JP2649562B2 - Method for producing grain-oriented electrical steel sheet with metallic luster and excellent punchability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a grain-oriented electrical steel sheet having a metallic luster with excellent punching properties.

(Prior Art) A grain-oriented electrical steel sheet is generally manufactured as follows.
Electromagnetic steel slab containing 4.0% or less of Si is hot-rolled, and after hot-rolled sheet annealing or hot-rolled sheet annealing, cold rolling is performed twice or more with one or intermediate annealing to obtain the final sheet thickness, An oxide film containing SiO ₂ is generated on the steel sheet surface by performing decarburizing annealing, and then an annealing separator containing MgO as a main component is applied and dried,
It is wound around a coil and then subjected to finish annealing to develop secondary recrystallized grains having a Goss orientation, and to form a glass film by the reaction between the above-mentioned SiO ₂ and MgO in order to improve insulating properties and magnetic properties. Next, an insulating coating liquid is applied as required, and 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 iron core is usually punched with a mold,
Alternatively, it is manufactured by laminating a large number of iron core single plates having a predetermined shape by shearing. For example, manufacturing a core of a turbine generator requires 100,000 to 200,000 single-plate iron cores, depending on the capacity. It is important that these iron core veneers have a small punch-back, for example, 30 μm or less, in order to prevent an abnormal increase in iron loss due to short-circuiting of the end faces of the iron core when the iron core veneers are laminated. It is also desirable that the punch-back is small in order to facilitate the iron core manufacturing process.

The grain-oriented electrical steel sheet is formed with a glass coating or a double insulating coating of the coating and the insulating coating. These insulating coatings have the effect of reducing the iron loss by applying tension to the steel sheet, but on the other hand, the glass coating is hard and causes the die to wear when punching. Therefore, for example,
When punching is performed 00 times, punch-back occurs more than a predetermined value, and the die must be re-ground or replaced with a new one.
This significantly lowers workability and increases costs.

In order to enhance the punchability, a method for producing a grain-oriented electrical steel sheet in which the formation of a glass coating is suppressed has been proposed. For example, in Japanese Patent Application Laid-Open No. 53-22113, the thickness of the oxide film on the surface of the magnetic steel sheet formed by decarburizing annealing is set to 3 μm or less, and the steel sheet is coated with fine alumina mixed with hydrated silicate mineral powder as an annealing separator. , Finish annealing. In this way, the steel sheet is formed with a thin oxide film and a glass coating which is easily peeled off by the annealing separator containing alumina as a main component, thereby improving the punching property.

In JP-A-59-96278, as an annealing separator,
The use of fine-grain alumina with a grain size of 10 μm or less and inert MgO fired at a high temperature of 1300 ° C. or more suppresses the reaction with the oxide film on the steel sheet surface, preventing the formation of a glass film or easily peeling off. To improve the punching performance.

(Problems to be Solved by the Invention) According to these, there is a certain effect, the formation of a glass film on the surface of the grain-oriented electrical steel sheet is suppressed, and the punching property is improved to some extent. However, the oxide film formed by the decarburizing annealing has a thickness variation in the steel sheet surface because the original purpose of the decarburizing annealing is carbon removal. For example, both sides of the steel sheet are thicker than others, or a difference occurs in the length direction of the steel sheet. Further, in the conventional prevention of glass film formation, alumina is used as a main component of the annealing separator, which has a low reactivity with SiO ₂ in the oxide film, and attempts to suppress the film formation. Due to the difference in film thickness, a glass film may be partially formed, and it is difficult to say that the punching property is sufficiently good.

The present invention makes SiO ₂ in an oxide film generated by decarburizing annealing ineffective for glass film formation, preventing the formation of a glass film,
An object is to obtain a grain-oriented electrical steel sheet having extremely excellent punching properties.

(Means for Solving the Problems) The gist of the present invention is to provide a method for manufacturing a grain-oriented electrical steel sheet, in which a sulfide of an alkali metal or an alkaline earth metal is applied during application of an annealing separator from cold rolling. After attaching one or more of polysulfide, sulfate, carbonate, phosphate, nitrate, borate, hydroxide, and chloride to the steel sheet, apply an annealing separator and finish. An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet having a metallic luster and excellent punching characteristics, wherein the coating is performed without annealing and smoothing.

 Hereinafter, the present invention will be described in detail.

Grain-oriented electrical steel sheets are generally hot-rolled from electrical steel slabs containing 4.0% or less of Si, and then cold-rolled as hot rolled sheets or after hot-rolled sheet annealing, once or twice with intermediate annealing in between. It is subjected to decarburizing annealing, applied with an annealing separating agent, dried, wound on a coil and finish-annealed. In the present invention, the steel components and the steps up to cold rolling are not particularly required and are optional.

Cold rolling is performed once or twice or more with intermediate annealing interposed, then decarburized and applied with an annealing separator,
During this time, the glass film formation inhibitor is attached to the steel sheet.

For example, it is deposited before or after decarburizing annealing. As a glass film formation inhibitor, alkali metal such as Li, Na, K or sulfide of alkaline earth metal such as Ca, Ba, Mg, Sr is used. , Polysulfides, chlorides, hydroxides, sulfates, carbonates, phosphates, nitrates, borates.

If these glass film formation inhibiting agents are attached to the steel sheet before the decarburizing annealing, they chemically enter into the oxide film formed on the steel sheet surface by the decarburizing annealing or seal the steel sheet from the decarburizing annealing atmosphere.

The glass film formation inhibitor that has entered the oxide film inhibits the reaction between SiO ₂ in the oxide film and MgO as an annealing separating agent in the finish annealing, thereby preventing the formation of a glass film. In addition, since the glass film formation inhibitor has a sealing effect as described above, the oxide film itself is also thinned, and from this point, there is an effect of not forming a glass film. Even when the glass film forming inhibitor is attached to the steel sheet after the decarburizing annealing, the chemical chemically penetrates into the oxide film generated by the decarburizing annealing, and similarly inhibits the formation of the glass film.

0.01-5.0g as the amount of glass film formation inhibitor
/ m ² , and one of the sulfides, polysulfides, chlorides, hydroxides, sulfates, carbonates, phosphates, nitrates and borates of the alkali metals and alkaline earth metals. Seed or 2
More than one species is used.

The glass film formation inhibitor is attached to the steel sheet, and thereafter, an annealing separator is applied to the steel sheet, and the finish annealing is performed.
The grain-oriented electrical steel sheet has a metallic luster surface state, and has excellent punching properties.

In the case of flattening annealing after finish annealing, an inorganic coating agent such as phosphate such as phosphoric acid, aluminum phosphate, and magnesium phosphate, and chromic acid such as chromic acid, aluminum chromate, and magnesium chromate are applied to the surface of the metallic bright steel sheet. One or more of salt, bichromate, and colloidal silica may be applied and flattened and annealed.

After the flattening annealing, an organic coating agent, for example, an acrylic, styrene, polyvinyl, melamine, phenol, vinyl acetate, epoxy coating agent or the like is applied and baked. A semi-organic coating agent can be used, and in any case, the punching property is further improved. 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: 0.065%, S; 0.023%, the remainder being a hot-rolled 2.3 mm thick grain-oriented electrical steel sheet slab consisting of iron and unavoidable impurities, and then 980 ° C Cold rolling was performed twice by sandwiching intermediate annealing for 3 minutes to obtain a cold-rolled sheet having a sheet thickness of 0.30 mm.

Next, after removing the cold-rolled oil adhering to the steel sheet, a chemical solution having the composition shown in Table 1 was applied by a coating roll so as to have a dry weight of 0.1 g / m ² and dried in an air furnace at 350 ° C. later, 850 ℃ × 3 _{'between, N 2 + H 2 PH 2} O / PH 2 = 0.45
Under the conditions described above, decarburizing annealing and baking were performed. After that, MgO powder was applied as a slurry as an annealing separator, and then applied at 1200 ° C.
For 20 hours. An aluminum phosphate + colloidal silica-based coating solution was applied to this steel sheet and baked while also performing flattening annealing. Table 2 shows the results of investigations on the appearance, punching properties, and magnetic properties of each of the obtained test materials.

<Example 2> A cold rolled sheet having a sheet thickness of 0.30 mm obtained in the same manner as in Example 1 was used for 850.
Decarburization annealing was performed in an atmosphere of N ₂ + H ₂ PH ₂ O / PH ₂ = 0.48 at ° C. for 3 minutes.

A solution of a chemical having the composition shown in Table 3 was applied to this steel sheet, applied at a dry weight of 0.2 g / m ² , and allowed to adhere.
The baking treatment was performed in an atmosphere furnace at 00 ° C. for 30 seconds. This steel sheet was coated with MgO as an annealing separator, dried, subjected to finish annealing at 1200 ° C. for 20 hours, and then subjected to a baking treatment of an insulating film in the same manner as in Example 1. Table 4 shows the results of the appearance, punching properties, and magnetic properties of each of the obtained test materials.

<Example 3> When the same material as in Example 1 was subjected to intermediate annealing at 980 ° C for 3 minutes, a chemical having a composition shown in Table 5 was dried at a weight of 0.5 g / m2.
After coating at a rate of ² , annealing was performed, and final cold rolling was performed to a final sheet thickness of 0.35 mm. PH ₂ O / PH in N ₂ + H ₂ at 850 ° C for 3 minutes
₂ Decarburizing annealing at 0.50, applying MgO as an annealing separator,
Final finish annealing at 1200 ° C. for 20 hours was performed. This steel sheet was subjected to the same insulating film treatment as in Examples 1 and 2 to obtain a final product. Table 6 shows the results of investigations on the appearance, punchability, and magnetic properties of each of the obtained test materials.

(Effects of the Invention) According to the present invention, a grain-oriented electrical steel sheet is obtained in which a glass coating is not formed as described above, the steel sheet exhibits a metallic luster over the entire surface, and the punching property is remarkably excellent without performing a smoothing treatment. Can be

Further, it can be obtained without being affected by the conditions of the preceding process such as decarburization annealing.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-107784 (JP, A) JP-A-1-176063 (JP, A) JP-A-64-62417 (JP, A) JP-A 64-64 62476 (JP, A)

Claims (1)

(57) [Claims] 1. An electromagnetic steel slab is hot-rolled, and as-rolled, or after hot-rolled sheet annealing, cold-rolled one or more times with intermediate annealing interposed therebetween, decarburized and then annealed. In the method for manufacturing a grain-oriented electrical steel sheet to apply a finishing agent and finish annealing, during the application of the annealing separator from cold rolling, sulfide of alkali metal or alkaline earth metal, polysulfide, sulfate, carbonate, Apply one or more of phosphate, nitrate, borate, hydroxide, and chloride to steel sheet, apply annealing separator, finish annealing, and perform coating without smoothing treatment. A method for producing a grain-oriented electrical steel sheet having a characteristic metallic luster and excellent punching properties.