KR20180008732A - Mixed powder for iron powder metallurgy, method for producing the same, sintered body made using the same and method for producing the same - Google Patents

Abstract

The mixed powder for iron powder metallurgy according to the present invention comprises at least one selected from the group consisting of iron powder and calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide and calcium hydrogen sulfate, And the CaS raw material powder is covered with either or both of a lubricant and a binder.

Description

Mixed powder for iron powder metallurgy, method for producing the same, sintered body made using the same and method for producing the same

The present invention relates to a mixed powder for iron-based powder metallurgy, a method for producing the same, a sintered body produced using the same, and a method for producing the same. More specifically, the present invention relates to a sintered body made of calcium sulfide powder coated with either or both of a lubricant and a binder Or semi-aqueous calcium sulfate powder, a sintered body produced using the same, and a method for producing the same.

Powder metallurgy is widely used as an industrial production method for various mechanical parts. The iron powder metallurgy is firstly prepared by mixing an iron powder, an alloy powder such as copper (Cu) powder or nickel (Ni) powder, graphite powder and a lubricant. Next, this mixed powder is filled in a metal mold, press molded, and sintered to produce a sintered body. Finally, the sintered body is subjected to cutting such as drilling or turning to adjust it to a mechanical part of a desired shape.

The ideal of powder metallurgy is to process the sintered body so that it can be used as a mechanical part without cutting the sintered body. However, the sintering may cause uneven shrinkage of the raw material powder in some cases. In recent years, dimensional accuracy required for mechanical parts is high, and the shape of parts is complicated. For this reason, it is necessary to subject the sintered body to a cutting process. From such technical background, machinability is imparted to the sintered body so as to smoothly process the sintered body.

As a means for imparting the machinability, there is a method of adding MnS powder to the mixed powder. The addition of manganese sulfide powder is effective for relatively low-speed cutting such as drilling. However, addition of manganese sulfide powder is not necessarily effective in recent high-speed cutting processing, there is a problem that the sintered body is contaminated, and mechanical strength is lowered.

Patent Document 1 (Japanese Patent Publication No. 52-16684) discloses a method of imparting machinability other than the addition of manganese sulfide. Patent Document 1 discloses an iron-based raw material powder containing 0.1 to 1.0% of calcium sulfide (CaS), 0.1 to 2% of carbon (C), 0.5 to 5.0% Of copper (Cu).

The inclusion of the calcium sulfide disclosed in Patent Document 1 in the iron-based raw material powder has a problem that the strength of the mechanical parts is greatly reduced and that the mixed powder changes in time and the quality is not stabilized. Further, when the sintered steel disclosed in Patent Document 1 is machined by a cutting tool, it is difficult for the chip to be finely divided. From this, it can not be said that the sintered steel disclosed in Patent Document 1 is excellent enough to satisfy the demand for the current chip processability.

The present invention has been made in view of the above problems, and an object thereof is to provide a mixed powder for iron powder metallurgy capable of producing a sintered body of stable quality and performance.

Japanese Patent Publication No. 52-16684

The mixed powder for iron powder metallurgy according to the present invention comprises at least one selected from the group consisting of iron powder and calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide and calcium hydrogen sulfate, And the CaS raw material powder is covered with either or both of a lubricant and a binder.

The present invention is a sintered body produced by sintering the iron powder metallurgy mixed powder.

The method for producing a mixed powder for iron powder metallurgy according to the present invention is a method for producing iron powder metallurgy mixed powder comprising at least one selected from the group consisting of calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide, A step of coating the CaS raw material powder with either or both of a lubricant and a binder; and a step of mixing the CaS raw material powder and the iron base powder mixed with each other.

The method for producing a sintered body according to the present invention includes the step of sintering a mixture powder for iron powder metallurgy produced by the above production method to obtain a sintered body, wherein the sintered body contains CaS in a weight ratio of 0.01 wt% to 0.1 wt% .

In order to achieve the above object, the present inventor investigated why sintered bodies disclosed in Patent Document 1 were degraded in quality and performance over time. The inventors of the present invention have found that the quality and performance of the sintered body are deteriorated by containing calcium sulfide and calcium sulphate (hereinafter, these two components are referred to as "CaS component"). That is, the present inventors have found that the CaS component changes into calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) by absorbing moisture in the atmosphere, or the CaS component aggregates by the curing reaction to form a coarse grain of 63 μm or more I found that. As a result, it has become clear that the CaS component is dispersed unevenly in the mixed powder or the sintered body to lower the machinability of the sintered body, or the water adsorbed to the CaS component expands during sintering to become steam and lower the strength of the sintered body.

The present inventors have completed the present invention described below by further examining the constitution of a CaS component which is difficult to absorb moisture on the basis of the above knowledge.

According to the present invention, it is possible to provide a mixed powder for iron powder metallurgy capable of producing a sintered body having stable quality and performance.

Hereinafter, the mixed powder for iron powder metallurgy of the present invention and a method for producing the same will be described in detail.

<Mixed powder for iron powder metallurgy>

The mixed powder for iron powder metallurgy according to the present invention comprises at least one selected from the group consisting of iron powder and calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide and calcium hydrogen sulfate, Is mixed with CaS raw material powder. And the CaS raw material powder is covered with either or both of a lubricant and a binder. Various additives such as a ternary oxide, a binary oxide, an alloy powder, a graphite powder, a lubricant, and a binder may be appropriately added to the mixed powder. In addition to these, a small amount of unavoidable impurities may be contained in the mixed powder during the production of the iron powder metallurgy mixed powder. The sintered body can be obtained by filling the iron powder metallurgy mixed powder of the present invention with a metal mold, molding and then sintering. The sintered body thus produced can be used for various mechanical parts by performing cutting processing. The use and manufacturing method of the sintered body will be described later.

<Iron powder>

The iron powder is a main component constituting the mixed powder for the iron powder metallurgy, and it is preferable that the iron powder is contained at a weight ratio of 60 wt% or more with respect to the whole iron powder powder metallurgical mixed powder. On the other hand, the weight% of the iron powder here means the ratio of the iron powder powder to the total weight other than the lubricant in the mixed powder for metallurgical metallurgy. In the following, in the case where the weight% of each component is specified, it means that the weight ratio of the component powder to the total weight of the iron powder metallurgy mixed powder excluding the lubricant is all.

Examples of the iron powder include pure iron powder such as atomized iron powder and reduced iron powder, partially-diffused alloyed steel powder, fully alloyed steel powder, or hybrid steel powder obtained by partially diffusing an alloy component into a completely alloyed steel powder Can be used. The iron-based powder preferably has a volume-average particle diameter of 50 탆 or more, and more preferably 70 탆 or more. When the volume average particle diameter of the iron powder is not less than 50 占 퐉, the handling property is excellent. The iron-based powder preferably has a volume-average particle diameter of 200 탆 or less, more preferably 100 탆 or less. When the volume average particle diameter of the iron powder is not more than 200 mu m, it is easy to form a precise shape and sufficient strength can be obtained.

&Lt; CaS raw material powder >

The mixed powder for iron powder metallurgy according to the present invention is a CaS raw material powder containing at least one selected from the group consisting of calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide and calcium hemisulfate And the CaS raw material powder is covered with either or both of a lubricant and a binder. By using the CaS raw material powder coated with the lubricant and / or the binder in this way, it is possible to suppress the water absorption of the CaS raw material powder, thereby stably increasing various performances of the sintered body.

Conventionally, calcium sulfate (CaS), hydrated gypsum (CaSO ₄ .2H ₂ O), anhydrous calcium sulfate (III type CaSO ₄ ), hemihydrate gypsum (CaSO ₄ .1 / 2H ₂ O) and so on. However, each of the above components occasionally absorbed moisture with the lapse of time, thereby lowering the machinability of the sintered body. In addition, the water absorbed in the raw material to become CaS by sintering expands during sintering to become steam, thereby lowering the density of the sintered body, or the steam of high temperature oxidizes the iron powder in the sintered body to lower the strength of the sintered body There was a case. On the contrary, in the present invention, CaS raw material powder coated with a lubricant or a binder is added as described above. Therefore, CaS raw material powder hardly absorbs moisture even if it is contained in a mixed powder for iron powder metallurgy for a certain period of time. By this effect, various properties of the sintered body as designed (sintered body density, pressing strength, machinability, etc.) are stabilized. In addition, the CaS raw material powder coated as above changes into CaS after sintering, and the machinability of the sintered body can be increased.

The CaS raw material powder preferably contains one or both of calcium sulfide and calcium hemi-sulfate as a main component, and is preferably composed of calcium dihydrogen sulfate (CaSO ₄ .2H ₂ O), calcium sulfate anhydrous type II (II type CaSO ₄ ) Type III calcium sulfate (III type CaSO ₄ ), and the like.

Here, &quot; the CaS raw material powder is covered with either or both of a lubricant and a binder &quot; means that the entire surface of the CaS raw material powder is partially covered with the sun which is covered with either or both of a lubricant and a binder Includes the sun. The thickness of the lubricant or binder is not particularly limited as long as the anhydrous calcium sulfate of the type III, calcium dihydrogen sulfate, calcium sulfide and calcium hemi-sulfate are not in contact with the outside atmosphere. It is preferable that the thickness is uniform on the surface of the CaS raw material powder, but the thickness may be partially thick or thin.

The amount of the lubricant to be added can be suitably set, and is preferably 0.1 wt% or more and 1.5 wt% or less with respect to the weight of the iron powder metallurgy mixed powder. The amount of the binder to be added can be appropriately set, and it is preferably 0.02 wt% or more and 0.5 wt% or less with respect to the weight of the iron powder metallurgy mixed powder. If the lubricant and the binder are excessively added, the compressibility at the time of press forming is lowered, and the density is lowered. On the contrary, if the addition of the lubricant and the binder is too small, the CaS raw material powder tends to come into contact with the outside atmosphere, or it is difficult to release the mold from the mold at the time of press molding.

The coating with the lubricant is performed by mixing CaS raw material powder together with a lubricant in a mixing vessel and heating. Alternatively, a pre-coated CaS raw material powder may be prepared, or the surface of the CaS raw material powder may be coated with a lubricant by a hot-melt method. The order of the hot-melt method is as follows. First, each of the powders other than the lubricant constituting the iron powder metallurgy mixed powder is filled with a lubricant in the mixing vessel. These powders are mixed while being heated and then cooled to room temperature. As a result, each powder constituting the mixed powder for iron powder metallurgy is covered with a lubricant.

As another coating method, all the powders except for the lubricant among the powders constituting the mixed powder for the iron powder metallurgy are charged into the mixing vessel. Next, a binder solution obtained by dissolving a binder in a solvent is added to the mixing vessel and mixed. Thereafter, the solvent contained in the binder solution is volatilized. Finally, CaS raw material powder may be coated with a lubricant and / or a binder by adding a lubricant. In this case, each powder is coated with a lubricant and / or a binder. Details of this process will be described later.

The CaS raw material powder is preferably contained in the mixed powder for iron powder metallurgy so that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less. More preferably, CaS raw material powder is contained so that the weight ratio of CaS after sintering is 0.02 weight% or more, and CaS raw material powder is more preferably contained so that the weight ratio of CaS after sintering is 0.03 weight% or more. The sintered body containing CaS at such a weight ratio is particularly excellent in machinability. On the other hand, the CaS raw material powder is preferably contained so that the weight ratio of CaS after sintering is 0.09 wt% or less, more preferably 0.08 wt% or less. By including CaS in such a weight ratio, the strength of the sintered body can be increased.

Here, the &quot; weight ratio of CaS after sintering &quot; means the weight ratio of CaS in the sintered body obtained by sintering the iron powder metallurgy mixed powder. The weight ratio of CaS contained in the sintered body after sintering can be adjusted by the weight ratio of CaS raw material powder contained before sintering.

The weight ratio of CaS contained in the sintered body is determined by calculating the weight of Ca obtained by quantitatively analyzing the weight of Ca contained in the sample piece by collecting the sample piece by processing the sintered body with a drill or the like, . This conversion is carried out by dividing by the atomic weight of Ca (40.078) and integrating the molecular weight of CaS (72.143). Since Ca rarely disappears in reaction at sintering, the weight of Ca does not change before and after sintering, and Ca and S are bonded at a ratio of 1: 1.

The volume average particle size of the CaS raw material powder is preferably 0.1 占 퐉 or more, more preferably 0.5 占 퐉 or more, and further preferably 1 占 퐉 or more. The volume average particle diameter of the CaS raw material powder is preferably 60 占 퐉 or less, more preferably 30 占 퐉 or less, and further preferably 20 占 퐉 or less. The CaS raw material powder having such a volume average particle size can be obtained by pulverizing and classifying commercially available CaS raw material powder with a known pulverizing machine. The CaS raw material powder composed of the anhydrous type II calcium sulfate can be obtained, for example, by pulverizing and classifying a semi-gypsum obtained by heating the gypsum at 350 to 900 DEG C for 1 hour to 10 hours. The smaller the volume average particle size of the CaS raw material powder, the better the machinability of the sintered body can be, even if the CaS raw material powder is added in a small amount. The volume average particle diameter is a value of the particle size D ₅₀ at an integrated value of 50% in the particle size distribution obtained by using a laser diffraction particle size distribution measuring apparatus ("Micro Model" MODEL9320-X100, manufactured by Nikkiso Co., Ltd.).

<Lubricant>

The lubricant covering the CaS raw material powder is added to suppress the hygroscopicity of calcium sulfate anhydrous type III, calcium dihydrogen sulfate, calcium sulfide and calcium hepta sulfate. The lubricant also has a function of making it easy to take out a molded body obtained by compressing mixed powder for iron powder metallurgy in a mold from a mold. That is, when a lubricant is added to the mixed powder for iron powder metallurgy, the extraction pressure at the time of taking out the molded body from the metal mold can be reduced to prevent cracking of the molded body and damage to the metal mold. Further, when the hot-melt method is used, the lubricant exerts the function of attaching the alloy powder and the graphite powder to the surface of the iron powder, so that it is possible to prevent segregation of the iron-base powder mixture. On the other hand, in addition to the lubricant for coating the CaS raw material powder, a lubricant may be added during the production of the mixed powder for iron powder metallurgy, or a lubricant may be applied to the surface of the metal mold when the mixed powder for iron powder metallurgy is filled in the metal mold do.

The lubricant is preferably contained in an amount of 0.01 wt% or more, more preferably 0.1 wt% or more, and still more preferably 0.2 wt% or more, based on the weight of the iron powder metallurgy mixed powder. When the content of the lubricant is 0.01% by weight or more, the effect of stabilizing the performance of the sintered body by suppressing contact of the CaS raw material powder with the outside atmosphere tends to be obtained. The lubricant is preferably contained in an amount of 1.5 wt% or less, more preferably 1.2 wt% or less, and further preferably 1.0 wt% or less, based on the weight of the iron powder metallurgy mixed powder. When the content of the lubricant is 1.5% by weight or less, it is easy to obtain a high-density sintered body, and a sintered body having high strength can be obtained.

The lubricant is preferably a wax-based lubricant. From the viewpoint that the performance of attaching the alloy powder, the graphite powder, etc. to the surface of the iron powder is good and the segregation of the iron-base mixed powder is easy to be alleviated, Is more preferable. Examples of the amide-based lubricant include stearic acid monoamide, fatty acid amide, and amide wax. As the lubricant other than the amide-based lubricant, at least one selected from the group consisting of hydrocarbon wax, zinc stearate and crosslinked (meth) acrylic acid alkyl ester resin can be used.

<Binder>

The binder covering the CaS raw material powder is added to suppress moisture absorption of the anhydrous calcium sulfate, calcium dihydrogen sulfate, calcium sulfide and calcium hepta sulfate, and to prevent segregation of the iron-base mixed powder. The binder also has the function of attaching the alloy powder to the iron powder surface. On the other hand, in addition to the binder for covering the CaS raw material powder, a binder may be added in the process of producing the mixed powder for iron powder metallurgy.

The CaS raw material powder is coated with a binder by first dissolving the binder in an organic solvent such as toluene to prepare an organic solvent containing a binder. Next, the organic solution is mixed with the CaS raw material powder. Finally, the CaS raw material powder is coated with a binder by volatilizing the organic solvent.

The binder is more preferably one or more selected from the group consisting of styrene-butadiene rubber, isoprene rubber, butene-based polymer and methacrylic acid-based polymer. As the butene-based polymer, it is preferable to use a 1-butene homopolymer made of butane alone or a copolymer of butene and an alkene. The alkene is preferably a lower alkene, preferably ethylene or propylene. Examples of the methacrylic acid-based polymer include a methacrylic acid-based polymer having 1 to 10 carbon atoms selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, ethylhexyl methacrylate, lauryl methacrylate, More than species can be used.

The binder is preferably contained in an amount of 0.01 wt% or more, more preferably 0.05 wt% or more, based on the weight of the iron powder metallurgy mixed powder. When the binder is contained in an amount of 0.01% by weight or more, hygroscopicity of calcium sulfate anhydrous type III, calcium dihydrogen sulfate, calcium sulfide and calcium hydrogen sulfate can be suppressed. The binder is preferably contained in an amount of 0.5% by weight or less, more preferably 0.4% by weight or less, and still more preferably 0.3% by weight or less based on the weight of the mixed powder for iron powder metallurgy. By setting the content of the binder to 0.5 wt% or less, it becomes easy to obtain a high-density molded article at the time of press molding.

<3-element oxide>

The ternary oxide may be added in order to improve the machinability when the sintered body is used for cutting for a long time. The ternary oxide may be combined with the CaS raw material powder to significantly increase the machinability of the sintered body. Here, the ternary oxide refers to a composite oxide of three kinds of elements, specifically, three kinds of elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn And more preferably a Ca-Al-Si-based oxide, a Ca-Mg-Si-based oxide, or the like. Examples of the Ca-Al-Si-based oxide include 2CaO-Al ₂ O ₃ -SiO ₂ and the like. As the Ca-Mg-Si-containing oxide, and the like 2CaO · MgO · 2SiO _2. Among them, it is preferable to add 2CaO.Al ₂ O ₃ .SiO ₂ . The _{2CaO · Al 2 O 3 · SiO} 2 may be reacted with TiO ₂ contained in the coating carried out in or during a cutting tool cutting tool, so to form a protective film, and significantly improves the wear resistance of the cutting tool on the surface of the cutting tool have.

The shape of the ternary oxide is not particularly limited, but it is preferably a spherical shape or a distorted shape thereof, that is, a shape having a rounded shape as a whole.

The lower limit of the volume average particle diameter of the ternary oxide is preferably 0.1 占 퐉 or more, more preferably 0.5 占 퐉 or more, and further preferably 1 占 퐉 or more. The smaller the volume average particle diameter, the more the machinability of the sintered body can be improved by the addition of a small amount. The upper limit of the volume average particle diameter of the ternary oxide is preferably 15 占 퐉 or less, more preferably 10 占 퐉 or less, and further preferably 9 占 퐉 or less. If the volume average particle diameter is too large, it is difficult to improve the machinability of the sintered body. The volume average particle diameter of the ternary oxide is a value measured by the same measurement method as that of the CaS raw material powder.

The lower limit of the content of the ternary oxide is preferably 0.01 wt% or more, more preferably 0.03 wt% or more, and still more preferably 0.05 wt% or more. The upper limit of the content of the ternary oxide is preferably 0.25% by weight or less, more preferably 0.2% by weight or less, and still more preferably 0.15% by weight or less. By incorporating in such a weight ratio, it is possible to obtain a sintered body having excellent machinability even in a long-term cutting process while suppressing the cost. By using the ternary oxide in combination with the CaS raw material powder, it is possible to improve the machinability in long-time cutting work even if the amount of the ternary oxide added is small.

The weight ratio of the ternary oxide and CaS after sintering is preferably in a ratio of 1: 9 to 9: 1, more preferably 3: 7 to 9: 1, and still more preferably 4: 6 to 7: 3 . By including both components in such a weight ratio, the machinability of the sintered body can be remarkably improved.

&Lt; Binary Oxides >

The binary oxide may be added in order to improve the machinability at the beginning of cutting when the sintered body is used for cutting. Herein, the binary oxide means a composite oxide of two kinds of elements, specifically, two kinds of elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn , More preferably a Ca-Al-based oxide, a Ca-Si-based oxide, or the like. As the Ca-Al-based oxide, and the like _{CaO · Al 2 O 3, 12CaO} · 7Al 2 O 3. Examples of the Ca-Si-based oxide include 2CaO-SiO ₂ and the like.

The shape of the binary oxide, the volume average particle diameter, the measuring method thereof, and the weight ratio are preferably the same as those of the above-mentioned ternary oxide.

<Binary Oxides and Ternary Oxides>

The iron powder metallurgy mixed powder of the present invention preferably contains both a binary oxide and a ternary oxide in an amount of 0.02 wt% or more and 0.3 wt% or less in total weight. The total weight of the oxides is preferably 0.05 wt% or more, and more preferably 0.1 wt% or more. From the viewpoint of cost, the weight ratio of the binary oxide and the ternary oxide is preferably as small as possible. The total weight of the oxide is preferably 0.25% by weight or less, more preferably 0.2% by weight or less. When the total weight of the oxides is 0.25 wt% or less, the pressing strength of the sintered body can be sufficiently secured.

The weight ratio of the binary oxide and CaS after sintering is preferably in a ratio of 1: 9 to 9: 1, more preferably 3: 6 to 9: 1, and still more preferably 4: 6 to 7: 3 . By including both components in such a weight ratio, it is possible to manufacture a sintered body having excellent machinability at the beginning of cutting.

<Powder for Alloy>

The powder for alloying is added to promote the bonding between the iron powder and to increase the strength of the sintered body after sintering. Such an alloy powder is preferably contained in an amount of 0.1 wt% or more and 10 wt% or less with respect to the total of the iron powder metallurgy mixed powder. When the content is 0.1% by weight or more, the strength of the sintered body can be increased. When the content is 10% by weight or less, dimensional accuracy at the time of sintering of the sintered body can be secured.

Examples of the alloy powder include copper (Cu) powder, nickel (Ni) powder, Mo powder, Cr powder, V powder, Si powder, Mn powder and the like, and copper oxide powder. Or two or more of them may be used in combination.

&Lt; Method for producing mixed powder for iron powder metallurgy &

The iron powder metallurgical mixed powder of the present invention can be produced, for example, by the following production methods (1) to (3).

(1) The surface of the CaS raw material powder is coated with a lubricant. Next, the coated CaS raw material powder, the iron powder, and the powders of other components are mixed by a mechanical stirring mixer to prepare a mixed powder for iron powder metallurgy.

(2) The surface of the CaS raw material powder is not coated with a lubricant in advance, but the powders of the whole components are mixed while being heated in the closed container. Next, the surface of the powders of the whole components is coated with a lubricant using a hot-melt method to prepare a mixed powder for iron powder metallurgy.

(3) Iron powder Powder of all powders constituting the mixed powder for metallurgy is added to the closed vessel except for the lubricant. Then, an organic solution in which the binder is dissolved in the closed container is added and mixed, and then the organic solvent is volatilized. Finally, a lubricant is added to the closed vessel and each powder constituting the mixed powder for iron powder metallurgy is mixed. In this manner, the surface of all powders except for the lubricant is coated with a lubricant and / or a binder to prepare a mixed powder for iron powder metallurgy. The volume average particle diameter of the CaS raw material powder is preferably 0.1 mu m or more and 60 mu m or less.

The heating temperature in the hot melt method is preferably 50 ° C or more and 150 ° C or less, for example, although the optimum temperature differs depending on the melting point of the lubricant. If the heating temperature is 50 DEG C or higher, the fluidity of the lubricant can be easily increased. If the heating temperature is 150 DEG C or lower, the oxidation of the iron powder can be suppressed in the process of producing the mixed powder, and the cost required for heating can be reduced.

The heating time in the hot-melt method is preferably not less than 10 minutes and not more than 5 hours. The higher the heating temperature, the shorter the heating time. When the heating time is short, there is a possibility that the entire surface of the CaS raw material powder becomes difficult to be covered with the lubricant and / or the binder.

The iron powder metallurgy mixed powder of the present invention can be produced by mixing, for example, an iron powder with the CaS raw powder prepared above using a mechanical stirring mixer. In addition to these powders, various additives such as a ternary oxide, an alloy powder, a graphite powder, a binary oxide, a binder and a lubricant may be appropriately added. Examples of the mechanical stirring type mixer include a high speed mixer, a Nauta mixer, a V type mixer, and a double cone blender. The mixing temperature is not particularly limited, but is preferably 150 DEG C or lower from the viewpoint of suppressing the oxidation of the iron powder in the mixing step.

&Lt; Manufacturing method of sintered body >

The iron powder powder metallurgical mixed powder prepared above is filled in a metal mold, and a pressure of 300 MPa or more and 1200 MPa or less is applied to produce a green compact. The molding temperature at this time is preferably 25 ° C or more and 150 ° C or less.

The sintered body can be obtained by sintering the above-mentioned powder compacted body by a usual sintering method. The sintering condition may be a non-oxidizing atmosphere or a reducing atmosphere. It is preferable that the above-mentioned compacted compact is sintered at a temperature of 1000 占 폚 to 1300 占 폚 for 5 minutes to 60 minutes in a nitrogen atmosphere, a mixed atmosphere of nitrogen and hydrogen, and an atmosphere of hydrocarbon.

<Sintered body>

The sintered body produced as described above preferably contains CaS in an amount of 0.01 wt% or more and 0.1 wt% or less. The upper limit of CaS in the sintered body is preferably 0.09% by weight or less, more preferably 0.08% by weight or less. The lower limit of CaS in the sintered body is preferably 0.02 wt% or more, and more preferably 0.03 wt% or more. The sintered body can be used as a mechanical part of an automobile, an agricultural equipment, an electric power tool, and an electric appliance by processing with various tools such as a cutting tool, if necessary. Examples of the cutting tool for machining the sintered body include a drill, an end mill, a cutting tool for pricing, a cutting tool for turning, a reamer, and a tap.

According to the mixed powder for iron powder metallurgy of the above embodiment, since the surfaces of the calcium sulfide and the calcium hemi sulfate are coated with a lubricant or a binder, hygroscopicity of these components can be suppressed, and various performances of the sintered body can be stably increased .

The iron powder metallurgy mixed powder further includes at least one ternary oxide selected from the group consisting of Ca-Al-Si oxide and Ca-Mg-Si oxide, so that the machinability in long- Can be improved.

The iron powder metallurgy mixed powder contains the CaS raw material powder so that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less, so that the sintered body after sintering has excellent machinability.

The iron powder metallurgy mixed powder contains a ternary oxide and a CaS raw material powder so that the weight ratio of the ternary oxide and CaS after sintering is 3: 7 to 9: 1, so that the machinability in the long term cutting is improved .

The CaS raw material powder has a volume-average particle diameter of from 0.1 to 60 탆, and therefore the machinability of the sintered body can be increased.

The sintered body produced using the iron powder metallurgy mixed powder is excellent in various characteristics such as stability and machinability. Also, the mixed powder for iron powder metallurgy produced by the above production method shows stable performance because the CaS raw material powder hardly absorbs moisture.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

(Example 1)

First, commercially available calcium sulfide powder was classified by sieving to -63 / + 45 mu m (volume average particle size 54 mu m). The classified calcium sulfide powder was put in a closed container in an amount such that the weight of CaS after sintering became 0.5 wt%. 0.75 wt% of an amide-based lubricant (trade name: Accra Wax C (LONZA)) was added to the sealed container. The surface of the calcium sulfide powder was coated with an amide-based lubricant by mixing for 10 minutes while heating to 100 캜.

Next, 2 wt% of a copper powder (product name: CuATW-250 (manufactured by Fukuda Metal Powder Co., Ltd.)) and 0.8 wt% of graphite powder (product name: Atmel 300M (product of Kobe Steel Co., (Product name: CPB (manufactured by Nippon Graphite Industry Co., Ltd.)) and the calcium sulfide powder coated with the above-prepared lubricant were mixed to prepare a mixed powder for iron powder metallurgy. On the other hand, the graphite powder was added in such an amount that the amount of carbon after sintering became 0.75% by weight. The calcium sulfide powder coated in the above was added in an amount such that the weight of CaS after sintering became 0.5 wt%.

(Example 2)

In Example 1, calcium sulfide powder and an amide-based lubricant (product name: Accra Wax C, manufactured by LONZA) were placed in a hermetically sealed container and heated to 100 ° C. In Example 2, the powder of the whole components used in Example 1 was sealed The mixture was placed in a container, heated at 100 占 폚 using a hot-melt method, and mixed for 30 minutes to coat the entire surface of the powder with an amide-based lubricant. Thereafter, the mixture was cooled to room temperature to prepare a mixed powder for iron powder metallurgy.

(Example 3)

In Example 3, the same powders as in Example 2 were mixed except that the amide-based lubricant used in Example 2 was replaced by a toluene solution containing styrene-butadiene rubber. The toluene solution was added so that the weight of the styrene-butadiene rubber after the toluene volatization was 0.1 wt%. Thereafter, toluene was volatilized at 100 占 폚, whereby styrene-butadiene rubber was coated on the surface of the CaS raw material particles. Thereafter, an amide-based lubricant used in Example 1 was added in an amount equivalent to that used in Example 1 and mixed to prepare a mixed powder for iron powder metallurgy of Example 3.

(Comparative Examples 1 to 3)

In Comparative Example 1, a mixed powder for iron powder metallurgy was produced in the same manner as in Example 1, except that the CaS raw material powder was not added. In Comparative Examples 2 and 3, CaS raw material powder shown in the column of "CaS component" in Table 1 was used, but a mixture powder for iron powder metallurgy was produced in the same manner as in Example 1 except that the CaS raw material powder was not coated with a lubricant and a binder did.

Two types of sintered bodies were produced using the iron powder metallurgy mixed powder of each of the above Examples and Comparative Examples. One is a sintered body (hereinafter referred to as &quot; immediately after sintered body &quot;) produced by using a mixed powder for iron powder metallurgy immediately after fabrication, and the other is a sintered body (Hereinafter referred to as &quot; sintered body after 10 days &quot;).

Immediately after the sintered body was manufactured, a mold was filled with a powder mixture for iron powder metallurgy immediately after fabrication, and a test piece was molded in a ring shape having an outer diameter of 64 mm, an inner diameter of 24 mm and a thickness of 20 mm, and a molding density of 7.00 g / cm ³ . Next, this ring-shaped test piece was sintered at 1130 캜 for 30 minutes under an atmosphere of 10% by volume of H ₂ -N _{2 to} prepare a sintered body. On the other hand, after 10 days, the sintered body was fabricated in the same manner as the sintered body immediately after the iron powder metallurgy mixed powder was prepared, except that the iron powder powder was filled in the mold after being left in the atmosphere for 10 days.

<Evaluation>

In Table 1, the results of the evaluation of the compact density, the sinter density, the pressing strength and the tool wear amount are described as &quot; sintered body immediately after / 10 days after sintering &quot;. This notation is the evaluation result of the sintered body immediately after the value on the left side with the slash interposed therebetween, and the evaluation result of the sintered body after 10 days on the right side with the slash in between.

The densities of the sintered bodies immediately after each of the Examples and Comparative Examples and the densities of the sintered bodies after 10 days and the density of the sintered bodies were measured according to the Japanese Powder Metallurgy Industry Association (JPMA M 01). In addition, the pressing strength was measured in accordance with JIS Z 2507-2000. The higher the pressing strength, the more difficult it is to break the sintered body and the higher the strength.

Using a sintered body manufactured in each of the examples and comparative examples, a sintered body having a circumferential speed of 160 m / min, an infeed of 0.5 mm / pass and a feed of 0.1 mm / rev using a cermet tip (ISO product number: SNGN120408 nonbreaker) , The tool wear amount (μm) of the cutting tool when it was turned at 1150 m under the dry condition was measured by a tool microscope. The results are shown in the column of &quot; tool wear amount &quot; in Table 1. On the other hand, the smaller the value of the tool wear amount, the better the machinability of the sintered body.

From the results of the Examples and Comparative Examples shown in Table 1, CaS raw material powder was coated with a lubricant or a binder as in each Example, and various properties of the sinter immediately after the sinter and after 10 days (sinter density, Wear amount) were almost equal to each other. On the other hand, Comparative Examples 2 and 3 contain CaS alone or semi-gypsum as a CaS component, but since no surface treatment is carried out on the surface, various characteristics of the sintered body after 10 days are significantly deteriorated .

The reason why the quality and performance of the sintered body deteriorated after 10 days in Comparative Examples 2 and 3 is that CaS or hemihydrate gypsum in the mixed powder for iron powder metallurgy absorbs moisture while the mixed powder for iron powder metallurgy is left for 10 days It is thought to be caused by one thing. That is, in Comparative Examples 2 and 3, the CaS single body or semi-gypsum in the mixed powder for iron powder metallurgy absorbed moisture during storage under the atmosphere for 10 days, whereby the density of the sintered body was lowered or the pressing strength was lowered I think. On the other hand, since Comparative Example 1 does not contain a CaS component, the sintered body immediately after the sintered body immediately after the sintered body has remarkably high tool wear amount, and the machinability of the sintered body is remarkably low.

From the results shown in Table 1, various characteristics (sintered body density, pressing strength and tool wear amount) of the sintered body immediately after the sintered body and the sintered body after 10 days were almost equal by coating the CaS raw material powder with a lubricant or a binder, It is clear that the performance is stable, and the effect of the present invention has been shown.

Claims (8)

Iron powder containing an iron powder and a CaS raw material powder containing at least one selected from the group consisting of calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulfate, calcium sulfide and calcium hepta sulphate As a mixed powder,
Wherein the CaS raw material powder is coated with either or both of a lubricant and a binder. The method according to claim 1,
Ca-Al-Si-based oxide, and Ca-Mg-Si-based oxide. 3. The method according to claim 1 or 2,
Wherein the ternary oxide and the CaS raw material powder are mixed so that a weight ratio of the ternary oxide and CaS after sintering is 3: 7 to 9: 1. The method according to claim 1,
Wherein the CaS raw material powder is contained so that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less. The method according to claim 1,
Wherein the CaS raw material powder has a volume-average particle diameter of 0.1 占 퐉 or more and 60 占 퐉 or less. A sintered body produced by sintering the iron powder metallurgy mixed powder according to claim 1. A CaS raw material powder containing at least one selected from the group consisting of anhydrous calcium sulfate, calcium sulfate anhydrous type III, calcium sulfate anhydrous type II, calcium dihydrogen sulphate, calcium sulphate and calcium hepta sulphate is mixed with one or both of a lubricant and a binder A step of coating,
And a step of mixing the coated CaS raw material powder with an iron base powder. A method for producing a sintered body, comprising the steps of: sintering a mixture powder for iron powder metallurgy produced by the manufacturing method according to claim 7;
Wherein the sintered body contains CaS in a weight ratio of not less than 0.01 wt% and not more than 0.1 wt%.