JPH04191301A - Iron-based powder mixed material for powder meatallurgy - Google Patents

Abstract

PURPOSE:To obtain an iron-based powder mixed material for powder metallurgy excellent in fluidity, high compressibility and formability by adding lead stearate and zinc olein to the iron-based powder or the mixed powder of iron-based powder and powder for alloy. CONSTITUTION:The lead stearate and the zinc olein are added as a lubricator to the iron-based powder or the mixed powder of iron-based powder and powder for alloy. Water atomized iron powder for powder metallurgy, alloy steel powder, etc., as the above-mentioned iron-based powder and graphite powder, electrolytic copper powder, etc., as the powder for alloy are used. The above-mentioned lubricator is used preliminarily mixing the iron-based powder, the mixed powder, etc., and this adding quantity is preferable to be 0.2-2.5wt.%. The iron-based powder mixed material for powder metallurgy obtd. with this has the excellent compressibility and formability together with the fluidity and is compacted in a die to obtain a good green compact. Further, at the time of heating for sintering this green compact, the above-mentioned lubricator is easily decomposed and separated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an iron-based powder mixture for powder metallurgy.

[Prior Art] The fluidity of iron-based powder mixtures for powder metallurgy, like compressibility and formability, is an essential characteristic for producing high-density, high-strength sintered bodies. In other words, the fluidity of the raw powder mixture is important when molding parts with complex shapes, and various studies have been conducted on lubricants and methods of adding them that improve fluidity without impairing compressibility and moldability. It's here.

For example, Japanese Patent Publication No. 63-16441 describes a method of heating and melting zinc stearate and adding it.
No. 3810 discloses a method of adding microcapsules containing an organic liquid lubricant coated with a solid lubricant.

However, in the method using zinc stearate, although the fluidity is improved, the compressibility is only slightly improved compared to the case where zinc stearate is mixed and added at room temperature.

In addition, with the method of using microcapsules coated with a solid lubricant, the compressibility improved only slightly and the fluidity decreased by 30 seconds.
50 g or more, and practical fluidity of 750 g or less for 20 seconds has not been obtained.

[Problem to be solved by the invention]

The present invention aims to simultaneously improve fluidity, compressibility, and moldability, which has been difficult with the prior art as described above.

[Means for Solving the Problems 1] In order to solve the above problems, the present invention provides that lead stearate or zinc oleate is added to an iron-based powder or a mixed powder of an iron-based powder and an alloying powder. The present invention provides an iron-based powder mixture for powder metallurgy, in which the amount of lead stearate or zinc oleate added is 0.2 to the iron-based powder or the mixed powder of iron-based powder and alloying powder. It is preferably 2.5% by weight.

[Effect]

The reason for coating the surface of metal powder particles with lubricant is
It prevents segregation of the lubricant when mixed with metal powder, and causes a uniform and effective lubrication effect at the contact points between each metal powder particle and the contact point between the metal powder particle and the inner surface of the mold during pressure molding. This is to improve fluidity, compressibility, and moldability.

In the present invention, lead stearate or zinc oleate is used as the lubricant. These lubricants include iron-based powder,
Alternatively, it is used by pre-mixing a mixed powder of iron-based powder and alloying powder, and is melted by the frictional heat during pressure molding in the mold and coats the metal powder surface, providing lubrication between the metal powders and molding. Mainly acts as a lubricant with the inner surface of the die.

The reason why lead stearate or zinc oleate is used is that the melting point of these lubricants is 75°C or higher.

This is because if the temperature is below 90°C and the melting point is above 90°C, the melting lubrication effect of the lubricant due to frictional heat will be weakened, and the lubrication effect between the metal powders and the lubrication effect between the mold and the inner surface of the die will be reduced. Further, if the melting point is lower than 75°C, the fluidity of the mixture pre-mixed with the metal powder cannot be obtained.

In addition to the melting point, most of the constituent elements are C10, H
This is because when the molded body of the mixture is heated and sintered, the lubricant easily decomposes and separates from the molded body.

It has been known that if the amount of lubricant added is too small, the fluidity will be poor, and if it is too much, the compressibility and formability will be reduced. The amount is 0.2 to 2.5 based on the metal powder.
% by weight is preferable, and since it has superior compressibility and moldability compared to conventional zinc stearate, etc., it has the advantage of being economical because it can be molded with a smaller amount of lubricant added.

In addition, the iron-based powder in the present invention includes water atomized iron powder for powder metallurgy, alloy copper powder, etc., and the alloy powder includes:
Graphite powder and electrolytic copper powder are used.

〔Example〕

Example 1.2 Comparative Examples 1 to 9 0.5% by weight of zinc oleate as Example 1 and 0.5% by weight of lead stearate as Example 2 were added to water atomized iron powder for powder metallurgy to form a powder mixture. The mixture was heated on a heating stand at ℃ for 10 minutes.

In addition, oleic acid as Comparative Example 1, lead oleate as Comparative Example 2, copper oleate as Comparative Example 3, nickel oleate as Comparative Example 4, stearic acid as Comparative Example 5,
Zinc stearate as Comparative Example 6, copper stearate as Comparative Example 7, nickel stearate as Comparative Example 8, and ethylene bisstearamide wax as Comparative Example 9 were mixed with iron powder in the same manner as in Example 1. did.

Table 1 shows Examples 1.2. The melting point of the lubricant used in Comparative Examples 1 to 9 and the fluidized bed of the heated mixture with iron powder, 7 t/
The green powder density and green powder transverse rupture strength at a molding pressure of cr rr1'' are shown.

Example 1.2 has a melting point of 75°C or higher and 90°C or lower, so
A fluidized bed, green powder density, and green compact transverse rupture strength superior to those of the conventional lubricant shown in Comparative Example 16 were obtained. In particular, zinc oleate has a remarkable improvement in green density, reaching 80 kgf/crn.
The transverse rupture strength of the green compact was improved by more than 20%.

However, in Comparative Examples 1, 2, 3, and 4, the melting point was 75°C.
Since the amount of zinc stearate was less than that, fluidity could not be obtained, and the result was inferior to the conventional zinc stearate shown in Comparative Example 16. Furthermore, since the melting point of Comparative Example 5.6.7.8.9 exceeded 90° C., it was not possible to simultaneously improve the fluidized bed, compressibility, and transverse rupture strength of the green compact.

Comparative Examples 10 to 15 The same method as in Example 1 was applied to the same iron powder as in Example 1, except that fatty acid zinc soap with a different carbon content was used as a lubricant.
Zinc caprylate was used as Comparative Example 10, zinc caprate was used as Comparative Example 11, zinc laurate was used as Comparative Example 12, zinc myristate was used as Comparative Example 13, zinc palmitate was used as Comparative Example 14, and zinc behenate was used as Comparative Example 15. .

Table 2 shows the melting points of the lubricants used in Comparative Examples 10 to 15 and the fluidized bed of the mixture with iron powder, 7 t/c rrI''
The green density and transverse rupture strength of the green compact at the molding pressure are shown. In either case, the melting point was around 130°C and higher than 90°C, so there was no improvement in compressibility.

Example 3 Comparative Examples 16-17 A lubricant was added to iron powder in the same manner as in Example 1, and the mixture was mixed at room temperature for 10 minutes. However, the lubricants used were zinc oleate in Example 3, conventional zinc stearate in Comparative Example 16, and oleic acid microcapsules coated with 20% by weight of zinc stearate in Comparative Example 17.

Table 3 shows the fluidized bed of the mixture of lubricant and iron powder used in Example 3 and Comparative Examples 16 to 17, 7 t/ct T1''
The green density and transverse rupture strength of the green compact at the molding pressure are shown. In Example 3, since zinc oleate was used, high compressibility and improvement in transverse rupture strength of the green compact were obtained even when mixed at room temperature, and fluidity was also improved. Comparative Example 17 had extremely poor fluidity.

Examples 4 to 8 Same method as Example 1, except that the amount of zinc oleate added was 0.2% by weight in Example 4, 0.3% by weight in Example 5, and 1.0% in Example 6. % by weight, Example 7 is 1.5% by weight
In Example 8, the content was 2.0% by weight.

Table 4 shows the melting points of the lubricants used in Examples 4 to 8, and the compact density and compact resistance of the mixtures in a fluidized bed and at a molding pressure of 7 t/crn''. fluidized bed,
The compact density and transverse rupture strength of the compact were improved.

Note that almost similar results were obtained even when lead stearate was used in place of zinc oleate.

Examples 9-11 Comparative Examples 18-20 Zinc oleate was added as a lubricant to iron-based powder in the same manner as in Example 1. However, in Example 9, 0.8% by weight of graphite powder was added as an alloying powder to the iron powder to form a mixed powder, and in Example 10, 1.8% by weight of electrolytic copper powder was added to the iron powder as an alloying powder.
0% by weight was added to make a mixed powder, and in Example 11, 1.0% by weight Ni, 0.3% by weight Cu, and 0.2% by weight were added in place of iron powder.
Iron-based powder alloyed with MO was used.

Moreover, in addition to the zinc oleate used in Examples 9 to 11, zinc stearate was used in Comparative Examples 18 to 20. As compared to the comparative example, each of the examples achieved high compressibility and transverse rupture strength of the green compact as shown in Table 5, together with fluidity.

[Effects of the Invention] The present invention can provide an iron-based powder mixture for powder metallurgy that has excellent fluidity, high compressibility, and high formability, and facilitates the production of high-density, high-strength sintered parts. It becomes possible to achieve this.

Claims (1)

[Scope of Claims] 1. An iron-based powder mixture for powder metallurgy, characterized in that lead stearate or zinc oleate is added to an iron-based powder or a mixed powder of an iron-based powder and an alloying powder. 2. Powder metallurgy according to claim 1, wherein the amount of lead stearate or zinc oleate added is 0.2 to 2.5% by weight based on the iron-based powder or the mixed powder of iron-based powder and alloying powder. Iron-based powder mixture for use.