KR102102584B1 - Mixed powder for iron powder metallurgy and manufacturing method therefor, and sintered body produced therefrom and manufacturing method thereof - Google Patents

Abstract

The mixed powder for iron powder metallurgy of the present invention includes at least one selected from the group consisting of iron powder, calcium anhydride type III, calcium sulfate anhydride type II, calcium dihydrate, calcium sulfide, and calcium hemihydrate. It contains the CaS raw material powder, and the CaS raw material powder is coated with either or both of a lubricant or a binder.

Description

Mixed powder for iron powder metallurgy and manufacturing method therefor, and sintered body produced therefrom and manufacturing method thereof

The present invention relates to a mixed powder for iron powder metallurgy, a method for manufacturing the same, and a sintered body produced using the same, and a method for manufacturing the same, more specifically, a calcium sulfide powder coated by either or both of a lubricant or a binder Or it relates to a mixed powder for iron-based powder metallurgy containing half-calcium sulfate powder and a method for manufacturing the same, and a sintered body produced using the same and a method for manufacturing the same.

Powder metallurgy is widely used as an industrial production method for various mechanical parts. The order of the iron-based powder metallurgy, first, the mixed powder is prepared by mixing an iron-based powder, an alloy powder such as a copper (Cu) powder, a nickel (Ni) powder, a graphite powder, and a lubricant. Next, the mixed powder is filled into a mold, press-molded, and sintered to produce a sintered body. Lastly, the sintered body is adjusted to a machine part having a desired shape by cutting such as drilling or turning.

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, in some cases, uneven shrinkage of the raw material powder may occur due to the sintering. In recent years, the dimensional accuracy required for mechanical parts is high, and the part shape is complicated. For this reason, it is becoming essential to cut the sintered body. From this technical background, machinability is provided to the sintered body so that the sintered body can be processed smoothly.

As a means for imparting machinability, there is a technique of adding manganese sulfide (MnS) powder to the mixed powder. The addition of manganese sulfide powder is effective for relatively low-speed cutting such as drill drilling. However, the addition of manganese sulfide powder has problems such as not being effective in recent high-speed cutting, contamination of the sintered body, and deterioration of mechanical strength.

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

By including the calcium sulfide disclosed in Patent Document 1 in the iron-based raw material powder, there are problems such as that the strength of mechanical parts is significantly reduced, and the mixed powder changes over time and the quality is not stable. In addition, when the sintered steel disclosed in Patent Document 1 was processed with a cutting tool, it was difficult for chips to be finely divided. From this, it is difficult to say that the sintered steel disclosed in Patent Document 1 is excellent enough to satisfy the demands of the present chip processability.

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

Japanese Patent Publication No. 52-16684

The mixed powder for iron powder metallurgy of the present invention includes at least one selected from the group consisting of iron powder, calcium anhydride type III, calcium sulfate anhydride type II, calcium dihydrate, calcium sulfide, and calcium hemihydrate. It contains the CaS raw material powder, and the CaS raw material powder is coated with either or both of a lubricant or a binder.

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

The method for producing a mixed powder for iron powder metallurgy of the present invention includes at least one selected from the group consisting of calcium sulfate anhydride type III, calcium sulfate anhydride type II, calcium disulfate, calcium sulfide and calcium hemihydrate. It characterized in that it comprises the step of coating the CaS raw material powder with either or both of a lubricant or a binder, and a step of mixing the coated CaS raw material powder with an iron powder.

The method for producing a sintered body of the present invention includes a step of obtaining a sintered body by sintering a mixed powder for iron powder metallurgy produced by the above production method, wherein the sintered body has a weight ratio of CaS of 0.01% by weight or more and 0.1% by weight or less. Includes.

In order to achieve the above object, the present inventors investigated why the sintered body disclosed in Patent Document 1 deteriorates in quality and performance over time. Then, the present inventors have found that the quality and performance of the sintered body are deteriorated by including calcium sulfide and calcium hemisulphate (hereinafter, these two components are referred to as "CaS components"). That is, the present inventors say that the CaS component changes to calcium sulfate dihydrate (CaSO ₄ · 2H ₂ O) by absorbing moisture in the atmosphere, or the CaS component aggregates by a curing reaction to form granules of 63 μm or more. Found something. As a result, it became clear that the CaS component was dispersed non-uniformly in the mixed powder or sintered body to decrease the machinability of the sintered body, or the moisture adsorbed on the CaS component expands during sintering to become water vapor to lower the strength of the sintered body.

Based on the above knowledge, the present inventor has completed the present invention shown below by further studying the structure of the CaS component that is difficult to absorb moisture.

ADVANTAGE OF THE INVENTION According to this invention, the mixed powder for iron powder metallurgy which can manufacture a sintered compact of stable quality and performance can be provided.

Hereinafter, the mixed powder for iron-based powder metallurgy of the present invention and a manufacturing method thereof will be described in detail.

<Mixed powder for iron powder metallurgy>

The mixed powder for iron powder metallurgy of the present invention includes at least one selected from the group consisting of iron powder, calcium anhydride type III, calcium sulfate anhydride type II, calcium dihydrate, calcium sulfide, and calcium hemihydrate. It is a mixed powder formed by mixing CaS raw material powder. This CaS raw material powder is characterized by being coated with either or both of a lubricant or a binder. Various additives such as ternary oxide, binary oxide, alloy powder, graphite powder, lubricant, and binder may be appropriately added to the mixed powder. In addition to these, a trace amount of unavoidable impurities may be contained in the mixed powder in the manufacturing process of the mixed powder for iron powder metallurgy. The mixed powder for iron powder metallurgy of the present invention can be obtained by filling a mold or the like, molding it, and then sintering it. The sintered body thus produced can be used for various mechanical parts by cutting. The use and manufacturing method of this sintered compact are mentioned later.

<Iron powder>

Iron-based powder is a main component constituting the mixed powder for iron-based powder metallurgy, and is preferably included in a weight ratio of 60% by weight or more with respect to the entire mixed powder for iron-based powder metallurgy. On the other hand, the weight percentage of the iron-based powder herein refers to a proportion of the total weight of the iron powder other than the lubricant in the powder mixture for metallurgy. When the weight percent of each component is defined below, all of the regulations shall refer to the weight ratio of the total weight of the mixed powder for iron powder metallurgy excluding lubricant.

Examples of the iron-based powder include pure iron powders such as atomized iron powders and reduced iron powders, partially diffusion alloyed steel powders, fully alloyed steel powders, or hybrid steel powders in which alloy components are partially diffused into fully alloyed steel powders. Can be used. The volume average particle diameter of the iron-based powder is preferably 50 μm or more, and more preferably 70 μm or more. When the volume average particle diameter of the iron-based powder is 50 µm or more, the handleability is excellent. Moreover, the volume average particle diameter of the iron-based powder is preferably 200 μm or less, and more preferably 100 μm or less. When the volume average particle diameter of the iron-based powder is 200 μm or less, it is easy to form a precise shape, and sufficient strength is obtained.

<CaS raw material powder>

The mixed powder for iron powder metallurgy of the present invention is a CaS raw material powder containing at least one selected from the group consisting of calcium sulfate anhydride type III, calcium sulfate anhydride type II, calcium dihydrate, calcium sulfide and calcium hemihydrate. It is characterized by including, and the CaS raw material powder is coated with either or both of a lubricant or a binder. By using the CaS raw material powder coated with a lubricant and / or a binder in this way, the water absorbency of the CaS raw material powder can be suppressed, whereby various performances of the sintered body can be stably increased.

Conventionally, as a raw material to be sintered to become CaS, calcium sulfide (CaS), gypsum (CaSO ₄ · 2H ₂ O), anhydrous type III calcium sulfate (Type III CaSO ₄ ), half-water gypsum (CaSO ₄ · 1 / 2H) ₂ O) and the like were added. However, each of the above components absorbs moisture with the passage of time, and the machinability of the sintered body may be reduced. In addition, the moisture absorbed by the raw material which becomes sintered and becomes CaS expands during sintering to become water vapor to decrease the density of the sintered body, or hot water vapor decreases the strength of the sintered body by oxidizing iron powder in the sintered body. There were cases. In contrast, in the present invention, since the CaS raw material powder coated with a lubricant or a binder is added as described above, it is difficult for the CaS raw material powder to absorb moisture even if it is stored for a period of time in a state contained in a mixed powder for iron powder metallurgy. By these effects, various characteristics (sintered body density, crushing strength, machinability, etc.) of the sintered body as designed are stabilized. In addition, the coated CaS raw material powder can be changed to CaS after sintering to increase the machinability of the sintered body.

The CaS raw material powder preferably contains either or both of calcium sulfide or calcium hemisulfate as a main component, calcium dihydrate (CaSO ₄ · 2H ₂ O), anhydrous type II calcium sulfate (Type II CaSO ₄ ), anhydrous Calcium sulfate (Type III CaSO ₄ ) of type III may be included.

Here, the term &quot; CaS raw material powder is coated with either or both of the lubricant or binder &quot; means that the entire surface of the CaS raw material powder is partially covered with the sun coated with either or both of the lubricant or binder. That includes the sun. The thickness of the lubricant or binder is not particularly limited as long as the anhydrous type III calcium sulfate, calcium dihydrate, calcium sulfide, and hemihydrate calcium sulfate do not contact the outside atmosphere. The thickness is preferably uniform on the surface of the CaS raw material powder, but may be partially thick or thin.

The amount of the lubricant to be added can be appropriately set, and it is preferable that it is 0.1% by weight or more and 1.5% by weight or less with respect to the weight of the mixed powder for iron powder metallurgy. Moreover, the addition amount of a binder can be set suitably, and it is preferable that it is 0.02 weight% or more and 0.5 weight% or less with respect to the weight of the mixed powder for iron powder metallurgy. When the lubricant and the binder are added in excess, the compressibility during press molding decreases and the density decreases. Conversely, if the addition of the lubricant and the binder is too small, the CaS raw material powder is liable to come into contact with the outside atmosphere, or it is difficult to release from the mold at the time of press molding, thus possibly damaging the mold.

The coating with the lubricant is performed by mixing and heating the CaS raw material powder together with the lubricant in a mixing vessel. Alternatively, a CaS raw material powder coated in advance may be prepared, or a lubricant may be coated on the surface of the CaS raw material powder using a hot melt method. In the order of the hot-melt method, first, the lubricant is filled in the mixing container together with each powder other than the lubricant constituting the mixed powder for iron powder metallurgy. Each powder is mixed while heating, and then cooled to room temperature. Thereby, each powder constituting the mixed powder for iron powder metallurgy is coated with a lubricant, respectively.

As another coating method, the entire powder excluding the lubricant from each powder constituting the mixed powder for iron powder metallurgy is filled in a mixing container. Next, a binder solution in which a binder is dissolved in a solvent is added to the mixing container and mixed. Then, the solvent contained in the binder solution is volatilized. Finally, the 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, respectively. Details of this process will be described later.

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

Here, "the weight ratio of CaS after sintering" means the weight ratio of CaS in the sintered body obtained by sintering the mixed powder for iron powder metallurgy. 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 obtained by collecting a sample piece by processing a sintered body with a drill or the like, and converting the weight of Ca obtained by quantitatively analyzing the weight of Ca contained in the sample piece into the weight of CaS. Is calculated by This conversion is performed by dividing the atomic weight of Ca (40.078) and integrating the molecular weight of CaS (72.143). Since Ca rarely reacts and disappears during sintering, the weight of Ca does not change before and after sintering, and Ca and S are bound 1: 1.

The volume average particle diameter of the CaS raw material powder is preferably 0.1 μm or more, more preferably 0.5 μm or more, and still more preferably 1 μm or more. In addition, the volume average particle diameter of the CaS raw material powder is preferably 60 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The CaS raw material powder having such a volume average particle diameter can be obtained by pulverizing and classifying commercially available CaS raw material powder by a known grinder. The CaS raw material powder composed of anhydrous type II calcium sulfate can be obtained by, for example, pulverizing and classifying a half gypsum heated at 350 ° C or higher and 900 ° C or lower for 1 hour to 10 hours. The smaller the volume average particle size of the CaS raw material powder, the more the amount of CaS raw material powder added, the more the machinability of the sintered body can be improved. The volume average particle diameter is the integrated value of the particle size D ₅₀ value of 50% in a laser diffraction type particle size distribution measuring device, the particle size obtained using the (nitki scavenger Microtrac "MODEL9320-X100") distribution.

<Lubricant>

A lubricant coating the CaS raw material powder is added to suppress the hygroscopicity of anhydrous type III calcium sulfate, calcium dihydrate, calcium sulfide, and hemihydrate calcium sulfate. The lubricant also has a function of easily extracting a molded product obtained by compressing a mixed powder for iron powder metallurgy in a mold from the mold. That is, when a lubricant is added to the mixed powder for iron powder metallurgy, it is possible to reduce the subtraction pressure when the molded body is taken out from the mold and prevent cracking of the molded body or damage to the mold. In addition, when the hot-melt method is used, since the lubricant exerts a function of adhering the alloy powder and graphite powder to the surface of the iron-based powder, segregation of the iron-based mixed powder can also be prevented. On the other hand, apart from the lubricant coating the CaS raw material powder, a lubricant may be added in the process of preparing a mixed powder for iron powder metallurgy, or a lubricant may be applied to the surface of the mold when filling the mold with the mixed powder for iron powder metallurgy. do.

The lubricant is preferably contained in an amount of 0.01% by weight or more, more preferably 0.1% by weight or more, and more preferably 0.2% by weight or more based on the weight of the mixed powder for iron powder metallurgy. When the content of the lubricant is 0.01% by weight or more, the CaS raw material powder is suppressed from contacting the outside atmosphere, and it is easy to obtain an effect that the performance of the sintered body is stable. Moreover, it is preferable that it is contained 1.5 weight% or less with respect to the weight of the mixed powder for iron powder metallurgy, More preferably, it is 1.2 weight% or less, More preferably, it is contained 1.0 weight% or less. When the content of the lubricant is 1.5% by weight or less, a high-density sintered body is easily obtained, and a high-sintered sintered body can be obtained.

The lubricant is preferably a wax-based lubricant, and an amide-based lubricant is used from the viewpoint of good adhesion to an alloy powder, graphite powder, or the like on the surface of the iron-based powder, and ease of segregation of the iron-based mixed powder. It is more preferable. Examples of the amide lubricant include stearic acid monoamide, fatty acid amide, and amide wax. As the lubricant other than the amide-based lubricant, one or more selected from the group consisting of a hydrocarbon-based wax, zinc stearate, and a crosslinked (meth) acrylic acid alkyl ester resin can be used.

<Binder>

The binder coating the CaS raw material powder is added to suppress the hygroscopicity of the anhydrous type III calcium sulfate, calcium disulfate, calcium sulfide and hemihydrate calcium sulfate, and also to prevent segregation of the iron mixed powder. The binder also has a function of adhering the alloy powder to the iron-based powder surface. On the other hand, a binder may be added in the process of producing a mixed powder for iron-based powder metallurgy separately from the binder coating the CaS raw material powder.

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

It is more preferable to use one or more binders selected from the group consisting of styrene-butadiene rubber, isoprene rubber, butene-based polymers and methacrylic acid-based polymers. As the butene-based polymer, it is preferable to use a 1-butene homopolymer composed of butene alone or a copolymer of butene and alkene. The alkene is preferably a lower alkene, preferably ethylene or propylene. The methacrylic acid-based polymer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, ethylhexyl methacrylate, lauryl methacrylate, methyl acrylate and ethyl acrylate. More than one species can be used.

The binder is preferably contained in an amount of 0.01% by weight or more, and more preferably 0.05% by weight or more, based on the weight of the mixed powder for iron powder metallurgy. By containing 0.01% by weight or more of the binder, the hygroscopicity of anhydrous type III calcium sulfate, calcium dihydrate, calcium sulfide, and hemihydrate calcium sulfate can be suppressed. Moreover, it is preferable that it is 0.5 weight% or less with respect to the weight of the mixed powder for iron powder metallurgy, More preferably, it is contained 0.4 weight% or less, More preferably, it is 0.3 weight% or less. By setting the content of the binder to 0.5% by weight or less, it is easy to obtain a high-density molded body during press molding.

<Ternary oxide>

The ternary oxide may be added to improve the machinability when the sintered body is used for a long time in cutting. The ternary oxide can significantly increase the machinability of the sintered body by interlocking with the addition of CaS raw material powder. Here, the ternary oxide refers to a complex oxide of three elements, specifically, three elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn. It is preferably a composite oxide of, more preferably Ca-Al-Si-based oxide, Ca-Mg-Si-based oxide and the like. Examples of Ca-Al-Si oxides include 2CaO · Al ₂ O ₃ · SiO ₂ and the like. Examples of Ca-Mg-Si oxides include 2CaO · MgO · 2SiO ₂ and the like. Among them, it is preferable to add a _{2CaO · Al 2 O 3 · SiO} 2. The 2CaO · Al ₂ O ₃ · SiO ₂ reacts with TiO ₂ contained in the coating applied to the cutting tool or in the cutting tool, thereby forming a protective film on the surface of the cutting tool, thereby significantly improving the wear resistance of the cutting tool. have.

The shape of the ternary oxide is not particularly limited, but a spherical shape or a crushed shape, that is, a shape having a roundness as a whole is preferable.

The lower limit of the volume average particle diameter of the ternary oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. The smaller the volume average particle diameter, the more it tends to improve the machinability of the sintered compact by adding a small amount. In addition, the upper limit of the volume average particle diameter of the ternary oxide is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 9 μm or less. When 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 a measuring method similar to the CaS raw material powder.

The lower limit of the content of the ternary oxide is preferably 0.01% by weight or more, more preferably 0.03% by weight or more, and even more preferably 0.05% by weight 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 even more preferably 0.15% by weight or less. By including in such a weight ratio, a sintered body excellent in machinability can be obtained even in long-term cutting while suppressing cost. By using the ternary oxide in combination with the CaS raw material powder, even if the amount of the ternary oxide added is small, the machinability in long-term cutting can be improved.

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

<Binary oxide>

The binary oxide may be added to improve the machinability at the beginning of cutting when the sintered body is used for cutting. Here, the binary oxide means a complex oxide of two elements, and specifically, two elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn. It is preferably a composite oxide of, and more preferably Ca-Al-based oxide, Ca-Si-based oxide and the like. Examples of Ca-Al oxides include CaO · Al ₂ O ₃ , 12CaO · 7Al ₂ O ₃ and the like. Examples of Ca-Si-based oxides include 2CaO · SiO ₂ and the like.

It is preferable that the shape of the binary oxide, the volume average particle diameter, the measuring method thereof, and the weight ratio are the same as those of the above-mentioned binary oxide.

<Binary oxide and ternary oxide>

It is preferable that the mixed powder for iron powder metallurgy of the present invention contains both the binary oxide and the ternary oxide in a total weight of 0.02% by weight or more and 0.3% by weight or less. The total weight of the oxide is preferably 0.05% by weight or more, and more preferably 0.1% by weight or more. From the viewpoint of cost, the smaller the weight ratio of the binary-based oxide and the ternary-based oxide is, the more preferable. Moreover, it is preferable that the total weight of the said oxide is 0.25 weight% or less, More preferably, it is 0.2 weight% or less. When the total weight of the oxide is 0.25% by weight or less, the crushing strength of the sintered body can be sufficiently secured.

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

<Powder for alloy>

The alloy powder is added to promote the bonding between the iron-based powders and to increase the strength of the sintered body after sintering. It is preferable that the powder for the alloy is contained in an amount of 0.1% by weight or more and 10% by weight or less with respect to the total mixture powder for iron powder metallurgy. The strength of the sintered body can be increased by being 0.1% by weight or more, and the dimensional accuracy during sintering of the sintered body can be ensured by being 10% by weight or less.

Examples of the powder for alloys include copper (Cu) powder, nickel (Ni) powder, Mo powder, Cr powder, V powder, Si powder, Mn powder, and other non-ferrous metal powders, copper oxide powder, and the like. It may be used as, or may be used in combination of two or more.

<Method for manufacturing mixed powder for iron powder metallurgy>

The mixed powder for iron powder metallurgy 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 mixed powder for iron powder metallurgy is produced by mixing the coated CaS raw material powder, iron powder and powders of other components with a mechanical stirring mixer.

(2) The surface of the CaS raw material powder is not coated with a lubricant in advance, but is mixed while heating the powder of all components in a sealed container. Next, a mixed powder for iron powder metallurgy is produced by coating the surface of the powder of all components with a lubricant using a hot melt method.

(3) Iron powder The whole powder excluding lubricant among the powders constituting the mixed powder for metallurgy is added to the sealed container. Then, after adding and mixing the organic solution in which the binder is dissolved in the sealed container, the organic solvent is volatilized. Finally, a lubricant is added into the sealed container and each powder constituting the mixed powder for iron powder metallurgy is mixed. In this way, the surface of the entire powder except the lubricant is coated with a lubricant and / or a binder to produce a mixed powder for iron powder metallurgy. It is preferable that the volume average particle diameter of the CaS raw material powder is 0.1 μm or more and 60 μm or less.

Although the optimum temperature differs depending on the melting point of the lubricant, the heating temperature in the hot melt method is preferably 50 ° C or higher and 150 ° C or lower, for example. When the heating temperature is 50 ° C or higher, it is easy to increase the fluidity of the lubricant. When the heating temperature is 150 ° C or lower, in the process of manufacturing the mixed powder, oxidation of the iron-based powder can be suppressed, and further, the cost required for heating can be reduced.

The heating time in the hot melt method is preferably 10 minutes or more and 5 hours or less. The higher the heating temperature, the shorter the heating time. When the heating time is short, there is a possibility that it is difficult to coat the entire surface of the CaS raw material powder with a lubricant and / or a binder.

The mixed powder for iron powder metallurgy of the present invention can be produced, for example, by mixing the iron powder and the CaS raw material powder prepared above using a mechanical stirring mixer. In addition to these powders, various additives such as ternary oxides, alloy powders, graphite powders, binary oxides, binders, and lubricants may be added as appropriate. Examples of the mechanical stirring mixer include a high-speed mixer, a nauta mixer, a V-type mixer, and a double cone blender. Although the mixing temperature is not particularly limited, 150 ° C. or less is preferable from the viewpoint of suppressing oxidation of the iron-based powder in the mixing step.

<Method of manufacturing sintered body>

After the mixed powder for iron powder metallurgy prepared above is filled into a mold, a green compact is produced by applying a pressure of 300 MPa or more and 1200 MPa or less. 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 green compact formed as above by a conventional sintering method. The sintering condition may be a non-oxidizing atmosphere or a reducing atmosphere. The green compact is preferably sintered for 5 minutes or more and 60 minutes or less at a temperature of 1000 ° C or more and 1300 ° C or less under a nitrogen atmosphere, a mixed atmosphere of nitrogen and hydrogen, or an atmosphere such as hydrocarbon.

<Sintered body>

It is preferable that the sintered body produced as described above contains 0.01% by weight or more and 0.1% by weight or less of CaS. The upper limit of CaS in the sintered body is preferably 0.09% by weight or less, and more preferably 0.08% by weight or less. Moreover, it is preferable that the lower limit of CaS in a sintered compact is 0.02 weight% or more, More preferably, it is 0.03 weight% or more. The sintered body can be used as a machine part for automobiles, farm equipment, power tools, and household appliances by processing with various tools such as cutting tools as necessary. Examples of cutting tools for processing the sintered body include drills, end mills, cutting tools for price processing, cutting tools for turning, reamers, tabs, and the like.

According to the mixed powder for iron-based powder metallurgy of the above embodiment, since the surfaces of calcium sulfide and calcium hemisulfate 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 mixed powder for iron powder metallurgy further includes one or more ternary oxides selected from the group consisting of Ca-Al-Si-based oxides and Ca-Mg-Si-based oxides, so that machinability in long-time cutting is avoided. Can be improved.

The mixed powder for iron powder metallurgy includes the CaS raw powder so that the weight ratio of CaS after sintering is 0.01% by weight or more and 0.1% by weight or less, and thus, the machinability of the sintered body after sintering is excellent.

The mixed powder for iron powder metallurgy includes ternary oxide and CaS raw material powder so that the weight ratio of ternary oxide and CaS after sintering is 3: 7 to 9: 1, thereby improving machinability in long-term cutting. You can.

Since the CaS raw material powder has a volume average particle diameter of 0.1 μm or more and 60 μm or less, the machinability of the sintered body can be improved.

The sintered body produced by using the mixed powder for iron powder metallurgy is stable and has excellent properties such as machinability. Further, the mixed powder for iron powder metallurgy produced by the above production method exhibits stable performance because the CaS raw material powder is difficult to absorb moisture.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these.

(Example 1)

First, commercially available calcium sulfide powder was sorted by a sieve to obtain -63 / + 45 μm (volume average particle size 54 μm). The classified calcium sulfide powder was placed in a sealed container in an amount such that the weight of CaS after sintering was 0.5% by weight. To this sealed container, 0.75% by weight of an amide-based lubricant (product name: Accrawax C (manufactured by LONZA)) was added. Then, the surface of the calcium sulfide powder was coated with an amide lubricant by mixing for 10 minutes while heating at 100 ° C.

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

(Example 2)

In Example 1, the calcium sulfide powder and the amide-based lubricant (product name: Accrawax C (manufactured by LONZA)) were placed in a sealed container and heated to 100 ° C., but in Example 2, the powder of all components used in Example 1 was sealed. The mixture was placed in a container, heated to 100 ° C using a hot melt method, and mixed for 30 minutes to coat an amide-based lubricant on the surface of the powder of all components. Thereafter, a mixed powder for iron powder metallurgy was produced by cooling to room temperature.

(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 with a toluene solution containing styrene-butadiene rubber. The toluene solution was added so that the weight of the styrene-butadiene rubber after volatilization of toluene was 0.1% by weight. Then, styrene-butadiene rubber was coated on the surface of the CaS raw material particles by volatilizing toluene at 100 ° C. Thereafter, the amide-based lubricant used in Example 1 was added and mixed with the same amount used in Example 1 to mix, thereby producing a mixed powder for iron powder metallurgy of Example 3.

(Comparative Examples 1 to 3)

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

Two types of sintered bodies were produced using the mixed powders for iron powder metallurgy of each of the examples and comparative examples. One is a sintered body produced using a mixed powder for iron powder metallurgy immediately after production (hereinafter referred to as a "sintered body immediately afterwards"), and the other is a sintered body produced using a mixed powder for iron powder metallurgy 10 days after production. (Hereinafter referred to as "sintered body after 10 days").

Immediately after, the order of production of the sintered compact was first filled with a mixture powder for iron powder metallurgy immediately after production into a mold, and a test piece was formed in a ring shape having an outer diameter of 64 mm, an inner diameter of 24 mm, and a thickness of 20 mm, so that the molding density was 7.00 g / cm ³ . . Next, the sintered body was produced by sintering the ring-shaped test piece at 1130 ° C for 30 minutes in an atmosphere of 10 vol% H ₂ -N ₂ . On the other hand, after 10 days, the sintered body was produced in the same manner as the sintered body immediately after the mixed powder for iron powder metallurgy was prepared and then left in the atmosphere for 10 days in a mold.

<Evaluation>

In Table 1, the evaluation results of the molded body density, the sintered body density, the crushing strength, and the amount of tool wear were described as "sintered body immediately after sintered body after 10 days". Such a notation is an evaluation result of the sintered body immediately after the value on the left side with a slash in between, and an evaluation result of the sintered body 10 days after the value on the right side with a slash in between.

Immediately after each example and each comparative example, the molded body density and the sintered body density of the sintered body and the sintered body after 10 days were adopted in accordance with the Japan Powder Metallurgy Industry Standard (JPMA M 01). In addition, the value measured according to JIS Z 2507-2000 was adopted as the crushing strength. It shows that the sintered body is hard to break, so that the crushing strength is high, and the strength is high.

Using the sintered body prepared in each example and each comparative example, using a cermet tip (ISO part number: SNGN120408 non-breaker), circumferential speed 160 m / min, infeed 0.5 mm / pass, feed 0.1 mm / rev , The tool wear amount (μm) of the cutting tool when turning 1150 m under dry conditions was measured by a tool microscope. The results are shown in the column of "Tool wear amount" 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 each of the Examples and Comparative Examples shown in Table 1, by coating the CaS raw material powder with a lubricant or a binder as in each Example, various characteristics (sintered density, crushing strength and tools of the sintered body immediately after and 10 days later) It was found that the amount of wear) became almost equal. On the other hand, although Comparative Examples 2 and 3 contain CaS simple substance or half gypsum as a CaS component, since no coating treatment is performed on the surface, various characteristics of the sintered body after 10 days are significantly deteriorated compared to that of the sintered body immediately after. It was.

In Comparative Examples 2 and 3, the reason why the quality and performance of the sintered body deteriorated after 10 days was that CaS or hemihydrate gypsum in the mixed powder for iron powder metallurgy absorbed moisture while the mixed powder for iron powder metallurgy was left for 10 days. I think it is due to one thing. That is, in Comparative Examples 2 and 3, the density of the sintered body was lowered or the crushing strength was lowered by CaS simple substance or hemihydrate gypsum in the mixed powder for iron powder metallurgy absorbing moisture during storage under the atmosphere for 10 days. I think. On the other hand, since Comparative Example 1 does not contain a CaS component, the sintered body immediately after 10 days, the sintered body also has a significantly high tool wear amount, and the machinability of the sintered body is remarkably low.

From the results shown in Table 1, by coating the CaS raw material powder with a lubricant or a binder, various properties (sintered body density, crushing strength and tool wear amount) of the sintered body immediately after 10 days and the sintered body became almost equal, and the quality of the sintered body and It became clear that the performance was stable, and the effect of the present invention was exhibited.

Claims (8)

For iron powder metallurgy including iron powder and CaS raw material powder containing at least one selected from the group consisting of calcium sulfate anhydride type III, calcium sulfate anhydride type II, calcium dihydrate, calcium sulfide and calcium hemihydrate As a mixed powder,
The CaS raw material powder is included so that the weight ratio of CaS after sintering is 0.01% by weight or more and 0.1% by weight or less,
The CaS raw material powder is a mixed powder for iron powder metallurgy, which is coated by either or both of a lubricant or a binder. According to claim 1,
A mixed powder for iron powder metallurgy, further comprising one or more ternary oxides selected from the group consisting of Ca-Al-Si oxides and Ca-Mg-Si oxides. According to claim 2,
A mixed powder for iron powder metallurgy, comprising the ternary oxide and the CaS raw material powder so that the weight ratio of the ternary oxide and the sintered CaS is 3: 7 to 9: 1. delete According to claim 1,
The CaS raw material powder has a volume average particle diameter of 0.1 μm or more and 60 μm or less, a mixed powder for iron powder metallurgy. A sintered body produced by sintering the mixed powder for iron powder metallurgy according to claim 1. CaS raw material powder containing at least one member selected from the group consisting of calcium sulfate anhydrous type III, calcium sulfate anhydrous II, calcium dihydrate, calcium sulfide, and calcium hemisulphate by either or both of a lubricant or a binder. The covering step,
The step of obtaining a sintered body by sintering the mixed powder for iron powder metallurgy produced by a manufacturing method comprising the step of mixing the coated CaS raw material powder and iron powder,
The sintered body comprises a CaS in a weight ratio of 0.01% by weight or more and 0.1% by weight or less. delete