AN ALUMINIUM ALLOY, MECHANICAL PARTS MADE THEREFROM, AND
USE THEREOF
Field of the Invention
The present invention relates to aluminium alloys, and particularly to aluminium
alloys for use in manufacturing high-strength, light-weight die-cast escalator step or
auto-walk pallet.
Background of the Invention
Current escalator steps or auto-walk pallets are manufactured via two distinctively
different manufacturing routes, namely
a) High-pressure die-casting of aluminium alloys to produce a one-piece casting of
full step body,
b) Fabricated, mechanical assembly of separate components of cold-rolled stainless
steels, low-carbon cold-rolled sheet assembled with cast-iron and other metallic and
polymer parts welded or mechanically joined to form a step body.
Yield strength and tensile strength are two basic parameters widely used in
engineering field. They are used for measuring the ability of metal materials to resist
deformation and fracture under a loaded force. A die-cast aluminium alloy typically has
yield strength up to 80-100 MPa but fractures at low total elongation of 1-2 %. Due to the
low strength and brittle fracture behavior of die-cast aluminium alloy, die-cast aluminium
alloy steps are likely to break during service, and thus lead to risk of passenger injury.
Strength/weight ratio is another parameter to evaluate the performance of metal
materials, which is the ratio between tensile strength and apparent density. A higher
strength/weight ratio indicates that less mass of the material is required to reach a
determined strength. So far the known attempts to improve strength/weight ratio of
escalator step or auto-walk pallet castings are as follows:
- Improve the strength of aluminium-silicon alloy. Aluminium-silicon alloys (8-13%
Si) are the most extensively used alloys in die-casting. Thysse-Kxupp has published studies
to use rare-earth metals (as grain refiner during solidification) to produce an
aluminium-silicon casting alloy material with improved properties. The resulting strength
of silicon alloy material is lower than that of aluminium-magnesium alloys if used with
current casting practice. The resulting ductility of silicon alloy material has not been

observed to be improved.
- Use high strength steel materials in combination with aluminium alloy materials,
to achieve a safe and ductile behavior of the resulting escalator step or auto-walk pallet
castings. This approach requires a long assembly process, and involves joining processes
as well. Separate joining parts are costly in terms of, for instance, the associated labor and
inspection, intermediate finishing and individual part fabrication.
- Thyssen has published escalator steps made from fiber-reinforced plastics as a
low-weight, less-noise solution. However material cost, production cost and fire-resistance
may appear problems of implementation.
Automotive industry has developed aluminium-magnesium cast alloys for
automotive body parts, shock absorber supports and wheel suspension parts because of
energy-efficiency, fuel-efficiency and material saving.
Object and Summary of the Invention
The present invention is directed to an aluminium alloy, the mechanical parts made
therefrom, and the use thereof. The aluminium alloy and the mechanical parts according to
the present invention are suitable for use in a high-strength, light-weight die-cast escalator
step or auto-walk pallet.
In one aspect of the invention, an aluminium alloy is provided. The aluminium alloy
according to the present invention comprises:
4 to 6 % by weight of magnesium;
0.3 to 0.9 % by weight of ferrum;
0.1 to 0.6 % by weight of manganese; and
0.2 to 2 % by weight of silicon.
It has been observed that the aluminium alloy of the present invention has achieved
higher strength, higher ductility and lower weight, as compared with existing aluminium
alloys.
In another aspect of the invention, a mechanical part made from the aluminium alloy
according to the present invention is provided. Specifically, the mechanical part is an
escalator step, or an auto-walk pallet, for example.
It has been observed that the resulting escalator step or auto-walk pallet exhibited
excellent performances including, but not limited to, lower weight, higher strength, and
higher total elongation, as compared with the current escalator step or auto-walk pallet.

In still another aspect of the invention, use of the aluminium alloy according to the
present invention is provided. By virtue of the enhanced performance, the aluminium alloy
according to the present invention is suitable for use in manufacturing mechanical parts,
especially for those are required to constantly or frequently withstand a high loaded force,
such as mechanical parts of escalator steps or auto-walk pallets.
Detailed Description
Reference will now be made to embodiments of the disclosure, one or more examples
of which are illustrated in the figures. The embodiments are provided by way of
explanation of the disclosure, and are not meant as a limitation of the disclosure. For
example, features illustrated or described as part of one embodiment may be used with
another embodiment to yield still a further embodiment. It is intended that the disclosure
encompass these and other modifications and variations as come within the scope and
spirit of the disclosure.
According to one embodiment of the present invention, the aluminium alloy of the
disclosure comprises 4 to 6 % by weight of magnesium; 0.3 to 0.9 % by weight of ferrum;
0.1 to 0.6 % by weight of manganese; and 0.2 to 2 % by weight of silicon.
One of ordinary skill in the art should understand that the aluminium alloy of the
disclosure may comprise unavoidable impurities.
The aluminium alloy of the present invention has the required strength and higher
fatigue strength to enable weight reduction.
The aluminium alloy of the present invention is suitable for use in manufacturing
mechanical parts. Specifically, the aluminium alloy may be cast into the thin-walled
escalator step or the auto-walk pallet. The resulting escalator step or auto-walk pallet has
yield strength of 160 MPa and high ductility of 16 % against step/pallet break. Furthermore,
the escalator step or auto-walk pallet of the present invention meets the step/pallet ultimate
breaking test load at lower step/pallet weight level, 15-20 %, due to the lower material
specific weight and the smaller cross-sectional area of the load carrying members.
The aluminium alloy of the present invention can be cast into a thin-wall thickness of
1.0-1.2 mm at minimum, by using tools according to the state-of-art, such as steel molds
and dies, and by using currently known casting practices. The step cross section

higher strength and higher total elongation, which is more safe for escalator passenger in
case of step breaking due to escalator misuse, unexceptional loading of step due to
mechanical failure of other components, such as falling of foreign objects on step band,
mechanical material fatigue, wear, aging and corrosion.
Escalators and auto-walks have several safety devices to prevent injury due to step
crash. Step crash may occur due to mechanical failure of the guiding parts, chain, chain
guide, step roller, drive chain or any dislocation, chain break, wear and misuse. In case of
such crash the advantage of high-strength ductile material is that it does not break in brittle
way but deforms preventing passenger fall.
Auto-walks operate in horizontal direction where the lower step weight contributes to
lower power consumption because of reduction of moving masses vs passenger load and
the associated lower friction force.
The die-cast escalator step or auto-walk pallet of the disclosure has the structural
design and material properties as defined by the industry prior art as well as international
codes and norms:
- load forces determined by the step area where passengers can stand, 6000 N/m2,
including additional strength due to safety factor of 3-4;
- fatigue resistance up to 6 million load cycles;
- corrosion resistance against road salt, marine climate;
- friction coefficient against passenger footwear to prevent falling due to slippery,
especially when escalator/auto-walk stops via safety devices activation;
- corrosion resistance for outdoor use, in public transport facilities like metro
stations, airports, against direct rainfall in marine climate;
- corrosion resistance due to road salt in climatic zones of seasonal sub-zero
temperatures for outdoor and indoor use;
- thread design to allow smooth conduction of passenger over comb area;
- wear resistance to keep the comb safety gap;
- wear and dimensional stability (castability) to keep the skirting gap and comb gap
safety function.
It should be noted that the above described embodiments are given for describing
rather than limiting the invention, and it is to be understood that modifications and
variations may be resorted to without departing from the spirit and scope of the invention

considered to be within the scope of the invention and the appended claims. The protection
scope of the invention is defined by the accompanying claims. In addition, any of the
reference numerals in the claims should not be interpreted as a limitation to the claims. Use
of the verb "comprise" and its conjugations does not exclude the presence of elements or
steps other than those stated in a claim. The indefinite article "a" or "an" preceding an
element or step does not exclude the presence of a plurality of such elements or steps.

What is claimed is:
1. An aluminium alloy comprising:
4 to 6 % by weight of magnesium;
0.3 to 0.9 % by weight of ferrum;
0.1 to 0.6 % by weight of manganese; and
0.2 to 2 % by weight of silicon.
2. A mechanical part made from the aluminium alloy according to claim 1.
3. The mechanical part according to claim 2, wherein the mechanical part includes at
least one of:

- an escalator step;
- an auto-walk pallet.

4. Use of the aluminium alloy according to claim 1 in manufacturing a mechanical part.
5. The use of the aluminium alloy according to 4, wherein the mechanical part includes at
least one of:

- an escalator step;
- an auto-walk pallet.