JP3446322B2 - Alloy steel powder for powder metallurgy - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a Mo-V prealloy for powder metallurgy, which is suitable for producing high-strength sintered materials, sintered carburized and hardened materials, sintered forged materials and sintered forged carburized and hardened materials. Steel powder and
The present invention relates to a partially diffused Mo-V prealloyed steel powder obtained by partially diffusing one or more kinds of Mo powder, Cu powder, Ni powder, Co powder and W powder, and is suitable for heat treatment such as carburizing, nitriding and quenching. Used for.

[0002]

2. Description of the Related Art Sintered materials, sinter-carburized and hardened materials, sinter-forged materials, which are manufactured by powder metallurgy using alloy steel powder as a raw material,
Sintered forging, carburizing and quenching materials, etc. (Sizing, coining, cutting and drilling, etc. to correct and shape dimensions and shapes,
The surface treatment such as shot peening and carbonitriding is included, and hence "sintered heat treatment material") is gradually being expanded to the area of high strength parts. For example, high tensile strength and fatigue strength are required for gears as automobile parts. When manufacturing automobile gears by powder metallurgy, Mo, Cu, Ni, Co, W, Mn, C to improve tensile strength and fatigue strength.
An iron-based sintered heat-treated material in which r, V, P, Si, etc. are alloyed is manufactured and subjected to carburizing, nitriding-quenching-tempering heat treatment.
In general, iron-based sintered heat-treated materials have higher fatigue strength as their tensile strength is higher. Therefore, alloy steel powder having higher tensile strength has been developed. In order to increase the strength of iron-based sintered heat-treated materials, strengthening the matrix (also called matrix),
It is necessary to achieve high compressibility (reduction of pores) and low oxygen content (reduction of inclusions). In the manufacturing process of iron powder or the mixing process before compression molding (also referred to as raw material powder stage),
Alloying elements such as C, Mo, Cu, Ni, Co, W, Mn, Cr, V, P and Si are added.

At the stage of raw material powder, C, Mo, Cu, Ni, Co,
As a powder with alloy elements such as W, Mn, Cr, V, P, and Si added, (1) Mixed powder in which each alloy element powder is mixed with pure iron powder (2) Prealloy completely alloyed with each element Steel powder (3) Partially diffused alloy steel powder (also referred to as complex alloy steel powder) is manufactured in which each alloy element powder is partially diffused and adhered to the surface of pure iron powder or prealloyed steel powder.

The mixed powder obtained by mixing the alloy element powders with the pure iron powder of (1) has an advantage that high compressibility comparable to that of pure iron powder can be secured. However, it was added during sintering.
Active metals such as Mn, Cr, V, and Si are less than Fe, and the CO ₂ concentration and dew point in the sintering atmosphere and carburizing atmosphere are not strictly controlled to be low. There is a problem in that the elements cannot be sufficiently diffused into Fe and the matrix strengthening cannot be achieved with a heterogeneous structure.

For this reason, the mixed powder obtained by blending the pure iron powder with each alloy element powder in (1) cannot meet the recent demand for higher strength, and is in a state of being unused. In contrast,
The pre-alloyed steel powder obtained by completely alloying each element of (2) is produced by atomizing molten steel, and therefore causes solid solution hardening due to oxidation and complete alloying in the atomizing process of molten steel.
By limiting the types and amounts of alloying elements such as o, Mn, Cr, V, and Si, it is possible to secure low oxygen content and high compressibility comparable to pure iron powder. In addition, there is a possibility of strengthening the base by completely alloying it, and it is being developed as a prealloyed steel powder for high strength.

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 produce a pure alloy powder. Since each metal powder is partially diffusion-bonded to the surface of iron powder or prealloyed steel powder, the advantages of the mixed powder of (1) and the prealloyed steel powder of (2) can be combined. Therefore, it is possible to secure low oxygen content and high compressibility comparable to that of pure iron powder, and there is a possibility of strengthening the matrix as a composite structure consisting of a complete alloy phase and a partially concentrated phase. It is being developed as a partial diffusion prealloyed steel powder.

Mo is often used as a basic alloying component of the prealloyed steel powder and the partial diffusion prealloyed steel powder.
This is for the same reason that Mo is used as a strengthening element for steel materials. In other words, Mo prevents the formation of ferrite in steel materials, transforms and strengthens the matrix (matrix) by forming a bainite structure, partitioning the matrix into carbides and solid solution strengthening the matrix and forming fine carbides. Precipitate and strengthen the phase. Further, since it has good gas carburizing property and is a non-grain boundary oxidation element, it is carburized and strengthened.

Therefore, Mo is indispensable and Mn, Cr, V,
As regards high-strength prealloyed steel powder with limited Si, Japanese Patent Publication No. 58-10962, Japanese Patent Publication No. 4-74406, Japanese Patent Publication No. 59-226153, Japanese Patent Publication No. 4-59361, JPA
61-295302 and WO90 / 06198 are known. Further, as a mother powder, a high-strength prealloyed steel powder containing Mo as an essential element and Mn, Cr, V, and Si restricted, and Cu powder or Cu oxide powder and Ni powder or Ni oxide powder partially Regarding the partially diffused prealloyed steel powder that has been diffused and adhered, Japanese Patent Publication No. 63-66362, Japanese Patent Publication No. 5-68522 and Japanese Patent Publication No.
The 6-19081 publication is known.

[0009]

[Problems to be Solved by the Invention] Including Mo as an essential element,
There are the following problems with the known high-strength prealloyed steel powders with limited Mn, Cr, V, and Si. The prealloyed steel powder described in JP-B-58-10962 has a high Mn of 0.35 to 1.50%,
Since Mn is oxidized in each step of water atomization, reduction annealing, sintering and carburizing and quenching, and the carburizing and quenching material increases retained austenite, there is a problem that the strength is low relative to the amount of alloy.

Japanese Patent Publication No. 4-74406 and Japanese Patent Laid-Open No. 59-226
The prealloyed steel powder described in Japanese Patent No. 153 has a problem of poor compressibility because it has a high C content of 0.03 to 0.4%. Tokkyo 4-
The prealloyed steel powder described in 59361 has a Cr content of 0.1 to 0.3%.
Therefore, since Cr is oxidized in each step of water atomizing, reduction annealing, sintering and carburizing and quenching, and the retained austenite increases in the carburized and quenched material, there is a problem that the strength is low relative to the amount of alloy.

JP-A-61-295302 and WO90 / 06198
Since the prealloyed steel powder described in Japanese Patent Publication is a single-element prealloy containing 0.2 to 2.5% of Mo, it has a problem that the strength of the carburized and quenched material is low. Also, Mo is included as an essential element,
Known partial diffusion in which high-strength prealloyed steel powder with limited Mn, Cr, V, Si, etc. is used as the mother powder, and Cu powder or Cu oxide powder and Ni powder or Ni oxide powder are partially diffused and adhered to it. The pre-alloyed steel powder also has the following problems.

Japanese Patent Publication No. 63-66362 and Japanese Patent Publication No. 5-6852
The partially-diffused prealloyed steel powder described in Japanese Patent No. 2 is a single-element prealloy having a Mo content of 0.1 to a maximum of 2.0%, and therefore has a problem that the strength of the carburized and quenched material is low. The partially diffused prealloyed steel powder described in Japanese Examined Patent Publication No. 6-19901 has an Mn of 0.05 to 0.25%.
However, since Mo is 0.2-1.5%, Mn
There is no base strengthening. Therefore, this is also the same as the pre-alloy of a single element of Mo and has a problem that the strength of the carburized and quenched material is low.

The present invention ensures the low oxygen content in the powder stage and the high compressibility comparable to that of pure iron powder, which is the above-mentioned problem, and the low oxygen content in the sintered material or the carburized and hardened material. An object of the present invention is to provide a high-strength prealloyed steel powder and partially diffused prealloyed steel powder that have achieved matrix strengthening and contain Mo and V as essential elements.

[0014]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems by ensuring a low oxygen content in the powder stage and a high compressibility comparable to that of pure iron powder, and by sintering or carburizing and quenching. Improved base strengthening with low oxygen content in 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, O: 0.25% or less, Mo: 0.1-6.0% and V: 0.05
Steel powder containing a pre-alloy with a basic composition of ~ 2.0%.

The Mo-V pre-alloyed steel powder of the present invention is obtained by limiting the amount of easily oxidizable elements lower than that of Fe in heat treatment processes such as atomization process, reduction annealing process, sintering process and carburizing and quenching process of molten steel. Based on the finding that low oxygen content can be achieved. The Mo-V prealloyed steel powder of the present invention is based on the finding that a high compressibility comparable to that of pure iron powder can be secured because the oxygen content is reduced, the carbon content is reduced, and the hardness of the matrix is equivalent to that of pure iron.

When the Mo-V prealloyed steel powder of the present invention is mixed with graphite and sintered as compared with the Mo single prealloyed steel powder and further heat-treated, in addition to Mo carbide, the mutual content of Mo-V is increased. It is based on the finding that finer V carbides are precipitated by the action and the structure is refined, so that higher strength can be achieved. The pre-alloyed steel powder containing Mo-V of the present invention and further containing at least one of Cu, Ni, Co and W strengthens the matrix in a sintered heat treatment material containing C in a solid solution and has a fine structure. Therefore, it is based on the knowledge that higher strength can be achieved.

The Mo-V of the present invention is essential, or
Pre-alloyed steel powder containing at least one of Cu, Ni, Co and W by pre-alloying and at least one of Nb and B is solid solution strengthening of the matrix in the sintered heat treated material containing C, Nb
It is based on the finding that carbonitrides of B and B are precipitated and the structure can be made finer to further enhance the strength.

The pre-alloyed steel powder of the present invention containing at least one of Mo powder, Cu powder, Ni powder, Co powder and W powder is a pre-alloyed steel powder having the same composition. Compared with the above, it is based on the finding that the sintered heat-treated material containing C can achieve higher strength because of its superior compressibility. Of the present invention
Pre-alloyed steel powder that contains Mo-V as an essential material,
Mo powder or Mo oxide powder, Cu powder or Cu oxide powder, Ni powder or Ni oxide powder, Co powder or Co oxide powder and W powder or W oxide
The partially diffused prealloyed steel powder in which one or more kinds of powders are partially diffused and adhered as Mo, Cu, Ni, Co and W has a C content compared with the partially diffused prealloyed steel powder using the Mo single prealloyed steel powder. It is based on the finding that in a sintered heat-treated material containing, since the structure becomes complex and finer, higher strength can be achieved.

That is, the present invention comprises the following means. % By weight, 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, Mo: 0.1 to 6.0%, V: 0.05
To 2.0%, O: 0.25% or less only contains the balance of a powder metallurgical pre alloy steel powder, characterized in that it consists of Fe and unavoidable impurities, C in weight%: 0.02% or less, Si: 0.1% Below, 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 to 2.0%, O: 0.25% or less, Cu: 4.0%
Hereinafter, Ni: 6.0% or less, Co: 10.0% or less, W: 4.0% seen contains and one or more of the following, for powder metallurgy pre alloy steel balance being Fe and unavoidable impurities Powder, C: 0.02% or less by weight, Si: 0.1% or less, M
n: 0.3% or less, P: 0.03% or less, S: 0.03% or less, C
r: 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 and, Nb: 0.10% or less, or B: a 0.03% of one or more look-containing, powder metallurgy balance being Fe and unavoidable impurities a use pre alloyed steel powder, C in weight%: 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, Mo: 0.1 to
6.0%, V: 0.05 to 2.0%, O: 0.25% or less, Cu: 4.
0% or less, Ni: 6.0% or less, Co: 10.0% or less, W: 4.0
% Or less, and Nb: 0.10% or less,
B: see contains the 0.03% of one or more, the balance is a powder metallurgical pre coupling <br/> alloy steel powder, characterized in that it consists of Fe and unavoidable impurities, each of the claims 1 to 4 % By weight of the prealloyed steel powder, Mo powder: 4% or less, Cu powder: 4% or less, Ni
Powder: 10% or less, Co powder: 2.5% or less and W powder: a powder metallurgy alloy steel powder, characterized by comprising combined distribution of one or more powders of below 4%, claim 1 On the surface of the pre-alloyed steel powder described in each of 4 to 4, the Mo content: 4% or less, the Cu content: 4% or less, the Ni content: 10% or less, the Co content: 4% or less and the W content: The alloy steel powder for powder metallurgy is characterized in that 4% or less of one or more kinds of metal powder are partially diffused and adhered.

[0020]

The present invention is a low oxygen, low carbon Mo-V prealloyed steel powder and a partially diffused Mo-V prealloyed steel powder having a compressibility as high as that of pure iron powder. Alternatively, compared with the partially diffused prealloyed steel powder, the sintered heat-treated material containing C has further improved strength. Therefore, in the present invention,
Its oxide is Mo, Cu, N, which are more reducing elements than Fe oxide.
Although i, Co and W can be contained in a prealloy or partially diffused and adhered, their oxides limit the amounts of Si, Mn and Cr, which are hard-to-reduce elements, to Fe, to less than Al, Ti, Zr. , C
The amounts of a, Mg, etc. are inevitably mixed with the current molten steel refining technology. The effect of each alloying element in the steel powder of the present invention and the reasons for limiting the content will be described below.

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
%, Al: 0.1% or less, O: 0.25% or less of prealloy; C, Si, Mn, P, S, Cr and O tend to have higher compressibility as the amount of prealloy is lower. C, P, and S are elements that have a large hardening effect on the ferrite phase of the steel powder and significantly deteriorate compression workability. Further, Si, Mn, Cr, and Al have a positive correlation with the O amount of the steel powder, and further have a positive correlation between the O amount of the steel powder and the green compact density. Si: 0.1% or less, Mn: 0.3% or less, Cr: 0.1% or less, Al: 0.1% or less O:
This is the condition under which steel powder of 0.25% or less can be produced. In addition to this, when C: 0.02% or less, P: 0.03% or less, and S: 0.03% or less, it is possible to produce a steel powder having a green compact density similar to that of pure iron powder.

That is, when 1 wt% of zinc stearate powder was mixed as a lubricant and molded at 686 MPa based on JSPM Standard 1-64 and the powder density was measured, it was as high as 7.0 Mg / m ³ or more of pure iron powder. To obtain the green compact density of C: 0.02% or less, Si: 0.1
% Or less, Mn: 0.3% or less, P: 0.03% or less, S: 0.03%
Below, Cr: 0.1% or less, Al: 0.1% or less, O: 0.25% or less.

Mo: 0.1-6.0%, V: 0.05-2.0% of pre-alloy; Mo and V both have a small hardening effect on the ferrite phase of the steel powder and have good compressibility, excellent carbonitriding properties, and C It is an essential element for achieving high strength in a sintered heat-treated material containing s, which transforms into a bainite phase or a martensite phase and precipitates fine carbonitrides to refine the structure. If Mo: less than 0.1% and V: less than 0.05%, there is no strength improving effect, and if Mo: more than 6.0% and V: more than 2.0%, a green compact density comparable to that of pure iron powder cannot be obtained. Therefore, Mo is limited to 0.1 to 6.0% and V is limited to 0.05 to 2.0%.

Cu: 4.0% or less, Ni: 6.0% or less, Co: 1
Pre-alloy with 0.0% or less and W: 4.0% or less; Pre-alloyed steel powder that requires Mo-V contains at least one of Cu, Ni, Co, and W as a pre-alloy, so that it is burned with graphite. During binding and heat treatment, in the sintered material the bainite phase or martensite phase transformation start is shifted to the low temperature side to make the structure finer, and in the carburized and tempered material the martensite transformation start is shifted to the low temperature side to strengthen the matrix. The strength is increased in both the sintered material and the carburized and hardened material. Cu: 4.0%
If the content of Ni exceeds 6.0%, Ni exceeds 6.0%, Co exceeds 10.0%, and W exceeds 4.0%, the green compact density decreases too much, and the retained austenite of the carburized and hardened material increases, and the strength decreases. Therefore,
Cu: 4.0% or less, Ni: 6.0% or less, Co: 10.0% or less,
W: Limited to 4.0% or less.

Pre-alloy of Nb: 0.10% or less or B: 0.03% or less; Mo-V pre-alloyed steel powder and a pre-alloy that essentially contains Mo-V containing at least one of Cu, Ni, Co and W By including at least one of Nb and B in the steel powder as a prealloy, carbonitride finely precipitates and further strengthens the matrix during sintering and heat treatment with graphite, but each Nb: exceeds 0.10%. , B: In the range of more than 0.03%, there is no strength improving effect. Therefore, it is limited to Nb: 0.10% or less and B: 0.03% or less.

Mo powder or Mo oxide powder containing less than 4% Mo, Cu
Less than 4% Cu powder or oxidized Cu powder, less than 10% Ni content
Ni powder or oxide Ni powder, Co powder with 4% or less of Co content or oxidation
About blending Co powder, W powder or oxidized W powder in an amount of 4% or less in W amount; Mo-V prealloyed steel powder or Mo-V containing at least one of Cu, Ni, Co and W is essential. The pre-alloyed steel powder to be used, or the pre-alloyed steel powder that requires Mo-V containing at least one of Cu, Ni, Co, W and at least one of Nb and B, is Mo powder, Cu.
Powder, Ni powder, Co powder, W powder are mixed together to sinter with graphite. When heat-treated, a composite structure consisting 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 material and the carburized and hardened material. At this time, the composite structure has a bainite phase in which carbon nitrides of Mo, V, and W are finely precipitated and a martensite phase due to a combination of C content and Mo powder, Cu powder, Ni powder, Co powder, and W powder. Will be distributed. Mixing in this case means that when Mo, Cu, Ni, Co, and W are metal powders, mixing and partial diffusion heat treatment are performed. When Mo, Cu, Ni, Co, and W are oxide powders, it means that a heat treatment that combines oxygen removal and partial diffusion is performed.

Mo content exceeds 4% and Cu content is 4%.
When the Ni content exceeds 10% and the Co content exceeds 4%, the green compact density is excessively decreased, and the retained austenite of the carburized and hardened material is increased to lower the strength. Therefore, Cu, N
The powder content of i, Co and W is 4% or less for each Mo content and C
The u content is limited to 4% or less, the Ni content is 10% or less, the Co content is 4% or less, and the W content is 4% or less.

[0028]

EXAMPLES Next, the present invention will be specifically described with reference to Examples. (Example 1) In Table 1, Mo-V manufactured by the water atomizing method is shown.
The chemical composition of the pre-alloyed steel powder of the system is shown.

[0029]

[Table 1]

These Mo--V type pre-alloyed steel powders are electrolytic Fe
After melting in Ar in a high frequency induction electric furnace with
Molten steel was allowed to flow naturally from an 8 mmφ refractory nozzle, and 0.3 m ³ / min of water was sprayed from an annular water nozzle at a pressure of 12 MPa to obtain powder. The alloy composition was adjusted by adding low carbon content ferroalloy and electrolytic metal to molten steel of electrolytic Fe. Mo
-V-type pre-alloyed steel powder is water atomized, dehydrated and vacuum dried, and then the steel powder that has passed through a 180 μm sieve is reduced in H ₂ gas (dew point 0 ° C) at 950 ° C x 45 min. It was annealed, crushed with a hammer mill, and passed through a 180 μm sieve once more to manufacture.

Regarding these Mo-V type prealloyed steel powders,
The green compact density, the tensile strength of the sintered material and the tensile strength of the carburized and tempered material were measured. The green density is 1-64 according to the JSPM standard, and 1 wt% zinc stearate powder is added as a lubricant,
It was molded at 686 MPa and measured. Tensile strength of sintered material is 0.9wt
% Graphite powder and 1 wt% zinc stearate powder, 68
After molding a bar of 10 × 10 × 55 mm at 6 MPa, N ₂ -10vol H ₂
Hold at 1150 ℃ × 60min in gas for 20 ~ 30 at 700 ~ 300 ℃
It was cooled at a rate of ° C / min, sintered, and machined into a small round bar test piece having a parallel portion of 5φ x 15 mm, and measured. The tensile strength of carburized and tempered materials is 0.15 wt% graphite powder and 1 wt%
Compounded with zinc stearate powder, 10 × 10 × 55mm at 686MPa
After molding the bar of 1150 ℃ × 60 in N ₂ -10vol H ₂ gas
min., chill and sinter between 700 and 300 ℃ at a rate of 20 to 30 ℃ / min, and machine into a small round bar test piece with a parallel part of 5 φ × 15 mm and a carbon potential of 0.9%. 920 ℃ × 150m in methanol-enriched enriched propane conversion gas
in Carburized in a methanol-drop-enriched propane metamorphic gas with a carbon potential of 0.7% 870 ℃ × 44min
Diffusion annealing, quenching in oil at 60 ℃, 180 ℃ × 60min
It was tempered in oil and measured.

From Table 1, C: 0.02% or less of the present invention, 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: 0.25
%, Mo: 0.1 to 6.0% and V: 0.05 to 2.0%, each of the Mo-V series prealloyed steel powders has a compaction density of 7.0 Mg / m ³ or more, which is similar to that of pure iron powder. The sintered and carburized and tempered products have high tensile strength.

On the other hand, the prealloyed steel powder is an easily oxidizable element than Fe.
When Si, Mn, Cr, Al, V exceeds a predetermined amount, the amount of O increases rapidly,
In addition, if C, P, S, Mo and V exceed a predetermined amount, the compressibility sharply decreases. Therefore, the strengths of the sintered body and the carburized and tempered body are sharply reduced. Further, even if Mo and V are pre-alloyed in excess of a predetermined amount, the compressibility sharply decreases, so that the strength of the sintered body and the carburized and tempered material sharply decreases despite the increase in the amount of alloy.

Example 2 Table 2 shows the chemical composition of the Mo-V-Cu-Ni-Co-W type prealloyed steel powder produced by the water atomizing method. These Mo-V-Cu-Ni-Co-W-based prealloyed steel powders were manufactured by the same method and conditions as the Mo-V-based prealloyed steel powders shown in Example 1, and were subjected to green compact density and firing. The tensile strength of the binder and the tensile strength of the carburized and tempered material were measured.

[0035]

[Table 2]

From Table 2, C: 0.02% or less of the present invention, 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: 0.25
% Or less, Mo: 0.1 to 6.0%, V: 0.05 to 2.0%,
Cu: 4.0% or less, Ni: 6.0% or less, Co: 10.0% or less,
W: Mo-V pre-alloyed with one or more of 4.0% or less
-Cu-Ni-Co-W system pre-alloyed steel powder is 7.0 Mg / m ³
The above-described powder densities comparable to those of pure iron powder are exhibited, and the tensile strengths of the sintered material and the carburized and tempered material thereof are much higher than those of the Mo-V type prealloyed steel powder shown in Table 1.

Example 3 Table 3 shows the chemical composition of the Mo-V-Nb-B type prealloyed steel powder produced by the water atomizing method.
These Mo-V-Nb-B-based prealloyed steel powders were manufactured by the same method and conditions as those of the Mo-V-based prealloyed steel powders shown in Example 1, as well as the green compact density and the tensile strength of the sintered material. Strength and tensile strength of the carburized and tempered material were measured.

[0038]

[Table 3]

From Table 3, C: 0.02% or less of the present invention, 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: 0.25
% Or less, Mo: 0.1 to 6.0%, V: 0.05 to 2.0%,
Mo-V-Nb-B pre-alloyed steel powder pre-alloyed with one or more of Nb: 0.008 to 0.10% and B: 0.0008 to 0.03% is as pure iron powder as 7.0 Mg / m ³ or more. The green compact density is shown in Table 1. The tensile strengths of the sintered material and the carburized and tempered material are much higher than those of the Mo-V type prealloyed steel powder shown in Table 1.

(Example 4) Table 4 shows the chemical composition of the Mo-V-Cu-Ni-Co-W-Nb-B type prealloyed steel powder produced by the water atomizing method. These Mo-V-Cu-Ni-Co-W-based prealloyed steel powders were manufactured by the same method and conditions as the Mo-V-based prealloyed steel powders shown in Example 1, and were subjected to green compact density and firing. The tensile strength of the binder and the tensile strength of the carburized and tempered material were measured.

[0041]

[Table 4]

From Table 4, C: 0.02% or less of the present invention, 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: 0.25
% Or less, Mo: 0.1 to 6.0%, V: 0.05 to 2.0%,
Cu: 4.0% or less, Ni: 6.0% or less, Co: 10.0% or less,
W: One or more of 4.0% or less and Nb: 0.008
~ 0.10%, B: 0.0008 to 0.03% of one or more pre-alloyed Mo-V-Cu-Ni-Co-W-Nb-B based pre-alloyed steel powder,
Both show a green compact density equivalent to that of pure iron powder of 7.0 Mg / m ³ or more,
Table 2 shows the tensile strengths of the sintered material and the carburized and tempered material.
It is much larger than the Mo-V-Cu-Ni-Co-W-based prealloyed steel powder shown in FIG.

(Example 5) In Table 5, 2.10% Mo-0.55V prealloyed steel powder (A), 2.10% Mo-0.55% V-2.50% Ni-2.50
% Cu-6.50% Co-2.50% W pre-alloyed steel powder (B) and 2.10
% Mo-0.55% V-6.00% Ni-4.00% Cu-10.00% Co-4.
Chemical composition of 00% W-0.046% Nb-0.01% B pre-alloyed steel powder (C) and Table 6 show Mo powder: 4% or less, Cu powder: 4% or less, Ni powder: 10% or less, respectively. The following shows the state of blending one or more metal powders of Co powder: 4% or less and W powder: 4% or less.

[0044]

[Table 5]

[0045]

[Table 6]

These 2.10% Mo-0.55V prealloyed steel powders, 2.
10% Mo-0.55% V-2.50% Ni-2.50% Cu-6.50% Co-2.
50% W pre-alloyed steel powder and 2.10% Mo-0.55% V-6.00% Ni
-4.00% Cu-10.00% Co-4.00% W-0.046% Nb-0.01
All the% B prealloyed steel powders were manufactured by the same method and conditions as the Mo-V based prealloyed steel powders shown in Example 1. Also,
Mo powder, Cu powder, Ni powder, Co powder and W powder are both engaged distribution using the 25μm following metal powder obtained by reducing an oxide. The green compact density, the tensile strength of the sintered material and the tensile strength of the carburized and tempered material were manufactured by the same method and conditions as in Example 1,
It was measured.

From Table 5, 2.10% Mo-0.55V prealloyed steel powder of the present invention, 2.10% Mo-0.55% V-2.50% Ni-2.50% Cu-6.
50% Co-2.50% W pre-alloyed steel powder and 2.10% Mo-0.55% V
−6.00% Ni−4.00% Cu−10.00% Co−4.00% W−0.046
% Nb-0.01% B pre-alloyed steel powder with Mo powder: 4% or less, Cu powder: 4
% Or less, Ni powder: 10% or less, Co powder: 4% or less and W powder:
Steel powder containing one or more metal powders of 4% or less is
Both of them show a higher green density than their original prealloyed steel powders, and the tensile strength of their sintered and carburized and tempered materials is much higher than their respective prealloyed steel powders.

Example 6 In Table 7, 2.10% Mo-0.55% V
-0.046% Nb-0.01% B pre-alloyed steel powder (D) and 2.10%
Mo-0.55% V-6.00% Ni-4.00% Cu-10.00% Co-4.00
% W-0.046% Nb-0.01% B composition of pre-alloyed steel powder (C) and Table 8 shows that Mo content is 4% or less for each.
Powder or Mo oxide powder, Cu powder or Cu oxide with a Cu content of 4% or less
Powder, Ni powder with Ni content less than 10% or Ni oxide powder, Co content 4%
The following shows the state of blending one or more powders of the following Co powder or oxidized Co powder and W powder or oxidized W powder with a W content of 4% or less.

[0049]

[Table 7]

[0050]

[Table 8]

The pre-alloyed steel powders were all Mo shown in Example 1.
It was manufactured by the same method and conditions as the -V type prealloyed steel powder. Further, Mo powder of 25 μm or less, Cu powder of 45 μm or less, Ni powder of 45 μm or less, Co powder of 25 μm or less, and W powder of 25 μm or less were used and mixed. Furthermore, as oxides, Mo oxide powders, Cu oxide powders of 10 μm or less,
The Ni oxide powder, the Co oxide powder, and the W oxide powder were used for mixing.
Diffusion adhesion of these metal powders and metal oxide powders to the pre-alloyed steel powder was performed by heat treatment in a continuous furnace with a temperature gradient of 800 to 900 ° C in an H ₂ stream, crushing with a hammer mill, and 180 μ
The powder was passed through a m 2 sieve. The green compact density, the tensile strength of the sintered material, and the tensile strength of the carburized and tempered material were manufactured and measured by the same method and conditions as in Example 1.

From Table 6, 2.10% Mo-0.55% V-of the present invention
0.046% Nb-0.01% B pre-alloyed steel powder and 2.10% Mo-0.55
% V-6.00% Ni-4.00% Cu-10.00% Co-4.00% W-0.
046% Nb-0.01% B pre-alloyed steel powder with 4% or less of Mo
Powder or Mo oxide powder, Cu powder or Cu oxide with a Cu content of 4% or less
Powder, Ni powder with Ni content less than 10% or Ni oxide powder, Co content 4%
The following Co powder or oxidized Co powder and one or more powders of W powder or oxidized W powder of 4% or less in W content are mixed, and Mo powder, Cu powder, Ni powder, Co The steel powder in which one or more of the W powder and the W powder are partially diffused and adhered has a higher green density than the respective original pre-alloyed steel powders, and its sintered material and carburized and tempered material The tensile strength is also much higher than that of each prealloyed steel powder.

[0053]

The Mo-V prealloyed steel powder of the present invention has a C: 0.02
% Or less, Si: 0.1% or less, Mn: 0.3% or less, P: 0.03%
Below, S: 0.03% or less, Cr: 0.1% or less, O: 0.25% or less, and Mo: 0.1-6.0% and V: 0.05-2.0% are the basic compositions, so the atomizing process and reduction annealing process of molten steel are performed. , It became possible to control the oxidation in the sintering process and the heat treatment process such as carburizing and quenching to a minimum, and to make the hardness of the Fe base in the steel powder stage as good as that of pure iron powder. Therefore, the Mo-V prealloyed steel powder of the present invention exhibits high compressibility comparable to that of pure iron powder in the compression molding process, and a high-density compact can be easily obtained.

The Mo-V prealloyed steel powder of the present invention is finer than the Mo single prealloyed steel powder, in addition to the precipitation of Mo carbide in the sintered material containing C and the heat treated material such as carburizing and quenching, fine V carbide. It has become possible to achieve higher strength due to the precipitation of fine particles and the refinement of the structure. The pre-alloyed steel powder containing Mo-V of the present invention as an essential component and further containing at least one of Cu, Ni, Co and W strengthens the solid solution of the Fe base in the sintered material containing C and the heat treated material such as carburizing and quenching. At the same time, there is an effect that further strengthening can be achieved because the structure is refined.

Mo-V of the present invention is essential, or
Pre-alloyed steel powder containing at least one of Cu, Ni, Co and W pre-alloyed and at least one of Nb and B is Nb in a sintered material containing C and a heat treated material such as carburizing and quenching. Since the carbonitrides of B and B are finely precipitated and the structure is refined, there is an effect that higher strength can be achieved.

The steel powder prepared by mixing one or more kinds of Mo powder, Cu powder, Ni powder, Co powder and W powder with the prealloyed steel powder containing Mo-V as an essential component of the present invention is a prealloyed steel powder having the same composition. In comparison, the compressibility is excellent, and since the structure is compounded in the sintered material containing C and the heat treated material such as carburizing and quenching, there is an effect that higher strength can be achieved. A pre-alloyed steel powder containing Mo-V of the present invention as an essential component is used as a base powder, and Mo powder or oxidized Mo
Powder, Cu powder or Cu oxide powder, Ni powder or Ni oxide powder, Co powder or Co oxide powder and W powder or W oxide powder for Mo, Cu, Ni,
Compared with the partial diffusion prealloyed steel powder using Mo single prealloyed steel powder, the partially diffused prealloyed steel powder in which one or more kinds of Co and W are partially diffused and adhered is a sintered material containing C and carburized. Since the structure of the heat treated material such as quenching becomes complex and the structure becomes finer, there is an effect that the strength can be more easily increased.

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Claims (6)

(57) [Claims] 1. By weight%, 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, Mo: 0.1-6.0
%, V: 0.05~2.0%, O : 0.25% or less only contains, it is the balance
Powder metallurgical pre alloy steel powder, characterized in that it consists of Fe and unavoidable impurities. 2. By weight%, 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, Mo: 0.1-6.0
%, V: 0.05 to 2.0%, O: 0.25% or less, Cu: 4.0%
Hereinafter, Ni: 6.0% or less, Co: 10.0% or less, W: 4.0% seen contains and one or more of the following, for powder metallurgy pre alloy steel balance being Fe and unavoidable impurities powder. 3. By weight%, 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, Mo: 0.1-6.0
%, V: 0.05 to 2.0%, O: 0.25% or less, Nb: 0.10%
Is a 0.03% or less of one or more viewing including, the balance or less or B
Powder metallurgical pre alloy steel powder, characterized in that it consists of Fe and unavoidable impurities. 4. By weight%, 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, Mo: 0.1-6.0
%, V: 0.05 to 2.0%, O: 0.25% or less, Cu: 4.0%
Hereinafter, Ni: 6.0% or less, Co: 10.0% or less, W: and one or more of 4.0% or less, further Nb: 0.10% or less, or B: see contains the 0.03% of one or more, the balance powder metallurgical pre coupling <br/> alloy steel powder, characterized in that it consists of Fe and unavoidable impurities. 5. The pre-alloyed steel powder according to each of claims 1 to 4, in weight%, Mo powder: 4% or less, Cu powder: 4% or less, Ni
Powder: 10% or less, Co powder: 2.5% or less and W powder: 4% for powder metallurgy alloy steel powder, characterized by comprising combined distribution of one or more powders of the following. 6. On the surface of the pre-alloyed steel powder according to each of claims 1 to 4, in weight%, Mo amount: 4% or less, Cu amount: 4%
Below, Ni content: 10% or less, Co content: 4% or less and W content: 4
% Or less of one or more kinds of metal powder partially diffused and adhered to the alloy steel powder for powder metallurgy.