JPH01198430A - Production of grain oriented electrical steel sheet having extremely good iron loss characteristics and film adhesiveness - Google Patents

Abstract

PURPOSE:To improve the iron loss characteristic and film adhesiveness of a grain oriented electrical steel sheet formed with an insulating film by imparting specific fine linear flaws to the surface of the steel sheet prior to or after decarburization annealing and specifying the heating up and atmosphere gas of final finish annealing in production of said steel sheet. CONSTITUTION:The cold-rolled grain oriented electrical steel sheet having the final sheet thickness is subjected to the decarburization annealing and an SiO2 scale layer is formed on the surface. An annealing and separating agent of an MgO system is coated thereon and thereafter, the steel sheet is subjected to the final finish annealing by which the insulating film is formed thereon. The fine linear flaws of <=5mm interval, <=1mm width and 0.3-5 depth in Ra value are imparted to the surface of the steel sheet prior to or after the decarburization annealing within 30 deg. with the direction perpendicular to the rolling direction thereof in the process for producing the above- mentioned grain oriented electrical steel sheet. The holding time of >=1 hour is provided at 700-950 deg.C heating process in the final finish annealing and further the PH2O/PH2 of the atmosphere gas is maintained at 0.01-0.2 during this time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet with extremely excellent iron loss and excellent film adhesion.

[Conventional technology]

Grain-oriented electrical steel sheets are produced by melting a silicon steel material containing Si of 4% or less, usually about 3%, continuous casting or ingot forming, forming a slab by blooming rolling, and then hot rolling and then one-time or intermediate annealing. The final plate thickness is achieved by two intervening cold rollings, followed by decarburization annealing and high-temperature box annealing. In addition, the crystal texture is called a Goss texture in which the axis of easy magnetization is aligned in the rolling direction (110
) (001) orientation, and is widely used as an iron core material for various power distribution applications.

When such grain-oriented electrical steel sheets are used as core materials for transformers, they are generally laminated as thin steel sheets. As a characteristic, it is required to uniformly form a highly electrically insulating film on the surface of the steel sheet in order to reduce eddy current loss.

In addition, in order to prevent the coating from falling off or peeling during slitting or cutting, winding, pressing, annealing, lacing, etc. in the core processing process, it is necessary to have a glass coating with good adhesion. required.

By the way, among the properties of these grain-oriented electrical steel sheets, the iron loss properties are particularly important, and various proposals have been made for reducing these properties.

For example, in order to improve iron loss, there are measures such as increasing the St content, improving the orientation of secondary recrystallized grains, and reducing the size of secondary recrystallized grains. Another method is to reduce the plate thickness.

In recent years, there has been a method to improve iron loss by refining the magnetic domains of secondary recrystallized grains in product sheets, and Japanese Patent Publication No. 57-2252 discloses a method in which a laser beam is applied to the surface of a final product sheet at intervals of several eleven at approximately perpendicular to the rolling direction. A technology has been proposed to subdivide the magnetic domain width and reduce core loss by introducing high dislocation density regions on the surface of the steel sheet through irradiation.

Furthermore, in JP-A-61-139680, the inventors removed a part of the surface coating on the surface of the final product plate by laser irradiation, plated the penetrable metal, and then heat-treated the steel plate. This method expands the interstitial body and subdivides the magnetic domains. According to this method, the effect is not lost by subsequent heat treatment, but rather is improved.

In addition, Japanese Patent Application Laid-open No. 61-246376 describes a tension-applying coating that is applied on a normal forsterite coating that constitutes the surface coating of a grain-oriented silicon steel sheet for the purpose of improving magnetic properties and surface coating. It has been proposed that magnetic domain refinement of a steel sheet is facilitated by forming regions with different imparting effects.

JP-A-60-103183 discloses a method for producing grain-oriented electrical steel sheets whose properties do not deteriorate due to strain relief annealing.
The presence of a region consisting of a glass film with a composition different from that of forsterite locally is advantageous for refining the magnetic domain of the product, and the tension-applying insulating coating is created in the presence of such a heterogeneous glass film region. The effect is further enhanced by the combined action of the two.

In this invention, the width of the heterogeneous glass coating region is 0.0
5-2. It is said that a spacing of about 0*m and an interval of 1.0 to 3.0 is most effective.

All of these improve iron loss characteristics through the effect of magnetic domain refining, and some effects will likely be obtained.

[Problem to be solved by the invention]

By the way, the various techniques disclosed for improving core loss as described above lose their effectiveness or lose part of the coating due to annealing, and therefore require application and baking of an insulating coating. In addition to the problem of film insulation properties, there are also problems of manufacturing cost, and problems that are extremely difficult to realize industrially, as in JP-A-61-246376 and JP-A-60-103183. It's still not enough.

In order to solve the above problems, the present invention has extremely excellent iron loss,
This was done for the purpose of obtaining a grain-oriented electrical steel sheet with excellent film adhesion.

[Means to solve the problem]

The present inventors have found that when a fine oxide film and/or glassy film is formed in the steel sheet base iron during the decarburization annealing process or the final finish annealing process, an excellent film layer with a large magnetic domain refining effect is formed, resulting in iron loss. It has been found that a grain-oriented electrical steel sheet with extremely excellent properties and film adhesion can be obtained.

The present invention provides a method for industrially manufacturing such a steel plate, and the gist thereof is as follows.

One is to hot-roll a silicon steel slab and sandwich it through annealing.
A cold-rolled sheet that has been cold-rolled once or twice or more to have a final thickness is given fine linear or broken line-like flaws almost entirely on the steel sheet surface before or after decarburization annealing, One is to develop an oxide film and/or a glassy film into the steel sheet along the flaws in the subsequent decarburization process and/or final annealing process. After forming fine linear flaws, an oxidizing agent or oxidation promoter is applied to the flaws, and the oxide film and/or glassy coating is turned into fine linear flaws during the heat treatment of the decarburization annealing process and/or the final annealing process. It has extremely low iron loss and is characterized by being developed along the
The present invention provides a method for producing grain-oriented electrical steel sheets with excellent film adhesion.

The present invention will be explained in detail below.

As shown in FIGS. 1 and 2, the present inventors discovered that an oxidized layer and a broken line developed in a steel sheet within 30 degrees perpendicular to the rolling direction during the decarburization annealing or finish annealing process, as shown in FIGS. /Or grain-oriented electrical steel sheets with a glassy coating have a magnetic domain refining effect due to the action of the finely developed coating layer.
It was discovered that the iron loss was extremely low and the adhesion of the glass coating was excellent. The present invention provides a method for industrially manufacturing such a steel plate, and the steel plate is manufactured as follows.

As shown in FIG. 1, before or after decarburization annealing of the steel plate 1 cold-rolled to the final thickness, the angle is 30° with respect to the direction perpendicular to the rolling direction R.
A fine linear flaw 2 is provided within the width direction W of the coil. 2 is applied by brush roll, high-pressure water, grinder, sandpaper, shot, laser, mechanical, thermal, or chemical means after pickling to remove straight or broken line scratches on almost the entire surface of the steel plate. to be given.

The conditions for creating this fine linear flaw are the interval Il! 5N
Width a: 1 m or less, depth is Ra value 0.3 to 5.

The steel plate having such fine linear flaws is coated with acids, alkalis, or salts thereof, if necessary.

The coating agent at this time includes Na, K, Li,
Ca, Mg.

One or two of hydroxides such as Ba, sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid, boric acid, and sulfates, nitrates, phosphates, chlorides, fluorides, and borides made of various metals. Seeds or more are applied.

Next, after decarburization annealing, final finish annealing is performed.

In the present invention, in this final annealing, as shown in FIG. 2, over almost the entire surface of the steel plate before or after decarburization annealing,
The feature is that a fine linear oxidation layer and/or glassy coating 3 is locally developed from the surface toward the center of the steel sheet base from the finely applied linear flaws 2. In this process, an oxide layer and a glassy coating layer can be effectively grown by specifying the heat cycle and atmospheric conditions for the final annealing and the acids, alkalis, or salts applied to the flawed area as necessary. can be done.

As a result, although the depth of the linear flaws 2 formed on the steel sheet surface before or after decarburization annealing is as shallow as 0.3 to 5 in terms of Ra value, the steel sheet after final finish annealing is The depth of the oxidized layer etc. 3 that has developed reaches 5 to 40 um. In addition, during this film formation process, a glassy film develops and completely covers the flawed areas on the surface of the steel sheet.
These are the characteristics of the product according to the present invention.

It is believed that the extremely excellent core loss and excellent adhesion achieved by the present invention are due to the following reasons. - In the present invention, 2
After the completion of the next recrystallization, the depth of the fine oxide layer or glassy coating layer that develops in the W4 preliminary iron from the surface flaws reaches a depth of 5 to 40 degrees, as described above. One of the reasons for the improvement in iron loss is thought to be that magnetic poles are generated by this finely developed linear coating layer, resulting in a magnetic domain refining effect. The other is due to the difference in thermal expansion coefficient between the finely developed linear oxide layer and glass coating layer, and the magnetic domain due to the action of minute local stress on the steel sheet steel during the cooling process of final annealing. This is thought to be due to the segmentation effect.

The improvement in coating adhesion is due to the effect of a finely and deeply developed coating layer, and in the bending peel test after insulation coating treatment, a remarkable improvement is seen due to the effect of the strong structure of this linear coating layer.

Another advantage of the present invention is that there is very little reduction in magnetic flux density as with other domain control techniques. Therefore, iron loss can be improved in a wide range of magnetic fields from low magnetic fields to high magnetic fields, so that practically all customers can be satisfied.

Next, the reasons for the limitations of the present invention will be described.

In the present invention, an oxidized layer or a glassy film is developed in the steel sheet along the fine linear flaws formed on the surface of the steel sheet before or after decarburization and sintering, and the condition of the flaws formed on the surface Important requirements include coating agents such as acids, alkalis, and salts applied to the eaves and final annealing conditions.

First, the flaws applied to the steel plate may be linear or broken lines, preferably connected in a straight line as much as possible, and the direction in which the linear flaws are applied is perpendicular to the rolling direction. It is within 30°. This is to ultimately obtain the magnetic domain refining effect by the developed oxide layer or glassy coating starting from this eave part, and if the above angle deviates further than this, even if the effect of improving coating adhesion is obtained. This is because the iron loss improvement effect becomes weaker. The depth of the flaw is 0 in terms of Ra value.
．． It ranges from 3 to 54. If it is smaller than 0.3 ts, the film layer from the eaves will not develop sufficiently during annealing, and the depth will not be obtained, so the iron loss improvement effect will be weak. The growth becomes too deep, resulting in a decrease in magnetic flux density, which adversely affects core loss or excitation characteristics in high magnetic fields.

The most preferable flaw depth is an Ra value of 1 to 3-3.

Further, the distance between the flaws is within 5 mm. Depth and width of linear flaws
Although it depends on the type and amount of coating agent applied to the eaves, in the method of the present invention, the effect of a coating layer that develops in very fine lines is expected, so the narrower the spacing, the better the results. It will be done.

The preferred range is 50-1000. Bottom width is lfi
It is as follows. A depth of 1 sIA or more is not preferable because the magnetic flux density decreases due to an increase in the volume of the coating material, similar to when the depth is too deep. Moreover, a large number of experimental results have shown that the smaller the base width, the better the results. In particular, the range in which good results in improving iron loss and film adhesion can be obtained is in the range of 20 to 200.

The alkalis, acids, or salts of these applied to the eaves may cause the compounds to etch the eaves during annealing.
Any material may be used as long as it promotes the development of the oxide layer and glassy film from the eaves, or helps the growth of recesses in the eaves by etching. According to experiments, Na, K
, hydroxides of alkali and alkaline earth metals such as Li, Ca, Mg, and Bas, and nitrate were effective.

The amount of these alkalis, acids, and salts to be applied varies depending on the condition of the linear scratches (depth, width, spacing, etc.), but the amount of the substance applied is 0.2 to 30 g/per area of the eaves. r
It is effective if you apply about d.

The methods of applying these coating agents include printing, brushing, spraying, etc. on the eaves of the steel plate as a slurry.
Either is fine.

Next, as conditions for final annealing, the heating cycle during temperature rise and the P HtO/P Hz of the atmospheric gas are important in the present invention. The heating cycle is a heating process of 700-950℃
Provide a holding time of 1 hour or more, or hold at 10℃/h.
Heating is required at a temperature increase rate of r or less. This is to take advantage of the fact that a concentration reaction of Sing on the surface occurs rapidly at this time as a reaction in the film formation process, and it is necessary to provide a holding time of 1 hour or more at 700 to 950°C, or to hold the Sing at 15°C. By heating at a temperature increase rate of /hr or less, a remarkable effect is seen on the growth of a glassy film that develops finely from the eaves.

During this period, the atmospheric gas is P HtO/P
H! It is important to set 0.01 to 0.2. This is to make the growth of the oxide layer and the glassy film in the SiOg concentration region more effective due to the moisture in the atmospheric gas.

If it is less than 0.01, the water supply will be insufficient and no effect will be obtained. On the other hand, if it is 0.2 or more, the development of the coating layer is observed, but the moisture content is too large, resulting in excessive oxidation, and gas marks and pinhole-like defects are likely to occur throughout the glass coating.

〔Example〕

Example 1 C: 0.078, Si: 3.30, M in weight%
n; 0.055, A g HO, 032, N;
0.0082, S; 0.025, the remainder being unavoidable impurities and a grain-oriented silicon steel sheet material consisting of Fe was hot-rolled, hot-rolled sheet annealed, and cold-rolled to a final thickness of 0.225 t by a known method.
The steel sheet was then subjected to laser irradiation to form linear flaws under the conditions shown in Table 1 before and after decarburization annealing. Next, decarburization annealing was performed at 850° C. for 3 minutes in a humid atmosphere. After this, as an annealing separator, 100 parts by weight of MgO, T
An annealing separator consisting of 5 parts by weight of i1t and 0.5 parts of sodium borate was applied, and final finish annealing was performed using the heating cycle and atmosphere cycle shown in Table 1. Table 2 shows the investigation results of magnetic properties and film properties.

Margins below Table 1 Table 2 Example 2゜Final plate thickness adjusted in the same manner as Example 1 0.22511
Linear flaws were applied to the cold-rolled sheets using a brush roll in a direction perpendicular to the rolling direction under the conditions shown in Table 3. Next, the compound shown in the same table was applied at a rate of 1 g per 1 flaw area, and decarburization annealing was performed at 850°C for 3 minutes in a humid atmosphere. After applying an annealing separator containing 0.5 parts by weight of sodium, final annealing was performed at 1200° C. for 20 hours using the heating cycle shown in the same table.

The magnetic properties and film properties at this time are shown in Table 4.

According to the examples shown in Table 3 and Table 4 in the margins below, the present invention is compared to the comparative example in terms of BS(T) of the magnetic properties, but w+tzs.

(W/kg) was found to be quite low, and the film adhesion was also found to be good.

〔Effect of the invention〕

As described above, the present invention has extremely excellent magnetic properties, particularly iron loss properties, and excellent film adhesion, so it has great industrial effects in the method of manufacturing grain-oriented electrical steel sheets.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in which fine linear flaws are provided on the surface of a cold rolled steel sheet, and FIG. 2 is a schematic cross-sectional view showing the state of fine linear flaws in each process.

Claims (3)

[Claims] (1) A cold-rolled grain-oriented electrical steel material having a final plate thickness is subjected to decarburization annealing to form a scale layer mainly composed of SiO_2 on the surface, and an annealing separator mainly composed of MgO is applied on the scale. In a method for producing a grain-oriented electrical steel sheet in which an insulating film is formed by applying final finish annealing after coating, the surface of the steel sheet is coated with 5 mm at intervals of 5 mm within 30° to the direction perpendicular to the rolling direction before or after decarburization annealing. 1 mm or less in width, with a depth of 0.3 to 5 μm in Ra value, and at a heating temperature of 700 to 950°C during final annealing.
Production of a grain-oriented electrical steel sheet with extremely low core loss and excellent adhesion, characterized by providing a holding time of more than 100 hrs, and further setting the PH_2O/PH_2O of the atmospheric gas during this time to 0.01 to 0.2. Method. (2) A cold-rolled grain-oriented electrical steel material having a final plate thickness is subjected to decarburization annealing to form a scale layer mainly composed of SiO_2 on the surface, and an annealing separator mainly composed of MgO is applied on the scale. In a method for producing a grain-oriented electrical steel sheet in which an insulating film is formed by applying final finish annealing after coating, the surface of the steel sheet is coated with 5 mm at intervals of 5 mm within 30° to the direction perpendicular to the rolling direction before or after decarburization annealing. 700 to 9 in the temperature rising process during final annealing.
The temperature increase rate in the 50°C section shall be 10°C/hr or less,
Furthermore, during this period, the PH_2O/PH_2 of the atmospheric gas was set to 0.
01 to 0.2. A method for producing a grain-oriented electrical steel sheet with extremely low core loss and excellent adhesion. (3) Claim (1) characterized in that the linear flaws on the surface of the steel sheet are treated with one or more of acids, alkalis, or salts thereof before or after decarburization annealing. 1)
Or the method for producing a grain-oriented electrical steel sheet with extremely low iron loss and excellent adhesion as described in (2).