain a spheroidizing effect without using the present invention, and a short time for spheroidizing annealing. In order to deviate from the problem of the present invention, that is, the spheroidizing annealing is performed in a continuous annealing line that does not require a long facility from the viewpoint of productivity, the upper limit of the annealing time is set to less than 600 seconds. The treatment time for spheroidization is preferably 180 seconds or more. As long as the spheroidizing treatment can ensure a predetermined time within the temperature range of the present invention, the heat pattern is not particularly limited, and the heating rate and the cooling rate are not particularly limited. Moreover, although the equipment which performs a spheroidization process is not specifically limited, It is preferable to use the continuous annealing furnace which can perform heating and cooling in a short time, and is excellent in productivity. Moreover, you may carry out continuously by the annealing furnace which implements hot-rolled sheet annealing or intermediate annealing.

  The spheroidizing treatment is intended to spheroidize the layered carbide or martensite structure precipitated at a fine layer interval after the hot-rolled sheet annealing, so that the effect cannot be obtained even if it is performed before the hot-rolled sheet annealing. In addition, by performing the intermediate annealing, the fine pearlite structure and martensite structure are transformed back to austenite and returned to the original state, so that the effect of shortening the spheroidizing treatment cannot be obtained. Accordingly, the spheroidizing treatment needs to be performed after the hot-rolled sheet annealing and before the intermediate annealing after the first cold rolling.

  The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. Below 900 ° C, the recrystallized grains become finer and the Goss orientation nuclei in the primary recrystallized structure decrease, leading to a decrease in magnetic properties. On the other hand, when the temperature exceeds 1200 ° C., the grain size becomes too coarse as in the case of hot-rolled sheet annealing, so that it becomes difficult to obtain a primary recrystallized structure of sized particles.

  The rolling reduction in the final cold rolling is not particularly limited, but it is more than 70% for the purpose of increasing the {111} <112> orientation and {411} <148> orientation in the primary recrystallization texture. A high pressure is preferred. More preferably, it is 80% or more.

  The cold-rolled steel sheet rolled to the final thickness is subjected to decarburization annealing at a soaking temperature of 700 to 1000 ° C. When the soaking temperature is less than 700 ° C., primary recrystallization and decarburization do not proceed sufficiently, and a desired primary recrystallization texture cannot be obtained. On the other hand, when the temperature exceeds 1000 ° C., the primary grain size becomes too coarse, so that the driving force of secondary recrystallization is lost, and secondary recrystallization of Goss orientation grains may not occur in the subsequent finish annealing. Accordingly, the soaking temperature for decarburization annealing is preferably 700 to 1000 ° C.

  Here, in order to further increase the Goss orientation and {411} <148> orientation of the primary recrystallization texture, the heating rate of 500 to 700 ° C. in the heating process of decarburization annealing is set to 80 ° C./s or more. It is desirable. This is due to rapid heating in the range of 500-700 ° C, where the cold-rolled structure recovers and undergoes primary recrystallization. Strain tends to accumulate due to cold rolling, and recrystallization preferentially proceeds {111} / The purpose is to suppress recrystallization of / ND oriented grains and promote recrystallization of Goss orientation and {411} <148> orientation. As a result, an increase in {411} <148> orientation improves the magnetic flux density of the product, and an increase in Goss orientation reduces the secondary recrystallization grain size of the product and reduces iron loss. When the heating rate is less than 80 ° C./s, recrystallization in the {111} // ND orientation preferentially proceeds and the effect of rapid heating cannot be obtained. Therefore, the heating rate is preferably 80 ° C./s or more. More preferably, it is 120 ° C./s or more. In addition, recovery and recrystallization of {111} // ND oriented grains proceeds when the rapid heating start temperature exceeds 500 ° C, and Goss orientation and {411} <148 when the rapid heating stop temperature is less than 700 ° C. > Recrystallization of orientation is not promoted, and the effect of improving the primary recrystallization texture cannot be obtained. Accordingly, the temperature for rapid heating is preferably in the range of 500 to 700 ° C. More preferably, it is 300 degreeC-700 degreeC.

Other conditions relating to decarburization annealing may be in accordance with known methods, for example, for the purpose of promoting decarburization and forming an oxide layer on the steel sheet surface as a material for forming forsterite film during finish annealing. It is preferable to make the annealing atmosphere oxidizing. For example, by using an N ₂ · H ₂ mixed atmosphere containing water vapor, it becomes easy to control the oxidizing property and the decarburizing property.

  When steel sheet that has undergone decarburization annealing places importance on iron loss characteristics and transformer noise, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, dried, then subjected to finish annealing, and advanced in the Goss direction. It is preferable to develop a secondary recrystallized structure accumulated in the film and to form a forsterite film. On the other hand, when emphasizing the punching processability and not forming the forsterite film, it is not necessary to apply an annealing separator or to perform a final annealing using an annealing separator mainly composed of silica, alumina or the like. preferable. In addition, when a forsterite film is not formed, it is also effective to perform electrostatic coating without bringing moisture into the coating of the annealing separator. Further, a heat resistant inorganic material sheet (silica, alumina, mica) may be used in place of the annealing separator.

  When the forsterite film is not formed, the annealing temperature in the finish annealing is preferably in the range of 850 to 1100 ° C. At this time, when only the completion of the secondary recrystallization is intended, the finish annealing can be completed only by holding for several hours or more in the above temperature range. On the other hand, when a forsterite film is formed or when iron loss characteristics are emphasized and a purification treatment is performed, it is preferable to further raise the temperature to about 1200 ° C.

  After finishing annealing, the steel sheet can be cleaned by washing, brushing, pickling, etc., removing unreacted annealing separator adhering to the steel sheet surface, and then flattening annealing to correct the shape, thereby reducing iron loss. Is effective. This is because the finish annealing is usually performed in a coil state, so that the coil has wrinkles and this may cause deterioration in characteristics when measuring iron loss.

  Furthermore, in the case where the steel plates are laminated and used, it is effective to form an insulating film on the steel plate surface in the above-described flattening annealing or before and after that. In particular, in order to reduce iron loss, it is preferable to apply a tension-imparting film that imparts tension to the steel sheet as the insulating film. For the formation of a tension-imparting film, it is possible to apply a method of applying a tension film through a binder or a method of depositing an inorganic substance on a steel sheet surface by physical vapor deposition or chemical vapor deposition. Since an insulating film having a large loss reducing effect can be formed, it is more preferable.

  Furthermore, it is preferable to perform a magnetic domain fragmentation process to reduce iron loss. As a general processing method, the final product plate thickness has been reached, such as a method of grooving the final product plate or introducing thermal strain or impact strain linearly with a laser or plasma jet. A method may be used in which grooves are provided in advance in an intermediate product such as a cold rolled sheet.

  Other manufacturing conditions may follow the general manufacturing method of a grain-oriented electrical steel sheet.

Example 1
After heating a steel slab containing C: 0.06%, Si: 3.2%, Mn: 0.08%, Al: 0.025%, N: 0.008%, Se: 0.02% in mass% at a temperature of 1400 ° C, The sheet was rolled to a thickness of 2.2 mm and subjected to hot-rolled sheet annealing at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was set in the range of 10 ° C./s to 200 ° C./s. Next, a part of the steel sheets subjected to hot-rolled sheet annealing was subjected to heat treatment soaking in the range of 400 to 700 ° C. for 20 seconds to 3600 seconds. Then, after cold rolling to an intermediate thickness of 1.5 mm, an intermediate annealing of 1100 ° C. × 80 s was performed, and then final cold rolling was performed to a sheet thickness of 0.23 mm. Thereafter, decarburization annealing at 850 ° C. × 120 s was performed. Here, the heating rate of 500 ° C. to 700 ° C. in the decarburization annealing is set to 20 ° C./s, and the annealing is performed in an N ₂ / H ₂ mixed atmosphere containing water vapor of atmosphere oxidizing PH ₂ O / PH ₂ = 0.40. It was. Next, after applying an annealing separator mainly composed of MgO, a finish annealing was performed which also served as a purification annealing held at 1150 ° C. for 6 hours. With respect to the test piece after finish annealing thus obtained, the magnetic flux density 1.7T, the iron loss W _{17/50 at} an excitation frequency of 50 Hz, and the magnetic flux density B ₈ at a magnetizing force of 800 A / m were measured according to JIS C2550.
Table 1 shows the results of measuring the magnetic properties of the test pieces.

  As shown in Table 1, by setting the cooling rate of hot-rolled sheet annealing and the temperature and time of spheroidizing treatment within the scope of the present invention, the magnetic flux density is improved even in short-time spheroidizing annealing, It turns out that a favorable iron loss is obtained.

(Example 2)
After heating a steel slab containing C: 0.07%, Si: 3.6%, Mn: 0.05%, Al: 0.020%, N: 0.005%, S: 0.02% in mass% at a temperature of 1400 ° C, The sheet was rolled to a thickness of 2.4 mm and subjected to hot rolled sheet annealing at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was set to 80 ° C./s. Thereafter, a plurality of cold rolling was performed to a final thickness of 0.23 mm. Here, some of the samples after hot-rolled sheet annealing were subjected to cold rolling twice with one intermediate annealing, and the intermediate thickness was 1.8 mm. In addition, the remaining samples were subjected to cold rolling three times with two intermediate annealings, the intermediate thickness after the first cold rolling was 2.0 mm, and the intermediate thickness after the second cold rolling was 1.5 mm. did. Under any condition, the intermediate annealing was performed at 1100 ° C. for 80 s. In addition, some of the samples that had been cold-rolled twice were subjected to spheroidizing treatment at 700 ° C. for 300 seconds either before or after the first cold rolling or before or after the second cold rolling. . In addition, some samples subjected to three cold rollings were 300 ° C. at 700 ° C. either before or after the first cold rolling, before or after the second cold rolling, and before or after the third cold rolling. A second spheronization treatment was applied. Thereafter, the final cold-rolled sheet was subjected to decarburization annealing at 850 ° C. for 120 s. Here, the heating rate of 500 ° C. to 700 ° C. in the decarburization annealing is set to 20 ° C./s, and the annealing is performed in an N ₂ / H ₂ mixed atmosphere containing water vapor of atmosphere oxidizing PH ₂ O / PH ₂ = 0.40. It was. Next, after applying an annealing separator mainly composed of MgO, a finish annealing was performed which also served as a purification annealing held at 1150 ° C. for 6 hours. With respect to the test piece after finish annealing thus obtained, the magnetic flux density 1.7T, the iron loss W _{17/50 at} an excitation frequency of 50 Hz, and the magnetic flux density B ₈ at a magnetizing force of 800 A / m were measured according to JIS C2550.
Table 2 shows the results of measuring the magnetic properties of the test pieces.

  As shown in Table 2, good iron loss can be obtained either before or after the first cold rolling, that is, after the hot-rolled sheet annealing and after the first cold rolling. It can be seen that only when the spheroidizing process is performed.

(Example 3)
Heating a steel slab containing C: 0.07%, Si: 3.4%, Mn: 0.06%, Al: 0.022%, N: 0.010%, S: 0.008%, Se: 0.02% at a temperature of 1400 ° C. After that, it was hot-rolled to a thickness of 2.4 mm and subjected to hot-rolled sheet annealing at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was set to 100 ° C./s. Next, spheronization treatment was performed by soaking at 700 ° C. for 30 seconds or 580 seconds. Then, after cold rolling to an intermediate thickness of 1.5 mm, an intermediate annealing of 1100 ° C. × 80 s was performed, and then final cold rolling was performed to a sheet thickness of 0.23 mm.

  Here, some samples subjected to the final cold rolling were subjected to electrolytic etching followed by resist printing using a gravure roll, with a width of 100 mm and a depth extending from the plate width direction to a direction inclined by 30 ° within the rolling surface. Magnetic domain refinement treatment was performed to form grooves with a thickness of 30 μm at intervals of 5 mm in the rolling direction.

Next, decarburization annealing at 850 ° C. × 120 s was performed. Here, the heating rate of 500 ° C. to 700 ° C. in the decarburization annealing is set in the range of 50 ° C./s to 200 ° C./s, and the annealing is N ₂ · containing water vapor of atmospheric oxidizing PH ₂ O / PH ₂ = 0.40. Performed in H ₂ mixed atmosphere. Next, after applying an annealing separator mainly composed of MgO, a finish annealing was performed which also served as a purification annealing held at 1150 ° C. for 6 hours.

  Next, a part of the sample in which the etching groove was not formed after the final cold rolling was subjected to magnetic domain fragmentation treatment by laser irradiation or electron beam irradiation. Here, the magnetic domain fragmentation treatment by laser irradiation was performed by irradiating a continuous laser with a beam diameter of 0.3 mm and an output of 200 W horizontally at an operation speed of 100 m / s in the plate width direction and at intervals of 5 mm in the rolling direction. Further, the magnetic domain fragmentation treatment by electron beam irradiation was performed by irradiating an electron beam with an acceleration voltage of 100 kV and a beam current of 3 mA horizontally in the plate width direction and at intervals of 5 mm in the rolling direction.

With respect to the test piece after finish annealing thus obtained, the magnetic flux density 1.7T, the iron loss W _{17/50 at} an excitation frequency of 50 Hz, and the magnetic flux density B ₈ at a magnetizing force of 800 A / m were measured according to JIS C2550.
Table 3 shows the results of measuring the magnetic properties of the test pieces.

  As shown in Table 3, it can be seen that by setting the heating rate of 500 to 700 ° C. for decarburization annealing to 80 ° C./s or more, even better magnetic properties can be obtained. It can also be seen that better magnetic properties can be obtained by performing magnetic domain fragmentation treatment by etching grooves, laser irradiation or electron beam irradiation.

Example 4
The slabs having the components shown in Table 4 were heated at a temperature of 1400 ° C., and then hot-rolled to a thickness of 2.4 mm and subjected to hot-rolled sheet annealing at 1100 ° C. for 60 seconds. Here, in the cooling process of hot-rolled sheet annealing, the cooling rate from 800 ° C. to 400 ° C. was set to 100 ° C./s. Next, a spheronization treatment was performed by soaking at 700 ° C. for 580 seconds. Then, after cold rolling to an intermediate thickness of 1.5 mm, an intermediate annealing of 1100 ° C. × 80 s was performed, and then final cold rolling was performed to a sheet thickness of 0.23 mm. Next, decarburization annealing at 850 ° C. × 120 s was performed. Here, the heating rate of 500 ° C. to 700 ° C. of decarburization annealing is set to 50 ° C./s, and the annealing is performed in a N ₂ / H ₂ mixed atmosphere containing water vapor of atmosphere oxidizing PH ₂ O / PH ₂ = 0.40. It was. Next, after applying an annealing separator mainly composed of MgO, a finish annealing was performed which also served as a purification annealing held at 1150 ° C. for 6 hours. With respect to the test piece after finish annealing thus obtained, the magnetic flux density 1.7T, the iron loss W _{17/50 at} an excitation frequency of 50 Hz, and the magnetic flux density B ₈ at a magnetizing force of 800 A / m were measured according to JIS C2550.
Table 4 shows the results of measuring the magnetic properties of the test pieces.

As shown in Table 4, it is understood that good magnetic properties can be obtained by setting C, Si, Mn, Al, N, S, and Se within the scope of the present invention.
It can also be seen that even better magnetic properties can be obtained by adding Cr, Cu, P, Ni, Sb, Sn, Mo, B, Nb, and V within the scope of the present invention.

Claims (6)

% By mass
C: 0.002% to 0.150%,
Si: 2.5% to 6.0%,
Mn: 0.010 % or more and 0.800 % or less,
Al: 0.010% or more and 0.050% or less,
N: 0.003% or more and 0.020% or less, S: 0.002% or more and 0.030% or less, and Se: 0.002% or more and 0.100% or less, one or two selected, the balance consisting of Fe and inevitable impurities Hot-rolled steel slab having a composition is subjected to hot rolling,
Subjecting the hot-rolled steel sheet to hot-rolled sheet annealing,
The hot-rolled steel sheet after the hot-rolled sheet annealing is cold-rolled steel sheet by subjecting the hot-rolled steel sheet to cold rolling at least twice with intermediate annealing.
Subjecting the cold-rolled steel sheet to decarburization annealing,
A method for producing a grain-oriented electrical steel sheet for subjecting a cold-rolled steel sheet after decarburization annealing to finish annealing,
The cooling rate from 800 ° C. to 400 ° C. of the hot-rolled sheet annealing is 20 ° C./s or more,
A directional electromagnetic wave characterized by performing heat treatment for 30 seconds or more and less than 600 seconds at a temperature of 500 ° C. or more and 800 ° C. or less after the hot-rolled sheet annealing and before the intermediate annealing after the first cold rolling. A method of manufacturing a steel sheet. The component composition further includes:
% By mass
Cr: 0.01% or more and 0.50% or less,
Cu: 0.01% to 0.50%,
P: 0.005% to 0.500%,
Ni: 0.01% or more and 1.50% or less,
Sb: 0.005% to 0.500%,
Sn: 0.005% or more and 0.500% or less,
Mo: 0.005% or more and 0.100% or less,
B: 0.0002% to 0.0025%,
The method for producing a grain-oriented electrical steel sheet according to claim 1, comprising one or more selected from Nb: 0.0010% to 0.0100% and V: 0.001% to 0.010%. .   The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the decarburization annealing is performed at a heating rate from 500 ° C to 700 ° C of 80 ° C / s or more.   The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the cold-rolled steel sheet is subjected to a magnetic domain refinement process.   5. The method for producing a grain-oriented electrical steel sheet according to claim 4, wherein the magnetic domain refinement treatment is performed by irradiating the cold-rolled steel sheet after the finish annealing with a continuous laser beam.   5. The method for producing a grain-oriented electrical steel sheet according to claim 4, wherein the magnetic domain subdividing process is performed by electron beam irradiation to the cold-rolled steel sheet after the finish annealing.

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