JPH0121213B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention relates to a method for forming an Al--Si powder alloy,
In particular, it relates to a method for forming powder alloys that further improves the wear resistance of Al--Si alloys using rapid solidification powder metallurgy. Conventional technology Internal combustion engine cylinder blocks, cylinder liners, cylinder sleeves, pistons and valve train parts (valve lifters, valve spring retainers,
Valve seat rings, rocker arms, etc.), automobile synchronizer rings, compressor vanes, VTR cylinders, etc. require properties such as wear resistance, low thermal expansion, and heat resistance in sliding parts. Hypereutectic Al is an alloy with these properties.
A Si alloy has been proposed, but in the case of this alloy, the wear resistance improves as the Si content increases, but the machinability, workability, etc. become inferior due to the increased Si particle size. To solve this problem, P is added to the alloy and Si
It has not been possible to refine the particles to 30 to 40 μm or less, and the above problem has not been solved. Problems to be Solved by the Invention Recently, powder alloys produced by the rapid solidification method have been used, but when this powder is molded by the conventional method, the wear resistance is somewhat poor due to the small particle size of the primary Si. The problem was that it was inferior. Means for Solving the Problems In the end, it was discovered that in order to achieve excellent wear resistance, the average diameter of Si particles should be 5 to 15 μm, and the maximum diameter should be 11 to 30 μm. , discovered a heating method that increases the particle size of Si to a certain extent using a powder alloy. In other words, when molding Al-Si alloy powder, Al-
The temperature (temperature below the solidus line) and time that satisfies the Si-based alloy according to the following formula: T+40 logt≧520 ……………(1) (T: temperature °C, t: time Hr), That is, by a process including heating under the conditions shown in FIG.
This is a method for forming an Al--Si powder alloy with a maximum diameter of 11 to 30 μm. In the powder metallurgy method, molding is usually performed in the following steps. (A) Powder production - cold compaction - sintering (B) Powder production - cold compaction - can encapsulation - vacuum degassing - HIP (Hot Isostatic Pressing) (C) Powder production - can encapsulation - vacuum degassing - HFP (D) Powder production - cold compression - can encapsulation - vacuum degassing - extrusion (E) Powder production - cold compression - can encapsulation - vacuum degassing - hot pressing - canning - extrusion (or forging, rolling). In any of these steps, the present invention heats the material under the conditions of equation (1) above to grow Si particles to have an average particle diameter of 5 to 15 μm and a maximum diameter of 11 to 30 μm. On the other hand, if heat treatment is performed under conditions that do not satisfy equation (1) above, the growth of Si particles will not be sufficient;
Wear resistance is not improved. Also, when heated to a temperature above the melting point (solidus line), Si
This invention requires the temperature to be below the solidus because the particles will become too large. Note that the heating time follows the above equation (1), but for economical reasons it is usually set to a maximum of about 100 hours. The above heat treatment may be performed on raw material powder or cold compressed material, and may also be performed on sintering, vacuum degassing,
When heating in a process such as HIP, extrusion, hot pressing, etc., heat treatment that meets the above predetermined conditions may be performed. Furthermore, the heat treatment may be performed after forming the molded product, or it may be performed during the heat treatment (solution treatment) of the molded product. In addition, when performing heat treatment on the powder or its cold compressed product, it is desirable to perform the heat treatment in a non-oxidizing atmosphere to avoid oxidation of the powder surface. Alloys suitable for the forming method of this invention include hypereutectic
It is an Al-Si alloy containing 15 to 35% by weight of Si. Cu to further impart age hardenability,
Fe, Mn, etc. to impart heat resistance, such as Mg, Zn, etc.
There is no problem even if it contains Ni etc. As a powder manufacturing method using the rapid solidification method, the atomization method, the roll method (single roll method, twin roll method), the atomization roll method in combination thereof, the centrifugal spray method, etc. are usually used. EXAMPLES The present invention will be specifically described below with reference to Examples and comparative examples thereof. Example 1 Atoib powder of Al-20Si-2.5Cu-1Mg alloy was used and molded according to the step (A) above. In an example in which the sintering conditions were set to 540°C and 1 hour according to equation (1), the average diameter of the Si particles was 5.8 μm and the maximum diameter was 15 μm, as shown in Figure 2-a of the attached drawing. Comparative Example 1 The same raw material as in Example 1 was molded by the same process. However, the sintering conditions were 500°C and 1 hour. As shown in Figure 2-b, the results were that the average diameter of Si was 1.8 μm and the maximum diameter was 8.5 μm, which were too small. The test results of each sample produced by the methods of Example 1 and Comparative Example 1 are shown in Table 1 below.

【table】

【table】

[Table] Example 2 Atomized powder of Al-25Si-3Cu-0.5Mg-2Mn-1Fe-2Ni alloy was molded by the process (B) above. At that time, adjust the vacuum degassing to match equation (1),
When the molding was carried out at 500°C for 10 hours, the average diameter of the Si particles in the molded product was 5.3 μm and the maximum diameter was 15 μm, as shown in Figure 3-a. Comparative Example 2 In the method of Example 2 above, when the heat treatment conditions during vacuum degassing treatment were performed at 500°C for 2 hours,
As shown in Figure 3-b, the average diameter of Si particles is 2.3μ
m, and the maximum diameter was 9.6 μm. The test results of each sample manufactured by the methods of Example 2 and Comparative Example 2 are shown in Table 2 below.

[Table] Example 3 Using flakes of Al-30Si-0.5Mn-4Fe alloy formed by a roll method, a molded body was made according to the step (D) above. After molding, it was heat-treated at 475°C for 50 hours, and as shown in Figure 4-a, the average diameter was 9.4 μm and the maximum diameter was 20 μm. Comparative Example 3 In the method of Example 3, when the heat treatment was not performed after molding, the average diameter of the Si particles was 2.4 μm and the maximum diameter was 9.4 μm, as shown in Figure 4-b. Table 3 below shows the test results of samples having the same composition as the samples of Example 3 and Comparative Example 3, which were produced by any of the steps A to E above.

[Table] Test conditions for wear amount are the same as in Table 1. Effects of the invention According to the method of this invention, the wear resistance of Al-Si alloys formed using rapidly solidified powder is improved,
Moreover, a material with excellent workability and machinability can be obtained.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between temperature and holding time showing the heat treatment conditions in this invention, Fig. 2-a is a micrograph showing the metal structure of the compact of Example 1, and Fig. 2-b is a comparative example. Figure 3-a is a micrograph showing the metal structure of the molded body of Example 1, Figure 3-b is a microscope picture showing the metal structure of the molded body of Comparative Example 2. Photo, 4th
Figure 4-a is a microphotograph showing the metallographic structure of the compact of Example 3, and Figure 4-b is a microphotograph showing the metallographic structure of the compact of Comparative Example 3.

Claims (1)

[Claims] 1 When molding Al-Si alloy powder, Al-
By a process that includes heating the Si-based alloy at a temperature (but below the solidus line) and for a time that satisfies T+40 logt≧520 (T: temperature °C, t: time Hr), Si particles are heated. The average particle size of
m, characterized by a maximum diameter of 11 to 30 μm
Forming method for Al-Si powder alloy.