JP2003096533A - Iron-base powder mixture for warm compaction, iron-base powder mixture for warm die lubrication compaction, and method for manufacturing iron-base sintered compact using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an iron-base sintered compact by which an iron-base sintered compact having high density and high fatigue strength can be obtained by sintering a high-density green compact. SOLUTION: A preheated die is used as the die, and the iron-base powder mixture contains iron-base powder having <=75 μm maximum particle size of primary particles, graphite powder in an amount of 0.1 to 1.0 mass% based on the total amount of the iron-base powder mixture, and a lubricant for powder compaction in an amount of 0.05 to 0.80 mass%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based powder mixture for warm forming, an iron-based powder mixture for warm die lubrication forming, and a method for producing an iron-based sintered body using the same. The present invention relates to a method for manufacturing an iron-based powder sintered body having fatigue strength.

[0002]

2. Description of the Related Art An iron-based powder compact for powder metallurgy is an iron-based powder mixture obtained by mixing iron-based powder with an alloy powder such as copper powder or graphite powder and a lubricant such as zinc stearate or lithium stearate. Is generally manufactured by pressure molding after filling in a metal mold, and the density of the obtained iron-based powder compact is generally 6.6 to 7.1 Mg / m ³ .

[0003] These iron-based powder compacts are subjected to a sintering treatment to obtain a sintered compact, and if necessary, subjected to sizing and cutting to obtain a powder metallurgy product. Further, in the case of powder metallurgy products that require increased strength, heat treatment may be performed after the sintering treatment. In this way, powder metallurgical technology for manufacturing powder metallurgical products close to the product shape makes it possible to produce parts with high dimensional accuracy and complex shapes in the near net shape,
The cutting cost can be significantly reduced compared to the conventional manufacturing method using ingot material.

Further, in recent years, there has been a strong demand for iron-based powder metallurgy products to have high strength in order to reduce the size and weight of parts used for automobile mechanical parts and the like. In order to increase the strength of powder metallurgy products (sintered parts), it is generally effective to densify the compact by densifying the compact, and The higher the value, the less the voids in the sintered part, and the better the mechanical properties such as tensile strength and impact value as well as fatigue strength.

As a molding method capable of increasing the density of an iron-based powder compact, an iron-based powder mixture is subjected to usual pressure molding and sintering treatment, and then pressure molding and sintering treatment are repeated. Two-time molding, two-time sintering method or the like (for example, JP-A-10-3170).
No. 90), a sintering forging method is proposed in which forging is performed once and then hot forging is performed. In addition, for example, Japanese Patent Laid-Open No. 2-
No. 156002, Japanese Patent Publication No. 7-103404, USP No. 5,256,18
Japanese Patent No. 5 and USP No. 5,368,630 disclose a warm molding technique in which a metal powder is pressed while being heated.
This warm molding technology melts part or all of the lubricant during warm molding to evenly disperse the lubricant between powder particles, reducing friction resistance between particles and between the molded body and the mold. In order to improve the property, it is considered to be most advantageous in terms of cost among the above-mentioned methods for producing a high-density molded body.

[0006]

SUMMARY OF THE INVENTION
2-156002, Japanese Patent Publication No. 7-103404, USP No. 5,256,
No. 185, USP No. 5,368,630, JP 2000-2907
In the iron-based sintered body obtained by sintering the molded body obtained by the warm forming technique described in JP-A No. 03-2003, there is a problem that mechanical properties are insufficient depending on the parts using the iron-based sintered body. It was

Further, as a sintered body used for automobile machine parts and the like, an iron-based sintered body having a high fatigue strength is used from the viewpoints of high fatigue strength and cost reduction, and the pressure is applied once. It has been desired to develop a method for producing an iron-based sintered body that can be obtained by molding. The present invention advantageously solves the above-mentioned problems of the prior art, sintering the high-density molded body,
Iron-based powder mixture for warm forming, iron-based powder mixture for warm die lubrication forming, and iron-based sintered body manufacturing method using the same, which can be an iron-based sintered body with high density and high fatigue strength The purpose is to propose.

[0008]

Therefore, the present inventors have focused on the maximum particle size of iron-based powder. Conventional iron-based powders for powder metallurgy have a maximum particle size of primary particles of 150 to 180 μm, and the problem can be solved by reducing the maximum particle size of the primary particles. The present inventors have limited the maximum particle size of the primary particles of the iron-based powder, and used the warm-forming technology using the iron-based powder mixture in which the amounts of the graphite powder and the lubricant for powder molding are specified, and as described above. A high-density molded product is obtained by applying a warm mold lubrication technique of preheating a mold for press molding a complex iron-based powder mixture and applying a charged lubricant to the surface of the preheated mold. The inventors have completed the present invention by finding that an iron-based sintered body with high density and high fatigue strength can be manufactured by sintering this.

That is, according to the present invention, in a warm-forming iron-based powder mixture containing iron-based powder, graphite powder and a powder-forming lubricant, the maximum particle size of primary particles of the iron-based powder is 75 μm or less. The graphite powder is 0.1 to 1.0% by mass, and the powder molding lubricant is 0.05 to 0.80% by mass with respect to the total amount of the warm-forming iron-based powder mixture. It is an iron-based powder mixture for hot compacting. It is preferable that the iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less.

The present invention also provides an iron-based powder mixture for warm die lubrication molding, comprising an iron-based powder, a graphite powder, and a lubricant for powder molding, the maximum particle size of the primary particles of the iron-based powder. Is 75 μm or less, and the graphite powder is 0.1 to 1.0 with respect to the total amount of the iron-based powder mixture for warm die lubrication molding.
%, And the lubricant for powder molding is 0.05 to 0.40 mass%, which is an iron-based powder mixture for warm die lubrication molding. It is preferable that the iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less.

Further, according to the present invention, a mold is filled with a heated iron-based powder mixture, and then pressure-molded at a predetermined temperature to obtain an iron-based powder molded body, and then the iron-based powder molded body is sintered. In the method for producing an iron-based sintered body, which is a treated iron-based sintered body, the mold is a preheated mold, and the iron-based powder mixture has a maximum primary particle size of 75 μm or less. With respect to the iron-based powder and the total amount of the warm-forming iron-based powder mixture, 0.
A method for producing an iron-based sintered body, comprising 1 to 1.0% by mass of graphite powder and 0.05 to 0.80% by mass of a lubricant for powder molding. Further, the present invention, after filling the mold with the heated iron-based powder mixture, pressure-molded at a predetermined temperature to form an iron-based powder molded body, and then subjecting the iron-based powder molded body to a sintering treatment. In the method for producing an iron-based sintered body, which is a cast iron-based sintered body, the mold is a mold preheated, and a lubricant for warm mold lubrication is electrostatically adhered to the surface, and the iron-based powder mixture is used. Is an iron-based powder having a maximum primary particle size of 75 μm or less, 0.1 to 1.0% by mass of graphite powder, and 0.05 to 0.40% by mass of a lubricant for powder molding, based on the total amount of the iron-based powder mixture. The method for producing an iron-based sintered body is characterized by containing and. In the method for producing an iron-based sintered body, the iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less. It is preferable that Further, the present invention is a method for producing an iron-based sintered body, which is preferable to further heat-treat the iron-based sintered body produced by the above-described method for producing an iron-based sintered body.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION First, a warm forming technique according to the present invention will be described. This warm molding technique is a method of filling an iron-based powder mixture in a preheated mold and press-molding the iron-based powder mixture at a predetermined temperature to obtain an iron-based powder compact. At this time, the mold used for pressure molding is preheated to a predetermined temperature. The preheating temperature of the mold may be any temperature at which the iron-based powder mixture can be maintained at a predetermined pressure molding temperature during pressure molding. The predetermined pressure molding temperature referred to in the present invention is
It refers to the temperature of the iron-based powder mixture.

The heating temperature of the iron-based powder mixture is 70 to 200 ° C.
The temperature is preferably set to 100 to 160 ° C., and more preferably set to 100 to 160 ° C. If the heating temperature of the iron-based powder mixture is lower than 70 ° C, the yield stress of the iron powder is high and the density of the compact is lowered, while if the heating temperature of the iron-based powder mixture exceeds 200 ° C, the density of the There is no increase, and there is concern about oxidation of the iron-based powder.

For this reason, the heating temperature of the iron-based powder mixture is
It is desirable that the temperature range is 70 to 200 ° C. The iron-based powder mixture is obtained by mixing iron-based powder with graphite, a lubricant for powder molding, or an alloy powder such as copper powder. The method of mixing the iron-based powder with the graphite, the powder molding lubricant, or the alloy powder is not particularly limited, and a usual known mixing method is used.

The content of the lubricant for powder molding contained in the iron-based powder mixture of the present invention is 0.05 based on the total amount of the iron-based powder mixture.
~ 0.80 mass%. Content of lubricant for powder molding is 0.05
If it is less than mass%, the lubricating effect between the particles of the iron-based powder mixture is reduced, the density of the molded body is lowered, and molding cracks are likely to occur. On the other hand, if the content of the lubricant for powder compaction exceeds 0.80 mass%, the density of the compact decreases because it acts not to lubricate but to inhibit the plastic deformation of the particles, and the density of the sintered compact decreases.

As a powder molding lubricant to be blended with the iron-based powder mixture, Japanese Patent Publication No. 7-103404 and JP-A-9-104901 are available.
Any of the lubricants disclosed in JP-A-10-317001 and JP-A-10-317001 can be preferably used. Further, metal soaps such as zinc stearate, lithium stearate and calcium stearate, and lubricants usually called wax such as ethylene bisstearamide can be used alone or in combination.

The graphite contained in the iron-based powder mixture has the effect of diffusing into the sintered body and strengthening the sintered body by solid solution strengthening. The amount of graphite contained in the iron-based powder mixture is 1.0% by mass.
If it exceeds, the density of the molded product will decrease. On the other hand, if the amount of graphite contained is less than 0.1% by mass, the effect of strengthening the sintered body is small. Therefore, the graphite contained in the iron-based powder mixture is 0.1 to 1.0 mass% with respect to the total amount of the iron-based powder mixture.

In the iron-based powder used in the present invention, the maximum particle size of primary particles is limited to 75 μm or less. If the iron-based powder contains primary particles with a particle size of more than 75 μm, the driving force for sintering will be weakened, and coarse voids will be present around the iron-based powder with a primary particle size of more than 75 μm. Holes will be formed. Further, when the iron-based powder contains primary particles having a particle size of more than 75 μm, the primary product having a particle size of more than 75 μm was obtained during sintering of the molded body obtained by press-molding the iron-based powder mixture. The alloying elements do not sufficiently diffuse to the center of the iron-based powder having a particle size, and heat treatment for further strengthening the iron-based sintered body, for example, when performing gas carburizing quenching, bright quenching, induction hardening, etc. Poor penetrability results in a coarse and relatively soft ferrite structure or pearlite structure. Since both of these coarse pores and coarse soft structures easily become the starting points of fatigue fracture, the fatigue strength is reduced. Further, iron-based powder having a maximum primary particle size of 75 μm or less is used, and secondary particles are produced by granulating the iron-based powder to increase the apparent particle size. The fluidity of the mixture can be improved, and the filling property in the mold and the dimensional variation can be improved. Since the mechanical properties of the sintered body using this iron-based powder depend on the maximum particle size of the primary particles, the fatigue strength does not decrease as compared with the case where no granulation is performed. Two
If the maximum particle size of secondary particles exceeds 180 μm, the filling property into thin-walled areas will be reduced, so 180 μm or less is preferable. As a method for granulating the primary particles to produce the secondary particles, a known method may be used, and the particles may be granulated by heating or may be granulated with a binder. Iron-based powders are atomized pure iron powder, partially diffused alloyed steel powder, fully alloyed steel powder,
Alternatively, a mixed powder of these is preferable. Particularly preferred are partially diffused alloyed powder and / or fully alloyed steel powder, and the alloying component is one or more selected from Ni, Cu, and Mo.

The iron-based powder having a maximum primary particle size of 75 μm or less is classified by sieving with a sieve in order.
Powder that has passed through a 75 μm sieve (200 mesh) or powder that has passed through a sieve with a finer mesh than JIS Z8801 75 μm sieve may be used. Or
As an iron-based powder having a maximum particle size of 75 μm or less, for example, JI
S Z8801 75μm sieve (200mesh) powder that does not pass JIS Z8801 63μm sieve (250mesh) powder is -75 / + 63 powder, JIS Z8801 63μ
Powder that has passed through a m sieve (250 mesh) and JIS Z8
801 Powder that does not pass through a 45 μm sieve (325 mesh)
63 / + 45 powder is -75 / + 63 powder and-
63 / + 45 powder may be mixed at an appropriate ratio to adjust the particle size distribution. The particle size distribution of secondary particles is adjusted in the same manner. For example, JIS Z8801
Use the powder that has passed through a 180 μm sieve (80 mesh).

Next, the warm die lubrication molding technique according to the present invention will be described. Warm die lubrication molding involves applying a charged lubricant to the inner surface of a preheated die, filling the iron-based powder mixture in the die to which the lubricant has been applied, and then applying the iron-based powder mixture to a predetermined amount. This is a method of pressing at a temperature to obtain an iron-based powder compact. At this time, the mold used for pressure molding is preheated to a predetermined temperature. The preheating temperature of the mold is
Any temperature may be used as long as the iron-based powder mixture can be maintained at a predetermined pressure molding temperature. The predetermined pressure molding temperature referred to in the present invention means the temperature of the iron-based powder mixture.

In order to apply a charged mold lubricant to the inner surface of the preheated mold and charge the lubricant for mold lubrication to the inner surface of the mold, a mold lubricator (for example, Gasbarre Company) is used. Manufactured by Die Wall Lubricant System) can be used. To apply the lubricant for mold lubrication using this mold lubricator, the solid powder of the lubricant for mold lubrication is loaded into the mold lubricator, and the solid powder of the lubricant for mold lubrication and the device are applied. By contact charging with the inner wall, the lubricant for mold lubrication is charged, and the charged lubricant for lubricant for mold is sprayed on the inner surface of the mold,
A lubricant for die lubrication can be electrostatically attached to the inner surface of the die. The amount of the lubricant for die lubrication to be electrostatically adhered to the inner surface of the die is preferably 5 to 100 g / m ² . If the amount of lubricant for mold lubrication is less than 5 g / m ² , the lubrication effect will be insufficient and the extraction force after molding will be high. If the amount of lubricant for mold lubrication exceeds 100 g / m ^{2, it} will be extracted. The lubricant for mold lubrication remains on the surface of the molded body, resulting in poor appearance of the molded body.

As the lubricant for die lubrication, metal soaps such as zinc stearate, lithium stearate and calcium stearate, and lubricants usually called wax such as ethylene bis-stearamide can be used alone or in combination. . Then, the heated iron-based powder mixture is charged into a mold to which a lubricant for die lubrication has been electrified and pressure-molded to obtain an iron-based powder compact.

The heating temperature of the iron-based powder mixture is 70 to 200 ° C.
The temperature is preferably set to 100 to 160 ° C., and more preferably set to 100 to 160 ° C. If the heating temperature of the iron-based powder mixture is less than 70 ° C, the yield stress of the iron powder is high, and the density of the compact decreases, while if the heating temperature of the iron-based powder mixture exceeds 200 ° C, the density of the There is no increase, and there is concern about oxidation of the iron-based powder. Therefore, the heating temperature of the iron-based powder mixture is 70 to 200 ° C.
It is desirable to set the range to.

The iron-based powder mixture contains iron-based powder, graphite, and
A lubricant for powder molding, or an alloy powder such as copper powder is further mixed. The method of mixing the iron-based powder with the graphite, the powder molding lubricant, or the alloy powder is not particularly limited, and a usual known mixing method is used. The maximum particle size of the primary particles of the iron-based powder is 75 μm or less. The reason why the maximum particle size of the iron-based powder is limited to 75 μm, the type and adjusting method of the iron-based powder, the graphite content and the reason for the limitation are as described in the warm forming technique. The maximum secondary particle size is
180 μm or less is preferable. The reason for this is as explained in the warm forming technique.

The type of the lubricant for powder molding used in the warm die lubrication molding can be the same as that described in the warm molding technique. The content of the lubricant for powder molding contained in the iron-based powder mixture for warm die lubrication molding is 0.05 to 0.40 mass% with respect to the total amount of the iron-based powder mixture. When the content of the powder molding lubricant is less than 0.05% by mass, the lubricating effect of the particles of the iron-based powder mixture is reduced, the density of the molded product is lowered, and molding cracks are likely to occur. On the other hand, in the case of warm die lubrication molding, if the content of the lubricant for powder molding exceeds 0.40 mass%, the lubricating action is saturated, and rather the density of the compact is reduced because it acts to inhibit the plastic deformation of the particles. And the density of the sintered body decreases.

In the present invention, a high-density iron-based powder compact produced by the warm compaction technique or the warm die lubrication compaction technique is subjected to a sintering treatment to obtain an iron-based sintered compact. obtain.
The sintering treatment conditions in the present invention are not particularly limited, and any commonly known sintering method can be preferably used.
The sintering temperature is preferably in the range of 1100 to 1300 ° C,
The sintering atmosphere is preferably an end-thermic gas atmosphere (RX atmosphere), a nitrogen gas atmosphere containing hydrogen, an ammonia decomposition gas atmosphere, or a vacuum.
The higher the sintering temperature is, the higher the strength of the sintered body is. However, since the increase of the sintering temperature increases the sintering cost, it is preferable to appropriately select the sintering temperature in consideration of the strength and the cost.

In the present invention, the iron-based sintered body obtained as described above is preferably subjected to a heat treatment in order to further increase the fatigue strength. As the heat treatment, known heat treatments such as gas carburizing quenching, bright quenching, and induction hardening can be performed.

[0028]

[Examples] (Examples 1 to 3, Comparative Examples 1 and 2) As an iron-based powder, a partially alloyed steel powder having a composition of Fe-4Ni-0.5Mo-1.5Cu was used. Partially alloyed steel powder is atomized pure iron powder that has been classified by a sieve to change the maximum particle size as primary particles, and Ni, Mo, and Cu are mixed and diffused and adhered by heat treatment, while at the same time becoming secondary particles. It is obtained by granulating and classifying to a predetermined particle size with a sieve. Each of these partially alloyed steel powders was mixed with an amount of ethylenebisstearamide as a lubricant for powder molding shown in Table 1 and graphite with a V blender to obtain an iron-based powder mixture.

First, a pressure-molding die is preheated, and then the above-mentioned iron-based powder mixture heated to a pressure-forming temperature is filled into the die, and then pressure-molding is performed at a pressure of 686 MPa. ,
A molded body having a length of 80 mm, a width of 15 mm and a height of 15 mm was prepared. The obtained molded body was subjected to a sintering treatment at 1250 ° C. for 3600 s in an N ₂ -10vol% H ₂ atmosphere to obtain an iron-based sintered body. These iron-based sintered bodies were machined to a parallel part diameter of 8 mm and a parallel part length of 15.4 mm. As a heat treatment, the machined sintered body was brightly heat-treated at 900 ° C for 3600s, quenched in oil at 60 ° C, and tempered at 180 ° C for 3600s. A rotary bending fatigue test (JIS Z 2274) was performed on the heat-treated sintered body to measure the rotary bending fatigue strength. After the pressure molding, the extraction force at the time of extracting the molded product was measured, and the appearance of the obtained molded product was visually observed to examine the presence or absence of defects such as flaws and chips. In addition, the density of the obtained molded body and sintered body was measured by the Archimedes method. The Archimedes method is by immersing the measured object in ethanol and measuring the volume,
This is a method of measuring density. Further, the sintered body after the heat treatment was cut at the center, embedded in a resin and polished, and the presence or absence of pores and the structure in the cross section were observed with an optical microscope. As Comparative Examples 1 and 2, molded bodies and sintered bodies manufactured under the same conditions as in Example 1 were used, except that atomized pure iron powder having a maximum particle size outside the range of the present invention was used. The results are shown in Table 1.

[0030]

[Table 1]

From the results shown in Table 1, it can be seen that the sintered body according to the present invention has higher density and higher rotational bending fatigue strength than the sintered body of the comparative example. (Example 4, Comparative Example 3) Fe-4Ni-0.5Mo was used as the iron-based powder.
Partially alloyed steel powder with -1.5Cu composition was used. The partially alloyed steel powder is obtained by diffusing and adhering Ni, Mo, and Cu to atomized pure iron powder classified according to the same method as in Example 1 and having a different maximum particle size. Each of these partially alloyed steel powders was mixed with an amount of ethylene bisstearamide as a lubricant for powder molding shown in Table 1 and graphite in a V blender,
It was an iron-based powder mixture.

First, the mold for pressure molding is preheated, and Gassba is used.
Zinc stearate (ZnSt) as a lubricant for warm mold lubrication, which was charged by using a mold lubricator manufactured by rre, was sprayed into the mold and electrostatically adhered to the inner surface of the mold. The amount of the lubricant for warm die lubrication adhered was 10 g / m ² . Then, after filling the above iron-based powder mixture heated to the pressure molding temperature in the mold thus treated, pressure molding at a pressure of 686 MPa, length 80 mm × width 15 mm × height 15 mm It was a molded body. The obtained molded body was subjected to a sintering treatment at 1250 ° C. and 3600 _{S in} an N ₂ -10% H ₂ atmosphere to obtain an iron-based sintered body. These iron-based sintered bodies were machined into a parallel part diameter of 8 mm and a parallel part length of 15.4 mm and subjected to a rotary bending fatigue test (JIS Z 2274) to measure the rotary bending fatigue level. After the pressure molding, the method of extracting the molded product was measured, and the appearance of the resulting molded product was visually observed to investigate the presence of defects such as eaves and chips. In addition, the density of the obtained molded body and sintered body was measured by the Archimedes method.

As Comparative Example 3, a molded body and a sintered body manufactured under the same conditions as in Example 4 were used except that atomized pure iron powder having a maximum particle size outside the range of the present invention was used. The results are shown in Table 1 above. From the results in Table 1, it is understood that the sintered body according to the present invention has a higher density and a higher rotational bending fatigue strength than the sintered body of the comparative example.

(Examples 5 to 12, Comparative Examples 4 to 8) Except that the contents of the graphite and the lubricant for powder molding, the maximum particle size of the iron-based powder, and the pressure molding temperature were set to the respective conditions of Table 1, The iron-based sintered body produced under the same conditions as in Example 4 was machined, and then heat-treated at 900 ° C. for 7200 s and a carbon potential of 0.8%.
After carburizing with gas and quenching in oil at 60 ℃, 180 ℃, 3600s
Tempered. In this case, although the molded body and the sintered body were investigated by the same method as in Example 1,
As the sintered body, a sintered body after heat treatment was used. Comparative Example 4,
The molded bodies and sintered bodies produced under the same conditions as in Example 5 were used as 5 and 6 except that atomized pure iron powder having a maximum particle size outside the range of the present invention was used.

As Comparative Example 7, a molded body and a sintered body produced under the same conditions as in Example 8 were used, except that an iron-based powder mixture composition having a lubricant content outside the range of the present invention was used. As Comparative Example 8, a molded article was prepared by warm molding in the same manner as in Example 1 using a mixture of iron-based powders having the composition shown in Table 1 under the pressure molding conditions in which the pressure molding temperature was out of the range of the present invention. The molded product was used in the same manner as in Example 5, including sintering and heat treatment.

The results are shown in Table 1 above. From the results in Table 1, it is understood that the sintered body according to the present invention has a higher density and a higher rotational bending fatigue strength than the sintered body of the comparative example. Further, the fluidity of the iron-based powder mixture used in Examples 6, 8 and 9 was investigated, and the results are shown in Table 2.

[0037]

[Table 2]

The fluidity is the time when 100 g of the iron-based powder mixture flows down from the φ5 mm orifice.

[0039]

EFFECTS OF THE INVENTION According to the present invention, a high-density molded body can be easily manufactured by one-time molding, and a sintered body having high rotary bending fatigue strength can be easily obtained by one-time sintering. It has a great effect on industry.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Kaminozono             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. (72) Inventor Akira Fujiki             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Yukihiro Maekawa             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Yutaka Mabuchi             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F-term (reference) 4K018 AA24 AB10 AC01 BA13 BA20                       BB04 BC11 BC12 CA00 CA07                       CA11 DA00 FA08 KA01

Claims (8)

[Claims] 1. A warm-forming iron-based powder mixture containing iron-based powder, graphite powder and a powder-forming lubricant,
The maximum particle size of primary particles of the iron-based powder is 75 μm or less, the graphite powder is 0.1 to 1.0 mass% with respect to the total amount of the iron-based powder mixture for warm forming, and the lubricant for powder forming is The iron-based powder mixture for warm forming, wherein the agent is 0.05 to 0.80 mass%. 2. The iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less. Item 2. An iron-based powder mixture for warm forming according to Item 1. 3. An iron-based powder mixture for warm mold lubrication molding, comprising iron-based powder, graphite powder and a lubricant for powder molding, wherein the maximum particle size of primary particles of said iron-based powder is 75 μm or less. Yes, with respect to the total amount of the iron-based powder mixture for warm die lubrication molding, the graphite powder is 0.1 to 1.0 mass%,
The iron-based powder mixture for warm die lubrication molding, wherein the powder molding lubricant is 0.05 to 0.40% by mass. 4. The iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less. Item 3. An iron-based powder mixture for warm die lubrication molding according to Item 3. 5. A mold is filled with a heated iron-based powder mixture, and then pressure-molded at a predetermined temperature to form an iron-based powder compact, and then the iron-based powder compact is sintered. In the method for producing an iron-based sintered body, which is an iron-based sintered body, the die is a preheated die, and the iron-based powder mixture is an iron-based powder having a maximum primary particle size of 75 μm or less. And 0.1 to 1.0% by mass of graphite powder and 0.05 to 0.80% by mass of a lubricant for powder molding, based on the total amount of the iron-based powder mixture, Method. 6. A mold is filled with a heated iron-based powder mixture, and then pressure-molded at a predetermined temperature to obtain an iron-based powder compact, and then the iron-based powder compact is sintered. In the method for producing an iron-based sintered body, which is an iron-based sintered body, the mold is a mold that is preheated and has a lubricant for warm mold lubrication electrostatically attached to the surface thereof, and the iron-based powder mixture is An iron-based powder having a maximum primary particle size of 75 μm or less, and 0.1 to 1.0% by mass of graphite powder with respect to the total amount of the iron-based powder mixture;
~ 0.40% by mass of a powder molding lubricant, and a method for producing an iron-based sintered body. 7. The iron-based powder is a secondary particle obtained by granulating primary particles having a maximum particle size of 75 μm or less, and the maximum particle size of the secondary particle is 180 μm or less. Item 7. A method for manufacturing an iron-based sintered body according to Item 5 or 6. 8. A method for producing an iron-based sintered body, which further comprises heat-treating the iron-based sintered body produced by the method for producing an iron-based sintered body according to claim 5, 6, or 7. .