JP2017101280A - Mixed powder for powder metallurgy, production method for mixed powder for powder metallurgy, and iron-based powder-made sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixed powder for powder metallurgy capable of providing a sintered compact having excellent lathe machinability and excellent drilling machinability.SOLUTION: There is provided the mixed powder for powder metallurgy containing an iron-based powder, a powder for alloy, a powder for improving machinability and a lubricant. In the mixed powder for powder metallurgy, the powder for improving machinability contains a first powder for improving machinability which is at least one kind selected from a group consisting of an enstatite powder, a talc powder, a kaolin powder, a mica powder, a magnesium oxide (MgO) powder, a mixed powder of silica (SiO) and magnesium oxide (MgO), an alkali silicate powder, an alkali metal sulphate powder and an alkali earth metal sulphate powder, a second powder for improving machinability which is at least one kind selected from a chromium oxide powder and a titanium oxide powder and a third powder for improving machinability which is an oxide powder containing CaO, AlOand SiOand blended amount of the powder for improving machinability is 0.01 to 1.0% by mass% based on total amount of the iron-based powder, the powder for alloy and the powder for improving machinability.SELECTED DRAWING: None

Description

  The present invention relates to a powder for powder metallurgy mixed with an iron-based powder, an alloy powder, a machinability improving powder and a lubricant, suitable for automobile sintered parts, and a method for producing the same, and molding the mixed powder. The present invention relates to a sintered body made of iron-based powder obtained by sintering, and particularly aims to improve the machinability of the sintered body made of iron-based powder.

  Advances in powder metallurgy technology have made it possible to manufacture parts with complex shapes in a near net shape with high dimensional accuracy, so products using powder metallurgy technology are used in various fields. The powder metallurgy technique is characterized by a high degree of freedom in shape because powder is filled in a mold having a desired shape, and then sintered. For this reason, there are many cases in which powder metallurgy technology is used for manufacturing mechanical parts such as gears having complicated shapes.

  Also, in the field of iron-based powder metallurgy, iron-based powders in which iron-based powders are mixed with powders for alloys such as copper powder and graphite powder, and lubricants such as zinc stearate and lithium stearate, have a predetermined shape. After being filled in the mold, pressure molding is performed to form a molded body, and then a sintering process is performed to obtain a sintered part. Sintered parts obtained in this way are generally considered to have good dimensional accuracy. However, in recent years, extremely strict dimensional accuracy may be required, and it is necessary to perform further cutting after sintering. Is increasing. In this cutting process, precision machining such as turning with a lathe and drilling with a drill is performed at various cutting speeds.

  However, since the sintered component has a high content ratio of pores, cutting resistance tends to be higher than that of a metal material manufactured by a melting method. Therefore, conventionally, for the purpose of improving the machinability of the sintered body, Pb, Se, Te, or the like is added to the iron-based mixed powder as a powder, or alloyed and added to the iron powder or iron-based powder. Has been done.

  However, since Pb has a melting point as low as 330 ° C., it melts in the sintering process, but does not dissolve in iron, so that it is difficult to uniformly disperse in the matrix. Moreover, since Se and Te embrittle the sintered body, there is a problem that the mechanical properties of the sintered body are significantly deteriorated.

  Furthermore, since the holes described above have poor thermal conductivity, when the sintered body is processed, frictional heat during processing is accumulated, and the surface temperature of the tool tends to increase. Therefore, the cutting tool is easily worn out and has a short life, resulting in an increase in cutting cost and an increase in manufacturing cost of the sintered part.

  For these problems, for example, Patent Document 1 describes an iron powder mixture for manufacturing a sintered body in which fine manganese sulfide powder having a particle size of 10 μm or less is mixed with iron powder in an amount of 0.05 to 5% by weight. ing. According to the technique described in Patent Document 1, it is said that the machinability (cutability) of the sintered body can be improved without causing a large dimensional change and strength deterioration.

  Patent Document 2 describes a method for producing an iron-based sintered body in which an alkali silicate is added to an iron-based powder. According to the technique described in Patent Document 2, by adding 0.1 to 1.0% by weight of alkali silicate, the machinability of the sintered body can be improved without significant dimensional change and strength deterioration. Has been.

In Patent Document 3, a powder (ceramic powder) of a CaO—Al ₂ O ₃ —SiO ₂ based oxide having an average particle size of 50 μm or less, which is mainly composed of iron powder and has an anolsite phase and / or a gehlenite phase, is given as 0.0. An iron-based mixed powder for powder metallurgy containing 02 to 0.3% by weight is described. According to the technique described in Patent Document 3, the ceramic powder exposed on the work surface during cutting adheres to the tool surface to form a tool protective film (berak layer), and prevents material deterioration of the tool and improves machinability. It can be improved.

  Patent Document 4 discloses an iron-based powder obtained by mixing a lubricant in addition to manganese-based powder, calcium phosphate powder and / or hydroxyapatite powder as iron-based powder, alloy powder, and machinability improving powder. Have been described. Here, manganese sulfide powder effectively works to make chips finer, while calcium phosphate powder and hydroxyapatite powder adhere to the surface of the tool during cutting to form a veraque layer to prevent or suppress alteration of the tool surface. It is described that there is an effect. That is, according to the technique described in Patent Document 4, it is said that the machinability can be improved without deteriorating the mechanical properties of the sintered body.

  Further, in Patent Document 5, cutting resistance can be reduced by adding barium sulfate or barium sulfide alone or in a total of 0.3 to 3.0% by weight to iron or an iron-based alloy. It is described that workability can be improved.

  Furthermore, Patent Document 6 discloses an iron-based mixture for powder metallurgy containing a complex oxide having a viscosity at 800 ° C. of 105 (poise) or less in a range of 0.05 to 1.5% by mass with respect to the total mass. The powder is described. When the iron-based mixed powder for powder metallurgy contains the complex oxide, the complex oxide in the sintered body obtained by using the iron-based mixed powder for powder metallurgy is melted during cutting to iron. It is said that the powder interface becomes smooth, and as a result, the shear deformation force in the chips of the iron powder sintered body is reduced and tool wear is suppressed.

JP-A 61-147801 JP 60-145353 A JP-A-9-279204 JP 2006-89829 A Japanese Examined Patent Publication No. 46-39564 JP 2009-035796 A Japanese Patent Laying-Open No. 2015-157773

However, in the techniques described in Patent Documents 1 and 4, since the mixed powder contains manganese sulfide (MnS) powder, the appearance of the sintered body is deteriorated, and S or MnS remaining in the sintered body is reduced. There is a problem that the rusting of the sintered part is promoted and the corrosion resistance of the sintered body is lowered.
Furthermore, although MnS is excellent in improving the machinability in a low speed region where the cutting speed is 100 m / min or less, there is a problem that the effect of improving the machinability is small in high speed cutting of about 200 m / min.

  Moreover, in the technique described in Patent Document 2, since the chips are not miniaturized, in the case of drill cutting, the chip evacuation property is poor, and there remains a problem in the cutting performance using the drill.

  Furthermore, in the technique described in Patent Document 3, it is necessary to reduce the impurities in the ceramic powder and to adjust the particle size in order to prevent deterioration of the powder characteristics and sintered body characteristics. There is a problem that the material cost increases. Moreover, although the technique described in Patent Document 3 is excellent in improving machinability at high speed, there is a problem that the effect of improving machinability is small in cutting at low speed.

  In addition, although the machinability improvement by the formation of the verak layer described in Patent Documents 3 and 4 is effective in reducing the cutting power in turning, the chip is not refined. There is still a problem in the machinability using a drill due to poor chip evacuation.

  Further, the technique described in Patent Document 5 has a problem that the effect of improving the machinability in high-speed cutting of about 200 m / min is small as in the technique using MnS.

  In addition, the technique described in Patent Document 6 uses a low-melting-point composite oxide. However, when the sintered body generates a large amount of heat and becomes sufficiently higher than the melting point, it melts. There is a problem that the viscosity of the article is too low and the lubricating effect between the tool and the sintered body is lost.

  Furthermore, the technique described in Patent Document 7 has a problem that improvement in the surface roughness of the product is not sufficient, although the effect of improving machinability regarding tool wear and cutting resistance is remarkably recognized.

  The present invention advantageously solves the problems and problems of the prior art described above, and has excellent machinability, specifically, excellent lathe machinability (hereinafter also referred to as latheability) and excellent drill machinability. It is an object to provide a mixed powder for powder metallurgy capable of obtaining a body and a method for producing the same. Another object of the present invention is to provide an iron-based powder sintered body having excellent machinability and having excellent turning properties and drilling properties using the powder mixture for powder metallurgy.

  In order to achieve the above-mentioned object, the inventors diligently studied various factors on the machinability of the sintered body, particularly the influence of additives. As a result, it was found that excellent free machinability can be exhibited under various cutting conditions by adding a plurality of powders of a specific compound as a machinability improving powder to the mixed powder. According to the method, it is possible to simultaneously improve the machinability (turnability) on a lathe and the machinability (drill machinability) using a drill, and to improve the machinability of the sintered body and the roughness of the cut surface.

  The mechanism for improving the machinability and roughness is not clear at present, but is considered as follows. That is, by adding a combination of a plurality of powders of specific compounds such as oxides and sulfates as a powder for improving machinability, various melting points and hardnesses were obtained by a sintering reaction according to the aggregate state of the mixture particles. A variety of solid solutions are produced. As a result, since the sintered body has both a wide melting temperature range and hardness, it exhibits free machinability regardless of cutting conditions. Furthermore, by using chromium oxide or titanium oxide in combination as the machinability improving powder, the chromium oxide or titanium oxide present at the grain boundaries in the sintered body suppresses plastic deformation of the cutting surface, and the cutting surface. Suppresses the rise of

  In contrast, when only an oxide or compound having a low melting point is used as the powder for improving machinability, the heat generated by the sintered body during cutting becomes large, and the cutting state at a high temperature where the difference from the melting point is significant As a result, it was recognized that the viscosity of the melt was too low and the lubrication effect between the tool and the sintered body was lowered. In addition, when only an oxide or compound having a high melting point is used as the machinability improving powder, if the sintered body is cut at a low temperature, the heat generated during cutting of the sintered body is small and the difference from the melting point is significant. Alternatively, the compound does not melt and the lubricating effect between the tool and the sintered body does not occur.

Furthermore, the particular compound, CaO, Al ₂ O _3, and by a combination of an oxide powder containing SiO _2, and finding that, together with the fact that good drill machinability is obtained.

  Based on the above knowledge, the inventors have improved the surface roughness in addition to simultaneously improving two different characteristics of turning and drill cutting by using a powder of a specific compound as a powder for improving machinability. Has been found to improve.

The present invention has been completed based on such findings and further studies. That is, the gist configuration of the present invention is as follows.
1. An iron-based powder, an alloy powder, a machinability improving powder, and a powder mixture for powder metallurgy containing a lubricant,
The machinability improving powder is
Enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO), alkali silicate powder, alkali metal sulfate powder, and alkaline earth A first machinability improving powder that is at least one selected from the group consisting of metal sulfate powders;
A second machinability improving powder that is at least one selected from the group consisting of chromium oxide powder and titanium oxide powder;
A third machinability improving powder which is an oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ ;
Powder metallurgy mixing in which the blending amount of the machinability improving powder is 0.01 to 1.0% by mass% with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder. powder.

2. 2. The mixed powder for powder metallurgy according to 1, wherein the blending amount of the first machinability improving powder is 10% to 80% by mass% with respect to the total amount of the machinability improving powder.

3. The alkali metal of the alkali metal sulfate powder is at least one selected from the group consisting of Li, Na, and K, and the alkaline earth metal of the alkaline earth metal sulfate powder is Mg, Ca, The mixed powder for powder metallurgy according to 1 or 2, which is at least one selected from the group consisting of Sr and Ba.

4). In any one of 1 to 3 above, the third machinability improving powder is a CaO—Al ₂ O ₃ —SiO ₂ based composite oxide powder having at least one of an anolsite phase and a gehlenite phase. The mixed powder for powder metallurgy described.

5. The mixed powder for powder metallurgy according to any one of 1 to 4, wherein an average particle diameter of the third machinability improving powder is 50 µm or less.

6). A method for producing a mixed powder for powder metallurgy comprising mixing an iron-based powder, an alloy powder, a machinability improving powder, and a lubricant, and then mixing them into a mixed powder,
The machinability improving powder is
Enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO), alkali silicate powder, alkali metal sulfate powder, and alkaline earth A first machinability improving powder that is at least one selected from the group consisting of metal sulfate powder, and a second machinability improvement that is at least one selected from the group consisting of chromium oxide powder and titanium oxide powder Powder for
A third machinability improving powder which is an oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ ;
The blending amount of the machinability improving powder is 0.01% to 1.0% by mass% with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder,
Further, the mixing
The iron-base powder and the alloy powder are heated by adding a part or all of the machinability improving powder and a part of the lubricant, and melting at least one of the added lubricants. First mixing to be cooled and solidified after mixing,
A method for producing a mixed powder for powder metallurgy, which is performed by secondary mixing in which the machinability improving powder and the remainder of the lubricant are added and mixed.

7). 7. The method for producing a mixed powder for powder metallurgy according to 6, wherein the blending amount of the first machinability improving powder is 10 to 80% by mass% with respect to the total amount of the machinability improving powder.

8). The alkali metal of the alkali metal sulfate powder is at least one selected from the group consisting of Li, Na, and K, and the alkaline earth metal of the alkaline earth metal sulfate powder is Mg, Ca, Sr, 8. The method for producing a mixed powder for powder metallurgy according to 6 or 7, wherein at least one selected from the group consisting of Ba and Ba is used.

9. Said third machinability improving powder is a powder of CaO-Al ₂ O ₃ -SiO ₂ composite oxide having at least one of anole site phase and gehlenite phase, in any one of the 6 to 8 The manufacturing method of the mixed powder for powder metallurgy of description.

10. 10. The method for producing a mixed powder for powder metallurgy according to any one of 6 to 9, wherein the average particle size of the third machinability improving powder is 50 μm or less.

11. An iron-based powder sintered body using the powder metallurgy mixed powder according to any one of 1 to 5 above.

  According to the present invention, it is possible to produce a sintered body with excellent machinability at a low cost, which has both excellent turning properties and excellent drill machinability, so that the production cost of sintered metal parts can be significantly reduced. It has a very advantageous effect on the industry. Since the sintered body made of iron-based powder obtained by the present invention can be cut in a wide range of cutting conditions from low speed to high speed, the cutting speed changes greatly at the center and the peripheral edge like a drill. , Especially the effect. Moreover, if the mixed powder for powder metallurgy according to the present invention is used, there is an effect that a green compact can be obtained without causing a decrease in the green compact density and an increase in the output force during molding.

Hereinafter, the present invention will be specifically described.
First, the mixed powder for powder metallurgy according to the present invention will be described.
The mixed powder for powder metallurgy (or simply referred to as mixed powder) of the present invention is a mixed powder containing iron-based powder, alloy powder, machinability improving powder, and lubricant.

[Iron-based powder]
The iron-based powder is not particularly limited, and both pure iron powder and alloy steel powder can be used. Examples of the alloy steel powder include pre-alloyed steel powder (alloyed steel powder) obtained by pre-alloying alloy elements, partially-diffused alloyed steel powder obtained by partially diffusing alloy elements into iron powder, and pre-alloyed steel. Arbitrary things, such as the hybrid steel powder which further diffused the alloy element further to the powder, can be used. Moreover, as said iron-based powder, what was manufactured by arbitrary methods, such as an atomizing method and a reduction method, can be used.

[Alloy powder]
The alloy powder is not particularly limited, and any alloy powder such as graphite powder, non-ferrous metal powder such as Cu powder, Mo powder, Ni powder, and cuprous oxide powder can be used. . One or more kinds of the alloy powder can be selected and used according to desired sintered body characteristics. By mixing the alloy powder with the iron-based powder, the strength of the obtained iron-based powder-made sintered body can be increased, and a desired sintered part strength can be ensured.

  The blending amount of the alloy powder is preferably 0.1 to 10% by mass% based on the total amount of the metal powder, the alloy powder and the machinability improving powder, depending on the desired strength of the sintered body. . By setting the blending amount of the alloy powder to 0.1% by mass or more, the strength of the sintered body can be further improved. Moreover, the dimensional accuracy of a sintered compact can further be improved by making the compounding quantity of the powder for alloys into 10 mass% or less.

[Powder for improving machinability]
In the present invention, the machinability improving powder contains a specific powder as each of the first machinability improving powder, the first machinability improving powder, and the first machinability improving powder. is important.

(First powder for improving machinability)
Examples of the first machinability improving powder include enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO), alkali silicate At least one selected from the group consisting of powder, alkali metal sulfate powder, and alkaline earth metal sulfate powder is used.

When a mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO) is used as the first machinability improving powder, magnesium oxide is mixed by primary mixing described later, and silica is mixed by secondary mixing. Thus, both may be mixed separately, or a mixed powder in which silica and magnesium oxide are mixed in advance may be used.

  The alkali silicate is not particularly limited, and any one such as sodium silicate can be used. Examples of the alkali metal sulfate powder and alkaline earth metal sulfate powder that can be used include lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate.

(Second machinability improving powder)
As the second machinability improving powder, at least one selected from the group consisting of chromium oxide powder and titanium oxide powder is used. The chromium oxide powder is not particularly limited, and any one can be used. For example, a corundum type Cr ₂ O ₃ used as a pigment or an abrasive is preferably used. Further, the titanium oxide powder is not particularly limited and any one can be used. For example, anatase type or rutile type TiO ₂ used as a pigment is preferably used.

(Third machinability improving powder)
As the third machinability improving powder, an oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ is used.

The oxide powder containing CaO, Al ₂ O ₃ and SiO ₂ forms a solid solution in a wide composition range to be a composite oxide, and the composite oxide includes an anolsite phase, gehlenite phase, cristobalite phase, tridymite phase, wollast. It has crystal structure such as knight phase, mullite phase, corundum phase. Among them, anole site phase _{CaO · Al 2 O 3 · 2SiO} 2, gehlenite phase is a compound represented by _{2CaO · Al 2 O 3 · SiO} 2, a composite oxide having any even 1300 ° C. or higher and a high melting point It is. If a composite oxide having a high melting point is used in this way, a more excellent lubricating effect is exhibited when the sintered body at the time of cutting becomes high temperature, that is, when the cutting speed is high. Therefore, in the present invention, it is preferable to use a CaO—Al ₂ O ₃ —SiO ₂ composite oxide powder having at least one of an anolsite phase and a gehlenite phase as the third machinability improving powder.

  The particle size of the third machinability improving powder is not particularly limited and may be any value. However, if the particle size becomes excessively large, the amount of springback and the amount after sintering of the molded body are increased. The dimensional change rate may increase. Therefore, the average particle size of the third machinability improving powder is preferably 50 μm or less. Here, the “average particle diameter” is a median diameter measured by a microtrack method (laser diffraction / scattering method).

(Function)
Among the first machinability improving powders, enstatite powder, talc powder, kaolin powder, and mica powder contain at least one of Si atoms (SiO ₂ ) and Mg atoms (MgO) bonded to oxygen atoms. It is a mineral powder made of a metal compound. Therefore, the first machinability improving powder is selected from enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO). When at least one of these is used, the iron oxide layer present on the surface of the iron-based powder and the SiO ₂ and MgO contained in the first machinability improving powder react during sintering, and the melt Form a phase.

  Similarly, alkali silicate powders, alkali metal sulfate powders, and alkaline earth metal sulfate powders also form a melt phase.

In the present invention, since the oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ is used in combination as the third machinability improving powder, the melt phase and the third machinability improvement are provided. Composition such as MgO—SiO ₂ —CaO—Al ₂ O ₃ , NaO—SiO ₂ —CaO—Al ₂ O ₃ , or sulfate —CaO—Al ₂ O ₃ —SiO ₂ Produces.

Furthermore, in the present invention, since at least one of the chromium oxide powder and the titanium oxide powder is used in combination as the second machinability improving powder, the finally obtained iron-based powder sintered body contains these SiO ₂ , Depending on the abundance ratios of MgO, sulfate, chromium oxide, and titanium oxide, solid solutions having various compositions are formed, and they are considered to have various melting points and hardness depending on the composition.

  As described above, by using the first to third powders for improving machinability together, the iron-based powder sintered body according to the present invention has various types of sintered body temperatures that increase due to heat generated during cutting. Therefore, the lubrication effect between the tool and the sintered body can be obtained stably regardless of the cutting state. Moreover, since hard Si oxide makes a structure | tissue softening by making a sulfate and a compound, a chip | tip refines | miniaturizes especially and the exclusion property of the chip | tip in drill cutting improves significantly. Thus, by using the above-mentioned machinability improving powder, the drill machinability can be greatly improved. Furthermore, by using at least one of chromium oxide powder and titanium oxide powder, brittle deformation at the grain boundary is promoted, and plastic deformation of the cutting surface is suppressed, so that surface roughness can be improved.

(Mixing amount of powder for improving machinability)
The blending amount of the machinability improving powder in the powder metallurgy mixed powder of the present invention is 0.01% to 1% by mass with respect to the total amount of the iron base powder, the alloy powder, and the machinability improving powder. 0.0%. When the blending amount of the machinability improving powder is less than 0.01% by mass, the machinability improving effect cannot be sufficiently obtained. On the other hand, if the blending amount exceeds 1.0% by mass, the density of the green compact obtained by molding the powder mixture for powder metallurgy decreases, and the sintered body obtained by sintering the green compact Mechanical strength decreases.

(Amount of the first cutting performance improving powder)
The blending amount of the first machinability improving powder is not particularly limited, but is preferably 10 to 80% by mass% with respect to the total amount of the machinability improving powder. When the blending amount is 10% by mass or more, the combined effect with the second and third machinability improving powders can be further enhanced. Moreover, the effect of improving the machinability at high speed can be further enhanced by setting the blending amount to 80% by mass or less.

(2nd amount of powder for improving machinability)
The blending amount of the second machinability improving powder is not particularly limited, but is preferably 10 to 80% by mass% with respect to the total amount of the machinability improving powder. When the blending amount is 10% by mass or more, the combined effect with the first and third machinability improving powders can be further enhanced. Moreover, the improvement effect of surface roughness can further be heightened by the said compounding quantity being 80 mass% or less.

(3rd amount of powder for improving machinability)
The blending amount of the first machinability improving powder is not particularly limited, but is preferably 10 to 80% by mass% with respect to the total amount of the machinability improving powder. If the blending amount is 10% by mass or more, the combined effect with the first and second machinability improving powders can be further enhanced. Moreover, the effect of improving the machinability at high speed can be further enhanced by setting the blending amount to 80% by mass or less.

[lubricant]
The lubricant is not particularly limited, and any one or more kinds of lubricants can be used. Among them, metal soaps such as zinc stearate and lithium stearate, carboxylic acids such as oleic acid, and amide waxes such as stearic acid amide, stearic acid bisamide, and ethylene bisstearamide are preferably used.

  The blending amount of the lubricant is not particularly limited. As a so-called external addition amount, 0.1 to 1.0% by mass− with respect to 100% by mass of the total amount of metal powder, alloy powder, and machinability improving powder. It is preferable to make the outer split. By setting the blending amount to be 0.1% by mass or more, the friction with the mold is further reduced, the extraction force is reduced, and the mold life can be further extended. Moreover, a molding density can be raised and the sintered compact density can further be improved by making the said compounding quantity into 1.0 mass%-less.

  In addition, each said powder used for this invention and the mixed powder for powder metallurgy have components other than the above, for example, industrially acceptable types and amounts of inevitable impurities, as long as the effects of the present invention are not hindered. It is allowed to be included.

[Method for producing mixed powder for powder metallurgy]
Below, the manufacturing method of the mixed powder for powder metallurgy is demonstrated. The mixed powder for powder metallurgy can be manufactured by blending the iron-based powder, alloy powder, machinability improving powder, and lubricant, and then mixing them. In that case, the said mixing can be performed once or twice or more using arbitrary mixers. The above-mentioned machinability improving powder does not necessarily need to be mixed all at once. After mixing and mixing only a part (primary mixing), the remaining part (secondary mixed material) is mixed and mixed (secondary Mixing). The lubricant is preferably added (mixed) in two steps.

  In the present invention, at least one lubricant among the lubricants is first mixed while being melted by heating to a temperature equal to or higher than the minimum melting point of various lubricants blended in the mixed powder, and then cooled and solidified. Then, it is preferable to add a secondary mixed material composed of the powder for improving machinability and the remaining powder of the lubricant and perform secondary mixing.

  Further, as the mixing means, any mixer can be used without particular limitation, but a high-speed bottom-stirring mixer, an inclined rotary pan mixer, a rotary mulberry mixer, and It is preferable to use a conical planetary screw type mixer or the like.

  In the production of the mixed powder for powder metallurgy according to the present invention, a part or all of the powder for alloying and / or the powder for improving machinability is fixed to the surface with a binder for part or all of the iron-based powder. Segregation prevention treatment can also be performed. As the segregation prevention treatment, the segregation prevention treatment described in Japanese Patent No. 3004800 can be used.

[Method for producing sintered body made of iron-based powder]
Below, the preferable manufacturing method of the sintered compact using the mixed powder for powder metallurgy of this invention is demonstrated. First, the mixed powder for powder metallurgy is filled into a mold and compression molded to obtain a molded body. As the compression molding method, any molding method such as pressing can be used. By using the mixed powder for powder metallurgy according to the present invention, the molding pressure can be increased to a high pressure of, for example, 294 MPa or more, and further, molding can be performed at room temperature. In order to ensure stable moldability, it is preferable to heat the mixed powder or the mold to an appropriate temperature or apply a lubricant to the mold.

  Moreover, when performing compression molding in a heating atmosphere, it is preferable that the temperature of mixed powder or a metal mold shall be less than 150 degreeC. This is because the mixed powder for powder metallurgy of the present invention is rich in compressibility, and in addition to exhibiting excellent moldability even at a temperature of less than 150 ° C., there is a concern about deterioration due to oxidation when the temperature exceeds 150 ° C.

  The molded body obtained by the above molding process is then subjected to a sintering process to become a sintered body made of iron-based powder. The sintering temperature is desirably about 70% of the melting point of the metal powder expressed in Celsius. In the present invention, since iron-based powder is used, the temperature of the sintering treatment is preferably set to 1000 ° C. or higher and 1300 ° C. or lower. By setting the temperature of the sintering treatment to 1000 ° C. or higher, the density of the sintered body can be further improved. Moreover, by setting the temperature of the sintering treatment to 1300 ° C. or lower, it is possible to prevent abnormal grain growth during the sintering and decrease the strength of the sintered body.

  The atmosphere of the sintering treatment is not particularly limited, but an inert gas atmosphere such as nitrogen or argon, an inert gas-hydrogen gas mixed atmosphere in which hydrogen is further mixed in the inert gas atmosphere, or an ammonia decomposition gas, RX A reducing atmosphere such as gas or natural gas is preferable.

  After the sintering treatment, a heat treatment such as a gas carburizing heat treatment or a carbonitriding treatment may be performed as necessary to obtain a product (sintered part or the like) having desired characteristics. Needless to say, the obtained sintered body can be subjected to processing such as cutting as needed to obtain a product of a predetermined size.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following examples at all.

As the iron-based powder, the iron-based powder shown in Table 1 (both average particle diameter: about 80 μm) was used. In addition, each average particle diameter described in a present Example is calculated | required using the laser diffraction method. In Table 1, A to G are as follows.
A: Atomized pure iron powder,
B: Reduced pure iron powder,
C: partially diffused alloyed steel powder obtained by alloying Cu by partially diffusing Cu as an alloy element on the iron powder surface
D: partially diffused alloyed steel powder in which Ni, Cu, and Mo are partially diffused and alloyed as an alloy element on the iron powder surface,
E: Prealloyed steel powder prealloyed with Ni and Mo as alloy elements (fully alloyed steel powder)
F: Prealloyed steel powder prealloyed with Mo as alloying element (fully alloyed steel powder), and G: Fully alloyed steel powder with prealloyed Mo as alloying element, and Mo partially alloyed Steel powder (hybrid alloy steel powder).

  The iron-based powder was mixed with an alloy powder, a machinability improving powder, and a lubricant, and primary mixing was performed using a high-speed bottom stirring mixer (conical planetary screw type mixer). Table 2 shows the types and amounts of the iron-based powder, alloy powder, machinability improving powder, and lubricant used. In the primary mixing, the mixture was heated to 140 ° C. while mixing and then cooled to 60 ° C. or less. The natural graphite powder blended as an alloy powder was a powder having an average particle diameter of 5 μm, and the copper powder was a powder having an average particle diameter of 20 μm.

The symbols for the machinability improving powder in Table 2 mean the following powders.
(First powder for improving machinability)
B: Enstatite B: Talc C: Kaolin D: Mica E: MgO
F: SiO ₂
G: Sodium silicate H: Sodium sulfate Li: Lithium sulfate Nu: Potassium sulfate Lu: Barium sulfate (second powder for improving machinability)
a: Chromium oxide b: Titanium oxide (third powder for improving machinability)
x: Gehlenite (2CaO · Al ₂ O ₃ · SiO ₂ )
y: Anolite (CaO · Al ₂ O ₃ · 2SiO ₂ )

Moreover, the symbol of the lubricant in Table 2 means the following lubricant, respectively.
(lubricant)
ZN: Zinc stearate Li: Lithium stearate BS: Ethylene bisstearamide AM: Stearic acid monoamide AO: Oleic acid

  After the primary mixing, further mix the secondary mixing material consisting of the types and blending amounts of powders shown in Table 2 and a lubricant, and use the same high-speed bottom agitating mixer (conical) as used in the primary mixing. Secondary mixing was performed using a planetary screw type mixer. The rotation speed of the mixer in the secondary mixing was 1000 rpm, and the stirring time was 1 minute. After the secondary mixing, the mixed powder was discharged from the mixer. In some examples, only the lubricant was used as the secondary mixture.

  In Table 2, the compounding amount of the machinability improving powder is expressed in mass% with respect to the total amount of the iron-base powder, the alloy powder, and the machinability improving powder, and the compounding amount of the lubricant is externally added. It was expressed as mass% -outer percentage relative to 100 mass% of the total amount of the base powder, alloy powder, and machinability improving powder.

  Through the above steps, a mixed powder was obtained in which the iron-based powder, the alloy powder, and the machinability improving powder were uniformly mixed without causing segregation.

  Then, the obtained mixed powder was filled in a mold (two types for lathe cutting test and drill cutting test) and compression molded at a pressure of 590 MPa to obtain a molded body. Furthermore, the compact was subjected to a sintering treatment of 1130 ° C. × 20 min in an RX gas atmosphere to obtain a sintered compact. About each of the obtained sintered compact, the lathe cutting test, the drill cutting test, and the lathe cutting test (end surface) were implemented with the method described below. The obtained results are shown in Table 3.

(1) Lathe cutting test Three of the obtained sintered bodies (ring shape: outer diameter 60 mm x inner diameter 20 mm x length 20 mm) were stacked and the side surfaces were cut using a lathe. Cutting conditions were as follows: cutting speed: 100 m / min or 200 m / min, feed rate: 0.1 mm / turn, cutting depth: 0.5 mm, cutting distance: 1000 m, using a cermet lathe cutting tool The wear width of the flank of the cutting tool was measured. Here, the tool life is defined as a wear amount of approximately 0.25 mm, and when this tool life is reached at a cutting distance of less than 1000 m, it is described as less than 1000 m . Therefore, it is evaluated that the smaller the wear width of the flank of the cutting tool, the better the machinability of the sintered body.

(2) Drill cutting test To the obtained sintered body (disk shape: outer diameter 60 mm x thickness 10 mm), a high-speed steel drill (diameter: 2.6 mm), rotation speed: 5,000 rpm, feed rate: A through hole was drilled under the condition of 750 mm / min, and at that time, a thrust component was measured as a cutting resistance at the time of drilling using a cutting dynamometer. It is evaluated that the smaller the thrust component, the better the machinability of the sintered body.

(3) Lathe cutting test (end face)
The end surface of the obtained sintered body (ring shape: outer diameter 60 mm × inner diameter 20 mm × length 20 mm) was cut using a lathe. Cutting was performed using a boron nitride lathe cutting tool under conditions of cutting speed: 250 m / min, feed rate: 0.07 mm / turn, cutting depth: 0.2 mm, cutting distance: 5000 m. The surface roughness of the end face was measured. It is evaluated that the smaller the surface roughness, the better the machinability of the sintered body.

  As shown in Table 3, since all of the inventive examples according to the present invention show the result that the wear width of the cutting tool flank is small, it is understood that the lathe machinability is excellent. In addition, since the thrust component at the time of drilling shows a low value, it can be seen that the sintered body is excellent in drill machinability. Moreover, since the surface roughness of the end surface shows a small value, it is excellent in machinability from this viewpoint. On the other hand, the comparative example outside the scope of the present invention has a particularly poor surface roughness.

Claims (11)

An iron-based powder, an alloy powder, a machinability improving powder, and a powder mixture for powder metallurgy containing a lubricant,
The machinability improving powder is
Enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO), alkali silicate powder, alkali metal sulfate powder, and alkaline earth A first machinability improving powder that is at least one selected from the group consisting of metal sulfate powders;
A second machinability improving powder that is at least one selected from the group consisting of chromium oxide powder and titanium oxide powder;
A third machinability improving powder which is an oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ ;
Powder metallurgy mixing in which the blending amount of the machinability improving powder is 0.01 to 1.0% by mass% with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder. powder.   2. The mixed powder for powder metallurgy according to claim 1, wherein a blending amount of the first machinability improving powder is 10% to 80% by mass% with respect to a total amount of the machinability improving powder.   The alkali metal of the alkali metal sulfate powder is at least one selected from the group consisting of Li, Na, and K, and the alkaline earth metal of the alkaline earth metal sulfate powder is Mg, Ca, The mixed powder for powder metallurgy according to claim 1 or 2, which is at least one selected from the group consisting of Sr and Ba. 4. The powder according to claim 1, wherein the third machinability improving powder is a CaO—Al ₂ O ₃ —SiO ₂ composite oxide powder having at least one of an anolsite phase and a gehlenite phase. The mixed powder for powder metallurgy described in 1.   The mixed powder for powder metallurgy according to any one of claims 1 to 4, wherein an average particle size of the third machinability improving powder is 50 µm or less. A method for producing a mixed powder for powder metallurgy comprising mixing an iron-based powder, an alloy powder, a machinability improving powder, and a lubricant, and then mixing them into a mixed powder,
The machinability improving powder is
Enstatite powder, talc powder, kaolin powder, mica powder, magnesium oxide (MgO) powder, mixed powder of silica (SiO ₂ ) and magnesium oxide (MgO), alkali silicate powder, alkali metal sulfate powder, and alkaline earth A first machinability improving powder that is at least one selected from the group consisting of metal sulfate powder, and a second machinability improvement that is at least one selected from the group consisting of chromium oxide powder and titanium oxide powder Powder for
A third machinability improving powder which is an oxide powder containing CaO, Al ₂ O ₃ , and SiO ₂ ;
The blending amount of the machinability improving powder is 0.01% to 1.0% by mass% with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder,
Further, the mixing
The iron-base powder and the alloy powder are heated by adding a part or all of the machinability improving powder and a part of the lubricant, and melting at least one of the added lubricants. First mixing to be cooled and solidified after mixing,
A method for producing a mixed powder for powder metallurgy, which is performed by secondary mixing in which the machinability improving powder and the remainder of the lubricant are added and mixed.   The method for producing a mixed powder for powder metallurgy according to claim 6, wherein the blending amount of the first machinability improving powder is 10% to 80% by mass% with respect to the total amount of the machinability improving powder.   The alkali metal of the alkali metal sulfate powder is at least one selected from the group consisting of Li, Na, and K, and the alkaline earth metal of the alkaline earth metal sulfate powder is Mg, Ca, Sr, The method for producing a powder mixture for powder metallurgy according to claim 6 or 7, wherein at least one selected from the group consisting of Ba and Ba is used. The third powder for improving machinability is a powder of CaO—Al ₂ O ₃ —SiO ₂ based composite oxide having at least one of an anolsite phase and a gehlenite phase. A method for producing a mixed powder for powder metallurgy described in 1.   The method for producing a powder mixture for powder metallurgy according to any one of claims 6 to 9, wherein the average particle size of the third machinability improving powder is 50 µm or less.   A sintered body made of iron-based powder using the mixed powder for powder metallurgy according to any one of claims 1 to 5.