JP2014194077A - Method for manufacturing oriented electromagnetic steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oriented electromagnetic steel sheet having low iron loss, small variation of iron loss in a coil and high productivity.SOLUTION: In a method for manufacturing an oriented electromagnetic steel sheet that comprises a series of processes including hot rolling of a steel raw material containing C:0.002 to 0.10 mass%, Si:2.0 to 8.0 mass% and Mn:0.005 to 1.0 mass%, cold rolling to obtain a cold rolled sheet having a final thickness without hot rolled sheet firing or after conducting hot rolled sheet firing, primary recycling firing with decarbonization firing, then applying a firing separation agent to a surface of the steel sheet, and finish firing, final cold rolling is conducted by a tandem rolling, a heating process of the primary recycling firing is conducted by a rapid heating at 50°C/s or more from 200 to 700°C, and a retention treatment for retaining any temperature between 250°C or more and less than 550°C in the heating process for 0.5 to 10 seconds is conducted 1 to 4 times.

Description

  The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet, and more specifically to a method for producing a grain-oriented electrical steel sheet with low iron loss and small variation in iron loss within a coil.

  Electrical steel sheets are soft magnetic materials that are widely used as core materials for transformers and motors. Among them, grain oriented electrical steel sheets are highly integrated in the {110} <001> orientation, which is called the Goss orientation. Because of its excellent magnetic properties, it is mainly used for iron cores of large transformers. In order to reduce the no-load loss (energy loss) in the transformer, it is necessary that the iron loss is low.

  Iron loss reduction method for grain-oriented electrical steel sheets includes increasing Si content, reducing plate thickness, improving crystal orientation orientation, imparting tension to the steel sheet surface, smoothing the steel sheet surface, secondary recrystallization texture It is known that fine graining is effective.

Among these methods, the technology for refining secondary recrystallized grains includes rapid heating at the time of decarburization annealing, or heat treatment to be rapidly heated immediately before decarburization annealing, thereby providing a primary recrystallization texture. A method for improving the above has been proposed. For example, in Patent Document 1, when decarburizing and annealing a cold-rolled sheet rolled to the final sheet thickness, in a non-oxidizing atmosphere where P _H2O / _PH2 is 0.2 or less, the temperature is 100 ° C./s or more and 700 ° C. A technique for obtaining a grain-oriented electrical steel sheet with low iron loss by rapid heating to the above temperature is disclosed. Patent Document 2 discloses that the oxygen concentration in the atmosphere is set to 500 ppm or less, and is rapidly heated to 800 to 950 ° C. at a heating rate of 100 ° C./s or higher, and subsequently 775 to 840 ° C. lower than the temperature after the rapid heating. A technique for obtaining a grain-oriented electrical steel sheet with low iron loss by holding at a temperature of 815 ° C. and further holding at a temperature of 815 to 875 ° C. is disclosed. Patent Document 3 discloses that the film characteristics and the film characteristics are obtained by heating a temperature range of 600 ° C. or higher to 800 ° C. or higher at a rate of temperature increase of 95 ° C./s or more and appropriately controlling the atmosphere in this temperature range. A technique for obtaining an electrical steel sheet having excellent magnetic properties is disclosed. Furthermore, in Patent Document 4, the amount of N as AlN in the hot-rolled sheet is limited to 25 ppm or less, and heating at a heating rate of 80 ° C./s to 700 ° C. or more during decarburization annealing reduces low iron loss. A technique for obtaining a grain-oriented electrical steel sheet is disclosed.

  In these techniques for improving the primary recrystallization texture by rapid heating, the temperature range for rapid heating is from room temperature to 700 ° C. or higher, and the rate of temperature rise is uniquely defined. This technical idea suppresses the development of γ fibers (<111> // ND orientation) that are preferentially formed at a normal heating rate by raising the temperature to near the recrystallization temperature in a short time, The primary recrystallization texture is intended to be improved by promoting the generation of a {110} <001> structure that becomes the nucleus of secondary recrystallization. By applying this technique, the crystal grains (Goss-oriented grains) after the secondary recrystallization are refined, and the iron loss characteristics are improved.

Japanese Patent Laid-Open No. 07-062436 Japanese Patent Laid-Open No. 10-298653 JP 2003-027194 A Japanese Patent Laid-Open No. 10-130729

  However, according to the knowledge of the inventors, when the rate of temperature increase is increased, there is a problem that the variation in iron loss characteristics, which is considered to be caused by temperature unevenness inside the steel sheet at the time of temperature increase, becomes large. The iron loss evaluation at the time of product shipment generally uses the average value of the iron loss of the full width of the steel sheet. Therefore, if the variation is large, the iron loss of the entire steel sheet will be evaluated low, which is expected. The effect of rapid heating cannot be obtained.

  Moreover, in the prior art represented by the said patent document, in order to improve a magnetic characteristic, in the last cold rolling, the aging treatment which hold | maintains at a temperature of 100 degreeC or more for 1 minute or more in the middle of rolling is provided at least once or more. This is the basic idea. In order to carry out the aging treatment in actual operation, it is preferable to roll with a reverse mill. However, in reverse rolling, the steel sheet is cooled by removing heat from the inner winding part that contacts the mandrel during winding of the steel sheet on the coil, or by heat radiation from the outer peripheral surface of the coil after winding. Therefore, a desired aging effect cannot be obtained at both ends of the coil in the longitudinal direction, and the iron loss characteristic is deteriorated. Moreover, there is a problem that productivity is inferior compared with tandem rolling.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is a low iron loss compared to the prior art, a small variation in iron loss in the coil, and a high productivity direction. The purpose of this invention is to propose a method for producing a heat-resistant electrical steel sheet.

  The inventors have intensively studied to solve the above problems. As a result, when performing rapid heating in the heating process of primary recrystallization annealing, the temperature inside the steel sheet is made uniform by applying a holding treatment that holds for a predetermined time in the temperature range where recovery occurs, and the effect of rapid heating is reduced to the full width of the steel sheet <111> // ND orientation preferentially recovers and <111> // ND orientation after primary recrystallization decreases, and Goss nuclei increase instead, after secondary recrystallization. As a result of the recrystallization being further refined, it has been found that a grain-oriented electrical steel sheet having low iron loss and small variation in iron loss within the coil can be obtained. In addition, by applying the above heat treatment, it has been found that good iron loss characteristics can be obtained over the entire length in the longitudinal direction of the coil without applying an aging treatment in the middle of the final cold rolling, which has conventionally been essential, The present invention has been developed.

  That is, the present invention hot-rolls a steel material containing C: 0.002 to 0.10 mass%, Si: 2.0 to 8.0 mass%, and Mn: 0.005 to 1.0 mass%. After rolling and hot-rolled sheet annealing or hot-rolled sheet annealing, cold rolling is performed once or two or more times with intermediate annealing between them to form a cold-rolled sheet with the final thickness, and decarburized annealing In the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which an annealing separator is applied to the steel sheet surface after the primary recrystallization annealing also serves as a finish annealing, and the final cold rolling is performed by tandem rolling, and In the heating process of the primary recrystallization annealing, rapid heating is performed at a temperature of 200 to 700 ° C. at 50 ° C./s or more, and 0.5 to 10 at any temperature between 250 ° C. and less than 550 ° C. in the heating process. Apply the retention process for 1 to 4 times. Is a manufacturing method of a grain-oriented electrical steel sheet characterized by and.

Moreover, this invention hot-rolls and heat-rolls the steel raw material containing C: 0.002-0.10 mass%, Si: 2.0-8.0mass%, and Mn: 0.005-1.0mass%. After rolling and hot-rolled sheet annealing or hot-rolled sheet annealing, cold rolling is performed once or two or more times with intermediate annealing between them to form a cold-rolled sheet with the final thickness, and decarburized annealing In the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which an annealing separator is applied to the steel sheet surface after the primary recrystallization annealing also serves as a finish annealing, and the final cold rolling is performed by tandem rolling, and In the heating process of the primary recrystallization annealing, between 200 and 700 ° C. is rapidly heated at 50 ° C./s or more,
After the holding process of holding for 0.5 to 10 seconds at any temperature between 250 ° C. and less than 550 ° C. in the heating process 1 to 4 times, and further, 550 ° C. to less than 700 ° C. in the heating process It is a manufacturing method of a grain-oriented electrical steel sheet characterized by performing a holding process of holding for 0.5 to 3 seconds at any temperature in between, once or twice.

  Moreover, the said steel raw material used for the manufacturing method of the grain-oriented electrical steel sheet of this invention is Al: 0.010-0.050 mass%, N: 0.003-0.020 mass% other than said C, Si, and Mn. , Se: 0.003 to 0.030 mass% and / or S: 0.002 to 0.03 mass%, with the remainder having a component composition composed of Fe and inevitable impurities.

  In addition to the C, Si and Mn, the steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention is Se: 0.003-0.030 mass% and S: 0.002-0.03 mass%. It contains 1 type or 2 types chosen from these, The remainder has the component composition which consists of Fe and an unavoidable impurity.

  In addition to the C, Si and Mn, the steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention includes Al: less than 0.01 mass%, N: less than 0.0050 mass%, Se: 0.0030 mass. % And S: less than 0.0050 mass%, with the remainder having a component composition consisting of Fe and inevitable impurities.

  Moreover, in addition to the said component composition, the said steel raw material used for the manufacturing method of the grain-oriented electrical steel sheet of this invention is further Ni: 0.010-1.50 mass%, Cr: 0.01-0.50 mass%, Cu : 0.01 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.005 to 0 .50 mass%, Mo: 0.005-0.10 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.010 mass%, Nb: 0.0010-0.010 mass%, V: 1 type or 2 types or more chosen from 0.001-0.010mass% and Ta: 0.001-0.010mass% are contained, It is characterized by the above-mentioned.

  According to the present invention, after the final cold rolling is performed by tandem rolling, when rapid heating is performed in the primary recrystallization annealing, it is maintained for a predetermined time in a temperature range where recovery occurs, thereby reducing the iron loss value and the iron loss value. It becomes possible to manufacture grain-oriented electrical steel sheets with small variations with high productivity.

It is a figure explaining the temperature rising pattern in the primary recrystallization annealing of this invention. It is a graph which shows the influence which the holding process time in the middle of the heating of primary recrystallization annealing has on the iron loss _{W17 / 50} . It is a graph which shows the influence which the retention process temperature in the middle of the heating of primary recrystallization annealing has on the iron loss _{W17 / 50} .

First, an experiment that triggered the development of the present invention will be described.
<Experiment 1>
C: 0.060 mass%, Si: 3.32 mass%, Mn: 0.066 mass% Steel is melted and made into a steel slab by a continuous casting method, and then reheated to a temperature of 1400 ° C. Rolled to a hot-rolled sheet with a thickness of 2.2 mm, subjected to hot-rolled sheet annealing at 1050 ° C. × 60 seconds, and then subjected to primary cold rolling to an intermediate plate thickness of 1.8 mm, intermediate at 1120 ° C. × 80 seconds After annealing, tandem rolling or reverse rolling was performed to obtain a cold-rolled sheet having a final sheet thickness of 0.23 mm. At this time, in both tandem rolling and reverse rolling, the maximum temperature of the steel sheet due to processing heat generated during rolling was controlled at 200 ° C.

Next, the cold-rolled sheet was subjected to primary recrystallization annealing with decarburization annealing at 840 ° C. for 80 seconds in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ . The primary recrystallization annealing is a holding treatment in which the rate of temperature increase between 200 and 700 ° C. in the heating process up to 840 ° C. is 100 ° C./s, and the temperature is maintained at 450 ° C. during the heating for 0 to 30 seconds. Was given. Here, as shown in FIG. 1, the rate of temperature increase of 100 ° C./s is t _1, t ₃ and t ₅ excluding the holding time t ₂ and t ₄ from the time to reach 200 ° C. to 700 ° C. Means the average heating rate ((700−200) / (t ₁ + t ₃ + t ₅ )) (hereinafter the same).
Thereafter, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, dried, then recrystallized secondarily, and then subjected to a finish annealing in which a purification treatment is performed at 1200 ° C. for 7 hours in a hydrogen atmosphere. (Coil).

Ten test pieces each having a width of 100 mm and a length of 520 mm in the plate width direction were sampled from the longitudinal center and both ends of the product coil thus obtained, and the iron loss was measured by the method described in JIS C2556. W _17/50 was measured, and the average value of each position (both ends are average values of the _front end and the rear end) was obtained. This is because, according to this iron loss measurement method, when the variation in iron loss is in the sheet width direction, the measured value is deteriorated, so it is considered that the iron loss can be evaluated including the variation. The result is shown in FIG. 2 as the relationship between the _retention time at 450 ° C. and the iron loss W _17/50 . From this figure, the iron loss is reduced in the range of the holding time of 0.5 to 10 seconds, and in the above range, the iron loss deterioration at the coil tail end portion of the tandem rolling is suppressed. I understand.

<Experiment 2>
The cold rolled sheet having a final thickness of 0.27 mm obtained in Experiment 1 was subjected to primary recrystallization annealing with decarburization annealing at 840 ° C. for 80 seconds in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ . . In addition, the temperature increase rate in the heating process of the said primary recrystallization annealing was 100 degreeC / s, and the holding process which hold | maintains for 2 seconds once at the arbitrary temperature of the temperature range of 200-700 degreeC of the heating process was performed. Thereafter, an annealing separator mainly composed of MgO was applied to the steel sheet surface and dried, followed by secondary recrystallization, followed by a finish annealing in which a purification treatment was performed at 1200 ° C. for 7 hours in a hydrogen atmosphere.

A test piece was collected from the product plate thus obtained in the same manner as in Experiment 1, and the iron loss W _17/50 was measured by the method described in JIS C2556. The results are shown in FIG. 3 as the relationship between the retention treatment temperature and the iron loss W _17/50 . From this figure, by performing tandem rolling and setting the holding treatment temperature in the heating process of primary recrystallization annealing to a range of 250 to 550 ° C., the iron loss at both ends of the coil is improved, It can be seen that the iron loss difference is almost eliminated.

  The reason why the iron loss is reduced by applying the retention treatment at the appropriate temperature in the rapid heating process of the primary recrystallization annealing as in <Experiment 1> and <Experiment 2> is still sufficiently clear. However, the inventors think as follows.

  As described above, the rapid heat treatment suppresses the development of the <111> // ND orientation in the recrystallization texture, and the generation of Goss orientation grains ({110} <001>) serving as the nucleus of secondary recrystallization. There is an effect to promote. This is because, generally, in cold rolling, the <111> // ND orientation introduces a larger amount of strain than other orientations, so that the accumulated strain energy is high. For this reason, in primary recrystallization annealing in which heating is performed at a normal temperature increase rate, recrystallization occurs preferentially from a <111> // ND-oriented rolling structure in which accumulated strain energy is high. In recrystallization, since grains with <111> // ND orientation usually appear from a rolled structure with <111> // ND orientation, the structure after recrystallization has the <111> // ND orientation as the main orientation.

  However, since rapid heating gives more thermal energy than that released by recrystallization, recrystallization occurs even in the Goss orientation with a relatively low strain energy. <111> // ND orientation after recrystallization decreases, and Goss orientation ({110} <001>) increases. When the Goss orientation increases, many Goss orientation grains appear in the secondary recrystallization, so the secondary recrystallization grains become finer and the iron loss is reduced. This is the reason for the rapid heating in the prior art.

  Here, in the middle of rapid heating, when a retention treatment is performed to maintain the temperature at which recovery occurs for a predetermined time, the <111> // ND orientation with high strain energy recovers preferentially. Therefore, the driving force causing recrystallization of <111> // ND orientation generated from the rolled structure of <111> // ND orientation is selectively reduced, and other orientations cause recrystallization. As a result, the <111> // ND orientation after recrystallization is relatively further reduced. However, if the retention temperature is too high or if the retention time exceeds 10 seconds, recovery occurs over a wide range, so that the recovered structure remains as it is, and the structure is different from the primary recrystallized structure described above. End up. As a result, the secondary recrystallization is greatly adversely affected and the iron loss characteristics are deteriorated.

  In addition, according to the said idea, the magnetic property improvement effect by performing a short-time holding | maintenance process at the temperature where recovery | restoration in the middle of a heating is acquired is the temperature increase rate (10-20) using the conventional radiant tube etc. It is considered that the rate of temperature increase is higher than (° C./s), specifically, a rate of temperature increase of 50 ° C./s or more. Therefore, in the present invention, the rate of temperature rise in the temperature range of 200 to 700 ° C. for primary recrystallization annealing is defined as 50 ° C./s or more.

  On the other hand, as a demerit of performing rapid heating during primary recrystallization annealing, the time spent on initial oxidation during temperature rise is shortened, so the subscale structure after primary recrystallization annealing changes and during final annealing A film defect may occur, resulting in a secondary recrystallization defect, and the magnetic properties may deteriorate. However, in the present invention, since the temperature is maintained at a temperature between 250 ° C. and less than 550 ° C. during the temperature rise, proper initial oxidation is performed at the time of rapid heating, reducing the deterioration of the film and reducing the magnetic properties. Can be suppressed to some extent.

  However, in order to more reliably obtain the effect of improving the magnetic properties by improving the film, based on the above consideration, a temperature range (250 ° C. or higher and lower than 550 ° C.) in which recovery during the temperature rise occurs, and a temperature at which initial oxidation becomes active. It can be said that it is preferable to perform the retaining treatment in each temperature range (550 ° C. or more and less than 700 ° C.).

  The holding treatment in the temperature range where the recovery occurs (250 ° C. or more and less than 550 ° C.) needs to be held for at least 0.5 seconds in order to cause the recovery. However, if it recovers too much, it may not be recrystallized thereafter, so it is preferable to keep it within 10 seconds at the longest. In addition, the retention treatment in this temperature range may be performed a plurality of times, but if the number of times increases, it is preferable that the number of times is within 4 times because recovery may proceed excessively and recrystallization will not occur. In addition, when a plurality of holding processes are performed, the total holding time is more preferably within 10 seconds.

  Moreover, it is preferable to hold | maintain the retention process in the temperature range (550 degreeC or more and less than 700 degreeC) where initial oxidation becomes active, in order to acquire a film improvement effect, for 0.5 second or more. However, since this temperature range is a temperature range where recrystallization occurs, the retention time is preferably within 3 seconds from the viewpoint of avoiding recrystallization. Similarly, the number of holding treatments in this temperature range is preferably up to 2.

  Regarding the reason why the iron loss is improved at both ends in the coil longitudinal direction where the iron loss has deteriorated in the conventional reverse rolling by tandem rolling the final cold rolling, which is the previous step of the primary recrystallization annealing. Are not yet fully understood, but the inventors consider as follows.

  In reverse rolling, dynamic strain aging during cold rolling and fixation of solid solution elements (C, N, etc.) to dislocations by being held at a high temperature while being wound around a coil between rolling passes (Cottrell locking) ) Occurs. This cotrel locking further promotes dynamic strain aging in the next rolling pass, and is considered to form the origin of {110} <001> primary recrystallized grains that are advantageous for reducing the iron loss of the product plate. It is done. However, at the contact portion of the inner diameter of the coil with the mandrel and at both ends in the coil longitudinal direction of the outer periphery of the coil, the temperature decreases due to heat removal and heat dissipation during winding, so the diffusion rate of the solid solution element decreases. In addition, since the waiting time until the next rolling pass is long, the dislocation density is lowered and the formation of the Cottrell atmosphere becomes insufficient. As a result, it is considered that dynamic strain aging does not occur sufficiently at both ends in the longitudinal direction of the coil, causing deterioration of iron loss characteristics.

On the other hand, in tandem rolling, cot rel-locking does not occur, but since the time to the next pass is much shorter than in reverse rolling, the next pass is performed while maintaining the dislocation density introduced in the previous pass sufficiently. As a result, the dislocation density before rolling becomes higher. As a result, it is considered that the effect of dynamic strain aging during cold rolling is sufficiently developed. Furthermore, in principle, tandem rolling can continuously roll the coil including the welded joint between the coils, so that a uniform structure can be built in the coil longitudinal direction than reverse rolling. The iron loss deterioration at both ends of the coil in the longitudinal direction, which is a problem, is also suppressed.
The present invention has been developed based on the above experimental results.

Next, 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.
C: 0.002-0.10 mass%
If C is less than 0.002 mass%, the grain boundary strengthening effect due to C is lost, and cracks occur in the slab, which causes problems in production. On the other hand, when it exceeds 0.10 mass%, it becomes difficult to reduce C to 0.005 mass% or less at which no magnetic aging occurs by decarburization annealing. Therefore, C is in the range of 0.002 to 0.10 mass%. Preferably it is the range of 0.010-0.080 mass%.

Si: 2.0 to 8.0 mass%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If the effect is less than 2.0 mass%, it is not sufficient. On the other hand, if it exceeds 8.0 mass%, the workability deteriorates and it is difficult to roll and manufacture. Therefore, Si is set to a range of 2.0 to 8.0 mass%. Preferably it is the range of 2.5-4.5 mass%.

Mn: 0.005 to 1.0 mass%
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.005 mass%, it is not sufficient. On the other hand, if it exceeds 1.0 mass%, the magnetic flux density of the product plate is lowered. Therefore, Mn is set to a range of 0.005 to 1.0 mass%. Preferably it is the range of 0.02-0.20 mass%.

Components other than C, Si and Mn are classified into cases where an inhibitor is used and cases where no inhibitor is used in order to cause secondary recrystallization.
First, when an inhibitor is used to cause secondary recrystallization, for example, when an AlN-based inhibitor is used, Al and N are changed to Al: 0.010 to 0.050 mass%, N: 0.003, respectively. It is preferable to make it contain in the range of -0.020 mass%. Moreover, when utilizing a MnS * MnSe type | system | group inhibitor, it is preferable to contain Mn of the quantity mentioned above, and S: 0.002-0.030 mass% and / or Se: 0.003-0.030 mass%. When the addition amount is less than the above lower limit value, the inhibitor effect is not sufficiently obtained. On the other hand, when the upper limit value is exceeded, the inhibitor component remains undissolved during slab heating, and the inhibitor effect is reduced. Magnetic properties cannot be obtained. Of course, an AlN-based and MnS / MnSe-based inhibitor may be used in combination.

  On the other hand, when an inhibitor is not used to cause secondary recrystallization, the content of Al, N, S and Se, which are the above-described inhibitor forming components, is reduced as much as possible, Al: less than 0.01 mass%, N : It is preferable to use a steel material reduced to less than 0.0050 mass%, S: less than 0.0050 mass%, and Se: less than 0.0030 mass%.

In the steel material used for the grain-oriented electrical steel sheet of the present invention, the balance other than the above components is Fe and inevitable impurities.
However, for the purpose of improving magnetic properties, Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P: 0.005 to 0 .50 mass%, Sb: 0.005-0.50 mass%, Sn: 0.005-0.50 mass%, Bi: 0.005-0.50 mass%, Mo: 0.005-0.10 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.010 mass%, Nb: 0.0010-0.010 mass%, V: 0.001-0.010 mass%, and Ta: 0.001-0. One or more selected from 010 mass% may be contained as appropriate.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
A steel material (slab) may be manufactured by a conventional ingot-bundling rolling method or a continuous casting method after melting the steel having the above-described component composition by a conventional refining process, or directly. A thin slab having a thickness of 100 mm or less may be manufactured by a casting method. The slab is reheated to a temperature of about 1400 ° C. according to a conventional method, for example, when an inhibitor component is contained, and after reheating to a temperature of 1250 ° C. or less when no inhibitor component is contained. Used for hot rolling. In addition, when not containing an inhibitor component, you may use for hot rolling immediately after casting, without reheating a slab. In the case of a thin slab, the hot rolling may be omitted and the process may proceed as it is.

  Next, the hot-rolled sheet obtained by hot rolling is subjected to hot-rolled sheet annealing as necessary. 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 degreeC, the band structure formed by hot rolling will remain, it will become difficult to obtain the primary recrystallized structure of a sized grain, and the growth of a secondary recrystallized grain will be inhibited. 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.

  The steel sheet after hot-rolling or after hot-rolled sheet annealing is made into a cold-rolled sheet having a final sheet thickness by one or more cold rolling or two or more cold rollings sandwiching intermediate annealing. The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. When the temperature is lower than 900 ° C., the recrystallized grains after the intermediate annealing become finer, and the Goss nuclei in the primary recrystallized structure are reduced to deteriorate the magnetic properties of the product plate. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become too coarse as in the hot-rolled sheet annealing, and it becomes difficult to obtain a primary recrystallized structure of the sized grains.

  Further, as described above, the cold rolling (final cold rolling) with the final plate thickness needs to be performed by tandem rolling (unidirectional rolling) in order to obtain the effect of the present invention. In order to improve the primary recrystallization texture and further improve the magnetic properties, it is preferable to employ warm rolling in which the steel sheet temperature is raised to 100 ° C. to 300 ° C. for rolling.

The cold-rolled sheet having the final thickness is then subjected to primary recrystallization annealing that also serves as decarburization annealing.
The annealing temperature in the primary recrystallization annealing is preferably in the range of 800 to 900 ° C. from the viewpoint of promptly proceeding the decarburization reaction when decarburization annealing is involved, and the atmosphere is a moist atmosphere. Is preferred. However, this is not the case when a steel material with C: 0.005 mass% or less that does not require decarburization is used. Moreover, you may perform a primary recrystallization annealing and a decarburization annealing separately.

  Here, in the present invention, what is important is that in the heating process of the primary recrystallization annealing, a temperature of 200 to 700 ° C. is rapidly heated at 50 ° C./s or more, and any one of 250 ° C. or more and less than 550 ° C. That is, it is necessary to perform the holding process of holding at a temperature for 0.5 to 10 seconds 1 to 4 times. Here, the temperature increase rate (50 ° C./s or more) in the section of 200 to 700 ° C. is the temperature increase rate in the time excluding the holding time, as described above. Further, the retention treatment may be performed at any temperature between 250 ° C. and less than 550 ° C., but the temperature does not necessarily have to be constant, and if the temperature change is ± 10 ° C./s or less, Since the same effect as holding can be obtained, the temperature may be raised or lowered within a range of ± 10 ° C./s.

  In addition, what is important in the present invention is to suppress adverse effects due to rapid heating in the primary recrystallization annealing, and to obtain a product excellent in film properties and magnetic properties, 200 to 700 in the heating process of primary recrystallization annealing. After rapid heating at a temperature of 50 ° C./s or more between 1 ° C. and 1 to 4 times holding treatment for 0.5 to 10 seconds at any temperature between 250 ° C. and less than 550 ° C. Further, it is preferable to perform the holding treatment for holding for 0.5 to 3 seconds at any temperature between 550 ° C. and less than 700 ° C. in the heating process once or twice.

  Here, the temperature increase rate between 200 and 700 ° C. is the temperature increase rate during the time obtained by subtracting the retention time from the heating time between 200 and 700 ° C. as described above. Moreover, although the said temperature increase rate needs to be 50 degreeC / s or more, the range of 100-400 degreeC / s is preferable. Further, the temperature within the holding time does not need to be strictly constant, and can be considered constant as long as the temperature change is 10 ° C./s or less.

  For steel sheets that have undergone primary recrystallization annealing, when iron loss characteristics and transformer noise are important, an annealing separator mainly composed of MgO is applied to the steel sheet surface, dried, and then annealed in the Goss orientation. It is preferred to develop a highly integrated secondary recrystallized structure 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.

  As a condition for finish annealing, in the case of forming a forsterite film, the temperature is raised to a temperature of 1100 ° C. or higher after the secondary recrystallization is exhibited and completed by maintaining it at 800 to 1050 ° C. for 20 hours or longer. In the case where the iron loss characteristic is emphasized and the purification process is performed, it is more preferable to raise the temperature to about 1200 ° C. On the other hand, when the forsterite film is not formed, the secondary recrystallization may be completed, so that the annealing can be completed by raising the temperature to 800 to 1050 ° 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 coating, it is possible to apply a method of applying a tension coating via a binder or a method of depositing an inorganic substance on the surface of a steel sheet 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.

  Moreover, in order to further reduce the iron loss, it is preferable to perform a magnetic domain fragmentation process. As a processing method, a method of generally forming a groove in the final product plate, introducing a thermal strain or an impact strain in a linear or dotted manner by electron beam irradiation, laser irradiation, plasma irradiation, or the like, For example, a method of forming a groove by etching a steel sheet that has been cold-rolled to a final thickness or a steel sheet surface in an intermediate process can be used.

  C: 0.070 mass%, Si: 3.30 mass%, Mn: 0.06 mass%, Al: 0.025 mass%, Se: 0.025 mass% and N: 0.010 mass%, the balance being Fe and inevitable Steel having a component composition consisting of mechanical impurities is melted and made into a steel slab by a continuous casting method, then reheated to a temperature of 1400 ° C., hot-rolled into a hot rolled sheet having a thickness of 2.4 mm, and 1000 ° C. After hot-rolled sheet annealing for 50 seconds, primary cold rolling to an intermediate sheet thickness of 1.8 mm, intermediate annealing at 1100 ° C. for 20 seconds, followed by secondary cold rolling with a tandem mill or reverse mill ( (Final cold rolling) to finish a cold rolled sheet having a final thickness of 0.27 mm.

Thereafter, the cold-rolled sheet was subjected to primary recrystallization annealing with decarburization annealing at 840 ° C. for 100 seconds in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ . At this time, the heating rate between 200 and 700 ° C. in the heating process up to 850 ° C. is changed as shown in Table 1, and the temperature and time holding treatment shown in Table 1 is applied during the heating. did.
Next, an annealing separator mainly composed of MgO was applied to the steel sheet surface and dried, followed by secondary recrystallization, and then subjected to a finish annealing at a temperature of 1200 ° C. for 10 hours to obtain a product coil. The atmosphere of the finish annealing was H _{2 at} the time of maintaining at 1200 ° C. for the purification treatment, and N ₂ at the time of temperature increase and temperature decrease.

Ten test pieces each having a width of 100 mm and a length of 520 mm in the coil width direction were collected from each position from both ends and the center in the longitudinal direction of the product coil after finish annealing thus obtained, and described in JIS C2556. The iron loss W _17/50 is measured by the method, and the average value of each position (the coil both ends are the average value of the _front end portion and the rear end portion) and the iron loss difference between the coil end portions and the center portion are obtained. The results are also shown in Table 1. From the table, by applying the present invention, the iron loss at both ends in the longitudinal direction of the coil in tandem rolling is improved, which is almost the same level as the iron loss value at the center of the coil, and low over the entire length of the coil. It can be seen that a grain-oriented electrical steel sheet with iron loss is obtained.

  C: 0.027 mass%, Si: 3.12 mass%, Mn: 0.09 mass%, Al: 0.005 mass%, N: 0.0037 mass%, S: 0.0018 mass%, Sb: 0.041 mass%, P : 0.042 mass% and Mo: 0.013 mass%, the remainder of which is composed of Fe and unavoidable impurities is melted and made into a steel slab by continuous casting. Heated and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.2 mm, subjected to hot-rolled sheet annealing at 1000 ° C. for 50 seconds, and made an intermediate sheet thickness of 1.8 mm by primary cold rolling to 1100 ° C. × 20 After intermediate annealing for 2 seconds, secondary cold rolling (final cold rolling) was performed by a tandem mill or a reverse mill to finish a cold rolled sheet having a final thickness of 0.23 mm.

Thereafter, the cold-rolled sheet was subjected to primary recrystallization annealing with decarburization annealing at 820 ° C. for 100 seconds in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ . At this time, the heating rate between 200 and 700 ° C. in the heating process up to 820 ° C. was set to 150 ° C./s, and in the middle of the heating, the holding treatment was performed 0 to 4 times under the conditions described in Table 2. .
Next, an annealing separator mainly composed of MgO was applied to the steel sheet surface and dried, followed by secondary recrystallization, and then subjected to a finish annealing at a temperature of 1200 ° C. for 10 hours to obtain a product coil. The atmosphere of the finish annealing was H _{2 at} the time of maintaining at 1200 ° C. for the purification treatment, and N ₂ at the time of temperature increase and temperature decrease.

Ten test pieces each having a width of 100 mm and a length of 520 mm in the coil width direction were collected from each position from both ends and the center in the longitudinal direction of the product coil after finish annealing thus obtained, and described in JIS C2556. The iron loss W _17/50 is measured by the method, and the average value of each position (the coil both ends are the average value of the _front end portion and the rear end portion) and the iron loss difference between the coil end portions and the center portion are obtained. The results are also shown in Table 2. From the table, by applying the present invention, the iron loss at both ends in the longitudinal direction of the coil in tandem rolling is improved, which is almost the same level as the iron loss value at the center of the coil, and low over the entire length of the coil. It can be seen that a grain-oriented electrical steel sheet with iron loss is obtained.

  Steels of reference signs A to L having the composition shown in Table 3 were melted, made into a steel slab by a continuous casting method, reheated to a temperature of 1380 ° C., and then hot-rolled to heat 2.0 mm in thickness. The sheet was subjected to hot-rolled sheet annealing at 1030 ° C. for 40 seconds, and then finally cold-rolled by a tandem mill or reverse mill to finish a cold-rolled sheet having a final sheet thickness of 0.23 mm.

Then, primary recrystallization annealing with decarburization annealing at 840 ° C. for 60 seconds was performed in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ . Under the present circumstances, the temperature increase rate between 200-700 degreeC in the heating process to 840 degreeC was 80 degreeC / s, and also the retention process hold | maintained for 5 second at the temperature of 450 degreeC in the middle of the heating was performed.
Next, after applying and drying an annealing separator mainly composed of MgO on the surface of the steel sheet, secondary recrystallization was performed, and then finishing annealing was performed to perform a purification treatment at 1180 ° C. for 5 hours to obtain a product coil. The atmosphere of the finish annealing was H _{2 at} the time of 1180 ° C. to be purified and Ar at the time of temperature rise and temperature drop.

Ten test pieces each having a width of 100 mm and a length of 520 mm in the coil width direction were collected from each position from both ends and the center in the longitudinal direction of the product coil after finish annealing thus obtained, and described in JIS C2556. The iron loss W _17/50 is measured by the method, and the average value of each position (the coil both ends are the average value of the _front end portion and the rear end portion) and the iron loss difference between the coil end portions and the center portion are obtained. It was. The results are also shown in Table 3. From the same table, by applying the present invention, the iron loss at both ends of the coil in the tandem rolling direction is improved, and the iron loss value at the coil central portion is almost the same level, over the entire coil length and width. It can be seen that a grain-oriented electrical steel sheet with low iron loss is obtained.

  Since the technique of the present invention is suitable for controlling the texture of cold-rolled steel sheets, it can also be applied to a method for manufacturing automobile steel sheets and the like that require workability.

Claims (6)

A steel material containing C: 0.002-0.10 mass%, Si: 2.0-8.0 mass%, and Mn: 0.005-1.0 mass% is hot-rolled to form a hot-rolled sheet, After re-annealing without hot-rolling or after hot-rolling annealing, cold rolling is performed once or two times or more with intermediate annealing to obtain a cold-rolled steel plate with the final thickness, which is also used for decarburization annealing. In the manufacturing method of grain-oriented electrical steel sheet comprising a series of steps of applying annealing separator to the steel sheet surface and finishing annealing after annealing.
Final cold rolling is performed by tandem rolling, and rapid heating is performed at a rate of 50 ° C./s or more between 200 to 700 ° C. in the heating process of the primary recrystallization annealing.
A method for producing a grain-oriented electrical steel sheet, characterized in that a retaining treatment is performed 1 to 4 times for 0.5 to 10 seconds at any temperature between 250 ° C. and less than 550 ° C. in the heating process. A steel material containing C: 0.002-0.10 mass%, Si: 2.0-8.0 mass%, and Mn: 0.005-1.0 mass% is hot-rolled to form a hot-rolled sheet, After re-annealing without hot-rolling or after hot-rolling annealing, cold rolling is performed once or two times or more with intermediate annealing to obtain a cold-rolled steel plate with the final thickness, which is also used for decarburization annealing. In the manufacturing method of grain-oriented electrical steel sheet comprising a series of steps of applying annealing separator to the steel sheet surface and finishing annealing after annealing.
Final cold rolling is performed by tandem rolling, and rapid heating is performed at a rate of 50 ° C./s or more between 200 to 700 ° C. in the heating process of the primary recrystallization annealing.
After the holding process of holding for 0.5 to 10 seconds at any temperature between 250 ° C. and less than 550 ° C. in the heating process 1 to 4 times, and further, 550 ° C. to less than 700 ° C. in the heating process A method for producing a grain-oriented electrical steel sheet, wherein a retaining treatment is performed once or twice for 0.5 to 3 seconds at any temperature in between. In addition to the C, Si and Mn, the steel material includes Al: 0.010 to 0.050 mass%, N: 0.003 to 0.020 mass%, Se: 0.003 to 0.030 mass% and / or The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein S: 0.002 to 0.03 mass% is contained, and the remainder has a composition composed of Fe and inevitable impurities. In addition to the C, Si and Mn, the steel material contains one or two selected from Se: 0.003-0.030 mass% and S: 0.002-0.03 mass%, The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the balance has a component composition comprising Fe and inevitable impurities. The steel material contains, in addition to C, Si and Mn, Al: less than 0.01 mass%, N: less than 0.0050 mass%, Se: less than 0.0030 mass% and S: less than 0.0050 mass%, The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the balance has a component composition comprising Fe and inevitable impurities. In addition to the component composition, the steel material further includes Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P: 0.00. 005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.005 to 0.50 mass%, Mo: 0.005 to 0.10 mass% , B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.010 mass%, Nb: 0.0010 to 0.010 mass%, V: 0.001 to 0.010 mass%, and Ta: 0.001. It contains 1 type, or 2 or more types chosen from -0.010 mass%, The manufacturing method of the grain-oriented electrical steel sheet of any one of Claims 1-5 characterized by the above-mentioned.

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