RU1770432C - Aluminium based alloy - Google Patents

Abstract

The alloy is intended for use as parts of friction units. The alloy contains, wt.%: Magnesium 0.3-1.5; graphite 0.5-3.0; copper 4.5-30.0; silicon 0.5-6.5; iron 0.1-0.5; nickel 0.1-0.5; aluminum is the rest. The properties of the alloy are as follows: wear arr. 0.021-0.040, cont. 0.009-0.031, coefficient friction 0.013-0.073, includes elongation 1.4-3..0; HB 48-89. 1 tab.

Description

The invention relates to the field of metallurgy of aluminum materials combining high antifriction and mechanical strength, and can be applied to friction units.

In order to increase the antifriction properties in most known aluminum alloys for friction units, elements are introduced: tin, lead, antimony, and others in an amount of 5-40% (N. Bush and others. Bearings made of aluminum alloys. - M .: Transport, 1974, p. 16-17). However, these elements are expensive and scarce.

Due to the lack of deficit and low cost, composite materials with graphite inclusions in an unbound state in the structure are of undoubted interest.

Of the known solutions, the closest in technical essence and the achieved effect is an aluminum-based casting alloy comprising silicon 2-20%, graphite 0.5-15%, magnesium 0.3-1.5%. the rest is aluminum (ed. St. No. 479814, class C 22 C 21/04).

However, studies have shown that with prolonged curing of the molten base aluminum, silicon at elevated temperatures metal carbides appear. fishing Moreover, the presence of a large amount of a carbide forming element in the alloy is silicon, along with the fact that it promotes the formation of silicon carbide SiC. also intensifies the formation of aluminum carbide AleCj. The inclusion of carbides sharply increases the wear of the friction unit, reduces the mechanical properties, in addition, worsens the workability of the material, leads to an increase in porosity, and reduces its corrosion resistance. The stability of high antifriction and mechanical properties is very low.

At the same time, characteristic of foundry aluminum alloys (see. Structure and properties of aluminum alloys. / LF Mondolfo. Trans. From English.-M.: Metallurgists, 1979, Aluminum / Ed. By Tumanov.- M: Metallurgists, 1972) is the presence of carbide-forming elements (silicon, iron, nickel) in the composition. Thus, silicon additives improve technological (foundry) properties. Iron and nickel are introduced into antifriction, bearing alloys to increase heat resistance, and also often with

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the production of cast aluminum alloys, they are present in the form of impurities.

The aim of the invention is to increase the antifriction and mechanical properties.

The goal is achieved in that the aluminum-based material, including silicon, magnesium, graphite, additionally contains copper, iron and nickel in the following ratio, wt.%:

Magnesium 0.3-1.5

Graphite 0.5-3.0

Copper 4.5-30.0

Silicon: 0.5-6.5

Iron0.1-0.5

Nickel 0.1-0.5

Aluminum Else

Moreover, the ratio of the total content of silicon, iron and nickel to the content of copper does not exceed the condition 1: 4.

Comparative analysis with the prototype shows that the claimed composition differs from the known one by the following features: the presence and content of copper, iron and nickel, by the condition of the ratio of the components.

The essence of the technical solution is as follows.

Copper does not interact with graphite and, as studies have shown, its presence in the claimed amount does not contribute to the formation of carbides. It has also been established that, with the claimed ratio of non-carbide forming element to copper and carbide forming elements, which are most often used in most aluminum alloys, the thermal stability of the alloy is also achieved. In other words, in order to exclude the formation of carbides, it is necessary that the copper content in the composition of a casting - aluminum alloy exceeds the content of carbide-forming elements (silicon, iron, nickel) by at least 4 times. Otherwise, as shown by the studies, metal carbides appear in the structure, and, as can be seen from the table. 1, the properties in this case are reduced.

As follows from the table. 1 (N ° 1-4), the most optimal copper additives are regulated in the range of 4.5-30%. The lower limit is due to insufficient strength properties. With an increase in the copper content of more than 30%, the base of the alloy becomes brittle, the plastic properties decrease, and the wear of the sample and counterbody increase.

The presence of silicon in the alloy is along with that. which favorably affects the technological qualities, also leads to the formation of carbides - the stability of the properties decreases. The increase in silicon is greater than the boundary value of 6.5 (No. 5, 6, table. 1)

highly undesirable. To eliminate carbide formation, an even greater (more than 30%) copper content is necessary, which sharply embrittles the material. As can be seen from the table. 1 Kb 7. 8, noticeable enhancement effect

0 strength and anti-friction properties were noted with a silicon content of more than 0.5%. This is mainly due to an increase in the fluidity and, consequently, the density of the workpieces.

5 Nickel is introduced into aluminum-copper alloys to increase heat resistance, which is important for antifriction materials operating at high temperatures (for example, piston-cylinder) together with nickel, iron is added specifically to increase resistance to corrosion, and in alloys containing and magnesium to reduce abnormal grain growth. When the content of iron and nickel is less than 0.1% (see No. 7,

5 9, 10 tab. 1) an increase in wear and a decrease in hardness were noted. An increase in the carbide-forming elements iron and nickel (see No. 11 of Table 1) is undesirable, since it leads to the formation of carbides, in addition,

0 iron additives of more than 0.5% embrittle the material, and the introduction of nickel is limited by economic inexpediency,

When the minimum boundary values of magnesium (see Nfe 13, 14, Table 1) are exceeded, the hardness drops sharply, while the antifriction properties also decrease. With a larger value that goes beyond the boundary values (see No. 15.16, Table 1), the strength characteristics practically do not change, but their ductility decreases by more than 2 times, and antifriction decreases.

The optimum graphite content of 0.5-3.0% (No. 17-20. See table. 1) is due to: at a lower content, wear and coefficient

5 frills are very high; at greater, exceeding the boundary values, the metal monolithicity is lost - the mechanical properties are reduced by 1.2-1.3 times, as well as antifriction.

0 It should be emphasized that despite the fact that the material may contain intermediate declared values of the elements, and the declared ratio (Si + Fe + Ni / Cu.%) Is not observed, the properties of such a material are sharply reduced (see N; 12, table 1).

An example of a specific implementation. The materials were obtained using the ligature aluminum - 8% graphite, which was manufactured by extrusion of the initial components of the powders of aluminum powders PA-4 and

graphite C-1. The ligature was introduced into a melt heated to a temperature of 725 ° C (compositions No. 1–10, see Table 1), after which the molten mass was mixed for 0.5 hours and poured into a copper chill mold of the following sizes: inner and outer diameters, respectively, 20 and 110 mm, height - 100 mm. Test specimens were cut from cast blanks.

The atifriction properties were evaluated on a friction machine of the AE-5 type under conditions of limited lubricant supply (1 drop in 10 s at a load of 220-240 kg / cm). Counterbody material - steel 40x (heat-treated). Greasing - D-16 diesel oil. Mechanical properties (d - elongation, HB - Brinell hardness) were evaluated according to standard methods (GOST 9657-73).

Appropriate aluminum alloy compositions were pre-alloyed in an electric resistance furnace in air. The charge materials were: aluminum A7, copper electrolytic, silicon KO. magnesium Mg99, iron iron.

Magnesium was added to the melt (including the prototype) wrapped in aluminum foil. ESU; And compare the values of the properties of the material - the prototype (M 11), manufactured under the same conditions as the claimed material, then the properties of the latter are 1.5-10 times higher.

Metallographic and microstructural studies show that aluminum carbides are absent in the compositions of the claimed alloy, while silicon and iron carbides were found in addition to aluminum carbide in the structure of the prototype material and the material whose elements are out of bounds. nickel.

The use of low-cost and affordable elements (copper, silicon) as a base hardener for aluminum alloys, as well as a graphite component, which sharply increases antifriction

properties, combined with the possibility of holding at elevated temperatures, provide the alloy with accessibility to mass introduction. Materials are recommended instead of expensive and scarce

alloys on a copper and iron basis. As necessary, to increase the strength properties of the alloy can be subjected to heat treatment.

Claims (1)

The claims An aluminum based alloy containing magnesium, silicon and graphite, characterized in that which, in order to increase the antifriction and mechanical properties, it additionally contains copper, iron and nickel in the following ratio of components, May. %: Magnesium 0.3-1.5 Graphite 0 5-3.0 Copper 4.5-30.0 Silicon 0.5-6.5 Iron0.1-0.5 Nickel 0.1-0.5 Aluminum Else, moreover, the ratio of the total content of silicon, iron and nickel to the content of copper is 1: 4.