KR20190078229A - Grain oriented electrical steel sheet, and method for manufacturing grain oriented electrical steel sheet - Google Patents

Abstract

An embodiment of the present invention relates to a grain-oriented electrical steel sheet and, more specifically, to a grain-oriented electrical steel sheet enabling a ceramic layer to be formed on a base steel sheet from which a forsterite layer is removed. The grain-oriented electrical steel sheet comprises: a base steel sheet; and a ceramic layer located on and coming in contact with a surface of the base steel sheet. Moreover, average roughness of an interface of the base steel sheet and the ceramic layer can be 0.03 to 0.5 μm.

Description

TECHNICAL FIELD [0001] The present invention relates to a directional electric steel sheet and a method for manufacturing a directional electric steel sheet,

A directional electric steel sheet and a method of manufacturing a directional electric steel sheet. More specifically, the present invention relates to a directional electrical steel sheet having a ceramic layer formed on a base steel sheet from which a forsterite layer (base coating layer, primary coating) has been removed, and a method for producing a directional electrical steel sheet.

A grain-oriented electrical steel sheet is an electrical steel sheet containing a Si component and having an aggregate structure in which the grain orientations are aligned in the {110} < 001 > direction, and has extremely excellent magnetic properties in the rolling direction.

In particular, iron core materials for transformers are required to have low iron losses in order to reduce energy loss. Since it is effective to apply a tensile force to a steel sheet in order to manufacture an electrical steel sheet having a small iron loss, methods of imparting tensile force to the steel sheet and reducing iron loss by forming a film made of a material having a lower thermal expansion coefficient at a higher temperature than the steel sheet have.

In a conventional case, a technique of applying an insulating coating on a forsterite base coat is a method in which a film tension is improved by using colloidal silica having a high glass transition temperature and a method in which an alumina sol and a boric acid mixture A technique of forming a high-strength oxide film on an electric steel sheet has been proposed. In addition, an environmentally friendly coating technique has been proposed in which a coating film containing colloidal silica, hematite sol or nickel as a main component is formed to provide a stronger film tension effect. However, the above-described conventional techniques are a method of imparting tension to the forester coating film, and there is a limit to the iron loss improving effect.

Recently, a specular-surface electric steel sheet has been proposed in which a forsterite coating film is removed by means such as pickling or the production thereof is intentionally prevented. The specular surface directional electric steel sheet has the advantage of smoothly moving the magnetic field by removing the pinning site of the surface which obstructs the magnetic field movement, thereby lowering the hands of the magnetic history.

In addition, a method of forming an amorphous silica oxide film on the surface of the steel sheet after the secondary recrystallization annealing process of the oriented electrical steel sheet has been proposed, and the film adhesion is somewhat improved. However, the amorphous silica formed between the steel sheet and the tension coating, It is pointed out that the magnetic characteristics are deteriorated by disturbance.

In addition, a method of adding an organic metal compound having an organic bonding group to the surface of a grain-oriented electric steel sheet suppressing the formation of a forsterite coating has been proposed. However, when heat treatment is performed at a high temperature, organic bonding groups are decomposed to cause color deviation defects on the surface, It is pointed out that a film peeling occurs.

A directional electric steel sheet and a method for manufacturing a directional electric steel sheet are provided. More specifically, the present invention relates to a directional electrical steel sheet having a ceramic layer formed on a base steel sheet from which a forsterite layer (base coating layer, primary coating) has been removed, and a method for producing a directional electrical steel sheet.

A directional electrical steel sheet according to an embodiment of the present invention includes: a base steel sheet; And a ceramic layer placed in contact with the surface of the base steel sheet.

The average roughness at the interface between the base steel sheet and the ceramic layer may be 0.03 to 0.50 탆.

The porosity of the ceramic layer is 1% or less.

The ceramic layer may have a surface roughness of 1 mu m or less.

The thickness of the ceramic layer may be 0.1 to 3.5 mu m.

The grain-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula (1).

[Formula 1]

0.029? [S] / [C]? 3.5

(Where, S represents the thickness (mm) of the base steel sheet and C represents the thickness (占 퐉) of the ceramic layer.

The ceramic layer may be made of a ceramic powder.

The ceramic powder includes at least one selected from Li, B, Ca, Sr, Mg, Al, Si, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Oxide, nitride, carbide, or oxynitride.

The ceramic powder may be at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO · Al ₂ O ₃ , 2MgO · SiO ₂ , MgO · SiO ₂ , 2MgO · TiO ₂ , MgO · TiO ₂ , MgO · 2TiO ₂ , Al _{2 O 3 · SiO 2, 3Al} 2 O 3 · 2SiO 2, Al 2 O 3 · TiO 2, ZnO · SiO 2, ZrO 2 · SiO 2, ZrO 2 · TiO 2, 9Al 2 O 3 · 2B 2 O 3, _{2Al 2 O 3 · B 2 O} 3, 2MgO · 2Al 2 O 3 · 5SiO 2, Li 2 O · Al 2 O 3 · SiO 2, Li 2 O · Al 2 O 3 · 4SiO 2, BaO · Al 2 O 3 _{· SiO 2, AlN, SiC,} TiC, TiN, BN, ZrN, CrN, BaTiO 3, SrTiO 3, FeTiO 3, MgTiO 3, CaO, FeAl 2 O 4, CaTiO 3, MgAl 2 O 4, FeTiO 4, SrZrO 3 , Y ₂ O ₃ , CoAl ₂ O ₄ , and ZrSiO ₄ .

A directional electrical steel sheet according to another embodiment of the present invention is characterized in that a ceramic layer is formed on a part of the surface of a base steel sheet and a portion where the ceramic layer is formed and a portion where the ceramic layer is not formed are alternately repeated can do.

The width of the portion where the ceramic layer is formed may be 2 mm or more.

The interval between the portions where the ceramic layers are formed may be 2 mm or more.

The base steel sheet comprises 2.6 to 5.5 wt% of silicon (Si), 0.020 to 0.040 wt% of aluminum (Al), 0.01 to 0.20 wt% of manganese (Mn), antimony (Sb), tin (Sn) By weight and 0.01 to 0.15% by weight, the remainder being Fe and other unavoidable impurities.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of: preparing a base steel sheet having a forsterite coating removed on one surface or both surfaces thereof, or a formation of a forsterite coating is suppressed; And forming a ceramic layer by spraying a ceramic powder onto the base steel sheet.

The step of preparing a ground steel sheet on which the forester coating is removed on one surface or both surfaces or the formation of the forester coating is suppressed includes the steps of: preparing a cold rolled steel sheet; A first recrystallization annealing step of a cold-rolled steel sheet; And applying an annealing separator to a steel sheet subjected to primary recrystallization annealing; And secondary recrystallization annealing the steel sheet coated with the annealing separator.

The annealing separator may be a solid, containing 5 to 80% by weight of nitride and the balance magnesium oxide or magnesium hydroxide.

The step of producing the cold-rolled steel sheet comprises the steps of: preparing a slab; Heating the slab; Hot rolling the slab to produce a hot-rolled steel sheet; And cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet.

After the step of secondary recrystallization annealing, a step of pickling may be further included.

The nitride may include at least one of Mg, Si, Al, Ti, B, Ta, Ga, Ca, In, Zr, Ge, Nb, Sr and Ba.

The step of forming the ceramic layer by spraying the ceramic powder onto the base steel sheet comprises the steps of supplying a ceramic powder to a heat source which is made into a plasma with an output of 20 to 300 kW at a gas containing at least one of Ar, H ₂ , N ₂ , And spraying the ceramic powder to the base steel sheet.

The average particle size of the ceramic powder may be 10 to 1000 nm.

The directional electrical steel sheet according to an embodiment of the present invention improves the adhesion between the base steel sheet and the ceramic layer and improves the magnetic properties.

Further, the grain-oriented electrical steel sheet according to an embodiment of the present invention has low iron loss and excellent insulation characteristics.

1 is a schematic view schematically showing a cross section of a directional electric steel sheet according to an embodiment of the present invention.
2 is a schematic view schematically showing a rolled surface of a grain-oriented electrical steel sheet according to another embodiment of the present invention.
3 is a photograph of a cross section of a directional electric steel sheet produced in Example 8 by a scanning electron microscope (SEM).

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.

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).

"A to B" means not less than A and not more than B unless otherwise defined.

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.

1 schematically shows a cross section of a directional electrical steel sheet according to an embodiment of the present invention. As shown in FIG. 1, the directional electrical steel sheet 100 according to one embodiment of the present invention includes a base steel sheet 10; And a ceramic layer (20) placed in contact with the surface of the base steel sheet (10). The directional electrical steel sheet of Fig. 1 is only for illustrating the present invention, and the present invention is not limited thereto.

The base steel sheet 10 is composed of 2.6 to 5.5% by weight of silicon (Si), 0.020 to 0.040% by weight of aluminum (Al), 0.01 to 0.20% by weight of manganese (Mn), antimony (Sb) 0.01 to 0.15% by weight of the combination thereof, and the balance of Fe and other unavoidable impurities.

Hereinafter, the reason for limiting the constituents of the base steel sheet 10 will be described.

Si: 2.6 to 5.5 wt%

Silicon (Si) increases the resistivity of the steel to reduce iron loss. When the content of Si is too small, the resistivity of the steel becomes small and the iron loss characteristic deteriorates. In the high temperature annealing, Problems can arise. If the content of Si is too large, the brittleness is increased and cold rolling may become difficult. Therefore, the content of Si can be controlled within the above-mentioned range. More specifically, Si may be contained in an amount of 2.6 to 4.3% by weight.

Al: 0.020 to 0.040 wt%

Aluminum (Al) is finally a component that acts as an inhibitor by being made of nitride of (Al, Si, N), (Al, Si, Mn) N type. When the content of Al is too small, it is difficult to expect a sufficient effect as an inhibitor. When the content of Al is too large, the nitride of the Al system precipitates and grows too much, so that the effect as an inhibitor may become insufficient. Therefore, the content of Al can be controlled within the above-mentioned range.

Mn: 0.01 to 0.20 wt%

Mn has the effect of increasing the resistivity and decreasing the iron loss by the same way as Si and reacting with the nitrogen introduced by the nitriding treatment together with Si to form precipitates of N (Al, Si, Mn), whereby the growth of the primary recrystallized grains And it is an important element for causing secondary recrystallization. However, when the content of Mn is too large, it accelerates the austenite phase transformation during hot rolling so that the size of the primary recrystallized grains is reduced to make the secondary recrystallization unstable. When the content of Mn is too small, the effect of increasing the austenite fraction during hot-rolling reheating as the austenite forming element to increase the amount of precipitates and thus to make the primary recrystallization through MnS formation not too much It can occur insufficiently. Therefore, the content of Mn can be controlled within the above-mentioned range.

Sb, Sn or a combination thereof: 0.01 to 0.15 wt%

Since Sb or Sn is an element which interferes with the grain boundary movement as a grain boundary segregation element, generation of goss grain in the {110} < 001 > orientation is promoted as a grain growth inhibitor so that secondary recrystallization is well developed, to be. If the content of Sb or Sn added alone or in combination is too small, the effect may be deteriorated. If the content of Sb or Sn added alone or in combination is too large, grain boundary segregation occurs severely and the brittleness of the steel sheet becomes large, so that plate breakage may occur during rolling.

In order to improve the noise characteristics, the grain size of the high-temperature annealing grain is miniaturized in the steel sheet to reduce the 90 ° magnetic domain because the noise of the grain-oriented electrical steel sheet is caused by vibration caused by magnetostriction. However, in a conventional method for producing a grain-oriented electrical steel sheet, the crystal grain size is large and non-uniform, and the noise improving effect is insufficient.

The base steel sheet 10 according to an embodiment of the present invention has excellent effect of improving transformer noise by controlling Sb or Sn alone or in combination to have a grain size of 10 to 60 mm. If the grain size is too small, the magnetic flux density is insufficient, which is not enough to produce a product such as a transformer. If the crystal grain size is too large, the magnetostriction becomes severe and it becomes difficult to manufacture a low noise transformer. In this case, the grain size means a circle equivalent diameter measured using the intercept method.

In one embodiment of the present invention, the ceramic layer 20 is placed in contact with the surface of the substrate steel sheet 10. Means that a separate layer such as a forsterite layer is not formed between the base steel sheet 10 and the ceramic layer 20. In one embodiment of the present invention, after the forsterite layer is formed on the base steel sheet 10, the forsterite layer can be removed or the formation of the forsterite layer itself can be suppressed. Thereafter, the ceramic layer 20 can be formed on the base steel sheet 10.

Since the base steel sheet 10 in which the forsterite layer is removed or suppressed has a beautiful surface and low roughness, it is difficult to obtain sufficient adhesion with the conventional coating agent composed of colloidal silica and phosphate and the effect of improving the iron loss by the film tension is insignificant .

Therefore, in the embodiment of the present invention, a method of forming the ceramic layer 20 by spraying ceramic powder so that the ceramic layer 20 can be closely adhered to the surface of the base steel sheet 10 without the forsterite layer Can be used.

The ceramic layer 20 formed by the method of forming the ceramic layer 20 by spraying the ceramic powder has a very low porosity and is excellent in adhesion with the base steel sheet 10. Specifically, the porosity of the ceramic layer 20 is 1% or less. Here, the porosity means the area fraction occupied by the pores with respect to the total cross-sectional area of the ceramic layer 20.

The ceramic layer 20 formed by the method of forming the ceramic layer 20 by spraying the ceramic powder has a very small surface roughness Ra. By forming the ceramic layer 20 to have a small surface roughness Ra, it is possible to improve the dropping rate and to prevent the problem that the no-load hand of the transformer is lowered. Specifically, the surface roughness of the ceramic layer 20 may be 1 占 퐉 or less.

The average roughness (Ra) at the interface (A) between the base steel sheet (10) and the ceramic layer (20) is also very small. By forming the average roughness at the interface (A) of the base steel sheet 10 and the ceramic layer 20 to be very small, the tension can be uniformly applied to the entire base steel sheet 10 and the magnetic effect is excellent. Specifically, the average roughness (Ra) at the interface (A) between the base steel sheet (10) and the ceramic layer (20) may be 0.03 to 0.50 m.

The thickness of the ceramic layer 20 may be 0.1 to 3.5 占 퐉. If the thickness of the ceramic layer is too small, the size of the tensile force generated on the surface of the grain-oriented electrical steel sheet by the ceramic layer is small, and the iron loss reducing effect and insulating effect may be insufficient. On the other hand, if the thickness of the ceramic layer is too thick, the adhesion of the ceramic layer becomes low, and peeling may occur. More specifically, the thickness of the ceramic layer 20 may be 1 to 3 占 퐉.

The grain-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula (1).

[Formula 1]

0.029? [S] / [C]? 3.5

(Where S represents the thickness (mm) of the base steel sheet 10 and C represents the thickness (占 퐉) of the ceramic layer 20).

If the value of [S] / [C] is too low in Equation 1, the drop rate of the oriented electrical steel sheet becomes low, making it difficult to manufacture an efficient transformer. If the value of [S] / [C] is too high, the insulation and corrosion resistance may become insufficient and it may be insufficient to be produced by a product such as a transformer. Therefore, the range of A / B can be limited as shown in Equation (1). More specifically, 0.040? [S] / [C]? 0.7.

The ceramic layer 20 may be made of a ceramic powder. The ceramic powder includes at least one selected from Li, B, Ca, Sr, Mg, Al, Si, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Oxide, nitride, carbide, or oxynitride. More specifically, the ceramic powder may be selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO · Al ₂ O ₃ , 2MgO · SiO ₂ , MgO · SiO ₂ , 2MgO · TiO ₂ , MgO · TiO ₂ , MgO · 2TiO _{2, Al 2 O 3 · SiO} 2, 3Al 2 O 3 · 2SiO 2, Al 2 O 3 · TiO 2, ZnO · SiO 2, ZrO 2 · SiO 2, ZrO 2 · TiO 2, 9Al 2 O 3 · 2B 2 _{O 3, 2Al 2 O 3 ·} B 2 O 3, 2MgO · 2Al 2 O 3 · 5SiO 2, Li 2 O · Al 2 O 3 · SiO 2, Li 2 O · Al 2 O 3 · 4SiO 2, BaO · Al _{2 O 3 · SiO 2, AlN} , SiC, TiC, TiN, BN, ZrN, CrN, BaTiO 3, SrTiO 3, FeTiO 3, MgTiO 3, CaO, FeAl 2 O 4, CaTiO 3, MgAl 2 O 4, FeTiO 4 _{, SrZrO 3, Y 2 O 3} , CoAl may include at least one selected from ₂ O _4, and ZrSiO _4.

The average particle diameter of the ceramic powder may be 10 to 1000 nm. If the particle diameter of the ceramic powder is too small, the formation of the ceramic layer 20 may become difficult. If the particle diameter of the ceramic powder is too large, the surface roughness may become coarse and surface defects may occur. Therefore, the particle diameter of the ceramic powder can be adjusted to the above-mentioned range.

The ceramic powder may be in the form of any one or more selected from the group including spherical, plate-like, and needle-shaped.

2 schematically shows a rolled surface of a grain-oriented electrical steel sheet according to another embodiment of the present invention. 2, the directional electrical steel sheet according to another embodiment of the present invention is characterized in that a ceramic layer 20 is formed on a part of the surface of the base steel sheet 10 and a portion where the ceramic layer 20 is formed, The portion where the electrode 20 is not formed can be alternately repeated a plurality of times to form a pattern. More specifically, as shown in Fig. 2, a pattern can be formed along the rolling direction (RD direction) of the grain-oriented electrical steel sheet.

1, the portion where the ceramic layer 20 is formed and the portion where the ceramic layer 20 is not formed and the base steel sheet 10 is exposed are alternately repeated a plurality of times along the width direction of the directional electrical steel sheet Pattern. At this time, the width w of the portion where the ceramic layer 20 is formed may be 2 mm or more. If the width w is too small, the effect of improving the iron loss due to the application of the tensile force is insignificant, and a large number of coating nozzles must be formed. When the ceramic layer 20 is formed in the entire region of the base steel sheet 10, the width w may be infinitely increased, so that the upper limit of the width is not limited.

The distance d between the portions where the ceramic layers 20 are formed may be 2 mm or more. By appropriately forming the width w and the spacing d, it is possible to maximize the effect of improving the iron loss due to the application of the tensile force.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of: preparing a base steel sheet having a forsterite coating removed on one surface or both surfaces thereof, or a formation of a forsterite coating is suppressed; And forming a ceramic layer by spraying a ceramic powder onto the base steel sheet.

Each step will be described in detail below.

The base steel sheet 10 without the forsterite layer can be obtained by removing the forsterite layer formed on the surface of the base steel sheet 10 by means such as pickling, The use of alumina (Al ₂ O ₃ ) in place of magnesium oxide (MgO) for the annealing separator to be applied can be prevented intentionally.

The step of preparing a ground steel sheet on which the forester coating is removed on one surface or both surfaces or the formation of the forester coating is suppressed includes the steps of: preparing a cold rolled steel sheet; A first recrystallization annealing step of a cold-rolled steel sheet; Applying an annealing separator to a steel sheet subjected to primary recrystallization annealing; A second recrystallization annealing step of annealing the steel sheet coated with the annealing separator; And removing the forsterite coating formed on the secondary recrystallized annealed steel sheet.

The step of producing the cold-rolled steel sheet comprises the steps of: preparing a slab; Heating the slab; Hot rolling the slab to produce a hot-rolled steel sheet; And cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet.

In the step of producing the slab, the slab may contain silicon (Si) in an amount of 2.6 to 5.5 wt%, aluminum (Al) in an amount of 0.020 to 0.040 wt%, manganese (Mn) in an amount of 0.01 to 0.20 wt%, antimony (Sb) , Or a combination thereof in an amount of 0.01 to 0.15% by weight, the balance being Fe and other unavoidable impurities. Since the components of the slab are the same as those of the above-described directional electrical steel sheet, the overlapping description will be omitted.

The step of heating the slab may first be heated to 1200 DEG C or less before hot rolling the slab. Further, the hot-rolled steel sheet produced after hot-rolling can be annealed. In addition, decarburization, decarburization and soaking can be performed during the primary recrystallization annealing. Since this process is performed according to a normal process, a detailed description is omitted.

As described above, in the series of steps of subjecting the slab having the composition according to an embodiment of the present invention to the hot rolling-cold rolling-primary recrystallization annealing-secondary recrystallization annealing, the average grain size of the grain after the secondary recrystallization annealing is 10 to 60 mm The process conditions can be controlled to meet the range.

After the primary recrystallization annealing, the annealing separator is applied to prevent sticking between the base steel sheets 10 during the secondary recrystallization annealing for forming the secondary recrystallization. At this time, by including nitride in the annealing separator component, the formation of the forsterite coating can be suppressed and the removal of the forsterite coating can be facilitated.

Specifically, the case where magnesium nitride (Mg ₃ N ₂ ) is used as the nitride is described as an example. By reacting as in the following reaction formula, ammonia and nitrogen gas are released, formation of the forsterite coating is suppressed, It is possible to facilitate removal of the light coating.

[Reaction Scheme]

Mg ₃ N ₂ + H ₂ O → 3Mg (OH) ₂ + 2NH ₃ ↑ → 3Mg (OH) ₂ + N ₂ ↑ + 3H ₂ ↑

Magnesium nitrides have been exemplified, but the effects described above are not limited to the same as those described above. Specifically, the nitride may include at least one of Mg, Si, Al, Ti, B, Ta, Ga, Ca, In, Zr, Ge, Nb, Sr and Ba. More specifically, the nitrides are selected from the group consisting of magnesium nitride (Mg ₃ N ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), titanium nitride (TiN), boron nitride (BN), tantalum nitride _{GaN), Calcium nitride (Ca 3} N 3), Indium nitride (InN), Zirconium nitride (ZrN), Germanium nitride (Ge 3 N 4), Niobium nitride (NbN), Strontium nitride (Sr 3 N 2) , and Barium nitride (Ba ₃ N ₂ ). The base steel sheet 10 in which the forsterite coating is suppressed or removed has insufficient coating tension imparting effect, which has a limitation in reducing iron loss.

The nitride may be contained in an amount of 5 to 80% by weight based on 100% by weight of the solid content of the annealing separator. When the nitride is contained in an excessively small amount, the effect of inhibiting the formation of the forsterite film may not be sufficiently exhibited. More specifically, it may contain 8 to 70% by weight of nitride.

And the remainder is magnesium oxide or magnesium hydroxide. In one embodiment of the present invention, the annealing separator composition may be present in the form of a slurry for easy application to the surface of the base steel sheet 10. When the slurry contains water as a solvent, the Mg oxide readily dissolves in water and may be present in the Mg hydroxide form. Therefore, in one embodiment of the present invention, Mg oxide and Mg hydroxide are treated as one component.

Next, the steel sheet coated with the annealing separator is subjected to secondary recrystallization annealing to form a coating layer on the surface of the steel sheet.

The secondary recrystallization annealing step includes a step of primary cracking at 600 to 750 ° C, a step of raising the temperature to 5 to 20 ° C / s, and a secondary cracking at 950 to 1300 ° C, for the steel sheet coated with the annealing separator . The primary cracking step and the step of heating can be performed in 10 to 60% by volume of hydrogen and the remaining nitrogen atmosphere, and the secondary cracking step can be performed in a hydrogen atmosphere of 90 vol% or more.

As described above, the formation of the forsterite coating is suppressed by adding the nitride to the annealing separator, but it may further include pickling to reliably remove the forsterite coating.

Next, the ceramic layer 20 is formed by spraying the ceramic powder onto the base steel sheet. As a method of forming the ceramic layer 20, plasma spray coating, high velocity oxy fuel, aerosol deposition, and cold spray coating are applied .

More specifically, a plasma spray for spraying a ceramic powder onto a base steel sheet 20 by supplying a ceramic powder to a heat source obtained by plasmatizing a gas containing at least one of Ar, H ₂ , N ₂ or He at an output of 20 to 300 kW Coating method can be used.

The ceramic layer 20 can be formed by supplying the mixture of the ceramic powder and the solvent in suspension form to the plasmaized heat source. At this time, the solvent may be water or alcohol.

The ceramic powder includes at least one selected from Li, B, Ca, Sr, Mg, Al, Si, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Oxide, nitride, carbide, or oxynitride.

The ceramic powder may be at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO · Al ₂ O ₃ , 2MgO · SiO ₂ , MgO · SiO ₂ , 2MgO · TiO ₂ , MgO · TiO ₂ , MgO · 2TiO ₂ , Al _{2 O 3 · SiO 2, 3Al} 2 O 3 · 2SiO 2, Al 2 O 3 · TiO 2, ZnO · SiO 2, ZrO 2 · SiO 2, ZrO 2 · TiO 2, 9Al 2 O 3 · 2B 2 O 3, _{2Al 2 O 3 · B 2 O} 3, 2MgO · 2Al 2 O 3 · 5SiO 2, Li 2 O · Al 2 O 3 · SiO 2, Li 2 O · Al 2 O 3 · 4SiO 2, BaO · Al 2 O 3 _{· SiO 2, AlN, SiC,} TiC, TiN, BN, ZrN, CrN, BaTiO 3, SrTiO 3, FeTiO 3, MgTiO 3, CaO, FeAl 2 O 4, CaTiO 3, MgAl 2 O 4, FeTiO 4, SrZrO 3 , Y ₂ O ₃ , CoAl ₂ O ₄ , and ZrSiO ₄ .

The particle size of the ceramic powder may be 10 to 1000 nm. If the particle size of the ceramic powder is too small, the formation of the ceramic layer may become difficult. If the particle diameter of the ceramic powder is too large, the surface roughness may become coarse and surface defects may occur. Therefore, the particle diameter of the ceramic powder can be adjusted to the above-mentioned range.

The ceramic powder may be in the form of any one or more selected from the group including spherical, plate-like, and needle-shaped.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Experimental Example  1 - Nitride type and ceramic powder type

Example 1

, 0.04 wt% of antimony (Sb), 0.09 wt% of tin (Sn), and nickel (Ni) were added in an amount of 3.4 wt% of silicon (Si), 0.03 wt% of aluminum (Al) 0.02 wt% of carbon (C), 0.06 wt% of carbon (C) and 40 wt% of nitrogen (N), and the balance of Fe and other unavoidable impurities.

The slab was heated at 1150 占 폚 for 220 minutes and hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled steel sheet.

The hot-rolled steel sheet was heated to 1120 占 폚, held at 920 占 폚 for 95 seconds, quenched in water and pickled, and then cold-rolled to a thickness of 0.23 mm to prepare a cold-rolled sheet.

The cold-rolled sheet was placed in a furnace maintained at 850 캜, maintained in a mixed atmosphere of 74% by volume of hydrogen, 25% by volume of nitrogen and 1% by volume of dry ammonia gas for 180 seconds, Annealing were simultaneously carried out to produce a primary recrystallized annealed steel sheet.

As the annealing separator composition, 40% by weight of magnesium nitride (Mg ₃ N ₂ ), 5% by weight of titanium oxide, 5% by weight of Sb ₂ (SO ₄ ) ₃ and the balance magnesium oxide (MgO) And the slurry was applied to a steel sheet subjected to primary recrystallization annealing using a roll, followed by secondary recrystallization annealing.

The primary and secondary cracking temperatures were set to 700 ° C and 1200 ° C, respectively, during the second recrystallization annealing, and to 15 ° C / hr during the temperature rise period. In addition, up to 1200 deg. C, a mixed gas atmosphere of 50 vol% nitrogen and 50 vol% hydrogen was set. After reaching 1200 deg. C, it was maintained in a hydrogen gas atmosphere of 100 vol% for 20 hours and then furnace cooled.

Thereafter, CoAl ₂ O ₄ was supplied as a ceramic powder to a heat source in which argon (Ar) gas was converted into plasma at an output of 250 kW to form a ceramic layer having a thickness of 0.9 μm on the final annealed plate surface.

3 is a cross-sectional photograph of a directional electrical steel sheet having a ceramic layer formed on a base steel sheet. In FIG. 3, the darkest portion is the base steel sheet, and the gray portion just above it is the ceramic layer. As shown in FIG. 3, it can be confirmed that the roughness at the interface between the base steel sheet and the ceramic layer is very small and the surface roughness of the ceramic layer is small.

Examples 2 to 9

The same procedure as in Example 1 was carried out except that the magnesium nitride (Mg ₃ N ₂ ) component in the annealing separator was replaced with a secondary recrystallization annealing as shown in Table 1 below. Ceramic powder prepared in the following Table 1 was applied to a base steel sheet to form a ceramic layer.

Comparative Example 1

The same procedure as in Example 1 was carried out except that no nitride was mixed in the annealing separator and the forsterite coating was not removed. Thereafter, no ceramic layer was formed.

Comparative Example 2

The same procedure as in Example 1 was carried out except that the magnesium nitride (Mg ₃ N ₂ ) component in the annealing separator was replaced with a secondary recrystallization annealing as shown in Table 1 below. Thereafter, no ceramic layer was formed.

Comparative Example 3

The same procedure as in Example 1 was carried out except that no nitride was mixed in the annealing separator and the forsterite coating was not removed. A ceramic layer was formed on the forsterite coating by applying the ceramic powder set forth in Table 1 below.

Comparative Example 4

Ceramic powder was added to the tensile coating solution containing colloidal silica and metal phosphate as the main components, and the coating was applied and dried in the same manner as in Example 1.

Iron loss was measured at 1.7 Tesla and 50 Hz using the single sheet measurement method manufactured in Examples 1 to 9 and Comparative Examples 1 to 3. The iron loss was measured under the magnetic field of 800 A / Were measured. Each iron loss value represents the average by condition. The magnetic flux density and iron loss are summarized in Table 1 below.

The insulation was measured using a Franklin meter according to ASTM A717 international standard.

The adhesion is represented by the minimum arc diameter without film peeling when the specimen is bent by 180 ° in contact with a 10 to 100 mm arc.

division Annealing separator
(weight%) Type of ceramic powder Interfacial roughness (㎛) Iron loss
(W17 / 50, W / kg) Magnetic flux density
(B8, T) Isolation
(mA) Adhesiveness
(mmΦ) Comparative Example 1 MgO 100 wt% - 0.86 0.981 1.907 982 30 Comparative Example 2 Mg ₃ N ₄ (40) - 0.65 0.87 1.910 965 40 Comparative Example 3 MgO 100 wt% CoAl ₂ O ₄ 0.62 0.86 1.908 380 30 Comparative Example 4 Mg ₃ N ₄ (40) CoAl ₂ O ₄
+ Mg phosphate (wet coating) 0.80 0.962 1.908 350 50 Example 1 Mg ₃ N ₄ (40) CoAl ₂ O ₄ 0.30 0.71 1.93 176 20 Example 2 Si ₃ N ₄ (20) TiO ₂ 0.03 0.64 1.932 145 20 Example 3 AlN (10) Al ₂ O ₃ 0.10 0.68 1.938 38 20 Example 4 TiN (8) MgTiO ₃ 0.50 0.81 1.921 20 15 Example 5 Ca ₃ N ₄ (30) FeAl ₂ O ₄ 0.20 0.8 1.916 450 15 Example 6 Sr ₃ N ₂ (25) SrZrO ₃ 0.25 0.75 1.928 310 30 Example 7 Ba ₃ N ₂ (50) ZrO ₂ 0.17 0.72 1.935 280 30 Example 8 Mg ₃ N ₂ (10) MgAl ₂ O ₄ 0.40 0.62 1.937 70 15 Example 9 Mg ₃ N ₂ (70) Y ₂ O ₃ 0.39 0.64 1.94 110 20

As shown in Table 1, it can be confirmed that the properties of Examples 1 to 9 are superior to those of Comparative Examples 1 to 4.

Experimental Example  2 - S / C control

Examples 10 to 17

(Si) in an amount of 3.6 wt%, aluminum (Al) in an amount of 0.03 wt%, manganese (Mn) in an amount of 0.07 wt%, antimony (Sb) in an amount of 0.05 wt% and tin (Sn) in an amount of 0.05 wt% And other unavoidable impurities were prepared.

The slab was heated at 1150 占 폚 for 220 minutes and hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled steel sheet.

The hot-rolled steel sheet was heated to 1120 占 폚, held at 920 占 폚 for 95 seconds, quenched in water and pickled, and then cold-rolled to a thickness of 0.23 mm to prepare a cold-rolled sheet.

The cold-rolled sheet was put into a furnace maintained at 850 ° C, and then the dew point temperature and the oxidizing ability were controlled. In the hydrogen, nitrogen, and ammonia mixed gas atmosphere, decarburization and primary recrystallization annealing were simultaneously performed, A steel sheet was produced.

Thereafter, distilled water was mixed with an annealing separator containing 50% by weight of Ca ₃ N ₄ and 50% by weight of MgO to prepare a slurry. The slurry was applied to a decarburized steel sheet using a roll or the like, And annealed.

During the final annealing, the primary cracking temperature was 700 ° C, the secondary cracking temperature was 1200 ° C, and the temperature was 15 ° C / hr in the temperature rising period. In addition, the mixed gas atmosphere of nitrogen gas of 25 vol% and hydrogen gas of 75 vol% was heated up to 1200 deg. C, and after reaching 1200 deg. C, maintained in a hydrogen gas atmosphere of 100 vol% for 15 hours and then furnace cooling.

In the secondary recrystallization annealing, the steel sheet from which the forsterite coating was removed was washed with water at room temperature and dried at 200 ° C for 45 seconds.

Thereafter, hydrogen (H ₂ ) gas and oxygen (O ₂ ) gas are injected into the flame spray coating apparatus and ignited to form a high temperature and high pressure flame, ceramic powder is supplied to the flame, (RD direction) with a 20 mm coating width (w) and a 20 mm coating distance (d). The characteristics of the ceramic layer are summarized in Table 3 below, and the insulating properties, the dropping rate, and the adhesiveness were evaluated according to Test Example 2, and the results are shown in Table 3 below.

The spot rate was measured using a measuring instrument according to JIS C2550 international standard. A uniform pressure of 1 MPa was applied to the surface after laminating a plurality of electric steel plate specimens, and then the practical ratio of the electric steel plate lamination was measured by dividing the ratio by the theoretical weight through the precision measurement of the height of the four faces of the specimen.

division Characteristics of ceramic layer Dotting rate Adhesiveness Powder type Thickness of steel sheet Ceramic layer thickness S / C Isolation (%) (mmΦ) (S, mm) (C, 占 퐉) (mA) Example 10 CoAl ₂ O ₄ 0.23 0.7 0.329 115 98 15 Example 11 TiO ₂ 0.23 2 0.115 30 97.0 25 Example 12 Al ₃ O ₃ .TiO ₂ 0.27 One 0.27 80 98 20 Example 13 TiO ₂ 0.27 0.5 0.54 110 98.5 15 Example 14 ZrSiO ₄ 0.3 3.5 0.086 0 96.7 20 Example 15 FeAl ₂ O ₄ 0.18 1.5 0.12 430 95.7 Surface crack Example 16 Al ₂ O ₃ 0.15 1.2 0.125 345 96.1 30 Example 17 Y ₂ O ₃ 0.35 0.1 3.5 675 96.2 30

As shown in Table 2, it can be confirmed that the results of Examples 10 to 14 are excellent in insulation, dropping rate, and adhesion. It can be confirmed that the effect achieved by controlling the base steel thickness (S, mm) and the ceramic coating thickness (C, um) by 0.029? [S] / [C]? 3.5.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: directional electric steel plate, 10: base steel plate,
20: ceramic layer, A: interface

Claims (19)

Base steel sheet; And
And a ceramic layer disposed in contact with the surface of the base steel sheet,
Wherein the average roughness at the interface between the base steel sheet and the ceramic layer is 0.03 to 0.5 占 퐉. The method according to claim 1,
Wherein the ceramic layer has a porosity of 1% or less. The method according to claim 1,
Wherein the ceramic layer has a surface roughness of 1 占 퐉 or less. The method according to claim 1,
Wherein the ceramic layer has a thickness of 0.1 to 3.5 占 퐉. The method according to claim 1,
A directional electrical steel sheet satisfying the following formula (1).
[Formula 1]
0.029? [S] / [C]? 3.5
(Where, S represents the thickness (mm) of the base steel sheet and C represents the thickness (占 퐉) of the ceramic layer. The method according to claim 1,
Wherein the ceramic layer is made of ceramic powder. The method according to claim 6,
The ceramic powder may include at least one selected from Li, B, Ca, Sr, Mg, Al, Si, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Wherein the oxide, nitride, carbide, or oxynitride is contained. The method according to claim 6,
The ceramic powder may be selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO · Al ₂ O ₃ , 2MgO · SiO ₂ , MgO · SiO ₂ , 2MgO · TiO ₂ , MgO · TiO ₂ , MgO · 2TiO ₂ , _{Al 2 O 3 · SiO 2,} 3Al 2 O 3 · 2SiO 2, Al 2 O 3 · TiO 2, ZnO · SiO 2, ZrO 2 · SiO 2, ZrO 2 · TiO 2, 9Al 2 O 3 · 2B 2 O 3 _{, 2Al 2 O 3 · B 2} O 3, 2MgO · 2Al 2 O 3 · 5SiO 2, Li 2 O · Al 2 O 3 · SiO 2, Li 2 O · Al 2 O 3 · 4SiO 2, BaO · Al 2 O _{3 · SiO 2, AlN, SiC} , TiC, TiN, BN, ZrN, CrN, BaTiO 3, SrTiO 3, FeTiO 3, MgTiO 3, CaO, FeAl 2 O 4, CaTiO 3, MgAl 2 O 4, FeTiO 4, SrZrO ₃ , Y ₂ O ₃ , CoAl ₂ O ₄ , and ZrSiO ₄ . The method according to claim 1,
The ceramic layer is formed on a part of the surface of the base steel sheet,
Wherein a portion where the ceramic layer is formed and a portion where the ceramic layer is not formed alternately repeat a plurality of times to form a pattern. The method according to claim 1,
Wherein a width of a portion where the ceramic layer is formed is 2 mm or more. The method according to claim 1,
Wherein a distance between the portions where the ceramic layers are formed is 2 mm or more. The method according to claim 1,
The base steel sheet comprises 2.6 to 5.5% by weight of silicon (Si), 0.020 to 0.040% by weight of aluminum (Al), 0.01 to 0.20% by weight of manganese (Mn), antimony (Sb) Wherein the composition comprises 0.01 to 0.15 wt% of the composition, the balance being Fe and other unavoidable impurities. Preparing a ground steel sheet on which a forester coating is removed on one surface or both surfaces, or formation of a forsterite coating is suppressed; And
And forming a ceramic layer by spraying a ceramic powder onto the base steel sheet. 14. The method of claim 13,
The step of preparing a ground steel sheet on which the forsterite coating is removed on one surface or both surfaces, or the formation of the forester coating is suppressed,
Producing a cold rolled steel sheet;
A first recrystallization annealing step of the cold-rolled steel sheet;
Applying an annealing separator to a steel sheet subjected to primary recrystallization annealing; And
And secondary recrystallization annealing the steel sheet coated with the annealing separator,
Wherein the annealing separator comprises a solid content of 5 to 80% by weight of nitride, and the balance magnesium oxide or magnesium hydroxide. 15. The method of claim 14,
The step of manufacturing the cold-
Producing a slab;
Heating the slab;
Hot-rolling the slab to produce a hot-rolled steel sheet; And
And cold rolling the hot rolled steel sheet to produce a cold rolled steel sheet. 15. The method of claim 14,
Further comprising a step of pickling after the secondary recrystallization annealing step. 15. The method of claim 14,
Wherein the nitride comprises at least one of Mg, Si, Al, Ti, B, Ta, Ga, Ca, In, Zr, Ge, Nb, Sr and Ba. 14. The method of claim 13,
The step of forming a ceramic layer by spraying a ceramic powder onto the ground steel sheet comprises:
Supplying a ceramic powder to a heat source which has been plasmaized at a power of 20 to 300 kW with a gas containing at least one of Ar, H ₂ , N ₂ , and He, and spraying ceramic powders onto the ground steel sheet. &Lt; / RTI &gt; 14. The method of claim 13,
Wherein the average particle diameter of the ceramic powder is 10 to 1000 nm.

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