JPH08143974A - Production of grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE: To obtain the excellent magnetic characteristic without lowering the productivity at the time of finish annealing and without developing the unevenness over the whole length and the whole width of a coil. CONSTITUTION: At the time of producing a grain-oriented silicon steel sheet, i) draft of cold-rolling is made to be 80-87% and an aging treatment holding >=1sec at 100-300 deg.C on the way of cold-rolling. ii) The ratio of steam partial pressure to hydrogen partial pressure, P(H2 O)/P(H2 ) is adjusted and this ratio at the soaking process is made to be <0.7, and this ratio at the temp. raising process is set to be lower than that at the soaking process. iii) At the time of the last finish annealing, in the secondary recrystallizing temp. range of 850-1000 deg.C, the temp. is raised at 15-100 deg.C/h speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented silicon steel sheet, and in particular, by improving the cold rolling, decarburizing annealing and finish annealing, it is possible to improve the magnetic properties over the entire length and width of the coil. It is intended to be realized while improving productivity.

[0002]

2. Description of the Related Art Directional silicon steel sheets are used as soft magnetic materials.
It is mainly used as an iron core material for transformers and rotating machines, and is required to have high magnetic flux density as magnetic characteristics and small iron loss and magnetostriction.

Such a grain-oriented silicon steel sheet is obtained by heating an slab for grain-oriented silicon steel containing an inhibitor necessary for secondary recrystallization, for example, MnS, MnSe, AlN, etc., followed by hot rolling, and then if necessary. After hot-rolled sheet annealing has been performed, the final product sheet thickness is obtained by cold rolling once or twice or more with intermediate annealing sandwiched between them, and then decarburization annealing is performed, and then an annealing separator such as MgO is applied to the steel sheet. Manufactured by finishing annealing. In addition, a forsterite (Mg ₂ SiO ₄ ) insulating coating is usually formed on the surface of the grain-oriented silicon steel sheet, except in special cases. This coating contributes not only to electrical insulation of the surface but also to improvement of iron loss and magnetostriction by giving tensile stress to the steel sheet by utilizing its low thermal expansion property.

Such a forsterite insulating coating is formed in finish annealing, and its formation behavior is Mn in steel.
Since it affects the behavior of inhibitors such as S, MnSe, and AlN, it also affects secondary recrystallization itself, which is an essential process for obtaining excellent magnetism. The film formed further,
By purifying the steel by sucking up the inhibitor component, which has become unnecessary after the secondary recrystallization, into the coating, the development of the magnetic properties of the steel sheet is also fully assisted. Therefore, controlling the film formation process to form a uniform film is one of the important points that affect the product quality of grain-oriented silicon steel sheets.

That is, the formed coating film must naturally be uniform and free from defects, and must have excellent adhesion to withstand shearing, punching, bending and the like. Further, it must be smooth and exhibit a high space factor when laminated as an iron core.

To form a forsterite insulating coating on a grain-oriented silicon steel sheet, after cold rolling to a desired final thickness, continuous annealing is performed in wet hydrogen at a temperature of 700 to 900 ° C. The structure after hot rolling is changed to a primary recrystallized texture that causes proper secondary recrystallization, and at the same time secondary recrystallization is performed completely to improve the magnetic properties.
Decarburize carbon contained in 0.01 to 0.10 wt% to 0.003 wt% or less.

Further, at the same time, by oxidation, SiO ₂
A subscale mainly composed of is generated on the surface of the steel sheet.
After that, an annealing separator containing MgO as the main component is applied to the steel sheet, wound into a coil, and subjected to high-temperature finish annealing at a temperature of about 1000 to 1200 ° C in a reducing or non-oxidizing atmosphere. , A forsterite insulating coating is formed by a solid-phase reaction represented by the following formula. 2MgO + SiO ₂ → Mg ₂ SiO ₄

This forsterite insulating coating has a thickness of 1 μm
This is a ceramic film in which fine crystals before and after are densely integrated.As described above, during decarburization annealing, the oxide formed on the surface layer of the steel sheet is used as one of the raw materials and is formed on the steel sheet. Type, quantity, distribution, etc.
It is involved in the nucleation and grain growth behavior of forsterite, and also affects the grain boundaries of the coating crystal grains and the strength of the grains themselves, and thus greatly affects the coating quality after finish annealing.

Further, annealing separator consisting mainly of MgO which is the other raw materials, to be applied to the steel sheet as a slurry suspended in water, after being dried was also physically adsorbed H ₂ O
Other carrying, since a part is changed to hydrated Mg (OH) _2, to around 800 ° C. during finish annealing, a small amount while H ₂
Continues to release O 2. Therefore, the steel sheet surface is subjected to so-called additional oxidation by this H ₂ O. This oxidation also affects the generation behavior of forsterite and leads to the oxidation and decomposition of the inhibitor, so if it is large, it becomes a factor that deteriorates the magnetic properties. The susceptibility to this additional oxidation also largely depends on the physical properties of the oxide layer on the surface of the steel sheet produced by decarburization annealing.

In particular, in the grain-oriented silicon steel sheet using AlN as an inhibitor, the physical properties of the oxide layer affect the denitrification behavior during finish annealing or the penetration behavior of N from the annealing atmosphere, resulting in magnetic properties. Also affects. As described above, controlling the state of the steel sheet surface layer during decarburization annealing is one of the important points in the production of grain-oriented silicon steel sheets.

Regarding the conventional decarburization annealing of grain-oriented silicon steel sheets, a method for controlling the dew point of the annealing atmosphere at 50 to 75 ° C., as disclosed in, for example, JP-A-59-185725, A method is known in which the degree of oxidation of the atmosphere is set to 0.15 or more in the first half of decarburization and to 0.75 or less in the latter half and lower than that in the first half, as disclosed in Japanese Patent Publication No. 54-160514.

However, even if the above atmosphere control is performed, a forsterite coating having sufficient quality is not always produced, and a defective adhesion portion is generated in the strip width direction or the longitudinal direction, and appearance, coating thickness,
Alternatively, a case in which a forsterite particle size or the like becomes non-uniform sometimes occurs. Furthermore, the coating film may be locally peeled off in a dot-streak shape or a porous coating film may be formed.

By the way, in order to develop sufficient magnetic properties in the grain-oriented silicon steel sheet, as described above, sufficient secondary recrystallization is performed in the finish annealing at high temperature and for a long time, and thereafter it is harmful to the magnetic properties. We are trying to remove various components. Conventionally, in this finish annealing as well, various measures have been taken in order to improve the magnetic properties. For example, in Japanese Patent Laid-Open No. 50-134917, the dew point during secondary recrystallization annealing is controlled within a specific range. A method has been proposed. However, the finish annealing of grain-oriented silicon steel sheet is performed in a tightly wound state so that the lower part of the coil is not deformed even by annealing at high temperature for a long time. Extremely difficult control was required to carry out the secondary recrystallization by contacting with the atmospheric gas.

Further, Japanese Patent Application Laid-Open No. 54-40227 proposes a method of extremely slowing the rate of temperature rise during the secondary recrystallization annealing. However, this method causes a remarkable deterioration of productivity, and the recent There is a disadvantage that goes against the demand for energy conservation. In this respect,
In JP-A-55-21531, the temperature rising rate during secondary recrystallization annealing of ≧ 15 ° C./h is achieved by devising the atmosphere and temperature in the latter half of the decarburization annealing step. However, even with this method, there is a large variation in the magnetic characteristics in the longitudinal direction of the coil, and there is a problem in that the magnetic flux density is lowered particularly in the innermost winding portion of the coil.

[0015]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and by devising cold rolling and decarburizing annealing, the productivity in finish annealing is not reduced. An object of the present invention is to propose an advantageous method for producing a grain-oriented silicon steel sheet having excellent magnetic properties over the entire length and width of the coil.

[0016]

Means for Solving the Problems The clarification process of the present invention will be described below. By the way, the inventors first of all filed Japanese Patent Application No. 5
-127039, the ratio P (H of the partial pressure of water vapor to the partial pressure of hydrogen to the partial pressure of hydrogen in the temperature raising process and the soaking process of decarburization annealing.
_A technique for improving magnetic properties by adjusting ₂ O) / P (H ₂ ) was proposed. This technology uses P (H
₂ O) / P (H ₂ ) less than 0.7, while P
By setting (H ₂ O) / P (H ₂ ) lower than that in the soaking process, the film properties of the forsterite insulating film are improved, and thus the magnetic properties are improved.

Therefore, the inventors have found that P (H ₂ O) / P (H
₂ ) We examined the pros and cons of increasing the rate of temperature rise during the manufacturing process, especially during finish annealing, when the ratio adjustment technology, that is, the atmosphere oxidization adjustment technology is applied. At this time, as the cold rolling treatment, a so-called one-time cold rolling method by one cold rolling was premised from the viewpoint of productivity. As a result, if the cold rolling reduction rate is limited to a predetermined range, by applying the above-described atmosphere oxidative adjustment technique, even if the temperature rising rate at the time of finish annealing is high, even in the coil innermost winding portion. It was found that sufficiently satisfactory magnetic characteristics can be obtained. In the trial experiment described above, there were some cases where the magnetic characteristics were somewhat dispersed in the width direction,
It was also found that this point can be advantageously solved by performing a short aging treatment during cold rolling or performing warm rolling. The present invention is based on the above findings.

That is, according to the present invention, a slab for grain-oriented silicon steel containing Al and N as main inhibitor components is hot-rolled, then hot-rolled sheet annealed, and then cold-rolled once to obtain the final thickness. Then, decarburization annealing is performed, then an annealing separator is applied, and then a final finish annealing is performed to produce a grain-oriented silicon steel sheet. I) The cold rolling reduction ratio is 80 to 87%, and during this cold rolling, perform an aging treatment by holding at a temperature of 100 to 300 ° C for 1 second or longer, ii) partial pressure of water vapor relative to hydrogen partial pressure in the temperature rising process and soaking process of decarburizing annealing the ratio of _{P (H 2 O) / P} (H 2) was adjusted while P in the soaking process (H ₂ O) / P a (H ₂₎ of less than 0.7,
Set P (H ₂ O) / P (H ₂ ) in the temperature rising process lower than that in the soaking process, iii) During the final finish annealing, the secondary recrystallization temperature range from 850 ℃ to 1000 ℃ Of a grain-oriented silicon steel sheet, characterized in that the temperature is raised at a rate of 15 to 100 ° C / h (first invention)
Is.

The present invention also provides a slab for grain-oriented silicon steel containing Al and N as main inhibitor components,
A series of steps in which hot rolling is performed, then hot-rolled sheet annealing is performed, and then cold rolling is performed once to obtain the final sheet thickness, decarburization annealing is performed, and then an annealing separator is applied, followed by final finishing annealing. In the production of grain-oriented silicon steel sheet by: i) cold rolling is performed at a rolling temperature of 100 to 300 ° C.,
And, the reduction rate is set to 80 to 87%, ii) Adjusting the ratio P (H ₂ O) / P (H ₂ ) of the partial pressure of water vapor to the partial pressure of hydrogen in the heating process and soaking process of decarburization annealing. However, while P (H ₂ O) / P (H ₂ ) in the soaking process is less than 0.7,
Set P (H ₂ O) / P (H ₂ ) in the temperature rising process lower than that in the soaking process, iii) During the final finish annealing, the secondary recrystallization temperature range from 850 ℃ to 1000 ℃ Of a grain-oriented silicon steel sheet, characterized in that the temperature is raised at a rate of 15 to 100 ° C / h (second invention)
Is.

The present invention will be specifically described below. First, a magnetic characteristic improvement technique by adjusting the P (H ₂ O) / P (H ₂ ) ratio will be described. Now, as a result of detailed investigation of the cause of the quality variation of the forsterite coating on the strip, the inventors have found that the variation in the amount and quality of the subscale generated on the surface layer of the steel sheet during decarburization annealing has a large influence. . This means that the subscale formation reaction does not necessarily occur uniformly in the width direction or the length direction of the strip. Furthermore, it was also found that the cause of this is a change in the atmospheric oxidizability in the temperature rising process of decarburization annealing.

Therefore, the atmospheric oxidizability in decarburization annealing, that is, the ratio of the partial pressure of water vapor to the partial pressure of hydrogen P (H ₂ O) / P (H ₂ )
The following experiments were conducted to investigate the effect of the on the forsterite coating. Mn as an inhibitor
3.3wt% silicon steel sheet containing Se and Sb (sheet thickness 0.23mm)
Was decarburized and annealed at 840 ° C for 2 minutes in a wet hydrogen atmosphere. At this time, the atmospheric oxidizability of the temperature raising process and the soaking process was adjusted by adjusting the dew point and the H ₂ gas concentration to P (H ₂ O) / P (H ₂ ): 0.2 to 0.8
Were controlled separately. Then on the steel plate
After applying the annealing separating agent whose main component is MgO,
Secondary recrystallization annealing for 50 hours, followed by 120 in H ₂ atmosphere
Purification annealing was performed at 0 ° C for 5 hours. When the uniformity of the thus-obtained forsterite coating was examined, the results shown in FIG. 1 were obtained.

As shown in the figure, P (H ₂ O) /
When P (H ₂ ) is less than 0.7 and P (H ₂ O) / P (H ₂ ) in the heating process is lower than that in the soaking process, a beautiful glossy gray uniform film is obtained. Was given. On the other hand, P (H
_{When 2} O) / P (H ₂ ) is 0.7 or more, P (H ₂ O) / P during the temperature rising process
Even if (H ₂ ) was made lower than that in the soaking process, a film having excellent properties was not obtained.

Here, according to the equilibrium diagram of oxides formed on the surface of the silicon steel sheet shown in FIG. 2, P (H ₂ O) / P
(H ₂ ): 0.7 is clearly the FeO formation region, and the subscale formed under such conditions has poor protection and more additional oxidation during finish annealing, resulting in deterioration of the forsterite coating. Conceivable. The reason why the film quality of the forsterite coating is improved by lowering the atmospheric oxidative property during the temperature rising process is not clear, but the subscale generated during the temperature rising process protects the subscale generated during the soaking process. It is thought to increase.

Further, it was clarified by the following experiment that the decrease in the atmospheric oxidizability during the temperature rising process also has the effect of promoting decarburization and oxidation. That is, C:
A 0.23 mm thick silicon steel sheet containing 0.045 wt% was subjected to decarburization annealing at 840 ° C for 2 minutes in a wet hydrogen atmosphere, and the P (H ₂ O) / P (H ₂ ) Is fixed at 0.55,
The P (H ₂ O) / P (H ₂ ) in the atmosphere during the temperature rising process was adjusted to be in the range of 0.25 to 0.7, and the C content and the oxygen basis weight of the surface of the obtained steel sheet were measured. The results obtained are shown in Table 1.

[0025]

[Table 1]

From Table 1, the atmosphere P (H ₂ O) / P (H
By lowering ₂ ), it is possible to realize a treatment with a lower C content and a higher oxygen basis weight. Therefore, it is possible to increase the speed of the operation line, which greatly contributes to productivity improvement. It is considered that this is because the surface reaction in the soaking process is promoted by lowering P (H ₂ O) / P (H ₂ ) in the temperature rising process.

Then, the inventors next examined the influence of the above-described atmosphere oxidization adjusting technique upon finish annealing.
In particular, the relationship with the heating rate was investigated. That is, 3.3 wt containing AlN, MnSe and Sb as inhibitors
% Hot-rolling a silicon steel material to a thickness of 2.2 mm, annealing the hot-rolled sheet at 1000 ° C, and then performing one cold rolling to a sheet thickness of 0.35 mm, and then decarburizing at 840 ° C for 120 seconds. It was annealed. This decarburization annealing is performed in accordance with the conventional method in both the temperature raising process and the soaking process
In the case of (H ₂ O) / P (H ₂ ) = 0.50 (constant) and according to the present invention, the atmosphere oxidizing property is changed in the temperature raising process and the soaking process,
Heating process _{P (H 2 O) / P} (H 2) = 0.40, the soaking process P (H ₂ O) /
Was carried out in two conditions in the case of a P (H ₂₎ = 0.50. Then, after applying an annealing separating agent, finish annealing was performed.
In this finish annealing, the secondary recrystallization temperature range of 850 to 10
In the range of 00 ° C, the temperature rising rate was variously changed from 5 ° C / h to 150 ° C / h and annealing was performed, followed by purification annealing of 1200 ° C for 5 hours. The coil size during finish annealing was set to an inner diameter of 500 mm and an outer diameter of 1000 mm.

FIG. 3 shows the results of an examination of the relationship between the heating rate during finish annealing and the magnetic flux density B ₈ . As is apparent from FIG. 3, when the atmospheric oxidizability during decarburization annealing is adjusted according to the present invention, good magnetic properties are obtained in both the inner and outer winding portions when the temperature rising rate is in the range of 15 to 100 ° C./h. Was obtained.

In the above experiment, in order to improve the magnetic properties, it is not enough to adjust the atmospheric oxidizability during decarburization annealing. It was also found that the reduction rate in hot rolling is important. The result of the survey on this point is shown in FIG. In this experiment, a hot-rolled sheet of the same composition hot-rolled to a thickness of 1.6 to 2.8 mm was
In the same way as in the case of Fig. 3, after applying the annealing separating agent coating treatment, the final annealing is performed by raising the temperature range of 850 to 1000 ° C at a rate of 50 ° C / h and then performing the same purification annealing. is there. As shown in Fig. 4, in order to obtain good magnetic properties in both the outer wound portion and the inner wound portion, the cold rolling reduction ratio is 80 to 97%.
It turns out that it is necessary to limit the range.

As described above, by keeping the cold rolling reduction ratio and the atmospheric oxidizability of decarburization annealing within the above ranges, the inside and outside of the coil, that is, the total length of the coil, can be increased even if the temperature rising rate during secondary recrystallization is increased. It became possible to obtain good magnetic properties over the entire length of the sheet, but there were occasional variations in the magnetic characteristics in the plate width direction. Therefore, as a result of further experiments and studies in order to solve this point, the inventors have found that with respect to the variation in the strip width direction, an aging treatment is performed during the cold rolling, or a hot rolling is performed. It was clarified that it is effectively eliminated by applying

The results of the above experiment will be described when the aging treatment is performed. 3.25 wt% silicon steel material containing AlN, MnSe and Sb as inhibitors, width: 1000 m
m, plate thickness: hot rolled to 2.2 mm, hot-rolled sheet annealed at 1000 ° C., and then cold rolled once to a plate thickness of 0.35 mm. During this cold rolling, when the strip thickness reached 0.9 mm,
Aging treatment was performed for 10 minutes at various temperatures up to 400 ° C.
Then, decarburization annealing was performed at 840 ° C for 120 seconds. This decarburization annealing is performed in accordance with the conventional method in both the temperature raising process and the soaking process
In the case of (H ₂ O) / P (H ₂ ) = 0.50 (constant) and according to the present invention, the atmosphere oxidizing property is changed in the temperature raising process and the soaking process,
Heating process _{P (H 2 O) / P} (H 2) = 0.40, the soaking process P (H ₂ O) /
Was carried out in two conditions in the case of a P (H ₂₎ = 0.50. Then, after applying an annealing separating agent, finish annealing was performed.
In this finish annealing, the secondary recrystallization temperature range of 850 to 10
For the range of 00 ℃, set the heating rate to 50 ℃ / h and continue
Purification annealing was performed at 1200 ° C for 5 hours.

From the product coil thus obtained, 30 mm ×
Fig. 5 shows the results of examining the maximum, minimum and average iron loss values by collecting 33 pieces of 280 mm test pieces in the coil width direction and measuring the magnetism one by one. As shown in the figure, as long as decarburization annealing is performed under appropriate atmospheric oxidizability, aging treatment is performed in the temperature range of 100 to 300 ° C during cold rolling to reduce iron loss in the strip width direction. The variation could be effectively reduced.

Next, FIG. 6 shows the results of an examination of the relationship between the variation in the magnetic properties in the sheet width direction and the rate of temperature rise when cold rolling was performed warm. In this experiment, 3.2 wt% silicon steel material containing AlN, MnSe and Sb as inhibitors was hot-rolled to a strip width of 1000 mm and a strip thickness of 2.2 mm, and then 1050
After annealing the hot-rolled sheet at ℃, cold rolling from 0.7mm
Roll up to 0.35 mm at 180 ° C using a heater-embedded roll, and then perform decarburization annealing at 840 ° C for 120 seconds. (H ₂ O) / P (H ₂ ) = 0.55 (constant), the other is according to the present invention P (H ₂ O) / P (H ₂ ) = 0.4
5, P (H ₂ O) / P (H ₂ ) = 0.55 in the soaking process, then apply the annealing separator, and then the secondary recrystallization temperature range of 850 ~ 1000 ℃ For, the temperature rising rate was variously changed from 5 ℃ / h to 150 ℃ / h, annealing was performed, and then 1200
30mm from the product coil obtained by subjecting to purification annealing at ℃ for 5h
33 x 280 mm specimens were taken in the coil width direction, and the iron loss of each of these specimens was investigated.

As is clear from the figure, when the cold rolling is carried out warm according to the present invention, the temperature rising rate is 15 to 100 ° C./h.
In this range, extremely good iron loss characteristics can be obtained, and the variation is extremely small.

As described above, by performing cold rolling and decarburizing annealing under the preferred conditions according to the present invention, good magnetic properties can be obtained over the entire length and width of the coil even if the temperature rising rate during secondary recrystallization is increased. The reason why is obtained has not been clarified yet, but since the forsterite is homogenized by decarburization annealing under proper atmospheric oxidization, even if the temperature rising rate in finish annealing is fast, it extends over the coil width direction. It is considered that the inhibitor change also occurs uniformly, and as a result, the primary recrystallization structure improved by the aging treatment during cold rolling is stably secondary recrystallized.

[0036]

The preferred composition range of the grain-oriented silicon steel material according to the present invention will be described below. C: 0.02 to 0.15 wt% C is a component necessary for improving the crystal structure by utilizing α-γ transformation during hot rolling, but if it is less than 0.02 wt%, its addition effect is poor. On the other hand, if a large amount is added in excess of 0.15 wt%, subsequent decarburization becomes difficult, so 0.02〜
About 0.15 wt% is preferable. The C content is 0.10 to 0.15 wt%
The high C region of the above is a region where it was conventionally difficult to decarburize due to too much C, but the decarburizing annealing method according to the present invention described later has a much higher decarburizing ability than the conventional one, so it is sufficient. This is an area where decarburization is possible.

Si: 2.0 to 4.5 wt% Si is a useful component for improving the iron loss characteristics by increasing the electric resistance of the steel sheet, but if it is less than 2.0 wt%, the electric resistance of the steel sheet becomes small and the vortex is generated. Good iron loss characteristics cannot be obtained because the current loss increases. On the other hand, if it exceeds 4.5 wt%, cold rolling becomes difficult, so it is preferable to set it to about 2.5 to 4.5 wt%.

In addition to C and Si, in the grain-oriented silicon steel sheet material, only grains with a Goss orientation are selectively grown by suppressing grain growth in the primary recrystallization structure other than the Goss orientation. It is essential to include an inhibitor-forming component having an essential function for secondary recrystallization. Two types of inhibitors are known, one that functions as a fine precipitate such as AlN, MnSe, and MnS, and the other that functions by segregating at grain boundaries such as Sb and Sn. In the present invention, of these, the AlN inhibitor is indispensable. This is because the cold rolling one-time method inevitably increases the rolling reduction, but under such high pressure rolling, the AlN inhibitor is particularly advantageous. Here, a suitable amount of AlN
To obtain an inhibitor, sol.Al: 0.01-0.05 wt%,
N: 0.004 to 0.012 wt% is required. Because Al
If the amount is less than 0.01 wt%, the magnetic flux density will decrease, while 0.05
This is because the secondary recrystallization becomes unstable if it exceeds wt%,
If the amount of N is less than 0.004 wt%, the amount of AlN inhibitor will be insufficient and the magnetic flux density will decrease, while if it exceeds 0.012 wt%, surface defects called blister will frequently occur in the product.

In the present invention, so-called MnSe such as MnSe or MnS is contained as long as it contains AlN as the main inhibitor.
There is no problem in using Se inhibitors together. Here, the preferable range of each forming component of the MnSe-based inhibitor is as follows. Mn: 0.03 to 0.30 wt% If the Mn amount is less than 0.03 wt%, the absolute amount as an inhibitor component is insufficient, while if it exceeds 0.30 wt%, the particle size of the inhibitor becomes coarse and the grain growth inhibitory power is reduced. 0.
A range of 30 wt% is preferred.

Se and / or S: 0.01 to 0.05 wt% If the Se and S contents are less than 0.01 wt%, the absolute amount as an inhibitor component is insufficient, while if it exceeds 0.05 wt%, purification by finish annealing becomes difficult. Therefore, the range of 0.005 to 0.05 wt% is preferable in either case of using alone or in combination.

Further, in the present invention, the above grain boundary segregation type inhibitors Sb, Sn and the like can be used in combination. In particular, in producing a high-grade grain-oriented silicon steel sheet having extremely excellent magnetic properties with a magnetic flux density B ₈ value of 1.92 T or more, not only precipitate type but also grain boundary segregation type inhibitors are used together. It is advantageous to maximize the inhibitory effect of Sb here
Grain boundary segregation-type inhibitor components such as Sn have a small effect of improving the magnetic properties when the addition amount is too small, while on the other hand, when they are too large, the embrittlement and the forsterite coating are adversely affected. Is preferred.

Further, it is also effective to add 0.10 wt% or less of Mo in order to prevent surface defects due to surface embrittlement during hot rolling.

Next, preferable manufacturing conditions of the present invention will be described. The molten steel adjusted to the above preferable composition is made into a slab having a predetermined thickness by continuous casting or ingot-casting method, and then 1350 to 1450 in order to completely dissolve the inhibitor components Al, Se and S in solid solution. Heat to ℃. After the above slab heating, hot rolling is performed, then the structure is homogenized, and 2
Hot-rolled sheet annealing is performed to stabilize the subsequent recrystallization.

Then, by a single cold rolling method, 0.23 to 0.35 mm
Finish the final product board thickness. At this time, the cold rolling reduction rate is
It should be 80-87%. This is because if the reduction ratio deviates from this range, as shown in FIG. 4 above, even if the atmospheric oxidation rate in the subsequent decarburization annealing is proper, sufficiently satisfactory magnetic properties cannot be obtained. is there.

In the present invention, during the cold rolling, an aging treatment is carried out at a temperature of 100 to 300 ° C. for a time of 1 second or more, or warm rolling is performed at a temperature of 100 to 300 ° C. is important. Here, such aging treatment may be performed at any plate thickness during cold rolling, and the number of times is not limited. Further, the treatment time is not particularly limited as long as it is 1 second or more, but it is preferably 20 hours or less from the viewpoint of energy saving and workability. It should be noted that the cold rolling to be subjected to such an aging treatment may be either reverse rolling using a Zenzimer rolling mill or continuous rolling using a tandem rolling mill.

Next, decarburization annealing is carried out. In the present invention, this decarburization annealing is also important. That is, in the present invention, during such decarburization annealing, P (H ₂ O) / P (H ₂ ) in the temperature raising process and the soaking process is adjusted, and P (H ₂ O) / P (H ₂ ) is less than 0.7, while it is important to set P (H ₂ O) / P (H ₂ ) in the temperature raising process lower than that in the soaking process. This is because when P (H ₂ O) / P (H ₂ ) in the soaking process is 0.7 or more, as shown in FIG. 1 above, a glossy, beautiful and gray uniform forsterite film cannot be obtained, This is because good magnetic characteristics cannot be obtained. Also, P (H ₂ O) / P (H ₂ ) in the soaking process is
Even if it is less than 0.7, P (H ₂ O) / P (H ₂ ) in the heating process
Is equal to or larger than that in the soaking process, as shown in FIG. 1 above, a glossy and beautiful gray uniform forsterite coating and thus good magnetic properties cannot be obtained. Therefore, P (H ₂ O) / P (H ₂ ) in the soaking process during decarburization annealing should be less than 0.7 (preferably 0.3 or more), and P (H ₂ O) / P (H ₂ ) Is set lower than that in the soaking process (preferably 0.05 or more).

The rate of temperature rise during decarburization annealing is not limited to the usual rate of 10 to 20 ° C./s, but should be suitably performed in a range of 5 to 30 ° C./s, which is somewhat wider than this range. You can If the heating rate is less than 5 ° C./s or more than 30 ° C./s, a good forsterite coating cannot be obtained even if the atmospheric oxidizability satisfies the preferable conditions.

After that, an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and then finish annealing including secondary recrystallization annealing and purification annealing is performed. In this finish annealing, the temperature is raised at a rate of 15 to 100 ° C / h or more in the secondary recrystallization temperature range of at least 850 to 1000 ° C. I mean,
This is because good magnetic properties can be obtained in both the inner and outer winding portions within this temperature increase rate range. As mentioned above, conventionally, it was said that at a heating rate of 15 ° C / h or more in finish annealing, sufficiently satisfactory excellent magnetic properties could not be obtained.
Only by utilizing the decarburization annealing according to the present invention described above, it becomes possible to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties without variation even at a high temperature rising rate. After the secondary recrystallization annealing described above, 1100-12
Purification annealing is performed at 00 ° C for about 1 to 30 hours to obtain a product plate.
It is also advantageous to apply further phosphate-based topcoats thereafter.

[0049]

【Example】

Example 1 C: 0.065%, Si: 3.20%, Mn: 0.07%, Se: 0.019
%, Sol.Al: 0.025%, N: 0.0072% and Sb: 0.024
%, With the balance essentially Fe composition, hot-rolled material for grain-oriented silicon steel with a thickness of 1.6 mm to 2.8 mm, hot-rolled at 1000 ℃ The final plate thickness of 0.35 mm was obtained by rolling (using a Zenzimer rolling machine). At this time, when the plate thickness shown in Table 2 was used, the aging treatment was similarly performed under various conditions shown in Table 2. Then, 840 ° C. in H ₂ -N ₂ -H ₂ in O atmosphere,
Decarburization annealing was performed for 120 seconds. At this time, P (H ₂ O) / P (H ₂ ) in the atmosphere during the temperature raising process and the soaking process was adjusted to the values shown in Table 2 by changing the H ₂ concentration and the dew point. The rate of temperature rise was 10 ° C / s in all cases. Then, after applying an annealing separator containing MgO as a main component, finish annealing was performed in an H ₂ atmosphere. At this time, for the secondary recrystallization temperature range from 850 ° C to 1000 ° C, the heating rate is from 20 ° C / h to 120 ° C / h.
Variously changed, and further subjected to purification annealing at 1200 ° C. for 10 hours.

From the product coil thus obtained, 33 pieces of 30 mm × 280 mm sample were sampled in the width direction, and the iron loss W
Table 2 shows the results of an examination of _17/50 (iron loss at 1.7 T, 50 Hz), magnetic flux density B ₈ (magnetic flux density at a magnetic field of 800 A / m), bending adhesion of the coating and appearance of the coating. The magnetic flux density B ₈ is the average value and the iron loss W _17/50
Is indicated by the difference between the average value and the maximum and minimum values. Further, the bending adhesion of the coating film was evaluated by the minimum diameter at which the coating film did not peel off when the test piece was wound around a round bar having various diameters (5 mm interval).

[0051]

[Table 2]

As is clear from Table 2, when manufactured under the conditions according to the method of the present invention, excellent magnetic properties were obtained with very little variation, and the adhesion and appearance of the coating were also good.

Example 2 C: 0.069%, Si: 3.20%, Mn: 0.07%, Se: 0.016
%, Sol.Al: 0.026%, N: 0.0070% and Sb: 0.024
%, With the balance substantially Fe composition, hot-rolled grain-oriented silicon steel material with a thickness of 1.8 mm to 2.2 mm, and after annealing the hot-rolled sheet at 1075 ° C. Cold rolling (using a Zenzimer rolling machine) was performed to a reduction ratio of 0.27 mm. At this time,
At the plate thicknesses shown in Table 3, the aging treatment was performed under the various conditions shown in Table 3 as well. Then, in H ₂ -N ₂ -H ₂ in O atmosphere
Decarburization annealing was performed at 820 ° C for 120 seconds. At this time, P (H ₂ O) / P (H ₂ ) in the atmosphere during the temperature raising process and the soaking process was adjusted to the values shown in Table 3 by changing the H ₂ concentration and the dew point. The rate of temperature rise was set to 15 ° C / s2 in all cases. Then, apply an annealing separator containing MgO as the main component, and then apply H ₂
Finish annealing was performed in the atmosphere. At this time, 850 ℃ to 10
For the secondary recrystallization temperature range of 00 ℃, increase the heating rate to 20 ℃ / h.
To 120 ° C / h for 5 hours at 1200 ° C
Purified annealing was performed. Iron loss W of the product plate thus obtained
Table 3 shows the results of an examination of _17/50 (iron loss at 1.7 T, 50 Hz), magnetic flux density B ₈ (magnetic flux density at a magnetic field of 800 A / m), bending adhesion of the coating and appearance of the coating.

[0054]

[Table 3]

As is clear from Table 3, when manufactured under the conditions according to the method of the present invention, excellent magnetic properties were obtained with little variation, and the adhesion and appearance of the coating were good.

Example 3 C: 0.068 wt%, Si: 3.30 wt%, Mn: 0.07 wt%, Se: 0.
016 wt%, sol.Al: 0.024 wt%, N: 0.0060 wt% and
Sb: 0.020 wt% is contained, the balance is essentially Fe composition. A material for grain-oriented silicon steel is hot-rolled to a thickness of 2.2 mm and heated to 1050 ° C.
After the hot-rolled sheet was annealed at 3, the sheet was warm-rolled at various temperatures shown in Table 4 by a three-stand tandem rolling mill equipped with a heater-embedded rolling roll having a roll diameter of 335 mm to give a final sheet thickness of 0.35 mm. Then, the same treatment as in Example 1 was performed to obtain a product plate. Iron loss W of the product plate thus obtained
Table 4 shows the results of an examination of _17/50 (iron loss at 1.7 T, 50 Hz), magnetic flux density B ₈ (magnetic flux density at a magnetic field of 800 A / m), bending adhesion of the coating and appearance of the coating.

[0057]

[Table 4]

As is clear from Table 4, good magnetic properties were obtained when manufactured under the conditions according to the method of the present invention.

Example 4 C: 0.070 wt%, Si: 2.90 wt%, Mn: 0.06 wt%, Se: 0.
019 wt%, sol.Al: 0.028 wt%, N: 0.0070 wt% and
Sb: 0.040 wt% is contained, and the balance is composed of Fe. The material for grain-oriented silicon steel is hot-rolled to a thickness of 2.2 mm at 1100 ° C.
After the hot-rolled sheet was annealed at 3 mm, it was rolled by a three-stand tandem roll with a roll diameter of 335 mm to a final sheet thickness of 0.35 mm. At this time, the plate was sagged between the first stand and the second stand, and an aging treatment was performed in which the plate was heated to various temperatures with a burner for 1 second. Then, the same treatment as in Example 1 was performed to obtain a product plate. Iron loss of the product plate thus obtained W _17/50 (1.7
T, iron loss at 50 Hz), magnetic flux density B ₈ (magnetic field 800 A / m
Table 5 also shows the results of an examination of the magnetic flux density in the above), the bending adhesion of the coating, and the appearance of the coating.

[0060]

[Table 5]

As is clear from Table 4, good magnetic properties were obtained when manufactured under the conditions according to the method of the present invention.

[0062]

As described above, according to the present invention, a grain-oriented silicon steel sheet having excellent magnetic properties over the entire length and width of the coil can be obtained even under a high temperature rising rate of 15 ° C./h or more during finish annealing. It can be stably obtained, and not only the product quality is improved, but also the work efficiency is improved by the single cold rolling method, which greatly contributes to the improvement of productivity.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of P (H ₂ O) / P (H ₂ ) on the appearance of the forsterite coating film after finish annealing in the temperature rising process and soaking process of the decarburization annealing process.

FIG. 2 is an equilibrium diagram of oxides produced in wet hydrogen of 3% silicon steel.

FIG. 3 is a graph showing the relationship between the temperature rising rate and the magnetic flux density during finish annealing as a parameter of the atmospheric oxidizability of decarburizing annealing.

FIG. 4 is a graph showing the relationship between cold rolling reduction and magnetic flux density.

FIG. 5 is a graph showing the relationship between aging temperature and iron loss during cold rolling, using the atmospheric oxidizability of decarburization annealing as a parameter.

FIG. 6 is a graph showing the relationship between the temperature rising rate and iron loss during finish annealing as a parameter of the atmospheric oxidizability of decarburizing annealing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohito Ishihii 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (no address) Inside the Mizushima Steel Works, Kawasaki Steel Co., Ltd. (72) Takashi Obara Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture 1 chome (without street number) Kawasaki Steel Works Mizushima Steel Works

Claims (2)

[Claims] 1. A slab for grain-oriented silicon steel containing Al and N as main inhibitor components is hot-rolled, then hot-rolled sheet is annealed, and then cold-rolled once to obtain a final sheet thickness. When producing a grain-oriented silicon steel sheet by a series of steps in which decarburization annealing is performed, then an annealing separator is applied, and then final finishing annealing is performed, i) the reduction ratio of cold rolling is set to 80 to 87%, In addition, during the cold rolling, an aging treatment of holding at a temperature of 100 to 300 ° C. for 1 second or more is performed. _{H 2 O) / P (H} 2) was adjusted while the _{P (H 2 O) / P} (H 2) in the soaking process and less than 0.7,
Set P (H ₂ O) / P (H ₂ ) in the temperature rising process lower than that in the soaking process, iii) During the final finish annealing, the secondary recrystallization temperature range from 850 ℃ to 1000 ℃ The method for producing grain-oriented silicon steel sheet is characterized in that the temperature is raised at a rate of 15 to 100 ° C / h. 2. A slab for grain-oriented silicon steel containing Al and N as main inhibitor components is hot-rolled, then hot-rolled sheet annealed, and then cold-rolled once to obtain a final sheet thickness. When producing a grain-oriented silicon steel sheet by a series of steps in which decarburization annealing is performed, then an annealing separator is applied, and then final finishing annealing is performed, i) cold rolling is performed at a rolling temperature of 100 to 300 ° C. Done between
And, the reduction rate is set to 80 to 87%, ii) Adjusting the ratio P (H ₂ O) / P (H ₂ ) of the partial pressure of water vapor to the partial pressure of hydrogen in the heating process and soaking process of decarburization annealing. However, while P (H ₂ O) / P (H ₂ ) in the soaking process is less than 0.7,
Set P (H ₂ O) / P (H ₂ ) in the temperature rising process lower than that in the soaking process, iii) During the final finish annealing, the secondary recrystallization temperature range from 850 ℃ to 1000 ℃ The method for producing grain-oriented silicon steel sheet is characterized in that the temperature is raised at a rate of 15 to 100 ° C / h.