WO2002081125A1

WO2002081125A1 - Process, plant and material for producing rims made of an aluminium alloy for vehicles, and rims obtained thereby

Info

Publication number: WO2002081125A1
Application number: PCT/IT2001/000173
Authority: WO
Inventors: Felice Maritano
Original assignee: Alkadia S.R.L.
Priority date: 2001-04-03
Filing date: 2001-04-03
Publication date: 2002-10-17

Abstract

A plant and a process are disclosed for producing rims (1) made of an aluminium alloy for vehicles, through the steps of: providing thixotropic billets made of an aluminium alloy; obtaining crop ends of material by sizing the billets; heating the crop ends between 580 °C and 600 °C in heating furnaces (5); loading the heated crop ends in a die-casting machine (11) for products of the 'Semi Solid Material' type; forming a molding with the die-casting machine (11); extracting the molding; depositing the molding onto a conveyor belt (15); and controlling a quality of the obtained molding, sending then it to mechanical workings and/or an heat treatment; alternatively, previously cooling the molding in a tank (16); and depositing the cooled molding on a shearing die for shearing feedheads and/or risers.

Description

PROCESS, PLANT AND MATERIAL FOR PRODUCING RIMS MADE OF AN ALUMINIUM . ALLOY FOR VEHICLES , AND RIMS OBTAINED THEREBY

The present invention refers to a process and a plant for producing rims made of an aluminium alloy for vehicles, to the material to be used for producing such rims, and to the rims obtained through the above-stated process, plant and material .

In the field of parts made of an aluminium alloy for vehicles, among others, rims for wheels are known in the art and they are the commercial and quality surplus for the most exclusive models of vehicles and they are nowadays becoming more and more requested by the market.

This type of rims has still, however, a high final cost for the end user, due to the very high production costs that current technologies are not able to reduce.

Object of the present invention is solving the above prior-art problems, by providing a rim made of an aluminium alloy for vehicles whose cost is much lower than the current one and that keeps, and preferably highly improves, the quality characteristics of current products.

A further object of the present invention is providing a process and a plant that are adapted to realise a rim as mentioned above and that are such that the end product needs only reduced workings:, this allows simplifying the production processes and highly reducing their costs, obviously at a benefit for the end product.

The above and other objects and advantages of the invention, as will appear from the following- description, are obtained by a process, a plant, a material and an end product as those claimed, respectively, in Claims 1, 9, 23 and 24. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims .

The present invention will be better described by some preferred embodiments thereof, given as a non-limiting example, with reference to the enclosed drawings, in which:

- Figure 1 is a perspective view of a rim for vehicles that can be realised by the present invention; and - Figure 2 is a schematic diagram of the plant adapted to realise the process of the present invention to produce the rim in Fig. 1.

The process .and the plant of the invention will be disclosed hereinbelow in their embodiment that is adapted to produce rims 1 for motor vehicles as shown in Fig. 1. It is obvious that the_ process and the plant could be used, practically without modifications apart from the dimensional ones, for producing rims for motorbykes, trucks, tricars, buses, go-karts and the like.

Fig. 2 is a schematic view of the plant for producing rims 1 for vehicles of the invention; first of all, such plant comprises means 5 for heating the crop ends formed of thixotropic billets made of an aluminium alloy (as can be better seen below) , in which such billets are sized depending on the ratio between weight and size of the rim 1. The means 5 are fed by a loader 4 and heat the crop ends at temperatures included between 580 °C and 600 °C, and in the preferred embodiment of the invention are composed of heating furnaces 5, that in particular are electromagnetic induction furnaces 5 comprising modular stations that are able to be componed. The induction heating furnace guarantees, in addition to keeping the temperature within very restricted tolerances, an energy induction into the billets, which guarantees that a perfect metallographic structure re-forms at an intermediate physical state between the solid state and the liquid state. Therefore, the temperature of the piece is detected by measuring the active power of the induced energy in the material in a predetermined period of time.

The inventive plant further comprises means 9 for loading the heated crop ends in a vessel for further workings, that must have specific characteristics for products of the "Semi Solid Material" (S.S.M.) type; the loading means 9 are composed' of a first handling robot, that is an anthropomorphic robot equipped with a mechanical gripping hand adapted to handle the vessel in which the billets are placed in order to be heated and transported.

The plant then comprises means 11 for forming a molding, which operate with injection steps that are specific of the S.S.M. process; in particular, such means 11 for forming are composed of a die- casting machine, that is equipped with a die 8 adapted to produce rims 1 in S.S.M. The die 8 is lubricated by lubricating means 12 before every injection of metal through a detaching agent.

Preferably, the die-casting machine 11 is equipped with an. injection unit controlled by a closed-loop system, that allows a real-time control of a first .and a second injection steps and of a third gearing step.

With the above-mentioned arrangements, the press with which the die-casting machine 11 is equipped has a very powerful injection system that is able to manage the injection step with a high dynamicity, and a maximum increasing speed of the injection force according to the construction specifications. This is made possible by controlling the injection process through a closed- loop system that allows a real-time control. A high dynamicity is then realised not only as regards the speed, but also for acceleration, braking and repeatability and programmability of the process. The closed loop allows a programmability on at least ten injection variables with 0.1 m/s resolutions. The suitably-adjusted press injects the billet inside the recesses of the die 8.

Further preferably, the lubricating means 12 are composed of a lubricating robot equipped with a lubricating head adapted to spray water, air and a detaching agent onto the die 8; such operation can also be performed through a manual nozzle.

Returning to Fig. 2, the plant of the invention further comprises means 13 for extracting the molding, and means for depositing the molding from the extracting means 13 onto a conveyor belt 15, that are preferably composed of a second handling robot or of extracting means 13 of a manual type.

In a variation of the inventive plant, the means for depositing the molding are replaced by means 16 for previously cooling the molding, and means for depositing the cooled molding onto a shearing die installed on a shearing press 17 for shearing feedheads and/or risers, that are unloaded through unloading means 20.

In particular, the means 16 for previously cooling can be composed of a tank 16 containing heated and heat-adjusted water.

In Fig. 2 a station 26 is further provided for cleaning the vessel prepared when going out of the furnace 5.

Finally, the inventive plant comprises means for controlling the quality of the obtained molding, before sending the molding to downstream mechanical workings and/or an heat treatment. Such means for controlling the quality of the obtained molding are composed of a device 27 for detecting the presence of the molding, a control pulpit 29, control panels 31 for the billet heater, process control panels 33, a control panel 35 of the extractor 13 and a control panel 37 of the conveyor 15 for the finished pieces.

In the above-described plant, the die 8 installed on the press for producing rims 1 is in particular equipped with four carriages for defining a channel of the rim 1 and is equipped with air vents. The die 8 is further equipped with shearing or tearing plates in order to remove the feehead -from the molding, and with internal heat- adjusting channels.

In order to use such a die 8, the plant is further equipped with units 25 for heat-adjusting the die 8 itself, that are composed of a modular system equipped with resistances or gas boilers for heating water or diathermic oil, and with pipings for flowing such water or oil from a pump of the unit inside the heat-adjusting channels of the die The above-described plant is adapted to realise the process for producing rims (1) for vehicles of the invention, which process comprises the steps of:

- providing thixotropic billets made of an aluminium alloy;

- sizing . said billets depending on the ratio between weight and size of the^' rim 1 to be_ produced, thereby obtaining crop ends of material;

- heating the crop ends at temperatures included between 580 °C and 600 °C in heating means 5

(of the modular induction furnaces type) ;

- loading, through loading means 9, the heated crop ends in a vessel for further workings with machines with specific characteristics for products of the "Semi Solid Material"

(S.S.M.) type;

- forming a molding with a die-casting machine 11 with injection steps that are specific of the S.S.M. process;

- extracting the molding through extracting means 13;

- depositing the molding from the extracting means 13 onto a conveyor belt 15; and

- controlling the quality of the obtained molding, and then sending the molding itself to downstream mechanical workings and/or an heat treatment.

Alternatively, the process of the invention can be realised so that the step of depositing the molding is replaced by the steps of: previously cooling the molding in a tank 16 containing heated and heat-adjusted water; and depositing the cooled molding onto a shearing die installed on a shearing press 17 for shearing feedheads and/or risers. In order to allow an optimum use of the above- stated process and plant, it is also necessary to provide a suitable material, that has an innovative composition and concept when is applied to such process and plant. This material allows producing rims 1 in an aluminium alloy for vehicles of the invention and is composed of an aluminium alloy having the following characteristics:

- centesimal chemical composition according to UNI, EN-AB, A 356/357 standardization tables; and - finely-divided, metallographic structure of the globular type, that is a thixotropic structure. The globular microstructure provides the billet with a high fluidodynamic property even with high fractions of matter at a solid state. This allows performing the die- casting process at temperatures that are near the solidification one. The main characteristic of the aluminium alloys that are die-cast with the thixotropic system consists (when they are in a partial solidification phase) in the dreastic reduction of the so-called "casting errors", that are the macro- and micro- cavities from shrinking or gas. The production cycle of a part produced with a thixotropic alloy can have, different results according to the system being used for the mixing action and the degassing system used in the billet-production step. With the above-described process and system, and using the above material, it is possible to realise rims 1 made of an aluminium alloy whose characteristics are equal to or better than those of similar currently-marketed rims.

In particular, the advantages of the die-casting with the S.S.M. process when producing rims 1 for vehicles are as follows: product with high metallurgic and mechanical performance characteristics; innovative solutions that are able to improve the reliability under operating conditions; high health of the part; reduction of scraps; reduction of mechanical workings;

exceptional mechanical characteristics with a possible heat treatment:

• minimum traction strength: 300 mpa

• minimum ultimate tensile strength: 225 mpa

• minimum elongation: 12%

(all the above results being obtained with reference to an A 356.0 alloy).

It is further necessary to point out the positive results due to the S.S.M. process that cannot be directly measured on the product, but are connected thereto, such as for example lower working temperatures that have as a direct consequence energy savings, lower emissions of smokes and powders and consequently better environmental conditions.

Claims

1. Process for producing rims (1) made of an aluminium alloy for vehicles, characterised in that the process comprises the steps of:

- providing thixotropic billets made of an aluminium alloy;

- sizing . said billets depending on a ratio between weight and size of the rim (1) to be_ produced, thereby obtaining crop ends of material;

- heating said crop ends at temperatures included between 580 °C and 600 °C in heating means (5) ;

- loading, through loading means (9), said heated crop ends in a vessel for further workings with machines with specific characteristics for products of the "Semi Solid Material" (S.S.M.) type;

- forming a molding with a die-casting machine (11) with injection steps that are specific of the S.S.M. process;

- extracting the molding through extracting means (13) ;

- depositing the molding from said extracting means (13) onto a conveyor belt (15); and - controlling a quality of the obtained molding, said molding being then sent to downstream mechanical workings and/or an heat treatment.

2. Process according to Claim 1, characterised in that said step of depositing the molding is replaced ,by the steps of: previously cooling the molding in a tank (16) _ containing heated and heat-adjusted water; and

depositing the cooled molding onto a shearing die installed on a shearing press (17) for shearing feedheads and/or risers.

3. Process according to Claim 1, characterised in that said heating means (5) are modular induction furnaces (5) comprising a plurality of sections .

4. Process according to Claim 1, characterised in that said loading means (9) are composed of a first handling robot, said first handling robot being an anthropomorphic robot equipped with a mechanical gripping hand adapted to handle the vessel in which the billets are placed in order to be heated and transported.

5. Process according to Claim 1, characterised in that said die-casting machine (11) is equipped with a die (8) adapted to produce rims (1) in S.S.M., said die (8) being lubricated by lubricating means (12) before every injection of metal through a detaching agent.

6. Process according to Claim 5, characterised in that said die-casting machine (11) is equipped with an injection unit controlled by a closed- loop system, said closed-loop control system allowing a real-time control of a first and a second injection steps and of a third gearing step.

7. Process according to Claim 5, characterised in that said lubricating means (12) are composed of a lubricating robot equipped with a lubricating head adapted to spray water, air and detaching agent onto the die (8) , or through a manual nozzle .

8. Process according to Claim 1, characterised in that said extracting means (13) are composed of a second handling robot, said second handling robot being an anthropomorphic robot equipped with a mechanical gripping hand adapted to handle the moldings composed of raw rims, said extracting means (13) being also able to perform a manual extraction.

9. Plant for producing rims (1) made of an aluminium alloy for vehicles, characterised in that it comprises:

- means (5) for heating crop ends formed of thixotropic billets made of an aluminium alloy, said billets being sized depending on a ratio between weight and size of the rim (1), said means (5) heating said crop ends at temperatures included between 580 °C and 600 °C;

- means (9) for loading said heated crop ends in a vessel for further workings with machines with specific characteristics for products of the "Semi Solid Material" (S.S.M.) type;

- means (11) for forming a molding, said means

(11) operating with injection steps that are specific of the S.S.M. process;

- means (13) for extracting the molding;

- means for depositing the molding from said extracting means (13) onto a conveyor belt (15); and

- means (27, 29, 31, 33, 35, 37) for controlling a quality of the obtained molding, said molding being then sent to downstream mechanical workings and/or an heat treatment.

10. Plant according to Claim 9, characterised in that said means for depositing the molding are replaced by: means (16) for previously cooling the molding; and means for depositing the cooled molding onto a shearing die installed on a shearing press (17) for shearing feedheads and/or risers.

11. Plant according to Claim 9, characterised in that said heating means (5) are composed of electromagnetic induction furnaces (5) comprising modular stations that are able to be componed.

12. Plant according to Claim 9, characterised in that said loading means (9) are composed of a first handling robot, said first handling robot being an anthropomorphic robot equipped with a mechanical gripping hand adapted to handle the vessel in which the billets are placed in order to be heated and transported.

13. Plant according to Claim 9, characterised in that said means (11) for forming are composed of a die-casting machine, said die-casting machine (11) being equipped with a die (8) adapted to produce rims (1) in S.S.M., said die (8) being lubricated by lubricating means (12) before every injection of metal through a detaching agent.

14. Plant according to Claim 13, characterised in that said die-casting machine (11) is equipped with an injection unit controlled by a closed- loop system, said closed-loop control system allowing a real-time control of a first and a second injection steps and of a third gearing step.

15. Plant according to Claim 13, characterised in that said lubricating means (12) are composed of a lubricating robot equipped with a lubricating head adapted to spray water, air and detaching agent onto the die (8), or through a manual nozzle.

16. Plant according to Claim 9, characterised in that said extracting means (13) are composed of a second handling robot, or of manual extracting means .

17. Plant according to Claim 9, characterised in that said means (16) for previously cooling are composed of a tank (16) containing heated and heat-adjusted water.

18. Plant according to Claim 9, characterised in that the die (8) installed on the press for producing rims (1) is equipped with four carriages for defining a channel of the rim (1) and is equipped with air vents.

19. Plant according to Claim 18, characterised in that said die (8) is further equipped with shearing or tearing plates in order to remove the feehead from the molding.

20. Plant according to Claim 18, characterised in that said die (8) is further equipped with internal heat-adjusting channels.

21. Plant according to Claim 9, characterised in that said plant is further equipped with units (25) for heat-adjusting the die (8) .

22. Plant according to Claim 21, characterised in that said heat-adjusting units are a modular system equipped with resistances or gas boilers for heating water or diathermic oil, and with pipings for flowing such water or oil from a pump of the unit inside the heat-adjusting channels of the die (8) .

23. Material for producing rims (1) made of an aluminium alloy for vehicles, characterised in that it is composed of an aluminium alloy having the following characteristics:

- centesimal chemical composition according to UNI, EN-AB, A 356/357 standardization tables; and

- finely-divided, metallographic structure of the globular type, that is a thixotropic structure.

24. Rims (1) made of an aluminium alloy for vehicles, characterised in that they are produced through the process according to any one of Claims 1 to 8, through the plant according to any one of Claims 9 to 22 and using the material according to Claim 23.

25. Rims (1) for vehicles according to Claim 24, characterised in that said vehicles are cars, motor vehicles, trucks, tricars, buses and go- karts .