KR101526657B1 - Wear-resistant alloys having a complex microstructure - Google Patents

Abstract

A wear-resistant alloy having a composite microstructure composed of a composition containing 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of tin (Sn), 7.6 to 11 wt% of silicon (Si), and the balance aluminum Is introduced.

Description

[0001] Wear-resistant alloys having a complex microstructure [

More particularly, the present invention relates to an aluminum alloy having a composite microstructure composed of abrasion resistant hard particles and self-lubricating soft particles. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an aluminum alloy used for automotive parts requiring wear resistance and self-

Generally, as a wear-resistant aluminum alloy for automobile parts, an over-process Al-Si alloy having a silicon (Si) content of 13.5 to 18 wt% (that is, 12 wt% or more) and a copper (Cu) content of 2 to 4 wt% is used . The over-process Al-Si alloy has excellent wear resistance compared to a general Al-Si alloy because the fine silicon (Si) particles having a size of 30 to 50 탆 are formed on the microstructure, and the shift fork, rear cover , Swash plate, and other parts requiring abrasion resistance.

Typical commercial alloys include Ryobi R14 alloy from Japan, K14 alloy, a similar domestic developed alloy, and A390 alloy, used for monoblock or aluminum liner.

However, such an over-alloy has a disadvantage in that it has poor main constitution due to a high Si content, is difficult to control the size and distribution of Si particles, has a low impact resistance and is a specially developed alloy. There are high disadvantages.

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

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

KR 10-2008-0102560 A

In order to obtain a high-strength wear-resistant alloy having a new concept of self-lubricating property simultaneously having both wear resistance and Al-Sn system self-lubricating property of an over-process Al-Si alloy, a composite fine It is intended to propose new alloys.

In order to achieve the above object, the wear-resistant alloy having a complex microstructure according to the present invention comprises 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of tin (Sn), 7.6 to 11 wt% of silicon (Si) Al) and other inevitable impurities.

Further, it may be composed of a composition further containing 1 to 3 wt% of copper (Cu).

Further, it may be composed of 0.3 to 0.8 wt% of magnesium (Mg).

Further, it may be composed of a composition further containing 1 to 3 wt% of copper (Cu) and 0.3 to 0.8 wt% of magnesium (Mg).

Another abrasion resistant alloy having a complex microstructure according to the present invention comprises 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of bismuth (Bi), 7.6 to 11 wt% of silicon (Si) And a composition containing impurities.

According to the wear-resistant alloy having the composite microstructure having the above-described structure, a high-strength wear-resistant alloy having a new concept of self-lubricating property simultaneously having the wear resistance of the over-process Al-Si alloy and the Al- .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph relating to Examples and Comparative Examples for confirming low friction characteristics of soft particles of a wear resistant alloy having a complex microstructure according to an embodiment of the present invention. FIG.

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

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

In general, alloying elements that generate self-lubricating particles from aluminum alloys include Sn, Pb, Bi, and Zn. These elements have unique characteristics that they are not chemically reactive with aluminum and do not produce intermetallic compounds and phase-separated. Also, it has a relatively low melting point and has a unique characteristic that it has a self-lubricating ability to form a lubricating film by being partially melted under severe friction conditions.

Among the four chemical elements mentioned above, Pb is the best self-lubricating particle generating element in terms of self-lubricating and cost, but it is classified as a harmful metal element and can not be used in the automobile field. Therefore, Sn is the most widely used substitute element of Pb, and in some cases Bi is used for the same purpose. On the other hand, Zn has a disadvantage that its melting point is higher than that of Sn and Bi, and self lubrication characteristics are much lowered, and thus it has a disadvantage of adding a relatively large amount. However, since it has a very cheap price, As a soft particle generation element that partially replaces the costly Sn or Bi content.

Next, alloying elements for producing hard particles are Si and Fe. Si and Fe have eutectic reaction characteristics with Al and have the characteristic of producing hard-grains of angular shape when added over a specific amount. Si is the most representative hard particle generation element among the most aluminum alloys. When added in an amount of more than 12.6 wt% in the Al-Si binary alloy, it forms primary Si particles and has a wear resistance characteristic. However, when it is added together with Zn, which is a soft grain forming element, the Si content varies depending on the Zn content in order to produce hard particles. For example, when the Zn content is about 10 wt%, the Zn content is 7 wt% to 14 wt% . At this time, hard particles are not generated when Si is added in a quantity less than the minimum amount, and hard particles are excessively added when added in an amount exceeding the maximum, thereby causing a problem of adversely affecting mechanical properties and abrasion resistance.

In the case of Fe, it is generally known as an impurity in an Al-Si-based alloy, but an Al-Fe binary-based alloy without Si also forms an Al-Fe intermetallic compound particle having abrasion resistance when added in an amount of more than 0.5 wt% On the other hand, if it is added in an amount of 3 wt% or more, there is a problem that the metal sintered product is excessively formed, the mechanical properties are lowered and the melting point is increased.

Alloying elements for basic strength reinforcement of aluminum alloys are Cu and Mg. Cu has an effect of increasing the strength by forming an intermetallic compound through chemical reaction with Al. The effect of Cu differs depending on the content of Cu, the casting / cooling condition of the alloy, and the heat treatment conditions. Mg has the effect of increasing the strength by forming an intermetallic compound through chemical reaction with Si or Zn. As with Cu, the effect varies depending on the content, the casting / cooling conditions of the alloy, and the heat treatment conditions.

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

The aluminum alloy according to the present invention comprises aluminum (Al) as a main component and further contains 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of tin (Sn), 1 to 3 wt% of copper (Zn) is added in an amount of not more than 19 wt%, the amount of the Zn phase, which is a soft particle, is small and the amount of the Zn (Zn) It is difficult to obtain self-lubricating property. When the content is more than 27 wt%, the solidus of the alloy becomes too low, which is disadvantageous in terms of casting conditions.

In the case of tin (Sn), which has a stronger magnetic lubricating property than zinc (Zn) but has a higher price, it is difficult to compensate for insufficient self-lubrication of Zn phase due to a small amount of Sn phase which is soft particles when added in an amount of 3 wt% The achievable friction reduction effect has no significant effect on the driving conditions and minimizes the amount in terms of efficiency.

In the case of silicon (Si) for producing hard particles, it is difficult to secure the wear resistance because the hard particles, ie, hard Si, are not sufficiently generated (less than 0.5%) when applied at 7.6 wt% or less. Excessive (more than 5%) is generated and coarsened, adversely affecting abrasion resistance and mechanical properties.

Copper (Cu) added to improve mechanical properties should be added in an amount of 1 wt% or more to ensure proper mechanical properties, but if it exceeds 3 wt%, other elements and intermetallic compounds may be formed and the mechanical properties may be deteriorated. And the addition of magnesium (Mg) in an amount of 0.3 wt% or more can be achieved to further improve the mechanical properties. Instead, magnesium (Mg) also can form compounds which are detrimental to mechanical properties when added in an amount of 0.8 wt%, which limits the amount of the compound.

As an example and a comparative example for confirming the low friction property by the soft particles in the Al-Zn-Sn based alloy according to the present invention, an alloy is produced by varying Zn and Sn contents as shown in FIG. 1, The change in the coefficient of friction was observed. As a result, low friction characteristics (friction coefficient of less than 0.150) required in the 3Sn-19Zn alloy of the embodiment was obtained under the condition of 3 wt% Sn, and the result was dissatisfied in the comparative example 3Sn-17Zn. From this result, it was confirmed that the desired low friction characteristics can be obtained by adding at least 19 wt% of Zn at the minimum Sn content of 3 wt%, and satisfactory low friction characteristics can be obtained even when the content of Sn and Zn is increased.

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

In the case of the Al-25Zn-3Sn-xSi alloy system shown in Table 1, in the comparative example in which the Si content is 7.4 wt%, it is difficult to obtain sufficient abrasion due to the generation of a small amount of Si particles as hard particles, whereas the Si content of the embodiment is 7.6 to 11 wt% , It is confirmed that hard particles are generated up to 5% and sufficient abrasion resistance can be ensured. However, when the Si content exceeds 11.2 wt% and the Si content exceeds 5%, it is judged that the coarsening and segregation problems of the Si particles are large.

It was confirmed that the strength was 335 ~ 345 MPa regardless of the content of Si, and it can be understood that there is no problem in using it as a structural material.

Another abrasion resistant alloy having a complex microstructure according to the present invention comprises 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of bismuth (Bi), 7.6 to 11 wt% of silicon (Si) And a composition containing impurities. Like bismuth (Sn), bismuth (Bi) can be used as a substitute for tin (Sn) as a strong self-lubricating material.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

Claims (5)

And a composition comprising 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of tin (Sn), 7.6 to 11 wt% of silicon (Si) and the balance aluminum (Al) and other unavoidable impurities, Wherein the wear-resistant alloy has a composite microstructure. The method according to claim 1,
And 1 to 3 wt% of copper (Cu), wherein the wear-resistant alloy has a composite microstructure. The method according to claim 1,
And 0.3 to 0.8 wt% of magnesium (Mg), wherein the wear-resistant alloy has a composite microstructure. The method according to claim 1,
1 to 3 wt% of copper (Cu) and 0.3 to 0.8 wt% of magnesium (Mg). (Si), aluminum (Al) and other unavoidable impurities, in the range of 19 to 27 wt% of zinc (Zn), 3 to 5 wt% of bismuth (Bi) Wherein the wear-resistant alloy has a composite microstructure.

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