KR960003900B1 - Process for the production of oriented electrical steel sheet having excellent magnetic properties - Google Patents

Abstract

The manufacturing method improves magnetic properties of silicon steel by controlling coiling temperatures and phosphor content. The manufacturing method comprises controlling phosphor content of 0.03˜0.2 wt.% in silicon steel slab consisting of 0.030-0.100 wt.%, 2.50-4.00 wt% Si, 0.030-0.150 wt.% Mn, 0.010-0.050 wt.% S, 0.010-0.050 wt.% sol Al, 0.0030-0.0120 wt.% N, 0.030-0.300 wt.% Cu, P and balance Fe, and coiling the hot rolled plate at 150˜550≰C after hot rolling the slab to 2.0˜2.3mm thickness.

Description

Manufacturing method of oriented electrical steel sheet with excellent magnetic properties

1 is a graph showing the change of primary recrystallized texture according to the amount of P added and the coiling temperature.

2 is a graph showing the change of grain boundary segregation amount of P according to the addition amount of P and the coiling temperature.

The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties used for iron cores of electrical equipment such as transformers and generators, and more particularly, has excellent magnetic properties with low iron loss and high magnetic flux density, which can be applied to a thin article. It relates to a method for producing a grain-oriented electrical steel sheet.

In general, a grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction of the steel sheet, and is required to have a property of easy excitation and low iron loss. The excitation characteristic is evaluated as the magnitude of the magnetic flux density (B ₁₀ ) induced in the iron core by the magnetic field of constant intensity (1000A / m), and the iron loss characteristic is the predetermined magnetic flux density (1.7 Tesla) by the alternating frequency of the constant frequency (50Hz). ) Is estimated according to some of the energy loss (W _17/50 ) wasted inferiorly within the iron core. The use of materials with high magnetic flux density enables the manufacture of small, high-performance electrical devices, and the fewer the iron losses, the greater the loss of electrical energy.

In the grain-oriented electrical steel sheet, in order to improve the magnetic flux density and the iron loss characteristics, it is required that the direction of magnetization of the silicon steel having the BCC structure coincide with the rolling direction of the steel sheet, that is, the improvement of the orientation. .

A grain-oriented electrical steel sheet composed of grains in the (110) [001] orientation by the Miller index is industrially produced when the final cold annealing of a cold rolled steel sheet through decarbonization annealing at a high temperature of about 1000 ° C. or higher. It is manufactured using the so-called secondary recrystallization phenomenon. Secondary recrystallization in this grain-oriented electrical steel sheet indicates the degree of directional improvement, in which primary recrystallized grains (referred to as nuclei of secondary recrystallization) of a relatively large grain size (110) [001] range have a different orientation. It is a phenomenon that grows rapidly while encroaching on recrystallized grains.

As a result, in order to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties, it is important to completely generate such secondary recrystallization and at the same time make the secondary recrystallization grains excellent. For this purpose, grain growth inhibitors such as MnS, AIN, Cu ₂ S or grain boundaries such as Sn, P, Sb, etc. are used to prevent normal growth of primary recrystallized grains other than the (110) [001] orientation until secondary recrystallization occurs completely. It is necessary to add segregation elements and to form a primary recrystallized texture in which secondary recrystallization nuclei of different orientations can be easily encroached on secondary recrystallization nuclei in the (110) [001] orientation. Here, the primary recrystallized texture refers to the texture of the specimen after decarbonization annealing during the manufacturing process, which will vary depending on the manufacturing process conditions, such as steel components, heat treatment temperature and rolling rate. In oriented electrical steel sheets having high magnetic flux density using precipitates such as MnS and AIN as inhibitors, the primary recrystallized texture is strengthened (111) [112] with a strong (100) [011] orientation for improving the direction line. It is known to form weak ones.

On the other hand, the desire to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties by improving the iron loss characteristics by improving the reflectivity as well as the thickness of the steel sheet has been progressing smoothly in recent years in terms of energy saving. This is because the vortex loss, which accounts for a large part of the iron loss, is proportional to the square of the plate thickness, so that the thinner the plate thickness, the lower the iron loss. However, when the thickness of the plate becomes thin, not only the secondary recrystallization becomes unstable, but also because the orientation tends to deteriorate even when the secondary recrystallization occurs, the lower limit of the thickness of the grain-oriented electrical steel sheet which can be stably manufactured by the conventional method is 0.30 mm. It is only about. Therefore, in order to produce a high magnetic flux density oriented electrical steel sheet having excellent magnetic properties by stably producing secondary recrystallization having excellent directionality in the case of thinner thickness, the above-mentioned primary recrystallization grain growth suppression force is more than that of the normal thickness. In addition to strengthening, it is known to form an optimal primary recrystallized texture.

The inventors of the present invention, in Patent Publication 93-4849, proposed a method for producing a thin magnetic flux density oriented electrical steel sheet having excellent magnetic properties by addition of an element contributing to strengthening the primary recrystallization grain restraint. In other words, by adding Cu and P to reinforce the primary recrystallization grain growth inhibition by precipitates and grain boundary segregation, the secondary recrystallization is stably developed and the direction of the secondary recrystallization is improved to improve the magnetic properties 0.15-0.27 A method of manufacturing a thin magnetic flux-high density oriented electrical steel sheet having a thickness of mm is proposed.

However, the inventors of the present invention have repeatedly performed various process change experiments using the inventive steel slab, and thus, by controlling the coiling conditions after hot rolling, an optimal primary recrystallized texture is formed. It was confirmed that a high magnetic flux density oriented electrical steel sheet having excellent magnetic properties could be manufactured.

Therefore, the present invention has been proposed to further improve the above-described conventional invention, and is a method of forming an optimal primary recrystallized texture by precisely controlling the winding temperature and the content of P. It is an object of the present invention to provide a method for manufacturing a fast density oriented electrical steel sheet.

Hereinafter, the present invention will be described.

In the present invention, C: 0.030-0.100%, Si: 2.50-4.00%, Mn: 0.030-0.150%, S: 0.010-0.050%, acid soluble Al: 0.010-0.050%, N: 0.0030-0.0120%, Cu: 0.030-0.300%, The steel sheet thickness is 0.15- by the hot-rolling, precipitation annealing, pickling, cold rolling, decarbonization, application of annealing separator, and hot annealing of the silicon steel slab composed of P and the balance Fe. In the method for producing a 0.27mm grain oriented electrical steel sheet, P in the silicon steel slab is controlled to be 0.030-0.200% by weight, hot-rolled to a thickness of 2.0-2.3mm, and then hot-rolled coiling temperature 150-550 ℃ The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by winding up.

The reason for numerical limitation of the components of the silicon steel slab of the present invention is described below.

When C is less than 0.030% by weight (hereinafter referred to as "%"), it is not good because grains grow coarsely in the slab heating process and the development of secondary recrystallization becomes unstable at the final high temperature annealing. It takes a long time, which is undesirable.

If the Si is less than 2.50%, excellent iron loss characteristics are not obtained, and if it exceeds 4.00%, the cold rolling property is deteriorated, which is not preferable.

The Mn and S are elements necessary for the formation of MnS precipitates, and Mn does not have an appropriate MnS distribution for suppressing grain growth if it is out of the component range of 0.030-0.150%, and in case of S, the final high temperature exceeds 0.050%. In the annealing, sufficient dehydration does not occur, leading to deterioration of the magnetic properties. If it is less than 0.010%, it is not preferable to obtain a sufficient amount of emulsion-type precipitates. The acid-soluble Al and N are elements necessary for the formation of AlN precipitates, and when the acid-soluble Al is less than 0.010%, the direction of the secondary recrystallization is deteriorated, and the magnetic flux density is lowered. It is not good because it becomes, and the more preferable component range of acid-soluble Al is 0.020-0.030%. On the other hand, the N is less than 0.0030% AlN is insufficient in the amount, if it exceeds 0.0120% is not preferable because a defect in the form of a bulster (Blister) occurs in the product.

Cu is an element necessary for the formation of Cu ₂ S precipitates, and when less than 0.030%, Cu ₂ S precipitates are not obtained in an appropriate amount, and when manufactured to a thickness thinner than the normal thickness, it is difficult to stably cause secondary recrystallization, 0.300% If it exceeds, secondary recrystallization occurs, but its orientation is deteriorated, which is not preferable.

P is a grain boundary segregation element, which is basically required for improving grain growth inhibition, and also serves to change the strength of the (111) [112] orientation in the primary recrystallization aggregate structure. However, this role depends on the amount of P added and the coiling temperature, which will be described with reference to FIGS. 1 and 2.

1 is weight%, 0.015 in molten steel containing C: 0.045%, Si: 3.16%, Mn: 0.075%, S: 0.024%, acid soluble Al: 0.026%, N: 0.0090%, Cu: 0.082% By using two kinds of slab steels containing% and 0.087% of P, a oriented electrical steel sheet having a thickness of 0.23 mm was manufactured by a conventional method, and the example showing the change of the primary recrystallized texture according to the winding temperature, In the case of steel (a) having an addition amount of 0.087%, the (111) surface coefficient of the decarbonized annealing plate increases as the winding temperature decreases, whereas the amount of P added in the steel (b) is low. In this case, the change in the (111) plane intensity hardly appears. In general, the (111) surface strength is proportional to the strength of the (111) [112] direction in electrical steel sheets. Therefore, in the case of a oriented electrical steel sheet having a certain amount of P added, when the winding temperature is decreased, the (111) [112] orientation becomes It can be seen that strong preferred primary recrystallization texture can be formed. On the other hand, the strengths of the (110) [001] and (100) [011] orientations show little change with the amount of P added and the coiling temperature.

In addition, FIG. 2 is an example showing the change in the grain size segregation of P in the hot rolled plate according to the winding temperature in the specimen of FIG. 1, wherein the grain size segregation is erroneous with respect to the grain boundary fracture site after breaking the specimen in vacuum. Mean value quantified using an Auger electron microscope.

As shown in FIG. 2, in the case of the steel (a) to which a certain amount of P is added, the segregation amount of P decreases as the coiling temperature decreases, which is considered to be because the cooling rate increases as the coiling temperature is lowered. . However, in the case of steel (b) having a small amount of P added, the grain size segregation of P hardly changes with the winding temperature. Since the decrease in the amount of grain boundary segregation means an increase in the amount of intragranular presence, it can be seen that the amount of P present in the mouth increases as the winding temperature decreases.

As can be seen in the examples of FIGS. 1 and 2 above, when a certain amount of P is added, the increase in the (111) [112] orientation with the decrease in the winding temperature is related to the increase in the amount of P present in the mouth. Although this has not been identified at present, it is thought that the mobility of grain boundary changes according to the change of the amount of P present in the mouth, and thus, the texture of the aggregate changes. On the other hand, when a small amount of P is added at a normal level, if the amount of P present in the mouth hardly changes according to the coiling temperature, it can be seen that the texture of the tissue changes accordingly.

However, when P is less than 0.03%, winding is performed at a coiling temperature of 150-550 ° C. because the strength change of the (111) [112] orientation according to the coiling temperature, that is, the improvement strength of the primary recrystallized texture is weak. Even if the excellent magnetic properties are not obtained, if it exceeds 0.200% cold rolling is deteriorated is not preferable.

The silicon steel slab of the present invention, which is composed as described above and composed of other unavoidable trace impurities and the balance Fe, is a material suitable for the subsequent process of a conventional high magnetic flux density oriented electrical steel sheet using a conventional dissolution method, an ingot method, a playing method, and the like. It can be prepared as.

Hereinafter, the manufacturing process of a high magnetic flux density oriented electrical steel sheet using the silicon steel comprised as mentioned above as a raw material is demonstrated.

The silicon steel slabs constructed in accordance with the invention are rolled to a thickness of usually 2.0-2.3 mm after heating, followed by a conventional hot rolling process, and then wound. The reason why the thickness of the hot rolled sheet is limited as described above is that the thickness in this range is effective for obtaining an appropriate final cold reduction ratio. Furthermore, less than 2.0 mm is not preferable because the winding work of the hot rolled coil tip becomes difficult, and more than 2.3 mm is not preferable because a larger capacity cooling device is required to cool the winding temperature of the present invention.

At this time, the preferred range of the coiling temperature is 150-550 ° C. The reason for this is that when the coiling temperature exceeds 550 ° C, not only the formation of the preferred primary recrystallized joint structure is insufficient, but also precipitates such as Cu ₂ S and AlN are coarsened. This results in non-uniform distribution, leading to a decrease in magnetic properties. On the other hand, if it is less than 150 ° C., the magnetic properties are not deteriorated, but the brittleness of the hot rolled sheet increases, which makes winding work difficult.

The hot rolled plate is quenched after precipitation annealing at 950-1200 ° C. for 30 seconds to 30 minutes to control the precipitation state of AlN.

The precipitated annealing plate is pickled and then subjected to two or more cold rollings including one cold rolling or intermediate annealing. The final cold rolling rate (in the case of one cold rolling) is 65-95%, Preferably it is necessary to cold roll at a reduction ratio of 80-92%. Here, since the reduction ratio in cases other than final rolling is not important, it does not separately prescribe. In the present invention, when the aging treatment is performed at 100-300 ° C for 30 seconds to 30 minutes between multiple passes during cold rolling, the magnetic properties are improved. In addition, the thickness of the cold rolled sheet is preferably in the range of 0.15-0.35mm, the reason is that when the steel sheet thickness is less than 0.15mm the secondary recrystallization becomes unstable, the magnetic properties deteriorate, if it exceeds 0.35mm This is because secondary recrystallization develops stably but excellent magnetic properties are not obtained. However, the more preferable range of cold rolled sheet thickness to obtain excellent iron loss characteristics is 0.15-0.27 mm.

The cold rolled steel sheet as described above is decarbonized and annealed and recrystallized in a conventional manner. In the case of the present invention, the decarbonization annealing is preferably performed in a mixed atmosphere of wet hydrogen or wet hydrogen and nitrogen at 800-900 ° C. for 30 seconds to 1 minute. After decarbonization annealing is applied to the surface of the steel sheet to prevent bonding between the plates during final high temperature annealing and to create a glass coating. Although the composition of the annealing separator is not particularly defined, it is preferable to have MgO, TiO ₂ , Na ₂ B ₄ O _n as a main component. The steel sheet is subsequently subjected to final hot annealing at 1200 ° C. for at least 5 hours for secondary recrystallization and purification. In this case, as the annealing atmosphere, a dry pure hydrogen or a mixed atmosphere of hydrogen and nitrogen is used. After the annealing, an inorganic glass film is formed on the surface of the steel sheet, but it is preferable to apply a tension coating for the purpose of improving the insulation and improving the iron loss due to the fine grain size.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

By weight%, P was added to silicon steel containing C: 0.073%, Si: 3.12%, Mn: 0.070%, S: 0.025%, acid solubility A: 0.024%, N: 0.0071%, Gu: 0.11%. ) 0.025%, (B) 0.050%, (C) 0.100% of the added silicon steel slabs were hot rolled to a thickness of 2.3 mm by a conventional method, and then they were respectively 50 in the range of 150-650 ° C. Winding was performed by varying the temperature at ℃ intervals.

Thereafter, after annealing at 1100 ° C. for 3 minutes, slow cooling to 950 ° C., followed by precipitation annealing with 100 ° C. boiling water, followed by pickling the precipitation annealing plate to obtain a cold rolled steel sheet having a final plate thickness of 0.23 mm by cold rolling. At this time, the cold rolling pass was subjected to aging treatment for about 200 ° C. for 5 minutes, and then tantalum annealing was performed in a mixed atmosphere of 25% hydrogen and 75% nitrogen having a dew point of 50 ° C. at 840 ° C. for about 90 seconds. Subsequently, MgO was coated with annealing separators containing TiO ₂ and Na ₂ B ₄ O ₇ , followed by final high temperature annealing at 1200 ° C. for 20 hours, followed by tension based on aluminum phosphate, chromic anhydride, colloidal silica, etc. The coating solution was coated and then subjected to planarization annealing at 800 ° C. for 1 minute and 30 seconds, and the magnetic properties thereof were measured. The results are shown in Table 1 below.

TABLE 1

As shown in Table 1, the influence of the winding temperature on the magnetic properties is different depending on the amount of P added. That is, in the case of steel (A) having an amount of P added less than 0.03%, the magnetic properties hardly change with the winding temperature at 150-600 ° C., whereas the steels (B) and steel (C) of the present invention are 150 Excellent magnetic properties are obtained at -550 ° C, and it can be seen that the steel (C) having a larger amount of P added improves the magnetic properties by decreasing the coiling temperature than the steel (B). This means that within the addition range of P of the present invention, the more the amount of P added, the better the magnetic properties can be obtained by winding at the lowest possible temperature.

As described above, the present invention provides a low iron loss high magnetic flux density anticorrosion steel sheet having excellent magnetic properties that can be applied to a product by forming an optimal primary recrystallized texture by appropriately controlling the amount of P added and the coiling temperature. It works.

Claims (1)

By weight, C: 0.030-0.100%, Si: 2.50-4.00%, Mn: 0.030-0.150%, S: 0.010-0.050%, acid soluble Al: 0.010-0.050%, N: 0.0030-0.0120%, Cu: The steel sheet thickness is 0.15-0.27mm by the hot rolling, precipitation annealing, pickling, cold rolling, decarbon annealing, annealing separation coating, and high temperature annealing of the silicon steel slab composed of 0.030-0.300%, P and the balance Fe. In the method for producing a oriented electrical steel sheet, P in the silicon steel slab is controlled to be 0.030-0.200% by weight, hot-rolled to a thickness of 2.0-2.3mm, and then wound at a coiling temperature of 150-550 ℃ Method for producing a grain-oriented electrical steel sheet having excellent magnetic properties.