Aluminium alloy for structural shaped elements of vehicles and process for manufacturing said elements

Claim 2

Aluminium alloy for shaped elements of vehicles and the like, in particular shaped elements for composite components of motor vehicles, characterized by the following composition (% by weight) : - Si : from 0.25 to 0.35% - Fe : from 0.20 to 0.30% - Mg : from 0.85 to 1.1% - Cu : from 0.10 to 0.25% - Other elements constituting impurities: each below 0.1%, in total below 0.2% - Al : the balance to 100%, said amounts of Mg and Si being present in such a ratio that Mg is in a stoichiometric excess in respect of the compound Mg 2 Si, said excess ranging from 0.25 to 0.67%.

Claim 3

A process for manufacturing shaped elements of vehicles, in particular simple or composite-box-type shaped elements for motor vehicles, such as hoods for motors and for baggage compartments,doors,mudguards,roofs and the like, characterized in that it comprises the following operations : (a) casting a body for plastic working in Al alloy, in the form of a plate or the like, having the following composition (% by weight) : - Si : from 0.25 to 0.35% - Fe : from 0.20 to 0.30% - Mg : from 0.85 to 1.1% - Cu : from 0.10 to 0.25% - Elements representing impurities: each below 0.1%, in total below 0.2%. - Al : the balance to 100%, said Mg and Si aounts being selected in such way that Mg is in a stoichiometric excess with respect to the compound Mg 2 Si, said excess being in the range of from 0.25 to 0.67%; (b) homogenizing of said Al-alloy body at a temperature ranging from 540 to 580°C, for a time of from 8 to 24 hours, followed by quenching; (c) working said body in Al alloy, thus homogenized, to the form of semifinished products such as sheets, structural shapes and the like; (d) solution heat-treatment of said semifinished products at a temperature in the range from 525 to 535°C for a period of time from 5 to 10 minutes, and successive hard enin g of the semifinished products, which are so caused to assume, after 15 days of natural ageing.at room temperature, a yielding strength (RP 0.2) and a modulus of elasticity (E), the values of which are in a ratio to each other (RP0.2/E) that ranges from 1.2×10 -3 to 1.7×10 -3 ; (e)forming of said semifinished products to shaped elements; (f) artificial ageing of said shaped elements to increase their mechanical strength to a level of substantial stability, with a yielding strength Rp0.2 ranging from 165 to 200 N/mm 2 .

Claim 4

A process for manufacturing shaped elements of vehicles, in particular simple or composite-box-type shaped elements for motor vehicles, such as hoods for motors and for baggage compartments,doors,mudguards,roofs and the like, characterized in that it comprises the following operations : (a) casting a body for plastic working in Al alloy, in the form of a plate or the like, having the following composition (% by weight) : - Si : from 0.25 to 0.35% - Fe : from 0.20 to 0.30% - Mg : from 0.85 to 1.1% - Cu : from 0.10 to 0.25% - Elements representing impurities: each below 0.1%, in total below 0.2%. - Al : the balance to 100%, said Mg and Si aounts being selected in such way that Mg is in a stoichiometric excess with respect to the compound Mg 2 Si, said excess being in the range of from 0.25 to 0.67%; (b) homogenizing of said Al-alloy body at a temperature ranging from 540 to 580°C, for a time of from 8 to 24 hours, followed by quenching; (c) working said body in Al alloy, thus homogenized, to the form of semifinished products such as sheets, structural shapes and the like; (d) solution heat-treatment of said semifinished products at a temperature in the range from 525 to 535°C for a period of time from 5 to 10 minutes, and successive hard enin g of the semifinished products, which are so caused to assume, after 15 days of natural ageing.at room temperature, a yielding strength (RP 0.2) and a modulus of elasticity (E), the values of which are in a ratio to each other (RP0.2/E) that ranges from 1.2×10 -3 to 1.7×10 -3 ; (e)forming of said semifinished products to shaped elements; (f) artificial ageing of said shaped elements to increase their mechanical strength to a level of substantial stability, with a yielding strength Rp0.2 ranging from 165 to 200 N/mm 2 .

Claim 5

The process according to claim 2, characterized in that said working (c) includes a rolling which imparts a shape of sheet to said body.

Claim 6

The process according to claim 2, characterized in that said working (c) comprises an extrusion which imparts the form of a structural shape to said body.

Claim 7

The process according to claim 2, characterized in that said artificial ageing (f) is accomplished at a temperature from 180 to 220°C for a time ranging from 30 to 90 minutes.

Claim 8

The process according to claim 2, characterized in that said shaped elements are endowed with a surface coating susceptible of hot hardening, said hardening being accomplished during said artificial ageing (f).

Claim 9

Composite-box-type components of vehicles and the like, in particular composite-box-type components of motor vehicles, such as motor hoods, baggage compartments hoods, doors,mudguards,roofs and the like,characterized in that they comprise at least two shaped elements obtained by the process according to claims 2 to 6.

Claim 10

The Al alloy as claimed in claim 1,' characterized in that it is particularly suitable for manufacturing semifinished products such as sheets and the like, easily and stably shapable in conventional dies as are used for the shaping of steel semifinished articles and the like.