KR101190826B1 - The method for producing high silicon steels with a clean surface - Google Patents

Abstract

The present invention comprises the steps of preparing at least one silicon injection source selected from the group consisting of SiO ₂ , SiC and Si in powder form and a steel sheet having a silicon content of 0 to 3%; Inserting a shield between the silicon injection source and the steel sheet to form a laminated structure; And a method for producing a high silicon steel sheet having a good surface state consisting of the heat treatment of the laminated structure in a hydrogen atmosphere is provided.
According to the present invention, in manufacturing a high silicon steel sheet by impregnating Si on a low silicon steel sheet, a ceramic fabric or a ceramic paper is inserted between the silicon injection source and the steel sheet as a shield, so that the surface roughness of the steel sheet can be maintained well after immersion. It is possible to provide a method for producing a silicon steel sheet.

Description

The method for producing high silicon steels with a clean surface

The present invention relates to a method for producing a high silicon steel sheet having a good surface state, and more particularly, at least one silicon injection source selected from the group consisting of SiO ₂ , SiC and Si in powder form, and silicon content of 0 to 3 Preparing a steel sheet which is%; Inserting a shield between the silicon injection source and the steel sheet to form a laminated structure; And it relates to a method for producing a high silicon steel sheet having a good surface state consisting of the heat treatment of the laminated structure in a hydrogen atmosphere.

Conventionally, a silicon steel sheet having a silicon content of less than 3% has been mainly used as an iron core of a transformer or a motor using 60 Hz as a power frequency. On the other hand, as silicon content increases, eddy current loss decreases due to increased electrical resistance, and maximum permeability is the highest at silicon content of 6.5%, and noise is minimized because magnetic deformation becomes zero. There is an advantage to this. Nevertheless, the reason why the 3% silicon steel sheet has been mainly used for the transformer as described above is that the workability of the silicon steel sheet is significantly worsened at 4% or more of silicon, which makes cold rolling difficult, and therefore, mass production is difficult, thereby increasing manufacturing costs. to be. For this reason, a method of manufacturing a silicon steel sheet having a silicon content of less than 3% first and then adding silicon therein has been generally used as a method for producing a high silicon steel sheet having a silicon content of 4% or more. On the other hand, in order to produce a high silicon steel sheet as described above, the operation of diffusing silicon on the surface of the steel sheet to create a corrosion-resistant coating is called 'siliconizing' (浸 硅).

In connection with such a deposition method, the Physical Vapor Deposition (PVD) method (Korean Patent Publication No. 2002-0050012), the Chemical Vapor Deposition (CVD) method using SiCl ₄ gas (Japanese Laid-Open Patent Publication No. 1993-049745), Fe-Si powder And the like have been proposed. However, the PVD method has a disadvantage in that a deposition rate is slow by depositing Si on both surfaces of a low silicon steel and diffusion heat treatment, and it is difficult to continuously process a large capacity because it is performed in a vacuum chamber. On the other hand, CVD method is a method of depositing Si on the surface by using SiCl4 gas. In the continuous process, the acupuncture treatment unit, iron chloride collection zone, unreacted, and the low silicon steel heating zone, the needle zone, the diffusion zone, and the cooling zone are arranged in order from the inlet side. The system consists of an exhaust gas treatment unit equipped with a silicon chloride recovery tank, a vaporization zone, and a gas heater, and uses highly reactive silicon tetrachloride to use a reaction chamber for controlling oxygen and water vapor in a gas atmosphere. Due to this complexity, manufacturing costs increased. In addition, the method by Fe-Si powder is Fe-Si powder, colloidal silica, aluminum oxide mixture (Korean Patent Publication No. 2004-0046398, 2004-0041773, 2004-41772, 2004-0046401), or Fe-Si powder MgO powder mixture (Korean Patent Publication No. 2004-0041774) is used, which is a solid-solid phase in which the diffusion of Si from the Fe-Si powder to the low silicon steel sheet occurs only when the Fe-Si powder and the solid steel sheet are in contact with each other. Because of the reaction, the reaction time was long and the shape of the surface of the material was deteriorated.

In order to make up for the disadvantages of the prior art, a method of manufacturing a high silicon steel sheet using a combination of SiO ₂ powder and metal fluoride powder (Korean Patent Application No. 10-2008-0095142) has recently been filed. In this method, a solid powder that is easy to handle is used, and at the same time, a silicon source can be supplied in the form of a gas containing silicon, hydrogen, and fluorine elements, so that the device can be easily and quickly settled. However, this method also has a disadvantage in that when the powder and the steel sheet directly contact, the powder adheres to the steel sheet, thereby deteriorating the surface state, resulting in iron loss, and thus deteriorating magnetic properties.

Under such technical background, the present invention has been completed as a result of intensive efforts to invent a method for producing a high silicon steel sheet having a good surface state when the high silicon steel sheet is immersed in a low silicon steel sheet.

After all, an object of the present invention is to provide a method for producing a high silicon steel sheet having a good surface state.

According to an aspect of the present invention, there is provided a method for preparing a steel sheet having at least one silicon infusion source selected from the group consisting of SiO ₂ , SiC, and Si in a powder form, and a silicon content of 0 to 3%; Inserting a shield between the silicon injection source and the steel sheet to form a laminated structure; And a method for producing a high silicon steel sheet having a good surface state consisting of the heat treatment of the laminated structure in a hydrogen atmosphere is provided.

According to a preferred embodiment of the present invention, the shield may be a ceramic fabric or ceramic paper.

According to a preferred embodiment of the invention, the shield may be a ceramic fabric or ceramic paper comprising SiO ₂ .

According to one aspect of the invention, the step of preparing a steel sheet and shield having a silicon content of 0 to 3%; Wrapping both sides of the steel sheet with the shield to form a laminated structure; Applying metal fluoride in powder form to the shield in a spray or slurry form; And a method for producing a high silicon steel sheet having a good surface state consisting of the heat treatment of the laminated structure in a hydrogen atmosphere is provided.

According to a preferred embodiment of the invention, the shield may be a ceramic fabric or ceramic paper comprising SiO ₂ .

According to a preferred embodiment of the present invention, the metal fluoride may be any one selected from the group consisting of MgF ₂ , AlF ₃ and NaF.

According to a preferred embodiment of the present invention, the heat treatment of the laminated structure in a hydrogen atmosphere may be performed in a hydrogen atmosphere having a purity of 97% or more.

According to an aspect of the present invention, there is provided a high silicon steel sheet having a good surface state manufactured by any one of the above method of manufacturing a high silicon steel sheet.

According to the present invention, in manufacturing a high silicon steel sheet by impregnating Si on a low silicon steel sheet, a ceramic fabric or a ceramic paper is inserted between the silicon injection source and the steel sheet as a shield, so that the surface roughness of the steel sheet can be maintained well after immersion. It is possible to provide a method for producing a silicon steel sheet.

1 shows a state in which a silicon injection source 1 is laminated with a shield 3 between steel sheets 2.
2 is a surface roughness measurement result of the state of the steel sheet according to the manufacturing process of high silicon steel sheet under the conditions of SiO ₂ + Si + MgF ₂ system, SiO ₂ + Si + MgF ₂ system (without shield) and SiO ₂ + AlF ₃ system A graph representing.
FIG. 3 is a graph showing the result of increasing the silicon content as compared with the case without NaF as a result of placing the NaF powder as a metal fluoride near the specimen.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in the present specification, the term 'siliconizing' refers to an operation of diffusing silicon on the surface of a steel sheet to produce a high silicon steel sheet to form a corrosion resistant film. In the present invention, the acupuncture process was performed by a heat treatment and a furnace cooling process.

Method for producing a high silicon steel sheet according to an aspect of the present invention comprises the steps of preparing a steel sheet having a silicon content of 0 to 3% and at least one silicon injection source selected from the group consisting of SiO ₂ , SiC and Si in powder form ; Inserting a shield between the silicon injection source and the steel sheet to form a laminated structure; And heat treating the laminated structure in a hydrogen atmosphere. The steel sheet having a silicon content of 0 to 3% means a steel sheet containing no silicon or a low silicon steel sheet having a low silicon content, and also includes a case where the silicon content is 0, and the numerical limitation is related to an optional component. It contains zeros.

As described above, the present invention has devised a method of isolating each other by inserting a medium having a low reactivity with the steel sheet between the steel sheet and the powder mixture in order to solve the problems of the prior art. Such media are referred to herein as shields. In general, ceramics have a weak reactivity with iron, so they were used as shields. Ceramics or ceramic papers are made of oxides in the form of fibers or whiskers, woven into paper or paper. They have a space through which gas can pass and have a weak reactivity with steel sheets. Therefore, such a ceramic fabric or ceramic paper serves as a smooth passage in the immersion method using a gas phase movement including Si, and at the same time, isolates the silicon injection source and the steel sheet to maintain a good steel sheet state. Do it. The medium serving as a shield can be used as long as the medium is not ceramic cloth or paper, but has a space through which gas can pass, and is weak in reactivity with a steel sheet or a silicon injection source.

One aspect of the present invention is a method of heat-treating the silicon injection source (1) with a shield (shield) 3 between the low silicon steel sheet (2) as shown in FIG. Depending on the situation, in addition to the repetitive lamination of FIG. 1, the shield and the silicon injection source may be placed on one low silicon steel sheet and both surfaces or cross sections, and a method of invading the continuous process in the form of a single plate or a long coil may be possible.

In addition, according to an embodiment of the present invention, the shield is a ceramic fabric or ceramic paper containing SiO ₂ , the metal fluoride in powder form may be applied in the form of spray or slurry to the ceramic fabric or ceramic paper. In this case, the silicon injection source is unnecessary. In the case of using a ceramic fabric containing SiO ₂ as the shield, since the silicon itself serves as a source of silicon, it is possible to settle without a separate powder source of silicon. In this case, however, it is desirable to manufacture the metal fluoride together in an industrially fast and economical manner. In addition, when the metal fluoride is in the form of powder, it is preferable to spray the shield in an appropriate amount or to apply it in the form of a slurry, and the metal fluoride is preferably any one selected from the group consisting of MgF ₂ , AlF ₃ and NaF. In the above, the heat treatment of the laminated structure in a hydrogen atmosphere may be performed in a hydrogen atmosphere having a purity of 97% or more.

In this case, the reason for using the metal fluoride together is as follows.

In case of using only SiO ₂ , the possibility of moving to the right side in Equation (1) below will be examined in terms of thermodynamics.

SiO ₂ + 2H ₂ = Si + 2H ₂ O (1)

Based on Barin's data sheet (I. Barin, Thermochemical Data of Pure Substances Part I, VCH, Germany, 1989), the free energy for the formation of silicon dioxide and water vapor in the range 1200-1700K is given by

Si + O ₂ = SiO ₂ , ΔG ⁰ _{SiO 2} = -900.74 + 0.171 T (kJ) (2)

_{H 2 + 0.5O 2 = H 2} O, △ G 0 H2O = -250.0 + 0.057 T (kJ) (3)

The change in free energy of formation of equation (1) is expressed as 400.74-0.057T (kJ). As a result, it can be seen that the conditional expression for the reaction (1) to proceed to the right is as follows.

0 = 400,740-57 T + 2.303 * R * T log [P _H2O / P _H2 ] ² (4)

Summarizing equation (4),

P _H2O / P _H2 = 10 ^{1.49-10,465 / T} (5)

It can be seen from Equation (5) that Si can be formed by hydrogen reduction of SiO ₂ when P _{H 2 O} / P _{H 2} is 10 ⁻⁵ , that is, when the purity of hydrogen gas is about 5N, or more than 1612 K. have. If the value of P _H2O / P _H2 is 10 ^-6 , 1397K or more; if the value of P _H2O / P _H2 is 10 ^-7 , 1233K or more; if the value of P _H2O / P _H2 is 10 ^-8, It is possible to produce and the resulting Si is diffused into the low silicon steel sheet at that temperature.

Since the generated Si reacts with Fe or diffuses into the Fe matrix, the activity of Si is lowered rather than 1 in a pure state as shown in Equation (1). Assuming that Si generated by hydrogen reduction goes through an intermediate process of reacting with Fe to form FeSi, the free energy of formation of FeSi is expressed as -85,754+ 9.75 T (Joule). In view of this, equation (5) is expressed by equation (6).

P _H2O / P _H2 = 10 ^{1.234-8,225 / T} (6)

In this case, if the value of P _H2O / P _H2 is 10 ^-5, the deposition of Si becomes possible at 1320K or more. This means that the operating temperature can be reduced by about 290 ° C or more than when pure Si is produced. If the value of P _H2O / P _H2 is 10 ^-6 or more, 1137K (approximately 260 ° C temperature drop), and if the value of P _H2O / P _H2 is 10 ^-7 , the temperature can be maintained at 1000K or more, it is possible to generate Si element. Si diffuses into the low silicon steel sheet at that temperature.

When metal fluoride is added to SiO ₂ , various gas forms of chemistry such as Si, hydrogen, and fluorine include SiF ₄ , SiF ₃ , SiF ₂ , SiF, SiHF ₃ , SiH ₂ F ₂ , SiH ₃ F, and SiH ₄ The species are formed, and they move to the surface of the low silicon steel sheet through the pores present in the powder mixture, and silicon is deposited on the surface by decomposition reaction or reduction by hydrogen (Yun Jin-guk, Ji-young Byun, Jae-soo Kim, Choi Sul-sul, “Pack siliconizing of Mo”). Thermodynamics and Kinetic Studies on Metals ”, Vol.36, No.1 (1998) pp. 59-69.). The deposited silicon penetrates into the inside of the steel sheet by the diffusion reaction in the heat treatment process for a longer time to produce a high silicon steel sheet. This method provides the great advantage of producing a better surface steel sheet through the movement of gas species including Si while using solid powders that are easy to handle.

For example, considering the situation where the SiO ₂ -AlF ₃ mixture is present on the surface of the low silicon steel sheet and maintains the surroundings in a hydrogen atmosphere, the reduction reaction of SiO ₂ with hydrogen in the presence of AlF ₃ is represented by the following equation (7). Can be expressed as

4SiO ₂ (s) + 4AlF ₃ (s) + 2H ₂ (g) = Si ( _{in Si Steel} ) + 2Al ₂ O ₃ (s) + 3SiF ₄ (g) + 2H ₂ O (g) (7)

On the other hand, since aluminum fluoride exists in the solid phase up to 1548 K (1275 ° C.), the solid fluoride exists in the solid phase even at a temperature of 1273 to 1473 K at the time of the present invention, but its vapor pressure is 14.4 mbar at 1300 K, 91 mbar at 1400 K, and 441 mbar at 1500 K. Has a value (I. Barin, Thermochemical Data of Pure Substances Part I, VCH, Germany, 1989). Equation (7) considers that the solid phase-solid phase reaction between SiO ₂ and AlF ₃ takes place, but the vapor pressure of AlF ₃ is high at that temperature, and it can be seen that the solid phase SiO ₂ and AlF ₃ in the gas phase participate in the reaction. Solid-solid reactions are slow because the reaction occurs only at the point of contact between the two materials. Based on this, equation (7) can be expressed by equation (8).

4SiO ₂ (s) + 4AlF ₃ (g) + 2H ₂ (g) = Si ( _{in Si Steel} ) + 2Al ₂ O ₃ (s) + 3SiF ₄ (g) + 2H ₂ O (g) (8)

The Gibbs free energy change at standard conditions at 1400K is calculated as +77,263 Joules (I. Barin, Thermochemical Data of Pure Substances Part I and Part II, VCH, Germany, 1989). The conditions under which the reaction proceeds to the right are calculated on the assumption that the vapor pressure of AlF ₃ is 91 mbar at 1400 K and 1.5 mol of SiF ₄ and 1 mol of H ₂ O are produced when 1 mol of hydrogen is consumed. It can be seen that it is necessary to have more than%.

As described above, when pure SiO ₂ is directly reduced from 1400K to hydrogen, high purity hydrogen of about 99.9999% is required. However, when AlF ₃ , a metal fluoride, is added, the purity of hydrogen may be lowered to 97%. Therefore, it can be seen that the addition of metal fluoride is very effective industrially.

Hereinafter, the present invention will be described in more detail with reference to Examples. It should be understood, however, that these examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention.

Example  One : Of high silicon steel  In manufacturing shield  Improvement of surface condition of steel sheet when applied

In order to confirm that the surface condition of the steel sheet is improved when the shield is applied to the manufacturing method of the high silicon steel sheet, the following experiment was performed, and the steel sheet state according to each of the precipitating processes was measured and compared with the surface roughness measuring instrument.

The upper and lower portions of a 3% silicon steel specimen having a thickness of 0.15 mm, a length of 12 cm, and a width of 10 cm, the bottom of the ceramic fabric, i.e., a silica fabric comprising 12 cm wide, 14 cm long and 0.8 mm thick silica (SiO ₂ ) Wrapped in), SiO ₂ + Si + MgF ₂ system, SiO ₂ + AlF ₃ The precipitation process was performed under the conditions of the SiO ₂ + Si + MgF ₂ system without the ceramic fabric containing silica (SiO ₂ ) system conditions. Each specimen was heat-treated at 1200 ° C. under a hydrogen atmosphere and then furnace cooled to confirm silicon content. 2 is a surface roughness measurement result of the state of the steel sheet according to the manufacturing process of high silicon steel sheet under the conditions of SiO ₂ + Si + MgF ₂ system, SiO ₂ + Si + MgF ₂ system (without shield) and SiO ₂ + AlF ₃ system A graph representing. As shown in FIG. 2, the surface roughness of all cases was gradually increased as the silicon content was increased. Particularly, when the silicon dioxide is directly contacted with the steel sheet without the shield when the SiO ₂ + Si + MgF ₂ system is aerated, the surface roughness of the steel sheet with 6.2% of silicon increased by 12 times compared to the surface roughness at 3%. , The surface roughness of the steel sheet with a silicon content of 6.2% manufactured by using a ceramic fabric containing silica (SiO ₂ ) as a shield increased three times compared to a 3% state, thereby obtaining a relatively good surface state. Even in SiO ₂ + AlF ₃ system, when the ceramic fabric containing silica (SiO ₂ ) is used to immerse up to 6% of silicon, the surface roughness increases about 4 times compared to that of 3% of silicon. And it was found.

Example  2: silica ( SiO ₂ By ceramic fabric containing When Metal fluoride  effect

In order to confirm the effect of the metal fluoride during immersion by the ceramic fabric containing silica (SiO ₂ ) was carried out as follows. A ceramic fabric, i.e., a silica fabric, comprising silica (SiO ₂ ) having a width of 12 cm, a length of 14 cm, and a thickness of 0.8 mm, on both sides of a 3% silicon steel specimen of 0.15 mm thickness, 12 cm length, and 10 cm width. Buil safetech) was wrapped and heat-treated at 1200 ℃ for hours under hydrogen atmosphere to confirm the silicon content by the furnace cooling. As a result, as shown in FIG. 3, it was found that even if only a ceramic fabric including silica (SiO ₂ ) was used without adding a silicon injection source, a high silicon steel sheet having a good surface state could be manufactured. The silicon content was calculated by assuming that the weight change was based on the addition of Si, and after 22 hours, the silicon content reached 6.5% and the silicon content increased by about 0.16% per hour.

In addition, the experiment was carried out in the same manner as the above experimental method, but after placing about 5 g of NaF powder in the vicinity of the specimen was settled. FIG. 3 shows that the silicon content is increased when the NaF powder is disposed as a metal fluoride in the vicinity of the specimen, and then precipitated. As shown in FIG. 3, it was confirmed that the silicon content was relatively increased compared to the case where there was no metal fluoride.

Reference Example  One

In the present invention, as well as a ceramic fabric containing silica (SiO ₂ ) as well as a medium capable of passing gas, it can be used as a shield, and when the shield is used together with a silicon injection source, it is confirmed that the deposition rate decreases. In order to perform the following experiment.

Coils A and B were made by inserting a long 3% silicon steel sheet having a width of 3 cm and a thickness of 0.15 mm and a weight of 30.5662 g and 29.6142 g, respectively, in a spirally grooved alumina holder with 5 mm intervals. Coil A is a ceramic fabric containing two sheets of silica (SiO ₂ ), ie, a silica fabric (Buil Safetech Co., Ltd.) between steel sheets, and a weight ratio of 2% MgF ₂ and 3.23% based on SiO ₂ powder therebetween. A total of 49.9 g of the powder mixture including Si were evenly filled. Coil B evenly filled a total of 122.4 g of a powder mixture containing 2% MgF ₂ , 0.83% Si by weight, based on SiO ₂ powder, without inserting a ceramic fabric comprising silica (SiO ₂ ). After immersing the two coils simultaneously at 1150 ° C. for 6 hours, the weight was confirmed. As a result, coil A increased to 32.2762 g and coil B increased to 30.938 g.

From the above results, the followings were found. Because of the highest activity of pure Si, they can be seen to have penetrated the entire steel sheet during the immersion process (49.9g X 0.0323 = 1.6117g for coil A, 122.4g X 0.0083 = 1.0159g for coil B), and the weight of the coil The increase in weight of the remaining portion in consideration of the increase can be seen as a precipitate from a ceramic fabric containing SiO ₂ powder or silica (SiO ₂ ), so for coil A only 0.1 g contains SiO ₂ and silica (SiO ₂ ). It will inflow from the ceramic fabric, in the case of the coil B 0.3 g degree of SiO ₂ It was found that it came from the powder. Therefore, it can be seen that the gas species composed of silicon, fluorine, and hydrogen generated in the powder mixture passed through the ceramic fabric containing silica (SiO ₂ ) to the steel sheet, and also the ceramic fabric containing silica (SiO ₂ ) Rather, it was found that aerosols can be equivalent to media that can pass gas. In addition, it was found to be very useful in terms of maintaining a good surface state of the steel sheet, although the rate of aggression was slightly lowered compared with the case where it is not present when the shield is used.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

1: silicon injection
2: steel sheet
3: shield

Claims (8)

Preparing at least one silicon injection source selected from the group consisting of SiO ₂ , SiC and Si in powder form and a steel sheet having a silicon content of 0 to 3% by mass;
Forming a laminated structure by inserting a shield between the silicon injection source and the steel sheet and having a space through which gas can pass, and having a characteristic of not reacting with the steel sheet; And
Heat-treating the laminated structure at 727 ° C. (1000 K) to 1200 ° C. (1473 K) in a hydrogen atmosphere to allow Si to diffuse into the steel sheet.
A method for producing a steel sheet having a silicon content of more than 3.0% by mass and 6.5% by mass or less. The method of claim 1,
And said shield is a ceramic fabric or ceramic paper. The method of producing a steel sheet having a silicon content of more than 3.0% by mass and 6.5% by mass or less. The method of claim 2,
And said shield is a ceramic fabric or ceramic paper comprising SiO ₂ , wherein the silicon content is greater than 3.0% by mass and less than 6.5% by mass. Preparing a shield having a silicon content of 0 to 3% by mass and a space through which a gas can pass, and having a characteristic of not reacting with the steel sheet;
Wrapping both sides of the steel sheet with the shield to form a laminated structure;
Applying metal fluoride in powder form to the shield in a spray or slurry form; And
So that Si can diffuse into the steel sheet
Heat-treating the laminated structure at 727 ° C. (1000 K) to 1200 ° C. (1473 K) in a hydrogen atmosphere.
A method for producing a steel sheet having a silicon content of more than 3.0% by mass and 6.5% by mass or less. The method of claim 4, wherein
And said shield is a ceramic fabric or ceramic paper comprising SiO ₂ , wherein the silicon content is greater than 3.0% by mass and less than 6.5% by mass. The method of claim 4, wherein
Wherein said metal fluoride is any one selected from the group consisting of MgF ₂ , AlF ₃ and NaF, wherein the silicon content is greater than 3.0% by mass and less than 6.5% by mass. delete Steel sheet manufactured by the method of any one of Claims 1-6 more than 3.0 mass% and 6.5 mass% or less.

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