KR102572660B1 - Adhesive composition for electrical steel sheet, electrical steel sheet laminate and manufacturing method for the same - Google Patents

Abstract

An adhesive composition for an electrical steel sheet according to an embodiment of the present invention includes a bioplastic comprising 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

Description

Adhesive composition for electrical steel sheet, electrical steel sheet laminate and manufacturing method thereof

It relates to an adhesive composition for electrical steel sheet, an electrical steel sheet laminate, and a manufacturing method thereof. Specifically, the present invention relates to an adhesive composition for electrical steel sheet, which is widely used as an important part of a rotating machine and has excellent magnetism and strength after heat treatment, an electrical steel sheet laminate, and a manufacturing method thereof.

In general, non-oriented electrical steel sheet is an important iron core material required to convert electrical energy into mechanical energy in a rotating machine, and it is important to have magnetic properties, that is, low iron loss, in order to save energy. Here, iron loss is energy lost by being converted to heat during the energy conversion process, so the lower the iron loss, the more efficient it is.

Recently, technology for converting existing internal combustion engine vehicles into HEV (hybrid vehicles) / EV (electric vehicles) is rapidly developing as a countermeasure for fossil fuel shortage and greenhouse gas reduction. These HEV/EVs are vehicles that convert some or all of their driving methods to electric motors to achieve better fuel efficiency while reducing the use of gasoline or diesel, which are conventional internal combustion engine fuels.

A motor used in such a vehicle rotates at high speed during high-speed driving. Therefore, the non-oriented electrical steel sheet, which is the core material of the motor, should have low high-frequency iron loss during high-speed rotation. In general, high-frequency iron loss means iron loss at a frequency of 200 Hz or more, but a value of W _10/400 is mainly used in non-oriented electrical steel sheets for automobiles. In addition, in the field of home appliances, iron loss in the high-frequency iron loss range is becoming increasingly important due to the adoption of BLDC motors.

In order to improve the high-frequency iron loss, the alloy elements such as Si, Al, and Mn, which are non-resistive elements of the electrical steel sheet, must be increased, impurities must be reduced to facilitate the movement of magnetic domains, and the thickness of the electrical steel sheet must be thinned.

However, when non-magnetic alloy elements such as Si, Al, and Mn are contained in high amounts, rolling becomes difficult and has limitations, and when the thickness is thinned, there is a difficulty in increasing the production cost and the processing cost on the customer side.

In order to improve high-frequency iron loss, an electrical steel sheet laminate (so-called “sandwich steel sheet”) has been proposed in which electrical steel sheets are bonded by adding an insulating layer (or adhesive layer) therein. As an adhesive composition for an electrical steel laminate, an organic adhesive composition or an inorganic adhesive composition has been proposed. However, the organic adhesive composition has a problem in that the adhesive ability is significantly inferior when treated at a high temperature. In addition, the inorganic adhesive composition has a problem in that it is impossible to wind it because the material for bonding is brittle due to low elasticity during winding.

An embodiment of the present invention is to provide an adhesive composition for electrical steel sheet and a method for manufacturing an electrical steel sheet laminate that simultaneously improves high-frequency iron loss and strength by providing an adhesive composition for electrical steel sheet and an electrical steel sheet to which an adhesive layer is added therein.

An embodiment of the present invention is an adhesive composition for electrical steel sheet having excellent high-frequency iron loss and strength at the same time so as to suppress an increase in production cost due to thinning and not increase the customer's processing cost by inserting an adhesive layer in the middle of the final electrical steel sheet, and electrical It is intended to provide a steel plate laminate.

An adhesive composition for an electrical steel sheet according to an embodiment of the present invention includes a bioplastic comprising 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

An adhesive composition for an electrical steel sheet according to an embodiment of the present invention may include 1 to 30% by weight of bioplastic and 70 to 99% by weight of a solvent.

The viscosity of the adhesive composition for electrical steel sheets according to an embodiment of the present invention may be 100 to 1000 cp.

A method for preparing an adhesive composition for electrical steel sheet according to an embodiment of the present invention includes preparing a mixed solution by adding an acid aqueous solution to an aqueous starch solution; and kneading the mixed solution at 70 to 120°C.

In the step of preparing the mixed solution, the mixed solution may have a pH of 3 to 5.

The mixed solution may include 10 to 50% by weight of starch and 0.1 to 1% by weight of the acid.

An electrical steel sheet laminate according to an embodiment of the present invention includes electrical steel sheets laminated in two or more layers; and an adhesive layer formed between each of the electrical steel sheets and including a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

Electrical steel sheet, by weight %, Si: 3.5% or less (but excluding 0%), Al: 2.5% or less (but excluding 0%), Mn: 3% or less (but excluding 0%), P : 0.1% or less (but 0% excluded), C: 0.04% or less (but 0% excluded), S: 0.01% or less (but 0% excluded), N: 0.01% or less (but 0 %) and balance Fe and other unavoidable impurities.

An average grain size of the electrical steel sheet may be 30 to 150 μm.

The adhesive layer may have a thickness of 0.3 to 0.7 μm.

The overall thickness of the laminate may be 0.3 to 0.5 mm.

A method of manufacturing an electrical steel sheet laminate according to an embodiment of the present invention includes the steps of hot rolling a slab to prepare a hot rolled sheet; Cold-rolling a hot-rolled sheet to produce a cold-rolled sheet; Laminating cold-rolled sheets by inserting an adhesive composition in the middle of each layer; Final annealing of the laminated cold-rolled sheets to prepare an annealed sheet; and producing a re-cold-rolled sheet by re-cold-rolling the annealed sheet.

The adhesive composition includes a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

After the step of manufacturing the hot-rolled sheet, a step of annealing the hot-rolled sheet at a temperature of 850 to 1,150° C. may be further included.

In the lamination step, 5 to 30 parts by weight of a solvent may be additionally inserted with respect to 100 parts by weight of the adhesive composition together with the adhesive composition to be laminated.

After the laminating step, a step of drying at 100 to 250° C. may be further included.

After the laminating step, a cold rolling step may be further included.

The final annealing step may be annealing at 500 to 1200 ° C.

By manufacturing an electrical steel sheet laminate according to an embodiment of the present invention, it is possible to finally provide an electrical steel sheet laminate excellent in high frequency characteristics.

When an electrical steel sheet laminate is made in a laminated structure according to an embodiment of the present invention, iron loss characteristics are improved compared to conventional electrical steel sheets having the same components.

The adhesive composition for electrical steel sheet according to an embodiment of the present invention does not require heat treatment for curing, maintains adhesive strength and elasticity even after final annealing, and is environmentally friendly.

1 is a diagram schematically illustrating the process of gelatinization and aging of starch.
2 is a schematic view of acid decomposition, gelatinization, and aging processes of bioplastics.
3 is a view schematically showing a cross section of an electrical steel sheet laminate according to an embodiment of the present invention.
4 is a view schematically illustrating a process of manufacturing a laminate from a cold-rolled sheet when manufacturing an electrical steel laminate according to an embodiment of the present invention.

Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only for referring to specific embodiments and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising" as used herein specifies particular characteristics, regions, integers, steps, operations, elements and/or components, and the presence or absence of other characteristics, regions, integers, steps, operations, elements and/or components. Additions are not excluded.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part or may be followed by another part therebetween. In contrast, when a part is said to be “directly on” another part, there is no intervening part between them.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

In addition, unless otherwise specified, % means weight%, and 1ppm is 0.0001 weight%.

In one embodiment of the present invention, the meaning of further including an additional element means replacing and including iron (Fe) as much as the additional amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

An adhesive composition for an electrical steel sheet according to an embodiment of the present invention includes a bioplastic comprising 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

In one embodiment of the present invention, since the bioplastic is included, adhesive strength is maintained even after high-temperature final annealing, so that a plurality of laminated steel sheets can be fixed.

In one embodiment of the present invention, the bioplastic is composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

Bioplastics can be derived from starch, and the mechanism by which starch is transformed into bioplastics will be described in detail.

Starch is composed of 20 to 30% by weight of amylose and 70 to 80% by weight of amylopectin. Since amylose has a linear helix structure, it is elastic and can be effectively applied to a medium. It is also very effective as a binder because it is applied at a high density. However, since amylopectin has a branched structure and is hard, it cannot be effectively applied to the material to be bound. In addition, since the branched structure has a low density compared to the linear structure, the strength of the binder portion after binding is weak, so it is vulnerable to deformation due to external pressure and has weak viscoelastic ability.

The following [Formula 1] schematically shows the chemical structure of amylose, and Formula 2 schematically shows the macro structure of amylose.

[Formula 1]

[Formula 2]

The chemical structure of amylose is schematically shown in the following [Formula 3], and the macrostructure is schematically shown in [Formula 4].

[Formula 3]

[Formula 4]

In one embodiment of the present invention, it includes bioplastics instead of starch, and the amylose structure, which is advantageous in terms of adhesive ability, increases and the amylopectin structure decreases, so that the adhesive strength is improved.

The change in structure according to gelatinization and aging of starch is shown in FIG. 1 .

Amylose and amylopectin present in starch have a crystal structure. Amylose (1) is linear and amylopectin (7) is a structure with branches in the amylose structure. When heat is applied and water is added (gelatinization), the water penetrates into the crystal. At room temperature, it is difficult for water to penetrate between crystals. Water penetrating between crystals binds amylose (1) and amylopectin (7) by hydrogen bonding. When water penetrates into the crystal gap of amylose (1), hydrogen bonding occurs, and the hydrophilic OH group is directed outward and the hydrophobic C-C bond is turned inward due to the interaction of the hydrophilic group and the hydrophobic group, resulting in transformation into a helix structure. . In addition, it combines with the polar lipid (3) present in starch to form a double helix structure (5) centered on the polar lipid. Thereafter, when aged or cooled to room temperature, helices not bonded to polar lipids 3 form a double helix structure 4 between helices. Amylose is also shared as a double helix, then water is discharged to the outside and a crystal structure (2) is formed.

The principle of forming bioplastics from starch is shown in FIG. 2 .

As described above, amylose is composed of glucose with alpha 1,4-bonding. The main backbone of amylopectin is composed of 1,4-bonding, and the branch portion is connected to the backbone through alpha 1,6-bonding.

Between pH 4 and 5 and at a temperature of 50 ° C or higher, alpha 1,4-bonding is not incised, while α-1,6-bonding is incised. Therefore, selective α-1,6-bonding incision is possible in the presence of acid. Therefore, it is possible to cut off the branches of amylopectin and make them linear, similar to amylose. Through the subsequent gelatinization and aging process, amylose and amylopectin are crystallized, and bioplastics contain more amylose than starch due to the incision of α-1,6-bonding during acid decomposition.

Through this process, a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose can be synthesized. Bioplastics have a relatively high density, so the strength of the adhesive layer increases, and linear molecules form a helix structure, enabling effective adhesion to the surface of the electrical steel sheet.

The bioplastic may be included in an amount of 1 to 30% by weight based on the total weight of the adhesive composition. If too little bioplastic is included, the aforementioned adhesive performance cannot be adequately obtained. On the other hand, if too much is included, a problem may arise in elasticity. Specifically, bioplastics may be included in 5 to 10% by weight.

The viscosity of the adhesive composition for electrical steel sheets according to an embodiment of the present invention may be 100 to 1000 cp. If the viscosity is too low, the adhesion of the adhesive layer may not be sufficient. If the viscosity is too high, uniform application of the adhesive composition may become difficult. At this time, the viscosity can be measured by the Brookfield method.

A solvent may be further included in addition to the aforementioned bioplastics. The solvent may be water or alcohol. The solvent may include 70 to 99% by weight. More specifically, it may include 90 to 95% by weight.

In one embodiment of the present invention, additional components may be further included in addition to the components described above.

A method for preparing an adhesive composition for electrical steel sheet according to an embodiment of the present invention includes preparing a mixed solution by adding an acid aqueous solution to an aqueous starch solution; and kneading the mixed solution at 70 to 120°C.

First, a mixed solution is prepared by adding an aqueous acid solution to an aqueous starch solution.

As described in relation to the synthesis of the above-mentioned bioplastics, α-1,6-bonding incision is possible in amylopectin in starch at pH 3 to 5. To this end, an aqueous acid solution is added to the aqueous starch solution. An aqueous acid solution may be added in an appropriate amount to adjust the mixed solution to a pH in the range of 3 to 5.

The mixed solution may include 10 to 50% by weight of starch and 0.1 to 1% by weight of acid. If too little starch is included, too little bioplastic is synthesized, and it is difficult to secure adequate adhesive strength. If too much starch is included, the remaining starch makes it difficult to secure adequate adhesive strength. If the concentration of the aqueous acid solution is too high or too low, it is difficult to properly adjust the pH. The acid can be acetic acid.

The mixture is kneaded at 70 to 120°C. As described above, since the synthesis of bioplastics occurs at an appropriate temperature with an appropriate pH concentration, it is necessary to knead at the aforementioned temperature.

3 schematically shows a cross section of an electrical steel sheet laminate according to an embodiment of the present invention. As shown in FIG. 3, the electrical steel sheet laminate 100 according to an embodiment of the present invention includes electrical steel sheets 10 stacked in two or more layers; and an adhesive layer 20 formed between each of the electrical steel sheets 10 and including a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

In one embodiment of the present invention, as the effect can be obtained due to the components of the adhesive layer 20, a generally known electrical steel sheet can be used as the electrical steel sheet 10 without limitation. As the electrical steel sheet, non-oriented electrical steel sheet and grain-oriented electrical steel sheet may be used without limitation. Specifically, a non-oriented electrical steel sheet may be used.

Various types of electrical steel sheets may be used as the electrical steel sheet without restrictions on alloy components. For example, electrical steel sheet is weight %, Si: 3.5% or less (but excluding 0%), Al: 2.5% or less (but excluding 0%), Mn: 3% or less (but excluding 0%) , P: 0.1% or less (but excluding 0%), C: 0.04% or less (but excluding 0%), S: 0.01% or less (but excluding 0%), N: 0.01% or less (but excluding 0%) , 0%) and balance Fe and other unavoidable impurities.

Hereinafter, alloy components of the electrical steel sheet will be supplementarily described.

Si: 3.5% by weight or less

Silicon (Si, silicon) serves to lower the iron loss by increasing the specific resistance of the material, and when too much is added, the hardness of the material increases and productivity and punching performance may be inferior. More specifically, 2.0 to 3.5% by weight of Si may be included.

Al: 2.5% by weight or less

Aluminum (Al) increases the specific resistance of the material, lowers iron loss, and suppresses the formation of fine nitrides. However, if too much is added, problems may occur in all processes such as steelmaking, continuous casting, and hot rolling, thereby greatly reducing productivity. More specifically, 0.5 to 2.0% by weight of Al may be included.

Mn: 3.0% by weight or less

Manganese (Mn) serves to improve iron loss and form sulfide by increasing the specific resistance of the material. If too little is added, MnS is finely precipitated to deteriorate magnetism, and if too much is added, magnetic flux density may decrease. More specifically, 0.5 to 2.5% by weight of Mn may be included.

P: 0.1% by weight or less

Phosphorus (P) is mostly dissolved in steel to show the effect of improving iron loss, but if it is contained too much, it is undesirable because it is segregated at the grain boundary and lowers the toughness of the material, resulting in inferior productivity and punchability. More specifically, 0.005 to 0.05% by weight of P may be included.

C: 0.04% by weight or less

Carbon (C) is an effective element for increasing strength, but when it is included too much, the reduction of magnetism is greater than the effect of increasing strength. Therefore, when iron loss is important, since carbon causes self-aging, it is necessary to control the content. More specifically, C may be included in an amount of 0.01% by weight or less. More specifically, C may be included in an amount of 0.005% by weight or less.

S: 0.01% by weight or less

Sulfur (S) is preferably managed at a low level because it forms fine precipitates such as MnS and CuS to deteriorate magnetic properties. Since it is an element that is indispensably present in steel, it is better to contain it as little as possible through the refining process in steelmaking. More specifically, S may be included in an amount of 0.005% by weight or less.

N: 0.01% by weight or less

Nitrogen (N) forms fine and long AlN precipitates inside the base material to suppress crystal grain growth and deteriorate iron loss, so it is preferable to contain nitrogen (N) as little as possible. More specifically, N may be included in an amount of 0.005% by weight or less.

Other unavoidable impurity elements

In addition to the above impurity elements, impurities such as Ti and Nb that are unavoidably incorporated may be included. Since Ti and Nb promote the growth of the [111] texture, which is an undesirable crystal orientation in electrical steel sheets, they should be limited to 0.004 wt% or less (excluding O%), more specifically, 0.002 wt% or less (excluding O%). can

In addition to the above-mentioned components, the remainder includes Fe. In addition to the above components, it is not excluded that additional components are further included, and when additional elements are further included, they may be added in place of Fe.

In one embodiment of the present invention, since the components are not substantially changed during the manufacturing process of the electrical steel sheet laminate, the components of the slab may be substantially the same as the components of the electrical steel sheet described above.

An average grain size of the electrical steel sheet may be 30 to 150 μm. Iron loss may be excellent in the aforementioned range.

Each electrical steel sheet 10 may have a thickness of 0.5 mm or less. In one embodiment of the present invention, even if the electrical steel sheet 10 is thinned, the overall thickness of the laminate 100 is similar to that of the conventional electrical steel sheet, so that the customer's processing cost is not increased. At the same time, there is an effect of improving high-frequency iron loss through thinning. More specifically, the electrical steel sheet 10 may have a thickness of 0.3 to 0.5 mm.

The adhesive layer 20 is interposed between the electrical steel sheets 10 to adhere the electrical steel sheets to each other. The adhesive layer 20 is formed by applying the above-described adhesive composition to the surface of the electrical steel sheet 10 and heat-treating it. Since the adhesive composition has been described above, it is omitted.

However, volatile components such as solvents in the adhesive composition are removed by heat treatment during the manufacturing process, and the ratio of components in the adhesive layer 20 may be different from those in the adhesive composition. The adhesive layer 20 includes a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose. More specifically, the adhesive layer 20 may be made of bioplastics including 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose.

The adhesive layer 20 may have a thickness of 0.3 to 0.7 μm. If the thickness of the adhesive layer is too thin, it may be difficult to secure adequate adhesive strength. If the thickness of the adhesive layer is too thick, additional adhesive strength cannot be secured, and space factor and magnetism may be deteriorated. More specifically, the adhesive layer 20 may have a thickness of 0.4 to 0.7 μm.

The overall thickness of the laminate may be 0.3 to 0.5 mm. If the thickness of the laminate is too thin, energy and processes are excessively consumed for rolling, and if the thickness is too thick, properties not suitable for high frequency use may be exhibited. In this way, when an electrical steel sheet laminate is manufactured with a structure of two or more layers, high-frequency iron loss (W10/400) characteristics may be improved by 20% or more compared to existing electrical steel sheets having the same composition.

The electrical steel sheet laminate 100 according to an embodiment of the present invention may further include an insulating film 30 positioned on the outermost surface of the electrical steel sheet 10 . The insulating film 30 may be located on a surface opposite to the surface where the electrical steel sheet 10 and the adhesive layer 20 are in contact.

Since the insulating film 30 is widely known, a detailed description thereof will be omitted.

4 schematically shows a part of a manufacturing method of an electrical steel sheet laminate according to an embodiment of the present invention.

A method of manufacturing an electrical steel sheet laminate according to an embodiment of the present invention includes the steps of hot rolling a slab to prepare a hot rolled sheet; Cold-rolling a hot-rolled sheet to produce a cold-rolled sheet; Laminating cold-rolled sheets by inserting an adhesive composition in the middle of each layer; Final annealing of the laminated cold-rolled sheets to prepare an annealed sheet; and producing a re-cold-rolled sheet by re-cold-rolling the annealed sheet.

Hereinafter, a method for manufacturing an electrical steel sheet laminate according to an embodiment of the present invention will be described in detail for each step.

First, a slab is manufactured by solidifying molten steel controlled within the above-described component range in a continuous casting process. Since the components of the slab are substantially the same as those of the electrical steel sheet described above, overlapping descriptions will be omitted.

Before manufacturing a hot-rolled sheet, molten steel is first solidified in a continuous casting process to produce a slab. The slab is charged into a heating furnace and reheated at 1,050 to 1,200 ° C. Since it is preferable to reheat at a temperature as low as possible in order to prevent re-dissolution of the precipitate during heating, it is necessary to heat at 1,200 ° C or less, and it is difficult to roll because the deformation resistance is too large during hot rolling at less than 1,050 ° C.

Thereafter, the slab is hot-rolled to manufacture a hot-rolled sheet. It may be hot rolled so that the thickness of the hot-rolled sheet is 2.5 mm or less. This is to minimize the formation of (111) recrystallized texture, which is disadvantageous when the reduction ratio is high during subsequent cold rolling.

Next, the hot-rolled sheet may be subjected to hot-rolled sheet annealing if necessary. At this time, the hot-rolled sheet may be annealed at a temperature of 850 to 1,150 ° C. If the hot-rolled sheet annealing temperature is less than 850 ℃, the structure does not grow or grows finely, so the effect of increasing the magnetic flux density is small. this can go bad Therefore, it can be limited to the aforementioned temperature range. More specifically, the hot-rolled sheet annealing temperature may be 950 to 1,150 ℃.

Next, the hot-rolled sheet is cold-rolled to manufacture a cold-rolled sheet. At this time, the thickness of the cold-rolled sheet may be 1 mm or less. Hot-rolled sheet can be pickled and then cold-rolled. It is possible to bond the two layers immediately after pickling without cold rolling, but in that case, the roughness of the pickling surface is high, and insulation by the intermediate adhesive may be destroyed during subsequent rolling. Therefore, a hot-rolled sheet can be cold-rolled to a thickness of 1 mm or less.

Next, the cold-rolled sheets are laminated, but laminated by inserting an adhesive composition in the middle of each layer. As disclosed in FIG. 4, the cold-rolled sheet may be degreased before the adhesive is inserted. Since the adhesive composition has been described above, overlapping descriptions will be omitted. The adhesive composition may be inserted in the form of a slurry together with the solvent, and the adhesive composition in the form of a powder and the solvent may be separately inserted. When the solvent is separately inserted, 5 to 30 parts by weight of the solvent may be additionally inserted based on 100 parts by weight of the adhesive composition.

A method of inserting the adhesive composition may be a step of applying bioplastic to one surface of a cold-rolled sheet and laminating the coated surfaces. Bioplastics can be applied to the top or bottom of the steel sheet by spray, doctor blade, roll-to-roll, or slot die methods in the form of a solution.

After the laminating step, a step of drying at 100 to 250° C. may be further included. The drying step is performed at a low temperature and is a process for removing the solvent. In one embodiment of the present invention, since the adhesive composition includes cellulose acetate, adhesive strength can be secured only by drying at a low temperature. On the other hand, when using an acrylic resin, an epoxy resin, etc., it is necessary to annealing at a relatively high temperature for curing.

A rolling process may be further included after laminating the adhesive composition to form an adhesive layer having a uniform thickness on the steel sheet. However, the additional rolling process may be omitted.

Next, the laminated sheet is subjected to final annealing. The final annealing temperature may be 500 to 1200 °C. If the final annealing temperature is less than 500 ° C, recrystallization does not sufficiently occur, and if the final annealing temperature exceeds 1,200 ° C, melting of the steel sheet may occur. The atmosphere of the final annealing is a mixed gas atmosphere in which 20% hydrogen and 80% nitrogen is mixed, and the annealing time is preferably 2 minutes or more.

Next, the annealed sheet is re-cold-rolled to manufacture a re-cold-rolled sheet. In order for the laminate to have a uniform thickness, re-cold rolling is required. Re-cold rolling has a reduction ratio of 10 to 20%, and is different from simple pressing in which thickness variation does not substantially occur. At this time, the reduction ratio is calculated as ([thickness of the laminate before rolling] - [thickness of the laminate after rolling])/[thickness of the laminate before rolling].

After the re-cold rolling, forming an insulating layer on the surface of the outermost electrical steel sheet of the laminate may be further included. The insulating layer may be formed using a conventional insulating layer composition, and is not particularly limited.

Thereafter, purification annealing may be further included. Purification annealing may be performed at a temperature range of 650 to 850 ° C., and may be performed in a nitrogen 100% by volume atmosphere gas. When the purification annealing is performed, a structure advantageous to iron loss is obtained. When a laminate of non-oriented electrical steel sheets completed with purification annealing is used, it can be used for the stator.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for exemplifying the present invention, and the present invention is not limited thereto.

manufacturing example

An acid was added to the aqueous starch solution to prepare a mixed solution having an acid content of 30% by weight and an acid content summarized in Table 1 below. An adhesive composition was prepared by mixing the mixed solution at 100° C. for 5 minutes. The content of amylopectin and amylose in the bioplastic synthesized in the adhesive composition was analyzed and summarized in Table 1 below.

acid content pH amylopectin
(weight%) amylose
(weight%) Preparation Example 1 1.0% by weight 3 50 50 Preparation Example 2 0.5% by weight 4.5 30 70 Comparative Preparation Example 1 0% (no acid added) 7 70 30

Example

In weight percent, a slab composed of Si 3.1%, Al 0.9%, Mn 0.3%, N 0.002%, C 0.003%, P 0.01%, S 0.002%, N 0.0015% and other unavoidable impurities was prepared.

After heating the slab at a temperature of 1150 ° C. for 90 minutes, hot rolling was performed to prepare a hot-rolled sheet having a thickness of 2.0 mm. The hot-rolled sheet was annealed at 1100° C. for 1 minute, pickled and then cold-rolled to a thickness of 0.27 mm, and then the cold-rolled sheet was laminated, and the adhesive composition prepared in Preparation Example was applied between the cold-rolled sheets. Thereafter, drying was performed at the following temperature of 150° C. for 2 minutes, and final annealing was performed at 1050° C. for 2 minutes at 20% hydrogen and 80% nitrogen. Thereafter, rolling was performed at a reduction rate of about 15%. Then, an insulating coating was applied.

High-frequency iron loss (W _10/400 ) was measured in the rolling direction and in the direction perpendicular to the rolling direction using a 60 X 60 mm ² single plate measuring instrument and averaged, and the results are summarized in Table 2 below.

In Comparative Example 1, the cold-rolled sheet was not laminated, but was manufactured to the same thickness as the laminate.

Room-temperature Peel test: Specimen specifications for the T-Peeloff measurement were prepared in accordance with ISO 11339. After bonding two 25 x 200mm specimens with an area of 25 x 150mm ² , the unbonded area was bent at 90 degrees to produce a T-shaped tensile specimen. A specimen manufactured by the peeloff method (T-Peeloff) was fixed to the upper/lower jig (JIG) with a constant force, and then pulled at a constant speed and measured using a device for measuring the tensile force of the stacked samples. At this time, in the case of the shear method, the measured value was measured at the point where the interface with the minimum adhesive force was eliminated among the interfaces of the stacked samples. After maintaining the temperature of the specimen at 60 ℃ through a heating device, the adhesive strength was measured.

Hot Peel test: Specimen specifications for T-Peeloff measurement were prepared in accordance with ISO 11339. After bonding two 25 x 200mm specimens with an area of 25 x 150mm ² , the unbonded area was bent at 90 degrees to produce a T-shaped tensile specimen. A specimen manufactured by the peeloff method (T-Peeloff) was fixed to the upper/lower jig (JIG) with a constant force, and then pulled at a constant speed and measured using a device for measuring the tensile force of the stacked samples. At this time, in the case of the shear method, the measured value was measured at the point where the interface with the minimum adhesive strength was eliminated among the interfaces of the stacked samples. After maintaining the temperature of the specimen at 1000 ° C. for 1 minute through a heating device, the adhesive force was measured as described above after cooling.

adhesive composition adhesive layer thickness
(μm) W10/400 Room temperature peel test Hot peel test Comparative Example 1 - - 13.8 - - Example 1 Preparation Example 1 0.4 5.8 0.5 0.5 Comparative Example 2 Comparative Preparation Example 1 0.4 11.6 0.1 0 Comparative Example 3 Comparative Preparation Example 1 0.1 11.3 0.1 0 Example 2 Preparation Example 2 0.1 11.4 0.3 0.1 Example 3 Preparation Example 2 0.4 8.7 0.3 0.1

As shown in Table 2, it can be confirmed that Examples 1 to 3 laminated using the adhesive composition containing bioplastics have excellent adhesive strength and excellent iron loss at the same time. Among Examples 1 to 3, it can be confirmed that Examples 1 and 3 are superior in adhesive force and iron loss compared to Example 2 having a thin adhesive layer.

In Comparative Example 1, it can be confirmed that iron loss is inferior to that of the electrical steel laminate.

Comparative Example 2 and Comparative Example 3 using the adhesive composition containing starch can confirm that the adhesive strength is inferior.

The adhesive layer of Example 1 was analyzed. It was confirmed that the adhesive layer was made of bioplastic, and the contents of amylose and amylopectin in the bioplastic were the same as those of the adhesive composition.

The present invention is not limited to the examples and can be manufactured in various different forms, and those skilled in the art to which the present invention pertains may change other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that this can be implemented. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

1: amylose, 2: crystallized amylose
3: polar lipid, 4: swollen double helix amylose,
5: double helix amylose swollen with a polar lipid center,
6: crystallized double helix amylose,
7: crystallized amylopectin, 8: swollen amylopectin,
100: electrical steel laminate, 10: electrical steel,
20: adhesive layer, 30: insulating film

Claims (17)

delete delete delete delete delete delete electrical steel sheets laminated in two or more layers; and
An adhesive layer formed between each electrical steel sheet and containing a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose;
The thickness of the adhesive layer is 0.3 to 0.7㎛ electrical steel sheet laminate. According to claim 7,
In the electrical steel sheet, by weight %, Si: 3.5% or less (but excluding 0%), Al: 2.5% or less (but excluding 0%), Mn: 3% or less (but excluding 0%), P: 0.1% or less (but excluding 0%), C: 0.04% or less (but excluding 0%), S: 0.01% or less (but excluding 0%), N: 0.01% or less (but, 0%) and the balance of the electrical steel sheet laminate containing Fe and other unavoidable impurities. According to claim 7,
An electrical steel sheet laminate having an average grain size of 30 to 150 μm of the electrical steel sheet. delete According to claim 7,
The electrical steel sheet laminate having a total thickness of 0.3 to 0.5 mm of the laminate. Preparing a hot-rolled sheet by hot-rolling the slab;
manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;
Laminating the cold-rolled sheets by inserting an adhesive composition in the middle of each layer;
Final annealing of the laminated cold-rolled sheets to prepare an annealed sheet; and
Re-cold-rolling the annealed sheet to produce a re-cold-rolled sheet,
The adhesive composition includes a bioplastic composed of 25 to 35% by weight of amylopectin and 65 to 75% by weight of amylose,
After the step of manufacturing the re-cold-rolled sheet, the thickness of the adhesive layer is 0.3 to 0.7㎛ manufacturing method of the electrical steel sheet laminate. According to claim 12,
After the step of manufacturing the hot-rolled sheet, the manufacturing method of the electrical steel sheet laminate further comprising the step of annealing the hot-rolled sheet at a temperature of 850 to 1,150 ℃. According to claim 13,
A method of manufacturing an electrical steel laminate in which 5 to 30 parts by weight of a solvent is additionally inserted and laminated with respect to 100 parts by weight of the adhesive composition together with the adhesive composition in the laminating step. According to claim 13,
A method of manufacturing an electrical steel laminate, further comprising drying at 100 to 250 ° C after the step of laminating. According to claim 13,
A method of manufacturing an electrical steel laminate, further comprising performing cold rolling after the step of laminating. According to claim 13,
The final annealing step is an annealing method of an electrical steel sheet laminate at 500 to 1200 ° C.