JP4359409B2 - Metal composite and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal composite having aluminum or an aluminum alloy (hereinafter collectively referred to as an aluminum alloy) as a matrix.
[0002]
[Prior art]
As a composite material with excellent wear resistance and light weight, molten forging into a preform molded into a desired shape by adding an appropriate excipient to fibers, whiskers or particles of ceramics such as alumina, silicon carbide, titanium carbide, etc. Aluminum matrix composites impregnated with molten aluminum alloy are known.
[0003]
This aluminum matrix composite material has limited heat resistance and wear resistance due to the softness of the aluminum alloy of the matrix metal. Especially, it has limited wear resistance at high temperatures. The bearing material used in the atmosphere could not satisfy the required characteristics.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to provide excellent performance such as hardness, heat resistance, wear resistance, moderate friction coefficient, stability of friction coefficient, etc. required for sliding materials for brakes, and for high temperature bearings. It is an object of the present invention to provide a metal composite having excellent performance such as required performance, particularly hardness, heat resistance, wear resistance, and a very small coefficient of friction.
[0005]
Another object of the present invention is to provide a suitable method for producing the above metal composite.
[0006]
[Means for Solving the Problems]
The present invention (1) is formed in silicon carbide particles (2) and the metallic titanium powder, the volume ratio of the titanium metal powder Ri from 0.5 to 15% der, volume ratio Ru 45-75% der preliminary The present invention relates to a metal composite obtained by impregnating a molded body with aluminum or an aluminum alloy.
[0007]
The present invention is also formed by the (1) silicon carbide particles (2) metallic titanium powder, the volume ratio of the titanium metal powder Ri from 0.5 to 15% der, volume rate of 45 to 75% The present invention relates to a method for producing a metal composite, wherein a preform is impregnated with aluminum or an aluminum alloy by molten metal forging.
[0008]
The preferred particle size of the coal of the silicon particles is 50 to 250 [mu] m.
[0009]
The volume fraction Vf [(1) silicon carbide particles and (2) volume fraction of metal titanium powder] of the preform used in the metal composite of the present invention is 45 to 75% . When the volume ratio Vf is less than 45 %, the final product metal composite has insufficient heat resistance and wear resistance. For example, the required performance is required for a brake rotor or a bearing used in a high temperature atmosphere. There is a tendency that it cannot be secured. On the other hand, if it exceeds 75%, the toughness of the metal composite tends to decrease. From the viewpoint of ease of making the preform, the volume ratio Vf is preferably more than 50% and 75% or less.
[0010]
The titanium metal powder constituting the preform used in the metal composite of the present invention is 0.5 to 15% by volume. When the aluminum alloy is impregnated, a part of the Al—Ti intermetallic compound is formed, heat resistance and hardness are increased, and an appropriate friction coefficient and stability of the friction coefficient can be ensured. If the volume fraction of the metal titanium powder is less than 0.5%, the heat resistance of the material is insufficient, and if it exceeds 15%, most of the aluminum alloy becomes an Al-Ti intermetallic compound and the toughness of the metal composite decreases. Becomes remarkable. The volume ratio of the metal titanium powder is preferably more than 5% and 15% or less from the viewpoint of the uniformity of dispersion of the metal titanium powder.
[0011]
A suitable method for impregnating such a preform with an aluminum alloy is a molten metal forging method in which a high pressure is applied to the molten aluminum alloy to solidify it.
[0012]
In the method for producing a metal composite of the present invention, the preform includes (1) silicon carbide particles mixed with (2) metal titanium powder, water, a binder such as PVA (polyvinyl alcohol), and an excipient such as silica sol. Are appropriately mixed, formed into a predetermined shape by pressing or the like using a molding die, and dried as necessary to obtain a porous molded body. It is preferable to use 1-3 volume% of binders with respect to the preform material.
[0013]
As the aluminum alloy used for impregnation of the preform, Al pure metal, Al—Mg alloy, Al—Mn alloy, or the like can be used.
[0014]
The preform thus obtained is placed in a predetermined mold for forging a molten metal, and a molten aluminum alloy is poured into the molten metal to give a high pressure to the metal composite of the present invention.
[0015]
When the obtained metal composite is subjected to a heat treatment at 550 ° C. or higher, the hardness and strength are further improved. As a condition for the heat treatment, a temperature range that is lower than the melting point of the aluminum alloy (aluminum or aluminum alloy) and lower than the melting point of the aluminum alloy (aluminum or aluminum alloy) by 100 ° C. or higher is desirable. Although it varies depending on the shape, it is preferably 0.5 to 24 hours, more preferably 3 to 24 hours.
[0016]
The metal composite obtained as described above produces an Al—Ti intermetallic compound even in the process of molten metal forging, but a heat treatment step is required to further promote the production of the intermetallic compound.
[0017]
An example of a process chart for producing the metal composite of the present invention is shown in FIG. As shown in FIG. 1 (a), a preform 1 made of (1) silicon carbide particles and (2) titanium metal powder is placed in a predetermined position on a pre-heated mold 2 for forging a molten metal. Attach to. Next, a molten aluminum alloy is poured. The preform 1 and the mold 2 are preferably preheated. This preheating improves the fluidity of the aluminum alloy, and the impregnation of the preform 1 is smooth. The temperature of the molten aluminum alloy itself is preferably 50 to 450 ° C. higher than its melting point in order to facilitate the impregnation of the preform 1. Next, as shown in FIG. 1B, the punch 3 is set on the mold 2 and pressure is applied. The pressure is preferably 10 to 100 MPa so that the molten metal is sufficiently impregnated into the preform and the effect of crystal refining is obtained, and this pressure is preferably applied until the molten metal is completely solidified. Next, as shown in FIG. 1 (c) or (d), a forging material is obtained in which a metal composite 4 in which a preform is impregnated with an aluminum alloy and a solidified molten metal 5 are integrally bonded to each other. It is taken out from the mold 2 by a knockout pin 6 as shown in FIGS. 1 (a) and 1 (b) arranged at the bottom of the mold. This forged metal composite 4 has a hardness of about HB200, but this is not the desired level as a sliding material for a brake or a heat-resistant bearing material. Next, the forged material taken out is cut into a brake rotor 7 as shown in FIG. 1E, or cut into a bearing 8 as shown in FIG.
[0018]
The metal composite thus obtained is further heat-treated to promote the reaction of the Al—Ti intermetallic compound. This increases the hardness and heat resistance of the metal composite, and ensures the necessary and appropriate friction coefficient and stabilization of the friction coefficient as a sliding material for a brake and a heat-resistant bearing.
[0019]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples.
[0020]
Example 1
In the manufacturing method shown in FIG. 1, silicon carbide particles (average particle size 120 μm) and metal titanium powder (average particle size 20 μm) are mixed, and an organic binder PVA is added to form a silicon carbide volume fraction of 52%. A preform with a volume fraction of 8% powder and a volume fraction of PVA of 2% (volume ratio 60%) was obtained. This was preheated to 800 ° C. in argon, then placed in a mold, poured with an Al-0.5 wt% Mg alloy melt at 800 ° C., and a pressure of 100 MPa was applied to obtain a metal composite.
The metal composite thus obtained was processed into a disk shape, and the brake rotor was processed into a round bar shape to produce a bearing. Then, when it heat-processed at 600 degreeC for 5 hours, hardness became 420 by HB.
[0021]
When this brake rotor was mounted on an actual vehicle and descended while braking a steep slope, the surface temperature became 560 ° C., and the surface hardness was 425 in HB, which was stable. In addition, the friction coefficient at this time was 0.38 to 0.42, no change, and no change was observed on the surface of the rotor.
[0022]
Next, a round bar bearing having a diameter of 3 mm and a length of 15 mm was put in a case made of heat-resistant steel halostay B, and used as a bearing of the same fan in a hot air axial fan atmosphere at 480 ° C. for one week. The hardness of the bearing surface after use was 450 in HV. Moreover, the friction coefficient of the surface of this thing was 0.004, and there was no change before and behind use.
[0023]
Example 2
A preform with a volume ratio of 65% was prepared in the same manner as in Example 1 except that the volume ratio of the metal titanium powder was 13%, and a brake rotor was manufactured in the same manner as in Example 1.
The hardness of the brake rotor is 460 in HB. When this brake rotor is mounted on an actual vehicle and descending while braking a steep slope, the surface temperature becomes 600 ° C., and the surface hardness is 460 to 480 in HB. It was stable. In addition, the friction coefficient at this time was 0.38 to 0.42, no change, and no change was observed on the surface of the rotor.
[0024]
Comparative Example 1
A metal composite was obtained in the same manner as in Example 1 except that silicon carbide particles were used and no metal titanium powder was used. When this was used as a brake rotor, it softened and deformed at 510 ° C. and thereafter could not be used as a rotor. The hardness of this product did not change as 140 in HB before and after use.
[0025]
【The invention's effect】
According to the present invention, a metal composite suitable for a member requiring hardness, heat resistance, wear resistance, and an appropriate friction coefficient was obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a process of a production method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Preliminary body 2 Mold 3 Punch 4 Metal composite 5 Solidified molten metal 6 Knockout pin 7 Brake rotor 8 Bearing

Claims (3)

(1) is formed in silicon carbide particles (2) and the metallic titanium powder, Ri volume ratio of from 0.5 to 15% der titanium metal powder, the preform volume ratio of Ru 45-75% der, A metal composite impregnated with aluminum or an aluminum alloy. (1) it is formed in silicon carbide particles (2) and the metallic titanium powder, the volume ratio of the titanium metal powder Ri from 0.5 to 15% der, the preform volume fraction is 45 to 75% melt A method for producing a metal composite comprising impregnating aluminum or an aluminum alloy by forging. A metal composite obtained by impregnating a preform with aluminum or an aluminum alloy by melt forging is 0 in a temperature range not lower than the melting point of aluminum or aluminum alloy and not lower than 100 ° C. below the melting point of aluminum or aluminum alloy. The method for producing a metal composite according to claim 2, further comprising a step of heat-treating for 5 to 24 hours.

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