KR20050081168A - Casting of an aluminium alloy - Google Patents

Abstract

A casting process for producing a cast product comprises providing an aluminum alloy comprising (wt.%) magnesium (2-4), silicon (0.9-1.5), manganese (0.1-0.4), chromium (0.1-0.4), iron (=0.2), copper (=0.1), zinc (=0.2), titanium (=0.2), zirconium (=0.3), beryllium (=0.008), vanadium (=0.5), and aluminum (balance), with further elements and production-induced contaminants (=0.2); and casting the aluminum alloy to produce a cast product. An independent claim is also included for an aluminum alloy with good heat resistance, comprising (wt.%) magnesium (2-4), silicon (0.9-1.5), manganese (0.1-0.4), chromium (0.1-0.4), iron (=0.2), copper (=0.1), zinc (=0.2), titanium (=0.2), zirconium (=0.3), beryllium (=0.008), vanadium (=0.5), and aluminum (balance), with further elements and production-induced contaminants (=0.2).

Description

Casting of Aluminum Alloys {CASTING OF AN ALUMINIUM ALLOY}

The present invention relates to a casting of an aluminum alloy having good heat resistance.

AlSi alloys are commonly used for today's thermally stressed parts, and heat resistance is obtained by adding Cu to these alloys. However, copper increases the heat crack propensity and adversely affects castability. In particular, an area where heat resistance is required is an automobile cylinder head field. See, eg, F. J. Feikus, "Optimisation of Aluminum Silicon Casting Alloys for Cylinder Heads". See Giesserei-Praxis 1999, Vol. 2, pages 50-57.

Patent document WO-A-0043560 discloses an aluminum alloy for the production of safety parts by die casting, squeeze casting, thixoforming and thixoforging processes. Wt% Si, 0.3-0.49 wt% Mn, 0.1-0.3 wt% Cr, up to 0.15 wt% Fe, up to 0.00005 wt% Ca, up to 0.00005 wt% Na, up to 0.0002 wt% P, and Impurities of other components, each having a maximum of 0.02% by weight, and an aluminum alloy consisting of the remainder are described.

The present invention is suitable for the production of parts subjected to thermal stress, and an object thereof is to provide an aluminum alloy having good heat resistance. This alloy is particularly suitable for gravity die casting, low pressure chilled casting and sand casting.

Parts cast from the alloy should have high strength with respect to high ductility. Preferred mechanical properties of these parts are defined as follows.

Yield strength Rp0.2> 170 MPa

Tensile Strength Rm> 230 MPa

Elongation at break A5> 6%

Because of the specificity of the field in which these alloys are used, these alloys should be kept as low as corrosive and have good fatigue strength. The castability of the alloy should be better than the AlSiCu main alloys currently in use and no heat cracks would be generated.

In the present invention, the term "casting" includes pure castings which are produced only by casting, preformed castings, and products molded into final dimensions by cold or hot forming.

Examples of pure castings are sand casting, gravity die casting, low pressure chilled casting, die casting, thixocasting or squeeze casting.

Molding operations performed in castings preformed by shaping include forging and semi-melting forging.

The object according to the invention is achieved by an aluminum alloy having the following composition.

2-4% by weight magnesium,

0.9-1.5 weight percent silicon,

0.1-0.4% by weight manganese,

0.1-0.4% by weight of chromium,

Up to 0.2% by weight of iron,

Up to 0.1% by weight of copper,

Up to 0.2% by weight of zinc,

Up to 0.2 wt% titanium,

Up to 0.3% zirconium,

Up to 0.008% beryllium,

Vanadium up to 0.5% by weight,

Other components, production impurities, and the remainder of aluminum, each up to 0.02% by weight but not more than 0.2% by weight in total.

Each alloy element preferably has the following composition range.

Mg 2.5-3.5 wt%, especially 2.7-3.3 wt%,

Si 0.9-1.3 wt%,

Mn 0.15-0.3 wt%,

Cr 0.15-0.3 wt%,

Ti 0.05-0.15 wt%,

Fe max 0.15% by weight,

Up to 0.05 wt% Cu,

Be 0.002-0.005 wt%,

V 0.01-0.1 wt%, and

Zr 0.1-0.2 wt%.

The effect of the alloying element is as follows.

Silicon combined with magnesium allows the curing to take place, especially when heat curing is required. For example, it is suitable for heat treatment in a T6 state, that is, annealing at 550 ° C. for 12 hours and artificial aging at 160-170 ° C. for 8 to 10 hours.

The combination of manganese and chromium gives good heat resistance at sustained temperatures up to 180 ° C.

Titanium and zirconium are used for grain refining. Good atomization substantially contributes to the improvement of castability.

Beryllium together with vanadium reduces the formation of dross.

Applications of the castings according to the invention include components which are thermally stressed, in particular pressure vessels, compressor housings, engine parts such as automobile cylinder heads and the like.

Referring to the present invention in more detail based on the accompanying drawings as follows.

As an alloy AlMg 3 SiMnCr of the present invention having a composition shown in Table 1 below and a comparative alloy, F.J.Feikus, "Optimisation of Aluminum Silicon Casting Alloys for Cylinder Heads". The alloy AlSi7MgCu1, presented in Giesserei-Praxis 1999, Vol. 2, pages 50-57, was compared with temperature at constant temperature loading.

Table 1 : Chemical Composition of Alloys (wt%)

alloy Si Fe Cu Mn Mg Cr Zn Ti Be V Zr AlSi7MgCu1 6.97 0.11 0.94 0.005 0.38 0.008 0.03 AlMg3SiMnCr 1.10 0.07 0.001 0.20 3.2 0.21 0.002 0.12 0.003 0.03 0.0005

The alloy according to the invention was cast into round bars of 16 mm diameter in a test rod mold of Deiz. At various temperatures with a continuous temperature load of 500 hours, the yield strength (Rp0.2), tensile strength (Rm) and elongation (A5) for the test rods were measured at T6 (165 ° C / 6 hours). Values for the corresponding comparative alloys were obtained from the above paper by F.J.Feikus. The results are shown in FIG.

The alloy AlMg3SiMnCr according to the present invention did not reach the maximum value of the comparative alloy AlSi7MgCu1 in yield strength and tensile strength, but exhibited "little modification" in temperature characteristics. This change results in a rupture result in the work because even a light change in temperature shows a large change in the mechanical properties. The yield strength of the alloy according to the present invention was maintained at about the same level up to around 180 ° C. and gradually decreased to 200 ° C. and then started to decrease continuously above 200 ° C. This continuous decrease was less than that of the alloy AlSi7MgCu1.

In elongation at break, the alloy according to the invention has an almost constant value up to 180 ° C. High values of elongation provide good break / break characteristics. Visible deformation occurs first before the part breaks. Above 180 ° C., the elongation increased continuously. The comparative alloy AlSi7MgCu1 showed a clear curing effect. Low values of elongation are undesirable for fracture. In other words, since the part is slightly deformed or not deformed at all, the part breaks without any sign at the maximum load.

1 to 3 are graphs showing tensile strength, yield strength and elongation with time at a sustained temperature load of 500 hours, respectively, in order to compare the alloy according to the present invention with the prior art alloy.

Claims (13)

The casting of the aluminum alloy which has favorable heat resistance characterized by including the following components. 2-4% by weight magnesium, 0.9-1.5 weight percent silicon, 0.1-0.4% by weight manganese, 0.1-0.4% by weight of chromium, Up to 0.2% by weight of iron, Up to 0.1% by weight of copper, Up to 0.2% by weight of zinc, Up to 0.2 wt% titanium, Up to 0.3% zirconium, Up to 0.008% beryllium, Vanadium up to 0.5% by weight, Other components, production impurities, and the remainder of aluminum, each up to 0.02% by weight but not more than 0.2% by weight in total. The casting of claim 1 wherein the alloy comprises 2.5-3.5 wt.% Mg, in particular 2.7-3.3 wt.% Mg. The casting as claimed in claim 1 or 2, wherein the alloy comprises 0.9-1.3% by weight of Si. The casting according to any one of claims 1 to 3, wherein the alloy comprises 0.15-0.3% by weight of Mn. The casting according to any one of claims 1 to 4, wherein the alloy contains 0.15-0.3% by weight of Cr. The casting according to any one of claims 1 to 5, wherein the alloy contains 0.05-0.15% by weight of Ti. The casting according to any one of claims 1 to 6, wherein the alloy contains at most 0.15% by weight of Fe. The casting as claimed in claim 1, wherein the alloy comprises at most 0.05% by weight of Cu. The casting according to any one of claims 1 to 8, wherein the alloy comprises 0.002-0.005% by weight of Be. The casting according to any one of claims 1 to 9, wherein the alloy contains 0.01 to 0.1 wt% of V. The casting according to any one of claims 1 to 10, wherein the alloy comprises 0.1-0.2 wt% Zr. The casting as claimed in claim 1, produced by a sand casting or chilled casting process. Use of a casting according to any of claims 1 to 12 for engine parts such as pressure vessels, compressor housings, and cylinder heads of motor vehicles.