AU592808B2

AU592808B2 - Aluminium alloy

Info

Publication number: AU592808B2
Application number: AU59773/86A
Authority: AU
Inventors: Warren Stephen Groves
Original assignee: AUTOMOTIVE COMPONENTS Ltd
Current assignee: AUTOMOTIVE COMPONENTS Ltd
Priority date: 1985-07-05
Filing date: 1986-07-04
Publication date: 1990-01-25
Anticipated expiration: 2006-07-04
Also published as: AU5977386A

Description

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AUSTRALIA

Patents Act 592808 COMPLETE SPECITFICATION

(ORIGINAL)

Class Int. Clas Application Number: Lodged: Comiplete Specification Lodged: Accepted: Pubhished: 'Priority T his docutylbrt conltains the [,:e~ti011 49 and. is correct for Related Art: APPLICANT'S REF: C.A.P. of PH 1340 Namne(s) of Applicant(s): Address(es) of Applicant(s): REPCO LIMITED-- 630 St. Kilda Road

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Melbourne, Victoria 3-004 Actual inventor(s): Address for Service is: P HILl I1PS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 300 Complete Specification for the invention entitled: ALUMINIUM ALLOY The following statement is a full description of this invention, including the best method of performing it known to applicant(s)' P19/3/84 This invention relates to aluminium alloys and particularly such alloys as used in the manufacture of plain bearings. It will be convenient to hereinafter describe the invention with reference to plain bearings as used in automotive engines to support the crank shaft but it is to be understood that the invention has other applications.

Plain bearings as used with automotive engines are manufactured from bi-metal strip which comprises a steel backing to which is bonded a specially formulated bearing alloy. The alloy forms thE bearing surface which surrounds and engages the crank shaft and in the course of operation that surface is subjected to load pulses transmitted to it through an oil film which normally separates the bearing ffm the shaft. In abnormal or faulty conditions the bearing surface may come into direct metal -metal contact with the rotating shaft. It is theorfore necessary for bearing alloys to have: S strength to avoid fracture or distortion from S repeated application of load, seizure resistance to withstand occasional contact with the shaft, the ability to maintain the foregoing properties over long periods of service at sump oil temperatures of proximately 130°C, and the ability to be economically manufactured in the form of thin strips which are securely bonded to a steel backing.

The balance between seizure resistance and strength in aluminium based bearing alloys is a delicate and conflicting one since the former property is conferred by lead and/or tin additions which are insoluble in the solid aluminium and which act to reduce strength because they are present as relatively soft "islands" in the aluminium matrix. Many attempts have been made to produce an aluminium alloy which satisfactorily meets the competing demands of strength and seizure resistance, but the problem continues to persist.

It is an object of the present invention to provide an improved aluminiLum alloy which is particularly although not 39 exclusively suited for use in the manufacture of plain -2bearings for automotive engines. It is a further object of the invention Lo provide such alloy having good seizure resistance properties in addition to high strength.

According to the present invention, there is provided a body formed of an Al alloy having a principal soft phase constituent which is either Sn or Pb and which is present in the alloy in the range of 5 to 10% inclusive, said body having two oppositely facing sides and said principal constituent is disbursed throughout said body so that it is present iii a To larger quantity adjacent one said side than it is adjacent the o other said side, said laraer quantity being in the range 8 to 17% of the total compoF,ition of said alloy, and said smaller quantity being in the range 0 to 5% of the total composition of said alloy.

0 0 One known method of improving the high temperature strength of aluminium-tin alloys is to include a quantity of chromium. It has been found, somewhat suri-risingly, that zirconium can be used in place of at least some of the chromium which was previously considered necessary for 2'00 satisfactory high temperature strength. In addition, the zirconium content need not be as high as the amount of chromium which it replaced the zirconium content may be approximately half that of the chromium which it replaced.

Furthermore, manganese and vanadium have been found to be similar to zirconium in their ability to impart high temperature strength to an aluminium-tin alloy, and consequently either or both can be used as an alternative to zirconium or in addition to zirconium.

According to another aspect of the invention, it has been found that seizure resistance is improved if the low melting phase of the alloy exists in the form of relatively small discrete islands scattered throughout the aluminium matrix. Stated briefly, the invention resides in controlling the size and dispersion of the low melting phase components and in appropriate selection of the composition of that phase.

In one embodiment of the invention, the body is formed of an Al-Sn alloy in which said Sn is presert in the range of to wherein the content of said Sn varies between two 39.. opposite sides of said body so as to be present in the range t- of 0 to 3% adjacent one said side and 10 to 17% adjacent the other said side. In an alternative embodiment, the body is formed of an f S 1 I ii II I I

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-3ar i il_ I- -il. 1- ~--nxar~ Al-Pb alloy in which Pb is present in the range of 5 to 8%, wherein the content of Pb varies between two opposite sides of said body so as to be present in the range of 0 to 2% adjacent one said side and 8 to 13% adjacent the other side.

Preferably, said variation occurs in substantially regular progression between said sides of the body.

The invention kalso provides an Al-Sn alloy including to 20%, preferably 5 to 10%, Sn, and 0.1 to 0.5% of at least one of Cr, Zr, Mn and V, and optionally including 0.1 to Pb. Preferably there is a progressive distribution of Sn throughout said alloy ranging from 0 to 3% adjacent one side of a body of said alloy to 10 to 17% adjacent an opposite side thereof.

The invention till- furtho]- provides an Al-Pb alloy S including 5 to 15%, preferably 5 to 10%, Pb, and 0.1 to of at least one of Cr, Zr, Mn and V, and optionally including 0.5 to 1.5% Sn. Preferably there is a progressive distribution of Pb throughout said alloy ranging from 0 to 2% adjacent one side of a body of said alloy to 8 to 17%, preferably 8 to 13% adjacent an opposite side thereof.

In an alloy according to the invention, both Cr and S at least one of Zr, Mn and V may be present with the Cr content being at least 0.1%.

An alloy according to the invention may include 1.25 S to 3.5% Si, 0.2 to 1.5% Cu, 0.1 to 0.6% Sb, and 0.3 to 1.5% in tutal of any one or more of the normal aluminium bearing alloy addition elements Fe, Mn, Mg and Ni.

In an alley according to the invention, the low melting phase may be distributed throughout the Al matrix in the form of discrete islands or particles of roughly spherical shape which have a diameter in the range of 1 to 20 microns.

The islands or particles preferably have a diameter of less than 10 microns, most preferably of less than 4 microns.

An aluminium alloy acccording to the invention includes lead, tin and silicon in appropriate quantities as hereinafter discussed and also includes one or more of the following elements as constituents of the low melting phase in, Tl, Ti, Bi, Cd and Ga.

8 U\ The principal constituent of the low melting phase 4-4- I _I i

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may be either lead or tin and it is preferred thal it be present in a quantity not significantly less than For example, if tin is the principal constituent of the low melting phase it may be present in the range of 5-20%, preferably 5-10%, inclusive. If on the other hand lead is the principal constituent, it may be present in the range of 5-15%, preferably 5-10%, inclusive, but it is preferred that in such case the lead is combined with one or more of the additional elements listed above and that the resulting combination is present in the range of 5-15%, preferably 5-10%, inclusive.

It is further preferred that the alloy includes no more than 3% of whichever of the two constituents lead and tin is :.ot the principal constituent of the low melting phase. If tin is present in an amount less than it is preferred that the chromium content is 0.1% or greater, whereas less than 0.1% chromium may be used if the tin content is 3% or more.

It is usually sufficient to provide 0.5% or less zirconium.

All percentages as quoted throughout this specification are percentages by weight.

The following is an example aluminium-lead alloy according to the invention which has been found to possess good seizure and strength qualities.

Example 1 5-15%, such as 5-10%, Pb plus one or more of the elements In, Ti, Ti, Bi, Cd and Ga up to 3% Sn 1-5% Si 0-1% Cu 0-0.6% Sb up to 0.3% Zr up to 0.5% Cr 0-0.5% V 0-0.5 Mn Balance Al The above alloy might also benefit from the addition of some iron up to Furthermore it may be beneficial to completely exclude copper as copper could 39 possibly inhibit the operation of zirconium and or chromium in r improving hot strength characteristics.

An example aluminium tin alloy according to the invention is set out below and the foregoing comments concerning iron and copper may also apply to that example.

Example 2 5-20%, such as 5-10% Sn up to 3% Pb plus one or more of the elements In, Tl, Ti, Bl, Cd and Ga 0.1-5% Si 0-1% Cu 0-0.6% Sb up to 0.5% Zr 0-0.5% V 0-0.5% Mn S up to 0.1% Cr Balance Al t I It will be understood that the above example alloys will include such impurities as might be expected in commercially available constituent metals.

The low melting phase of each of the above example alloys is formed primarily by constituents and Constituents to provide a satisfactory environment for that phase and assist in strengthening the aluminium matrix.

It is thought that the low melting phase is distributed throughout the alloy matrix in the form of discrete islands or particles which are roughly spherical in shape. Those spherical particles may have a diameter in the range of 10 to microns but a diameter less than 10 microns is preferred and best results are achieved if the diameter is less than 4 microns. It has been observed that the seizure resistance of such an alloy can be improved by reducing the size of the spherical particles, or a particular level of seizure resistance can be maintained by reducing both the size of the spherical particles and the concentration of the low melting phase.

The strength of the alloy is also improved if the low melting phase particles are relatively small in size and further improvement can be achieved by reducing the 39 concentration of that phase. It is therefore possible to -6 adjust those variables particle size and concentration so as to adjust both the strength and seizure resistance characteristics of the alloy.

A satisfactory composition of the low melting phase may be achieved by selecting from the elements Pb, Sn, In, Tl, Ti, Cd, Bi and Ga such that optimum seizure resistance is J achieved without causing a significant reduction in alloy strength. A preferred combination of those elements will optimise melting behaviour.

An alloy according to the invention is preferably cast in billet form and the particle size of the low melting phase can be controlled to some extent at least by appropriate regulation of the casting conditions, For example, relatively I rapid chilling will generally contribute to the existence of relatively small particles.

The alloy may be also cast in such a way as to achieve an advantageous form of lead gradient through its thickness and that is particularly applicable in the case of an alloy having a relatively high lead content such as that according to example i. This feature relies on the tendency of lead to fall towards the bottom of the alloy body while the alloy is in a molten state. It is then possible with appropriate control of casting, rolling and subsequent fabrication to achieve a buaring having a relatively low lead content adjacent the interface between the bearing alloy and the steel backing, and a relatively high lead content adjacent the bearing surface of the bearing. This result can be achieved by ensuring that the rate of solidification of the casting is maintained between i and 1.5 seconds per millimeter of thickness.

The consequence of the foregoing is that a relatively high seizure resistance characteristic can be achieved without detriment to alloy strength.

Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

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Claims

1. A body formed of an Al alloy having a principal soft phase constituent which is either Sn or Pb and which is present in the alloy in the range of 5 to 10% inclusive, said body having two oppositely facing sides and said principal constituent is disbursed throughout said body so that it is present in a larger quantity adjacent one said side than it is adjacent the other said side, said larger quantity being in the range 8 to 17% of the total composition of said alloy, and said smaller quantity being in the range 0 to 5% of the total So composition of said alloy. S 2. A body according to claim 1, wherein alloying elements are present in the range 0.1 to 0.5% inclusive, and said alloying elements include one or more elements of the group o oCr, Zr, Mn and V. o" 3. A body according to claim 1 or 2 including 1.25 to Si, 0.1 to 1.5% Cu, 0.1 to 0.6 Sb, and from 0.3 to inclusive of any one or more of the elements Fe, Mn, Mg and Ni. S4. A body according to any preceding claim, wherein said principal constituent is Sn, said larger quantity is in the range 10 to 17% inclusive, and said smaller quantity is in the S range 0 to 3% inclusive. A body according to any preceding claim, including Pb in the range 0.1 to 0.5% inclusive.

6. A body according to claim 1, 2, or 3, wherein said principal constituent is Pb, said larger quantity is in the range 10 to 17% inclusive, and said smaller quantity is in the range 0 to 2% inclusive.

7. A body according to any one of claims 1 to 3 and 6, wherein Sn is present in the range 0.1 to 1.5% inclusive.

8. A body according to any preceding claim, wherein there is a substantially regular increase in the content of said principal constituent from said other side to said one side.

9. A body according to any preceding claim, wherein the soft phase constituent is distributed throughout the aluminium based alloy matrix in the form of discrete islands or particles of roughly spherical shape which have a diameter in the range of 1 to 20 microns. 39 10. A body according to claim 9, wherein said diameter is tr 'i t, g ~r -J 1 I 1C i I I i IUu i -I~IC LC~L~~il~. I less than 10 microns.

11. A body according to claim 9 or 10, wherein said diameter is less than 4 microns.

12. A bearing including a stee.l backing and a body of bearing material roll bonded to a surface of said backing, said body being in accordance with any one of claims 1 to 11. *o DATED: llth September, 1989 010 AUTOMOTIVE COMPONENTS LIMITED By its Patent Attorneys: o PHILLIPS, ORMONDE FITZPATRICK Sto