JPH0332403B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is directed to a hypereutectic silicon-aluminum alloy, particularly an Al-Si-Cu based hypereutectic silicon alloy, which has excellent wear resistance, machinability, high-temperature strength, and workability.
This invention relates to a method for producing aluminum gold extrusions. In this specification, all "%" regarding alloy components indicate "% by weight". BACKGROUND ART Conventionally, A4032 alloy containing 11.0 to 13.5% Si is known as a wrought aluminum alloy material with excellent high-temperature properties. This A4032 alloy wrought material has excellent heat resistance, wear resistance, and low coefficient of thermal expansion, but this alloy was originally intended for forging, and the above properties can only be obtained through forging. The alloy material itself does not have the above characteristics, and it is difficult to say that it has particularly excellent machinability. For this reason, it was only used in extremely limited fields such as pistons and cylinder heads. Therefore, aluminum alloy castings are generally used for applications where particularly high wear resistance is required. Aluminum alloy castings with excellent wear resistance include Al containing approximately 10 to 24% Si.
-Si type e.g. AC3A, AC8A~C, AC9A~B
These alloys are well known. However, since these alloys are cast alloys, there are restrictions on the product shape, and it is difficult to obtain a product shape as free as wrought materials, which also limits their uses. Ta. Moreover, since these alloy materials are manufactured by casting, the truncated Si particles and eutectic Si particles, which are the main elements that improve wear resistance, are both relatively coarse. It is large and irregularly shaped, and its distribution is uneven. For example, primary Si particles are generally coarse, with many particles reaching approximately 150 μm in diameter.
The eutectic Si particles also have a needle shape, including ones with a length of about 30 μm, and all of them are unevenly distributed. For this reason, it was not possible to obtain a high degree of satisfaction in either wear resistance or machinability.
Although the particle size of primary Si particles can be slightly reduced through improved processing, it is still only possible to reduce the size to about 100μ or less, and eutectic
It is impossible to improve the Si particles, and moreover, it is impossible to correct the uneven distribution state.
Only products with large variations in wear resistance could be obtained. On the other hand, due to the recognition of the problems mentioned above,
Various studies have been conducted on the refinement of primary and eutectic Si crystallized particles. As one result, for example, as shown in Japanese Patent Publication No. 53-20242, the cooling rate of molten metal during casting was increased to 50℃/
It has been proposed that the growth of crystallized substances can be suppressed and the particle diameters of primary Si and eutectic Si can be made extremely fine by making the crystallization extremely rapid. That is, according to this prior art, the maximum diameter of the primary Si particles does not exceed 40μ, and the eutectic Si particles
It has been reported that most of the particles do not exceed 20μ in maximum length. Problems to be Solved by the Invention However, according to the research of the present inventor, making the primary Si particles in the alloy structure as small as possible does not necessarily reduce the wear resistance of the alloy. It was found that there was no proportional improvement. In other words, the wear resistance of the alloy is, of course, achieved by the individual crystallized Si particles absorbing the surface pressure during friction, but if the Si particles are too fine in the matrix, On the contrary, it can be inferred from many experimental results that the ability to absorb surface pressure during friction decreases, and as a result, it cannot contribute to the improvement of wear resistance as much as expected. Ivy. Therefore, based on this knowledge, this invention developed primary crystal Si that can contribute to the maximum improvement of wear resistance.
Various studies were conducted to understand the particle size distribution of particles and eutectic Si particles. However, primary Si particles have a maximum diameter of 80μ or less, and moreover, a diameter of 40 to 80μ.
The best wear resistance is obtained by having a relatively large proportion of them distributed in a range of particle sizes of about
It has been found that Si particles can ensure the best machinability by breaking needle-like crystals and uniformly distributing them as small particles as possible. Therefore, one of the main objects of the present invention is to produce hypereutectic silicon particles that can control the primary Si particles and eutectic Si particles contained in the alloy within the above particle size range.
An object of the present invention is to provide a method for producing an aluminum alloy. For this purpose, a hypereutectic silicon-aluminum alloy is first cast, and then this ingot is
This can only be achieved by using specific extrusion conditions for extrusion processing. Conventionally,
Extrusion of hypereutectic silicon-aluminum alloy is
Since the deformation resistance itself is extremely high, it has generally been considered extremely difficult and unsuitable.
Furthermore, even if extrusion processing were to be carried out, it was thought that the extrusion temperature would have to be as high as possible and the extrusion speed should be slowed down in order to improve the fluidity of the alloy. However, when extruding according to such common-sense extrusion conditions,
It is not possible to control the state of each particle of primary Si and eutectic Si in the aluminum alloy within the above-mentioned preferred range, and the extruded product has significant defects such as surface cracks and rough skin, making it impossible to put it into practical use. Suitable materials cannot be obtained. Therefore, a more specific object of the present invention is to present the most suitable extrusion conditions for an alloy ingot in order to obtain a hypereutectic silicon-aluminum alloy material with excellent wear resistance and machinability. be. This extrusion condition is completely contrary to the conventional common sense concept, and is to increase the extrusion speed while keeping the extrusion temperature low. Means for Solving the Problems In the above, the present invention provides a hypereutectic silicon-aluminum alloy containing Si in the hypereutectic range, particularly containing 12-30% Si, 0.3-7.0% Cu, or further
Using an alloy containing 0.3 to 2.0% Mg, with the balance consisting of aluminum and unavoidable impurities, the essential steps are casting the alloy into a billet and extruding it, and the above extrusion is carried out.Bearing length: 5 Using ~15mm dice,
The present invention provides a method for manufacturing a wear-resistant aluminum alloy extruded material, characterized in that the process is carried out under the following conditions: billet temperature: 350-420°C, extrusion ram speed: 0.03-0.2 m/min, and pressing ratio: 10-40. The hypereutectic silicon-aluminum alloy used in this invention contains Si in a hypereutectic composition range, and suitable compositions include, for example, 12 to 30% Si;
Examples include those containing 0.3 to 7.0% Cu, or further containing 0.3 to 2.0% Mg, with the remainder consisting of aluminum and inevitable impurities. In addition to the above-mentioned component elements, it is permissible for various meaningful additives to be included in amounts exceeding the amount of unavoidable impurities. For example, Ni, Fe, and Mn are each 0.5 to 3.0%.
It is also preferable to contain one or more types within the range of . The significance of each of the above alloy components is as follows. As is well known, Si is effective as a component for improving wear resistance, and if it is less than 12%, the wear resistance will be poor. On the other hand, if it is contained in excess of 30%, casting will be impaired. It becomes difficult. The eutectic point in the aluminum-silicon binary alloy exists at 11.7% silicon, but when a third element is added, the eutectic point shifts. Therefore, the alloy according to the present invention must contain at least 12% Si in the hypereutectic range. The most suitable Si content is in the range of about 16 to 20%. Both Cu and Mg contribute to improving the strength of the alloy, and if it is less than 0.3%, the effect is insufficient. However, when Cu exceeds 7%,
Corrosion resistance deteriorates significantly. Moreover, when Mg exceeds 2%, the above-mentioned effects are not particularly enhanced, but rather coarse crystallized substances are formed and the mechanical properties are deteriorated. The most suitable Cu content obtained from the experimental results is
It is approximately 4 to 6%, and the Mg content is
It is about 0.45-0.65%. In addition to the above-mentioned components, it is also permissible to include various meaningful additives. For example, inclusion of Sr and P is allowed. All of these elements are equivalent in that they act as refining agents to refine primary Si particles during casting, and it is sufficient to contain at least one of them, but if each is less than 0.005%, the above effects will not be achieved. lacking in
Even if it exceeds 0.1%, no particular increase in effect can be expected. Furthermore, Ni, Fe, and Mn can be mentioned as other optional additive elements. All of these effectively contribute to improving the durability of the alloy, and in terms of this effect, they are all equivalent, and it is sufficient to contain at least one or two or more of them, but each component should be 0.5 If it is less than 3%, it is difficult to achieve the above effects, and if it exceeds 3%, the machinability becomes extremely poor. The extruded alloy material according to the present invention having the above-mentioned component range is manufactured through a predetermined extrusion process after casting in order to control the structure within a specific range. That is, first, the above aluminum alloy is produced into an aluminum alloy ingot by melting and casting according to a conventional conventional method. The primary Si particles contained in the ingot obtained by this casting process are as described above.
Although it can be made finer to some extent by adding Sr and/or P, the grain size as a whole is still quite large, including some that reach 100 μm or more. Moreover, the eutectic Si particles are also quite large as a whole, including particles with a particle size of about 30 μm, and their morphology is also acicular. Therefore, in the present invention, an ingot containing these relatively coarse primary and eutectic Si particles is further hot extruded. Here, this hot pressing process was performed using an extrusion die with a bearing length of 5 to 15 mm, billet temperature: 350 to 420°C, extrusion ram speed: 0.03 to 0.2 m/min, and extrusion ratio. : It is necessary to carry out the extrusion processing under such conditions. In addition, the eutectic Si particles are refined so that the grain size is in the range of 10 to 80 μm, with a relatively large proportion of particles of 40 μm or more, and the distribution is made uniform. The shape is divided into granules by dividing in the direction, and almost all of this is made into particles with a particle size.
It can be made finer in the range of 15 μm or less and in which particles of 10 μm or less occupy a relatively large proportion. By the way, the reasons for limiting the above extrusion conditions are as follows. First, the shape of the die used for extrusion also has a significant effect on the quality of the extruded product. Conventionally, dies commonly used for extruding aluminum alloy wrought materials have bearing lengths of about 3 mm, but in the case of hypereutectic silicon-aluminum alloys, such as the workpiece of this invention, With the above-mentioned die, there is a tendency for significant surface cracks to occur in the extruded product, making it impossible to obtain a good product.
Therefore, it is necessary to use a die with a bearing length of 5 mm or more. However, the bearing length
If the diameter exceeds 15 mm, the extrusion resistance becomes large, which is a disadvantage and no particular advantage can be enjoyed. Therefore, a die with a bearing length in the range of 5 to 15 mm should be used, most preferably a die in the range of 6 to 12 mm. If the billet temperature is less than 350℃, the extrusion operation becomes difficult due to excessive deformation resistance, whereas if the billet temperature exceeds 420℃, surface cracks will occur in the extruded product, making it difficult to obtain a product with a good surface condition. I can't. The most preferred billet temperature range is 380-400°C. The ram speed is adjusted in relation to the extrusion ratio or extrusion speed, but a slow speed of less than 0.03 m/min has the effect of refining the primary and eutectic Si particles in the alloy to a suitable range. becomes insufficient. On the other hand, if the speed exceeds 0.2 m/min, significant cracking will occur in the extruded product. The optimum ram speed is 0.05-0.15m/
It is about min. Furthermore, if the pressing ratio is less than 10, the effect of extrusion processing will not be sufficient and the effect of improving the structure of the alloy will not be obtained.On the other hand, if the pressing ratio exceeds 40, the deformation resistance of the alloy will be large. As a result, smooth extrusion operation becomes difficult. A suitable pressing ratio range is approximately 20 to 30. Effects of the Invention According to the manufacturing method of the present invention as described above, in terms of wear resistance, machinability, and workability, it is not only compared to wear-resistant alloys such as A4032, which are conventionally known as wrought materials, but also has better wear resistance. It is possible to obtain an aluminum alloy extruded material that has better performance than alloys for steel castings and has less variation in wear resistance. Furthermore, since it is manufactured by extrusion processing, it can be easily manufactured into various shapes that are difficult to manufacture with alloy castings, and unlike castings, it has elongation. As a result, many advantages such as better workability and forgeability are realized. Examples Next, examples of the present invention will be shown in comparison with comparative examples. A hypereutectic silicon-aluminum alloy containing 18% Si, 4.5% Cu, 0.5% Mg, and 0.04% Sr, with the balance being aluminum and unavoidable impurities was first manufactured into a billet with a diameter of 120 mm by semi-continuous casting. .
Primary crystals contained in the ingot in the as-cast state
The particle size of the Si particles was generally in the range of 10 to 100 μm, and the particle size of the eutectic Si particles was approximately 30 μm or less and had an acicular shape. Next, this billet was homogenized at 495°C for 8 hours, cooled in the air at room temperature, and then
It was extruded into a round bar with a diameter of 30 mm under various extrusion conditions shown in the table.

[Table] When the structure of the extruded materials obtained in Examples 1 to 6 was examined, all of the primary Si particles contained therein were in the particle size range of 10 to 80μ. Most of the particles were in the range of 40 to 80 μm and were uniformly distributed. and eutectic Si
The particles are also miniaturized, all of them at least 15μ
Within the following particle size range, the majority of all eutectic Si particles were 10 μm or less. Then, the test pieces of Examples 1 to 6 were tested for wear resistance using an Okoshi type wear tester using a rotating disk (test conditions...friction distance: 600 m, friction speed:
2m/min, mating material: FC-30),
The specific wear amount of these was 0.9 to 1.1×10 ⁻⁶ mm/Kg. On the other hand, in Comparative Examples 1 to 4, the billet temperature was too high or the extrusion speed was too slow or too fast, resulting in significant roughness on the surface or cracks in the material. ,
In either case, it was not possible to obtain an extruded material that could be put to practical use. That is, in Comparative Examples 1 and 3, cracks occurred in the extruded materials, and in Comparative Examples 2 and 4, the surfaces of the extruded materials had significant roughness.

Claims (1)

[Claims] 1. Hypereutectic silicon containing Si in the hypereutectic range.
Using an aluminum alloy, the essential process is to cast the alloy into a billet and then extrude it,
Furthermore, the above extrusion can be carried out using a die with a bearing length of 5 to 15 mm.
A method for producing a wear-resistant aluminum alloy extruded material, characterized in that the process is carried out under the following conditions: billet temperature: 350 to 420°C, extrusion ram speed: 0.03 to 0.2 m/min, and pressing ratio: 10 to 40. 2 Using an aluminum alloy containing 12-30% Si, 0.3-7.0% Cu, and the balance consisting of aluminum and unavoidable impurities, an essential step is to cast the alloy into a billet and then extrude it. Length: Using 5-15mm dice,
A method for producing a wear-resistant aluminum alloy extruded material, characterized in that the process is carried out under the following conditions: billet temperature: 350 to 420°C, extrusion ram speed: 0.03 to 0.2 m/min, and pressing ratio: 10 to 40. 3. An aluminum alloy containing 12-30% Si, 0.3-7.0% Cu, and 0.3-2.0% Mg is used, with the balance being aluminum and unavoidable impurities, and the essential steps include casting the alloy into a billet and then extruding it. , Moreover, the above extrusion is carried out using a die with a bearing length of 5 to 15 mm.
A method for producing a wear-resistant aluminum alloy extruded material, characterized in that the process is carried out under the following conditions: billet temperature: 350 to 420°C, extrusion ram speed: 0.03 to 0.2 m/min, and pressing ratio: 10 to 40.