JPH02107781A - Production of grain-oriented electrical steel sheet having metallic luster and superior suitability for blanking - Google Patents

Abstract

PURPOSE:To produce the title steel sheet having superior suitability for blanking and metallic luster by adhering chemicals for inhibiting the formation of a glass film to a steel sheet between a cold rolling stage and a stage for applying a separating agent for annealing when a grain-oriented electrical steel sheet is produced. CONSTITUTION:An electrical steel slab is successively subjected to hot rolling, cold rolling and decarburization annealing, a separating agent for annealing is applied to the resulting steel sheet and finish annealing is carried out to produce a grain- oriented electrical steel sheet. At this time, chemicals for inhibiting the formation of a glass film are applied to the steel sheet by about 0.01-5.0g/m<2> between the cold rolling and applying stages. One or more kinds of sulfides, polysulfides, sulfates, carbonates, phosphates, nitrates, borates, hydroxides or chlorides of alkali metals such as Li, Na and K or alkaline earth metals such as Ca, Ba and Mg are used as the chemicals. The formation of a glass film on the steel sheet is prevented and a grain-oriented electrical steel sheet having superior suitability for blanking and metallic luster over the entire surface is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing grain-oriented electrical steel sheets with excellent punchability and metallic luster.

(Prior Art) Grain-oriented electrical steel sheets are generally manufactured as follows. S
Hot rolling a magnetic steel slab containing 4.0% or less of i,
As a hot-rolled sheet or after annealing a hot-rolled sheet, cold rolling is performed once or twice or more with intermediate annealing to obtain the final sheet thickness, and decarburization annealing is performed to generate an oxide film containing Sing on the surface of the steel sheet. Then, an annealing agent containing MgO as a main component, '1iit agent is applied, dried, and wound into a coil.Final annealing is then performed to develop secondary recrystallized grains with Goss orientation, and to improve insulation and The SiO□
A glass coating is formed by the reaction between . Then, if necessary, an insulating coating liquid is applied and a baking heat treatment is performed to form an insulating coating film.

Grain-oriented electrical steel sheets are used as core materials for electrical equipment such as generators and transformers. The core is usually manufactured by stacking a large number of core single plates that are punched out using a die or cut into a predetermined shape by shearing. For example, manufacturing the core of a turbine generator requires 100,000 to 200,000 core veneers, depending on its capacity.

These iron core veneers have a small punching return, for example 30 μm.
It is important that the thickness be less than m in order to prevent an abnormal increase in iron loss due to a short circuit at the end face of the iron core when the core veneers are laminated. In addition, it is desired that the punching return be small in order to facilitate the manufacturing process of the core.

A grain-oriented electrical steel sheet is provided with a glass coating or a double insulation coating consisting of the glass coating and an insulating coating. These insulating coatings have the effect of applying tension to the steel plate and reducing iron loss, but on the other hand, since glass coatings are hard, they cause abrasion of the mold during punching. For this reason, for example, the number 10
If the die is punched 00 times, the die will return more than a predetermined value, and the die must be re-polished or replaced with a new one. This significantly reduces workability and increases costs.

In order to improve punchability, a method for manufacturing grain-oriented electrical steel sheets has been proposed in which the formation of a glass film is limited to one occasion. For example, in JP-A-53-22113, the thickness of the oxide film on the surface of the electrical steel sheet formed by decarburization annealing is set to 3 μm or less, and fine-particle alumina mixed with hydrated silicate mineral powder is used as an annealing separator to coat the steel sheet. , finish annealing. In this way, a glass film that is easily peeled off is formed on the steel plate by the thin oxide film and the annealing separator mainly composed of alumina, thereby improving the punching property.

Furthermore, in JP-A No. 59-96278, fine particle alumina with a particle size of 10 μm or less and 13
By using inert HGO fired at a high temperature of 00°C or higher, the reaction with the oxide film on the surface of the steel sheet is suppressed, preventing the formation of a glass film or making it easier to peel off, thereby improving punching performance. .

(Problems to be Solved by the Invention) These have certain effects, suppressing the formation of a glass film on the surface of grain-oriented electrical steel sheets, and achieving a certain degree of improvement in punchability. However, since the original purpose of decarburization annealing is to remove carbon, the thickness of the oxide film formed by decarburization annealing varies within the surface of the steel sheet.

For example, both sides of the steel plate may be thicker than the other sides, or differences may occur in the length direction of the steel plate. Furthermore, conventional methods for preventing glass film formation utilize the fact that alumina, the main component of the annealing separator, has weak reactivity with SiO□ in the oxide film to suppress film formation. 11 Due to the influence of the difference in thickness, a glass film may be formed partially, and it is difficult to say that the punching property is sufficiently good.

The object of the present invention is to prevent the formation of a glass coating by preventing the formation of a glass coating by making Sin in the oxide film produced during decarburization annealing, and to obtain a grain-oriented electrical steel sheet having extremely excellent punchability.

(Means for Solving the Problems) The gist of the present invention is that in a method for manufacturing grain-oriented electrical steel sheets, between cold rolling and applying an annealing separator,
alkali metal or alkaline earth metal sulfides, polysulfides, sulfates 1, carbonates, phosphates, nitrates, borates,
A grain-oriented electrical steel sheet with metallic luster and excellent punchability, characterized by adhering one or more of hydroxides and chlorides to the steel sheet, then applying an annealing separator and final annealing. It is in the manufacturing method.

The present invention will be explained in detail below.

Grain-oriented electrical steel sheets are generally produced by hot-rolling electrical steel slabs containing 4.0% or less of Si, and then cold-rolling them either once or twice or more with intermediate annealing in between as hot-rolled sheets or after annealing the hot-rolled sheets. It is rolled to the final thickness, decarburized and annealed, coated with an annealing separator, dried, wound into a coil, and finished annealed. In the present invention, the steel composition and the steps up to cold rolling do not need to be specified and are arbitrary.

Cold rolling is performed once or twice or more with intermediate annealing in between, and then de-rolling;! The steel plate is annealed and coated with an annealing separation agent, during which time a glass film formation inhibiting agent is applied to the steel plate.

For example, sulfides and polysulfides of alkali metals such as LiNa and K, or alkaline earth metals such as Ca, Ba, and MgSr can be attached before or after decarburization annealing. , chlorides, hydroxides, sulfates, carbonates, phosphates, nitrates, and borates.

When these glass film formation inhibiting agents are attached to a steel sheet before decarburization annealing, they chemically enter the oxide film generated on the surface of the steel sheet during decarburization annealing, or seal the steel sheet from the decarburization annealing atmosphere.

The glass film formation inhibiting agent that has entered the oxide film inhibits the reaction between SiO□ in the oxide film and the annealing separation agent NGO during final annealing, thereby preventing the formation of a glass film.

Furthermore, since the glass film formation inhibiting agent has a sealing effect as described above, the oxide film itself becomes thinner, and from this point of view as well, it has the effect of preventing the formation of a glass film.

Even when the glass film formation inhibiting agent is attached to a steel sheet after decarburization annealing, it chemically enters the oxide film produced during decarburization annealing and similarly inhibits the formation of a glass film.

The adhesion amount of the glass film formation inhibiting agent is 0.01 to 5.
．． 0 g/rl (sulfides, polysulfides, chlorides, hydroxides, etc. of the alkali metals and alkaline earth metals,
1 of sulfates, carbonates, phosphates, nitrates, borates
A species or two or more species may be used.

The glass film formation inhibiting agent is applied to the steel sheet, and then an annealing separator is applied to the steel sheet and finish annealing is performed, but the grain-oriented electrical steel sheet has a metallic luster surface and has extremely excellent punchability. Become.

During flattening annealing after final annealing, inorganic coating agents such as phosphoric acid, phosphates such as aluminum phosphate, and magnesium phosphate, chromic acids such as chromic acid, aluminum chromate, and magnesium chromate are applied to the surface of the metallic gloss steel sheet. One or more of salt, dichromate, and colloidal silica may be applied and flattened annealed.

Further, after flattening annealing, an organic coating agent such as acrylic, styrene, polyvinyl, melamine, phenol, vinyl acetate, or epoxy coating agent is applied and baked. A semi-organic coating agent may also be used, and in either case, the punching properties will be even better. When such an organic or semi-organic coating agent is applied, an inorganic coating agent may or may not be applied during flattening annealing.

Next, examples will be described.

<Example 1>C; 0.052%, Si; 3.10%, Mn; 0
．． A grain-oriented electrical steel sheet slab consisting of 0.065%, S, 0.023%, the balance being iron and unavoidable impurities was hot rolled to a thickness of 2.3 mm, and then cooled twice with intermediate annealing at 980°C for 3 minutes. Inter-rolling was performed to obtain a cold-rolled plate with a thickness of 0.30 mm.

Next, after removing the cold rolling oil adhering to the steel plate, a chemical solution having the composition shown in Table 1 was applied with a coating roll to a dry weight of 0.1 g/bo, and then dried in an atmospheric oven at 350°C. After that, N2+H□ for 850°C x 3'
Decarburization annealing and baking treatment were performed under the conditions of pH20/P)12 = 0.45. Thereafter, after applying HGO powder in slurry form as an annealing separator, final annealing was performed at 1200°C for 20 hours. A coating liquid containing AI phosphate and colloidal silica was applied to this steel plate, and the steel plate was subjected to flattening annealing and baking. Table 2 shows the results of investigating the appearance, punchability, and magnetic properties of each test material obtained.

<Example 2> A cold-rolled plate with a thickness of 0.30 mm obtained in the same manner as in Example 1 was heated at 850°C for 3 minutes to Nz+IIz PI+20/P
Decarburization annealing was performed in an atmosphere of H2=0.48.

A solution of a chemical having the composition shown in Table 3 was added to this steel plate, and the weight after drying was 0.2 g/rT? The film was coated and adhered, and baked for 30 seconds in an atmospheric furnace at a furnace temperature of 500°C. MgO was applied as an annealing separator to this steel plate, and after drying, finish annealing was performed at 1200°C for 20 hours, and then the insulation coating was baked in the same manner as in Example 1. Table 4 shows the results of the appearance, punchability, and magnetic properties of each test material obtained.

"Wheat"-" 81 unidentified traps <Example 3> When the same material as in Example 1 was intermediately annealed at 980° C. for 3 minutes, a chemical having the composition shown in Table 5 was used at a dry weight of 0.
Annealed after coating at a rate of 5 g/n (final plate thickness 0.35
Final cold rolling was carried out to a thickness of mm. This steel plate was heated to 850'C for 3
Minute N2fII □ medium temperature Pi20 /pHz =0.50
After decarburization annealing and applying MgO as an annealing separator, 12
Final annealing was performed at 00°C for 20 hours. This steel plate was subjected to the same insulation coating treatment as in Example 1.2 to obtain a final product. Table 6 shows the results of investigating the appearance, punchability, and magnetic properties of each test material obtained.

LLJ! . Production (Effects of the Invention) According to the present invention, as described above, a grain-oriented electrical steel sheet is obtained in which no glass film is formed, the steel sheet exhibits metallic luster over the entire surface, and has extremely excellent punchability.

Moreover, this can be achieved without being affected by the conditions of previous processes such as decarburization annealing.

Claims (1)

[Claims] Hot-rolled electromagnetic steel slab, either as a hot-rolled plate or after annealing the hot-rolled plate, cold-rolling once or twice or more with intermediate annealing in between, decarburizing annealing, and finishing by applying an annealing separator. In the method for manufacturing a grain-oriented electrical steel sheet to be annealed, during the period from cold rolling to application of an annealing separator, alkali metal or alkaline earth metal sulfides, polysulfides, sulfates, carbonates, phosphates,
One or more of nitrates, borates, hydroxides, and chlorides is attached to a steel plate, an annealing separator is applied, and finish annealing is performed. A direction with metallic luster and excellent punchability. manufacturing method of magnetic steel sheet.