GB2023648A - Aluminium Bearing Alloy - Google Patents

Abstract

An aluminium alloy of the following composition has antifriction properties of an order which enables its use in sliding bearings without the addition of a soft layer: <IMAGE>

Description

SPECIFICATION Bearing Aluminum Alloy The present invention relates to antifriction alloys, and more particularly to aluminum-base bearing alloys used for manufacturing various sliding members, such as for example, bimetallic shells of crankshaft journal bearings and camshaft bushings employed in internal combustion engines,-as well as in compressors and other machinery where the maximum pressure per unit area of bearing is from 400 to 450 kg/cm2.

It is therefore an object of the present invention to provide an alloy which will have all the properties mentioned above.

The invention provides bearing aluminum alloy comprising antimony, copper, titanium, lead, as well as tellurium or phosphorus or selenium, said components being contained therein in the following amounts: Per cent by weight antimony - 2 to 8 copper 0.3 to 1.5 titanium 0.02 to 0.1 5 tellurium or phosphorus or selenium 0.01 to 0.5 lead 1 to 15 aluminum, the balance The alloy composition according to the invention is selected from the following considerations.

The alloys which contain less than 2 per cent by weight of antimony are characterized by low antifriction properties, being liable to seizure, whereas the alloys containing more than 8 per cent by weight of antimony have low plasticity, which impairs their performance characteristics such as conformability and embedding ability, as well as their good workability during rolling the alloy and cladding steel therewith.

The addition of copper to the alloy in an amount of less than 0.3 per cent by weight does not lead to any appreciable increase in strength thereof, whereas the copper contents in an amount of more than 0.3 per cent by weight will permit the alloy strength, and, specifically, its fatigue strength, to be increased.

With the copper contents amounting to more than 1.5 per cent by weight, the alloy strength is improved while its brittieness increases, which renders it practicaily unsuitable for working used in the production of steel-base composite metal.

The titanium contents in the alloy of the invention within the range of 0.02 to 0.1 5 per cent by weight is considered to be optimal in view of the importance to ensure fine grained structure of the alloy. The content of titanium in the alloy below 0.02 per cent by weight will not effect the grain size in the alloy, whereas the titanium content above 0.15 per cent by weight practically fails to effect to any appreciable extent the grain size.

The amount of a modifier, such as tellurium or phosphorus or selenium, added to the alloy of the invention with the purpose to reduce size and change the shape of the aluminum antimonide phase particles, is determined by the contents of antimony in the alloy and is related directly thereto provided the amount of antimony contained therein ranges.from 2 to 8 per cent by weight.

The content of a modifier, such as tellurium or phosphorus or selenium, below 0.01 per cent by weight fails to produce any significant modifying effect on the structure of the antimony-containing aluminum alloys. The content of the modifier above 0.5 per cent by weight fails to increase the modifying effect thereof.

The content of lead in the alloy within the range of 1 to 1 5 per cent by weight ensures its high antifriction properties, such as working-in and seizure-resistant properties thereof. With the lead contents amounting to less than 1 per cent by weight, the seizure-resistance property of the alloy is basically the same as that of the alloy free from lead. The coefficient of friction of the lead-containing alloy is equai to that of the lead-free alloy.

With the lead contents amounting to more than 1 5 per cent by weight, the alloy will have no advantages over the alloy containing 1 5 per cent by weight of lead and will have its mechanical properties impaired thereby.

The bearing aluminum alloy according to the invention may have the following compositions, in per cent by weight: 1. antimony 6 copper 0.9 titanium 0.08 tellurium 0.2 lead 6 aluminum, the balance.

2. antimony 6 copper 0.9 titanium 0.08 tellurium 0.15 lead 15 aluminum, the balance.

3. antimony 5 copper 1 titanium 0.1 phosphorus 0.1 lead 3 aluminum, the balance.

The alloy according to the. invention has the following advantages over the known alloys used for similar purposes, viz., as to its strength, ductility and impact strength this alloy favourably compares with the best bearing aluminum alloys known in the art, and as to its antifriction property, the alloy of the invention is superior to the known tin-free alloys.

The physical-and-mechanical properties of the alloy of the invention render it suitable for rolling and for steel cladding.

Owing to high antifriction properties of the alloy according to the invention, it becomes adaptabie for use in sliding bearings without the need to apply thereon an additional third soft layer, which, in turn, makes it possible to achieve an appreciable technical and economic effect due to simpler construction of such bearings, its high production effectiveness, lower consumption of power angel materials, such as chemicals employed in plating technique.

All the above-mentioned advantages of the alloy according to the invention are possible to obtain provided the alloy composition is maintained strictly in compliance with specified amounts of its components.

The desired properties of the alloy will not be attained if one of the components thereof is contained in amounts other than those specified above.

The alloy of the invention can be produced in accordance with the known production processes, viz., by means of smelting in induction or flame furnaces and subsequent casting in iron-moulds; by means of smelting. in induction or flame furnaces, followed by continuous casting.

It is possible to obtain blanks from the alloy of the invention according to the production process whereby granules are formed as the drops of atomized melt cool in water, said granules undergoing compression thereafter.

The invention will ba further described with reference to the following illustrative Examples.

Example 1 The aluminum alloy smelted at a temperature of 9000C in a high-frequency induction furnace in a graphite crucible had the following composition, in per cent by weight: antimony, 5; copper, 1; titanium, 0. 1; tellurium, 0.1; with lead being added thereto in an amount of 3 per cent by weight. The total cast weight was 50 kg. The charge was composed of pure metals, such as aluminum, antimony, copper, titanium and tellurium. However, master-alloys may be recommended for use in mass production, such as aluminum with 10 per cent by weight of antimony, aluminum with 50 per cent by weight of copper.

The alloy was poured into non-cooled moulds with a size of 40x 11 5x50 (without shrinkage head). Chemical analysis of the samples taken from various placed of ingots showed uniform distribution of lead over the entire cross-section of the ingot; the content of lead in the top and bottom portions of the ingot was practically the same. Segregation of lead did not exceed 1 per cent by weight.

Metallographic analysis of the alloy samples showed that with sufficiently fine-grained structure of solid solution there were observed uniformly distributed inclusions of the lead component along with a small amount of polyhedral crystals of the antimonide component AlSb and inclusions of phase CuAl2.

Mechanical properties of the alloy according to the invention determined at different temperatures are given below in Table 1.

Table 1 Mechanical Properties of the Alloy at Different Temperatures Temperature, C Characteristics Temperature, 0C 20 100 200 300 350 400 450 500 IJltimate tensile strength , kg/mm2 8.4 8.3 6.5 3.4 2.6 1.7 1.4 1.2 Elongation at break b % 5.6 5.6 6.7 8.3 11.6 10.3 12.8 1 1.2 Reductionofarna'ii'% 10.5 8.1 8.1 8.2 11.2 12.1 10.4 8.1 Impact strength 1.6 1.4 1.4 1.1 1.1 1.1 1.1 1.1 kgm a k cm2 Example 2 Seven alloys were produced as described in Example 1. Samples were cut from the ingots to undergo friction testing.

The tests were run on a friction test rig using the pin-lubricating bush systems. The specimens of bushes fabricated from the alloys of the invention were operated in pair with pins fabricated from medium-carbon chromium-nickel steel with hardness HRC40. The compositions of the alloys and the coefficients of friction are given below in Table 2.

Table 2 Composition and Friction Coefficients of the Alloys under Testing Number Friction of Chemical composition, wt. % Friction alloy Sb Cu Pb Ti Te Se ~ P Al 1 1 1 9 0.1 0.2 - - balance 2 8 1.5 15 0.15 0.5 - - balance 0.007 3 5 1 5 0.1 0 - - balance 0.011 4 8 0.3 1 0.02 - - 0.01 balance 0.061 5 3 0.5 5 0.1 0.2 - - balance 0.011 6 5 0.5 1 0.1 0.2 - - balance 0.060 7 5 1 0 0.1 0.2 - - balance 0.103 The values of friction coefficients given in Table 2 indicate, depending on the alloy composition, that the addition of lead allows for drastic decrease (for an order of magnitude) in the friction coefficient as compared, to its value (0.103) in the event of the known alloy free from lead (alloy No.

7). This improves working-in and seizure-resistant properties of the alloy, as well as reduces mechanical iosses due to friction in the course of operation.

Example 3 This example is given to illustrate various working conditions to which the alloy was subjected.

The ingots produced from the alloy containing 4 wt.% of antimony, 1 wt.% of copper, 0.1 wt.% of titanium, 0.1 wt.% of tellurium, 5 wt.% of lead, aluminum being the balance, were subjected to rolling at various temperatures. The ingots fabricated from the lead-containing alloys were found to develop crackings; when cold-rolled, the alloy was intensively cold hardening, its maximum total reduction was not more than 50 per cent.

The most favourable working conditions for the alloy were found to be warm rolling at a temperature of up to 2500C.

Example 4 This example is given to show the working of the alloy of the invention by pressing, whereby bimetal strips composed of steel and of the proposed alloy, were produced by clad rolling.

The alloy was smelted as described in Example 1. The alloy had the following composition, in per cent by weight: antimony, 6; copper, 0.9; titanium, 0,08; tellurium, 0.2; lead, 6.5; aluminum, the balance.

The alloy was cast by a semi-continuous method in a copper chromium-plated water-cooled mould. The casting temperature was 880 to 9000C, the rate of casting was 12 m/h, the mould was 45 to 125 mm in cross-section.

Chemical analysis of the samples taken from various places of ingots showed uniform distribution of lead lengthwise and transversely of the ingot (the lead segregation was not more than 1.5 to 2.0 per cent).

Metallographic analysis of the alloy confirmed uniform distribution of inclusions of lead component therein.

After milling the ingots of the alloy to a thickness of 37 mm, they were subjected to rolling at a temperature of 2500C, and reduced in thickness to 25 mm. The rolled strips were annealed at a temperature of 4000C for a time period of 2 hours, whereupon they were subjected to cold rolling until reduced in thickness to 9 mm. Thereafter, the strips were annealed, degreased, abrated by an emery belt and coated with a layer of aluminum, 0.8 thick, (also degreased and abrated) while being subjected to rolling on a duo mill with working rolls having 470 mm in diameter (dye 470) in accordance with the following schedule: 9.8#5#4.0#3.2#2.65mm The rolled strips were cut to a size of 2.65x 105x 1000 mm.

After degreasing and brush-cleaning operations, the aluminum strips were applied onto steel strips having 6.6 by 107 by 1200 mm in size, which were also degreased and dressed by an emery bolt.

The packets were subjected to rolling on duo 470 mill in accordance with the following rolling scheduie: 2.65+6.6=9.25 5+0.10 mm (reduction was 45.6 per cent).

The rolled strips were annealed at a temperature of 3550C for a time period of 2.5 hours, whereupon they were sized to 2.1+0.10 mm and thereafter annealed at a temperature of 4000C for a time period of 3 hours.

Thus produced bimetallic strips were used for manufacturing sliding bearings.

Example 5 This example is given to illustrate the technique of obtaining the alloy granules and the method of producing bimetal.

The granules of the alloy containing 1 5 per cent by weight of lead, 3 per cent by weight of antimony, 0.9 per cent by weight of copper, 0.08 per cent by weight of titanium and 0.15 per cent by weight of tellurium, aluminum being the balance, were prepared in a centrifugal apparatus. The alloy overheating temperature prior to casting was 11 000C. Owing to high speed of crystallization, the distribution of lead in granules was uniform and of high dispersity. After vacuum annealing (under vacuum of 10-1 mm Hg carried out at a temperature of 350 C for a time period of 10 hours, the granules were compressed. The strips 10 by 100 mm in cross-section were subjected to pressing conducted at the rate of 15 cm per min., and at a temperature of 280 to 3100C.

The thus presses strips were cut to lengths of 500 mm each. Thereafter the strips were decreased, dressed by an emery belt and then coated with a layer of aluminum, 0.8 mm thick, also degreased and brush-cleaned, while being subjected to rolling on the duo 470 mill in accordance with the following rolling schedule: 1 0.85,44.03.22.65 mm The rolled strips were then cut to a size of 2.65 by 95 by 1000 mm. Degreased and brushcleaned, the.aluminum strips were applied by means of the clad rolling process onto steel strips 6.6 by 97 by 1200 mm in size, which were also degreased and dressed by an emery belt. The packets were rolled on the duo 470 mill according to the following rolling scheme: 2.65+6.6=9.25 5+0.10 mm (reduction ratio was 45.6 per cent) The rolled strips 5 mm thick were annealed at a temperature of 3550C for a time period of 2.5 hours, then sized to 3.1+0.10 mm and annealed at a temperature of 4000C for a time period of 3 hours.

Thus produced bimetallic strips were used for manufacturing sliding bearings Example 6 Bimetal produced as described in Examples 4 and 5, as well as a steel-base bimetal clad with the lead-free bearing alloy containing 5 per cent by weight of anti ony, 1 per cent by weight of copper, 0.15 per cent by weight of titanium, 0.06 per cent by weight of tellurium, aluminum being the balance, were subjected to mechanical testing. The results of this testing are given below in Table 3.

Table 3 Characteristics of Bimetallic Strips from the Alloys of the Invention and From the Known Alloys Type of Characteristics bimetal Adhesion Hardness Hardness strength of alloy of steel of layers Tensile Yield in bimetal in bimetal in bimetal strength, point, kgf kgf kgf Ttp ass - 'Joa Elongation, HB HV HB HV ~ mm2 ~. mm2 mm2 Bimetal according toEx.4 35 36 210 213 7.6 50.8 48.6 5 Bimetal according toEx.5 40.5 43 212 215 7.5 52.2 52 4.5 Bimetal with the known lead-free alloy 38 - 205 - 7.6 51.4 50 5 As is seen from the above Table 3, the characteristics of bimetallic strips composed of steel and of the alloy according to the invention, the latter containing lead in various amounts, practically have no distinction from the characteristics of the bimetallic strips composed of steel and of the lead-free alloy. This confirms the possibility and expediency of using bimetals with the bearing alloy of the invention for manufacturing sliding bearings.

Example 7 The bimetal produced as described in Example 4 was used for manufacturing crankshaft halfbearings employed in engines, with leads of 320 kg per sq. cm. acting on bearings at rated performance.

The manufactured crankshaft bearings were installed in engines to be tested for operating reliability (running-in test, conformability, resistance to wear and fatigue break-down). The testing was run in cycles, each operating cycle lasting for a period of 8 hours and carried on under normal operating conditions which took up 80 per cent of its total time.

The engine was examined after 8, 24, 96 and 800 hours. It had been found that the working-in and unformability of the material for bearings enabled their operation in conjunction with a steel shaft without their seizing. the material of the bearing brasses provides for high wear resistance of the bearing liner-shaft pair. After 800 hours of operation, the total value of wear was not more than 0.01 to 0.02 mm; there were no signs of fatigue cracking. Moreover, the bearings were installed in the engines which had gone through long operating testing. There were no cases of seizing or fatigue fractures.

Example 8 In order to assess the wear and seizure-resistant properties of the alloys, the bearing brasses manufactured from the bimetals containing the alloy of the invention, produced as described in Ex. 1, as well as those containing the known alloys, were put to test.

The bearings were tested on a special test rig ensuring contact loading carried out intermittently in oil at elevated temperatures.

The test results are given below in Table 4.

Fatigue Test Results Table 4 Relative Composition of resistance alloys, wt.% to fatigue No. (aluminum, the balance) fracture The prior-art alloys 1 antimony,4 magnesium, 0.7; 1 2 tin, 20; copper, 1; 1.29 3 tin, 6; copper, 1; nickel, 1; titanium, 0.1; 1.38 4 antimony, 5; copper, 1; titanium, 0.15; teliurium, 0.06; with a lead-base coating containing 10% Sn and 1% Cu 1 A3 The Alloy of the Invention antimony, 5; copper, 0.9; titanium, 0.08; tellurium, 0.2; lead, 6; without additional 5 coating layer 1.43 As is seen from the Table 3, the bearings manufactured from the alloy (No. 5) of the invention are superior, as to wear resistance, to the rest of the bearing brasses and similar to the bearings substantially of the same composition, though free from lead.

In addition, short-term testing was carried out to compare the bearings from the alloys composed of the bearing alloys indicated in the Table 4 (Nos. 2, 4, 5). The testing was performed on diesel engine, with leads acting on the bearings amounting to 550-600 kg per sq. cm. The alloy (No. 5) ofthe invention had been found to have good working-in property, high resistance to fatigue fracturing and seizinq.

It has therefore been found in the course of extensive testing that the alloys according to the invention are superior, with regard to their durability, to the known bearing aluminum alloys presently used in industry, and equal to the alloys free from lead, possessing good seizure-resistant properties and a minimum friction coefficient (0.011) for high-strength bearing aluminum alloys.

From the test results it was concluded that the bearina aluminum alloy accordina to the invention was a suitable material for manufacturing bimetallic vearing brasses to be employed in heavy-duty engines, which material can also be used to substitute aluminum-tin alloys, thereby eliminating the necessity of applying an additional running-in coating, i.e. the third seizure-resistant layer, to the bearing surface, this being highly expensive operation.

Claims (5)

Claims

1. A bearing aluminum alloy comprising antimony, titanium, copper, lead, as well as tellurium or phosphorus or selene, said components being contained therein in the following amounts: Per cent by weight antimony 2 to 8 copper 0.3 to 1.5 titanium 0.02 to 0.15 tellurium or 1 phosphorus > 0.01 to 0.5 orselene lead 1 to 15 aluminum, the balance

2. A bearing aluminum alloy as claimed in claim 1, comprising antimony, copper, titanium, tellurium, lead, aluminum, said components being contained therein in the following amounts: Per cent by weight antimony 6 copper 0.9 titanium 0.08 tellurium 0.2 lead 6 aluminum, the balance.

3. A bearing aluminum alloy as claimed in claim 1 , comprising antimony, copper, titanium, tellurium, lead, aluminum, said components being contained therein in the following amounts: Per cent by weight antimony 3 copper 0.9 titanium 0.08 tellurium 0.15 lead 15 aluminum, the balance.

4. A bearing aluminum alloy as claimed in claim 1, comprising antimony, copper, titanium, tellurium, lead, aluminum, said components being contained therein in the following amounts: Per cent by weight antimony 5 copper 1 titanium 0.1 tellurium 0.1 lead 1 aluminum, the balance

5. An antifriction aluminum alloy substantially as herein described in any of the foregoing Examples.