JPS6396216A - Production of grain oriented electrical steel sheet having high adhesiveness of glass film and excellent iron loss characteristic - Google Patents

Abstract

PURPOSE:To produce a grain oriented electrical steel sheet having high adhesiveness of a glass film and excellent iron loss characteristic by forming ruggedness on the surface of a steel sheet by mechanical means, etc. prior to decarburization annealing in a process for producing the grain oriented electrical steel sheet, subjecting the steel sheet to the decarburization annealing then coating an annealing and finishing agent thereon and subjecting the steel sheet to the final finish annealing. CONSTITUTION:The grain oriented electrical steel sheet is produced by subjecting a silicon steel slab to respective treatments of hot rolling, annealing, cold rolling, decarburization annealing and finish annealing. The sharp and fine ruggedness (about 0.3-5mu surface roughness) is formed over the entire surface of the steel sheet at <=1mm intervals in the direction within 30 deg. with respect to the direction orthogonal with the rolling by mechanical means such as brush roll, buffing, scribing or grinding or/and optical means such as laser projection. The steel sheet is then subjected to the decarburization annealing and after the annealing and separating agent is coated thereon, the steel sheet is subjected to the final finish annealing. The grain oriented electrical steel sheet which has the glass film having large film tension and high adhesiveness and has the low iron loss is thereby produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing grain-oriented electrical steel sheets having both excellent glass film properties and magnetic properties.

(Prior art) Grain-oriented electrical steel sheets are used as cores for electrical equipment such as transformers and generators, and they have good magnetic properties such as core loss and excitation properties, and excellent glass coating properties. is important.

Normally, grain-oriented electrical steel sheets are made by hot rolling a silicon steel material containing Si: 4% or less, and annealing the hot rolled sheet as necessary.
A cold-rolled sheet with the final finish thickness is obtained by one or two cold rolling processes, then decarburized annealed, an annealing separator containing MgO as the main component is applied, and final finish annealed is performed. It is manufactured through a process of developing secondary recrystallized grains with Goss orientation, removing impurities such as S and N, and forming a glass film, followed by flattening stress-relieving annealing and insulation coating treatment. .

Improvements in the glass coating and magnetic properties of grain-oriented electrical steel sheets are being considered.

Regarding the improvement of glass film, for example, Japanese Patent Application Laid-Open No. 50-715
Publication No. 26 discloses that the surface layer of a grain-oriented electrical steel sheet that has been cold-rolled to the final thickness is 3 g/m before decarburization annealing.
Pickling is carried out to remove surface deposits and the surface layer of the steel, allowing the decarburization reaction and oxide formation reaction to proceed evenly, and after decarburization annealing, an annealing separator is applied, and final annealing is performed. It is described that a MgO5iOz-based insulating film with good uniformity and adhesion is formed by applying the following steps.

Furthermore, Japanese Patent Application Laid-open No. 57-101673 discloses that after decarburization annealing of a grain-oriented electrical steel strip that has been cold-rolled to the final thickness, one surface of the steel strip is coated with an annealing separator such as MgO. 0.025 to 0.5 g/m by grinding or pickling to remove the oxide film on the surface layer of the steel plate, then apply an annealing separator and finish annealing to create a uniform gray color with good adhesion. It has been described that a glass film having a glass appearance is formed.

Furthermore, in JP-A-61-96082, the surface of a steel plate before decarburization annealing is ground by a grinding means made of a soft material containing carborundum abrasive grains and alundum abrasive grains without forming irregularities on the surface of the steel plate. Cleaned and smooth SiO□
It has been proposed to generate subscales by decarburization annealing and to form a uniform and dense glass film by final annealing.

(Problems to be Solved by the Invention) Through these efforts, improvements have been made in film properties such as adhesion of glass films, and improvements have also been made in magnetic properties, but these are not sufficient. , needs further consideration.

By the way, when trying to thicken the glass film in order to improve the film properties, it is effective to thicken the oxide layer consisting mainly of St and 2 during decarburization annealing.
Actions such as increasing the HzO/P Hz and lengthening the soaking time are required. In such a case, the amount of Fe-based oxides such as Fayalite (Fc43iO4) and FeO inevitably increases, leading to a decrease in the quality of the glass film and affecting the inhibitor. Furthermore, in order to reduce magnetic properties, especially iron loss, high-Si materials and materials to which special constituent elements or their compounds are added as inhibitors may cause concentration or selective oxidation of these constituent elements in the surface layer. decarburization may occur or the formation of a decarboxylation film may be impaired.

This may impair the formation of a high-quality glass or cause magnetic defects.

The purpose of the present invention is to obtain a glass film with excellent film properties such as adhesion, film tension, and appearance, as well as a grain-oriented electrical steel sheet with low core loss properties, which was difficult to manufacture using conventional technology. The purpose is to produce grain-oriented electrical steel sheets with good glass film adhesion and low core loss without impairing productivity even with high Si materials and special element additives.

(Means for Solving the Problem) The inventors of the present invention previously discovered that by forming an oxide partially penetrated into the steel sheet substrate, an anchor effect is produced and the adhesion of the glass film is significantly reduced. It has been found that a grain-oriented electrical steel sheet with low core loss can be obtained by improving the tensile strength of the film and dramatically improving the tensile effect of the film.

Further investigation revealed that mechanical means such as brush rolls, buffing, scribing, grinding, etc. were applied to the surface of the steel sheet before decarburization annealing at intervals of less than 1 n+ in directions within ±30 degrees to the direction perpendicular to the rolling direction. Or/and by forming sharp and fine irregularities by optical means such as laser irradiation, activating and decarburizing annealing, a locally thick decarboxylated film is formed in the form of protruding into the base steel sheet, It has been discovered that the glass coating has excellent properties, and also has a magnetic domain refining effect, resulting in a significant reduction in iron loss.

The present invention was constructed based on this knowledge, and will be explained in detail below.

As previously proposed in Japanese Patent Application No. 60-273421, the present inventors have discovered that by forming sharp and fine irregularities on the surface of a grain-oriented electrical steel sheet before or after decarburization annealing to activate the surface of the steel sheet, It has been found that during decarburization annealing or finish annealing, internal oxides are formed that partially protrude into the base steel of the steel sheet, resulting in a glass film with excellent adhesion and a reduction in iron loss.

Furthermore, we investigated ways to reduce iron loss and improve the glass coating. As a result, when forming sharp, fine irregularities on the surface of the oriented electromagnetic steel sheet, the interval between them should be extremely narrow, less than 1 x 1, and the direction should be within ±30 degrees with respect to the direction perpendicular to the rolling direction. We have newly discovered that it is possible to achieve a significant reduction in iron loss by doing this.

Further, the timing of its formation is preferably before the end of decarburization annealing, preferably before starting decarburization annealing or during the temperature raising process in decarburization annealing.

In order to reduce iron loss, it has been known to form minute marks such as linear flaws at intervals on a grain-oriented electrical steel sheet to subdivide the magnetic domains. However, it is said that the conventional micro-scar formation interval is 1 m11 or more, but in reality it is 3 to 12 m2.
mm, and it was said that a minute spacing of less than 1 inch would actually increase iron loss.

Unlike such conventional magnetic domain refining technology, the present invention forms a locally protruding decarboxylation film on the steel plate base, improving the glass film and reducing iron loss. In some cases, forming sharp and fine irregularities at minute intervals of less than 1 mm, preferably 0.5 mm or less, has an effect as shown in Figure 1, and when it is 1 mm or more, the effect of reducing iron loss is reduced. , the adhesion of the glass film also weakens. Further, in this case, the direction in which the unevenness is formed is preferably within ±30 degrees with respect to the direction perpendicular to the rolling direction.

If this value is exceeded, the decrease in iron loss tends to become smaller.

The sharp and fine irregularities are formed by mechanical means such as a brush roll, buffing, grinder, and scriber, or by optical means using laser irradiation such as a CO□ laser or a YAG laser. The average roughness of the unevenness is 0.3~
The thickness is preferably about 5 μm.

The irregularities are formed on one or both sides of the steel plate. The timing of its formation is before the end of decarburization annealing, and it is formed before decarburization annealing, such as after cold rolling or during cold rolling. Alternatively, it may be formed during heating during decarburization annealing.

In this way, when decarburization annealing is performed by forming sharp and fine irregularities at minute intervals of less than 1 square inch in a direction within ±30 degrees with respect to the orthogonal rolling direction, the steel plate during decarburization annealing is Si on the surface
The O□ formation reaction is promoted, and a thick oxide film is locally formed that protrudes into the steel plate base, has a low iron oxide component, and is rich in S10□ components. At the same time, the oxide film is formed along the unevenness. Due to these synergistic effects, the grain-oriented electrical steel sheet that is then finish annealed forms a glass film with excellent film properties such as adhesion and appearance, and also has a magnetic domain refining effect, which significantly reduces iron loss. You get what you get.

It is not necessary to specify the steel composition of grain-oriented electrical steel sheet and the manufacturing conditions until cold rolling. For example, C is 0.04 to 0.
．． 10%, Si is 2.0-4.0%, and AI as an inhibitor! An appropriate material containing N and MnS as main constituents is used, and other elements may also be contained if necessary. An electromagnetic steel slab is hot rolled, annealed, and then cold rolled once or twice or more with intermediate annealing to achieve a desired final thickness.

Next, as described above, before decarburization annealing, sharp and fine irregularities are formed at minute intervals on the surface of the steel sheet.

In decarburization annealing, a Sin-rich oxide film is formed along with decarburization, but at 800 to 860°C in an atmosphere containing N2 and ■2 as main components, for example, PH20/pH□ is 0.35 to 0.
It is done as 50.

When the above-mentioned unevenness is formed during the temperature increase during decarburization annealing, it is preferable to perform the formation at a temperature of 750° C. or lower from the viewpoints of adhesion of the glass film, appearance, and reduction in iron loss. After decarburization annealing, an annealing separator containing MgO as a main component and additives such as TiO2, B compounds, SrS, SnS, and CuS is applied, dried, and final annealed.

In final annealing, the oxide film formed during decarburization annealing reacts with the annealing separator to form a glass film. Since the oxide film is formed as described above, the glass film also penetrates locally into the steel sheet base, and its spacing and orientation are also regulated. As a result, the tension of the glass film is high, and the magnetic domains are subdivided, leading to a significant reduction in iron loss. Furthermore, the adhesion of the glass film is extremely good, and it does not peel off even when it is bent, for example, by 10 mm.

Thereafter, if necessary, flattening annealing is performed, and the steel plate is treated with phosphoric acid, phosphates such as aluminum phosphate, magnesium phosphate, zinc phosphate, calcium phosphate, etc., chromates such as chromic acid and magnesium chromate, etc. An insulating coating solution containing one or more of dichromate, colloidal silica, etc. is applied and baked at a temperature of 350° C. or higher to form an insulating coating.

(Example) Next, examples will be shown.

C in weight%, 0,060%, St; 2.95%, Mn;
0.070%, 810.029%, S; 0.025
%, the balance being iron, hot-rolled by a known method.
Annealed and cold-rolled to a plate thickness of 0.27mm, and brushed and buffed to a pitch of 0.8n in the direction perpendicular to the rolling direction.
The average roughness is 0.5 μm so that there are 5 dragons.

Sharp and fine irregularities of 2.0 μm were formed.

Then, at 850°C in N2+H, humid atmosphere (PIIzO/
After performing decarburization annealing for 120 seconds at PH2'=0.40), an annealing separator was applied, and final finish annealing was performed at 1200°C for 20 hours. Table 1 shows the glass film properties and magnetic properties at this time.

As described above, according to the present invention, a grain-oriented electrical steel sheet having a glass film with high film tension and excellent adhesion and low core loss can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the influence of the spacing between concavities and convexities formed on the surface of a steel plate on iron loss.

Claims (1)

[Claims] A method for producing a grain-oriented electrical steel sheet in which a silicon steel slab is hot-rolled, annealed and cold-rolled once or twice or more with intermediate annealing in between, and after decarburization annealing, an annealing separator is applied and finish annealing is performed. , the surface of the steel sheet before decarburization annealing is subjected to mechanical means such as a brush roll, buffing, scribing, grinder, etc., or/and optical means such as laser irradiation, in a direction within ±30 degrees with respect to the orthogonal direction of rolling. After forming sharp and fine irregularities on the entire surface with a spacing of less than 1 mm, decarburization annealing is performed, an annealing separating agent is applied, and final annealing is performed.The glass coating has good adhesion and reduces iron loss. An excellent method for producing grain-oriented electrical steel sheets.