JPH0987747A - Production of grain oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To industrially produce a silicon steel sheet low in core loss and having high magnetic flux density, in a method for producing a grain oriented silicon steel sheet using AlN as an inhibitor, by numerously forming secondarily recrystallized nuclei in the optimum orientation and next promoting the growth thereof. SOLUTION: A silicon steel slab contg., by weight, 0.02 to 0.12% C, 2.5 to 4.0% Si, 0.03 to 0.15% Mn, 0.01 to 0.05% sol.Al and 0.004 to 0.01% N, furthermore contg. 0.01 to 0.05% S and/or Se, and the balance Fe is subjected to hot rolling and is thereafter subjected to hot rolled sheet annealing and rapid cooling treatment. This steel sheet is subjected to cold rolling for one time or two times including process annealing at >=80% final draft, is thereafter subjected to decarburizing annealing and is then subjected to finish annealing to produce the grain oriented silicon steel sheet. In this method, it is heated to a temp. higher than the secondarily recrystallized nuclei forming temp. N-TSR in the finish annealing to numerously form secondarily recrystallized nuclei in the optimum orientation, and successively, it is cooled to be in a temp. range of less than the secondarily recrystallized nuclei forming temp. to more than the secondarily recrystallized grain growable temp. G-TSR to promote the growth of the secondarily recrystallized nuclei in the optimum orientation.

Description

Detailed Description of the Invention

[0001]

The present invention relates to Al as an inhibitor.
The present invention relates to a method for manufacturing a unidirectional silicon steel sheet using N.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are mainly used as core materials for transformers, and in response to the recent demand for energy-saving, they are becoming increasingly low in iron loss and high in magnetic flux density. . In order to have such excellent magnetic properties, it is necessary that the [001] direction, which is the easy axis of iron, be composed of a group of crystal grains that are highly integrated in the rolling direction of the steel sheet. The formation of such a crystal group, in the production of general grain-oriented silicon steel sheet,
At the time of final annealing, it is called so-called Goss grain (110)
This can be almost achieved by preferentially developing and growing the crystal grains of the [001] orientation as secondary recrystallized grains. However, by suppressing the growth of crystal grains unfavorable in magnetic properties other than the Goss orientation and developing only grains close to the Goss orientation, high magnetic flux density can be achieved, but in order to further reduce iron loss, It is necessary to reduce the size of the grains.

In the finish annealing step, in order to perform control so as to satisfy both fine graining and high degree of integration into goss, nucleation and growth process of secondary recrystallized grains are separated and precisely Need to control. In other words, ideally, a large number of nuclei having an orientation close to Goss are generated in the nucleation process, and only these nuclei are grown in the growth process to suppress the nucleation of the oriented grains deviated from other Goss.

Various methods have been proposed as a finishing annealing method for obtaining such a fine grained grain of a grain-oriented silicon steel sheet using AlN as an inhibitor and having a high degree of accumulation in Goss grains. For example, in Japanese Patent Laid-Open No. 54-40227, 700-
Although it is disclosed that the temperature is raised from 900 ° C. at 15 to 100 ° C./hr and the temperature range of 900 to 1010 ° C. at which the secondary recrystallization proceeds by 50%, the annealing is performed at 2 to 10 ° C./hr. , As described above, most of the conventional techniques simply maintain the temperature or raise the temperature during the growth process of the Goss grains, so that the nucleation and growth of grains other than the Goss are allowed in this process, resulting in deterioration of magnetism. There was a problem.

Further, Japanese Patent Application Laid-Open No. 55-24972 discloses 750
A technique for growing surface crystal grains at ˜1150 ° C. under N ₂ ≧ 10% and secondary recrystallization under a lower N ₂ partial pressure is disclosed in Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 55-47324 discloses a technique in which N ₂ partial pressure is 20% or less at 850 to 950 ° C. and then secondary recrystallization is performed at N ₂ partial pressure of 3% or more. In the method of controlling the secondary recrystallization, the coil longitudinal direction,
In addition, magnetic nonuniformity occurs in the width direction. That is,
Since the finish annealing is performed in the coil state, outside the coil,
This is a technique that cannot be industrially used because there is a problem in that there is a difference in the atmosphere flowability in the middle, inner winding, and coil width directions.

On the other hand, among the prior art of grain-oriented silicon steel sheet using MnSe system as an inhibitor, Japanese Patent Laid-Open No. 2-4925 discloses that the temperature is 5 to 20 ° C. higher than the secondary recrystallization start temperature by 5 to 20 ° C. Holding it for a long time promotes the generation of many Goss nuclei,
Furthermore, the temperature around the secondary recrystallization start temperature or 5-15
A method of growing only the nuclei of oriented grains close to Goth to improve the magnetism is disclosed by holding at a temperature lower by ℃.
However, according to the experiments by the authors, this method is effective only for grain-oriented silicon steels using the MnSe system as an inhibitor, and a technique for controlling the secondary recrystallization grain of grain-oriented silicon steels using the AlN system as an inhibitor. It turns out that it cannot be.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to obtain industrially stable low iron loss and high magnetic flux density in a method for producing a grain-oriented silicon steel sheet using AlN as a main inhibitor. There is a proposal of a manufacturing method that can be performed.

[0008]

The present invention provides C: 0.02 to 0.
12wt%, Si: 2.5-4.0wt%, Mn: 0.03-0.15wt%, so
l, Al: 0.01 to 0.05 wt%, N: 0.004 to 0.01 wt%,
Furthermore, it contains 0.01 to 0.05 wt% of S and / or Se in total.
In addition, if necessary, Sb: 0.01 to 0.20 wt%, M
o: 0.005-0.05wt%, Sn: 0.02-0.20wt% and Cu:
It contains at least one of 0.02 to 0.20 wt% and the balance Fe
Rolling of silicon steel slabs consisting of inevitable impurities and unavoidable impurities
After hot-rolled sheet annealing and quenching treatment, once
Alternatively, two cold rolling steps with intermediate annealing may be performed to obtain the final rolling rate.
80% or more, then decarburization annealing, then finish annealing
In the manufacturing method of unidirectional silicon steel sheet consisting of a series of processes
Then, the finish annealing is performed at the secondary recrystallization nucleation temperature (N-
T_SR) Heating to a higher temperature to increase the number of secondary recrystallization nuclei in the proper orientation.
For a number of times, followed by secondary recrystallization nucleation temperature
Temperature at which secondary recrystallized grains can grow (GT_SR) Above temperature range
The secondary recrystallization in the proper orientation is performed by cooling to
Characterized by purifying annealing after promoting the growth of nuclei
A method of manufacturing unidirectional silicon steel sheet with excellent magnetic properties.
More specifically, the heating rate until the start of secondary recrystallization
Of 5 to 50 ° C./hr and the secondary recrystallization nucleation temperature (N-
T_SR) 3 to 50 ℃ higher temperature than 1 to 5 hours of nucleation treatment
Followed by (N-T _SR) Lower temperature that can grow secondary grains
Degree (GT_SR) Grain growth process by isothermal annealing
A finish annealing that consists of
A method of manufacturing grain-oriented silicon steel sheet, or secondary recrystallization
Nucleation temperature (N-T_SR) 3 to 50 ℃ higher than 5 to 50
Nucleation treatment to raise the temperature at ℃ / hr followed by 3-8 ℃ /
NT at a cooling rate of hr_SRThe temperature at which secondary recrystallized grains can grow
Degree (GT_SR) Grain growth process with more cooling, and usually
Unidirectional silicon steel with finish annealing consisting of refining
It is a method of manufacturing a plate.

In the present invention, the secondary recrystallization starting temperature (T _SR ), the secondary recrystallization nucleation temperature (N-T _SR ) and the secondary recrystallizable grain growth temperature (G-T _SR ) are respectively set. The definition or measurement method is defined as follows. Secondary recrystallization starting temperature (T _SR ): Temperature of the growth front of secondary recrystallization after heating for 30 hours or more in an annealing furnace having a temperature gradient of 1 to 10 ° C / cm.

Secondary recrystallization nucleation temperature (N-T _SR ): The minimum temperature at which secondary recrystallized grains of 2 mm or more are formed after annealing for 1 hour in an annealing furnace without temperature gradient. Secondary Recrystallizable Grain Growth Temperature (G-T _SR ) After reaching the N-T _SR and holding the steel sheet once taken out for 2 hours in an annealing furnace without temperature gradient, secondary recrystallized grain growth is observed. temperature.

[0011]

Although a large number of heat cycles for secondary recrystallization have been proposed and attempted in the past, the reality is that they have not yet reached a completely satisfactory state. Especially when the inhibitory power of the inhibitor becomes strong and the degree of accumulation of the primary recrystallization texture is high, it is often experienced that the secondary recrystallization behavior is greatly affected by a very small change in the conditions. It is extremely difficult to optimize the heat cycle in such a case only by experience.
It is necessary to have a way of thinking to understand the phenomenon correctly.

However, it must be said that the metallurgical understanding of the process of secondary recrystallization is extremely insufficient. The present inventors considered what is the essential phenomenon occurring in the process of secondary recrystallization. As a result, we have found that the process of secondary recrystallization can be understood and controlled very reasonably by considering the following.

That is, the process of secondary recrystallization can be completely separated into the process of (a) nucleation and the process of (b) grain growth, and the control of the heat cycle also completes these two processes. It should be done separately. This idea does not simply classify the heat cycle forms, but proposes the following new technical concepts.

That is, according to the conventional understanding, it was considered that the secondary recrystallization starts at a certain temperature or higher, and that temperature is very important for heat cycle control. That temperature was defined as the secondary recrystallization onset temperature T _SR . This defines the temperature at which the secondary recrystallization starts at a certain heating rate as disclosed in JP-A-2-4925.

As a result of detailed experiments on the initial stage of the secondary recrystallization, the present inventors have found that the secondary recrystallization can be clearly separated into a nucleation stage and a grain growth stage. And, in particular, it was found that the nucleation possible temperature and the grain growth possible temperature exist independently. The former is defined as N-T _SR and the latter as G-T _SR . It is presumed that the conventional secondary recrystallization starting temperature T _SR was considered and measured as a temperature combining them, probably because the measurement accuracy was insufficient or there was no such technical idea. The present invention has been achieved by introducing the new technical idea as described above.

With the introduction of such a technical idea, the NT
_{It has been found that SR} and G-T _SR often have different temperatures, and that G-T _SR is affected by the generation processing conditions. It was also found that only secondary grains larger than a certain critical size can grow stably thereafter, as in the case where classical nucleation theory is applied to phenomena such as precipitation.

Further, in the nucleation stage, the generation frequency of nuclei capable of secondary recrystallization and the proportion of grains having the preferred orientation (110) [001] orientation, that is, Goss orientation, are divided. We also newly discovered that it should be measured. As described above, the present invention is intended to control not only the concept but also the manufacturing factor that influences the previously uncontrolled product characteristic factor by the introduction of such a technical idea.

A typical example of various cases is schematically shown in FIG. (A) the stage that initiated secondary recrystallization at time t _1, (b) case is very large grain growth rate at time t _2, when (c) is Goss orientation grains infrequent at time t _2, (D) is the case where the Goss orientation grain frequency is high and the growth rate is low at time t ₂ .

The experiments leading to the development of the present invention will be described below. (Experiment 1) C: 0.06%, Si: 3.1%, Mn: 0.07%, Se:
0.020%, Al: 0.025%, N: 0.0070%, Sb: 0.02%,
Steel containing Mo: 0.02% was obtained by the normal double cold rolling method.
After processing to 23 mm, decarburization annealing and finish annealing were performed under various conditions.

In a preliminary experiment, the secondary recrystallization nucleation temperature was accurately measured and the temperature was designated as N-T _SR . Further, the temperature at which the grain growth can proceed thereafter is G-T _SR . The heat cycle shown in Table 1 is (1) Heated at various rates up to 1200 ° C. (2) _Heated at various rates up to N-T _SR and 4 from N-T _SR
After being kept at a temperature higher by 3 ° C. for 3 hours, it was further kept at that temperature for 20 hours.

(3) _Heating up to N-T _{SR under} various conditions,
After being held at a temperature 4 ° C higher than N-T _{SR for} 3 hours, G-T
_The temperature was maintained at 3 ° C higher than _SR for 5 hours, and then the temperature was raised to 1200 ° C.
Furthermore, after each treatment, a purification treatment was performed at 1200 ° C. for 15 hours. The result is shown in FIG. The heat-up rate dependence was observed in all types of heat cycles. In the heat cycle 1 or 2 which has been widely known from the past, the range of the heating rate at which relatively good characteristics are obtained is wide.

However, in Heat Cycle 3, good characteristics were obtained only at 10 ° C./hr, but it was found that even the same material can obtain much better characteristics than others. Therefore, the usefulness of heat cycle like No. 3 type was confirmed. Therefore, more experiments were conducted on this type of heat cycle. (Experiment 2) Superheat of No. 3 type heat cycle of Experiment 1, that is, the difference ΔT between N-T _SR and nucleation temperature.
We investigated the frequency (N) and the exact Goss orientation grains of the fraction of Goss orientation nuclear case of changing the (℃) (f _G). Note that f _G is defined as a ratio of grains having deviations from just goth around ND, RD, and TD within 10 ° C. to all secondary grains.

FIG. 3 shows the results. It was found that when ΔT was changed, both the frequency of nuclear generation and the accurate distribution of Goss nuclei changed significantly. It was found that the object of the present invention can be achieved by selecting the optimum range under these conditions. This relationship also changed greatly depending on the holding time, the components, the pretreatment conditions, and the atmosphere.

The relationship between the optimum N and f _G also changed depending on the subsequent grain growth conditions. 7 from N-T _SR in N ₂ atmosphere
FIG. 4 shows an example of a suitable range obtained when the temperature is kept high for 6 hours. (Experiment 3) Next, C: 0.065 wt%, Si: 3.12 wt%, Mn:
0.075 wt%, Se: 0.023 wt%, sol, Al: 0.024 wt%,
A silicon steel slab consisting of N: 0.0080 wt%, Sb: 0.024 wt% and the balance Fe is heated at 1420 ° C for 20 minutes and then hot rolled to 2.2 mm.
A thick hot rolled sheet was used. This hot-rolled sheet was heated at 1100 ℃ for 2 minutes, then rapidly cooled by mist injection, then cold-rolled to 0.22mm.
Finished thick.

After cold rolling, decarburization annealing that also serves as recrystallization was performed at 830 ° C. for 3 minutes, and the steel sheet coated with MgO had a temperature of 950 ° C.
To 10 ° C in increments of 1 to 10 hours, followed by isothermal annealing at 950 ° C for 20 hours, followed by purification annealing in hydrogen at 1200 ° C for 5 hours. went. However, in the case of 950 ° C in the first stage, no restraint was applied. The results of examination of the magnetic properties B ₈ and W _17/50 values at this time are shown in FIG. 5 in relation to the holding temperature and holding time of the first stage. The N-T _SR of this material is 977 ℃, G-T
_SR was 950 ° C.

[0026] In 3 to 50 ° C. higher temperature than N-T _SR final annealing initially as can be seen from Figure 5 after subjected to 1~5hr retention annealing, high magnetic flux density in the case of performing the isothermal annealing, in particular iron A low-loss unidirectional silicon steel sheet was obtained. Similar investigations were carried out for silicon steels having other component compositions, and almost the same results as in FIG. 5 were obtained.

(Experiment 4) C: 0.070% by weight, Si: 3.
32%, Mn: 0.05%, Al: 0.025%, N: 0.0080%, Se:
Unidirectional silicon steel slab containing 0.020% at 1420 ℃ 30
After reheating for a minute, it was hot rolled to a plate thickness of 2.0 mm. 1100 ° C ×
After normalizing for 30 seconds, after pickling, a final plate thickness of 0.23 mm was obtained by a double cold rolling method with intermediate annealing of 1100 ° C. for 30 seconds. After primary recrystallization annealing that also serves as decarburization at 870 ° C for 1 minute, an annealing separator containing MgO as the main component is applied, and N-T _SR is applied.
Was measured to be 950 ° C. For the same material,
In the pattern shown in FIG. 6A, v ₁ ° C /
After heating up to T ₁ = 977 ° C in hr, at various cooling rates v ₂ ° C /
After cooling to T ₂ = 940 ° C. in hr, the magnetic properties were measured when purification annealing was performed at 1200 ° C. × 5 hrs.

The results are shown in FIG. 6 (b). It is clear from FIG. 6B that by defining the cooling rate in the pattern of FIG. 6A, stable magnetism can be obtained for a wider range of heating rate v ₁ . Preferred v ₁ and v ₂ are 5 to 50 ° C./hr and 3 to 8 ° C./hr, respectively. (Experiment 5) The MgO coated sheet before finish annealing used in Experiment 3 was heated to T ₁ ° C shown in Fig. 7 at a temperature rising rate of 10 ° C / hr, then cooled to T ₂ ° C at 5 ° C / hr, and then 1200 ° C. Magnetic properties were measured when purification annealing was performed for 5 hours. N- of this material
The T _SR was 950 ° C and the G-T _SR was 935 ° C.

The results are shown in FIG. As is clear from FIG. 7, T ₁ is 3 to 50 ° C. higher than N-T _SR , and T ₂ is N-T _SR.
Must be lower than G-T _{SR and} higher. As is clear from the above description, the present invention is completely different in the basic idea from the prior arts known in the art, and is superior in the effect to the conventional method especially in the iron loss.

Next, the preferred range of the components of the silicon steel material in the present invention will be described. C: 0.02 to 0.12 wt% When C is less than 0.02 wt%, secondary recrystallization becomes poor, while
If it exceeds 12 wt%, the decarburizing property and the magnetic properties will be deteriorated, so the range was made 0.02 to 0.12 wt%. Si: 2.5-4.0 wt% Good iron loss cannot be obtained when Si is less than 2.5 wt%, while 4.0
If it exceeds wt%, the cold rolling property deteriorates significantly, so 2.5-
The range was 4.0 wt%.

Mn and S and / or Se are MnS and / or
It is a component for forming MnSe. First, Mn must be at least 0.03wt% to exert its effect as an inhibitor.
%, On the other hand, when it exceeds 0.13 wt%, the solid solution temperature of MnS and MnSe becomes high, and it does not form a solid solution at the usual slab heating temperature and the magnetism deteriorates, so the range was made 0.03 to 0.15 wt%.

If S and / or Se exceeds 0.05 wt%, purification by purification annealing becomes difficult, while if it is less than 0.01 wt%, the amount of the inhibitor is insufficient, so 0.01 to 0.05 wt% in total.
And However, the magnetic flux density is further improved by limiting S to less than 0.01 wt%. Al and N are necessary to form AlN, and the Al content is set to the range of 0.01 to 0.05 wt%. That is, if the amount of Al is too small, the magnetic flux density becomes low, and if it is too large, the secondary recrystallization becomes unstable. Furthermore, N is
If it is less than 0.004 wt%, the amount of AlN will be insufficient, and if it exceeds 0.012 wt%, blisters will occur in the product, so 0.004 to 0.01
The range is 2 wt%.

If Sb is less than 0.01% by weight, the effect of surface purification is not obtained, and if it exceeds 0.20% by weight, problems occur in decarburization and formation of a surface coating, so Sb is set to 0.01 to 0.20% by weight. Cu can be added to further improve the magnetic flux density. If the Cu content is less than 0.02 wt%, it has no effect.
If it exceeds 0.20 wt%, pickling properties and brittleness will deteriorate, so
0.02 to 0.20 wt% Further, it is advantageous to add Sn for improving iron loss, and if the Sn content is less than 0.02 wt%, there is no effect, and if it exceeds 0.20 wt%, the brittleness deteriorates, so 0.02 to 0.20 wt% Restricted to.

Further, Mo may be contained in order to improve the surface properties. Less than 0.005 wt% has no effect, 0.05
If it exceeds wt%, the decarburizing property deteriorates, so 0.005 to 0.05 wt%
And Next, the silicon steel slab containing the above-mentioned phosphorus component is heated and then hot rolled. Hot rolled sheet is 900-1200
After annealing at 0 ° C, quenching is performed, and then cold rolling is performed once or twice with intermediate annealing at a final rolling reduction of 80% or more.

The reason for limiting the final cold rolling rate to 80% or more is that the primary recrystallized structure for exerting a strong inhibitory force of AlN cannot be obtained at a rolling reduction of less than 80%. After cold rolling, decarburization annealing is performed, an annealing separator is applied, and finish annealing is performed. Finish annealing is 1 to 5 at 3 to 50 ° C higher temperature than N-T _SR.
After being held for hr, isothermal annealing is performed by G-T _SR until completion of secondary recrystallization, and then heating is performed to a temperature range of purification annealing, for example, 1200 ° C.

When the holding temperature of the secondary recrystallization nucleation treatment in the initial stage of finish annealing is less than N-T _SR , the magnetic properties are not improved.
At temperatures higher than 50 ° C higher than N- _TSR, secondary grain nuclei with poor orientation were generated. When the holding time was less than 1 hr, the magnetic properties were not improved, and when the holding time was more than 5 hr, many secondary grain nuclei with bad orientation were generated. In this way, it was possible to achieve low iron loss by generating a large number of secondary grains with good orientation, which are effective in reducing iron loss, by using new concepts called G-T _SR and N-T _SR. It is thought that it was possible to control the original.

In the finish annealing, it is 3 to 50 from N-T _SR.
Good magnetic characteristics cannot be obtained outside this range unless the temperature is raised to a high temperature of 5 to 50 ° C./hr and the temperature is cooled to N-T _SR or less at a cooling rate of 3 to 8 ° C./hr. Hereinafter, embodiments of the present invention will be described.

[0038]

【Example】

Example 1 C: 0.062 wt%, Si: 3.10 wt%, Mn: 0.070 wt%, Se:
0.024 wt%, sol, Al: 0.025 wt%, N: 0.0086 wt%
%, Sb: 0.029 wt% 14 silicon steel slab consisting of balance Fe
After heating at 20 ° C for 20 minutes, hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.3 mm. The hot-rolled sheet was heated at 1050 ° C. for 2 minutes, quenched by mist jetting, and then cold-rolled to a thickness of 0.23 mm. After cold rolling, decarburization annealing was performed at 800 ° C for 4 minutes, which also served as recrystallization, and then MgO was applied and finish annealing was performed. The conditions of finish annealing are as follows. The magnetic properties of the product plate thus obtained are shown in Table 1. In this material, N-T _SR =
It was 960 ° C and G-T _SR = 950 ° C. Note a, T = 965 ℃ for 30 hours after holding annealing, then 1200 ℃ hydrogen purification annealing.

B, T = 1000 ° C., hold for 1 hr, then 950
The temperature was lowered to ℃, and the annealing was carried out for 30 hours, followed by purification annealing in hydrogen at 1200 ℃. c, T = 980 ℃, hold for 2 hours, then cool to 955 ℃
After 30 hour holding annealing, purification annealing in 1200 ℃ hydrogen. The heating rate up to the first holding temperature was 15 ° C./hr under any of the conditions a, b, and c.

[0040]

[Table 1]

Example 2 C: 0.065 wt%, Si: 3.05 wt%, Mn: 0.075 wt%, Se:
0.020 wt%, sol, Al: 0.024 wt%, N: 0.0080 wt%, S
n: 0.09wt% Silicon steel slab consisting of balance Fe at 1420 ℃ 20
After heating for a minute, hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.2 mm.
The hot-rolled sheet was heated at 1075 ° C. for 2 minutes, then rapidly cooled by mist injection, and then cold-rolled to a 0.20 mm thickness. After cold rolling, decarburization annealing was performed at 845 ° C for 4 minutes, which also served as recrystallization, and then MgO was applied and finish annealing was performed. The conditions of finish annealing are as follows. The magnetic properties of the product plate thus obtained are shown in Table 2. However, with this material, N-T _SR = 940
C, G-T _SR = 935 ° C. Note a, T = 945 ° C, 30 hour holding annealing, then 1200 ° C hydrogen purification annealing.

B, T = 960 ° C for 2 hours, then 938
The temperature was lowered to ℃, and the annealing was carried out for 30 hours, followed by purification annealing in hydrogen at 1200 ℃. c, T = 975 ℃, hold for 1 hour, then cool to 930 ℃
After 30 hour holding annealing, purification annealing in 1200 ℃ hydrogen. The heating rate up to the first holding temperature was 20 ° C./hr under any of a, b, and c conditions.

[0043]

[Table 2]

As described above, in the examples, the iron loss was remarkably improved. Example 3 C: 0.070 wt%, Si: 3.15 wt%, Mn: 0.065 wt%, Se:
0.022 wt%, sol, Al: 0.023 wt%, N: 0.0082 wt%, S
A silicon steel slab consisting of b: 0.029 wt% and Mo: 0.01 wt% balance Fe was heated at 1410 ° C for 20 minutes and then hot-rolled to form a 2.4 mm thick hot-rolled sheet. The hot-rolled sheet was heated at 1125 ° C. for 2 minutes, then rapidly cooled by mist injection, and then cold-rolled to a thickness of 0.30 mm. After cold rolling, decarburization annealing which doubles as recrystallization was performed at 890 ° C for 4 minutes, and then MgO was applied and finish annealing was performed.

The conditions of finish annealing are as follows. Table 3 shows the magnetic properties of the product plate thus obtained. However,
With this material, N-T _SR = 975 ° C and G-T _SR = 960 ° C. Note a, T = 980 ° C, 30 hour holding annealing, then 1200 ° C hydrogen purification annealing.

B, T = 990 ° C, after 2 hour holding annealing, 965 ° C
The temperature is lowered to 30 ° C., and the annealing is performed for 30 hours. c, T = 1000 ℃, hold for 1 hour, then cool to 970 ℃
After a 25-hr holding annealing, a refining annealing was carried out in hydrogen at 1200 ° C. The heating rate up to the first holding temperature was 12 ° C./hr under any of the conditions a, b, and c.

[0047]

[Table 3]

As described above, in the examples, a remarkable improvement in iron loss was obtained. Example 4 C: 0.055 wt%, Si: 3.20 wt%, Mn: 0.082 wt%, Se:
0.020 wt%, sol, Al: 0.021 wt%, N: 0.0090 wt%, S
b: 0.024 wt%, Sn: 0.01 wt%, Cu: 0.03 wt% After heating a silicon steel slab consisting of the balance Fe for 15 minutes at 1420 ° C, hot rolling it to a thickness of 2.6 mm, and then heating for 1 minute at 1100 ° C Washed, 1.8 mm
After intermediate cold rolling to a thick thickness, 1075 ° C, after 1 minute of intermediate annealing,
Finished cold rolled to a thickness of 0.34 mm. After that, decarburization annealing was performed at 840 ° C. for 3 minutes, which also served as recrystallization, and then MgO was applied and finish annealing was performed.

The conditions of finish annealing are as follows. Table 4 shows the magnetic properties of the product plate thus obtained. However,
This material had N-T _SR = 952 ° C and G-T _SR = 938 ° C. Note a, T = 960 ℃ for 25 hours after holding annealing, then 1200 ℃ hydrogen purification annealing.

B, T = 955 ° C., hold for 3 hours, then 940
The temperature is lowered to ℃, and the annealing is carried out for 25 hours, and then purified annealing is performed in hydrogen at 1200 ℃. c, T = 980 ℃, hold for 1 hour, then cool to 945 ℃
After a 25-hr holding annealing, a refining annealing was carried out in hydrogen at 1200 ° C. The heating rate up to the first holding temperature was 5 ° C./hr under any of the conditions a, b, and c.

[0051]

[Table 4]

Example 5 C: 0.075%, Si: 3.28%, Mn: 0.060%, A by weight%
l: 0.028%, N: 0.0082%, Se: 0.022%, Sb: 0.015
 %, Mo: 0.0055% containing slab with the same conditions as in Experiment 3.
Process and NT_SRWas measured at 945 ° C.
Was. Also GT_SRWas 938 ° C. This material is shown in Figure 6.
In the pattern shown in (a), ν₁, T₁, Ν₂, T ₂Various
The magnetism was measured by changing. Table 5 shows the results.

[0053]

[Table 5]

Example 6 C: 0.07% by weight, Si: 3.3%, Mn: 0.05%, Al: 0.
A slab containing 025%, N: 0.008%, S: 0.020% was treated under the same conditions as in Experiment 3, and N-T _SR and G-T _SR were measured and found to be 953 ° C and 948 ° C, respectively. This material is v ₁ , T ₁ , v ₂ , T in the pattern shown in FIG.
_The magnetism was measured by changing ₂ variously. Table 6 shows the results.

[0055]

[Table 6]

As described above, according to the present invention, good magnetic characteristics, especially high magnetic flux density characteristics can be obtained.

[0057]

According to the present invention, a grain-oriented silicon steel sheet having a high magnetic flux density and a low iron loss can be manufactured industrially and stably.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the state of generation of secondary recrystallization nuclei.

FIG. 2 is a diagram showing a relationship between heat cycle and magnetic characteristics.

FIG. 3 is a graph showing a relationship between a nucleus generation frequency N and an accurate fraction of Goss nuclei f _G when the temperature is held at a temperature ΔT (° C.) higher than the secondary recrystallization nucleation temperature.

FIG. 4 is a graph showing the influence of the accurate Goss azimuth fraction f _G and the nucleus generation frequency N on the magnetic characteristics.

FIG. 5 is a graph showing the influence of the first-stage holding temperature and time on the magnetic characteristics.

FIG. 6 is a graph showing the relationship between heat cycle and magnetic properties.

FIG. 7 is a graph showing the effect of nucleation heating temperature and cooling temperature on magnetic properties.

Claims (4)

[Claims] 1. C: 0.02-0.12 wt%, Si: 2.5-4.0 wt
%, Mn: 0.03 to 0.15 wt%, sol, Al: 0.01 to 0.05 wt%,
N: 0.004 to 0.01 wt%, S and / or Se
Of 0.01 to 0.05 wt% in total, with the balance being Fe and unavoidable impurities, and hot-rolling a silicon steel slab, followed by hot-rolled sheet annealing and quenching, and then one or intermediate annealing. In a method for manufacturing a unidirectional silicon steel sheet, which comprises a series of steps in which a cold rolling is performed twice at a final rolling rate of 80% or more, followed by decarburization annealing and then finish annealing, the finish annealing is a secondary recrystallization. By heating to a temperature higher than the nucleation temperature (N-T _SR ), a large number of secondary recrystallized nuclei of proper orientation are generated,
Then, by performing cooling treatment at a temperature below the secondary recrystallization nucleation temperature to a temperature above the secondary recrystallizable grain growth temperature (G- _TSR ), the growth of the secondary recrystallization nuclei in the proper orientation is promoted. A method for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by performing a refining annealing after that. 2. C: 0.02-0.12 wt%, Si: 2.5-4.0 wt
%, Mn: 0.03 to 0.15 wt%, sol, dl: 0.01 to 0.05 wt%,
N: 0.004 to 0.01 wt%, S and / or Se
Containing 0.01 to 0.05 wt% in total with the balance being Fe and unavoidable impurities, hot-rolled, subjected to hot-rolled sheet annealing and quenching, and then once or in between. In the method of manufacturing a unidirectional silicon steel sheet, which comprises a series of steps in which cold rolling is performed twice at a final rolling rate of 80% or more, followed by decarburization annealing and then finish annealing, the temperature rise until the start of secondary recrystallization At a rate of 5 to 50 ° C / hr and at a temperature 3 to 50 ° C higher than the secondary recrystallization nucleation temperature (N-T _SR ).
A finish annealing consisting of a nucleation treatment for 5 hours, followed by a grain growth treatment by isothermal annealing at a temperature (G-T _SR ) lower than (N-T _SR ) at which the secondary grain growth is possible, and a normal purification treatment are performed. A method for manufacturing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by carrying out. 3. C: 0.02-0.12 wt%, Si: 2.5-4.0 wt
%, Mn: 0.03 to 0.15 wt%, Al: 0.01 to 0.05 wt%, N: 0.
004-0.01 wt%, and 0.01-0.05 wt% of S and / or Se in total, the balance of which is Fe and inevitable impurities. A unidirectional silicon steel sheet consisting of a series of steps in which a quenching treatment is performed, and then one or two cold rollings with intermediate annealing are performed at a final rolling rate of 80% or more, followed by decarburizing annealing and then finish annealing. 5 to 50 ° C., which is 3 to 50 ° C. higher than the secondary recrystallization nucleation temperature (N-T _SR ).
Nucleation treatment to raise the temperature at 1 / hr and subsequent grain growth treatment to cool the secondary recrystallized grain growth temperature (G-T _SR ) or more at N-T _SR or less at a cooling rate of 3 to 8 ° C / hr, Then, a method for producing a unidirectional silicon steel sheet having excellent characteristics is characterized in that a finish annealing consisting of a normal purification treatment is performed. 4. The silicon steel material is C: 0.02 to 0.12 wt%,
Si: 2.5-4.0 wt%, Mn: 0.03-0.15 wt%, sol, Al: 0.
01-0.05wt%, N: 0.004-0.01wt%, and S
And / or Se in a total amount of 0.01 to 0.05 wt%, and S
b: 0.01 to 0.20 wt%, Mo: 0.005 to 0.05 wt%, Sn: 0.02
To 0.20 wt% and Cu: 0.02 to 0.20 wt%, the balance being Fe and inevitable impurities, and the unidirectional silica excellent in magnetic properties according to claim 1, 2 or 3. Manufacturing method of plain steel sheet.