Page 47 - MetalForming January 2020

Fig. 2—This image of a B-pillar inner rein- forcement, formed from a tailor rolled blank, shows regions of differing thick- nesses. When extricating vehicle-crash victims, rescue crews must know which areas are easiest to cut. These areas dif- fer with various vehicle models.
able-thickness blanks allow OEMs to control thickness profiles in the formed components to optimize crash response (Fig. 2). First responders must know vehi- cle-specific designs to ensure targeting of the thinnest areas when cutting.
The instrument-panel structure in an increasing number of vehicles is made from a magnesium alloy, which allows for significant weight reduction. Magnesium may fracture into pieces when stressed by direct contact from rescue tools, with shards flying near the pinned occupants. Different prac- tices are needed to extricate occupants pinned by the structure.
Accident Repair
Fortunately, most accidents do not require first responders. But different techniques may be needed to repair parts made from newer steel grades. AHSS get their properties from a microstructure produced after a tightly specified thermal cycle. In moderately severe accidents, standard practice had been to flame-straighten certain parts such as rails. Automakers publish man- uals for each vehicle stating required repair procedures, and in some cases forbid the use of previously common practices. To avoid using heat, large
vehicle sections now may require replacement at factory-engineered locations, rather than repair of a small- er section surrounding the local dam- age. Remember that welding changes the local microstructure and, therefore, the local properties.
The increasing use of aluminum alloys also promotes downstream changes. Repair shops have incurred significant costs to become certified locations. The certification process typ- ically required them to separate steel- panel repairs from repairs performed on aluminum due to the cross-conta- mination risk of corrosion (aluminum does not rust, but it can corrode). In addition to performing repairs in sep- arate areas, shops needed to purchase duplicate sets of tools to ensure that no one tool would be used on both types of metal. Fortunately, recent stud- ies have shown that repair costs are comparable, at least partially due to components that have been designed
with repairability in mind.
The presence of aluminum also
affects scrap handling, as magnets no longer are useful. Aluminum has a much higher scrap value than steel, though only realized only after segre- gating the different alloys. The alloy used for beverage-can bodies (3XXX series) is not used to produce automo- tive stampings. Automotive aluminum parts stamped at room temperature are made from 5XXX- and 6XXX-series alloys, with segregation of their scrap streams critical in maintaining their scrap value.
Hear Danny Schaeffler’s presenta- tion, The Role of Engineered Lubricants in Advanced Automotive Body Structure Construction, at the Lubrication Tech- nology for Metal Formers and Die Shops event, sponsored by MetalForming mag- azine and held in Novi, MI, February 12-13. For more, visit www.metalform- ingmagazine.com/lubetech. MF
The Science of Forming
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Transition zone 1.8 mm
Transition zone
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