WO2013174547A1 - Method for producing a light-weight metal component; light-weight metal component, and internal combustion engine comprising a cylinder liner consisting of a light-weight metal component - Google Patents

Description

 Method for producing a light metal part; Alloy Part

 and internal combustion engine with

 Cylinder liner made of light metal part

Description:

The invention relates to a method for producing a light metal part, in which a bolt made of a hypereutectic high-performance aluminum alloy with a Si content of 17-35 wt .-% is formed by extrusion to a hollow end profile.

The invention further relates to a light metal part produced by this method and to an internal combustion engine having at least one cylinder liner, which is formed by such a light metal part.

From the prior art, it is particularly known to produce tubular hollow sections such as cylinder liners for internal combustion engines in a two-layer construction of different light metals, the manufacturing process comprises several steps. For example, the inner layer is first made by means of stud formation by spray compacting or casting, and then the post thus produced is reworked. This is followed by an extrusion to produce a tube shape and a rotary swaging to adjust the final geometry. This is followed by the cut to what

Corundum blasting and ultimately coating with an outer light metal layer follows, which can be done for example by flame spraying.

However, this type of production of a light metal part is expensive, especially since usually each cut cylinder liner is coated individually with a light metal. Furthermore, thin-walled hollow sections of light metal can be realized only with restrictions by extrusion, in particular when using high-strength DISPAL alloys. Limits are given here, for example, by the press ratio, ie the ratio of the diameter of the inserted block to the cross section of the profile extruded therefrom can only be selected to a limited extent. The maximum degree of deformation is also limited, and it may be necessary very high forming forces. Furthermore, a pressing on the final geometry is not possible, especially in cylinder liners, since the temperature control for material and tools is in the critical range. The final geometry must therefore be set by further process steps such as rotary swaging. The object of the invention is therefore to provide a method for producing a light metal part, in particular a cylinder liner, by means of extrusion, with the higher degrees of deformation and smaller profile cross sections are possible without this leading to unfavorable process parameters at the limit of feasibility.

According to the invention, this object is achieved by a method according to independent claim 1. Advantageous developments of the method will become apparent from the dependent claims 2-1 first The object is further achieved by a light metal part according to one of claims 12 and 13 and an internal combustion engine with such a light metal part according to claim 14.

The method according to the invention for producing a light metal part comprises at least the following steps:

 Preparation of a high-performance supereutectic aluminum alloy stud having a Si content of 17-35% by weight;

 Forming of the bolt in a first stage by means of extrusion with a first degree of deformation to an intermediate hollow profile;

 Forming the intermediate hollow section in a second stage by means of extrusion with a second degree of deformation to an end profile, the Gesamtumformgrad over both stages in the order of 1:36 to 1:90, and by the extrusion geometric dimensions, tolerances and / or material properties of the light metal part be set at the end profile.

As a result of the at least two-stage forming of a bolt by means of extrusion, considerably higher overall degrees of deformation can be achieved compared to single-stage extrusion processes, which enables smaller profile cross sections and thus also smaller wall thicknesses in the final profile. This is particularly advantageous for the hyper-eutectic high-performance aluminum alloys used having a Si content of 17-35 wt .-%, as these

are difficult to press and difficult to form. With the method according to the invention, therefore, the favorable material properties of the hypereutectic high-performance aluminum alloys can be utilized, without thereby being limited to the profile cross-sections achievable.

Furthermore, the process parameters present in the individual extrusion stages are favorable, so that they do not reform at the feasibility limit. As a result, the geometric and mechanical properties of the final profile are homogeneous, and the achievable surface finishes are higher than in conventional methods. This is advantageous since further steps required for setting a final geometry, such as the rounding th this can be omitted, because desired geometrical dimensions, tolerances and / or material properties can already be adjusted by the last stage of extrusion. However, in order to be able to realize such a final deformation for hypereutectic high-performance aluminum alloys with an Si content of 17-35% by weight (DISPAL), the first transformation to an intermediate hollow profile is required.

In this case, preferably two forming stages are used, but between the first and second stages, further forming stages can be carried out by means of extrusion. It can thus be extruded, for example, in three or more stages before the geometric dimensions, tolerances and / or material properties of the light metal part are set in the final stage on the final profile. In a two-stage process, for example, the first degree of deformation is of the order of 1: 3 to 1: 5, while the second degree of deformation is of the order of 1:12 to 1:30. This results in the Gesamtumformgrad invention in the order of 1:36 to 1:90. The resulting inner diameter of the end profile can then be of the order of 50 mm and 105 mm, while the outer diameter of the end profile can be between 60 mm and 195 mm. The corresponding wall thicknesses then result in 3mm to 90mm. In one embodiment of the invention, the bolt is manufactured by spray compacting or a casting process. Further, it is possible that before forming by extrusion in the first stage, a shell made of a second light metal on the bolt is made, and the bolt is formed together with the shell in at least two extrusion stages to the final profile. The resulting end profile then has an inner layer of a first light metal, which is the hypereutectic high performance aluminum alloy, and an outer layer is of a different light metal.

Compared to manufacturing processes in which an outer layer of a second light metal is applied to this hollow profile by extrusion to form a hollow profile after forming a bolt, this approach has the advantage that a particularly good metallurgical connection of the two light metals can be ensured to each other. In addition, the reshaping of the already sheathed bolt makes it possible in a simple manner for the outer layer to be located along the entire length of the hollow profile when it is cut to the desired sections. The second layer of light metal would otherwise have to be applied to several already cut to length pieces, which is associated with greater effort. The casing can be produced for example by casting the bolt with the second light metal, which is a simple production with good metallurgical connection. Alternatively, however, the sheath can also be made by thermally overmolding the bolt with the second light metal or by spray compacting the second light metal on the bolt. Such alternatives can be particularly preferred when the material of the casing casting technology is problematic.

In one embodiment of the invention, the second light metal is an Al-Mg casting alloy, which is in particular an Al casting alloy of the AISM 2 or AISi9Cu3 type.

The invention furthermore encompasses a light metal part produced by the method according to the invention, which thus has the stated advantages in the end profile, which can be used for various applications of the light metal part. In particular, such a light metal part can then be formed by further process steps as a cylinder liner for a reciprocating piston of an internal combustion engine. Thus, an internal combustion engine with at least one piston with a cylinder liner of the invention is also included, wherein the cylinder liner is formed by such a light metal part.

Further advantages, features and expedient developments of the invention will become apparent from the dependent claims and the following description of preferred embodiments with reference to the drawings.

The figures show: a schematic representation of a first extrusion stage for producing a light metal part; and a schematic representation of a second extrusion stage for producing the light metal part.

In Fig. 1, the first stage of a forming process by extrusion in an extrusion press 40 is shown schematically. In addition, at least with a second extrusion stage in an extruder 40 ', which is shown schematically in Fig. 2, can be made of a bolt 10, a light metal part in the form of an end profile with the desired properties. The extrusion process can be performed as direct or indirect extrusion, but indirect extrusion has proven to be more advantageous for an organized profile cross-section. A bolt 10 is thus introduced into a receptacle 42 within the extrusion press 40 and formed into an intermediate hollow profile 20 by pressing a die 42 against the bolt 10 through the receptacle 42. The intermediate profile 20 pressed out of the bolt 10 is here indicated by dashed lines. In this case, the bolt 10 is further penetrated by a mandrel to produce a hollow profile.

The pressure in this first forming step is 10-30% of the original geometry, or degrees of deformation of the order of 1: 3 to 1: 5 are achieved. For example, the bolt 10 may have an exit diameter of 325mm, which is reduced to 180mm by extrusion in the first stage. The inner diameter of the resulting intermediate hollow profile 20 produced by the mandrel 43 can then already be on the order of 50 mm to 105 mm. However, it is also possible to set smaller internal diameters, which are then enlarged again by a mandrel in a second pressing stage. Furthermore, in this first stage, the die 41 preferably does not yet produce the final geometry of the light metal part to be produced, but, for example, first of all a simple round outer cross section.

The starting bolt 10 itself can be made, for example, by spray compacting, and consists of a hypereutectic high-performance aluminum alloy having an Si content of 17-35% by weight. For example, AISi25Cu4Mg1 can be selected (DISPAL). However, before the first extrusion stage is applied to the bolt 10, it may be provided with a sheath of a second light metal, which may be done in various ways.

If the jacket is produced by a casting process, the bolt 10 is inserted into a mold, for example, so that a circular edge gap is formed around the bolt 10. The wrapping material is then poured in the molten state into the remaining edge gap, so that the bolt 10 receives a casing of this second light metal, which is not shown in the figures. In this case, the casting method is not limited to the described method, but it can be used any conventional and suitable casting method, for example, sand casting, die casting, low-pressure sand casting, chill casting, etc. may be used. For example, the cladding material may be molten AISM2 or AISi9Cu3, and the area fraction of the encapsulation layer may be about 5-65% of the total cross-sectional area of the stud encapsulated with the encapsulation layer. With or without sheathing, an intermediate hollow profile 20 is thus formed in the first stage from the bolt 10, which can then be fed to at least one further extrusion stage, which is shown schematically in FIG. 2 for a second stage. For this purpose, the inner diameter of a receptacle 42 'of a second extruder 40' is smaller than in the first extruder 40, so that the intermediate hollow profile 20 is received therein. Furthermore, another die 41 'is now used, which likewise forms the outer contour of an end profile 30 from the intermediate hollow profile 20 by indirect extrusion. In this way, the outer diameter can be further reduced to the final dimension, which is also indicated by dashed lines in Fig. 2. In this case, the pressure can be 70-90% of the original geometry or it can be realized from 1: 12 to 1: 30 degrees of deformation. This leads to a Gesamtumformgrad in the order of 1:36 to 1: 90 over both stages. Furthermore, geometric dimensions, tolerances and / or material properties of the light metal part are formed on the end profile in this second stage, wherein in particular the desired outer contour of the light metal part 30 is produced by the die 41 '.

The end profiles that can be produced in this way can be tubes, tubes with a profiled outer contour, hollow profiles with a profiled outer contour and non-rotationally symmetrical semi-finished products with or without a bore. In particular, multilayer pipes and hollow profiles with a core of a DISPAL alloy and a profiled outer contour made of a different alloy can be produced by the method according to the invention. By profiled outer contour, for example, cooling fins can be formed. Furthermore, in particular a cylinder liner for an internal combustion engine with at least one reciprocating piston can be produced from the produced end profile 30. If the bolt 10 is already fed to the two extruder stages together with the described casing, the two layers behave in such a way that they find themselves again in corresponding regions of the pipe cross-section in accordance with the forming ratios of the extruders 40, 40 '. Therefore, one can also speak of coextrusion.

The end profile or light metal part 30 can then be supplied to further processing steps, but no further step is absolutely necessary in order to set a final geometry, because these can be adjusted with the inventive already by the extrusion or coextrusion. Process steps such as rotary swaging could thus be dispensed with. The dimensions of the bolt 10 made of a first light metal and a jacket made of a second light metal are correspondingly selected such that, for example, a second layer of a light metal can be formed in the end profile 30; ren thickness in the order of 200μηι to 60 μηι lies. For typical applications, this means that the sheath of the bolt 10 originally had a thickness of about 3mm to 15mm. The inner layer of the hypereutectic high-performance aluminum alloy is then made correspondingly thicker to come to end wall thicknesses in the order of magnitude of 3mm to 90mm, so that the resulting light metal part of an inner, thicker layer of a first light metal and an outer, thinner layer of a having second light metal.

In a subsequent method step, the coextruded end profile 30 can be cut to length, after which the cut-to-length pipe sections can be chamfered and edge-broken. In this way, pipe sections are obtained which are suitable as cylinder liners for reciprocating pistons in high performance internal combustion engines and then comprise a thicker inner liner layer and a thinner outer cladding layer. In a final process step, the resulting liners can be blasted with corundum so that the outer surface of the second light metal is pretreated accordingly to be connected to a motor look. In general, the connection of the liners is done with a motor block in a casting process, wherein the liners are surrounded by an engine block.

If a starting bolt has not already been coextruded with a jacket, the jacket of a second light metal is preferably applied to the cut and reworked pipe sections after the corundum radiation. This should take place in a timely manner in order to prevent renewed oxidation and can be carried out, for example, by flame spraying with a coating agent made from AISi12 wire.

LIST OF REFERENCE NUMBERS

10 bolts, jacketed bolt 20 intermediate hollow profile

30 end profile, light metal part

40.40 'extruder

 41, 41 'matrix

 42.42 'transducer

43,43 'thorn

Claims

claims: 1 . Process for producing a light metal part comprising at least the following steps:  - Producing a bolt (10) of a hypereutectic high-performance aluminum alloy with a Si content of 17-35 wt .-%;  Forming of the bolt (10) in a first stage by means of extrusion with a first degree of deformation to an intermediate hollow profile (20);  Forming of the intermediate hollow profile (20) in a second stage by extrusion with a second degree of deformation to an end profile (30), the Gesamtumformgrad over both stages in the order of 1:36 to 1: 90, and by the extrusion geometric dimensions , Tolerances and / or material properties of the light metal part at the end profile (30) can be adjusted. Method according to claim 1,  characterized in that the first degree of deformation is of the order of 1: 3 to 1: 5, while the second degree of deformation is of the order of 1: 12 to 1: 30. Method according to claim 1,  characterized in that between the first and second stage further forming stages are carried out by extrusion. 4. The method according to one or more of claims 1 to 3,  characterized in that the bolt (10) is made by spray compacting or a casting process. 5. The method according to one or more of claims 1 to 4,  characterized in that the inner diameter of the end profile (30) in the Magnitudes of 50mm and 105 mm, while the outer diameter of the end profile is between 60mm and 195mm. 6. The method according to one or more of claims 1 to 5, characterized in that prior to forming by extrusion in the first stage a casing of a second light metal is produced on the bolt (10), and the bolt (10) is formed together with the casing in at least two extrusion stages to the end profile (30) , 7. The method according to claim 6,  characterized in that the sheath is produced by molding the bolt (10) with the second light metal. 8. The method according to claim 6,  characterized in that the sheath is produced by thermal encapsulation of the bolt (10) with the second light metal. 9. The method according to claim 6,  characterized in that the jacket is made by spray compacting the second light metal on the bolt (10). Method according to one or more of claims 6 to 9,  characterized in that the second light metal is an Al-Mg casting alloy. Method according to claim 10,  characterized in that the second light metal is an Al casting alloy type AISM 2. 12. light metal part,  characterized in that it has been produced according to one of claims 1 to 11. 13. Light metal part according to claim 12,  characterized in that it is formed by further process steps as a cylinder liner for a reciprocating piston of an internal combustion engine. 14. internal combustion engine with at least one reciprocating piston with a cylinder liner, characterized in that the cylinder liner is formed by a light metal part according to claim 12.