KR101919527B1 - Oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

A method for producing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes: a slab including 1.0 to 4.0% of Si, 0.1 to 0.4% of Si, and a balance of Fe and other inevitably incorporated impurities, ; Reheating the slab; Hot rolling the slab to produce a hot-rolled steel sheet; Hot-rolled sheet annealing the hot-rolled steel sheet; A first cold rolling step of hot-rolled steel sheets annealed; Decarburizing and annealing the primary cold-rolled steel sheet; Secondarily cold-rolling the steel sheet after decarburization annealing; Final annealing the steel sheet after completion of the second cold rolling; Pickling the steel sheet after completion of the final annealing; And forming a ceramic coating layer on the pickled steel sheet.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a directional electric steel sheet,

To a directional electric steel sheet and a manufacturing method thereof.

The grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction, consisting of crystal grains having a Goss orientation in which the crystal orientation of the steel sheet is {110} < 001 >.

The oriented electrical steel sheet is rolled to a final thickness through hot rolling, hot rolling annealing, and cold rolling after the slab is heated, followed by high temperature annealing for primary recrystallization annealing and secondary recrystallization.

At this time, it is known that, at a high temperature annealing, the degree of integration of the Goss orientation to be secondary recrystallized becomes higher as the temperature increase rate is slower, and the magnetism is excellent. In general, the rate of increase in temperature during high temperature annealing of a directional electric steel sheet is not more than 15 ° C per hour, and not only takes 2 to 3 days to raise the temperature, but also requires energy annealing more than 40 hours. In addition, since the current high-temperature annealing process is performed in a batch-type annealing in a coil state, the following difficulties arise in the process. First, a temperature deviation of the outer and inner windings of the coil occurs due to the heat treatment in the coil state, so that the same heat treatment pattern can not be applied to each part, resulting in magnetism deviation between the outer and inner windings. Second, since the MgO is coated on the surface after decarburization annealing and various surface defects are formed in the process of forming the base coating during the high temperature annealing, the rate of water drop is decreased. Third, since the decarburized annealed annealed decarburized plate is wound in a coil form, then annealed at high temperature, and then subjected to planarization annealing, the insulating coating is performed. Thus, the production process is divided into three stages, thereby causing a problem of a low yield rate.

In one embodiment of the present invention, a method for manufacturing a directional electrical steel sheet and a directional electrical steel sheet produced by the method are provided.

A method for producing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes: a slab including 1.0 to 4.0% of Si, 0.1 to 0.4% of Si, and a balance of Fe and other inevitably incorporated impurities, ; Reheating the slab; Hot rolling the slab to produce a hot-rolled steel sheet; Hot-rolled sheet annealing the hot-rolled steel sheet; A first cold rolling step of hot-rolled steel sheets annealed; Decarburizing and annealing the primary cold-rolled steel sheet; Secondarily cold-rolling the steel sheet after decarburization annealing; Final annealing the steel sheet after completion of the second cold rolling; Pickling the steel sheet after completion of the final annealing; And forming a ceramic coating layer on the pickled steel sheet.

And a decarburization process in the step of annealing the hot-rolled steel sheet.

The step of annealing the hot-rolled sheet may include a step of annealing at a temperature of 850 캜 to 950 캜 and a dew-point temperature of 50 캜 or higher, and a step of annealing at a temperature of 1000 캜 to 1200 캜 and a dew-point temperature of 0 캜 or lower.

The step of decarburizing and annealing the primary cold-rolled steel sheet may include a step of annealing at a temperature of 850 캜 to 950 캜 and a dew-point temperature of 50 캜 or higher, and a step of annealing at a temperature of 1000 캜 to 1200 캜 and a dew-point temperature of 0 캜 or lower .

The step of decarburization annealing the primary cold-rolled steel sheet and the step of secondary cold-rolling the steel sheet after the decarburization annealing can be repeated twice or more.

The step of finish-annealing may include the step of annealing at 850 ℃ to 1000 ℃ temperature and dew point temperature step of annealing at less than 70 ℃ and 1000 ℃ to 1200 ℃ temperature and H ₂ 50 vol% or more in the atmosphere.

The pickling step may be carried out at a temperature of 50 to 100 DEG C for 5 to 100 seconds using an aqueous acid solution of 5 to 50 wt%.

In the step of forming the ceramic coating layer, a ceramic coating layer may be formed by supplying a ceramic powder to a heat source in which an inert gas is plasmaized.

Ceramic powder may comprise _{Al 2 O 3, SiO 2,} TiO 2 or ZrO _2.

The primary cold rolling step or the step of forming the ceramic coating layer may be performed continuously.

The grain-oriented electrical steel sheet according to one embodiment of the present invention comprises 1.0 to 4.0% of Si, 0.002% or less of C (does not include 0%), and the balance of Fe and other inevitably incorporated impurities (D2 / D1) of a diameter (D1) of a circumscribed circle to a diameter (D2) of an inscribed circle is set to be smaller than a ratio 0.5 or more of the entire goss grain grains.

The substrate may comprise an oxygen-deficient layer formed from the surface of the substrate to the interior of the substrate.

The oxygen depletion layer may contain up to 500 ppm of oxygen.

The oxygen depletion layer may contain less than 100 ppm of Mg.

The thickness of the ceramic coating layer may be 10 nm to 4 탆.

Ceramic coating layer may include _{Al 2 O 3, SiO 2,} TiO 2 or ZrO _2.

The ceramic coating layer can form a pattern having a width (w) of 10 to 100 mm and an interval (d) of 10 to 100 mm in the rolling direction.

The base material may have a ratio of crystal grains having a grain size of 20 to 500 占 퐉 of 80% or more.

According to an embodiment of the present invention, it is possible to provide a method of manufacturing a grain-oriented electrical steel sheet capable of performing continuous annealing without performing annealing in the form of a batch in a coil state at the final annealing.

Further, it is possible to produce a grain-oriented electrical steel sheet with only a short time of annealing.

Unlike the conventional method for producing a grain-oriented electrical steel sheet, a step of winding a cold-rolled steel sheet is not required.

In addition, a method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention can provide a grain-oriented electrical steel sheet that does not use a grain growth inhibitor.

In addition, steep annealing can be omitted.

1 is a schematic cross-sectional view of a directional electric steel sheet according to an embodiment of the present invention.
2 is a schematic perspective view of a directional electric steel sheet according to another embodiment of the present invention.
3 is a photograph showing the Goss crystal grain distribution on the plane perpendicular to the thickness direction of the substrate in the production example through EBSD analysis.
4 is a photograph showing a crystal grain distribution on a plane perpendicular to the thickness direction of the substrate in Comparative Production Example.

The terms first, second and third, etc. are used to describe various portions, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish any moiety, element, region, layer or section from another moiety, moiety, region, layer or section. Thus, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

When referring to a portion as being "on" or "on" another portion, it may be directly on or over another portion, or may involve another portion therebetween. In contrast, when referring to a part being "directly above" another part, no other part is interposed therebetween.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Unless otherwise stated,% means% by weight, and 1 ppm is 0.0001% by weight. Also, goss crystal grains means crystal grains having a crystal orientation within 15 degrees from {110} < 001 >.

In an embodiment of the present invention, the term further includes an additional element, which means that an additional amount of the additional element is substituted for the remaining iron (Fe).

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises firstly, 1.0 to 4.0% of Si, 0.1 to 0.4% of Si, and the balance of Fe and other inevitably incorporated impurities, Lt; / RTI &gt; The slab may further contain Mn in an amount of more than 0% and not more than 0.1% and S in an amount of more than 0% and not more than 0.005% by weight. The slab may further contain 0.001 to 0.1% by weight of Bi.

The reason for limiting the composition is as follows.

Silicon (Si) reduces the magnetic anisotropy of the electrical steel sheet and increases the resistivity to improve the iron loss. When the Si content is less than 1.0%, the iron loss is inferior, and when the Si content is more than 4.0%, the brittleness is increased. Therefore, the content of Si in the grain-oriented electrical steel sheet after the slab and the final annealing step may be 1.0% to 4.0%.

Carbon (C) is required to process C during the intermediate decarburization annealing and final decarburization annealing so that the Goss crystal grains in the surface layer diffuse to the center, so that the content of C in the slab may be 0.1 to 0.4 wt% . Further, the amount of carbon in the grain-oriented electrical steel sheet after the final annealing step in which decarburization is completed may be 0.0020 wt% or less.

Manganese (Mn) and sulfur (S) form MnS precipitates and interfere with the growth of Goss grains that diffuse to the core during the decarburization process. Therefore, it is preferable that Mn and S are not added. However, in consideration of the amount that is inevitably incorporated during the steelmaking process, Mn and S in the grain-oriented electrical steel sheet after the slab and final annealing step are preferably controlled to Mn: 0.1% or less and S: 0.005% or less.

Bismuth (Bi) is a segregating element with high volatility. When it is located in the surface layer, it is volatilized on the surface, making the crystal grain of the surface layer coarse. On the contrary, it has the effect of refining the crystal grains in the center of the steel. If the content is less than 0.001% by weight, the effect may be insignificant. On the contrary, when it is added in an amount exceeding 0.1% by weight, it causes unevenness in the size of the surface crystal grain, so it is preferably added in an amount of 0.001 to 0.1% by weight.

The slab having the above composition is reheated. The slab reheating temperature may be 1100 ° C to 1350 ° C higher than the normal reheat temperature.

When the slab is heated at a high temperature, there is a problem that the hot-rolled structure is coarsened and adversely affects magnetism. However, in the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, the hot-rolled structure is not coarsened even when the slab reheating temperature is high, It is advantageous.

Next, the heated slab is hot-rolled to produce a hot-rolled steel sheet.

Next, the hot-rolled steel sheet is subjected to hot-rolled sheet annealing. At this time, the hot-rolled sheet annealing may include a decarburization process. Specifically, the hot-rolled sheet annealing may include a step of annealing at a temperature of 850 to 950 占 폚 and a dew-point temperature of 50 占 폚 or more, and a step of annealing at a temperature of 1000 占 폚 to 1200 占 폚 and a dew point temperature of 0 占 폚 or lower.

Next, hot rolled steel sheet decarburization annealing is performed, pickling is carried out, and primary cold rolling is performed to produce a cold rolled steel sheet.

Next, the cold-rolled steel sheet is decarburized and annealed. At this time, the step of decarburization annealing can be carried out in a region where austenite single phase region or a composite phase of ferrite and austenite exist. Specifically, a step of annealing at a temperature of 850 to 950 占 폚 and a dew-point temperature of 50 占 폚 or more, and a step of annealing at a temperature of 1000 占 폚 to 1200 占 폚 and a dew point temperature of 0 占 폚 or lower. The decarbonization amount in the decarburization annealing may be 0.0300 wt% to 0.0600 wt%. Further, the atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. In this decarburization annealing process, the grain size on the surface of the electric steel sheet grows to a great extent, but the crystal grains inside the electric steel sheet remain as a fine structure. After the decarburization annealing, the size of the surface ferrite grains may be 150 μm to 250 μm.

Next, the steel sheet having undergone decarburization annealing is subjected to secondary cold rolling. It is known that it is effective to carry out cold rolling at a high pressure lowering rate which is close to 90% once in the manufacturing process of a conventional high magnetic flux density directional electric steel sheet. This is because only Goss crystal grains in the primary recrystallized grains create an environment favorable for grain growth.

However, since the method of manufacturing the grain-oriented electrical steel sheet according to an embodiment of the present invention internally diffuses Goss grains in the surface layer caused by decarburization annealing and cold rolling without using abnormal grain growth of Goss orientation grains, It is advantageous to form them so as to have a large distribution.

Therefore, when cold rolling is carried out at a reduction ratio of 50% to 70% in the cold rolling, many goss texture can be formed in the surface layer portion. Or 55% to 65%.

The step of decarburizing and annealing the cold-rolled steel sheet and the step of cold-rolling the steel sheet after the decarburization annealing can be repeated two or more times. By repeating this operation two or more times, a large number of Goss texture can be formed in the surface layer portion.

Next, final annealing is performed on the electric steel sheet after decarburization annealing and secondary cold rolling.

In the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, unlike the conventional batch method, final annealing can be performed successively after cold rolling.

In a method of manufacturing a grain-oriented electrical steel sheet according to one embodiment of the present invention, the final annealing is at 850 ℃ to 1000 ℃ temperature and dew point temperature step of annealing at less than 70 ℃ and 1000 ℃ to 1200 ℃ temperature and H ₂ 50 vol% or more in the atmosphere And annealing. The atmosphere in the second stage was H ₂ 90 vol% or more.

The cold-rolled sheet before final annealing is in a state in which decarburization annealing proceeds so that the amount of carbon black remaining in the slab is 40 wt% to 60 wt% of the minimum amount of carbon in the slab. Therefore, at the first stage of the final annealing, the carbon grains are removed and the crystal grains formed in the surface layer are diffused inside. In the first step, decarburization can be performed so that the amount of carbon in the steel sheet is 0.01 wt% or less.

Thereafter, in the second step, a texture having a Goss orientation diffused in the first step is grown. In the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, grain size of crystal grains may be less than 1 mm, unlike the case where grains are grown by conventional abnormal grain growth. Therefore, it is possible to have an aggregate structure in which a plurality of goth grain grains having a grain size smaller than that of a conventional grain-oriented electrical steel sheet exist.

The thus prepared steel sheet has a ratio of 95% or more of the entire goss grain grains to the surface perpendicular to the thickness direction of the steel sheet, wherein the ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) . The crystal structure of the steel sheet will be specifically described with respect to a directional electrical steel sheet to be described later.

On the other hand, MgO coating layer is present because the annealing separator containing MgO as a main component is applied in the final batch annealing in the batch form, but the grain-oriented electrical steel sheet according to one embodiment of the present invention is not a batch type, Since the final annealing can be performed, the MgO coating layer may not exist.

Accordingly, the Mg content in the directional steel sheet according to an embodiment of the present invention can be 100 ppm or less from the surface of the steel sheet to the depth of 2 to 5 탆.

Next, the finished steel sheet is pickled. Through the pickling process, the oxide layer formed naturally on the surface of the steel sheet is removed. As a result, an oxygen-deficient layer containing oxygen at 500 ppm or less is formed from the surface portion of the steel sheet to the depth of 2 to 5 탆. On the other hand, in the so-called glassy process in which a base metal layer (base coating layer) is formed by using an annealing separator such as MgO in the final annealing process and the base metal layer is removed again, even if the base metal layer is removed, Oxygen is partially left on the surface layer of the steel sheet, and oxygen is contained in the surface layer.

The pickling step may use an aqueous acid solution of 5 to 50% by weight. At this time, an aqueous solution containing inorganic acid such as hydrochloric acid, nitric acid or sulfuric acid can be used as the acid aqueous solution. If the concentration of the aqueous acid solution is too low, proper pickling may not be achieved. In addition, when the concentration of the acid aqueous solution is too large, the surface roughness of the steel sheet becomes too high, which may adversely affect magnetism.

The pickling step may be carried out at a temperature of from 50 to 100 &lt; 0 &gt; C. If the temperature is too low, pickling may not be done properly. If the temperature is too high, re-oxidation may occur.

The pickling step may be pickled for 5 to 100 seconds. If the time is too short, the removal of the oxide layer may not be sufficiently performed. If the time is too long, the magnetic properties may be rather poor due to the non-uniformity of the acid pickling ability between the crystal grains and the inside of the crystal grains. More specifically, the pickling step can be pickled for 15 to 35 seconds.

Through the pickling process under appropriate conditions, an oxygen depletion layer is formed in the substrate, the magnetic migration is smooth, the magnetic hysteresis loss is reduced, and the magnetic property can be further improved.

Next, a ceramic coating layer is formed on the pickled steel sheet.

The step of forming the ceramic coating layer may use a plasma. Specifically, a ceramic coating layer can be formed by supplying a ceramic powder to a heat source in which an inert gas is plasmaized. As a method for forming a ceramic coating layer, a coating method using a plasma may be used in one embodiment of the present invention.

Ceramic powder may comprise _{Al 2 O 3, SiO 2,} TiO 2 or ZrO _2. The inert gas may include argon gas.

As described above, in one embodiment of the present invention, the final annealing process operated in the conventional batch mode can be operated as a continuous annealing process, and the steps of forming the first cold rolling step to the ceramic coating layer can be continuously performed.

1 schematically shows a cross section of a directional electrical steel sheet according to an embodiment of the present invention. 1, a directional electrical steel sheet 100 according to an embodiment of the present invention includes a base material 10 and a ceramic coating layer 20 formed on the surface of the base material 10. Hereinafter, each configuration will be described in detail. In Fig. 1, the x direction indicates the width direction of the steel sheet, and the z direction indicates the thickness direction of the steel sheet. Although not shown in FIG. 1, the y direction indicates the rolling direction of the steel sheet.

The substrate comprises 1.0% to 4.0% of Si, 0.002% or less of C (not including 0%), and the balance of Fe and other inevitably incorporated impurities. The element content and the reason for the base material have been described in detail with respect to the above-described production method of the grain-oriented electrical steel sheet, and therefore, a repetitive description thereof will be omitted. As described above, the carbon content in the substrate may be 0.002 wt% or less, unlike the carbon content in the slab, since it includes a decarburization process in the manufacturing process. Further, the base material may further contain Mn: more than 0% and not more than 0.1% by weight, and S: not more than 0% and not more than 0.005%. The base material may further contain 0.001 to 0.1% by weight of Bi.

The base material may include 95% or more of the entire goth grain grains in the goss grain with a ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) of the inscribed circle of 0.5 or more with respect to the plane perpendicular to the thickness direction of the steel sheet have. Here, the circumscribed circle means the smallest circle among the virtual circles surrounding the outside of the crystal grains, and the inscribed circle means the largest circle of the virtual circles included in the crystal grains.

In the structure of the base material according to the embodiment of the present invention, since the goth crystal grains on the surface grow into the inside of the steel sheet, a round grain shape is produced. On the other hand, in the conventional directional electrical steel sheet, grain of elliptical shape longer than the structure according to one embodiment of the present invention is produced.

As described above, due to the unique base structure according to one embodiment of the present invention, more excellent magnetic properties can be obtained.

According to an embodiment of the present invention, the size of the crystal grains of the base material may be 20 to 500 탆 of 80% or more of the total crystal grains.

The substrate 10 may comprise an oxygen-depleted layer 11 formed from the surface of the substrate 10 into the interior of the substrate. More specifically, the oxygen-depleted layer 11 may be formed at a depth of 2 to 5 占 퐉 from the surface of the substrate 10 to the inside of the substrate.

The oxygen-depletion layer 11 may contain oxygen at 500 ppm or less. The remaining composition is the same as the alloy composition of the above-described base material. Unlike the conventional base coated free steel sheet, since the base coating is not formed after the formation of the base coating, an oxide layer formed naturally can be removed through pickling to form an oxygen depleted layer on the surface of the steel sheet.

By forming the oxygen-deficient layer 11, the magnetic domain movement is smooth and the magnetic hysteresis loss is reduced, and the magnetic property can be further improved. More specifically, the oxygen-depleted layer 11 may contain oxygen at 100 ppm or less. In addition, since the base coating layer containing forsterite is not formed, Mg is contained in the oxygen-depleted layer 11 in the impurity range. Specifically, Mg may be contained in an amount of 100 ppm or less.

On the surface of the substrate 10, a ceramic coating layer 20 is formed. The ceramic coating layer 20 may be formed on the oxygen-depleted layer 11 when the oxygen-deficient layer 11 is contained in the substrate 10. [ A strong tensile force can be applied to the steel sheet by the ceramic coating layer 20 and the effect of miniaturization of the magnetic domain and improvement of iron loss can be maximized.

The thickness of the ceramic coating layer 20 may be 10 nm to 4 占 퐉. If the thickness is too thin, the tension effect is hard to occur. If the thickness is too large, the effect of improving the iron loss no longer occurs. Instead, the load factor of the transformer iron core after lamination of the steel sheet is lowered, which may cause an increase in no-load operation of the transformer.

The ceramic coating layer 20 may comprise Al ₂ O ₃ , SiO ₂ , TiO ₂ or ZrO ₂ .

The ceramic coating layer 20 may be formed on the entire surface of the substrate 10, but only on a part of the surface of the substrate. In the case where it is formed on a part of the surface of the substrate, it is also possible to form a pattern. Specifically, the ceramic coating layer 20 can form a pattern having a width w of 10 to 100 mm and an interval d of 10 to 100 mm in the rolling direction. 2 schematically shows an example in which the ceramic coating layer 20 forms a pattern. When the ceramic coating layer 20 forms a pattern in this manner, the magnetic property can be further improved.

Hereinafter, the embodiment will be described in detail. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

Manufacturing example  : Manufacture of Directional Electrical Sheets

3.23% of Si and 0.25% of C and the balance of Fe and unavoidable impurities was heated at a temperature of 1250 占 폚 and then hot-rolled to a thickness of 1.6 mm and then annealed at a temperature of 870 占 폚, a dew point temperature of 60 占 폚 Annealing was performed at a dew point temperature of 0 ° C or less in a hydrogen and nitrogen mixed gas atmosphere at an annealing temperature of 1100 ° C for 200 seconds, followed by cooling, pickling, and primary cold rolling at a reduction ratio of 60% .

The cold-rolled steel sheet was annealed again at an annealing temperature of 870 ° C and a dew point temperature of 60 ° C for 60 seconds and thereafter subjected to decarburization annealing at an annealing temperature of 1100 ° C and 50 seconds in a hydrogen and nitrogen gas atmosphere at a hydrogen and dew point temperature of 0 ° C or lower, Pickled and subjected to secondary cold rolling at a reduction ratio of 60%. The final thickness was 288 mu m.

Thereafter, at the final annealing, annealing was performed at a temperature of 900 ° C for 60 seconds in a mixed gas atmosphere of hydrogen and nitrogen (dew point temperature: 60 ° C), followed by annealing for 3 minutes in a 100% H ₂ atmosphere at 1050 ° C. The carbon content of the final steel sheet was 30 ppm.

FIG. 3 is a photograph showing the Goss crystal grain distribution on the plane perpendicular to the thickness direction through EBSD analysis.

Table 1 is a table showing the relative sizes of the inscribed circle and the circumscribed circle of the Goss crystal grains in the production example shown in FIG. 3 and showing the ratio (D2 / D1).

Circumscribed circle D1 Inscribed circle (D2) The ratio (D2 / D1) 2.4 1.6 0.67 2.6 1.5 0.58 2.8 2 0.71 1.7 1.1 0.65 1.9 1.3 0.68 2.5 1.3 0.52 2.2 1.2 0.55 2.9 1.7 0.59 2.2 1.4 0.64 1.9 1.1 0.58 1.3 0.9 0.69 1.8 1.2 0.67 1.2 0.7 0.58 1.7 1.1 0.65 1.8 One 0.56 1.7 0.9 0.53 1.2 0.8 0.67 1.3 One 0.77 2 One 0.5 1.5 0.9 0.6 1.2 0.7 0.58

As shown in Table 1, it can be seen that the ratio (D2 / D1) of all the grains of Goss is 0.5 or more.

Comparative Manufacturing Example  : Manufacture of Directional Electrical Sheets

3.23% of Si, 0.25% of C, and the balance of Fe and inevitable impurities was heated at a temperature of 1250 占 폚 and then hot-rolled to a thickness of 1.6 mm. Subsequently, the slab was mixed with hydrogen and nitrogen Hot-rolled sheet annealing was carried out in a gas atmosphere at an annealing temperature of 1100 ° C and 200 seconds, followed by cooling and pickling, followed by cold rolling to a thickness of 288 μm.

The cold-rolled steel sheet was annealed again at an annealing temperature of 870 ° C and a dew point temperature of 60 ° C for 60 seconds and thereafter subjected to decarburization annealing at an annealing temperature of 1100 ° C and 50 seconds in a hydrogen and nitrogen gas atmosphere at a hydrogen and dew point temperature of 0 ° C or lower, Of 100% H ₂ atmosphere for 3 minutes.

FIG. 4 is a photograph showing the Goss crystal grain distribution on the plane perpendicular to the thickness direction through EBSD analysis.

Table 2 is a table showing the ratio (D2 / D1) of the relative size of the inscribed circle and the circumscribed circle of the grain-oriented electrical steel sheet shown in Fig.

Circumscribed circle D1 Inscribed circle (D2) The ratio (D2 / D1) 1.6 0.8 0.5 2.2 1.2 0.55 2.6 0.9 0.35 3.3 1.6 0.48 4.7 1.7 0.36 1.1 0.5 0.45 2.5 0.9 0.36 One 0.5 0.5 2.3 1.4 0.61 1.2 0.9 0.75 5.1 2.3 0.45 1.9 0.7 0.37 3.6 2.1 0.58 2.7 1.7 0.63 1.4 0.6 0.43 0.8 0.4 0.5 1.3 0.5 0.38 0.7 0.3 0.43 1.8 1.1 0.61 1.1 0.5 0.45 0.9 0.35 0.39

As shown in Table 2, it can be seen that the value of D2 / D1 is smaller than that of the substrate according to the embodiment of the present invention since the substrate prepared in the comparative example is a crystal having a long elliptical structure.

Example 1

The directional electric steel sheet substrate produced in Production Example was pickled with an aqueous solution of HCl at a concentration of 25% by weight at 80 캜. Thereafter, an Al ₂ O ₃ coating film was formed to a thickness of 3 탆 on the entire surface of the steel sheet.

Table 3 shows the variation of the thickness of the steel sheet and the change of the magnetic properties with the picking time. The amount of oxygen in the oxygen-deficient layer from the surface to a depth of 3 mu m was measured and shown in Table 3 below. Also, the core loss was measured magnetic flux density using a single sheet measuring method, to measure the magnetic flux density (B ₁₀₎ is derived under the iron loss (W _17/50) and 1000A / m magnetic field until magnetization from 50Hz to 1.7Tesla. The results are summarized in Table 3 below.

Picking time (seconds) Oxygen amount (ppm) Thickness of base steel sheet (㎛) B ₁₀
(Tesla) W _17/50
(W / kg) Remarks 0 876 288 1.85 1.10 Comparison 1 5 407 285 1.87 1.08 Inventory 1 10 226 283 1.87 1.05 Inventory 2 15 95 282 1.89 1.00 Inventory 3 20 46 281 1.90 0.99 Invention 4 25 39 281 1.90 0.99 Invention Article 5 30 35 279 1.90 0.98 Inventions 6 40 33 275 1.88 1.08 Invention 7

As shown in Table 3, it can be confirmed that the inventive material 1 to the inventive material 7 subjected to the pickling process are superior to the comparative material 1 in which the pickling process is not performed at all. Particularly, it can be confirmed that Inventive Material 3 to Inventive Material 6, in which the pickling time is 15 to 30 seconds, are more excellent in magnetic properties than other inventive materials.

Example 2

The directional electric steel sheet substrate produced in Production Example was pickled with an aqueous solution of HCl at a concentration of 25% by weight at 80 캜. Then, a ceramic coating layer was formed by supplying ceramic powder to a heat source made of plasma (argon (Ar) gas) at an output of 200 kW. At this time, a pattern was formed with a coating width (w) of 30 mm and a coating distance (d) of 20 mm. The ceramic type, and the thickness of the ceramic coating layer were changed as shown in Table 4, and the changes of the magnetic properties thereof were summarized in Table 4.

Ceramic material Ceramic Coating Layer Thickness (탆) B ₁₀
(Tesla) W _17/50
(W / kg) Remarks Al ₂ O ₃ 0.8 1.91 0.95 Invention 8 Al ₂ O ₃ 1.3 1.92 0.92 Invention 9 Al ₂ O ₃ 2.4 1.92 0.94 Inventions 10 Al ₂ O ₃ 3.5 1.91 0.93 Invention invention 11 SiO ₂ 0.5 1.91 0.99 Invention 12 SiO ₂ 0.9 1.92 0.96 Invention invention 13 SiO ₂ 1.2 1.92 0.94 Invention Article 14 SiO ₂ 2.5 1.92 0.92 Invention material 15 SiO ₂ 3.5 1.91 0.93 Invention material 16 TiO ₂ 0.4 1.91 0.98 Inventions 17 TiO ₂ 0.7 1.92 0.96 Inventions 18 TiO ₂ 1.1 1.92 0.94 Inventions 19 TiO ₂ 1.5 1.92 0.91 Inventions 20 TiO ₂ 2.3 1.92 0.90 Invention Article 21 TiO ₂ 3.3 1.91 0.90 Invention Article 22 ZrO ₂ 1.0 1.91 0.97 Invention Article 23 ZrO ₂ 3.4 1.91 0.95 Invention 24

As shown in Table 4, by appropriately forming the ceramic coating layer, the magnetic property can be further improved.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

100: directional electric steel sheet 10: base material
11: oxygen depletion layer 20: ceramic coating layer

Claims (18)

Providing a slab comprising, by weight percent, 1.0% to 4.0% Si, 0.1% to 0.4% C, and the balance Fe and other inevitably incorporated impurities;
Reheating the slab;
Hot-rolling the slab to produce a hot-rolled steel sheet;
Annealing the hot-rolled steel sheet by hot-rolling;
Subjecting the hot-rolled steel sheet annealed to a primary cold-rolling;
Decarbonizing the primary cold-rolled steel sheet;
Subjecting the steel sheet after the decarburization annealing to secondary cold rolling;
Final annealing the steel sheet after completion of the secondary cold rolling;
Pickling the steel sheet after completion of the final annealing; And
A step of forming a ceramic coating layer on the pickled steel sheet
Lt; / RTI &gt;
Wherein said pickling is carried out at a temperature of 50 to 100 DEG C for 15 to 100 seconds using an aqueous acid solution of 5 to 50 wt%. The method according to claim 1,
And a decarburization step in the step of annealing the hot-rolled steel sheet. The method according to claim 1,
Wherein the step of annealing the hot-rolled sheet comprises a step of annealing at a temperature of 850 to 950 占 폚 and a dew-point temperature of 50 占 폚 or more, and a step of annealing at a temperature of 1000 占 폚 to 1200 占 폚 and a dew point temperature of 0 占 폚 or lower. The method according to claim 1,
The step of decarburizing and annealing the primary cold-rolled steel sheet comprises a step of annealing at a temperature of 850 캜 to 950 캜 and a dew-point temperature of 50 캜 or higher, and a step of annealing at a temperature of 1000 캜 to 1200 캜 and a dew- A method of manufacturing an electrical steel sheet. The method according to claim 1,
Wherein the step of decarburization annealing the primary cold-rolled steel sheet and the step of secondary cold-rolling the steel sheet after the decarburization annealing are repeated twice or more. The method according to claim 1,
Wherein the final annealing is 850 ℃ to 1000 ℃ temperature and dew point temperature step of annealing at less than 70 ℃ and 1000 ℃ to 1200 ℃ temperature and H ₂ 50 production method of the grain-oriented electrical steel sheet comprising the step of annealing at a volume% or more of the atmosphere . delete The method according to claim 1,
Wherein the ceramic coating layer is formed by supplying a ceramic powder to a heat source in which an inert gas is plasmaized to form a ceramic coating layer. 9. The method of claim 8,
Wherein the ceramic powder comprises Al ₂ O ₃ , SiO ₂ , TiO ₂ or ZrO ₂ . The method according to claim 1,
Wherein the first cold rolling step and the ceramic coating layer forming step are continuously performed. By weight, Si: 1.0% to 4.0%, C: 0.002% or less (not including 0%) and the remainder being Fe and other inevitably incorporated impurities; and
And a ceramic coating layer formed on the surface of the substrate,
The base material contains 95 percent by area or more of the whole goss grain grains having a ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) of the inscribed circle of 0.5 or more with respect to the plane perpendicular to the thickness direction of the steel sheet ,
Wherein the substrate comprises an oxygen-deficient layer formed inside the substrate from the surface of the substrate,
Wherein the oxygen depletion layer contains oxygen at 100 ppm or less. delete delete 12. The method of claim 11,
Wherein the oxygen depletion layer contains Mg in an amount of 100 ppm or less. 12. The method of claim 11,
Wherein the thickness of the ceramic coating layer is 10 nm to 4 占 퐉. 12. The method of claim 11,
It said ceramic coating layer is _{Al 2 O 3, SiO 2,} TiO 2 , or grain-oriented electrical steel sheet containing ZrO _2. 12. The method of claim 11,
Wherein the ceramic coating layer forms a pattern having a width (w) of 10 to 100 mm and an interval (d) of 10 to 100 mm in the rolling direction. 12. The method of claim 11,
Wherein the base material has a ratio of crystal grains having a grain size of 20 占 퐉 to 500 占 퐉 of 80% or more.

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