KR20100063284A - The grain-oriented electrical steel sheets with high magnetic property and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A grain-oriented electrical steel sheet with superior magnetic property and a manufacturing method thereof are provided to form uniform hot-rolled texture and precipitate by controlling the austenite fraction to 60~100% or less. CONSTITUTION: A manufacturing method of a grain-oriented electrical steel sheet with superior magnetic property is as follows. A slab for an electric steel sheet is heated again, hot rolled and then coiled. The hot rolled steel sheet is cold rolled into the final thickness, omitting hot-rolled annealing. Primary and secondary recrystallization annealing are carried out. The slab is re-heated at 1050~1250°C in order to control the austenite fraction within the complex tissue of austenite and ferrite to 60~100% or less.

Description

Thick electrical steel with excellent magnetic properties and manufacturing method thereof {THE GRAIN-ORIENTED ELECTRICAL STEEL SHEETS WITH HIGH MAGNETIC PROPERTY AND MANUFACTURING METHOD THEREOF}

The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet used as a core material of a large rotating machine such as a generator and various transformers and electronic devices, and more particularly contains a high content of Mn and component contents such as C, Si, Mn, etc. Directional electrical steel sheet with excellent magnetic properties by controlling the austenite fraction to 60% or more and 100% or less by reheating the slab to form a high density aggregate structure of the (110) [001] orientation during final annealing. It relates to a method of manufacturing.

In general, a grain-oriented electrical steel sheet refers to a material having an aggregate structure (also called a 'goth aggregate structure') in which the (110) [001] direction is oriented in the rolling direction through cold rolling and annealing processes. In such a grain-oriented electrical steel sheet, the (110) [001] direction is a direction in which the magnetization of iron is easy, and the higher the degree of orientation thereof, the better the magnetic characteristics.

In general, the properties required for grain-oriented electrical steel sheet include magnetic flux density and iron loss. The greater the magnetic flux density is, the better, the value of B10 measured at 1000 Amp / m is used. Also, the smaller the iron loss is, the better it is expressed as loss per Kg (Watt) at a frequency of 50 Hz and a magnetic field of 1.7T (Tesla).

On the other hand, the secondary recrystallization process of the grain-oriented electrical steel sheet is a Goss texture by selectively growing only Goss grains with excellent magnetic properties while the normal growth of the first recrystallized particles by the grain growth inhibitor is suppressed ) Process. Therefore, in order for the grain-oriented electrical steel sheet to exhibit excellent magnetic properties through the secondary recrystallization process, the precipitates such as AlN and MnS, which are grain growth inhibitors, are finely precipitated to suppress the normal growth of the primary recrystallized grains, thereby driving the driving force of the secondary recrystallization. Increasing Goss Group should be strengthened.

Typical oriented electrical steel sheet mainly contains 2 ~ 4% silicon and MnS as an inhibitor of grain growth, and ingot or playing slabs until recently since NP Goss invented a method of manufacturing oriented electrical steel sheet by cold rolling. After casting into slab through the process, it is completed by the process of reheating-hot rolling-pre-annealing, two times cold rolling including intermediate annealing-decarbonization-application of fusion inhibitor-final high temperature annealing.

It is no exaggeration to say that the history of research on oriented electrical steel sheet is a history of efforts to reduce iron loss. The main improvements of these studies are thinning the product, adding various elements to the components, and thermal or mechanical treatment on the product. To finer the magnetic domain.

That is, Japanese Laid-Open Patent Publication No. 5-302122 discloses a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties with a steel sheet thickness of 0.1 to 0.25 mm. The hot rolled sheet is pre-cold rolled at a cold rolling rate of 10 to 50%, and 80 Final cold rolling with a cold rolling rate of more than% to produce an electrical steel sheet of 0.1 ~ 0.25 mm in the final thickness, there is a problem that the manufacturing cost is increased by two cold rolling.

In addition, Japanese Patent Application Laid-Open No. Hei 1-283324 discloses a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties by adding elements such as B and Se, but B is very difficult to control in the steelmaking step even when a trace amount is added. In addition, Se acts as a grain growth inhibitor (Inhibitor) as MnSe, but it is necessary to increase the reheating temperature of the slab or to increase the annealing time for the complete solution. have.

In addition, Japanese Patent Laid-Open Publication No. 2000-109961 and Korean Patent Laid-Open Publication No. 2002-63515 disclose magnetic domain miniaturization techniques for forming linear or dot-array grooves on a surface. Since the final product is further processed, manufacturing costs are increased.

However, as described above, these methods are able to reduce iron loss to some extent, but increase the manufacturing cost and complicate the manufacturing method.

Therefore, in recent years, while researches to improve such magnetism have reached a limit, a manufacturing method for stably producing oriented electrical steel sheets having excellent magnetic properties while reducing manufacturing costs has been requested.

The present invention has been made to solve the above problems, and relates to a grain-oriented electrical steel sheet used as iron core materials such as transformers, electric motors, generators and other electronic devices, inexpensive elements in the steelmaking step for the quantitative increase of the goose aggregate structure The content of phosphorus Mn is high, the content of C, Si, Mn, etc. is controlled to satisfy 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3, and the slab is reheated so that the austenite fraction is 60% or more 100 It controls to be less than%, regulates the cooling rate from the hot rolling to the winding section, promotes the homogenization of the hot rolled tissue and the homogenization of the precipitates through hot rolled sheet annealing, and the growth of primary recrystallized grains through decarburization and nitride annealing. Method to manufacture oriented electrical steel sheet having excellent magnetic properties at low cost and stably without complicated control of the process by controlling the density and forming the goth aggregate structure at the time of final annealing. The purpose is to provide for.

The present invention, after reheating the slab for electrical steel, the hot-rolled slab is wound up after hot rolling, after performing hot-rolled sheet annealing, and then once cold-rolled to a final plate thickness, the first recrystallization annealing and subsequent secondary recrystallization In the method for producing a grain-oriented electrical steel sheet subjected to the annealing, the slab reheating is by weight% C: 0.03 ~ 0.10%, Si: 2.0 ~ 4.5%, Mn: 1.0 ~ 2.0%, acid soluble Al: 0.005 ~ 0.04%, S: 0.01% or less, P: 0.005 to 0.05%, N: 0.01% or less and at the same time contains one or two kinds selected from Sn: 0.01 to 0.3% and Sb: 0.01 to 0.3%, and the balance is Fe And reheating the steel slab made of other unavoidable impurities at a temperature of 1050 to 1250 ° C. to control the fraction of austenite in the composite structure of ferrite and austenite to be 60% or more and 100% or less. 2 excellent directional electricity It provides a method for producing a steel sheet.

In addition, the present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the C, Si, Mn in the steel slab has a chemical composition satisfying 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3 to provide.

In addition, the hot rolling of the present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that hot-rolled to a thickness of 1.5 ~ 2.5 mm hot rolled sheet.

In addition, the winding of the present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the cold rolling to the temperature of less than 600 ℃ at a cooling rate of 15 ℃ / sec or more after the hot rolling.

In addition, the hot-rolled sheet annealing of the present invention is carried out within 5 minutes at 900 ~ 1200 ℃ temperature, provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the quenching.

In addition, the quenching of the present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the cooling at a cooling rate of 15 ℃ / sec ~ 500 ℃ / second.

In addition, the cold rolling of the present invention provides a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the final sheet thickness is cold rolled by 0.15 ~ 0.50 mm by a single cold rolling method.

In addition, the primary recrystallization annealing of the present invention to produce a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that at the temperature of 800 ~ 950 ℃ after cold rolling at the same time decarbonized annealing and nitride annealing in a mixed gas atmosphere of hydrogen and nitrogen Provide a method.

In addition, the secondary recrystallization annealing of the primary recrystallization annealing of the present invention by controlling the size of 12 ~ 28 ㎛ of the oriented electrical steel sheet having excellent magnetic properties, characterized in that for performing the secondary recrystallization annealing at a starting temperature of 1050 ~ 1200 ℃ It provides a manufacturing method.

In addition, the present invention provides a grain-oriented electrical steel sheet excellent in magnetic properties produced by any one of the above manufacturing methods.

As described above, the present invention can reduce the production cost by containing a high content of Mn, which is an inexpensive element rather than an expensive alloy element, and controls the content of C, Si, Mn in the steelmaking step, and maintains a constant temperature when reheating the slab. By maintaining the austenite fraction to 60% or more and 100% or less to form a goth aggregate structure having a high degree of integration of the (110) [001] orientation at the time of final annealing, it is magnetically inexpensive and stable without any complicated control of the process. There is an effect to secure a directional electrical steel sheet excellent in properties.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated in detail.

In order to achieve the above object, the present invention is to reheat the slab for electrical steel, and then to re-heat the slab after hot rolling, the hot-rolled sheet annealing, and then cold rolled once to make the final plate thickness, the first recrystallization In the method for producing a grain-oriented electrical steel sheet subjected to annealing and subsequent secondary recrystallization annealing, the slab reheating is by weight% C: 0.03 to 0.10%, Si: 2.0 to 4.5%, Mn: 1.0 to 2.0%, acid solubility One or two selected from Al: 0.005 to 0.04%, S: 0.01% or less, P: 0.005 to 0.05%, N: 0.01% or less, and Sn: 0.01 to 0.3% and Sb: 0.01 to 0.3% Type and the balance is reheated the steel slab composed of Fe and other unavoidable impurities at a temperature of 1050-1250 ° C. to control the fraction of austenite in the composite structure of ferrite and austenite to be 60% or more and 100% or less. Characterized It provides a process for the production of grain-oriented electrical steel sheet excellent in characteristic groups.

If you want to manufacture oriented electrical steel sheets with good magnetic properties after final annealing by reheating the steel slab with only a high carbon content at a certain temperature to make the austenite fraction more than 60%, decarbonization heat treatment before cold rolling is additionally required. There will be a problem that the process is complicated and necessary, the manufacturing cost increases.

The inventors of the present invention contain a high content of Mn, which is an inexpensive element, in the steelmaking step in order to quantitatively increase the goose aggregate structure, and the component content of C, Si, Mn, etc. is 1.3 ≦ Si / (Mn + C + 0.4) ≦ 2.3 After the slab is reheated, the austenite fraction is controlled to be 60% or more and 100% or less, thereby forming a highly oriented goth aggregate in the (110) [001] orientation during final annealing, without complicated control of the process. It has been found that inexpensive and stable manufacturing methods can produce oriented electrical steel sheets having excellent magnetic properties.

Hereinafter, the reason for component limitation of the present invention will be described in more detail.

C: 0.03 ~ 0.1 wt%

C is an important element of the present invention by adding 0.03% by weight or more to increase the austenite fraction in the slab, and by controlling the cooling rate can transform the austenite phase to a high bainite phase or martensite phase, The bainite phase or martensite phase transformed by this provides a nucleus growth plant in the hot-rolled sheet annealing process to ensure homogenization of microstructures, and to homogenize precipitates such as AlN, and thus, the orientation degree in the (110) [001] direction. It is possible to form a very high goth assembly with a high. However, adding 0.1 wt% or more has a positive aspect of promoting austenite formation on the slab, but coarse carbides may be formed during winding and cooling, and Fe ₃ C (cementite) is formed at room temperature to form ferrite and The formation of pearlite (graphite) or graphite (graphite), which is a mixed structure of cementite, causes non-uniform structure and quality degradation due to self aging. Therefore, the content of carbon is preferably limited to 0.03 to 0.1% by weight.

Si: 2.0 ~ 4.5 wt%

Si is an important element of the present invention increases the specific resistance of the steel and serves to reduce the iron loss. If the content of Si is less than 2.0% by weight, the specific resistance of the steel is small, the iron loss characteristics are deteriorated, and the phase transformation section is present at high temperature annealing, which is not preferable because the secondary recrystallization becomes unstable. It is not good because rolling becomes extremely difficult and secondary recrystallization becomes unstable. Therefore, the content of Si is limited to 2.0 to 4.5% by weight.

Acid Soluble Al: 0.005 ~ 0.04 wt%

Acid-soluble Al is a nitride of (Al, Si, Mn) N form by combining nitrogen ions with Al, Si, Mn in solid solution in the steel in the annealing process after cold rolling, in addition to AlN finely precipitated during the hot rolling process. It forms a strong grain growth inhibitor, and when the content is less than 0.005% by weight can not be expected to suppress the grain growth, when the content exceeds 0.04% by weight, the grain growth by forming coarse AlN The deterrent falls. Therefore, the content of acid-soluble Al is limited to 0.005 ~ 0.04% by weight.

Mn: 1.0 ~ 2.0 wt%

Mn is a key element of the present invention, which has the effect of reducing the iron loss by increasing the resistivity and expanding the stable region of austenite, not only actively transforming during heat treatment, but also reacting with nitrogen introduced by nitriding (Al, It is an important element for suppressing the growth of primary recrystallized grains by forming precipitates of Si and Mn) N to cause secondary recrystallization. In the present invention, the steel slab containing 1.0 wt% or more and satisfying the relation of 1.3 ≦ Si / (Mn + C + 0.4) ≦ 2.3 is reheated to a temperature of 1050 to 1250 ° C. so that the austenite fraction is 60 to By securing 100%, it is possible to produce a grain-oriented electrical steel sheet having excellent magnetic properties by subsequent heat treatment. However, if the content exceeds 2.0% by weight, excessive Mn oxide (Mn Oxide) is formed in addition to Fe ₂ SiO ₄ on the surface of the steel sheet not only deteriorates iron loss, but also prevents the base coating formed during high temperature annealing, thereby significantly improving the surface quality. Will fall. Therefore, the content of Mn is limited to 1.0 to 2.0% by weight.

S: 0.01 wt% or less

If the S content exceeds 0.01% by weight, it is preferable to control it so that it is segregated in the center of the slab during casting, making it difficult to control the microstructure in subsequent processes and increasing the solid solution temperature during hot rolling. It is a kind of inevitable impurities contained. In the present invention, since MnS is not used as a grain growth inhibitor, it is not preferable that S contain more than 0.01% by weight to precipitate MnS.

P: 0.005 ~ 0.05 wt%

P segregates in the grain boundary and may serve as a secondary role in preventing the movement of the grain boundary and at the same time inhibiting grain growth and improving the (110) [001] texture. If the content of P is less than 0.005% by weight, the effect is insignificant. If the content is more than 0.05% by weight, the brittleness is increased and the cold rolling property is deteriorated. Therefore, the content of P is limited to 0.005 to 0.05% by weight.

N: 0.01 wt% or less

N is an important element that reacts with Al to form AlN. Since N is reinforced in the annealing process, it is sufficient to enter an impurity during dissolution. However, when the N content exceeds 0.01% by weight, hot rolling becomes difficult and causes a surface defect called Blister by nitrogen diffusion in the post-hot rolling process.

Sn: 0.01 to 0.3 wt%

Since Sn is a grain boundary segregation element, it is an element that prevents the movement of grain boundary, and it is a grain growth inhibitor and promotes the generation of goth grains in the (110) [001] orientation so that secondary recrystallization is well developed, so that AlN, (Al, Si, In addition to Mn) N, it is an important element for reinforcing grain growth inhibition. If the Sn content is less than 0.01% by weight, the effect is inferior, and if it exceeds 0.3% by weight, hard grain-based segregation occurs severely, and the brittleness of the steel sheet increases, causing plate breakage during rolling. Therefore, the content of Sn is limited to 0.01 to 0.3% by weight.

Sb: 0.01 to 0.3 wt%

Like Sn, it has the effect of a grain growth inhibitor as a grain boundary segregation element, and has an effect of improving the iron loss by improving the adhesion between the steel sheet and the oxide layer by suppressing the oxide layer on the surface of the steel sheet formed during secondary recrystallization. If the Sn content is less than 0.01% by weight, the effect is insignificant, and if it exceeds 0.3% by weight, brittleness is increased and sheet breakage occurs during rolling. Therefore, the content of Sb is limited to 0.01 to 0.3% by weight.

1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3

The inventors found that the austenitic fractions were changed according to the carbon content. The inventors also found that the C and Si contents were changed depending on the Mn content. As a result, the content ratio of C, Si, and Mn was 1.3 ≤ Si / (Mn When + C + 0.4) ≤ 2.3, it was confirmed that the austenite fraction in the steel sheet can be obtained from 60 to 100%, and the content of C, Si, and Mn satisfies the above formula in the range that satisfies the content of each component. Should be. If the value is less than 1.3, there is a problem that the deposition amount of carbides is increased, decarburization is incomplete in the post-decarbonization annealing process, and carbides remain in the final product. If the value exceeds 2.3, brittleness of the steel sheet is exceeded. Larger cold rolling becomes extremely difficult and secondary recrystallization becomes unstable.

In addition to the above components, the steel contains Fe and other unavoidable impurities.

The present invention described above is largely steelmaking step, reheating step of steel slab, hot rolling step, winding step, hot rolling annealing step, cold rolling step, primary recrystallization step (decarbon annealing and nitride annealing step), secondary recrystallization step (final) Annealing step). The present invention provides a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density by controlling the process conditions of each step, hereinafter will be described in detail the configuration and operation effects of each step.

In the steelmaking stage, the contents of C, Si, and Mn are important in order to secure the austenite fraction to the maximum. In terms of weight%, C should be 0.03 to 0.1%, Si should be 2.0 to 4.5%, and Mn should be 1.0 to 2.0%. It is preferable that the contents of C, Si, and Mn satisfy a relation of 1.3 ≦ Si / (Mn + C + 0.4) ≦ 2.3.

The present invention employs a precipitate, such as AlN, which acts as a grain growth inhibitor by reheating the slab at a temperature of 1050 to 1250 ° C. where the austenite fraction becomes 60 to 100%. In particular, when the content of C, Si, and Mn satisfies the relation of 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3, the austenite fraction is secured to 60 to 100% at the slab reheating temperature of 1050 to 1250 ° C. Within this range, the AlN precipitates present in the slab have a very high solid solution rate compared to the ferrite phase, so that the precipitates are sufficiently dissolved even at a normal slab heating temperature.

On the other hand, the theoretical relation found in the literature on the degree of solubility of AlN in ferrite is the following formula proposed by IWAYAMA, reported in the 1980 Journal of Magnetism and Magnetic Materials. Where T is the absolute temperature.

As an example, assuming that the acid-soluble Al is 0.026% by weight and N is 0.005% by weight, the theoretical solid solution temperature T according to the IWAYAMA equation is 1258 ° C. In order to heat the slab of such an electrical steel sheet, it must be heated to 1300 ° C or more. However, when the slab is heated to such a high temperature, the energy used for heating the slab increases, molten slag is excessively formed, and the real rate decreases. In addition, the slag flowing down and the roadbed react to be repaired. There is a problem.

In addition, the AlN solid solution on austenite was obtained by Darken and Leslie as follows.

According to the above formula, the solid solution temperatures of 0.028 wt% of acid-soluble Al and 0.005 wt% of N are 1112 占 폚 and 1002 占 폚, which are much lower than the solid solution temperature of 1258 占 폚 on ferrite according to the above-mentioned IWAYAMA equation. Therefore, the more austenite phase in the slab, the lower the AlN solution temperature is, and the cost and productivity are improved. This effect can maximize the solid solution of AlN by adding a large amount of C and Mn, and eventually it is possible to secure sufficient grain growth inhibition.

After the slab reheating step is hot rolling, the thickness of the hot rolled sheet is hot rolled to 1.5 ~ 2.5 mm, and then wound to a temperature of less than 600 ℃ at a cooling rate of 15 ℃ / sec or more. If the thickness of the hot rolled sheet exceeds 2.5 mm, the cooling rate decreases during the quenching process after hot rolled to form coarse carbides. If the thickness of the hot rolled sheet is less than 1.5 mm, the rolling load increases and the thickness control becomes difficult. It is limited to 2.5mm. In addition, when the hot rolled coil is wound at a temperature exceeding 600 ° C, coarse carbides are formed, so the coiling temperature is limited to a temperature of 600 ° C or less. However, the winding temperature is preferably 400 ℃ or more. It is because grain growth will not become good when it winds to less than 400 degreeC.

On the other hand, when winding at a cooling rate of less than 15 ° C./sec, coarse carbides are formed, and fralite, a weak layer of Fe ₃ C and ferrite, is formed, resulting in diffusion of bainite and diffusion-free martensite. Since the delay is not easy to effect the one-time cold rolling, the cooling rate is limited to 15 ℃ / sec or more.

On the other hand, in the hot rolled hot rolled plate there is a structure stretched in the rolling direction by the stress, and precipitates such as AlN precipitate during the hot rolling. Therefore, for homogeneous distribution of uniform recrystallized microstructure and precipitates such as AlN before cold rolling, it is necessary to recrystallize the deformed structure by heating the hot rolled sheet once again and to promote the solid solution of precipitates such as AlN. Therefore, the hot rolled hot rolled plate in the present invention undergoes a hot rolled sheet annealing process, the annealing temperature is preferably heated to 900 ~ 1200 ℃ within 5 minutes.

In addition, after the annealing of the hot rolled sheet, before the cold rolling, a quenching process using air cooling, water cooling, oil cooling, or two or more cooling methods is required. In the quenching process, the austenite phase undergoes a hard transformation of hard bainite or martensite phase or two phases with high strength. In addition, the quenching is preferably limited to a cooling rate of 15 ° C / sec ~ 500 ° C / sec, when the slow cooling at a cooling rate of less than 15 ° C / sec is due to the additional precipitation of precipitates such as AlN due to the amount of acid-soluble Al It becomes smaller, and the coarse layered structure of pearlite, which is a mixed structure of cementite and ferrite, is formed, and thus the shear deformation zone is weakened by work hardening during cold rolling, and the structure becomes uneven, resulting in a problem of formation of highly oriented goth aggregated tissue. do. On the other hand, when quenching at a cooling rate of more than 500 ℃ / sec transformed the austenite phase to the martensite phase with high total strength, the cold rolling process is subjected to a load, the quality of the cold rolled plate worsens.

After the hot-rolled sheet annealing process using a reverse rolling mill or a Tandom rolling mill cold rolled to a thickness of 0.15 ~ 0.50 mm or less, and rolling to the thickness of the final product straight from the initial hot rolled thickness without performing annealing heat treatment of the intermediate deformed structure It is preferable to carry out by cold rolling once, and to cold roll to 90% or more. Due to the cold rolling, the shear deformation band is significantly increased than that of the ferrite, which is known as the matrix structure. As a result, in this single cold rolling, the low-density orientations of (110) [001] are rotated in the deformation direction, and only the goth crystal grains arranged best in the (110) [001] orientation exist in the cold-rolled sheet. do.

On the other hand, since the grains of the (110) [001] orientation, which are the nucleus of the secondary recrystallization inside the shear deformation zone, are easily recrystallized, the texture of the (110) [001] orientation increases in the primary recrystallized texture. By increasing the integrated strength of the recrystallized (110) [001] goth-assembly structure, it is possible to secure excellent magnetic properties.

After the first cold rolling, the first recrystallization annealing, that is, decarbonization annealing and nitride annealing is performed. Either method of finishing decarbonization annealing, or simultaneously performing decarburization and nitride annealing has no problem in achieving the effect of the present invention. However, it is preferable to simultaneously perform decarburization and annealing in terms of production cost. It is preferable to maintain the annealing temperature of the steel sheet during the decarburization and annealing at 800 ~ 950 ℃. If the annealing temperature is lower than 800 ℃, the decarburization time is long, and the SiO ₂ oxide layer is densely formed on the surface of the steel sheet, resulting in coating defects. This decrease prevents the formation of stable secondary recrystallization. The annealing time is not a big problem in achieving the effect of the present invention, but it is preferable to treat it within 5 minutes in view of productivity.

In addition, a certain amount of carbon must be maintained in order to prevent coarse growth of columnar tissues and central segregation of S (Sulfur), which adversely affects the magnetism generated when the slab is reheated at a high temperature.These carbons prevent phase transformation of ferrite-austenite. It inhibits the formation of columnar tissue, promotes the employment of AlN, a grain growth inhibitor, and inhibits the central segregation of S.

However, when carbon remains in the final product, the magnetic aging phenomenon of the magnetic properties of the material decreases with time as the final consumer uses the oriented electrical steel sheet product. This is because the residual carbon dissolved in the material mainly precipitates as carbides such as Fe ₃ C (cementite) at grain boundaries due to thermal energy generated during the use of the product. Therefore, the present invention does not exceed 50 ppm residual carbon content during production through the decarbonization process. In addition, the thinner the steel sheet, the shorter the carbon removal time is, so that the plate thickness of the final product is preferably 0.23 mm or less, so that the decarburization time can be reduced, thereby reducing the production cost burden.

The annealing of the present invention forms a nitride of (Al, Si, Mn) N form by combining with Al, Si and Mn in which nitrogen ions are dissolved in steel in a mixed gas atmosphere of hydrogen and nitrogen containing ammonia gas. Thereby acting as a reinforcement for potent grain growth inhibitors. The present invention is to suppress the grain growth through the primary recrystallization annealing to control the size of the recrystallized grain to 12 ~ 28 ㎛, in the second recrystallization annealing by controlling the primary recrystallized grain size in the range of 12 ~ 28 ㎛ By controlling the start temperature to 1050 ~ 1200 ℃ it is possible to secure a goth aggregate structure exhibiting excellent magnetic properties.

Finally, in the manufacture of grain-oriented electrical steel sheet, an annealing separator based on MgO is applied to the steel sheet, followed by final annealing at a high temperature for a long time to generate secondary recrystallization, so that the (110) plane of the steel sheet is parallel to the rolled surface and is in the [001] direction. By forming the (110) [001] texture parallel to the rolling direction, a grain-oriented electrical steel sheet having excellent magnetic properties is produced. That is, the Goss texture exhibiting excellent magnetic properties by selectively growing only Goss grains having excellent magnetic properties while the normal growth of the first recrystallized particles is suppressed by the recrystallization growth inhibitor (Inhibitor). ) Can be secured.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited only to these examples.

Example 1

By weight%, the content of C is 0.034 ~ 0.095%, the content of Si is 3.19 ~ 3.22%, the content of Mn is 0.09 ~ 1.79%, and the value of Si / (Mn + C +0.4) within the range of 1.4 ~ 5.8 The steel slab containing S: 0.003%, N: 0.004%, acid-soluble Al: 0.028%, P: 0.026%, Sn + Sb: 0.10%, and the balance Fe and other unavoidable impurities was heated to a temperature of 1150 ° C. After reheating it was hot rolled to a thickness of 2.3 mm and wound up to 600 ° C. at a cooling rate of 50 ° C. per second. The hot rolled hot rolled sheet was annealed at a temperature of 1050 ° C. for 180 seconds, quenched to 200 ° C. per second, pickled, and cold rolled once to a thickness of 0.27 mm. The cold rolled plate was maintained at a temperature of 850 ° C. for 180 seconds in a humid hydrogen, nitrogen, and ammonia mixed gas atmosphere, and subjected to simultaneous decarburization and nitriding annealing so that the nitrogen content was 200 ppm.

MgO, an annealing separator, was applied to the heat-treated steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen and 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for at least 10 hours and then cooled. The measured values of magnetic properties such as magnetic flux density and iron loss for each condition are shown in Table 1.

At this time, the iron loss W17 / 50 is the amount of energy lost by heat when the magnetic flux density of 1.7 T is induced to the iron core at an alternating current of 50 Hz, and the magnetic flux density B10 is induced at an excitation force of 1000 Amp / m.

                          TABLE 1

C (%) Si (%) Mn (%) Si / (Mn + C + 0.4) Magnetic flux density
(B10) Iron loss
(W17 / 50) division 0.065 3.22 0.09 5.8 1.922 0.975 Comparative material 0.074 3.20 0.27 4.3 1.923 0.982 Comparative material 0.077 3.19 0.52 3.2 1.919 0.976 Comparative material 0.034 3,20 1.09 2.1 1.929 0.963 Invention 0.083 3.21 1.30 1.8 1.933 0.959 Invention 0.095 3.20 1.79 1.4 1.937 0.951 Invention

As shown in Table 1 above, Mn contains 1.0 to 2.0% by weight, and at the same time C, Si, Mn is in the range of 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3 is out of the range Compared with the comparative material, it was confirmed that the magnetic properties are excellent. Specifically, when the content of C, Si, and Mn satisfies 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3, the austenite fraction is secured to 60 to 100% at the slab reheating temperature of 1050 to 1250 ° C. Within this range, precipitates such as AlN, which existed in the slabs, are very fast in solid solution compared to the ferrite phase, so that the precipitates are sufficiently dissolved even at ordinary slab heating temperatures, and precipitates such as AlN during hot-rolled sheet annealing. This homogeneous precipitate acts as an inhibitor of grain formation, thereby developing a goth aggregate and having excellent magnetic properties.

Example 2

By weight%, the content of C is 0.035 ~ 0.093%, the content of Si is 3.27 ~ 3.29%, the content of Mn is 0.2 ~ 1.7%, and the value of Si / (Mn + C +0.4) within the range of 1.5 ~ 5.0 Let's

Steel slab containing S: 0.003%, N: 0.004%, acid soluble Al: 0.027%, P: 0.027%, Sn + Sb: 0.10% and the balance Fe and other unavoidable impurities were reheated to a temperature of 1150 ° C. It was then hot rolled to 2.3 mm in thickness and wound up to 600 ° C. at a cooling rate of 50 ° C. per second. The hot rolled hot rolled sheet was changed within a temperature range of 1100 to 1200 ° C. according to the test material, followed by quenching at 180 ° C. per second for 200 seconds, pickling, and cold rolling once to a thickness of 0.27 mm. The cold rolled plate was maintained at a temperature of 850 ° C. for 180 seconds in a humid hydrogen, nitrogen, and ammonia mixed gas atmosphere, and subjected to simultaneous decarburization and nitriding annealing so that the nitrogen content was 200 ppm.

MgO, an annealing separator, was applied to the heat-treated steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen and 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for at least 10 hours and then cooled. The measured values of magnetic properties such as magnetic flux density and iron loss for each condition are shown in Table 2.

                           TABLE 2

C (%) Si (%) Mn (%) Si /
(Mn + C + 0.4) Hot Rolled Annealing Temperature
(℃) Austenitic fraction (%) Magnetic flux density
(B10) Iron loss
(W17 / 50) division 0.054 3.27 0.2 5.0
1100 26 1.913 0.881 Comparative material 1200 26 1.911 0.925 Comparative material 0.035 3.27 1.2 2.0
1100 81 1.932 0.843 Invention 1200 100 1.927 0.857 Invention 0.093 3.29 1.7 1.5
1100 100 1.929 0.851 Invention 1200 100 1.930 0.864 Invention

As shown in Table 2, the present invention satisfies the content range of C, Si, Mn of the present invention and the range of 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3, the austenite fraction is 60% or more Compared with the comparative material outside the range, the magnetic flux density is high and the iron loss is low, so the magnetic properties are excellent. Specifically, in the case of the invention material satisfying the above range, a uniform recrystallized microstructure and a homogeneous distribution of precipitates such as AlN are formed through a hot-rolled sheet annealing process, followed by decarburization, nitride annealing, and final annealing. While normal growth of the primary recrystallized particles is suppressed, only Goss grains having excellent magnetic properties are selectively grown to obtain a Goss texture, thereby improving magnetic properties.

Claims (10)

After reheating the slabs for electrical steel, the hot slabs are wound up after hot rolling, hot rolled annealing, then cold rolled once to obtain the final sheet thickness, followed by primary recrystallization annealing and subsequent secondary recrystallization annealing. In the method of manufacturing a grain-oriented electrical steel sheet, The slab reheating is by weight% C: 0.03 ~ 0.10%, Si: 2.0 ~ 4.5%, Mn: 1.0 ~ 2.0%, acid soluble Al: 0.005 ~ 0.04%, S: 0.01% or less, P: 0.005 ~ 0.05%, It contains N or 0.01% or less and at the same time contains one or two kinds selected from Sn: 0.01 to 0.3% and Sb: 0.01 to 0.3%, and the balance is 1050 to 1250 ° C for steel slabs made of Fe and other unavoidable impurities. A method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that it is reheated at a temperature and controlled so that the fraction of austenite is 60% or more and 100% or less in the composite structure of ferrite and austenite. The method of claim 1, C, Si, Mn in the steel slab has a chemical composition satisfying 1.3 ≤ Si / (Mn + C + 0.4) ≤ 2.3, characterized in that the manufacturing method of a grain-oriented electrical steel sheet having excellent magnetic properties. The method according to claim 1 or 2, The hot rolling is a method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the hot rolling of the hot rolled sheet thickness of 1.5 ~ 2.5 mm. The method according to claim 1 or 2, The winding is a method of producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the cold rolling to a temperature of less than 600 ℃ at a cooling rate of 15 ℃ / sec or more after the hot rolling. The method according to claim 1 or 2, The hot rolled sheet annealing is carried out within 900 minutes at 900 ~ 1200 ℃ temperature, quenching method of producing a grain-oriented electrical steel with excellent magnetic properties, characterized in that the. The method of claim 5, The rapid cooling is a method of producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the cooling at a cooling rate of 15 ℃ / sec ~ 500 ℃ / second. The method according to claim 1 or 2, The cold rolling is a method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the final plate thickness cold rolled by 0.15 ~ 0.50 mm by a single cold rolling method. The method according to claim 1 or 2, The primary recrystallization annealing is a method of producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the carbonaceous annealing at the temperature of 800 ~ 950 ℃ after the cold rolling and the annealing in a mixed gas atmosphere of hydrogen and nitrogen at the same time. The method according to claim 1 or 2, A method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the secondary recrystallization annealing is performed at a starting temperature of 1050 to 1200 ° C by controlling the recrystallized grain of the primary recrystallization annealing to a size of 12 to 28 μm. The grain-oriented electrical steel sheet excellent in magnetic properties produced by the manufacturing method of any one of claims 1 to 9.