JPH08225843A - Production of grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE: To stably produce a grain-oriented silicon steel sheet having high magnetic flux density by subjecting a silicon steel slab having a specified compsn. to hot rolling, cold rolling, nitriding treatment or the like under specified conditions. CONSTITUTION: As for a silicon steel slab having a compsn. contg., by weight, 0.015 to 0.100% C, 2.0 to 4.5% Si, 0.020 to 0.060% acid soluble Al, 0.005 to 0.010% N, 0.010 to 0.040% of one or more kinds of S and Se, 0.01 to 1% Cu, 0.01 to 0.5% Mn, 0.001 to 0.3% Sn, and the balance Fe, rough rolling is started in the temp. range of 1150 to 1400 deg.C, and finish rolling is executed to form into a hot rolled sheet having 2.5 to 1.0mm thickness. Next, it is heated at 950 to 1150 deg.C for 1 to 160 sec, is thereafter cooled at a cooling rate slower than that of air cooling, is subsequently cooled at a rate higher than that of air cooling and is rolled by cold rolling for one time to regulate its thickness to 0.30 to 0.10mm. Next, it is subjected to decarburizing annealiang, secondary heating and nitriding treatment under specified conditions, is coated with a separation agent for annealing and is subjected to secondary recrystallization annealing to produce a grain-oriented silicon steel sheet having high magnetic flux density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented silicon steel sheet (hereinafter referred to as grain-oriented electrical steel sheet) having a thickness of 0.30 mm to 0.10 mm, which is thinner than that defined in JIS C2553.

[0002]

2. Description of the Related Art A precipitate or solute atom that suppresses grain growth is called an inhibitor. AlN is used as a main inhibitor, and the cold rolling rate before primary recrystallization is 75% or more.
% Or less, the grain-oriented electrical steel sheets manufactured by the method are Japanese Patent Publication No. 9419, 62-54846, 59-4.
8935,60-48862,63-11406,63
-114407 and other manufacturing methods (hereinafter referred to as method A)
And the manufacturing method disclosed in Japanese Patent Publication No. 61-60896, 62-45285 (hereinafter referred to as method B) is known.

In the method A, finely dispersed AlN and MnS are mainly used as inhibitors necessary for secondary recrystallized grain growth. For this reason, these precipitation phases are completely melted at the time of heating the slab, and then finely precipitated in the hot rolling and hot rolled sheet annealing steps. Therefore, it is necessary to set the slab heating temperature to a high temperature of about 1400 ° C. Due to the presence of such finely dispersed precipitates, the primary recrystallized grain size is as small as about 8 μm.

On the other hand, in method B, AlN is mainly used as an inhibitor. The main part of this AlN is formed by substantially uniformly precipitating nitrides of the steel sheet surface phase formed by nitriding after primary recrystallization as AlN in the plate thickness direction in the secondary recrystallization annealing process. In the method B, the slab heating temperature is as low as about 1150 ° C. Since AlN has already precipitated at this stage, finely dispersed A during primary recrystallization annealing
Almost no 1N or MnS precipitates are present. Therefore, the crystal grain size after primary recrystallization annealing at a primary recrystallization annealing temperature of about 840 ° C., which is almost the same as in method A, is as large as about 24 μm. Therefore, in the method B, the inhibitor strength is weak in the state after the primary recrystallization annealing. Therefore, in order to strengthen the inhibitor in the secondary recrystallization annealing process, the nitriding treatment is performed after the primary recrystallization annealing so that the nitrogen content is 20%.
It is about 0 ppm.

Although the magnetic flux density of the final product is slightly higher in the A method than in the B method, it is necessary to heat the slab at an extremely high temperature, and since S content is about 0.03%, there is a problem of ear cracking during hot rolling. It has the drawback of frequent occurrence. Method B does not require such high temperature heating, and since S is low, ear cracking does not occur. However, it has a drawback that the magnetic flux density is slightly lower than that of the method A.

By the way, when a thin grain-oriented electrical steel sheet is manufactured by the method A, for example, when the hot rolling thickness is 2.3 mm and the product sheet thickness is 0.15 mm, the cold rolling rate becomes as high as about 93.5%. . Since magnetic properties deteriorate at such a high cold rolling rate, cold rolling is usually performed on a hot rolled sheet and then hot rolled sheet annealing is performed to make the cold rolling rate before primary recrystallization about 87%. . Therefore, 2 with annealing sandwiched to reach the final thickness
It requires cold rolling once.

In order to omit such a cold rolling step, the hot rolled sheet may be determined from the beginning according to the thickness of the final product. However, the thinner the hot rolled sheet is made to be 1.8 mm or less, the finish rolling is performed. There is a problem that the temperature of the steel sheet is remarkably lowered in the process, the precipitate grows large during this period, the inhibitor effect is weakened, and the secondary recrystallization is hard to occur.

On the other hand, in the method B, since the fine dispersion of the inhibitor is unnecessary in the hot rolling step, the temperature drop caused by reducing the thickness of the hot rolled sheet does not affect the secondary recrystallization, so that it is suitable for the final product thickness. It is possible to manufacture a product with one cold rolling using a hot rolled sheet.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a technique for stably and inexpensively producing a grain-oriented electrical steel sheet having a high magnetic flux density equal to or higher than that of the A method by one cold rolling. .

[0010]

Means for Solving the Problems The present invention is to solve the above problems, and in% by weight (hereinafter the same), C: 0.0
15 to 0.100%, Si: 2.0 to 4.5%, acid-soluble Al (solAl): 0.020 to 0.060%,
N: 0.005 to 0.010%, one or both of S and Se: 0.010 to 0.040%, Cu: 0.01 to 1
%, Mn: 0.01 to 0.5%, Sn: 0.001 to
A silicon steel slab containing 0.3% and the balance being Fe and unavoidable impurities is roughly rolled in a temperature range of 1150 ° C. to 1400 ° C., followed by finish rolling to a thickness of 2.5 mm to 1 mm. After making a hot rolled sheet of 0.0mm, 950 ℃
After heating at a temperature of 1150 ° C. or more for 1 second or more and 60 seconds or less, a cooling rate slower than air cooling after heating, preferably 4 ° C./sec or less and 9
After cooling to 00 ℃, faster than air cooling, preferably 13 ℃
/ 0 sec / sec or more, thickness of 0.30 in one cold rolling
mm to 0.10 mm, after heating in a decarburizing atmosphere at a temperature of 830 ° C. to 860 ° C. for 20 seconds or more and 200 seconds or less (hereinafter referred to as decarburizing heating), the rough rolling start temperature and S of the steel sheet or Dew point 0 in the temperature range shown in FIG. 1 according to the Se amount
℃ or less -40 ℃ or more in reducing atmosphere of 10 seconds or more 180
After heating within seconds (hereinafter referred to as secondary heating), the total nitrogen content is 100
This is a method for producing a grain-oriented silicon steel sheet, which comprises applying an annealing separator after adjusting the content to be not less than 200 ppm and not more than 200 ppm. In addition, the silicon steel slab may further include B
i: 0.0050 to 0.15%, P: 0.001 to 0.
15%, Sb: 0.001 to 0.15%, Pb: 0.0
It is effective to contain one or more of these within the range of 01 to 0.15% and B: 0.0010 to 0.1%.

[0011]

The present inventors have found that the grain-oriented electrical steel sheet (110) [0
01] The conditions for preferential expression of secondary recrystallized grains were studied, and the following conclusions were obtained. In general, the inhibitor suppresses the growth of primary recrystallized grains to reduce the primary recrystallized grain size, suppresses the growth of matrix crystal grains in the secondary recrystallization annealing process, and affects and initiates the secondary recrystallization start temperature. Affects the choice of secondary recrystallization orientation.

In order to make it easier to understand the role of the inhibitor that acts from the formation of the primary recrystallized structure to the completion of the secondary recrystallization, the inhibitor which should also determine the primary recrystallized grain size is referred to as a primary inhibitor. The primary inhibitor is formed in a process from melting to primary recrystallization, and should be called an innate inhibitor in contrast to the B method in which the inhibitor is added by performing nitriding treatment after primary recrystallization annealing. The higher the primary inhibitor strength, the smaller the primary recrystallized grain size.

An inhibitor from the completion of primary recrystallization to the appearance of secondary recrystallization is called a secondary inhibitor. The first purpose of the nitriding treatment of Method B is to provide a secondary inhibitor. This addition of inhibitor by nitriding should be called acquired inhibitor. Since the driving force of the secondary recrystallized grains is grain boundary energy, the smaller the driving force, that is, the larger the matrix grain size, the higher the secondary recrystallization temperature becomes.
If the crystal grain size is the same, the higher the secondary inhibitor strength, the higher the secondary recrystallization temperature. The secondary recrystallization temperature cannot be determined only by the strength of the secondary inhibitor, but here, considering the crystal grain size, the secondary inhibitor is weak when the secondary recrystallization temperature is low. Described as having a strong secondary inhibitor.

The inhibitor strength during the process in which the secondary recrystallized grains are selectively grown, that is, the inhibitor strength which is deeply involved in the selection of the secondary recrystallized orientation is called the tertiary inhibitor strength. The stronger the tertiary inhibitor strength, the larger the grain boundary migration difference between the general grain boundary and the corresponding grain boundary, and the stronger the secondary recrystallization orientation selectivity. The inhibitor strength at the start of secondary recrystallization can be said to be the secondary inhibitor strength by emphasizing the initiation of secondary recrystallization, and also the tertiary inhibitor by emphasizing that secondary recrystallized grains are being generated and growing. I can say. In the method B in which the nitriding treatment is performed after the primary recrystallization annealing, the inhibitor strength is significantly different between the completion of the primary recrystallization and the start of the secondary recrystallization annealing. It is the same as the secondary inhibitor strength.

As described above, the primary recrystallized grain size is almost determined by the strength of the primary inhibitor. In the method A, for example, when only MnS is used as an inhibitor, the thickness is 18 μm, when only AlN is 14 μm, and when the normal method A using AlN and MnS together is 8 μm. Further, the same AlN is used in the case of the B method in which the slab heating temperature is as low as 1150 ° C. However, the primary recrystallized grain size is as large as about 24 μm because the primary inhibitor is weak due to the large precipitation size of AlN.

The slab heating temperature of the steel of the present invention is higher than that of the B method and is the same as that of the A method or lower than that of the A method. The reason why the slab heating temperature of the steel of the present invention is higher than that of the B method will be described. Since S and Se have metallurgical equivalent functions, the following description will be limited to S. The steel of the present invention contains S as an inhibitor in the range of 0.010% to 0.040%. In order to completely dissolve such high S, it is necessary to set the slab heating temperature to a high temperature of 1300 ° C. or higher. But S
Is completely dissolved, the sulfide is finely and uniformly precipitated during hot rolling, the primary inhibitor strength becomes too strong, and the crystal grain size after primary recrystallization becomes small, which causes the drawbacks described later.

Therefore, in the present invention, the temperature of the rough rolling is lowered so as to precipitate relatively coarsely in the rough rolling stage or the finish hot rolling step, and the thickness of the hot rolled sheet is reduced to increase the temperature drop during the finish rolling. I did it. When a hot-rolled sheet is produced under such conditions, a relatively large amount of sulfide is precipitated in the hot-rolling process as compared with the method A, and the primary inhibitor strength is weakened, and the grain size can be adjusted in the primary recrystallization annealing process. . However, when the rough rolling temperature is lower than 1150 ° C, the sulfide dispersion is non-uniform and the size becomes too large, the tertiary inhibitor strength becomes weak and the magnetic flux density becomes low. did.

Further, the rough rolling start temperature is set to 1400 ° C. or lower because when the rough rolling start temperature is set higher than this and the hot rolled thickness is defined in the present invention, the sulfides are too fine in the hot rolling step and the primary inhibitor is produced. Is too strong and a high magnetic flux density cannot be obtained. When the secondary heating is carried out within the range shown in FIG. 1 after adjusting the components and hot rolling conditions in this way, the primary recrystallized grain size can be increased as compared with Method A, and the tertiary inhibitor strength is A
It can be strengthened to the same level as the law or higher
0) The [001] secondary recrystallized structure develops.

Grain growth due to grain boundary migration occurs slightly due to the secondary recrystallization annealing, but when a certain temperature is reached, there is a large difference in grain boundary migration speed between the general grain boundary and the corresponding grain boundary.
In this state, the crystal orientation with the highest probability of contact with the corresponding grain boundary eats the surrounding crystal grains and becomes large, and the size effect (dimensional advantage) is obtained to start abnormal growth. That is, it is the manifestation of secondary recrystallization.

Corresponding grains having a high frequency of occurrence that are involved in the secondary recrystallization of the grain-oriented electrical steel sheet are present in the corresponding grain boundaries that easily move during the secondary recrystallization grain growth process, from grain boundaries corresponding to Σ5 to grain boundaries corresponding to Σ33. There are three types of boundaries, Σ5, Σ7, and Σ9. Among them, the Σ7 grain boundary is a unidirectional electrical steel sheet and its existence frequency is low, so the Σ5 grain boundary and the Σ9 grain boundary may be considered. In the primary recrystallized plate of the present invention, the (110) [001] oriented grain has the highest probability of forming a Σ9-corresponding grain boundary as compared with other orientations. In addition, there is a high probability that a Σ5-corresponding grain boundary is formed in an orientation deviating from the ideal (110) [001] orientation.

The Σ5 compatible grain boundary and the Σ9 compatible grain boundary have slightly different temperature regions in which they easily move. When the Σ5 grain boundary and the Σ9 grain boundary coexist, the Σ5 grain boundary becomes easier to move preferentially at a lower temperature. . Therefore, in order to preferentially grow the secondary recrystallized grains with high (110) [001] integration, Σ5
In the temperature range where the grain boundaries preferentially move, the secondary inhibitor is strongly required to prevent secondary recrystallization from occurring.

Since the primary crystal grain size of Method A is small, the secondary inhibitor is weak and secondary recrystallization occurs at low temperature. In method A, Al is in the range of 0.022% to 0.030%,
If Al is low in this range, the primary recrystallized grain size becomes small by about 1 to 2 μm. More strictly speaking, all N in the steel is Al
If it is assumed that N, then A can be expressed by equation (1).
It has been found that as l _R (a value that can be said to be an index indicating the amount of solid solution Al that does not form a nitride) increases, the crystal grain size during primary recrystallization annealing increases, that is, the primary inhibitor strength tends to decrease. Al _R [ppm] = solAl [ppm] − (27/14) N [ppm] (1)

For example, if N is 100 ppm and solAl is 0.0240%, if N is 50 ppm and solAl is 0.0143%, or if N is 140 ppm and solAl is 0.0317%, Al _R is 47 and Al
, The primary recrystallized grain size remains the same even when the value changes from 0.0143 to 0.0317%. Therefore, it is necessary to consider Al _R when considering the primary inhibitor strength. However, the decrease in secondary inhibitor strength due to de-Al is more remarkable as the absolute amount of Al is smaller, and the tertiary inhibitor strength, which directly affects the orientation selectivity of the secondary recrystallized grains, is also reduced.
_{If R} is the same, it becomes weak if the absolute amount of Al is small.

During the secondary recrystallization annealing process, Al is oxidized and the amount of Al in the vicinity of the surface of the steel sheet is reduced, so that the inhibitor strength of this portion is weakened. Therefore, secondary recrystallization appears from this portion, but when Al _R is small and the driving force is large and the absolute value of Al is originally small, the temperature at which secondary recrystallization appears is a low temperature of 925 ° C. or lower, At this temperature, the Σ5 grain boundary moves preferentially, so the secondary recrystallization orientation that develops is ideal G
The azimuth is 10 degrees or more away from the oss azimuth.

On the other hand, when Al is as high as 0.033% or more and Al _R is large, the driving force is decreased because the primary particle size becomes large, and the Al concentration itself is high.
Since AlN is immediately formed and the inhibitor strength does not decrease, the secondary inhibitor becomes relatively strong, and the occurrence of secondary recrystallization at low temperature can be prevented. Therefore, it is possible to prevent the occurrence of secondary recrystallization having a bad orientation due to the preferential grain boundary movement of the Σ5 grain boundary.

However, the secondary recrystallization temperature is 1100 ° C.
At the above high temperature, Al is rapidly oxidized, the tertiary inhibitor strength is rapidly reduced, and selective grain boundary migration becomes difficult to occur, so that secondary recrystallization does not occur and a so-called fine grain structure is formed. Therefore, in order to develop the secondary recrystallization having a high degree of integration of the (110) [001] orientation by the method A, it is necessary to prevent the secondary recrystallization from appearing at a low temperature and to rapidly increase the tertiary inhibitor strength at a high temperature. In order to prevent the decrease and the generation of fine particles, it is necessary to control the Al content and the Al _R value within an extremely narrow range.

On the other hand, in the method B, the Al content is low, and Al near the surface phase
, The grain size is large even if it decreases, so that the Σ5 grain boundary preferentially moves. Secondary recrystallization does not occur at a low temperature of 925 ° C. or less. Since AlN is immediately formed, it is possible to prevent the decrease of the inhibitor in the vicinity of the surface phase and prevent the occurrence of secondary recrystallization at a low temperature of 925 ° C. or lower.

However, since the primary inhibitor strength is weak in the B method, the primary recrystallized grain size is likely to vary due to variations in the finish hot rolling start temperature, solid solution Al, primary recrystallization annealing temperature, and the like. If the primary recrystallization grain size is too large or the nitriding amount is too large, the secondary recrystallization temperature becomes 1100 ° C. or higher, the oxidation rate of Al remarkably increases, the tertiary inhibitor strength decreases sharply, and the Σ9 grain boundary The selective moving speed becomes relatively slow, and the integration degree of the (110) [001] -oriented secondary recrystallization decreases.

In method A, secondary recrystallization occurs at a lower temperature than method B, but the secondary recrystallization orientation (110) [0]
01] The orientation integration degree is equal to or higher than that of the B method.
The reason for this is that in method A, since finely dispersed MnS exists in addition to finely dispersed AlN, the tertiary inhibitor strength is equal to or higher than that in method B as compared with method B in which the inhibitor is mainly composed of only AlN. Because it is.

In method B, nitriding is performed after primary recrystallization, and since the primary recrystallization grain size is large, almost no grain growth is observed until secondary recrystallization occurs, and the secondary recrystallization starting temperature is higher than in method A. . That is, the strength of the secondary inhibitor is stronger than that of Method A. However, the degree of orientation integration of the secondary recrystallized grains that appear is equal to or slightly inferior to that of the method A. This is because the tertiary inhibitor is equal to or slightly weaker than Method A.

In the case of the steel of the present invention, the primary inhibitor strength is weaker than that of the A method because the precipitation size of sulfide is large, but compared with the B method, a large amount of uniformly dispersed sulfides such as Mn and Cu are present. Since the fine dispersion of AlN with the sulfide as the nucleus is achieved, the primary inhibitor is stronger than the B method, and if necessary, P, Sn, Pb, B, Sb is used.
In addition to these effects, the tertiary inhibitor is not only stronger than the B method but also stronger than the A method due to these effects and the nitriding effect after primary recrystallization. Since primary recrystallization grain diameter is large that no risk of expression of secondary recrystallization at a low temperature, since the tertiary inhibitor is strong, rapidly because a possibility that the inhibitor strength is weakened less strictly a value as Method A Al _R There is no need to control.

However, when the material of the present invention is subjected to the primary recrystallization annealing which is usually employed in the methods A and B, the grain size is small and, as a result, the secondary inhibitor becomes weak and the secondary recrystallization appears at low temperature. There is danger. The first reason for performing the secondary heating in the primary recrystallization annealing process in the present invention is to control the crystal grain size. In the method A, the primary inhibitor is too strong, and even if such secondary heating is performed, the primary recrystallized grain size hardly changes. In method B, the primary inhibitor is weak, so
The primary recrystallized grain size becomes large even if the high temperature secondary heating as shown in FIG.

Therefore, the grain size after primary recrystallization of the material of the present invention is larger than that of method A and smaller than that of method B. The secondary recrystallization starting temperature in the case of the method of the present invention is almost the same as or slightly lower than that of the method B, although it is smaller than that of the method B, and higher than that of the method A. The reason for this is that the particle size is larger than in method A. Although the particle size is smaller than that of the B method, the strength of the secondary inhibitor is B because the amount of precipitates and solute atoms is large.
The temperature is slightly weaker than that of Method B, and the secondary recrystallization starting temperature is about the same as or slightly lower than that of Method B.

(11) of the secondary recrystallization developed by the method of the present invention
0) [001] orientation integration is slightly better than either method A or B. The reason is that the tertiary inhibitor is A, B
This is because it is stronger than either method.

The second reason for carrying out the secondary heating in the primary recrystallization process in the present invention is to control the amount and morphology of the surface oxide. Therefore, the dew point is set to 0 ° C. or lower and −40 ° C. or higher by reducing the atmosphere during the secondary heating. The reason for this is that when the dew point is raised to a higher temperature, the F formed in the decarburization annealing process
This is because the reduction of eO is insufficient and the amount of FeO is too large, which adversely affects the formation of the glass film in the secondary recrystallization annealing process. When the dew point is -40 ° C or less, a large amount of SiO ₂ is formed on the surface of the steel sheet.
This SiO ₂ reacts with Al in the steel sheet to reduce the amount of Al in the steel, and as a result, the strength of the tertiary inhibitor becomes weak and the degree of accumulation of (110) [001] orientation secondary recrystallization decreases. This is because the magnetic flux density decreases. Since it is difficult to determine the dew point by measuring the optimum FeO amount and SiO ₂ amount each time, as a guideline, the dew point of secondary heating should be set so that the oxygen amount of the steel sheet after primary recrystallization annealing falls within 500 to 800 ppm. Just decide. This is because if the amount of oxygen is less than this, the film formation is insufficient, and if the amount of oxygen exceeds this, the tertiary inhibitor strength decreases due to the selective oxidation of Al.

The reason for limiting the other conditions will be described below. If the treatment according to the method of the present invention is performed, secondary recrystallization having a high magnetic flux density can be obtained even if C is less than 0.015%. However, when the rough rolling start temperature is 1300 ° C. or higher, the secondary recrystallization becomes incomplete and so-called fine recrystallization is performed. The lower limit was set to 0.015% because crystal grains called (110) [001] orientation called grains are formed. Further, the upper limit is set to 0.1% because if it exceeds C, the decarburization time of the primary recrystallization annealing becomes long and it is not economical.

As the content of Si increases, the specific resistance increases and the eddy current loss of the product decreases. Therefore, the more Si, the better in order to reduce the eddy current loss. The reason why Si is limited to 2% or more is that the lower limit is 2% because eddy current loss is large and it is not preferable if Si is less than this. However, Si becomes more likely to crack in the cold rolling process as the added amount increases. If the Si content exceeds 4.5%, the cold rolling requires special measures and the production of the steel is economically disadvantageous. Therefore, the upper limit is set to 4.5%.

Although Al forms (Al, Si) N and acts as an inhibitor, the effect is not exhibited unless the acid-soluble Al is 0.02% or more, so the lower limit was made 0.02%. The upper limit of 0.06% is Al exceeding this
This is because the presence of the compound makes it ineffective as an inhibitor.

N forms (Al, Si) N and acts as an inhibitor, but its effect is not exhibited unless it is 0.005% or more at the stage of slab, so the lower limit was made 0.005%. The upper limit of 0.01% is set to 0.01% because improvement in magnetic properties is not observed even if the upper limit is exceeded.

The following elements have the function of strengthening the primary inhibitor, but are added mainly for the purpose of strengthening the tertiary inhibitor. One or both of S and Se may be in the range of 0.010 to 0.040% in total. The reason for this limitation is that in the material component of the present invention, when S or Se is less than 0.010%, the tertiary inhibitor is weak and secondary recrystallized grains deviating from (110) [001] increase. The higher the content of Se and S, the stronger the effect of strengthening the tertiary inhibitor, and the higher the magnetic flux density. However, if it exceeds 0.040%, ear cracks tend to occur during hot rolling, so the upper limit was made 0.040%.

Cu has a function of forming a precipitate with S and Se or strengthening the tertiary inhibitor by itself,
If less than 0.01%, the effect is small, so the lower limit is 0.0
It was set to 1%. Although addition of more than 1% has the effect of strengthening the tertiary inhibitor, it is not economical to add more than that, so the upper limit was made 1%.

Mn has a function of forming a precipitate with S and Se to strengthen the tertiary inhibitor, but if it is less than 0.01%, its effect is small, so the lower limit was made 0.01%. 0.
Addition of more than 5% has the effect of strengthening the tertiary inhibitor, but it is not economical to add more than that, so the upper limit was made 0.5%.

Sn has a function of strengthening the tertiary inhibitor, but if it is less than 0.001%, the effect is small, so the lower limit was made 0.001%. Sn is effective even if it exceeds 0.3%, but it is not economical to add more than this, so the upper limit was made 0.3%.

The following elements are contained in one or more of these as required. Bi has a function of strengthening the tertiary inhibitor, but the effect is small at less than 0.0050%, so the lower limit was made 0.005%. Although Bi is effective even if it exceeds 0.15%, it is not economical to add more than Bi, so the upper limit was made 0.15%.

P has the function of strengthening the tertiary inhibitor, but if it is less than 0.001%, the effect is small, so the lower limit was made 0.001%. P is effective even if it exceeds 0.15%, but it is not economical to add more than this, so the upper limit was made 0.15%.

Sb has the function of strengthening the tertiary inhibitor, but if it is less than 0.001%, the effect is small, so the lower limit was made 0.001%. Sb is effective even if it exceeds 0.15%, but it is not economical to add more than this, so the upper limit was made 0.15%.

Pb has a function of strengthening the tertiary inhibitor, but if it is less than 0.001%, the effect is small, so the lower limit was made 0.001%. Pb is effective even if it exceeds 0.15%, but it is not economical to add more than this, so the upper limit was made 0.15%.

B has a function of strengthening the tertiary inhibitor, but if it is less than 0.001%, the effect is small, so the lower limit was made 0.001%. B is effective even if it exceeds 0.1%, but it is not economical to add more than 0.1%, so the upper limit was made 0.1%.

The reason why the crude hot rolling start temperature is set to 1150 ° C. or higher is that it is uneconomical because the rolling force at the time of hot rolling becomes large at a temperature lower than this temperature. This is because the magnetic flux density cannot be obtained. On the other hand, if the hot-rolled finish thickness is 1.6 mm or less and the sulfide size increases and a high magnetic flux density can be obtained even if it exceeds 1400 ° C, the upper limit is set to 1400 ° C or less because it is not thermally economical.

The thickness of the hot-rolled sheet is set to 2.5 mm or less because a magnetic flux density cannot be obtained by one cold rolling if the thickness exceeds this value, which is set to 2.5 mm or less. The thickness of 1 mm or more is because it is difficult to obtain a high magnetic flux density with a hot rolled sheet thinner than this. The reason why the temperature of hot-rolled sheet annealing is 950 ° C. or higher is that a high magnetic flux density cannot be obtained below 950 ° C., and the temperature of 1150 ° C. or lower gives a high magnetic flux density at a temperature higher than 1150 ° C. Since a high magnetic flux density can be obtained even at a temperature of ℃ or less, it is thermally uneconomical. Cooling at a rate slower than air cooling up to 900 ° C., preferably 4 ° C./sec or less is because the magnetic flux density decreases at a faster rate, and cooling from this temperature is faster than air cooling, preferably 13 ° C./sec or more. This is because the magnetic flux density decreases when cooled at a slower rate than air cooling.

A product thickness of 0.30 mm or less is set to 0.30 mm because a high magnetic flux density can be obtained even when the product thickness is thicker than this, but iron loss is deteriorated. In addition, the product plate thickness is 0.1
The reason why the thickness is 0 mm or more is that when the thickness is smaller than this, secondary recrystallization is incomplete and the magnetic flux density decreases.

The decarburization annealing temperature of the primary recrystallization annealing is set to 830 ° C.
To 860 ° C. is because decarburization is most efficient in this temperature range, and decarburization is hard to occur outside this temperature range. The reason why the time is set to 20 seconds or more and 200 seconds or less is that it is impossible to decarburize to 0.0020% or less when the time is less than 20 seconds, and the reason why the time is 200 seconds or less is that the C content of the steel sheet is longer even if heated for a long time. Is almost unchanged and uneconomical.

FIG. 1 shows the secondary heating temperature region of the method of the present invention. Region A of the diagram is a region in which S or Se is 0.015% or less, and B is more than 0.015% and 0.030%. Up to 0.030% to 0.040%, the area is 0.040%. It is shown that the secondary heating temperature needs to be changed depending on the rough rolling start temperature and the content of S or Se. The secondary heating condition in FIG. 1 is divided into A, B, and C by the amount of S or Se. Alternatively, the larger the amount of Se, the more difficult it is for grain growth in primary recrystallization, so that secondary recrystallization structure having a high magnetic flux density cannot be obtained unless secondary heating is performed in such a region. The heating time is set to 10 seconds or more because the magnetic flux density tends to fluctuate if the heating time is shorter than this, and the heating time is set to 180 seconds or less, the magnetic flux density is not improved even if the heating time is longer than this, which is economical. Because it is not.

If necessary, a nitriding treatment is performed so as to adjust the total nitrogen amount after the primary recrystallization to 100 ppm or more and 200 ppm or less. The nitrogen amount after the primary recrystallization annealing is 100%.
The reason why the content is higher than or equal to ppm is that the tertiary inhibitor is weak and a high magnetic flux density cannot be obtained if the content is less than 100 ppm. Further, the reason for limiting the content to 200 ppm or less is that a higher magnetic flux density can be obtained even if the content is higher than this, but it is not economical to perform the nitriding treatment to increase the nitrogen content further.

[0055]

EXAMPLES The present invention will be described in detail below with reference to examples. (Example 1) C: 0.070%, Si: 3.27%, M
n: 0.073%, P: 0.060%, solAl:
0.0270%, S: 0.030%, Sn: 0.13
%, Cu: 0.08%, N: 0.0070% as a main component, rough rolling was started at a temperature of 1200 ° C., and finish rolling was performed to obtain a hot rolled sheet having a thickness of 1.35 mm. The steel sheet is heated at 1130 ° C for 10 seconds and then 900 ° C over 120 seconds.
After cooling to water, it was cooled with water. Then, after pickling, cold rolling was performed to a thickness of 0.19 mm. In this case, the plate thickness 1.
55 mm, 1.2 mm, 0.8 mm, 0.6 mm, 0.
Cold rolling was carried out under the conditions of holding each thickness of 4 mm and 0.3 mm for 20 minutes at 250 ° C. to obtain a thickness of 0.19 mm.

Then, at a temperature of 850 ° C., a dew point of 66 ° C., 75
After heating for 120 seconds in a% H ₂ —N ₂ atmosphere, continue to 900
15 seconds at a temperature of ℃, dew point -20 ℃, 75% H ₂ -N ₂
After heating in the atmosphere, 6% NH for 60 seconds at 750 ° C
Nitrogen treatment is performed in an atmosphere containing ₃ and the amount of nitrogen is 120 p.
pm. Next, 5 parts of TiO ₂ was added to 100 parts of MgO.
Part, Sb ₂ (SO _{4) 3} and 0.3 part, the NaBO ₃ 0.
The annealing separating agent mixed at a ratio of 3 parts was applied, and 95% N ₂ was applied.
It was heated to 1200 ° C. at a temperature rising rate of 15 ° C./hr in an atmosphere of —H ₂ , heated in a 100% H ₂ atmosphere for 20 hours, and then cooled. Then, the result of strain relief annealing and measurement of the magnetic flux density is shown in Table 1 as the product (1) of the present invention.

[0057]

[Table 1]

For comparison, the same slab was heated at 1350 ° C. for 2 hours and then hot rolling was started to obtain hot-rolled sheets having thicknesses of 1.55 mm and 2.3 mm. The hot rolled sheet rolled to 2.3 mm is 1000
After heating at ℃ for 5 minutes, water-cooling and cold-rolling to a thickness of 1.5
It was set to 5 mm. Then, these materials were annealed and cold rolled in the same manner as in the present invention to have a thickness of 0.19 mm. Then 850
Dew point 66 ° C at 75 ° C, 75% in H ₂ -N ₂ atmosphere 1
Heated for 20 seconds.

Next, the same annealing separator as that of the present invention was applied, and the temperature rising rate was 15 ° C./hr in an atmosphere of 15% N ₂ —H _2.
To 1200 ° C., heated in a 100% H ₂ atmosphere for 20 hours and then cooled. Then, strain relief annealing is performed and the magnetic flux density is measured and shown in Table 1 as Comparative Example (1). As shown in Table 1, the magnetic steel sheet produced by the present invention has a remarkably high magnetic flux density. In the comparative material (1) cold-rolled to the same thickness as the present invention, so-called fine grains were generated in the secondary recrystallized portion, and the magnetic flux density was extremely low. In addition, 2.3 mm hot rolled plate
The material (referred to as comparative material (2)) having the final thickness after the cold rolling exhibited 100% secondary recrystallization, but the magnetic flux density was slightly lower than that of the product of the present invention.

(Example 2) C: 0.091%, Si:
3.25%, Mn: 0.071%, P: 0.016%,
solAl: 0.0238%, S: 0.014%, S
e: 0.014%, Sn: 0.12%, Cu: 0.08
%, N: 0.0082%, Sb: 0.024% as a main component, rough rolling was started at a temperature of 1250 ° C., and finish rolling was performed to obtain a hot-rolled sheet having a thickness of 1.40 mm. The steel sheet was heated to 1130 ° C for 120 seconds, cooled to 900 ° C over 120 seconds, and then water-cooled. Then, after pickling, cold rolling was performed to a thickness of 0.145 mm. In this case, plate thickness during cold rolling: 1.55mm, 1.2mm, 0.8mm, 0.6m
Cold rolling was carried out under the conditions that the thicknesses of m, 0.4 mm and 0.3 mm were held at 250 ° C. for 20 minutes.

Then, at a temperature of 850 ° C., a dew point of 66 ° C., 75
% H ₂ -N continued after heating for 100 seconds in a ₂ atmosphere 900
15 seconds at a temperature of ℃, dew point -20 ℃, 75% H ₂ -N ₂
After heating in the atmosphere, nitriding was performed at a temperature of 750 ° C. in an atmosphere containing 6% NH ₃ to adjust the amount of nitrogen to 120 ppm. Next, to 100 parts of MgO, 5 parts of TiO ₂ and Sb ₂
(SO ₄ ) ₃ was mixed at 0.3 parts and NaBO ₃ was mixed at a ratio of 0.3 parts, and the annealing separator was applied and the temperature rising rate was 15 ° C./hr up to 1200 ° C. in an atmosphere of 15% N ₂ —H _2. Heat 1
It was heated in a 00% H ₂ atmosphere for 20 hours and then cooled. Next, the results of strain relief annealing and measurement of the magnetic flux density are shown in Table 2 as the product (2) of the present invention.

[0062]

[Table 2]

For comparison, the same slab was heated at 1350 ° C. for 2 hours and then hot rolling was started to obtain thicknesses of 1.45 mm and 1.80 mm.
It was a hot rolled sheet. The hot rolled sheet rolled to 1.80 mm is 12
It was heated to 1000 ° C. in 0 seconds, air-cooled to 900 ° C., and then water-cooled. Then, cold rolling was performed to a thickness of 1.12 mm. Then, these materials were annealed and cold rolled in the same manner as in the present invention to have a thickness of 0.145 mm. Next, it was heated at a temperature of 850 ° C. in a 75% H ₂ —N ₂ atmosphere with a dew point of 66 ° C. for 120 seconds.

Next, the same annealing separator as that of the present invention was applied, and the temperature rising rate was 25 ° C./hr in an atmosphere of 15% N ₂ —H _2.
To 1200 ° C., heated in a 100% H ₂ atmosphere for 20 hours and then cooled. Then, strain relief annealing is performed and the magnetic flux density is measured and shown in Table 2 as Comparative Example (3). As shown in Table 2, the magnetic steel sheet produced by the method of the present invention has a remarkably high magnetic flux density. In the comparative material (3) hot-rolled to the same thickness as the present invention, so-called fine grains were generated in 10% of the total area in the secondary recrystallized portion, and the magnetic flux density was extremely low. Also 1.8
A material (referred to as Comparative Material (4)) having a final thickness of 2 times cold rolling after hot rolling to 100 mm exhibited 100% secondary recrystallization, but had a slightly lower magnetic flux density than the product of the present invention. Although the hot rolling temperature is lower than that of the comparative material, the present invention exhibits 100% secondary recrystallization and high magnetic flux density.

(Example 3) C: 0.084%, Si:
3.24%, Mn: 0.068%, P: 0.011%,
solAl: 0.0253%, S: 0.026%, S
n: 0.11%, Cu: 0.09%, N: 0.0071
%, Sb: 125 slabs containing 0.025% as a main component
Rough rolling was started at a temperature of 0 ° C., and finish rolling was performed to obtain a hot-rolled sheet having a thickness of 1.40 mm. 1 in 120 seconds
After heating to 130 ° C., it was cooled to 900 ° C. over 120 seconds and then cooled with water. Then, after pickling, cold rolling is performed to a thickness of 0.145.
mm. In this case, the plate thickness during cold rolling is 1.55 mm,
1.2mm, 0.8mm, 0.6mm, 0.4mm,
Cold rolling was performed under the condition of holding each thickness of 0.3 mm at 250 ° C. for 20 minutes.

Next, at a temperature of 850 ° C., a dew point of 66 ° C., 75
After heating for 100 seconds in a% H ₂ —N ₂ atmosphere, continue with 930
15 seconds at a temperature of ℃, dew point -20 ℃, 75% H ₂ -N ₂
After heating in the atmosphere, nitriding was performed at a temperature of 750 ° C. in an atmosphere containing 6% NH ₃ to adjust the amount of nitrogen to 150 ppm. Next, to 100 parts of MgO, 5 parts of TiO ₂ and Sb ₂
(SO ₄ ) ₃ was mixed at 0.3 parts and NaBO ₃ was mixed at a ratio of 0.3 parts, and the annealing separator was applied and the temperature rising rate was 15 ° C./hr up to 1200 ° C. in an atmosphere of 15% N ₂ —H _2. After heating, 1
It was heated in a 00% H ₂ atmosphere for 20 hours and then cooled. Next, the results of measuring the magnetic flux density by performing strain relief annealing are shown in Table 3 as the product (3) of the present invention.

[0067]

[Table 3]

For comparison, after heating the same slab at 1350 ° C. for 2 hours, hot rolling was started and the thicknesses were 1.45 mm and 1.80 mm.
It was a hot rolled sheet. The hot rolled sheet rolled to 1.80 mm is 12
It was heated to 1000 ° C. in 0 seconds, air-cooled to 900 ° C., and then water-cooled. Then, cold rolling was performed to a thickness of 1.12 mm. Then, these materials were annealed and cold rolled in the same manner as in the present invention to have a thickness of 0.145 mm. Next, it was heated at a temperature of 850 ° C. in a 75% H ₂ —N ₂ atmosphere with a dew point of 66 ° C. for 120 seconds.

Next, the same annealing separator as that of the present invention was applied, and the temperature rising rate was 25 ° C./hr in an atmosphere of 15% N ₂ —H _2.
To 1200 ° C., heated in a 100% H ₂ atmosphere for 20 hours and then cooled. Then, strain relief annealing is performed and the magnetic flux density is measured and shown in Table 3 as Comparative Example (5). As shown in Table 3, the magnetic steel sheet produced by the method of the present invention has a remarkably high magnetic flux density. In the comparative material (5) hot-rolled to the same thickness as the present invention, so-called fine grains were generated in 50% of the total area in the secondary recrystallized portion, and the magnetic flux density was extremely low. Also 1.8
The material (referred to as comparative material (6)) having a final thickness of 2 mm in cold rolling after hot rolling to 20 mm had fine magnetic particles of about 20% of the total area, and the magnetic flux density was considerably lower than that of the product of the present invention. Although the hot rolling temperature is lower than that of the comparative material, the product of the present invention exhibits 100% secondary recrystallization and has a high magnetic flux density.

(Example 4) C: 0.080%, Si:
3.21%, Mn: 0.073%, P: 0.010%,
solAl: 0.0263%, S: 0.017%, S
e: 0.016%, Sn: 0.12%, Cu: 0.08
%, N: 0.0092%, Sb: 0.023% as a main component, rough rolling was started at a temperature of 1200 ° C., and finish rolling was performed to obtain a hot-rolled sheet having a thickness of 1.20 mm. The steel sheet was heated to 1130 ° C for 120 seconds, cooled to 900 ° C over 120 seconds, and then water-cooled. Then, after pickling, cold rolling was performed to a thickness of 0.145 mm. In this case, plate thickness during cold rolling: 1.55mm, 1.2mm, 0.8mm, 0.6m
Cold rolling was carried out under the conditions that the thicknesses of m, 0.4 mm and 0.3 mm were held at 250 ° C. for 20 minutes.

Next, at a temperature of 850 ° C., a dew point of 66 ° C., 75
After heating for 100 seconds in a% H ₂ —N ₂ atmosphere, continue to 950
15 seconds at a temperature of ℃, dew point -20 ℃, 75% H ₂ -N ₂
After heating in the atmosphere, nitriding was performed at a temperature of 770 ° C. in an atmosphere containing 6% NH ₃ to adjust the amount of nitrogen to 180 ppm. Next, to 100 parts of MgO, 5 parts of TiO ₂ and Sb ₂
(SO ₄ ) ₃ was mixed at 0.3 parts and NaBO ₃ was mixed at a ratio of 0.3 parts, and the annealing separator was applied and the temperature rising rate was 15 ° C./hr up to 1200 ° C. in an atmosphere of 15% N ₂ —H _2. After heating, 1
It was heated in a 00% H ₂ atmosphere for 20 hours and then cooled. Then, the results of measuring the magnetic flux density by performing strain relief annealing are shown in Table 4 as the product (4) of the present invention.

[0072]

[Table 4]

For comparison, the same slab was heated at 1350 ° C. for 2 hours and then hot rolling was started to obtain thicknesses of 1.20 mm and 1.80 mm.
It was a hot rolled sheet. The hot rolled sheet rolled to 1.80 mm is 12
It was heated to 1000 ° C. in 0 seconds, air-cooled to 900 ° C., and then water-cooled. Then, cold rolling was performed to a thickness of 1.12 mm. Then, these materials were annealed and cold rolled in the same manner as in the present invention to have a thickness of 0.145 mm. Next, it was heated at a temperature of 850 ° C. in a 75% H ₂ —N ₂ atmosphere with a dew point of 66 ° C. for 120 seconds.

Then, the same annealing separator as that of the present invention was applied, and the temperature rising rate was 25 ° C./hr in an atmosphere of 15% N ₂ —H _2.
To 1200 ° C., heated in a 100% atmosphere for 20 hours, and then cooled. Then, strain relief annealing is performed and the magnetic flux density is measured and shown in Table 4 as Comparative Example (7). As shown in Table 4, the magnetic steel sheet produced by the method of the present invention has a remarkably high magnetic flux density. In the comparative material (7) hot-rolled to the same thickness as the present invention, the so-called fine grains were generated in 5% of the total area in the secondary recrystallized portion, and the magnetic flux density was slightly low. Also, a material having a final thickness obtained by hot rolling to 1.8 mm and then cold rolling twice (comparative material (8)
Fine particles were not generated, but the magnetic flux density was lower than that of the product of the present invention. Although the hot rolling temperature is lower than that of the comparative material, the product of the present invention exhibits 100% secondary recrystallization and has a high magnetic flux density.

[0075]

According to the present invention, a thin grain oriented silicon steel sheet having excellent magnetic properties can be manufactured at low cost. That is, by optimizing the combination of the component range, the hot rolling conditions, and the annealing step for controlling the inhibitor, the hot rolled sheet can be processed in one cold rolling step.

[Brief description of drawings]

FIG. 1 is a graph showing a secondary heating temperature region in annealing after cold rolling.

Claims (2)

[Claims] 1. By weight%, C: 0.015 to 0.100.
%, Si: 2.0 to 4.5%, acid-soluble Al: 0.02
0-0.060%, N: 0.005-0.010%,
One or both of S and Se: 0.010 to 0.040
%, Cu: 0.01 to 1%, Mn: 0.01 to 0.5
%, Sn: 0.001 to 0.3%, with the balance being Fe
And silicon steel slab, which is an unavoidable impurity, for 1150
After starting rough rolling in the temperature range of ℃ to 1400 ℃, and then finishing rolling to make hot-rolled sheet with a thickness of 2.5mm to 1.0mm, 1 at a temperature of 950 ℃ to 1150 ℃
900 seconds at a slower cooling rate than air cooling after heating over 60 seconds
After cooling to ℃, it is cooled at a speed faster than air cooling, and is rolled by one cold rolling within a thickness range of 0.30 mm to 0.10 mm, then at a temperature of 830 ° C. to 860 ° C. for 20 seconds or more 200
After heating in a decarburizing atmosphere for less than a second, start temperature of rough rolling and S of steel sheet
Or, depending on the Se amount, point D (860, 140) in FIG.
0), E point (880, 1150), F point (1050, 1)
150), and a total nitrogen amount of 100 pp after heating for 10 seconds or more and 180 seconds or less in a reducing atmosphere having a dew point of 0 ° C or lower and -40 ° C or higher in a temperature range surrounded by a range of G point (920, 1400).
A method for producing a grain-oriented silicon steel sheet, which comprises applying an annealing separator after adjusting the m to 200 ppm or less and performing finish annealing. 2. The silicon steel slab further comprises Bi: 0.00.
50-0.15%, P: 0.001-0.15%, S
b: 0.001 to 0.15%, Pb: 0.001 to 0.
15%, B: 0.0010 to 0.1% in the range of 1 or more of these are contained.
A method for manufacturing the grain-oriented silicon steel sheet described.