JP6480265B2 - Mixed powder for iron-based powder metallurgy, method for producing the same, sintered body and method for producing the same - Google Patents

Description

  TECHNICAL FIELD 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, and a calcium sulfide powder or semi-water coated with one or both of a lubricant and a binder. The present invention relates to a mixed powder for iron-based powder metallurgy containing calcium sulfate powder, a method for producing the same, a sintered body produced using the powder, and a method for producing the same.

  Powder metallurgy is widely used as an industrial production method for various machine parts. The procedure for iron-based powder metallurgy is to first prepare a mixed powder 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 in a mold, press-molded, and sintered to produce a sintered body. Then, a machine part having a desired shape is prepared by performing cutting such as drilling or turning on the sintered body.

  The ideal of powder metallurgy is to process the sintered body so that it can be used as a machine part without cutting the sintered body. However, the sintering may cause uneven shrinkage of the raw material powder, and in recent years, the dimensional accuracy required for mechanical parts is high, and the part shape may be complicated. For this reason, it is becoming essential to cut the sintered body. From such a technical background, a technique for imparting machinability to a sintered body has been studied so that the sintered body can be processed smoothly.

  As means for imparting the 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 drilling. However, the addition of manganese sulfide powder is not necessarily effective in recent high-speed cutting, and there are problems such as generation of dirt on the sintered body and reduction in mechanical strength.

  For this reason, as a document disclosing a method for imparting machinability other than adding the above-mentioned manganese sulfide, for example, Patent Document 1 discloses that iron-based raw material powder containing a necessary amount of iron powder and copper is contained. Sintered steel containing 0.1 to 1.0% calcium sulfide (CaS), 0.1 to 2% carbon (C), and 0.5 to 5.0% copper (Cu) Is disclosed.

Japanese Patent Publication No. 52-16684

  By including calcium sulfide as disclosed in Patent Document 1, there are problems such as a significant decrease in the strength of mechanical parts and a deterioration in quality due to the mixed powder changing over time. Moreover, when the sintered steel disclosed in Patent Document 1 was processed with a cutting tool, it was difficult for the chips to be finely divided. From this, it is difficult to say that the chip disposability evaluated as good in the disclosure of Patent Document 1 is excellent enough to satisfy the current chip disposability requirements.

  This invention is made | formed in view of said subject, The place made into the objective is providing the mixed powder for iron-base powder metallurgy which can produce the sintered compact of the stable quality and performance.

In order to achieve the above object, the present inventor investigated why the sintered body disclosed in Patent Document 1 deteriorates in quality and performance with the passage of time, and the cause thereof is calcium sulfide and calcium hemihydrate sulfate ( In the following, it was found that these two components were included as “CaS component”). That is, the present inventor changed the calcium sulfate component to calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) by absorbing moisture in the atmosphere, or the CaS component aggregated by a curing reaction to cause a coarse particle size of 63 μm or more. It was found that grains were formed. As a result, the CaS component is dispersed unevenly in the mixed powder or the sintered body to reduce the machinability of the sintered body, or the moisture adsorbed on the CaS component expands during the sintering to become water vapor, which is sintered. It became clear that the strength of the body was lowered.

  Based on the above findings, the present invention shown below was completed by further diligently examining the configuration of the CaS component that hardly absorbs water.

  That is, the iron-based powder metallurgy mixed powder of the present invention is selected from the group consisting of iron-based powder and anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium half-water sulfate. A CaS raw material powder containing one or more of the above, wherein the CaS raw material powder is coated with one or both of a lubricant and a binder.

  Calcium sulfide and calcium hemihydrate sulfate are highly hygroscopic and absorb moisture in the atmosphere, so that mass increases when stored in the atmosphere for a certain period. Therefore, by covering the surfaces of calcium sulfide and calcium hemihydrate sulfate with a lubricant or a binder, the hygroscopicity of these components can be suppressed, and various performances of the sintered body can be stably improved.

  The mixed powder for iron-based powder metallurgy preferably further includes one or more ternary oxides selected from the group consisting of Ca—Al—Si oxides and Ca—Mg—Si oxides. By including such a ternary oxide, the machinability in long-time cutting can be improved.

  The mixed powder for iron-based powder metallurgy preferably 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. The iron-based powder metallurgy mixed powder containing the CaS raw material powder at such a weight ratio is excellent in machinability of the sintered body after sintering.

  It is preferable that the ternary oxide and the CaS raw material powder are included so that the weight ratio of the ternary oxide to CaS after sintering is 3: 7 to 9: 1. By including the ternary oxide and the CaS raw material powder at such a weight ratio, the machinability in long-term cutting can be improved.

  The CaS raw material powder preferably has a volume average particle size of 0.1 μm or more and 60 μm or less. By having such a volume average particle diameter, the machinability of the sintered body can be enhanced.

  The present invention is a sintered body produced by sintering the mixed powder for iron-based powder metallurgy. A sintered body produced using the above mixed powder for iron-based powder metallurgy is stably excellent in various properties such as machinability.

  The method for producing a mixed powder for iron-based powder metallurgy according to the present invention is one selected from the group consisting of anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, dihydrated calcium sulfate, calcium sulfide, and calcium hemihydrate sulfate. It includes a step of coating the CaS raw material powder containing the above with either or both of a lubricant and a binder, and a step of mixing the coated CaS raw material powder with an iron-based powder. The mixed powder for iron-based powder metallurgy thus produced exhibits stable performance because the CaS raw material powder hardly absorbs moisture.

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

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

  Hereinafter, the mixed powder for iron-based powder metallurgy according to the present invention and the production method thereof will be described in detail.

<Mixed powder for iron-based powder metallurgy>
The mixed powder for iron-based powder metallurgy of the present invention is selected from the group consisting of iron-based powder and anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium hemihydrate sulfate. It is a mixed powder obtained by mixing a CaS raw material powder containing one or more kinds. This CaS raw material powder is characterized by being coated 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 trace amount of inevitable impurities may be included in the production process of the mixed powder for iron-based powder metallurgy. The mixed powder for iron-based powder metallurgy according to the present invention can be obtained by filling a metal mold or the like and molding it, followed by sintering. The sintered body produced in this way can be used for various machine parts by cutting. The use and manufacturing method of this sintered body will be described later.

<Iron-based powder>
The iron-based powder is a main component constituting the mixed powder for iron-based powder metallurgy, and is preferably contained in a weight ratio of 60% by weight or more with respect to the entire mixed powder for iron-based powder metallurgy. In addition, the weight% of iron-base powder here means the ratio for the total weight other than a lubricant among the mixed powder for iron-base powder metallurgy. In the following, when the weight percent of each component is defined, the definition means the weight ratio in the total weight of the iron-based powder metallurgy mixed powder excluding the lubricant.

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

<CaS raw material powder>
The mixed powder for iron-based powder metallurgy according to the present invention includes one or more selected from the group consisting of anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, dihydrated calcium sulfate, calcium sulfide, and calcium hemihydrate sulfate. CaS raw material powder is included, and the CaS raw material powder is covered with either or both of a lubricant and a binder. Thus, by using the CaS raw material powder coated with the lubricant and / or the binder, the water absorption of the CaS raw material powder can be suppressed, and thus various performances of the sintered body can be stably improved. it can.

Conventionally, calcium sulfide (CaS), dihydrate gypsum (CaSO ₄ .2H ₂ O), anhydrous type III calcium sulfate (III type CaSO ₄ ), hemihydrate gypsum (CaSO ₄₎・ 1 / 2H ₂ O) and the like were added. However, each of these components absorbs moisture over time, and may reduce the machinability of the sintered body. In addition, the water absorbed in the raw material that is sintered and becomes CaS expands during the sintering to become water vapor, thereby reducing the density of the sintered body, or high-temperature water vapor causes the iron-based powder in the sintered body to be reduced. Oxidation sometimes reduces the strength of the sintered body. On the other hand, in the present invention, since the CaS raw material powder coated with the lubricant or the binder is added as described above, the CaS raw material powder is stored for a certain period in a state of being included in the mixed powder for iron-based powder metallurgy. Is difficult to absorb moisture. With such an effect, it becomes possible to stabilize various characteristics (sintered body density, crushing strength, machinability, etc.) of the sintered body as designed. In addition, the coated CaS raw material powder can be changed to CaS after sintering to enhance the machinability of the sintered body.

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

  Here, “CaS raw material powder is covered with either or both of lubricant and binder” means that the entire surface of CaS raw material powder is covered with either or both of lubricant and binder. Of course, a partially coated embodiment is also included. The thickness of the lubricant or binder that coats the surface of the CaS raw material powder is not particularly limited as long as anhydrous type III calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium halfhydrate sulfate do not come into contact with the outside air. The thickness is preferably uniform on the surface of the CaS raw material powder, but may be partially thick or thin.

  The addition amount of the lubricant can be appropriately set, and is preferably 0.1% by weight or more and 1.5% by weight or less based on the weight of the mixed powder for iron-based powder metallurgy. Moreover, the addition amount of a binder can be set suitably and it is preferable that they are 0.02 weight% or more and 0.5 weight% or less with respect to the weight of the mixed powder for iron-base powder metallurgy. If an excessive amount of lubricant and binder is added, the compressibility during press molding may be reduced, and the density may be reduced. On the contrary, if the addition of the lubricant and the binder is too small, the CaS raw material powder is likely to come into contact with the outside air, or it is difficult to release from the mold during press molding, and the mold may be damaged. is there.

  For coating with the lubricant, the CaS raw material powder coated in advance may be prepared by mixing and heating the CaS raw material powder together with the lubricant in a mixing container. Alternatively, a hot melt method may be used in which a lubricant is filled in a mixing container together with powders other than the lubricant constituting the iron-based powder metallurgy mixed powder, mixed while heating and then cooled to room temperature. In this case, each powder constituting the mixed powder for iron-based powder metallurgy is coated with a lubricant. Furthermore, as another coating method, all the powders constituting the mixed powder for iron-based powder metallurgy, excluding the lubricant, are filled into a mixing container, and a binder solution in which the binder is dissolved in a solvent is added to the mixing container. After mixing, the CaS raw material powder may be covered with a lubricant and / or a binder by volatilizing the solvent and finally adding a lubricant. In this case, each powder is coated with a lubricant and / or a binder. Details of this step will be described later.

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

  Here, “weight ratio of CaS after sintering” means the weight ratio of CaS in the sintered body obtained by sintering the mixed powder for iron-based powder metallurgy. The weight ratio of CaS contained in the sintered body after sintering can be adjusted by the weight ratio of the CaS raw material powder contained before sintering.

  The weight ratio of CaS contained in the sintered body is the weight of Ca obtained by taking a sample piece by processing the sintered body with a drill or the like and quantitatively analyzing the weight of Ca contained in the sample piece. It can be calculated by converting to the weight of CaS. This conversion is performed by integrating the molecular weight of CaS (72.143) by dividing by the atomic weight of Ca (40.078). This is because Ca hardly reacts and disappears during sintering, so the weight of Ca does not change before and after sintering, and Ca and S are combined at 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 further preferably 1 μm or more. Further, the volume average particle diameter of the CaS raw material powder is preferably 60 μm or less, more preferably 30 μm or less, and still 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 with a known pulverizer. The CaS raw material powder composed of anhydrous type II calcium sulfate can be obtained by, for example, heating hemihydrate gypsum to 350 ° C. or more and 900 ° C. or less and pulverizing and classifying what is held for 1 hour or more and 10 hours or less. it can. As the volume average particle diameter of the CaS raw material powder is smaller, the machinability of the sintered body can be improved even if the addition amount of the CaS raw material powder is small. The volume average particle size is a particle size value of an integrated value of 50% in the particle size distribution obtained using a laser diffraction particle size distribution measuring apparatus (Nikkiso Microtrack “MODEL 9320-X100”).

<Lubricant>
The lubricant that coats the CaS raw material powder is added to suppress the hygroscopicity of anhydrous type III calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium hemihydrate sulfate. The lubricant also has a function of making it easy to take out a molded body obtained by compressing the iron-based powder metallurgy mixed powder in the mold. That is, when a lubricant is added to the mixed powder for iron-based powder metallurgy, it is possible to reduce the drawing pressure when taking out the molded body from the mold, and to prevent cracking of the molded body and damage to the mold. Moreover, when using the hot melt method, the lubricant exhibits the function of attaching the alloy powder and the graphite powder to the surface of the iron-based powder, and can prevent segregation of the iron-based mixed powder. Apart from the lubricant that coats the CaS raw material powder, a lubricant may be added in the process of producing the iron-based powder metallurgy mixed powder, or when the iron-based powder metallurgy mixed powder is filled in the mold A lubricant may be applied to the surface of the mold.

  The lubricant is preferably contained in an amount of 0.01% by weight or more, more preferably 0.1% by weight or more, and further preferably 0.2% by weight or more based on the weight of the mixed powder for iron-based powder metallurgy. It is. When the content of the lubricant is 0.01% by weight or more, the CaS raw material powder is prevented from coming into contact with the outside air, and the effect of stabilizing the performance is easily obtained. The lubricant is preferably contained in an amount of 1.5% by weight or less, more preferably 1.2% by weight or less, and further preferably 1.0% by weight or less based on the weight of the mixed powder for iron-based powder metallurgy. That is. 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 high-strength sintered body can be obtained.

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

<Binder>
The binder that coats the CaS raw material powder is added to suppress the hygroscopicity of anhydrous type III calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium hemihydrate sulfate, and to prevent segregation of the iron-based mixed powder. . The binder also has a function of attaching the alloy powder to the surface of the iron-based powder. In addition, you may add a binder in the process of producing the mixed powder for iron-base powder metallurgy separately from the binder which coat | covers CaS raw material powder.

  When coating the CaS raw material powder with a binder, the binder is dissolved in an organic solvent such as toluene so that the organic solvent contains the binder, and then the organic solution is mixed with the CaS raw material powder to volatilize the organic solvent. Thus, the surface of the CaS raw material powder can be coated with the binder.

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

  The binder is preferably contained in an amount of 0.01% by weight or more, more preferably 0.05% by weight or more based on the weight of the mixed powder for iron-based powder metallurgy. By including 0.01% by weight or more of the binder, it is possible to suppress the hygroscopicity of anhydrous type III calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium half water sulfate. Further, the binder is preferably contained in an amount of 0.5% by weight or less, more preferably 0.4% by weight or less, and further preferably 0.3% by weight or less based on the weight of the mixed powder for iron-based powder metallurgy. is there. By setting the binder content to 0.5% by weight or less, it becomes easy to obtain a compact with a high density during press molding.

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

  The shape of the ternary oxide is not particularly limited, but a spherical shape or a shape in which it is crushed, that is, a shape having a round shape 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 further preferably 1 μm or more. As the volume average particle size is smaller, there is a tendency that the machinability of the sintered body can be improved by adding a small amount. Further, 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 still more preferably 9 μm or less. When the volume average particle diameter is too large, it becomes difficult to improve the machinability of the sintered body. As the volume average particle diameter of the ternary oxide, a value measured by the same measurement method as that for the CaS raw material powder is adopted.

  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 still 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 still 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 during long-term cutting while suppressing cost. By using the ternary oxide in combination with the CaS raw material powder as in the present invention, the machinability in long-term cutting can be improved even if the addition amount of the ternary oxide is small.

  The weight ratio of the ternary oxide to the sintered CaS is preferably included 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 significantly improved.

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

  It is preferable that the shape, volume average particle diameter, measurement method, and weight ratio of the binary oxide are the same as those of the ternary oxide.

<Binary oxide and ternary oxide>
The mixed powder for iron-based powder metallurgy of the present invention preferably contains 0.02 wt% or more and 0.3 wt% or less of both binary oxide and ternary oxide in terms of the total weight. The total weight of the oxides 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 oxide and the ternary oxide, the better. The total weight of the oxides 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% by weight or less, the crushing strength of the sintered body can be sufficiently ensured.

  The weight ratio of the binary oxide and the sintered CaS is preferably included 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, a sintered body excellent in machinability at the initial stage of cutting can be produced.

<Alloy powder>
The alloy powder is added to promote bonding between the iron-based powders 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 entire mixed powder for iron-based powder metallurgy. When the content is 0.1% by weight or more, the strength of the sintered body can be increased, and when the content is 10% by weight or less, dimensional accuracy during sintering of the sintered body can be ensured.

  Examples of the alloy powder include non-ferrous metal powders such as copper (Cu) powder, nickel (Ni) powder, Mo powder, Cr powder, V powder, Si powder, and Mn powder, and cuprous oxide powder. You may use individually by 1 type and may use 2 or more types together.

<Method for producing mixed powder for iron-based powder metallurgy>
In the mixed powder for iron-based powder metallurgy of the present invention, the surface of the CaS raw material powder is coated with a lubricant, and then the coated CaS raw material powder, the iron-based powder, and the powders of other components are mixed with a mechanical stirring mixer. You may produce by doing. Also, the surface of the CaS raw material powder is not coated with a lubricant in advance, and all the component powders are mixed in a closed container while heating, and the surface of all the component powders is lubricated using a hot melt method in which the powder is coated with the lubricant. It may be coated with an agent. Alternatively, all the powders that make up the mixed powder for iron-based powder metallurgy, excluding the lubricant, are added to the sealed container, and the organic solvent in which the binder is dissolved is added to the sealed container and mixed, and then the organic solvent is volatilized. Finally, the surface of the entire powder excluding the lubricant may be coated with the lubricant and / or binder by adding and mixing the lubricant. The volume average particle size of the CaS raw material powder is preferably 0.1 μm or more and 60 μm or less.

  The heating temperature in the hot melt method is difficult to define uniformly because the optimum temperature differs depending on the melting point of the lubricant, but it is preferably, for example, 50 ° C. or more and 150 ° C. or less. When the heating temperature is 50 ° C. or higher, the fluidity of the lubricant is easily increased. When the heating temperature is 150 ° C. or lower, oxidation of the iron-based powder can be suppressed in the mixed powder production step, and the cost required for heating can be reduced.

  The heating time 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, it may be difficult to coat the entire surface of the CaS raw material powder with a lubricant and / or a binder.

  The mixed powder for iron-based powder metallurgy according to the present invention can be produced by mixing the iron-based powder and the CaS raw material powder produced above using, for example, 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 nauter mixer, a V-type mixer, and a double cone blender. The mixing temperature is not particularly limited, but is preferably 150 ° C. or lower from the viewpoint of suppressing oxidation of the iron-based powder in the mixing step.

<Method for producing sintered body>
After the mixed powder for iron-based powder metallurgy prepared above is filled in a mold, a compacted body is manufactured by applying a pressure of 300 MPa to 1200 MPa. The molding temperature at this time is preferably 25 ° C. or higher and 150 ° C. or lower.

  A sintered compact can be obtained by sintering the compacting body produced above by a normal sintering method. The sintering condition may be a non-oxidizing atmosphere or a reducing atmosphere, but in a nitrogen atmosphere, a mixed atmosphere of nitrogen and hydrogen, an atmosphere of hydrocarbon, etc., at a temperature of 1000 ° C. to 1300 ° C. for 5 minutes to 60 minutes. It is preferable to perform sintering.

<Sintered body>
The sintered body produced as described above preferably 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 minimum of CaS in a sintered compact is 0.02 weight% or more, More preferably, it is 0.03 weight% or more. The said sintered compact can be used as a machine part of a motor vehicle, an agricultural tool, an electric tool, and household appliances by processing with various tools, such as a cutting tool, as needed. Examples of the cutting tool for processing the sintered body include a drill, an end mill, a milling cutting tool, a turning cutting tool, a reamer, and a tap.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
First, commercially available calcium sulfide powder was classified with a sieve to obtain −63 / + 45 μm (volume average particle diameter 54 μm). The classified calcium sulfide powder was put in an airtight container in such an amount that the weight of CaS after sintering was 0.5% by weight. The surface of the calcium sulfide powder is obtained by adding 0.75% by weight of an amide-based lubricant (product name: Accra wax C (manufactured by LONZA)) to this sealed container and mixing for 10 minutes while heating to 100 ° C. Was coated with an amide-based lubricant.

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

(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 sealed container and heated to 100 ° C., but in Example 2, the same as in Example 1 was used. The powder of all components was put in a sealed container, heated to 100 ° C. using a hot melt method, and mixed for 30 minutes to coat the surface of the powder of all components with an amide-based lubricant. Then, the mixed powder for iron-base powder metallurgy was produced by cooling to room temperature.

(Example 3)
In place of the toluene solution containing styrene / butadiene rubber, the amide-based lubricant used in Example 2 was added so that the weight of the styrene / butadiene rubber after volatilization of toluene was 0.1% by weight, and other components. After mixing the same as in Example 2, the surface of the CaS raw material particles was coated with styrene-butadiene rubber by volatilizing toluene at 100 ° C. Thereafter, the same amount of the amide-based lubricant used in Example 1 as that used in Example 1 was added and mixed to prepare a mixed powder for iron-based powder metallurgy of Example 3.

(Comparative Examples 1-3)
Comparative Example 1 produced a mixed powder for iron-based powder metallurgy in the same manner as in Example 1 except that the CaS raw material powder was not added. In Comparative Examples 2 and 3, the CaS raw material powder shown in the column of “CaS component” in Table 1 was used, but the iron-based powder was the same as in Example 1 except that it was not coated with a lubricant and a binder. A mixed powder for metallurgy was prepared.

  Two types of sintered bodies were prepared using the mixed powder for iron-based powder metallurgy of each of the above Examples and Comparative Examples. One is a sintered body (hereinafter referred to as “immediately sintered body”) using the mixed powder for iron-based powder metallurgy immediately after the production, and the other is for iron-based powder metallurgy after 10 days from the production. A sintered body using the mixed powder (hereinafter referred to as “sintered body after 10 days”).

Immediately after the production process of the sintered body, the mixed powder for iron-based powder metallurgy immediately after production was filled in a mold, and the ring shape was an outer diameter of 64 mm, an inner diameter of 24 mm, and a thickness of 20 mm, and the molding density was 7.00 g / cm ^3. A test piece was molded so that Next, this ring-shaped test piece was sintered at 1130 ° C. for 30 minutes in a 10 volume% H ₂ —N ₂ atmosphere to produce a sintered body. On the other hand, the procedure for preparing the sintered body after 10 days was the same as that of the immediately after sintered body, except that the mold was filled with iron-based powder metallurgy mixed powder and left in the atmosphere for 10 days. Thus, a sintered body was produced.

<Evaluation>
In Table 1, the evaluation results of the green body density, the sintered body density, the crushing strength, and the tool wear amount are shown as “immediately sintered body / 10 days after sintered body”. In this notation, the value on the left side with the slash sandwiched is the evaluation result of the sintered body immediately after, and the value on the right side with the slash sandwiched is the evaluation result of the sintered body after 10 days.

  Immediately after each example and each comparative example, the sintered body density and the sintered body density of the sintered body after 10 days employ values measured according to the Japan Powder Metallurgy Industry Association Standard (JPMA M 01), For the crushing strength, a value measured according to JIS Z 2507-2000 was adopted. It shows that the higher the crushing strength, the harder the sintered body is broken and the higher the strength.

  Using the sintered body produced in each example and each comparative example, using a cermet chip (ISO model number: SNGN120408 non-breaker), peripheral speed 160 m / min, cutting 0.5 mm / pass, feed 0.1 mm / The tool wear amount (μm) of the cutting tool when turning 1150 m under rev and dry conditions was measured with a tool microscope. The result is shown in the column of “Tool wear” in Table 1. In addition, it has shown that the machinability of a sintered compact is excellent, so that the value of tool wear amount is small.

  From the results of each Example and each Comparative Example shown in Table 1, by coating the CaS raw material powder with a lubricant or a binder as in each Example, various properties (sintered) It was found that the density (condensation density, crushing strength, and tool wear amount) were almost equal. On the other hand, Comparative Examples 2 and 3 contain CaS alone or hemihydrate gypsum as the CaS component, but since the surface is not subjected to any coating treatment, the various properties of the sintered body after 10 days are comparable to those of the immediately sintered body. It was extremely deteriorated.

  The reason why the quality and performance of the sintered body deteriorated after 10 days in Comparative Examples 2 and 3 was that CaS in the iron-based powder metallurgy mixed powder or half-sintered while the iron-based powder metallurgy mixed powder was allowed to stand for 10 days. This is probably because the water gypsum absorbed water. In other words, in Comparative Examples 2 and 3, the density of the sintered body decreases due to the CaS simple substance or hemihydrate gypsum in the mixed powder for iron-based powder metallurgy absorbing water during storage in the atmosphere for 10 days. It is considered that the crushing strength has decreased. Since Comparative Example 1 does not contain a CaS component, both the immediately sintered body and the sintered body after 10 days have significantly high tool wear, and the machinability of the sintered body is significantly low.

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

Claims (8)

Including iron-based powder and anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, calcium dihydrate sulfate, calcium sulfide raw material powder containing one or more selected from the group consisting of calcium sulfide and hemihydrate calcium sulfate A mixed powder for iron-based powder metallurgy,
The CaS raw material powder is a mixed powder for iron-based powder metallurgy, which is coated with one or both of a lubricant and a binder.   The mixed powder for iron-based powder metallurgy according to claim 1, further comprising one or more ternary oxides selected from the group consisting of Ca-Al-Si oxides and Ca-Mg-Si oxides.   The iron group according to 1 or 2, comprising the ternary oxide and the CaS raw material powder so that a mass ratio of the ternary oxide to CaS after sintering is 3: 7 to 9: 1. Mixed powder for powder metallurgy.   The iron-based powder metallurgical mixing according to any one of 1 to 3, which includes the CaS raw material powder so that the mass ratio of CaS after sintering is 0.01% by mass or more and 0.1% by mass or less. powder.   The mixed powder for iron-based powder metallurgy according to any one of claims 1 to 4, wherein the CaS raw material powder has a volume average particle diameter of 0.1 µm or more and 60 µm or less. Using the mixed powder for iron-based powder metallurgy according to any one of claims 1 to 5, after forming a green compact at a molding temperature of 25 ° C or more and 150 ° C or less at a pressure of 300MPa or more and 1200MPa or less, the powder compact A sintered body produced by sintering a molded body for 5 minutes to 60 minutes at a temperature of 1000 ° C. to 1300 ° C. in a non-oxidizing atmosphere or a reducing atmosphere . CaS raw material powder containing at least one selected from the group consisting of anhydrous type III calcium sulfate, anhydrous type II calcium sulfate, calcium dihydrate sulfate, calcium sulfide, and calcium hemihydrate sulfate, either lubricant or binder Coating with one or both;
A method for producing a mixed powder for iron-based powder metallurgy, comprising the step of mixing the coated CaS raw material powder and an iron-based powder. A step of obtaining a sintered body by sintering the mixed powder for iron-based powder metallurgy produced by the production method of claim 7;
The said sintered compact is a manufacturing method of a sintered compact containing CaS of 0.01 mass% or more and 0.1 mass% or less of mass ratio.