Method for producing an engine component, engine component, and use of an aluminium alloy

Abstract

A method for producing an engine component, more particularly a piston for an internal combustion engine, in which an aluminum alloy is cast using the gravity die casting method is provided. The aluminum alloy comprises: 9 to 10.5% by weight silicon, >2.0 to <3.5% by weight nickel, >3.7 to 5.2% by weight copper, <1% by weight cobalt, 0.5 to 1.5% by weight magnesium, 0.1 to 0.7% by weight iron, 0.1 to 0.4% by weight manganese, >0.1 to <0.2% by weight zirconium, >0.1 to <0.2% by weight vanadium, 0.05 to <0.2% by weight titanium, 0.004 to 0.008% by weight phosphorus, with aluminum and unavoidable impurities constituting the rest. An engine component, in particular a piston, wherein the engine component consists, at least partially, of the aluminum alloy, and the use of an aluminum alloy to produce the engine component, is also provided.

Claims

1. A method of producing an engine component by gravity die casting, wherein an aluminium alloy is cast consisting of the following alloy elements: Silicon: 9% by weight to 10.5% by weight, Nickel: >2.0% by weight to <3.5% by weight, Copper: >3.7% by weight to 5.2% by weight, Cobalt: to <1% by weight, Magnesium: 0.5% by weight to 1.5% by weight, Iron: 0.1% by weight to 0.7% by weight, Manganese: 0.1% by weight to 0.4% by weight, Zirconium: >0.1% by weight to <0.2% by weight, Vanadium: >0.1% by weight to <0.2% by weight, Titanium: 0.05% by weight to <0.2% by weight, Phosphorus: 0.004% by weight to 0.008% by weight, with aluminium and unavoidable impurities constituting the rest.

2. The method according to claim 1, wherein the magnesium is in the range of 0.6% by weight to 0.8% by weight of magnesium.

3. The method according to claim 1, wherein the iron is in the range of 0.4% by weight to 0.6% by weight of iron.

4. The method according to claim 1, wherein the weight ratio of iron to manganese in the aluminium alloy is at most approximately 5:1.

5. The method according to claim 4, wherein said weight ratio of iron to manganese is approximately 2.5:1.

6. The method according to claim 1, wherein the total of nickel and cobalt is >2.0% by weight and <3.8% by weight.

7. The method according to claim 1, wherein the engine component is a piston that has a bowl rim area and wherein the aluminium alloy has a fine microstructure with a low content of pores and inclusions and/or little and small primary silicon, at least in the bowl rim area, with the porosity being <0.01% and/or the content of primary silicon being <1%, the primary silicon having lengths of, on average, <5 m and/or maximum lengths of <10 m, and the intermetallic phases and/or primary precipitates having lengths of, on average, <30 m and/or maximum lengths of <50 m.

8. The method according to claim 1, wherein the engine component is a piston that has a bowl rim area and wherein the aluminium alloy, at least in the bowl rim area, has an average value of an area of silicon precipitates of <approximately 100 m.sup.2 and/or an average value of an area of the intermetallic phases of <approximately 200 m.sup.2.

Description

DESCRIPTION OF THE INVENTION

(1) One object of the present invention is to provide a method for producing an engine component, in particular a piston for an internal combustion engine, wherein an aluminium alloy is cast using the gravity die casting method such that a highly heat resistant engine component can be produced using the gravity die casting method.

(2) This object is solved by the method according to claim 1. Further preferred embodiments of the invention are apparent from the sub-claims relating hereto.

(3) It is a further object of the invention to provide an engine component, in particular a piston for an internal combustion engine, which is highly heat resistant and thereby consists at least partially of an aluminium alloy.

(4) This object is solved by the subject matter of claim 8 and further preferred embodiments are apparent from the sub-claims relating hereto.

(5) In a method according to the invention, the aluminium alloy comprises the following alloy elements:

(6) Silicon: 9% by weight to 10.5% by weight,

(7) Nickel: >2.0% by weight to <3.5% by weight,

(8) Copper: >3.7% by weight to 5.2% by weight,

(9) Cobalt: to <1% by weight,

(10) Magnesium: 0.5% by weight to 1.5% by weight,

(11) Iron: 0.1% by weight to 0.7% by weight,

(12) Manganese: 0.1% by weight to 0.4% by weight,

(13) Zirconium: >0.1% by weight to <0.2% by weight,

(14) Vanadium: >0.1% by weight to <0.2% by weight,

(15) Titanium: 0.05% by weight to <0.2% by weight,

(16) Phosphorus: 0.004% by weight to 0.008% by weight, with aluminium and unavoidable impurities constituting the rest.

(17) The aluminium alloy preferably comprises:

(18) from >approximately 9approximately 10.5, further preferred <approximately 10, particularly preferred <approximately 9.5, or further preferred from approximately 9.5 to approximately 10.5% by weight of silicon;

(19) from >approximately 2.3, further preferred >approximately 3 to <approximately 3.5, or further preferred from approximately 2.5, particularly preferred approximately 2.9 to approximately 3% by weight of nickel;

(20) from >approximately 3.8, further preferred >approximately 4 and particularly preferred >approximately 4.8 to approximately 5.2, or further preferred from >approximately 3.7 to approximately <5, particularly preferred <4, or further preferred of approximately 4, particularly preferred approximately 4.1 to approximately 4.6% by weight of copper;

(21) from >approximately 0.5 and further preferred >approximately 0.9 to <approximately 1% by weight of cobalt;

(22) from approximately 0.5 and further preferred >approximately 0.6 and in particular approximately 0.7 to <approximately 1.5, further preferred <approximately 0.8 or further preferred from >approximately 1, further preferred >approximately 1.3 to approximately 1.5% by weight of magnesium;

(23) from >approximately 0.5, further preferred >approximately 0.6 to approximately 0.7 or further preferred approximately 0.45 to approximately 0.5% by weight of iron;

(24) from approximately 0.1 to <approximately 0.2 or further preferred from >approximately 0.25 to approximately 0.4% by weight of manganese;

(25) from approximately 0.12, further preferred approximately 0.13 to approximately 0.19% by weight of zirconium;

(26) from approximately 0.12 to approximately 0.14% by weight of vanadium;

(27) from approximately 0.05 to <approximately 0.15 or further preferred from approximately 0.11, particularly preferred approximately 0.12, to approximately 0.13% by weight of titanium; and

(28) from approximately 0.005 to approximately 0.006% by weight of phosphorus.

(29) Owing to the selected aluminium alloy, it is possible to produce an engine component using the gravity die casting method, which has a high proportion of finely distributed, high-temperature resistant, thermally stable phases and a fine microstructure. Owing to the selection of the alloy according to the invention, the susceptibility to crack initiation and crack growth, for example at oxides or primary phases, and the TMF-HCF lifespan is reduced as compared to the hitherto known methods for producing pistons and similar engine components.

(30) The alloy according to the invention, in particular the comparatively low silicon content, also leads to there being comparatively less and finer primary silicon at least in the thermally highly-stressed bowl rim area of a piston produced in accordance with the invention, such that the alloy leads to particularly good properties of a piston produced in accordance with the invention. A highly heat resistant engine component can thus be produced using the gravity die casting method. The proportions of copper, zirconium, vanadium and titanium as according to the invention, in particular the comparatively high contents of zirconium, vanadium and titanium, produce an advantageous proportion of strengthening precipitates, without, however, causing large plate-like intermetallic phases. The proportions of cobalt and nickel according to the invention are furthermore advantageous for increasing the heat resistance of the alloy. Nickel thereby contributes to forming thermally stable intermetallic phases. Furthermore, cobalt increases the hardness and, in general, the strength of the alloy. Phosphorus, as the nucleating agent, helps to ensure that primary silicon precipitates are precipitated as finely and homogenously distributed as possible.

(31) The aluminium alloy advantageously preferably comprises 0.6% by weight to 0.8% by weight of magnesium, which contributes, in the preferred concentration range, in particular to an efficient formation of secondary strengthening phases without the occurrence of excessive oxide formation. The alloy furthermore alternatively or additionally comprises preferably 0.4% by weight to 0.6% by weight of iron, which reduces the adhesive tendency of the alloy in the casting mould, whereby the formation of plate-like phases remains limited in the cited concentration range.

(32) The weight ratio of iron to manganese in the aluminium alloy is advantageously at most approximately 5:1, preferred approximately 2.5:1. In this embodiment, the aluminium alloy thus contains at most five parts of iron to one part of manganese, preferably approximately 2.5 parts of iron to one part of manganese. Particularly advantageous strength properties of the engine component are achieved with this ratio.

(33) It is furthermore preferred for the total of nickel and cobalt to be >2.0% by weight and <3.8% by weight. The lower limit thereby ensures an advantageous strength of the alloy and the upper limit advantageously ensures a fine microstructure and prevents the formation of course, plate-like phases that would reduce the strength.

(34) The aluminium alloy advantageously has a fine microstructure with a low content of pores and inclusions and/or little and small primary silicon, in particular in the highly-stressed bowl rim area. A low content of pores is thereby preferably to be understood as a porosity of <0.01%, and little primary silicon is to be understood as <1%. The fine microstructure is furthermore advantageously described in that the average length of the primary silicon is approximately <5 m and the maximum length thereof is approximately <10 m, and the intermetallic phases and/or primary precipitates have lengths of, on average, approximately <30 m and at most <50 m.

(35) It is furthermore preferred for the aluminium alloy, in particular in the bowl rim area, to have an average value of an area of silicon precipitates of <approximately 100 m.sup.2 and/or an average value of an area of the intermetallic phases of <approximately 200 m.sup.2.

(36) The characterisation of the microstructure of the aluminium alloy preferably occurs by means of quantitative microstructural analysis. A metallographic section is first of all prepared for this purpose and corresponding micrographs are taken using optical microscopy in particular of the particularly technologically important bowl rim area. An inverted light microscope can, as an example, be used herefor. Individual images are then taken therewith at a defined magnification, are assembled by computer into an area (for example 5.5 mm4.1 mm), and the areas and area proportions of specific phases are determined by means of image processing software.

(37) The fine microstructure in particular contributes to improving the thermomechanical fatigue strength. Limiting the size of the primary phases can reduce the susceptibility to crack initiation and crack growth and thus significantly increase the TMF-HCF lifespan. Owing to the notch effect of pores and inclusions, it is furthermore particularly advantageous to keep the content thereof low.

(38) An engine component according to the invention consists at least partially of one of the aforementioned aluminium alloys. A further independent aspect of the invention lies in the use of the aforementioned aluminium alloy for the production of an engine component, in particular a piston of an internal combustion engine. The discovered aluminium alloy is thereby in particular processed using the gravity die casting method.

EXAMPLES

(39) Cited as examples of the aluminium alloy described above are an alloy 1 having 10.5% by weight of silicon; 3% by weight of nickel; 4.1% by weight of copper; 0.7% by weight of magnesium; 0.5% by weight of iron; 0.2% by weight of manganese; 0.13% by weight of zirconium; 0.12% by weight of vanadium; 0.13% by weight of titanium and 0.006% by weight of phosphorus, an alloy 2 having 9.5% by weight of silicon; 2.9% by weight of nickel; 4.0% by weight of copper; 0.7% by weight of magnesium; 0.45% by weight of iron; 0.2% by weight of manganese; 0.12% by weight of zirconium; 0.12% by weight of vanadium; 0.12% by weight of titanium and 0.006% by weight of phosphorus, and an alloy 3 having 9.5% by weight of silicon; 2.5% by weight of nickel; 4.6% by weight of copper; 0.7% by weight of magnesium; 0.45% by weight of iron; 0.2% by weight of manganese; 0.19% by weight of zirconium; 0.14% by weight of vanadium; 0.11% by weight of titanium and 0.005% by weight of phosphorus, with aluminium and unavoidable impurities in each case constituting the rest.