JP2000160206A - Iron base powdery mixture for powder metallurgy and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an iron base powdery mixture excellent in fluidity and hopper exhaustibility by using a lubricant contg. no metallic components contaminating the inside of a sintering furnace and to provide a method for producing it. SOLUTION: This iron base powdery mixture contains iron base powder and 0.05 to 0.50 wt.% thermoplastic resin powder contg. at least one kind of monomeric units selected from acrylic ester, methacrylic ester and an aromatic vinyl compd. by >=50 wt.%, in which the primary average grain size is controlled to 0.03 to 5 μm, the aggregated average grain size is controlled to 5 to 50 μm, and the average molecular weight measured by a solution specific viscosity method is controlled to thirty thousand to a five million as free powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based powder mixture for powder metallurgy, which does not contain a metal component in a lubricant to be mixed and has excellent fluidity and outflow from a hopper, and a method for producing the same.

[0002]

2. Description of the Related Art An iron-based powder mixture for powder metallurgy is prepared by adding an iron powder as a base iron powder, an alloy powder such as copper powder, graphite powder, iron phosphide powder and a lubricant such as zinc stearate. Is generally mixed, and if necessary, a powder for improving machinability is added. However, such a mixture
It has the following disadvantages. First, its disadvantage is that such mixtures tend to segregate in terms of particle size, shape and chemical composition. In other words, since the mixture contains a plurality of types of powders having different sizes, shapes and densities, transportation after mixing, charging into a hopper, discharging, or filling in a mold to perform a pressure molding process and the like. During the process, the particles are not uniformly distributed in the mixture, and the above-described segregation occurs. For example, in a mixture of iron powder and graphite powder, the iron powder and graphite powder move and move independently in the transport container due to vibration during truck transportation, and the powder is not uniformly distributed in the mixture. It is well known that graphite powder having a low specific gravity emerges on the surface. It is also well known that the mixture charged in the hopper segregates due to movement in the hopper, and the mixture discharged from the hopper has a different graphite powder concentration at the initial, middle and final stages of discharge. ing.

[0003] When the segregated mixture is molded under pressure (compression) and the molded body is sintered to produce a sintered body as a final product, the composition of the sintered body varies from product to product. In addition, the size and strength vary greatly, resulting in defective products. Further, the copper powder, graphite powder, iron phosphide powder and the like to be mixed are all finer than iron powder, so that the specific surface area of the mixture is increased and its fluidity is reduced. Such a decrease in the fluidity of the mixture lowers the filling rate of the mixture into a molding die, which causes a reduction in the production rate of a molded body (also referred to as a green compact).

[0004] In order to prevent the segregation of such a mixture, Japanese Patent Publication No. 5-27682 discloses an iron-based powder containing at least one powder.
Kind Code: A1 A composition comprising a powder for alloys and a binder for the iron-based powder and alloy powder, wherein the composition mechanically adds the binder to the iron-based powder and the alloy powder. An improved composition, formed by mixing, wherein the binder is a methacrylic polymer, a resin substantially insoluble in water, and wherein the binder is about 0.04%.
Disclosed is a powder composition characterized in that it contains from 0.05 to 1.0% by weight. Further, the detailed description of the invention in the publication discloses a homopolymer of methyl methacrylate (polymethyl methacrylate) as a methacrylic polymer. However, this Japanese Patent Publication 5-27682
The mixture described in the above publication contains polymethyl methacrylate as a binder for adhering the alloy powder to the iron-based powder, but not as a powder, so that polymethyl methacrylate as a binder naturally segregates. Can be prevented, but the dischargeability from the hopper (hereinafter simply referred to as hopper dischargeability) is insufficient, and it is necessary to improve it. Another problem is that the cost of recovering the organic solvent is increased because the surface of the iron-based powder is thinly coated by dissolving the liquid resin as a binder with an organic solvent.

As another segregation preventing technique, Japanese Patent Application Laid-Open No. 1-219101 discloses a mixed powder in which zinc stearate is used as a binder and graphite powder is adhered to the surface of an iron-based powder. Further, the present inventors have previously described in Japanese Patent Laid-Open No.
No. 2502 proposed a method using a metal soap and a fatty acid as a binder. However, the mixtures described in these publications all contain zinc and other metal elements in the binder, and the metal elements in the binder become oxides during sintering of the molded body, so that the inside of the sintering furnace is There were problems such as contamination and a change in the chemical composition of the sintered body. Therefore, as a method of solving such a problem, Japanese Patent Publication No. 60-502158 and Japanese Patent Laid-Open No. 21740/1990 are known.
No. 3 proposed a mixture using a binder containing no metal element. However, the technology described in this publication also
Since the binder itself has no lubricating action, zinc stearate is finally added as a lubricant, and the above-mentioned problem of hopper discharge property has not been solved.

[0006] In view of these problems, the present inventors have:
The solution has been disclosed in Japanese Patent Application Laid-Open No. 5-148505. That is, stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, one or more binders selected from ethylenebisstearic acid amide, alloy powder, iron The base powder is mixed, heated and then cooled, and the alloy powder and the like are fixed to the iron base powder with the solidified binder, and further, the same kind of powder as the above binder and zinc stearate. An iron-based mixture for powder metallurgy, in which powder was added and mixed as a lubricant, and a method for producing the same were proposed. It has also been suggested that when a hot melt of higher fatty acids, higher fatty acid amides, waxes and zinc stearate is used as the binder, lithium stearate should be used as the lubricant. However, even with such a technique, since a small amount of metal soap such as zinc stearate or lithium stearate is still blended, the internal contamination of the sintering furnace could not be completely eliminated. The reason is that when a lubricant containing no metal soap such as zinc stearate or lithium stearate is used, that is, a lubricant consisting of only an organic substance containing no metal component is used, the fluidity and hopper discharge of the obtained iron-based powder mixture are reduced. This is because the sex deteriorates.

The present invention has been made in view of the above circumstances, and provides an iron-based powder mixture excellent in fluidity and hopper dischargeability using a lubricant that does not contain metal components that contaminate the inside of a sintering furnace, and a method for producing the same. It is intended to be.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors reviewed conventional iron-based powder mixtures for powder metallurgy and obtained many new findings described later. Even if a lubricant composed of only an organic substance containing no metal component is used, the powder and the compact can maintain the characteristics of the conventional powder sufficiently, and a powder having excellent fluidity and hopper discharge property can be obtained. It was confirmed that the present invention was completed, and the present invention was completed.

That is, the present invention comprises an iron-based powder and at least 50% by weight of at least one monomer unit selected from acrylates, methacrylates and aromatic vinyl compounds. Average particle size 0.03-5μ
m, a thermoplastic resin powder having a coagulation average particle size of 5 to 50 μm and an average molecular weight of 30,000 to 5,000,000 as measured by a solution specific viscosity method as a free powder, containing from 0.05% by weight to 0.50% by weight. An iron-based powder mixture for powder metallurgy characterized by the following. In addition, the present invention provides an iron-based powder, 0.1% by weight or more and 1.0% by weight or less of one or more kinds of lubricants selected from the following attached to the iron-based powder; 50% by weight or more of an alloy powder and / or a machinability improving powder attached to the iron-based powder and at least one monomer unit selected from acrylates, methacrylates and aromatic vinyl compounds Containing, having a primary average particle size of 0.1.
A thermoplastic resin powder having a particle size of from 03 to 5 μm, an average particle diameter of aggregation of from 5 to 50 μm, and an average molecular weight of 30,000 to 5,000,000 as measured by a solution specific viscosity method is from 0.05% by weight to 0.50% by weight as a free powder. It is an iron-based powder mixture for powder metallurgy characterized by containing. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide.

The present invention is characterized in that the iron-based powder mixture for powder metallurgy further contains 0.5% by weight or less of one or more lubricant powders selected from the following as free powder. Is an iron-based powder mixture for powder metallurgy. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene.

[0011] The present invention also relates to the iron-based powder mixture for powder metallurgy, further comprising at least one organic liquid lubricant selected from oleic acid, spindle oil and turbine oil.
It is an iron-based powder mixture for powder metallurgy characterized by containing not less than 01% by weight and not more than 0.3% by weight.

Further, the present invention provides an iron-based powder, a powder for alloying and / or a powder for improving machinability, and a powder of at least 0.1% by weight of at least one lubricant selected from the following. 0% by weight or less and at least one selected from acrylates, methacrylates and aromatic vinyl compounds.
Containing 50% by weight or more of various kinds of monomer units, having a primary average particle size of 0.03 to 5 μm, an aggregation average particle size of 5 to 50 μm, and an average molecular weight of 30,000 to 5,000,000 as measured by a solution specific viscosity method. And 0.05 to 0.50% by weight of a thermoplastic resin powder of the present invention. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene.

[0013] In addition, the present invention is also an iron-based powder mixture for powder metallurgy, wherein the thermoplastic resin powder is polymethyl methacrylate.

The invention also relates to a manufacturing method. First, the present invention relates to an iron-based powder, a powder for alloying and / or a powder for improving machinability, and one or more lubricants selected from the following.
After mixing 1% by weight or more and 1.0% by weight or less, the mixture is further mixed with the lubricant at a temperature higher than the melting point of the lubricant by 10 ° C or more and 100 ° C or less when one kind of the lubricant is used. Is composed of two or more kinds, mixing while heating at a temperature of 10 ° C. or more higher than the lowest melting point of the lubricant and not more than the highest melting point, melting at least one kind of the lubricant, and subsequently cooling, After the alloy powder and / or the powder for improving machinability are adhered to the iron-based powder by the molten lubricant, the mixture after the adhesion is selected from acrylates, methacrylates, and aromatic vinyl compounds. 50% by weight or more of at least one selected monomer unit, a primary average particle diameter of 0.03 to 5 μm, an aggregation average particle diameter of 5 to 50 μm, and an average molecular weight measured by a solution specific viscosity method. 30,000-5,000,000 heat A method for producing an iron-based powder mixture for powder metallurgy, comprising mixing 0.05% by weight or more and 0.50% by weight or less of a plastic resin powder. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide.

Further, the present invention provides an iron-based powder, an alloy powder and / or a machinability improving powder, and 0.1% by weight or more and 1.0% by weight or more of one or more kinds of lubricants selected from the following. % Or less and one or more organic liquid lubricants selected from among oleic acid, spindle oil and turbine oil in an amount of 0.01% by weight or more and 0.3% by weight or less. When one kind of the agent is used, the mixture is heated and mixed at a temperature higher than the melting point of the lubricant by 10 ° C. or more and 100 ° C. or less.
If it consists of more than one kind, it is heated and mixed at a temperature of 10 ° C. or more of the lowest melting point or more and the highest melting point or less, melts at least one kind of lubricant, and then cools it, After the powder and / or the machinability improving powder are adhered by the molten lubricant, the mixture after the adhesion treatment is added to at least one kind selected from acrylates, methacrylates and aromatic vinyl compounds. A monomer unit is contained in an amount of 50% by weight or more, and the primary average particle size is 0.1%.
A mixture of 0.05 to 0.50% by weight of a thermoplastic resin powder having an average molecular weight of 30,000 to 5,000,000 as measured by a solution specific viscosity method, having a mean particle size of from 3 to 5 μm, an aggregation average particle size of 5 to 50 μm. A method for producing an iron-based powder mixture for powder metallurgy, which is a feature of the present invention. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide.

Further, the present invention is characterized in that 0.5% by weight or less of powder of one or more lubricants selected from the following is further added to the mixture after the above-mentioned adhesion treatment and mixed. It is also a method for producing an iron-based powder mixture for powder metallurgy. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene.

Further, the present invention is also a method for producing an iron-based powder mixture for powder metallurgy, wherein the thermoplastic resin powder is polymethyl methacrylate.

[0018]

Embodiments of the present invention will be described below in detail. First, the iron-based powder mixture for powder metallurgy according to the present invention (hereinafter, often referred to simply as the mixture according to the present invention) is an iron-based powder, as a free powder, which has not been used for powder metallurgy in the past. 50% or more of at least one monomer unit selected from acrylic acid esters, methacrylic acid esters and aromatic vinyl compounds, having a primary average particle size of 0.03 μm to 5 μm and an aggregation average particle size of A significant point is that a thermoplastic resin powder having a particle size of 5 to 50 μm and an average molecular weight of 30,000 to 5,000,000 is mixed at 0.05% by weight or more and 0.50% by weight or less. Thereby, the fluidity and the hopper discharge property of the mixture according to the present invention can be improved as compared with the conventional one. Here, as the iron-based powder, mill scale generated during the production of steel materials, reduced iron powder obtained by reducing iron ore, pure iron powder and / or alloyed iron powder produced by atomizing molten steel is preferable. Graphite powder, copper powder, various alloy powders, etc. are used as the alloy powder to be mixed with the alloy powder. When the sintered body is formed, the machinability improving powder for improving the machinability is talc, metal sulfide, or the like. Are selected in consideration of the characteristics required for the product sintered body. The alloy powder is preferably mixed in a total of 5.0% by weight or less, and the machinability improving powder is preferably mixed in a total of 5.0% by weight or less. When the thermoplastic resin powder is blended in an amount of 0.05% or more and 0.5% or less, the hopper discharge property decreases when the addition amount is less than 0.05%, and the compressibility decreases when the addition amount exceeds 0.5%. That's why.

The primary average particle size is an average value of individual particles (referred to as primary particles 1) of the thermoplastic resin powder as shown in FIG. 2 is not the average value of the particle diameters. Specifically, it
The so-called SEM photograph is taken by observing the aggregated particles 2 with an electron microscope, and the diameter (primary particle diameter 3) of about 50 primary particles 1 forming the aggregated particles 2 is actually measured and averaged.
Similarly, the average particle size of the aggregated particles 2 is also determined from the result of observing the aggregated particle size 4 with an electron microscope (SEM photograph). The reason for limiting the particle size to the above range will be described later. The thermoplastic resin powder preferably contains at least 50% by weight of at least one monomer unit selected from acrylates, methacrylates, and aromatic vinyl compounds. 50% by weight
If less than, when used as a lubricant for iron-based powder,
This is because the thermoplastic resin powder may not sufficiently improve the fluidity of the mixture. In addition, these monomers are 1
The species may be used alone or in combination of two or more.

The acrylic ester as a monomer unit of the thermoplastic resin powder includes, for example, methyl methacrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, Examples include t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. Also, as methacrylic acid ester,
For example, methyl methacrylate, ethyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like can be mentioned. Among these monomers, methyl methacrylate can be particularly preferably used.

Further, as the aromatic vinyl compound, for example, styrene, α-methylstyrene, divinylbenzene and the benzene nucleus of these monomers are substituted with methyl group, ethyl group, propyl group, butyl group and the like. Monomers such as vinyltoluene and isobutylstyrene can be exemplified.

Other monomers copolymerizable with the above three types of monomer units include, for example, acrylic acid, methacrylic acid,
Unsaturated monocarboxylic acids such as 2-ethylacrylic acid, crotonic acid and cinnamic acid; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, citraconic acid and chloromaleic acid, and anhydrides thereof: monomethyl maleate; Monoesters and derivatives of unsaturated dicarboxylic acids such as monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate and monobutyl itaconate; glycidyl methacrylate, glycidyl acrylate, glycidyl-p-vinylbenzoate; Methyl glycidyl itaconate, ethyl glycidyl maleate, glycidyl vinyl sulfonate, glycidyl ethers; butadiene monoxide, vinylcyclohexene monoxide, 5.6-epoxyhexene,
Epoxide olefins such as -methyl-5.6-epoxyhexene; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate, vinyl propionate, vinyl myristate, vinyl oleate and vinyl benzoate Conjugated diene compounds such as butadiene, isoprene, 1,3-pentadiene and cyclopentadiene; and non-conjugated diene compounds such as 1,4-hexadiene, dicyclopentadiene and ethylidene norbornene. Further, as a copolymerizable monomer, a crosslinkable monomer having two or more double bonds having substantially the same reactivity is used in an amount of 0.1 to 2% by weight of the whole monomer.
It may be added. It is preferable to add such a crosslinkable monomer in an amount of 0.1 to 2% by weight of the whole monomer. Such crosslinkable monomers include ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylol Methylolpropane trimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, oligoxyethylene diacrylate, oligoxyethylene dimethacrylate, aromatic divinyl monomers such as divinylbenzene, triallyl trimellitate, triallyl isocyanurate, etc. Can be used.

In the present invention, the primary average particle size (by weight) of the thermoplastic resin powder is limited to 0.03 to 5.0 μm. If the primary average particle size is less than 0.03 μm, the production cost of the mixture according to the present invention increases, and the mixture is not suitable for application to industrial products. If it exceeds 5.0 μm, the mixture is filled into a mold. This is because the density (hereinafter, simply referred to as compressibility) of a molded article obtained by pressure molding decreases. However, in practical use, the thickness is more preferably 0.05 to 3.0 μm. The resin powder has an average coagulation particle size of 5 to 5.
It is limited to 50 μm. When the agglomeration average particle size is 5 μm or less, the fluidity and the hopper discharge property of the mixture according to the present invention decrease. This is because the tensile strength is lower than that of a sintered body obtained from a conventional mixture. However, the agglomerated average particle size is also 10 to 40 μm.
m is more preferable. Further, as the thermoplastic resin powder, two or more kinds of thermoplastic resin powders having different average single particle diameters can be mixed. In this case, the primary average particle diameter is defined as the total of the mixed powders. The mixing ratio is adjusted so that the weight-based average value is 0.03 to 5.0 μm.

In addition, in the present invention, the thermoplastic resin powder has an average molecular weight of 30,000 to 500 measured by a solution specific viscosity method.
Limited to those within the range of 10,000. If the average molecular weight is less than 30,000, the production cost of the mixture according to the present invention becomes too high, and it is not suitable for application to industrial products. If it exceeds 5,000,000, the fluidity and hopper discharge property of the mixture are lower than conventional products. Because you do. Here, the solution specific viscosity method refers to a sample resin 0.2
g in 50 ml of tetrahydrofuran.
In this method, the viscosity at 5 ° C. is determined as a ratio to the viscosity of the solvent at the same temperature, and the average molecular weight of the sample resin is determined from the relationship of specific viscosity-average molecular weight predetermined by various standard polystyrenes having known average molecular weights.

In addition, there is no particular limitation on the production of the above-mentioned thermoplastic resin powder, and methods conventionally used for producing fine resin powders such as polymethyl methacrylate, for example, fine suspension polymerization, An emulsion polymerization method, a seeded emulsion polymerization method, or the like may be employed. Among these methods, a polymerization method in which the particle size is not extremely fine and spherical particles are obtained is particularly preferable. As the fine suspension polymerization method, a method in which an oil-soluble initiator is used as a radical polymerization initiator, the particle size of monomer oil droplets is homogenized before the polymerization is started, and the particle size is adjusted in advance, and homogenous dispersion polymerization is preferably performed. It is.

Examples of the oil-soluble radical polymerization initiator include diacyl peroxides such as benzoyl peroxide, di-3,5,5-trimethylhexanoyl peroxide and dilauroyl peroxide, and diisopropylperoxydicarbonate. Peroxydicarbonates such as di-sec-butylperoxydicarbonate and di-2-ethylhexylperoxydicarbonate; peroxyesters such as t-butylperoxypivalate and t-butylperoxyneodecanoate Or organic peroxides such as acetylcyclohexylsulfonyl peroxide and disuccinic acid peroxide; furthermore, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, , 2'-Azobisdim Or the like can be used azo compounds such as Le valeronitrile. These radical polymerization initiators can be used alone or in combination of two or more. The amount used can be appropriately selected depending on the type and amount of the monomer, the preparation method, and the like, but is usually used in the range of 0.001 to 5.0 parts by weight per 100 parts by weight of the monomer used. Is preferred.

In carrying out the fine suspension polymerization method, usually,
Surfactants and dispersants are used. Examples of the surfactant include alkyl sulfates such as sodium lauryl sulfate and sodium myristyl sulfate; alkyls such as sodium dodecylbenzenesulfonate and potassium dodecylbenzenesulfonate. Aryl sulfonates; sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate; fatty acid salts such as ammonium laurate and potassium stearate; polyoxyethylene alkyl sulfates; polyoxyethylene alkyl aryl sulfates; Further, anionic surfactants such as sodium dodecyl diphenyl ether disulfonate; sorbitan monooleate, polyoxyethylene sorbita; Sorbitan esters such as monostearate; polyoxyethylene alkyl ethers; nonionic surfactants such as polyoxyethylene alkyl phenyl ethers; cetylpyridinium chloride,
Cationic surfactants such as cetyltrimethylammonium bromide can be mentioned. Further, as a dispersant, polyvinyl alcohol, methyl cellulose,
Polyvinylpyrrolidone and the like can be mentioned. These surfactants and dispersants may be used alone or in combination with two or more.
A combination of more than one species may be used. The amount used can be appropriately selected usually from 0.05 to 5 parts by weight, preferably from 0.2 to 4 parts by weight, per 100 parts by weight of the monomer used.

In the fine suspension polymerization method, first, an oil-soluble initiator, a monomer, a surfactant and, if necessary, a polymerization aid such as a higher fatty acid or a higher alcohol in an aqueous medium. Other additives are added and mixed in advance, and homogenized by a homogenizer to adjust the particle diameter of oil droplets. As the homogenizer, for example, a colloid mill, a vibration stirrer, a two-stage high-pressure pump, high-pressure ejection from a nozzle or an orifice, ultrasonic stirring, or the like can be used. In addition, the adjustment of the oil droplet size is affected by the control of the shear force during the homogenization treatment, the stirring conditions during the polymerization, the type of the reactor, the amount of the surfactant and the additives, etc. Appropriate conditions can be selected by simple preliminary experiments. Then, the homogenized solution of all the monomers is sent to a polymerization vessel, and the temperature is increased while stirring slowly, and polymerization is usually performed at a temperature in the range of 30 to 80 ° C.

In this way, the primary average particle size is from 0.03 to
An emulsion or suspension in which particles of a 5.0 μm thermoplastic resin powder are homogeneously dispersed can be obtained. The emulsion or suspension is spray-dried, or the particles of the thermoplastic resin are agglomerated, then filtered to separate the plasma, dried and pulverized to obtain a thermoplastic resin powder. The weight average molecular weight of the thermoplastic resin may be adjusted to a desired value with a reaction temperature or a polymerization degree regulator.

In the present invention, in addition to the above-mentioned mixture, there is also provided a mixture having an excellent segregation preventing effect of alloy powder or machinability improving powder. It is selected from iron-based powder, stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylene bis-stearic acid amide, and ethylene bis-stearic acid amide fused and adhered to the iron-based powder. One or more lubricants
1% by weight or more and 1.0% by weight or less, an alloy powder and / or a machinability improving powder adhered to the iron-based powder by the lubricant, and at least the acrylic ester, methacrylic ester and aromatic vinyl compound Containing 0.05% to 0.50% by weight of a thermoplastic resin powder containing 50% or more of one type of monomer unit selected from the group consisting of stearic acid and olein, if necessary. Acid amide, stearic acid amide, molten mixture of stearic acid amide and ethylene bis stearic acid amide, ethylene bis stearic acid amide, polyethylene having a molecular weight of 10,000 or less, molten mixture of ethylene bis stearic amide and polyethylene having a molecular weight of 10,000 or less 1 selected from the group
It contains a free powder containing 0.50% by weight or less of at least one kind of lubricant. Thereby, without using a metal soap such as zinc stearate as a lubricant, not only segregation in a mixture such as alloy powder is prevented, but also
The characteristics of the powder and the green compact comparable to conventional products are sufficiently maintained,
This is because the fluidity and the hopper discharge property are excellent.
The reason why segregation is prevented is that the lubricant attached to the iron-based powder exerts a binding action and fixes the alloy powder and / or the machinability improving powder to the iron-based powder surface.

Further, in the present invention, without using a lubricant exhibiting a binding action, it is selected from the group consisting of iron-based powder, powder for alloying and / or powder for improving machinability, and the same lubricant as described above. And at least one monomer unit selected from the above-mentioned predetermined acrylate, methacrylate and aromatic vinyl compounds. Of a thermoplastic resin containing at least 50% by weight and a free powder of at least 0.05% by weight and at most 0.50% by weight, to thereby sufficiently maintain the properties of powder and green compact comparable to conventional products. Further, the present invention also provides an iron-based powder mixture (hereinafter, sometimes referred to as a simple mixed powder) having excellent fluidity and hopper dischargeability. Next, a method for producing a mixture according to the present invention is performed sequentially in the following steps.

(1) 1 selected from the following lubricant group
0.1% by weight or more and 1.0% by weight or less of the seed or more, the alloy powder and / or the machinability improving powder, and the iron-based powder are mixed. Note: Stearic acid, oleic acid amide, stearic acid amide, molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide (2) In the case of plus 10 to 100 ° C. and two or more lubricants, the lowest melting point among those melting points plus 10 ° C.
Above, at a temperature below the highest melting point, mixing while heating,
At least one or more lubricants are melted. (3) The mixture is cooled, and the alloy powder and / or the machinability improving powder are firmly adhered to the surface of the iron-based powder. (4) Thereafter, at least less than the minimum melting point of the organic lubricant, preferably at room temperature, at least one monomer unit selected from the above-mentioned predetermined acrylic ester, methacrylic ester and aromatic vinyl compound is used. % Of thermoplastic powder containing 0.05% by weight or more and 0.50% by weight or less. (5) Further, if necessary, 0.50% by weight or less of powder of one or more lubricants selected from the following lubricant group is added and mixed. Stearic acid (melting point 69 ° C.), oleic acid amide (melting point 76 ° C.), stearic acid amide (melting point 103 ° C.), molten mixture of stearic acid amide and ethylenebisstearic acid amide (melting point 125 ° C.), ethylenebisstearic acid Amide (melting point: 147 ° C), polyethylene having a molecular weight of 10,000 or less (melting point: 110 to 150 ° C), melt mixture of ethylenebisstearic acid amide and polyethylene having a molecular weight of 10,000 or less (130 to 140 ° C).

These lubricants are used because zinc stearate containing a metal element which has been conventionally used (melting point: 120 ° C.)
Similarly to the above, when the iron-based powder mixture is pressed and molded in a mold, the mixture is melted or softened by frictional heat to work as an original lubricant. The degree of adhesion of the alloy powder and / or the machinability improving powder to the iron-based powder is improved by the heat melting and mixing. If the amount of the lubricant which is heated and melted and exerts the binding action is less than 0.1% by weight, the amount of the lubricant adhered to the surface of the iron-based powder such as alloy powder is reduced, and the segregation in the mixture is increased. If the amount of the lubricant exceeds 1.0% by weight, the hopper discharge property cannot be improved.

In the step (5), at room temperature, 0.50% by weight or less of one or more powders selected from the group consisting of the same lubricants as described in (5) is added. This is because, as described above, when pressure molding is performed in a mold, the lubricant is melted or softened by frictional heat to function as a lubricant. If it is added in excess of 0.50% by weight, it cannot be discharged smoothly from the hopper.

Further, the mixture according to the present invention contains at least 0.01% by weight and at least 0.3% by weight of one or more organic liquid lubricants selected from oleic acid, spindle oil and turbine oil.
The following may be added with the lubricant: Thereby, the adhesion of the alloy powder to the iron-based powder becomes strong, and the apparent density value of the mixture itself is stabilized. When the amount of addition is less than 0.01% by weight, there is no effect of stabilizing the apparent density value, and when it exceeds 0.3% by weight,
Hopper discharge is reduced. It is preferable to add these liquid lubricants before mixing the iron-based powder (iron powder) with other additives (such as alloy powder). The reason is that the liquid lubricant quickly covers the surface of the iron powder during stirring and mixing of the iron powder and other additives, suppresses surface friction of the iron powder particles caused by stirring, deformation due to collision, This is because it has a function of suppressing a decrease in the hopper discharge property due to the deformation and facilitating uniform attachment of the additive to the surface of the iron powder. By adding during mixing, the effect of stabilizing the apparent density value is small,
The hopper discharge property also decreases, and if added after mixing, both the effect of stabilizing the apparent density value and the hopper discharge property decrease. Also in the case of using this liquid lubricant, the amount of the organic lubricant that exerts the binding action by heating and melting and mixing may be equivalent to the case where no liquid lubricant is used.

Further, in the present invention, the heating temperature is set to the melting point plus 10 ° C. or more and 100 ° C. or less when one kind of lubricant (lubricant excluding liquid lubricant) is used. Is equal to or higher than the melting point of the lubricant having the lowest melting point plus 10 ° C. and equal to or lower than the melting point of the lubricant having the highest melting point. In the case of one kind of lubricant, it is melted by heating at the melting point plus 10 ° C or more,
By exhibiting the bonding function and setting the melting point to 100 ° C. or lower, it is possible to prevent the deterioration of the bonding function due to the thermal decomposition of the lubricant. When two or more lubricants are used, at least one of the lubricants is melted at a temperature higher than the melting point of the lubricant having the lowest melting point plus 10 ° C. or more to exhibit a bonding function, and the melting point of the lubricant having the highest melting point is lower than the melting point of the lubricant having the highest melting point. By doing so, it is possible to prevent functional deterioration due to thermal decomposition and to improve hopper discharge performance.

On the other hand, in the production of the simple mixed powder, at least one selected from the group consisting of the following lubricants is used in an amount of 0.1% by weight or more and 1.0% by weight or less, and 0.05% by weight or more and 0.50% by weight or more of thermoplastic resin powder containing 50% or more of at least one monomer unit selected from esters and aromatic vinyl compounds.
% By weight or less as a lubricant of a free powder is simply added to and mixed with an iron-based powder, an alloy powder, a powder for improving machinability, and the like.
This is because the iron-based mixed powder having sufficient fluidity and hopper discharge property can be obtained by sufficiently maintaining the conventional powder properties and green compact properties. 1 selected from the group of the following lubricants
When the amount of the seeds is set to 0.1% by weight or more and 1.0% by weight or less, if it is less than 0.1% by weight, the ejection force (hereinafter, simply referred to as ejection force) of the molded article from the mold becomes too high. If the content exceeds 1.0% by weight, the fluidity decreases. Also,
The addition amount of the thermoplastic fine powder containing 50% or more of at least one monomer unit selected from acrylates, methacrylates and aromatic vinyl compounds is 0.05% by weight to 0.50% by weight. The reason why it is added in an amount of not more than 0.05% by weight is that if the amount is less than 0.05% by weight, the hopper discharge property is reduced, and if it is more than 0.5% by weight, the compressibility is reduced. Further, the reason that the shape of the fine powder of the thermoplastic resin is specified to have a primary particle diameter of 0.03 μm or more and 5 μm or less and an average agglomeration diameter of 5 to 50 μm is the same as above. In addition, V type blender or W
It is preferable to use a mold cone mixer or the like. Note stearic acid, oleic acid amide, stearic acid amide, a molten compound of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide,
Polyethylene having a molecular weight of 10,000 or less, ethylene bisstearic acid amide and a polyethylene melt mixture having a molecular weight of 10,000 or less.

[0038]

EXAMPLES Table 1 shows the types of thermoplastic resin powders used in the examples of the present invention, their compositions and polymerization methods. Further, in the examples, the group (A) relating to the mixture with emphasis on segregation prevention and the group (B) relating to the simple mixture are described.
We went into groups.

[0039]

[Table 1]

(Group A) In order to manufacture the powder mixture for powder metallurgy according to the present invention, first, graphite powder (alloy powder) having an average particle diameter of 23 μm was added to iron powder (iron-based powder) having an average particle diameter of 78 μm. % By weight, 2% by weight of electrolytic copper powder (powder for alloy) having an average particle size of 25 μm, and a primary-mixed lubricant (organic lubricant and liquid lubricant) shown in Table 2 were mounted on a heating mixer. And mixed well. Then, at a temperature not lower than the lowest melting point of the mixed organic lubricant + 10 ° C. and not higher than the highest melting point,
The mixture was heated while continuing to mix (this is called primary mixing). Subsequently, the mixture was cooled to 85 ° C. or lower while mixing. Further, after cooling to 40 ° C., a secondary-mixed lubricant shown in Table 3 as a free powder, that is, a lubricant (b) and / or a thermoplastic resin powder is added and mixed so as to be uniform (secondary mixing). ) And discharged from the heating mixer.

[0041]

[Table 2]

[0042]

[Table 3]

On the other hand, in order to compare the properties with the mixture according to the present invention produced as described above, the powder used was the same, and the blending of the lubricant and the production conditions were changed as shown in Tables 5 and 6. A mixture was separately manufactured (hereinafter, referred to as a comparative example).

[0044]

[Table 5]

[0045]

[Table 6]

In all the tables described in this specification,
In the embodiment according to the present invention, those of the group A are denoted by the symbol A
４３43 and B group are represented by symbols B-44４４77, and the comparative examples are represented by A ratio 1１〜14 for group A and B ratio 15〜26 for group B.

Next, the mixture was filled in a mold, and molded into a tablet having a diameter of 25 mm and a height of 20 mm as a molded body at a pressure of 5 t / cm 2. Table 4 shows the ejection force of the molded body manufactured using the mixed powder according to the present invention and the mixture 100
The value of the fluidity of the mixture was indicated by the time from when g was filled into a container having an orifice diameter of 5 mm until the container was discharged. Also,
The hopper discharge property of this mixture is 100 mm in inner diameter and 2 mm in height.
The evaluation was performed by the number of times of vibration until 1000 g of the mixture was completely discharged through an orifice having a diameter of 2.0 mm provided at the center of the bottom of a 00 mm container. Further, after measuring the molding density of the molded body, the molded body was heated at 1130 ° C. in an atmosphere of RX gas.
Table 4 also shows the results of visually determining whether or not soot was present on the surface of the sintered body. The measured compacting density of the compact was used as an index for evaluating the compressibility of the mixture. On the other hand, after the mixture was molded into a molded body having a molding density of 6.8 Mg / m3, the molded body was sintered under the conditions described above, and the tensile strength of the sintered body was measured. Further, as a scale indicating the degree of segregation of the graphite powder contained in the mixture, the degree of adhesion of carbon C was also evaluated. The degree of adhesion was determined by sieving the mixed powder and performing quantitative analysis of carbon by the following equation. The larger the value, the smaller the segregation of the graphite powder in the mixed powder.

Degree of adhesion of carbon C = (100 mesh (15
0 μm) and 200 mesh (75 μm)
m) C analysis value of iron-based mixed powder up to a particle size not passing through m) / (C analysis value of iron-based mixed powder) × 100 (%)

[0049]

[Table 4]

As shown in Tables A-A1 to A-A43, if an iron-based powder mixture is produced by mixing the powder and the lubricant according to the present invention, zinc stearate containing a metal element in the lubricant can be used. Even if lithium stearate is not used, the fluidity is 10.1 / 100 g to 11.9 seconds / 100 g, the hopper discharge property is excellent once or twice, and the ejection force is 115 to 129 kgf.
/ Cm 2, soot is not observed on the sintered body, and an iron-based powder mixture for powder metallurgy having an adhesion ratio of C of 80 to 91% can be obtained. On the other hand, as described below, the comparative example is inferior in any of the characteristics.

The same evaluations as in the examples were carried out for the mixtures produced under the conditions as comparative examples, and the results are shown in Table 7. From Table 7, since the mixture of A ratio 1 has an average molecular weight of the thermoplastic resin powder exceeding 5,000,000, the mixture of A ratios 3 and 4 has a coagulation average particle size of the thermoplastic resin powder of 5 μm.
It is clear that the fluidity of the mixture and the hopper discharge are low because it is less than m. Further, the mixture having a ratio A of 2 in which the average primary particle size of the thermoplastic resin powder exceeds 5 μm has a compressibility of the mixture which is lower than that of the mixture of the solid A2 having the same lubricant composition other than the resin powder. Decreased by 0.15 Mg / m3.
Furthermore, since the mixture having an A ratio of 5 has a thermoplastic resin powder having an agglomeration average particle size of more than 50 μm, the tensile strength of the sintered body produced therefrom is as follows: For tensile strength of 410 to 440 MPa, 3
It was as low as 60 MPa. In the mixture having the A ratio of 6, the blending amount of the thermoplastic resin powder was small, and the fluidity and the hopper discharge property were reduced. Since the blending amount of the thermoplastic resin powder in the mixture of A ratio 7 exceeds 0.5% by weight, the same lubricant as that of the mixture of A ratio 7 except for the thermoplastic resin powder is blended with the mixture of A ratio 7. The compressibility is 0.07 Mg /
m3 lower. The mixture with the A ratio of 8 has a poor fluidity and hopper discharge property because the amount of the lubricant to be heated and mixed exceeds 1% by weight. At less than 1% by weight, the C adhesion amount is low. The mixture having an A ratio of 10 contains a large amount of a lubricant other than the thermoplastic resin added in the secondary mixing, and the A ratios of 11 and 12 contain a large amount of a liquid lubricant as a binder. And hopper discharge property are poor.

It should be noted that no soot was generated in any of the sintered bodies manufactured in the comparative example and the example. Also,
The output of the molded product from the mold was not different between the example and the comparative example.

[0053]

[Table 7]

(Group B) 1% by weight of graphite powder (alloy powder) having an average particle diameter of 23 μm and copper powder (alloy powder) having an average particle diameter of 25 μm were added to iron powder for powder metallurgy (iron-based powder) having an average particle diameter of 78 μm. Powder for use), 1% by weight of the lubricant (c) shown in Table 8, and the thermoplastic resin powder were simply mixed in a V-type blender for 15 minutes to obtain a mixture. Also, as described above, the lubricant (c)
And a thermoplastic resin powder, as shown in Table 11, a mixture as a comparative example was also produced. Evaluation of these mixtures was performed in the same manner as in the group A, and the results in Tables 9 and 10 were obtained.

[0055]

[Table 8]

[0056]

[Table 11]

As shown in Examples B-44 to B-77 in Table 9, the mixture according to the present invention has a high fluidity without using zinc stearate or lithium stearate containing a metal element as a lubricant. Is 12.0-12.7 seconds / 100
g, excellent hopper discharge (1 time or less), and withdrawal power of 112
It is as low as ~ 128 kgf / cm2, and the iron-based powder mixture for powder metallurgy has no problem in all properties such as compressibility, tensile strength of the sintered body, and no soot adhered to the sintered body. On the other hand, as described later, the comparative example is inferior in any of the characteristic values.

[0058]

[Table 9]

[0059]

[Table 10]

Mixtures having a B ratio of 13, 14 and 15 were prepared by mixing stearic acid amide, a molten mixture of stearic acid amide and ethylene bis stearic acid amide, and ethylene bis stearic acid amide alone as a lubricant. And hopper discharge property. In addition, since the blending ratio of the thermoplastic resin powder of the mixture having a B ratio of 16 exceeds 0.5% by weight, the mixture having a compressibility of less than that of the blend of B-B52 mixed with the same lubricant except for the blending amount is used. Is 0.
It has decreased by 07 Mg / m3. The mixture having a B ratio of 17 has a thermoplastic resin powder having an average molecular weight of more than 5,000,000, and the mixture having a B ratio of 19 or 20 has a fluidity of less than 5 μm because the thermoplastic resin powder has an aggregation average particle size of less than 5 μm. Low hopper discharge. Furthermore, since the mixture having a B ratio of 18 has a thermoplastic resin powder having a primary particle size of more than 5 μm, it has a compressibility of only 0.15 Mg / m 3 as compared with B Ex. 49 containing the same lubricant. Low. Since the B ratio 21 is such that the average aggregation diameter of the thermoplastic resin powder exceeds 50 μm,
The tensile strength is 400 for all the mixtures of B-44-77.
440 MPa, whereas the mixture having a B ratio of 21 decreased to 370 MPa. Further, the mixture having a B ratio of 22 has a high extraction output when the total amount of the lubricant other than the thermoplastic resin powder added is less than 0.1% by weight, and the mixture having a B ratio of 23 has a total addition amount of the lubricant. Is more than 1% by weight, so that the fluidity and the hopper discharge property are poor.

[0061]

As described above, according to the present invention, a lubricant containing no metal element is used, does not contaminate the sintering furnace, and maintains the same extraction force and C adhesion as the conventional mixture. hand,
It has become possible to provide an iron-based powder mixture for powder metallurgy excellent in fluidity and hopper discharge, and a method for producing the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing aggregated particles of a thermoplastic resin powder.

[Explanation of symbols]

 1 primary particle 2 aggregated particle 3 primary particle size 4 aggregated particle size

Continuing from the front page (72) Inventor Yukiko Ozaki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba In the Technical Research Institute of Kawasaki Steel (72) Kuniaki Ogura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel (72) Inventor Toshio Nagase 1-2-1, Yoko, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Kawasaki Research Laboratory, ZEON Kasei Co., Ltd. (72) Takeo Kobayashi, 2-4-1 Shiba Park, Minato-ku, Tokyo Zeon Kasei Co., Ltd. F term (reference) 4K018 AA24 AB05 AB07 AC01 BA13 BC01 BC12 BC15 BC30 CA09

Claims (10)

[Claims] 1. An iron-based powder comprising at least 50% by weight of at least one monomer unit selected from an acrylate ester, a methacrylate ester and an aromatic vinyl compound; 0.03
Thermoplastic resin powder having an average molecular weight of 30,000 to 5,000,000 measured by a solution specific viscosity method of 0.05 to 0.50% by weight. An iron-based powder mixture for powder metallurgy. 2. An iron-based powder; 0.1% by weight or more and 1.0% by weight or less of one or more lubricants selected from the following attached to the iron-based powder; Contains 50% by weight or more of alloy powder and / or powder for improving machinability attached to the base powder and at least one monomer unit selected from acrylates, methacrylates and aromatic vinyl compounds And the primary average particle size is 0.03
Thermoplastic resin powder having an average molecular weight of 30,000 to 5,000,000 measured by a solution specific viscosity method of 0.05 to 0.50% by weight. An iron-based powder mixture for powder metallurgy. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide. 3. The iron-based powder mixture for powder metallurgy according to claim 2, further comprising 0.5% by weight or less of a powder of one or more lubricants selected from the following. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene. 4. In addition to claim 2 or 3, further selected from oleic acid, spindle oil and turbine oil.
An iron-based powder mixture for powder metallurgy comprising at least 0.01% by weight and at most 0.3% by weight of at least one kind of organic liquid lubricant. 5. An iron-based powder, a powder for alloying and / or a powder for improving machinability, and a powder of at least one lubricant selected from the group consisting of 0.1% by weight or more and 1.0% by weight or less. And at least one monomer unit selected from acrylates, methacrylates and aromatic vinyl compounds in an amount of 50% by weight or more, and a primary average particle size of 0.03
Thermoplastic resin powder having an average molecular weight of 30,000 to 5,000,000 measured by a solution specific viscosity method of 0.05 to 0.50% by weight. An iron-based powder mixture for powder metallurgy. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene. 6. The iron-based powder mixture for powder metallurgy according to claim 1, wherein the thermoplastic resin powder is polymethyl methacrylate. 7. An iron-based powder, an alloy powder and / or a machinability improving powder, and 0.1% by weight or more and 1.0% by weight or less of one or more lubricants selected from the following: After mixing, the mixture is further heated at a temperature higher than the melting point of the lubricant by 10 ° C. or more and 100 ° C. or less when the lubricant is one kind,
When the lubricant is composed of two or more kinds, the mixture is heated and mixed at a temperature higher than the lowest melting point of the lubricant by 10 ° C. or higher and lower than the highest melting point. After the powder for use in grinding and / or the powder for improving machinability is adhered by the molten lubricant, the mixture after the adhering treatment is mixed with at least one selected from acrylates, methacrylates and aromatic vinyl compounds. Having a primary average particle size of 0.03 to 5 μm, an aggregation average particle size of 5 to 50 μm, and an average molecular weight of 3 measured by a solution specific viscosity method.
A method for producing an iron-based powder mixture for powder metallurgy, comprising mixing 0.05 to 0.50% by weight of thermoplastic resin powder of 10,000 to 5,000,000. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide. 8. An iron-based powder, a powder for alloying and / or a powder for improving machinability, and 0.1% by weight or more and 1.0% by weight or less of one or more lubricants selected from the following: oleic acid,
After mixing at least 0.01% by weight or more and at most 0.3% by weight of an organic liquid lubricant selected from spindle oil and turbine oil, the mixture is further mixed with one type of lubricant. In this case, at a temperature higher than the melting point of the lubricant by 10 ° C or more and 100 ° C or less,
When the lubricant is composed of two or more kinds, the lowest melting point of 1
After mixing while heating at a temperature of 0 ° C. or higher and lower than the maximum melting point, followed by cooling, the powder for alloying and / or the powder for improving machinability is adhered to the iron-based powder by the molten lubricant. The mixture after the adhesion treatment contains at least one monomer unit selected from an acrylate ester, a methacrylate ester, and an aromatic vinyl compound in an amount of 50% by weight or more, and has a primary average particle size of 0.03% or more. -5 μm, agglomeration average particle size is 5-50 μm, average molecular weight measured by solution specific viscosity method is 3
A method for producing an iron-based powder mixture for powder metallurgy, comprising mixing 0.05 to 0.50% by weight of thermoplastic resin powder of 10,000 to 5,000,000. Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide. 9. The mixture after the adhesion treatment described in claim 7 or 8 is further mixed with 0.5% by weight or less of one or more lubricant powders selected from the following. A method for producing an iron-based powder mixture for powder metallurgy, comprising: Note stearic acid, oleic acid amide, stearic acid amide, a molten mixture of stearic acid amide and ethylenebisstearic acid amide, ethylenebisstearic acid amide, polyethylene with a molecular weight of 10,000 or less, ethylenebisstearic acid amide with a molecular weight of 10,000 or less Melt mixture with polyethylene. 10. The method for producing an iron-based powder mixture for powder metallurgy according to claim 7, wherein the thermoplastic resin powder is polymethyl methacrylate.