JP2013021228A - Soft magnetic sintering material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic sintering material, having high magnetic flux density and high sintering contraction amount, capable of obtaining high bonding strength of a sintered component as a result, and applicable to a small component.SOLUTION: The soft magnetic sintering material, in which Co powders or Co alloy powders of 30 μm or smaller in grain size are added to alloy powders containing Fe of 80 mass% or more as a main constituent, is characterized by that a Co content is less than 15 mass% (without including 0) of a total mass.

Description

  TECHNICAL FIELD The present invention relates to a soft magnetic sintered material, and more specifically, soft magnetic sintering suitable for electromagnetic valve parts such as an armature for an injector of a common rail system in which the magnetic flux density and joint strength of the sintered parts are simultaneously increased. Regarding materials.

  Soft magnetic sintered materials are used for electronics control and the like in automobiles, machine tools, and the like by utilizing their high magnetic permeability and high magnetic flux density. Specifically, this soft magnetic sintered material is used for, for example, an injector armature, a motor core, and the like.

  In general, in order to obtain a high magnetic flux density, a sintered soft magnetic material promotes a sintering action by adding a sintering promoting element such as silicon (Si) or phosphorus (P) to iron (Fe) as a main component. As a result, a technique for improving the density is adopted. The obtained sintered body is, for example, a sintered body such as an Fe—P alloy or an Fe—Si—P alloy.

  Patent Document 1 discloses a sintered soft magnetic material capable of realizing both high magnetic flux density and high strength by preventing the coarsening of crystal grains and the occurrence of embrittlement due to the promotion of sintering in this way. 1 is disclosed.

JP 2009-102711 A

  Soft magnetic sintered parts are required to be smaller in size and higher in magnetic flux density. However, when the parts are downsized, the bonding strength of the sintered material is reduced, and the conventional technique cannot solve the problem of the reduction in the bonding strength.

  The present invention has been considered in view of the above circumstances, and has a higher magnetic flux density and higher sintering shrinkage compared to conventional soft magnetic sintered materials, and as a result, sintered parts. It is an object of the present invention to provide a soft magnetic sintered material that can be applied to small parts and that can obtain a high bonding strength during manufacturing.

  The present inventors diligently studied to obtain a soft magnetic sintered material having both high magnetic flux density and high sintering shrinkage. As a result, it has been found that a high magnetic flux density can be obtained by adding Co having ferromagnetism to a sintered material such as Fe-Si-P. Furthermore, it has been found that by adding fine Co, a high amount of sintering shrinkage can be obtained, and as a result, high bonding strength can be obtained when used for sintered parts.

  The present invention is a soft magnetic sintered material made on the basis of the above knowledge, and Co powder or Co alloy powder having a particle size of 30 μm or less is added to an alloy powder containing 80 mass% or more of Fe as a main component. A soft magnetic sintered material, characterized in that the Co content is less than 15% by mass (excluding 0) with respect to the total mass.

  By adding fine Co powder or Co alloy powder having a high magnetic flux density, a soft magnetic sintered material having a high magnetic flux density and a high sintering shrinkage can be obtained. As a result, even when applied to small sintered parts, high joint strength can be obtained, and it can be applied to electromagnetic valve parts such as injector armatures for common rail systems.

  The present invention further provides a soft magnetic ceramic containing one or two of P: less than 1.0% by mass (excluding 0) and Si: 1.5-3.5% by mass with respect to the total mass. Provide ligation material.

  By adding P, sintering is promoted. Further, the soft magnetic sintered body is densified to improve the saturation magnetic flux density. By adding Si, iron loss can be reduced and magnetic permeability can be improved.

  The present invention further provides a soft magnetic sintered material containing V: less than 0.6% by mass (excluding 0) with respect to the total mass. By adding V, coarsening of crystal grains due to the promotion of sintering can be suppressed.

  The present invention further provides a soft magnetic sintered material characterized in that the content of elements other than Fe, Co, V, P, and Si is less than 0.65 mass% with respect to the total mass. .

  The present invention further provides a soft magnetic sintered material having a Co content of 5% by mass or more.

  The present invention is further characterized in that it is obtained by pressure-molding the soft magnetic sintered material, forming a green compact having a predetermined shape, and then sintering the green compact. A soft magnetic sintered body is provided.

  The present invention further provides a soft magnetic sintered part obtained by diffusion bonding the above soft magnetic sintered body and a steel material.

It is a figure explaining the outline of the manufacturing method of the sintered component using a sintered material. It is a figure which shows the outline of the test piece in the Example of this invention, (a) is a test piece for a crystal grain coarsening rate and a joint strength measurement, (b) is a test piece for shrinkage | contraction amount measurement. It is a figure which shows the outline of a joining strength measuring apparatus. It is a figure which shows the relationship between Co alloy powder addition amount and magnetic flux density of the soft magnetic sintering material of this invention. It is a figure which shows the relationship between the amount of Co alloy powder addition, and the coarsening rate of a crystal grain of the soft-magnetic sintered material of this invention. It is a figure which shows the relationship of Co alloy powder addition amount, shrinkage | contraction amount, and joining strength of the soft magnetic sintering material of this invention, (a) is what used Fe-49Co-2V for Co alloy powder, (b ) Uses Fe-50Co as Co alloy powder.

  Soft magnetic sintered parts are required to be smaller in size and higher in magnetic flux density. High magnetic flux density can be realized by increasing the molding density of the sintered body or by increasing the sintering temperature. However, with this method, the crystal grains become coarse and the static strength of the sintered body decreases. In addition, in a part that requires high joint strength with downsizing, the shrinkage amount of the sintered part is reduced, and joint strength is lowered.

  The present invention solves the above problems by increasing the magnetic flux density and the amount of shrinkage of a soft magnetic sintered material and adding fine Co powder or Co alloy powder. Embodiments of the present invention will be described below. The present invention is not limited to the forms exemplified below. In the following description, “%” represents “mass%”.

  The soft magnetic sintered material of the present invention has both high magnetic flux density and high shrinkage by adding fine Co powder or Co alloy powder having a particle size of 30 μm or less to an alloy containing Fe as a main component. It features. The base sintered material is not particularly limited as long as it is an Fe-based material, but an Fe-Si-P-based alloy, an Fe-P-based alloy, or the like is preferable. Hereinafter, the elements and addition amounts contained in the soft magnetic sintered material of the present invention will be described.

  Since Co powder and Co alloy powder are materials having a high saturation magnetic flux density, the magnetic flux density of the soft magnetic sintered material is improved by adding them. Further, by adding fine Co powder or Co alloy powder, sintering is promoted, and the shrinkage of the sintered body is increased. As a result, when the sintered part is manufactured, the contact area between the molten material and the sintered body is increased, the mutual diffusion between the molten material and the sintered body is promoted, and the bonding strength is improved.

  FIG. 1 shows an outline of manufacturing a sintered part. In the production of sintered parts, the molten material 2 is assembled to the molded body of the sintered material 1 with a predetermined fitting allowance d, the sintered material 1 is sintered, and at the same time, the sintered material 1 and the molten material 2 are diffused. Integrate by joining.

  Even if a small amount of Co is added, an effect of suppressing the coarsening of crystal grains can be obtained. However, in order to obtain a higher effect, that is, a high bonding strength in a sintered part, the amount of Co added is 2. 5% or more is preferable, and in order to obtain a high magnetic flux density, 5% or more is preferable.

  If the amount of Co added is too large, the moldability of the soft magnetic sintered material is deteriorated, and cracks may occur during molding. Therefore, the addition amount of Co is set to 15% or less.

  Si is an element that reduces iron loss and further improves magnetic permeability. As a result, the responsiveness of a solenoid valve or the like can be improved and added as necessary. Further, the sintering is promoted and the sintered soft magnetic material is densified to improve the saturation magnetic flux density. In order to obtain these effects, the addition amount is 1.5% or more of the total mass of the sintered material.

  As the amount of Si increases, the occupation ratio of Fe in the soft magnetic sintered material decreases, and as a result, the saturation magnetic flux density decreases. Further, when the sintering is promoted, the crystal grains become coarse, and as a result, the strength of the sintered body decreases. Therefore, the addition amount is 3.5% or less, preferably 2.5% or less.

  P is an element that promotes sintering and densifies the sintered soft magnetic material to improve the saturation magnetic flux density, and is added as necessary. However, if the sintering is promoted too much, the crystal grains are coarsened, and as a result, the strength of the sintered body is lowered. A preferable addition amount of P is 0.2 to 0.6%.

  V is an element that suppresses the coarsening of crystal grains due to the promotion of sintering due to the pinning effect, and is added as necessary. In order to obtain this effect, the amount of V is 0.1% or more. As the amount of added V increases, the occupation ratio of Fe decreases, and as a result, the saturation magnetic flux density decreases. Therefore, the added amount is set to 0.6% or less.

  In addition, for example, elements other than Fe, Si, P, Co, and V such as Ti, Nb, Mn, S, C, and N may be added for the purpose of improving the characteristics of the soft magnetic sintered material. However, when the addition amount of other elements increases, the occupation ratio of Fe decreases, and as a result, the saturation magnetic flux density decreases. Therefore, the addition amount of elements other than Fe, Si, P, Co, and V, including inevitable impurities, is less than 0.65% with respect to the total mass of the soft magnetic sintered material.

  The soft magnetic sintered material of the present invention is, for example, an alloy powder obtained by mixing a small amount of Si powder and P powder with atomized iron powder (Fe), Co powder having a particle size of 30 μm or less, or Fe-50Co, Fe-49Co. It is obtained by adding a mixed metal powder containing a Co alloy powder such as −2 V so that the amount of Co added is less than 15% with respect to the total mass.

  Furthermore, a powder of a crystal grain refining element, for example, Mn powder or S powder may be mixed within a range that does not adversely affect the characteristics of the soft magnetic sintered material of the present invention.

  If this soft magnetic sintered material is usually pressure-molded at about 500 to 850 MPa, then a green compact having a predetermined shape is formed, and then the green compact is sintered at an elevated temperature. A soft magnetic sintered body is obtained.

  The sintering treatment can be performed under various processing conditions depending on the composition of the molded body. For example, the sintering process can be performed by heating the molded body for about 1 to 2 hours at a temperature of about 1100 to 1300 ° C. in an atmosphere of a non-oxidizing gas such as argon gas under vacuum conditions.

  Before pressing, a mixed lubricant is mixed with the mixed metal powder, and after pressing, about 600 under an atmosphere of reducing gas such as hydrogen gas, argon gas, non-oxidizing gas, etc. under vacuum conditions. A step of degreasing the green compact at a temperature of ˜700 ° C. for about 1 to 2 hours to remove the lubricant may be included.

  A step of heat-treating the obtained sintered body may be further included after the sintering in order to increase the strength. The heat treatment is preferably quenching and subsequent tempering (so-called QT treatment). Quenching can be performed at a temperature of about 1100 to 1200 ° C, for example, and tempering can be performed at a temperature of about 500 to 600 ° C, for example. After the QT treatment, the sintered body may be further heat-treated as necessary.

  The soft magnetic sintered material of the present invention manufactured by the above method has a high magnetic flux density and a high amount of sintering shrinkage. Therefore, even when used for a small sintered part, it has a high bonding strength. Demonstrate. Therefore, it can be applied to electromagnetic valve parts such as injector armatures for common rail systems.

  Of course, needless to say, the application object of the soft magnetic sintered material of the present invention is not limited to the solenoid valve component. Further, the present invention is not limited to the description of the embodiment of the above invention. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

  A soft magnetic sintered material is prepared by mixing Si powder and P powder with atomized iron powder (Fe) and further mixing Co alloy powder (Fe-49Co-2V or Fe-50Co) with a particle size of 30 μm or less. did.

  The addition amount of Co alloy powder was changed as appropriate, and a plurality of soft magnetic sintered materials having different Co addition amounts were produced. The addition amount of Si powder was 2.0%, and the addition amount of P powder was 0.35%. The average particle diameter of the Fe—Si—P mixed powder was about 80 μm.

  A molding lubricant was added to the produced soft magnetic sintered material, and then the mixed powder was filled in a mold and a test piece was produced by pressure molding. The test piece is an annular test piece having an outer diameter of 19 mm, an inner diameter of 13 mm, and a height of 3.5 mm for measuring the magnetic flux density, and a shaft attached to the annular test piece for measuring the crystal grain coarsening rate and bonding strength. A test piece shown in FIG. 2B without a shaft was prepared for measuring the shrinkage and the test piece shown in a).

The pressure molding was performed by applying a pressure of about 500 to 700 MPa to obtain a molded body having a molding density of 6.7 to 6.8 g / cm ³ . Next, the obtained molded body was heated in a vacuum atmosphere at a temperature of about 650 ° C. for about 1 hour to volatilize the lubricant and degrease.

  After completion of the degreasing treatment, the compact was sintered by heating at a temperature of about 1200 ° C. for about 1 hour under vacuum to obtain a sintered body (product of the present invention). About the obtained test piece, it tested about the following item.

[Magnetic flux density]
The magnetic flux density of the produced test piece was measured using a commercially available DC magnetization characteristic device (manufactured by Riken Denshi Co., Ltd.). FIG. 4 shows the relationship between the magnetic flux density and the amount of added Co alloy powder in a soft magnetic sintered body using Fe-49Co-2V and Fe-50Co as Co alloy powder, and as a comparative example, Fe- without adding Co. The magnetic flux density in the sintered compact manufactured by making a molding density and sintering temperature high with Si-P type sintered material is shown.

  In addition, the horizontal axis of FIG. 4 is the addition ratio of Co alloy powder (Fe-49Co-2V or Fe-50Co), and the Co content ratio of the soft magnetic sintered material is the value of the horizontal axis in the alloy powder. This is a value obtained by multiplying the Co content ratio (hereinafter the same in FIGS. 5 and 6).

  From the results shown in FIG. 4, in the soft magnetic sintered material of the present invention, the magnetic flux density increases as the amount of Co increases, and particularly when the Co alloy powder exceeds 10%, the Fe—Si—P system in which Co is not added. It was confirmed that the magnetic flux density was higher than that of the sintered material.

[Grain coarsening rate]
The cross-sectional structure of the sintered armature sintered body (sintered body 1 in FIG. 1) is observed with a metal microscope, the area of coarsened crystal grains in the observed region is measured, and the area of the observed region is measured. The ratio was defined as the crystal grain coarsening rate. Here, the coarsened crystal grains refer to those having an equivalent circle diameter of 200 μm or more.

  FIG. 5 shows the relationship between the crystallization coarsening rate and the amount of added Co alloy powder of a soft magnetic sintered body using Fe-49Co-2V and Fe-50Co as Co alloy powder, and Co is added as a comparative example. The crystal grain coarsening rate in the sintered compact manufactured by making a molding density and sintering temperature high with the Fe-Si-P type sintered material which does not do is shown.

  From the results of FIG. 5, it was confirmed that the soft magnetic sintered body of the present invention can greatly suppress the coarsening of crystal grains as compared with the Fe—Si—P based sintered body.

[Shrinkage, bonding strength]
The amount of shrinkage was determined by measuring the inner diameter of the test piece for measuring the amount of shrinkage shown in FIG. The bonding strength is determined by applying a load to the shaft 12 with the pin 21 of the apparatus shown in FIG. 3 using the test piece for measuring the bonding strength shown in FIG. It was.

  FIG. 6 (a) shows the relationship between the shrinkage and bonding strength of the soft magnetic sintered body using Fe-49Co-2V as the Co alloy powder and the amount of Co alloy powder added, and FIG. 6 (b) shows the Co alloy powder. The relationship between the shrinkage amount and bonding strength of the soft magnetic sintered body using Fe-50Co and the addition amount of Co alloy powder is shown. FIG. 6 (a) also shows the amount of shrinkage and the bonding strength of a sintered body produced with an Fe-Si-P system and with a higher molding density and sintering temperature.

  From the results of FIG. 6, it was confirmed that the soft magnetic sintered body of the present invention can obtain a good shrinkage and bonding strength as compared with the Fe—Si—P-based sintered material.

  As mentioned above, although this invention was demonstrated more concretely with reference to the Example, it cannot be overemphasized that this invention is not limited by these Examples.

DESCRIPTION OF SYMBOLS 1 Sintered body 2 Melted material 11 Sintered body 12 Shaft 21 Pin (SKT51 which processed QT)
d Mating allowance

Claims (7)

  A soft magnetic sintered material obtained by adding Co powder or Co alloy powder having a particle size of 30 μm or less to alloy powder containing Fe of 80% by mass or more as a main component, the Co content being 15% of the total mass A soft magnetic sintered material characterized by being less than mass% (not including 0). For the total mass,
P: Less than 1.0% by mass (excluding 0)
Si: 1.5 to 3.5% by mass
The soft magnetic sintered material according to claim 1, comprising one or two of the following. For the total mass,
V: 0.6 mass% or less (excluding 0)
The soft magnetic sintered material according to claim 1, wherein the soft magnetic sintered material is contained.   The soft element according to any one of claims 1 to 3, wherein the content of elements other than Fe, Co, V, P, and Si is less than 0.65 mass% with respect to the total mass. Magnetic sintered material.   Co soft content is 5 mass% or more, The soft-magnetic-sintering material of any one of Claims 1-4 characterized by the above-mentioned. Press-molding the soft magnetic sintered material according to any one of claims 1 to 5,
Forming a green compact with a predetermined shape, then
A soft magnetic sintered body obtained by sintering a green compact.   A soft magnetic sintered part obtained by diffusion-bonding the soft magnetic sintered body according to claim 6 and a steel material.

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