Aluminium die-casting alloy

Details Aluminium die-casting alloy Aluminium die-casting alloy

2001-03-26

2004-08-10

Wyszomierski, George (Department: 1742)

Alloys or metallic compositions

Aluminum base

Zinc containing

C420S544000, C420S543000, C420S553000

Reexamination Certificate

active

06773664

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an aluminum-magnesium alloy for casting operations and to the use of this aluminum-magnesium alloy in casting operations, in particular in die-casting operations. Further the invention relates to the application of the AlMg casting alloy in automotive components.
BACKGROUND OF THE INVENTION
Conventional aluminum-magnesium casting alloys have many attractive properties, such as high ultimate tensile strength (>170 MPa) and elongation (>8%) with moderate yield strength (>120 MPa). However, there is a demand for aluminum cast alloys combining improved mechanical properties with a good corrosion resistance.
Some disclosures of aluminum-magnesium casting alloys found in the prior art is literature will be mentioned below.
WO-96/15281 discloses a casting alloy consisting of, in weight percent:
Mg
3.0-6.0
Mn
0.5-2.0
Ti
<0.2 
Fe
<0.15
Si
1.4-3.5
balance aluminum and impurities.
The alloy may be used in a die-casting operation, and appears to be particularly suitable for use in thixocasting and rheocasting operations.
WO-96/25528 discloses a casting alloy consisting of, in weight percent:
Mg
2.5-4.5, preferably 2.7-3.0
Mn
0.2-0.6, preferably 0.2-0.6
Fe
<0.6
Si
<0.45
Cu
<0.10
Be
<0.003, preferably <0.001
balance aluminum and impurities.
Optionally the alloy may further comprise 0.01-0.04% Ti and/or 0.01-0.10% Zn. The alloy can be employed in die-casting operations, the alloy is capable of having a yield strength greater than or equal to 110 MPa and an elongation greater than or equal to 17%.
WO-96/30554 discloses a casting alloy consisting of, in weight percent:
Mg
2.0-5.0, preferably 2.5-4.0
Mn
0.2-1.6, preferably 0.4-0.8
Zr
0.1-0.3
Fe
<1.0
Si
<0.3
balance aluminum and impurities.
The alloy may be used in die-casting operations. The casting alloy is particularly suitable for manufacturing safety components for cars. Typical strength levels disclosed in a T5-temper are YS of 116 MPa and UTS of 219 MPa and elongation of 19%.
JP-A-09-003582 discloses an aluminum casting alloy having, in weight percent:
Mg
3.0-5.5
Zn
1.0-2.0, such that Mg/Zn-ratio is 1.5-5.5
Mn
0.05-1.0
Cu
0.05-0.8
Fe
0.10-0.8
balance aluminum and inevitable impurities.
The cast products have in its matrix dispersed crystallised products in a spheroidising way.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an aluminum-magnesium alloy that can be used in a variety of casting operations.
It is another object of this invention to provide an aluminum-magnesium alloy ideally suited for use in die-casting operations.
It is also an object of this invention to provide improved cast products and components consisting of an improved aluminum-magnesium alloy cast members that ideally are suited for automotive applications.
It is also an object of this invention to provide an aluminum-magnesium alloy having in the as-cast condition the following minimum mechanical properties: yield strength of at least 120 MPa, a tensile strength of at least 180 MPa and an elongation of at least 7%.
According to the invention there is provided an aluminum-magnesium casting alloy, having the following composition in weight percent:
Mg
2.7-6.0
Mn
0.4-1.4
Zn
0.10-1.5 
Zr
0.3 max.
V
0.3 max.
Sc
0.3 max.
Ti
0.2 max.
Fe
1.0 max.
Si
1.4 max.
balance aluminum and inevitable impurities.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
By the invention cast products or cast bodies can be provided having higher strength in combination with higher elongation. In addition these products have a good corrosion resistance and can be welded using known welding techniques for this type of casting alloys. Alloys of the present invention have also been found with a good castability, in particular in die-casting operations, and no soldering occur when using the casting alloy. The aluminum casting alloy according to the invention is capable of achieving in the as-cast condition a yield strength of more than 140 MPa, in combination with a tensile strength of more than 200 MPa and an elongation at fracture of more than 7%.
The invention also includes products made from the aluminum casting alloy set out above. Typical examples of such products are die-cast, in particular high pressure die-cast, products such as safety components, vehicle wheels, steering wheels, steering columns, airbag modules/cans, brake drums and frame members for a vehicle. The alloy is particularly suited for any application having load and impact requirements where properties of high strength and high elongation are desirable. Typical safety components for cars include structural parts for crush zones or otherwise protecting car passengers. It is known to provide one or more crush zones in a frame of a vehicle such as an automobile. The crush zones are designed to crush, or deform, in the event of a vehicle collision. The deformation of the frame absorbs energy of the collision to help protect an occupant of the vehicle. The frame may be configured to deform in a certain manner upon the application of force exceeding a predetermined amount.
The present aluminum-magnesium alloy is environmentally friendly and is readily recyclable because it does not contaminate the wrought alloy stream of recycled materials. The alloy is typically solidified into ingot-derived stock by continuous casting or semi-continuous casting into a shape suitable for remelt for casting, which shape is typically an ingot billet.
It should be mentioned here that from WO-97/38146, incorporated herein by reference, an aluminum wrought alloy is known for application as rolled sheet or plate or as an extrusion, and having a composition, in weight percent:
Mg
5.0-6.0, preferably 5.0-5.6, and more preferably 5.2-5.6
Mn
>0.6-1.2, preferably 0.7-0.9
Zn
0.4-1.5
Zr
0.05-0.25
Cr
0.3 max.
Ti
0.2 max.
Fe
0.5 max.
Si
0.5 max.
Cu
0.4 max.
Ag
0.4 max.
balance Al and inevitable impurities.
The aluminum wrought alloy disclosed in this international patent application is also subject of the Aluminum Association registration number AA5069.
From WO-99-42627, incorporated herein by reference, an aluminum-magnesium alloy in the form of a rolled product or an extrusion is known, having the following composition, in weight percent:
Mg
>3.0-4.5, preferably 3.5-4.5
Mn
0.4-1.2,
Zn
0.4-1.7, preferably 0.4-0.75
Zr
0.05-0.25
Cr
0.3 max.
Ti
0.2 max.
V
0.2 max.
Li
0.5 max.
Sc
0.5 max.
Fe
0.5 max., such that preferably Fe/Mn ratio is 0.3-1.0
Si
0.5 max.
Cu
0.15 max.
Ag
0.4 max.
balance Al and inevitable impurities.
However, neither in WO-97/38146, nor in WO-99/42627 it is mentioned or suggested that the aluminum wrought alloy could be successfully used as an aluminum casting alloy, in particular as an aluminum die-casting alloy.
It is believed that the improved properties available with the casting alloy of the invention, particularly higher strength levels and high elongation in combination with good casting characteristics, result from the combined additions of Mg, Mn and Zn in the given ranges. The aluminum casting alloy is therefore ideally suited for the improved post casting processing, i.e. the elimination of conventional high temperature solution heat treating and optionally ageing at room temperature or elevated temperature, while providing even complexly shaped die-cast products with improved dimensional stability and mechanical properties.
The reasons for the limitations of the alloying elements of the aluminum casting alloy according to the present invention are described below. All composition percentages are by weight.
Mg is the primary strengthening element in the alloy. Depending on the field of application, the magnesium content is preferably in the range of 2.7 to 6.0%. Mg levels below 2.7% do not provide the required strength and when the addition exceeds 6.0%, problems during casting occur. A more preferred minimum Mg level is 3.0%. The preferred level of Mg is 4.5 to 6.0%, more preferably 5.0 to 6.0%, and most preferably 5.2 to 5.8%, as a compromise between ease of casting, strength and corrosion resistance.
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