JP2005262217A - Method for producing grain oriented silicon steel sheet having excellent magnetic property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a cold-rolled sheet which is tandem rolled into a sheet in which strain is highly accumulated by utilizing molten carbon in steel or carbide which is finely precipitated and to make its texture into a structure which is suitable to development of grains in goss azimuth. <P>SOLUTION: When producing a grain oriented silicon steel sheet by a series of processes including the cold rolling with a tandem mill, the annealing of a hot-rolled sheet is performed by cooling the temperature range of 900-500°C at the rate of 30-250°C/s after heating the sheet to ≥ 900°C, next, cooling the temperature range of 500-200°C at the rate of 50-150°C/s and further continuing cooling. Interstand aging treatment is performed at the duration time of 1-60 s at 150-300°C in at least one succeeding place between stands after performing the rolling with the tandem mill at the cumulative draft of ≥ 30%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet, and more particularly to a method for producing a grain-oriented electrical steel sheet using a tandem rolling mill in the final rolling process.

  In order to improve the magnetic properties of grain-oriented electrical steel sheets, it is necessary that the steel sheets have a group of crystal grains in which the <001> direction, which is the easy axis of iron, is highly integrated in the rolling direction of the steel sheet. The generation of such a crystal grain group is to preferentially develop and grow the crystal grains of so-called {110} <001> orientation (referred to as “Goth orientation”) as secondary recrystallized grains during final finish annealing. Has been achieved.

  In order to develop secondary recrystallized grains in the Goss orientation, it is well known to use an inhibitor that strongly suppresses the growth of grains having orientations other than {110} <001> orientation in the secondary recrystallization process, As such an inhibitor, fine precipitates such as MnS, MnSe or AlN are widely used. Furthermore, in addition to the precipitation type inhibitor described above, a method for reinforcing the effect of suppressing grain growth by a combined addition of grain boundary segregation type elements such as Sb, Bi, Sn, Pb, and Te is also well known. In addition to the method of developing goth-oriented grains using such precipitation type inhibitors, the selection of goth-oriented grains using texture inhibition by purifying the material without containing inhibitor-forming components. Means for achieving a desired growth is described in Patent Document 1 and the like.

  By the way, the grain-oriented electrical steel sheet is obtained by hot-rolling the starting material slab, subjecting the obtained hot-rolled sheet to hot-rolled sheet annealing, and then cold-rolling to obtain a cold-rolled sheet having a final thickness. Manufactured by a process of applying carbon annealing and final finishing annealing. In recent years, in this production, performing cold rolling by tandem rolling has become a key point for improving productivity.

  Also in tandem rolling, the action of the inhibitor or the texture inhibition appears at the stage where the cold-rolled cold-rolled sheet is recrystallized first and then recrystallized. Therefore, it is necessary to prepare the texture of the cold-rolled sheet that has been tandem-rolled so that the goth-oriented grains are sufficiently developed before the primary recrystallization annealing (which also serves as decarburization annealing). It is also well known that in order to obtain such a texture, it is necessary to obtain a texture in which tandem rolling is highly strained.

  In general, as means for accumulating highly strain in the cold-rolled sheet, means using C dissolved in steel or carbide precipitated finely is known. For example, Patent Document 2 discloses that a hot rolled sheet is rapidly cooled from a temperature of 790 ° C. or more to a temperature of 540 ° C. or less prior to the step of performing cold rolling twice with intermediate annealing to obtain a final sheet thickness. And a method of precipitating lens-shaped carbide having a visible size (several μm) of an optical microscope in crystal grains while being maintained in a temperature range of 310 ° C. to 480 ° C. has been proposed.

  On the other hand, in Patent Documents 3 and 4, as a method of using solid solution C or fine carbide in crystal grains in a cold rolling process, a hot rolled sheet containing AlN as a precipitation inhibitor is rapidly cooled after high-temperature annealing. Discloses a method of performing an aging treatment at least once between passes of cold rolling when performing strong cold rolling with a final cold rolling reduction of 80% or more. Patent Document 5 discloses a method in which a temperature of 600 to 300 ° C. after the intermediate annealing is cooled at a cooling rate of 150 ° C./min or more, and an aging treatment is performed at a stage before the final cold rolling. Further, Patent Document 6 discloses that in the annealing before the final cold rolling, by strictly controlling the cooling time in the temperature range of 300 ° C. to 150 ° C., the in-grain carbide is within a very specific range. By controlling these to a large amount and uniformly dispersing, the {110} <001> orientation accumulation degree in the primary recrystallized aggregate fiber is increased, and the secondary recrystallized grains in that orientation are sufficiently grown. A method for obtaining the magnetic characteristics is disclosed. In addition, Patent Document 7 discloses that cold rolling performed at a high rolling reduction is performed in a material temperature range of 50 to 350 ° C. and continuation of thermal aging from the end of high-temperature annealing performed before this cold rolling to the start of cold rolling. Means have been proposed for adjusting the time according to the material temperature.

JP2003-213339 Japanese Patent Publication No. 38-14009 Japanese Patent Publication No.54-18846 Japanese Patent Publication No.54-29182 Japanese Patent Publication No.56-3892 Japanese Patent Publication No.2-4166S JP 48-46511 A

  However, the means described in Patent Document 2 uses a relatively large size carbide formed in a hot-rolled sheet for fragmentation of coarse hot-drawn long grains. It is thought that it plays a role of annihilating the grains of {100} to {110} <001> orientation, which are harmful to development, at the initial stage of the cold rolling process. In the case where the elapsed time is short, it is impossible to obtain a texture in which distortion is sufficiently accumulated.

  In addition, the proposals related to Patent Document 3 and Patent Document 4 are for aging treatment in a temperature range of 50 ° C. to 350 ° C. for 1 minute or longer (in the case of Patent Document 3) or in a temperature range of 300 ° C. to 600 ° C. for 1 to 30 seconds. (In the case of Patent Document 4), it is necessary to hold these materials many times. However, it is difficult to secure an aging time between the stands in tandem rolling, while intermediate annealing is required. If the aging treatment is to be carried out, there arises a problem that the cold rolling ability is greatly reduced and the heating cost of the steel sheet is increased, thereby impairing the economy. The means described in Patent Document 5 has the same problem.

  On the other hand, although the means described in Patent Document 6 is experimentally recognized as an effect of improving magnetic properties, there is a problem that sufficient texture improvement results may not be obtained in tandem rolling. In addition, the proposal described in Patent Document 7 depends on the material temperature for the duration of thermal aging from the end of high-temperature annealing to the start of cold rolling, and therefore, in a manufacturing process including tandem rolling that requires high productivity. Has a problem that it is difficult to adopt.

  The present invention solves these problems related to the prior art, and highly strained accumulated cold-rolled sheets tandem-rolled using C or solidly precipitated carbides in steel. It is a new proposal to make the texture suitable for the growth of goth-oriented grains during secondary recrystallization.

  As a result of intensive research to solve the above problems, the present inventors have adjusted the annealing conditions before the final tandem rolling, especially the cooling conditions, and a state in which a large number of ultrafine carbides are uniformly dispersed in the crystal grains. This is subjected to rolling with the reduction ratio adjusted by tandem rolling, and then subjected to inter-stand aging to dissolve the ultrafine carbide in the crystal grains and to fix the dissolved C to the dislocation, and in this state, further reduction is applied. As a result, it has been found that it is possible to make the crystal grains in a highly strained state, whereby a grain-oriented electrical steel sheet having excellent magnetic properties can be produced during tandem rolling.

  The present invention includes, as a starting material, a steel slab containing, by mass ratio, C: 0.015-0.15%, Si: 2.0-4.5%, Mn: 0.01-0.5%, and the balance Fe and inevitable impurities, Is subjected to hot rolling to obtain a hot-rolled sheet, and the hot-rolled sheet is subjected to hot-rolled sheet annealing and then cold-rolled by a tandem rolling mill to obtain a cold-rolled sheet having a final thickness. In producing a grain-oriented electrical steel sheet by a process of decarburizing annealing and final finishing annealing on a rolled sheet, the hot rolled sheet annealing is heated to 900 ° C. or more and 1500 ° C. or less, and the temperature range of 900 to 500 ° C. is 30 ° C. / cooling at a rate of s to 250 ° C./s, then cooling to a temperature range of 500 to 200 ° C. at a rate of 50 ° C./s to 150 ° C./s, and continuing cooling, and the tandem After rolling with a rolling mill at a cumulative reduction rate of 30% or more, between 150 ° C and 300 ° C between at least one subsequent stand Applying interstand aging treatment duration 60 seconds in the lower is for a final sheet thickness by further continuing the rolling.

  The above-described invention can also be applied to the case where cold rolling is performed to the final sheet thickness with an intermediate annealing such as a so-called cold rolling two-way method, in which case the final intermediate annealing condition of the intermediate annealing is set to a heating temperature of 900. A cooling rate in the temperature range of ≧ 900 ° C. and over 900 to 500 ° C. is 30 ° C./s to 250 ° C./s and a cooling rate in the temperature range of 500 to 200 ° C. is 50 ° C./s to 150 ° C./s And

  The starting material in each of the above inventions may further contain Al: 0.01 to 0.08% and N: 0.0015 to 0.015%, or contain S or Se in a total of 0.01 to 0.05%. The present invention can also be applied to means for purifying the raw material and using texture inhibition to achieve selective growth of goth-oriented grains, in which case the starting material is Al: less than 100 ppm, N: 60 ppm. Less than, S: less than 50 ppm and Se: less than 50 ppm. These starting materials further include one or more selected from Cu, Sb, Sn, Bi, Mo, Cr, Ni, 0.01 to 0.5% for Cu, Sb, Sn, Mo, Cr, Ni, Bi About 0.001 to 0.18% can be contained.

  According to the present invention, cold rolling including warm rolling can be performed by a tandem rolling mill which is a continuous rolling mill, and a grain-oriented electrical steel sheet having stable and excellent magnetic properties can be economically manufactured.

  The steel slab, which is the starting material according to the present invention, basically contains, by mass ratio, C: 0.015-0.15%, Si: 2.0-4.5%, Mn: 0.01-0.5%, and the balance Fe and unavoidable impurities. Become. C is an important component that improves the crystal structure by utilizing the γ-α transformation during hot rolling and contributes to the improvement of magnetic properties as an intragranular fine carbide. However, if the content is less than 0.015%, The effect is poor, and if it exceeds 0.15%, sufficient decarburization becomes difficult in the subsequent process, and the amount of grain boundary cementite increases too much, resulting in magnetic deterioration due to uneven structure. Therefore, the content is in the range of 0.015% or more and 0.15% or less. Si is an effective component for increasing the specific resistance of steel sheets and reducing iron loss. However, when the content is less than 2.0%, the steel sheet has low electrical resistance and eddy current loss. Cannot be obtained. On the other hand, if it exceeds 4.5%, the saturation magnetic flux density is lowered and the cold workability is lowered. Therefore, Si should be in the range of 2.0% to 4.5%. Mn is a component that increases specific resistance and is effective in reducing iron loss. It is an element necessary for improving hot workability, but if it is less than 0.01%, there is no effect, and if it exceeds 0.5%, the magnetic flux density decreases, so the Mn content is 0.01% or more and 0.5%. The following.

  Other compositions can be inevitable impurities except for Fe, but they can contain precipitation inhibitor-forming elements as shown below, and the content of these elements can be limited to direct by texture inhibition. An electromagnetic steel sheet material can also be used. The additional composition in each of these cases is as follows:

When using AlN inhibitors
Al: 0.01% to 0.08%, N: 0.0015 to 0.015%
As an inhibitor, AlN has a stronger ability to suppress primary recrystallized grain growth than other inhibitors. However, if Al is less than 0.01%, the restraining force is insufficient, and the magnetic flux density decreases. On the other hand, if it exceeds 0.08%, secondary recrystallization becomes unstable. Therefore, the content is desirably in the range of 0.01% to 0.08%. N is an important element that constitutes an AlN-based inhibitor. However, if the content exceeds 0.015%, the hysteresis loss is increased and a bend failure is caused. In addition, it causes frequent surface defects called blisters. On the other hand, if it is less than 0.0015%, the amount of the AlN inhibitor will be insufficient. Therefore, the content is preferably in the range of 0.0015% to 0.0150%.

When using Mn (Se, S) inhibitors
S + Se: 0.01% to 0.05%
S and Se both bind Mn in steel and contribute to the formation of Mn (Se, S) inhibitors. However, if the total content thereof is less than 0.01%, the absolute amount of the inhibitor component is insufficient, and magnetic deterioration due to non-uniformity of the inhibitor exceeding 0.05% and crack generation are caused. Therefore, in either case of single or combined use, the total content is preferably in the range of 0.01% to 0.05%. In addition, Mn necessary for forming the Mn (Se, S) -based inhibitor is contained as a basic component, and the content thereof is in the range of 0.01% to 0.5% as an inhibitor-forming element. If it is less than 0.01%, the absolute amount as an inhibitor component is insufficient, and a low melting point compound is formed during hot rolling, causing problems such as frequent cracking. On the other hand, if it exceeds 0.5%, the slab heating temperature for dissociation and dissolution of the inhibitor becomes high, and the inhibitor becomes coarse and causes a decrease in the crystal grain growth inhibiting power.

  The AlN-based inhibitor and the Mn (Se, S) -based inhibitor can be used in combination, and the preferred range of the content in that case is as described above.

When Texture Inhibition is Used The present invention can also be applied to the case where secondary recrystallized grains are developed by texture inhibition without using the above precipitation-type inhibitor. In that case, since the presence of the precipitation type inhibitor hinders the expression of secondary crystal grains, these elements are limited to Al: less than 100 ppm, N: less than 60 ppm, and S and Se, respectively, less than 50 ppm. N is preferably 50 ppm or less in order to prevent the formation of Si nitride after purification annealing. It is also desirable to reduce the nitride forming elements Ti, Nb, B, Ta, and V to 50 ppm or less, respectively. This is because the deterioration of the iron loss is prevented so as not to interfere with the action of the texture inhibition according to the present invention, and good processability is ensured.

In addition to the above components, one or more selected from Cu, Sb, Sn, Bi , Mo, Cr and Ni, 0.01 to 0.5% for Cu, Sb, Sn, Mo, Cr and Ni, about Bi May be contained in an amount of 0.001 to 0.1%. Of these, Ni is a useful element that improves the magnetic properties by improving the hot-rolled sheet structure. However, when the content is less than 0.01%, the amount of improvement in magnetic properties is small, while when it exceeds 0.5%, secondary recrystallization occurs. When it is added, the content is preferably 0.01% or more and 0.5% or less. Cu, Sb, Sn, Bi, and Cr are elements that are useful for improving the iron loss value, but if any of them does not reach the lower limit of the above range, the effect of improving the iron loss is small, while the upper limit is exceeded. And the development of secondary recrystallization is inhibited. Accordingly, when these elements are added, Cu, Sb, Sn, and Cr are preferably 0.01% to 0.5%, and Bi is preferably 0.001% to 0.1%. Mo is useful for preventing surface defects caused by surface embrittlement during hot rolling, and can be added in an effective range of 0.01% to 0.5%.

  As long as the said starting material has the said composition component, it does not ask | require the adjustment method or form in particular. For example, it may be adjusted by a known method such as a converter or an electric furnace, subjected to vacuum treatment if necessary, and manufactured into a slab by a normal ingot-making method or a continuous casting method. Alternatively, a thin cast piece having a thickness of 100 mm or less may be used as a starting material by a direct casting method.

  The hot rolling process can freely adopt known means. However, when using precipitation type inhibitors such as AlN or Mn (Se, S), it is desirable to heat these elements to a temperature range of 1350 to 1450 ° C. to completely dissolve these elements. On the other hand, when texture inhibition is used, it is desirable that the slab heating temperature be, for example, 1250 ° C. or lower. Thereby, the production amount of the scale brought about by the high temperature heating of the slab is suppressed, and the effect of improving the yield can be obtained. Other hot rolling conditions are not particularly limited, and known means can be employed.

  The obtained hot rolled sheet is subjected to cold rolling by a tandem rolling mill. At this time, in the first embodiment of the present invention, the hot-rolled sheet is subjected to hot-rolled sheet annealing and is rolled by a tandem rolling mill by a so-called one-time method. In the second embodiment, the hot-rolled sheet is rolled by a tandem rolling mill twice or more with intermediate annealing. In any of these cases, the annealing conditions before the final rolling by the tandem rolling mill are performed as follows, so that uniform and ultrafine carbide exists in the grains. Specifically, the annealing before the final cold rolling (hot rolling sheet annealing in the first embodiment, intermediate annealing immediately before the final cold rolling in the second embodiment) is heated to 900 ° C. or higher, and then 900 to 500 ° C. The temperature range is cooled at a rate of 30 ° C./s to 250 ° C./s, then the temperature range of 500 to 200 ° C. is cooled at a rate of 50 ° C./s to 150 ° C./s, and further cooling is continued. Shall.

  The reason why the heating temperature is set to 900 ° C. or higher is that in order to precipitate as much fine carbide as possible in the subsequent cooling process, it is necessary to dissolve a large amount of C in the ferrite phase. Insufficient dissolution. The upper limit of the heating temperature is desirably 1150 ° C. or less from the viewpoint of economy.

  The steel plate heated to the above temperature is first subjected to a first stage cooling in which the cooling rate in the temperature range of 900 to 500 ° C. is set to 30 ° C./s or more and 250 ° C./s or less. In this first stage cooling, the cooling rate in the temperature range of 900 to 500 ° C. is set to 30 ° C./s or more and 250 ° C./s or less in order to finally precipitate fine carbide in the above temperature range ( This is because the precipitation of carbide at 900 to 500 ° C. is suppressed and the solid solution state of C is maintained until the subsequent second stage. When the cooling rate is less than 30 ° C./s, carbides having a particle size exceeding 70 nm are recognized, the curing at the initial stage of tandem rolling is insufficient, and the dissolution of carbides during inter-stand aging. This is because solid solution C cannot be fixed to dislocations, and a texture in which strain is sufficiently accumulated cannot be obtained by rolling to the final thickness. However, if the cooling rate exceeds 250 ° C./s, the above effect is saturated and economically disadvantageous.

  Following the first stage cooling, the second stage cooling is performed at a cooling rate in the temperature range of 500 to 200 ° C. to 50 ° C./s or more and 150 ° C./s or less, and carbide precipitation is driven in this temperature range. A large amount of ultrafine carbide and uniform precipitation can be achieved by utilizing the large force. The reason why the cooling rate in this temperature range is 50 ° C./s or more is that when the cooling rate is less than 50 ° C./s, the carbide driving force is large, and the carbide diameter easily exceeds 70 nm and becomes coarse. On the other hand, the reason why the temperature is set to 150 ° C./s or less is that when C is rapidly cooled to over 150 ° C./s, C remains in a solid solution, the precipitation amount of fine carbide is insufficient, and hardening at the initial stage of tandem rolling does not proceed. Because.

  In short, in the present invention, it is necessary to precipitate ultrafine carbide in the cooling process in the annealing before the final cold rolling. Here, the ultrafine carbide means a size of 70 nm or less. Such ultrafine carbide can be generally observed with an electron microscope having a magnification of about 50,000 times. However, even when the presence is not confirmed even by observation with an electron microscope at a magnification of 50,000 times or more, the effect of the present invention can be obtained as long as the annealing condition is satisfied. This is obtained between the case where ultrafine carbide of about 10 to 70 nm is precipitated and the case where the presence of the ultrafine carbide satisfies the annealing condition of the present invention but is not confirmed even by observation with an electron microscope at a magnification of 50,000 times or more. This is supported by the fact that the difference in the properties obtained is not recognized, and it is thus presumed that ultrafine carbide is precipitated in both cases.

  The steel plate in which ultrafine carbide is precipitated in the crystal grains in this way is then subjected to tandem rolling. This rolling includes cold rolling, subsequent aging between stands, and further cold rolling to the final thickness. Specifically, after rolling with a cumulative reduction ratio of 30% or more, between the subsequent stands, perform aging treatment between the stands at 150 ° C or more and 300 ° C or less for a duration of 1 to 60 seconds, and further continue rolling to finish Including the step of thickness.

  The cold rolling reduction of the rolling performed in the present invention must be 30% or more. This is because when the cold rolling reduction ratio is less than 30%, the accumulation of ultrafine carbide is not promoted because the accumulation of strain is small. It should be noted that the condition of the rolling reduction may be achieved as a cumulative rolling reduction before the subsequent inter-stand aging treatment, and is not necessarily achieved by a single rolling stand. Further, at this time, setting the steel plate temperature to 150 ° C. or more and 300 ° C. is advantageous from the viewpoint of accumulation of strain and re-solution of C in the rolling stage.

  Subsequent to the above rolling, inter-stand aging treatment is performed. In this inter-stand aging treatment, the steel plate temperature is maintained at 150 to 300 ° C. between the stands after the above-described rolling, and the time for the steel plate to pass between the stands (inter-stand time, inter-pass time) Perform by setting 1 to 60 seconds. By setting this temperature range, dissolution (re-solid dissolution) of carbide is promoted, and subsequently, accumulation of strain proceeds in the crystal through fixing to dislocations and the like. When the steel plate temperature is less than 150 ° C, thermal energy is insufficient, so even ultra-fine carbides do not dissolve, while at temperatures higher than 300 ° C, coarse carbides are generated and dissolved in the crystal grains. Solid solution) becomes impossible. Thereafter, the dissolved (re-solidified) C re-adheres to the dislocations generated by rolling, and age hardens the steel sheet.

  If the time between stands in a tandem rolling mill is less than 1 second, the progress of age hardening is insufficient, and sufficient strain cannot be accumulated in the subsequent cold rolling. On the other hand, even if it exceeds 60 seconds, not only the age hardening is saturated, but also the rolling speed is lowered, resulting in poor productivity. The securing of the time between passes may be achieved between any of the rolling stands after the rolling, but the reduction after age hardening is achieved between the stands immediately after the stand satisfying the condition of the rolling reduction. Most preferred in terms of increased rate.

  The tandem rolling mill is normally composed of 4 to 6 continuous rolling stands, but in order to carry out the present invention, cold rolling is performed at the initial stage to ensure a desired reduction rate, After performing inter-stand aging, it is preferable to take a step of cold rolling in one or two stands including the final stand. By taking the above-described steps, the ultrafine carbide precipitated in the annealing before the final cold rolling contributes to hardening at the initial stage of rolling, and greatly contributes to the accumulation of strain and hence the formation of a good texture. In addition, these uniform and ultra-fine carbides are easily dissolved by inter-stand aging for high-density lattice defects that occur in the subsequent rolling process, and further hardening by inter-stand aging followed by cold rolling to the final thickness. Thus, the formation of a good texture is promoted. In the present invention, it is considered that good magnetic properties were obtained by these mechanisms.

  The rolling after the inter-stand aging treatment is preferably 30 to 80%. By setting it to 30% or more, it can be strengthened by improving the texture by increasing dislocations in rolling after aging treatment. In addition, in order to secure the rolling reduction before aging, the rolling reduction after aging should be 80% or less.

  The cold-rolled sheet having the final sheet thickness by the cold rolling is then subjected to decarburization annealing. The decarburization annealing after the final cold rolling is performed in a range of 700 to 1000 ° C. using a humid atmosphere for the purpose of reducing C to 50 ppm or less, preferably 30 ppm or less without causing magnetic aging. It is. It is also possible to perform means for increasing the amount of Si by decarburization after decarburization annealing.

  Thus, the obtained decarburized cold-rolled steel sheet is coated with an annealing separator mainly composed of MgO by a known means, wound around a coil, and subjected to secondary recrystallization annealing and purification annealing. It is subjected to a final finish annealing consisting of to make a product plate.

  Annealing temperature for a hot-rolled sheet with a thickness of 2.2 mm containing Si: 3.25%, C: 0.04%, Mn: 0.07%, Al: 0.07%, N: 0.0038%, S: 0.0025%, Se: 0.001% Then, hot-rolled sheet annealing was performed while changing the cooling rate. Using a 4-pass tandem rolling mill with a roll diameter of 100 mm, the obtained hot-rolled sheet was cold-rolled while changing the rolling reduction and inter-pass temperature as shown in Table 1 to a final sheet thickness of 0.3 mm. . The temperature between passes of the tandem rolling mill is adjusted using a high-frequency induction heating device between the No. 2 stand and No. 3 stand, and the time between passes can be adjusted (heated) between the stands. This was done by providing a looper. Thereafter, the obtained cold-rolled sheet was subjected to decarburized pure at 850 ° C. for 2 minutes in a wet hydrogen atmosphere and final finish annealing at 1150 ° C. for 5 hours to obtain a product sheet.

  Table 1 shows the magnetic properties of the obtained product plate together with the hot-rolled sheet annealing conditions and rolling conditions. As is apparent from Table 1, it can be seen that the magnetic properties are superior to the comparative example when the conditions of the present invention are met.

  Hot rolling for hot rolled sheet with 2.2mm thickness including Si: 3.10%, C: 0.06%, Mn: 0.07%, Al: 0.022%, N: 0.008%, S: 0.0025%, Se: 0.020% Plate annealing was performed, and a product plate was obtained in the same manner as in Example 1. Table 2 shows the magnetic properties of the obtained product plate together with hot-rolled sheet annealing conditions and rolling conditions. As is apparent from Table 2, it can be seen that the magnetic properties are superior to the comparative example when the conditions of the present invention are met.

  The steel slab having the components shown in Table 3 was hot-rolled to 2.2 mm. Then, after cold-rolling with a tandem rolling mill to 1.5 mm, intermediate annealing was performed at 1000 ° C. During this intermediate annealing, the cooling rate was set to 35 ° C./s for 900 ° C. to over 500 ° C., and 60 ° C./s to 500 ° C. or less and 200 ° C. The steel plate thus subjected to the intermediate annealing was finally rolled by a 4-pass tandem rolling mill having a roll diameter of 100 mm to obtain a final cold rolled sheet having a thickness of 0.3 mm. At that time, 73% reduction was applied to the No.3 stand, held at 250 ° C for 3 seconds between the last stand and the stand immediately before, and then rolling with a reduction rate of 50% was performed on the final (No.4) stand. It was.

Since all the steels shown in Table 3 were processed under the conditions according to the present invention, excellent magnetic properties were obtained.

Claims (6)

A steel slab containing C: 0.015-0.15%, Si: 2.0-4.5%, Mn: 0.01-0.5% and the balance Fe and unavoidable impurities as a starting material, and hot rolling to the starting material To obtain a hot-rolled sheet, and then subjecting the hot-rolled sheet to hot-rolled sheet annealing, rolling with a tandem rolling mill to obtain a cold-rolled sheet having a final thickness, and decold-annealing the obtained cold-rolled sheet And in producing grain-oriented electrical steel sheets by the process of final finishing annealing,
After the hot-rolled sheet annealing is heated to 900 ° C. or more and 1150 ° C. or less, the temperature range of 900 to 500 ° C. is cooled at a rate of 30 ° C./s or more and 250 ° C./s or less, and then the temperature range of 500 to 200 ° C. is reduced to 50 ° C. Cooling at a rate of ℃ / s to 150 ℃ / s and continuing cooling, and
Rolling by the tandem rolling mill is subjected to rolling with a cumulative reduction ratio of 30% or more, and then subjected to aging treatment between stands at a temperature of 150 ° C. or more and 300 ° C. or less between at least one subsequent stand, A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that rolling is continued to a final thickness. A steel slab containing C: 0.015-0.15%, Si: 2.0-4.5%, Mn: 0.01-0.5% and the balance Fe and unavoidable impurities as a starting material, and hot rolling to the starting material To obtain a hot-rolled sheet, cold-rolled by a tandem rolling mill twice or more with intermediate annealing between the hot-rolled sheet to obtain a cold-rolled sheet having a final thickness, and to the obtained cold-rolled sheet In producing grain-oriented electrical steel sheets by the process of decarburization annealing and final finish annealing,
After the intermediate annealing is heated to 900 ° C. to 1150 ° C., the temperature range of 900 to 500 ° C. is cooled at a rate of 30 ° C./s to 250 ° C./s, and then the temperature range of 500 to 200 ° C. is set to 50 ° C. / cooling at a rate of not less than s and not more than 150 ° C./s, and continuing cooling, and
Rolling by the tandem rolling mill is subjected to rolling at a cumulative reduction rate of 30% or more, and then subjected to an aging treatment between the stands of 1 to 60 seconds at a temperature of 150 ° C. to 300 ° C. between at least one subsequent stand, A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that rolling is continued to a final thickness.   The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the starting material further contains Al: 0.01 to 0.08% and N: 0.0015 to 0.015%.   The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the starting material further contains 0.01 to 0.05% of S or Se in total.   The starting material is limited to Al: less than 100 ppm, N: less than 60 ppm, S: less than 50 ppm and Se: less than 50 ppm, The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2. The starting material is one or more selected from Cu, Sb, Sn, Bi, Mo, Cr, Ni and 0.01 to 0.5% for Cu, Sb, Sn, Mo, Cr, Ni, and about Bi The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 5, characterized by comprising 0.001 to 0.18%.