JP5196668B2 - Ferritic stainless steel soft magnetic material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a soft magnetic material used for, for example, sensor parts, electromagnetic valve parts, fuel injection parts, solenoid cores, various magnetic circuit yokes, etc., in an environment where severe wear is expected to occur. The present invention relates to a ferritic stainless steel soft magnetic material used as a magnetic material while imparting a desired degree of corrosion resistance to the ferritic stainless steel material, and a method for producing the same.

  Conventionally, among magnetic members used for the above-described applications, for example, a magnetic member driven by turning on and off of an electric current is used in a state where mechanical collision and contact due to driving are repeated many times. Such a magnetic member may have impact resistance and wear resistance enough to withstand many mechanical collisions and contacts while having the corrosion resistance desired for ferritic stainless steel. For example, a surface hardness that is not too low without being too low, such as about 200 to 300 HV, is desired. In addition, in order to perform the operation of the device with good responsiveness, it is necessary to have a magnetic characteristic that can quickly perform magnetization and demagnetization (also referred to as demagnetization) when the current is turned on and off. A magnetic flux density (B10) of 0.0 T or more, a maximum magnetic permeability of 2500 or more, and a coercive force of 150 A / m or less that is somewhat small are desired.

  A magnetic member having a surface hardness of about 200 to 300 HV, which is suitable for the above-described uses, and having the above-described magnetic properties may have magnetic properties by magnetic annealing under appropriate conditions. Desired products by machining such as cutting bar shapes, squares, blocks, etc. made of ferritic stainless steel, which is a relatively inexpensive and easily available soft magnetic material, and cutting the product shape from such materials I got the shape. However, although the above-mentioned steel materials themselves are relatively inexpensive and easy to obtain, they are manufactured by machining such as carving out the product shape from the materials, so the material yield is low and the number of processing steps is required, so the mass productivity and low price of magnetic members are reduced. Therefore, technical improvement was desired.

  Therefore, as described above, a metal that can have a shape approximate to the desired product shape, instead of the conventional machining means that uses ferritic stainless steel material that is unsatisfactory for mass production and cost reduction of the magnetic member. Proposals for forming a magnetic member made of a sintered body have been made. For example, Japanese Patent Application Laid-Open No. 7-138693 (Patent Document 1) and Japanese Patent Application Laid-Open No. 7-155788 (Patent Document 2) relating to an iron-chromium-based magnetic alloy, also called electromagnetic stainless steel, have been put into practical use. Examples of iron-chromium-based magnetic alloys that are used in public use are K-M31 (Tohoku Special Steel Co., Ltd., 13% by mass and 2% Si) and TICS (Daido Special Steel Co., Ltd., 13% by mass). %, Si is 1%).

JP-A-7-138893 JP-A-7-1557838

  The present inventor has studied to obtain a ferrite stainless steel soft magnetic material having a chemical component of a ferrite stainless material and made of the above-described sintered metal. Specifically, SUS410L (mass%, Cr: 11.0 to 13.5%, Si: 1.0% or less, Mn: 1.0%, which is a ferritic stainless steel specified in JIS-G4303 and the like. Hereinafter, a metal sintered body having a chemical component equivalent to Ni: 0.60% or less, the balance Fe and unavoidable impurities) is easily obtained by a metal powder injection molding method (hereinafter referred to as MIM method). The ferrite sintered stainless soft magnetic material was formed by magnetically annealing the obtained metal sintered body under appropriate conditions.

  However, the obtained ferritic stainless steel soft magnetic material made of sintered metal is compared with the ferritic stainless steel soft magnetic material formed by machining a stainless steel material having a chemical component equivalent to SUS410L. Although it has a chemical component equivalent to this, the magnetic characteristics deteriorated and the surface hardness of the magnetic member also deteriorated.

  The object of the present invention is to have the same or better magnetic properties as compared with a magnetic part formed by machining a stainless steel material having a chemical component equivalent to SUS410L as a raw material. The present invention also provides a ferritic stainless steel soft magnetic material made of a sintered metal having a suitable surface hardness and a method for producing the same.

  In view of the above-mentioned problems, the present inventor has studied the improvement of magnetic properties and the surface hardness of a sintered metal that is a ferritic stainless steel soft magnetic material, and has optimized the chemical components of the sintered metal. I planned. In other words, in the sintered metal, Si (silicon) or an unavoidable impurity contained in the metal with respect to Fe (iron) and Cr (chromium), which are the main components of the ferritic stainless steel soft magnetic material. The allowable ranges of O (oxygen) and C (carbon), which are considered to have a particularly large effect on various properties of the sintered body, were examined. And by optimizing the content range of Si, O, and C with respect to Fe and Cr in the sintered metal, the magnetic properties are improved and the surface hardness is increased in a suitable range in the obtained ferritic stainless steel soft magnetic material. The inventors have found that it is possible to achieve the present invention.

That is, the present invention contains, in mass%, Cr in an amount of 8.0 to 13.5%, Si in an amount of 3.0 to 5.0%, the balance Fe and unavoidable impurities. Ferritic stainless steel made of a metal sintered body that is suppressed to contain 30% or less and C is 0.07% or less, and the C / O content ratio C / O is 0.5 to 1.4. Soft magnetic material.

  The ferrite stainless steel soft magnetic material of the present invention can have a relative density of 96% or more and a surface hardness of 200 to 300 HV.

  Moreover, it can have maximum magnetic permeability 2500 or more, magnetic flux density (B10) 1.0T or more, and coercive force 150A / m or less.

  Moreover, it is desirable that the metal powder injection molded body is a sintered metal body that is sintered.

The ferritic stainless steel soft magnetic material of the present invention described above is sintered after degreasing a metal powder molded body formed by a metal powder injection molding method, and is 8.0% to 13.5% Cr and 3% Si in mass%. .0～5.0%, contain the remainder Fe and unavoidable impurities, O 0.30% or less and C of the unavoidable impurities are suppressed to the inclusion of 0.07% or less, the said C O A manufacturing method obtained by forming a metal sintered body having a C / O content ratio of 0.5 to 1.4 and magnetically annealing the metal sintered body can be applied.

  Further, the metal sintered body adjusted to a relative density of 96% or more and a surface hardness of 200 to 300 HV and sintered is subjected to magnetic annealing to maintain a maximum permeability of 2500 or more and a magnetic flux density (B10) of 1.0 T or more. A manufacturing method obtained by adjusting the magnetic force to 150 A / m or less can be applied.

  The ferrite stainless steel soft magnetic material of the present invention is a soft magnetic material having a suitable surface hardness while having a magnetic property equal to or higher than that of a soft magnetic material formed using a conventional ferritic stainless steel material. In addition, since it is a sintered metal having excellent approximation to the product shape, it is possible to improve the mass productivity of the ferritic stainless steel soft magnetic material and to reduce the cost. In addition, the ferritic stainless steel soft magnetic material of the present invention, which has a high surface hardness and excellent wear resistance, is an environment in which severe wear is expected to be generated by driving, such as a magnetic component driven by turning on and off of current. It is suitable for the use of various magnetic members and magnetic parts that are used with the desired degree of corrosion resistance applied to the ferritic stainless steel.

  In the above-described applications, magnetic properties desired for the ferrite stainless steel soft magnetic material include, for example, a maximum magnetic permeability of 2500 or more, a magnetic flux density (B10) of 1.0 T or more, and a coercive force of 150 A / m or less. Ferritic stainless steel soft magnetic materials with such magnetic properties have good responsiveness to magnetization and demagnetization, and are therefore suitable for application to magnetic members and magnetic parts where it is desired to operate the equipment quickly and reliably. It becomes. Note that the maximum magnetic permeability depends on how much magnetic flux density is newly generated in the magnetic material when a further minute external magnetic field is applied in the magnetic field, and the magnetic field strength (magnetic field) strength H and magnetic flux density B Is the maximum value of the proportionality constant μ (permeability) when B = μH and indicates the ease of magnetization of the magnetic material, and practically the maximum value of the relative permeability is the maximum permeability. This is followed in the present invention. The magnetic flux density (B10) indicates the magnetic flux per unit area in the magnetic material when an external magnetic field of 10 A / m is applied. The coercive force indicates the strength of the magnetic field that makes the magnetic flux density in the magnetic material zero when the external magnetic field is removed from the state where the external magnetic field is applied and magnetized in the opposite direction.

  In the ferritic stainless steel soft magnetic material of the present invention that can have the preferred magnetic properties described above, the important feature is related to the chemical component of the ferritic stainless steel soft magnetic material made of a sintered metal and is the main component. The reason is that the Si content is optimized with respect to Fe and Cr, and at the same time, the allowable range of O and C, which are inevitable impurities, is clarified. Specifically, the ferritic stainless steel soft magnetic material of the present invention contains, in mass%, Cr of 8.0 to 13.5%, Si of 3.0 to 5.0%, the balance Fe and inevitable impurities. Of the inevitable impurities, O is suppressed to 0.30% or less and C is suppressed to 0.07% or less. Hereinafter, unless otherwise specified, the element content is expressed in mass%.

  In the present invention, the first important thing is to suppress O to 0.30% or less among impurities inevitably contained in the ferritic stainless steel soft magnetic material made of a metal sintered body. As a result, sintering defects such as pores are less likely to be inherent in the metal sintered body, and the sintered density, that is, the relative density of the metal sintered body is further increased. The sintered metal body having the above-described chemical components can have soft magnetism by magnetic annealing under appropriate conditions. At this time, the higher the relative density of the sintered metal body, the more suitable the magnetic field for the above-described use. It becomes easy to obtain a soft magnetic material having characteristics. Specifically, it is a soft magnetic material having magnetic properties such as maximum magnetic permeability and magnetic flux density, and low coercive force.

  In the present invention, the relative density of the sintered metal body is ideally 100%, but desirably has a relative density of at least 96% or more, and can have a magnetic property equivalent to or higher than that of the prior art. A ferrite stainless soft magnetic material having a relative density of less than 96% may not have good magnetic properties and suitable surface hardness.

Here, the relative density of the ferrite stainless steel soft magnetic material made of the above-described sintered metal will be described. The relative density as used in the present invention means a true density ρ ₀ corresponding to the theoretical density of a solid itself that does not contain pores of a metal powder that becomes a sintered metal body by sintering, and a metal powder obtained by sintering the metal powder. The ratio ρ ₁ / ρ ₀ that can be defined by the bulk density ρ ₁ , which is a value obtained by dividing the mass of the bonded body by its bulk volume, refers to a value expressed in percent (%). The true density ρ ₀ of the metal powder can be obtained by a commercially available true density measuring apparatus to which a pycnometer method or the like defined in JIS-Z9301 is applied. Moreover, the bulk density ρ ₁ of the metal sintered body can be obtained by a measuring method such as a wet Archimedes method.

  In the present invention, the second important thing is to suppress C to 0.07% or less among impurities inevitably contained in the ferritic stainless steel soft magnetic material made of a sintered metal. In the present invention, when C exceeds 0.07%, the surface hardness becomes slightly high and the coercive force tends to decrease, but the maximum magnetic permeability and magnetic flux density may be impaired. Therefore, the allowable range of the impurity C is 0.07% or less, preferably 0.05% or less, and more preferably 0.03% or less. In addition, although C is an impurity that causes deterioration of magnetic properties, the effect of improving the surface hardness can be expected by dispersing the generated carbide by containing C or more by 0.01% or more, and more surface hardness is expected. In that case, it may be contained by 0.02% or more.

  As described above, O and C are impurities that easily deteriorate sinterability and magnetic characteristics in the present invention, and their content is ideally 0%. However, in the present invention, it is obtained by controlling the content ratio C / O in the range of 0.5 to 1.4 while controlling O to be 0.30% or less and C to be 0.07% or less. The magnetic properties and surface hardness of the obtained soft magnetic material can be made more suitable for the above-described use. Specifically, it has a relative density of 96% or more, a maximum magnetic permeability of 4000 or more, a magnetic flux density (B10) of 1.1 T or more, a coercive force of 100 A / m or less, and a surface hardness of 230 to 260 HV.

  The third important point in the present invention is that Si is contained in the range of 3.0 to 5.0% in the ferritic stainless steel soft magnetic material made of a metal sintered body. As a result, the Si compound is suitably dispersed and generated in the sintered structure of the metal sintered body, the surface hardness can be increased, and the surface hardness suitable for the above-described use is 200 to 300 HV. be able to. When Si is less than 3.0%, it is difficult to obtain a surface hardness of 200 HV or higher, which is desired for the above-mentioned applications. When Si exceeds 5.0%, the surface hardness can be improved. Becomes too large, and wear resistance is deteriorated due to surface embrittlement. Therefore, by controlling Si to 3.0 to 5.0%, it is possible to obtain a ferritic stainless steel soft magnetic material that has suitable wear resistance but is difficult to become brittle. And the ferritic stainless steel soft magnetic material which has suitable surface hardness 200-300HV is used in the environment where generation | occurrence | production of severe wear is estimated by a drive like the magnetic member driven by the on / off of an electric current, for example. Application to applications of magnetic members and magnetic parts is preferable. In the above-described applications, the wear resistance is insufficient when the surface hardness is less than 200 HV, and the impact resistance is insufficient because it tends to become brittle when the surface hardness exceeds 300 HV.

  The ferritic stainless steel soft magnetic material of the present invention is desired as a stainless steel material in order to optimize the content range of each element of O, C, and Si described above, and to generate a ferrite phase having magnetism. In order to obtain high corrosion resistance, Cr is contained in the range of 8.0 to 13.5% with respect to Fe. However, if the Cr content is less than 8.0%, the corrosion resistance as a stainless steel material may be insufficient, and if it exceeds 13.5%, the magnetic properties desired for the above-described applications may be impaired. In addition, in the case of containing Cr, the upper limit is desirably set to 11.0% when better magnetic properties are desired, and the lower limit is desirably set to 9.0% when better corrosion resistance is desired. .

  The permissible impurity range for elements other than the above-described O, C, Si and Cr with respect to Fe will be described as not impairing the effects of the present invention. In the present invention, if a large amount of Ni (nickel) is contained, the formation of a ferrite phase is hindered and a non-magnetic austenite phase is formed. Therefore, it is desirable to keep Ni to 0.60% or less. Further, since elements such as Mn (manganese), P (phosphorus), and S (sulfur) may affect the sinterability, mechanical strength, and magnetic properties of the sintered metal, Mn is 1.0. % Or less, P is preferably 0.04% or less, and S is preferably 0.03% or less, and ideally 0% which is not contained at all.

  As described above, the ferritic stainless steel soft magnetic material of the present invention is a soft magnetic material belonging to a ferritic stainless material capable of having magnetism, and is made of a sintered metal. In the present invention, the relative density is increased by suppressing the impurity O, which may be inevitably contained in the sintered metal body, to 0.30% or less, and at the same time, the impurity C is 0.07%. By suppressing to less than or equal to%, the magnetic characteristics are prevented from deteriorating, and Si is positively contained in the range of 3.0 to 5.0% to increase the surface hardness to a suitable range.

  Next, the metal sintered body in the present invention will be described. The metal sintered body may be a metal sintered body formed by applying a metal sintering method such as the MIM method described above, and has a shape (near net shape) that approximates a desired product shape. Can do. Thus, if it is a metal sintered compact which has an approximate shape with respect to a desired shape, it can have easily the shape of the complicated member and component which could not be formed by machining, such as the conventional cutting. In addition, it is possible to easily perform finish processing such as processing of grooves and holes, peripheral polishing, and post-processing such as coating on a sintered metal body having a shape approximate to a desired shape. Therefore, even if it is a ferritic stainless steel soft magnetic material having a complicated shape, the ferritic stainless steel soft magnetic material made of a sintered metal is machined from roughing to finishing as before. Therefore, production efficiency and manufacturing cost are remarkably improved.

  The ferritic stainless steel soft magnetic material of the present invention is sintered after degreasing a metal powder molded body formed by, for example, a metal powder injection molding method (MIM method), and Cr is 8.0 to 13.5% by mass%. Further, a metal containing Si in an amount of 3.0 to 5.0%, the balance Fe and unavoidable impurities, in which O is suppressed to be 0.30% or less and C is 0.07% or less. The sintered body may be a metal sintered body obtained by magnetic annealing under appropriate conditions.

In the present invention, the metal sintered body described above can be formed by a manufacturing method to which the following MIM method is applied, for example. First, as a powder raw material, for example, Si powder is added to metal powder having a chemical component approximate to SUS410L, or Si powder is added to metal powder having a chemical component approximate to SUS430L. Prepare to adjust to a desired chemical component by adding approximately 12 to 14%. Then, the powder raw material is mixed and kneaded with paraffin wax or polypropylene serving as a binder to obtain an injection molding material. Next, the injection molding material is injected into a mold having a cavity corresponding to a desired shape to form a metal powder molded body. Then, the metal powder formed body is immersed in a solvent to remove paraffin wax, and then heated to remove polypropylene, and thereafter, for example, held at a temperature of 1240 to 1250 ° C. for 3 to 5 hours to burn the metal powder. It is a manufacturing method by a manufacturing process such as binding. According to such a manufacturing method, the metal sintered body can have, for example, a relative density of 96% or more and a surface hardness of 200 to 300 HV. In addition, the conditions for sintering the above-described metal powder can be appropriately adjusted according to chemical components, desired surface hardness, and the like.

  In the present invention, as the powder raw material, the above-mentioned Si powder, SUS410L metal powder or SUS430L metal powder has an average particle size of about 7 to 13 μm, generally called carbonyl iron powder, and containing C at 1% or less, It is desirable to mix and use 10 to 20% by mass of fine iron powder having an average particle size of about 3 to 8 μm. When an appropriate amount of carbonyl iron powder having an average particle size smaller than that of the metal powder serving as the base material is added, the sinterability of the metal powder is improved, so that an effect of increasing the relative density of the obtained metal sintered body can be expected. Further, C contained in the carbonyl iron powder causes a CO reaction with O which is easily contained excessively due to kneading treatment in the manufacturing process of the material for injection molding. This CO reaction has the effect of reducing the content of O and C which are easily contained excessively in the metal sintered body and tend to deteriorate the magnetic properties. Therefore, particularly the maximum magnetic permeability and the retention of the soft magnetic material obtained from the metal sintered body are obtained. Further optimization of the magnetic force can be expected.

In the present invention, as described above, the surface hardness of the soft magnetic material is increased to a suitable range by containing Si. However, Si combines with O to generate SiO ₂ , and when SiO ₂ is excessively generated, the magnetic characteristics may be deteriorated. Therefore, in the present invention, as described above, it is desirable that the carbonyl iron powder is mixed to cause the CO reaction, thereby inducing the refinement and dispersion of SiO ₂ produced by consuming O.

  In the present invention, the metal sintering method for obtaining the above-described metal sintered body is not limited to the above-described MIM method, and a press sintering method, a plasma sintering method, and the like are applicable. In general, the MIM method is known as a powder sintering method capable of forming a complicated shape with high dimensional accuracy. For example, even a magnetic component having a suitable shape can be easily formed to improve the operation characteristics of the device. Therefore, it is suitable for forming a metal sintered body.

  In the above-described method for producing a ferritic stainless steel soft magnetic material of the present invention, the sintered metal can be sintered under appropriate conditions to have a relative density of 96% or more and a surface hardness of 200 to 300 HV. Moreover, by magnetically annealing the metal sintered body under appropriate conditions, it is possible to have magnetic characteristics with a maximum magnetic permeability of 2500 or more, a magnetic flux density (B10) of 1.0 T or more, and a coercive force of 150 A / m or less.

  For example, the above-described magnetic annealing applied to the sintered metal body uses a heat treatment furnace to which an external magnetic field is applied, and is held at a furnace temperature of 920 to 980 degrees for 2 to 4 hours, and then the temperature is lowered at 130 to 170 degrees / hour. Conditions can be applied. By subjecting a sintered metal body to magnetic annealing under such conditions, for example, a metal whose magnetic properties are a maximum permeability of 2500 or more, a magnetic flux density (B10) of 1.0 T or more, and a coercive force of 150 A / m or less. A sintered body, that is, the ferritic stainless steel soft magnetic material of the present invention can be obtained. The conditions for magnetic annealing can be appropriately adjusted according to the desired magnetic properties.

  Further, in the production method of the present invention, the content ratio C / O of O and C contained in the metal sintered body is controlled in the range of 0.5 to 1.4, and By performing the same magnetic annealing, for example, the metal sintered body having a maximum magnetic permeability of 4000 or more, a magnetic flux density (B10) of 1.1 T or more, and a coercive force of 100 A / m or less, that is, the ferrite stainless steel of the present invention. -Based soft magnetic material can be obtained.

  In order to evaluate the surface hardness and magnetic properties of the ferrite stainless steel soft magnetic material of the present invention, a ferrite stainless steel soft magnetic material having the chemical components shown in Table 1 and having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 2 mm. Test specimens having a shape (Examples of the present invention: A to H, Comparative examples: a to f) were produced. In manufacturing these test bodies (A to H, a to f), a metal sintered body formed by the MIM method was used. Each test specimen actually contains other elements such as Ni, Mn, S, and P, which are not shown in Table 1, and is included in the balance shown in the column of Fe.

  Specifically, the metal sintered body was manufactured by the following procedure. First, a metal powder having an average particle size of 9.2 μm having a chemical component approximate to SUS410L, or a metal powder having an average particle size of 8.9 μm having a chemical component approximate to SUS430L is used. Add an appropriate amount of Si powder having the same average particle size according to the chemical composition of the desired test specimen, and add an appropriate amount of carbonyl iron powder with an average particle size of 4.3 μm depending on the test specimen. A powder raw material was prepared. The powder raw material was mixed and kneaded with paraffin wax or polypropylene serving as a binder to obtain a material for injection molding. And this injection molding raw material was inject | poured in the metal mold | die which has a cavity corresponding to a desired shape, and formed the metal powder molded object. A furnace immersed in a solvent to remove paraffin wax from the resulting metal powder former, and then heated to remove the polypropylene, and subsequently temperature controlled to 1240-1250 degrees depending on the desired chemical composition of the specimen. The metal powder was sintered by holding for 4 hours, and a metal sintered body substantially corresponding to the ring shape described above and having substantially the respective chemical components shown in Table 1 was obtained.

  Next, the obtained metal sintered body was magnetically annealed. In the magnetic annealing, each metal sintered body is held for 3 hours in a temperature-controlled furnace so that the temperature is raised to 950 degrees in about 3 hours from room temperature, and then lowered to 200 degrees at 150 degrees / hour. The temperature was controlled, and then each metal sintered body was taken out of the furnace and cooled to room temperature (approximately 20 degrees).

  A ferritic stainless steel soft magnetic material which is a ring-shaped metal sintered body having the chemical components shown in Table 1 after the magnetic annealing described above, and is a test body (A to H) which is an example of the present invention and a comparison Example specimens (af) were obtained. For each of the obtained ring-shaped specimens (A to H, a to f), the relative magnetic density, surface hardness (Vickers hardness), and magnetic properties such as maximum permeability, magnetic flux density (B10), The magnetic force was measured. The measurement results are shown in Table 2. The relative density is measured with a commercially available true density measuring device to which the pycnometer method is applied, and the bulk density of a specimen made of a sintered metal is measured with a wet Archimedes method. I asked for it.

[Relative density]
The relative density of each specimen shown in Table 2 reached 96.0% except for specimen f, which was 95.3%, and in particular, specimen a was high and reached 98.8%. In light of the chemical components shown in Table 1, this is presumed that the relative density of the specimen f was the lowest because the O content exceeded 0.30%. On the other hand, the relative density of the specimen a was the highest because the O content was relatively low at 0.133% and the C content was 0.004%, which was the smallest among the specimens. I was able to guess. Moreover, when O content was compared also about this other test body, it turned out that there exists a tendency for the relative density of a test body to become high, so that there is little O content like test body AD.

  Therefore, in the present invention, the relative density of the ferrite stainless steel soft magnetic material made of the metal sintered body can be adjusted to 96% or more by suppressing the O content of the metal sintered body to 0.30% or less. understood.

[Surface hardness]
The surface hardness of each specimen shown in Table 2 exceeded 200 HV for specimens A to H and specimens b, e, and f, while specimens a, c, and d did not reach 200 HV. In light of the chemical components shown in Table 1, the surface hardness of the specimens containing a large amount of Si, such as specimens E, b, and e, is clearly harder and contains 3.0% or more of Si. It turns out that it has surface hardness of 200HV or more only for the test body to do. On the other hand, when the surface hardness exceeds 300 HV and becomes too hard, as described above, the soft magnetic material tends to become brittle and may cause problems such as wear and damage. The test body b shown in Table 2 exceeds 300 HV, which can cause embrittlement, and contains more than 5.0% of Si among chemical components.

  Therefore, in the present invention, by setting the Si content of the metal sintered body to 3.0% or more, the surface hardness of the ferrite stainless steel soft magnetic material made of the metal sintered body can be adjusted to 200 HV or more. It was found that the amount can be adjusted to 300 HV or less by adjusting the amount to 5.0% or less. Further, the surface hardness of the specimens a and c having a C content of less than 0.01% was 150 HV or less, and the surface hardness of other specimens containing 0.01% or more of C was 150 HV. It was over. Therefore, although C is an impurity, it was confirmed that the surface hardness is improved by the slight C content. Moreover, since the test bodies A to F had a surface hardness of 230 HV or higher, it was confirmed that the surface hardness was further improved by containing 0.02% or more of C.

[Maximum permeability]
Among the magnetic properties of the respective test specimens shown in Table 2, the maximum magnetic permeability was 2500 or more excluding the test specimens e and f. Moreover, the test bodies A to C had a suitable surface hardness of 200 to 300 HV, and the maximum magnetic permeability had reached 4000. This is because, in light of the chemical components shown in Table 1, the C content exceeded 0.07% in the specimen e having a small maximum magnetic permeability, and similarly, the O content in the specimen f was 0.30. It was possible to guess that it was caused by the fact that the percentage exceeded. On the other hand, for the specimens having a maximum magnetic permeability of 2500 or more, the O content is 0.30% or less and the C content is 0.07% or less in any specimen.

  Therefore, in the present invention, in the ferritic stainless steel soft magnetic material made of a metal sintered body, inevitably contained impurities O are suppressed to 0.30% or less and impurities C to 0.07% or less. Thus, it was found that the maximum permeability of the ferrite stainless steel soft magnetic material made of a metal sintered body can be adjusted to 2500 or more.

[Magnetic flux density (B10)]
The magnetic flux density (B10) among the magnetic properties of the respective test bodies shown in Table 2 was 1.0 T or more, which is desirable as a soft magnetic material in all the test bodies. Therefore, it contains 8.0 to 13.5% of Cr, 3.0 to 5.0% of Si, the balance Fe and unavoidable impurities. Of the unavoidable impurities, O is 0.30% or less and C is contained. It was found that the ferritic stainless steel soft magnetic material made of the metal sintered body of the present invention, suppressed to contain 0.07% or less, can obtain a magnetic flux density (B10) of 1.0 T or more.

[Coercivity]
Of the magnetic properties of each specimen shown in Table 2, the coercive force did not exceed 150 A / m in any specimen, and had a small coercive force that was desirable as a soft magnetic material. . In particular, the test bodies A to E had a suitable surface hardness of 200 to 300 HV and still had a small coercive force of 100 A / m or less.

[Content ratio C / O]
Specimens A to C corresponding to the examples of the present invention have better surface properties of 230 to 260 HV, and better magnetic properties, that is, 4000 or more in the above-described use of the ferrite stainless steel soft magnetic material. The maximum magnetic permeability, magnetic flux density (B10) of 1.1 T or more, and coercive force of 100 A / m or less could be obtained. In this regard, in light of the chemical components shown in Table 1, it can be confirmed that the content ratio C / O of O and C is in the range of 0.5 to 1.4 only in the test bodies A to C. Therefore, in forming a metal sintered body used as a raw material, by controlling the content ratio C / O of impurities O and C to a range of 0.5 to 1.4, as described above, a more suitable range. It was found that a ferritic stainless steel soft magnetic material made of a sintered metal having a surface hardness and better magnetic properties can be obtained.

[Cr content]
In the present invention, in the test bodies A to H in which the contents of Si, O, and C are controlled in an appropriate range, the Cr content is changed in the range of 8.52 to 13.36%. However, the ferritic stainless steel soft magnetic material comprising the sintered metal body of the present invention has a surface hardness of 200 to 300 HV, a maximum magnetic permeability of 2500 or more, and a magnetic flux density (B10) of 1.0 T in any of the test bodies A to H. As described above, it has been found that it has a coercive force of 150 A / m or less and is hardly affected by the Cr content. Therefore, the Cr content capable of imparting corrosion resistance to the soft magnetic material is selected when a chemical component such as the test specimens A to D is selected when better magnetic properties are desired, and is tested when better corrosion resistance is desired. It could be assumed that it is desirable to select chemical components such as the bodies E to H.

  As described above, Cr contains 8.0 to 13.5% Cr, 3.0 to 5.0% Si, the balance Fe and unavoidable impurities, and O of the unavoidable impurities is 0. From the sintered metal body having a shape approximating a desired ring shape, the ferrite stainless-based soft magnetic material of the present invention, which is a sintered metal body containing 30% or less and C containing 0.07% or less. I was able to get it. Moreover, the ferritic stainless steel soft magnetic material of the present invention made of a metal sintered body having a relative density of 96% or more and a surface hardness of 200 to 300 HV could be obtained. Moreover, the ferritic stainless steel of the present invention has magnetic characteristics that the maximum magnetic permeability is 2500 or more, the magnetic flux density (B10) is 1.0 T or more, and the coercive force is 150 A / m or less by magnetic annealing of the sintered metal under appropriate conditions. -Based soft magnetic material could be obtained.

  Further, in forming a sintered metal body, by controlling the C / O content ratio in the range of 0.5 to 1.4, the metal has a relative density of 96% or more, a surface hardness of 230 to 260 HV, and a maximum permeability. It was possible to obtain a more excellent ferritic stainless steel soft magnetic material having magnetic properties of a magnetic permeability of 4000 or more, a magnetic flux density (B10) of 1.1 T or more, and a coercive force of 100 A / m or less.

Claims (6)

In mass%, Cr contains 8.0 to 13.5%, Si contains 3.0 to 5.0%, the balance Fe and unavoidable impurities, and among the unavoidable impurities, O is 0.30% or less and Ferrite stainless steel soft, characterized in that it is made of a metal sintered body in which C is suppressed to 0.07% or less and the C / O content ratio C / O is 0.5 to 1.4. Magnetic material. 2. The ferritic stainless steel soft magnetic material according to claim 1 , having a relative density of 96% or more and a surface hardness of 200 to 300 HV. The ferritic stainless steel soft magnetic material according to claim 2 , having a maximum magnetic permeability of 2500 or more, a magnetic flux density (B10) of 1.0 T or more, and a coercive force of 150 A / m or less. The ferrite stainless steel soft magnetic material according to any one of claims 1 to 3 , wherein the metal powder injection molded body is a sintered metal sintered body. A metal powder molded body formed by a metal powder injection molding method is sintered after degreasing, and by mass%, Cr is 8.0 to 13.5%, Si is 3.0 to 5.0%, the remainder Fe and unavoidable Impurities are contained, and among the inevitable impurities, O is suppressed to 0.30% or less and C is suppressed to 0.07% or less, and the content ratio C / O of C to O is 0.5 to 1. A method for producing a ferritic stainless steel soft magnetic material, comprising forming a sintered metal body 4 and magnetically annealing the sintered metal body. The metal sintered body adjusted to a relative density of 96% or more, surface hardness of 200 to 300 HV and sintered is subjected to magnetic annealing to obtain a maximum magnetic permeability of 2500 or more, a magnetic flux density (B10) of 1.0 T or more, and a coercive force of 150 A. The method for producing a ferritic stainless steel soft magnetic material according to claim 5 , wherein the ferritic stainless steel soft magnetic material is obtained by adjusting to / m or less.