KR101664603B1 - Powder metallurgical method - Google Patents

Abstract

More particularly, the present invention relates to a powder metallurgy method, and more particularly, to a method for producing a liquid lubricant by mixing a lubricant component having a constant composition ratio of ethylenebisstearamide and erucamide at 150 to 170.degree. And adding the solid lubricant to the metal base powder to reduce the amount of the lubricant added to the metal base powder to a minimum amount while maintaining the molding energy and the extraction energy at the same or improved level, The present invention relates to a powder metallurgy process.

Description

Powder metallurgical method

More particularly, the present invention relates to a powder metallurgy method, and more particularly, to a method for producing a liquid lubricant by mixing a lubricant component having a constant composition ratio of ethylenebisstearamide and erucamide at 150 to 170.degree. And adding the solid lubricant to the metal base powder to reduce the amount of the lubricant added to the metal base powder to a minimum amount while maintaining the molding energy and the extraction energy at the same or improved level, The present invention relates to a powder metallurgy process.

As engine power increases, automotive engines and transmission components must have higher mechanical properties. Various molding technologies have been developed to increase the mechanical properties, but the molding technology has been limited due to the increase in the manufacturing cost of the parts and the breakage of the mold in the high pressure molding. Among many high-density molding technologies, there is a method of reducing the addition amount of the lubricant as a method of securing a high density at a pressure (400 to 700 MPa) similar to the conventional molding.

In the field of powder metallurgy, lubricants are used for the purpose of reducing the internal friction between metal-based powder particles during molding and compression, uniformly compressing the powder metallurgy, and minimizing damage to the die. However, when the metal base powder containing the lubricant is extruded, the lubricant remains between the metal base powder particles, so that a high-density molded body can not be obtained. However, if the addition amount of the lubricant added to the metal base powder is decreased, the frictional resistance between the green compact and the wall surface of the mold increases, and the demolding force at the time of withdrawing the green compact from the mold increases, . In addition, when the metal-based powder particles are rearranged along with the compression molding, the lubricity between the powder particles is also lowered, resulting in a limit in improving the density of the green compact. As the lubricant for high-density molding, an amide-based polymer including ethylene-bis-stearamide (EBS) is generally used. [Patent Literatures 1 and 2]

On the other hand, as a method of mixing a lubricant with a metal base powder, there are 1) a simple mechanical mixing method and 2) a polymerization method of polymerizing a monomer as a lubricant base material.

In the mechanical mixing method, the lubricant base material is crushed to a size of 25 mu m or less, and then the metal base powder and the lubricant base material are added to the mixer and mixed. Thus, the process is relatively simple. On the other hand, it has disadvantages in that it can not reduce the addition amount of the lubricant due to a high extraction energy and is disadvantageous in ensuring a low surface roughness of the formed body.

In the polymerization method, a polymerization solvent is added to a polymerization reactor, monomers for preparing a lubricant and a metal base powder are charged and heated to about 100 ° C to polymerize. Since the polymerization method induces intermolecular chemical bonding of the lubricant base material, it has the advantage of ensuring homogeneity and low extraction energy, but has a disadvantage that the process is complicated and the process cost is greatly increased.

At present, in the field of powder metallurgy, it is urgently required to develop a metallurgy method which can obtain a high-density molded body by minimizing the addition amount of the lubricant and keep the extraction energy at the time of taking out after completion of the molding press.

Korean Patent Publication No. 10-2007-0046958 Korean Unexamined Patent Application Publication No. 10-2007-0132455

It is an object of the present invention to provide an improved powder metallurgy method for manufacturing a high-density molded article while minimizing the content of the lubricant added to the metal base powder and maintaining the same output or molding pressure at the same or improved level. .

In order to solve the above problems,

Preparing a liquid lubricant by a high temperature stirring process in which 60 to 70% by weight of ethylenebisstearamide and 30 to 40% by weight of erucamide are mixed at 150 to 170 占 폚;

Cooling and pulverizing the liquid lubricant to produce a solid lubricant;

Mixing 0.4 to 0.75 parts by weight of the solid lubricant with 100 parts by weight of the metal base powder to produce a powder metallurgy composition; And

And a step of compressively molding the powder metallurgy composition to produce a molded body.

In the present invention, by using a lubricant having a specific composition and a high-temperature stirring process, it is possible to increase the density of the molded body by using a small amount of lubricant, improve the surface roughness, and maintain the molding energy and the extraction energy at a low level have.

Therefore, according to the powder metallurgy method of the present invention, the lubricant can be reduced to 0.4 parts by weight with respect to 100 parts by weight of the metal base powder, and a high-density molded body of 7.3 g / cm 3 can be produced.

FIG. 1 is a graph showing the relationship between the content ratio of the lubricant component of ethylene bisstearamide and erucamide in the production of a powder metallurgy compact by using 100 parts by weight of metal base powder and 0.75 part by weight of a lubricant prepared through a high- Output.
Fig. 2 is a graph showing the relationship between the ratio of the ethylene-bis-stearamide and erucamide in the composition ratio of erucamide to that of the lubricant prepared through the high-temperature stirring step of 100 parts by weight of the metal-based powder, FIG.
Fig. 3 is a graph showing the results obtained when a powder metallurgical compact is produced using 100 parts by weight of a metal base powder and 0.4 parts by weight of a lubricant prepared by a high temperature stirring process (composition ratio of ethylenebisstearamide and erucamide to 70:30% by weight) The graphs show the comparison of the amount of addition and the extraction output according to the molding pressure change.
Fig. 4 is a graph showing the results of the comparison of the composition of the lubricant composition of ethylene biststearamide and erucamide with that of the lubricating composition of ethylenebisstearamide and erucamide in the production of a powder metallurgy compact by using 100 parts by weight of metal base powder and 0.75 part by weight of a lubricant prepared by mechanical mixing at room temperature, In the graph of FIG.
5 is a graph showing the relationship between the content ratio of the lubricant composition components of ethylene biststearamide and erucamide in the production of a powder metallurgical compact by using 100 parts by weight of the metal base powder and 0.75 part by weight of the lubricant prepared through the polymerization process, And a graph showing a comparison of the output values according to the change.
6 is a photograph comparing the surface roughnesses of the powder metallurgy compacts produced in Example 1 (high temperature stirring), Comparative Example 1 (mechanical mixing at room temperature) and Comparative Example 2 (polymerization).

The powder metallurgy method according to the present invention will be described in more detail with reference to the following steps.

The first step is to prepare the lubricant.

In the present invention, an amide-based lubricant containing ethylene bis stearamide and erucamide is used as a lubricant, and a high temperature stirring process is performed to disperse these lubricant components evenly.

That is, in the present invention, among the amide-based lubricants conventionally used in the field of powder metallurgy, ethylene bisteostearamide and erucamide are selectively used and the optimum content ratio between the two components is presented, thereby minimizing the addition amount of the lubricant, The energy of the energy and the extraction energy of the molded body can be kept low. According to the present invention, it is preferable that the lubricant has a composition ratio of 60 to 70% by weight of ethylenebisstearamide and 30 to 40% by weight of erucamide, more preferably 70% by weight of ethylenebisstearamide and 30% by weight of erucamide, .

In the present invention, the lubricant having the specific composition ratio as described above is stirred at a high temperature to prepare a uniformly dispersed liquid lubricant. After the liquid lubricant is cooled to convert it into a cake-like solid, the solid lubricant is pulverized, It is mixed with powder.

As a conventional method of producing a lubricant, the 'mechanical mixing' method is performed at room temperature, which has a limitation in inducing uniform dispersion of lubricant composition components. However, in the present invention, the 'hot agitation' process of mixing the lubricant components while maintaining the internal temperature of the mixer at 150 to 170 ° C. induces even dispersion between the lubricant components, ultimately lowering the extraction energy of the formed body, It is possible to safely demold the molded article without worn out. If the temperature of stirring at a high temperature in the process of producing the lubricant according to the present invention is less than 150 ° C, the uniform distribution of ethylene biststearamide and erucamide is not achieved and there is a limit in lowering the extraction energy. A high molded article can be produced. On the other hand, when the high temperature agitation temperature exceeds 170 ° C, oxidation of erucamide having a low melting point occurs, discoloration and viscosity increase, which may be disadvantageous at the time of crushing.

Further, in order to convert the liquid lubricant prepared through the high-temperature stirring step into a solid phase, a step of cooling and pulverizing by a conventional method is carried out. That is, the liquid lubricant is cooled to convert into a cake form. The cooling is performed at a temperature around room temperature, specifically, to a temperature of 10 to 30 ° C. The cake type lubricating oil is pulverized for uniform mixing with the metal base powder, and the average particle size of the pulverized solid lubricant is preferably in the range of 10 to 40 mu m.

The second step is to prepare the powder metallurgy composition.

In the present invention, 0.4 to 0.75 parts by weight of a lubricant is mixed with 100 parts by weight of a metal base powder to prepare a powder metallurgy composition. That is, the addition amount of the lubricant can be reduced to a minimum amount in the step of preparing the powder metallurgy composition of the present invention.

The third step is a step of producing a high-density molded body by compression molding.

In the present invention, compression molding is performed by a conventional metallurgical technique. That is, the powder metallurgy composition is filled in a die and compressed at a pressure of 500 to 600 MPa to produce a molded article. The produced molded body is separated from the die by applying an output power of 900 to 1400 Kgf.

The compacts produced by the above method have a density of 7.1 to 7.3 g / cm 3. In addition, according to the powder metallurgy method of the present invention, when the lubricant is added in an amount of 0.4 part by weight based on 100 parts by weight of the lubricant based on 100 parts by weight of the metal base powder, the output is reduced by 200 Kgf, Cm < 3 >.

In the powder metallurgy method of the present invention described above, more preferably,

I) preparing a liquid lubricant by a high-temperature stirring process in which 60 to 70% by weight of ethylenebisstearamide and 30 to 40% by weight of erucamide are mixed at 150 to 170 DEG C;

Ii) cooling and pulverizing the liquid lubricant to produce a solid lubricant;

Iii) mixing 0.4 to 0.5 parts by weight of the lubricant with 100 parts by weight of the metal base powder to produce a powder metallurgy composition; And

Iv) compression molding the powder metallurgy composition at a pressure of 500 to 600 MPa and applying an output of 900 to 1100 Kgf to produce a compact having a density of 7.2 to 7.3 g / cm 3; .

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited by the following examples.

[Example]

Example 1. Confirmation of change in output power depending on the composition ratio of ethylenebisstearamide and erucamide

The composition ratio of ethylene biststearamide and erucamide was changed to 50, 50, 55:45, 60:40, and 70:30 weight% as lubricant composition components, respectively, to prepare respective lubricants. That is, the lubricant component was stirred at 160 DEG C for 60 minutes at a high temperature to obtain a liquid lubricant. Then, the liquid lubricant was cooled while being left at room temperature to obtain a cake-like lubricant, and then pulverized to obtain a hard lubricant in the range of 10 to 40 μm.

HSPP (Hyundai Steel Pure Iron Powder) was used as the iron base powder. To 100 parts by weight of the iron base powder, 0.75 part by weight of the solid lubricant prepared above was mixed to prepare a powder metallurgy composition. The powder metallurgy composition was placed in a die and a forming pressure of 500 MPa was applied to produce a compact having a density of 7.12 g / cm < 3 >.

In order to confirm the output power depending on the composition ratio of ethylene bisstearamide and erucamide constituting the lubricant, the output power was measured based on MPIF Standard 45, and the results are shown in FIG.

1, the ejection force decreases as the composition ratio of ethylenebisstearamide (EBS) and erucamide (ERu) is changed to 50: 50, 55:45, 60:40, and 70:30% by weight . That is, as the content of erucamide contained in the lubricant was lowered, the exhaust power was lowered from 1400 kgf to 1100 kgf, and when the composition ratio of ethylenebisstearamide and erucamide was 70:30 wt%, the output was 1100 kgf Low.

Example 2. Confirmation of Density Change of Molded Particle According to Lubricant Addition Amount

A molded article was prepared using the solid lubricant having a composition ratio of ethylene biststearamide and erucamide of 70:30 wt% by the metallurgical method of Example 1, except that the addition amount of the solid lubricant based on 100 parts by weight of the iron base powder And 0.75 parts by weight or 0.40 parts by weight, respectively.

FIG. 2 is a graph showing the measurement results obtained by adding 0.75 parts by weight of a lubricant based on 100 parts by weight of the iron base powder and measuring the output three times. 2, the output power was as low as 1100 kgf, and a compact having a density of 7.11 g / cm3 was produced by applying a molding pressure of 500 MPa.

FIG. 3 is a graph showing the results obtained by repeating three times repetition of the addition of 0.40 parts by weight of a lubricant based on 100 parts by weight of the iron base powder and changing the addition amount of the lubricant and the molding pressure according to FIG. As shown in FIG. 3, the output power was as low as 900 kgf, and a compact having a density of 7.30 g / cm 3 was produced by applying a molding pressure of 500 MPa.

2 and 3, when a lubricant having a composition ratio of ethylene bisteostearide and erucamide of 70:30 wt% is used, the amount of lubricant added is reduced from 0.75 part by weight to 0.40 part by weight, It is possible to lower the density of the molded body by 0.19 g / cm < 3 >.

COMPARATIVE EXAMPLE 1 AND COMPARATIVE EXAMPLE 2 Comparison of output power by conventional metallurgical method

(Comparative Example 1) or heat polymerization (Comparative Example 2) at room temperature as a conventional method for producing a powder metallurgy composition by mixing the iron base powder with the lubricant by the method of Example 1 Respectively.

4 and 5 show changes in the composition ratios of ethylenebisteamide (EBS) and erucamide (ERu) constituting the lubricant to 50, 50, 55, 45, 60, Ejection force, respectively.

6 shows photographs comparing the surface roughnesses of the powder metallurgy compacts produced in Example 1 (high temperature stirring), Comparative Example 1 (mechanical mixing at room temperature) and Comparative Example 2 (polymerization).

Table 1 below summarizes the results of comparison and confirmation through Examples 1 and 2 and Comparative Examples 1 and 2.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2
slush Configuration
(weight%) Ethylene bisstearamide: content ratio of erucamide
70:30 Addition amount
(Parts by weight) 0.75 0.4 0.75 0.75 Mixing method 160 ℃ high temperature mixing Room temperature mixing polymerization Output power (kgf) 1100 to 1400 900 1500 to 2250 1500 Molding pressure (MPa) 500 500 500 500 Shaped body Density (g / cm3) 7.12 7.30 7.11 7.10 Surface roughness (Ra) 0.6 0.8 1.1 0.9

As described above, according to the metallurgical process of the present invention, the powder metallurgy composition is produced by mixing at a high temperature while limiting the composition ratio of ethylene biststearamide and erucamide to a specific range, which constitutes the lubricant, A high density molded body having a density of up to 7.3 g / cm 3 can be manufactured by reducing the amount of the lubricant added to the weight and lowering the extraction energy. According to the results of Table 1, it is also possible to keep the surface roughness low.

Claims (5)

Preparing a liquid lubricant by a high temperature stirring process in which 60 to 70% by weight of ethylenebisstearamide and 30 to 40% by weight of erucamide are mixed at 150 to 170 占 폚;
Cooling the liquid lubricant to a temperature of 10 to 30 DEG C and pulverizing the liquid lubricant to a mean particle size of 10 to 40 mu m to prepare a solid lubricant;
Mixing 0.4 to 0.75 parts by weight of the solid lubricant with 100 parts by weight of the metal base powder to produce a powder metallurgy composition; And
A process for producing a molded article by compression molding of a powder metallurgy composition;
≪ / RTI >
The method according to claim 1,
Wherein the metal base powder is an iron base powder.
The method according to claim 1,
Wherein the compression molding is performed at a pressure of 500 to 600 MPa.
The method according to claim 1,
Wherein the molded body is taken out from the mold by applying an extraction output of 900 to 1400 Kgf.
The method according to claim 1,
Preparing a liquid lubricant by a high temperature stirring process in which 60 to 70% by weight of ethylenebisstearamide and 30 to 40% by weight of erucamide are mixed at 150 to 170 占 폚;
Cooling the liquid lubricant to a temperature of 10 to 30 DEG C and pulverizing the liquid lubricant to a mean particle size of 10 to 40 mu m to prepare a solid lubricant;
Mixing 0.4 to 0.75 parts by weight of the solid lubricant with 100 parts by weight of the metal base powder to produce a powder metallurgy composition; And
Compressing the powder metallurgy composition under a pressure of 500 to 600 MPa and applying an output of 900 to 1100 Kgf to produce a compact having a density of 7.2 to 7.3 g / cm 3;
≪ / RTI >

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