JP2016222942A - Mixed powder for iron-based powder metallurgy and sintered body manufactured by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixed powder for iron-based powder metallurgy capable of manufacturing a sintered body excellent in machinability even at early period of cutting and during long time cutting.SOLUTION: The mixed powder for iron-based powder metallurgy contains one or more kind of ternary oxide selected from a group consisting of a Ca-Al-Si oxide and a Ca-Mg-Si oxide, and one or more kind of binary oxide selected from a group consisting of a Ca-Al oxide and a Ca-Si oxide with the total weight of the ternary oxide and the binary oxide of 0.025 wt.% to 0.3 wt.%.SELECTED DRAWING: None

Description

  The present invention relates to a mixed powder for iron-based powder metallurgy and a sintered body produced using the same, and a mixed powder for iron-based powder metallurgy containing a binary oxide and a ternary oxide in a specific weight ratio, and The present invention relates to a sintered body produced using 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 into 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, non-uniform shrinkage may occur in the raw material powder due to the above-mentioned sintering, 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 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 MnS powder is effective for relatively low-speed cutting such as drilling. However, the addition of manganese sulfide powder is not necessarily effective for high-speed cutting in recent years, and there are problems such as generation of dirt on the sintered body and reduction in mechanical strength.

  For this reason, as a method other than adding the above-described manganese sulfide, for example, additives disclosed in Patent Documents 1 to 4 have been proposed.

  Patent Document 1 discloses that 0.1 to 1.0% of calcium sulfide and 0.1 to 2% of carbon (C) with respect to iron-based raw material powder containing a required amount of iron powder and copper. And sintered steel containing 0.5 to 5.0% copper (Cu) is disclosed.

Patent Document 2 discloses a metallurgical powder composition containing a powder containing calcium aluminate. Powder containing the calcium aluminate, and 51 to 57 wt% of alumina, and calcium oxide 31-37% by weight, and SiO ₂ of less than 6.0 wt%, less than 2.5 wt.% Fe ₂ O ₃ If, comprising the TiO ₂ of less than 3.0 wt%, and 2.0 wt% less than MgO, and K ₂ O of less than 0.2 wt%, less than 0.2 wt% of sulfur.

Patent Document 3 discloses an iron-based mixed powder containing SiO ₂ —CaO—MgO-based oxide powder at a ratio of 0.01 to 1.0 part by mass with respect to 100 parts by mass of iron-based powder. .

Patent Document 4 discloses an iron-based powder metallurgy containing 0.02-0.3 wt% of a CaO—Al ₂ O ₃ —SiO ₂ -based composite oxide powder mainly composed of iron powder and having an average particle size of 50 μm or less. Mixed powders are disclosed.

Japanese Patent Publication No. 52-16684 Special table 2008-502807 gazette JP 2010-236061 A JP 09-279204 A

  By including the calcium sulfide disclosed in Patent Document 1, there are problems such that the strength of mechanical parts is significantly reduced, and that the mixed powder changes with time and the quality is not stable. 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 requirements.

The technique described in Patent Document 2 includes CaO: Al ₂ O ₃ = 35.5: 64.5, which is a theoretical ratio of monocalcium aluminate, while Al ₂ O ₃ is insufficient and CaO is excessively contained. . When this excessive amount of CaO reacts with other oxides or sulfur or is present alone, the characteristics of the sintered body are difficult to stabilize.

  In the techniques described in Patent Documents 3 and 4, the ceramic powder exposed on the processed surface during cutting adheres to the tool surface to form a tool protective film. This tool protective film prevents material deterioration of the tool and improves machinability. However, the sintered body made of the iron-based mixed powder disclosed in Patent Documents 3 and 4 is required to further improve machinability immediately after the start of cutting (the initial stage of cutting).

  The present invention has been made in view of the above-described present situation, and an object of the present invention is to provide an iron-based powder capable of producing a sintered body excellent in machinability both in the initial stage of cutting and in long-term cutting. It is to provide mixed powder for metallurgy.

In order to achieve the above object, the inventor of the present invention includes an oxide (2CaO.Al ₂ O ₃ .SiO ₂ powder) contained in a sintered body and a titanium oxide (TiO ₂ ) powder contained in a cutting tool or a cutting tool coating. The reaction mechanism was confirmed. Specifically, a mixed powder of 2CaO · Al ₂ O ₃ · SiO ₂ powder and TiO ₂ powder was heated in an atmosphere under no pressure, and the reaction product was analyzed by X-ray diffraction.

As a result, when the mixed powder was heated for 5 minutes at 700 ° C., if it does not react with TiO ₂ and _{2CaO · Al 2 O 3 · SiO} 2, where the above-described mixed powder is heated for 1 hour at 700 ° C. The _{, 2CaO · Al 2 O 3 ·} SiO 2 is decomposed into various oxides such as _{CaO · Al 2 O 3 · 2SiO} 2, 2CaO · SiO 2, was found to be further CaO · TiO ₂ also produced .

Based on the results of this analysis, the present inventor did not sufficiently react with the ternary oxide and TiO ₂ in the tool immediately after the start of the cutting process and the cutting edge temperature of the cutting tool was low. It was assumed that it was difficult to form. In addition, the present inventor forms a protective film on the tool surface by reacting TiO ₂ on the tool surface with Ca in the ternary oxide when the cutting edge temperature increases from the start of cutting and a certain period of time elapses. In the binary oxide, Ca in the binary oxide is lost by reacting with TiO _{2 on} the surface of the cutting tool, and hard Al ₂ O ₃ , SiO. _{Since 2} is generated and causes tool wear, it was assumed that binary oxides have less tool wear suppression effect than ternary oxides in long-term cutting.

Based on the above assumptions, the inventor has improved the machinability at the initial stage of cutting with a _binary oxide, and cuts in long-time cutting with a ternary oxide in which hard Al ₂ O ₃ and SiO ₂ are not easily generated. As a result, the present invention shown below was completed.

  That is, the mixed powder for iron-based powder metallurgy according to the present invention includes one or more ternary oxides selected from the group consisting of Ca—Al—Si oxides and Ca—Mg—Si oxides; One or more binary oxides selected from the group consisting of -Al-based oxides and Ca-Si-based oxides, and the total weight of the ternary oxides and the binary oxides is 0 0.025 wt% or more and 0.3 wt% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the sintered compact excellent in the machinability in the early stage of cutting can be obtained because the mixed powder for iron-based powder metallurgy contains a binary system oxide. Moreover, when the mixed powder for iron-based powder metallurgy contains a ternary oxide, a sintered body excellent in machinability in long-term cutting can be obtained. When the total weight of the binary oxide and the ternary oxide is in the above range, the machinability in the initial stage of cutting and the machinability in long-term cutting can be made highly compatible.

  In the above configuration, the iron-based powder metallurgy mixed powder preferably includes a ternary oxide and a binary oxide in a weight ratio of 9: 1 to 1: 9. By including the ternary oxide and the binary oxide in such a weight ratio, the balance between the machinability at the initial stage of cutting and the machinability of long-term cutting is improved.

  In the above configuration, the mixed powder for iron-based powder metallurgy preferably includes a ternary oxide and a binary oxide in a total weight of 0.05% by weight to 0.2% by weight. By including such a weight ratio, a sintered body excellent in the balance between the machinability at the initial stage of cutting and the machinability of long-term cutting can be produced.

The binary oxide is preferably at least one selected from the group consisting of CaO · Al ₂ O ₃ , 2CaO · SiO ₂ and 12CaO · 7Al ₂ O ₃ . The ternary oxide is preferably at least one selected from the group consisting of 2CaO · MgO · 2SiO ₂ and 2CaO · Al ₂ O ₃ · SiO ₂ .

  This invention is also the sintered compact produced by sintering the said mixed powder for iron-based powder metallurgy.

  ADVANTAGE OF THE INVENTION According to this invention, the mixed powder for iron-base powder metallurgy which can produce the sintered compact excellent in machinability in the initial stage of cutting and long-term cutting 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 preferably formed by mixing an iron-based powder, a ternary oxide, and a binary oxide. Various additives such as alloy powders, graphite powders, lubricants, binders, and machining accelerators 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 volume average particle diameter of the iron-based powder is 50 μm or more, the handleability 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.

<Binary oxide and ternary oxide>
The mixed powder for iron-based powder metallurgy according to the present invention is characterized by containing both a binary oxide and a ternary oxide in a total weight of 0.025 wt% or more and 0.3 wt% or less. The binary oxide can improve the machinability at the initial stage of cutting when the sintered body is used for cutting. The ternary oxide can improve the machinability when cut for a long time. By containing both oxides in such a weight ratio, a sintered body excellent in machinability can be produced both in the initial stage of cutting and in long-term cutting.

  The total weight of the oxide is preferably 0.03% by weight or more, more preferably 0.04% by weight or more, further preferably 0.05% by weight or more, and particularly 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.

Here, the binary oxide means a complex oxide of two elements, and the ternary oxide means a complex oxide of three elements. The binary oxide is preferably a composite oxide of two elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe, and Zn. More preferred are system oxides, Ca—Si oxides, 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 .

The ternary oxide is preferably a complex oxide of three elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe, and Zn. -Si-based oxides, Ca-Mg-Si-based oxides and the like are more preferable. 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, by forming a protective film on the surface of the cutting tool, the machinability It can be remarkably improved.

  The shape of the binary oxide and 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 volume average particle diameter of the binary oxide and 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 volume average particle diameter is preferably 15 μm or less, more preferably 10 μm or less, and further preferably 9 μm or less. If the volume average particle diameter is too large, it becomes difficult to improve the machinability of the sintered body. The volume average particle size is a value of the particle size D ₅₀ of 50% of the integrated value in the particle size distribution obtained using a laser diffraction particle size distribution measuring device (Microtrack “MODEL 9320-X100” manufactured by Nikkiso Co., Ltd.). By using a combination of a binary oxide and a ternary oxide as in the present invention, the amount of both oxides added can be reduced and the raw material cost can be reduced.

  The binary oxide is preferably contained in an amount of 0.01% by weight or more, more preferably 0.03% by weight or more, and further preferably 0.05% by weight or more. The binary oxide is preferably contained in an amount of 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 such a weight ratio, it is possible to obtain a sintered body excellent in machinability at the initial stage of cutting while suppressing cost.

  The ternary oxide is preferably contained in an amount of 0.01% by weight or more, more preferably 0.03% by weight or more, and further preferably 0.05% by weight or more. Further, the ternary oxide is preferably contained in an amount of 0.25% by weight or less, more preferably 0.2% by weight or less, and further preferably 0.15% by weight or less. By including such a weight ratio, it is possible to obtain a sintered body excellent in machinability even during long-term cutting while suppressing cost.

  The weight ratio of the ternary oxide and the binary oxide is preferably included in a ratio of 9: 1 to 1: 9, more preferably 9: 1 to 3: 7, and even more preferably 7: 3 to 4. : 6. By including both oxides in such a weight ratio, a sintered body that is easy to be cut can be produced both in the initial stage of cutting and in long-term cutting.

<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 it is 0.1% by weight or more, the strength of the sintered body can be increased, and when it 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.

<Lubricant>
The lubricant is added in order to make it easy to take out the molded body obtained by compressing the mixed powder for iron-based powder metallurgy 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. The lubricant may be added to the iron-based powder metallurgy mixed powder, or may be applied to the surface of the mold. When the lubricant is added to the iron-based powder metallurgy mixed powder, the lubricant is preferably contained in an amount of 0.01% by weight or more, and 0.1% by weight or more, based on the weight of the iron-based powder metallurgy mixed powder. More preferably. When the content of the lubricant is 0.01% by weight or more, it is easy to obtain the effect of reducing the punching pressure of the sintered body. The lubricant is preferably contained in an amount of 1.5% by weight or less, more preferably 1.2% by weight or less, based on the weight of the mixed powder for iron-based powder metallurgy. 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 selected from the group consisting of metal soap (lithium stearate, calcium stearate, zinc stearate, etc.), stearic acid monoamide, fatty acid amide, amide wax, hydrocarbon wax and cross-linked (meth) acrylic acid alkyl ester resin. One or more of them can be used. Among these, it is preferable to use an amide-based lubricant from the viewpoint that the performance of attaching the alloy powder, the graphite powder, and the like to the surface of the iron-based powder is good and the segregation of the iron-based mixed powder is easily reduced.

<Binder>
The binder is added to adhere the alloy powder and the graphite powder to the surface of the iron-based powder. As the binder, a butene polymer, a methacrylic acid polymer, or the like is used. 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 here 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 content of the binder is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and further preferably 0.1% by weight or more based on the weight of the iron-based powder metallurgy mixed powder. It is contained by weight% or more. The binder content is preferably 0.5% by weight or less, more preferably 0.4% by weight or less, and still more preferably 0.8% by weight or less with respect to the weight of the mixed powder for iron-based powder metallurgy. 3% by weight or less.

<Machining accelerator>
The machining accelerator is added in order to improve the machinability of the sintered body obtained by sintering the mixed powder for iron-based powder metallurgy. It is preferable to use calcium sulfide as the machining accelerator. When calcium sulfide is used as a machining accelerator, calcium sulfide is hygroscopic and may impair the stability of the performance. Therefore, the surface of the powder made of calcium sulfide is coated, or the powder of calcium sulfide is preliminarily 300 It is preferable to heat to ℃ -900 ° C to form II type calcium sulfate. Thereby, the hygroscopic property of the powder made of calcium sulfide can be suppressed, and the performance of the sintered body can be stabilized. In addition, since the type II calcium sulfate has extremely low hygroscopicity, the performance of the sintered body can be stabilized. For the coating of the powder made of calcium sulfide, an amide polymer material, an organic material such as styrene / butadiene rubber, or the like can be used.

  The content of the machining accelerator is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and still more preferably, based on the weight of the mixed powder for iron-based powder metallurgy. It is contained 0.1% by weight or more. The content of the machining accelerator is preferably 1% by weight or less, more preferably 0.4% by weight or less, and still more preferably 0.3% by weight with respect to the weight of the mixed powder for iron-based powder metallurgy. % By weight or less.

<Method for producing mixed powder for iron-based powder metallurgy>
The mixed powder for iron-based powder metallurgy of the present invention can be produced by mixing iron-based powder, ternary oxide, and binary oxide using, for example, a mechanical stirring mixer. In addition to the above powders, various additives such as alloy powders, graphite powders, lubricants and binders 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 order of mixing the powders is not particularly limited. 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 can be 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.

  And the sintered compact is 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 under 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 the following sintering.

<Sintered body>
The sintered body produced as described above can be used as machine parts such as automobiles, agricultural equipment, electric tools, and home appliances by processing with various tools such as cutting tools as necessary. Examples of such cutting tools 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.

(Examples 1-6 and Comparative Examples 1-6)
In each example and each comparative example, 2 wt% copper powder (product name: CuATW-250 (Fukuda Metal Foil Powder Industrial Co., Ltd.) with respect to pure iron powder (product name: Atmel 300M (manufactured by Kobe Steel)) Made by the company)), and the composition and weight% of binary oxide and / or ternary oxide shown in the column of “binary oxide” and / or “ternary oxide” in Table 1, A mixed powder for iron-based powder metallurgy was prepared by mixing graphite powder (product name CPB (manufactured by Nippon Graphite Industry Co., Ltd.)) and 0.75 wt% zinc stearate. The graphite powder was added in an amount such that the amount of carbon after sintering was 0.75% by weight. As the binary oxide and ternary oxide, those having a volume average particle diameter of 2 μm were used.

The above mixed powder for iron-based powder metallurgy was filled in a mold, 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 so that the molding density was 7.00 g / cm ³ . This ring-shaped test piece was sintered at 1130 ° C. for 30 minutes in a 10% by volume H ₂ —N ₂ atmosphere to produce a sintered body.

  Using the sintered body thus produced, using a cermet chip (ISO model number: SNGN120408 non-breaker), peripheral speed 160 m / min, depth of cut 0.5 mm / pass, feed 0.1 mm / rev, dry type The amount of tool wear of the cutting tool was measured by turning under conditions. The amount of wear of the tool was measured using a tool microscope for the amount of wear (μm) of the cutting tool when 330 m was cut from the start of cutting and the amount of wear (μm) of the cutting tool after cutting 1150 m. The evaluation result of the wear amount is shown in each column of “Tool wear amount” in Table 1. In addition, it has shown that the machinability of a sintered compact is excellent, so that the value of abrasion amount is small.

  In Table 1, a value measured according to the Japan Powder Metallurgy Industry Association Standard (JPMA M 01) was adopted as the sintered body density, and a value measured according to JIS Z 2507-2000 was adopted as the crushing strength. It shows that the higher the crushing strength, the harder the sintered body is broken and the higher the strength.

As shown in Table 1, Examples 1 to 6 are sintered bodies containing a combination of a binary oxide and a ternary oxide. Comparative Example 1 is a sintered body containing neither binary oxide nor ternary oxide. Comparative Examples 3 and 4 are sintered bodies containing only ternary oxides. Comparative Examples 2, 5, and 6 are sintered bodies containing only binary oxides. In Comparative Example 2, the component (CaO.Al ₂ O ₃ ) disclosed in Patent Document 1 is used. In Comparative Example 3, the component (2CaO · MgO · 2SiO ₂ ) disclosed in Patent Document 3 is used. In Comparative Example 4, the component (2CaO.Al ₂ O ₃ .SiO ₂ ) disclosed in Patent Document 4 is used.

  The sintered bodies of Examples 1 to 6 significantly reduce the amount of tool wear both at the time of 330 m cutting (initial wear) and at the time of 1150 m cutting (long-time wear) compared to those of Comparative Examples 1 to 6. It became clear that we could do it. This is probably because the binary oxide improves the machinability at the beginning of cutting and the ternary oxide improves the machinability of the cutting for a long time. This is considered to be because the machinability of the sintered body was enhanced in any period cutting.

  Comparing Comparative Example 1 with Comparative Examples 2, 5, and 6, it can be seen that the addition of the binary oxide has an effect of suppressing the initial wear of the cutting tool. Further, comparing Comparative Example 1 with Comparative Examples 3 and 4, it can be seen that the addition of the ternary oxide has an effect of suppressing the wear of the cutting tool during long-time cutting.

  From the results of each Example and each Comparative Example shown in Table 1, by including 0.1% by weight of the binary oxide and the ternary oxide in the total weight, both in the initial cutting time and in the long-time cutting. As a result, it became clear that a sintered body easily machinable was obtained, and the effect of the present invention was shown.

(Examples 7 to 18)
The total weight of the binary oxide and ternary oxide is fixed at 0.1% by weight, and the weight ratio and composition of the “binary oxide” and “ternary oxide” in Table 2 are as follows. A mixed powder and sintered body for iron-based powder metallurgy were produced in the same manner as in Example 1 except that the composition and weight% shown in the column were changed. The amount of tool wear was evaluated in the same manner as in Example 1 for the sintered body thus produced. These results are shown in Table 2 below.

  From the results shown in Table 2, by including the ternary oxide and the binary oxide in a weight ratio of 9: 1 to 1: 9, the machinability in the initial stage of cutting and the machinability in long-time cutting It became clear that both can be achieved. In particular, it has been clarified that when the weight ratio is 9: 1 to 3: 7, both the machinability in the initial stage of cutting and the machinability in long-time cutting can be achieved at a high level.

(Examples 19 to 21 and Comparative Examples 7 to 9)
Implemented except that the weights of the binary oxide and ternary oxide were changed to the compositions and weight percentages shown in the columns of “binary oxide” and “ternary oxide” in Table 3. In the same manner as in Example 1, a mixed powder for iron-based powder metallurgy and a sintered body were produced. The amount of wear was evaluated for the sintered body thus produced by the same method as in Example 1. These results are shown in Table 3 below.

From the results shown in Table 3, when the total content of the binary oxide and the ternary oxide is 0.025 wt% or more and 0.3 wt% or less, the machinability in the initial cutting and long-time cutting It was clarified that both the machinability and the machinability can be achieved, and the effect of the present invention was shown. On the other hand, if the total weight% of the binary oxide and the ternary oxide is less than 0.025 wt% (Comparative Examples 7 and 8), the effect of improving the machinability cannot be obtained sufficiently, and 2 When the total weight of the ternary oxide and the ternary oxide exceeds 0.3% by weight (Comparative Example 9), it has become clear that the crushing strength is less than 800 MPa and the strength of the sintered body is insufficient.

Claims (6)

It consists of one or more ternary oxides selected from the group consisting of Ca—Al—Si oxides and Ca—Mg—Si oxides, and Ca—Al oxides and Ca—Si oxides. And one or more binary oxides selected from the group,
A mixed powder for iron-based powder metallurgy containing the ternary oxide and the binary oxide in a total weight of 0.025 wt% or more and 0.3 wt% or less.   The mixed powder for iron-based powder metallurgy according to claim 1, wherein a weight ratio of the ternary oxide and the binary oxide is included in a ratio of 9: 1 to 1: 9.   The mixed powder for iron-based powder metallurgy according to claim 1 or 2, comprising the ternary oxide and the binary oxide in a total weight of 0.05 wt% or more and 0.2 wt% or less. The binary oxides, according to CaO · Al ₂ O _3, claim 1 is 2CaO · SiO ₂ and 12CaO · 7Al 1 or more selected from the group consisting of ₂ O ₃ Mixed powder for iron-based powder metallurgy. 5. The iron according to claim 1, wherein the ternary oxide is at least one selected from the group consisting of 2CaO · MgO · 2SiO ₂ and 2CaO · Al ₂ O ₃ · SiO _2. Mixed powder for base powder metallurgy. The sintered compact produced by sintering the mixed powder for iron base powder metallurgy as described in any one of Claims 1-5.