JPH09291313A - Production of grain oriented silicon steel sheet excellent in magnetic property and film characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain oriented silicon steel sheet excellent in magnetic properties and film characteristic by controlling respective degrees of oxidation of atmosphere in a stage of temp. raise and in a soaking stage at the time of decarburizing annealing. SOLUTION: Hot rolling is performed by using a slab for grain oriented silicon steel sheet, having a composition containing, by weight, 0.01-0.05% sol.Al and 0.004-0.012% N, as a stock. The resultant steel plate is cold-rolled once or is cold-rolled two or more times while process-annealed between cold rolling stages. After decarburizing annealing, a separation agent at annealing is applied and final finish annealing is carried out. The grain oriented silicon steel sheet is produced by means of a series of stages mentioned above. At this time, the value of the ratio of partial pressure of water vapor to partial pressure of hydrogen in the atmosphere in the decarburizing annealing process is regulated so that it is <0.70 in the soaking stage and lower in the stage of temp. raise than in the soaking stage. Further, the separation agent at annealing is prepared by combinedly adding 0.5-15 pts.wt. TiO2 , 0.1-10 pts.wt. SnO2 , and 0.1-10 pts.wt. of Sr compound expressed in terms of Sr to 100 pts.wt. of MgO. By this method, the grain oriented silicon steel sheet excellent in magnetic properties and film characteristic can be produced.

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 particularly to improve the magnetic properties and coating properties by devising the decarburizing annealing step and the composition of the annealing separator. is there.

[0002]

2. Description of the Related Art Grained silicon steel sheets are mainly used as iron core materials for transformers and rotating equipment, and are required to have high magnetic flux density and small iron loss and magnetostriction as magnetic characteristics. In order to obtain a grain-oriented silicon steel sheet having excellent magnetic properties, it is important to obtain a secondary recrystallized structure highly integrated in the {110} <001> orientation, the so-called Goss orientation.

Such a grain-oriented silicon steel sheet is obtained by heating a grain-oriented silicon steel slab containing an inhibitor necessary for secondary recrystallization, such as MnS, MnSe, AlN, etc., and hot rolling it.
Annealing is performed as necessary, and cold rolling is performed once or twice or more with intervening intermediate annealing to obtain the final thickness, and then decarburization annealing is performed, and then an annealing separator containing MgO as a main component is applied to the steel sheet. Then, it is manufactured by performing final finish annealing. And on the surface of this grain-oriented silicon steel sheet,
Except for special cases, a forsterite (Mg ₂ SiO ₄ ) insulating film (hereinafter simply referred to as forsterite insulating film or forsterite film) is usually formed. This coating not only electrically insulates the surface, but also imparts tensile stress due to its low thermal expansion property to the steel sheet, thereby effectively improving iron loss and magnetostriction.

[0004] This forsterite film is formed by finish annealing, and its film forming behavior is based on MnS, MnS
e, Influences the behavior of inhibitors such as AlN, thus affecting the secondary recrystallization itself, which is an essential process for obtaining excellent magnetic properties. Further, the formed forsterite coating also contributes to the improvement of the magnetic properties of the steel sheet by absorbing the inhibitor component, which becomes unnecessary after the secondary recrystallization, into the coating to purify the steel. Therefore, it is very important to control the forsterite film formation process to uniformly form a film in order to obtain a grain-oriented silicon steel sheet of excellent quality.

[0005] Naturally, the formed forsterite film has a uniform appearance and is free from defects, and has excellent adhesion in order to prevent peeling of the film during shearing, punching, bending and the like. Is required. Further, the surface thereof is required to be smooth and have a high occupation rate when laminated as an iron core.

The forsterite insulating coating, which has a great influence on the product quality, is generally formed by the following steps. First, the final cold-rolled sheet for grain-oriented silicon steel sheet cold-rolled to the desired final sheet thickness is heated to 700-90 in wet hydrogen.
Continuous annealing is performed at a temperature of 0 ° C. By this annealing (decarburization annealing), the structure after cold rolling is primary recrystallized so that proper secondary recrystallization occurs in the final finish annealing, and the secondary recrystallization in the final finish annealing is performed completely. In order to prevent aging deterioration of the magnetic properties of the product, 0.003% of carbon is contained in steel in the range of 0.01 to 0.10wt%.
It is decarburized to below a certain level and the subscale containing SiO ₂ is generated on the surface layer of the steel sheet by the oxidation of Si in the steel. After that, an annealing separator containing MgO as the main component is applied to the steel sheet, wound into a coil and subjected to final re-annealing and purification annealing in a reducing or non-oxidizing atmosphere at a maximum of 1200 ° C. The forsterite insulating film is formed mainly by a solid-phase reaction represented by the following reaction formula by carrying out at about the temperature.

[Equation 1] 2MgO + SiO ₂ → Mg ₂ SiO ₄

This forsterite insulating coating is 1 μm
This is a ceramic coating film in which the front and rear fine crystals are densely integrated, and as described above, the Si formed on the surface layer of the steel sheet by decarburizing annealing.
Since the subscale containing O ₂ is formed on the steel sheet as one of the raw materials, the type, amount, distribution, etc. of this subscale contribute to the nucleation and grain growth behavior of forsterite, and It also affects the grain boundaries of the crystal grains and the strength of the grains themselves, and thus has a great effect on the coating quality after finish annealing.

Further, the annealing separating agent mainly composed of MgO, which is the other raw material, is applied to the steel sheet as a slurry suspended in water, and therefore H ₂ which is physically adsorbed even after being dried is used.
In addition to possessing O ₂ , it is partially hydrated and converted to Mg (OH) ₂ . Therefore, during the finish annealing, a small amount of H ₂ O is continuously released up to around 800 ° C. This H ₂ O oxidizes the steel sheet surface during finish annealing. This oxidation also affects the behavior of forsterite as well as the behavior of the inhibitor, and if this additional oxidation is large, it becomes a factor that deteriorates the magnetic properties. The easiness of oxidation by H ₂ O released from this MgO is also greatly affected by the physical properties of the subscale formed by decarburization annealing. In addition, as a matter of course, additives other than MgO 2 mixed in the annealing separator have a great influence on the film formation and the secondary recrystallization process even if the amount added is small.

Particularly in grain-oriented silicon steel sheets containing AlN as an inhibitor component, the physical properties of this subscale have a great influence on the denitrification behavior during finish annealing or the nitriding behavior from the annealing atmosphere, and therefore also on the magnetic properties. Have a great impact. That is, if denitrification proceeds too much, the inhibitory force of the inhibitor weakens and secondary recrystallization does not occur sufficiently, resulting in deterioration of magnetic properties. On the contrary, if the nitriding progresses too much, even if the inhibitory force of the inhibitor becomes excessive and secondary recrystallization occurs, normal secondary recrystallization becomes difficult to occur, and also in this case, the magnetic characteristics deteriorate. Thus, when AlN is used as the inhibitor, a high magnetic flux density can be obtained, but
Secondary recrystallization tends to become unstable, and it is thought that one of the main causes is the variation in the physical properties of the subscale.

As described above, controlling the physical properties of the subscale formed on the surface layer of the steel sheet during decarburization annealing is performed in order to form an excellent forsterite insulating coating uniformly at an appropriate temperature. This technology is essential for the normal development of secondary recrystallization and is one of the important items in the production technology of grain-oriented silicon steel sheets.

Regarding decarburization annealing of grain-oriented silicon steel sheets, a method for controlling the oxygen content of the steel sheet after decarburization annealing, as disclosed in, for example, JP-A-59-185725, has been disclosed. As disclosed in Japanese Patent Publication No. 57-1575, the degree of oxidation of the atmosphere is set to 0.15 or more in the front region of decarburization annealing,
A method in which the degree of oxidation in the subsequent rear region is 0.75 or less and lower than that in the front region is disclosed in JP-A-2-240215 and JP-B-54.
No. 24686, a method of performing heat treatment at 850 to 1050 ° C. in a non-oxidizing atmosphere after decarburization annealing, or as disclosed in Japanese Patent Publication No. 3-57167,
When the cooling after decarburization annealing is performed in the temperature range of 750 ° C or less, the degree of oxidation is 0.
A method of cooling as 008 below is known.

In addition to the above-mentioned proposal concerning decarburization annealing, it is disclosed in Japanese Patent Publication No. 54-14567 as an additive other than MgO to be incorporated in an annealing separator for the purpose of improving magnetic properties. As described above, a method of adding 0.01 to 15 parts by weight (as a metal element) of Cu, Sn, Ni, Co or a compound containing them, TiO ₂ or TiO ₂ as disclosed in JP-A-60-243282. 0.5-10 parts by weight and SrS, SnS, CuS
0.1 to 5.0 parts by weight, or 0.05 to 2.0 parts by weight of antimony nitrate in addition thereto.
As shown in Japanese Patent Publication, colloidal Sb or
A method of adding a compound containing Sb or colloidal Sn or a compound containing Sn is known.

On the other hand, with respect to the improvement of coating properties, many techniques have been disclosed in which an annealing separator contains a Ti compound such as TiO ₂ in addition to MgO which is a main component. For example, Japanese Patent Publication Sho 51
No. 12451 discloses a method of improving uniformity and adhesion of a forsterite coating by adding 2 to 40 parts by weight of a Ti compound to 100 parts by weight of a Mg compound. . Further, Japanese Patent Publication No. 56-15466 discloses a method of eliminating black dot deposits made of a Ti compound by making fine particles of TiO ₂ used as an annealing separator. Further, in Japanese Patent Publication No. 57-32716, a method for forming a forsterite insulating coating with good adhesion and excellent uniformity is described using Sr compounds as Sr compounds.
A technique of blending 0.1 to 10 parts by weight in conversion has been proposed.

[0014]

However, the above-mentioned atmosphere control method during decarburization annealing is not always sufficient although certain effects can be recognized, and the magnetic field is controlled in the width direction or the longitudinal direction of the strip. The characteristics, adhesion, thickness, or uniformity of the forsterite insulating coating may deteriorate, and there is still room for improvement in order to stably produce products with excellent quality and further improve yield. there were. In particular, as mentioned above, AlN
When a grain-oriented silicon steel sheet having a high magnetic flux density is produced by utilizing γ as an inhibitor, secondary recrystallization is often unstable and magnetic properties tend to vary.

In addition, the MgO compounded in the annealing separator is
Although the effects of each of the additives other than those mentioned above were recognized, they were not always sufficient. Furthermore, since the forsterite insulation coating forms the subscale produced during decarburization annealing as one raw material and the annealing separator mainly composed of MgO as the other raw material, both of them are forsterite insulating coatings. Although it seems that it has a great influence on the variation of coating quality and the variation of magnetic properties, from this point of view, there was no example in which they were studied at the same time in consideration of the interrelationship between the subscale and the annealing separator.

The present invention is intended to advantageously solve the above-mentioned problems, and has a forsterite insulating coating film which is uniform and has excellent adhesion without defects over the entire width and the entire length of the coil, and has excellent magnetic properties. Another object is to propose a manufacturing method for obtaining an excellent grain-oriented silicon steel sheet.

[0017]

[Means for Solving the Problems] As described above, the forsterite insulating coating forms the subscale produced during decarburization annealing as one of the raw materials and the annealing separator mainly composed of MgO as the other raw material. Therefore, it is considered that both of them greatly influence the variation in quality and the variation in magnetic characteristics of the forsterite insulating coating. Based on this viewpoint, the inventors have investigated in detail the causes of the variations in the quality and magnetic properties of the forsterite insulating coating in the strip, and as a result, the amount and quality of the subscale generated in the steel sheet surface layer during decarburization annealing I found that the variation had a great influence. This means that the subscale formation reaction does not necessarily occur uniformly in the width direction or the length direction of the strip.

As a result of further investigation on the cause of this, it was found that the fluctuation of the oxidizing property of the atmosphere was involved especially in the temperature rising process of decarburization annealing. In addition to MgO, we investigated the additives to be added to the annealing separator.
It was found that the combined addition of TiO ₂ , SnO ₂ , and Sr compounds is effective in further improving the magnetic properties and coating properties. That is, no matter how evenly the subscale is generated, as long as the steel sheet is wound into a coil and subjected to final finish annealing, there will be some difference in magnetic properties and coating properties between the inner, middle and outer windings of the coil. It was found that these additives are effective in suppressing the difference and further improving the characteristics. The present invention has been made based on the above findings, and the gist thereof is as follows.

Sol Al: 0.01 to 0.05 wt% and N: 0.00
Using a slab for grain-oriented silicon steel sheet containing 4 to 0.012 wt% as a raw material, hot rolling was performed, and then cold rolling was performed once or twice or more with intermediate annealing sandwiched, and then decarburization annealed. After that, in order to manufacture the grain-oriented silicon steel sheet by a series of processes in which the annealing separator mainly composed of MgO is applied and then the final finish annealing is performed, the partial pressure of water vapor relative to the hydrogen partial pressure in the atmosphere in the decarburization annealing process is Ratio: P (H ₂ O) / P
The value of (H ₂ ) is less than 0.70 in the soaking process, and is lower than the soaking process in the heating process, and the annealing separator is
: 0.5 to 15 parts by weight of TiO ₂ with respect to 100 parts by weight, SnO ₂
Of 0.1 to 10 parts by weight and Sr compound in the range of 0.1 to 10 parts by weight in terms of Sr in the respective ranges, and a method for producing a grain-oriented silicon steel sheet having excellent magnetic properties and coating properties. Is.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention will now describe the oxidizing property of the atmosphere during 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 ) (hereinafter Simply P (H ₂ O) /
The effects of P (represented by P (H ₂ )) and additives added to MgO _{2 in the} annealing separator on the film appearance, adhesion and magnetic properties and the uniformity of those properties were investigated in detail. The results of these surveys are listed below.

Experiment 1 C: 0.07 wt% (hereinafter simply expressed as%), Si: 3.30%, Mn:
0.069%, Se: 0.020%, sol Al: 0.025%, N: 0.008
5%, and Sb: 0.025%, with the balance being essentially Fe.
Each of the slabs for grain-oriented silicon steel sheets having the composition of No. 1 is hot-rolled, homogenized at 1000 ° C, and then annealed for 2 minutes at 1000 ° C. 2
Final cold-rolled sheet thickness: 0.23 mm was obtained by performing cold rolling once. Then, these cold-rolled sheets were degreased to clean their surfaces, and then decarburized and annealed at a temperature of 840 ° C. for 2 minutes in an H ₂ —H ₂ O—N ₂ atmosphere.

During the decarburization annealing, the P (H ₂ O) / P (H ₂ ) of 0.2 to 0.8 can be adjusted by adjusting the dew point and the H ₂ gas concentration of the oxidizing property of the atmosphere during the temperature rising process and the soaking process. Each range was changed independently.

Then, an annealing separator containing 6% of TiO ₂ mixed with MgO was made into a slurry and applied to each decarburized annealed plate coil and dried, and then the secondary separation was conducted at 1200 ° C. for 10 hours in a H ₂ atmosphere. It was subjected to recrystallization / purification annealing (finish annealing).

[0024] Thus with assessing the appearance and uniformity of the forsterite film in in-and outdoor winding portion coils obtained were investigated magnetic properties (magnetic flux density B _8, iron loss W _17/50).

The evaluation results of the forsterite coating are shown in FIG.
3 is shown. Here, FIG. 1 is an inner coil winding portion, FIG. 2 is an inner coil winding portion, and FIG. 3 is an outer coil winding portion. P (H ₂ O) / P (P (H ₂ O) / P ( 3 is a graph showing the relationship between H ₂ ) and the appearance of the forsterite coating after finish annealing.

As is clear from FIGS. 1 to 3, the value of P (H ₂ O) / P (H ₂ ) in the soaking process during decarburization annealing is less than 0.7, and P (H 2 _When the value of ₂ O) / P (H ₂ ) is lower than that in the soaking process, a glossy, beautiful gray uniform coating is obtained. However, the uniformity of the coating film in the coil middle winding portion, which is considered to have poor circulation of the atmosphere between the coil layers, is slightly inferior to the inner winding portion and outer winding portion of the coil. On the other hand, when the value of P in the soaking process _{(H 2 O) / P (} H 2) and 0.7 or more, independent of the value of P in the heating process _{(H 2 O) / P (} H 2) Therefore, excellent coating properties cannot be obtained.

Next, an example of the results of investigation of magnetic properties is shown in Table 1.
Shown in

[0028]

[Table 1]

As is clear from Table 1, P in the soaking process
Good magnetic properties only when the value of (H ₂ O) / P (H ₂ ) is less than 0.7 and P (H ₂ O) / P (H ₂ ) in the heating process is lower than in the soaking process. Has been obtained. However, the magnetic characteristics of the middle winding part of the coil are slightly inferior to those of the inner winding part and the outer winding part.

FIG. 4 shows an equilibrium phase diagram of oxides formed on the surface of a silicon steel sheet. According to this FIG. 4, P (H
₂ O) / P (H ₂ ) = 0.7 is clearly the FeO ₂ production region. Therefore, it is considered that the subscales formed under such conditions have poor protection properties and are heavily oxidized by H ₂ O released by MgO during finish annealing, and a good forsterite coating cannot be obtained. .

The detailed reason why the quality of the forsterite coating is improved by lowering P (H ₂ O) / P (H ₂ ) in the temperature rising process than in the soaking process is not clear, but It is considered that the subscale generated during the temperature raising process enhances the protection of the subscale generated during the soaking process.

Experiment 2 Since the coating properties and magnetic properties of the middle winding part of the coil are inferior to those of the inner winding part and the outer winding part, Mg
The effects of the additives added to the O 2 -based annealing separator on the magnetic properties were investigated.

C: 0.065%, Si: 3.35%, Mn: 0.072
%, Se: 0.018%, sol Al: 0.023%, N: 0.0080%,
And Sb: 0.026%, and the balance is composed of a plurality of slabs for grain-oriented silicon steel sheets, each of which has a substantially Fe composition. Each slab is hot-rolled, and then an intermediate annealing is performed at a temperature of 1000 ° C. for 2 minutes. Final cold-rolled sheet thickness: 0.23 mm was obtained by performing cold rolling once. Then, after degreasing these cold-rolled sheets to clean the surface, P (H ₂ O) / P (H ₂ ): 0.4 in the temperature rising process, P (H ₂ O) / P ( H ₂ ): In a H ₂ —H ₂ O—N ₂ atmosphere of 0.5 condition, decarburization annealing was performed at a temperature of 840 ° C. for 2 minutes.

Then, TiO _{2 was} added to 100 parts by weight of MgO.
As 0 to 20 parts by weight, SnO ₂ as 0 to 15 parts by weight, as Sr compound
Annealing separating agent mixed by changing Sr (OH) ₂ .8H ₂ O in the range of 0 to 15 parts by weight in terms of Sr is applied as slurry to the decarburized annealed plate coil, dried, and finally finished. As the annealing, the temperature was raised to 1200 ° C. at a temperature rising rate of 15 ° C./h in an H ₂ stream containing 25% N _2, and subsequently, annealing was performed at 1200 ° C. for 5 hours in an H ₂ atmosphere. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

Inner winding part of each product coil thus obtained,
Magnetic flux density (B ₈ ) and iron loss (W
_17/50 ), and the bending adhesion of the coating and the appearance of the coating were investigated.

The bending adhesion of the coating is measured by winding a test piece around a round bar having various diameters at intervals of 5 mm and measuring the minimum diameter at which the coating does not peel. Table 2 shows these results.
~ 4.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040] Here, Table 2 if you constant at 6 parts by weight the amount of TiO _2, Table 3 if you constant at 5 parts by weight the amount of SnO _2, Table 4 Sr (OH) ₂・ 8H ₂ O is added in a constant amount of 5 parts by weight in terms of Sr.

As is clear from these tables, MgO: 10
0 to 15 parts by weight of TiO ₂ in the range of 0.5 to 15 parts by weight, SnO ₂
In the range of 0.1 to 10 parts by weight, and Sr compounds in the range of 0.1 to 10 in terms of Sr.
In the annealing separator which was added in the range of parts by weight, P (H ₂ O) / P (H ₂ ) in the soaking process was less than 0.70, and P (H 2
₂ O) / P (H ₂ ) is applied to a steel sheet having a subscale produced by decarburizing annealing under conditions where the temperature is lower than that in the soaking process, and finish annealing is performed to obtain coating properties and magnetic properties. It can be seen that an extremely excellent product can be obtained over the entire length of the coil.

In particular, it can be seen that the effect of improving both the coating and magnetic properties in the coil middle winding portion where the atmosphere has poor flowability is great. Further, in the coil outer winding portion and the inner winding portion, those coated with the annealing separator which is a composite addition of additives within the above range,
The iron loss is significantly improved, although the coating properties and the magnetic flux density (B ₈ ) are the same, as compared with those that are not.

As described above, the coating properties and magnetic properties (both magnetic flux density and iron loss) are greatly improved in the coil middle winding portion where the atmosphere does not flow well during final finish annealing. Of TiO ₂ , SnO ₂ and Sr compounds
It is conceivable that the coexistence of a person causes a large change in the film formation process, and the secondary recrystallization process also changes due to the change.

The results of a few investigations relating to these phenomena are described below. MgO: 100 parts by weight, TiO ₂ : 6 parts by weight, Sn
FIG. 5 shows Sn analysis results in the finish annealing process when finish annealing was performed using an annealing separator having a composition of O ₂ : 5 parts by weight and Sr compound in terms of Sr: 2 parts by weight. FIG.
(a) is the relationship between the temperature and the Sn content of the coated steel sheet, Fig. 5
(b) is a graph of the relationship between temperature and Sn content in steel.

As can be seen from these figures, SnO ₂ decomposes during finish annealing and Sn penetrates into the steel. At this time, of course, it is considered that oxygen is released due to the decomposition of SnO ₂ and affects the atmosphere between the coil layers.

Next, as an annealing separator, TiO ₂ : 6 parts by weight was added to A --- MgO: 100 parts by weight (incompatible with the present invention) B --- MgO: 100 parts by weight TiO ₂ : 6 parts by weight, SnO ₂ :
_Two parts of 3 parts by weight and Sr (OH) ₂ .8H ₂ O as Sr compound in terms of Sr: 2 parts by weight composite addition (conforming to this invention) were applied to the decarburized annealed plate respectively, and the sample was subjected to finish annealing. Was taken out, and fluorescent X-ray analysis (oxygen) measurement of the steel plate surface at each temperature was performed. The results of these measurements are shown in FIG. 7 and 8 show that 900 ° C and 10 ° C during finish annealing.
The result of having measured the reflection infrared absorption spectrum in the steel plate surface in the temperature of 50 degreeC is shown.

From these figures, in the case of using B as compared with the case of using A as the annealing separator, it was found that 95% before the start of secondary recrystallization.
Formation of the film (olivine) is suppressed at temperatures below 0 ° C, but secondary recrystallization is in progress or has progressed at 975 ° C.
On the contrary, it was found that the formation of the coating (forsterite) was promoted at the above temperature, and TiO ₂
Formation conditions of the film indicates a different apparent in what was added in combination have been added and the TiO _2, SnO ₂ and Sr compound alone.

Further, as an annealing separator mainly composed of MgO, Ti
In order to investigate the reason why the magnetic properties (especially iron loss) are improved when O ₃ , SnO ₂ and Sr compounds coexist, the above annealing separators A and B were applied to decarburized annealed sheets, respectively. , 1.7 (T) ・ 50Hz for the product sheet after finish annealing
DC magnetization iron loss (Wh _17/50 ), that is, hysteresis loss at was measured. The results are shown in FIG.

FIG. 9 shows that the annealing separator is A (TiO 2)._Two(Single addition)
And B (TiO_Two, SnO_TwoAnd Sr compound combined addition)
Magnetic flux density (B₈) And hysteresis loss
 (Wh _17/50) Is a graph showing the relationship with.

From this figure, when B is used as the annealing separator, the hysteresis loss is low as compared with the case where A is used, even though the magnetic flux density (B ₈ ) shows the same value. I understand. Therefore, TiO ₂ , SnO ₂
It is considered that the decrease in hysteresis loss largely contributes to the effect of improving the magnetic properties when the alloy and the Sr compound are added in combination.

Experiment 3 In addition, when manufactured under the conditions compatible with the present invention,
That is, P (H _TwoO) / P (H_Two) Is less than 0.70,
, P (H_TwoO) / P (H_Two) Is more than that of the soaking process
Decarburization annealing under low conditions to generate subscale
Steel sheet with additives in the annealing separator containing MgO as the main component.
Then TiO_Two, SnO_TwoAnd three Sr compounds coexist
A study was conducted on the improvement of the hysteresis loss of.

C: 0.062%, Si: 3.25%, Mn: 0.071
%, Se: 0.022%, sol Al: 0.027%, N: 0.0082% and Sb: 0.026% with the balance substantially Fe composition. After that, homogenized annealing was performed at a temperature of 1000 ° C., and then cold rolling was performed twice at a temperature of 1000 ° C. with an intermediate annealing for 2 minutes to obtain a final cold-rolled sheet thickness: 0.23 mm. Then, after the surface was cleaned by degreasing these cold-rolled sheet, the heating process _{P (H 2 O) / P} (H 2): 0.35, the soaking process P (H ₂ O) / P
(H ₂ ): Decarburization annealing was performed for 2 minutes at a temperature of 840 ° C. in an H ₂ —H ₂ O—N atmosphere of 0.4.

Then, as an annealing separator, 10 parts by weight of TiO ₂ was added to 100 parts by weight of C --- MgO (incompatible with the present invention). D --- MgO was added to 100 parts by weight of TiO 2. ₂ kinds of slurry (complying with the present invention) in which 10 parts by weight of ₂ is added by 5 parts by weight of SnO ₂ and 5 parts by weight of SrSO ₄ as an Sr compound (conforming to the present invention) are applied to a decarburized annealed plate coil and dried. Then, after subjecting to secondary recrystallization and purification annealing at a temperature of 1150 ° C. for 5 hours and at a temperature of 1200 ° C. for 5 hours in an H ₂ atmosphere, magnesium phosphate and colloidal silica as main components Coated.

In the product coil thus obtained, the magnetic flux density (B ₈ ) and core loss (W ₈ ) of the inner winding part, the middle winding part and the outer winding part
_17/50 ), hysteresis loss (Wh _17/50 ), adhesion of the coating and its appearance were investigated. Table 5 summarizes the results of these investigations.

[0055]

[Table 5]

From Table 5, as compared with the case where the annealing separator which is incompatible with the present invention is used, when the annealing separator suitable for the present invention is used, when the purification annealing temperature is 1200 ° C., the coating properties and the magnetic properties are improved. Although it is significantly improved, it can be seen that even at a low temperature of 1150 ° C, the deterioration of the film characteristics and the magnetic characteristics is small, and particularly the deterioration of the hysteresis loss is small.

This phenomenon, as described above, accelerates the film formation when the secondary recrystallization proceeds in the final annealing when the annealing separator composition suitable for the present invention is used. Therefore, even if the purification annealing is as low as 1150 ° C, the absorption of the inhibitor component into the coating proceeds sufficiently, and
Since the film is sufficiently formed, it is considered that the film properties and magnetic properties are less deteriorated.

As described above, according to the present invention, even if the purification annealing temperature is lowered to 1150 ° C., it is possible to obtain a product having coating properties and magnetic characteristics higher than those of the conventional products, that is, the purification annealing temperature can be lowered. Since less energy is used, the economical advantage is large, and the ear strain generated on the lower side of the coil during the final annealing is also small, which is very effective in improving the yield of products. In addition, when the annealing is performed at a temperature of 1200 ° C., the film characteristics and magnetic characteristics are significantly improved.

From the results of the above series of experiments, decarburization annealing was performed.
P (H in the soaking process_TwoO) / P (H _Two) Is less than 0.7,
P (H_TwoO) / P (H_Two) Than that of the soaking process
Decarburization annealing is performed under low conditions to generate subscale,
The MgO that is applied to the steel plate that produced this subscale is mainly
In the annealing separator that forms the body, TiO_Two, SnO_TwoAnd Sr compound
Excellent coexistence over the entire length of the coil
To obtain a product with coating and magnetic properties,
The improvement effect of magnetic properties is mainly due to the decrease of hysteresis loss
It became clear that it was thought to be a thing.

Although the reason for them is not clear, coupled with the fact that the subscale generated during decarburization annealing is fairly uniform and has a high protective property, TiO ₂ and SnO ₂ are contained in the annealing separator.
Since Sr and Sr compounds coexist, the action of the additives in the annealing separator also differs greatly from the conventional one, resulting in a difference between the film formation process and the secondary recrystallization process that reflects it, resulting in extremely large film properties. It is believed that this has resulted in improvement of magnetic properties.

Regarding the action of the additives to the conventionally known annealing separator, according to the above-mentioned Japanese Patent Publication No. 51-12451, TiO ₂ is MgO-TiO ₂ produced during secondary recrystallization.
In order to improve the uniformity and adhesion of the coating in order to form a high quality glassy coating by reacting the mixture of SiO ₂ with SiO _{2 on the} surface of the steel sheet, according to Japanese Patent Publication No. 54-14567, Sn or
The Sn compound improves the magnetic properties by adjusting the atmosphere during finish annealing, and according to JP-B-57-32716, the Sr compound improves the magnetic properties by eliminating the forsterite grains just below the surface of the steel sheet. It is only described that each has an effect.

Next, the reasons for limiting the component composition of the present invention and the preferable ranges will be described. The composition of the slab for silicon steel sheet that is the subject of the present invention, sol Al 0.01 ~
The composition may be that which is usually used as a grain-oriented silicon steel sheet containing 0.05% and N in the range of 0.004 to 0.012%. For example, C: 0.02 to 0.10%, Si: 2.0 to 4.0%, M
n: 0.02 to 0.20%, and at least one of S and Se alone or 0.010 to 0.040 in total
% Is preferred. In addition, if necessary, Sb:
0.01 to 0.20%, Cu: 0.02 to 0.20%, Mo: 0.01 to 0.05%,
Sn: 0.02-0.30%, Ge: 0.02-0.30% and Ni: 0.01-
It may be contained in the range of 0.20%.

Sol Al and N are needed to form the AlN inhibitor. If the Al content is too low, the magnetic flux density will decrease, and if it is too high, the secondary recrystallization will become unstable.
The content of solAl is limited to the range of 0.01 to 0.05%. When N is too small, the amount of AlN inhibitor is insufficient and the magnetic flux density is lowered, and when it is too large, surface defects called blister frequently occur in the product, so the content is 0.004 to 0.01.
The range is 2%.

C is an important component for improving the crystal structure by utilizing the α-γ transformation during hot rolling. If the content is less than 0.02%, a good primary recrystallized structure is obtained. If it exceeds 0.10%, decarburization becomes difficult and decarburization becomes poor and the magnetic properties deteriorate, so about 0.02 to 0.10% is preferable.

Si is an important component for increasing the electric resistance of the product and reducing the eddy current loss. If the content is less than 2.0%, the crystal orientation is changed by α-γ transformation during final finish annealing. If it exceeds 4.0%, there is a problem in cold rolling property, so 2.0 to 4.0% is preferable.

Mn, Se and S function as inhibitors. If the amount of Mn is less than 0.02% or the amount of S or Se alone or in total is less than 0.010%, the inhibitor function becomes insufficient and the amount of Mn is 0.20. %, Or the total amount of S and Se alone or in total exceeds 0.040%, the temperature required for slab heating is too high to be practical, so Mn is 0.
02 to 0.20%, S or Se alone or as a total amount of 0.
Preferably, it is 010 to 0.040%.

To further improve the magnetic flux density, Sb, C
It is possible to add u, Sn, Ge, Ni, etc. alone or in combination. If the content of Sb exceeds 0.20%, the decarburization property deteriorates, and if it is less than 0.01%, there is no effect, so the content is preferably 0.01 to 0.20%. Cu content is 0.20%
If the content exceeds 0.01%, the acid washability deteriorates, and if the content is less than 0.01%, there is no effect. Sn,
If the content of Ge exceeds 0.30%, a good primary recrystallized structure cannot be obtained, and if the content is less than 0.02%, there is no effect. Therefore, the content of each is preferably 0.02 to 0.30%. Ni content 0.20%
If the content exceeds 0.01%, the hot strength decreases, and if it is less than 0.01%, there is no effect, so the content is preferably 0.01% to 0.20%.

Mo may be added to improve the surface properties. If the content exceeds 0.05%, the decarburization property deteriorates,
If less than 0.01%, there is no effect, so the content is 0.01
~ 0.05% is preferred.

Next, the manufacturing conditions of the grain-oriented silicon steel sheet which is the subject of the present invention will be described. The molten steel adjusted to the above-mentioned composition by the steelmaking method conventionally used is cast by a continuous casting method or an ingot making method, and a slab is obtained by sandwiching a slabbing step if necessary, followed by hot rolling, If necessary, perform hot-rolled sheet annealing, then insert once or intermediate annealing 2
A cold rolled sheet with the final sheet thickness is obtained by performing cold rolling more than once.

Then, decarburization annealing in which P (H ₂ O) / P (H ₂ ) is controlled in the atmosphere according to the present invention described above is performed. The temperature rising rate in this decarburization annealing is not limited to the usual range of 10 to 20 ° C / s, but can be performed in a wider range of 5 to 30 ° C / s. However, 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 decarburization annealing satisfies other conditions. There is.

On the surface of the decarburized and annealed steel sheet, an annealing separator, which is obtained by adding TiO ₂ , SnO ₂ and Sr compound to MgO according to the present invention, is applied in a slurry form and then dried.

Here, the MgO used as the annealing separator has a hydration amount (amount of hydration at 20 ° C. for 6 minutes and then a loss of 100 ° C. for 1 hour due to ignition) in the range of 1 to 5%. Good to use. This is because if the hydration amount of MgO is less than 1%, the formation of forsterite coating is insufficient, and if it exceeds 5%, the amount of water carried into the coil layer becomes too large and the amount of additional oxidation of the steel sheet increases, which is good. This is because there is a possibility that a good forsterite coating may not be obtained.

Further, the coating amount of the annealing separator can be applied in the range of 4 to 10 g / m ² per one side of the steel sheet. this is,
This is because if the coating amount is less than 4 g / m ² , the forsterite is insufficiently produced, and if it exceeds 10 g / m ² , the forsterite coating is excessively produced and becomes thick, resulting in a decrease in space factor.

The Sr compound, which is one of the additives to the annealing separator, is a conventionally known compound such as SrSO ₄ , Sr (O
H) ₂ · 8H ₂ O, SrCO ₃ , Sr (NO) _{3, and the} like, and one or more selected from these may be added alone or in combination.

After the annealing separator is applied, secondary recrystallization / purification annealing (finish annealing) is performed in a temperature range of 1000 to 1200 ° C. for about 3 to 50 hours to obtain a product plate.

It is then advantageous to further apply a phosphate-based insulating coating, preferably a tension-imparting insulating coating. Further, a known domain refinement treatment may be performed after the final cold rolling, after the final finish annealing or after the insulating coating, which is effective in further reducing the iron loss.

[0077]

【Example】

Example 1 C: 0.071%, Si: 3.34%, Mn: 0.069%, Se: 0.019
%, Al: 0.025%, N: 0.090%, Cu: 0.10% and S
b: a plurality of silicon steel slabs containing 0.027% and the balance being substantially Fe, each at a temperature of 1430 ° C.
After heating for a minute, hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.2 mm. Then, after hot-rolled sheet annealing at 1000 ° C for 1 minute, cold rolled to a sheet thickness of 1.5 mm, after intermediate annealing at 1100 ° C for 2 minutes, final cold rolled sheet has a final sheet thickness of 0.23 mm. Finished.

These cold-rolled sheets were subjected to decarburization annealing at 840 ° C. for 2 minutes in an H ₂ —H ₂ O—N ₂ atmosphere. At this time, the oxidizing atmosphere of the heating process and a soaking process _{[P (H 2 O) / P} (H
₂ )] was changed as shown in Table 6.

[0079]

[Table 6]

Then, the annealing separator having the composition shown in Table 6 was applied to each of the steel sheets, followed by holding at 850 ° C. for 20 hours in an N ₂ atmosphere, followed by H ₂ : 75 vol% and N ₂ : 25 vol%. In this atmosphere, secondary recrystallization annealing was performed by raising the temperature to 1150 ° C at a rate of 20 ° C / h, followed by purification annealing for 5 hours in H ₂ atmosphere at 1200 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

The magnetic flux density (B ₈ ), iron loss (W _17/50 ), bending adhesion of the coating and appearance of each of the products thus obtained were investigated. The results of these investigations are also shown in Table 6 above.

As is apparent from Table 6, all the conforming examples manufactured under the conditions according to the present invention show good magnetic properties and coating properties.

Example 2 C: 0.075%, Si: 3.27%, Mn: 0.068%, Se: 0.021
%, Al: 0.026%, N: 0.0085%, and Sb: 0.025%, the balance consisting of a plurality of silicon steel slabs consisting essentially of Fe was heated for 30 minutes at a temperature of 1430 ° C. Hot rolling was performed by hot rolling with a plate thickness of 2.2 mm. Then
After hot-rolled sheet annealing at 1000 ℃ for 1 minute, cold rolled sheet thickness: 1.
After 5 mm, intermediate annealing at 1100 ° C. for 2 minutes, and the second cold rolling, the final thickness was 0.23 mm.

These cold-rolled sheets were subjected to decarburization annealing at 840 ° C. for 2 minutes in an H ₂ —H ₂ O—N ₂ atmosphere. At this time, the oxidizing properties of the atmosphere during the temperature raising process and the soaking process were changed as shown in Table 7.

[0085]

[Table 7]

Then, each of the annealing separators having the compositions shown in Table 7 was applied to the steel sheet, followed by holding at 850 ° C. for 20 hours in an N ₂ atmosphere, followed by H ₂ : 85 vol%, N ₂ : 15 vol%. In this atmosphere, secondary recrystallization annealing was performed at a rate of 15 ° C./h to a temperature of 1100 ° C., followed by purification annealing for 5 hours in an H ₂ atmosphere of 1160 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

The same investigation as in Example 1 was conducted on each of the products thus obtained. The survey results are shown in Table 7 above.
Are shown together. As is apparent from Table 7, all the conforming examples of the present invention show good magnetic properties and coating properties.

Example 3 C: 0.073%, Si: 3.30%, Mn: 0.070%, Se: 0.020
%, Al: 0.027%, N: 0.0083%, Cu: 0.08% and S
b: a plurality of silicon steel slabs containing 0.026% and the balance being substantially Fe, each at a temperature of 1430 ° C.
After heating for a minute, hot rolling was performed to obtain a hot rolled sheet having a plate thickness of 2.7 mm. Then, after hot-rolled sheet annealing at 1000 ° C for 1 minute, cold rolled to a sheet thickness of 2.0 mm, after intermediate annealing at 1100 ° C for 2 minutes, the final sheet thickness by a second cold rolling: 0.35 mm. Finished.

These cold-rolled sheets were subjected to decarburization annealing at 840 ° C. for 3 minutes in an H ₂ —H ₂ O—N ₂ atmosphere. At this time, the atmospheric oxidizability during the temperature raising process and the soaking process was changed as shown in Table 8.

[0090]

[Table 8]

Then, the annealing separator having the composition shown in Table 8 was applied to each of the steel sheets, and the steel sheet was held in an N ₂ atmosphere at 850 ° C. for 20 hours, followed by H ₂ : 75 vol% and N ₂ : 25 vol%. Secondary recrystallization annealing was performed at a rate of 15 ° C./h to 1150 ° C. in the atmosphere, followed by purification annealing for 5 hours in an H ₂ atmosphere at a temperature of 1180 ° C. After that, a coating containing magnesium phosphate and colloidal silica as main components was applied.

Regarding the product thus obtained, Example 1
The same survey was conducted. The results of these investigations are also shown in Table 8 above. As can be seen from Table 8, the adaptations of this invention show good magnetic and coating properties.

[0093]

Effects of the Invention The present invention, in the production of grain oriented silicon steel sheet having an AlN-based inhibitor, together with controlling the degree of oxidation of atmosphere in the Atsushi Nobori process and soaking processes of decarburization annealing, respectively, TiO ₂ According to the present invention, it is possible to stably produce a grain-oriented silicon steel sheet having excellent magnetic properties and coating properties, by using an annealing separating agent mainly composed of MgO to which SnO ₂ and Sr compounds are added in combination. Will be able to. Further, since the final finishing temperature can be lowered, it is excellent in economic efficiency and can contribute to the improvement of product yield and the improvement of productivity.

[Brief description of drawings]

FIG. 1 shows the relationship between P (H ₂ O) / P (H ₂ ) in the temperature rising process and soaking process during decarburization annealing and the appearance of the forsterite film after finish annealing in the coil inner winding part. It is a graph shown.

FIG. 2 shows the relationship between P (H ₂ O) / P (H ₂ ) in the temperature rising process and soaking process during decarburization annealing in the middle coil part and the appearance of the forsterite coating film after finish annealing. It is a graph shown.

FIG. 3 shows the relationship between P (H ₂ O) / P (H ₂ ) in the temperature rising process and soaking process during decarburization annealing in the outer coil part of the coil and the appearance of the forsterite coating film after finish annealing. It is a graph shown.

FIG. 4 is an equilibrium state diagram of oxides formed on the surface of a silicon steel sheet.

FIG. 5 is a graph showing a Sn analysis result in a finish annealing process. (a) is a graph of the relationship between temperature and Sn content of a coated steel sheet. (b) is a graph of the relationship between temperature and Sn content in steel.

FIG. 6 is a graph showing the results of fluorescent X-ray oxygen analysis of the steel sheet surface at each temperature during finish annealing.

FIG. 7 is a graph showing the relationship between wave number and absorption spectrum intensity at a temperature of 900 ° C. during finish annealing.

FIG. 8 is a graph showing the relationship between wave number and absorption spectrum intensity at a temperature of 1050 ° C. during finish annealing.

FIG. 9: A (TiO ₂ alone added) and B (TiO ₂ ,
3 is a graph showing the relationship between the magnetic flux density (B ₈ ) and the hysteresis loss (Wh _17/50 ) when SnO ₂ and Sr compound are added _together ).

Claims (1)

[Claims] 1. Sol Al: 0.01 to 0.05 wt% and N: 0.
A slab for grain-oriented silicon steel sheet containing 004 to 0.012 wt% was hot-rolled, then hot-rolled once or twice or more with intermediate annealing sandwiched, and then decarburized-annealed. After that, in order to manufacture grain-oriented silicon steel sheets by a series of processes in which an annealing separator mainly composed of MgO is applied and then final finishing annealing is performed, the partial pressure of water vapor relative to the hydrogen partial pressure in the atmosphere during the decarburization annealing process is Ratio: P (H ₂ O) / P (H ₂ ) value in the soaking process
It is less than 0.70, lower than the soaking and heating process in the temperature rising process, and the annealing separator has 0.5% of TiO ₂ with respect to 100 parts by weight of MgO.
~ 15 parts by weight, 0.1 to 10 parts by weight of SnO ₂ and Sr compound to Sr.
A method for producing a grain-oriented silicon steel sheet having excellent magnetic properties and coating properties, which is characterized by being added in a combined amount within the range of 0.1 to 10 parts by weight.