JPH0663036B2 - Method for producing grain-oriented electrical steel sheet having metallic luster - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a grain-oriented electrical steel sheet having metallic luster, and relates to a method for obtaining a grain-oriented electrical steel sheet having no glass coating and having an excellent punchability.

(Prior Art) A grain-oriented electrical steel sheet is generally manufactured as follows. That is, hot rolling a silicon steel slab containing Si 4.0% or less,
Annealing is performed once or cold rolling is performed twice or more with intervening intermediate annealing to obtain the final plate thickness, and decarburization annealing is performed on the steel plate surface.
An oxide film containing SiO ₂ is generated, then an annealing separator containing MgO as a main component is applied, dried, and wound into a coil.
After that, high-temperature finish annealing is performed to develop secondary recrystallized grains having a Goss orientation, a glass film is formed, and then an insulating coating solution is applied as necessary and annealing heat treatment is performed to form the insulating coating film.

The grain-oriented electrical steel sheet is used as a core material for electric devices such as generators and transformers. The iron core is usually manufactured by punching with a die or shearing and laminating a plurality of iron core single plates having a predetermined shape. For example, manufacturing an iron core of a turbine generator requires about 100,000 to 200,000 single iron core plates depending on its capacity. In addition, it is important that the punching back is a predetermined value, for example, about 15 μm or less for preventing an abnormal increase in iron loss due to end face short circuit when the iron core veneers such as a turbine generator are laminated.

The grain-oriented electrical steel sheet has a glass coating or a double insulating coating of the coating and the insulating coating. Since the glass coating is hard, the die wears when punching. Therefore, for example, when punching a few thousand times, punching back occurs, and the mold must be re-polished or replaced with a new one. This significantly lowers the workability and raises the cost.

As a method for producing a grain-oriented electrical steel sheet having a metallic luster, for example, there is one disclosed in JP-A-53-22113. This is performed by decarburizing annealing to make the thickness of the oxide film 3 μm or less, and using fine particle alumina containing 5 to 40% of hydrous silicate mineral powder as an annealing separating agent, this is applied to a steel sheet and finish annealing. According to this method, the oxide film is thinned, and further, the glass film which is easily peeled off is formed by blending the hydrated silicate mineral powder, and a glass having metallic luster can be obtained.

(Problems to be solved by the invention) However, in the actual operation line, for example, decarburization annealing may change the dew point and composition of the atmospheric gas, and the thickness of the oxide film formed on the surface of the steel sheet partially changes. . In addition, the steel sheet itself is slightly different in the way of being oxidized in the width direction and the length direction depending on the history. Further, peeling unevenness may occur in the method of peeling the formed glass film. At present, it has not been possible to sufficiently stably manufacture grain-oriented electrical steel sheets having metallic luster.

An object of the present invention is to stably obtain a grain-oriented electrical steel sheet having a uniform metallic luster without forming a glass coating and having an excellent punching property.

(Means for Solving Problems) The gist of the present invention is to perform decarburization annealing of a grain-oriented electrical steel sheet cold-rolled by a known method to obtain a final thickness, apply an annealing separator, and finish-anneal a grain-oriented electromagnetic sheet. In the method of manufacturing a steel sheet, decarburization annealing is performed at 800 to 850 ° C., and PH ₂ O / PH ₂ in the atmosphere is set at 0.25 to 0.5.
5 per 100 parts by weight of magnesia, 1 or 2 of chloride of alkali metal or alkaline earth metal
It is a method for producing a grain-oriented electrical steel sheet having a metallic luster, which comprises applying an annealing separator made by mixing 2 to 40 parts by weight of at least one kind and finishing annealing.

The present invention will be described in detail below.

Generally, the grain-oriented electrical steel sheet is annealed by hot rolling and then is annealed once or is cold-rolled twice or more by interposing intermediate annealing to a final thickness, decarburized and annealed, and an annealing separator is applied. It is wound on a coil and finish annealed. In the present invention, it is not necessary to specify the steel composition and the final plate thickness, and it is optional.

The grain-oriented electrical steel sheet cold-rolled to the final thickness is decarburized and annealed. By this decarburization annealing, carbon in the steel is removed, primary recrystallization is performed, and an oxide film containing SiO ₂ is formed on the surface of the steel sheet. In the present invention, if the annealing temperature is low, the time required for decarburization becomes long and decarburization becomes insufficient. On the other hand, if the temperature becomes higher, decarburization becomes difficult, and the oxide layer is formed more often, and unevenness of the glass coating film after the final annealing is likely to occur, so the temperature is set to 850 ° C. or less. The decarburization annealing time does not have to be specified, but it is preferably 90 to 180 seconds. The atmosphere gas is H ₂ , N ₂ , Ar,
H ₂ O, a small amount of CO, and CO ₂ gas are used. It is important to regulate the degree of oxidation of this atmosphere gas. Since you及affect the magnetic properties decarburization shortages and low degree of oxidation PH ₂ O / PH ₂ occurs PH ₂ O
/ PH ₂ value should be 0.25 or more. If the degree of oxidation is large, the amount of oxide layer formed is large, and unevenness of the glass coating is likely to occur after the final annealing.

After decarburization annealing, the annealing separator is applied to the grain-oriented electrical steel sheet, dried and wound on a coil for finish annealing.However, the composition of this annealing separator is such that the glass film does not form a glass film during finish annealing. It is important for achieving a glossy steel plate surface condition.

In the present invention, the annealing separator is magnesia (MgO) 10
2 to 40 parts by weight of one or more chlorides of alkali metals such as Li, Na, K, and Rb or alkaline earth metals such as Ca, Ba, Mg, and Sr are added to 0 parts by weight. Use the one.

When 2 parts by weight or more of alkali metal or alkaline earth metal chloride is mixed with 100 parts by weight of magnesia, the reaction between magnesia and SiO _{2 in} the oxide film on the steel sheet surface is suppressed by finish annealing, and no glass film is formed. . This is because the chloride in the annealing separator decomposes SiO ₂ in the oxide film and does not lead to the formation of a glass film. 2 parts by weight or more is required for 100 parts by weight of magnesia in order to achieve the above effect. If it is less than this range, a glass film having adhesiveness is formed, or a glass film is partially formed, resulting in a non-uniform appearance and deterioration. On the other hand, when this blending amount is large, seizure occurs in finish annealing. Further, when the insulating coating solution is applied and heat-treated to form the insulating coating, it becomes difficult to remove the annealing separating agent by the pretreatment of lithoule (light pickling). In order to prevent these, the amount is 40 parts by weight or less.

When this annealing separator is applied to grain-oriented electrical steel and finish-annealed, even if the oxide film has uneven thickness during decarburization annealing, no glass coating is formed over the entire surface and the entire length of the steel and it has a metallic luster. It is possible to obtain a die having excellent punchability.

(Example) Next, an example will be described.

Example 1 C: 0.045%, Si: 3.08%, Mn: 0.060%, S: 0.024%
Hot rolled grain oriented electrical steel sheet slab containing 2.3% and the balance iron and unavoidable impurities to a thickness of 2.3 mm, and then 950
Cold rolling was performed twice with intermediate annealing at 3 ° C. for 3 minutes to obtain a cold rolled sheet having a sheet thickness of 0.35 mm. Then, decarburization annealing was performed under the conditions shown in Table 1. After applying the annealing separator shown in Table 1 to this steel sheet, finish annealing was performed at 1200 ° C. for 20 hours. After that, a phosphate + colloidal silica-based coating liquid was applied and baked also as flattening annealing. The appearance, punchability and magnetic properties of each of the obtained test materials were investigated, and the results are shown in Table 2.

810 ° C. PH ₂ O / PH ₂ = 0.28, 0.45, 80 under the conditions of the present invention
At 0 ° C. PH ₂ O / PH ₂ = 0.35, no film was uniformly formed, and metallic luster was exhibited, and punchability was also good.
On the other hand, in the case of the comparative material, the film is formed uniformly, so that the punchability is poor, and under No. 3 condition where PH ₂ O / PH ₂ is too high and No. 5 where the temperature is high, unevenness due to film formation on the edge part occurs As a result, a slight film was formed on the whole, and the punchability was poor. Further, in the analysis result of the residual C after decarburization, an abnormality was found in No. 5 having a high temperature.

Example 2 A cold-rolled sheet having a final sheet thickness of 0.35 mm prepared in the same manner as in Example 1 was N ₂ + H ₂ , PH ₂ O / PH ₂ = 0.3 at 820 ° for 150 seconds.
Decarburization annealing was performed at 5. Then, the composition having the composition shown in Table 3 was applied as an annealing separator, and then a final annealing at 1200 ° C x 20H was performed. Next, heat flattening and colloidal silica / chlorine phosphate-based coating were baked on a continuous coating line. The characteristics of the product are also shown in Table 3.

In the comparative example, the glass film was uniformly formed and the punchability was poor, whereas the products using the additive of the present invention did not form a uniform film and exhibited metallic luster. The punchability was also good.

(Effect of the Invention) As described above, according to the present invention, a grain-oriented electrical steel sheet having excellent punchability can be obtained. It also has good appearance and magnetic properties.

Claims (1)

[Claims] 1. A method for producing a grain-oriented electrical steel sheet, comprising decarburizing-annealing a grain-oriented electrical steel sheet cold-rolled to a final thickness, applying an annealing separator, and finishing annealing.
At a temperature of 850 ° C., the atmosphere pH ₂ O / PH ₂ is changed to 0.25 to 0.55.
For 100 parts by weight of magnesia, 1 or 2 of chloride of alkali metal or alkaline earth metal
A method for producing a grain-oriented electrical steel sheet having a metallic luster, which comprises applying an annealing separating agent containing 2 to 40 parts by weight of at least one kind and finishing annealing.