JPH1088242A - Magnesium oxide powder for separation agent at annealing used manufacture of grain oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform forsterite glass film having excellent film character istic by measuring the grain size distribution of an MgO slurry, prepared by suspending MgO powder in water, and using, for a separation agent at annealing, an MgO powder having a cumulative 90% diameter satisfying specific conditions. SOLUTION: At the time of suspending an MgO powder for a separation agent at annealing in water to form MgO slurry, the grain size distribution of this MgO slurry is measured by means of a laser diffraction type grain size distribution meter. An MgO powder, having a cumulative 90% diameter satisfying the range enclosed with lines connecting point A (400, 20), point B (1000, 3.5), point C (1500, 2.5), point D (1500, 8.0), point E (1000, 10), and point F (400, 90) in the figure at this measurement, is used for a separation agent at annealing. By this method, the uniform forsterite glass film having excellent film characteristic can be formed in the final finish annealing stage and also excellent magnetic properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to form a forsterite glass coating having uniform and excellent coating properties and to obtain excellent magnetic properties during the manufacturing process of grain-oriented electrical steel sheets, especially in the final finishing annealing step. For MgO powder for an annealing separator used for this purpose.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as soft magnetic materials.
It is mainly used as an iron core material for transformers or rotating machines, and is required to have high magnetic flux density and small iron loss and magnetostriction in terms of characteristics. Except for special cases, forsterite (Mg ₂ SiO ₄ )
Generally, a glassy coating is formed. This coating contributes not only to the electrical insulation of the surface but also to the improvement of iron loss and magnetostriction by imparting tensile strength to the steel sheet due to its low thermal expansion property.

[0003] The formed glass coating must, of course, be uniform and defect-free and have excellent adhesion to withstand shearing, punching and bending. Further, it must be smooth and have a high space factor when laminated on an iron core.

[0004] In order to form a glass coating on the surface of a grain-oriented electrical steel sheet, cold rolling is performed to a predetermined final sheet thickness, followed by decarburization.
Primary recrystallization annealing, that is, continuous annealing at a temperature of 700 to 900 ° C. in wet hydrogen makes the structure after cold rolling primary recrystallized and also reduces C which causes magnetic after-effect as much as possible. At the same time, a sub-scale mainly composed of silica is formed on the surface of the steel sheet by oxidation, and then an annealing separator mainly composed of MgO is applied onto the steel sheet, and then wound around a coil, and then reduced or non-oxidized. This is performed by performing high-temperature finish annealing at a temperature of about 1000 ° C. to 1200 ° C. in an atmosphere. Thus, a reaction represented by the following formula occurs,
A forsterite insulating coating is formed. 2MgO + SiO ₂ → Mg ₂ SiO ₄

[0005] As described above, this glass film is formed at the time of finish annealing, and its formation behavior affects the behavior of MnS, MnSe, AlN and the like, which are inhibitor components in steel. Also affects the secondary recrystallization itself, which is an essential process for obtaining the recrystallization. In other words, if the film formation reaction is delayed or uneven in the temperature range around 900 ° C during the finish annealing, or if the formed film has a porous structure, the annealing atmosphere Therefore, O and N easily enter the steel, so that the inhibitors in the steel are decomposed, coarsened, or excessively increased. Further, when the film forming reaction proceeds from a low temperature range, the inhibitor is sucked into the film at a low temperature, resulting in a shortage of the inhibitor in the steel. When such a phenomenon occurs, the degree of integration of the secondary recrystallized structure in the Goss orientation decreases, and the magnetic characteristics deteriorate.

Further, the formed glass coating has a function of absorbing unnecessary inhibitor components after the completion of the secondary recrystallization into the glass coating and purifying the steel, thereby helping to reduce the hysteresis loss of the steel plate. Therefore, forming the glass coating uniformly is one of the important points that affect the product quality of the grain-oriented electrical steel sheet.

[0007] The stability of the inhibitor in the finish annealing is affected by the subscale formed on the steel sheet surface by the decarburizing annealing, the annealing separator, the thermal cycle during the finish annealing, the atmospheric conditions, and the like. Among these, the properties of MgO used as the main agent for the annealing separator have a great effect on the glass film formation speed, formation start temperature, formation amount, film uniformity, film adhesion, and the degree of atmospheric oxidation between coil layers. Affects and affects the stability of inhibitors in steel through the formation of a glass coating.

In forming such a glass film, MgO
In addition to properties such as particle size, purity and activity, the amount of hydration during application to steel sheet, the amount of annealed separating agent applied, the uniformity of annealed separating agent coated film, the adhesion between annealed separating agent and decarburized annealed sheet In addition, the type and amount of additives added for the purpose of accelerating the formation of the glass film and the state of dispersion on the steel sheet surface depend on the glass film formation speed, formation start temperature, formation amount, and uniformity of the film. Affects the properties and coating adhesion. As described above, it is important to control the properties of MgO and the application state of the annealing separator on the steel sheet surface for the glass coating and magnetic properties that are important in determining the product quality of grain-oriented electrical steel sheets. Currently, the development of these technologies is an important issue. In recent years, the passing speed of a production line has been increased for mass production, and in that sense, control of the application state of an annealing separating agent has become an important issue.

As an annealing separator for grain-oriented electrical steel sheets, various additives such as MgO and an additive for promoting the formation of a forsterite glass film or an additive for reinforcing an inhibitor are added and blended, and suspended in water. The slurry is stirred and dispersed in a tank equipped with a stirring device such as a shear impeller, and then applied onto the surface of the steel sheet by a coating device such as a rubber roll, and subsequently dried. In this case, MgO
Even after drying, H ₂ O physically adsorbed on the surface is present on the surface, and a part of the H ₂ O is hydrated and changed to Mg (OH) ₂ . Since H ₂ O continues to be released in a small amount up to around 800 ° C. during the finish annealing, the steel sheet surface is oxidized. Such an oxidation phenomenon is called additional oxidation, which affects the formation behavior of forsterite, and also leads to oxidation and decomposition of the inhibitor.

In the case where the above-mentioned additional oxidation is suppressed by using low-hydration MgO, Mg which has been sintered at a high temperature in the MgO production process is used.
O is adopted. However, when firing at high temperature,
The fine crystals in the MgO particles tend to sinter, and the MgO particles tend to agglomerate and sinter together.On the steel sheet surface after the application of the annealing separator, the annealing separator due to the reduced contact area between the steel sheet and MgO Not only does the adhesion decrease, but also the film thickness and density when the annealing separator is applied become non-uniform. In addition, in such a case, the viscosity of the slurry is excessively reduced, and the slurry on the steel sheet is caused to flow into the airflow in the drying furnace during drying, so that a very non-uniform pattern is exhibited, and high-speed coating property is reduced. to degrade.

In order to enhance the intrinsic solid phase reactivity of MgO, when fine MgO having a content of 1.0 μm or less and 70% or more (measured by a laser diffraction particle size analyzer) is used,
Agglomeration between MgO particles is easy to occur, and when suspended in water, coarse particles are formed and the uniformity of the surface of the coated annealing separator is not only impaired, but also the addition of the annealing separator in the coarse aggregated MgO particles Since the material concentration decreases, the uniform dispersion of the annealing separator additive is hindered, and it becomes impossible to apply the annealing separator additive to the steel sheet surface in a uniformly dispersed state.

As means for solving the problems caused by the non-uniformity of the film formation reaction and the decrease in reactivity due to the over-sintering of MgO and the agglomeration in the MgO slurry and the decrease in adhesion between the annealing separator and the steel sheet, Conventionally, a method of appropriately adjusting the hydration property of MgO itself and a method of controlling the MgO physical property value in the MgO manufacturing process to prevent agglomeration have been proposed, but it is said that a sufficient effect has been obtained. It's hard to say. For example, Japanese Patent Publication No. 60-338
No. 96 discloses that MgO impurities are eliminated by high-temperature firing,
In addition, a method of activating only the outermost surface of MgO in the MgO slurry preparation step to reduce the amount of water carried in (the amount of hydrated MgO) is disclosed in JP-A-62-156226. A method is disclosed in which a predetermined amount of a hydrated layer is formed only on a very surface layer of hydrated MgO and activated MgO is used. Further, JP-A-2-267278 discloses that MgO is 1
Was treated with 00 ° C. water vapor-containing gas phase, the OH chemical adsorption layer H ₂
A method is disclosed in which O is formed in the range of 0.8 to 2.5% based on the weight of MgO in terms of O.

[0013] When applying an annealing separator slurry to the surface of a steel sheet, the surface energy of MgO is reduced by performing a special treatment on the surface of the MgO particles at a high temperature.
This is a technique for reducing aggregation between Os. Outermost surface layer of MgO is intended to secure a film formed by MgO of in the middle of the Mg (OH) ₂ turned into and, finishing Mg (OH) ₂ the surface layer annealing. However, since the inside of the MgO particles is fired at a high temperature during the production of MgO, the solid phase reactivity inside the MgO is low, so it is not only indispensable to add an additive more than necessary for the purpose of accelerating the reaction, In some cases, the ability to form a forsterite glass coating of MgO is insufficient.

In addition, Japanese Patent Application Laid-Open No. 5-295423 discloses that when a low hydration MgO is used and a slurry in which MgO is suspended in water is applied to a steel sheet, ultra-fine particles are formed in the process from the slurry adjustment to the application of the steel sheet. A method is disclosed in which a glass film is formed uniformly by performing fineness and activation with a powder device, and excellent magnetic properties are obtained. According to this method, by uniformly breaking the annealing separator coating liquid between the slurry adjustment and the steel sheet coating, the coating uniformity of the steel sheet surface can be ensured, but the MgO slurry is easily settled and solidified. Due to the nature, there is a risk that the narrow gap of the crusher will be blocked. In addition, since maintenance is complicated, there is a disadvantage that it is not suitable for mass production lines.

[0015]

SUMMARY OF THE INVENTION The present invention is intended to solve the following problems when applying an annealing separator during the production of grain-oriented electrical steel sheets. Problem 1 When MgO fired at a high temperature is used, the fine crystals in the MgO particles tend to sinter, and the MgO particles tend to agglomerate and sinter together. A decrease in the adhesion of the annealing separator due to a decrease in the contact area of MgO, and an unevenness in the thickness and density of the coating layer of the annealing separator occur. In addition, in such a case, the viscosity of the slurry is excessively reduced, and the slurry on the steel plate is caused to flow into the airflow in the drying furnace during drying, so that a very uneven pattern is generated and the high-speed coating property is deteriorated.

Problem 2 In order to increase the intrinsic solid phase reactivity of MgO, when fine MgO having a content of 1.0 μm or less and a content of 70% or more (measured by a laser diffraction type particle size analyzer) is used, the MgO particle Agglomeration easily occurs, and when suspended in water, coarse particles are formed, which not only impairs the uniformity of the surface coated with the annealing separator, but also decreases the additive concentration of the annealing separator in the MgO coarse aggregates. Therefore, the uniform dispersion of the annealing separator additive is hindered, and the uniform dispersion of the annealing separator additive on the steel sheet surface is hindered.

According to the present invention, the above-mentioned problem is advantageously solved, and when the annealing separator is applied during the production of a grain-oriented electrical steel sheet, the high-speed applicability is excellent and the problem due to the formation of the aggregate of the MgO slurry does not occur. Providing MgO powder for an annealing separator, and in the final finishing annealing process in the production of grain-oriented electrical steel sheets, form a forsterite-like glass coating with uniform and excellent coating properties and obtain excellent magnetic properties The purpose is to:

[0018]

Means for Solving the Problems In the process of forming a forsterite glass coating from decarburizing annealing to finish annealing of grain-oriented electrical steel sheets, the present inventors have formed a uniform glass coating and obtained excellent magnetic properties. The manufacturing method which can obtain the characteristic was examined. In particular, as a result of examining the effect of the properties of MgO for the annealing separator on the formation of agglomerates in the slurry, the intended purpose is achieved by using the MgO powder in which the agglomeration characteristics of the MgO slurry are within a specific range. I got the knowledge of that. The present invention is based on the above findings.

That is, the present invention provides a method for producing Mg for an annealing separator.
O powder, when the MgO powder was suspended in water to form an MgO slurry, the cumulative 90% diameter of the MgO slurry measured by a laser diffraction type particle size distribution analyzer was the point A in FIG. ,
An MgO powder for an annealing separator in the production of grain-oriented electrical steel sheets, characterized by satisfying a range surrounded by B, C, D, E and F. Here, the coordinates of each point in FIG. 1 (stirring speed; rpm, cumulative 90% diameter; μm) are as follows. Point A = (400, 20), Point B = (1000, 3.5), Point C
= (1500, 2.5), point D = (1500, 8.0), point E = (10
00, 10), point F = (400, 90).

In the present invention, MgO powder obtained by stirring or mixing MgO obtained by batch furnace or rotary kiln firing is particularly advantageously applicable.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the procedure of a MgO cohesion test for measuring the particle size distribution of aggregated particles generated when MgO is suspended in water with a laser diffraction type particle size analyzer will be described. Procedure 1) 80 g of MgO is mixed with 500 cc of water at 20 ° C. in a 1000 ml tall beaker (based on JIS R 3503) to form an MgO slurry. At this time, using a paddle-shaped stirrer with four blades (wing length: 25 mm), set the blades at the center of the tall beaker and at a height of 30 mm from the bottom of the beaker, and at a predetermined stirring speed. Stir for 5 minutes. During the stirring, the temperature of the slurry is kept at 20 ° C. Procedure 2) When the MgO slurry stirring process for 5 minutes is completed,
The slurry liquid is immediately collected, and the particle size distribution is measured with a laser diffraction type particle size distribution meter. At this time, water is used as a dispersion medium of the particle size distribution meter, and the liquid temperature of the water is room temperature (15 to 25 ° C.). Procedure 3) Change the slurry stirring speed, and
Repeat 2).

Now, the results of investigating the agglomerated particle distribution of the MgO slurry with respect to the MgO powder having the powder characteristics shown in Table 1 and FIG. 2 are shown in FIGS. 3 and 4.

[0023]

[Table 1]

FIG. 2 shows the results of measuring the average particle size of the MgO powder No. 1 by a laser diffraction particle size distribution analyzer using an ultrasonic homogenizer. FIG. 3 shows the particle size distribution of the aggregated particles generated when the No. 1 MgO powder is slurried, and the slurry stirring speed at this time is 1000 rpm. As shown in FIG. 2, the average particle size of the No. 1 particles is as small as 0.59 μm, and the ratio of the particles having a particle size of 1 μm or less is as small as 86%. As shown in FIG.
The coarse aggregates before and after are generated, and the cumulative 90% diameter is 49.4 μm.

FIG. 4 shows the slurry aggregating characteristics of No. 1 MgO, in which the particle size distribution of the MgO slurry was measured by changing the slurry stirring speed, and the change of the 90% cumulative diameter was measured. As is clear from the figure, it can be seen that the higher the stirring speed at the time of preparing the MgO slurry, the smaller the cumulative 90% diameter becomes, and the smaller the agglomerated particle size becomes. In addition, besides evaluating the cumulative 90% diameter, the aggregated particle generation behavior can be evaluated, for example, by the particle content of 10, 20 μm or more, the cumulative 80% diameter, and the weight ratio of the dispersed particles to the aggregated particles. The size and amount of agglomerated particles generated when MgO is slurried can be quantitatively evaluated by the aggregability test described above.

Next, a detailed investigation was conducted on the structure of the aggregated particles of the MgO powder No. 1. As a result, the aggregated particles were elongated to 10 to 20 μm.
It was found that long low-order aggregates formed a network, and coarse aggregates were high-order aggregates obtained by flocculating the low-order aggregates. Then, the present inventors have next thoroughly studied the influence of the MgO powder characteristics on the formation of such higher-order aggregates and a method for preventing the formation of higher-order aggregates, and have obtained the following findings.

The properties of MgO powder related to the formation of higher order aggregates
Influence (1) The formation of high-order aggregates is due to the content of particles of 1 μm or less (result of MgO particle size distribution by laser diffraction particle size analyzer)
When it becomes 50% or more, it becomes obvious. (2) When the MgO particle size distribution and the citric acid activity distribution are relatively sharp, a higher-order aggregate is easily formed. (3) In MgO such as No. 1 where the formation of higher order aggregates is remarkable,
Aggregation is not easily destroyed even by increasing the stirring speed and the stirring time.

Method for Preventing the Formation of Higher Order Aggregates (1) In order to prevent the formation of higher order aggregates, it is important to prevent flocculation of lower order aggregates. (2) Flocculation of low-order aggregates is prevented by the presence of adjacent MgO having a different citric acid activity and particle size distribution from MgO forming low-order aggregates. That is, flocculation of low-order aggregates can be prevented by mixing several types of MgO. (3) Mg with relatively wide MgO particle size distribution and citric acid activity
In the case of O, when the stirring treatment is performed before the preparation of the MgO slurry, the generation of aggregated particles is further suppressed.

The following experiments were conducted based on the above findings. For the various MgO powders shown in Table 2 with different MgO production conditions, the MgO slurry aggregation characteristics and the MgO slurry application /
The appearance and adhesion after drying were investigated. The results obtained are shown in FIG. The MgO powder No. 8 in FIG.
To 11 are each obtained by performing the following processing. MgO powder No.8: 80% of No.1 mixed with 20% of No.4. MgO powder No.9: 50% of No.2, 40% of No.3 and 10% of No.4 mixed. MgO powder No.10: No.5 only after stirring. MgO powder No.11: A mixture obtained by stirring No.7 alone.

[0030]

[Table 2]

[0031]

[Table 3]

As shown in Table 3, as a result of the cohesion test, it was found that MgO having a large cumulative 90% diameter deteriorated in appearance after the application of the MgO slurry. That is, No. 1 alone forms huge agglomerated particles, and the appearance after application of the MgO slurry is poor. However, in No. 8 which was mixed with No. 4, the cumulative 90% diameter during the cohesion test was significantly lower, and the appearance after application of the MgO slurry was significantly improved. The reason is that No.4, which has lower activity than No.1,
By mixing, the aggregation of No. 1 low order aggregates
This is because the MgO particles of No. 4 hinder, and as a result, the formation of flocculate of low-order aggregates is hindered. Similarly, although large aggregates were formed by No. 2 alone, No. 2: 50%,
In No. 9 in which No. 3: 40% and No. 40: 10% were mixed, the appearance after application of the MgO slurry and the adhesion to the steel sheet were improved as compared with the case of using each MgO alone.

Nos. 5, 7 having a wider activity distribution than Nos. 1, 2, 3, 4, and 6 constitute
Because of the variation in the particle size and activity of MgO, flocculation of low-order aggregates is not easily generated, and therefore, the cumulative 90% diameter in the cohesion test is relatively small, and the appearance of the MgO slurry applied is good. In addition, in Nos. 5 and 7, the dispersion of the particle size and activity of the constituting MgO is effectively utilized by performing the stirring treatment of the powder before preparing the slurry (Nos. 10 and 11). It turns out that cohesiveness falls. In addition, the method of the stirring process or the mixing process, the processing amount, the processing time, and the like are not particularly limited, and the points A, B, C, and C in FIG.
It is important that the MgO slurry has a cohesive property satisfying the region surrounded by D, E and F.

Next, when MgO of Nos. 1 to 11 in FIG. 5 was used, the influence on the forsterite glass coating film properties and the magnetic properties was investigated. C: 0.07 wt%, Si: 3.25 wt%, Al: 0.025 wt%, N: 0.
0080 wt%, Mn: 0.07 wt%, Se: 0.02 wt%, Sb: 0.025 wt
% And Cu: 0.08 wt%, the balance being substantially Fe, the slab for electromagnetic steel was heated at 1380 ° C. for 30 minutes, and then hot-rolled to a thickness of 2.2 mm. The steel sheet was finished to a final thickness of 0.22 mm by performing two cold rollings with an intermediate annealing for one minute. Then, after the cold rolled sheet was decarburized and annealed, No. 1 to 11
Of MgO: 100 parts by weight of TiO ₂
Of water and 8 parts by weight of SnO ₂ and 2 parts by weight of SnO ₂ were slurried under the same mixing conditions (stirring speed: 1000 rpm) as in the cohesion test described above, and 6 parts per side.
g / m ² was applied. Thereafter, a secondary crystal annealing is performed to increase the temperature to 1100 ° C. at a rate of 12 ° C./h.
5 ° C. for 5 hours. Table 4 shows the results obtained by examining the appearance and magnetic properties of the forsterite glass coating of the steel sheet thus obtained.

[0035]

[Table 4]

As shown in Table 4, excellent in Table 3
Appearance of MgO slurry application and adhesion to steel plate were obtained.
When using MgO powder, good forsterite glass coating and magnetic properties were obtained. That is, MgO
It was confirmed that when the aggregating property of the slurry was in a specific range, excellent film properties and magnetic properties were obtained.

In the same manner as described above, a number of MgO powders were examined for the relationship between the MgO slurry cohesion properties and the forsterite glass coating and magnetic properties.
When preparing MgO slurry by suspending O powder and water,
When the particle size distribution of the slurry was measured by a laser diffraction type particle size distribution analyzer, 90% of the cumulative values obtained in points A, B, C, D, and
When the range surrounded by E and F is satisfied, a uniform appearance after application of the MgO slurry and excellent adhesion to the steel sheet can be obtained, and as a result, an excellent forsterite glass coating and magnetic properties can be obtained. It was found to be possible.

The reason why the range surrounded by points A, B, C, D, E and F in FIG. 1 is an appropriate range is as follows. First, it is more cumulative than the line connecting points A, B, and C.
If the 90% diameter is small, on the steel sheet surface after the application of the annealing separator, the adhesion of the annealing separator decreases due to the decrease in the contact area between the steel sheet and MgO, and the film thickness and density of the annealing separator coating layer become uneven. Is generated. In such a case, the slurry viscosity generally decreases excessively, and during drying, the slurry on the steel plate is flowed into the airflow in the drying furnace to generate a very uneven pattern, thereby deteriorating the high-speed coating property. . Also belongs to this area
MgO generally has poor reactivity with the surface oxide layer of the decarburized annealed sheet, and a white film-like film is formed, and the magnetic properties are also degraded through such film formation. On the other hand, if the cumulative 90% diameter is larger than the line connecting the points C, D, and F, the MgO particles are likely to agglomerate, and when suspended in water, coarse particles are formed and the annealing separator is applied. Not only does the surface uniformity suffer,
Because the additive concentration of the annealing separator in the MgO coarse aggregates decreases, the uniform dispersion of the annealing separator additive is inhibited,
The steel sheet cannot be applied in a state where the annealing separator additive is uniformly dispersed on the steel sheet surface. In such a case, the uniformity of the annealing separator on the surface of the steel sheet is deteriorated, so that it is difficult to form a uniform forsterite glass coating.

The MgO of the present invention has a MgO slurry cohesive property satisfying a region surrounded by points A, B, C, D, E and F shown in FIG. It is preferable that As chemical components, CaO: 0.25 to 0.75 wt%, halogen: 0.005 to 0.080
wt%, B: 0.06~0.180 wt% , SO 3: contains less 0.70wt%, it is preferable balance being made of unavoidable impurities and substantially MgO. Here, CaO effectively contributes to the promotion of film formation, but if it is less than 0.25% by weight, the adhesion between the forsterite glass film and the steel sheet decreases, while 0.75% by weight.
If it exceeds wt%, the film thickness becomes too thick, and the space factor decreases. Therefore, CaO is preferably in the range of 0.25 to 0.75 wt%.
Halogen refers to Cl and F in particular, and improves the sinterability of the forsterite film. However, if the content is less than 0.005 wt%, the effect is not exhibited. Occurs. Therefore, halogen is 0.0
The range of 05 to 0.080 wt% is preferred. B promotes the formation of a glass film, but if it is less than 0.06% by weight, the film becomes thin, and if it exceeds 0.18% by weight, the bend characteristics deteriorate. Therefore, B is contained in the range of 0.06 to 0.18% by weight. Is preferred. SO ₃ has a function of improving film adhesion and a function of reinforcing an inhibitor in an electromagnetic steel sheet material containing an MnS or MnSe-based inhibitor. However, since the point-like separation of the glass film occurs exceeds 0.70wt%, SO ₃ is preferably set to less 0.70wt%.

The hydration amount was determined by a hydration test at 20 ° C. for 30 minutes.
Preferably it is 0.5 to 3.5 wt%. This is an element that affects the oxidizing property of the atmosphere during the finish annealing, and is preferably adjusted to an appropriate hydration amount. If the amount of hydration is less than 0.5 wt%, the adhesion of the glass coating is liable to deteriorate, while if it exceeds 3.5 wt%, the inhibitor is oxidized and the possibility of magnetic properties becoming poor increases.

Further, it is preferable that the final reaction rate 40% value of CAA activity (CAA 40%) measured at a liquid temperature of 30 ° C. is in the range of 40 to 150 seconds. If the CAA content is less than 40 seconds, the amount of hydration becomes excessive, while if it exceeds 150 seconds, defects in the glass coating due to a decrease in the amount of hydration and a decrease in solid-phase reactivity tend to occur.

In addition, if the cumulative 50% diameter (by volume) of MgO measured by a laser diffraction type particle size distribution analyzer exceeds 4 μm, the formation of a forsterite glass film is delayed, so that it is preferably 4 μm or less. . More preferably, it is 2 μm or less.

As the annealing separating agent, it is possible to add components normally added to the separating agent, for example, TiO ₂ , titanate, boric acid or borate, Sr compound, Mn compound, Sn compound and the like. . Further, the present invention is applicable to all electromagnetic steel sheets. further,
There is no particular limitation on the manufacturing method, and it may be performed in accordance with a conventional method. That is, the raw steel slab is heated by a known method, hot-rolled, and then cold-rolled once or a plurality of times with intermediate annealing therebetween to obtain a final sheet thickness. If necessary, the hot rolled sheet may be annealed before cold rolling. After these treatments, conventionally known decarburization annealing is performed, and then the annealing separator according to the present invention is applied, and then finish annealing is performed. The finish annealing may be performed by a conventionally known method. After these series of treatments, an insulating tension coat is applied and flattening annealing is performed to finish the product. Thus, a grain-oriented electrical steel sheet having an excellent forsterite glass coating and magnetic properties can be obtained.

[0044]

【Example】

Example 1 C: 0.075 wt%, Si: 3.40 wt%, Al: 0.02 wt%, N: 0.
0075wt%, Mn: 0.07wt%, Se: 0.02wt%, Sb: 0.026wt
% And Cu: 0.08 wt%, and the balance is substantially Fe. The slab for electromagnetic steel is heated at 1400 ° C. for 30 minutes, hot-rolled to a sheet thickness of 2.2 mm, and then heated at 1050 ° C. and 1%. The steel sheet was finished to a final thickness of 0.22 mm by performing two cold rollings with an intermediate annealing for one minute. This cold rolled sheet was subjected to decarburizing annealing, and then MgO powder N shown in Table 5
using MgO in o.1~12 principal ingredient, the MgO: 100 parts by weight of TiO _2: 8 parts by weight of Sr (OH) _2: were obtained by mixing with water annealing separator prepared by adding 3 parts by weight The annealing separator slurry was applied to a decarburized annealed plate at a rate of 6 g / m ² per side.
Table 5 also shows the appearance of the annealed separating agent slurry applied, the condition after drying, and the results of the MgO cohesion test. Then, from 850 ° C in a N ₂ + H ₂ mixed atmosphere
Secondary recrystallization annealing was performed in which the temperature was raised to 1100 ° C. at a rate of 12.5 ° C./h, followed by purification annealing in hydrogen at 1180 ° C. for 5 hours. Table 5 also shows the results of an investigation on the appearance and magnetic properties of the forsterite glass coating of the steel sheet thus obtained.

[0045]

[Table 5]

As is evident from Table 5, when MgO powder satisfying the MgO aggregation characteristics specified in the present invention was used, MgO
The appearance of the O slurry application and the adhesion to the steel sheet were excellent, and the forsterite glass coating after the finish annealing and the magnetic properties were also very good.

Example 2 C: 0.040 wt%, Si: 3.40 wt%, Mn: 0.07 wt%, Se: 0.
A slab for electromagnetic steel containing 02 wt%, Sb: 0.025 wt% and Cu: 0.08 wt%, with the balance being substantially Fe, at 1400 ° C
After heating for 30 minutes at a temperature of 980 mm
℃ 2 times cold rolling with 1 minute intermediate annealing
Finished to a final thickness of mm. After decarburizing annealing this cold rolled sheet,
Using MgO of MgO powder Nos. 1 to 12 shown in Table 6 as a main ingredient,
O: 100 parts by weight, TiO ₂ : 2 parts by weight, and SrSO ₄ : 1.5 parts by weight were added to the annealed separating agent mixed with water. An annealed separating agent slurry was applied to a decarburized annealed plate at 6 g / m 2 per side. ² was applied. Table 6 also shows the results of investigation on the appearance of the annealed separating agent slurry applied, the condition after drying, and the MgO cohesion test. Then, in an N ₂ atmosphere, 845
℃, 50 hours of secondary recrystallization annealing, then in hydrogen
Purification annealing was performed at 1180 ° C. for 5 hours. Table 6 also shows the results of an investigation on the appearance and magnetic properties of the forsterite glass coating of the steel sheet thus obtained.

[0048]

[Table 6]

As is apparent from FIG.
When the MgO powder was used, the appearance of the coated MgO slurry and the adhesion to the steel sheet were excellent, and the forsterite glass coating after the finish annealing and the magnetic properties were also very good.

Example 3 C: 0.030 wt%, Si: 3.19 wt%, Al: 0.013 wt%, N:
0.0086 wt%, Mn: 0.007 wt%, Se: 0.001 wt%, S: 0.
009 wt% and Sb: 0.012 wt%, with the balance being substantially
The slab for magnetic steel, which has the Fe composition, is heated at 1200 ° C, hot-rolled to a thickness of 2.2 mm, then hot-rolled at 900 ° C for 1 minute, pickled, and cold-rolled once. To a final thickness of 0.34 mm. This cold-rolled sheet was subjected to decarburizing annealing at 840 ° C. for 90 seconds, and thereafter MgO powders Nos. 1 to 12 shown in Table 7 were used as a main component, and 100 parts by weight of MgO and 8 parts by weight of TiO ₂ were used. An annealing separator slurry obtained by mixing an annealing separator containing 3 parts by weight of Sr (OH) ₂ with water was applied to a decarburized annealing plate at a rate of 6 g / m ² per side. Table 7 also shows the results of an investigation on the appearance of the annealed separating agent slurry applied, the condition after drying, and the MgO cohesion test. Thereafter, the temperature is raised to 850 ° C in an N ₂ atmosphere, and the temperature is increased from 850 ° C to 1080 ° C.
N ₂ + H ₂ perform secondary recrystallization annealing for heating the Noborinetsu roughness at 20 ° C. / h at a mixed atmosphere, subsequently 1080 ° C. in an atmosphere of H ₂ 5
Time purification annealing was performed. Table 7 also shows the results of an investigation on the appearance and magnetic properties of the forsterite glass coating of the steel sheet thus obtained.

[0051]

[Table 7]

As is apparent from FIG.
When the MgO powder was used, the appearance of the coated MgO slurry and the adhesion to the steel sheet were excellent, and the forsterite glass coating after the finish annealing and the magnetic properties were also very good.

[0053]

The MgO powder for an annealing separator according to the present invention has a specific MgO slurry aggregating property, and when applied as an annealing separator slurry to the surface of a steel sheet, does not generate coarse aggregates and is uniform. A good forsteritic glass coating can be formed much more stably than before, and the magnetic properties can be improved through the formation of such a coating. Can also be stabilized.

[Brief description of the drawings]

FIG. 1 is a view showing an appropriate range of MgO slurry aggregation characteristics of an MgO powder according to the present invention.

FIG. 2 is a view showing the particle size distribution of No. 1 MgO powder.

FIG. 3 is a graph showing the results of measuring the MgO slurry cohesion of No. 1 MgO powder at a stirring speed of 1000 rpm.

FIG. 4 is a view showing the MgO slurry aggregation characteristics of No. 1 MgO powder.

FIG. 5 is a graph showing MgO slurry aggregation characteristics of various MgO powders.

Claims (2)

[Claims] 1. An MgO powder for an annealing separator, wherein the MgO powder is
When the O powder is suspended in water to form an MgO slurry, the cumulative 90% diameter when the particle size distribution of the MgO slurry is measured by a laser diffraction type particle size distribution meter is indicated by points A, B, C, D, and D in FIG. An MgO powder for an annealing separator in the production of grain-oriented electrical steel sheets, characterized by satisfying a range surrounded by E and F. 2. The MgO powder according to claim 1, wherein the MgO powder is obtained by stirring or mixing MgO obtained by baking in a batch furnace or rotary kiln.