Soft magnetic component, and, method for producing soft magnetic component

Abstract

To improve rust resistance.SOLUTION: The soft magnetic component according to an embodiment of the present invention has a zinc layer formed on the surface of a sintered body made of nickel-coated iron powder. That is, in the soft magnetic component according to an embodiment of the present invention, the sintered body is formed from nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer. This suppresses the exposure of iron and improves rust resistance. Moreover, the method for producing the soft magnetic component according to an embodiment of the present invention is characterized by including a step of forming a zinc layer on the surface of a sintered body made of nickel-coated iron powder. That is, in the method for producing the soft magnetic component according to an embodiment of the present invention, the sintered body is formed from nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer. This suppresses the exposure of iron and improves rust resistance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic part that can improve rust prevention properties, and a method for manufacturing a soft magnetic part. [Background technology]

[0002] BACKGROUND ART Conventionally, soft magnetic parts made by sintering iron powder have been known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-145370 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional soft magnetic parts are prone to oxidation, and to improve their rust resistance, they must be immersed in rust-preventive oil or plated. If rust-preventive oil is used, they cannot be used in applications where oil is not permitted. On the other hand, if plating is performed, problems occur when the treatment solution penetrates into the pores, so a sealing process is required. As a result, a plating film is not formed in the sealing process, which may result in a decrease in rust resistance. An object of the present invention is to provide a soft magnetic part that can improve rust resistance, and a method for manufacturing a soft magnetic part. [Means for solving the problem]

[0005] In order to solve the above problems, a soft magnetic part according to a first invention is characterized in that a zinc layer is formed on the surface of a sintered body made of nickel-coated iron powder. In the soft magnetic component according to the first aspect of the present invention, the sintered body is formed from nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer, which prevents the iron from being exposed and improves rust resistance. Here, the soft magnetic parts include soft magnetic parts described below.

[0006] A method for producing a soft magnetic component according to a second aspect of the present invention is characterized by including a step of forming a zinc layer on the surface of a sintered body made of nickel-coated iron powder. In the method for manufacturing a soft magnetic component according to the second aspect of the present invention, the sintered body is formed from nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer, which prevents the iron from being exposed and improves rust resistance. Here, the process for forming the zinc layer corresponds to a sintering and zinc coating process or a degreasing, sintering and zinc coating process, which will be described later. [Effects of the Invention]

[0007] According to the soft magnetic part and the method for manufacturing the soft magnetic part of the present invention, it is possible to improve rust prevention properties. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing the components of the nickel-coated iron powder according to Examples 1 and 2. [Figure 2] 10 is a diagram showing the results of comparing the magnetic properties of the soft magnetic parts according to Examples 1 and 2 and the soft magnetic part according to Comparative Example 3. FIG. [Figure 3] 1 is a diagram showing the results of comparing rust prevention properties of the soft magnetic parts according to Examples 1 and 2 and the soft magnetic parts according to Comparative Examples 1 to 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] A soft magnetic part (hereinafter referred to as "soft magnetic part") according to an embodiment of the present invention will be described below. Soft magnetic parts can be applied to iron cores (plungers) used in electromagnetic actuators (electromagnetic valves, relays, solenoids, etc.) Soft magnetic parts are particularly suitable for use in environments where oil cannot be present, such as underwater or in coolant.

[0010] (Soft magnetic component configuration) First, the configuration of the soft magnetic part will be described. The soft magnetic part is formed by forming a zinc layer (zinc coating) on ​​the surface of a sintered body made of nickel-coated iron powder. In particular, the sintered body maintains a state in which the iron (component) is coated with nickel (component). That is, the sintered body is formed by mutually bonding particles of iron coated with nickel. The surface of the sintered body is then coated with zinc. The zinc layer is a layer in which zinc (Zn) is dispersed. In soft magnetic components, if the nickel content is less than 10 parts by mass per 100 parts by mass of iron, the rust prevention properties may be reduced. On the other hand, if the nickel content exceeds 30 parts by mass per 100 parts by mass of iron, the magnetic properties may be reduced. Therefore, it is preferable that the nickel content be 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of iron. Furthermore, in soft magnetic parts, if the zinc content is less than 0.1 parts by mass per 100 parts by mass of iron, the rust prevention properties may be reduced. On the other hand, if the zinc content exceeds 2.0 parts by mass per 100 parts by mass of iron, the magnetic properties may be reduced. Therefore, it is preferable that the zinc content be 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of iron. Furthermore, if the density of the soft magnetic part is less than 6.5, the magnetic properties may be degraded. On the other hand, if the density of the soft magnetic part is more than 7.6, the mold may be damaged. Therefore, it is preferable that the density of the soft magnetic part is in the range of 6.5 to 7.6. In soft magnetic parts, the surface of the iron is coated with a nickel layer. This prevents the iron from being exposed, improving rust resistance. In sintered bodies made of nickel-coated iron powder, pinholes may form in the nickel layer coating the iron, or the iron and nickel may interdiffuse, potentially exposing the iron at the surface of the nickel layer. Therefore, in soft magnetic parts, the surface of the sintered body is coated with a zinc layer. This allows the zinc layer to cover the iron exposed by pinholes or interdiffusion, preventing the iron from being exposed and improving rust resistance.

[0011] (Manufacturing method for soft magnetic parts) Next, a method for manufacturing a soft magnetic part will be described.

[0012] (Example 1) First, a method for manufacturing a soft magnetic component according to a first example will be described. The method for manufacturing a soft magnetic component according to the first example includes a stirring step, a powder compacting step, a degreasing step, and a sintering and zinc coating step. First, a stirring step is performed. In the stirring step, a die lubricant is added to the nickel-coated iron powder, and the mixture is stirred and mixed to produce a raw powder. Nickel-coated water-atomized iron powder can be used as the nickel-coated iron powder. In particular, Ni-P-based nickel-coated iron powder, Ni-B-based nickel-coated iron powder, and the like can be used as the nickel-coated iron powder. When using Ni-P-based nickel-coated iron powder, the P (phosphorus) content relative to the total amount of the nickel-coated iron powder is preferably within a range of 2% by weight to 13% by weight. When using Ni-B-based nickel-coated iron powder, the B (boron) content relative to the total amount of the nickel-coated iron powder is preferably within a range of 0.3% by weight to 1.0% by weight. Examples of die lubricants that can be used include powders of metal soaps, such as zinc stearate and lithium stearate, powders of fatty acid amides, such as ethylene bisstearamide, and powders of wax-based lubricants, such as polyethylene. In this embodiment, 0.7 parts by mass of ethylene bisstearamide (EBS) was added as a die lubricant to 100 parts by mass of nickel-coated iron powder to produce a raw material powder. Note that the raw material powder contains unavoidable impurities. Next, a powder compacting step is carried out. In the powder compacting step, the raw material powder is press-molded in a mold at a pressure of about 400 MPa to 1500 MPa to form a green compact. Next, a degreasing step is carried out. In the degreasing step, the green compact is heated under predetermined conditions in a predetermined atmosphere and at predetermined temperatures to sublimate and remove the die lubricant from the green compact. In this embodiment, degreasing is carried out in a degreasing furnace in an air atmosphere, an inert atmosphere, a reducing atmosphere, or a vacuum atmosphere, at a heating temperature in the range of 400°C to 800°C, and for a heating time in the range of 15 to 75 minutes. Here, the heating temperature in the degreasing step is lower than the heating temperature in the sintering and zinc coating steps.

[0013] Next, the sintering and zinc coating process is carried out. In this process, the powder compact is embedded in zinc oxide powder and heated under a predetermined atmosphere and temperature conditions to form a sintered body and a zinc layer (zinc coating) on ​​the surface of the sintered body. In this embodiment, the powder compact is embedded in zinc oxide powder filled in an alumina boat and heated with a porous or dense ceramic setter as the lid. In this embodiment, heating is carried out in a sintering furnace in a reducing atmosphere (to reduce oxygen in the powder compact and reduce zinc oxide to zinc), at a heating temperature ranging from 775°C to 975°C, and for a heating time ranging from 5 minutes to 120 minutes. In other words, if the heating temperature is below 775°C, sufficient zinc vapor may not be generated, resulting in an insufficient zinc layer on the surface of the sintered body. On the other hand, if the heating temperature exceeds 975°C, zinc may be sublimated, resulting in an insufficient zinc layer on the surface of the sintered body. Therefore, by setting the heating temperature within the range of 775°C to 975°C, it is possible to prevent the formation of an insufficient zinc layer on the surface of the sintered body. Furthermore, if the heating time is less than 5 minutes, zinc may not diffuse, resulting in an insufficient zinc layer on the surface of the sintered body. On the other hand, if the heating time exceeds 120 minutes, the iron may be exposed due to interdiffusion between iron, nickel, and zinc, resulting in a decrease in rust prevention properties. Therefore, by setting the heating time within the range of 5 to 120 minutes, it is possible to improve rust prevention properties. It is known that iron and nickel interdiffuse at approximately 600°C, and iron and zinc interdiffuse at approximately 500°C. The reducing atmosphere can be a mixture of nitrogen gas and hydrogen gas, a mixture of argon gas and hydrogen gas, or hydrogen gas. In this embodiment, heating is performed in an atmosphere of a mixture of nitrogen gas (93%) and hydrogen gas (7%). In this way, the soft magnetic part is manufactured.

[0014] In the first example of a manufacturing method for soft magnetic components, the degreasing process, which removes die lubricant from the green compact, and the sintering and zinc coating process, which form a sintered body and a zinc layer, are separate processes. This prevents decomposition gases from the die lubricant generated during degreasing from interfering with the generation of zinc vapor, and also prevents impurities generated during degreasing from interfering with the contact of zinc vapor with the surface of the sintered body, thereby improving rust resistance. Furthermore, by removing the die lubricant before sintering, it is possible to prevent impurities from remaining in the sintered body, which in turn prevents a deterioration in the magnetic properties of the soft magnetic component.

[0015] (Example 2) Next, a method for manufacturing a soft magnetic component according to a second example will be described. The method for manufacturing a soft magnetic component according to the second example includes a stirring step, a powder compacting step, and a degreasing, sintering, and zinc coating step. First, the stirring step is carried out. The details of the stirring step according to the second example are the same as those of the stirring step according to the first example. Next, a powder compacting step is carried out. The powder compacting step according to the second example is the same as the powder compacting step according to the first example. Next, the degreasing, sintering, and zinc coating process is carried out. In this process, the green compact is embedded in zinc oxide powder and heated under predetermined conditions in a predetermined atmosphere and at a predetermined temperature to sublimate and remove the die lubricant from the green compact, form a sintered body, and form a zinc layer (zinc coating) on ​​the surface of the sintered body. In this embodiment, the green compact is embedded in zinc oxide powder filled in an alumina boat and heated with the boat covered with a porous alumina setter. In this embodiment, degreasing is carried out in the same furnace in a reducing atmosphere (to reduce oxygen in the green compact and reduce zinc oxide to zinc), at a heating temperature of 300°C to 600°C, and for a heating time of 15 to 75 minutes. Subsequently, sintering and zinc layer formation are carried out at a heating temperature of 775°C to 975°C and for a heating time of 5 to 120 minutes. The reducing atmosphere can be a mixed gas of nitrogen gas and hydrogen gas, a mixed gas of argon gas and hydrogen gas, hydrogen gas, etc. In this embodiment, debinding and sintering are carried out in an atmosphere of a mixture of nitrogen gas (93%) and hydrogen gas (7%). In this way, the soft magnetic part is manufactured.

[0016] In the manufacturing method for a soft magnetic component according to the second example, degreasing to remove die lubricant from the green compact, forming a sintered body, and forming a zinc layer are carried out in a single step, which simplifies the manufacturing process.

[0017] (Example) Next, an embodiment of the present invention will be described. Fig. 1 is a diagram showing the components of the nickel-coated iron powder according to Examples 1 and 2. Fig. 2 is a diagram showing the results of comparing the magnetic properties of the soft magnetic parts according to Examples 1 and 2 and the soft magnetic part according to Comparative Example 3. Fig. 3 is a diagram showing the results of comparing the rust prevention properties of the soft magnetic parts according to Examples 1 and 2 and the soft magnetic parts according to Comparative Examples 1 to 3. As Examples 1 and 2 of the present invention, soft magnetic parts were manufactured using the soft magnetic part manufacturing method according to the first example described above. In the powder compacting process, a cylindrical green compact with an outer diameter of 16 mm, an inner diameter of 8 mm, and a total length of 5 mm was formed at a green compaction pressure of 800 MPa. In the debinding process, a debinding treatment was performed in a vacuum atmosphere at a heating temperature of 600°C for 45 minutes. In the sintering and zinc coating process, the green compact was embedded in zinc oxide powder packed in an alumina boat and sintered and zinc coated with the boat covered with a porous alumina setter. In the sintering and zinc coating process, a reducing atmosphere (a mixture of nitrogen gas (93%) and hydrogen gas (7%)) was used at a heating temperature of 875°C for 15 minutes. The average particle size of the zinc oxide powder was 0.6 μm. In particular, in Example 1, 0.7 parts by mass of ethylene bisstearamide (EBS) was added as a die lubricant to 100 parts by mass of Ni-P based nickel-coated iron powder in the stirring step to produce a raw material powder. Meanwhile, in Example 2, 0.7 parts by mass of ethylene bisstearamide (EBS) was added as a die lubricant to 100 parts by mass of Ni-B based nickel-coated iron powder in the stirring step to produce a raw material powder. As shown in FIG. 1 , the nickel-coated iron powder of Example 1 contained 23% by mass of Ni and 0.47% by mass of P relative to the total amount of the nickel-coated iron powder, with the remainder being Fe and unavoidable impurities. Meanwhile, the nickel-coated iron powder of Example 2 contained 14% by mass of Ni and 0.14% by mass of B relative to the total amount of the nickel-coated iron powder, with the remainder being Fe and unavoidable impurities.

[0018] In Comparative Examples 1 and 2, soft magnetic parts were manufactured without zinc coating. Specifically, in Comparative Examples 1 and 2, 0.7 parts by mass of ethylene bisstearamide (EBS) was added as a die lubricant to 100 parts by mass of nickel-coated water-atomized iron powder to produce a raw material powder. A cylindrical green compact with an outer diameter of 8 mm, an inner diameter of 8 mm, and a total length of 5 mm was formed from the raw material powder at a compaction pressure of 800 MPa. The green compact was then sintered in a reducing atmosphere (a mixture of 93% nitrogen gas and 7% hydrogen gas) at a heating temperature of 600°C for 30 minutes to produce a soft magnetic part. In particular, in Comparative Example 1, the same Ni-P-based nickel-coated iron powder as in Example 1 was used as the nickel-coated iron powder. In Comparative Example 2, the same Ni-B-based nickel-coated iron powder as in Example 2 was used as the nickel-coated iron powder. Furthermore, as Comparative Example 3, a soft magnetic part was manufactured using iron powder without nickel coating. Specifically, in Comparative Example 3, 0.7 parts by mass of ethylene bisstearamide (EBS) was added as a die lubricant to 100 parts by mass of pure iron powder to produce a raw material powder. A cylindrical green compact with an outer diameter of 16 mm, an inner diameter of 8 mm, and a total length of 5 mm was formed from the raw material powder at a compacting pressure of 800 MPa. The green compact was then degreased in a reducing atmosphere (a mixture of 93% nitrogen gas and 7% hydrogen gas) at 400°C for 15 minutes, and subsequently sintered at 1100°C for 15 minutes. The sintered compact was then embedded in zinc oxide powder packed in an alumina boat, and zinc-coated with the boat covered with a porous alumina setter to produce a soft magnetic part. The zinc coating treatment was carried out in a reducing atmosphere (a mixture of nitrogen gas (93%) and hydrogen gas (7%)), at a heating temperature of 875°C, for 15 minutes. The average particle size of the zinc oxide powder was 0.6 μm.

[0019] For each of the soft magnetic parts according to Examples 1 and 2 and Comparative Example 3, the maximum magnetic flux density and magnetic permeability were measured when a magnetizing force of 4000 A / m was applied. As a result, as shown in Fig. 2, the soft magnetic component according to Example 1 had a maximum magnetic flux density of 0.74 T and a magnetic permeability of 325 μm. On the other hand, the soft magnetic component according to Example 2 had a maximum magnetic flux density of 0.83 T and a magnetic permeability of 227 μm. On the other hand, the soft magnetic component according to Comparative Example 3 had a maximum magnetic flux density of 1.52 T and a magnetic permeability of 3746 μm. This confirmed that although the soft magnetic parts of Examples 1 and 2 had lower magnetic properties than the soft magnetic part of Comparative Example 3, they still had the magnetic properties required of general soft magnetic parts.

[0020] Furthermore, the soft magnetic parts according to Examples 1 and 2 and Comparative Examples 1 to 3 were immersed in distilled water and the occurrence of rust over time was visually observed. As a result, as shown in FIG. 3, for the soft magnetic part according to Example 1, a thin brown color spread in distilled water after approximately 48 hours, confirming that only slight rust had occurred. On the other hand, for the soft magnetic part according to Example 2, no rust had occurred after approximately 96 hours. On the other hand, for the soft magnetic part according to Comparative Example 1, rust spots had occurred after approximately 24 hours. On the other hand, for the soft magnetic part according to Comparative Example 2, a thin brown color spread in distilled water after approximately 24 hours, confirming that only slight rust had occurred. On the other hand, for the soft magnetic part according to Comparative Example 3, rust had occurred after approximately 24 hours. This confirmed that the soft magnetic parts according to Examples 1 and 2 had higher rust prevention properties than the soft magnetic parts according to Comparative Examples 1 to 3. In particular, it was confirmed that the soft magnetic part according to Example 2 had higher rust prevention properties than the soft magnetic part according to Example 1. This is thought to be because P promoted the interdiffusion of nickel and iron in the soft magnetic part according to Example 1. That is, because Ni-P-based nickel-coated iron powder contains a large amount of P, it is thought that this promoted the diffusion of iron when the sintered body was subjected to a zinc coating process, resulting in a large amount of iron components being exposed on the surface of the sintered body.

[0021] Furthermore, for each of the soft magnetic parts according to Examples 1 and 2 and Comparative Example 3, the change in weight of the sintered body before and after zinc coating treatment was measured (n=2 average). As a result, the weight of the soft magnetic part according to Example 1 increased by 1.36% due to the zinc coating treatment. On the other hand, the weight of the soft magnetic part according to Example 2 increased by 0.81% due to the zinc coating treatment. On the other hand, the weight of the soft magnetic part according to Comparative Example 1 increased by 0.18% due to the zinc coating treatment. This confirmed that the soft magnetic components according to Examples 1 and 2 were more susceptible to the formation of a zinc layer than the soft magnetic component according to Comparative Example 3.

[0022] (Action of the present invention) In the soft magnetic component according to the embodiment of the present invention, a zinc layer is formed on the surface of a sintered body made of nickel-coated iron powder. That is, in the soft magnetic component according to the embodiment of the present invention, the sintered body is made of nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer. This prevents the iron from being exposed, and improves rust resistance. Furthermore, a method for manufacturing a soft magnetic component according to an embodiment of the present invention is characterized by including a step of forming a zinc layer on the surface of a sintered body made of nickel-coated iron powder. That is, in the method for manufacturing a soft magnetic component according to an embodiment of the present invention, the sintered body is formed from nickel-coated iron powder, and the surface of the sintered body is coated with a zinc layer. This prevents exposure of the iron and improves rust resistance.

Claims

1. A soft magnetic part characterized in that a zinc layer is formed on the surface of a sintered body made of nickel-coated iron powder.

2. A method for manufacturing a soft magnetic part, comprising the step of forming a zinc layer on the surface of a sintered body made of nickel-coated iron powder.

Images