JPH10219410A - High density sintered alloy material, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent mechanical properties, fatigue strength, sliding characteristic, etc., without using Cu and high carbon Fe alloy, to secure joining property, and to enable application to a joining member by providing an Fe-Ci-C alloy of specific composition, forming the structure at the time of sintering into the structure of two- phase region of α-phase and α+γ phase, regulating relative density after sintering to a specific value or above, and performing cooling from the above two-phase region. SOLUTION: This alloy has a composition consisting of, by weight, 2.0-6.0% Si, 0-0.5% C, and the balance iron. In this alloy, the structure at the time of sintering in a vacuum, reducing, or neutral atmosphere of >=1000 deg.C is formed into that of two- phase region of α-phase and/or α+γ phase and relative density after sintering is regulated to >=90%. Further, cooling is performed from the above two-phase region. By this method, high densification property at low temp. (1000-1150 deg.C) by high diffusivity of α-phase can be improved, the communication of pores with the surface can be shut off by spheroidizing the flat pores, crystalline grains can be refined and the coarsening of the crystalline grains can be prevented, heat treating property can be added, and further the coarsening of the crystalline grains can be prevented even if sintering is performed at >=1150 deg.C for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Fe--Si--C high-density sintered alloy material and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, high-density sintered alloys have been produced mainly for the purpose of improving strength and toughness, improving wear resistance, or improving airtightness against air / oil pressure. Various methods are adopted according to each purpose. Among these, as a typical production method, a method using a liquid phase sintering method in which a high carbon Fe alloy or Cu is mixed and liquefied at a high sintering temperature,
The first compact is cooled to a low temperature (700
After annealing at 成形 900 ° C.), there are known a method of performing pressure molding again to increase the density and sintering again, and a sintering forging method of hot-forming a compact or a preform in a heated state.

[0003] Particularly in the field of mechanical structural parts,
In order to improve better fatigue strength and wear resistance, various alloy steel powders or diffusion alloy steel powders were made to contain carbon and sintered at high density by re-pressing, re-sintering or sintering forging. Later, carburizing and quenching or gas nitrocarburizing and nitriding are used as a post-treatment.

[0004]

However, the liquid phase sintering method using a high-carbon Fe alloy generally has a melting start temperature near 1150 ° C. and is carried out at a high temperature of 1150 ° C. or more. Often (for example,
No. 19722). Particularly, in a sintered alloy steel containing a large amount of Cr and Mo in high carbon, the sintering temperature is 1%.
It is generally known that the density is not increased below 150 ° C.

[0005] From this fact, it is considered that the iron-based alloy is formed into two layers with the Cu-based sintered alloy material and then sintered simultaneously, or the iron-based sintered material is bonded and sintered to the ingot Cu-based material. There is a problem that the use is restricted when the inherent characteristics of the technology are used. That is, in order to enable two-layer joining sintering with a Cu-based sintered material, at least 1000 to 1000
It is necessary to increase the density in a low temperature range of 1150 ° C.

In general, in order to increase the strength of a sintered steel (improve fatigue strength), unlike the improvement of wear resistance of a tool or the like, the carbon concentration in a sintered alloy steel is reduced. Hold down,
Since it is necessary to carry out a surface hardening treatment such as carburizing or nitriding and minimize precipitation of carbides and the like in the base structure, the sintering temperature for higher density is increased,
In addition to the two-layer molding and sintering with the above-mentioned Cu-based sintered material, energy costs are required during sintering, and the jig becomes more expensive than an inexpensive graphite material, and the sintering cost is expensive. I have to be.

On the other hand, a method for realizing high density in a low temperature range
As a method, Cu-based materials whose melting onset temperature is in a lower temperature range
Liquid sintering technology that uses a Cu-based liquid phase by mixing
It is conceivable that when this is done, C
contains as much as 15 to 25% by weight of a u alloy, for example,
As can be seen from the mechanical properties equivalent to 6 types of SMF, ductility
And poor toughness and, for example,
30kg / mm labor limit ^TwoIt is almost impossible to improve
Lack of expectations and extremely high costs
There is a point.

Further, the re-pressing / re-sintering method or the sinter forging method also has a problem that the cost is extremely high because the number of manufacturing steps is remarkably increased. However, for example, the rotational bending fatigue strength is remarkably improved as compared with the above-mentioned Cu-based liquid phase sintered material. Approx. 55k if gas carburizing, quenching and tempering after resintering
g / mm ² level. However, even in this case, the strength is improved by only about 70% as compared with the same treated steel of the ingot material, and the pores contained in the sintered body still have a powder grain boundary larger than the measured porosity. It is considered that the surface remains as a surface defect, causing a reduction in strength.

[0009] Further, in the case of parts that do not like quenching distortion such as carburizing and quenching, it is common practice to perform nitriding or gas nitrocarburizing, which can perform heat treatment at a low temperature. Even after re-pressing and re-sintering, the nitride phase (ε phase or γ 'phase) precipitates at the grain boundary during gas nitrocarburizing treatment, causing significant deterioration in strength. Is a disadvantage.

[0010] In general, the surface layer is made to be a closed pore.
For example, shot peening or steaming is required, but these are not completely decisive for improving strength.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and is intended to provide high-density sintering having good mechanical properties without using Cu or a high-carbon Fe alloy. It is an object of the present invention to provide a gold material at a low cost, develop more favorable fatigue strength and sliding characteristics, and ensure that the material can be applied to a joining member by securing the joining property.

[0012]

In order to achieve the above-mentioned object, the high-density sintered alloy material according to the first invention has a silicon content of 2.0 to 6.0 wt% and a carbon content of Is an alloy composition consisting of 0 to 0.5 wt% and the balance substantially consisting of iron, and has a structure of α phase and / or α + γ phase when sintered in a vacuum, reducing or neutral atmosphere at 1000 ° C. or higher. 90% relative density after sintering
It is characterized by being cooled from the two-phase region of α phase and / or α + γ phase.

According to the present invention, the alloy composition is adjusted so as to obtain a state in which two phases of α phase and / or α + γ phase coexist at the sintering temperature. Low temperature (10
(100 to 1150 ° C.). While strengthening the solid solution by high silicon content,
The connection with the surface of the void can be broken by making the flat void shape spherical. When cooling from the α-phase single-phase region, γ
By depositing the phase, the crystal grains can be refined, and coarsening of the crystal grains can be prevented by the two-phase coexistence effect (pinning effect) during sintering in the two-phase coexistence region. Since the γ phase precipitated during sintering or cooling can be rapidly cooled and controlled to a structure such as martensite or bainite, heat treatment can be added. In addition to low-temperature sintering, sintering at a high temperature of 1150 ° C or more prevents sintering for a long period of time, thereby preventing the crystal grains from becoming coarser, thereby further densifying and refining the crystal grains. Can be used to improve the strength.

Next, the high-density sintered alloy material according to the second invention has a silicon content of 3.0 to 5.0 wt%, Mn, N
One or more of i and Cu are 2.0 to 6.0 wt.
%, The content of carbon is 0.05 to 0.4 wt%, and the balance is substantially iron. The structure at the time of sintering in a vacuum, reducing or neutral atmosphere at 1000 ° C. or more has an α phase. And / or a two-phase region of α + γ phase, a relative density after sintering is 90% or more, and a γ single-phase region is secured at a quenching temperature.

In the present invention, Mn, Ni, and Cu are 1
At 150 ° C. or lower, it is added to expand the γ-phase region and adjust the heat treatment property from the austenitic single-phase region. If the addition amount is controlled within the range of 2.0 to 6.0 wt%, the object of the present invention can be sufficiently achieved, and it is considered that adding more than this increases the cost.

Further, the high-density sintered alloy material according to the third invention has a silicon content of 2.0 to 6.0 wt%, a Cr content of 5.0 to 15.0 wt%, and a carbon content of 0.05 to 1%. .
0 wt%, with the balance being substantially iron
When sintering in a vacuum, reducing or neutral atmosphere at a temperature of 00 ° C. or more, the structure becomes a two-phase region of α phase and / or α + γ phase, the relative density after sintering is 90% or more, and It is characterized in that a γ single phase region is secured at the input temperature.

In the present invention, Cr acts as a ferrite stabilizing element on the high temperature side, but is considered to be a special element which functions as an austenite stabilizing element at about 1000 ° C. or less. Propose that it can be used in.

In each of the above inventions, Cr, Mo, V, Ti, A other than silicon for stabilizing the BBC phase of iron are used.
Preferably, at least one of l, P and Sn is added up to 2 wt%. The reason for setting the addition amount within 2 wt% is that it becomes too expensive from the viewpoint of cost,
This is because it is considered that when a large amount of Al, Sn, or the like is added, it becomes fragile.

Further, it is preferable to perform various heat treatments such as carburizing, carburizing and nitriding, nitriding, and nitrocarburizing for the purpose of increasing strength, imparting wear resistance and improving sliding characteristics. By performing these treatments, it is possible to prevent the precipitation of various coarse compounds in the voids and achieve higher strength.

A method for producing a high-density sintered alloy material according to a fourth aspect of the present invention is the method for producing a high-density sintered alloy material described above, wherein silicon powder having an average particle diameter of 10 μm or less;
A mixture of 40 to 60% by volume of a binder is mixed and kneaded with a mixture of iron diameter powder having an average particle size of 45 μm or less, and after the composition obtained by the mixing and kneading is injection-molded or extruded, the added binder is removed. And sintering.

In the present invention, the apparent density of the mixed powder can be increased by reducing the iron raw material powder to about 45 μm or less because the silicon raw material is easily crushed finely. In addition, by kneading and using it as an injection molding raw material, it can greatly contribute to cost reduction of injection molded parts.

Further, the high-density sintered alloy material can be joined and sintered with a copper-based material, and the high-density sintered alloy material is joined by two-layer forming, assembly joining, brazing joining, or welding joining. You can do it. As described above, in the present invention, it is possible to increase the density even in a low temperature range by adding a high concentration of silicon. Can be applied to joint sintering.

Further, according to the present invention, since high densification can be achieved in each single step without the need of twice pressing and sintering as in the repressing and resintering method, airtightness is required. In the application to the pneumatic component and the hydraulic component, the sealing process is not required, and the process can be performed at low cost. Further, in the re-pressing / re-sintering method, flat voids remain even after the re-pressing / re-sintering, and for example, during gas nitrocarburizing, the nitride is precipitated on the original powder grain boundary, so that the strength is deteriorated. On the other hand, in the present invention, the void shape is spherical,
Since the connection with the surface portion is broken, a remarkable strength improvement effect is obtained, and this effect enables an improvement effect more than the strength of re-pressing and re-sintering.

Further, according to the present invention, the γ phase coexists or exists as a single phase in the temperature range during sintering or during cooling, so that the heat treatment property not found in the conventional Fe—Si soft magnetic material is obtained. In addition, it has a strengthening function as a sintered alloy for mechanical structures.

[0025] In this way, by obtaining a high-density iron-based sintered body by sintering in a low temperature range with relatively inexpensive silicon as an added main component, a two-layer forming with a copper-based material can be performed.
If sintering or joining sintering is enabled, and it is applied to, for example, a group of components as a sliding material, it can greatly contribute to improvement in strength, functionality, and cost reduction. In addition, even if the sintered material is used alone, it greatly contributes to high strength, and can be combined with various heat treatments such as carburizing, carbonitriding, nitriding, and nitrocarburizing to achieve high fatigue strength. It is possible to greatly contribute to expansion.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a method for adding silicon, a powder obtained by alloying iron powder with a predetermined silicon wt% in advance or a Fe--Si alloy having a silicon concentration is mixed with iron powder as a mother alloy. However, it is desirable to use a silicon material powder because the mixed powder has excellent press moldability and shrinkage during sintering. Further, it is desirable that 50 wt% or more of the iron powder to be used is composed of iron powder of 45 μm or less.

When the material composition of the present invention is used as a raw material for injection molding, the iron powder is desirably 45 μm or less in consideration of the separability from the binder contained in the raw material. The flowability of the raw material during injection molding can be improved by mixing and adding the raw material powder as a fine powder having a size of 10 μm or less.

The content of silicon is 2.5 to 5.0.
More preferably, it is set to wt%. The reason is 5wt%
This is because, if it exceeds 2,000, the ductility sharply decreases, and if it is less than 2.5 wt%, it becomes difficult to adjust the components for high density.

[0029]

Next, specific embodiments of a high-density sintered alloy material and a method for producing the same according to the present invention will be described with reference to the drawings.

Example 1 In order to investigate the effect of sintering and densification due to the addition of Si, iron powder of -100 mesh or less (average particle size of about 150 μm) and iron powder of −300 mesh or less (average particle size of about 60 μm) were used. Powder, S less than -300 mesh
i powder, ferrosilicon of -350 mesh or less (51
wt%), SUS430 with an average particle size of 10 μm (17 wt%)
% Cr), graphite having an average particle size of 5 μm, and a phosphorus iron alloy (27 wt.
% P) and mix each powder in the formulation shown in Table 1,
Further, 0.5% by weight of Zn stearate as a lubricant is added.
After mixing, a tensile test piece for powder metallurgy was press-molded at a molding pressure of 5 ton / cm ² . Sintering is performed in a vacuum atmosphere (1
After sintering at 1100 ° C. and 1200 ° C. for 15 minutes, 1 hour and 4 hours under 0 ⁻² torr), the resultant was cooled with nitrogen gas at 600 torr. In addition, No. 1 to No. 31 is-
No. 300 iron powder or less. Numeral 32 indicates the case of iron powder of -100 mesh or less.

[0031]

[Table 1]

FIGS. 1 to 4 show a typical relationship between the amounts of Si and carbon to be added and densification (shrinkage) by sintering. As is apparent from these figures, 1100
2w in both temperature ranges of 1200 ° C and 1200 ° C
At t% or more, the density rapidly starts to increase, and when the Si content is 4.5 wt% and 6.0 wt%, the carbon content is 0.1 to 0.1%.
It can be seen that the density is maximized at 0.2 wt%. It is well known that the addition of carbon is an important factor in imparting heat treatment properties to a sintered material. For example, about 0.2 wt% of carbon steel is used for carburizing steel.

In FIG. 1, for example, 4.5 wt%
In the case of an alloy of Si and 6.0 wt% Si, the amount of added carbon is 0.1%.
The shrinkage clearly decreases around 6 to 0.9 wt%, which is considered to be a sintering delay phenomenon due to the precipitation of graphite, and this is more remarkable even at the high temperature side of 1200 ° C. Such a phenomenon is undesirable for high-strength materials. This phenomenon is caused by, for example, Cr, V, Mo, which is a ferrite stabilizing element and has a high affinity for carbon.
It is well known that it can be effectively prevented by the addition of a small amount of Ti or the like. Usually, it is recognized that the addition of 0.2 wt% or more stabilizes these ferrites such as Cr, V, Mo, Ti, etc. It is preferable to add an alloying element having an excellent affinity with the alloy. Also, in order to add heat treatment properties later, it is preferable to consider adding these elements at a maximum of 2 wt% or less. In addition, the addition of an alloy element more than this increases the cost. Also, as for austenite stabilizing elements such as Mn, Ni, Cu, etc., it is preferable to add up to 2% by weight in the same manner as the above elements from the viewpoint of ensuring heat treatment after quenching of austenite.

Further, as described later, Mn, Ni, Cu
The addition of an austenite stabilizing element such as that described above is controlled in relation to the amount of Si added. In particular, 2.0 to 6.0 wt% is used to expand the austenite region below 1000 ° C. and form the austenitic single phase region of the present invention. Add within the range.

Further, as described above, the use of a hardening and strengthening mechanism by the precipitation of nitrogen compounds such as carburizing / nitriding, nitriding, nitriding, and nitrocarburizing makes the addition of Al which is a ferrite stabilizing element effective. Some things are well-known facts,
2 wt% is used as the upper limit. The reason for setting the upper limit in this manner is that when the amount of Al added is increased, the risk of embrittlement due to a synergistic effect with Si is great.
In addition, P shows a liquid phase in a low temperature range and is a strong ferrite stabilizing element, so that an auxiliary effect of Si is recognized.
It is better to set wt% as the upper limit. It is known that when Si does not coexist, P functions as an expansion element when C coexists, but when Si coexists, that is, in the sintering condition region where ferrite or ferrite and austenite coexist, P Contributes as a shrinkage element, but does not contribute to shrinkage more than Si, and has an assisting feature to the last.

FIGS. 5 and 6 show that the Si content is 4.5, 6.
The influence of the sintering time at 1100 ° C and 1200 ° C at 0 wt% is shown. From these figures, it can be seen that even when the practical sintering time is within the range of 10 hours, even at 1100 ° C., the shrinkage achieved at 1200 ° C. is reached.
It can be seen that the alloy system of the present invention is very effective in increasing the density in a low temperature range. In FIGS. 5 and 6, the solid line indicates data at 1200 ° C., and the broken line indicates 1
Data at 100 ° C. are shown. FIG. 6 also shows data on Fe-6Si-0.4C at 1000 ° C. by a dashed line.

FIGS. 7 and 8 show the temperature dependence of the shrinkage at each sintering temperature. From these figures, it can be estimated that the shrinkage rates at 1 hour and 4 hours at 1000 ° C. are 1.2% and 2.5%, respectively, and from the same relationship as shown in FIG. 4%. This shows that within the range of the present invention, the sintering densification in a low temperature range is excellent. From this, for example, two-layer forming and sintering with a Cu-based sintered alloy (pure Cu has a melting point of about 1070 ° C., and a Corson alloy-based sintering temperature of about 1050 to 1070 ° C.), and joining with a molten Cu alloy-based It can be seen that sintering becomes possible. In particular, it has been reported that significant contraction of only the copper-based sintered layer during two-layer molding and sintering causes large deformation such as cracking and warpage at the two-layer molding interface. It can be said that the point which can be solved is a great achievement of the present invention.

9 and 10, 1100 ° C. for 4 hours,
The tensile strength of each test piece after sintering at 1200 ° C. for 4 hours is shown. Characteristic of the result at 1100 ° C. is that Si
The strength increases with the addition of
At less than wt%, a sharp improvement in strength is observed. At 1200 ° C., almost the same tendency is observed, but no clear improvement in strength is observed even with the addition of 4.5 wt% or more of Si. Therefore,
In the sintering temperature range of 1200 ° C. or more, it is desirable that the maximum amount of Si added be about 5 wt%.

FIG. 11 shows that 1100 ° C.
The effect of the amount of Si on the tensile strength and elongation (%) after rupture of the sintered body at −4 hr and 1200 ° C. for 1 hr is shown, but basically the embrittlement is remarkable due to the addition of 6 wt% Si. When applied to a product in which strength is emphasized, it is desirable to use it with the content suppressed to 5 wt% or less. When the amount of carbon exceeds 0.5 wt%, the elongation decreases to 5% or less. Therefore, it is desirable to keep the carbon content to 0.4 wt% or less if possible.

Regarding the effect of the size of the iron powder used, see Table 1 As shown at 32, -100
4.5 w using a mesh or less (average particle size of about 60 μm)
Investigation was conducted on t% Si, but basically, the size effect was only slightly delayed, and was not considered to have a significant effect on the gist of the present invention.

FIG. 12 is a phase diagram showing a stable region of the ferrite phase and the austenite phase when carbon is added to the Fe-4.5Si alloy. Comparing with the results of FIGS. 1 and 3, it can be seen that the region where remarkable sintering shrinkage coincides well with the range where the ferrite phase is precipitated.

Next, FIG. 13 to FIG. 13 show calculation results obtained by examining the influence of the above-described typical alloying elements in a state diagram in the same manner.
As shown in FIG. 13 to 15 show the results of studies on the effect of adding Mo as a representative of a ferrite stabilizing element and Mn and Cr as a representative of an austenite stabilizing element. The effect of the addition of Mo shown in FIG. 13 is the expansion of the simple ferrite phase region and the expansion of the (α + γ) two-phase region. The influence of Mn shown in FIG. 14 clearly remarkably expands the austenite (γ phase) region in the low temperature range, for example, 0.1%.
In a temperature range of 1000 ° C. or more with a carbon content of wt% or more, (α +
γ) Enables sintering in the two-phase region, and realizes an austenitic single-phase region in the temperature region below that, and complete heat treatment from this temperature region provides complete martensite, realizing effective heat treatment. We can see that we can do it. Also,
When Mn is added in an amount of 6 wt% or more, the (α + γ) two-phase region is sharply narrowed, and the above-described effect cannot be substantially realized.

FIG. 15 shows the effect of adding Cr. From this figure, it can be seen that on the high temperature side, the same heat-contribution as the above-mentioned heat treatment is exhibited, because the same contributes to the expansion of the ferrite region as Mo and the lower temperature side contributes to the expansion of the same austenite region as Mn. The reason for setting the maximum amount of Cr to be within 20 wt% is that it is judged that there is no necessity in view of the strength characteristics of the conventional high Cr steel.
In addition, the minimum addition amount was set in consideration of substantial heat treatment.

(Example 2) For investigating fatigue strength, -30 was used.
Iron powder of 0 mesh or less, Si of -300 mesh or less
Powder, graphite having an average particle size of 3 μm, S having an average particle size of 10 μm or less
Using US430 (17 wt% Cr), each powder was mixed in the composition shown in Table 2, and 0.5 wt% of a zinc stearate as a lubricant was added and mixed.
A rotation bending test piece material was prepared at n / cm ² . The sintering was performed under the same conditions as in Example 1 by vacuum sintering at 1100 ° C. for 10 hours. The sintered material was machined into an 8-diameter Ono-type rotating bending fatigue test piece, and then subjected to gas soft nitriding. The gas soft nitriding treatment was performed at 570 ° C. for 5 hours. In addition, using various ferromagnetic iron powders shown in Table 3 as reference comparative materials,
The repressing and resintering levels were also performed.

[0045]

[Table 2]

[Table 3]

As a result, although the strength was deteriorated by gas nitrocarburizing according to the conventional repressurizing and resintering method, the steel of the present invention showed remarkable improvement in fatigue strength by gas nitrocarburizing. It has been found that the reason for this is that there is no stress concentration due to the precipitation of the nitride on the original powder grain boundary due to the disconnection of the connection with the surface of the void in the sintered body. Furthermore, nitrogen was infiltrated into the surface by the additional carburizing / nitriding treatment, quenching was performed, and the fatigue strength was examined (test steels No. 4 and No. 5 in Table 2). A further improvement in fatigue strength was observed. In addition, carburizing is performed under the condition of a carbon potential of 1.1%.
According to the N ₂ -based carburizing method at 930 ° C. for 8 hours, the nitriding treatment was carried out by introducing ammonia into the furnace at 870 ° C. for 1 hour. No. 1 quenched from the austenitic single phase region with fine crystal grains. The Mn-added sintered material of No. 4 is
It is strengthened to almost the same strength as the carburized material of a normal molten steel material, and the effect of the present invention can be confirmed.

Example 3 A compound for metal injection molding was prepared by selecting iron powder having a size of -300 mesh or less and using Si powder having an average particle size of 4 μm. As the binder, JP-A-7-30
The one described in JP-A-5101 was used. In addition, iron powder and Si powder are 0.0, 3.0, 4.5, 6.0 wt%.
The mixture was mixed so as to be Si, and further added so that the added amount of the binder was 7 to 14 wt% in combination with the above-mentioned mixed powder, and the mixture was heated and kneaded to obtain a compound for injection molding. In order to investigate the flow characteristics of the compound, the flow value (gr / sec) at 150 ° C. was measured using a flow meter (manufactured by Shimadzu Corporation).

The result is shown in FIG. In the case of iron powder to which Si was not added, no fluidity was observed even when 12 wt% of the binder was added, and the fluidity began to appear at 14 wt%, but separation of the powder and the binder (dilatancy phenomenon) occurred, and substantial It was found that it could not be used as a compound for injection molding. But,
3.0, 4.5, 6.0 w of Si powder having an average particle size of 4 μm
When t% is added, good fluidity is exhibited without occurrence of a dilatancy phenomenon. In addition, compounds generally used at present for injection molding require 11 to 12% by weight of a binder. Equivalent effects were expressed, confirming the effectiveness of the present invention. Further, these compacts were gradually heated in the air to 300 ° C. over 24 hours to thermally degreasing the binder, and then 1100
As a result of sintering at 1100 ° C. for 1 hour at the same temperature as in the above example, it was confirmed that the sintering density reached approximately 1100 ° C. for 4 hours. From this, although the effect of shortening the sintering time due to the use of the fine Si powder is recognized, it is essentially the same as the gist regarding the low-temperature sinterability of the present invention.

An example of a mixture of a coarse metal powder and a fine metal powder in which the fluidity of a raw material for injection molding is improved is disclosed in Japanese Patent Publication No. 4-44441. It has been known that when coarse metal powder is added to fine metal powder as in the invention of the present invention, the sinterability is remarkably deteriorated, which is described in "RM Germa".
n: METALAGICAL TRANSACTION
A, 23A (1992), 1455/1464 ".

As a comparative example, a blending example of iron powder of -300 mesh or less (60 wt%) and carbonyl iron powder (40 wt%) having an average particle diameter of 5 μm, which was adjusted to have a composition of Fe-0.8 wt% C. 122
At 0 ° C. and 1 hr, the density of the sintered body of 100% by weight of carbonyl iron powder is 7.75 gr / cm ³ , whereas 6.
It has been found that the density is only about 89% in relative density of 93 gr / cm ³ .

The present invention realizes high density in a low temperature range as described above. Unlike the above-mentioned prior invention, the present invention uses Si, which is a nonmetallic element, as a fine powder. This is an effective one based on a unique idea of diffusing and dissolving Si into iron powder instead of fusing iron powder. Furthermore, according to the present invention, it is possible to provide a high-density sintered body at a low cost because it does not require the use of expensive metal fine powder and can achieve remarkable densification by sintering in a low temperature range. I have.

(Example 4) Two-layer molding with a copper-based sintered material
To investigate the sintering properties, iron powder of -300 mesh or less,-
Si powder of 300 mesh or less, graphite having an average particle size of 5 μm, SUS430 having an average particle size of 10 μm (17 wt% C
Using r), the respective powders were mixed according to the formulation shown in Table 4, and 0.5 wt% of Zn stearate as a lubricant was added and mixed to prepare a raw material. Further, as a copper-based material, electrolytic Cu powder of -150 mesh or less (manufactured by Fukuda Metal Foil Powder Co., Ltd., C
E15) and electrolytic Ni powder (-250 mesh or less),-
Using Si powder of 250 mesh or less, the respective powders were mixed in the composition shown in Table 4, and 0.5 wt% of Zn stearate was further added and mixed to prepare a raw material. The shape of the test piece was a disk shape as shown in FIG. 17, and a two-layer molded / sintered test material was prepared at a forming pressure of 5 ton / cm ² . Using such a test piece, sintering was performed at 1050 ° C.
Performed under vacuum for 4 hr.

[0053]

[Table 4]

As a result, the amount of warpage of the disk-shaped flat portion and the presence or absence of cracks at the joint surface were investigated. And no cracking occurred at the interface of the joint.

The above results indicate that deformation and cracking at the joint interface can be prevented by adjusting the amount of shrinkage when joining two types of dissimilar materials. The effectiveness of the present invention, which combines the shrinkability of the iron-based sintered material with the binding properties, has been proven. It can be seen that the above results can also be applied to the joining of an iron-based sintered body to a molten Cu-based material.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between dimensional shrinkage due to sintering at 1100 ° C. for 4 hours and carbon concentration.

FIG. 2 is a graph showing the relationship between the dimensional shrinkage due to sintering after 1100 ° C. and 4 hours and the Si concentration.

FIG. 3 is a graph showing a relationship between a dimensional shrinkage ratio due to sintering at 1200 ° C. for 1 hour and a carbon concentration.

FIG. 4 is a graph showing a relationship between a dimensional shrinkage ratio due to sintering at 1200 ° C. for 1 hour and a Si concentration.

FIG. 5 shows the results at 4 ° C. at 1100 ° C. and 1200 ° C.
It is a graph which shows the relationship between the dimensional shrinkage rate of 5 wt% Si-Fe system, and sintering time.

FIG. 6 shows the results obtained at 1100 ° C. and 1200 ° C .;
It is a graph which shows the relationship between the dimensional shrinkage rate of 0 wt% Si-Fe system, and sintering time.

FIG. 7 is a graph showing the effect of the sintering temperature on the dimensional shrinkage of a 4.5 wt% Si—Fe-based material.

FIG. 8 is a graph showing the effect of the sintering temperature on the dimensional shrinkage of a 6.0 wt% Si—Fe system.

FIG. 9 is a graph showing the influence of Si and C on the tensile strength of a sintered body at 1100 ° C. for 4 hours.

FIG. 10 is a graph showing the influence of Si and C on the tensile strength of a sintered body at 1200 ° C. for 1 hour.

FIG. 11 is a graph showing the relationship between the elongation at break of 1100 ° C. and 1200 ° C. sintered bodies and the amount of Si added.

FIG. 12 is a calculation cut-away diagram of an Fe-4.5 wt% Si—C-based alloy.

FIG. 13 is a graph showing the effect of Mo addition on the phase stability of an Fe-4.5 wt% Si—C-based alloy.

FIG. 14 is a graph showing the influence of Mn addition on the phase stability of a Fe-4.5 wt% Si—C-based alloy.

FIG. 15 is a graph showing the effect of adding Cr on the phase stability of an Fe-4.5 wt% Si—C-based alloy.

FIG. 16 is a graph showing the relationship between the fluidity of the metal injection molding compound and the mixing ratio of the Si fine powder.

FIG. 17 is a cross-sectional view of a test piece for joining test.

Claims (14)

[Claims] 1. A silicon content of 2.0 to 6.0 wt.
%, A carbon content of 0 to 0.5 wt%, and a balance substantially composed of iron, and the structure when sintered in a vacuum, reducing or neutral atmosphere at 1000 ° C. or more has an α phase and / or A high-density sintered alloy characterized by being a two-phase region of α + γ phase, having a relative density after sintering of 90% or more, and being cooled from a two-phase region of α-phase and / or α + γ phase material. 2. A method for stabilizing a BBC phase of iron.
The high-density sintered alloy material according to claim 1, wherein one or more of r, Mo, V, Ti, Al, P, and Sn are added up to 2 wt%. 3. A heat treatment, such as carburizing, carburizing, nitriding, nitriding, or nitrocarburizing, for the purpose of increasing strength, imparting wear resistance, and improving sliding characteristics. 3. The high-density sintered alloy material according to 1 or 2. 4. A silicon content of 3.0 to 5.0 wt.
%, Mn, Ni, and Cu are 2.0 to 2.0% or more.
6.0 wt%, carbon content 0.05-0.4 wt%,
The balance is an alloy composition consisting essentially of iron, and the structure when sintered in a vacuum, reducing or neutral atmosphere at 1000 ° C. or higher becomes a two-phase region of α phase and / or α + γ phase,
A high-density sintered alloy material having a relative density after sintering of 90% or more and securing a γ single phase region at a quenching temperature. 5. A method for stabilizing a BBC phase of iron.
The high-density sintered alloy material according to claim 4, wherein at least one of r, Mo, V, Ti, Al, P, and Sn is added up to 2 wt%. 6. A heat treatment, such as carburizing, carburizing, nitriding, nitriding, or nitrocarburizing, for the purpose of increasing strength, imparting wear resistance, and improving sliding characteristics. 6. The high-density sintered alloy material according to 4 or 5. 7. A silicon content of 2.0 to 6.0 wt.
%, Cr is 5.0 to 15.0 wt%, and carbon content is 0.1%.
0.5 to 1.0 wt%, with the balance being substantially iron, having an α phase and / or α + γ when sintered in a vacuum, reducing or neutral atmosphere at 1000 ° C. or higher.
A high-density sintered alloy material comprising a two-phase region of a phase, a relative density after sintering of 90% or more, and a γ single-phase region secured at a quenching temperature. 8. A method for stabilizing a BBC phase of iron.
The high-density sintered alloy material according to claim 7, wherein at least one of r, Mo, V, Ti, Al, P, and Sn is added up to 2 wt%. 9. A heat treatment, such as carburizing, carburizing, nitriding, nitriding, or nitrocarburizing, for the purpose of increasing strength, imparting wear resistance, and improving sliding characteristics. 9. The high-density sintered alloy material according to 7 or 8. 10. The high-density sintered alloy material according to claim 1, wherein the silicon raw material powder is a silicon raw material. 11. The high-density sintered alloy material according to claim 1, wherein the iron-based powder used has an average particle size of 45 μm or less. 12. The method for producing a high-density sintered alloy material according to claim 1, wherein the silicon powder has an average particle size of 10 μm or less, and the average particle size is 45 μm.
Binder is mixed and kneaded with a mixture of the following iron powder and 40 to 60% by volume, and after the composition obtained by the mixing and kneading is injection-molded or extruded, the added binder is removed and sintering is performed. A method for producing a high-density sintered alloy material, comprising: 13. A method for producing a high-density sintered alloy material, comprising bonding and sintering the high-density sintered alloy material according to claim 12 to a copper-based material. 14. A method for producing a high-density sintered alloy material according to claim 12, wherein the high-density sintered alloy material according to claim 12 is joined by two-layer forming, assembly joining, brazing joining, or welding joining.