JPH06145701A - Iron base powder mixture for powder metallurgy - Google Patents

Abstract

PURPOSE:To obtain an iron base powder mixture small in the segregation of added substance such as alloy powder, excellent in fluidity and stable feedability from a hopper and low in extracting force from a die at the time of compacting. CONSTITUTION:A machining improving agent essentially consisting of atomized iron powder having 78mum average grain size, electrolyzed copper powder for alloying having <16mum grain size, graphite powder, MgO and SiO2 is mixed with a soln. dissolved in methanol together with polyvinyl butyral and nylon 6 as a binder at an ordinary temp. for 5min, which is added with lubricant powder, and mixing is executed for 2min to evaporate the liquid components at an ordinary temp. Satisfactory results can be obtd. in the case of 0.05 to 0.3wt.% binder and 0.5 to 2.0wt.% lubricant.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has little segregation of additives, excellent outflow from the hopper and stable supply, low ejection force from the mold at the time of molding, and containing no or little zinc. TECHNICAL FIELD The present invention relates to an iron-based powder mixture for powder metallurgy and a method for producing the same.

[0002]

2. Description of the Related Art Iron-based powder mixtures for powder metallurgy are used to produce iron powder.
Generally, alloy powders such as copper powder, graphite powder, iron phosphide powder and lubricants such as zinc stearate are mixed, and if necessary, machinability-improving powder is added to manufacture. But,
Such a mixture has the following drawbacks.

First, the disadvantage is that such a mixture causes segregation. Speaking of segregation, the mixture contains powders of different sizes, shapes and densities,
Segregation easily occurs during transportation after mixing, charging into a hopper, discharging, or a molding process. For example, it is well known that a mixture of iron-based powder and graphite powder causes segregation in the transportation container due to vibration during truck transportation, and the graphite powder floats up. It is also known that when the graphite charged in the hopper is discharged from the hopper due to segregation in the hopper, the concentration of the graphite powder is different in the initial, middle, and final discharging stages. These segregations cause variations in the composition of the product, resulting in large dimensional changes and variations in strength, which cause defective products. Further, since graphite powder and the like are all fine powders, the specific surface area of the mixture is increased, and as a result, the fluidity is reduced. Such a decrease in fluidity also reduces the filling rate into the molding die, which also has the drawback of reducing the production rate of the green compact.

[0004]

As a technique for preventing the segregation of such a mixture, JP-A-1-219101 discloses a powder in which zinc stearate is used as a binder and graphite is attached to the surface of an iron-based powder. Has been done. Further, the present inventors have previously proposed a method of using a metal soap and a fatty acid as a binder in Japanese Patent Application Laid-Open No. 3-162502.
However, all of these contain zinc and other metal elements in the binder, and during sintering, the metal elements in the binder contaminate the furnace as oxides and change the composition of the sintered body. However, there is a problem that defective products increase.

In order to solve such a problem, Japanese Patent Publication No. 60-502158 and Japanese Unexamined Patent Publication (Kokai) No. 2-21740.
As disclosed in Japanese Patent Publication No. 3, there are some which use binders containing no metal element, but since these binders themselves do not have a lubricating action, finally zinc stearate is added as a lubricant. The above-mentioned problems have not been solved.

The present invention, while maintaining the conventional powder characteristics and green compact characteristics, has a small segregation, and the outflow property from the hopper,
An iron-based powder mixture for powder metallurgy, which has excellent powder supply stability and does not contain zinc or has a small content, and a method for producing the same.

[0007]

The present invention has been made to solve the above problems, and 0.05 weight of one or more binders selected from the first group of polyamide, polyvinyl butyral and polyvinyl formal. % To 0.30% by weight and 0.50% to 1.5% by weight of a powder lubricant selected from a second group of higher fatty acid amides, higher fatty alcohols and higher fatty acid esters, and the balance is An iron-based powder mixture for powder metallurgy, characterized in that 0.1% by weight or more and 5.0% by weight or less of the alloy powder and / or the machinability improving powder is an iron-based powder adhered to the surface. In this case, it is preferable to further include 0.20% by weight or less (not including 0% by weight) of zinc stearate which is a powder lubricant.

A second invention of the present invention is one or more kinds of melt binders selected from the first group of higher fatty acids, higher fatty alcohols and higher fatty esters, 0.05% by weight or more and 0.3% by weight or more.
0% by weight or less and 0.5% by weight or more and 1.5% by weight or less of one or more powder lubricants selected from the second group of higher fatty acid amides and higher fatty alcohols having a melting point higher than that of the binder. An iron-based powder mixture for powder metallurgy, characterized in that the balance is an iron-based powder having an alloy powder and / or a machinability improving powder in an amount of 0.1% by weight or more and 5.0% by weight or less fixed to the surface. Is provided. Furthermore, 0.20% by weight of zinc stearate, which is a powder lubricant, is added to this component.
It is preferable to include the following (excluding 0% by weight).

The method for producing the iron-based powder mixture for powder metallurgy of the present invention comprises at least one selected from the group consisting of alloy powder and / or machinability improving powder and polyamide, polyvinyl butyral and polyvinyl formal. And the binder is mixed at a temperature equal to or higher than the melting point of the binder, and then one or more powder lubricants selected from the second group of higher fatty acid amides, higher fatty alcohols and higher fatty acid esters are added, and A method for producing an iron-based powder mixture for powder metallurgy, which comprises mixing at a temperature not lower than the melting point of the binder and lower than the melting point of the powder lubricant.

The method for producing an iron-based powder mixture for powder metallurgy according to the second aspect of the present invention is a method for producing an alloy powder and / or a machinability improving powder, a higher fatty acid, a higher fatty alcohol and a higher fatty ester. Selected from the second group of higher fatty acid amides and higher fatty alcohols having a melting point higher than that of the melt binder after mixing with one or more melt binders selected from the one group at a temperature above the melting point of the melt binder. One or more powder lubricants are added and mixed at a temperature not lower than the melting point of the molten binder and lower than the melting point of the powder lubricant.

Another method for producing an iron-based powder mixture for powder metallurgy according to the first aspect of the present invention is to dissolve one or more binders selected from the first group of polyamide, polyvinyl butyral and polyvinyl formal in a solvent. A powder lubricant selected from the second group of higher fatty acid amides, higher fatty alcohols and higher fatty acid esters, after mixing powders for alloys and / or powders for improving machinability and adhering them with a binder. Is added and the powder lubricant is adhered to the mixture, which is a method for producing an iron-based powder mixture for powder metallurgy.

Another method for producing the iron-based powder mixture for powder metallurgy according to the second aspect of the present invention is one selected from the first group of higher fatty acids, higher fatty alcohols and higher fatty esters.
One or more melt binders are dissolved in a solvent, alloy powder and / or machinability improving powder are mixed, and after adhering with the melt binder, a higher fatty acid amide having a higher melting point than the melt binder is added to the mixture. And higher fatty alcohol second
The method is characterized in that one or more powder lubricants selected from the group are added, and the lubricant is adhered to this mixture.

[0013]

The inventors of the present invention maintained the conventional powder characteristics and green compact characteristics while maintaining a stable apparent density, little segregation, excellent outflow from the hopper, and no zinc content. As a result of earnestly researching an iron-based powder mixture for powder metallurgy in a small amount, the present invention has been achieved with the following findings.

That is, as a result of intensive studies on an iron-based powder mixture for powder metallurgy, (a) using polyamide, polyvinyl butyral, and polyvinyl formal as a binder, an alloy powder and / or a machinability improving agent on the surface of the iron-based powder. To attach powder and powdered lubricant component. (B) The alloy powder and / or the machinability improving powder and the powdered lubricant component are attached to the surface of the iron-based powder by using the higher fatty acid, the higher fatty alcohol and the higher fatty ester as a binder. (C) The iron-based powder and the alloy powder and / or the machinability improving powder and the binder component are mixed, and the alloy powder and / or the machinability improving powder are mixed with iron by stirring at a temperature at which the binder melts. To be applied to the surface of the system powder, followed by secondary addition of a powdery lubricating component that does not melt at that temperature and to be applied to the surface. By maintaining the conventional powder characteristics and green compact characteristics, segregation is small, the outflow from the hopper and the supply stability are excellent, and the extrudability after molding is good and low zinc content is achieved. We have come to the conclusion that it is possible.

The binder preferably has a function of adhering the alloy powder and / or the machinability improving powder and the lubricant powder to the surface of the iron-based powder and does not impair the powder fluidity, such as polyamide, polyvinyl butyral, Polyvinyl formal has excellent properties. Polyamide includes nylon 6, nylon 66 and the like, but since it is substantially insoluble in water and soluble in methanol, it can be easily added to the mixed powder as a solution type binder. Polyvinyl acetal includes polyvinyl butyral and polyvinyl formal, which are practically unnecessary in water.Polyvinyl butyral is soluble in acetone and methanol, and polyvinyl formal is soluble in cyclohexane and furfural. Can be added to.

In addition, various investigations revealed that stearic acid (melting point: 70 ° C.), behenic acid (at the same temperature: 80 ° C.), cetyl alcohol (at the same temperature: 48 ° C.) and stearyl alcohol (at the same temperature: 58 ° C.) have good wettability with iron-based powder. , Behenyl alcohol (70
℃), C30 alcohol ester of behenic acid (at 75 ℃)
Etc. have been found to show good performance. From these,
It may be selected according to the melting point of the lubricant.

The amount used as the binder is 0.05% by weight.
It is above 0.3% by weight. In each case, as shown in Comparative Examples below, the ratio of the amount of C contained in the powder of 100 mesh or less, 200 mesh or more in the mixture to the amount of C contained in the mixture as a whole is less than 0.05% by weight. This is because (referred to as C adhesion) drops sharply. On the other hand, when the content is more than 0.3% by weight, the green compact density is rapidly reduced, but it is also because the sufficient C adhesion can be achieved at 0.3% by weight.

In order to maintain the good outflow property of the powder and the good withdrawal property after molding, the point is to attach the powdery lubricant without melting it. Therefore, it is preferable that the alloy powder and / or the machinability improving powder be adhered to the surface of the iron-based powder, and then the lubricant powder is secondarily added in a state in which the powder is not melted and adhered to the surface. (B) can be compatible. (A) To prevent deterioration of the extractability due to melting of the lubricant powder or miniaturization due to stirring force. (B) To improve the low fluidity of the lubricant powder in a free mixed powder state by adhering it to the surface of the iron-based powder.

The binder used in the present invention has a melting point lower than that of the lubricant powder.
It is known that the lubricant powder preferably has a melting point of about 100 ° C. so that it is softened by frictional heat when pressure-molded in a mold and enhances the function of lubricating performance. ℃), ethylenebisstearic acid amide (145 ° C), a molten mixture of stearic acid monoamide and ethylenebisstearic acid amide (125 ° C), C
30 alcohols (at 90 ° C), C50 alcohols (at 9 ° C)
8 ° C), C60 alcohol (at 110 ° C), behenic acid C
30 alcohol ester (at 75 ° C.) and the like.

After the alloy powder and / or the machinability improving powder is adhered to the surface of the iron-based powder, the lubricant powder is secondly added and adhered to the surface in the state where the lubricant powder is not melted. Prevent deterioration of extractability due to melting or miniaturization by stirring force. (2) To improve the low fluidity of the lubricant powder in a completely mixed state by adhering it to the surface of the iron-based powder. This is because both of the two conditions are satisfied.

The addition amount of the lubricant powder is set to 0.5% by weight or more and 1.5% by weight or less, because if it is less than 0.5% by weight, the extraction property at the time of mold molding is deteriorated. 0.5% by weight
The reason why the content is below is that the fluidity decreases when the content exceeds 1.5% by weight. Zinc stearate is preferably added in order to further improve the fluidity, but is limited to 0.2% by weight or less in order to prevent roughening of the sintered body.

[0022]

【Example】

Example-1 Hereinafter, the present invention will be described in comparison with Comparative Examples. A mixture was prepared under the following conditions in both the examples and comparative examples. As the iron powder, atomized iron powder or reduced iron powder having an average particle size of 78 μm was used. As the electrolytic copper powder for alloy and graphite powder, -16 μm powder was used. As the cutting improving agent, talc containing MgO and SiO ₂ as main components was used.

Both polyvinyl butyral and nylon 6 were dissolved in methanol as a binder to prepare a 10% solution, which was then added so as to obtain a predetermined amount of each binder. After mixing the iron powder, the 10% binder solution, the alloy powder and / or the machinability improving powder at room temperature for 5 minutes, the lubricant powder was added and further mixed for 2 minutes. After that, the liquid component was volatilized and dried at room temperature.

The degree of adhesion of graphite (C) in the powder is 100 to 100 in this mixture with respect to the amount of C in the mixture after heat-melt mixing.
The ratio of the amount of C in a powder having a particle size of 200 mesh, the degree of C adhesion = {(the amount of C in 100 to 200 mesh) / (the amount of C in the whole)} × 100 (%) (1).

The powder outflow is 100 mm in inner diameter and 200 in height.
Put 1 kg of the mixture after powder mixing at room temperature into a mm container, let the mixture flow out from an orifice with a diameter of 3.0 mm provided at the center of the bottom of the container, and let it flow out without vibrating the container (marked with ◯). , If it spilled when the container was vibrated, or if it still did not spill (X
Mark).

The green compact density is shown as a value when a tablet having a diameter of 25 mm and a height of 20 mm is molded in a mold at a molding pressure of 6 t / cm ² . Extraction output is 25 mm in diameter and 20 m in height
The pressure at the time of molding in the mold so that the green compact density of the tablet of m was 6.9 g / cm ³ and then withdrawing from the mold was shown.

As for the dirt of the sintered body, the mixture density of each mixture was 6.9.
After press-molding to 0 g / cm ³ in a mold, sintering on the surface of the sintered body was observed after sintering at 1130 ° C. for 20 minutes in a propane-metamorphic gas atmosphere. Examples are shown in Tables 1 to 3. It showed good flowability and good sinter surface. Figures 1-3
Shows the data that is the basis for designating the ranges of the binder amount and the lubricant amount of the present invention. If the amount of the binder is less than 0.05% by weight, the C adhesion degree will be reduced to 70% or less. The binder is 0.
When it exceeds 3% by weight, the green compact density drops sharply.

When the amount of lubricant is less than 0.5% by weight, the ejection force increases rapidly, and when it exceeds 2.0% by weight,
As shown in the comparative example, there is a problem with the outflow property. Tables 4 and 5 show comparative examples. If the amount of lubricant exceeds 2.0% by weight,
Reduced runoff is shown. Further, when the content of zinc stearate exceeded 0.2% by weight, the surface of the sintered body was contaminated.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

Example-2 A mixture of Examples was prepared under the following conditions. The same applies to the comparative example. As the iron powder, atomized iron powder or reduced iron powder having an average particle size of 78 μm was used. The electrolytic copper powder used as the alloy powder had an average particle size of 28 μm, and the graphite powder had an average particle size of 16 μm or less. For the machinability improving powder, MgO, SiO
Talc mainly composed of ₂ was used.

After the iron powder, the binder, the alloy powder and / or the machinability improving powder are heated and mixed for 10 minutes at + 10 ° C. which is the melting point of each binder, a lubricant powder having a melting point higher than the heating temperature is added. Then, the mixture was mixed for 2 minutes and then cooled. The powder density is 6 t / c for tablets with a diameter of 25 mm and a height of 20 mm.
It is shown as a value when molded in a mold with a molding pressure of m ² .

With respect to the ejection force, a tablet having a diameter of 25 mm and a height of 20 mm was molded in a mold so that the powder density was 6.9 g / cm ^3, and the pressure at the time of extraction from the mold was shown. As for the dirt of the sintered body, the powder density of each mixture was 6.90 g / c.
After press-molding to m ³ in a metal mold, stains on the surface of the sintered body were observed when sintered at 1130 ° C. for 20 minutes in a propane-modified gas atmosphere.

Examples are shown in Tables 6-8. It showed good flowability and good sintered body surface. 4 to 6 show data that are the basis for designating the ranges of the binder amount and the lubricant amount of the present invention. If the amount of binder is less than 0.05% by weight, the degree of C adhesion is 7
It will fall below 0%. When the amount of the binder exceeds 0.3% by weight, the green compact density drops sharply. The amount of lubricant is 0.
If the amount is less than 5% by weight, the ejection output will increase rapidly.
When it exceeds 0% by weight, there is a problem in the outflow property as shown in Comparative Examples.

Tables 9 and 10 show comparative examples. When the amount of the lubricant exceeds 2.0% by weight, the outflow property is decreased. Further, when the content of zinc stearate exceeded 0.2% by weight, the surface of the sintered body was contaminated.

[0039]

[Table 6]

[0040]

[Table 7]

[0041]

[Table 8]

[0042]

[Table 9]

[0043]

[Table 10]

[0044]

According to the present invention, compared with the conventional mixture,
The segregation of the alloy powder and the machinability improving powder is small, so the quality of the powder metallurgy product is stable and the machinability is improved, and the outflow from the hopper is excellent, the apparent density is stable, and the ejection force from the die is excellent. Iron-based powder mixture for powder metallurgy and its production, because it is small, so there is no damage to the compact, and there is little change in the composition of the sintered compact or contamination of the sintering furnace because there are few metal components in the binder and lubricant. I was able to get a way.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of binder (PVB, nylon 6) added and the degree of C attachment.

FIG. 2 is a graph showing the relationship between the amount of binder (PVB, nylon 6) added and the green compact density during molding.

FIG. 3 is a graph showing the relationship between the lubricant addition amount and ejection force.

FIG. 4 is a graph showing the relationship between the added amount of a binder (stearic acid, stearyl alcohol, behanic acid C30 alcohol ester) and the C attachment degree.

FIG. 5 is a graph showing the relationship between the added amount of a binder (stearic acid, stearyl alcohol, behanic acid C30 alcohol ester) and the green compact density during molding.

FIG. 6 is a graph showing the relationship between the lubricant addition amount and ejection force.

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[Procedure amendment]

[Submission date] November 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043]

[Table 10]

Claims (7)

[Claims] 1. One or more binders selected from the first group consisting of polyamide, polyvinyl butyral and polyvinyl formal, in an amount of 0.05% by weight to 0.30% by weight, a higher fatty acid amide, a higher fatty alcohol and a higher fatty acid. 0.50 wt% or more and 1.5 wt% or less of a powder lubricant selected from the second group of esters, and the balance of 0.1% by weight or more and 5.0% by weight or more of alloy powder and machinability improving powder.
An iron-based powder mixture for powder metallurgy, characterized in that less than or equal to wt% is an iron-based powder adhered to the surface. 2. One or more melt binders selected from the first group consisting of higher fatty acids, higher fatty alcohols and higher fatty esters, in an amount of 0.05% by weight or more and 0.30% by weight or less and having a melting point higher than that of the binder. Higher fatty acid amide and one or more powder lubricants selected from the second group of higher fatty alcohols in an amount of 0.5% by weight or more and 1.5% by weight or less, with the balance being powder for alloy and / or improvement of machinability Powder 0.1% by weight
As described above, 5.0% by weight or less of the iron-based powder adhered to the surface is an iron-based powder mixture for powder metallurgy. 3. Zinc stearate which is a powdered lubricant.
The iron-based powder mixture for powder metallurgy according to claim 1 or 2, comprising 20% by weight or less (not including 0% by weight). 4. An alloy powder and / or a machinability improving powder, and one or more binders selected from the first group of polyamide, polyvinyl butyral and polyvinyl formal, at a temperature not lower than the melting point of the binder. And then mixed with one or more powder lubricants selected from the second group consisting of the higher fatty acid amide, the higher fatty alcohol and the higher fatty acid ester, and having a melting point of the binder or more and less than the melting point of the powder lubricant. A method for producing an iron-based powder mixture for powder metallurgy, which comprises mixing at a temperature. 5. A melt binder comprising an alloy powder and / or a machinability improving powder and one or more melt binders selected from the first group of higher fatty acids, higher fatty alcohols and higher fatty esters. After mixing at a temperature equal to or higher than the melting point of the melt binder, one or more powder lubricants selected from the second group of higher fatty acid amides and higher fatty alcohols having a higher melting point than the melt binder are added to obtain a melting point of the melt binder. A method for producing an iron-based powder mixture for powder metallurgy, comprising mixing at a temperature lower than the melting point of the powder lubricant. 6. A binder, which comprises one or more binders selected from the first group consisting of polyamide, polyvinyl butyral, and polyvinyl formal, is dissolved in a solvent, and the alloy powder and / or the machinability improving powder are mixed and adhered to the binder. After that, a powder lubricant selected from the second group of higher fatty acid amides, higher fatty alcohols and higher fatty acid esters is added to the mixture, and the powder lubricant is adhered to the mixture. A method for producing an iron-based powder mixture for metallurgy. 7. A melt binder containing at least one selected from the first group consisting of higher fatty acids, higher fatty alcohols and higher fatty esters is dissolved in a solvent, and the alloy powder and / or the machinability improving powder are mixed. After adhering with the melt binder, one or more powder lubricants selected from the second group of higher fatty acid amides and higher fatty alcohols having a higher melting point than the melt binder are added to the mixture, and the mixture is added to the mixture. A method for producing an iron-based powder mixture for powder metallurgy, which comprises depositing the lubricant.