Materials - BMW F11 Service Training

F11￿Body.
2.￿Body.
Highlights
• Cast￿aluminum￿suspension￿strut￿dome
• High￿percentage￿of￿multi-phase￿steels￿(20%￿of￿weight￿of￿body￿skeleton).
• High￿percentage￿of￿hot￿formed￿steels￿(9￿%￿of￿weight￿of￿body￿skeleton).
The￿load-optimized￿component￿design￿of￿the￿cast￿aluminum￿suspension￿strut￿domes￿reinforces
the￿front￿end.￿In￿comparison￿to￿conventional￿steel￿shell￿design,￿the￿compact￿design￿has￿significantly
reduced￿the￿space￿requirements￿and￿decreased￿the￿weight￿in￿the￿front￿end.￿This￿has￿led,￿among￿other
things,￿to￿more￿uniform￿axle￿load￿distribution.
The￿high￿strength￿multi-phase￿steels￿and￿high￿strength￿hot￿formed￿steels￿ensure￿low￿weight￿while
providing￿maximum￿strength￿for￿the￿passenger￿safety￿cell￿thus￿contributing￿to￿the￿passive￿safety￿to￿a
high￿degree.
An￿innovative￿advancement￿in￿the￿form￿of￿passive￿corrosion￿protection￿is￿used￿on￿the￿hot￿formed
steels.￿Until￿now￿suitable￿hot￿formed￿sheet￿metal￿materials￿with￿cathodic￿corrosion￿protection￿were
not￿available￿on￿the￿market.￿Development￿of￿press￿hardening￿technology￿has￿provided￿a￿mass
production￿process￿for￿production￿of￿galvanized,￿hot￿formed￿components.
With￿this￿process￿galvanized￿sheet￿metal￿is￿first￿cold￿formed￿and￿then￿heated￿to￿a￿temperature￿of
approx.￿900￿°C.￿Immediately￿thereafter￿the￿components￿are￿cooled￿down￿to￿approx.￿70°C￿within
seconds￿directly￿in￿the￿water￿cooled￿pressing￿tools,￿hardening￿the￿components.￿This￿process
produces￿components￿with￿a￿minimum￿yield￿strength￿significantly￿greater￿than￿1000￿MPa.
Components￿produced￿in￿this￿manner￿can￿be￿used￿in￿wet￿areas￿without￿any￿corrosion￿to￿the￿base
material.￿Additional￿corrosion￿protection￿measures￿are￿eliminated￿for￿such￿steel.
2.1.2.￿Materials
Modern￿automotive￿bodies￿must￿satisfy￿many￿requirements.￿In￿spite￿of￿minimum￿outer￿dimensions
they￿must￿provide￿the￿largest￿possible￿interior￿space.￿Passengers￿must￿be￿protected￿optimally￿against
injury￿in￿the￿event￿of￿an￿accident.￿The￿torque￿generated￿by￿all￿assemblies￿such￿as￿the￿engine￿and
transmission￿is￿supported￿by￿the￿body.￿Moreover￿the￿body￿must￿provide￿high￿static￿and,￿above￿all,
dynamic￿rigidity￿to￿guarantee￿the￿exceptional￿driving￿characteristics￿typical￿for￿BMW.
Last,￿but￿not￿least,￿the￿supporting￿structure￿of￿the￿vehicle￿must￿have￿high￿fatigue￿strength￿and￿be
capable￿of￿repair￿at￿reasonable￿expense￿in￿the￿event￿of￿an￿accident.
To￿satisfy￿all￿of￿these￿requirements￿optimally,￿BMW￿pursues￿a￿strategy￿of￿producing￿every￿component
using￿the￿material￿best￿suited￿for￿the￿specific￿function.
The￿two￿terms,￿aluminum￿and￿steel,￿are￿only￿the￿generic￿terms￿for￿a￿variety￿of￿alloys￿with￿highly
differing￿properties.
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