KR101536465B1 - Soft silicon steel and manufacturing method thereof - Google Patents

Abstract

More particularly, the present invention relates to a high-silicon steel sheet having a silicon content of more than 4%, but having a ductility characteristic and being capable of being produced as a steel sheet having a high silicon content by only rolling To a soft high silicon steel sheet.
The soft silicon steel sheet according to the present invention comprises Si: Al: 5 to 7%, Cr: 1 to 20%, Si: 4 to 7% 20%. ≪ / RTI >

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-

More particularly, the present invention relates to a high-silicon steel sheet having a silicon content of more than 4%, but having a ductility characteristic and being capable of being produced as a steel sheet having a high silicon content by only rolling To a soft high silicon steel sheet.

High silicon steel sheets are steel sheets used for iron core materials such as transformers, electric motors, generators and other electronic devices, and are usually called electric steel sheets. Typical properties required for the high silicon steel sheet include high magnetic flux density and low iron loss.

The magnetic flux density represents the number of magnetic fluxes per unit area, and as the magnetic flux density is higher under the same use conditions, the amount of iron cores is smaller, so that the size of the electric device can be reduced. The iron loss refers to the energy loss that occurs when the iron core is placed in a magnetic field that changes in time, and is composed of an eddy current loss and a hysteresis loss. Among them, the eddy current loss is caused by the eddy current generated when the magnetic core induces a magnetic field.

Silicon is an effective element to reduce this eddy current loss and is added as a key element to the electrical steel sheet. In particular, when silicon is added up to 6.5%, the magnetostriction, which causes noise, can be reduced to almost zero and the permeability can be maximized. In addition, the high silicon content has the advantage that iron loss can be reduced and utilization efficiency can be maximized when used at a high frequency (for example, 50 Hz or more, preferably 400 Hz or 1000 Hz, etc.). Therefore, high silicon steel sheets can be advantageously used for high value-added electric equipment such as inverters and reactors, generator induction heating devices for gas turbines, reactors of uninterruptible power supply units, etc., considering their properties.

For this reason, it is advantageous to add silicon as much as possible in view of the characteristics of the steel sheet. However, when silicon is added in a large amount, workability is deteriorated. In general, when silicon is added in an amount of 3.5 wt% or more, cold rolling becomes very difficult by a conventional method.

Japanese Unexamined Patent Publication No. 56-3625 proposes a method of rapidly cooling and solidifying a melt by ejecting a melt to the rotating body to overcome this problem. In addition, as a method therefor, Japanese Unexamined Patent Publication (Kokai) No. Hei 5-171281 discloses a method in which high-grade steel is put in the inside and a steel material in which the periphery is clad with low silicon steel is rolled. However, these techniques have not yet been practically used industrially.

As another method, in Korean Patent Registration No. 10-0374292, a high-silicon steel block made of a powder made of powder instead of a high silicon steel sheet is formed by powder metallurgy and used as a substitute for high silicon steel sheet. In this document, pure iron powder cores, high-low-strength steel powder cores, and sandstorm powder cores are used in combination, but due to the limitations of the powders, soft magnetic properties are lower than those of high-silicon steel sheets.

As a technique currently used as a mass production technique of a steel sheet, a CVD (Chemical Vapor Deposition) method as described in Japanese Patent Publication No. 38-26263, Japanese Patent Publication No. 45-21181, Japanese Patent Application Laid-Open No. 62-227078 This is a method of preparing a steel sheet containing about 3% of silicon, and then impregnating and diffusing the silicon by using SiCl ₄ on the steel sheet. The above method is a technique for lowering the silicon content of the steel sheet and processing the steel sheet while maintaining workability, and then increasing the silicon content to a desired level by diffusion. However, such a method requires the use of toxic SiCl ₄ , and it takes much time to perform diffusion annealing, which results in a problem that the productivity is low.

In addition, Japanese Patent Application Laid-Open No. 1-299702 has attempted to produce a thin steel sheet by hot rolling the high silicon steel sheet without hot rolling at a temperature of, for example, 350 ° C or higher. However, since not only cold rolling but also hot rolling may have a problem of processability, raising the rolling temperature is not enough to secure the workability of the steel sheet. That is, it is necessary to reheat the slab in order to secure the hot rolling temperature when the slab is manufactured by the continuous casting in the usual manner. In this case, cracks occur due to the temperature difference between the slab, the surface portion and the center portion, It is liable to be ruptured even when hot rolling is performed. Fig. 1 is a photograph showing a shape in which a plate is broken when a high silicon steel plate containing 6.5% of silicon is heated in an argon gas atmosphere at 1100 DEG C for 1 hour 30 minutes and then hot-rolled. As can be seen from the drawing, the high silicon steel sheet has a large risk of plate breakage not only in cold rolling but also in hot rolling. Therefore, it is difficult to control the workability of the steel sheet simply by adjusting the rolling temperature.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art described above. According to one aspect of the present invention, there is provided a method of manufacturing an electrical steel sheet having a relatively low silicon content of 4% or less, There is provided a soft high silicon steel sheet which can be produced by the following method.

According to still another aspect of the present invention, a soft high silicon steel sheet having a high magnetic flux density and a low iron loss can be provided.

The object of the present invention is not limited to the above description. Those skilled in the art will appreciate that the present invention may be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings.

The soft silicon steel sheet of the present invention may have a composition containing Si in an amount of more than 4% to 7%, Cr in an amount of 1 to 20% and B in an amount of 0.01 to 0.05% by weight.

The high silicon steel sheet may further contain 0.1 to 3% by weight of Total Al, and Si + Total Al, which is the sum of Si and Total Al, may range from more than 4.1% to 7%.

The soft silicon steel sheet according to still another aspect of the present invention may have a composition including 5 to 7% of Si + Total Al, 1 to 20% of Cr, and 0.01 to 0.05% of B in terms of% by weight.

At this time, these steel sheets may further contain at least one selected from the group consisting of Mo: not more than 0.1%, Ni: not more than 0.01%, P: not more than 0.05% and Cu, not more than 0.01% May be limited to C: not more than 0.05% and N: not more than 0.05%.

According to still another aspect of the present invention, there is provided a method of manufacturing a soft high strength steel comprising the steps of: preparing a steel material having a composition including Si: more than 4% to 7% and Cr: 1 to 20% by weight; Hot rolling the steel material at a temperature of 800 캜 or more to obtain a hot rolled steel sheet; And cold rolling the hot rolled sheet at a temperature of 150 to 300 ° C.

At this time, the steel may have a composition further containing 0.1 to 3% by weight of Total Al.

At this time, the steel material may contain impurities such that the content of C and N is limited to C: not more than 0.05% and N: not more than 0.05%.

The steel material may further include one or more selected from the group consisting of Mo: 0.1% or less, Ni: 0.01% or less, P: 0.05% or less, Cu, 0.01%

At this time, the steel may be manufactured by continuous casting or strip casting.

In addition, the hot-rolled sheet has an inner structure with a grain size of 150 to 250 占 퐉 and excellent workability.

The step of obtaining the hot rolled sheet may further include a step of cooling the hot rolled sheet at a cooling rate of not less than 30 DEG C / sec in a temperature range of 800 to 100 DEG C after the hot rolling, in order to further improve the workability by reducing the rule- .

As an alternative, the method may further include a step of heat-treating the hot-rolled sheet at a temperature of 800 to 1200 ° C. and cooling the temperature zone at a temperature of 800 to 100 ° C. at a cooling rate of 30 ° C./second or more It is possible.

As described above, the present invention can provide a soft silicon steel sheet having a silicon (Si) content exceeding 4%, which can be produced even by a conventional process of producing an electric steel sheet, by appropriately controlling the composition thereof.

Further, the present invention can prevent the deterioration of workability in the production of steel sheet by controlling the proportion of the steel sheet inside the steel sheet, so that a high silicon steel sheet can be manufactured without the same method as the steel ingot treatment.

Fig. 1 is a photograph showing a phenomenon in which a plate breaks when hot rolling a high-grade steel.
Fig. 2 is a state diagram of the Fe-Si binary system to explain the generation of a regular phase inducing brittleness of steel in high silicon steel.
3 is a graph showing the results of observing the uniform elongation at 400 ° C and 200 ° C according to the amount of Cr added to 5% Si - 1% Al steel sheet. The graphs are the results of 400 ° C on the left side and 200 ° C on the right side.
FIG. 4 shows the results of observation of grain size and texture after hot rolling of a high silicon steel sheet without addition of chromium. And,
5 shows the results of observation of crystal grain size and texture after hot rolling of the high silicon steel sheet to which chromium was added.

Hereinafter, the present invention will be described in detail.

The present invention is directed to a high silicon steel sheet having a silicon (Si) content of 4% or more based on the weight of the silicon (Si) basis (hereinafter, the content of the additive element is based on weight unless otherwise specified). As described above, when the content of silicon exceeds 4%, the magnetic flux density and iron loss of the steel sheet are remarkably improved, and the steel is very suitable for use as a high frequency iron core material. However, if the silicon content is excessively high, the workability is markedly deteriorated, so the upper limit of the content is set at 7%. Therefore, the high silicon steel sheet of the present invention means a steel sheet containing more than 4% to 7% of silicon.

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted various studies to solve the above-described problems of the present invention. As a result, it has been found that when the elements to be added and the composition thereof are controlled in an appropriate range, the high silicon steel sheet is softened, .

There have been some reports on the use of nickel (Ni), manganese (Mn), etc. as the third elements that can be added to the steel sheet.

For example, C. A. Clark et al., "Effect of Nickel on the Properties of Grain-Oriented Silicon-Iron Alloys", Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 2, February 1966, pages 345-351 The effect of nickel addition was reported. Narita et al. Reported the effect of addition of manganese in IEEE Transactions, 1979, "Effect of ordering on magnetic properties of 6.5-percent silicon-iron alloy". However, since the additional elements described in these documents can not improve the workability of the steel sheet to such an extent that the steel sheet can be produced by cold rolling, there is still a problem that it is difficult to manufacture the steel sheet by cold rolling.

The inventors of the present invention have found that it is effective to add chromium (Cr) in an amount of 1 to 20% by weight as an additive element of a steel sheet, leading to the present invention. When chromium is added in an amount of 1% by weight or more, it is very useful for solving the problems of the present invention for the following reasons. This is because not only the chromium can prevent the formation of the regular phase in the steel sheet, but also the generation of the origin of the crack occurrence of the steel sheet can be prevented.

That is, referring to the Fe-Si binary phase diagram of FIG. 2, when silicon is added in an amount of more than 4% as in the present invention, B2 and DO ₃ phases called regular phases are formed in the steel sheet. They cause brittleness in the steel sheet, which is very disadvantageous in workability. Is expected to increase the brittleness of the steel sheet due to one or more of the following two reasons compared to the irregular phase (A2 phase as shown in Fig. 2).

The rule lattice dislocations moving within the rule phase are difficult to cross slip, and consequently, stress concentration and grain boundary destruction are easy to occur in the grain boundaries. (2) Since the grain boundary structure of the regular alloy is unique, the energy of the crack propagating along the grain boundary is low It is easy to break down the grain boundary. Therefore, in order to alleviate the brittleness of the high silicon steel sheet, it is preferable to suppress the formation of the regular phase. For this purpose, it is advantageous to add 1 wt% or more of chromium. When 1% by weight or more of chromium is added, the proportion of the irregular phase A2 phase increases at room temperature, thereby reducing the brittleness of the steel sheet. The addition of chromium is advantageous for the improvement of the magnetic properties because the regular phase interferes with not only the dislocation but also the migration of the magnetic domain.

However, it can be seen that when chromium is added, the uniform elongation is greatly increased. That is, FIG. 3 shows the change of the uniform elongation according to the change of the chromium content of the steel sheet containing 5% silicon and 1% aluminum. As shown in the drawing, when the chromium content is 0%, the uniform elongation ) Was about 10% to 15% at 400 ° C and about 10% at 200 ° C, but it shows that the uniform elongation increases with increasing chromium content in any case.

In addition, the high-quenched steel to which chromium has been added can control the grain size after hot rolling to be small, and is excellent in hot rolling and cold rolling (or hot rolling). 4 shows the microstructure after hot rolling (finish of hot rolling at 1100 占 폚, hot-rolled sheet thickness of 2.5 mm) of a high silicon steel sheet containing 5.1% of silicon and 1% of aluminum without chromium, The microstructure after hot rolling of steel containing 8% of chromium added to the same silicon and aluminum content as that of the steel sheet of Fig. The slab thickness, hot rolling temperature and final steel sheet thickness were the same in both cases. As can be seen from the figure, the crystal grains of the chromium-doped steel of FIG. 5 were much finer controlled than the chromium-free steel of FIG. Therefore, in the present invention, the addition of 1% or more of chromium is very important for securing the processability of the high silicon steel sheet.

In addition, when the slabs cast for hot rolling are reheated, a low melting point oxide called Fe ₂ SiO ₄ is formed at the reheating temperature. These oxides erode the surface and the side of the slab, It is easy to form. However, when chromium is added in the range limited by the present invention, it is possible to suppress the formation of wave lite and significantly reduce the origin of cracks. Therefore, compared with the case where chromium is not added, a plate having a thickness of, for example, 1 to 3 mm can be manufactured by cracking or hot rolling without breaking the plate. When the strip casting apparatus and the hot rolling apparatus are directly connected, Can be produced while maintaining high productivity.

In addition, as the {100} < 001 > formation, which is called a cube texture, is formed in a high silicon steel sheet, the magnetic properties are improved. When chromium is added, the fraction of the cube texture is increased .

However, when the content of chromium is excessive, since a large number of edge cracks occur during hot rolling, the rolling property may be deteriorated. Therefore, the chromium is preferably added in an amount of 20% or less, desirable.

In addition, when boron is added in an amount of 0.01 to 0.05%, preferably 0.01 to 0.03% in order to further improve the rolling property, the workability of the material is further secured during cold rolling at a low temperature, can do. That is, in order to secure the rolling property, it is advantageous to add B but add the appropriate amount. When controlling the Si content and the Cr content as in the present invention, the optimum content of B is 0.01 to 0.05%, preferably 0.01 To 0.03%. This is also true when the Si + Al content is controlled in an appropriate range as described below.

Accordingly, the soft high silicon steel sheet according to one aspect of the present invention may have a composition including more than 4% to 7% of Si, 1 to 20% of Cr and 0.01 to 0.05% of B in a weight ratio.

According to another advantageous aspect of the present invention, the soft silicon steel sheet may further comprise 0.1 to 3% of aluminum (Total Al). When the total amount of aluminum (Total Al) is 0.1% or more, it is effective to improve the rolling property. However, when it is added in an excess amount, the rolling property deteriorates rather than 3%.

When aluminum is added together with silicon, it is possible to share the magnetic property improving effect such as the improvement of the magnetic flux density and the reduction of the iron loss due to the addition of silicon, so that the addition amount of silicon can be reduced. For this reason, according to one aspect of the present invention, the sum (Si + Total Al) of the addition amount of silicon and aluminum may be 4% or more, and may be 4.1% or more according to another aspect, Or more. However, if the Si + total Al exceeds 7%, the rolling property may decrease, so the upper limit of the Si + total Al is set at 7%.

This effect can be further exerted when chromium is added in an amount of 1 to 20%, preferably 1 to 16%, as described above. Therefore, the soft silicon steel sheet according to another aspect of the present invention is characterized in that the sum of silicon and aluminum contents (Si + Total Al) is controlled to 5 to 7%, Cr is 1 to 20%, B is 0.01 to 0.05% Is added.

In order to improve the magnetic properties of the steel sheet, the steel sheet may further include one or more of Mo: 0.1% or less, Ni: 0.01% or less, P: 0.05% or less, Cu, 0.01% When these elements are added, the magnetic properties, brittleness and the like of the steel sheet can be improved. In particular, hydrogen embrittlement may occur in the case of a high silicon electrical steel sheet, but the addition of Mo in an amount of 0.1% or less has an advantage that hydrogen embrittlement can be effectively suppressed.

The remainder of the high silicon steel of the present invention is an impurity that is inevitably incorporated in Fe and other manufacturing processes. Further, the present invention does not specifically exclude that the steel sheet additionally contains the additional elements contained in the steel sheet used for the iron core material, as long as it does not contradict the present invention of the present invention.

Examples of the impurities which can be included in the steel sheet of the present invention include not more than 0.05% of C and not more than 0.05% of N, As the content of these elements increases, the brittleness of the steel becomes worse and the rolling property may be deteriorated. Therefore, it is preferable to allow addition of up to 0.05% only.

In the high silicon steel sheet of the present invention, the ratio of the cube assembly texture may be about 13 to 25% on an area basis. This can be achieved by high silicon and chromium addition and the like. In view of the fact that the cube assembly ratio of the conventional steel sheet is 12% or less, the high silicon steel sheet of the present invention exhibits excellent magnetic properties .

The advantageous soft high silicon steel sheet of the present invention described above can be produced by a process including hot rolling and cold rolling or hot rolling and low temperature warm rolling. As long as it is manufactured by such a process, the detailed conditions are not particularly limited. Those skilled in the art will appreciate that the high silicon content of the high silicon steel sheet of the present invention There will be no difficulty in obtaining steel plates.

However, one advantageous manufacturing condition derived by the inventors of the present invention will be described as follows.

Slab hot rolling temperature: 800 ℃ or higher

Hot rolling does not only play a role of first adjusting the thickness of the steel sheet but also has an effect of finely improving the structure of the steel sheet, so that subsequent cold rolling and hot rolling can be facilitated. At this time, the slab hot rolling temperature is desirably set to 800 DEG C or higher. If the rolling is performed at a temperature lower than 800 캜, the brittleness of the steel sheet becomes strong and the fracture may occur. The upper limit of the hot rolling temperature is not particularly limited as long as it is in the ordinary hot rolling temperature range of the high silicon steel sheet. However, in case of a non-limiting example, the hot rolling temperature can be set to less than 1200 ° C for uniform slab heating and surface quality control have.

The hot rolling described above may be performed immediately without reheating before the slab is cooled after casting or may be performed by reheating the cooled slab. However, in order to prevent generation of wave lite due to reheating, It is more preferable to perform the slab immediately. When the slab is reheated, it is not necessarily limited to this, but it is preferable to reheat the slab when the surface temperature of the cast steel after coagulation does not decrease to less than 700 캜. In one preferred embodiment, the slab is not manufactured by casting but may be hot rolled by a hot rolling process which is directly followed by casting of the thin steel sheet through strip casting. Strip casting is a technique of casting molten steel into a thin steel plate by injecting molten steel into a pair of rolls rotating in opposite directions (twin-roll method) or one rotating roll surface (single-roll method) It will be apparent to those skilled in the art that there is no particular difficulty in carrying out the invention. However, even in this case, the hot rolling temperature is preferably limited to 800 DEG C or higher.

The thickness of the steel sheet (hot rolled sheet) obtained by the hot rolling is preferably 3 mm or less. If the thickness of the hot-rolled sheet is too large, the amount of reduction of the steel sheet during subsequent cold rolling or warm rolling may become large, which may cause problems such as sheet breakage. Even if the thickness of the hot-rolled sheet is thin, there is no particular problem in implementing the present invention, so that the lower limit of the hot-rolled sheet thickness is not specifically defined. However, when the thickness of the hot-rolled sheet is excessively reduced, the rolling load becomes large, which may cause problems such as breakage or cracking of the hot-rolled sheet. Therefore, the lower limit of the thickness of the hot-rolled sheet may be set at 2 mm. Particularly, when the steel sheet is manufactured by strip casting, the lower limit of the steel sheet thickness can be reduced to 1.0 mm. It should be noted, however, that when the hot rolling technique is improved, the lower limit of the hot rolled sheet thickness can be further reduced, and therefore, the hot rolled sheet thickness is not necessarily limited to the above-mentioned range.

The hot-rolled steel sheet produced by the above-described process has a grain size of 150 to 250 탆 and has excellent workability as compared with a normal hot-rolled steel sheet, so that it can be rolled with good workability in the subsequent cold rolling. Considering that a conventional high silicon steel hot-rolled steel sheet has a grain size of 500 mu m or more, it can be seen that the hot-rolled steel sheet of the present invention has a very fine grain size.

Cold rolling: 150 to 300 ° C

Since the steel sheet composition of the present invention can improve the workability of the steel sheet compared to the prior art, the steel sheet can be produced at a rolling temperature after hot rolling of 300 占 폚 or lower, preferably 250 占 폚 or lower. However, if the rolling temperature is too low, the steel sheet may be broken. Therefore, the lower limit of the temperature is set at 150 ° C.

The steel sheet produced by the cold rolling may have a thickness of 0.1-0.5 mm depending on the properties of the final product desired.

Accordingly, the method for manufacturing a soft silicon steel sheet of the present invention comprises the steps of: preparing a slab of the above composition; Hot rolling the slab at a temperature of 800 ° C or higher to obtain a hot rolled sheet; And cold-rolling the hot-rolled sheet to obtain a steel sheet having a final thickness.

In this case, the cold rolling may be performed immediately after the hot rolling, but it is more preferable to perform the cold rolling after the heat treatment in order to develop the aggregate structure favorable to the magnetic properties, to control the grain size, . Therefore, according to one advantageous aspect of the present invention, a heat treatment process may further be included between the hot rolling and the cold rolling.

Heat treatment temperature: 800 ~ 1200 ℃

Since the hot rolled steel sheet has a large number of regularly arranged inside thereof, if cold rolling or low temperature warm rolling is carried out, plate breakage may occur and the rolling property may be deteriorated. Thus, in one preferred embodiment of the present invention, a heat treatment may be performed at a temperature of 800 DEG C or higher before cold rolling or warm rolling. The heat treatment temperature of 800 ° C or higher is intended to remove the regular phase existing in the steel sheet due to the phase transformation. However, if the heat treatment temperature is too high, the energy cost may increase and the scale may increase on the surface of the steel sheet. Therefore, the upper limit of the temperature is set at 1200 ° C. A more preferable heat treatment temperature is 900 to 1200 占 폚.

Atmosphere during heat treatment

When scale is generated on the surface of the steel sheet during the heat treatment, the rolling property may be deteriorated. Therefore, it is preferable to perform the heat treatment in a non-oxidizing atmosphere where scales are not generated as much as possible. Therefore, as the atmospheric gas during the heat treatment, an inert gas composed of nitrogen, argon or a mixed gas of nitrogen and argon, or a reducing gas containing less than 35 vol% (%) of hydrogen gas may be used.

Cooling after heat treatment: The temperature range including the range from 800 ° C to 100 ° C is cooled at a cooling rate of 30 ° C / sec or more

Although the regular phase is removed inside the high-temperature steel sheet heated to the above-mentioned temperature, it is necessary to cool the steel sheet at a cooling rate of 30 ° C / sec or more in order to suppress the formation of the regular phase, have. The higher the cooling rate is, the better, and the upper limit of the cooling rate is not particularly defined. For example, the steel sheet may be quenched and cooled. However, when cooling is initiated at a temperature lower than 800 ° C or when the temperature is stopped at a temperature higher than 100 ° C, there is a possibility that a large amount of heat may be formed at an undesirable level, so that the cooling section includes a section from 800 ° C to 100 ° C desirable. However, this cooling condition is intended to further improve the workability (rolling property) of the steel sheet, and is not necessarily indispensable in all the composition ranges of the steel sheet corresponding to the composition range of the present invention. As a result of the significant improvement in processability due to the addition, rolling in a subsequent cold rolling process may be possible even if cooled at a relatively low cooling rate such as air cooling.

As described above, the heat treatment and the cooling process are included in order to suppress the generation of a rule before cold rolling or warm rolling. If the above-mentioned heat treatment process is not carried out, the hot rolling may be terminated and the process of quenching at a cooling rate of 30 DEG C / sec or more at a temperature of 800 DEG C or more and a temperature of 100 DEG C or less may be performed instead. The upper limit of the cooling rate is not particularly limited as long as it is after the heat treatment. However, in order to effectively control the structure of the steel sheet, heat treatment is more advantageous.

After the steel sheet is cold-rolled or warm-rolled, it can be finally annealed in a usual manner. The final annealing is preferably carried out in a temperature range of 900 to 1200 캜. That is, in order to increase the ratio of the cube assembly structure, it is preferable that the final annealing is performed at a temperature of 900 ° C or higher. However, if the temperature exceeds 1200 ° C, the effect is saturated and the energy cost increases. Therefore, the upper limit of the final annealing temperature can be set at 1200 ° C.

It should be noted that the manufacturing conditions not specifically described in this specification can be applied in accordance with the ordinary manufacturing conditions, and that a commonly used process may be newly added.

Hereinafter, the present invention will be described in detail by way of examples. It should be noted, however, that the following embodiments are merely illustrative and illustrative of the present invention, and are not intended to limit the scope of the present invention. And the scope of the present invention is determined by the matters described in the claims and the matters reasonably deduced therefrom.

(Example)

Example 1

An electric steel sheet cast was cast in the composition shown in Table 1 below. The major components of the impurities not listed in the table were controlled to 0.005% and 0.0033% as C and N, respectively. Thereafter, the cast steel was heated at 1100 DEG C for 1 hour, then hot rolled at a temperature of 1050 DEG C, and finished at 850 DEG C. [ The billet having a thickness of 30 mm was rolled into a hot-rolled sheet of 2.5 mm by hot rolling. The hot-rolled silicon steel sheet was heat-treated at 1000 캜 for 5 minutes in an atmosphere of 20% by volume of hydrogen and 80% by volume of nitrogen, and then cooled to room temperature to obtain a heat-treated hot-rolled sheet. Thereafter, the hot rolled plate was pickled to remove the surface oxide layer. The hot rolled sheet was subjected to cold rolling (warm rolling) at a temperature of 400 DEG C and 150 DEG C, respectively, to a final thickness of 0.2 mm.

In each case, the rolling properties at the time of rolling were evaluated and are shown together in Table 1. Ii) the case where the final thickness is reached but a crack of more than 1cm in length is found on the rolled plate is 'bad'; and iii) the case where a crack of less than 1 cm , And iv) the case where no cracks were found in the final rolled plate were classified as 'excellent'.

Component (% by weight) Mechanical properties Si Al Cr B Rolling property [400 ° C] Rolling property [150 ° C] Comparative Example 1 3.8 0.1 1.2 0.011 Great Great Comparative Example 2 7.2 0.1 1.3 0.012 Fracture Fracture Comparative Example 3 5 0.9 0.8 0.011 Bad Fracture Comparative Example 4 5.1 0.9 21.2 0.013 Bad Fracture Comparative Example 5 4.1 3.3 1.1 0.011 Fracture Fracture Comparative Example 6 4.5 2 1.2 0.008 usually Bad Comparative Example 7 4.5 1.9 1.2 0.052 Bad Fracture Inventory 1 5.1 0.001 1.1 0.011 Great usually Inventory 2 5.2 0.003 19.7 0.012 Great Great Inventory 3 4 2.9 1.1 0.013 Great Great Honorable 4 4.5 1.9 1.1 0.011 Great usually Inventory 5 4.5 2.1 1.2 0.048 Great Great Inventory 6 5 0.9 1.2 0.014 Great Great Honorable 7 5.2 One 19.8 0.011 Great Great

As shown in Table 1, when the Si content was excessively added as in Comparative Example 2, plate fracture occurred at both 400 ° C and 150 ° C rolling though Cr and B were added at a certain level or more. Further, in Comparative Example 3, the Cr content was below the range specified in the present invention. As a result of failing to sufficiently prevent the generation of the rule, the rolling property was also unsatisfactory. In Comparative Example 4, the Cr content was excessive, which also showed poor rolling resistance. Comparative Example 5 was a case where Al was added in an amount exceeding the range specified in the present invention, which also caused plate breakage. Comparative Example 6 was a case where the content of B was insufficient and the rolling property at 400 ° C was normal, but it was found to be poor at 150 ° C. Therefore, it was confirmed that B is also an element necessary for securing the rolling property. However, in the case of excess of B (Comparative Example 7), the rolling property deteriorated and it was judged to be defective even at 400 ° C.

However, the inventive examples satisfying the conditions of the present invention exhibited excellent rolling properties at 400 ° C and exhibited ordinary rolling properties even at a low temperature of 150 ° C, which is one example of the present invention Crack size was less than 0.2 cm). In particular, Inventive Examples 1 and 2 show cases in which Al is not substantially added.

Example 2

In the same manner as in Example 1, the steel sheet obtained by rolling to a thickness of 0.2 mm was subjected to annealing at 1000 ° C for 10 minutes in a dry atmosphere of 20% by volume of hydrogen, 80% by volume of nitrogen and a dew point of -10 ° C The magnetic properties were measured and the results are shown in Table 2 below. In addition, fractions of <100> {001} texture (so-called cube structure) of the hot rolled plate were compared and analyzed in Table 2 using EBSD equipment of scanning electron microscope (SEM). The cube structure ratio of the hot rolled plate (hot rolled plate) greatly affects the magnetic properties of the final plate. As the fraction of the <100> {001} texture is increased, the magnetic properties can be improved.

Component (% by weight) Magnetic property Hot-rolled plate
<100> {001} Tissue volume fraction [%] Si Al Cr B W10 / 400
[W / kg] W10 / 1000
[W / kg] Comparative Example 8 3.8 0.02 1.2 0.011 14.3 65 11.3 Honors 8 4.1 0.9 4.1 0.012 6.5 23.2 15.7 Proposition 9 5.1 One 8.2 0.011 5.86 21.4 19.7 Inventory 10 6.7 0.01 16.3 0.013 5.65 19.7 20.1

As described above, it can be seen that Comparative Example 8 in which the Si content is low has a very high iron loss as compared with the case of the present invention. The higher the core loss, the greater the energy loss, which is not suitable as an electrical steel sheet. On the other hand, all of the inventive examples satisfying the composition conditions of the present invention exhibited excellent iron loss values. Particularly, the inventive example according to the condition of the present invention shows a low iron loss value even at a high frequency of 1000 Hz, and thus it is confirmed that it is suitable for use as a high frequency iron core material.

Example 3

A silicon steel alloy containing Si: 5%, Al: 1%, Cr: 12%, C: 0.002% and N: 0.003% by weight was formed into a thickness of 2.0 mm using a vertical twin roll strip caster Respectively. A hot rolled steel sheet having a thickness of 2.0 mm was hot-rolled to a thickness of 1.0 mm using a hot rolling mill connected to the strip casting. The hot rolling start temperature in hot rolling was 1000 占 폚 and the ending temperature was 850 占 폚. The hot-rolled high silicon steel sheet was heated at 1000 캜 for 5 minutes in an atmosphere of 20% by volume of hydrogen and 80% by volume of nitrogen, and then cooled. Two kinds of cooling speeds of 800 ° C to 100 ° C were used for cooling at 100 ° C / second and 10 ° C / second for cooling. The cooled steel sheet was pickled with hydrochloric acid solution to remove the oxide layer on the surface, and then warm-rolled at a temperature of 150 ° C. Both of them were able to be rolled to a thickness of 0.1 mm irrespective of the cooling rate, but the rollability was better when the cooling rate was 100 ° C / sec. This is a result of substantially improving the rolling property by suppressing the regular phase by adding Cr and suppressing the occurrence of the rule in the cooling process as much as possible.

Claims (14)

Si: from more than 4% to less than 7%, Cr: from 1 to 20%, and B: from 0.01 to 0.05%.
The soft silicon steel sheet according to claim 1, further comprising 0.1 to 3% by weight of Total Al.
The soft silicon steel sheet according to claim 2, wherein Si + Total Al satisfies the range of more than 4.1% to 7%.
The steel sheet according to any one of claims 1 to 3, further comprising at least one selected from the group consisting of Mo: not more than 0.1%, Ni: not more than 0.01%, P: not more than 0.05%, Cu, not more than 0.01% High silicon steel sheet.
The soft silicon carbide according to any one of claims 1 to 3, wherein the content of C and N is limited to C: not more than 0.05% and N: not more than 0.05%.
Preparing a steel material having a composition including Si: more than 4% to 7% and Cr: 1 to 20% by weight;
Hot rolling the steel material at a temperature of 800 캜 or more to obtain a hot rolled steel sheet; And
Cold rolling the hot rolled sheet at a temperature of 150 to 300 캜;
Silicon steel sheet.
The method of manufacturing a soft silicon steel plate according to claim 6, wherein the steel further comprises 0.1 to 3% by weight of Total Al.
The production method of a high-soft silicon steel sheet according to claim 7, wherein Si + Total Al satisfies a range of more than 4.1% to 7%.
9. The method for producing a soft silicon steel plate according to any one of claims 6 to 8, wherein the steel contains C and N in an amount of C: not more than 0.05% and N: not more than 0.05%.
9. The steel material according to any one of claims 6 to 8, wherein the steel material further contains one or more selected from the group consisting of Mo: 0.1% or less, Ni: 0.01% or less, P: 0.05% Silicon steel sheet.
9. The method according to any one of claims 6 to 8, wherein the steel material is produced by continuous casting or strip casting.
9. The method for manufacturing a soft silicon steel plate according to any one of claims 6 to 8, wherein a grain size of the internal structure of the hot-rolled sheet is 150 to 250 mu m.
The method as claimed in any one of claims 6 to 8, wherein the step of obtaining the hot rolled sheet comprises cooling the hot rolled sheet at a cooling rate of at least 30 ° C / A method of manufacturing a steel sheet.
The method as claimed in any one of claims 6 to 8, wherein after the step of obtaining the hot-rolled sheet, the hot-rolled sheet is heat-treated at a temperature of 800 to 1200 占 폚 and then cooled at a cooling rate of 30 占 폚 / And then cooling the steel sheet to a predetermined temperature.

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