JP2003034803A - Iron-base mixed powder for powder metallurgy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron-base mixed powder which improves machinability of a sintered compact without generating degradation of the mechanical properties. SOLUTION: This iron-base mixed powder includes calcium phosphate and/or hydroxyapatite, or further calcium fluoride, of 0.02-0.39 mass% in total in Ca terms, as a powder for improving machinability, against the total quantity of an iron-base powder, a powder for an alloy and the powder for improving machinability, when being manufactured by means of mixing the powder for the alloy, the powder for improving machinability and a lubricant, with the iron-base powder. The ratio of a calcium fluoride content to a total content of calcium phosphate and/or hydroxyapatite is preferably 0.8 or more, in order to improve the machinability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based mixed powder for powder metallurgy, and in particular, it is possible to prevent S from contaminating a heating element of a sintering furnace, a conveyor belt, etc. The present invention relates to an iron-based mixed powder for powder metallurgy that enables improvement.

[0002]

2. Description of the Related Art Advances in powder metallurgy have made it possible to manufacture parts with high dimensional accuracy and complicated shapes in a near net shape. Iron-based powder metallurgy products are iron-based powders,
Alloy powder such as copper powder and graphite powder, zinc stearate,
After filling an iron-based mixed powder mixed with a lubricant such as lithium stearate into a mold, press-molding it, then subjecting it to a sintering process to obtain a sintered body, and then cutting if necessary. , As a product. The sintered body produced in this manner has a high content ratio of voids, and has a higher cutting resistance than the metal material produced by the melting method. Therefore, conventionally, various powders such as Pb, Se, Te, MnS, and S have been added to the iron-based mixed powder or alloyed with the iron powder to improve the machinability of the sintered body. Has been done. However, since Pb has a low melting point of 330 ° C, it melts during the sintering process, and there is a problem that it is difficult to uniformly disperse it in the matrix because it does not form a solid solution in iron. However, there is a problem that the mechanical properties of the sintered body are significantly deteriorated. In addition to these powders, it has been proposed to use various powders as the machinability improving powder.

For example, Japanese Patent Publication No. 46-39654 discloses a free-cutting metal material produced by powder metallurgy in which BaSO ₄ and BaS are added alone or in combination to iron or an iron-based alloy. ing. It is said that this technology improves machinability such as cutting by adding BaSO ₄ and BaS alone or in combination. Further, Japanese Patent Laid-Open No. 52-16684 proposes a method for producing a free-cutting sintered steel in which a mixed powder obtained by adding calcium sulfide CaS or calcium sulfate CaSO ₄ to an iron-based raw material powder is compression-molded and then sintered. Has been done.

However, as the machinability improving powder,
When S or compounds containing S such as MnS are mixed, H ₂ S generated during sintering contaminates the refractory in the sintering furnace, the mesh belt for transportation, the heating element, etc. and shortens the life of these parts. There was a problem. In addition, there is also a problem that the appearance of the sintered body is poor, and it is avoided to mix the S-containing compound powder with the iron-based mixed powder as the machinability improving powder. Also, if BaS, CaS, etc. remain in the sintered body, BaS
However, there is also a problem that the sintered body is easily rusted due to the hygroscopicity of CaS.

To solve such a problem, for example, Japanese Patent Laid-Open No. 57-57
-198201 discloses that Ca: 0.001 to 0.10%, O: 0.05 to
Disclosed is a steel powder for sintering which gives a sintered body containing 1.0% and having good machinability. However, JP-A-57-19820
The sintered body manufactured with the sintering powder described in Japanese Patent No. 1 does not contain S, so that there is no problem of contamination of the sintering furnace, but since calcium oxide has hygroscopicity, the powder flow There is a problem in that the molding deteriorates and the molding becomes unstable.

In addition, in Japanese Patent Publication No. 7-507358, an iron-based powder composition contains 0.1 to 0.6% by weight of calcium fluoride CaF ₂
There has been proposed a powder composition containing the above to improve machinability. However, the impurities of calcium fluoride CaF ₂ are
Affects dimensional changes and mechanical properties. Therefore, it is necessary to use high-purity calcium fluoride, which is a cost problem.

Further, Japanese Patent Laid-Open No. 9-279204 discloses a CaO-Al ₂ O ₃ -SiO ₂ -based composite oxide mainly composed of iron powder and having an anorthite phase and / or a grenenite phase and having an average particle size of 50 μm or less. Of the iron-based mixed powder for powder metallurgy containing 0.02 to 0.3% by weight of the above powder. However, there is a problem that unless the powder of the CaO-Al ₂ O ₃ -SiO ₂ composite oxide containing a small amount of impurities and having a limited particle size is used, the powder characteristics and the sintered body characteristics are deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides an iron-based mixed powder capable of improving the machinability without deteriorating the mechanical properties of the sintered body. To aim.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly studied a machinability improving powder capable of improving machinability without causing deterioration of mechanical properties of a sintered body. as a result,
It has been found that calcium phosphate is effective for this purpose. First, the basic experimental results conducted by the present inventors will be described.

Water atomized iron powder as an iron-based powder, graphite powder having an average particle size of 4 μm as an alloy powder, zinc stearate as a lubricant, and tricalcium phosphate powder (Ca ₃ (PO ₄ ) ₂ ) was charged into a mixer and mixed to obtain an iron-based mixed powder.
The blending amount was 0.7% by mass of the graphite powder and 0 to 1.2% by mass of the machinability improving powder with respect to the total amount of the iron-based powder, the alloying powder and the machinability improving powder. Further, the compounding amount of the lubricant was 0.75 part by weight based on 100 parts by weight of the total amount of the iron-based powder, the alloying powder and the machinability improving powder.

These iron-based mixed powders are inserted into a mold, compression-molded, an outer diameter 35 mm × an inner diameter 14 mm × a height 10 mm, a ring-shaped test piece for a crushing test, and an outer diameter 60 mm × a height 10 mm, a drilling test. A disc-shaped test piece was prepared. Then, these test pieces were used in a RX gas atmosphere using a mesh belt furnace at 1130 ° C for 20 min.
Sintered. Using these sintered test pieces, a crushing test according to JIS Z 2507 and a drilling test under the conditions of a rotation speed of 10,000 rpm and a feed of 0.012 mm / rev were carried out, respectively, and the crushing strength and the number of holes were determined. I asked. The number of drilled holes was the number of holes opened before the drill (1.2 mmφ made by HSS) was broken. The results are shown in FIGS. 1 and 2.

It can be seen from FIG. 1 that the number of perforations increases almost linearly as the content of the tricalcium phosphate powder in the iron-based mixed powder increases. On the other hand, when the content of tricalcium phosphate powder is 1.0% by mass or more, it is saturated. Also from FIG.
The content of tricalcium phosphate powder in the iron-based mixed powder is 1.0
When it exceeds the mass%, the crush strength is rapidly reduced. From these facts, by setting the content of the tricalcium phosphate powder in the iron-based mixed powder in the range of 0.05 to 1.0 mass%, it is possible to have both excellent machinability and high crush strength. I got the knowledge.

The present inventors have also found that hydroxyapatite, like calcium phosphate, can improve the machinability without deteriorating the mechanical properties of the sintered body. Furthermore, the present inventors have found that the amount of calcium phosphate and / or hydroxyapatite added is
Alternatively, as described later, the amount of calcium fluoride added additionally was examined. As a result, it was found that the effect of improving the machinability without deteriorating the mechanical properties of the sintered body depends on the addition amount of the above chemical species calculated as Ca. That is, the addition amount range of the above-mentioned tricalcium phosphate in the iron-based mixed powder is 0.05 to 1.0% by mass.
Found that the same effect can be obtained even if the addition amount of the above chemical species in terms of Ca is 0.02 to 0.39% by mass.

The present invention has been completed by further studies based on the above findings. That is, the present invention is an iron-based powder, an alloy powder, a machinability improving powder and an iron-based mixed powder prepared by mixing a lubricant, wherein the machinability improving powder is calcium phosphate and / or hydroxyapatite, and 0.02 to 0.39 mass% in total of Ca based on the total amount of base powder, alloy powder and machinability improving powder
It is an iron-based mixed powder for powder metallurgy characterized by containing. In the present invention, the machinability improving powder further contains calcium fluoride in addition to calcium phosphate and / or hydroxyapatite, and the machinability improving powder is an iron-based powder, an alloy powder and a machinability improving powder. It is preferable to contain 0.02 to 0.39 mass% in total in terms of Ca based on the total amount of. Further, in the present invention, the calcium fluoride and the calcium phosphate and / or hydroxyapatite, in terms of Ca, (content of calcium fluoride)
It is preferable that the content of (/ total content of calcium phosphate and / or hydroxyapatite) be 0.8 or more.

In the present invention, the calcium phosphate is preferably one or more selected from tricalcium phosphate, calcium monohydrogen phosphate and calcium dihydrogen phosphate. Further, in the present invention,
The content of the alloy powder is preferably 5% by mass or less with respect to the total amount of the iron-based powder, the alloy powder and the machinability improving powder.

Further, in the present invention, the content of the lubricant is preferably 0.2 to 1.5 parts by weight based on 100 parts by weight of the total amount of the iron-based powder, the alloy powder and the machinability improving powder. Further, in the present invention, it is preferable that a part or all of the iron-based powder has an alloy powder and / or a machinability improving powder adhered to the surface thereof.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The iron-based mixed powder for powder metallurgy of 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. The powder for use is calcium phosphate and / or hydroxyapatite, and the total content of iron-based powder, alloy powder and machinability improving powder is 0.02 to 0.39 mass% in terms of Ca.

The iron-based mixed powder of the present invention is characterized by using calcium phosphate and / or hydroxyapatite as the machinability improving powder. Calcium phosphate,
By using hydroxyapatite, the mechanical properties are less deteriorated and the machinability is remarkably improved. Calcium phosphate contains tricalcium phosphate (Ca
₃ (PO ₄ ) ₂ ), calcium monohydrogen phosphate (CaHPO ₄ or
CaHPO ₄ · 2H ₂ O), calcium dihydrogen phosphate _{(Ca (H 2 PO 4)} 2
Alternatively, there is Ca (H ₂ PO ₄ ) ₂ · H ₂ O), and any of them can be preferably used in the present invention. Above all, it is preferable to use tricalcium phosphate (Ca ₃ (PO ₄ ) ₂ ) and calcium monohydrogen phosphate (CaHPO ₄ or CaHPO ₄ · 2H ₂ O).

Hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆
(OH) ₂ ) has the same effect as calcium phosphate, and can be used alone or in combination with calcium phosphate. Even when used in combination, it has the same or more effects as the single use. Calcium phosphate in iron-based mixed powder and /
Alternatively, the content of hydroxyapatite is 0.02 to 0.39 mass% in total in terms of Ca based on the total amount of the iron-based powder, the alloy powder and the machinability improving powder. Calcium phosphate and / or hydroxyapatite content (total) is Ca
If it is less than 0.02% by mass, the machinability is not significantly improved. On the other hand, when it exceeds 0.39 mass% in terms of Ca, mechanical properties such as a decrease in compressibility and a decrease in crush strength are deteriorated. Therefore, the content of calcium phosphate and / or hydroxyapatite in the iron-based mixed powder is 0.02 in total in terms of Ca.
It was set to 0.39 mass%. In addition, tricalcium phosphate (Ca ₃ (PO
₄ ) When ₂ ) is used alone, its content is preferably in the range of 0.05 to 0.6 mass%. Within this range, the dimensional change rate of the sintered body is small, and there is no problem in dimensional accuracy. The maximum particle size of the machinability improving powder is 45μ.
It is preferably m or less from the viewpoint of homogenization of mixing.
In the present invention, the particle size is a value measured by the microtrack method using a laser.

The machinability-improving powder may contain calcium fluoride CaF ₂ in addition to the above-mentioned calcium phosphate and / or hydroxyapatite. In this case, the content of the machinability improving powder, that is, the content of calcium phosphate and / or hydroxyapatite and calcium fluoride is calculated in terms of Ca with respect to the total amount of the iron-based powder, the alloy powder and the machinability improving powder. 0.02 to 0 in total.
It is preferably 39% by mass. The content of calcium fluoride CaF ₂ is preferably in the range of 0.05 to 0.15 mass% in terms of Ca with respect to the total amount of the iron-based powder, the alloy powder and the machinability improving powder. By containing calcium fluoride in combination with calcium phosphate and / or hydroxyapatite, workability is improved as compared with the case where calcium fluoride is contained alone.

When calcium fluoride is contained as a machinability-improving powder in combination with calcium phosphate and / or hydroxyapatite, the content of calcium fluoride and calcium phosphate and / or calcium phosphate in terms of Ca
Or the ratio of hydroxyapatite content, FC value = (
The content of calcium fluoride) / (total content of calcium phosphate and / or hydroxyapatite) is 0.
It is preferable that the content be 8 or more. Thereby, the wear amount of the tool can be remarkably reduced, the mechanical properties of the sintered body are less deteriorated, and the machinability is remarkably improved. In addition, in order to significantly improve the machinability of the tool when evaluated by the amount of flank wear, the content (total) of calcium fluoride, calcium phosphate and / or hydroxyapatite should be iron-based powder, alloy powder and cutting powder. It is preferably 0.05% by mass or more in terms of Ca based on the total amount of the property improving powder. The calcium phosphate is more preferably tricalcium phosphate.

As the alloy powder contained in the iron-based mixed powder, graphite powder, copper powder, etc. are selected and contained according to the characteristics required for desired product characteristics. In the present invention, as the iron-based powder, atomized iron powder, pure iron powder such as reduced powder, or steel powder in which alloy elements are prealloyed in place of iron powder (prealloyed steel powder), or alloy elements are partially alloyed Any of the produced steel powder (partially alloyed steel powder) can be preferably used.
Needless to say, these may be mixed and used.

As the lubricant contained in the iron-based mixed powder,
Metal soap such as zinc stearate and lithium stearate, or wax is preferable. The amount of the lubricant blended is preferably 0.2 to 1.5 parts by weight based on 100 parts by weight of the total amount of the iron-based powder, the alloy powder and the machinability improving powder. If the amount of the lubricant compounded is less than 0.2 parts by weight, the friction with the mold increases remarkably and the ejection force increases, so that the mold life is shortened. On the other hand, if it exceeds 1.5 parts by weight, the density of the compact will be remarkably reduced and the density of the sintered body will be reduced.

The iron-based mixed powder of the present invention is prepared by adding the above-mentioned alloy powder, machinability improving powder and lubricant to the above-mentioned iron-based powder to obtain a generally known V blender, double cone blender or the like. By using a mixer, the iron-based mixed powder can be obtained by mixing at once, or by dividing the mixture into two or more times to obtain an iron-based mixed powder, or by using an alloy powder and / or a machinability improving powder with a binder. It may be an iron-based mixed powder that has been subjected to a segregation-preventing treatment that adheres to the. By using such an iron-based powder, it is possible to obtain an iron-based mixed powder with less segregation and excellent fluidity.

As the segregation prevention treatment, for example, Patent No. 30
As disclosed in 04800, an iron-based powder, an alloy powder, and a machinability improving powder are mixed with a specific organic compound having the action of a binder, and then at least one of the specific organic compounds is mixed. Heat to the minimum melting point + 10 ℃ or higher,
A method is preferred in which one of the organic compounds is melted and then cooled and solidified to fix the alloy powder and / or the machinability improving powder to the surface of the iron-based powder. As the specific organic compound, higher fatty acid, higher fatty acid amide, and wax are preferable. Examples of the higher fatty acid or higher fatty acid amide include stearic acid, oleic acid amide, stearic acid amide, ethylenebisstearic acid amide, and a molten mixture of stearic acid amide and ethylenebisstearic acid amide.

[0026]

(Example 1) Water atomized iron powder (trade name: KIP301 A made by Kawasaki Steel) was used as an iron-based powder, and 100 kg of the iron-based powder was used as a graphite powder (average particle size 4
μm) or electrolytic copper powder (average particle size 35 μm) in the amount shown in Table 1 (mass%) with respect to the total amount of iron-based powder, alloy powder, and machinability improving powder, and further machinability improving powder. As various types of calcium phosphate powders, hydroxyapatite powders, calcium fluoride powders in the blending amounts (% by mass) shown in Table 1, zinc stearate (average particle size: 20 μm) as a lubricant, an iron-based powder and an alloy powder. The amount (parts by weight) shown in Table 1 with respect to 100 parts by weight of the total amount of the powder for improving machinability was charged into a V blender and uniformly mixed to obtain an iron-based mixed powder. As the iron-based powder, in some iron-based mixed powders, mill scale reduced iron powder (trade name: Kawasaki Steel KI
P255 M), or Ni, Mo, on the surface of water atomized iron powder
Partially alloyed steel powder (4mass% Ni-0.5mass) with Cu diffused and adhered
% Mo-1.5mass% Cu-Fe), and water-atomized iron powder and partially alloyed steel powder with Ni, Mo and Cu diffused and adhered to the iron powder surface (2
mass% Ni-0.5mass% Mo-1.5mass% Cu-Fe) was used. In addition, some iron-based mixed powders do not contain the machinability improving powder and those that use MnS as the machinability improving powder are also included.

These iron-based mixed powders were inserted into a mold, and the surface pressure:
A ring-shaped test piece compact for compression testing and outer diameter 35 mm x inner diameter 14 mm x height 10 mm and outer diameter dimensional change rate compression-molded at 392 MPa, and a disk for drilling test of outer diameter 60 mm x height 10 mm. The test piece molded body was a rectangular parallelepiped molded body of 10 × 10 × 55 mm. The density of the rectangular parallelepiped molded body was measured using the Archimedes method. The Archimedes method is a method of measuring the density by immersing a molded article as an object to be measured in water and measuring the volume.

Next, these test piece compacts were sintered in a RX gas atmosphere using a mesh belt furnace at 1130 ° C. for 20 minutes to obtain sintered bodies. For these sintered bodies (test pieces),
Crush test according to JIS Z 2507, outer diameter dimension change rate measurement test, rotation speed 10,000 rpm, feed: 0.012 mm / rev
The drilling test was carried out under the conditions of No. 1 to obtain the crush strength (N / mm ² ), the outer diameter dimensional change rate, and the number of holes (pieces). The crushing strength (N / mm ² ) was determined in accordance with the regulations of JIS Z 2507. The outer diameter dimensional change rate is obtained by measuring the outer diameter of the ring-shaped test piece after sintering with reference to the outer diameter of the mold, and changing the outer diameter of the mold (= {(average of ring-shaped test piece after sintering. Outer diameter−Mold outer diameter) / (Mold outer diameter)} × 100%) was obtained and used as the outer diameter dimensional change rate. The number of holes (pieces) was defined as the number of holes opened before the drill (1.2 mmφ made by HSS) was broken.

The results are shown in Table 1.

[0030]

[Table 1]

[0031]

[Table 2]

In each of the examples of the present invention, the density of the molded body is high,
Furthermore, the crush strength of the sintered body is high, the outside diameter dimensional change rate is small, the number of holes is large, and a sintered body with excellent machinability can be formed, and it has excellent properties as an iron-based mixed powder for powder metallurgy. ing. On the other hand, in Comparative Examples and Conventional Examples out of the scope of the present invention, the compact density is low, the crush strength is low, the outer diameter dimensional change rate is large, or the machinability is deteriorated. It was In addition, with the iron-based mixed powder (conventional example) containing the machinability-improving powder containing S, a poor appearance was observed in the sintered body. (Example 2) As the iron-based powder, water atomized iron powder (trade name: Kawasaki Steel KIP301 A) was used.
In kg, natural graphite powder as an alloy powder (average particle size 4 μm
), Or an amount of electrolytic copper powder (average particle size 35 μm) shown in Table 2 with respect to the total amount of iron-base powder, alloy powder and machinability improving powder, and further machinability improving powder. as a blending amount shown in Table 2 tricalcium phosphate powder (mass%) (maximum particle size: 45 [mu] m or less), calcium hydrogen phosphate CaHPO ₄ · 2H ₂ O (maximum particle size: 28 .mu.m), dihydrogen phosphate Calcium Ca (HPO ₄ ) ₂ · H ₂ O (maximum particle size: 31 μm)
And zinc stearate as a binder (melting point: 120
℃) was added 0.4 parts by weight to 100 parts by weight of the total amount of iron-based powder, alloying powder and machinability improving powder, and the mixture was primary mixed and then heated to 120 ° C and mixed while heating and melting the binder. Then, the powder for alloying and / or the powder for improving machinability was fixed to the surface of the iron-based powder and subjected to segregation prevention treatment to obtain an iron-based powder. Then, the iron-based powder that had been subjected to such segregation prevention treatment was further coated with zinc stearate (average particle size: 20 μm) as the total amount of the iron-based powder, the alloy powder, and the machinability improving powder to 100%. The amount (parts by weight) shown in Table 2 was added to parts by weight and uniformly mixed to obtain an iron-based mixed powder.

These iron-based mixed powders were treated in the same manner as in Example 1,
Inserted in the mold, compression molded at a surface pressure of 490 MPa, outer diameter 35 mm ×
Ring-shaped test piece compact for inner diameter 14 mm × height 10 mm for crush test and outer diameter dimensional change rate, and outer diameter 60 mm × height
Disc-shaped test piece compact for 10 mm drilling test, 10 × 10 ×
A 55 mm rectangular parallelepiped molded body was used. The density of the rectangular parallelepiped molded body was measured using the Archimedes method.

Next, these test piece compacts were sintered in a RX gas atmosphere using a mesh belt furnace at 1120 ° C. × 15 min to obtain sintered bodies. For these sintered bodies (test pieces),
In the same manner as in Example 1, a crushing test, an outer diameter dimensional change rate measurement test, and a drill piercing test were performed, respectively, and the crush strength (N / mm ² ), the outer diameter dimensional change rate, and the number of holes (pieces) ) Was asked.

The results are shown in Table 2.

[0036]

[Table 3]

In each of the examples of the present invention, the density of the molded body is high,
Furthermore, the crush strength of the sintered body is high, the outside diameter dimensional change rate is small, the number of holes is large, and a sintered body with excellent machinability can be formed, and it has excellent properties as an iron-based mixed powder for powder metallurgy. ing. On the other hand, a comparative example outside the scope of the present invention is
The machinability was reduced. (Example 3) Water atomized iron powder (trade name: Kawasaki Steel KIP301 A) was used as the iron-based powder, and 100 kg of the iron-based powder was used.
In addition, natural graphite powder as alloy powder (average particle size 4 μm)
And the amount of electrolytic copper powder (average particle size 35 μm) shown in Table 3 with respect to the total amount of the iron-based powder, the alloy powder and the machinability improving powder, and further as the machinability improving powder. Compounding amount (mass%) of tricalcium phosphate powder shown in 3 (maximum particle size
45 μm), calcium fluoride powder (average particle size 30 μm)
In addition, zinc stearate as lubricant (average particle size:
20 μm) of the total amount of iron-based powder and powder for improving alloy machinability of 100 parts by weight, and the amount (parts by weight) shown in Table 3 were charged into a V blender and uniformly mixed to form an iron-based powder. It was mixed powder. In addition, as a powder for improving machinability, hydroxyapatite powder was added to some iron-based mixed powders. In addition, some iron-based mixed powders did not include the machinability improving powder.

These iron-based mixed powders were inserted into a mold, compression-molded so that the density of the molded body was 6.8 Mg / m ³ , and a ring-shaped test piece for outer diameter 60 mm × inner diameter 20 mm × height 30 mm for turning test. It was a molded body. Next, these test piece compacts were sintered in a RX gas atmosphere using a mesh belt furnace at 1130 ° C. for 20 minutes to obtain sintered compacts. An outer diameter turning test was performed on these sintered bodies (test pieces) using an NC machining center.
Turning test conditions are cutting speed 100m / min, depth of cut: 0.4m
m, the tool used was a cermet tool (Toshiba Tungaloy).

Each time the outer diameter was turned by 1000 m, the tip of the tool was observed using a projector with a magnification of 50, and the tool was turned up to 5000 m to measure the flank wear amount of the tool. The amount of flank wear is
It is the amount measured according to JIS B 4011 and refers to the change in the wear condition of the tool after the test. Further, the presence or absence of appearance gloss was visually observed on the cut surface of the test piece after the test.
The results obtained are shown in Table 3.

[0040]

[Table 4]

Each of the examples of the present invention is a sintered body having a small amount of flank wear and excellent machinability. In the present invention example in which the ratio of the amount of calcium fluoride to the amount of tricalcium phosphate and / or the amount of hydroxyapatite (total amount) in the machinability improving powder, FC value was 0.8 or more, the flank wear amount was small and the cutting was performed. It is a sintered body (product) with a glossy surface and an excellent appearance.

On the other hand, the comparative examples which are out of the range of the present invention are sintered bodies having a large amount of flank wear and poor machinability.

[0043]

As described above, according to the present invention,
The machinability can be improved without deteriorating the mechanical properties of the sintered body. Further, according to the present invention, the machinability improving powder can be a powder not containing S, and there is no contamination in the furnace at the time of sintering by S and no adverse effect on the sintered body, so that a sintered product can be manufactured. It is possible and produces a remarkable effect in industry.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of holes and the calcium phosphate content in a drill hole test.

FIG. 2 is a graph showing the relationship between crush strength and calcium phosphate content in a crush test.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akio Sonobe             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. F term (reference) 4K018 AA29 AA30 BA15 BC12 CA07                       CA08 CA11 DA11 KA01 KA51

Claims (5)

[Claims] 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 is calcium phosphate and / or hydroxyapatite. A total of 0.02 in terms of Ca based on the total amount of base powder, alloy powder and machinability improving powder
An iron-based mixed powder for powder metallurgy, which contains 0.39% by mass. 2. The machinability improving powder further contains calcium fluoride, and the machinability improving powder has a total of 0.02 in terms of Ca based on the total amount of the iron-based powder, the alloying powder and the machinability improving powder. The iron-based mixed powder for powder metallurgy according to claim 1, wherein the iron-based mixed powder is contained in an amount of ˜0.39 mass%. 3. The calcium fluoride and the calcium phosphate and / or hydroxyapatite have a (calcium fluoride content) / (total content of calcium phosphate and / or hydroxyapatite) of 0.8 or more in terms of Ca. The iron-based mixed powder for powder metallurgy according to claim 2, characterized in that it is contained as follows. 4. The calcium phosphate is one kind or two or more kinds selected from tricalcium phosphate, calcium monohydrogen phosphate and calcium dihydrogen phosphate. Iron-based mixed powder for powder metallurgy according to any one of claims. 5. The iron-based powder according to claim 1, wherein a part or all of the iron-based powder has an alloy powder and / or a machinability-improving powder fixed to the surface by a binder. Iron-based mixed powder for powder metallurgy according to.