JPS6236803A - One directional electromagnetic steel plate with superior film adhesiveness and its manufacture - Google Patents

Abstract

PURPOSE:To increase the adhesiveness of a directional electromagnetic steel plate on a glass film and to improve magnetic characteristics by forming an oxide dispersion phase in matrix iron under the glass film which is formed at the time of a normal finish annealing. CONSTITUTION:A steel plate that has undergone the finish annealing is heat- treated in an atmosphere with the ratio of H2O partial pressure and H2 partial pressure (PH2O/PH2), that is to say, the oxidation degree of 0.05-0.70 within the temperature range of 650 deg.C-900 deg.C for 20-30sec so that an oxide disparsion phase on matrix iron is formed under the glass film formed at the time of finish annealing, thereby increasing adhesiveness and tension in producing cool rolling steel plate with normal process. First, a slab containing Si below 4% is heated and hot-rolled to an intermediate plate thickness, and the hot-rolled plate undergoes two times of cool-rolling with intermediate annealing or one time of cool-rolling to provide a final thickness. After that,normal decarbonizing is performed, and normal finish annealing after annealing separation agent has been applied to the plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a grain-oriented electrical steel sheet with excellent film adhesion and magnetic properties.

[Conventional technology]

In grain-oriented electrical steel sheets, the glass film is composed of firelite and silica that are generated when cold-rolled sheets are decarburized and annealed.
It is produced by reacting with a magnesia-based coating such as that disclosed in Japanese Patent No. 1011586 at a high temperature during final annealing. This glass coating has the meaning of imparting tension to the steel plate and improving its magnetic properties, as well as increasing the interlayer resistance when the steel plates are laminated as an iron core. On the other hand, the glass coating must be difficult to peel off when the grain-oriented electrical steel sheet is subjected to bending. From the above point of view, it has been desired that conventional coatings be further improved in terms of coating tension and adhesion.

[Problem to be solved by the invention]

The glass film after final annealing is usually made of an oxide mainly composed of forsterite, and a tension imparting treatment liquid is applied to this glass film and baked to form a finished film. This glass film is usually bonded to the substrate by an internal oxidation layer called the root of the glass film. This internal oxidation layer is affected by the dew point during decarburization annealing, the atmosphere during final annealing, the composition of the annealing separator, etc., and it has been difficult to obtain an internal oxidation layer with stable adhesion and tension over the entire length of the coil.

Therefore, it has been difficult to create a glass film with sufficient adhesion and uniform tension over the entire length of the product.

The present invention provides a steel sheet and a method for producing the same, which improve the adhesion of a grain-oriented electrical steel sheet to a glass coating compared to conventional materials, and at the same time improve magnetic properties.

[Means for solving problems]

In order to solve the above problems, the present invention provides a steel plate after final annealing with a ratio of 11.0 partial pressure to H2 partial pressure (PH2O/PH2
), that is, in an atmosphere with an oxidation degree of 0.05 to 0.70.
By performing heat treatment for 20 seconds to 300 seconds at a temperature range of °C to 900 °C, an oxide dispersed phase is formed in the base steel under the glass film formed during final annealing, resulting in remarkable adhesion. The aim is to increase tension and tension. In the present invention, a cold-rolled steel sheet is manufactured by a normal process.

First, a slab containing 4% or less of Si is heated and hot-rolled to an intermediate plate thickness, and the hot-rolled hot-rolled plate is pickled,
If necessary, a heat treatment is performed at this stage, and the hot-rolled sheet is cold-rolled twice with intermediate annealing in between, or cold-rolled once to reach the final thickness.

After this, normal decarburization annealing is performed, and after applying an annealing separator, normal finishing annealing is performed.

There is a relationship between the tension of the produced glass film and its magnetic properties, and generally as the tension increases, the iron content decreases, so it is desired to improve the tension. The present inventor focused on the fact that the surface of the glass film after final annealing is scattered with pores that are thought to have been generated during dulling. We thought that the adhesion and tension of the glass film could be improved by forming an oxide dispersed phase in the forsterite layer. It has been newly discovered that when a steel plate with a glass coating is annealed, the coating adhesion and magnetic properties are improved. In particular, the effect of improving the adhesion of the glass film is remarkable4). Specifically, after cooling a steel plate having a glass film formed during final annealing, pH□O/P Hz: 0.05~
By annealing again in an atmosphere of 0.70° C. at a temperature of 650 to 900° C. for a time of 20 to 300 seconds, an insulating film with excellent adhesion and magnetic properties can be obtained.

A film similar to this can also be obtained during final annealing by selecting an appropriate oxygen potential that forms an oxide dispersed phase on the base during the cooling process after the annealing process, but the outer periphery of the inner winding of the coil can be uniformly coated. It is difficult to maintain the same temperature in a similar atmosphere, so by passing the final annealed coil through a continuous annealing furnace, oxides are dispersed in the base steel under the glass film formed during final annealing. Forming a layered phase is most suitable for obtaining a stable film from the viewpoint of adhesion and magnetic properties.

Next, the reason for limiting the oxygen potential, temperature, and time in the film stabilization annealing step after final annealing will be described.

Normally, under thermodynamic equilibrium, po! at 650°C! O/P
rl□Pnzo/at 0.05~0.47.900℃
When P Ilz is in the range of 0.27 to 0.66, firerite is formed on the surface of the silicon steel sheet, but when annealing for a short time (20 to 300 seconds) in a non-equilibrium state, base iron is formed under the forsterite film. A layered phase in which silica is dispersed is formed. 900℃, P HJ/P Hz; 0.6
6 to 0.70, bustite is formed in an equilibrium state, and a phase in which silica is dispersed in the base metal is also formed. PToO/P11
．． When χ0.70 is exceeded, bustite begins to form even in a short period of time, and the adhesion of the film rapidly deteriorates. For the above reasons, the oxygen degree was limited to 0.05 to 0.70.

The reason for limiting the temperature to 650°C to 900°C is 6.
If the temperature is lower than 50°C, the time required for the reaction becomes longer, making it impractical. The upper limit of the temperature range was set because if the temperature was higher than 900°C, the plate would elongate in the continuous annealing line. This does not apply when annealing is performed in a state where no tension is applied.

Next, regarding time, the effect of improving adhesion and magnetism starts to be seen after about 20 seconds, but if the time is too long, the thickness of the oxide dispersed phase in the base metal becomes thicker, and B (magnetic flux density) decreases. Therefore, the upper limit of the annealing time was set to 300 seconds. 850℃,
When annealing for 300 seconds at P H20/ P It2 = 0.65, the decrease in 88 was approximately 200 Gauss compared to the comparative material, but the decrease in iron loss was 0.05 at w+, /so.
w/kg. From the viewpoint of BF (Building Factor), as B8 decreases, iron... decreases, so it is possible to obtain a BF with good characteristics.

Figure 1 (ta+) and (bl) show cross-sectional optical micrographs of glass coatings obtained by the method of the present invention and the conventional method, respectively.The method of the present invention, as shown in Figure 1 (a), In addition to the film that is formed, an oxide dispersed phase in the base metal that has a slightly dull color tone is formed under the forsterite film.As a result of analysis by ESCA, most of the phase is silica dispersed in the base metal. The reason why it exhibits a slightly pale color tone is that it has a high reflectance to light because it contains metal in the oxide.

The reason why the adhesion of the glass film is improved by forming an oxide-dispersed phase under the forsterite film in a new steel base other than forsterite is not known in detail at present, but oxide dispersion into the base steel Since the phase consists of a layer in which fine oxides are dispersed in the base iron, it is thought that it plays the role of a medium that exhibits a strong binding force for both the base iron and forsterite. In contrast, the conventional bond between forsterite and base iron is thought to be weak because the metal and oxide, which have completely different properties, are directly bonded at an interface.

The primary reason for the improvement in film tension is thought to be that the bonding strength has increased due to the formation of an oxide-dispersed layer on the base steel as described above, but the form of oxidation at the interface between forsterite and the base steel has also changed. Therefore, it is thought that the part caused by this also contributed.

[Example 1] A cold-rolled sheet finished to a thickness of 0.23 t by one-time cold rolling was subjected to normal decarburization annealing, and then an annealing separator was applied and normal finish annealing was performed. After final annealing, unreacted MgO powder was removed and light pink ringing was performed in sulfuric acid. After that, PHI□O/PH,=0.10°0.40.
Annealing was performed at a temperature of 850° C. for 45 seconds, 90 seconds, and 210 seconds in each atmosphere of 0.65°C, and after cooling, the film tension was measured. After measuring the tension, a tension imparting coating treatment solution was applied, baking was performed, and coating adhesion and magnetism were measured. After light pink ringing, the comparison material was subjected to tension measurement, and the tension imparting treatment solution was applied immediately thereafter.It can be seen that the steel of the present invention is superior to the comparison steel in terms of tensile magnetic properties and film adhesion.

The following margins are shown in each column: Top row: 5-level evaluation of film adhesion after 180 degree bending test in 10tm (X, X, △, O, @) Middle row: W + 715 in the rolling direction after applying the tension film゜Iron loss I 1α Lower row: Film tension in as glass [Example 2] A cold-rolled sheet finished to 0.230 thickness by two-time cold rolling was subjected to normal decarburization annealing, and then an annealing separator was applied. Ordinary final annealing was performed. After final annealing, unreacted MgO powder was removed and light pink ringing was performed in sulfuric acid. After that, PH20/PI+! = 0.20.

Annealing was carried out at a temperature of 750° C. for 40 seconds, 120 seconds, and 250 seconds in each atmosphere of 0.48 and 0.65, and the film tension was measured. After measuring the tension, a tension imparting coating treatment solution was applied and baked, and the magnetic adhesion of the coating was measured. The comparison material was one in which the tension was measured after light pink ringing, and then a tension imparting treatment liquid was applied and baked. The tension, magnetic properties, and adhesion of each glass film were
Shown in the table. It can be seen that the steel of the present invention has better tensile magnetic properties and film adhesion than the comparative steel.

Margins below 2 Table columns Top row = 10 ■ 5-level evaluation of film adhesion after φ180 degree bending test (X, X, △, ○, ◎) Middle row: W in the rolling direction after applying the tension film, 9. ,. Lower iron loss value: Film tension in as glass [Effects of the invention] According to the present invention, since the glass film has excellent adhesion and tension, the iron loss value is lower than that of the conventional method, and severe bending is not required. It has the advantage that the glass film does not easily peel off even if it is added, and has a very large industrial effect.

[Brief explanation of the drawing]

Figure 1 fat is 850℃, PH2 (1'PHz=0.5
5. A metallurgical microstructure photograph of a cross section of a grain-oriented electrical steel sheet with a glass film on which a tension film was applied after being held in an atmosphere for 90 seconds. Figure (b) shows the glass film on which a tension film was applied after final annealing. It is a metal microscopic structure photograph of a cross section of a grain-oriented electrical steel sheet having a film. (a) Figure 1 Procedural Amendment (Voluntary) September 1985 Today, Commissioner of the Patent Office Kuro 1) Akio Yu 1, Indication of the case 1985 Patent Application No. 155366 2, Name of the invention Film adhesion Curved unidirectional electrical steel sheet and method for manufacturing the same 3. Relationship with the amended case. Applicant for patent. Name (665) Nippon Steel Corporation 4, Agent 5, "Detailed Description of the Invention" column 6 of the specification subject to amendment, Contents of the amendment (1) "Slowing down" on page 4, line 11 of the specification Purify time
Correct. (2) "After blunting treatment" on page 5, line 6 of the specification is corrected to "after purification treatment."

Claims (1)

[Claims] 1. A unidirectional electrical steel sheet with excellent film adhesion, characterized in that an oxide dispersed phase is formed in the base iron under the glass film formed during normal final annealing. 2. After finish annealing, the steel plate is annealed in an atmosphere where the ratio of H_2O partial pressure to H_2 partial pressure (PH_2O/PH_2) is 0.05 to 0.70 at a temperature of 650°C or higher and 900°C or lower for 20 hours.
A method for producing a unidirectional electrical steel sheet with excellent film adhesion, characterized by annealing for a period of not less than 2 seconds and not more than 300 seconds.