Structural component of a motor vehicle shell
The invention relates to a method for manufacturing a stamped motor vehicle bodywork or shell-structure component made of an aluminium alloy, comprising the steps of manufacturing a metal sheet or strip with a thickness of 0 to 3.5 mm made of an alloy with the following composition (wt %): Si: 0.60-0.85; Fe: 0.05-0.25; Cu: 0.05-0.30; Mn: 0.05-0.30; Mg: 0.50-0.00; Ti: 0.02-0.15; V: 0.00-0.15; other elements <0.05 each and <0.15 in total, remainder aluminium, with Mg<−2.67×Si+2.87, solution heat treating and quenching, pre-tempering, ageing for 72 hours to 6 months, stamping, tempering at a temperature of around 205° C. with a dwell time of 180 to 480 minutes or tempering at an equivalent time and temperature, painting and “bake hardening” at a temperature of 150 to 190° C. for 15 to 30 min. The invention also relates to a stamped motor vehicle bodywork or shell-structure component, further referred to as “body in white” produced by such a method.
1. A method of manufacturing a stamped body component or bodywork structure, or body in white made of aluminum alloy for absorbing energy irreversibly during an impact, comprising:
manufacturing a sheet or strip of thickness between 1 and 3.5 mm of alloy with composition, comprising as a percentage by weight: Si: 0.60-0.85%; Fe: 0.05-0.25%; Cu: 0.05-0.30%; Mn: 0.05-0.30%; Mg: 0.50-1.00%; Ti: 0.02-0.15%; V: 0.00-0.15% other elements <0.05% each and <0.15% in total, the rest aluminum, with Mg<−2.67×Si+2.87%,
solution heat treating, and quenching
natural aging at room temperature,
forming by press stamping, to obtain a three-dimensional part,
aging the workpiece at a temperature of substantially 205° C. with a holding time of between 180 and 480 minutes, or time-temperature equivalent aging, and
painting and bake hardening at a temperature of 150 to 190° C. for 15 to 30 min.
2. The method according to claim 1 , wherein the holding time at 205° C. is between 240 and 480 minutes or at equivalent time-temperature.
3. The method according to claim 1 , wherein the Si content of the sheet or strip is between 0.60% and 0.75%.
4. The method according to claim 1 , wherein the Fe content of the sheet or strip is between 0.05% and 0.20%.
5. The method according to claim 1 , wherein the Cu content of the sheet or strip is at most 0.20%.
6. The method according to claim 1 wherein the Mn content of the sheet or strip is between 0.10% and 0.15%.
7. The method according to claim 1 , wherein the Mg content of the sheet or strip is between 0.60% and 0.70%.
8. The method according to claim 1 , wherein the Ti content of the sheet or strip is between 0.03% and 0.10%.
9. The method according to claim 1 wherein the V content of the sheet or strip is between 0.05% and 0.10%.
10. The method according to claim 1 wherein the manufacturing of the sheet or strip before stamping comprises:
casting typically vertical semi-continuous casting of a rolling ingot and its scalping,
homogenizing of this rolling ingot at a temperature of 530 to 570° C. with a holding between 2 and 12 hours,
hot rolling of the rolling ingot into a strip of thickness between 3.5 and 10 mm,
cold rolling down to final thickness.
11. A stamped bodywork component or automotive bodywork structure or body in white, produced by a method according to claim 1 , wherein a tensile yield strength thereof, determined according to standard NF EN ISO 6892-1, is ≥260 MPa.
12. A stamped bodywork component or automotive bodywork structure, or body in white, produced by a method according to claim 1 wherein a three point folding angle αnorm thereof, determined according to standard NF EN ISO7438 and procedures VDA 238-100 and VDA 239-200, is at least 90°.
13. A stamped bodywork component or automotive bodywork structure or body in white, according to claim 11 , which is chosen from the group comprising lining or reinforcement for a door, hood, trunk lid, roof, or spars, walls, load floors, tunnels and front, middle and rear feet or uprights, or shock absorbers or crashboxes.
14. The method according to claim 1 , further comprising pre-aging at a temperature generally between 50 and 100° C. for a period of at least 12 hours after quenching and before natural aging.
15. The method according to claim 14 , wherein the pre-aging is obtained by coiling at a temperature of at least 60° C. followed by cooling in the open air.
16. The method according to claim 1 , wherein the painting and bake hardening is at a temperature of 170 to 190° C. for 15 to 30 min.
17. The method according to claim 10 , wherein the homogenizing of the rolling ingot is at a temperature of 530 to 570° C. with a holding between 4 and 6 hours.
18. The method according to claim 1 , wherein the time-temperature equivalent aging is according to the equation,
∫
0
t
exp
(
-
Q
RT
)
dt
=
∫
0
teq
exp
(
-
Q
RTeq
)
dt
where Q is substantially 82915 J, where T is the instantaneous temperature expressed in Kelvin which changes with time t, and T eq is the reference temperature of 205° C. (478 K), and teq is the equivalent time.
19. The method according to claim 1 , wherein the Cu content of the sheet or strip is between 0.08% and 0.15%.
20. The method according to claim 1 , wherein natural aging at room temperature is between 72 hours and 6 months.