JP2017214616A - Magnetic shield steel sheet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic shield steel sheet having magnetic shield properties and plating adhesiveness in a high magnetic field.SOLUTION: There is provided a magnetic shield steel sheet having a mother steel sheet having a chemical composition of Si:1.5 to 4.0%, Al:0.1 to 3.0%, Mn:0.1 to 2.4% and the balance Fe with impurities, one or more plating layer formed on at least a single sided surface of the mother steel sheet and a transition zone formed between one surface and the plating layer. The transition zone is a zone in which Fe concentration in a sheet thickness direction of the mother steel sheet changes from 90% to 10% of Fe concentration at a center position in the sheet thickness direction of the mother steel sheet and satisfies X/Y≥1.4. X is a maximum value (mass%) of total concentration of one or more of P, Sn, Sb, Ni and Mo in the transition zone and Y is total concentration (mass%) of one or more of P, Sn, Sb, Ni and Mo in the mother steel sheet.SELECTED DRAWING: None

Description

  The present invention relates to a magnetic shield steel plate and a manufacturing method thereof.

  An electric device or the like is provided with a magnetic shield material made of a magnetic material such as iron for the purpose of preventing leakage of magnetic flux outside the specific space or for preventing the influence of magnetic flux from outside the specific space. The characteristics required for the magnetic shield material differ depending on the magnetic and electromagnetic wave frequencies to be shielded. When shielding magnetism of 1 Hz or less, the magnetic shield material is required to have a high DC permeability.

  The magnetic permeability of the steel plate used for the magnetic shield steel plate that secures the magnetic shielding property by the steel plate is highest near the magnetic flux density of 1T. For this reason, it is general that the magnetic flux density flowing in the steel plate is designed to be 1 T or less, and the plate thickness of the steel plate is increased or a plurality of sheets are used as necessary.

  The magnetization process near the magnetic flux density of 1T is mainly due to the domain wall motion. For this reason, in order to increase the permeability of the steel sheet, the grain size is increased to reduce grain boundaries, to reduce precipitates, to reduce compressive stress in the magnetization direction, to reduce residual strain, It is effective to reduce the unevenness of the film, to increase <100> that is the easy magnetization direction of Fe in the magnetization direction (or to reduce the angle formed by the magnetization direction and <100>).

  A magnetic shield steel sheet is often required to have corrosion resistance as well as a normal steel sheet, in addition to magnetic shield properties. Patent Documents 1 to 9 propose a large number of magnetic shield steel plates whose surfaces are coated with Zn.

Of these Zn-based plated magnetic shield steel plates, particularly Si contained in the base steel plate has a problem in containing a large amount from the viewpoint of plating properties. However, in order to ensure magnetic shielding properties at a low magnetic field of a magnetic field level (magnetic field of less than 10 ⁻⁵ T) as in the case of magnetic shield steel sheets for electronic parts, it is not necessary to contain a large amount of Si in the first place. There is no problem. Rather, there is a limit to the content of Si as a solid solution strengthening element for increasing strength in applications such as heat shrink bands.

  A large number of Zn-based platings on high-Si steels have been investigated with respect to high-strength steel sheets rather than with magnetic shield steel sheets. In the field of high-strength steel sheets, in order to avoid plating unevenness and deterioration of plating adhesion specific to high Si-containing steel, as disclosed in Patent Documents 10 to 14, electrolytic treatment and pickling treatment before Zn-based plating Or Ni plating is performed in advance as disclosed in Patent Documents 15 and 16.

  In general, these magnetic shield steel plates are installed as other members between other structural members or functional members. However, in some applications, there is a demand for the magnetic shield steel plate itself to have the function of an exterior material or an interior material.

  In particular, in applications of linear motor cars that have been attracting attention in recent years, not only is it necessary to ensure magnetic shielding, but there is a strong demand for weight reduction from the viewpoint of speeding up and energy saving. There is also a strong demand for component integration from the viewpoint of securing and cost reduction.

  As techniques for meeting such demands, Patent Documents 17 to 19 disclose that an organic film is formed on a steel plate or a plated steel plate manufactured in consideration of magnetic shielding properties.

Japanese Patent Laid-Open No. 10-251891 JP-A-11-106876 JP 2000-59086 A JP 2000-91113 A JP 2000-290759 A International Publication No. 99/023268 Pamphlet JP 2003-171748 A Special table 2004-516384 gazette JP 2008-163372 A JP-A-5-320981 JP-A-8-188898 JP 2000-104194 A JP 2001-262271 A JP 2003-64493 A JP-A-6-306664 JP-A-8-165593 JP 2000-303143 A International Publication No. 02/054435 Pamphlet JP 2010-43291 A

  As described above, the magnetic shield steel sheet that has been subjected to Zn-based plating for enhancing corrosion resistance on the steel sheet in consideration of the magnetic shield property, and further formed an organic film for improving the designability is appropriately combined with various known techniques. Can be manufactured.

  However, in consideration of the magnetic shielding properties in high magnetic fields such as the above-mentioned linear motor car applications, technical development focusing on magnetic shielding properties and plating adhesion when using high Si content steel as the base steel plate Not done enough.

  The object of the present invention is to use a high-Si content steel for the base steel sheet, and to achieve a high level of magnetic shielding and plating adhesion in a high magnetic field in a magnetic shielding steel sheet that has been subjected to Zn-based plating for imparting corrosion resistance. It is to provide a magnetic shield steel sheet and a method for producing the same that can improve the design.

  The present inventors have conducted various experiments and studies in order to obtain a magnetic shield steel sheet having both magnetic shielding properties and plating adhesion in a high magnetic field. Specifically, it was assumed that magnetic shielding properties were secured in an environment where the magnetic field was 0.1 T or more.

  However, the well-known magnetic shield material intended for low magnetic fields such as geomagnetism did not provide sufficiently satisfactory characteristics, and the importance of material development specialized for such preconditions was recognized. Then, from the viewpoint of corrosion resistance and cost, Zn plating is applied to the surface of the base steel plate made of high Si-containing steel manufactured to ensure sufficient magnetic shielding properties in a high magnetic field, and magnetic shielding properties and plating adhesion are provided. We examined in detail.

  When Zn-based plating is applied directly on the mother steel plate, some adhesion can be obtained if conditions such as electrolysis and pickling, which are known techniques, are adjusted. When a bending process or an embossing process is performed, peeling occurs, and a satisfactory result cannot be obtained.

  In addition, with such unstable plating, there was a tendency that the magnetic shielding properties at high magnetic fields deteriorated. These causes are presumed to be because an undesired stress is generated between the base steel plate and the plating.

In order to solve the above-mentioned problems, the present inventors have repeatedly studied paying attention to relaxation of stress generated between the mother steel plate and the plating,
(A) By performing an intermediate treatment in which one or more elements of P, Sn, Sb, Ni or Mo, which are surface segregation elements, are adhered to the surface of the base steel plate between the finish annealing and the plating treatment, sufficient Magnetic shielding can be ensured,
(B) In the base steel plate, an appropriate amount of one or more of the above-mentioned elements is contained, and furthermore, sufficient magnetic shielding properties can be secured by appropriately segregating these elements on the surface of the base steel plate in the heat treatment process before plating.
(C) At this time, the plating adhesion is increased at the same time. (D) These phenomena are caused by the concentration of these elements in the transition region between the base steel plate and the plating layer, and between the base steel plate and the plating layer. The present invention was completed by finding out that it is presumed that the cause is relaxation of the generated stress, and further studying. The present invention is listed below.

(1) It has a chemical composition which is Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, the balance Fe and impurities in mass%. A mother steel plate,
One or more plating layers formed on at least one surface of the mother steel plate;
A transition region formed between the one surface and the plating layer,
The transition region is a region where the Fe concentration in the thickness direction of the base steel plate changes from 90% to 10% of the Fe concentration at the center position in the thickness direction of the base steel plate,
A magnetic shield steel plate that satisfies the following formula (1).

X / Y ≧ 1.4 (1)
However, the code | symbol X in (1) Formula is the maximum value (mass%) of 1 or more types of total density | concentration of P, Sn, Sb, Ni, and Mo in the said transition area | region, and the code | symbol Y is the said in the said mother steel plate. The total concentration (mass%) of one or more of P, Sn, Sb, Ni, and Mo.

(2) By mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, P, Sn, Sb, Ni, Mo One or more of them: 0.01 to 0.20% in total, the base steel plate having a chemical composition that is the balance Fe and impurities,
One or more plating layers formed on at least one surface of the mother steel plate;
A transition region formed between the one surface and the plating layer,
The transition region is a region where the Fe concentration in the thickness direction of the base steel plate changes from 90% to 10% of the Fe concentration at the center position in the thickness direction of the base steel plate,
A magnetic shield steel plate that satisfies the following formula (1).

X / Y ≧ 1.4 (1)
However, the code | symbol X in (1) Formula is the maximum value (mass%) of 1 or more types of total density | concentration of P, Sn, Sb, Ni, and Mo in the said transition area | region, and the code | symbol Y is the said in the said mother steel plate. The total concentration (mass%) of one or more of P, Sn, Sb, Ni, and Mo.

  (3) The magnetic shield steel sheet according to 1 or 2, which satisfies the following formula (2).

X / Z> 1.0 (2)
However, the symbol Z in the formula (2) is the maximum value (mass%) of one or more total concentrations of P, Sn, Sb, Ni, and Mo in the base steel plate.

(4) By mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, balance Fe and chemical composition as impurities A method for producing a magnetic shield steel sheet that performs hot rolling, cold rolling, finish annealing, and plating on a slab,
The manufacturing method of the magnetic shield steel plate of 1 which performs the process which adheres 1 or more types of elements among P, Sn, Sb, Ni, and Mo to the surface of the steel materials which are intermediate products in the said process.

(5) By mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, P, Sn, Sb, Ni In addition, hot rolling, cold rolling, finish annealing, and plating treatment are performed on a slab containing a total of 0.01 to 0.2% of Mo and having a chemical composition that is Fe and impurities. A method for producing a magnetic shield steel sheet, comprising:
The manufacturing method of the magnetic shield steel plate of 2 which performs the process which adheres 1 or more types of elements among P, Sn, Sb, Ni, and Mo to the surface of the steel materials which are intermediate products in the said process.

(6) By mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, P, Sn, Sb, Ni In addition, hot rolling, cold rolling, finish annealing, and plating treatment are performed on a slab containing a total of 0.01 to 0.2% of Mo and having a chemical composition that is Fe and impurities. A method for producing a magnetic shield steel sheet, comprising:
The magnetic shield steel sheet according to item 2, wherein the residence time in the temperature range of 650 to 800 ° C in the temperature raising process of the finish annealing is set to 3 seconds or more, and the dew point of the atmosphere in the temperature range is set to 15 ° C or less. Production method.

  (7) The manufacturing method of the magnetic shield steel plate in any one of 4-6 whose said plating process is electroplating.

  According to the present invention, a magnetic shield steel sheet for high magnetic fields that can be compatible at a high level of magnetic shielding properties and plating adhesion in a high magnetic field, and has a function as an exterior material or interior material such as corrosion resistance and design properties is provided. can do.

  Thereby, space can be secured and costs can be reduced as compared with the case where the interior material, the magnetic shield material, and the exterior material are made of individual materials as in the prior art.

  Further, by using the magnetic shield steel plate according to the present invention as a constituent member of a moving body such as a linear motor car, the constituent members can be integrated and solid solution strengthening of Si, Al, Mn, etc. contained in a relatively large amount Since the element increases the strength of the magnetic shield steel plate, it is possible to reduce the thickness of the structural member, and it is also possible to achieve high speed and energy saving by reducing the weight of the vehicle body of the moving body.

  Hereinafter, modes for carrying out the present invention will be described. In the following description, “%” relating to chemical composition or concentration means “% by mass” unless otherwise specified, and “magnetic shielding” means “high magnetic field, eg, 0.1 T, unless otherwise specified. This means “magnetic shielding performance in a high magnetic field”.

1. First, the chemical composition of the base steel plate of the magnetic shield steel plate according to the present invention will be described.

  The mother steel plate is a main element for ensuring the magnetic shielding property in a high magnetic field, which is one of the characteristics of the magnetic shield steel plate according to the present invention. The base steel plate contains Si: 1.5 to 4.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 2.4%, preferably P, Sn, Sb, Ni And a total of 0.01 to 0.20% of Mo, and has a chemical composition that is Fe and impurities.

(1-1) Si: 1.5 to 4.0%
Si changes the texture of the base steel sheet after cold rolling annealing, increases the magnetic permeability, and improves the magnetic shielding properties in a high magnetic field. In addition, Si increases the transformation temperature from the α phase to the γ phase of the base steel sheet and anneals at higher temperatures to coarsen the grains, thereby increasing the maximum permeability and magnetic shielding properties in a high magnetic field. To improve.

  Further, Si not only effectively acts as a solid solution strengthening element to increase the strength of the base steel sheet, but also improves the magnetic shielding property in a high magnetic field by bringing the saturation magnetostriction constant close to 0 and increasing the magnetic permeability. For this reason, Si is contained actively.

  When the Si content is less than 1.5%, if the annealing is not performed for a long time at a temperature at which transformation does not occur, the crystal grains are not sufficiently coarsened, and continuous annealing cannot be performed, resulting in an increase in manufacturing cost. . For this reason, Si content is 1.5% or more.

  Although depending on the content of other elements, if the Si content is less than 2.0%, γ transformation may occur at high temperatures, so the Si content is preferably 2.0% or more, and more preferably Is 2.1% or more, and more preferably 2.6% or more.

  On the other hand, if the Si content exceeds 4.0%, the mother steel plate is embrittled, and further, the saturation magnetic flux density is lowered, and the increase in magnetic shielding properties in a high magnetic field is saturated. For this reason, Si content is 4.0% or less, Preferably it is less than 3.8%, More preferably, it is less than 3.6%.

(1-2) Al: 0.1 to 3.0%
Al, like Si, is also actively contained in the same manner as Si in order to increase the transformation temperature from the α phase to the γ phase of the base steel plate. On the other hand, when Al binds to N in steel and precipitates as AlN, crystal grain growth and domain wall movement are hindered and magnetic permeability is lowered.

  If the Al content is less than 0.1%, the AlN precipitates become finer and hinder crystal grain growth and domain wall movement. For this reason, Al content is 0.1% or more.

  When the Al content is increased, the size of the AlN precipitates is coarsened, and the number of AlN precipitates is reduced, thereby suppressing the adverse effect on the magnetic shielding properties in a high magnetic field. For this reason, Al content becomes like this. Preferably it is 0.3% or more, More preferably, it is 0.6% or more. Furthermore, in order to sufficiently obtain a coarse crystal grain due to an increase in the transformation temperature, the Al content is more preferably 0.9% or more, and even more preferably 1.2% or more.

  On the other hand, Al, like Si, reduces the saturation magnetic flux density, and if contained in a large amount, embrittlement of the mother steel plate becomes a problem. For this reason, Al content is 3.0% or less, Preferably it is less than 2.8%, More preferably, it is less than 2.6%.

(1-3) Mn: 0.1 to 2.4%
When Mn combines with S in steel and precipitates as MnS, it inhibits crystal grain growth and domain wall movement and lowers the magnetic permeability. If the Mn content is less than 0.1%, the precipitate of MnS becomes finer and hinders crystal grain growth and domain wall movement. For this reason, the Mn content is 0.1% or more.

  When the Mn content is increased, the size of the MnS precipitate is coarsened, and the number of MnS precipitates is decreased, thereby suppressing the adverse effect on the magnetic shielding property in a high magnetic field. For this reason, Mn content becomes like this. Preferably it is 0.15% or more, More preferably, it is 0.3% or more.

  On the other hand, Mn, unlike Si and Al, lowers the transformation temperature from the α phase to the γ phase of the base steel plate, so if it is contained excessively, it becomes difficult to coarsen the crystal grains by high-temperature annealing. Considering the manufacturing cost, the Mn content is 2.4% or less, preferably less than 2.1%, and more preferably less than 1.9%.

(1-4) Type A Element In the magnetic shield steel plate according to the present invention, one or more elements among P, Sn, Sb, Ni, and Mo are concentrated in the interface region between the plating layer and the base steel plate. In the present specification, these elements may be referred to as “type A elements”.

  By performing an intermediate treatment before performing the plating treatment on the base steel plate that does not include the A-type element, the A-type element can be formed in the interface region. It is also possible to concentrate the element within the necessary range in the interface region after finishing the elements and finishing annealing and plating processes. Here, the case where the mother steel sheet contains a type A element will be described.

  As described above, the magnetic shield steel plate according to the present invention contains Si: 1.5 to 4.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 2.4%, Furthermore, it contains 0.01 to 0.20% of one or more of P, Sn, Sb, Ni, and Mo in total.

In the finish annealing step of the magnetic shield steel plate targeted by the present invention, the A-type element segregates on the surface of the base steel plate and prevents the formation of SiO ₂ , thereby preventing subsequent plating deterioration and internal oxidation. The behavior is changed, the deterioration of the magnetic shield property at a high magnetic field due to the internal oxide layer is prevented, and the magnetic shield property at a high magnetic field is improved.

  Further, the A-type element is present in a concentrated manner in the interface region between the base steel plate and the plating layer, and thus preferably acts on the magnetic shielding property in a high magnetic field.

  In order to obtain this effect, the content of the A-type element is 0.01% or more, preferably 0.02% or more, and more preferably 0.04%.

  On the other hand, if the content of the A-type element exceeds 0.20%, not only the above effect is saturated, but if excessively contained, the ductility of the magnetic shield steel sheet is deteriorated, and the plateability at the time of production is lowered. Manufacturing cost increases. For this reason, the content of the A-type element is 0.20% or less, preferably 0.15% or less, and more preferably 0.09% or less.

  The type A element in the base steel plate can be contained in the above range when a special effect is expected in the present invention, but is not limited to this and is an element known to be contained in the electrical steel plate. The general content and its influence will be described below.

  The content of P is controlled for the purpose of strength adjustment, suppression of oxidation, nitriding, and carburization during production. In addition, when segregating to grain boundaries before cold rolling, the texture is improved and magnetic flux density is improved. It is known to improve the content and can be contained by 0.001% or more. In a general practical steel making method, it may be contained as 0.002% or more as an impurity.

  Ni content is controlled for the purpose of strength adjustment, corrosion resistance, and oxidation behavior control during production, and it is particularly known to improve high frequency characteristics, and can be contained in an amount of 0.001% or more. is there. In a practical steelmaking method in which scraps or the like are mixed, it may be contained in an amount of 0.01% or more as impurities.

  The content of Sn is controlled for the purpose of suppressing oxidation, nitridation, and carburization during production, and it is particularly known to improve high-frequency characteristics, and can be contained in an amount of 0.001% or more. . In a practical steelmaking method in which scraps and the like are mixed, 0.002% or more may be contained as impurities.

  Mo is known to improve the magnetic properties by forming a complex oxide containing oxides and carbides, and can be contained in an amount of 0.0001% or more. On the other hand, care must be taken because these precipitates may obstruct the domain wall motion and degrade the magnetic shielding properties.

  The content of Sb is controlled for the purpose of suppressing oxidation, nitriding, and carburization during manufacture, and it is particularly known to improve high frequency characteristics, and can be contained in an amount of 0.001% or more. .

  Furthermore, the magnetic shield steel sheet according to the present invention contains known elements contained in the electromagnetic steel sheet on the premise that compatibility at a high level of magnetic shielding properties and plating adhesion in a high magnetic field does not disappear. You may contain by quantity. Examples of such elements include C, N, S, Cr, Cu, B, Ti, Nb, Ca, Mg, and REM. In the following, some of these elements that have a relatively strong influence on the effects of the present invention will be described.

(1-5) C: 0.0040% or less C may form carbides and deteriorate the magnetic shielding properties in a high magnetic field. In addition, when magnetic aging occurs, the magnetic shielding property in a high magnetic field is also deteriorated, so that the C content is preferably low. For this reason, C content is preferably 0.0040% or less.

  From the viewpoint of manufacturing cost, it is advantageous to reduce the C content by degassing equipment (for example, RH vacuum degassing equipment) at the molten steel stage, and if the C content is 0.0030% or less, the effect of suppressing magnetic aging Is big. In the magnetic shield steel sheet according to the present invention, since non-metallic precipitates such as carbide are not used as the main means for increasing the strength, there is no merit of intentionally containing C, and the C content is preferably small. For this reason, C content becomes like this. Preferably it is 0.0020% or less, More preferably, it is 0.0015% or less. If a technique such as electrodeposition is used, it can be lowered to 0.0001% or less, which is below the limit of chemical analysis, and the C content may be 0%. On the other hand, considering the industrial cost, the lower limit is 0.0003%.

(1-6) N: 0.0040% or less N, like C, deteriorates magnetic shielding properties in a high magnetic field due to the formation of nitrides and magnetic aging. For this reason, the N content is preferably 0.0040% or less. The N content is preferably low in order to avoid deterioration of the magnetic shielding properties at high magnetic fields. If it is 0.0027% or less, the magnetic aging and the formation of nitrides will have a sufficient adverse effect on the magnetic shielding properties at high magnetic fields. Can be avoided. The N content is more preferably 0.0022% or less, and still more preferably 0.0015% or less. If a technique such as electrodeposition is used, it can be lowered to 0.0001% or less, which is below the limit of chemical analysis, and the N content may be 0%. On the other hand, considering the industrial cost, the lower limit is 0.0003%.

(1-7) S: 0.020% or less Since S may form sulfides and deteriorate the magnetic shielding properties in a high magnetic field, the S content is preferably low. The S content is preferably 0.020% or less, more preferably 0.0040% or less, even more preferably 0.0020% or less, and most preferably 0.0010% or less. The S content may be 0%.

(1-8) Cr: 20% or less Cr is known to improve the high-frequency characteristics, in addition to its content being controlled for the purpose of strength adjustment, corrosion resistance, and oxidation behavior control during production. It is possible to make it contain 0.001% or more. In a practical steelmaking method in which scraps or the like are mixed, it may be contained as an impurity by about 0.01% or more. On the other hand, excessive addition increases the cost of addition and lowers the magnetic properties, so the Cr content is preferably 20% or less, more preferably 5% or less.

(1-9) Cu: 0.2% or less Cu significantly reduces the saturation magnetic flux density Bs of the mother steel plate as a solid solution element. A decrease in the saturation magnetic flux density Bs leads to a decrease in magnetic shielding properties at a high magnetic field. For this reason, it is not necessary to darely contain Cu in the mother steel plate of the magnetic shield steel plate according to the present invention unless there is a special purpose. In a practical steelmaking method in which scraps or the like are mixed, it may be contained as 0.01% or more as impurities. Therefore, the Cu content is preferably 0.2% or less, and more preferably 0.15% or less. On the other hand, it is also known that the strength can be increased by Cu precipitation, and the magnetic steel sheet of the magnetic shield steel sheet according to the present invention can be used as appropriate according to known techniques.

(1-10) B: 0.01% or less B is not only controlled in content for the purpose of suppressing oxidation, nitriding, and carburizing during production, but also forms complex oxides including oxides and nitrides in particular. Thus, it is known to improve the magnetic properties, and the content can be 0.0001% or more. On the other hand, excessive addition causes the steel to become brittle and lower the magnetic properties, so the B content is preferably 0.01% or less, more preferably 0.005% or less.

(1-11) Ti: 0.0020% or less The content of Ti is controlled for the purpose of adjusting the strength by precipitates, and in particular, it improves the magnetic properties by forming a complex oxide containing oxides and sulfides. It is known that it can be contained in an amount of 0.0001% or more. In a practical steelmaking method in which scraps and the like are mixed, impurities may be contained in an amount of about 0.0002% or more. On the other hand, since these precipitates may inhibit the domain wall motion and greatly deteriorate the magnetic shielding property in a high magnetic field, the Ti content is preferably 0.0020% or less, more preferably 0.00. 0015% or less.

(1-12) Nb: 0.0020% or less Nb is effective in increasing the strength of precipitates such as NbC, but these precipitates inhibit the domain wall movement and greatly improve the magnetic shielding properties in a high magnetic field. Therefore, it is not necessary to add it. For this reason, the Nb content is preferably 0.0020% or less, and more preferably 0.0010% or less. In a practical steelmaking method in which scraps and the like are mixed, impurities may be contained in an amount of about 0.0002% or more.

(1-13) Ca: 0.050% or less Ca is known to improve magnetic properties by forming a complex oxide containing oxides and sulfides, and is contained in an amount of 0.0001% or more. It is possible. On the other hand, since these precipitates may inhibit the domain wall movement and significantly deteriorate the magnetic shielding property in a high magnetic field, the Ca content is preferably 0.050% or less, and more preferably 0.8%. It is 010% or less.

(1-14) Mg: 0.050% or less Mg is known to improve magnetic properties by forming a complex oxide containing oxides and sulfides, and is contained in an amount of 0.0001% or more. It is possible. On the other hand, since these precipitates may inhibit the domain wall motion and greatly deteriorate the magnetic shielding property in a high magnetic field, the Mg content is preferably 0.050% or less, and more preferably 0.8. It is 010% or less.

(1-15) REM: 0.050% or less REM is known to improve magnetic properties by forming complex oxides including oxides and sulfides, and is contained in an amount of 0.0001% or more. It is possible. On the other hand, since these precipitates may inhibit the domain wall movement and significantly deteriorate the magnetic shielding properties in a high magnetic field, the REM content is preferably 0.050% or less, more preferably 0.00. It is 010% or less.

(1-16) Remainder The mother steel plate of the magnetic shield steel plate according to the present invention has the above chemical composition, and the remainder is Fe and impurities. Examples of impurities include those contained in raw materials such as ore and scrap, and those contained in the manufacturing process. The above-mentioned C, N, S, Cr, Cu, B, Ti, Nb, Ca, Mg, REM, etc. may not be contained in the mother steel plate of the magnetic shield steel plate according to the present invention, but are contained as impurities. In some cases.

2. Next, the metal structure of the mother steel plate will be described.

  As described above, the texture and crystal grain size of the base steel plate are both controlled so as to favorably act on the magnetic shielding properties in a high magnetic field.

(2-1) Texture The texture of the mother steel sheet is basically a texture in which the deviation between the in-plane magnetization direction of the mother steel sheet and the <100> orientation that is the easy magnetization direction of the Fe crystal is reduced. It is preferable. Basically, it is preferably a texture having a small amount of {111} and a large amount of {100} and {110}. In other words, it is generally the same texture as the electromagnetic steel sheet whose magnetic flux density is controlled to be high.

  The base steel plate of the magnetic shield steel plate according to the present invention has a particularly high Si content and has a non-transformed chemical composition, thereby forming the texture as described above. A known magnetic shield steel plate using a low Si-containing steel as a base steel plate has a high {111}, which is not preferable for a magnetic shield application in a high magnetic field.

(2-2) Crystal grain size The crystal grain size of the mother steel plate is preferably 50 μm or more, more preferably 100 μm or more. In general, the smaller the contained element such as Si, the easier it is to increase the crystal grain size, but if the crystal grain size is increased in such a low Si-containing steel, {111} develops as a texture. Not suitable for magnetic shield applications in high magnetic fields. Further, as described above, when transformation occurs during annealing, the crystal grains are fragmented.

  The crystal grain size can be evaluated by a method, a counting method, a cutting method, and the like by comparison with a crystal grain size standard diagram described in JIS G0551: 2005, but in the present invention, it is evaluated by a cutting method.

3. Plating Next, plating will be described.

(3-1) Transition region In the present invention, the structure of the plating layer is defined. First, the boundary in the thickness direction will be described. In the present invention, the region where the Fe concentration changes from 90% to 10% of the Fe concentration at the center position in the thickness direction of the base steel plate from the base steel plate side toward the plating layer side, that is, in the thickness direction of the base steel plate. It is defined as a transition area. And the board thickness center side of a mother steel plate is a mother steel plate rather than the position where the Fe concentration is 90% of the Fe concentration at the center position in the thickness direction of the mother steel sheet, and the Fe concentration is at the center position in the board thickness direction of the mother steel plate. The outer surface side of the plating layer is a plating layer from the position where the Fe concentration is 10%.

  In the following description, “plating” is used as including a plating layer and a transition region unless it is particularly necessary to distinguish between them. In addition, the combined region may be described as a “plating region”.

(3-2) Concentration of type A element in transition region Plating is basically performed in order to ensure the corrosion resistance of the magnetic shield steel plate, but the magnetic shield steel plate according to the present invention has not only high corrosion resistance. This is done to ensure good magnetic shielding properties in a high magnetic field.

In the present invention, in order to achieve both magnetic shielding properties and plating adhesion in a high magnetic field, the A type element is concentrated in the transition region, and the degree of concentration is determined with respect to the total concentration of the A type element.
(Maximum concentration in the transition region) / (concentration in the base steel plate) ≧ 1.4 (1)
It prescribes. That is, X / Y ≧ 1.4, where X is the maximum value of the total concentration of the A-type elements in the transition region, and Y is the total concentration of the A-type elements in the mother steel plate.

  The total concentration of the class A element in the base steel plate is the total concentration of the class A element in the central region in the thickness direction in the inner region of the base steel plate.

  By setting the ratio (X / Y) to 1.4 or more, it is possible to achieve both at a level satisfying the magnetic shielding properties and the plating adhesion. The ratio (X / Y) is preferably 2.0 or more, and more preferably 3.0 or more.

  On the other hand, the thickness of the concentrated region of the A-type element is not particularly defined, but has the same extent as the transition region. As will be described later, the A-type element is mixed with these in the reaction between the plating metal and Fe of the base steel plate in the plating step. If the concentration of the A-type element in the concentration region is excessively high, a discontinuous concentration change such that a film of the A-type element is formed is generated, and undesirable stress is generated in the boundary region. There is a possibility that the magnetic shielding property in a magnetic field may be impaired. Further, in such a region, the deformation characteristics are also unique, and plating peeling is likely to occur, which causes a decrease in plating adhesion.

  For this reason, the ratio (X / Y) is 15.0 or less, preferably 10.0 or less, and more preferably 7.0 or less.

  In the present invention, the total concentration of the A-type elements is preferably (2) Formula: (maximum concentration in the transition region) / (maximum concentration in the base steel plate)> 1.0. That is, when the symbol X is the maximum value of the total concentration of the group A elements in the transition region and the symbol Z is the maximum value of the total concentration of the group A elements in the center position in the thickness direction of the mother steel plate, It is preferable that Z> 1.0.

  In the present invention, the type A element is concentrated on the surface of the finish annealed plate immediately before plating as described later. In the subsequent plating step, the A-type element concentrated on the surface of the finish annealed plate is mixed with the plated metal and Fe of the base steel plate to form a transition region.

  However, if the mixing of the seed A element, the plating metal and the Fe of the base steel sheet in the plating process is insufficient, the concentration of the seed A element present on the surface of the finish annealed sheet may remain. In the region where the Fe concentration is more than 90% and less than 100% of the Fe concentration at the center position in the plate thickness direction of the base steel plate (that is, the base steel plate region), the type A element is present at a high concentration.

  Even if the mixing is not inadequate, with the formation of the Fe concentration distribution at the time of mixing, the A-type element also forms a concentration distribution, so that the Fe concentration is the Fe concentration at the center position in the thickness direction of the mother steel plate. The concentration of the type A element at the point of 90% tends to be higher than a sufficient internal region of the mother steel plate.

  In the present invention, by mixing the A-type element in the transition region, the effect of improving the plating adhesion and the magnetic shielding property in a high magnetic field is obtained. Therefore, the A-type element should be mixed in the transition region as much as possible. . Equation (2) is defined as an index representing the degree of mixing. The ratio (X / Z) is preferably 1.5 or more.

  In the present invention, the concentration is defined by a relative value rather than an absolute value of the concentration of the A-type element in the transition region. However, there is a point to be considered in the mixing of the A-type element from the plating layer.

  Unless plating is performed intentionally containing the A-type element at a relatively high concentration, (maximum concentration in the transition region) / (maximum concentration in the plating layer)> 1.0. By the type A element mixed in the region, a clear peak of the type A element is formed in the transition region in the region extending from the plating layer to the base steel plate, and the effect of improving the magnetic shielding property in a high magnetic field by reforming the transition region is conscious It's easy to do.

  On the other hand, when plating that intentionally contains the A-type element, for example, Sn plating, Sn-Zn plating (trademark: Ecocoat-S), Ni plating, etc., the transition region can be achieved simply by plating. A large amount of element A is mixed from the plating layer.

  In this case, although depending on the content of the A-type element in the plating layer, in the case of plating as exemplified above, (maximum concentration in the transition region) / (maximum concentration in the plating layer) <1. It becomes 0 and it becomes difficult to be aware of the special meaning of the presence of the A-type element in the transition region.

  However, even in the transition region formed in this way, the transition region is characterized in that the stress relaxation effect is greater than that in the transition region that does not include the A-type element. To do.

  The reason why the concentration of the A-type element in such a transition region affects the magnetic shielding properties in a high magnetic field is not clear at present, but the present inventors have determined the thermal expansion coefficient between the base steel plate and the plated metal. Considering the stress at the interface due to the difference in Young's modulus as a factor, the estimation is as follows.

  That is, when a plating that is a film made of a different substance is formed on the surface of the base steel plate, stress is generated between the base steel plate and the magnetic domain in the steel plate. This is basically unfavorable for the magnetic shielding property in a high magnetic field. The transition region is a region that is interposed between the plating layer and the base steel plate and transmits this, but when the A-type element is concentrated in the transition region that has a certain extent, the effect of stress on the base steel plate is reduced. As a result, it is estimated that the adverse effect of the plating layer on the magnetic shielding property in a high magnetic field can be reduced.

  Although it is confirmed that this stress is very small as an absolute value, an appropriate stress range is unknown. However, it is generally known that stress affects the magnetic properties of the electrical steel sheet, and compressive stress is known to decrease the permeability, and tensile stress is known to increase the permeability. From this analogy, for example, it is estimated that the tensile stress due to the transition region in which the A-type element is concentrated relieves the compressive stress generated in the plating layer.

  The effect of the present invention will be explained by the influence on the stress due to the concentration of the A-type element in the transition region, which is an estimation mechanism by the present inventors. In the future, further studies will be carried out, and the fundamental parameters along with the mechanism will be clarified and expected to be clarified quantitatively.

(3-3) Thickness The plating layer is formed on the surface of the base steel plate for the purpose of improving the corrosion resistance of the magnetic shield steel plate according to the present invention. The metal element mainly used for plating is an element having lower magnetic properties than Fe, which is the main constituent element of the mother steel plate. When the plating layer becomes thick, the magnetic permeability of the entire magnetic shield steel plate decreases. For this reason, it is preferable that the thickness of a plating layer is thin within the range which ensures required corrosion resistance.

  In severe corrosive environments such as being exposed to wind and rain, a thickness of 100 μm or more may be required. On the other hand, for electrical appliances and interior applications installed in a general room, it is sufficient that the thickness of the plating layer is 1 μm, preferably 5 μm or less, and more preferably 3 μm or less.

  In the magnetic shield steel sheet according to the present invention, the thickness of the plating layer should also consider magnetic shielding properties. As described above, the plating layer is not preferable for the magnetic shielding property. If the thickness of the plating layer exceeds 10% of the thickness of the mother steel plate, the adverse effect on the magnetic shielding properties will increase. Therefore, the thickness of the plating layer is preferably 10% or less of the thickness of the base steel plate, preferably 5% or less of the thickness of the base steel plate, and more preferably 3% of the thickness of the base steel plate. It is as follows.

  When the thickness of the base steel plate is 0.80 mm as a general interior material, the thickness of the plating layer is preferably 80 μm or less.

  In order to exhibit magnetic shielding properties in a high magnetic field, the plating layer needs to have a certain thickness. Although there is a balance with the required magnetic shielding property in a high magnetic field, when the thickness of the plating layer is 1 μm or more, the magnetic shielding property in a high magnetic field is exhibited, and more preferably 2 μm or more. In addition, it cannot be overemphasized that the corrosion resistance of a member should also be considered for the minimum of the thickness of a plating layer as mentioned above.

  Another important point in the magnetic shield steel sheet according to the present invention is the thickness of the transition region. This influences the magnetic shielding property in a high magnetic field in relation to the concentration of the A-type element in the transition region. In the present invention, by setting the thickness of the transition region to 0.20 μm or more on both surfaces, the magnetic shielding property in a high magnetic field is preferably exhibited. In addition, the thickness of the transition region exhibits a favorable effect on the plating adhesion. If the thickness is less than 0.20 μm, it is difficult to ensure plating adhesion.

  At first glance, if the thickness of the plating layer is determined, it seems that the thickness of the transition region is determined accordingly, but this is not the case. That is, the thickness of the transition region is determined by the reaction between the plated metal and the base steel plate at the initial stage of the plating process, the heat treatment conditions after plating, or the like, but the thickness of the plated layer can be controlled independently of this. That is, if the transition region is formed at the initial stage of plating, the thickness of the plating layer formed thereafter can be controlled regardless of how much the thickness of the transition region is.

  In addition, when the transition region is developed by reacting the plating layer and the base steel plate by a heat treatment after plating, the plating layer is plated if the thickness of the plating layer is sufficient compared to the thickness of the transition region to be formed. The interface reaction is determined by the element concentration and the thermal history at the interface regardless of the layer thickness. That is, a transition region having the same thickness is formed regardless of the thickness of the plating layer on each surface.

  Thus, the thickness of the plating layer and the thickness of the transition region are completely independent indicators, and it is generally not conscious at all to control them independently, and it is special for those skilled in the art. It can be said that it is a control technology.

  The thickness of this transition region is preferably 0.40 μm or more, more preferably 0.6 μm or more, and even more preferably 0.8 μm or more. When the thickness of the transition region is small, that is, when the change of the Fe concentration is steep, the magnetic shielding property in a high magnetic field is deteriorated. The cause of this is that if the change in Fe concentration in the transition region is steep, the stress acting on the base steel plate becomes excessive, the absolute value of the magnetic shielding property itself in a high magnetic field deteriorates, and the result of subtle stress distribution It is estimated that it is difficult to confirm the effect of concentration of the A-type element on the transition region appearing as Moreover, it is estimated that such stress acts also on the adhesiveness of plating.

  There is no particular upper limit on the thickness of the transition region. In order to clearly demonstrate the effect of enrichment of the A element in the transition region, it is preferable that the thickness of the transition region is large and gradually changed. In addition, the thickness of the transition region is also large and gradually changes from the viewpoint of adhesion. It is because it is preferable to do. Note that when the thickness of the transition region is increased, the concentration of the A-type element in the transition region decreases if the amount of the A-type element mixed in the transition region is constant.

(3-4) Plating structure The plating region of the magnetic shield steel sheet according to the present invention is a single phase, and is within a range in which a phase that completely dissolves the contained metal element within a concentration change range is formed. preferable. For this reason, it is preferable to avoid this when a special metal phase such as an intermetallic compound that adversely affects magnetic shielding properties and plating adhesion is formed due to the chemical composition and thermal history of the plated metal. In particular, there are many points to be noted regarding intermetallic compounds.

The intermetallic compounds to be avoided vary depending on the metal contained in the plating, and also depend on the required characteristics, and therefore cannot be determined in a general manner. However, for example, in the case of an intermetallic compound of Fe—Zn, the adverse effect of an intermetallic compound such as FeZn ₁₃ called ζ phase and FeZn ₇ called δ ₁ phase is small, and Fe ₅ Zn ₂₁ and Γ phase called Γ ₁ phase are small. The adverse effect of hard intermetallic compounds such as Fe ₃ Zn ₁₀ called is great.

For example, if it is an intermetallic compound of Fe—Al, Fe ₃ Al called β ₁ phase, FeAl or Fe ₂ Al ₅ called a β ₂ phase, Fe ₃ Sn, if it is an intermetallic compound of Fe—Sn, In the case of an intermetallic compound of Fe ₃ Sn ₂ , FeSn, FeSn ₂ , and Ni—Al, NiAl called a β ′ phase can be cited as an intermetallic compound having an adverse effect.

  Thus, in the plating layer in the present invention, the formation of an intermetallic compound is basically not preferable. Even when the intermetallic compound is formed, it is preferable that the intermetallic compound is not a film-like form covering the entire surface of the specific depth region of the mother steel plate, and is not coarse. If it is a region away from the base steel plate, the influence of the intermetallic compound on the magnetic shielding properties and plating adhesion is negligible.

  In particular, if a large amount of intermetallic compound is formed in the transition region, the magnetic shielding property in a high magnetic field may be reduced. The reason for this is not clear, but it is presumed that the formation of the intermetallic compound acts to generate an undesirable stress.

  The presence of the intermetallic compound can be determined by X-ray diffraction or electron beam diffraction. X-ray diffraction can be measured in the state of a steel plate, and can also be measured in a state where the plating is peeled off to form a powder. In electron diffraction, a thin film sample is prepared using FIB, and a crystal structure can be identified by analyzing an electron beam diffraction image obtained by TEM.

  In both X-ray diffraction and electron beam diffraction, the presence of intermetallic compounds can be determined by detecting diffraction peaks and diffraction patterns at positions corresponding to the lattice spacing of various intermetallic compounds. . In addition, the kind of metal element can also be identified by using the EDS detector equipped in TEM.

  These judgments and identifications may be made according to the standards that are commonly performed by those skilled in the art.

(3-5) Plating type Known plating can be applied to the plating. The metal element to be plated is not particularly limited. For example, in the case of Zn-based plating, known Zn, Zn—Ni, Zn—Co, Zn—Fe, Zn—V, Zn—Sn, Zn—Mn, Zn—Cr, Zn—Bi, Zn—Sb, etc. Plating can be applied.

  Of course, other than the Zn-based plating, known plating such as Pb—Sn, Fe—Ni, Fe—Cr, etc. can also be applied.

As the plating means for these plating, electroplating, hot dipping, thermal spraying and the like can be applied without limitation. Furthermore, plating in which colloids such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ and fine particles are dispersed in the plating can also be applied.

  Furthermore, the plating layer on the base steel plate does not need to be a single type, and even with a known multi-layer plating, good magnetic shielding properties in a high magnetic field are not lost. As an example, it is possible to apply Ni-based plating as a lower layer of Zn-based plating, but it is preferable for known magnetic plating and plating adhesion required for a known number of platings with a limited number of trials. It is not difficult for those skilled in the art to determine the plating type and plating thickness that affect the plating.

  The above-described plating can also be used to contain the A-type element in the transition region. For example, when Zn plating is finally performed on the mother steel plate, pure Ni plating, Ni—Fe plating, Ni—Zn plating or Ni—Fe—Zn plating before Sn plating, Sn-based plating, etc. If plating containing a relatively high concentration of the A-type element is performed, the A-type element can be contained at a high concentration in the transition region formed between the final Zn plating and the base steel plate.

  The plating composition for aiming at such an effect may be appropriately determined in consideration of required corrosion resistance, manufacturing conditions, cost, and the like. In addition, when the plating of the component containing the A-type element at a high concentration is the intermediate plating and the plating of the component containing almost no A-type element is the outermost layer, the concentration of the A-type element in the transition region Can be remarkably increased, and the effect of the present invention of stress relaxation in the transition region tends to appear clearly.

  On the other hand, for example, even when Ni plating is applied as a single layer as a plating, as a result, the expression (1) of the present invention is satisfied. The effect on the transition region of is demonstrated.

  These concentrations can be evaluated by examining the emission intensity profile from the surface of the magnetic shield steel plate by GDS. The absolute value of the concentration can be specified by a calibration curve between the GDS emission intensity and the element content for the material in which the content of each element is changed.

  GDS is analyzed using, for example, Rigaku GDA750 at an anode diameter of 4 mm and a pressure of 3 hPa. Although the optimum sputtering time varies depending on the plating thickness, generally, the analysis can be performed up to the mother steel plate if it is performed for 200 seconds, and in the case of a plating thickness larger than that, the analysis can be performed by increasing the sputtering time.

(3-6) Absence of Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in the metal state Furthermore, in the magnetic shield steel sheet according to the present invention, the Li in the metal state is contained in the plating layer. , Na, K, Rb, Be, Mg, Ca, Sr, Ba or Al are preferably absent. In the present invention, the “metal state” means a state containing an intermetallic compound.

  In the present specification, Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in the plating layer may be referred to as “B-type element”.

  As described above, the intermetallic compound exerts an unfavorable effect on the magnetic shielding property in a high magnetic field. However, even if the B-type element is present in the plating layer even in a solid solution state, the high magnetic field Degradation of magnetic shielding at The reason for this is not clear, but it is presumed that the stress state and magnetic properties change due to changes in the physical properties of the plating layer.

  Whether or not the B-type element is contained in the plating layer can be detected by ICP analysis of the plating layer remaining after dissolving only the base iron. In addition, confirmation of whether or not they are in a metal state uses X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES), and a peak is present at a position corresponding to the valence of zeroization of each element. It can be determined by whether or not it exists. With regard to the presence of a peak, it is determined that there is a peak that can be confirmed from the baseline based on a sample that does not contain the element.

  XPS performs a wide area mapping of a maximum of 50 mm × 18 mm using, for example, JPS-9200 manufactured by JEOL. For AES, for example, JAMP-9500F manufactured by JEOL is used to identify elements with a resolution of 1 μm. For example, a metal element of 1 μm can be identified in a relatively wide range by cutting out a cross section including the base steel plate and the plating layer and combining an optical microscope and AES.

  In JAMP-9500F, since a standard sample of the intermetallic compound to be investigated can be investigated in advance and the chemical state of the analyzed metal element can be identified, the compound detected by the optical microscope can be used for high energy resolution by JAMP-9500F. By performing the waveform separation calculation from the Auger spectrum, it is possible to distinguish compounds having different chemical states and to identify the ratio.

(3-7) Treatment on plating layer Furthermore, it is also possible to perform a known treatment on the plating layer. For example, performing various chemical conversion treatments to improve corrosion resistance, painting, various chemical conversion treatments to improve paint adhesion, painting and film sticking to ensure design properties, etc. Although the influence is also conceivable, the effect of the present invention between the base steel plate and the plating layer is not lost. Rather, depending on the coating or film, it can effectively work to improve the magnetic shielding property in a high magnetic field. Conceivable.

4). Next, a method for manufacturing a magnetic shield steel sheet according to the present invention will be described.

(4-1) Manufacturing method of base steel plate The base steel plate of the magnetic shield steel plate according to the present invention is similar to a known electromagnetic steel plate, in which the steel is melted in a converter and is made into a slab by continuous casting, and then hot rolled. It is obtained by performing cold rolling and finish annealing.

  In addition to these steps, passing through the steps applied to known electromagnetic steel sheets such as hot-rolled sheet annealing, intermediate annealing during cold rolling, and decarburization annealing does not impair the effects of the present invention. In particular, when the crystal grain size of a hot-rolled annealed sheet is increased by annealing the hot-rolled sheet at a high temperature, the texture and crystal grain size after cold-rolled annealing are preferably changed to improve the magnetic shielding properties in a high magnetic field. To do.

  In addition, fine precipitates such as AlN and MnS formed according to the manufacturing conditions inhibit crystal grain growth and domain wall movement, and lower the magnetic shielding properties in a high magnetic field. In order to make these fine precipitates harmless, additive elements used in the known manufacturing process of electrical steel sheets, slab heating at low temperature, slow cooling technology after annealing, and the like can be used as appropriate.

  The manufacturing conditions for such a mother steel sheet may be appropriately selected from the manufacturing conditions that preferably control known magnetic properties (magnetic flux density, iron loss).

  In the case where the mother steel plate contains a type A element, it is important in the present invention to control the residence time and dew point in the temperature range of 600 to 800 ° C. during the temperature raising process of finish annealing in the above process. It is. As a result, the A-type element is significantly concentrated on the surface of the steel plate immediately before plating, and as a result, the A-type element is easily mixed into the transition region.

  Since the details of the mixing into the transition region will be described in the section of the plating conditions described later, here, the description will focus on the control of the surface state of the base steel plate in finish annealing.

  The high Si, high Al content steel material that is the base steel plate of the magnetic shield steel sheet according to the present invention generally forms a dense Si-based oxide film or Al-based oxide film (external oxide film) on the surface by heat treatment, and the surface Reactivity at is reduced. On the other hand, depending on the heat treatment conditions, it is known that an internal oxide layer (internal oxide region) formed by dispersing fine and complicated oxides in the steel material is formed.

  External oxidation is particularly from the viewpoint of plating adhesion and non-plating, while internal oxidation is because the oxide in a complex form in the Fe phase of the mother steel plate inhibits domain wall movement and degrades magnetic shielding properties. Each should be avoided.

  In the base steel plate containing the A-type element with the content specified in the present invention, the residence time in the temperature range of 600 to 800 ° C. in the temperature raising process of finish annealing is set to 3 seconds or more, and the dew point is set to 15 ° C. or less. When finish annealing is performed, the A-type element is concentrated on the surface of the mother steel plate, and at the same time, external oxidation and internal oxidation can be avoided.

  The reason is considered as follows. That is, the diffusion of the A-type element sufficiently occurs at 600 ° C. or higher, and the solid solubility of the A-type element in the Fe phase is small at 800 ° C. or lower. Segregation and segregation of Fe phase to grain boundaries are promoted.

  On the other hand, the temperature of 600 ° C. or higher is also a temperature range where remarkable oxidation of the mother steel plate starts, and the above-mentioned oxide may be formed on the surface and the Fe phase grain boundary before sufficient segregation of the seed A element occurs. High nature. In order to prevent this, it is effective to reduce the dew point in a temperature range of 600 ° C. or higher and to secure a time for sufficient segregation of the A-type element while suppressing oxidation.

  The holding time for this is 3 seconds or more, preferably 5 seconds or more, and more preferably 8 seconds or more. Of course, BAF annealing (annealing by a batch annealing furnace) or the like may be applied for 1 minute or longer, or even 10 minutes or longer.

  Moreover, the atmospheric dew point in this temperature range is 15 degrees C or less, Preferably it is 5 degrees C or less, More preferably, it is -5 degrees C or less.

  The heat treatment conditions at 800 ° C. or higher are not particularly limited. In normal BAF annealing, it is difficult to make the temperature 800 ° C. or higher from the viewpoint of seizure, but in continuous annealing, finish annealing at 1000 ° C. or higher is also generally performed.

  In the present invention, if a sufficient amount of seed A element is concentrated on the surface under the above conditions up to 800 ° C., external oxidation and internal oxidation of the mother steel plate are also suppressed, and therefore 800 ° C. or higher. The dew point of the atmosphere is not particularly limited.

  Depending on the chemical composition of the base steel sheet, the transformation behavior described above, and the processes prior to cold rolling, it is possible to select the temperature and time so that the crystal grain size of the base steel sheet becomes larger than 50 μm. It is preferable for the shielding property.

(4-2) Plating conditions Next, the plating conditions for the magnetic shield steel sheet according to the present invention will be described.

  The intermediate treatment for mixing the A-type element into the transition region defined in the present invention can be performed by various methods. For example, as described above, a method of interposing plating containing a relatively high concentration of the A-type element as intermediate plating before plating, applying a substance containing the A-type element to the steel plate before plating, Examples include a method in which elements are diffused by heat treatment, and a transition region is formed by mixing a material containing plating, a type A element, and Fe of a mother steel plate. These methods may be performed by appropriately adopting known conditions.

  In addition, as a plating means, a known surface treatment method such as hot dipping, electroplating, thermal spraying or the like can be used. However, in order to uniformly perform plating at a thickness within the above range and at a low cost, electroplating is possible. Is the best. Also, in the method of exposing to a high temperature state during plating such as hot dipping, an intermetallic compound consisting of a metal element to be plated and a metal element contained in the base steel plate is easily generated, and this intermetallic compound has a magnetic shielding property. And may adversely affect plating adhesion.

  Furthermore, in hot dip plating, thermal strain is generated during cooling, which may adversely affect the improvement of magnetic shielding properties by controlling the stress generated between the plating and the base steel plate, while in electroplating this stress Is very small. Also from this point, electroplating is preferable as a plating means for the magnetic shield steel sheet according to the present invention.

  Next, the behavior at the time of plating will be described focusing on the phenomenon in electroplating that is most suitable for the present invention in relation to the characteristics of the mother steel plate.

  In addition, the electroplating conditions in this invention do not need to be special, What is necessary is just to apply a well-known plating bath, bath composition, temperature, current density, and time. For example, in the above-described Zn-based plating preferable for the present invention, various plating baths such as an alkaline bath and an acidic bath can be applied to the plating bath. Moreover, plating methods such as an electroless method can also be used. Considering cost, application, and versatility, Zn plating using hydrochloric acid, sulfuric acid, boric acid bath based acid bath is optimal.

For example, a cold-rolled steel sheet is subjected to electrolytic degreasing treatment with alkali, followed by water washing and pickling treatment (sulfuric acid concentration 70 g / L, 25 to 40 ° C., immersion for 5 seconds), and then Zn concentration: 1.0 mol / L (0 .3 to 1.8 mol / L), if necessary, Ni concentration: 0.01 to 0.2 mol / L, pH: 1.9 (1.0 to 4.0), bath temperature: 50 ° C. (40 to 65) C.) sulfuric acid bath, current density: 50 A / dm ² (20 to 150 A / dm ² ) Performing electroplating is exemplified.

  Although “electroplating” itself applied in the present invention is not novel, it is preferable to be conscious of formation of a transition region in order to preferably exhibit magnetic shielding properties in a high magnetic field.

  The transition region is formed in the process where Fe is dissolved from the steel plate at the initial stage of electroplating and re-deposited together with the plated metal on the base steel plate. For this reason, basically, in the initial stage of plating, the dissolution of Fe occurs rapidly, and the thickness of the transition region increases under the condition that the electrodeposition of the plated metal occurs slowly.

  In general plating, there is no meaning to bother the base steel plate, and since the plating metal is positively electrodeposited, the surface of the base steel plate is covered with the plating metal before sufficient dissolution of Fe occurs. The thickness of the transition region becomes very narrow. Although it is possible to create a transition region having a wide thickness only by adjusting the plating conditions, the formation behavior of the transition region in consideration of the surface state of the steel sheet before plating will be described.

  When external oxidation is suppressed or an internal oxide layer is formed, the Fe metal phase is exposed on the surface in the region where the oxide is not exposed on the surface. When the surface of the base steel sheet is in such a state, the electroplating of the plating metal onto the surface of the base steel sheet during electroplating and plating of the seed A element concentrated on the surface of the base steel sheet (Fe metal atom) and the Fe phase Dissolution in the bath is likely to proceed. And the Fe atom and A-type element atom which melted in the plating bath are re-deposited on the surface of the mother steel plate together with the plating metal.

  For this reason, even if it does not aim at plating, it will contain a considerable amount of Fe atoms and A-type elements, and its melting and re-deposition will be a transition region where the change in Fe concentration from the base steel plate to the plating layer becomes a gradual transition region. Act.

  Furthermore, Fe on the outermost surface of the mother steel sheet dissolves in the plating bath, thereby reducing minute irregularities on the surface of the mother steel sheet and improving magnetic shielding performance in a high magnetic field by reducing inhibition of domain wall movement in the magnetic field. It is possible to make it.

  That is, when a suitable steel plate is manufactured, the magnetic shield steel plate according to the present invention having a transition region containing the A-type element can be obtained without special plating conditions.

  As described above, in order to obtain the above-described action in electroplating, external oxidation and internal oxidation before plating are avoided, but the base steel sheet of the present invention is a high Si, high Al component system. For this reason, not a few of these oxidations may occur.

  In this case, it is effective to perform pickling or electrolytic pickling after finish annealing and before electroplating, and most of the A-type elements concentrated on the surface of the mother steel plate are oxidized. Since it adheres again to the surface of the mother steel plate after the object is removed, the adverse effect on the magnetic shielding properties is not so great.

  In particular, the inner oxide layer, unlike the outer oxide film, can be removed relatively easily by pickling, and removing this improves the magnetic shielding properties at high magnetic fields, thus increasing the pickling cost. However, there is a meaning to implement.

  Steel having the chemical composition shown in Table 1 (remaining Fe and impurities, unit: mass%) was vacuum-melted to form a slab by continuous casting, followed by hot rolling to obtain a 4.0 mm hot-rolled steel sheet. In addition, the underline in Table 1 shows that it is outside the scope of the present invention.

  The hot-rolled steel sheet was pickled with sulfuric acid at 40 ° C., then cold-rolled to a thickness of 0.80 mm, and subjected to finish annealing under the conditions shown in Table 2 to obtain a base steel sheet. In addition, the thickness of the internal oxide layer of the steel sheet before and after pickling, the cross-section of the steel sheet was observed 3000 times with a high resolution SEM at 10 times the reflected electron composition image (COMPO image), and the average of the observed oxide layer thickness ,It was measured.

  Then, the pickling conditions before plating, presence / absence of intermediate treatment, plating means, plating type, plating layer thickness, and transition region thickness were changed to obtain a magnetic shield steel plate. It is very difficult for those skilled in the art to manufacture a large number of plated steel sheets as a business to control the plating thickness and the thickness of the transition region within the intended range with each plating means. It is not a thing.

  Then, it washed with water and the chemical conversion process by CT-E300N by Nippon Parkerizing Co., Ltd. was performed.

  The following characteristics and characteristics were examined for the samples thus produced.

(1) Plating layer thickness GDS investigated the concentration profile from the plating surface and measured.

(2) Transition region thickness Using a Rigaku GDA750, the thickness was measured by analyzing at an anode diameter of 4 mm and a pressure of 3 hPa.

(3) Presence of B-type element in the metal state in the plating region Measured by using X-ray photoelectron spectroscopy (XPS) based on whether or not a peak exists at a position corresponding to the valence of zeroization of each element. did.

(4) Presence / absence of intermetallic compounds in the plating region Measured by electron diffraction.

(5) Crystal grain size The crystal grain size was measured by the cutting method defined in JIS G0551 Appendix C.

(6) Chemical conversion treatment The salt spray test described in JIS Z2371: 2000 was performed, and the evaluation was made based on whether white rust was generated after 24 hours.

(7) Magnetic shielding property Using a test piece cut into a 55 mm square, measurement was performed with a single-plate magnetic test frame and a DC self-recording magnetometer.

  As described above, the magnetic shield property at a high magnetic field targeted by the present invention is a magnetic flux density region of 0.1 T or more as described above, but the magnetic flux inside the magnetic shield material is practically uniform. However, since concentration of magnetic flux also occurs, the permeability in a higher magnetic flux density region is often used as an index. In the present invention, the effect of the present invention is determined by the permeability at 1T. If the superiority of the present invention can be confirmed by this value, superior shielding performance can be obtained in a wide magnetic flux density region from 0.1 T or more to exceeding 1 T.

  The high magnetic field magnetic shielding property (1T magnetic permeability) is not related to the effect of the present invention by the A-type element, but the contained components other than the A-type element in the base steel plate, the crystal grain size and crystal orientation of the base steel plate, The absolute value also changes depending on the plating thickness. For this reason, in this example, while the conditions other than the effects of the present invention by the A-type element were made substantially the same, the influence on the magnetic shielding property by the A-type element was evaluated, and the improvement allowance was 0.0004 H / m or more. Those that were passed.

(8) Plating adhesion The test piece provided with the above-described polyester-based coating was cooled to −20 ° C. or lower in a freezer, and the cut surface was cut using a power shear at −20 ° C. with a magnifying glass. It observed using and observed and measured the peeling width of the plating layer. The smaller the peeling width, the better. The peeling width: 1.0 mm or less was determined to be acceptable.

  The results are summarized in Table 2. For example, even if the plating thickness and the thickness of the transition region are manufactured under the “same conditions”, the measured values may not completely match, but this is a problem of manufacturing accuracy and measurement error. is there. In addition, the underline in Tables 1 and 2 indicates that the result is out of the range defined in the present invention or the result is not good.

  Hereinafter, each sample No. The results of 1 to 73 will be described.

  Sample No. Nos. 1 to 22 are samples Nos. 1 and 2 whose reference material is steel A having a component of 3.1% Si-0.6% Al. 1 is an example using a mother steel plate in which the A-type element is changed. According to the value of the formula (1), the improvement in characteristics from the reference material can be confirmed.

  Sample No. In 9, 11, 17, and 21, the value of the expression (1) is excessively high, and the margin for improving the magnetic shielding property in a high magnetic field is rather small. In these materials, the thickness of the transition region is reduced at the same time, and the surface concentration of the type A element in the finish annealed plate before plating is excessive, which may inhibit the dissolution of Fe in the initial plating process. There is. Moreover, the tendency for plating adhesion to decrease is clear.

  In particular, no. No. 15, the transition region is very narrow, and a film-like region in which the A-type element is concentrated is formed at the interface between the mother steel plate and the transition region, so that the improvement of the magnetic shielding property in a high magnetic field is not seen. In addition, the plating adhesion is significantly reduced.

  In addition, the seed A element which is a surface organization element is segregated at the grain boundary at the same time inside the steel sheet and inhibits crystal grain growth. In the data containing excessively, the crystal grain size is not sufficiently coarsened, and there is a tendency for the magnetic shielding property to decrease in a high magnetic field. In No. 5, this tendency is remarkable, and the absolute value of the magnetic shielding property at a high magnetic field is remarkably lowered, and the effect of the present invention is impaired.

  Sample No. Nos. 23 to 25 use steel B, which is a medium Si component, as a reference material, and Nos. 26 to 28 have confirmed the influence of the A-type element contained in the base steel plate using steel C, which is a high Al component, as a reference material. Sample No. The result similar to 1-22 can be confirmed.

  Sample No. Nos. 29 and 30 use steel D, which is a low Si component, as a reference material. Nos. 31 and 32 confirm the influence of the A-type element contained in the base steel plate, using steel E, which is a low Al component, as a reference material.

  In the component system of this reference material, in addition to insufficient magnetic shielding properties in a high magnetic field, the growth of crystal grains of the base steel plate is not preferable, and type A on the surface of the base steel plate in finish annealing Concentration of elements does not easily occur, and a transition region is hardly formed by ordinary plating. For this reason, the effect of improving the magnetic shielding property in a high magnetic field cannot be obtained. Although it seems that it is possible to develop magnetic shielding properties in a high magnetic field by finely controlling the heat treatment conditions and sufficiently coarsening the crystal grain size and applying special plating after applying intermediate treatment, In view of industrial productivity and cost, these component systems are outside the scope of the present invention.

  Sample No. Nos. 33 to 53 are based on the concentration control of the A-type element on the steel sheet surface in the finish annealing and the effect thereof. Sample No. containing no type A element in the mother steel plate As a matter of course, in 33-39, even if the finish annealing conditions are controlled, the effect of improving the magnetic shielding property in a high magnetic field cannot be obtained.

  On the other hand, the sample No. containing a Class A element in the mother steel plate. In 40-53, by making finish annealing conditions in the range of the present invention, the value of the formula (1) becomes preferable, and the improvement of the magnetic shielding property in a high magnetic field from the reference material appears clearly.

  Sample No. Nos. 54 to 56 are obtained by heat treating a steel plate after electroplating at 400 ° C. to form an intermetallic compound in the plating region. Usually, such a heat treatment is not performed practically with an electroplated steel sheet, but in this example, it was performed in order to evaluate the influence of an intermetallic compound.

  Sample No. Nos. 54 to 56 were not subjected to heat treatment (no intermetallic compound was present). Compared with 26-28, it turns out that the absolute value of the magnetic shielding property in a high magnetic field falls by an intermetallic compound.

  Sample No. Nos. 57 to 61 are obtained by mixing the A-type element into the transition region by an intermediate treatment before plating, that is, Ni plating, Sn plating or phosphate treatment. Although this means requires an intermediate processing cost, it can be seen that the effect of improving the magnetic shielding property in a high magnetic field can be obtained even in a steel plate that does not contain a type A element in the base steel plate.

  Sample No. According to the comparison of 57 to 59, even when such an intermediate treatment is performed, the magnetic shielding property in a high magnetic field is improved by mixing the A-type element into the transition region from the side of the mother steel plate containing the A-type element. It can be seen that the effect is added.

  Sample No. 62-67 have confirmed the effect in the plating containing the A-type element. It can be seen that if the plating region satisfies the present invention, a magnetic shielding property in a high magnetic field sufficiently exceeding the reference material can be obtained.

  Sample No. 68 to 73 are examples particularly focusing on hot dipping. In these, since the thickness of the plating layer that causes stress generation, which is the point of the present invention, cannot be made as thin as electroplating, for example, Sample No. A simple comparison based on 1 is considered impossible. For this reason, sample no. The effect of the present invention was confirmed using 68 as a reference material.

  Sample No. Nos. 71 to 73 are sample Nos. Simulating a low quality ingot. A plating bath is used in which each of the 68 to 70 hot dip plating baths contains B element in a total amount of 1%. This plating bath is indicated as “Zn +” in Table 2. From these results, even with hot dip plating in which the thickness of the plating layer is thick and it is difficult to avoid the formation of an intermetallic compound, the effect of improving the magnetic shielding property in a sufficiently high magnetic field can be obtained, and the B element is preferred for the present invention. The tendency which is not a thing can be confirmed.

Claims (7)

% By mass
Si: 1.5-4.0%
Al: 0.1 to 3.0%,
Mn: 0.1 to 2.4%,
A mother steel plate having a chemical composition which is the balance Fe and impurities;
One or more plating layers formed on at least one surface of the mother steel plate;
A transition region formed between the one surface and the plating layer,
The transition region is a region where the Fe concentration in the thickness direction of the base steel plate changes from 90% to 10% of the Fe concentration at the center position in the thickness direction of the base steel plate,
A magnetic shield steel plate that satisfies the following formula (1).
X / Y ≧ 1.4 (1)
However, the code | symbol X in (1) Formula is the maximum value (mass%) of 1 or more types of total density | concentration of P, Sn, Sb, Ni, and Mo in the said transition area | region, and the code | symbol Y is the said in the said mother steel plate. The total concentration (mass%) of one or more of P, Sn, Sb, Ni, and Mo. % By mass
Si: 1.5-4.0%
Al: 0.1 to 3.0%,
Mn: 0.1 to 2.4%,
One or more of P, Sn, Sb, Ni, and Mo: 0.01 to 0.20% in total,
A mother steel plate having a chemical composition which is the balance Fe and impurities;
One or more plating layers formed on at least one surface of the mother steel plate;
A transition region formed between the one surface and the plating layer,
The transition region is a region where the Fe concentration in the thickness direction of the base steel plate changes from 90% to 10% of the Fe concentration at the center position in the thickness direction of the base steel plate,
A magnetic shield steel plate that satisfies the following formula (1).
X / Y ≧ 1.4 (1)
However, the code | symbol X in (1) Formula is the maximum value (mass%) of 1 or more types of total density | concentration of P, Sn, Sb, Ni, and Mo in the said transition area | region, and the code | symbol Y is the said in the said mother steel plate. The total concentration (mass%) of one or more of P, Sn, Sb, Ni, and Mo. The magnetic shield steel plate according to claim 1 or 2, which satisfies the following formula (2).
X / Z> 1.0 (2)
However, the symbol Z in the formula (2) is the maximum value (mass%) of one or more total concentrations of P, Sn, Sb, Ni, and Mo in the base steel plate. In a slab having a chemical composition that is Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, the balance Fe and impurities in mass%, A method of manufacturing a magnetic shield steel sheet that performs hot rolling, cold rolling, finish annealing, and plating treatment,
The manufacturing method of the magnetic shield steel plate of Claim 1 which performs the process which adheres 1 or more types of elements among P, Sn, Sb, Ni, and Mo to the surface of the steel materials which are intermediate products in the said process. In mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, P, Sn, Sb, Ni, Mo One or more of them are contained in a total of 0.01 to 0.2%, and the slab having a chemical composition that is Fe and impurities is subjected to hot rolling, cold rolling, finish annealing, and plating treatment. A method of manufacturing a shield steel plate,
The manufacturing method of the magnetic shielding steel plate of Claim 2 which performs the process which adheres 1 or more types of elements among P, Sn, Sb, Ni, and Mo to the surface of the steel materials which are intermediate products in the said process. In mass%, Si: 1.5-4.0%, Al: 0.1-3.0%, Mn: 0.1-2.4%, P, Sn, Sb, Ni, Mo One or more of them are contained in a total of 0.01 to 0.2%, and the slab having a chemical composition that is Fe and impurities is subjected to hot rolling, cold rolling, finish annealing, and plating treatment. A method of manufacturing a shield steel plate,
The magnetic shield steel sheet according to claim 2, wherein a residence time in a temperature range of 650 to 800 ° C in the temperature raising process of the finish annealing is set to 3 seconds or more, and a dew point of an atmosphere in the temperature range is set to 15 ° C or less. Manufacturing method.   The manufacturing method of the magnetic shield steel plate in any one of Claims 4-6 whose said plating process is electroplating.