JPH01201450A - Method for working wear-resistant aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain an alloy causing no damage to mating materials and having high wear resistance with superior unit consumption of material by making a powder mixture in which prescribed amounts of solid lubricant is added to an Al-alloy powder, and sintering and forging it under specific conditions. CONSTITUTION:A powder mixture prepared by adding 0.5-20%, by weight, of solid lubricant to an Al-alloy powder is compacted at a temp. between the ordinary temp. and 300 deg.C so as to be formed into a preform of 70-95% true density ratio, which is sintered in vacuum or in an inert atmosphere at 450-600 deg.C. Subsequently, forging is applied to the above in a forging die of near-final shape at 200-550 deg.C without delay, by which a sintered compact of >=95% true density ratio is obtained. Further, it is desirable that a powder prepared by atomizing a molten alloy which has a composition consisting of, by weight, 10-30% Si and the balance essentially Al and containing, if necessary, either or both of 0.5-5.0% Cu and 0.2-3.0% Mg is used as the above Al-alloy powder. Moreover, it is preferable that the solid lubricant is composed of the grains or chops of one or more kinds among BN, graphite powder, graphite chops, and MoS2.

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to the production of wear-resistant aluminum alloys, and particularly to a method for processing aluminum alloys that can be used for sliding members, mechanical parts, etc. that require high wear resistance. (Prior art) In recent years, with the rapid development of rapid solidification methods for molten metal,
High-strength, wear-resistant aluminum alloys with large amounts of Si added have been developed. In addition, research and development of composite materials in which ceramic particles such as SiC are added to this rapidly solidified aluminum alloy powder to further improve wear resistance properties is being actively conducted (Japanese Patent Application Laid-Open No. 109415-1988). reference)
. (Problems to be Solved by the Invention) By the way, as a method of adding ceramic particles to aluminum, research and development has been carried out with the aim of improving wear resistance by adding ceramic particles such as SiC to molten aluminum. There is. However, adding ceramic particles uniformly into molten metal requires extremely difficult techniques due to the difference in specific gravity between aluminum and ceramic particles. On the other hand, when rapidly solidified aluminum powder is used, it is relatively easy to combine it with ceramic particles, but when using the manufactured material as a sliding member, the ceramic particles are extremely hard compared to metal materials. Since it is a material, there is a problem that it can damage the metal of the other material. Furthermore, when rapidly solidified aluminum powder is used, hot extrusion is generally employed as a means for densification, but the material yield is poor and the processing steps are complicated. Moreover, when a solid nm agent, especially graphite powder, etc. is added to an aluminum alloy and hot extrusion is performed, the solid lubricant flows thinly in the extrusion direction, resulting in a failure to obtain high lubrication properties or areas where the lubricant is present. There are problems such as peeling off from the surface. Furthermore, aluminum alloys in which ceramic particles are dispersed have poor machinability, making them unsuitable for molding into mechanical parts, etc., and thus having a drawback in that their uses are limited. The present invention was made in order to solve the problems of the prior art described above, and it is possible to produce an aluminum alloy with high material yield without damaging the mating material and having high wear resistance.
The purpose is to provide a method that can be manufactured at low cost. (Means for Solving the Problems) The present inventors have conducted extensive research and development in order to solve the problems of the prior art. As a result, a specific amount of solid lubricant or solid lubricant and ceramic particles was added to aluminum alloy powder to form a mixed powder, which was first filled into a mold close to the final shape to form a preform with a true density ratio of 70 to 95%. After creating the product, if it is sintered in an inert atmosphere and then immediately hot forged in a forging die that approximates the final shape, a shape that is close to the final product can be obtained, and most post-processing such as cutting is not required. It has been found that a highly wear-resistant aluminum alloy can be produced at a low cost with good material yield without the need for this process. Moreover, it has been revealed that an aluminum alloy molded body having high wear resistance without damaging the mating material can be obtained due to the action of the solid lubricant. Therefore, the process conditions for these processes were further studied in detail, and the present invention has been completed. That is, in the present invention, a mixed powder obtained by adding and mixing 2 to 20 wt % of a solid lubricant to an aluminum alloy powder and 2 to 20 wt % of an added acid or solid lubricant and 2 to 20 νt % of hard particles is heated at room temperature to 300 kW. A preform with a true density ratio of 70 to 95% is produced by molding at a temperature of 450 to 600 °C, and then sintered in a vacuum or inert gas atmosphere at a temperature of 200 to 550 °C. It is characterized in that it is forged to obtain a compact with 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 hard particles are uniformly dispersed in the base. In particular, compared to the case where only hard particles are added, when a solid lubricant and hard particles are added together, wear resistance and strength can be further improved without damaging the mating material. The present invention will be explained in more detail below. Aluminum alloys are expected to be used in automobile parts such as pistons, connecting rods, and retainers due to their lightweight properties. In addition to strength, wear resistance is also required in these applications, and therefore, as mentioned above, many research and development efforts have been made to impart wear resistance to aluminum alloys. That is, as one method, an attempt has been made to improve wear resistance by combining an aluminum alloy and a solid lubricant to reduce the coefficient of friction between the mating material and the aluminum alloy. Due to the oxide film on the powder surface of aluminum alloy powder metallurgy, a strong bond between the powders cannot be obtained by normal powder compacting and sintering. Therefore, - quantitatively, hot extrusion methods are used for powder metallurgy of aluminum alloys. However, with this method, the solid lubricant is stretched by the large shearing force during hot extrusion and exists in the aluminum alloy, so the aluminum powder does not bond together sufficiently, and if the effect becomes large, it will The problem of cracking occurs. Therefore, in order to consider the application of the sinter forging method, the present inventors first conducted a basic experiment using Al-16,0% 5i-3 of less than 100 mesh obtained by the atmospheric atomization
,0%Cu-1,0%Mg alloy powder with 5w of solid lubricant
After adding t% and mixing, 35X95X by cold forming
A preform of 30 mm and a density ratio of 75% was created, and 50
Sintering was carried out in an N atmosphere under the conditions of 0'CX 30mln. Immediately after that, the surface pressure was 8 in a mold heated to 400℃.
It was forged in the atmosphere at ton/cm2. Abrasion test pieces were cut from these sintered forged materials and their wear characteristics were examined using an Odate type abrasion tester. The results are shown in FIG. From the figure, it is clear that the specific wear amount is on the order of 10-'mm/kg at any wear rate, showing extremely high wear resistance properties. Based on the positive results of the above basic experiments, and as a result of further detailed research on various conditions, we have discovered a method for processing wear-resistant aluminum alloys by adding a solid lubricant to aluminum alloy powder. Furthermore, since another method for improving wear resistance is compositing with ceramic particles, the present inventors have also conducted extensive research on techniques to apply this to the above method. In other words, the powder metallurgy method is more advantageous than the casting method in terms of uniform dispersion, but since ceramic particles are very hard, when used as a sliding member, There is a problem in that a phenomenon occurs in which the material is damaged and scraped off. Therefore, 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, in this case as well, it is unavoidable that simply hot extrusion does not lead to sufficient bonding due to the same reason as in Ichiki, and cracks are likely to occur.Furthermore, cracks may also occur during cutting after forming. easy. Therefore, as explained below, in the present invention, a mixed powder obtained by mixing an appropriate amount of an aluminum alloy powder with a solid lubricant or a solid lubricant and hard particles is preformed at a relatively high temperature, sintered, and then heated. By forging, it has become possible to obtain a molded product with a high yield without the occurrence of cracks and without cutting. Next, the reasons for the limitations of the present invention will be explained. The aluminum alloy powder used in the present invention is not particularly limited in terms of composition, but generally has high strength (room temperature strength,
Compositions that are used for members that require at least one of the following properties are often used: high temperature strength), high abrasion resistance, high rigidity, low thermal expansion, etc. For example, Al-high Si type, An-
Fe-Mo system, Al-Cu system, Al2-31-Mg system,
Examples include Al2 to Zn-Mg systems. To give a specific example, Al-10 to 30% Si or Cu: 0.5 to 5.0% and/or Mg: 0.
In the case of a composition containing 2 to 3.0%, it has excellent high-temperature strength, especially up to about 150°C, as well as excellent wear resistance, high rigidity, and low thermal expansion, so it can be used in automobiles such as connecting rods and rocker arms. Suitable for parts. Also AΩ-10~30
%5i-1 to 15% (at least one of Fe, Mn, and Ni) systems have excellent high-temperature strength, especially up to about 200°C, as well as excellent wear resistance, high rigidity, and low thermal expansion. Therefore, it is suitable for automobile parts such as pistons, connecting rods, and valve retainers. In addition, in the case of Al-6~10%Fe-1~4%Mo, it has excellent high temperature strength especially in the range of 200~350℃, high rigidity, and low thermal expansion, so it can be used for connecting rods, etc. Suitable for mechanical structural parts. In addition, A Q-1, 5-6.0% Cu 2000 series (
The AA standard alloy name (hereinafter the same) has excellent high rigidity and high strength at room temperature, so it is suitable for mechanical parts such as screws. Furthermore, Al-0,3-1.8%5i-0,4-1.
6% Mg (7) 6000 series has excellent high rigidity and high strength, so it is suitable for mechanical parts, vehicle parts, etc. Similarly, Al-3゜5~8.0%Zn-0,5
In the case of the 7000 series with ~3.5% Mg, it has excellent high rigidity and high strength, so it is suitable for mechanical parts, vehicle parts, aircraft materials, high-speed rotating bodies, etc. Note that the aluminum alloy powder preferably has a size of 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 aluminum alloy powder, or a mixed powder in which 2 to 20 wt% of hard particles are further mixed in addition to this solid lubricant is prepared, By subjecting this to subsequent processing, the solid lubricant or the solid lubricant and the highly hard hard particles are uniformly dispersed in the aluminum alloy base. The appropriate amount of solid lubricant added is 0.5 to 20 wt%. If the amount added is less than 0.5 wt%, wear resistance will not be improved and there will be no benefit to adding a solid lubricant.
If added in excess of wt%, powder molding becomes difficult, which is undesirable.As solid lubricants, those that do not decompose at high temperatures, such as BN, graphite powder, graphite chop, Mo82, etc., can be used, and one or two of these can be used. Use the above. In addition, 2
When more than one species is added, the total amount is preferably 2 to 20 νt%. The size may be powder of 5 to 50μ■, or 50μ■.
There is no problem even if it is a chop of about 500 μm. In addition, when adding hard particles together with a solid lubricant,
The appropriate amount of hard particles added is 2 to 20 wt%. If the amount added is less than 2 wt%, only the effect of a solid lubricant can be obtained, and there is no merit in adding it. Moreover, if it exceeds 20 wt%, molding is possible if only the hard particles are added, but if a solid lubricant is added at the same time, this causes problems in moldability, which is not preferable. The particle diameter of the hard particles is preferably in the range of 5 to 50 μm, and
~30 μm is preferable; if it is less than 5 μm, the activation energy on the particle surface will increase, particles will aggregate and become difficult to disperse in the base, and a high-cost method such as a high-energy ball mill will be required as a mixing means. , undesirable. Moreover, if it exceeds 50 μι, not only can no dispersion strengthening be expected, but also the hard particles will interfere with the contact of the Al alloy powder, resulting in poor moldability of the preform. Such hard particles include S x C, 313N
Particles of various high-strength carbides, nitrides, and oxides such as 4, Ajl, O, etc. can be used, and one or more of them can be added in the above-mentioned amounts. In addition, when adding two or more types, the total amount is 2 to 20wt.
In order to uniformly disperse the hard particles, which is desirably within the range of 1.5%, sufficient stirring may be performed using a V-type mixer or the like. Next, the mixed powder prepared as above was heated to room temperature to 300℃.
A preform having a true density ratio of 70 to 95% is produced by preforming at a temperature of .degree. If the true density ratio is less than 70%, handling problems such as chipping of a part of the corner of the preform will occur. If the true density ratio is 70% or more, such handling problems will not occur. However, in order to increase the true density ratio to 95% or more, it is necessary to increase the molding pressure and a large press is required, resulting in high equipment costs. This tendency is remarkable in the case of hard powders such as high alloy powders. Furthermore, setting the true density ratio after compaction to 95% or more has the problem of inhibiting degassing in the subsequent sintering process. When the true density ratio is 95% or more, many of the pores existing in the molded product are closed pores (C1osed P
ore), the oxide film formed on the surface of the Af1 alloy powder AI2.0.・Crystal water or adhering or adsorbed water of 3H and O is decomposed by heating, and gas mainly composed of hydrogen is prevented from escaping out of the molded body, and the molded body after sintering may contain a large amount of gas. Alternatively, there is a problem in that the surface of the molded product bulges, which is called a blister. To prevent this, it is effective to perform vacuum deaeration treatment or the like at a true density ratio of 95% or less to remove adsorbed water and crystal water. Mold molding, cold or hot isostatic pressing is used to mold the preform, but depending on the material, it is possible to mold at room temperature or at high temperatures up to 300°C.In particular, high-temperature molding allows for low molding. A high true density ratio is achieved at a pressure of 0, for example, 2
When hard particles are mixed with solid lubricant or solid lubricant together with aluminum alloy powder of No. 000 series to No. 7000 series, it can be molded at room temperature and the molding pressure is 3 tons.
On the other hand, when AM-high Si aluminum alloy powder is mixed with solid lubricant or hard particles together with solid lubricant, it is 6 t when molded at room temperature.
The molding pressure is about 2 tonf/cm", but when molding at a high temperature of about 200℃, it is 2 tonf/c+a2
High-temperature molding is preferred because it can be easily preformed at a molding pressure of about 100 ml. After preforming, the preform is sintered in a vacuum or inert atmosphere at 450-600°C. When sintered in the atmosphere, degassing does not proceed sufficiently. The amount of gas in the molded body is preferably 5 cc/100 g-A n mixture or less. For this reason, it is necessary to sinter in a vacuum or in an inert atmosphere. In the case of vacuum, the degree of vacuum is 0. I
It is preferable to set it to below Torr, preferably below 0.0 I Torr. In an inert atmosphere such as Ar or N2, it is preferable to control the inert atmosphere so that the dew point is below 110°C, preferably below 120°C. Sintering temperature is 45
If it is lower than 0℃, sintering progresses slowly, and moisture and crystal water adsorbed on the aluminum oxide surface cannot be completely removed.If it is higher than 600℃, sintering progresses, but the structure becomes coarse. The sintering temperature can be determined depending on the material, and when an Al-high Si aluminum alloy is used, it may be 450 to 550°C, but sintering temperature of 2000 to When a No. 7000 series aluminum alloy is used, the melting point of the matrix is high, so sintering is performed in the range of 450 to 600°C. Note that the sintering time is appropriately determined depending on the size of the preform to ensure uniform heating. Forging is performed at a temperature of 200 to 550°C, and the true density ratio of the hot-forged compact is 95% or more. In order to give sufficient plastic deformation to the A2 alloy powder by forging and destroy the oxide film formed on its surface to reveal a new active surface, the Al alloy powder must be heated at 200°C.
It is preferable to soften the preform by heating it to a temperature higher than If the temperature exceeds 550°C, the structure will coarsen and the mechanical properties will deteriorate, which is undesirable.The forging temperature should be determined according to the material, and A2
For those using alloy powder, a lower temperature may be used, but for those using Al-high Si type A2 alloy powder, it is better to select a higher temperature. In addition, it is desirable to heat the preform at the same time as heating during sintering.In order to reduce the temperature drop of the preform and the increase in gas amount due to exposure to the atmosphere, the forging should be performed immediately after taking it out of the sintering furnace. If the heating of the preform before forging is performed separately from the heating during sintering, it is necessary to heat the preform to 450 to 550 ° C in a vacuum or inert atmosphere. The considerations after removal from the furnace are the same as above. If the true density ratio of the compact after forging is lower than 95%, the mechanical properties will be poor, which is not preferable. Note that after forging, re-sintering (refining annealing) can be performed as necessary. It is preferable to perform resintering at 450 to 550°C. The purpose of resintering is to sufficiently sinter the new active surface generated during forging, and for this purpose, it is necessary to perform resintering at a temperature of 450°C or higher. There is. If the temperature is higher than 550° C., the structure will become coarser and mechanical properties such as tensile strength will deteriorate, which is not preferable. There is no problem in resintering in the air, but preferably in a vacuum or inert atmosphere.When resintering, the amount of gas in the forged compact is greater than 5 cc/ (100g/Al mixture) If this occurs, blisters may occur or mechanical properties may deteriorate, making it difficult to achieve the original purpose of resintering.

[Left below]

(Example) Next, an example of the present invention will be shown. Example 1 Al-3i alloy powder and Al-8i alloy powder prepared by adding Fe to Al-3i alloy powder and Al-8i alloy powder produced by atmospheric atomization method,
With the material combinations and addition amounts shown in Tables 1 and 2, BN, graphite powder, graphite chop and Mo were used as solid lubricants.
S2 and SIC, Si, N and A as hard particles.
Fl, 03 ceramic powder is used, and when adding solid lubricant alone, add 0°5 to 10 wt%, and when adding solid lubricant and ceramic powder in combination, add 2 wt% or 5 wt%, respectively, and the surface pressure is 6 tons. /cm” 35X95X
A 30 mm preform was created by cold forming. The true density ratio of the obtained preform was 73 to 78%. These preforms were then heated with N at a dew point of -20°C or lower.
Sintering was carried out under the conditions of 500'C13C13O in a 2 atmosphere. After sintering, the preform was taken out from the stool and forged in the air at 8 tons/cts in a mold heated to 400°C.The true density ratio 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 Odate type wear tester to measure the specific wear amount and evaluate the wear resistance. The result is the first
The test conditions shown in Figures 9 to 9 were as follows: Fe12 was used as the mating material, wear distance was 600 m, and the final load was 2,1
kg. In each figure, Na corresponds to the sample value in Table 1. In addition, the mechanical properties (tensile strength, elongation), hardness, and gas amount of the sintered forged materials were investigated. The results are shown in Tables 3 to 1.
As shown in Table 1, the gas analysis was performed by the vacuum melt extraction method (using stainless steel pipes). From Figures 1 to 9, according to the present invention, compared to the case of aluminum alloy alone (Nα1, Nα18), It is clear that a highly wear-resistant sintered forged aluminum alloy can be obtained. It also has good mechanical properties and hardness.

[Left below]

[1] Al-12%5i- produced by flame atmosphere atomization method
Mixed powders in which 10wt%, 15wt%, and 20wt% of graphite chops were added to 3%Cu-15%Mg-3%Fe alloy powder, and 20wt of graphite chops to the above Al alloy powder.
% and ceramic powder (Si, NiAl203.5iC)
The mixed powder containing 3 tit% of
cold-formed with "on/cy+" to 35 x 95 x 30 m
m preforms were created. The true density ratio of the obtained preform was 75 to 80%. These preforms were then sintered and forged under the same conditions as in Example 1. The true density ratio of the obtained sintered forged materials was all 99% or more. Regarding the sintered forged materials obtained in this way, Example 1
A wear test was conducted in the same manner as in the case of , and the wear resistance was evaluated. 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 large amounts of solid lubricant (graphite chop), such as 15 wt% and 20 νt%, compared to the case where no solid lubricant (graphite chop) is added. Moreover, from FIG. 11, it can be seen that even if 2Qwt% of solid lubricant is added, the wear resistance is improved by adding ceramic powder, especially when the wear rate is high. (Effects of the Invention) As detailed above, according to the present invention, a mixed powder obtained by adding and mixing an appropriate amount of a solid lubricant or a solid lubricant and hard particles to an aluminum alloy powder is sintered and forged under specific process conditions. Since this method is applied, aluminum alloys with excellent wear resistance can be manufactured with a high yield. In particular, the action of the solid lubricant prevents the mating material from being worn out. Therefore, it can be provided with high quality and at low cost for various members requiring high wear resistance, and the effect is very large.

[Brief explanation of the drawing]

Figures 1 to 11 are diagrams showing the relationship between specific wear amount and wear rate (wear resistance) for various additive materials and amounts; Figure 1 shows Al-16 with graphite chopped added. %5i-3%C
Figure 2 shows the case of the u-1%Mg alloy, Figure 2 shows the case of the Al-16%5i-3%Cu-1%Mg alloy with the addition of graphite powder, and Figure 3 shows the case of the Al-16%5i with the addition of BN. -3%Cu-1%
This is the case of Mg alloy, and Fig. 4 shows the case of MoS2-added An-16%5i-3%Cu-
This is the case of 1%Mg alloy, and Figure 5 shows A11l-16%5 with 5wt% solid lubricant added.
This is the case of i-3%Cu-1%Mg-6%Fe alloy, and FIG. 6 shows the case of 2wt% solid lubricant + 5wt% Af1. Figure 7 shows the case of Afl-16%5i-3%Cu-1%Mg alloy with 2wt% solid lubricant + 5wt% SiC added.
This is the case of l-16%5i-3%Cu-1%Mg alloy, and Figure 8 shows 2νt% solid lubricant +5%+1%Si, Al2-16%5i-3%Cu-1%Mg with N4 added. The case of alloy is shown in Figure 9: Afl-16%5i-3%Cu-1%Mg-6% with 2wt% graphite chop + 5wt% ceramics added.
This is the case of Fe alloy, and Fig. 10 shows the case of Al-
This is the case of 12%5i-3%Cu-1%Mg-3%Fe alloy, and Figure 11 shows the case of Al2 to 12%5i-3%Cu-1%Mg with 20wt% graphite chop + 3wt% ceramic powder added.
-3% Fe alloy. Patent Applicant Showa Denko K.K. Representative Patent Attorney Takashi Nakamura Figure 1 17 Shift & (Peng 15) Figure 2 Thickness L/i<-/s) Figure 3 4 Shift Ii/s) Figure 4 fI Torture iL and (m/s) Figure 5 Figure 6 R?? , f 1 tense d-ten (Net/S) Fig. 9, !iF i'!!, Lti'L I#/s) Fig. 10
Zumasa it Hama C→n

Claims (6)

[Claims] (1) Add solid lubricant to aluminum alloy powder from 0.5 to 0.5
The mixed powder containing 20 wt% is molded at a temperature of room temperature to 300°C to produce a preform with a true density ratio of 70 to 95%, and then the preform is sintered at 450 to 600°C in a vacuum or an inert atmosphere. A method for processing a wear-resistant aluminum alloy, which comprises curing and then forging at a temperature of 200 to 550°C to obtain a compact having a true density ratio of 95% or more. (2) Add solid lubricant to aluminum alloy powder from 0.5 to 0.5
A mixed powder containing 20 wt% and 2 to 20 wt% of hard particles is molded at a temperature of room temperature to 300°C to obtain a true density ratio of 7.
A preform with a true density ratio of 0 to 95% is manufactured, and then the preform is sintered in a vacuum or inert atmosphere at 450 to 600°C, and then forged at a temperature of 200 to 550°C to achieve a true density ratio of 95% or more. A method for processing a wear-resistant aluminum alloy, characterized by obtaining a compact. (3) The aluminum alloy powder contains Si: 10 to 30% in weight% (the same applies hereinafter), and further contains Cu: 0.5 to 5.0% and Mg: 0.2 to 3 as necessary. .0%
3. The method according to claim 1 or 2, wherein a molten alloy is atomized having a composition containing one or two of the above, and the remainder substantially consisting of Al. (4) The aluminum alloy powder has Si: 10 to 3.
0%, and 1 to 15% of at least one of Fe, Mn, and Ni, and further Cu: 0.5 to 5% as necessary.
3. The method according to claim 1 or 2, wherein a molten alloy is atomized having a composition of 0.0% Mg and 0.2 to 3.0% Mg, with the remainder substantially consisting of Al. (5) The method according to claim 1 or 2, wherein the solid lubricant comprises particles or chops of one or more of BN, graphite powder, graphite chops, and MoS_2. (6) The method according to claim 2, wherein the hard particles are made of one or more particles of SIC, Si_3N_4, and Al_2O_3, and have a particle size of 5 to 50 μm.