JPS5871352A - Wear-resistant sintered aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain a sintered Al alloy with superior wear resistance by adding specified percentages of Cu, Si, Mg and MoS2 to Al. CONSTITUTION:An alloy consisting of, by weight, 2-10% Cu, 10-29% Si, 0.2- 2% Mg, 1-4% MoS2 and the balance Al is prepared. The MoS2 is used after coating the powder surface with >= about 20% Cu. The Si is desirably added as Al-Si alloy powder contg. about 15-30% Si, and annealing is carried out at about 400-500 deg.C in an inert or nonoxidizing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to wear-resistant sintered aluminum alloys, particularly cylinder liners for internal combustion engines.

This invention relates to wear-resistant sintered aluminum alloys used for sliding materials such as oil pump side plates, bearings, pins, and current collectors.

Conventionally, there has been considerable demand for aluminum-based alloys with wear resistance, such as silicon (St) and lead (PB).

Aluminum alloy castings to which graphite, boron nitride
There are sintered aluminum alloys to which l, graphite, etc. are added.

By the way, Si is an element that is highly reactive with aluminum (At), hard, and has excellent wear resistance, but the wear resistance of At cannot be improved by just adding AtKSi in both casting and sintering. It is often insufficient to do so.

Therefore, various other elements are added to improve wear resistance, but under wear conditions where high loads are applied,
It is said that mobs exhibit this effect most. However, in aluminum alloy castings, MoS,
Not only is it difficult to uniformly disperse Mob, but Mob often decomposes when Mo82 is added to the molten metal during casting. On the other hand, MOS is formed on the surface of aluminum alloy by plating.

Although it is possible to attach vM-R, it suffers from vM-R properties.

On the other hand, it has been difficult until now to add MoS to sintered aluminum alloys. The reason for this is the ability to uniformly mix Mo82 according to instant setting, but Mo82 clears on the surface of the aluminum powder during mixing, and the MOS
This is because 2 does not react with aluminum and therefore acts as a sintering inhibitor, resulting in a significant reduction in sintering force. Therefore, in the past, Mo
Addition of S, or adhesion, did not result in a satisfactory result.

The purpose of the present invention is to provide an aluminum alloy with wear resistance, and by coating the MoS and powder surfaces with Cu in advance, MoS and powder will not adhere to the KL powder surface during powder mixing. There is no Mo in At powder.
It reacts with the homogeneously mixed 5s powder to generate a liquid phase at about 548°C, which is considerably lower than the melting point of At, to advance the sintering, and this 0%1 not only strengthens At1ft: Reliably retains MOS, even when used for long periods of time.

Focusing on the fact that MOS acts to prevent it from falling off, we solved the difficulty of adding MOS to roux, and created an alloy composition of tcu:
2-10%, Sl: 10-29%%Mg: 0.2
~2'4. Mob: 1 to 45k, with the remainder being AA to solve the above problem.

Next, the composition range of the sintered aluminum alloy according to the present invention (
The reason for limiting the weight ts) will be explained.

Cu #iMob, Table Wit - It can be added not only as the ninth element to coat, but also alone. However, if the total weight of Cu exceeds 10 inches, the amount of liquid phase during sintering becomes too large, resulting in deformation of the powder compact during sintering or papermaking with reduced strength. Also, if it is less than 211,
The Mo8B powder is not sufficiently coated with Cu, and the uncoated MOS powder acts as a sintering inhibitor. Therefore, the total weight of Cu is preferably 2 to 109 II.

Further, when Cu is added alone, the Cu powder is preferably At-Cu alloy powder, electrolytic powder, or atomized powder. On the other hand, when ground powder is used, the tensile strength varies greatly, probably due to impurities contained in the ground powder or oxidation of the powder. When powder other than ground powder is used, the variation in tensile strength can be suppressed to within ±7 (#/■3) compared to the company average value, whereas when ground powder is used, the variation in tensile strength is ±13 kg. / m” or so.

Ceramic not only dissolves in Kl and strengthens the base material Aj, but also partially reacts with Si to precipitate 81 and At
improve the mechanical properties of The amount of Mg useful for this purpose is 0.2-2%. If the diameter of the ceramic is less than 0.216 mm or greater than 2 mm, it becomes impossible to sinter effectively.

It is an element that has an excellent effect of improving the wear resistance of 5itiAt under high loads, and it can be said that it is necessary to add it in a large amount, but if it is added in a large amount in the form of a siv nest, the strength will drop significantly, making it unusable. Therefore, when a large amount of 5lt is added to impart wear resistance to At, it is desirable to add At-81 alloy powder.

In this case, the amount of 81 in the AA-8k alloy powder is 15~3°-
is desirable. That is, when the amount of Si is less than 151, the amount of Si precipitated is small and the effect of improving wear resistance is reduced. Furthermore, when the amount of 81 exceeds 30, the moldability deteriorates and is not suitable for practical use. Therefore, the total 81
The amounts are Mg and Cu.

It is determined by the ratio of the amount of Mo8 g added and the amount of Si in the At-8k alloy, but the maximum value is 29 g. In addition, At-81 alloy powder has high powder hardness and has extremely poor formability when atomized. For this reason, the At-8k alloy powder requires treatment to reduce the powder hardness In. Annealing is appropriate for this treatment, and the conditions are 400 to 500°C in an inert, non-oxidizing atmosphere.

0.5 to 2 hours is desirable.

In other words, AA-81 alloy powder is easily oxidized, and when oxidized, its oxide film is strong and acts as a sintering inhibitor, so the annealing atmosphere should be an inert, non-oxidizing atmosphere. desirable. In this case, the annealing temperature is 40
Below 0℃, the effect is small, and when it exceeds 550'Ci, there is not only little effect of increasing the temperature f, but also Aj-8
Exceeding the co-roaring temperature of No. 1 (approximately 577° C.) is not preferable because a liquid phase is partially generated. Further, the shorter the treatment time, the lower the possibility of oxidation, so it can be said that the shorter the treatment time, the better, but if it is shorter than 0.5 hours, the annealing effect will be small. Further, even if the Akatsuki annealing treatment is performed for more than 2 hours, there is little effect (because the possibility of oxidation of the Aj-8t powder increases, the annealing treatment is preferably performed for 0.5 to 2 hours.

Mob is a substance with excellent cleavage properties, and exhibits extremely excellent wear resistance and a reduction in the coefficient of friction. When Mob is added to impart wear resistance to aluminum, a small amount of Mob may be added, and the effect is exhibited when Mob is added in an amount of 1 or more.

However, addition of more than 4 inches is not preferable because it not only has little effect on improving wear resistance but also reduces the strength of the aluminum sintered body.

In addition, the amount of overlapping of Cu with respect to MoS @ is MoS z
If the thickness is less than 20 inches, the effect of the Cu coating cannot be obtained, resulting in a decrease in strength. Therefore, the addition of Mob adds 201% Cu to the surface! MoS coated above, l)
Do what you want, Mob! It is desirable to add the amounts so that the amount becomes 1 to 4 ts.

Examples of the present invention will be described below along with comparative examples.

Table 1 shows the mixing ratio of the sintered powder used in the Examples and Comparative Examples of the present invention and the performance of the obtained sintered bodies.

In Table I, the AA powder used for /l&1-21 was 8
Particle size that passes through a sieve with 0 mesh (-80 mesh)
It is a powder with a purity of 99.7- or higher. It was,
The At-81 alloy powder used for flattening l~21 was heated at 500°C x 1
time, N with dew point below -40°C.

Nine samples were annealed in an atmosphere and were -80 mesh powders. Furthermore, 41.3~10°12.1
3. The Cu powder used in Examples 15 to 21 is a -350 mesh atomized powder with a purity of 99.0 mm or higher.

Furthermore, the powder used for Jt61-21 is -200
It is mesh powder with a purity of 99.5 or higher.

In addition, the copper-covered 1iWio8. used for A1-21. is -1
00 mesh powder.

At this time, the surface of the Mob was coated with copper by immersing MoS into an electroless Cu plating solution for a predetermined time after activating the Mob.

Therefore, each powder was weighed to have the component ratio shown in Table 1, and 1.0 wt. wt. of a lubricant was added to each powder as is commonly used to prevent the powder from adhering to the mold during molding. The powders were mixed for 20 minutes using a V-type mixer to prepare powder for sintering. Next, the above sintering powder was placed in a tensile test mold and compacted at a pressure of 3.5 ton/x". After compacting, it was held at 400°C for 1 hour in a nitrogen gas atmosphere and the above The lubricant was removed, and then sintered by holding in a pixel gas atmosphere with a dew point of -40°C or lower for 1 hour.
The sintering temperature was 550°C for sample materials A1-7, 9-18, and 20°21, and 570°C for sample attachments 8 and 19. Also, be sure to perform T6 treatment on each after sintering. The treatment conditions were as follows: Sample materials 1 to 21 were held at 490°C for 1 hour, then heated with phosphorus at 80°C, and then heated at 160°C for 1 hour.
The conditions were an 8-hour aging treatment.

Each test piece obtained through the above process was subjected to a tensile test using an Instron tensile tester. The results are also shown in Table 1. In addition, a test piece was prepared using a mold for the Chimken abrasion test under the same conditions, and the abrasion test was carried out. The test conditions at this time were a load of 20 Zba
e Circumferential speed 2m/sec.

Lubricating oil (machine oil +50) 0.5 CC/min
Please make sure to complete the exam within 50 hours. A gray cast iron product (Fe12) was used as the mating material, and the width of the wear scar formed on one side of the test was taken as the test result. The results are also shown in Table 1.

As is clear from Table 1, the tensile strength of the comparative material (JK12), which is insufficiently coated with Cu, decreases considerably when powder is added, whereas MOS, which is sufficiently coated with Cu, is used. It can be seen that the materials of the present invention (Cliffs 1 to 11) all have excellent tensile strength and good abrasion resistance.

In addition, a comparative material (Cliff 1
In case 3), melting occurred during sintering, resulting in a decrease in strength and deformation.

Further, as in the comparative material (A20), if the amount of Mob is less than 1, there is no effect, and as in the comparative material (Ban 21), when it exceeds 4, the strength decreases significantly. Also, comparative material (419)
If the Si content is less than 101, the wear resistance will be poor. Furthermore, in At-8t alloy powder, comparative material (
At-8t powder with a Si content of less than 15 parts as in No. 17) has poor wear resistance. Please note that At-8i powder with a Si content of more than 301, like the comparative material (Mu18), has poor moldability and lacks strength. Also, comparative materials (415, 16)
If porcelain is added outside the range of 0.2 to 2 inches, proper sintering cannot be achieved, resulting in a g1 degree deficiency.

Next, we will discuss the influence of the Akatsuki annealing conditions on Aj-8t alloy powder t-
Table 2 shows the threshold results.

In Table 2, AA powder, Mob, and powder used as test materials.

Cu powder and milled powder are the same as those used in Table 1, and M
is, the Cu coating amount of the powder is 50%, the Cu powder is atomized powder, and the At-8i alloy powder is AA-2091S.
It is powder. As a component of the sintered alloy, At-
17%Si -4%Cu -0,5*hk -2Mo
8. I made it so that Note that the annealing atmosphere is a N atmosphere with a dew point of -40°C or lower.

As a result, as is clear from Table 2, 1. U-St.

Regarding the annealing conditions for the alloy powder, if the annealing temperature is less than 400°C, the powder hardness will be too high, and if the temperature is more than 550°C, partial dissolution will occur. Furthermore, the sintering time is 0.5
If it is less than 2 hours, the effect of the annealing treatment will be small and the powder hardness will be too high, and if it exceeds 2 hours, not only will the effect of lengthening the time be small, but the strength will decrease.

Figures 1 to 4 are A31.42 shown in Table 2, respectively.
2.426, is a microscopic structure photograph (X400) of Mu23, and shows the results of corroding each sample material with 10-N dichloromethane solution (70° C.). From the results shown in the figure,
It is clear that the structure differs considerably depending on the annealing conditions, and from the results in Table 2, the annealing condition 1 of KL-8i alloy powder is 400 to 550°C for 0.5 to 2 hours. It was clear that it would be desirable to do so.

In addition, in the material of the present invention, the residual rate of Mob was -
Approximately 92 inches remained in the solid area, and in this invention, Mob!
It is also thought to be effective in preventing the decomposition of.

As described above, according to the present invention, it is fully usable without processing such as forging after sintering, and not only contributes to cost reduction, but also allows manufacturing of parts with complex shapes. It brings excellent effects such as improved productivity. In addition, in order to further increase the appeal of the product of the present invention, there is no problem in performing processing such as forging after sintering.

[Brief explanation of the drawing]

Figures 1 to 4 are micrographs (400x) showing the results of examining the changes in the structure of At-8i alloy powder depending on the annealing conditions. Figure 2 shows annealing at 400°C for 1 hour, and Figure 3 shows annealing at 500°C.
Figure 4 shows the results of annealing at 550°C for 1 hour. Patent applicant Nissan Motor Co., Ltd.

Claims (3)

[Claims] (1) Weight - Steel: 2-10-1 Silicon 10-29
%, Magnesium: 0.2-2 mo, Molybdenum disulfide =
A wear-resistant sintered aluminum alloy characterized by having a composition of 1 to 4% aluminum and the balance being aluminum. (2) The claim that molybdenum disulfide is added as a powder coated with steel before sintering! The wear-resistant #IN aluminum alloy described in (1). (3) Silicon is added as an aluminum-silicon alloy powder that has been annealed in an inert atmosphere before sintering.
) Aluminum alloy with improved wear resistance as described in item 2.