JPH08209274A - Wear resistant aluminum-base sintered alloy - Google Patents

Abstract

PURPOSE: To produce a lightweight Al-Si-base sintered alloy excellent in sliding characteristics, furthermore having wear resistance and low in the coefficient of friction. CONSTITUTION: This wear resistant aluminum-base sintered alloy is the one in which the compsn. of the whole body is constituted of, by weight, 1.3 to 23.3% Si, 1.1 to 5% Cu, 0.1 to 1.5% Mg, 0.005 to 1% of one or >= two kinds of transition metals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Zr and Nb, 1 to 45% solid lubricant, and the balance Al with inevitable impurities, as for the Al alloy part, a dotted structure of Al-Si-base alloy phases in which primary crystal Si is dispersed and Al solid solution phases is shown, the area of the Al solid solution phases occupied in the area of the dotted structure is regulated to 20 to 80%, and a solid lubricant is dispersed in the grain boundaries of the Al alloy part, and the alloy is the one having the compsn. same as that of the above, and in which the maximum grain size of primary crystal Si at least in the part to be applied with friction of the Al-Si-base alloy phases is regulated to 5 to 60μm, and the grain size of primary crystal Si in the other part is regulated to <=5μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-based material suitable as a material for parts such as gears, pulleys, vanes for compressors, connecting rods, pistons, etc., which are required to be lightweight and have high strength and wear resistance. It relates to a sintered alloy.

[0002]

2. Description of the Related Art In order to improve mechanical efficiency and save energy, mechanical elements are being replaced with lightweight materials. Among them, the aluminum-based sintered alloy is expected as a material excellent in specific strength and wear resistance because it can make primary crystal Si finer and can increase Si content as compared with a cast alloy.

As a conventional sintered Al-Si alloy, for example, as disclosed in JP-A-53-128512, powders of elements constituting the composition or a mother alloy thereof are mixed and compacted. There is a method of binding and manufacturing. The alloy produced in this way is a primary crystal S refined by liquid phase sintering.
By uniformly dispersing i, a material having a relatively high tensile strength can be obtained. Further, since a soft metal powder can be used, it has a good powder formability and can be formed into a near net shape by die molding.

Further, as described in Japanese Patent Laid-Open No. 62-10237, there is a method using a rapidly solidified aluminum alloy powder containing an element other than Si. According to the publication, by hot forging the green compact, a structure in which primary crystal Si is uniformly dispersed in the Al-Si alloy base is obtained, and the tensile strength is further improved. Although this alloy has a relatively high strength, it is difficult to form a near net shape by mold forming because the powder is hard, and since a liquid phase does not occur during sintering, it is not possible to simply mix the powder with each other. However, there is a problem in that several compression steps such as extrusion from a billet shape and forging are required because a sufficient bond cannot be achieved.

Further, in order to solve such a problem,
The sintered alloy proposed in Japanese Unexamined Patent Publication No. 5-156399 is a rapidly solidified Al-Si alloy powder containing a predetermined amount of pure Al.
5 to 20% by volume of Al solid solution grains deformed by hot forging are produced in a eutectic Al-Si matrix in which fine primary crystal Si is dispersed, which is manufactured by hot forging a green compact of powder mixed with powder. It has a dispersed structure. In this alloy, the Al solid solution particles act as an adhesive, improve the mutual adhesion of hard grain boundaries, and improve the wear resistance and toughness.

On the other hand, Japanese Patent Application No. 6-3760 filed by the present applicant.
The aluminum-based sintered alloy proposed in No. 6 has a total composition of Si: 2.4 to 23.5% by weight and Cu: 2 to 5 by weight ratio.
%, Mg: 0.2-1.5%, Ti, V, Cr, Mn, F
One or more transition metals selected from e, Co, Ni, Zr and Nb: 0.01 to 1%, balance Al
And unavoidable impurities with a maximum particle size of 5 to 60 μm
Of Al-Si alloy phase having primary crystal Si dispersed therein and the Al solid solution phase, and the area of the Al solid solution phase occupying the surface of the mottled texture is 20 to 80%. This sintered alloy reduces the Cu alloy phase in the grain boundaries by containing a transition metal, has excellent ductility, and has both strength and wear resistance.

Further, as an improvement of the above-mentioned sintered alloy, the aluminum-based sintered alloy proposed in Japanese Patent Application No. 6-335712 was modified by changing the sintering method of the above-mentioned sintered alloy, and first, the Al-Si-based alloy phase was changed. After producing a sintered body in which the grain size of the primary crystal Si is 5 μm or less, the alloy surface is heated to
The maximum grain size of primary Si in the 1-Si alloy phase is 5 to 60 μm.
The surface portion has the same properties as the above-mentioned sintered alloy, and the inside of the sintered alloy has the strength improved by fine primary crystal Si.

[0008]

The above-mentioned sintered alloy proposed by the present applicant is an excellent alloy having both strength and wear resistance. However, the strength and wear resistance of this alloy should be reduced. However, if the friction coefficient can be further reduced, the range of application to the mechanical element having the sliding portion can be expanded. An object of the present invention is to provide an Al-Si based sintered alloy having a low friction coefficient from such a viewpoint.

[0009]

The present inventors have arrived at the present invention as a result of extensive studies to achieve the above-mentioned object. That is, the sintered alloy of the present invention contains a solid lubricant in an aluminum alloy,
The total composition is Si: 1.3 to 23.3% by weight and Cu:
1.1-5%, Mg: 0.1-1.5%, Ti, V, C
One or more transition metals selected from r, Mn, Fe, Co, Ni, Zr and Nb: 0.005 to 1
%, Graphite, MoS ₂ , BN, WS ₂ , one or more solid lubricants such as mica, talc and zinc white: 1 to
45%, and the balance of Al and unavoidable impurities, and the Al alloy portion has a maximum grain size of 5 to 60 μm of primary crystal S.
The Al-Si alloy phase in which i is dispersed and the Al solid solution phase exhibit a mottled structure, the area of the Al solid solution phase occupying the mottled surface is 20 to 80%, and the grain boundary of the Al alloy portion is It is characterized in that the solid lubricant is dispersed.
Further, in another second invention, the entire composition is the same as the above, and the Al of the surface portion of the alloy or at least the sliding surface portion is formed.
-The maximum grain size of primary Si in the Si-based alloy phase is 5 to 60 m.
And the primary crystal S in the Al-Si alloy phase in the other parts.
The particle size of i is 5 μm or less.

The solid lubricant in these sintered alloys has a content corresponding to 1 to 20% by volume ratio of the alloy excluding pores. This sintered alloy can be used as a sintered body as it is, but for the purpose of increasing the density and strength, the sintered body is subjected to plastic working by extrusion, forging, rolling, etc. at room temperature or hot. Alternatively, solution treatment and aging treatment which are usually performed in this alloy system can be performed.

[0011]

Next, each constituent element of the present invention will be described. (1) Grain structure and grain size of primary crystal Si The mottle structure is composed of Al-Si alloy phase in which primary crystal Si is dispersed and A
and a solid solution phase. Al- with primary crystal Si dispersed
The Si-based alloy phase is a solid solution in which Mg, Cu, and a transition metal element are diffused in the phase, and primary crystal Si is dispersed in the base material, and is a relatively hard phase, and mainly the material strength and Contributes to wear resistance.

The Al solid solution phase is a solid solution in which Si, Mg, Cu and a transition metal are diffused in Al added in the form of pure aluminum powder, is relatively soft, and contributes to the toughness of the alloy. , Al-S due to initial wear
It forms an oil reservoir between the i-based alloys and contributes to the lubricity and the compatibility with the mating material during friction. Further, since it is easily plastically deformed, hard primary crystal Si particles in the vicinity of the sliding surface are likely to fall off as abrasion powder, and when they fall off, they are buried and the Si particles do not act as abrasive particles. effective.

Al-Si in which the primary Si particles are dispersed
The two phases of the Al-based alloy phase and the soft Al solid solution phase are Al-S
When the i-based alloy phase is less than 20% in area ratio of the alloy cross section,
Since the amount of primary crystal Si is small, the wear resistance becomes significantly low. In addition, when the Al-Si alloy phase exceeds 80%, Al for burying Si particles that have fallen off due to frictional sliding is embedded.
The wear resistance is also low due to the small amount of solid solution phase. Therefore, the two phases have an area ratio of the alloy cross section of 20
In the case of a composite structure in which mottled mixture is present at a ratio of -80: 80-20, the strength and wear resistance are improved by the interaction of both phases.

When the grain size of the primary crystal Si becomes large, the edge of the grain becomes an acute angle, and the hard primary crystal Si grains take the form of protrusions to scratch and wear the mating material. On the other hand, when the amount of the primary crystal Si is small or the grain size of the primary crystal Si is small, the primary crystal Si falls off from the base material during frictional sliding, and the primary crystal Si that has fallen off acts as abrasive particles, which promotes wear. Therefore, from the viewpoint of wear resistance, it is necessary that the grain size of the primary crystal Si be an appropriate size, and the maximum grain size is preferably 5 to 60 μm. On the other hand, in terms of strength, the larger the primary crystal Si, the lower the strength. That is, the smaller the grain size of the primary crystal Si, the higher the strength is, which is preferable, and the grain size of 5 μm or less is preferable. Therefore, the primary grain Si existing on the surface of the friction member or at least on the sliding portion has a maximum grain size of 5 to 60 μm in consideration of wear resistance, and the primary grain Si inside has strength of the entire alloy. Considering the above, by setting the particle size to 5 μm or less, it becomes possible to improve both wear resistance and strength.

(2) Si In the aluminum alloy, Si generally has the effects of lowering the coefficient of thermal expansion and improving wear resistance. The amount of Si seen from the overall composition is the A in which primary crystal Si described below is dispersed.
The 1-Si alloy and the Al solid solution phase are determined in a range such that they exhibit a mottled structure, and a range of 1.3 to 23.5% by weight is suitable. If the amount of Si in the overall composition is too small, the primary crystal Si
Means that the amount of Si in the dispersed Al-Si alloy is small, or that the proportion of the Al solid solution phase is large,
In that case, the wear resistance becomes insufficient because the amount of primary crystal Si that contributes to the wear resistance is small. On the other hand, when the amount of Si is too large, contrary to the above, the amount of Si in the Al-Si alloy in which the primary crystal Si is dispersed is too large, or the proportion of the Al solid solution phase is small, and the wear resistance also decreases. To do.

Si is added in the form of Al-Si alloy powder. In order to crystallize the primary crystal Si by rapid solidification during the powder production of the Al-Si alloy, the Si content is 13% by weight.
It is necessary to be above. On the other hand, the Si content is 30
When the content of Si exceeds 13% by weight, the temperature of the molten metal during powder production becomes high. Therefore, the Si content is preferably 13 to 30%. The portion of the Al-Si alloy powder after sintering is Cu, N as described later.
Al-S in which some of i and Mg are in solid solution and primary crystal Si is dispersed
It becomes an i-based alloy and constitutes one alloy phase of the uneven texture of the sintered alloy.

(3) Mg Mg produces a liquid phase during sintering and forms a solid solution in the matrix. The effect is to promote sintering and Mg ₂ Si that precipitates by aging.
To strengthen the base and improve wear resistance.
If the total amount of Mg is less than 0.1% by weight, the effect is insufficient. On the other hand, if the amount of Mg is more than 1.5% by weight, no additional effect is exhibited. The range is 0.5% by weight, but the preferred range is 0.3 to 0.7% by weight.

As a means of addition, the Mg content is 3
It is performed in the form of 5 wt% or more of Al-Mg alloy powder or Mg powder. This is because the Al—Mg binary alloy has a low melting point of about 460 ° C. when the Mg content is 33 to 70%. That is, in the case of pure Mg powder,
During the sintering process, a solid phase diffuses with the Al base material to lower the Mg concentration, thereby generating a liquid phase. On the other hand, in the case of using Al-Mg alloy powder, if the Mg content is set to 33%, for example, the melting point rises due to the decrease of the Mg concentration due to the diffusion with Al and the effective liquid phase is formed. Since it cannot be used, it is desirable that the Mg content be 35% by weight or more.

(4) Cu and transition metals Cu is an element that strengthens the Al alloy substrate, and exhibits a greater effect by aging treatment. The Cu content is 1.1% by weight to 5% by weight in the whole composition, and if the Cu content is less than 1.1% by weight, the desired improvement in strength is not observed, and conversely, if it exceeds 5% by weight, It is not preferable because a large amount of an intermetallic compound containing Cu as a main component is precipitated in the vicinity of the powder grain boundaries to lower the toughness. In addition, the suitable Cu content is 3.5 to 4.5.
% By weight. When Cu is added in the form of Cu powder,
When the heating required to form a solid solution of Cu in the matrix is performed, the primary crystal Si is coarsened like a melted material, and conversely, when the heating temperature is lowered and the time is shortened, the Cu-metal intermetallic Compounds such as Al ₂ CuMg and Al ₆ CuMg ₄ remain to cause a decrease in strength. Therefore, appropriate amount of Ti, V, C
When a transition metal such as r, Mn, Fe, Co, Ni, Zr, or Nb coexists, the intermetallic compound can be eliminated by solution treatment and aging treatment. This phenomenon causes the transition metal and Cu and Si to combine with each other when Cu, which is a supersaturated solid solution in the matrix, precipitates as a stable compound by aging treatment, and partially reduces the amounts of Cu and Si in the matrix. At the same time, it is considered that Cu, which is an intermetallic compound, diffuses into the matrix.

When the amount of transition metal in the total composition is less than 0.005% by weight in the above range of Cu content, the effect is not recognized, while when it exceeds 1% by weight, the transition metal is the main component. The intermetallic compound precipitates and the toughness decreases, so the content was made 0.005 to 1% by weight. Further, it is preferably in the range of 0.1 to 0.5%. Since the transition metal is difficult to diffuse when added alone, it is added in the form of Cu-transition metal alloy powder. Although the Cu-transition metal alloy has a high melting point, solid-phase diffusion of elements such as Al and Mg in the sintering process lowers the melting point to generate a liquid phase. The amount of transition metal in the alloy powder is
Considering the amount of Cu and the amount of transition metal required for the overall composition, 0.2% by weight or more is necessary, but if it exceeds 30% by weight, the melting point of the alloy powder becomes too high and the liquid phase is formed during sintering. Since it does not occur, it must be in the range of 0.2 to 30% by weight. Further, it is preferably in the range of 2 to 10% by weight.

(5) Solid Lubricant The friction coefficient under metal contact is determined by the condition of the contact surface such as hardness, strength and roughness of the material. Generally, the higher the hardness, the lower the coefficient of friction. Primary crystal Si plays that role. Further, in order to improve the seizure resistance, it is effective to reduce the contact area between the aluminum alloy and the mating material. Graphite, MoS ₂ , BN, W
When a solid lubricant such as S ₂ , mica, talc, or zinc white is added, these adhere to the friction surface to form a solid lubricant film. By interposing this solid lubricating coating, seizure with the mating material is suppressed, and the friction coefficient of the metal contact portion becomes close to that of the solid lubricating material having a layered structure. As a solid lubricant, M is used when a sintered alloy is used in vacuum.
It is preferable to use BN when using oS ₂ at a high temperature, and WS ₂ when using under a high load, depending on the operating atmosphere of the sintered alloy, operating temperature, load, etc. It can be selected appropriately. If the addition amount of the solid lubricant is 1% by volume or less, the effect of addition is not obtained, while if it is 20% by volume or more, the strength of the alloy decreases, which is not preferable in terms of cost. Converting volume% to weight%, 1 volume% is about 1 weight% in the case of graphite having a true specific gravity of 2.2.
The volume% corresponds to 45% by weight in the case of WS ₂ having a true specific gravity of 7.4. Since WS ₂ has a high specific gravity, it is preferable to reduce the addition amount.

[0022]

EXAMPLES The present invention will be further described below with reference to examples. The mixing ratio and composition are% by weight. As raw material powder, Al-20% Si alloy powder, pure Al powder, Cu-4% N
i alloy powder and Al-50% Mg alloy powder were used. Of these, Cu-4% Ni alloy powder 3.13% by weight and Al-
1% by weight of 50% Mg alloy powder was blended to obtain a base material. The mixed powders of sample numbers 1 to 9 blended with the base material by changing the type and the addition amount of the solid lubricant were compacted into a predetermined shape.
After dewaxing the green compact at 400 ° C., sintering at 540 ° C. for 60 minutes, and hot forging to a density ratio of 100%,
The solution treatment was performed at 490 ° C and the aging treatment was performed at 240 ° C. For each sample, the tensile strength and the amount of wear by the pin-on-disk friction and wear test were measured and compared. In the pin-on-disk friction and wear test, a sample was used as a pin, and a heat-treated product of S48C material (carbon steel for machine structure) was used as a mating material disk under the conditions of a sliding speed of 5 m / sec and a surface pressure of 49 MPa under lubrication with intermittent mineral oil went. The test results are shown in Table 1.

[0023]

[Table 1]

The aluminum sintered alloy sample containing the solid lubricant has a low coefficient of friction and a small amount of wear, while
When the content of the solid lubricant increases, the tensile strength decreases. As a member that does not require high strength, it is considered that the solid lubricant content of 30% by volume can be used. However, if the content of solid lubricant exceeds 20% by volume, the strength is largely decreased. Is desirable.

[0025]

As described above, the alloy of the present invention containing 1 to 45% by weight of a solid lubricant in an aluminum-based alloy matrix of a specific composition having a mottled structure has a strength comparable to that of conventional materials. Since it has a low friction coefficient and high wear resistance, it can be applied to various mechanical elements that are required to be lightweight, have excellent sliding characteristics, and have wear resistance. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Shikata 1-48-1 Okanedai, Matsudo City, Chiba Prefecture (72) Hideo Urata 1-4-1 Chuo, Wako City, Saitama Stock Company Honda Technical Research Institute (72) Inventor, Shoji Kawase, 1-4-1, Chuo, Wako-shi, Saitama, Ltd., Honda R & D Co., Ltd. (72) Inventor, Junichi Ueda, 1-4-1, Chuo, Wako, Saitama, Ltd., Honda R & D Co., Ltd.

Claims (2)

[Claims] 1. The total composition of Si: 1.3 to 23 by weight.
3%, Cu: 1.1-5%, Mg: 0.1-1.5%, T
i, V, Cr, Mn, Fe, Co, Ni, Zr and N
One or more transition metals selected from b: 0.
005 to 1%, solid lubricant: 1 to 45%, the balance consisting of Al and unavoidable impurities, and the Al alloy part has an Al-Si based alloy phase in which primary crystal Si having a maximum grain size of 5 to 60 μm is dispersed. The area of the Al solid solution phase presenting a mottled structure with the Al solid solution phase and occupying the mottled tissue surface is 20 to 80%.
A wear-resistant aluminum-based sintered alloy, characterized in that a solid lubricant is dispersed in the grain boundaries of the alloy portion. 2. The total composition of Si: 1.3 to 23 by weight.
3%, Cu: 1.1-5%, Mg: 0.1-1.5%, T
i, V, Cr, Mn, Fe, Co, Ni, Zr and N
One or more transition metals selected from b: 0.
005 to 1%, solid lubricant: 1 to 45%, the balance consisting of Al and unavoidable impurities, and the Al alloy part has a mottled structure of an Al-Si alloy phase in which primary crystal Si is dispersed and an Al solid solution phase. And the area of the Al solid solution phase occupying the mottled tissue surface is 2
0 to 80%, which is an aluminum-based sintered alloy in which a solid lubricant is dispersed in the grain boundaries of the Al alloy portion, in the Al-Si alloy phase of the alloy surface portion or at least the planned sliding surface portion. The maximum grain size of primary crystal Si is 5 to 60 μm,
A wear-resistant aluminum-based sintered alloy, characterized in that the grain size of primary crystal Si in the Al-Si-based alloy phase in the other portion is 5 μm or less.