JPH11158555A - Production of separation agent for annealing and grain oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation agent for annealing capable of efficiently applying finish annealing to a high-Mn grain oriented silicon steel sheet and also to provide a method of production of a high-Mn grain oriented silicon steel sheet using the above separation agent for annealing. SOLUTION: The separation agent for annealing is composed of a mixed composition containing alumina powder of 0.5-10 μm average grain size and a V compound having V in an amount equivalent to 0.1-10 pts.wt. based on 100 pts.wt. of the alumina powder. The high-Mn grain oriented silicon steel sheet can be produced by subjecting a steel stock, having a composition which consists of, by weight, <=0.01% C, 1.5-4% Si, 1-4% Mn, 0.003-0.03% acid soluble Al, 0.001-0.01% N, and the balance Fe with inevitable impurities and in which the content of S as an inevitable impurity is regulated to <=0.015%, to hot rolling and to cold rolling, annealing the resultant steel sheet continuously in a noncarburizing atmosphere, applying the above separation agent for annealing to the steel sheet so that coating weight after drying becomes (0.5 to 10) g/m<2> , drying it, applying secondary recrystallization annealing at 825-925 deg.C, and then subjecting the steel sheet to purification annealing at 900-1050 deg.C for a time not shorter than the time determined according to purification annealing temp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annealing separator used in finish annealing when manufacturing a grain-oriented electrical steel sheet widely used as an iron core material of a transformer or a generator or a magnetic shielding material, and the like. The present invention relates to a method for producing a grain-oriented electrical steel sheet using the same.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is a soft magnetic material having a {110} <001> crystal orientation called Goss orientation and having excellent excitation and iron loss characteristics in the rolling direction.

[0003] As a method for producing a grain-oriented electrical steel sheet, there are three methods.
A silicon steel material containing about wt% (hereinafter, “% representing the chemical composition of steel means wt%”) and a small amount of a secondary recrystallization inhibitor such as MnS or MnSe was prepared by using 130%
Heating to 0 ° C or higher, hot rolling, annealing and cold rolling once or twice to the final product thickness, primary recrystallization annealing combined with decarburizing annealing After forming an Si oxide layer and applying an annealing separator, 1100 ° C. to 1
A method of finish annealing at 200 ° C. is known. After the finish annealing, the annealing separator is removed, an insulating coating is applied, and flattening annealing that also serves as coating baking is performed.

A slurry containing MgO as a main component is used as an annealing separator in this method. By applying an annealing separating agent to the surface of the steel sheet before the finish annealing, the steel sheet is prevented from seizing, and after the secondary recrystallization, unnecessary inhibitor precipitates in the steel are removed (purified). Furthermore, Si oxide and M
gO is reacted to form a forsterite film (Mg ₂ Si
O ₄ ) acts to form a base glass film having an insulating property and a sealing function. Those containing MgO as a main component facilitate preparation of a slurry and are suitable for continuous coating by a roll coater method.

[0005] However, in the above-mentioned manufacturing method, heat treatment at an extremely high temperature such as heating at an ultra-high temperature of about 1300 ° C. before hot rolling, decarburizing annealing after cold rolling, and finish annealing at 1200 ° C. Requires special annealing. Therefore, it is not easy to reduce the manufacturing cost.

[0006] Japanese Patent Application Laid-Open No. 1-119644 discloses a method of manufacturing a low-cost unidirectional magnetic steel sheet.
It is a method using an ultra-low carbon steel containing 0.5 to 2.5% of Si and 1 to 2% of Mn and trace amounts of Al and N, and finish annealing is performed at 800 to 950 ° C. According to this method, ultra-high-temperature heating before hot rolling and decarburizing annealing after cold rolling become unnecessary, and the finish annealing can be performed at a much lower temperature than the conventional method. Therefore, the manufacturing cost of the grain-oriented electrical steel sheet can be significantly reduced (the steel sheet obtained by this manufacturing method is hereinafter simply referred to as “high M steel sheet”).
n-type unidirectional magnetic steel sheet ").

In a method for producing a high Mn-based grain-oriented electrical steel sheet, a nitride such as AlN is used as an inhibitor. In addition to the N contained in the steel during steel making, this nitride also forms the N absorbed in the steel from the annealing atmosphere during the secondary recrystallization at the initial stage of the finish annealing. Further, during the purification annealing in the latter half of the finish annealing, nitrogen in the steel forming nitride is released into the atmosphere and denitrified to purify the steel. For this reason, it is important to secure an appropriate gap between the steel sheets during the finish annealing, and the selection of the annealing separator plays an important role.

[0008] The annealing separator used in this method is a chemical which forms an oxide or a glass film on the surface of the steel sheet, which can provide an appropriate space between the steel sheets and which may inhibit the nitrogen absorption and denitrification reactions. Those which do not cause a reaction are desirable.

Japanese Patent Application Laid-Open No. 4-259329 discloses, as an annealing separating agent, an alumina powder having a particle diameter of 80% or more in the range of 3 to 100 μm is electrostatically applied to the surface of a steel sheet and finish annealing is performed as the annealing separating agent. A method for producing a high Mn-based grain-oriented electrical steel sheet is disclosed. Here, in order to secure the flow of the atmosphere gas in the coil gap at the time of finish annealing, the particle size of alumina is specified, and electrostatic coating is applied to prevent moisture from being introduced between the steel sheets and prevent surface oxidation. I have. But,
Alumina powder is easily scattered to the outside during electrostatic coating, and workability is not preferable.

JP-A-7-62427 discloses a slurry prepared by adding 0.1 to 2% by weight of a water-soluble polymer binder to alumina powder having an average particle size of 1 to 40 μm to improve the adhesion. Are disclosed. The purpose of this method is to improve the punching properties by annealing without forming a glass film, or to improve the magnetic properties by smoothing the steel sheet surface to a mirror surface. However, in this method, decarburization annealing is required, and pickling for removing an oxide film generated at the time of decarburization annealing is also required.

Japanese Patent Publication No. Sho 58-44152 discloses an annealing separator using an alumina powder to which a hydrated silicate and a compound containing an alkaline earth metal such as Sr, Ba and Ca are added.
A method for producing a grain-oriented electrical steel sheet having no glass film and excellent in punching properties is disclosed. According to this method,
Inhibitors that do not form a glass film and are no longer needed can be efficiently removed by the presence of the alkaline earth metal compound.

However, in this method, during decarburization annealing, an oxide film containing only 0.2 to 1.0 g / m ² as oxygen content on the steel sheet surface (corresponding to an oxide film having a thickness of 0.6 to 3 μm). ) Is required, which is not preferable because a load is applied to the decarburizing annealing step. Further, the precipitates that can be removed by the annealing separator are limited to MnS and MnSe, and are AlN and (, which are inhibitors used in the production of high Mn-oriented unidirectional electrical steel sheets proposed by the present inventors. No consideration is given to Al, Si, Mn) N.

JP-A-3-2380 discloses an annealing separator comprising a mixture of alumina, MgO and a V compound. V is added for the purpose of promoting the removal of S and Se in the steel. According to this method, the ability to remove S and Se to purify the steel is high, and the surface of the steel sheet can be made smooth. However, the annealing separator contains MgO, which reacts with the surface oxide to form a glassy film. For this reason, when manufacturing a high Mn-based magnetic steel sheet, the formation of an inhibitor due to nitrogen absorption from a nitrogen atmosphere hardly occurs, which is not preferable.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an annealing separator capable of efficiently performing finish annealing of a high Mn-based grain-oriented electrical steel sheet, and a high Mn using the same. An object of the present invention is to provide a method for producing a system-oriented electrical steel sheet.

[0015]

The gist of the present invention lies in an annealing separator described in (1) below and a method for producing a grain-oriented electrical steel sheet described in (2).

(1) An annealing separator used for finish annealing of a grain-oriented electrical steel sheet, comprising alumina powder having an average particle size of 0.5 to 10 μm and 100 parts by weight of alumina powder.
V: An annealing separator substantially consisting of a mixed composition with a V compound in an amount corresponding to 0.1 to 10 parts by weight.

(2) The chemical composition is% by weight and C: 0.01
% Or less, Si: 1.5 to 4%, Mn: 1 to 4%, acid-soluble Al: 0.003 to 0.03%, N: 0.001 to
0.01%, balance: Fe and unavoidable impurities, hot rolled a steel material having S as an unavoidable impurity of 0.015% or less, and cold-rolled once or twice including intermediate annealing , A primary recrystallization annealing for continuous annealing in a non-decarburizing atmosphere is performed, and a finish annealing including a secondary recrystallization annealing at 825 ° C to 925 ° C and a purification annealing at 900 ° C to 1050 ° C is performed. In the method for producing a grain-oriented electrical steel sheet, the annealing separator according to the above (1) is used as a slurry, and the coated amount after drying on the steel sheet after primary recrystallization annealing is 0.5 to 1
A method for producing a grain-oriented electrical steel sheet which is applied so as to be within the range of 0 g / m ² , dried and subjected to purification annealing in which the time determined by the following formula is the lower limit of the purification annealing time.

T _min. = (1120-T) / 10 where t _min. Is the lower limit (time) of the purification annealing time, and T is the purification annealing temperature (° C.).

The present inventors have conducted the following experiments regarding the effect of the annealing separator on the removal of nitride inhibitors during purification annealing. As a result, the average particle size is 0.5 to
Annealing separating agent consisting of a mixture of 10 μm alumina powder and V compound is used for the inhibitor AlN and (A
The inventors have found that the present invention is effective in promoting the purification of (1, Si, Mn) N, and completed the present invention.

The present inventors have found that C: 0.003%, Si:
2.35%, Mn: 1.53%, acid-soluble Al: 0.0
10%, N: 0.0042%, balance: Steel having a chemical composition consisting of Fe and unavoidable impurities is hot-rolled, hot-rolled sheet is annealed, pickled, and cold-rolled twice by intermediate annealing. .3
A 5 mm-thick cold-rolled sheet was subjected to continuous annealing for primary recrystallization. A water slurry composed of a mixture of α-alumina powder having an average particle size of 2 μm and V ₂ O ₅ mixed at various ratios is prepared, applied to a steel sheet which is primarily recrystallized, dried, and finished. After annealing and finish annealing, the annealing separator was removed, insulation coating and flattening annealing were performed, and the N content and iron loss ( _{W17 / 50} ) of the obtained steel sheet were measured.

FIG. 1 is a graph showing the results obtained in the above experiment, wherein the vertical axis represents the N content and iron loss of the product, and the horizontal axis represents the V content relative to 100 parts by weight of alumina in the annealing separator. Represents parts by weight of V in the compound. As can be seen from these results, the use of an annealing separator containing 0.1 part by weight or more of V in alumina powder can significantly reduce the N content of the product. Further, the iron loss of the steel sheet becomes particularly good when V is contained in an amount of 0.1 to 10 parts by weight. The iron loss deteriorates in the region where V in the annealing separator exceeds 10 parts by weight because V diffuses and enters the steel sheet.

The present inventors have further found from the experimental results described below that the use of the above-mentioned annealing separator can significantly reduce the time of purification annealing in finish annealing. After preparing a water slurry composed of a mixture of V ₂ O ₅ containing an amount of V corresponding to 1 part by weight with respect to 100 parts by weight of the alumina powder, applying the slurry to the primary recrystallized steel plate and drying the slurry. Then, secondary recrystallization annealing was performed in a nitrogen-hydrogen mixed atmosphere gas, and further, purification annealing was performed in an atmosphere of 100% hydrogen gas by changing the annealing temperature and annealing time variously. Thereafter, the annealing separator was removed, and the iron loss (W _17/50 ) of the steel sheet obtained by performing the insulating coating and the flattening annealing was measured.

FIG. 2 shows the obtained iron losses arranged in the following categories.

A: 1.15 to 1.20 W / kg O: 1.21 to 1.30 W / kg x: 1.31 to 1.40 W / kg Δ: 1.41 to 1.50 W / kg ●: 1 As shown in FIG. 2, good iron loss was obtained when purification annealing was performed in a temperature range of 900 to 1050 ° C. for a certain period of time or more. When the purification annealing was performed at 1100 ° C., the iron loss level worsened. W considered good iron loss level
_The annealing time required to realize _17/50 of 1.30 W / kg or less is based on the _case where the annealing time t (time) is set to (1120-T) / 10 or more according to the annealing temperature T (° C.). It turned out to be obtained. In addition, it was found that the long-time purification annealing exceeding (1270-T) / 10 has little effect of improving iron loss.

[0025]

Embodiments of the present invention will be described below in detail.

(A) Annealing Separating Agent Alumina powder: Alumina powder has a role of preventing seizure of a steel sheet and a role of maintaining a gap for a nitrogen absorption and desorption inhibitor between coil layers.

Alumina, unlike MgO or the like, does not react with steel even when used as an annealing separator interposed between silicon-containing steel sheets heated at a high temperature, and does not inhibit nitrogen absorption and denitrification. There is no danger of forming a film. These alumina powders are preferably applied to a steel sheet as a slurry dispersed in water. As alumina, it is appropriate to use α-Al ₂ O ₃ which does not cause structural change during annealing.
₂ O ₃ or γ-Al ₂ O ₃ may be used.

The average particle size is 0.5 μm or more and 1
It is preferable to use one having a size of 0 μm or less. When the average particle size is less than 0.5 μm, the gap maintained between the coil layers becomes small, and the nitrogen absorption and deinhibition reactions are slowed, so that the magnetic properties are not improved. If the average particle size exceeds 10 μm, the alumina powder tends to settle during slurrying, making it difficult to apply the slurry uniformly and stably. In addition, alumina powder is pushed into the surface of the steel sheet, and the shape of the surface of the steel sheet is damaged, and the magnetic properties are likely to be damaged. Preferably, alumina powder having an average particle size of 1 to 5 μm is used. The average particle size of alumina is measured by a laser diffraction method.

V compound: It is added as a purifier for purifying the nitride as an inhibitor. V may be contained as metal V, but from the viewpoint of workability, safety, economy, etc., V
It is preferable to contain it in the form of an oxide or V sulfide. V
The types of oxides and V sulfides are V ₂ O ₅ , V ₂ O ₅ .nH
₂ O, V ₂ O ₃ , VO ₂ , NH ₄ VO ₃ , V ₂ S ₃ , VOSO ₄
Etc. can be used.

The content of the V compound is as follows: alumina powder: 10
It is an amount necessary for the content of V to be 0.1 part by weight or more, preferably 1 part by weight or more based on 0 part by weight. The upper limit is an amount at which the V content is 10 parts by weight or less, preferably 5 parts by weight or less based on 100 parts by weight of the alumina powder. When the content of V in the annealing separator is less than the above lower limit, the effect of promoting purification is not exhibited, and when the content exceeds the above upper limit, V penetrates into the steel sheet to deteriorate magnetic properties. It is not preferable because it may occur. When the V compound is contained, the average particle size is 0.5 to 10 which is the same as that of alumina.
It is advisable to add as a powder in the range of μm.

The annealing separator of the present invention is substantially composed of a mixed composition of alumina powder and a V compound. In order to enhance the dispersibility of the alumina powder in the slurry, the addition of a commercially available dispersing aid such as polyacrylic acid to the extent that carburization does not occur in the steel sheet does not reduce the effects of the present invention, It may be added. The term “substantially” means that there may be such an additive or an impurity that is unavoidably mixed. When using a dispersing aid, the amount is 0.1%.
The content is preferably in the range of １1% by weight. However, Si in steel
MgO or the like which may form a glass film by reacting with TiO 2 is not contained.

(B) Chemical composition of steel C: In the present invention, the formation of an oxide film on the surface of the steel sheet is suppressed in order to promote nitrogen absorption during finish annealing and not to impair the punchability of the product. . Therefore, the primary recrystallization annealing is not performed in a decarburization annealing atmosphere. Since carbon is not decarburized during annealing, the C content of the steel is reduced to 0.01% or less at the steelmaking stage. The lower the C in the steel, the better, but if the content is 0.01% or less, there is no adverse effect on secondary recrystallization during finish annealing or magnetic aging of the final product.

Si: Since Si has the effect of increasing the electrical resistance of steel, when Si is contained, eddy current loss is reduced and iron loss is reduced. In order to obtain an iron loss reducing effect, the content is preferably 1.5% or more. However, when the content exceeds 4%, the secondary recrystallization becomes unstable, and the workability is reduced, so that the cold rolling becomes difficult. Therefore, the Si content is 1.5 to 4%.
It is good to do.

Mn: In the production method of the present invention, the steel undergoes α-γ transformation during hot rolling. Thereby, the structure of the hot-rolled sheet during hot rolling is refined and uniformized, and secondary recrystallization with a high degree of integration in the Goss orientation during the finish annealing is stably generated. Mn is an element effective for causing α-γ transformation in a high Si ultra-low carbon steel. To cause the α-γ transformation, Mn is preferably contained at 1% or more.

Since Mn also has the effect of increasing the electrical resistance of steel, like Si, increasing Mn content also has the effect of reducing iron loss. However, if Mn is excessively contained, cold workability is impaired and rolling becomes difficult. Therefore, the upper limit of the content is preferably set to 4%.

Acid-soluble Al: An important element that forms a nitride such as AlN or (Al, Si) N which is an inhibitor in the production method of the present invention. When the content of the acid-soluble Al is less than 0.003%, the inhibitor effect is insufficient. However, the content of acid-soluble Al is 0.03%
If it exceeds 3, the dispersed state of the nitride becomes inappropriate and stable secondary recrystallization does not occur. For this reason, the range of the acid-soluble Al content is preferably set to 0.003 to 0.03%.

N: An element necessary for forming a nitride serving as an inhibitor until completion of secondary recrystallization.
When the N content at the stage of the steel material is less than 0.001%, the inhibitor effect is insufficient. If the N content of the steel material exceeds 0.01%, the inhibitor effect is saturated, and a long time treatment is required at the time of purification, which is not economical. Therefore, the N content is 0.001 to 0.01.
%.

Elements other than the above are Fe and inevitable impurities. In particular, S as an unavoidable impurity combines with Mn to form MnS, and deteriorates iron loss of a product. For this reason, the lower the S content, the better, and preferably the content is 0.015% or less. Preferably it is 0.005% or less, more preferably 0.002% or less.

(C) Rolling and heat treatment The steel material having the above chemical composition is melted in a converter, an electric furnace, or the like, and if necessary, subjected to a process such as vacuum degassing. It is made into a slab by a method such as a steel ingot and slab rolling.

Hot rolling: There are no particular restrictions on the hot rolling conditions of the slab, but it is preferred that the slab be heated in the range of 1150 ° C to 1270 ° C and the hot rolling be completed in the range of 700 ° C to 900 ° C. .

Cold rolling: A hot rolled sheet is pickled by a conventional method, and then rolled to a product thickness by one or more cold rollings. Hot rolled sheet is annealed before cold rolling (Hot rolled sheet annealing)
May be. When the hot-rolled sheet is annealed, the dispersion state of the precipitate is optimized, and the crystal structure is made uniform by recrystallization of the hot-rolled sheet, so that the secondary recrystallization is stabilized. The conditions for hot-rolled sheet annealing are not specified, but in the case of continuous annealing, 750 ° C.
It is preferable to heat at 1100 ° C. for 10 seconds to 5 minutes, and in the case of box annealing, it is preferable to heat at 600 ° C. to 950 ° C. for 30 minutes to 24 hours.

When the cold rolling is performed twice or more, intermediate annealing is performed during the cold rolling. Intermediate annealing is 65
It is desirable to carry out at a temperature of 0 ° C to 1000 ° C. Further, in order to obtain a good crystal structure at the time of primary recrystallization annealing described below, the rolling reduction at the time of final cold rolling is preferably set to 40 to 90%.

Primary Recrystallization Annealing: In order to generate stable secondary recrystallization during finish annealing, the heating rate during primary recrystallization annealing is preferably rapid heating. For this reason, it is desirable that the primary recrystallization annealing be performed by a continuous annealing method. Annealing temperature is 700 ℃
The range of -950 ° C is good.

Application of annealing separating agent: After primary recrystallization annealing,
The annealing separator described in (a) is applied to the steel sheet surface. The annealing separator is preferably applied as a slurry mixed with water and dried. Solid content in the slurry is 10-50% by weight
It is preferred that When the weight ratio of the solid content in the slurry is less than 10% by weight, it takes a long time for drying, which is not preferable. When the weight ratio exceeds 50% by weight, the viscosity becomes too high and the application state to the steel sheet becomes unstable. .

The coating amount is 0.5 to 10 by weight after drying.
g / m ² . If the amount is less than 0.5 g / m ² , seizure between the steel sheets occurs or a gap between the steel sheets is not secured, and a product having stable and good magnetic properties cannot be obtained. If it exceeds 10 g / m ² , the adhesion of the annealed separating agent after drying is weakened, dust is easily generated, and the effect of accelerating the purification is saturated, which is disadvantageous in cost. The method of applying the slurry and the method of drying after the application are arbitrary. For example, a known method such as applying by a roll coater method and drying with a hot air oven can be used.

Finish Annealing: Finish annealing consists of two stages, secondary recrystallization annealing and purification annealing.

The purpose of the secondary recrystallization annealing is to grow a recrystallization nucleus having a Goss orientation generated by the primary recrystallization annealing. For good secondary recrystallization, annealing is preferably performed in an atmosphere containing nitrogen gas. By using an atmosphere containing nitrogen gas, the nitride as an inhibitor is prevented from being denitrified. Further, by absorbing nitrogen in the annealing atmosphere into the steel sheet (nitridation) and increasing the amount of nitride serving as an inhibitor, secondary recrystallization with a high degree of integration in the Goss orientation can be stably performed. It is desirable that the concentration of the nitrogen gas in the annealing atmosphere is 10% by volume or more (hereinafter,% representing the composition of the atmosphere gas means volume%). Hydrogen gas or argon gas can be used as the atmospheric gas components other than nitrogen gas, but the former is generally used.

[0048] The secondary recrystallization temperature is preferably in the range of 825 to 925 ° C. If the secondary recrystallization annealing temperature is lower than 825 ° C., the inhibitor has a too strong ability to suppress the grain growth, so that secondary recrystallization does not occur. In a temperature region exceeding 925 ° C., the inhibitor effect becomes weak, and crystal grains having an orientation other than the Goss orientation, such as {211} <111>, grow, and the secondary recrystallized structure having a low degree of integration in the Goss orientation. Occurs. The annealing time is preferably 4 hours or more, but if it exceeds 100 hours, the secondary recrystallization does not proceed any further, so it is meaningless and disadvantageous in cost.

Purification annealing: Nitride in the product impairs the magnetic properties of the product. For this reason, after the end of the secondary recrystallization annealing, purification annealing is performed to remove the inhibitor. The purification annealing atmosphere is preferably a 100% hydrogen gas atmosphere. During the purification annealing, C harmful to magnetic properties is also removed. If the purification annealing temperature is less than 900 ° C., the denitrification effect is small.
The temperature is preferably set to 00 ° C. or higher. However, when the temperature exceeds 1050 ° C., the decarburization and denitrification reactions are saturated, and the γ-transformation may deteriorate the magnetic flux density. For this reason, the purification annealing temperature is preferably in the range of 900 to 1050C.

Since the purification reaction mainly including the denitrification reaction is accelerated as the annealing temperature is increased, the annealing time required for the purification is shorter as the annealing temperature is higher. For this reason, the lower limit (t _min. ) Of the purification annealing time is a value (unit: time) obtained by the following equation when the purification annealing temperature is T (° C.).
It is preferred that

_Tmin. = (1120-T) / 10 If the annealing time is shorter than the above-mentioned time, purification becomes insufficient and iron loss of the product does not improve. Furthermore, iron loss is 1.
To reduce to 20W / kg or less (1270-T) / 10)
Is preferably the lower limit.

After the finish annealing, the annealing separator is removed by a method such as water washing or pickling. Subsequent steps may be performed in the same manner as in the case of a general grain-oriented electrical steel sheet, and if necessary, a known insulating coating containing a phosphate as a main component, flattening annealing and the like can be applied.

[0053]

EXAMPLES (Example 1) C: 0.003%, Si: 2.35%, Mn: 1.
53%, acid-soluble Al: 0.010%, N: 0.004
A steel slab having a chemical composition of 2%, balance: Fe and unavoidable impurities, and having an S content of 0.002% as an unavoidable impurity was heated at a temperature of 1180 ° C and a finishing temperature of 820 ° C.
The sample was hot-rolled at 2.0 ° C. to a thickness of 2.0 mm. On this hot rolled sheet,
After subjecting the hot-rolled sheet to annealing at 880 ° C. for 40 seconds, it was pickled and cold-rolled to a thickness of 0.35 mm by one cold rolling. Furthermore, in a non-decarburizing atmosphere gas consisting of 78% of nitrogen gas and 22% of hydrogen gas, continuous annealing was performed by heating at 880 ° C. for 30 seconds to perform primary recrystallization.

Thereafter, an annealing separator was applied to the surface of the steel sheet under various conditions.

The annealing separator is composed of α-alumina powder having an average particle size of 2 μm and various V powders per 100 parts by weight of alumina powder.
A water slurry containing 30% by weight of a mixture consisting of V ₂ O ₅ powder having an average particle diameter of 0.5 μm in an amount corresponding to parts by weight was prepared, and the amount of adhesion after drying on one surface of the steel plate which was primarily recrystallized was determined. 5 g / m ² by roll coating method,
It was dried at 0 ° C. for 30 seconds and wound into a coil. further,
For comparison, a steel sheet (sample No. 10 shown in Table 1) obtained by applying 5 g / m ^{2 of} an alumina powder having an average particle diameter of 5 μm by an electrostatic coating method and winding it into a coil shape, and 10% by weight of a MgO powder
The contained water slurry was applied so that the adhesion amount after drying was 5 g / m ^2, and dried to prepare a coiled steel sheet (test number 11 shown in Table 1).

These steel sheets were subjected to finish annealing in an atmosphere gas consisting of 25% of nitrogen gas and 75% of hydrogen gas.
After performing secondary recrystallization annealing heating at 85 ° C. for 24 hours,
Switch to an atmosphere of 100% hydrogen gas, 24 hours at 940 ° C
Purification annealing for heating for hours was performed. After the finish annealing, the annealing separator is removed by washing with water, and a known insulating coating mainly composed of phosphate is applied to both surfaces so as to have an adhesion amount of 3 g / m ^2, and nitrogen gas 80% and hydrogen gas 20 % Flattening annealing at 800 ° C. for 1 minute in an atmosphere gas. The N content and the V content of the obtained steel sheet were measured by chemical analysis, and the magnetic properties were measured according to the measurement method specified in JIS-C-2550.

Table 1 shows the results of these measurements.

[0058]

[Table 1]

As shown in Table 1, in Test Nos. 1 to 6 produced using the annealing separator specified in the present invention, a sufficient purifying effect was observed by adding the V compound, and the iron loss was reduced to the target value. 1.30 W / kg or less, and the magnetic flux density was also good. On the other hand, in Test No. 7 in which no V compound was added to the annealing separator, and in _Test No. 8 in which the amount of the V compound added was too small, denitrification was insufficient and iron loss (W _17/50 )
Was not preferred. In Test No. 9 in which the added amount of the V compound was too large, denitrification was sufficiently performed, but V penetrated into the steel sheet, and the iron loss became worse. In Test No. 10 in which alumina powder was electrostatically applied, the denitrification was insufficient, and in Test No. 11 in which MgO powder was applied in slurry, the inhibitor was insufficient due to insufficient nitrogen absorption during secondary recrystallization annealing. Insufficient formation of Goss orientation resulted in an increase in magnetic flux density,
Denitrification was insufficient and iron loss was not good. (Example 2) A steel slab having the same chemical composition used in Example 1 was hot-rolled at a heating temperature of 1180 ° C and a finishing temperature of 820 ° C to obtain a hot-rolled sheet having a thickness of 2.3 mm. After pickling, rolling reduction 52
%, Was subjected to intermediate annealing by heating at 650 ° C. for 12 hours, and was subjected to a second cold rolling (a reduction of 68%) to a thickness of 0.35 mm. This cold-rolled sheet was subjected to continuous annealing by heating at 880 ° C. for 30 seconds in a non-decarburizing atmosphere gas consisting of 78% of nitrogen gas and 22% of hydrogen gas, to cause primary recrystallization. Then, α of various average particle sizes
-Alumina powder and 100 parts by weight of alumina powder,
V having an average particle size of 0.5 μm corresponding to 1.0 part by weight of V
A water slurry containing 25% by weight of a mixture with ₂ O ₅ or V ₂ S ₃ powder was prepared, and the adhesion amount after drying was 5 g / m ^2.
Then, it was applied to one side of a steel plate which had been subjected to primary recrystallization by a roll coating method, dried at 250 ° C. for 30 seconds, and wound up in a coil shape.

Thereafter, as the finish annealing, nitrogen gas 25
% And hydrogen gas at 75% for 24 hours at 885 ° C. and 100% hydrogen gas.
Purification annealing was performed by heating at 940 ° C. for 24 hours in an atmosphere gas of. After the finish annealing, it was washed with water to remove the annealing separating agent, and the insulating coating and the flattening annealing were performed in the same manner as in Example 1. The N content and the V content of the obtained steel sheet were measured by chemical analysis, and the magnetic properties were measured according to the measurement method specified in JIS-C-2550. Further, the adhesion of the annealing separator after applying and drying the annealing separator was evaluated according to the following criteria.

：: No peeling, no generation of dust, etc.

Δ: Slight peeling, dust generation of less than 2 mg / m ³ .

(Measurement of the amount of dust is in accordance with the provisions of JIS-B-9921) ×: Dust of 2 mg / m ³ or more is generated, and uneven application of the annealing separator occurs.

Table 2 shows the results.

[0065]

[Table 2]

Test Nos. 15 to 18, 20, and 21 manufactured within the condition range specified by the present invention had good magnetic flux density and iron loss.

In Test No. 19, in which the applied amount of the annealing separator was large, dust was remarkably generated when the coil was dried and wound up in a coil shape. Seizure of the steel sheets occurred. In Test No. 21, slight peeling of the annealing separator and generation of dust were observed, but at a level at which there was no problem in operation.

Test No. 1 using an annealing separator having an average alumina particle size of less than 0.5 μm, which was tested as a comparative material
Sample Nos. 2, 13 and 14 where the amount of the applied annealed separating agent was too small were poor in both magnetic flux density and iron loss. It is considered that the degree of integration of Goss orientation was lowered because the nitrogen absorption was not sufficiently performed and the inhibitor required for stable secondary recrystallization was not formed. In Test Nos. 22 and 23 in which the average particle size of alumina exceeded 10 μm, coating unevenness occurred along with peeling of the annealing separator and generation of dust. Further, the alumina powder was pushed into the steel plate, etc., and the surface of the steel plate became uneven, resulting in poor magnetic properties.

(Example 3) A steel slab having the same chemical composition used in Example 1 was hot-rolled under the same conditions as in Example 2 to obtain a hot-rolled sheet having a thickness of 2.3 mm. Under the same conditions as in Example 2, two cold rollings with an intermediate anneal were performed to obtain 0.35
A cold-rolled sheet having a thickness of mm was subjected to continuous annealing under the same conditions as in Example 2 to cause primary recrystallization. Then, an α-alumina powder having an average particle diameter of 3 μm and V powder having an average particle diameter of 0.5 μm in an amount corresponding to 1 part by weight of V with respect to 100 parts by weight of the alumina powder.
A water slurry containing 30% by weight of a mixture with ₂ O ₅ powder was prepared and applied to one side of a steel sheet which had been primary recrystallized by a roll coating method so that the adhesion amount after drying was 5 g / m ^2. After drying at 30 ° C. for 30 seconds, it was made into a coil and subjected to finish annealing. Finish annealing: nitrogen gas 25%, hydrogen gas 75
% In an atmosphere gas consisting of 870 ° C. for 24 hours, and then switched to an atmosphere of 100% hydrogen gas and a temperature range of 870 to 1100 ° C. for 5 to 50 hours.
Time purification annealing. After finishing annealing, insulating coating and flattening annealing were performed in the same manner as in Example 1. The iron loss W _17/50 of the obtained steel sheet was measured according to a measurement method specified in JIS-C-2550.

Table 3 shows the obtained iron loss.

[0071]

[Table 3]

As shown in Table 3, when iron was purified and annealed at a temperature of 900 ° C. or more for an annealing time longer than the time calculated by the equation, good iron loss was obtained. On the other hand, for comparison, trial Nos. 24 and 25 in which the purification annealing temperature was less than 900 ° C., or the purification annealing temperature of 900
Even if the temperature is not less than ℃, the iron loss is 1.C in the test numbers 26, 30 and 35 in which the annealing time was less than the time required by the formula.
It exceeded 30 W / kg. In sample numbers 39 to 41 in which the purification annealing temperature was 1100 ° C., iron loss was not preferable.

[0073]

According to the present invention, the annealing separator prepared by mixing the V compound with the alumina powder can be applied as a slurry with water, so that the application operation is easy. Since this annealing separator does not form a glass film on the surface of the steel sheet, the steel can be easily purified at the time of finish annealing high Mn silicon steel. For this reason, finish annealing becomes possible at low temperature and in a short time,
A grain-oriented electrical steel sheet using a high Mn-based silicon steel excellent in magnetic properties can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of a V compound added to an annealing separator and the iron loss and N content of a product.

FIG. 2 is a view showing a situation in which the purification annealing temperature and time affect iron loss when finish annealing is performed using the annealing separator of the present invention.

Claims (2)

[Claims] 1. An annealing separator used for finish annealing of a grain-oriented electrical steel sheet, comprising: an alumina powder having an average particle size of 0.5 to 10 μm;
An annealing separator substantially consisting of a mixed composition with a V compound in an amount corresponding to 0.1 to 10 parts by weight. 2. Chemical composition in weight%, C: 0.01% or less, Si: 1.5-4%, Mn: 1-4%, acid soluble A
l: 0.003 to 0.03%, N: 0.001 to 0.0
1%, balance: steel material consisting of Fe and unavoidable impurities and having S as an unavoidable impurity of 0.015% or less is hot-rolled and subjected to one or two cold rolling operations including intermediate annealing. After that, a primary recrystallization annealing for continuous annealing in a non-decarburizing atmosphere is performed, and a finish annealing including a secondary recrystallization annealing at 825 ° C. to 925 ° C. and a purification annealing at 900 ° C. to 1050 ° C. is performed. In the method for producing a conductive magnetic steel sheet, the annealing separator according to claim 1 is used as a slurry, and the coated amount after drying on the steel sheet after primary recrystallization annealing is in the range of 0.5 to 10 g / m ^2. A method for producing a grain-oriented electrical steel sheet which is subjected to purification annealing with the time determined by the following formula as the lower limit of the purification annealing time. t _min. = (1120−T) / 10 where t _{min .} : lower limit (time) of the purification annealing time, T: purification annealing temperature (° C.).