JP6677082B2 - Magnetic shield steel sheet and method of manufacturing the same - Google Patents

Description

  The present invention relates to a magnetic shield steel sheet and a method for manufacturing the same.

  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 to the outside of a specific space or for preventing the effect of magnetic flux from the outside of a specific space. The characteristics required for the magnetic shield material differ depending on the magnetism to be shielded and the frequency of the electromagnetic wave. When shielding magnetism of 1 Hz or less, a high magnetic permeability is required for the magnetic shield material.

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

  The magnetization process in the vicinity of the magnetic flux density of 1T is mainly due to domain wall movement. Therefore, in order to increase the magnetic permeability of the steel sheet, it is necessary to increase the crystal grain size to reduce the grain boundaries, reduce precipitates, reduce the compressive stress in the magnetization direction, reduce the residual strain, It is effective to reduce the unevenness of the magnetic field and to increase <100>, which is the direction of easy magnetization of Fe, in the magnetization direction (or to decrease the angle between the magnetization direction and <100>).

  Magnetic shielded steel sheets are often required to have corrosion resistance as well as ordinary steel sheets, in addition to magnetic shielding properties. Patent Literatures 1 to 9 propose a number of magnetically shielded steel sheets whose surfaces are plated with Zn.

From the viewpoint of plating properties, there is a problem in that a large amount of Si contained in the Zn-plated magnetic shield steel sheet, particularly in the base steel sheet, is contained. However, in order to secure magnetic shielding properties in a low magnetic field of a geomagnetic level (magnetic field is less than 10 ⁻⁵ T) such as a magnetic shielding steel sheet for electronic parts, it is not necessary to include a large amount of Si in the first place, and particularly large No problem has occurred. Rather, the content of Si as a solid solution strengthening element for increasing strength in applications such as heat shrink bands is limited.

  Numerous studies have been made on Zn-based plating on high-Si content steels on high-strength steel sheets, rather than on magnetically shielded steel sheets. In the field of high-strength steel sheets, electrolytic treatment or pickling treatment before Zn-based plating is performed as disclosed in Patent Documents 10 to 14 in order to avoid plating unevenness and reduction in plating adhesion unique to high Si content steel. Or Ni plating is performed in advance as disclosed in Patent Documents 15 and 16.

  When these magnetic shield steel plates are used, they are generally installed as another members between other structural members or functional members. However, in some applications, there is a demand that the magnetically shielded steel sheet itself has the function of an exterior material or an interior material.

  In particular, in the application of linear motor cars, which are attracting attention for practical use in recent years, not only is it necessary to secure magnetic shielding properties, but there is also a strong demand for lighter vehicle bodies from the viewpoint of high speed and energy saving, and furthermore, there is a demand for passenger car space. There is also a strong demand for integration of members from the viewpoint of securing and reducing costs.

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

JP-A-10-251891 JP-A-11-106876 JP 2000-59086 A JP 2000-91113 A JP 2000-290759 A WO 99/023268 pamphlet JP 2003-171748 A JP-T-2004-516384 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-6-306677 JP-A-8-165593 JP 2000-303143 A WO02 / 054435 pamphlet JP 2010-43291 A

  As described above, a magnetically shielded steel sheet on which a Zn-based plating for enhancing corrosion resistance is applied on a steel sheet in consideration of the magnetic shielding property and an organic film for further improving the design property is formed by appropriately combining various known techniques. If it is, it is considered that it can be manufactured.

  However, taking into account the magnetic shielding properties in high magnetic fields such as the above-mentioned linear motor car applications, technology development focusing on the magnetic shielding properties and plating adhesion when using high Si content steel as the base steel sheet, Not done enough.

  An object of the present invention is to provide a magnetic shield steel sheet which uses a high Si content steel as a base steel sheet and has been subjected to Zn-based plating for imparting corrosion resistance. To provide a magnetically shielded steel sheet and a method for manufacturing the same, which can further improve the design.

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

  However, well-known magnetic shielding materials for low magnetic fields such as terrestrial magnetism cannot obtain sufficiently satisfactory characteristics, and the importance of material development specialized for such prerequisites has been recognized. Then, from the viewpoints of corrosion resistance and cost, Zn-based plating is applied to the surface of the base steel plate made of high Si content steel manufactured to secure sufficient magnetic shielding performance in a high magnetic field, thereby improving magnetic shielding performance and plating adhesion. Considered in detail.

  However, when the Zn-based plating is applied directly on the base steel sheet, a certain degree of plating adhesion can be obtained by adjusting the conditions of known techniques such as electrolysis and pickling, but the magnetic field in a high magnetic field can be obtained. The shielding properties were not so different from the conventional materials, and satisfactory results could not be obtained.

  Although the cause is not clear, the slight difference in physical properties (deformation behavior) between the base steel sheet and the Zn-based plating causes the bending tension in the coil production process to overlap with the passing tension, and the interface between the base steel sheet and the Zn-based plating It is conceivable that stress was generated on the base steel sheet, thereby decreasing the magnetic permeability of the base steel sheet, which deteriorated the magnetic shielding property in a high magnetic field.

  The present inventors have focused on the effect of plating thickness and plating structure on magnetic shielding properties in a high magnetic field in order to solve the above-mentioned problems, and appropriately adjust the concentration variation from the base steel sheet to the plating layer due to Zn-based plating. It was found that sufficient magnetic shielding properties can be ensured by controlling the magnetic field. In addition, the present inventors have found that by controlling the fluctuation of the concentration from the base steel sheet to the plating layer in this manner, a favorable influence is also exerted on the plating adhesion.

  Furthermore, the present inventors have found that applying Ni-based plating before Zn-based plating has a more favorable effect on magnetic shielding properties and plating adhesion than when only Zn-based plating is applied. . This is considered to be because Ni-based plating has a greater effect on stress generation at the interface than Zn-based plating.

  The present invention completed based on these new findings is as listed below.

(1) In terms of mass%, Si has a chemical composition of 1.5 to 4.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 2.4%, the balance being Fe and impurities. Base steel sheet, formed on at least one surface of the base steel sheet, a magnetic shield steel sheet comprising one or more plating layers,
A transition region in which the Fe concentration changes from 75% to 25% of the Fe concentration at the center position in the thickness direction of the base steel sheet from the base steel sheet side toward the plating layer side;
A magnetically shielded steel sheet wherein the thickness of the transition region is 0.2 μm or more.

  (2) The magnetic shield steel sheet according to item 1, wherein the plating layer has a multilayer structure.

  (3) The magnetic shield steel sheet according to (1) or (2), wherein the transition region has no intermetallic compound.

  (4) The magnetic shield steel sheet according to (2) or (3), wherein at least one of the plating layers is a Zn-based plating layer.

  (5) In any one of the above items 2 to 4, wherein at least one of the plating layers has no metallic state of Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al. The magnetically shielded steel sheet as described.

  (6) The magnetic shield steel sheet according to any one of (2) to (5), wherein the intermediate plating layer among the plating layers is a Ni-based plating layer.

  (7) The magnetic shield steel sheet according to any one of Items 2 to 6, wherein the half-value thickness of the concentration distribution of the metal element forming the intermediate plating layer among the plating layers is 0.2 to 2.0 μm.

  (8) The magnetic shield steel sheet according to any one of Items 1 to 7, wherein the base steel sheet has a crystal grain size of 50 to 200 µm.

  (9) By mass%, a slab composed of 1.5 to 4.0% of Si, 0.1 to 3.0% of Al, 0.1 to 2.4% of Mn, and the balance of Fe and impurities is heated. 9. The method for producing a magnetic shielded steel sheet according to any one of 1 to 8, wherein the surface is subjected to a plating treatment after performing cold rolling, cold rolling and finish annealing, wherein the maximum temperature of the finish annealing is 950 ° C. The above is a method for manufacturing a magnetic shield steel sheet.

  (10) The method for producing a magnetically shielded steel sheet according to item 9, wherein the dew point of the atmosphere at 650 ° C to 800 ° C during the temperature rise process of the finish annealing is more than −10 ° C and 40 ° C or less.

  (11) The method for producing a magnetic shielded steel sheet according to (9) or (10), wherein pickling is performed after the finish annealing and before the plating treatment.

  (12) The method for producing a magnetic shielded steel sheet according to any of items 9 to 11, wherein the plating treatment is electroplating.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a magnetically shielded steel sheet for a high magnetic field having a function as an exterior material or an interior material such as corrosion resistance and designability, which can achieve both a magnetic shielding property and a plating adhesion in a high magnetic field. .

  As a result, it is possible to secure space and reduce costs as compared with the related art in which the interior material, the magnetic shield material, and the exterior material are separately used.

  Further, by using the magnetic shielded steel sheet 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 a relatively large amount of solid material such as Si, Al, and Mn can be contained. Since the solution strengthening element increases the strength of the steel sheet, it is possible to reduce the thickness of the constituent members, and it is also possible to increase the speed and energy saving by reducing the weight of the vehicle body of the moving body.

  Hereinafter, embodiments for implementing the present invention will be described. In the following description, “%” regarding the chemical composition means “% by mass” unless otherwise specified, and “magnetic shielding property” means “high magnetic field, for example, 0.1 T or more,” unless otherwise specified. Magnetic shield in high magnetic field ".

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

  The base steel sheet is a main element for ensuring the magnetic shielding property, which is one of the features of the magnetic shield steel sheet according to the present invention. The base steel sheet has a chemical composition consisting of Si: 1.5 to 4.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 2.4%, the balance being 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 magnetic permeability, and preferably acts on magnetic shielding. Further, Si increases the transformation temperature of the base steel sheet from the α phase to the γ phase, and enables annealing at a higher temperature to increase the crystal grain size. Increasing the crystal grain size increases the maximum magnetic permeability and improves the magnetic shielding properties. Further, Si not only effectively acts as a solid solution strengthening element to increase the strength of the base steel sheet, but also has the effect of increasing the magnetic permeability by bringing the saturation magnetostriction constant close to 0 and improving the magnetic shielding properties. It is an element that should be actively contained.

  If the Si content is less than 1.5%, the crystal grains will not be sufficiently coarsened unless annealing is performed for a long time at a temperature at which transformation does not occur, which is disadvantageous in terms of manufacturing cost such that continuous annealing cannot be applied. Therefore, the 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, more preferably Is at least 2.1%, even more preferably at least 2.6%.

  On the other hand, if the Si content exceeds 4.0%, the base steel sheet is embrittled, the saturation magnetic flux density is further reduced, and the increase in the magnetic shielding properties is saturated. Therefore, the Si content is 4.0% or less, preferably less than 3.8%, and more preferably less than 3.6%.

(1-2) Al: 0.1 to 3.0%
Al, like Si, is positively contained, like Si, in order to raise the transformation temperature of the base steel sheet from the α phase to the γ phase. On the other hand, when Al combines with N in steel and precipitates as AlN, it inhibits crystal grain growth and domain wall movement and lowers magnetic permeability.

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

  When the Al content increases, the size of the AlN precipitates becomes coarse, and the number of AlN precipitates decreases, so that the adverse effect on the magnetic shielding properties can be reduced. Therefore, the Al content is preferably at least 0.3%, more preferably at least 0.6%. Further, in order to sufficiently obtain the coarsening of crystal grains due to an increase in the transformation temperature, the Al content is more preferably 0.9% or more, and still more preferably 1.2% or more.

  On the other hand, Al reduces the saturation magnetic flux density similarly to Si, and embrittlement of the base steel sheet becomes a problem when contained in a large amount. Therefore, the Al content is 3.0% or less, preferably less than 2.8%, and more preferably less than 2.6%.

(1-3) Mn: 0.1 to 2.4%
When Mn combines with S in steel and precipitates as MnS, it impairs crystal grain growth and domain wall movement and lowers 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.

  As the Mn content increases, the size of the MnS precipitates becomes coarse, and the number of MnS precipitates decreases, thereby reducing the adverse effect on the magnetic shielding properties. Therefore, the Mn content is preferably at least 0.15%, more preferably at least 0.3%.

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

  The base steel sheet of the magnetic shield steel sheet according to the present invention has the above chemical composition, and is composed of the balance Fe and impurities. The effect of the present invention is not lost even if an element known to be contained in an electromagnetic steel sheet is contained in a known range instead of Fe. Examples of these elements include C, N, S, P, Cr, Ni, Cu, Sn, B, Ti, Nb, Mo, Sb, Ca, Mg, and REM. Hereinafter, these elements, which exert a relatively strong influence on the effects of the present invention, will be described.

(1-4) C: 0.0040% or less C may form carbides to deteriorate magnetic shielding properties. Further, if magnetic aging occurs, the magnetic shielding property also deteriorates, so that it is preferable to lower the C content. Therefore, the 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. Is big. In the magnetic shielded steel sheet according to the present invention, since non-metallic precipitates such as carbides are not used as a main means of increasing the strength, there is no merit of intentionally containing C, and the C content is preferably small. Therefore, the C content is preferably 0.0020% or less, and more preferably 0.0015% or less. If a technique such as electrodeposition is used, it can be reduced 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%.

(1-5) N: 0.0040% or less N, like C, deteriorates the magnetic shielding property due to nitride formation and magnetic aging. Therefore, the N content is preferably 0.0040% or less. The N content is preferably as low as possible to avoid the deterioration of the magnetic shielding property. When the N content is 0.0027% or less, the adverse effect on the magnetic shielding property due to magnetic aging and nitride formation can be sufficiently avoided. The N content is more preferably 0.0022% or less, and even more preferably 0.0015% or less. If a technique such as electrodeposition is used, it can be reduced 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%.

(1-6) S: 0.020% or less Since S may form sulfides to deteriorate the magnetic shielding property, the S content is preferably low. The S content is preferably 0.020% or less, more preferably 0.0040% or less, still more preferably 0.0020% or less, and most preferably 0.0010% or less. The S content may be 0%.

(1-7) P: 0.5% or less P is not only controlled in content for the purpose of strength adjustment, suppression of oxidation, nitridation, and carburization during production, but also more particularly segregates at grain boundaries before cold rolling. In such a case, it is known that the texture is improved to improve the magnetic flux density, and the content can be 0.001% or more. In a general practical steelmaking method, about 0.002% or more may be contained as an impurity. On the other hand, excessive addition makes the steel brittle and lowers the cold rolling property and the workability of the product, so the P content is preferably 0.5% or less, more preferably 0.3% or less. .

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

(1-9) Ni: 10% or less Ni is not only controlled in its content for the purpose of strength adjustment, corrosion resistance, and control of oxidation behavior during production, but is also known to improve particularly high frequency characteristics. 0.001% or more. In a practical steelmaking method in which scraps and the like are mixed, about 0.01% or more may be contained as an impurity. On the other hand, excessive addition increases the addition cost and lowers the magnetic properties. Therefore, the Ni content is preferably 10% or less, more preferably 3% or less.

(1-10) Cu: 0.2% or less Cu significantly lowers the saturation magnetic flux density Bs of the base steel sheet as a solid solution element. A decrease in the saturation magnetic flux density Bs leads to a decrease in the magnetic shielding property. For this reason, in the base steel sheet of the magnetic shield steel sheet according to the present invention, it is not necessary to intentionally contain Cu unless there is a special purpose. In a practical steelmaking method in which scraps and the like are mixed, about 0.01% or more may be contained as an impurity. Therefore, the Cu content is preferably 0.2% or less, more preferably 0.15% or less. On the other hand, it is known that the strength can be enhanced by the precipitation of Cu, and the like, and the base steel sheet of the magnetic shielded steel sheet according to the present invention can be appropriately used according to a known technique.

(1-11) Sn: 0.5% or less It is known that the content of Sn is controlled for the purpose of suppressing oxidation, nitridation, and carburization during production, and it is particularly known that the high-frequency characteristics are improved. 0.001% or more can be contained. In a practical steelmaking method in which scrap and the like are mixed, about 0.002% or more may be contained as an impurity. On the other hand, since excessive addition increases the addition cost and lowers the magnetic properties, the Sn content is preferably 0.5% or less, more preferably 0.3% or less.

(1-12) B: 0.01% or less B is not only controlled in content for the purpose of suppressing oxidation, nitridation and carburization during production, but also forms a complex oxide containing oxides and nitrides in particular. It is known that the magnetic properties can be improved by increasing the magnetic properties. On the other hand, excessive addition makes the steel brittle and lowers the magnetic properties. Therefore, the B content is preferably 0.01% or less, more preferably 0.005% or less.

(1-13) Ti: 0.0020% or less In addition to controlling the content of Ti for the purpose of adjusting the strength by the precipitates, particularly, forming a composite oxide containing oxides and sulfides to improve magnetic properties. It is known that it can be contained at 0.0001% or more. In a practical steelmaking method in which scrap and the like are mixed, the content may be about 0.0002% or more as an impurity. On the other hand, the Ti content is preferably 0.0020% or less, more preferably 0.0015% or less, because these precipitates hinder domain wall movement and significantly deteriorate magnetic shielding properties. is there.

(1-14) Nb: 0.0020% or less Nb, although precipitates such as NbC effectively act to increase the strength, but these precipitates hinder domain wall movement and greatly deteriorate magnetic shielding properties. There is no need to intentionally include it. Therefore, the Nb content is preferably 0.0020% or less, and more preferably 0.0010% or less. In a practical steelmaking method in which scrap and the like are mixed, the content may be about 0.0002% or more as an impurity.

(1-15) Mo: 0.0020% or less Mo is known to form a composite oxide containing oxides and carbides in particular to improve magnetic properties. Mo is contained at 0.0001% or more. Is possible. On the other hand, the Mo content is preferably 0.0020% or less, more preferably 0.0015% or less, because these precipitates hinder domain wall movement and significantly deteriorate magnetic shielding properties. is there.

(1-16) Sb: 0.5% or less Sb is not only controlled in content for the purpose of suppressing oxidation, nitridation and carburization during production, but is also known to improve particularly high frequency characteristics and the like. 0.001% or more can be contained. On the other hand, since excessive addition increases the addition cost and lowers the magnetic properties, the Sb content is preferably 0.5% or less, more preferably 0.3% or less.

(1-17) Ca: 0.050% or less Ca is known to form a composite oxide containing oxides and sulfides in particular to improve magnetic properties, and is contained at 0.0001% or more. It is possible. On the other hand, since these precipitates hinder domain wall movement and significantly deteriorate magnetic shielding properties, the Ca content is preferably 0.050% or less, more preferably 0.010% or less. is there.

(1-18) Mg: 0.050% or less The content of Mg is controlled for the purpose of suppressing oxidation, nitridation, and carburization during production, and in particular, forms a complex oxide containing oxides and sulfides. It is known that the magnetic properties can be improved by increasing the magnetic properties. On the other hand, since these precipitates may hinder domain wall movement and significantly degrade the magnetic shielding property, the Mg content is preferably 0.050% or less, more preferably 0.010% or less. is there.

(1-19) REM: 0.050% or less REM is known to form a composite oxide containing oxides and sulfides in particular to improve magnetic properties, and is contained at 0.0001% or more. It is possible. On the other hand, since these precipitates may hinder domain wall movement and significantly degrade the magnetic shielding property, the REM content is preferably 0.050% or less, more preferably 0.010% or less. is there.

(1-20) Balance The base steel sheet of the magnetic shield steel sheet according to the present invention has the above chemical composition, and the balance is Fe and impurities. Examples of impurities include those contained in raw materials such as ores and scraps, and those contained in the production process. The above-mentioned C, N, S, P, Cr, Ni, Cu, Sn, B, Ti, Nb, Mo, Sb, Ca, Mg, REM, etc. are not contained in the base steel sheet of the magnetic shield steel sheet according to the present invention. In some cases, it may be contained as an impurity.

2. Next, the metal structure of the base steel sheet will be described.

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

(2-1) Texture The texture of the base steel sheet is basically a texture in which the deviation between the in-plane magnetization direction of the base steel sheet and the <100> orientation that is the easy magnetization direction of the Fe crystal is small. Is preferred. Basically, the texture has a small number of {111} and a large number of {100} and {110}. In other words, in general, it has the same texture as the magnetic steel sheet whose magnetic flux density is controlled to be high.

  The base steel sheet of the magnetic shield steel sheet according to the present invention particularly has a high Si content and a non-transformed chemical composition, whereby the above-described texture is formed. Known magnetic shield steel sheets having a low Si content steel as a base steel sheet have a high {111}, which is not preferable for magnetic shield applications in a high magnetic field.

(2-2) Crystal Grain Size The crystal grain size of the base steel sheet is preferably 50 μm or more, and more preferably 100 μm or more. In general, the smaller the content of elements such as Si, the larger the grain size is. However, if the grain size is increased in such a low-Si content steel, {111} is developed as a texture. The result is a base steel sheet that is not suitable for the purpose of magnetic shielding in a magnetic field. Further, as described above, if transformation occurs during annealing, crystal grains are undesirably fragmented.

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

3. Plating Next, plating will be described.

  In the present invention, the plating structure is defined. First, the boundary in the thickness direction will be described. In the present invention, a position where the Fe concentration is 80% of the Fe concentration at the center position in the thickness direction of the base steel sheet from the base steel sheet side to the plating side is defined as the boundary between the base steel sheet and the plating, and the Fe concentration is the base steel sheet. The region where the plating metal is present on the surface side of the center position in the thickness direction of (1) above the position where the Fe concentration is 80% becomes the plating (layer).

  Further, a region where the Fe concentration changes from 80% to 20% of the Fe concentration at the center position in the thickness direction of the base steel sheet is defined as a transition region. In the following description, “plating” or “plating layer” is used as including the above-mentioned transition region unless it is particularly necessary to distinguish it.

(3-1) Thickness of transition region: 0.2 μm or more The magnetic shielded steel sheet according to the present invention has a concentration from the base steel sheet to the plating layer in order to achieve both a magnetic shielding property in a high magnetic field and plating adhesion. An important feature is the gradual change.

  In the present invention, this is defined by the thickness of the transition region. By setting the thickness of the transition region to 0.2 μm or more, both the magnetic shielding property in a high magnetic field and the plating adhesion can be achieved at a high level.

  The thickness of the transition region is preferably at least 0.5 μm, more preferably at least 1.0 μm, and even more preferably at least 1.5 μm. If the thickness of the transition region is small, that is, if the change in the Fe concentration is sharp, the magnetic shielding property in a high magnetic field is reduced as described above, and the plating adhesion is also reduced. Although the cause of the decrease in plating adhesion is unknown, it is estimated that a sharp change in the Fe concentration in the transition region causes strong stress to occur in the boundary region including the transition region.

  It is also a point of the present invention that the magnetic shielding property changes depending on the state of plating on the base steel sheet, particularly the state of the transition region, but the reason is not clear at present. However, generally, the influence of stress on the magnetic properties of electrical steel sheets is known, and it is known that compressive stress lowers magnetic permeability.

  The present inventors presume that the stress at the interface due to the difference in the coefficient of thermal expansion and the Young's modulus between the base steel sheet and the plated metal is the cause.

  There is no particular upper limit on the thickness of the transition region. This is because it is clear that the larger the thickness of the transition region is, the more gradual the change is, the better the magnetic shielding property in a high magnetic field and the improvement in plating adhesion, which are phenomena specific to the magnetic shielded steel sheet according to the present invention. However, on the other hand, in the method of controlling the thickness of the transition region by the surface oxidation of the base steel plate in the finish annealing and the electroplating method, which will be described later, under the condition that the thickness of the transition region is wide, the thickness of the internal oxide layer is large. Care must be taken because the internal oxide layer may hinder the domain wall movement and degrade the magnetic shielding property in some cases. When applying this method, the thickness of the transition region is preferably less than 3.0 μm, more preferably 2.6 μm or less.

  On the other hand, if the Fe concentration becomes too high on the surface side of the plating, the corrosion resistance may decrease. Therefore, the transition region is preferably 50% or less of the total plating thickness, more preferably 30% of the total plating thickness. % Or less. If this ratio is reduced in consideration of the plating thickness, the thickness of the transition region itself becomes thinner, which leads to a sharp change in concentration. Therefore, it is necessary to balance these.

(3-2) Thickness Plating is formed on the surface of the base steel sheet for the purpose of improving the corrosion resistance of the magnetic shielded steel sheet according to the present invention. The metal element mainly used for plating is an element having lower magnetism than Fe, which is the main constituent element of the base steel sheet, and the thicker the plating, the lower the magnetic permeability of the entire magnetic shielded steel sheet. It is preferable to reduce the thickness within a range that ensures the required corrosion resistance.

  In a harsh environment, such as that exposed to the elements, such as electrical appliances and interior applications installed in general rooms, a plating thickness of 10 μm is sufficient, and preferably 5 μm or less. And more preferably 3 μm or less.

(3-3) Plating Structure In the plating of the magnetic shielded steel sheet according to the present invention, one plating layer is a single phase, and the plating layer is a phase in which the contained metal element is completely dissolved within a range of concentration change. Is preferably within the range of forming. For this reason, when a special metal phase such as an intermetallic compound that adversely affects the magnetic shielding property and plating adhesion in a high magnetic field due to the chemical composition and heat history of the plating metal is preferably avoided. . In particular, there are many points to note about intermetallic compounds.

The intermetallic compound to be avoided varies depending on the metal contained in the plating and depends on the required properties, and cannot be unconditionally determined. However, for example, in the case of an intermetallic compound of Fe—Zn, an 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 called Γ ₁ phase and Γ phase are used. The adverse effect of a hard intermetallic compound such as Fe ₃ Zn _{10 which} is referred to as a compound is significant.

If other example intermetallic compound FeAl, _Fe 3 Al called beta ₁ phase, if an intermetallic compound of FeAl and _Fe 2 _Al 5, _Fe-Sn called beta _2-phase, Fe 3 Sn, Fe ₃ Sn _{2, FeSn,} if FeSn 2, NiAl intermetallic compounds, such as NiAl called beta 'phase are listed as adversely affect the intermetallic compound.

  As described above, in the plating on the magnetic shielded steel sheet according to the present invention, formation of an intermetallic compound is basically undesirable. Even if an intermetallic compound is formed, it is preferable that the intermetallic compound does not have a film-like form that entirely covers the specific depth region of the steel sheet and is not coarse.

  In a region away from the base steel sheet, the effect of the intermetallic compound on magnetic shielding properties and plating adhesion in a high magnetic field is negligible. Attention must be paid to the fact that the intermetallic compound is easily formed particularly in the transition region, which is the point of the present invention, and may have a significant adverse effect on the magnetic shielding properties.

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

  In both X-ray diffraction and electron diffraction, the presence of an intermetallic compound can be determined by detecting a diffraction peak or a diffraction pattern at a position corresponding to the lattice spacing of various intermetallic compounds. The type of the metal element can be identified by using the EDS detector provided in the TEM.

  These determinations and identifications may be made based on the standards usually used by those skilled in the art.

(3-4) Plating type Known plating can be applied to 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, a known plating such as Pb-Sn, Fe-Ni, and Fe-Cr can be applied.

Electroplating, hot-dip plating, thermal spraying and the like can be applied to these plating means without limitation. Further, plating in which colloids or fine particles of SiO ₂ , Al ₂ O ₃ , TiO _2, or the like are dispersed in the plating layer is also applicable.

(3-5) Multi-layer structure As described above, when there is only one layer of plating on the base steel sheet, it is effective to form a multi-layer plating in order to promote the buffer between the plating and the base steel sheet. It may be. For example, a Ni-based plating layer is formed as an intermediate plating layer between the outermost Zn-based plating layer and the base steel sheet that are responsible for corrosion resistance.

  The reason for this is not clear, but for the properties that cause interfacial stress, such as the coefficient of thermal expansion and the Young's modulus, by interposing an intermediate plating layer having an intermediate property between the outermost plating layer and the base steel sheet. It is estimated that stress concentration can be avoided.

  When an intermediate plating layer is present, the present invention can be defined by a change in the concentration of a metal element in the intermediate plating. In the present invention, in the concentration distribution of the specific metal element X from the base steel sheet to the plating surface, the intermediate plating layer is defined as an average concentration of the specific metal element X in the base steel sheet as Xa, and the plating layer is formed from the interface with the base steel sheet. When the average concentration at the position of 1/10 of the thickness of X is defined as Xb, if the maximum point of the concentration of (Xa + Xb) × 2 or more exists, it is defined that the intermediate plating layer containing the metal element X exists. .

  In other words, this rule indicates that, in the elemental configuration ranging from the base steel sheet to the plating surface, there is a layer between the base steel sheet and the outermost plating layer that has a clearly different chemical composition from these layers. It is. In the present invention, when satisfying this concentration distribution, it is assumed that the plating has a multilayer structure.

  Such a change in chemical composition can be formed by performing plating of different chemical compositions a plurality of times, but even when only one type of plating is applied, such as a plating formation process and atomic diffusion due to a heat treatment after plating. This does not exclude the case where any element-enriched layer is formed. In the present invention, it is assumed that the intermediate plating layer exists including such a case.

(3-6) Half-value thickness of intermediate plating layer: 0.2 to 2 μm
In the present invention, the half-value thickness of the intermediate plating layer is preferably 0.2 to 2 μm.

  When the half-value thickness of the intermediate plating layer is less than 0.2 μm, the effect on the magnetic shielding property and plating adhesion in a high magnetic field is reduced. Therefore, the half-value thickness of the intermediate plating layer is preferably 0.2 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and most preferably 1.5 μm or more. is there.

  On the other hand, if the half-value thickness of the intermediate plating layer exceeds 2.0 μm, the effect is saturated and the cost increases. Therefore, the half-value thickness of the intermediate plating layer is preferably 2.0 μm or less.

(3-7) Type of Intermediate Plating Layer The type (chemical composition) of a preferable intermediate plating layer varies depending on the type of plating applied to the outermost layer in order to ensure corrosion resistance and appearance, and the required characteristics are also required. Because it depends, it cannot be decided unconditionally.

  As an example, Ni-based plating may be applied as a lower layer of the above-mentioned Zn-based plated layer. It is not difficult for those skilled in the art to determine a plating type, a plating thickness, and the like that have a favorable effect on the properties.

  The above-mentioned plating is also effective to use alloy plating in order to moderate the concentration change in the transition region. For example, when a Zn-based plating is applied directly on a base steel plate, the change in concentration can be moderated by using Zn-Fe plating. Further, when Ni plating is applied before Zn-based plating, the concentration change becomes gentle if Ni-Fe plating, Ni-Zn plating or Ni-Fe-Zn plating is applied instead of pure Ni plating. Is advantageously obtained. The plating composition in the case of aiming for such an effect may be appropriately determined in consideration of characteristics such as a change in concentration and required corrosion resistance, and practicality such as a known plating range and manufacturing conditions.

  These concentrations can be evaluated by examining the emission intensity profile from the surface of the magnetic shield steel sheet by GDS. The absolute value of the concentration can be specified by a calibration curve of the emission intensity of GDS and the element content of the material in which the content of each element is changed. The GDS is analyzed using, for example, Rigaku GDA750 at an anode diameter of 4 mm and a pressure of 3 hPa. The optimum sputtering time varies depending on the plating thickness, but generally, analysis can be performed up to the base steel plate if the plating is performed for 200 seconds, and if the plating thickness is longer than that, analysis can be performed by increasing the sputtering time.

(3-8) Absence of Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in Metallic State Further, in the magnetic shielded steel sheet according to the present invention, Li, in metallic state during plating, Preferably, there is no Na, K, Rb, Be, Mg, Ca, Sr, Ba or Al. In the present invention, the “metal state” means a state including an intermetallic compound.

  As described above, the intermetallic compound exerts an undesired action. However, even if these elements are present in the plating, even if they are in a solid solution state, the magnetic shielding performance deteriorates. Although the reason for this is not clear, it is presumed that the stress state and the magnetic properties change due to changes in the physical properties of the plating.

  Whether or not these elements are contained in the plating can be detected by dissolving only the base iron and subjecting the remaining plating to ICP analysis. To confirm whether or not they are in a metal state, a peak is present at a position corresponding to the valence of zeroization of each element using X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES). It can be determined by whether or not to do. Regarding the presence of a peak, it is determined that there is a peak whose peak can be confirmed from the baseline based on a sample not containing the element.

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

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

(3-9) Treatment on Plating Further, a known treatment can be performed on the plating. Various chemical treatments to enhance corrosion resistance, painting, various chemical treatments to enhance coating adhesion, painting and film sticking to ensure design, etc. are affected by new stresses caused by these paintings and films. However, the effect of the present invention between the base steel sheet and the plating is not lost. Rather, depending on the coating or film, it is conceivable that the effect of the present invention is effectively exerted.

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

(4-1) Manufacturing method of base steel sheet The base steel sheet of the magnetic shielded steel sheet according to the present invention is prepared by melting steel in a converter, forming a slab by continuous casting, and then hot rolling, similarly to a known electromagnetic steel sheet. 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 decarburizing annealing, does not impair the effects of the present invention at all. In particular, when the crystal grain size of the hot-rolled annealed sheet is increased by annealing the hot-rolled sheet at a high temperature, the texture and the crystal grain size after the cold-rolled annealing are preferably changed to improve the magnetic shielding property.

  Further, fine precipitates such as AlN and MnS formed according to the manufacturing conditions inhibit crystal grain growth and domain wall movement, and lower magnetic shield performance. In order to render these fine precipitates harmless, the additive elements utilized in the known electromagnetic steel sheet manufacturing process, the slab heating / lowering, and the slow cooling technique after annealing can be appropriately utilized.

  As the manufacturing conditions of such a base steel sheet, known manufacturing conditions for favorably controlling magnetic properties (magnetic flux density, iron loss) may be appropriately applied.

  It is important that the temperature of the finish annealing be set to 950 ° C. or higher in the above-described steps when the electroplating method is employed in the method for manufacturing a magnetic shielded steel sheet according to the present invention. In the base steel sheet used in the present invention, which contains Si and Al in a relatively high concentration in steel, Si and Al oxidize on the surface during finish annealing to form a dense oxide film and inhibit adhesion of plating. Not only that, when performing electroplating, the content of Fe atoms in the plating decreases, and the concentration change from the base steel sheet to the plating becomes sharp.

  Although the details will be described in the section of plating conditions described below, by performing the finish annealing at 950 ° C. or more, the concentration change from the base steel sheet to the plating during electroplating becomes gentle. The temperature of the finish annealing is preferably more than 1000 ° C, more preferably more than 1050 ° C.

  Further, when the atmosphere dew point at 650 ° C. to 800 ° C. in the temperature rise process of the finish annealing is set to be higher than −10 ° C. to 40 ° C. or less, the concentration change from the base steel sheet to the plating during electroplating can be further moderated. it can. The ambient dew point is preferably above 0 ° C., more preferably above 10 ° C., even more preferably above 20 ° C. Further, the temperature range of the temperature raising process for controlling the atmospheric dew point is preferably more than 500 ° C, more preferably more than 0 ° C. This cause will be described later together with the change in the plating behavior in the description of the plating conditions.

  Further, the temperature of the finish annealing directly affects the crystal grain size of the base steel sheet. Although it depends on the chemical composition of the base steel sheet and the transformation behavior described above, and the process before cold rolling, the crystal grain size of the base steel sheet is determined as described above, taking into account these conditions and further considering favorable conditions for the plating behavior. It is not so difficult for a person skilled in the art to set the conditions of the finish annealing so as to be within the range.

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

  The change in concentration of the transition region defined in the present invention can be controlled by various methods. For example, as described above, intervening plating having an intermediate component of each layer, plating a plurality of platings having different chemical compositions, and diffusing elements by heat treatment after plating are exemplified. These methods may be performed under known conditions as appropriate.

  Known plating methods such as hot-dip plating, electroplating, and thermal spraying can be used as plating means. However, in order to perform uniform plating at a thickness in the above range and at low cost, it is necessary to use electroplating. Is optimal. In addition, in a method such as hot-dip plating, which is exposed to a high temperature state during plating, an intermetallic compound composed of a metal element plated at an interface and a metal element contained in a base steel sheet is easily generated, and this intermetallic compound is magnetic. It may adversely affect the shielding properties and plating adhesion.

  As described above, one of the features of the present invention is that there is an effect of improving the magnetic shielding property by controlling the stress generated between the plating layer and the base steel sheet. It has been confirmed that this stress is very small in the case of electroplating, which can cause adverse effects due to distortion. Even in view of this, it can be said that electroplating is optimal as a plating means for the magnetic shielded steel sheet according to the present invention.

  Here, the behavior at the time of plating will be described focusing on the phenomenon in electroplating which is optimal for the present invention in relation to the characteristics of the base steel plate.

  First, the electroplating conditions in the present invention need not be special, and any known plating bath, bath composition, temperature, current density, and time may be applied. For example, in the preferred Zn-based plating for the present invention, various plating baths such as an alkaline bath and an acidic bath can be applied as the plating bath.

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, immersion at 25 to 40 ° C. for 5 seconds), and then Zn concentration: 1.0 mol / L (0 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.) and a current density of 50 A / dm ² (20 to 150 A / dm ² ).

  Further, a plating method such as an electroless method or an electroplating method can be used. Considering the cost, application, and versatility, Zn-based plating using an acidic bath of hydrochloric acid, sulfuric acid, or boric acid bath is most suitable.

  Characteristic in the electroplating process is the relationship between the plating behavior occurring in a specific base steel sheet and the effect of the present invention developed thereby.

  As described above, the chemical composition of the base steel sheet of the present invention is characterized by high Si content and high Al content, and it is preferable that the steel sheet be manufactured at a high temperature and a high dew point as a manufacturing method. When such a steel sheet is electroplated, a change is observed in the plating behavior. Specifically, the change in density in the transition region becomes gentle. Although this mechanism is not clear, it is presumed as follows.

  In general, a high Si, high Al content steel material forms a dense Si-based oxide film or Al-based oxide film (external oxide film) on the surface during heat treatment, and the reactivity on the surface decreases. On the other hand, depending on the heat treatment conditions, internal oxidation is likely to occur in a high Si or high Al content steel material, and a fine and complicated form of oxide is dispersed and formed inside the steel material instead of the external oxide film on the surface. It is known that an internal oxide layer (an internal oxide region) is formed.

  When the internal oxide layer is formed, the region where the oxide is not exposed on the surface has the Fe metal phase exposed on the surface. If the surface of the steel sheet is in such a state, the electroplating of the plating metal on the surface of the base steel sheet during electroplating and the dissolution of the base steel sheet (Fe metal atoms) in the plating bath easily progress. Then, the Fe atoms dissolved in the plating bath are re-deposited on the surface of the base steel sheet together with the plating metal.

  For this reason, the plating undesirably contains a considerable amount of Fe atoms, and its dissolution and re-deposition work to moderate the change in the Fe concentration in the transition region. In addition, it is considered that the microscopic irregularities on the surface of the base steel sheet are reduced by dissolving Fe on the outermost surface of the base steel sheet in the plating bath, and the magnetic shielding property is improved by reducing the inhibition of domain wall movement in a magnetic field. Can be

  That is, if a suitable base steel sheet is manufactured, the magnetic shield steel sheet according to the present invention in which the change in Fe concentration in the transition region is gradual can be obtained without special plating conditions.

  It is considered that the formation of such an easily dissolvable internal oxide layer involves high Si, high Al content steel, finish annealing at a high temperature, a high dew point in the temperature rise process of the finish annealing, and the like. In particular, increasing the annealing temperature is expected to have the effect of destroying the dense external oxide film formed on the surface as the crystal grains of the base steel plate grow and transforming it into a porous one. Is considered to act to form the starting point of internal oxidation at an early stage and to inhibit the progress of external oxidation at a high temperature after that.

  Of course, the highly active surface where a large amount of Fe phase is exposed immediately before plating is subjected to a heat treatment in which oxidation is completely suppressed, or after the heat treatment, strong acid washing or mechanical grinding is performed to remove an external oxide layer. It is also possible.

  However, it is difficult to completely suppress external oxidation during high-temperature heat treatment with high-Si, high-Al-containing steel such as the magnetic shielded steel sheet according to the present invention. Difficult and mechanical processing not only leaves residual strains that have a significant adverse effect on the magnetic shielding properties, but these methods also increase manufacturing costs.

  For this reason, control of internal oxidative behavior by the above-described finish annealing conditions and melting of the base steel sheet when it is applied to the electroplating method and utilizing re-deposition behavior are extremely industrially very difficult. Brings great benefits.

  On the other hand, since the internal oxide layer of Si and Al also forms micro unevenness at the interface with the ground iron, if the internal oxide layer is excessive, it impedes domain wall movement and deteriorates the magnetic shielding property in a high magnetic field. There is a risk. In order to avoid this, it is important to appropriately control the conditions of the finish annealing.

  To positively eliminate the adverse effects of internal oxidation, it is effective to perform pickling after finish annealing and before electroplating. Unlike the external oxide film, the internal oxide layer can be relatively easily removed by pickling. If the thickness of the internal oxide layer is reduced to 50% or less of that before the acid pickling by pickling before electroplating, for example, electrolytic pickling or the like, melting of the base steel plate at the time of subsequent plating also occurs. The adverse effects are almost eliminated.

  The final thickness of the internal oxide layer is preferably not more than 1.0 μm, more preferably not more than 0.6 μm, and if it is not more than 0.3 μm, the adverse effect on the characteristics is very small. Of course, it is preferable to select the pickling and plating conditions that completely eliminate the internal oxide layer in order to achieve the effects of the present invention.

  Steels A to G having the chemical compositions shown in Table 1 were melted in vacuum, made into a steel slab by continuous casting, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.0 mm. The underline in Table 1 indicates that the value is out of the range specified in the present invention.

  The hot-rolled steel sheet was pickled with sulfuric acid at 40 ° C., cold-rolled to a thickness of 0.50 mm, and subjected to finish annealing under the conditions shown in Table 2. In addition, the thickness of the internal oxide layer of the steel sheet before and after pickling was determined by observing the cross section of the steel sheet with a high-resolution SEM at 3000 times at a reflected electron composition image (COMPO image) in 10 visual fields, and as an average of the observed oxide layer thickness. ,It was measured.

Thereafter, plating was performed by changing the pickling conditions before plating, the presence or absence of intermediate plating, the upper layer plating means, and the type of upper layer plating. Although these settings are shown in Table 2, the plating conditions and the like are not particularly limited as described above, and may be set under known conditions in consideration of required characteristics and the like. It is unified under general conditions. In the present embodiment, for example, the electro-Zn plating of the present embodiment uses a sulfuric acid bath, and is applied to both sides at a basis weight of 20 g / m ² on one side.

  After that, it was washed with water and subjected to a chemical conversion treatment using CT-E300N manufactured by Nippon Parkerizing Co., Ltd.

  The sample No. manufactured in this manner was used. The following features and characteristics were examined for 1-33.

(1) Thickness of transition region The thickness was measured by using Rigaku GDA750 at an anode diameter of 4 mm and a pressure of 3 hPa.

(2) Half value thickness of the intermediate plating layer (Ni plating layer) The concentration profile from the plating surface was examined by GDS and measured.

(3) Presence of Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in a metal state during plating Using X-ray photoelectron spectroscopy (XPS), the valency of each element for zeroization The measurement was made based on whether or not a peak was present at a position corresponding to.

(4) Presence or absence of intermetallic compound during plating It was measured by electron beam diffraction.

(5) Crystal grain size It was measured by the cutting method prescribed in JIS G0551 Appendix C.

(6) Chemical conversion property A salt spray test described in JIS Z2371: 2000 was performed, and the evaluation was made based on the presence or absence of white rust after 24 hours.

(7) Low magnetic field magnetic shielding and high magnetic field magnetic shielding (permeability)
Using a test piece cut into a 55 mm square, measurement was performed with a single-plate magnetic test frame and a direct current magnetic fluxmeter.

  As described above, the magnetic shielding property in a high magnetic field targeted by the present invention is applied to a magnetic flux density region of 0.1 T or more, but practically, the magnetic flux inside the shielding material is not uniform. In addition, since magnetic flux concentration occurs, the magnetic 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 magnetic permeability at 1T. If the superiority of the present invention can be confirmed with this value, superior shielding properties can be obtained in a wide magnetic flux density region from 0.1 T or more to over 1 T.

  For high magnetic field magnetic shielding properties (permeability of 1T), 0.0060 H / m or more was judged to be acceptable, and for low magnetic field magnetic shielding properties (magnetic permeability equivalent to terrestrial magnetism), 0.0005 H / m or more was judged to be acceptable.

(8) Plating Adhesion The test piece provided with the polyester coating described above was cooled to −20 ° C. or lower in a freezer, and the sheared surface was sheared with a power shear at −20 ° C. Observed and measured the peeling width of the plating. The smaller the peel width, the better, and a peel width of 1 mm or less was judged to be acceptable.

(9) Corrosion resistance A test piece having a known chromate-free film applied thereon, and a polyester-based coating applied thereon with a thickness of 20 μm was prepared on the upper layer, and a cross cut was made to reach the base steel sheet, and the test was performed in accordance with JIS Z2371. The salt spray test was used to evaluate the swelling width after one week. The smaller the swollen width, the better. The swollen width: <2 mm was judged to be acceptable.

(10) Tensile strength A JIS No. 5 test piece was cut out and the tensile strength was measured.

  The results are summarized in Table 2.

  Hereinafter, the sample No. The effects of the present invention will be described based on the results of 1 to 33. The underline in Table 2 indicates that the range is out of the range specified in the present invention or not in the preferable range.

  First, the sample No. Nos. 1 to 8 mainly confirm the influence of the chemical composition of the base steel sheet.

  The sample No. Reference numeral 1 denotes a known general magnetic shield material, but since a transition region which is a feature of the present invention is not formed, it is not possible to obtain a good magnetic shield property in a high magnetic field.

  Sample No. which is a comparative example. Nos. 2, 7, and 8 are obtained by performing a finish annealing under a finish annealing condition for forming a transition region, which is a feature of the present invention, based on a conventionally known general magnetic shield material. However, since the chemical composition of the base steel sheet does not satisfy the range specified in the present invention, under such finish annealing conditions, transformation and fine precipitation of the base steel sheet will occur, and the crystal grains will be refined and the magnetic properties in a good high magnetic field Shielding properties cannot be obtained.

  Sample No. of the present invention example. In Nos. 3 to 5, the chemical composition of the base steel sheet is preferable for the formation of the transition region required by the present invention, and all have a high magnetic shielding property in a high magnetic field.

  Sample No. which is a comparative example. In No. 6, since the Si content of the base steel sheet exceeded the upper limit specified in the present invention, the base steel sheet was embrittled and fractured during cold rolling.

  Next, the sample No. Nos. 9 to 14 were obtained by changing the surface oxidation state of the base steel sheet immediately before plating by controlling the dew point of the finish annealing, and confirming the effect of forming a preferable transition region by electroplating.

  Sample No. which is a comparative example. In Nos. 9, 10 and 15, since the dew point in the temperature rise process of the finish annealing is not in the preferred range of the present invention, a dense external oxide film is formed in the finish annealing, and a good transition region is formed in the subsequent electroplating. Since it is no longer formed, the magnetic shielding property in a high magnetic field does not increase. In addition, the adhesion of the plating decreases, and the corrosion resistance also decreases.

  Sample No. which is a comparative example. In No. 14, although a dense external oxide film was not formed, the internal oxide layer was too thick, and the internal oxide layer hindered domain wall movement, resulting in a decrease in magnetic shielding properties in a high magnetic field.

  Sample No. of the present invention example. In Nos. 11 to 13, a suitable transition region is formed in the electroplating method by setting appropriate conditions, and the magnetic shielding properties, plating adhesion, and corrosion resistance in a high magnetic field are all at a high level.

  Sample No. of the present invention example. Nos. 16 to 18 were obtained by changing the crystal grain size depending on the temperature of the finish annealing and confirming the influence on the magnetic shielding property in a high magnetic field.

  Since the finish annealing conditions themselves also depend on other conditions such as the chemical composition of the base steel sheet and the hot rolling conditions, the finish annealing temperature specified in the present invention is not an absolute control temperature. . Nos. 16 to 18 indicate that it is difficult to obtain a good magnetic shielding property in a high magnetic field if the crystal grain size is less than 50 μm.

  Sample No. of the present invention example. Nos. 19 and 20 confirm the influence of pickling immediately before electroplating. The above sample No. In comparison with the above, the pickling described above changes the thickness of the transition region through the removal of the internal oxide layer, and finally affects the magnetic shielding property in a high magnetic field. It is a factor to be done.

  Sample No. of the present invention example. 21 to 23 change the half value thickness of the intermediate plating in the transition region formed by the subsequent electric Zn plating by changing the plating amount of the intermediate plating (electric Ni plating) performed before the final electric Zn plating. It has changed. Sample No. was the same condition except for the plating amount of the intermediate plating. Comparing the change of the magnetic shielding property under a high magnetic field together with that of No. 5, it can be seen that a preferable region exists in the thickness of the intermediate plating.

  Sample No. of the present invention example. In Nos. 24 to 27, plating layers are formed by hot-dip plating. Sample No. Samples Nos. 24 and 25 set conditions so that the intermetallic compound was easily formed and the residence time in the temperature range near 400 ° C. in the cooling process after plating was longer. Nos. 26 and 27 suppress the formation of intermetallic compounds by passing through this region in a short time. In addition, the sample No. Nos. 24, 25, and 27 simulate a low-grade ingot and contain Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in molten Zn so as to have a total content of 1%. The plating bath was used. This plating bath is described as "Zn +" in Table 2.

  Sample No. From the results of Nos. 24 to 27, it can be confirmed that the intermetallic compound and the above elements tend not to be preferable for the magnetic shielding property in a high magnetic field.

  Sample No. Examples 28 to 33 are examples in which general Zn-15% Ni plating, Ni plating, Sn plating or the like is applied as plating other than Zn. The transition region has a sufficiently large thickness. Nos. 28, 30, and 32 are referred to as Nos. 28 and 30 in which the thickness of the transition region is small. Comparing with 29, 31, and 33, respectively, it can be seen that the effect of the present invention on the magnetic shielding property in a high magnetic field is obtained regardless of the plating type.

  The sample No. In Nos. 30 to 33, the chemical conversion treatment was not performed, and thus the chemical conversion treatment property was not evaluated.

Claims (12)

In mass%,
Si: 1.5 to 4.0%,
Al: 0.1 to 3.0%,
Mn: 0.1 to 2.4%,
A base steel sheet having a chemical composition that is a balance of Fe and impurities;
A magnetic shield steel sheet comprising at least one plating layer formed on at least one surface of the base steel sheet,
A transition region in which the Fe concentration changes from 75% to 25% of the Fe concentration at the central position in the thickness direction of the base steel sheet from the base steel sheet side toward the plating layer side;
A magnetically shielded steel sheet wherein the thickness of the transition region is 0.2 μm or more and less than 3.0 μm .   The magnetic shield steel sheet according to claim 1, wherein the plating layer has a multilayer structure.   The magnetic shield steel sheet according to claim 1, wherein the transition region has no intermetallic compound.   The magnetic shield steel sheet according to claim 2, wherein at least one of the plating layers is a Zn-based plating layer.   The method according to claim 2, wherein at least one of the plating layers does not include Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, or Al in a metal state. Magnetic shield steel plate.   The magnetic shield steel sheet according to claim 2, wherein the intermediate plating layer among the plating layers is a Ni-based plating layer.   The magnetic shield steel sheet according to claim 2, wherein a half-value thickness of a concentration distribution of a metal element forming an intermediate plating layer in the plating layer is 0.2 to 2.0 μm.   The magnetic shield steel sheet according to claim 1, wherein the base steel sheet has a crystal grain size of 50 to 200 μm.   Hot rolling to a steel slab consisting of 1.5 to 4.0% Si, 0.1 to 3.0% Al, 0.1 to 2.4% Mn, balance Fe and impurities by mass% The method for producing a magnetic shielded steel sheet according to any one of claims 1 to 8, wherein after performing cold rolling and finish annealing, the surface is subjected to plating treatment, wherein the maximum ultimate temperature of the finish annealing is 950 ° C or more. A method for manufacturing a magnetic shielded steel sheet.   The method for producing a magnetically shielded steel sheet according to claim 9, wherein the dew point of the atmosphere at 650 ° C. to 800 ° C. in the temperature rise process of the finish annealing is more than −10 ° C. and 40 ° C. or less.   The method according to claim 9, wherein pickling is performed after the finish annealing and before the plating treatment.   The method according to claim 9, wherein the plating is electroplating.