Manufacturing method of FE-XSI (X = 4 - 10.0 WT%) alloy powder magnetic core by hot forming

Abstract

The present invention relates to a method for manufacturing an Fe-xSi (x = 4-10.0 wt%) alloy powder core having a high molding density, high magnetic permeability, and low iron loss, as compared with conventional room-temperature molding methods, and to an Fe-xSi (x = 4-10.0 wt%) alloy powder core by high-temperature molding manufactured by the manufacturing method. The method comprises: (a) a coating step of coating a metal alloy powder with an insulating agent (coating agent); (b) a lubricant mixing step of mixing a lubricant with the metal alloy powder coated with the insulating agent (coating agent); (c) a primary molding step of molding the coated metal alloy powder at room temperature; (d) a secondary molding step of molding the coated metal alloy powder at a high temperature; and (e) a heat treatment step. The present invention relates to a method for manufacturing an Fe-xSi (x = 4-10.0 wt%) alloy powder core by high-temperature molding, characterized by comprising the above steps.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an Fe-xSi (x = 4-10.0 wt%) alloy powder magnetic core with a high molding density, high magnetic permeability, and low iron loss compared to conventional room-temperature molding methods, and an Fe-xSi (x = 4-10.0 wt%) alloy powder magnetic core produced by high-temperature molding manufactured by the manufacturing method.

Background Art

[0002] The Fe-xSi (x = 4-10.0 wt%) alloy powder becomes softer linearly as the Si content increases. When the Si content is 3.5 wt% or more, surface cracks occur during rolling at room temperature, and it is very difficult to exceed 80% of the true density even during powder molding. As a result, the powder magnetic core formed at room temperature has a magnetic permeability that is difficult to exceed 60, and the iron loss value is very high, making it difficult to apply to large-current components such as electric vehicles and solar power.

[0003] In the prior art related to the manufacturing method of powder magnetic cores, Korean Registered Patent Publication No. 10-1640559 (registered on July 12, 2016), there is a method for manufacturing a magnetic powder paste, which includes: (i) considering the characteristics of the magnetic core and the workability of the paste, uniformly stirring a polymer resin for a predetermined time to produce an organic vehicle (step s10); (ii) treating magnetic powder with phosphoric acid, washing and polishing the surface of the magnetic powder particles, and adding the phosphoric acid-treated magnetic powder to the organic vehicle (step s20); and (iii) roll mixing milling the magnetic powder and the organic vehicle (step s30). The addition of the magnetic powder in step (ii) is characterized by a composition ratio of 50 wt% to 97 wt% of the magnetic powder and 3 wt% to 50 wt% of the organic vehicle.

[0004] In addition, Korean Patent Registration Publication No. 10-1499297 (registered on February 27, 2015) discloses a method for manufacturing an amorphous and nanocrystalline alloy powder magnetic core with very low iron loss, in which a phosphoric acid coating and a double coating with a polyimide-based material are applied as insulating agents between powders, and automatic compression molding is performed at 200 to 550 °C using MoS2 or graphite powder capable of lubricating the powders at high temperatures, resulting in high-frequency characteristics and an effective magnetic permeability of 85 or more at 100 kHz, and an iron loss (50 kHz, 0.1 T) of 300 mW / cc or less.

[0005] In addition, Korean Patent Registration Publication No. 10-1607483 (registered on March 24, 2016) discloses a method for manufacturing a nanocrystalline powder magnetic core with an effective magnetic permeability of more than 150 at below 100 kHz, which is impossible in conventional room-temperature molding, in which the saturation magnetic flux density of the powder produced by a high-pressure water injection method and a rapid solidification method is 1.5 T or more, and the iron loss value shows 300 mW / cc or less at 50 kHz and below 100 Gauss when manufacturing the powder magnetic core by a warm molding method using this powder.

[0006] In addition, Korean Patent Publication No. 10-2018-0034682 (published on March 8, 2018) relates to an Fe-based soft magnetic alloy, and more specifically, discloses an Fe-based soft magnetic alloy having a high saturation magnetic flux density, suitable for implementation in small and lightweight components, and capable of exhibiting excellent magnetic performance with low self-loss, and a technology related to magnetic components through this alloy.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] As can be seen from the prior art, when molding at a high temperature of 400°C or higher compared to normal temperature, it can be seen that the molding density surely increases. However, since the molding temperature has to be increased, lubricants and insulating agents that can withstand high temperatures are required. Since the insulating coating agent softens, the charging of the powder is not uniform, so the weight of the compacted magnetic core becomes uneven and the soft magnetic properties are not uniform.

[0009] The present invention aims to solve the above problems. After insulating coating to enhance the insulation and bonding properties of Fe-xSi (x = 4 - 10.0 wt%) alloy powder, a metal oxide-based lubricant that maintains lubricity even at high temperatures is applied and mixed to produce molding powder. Then, the molding size is made smaller than the final part at normal temperature and primary molding is performed using a mold designed and fabricated to be easily inserted into the final secondary mold.

[0010] Also, the present invention aims to insert the primary molded core into a secondary mold maintained at 400°C or higher and then perform secondary molding, so that the density of the compacted magnetic core is 6.6 g / cc or more and can reach 90% or more of the true density, and to manufacture a compacted magnetic core with high effective magnetic permeability and low iron loss value by an automatic molding technique.

[0011] Also, the present invention aims to manufacture an Fe-xSi (x = 4 - 10.0 wt%) compacted magnetic core having a high molding density, no surface cracks, good insulation between particles, little frequency dependence, and a high magnetic permeability that does not change even in a high-frequency band.

Means for Solving the Problems

[0012] The present invention aims to solve the above problems, and relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy powder compact magnetic core by high-temperature forming, which comprises: [1] (a) a coating step of coating a metal alloy powder with an insulating agent (coating agent); (b) a lubricant mixing step of mixing a lubricant into the metal alloy powder coated with the insulating agent (coating agent); (c) a primary forming step of primarily forming the coated metal alloy powder at room temperature; (d) a secondary forming step of secondarily forming the coated metal alloy powder at a high temperature; and (e) a heat treatment step.

[0013] Further, the present invention relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy powder compact magnetic core by high-temperature forming, which is characterized in that, in [2] the above [1], the metal alloy powder is an Fe-xSi (x = 4 - 10 wt%) alloy or an Fe-10wt%Si-6wt%Al alloy (Sendust) that is highly brittle in room-temperature forming, has high strength, and cannot have a forming density of 80% or more of the true density.

[0014] Furthermore, the present invention relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy powder compact magnetic core by high-temperature forming, which is characterized in that, in [3] the above [1], in the coating step of coating the metal alloy powder with the insulating agent (coating agent), the coating agent contains at least one or more of a polyimide-based, phenol-based, polysilazane, and phosphoric acid (H3PO4), and the amount of the coating agent is 0.5 - 3.0 wt% of the total mass.

[0015] Furthermore, the present invention relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy compacted powder core by high-temperature forming, in which, in [4] the above [1], in the lubricant mixing step of mixing a lubricant with a metal alloy powder coated with an insulating agent (coating agent), the lubricant contains at least one of MoS2 or graphite powder, the average particle size of the lubricant powder is 1 to 10 μm, and the amount of the lubricant is 0.5 to 2.0 wt% of the total mass.

[0016] Furthermore, the present invention relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy compacted powder core by high-temperature forming, in which, in [5] the above [1], in the primary forming step of first forming the coated amorphous metal alloy powder at room temperature, the forming pressure is in the range of 12 to 25 tons / cm2, and in the secondary forming step of second forming the coated amorphous metal alloy powder at a high temperature, the forming temperature is in the range of 400 to 700 °C.

[0017] The forming pressure is in the range of 12 to 25 tons / m2, and the inner diameter and outer diameter of the mold in the primary forming step are formed 2 to 7% larger than the inner diameter and outer diameter of the mold in the secondary forming step.

[0018] Furthermore, the present invention relates to a method for manufacturing an Fe-xSi (x = 4 - 10.0 wt%) alloy compacted powder core by high-temperature forming, in which, in [6] the above [1], in the heat treatment step, the treatment is performed at a temperature of 700 to 900 °C, which is a temperature at which recrystallization of the metal alloy powder occurs and sintering does not occur, the heat treatment atmosphere is an inert gas or a reducing gas atmosphere, and the heat treatment time is 30 to 120 minutes.

[0019] Furthermore, the present invention relates to an Fe-xSi (x = 4 - 10.0 wt%) alloy compacted powder core by high-temperature forming, which is manufactured by the method for manufacturing any one of the compacted powder cores from [1] to [6] above.

Advantages of the Invention

[0020] Since the present invention is configured as described above, it reduces the occurrence of cracks in the compacted magnetic core by performing two - step molding at normal temperature and high temperature, has a molding density of 6.6 g / cm3 or more, and can economically and continuously produce an Fe - xSi (x = 4 - 10.0 wt%) compacted magnetic core with an effective magnetic permeability of 90 or more, which was impossible in conventional normal - temperature molding.

Brief Description of the Drawings

[0021]

Figure 1

Embodiments for Carrying Out the Invention

[0022] As shown in FIG. 1, the present invention comprises: (a) a coating step of coating Fe - xSi (x = 4 - 10.0 wt%) powder with an insulating agent (coating agent); (b) a lubricant mixing step of mixing a lubricant with the Fe - xSi (x = 4 - 10.0 wt%) powder coated with the insulating agent (coating agent); (c) a primary molding step of primarily molding the coated Fe - xSi (x = 4 - 10.0 wt%) at normal temperature; (d) a secondary molding step of secondarily molding the coated Fe - xSi (x = 4 - 10.0 wt%) powder at high temperature; and (e) a heat treatment step. Hereinafter, each of the above steps will be specifically described. [(a) Coating Step]

[0023] The Fe - xSi (x = 4 - 10 wt%) alloy powder used in the present invention can be manufactured by mechanical alloying method, rapid solidification method, water injection method, gas injection method, etc.

[0024] If the Si content is less than 4 wt%, the loss value is high; if it exceeds 10 wt%, the saturation magnetic flux density becomes as low as 1.7 T or less, and the iron loss gradually increases. Therefore, the Si content is limited as described above in the present invention.

[0025] However, in the present invention, in addition to the Fe-xSi (x = 4-10 wt%) alloy powder, Sendust (Fe-SiAl alloy) or the like, which is a material with high brittleness, high hardness, and difficulty in achieving a molding density of 80% or more during molding, can also be applied.

[0026] The said (a) coating step of the present invention is to coat an insulating agent (coating agent) on the alloy powder in order to enhance the insulating property of the Fe-xSi (x = 4-10 wt%) alloy powder and the bonding force during molding.

[0027] The coating agent in the said coating step must have a softening point lower than the heat treatment temperature of the Fe-xSi (x = 4-10 wt%) alloy powder in order to impart insulating property and bonding force during molding, and while showing an appropriate bonding strength at a temperature of 200 to 800°C, it must be able to suppress crack generation while maintaining the shape of the compacted magnetic core by the molding pressure.

[0028] As an appropriate insulating agent (coating agent), polysilazane, phosphoric acid, polyimide-based, etc. are desirable. In addition, phosphoric acid and polysilazane can also be applied.

[0029] The amount of the coating agent is preferably limited to 0.5 to 3.0 wt% of the total mass.

[0030] If the coating agent is less than 0.5 wt%, the bonding strength is weak and it is difficult to bulk the Fe-xSi (x = 4-10 wt%) alloy powder. If it exceeds 3.0 wt%, the bonding strength between the particles of the Fe-xSi (x = 4-10 wt%) alloy powder becomes strong, but the amount of the Fe-xSi (x = 4-10 wt%) alloy powder in the molded body decreases and the soft magnetic properties deteriorate.

[0031] The said total mass means the mass obtained by adding the Fe-xSi (x = 4-10 wt%) alloy powder and the coating agent that constitute the manufactured compacted magnetic core.

[0032] [(b) Lubricant mixing step]

[0033] In the (b) lubricant mixing step of the present invention, it is a step of mixing a lubricant with Fe-xSi (x = 4 - 10 wt%) alloy powder coated with an insulating agent (coating agent) in the above-mentioned (a) coating step.

[0034] In order to impart high-temperature lubricity to the Fe-xSi (x = 4 - 10 wt%) alloy powder mixed and produced with the insulating agent (coating agent), MoS2 or graphite powder is desirable, and the average particle size of the lubricant powder is preferably about 1 to 10 μm.

[0035] At this time, the amount of the lubricant is preferably limited to 0.5 to 2.0 wt% of the total mass. If it is less than 0.5 wt%, the lubricity between the powders is lacking, which will damage the punch for molding. If it exceeds 2.0%, the soft magnetic properties will deteriorate and the economy will decline.

[0036] [(c) Primary forming step]

[0037] The (c) primary forming step of the present invention is a step of primarily forming Fe-xSi (x = 4 - 10 wt%) alloy powder coated with an insulating agent (coating agent) mixed with a lubricant in the above-mentioned (b) lubricant mixing step.

[0038] The forming of the Fe-xSi (x = 4 - 10 wt%) alloy powder of the present invention proceeds with forming in two steps.

[0039] The forming in the (c) primary forming step is carried out at room temperature, and the forming pressure is carried out in the range of 12 to 25 tons / cm2.

[0040] Also, the primary mold in the primary forming step is preferably made smaller compared to the size of the secondary mold so that the primary forming core can be easily inserted into the secondary mold in the (d) secondary forming step described below.

[0041] At this time, it is desirable that the outer diameter of the primary mold in the primary molding step be in a range 2 to 7% smaller than that of the secondary mold. If it is less than 2%, the primary molding core cannot be easily inserted into the secondary mold, and if it exceeds 7%, surface cracks may occur during secondary molding, and the molding density may decrease.

[0042] On the other hand, it is desirable that the inner diameter of the primary mold be in a range 2 to 7% larger than that of the secondary mold, contrary to the outer diameter. If it is less than 2%, the primary molding core cannot be inserted into the secondary mold, and if it exceeds 7%, surface cracks may occur during secondary molding, and the molding density may decrease.

[0043] [(d) Secondary molding step]

[0044] The (d) secondary molding step of the present invention is a step of secondarily molding the primary molding core molded in the (c) primary molding step.

[0045] In the molding in the (d) secondary molding step, the primary molding core is inserted into a secondary mold for molding. At this time, the molding temperature is in a high temperature range of 400 to 700 °C, and the molding pressure is in a range of 12 to 25 tons / cm2.

[0046] At this time, if the molding temperature is lower than 400 °C, a molding density of 6.6 g / cm3 or more cannot be obtained, and if it exceeds 700 °C, the life of the mold drops sharply, and there is a risk of mold breakage.

[0047] On the other hand, if the molding pressure is less than 12 tons / cm2, a molding density of 6.0 g / cm3 or more cannot be obtained, and if it exceeds 25 tons / cm2, the life of the mold drops sharply, and there is a risk of mold breakage.

[0048] [(e) Heat treatment step]

[0049] The (e) heat treatment step of the present invention is a step of heat-treating the secondary molding core molded in the (d) secondary molding step.

[0050] The heat treatment temperature of the secondary molding core must be such that decomposition and sintering of the Fe-xSi (x = 4 - 10 wt%) insulator do not occur, and it is preferably set to 700 - 900 °C. If the temperature is lower than 700 °C, sufficient recrystallization of the structure will not occur, and if the temperature is higher than 900 °C, sintering between the powders may occur.

[0051] The heat treatment atmosphere should be an inert gas or a reducing gas atmosphere, and the time is preferably about 30 - 60 minutes. This is because if the heat treatment time is too short, sufficient stress removal and crystallization will not occur, and if it is too long, productivity will decrease.

[0052] Hereinafter, the present invention will be described based on more detailed examples. However, the present invention is not limited only to the examples described below.

[0053] [Example 1]

[0054] 1000 g of Fe-6.5 wt% Si alloy powder (average particle size of about 25 μm) produced by the high-pressure water injection method was coated with a solution prepared by dissolving 20 g of polyimide in a methylene chloride solution, and then dried to produce composite particle powder in which polyimide was uniformly coated on the surface of the Fe-6.5 wt% Si alloy powder with an average particle size of about 15 μm. After drying, 10 g of MoS2 powder with an average particle size of 3 μm was uniformly mixed.

[0055] The mixed composite particle powder was automatically charged to about 2.50 g inside a mold die with an outer diameter of 12.45 mm and an inner diameter of 7.77 mm whose secondary mold contrast 2% size was adjusted at room temperature, and then molded at a pressure of 18 tons / cm2 and a speed of 10 strokes per minute to produce a primary molding core.

[0056] The primary molding core was put inside a molding die with an outer diameter of 12.7 mm and an inner diameter of 7.65 mm maintained at 600 °C, and then charged at a pressure of 18 tons / cm2 and a speed of 10 strokes per minute to produce a secondary molding core.

[0057] The secondary formed core was heat-treated at 800 °C for 30 minutes in a nitrogen (N2) gas atmosphere to produce the final compacted powder core.

[0058] The characteristics of the density, presence or absence of crack generation, and effective permeability in various frequency bands measured for the compacted powder core in the manufactured state are shown in [Table 1].

[0059] Here, the density of the compacted powder core is a value calculated by dividing the weight of the compacted powder core by the volume of the compacted powder core. The presence or absence of crack generation is determined as crack generation when one or more cracks occur during the production of 10 compacted powder cores. The effective permeability is a value measured using an LCR meter with an external magnetic field of 10 mOe in each frequency band.

[0060] [Example 2]

[0061] It was carried out in the same manner as in Example 1, except that the size of the primary mold was set to an outer diameter of 11.81 mm and an inner diameter of 7.09 mm with a tolerance of 7% for the outer diameter and inner diameter ratio of the secondary mold.

[0062] Various characteristics of the manufactured compacted powder core are shown in [Table 1].

[0063] [Example 3]

[0064] It was carried out in the same manner as in Example 1, except that the molding temperature during secondary molding was set to 400 °C for molding.

[0065] Various characteristics of the manufactured compacted powder core are shown in [Table 1].

[0066] [Example 4]

[0067] It was carried out in the same manner as in Example 1, except that the heat treatment temperature was 750 °C using Fe-10wt%Si-6wt%Al (Sendust) alloy powder (average particle size of about 30 μm) manufactured by the high-pressure water injection method.

[0068] The characteristics of the manufactured compacted powder magnetic core are shown in [Table 1].

[0069] Hereinafter, comparative examples of the present invention will be described.

[0070] [Comparative Example 1]

[0071] The same procedure as in Example 1 was carried out except that the size of the primary mold was set to an outer diameter of 12.51 mm and an inner diameter of 7.51 mm with a 1.5% tolerance compared to the outer and inner diameters of the secondary mold.

[0072] The characteristics of the manufactured compacted powder magnetic core are shown in [Table 1].

[0073] [Comparative Example 2]

[0074] The same procedure as in Example 1 was carried out except that the size of the primary mold was set to an outer diameter of 11.68 mm and an inner diameter of 7.01 mm with an 8% tolerance compared to the outer and inner diameters of the secondary mold.

[0075] The characteristics of the manufactured compacted powder magnetic core are shown in [Table 1].

[0076] [Comparative Example 3]

[0077] The same procedure as in Example 1 was carried out except that the molding temperature was set to 300 °C during the secondary molding.

[0078] The characteristics of the manufactured compacted powder magnetic core are shown in [Table 1]. [Table 1] 1) Fe-6.5wt%Si 2) Fe-10wt%Si-6wt%Al

[0079] Here, referring to Display 1, it can be seen that when the tolerance of the size of the primary mold is 1.5% or less compared to the secondary mold, it is difficult to load into the secondary mold, and when the tolerance is 6% or more, the molding density decreases and a large amount of cracks occur during the secondary molding.

[0080] When the forming temperature is 400 °C or lower, the forming density cannot exceed 6.5 g / cm3, from which it can be seen that it is impossible for the magnetic permeability to be 90 or higher.

[0081] The above description has illustrated the present invention by way of example. The embodiments disclosed in the specification are not for limiting the technical idea of the present invention, but for the purpose of explanation. Therefore, those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and variations without departing from the technical idea of the present invention.

[0082] Therefore, the protection scope of the present invention should be interpreted according to the matters described in the claims, and technical matters within an equivalent scope thereto should also be construed as being included in the scope of rights of the present invention.

Claims

1. (a) A coating step of coating a metal alloy powder with an insulating agent (coating agent); (b) A lubricant mixing step of mixing a lubricant into the metal alloy powder coated with the insulating agent (coating agent); (c) A primary forming step of primarily forming the coated metal alloy powder at room temperature; (d) A secondary forming step of secondarily forming the coated metal alloy powder at a high temperature; and (e) a heat treatment step, characterized by comprising: A method for manufacturing an Fe—xSi (x = 4-10.0 wt%) alloy compact magnetic core by high-temperature forming.

2. In the method according to Claim 1, the metal alloy powder is an Fe—xSi (x = 4-10 wt%) alloy or an Fe-10 wt% Si-6 wt% Al alloy (Sendust) that is highly brittle in room-temperature forming, has a high strength, and cannot have a forming density of 80% or more of the true density, characterized by: a method.

3. In the method according to Claim 1, the coating step of coating the metal alloy powder in (b) with the insulating agent (coating agent) includes at least one or more of a polyimide-based, phenol-based, polysilazane, or phosphoric acid (H3PO4) as the coating agent; the amount of the coating agent is 0.5-3.0 wt% of the total mass, characterized by: a method.

4. In the method according to Claim 1, the lubricant mixing step of mixing a lubricant into the metal alloy powder coated with the insulating agent (coating agent) in (c) includes at least one of MoS2 or graphite powder as the lubricant; the average particle diameter of the lubricant powder is 1-10 μm; the amount of the lubricant is 0.5-2.0 wt% of the total mass, characterized by: a method.

5. In the method according to Claim 1, the primary forming step of primarily forming the coated amorphous metal alloy powder at room temperature in (c) sets the forming pressure in the range of 12-25 tons / cm2; the secondary forming step of secondarily forming the coated amorphous metal alloy powder at a high temperature in (d) sets the forming temperature in the range of 400-700°C; sets the forming pressure in the range of 12-25 tons / m2; the inner diameter and outer diameter of the mold in the primary forming step are formed 2-7% larger than the inner diameter and outer diameter of the mold in the secondary forming step, characterized by: a method.

6. In the method according to claim 1, the (e) heat treatment step is carried out at a temperature of 700 to 900 °C at which recrystallization of the metal alloy powder occurs and sintering does not occur, the heat treatment atmosphere is an inert gas or a reducing gas atmosphere, and the heat treatment time is 30 to 120 minutes, characterized in that method.

7. An Fe—xSi (x = 4 - 10.0 wt%) alloy powder compact core by hot forming manufactured by the manufacturing method of any one of the powder compact cores according to claims 1 to 6.

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