JP6431280B2 - Abrasion resistant alloy with composite microstructure - Google Patents

Description

  The present invention relates to an aluminum alloy used for automotive parts and its manufacturing method, which requires wear resistance and self-lubrication, and more specifically, is composed of wear-resistant hard particles and self-lubricating soft particles. The present invention relates to an aluminum alloy having a composite microstructure.

In general, the wear-resistant aluminum alloy for automobile parts is a hypereutectic Al-Fe alloy mainly containing silicon (Si) 13.5 to 18 wt% (that is, 12 wt% or more) and copper (Cu) 2 to 4 wt%. Is used. The hypereutectic Al—Fe alloy generates primary silicon (Si) particles having a particle size of 30 to 50 μm on a fine structure, and has excellent wear resistance compared to a general Al—Fe alloy. Of the parts, they are often used for parts that require wear resistance, such as shift forks, rear covers, and swash plates.
Typical commercial alloys include R14 alloy from Ryobi Corporation, K14 alloy, which is similar to Korea, and A390 alloy used for monoblocks and aluminum liners.

  However, such a hypereutectic alloy has the disadvantages that it is inferior in castability due to its high Si content, has many difficulties in adjusting the size and distribution of Si particles, and is inferior in impact resistance. Furthermore, it is a specially developed alloy and has a drawback that its price is very high compared to a general aluminum alloy.

  Next, as a self-lubricating aluminum alloy for automobile parts, there is an Al-Sn alloy. In the case of this alloy, tin (Sn) is contained in an amount of 8 to 15 wt%, and self-lubricating tin (Sn) soft particles are generated on the microstructure to reduce friction. It is used as a raw material for metal bearings used in places with high friction.

  However, in the case of this alloy, it has a disadvantage that it cannot be used for structural parts because it has a low strength of 150 MPa or less in spite of the strength reinforcing effect by silicon (Si).

Korean Application Publication No. 10-2008-0102560 JP 2001-316688 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a new simultaneously having the wear resistance of a hypereutectic Al-Si alloy and the self-lubricating property of an Al-Sn alloy. In order to obtain a high-strength, wear-resistant alloy having the concept of self-lubricating properties, it is an object of the present invention to provide a new composite microstructured alloy having hard particles and soft particles simultaneously on the microstructure.

  In order to achieve such an object, a wear-resistant alloy having a composite microstructure according to an embodiment of the present invention includes zinc (Zn) 19 to 27 wt%, tin (Sn) 3 to 5 wt%, and silicon (Si ) 7.6 to 11 wt%, and the remaining aluminum (Al) and inevitable impurities.

  Moreover, it has the composition which further contains 1-3 wt% of copper (Cu).

  Moreover, it has the composition which further contains magnesium (Mg) 0.3-0.8 wt%.

  Moreover, it has the composition which further contains copper (Cu) 1-3 wt% and magnesium (Mg) 0.3-0.8 wt%.

  The wear-resistant alloy having a composite microstructure according to another embodiment of the present invention includes zinc (Zn) 19 to 27 wt%, bismuth (Bi) 3 to 5 wt%, silicon (Si) 7.6 to 11 wt%, and It has a composition comprising the balance of aluminum (Al) and inevitable impurities.

  According to the wear-resistant alloy having a composite microstructure having the above-described structure, the new concept of self-lubricating, having both the wear resistance of a hypereutectic Al-Si alloy and the self-lubricating property of an Al-Sn alloy. A high strength wear resistant alloy having lubricating properties can be obtained.

It is a graph regarding the Example and comparative example for confirming the low friction characteristic by the soft particle | grains of the wear-resistant alloy which has the composite microstructure concerning this invention.

  Hereinafter, with reference to the accompanying drawings, a wear-resistant alloy having a composite microstructure according to a preferred embodiment of the present invention will be described.

  The present invention relates to a new alloy having a composite microstructure having both hard particles and soft particles in an aluminum matrix structure.

  Generally, there are Sn, Pb, Bi, Zn, and the like as alloy elements that generate self-lubricating particles in an aluminum alloy. Since these elements are not chemically reactive with aluminum, they do not produce intermetallic compounds and have the unique property of being phase separated. Furthermore, since it has a relatively low melting point, it has a unique characteristic of having a self-lubricating property that forms a lubricating film while partially melting under severe friction conditions.

  From the viewpoint of self-lubricity and cost, among the four chemical elements mentioned above, Pb is the best self-lubricant particle-forming element, but it is classified as a hazardous metal element and cannot be used in the automotive field. It is a situation. Therefore, Sn is most widely used as an alternative element for Pb, and in some cases, Bi is used for the same purpose. On the other hand, in the case of Zn, the melting point is higher than that of Sn and Bi, and the self-lubricating property is greatly inferior. Therefore, there is a disadvantage that a relatively large amount must be added, but the price is very low. Therefore, in order to secure the cost competitiveness of the material, it is used as a soft particle generating element that partially replaces the content of expensive Sn or Bi.

  Next, there are Si and Fe as alloy elements for producing hard particles. Si and Fe have a characteristic of eutectic reaction with Al (Eutectic reaction), and when added in a specific amount or more, have a characteristic of generating hard particles with corners. Si is the most representative hard particle forming element in aluminum alloys, and when added at 12.6 wt% or more in an Al—Si binary alloy, it produces primary Si particles and has wear resistance. have. However, when it is added together with Zn, which is a soft particle generating element, the Si content varies depending on the Zn content for the generation of hard particles. For example, if the Zn content is 10 wt% or less, the Si content is The range is from a minimum of 7 wt% to a maximum of 14 wt%. At this time, if Si is added in less than the minimum amount, hard particles will not be generated, and if Si is added in excess of the maximum amount, the hard particles will become very large, adversely affecting the mechanical properties and wear resistance. Problem occurs.

  In the case of Fe, Al—Si alloys are generally known as impurities, but Al—Fe binary alloys without Si have wear resistance when added at 0.5 wt% or more and less than 3 wt%. Al-Fe-based intermetallic compound particles can be formed to have wear resistance, but when added at 3 wt% or more, an intermetallic compound is excessively generated, the mechanical properties are lowered, and the melting point is reduced. There is a problem of rising.

  There are Cu and Mg as alloy elements for reinforcing the basic strength of aluminum alloys. In the case of Cu, it has the effect of forming an intermetallic compound through a chemical reaction with Al and increasing the strength, but the effect varies depending on the Cu content, the casting / cooling conditions of the alloy, and the heat treatment conditions. In the case of Mg, it has the effect of forming an intermetallic compound through a chemical reaction with Si or Zn and increasing the strength, but the effect differs depending on the content, the casting / cooling conditions of the alloy and the heat treatment conditions, as with Cu. .

  Hereinafter, the present invention will be described in more detail.

  The aluminum alloy according to the present invention contains aluminum (Al) as a main component, and zinc (Zn) 19 to 27 wt%, tin (Sn) 3 to 5 wt%, copper (Cu) 1 to 3 wt%, magnesium (Mg) 0.3 to 0.8 wt%, and 7.6 to 11 wt% of silicon (Si) that generates hard particles are added. Here, when the zinc (Zn) is added at 19 wt% or less, it is difficult to obtain a sufficient self-lubricating property due to a small amount of Zn phase generated as soft particles, and when added at 27 wt% or more. This is disadvantageous in terms of casting because the solidus of the alloy is too low.

  Even if tin (Sn), which has stronger self-lubricating property than zinc (Zn) but is expensive, is added at 3 wt% or less, the amount of Sn phase, which is a soft particle, is small and the self-lubrication is insufficient for the Zn phase. It is difficult to supplement the properties, and when it is added at 5 wt% or more, the obtained friction reduction effect is not very meaningful in terms of driving conditions. Therefore, the amount of tin (Sn) is minimized from the viewpoint of efficiency.

  When silicon (Si) for generating hard particles is added at 7.6 wt% or less, primary crystal Si as hard particles is not sufficiently generated (less than 0.5%), so that wear resistance can be ensured. It is difficult, and when added at 11 wt% or more, hard particles are excessively formed (exceeding 5%) and are coarsened, which adversely affects wear resistance and mechanical properties.

  Copper (Cu) added to improve mechanical properties must be added in an amount of 1 wt% or more in order to ensure proper mechanical properties, but if added in excess of 3 wt%, between other elements and metals The amount of the compound is limited because it may form a compound and deteriorate the mechanical properties. Instead, 0.3% by weight or more of magnesium (Mg) can be added to further improve the mechanical properties. Further, when adding 0.8 wt% of magnesium (Mg), there is a possibility that a compound disadvantageous in mechanical properties may be formed, so the amount thereof is limited.

  As an example and a comparative example for confirming low friction characteristics due to soft particles in an Al-Zn-Sn alloy according to the present invention, as shown in the graph of FIG. Manufactured and observed changes in friction coefficient by alloy. As a result, under the condition of 3 wt% Sn, the required low friction characteristic (friction coefficient 0.150 or less) was obtained with the 3Sn-19Zn alloy as an example, and an unsatisfactory result was obtained with a 3Sn-17Zn alloy as a comparative example. . From this result, it was confirmed that desired low friction characteristics can be obtained if Zn is added at least 19 wt% with a minimum Sn content of 3 wt%. Furthermore, satisfactory low friction characteristics were obtained even when the Sn and Zn contents were increased.

  Next, as comparative examples and examples for evaluating wear resistance and mechanical properties, an Al-25Zn-3Sn-xSi alloy as shown in Table 1 below was produced and evaluated.

  Looking at the Al-25Zn-3Sn-xSi alloy system in Table 1, in the case of the comparative example in which the Si content is 7.4 wt%, only a small amount of Si particles, which are hard particles, are produced, so that sufficient wear resistance can be obtained. Although it was difficult, in the case of the Example whose Si content is 7.6-11 wt%, it confirmed that hard particle | grains produced | generated to a maximum of 5% and sufficient abrasion resistance was securable. However, in the case where 11.2 wt% or more of Si particles are contained and primary crystal Si particles exceeding 5% are produced, it is judged that the problem of coarsening and segregation of Si particles is large, so the amount is limited.

  In the case of strength, it is confirmed that it has 335 to 345 MPa regardless of the content of Si, and it can be seen that there is no difficulty in using it as a structural material.

  Meanwhile, the wear-resistant alloy having a composite microstructure according to another embodiment of the present invention includes zinc (Zn) 19 to 27 wt%, bismuth (Bi) 3 to 5 wt%, and silicon (Si) 7.6 to 11 wt%. And the balance aluminum (Al) and inevitable impurities. Like tin (Sn), bismuth (Bi) is a strong self-lubricating material and can be used as a substitute for tin (Sn).

  While the invention has been illustrated and described in connection with specific embodiments, it will be understood that various modifications and changes may be made to the invention without departing from the spirit of the invention provided by the claims. This is obvious to those skilled in the art.

  The present invention is used in automotive parts and can be applied to the field related to aluminum alloys having a composite microstructure.

Claims (4)

It has a composition comprising zinc (Zn) 19 to 27 wt%, tin (Sn) 3 to 5 wt%, silicon (Si) 7.6 to 11 wt%, and the balance aluminum (Al) and inevitable impurities. A wear-resistant alloy with a composite microstructure.   The wear-resistant alloy having a composite microstructure according to claim 1, further comprising a composition further including 1 to 3 wt% of copper (Cu).   The wear-resistant alloy having a composite microstructure according to claim 1, further comprising a composition further including 0.3 to 0.8 wt% of magnesium (Mg). The wear-resistant alloy having a composite microstructure according to claim 1, further comprising a composition further including 1 to 3 wt% of copper (Cu) and 0.3 to 0.8 wt% of magnesium (Mg).

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