EP1012353B1 - Alloy and method for producing objects therefrom - Google Patents

Abstract

Aluminum alloy containing a fraction of uniformly distributed particles, preferably silicon particles, of less than 20% by weight, so as to increase the wear resistance, prior to processing or machining under hot conditions, and process for producing wear-resistant objects from such an aluminum alloy.

Description

The invention relates to the use of an alloy with a proportion of Particles and a method of making articles from such an alloy, especially with a Wear resistance increasing addition of particles in one Aluminum alloy.

Aluminum alloys with a wear resistance increasing proportion of particles, in particular in the form of Silicon primary crystals are, for example, as Hypereutectic aluminum-silicon casting alloys known. From this, z. B. whole engine blocks or just Pour cylinder liners. When cooling, they separate Silicon primary crystals. The wear resistance z. B. the tread is excreted by the harder Silicon primary crystals achieved by special Treatment processes, especially etching processes superficial be exposed. A disadvantage of these is hypereutectic Aluminum-silicon casting alloys that the Silicon primary crystals in the form of sharp-edged, in part needle-like crystals and in different, from the Solidification rate depending on size and distribution are available, so that the mechanical processing special tools required to get through the hard silicon primary crystals keep conditional wear within limits.

The production of entire cylinder blocks from one hypereutectic aluminum-silicon alloy is expensive because this material involves an increased effort in casting and how mentioned above because of the retired Silicon primary crystals require a lot of processing requires.

To overcome these machining difficulties on large castings avoid, it is also already known, for example in one from a conventional, easily pourable Aluminum alloy manufactured cylinder block Cylinder liners made of a hypereutectic To use aluminum-silicon alloy, especially to umgießen.

While the wear-resistant, hypereutectic Aluminum-silicon casting alloys for cylinder blocks predominantly a silicon content of about 17% by weight can have the separately manufactured Cylinder liners silicon contents from 20 to 30 wt .-% have, in which case, for example, first a Ingot by spray compacting a hypereutectic Aluminum-silicon alloy or powder metallurgy a powder of such a hypereutectic Aluminum-silicon alloy manufactured and then the Liner is made from it by hot extrusion. These hypereutectic aluminum-silicon alloys and the Manufacturing processes for cylinder liners are in the German patent 43 28 619 and the German Laid-open specification 44 38 550.

Are only the cylinder liners from one wear-resistant, hypereutectic Aluminum-silicon alloy is manufactured both at Spray compacting a hypereutectic Aluminum-silicon alloy as well powder metallurgical process disadvantageous that complete made of a hypereutectic aluminum-silicon alloy existing ingots are difficult to deform and due to the precipitated silicon primary crystals and intermetallic phases high tool wear cause.

Both in the well-known, hypereutectic Aluminum-silicon casting alloys for casting Engine blocks with a silicon content of about 17% by weight have, as well as by spray compacting or cylinder liners manufactured using powder metallurgy a silicon content of up to 30 wt .-% crystallize the wear resistance effecting silicon primary crystals and intermetallic phases from the hypereutectic Melt off on cooling and accordingly have the for Silicon primary crystals typical, sharp-edged and needle-like shapes. To the wear of in the Cylinders of such engine blocks sliding pistons these primary crystals and intermetallic phases too according to German patent application 44 38 550 suggested the silicon primary crystals and particles from intermetallic phase by a mechanical Expose fine machining while doing the exposed Plateau surfaces of the primary crystals or particles on their Edges spherical or rounded in the alloy base material to let pass

The invention is based on the problem, a aluminum alloy to use the the avoids disadvantages mentioned, d. H. the easy, in particular can be processed and machined by hot forming and / or machining and is still the one required, for example Wear resistance and / or uniform structure and has mechanical strength.

To solve this problem, an aluminum alloy is used, the in a matrix of an easily editable and editable Aluminum alloy an addition of evenly distributed Particles, preferably silicon particles or of particles a hypereutectic aluminum-silicon alloy, whereby the individual particles have high silicon contents, preferably have up to 50 wt .-%, the silicon content in the good machinable and editable aluminum alloy, however maximum Is 12% by weight.

The invention is based on the consideration that in itself an aluminum melt easily soluble silicon on it must be prevented from going into solution in the matrix because when silicon primary crystals are separated from the solution the relatively large increase the wear Crystals with angular and needle-like shapes are created. So it becomes a well machinable and editable aluminum alloy so with evenly distributed silicon particles and / or with particles of a hypereutectic Aluminum-silicon alloy mixed that undissolved silicon particles and / or silicon primary crystals in the Particles of the hypereutectic aluminum-silicon alloy can remain in the aluminum alloy originally introduced in the easily editable and editable Aluminum alloy matrix not in solution Silicon particles or Silicon primary crystals are not the same as for Crystallizing, unfavorable forms but keep their original shape or become even rounded off if necessary by superficial dissolving, so that they lose their distinctive tips and corners.

It is crucial that the matrix from the well machinable and editable aluminum alloy like this is composed that none of this aluminum alloy Silicon primary crystals can crystallize and that finely divided silicon particles or Particles containing silicon primary crystals hypereutectic aluminum-silicon alloy without in the Matrix alloy have gone into solution.

The matrix alloy does not need as a whole to be hypereutectic to contain silicon particles, such as this with the known, wear-resistant Aluminum-silicon alloys is required but can preferably an addition of a maximum of 12% by weight of silicon in Form of silicon particles and / or silicon primary crystals in the particles of the hypereutectic Aluminum-silicon alloy included, provided that too contains an processed aluminum alloy a minimum proportion of silicon particles and / or Particles containing silicon primary crystals hypereutectic aluminum-silicon alloy, at least 5% by weight of silicon particles and / or Silicon primary crystals in the particles of the hypereutectic Aluminum-silicon alloy based on the total amount, because it was found that such a proportion did not derive from the Matrix alloy deposited silicon particles, or Silicon primary crystals suffice to get the desired one Achieve wear resistance.

The proportion of silicon particles in the matrix alloy is preferably 5 to 20%.

The matrix alloy can preferably be used as a hot-formable Wrought aluminum alloy a composition of the type Have AlMgSiCu and with an addition of even distributed silicon particles and / or particles of one hypereutectic aluminum-silicon alloy of less than 20 wt .-% based on the total amount before one Be thermoformed. The wrought aluminum alloys are good thermoformable alloys, their Not even hot formability by adding Silicon particles or particles of a hypereutectic Aluminum-silicon alloy is lost. This addition of evenly distributed silicon particles or of particles a hypereutectic aluminum-silicon alloy can be relatively high, especially if part of it Silicon particles or the particles of a hypereutectic Aluminum-silicon alloy during hot forming and / or heat treatment goes into solution. Important is meanwhile, that a residual proportion of evenly distributed and silicon particles not dissolved and / or of Silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy, of at least about 5 wt .-% based on the total amount is retained, these silicon particles or the Silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy without pronounced tips and corners are present. Maybe you can dissolving due to heat treatment or hot forming and partial dissolution of the silicon particles or the Particles of a hypereutectic aluminum-silicon alloy occur while the undissolved silicon particles or silicon primary crystals of the particles hypereutectic aluminum-silicon alloy with a Share of preferably at least 5 wt .-% and have no pronounced tips and corners.

The grain size of the silicon particles in the aluminum alloy is preferably at most 80 microns, the grain size of Particles of a hypereutectic aluminum-silicon alloy is preferably at most 250 microns while the Silicon primary crystals in the particles of the hypereutectic Aluminum-silicon alloy is at most 20 µm.

The object can after the cutting deformation or the Thermoforming be subjected to a heat treatment. It it is conceivable that this heat treatment can lead to the fact that the silicon particles embedded in the aluminum alloy and / or the particles and those contained therein Silicon primary crystals of the hypereutectic Aluminum-silicon alloy superficially with the Aluminum alloy react, creating distinctive tips and Corners are removed. This effect can already be seen in Spray compacting, with the temperature of one Aluminum alloy melt begins to be achievable. As well hot forming alone can be the desired one Change in the surface of the silicon particles and / or Silicon primary crystals in the particles of one cause hypereutectic aluminum-silicon alloy.

Powder metallurgy allows aluminum alloys any composition from a mixture of powders various alloy components to manufacture by a subsequent hot forming can be homogenized. Become this mixture evenly distributed according to the invention Silicon particles and / or particles of a hypereutectic Aluminum-silicon alloy based on a maximum of 12 wt .-% added to the total amount, so the Silicon particles or the particles of a hypereutectic Aluminum-silicon alloy in the subsequent Hot working, as described above, evenly distributed and possibly superficially dissolved or partially dissolved so that in the thermoformed object finally at least 5% by weight based on the Total amount evenly distributed, not dissolved Silicon particles and / or silicon primary crystals in the Particles of a hypereutectic aluminum-silicon alloy are present that are not the tips and corners of one hypereutectic alloy melt excreted Have silicon primary crystals, but in the same way bring about the wear resistance of the aluminum alloy, which in this case is considered to be thermoformable Wrought aluminum alloy with the composition AlMgSiCu is trained.

The hot forming of the ingot or compact can, for. B. by Hot rolling or by hot extrusion into bars, tubes and profiles or by hot extrusion, one If necessary, subsequent heat treatment serves to desired properties of the aluminum alloy adjust.

It is particularly advantageous that the in this way manufactured, heat-formable aluminum alloy is suitable from hot rolled plates or to produce hot extruded rods and slugs through hot extrusion finished products such as cylinder liners to manufacture in the required final dimensions.

In particular, a compact, i.e. H. a slug in shape a round or a hollow round of powder Manufacture hydrostatic pressing that warmed up and afterwards is deformed by extrusion. Possibly. can one Connect heat treatment.

It is also advantageous to mix a powder Alloy components and silicon particles and / or Particles of a hypereutectic aluminum-silicon alloy or a powder of the alloy and of silicon particles and / or particles of a hypereutectic Aluminum-silicon alloy in a heated extrusion mold to give the powder mixture with the mold closed compress hydrostatically, then open the mold and a hot deformation by extrusion, in particular by Extruding a cylinder.

Another way to make bars or cylinders consists of a powder with alloy components or the alloy and silicon particles and / or particles one hypereutectic aluminum-silicon alloy into a shape too fill and at such pressure and such Sinter temperature that the required strength is reached and the minimum amount of silicon particles or Silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy is present. In this case too, there may be another Connect heat treatment.

All stages of the process carried out in the heat are to be coordinated so that the Processing and processing heat and / or the Heat treatment achieves the desired properties and definitely a residue of undissolved silicon particles or of silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy, with a share of 5 wt .-% based on the Total amount that is available.

It is possible to use the silicon particles or the particles of a hypereutectic aluminum-silicon alloy preferably with a hypoeutectic portion of the matrix alloy add if it is ensured that a silicon portion in the form of silicon particles and / or Silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy, in the amount of 5 wt .-% based on the total amount preserved.

It is particularly advantageous that any alloy compositions are possible, to which the Silicon particles or the particles of a hypereutectic Aluminum-silicon alloy in the manner according to the invention be added without going completely into solution, so that these added silicon particles or the particles of a hypereutectic aluminum-silicon alloy or the therein existing silicon primary crystals undissolved in the Matrix alloy are preserved and therefore none Silicon primary crystals excreted from the matrix alloy become. This is in contrast to the known ones hypereutectic alloys, in which when cooling from the Melt silicon primary crystals that are excreted have an angular or angular and needle-like shape. In addition, with the hypereutectic alloys, one Heat treatment for grain enlargement with needle formation leads, which is unfavorable for wear.

In contrast, those of the matrix alloy are in accordance with the invention added silicon particles or particles of a hypereutectic aluminum-silicon alloy at most superficially dissolved and retained during one Heat treatment largely its original shape even then, if the silicon content in the form of silicon particles and / or Silicon primary crystals in the particles of one hypereutectic aluminum-silicon alloy no more than 12 wt .-% based on the total amount, corresponding to the Eutectic aluminum-silicon.

Wear-resistant cylinder liners can be easily cast Aluminum alloy used for casting cylinder blocks is particularly suitable and easy to edit, pour in, post-processing the cast Cylinder liners may no longer be required if these made from hot-rolled or hot-extruded primary material and slugs made from it by hot extrusion are manufactured. A sufficient combination of materials between the Cast aluminum alloy for the cylinder block and the cast cylinder liners according to the invention can be with the in the German patent 43 28 619 achieve described methods without significant Disadvantages when using powder metallurgy produced ingots or compacts, which subsequently were thermoformed. The possibly required surface treatment of the cylinder liners etching does not change the dimensional accuracy, but rather only serves to round the silicon particles or Silicon primary crystals from the added particles of one to expose hypereutectic aluminum-silicon alloy.

Claims (9)

1. The use of an aluminium alloy consisting of a readily hot-deformable wrought aluminium alloy matrix of the type Al Mg Si Cu with a composition out of which no silicon primary crystals can crystallise, with a wear-resistance-increasing addition of uniformly distributed silicon particles and/or particles of a hypereutectic aluminium/silicon alloy for the production of cylinder liners and hydraulic or pneumatic working cylinders which are close to their final dimensions by hot flow pressing, the individual particles having high silicon contents, preferably of up to 50% by weight, and the addition is at most 12% by weight silicon in the form of silicon particles and/or of silicon primary crystals in the particles of the hypereutectic aluminium/silicon alloy, whereas the aluminium alloy which is processed into the object, after hot deformation or a subsequent heat treatment, has a minimum content of silicon particles and/or silicon primary crystals which have not dissolved and have not separated out from the matrix alloy in the particles of the hypereutectic aluminium/silicon alloy relative to the total quantity of at least 5% by weight.
2. The use of the aluminium alloy according to Claim 1, having a grain size of the silicon particles of at most 80 µm, the grain size of the particles of a hypereutectic aluminium/silicon alloy of preferably at most 250 µm and of the silicon primary crystals in the particles of the hypereutectic aluminium/silicon alloy of at most 20 µm.
3. The use of the aluminium alloy according to Claim 1, in which a bar is produced by spray-compacting a melt of a hot-deformable aluminium alloy and silicon in the form of silicon particles and/or silicon primary crystals is added to the aluminium alloy in the spray jet in the particles of a hypereutectic aluminium/silicon alloy of at most 12% by weight relative to the total quantity.
4. The use of the hot-deformable aluminium alloy according to Claim 1 or 2, in which a bar is produced from a matrix alloy powder with an addition of uniformly distributed silicon particles and/or of silicon primary crystals in particles of a hypereutectic aluminium/silicon alloy of at most 12% by weight relative to the total quantity and this bar is then hot-deformed.
5. The use of the hot-deformable aluminium alloy according to Claim 1 or 2, in which a bar is produced from a mixture of powders of differing alloying constituents with an addition of silicon in the form of uniformly distributed silicon particles and/or silicon primary crystals in particles of a hypereutectic aluminium/silicon alloy of at most 12% by weight relative to the total quantity and this bar is then hot-deformed.
6. The use of the aluminium alloy according to one of Claims 1 to 5, in which slugs are produced from hot-rolled plates or hot-extruded rods and the cylinder liners or hydraulic and pneumatic working cylinders are manufactured therefrom in the required final dimensions by hot flow-pressing.
7. The use of the aluminium alloy according to Claim 4 or 5, in which a compact in the form of a solid round compact or a hollow round compact is produced from powder by hydrostatic pressing, is heated up and then is processed further by hot flow-pressing, optionally with a subsequent heat treatment.
8. The use of the aluminium alloy according to Claim 4 or 5, in which a powder consisting of an aluminium alloy or alloying constituents and silicon particles or particles of a hypereutectic aluminium/silicon alloy is placed in a heated hot flow-pressing mould, is hydrostatically pressed with the mould closed and then is hot flow-pressed once the mould has been opened.
9. The use of the aluminium alloy according to Claim 4 or 5, in which the powder consisting of an aluminium alloy or alloying constituents and silicon particles and/or particles of a hypereutectic aluminium/silicon alloy is placed in a mould, is sintered under pressure and at elevated temperature and then optionally is subjected to a heat treatment.