JP2007169713A - Iron-based powdery mixture for powder metallurgy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an iron-based powdery mixture with which machinability of a sintered compact can be improved without bringing about deterioration in its mechanical properties. <P>SOLUTION: The iron-based powdery mixture is obtained by mixing iron-based powder with powder for alloy, powder for improving machinability and further, a lubricant. As the powder for improving machinability, manganese sulfide powder with the average particle diameter of 1 to 60 μm and/or calcium fluoride powder with the average particle diameter of 1 to 60 μm is used. The powder for improving machinability is comprised by 0.1 to 1.5 mass% to the total content of the iron-based powder, the powder for alloy and the powder for improving machinability. Further, the powder for improving machinability has a grain size distribution similar to the grain size distribution of holes in an iron-based sintered compact obtained by subjecting an iron-based powdery mixture mixed with iron-based powder, powder for alloy and a lubricant to pressure-compacting and sintering. In this way, the holes in the sintered compact can be reduced, intermittent impact to a tool is reduced, and the service life of the tool is prolonged. Further, a part or the whole of the iron-base powder can be used as the iron-based powder applying a segregation-preventive treatment, in which the powder for alloy and/or the powder for improving the machinability, are stuck on the surface with a binder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an iron-based mixed powder for powder metallurgy, and more particularly to an iron-based mixed powder for powder metallurgy that can improve the machinability of a sintered body and obtain good surface properties after cutting.

Advances in powder metallurgy technology make it possible to manufacture parts with complex shapes with high dimensional accuracy in a near net shape, and products using powder metallurgy technology are used in various fields.
Iron-based powder metallurgy products are obtained by filling a die with iron-based powder mixed with iron-based powder, alloy powder such as copper powder and graphite powder, and lubricant such as zinc stearate and lithium stearate. Then, it is pressure-molded and then subjected to a sintering treatment to obtain a sintered body, which is cut as necessary to obtain a product. The sintered body thus produced has a high content ratio of pores, and has a higher cutting resistance than a metal material (melted material) obtained by a melting method. For this reason, for the purpose of improving the machinability of sintered bodies, various powders such as Pb, Se, Te, etc. have been added to the iron-based powder, or alloyed with iron powder or iron-based powder. Has been done.

However, since Pb has a low melting point of 330 ° C., it has a problem that it melts during the sintering process, and does not dissolve in iron and is difficult to uniformly disperse in the matrix. Moreover, since Se and Te embrittle the sintered body, there was a problem that the mechanical properties of the sintered body deteriorated remarkably. In addition to these powders, it has been proposed to add various powders to improve machinability.
For example, Patent Document 1 proposes an iron powder mixture in which 0.05 to 5% by weight of manganese sulfide of 10 μm or less is mixed with iron powder. According to the technique described in Patent Document 1, the machinability of the sintered material can be improved without causing dimensional change or strength change.

Patent Document 2 includes atomized iron containing S: 0.04 to 0.2 wt%, Mn: 0.05 to 0.5 wt%, Si: 0.01 to 0.1 wt%, and 5% or more of the number of MnS particles containing oxygen. Powder has been proposed. It is said that a powder metallurgy product having excellent machinability can be manufactured by using this iron powder as a sintered body.
Patent Document 3 discloses an iron-base powder containing an alloy powder containing graphite powder and a lubricant, and an alkaline earth metal fluoride powder as an iron-base powder and alloy powder as a machinability improving powder. And an iron-based mixed powder for powder metallurgy containing 0.1 to 0.7% by mass with respect to the total amount of the powder for improving machinability, and containing the graphite powder and the powder for improving machinability fixed to the surface of the iron-based powder with a binder. Proposed. According to the technique described in Patent Document 3, the machinability can be improved without causing deterioration of mechanical properties of the sintered body.

Patent Document 4 discloses a free-cutting metal material manufactured by a powder metallurgy method, in which barium sulfate or barium sulfide is added alone or in a total amount of 0.3 to 3.0% by weight as iron or iron-based alloy as a powder for improving machinability. Has been proposed.
Patent Document 5 discloses a powder made of calcium fluoride and barium fluoride, preferably a powder made from a melt thereof, as an additive for improving the machinability of sintered products in an iron-based powder composition. An iron-based powder composition is proposed that is combined with one or more conventional machinability improvers that contain ˜1.0% by weight and further comprises MnS and MoS ₂ .

  In the techniques described in Patent Documents 1 to 5, when the cutting ability improving powder is dispersed in the sintered body as a chipping promoter, the cutting ability improving powder (particles) is dispersed when the cutting site is plastically deformed during cutting. It becomes a stress concentration point and refines the chips. By reducing the size of the chips, the contact area between the cutting tool and the chips is reduced, and tool wear is prevented or reduced by reducing the frictional resistance. However, these chipping promoting materials do not have a function to protect the tool surface, and the tool surface and the work material are in direct contact with each other during cutting, and heat is generated due to friction in the atmosphere, and the tool surface is oxidized. There is a problem that intermittent impact is applied to the tool due to the voids inside the sintered body, thereby causing a microcrack inside the tool, deteriorating the tool material, and the desired machinability cannot be improved.

For example, Patent Document 6 discloses a CaO—Al ₂ O ₃ —SiO ₂ composite oxide having an average particle size of 50 μm or less and mainly having iron powder and having an anolite phase and / or a gehlenite phase. An iron-based mixed powder for powder metallurgy containing 0.02 to 0.3% by weight of a powder has been proposed. In the technique described in Patent Document 6, ceramics having a low melting point are dispersed in advance in a work material, and ceramic particles exposed to the processing surface during cutting adhere to the tool surface to form a tool protection film (so-called bellage layer). In addition to preventing material deterioration of the tool and improving machinability, it is possible to reduce dimensional changes during sintering.
JP-A-61-147801 Japanese Patent No. 3443911 JP 2002-155301 A Japanese Patent Publication No.46-39564 Japanese Patent No. 3073526 JP-A-9-279204

However, in the technique described in Patent Document 6, it is necessary to make the CaO—Al ₂ O ₃ —SiO ₂ composite oxide a powder with few impurities and with a limited particle size. If a powder with few impurities and a limited particle size is not used, there is a problem that powder characteristics and sintered body characteristics are deteriorated. Further, depending on cutting conditions, frictional heat generation between the tool and the work material may be insufficient, the low melting point ceramic may not be softened, and a tool protective film may not be formed, and a desired machinability improvement cannot be obtained. There was a problem.

  It is an object of the present invention to provide an iron-based mixed powder for powder metallurgy that can advantageously solve the problems of the prior art and improve the machinability of a sintered body without deteriorating mechanical properties.

  In order to achieve the above-mentioned problems, the present inventors diligently studied the effects of the type and particle size of the machinability improving powder on further machinability improvement. As a result, in order to improve the machinability, the present inventors have reduced the number of vacancies in the sintered body and alleviated the intermittent impact caused by the collision between the free surface that forms vacancies during cutting and the tool. However, it is important to extend the tool life by suppressing the wear on the tool surface and the generation of micro cracks inside the tool. For this purpose, it is efficient to fill the holes with particles (powder) for improving machinability. I realized that Then, as the powder for improving machinability, manganese sulfide powder having an average particle diameter of 1 to 60 μm and calcium fluoride powder having an average particle diameter of 1 to 60 μm are used singly or in combination, whereby the machinability of the sintered body is obtained. Has been found to be significantly improved. In particular, it was found that coarse pores exceeding 30 μm can be filled, and the strong intermittent impact generated during cutting can be remarkably reduced.

This is because when the average particle size of the machinability improving powder is in the range of 1 to 60 μm, the pores in the sintered body are easily filled with the machinability improving powder particles, and the vacancies in the sintered body are substantially The present inventors believe that this is because the intermittent impact generated during cutting is reduced and the intermittent impact is reduced.
In addition, the present inventors have further studied that the particle size distribution of the machinability improving powder particles is a mixture of iron-based powder, alloy powder, and lubricant that does not include machinability improving powder. Efficient filling of pores with powder particles for improving machinability by adjusting the particle size distribution of the pores generated in the iron-based sintered body obtained by pressing and sintering the base mixed powder I found out that I can do it.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) An iron-based mixed powder obtained by mixing an iron-based powder, an alloy powder, a machinability improving powder, and a lubricant, wherein the machinability improving powder has an average particle size: 1 to 60 μm manganese sulfide powder and / or calcium fluoride powder having an average particle size of 1 to 60 μm, and the total of the machinability improving powder and the iron-base powder, alloy powder and machinability improving powder Iron-based mixed powder for powder metallurgy, characterized by containing 0.1 to 1.5% by mass relative to the amount.

(2) In (1), the powder for improving machinability is manganese sulfide powder having an average particle diameter of 1 to 10 μm and calcium fluoride powder having an average particle diameter of 10 to 60 μm, and the calcium fluoride powder is machinable. An iron-based mixed powder for powder metallurgy, characterized by containing 10 to 80% by mass% based on the total amount of powder for improvement.
(3) In (1) or (2), a part or all of the iron-based powder is formed by fixing the alloy powder and / or the machinability improving powder to a surface with a binder. Iron-based mixed powder for powder metallurgy.

(4) In any one of (1) to (3), the machinability improving powder is pressure-molded and sintered with an iron-based mixed powder obtained by mixing an iron-based powder, an alloy powder, and a lubricant. An iron-based mixed powder for powder metallurgy, characterized by being a machinability improving powder having a particle size distribution similar to the pore size distribution of the iron-based sintered body obtained as described above.
(5) An iron-based sintered body obtained by press-molding and sintering the iron-based mixed powder for powder metallurgy according to any one of (1) to (4).

  According to the present invention, it is possible to improve the machinability of a sintered body without deteriorating mechanical properties, and to remarkably improve the productivity of a sintered member that requires cutting, which is remarkable in the industry. The effect of.

  The iron-based mixed powder for powder metallurgy according to the present invention is an iron-based mixed powder obtained by mixing an iron-based powder, an alloy powder, a machinability improving powder, and a lubricant. In the present invention, manganese sulfide powder and / or calcium fluoride powder is used as the machinability improving powder. Both manganese sulfide powder and calcium fluoride powder become stress concentration points when cutting sintered bodies, miniaturize chips, reduce the contact surface between the cutting tool and chips, reduce frictional resistance, and improve machinability. Has the effect of Furthermore, depending on the particle size distribution of pores in the sintered body (pore size distribution), two types of particles with different particle size distributions are appropriately mixed with iron-based powder to form a mixed powder, which is molded and sintered Then, the void | hole in the obtained sintered compact is filled, and it also has the effect that a void | hole reduces substantially.

  In order to acquire such an effect, in this invention, the average particle diameter of manganese sulfide powder and a calcium fluoride powder is limited to the range of 1-60 micrometers. As a result, voids in the sintered body are substantially reduced, intermittent impact during cutting can be mitigated, tool surface wear and the occurrence of fine cracks inside the tool are suppressed, and tool life is increased. Can do. If the average particle size of the machinability improving powder is less than 1 μm, the particles are too fine to fill the pores sufficiently. On the other hand, if it exceeds 60 μm, the particles are too large to fill the pores, and the mechanical strength of the sintered body is reduced. For this reason, the average particle diameter of manganese sulfide powder and calcium fluoride powder was limited to a range of 1 to 60 μm. Thereby, coarse pores exceeding 30 μm can be filled.

  More preferably, the particle size distribution of the machinability improving powder is obtained by pressing and sintering an iron-based mixed powder obtained by mixing an iron-based powder, an alloy powder, and a lubricant. The particle size distribution is similar to the particle size distribution of the body pores (pore size distribution). Accordingly, the machinability improving powder can be efficiently filled into the pores in the sintered body, and the voids in the sintered body can be reduced substantially efficiently.

Here, the particle size of the powder for improving machinability is a value measured by a microtrack method using a laser, and the average particle size is a 50% cumulative transmitted particle size (d ₅₀ ). To do. In addition, regarding the distribution of pore diameters in the sintered body, an optical micrograph of the cross section of the sintered body is converted into an electronic image by a scanner, the brightness of the image is binarized into a bright part and a dark part, and the ratio of the number of pixels in the dark part is obtained. Was determined by In order to obtain a machinability improving powder having a particle size distribution similar to the pore size distribution, classification is performed using a sieve, and the particle size distribution is similar to the pore size distribution.

In the present invention, the total amount of the machinability improving powder having the average particle size as described above or the particle size distribution as described above, and the mass% with respect to the total amount of the iron base powder, the alloy powder and the machinability improving powder. 0.1 to 1.5%.
When the total content of the machinability improving powder is less than 0.1% by mass, no significant improvement in machinability is observed. On the other hand, when it exceeds 1.5% by mass, the compressibility and the crushing strength are remarkably lowered, which is not preferable. If the content of the machinability improving powder is within this range, the dimensional change rate of the sintered body is small, and there is no problem in dimensional accuracy. For this reason, the total content of the machinability improving powder is 0.1 to 1.5 mass% with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder. In addition, Preferably it is 0.3-1.0 mass% with respect to the total amount of iron-base powder, alloy powder, and machinability improvement powder.

Further, the machinability improving powder is made of manganese sulfide powder having an average particle diameter of 1 to 10 μm and calcium fluoride powder having an average particle diameter of 10 to 60 μm, and the calcium fluoride powder is in mass% with respect to the total amount of the machinability improving powder. It is preferable to blend 10 to 80%. As a result, an iron-based sintered body with improved machinability having a sintered density of 6.0 to 7.3 Mg / m ³ can be more easily produced.
The particle size distribution of the machinability improving powder having an effect of improving the machinability is preferably selected as appropriate so that the particle size distribution is similar to the distribution of pore diameters according to the density of the assumed sintered part. It is desirable to adjust the particle size distribution of the machinability improving powder by adjusting the mixing ratio of two kinds of powders having different average particle diameters. In the present invention, two kinds of powders of manganese sulfide powder and calcium fluoride powder are used as the machinability improving powder. The average particle diameter of these powders is adjusted within the range of 1-60 μm average particle diameter. Should be made larger and the other smaller.

  Since the hardness of manganese sulfide particles is higher than that of calcium fluoride particles, it is finely pulverized in advance before mixing with iron-based powder, and the average particle size of manganese sulfide powder is relative to that of calcium fluoride powder. Therefore, it is desirable that the average particle size of calcium fluoride powder be 10 to 60 μm. This is because if the average particle size of the manganese sulfide powder is relatively large, hard coarse particles are arranged in the pores in the sintered body, which may impact the tool during cutting and cause the tool to chip. This is because there is not.

Moreover, if the blending amount of the calcium fluoride powder is less than 10% by mass with respect to the total amount of the machinability improving powder, the pores in the sintered body cannot be sufficiently filled. On the other hand, if it exceeds 80%, coarse calcium fluoride particles more than the pore size distribution are present in the sintered body, leading to a decrease in the mechanical strength of the sintered body.
As the iron-based powder used in the present invention, pure iron powder such as atomized iron powder and reduced powder can be preferably used. Moreover, it can replace with iron powder and the prealloyed steel powder which alloyed the alloy element previously, or the partial alloyed steel powder by which the alloy element was partially alloyed to iron powder can use suitably. In addition, there is no problem even if these are mixed and used.

The alloy powder used in the present invention can be exemplified by graphite powder, copper powder, and the like, and it is preferable that the alloy powder is appropriately selected and contained in a predetermined amount according to desired product characteristics.
Moreover, as the lubricant contained in the iron-based mixed powder of the present invention, metal soaps such as zinc stearate and lithium stearate, or waxes are suitable. The blending amount of the lubricant is not particularly limited in the present invention, but is preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the total amount of the iron-based powder, the alloy powder, and the machinability improving powder. When the blending amount of the lubricant is less than 0.2 parts by mass, the friction with the mold increases, the extraction force increases, and the mold life decreases. On the other hand, if it exceeds 1.5 parts by mass, the molding density is lowered and the sintered body density is lowered.

Below, the preferable manufacturing method of the iron-based mixed powder of this invention is demonstrated.
A predetermined amount of alloying powder, machinability improving powder and lubricant are blended with the above iron-based powder, and using a commonly known mixer such as a Henshur mixer, a V blender, a double cone blender, etc. at once or It is preferable to divide the mixture into two or more times to obtain an iron-based mixed powder. It should be noted that a part or all of the iron-based powder is used, and an iron-based powder subjected to segregation prevention treatment for fixing a part or all of the alloy powder and / or the machinability improving powder to the surface using a binder. It may be iron-based mixed powder. Thereby, it becomes an iron-based mixed powder with less segregation and better fluidity.

  As the segregation preventing treatment, the method described in Japanese Patent No. 3004800 can be used. That is, the powder for alloying and / or the machinability improving powder is mixed with the iron-base powder together with the binder, and then heated to 10 ° C. or more, preferably 15 ° C. or more from the lowest value of the melting point of the binder. preferable. In addition, when two or more types of binders are used, the temperature is preferably set to 10 ° C. or more from the lowest value among the melting points of these binders and to the maximum value or less among the melting points of these binders. By this heating, at least one kind of binder is melted and then cooled and solidified to fix the alloy powder and / or the machinability improving powder on the surface of the iron-based powder. When the temperature is lower than the above lower limit temperature, the binding function of the binding material is not exhibited. When the temperature exceeds the above upper limit temperature, the bonding function is degraded due to thermal decomposition or the like, and the hopper discharging performance is degraded.

  The binder is preferably higher fatty acid, higher fatty acid amide or wax. As the higher fatty acid or higher fatty acid amide, one or two selected from stearic acid, oleic acid amide, stearic acid amide, ethylene bis stearic acid amide, and a melt mixture of stearic acid amide and ethylene bis stearic acid amide It is preferable to use a heated melt of one or more selected from oleic acid, spindle oil, and turbine oil and zinc stearate. In this invention, it is preferable that content of a binder shall be 0.1-1.0 mass part with respect to 100 mass parts of total amounts of iron-base powder, alloy powder, and machinability improvement particle powder. If the amount is less than 0.1 parts by mass, the effect of preventing segregation of the alloy powder is not observed. On the other hand, when it contains exceeding 1.0 mass part, the filling property of iron-based mixed powder will fall.

In addition, it cannot be overemphasized that the iron-based mixed powder of this invention is not limited to an above-described manufacturing method.
The iron-based mixed powder of the present invention can be used for the production of machine parts by applying a general method in powder metallurgy. Specifically, the iron-based mixed powder of the present invention is filled in a mold and compression-molded, and then sizing and sintering as necessary to obtain a sintered body. After sintering, heat treatment such as carburizing quenching, bright quenching, and induction quenching is performed to obtain a product (machine part, etc.). Needless to say, processing such as cutting is performed as needed to obtain a product with a predetermined size.

Example 1
Atomized pure iron powder A (brand: JIP 260A (manufactured by JFE Steel Co., Ltd.)) 100 kg as iron-based powder, graphite powder (average particle size: 4 μm) in the amount shown in Table 1 as alloy powder, and machinability The types, average particle diameters, and blending amounts of the machinability improving powder shown in Table 1 as the improvement powder were blended together with a lubricant, charged into a V blender, and uniformly mixed to obtain an iron-based mixed powder. The blending amount of the alloy powder and the machinability improving powder was set to mass% with respect to the total amount of the iron-base powder, the alloy powder, and the machinability improving powder. The lubricant was zinc stearate (average particle size: 20 μm). In some iron-based mixed powders, the machinability improving powder was not blended as a comparative example.

These iron-based mixed powders were charged into a mold and compression-molded to obtain molded bodies (ring-shaped test pieces A and B, tablet-type test pieces C). Ring-shaped specimen A (outer diameter 35mmφ x inner diameter 14mmφ x height 10mm) is for crushing test, ring-shaped specimen B (outer diameter 60mmφ x inner diameter 20mmφ x height 25mm) is for turning test, tablet type specimen C (outer diameter 60 mmφ × height 10 mm) was used for drill cutting test and hardness test. The density of the compact was fixed at 6.6 Mg / m ² . The density was measured by the Archimedes method.

Subsequently, these compacts were sintered at 1150 ° C. × 20 min using a mesh belt furnace in a 5 volume% H ₂ -nitrogen gas atmosphere to obtain sintered bodies. About the obtained sintered compact, the crushing test (Ring Rupture), the turning test, the drill cutting test, and the hardness test were implemented.
The crushing test was performed using the sintered body of the ring-shaped test piece A in accordance with the provisions of JIS Z 2507, and the crushing strength was obtained.

  In the turning test, three sintered bodies of the ring-shaped specimen B were stacked to form a cylinder with a length of 75 mm, and the side surface was cut with a carbide (HT105T) bite to wear the side flank. Turning until the depth reached 0.5mm. Turning conditions were a cutting speed: 92 m / min, a feed amount: 0.03 mm / rev, and a cutting depth: 0.89 mm. In addition, the wear form of a side flank is typically shown in FIG. After the turning test, the surface roughness Rz of the test piece cutting surface was measured on the cutting surface of the test piece using a contact-type surface roughness meter in accordance with the provisions of JIS B 0601-2001.

  The drill cutting test uses a sintered compact of tablet-type test piece C, and the plane of test piece C is a carbide (HT105T, Mitsubishi Materials HT105T) drill with an outer diameter of 3.0 mm, rotating speed: 800 rpm, feed amount : Drill cutting was performed at 0.02 mm / rev. The wear depth (flank wear depth) of the outer periphery of the drill when the 200-hole drilling was completed was measured. FIG. 2 shows the state of wear on the outer periphery of the drill. In addition, torque and its vibration width were measured as cutting resistance when machining 200 holes. The torque and its vibration width were determined by setting the test piece (work material) on a cutting dynamometer (Keithler) and determining the change over time in the torque during drill cutting as shown in FIG. Torque was obtained from the average value of the torque, and the vibration width of the torque was obtained from the vibration width on the rectangular wave.

The hardness test was performed using the sintered body of the tablet-type test piece C in accordance with the provisions of JIS Z 2245, and the Rockwell (B scale) hardness HRB was obtained.
The obtained results are shown in Table 2.

本発明例はいずれも、焼結体の圧壊強さが高く大きな強度低下がない焼結体となっている。また、本発明例は、施削後の試験片の表面粗さＲｚが低減し、切削加工面の外観が改善されており、旋削性に優れた焼結体となっている。また、本発明例は、ドリル摩耗量が少なく、切削抵抗が小さく、さらに切削抵抗の振動幅が小さい焼結体となっている。切削抵抗の振動幅は、断続的衝撃の発生に対応し、切削抵抗の振動幅が小さいことは、断続的衝撃の主たる原因となる焼結体内部の空孔が低減したことによるものと考えられる。このように、本発明例は鉄基混合粉として優れた特性を有する鉄基混合粉である。一方、本発明の範囲を外れる比較例は、圧壊強さが低いか、施削後の試験片の表面粗さが粗いか、切削抵抗が高いか、あるいは切削抵抗の振動が大きくなり、旋削性、切削性が低下している。

In all of the examples of the present invention, the sintered body has a high crushing strength and does not have a significant decrease in strength. In addition, the present invention example is a sintered body having a reduced surface roughness Rz of the test piece after cutting, an improved appearance of the cut surface, and excellent turning properties. Moreover, the example of the present invention is a sintered body with a small drill wear amount, a small cutting resistance, and a small vibration width of the cutting resistance. The vibration width of the cutting resistance corresponds to the occurrence of intermittent impact, and the small vibration width of the cutting resistance is thought to be due to the reduction of voids inside the sintered body, which is the main cause of intermittent impact. . Thus, the example of the present invention is an iron-based mixed powder having excellent characteristics as an iron-based mixed powder. On the other hand, the comparative examples that are out of the scope of the present invention have low crushing strength, rough surface roughness of the test piece after cutting, high cutting resistance, or large vibration of cutting resistance, and turning performance. The machinability is degraded.

It is explanatory drawing which shows typically the wear form of the cutting tool side flank. It is explanatory drawing which shows typically the abrasion condition of a drill outer peripheral part. It is a graph which shows an example of the time-dependent change of the torque at the time of drill cutting.

Claims (5)

  An iron-based mixed powder obtained by mixing an iron-based powder, an alloy powder, a machinability improving powder, and a lubricant, and the machinability improving powder has an average particle size of 1 to 60 μm. Manganese sulfide powder and / or calcium fluoride powder having an average particle size of 1 to 60 μm, and the total amount of the machinability improving powder with respect to the total amount of the iron-based powder, the alloy powder, and the machinability improving powder An iron-based mixed powder for powder metallurgy, characterized by containing 0.1 to 1.5% by weight.   The powder for improving machinability is a manganese sulfide powder having an average particle size of 1 to 10 μm and a calcium fluoride powder having an average particle size of 10 to 60 μm, and the calcium fluoride powder is in mass% with respect to the total amount of the powder for improving machinability. The iron-based mixed powder for powder metallurgy according to claim 1, wherein 10 to 80% is blended.   3. The powder metallurgy according to claim 1, wherein a part or all of the iron-based powder is formed by bonding the alloy powder and / or the machinability improving powder to a surface with a binder. 4. Iron-based mixed powder.   The pore size of the iron-based sintered body obtained by press-molding and sintering the iron-based mixed powder obtained by mixing the iron-based powder, the alloy powder, and the lubricant with the machinability improving powder. The iron-based mixed powder for powder metallurgy according to any one of claims 1 to 3, wherein the powder is a machinability improving powder having a particle size distribution similar to the distribution.   An iron-based sintered body obtained by press-molding and further sintering the iron-based mixed powder for powder metallurgy according to any one of claims 1 to 4.

Images