DE102011083970A1 - Method for producing an engine component and engine component - Google Patents

Abstract

The present application relates to a method for producing an engine component, in particular a piston for an internal combustion engine, in which an aluminum alloy is poured in the low-pressure casting process. In this case, the aluminum alloy has the following alloying elements: silicon: 9 wt .-% to 11 wt .-%, nickel: 1.7 wt .-% to 3.5 wt .-%, copper: 3.7 wt .-% to 5.2 wt.%, magnesium: 1.6 wt.% to 4.5 wt.%, iron: 0.1 wt.% to 0.7 wt.%, manganese: 0.05 Wt% to 0.2 wt%, zirconium: 0.04 wt% to 0.1 wt%, vanadium: 0.04 wt% to 0.1 wt%, strontium : 150 ppm to 250 ppm.

Description

TECHNICAL AREA

The present invention relates to a method for producing an engine component, in particular a piston for an internal combustion engine, in which an aluminum alloy is cast by low-pressure casting, an engine component which consists at least partially of an aluminum alloy, and the use of an aluminum alloy for producing such an engine component.

STATE OF THE ART

In recent years there has been an increasing demand for particularly economical and thus ecological means of transport, which have to meet high consumption and emission requirements. In addition, there is always the need to make engines as powerful and low-consumption. A key factor in the development of high-performance and low-emission combustion engines are pistons, which can be used at ever higher combustion temperatures and combustion pressures, which is essentially made possible by more efficient piston materials.

Basically, a piston for an internal combustion engine must have a high heat resistance and at the same time be as light and strong as possible. It is of particular importance how the microstructural distribution, morphology, composition and thermal stability of highly heat-resistant phases are formed. An optimization in this regard usually takes into account a minimum content of pores and oxide inclusions.

The material sought must be optimized for both isothermal fatigue strength (HCF) and thermo-mechanical fatigue strength (TMF). In order to design the TMF as well as possible, the goal is always to achieve the finest possible microstructure of the material. A fine microstructure reduces the risk of microplasticity or microcracks on relatively large primary phases (especially primary silicon precipitates) and hence the risk of crack initiation and propagation.

In principle, it is known that in the case of the low-pressure casting method, in contrast to the die-casting method, a lower porosity and a decreasing content of oxide inclusions can be set because only relatively slight melt flow turbulences occur here. As a result, a comparatively low defect density is obtained, which contributes significantly to good mechanical properties of the manufactured component. In particular with regard to HCF but also to TMF, the properties of a component produced in this way are advantageous.

Under TMF stress, microelasticities or microcracks occur on relatively large primary phases, especially primary silicon precipitates, due to different coefficients of expansion of the individual constituents of the alloy, namely the matrix and the primary phases, which can significantly reduce the life of the piston material. To increase the life is known to keep the primary phases as small as possible.

Strontium can be used for continuous refining of aluminum-silicon alloys, especially in low-pressure casting. Such finishing particularly affects the casting properties of the alloy and increases the ductility of the material. The targeted refining with strontium can cause the eutectic silicon in the alloy is not coarse-grained, but finely distributed and in a rounded form. This has an advantageous effect on the TMF and HCF properties of the alloy.

However, as with die casting, low pressure casting also has an upper limit on its concentration, up to which alloying elements should be introduced and, if exceeded, makes the casting of the alloy difficult or impossible. In addition, too high concentrations of strength-enhancing elements lead to the formation of large plate-shaped intermetallic phases, which drastically lower the fatigue strength.

PRESENTATION OF THE INVENTION

An object of the present invention is to provide a method for producing an engine component, in particular a piston for an internal combustion engine, in which an aluminum alloy is poured by low-pressure casting, so that a highly heat-resistant engine component can be produced by low-pressure casting.

The solution to this problem is given by the method according to claim 1. Further preferred embodiments of the invention will become apparent from the relevant subclaims.

A further object of the invention is to provide an engine component, in particular a piston for an internal combustion engine, which is highly heat-resistant and at least partially consists of an aluminum alloy.

This object is achieved by the subject matter of claim 6 and further preferred embodiments will become apparent from the relevant subclaims.

In a method according to the invention, the aluminum alloy has the following alloying elements:
Silicon: 9% by weight to 11% by weight,
Nickel: 1.7% to 3.5% by weight,
Copper: from 3.7% to 5.2% by weight,
Magnesium: 1.6% to 4.5% by weight,
Iron: 0.1% to 0.7% by weight
Manganese: 0.05% to 0.2% by weight,
Zirconium: 0.04 wt% to 0.1 wt%,
Vanadium: 0.04% to 0.1% by weight,
Strontium: 150 ppm to 250 ppm.

Due to the selected aluminum alloy, it is possible to produce a motor component in the low-pressure casting process, which contains a high proportion of finely divided, highly heat-resistant, thermally stable phases. The alloy also has a refined structure, which among other things leads to good casting properties and increased ductility. The choice of low-pressure casting method allows a particularly low expression of flow turbulence during the casting of the engine component, which leads to a low porosity and oxide formation. The susceptibility to crack initiation and propagation of pores, oxides or primary phases is reduced by the choice of the low pressure casting process in combination with the alloy of the invention over the hitherto known manufacturing processes of pistons and similar engine components. Thus, a highly heat resistant engine component can be produced by low pressure casting.

Advantageously, the aluminum alloy comprises from 0.4% to 0.6% by weight of iron and alternatively or additionally from 3.6% to 4.5% by weight of magnesium.

Advantageously, in the aluminum alloy, the weight ratio of iron to manganese is at most 6: 1, preferably about 4: 1. Thus, in this embodiment, the aluminum alloy contains at most six parts iron versus one part manganese, preferably about four parts iron versus one part manganese. By this ratio particularly advantageous strength properties of the engine component can be achieved.

Preferably, the aluminum alloy has a phosphorus content of less than 30 ppm. This helps to avoid primary silicon precipitates and, as well as a preferred silicon and strontium content of the alloy, serves to keep the piston near-primary silicon free. The preferred maximum phosphorus content thus also leads to particularly good TMF properties of the engine component.

Incidentally, the aluminum alloy has aluminum and unavoidable impurities.

An engine component according to the invention consists at least partially of one of the abovementioned aluminum alloys. Another independent aspect of the invention resides in the use of the above-described aluminum alloy for the manufacture of an engine component, in particular a piston of an internal combustion engine. In particular, the aluminum alloy found is processed in the low-pressure casting process.

Claims (10)

Method for producing an engine component, in particular a piston for an internal combustion engine, in which an aluminum alloy is poured by the low-pressure casting method, wherein the aluminum alloy has the following alloying elements: Silicon: 9 wt.% To 11 wt.% Nickel: 1.7% to 3.5% by weight Copper: from 3.7% to 5.2% by weight, Magnesium: 1.6% to 4.5% by weight, Iron: 0.1% to 0.7% by weight, Manganese: 0.05% to 0.2% by weight, Zirconium: 0.04 wt% to 0.1 wt%, Vanadium: 0.04% to 0.1% by weight, Strontium: 150 ppm to 250 ppm. The method of claim 1, wherein the aluminum alloy comprises from 0.4% to 0.6% by weight of iron and / or from 3.6% to 4.5% by weight of magnesium. Method according to one of the preceding claims, wherein in the aluminum alloy, the weight ratio of iron to manganese is at most 6: 1, preferably the weight ratio of iron to manganese about 4: 1. A method according to any one of the preceding claims, wherein the aluminum alloy has a phosphorus content of less than 30 ppm. Method according to one of the preceding claims, wherein the aluminum alloy further comprises aluminum and unavoidable impurities. Engine component, in particular piston for an internal combustion engine, which at least partially consists of an aluminum alloy, wherein the aluminum alloy has the following alloying elements: Silicon: 9% by weight to 11% by weight, nickel: 1.7% by weight to 3.5% by weight, copper: 3.7% by weight to 5.2% by weight, Magnesium: 1.6% by weight to 4.5% by weight, iron: 0.1% by weight to 0.7% by weight, manganese: 0.05% by weight to 0.2% by weight %, Zirconium: 0.04 wt.% To 0.1 wt.%, Vanadium: 0.04 wt.% To 0.1 wt.%, Strontium: 150 ppm to 250 ppm. An engine component according to claim 6, wherein the aluminum alloy comprises 0.4 wt% to 0.6 wt% iron and / or 3.6 wt% to 4.5 wt% magnesium. Engine component according to one of claims 6 and 7, wherein the aluminum alloy has a phosphorus content of less than 30 ppm. An engine component according to any one of claims 6 to 8, wherein in the aluminum alloy, the weight ratio of iron to manganese is at most 6: 1, preferably the weight ratio of iron to manganese is about 4: 1. Use of an aluminum alloy for producing an engine component, in particular a piston of an internal combustion engine, wherein the aluminum alloy has the following alloying elements: Silicon: 9% by weight to 11% by weight, Nickel: 1.7% to 3.5% by weight, Copper: from 3.7% to 5.2% by weight, Magnesium: 1.6% to 4.5% by weight, Iron: 0.1% to 0.7% by weight, Manganese: 0.05% to 0.2% by weight, Zirconium: 0.04 wt% to 0.1 wt%, Vanadium: 0.04% to 0.1% by weight, Strontium: 150 ppm to 250 ppm.