KR101286209B1 - Grain-oriented electrical steel sheets having excellent magnetic properties and method for manufacturing the same - Google Patents

Abstract

The present invention relates to the production of grain-oriented electrical steel sheet, in weight%, Si: 2.0 ~ 4.0%, C: 0.085% or less, acid soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less, Pb: 0.01 ~ 0.5% , N: 0.010% or less, S: 0.010% or less, a slab of remainder Fe and other unavoidable impurities is heated, hot rolled, and then subjected to cold rolling or intermediate annealing at least two times. After cold rolling, and then subjected to the first recrystallization annealing, the second recrystallization annealing, the first recrystallization annealing is an initial rapid heating step of heating up at an average heating rate of 300 ℃ / sec or more, and after the initial rapid heating step The temperature increase rate is lowered than the average temperature increase rate in the rapid rate increase process while the temperature rise rate is higher than 100 ℃ / sec, and the temperature rise rate lower than the average temperature increase rate in the rapid temperature increase process after the rapid temperature increase process Including a general heating process The magnetic made to provide a method for manufacturing a grain-oriented electrical steel sheet excellent. According to the present invention, the volume fraction of the Goss orientation, in particular the Exact Goss orientation grains, is applied to the first recrystallized steel sheet by introducing three steps of temperature rising patterns (starting temperature rising speed + rapid temperature rising temperature + general temperature rising) in the temperature rising process of the first recrystallization annealing. By increasing the crystal orientation density after the secondary recrystallization it can be produced a oriented electrical steel sheet of high magnetic flux density low iron loss.

Description

Oriented electrical steel with excellent magnetic properties and manufacturing method thereof {GRAIN-ORIENTED ELECTRICAL STEEL SHEETS HAVING EXCELLENT MAGNETIC PROPERTIES AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to the production of a grain-oriented electrical steel sheet, and more particularly to a method for manufacturing a grain-oriented electrical steel sheet to improve the magnetism by improving the degree of integration of the crystal orientation by improving the temperature heating pattern of the primary recrystallization annealing.

The directional electrical steel sheet is composed of crystal grains having a so-called Goss orientation in which the crystal orientation of the steel sheet face is {110} plane and the crystal orientation in the rolling direction is parallel to the <001> axis, It is a soft magnetic material.

This oriented electrical steel sheet is superior to the secondary recrystallized structure obtained by suppressing the growth of the primary recrystallized grains in the final annealing process after the primary recrystallization and selectively growing the grains of the {110} <001> orientation among the grains whose growth is suppressed. Since it is intended to exhibit magnetic properties, the growth inhibitor of the primary recrystallized grain (hereinafter referred to as 'inhibitor') is very important. Therefore, it is a grain-oriented electrical steel sheet that allows grains with stable structure of {110} <001> orientation to grow preferentially (hereinafter referred to as 'secondary recrystallization') in the final annealing process. It is the core of manufacturing technology.

Secondary recrystallization starts in the final annealing process because these inhibitors grow or decompose as the temperature increases and they lose their ability to inhibit the growth of the primary recrystallized grains. . In the final annealing process, the growth of all primary recrystallized grains should be suppressed until just before secondary recrystallization occurs. For this purpose, the precipitates should be uniformly distributed in sufficient quantity and in an appropriate size, and thermally stable up to the high temperature just before secondary recrystallization occurs. Should not be easily disassembled.

It is possible to obtain such {110} <001> texture by a combination of several manufacturing processes. In general, the slab heating, hot rolling, hot rolled sheet annealing, cold rolling, and primary recrystallization, as well as strict management of slab composition A series of process conditions, such as annealing and final annealing (secondary recrystallization annealing), must be strictly controlled.

 Primary recrystallization is a term commonly referred to as recrystallization, in which modified grains are nucleated and grain growth occurs without deformation above a certain temperature. The primary recrystallization is usually performed with decarburization annealing performed after cold rolling or immediately after decarburization annealing is performed. The primary recrystallization results in uniform and proper grain sizes. In general, the orientation of the recrystallized grains in a grain-oriented electrical steel sheet has a collective structure in which the orientations of the grains are dispersed in various directions or the non-goth-bearing orientations are arranged parallel to the surface orientation, and the ratio of the goth bearing to be finally obtained in the grain-oriented electrical steel sheet is Very low

As a technique for improving the magnetic properties by controlling the heating and heating conditions during the first recrystallization annealing, Japanese Patent Application Laid-Open No. 2003-3213, 2008-1978, 2008-1979, 2008-1980, 2008-1981, 2008-1982, 2008-1983 Techniques have been reported for introducing rapid heating in the temperature raising process of the decarburization annealing process.

Japanese Patent Laid-Open Publication No. 2003-3213 proposes a technique for producing a mirror-oriented electrical steel sheet having high magnetic flux density by controlling the ratio of I [111] / I [411] to 2.5 or less in the amount of nitriding treatment and the texture after annealing. In order to control the texture, it is shown that the heating rate of the aluminum and nitrogen amount and the temperature increase process of the decarburization annealing process should be controlled.

In the above-mentioned Japanese Patent Publication Nos. 2008-1978, 2008-1979, 2008-1980, 2008-1981, 2008-1982, 2008-1983, the lamellar spacing is adjusted at the same time by decarburizing during hot-rolled sheet annealing or by controlling the hot-rolled sheet annealing temperature. In the decarburization annealing, a method of improving the magnetic flux density by rapidly heating at a heating rate of 40 ° C./sec or more, preferably 75 ° C. to 125 ° C./sec, in a temperature range of 550 ° C. to 720 ° C. has been proposed. These patents report that the grains in the {411} orientation during the primary recrystallization affect the preferential growth of the secondary recrystallized grains in the {110} orientation, and the {111} / { It is proposed to produce a grain-oriented electrical steel sheet having a high magnetic flux density by adjusting the ratio to 3.0 or less, followed by nitriding and strengthening the inhibitor.

However, in the above patents, a temperature range with a large structure change in the temperature increase process of the decarburization annealing process is 700 to 720 ° C., and a rapid heating of the 550 to 720 ° C. temperature range including the temperature range improves the magnetic flux density. Only the method is proposed.

In addition, these patents are not intended to increase the proportion of grains having a Goth orientation directly in terms of their ideology, but indirectly affect the abnormal grain growth (secondary recrystallization) of Goth orientation during secondary recrystallization annealing after decarburization annealing. There is a limitation in that it is a technique only for attempting to increase the ratio of grains having a {411} orientation.

Even if the above prior arts are synthesized, the magnetic flux is improved by controlling the goose azimuth density on the decarburized plate through the three-stage temperature rising pattern of super rapid temperature rising, rapid temperature rising and general temperature rising by differently controlling the temperature rising rate during the first recrystallization annealing. There is no proposal about the manufacturing method of the grain-oriented electrical steel sheet which can be made.

JP 2003-3213 A (2003.1.08.) JP 2008-1978 A (2008.1.10.) JP 2008-1979 A (2008.1.10.) JP 2008-1980 A (2008.1.10.) JP 2008-1981 A (2008.1.10.) JP 2008-1982 A (2008.1.10.) JP 2008-1983 A (2008.1.10.)

The present invention has been made to solve the above-mentioned problems of the prior art, by introducing a three-stage temperature rising pattern consisting of super-rapid temperature, rapid temperature rise and general temperature rise in the temperature rising process of the first recrystallization annealing (Goss) orientation, in particular It is an object of the present invention to provide a new method for producing a grain-oriented electrical steel sheet to improve the magnetism by increasing the volume fraction of the Exact Goss azimuth grain and improving the crystal orientation density after the second recrystallization.

The oriented electrical steel sheet having excellent magnetic properties of the present invention for solving the above problems by weight, Si: 2.0 ~ 4.0%, C: 0.085% or less, acid-soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less, Pb: 0.01 to 0.5%, N: 0.010% or less, S: 0.010% or less, balance Fe and other unavoidable impurities, β-angle is 1.5 to 2.6 ° as the area-weighted average of the absolute value of the crystal orientation, δ It is characterized by an angle of 5 degrees or less. β angle is the average deviation angle from the {110} <001> ideal orientation around the rolling right angle direction of the secondary recrystallized texture, and δ angle is the average deviation angle between the <001> crystal orientation and the rolling direction in the secondary recrystallized texture. it means.

Method for producing a grain-oriented electrical steel sheet of the present invention for solving the above problems by weight, Si: 2.0 ~ 4.0%, C: 0.085% or less, acid-soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less, Pb: After heating a oriented electrical steel slab containing 0.01 to 0.5%, N: 0.010% or less, S: 0.010% or less, balance Fe and other unavoidable impurities, to a temperature of 1,280 ° C or lower, and hot rolling 1 Cold rolling or two times cold rolling between intermediate annealing is performed, followed by primary recrystallization annealing and secondary recrystallization annealing, wherein the primary recrystallization annealing is performed at an average temperature rise rate of 300 ° C./sec or more. A rapid warming-up process of increasing the temperature to a temperature-raising rate of 100 ° C./sec or more while being lower than the average heating rate of the super fast-heating process after the rapid warming-up process, and the rapid warming-up process after the rapid warming-up process Average temperature rise in Including normal temperature raising process of raising the temperature to a lower average temperature rising rate is characterized in that formed.

The rapid heating step is a temperature between 500 ~ 600 ℃ before the recrystallization, Ts (℃) in a section ranging from room temperature to Ts (℃) at a rapid temperature increase at an average temperature rise rate of 300 ℃ / sec or more, the rapid temperature rising process Is rapidly heated at an average temperature increase rate of 100 to 250 ° C / sec in a section ranging from Ts (° C.) to 700 ° C., and the general temperature rising process is performed at an average temperature of 40 ° C./sec or less in a section ranging from 700 ° C. to a decarburization annealing temperature. It is characterized by heating at a speed.

In addition, the method for manufacturing a grain-oriented electrical steel sheet according to the present invention is characterized in that the number of crystal grains having a size of 35 μm or more is less than 30 when the cross section of the steel sheet is observed after secondary recrystallization after primary recrystallization annealing.

In addition, the method for manufacturing a grain-oriented electrical steel sheet according to the present invention is based on a value measured in a layer that is 1/8 of the thickness from the surface of the steel sheet after the first recrystallization annealing and before the second recrystallization, {110} <001 > The volume fraction of the crystal grains having an orientation within 15 degrees from the ideal orientation is at least 2%, and the volume fraction of the grains having an orientation of 5 degrees below the orientation at least {110} <001> is at least 0.09%. do.

In addition, the method for manufacturing a grain-oriented electrical steel sheet according to the present invention, when based on the value measured for the steel sheet after the second recrystallization annealing, and control the β angle to 1.5 ~ 2.6 ° region as the area weighted average of the absolute value of the crystal orientation , δ angle is controlled to within 5 degrees. The β angle is the mean deviation angle from the orientation of {110} <001> or more around the rolling right angle direction of the secondary recrystallized texture, and the δ angle is the average deviation angle between the <001> crystal orientation and the rolling direction of the secondary recrystallized texture. Means.

According to the present invention, the volume fraction of the Goss orientation, in particular the Exact Goss orientation grains, is applied to the first recrystallized steel sheet by introducing three steps of temperature rising patterns (starting temperature rising speed + rapid temperature rising temperature + general temperature rising) in the temperature rising process of the first recrystallization annealing. By increasing the crystal orientation density after the secondary recrystallization it can be produced a oriented electrical steel sheet of high magnetic flux density low iron loss.

In addition, the introduction of Pb as a slab component in the proper temperature increase process during the first temperature recrystallization annealing process improves the structure of the hot-rolled sheet, and increases the temperature of the secondary recrystallization by increasing the temperature of the secondary recrystallization. By stably forming the recrystallization, it is possible to produce a grain-oriented electrical steel sheet having a very low iron loss and a high magnetic flux density.

Hereinafter, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated in detail.

The present inventors have studied the nucleation of primary recrystallization of oriented electrical steel, in particular the behavior of the first recrystallization of the Goss orientation ({110} <001>) that can grow into nuclei during secondary recrystallization. The nucleation of the goth bearing occurs in the shear band where the strain energy is concentrated during the first recrystallization after the strong deformation. The accumulated strain energy of the shear strain is partially increased in the temperature rising section during the first recrystallization annealing. It was inferred that the recovery would result in a reduction in energy, which would lead to a reduction in the goth nucleation site.

With this in mind, the present inventors have conducted studies and experiments on the elevated temperature conditions during the first recrystallization annealing to minimize the decrease in the accumulated strain energy of the shear deformation by recovery until the recrystallization interval, thereby increasing the nucleation of the Goth bearing. As a result, the first step of the recrystallization annealing, the temperature rising process of the two stages of rapid temperature rise (starting speed + rapid temperature rise) and the general temperature rise of three stages of temperature increase pattern is introduced, especially the rapid temperature rise of the second stage is a specific temperature range It was the first time for the first to find that the fraction of goth bearings, especially the Exact Goss bearings, can be significantly improved by introducing an ultra-rapid heating process that raises the temperature considerably higher than before.

In the present invention, by weight%, Si: 2.0 ~ 4.0%, C: 0.085% or less, acid soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less, Pb: 0.01 ~ 0.5%, N: 0.010% or less, S: A oriented electrical steel slab containing 0.010% or less and consisting of the balance Fe and other inevitably incorporated impurities is heated, hot rolled, and then subjected to two or more cold rollings including one cold rolling or intermediate annealing, and then In the method of manufacturing a grain-oriented electrical steel sheet subjected to the first recrystallization annealing, and then subjected to the second recrystallization annealing, a three-stage temperature rising pattern of super-high temperature rising temperature, rapid temperature rising and general temperature rising is applied during the temperature rising during the first recrystallization annealing. The rapid heating up process is a rapid heating up at an average heating rate of 300 ° C / sec or more in the temperature range from room temperature to Ts (℃), and the rapid heating up process is Ts to 700 ° C. Rapid temperature increase at average temperature increase rate of 100 ~ 250 ℃ / sec And, to characterized in that the temperature increase in a temperature range up to the decarburization annealing temperature from 700 ℃ to an average heating rate of less than 40 ℃ / sec.

The present invention introduces a new three-stage temperature rising pattern (super rapid heating up + rapid heating up + general heating up) that is not existing during the first recrystallization annealing, and the temperature is higher than 300 ℃ / sec from room temperature to the temperature before recrystallization (500 ~ 600 ℃) After the initial temperature increase in speed, in the recrystallization section, the temperature is rapidly increased to 100 ~ 250 ℃ / sec to reduce the energy of the goth bearing in shear deformation, that is, to minimize the recovery and to maximize the nucleation of the goth bearing. This is to allow growth to a good recrystallized grain.

The Ts (° C.) is a temperature that is converted from the rapid ramping up to the rapid ramping up process, and typically, since recrystallization is started in a temperature range of about 550 to 600 ° C., Ts is 500 to 600 ° C., more preferably 550 to 600 It is preferable to set it to the temperature between ° C and below the recrystallization start temperature.

The room temperature described above means the temperature of the steel sheet at the time when the temperature rising process is started in the first recrystallization annealing.

In addition, the present invention increases the fraction of the Exact Goss orientation as a seed that can cause secondary recrystallization by the rapid heating process under the recrystallization temperature during the first recrystallization annealing, thereby inducing nucleation of a highly integrated Goth bearing. As a result, it was completed with new knowledge to maximize the effect of improving magnetism.

In the case of introducing a conventional heating-up pattern that raises the temperature after rapid heating in the first recrystallization annealing process, the volume fraction of the orientation deviated to within 15 ° from the orientation of {110} <001> is only about 1%. On the contrary, in the present invention, in the temperature increase process during the first recrystallization annealing, the temperature is rapidly increased at a temperature rising rate of 300 ° C./sec or more (preferably 400 ° C./sec or more) at a temperature ranging from room temperature to about 550 ° C. or less, and 570. In the section that reaches below 700 ℃, the temperature is raised rapidly at a temperature rising rate of 100 ~ 250 ℃ / sec or more (more preferably 120 ~ 180 ℃ / sec or more), and in the section that reaches decarburization annealing temperature above 700 ℃ When the temperature is elevated at a temperature increase rate of not more than ℃ / sec, it is possible to control the volume fraction of crystal grains having an orientation within 15 ° from the orientation of {110} <001> or more to 2% or more, in particular, {110} <001. It is possible to control the volume fraction of exact Goss grains having an orientation of 5 degrees or less from the ideal orientation to 0.09% or more.

The inventors raised the temperature at the time of primary recrystallization annealing and 5 °, 10 °, 15 at the orientation of {110} <001> or higher in the lower layer by 1/8 of the total thickness from the surface in the sample in which the recrystallization immediately after rapid temperature increase was 95% or more. As a result of measuring the volume fraction of the grains within the range, the total goth bearing is increased at rapid heating, and in particular, from the orientation of {110} <001> or higher in the recrystallization formed by the rapid rising temperature + the rapid rising temperature + the general temperature rising. A maximum increase in the fraction of the Goss orientation within the range, ie the Exact Goss orientation, was observed.

As such, if the rate of increase of the orientation closer to the {110} <001> or higher orientation, that is, the Exact Goss orientation, is higher than the increase rate of the orientation that deviates much from the orientation of the {110} <001> or higher orientation, The magnetic flux density and iron loss are greatly improved because it directly affects the integration density of the goth bearing, which acts as a nucleus and grows as a secondary recrystallized grain.

However, if the temperature increase rate is too fast during rapid temperature increase after the initial rapid temperature increase, the magnetism is rather deteriorated. The reason can be estimated as follows. In other words, when the first stage of recrystallization annealing is applied, two-stage rapid heating (initial rapid heating + rapid heating), the grain size distribution is uniform up to a specific heating rate, but the temperature rising rate is 250 ℃ / sec to Ts (℃) ~ 700 ℃ If it exceeds, the nonuniformity of the crystal grains is increased, so that the fraction with grain size of 35 μm or more is excessively increased, and the magnetism deteriorates due to the growth of grains having poor orientation due to grain growth due to size advantage.

In addition, the goth bearing has high strain energy and is recrystallized first, and then {111} <112> and {411} <148> bearings are recrystallized. As the orientation fraction of {411} <148> and the like increase gradually, such orientation growth of {111} <112> and {411} <148> may reduce the goth orientation during the first recrystallization. It is not necessary to increase the temperature increase rate, and more preferably, it is preferable to heat at a temperature increase rate of 40 ° C./sec or less in a temperature section of 680 ° C. or higher.

Therefore, in the temperature raising process during the primary recrystallization annealing, the temperature is increased from the room temperature to the Ts temperature at an average heating rate of 300 ° C / sec or more, and then rapidly increased to an average heating rate of 100 to 250 ° C / Heating at an average heating rate of 40 DEG C / sec or less in the temperature range of 700 DEG C or higher is effective in increasing the magnetic fraction by raising the fraction of the Goss orientation.

Further, the present inventors measured the area weighted average of angles deviating from {110} < 001 > orientations of the secondary recrystallization grains with respect to the specimen obtained by raising the temperature in the three-stage heating pattern in the first recrystallization annealing. The main features of the measuring device used in the experiment are as follows. Based on the X-ray Laue method and measured with a fixed X-ray CCD detector, the X-ray diffraction occurs in the CCD detector and the specimen, and the tilt angle of the detector is controlled in 1 μm units so that no single crystal is subjected to deformation. The measurement accuracy was improved through the analysis of minimizing the orientation strain. While moving the specimen, measure the respective orientations at each position of the specimen, calculate the absolute value of the deviation angle from the ideal goth orientation at the orientation measured at each position, and then weight the area by weighting the area at all positions to obtain the absolute weight of the absolute value of the deviation angle. The average was measured.

The deviation angles were measured for four angles α, β, γ, and δ, and α angle was determined from the orientation of {110} <001> or more around the ND direction of the rolling plane of the secondary recrystallized texture. The mean deviation angle and β angle are mean deviation angles from the {110} <001> ideal orientation around the rolling right angle direction (TD) of the secondary recrystallized texture, and the γ angle is the rolling direction (RD) of the secondary recrystallized texture. The mean deviation angle from the {110} <001> ideal orientation in the circumference, δ angle, is defined as the average deviation angle between the <001> crystal orientation and the rolling direction RD in the secondary recrystallized texture.

As a result of the measurement, it was confirmed that all the deviation angles become small when the two-stage rapid heating conditions of the super rapid heating and the rapid heating are applied at the time of the first recrystallization. In particular, it was confirmed that the area weighted average β angle exhibits a low value close to 2 °, and the δ angle also decreases rapidly. When the β angle has a low value close to 2 °, the magnetic field width is reduced to minimize the field energy, and the magnetic field is improved by minimizing the disclosure magnetic field, which is harmful to magnetism.

According to the method of manufacturing a grain-oriented electrical steel sheet according to the present invention as described above, when the value measured for the steel sheet after the second recrystallization annealing, the β angle as the area weighted average of the absolute value of the crystal orientation is 1.5 ~ 2.6 ° region More preferably, it is possible to control within 1.5 to 2.4 degrees, and the angle δ can be controlled to within 5 degrees, more preferably within 4.5 degrees.

Hereinafter, the reason for component limitation of the grain-oriented electrical steel slab used in the present invention will be described.

Si increases the resistivity of the grain-oriented electrical steel sheet to lower core loss, that is, iron loss. If the Si content is less than 2.0%, the resistivity decreases and iron loss deteriorates. If the Si content exceeds 4.0%, the steel loss becomes brittle because of excessive brittleness, making cold rolling difficult and unstable secondary recrystallization. Therefore, Si is set at 2.0 to 4.0%.

Al finally becomes an AlN, (Al, Si, Mn) N type nitride and acts as an inhibitor. If the content is less than 0.015%, sufficient effect as an inhibitor cannot be expected. Adversely affects hot rolling workability. Therefore, Al is set at 0.015 to 0.04%.

Mn also has the effect of reducing the iron loss by increasing the specific resistance similar to Si, and the growth of primary recrystallized grains by forming precipitates of (Al, Si, Mn) N by reacting with nitrogen introduced by nitriding with Si. It is an important element to suppress the secondary recrystallization. However, when added in excess of 0.20%, the austenite phase transformation is promoted during hot rolling, thereby reducing the size of primary recrystallized grains, resulting in unstable secondary recrystallization. Therefore, Mn is made into 0.20% or less.

Pb improves the magnetic properties by improving the hot rolled sheet structure, acting as an auxiliary inhibitor, increasing the secondary recrystallization initiation temperature and stably forming the secondary recrystallization. However, if the amount of Pb added is less than 0.01%, the effect of the auxiliary inhibitor is insufficient, and the iron loss improving effect is insufficient. If the Pb content is more than 0.5%, the film deterioration is inevitable and the magnetic properties are also deteriorated. Therefore, it is preferable to contain Pb in 0.01 to 0.5% of range in a steel slab.

C, when added in an appropriate amount, promotes austenite transformation of the steel to refine the hot rolled structure during hot rolling to help form a uniform microstructure. However, if the content is too large, coarse carbides are precipitated and it becomes difficult to remove carbon during decarburization. Therefore, C should be less than 0.085%.

N is an element which reacts with Al and the like to refine the crystal grains. If these elements are properly distributed, as described above, it may be helpful to secure an appropriate primary recrystallized grain size by appropriately finely structured after cold rolling, but when the content is excessive, the primary recrystallized grain is excessively fined and As a result, fine grains are not preferable because the driving force causing grain growth at the time of secondary recrystallization is increased, so that grains of undesirable orientation can be grown. When N is contained in an amount exceeding 0.010%, the secondary recrystallization start temperature is increased to deteriorate the magnetic properties. Therefore, N is set to 0.010% or less. When the treatment of increasing the amount of nitrogen is carried out between cold rolling and secondary recrystallization annealing, it is sufficient that N of the slab is contained in 0.006% or less.

S is preferably an element which has a high solubility temperature and high segregation during hot rolling so as not to be contained as much as possible, but is an unavoidable impurity contained in steelmaking. In addition, since S forms MnS and affects primary recrystallized grain size, the content of S is preferably limited to 0.010% or less, and more preferably 0.006% or less.

In addition to the above components, it can be understood by those skilled in the art that various components included in the grain-oriented electrical steel sheet may be included as alloy components of the electrical steel sheet of the present invention. Commonly known combinations of components and their application are naturally within the scope of the present invention.

Hereinafter, a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties using the grain steel slab having the above composition will be described in more detail.

The grain-oriented electrical steel slab having the above composition is subjected to a reheating process before hot rolling. At this time, it is preferable that the slab is heated at a low temperature of 1,280 ° C. or lower, more preferably 1,200 ° C. or lower to partially solidify the precipitate. If the heating temperature of the slab is increased, the manufacturing cost of the steel sheet is increased, and the melting of the surface of the slab can repair the heating furnace and shorten the life of the heating furnace. In particular, when the slab is heated to a temperature of 1,200 ℃ or less to prevent the coarse growth of the slab columnar structure to prevent cracks in the width direction of the plate in the subsequent hot rolling process to improve the error rate.

After the directional electric steel slab is reheated, hot rolling is performed. By hot rolling, a hot rolled sheet having a thickness of 2.0 to 3.5 mm can be manufactured. When the hot rolled sheet is manufactured, the hot rolled sheet is subjected to annealing as needed, followed by cold rolling. In the case of annealing the hot-rolled steel sheet, the steel sheet can be annealed by heating at a temperature of 1,000 to 1,250 ° C, followed by cracking at a temperature of 850 to 1,000 ° C, followed by cooling. The hot-rolled sheet annealing is performed according to need, and this can be omitted.

Cold rolling may be carried out through a single hot rolling, or may be carried out through two or more rollings with an intermediate annealing in between. Cold rolled steel sheet may be manufactured to a final thickness of 0.1 ~ 0.5mm, more preferably 0.18 ~ 0.35mm.

The cold rolled steel sheet then undergoes primary recrystallization annealing. As described above, the present invention introduces a new super-fast temperature rise in the temperature rising process during the first recrystallization annealing, and the three steps of the temperature rising pattern of the rapid heating step, the rapid temperature rising process and the general temperature rising process in the temperature rising process during the first recrystallization annealing It is characterized by the application.

The average temperature increase rate of 300 ° C./sec or more in the range of temperature rise from 500 ° C. to 600 ° C., preferably from 550 ° C. to 600 ° C. Heating at a rapid rate, and in a rapid temperature increase process, the temperature is rapidly increased at an average temperature increase rate of 100 to 250 ° C / sec in a section from the specific temperature (Ts) to 700 ° C, followed by 40 ° C / By increasing the general temperature at an average temperature increase rate of sec or less, the magnetic properties of the grain-oriented electrical steel sheet can be improved, and the reason is as described above.

The heating method in the temperature rising process during the first recrystallization annealing is not particularly limited, but it is possible to use an induction heating furnace, and it is also possible to increase the temperature in three temperature rising patterns by a plurality of induction heating furnaces. For example, in the first induction furnace, at a rate of temperature increase of 300 ° C./sec or more, preferably 400 ° C./sec or more, the superheat is rapidly increased, and in the second induction furnace, 100 to 250 ° C./sec, more preferably 120 to 120 ° C. Rapidly increase the temperature at a temperature increase rate of 180 ° C / sec, and can be normally raised in a third induction heating furnace at a temperature increase rate of 40 ° C / sec or less.

The steel sheet heated during the first recrystallization annealing undergoes decarburization and annealing. Nitride annealing may be made as a separate process after the decarburization is completed, it is also possible to nitrate at the same time as the decarburization.

In the case of annealing simultaneously with decarburization, it can be carried out in a mixed gas atmosphere of ammonia, hydrogen, and nitrogen. According to the method in which the decarburization is first carried out after the temperature elevating process in the first recrystallization annealing and then the nitriding annealing is performed, precipitates such as Si ₃ N ₄ and (Si, Mn) N are generated in the surface layer portion of the steel sheet. (Al, Si, Mn) N, which is thermally stable in the final annealing process, which is a subsequent process, since the annealing temperature is controlled to 700 to 800 ° C. It is possible to perform a role as an inhibitor by re-precipitation. On the other hand, if decarburization and nitride annealing are performed at the same time, AlN or (Al, Si, Mn) N precipitates are formed at the same time, so it can be used as an inhibitor without transforming the precipitate during final annealing and thus does not require long processing time. Therefore, the method of simultaneously performing decarburization and annealing is more preferable.

However, the method for producing the grain-oriented electrical steel sheet of the present invention is not limited to the simultaneous decarburization and nitriding treatment during the primary recrystallization annealing, and the conventional nitriding annealing method after the decarburization annealing is also an advantageous method Which is effective in producing a directional electrical steel sheet.

The first recrystallized steel sheet is subjected to annealing for a long time after application of the annealing separator to produce a second recrystallization, so that the {110} plane of the steel sheet is parallel to the rolling surface, and the <001> direction is parallel to the rolling direction. 001> Collective tissue is formed. The annealing separator may be preferably one produced based on MgO, but is not particularly limited thereto.

In general, the purpose of final annealing is to remove impurities that impair insulation and impair magnetic properties by forming {110} <001> texture by secondary recrystallization, glass coating by reaction of oxide layer formed by decarburization with MgO. As the final annealing method, the nitride is inhibited by keeping the mixed gas of nitrogen and hydrogen at the temperature rising period before the secondary recrystallization, and the secondary recrystallization is well developed. After completion of the secondary recrystallization, 100% hydrogen It is kept in the atmosphere for a long time to remove impurities.

Hereinafter, the present invention will be described more specifically by way of examples.

By weight, Si: 3.18%, C: 0.056%, Mn: 0.09%, S: 0.0054%, N: 0.0051%, Sol. A slab of a grain-oriented electrical steel sheet containing Al: 0.028% and consisting of remaining Fe and other unavoidable impurities was heated at 1,150 ° C. for 210 minutes, followed by hot rolling to prepare a hot rolled sheet having a thickness of 2.3 mm. The hot rolled sheet was heated to a temperature of 1,100 DEG C or more, held at 910 DEG C for 90 seconds, quenched in water, and then pickled, followed by cold rolling to a thickness of 0.30 mm.

The cold rolled steel sheet was heated at a furnace speed and maintained at 845 ° C for 160 seconds in a mixed atmosphere of 65 ° C with a dew point temperature of 74.5% hydrogen, 24.5% nitrogen and 1% dry ammonia gas. It was. Nitrogen content of the nitrided steel sheet was controlled in the range of 170 ~ 210ppm. At this time, in the temperature range of room temperature ~ 570 ℃ temperature is heated at various heating rate of 30 ℃ / sec, 110 ℃ / sec, 420 ℃ / sec, 560 ℃ / sec, and 30 ℃ / in the temperature range of 570 ℃ ~ 700 ℃ sec, 70 ° C / sec, 110 ° C / sec, 140 ° C / sec, 190 ° C / sec, 270 ° C / sec, 350 ° C / sec and heated at various heating rates, and then from 700 ° C to decarburization annealing temperature of 845 ° C. It heated at the temperature increase rate of 30 degree-C / sec.

This steel sheet was coated with MgO as an annealing separator, and finally annealed in a coiled state. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1,200 ° C. After reaching 1,200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. The magnetic properties measured for each condition are shown in Table 1.

Room temperature ~ 570 ℃
Heating rate
(℃ / sec) 570 ~ 700 ℃
Heating rate
(℃ / sec) 700 ~ 845 ℃
Heating rate
(℃ / sec) Magnetic flux density (B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg)
division 30 30 30 1.88 1.04 Comparison 1 30 140 30 1.92 0.96 Comparative material 2 30 270 30 1.91 0.97 Comparative material 3 30 350 30 1.90 1.00 Comparison 4 420 30 30 1.91 1.01 Comparative material 5 420 70 30 1.91 0.98 Comparative material 6 420 110 30 1.95 0.92 Inventory 1 420 140 30 1.96 0.90 Inventory 2 420 190 30 1.96 0.91 Inventory 3 420 270 30 1.92 0.97 Comparison 7 420 350 30 1.91 0.99 Comparative Material 8 560 30 30 1.91 1.00 Comparative material 9 560 70 30 1.92 0.97 Comparative material 10 560 110 30 1.94 0.92 Invention 4 560 140 30 1.97 0.89 Invention Article 5 560 190 30 1.96 0.91 Inventions 6 560 270 30 1.92 0.98 Comparative material 11 560 350 30 1.91 1.00 Comparative material 12 110 110 30 1.92 0.98 Comparative material 13

As shown in Table 1, the comparative materials 1 to 4 which are generally elevated (normally elevated) at a temperature increase rate of 30 ° C./sec in the range of room temperature to 570 ° C., have a magnetic flux density compared to the case where the initial temperature is elevated rapidly at a temperature increase rate of 560 ° C./sec. Low and high iron loss.

In the first recrystallization, the comparative material 13 heated at a temperature increase rate of 110 ° C./sec in a temperature range of 700 ° C. to 700 ° C. in the first step was rapidly heated (two step temperature rising patterns). ) And iron loss is as high as 0.98 (W / kg).

On the contrary, in the first recrystallization, the invention materials 1 to 6 controlled by the three-stage heating pattern by applying the two-stage rapid heating (rapid heating + rapid heating) conditions as in the present invention have a magnetic flux density of 1.94 to 1.97 (Tesla). High iron loss and low 0.89 ~ 0.91 (W / kg).

By weight, Si: 3.25%, C: 0.048%, Mn: 0.07%, S: 0.005%, N: 0.0045%, Sol. A slab of a grain-oriented electrical steel sheet containing Al: 0.027% and consisting of remaining Fe and other unavoidable impurities is heated at 1,150 ° C. for 210 minutes, and then hot rolled to obtain 1.7 mm, 2.0 mm, 2.3 mm thick hot rolled sheet. Prepared. Each hot rolled sheet was heated to a temperature of 1,100 ℃ or more and then maintained at 910 ℃ for 90 seconds, quenched in water and pickled, and then cold rolled to a thickness of 0.23mm, 0.27mm, 0.30mm.

The cold rolled steel sheet was heated at a furnace speed and maintained at 845 ° C for 160 seconds in a mixed atmosphere of 65 ° C with a dew point temperature of 74.5% hydrogen, 24.5% nitrogen and 1% dry ammonia gas. It was. Nitrogen content of the nitrided steel sheet was controlled in the range of 170 ~ 210ppm. At this time, it is heated at a temperature increase rate of 30 ℃ / sec, 140 ℃ / sec, 160 ℃ / sec, 560 ℃ / sec in the temperature range of room temperature ~ 570 ℃, and 30 ℃ / sec, 140 in the temperature range of 570 ~ 700 ℃ It heated at the temperature increase rate of 350 degreeC / sec. Then, the temperature was raised to a temperature increase rate of 25 ℃ / sec to 700 ℃ decarburization annealing temperature 845 ℃.

This steel sheet was coated with MgO as an annealing separator, and finally annealed in a coiled state. The final annealing was carried out with a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1,200 ° C. After reaching 1,200 ° C, the annealing was maintained at 100% hydrogen atmosphere for at least 10 hours. The magnetic properties measured for each condition are shown in Table 2.

Hot-rolled plate
thickness
[mm] Cold rolled plate
thickness
[mm] Room temperature ~ 570 ℃
Heating rate
(℃ / sec) 570 ~ 700 ℃
Heating rate
(℃ / sec) Magnetic flux density (B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg) division 1.7 0.23 30 30 1.91 0.90 Comparative material 14 1.7 0.23 140 140 1.93 0.86 Comparative material 15 1.7 0.23 560 30 1.92 0.88 Comparative material 16 1.7 0.23 560 140 1.96 0.75 Invention Material 7 1.7 0.23 560 350 1.92 0.88 Comparative material 17 2.0 0.27 30 30 1.91 0.96 Comparative material 18 2.0 0.27 160 140 1.93 0.90 Comparative material 19 2.0 0.27 560 30 1.91 0.95 Comparative material 20 2.0 0.27 560 140 1.96 0.85 Invention Material 8 2.0 0.27 560 350 1.93 0.93 Comparative material 21 2.3 0.30 30 30 1.89 1.03 Comparative material 22 2.3 0.30 140 140 1.93 0.96 Comparative Material 23 2.3 0.30 560 30 1.91 1.00 Comparative Material 24 2.3 0.30 560 140 1.96 0.90 Invention Material 9 2.3 0.30 560 350 1.92 0.97 Comparative Material 25

As shown in Table 2, all of the invention materials 7 to 9 to which the temperature of the cold rolled plate is rapidly increased after the initial rapid temperature rise of the present invention at the time of the first recrystallization at the conditions of 0.23 mm, 0.27 mm, and 0.30 mm, Magnetic is excellent.

On the contrary, the comparative materials 14, 18, and 22 which are normally heated at a temperature increase rate of 30 ° C./sec in the range of room temperature to 570 ° C. are heated at a temperature increase rate of 140 to 160 ° C./sec in the range of room temperature to 700 ° C. The comparative materials 15, 19, and 23 obtained by increasing the temperature (two-step heating pattern) are less magnetic than the inventive materials 7 to 9, which are rapidly heated after the initial rapid heating.

By weight, Si: 3.25%, C: 0.052%, Mn: 0.105%, S: 0.0049%, N: 0.0048%, Sol. A slab of a grain-oriented electrical steel sheet containing Al: 0.028% and consisting of the balance Fe and other unavoidable impurities was heated at 1,150 ° C. for 210 minutes, followed by hot rolling to prepare a hot rolled sheet having a thickness of 2.3 mm. The hot rolled sheet was heated to a temperature of 1,100 DEG C or more, held at 910 DEG C for 90 seconds, quenched in water, and then pickled, followed by cold rolling to a thickness of 0.30 mm.

The cold rolled steel sheet was heated at a furnace speed and maintained at 845 ° C for 160 seconds in a mixed atmosphere of 65 ° C with a dew point temperature of 74.5% hydrogen, 24.5% nitrogen and 1% dry ammonia gas. It was. Nitrogen content of the nitrided steel sheet was controlled in the range of 170 ~ 210ppm.

At this time, the temperature is raised at a temperature increase rate of 30 ℃ / sec, 110 ℃ / sec, 560 ℃ / sec in the room temperature ~ 570 ℃ temperature range, 30 ℃ / sec, 110 ℃ / sec, in the temperature range of 570 ℃ ~ 700 ℃ It was heated at a heating rate of 140 ℃ / sec, 190 ℃ / sec, 350 ℃ / sec, and then heated to a temperature increase rate of 25 ℃ / sec to 700 ℃ decarburization annealing temperature 845 ℃.

This steel sheet was coated with MgO as an annealing separator, and finally annealed in a coiled state. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1,200 ° C. After reaching 1,200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. Magnetic properties measured for each condition are shown in Table 3.

In addition, the grain fraction of the Goss orientation measured on the decarburized plate at 1/8 layer thickness was measured within 5 ° and 15 ° of the deviation from the orientation over {110} <001>. The number of grains having a size of 35 µm or more in the cross section perpendicular to the rolling direction and the grain fraction having an orientation within 15 ° from the {411} <148> azimuth were measured and shown in Table 3. Here, the size of crystal grains was made into the average value of the longest length and the shortest length.

Room temperature ~
570 ℃
Heating
speed
(℃ /
sec)
570 ~
700 ℃
Heating
speed
(℃ /
sec)
Magnetic flux
Density (B ₁₀ ,
Tesla)
Iron loss
(W _17/50 ,
W / kg)
clay pipe
Crystal grain
amount
(35 μm
More than) {411}
<148>
Within 15 °
Bearing fraction
(%) Goss defense fraction


division Within 15 ° Within 5 °
(Exact Goss) defense
Fraction
(%) Comparative material
26 contrast
Growth rate Bearing fraction
(%) Comparative material
26 contrast
Growth rate 30 30 1.88 1.04 40 14.9 1.75 - 0.07 - Comparative Material 26 30 140 1.93 0.96 38 15.2 1.87 6.9 0.08 14.3 Comparative material 27 30 350 1.91 0.99 42 14.5 1.92 9.7 0.08 14.3 Comparative Material 28 560 30 1.91 0.99 35 14.8 1.85 5.7 0.08 14.3 Comparative Material 29 560 140 1.97 0.89 22 14.7 2.18 24.6 0.13 85.7 Inventions 10 560 190 1.95 0.91 27 16.0 2.34 33.7 0.12 71.4 Invention invention 11 560 350 1.92 0.97 42 16.0 2.34 33.7 0.12 71.4 Comparative Material 30 110 110 1.92 0.97 41 15.1 1.91 9.1 0.08 14.3 Comparative Material 31

As shown in Table 3, the comparative material 29 which increased the heating rate only in the temperature range of room temperature ~ 570 ℃ temperature, the comparative material 27, 28, the temperature increase temperature only in the temperature range of 570 ~ 700 ℃ and 570 ~ 700 ℃ All of the comparative materials 31 which increased the temperature increase rate in the temperature range increased the fraction of the Goss orientation somewhat compared to the comparative material 26, which is slower in the first recrystallization, but from the {110} <001> ideal bearing 5 The fractional increase of Exact Goss with an orientation within ° is very low at 14.3%. This can be explained from the fact that there is no significant change in the fraction of the {411} <148> orientation which is the main orientation among the grains of the {411} orientation during the primary recrystallization. In other words, when the temperature increase rate in the section of more than 570 ℃ is 140 ℃ / sec, the fraction of the {411} <148> orientation is slightly higher, the difference is less than 5%, and the {411} The growth of Goth defense is thought to have a modest impact on Exact Goss.

In contrast, inventive materials 10 and 11 belonging to the scope of the present invention had a volume fraction of more than 2% of grains having an orientation within 15 ° from an orientation of {110} <001> or higher, and in particular, directly increased the fraction of the Exact Goss orientation. This effect is very large, which can be seen from the fact that the gap between the invention and the comparative material becomes larger when the tolerance angle, which means the deviation from the goth azimuth ({110} <001>), is within 5 ° than when the angle is within 15 °. have.

That is, as described in the present invention, the invention material 10,11 which is heated up under the conditions of the second stage of rapid temperature increase during the first recrystallization annealing (high temperature rise in the range of 570-700 ° C. after the rapid increase in the temperature range from room temperature to 570 ° C.) is {110} <001. > The volume fraction of the crystal grains having an orientation of 5 ° or less from the ideal orientation is 0.09% or more, which is very different from the Goth orientation fraction of Comparative Materials 26-31. As such, according to the temperature raising condition of the present invention, the fraction of the bearings that are very close to the goth bearing, that is, the deviation (exact goss) that deviates within 5 ° from the {110} <001> or higher bearing, increases dramatically. Given that Goth grains are grown even if there is a very small amount of Goth bearings in the primary recrystallized grains, the Exact Goss bearings will increase dramatically, resulting in an increase in the number of nuclei that can grow into the final bearing, and thus the secondary recrystallization bearings. It can be seen that the magnetism is very close to the orientation is improved.

During the first recrystallization annealing, even if the temperature increase rate is higher than 250 ℃ / sec after the initial temperature increase in the temperature increase process, the goth bearing fraction increases but the effect of improving the magnetic properties is not large. When the cross section of the steel sheet before recrystallization annealing was observed, the number of large grains larger than 35 μm was excessively increased to 30 or more (Comparative Material 25), and the orientation that adversely affects the non-goth magnetism was caused by the size advantage. This is because many of the orientations of the final product version are out of orientation over {110} <001>.

By weight%, Si: 3.13%, C: 0.057%, Mn: 0.095%, S: 0.0045 N: 0.0049%, Sol. A slab of a grain-oriented electrical steel sheet containing Al: 0.029% and consisting of the balance Fe and other unavoidable impurities was heated at 1,150 ° C. for 210 minutes, followed by hot rolling to prepare a hot rolled sheet having a thickness of 2.3 mm. The hot rolled sheet was heated to a temperature of 1,100 DEG C or more, held at 910 DEG C for 90 seconds, quenched in water, and then pickled, followed by cold rolling to a thickness of 0.30 mm.

The cold rolled steel sheet was heated at a furnace speed and maintained at 845 ° C for 160 seconds in a mixed atmosphere of 65 ° C with a dew point temperature of 74.5% hydrogen, 24.5% nitrogen and 1% dry ammonia gas. It was. Nitrogen content of the nitrided steel sheet was controlled in the range of 170 ~ 210ppm. At this time, the temperature is raised at various temperatures of 30 ℃ / sec, 110 ℃ / sec, 560 ℃ / sec in the temperature range of room temperature ~ 570 ℃, 30 ℃ / sec, 110 ℃ / sec in the temperature range of 570 ℃ ~ 700 ℃ , 140 ° C./sec, 190 ° C./sec, and 350 ° C./sec at various heating rates, and then heated at 700 ° C. to a decarburization annealing temperature of 845 ° C. at 25 ° C./sec.

This steel sheet was coated with MgO as an annealing separator, and finally annealed in a coiled state. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1,200 ° C. After reaching 1,200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. Magnetic properties measured for each condition are shown in Table 4.

After the second recrystallization of each specimen, the area weighted average of angles deviated from the {110} <001> ideal orientation of the grains was measured and displayed in Table 4 together. Based on the X-ray Laue method and measured with a fixed X-ray CCD detector, the position is controlled in 1 µm increments to increase the measurement accuracy. Measure each bearing at each location, calculate the absolute value of the deviation angle with the ideal Goss direction from the direction measured at each location, and then calculate the area weighted average of the absolute values of the deviation angle at all locations. Measured.

Room temperature ~ 570 ℃
section
Heating rate
(℃ / sec)
570 ~ 700 ℃ temperature range
Heating rate
(℃ / sec)
Magnetic flux
density
(B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg)
In bearing over {110} <001>
Area weighted average of deviation angles (°) division
alpha β gamma δ 30 30 1.89 1.02 4.99 3.14 6.1 6.57 Comparative Material32 30 140 1.92 0.98 4.17 2.62 5.2 5.24 Comparative Material 33 30 350 1.91 0.99 3.89 2.84 4.52 5.27 Comparative Material 34 560 30 1.89 1.04 3.57 3.40 4.91 5.45 Comparative Material35 560 140 1.96 0.90 3.48 2.2 3.7 4.25 Invention 12 560 190 1.95 0.91 2.77 2.37 3.48 4.01 Invention invention 13 560 350 1.92 0.99 3.56 2.94 3.99 5.05 Comparative Material 36 110 110 1.92 0.98 3.49 2.64 4.03 5.01 Comparative Material 37

As shown in Table 4, Inventive Materials 9 and 10, which are rapidly warmed up after the rapid ramp-up as in the present invention, have an α angle of 3.48 ° or less, β angle of 1.5 to 2.4 °, gamma angle of 3.7 ° or less, and δ angle of 4.5. It was lower than °, especially the area weighted average β and δ angles are drastically lowered, improving the magnetism. This is directly related to the principle of improving magnetism in the present invention, since the magnetic domain width is minimized by the drastically lowered β and δ angles, thereby minimizing the electromagnetic energy of the field and at the same time minimizing Disclosure magnetic domains.

By weight, Si: 3.14%, C: 0.053%, Mn: 0.10%, S: 0.0047%, N: 0.0045%, Sol. A slab of a grain-oriented electrical steel sheet containing Al: 0.028% and Pb and consisting of the remaining Fe and other unavoidable impurities was heated at 1,150 ° C. for 210 minutes, and hot rolled to prepare a 2.0 mm thick hot rolled sheet. At this time, the content of Pb was variously changed as shown in Table 5. The hot rolled sheet was heated to a temperature of 1,100 ℃ or more, maintained at 920 ℃ for 90 seconds, quenched in water and pickled, then cold rolled to a thickness of 0.27mm.

Cold-rolled steel sheet was heated at a furnace speed and maintained at 845 ° C for 130 seconds in a mixed atmosphere of 65 ° C with a dew point temperature of 74.5% hydrogen, 24.5% nitrogen, and 1% dry ammonia gas. It was. Nitrogen content of the nitrided steel sheet was controlled in the range of 170 ~ 210ppm. At this time, it was heated at a temperature increase rate of 25 ℃ / sec, 450 ℃ / sec in the temperature range of room temperature ~ 570 ℃, and heated at a temperature rising rate of 25 ℃ / sec, 160 ℃ / sec in the temperature range of 570 ℃ ~ 700 ℃. Then, it heated at a temperature increase rate of 20 ℃ / sec to 700 ℃ decarburization annealing temperature 845 ℃.

This steel sheet was coated with MgO as an annealing separator, and finally annealed in a coiled state. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1,200 ° C. After reaching 1,200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. Magnetic properties measured for each condition are shown in Table 5.

Temperature rise rate (℃ / sec) Pb content
(weight%) Magnetic flux density
(B ₁₀ , Tesla) Iron loss
(W _17/50 , W / kg)
division Room temperature ~ 570 ℃
section 570 ~ 700 ℃
section 700 ~ 845 ℃
section 25 25 20 0.005 1.89 0.96 Comparative Material 38 450 160 20 0.005 1.91 0.93 Comparative Material 39 450 160 20 0.05 1.95 0.86 Invention Article 14 450 160 20 0.15 1.95 0.85 Invention material 15 450 160 20 0.40 1.93 0.87 Invention material 16 450 160 20 0.75 1.91 0.94 Comparative Material40

As shown in Table 5, the comparative material 38, which is generally elevated (normally elevated) at a temperature increase rate of 25 ° C./sec in the range of room temperature to 570 ° C., has a magnetic flux density higher than that of the invention material which has been rapidly heated at a temperature increase rate of 450 ° C./sec. Low and high iron loss.

As described in the present invention, the first recrystallization is controlled by three steps of temperature rising pattern by applying two-step rapid temperature rising (elementary rapid temperature rising + rapid temperature rising) conditions, and Pb of the invention material 14 to 16 added with 0.01 ~ 0.50% is a comparative material Magnetic properties superior to 39 are secured. Comparative Material 40 contains Pb in excess of 0.50% and is inferior in magnetism.

Claims (9)

By weight%, Si: 2.0 ~ 4.0%, C: 0.085% or less (excluding 0), acid soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less (excluding 0), Pb: 0.01 ~ 0.5%, N : 0.010% or less (excluding 0), S: 0.010% or less (excluding 0), remainder Fe and other unavoidable impurities, and β-angle is 1.5 to 2.6 as the area-weighted average of the absolute value of the crystal orientation. A grain-oriented electrical steel sheet having excellent magnetic properties having a δ angle of 5 ° or less.
However, β angle is the mean deviation angle from the {110} <001> ideal orientation around the rolling right angle direction of the secondary recrystallized texture, and δ angle is the average deviation between the <001> crystal orientation and the rolling direction in the secondary recrystallized texture. Sir. By weight%, Si: 2.0 ~ 4.0%, C: 0.085% or less (excluding 0), acid soluble Al: 0.015 ~ 0.04%, Mn: 0.20% or less (excluding 0), Pb: 0.01 ~ 0.5%, N : Slab containing 0.010% or less (excluding 0), S: 0.010% or less (excluding 0), remainder Fe and other unavoidable impurities, heated, hot rolled, and then cold rolled or Two or more cold rollings with annealing in between, followed by primary recrystallization annealing, and then secondary recrystallization annealing,
The first recrystallization annealing is carried out at an initial temperature increase rate of more than 300 ℃ / sec and the average temperature rising rate of 100 ℃ / sec or more while lowering than the average temperature rising rate in the beginners A method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties including a rapid heating process and a general heating process in which the temperature is raised at an average temperature increase rate lower than the average temperature increase rate in the rapid temperature increase process after the rapid temperature increase process. The method according to claim 2,
When Ts (° C.) is a temperature between 500 ° C. and 600 ° C. before recrystallization is started, the rapid temperature increase process is performed at an average temperature increase rate of 300 ° C./sec or more in a section from room temperature to Ts (° C.), and the rapid temperature increase process is performed. Is the temperature increase rate of 100 ~ 250 ℃ / sec in the section from Ts (℃) to 700 ℃, the general temperature increase process is the average temperature rising rate of 40 ℃ / sec or less in the section from 700 ℃ to decarburization annealing temperature Method for producing a grain-oriented electrical steel sheet excellent in magnetic properties to increase the temperature. The method according to claim 2,
When Ts (° C.) is a temperature between 500 ° C. and 600 ° C. before recrystallization is started, the rapid temperature increase process is performed at an average temperature increase rate of 400 ° C./sec or more in a section from room temperature to Ts (° C.), and the rapid temperature increase process is performed. The temperature is raised to an average temperature increase rate of 120 ~ 180 ℃ / sec in the section from Ts (℃) to 700 ℃, the general temperature increase process is the average temperature increase rate of 40 ℃ / sec or less in the section from 700 ℃ to decarburization annealing temperature Method for producing a grain-oriented electrical steel sheet excellent in magnetic properties to increase the temperature. The method according to any one of claims 2 to 4,
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties such that the number of crystal grains having a size of 35 µm or more is less than 30 when the cross section of the steel sheet after the primary recrystallization annealing and before the secondary recrystallization is observed. The method according to any one of claims 2 to 4,
Crystal grain having an orientation within 15 ° from the orientation of {110} <001> or more, based on the value measured in the layer which becomes 1/8 of the thickness from the surface of the steel sheet after the first recrystallization annealing and before the second recrystallization Method for producing a grain-oriented electrical steel sheet having excellent magnetic properties so that the volume fraction of 2% or more. The method according to any one of claims 2 to 4,
Crystal grain having an orientation of 5 ° or less from the orientation of {110} <001> or more, based on the value measured in the layer that becomes 1/8 of the thickness from the surface of the steel sheet after the primary recrystallization annealing and before the secondary recrystallization Method for producing a grain-oriented electrical steel sheet having excellent magnetic properties so that the volume fraction of the product is 0.09% or more. The method according to any one of claims 2 to 4,
Based on the measured value of the steel sheet after the second recrystallization annealing, the magnetic field is controlled by the area-weighted average of the absolute value of the crystal orientation to control the β angle to 1.5 to 2.6 degrees and the δ angle to within 5 degrees. Method for producing this excellent grain-oriented electrical steel sheet.
However, β angle is the mean deviation angle from the {110} <001> ideal orientation around the rolling right angle direction of the secondary recrystallized texture, and δ angle is the average deviation between the <001> crystal orientation and the rolling direction in the secondary recrystallized texture. Sir. The method according to any one of claims 2 to 4,
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties after annealing and hot roll annealing before cold rolling.