JP2584488B2 - Processing method of wear resistant aluminum alloy - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of wear-resistant aluminum alloys, and in particular, to the use of aluminum alloys that can be used for sliding members, machine parts, and the like that require high wear resistance. It relates to a processing method.

(Prior Art) In recent years, with the rapid development of the rapid solidification method of molten metal, a high-strength wear-resistant aluminum alloy to which a large amount of Si has been added has been developed. Also, research and development of a composite material in which ceramic particles such as SiC are added to the rapidly solidified aluminum alloy powder to further improve the wear resistance characteristics have been actively conducted (Japanese Patent Application Laid-Open No. 52-109415). reference).

(Problems to be Solved by the Invention) As a method of adding ceramic particles to aluminum, research and development aimed at improving wear resistance by adding ceramic particles such as SiC to molten aluminum have been conducted. I have. However, in order to uniformly add ceramic particles into the molten metal, a very difficult technique is required due to a difference in specific gravity between aluminum and the ceramic particles.

On the other hand, when using a rapidly solidified powder of aluminum,
Although compounding with ceramic particles is relatively easy,
When using the manufactured material as a sliding member, ceramic particles are very hard materials compared to metal materials,
There is a problem that the metal of the partner material is damaged.

When using rapidly solidified aluminum powder,
Hot extrusion is generally employed as a means for densification, but the material retention is poor and the processing steps are complicated. In addition, when a solid lubricant, especially graphite powder, is added to an aluminum alloy and hot extrusion is performed, the solid lubricant flows thinly in the extrusion direction, so that high lubrication characteristics cannot be obtained, or a portion in which a lubricant is interposed. There are problems such as peeling off from the surface.

Further, an aluminum alloy in which ceramic particles are dispersed has a disadvantage that the machinability deteriorates, so that the aluminum alloy is not suitable for forming into machine parts or the like, and its use is limited.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and there is provided a method for manufacturing an aluminum alloy having high wear resistance without damaging a mating material, with good material retention and at low cost. It is intended to provide.

(Means for Solving the Problems) The present inventors have intensively studied and developed in order to solve the problems of the conventional technology. As a result, a specific amount of a solid lubricant or a solid lubricant and ceramic particles are added to the aluminum alloy powder to form a mixed powder, and the mixed powder is first filled in a mold close to the final shape to form a preform having a true density ratio of 70 to 95%. After making, sintering in an inert atmosphere, and then immediately performing hot forging in a forging die close to the final shape, a shape close to the final product can be obtained, and most post-processing such as cutting It has been found that a high wear-resistant aluminum alloy can be produced at a low cost with good material retention and no need. Moreover, it has been clarified that an aluminum alloy compact having high wear resistance can be obtained without damaging the mating material due to the action of the solid lubricant.

Then, the process conditions for them are further examined in detail, and the present invention has been made here.

That is, the present invention relates to a method in which a solid lubricant is added to an aluminum alloy powder in an amount of 2 to 20 wt% or mixed.
-20% by weight and 2-20% by weight of hard particles are added and mixed at a temperature of room temperature to 300 ° C. to produce a preform having a true density ratio of 70-95%.
After sintering in a vacuum or inert gas atmosphere at 00 ° C, 200
Forging at a temperature of 550550 ° C. to obtain a molded body having a true density ratio of 95% or more. This makes it possible to obtain a structure in which the solid lubricant or the solid lubricant and the hard particles are uniformly dispersed in the matrix. In particular, when the solid lubricant and the hard particles are added together as compared with the case where only the hard particles are added, the wear resistance and the strength can be further improved without damaging the mating material.

 Hereinafter, the present invention will be described in more detail.

Aluminum alloy, taking advantage of its light weight characteristics,
Applications for automotive parts such as pistons, corrods, and retainers are expected. In these applications, wear resistance is required in addition to strength. Therefore, as described above, many studies and developments for imparting wear resistance to aluminum alloys have been made.

That is, as one method, an attempt has been made to improve abrasion resistance by compounding aluminum gold and a solid lubricant to reduce the friction coefficient between the mating material and the aluminum alloy. In powder metallurgy of aluminum alloys, strong powder-to-powder bonding cannot be obtained by ordinary compacting or sintering due to an oxide film on the surface of the powder. Therefore, hot extrusion is generally used for powder metallurgy of aluminum alloys. However, in this method, since the solid lubricant is stretched by the large shear force during hot extrusion and is present in the aluminum alloy, the bonding of the aluminum powder there does not sufficiently occur. The problem of cracking occurs.

In order to study the application of the sintering forging method, the present inventors first conducted, as a basic test, Al-16.0% Si-3.0% Cu-1 of 100 mesh or less obtained by the atmospheric atomization method.
The solid lubricant was added 5 wt% to 0% Mg alloy powder were mixed, by cold forming to create a density ratio of 75% Puripuomu at 35 × 95 × 30mm, N ₂ atmosphere under conditions of 500 ° C. × 30min Sintered. Immediately afterwards, a surface pressure of 8 in a mold heated to 400 ° C
Forged in the atmosphere at ton / cm ² .

Abrasion test pieces were cut out from these sintered forgings, and the wear characteristics were examined using an Ogoshi type abrasion tester. The result is
Shown in the figure. From this figure, it was clarified that the specific wear amount exhibited an extremely high wear resistance characteristic of the order of 10 ⁻⁸ mm / kg at any of the wear rates.

Based on the good results of the basic experiments described above, and further detailed studies on various conditions, they have found a method of processing a wear-resistant aluminum alloy by adding a solid lubricant to an aluminum alloy powder.

In addition, the present inventors have repeated research on a method of applying the method to the above-described method, because there is a method of improving the wear resistance by combining with ceramic particles. In other words, the powder metallurgy method is more advantageous in terms of uniform dispersibility than the casting method, but the ceramic particles are very hard. There is a problem that a phenomenon such as scratching and scraping occurs in reverse. Thus, it has been found that in the above processing method, if a solid lubricant is used in combination, the mating material can be protected by lowering the wear coefficient.

However, also in this case, if hot extrusion is performed, the bonding is sufficiently advanced for the same reason as described above, and the disadvantage that cracks are liable to occur is unavoidable, and cracks are likely to occur during cutting after molding.

Therefore, as described below, in the present invention,
Aluminum alloy powder is mixed with solid lubricant or a mixture of solid lubricant and hard particles in a suitable amount. Thus, it is possible to obtain a molded body with good yield by omitting the above.

 Next, the reasons for limitation of the present invention will be described.

The aluminum alloy powder used in the present invention is not particularly limited in composition, but generally has high strength (normal temperature strength,
High temperature strength), high abrasion resistance, high rigidity, low thermal expansion, and the like, are often used for components requiring at least one of the properties, such as Al-high Si, Al-Fe- Mo
System, Al-Cu system, Al-Si-Mg system, Al-Zn-Mg system and the like.

Specifically, in the case of Al-10 to 30% Si or a composition containing Cu: 0.5 to 5.0% and / or Mg: 0.2 to 3.0%, high-temperature strength particularly up to about 150 ° C. In addition to
It has excellent wear resistance, high rigidity and low thermal expansion, so it is suitable for automotive parts such as connecting rods and rocker arms. In the case of Al-10 to 30% Si-1 to 15% (at least one of Fe, Mn and Ni), it is particularly excellent in high temperature strength up to about 200 ° C. and also excellent in wear resistance. , High rigidity,
Since it has low thermal expansion, it is suitable for automotive parts such as pistons, connecting rods, and valve retainers.

In the case of Al-6 to 10% Fe-1 to 4% Mo-based alloys, connecting rods and the like have excellent high-temperature strength particularly in the range of 200 to 350 ° C, high rigidity, and low thermal expansion. Suitable for mechanical structural parts.

In addition, Al-1.5 to 6.0% Cu 2000 series (AA standard alloy name,
The same applies to the following), which is suitable for machine parts such as screws because of its high rigidity and excellent strength at room temperature. Further Al-0.
In the case of No. 6000 series of 3 to 1.8% Si-0.4 to 1.6% Mg, it is suitable for machine parts, vehicle parts, etc. because of its high rigidity and excellent strength, and also high strength. Similarly, Al-3.5 to 8.0% Zn-0.5 to 3.5%
In the case of Mg series 7000, it is suitable for machine parts, vehicle parts, aircraft materials, high-speed rotating bodies, etc. because of its high rigidity and excellent strength.

The aluminum alloy powder is desirably 100 mesh or less.

In the present invention, a mixed powder in which 0.5 to 20 wt% of a solid lubricant is mixed with such an aluminum alloy powder or a mixed powder in which 2 to 20 wt% of hard particles are further mixed in addition to the solid lubricant is prepared. By performing the subsequent processing, the solid lubricant or the solid lubricant and the highly efficient particles having high hardness are uniformly dispersed in the aluminum alloy matrix.

An appropriate amount of the solid lubricant is 0.5 to 20% by weight. If the addition amount is less than 0.5% by weight, the wear resistance is not improved, and there is no merit of adding a solid lubricant. Addition of more than 20% by weight is not preferable because powder molding becomes difficult.
BN, graphite powder, graphite chop, MoS ₂
For example, those that do not decompose at high temperatures can be used, and one or more of these can be used. When two or more kinds are added, the total content is desirably 2 to 20% by weight. Size is 5
A 50 μm powder or a 50-500 μm chop is acceptable.

When hard particles are added together with the solid lubricant, the amount of the hard particles is suitably 2 to 20% by weight. If the addition amount is less than 2 wt%, only the effect of the solid lubricant alone is obtained, and there is no merit of addition. If it exceeds 20 wt%,
Molding is possible with the addition of hard particles alone, but it is not preferable because simultaneous addition of a solid lubricant causes problems in moldability.

The particle diameter of the hard particles is preferably in the range of 5 to 50 μm.
-30 μm is preferred. When the particle size is 5 μm or less, the activation energy of the particle surface increases, and the particles are hardly aggregated and dispersed in the matrix, and a costly method such as a high energy ball mill is required as a mixing means, which is not preferable.
If it exceeds 50 μm, not only the dispersion strengthening cannot be expected, but also the hard particles hinder the contact of the Al alloy powder, and as a result, the moldability of the preform deteriorates.

As such hard particles, particles of various kinds of high-strength carbides, nitrides, and oxides such as SiC, Si ₃ N ₄ , and Al ₂ O ₃ can be used, and one or two of them can be used. The above can be added in the above-mentioned amount. When two or more kinds are added, the total content is desirably in the range of 2 to 20% by weight. In order to uniformly disperse the hard particles, sufficient stirring may be performed using a V-type mixer or the like.

Then, the mixed powder adjusted as described above is at room temperature to 300
It is preformed at a temperature of ° C. to produce a preform having a true density ratio of 70 to 95%. When the true density ratio is less than 70%, handling problems such as chipping of corners of the preform occur. If the true density ratio becomes 70% or more, such a problem in handling does not occur.

However, in order to make the true density ratio 95% or more, it is necessary to increase the molding pressure, and a large press is required, so that the equipment cost becomes high. This tendency is remarkable in the case of a hard powder such as a high alloy powder. Also, the true density ratio after compacting
When the content is 95% or more, there is a problem that degassing in the subsequent sintering process is hindered. When the true density ratio is 95% or more, many of the pores existing in the compact are closed pores (Cl
Osed Pore), the oxidized film formed on the surface of the Al alloy powder Al ₂ O ₃ · 3H ₂ O crystal water or adhesion, adsorbed water is decomposed by heating, generated outside the molded body of gas mainly composed of hydrogen The molded body after sintering contains a large amount of gas or has a problem that blisters on the surface of the molded body called blisters occur. In order to prevent this, it is effective to remove the adsorbed water and the crystallization water by performing a vacuum deaeration treatment or the like at a true density ratio of 95% or less.

Molding or cold or hot isostatic pressing is used to mold the preform, but depending on the material, it can be molded at room temperature or at a high temperature up to 300 ° C. High true density ratio is realized by pressure. For example, 20
When a solid lubricant or hard particles are mixed together with a solid lubricant or a solid lubricant in an aluminum alloy powder of No. 00 to No. 7000 series, molding can be performed at room temperature, and the molding pressure may be about 3 tonf / cm ² . On the other hand, Al- when mixing the hard particles with a solid lubricant or solid lubricant for high Si aluminum alloy powder, is a 6tonf / cm ² approximately molding pressure when molding at room temperature, of about 200 ° C. When molding at a high temperature, high-temperature molding is preferable because preforming can be easily performed at a molding pressure of about ² tonf / cm ² .

After preforming, the preform is detailed in a vacuum or inert atmosphere at 450-600 ° C. When sintering in air, degassing does not proceed sufficiently. The gas volume of the compact is 5cc / 10
It is preferably 0 g · Al mixture or less. For this reason, sintering in a vacuum or an inert atmosphere is required. For vacuum,
The degree of vacuum is 0.1 Torr or less, preferably 0.01 Torr or less. Ar, the dew point in an inert atmosphere such as N ₂ -10
The inert atmosphere may be controlled so as to be lower than or equal to -20 ° C, preferably lower than or equal to -20 ° C. If the sintering temperature is lower than 450 ° C., the progress of sintering is slow, and the water and crystal water adsorbed on the aluminum oxide surface cannot be completely removed. If the temperature is higher than 600 ° C., although sintering proceeds, the structure becomes coarse and mechanical properties deteriorate, which is not preferable. The sintering temperature can be determined according to the material,
When a Si-based aluminum alloy is used, the temperature may be 450 to 550 ° C, but when a No. 2000 to 7000-based aluminum alloy is used, sintering is performed in the range of 450 to 600 ° C because the melting point of the parent phase is high. The sintering time is appropriately determined according to the size of the preform, and uniform heating is performed.

Forging is performed at a temperature of 200 to 550 ° C., and the true density ratio of the compact after hot forging is set to 95% or more. In order to apply sufficient plastic deformation to the Al alloy powder by forging and break the oxide film formed on the surface to reveal a new active surface, the Al alloy mixed powder is heated to 200 ° C or more and softened. It is preferable to keep it. To do this, the preform is heated to 200 ° C
In addition to the above holding, the forging die may be heated and held at 200 ° C. or higher. If the temperature exceeds 550 ° C., it is not preferable because the structure becomes coarse and the mechanical properties deteriorate. The forging temperature is determined according to the material, from 2000 to 7000
The one using Al alloy powder of No. series may be at a lower temperature,
It is better to select a higher temperature for those using Al-high Si based Al alloy powder. In addition, it is desirable that the heating of the preform also serves as heating during sintering, and in order to reduce the temperature drop of the preform and increase in the amount of gas due to exposure to the atmosphere, forging immediately after taking out from the sintering furnace. It is desirable to do. If the preform before forging is to be heated separately from the heating during sintering, it is necessary to heat to 450-550 ° C in a vacuum or an inert atmosphere. Is the same as above.
If the true density ratio of the compact after forging is lower than 95%, the mechanical properties are inferior, which is not preferable.

After forging, resintering (temper annealing) can be performed as necessary. The resintering is preferably performed at 450 to 550 ° C. The purpose of resintering is to sufficiently sinter the newly active surface generated during forging. For this purpose, it is necessary to perform the sintering at 450 ° C. or higher.

If the temperature is higher than 550 ° C., the structure becomes coarse and mechanical properties such as tensile strength deteriorate, which is not preferable. Although resintering may be performed in the air, there is no problem, but a vacuum or an inert atmosphere is preferable. At the time of re-sintering, if the gas amount of the compact after forging is more than 5cc / (100g ・ Al mixture), blisters will occur or mechanical properties will deteriorate.
It becomes difficult to achieve the original purpose of resintering.

(Example) The following example of the present invention is shown.

Example 1 A solid lubricant was added to an Al-Si-based alloy powder produced by an atmospheric atomization method and an Al-alloy powder obtained by adding Fe to an Al-Si-based material in the material combinations and addition amounts shown in Tables 1 and 2. BN, graphite powder, graphite chop and MoS ₂ as ceramic particles of SiC, Si ₃ N ₄ , and Al ₂ O ₃ as hard particles, and 0.5 to 10 wt% when solid lubricant is added alone,
Each case of combined addition of the solid lubricant and ceramic powder was added 2 wt%, or 5 wt%, the surface pressure 6 ton / cm ² in 35 × 95 × 30
A preform of mm was prepared by cold forming. The true density ratio of the obtained preform was 73 to 78%.

Then, N ₂ of these preforms dew point -20 ° C. or less
Sintering was performed in an atmosphere at 500 ° C. for 30 minutes. After sintering, the preform was taken out of the furnace and forged at 8 ton / cm ² in the air using a mold heated to 400 ° C. The true density ratio of each of the obtained sintered forged materials was 99% or more.

A wear test piece was cut out from the sintered forged material thus obtained, and a wear test was performed using an Ogoshi-type wear tester to measure a specific wear amount and evaluate wear resistance. The results are shown in FIGS. The test conditions were as follows: FC25 was used as the mating material, the wear distance was 600 m, and the final load was 2.1 kg.
In each figure, No. corresponds to the sample No. in Table 1.

Further, the mechanical properties (tensile strength, elongation), hardness, and gas amount of the sintered forged material were examined. The results are shown in Table 3
The results are shown in Table 11. The gas analysis was performed by a vacuum melting extraction method (using a stainless steel pipe).

From FIG. 1 to FIG. 9, it is apparent that the present invention provides a sintered aluminum forged material having higher wear resistance than the case of using the aluminum alloy alone (No. 1, No. 18). is there. Also, the mechanical properties and hardness are good.

Example 2 Al-12% Si-3% produced by atmospheric atomization
Cu 15% Mg-3% Fe alloy powder with graphite chop 10wt%, 15wt%
wt%, 20wt% mixed powder, as well as the above Al alloy powder, graphite chop 20wt% and ceramic powder (Si ₃ N ₄ , Al
₂ O ₃ , SiC) 3 wt% added mixed powder, surface pressure 5
A preform of 35 × 95 × 30 mm was cold-formed at ton / cm ² . The true density ratio of the obtained preform is 75-80%
Met.

Next, these preforms were sintered and forged in the same manner as in Example 1. The true densities of the obtained sintered forgings were all 99% or more.

The sintered forged material thus obtained was subjected to a wear test in the same manner as in Example 1 to evaluate wear resistance. The results are shown in FIGS. 10 and 11.

From FIG. 10, it can be seen that the wear resistance is further improved by adding a large amount of 15 wt% or 20 wt% as compared with the case where no solid lubricant (graphite chop) is added. Also, the eleventh
From the figure, it can be seen that even when the fixed lubricant is added at 20 wt%, the addition of the ceramic powder improves the wear resistance especially when the wear rate is high.

(Effects of the Invention) As described above in detail, according to the present invention, a solid lubricant or a mixed powder obtained by adding an appropriate amount of a solid lubricant and hard particles to an aluminum alloy powder is mixed and sinter-forged under a specific process condition. Since the method is applied, an aluminum alloy having excellent wear resistance can be manufactured with high yield. In particular, the mating material is not worn by the action of the solid lubricant. Therefore,
Various members requiring high wear resistance can be provided with high quality and at low cost, and the result is very large.

[Brief description of the drawings]

1 to 11 are diagrams showing the relationship between the specific wear amount and the wear rate (wear resistance) under various added materials and amounts, and FIG. 1 shows Al-16 with graphite chop addition. % Si-3% Cu-1%
Fig. 2 shows the case of an Al-16% Si-3% Cu-1% Mg alloy with graphite powder added, and Fig.3 shows the case of Al-16% Si-3% Cu with BN added. is the case of -1% Mg alloy, FIG. 4 shows the case of Al-16% Si-3% Cu-1% Mg alloy of MoS ₂ added, Figure 5 is 5 wt% solid lubricant additives Al- 16% Si-3% Cu-
1% is the case of Mg-6% Fe alloy, FIG. 6 is 2 wt% solid lubricant + 5wt% Al ₂ O ₃ additive Al-16% S
Figure 7 shows the case of i-3% C-1% Mg alloy. Fig.7 shows 2wt% solid lubricant + 5wt% SiC added Al-16% Si
It is the case of -3% Cu-1% Mg alloy, FIG. 8 is 2 wt% solid lubricant + 5 wt% Si ₃ of N ₄ added Al-16% S
Figure 9 shows the case of i-3% Cu-1% Mg alloy. Fig. 9 shows 2wt% graphite chop + 5wt% ceramic addition.
Fig. 10 shows the case of Al-16% Si-3% Cu-1% Mg-6% Fe alloy. Fig.10 shows Al-12% Si-3 with addition of 10 ~ 20wt% graphite chop.
Fig. 11 shows the case of 20% by weight graphite chop + 3% by weight ceramic powder added Al-12% Si-3% C% -1% Mg-3% Fe alloy. Is the case.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Nakagawa 1505 Shimokagemori, Chichibu City, Saitama Prefecture Showa Denko Chichibu Laboratory (56) References JP-A-61-186457 (JP, A) JP-A-62- 224602 (JP, A)

Claims (5)

(57) [Claims] 1. An aluminum alloy powder containing at least one solid lubricant selected from the group consisting of BN, graphite and MoS ₂ in an amount of 0.5 to 2
The mixed powder added with 0 wt% is molded at a temperature of room temperature to 300 ° C to produce a preform having a true density ratio of 70 to 95%, and then the preform is sintered in a vacuum or an inert atmosphere at 450 to 600 ° C. After tying, forging at a temperature of 200-550 ° C, true density ratio 95%
A method for processing a wear-resistant aluminum alloy, which comprises obtaining the above-mentioned molded body. 2. An aluminum alloy powder containing at least one solid lubricant selected from the group consisting of BN, graphite and MoS ₂ in an amount of 0.5 to 2%.
A mixed powder containing 0 wt% and further 2-20 wt% of hard particles is molded at a temperature of room temperature to 300 ° C to produce a preform having a true density ratio of 70 to 95%.
After sintering in a vacuum or inert atmosphere at 00 ° C, 200-550
A method for processing a wear-resistant aluminum alloy, characterized by obtaining a compact having a true density ratio of 95% or more by forging at a temperature of ° C. 3. The aluminum alloy powder contains, by weight (hereinafter the same), Si: 10 to 30% and, if necessary, one of Cu: 0.5 to 5.0% and Mg: 0.2 to 3.0%. 3. The method according to claim 1, wherein the molten alloy is a mixture of two or more alloys, the balance being substantially Al. 4. The method according to claim 1, wherein the aluminum alloy powder comprises Si: 10 to 30.
% And at least one of Fe, Mn and Ni in an amount of 1 to 15%, and if necessary, Cu: 0.5 to 5.0% and Mg: 0.2 to 3.0%.
3. An alloy melt containing at least one of the following, wherein the balance is substantially Al.
The method described in. 5. The hard particles comprise one or more particles of SiC, Si ₃ N ₄ and Al ₂ O ₃ and have a particle size of 5
3. The method according to claim 2, wherein the thickness is from 50 to 50 [mu] m.