JP5130488B2 - Oriented electrical steel sheet with excellent magnetic properties and coating adhesion and method for producing the same - Google Patents

Description

  The present invention relates to a unidirectional electrical steel sheet used for a static inductor such as a transformer. In particular, the present invention relates to a uniform and excellent adhesive film that is resistant to pickling when removing an unreacted annealing separator and a unidirectional electrical steel sheet that stably has excellent magnetic properties.

Unidirectional electrical steel sheets are mainly used for static inductors represented by transformers. The characteristics to be satisfied are as follows: (1) Energy loss when excited by alternating current, that is, iron loss (represented by energy loss W _17/50 having a magnetic flux density of 1.7 T and a frequency of 50 Hz) is small (2 ) It has high permeability in the excitation range of equipment and can be excited easily. (3) The magnetostriction that causes noise is small.

  In particular, regarding (1), T. is an index representing the value of a transformer because it is continuously excited and generates energy loss over a long period from when the transformer is installed until it is discarded. O. C. This is the main parameter that determines (Total Owning Cost).

  Many developments have been made so far in order to reduce the iron loss of the unidirectional electrical steel sheet. That is, (1) Increasing accumulation in the {110} <001> orientation called Goss orientation, (2) Increasing the content of a solid solution element such as Si that increases electrical resistance, (3) Plate thickness of the steel plate (4) Applying a ceramic coating or insulating coating that imparts surface tension to the steel sheet, (5) Reducing the size of crystal grains, and (6) Introducing strain and grooves in a linear shape By subdividing the magnetic domain.

  One of typical techniques for improving the magnetic flux density is a manufacturing method disclosed in Patent Document 1. This is a manufacturing method in which AlN and MnS function as an inhibitor that suppresses crystal grain growth, and the rolling reduction in the final cold rolling step is over 80%.

By this method, the orientational degree of crystal grains in the {110} <001> orientation is increased, and a grain-oriented electrical steel sheet having a high magnetic flux density of B ₈ (magnetic flux density at an excitation force of 800 A / m) of 1.870 T or more is obtained. can get.

In particular, recently, there is an increasing demand for reducing power loss from the viewpoint of energy saving, and it is desired to increase the magnetic flux density of grain-oriented electrical steel sheets as a means of reducing iron loss to meet this demand. Furthermore, as a technique for improving the magnetic flux density, for example, Patent Document 2 discloses a method of adding 100 to 5000 g / T Bi to molten steel, and a product having B ₈ of 1.95 T or more is obtained. .

Such grain-oriented electrical steel sheets usually have an insulating coating (hereinafter, the entire coating is referred to as a forsterite coating) mainly composed of forsterite (Mg ₂ SiO ₄ ) on the surface layer. This is because, when performing decarburization annealing, the Si oxide formed on the surface layer, and the annealing separator mainly composed of MgO applied to prevent fusion between the steel plates when coil annealing is performed. However, it is formed by causing a solid phase reaction of 2MgO + SiO ₂ → Mg ₂ SiO ₄ during the finish annealing process.

  In addition to imparting insulation to the grain-oriented electrical steel sheet, this film applies tension to the steel sheet due to the difference in thermal expansion coefficient between the film and the steel sheet and the thermal stress generated based on the elastic modulus of the film. , Has the effect of reducing iron loss.

In the case of a grain-oriented electrical steel sheet using an AlN inhibitor, Al produced by the dissolution of AlN in the steel at a high temperature and Mg ₂ SiO ₄ on the steel sheet surface undergo a substitution reaction, and partly MgAl ₂ O ₄ This Mg ₂ AlO ₄ also contributes to the application of tension.

  Furthermore, the coating film is required to be a uniform and defect-free film with excellent adhesion that can withstand shearing, punching, and bending. In this regard, a number of techniques for incorporating a Ti compound into an annealing separator have been disclosed.

For example, Patent Document 3 contains 2 to 40 parts by weight of the Ti compound with respect to 100 parts by weight of the Mg compound, and Patent Document 4 discloses 2 to 2 parts by weight with respect to 100 parts by weight of the heavy low activity MgO. It is disclosed that the uniformity and adhesion of a forsterite film is improved by mixing 20 parts by weight of TiO ₂ .

  However, a technique for industrially satisfying these film characteristics and high magnetic characteristics has not been sufficiently established.

  In addition, in order to obtain a high space factor when magnetic steel sheets are laminated as an iron core, it is desired that the surface is smooth and that the forsterite film is thin.

  In order to smooth the surface, it is important to cleanly remove the unreacted annealing separator so that no unreacted annealing separator remains after the finish annealing. For this reason, many annealing separators with excellent cleaning and removing properties have been proposed. However, industrially, the adhesive is mechanically scraped off with a brush while applying water, and a thin acid is further removed. Usually, MgO is dissolved and removed by using the above-mentioned.

In particular, when the thickness of the forsterite film, which is a non-magnetic layer, is reduced to, for example, about 0.9 to 1.2 g / m ² per unit area of oxygen to improve substantial magnetic properties. In this pickling process, iron oxide is formed in the forsterite film because it tends to contain many defects. This causes poor coating appearance and poor adhesion. After this, aluminum phosphate and colloidal silica are used as an insulating layer. When applying and baking the slurry as the main component, there was a problem that a reaction layer was formed and the film adhesion deteriorated.

Japanese Patent Publication No. 40-15644 Japanese Patent Laid-Open No. 06-88171 Japanese Patent Publication No.51-12451 Japanese Patent Publication No.49-29049 JP-A-8-269552 JP-A-8-295937 Japanese Patent Laid-Open No. 9-118921 Japanese Patent Laid-Open No. 6-179777 JP-A-8-291390 JP-A-9-184017

  In the grain-oriented electrical steel sheet used as the electrical equipment iron core material, the present invention achieves both good magnetic properties and excellent film adhesion, and has acid resistance even when the forsterite film is thinned, And it aims at providing the grain-oriented electrical steel sheet which can be manufactured industrially stably, and its manufacturing method.

  In order to solve the above problems, the present invention has the following gist.

(1) A unidirectional electrical steel sheet containing, by mass%, Si: 2 to 5%, having a forsterite film on the surface of the steel sheet and having a saturation magnetic flux density B ₈ of 1.90 T or more, The stellite film has an oxygen basis weight of 0.85 to 1.20 g / m ² , contains one or two of Ce and La, and the forsterite film has a color of L ^* a ^* b ^* A unidirectional electrical steel sheet excellent in magnetic properties and coating adhesion, characterized in that the yellowness b ^* of the system color system color coordinates is 1.0 or more and less than 7.0.

(2) By mass%, C: 0.02-0.10%, Si: 2-5%, acid-soluble Al: 0.010-0.065%, N: 0.003-0.0150%, S And a total of one or two selected from Se: 0.001 to 0.040%, Mn: 0.02 to 0.30%, and the balance comprising Fe and inevitable impurities, After heating to a temperature of 1280 ° C. or higher, performing hot rolling, annealing, pickling, then performing cold rolling twice or once with annealing, followed by decarburization annealing, MgO In the manufacturing method for producing a unidirectional electrical steel sheet by applying an annealing separator having a main component, and performing final finish annealing, the Ti compound is added to the MgO mass in the annealing separator having the main component MgO. respect, 1-10% in terms of TiO _2, one of Ce compound and La compound Alternatively, two types are added in an amount of 0.5 to 10% in terms of (Ce + La) with respect to the mass of MgO, and the coil heating rate in the final finish annealing step is from 850 to T ° C. (T = 950 to 1050). Is 13 to 50 ° C./h, and T to 1150 ° C. is less than 3 to 13 ° C./h. A method for producing a grain-oriented electrical steel sheet excellent in magnetic properties and film adhesion.

  (3) In the annealing separator having MgO as a main component, 0.1 to 1% of sulfate is added in terms of S with respect to the mass of MgO, as described in (2) above A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and coating adhesion.

  (4) The slab further contains 0.0005 to 0.0200% Bi in mass%, and is excellent in magnetic properties and film adhesion as described in (2) or (3) above A method for producing a grain-oriented electrical steel sheet.

  In the grain-oriented electrical steel sheet used as an electrical equipment iron core material, the present invention includes a Ti compound and a Ce compound, or one or two La compounds in an annealing separator mainly composed of MgO in the production process. While adding an appropriate amount of seeds, the coil heating rate in the final finish annealing step is 13-50 ° C / h until 850-T ° C (T = 950-1050), and 3-13 ° C / h until T-1150 ° C. By performing the two-stage heat treatment for h, it is possible to provide a grain-oriented electrical steel sheet that is excellent in magnetic properties and coating adhesion, and further in coating appearance.

  In addition, according to the present invention, the coating properties can be further improved by using sulfate as an additive to the annealing separator, and Bi can be added to the slab to further improve the magnetic properties. Even in the case of improvement, it is possible to achieve both excellent film adhesion and appearance. Therefore, the effect of the present invention is very large in industry.

  Hereinafter, the present invention will be described in detail.

  In order to develop a technology for producing a grain-oriented electrical steel sheet having a uniform coating film with few coating defects and having good film adhesion and high magnetic flux density, the present inventors have added an additive to the annealing separator, The following experiment was conducted from the viewpoint of finish annealing conditions.

  In a vacuum melting furnace, by mass, C: 0.08%, Si: 3.25%, Al: 0.03%, N: 0.008%, S: 0.028%, Mn: 0.08 A steel ingot having a component composition of% was prepared, heated at 1350 ° C. for 1 hour, and then hot rolled. A hot-rolled sheet having a thickness of 2.2 mm was annealed at 1140 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.22 mm.

Further, the cold-rolled sheet was subjected to decarburization annealing at 850 ° C. for 100 seconds in wet hydrogen, and an annealing separator having 5% TiO ₂ added to MgO to MgO as an annealing separator. Furthermore, two types of annealing separators with 2% CeO ₂ added in terms of Ce to MgO were applied in water slurry, and finish annealing was performed under various heating conditions.

At this time, the wet hydrogen conditions for the decarburization annealing were adjusted so that the amount of oxygen per one side of the forsterite film formed was about 1.2 g / m ² .

  Thereafter, the obtained steel sheet was washed with water to remove the unreacted annealing separator. Since the color of the surface forsterite film was different depending on the conditions, the color of the film was measured using a Minolta CM2500-d color difference meter. Thereafter, the steel plate was sheared to a single plate magnetic measurement size, an insulating film forming composition liquid mainly composed of aluminum phosphate and colloidal silica was applied and baked, and magnetic flux density B8 and film adhesion were evaluated. .

Here, B ₈ is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz, and a higher value is preferable. The film adhesion is a film remaining rate when a bending test is performed with a curvature of 10 mmφ, and a higher one is preferable. In the evaluation, B ₈ ≧ 1.90T and a film remaining rate of 90% or more were determined to be good.

  Some steel plates were washed with water, immersed in a 5% HCl aqueous solution at 70 ° C. for 30 seconds, dried, then observed for appearance, and those with no coating deterioration such as red rust were washed. It was determined that the surface properties were good.

  In the finish annealing, the temperature is increased from 850 ° C. to 50 ° C./h in an atmosphere containing 75% nitrogen and 25% hydrogen, and then the temperature increase rate from 850 ° C. to 1200 ° C. is shown in A to E of Table 1. Thus, the temperature is changed in the range of 5 to 25 ° C./h, and further, as shown in F to J, the heating rate is switched from 15 ° C./h to 10 ° C./h, and the switching temperature is changed to 925 to 1075 ° C. It was. Further, after the temperature reached 1200 ° C., the holding annealing was performed in 100% hydrogen for 20 hours.

Table 1 shows the results. In A to E in which the heating rate of finish annealing is changed, B ₈ ≧ 1.90 T is obtained at a heating rate of 10 ° C./h or less, and the magnetic flux density is good. However, when only TiO ₂ is added at 10 ° C./h or less, the film adhesion deteriorates and the surface properties after pickling are also poor, so there is a condition for achieving both the magnetic flux density and the film adhesion. There wasn't.

Further, when CeO ₂ was added, the film adhesion was improved, but the surface properties after pickling remained poor. In F to J in which the switching temperature from 15 ° C./h to 10 ° C./h is changed, B ₈ ≧ 1.90 T in G, H, and I where the switching temperature T = 950 to 1050 ° C. It can be seen that the residual rate of 90% is compatible, and high magnetic flux density and good film adhesion are compatible.

However, the surface properties after pickling were insufficient when only TiO ₂ was added, but it was also found that those with CeO ₂ added were good.

In particular, in all of the good surface properties after pickling, the forsterite film has a yellow color, and the tristimulus values X, Y, and Z (JIS Z 8722) of the reflective object are measured using a color difference meter. (1982)) was measured, and the L ^* a ^* b ^* color specification specified in JIS Z 8729 (1980) was performed. In any case, the yellowness b ^* of the color coordinates was greater than 1.0. The product was found to have good resistance to pickling.

X-ray diffraction measurement of this yellow forsterite coating confirmed that TiN was present in the coating. Between the obtained b ^* value and the TiN X-ray diffraction peak intensity and Ti basis weight, However, no clear correlation was obtained.

For example, by chemical analysis, measurement of the Ti basis weight and N basis weight of the H1 and H2 of Table 1, H1, each, per side ^{0.158g / m 2, 0.061g / m} 2, H2 0. 123 g / m ^2, and 0.051 g / m ^2, the higher yellowness is necessarily did not mean high Ti and N content.

Although the cause is not clear, TiN exhibits a golden color in the case of a stoichiometric composition, whereas when excessive N or O enters the face-centered cubic crystal lattice of TiN, it will turn brown. Since the yellowness decreases, it is considered that whether or not the stoichiometric TiN is formed and the abundance ratio of TiN in the coating are important in determining b ^* .

TiN formation in the coating is not simply formed by reaction of the additive TiO ₂ with N ₂ in the finish annealing atmosphere. This is because TiN is not observed in the unreacted annealing separator, and MgTi ₂ O ₄ which is a composite oxide of Ti ₂ O ₃ and MgO generated by reduction of TiO ₂ is observed. I understand. That is, the formation of TiN requires reduction of TiO ₂ to Ti and reaction with active N.

In order to reduce TiO ₂ to Ti, a deoxidation reaction with a metal that is very easily oxidized is effective, and Al in steel formed by dissolving an AlN inhibitor in steel at a high temperature is a candidate. is there. In other words, Al diffused to the surface layer causes reduction of TiO _{2 on} the surface of the ground iron. Or the influence of Ti which dissolves in steel in the equilibrium between Fe and TiO ₂ is also considered.

  In any case, due to the reaction with Ti formed at the iron-iron interface, TiN itself seems to exist at the iron-iron interface. When actually observed with an electron microscope, TiN is in contact with the iron It is confirmed that it exists.

  Such TiN is considered to have a feature that it has high adhesion due to its good lattice matching with α-Fe, and has an effect of acid resistance by covering the exposed portion of the ground iron.

  In addition, it is confirmed by the fluorescent X-ray analysis or chemical analysis of the coating that Ce and La are present in the coating. Therefore, Ti, Ce, and La enter the forsterite coating, Therefore, it is possible that yellow coloration is caused, or Ce and La sulfide formed by reaction of Ce and La with S in steel may cause yellow coloration. I can't deny it.

However, in any case, it is confirmed that the yellow forsterite film has excellent film properties in acid cleaning, film adhesion, and magnetic properties. As a characteristic of the forsterite film, the yellowness b ^* is It becomes a direct judgment index.

From the above, the present inventors applied the annealing separator containing TiO ₂ and CeO _2, and then set the finish annealing heating rate relatively fast in the first half and gradually increasing the temperature from the middle, thereby increasing the yellowness. The present inventors completed the present invention by newly discovering that b ^* is high, resistance to pickling when removing the unreacted annealing separator, excellent film adhesion, and magnetic properties can be achieved.

  Subsequently, embodiments of the present invention will be described below.

  First, the components contained will be described in detail. In addition,% means the mass%.

  Si is an important element for increasing electrical resistance and reducing iron loss. When the content exceeds 5%, the material is easily broken during cold rolling, and rolling is impossible. On the other hand, if the Si amount is too low, the electrical resistance decreases and the iron loss in the product increases, so the lower limit is made 2%. A preferred lower limit is 2.5%, but a more preferred range is 2.8 to 3.5%.

  Although there are various roles of C, if it is too small, the crystal grain size at the time of slab heating becomes too large and the iron loss of the product increases. Moreover, when too much, in the decarburization annealing which is an intermediate process, long-time annealing will be forced and productivity will fall. Therefore, the lower limit is 0.02%, and the upper limit is 0.10%. Within this range, a more appropriate range is 0.05 to 0.09%.

  Acid-soluble Al and N are essential elements for bonding to form AlN that functions as an inhibitor. The range of acid-soluble Al is 0.010 to 0.065%, and the range of N is 0.003 to 0.015%. Below these lower limits, the function of AlN as an inhibitor is too weak and does not cause secondary recrystallization. On the other hand, when the upper limit is exceeded, the secondary recrystallization temperature becomes too high, resulting in poor secondary recrystallization. Will occur. In this range, the more appropriate amounts are 0.020 to 0.035% for acid-soluble Al and 0.006 to 0.010% for N.

  Mn is an important element forming MnS and / or MnSe called an inhibitor that influences secondary recrystallization. If it is less than 0.02%, the absolute amount of MnS and / or MnSe necessary for causing secondary recrystallization is insufficient, which is not preferable. On the other hand, if it exceeds 0.30%, not only solid solution during slab heating becomes difficult, but also the precipitation size during hot rolling tends to become coarse, and the optimum size distribution as an inhibitor is impaired, which is not preferable.

  S and / or Se is an important element that forms Mn and MnS and / or MnSe described above, and is added in a total amount of 0.001 to 0.040%. If it deviates from the above range, a sufficient inhibitor effect cannot be obtained.

  There is a technique for achieving a high magnetic flux density by adding Bi (see Patent Document 5) as an inhibitor constituent element other than AlN, MnS, and / or MnSe. The range of Bi is 0.0005 to 0.0200%. If it is less than the lower limit, there is no effect in increasing the magnetic flux density. Even if the upper limit is exceeded, the effect of improving the magnetic flux density is not only saturated, but also the film adhesion is deteriorated. In this range, a more appropriate amount is 0.0010 to 0.0100%.

  Moreover, Te, Cu, B, Pb, Mo, Sb, Sn, Ti, V, etc. exist as other inhibitor constituent elements, but these may be added.

  Subsequently, each process condition will be described.

  The molten steel for producing grain-oriented electrical steel sheets with the component composition adjusted as described above is cast by a normal method. In particular, the casting method is not limited. Then, it is rolled into a hot rolled coil by ordinary hot rolling.

  Usually, slab heating is performed at a high temperature of 1280 ° C. or higher in order to sufficiently dissolve AlN and an inhibitor component of MnS or MnSe. Although the upper limit of the slab heating temperature is not particularly defined, it is preferably 1450 ° C. or less from the viewpoint of equipment. Further, within this range, a more preferable temperature range is 1300 ° C. or higher, and 1330 ° C. or higher is more appropriate.

  The above-mentioned slab piece is made into a hot-rolled sheet by subsequent hot rolling. The thickness of the hot-rolled sheet is not particularly specified because it is related to the cold rolling rate described later, but is usually 1.8 to 3.0 mm. The hot-rolled sheet is cold-rolled immediately or after being annealed for a short time. This annealing is performed in the temperature range of 750 to 1200 ° C. for 30 seconds to 10 minutes, and is effective for enhancing the magnetic properties of the product. Cold rolling may be performed at a final cold rolling reduction rate of 80% to 95%. Further, cold rolling may be performed twice with annealing.

  Decarburization annealing is performed in a hydrogen-nitrogen-containing wet atmosphere, C is reduced to 20 ppm or less without magnetic aging deterioration, and at the same time, the cold-rolled strip is subjected to primary recrystallization to prepare for secondary recrystallization. To do. Prior to decarburization annealing, it is preferable to recrystallize at a heating rate of 80 ° C./sec or more in the previous stage in order to improve iron loss. Then, the slurry of the annealing separator which has MgO as a main component is apply | coated, and coil winding is performed.

  The wound coil is subjected to batch-type finish annealing, and then unwound to remove the unreacted annealing separator, and then an insulating film forming composition liquid mainly composed of aluminum phosphate and colloidal silica. Apply and bake to complete the product of grain-oriented electrical steel sheet.

  The finish annealing is a step of expressing good secondary recrystallization, which is most important in the manufacture of grain-oriented electrical steel sheets, and is usually performed in a hydrogen-nitrogen mixed atmosphere. From the viewpoint of productivity, it is preferable to anneal relatively quickly in the range of 20 to 100 ° C./h until annealing at 850 ° C.

  In the subsequent temperature range from 850 ° C. to 1150 ° C., secondary recrystallization was developed, followed by annealing at a temperature of 1150 to 1200 ° C. for about 20 hours, and N, S, Se, etc. were diffused outside the steel plate. As a result, the magnetic properties of the product plate are improved.

Here, in order for the yellowness b ^{* of the} forsterite film after finish annealing to be in the range of 1.0 to 7.0, a Ti compound is important as an additive to the annealing separator. In this case, the Ti compound, it is desirable to add in the range of 1-10% in terms of TiO _2. When the amount added in terms of TiO ₂ is less than 1%, the supply of Ti for exhibiting sufficient b ^* is insufficient, and acid resistance and film adhesion cannot be obtained.

On the other hand, if it exceeds 10%, the iron loss characteristic of the product plate deteriorates due to diffusion of Ti into the steel, so the amount of Ti compound added is limited to the above range. A more preferable range is 2 to 8%, and a further preferable range is 3 to 5%. Examples of the form of the Ti compound include TiO ₂ , Ti ₃ O ₅ , Ti ₂ O ₃ , TiO, and Ti (OH) ₄ .

In addition, it is essential to contain 0.5 to 10% by mass of Ce and La compound in terms of (Ce + La) in the annealing separator so that the b ^* of the forsterite film is 1.0 to 7.0. It is a requirement. If it is less than 0.5% by mass, sufficient b ^* is not reached, and if it exceeds 10%, conversely, b ^* becomes small. As (Ce + La) conversion, it is preferably 1 to 8% by mass, and more preferably 1 to 4% by mass.

The functions of Ce and La are not clear, but are considered as follows. If the cause of b ^* is stoichiometric TiN, it is necessary that Ti is not lost as another compound and that no impurities are mixed into TiN.

When there is an oxide of Ce or La (Ce and La compounds are considered to be in an oxide state due to moisture contained in MgO during finish annealing), the reduction of TiO ₂ by the reducing atmosphere is suppressed during finish annealing. This is because when the reduction of TiO ₂ proceeds, the color changes from white to gray and black due to oxygen deficiency of the oxide, whereas when the color of the annealing separator during the final annealing is investigated, Ce and It turns out that blackening is suppressed by addition of La compound.

This suppression of reduction delays the formation of the forsterite film in order to suppress the catalytic action of forsterite film formation by TiO ₂ . The absence of a coating promotes N diffusion from the atmosphere into the steel, increases the number of active N sources necessary for TiN formation, and also causes loss of Ti sources due to the formation of composite oxides of MgO and TiO _2. It is suppressed.

As a result, TiO ₂ is reduced with Al in the steel at a high temperature, and reacts with N in the steel to form stable TiN. On the other hand, when the amount of Ce or La oxide is too large, the reduction of TiO ₂ with Al at high temperature is suppressed and TiN formation is prevented, so that it is considered that there is an appropriate amount range.

Examples of the Ce compound include CeO ₂ , Ce ₂ O ₃ , Ce (OH) ₄ , Ce ₂ S ₃ , Ce (SO ₄ ) ₂ .nH ₂ O (n is a number of 0 or more), Ce ₂ (SO ₄ ) _3. · NH ₂ O (n is a number of 0 or more), etc., and La compounds include La ₂ O ₃ , La ₂ (SO ₄ ) ₃ · nH ₂ O (n is a number of 0 or more), etc. However, any form may be used in any combination.

  Further, when a forsterite film formed by adding a Ce and / or La compound to an annealing separator is irradiated with a 4 kW X-ray source using, for example, a ZSX-100E X-ray fluorescence analyzer manufactured by RIGAKU, Ce and La It can be seen that a significant peak appears at the position of the L line, and these compounds contribute to the film formation reaction, and as a result, are incorporated into the film.

Furthermore, adding 0.1 to 1% of sulfate in terms of S in the annealing separator is more effective in increasing b ^* . This is presumably because S produced by reduction of sulfate during finish annealing functions as a reducing agent for TiO ₂ at high temperatures.

If the amount is less than 0.1%, a sufficient addition effect is not observed. On the other hand, if the amount is more than 1%, the inhibitor component is affected and causes deterioration of magnetic properties such as poor secondary recrystallization. 1% or less is desirable. Examples of the sulfate include MgSO ₄ , Al ₂ (SO ₄ ) ₃ , (NH ₄ ) ₂ SO ₄ , SrSO ₄ , Sb ₂ (SO ₄ ) _{3 and the} like.

  Further, in the finish annealing, in order to stabilize the amount of oxygen in the atmosphere at a high temperature, the hydrogen concentration is set to 20 ° C. at a low temperature of 700 ° C. or lower before the secondary recrystallization annealing for the purpose of removing moisture in MgO. It is desirable to provide a dehydration step for maintaining the atmosphere in a reducing atmosphere of at least%.

  Subsequently, in the present invention, coil heating conditions in the temperature range of 850 ° C. to 1150 ° C. of finish annealing, which is another basis, will be described. T = 950 to 1050, the heating rate from 850 to T ° C. is from 13 ° C./h to 50 ° C./h, and the heating rate from T to 1150 ° C. is from 3 ° C./h to less than 13 ° C./h. .

The reason why the heating rate at 850 to T ° C. in the first half part is relatively high at 13 ° C./h or more and 50 ° C./h or less is that when it is less than 13 ° C./h, the film deteriorates and b ^* does not increase. It is. Moreover, when it exceeds 50 degreeC / h, when heating a coil of several tons scale in this temperature range, there exists a problem that the burden to an annealing facility becomes large too much.

  In this heating rate range, a more appropriate range is 15 to 40 ° C / h, and more preferably 20 to 30 ° C / h.

  Moreover, although the temperature increase rate differs in each site | part of an actual machine coil, it is preferable that the residence time to 900-950 degreeC becomes 200 minutes or less.

Decreasing the heating rate of the first half part increases the in-furnace time at a relatively low temperature, consumes TiO ₂ at a low temperature by forming a complex oxide with MgO, and the Ce and La compounds. It is considered that the oxygen release reaction proceeds at a low temperature and the effect of suppressing the reduction of TiO ₂ cannot be sufficiently exhibited, thereby inhibiting the formation of TiN at a high temperature, leading to film deterioration and b ^* reduction.

  Moreover, the reason for relatively slowing the heating rate at T to 1150 ° C. in the latter half part from 3 ° C./h to less than 13 ° C./h is that if it is less than 3 ° C./h, the annealing is too long and the productivity is poor. On the other hand, if it is 13 ° C./h or more, the magnetic flux density is inferior.

  The reason why the magnetic flux density is inferior is that secondary recrystallization, which is a metallographic phenomenon, does not occur stably. In particular, this tendency has a great influence on a portion where the soaking in the slab heating is insufficient, and causes a deviation in the magnetic characteristics in the coil in the actual machine. In this heating rate range, a more appropriate range is 5 to 12 ° C / h, and more preferably 7 to 12 ° C / h.

The heating rate switching temperature T ° C. was T = 950 to 1050. The reason for this is that when the temperature is lower than 950 ° C., the adhesiveness of the film is deteriorated, and b ^* is lowered, and when the temperature exceeds 1050 ° C., the magnetic flux density is deteriorated. In the range of T, a more appropriate range is T = 975 to 1025.

The b ^* of the forsterite film formed by the above process is measured using a commercially available color difference meter. The present invention is based on measurement results using a Minolta CM 2500-d. When the yellowness b ^{* of the} film is less than 1.0, the film properties are deteriorated by pickling to remove the unreacted annealing separator, and when it exceeds 7.0, there is a problem in insulation. More preferably, it is 1.5-6.5, More preferably, it is the range of 2-6.

  In many cases, after the final finish annealing, an insulating film is further applied on the forsterite film. In particular, an insulating coating obtained by applying an insulating film forming composition liquid mainly composed of phosphate and colloidal silica to a steel sheet surface and baking it has a large applied tension to the steel sheet and is effective for further improving iron loss.

Further, if the insulating film formed here is a colorless and transparent clear film, the value of yellowness b ^{* in} this state does not greatly differ from the value of b ^* of the forsterite film.

  Furthermore, it is desirable to subject the unidirectional electrical steel sheet to so-called magnetic domain subdivision treatment such as laser irradiation, plasma irradiation, groove processing by a tooth roll or etching, if necessary.

  Regarding Ti and N of the forsterite coating, for example, in Patent Document 8, the Ti concentration (mass%) of the steel sheet including the forsterite coating is 1.2 to 2 times the N concentration (mass%). A grain-oriented silicon steel sheet characterized by the following range has been proposed.

This is to increase the N ratio to suppress intrusion Ti into the steel, suppress the remaining Ti compound in the steel, and avoid bending characteristics and iron loss deterioration after strain relief annealing. However, the color of the coating is not mentioned here, and b ^* is assumed to be low even if TiN is formed due to an excessive N ratio, which is different from the present invention. .

Patent Document 9 is characterized in that the forsterite film is mainly composed of Mg ₂ SiO ₄ and TiN, the weight ratio of TiN is 1 to 30%, and TiN (200) peak I ₁ and Mg ₂ SiO. ₄ (211) When the intensity ratio I ₁ / I ₀ to the peak I ₀ is 3/100 or more and 50/100 or less, there is an effect of reducing iron loss due to the tension effect, and the directionality to provide film adhesion Silicon steel sheets have been proposed.

  Here, the yellowish color is mentioned, but the degree is not described, and the manufacturing method is also controlled by the winding tension after application of the separating agent, the opening rate of the base plate, and the amount of gas introduced. In addition, the aim is to lower the iron loss due to tension, and the effect of acid resistance on the magnetic flux density and thinning is unknown.

In particular, since the position of the Mg ₂ SiO ₄ (211) peak is substantially the same as that of the TiN (111) peak, it is not always possible to relate only TiN and Mg ₂ SiO ₄ .

In Patent Document 10, the oxygen basis weight of the forsterite coating: 2.5 to 4.5 g / m ² , the Ti basis weight: 0.25 to 0.90 g / m ² , and the Ti / N molar ratio: 1.2 or less A forsterite film of a high magnetic flux density unidirectional silicon steel sheet characterized by satisfying an average particle size of forsterite particles of 0.5 μm or less has been proposed. However, here too, the color of the coating is not described.

  In addition, Patent Document 5 states that “In producing a normal unidirectional electrical steel sheet containing AlN + MnS (Se) as a main inhibitor and containing 0.0005 to 0.05% Bi and characterized by a high rolling reduction ratio, In the next recrystallization finish annealing step, the heating speed in the temperature range of 900 to 1150 ° C. is set to 15 to 50 ° C./h, and the technique is performed at a higher heating speed than before.

  However, the present invention divides the heating temperature range into two, and implements the latter half at a relatively slow heating rate of less than 3-13 ° C./h, thereby providing a stable high magnetic flux density and good film adhesion. The difference in technology is obvious.

  In a vacuum melting furnace, in mass%, C: 0.07%, Si: 3.2%, Al: 0.03%, N: 0.009%, S: 0.025%, Mn: 0.08 A steel ingot having a component of%, Bi: 0.0035% was prepared, heated at 1360 ° C. for 1 hour, and then hot rolled. A hot-rolled sheet having a thickness of 2.7 mm was annealed at 1100 ° C. for 100 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.27 mm.

  The cold-rolled sheet was subjected to decarburization annealing at 840 ° C. for 110 seconds in wet hydrogen, and coated with an aqueous separator in which an additive having the composition shown in Table 2 was added to an annealing separator mainly composed of MgO.

  In the finish annealing, the temperature is increased from 850 ° C. to 50 ° C./h in an atmosphere containing 75% nitrogen and 25% hydrogen, and then the temperature increase rate from 850 ° C. to 1020 ° C. is 25 ° C./h. From 1 to 1150 ° C. was set to 10 ° C./h, and then subjected to holding annealing at 1150 ° C. for 20 hours.

The steel plate after annealing was washed with water, and b ^* was measured with a color difference meter. Further, the steel sheet was sheared to a single-plate magnetic measurement size, an insulating film forming liquid mainly composed of aluminum phosphate and colloidal silica was applied and baked, and magnetic flux density B ₈ and film adhesion were evaluated. Further, a part was washed with water, immersed in a 5% HCl 70 ° C. aqueous solution for 30 seconds, dried, and then surface properties were confirmed. The results are shown in Table 3.

Here, B ₈ is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz, and the film adhesion is a film remaining rate when a bending test is performed with a curvature of 10 mmφ. Evaluation determined that B ₈ ≧ 1.90T and the film remaining rate of 90% or more was good. In the acid resistance evaluation, it was determined that a coating having no alteration such as occurrence of red rust was good.

In addition, when the obtained forsterite film was chemically analyzed, the oxygen basis weight was 0.9 to 1.0 g / m ² per side, and an electrical steel sheet in which La or Ce compound was added to the annealing separator. In the forsterite films, the presence of Ce or La was confirmed by film composition analysis by fluorescent X-rays.

  In a vacuum melting furnace, in mass%, C: 0.07%, Si: 3.3%, Al: 0.03%, N: 0.009%, S: 0.025%, Mn: 0.08 %, Bi: A steel ingot having a component of 0 to 0.025% was prepared, heated at 1320 ° C. and 1360 ° C. for 1 hour, and then hot rolled. A hot-rolled sheet having a thickness of 2.3 mm was annealed at 1100 ° C. for 100 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.22 mm.

The cold-rolled sheet was decarburized and annealed at 840 ° C. for 110 seconds in wet hydrogen, and the annealing separator containing MgO as the main component was 4% TiO ₂ with respect to the MgO mass, and 4% in terms of La. Of La ₂ O ₃ and 0.5% (NH ₄ ) ₂ SO ₄ in terms of S were applied, and a final annealing was performed at 1190 ° C. for 20 hours under various heating conditions.

The steel plate after annealing was washed with water, and b ^* was measured with a color difference meter. The steel sheet was sheared to a single-plate magnetic measurement size, and an insulating film forming liquid mainly composed of aluminum phosphate and colloidal silica was applied and baked to evaluate magnetic flux density B ₈ and film adhesion. A portion was washed with water, immersed in a 5% HCl 70 ° C. aqueous solution for 30 seconds, dried, and then surface properties were confirmed.

  In the finish annealing, the temperature is increased from 850 ° C. to 50 ° C./h in an atmosphere containing 50% nitrogen and 50% hydrogen, and then the temperature increase rate from 850 ° C. to 1010 ° C. is set to 25 ° C./h. Heating is performed in two cycles: 1010 ° C to 1190 ° C from 10 ° C / h (cycle 1) and 850 to 1190 ° C at a constant heating rate of 20 ° C / h (cycle 2). Then, after the temperature reached 1190 ° C., it was maintained in 100% hydrogen for 15 hours.

Here, B ₈ is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz, and the film adhesion is a film remaining rate when a bending test is performed with a curvature of 10 mmφ. Evaluation determined that B ₈ ≧ 1.90T and the film remaining rate of 90% or more was good. In the acid resistance evaluation, a film having no alteration such as red rust was determined to be good.

  Two types of slab heating temperature materials are used. In actual slabs at the factory, deviations may occur in the slab heating temperature depending on the position. Therefore, evaluation is performed from the viewpoint of compatibility with actual coils. This is because the. Table 4 shows the results.

In both slab heating temperature materials, the condition that B ₈ ≧ 1.90T and the film adhesion 90% are compatible is that the Bi amount is 200 ppm or less and the cycle 1 is from A to F, Those having better characteristics than satisfying B ₈ ≧ 1.91T were from Bi to 5-200 ppm in Bi and from cycle B to F.

When the obtained forsterite film was chemically analyzed, the amount of oxygen per unit area was 0.85 to 0.95 g / m ² for each side, and the forsterite film had a fluorescent X The presence of La was confirmed by the film composition analysis using lines.

  In a vacuum melting furnace, by mass%, C: 0.06%, Si: 3.2%, Al: 0.03%, N: 0.008%, S: 0.003%, Se: 0.0200 %, Mn: A steel ingot having a component of 0.08% was prepared, heated at 1420 ° C. for 0.5 hours, and then hot rolled. A hot-rolled sheet having a thickness of 0.22 mm is annealed at 1000 ° C. for 120 seconds, pickled, and then cold-rolled twice with a thickness of 0.23 mm by performing cold rolling twice with intermediate annealing. A board was used.

The cold-rolled sheet is subjected to decarburization annealing at 850 ° C. for 120 seconds in wet hydrogen. An annealing separator mainly composed of MgO is 5% TiO ₂ with respect to the mass of MgO and 2% Ce in terms of Ce. (OH) ₄ and water slurry added with 0.4% SrSO ₄ in terms of S were applied, and finish annealing was performed under various heating conditions.

The steel plate after annealing was washed with water, and b ^* was measured with a color difference meter. Further, the steel sheet was sheared to a single-plate magnetic measurement size, an insulating film forming liquid mainly composed of magnesium phosphate and colloidal silica was applied, and baked to evaluate the magnetic flux density B ₈ and the film adhesion. Further, a part was washed with water, immersed in a 5% HCl 70 ° C. aqueous solution for 30 seconds, dried, and then surface properties were confirmed.

  In the finish annealing, the temperature is increased from 850 ° C. to 50 ° C./h in an atmosphere containing 25% nitrogen and 75% hydrogen, and then the heating rate (previous heating rate) from 850 ° C. to 1020 ° C. is set to Vf. The temperature was set to 10 ° C./h from 1020 ° C. to 1200 ° C., and after the temperature reached 1200 ° C., it was maintained in 100% hydrogen for 30 hours.

Here, B ₈ is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz, and the film adhesion is a film remaining rate when a bending test is performed with a curvature of 10 mmφ. Evaluation determined that B ₈ ≧ 1.90T and the film remaining rate of 90% or more was good. In the acid resistance evaluation, a film having no alteration such as red rust was determined to be good.

Table 5 shows the results. The conditions under which B ₈ > 1.90T and film adhesion 90% are compatible were B to F in which Vf is in the range of 13 to 50. Among these, B to D in which Vf is 15 or more and 30 or less is better because B ₈ ≧ 1.91T, and B and C in which Vf is 15 or more and 25 or less are B ₈ ≧ 1.92T. And is most preferable.

When the obtained forsterite film was chemically analyzed, the amount of oxygen per unit area was 0.9 to 1.1 g / m ² for each side, and the forsterite film had fluorescent X-rays. The presence of Ce was confirmed by the film composition analysis according to.

  In a vacuum melting furnace, in mass%, C: 0.06%, Si: 3.3%, Al: 0.03%, N: 0.009%, S: 0.004%, Se: 0.0180 Steel ingots having components of%, Mn: 0.08%, Bi: 0.0042% were prepared, heated at 1410 ° C. for 0.5 hours, and then hot rolled. A hot-rolled sheet having a thickness of 0.26 mm was annealed at 1020 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.27 mm.

The cold-rolled sheet is heated up to 800 ° C. by an electric heating method at 310 ° C./s, and then decarburized and annealed in wet hydrogen at 830 ° C. for 120 seconds to form an annealing separator mainly composed of MgO. Then, a water slurry containing 3% TiO ₂ and 1% Ce converted CeO ₂ with respect to the mass of MgO was applied, and finish annealing was performed under various heating conditions.

After annealing, the steel sheet was washed with water, and b ^* was measured with a color difference meter. Further, the steel sheet was sheared to a single-plate magnetic measurement size, and an insulating film forming composition liquid mainly composed of aluminum phosphate and colloidal silica was applied and baked to evaluate magnetic flux density B ₈ and film adhesion. . Furthermore, a part was washed with water, immersed in a 70% aqueous solution of 5% hydrochloric acid for 30 seconds, dried, and then surface properties were confirmed.

  In the finish annealing, the temperature is increased from 850 ° C. to 40 ° C./h in an atmosphere containing 75% nitrogen and 25% hydrogen, and then the rate of temperature increase from 850 ° C. to 990 ° C. is set to 15 ° C./h. The rate of temperature increase from 990 ° C. to 1200 ° C. (second-stage heating rate) was Vl ° C./h. After the temperature reached 1200 ° C., the temperature was maintained in 100% hydrogen for 20 hours.

Here, B ₈ is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz, and the film adhesion is a film remaining rate when a bending test is performed with a curvature of 10 mmφ. Evaluation determined that B ₈ ≧ 1.90T and the film remaining rate of 90% or more were good. In the acid resistance evaluation, a film having no alteration such as red rust was determined to be good.

Table 6 shows the results. The conditions under which B ₈ ≧ 1.90T and film adhesion 95% are compatible were A to E in which Vl is in the range of 3 or more and less than 13. Among these, B to E in which Vl is 5 or more and 12 or less is more favorable because B ₈ ≧ 1.94T, and further, C to E in which Vl is 7 to 12 is B ₈ ≧ 1.95T. And is most preferable.

When the obtained forsterite film was chemically analyzed, the amount of oxygen per unit area was 1.0 to 1.1 g / m ² on one side, and the forsterite film had fluorescent X-rays. The presence of Ce was confirmed by coating composition analysis by

Claims (4)

A unidirectional electrical steel sheet containing, by mass%, Si: 2 to 5%, having a forsterite film on the surface of the steel sheet and having a saturation magnetic flux density B ₈ of 1.90 T or more, the forsterite film Has an oxygen basis weight of 0.85 to 1.20 g / m ² , contains one or two of Ce and La, and the forsterite film has a color of L ^* a ^* b ^* A unidirectional electrical steel sheet excellent in magnetic properties and coating adhesion, characterized in that the yellowness b ^* of the color system color coordinates is 1.0 or more and less than 7.0. In mass%, C: 0.02 to 0.10%, Si: 2 to 5%, acid-soluble Al: 0.010 to 0.065%, N: 0.003 to 0.0150%, S and Se A slab containing one or two selected from among: 0.001 to 0.040%, Mn: 0.02 to 0.30%, with the balance being Fe and inevitable impurities, 1280 ° C or higher After performing hot rolling, annealing, pickling, and cold rolling twice or sandwiching annealing, then decarburizing annealing and MgO as the main component In the manufacturing method for producing a unidirectional electrical steel sheet by applying an annealing separator and applying final finish annealing, the Ti compound is added to the MgO mass in the annealing separator mainly composed of MgO. , 1-10% in terms of TiO _2, one of Ce compound and La compound or The seed is added in an amount of 0.5 to 10% in terms of (Ce + La) with respect to the MgO mass, and the coil heating rate in the final finish annealing step is 13 to 850 to T ° C. (T = 950 to 1050). The manufacturing method of the grain-oriented electrical steel sheet excellent in the magnetic characteristics and film adhesiveness characterized by being set to less than 3-13 degrees C / h from 50 degrees C / h and T-1150 degrees C.   The magnetic properties and film adhesion according to claim 2, wherein 0.1 to 1% of sulfate is added in terms of S to the mass of MgO in the annealing separator mainly composed of MgO. For producing a grain-oriented electrical steel sheet having excellent properties.   The slab further contains 0.0005 to 0.0200% Bi in mass%, The grain-oriented electrical steel sheet having excellent magnetic properties and coating adhesion according to claim 2 or 3 Production method.