JPH08218101A - Steel powdery mixture for powder metallurgy and material for sintering containing the same - Google Patents

Abstract

PURPOSE: To produce a steel powdery mixture for powder metallurgy showing high compressibility equal to that of pure iron powder by mixing Mo-V prealloy steel powder having a specified compsn. and iron-phosphorus powder in which the content of O is prescribed and preparing a steel powdery mixture in which the content of P is specified. CONSTITUTION: Prealloy steel powder having a compsn. contg., by weight, <=0.02% C, <=0.01% Si, <=0.3% Mn, <=0.03% P, <=0.03% S, <=0.1% Cr, <=0.1% Al, 0.1 to 0.6% Mo, 0.05 to 2% V, 0.25% O, and the balance Fe with inevitable impurities and iron-phosphorus powder in which the content of O is regulated to <=1.0% are mixed to prepare a steel powdery mixture in which the content of P is regulated to 0.1 to 0.6%. Thus, the steel powdery mixture for powder metallurgy having exceedingly high strength and high toughness can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed steel powder for powder metallurgy and a sintering material containing the same, and more specifically to Mo-V.
Mixed steel powder of pre-alloyed steel powder and iron-phosphorus powder, mixed steel powder of Mo-V pre-alloyed steel powder, iron-phosphorus powder and one or more of Mo powder, Cu powder, Ni powder, Co powder, W powder, Mo powder, Cu powder, Ni powder, C
Partial diffusion Mo-V pre-alloyed steel powder and iron-phosphorus powder mixed with one or more of O powder and W powder by partial diffusion bonding, and graphite powder, lubricant and organic binder to these mixed steel powder Among these, it relates to a sintering material in which one or more of them are mixed.

[0002]

2. Description of the Related Art Sintered bodies manufactured by molding and sintering alloy steel powder as a raw material in a powder metallurgy process, sintered carburized and quenched bodies, sintered forged bodies and sintered forged carburized and quenched bodies (sintered The term "sintered heat treated body" will be used later because it includes those that undergo size and shape correction / modeling by sizing, coining, cutting, drilling, etc., or surface treatment such as shot peening and carbonitrides. Said), its range of use is gradually expanding to the area of high-strength parts. For example, gears for automobile parts, which require high tensile strength, impact value and fatigue strength, are typical. When manufacturing this automobile gear, in order to improve its tensile strength, impact value and fatigue strength, iron, Mo, Cu, N
It is common to manufacture an iron-based sintered body by alloying i, Co, W, Mn, Cr, V, P, Si, etc., and then subject it to heat treatment such as carburizing, nitriding, and quenching-tempering. is there. However, in this iron-based sintered heat-treated body, the higher the tensile strength, the higher the fatigue strength, but on the other hand, the impact value often decreases, so focusing on the improvement of the raw material powder as a countermeasure,
Research and development have been carried out on alloy steel powders that enhance both tensile strength and impact value, or that balance tensile strength and impact value.

That is, in order to increase the strength and toughness of the iron-based sintered heat-treated body, (a) matrix (also called matrix) is used.
Strengthening, (b) densification of sintered body (reduction of vacancies),
(C) The necessity of reducing the oxygen content (reducing the amount of inclusions) is clarified, and the manufacturing process of the iron powder or alloy steel powder as the raw material powder or the mixing step before compression molding (also called the raw material powder stage) ), Iron, C, Mo, Cu, Ni, Co, W, M
Alloying elements such as n, Cr, V, P and Si came to be added. Then, in the stage of the raw material powder, as a powder to which the above alloying elements are added, (1) a mixed powder in which each alloying element powder is mixed with pure iron powder, (2) a preliminary alloy in which each element is completely alloyed in the molten steel stage in advance. Alloy steel powder (3) Partially diffused alloy steel powder (also called composite alloy steel powder) in which each alloy element powder is partially diffusion-bonded to the surface of pure iron powder or prealloyed steel powder has come to be manufactured. .

However, the mixed powder obtained by mixing the alloy element powders with the pure iron powder of (1) has the advantage that the high compressibility comparable to that of pure iron powder can be ensured with the intention of increasing the density of (b). However, if the CO ₂ concentration and dew point in the sintering atmosphere or the carburizing atmosphere are not strictly controlled at the time of sintering, the active metals Mn, Cr, V, Si, etc. will oxidize rather than the added Fe ( There is a problem that the oxygen content in (c) cannot be reduced, and further, each alloying element does not sufficiently diffuse into Fe and remains in a heterogeneous structure, so that the matrix strengthening in (a) cannot be achieved. Therefore, the mixed powder obtained by mixing the alloy element powders with the pure iron powder of (1) cannot meet the recent demand for higher strength, and has recently come to a state where it is not used.

On the other hand, the pre-alloyed steel powder obtained by completely alloying the respective elements of (2) is produced by atomizing molten steel with water, so that solid solution due to oxidation and complete alloying in the atomizing process of molten steel is performed. Hardening occurs, but Mo, Mn, Cr, V,
By limiting the types and amounts of alloying elements such as Si and P, it is possible to secure low oxygen content in (c) and high compressibility comparable to that of pure iron powder in (b). Further, there is a possibility of strengthening the base by completely alloying (a), and it is currently being developed as a high-strength, high-toughness prealloyed steel powder. Further, the partially diffused alloy steel powder of (3) is obtained by mixing pure iron powder or prealloyed steel powder with metal powder of each element and heating it in a non-oxidizing or reducing atmosphere to obtain pure iron powder or Since each metal powder is partially diffusion bonded to the surface of the pre-alloyed steel powder, the mixed powder of (1) and (2)
The advantages of pre-alloyed steel powder can be combined. Therefore, the low oxygen content of (c) and the high compressibility comparable to that of pure iron powder of (b) can be secured, and a composite structure consisting of a complete alloy phase and a partially concentrated phase is formed to strengthen the matrix of (a). Therefore, it is still under development as a partial diffusion prealloyed steel powder for high strength and high toughness.

Therefore, the prealloyed steel powder and the partial diffusion prealloyed steel powder will be described in detail below, but in many cases, Mo is used as the basic alloying component thereof. This is for the same reason that Mo is usually used as a strengthening element for steel materials. That is, in steel materials, Mo delays the formation of pearlite, transform-strengthens the matrix (matrix) as a bainite structure, distributes the matrix to the matrix and solidifies the matrix, and becomes a fine carbide. As a result, the matrix phase is precipitation-strengthened, and the gas carburizing property is good, and since it is a non-grain boundary oxidation element, it is carburized. Then, at the stage of sintering the pre-alloyed steel powder containing Mo, iron phosphorous powder is mixed with it to strengthen the matrix in (a) and reduce the pores and spheroidize the pores in (b). -P2 binary system and the eutectic temperature of the quaternary system of Fe-Mo-P-C, that is, the melt generated at 1050 ° C to 1180 ° C and the α-phase formation of Fe-Mo-P are used. Became.

[0007] For example, Japanese Patent Laid-Open No. 5-506482.
Japanese Patent Publication No. 5-507967 and Japanese Patent Laid-Open Publication No. 5-507967 disclosed a technique for obtaining a high-strength and high-toughness sintered body by mixing a prealloyed steel powder containing Mo as an essential component and limiting Cr and V and iron-phosphorus powder. .

[0008]

However, in the mixed powder and the sintered body thereof described in Japanese Patent Laid-Open No. 5-506482, Mo: 3 to such that the total amount of Mo + W is within the range of 3 to 20 wt%. 15 wt% and W: 3 to 20 wt%
Of pre-alloyed steel powder having a so-called high-speed steel composition in a P amount of 0.
2 ~ 1.0wt% Fe ₃ P and C amount 0.5 ~ 1.5w
This is a mixture of t% graphite powder and sintering. The pre-alloyed steel powder and the sintered body of the high speed steel composition can contain Cr and / or V in a total amount of less than 2 wt%, desirably less than 1 wt%, but Si, Mn,
There is no description or mention of the amounts of impurity elements such as P, S, and Al. Therefore, the pre-alloyed steel powder and the sintered body having the high speed steel composition have Si, Mn, Cr, and Cr in the respective steps of water atomizing, reduction annealing, sintering and carburizing and quenching.
Al oxidizes to increase the amount of O in the prealloyed steel powder, and P, S
It reduces the green compact density and sintered density by solid solution hardening of
There is a problem in that the strength of the sintered body and the strength and impact value of the carburized and quenched body are reduced. In particular, Mn and Cr have another problem that the retained austenite is increased and the strength is further decreased in the sintered and carburized and quenched body. Further, when Fe ₃ P powder having an O content of more than 1.0 wt% is used, the strength and toughness of the sintered / carburized and quenched body are not improved even though the Fe ₃ P powder is added. There is also.

On the other hand, the mixed powder and the sintered body thereof described in Japanese Patent Laid-Open No. 5-507967 have a Mo content of 0.3 to
In the pre-alloyed steel powder in the range of 3.5 wt%, the P amount was 0.1.
_{3 to} 0.7 wt% Fe ₃ P powder was mixed and sintered. Then, the mixed powder and the sintered body contain 0.1 w of C.
less than t%, preferably C less than 0.07 wt%, other alloying elements less than 2 wt%, optimally 0.5 wt%
%, The sintered body having a high impact value was manufactured. However, the pre-alloyed steel powder of this mixed powder is a single alloy of Mo, and when Fe ₃ P powder having an O content of more than 1.0 wt% is used, Fe ₃
Despite the addition of P powder, there was a problem in that the strength and toughness of the sintered / carburized / quenched body were not improved.

Therefore, in view of such circumstances, the present invention secures a low oxygen content in the powder stage and a high compressibility comparable to that of pure iron powder, and a low oxygen content in a sintered body or a carburized and hardened body, strengthening the base and Mo- that achieved reduction of pores and spheroidization
It is an object of the present invention to provide a mixed powder of V-based prealloyed steel powder and iron-phosphorus powder.

[0011]

Means for Solving the Problems The inventor has conducted diligent research in order to achieve the above object, and is more susceptible to oxidation than Fe in the heat treatment process such as atomization process, reduction annealing process, sintering process and carburizing and quenching of molten steel. It was found that a low oxygen content can be achieved by limiting the amount of elements to a low level and preventing oxygen mixed in from the iron phosphorus powder. In addition, when pre-alloyed steel powder that essentially requires Mo-V is mixed with iron phosphorus powder having an O content of 1.0 wt% or less and sintered, the P oxidation amount of the iron phosphorus powder is two elements of Fe-P and The basic knowledge was also obtained that sintering was promoted without inhibiting the generation and diffusion of the Fe-Mo-P-C quaternary melt.

The present invention embodies such findings, and in weight%, C: 0.02% or less, Si: 0.1%.
Hereinafter, Mn: 0.3% or less, P: 0.03% or less, S:
0.03% or less, Cr: 0.1% or less, Al: 0.1%
Hereinafter, Mo: 0.1 to 6.0%, V: 0.05 to 2.0
%, O: 0.25% or less, the balance being Fe and unavoidable impurities, and a prealloyed steel powder, and an O content of 1.0% or less, an iron phosphorus powder, and a P content of 0.1 to 0. It is a mixed steel powder for powder metallurgy characterized by being mixed so as to be 6%. Further, in the present invention, the prealloyed steel powder further comprises C by weight%.
u: 4.0% or less, Ni: 6.0% or less, Co: 10.
It is a mixed steel powder for powder metallurgy characterized by containing one or more kinds of 0% or less, and one or more kinds of Nb: 0.10% or less and B: 0.03% or less. Furthermore, the present invention provides the prealloyed steel powder according to any one of the above, in a weight% of Mo: 4.
% Or less, Cu: 4% or less, Ni: 10% or less, Co: 4
% Or less and W: 8% or less, one or more kinds of metal powders are partially diffused and adhered, or Mo is contained.
Powder: 4% or less, Cu powder: 4% or less, Ni powder: 10% or less, Co powder: 4% or less and W powder: 8% or less, which is simply mixed with one or more metal powders. It is also a characteristic mixed steel powder for powder metallurgy. And, in these mixed steel powders for powder metallurgy, in weight%, graphite powder: 1.2% or less and 2
% Or less of a lubricant and one or more kinds of organic binders are mixed, and a sintering material is also included in the present invention.

[0013]

In the present invention, C: 0.02% or less by weight%,
Si: 0.1% or less, Mn: 0.3% or less, P: 0.0
3% or less, S: 0.03% or less, Cr: 0.1% or less,
Al: 0.1% or less, Mo: 0.1 to 6.0%, V:
Pre-alloyed steel powder containing 0.05 to 2.0%, O: 0.25% or less, the balance being Fe and unavoidable impurities, and iron phosphorus powder having an O content of 1.0% or less, and a P content. The mixed steel powder for powder metallurgy is characterized by being mixed so as to be 0.1 to 0.6%. Therefore, heat treatment such as atomization process of molten steel, reduction annealing process, sintering process and carburizing quenching. Oxidation that occurs in the process can be reduced to a very small extent, and the hardness of the Fe base in the steel powder stage can be made as good as that of pure iron powder. As a result, the mixed powder with iron phosphorus powder, or the one in which graphite powder is mixed, exhibits high compressibility as when using pure iron powder, and further solid solution strengthening of P and spherical spheres are achieved. As a result of carbonization and precipitation of Mo carbide, it has become much stronger and tougher than Mo single alloy steel.

The meaning of P content of 0.1 to 0.6% is as follows.
The formula is as follows. Here _{P 2 / (W 1 + W} 2) × 100 = 0.1~0.6, W 1 is prealloyed steel powder weight, W ₂ is Tetsurinko weight, P ₂ is P content in Tetsurinko. Further, in the present invention, the above pre-alloyed steel powder contains C by weight%.
u: 4.0% or less, Ni: 6.0% or less, Co: 10.
0% or less of one or more, Nb: 0.10% or less, B: 0.03% or less of one or more, or the above two types of constituent elements are simultaneously included. Therefore, the above effect can be achieved more reliably.

Further, in the present invention, any one of the above pre-alloyed steel powders, in weight% Mo: 4% or less, Cu: 4
% Or less, Ni: 10% or less, Co: 4% or less and W: 8
% Or less, one or more kinds of metal powders are partially diffused and adhered, Mo powder: 4% or less, C
u powder: 4% or less, Ni powder: 10% or less, Co powder: 4% or less and W powder: 8% or less, for powder metallurgy, which is simply mixed with one or more kinds of metal powders. Since mixed steel powder is used, when these mixed steel powders are made into a sintered body and a heat treated body such as carburizing and quenching, their structures are compounded, and higher strength and high toughness can be achieved, Also, the moldability is improved.

Below, the effect of each alloying element, the iron-phosphorus powder, the graphite powder and the lubricant in the prealloyed steel powder in the mixed steel powder for powder metallurgy and the sintered body according to the present invention and the reasons for limiting the content are described. Describe. C: 0.02% or less, Si: 0.1% or less, Mn: 0.
3% or less, P: 0.03% or less, S: 0.03% or less,
Cr: 0.1% or less, Al: 0.1% or less, O: 0.2
For pre-alloy components of 5% or less; C, Si, Mn, P,
S, Cr and O show a tendency of improving the compressibility of the prealloyed steel powder as the amount of their alloys is lower. In particular, C, P, and S are elements that have a large hardening effect on the ferrite phase of the prealloyed steel powder and significantly deteriorate compression workability, so it is preferable that the addition amount be small. In addition, Si, Mn, Cr and A1 are
Since there is a positive correlation with the O content of the prealloyed steel powder and also with the green density, the object of the present invention cannot be achieved if there are many of them, and the O content exceeds 0.25%. When pre-alloyed steel powder is mixed with iron-phosphorus powder and sintered, the strength and toughness of the sintered / carburized / quenched body are not improved even though the Fe ₃ P powder is mixed. Therefore, in the present invention, Si: 0.1% or less, M
n: 0.3% or less, Cr: 0.1% or less, Al: 0.
1% or less, O: 0.25% or less as a condition of the pre-alloyed steel powder, and in addition to these conditions, C: 0.02% or less, P: 0.0
Pre-alloyed steel powder having a compaction density similar to that of pure iron powder could be obtained by setting the content to 3% or less and S: 0.03% or less.

That is, 1% by weight of zinc stearate powder as a lubricant was mixed with the prealloyed steel powder, and JPMA P 0 was added.
When the density of the green compact molded at a pressure of 686 MPa according to 9-1992 was measured, a green compact density equal to that of pure iron powder of 7.0 Mg / m ³ or more was obtained. In order to increase the strength and toughness of the sintered and carburized and hardened body obtained by mixing and shaping and sintering, the prealloyed steel powder is C: 0.02% or less, S
i: 0.1% or less, Mn: 0.3% or less, P: 0.03
% Or less, S: 0.03% or less, Cr: 0.1% or less, A
l: 0.1% or less and O: 0.25% or less had to be suppressed.

Mo: 0.1-6.0%, V: 0.05-
2.0% pre-alloying component; Mo and V both have a small hardening effect on the ferrite phase of the steel powder, have good compression workability, are excellent in carbonitriding, and are bainite in the sintered heat-treated body containing C. It is an essential element that achieves high strength because it transforms to the phase or martensite phase and precipitates fine carbonitrides to refine the structure. Further, when pre-alloyed steel powder containing Mo and V is mixed with iron phosphorus powder and sintered, transitional liquid phase sintering due to a melt generated at a Fe—P eutectic temperature: 1050-1180 ° C. , Fe-Mo-V-P α-phase sintering occurs to promote the reduction of pores and spheroidization, and thus the toughness of the sintered body is increased. When Mo: less than 0.1% and V: less than 0.05%, there is no effect in improving strength and toughness, while Mo:
With additions of more than 6.0% and V: more than 2.0%, it is not possible to obtain a green compact density comparable to that of pure iron powder. Therefore, M
o: 0.1 to 6.0%, V: 0.05 to 2.0%.

Pre-alloying components of Cu: 4.0% or less, Ni: 6.0% or less, Co: 10.0% or less, W: 4.0% or less; To powder, C
By including at least one of u, Ni, Co and W as a prealloy, the sintered heat-treated body (including C) is
The initiation of transformation to the bainite phase or martensite phase is shifted to the low temperature side to refine the structure. Further, in the carburized / quenched body, the base is strengthened by shifting the start of martensitic transformation to the low temperature side. Therefore, Cu, Ni, C
The addition of o and W contributes to the enhancement of strength in both the sintered body and the carburized / quenched body. Cu: more than 4.0%, N
i: more than 6.0%, Co: more than 10.0%, W: 4.0
If it exceeds%, the density of the green compact is excessively lowered, and the retained austenite of the carburized / quenched body is increased to lower the strength. Therefore, it is limited to Cu: 4.0% or less, Ni: 6.0% or less, Co: 10.0% or less, and W: 4.0% or less.

Pre-alloying components of Nb: 0.10% or less, B: 0.03% or less; Mo-V prealloyed steel powder, and C
When pre-alloyed steel powder that essentially contains Mo-V containing at least one of u, Ni, Co and W contains at least one of Nb or B as a pre-alloying component, a heat-treated sintered body (including C) ), The carbonitrides are finely precipitated to further strengthen the matrix. However, Nb: exceeds 0.10% and B: 0.03, respectively.
%, There is no strength improving effect. Therefore, N
It is limited to b: 0.10 or less and B: 0.03 or less.

Mo powder or Mo oxide with a Mo content of 4% or less
Powder, Cu powder with a Cu content of 4% or less or Cu oxide powder, Ni
10% or less of Ni powder or oxidized Ni powder, Co amount of 4
% Or less Co powder or oxidized Co powder, W content 4% or less M
Powder or oxidized W powder; Mo-V prealloyed steel powder, or prealloyed steel powder that requires Mo-V containing at least one of Cu, Ni, Co and W, or Cu, N
A pre-alloyed steel powder containing at least one of i, Co, and W and one or more of Nb and B, which requires Mo-V, contains Mo powder, Cu powder,
By mixing one or more of Ni powder, Co powder, and W powder, in the heat-treated sintered body (including C), a composite structure composed of a complete alloy phase and a partially concentrated phase is formed to strengthen the matrix. Therefore, the strength can be further enhanced in both the sintered body and the carburized / quenched body. The composite structure at this time has a bainite phase and a martensite phase in which Mo-VW carbonitrides are finely precipitated by a combination of C content and Mo powder, Cu powder, Ni powder, Co powder and W powder. Be distributed to. The compounding in this case means mixing or partial diffusion heat treatment when Cu, Ni, Co, and W are metal powders, respectively. Further, when Cu, Ni, Co, and W are oxide powders, it means that partial diffusion heat treatment that also serves as oxygen removal is performed.

When the Mo content exceeds 4%, the Cu content exceeds 4%, the Ni content exceeds 10%, and the Co content exceeds 4%, respectively, the density of the green compact is excessively lowered and the soaking effect is reduced. In a charcoal-quenched body, the retained austenite increases and the strength decreases. Therefore, the powder blending amounts of Cu, Ni, Co, and W are 4% or less for the Mo amount, 4% or less for the Cu amount, and 1% for the Ni amount, respectively.
The range is 0% or less, the Co content is 4% or less, and the W content is 4% or less.

O content of iron phosphorus powder: 1.0% or less, mixed with iron phosphorus powder
Total amount: 0.1 to 0.6% by weight of P, graphite powder: 1.2%
One or more of the following lubricants and organic binders: 2%
Regarding the following; in the pre-alloyed steel powder in which Mo-V is essential, O
Iron phosphorus powder with an amount of 1.0 wt% or less is 0.1 to 0.1 by P content weight.
0.6% and graphite powder less than 1.2% are mixed and sintered
Then, at a Fe-P eutectic temperature of 1050 to 1180 ° C
Transitional liquid phase sintering by the generated melt and Fe-Mo-V
-P α-phase sintering occurs, and the pores are made spherical and
In order to reduce the amount, the sintered and carburized and quenched body is strengthened.
In addition, in order to increase the strength and toughness of the sintered and carburized case.
Has a P content in the range of 0.2 to 0.6% and a graphite content of 0.
The range of 4 to 0.6% is preferable. However, iron phosphorus powder is P
More than 0.6% by weight and more than 1.2% graphite powder
When mixed by mixing, the sintered and carburized case will be
As the phase crystallizes and the pro-eutectoid cementite phase becomes coarse,
The pores are also coarsened and the strength and toughness are reduced. Also, of iron phosphorus powder
When the O amount exceeds 1.0 wt%, the transitional liquid phase generation amount and
Since the diffusion amount of P decreases, it is possible to mix iron phosphorus powder.
Nevertheless, the strength / toughness of the sintered / carburized / quenched body is not improved.
As the iron-phosphorus powder to be mixed, Fe ₃P powder and Fe₂P powder
If the particle size exceeds 75 μm and is too coarse, it is pressed.
The density is reduced, and the sintered / carburized and quenched body has a roughness of 100 μm or more.
Large voids are left behind and strength and toughness are reduced.
It Therefore, the iron phosphorus powder to be mixed should have a particle size of 75 μm or less.
The material used is 45 μm or less.

If the graphite powder to be mixed exceeds 1.2%, the pro-eutectoid cementite phase and the steadite phase in the sintered and carburized and quenched body are coarsened, and the strength and toughness thereof are reduced. Furthermore, in order to ensure the compressibility in mold molding,
It is necessary to mix 2% or less of one or more kinds of lubricants and organic binders, but if the amount exceeds 2% and becomes excessive, the above compressibility deteriorates, resulting in a sintered / carburized case. The number of residual vacancies increases and the strength and toughness are rather deteriorated. As the lubricant, metal soap powder such as stearic acid and zinc stearate can be used, and as the organic binder, camphor, wax, oleic acid, stearic acid monoamide, stearic acid diamide and the like can be used. The metal soap powder and the organic binder may not only be mixed at the time of molding, but may also be heated to a temperature higher than the melting point (melting temperature) and adhered to the surface of the steel powder in advance.

The contents of the present invention will be specifically described in the following examples.

[0026]

【Example】

(Example 1) Table 1 shows the chemical composition of six types of Mo-V based prealloyed steel powders produced by the water atomizing method (including comparative examples). These Mo-V type pre-alloyed steel powders are produced by melting high-purity electrolytic Fe as a main raw material in an Ar atmosphere using a high frequency induction electric furnace, and then allowing the molten steel to flow down naturally from a refractory nozzle of 8 mmφ. The powder was obtained by injecting 0.3 m ³ / min of water at a pressure of 15 MPa from an annular water nozzle. The composition of the prealloyed steel powder was adjusted by adding various low carbon ferroalloys and / or electrolytic metals to the molten steel in which the electrolytic Fe was dissolved. In addition, the above Mo
Each of the -V series prealloyed steel powders was dehydrated and vacuum dried after water atomization, and the 180μm sieve-passed powders were reduction-annealed in H ₂ gas (dew point was 30 ° C) under the condition of 950 ° C x 45min, Disintegrate with a hammer mill, then 18 more times
The powder is passed through a 0 μm sieve. It should be noted that Table 1 is shown in two stages because it has various chemical components.

Table 2 uses the Mo-V type prealloyed steel powder of Table 1 and Fe ₃ P having a grain size of 45 μm or less and an O content of 0.4%.
Powder (median diameter when measured with a laser light diffraction type particle size analyzer: 11 μm), 0.6% of P weight after mixing, green compact density, tensile strength and impact value of sintered body Indicates. At that time, the density of the green compact was measured by JPMA P 09.
According to -1992, 1 wt% of zinc stearate powder was blended as a lubricant, and a cylindrical sample molded at a pressure of 686 MPa was used. The impact value of the sintered body is JPMAM 05-
According to 1992, 1 wt% zinc stearate powder was blended and molded at 686 MPa, and the cylindrical sample was sintered under the following conditions and measured as a notched test piece. The tensile strength of the sintered body was 1 wt% of zinc stearate powder mixed to form a bar of 15 × 15 × 55 mm at 686 MPa and then sintered, and a small round bar having a parallel portion of 5φ × 15 mm. The test piece was machined and measured. Incidentally, the sintering of the holds between 1150 ° C. × 60min in a mixed gas of _{(N 2 -10vol% H 2)} , then 700-3
It was performed by cooling between 00 ° C at a rate of 20 to 30 ° C / min.

From Table 2, each of the Mo-V type prealloyed steel powders whose compositions are shown in Table 1, the grain size of 45 μm or less, and the O content of 0.4.
A mixed steel powder for powder metallurgy according to the present invention, which comprises 0% Fe ₃ P powder so that the P amount becomes 0.6% as a whole (hereinafter,
Simply mixed steel powder), the density of the green compact is 7.0 Mg / m
^{When it is 3} or more, it shows compressibility comparable to that of pure iron powder, and it is clear that the sintered body has high tensile strength and impact value. On the other hand, as shown in the comparative example of the table, in the pre-alloyed steel powder in which Si, Mn, Cr, Al, and V which are easily oxidizable elements than Fe exceed a predetermined amount, the O amount rapidly increases, and C, When P, S, Mo, and V exceed a predetermined amount, the compressibility (compacted powder density) is sharply reduced. It is also apparent that even if Mo and V are blended in amounts exceeding the limits specified in the present invention, the compressibility of the steel powder sharply decreases, so that the strength and toughness of the sintered body sharply decrease.

[0029]

[Table 1]

[0030]

[Table 2]

Example 2 Table 3 shows that 1.5% Mo-0.
It is a chemical composition of 15% V pre-alloyed steel powder (A). This pre-alloyed steel powder (A) has a particle size of 45 μm or less and an O content of 0.4
Mix 0% Fe ₃ P powder (median diameter: 11 μm),
Table 4 shows the effects of the O content and the P content on the density of the green compact and the tensile strength and impact value of the sintered body.

From Table 4, when the O content of the Fe ₃ P powder to be mixed is 1.0% or less, and when the P content is 0.1 to 0.
When it was 6%, the strength and toughness of the sintered body were further increased. The production of the pre-alloyed steel powder (A), the measurement of the green compact density, the sintering conditions, the tensile strength and the impact value of the sintered body were all the same as in Example 1. The production and density measurement of these green compact samples, the sintering conditions, the measurement of the tensile strength and impact value of the sintered body, etc. are common to the examples described below.

[0033]

[Table 3]

[0034]

[Table 4]

(Example 3) Tables 5 and 6 show water atomization.
Mo-V-Cu-Ni-Co pre-alloyed steel manufactured by the method
The chemical composition of the powder is shown. Further, Table 7 shows M of Table 5 and Table 6.
Using o-V-Cu-Ni-Co prealloyed steel powder,
Fe of less than 45 μm and O content of 0.40% ₃P powder (meji
(Am diameter: 11 μm) when 0.6% of P content is mixed
The density of the green compact and the tensile strength and impact value of the sintered body are shown.

From Table 7, Mo-V shown in Table 5 and Table 6
-Cu-Ni-Co pre-alloyed steel powder with a particle size of 45 μm
Fe with an O content of 0.40% below₃0.6 with P powder
% Of the mixed steel powder according to the present invention, compared with the comparative example,
The density of the powder is 7.0 Mg / m ³The same level of compression as pure iron powder
And the sintered body has high tensile strength and impact value.
I understand.

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

Example 4 Tables 8 and 9 show the chemical compositions of Mo-V-Nb-B type prealloyed steel powder produced by the water atomizing method. Table 10 shows Mo-V- of Tables 8 and 9.
Fe ₃ P powder with a grain size of 45 μm or less and an O content of 0.40% (median diameter: 11 μm) using Nb-B type prealloyed steel powder
The powder density, the tensile strength and the impact value of the sintered body when m) is mixed with 0.6% by P amount are shown.

From Table 10, Mo-VN of Table 8 and Table 9
The mixed steel powder according to the present invention in which the b-B system prealloyed steel powder and the Fe ₃ P powder having a grain size of 45 μm or less and an O amount of 0.40% are blended by 0.6% by P amount are comparative examples. In comparison with the above, the compact exhibits a compressibility comparable to that of pure iron powder having a green compact density of 7.0 Mg / m ³ or more, and the sintered body has high tensile strength and impact value.

[0042]

[Table 8]

[0043]

[Table 9]

[0044]

[Table 10]

(Example 5) Table 11 shows the chemical composition of the Mo-V-Cu-Ni-Co-Nb-B type prealloyed steel powder produced by the water atomizing method. Further, Table 12 shows M of Table 11.
o-V-Cu-Ni- Co-Nb-B -based using prealloyed steel powder having a particle size O amount is 0.40 percent by 45μm or less Fe ₃ P
The powder compact density of the mixed steel powder which mix | blended powder (median diameter: 11 micrometers) with 0.6% of P amount, and the tensile strength and impact value of a sintered body are shown.

From Table 12, Mo-V-Cu-N of Table 11
i-Co-Nb-B-based and prealloyed steel powder, 0.6% particle size and O amount 45μm or less 0.40% of the Fe ₃ P powder in the amount of P
The blended mixed steel powder according to the present invention exhibits a compressibility comparable to that of pure iron powder having a green compact density of 7.0 Mg / m ³ or more as compared with the comparative example, and the sintered body has a tensile strength and an impact value. Is clearly strong.

[0047]

[Table 11]

[0048]

[Table 12]

Example 6 In Table 13, 2.10% Mo-
0.55% V pre-alloyed steel powder (B), 2.10% Mo-0.
55V-2.50% Ni-0.50% Cu-6.50%
Co pre-alloyed steel powder (C) and 2.10% Mo-0.55%
V-2.50% Ni-0.50% Cu-6.50% Co
The chemical composition of -0.050% Nb-0.03% B pre-alloyed steel powder (D) is shown. Tables 14 and 15 use the B, C, and D prealloyed steel powders described in Table 13, and have a particle size of 45 μm.
Fe ₃ P powder with an O content of 0.40% (median diameter: 1
1 μm) in P content of 0.6%, Mo powder: 4% or less, Cu
Powder: 4% or less, Ni powder: 10% or less, Co powder: 4% or less, and W powder: 4% or less of a powder compact density and a sintered body when mixed with at least one kind of metal powder. Tensile strength and impact value. In addition, Mo powder, Cu powder, Ni powder, Co powder and W powder
As the powders, metal powders of 25 μm or less in which oxides were reduced were simply mixed.

From Tables 14 and 15, 2.10% Mo-
0.55% V pre-alloyed steel powder (B), 2.10% Mo-0.
55% V-2.50% Ni-0.50% Cu-6.50
% Co prealloyed steel powder (C) and 2.10% Mo-0.55
% V-2.50% Ni-0.50% Cu-6.50% C
o-0.050% Nb-0.03% B pre-alloyed steel powder (D)
And Fe ₃ P with a particle size of 45 μm or less and an O content of 0.40%
0.6% of P in powder, Mo powder: 4% or less, Cu powder: 4
% Or less, Ni powder: 10% or less, Co powder: 4% or less and W
Powder: The mixed steel powder according to the present invention mixed with one or more kinds of metal powder of 4% or less is higher in compaction than in the case of using each original prealloyed steel powder (comparative example) The density of the body is shown, and it can be seen that the tensile strength and impact value of the sintered body are stronger than those of the respective prealloyed steel powder alone.

[0051]

[Table 13]

[0052]

[Table 14]

[0053]

[Table 15]

Example 7 In Table 16, 2.10% Mo-
0.55% V-0.55% Nb-0.03% B pre-alloyed steel powder (E) and 2.10% Mo-0.55% V-6.00
% Ni-4.00% Cu-10.00% Co-0.05
The chemical composition of the% Nb-0.03% B prealloyed steel powder (F) is shown. Further, Table 17 shows that on the surface of the pre-alloyed steel powder of E and F shown in Table 16, the amount of Mo is 4% or less, the amount of Cu is 4% or less, N
One or more of an i content of 10% or less, a Co content of 4% or less, and a W content of 4% or less are diffused and adhered, and the particle size is 45
Green compact density of mixed steel powder and tensile strength of sintered body when Fe ₃ P powder (median diameter: 11 μm) having an O content of 0.40% or less and a P content of 0.6% is mixed. And the impact value. Furthermore, E, F to pre-alloyed steel powder, Mo, Cu, N
The diffusion adhesion of i, Co and W is 10 μm or less of MoO ₃
Powder, Cu ₂ O powder of 10 μm or less, carbonyl Ni powder of 45 μm or less, reduced Co powder of 25 μm or less and reduced W powder of 25 μm or less, and a temperature gradient of 800 to 900 ° C. in H ₂ gas flow. It was heat-treated in a continuous furnace, crushed with a hammer mill, and made a powder passing through a sieve of 180 μm.

From Table 17, 2.10% Mo-0.05%
Nb-0.03% B pre-alloyed steel powder (E) and 2.10% M
o-0.55% V-6.00% Ni-4.00% Cu-
10.00% Co-0.05% Nb-0.03% B pre-alloyed steel powder (F) with Mo, Cu, Ni, Co and W, respectively.
A mixture according to the present invention in which a pre-alloyed steel powder in which at least one of them is diffused and adhered is mixed with a Fe ₃ P powder having a particle size of 45 μm or less and an O amount of 0.40% and a P amount of 0.6%. As for the steel powder, when each original pre-alloyed steel powder was used (comparative example)
It is clear that it shows higher green compact density and that the tensile strength and impact value of the sintered body are much stronger than those of the respective prealloyed steel powders.

[0056]

[Table 16]

[0057]

[Table 17]

(Example 8) Table 19 shows the 2.10% Mo-0.55% V prealloyed steel powder (B) already described in Table 11.
In addition, when the particle size of the Fe ₃ P powder having an O amount of 0.40% and the compounding P amount were changed, and when the compounding amount of the graphite powder was changed, the amounts of the lubricant and the organic binder were changed. It is the green compact density, the tensile strength of the sintered body, and the impact value of the material for sintering. Further, the compounded powders shown in Table 18 were heated to 120 ° C. by a Henschel mixer and mixed for 15 minutes.

From Table 19, the particle size of the Fe ₃ P powder is 75 μm.
At the following times, when the P content is 0.1 to 0.6%, when the graphite content is 1.2% or less, and when the lubricant and the organic binder content is 2% or less, they are burned. It is clear that the binder material has a high green compact density and the sintered body has a high tensile strength and impact value. In addition, Fe ₃ P
The particle size of the powder is 45 μm or less, and the P content is 0.2 to 0.6.
%, When the graphite content is 0.40 to 0.9%, the tensile strength and impact value of the sintered body show much stronger values. In addition, when observing the structure of the cross section of the sintered body polished and etched with a 3% nitric acid alcohol solution with an optical microscope, a large number of coarse pores of about 150 μm exist when the particle size of Fe ₃ P powder is 100 μm. It was also observed that when the amount was 0.7%, the steadite phase was present at the crystal grain boundaries, and when the graphite content was 1.3%, the proeutectoid cementite phase was present at the crystal grain boundaries.

[0060]

[Table 18]

[0061]

[Table 19]

[0062]

As described above, according to the present invention, the oxidation of the prealloyed steel powder can be prevented as much as possible in the heat treatment process such as atomization process, reduction annealing process, sintering process and carburizing and quenching of molten steel, and Since the hardness of the Fe base in the powder stage can be made equal to that of pure iron powder, the mixed powder of the prealloyed steel powder and iron phosphorus powder, or the mixed powder of iron phosphorus powder and graphite powder is pure. When iron powder was used, it became as highly compressible as possible. Further, even in a sintered body containing P and a heat treated body such as carburizing and quenching, due to solid solution strengthening by P and spheroidization of pores, and in a sintered body containing C and P and a heat treating body such as carburizing and quenching. In addition, due to the solid solution strengthening of P, spheroidization of pores, and refinement of the structure in which fine V carbides were precipitated in addition to the precipitation of Mo carbides, the strength was further enhanced compared to when using a single Mo pre-alloy powder. A mixed steel powder for powder metallurgy and a sintered body thereof having high toughness were obtained. Furthermore, Mo powder, Cu powder, N
Since at least one of i powder, Co powder and W powder is mixed or partially diffused and contained, the structure becomes complex, and the sintered body and the heat treated body such as carburizing and quenching have higher strength and higher toughness. I can achieve it.

Claims (6)

[Claims] 1. C: 0.02% or less by weight%, Si:
0.1% or less, Mn: 0.3% or less, P: 0.03% or less, S: 0.03% or less, Cr: 0.1% or less, Al:
0.1% or less, Mo: 0.1 to 6.0%, V: 0.05
~ 2.0%, O: 0.25% or less, the balance is prealloyed steel powder consisting of Fe and unavoidable impurities, and O content is 1.0%.
A mixed steel powder for powder metallurgy, which is obtained by mixing the following iron-phosphorus powder so that the P content is 0.1 to 0.6%. 2. The prealloyed steel powder further comprises C by weight%.
u: 4.0% or less, Ni: 6.0% or less, Co: 10.
The mixed steel powder for powder metallurgy according to claim 1, characterized in that it contains one or more of 0% or less. 3. The prealloyed steel powder further comprises N in a weight percentage.
b: 0.10% or less, B: 0.03% or less, and one or more kinds are contained, The mixed steel powder for powder metallurgy according to claim 1 or 2. 4. The prealloyed steel powder according to claim 1, wherein Mo: 4% or less, Cu: 4% or less, N in weight%.
The metal powder of any one or more of i: 10% or less, Co: 4% or less and W: 8% or less is partially diffused and adhered, and the metal powder according to any one of claims 1 to 3. Mixed steel powder for powder metallurgy. 5. The prealloyed steel powder according to any one of claims 1 to 3, in terms of weight%, Mo powder: 4% or less, Cu powder: 4% or less,
Ni powder: 10% or less, Co powder: 4% or less and W powder: 8%
The mixed steel powder for powder metallurgy according to any one of claims 1 to 3, wherein one or more kinds of the following metal powders are mixed. 6. The mixed steel powder for powder metallurgy according to any one of claims 1 to 5, in which the weight% is graphite powder: 1.2% or less and 2%.
A sintering material characterized by being mixed with one or more of the following lubricants and organic binders.