JP2009013458A - Method for compacting large-sized high density green compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for compacting a large-sized high density green compact where, upon the compacting of a large-sized high density green compact by a die lubrication compacting process, a sound green compact free from galling and dents caused by the entanglement of a lubricant can be obtained. <P>SOLUTION: Regarding the method for compacting a large-sized high density green compact having a density of ≥7.60 g/cm<SP>3</SP>by a die lubrication compacting process or a warm die lubrication compacting process in a state where a die having a cavity with a depth of ≥9 cm and a volume of ≥700 cm<SP>3</SP>is used, and raw material powder is packed into the cavity, the upper half part of the inner wall face of the die is coated with a lubricant in an amount satisfying the range of 3 to 6 mg/cm<SP>2</SP>per unit area, and further, the lower half part is coated with a lubricant in an amount satisfying the range of 0.05 to 0.1 mg/cm<SP>2</SP>per unit area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molding method for a large-scale high-density compact, and is applied to, for example, a core material (stator, rotor) for a large motor by a mold lubrication molding method or a warm mold lubrication molding method. The present invention relates to a method for forming a high-density green compact.

  The mold lubrication molding method and the warm mold lubrication molding method basically do not mix the lubricant with the raw material powder, apply the lubricant to the inner wall surface of the mold and perform compression molding to form a compacted body. How to get. That is, prior to filling the mold cavity with the raw material powder, a lubricant is applied to the inner wall surface of the mold (mold cavity wall surface) in order to improve the compressibility and extraction from the mold. ing. Industrially, as a method for applying the lubricant to the inner wall surface of the mold, a method (A) in which the lubricant is suspended in water or an organic solvent and sprayed, and a method in which the lubricant is charged and electrostatically applied. There is (B).

  In the method (A), since the sprayed lubricant linearly flies through the cavity, it is not possible to apply the lubricant to a location corresponding to a shadow in the mold. Therefore, the method (A) is not suitable for a compact powder compact having a complicated shape.

On the other hand, since the method (B) is to apply a charged lubricant to the inner wall surface of the mold by electrostatic force, it is efficient and can be applied to a powder compact having a complicated shape. Is possible. When a lubricant is electrostatically applied to the inner wall surface of the mold and a powder compact is obtained by the mold lubrication molding method or the warm mold lubrication molding method, a sound powder compact that is free from galling and scratches is obtained. A method of forming a powder magnetic core has been proposed in which lubricant powder is applied to the inner wall surface of a mold in a range of 0.2 to 2.0 mg / cm ² per unit area (Japanese Patent Application Laid-Open No. 2004-342937). No. 2005-72112).

By the way, in recent years, in order to apply to a core material (stator, rotor) or the like for a large motor, it is required to obtain a large and high-density compact. Then, a large, and in order to obtain a high-density green compact, is 9cm more depth, and using a mold volume (volume) has a cavity is 700 cm ³ or more, the raw material in the cavity When filling a powder and molding a large-scale high-density compact with a density of 7.60 g / cm ³ or more by a mold lubrication molding method or a warm mold lubrication molding method, Since the amount of the raw material powder falling while contacting the upper part of the inner wall surface of the mold (the upper part of the cavity wall surface) is large, the lubricant adhering to the upper part of the inner wall surface of the mold is easily detached by the falling raw material powder. According to the present inventors, the amount of lubricant applied to the inner wall surface of the mold is insufficient in the range of 0.2 to 2.0 mg / cm 2 according to the prior art, and is used for extracting a compacted green compact. It was found that the extraction force was increased and galling was generated in the green compact.

  On the other hand, if the amount of lubricant applied to the entire inner wall surface of the mold is too large, the lubricant released from the upper surface of the inner wall surface of the mold accumulates on the bottom surface of the cavity, and the lubricant is formed on the surface portion of the green compact. It was found that a wound involving a lubricant (a minute dent) was generated.

JP 2004-342937 A (paragraphs [0006] to [0010]) Japanese Patent Laying-Open No. 2005-72112 (paragraphs [0009] and [0015])

Accordingly, an object of the present invention is to use a mold having a cavity having a depth of 9 cm or more and a volume of 700 cm ³ or more, filling the cavity with raw material powder, and performing a mold lubrication molding method or a warm process. When molding a large-scale high-density green compact having a density of 7.60 g / cm ³ or more by the mold lubrication molding method, a sound compact with no galling or lubricant entrainment can be obtained. An object of the present invention is to provide a method for forming a large, high-density, compacted compact.

  In order to solve the above problems, the present invention takes the following technical means.

The invention according to claim 1, is 9cm more depth, and using a mold having a cavity is volume 700 cm ³ or more, the raw material powder was filled in the cavity, the mold lubrication molding method or Yutakamakin This is a method for molding a large-scale high-density green compact having a density of 7.60 g / cm ³ or more by a mold lubrication molding method, wherein 3-6 mg / cm ² per unit area is formed on the upper half of the inner wall surface of the mold. A large-scale high-density powder compact characterized by applying an amount of lubricant satisfying the range and applying an amount of lubricant satisfying the range of 0.05 to 0.1 mg / cm ² per unit area to the lower half This is a molding method of a molded body.

  According to a second aspect of the present invention, in the method for forming a large-scale high-density green compact according to the first aspect, the upper half of the inner wall surface of the mold is charged when the lubricant is applied to the inner wall surface of the mold. A spray nozzle for the upper half of the mold inner wall surface that sprays the lubricant, and a spray nozzle for the lower half of the mold inner wall surface that sprays the charged lubricant to the lower half of the mold inner wall surface An electrostatic lubricant coating apparatus is used.

According to the method for forming a large-scale high-density green compact according to claim 1, the upper half of the inner wall surface of the mold is 3 per unit area so as not to cause a lubricant shortage due to the detachment of the lubricant when filling the raw material powder. By applying an amount of lubricant satisfying the range of ˜6 mg / cm ² , it is possible to create a state in which an appropriate amount of lubricant is held on the upper half of the inner wall surface of the mold after filling the raw material powder. In addition, 0.05 to 0 per unit area is provided in the lower half so as not to cause surplus lubricant by carrying the lubricant released from the upper half of the inner wall surface of the mold when the raw material powder is filled. by applying the amount of the lubricant to meet the range of .1mg / cm ^2, it can be an appropriate amount of lubricant can produce a state of being held in the lower half of the mold inner wall after the raw material powder filling. Therefore, a mold having a cavity having a depth of 9 cm or more and a volume of 700 cm ³ or more is used, and the cavity is filled with the raw material powder, and the mold lubrication molding method or the warm mold lubrication molding method is used. When molding a large-scale high-density compact with a density of 7.60 g / cm ³ or more, a sound compact with no galling or lubricant entrainment can be obtained.

  The molding method of the large-scale high-density compacting body according to claim 2 is provided in the upper half of the inner wall of the mold by the spray nozzle for the upper half of the inner wall of the mold provided in the electrostatic lubricant coating apparatus. A predetermined amount of lubricant is applied, and a predetermined amount of lubricant is applied to the lower half of the inner wall of the mold by the spray nozzle for the lower half of the inner wall of the mold provided in the electrostatic lubricant application device. I am doing so. Therefore, when a predetermined amount of lubricant is applied to the upper half and the lower half of the inner wall surface of the mold, variation in the amount of lubricant applied is small, and the lubricant can be applied stably. . Moreover, it can also contribute to automation of the manufacturing process of a compacting body.

The molding method of a large-scale high-density compact according to the present invention has a depth of 9 cm or more in consideration of the compact compact that can be applied to the core material (stator, rotor) for the large motor described above. , using a mold volume having a cavity is 700 cm ³ or more, filled by filling a raw powder into the cavity, the die wall lubrication molding method or warm die lubrication molding, thickness 3cm or more, density of 7 The object is to obtain a green compact having a density of .60 g / cm ³ or more (more preferably, a density of 7.65 g / cm ³ or more from the viewpoint of magnetic properties). In addition, about the upper limit of the cavity dimension of the said metal mold | die, depth (raw material powder filling depth): About 20 cm and a volume (raw material powder filling volume): About 1500 cm < ³ >.

  In the molding method of the present invention, a mold produced using a general mold material such as super hard material or die steel can be used as the mold.

  In the molding method of the present invention, as raw material powder, soft magnetic powder such as pure iron powder and iron-based alloy powder, powder obtained by mixing an insulating material with soft magnetic powder, and the surface of soft magnetic powder is coated with an insulating material. Powder or the like can be used. Examples of the insulating material include thermosetting resins such as phenol, epoxy, polyimide, and silicone, and organic materials such as thermoplastic resins such as polyamide. Furthermore, examples of the insulating material include inorganic materials such as an inorganic coating such as a phosphoric acid coating, oxides such as silica and alumina, and nitrides such as BN.

  In the molding method of the present invention, a known lubricant may be used as a lubricant. Specifically, metal salt powder of stearic acid such as zinc stearate, lithium stearate, calcium stearate, paraffin, wax, Examples include natural or synthetic resin derivatives.

In the molding method of the present invention, the upper half of the inner wall surface of the mold (the inner wall surface of the mold on the punch side higher than 1/2 the cavity depth) satisfies the range of 3 to 6 mg / cm ² per unit area. It is necessary to apply an amount of lubricant. When the amount of lubricant applied to the upper half of the inner wall surface of the mold is less than 3 mg / cm ² , the amount of lubricant attached to the inner wall surface of the mold decreases due to dropping off when filling the raw material powder. Scratches may occur, and the extraction pressure (extraction force) at the time of extracting the molded body may increase, and in the worst case, the green compact cannot be extracted from the mold. On the other hand, if it exceeds 6 mg / cm ² , the amount of lubricant adhering to the inner wall surface of the mold is too large, causing the lubricant to drop off when filling the raw material powder and dropping into the filled raw material powder. Lubricant becomes a lump and is mixed, and a sound compacting body cannot be obtained. Therefore, the amount of the lubricant applied to the upper half of the inner wall surface of the mold needs to satisfy the range of 3 to 6 mg / cm ² .

In addition, an amount satisfying the range of 0.05 to 0.1 mg / cm ² per unit area in the lower half of the inner wall surface of the mold (the inner wall surface of the mold on the punch side lower than ½ of the cavity depth) It is necessary to apply a lubricant. If the amount of lubricant applied to the lower half of the inner wall of the mold is less than 0.05 mg / cm ² , the absolute amount of lubricant in the lower half of the inner wall of the mold will be insufficient, and it will bite the side of the green compact Scratches may occur and the extraction pressure (extraction force) at the time of extracting the molded body may increase, and in the worst case, the green compact cannot be extracted from the mold. On the other hand, if it exceeds 0.1 mg / cm ² , the lubricant accumulates on the bottom surface of the cavity (lower punch surface), entrains the lubricant in the bottom surface portion of the green compact, and causes entrainment of the lubricant (small dents). Arise. Therefore, the amount of lubricant applied to the lower half of the inner wall surface of the mold needs to satisfy the range of 0.05 to 0.1 mg / cm ² .

  FIG. 1 is a schematic explanatory diagram for explaining an electrostatic lubricant application device used in the method of the present invention, and FIG. 2 is a diagram for explaining the lubricant applied to the inner wall surface of the mold in the method of the present invention. It is a typical explanatory view.

  In FIGS. 1 and 2, 1 is a mold for forming a cylindrical cavity, and 2 is a lower punch. In FIG. 1, 3 is a friction charging unit of the electrostatic lubricant application device, 4 is a spray nozzle for the upper half of the inner wall surface of the mold of the electrostatic lubricant application device, and 5 is an electrostatic lubricant application. It is a spray nozzle for the mold inner wall lower half part of an apparatus.

  The electrostatic lubricant application device used in the method of the present invention includes a lubricant supply hopper, a screw feeder, a drive motor, a connection clutch, a friction charging unit 3, a spray nozzle 4 for the upper half of the mold inner wall surface, and a mold. It is comprised by the spray nozzle 5 for inner wall lower half parts, and the control box. This electrostatic lubricant application device supplies a powdery lubricant, which is metered in a certain amount, to the frictional charging unit 3, and is charged positively by the frictional charging method at the frictional charging unit 3. The lubricant is sprayed on the cavity of the mold 1 and adhered to the inner wall surface of the mold by electrostatic force. The mold 1 is electrically grounded. Then, using the spray nozzle 4 for the upper half of the mold inner wall surface, a lubricant is applied to the upper half of the mold inner wall surface by electrostatic force, and the spray nozzle 5 for the lower half of the mold inner wall surface is used. The lubricant is applied to the lower half of the inner wall surface of the mold by electrostatic force.

  Examples of the present invention will be described below.

The green compact was molded under the molding conditions shown in Table 1. At this time, the filling depth and filling volume were changed by changing the position of the lower punch. And the presence or absence of the defect of the obtained compacting body was investigated visually. The results are shown in Tables 2-4. Here, with respect to the amount of lubricant applied to the upper half of the inner wall surface (cavity wall surface) of the mold, several pieces (8 pieces) of the same material (in this embodiment, SKD steel) as the mold (1 cm) ² ) is affixed to the upper half of the inner wall surface of the mold, and the mass difference between before and after the lubricant application is measured for each of these small pieces, and the lubricant application amount (lubricant adhesion amount) is determined by their average value. did. Similarly, the amount of lubricant applied to the lower half of the mold inner wall surface (cavity wall surface) was determined. Then, these small pieces in the upper half and the lower half were removed, and after forming the lubricant under the same conditions as those applied to the small pieces, molding was performed. Further, the density of the molded body is obtained by calculation from the mass of the molded body and the volume of the molded body (calculated from the outer dimensions).

As shown in Table 2, Examples 1 to 11 had no galling scratches or lubricant entrainment scratches, and were able to obtain sound compacted bodies. On the other hand, in Comparative Examples 1 to 4, since the amount of lubricant applied to the upper half of the inner wall surface of the mold is below the range defined in the present invention, the resulting green compacts are galling. It was. In Comparative Example 5 to Comparative Example 8, the amount of lubricant applied to the lower half of the inner wall surface of the mold exceeds the range specified in the present invention. It was. In Comparative Example 9 to Comparative Example 11, the amount of lubricant applied to the upper half of the inner wall surface of the mold is less than the range defined in the present invention, and the amount of lubricant applied to the lower half of the inner wall surface of the mold is the present invention. It exceeded the range specified in the above, and the resulting green compact had a galling wound. As shown in Reference Examples 1 to 3, when the filling depth of the raw material powder is less than 9 cm and the filling volume of the raw material powder is less than 700 cm ³ , the lubricant coating amount on the inner wall surface of the mold is determined by the present invention. Even if it was outside the specified range, no galling was observed on the green compact.

As shown in Table 3, Examples 12 to 15 were free from galling and lubricant entrainment, and were able to obtain sound compacts. On the other hand, in Comparative Examples 12 to 15, since the amount of lubricant applied to the upper half of the inner wall surface of the mold is below the range specified in the present invention, the resulting green compacts are galling. It was. In Comparative Examples 16 to 19, since the amount of the lubricant applied to the lower half of the inner wall surface of the mold exceeds the range specified in the present invention, the entrainment scratches on the obtained compacted green body are caused. It was. In Comparative Examples 20 to 22, the amount of lubricant applied to the upper half portion of the inner wall surface of the mold is less than the range defined in the present invention, and the amount of lubricant applied to the lower half portion of the inner wall surface of the mold is the present invention. It exceeded the range specified in the above, and the resulting green compact had a galling wound. Incidentally, as shown in Reference Example 4 Reference Example 6, below 9cm filling depth of the raw material powder, when the filling volume of the raw material powder is less than 700 cm ^3, the lubricant coating weight of mold walls in the present invention Even if it was outside the specified range, no galling was observed in the green compact. Table 4 shows Reference Examples 7 to 24 as reference examples.

It is typical explanatory drawing for demonstrating the electrostatic-type lubricant coating device used for the method of this invention. It is typical explanatory drawing for demonstrating the lubricant apply | coated to the metal mold | die inner wall surface in the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Lower punch 3 ... Friction charging part of electrostatic lubricant application device 4 ... Spray nozzle for upper half part of inner wall surface of electrostatic lubricant application device 5 ... Electrostatic lubricant application Spray nozzle for the lower half of the inner wall of the mold

Claims (2)

Using a mold having a cavity having a depth of 9 cm or more and a volume of 700 cm ³ or more, the cavity is filled with raw material powder, and the density is 7 by a mold lubrication molding method or a warm mold lubrication molding method. .60 g / cm ³ or more of a method for forming a large-scale high-density green compact, wherein the upper half of the inner wall surface of the mold satisfies the range of 3 to 6 mg / cm ² per unit area. And forming a large-scale, high-density, compacted green body in the lower half with an amount of lubricant satisfying a range of 0.05 to 0.1 mg / cm ² per unit area.   When applying the lubricant to the inner wall surface of the mold, a spray nozzle for the upper half of the mold inner wall surface that sprays the charged lubricant on the upper half of the mold inner wall surface; 2. A large-scale high-density powder compact according to claim 1, wherein an electrostatic-type lubricant applicator provided with a spray nozzle for the lower half of the inner wall of the mold for spraying the lubricant charged to the half is used. Molding method of the molded body.

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