Volkswagen Replaces Aluminum With Steel To Save Weight And Money

Bertel Schmitt
by Bertel Schmitt

Here is today’s other baffling science story: In its quest to save weight, Volkswagen is ripping aluminum out of plans and bills-of–material, to replace it – with steel. Not good old steel. They replace it with much better new steel. According to Reuters, “Volkswagen AG is using new high-strength steel to make cars lighter and comply with strict emissions rules, confounding forecasts that aluminum would be the metal of choice for reducing weight.”

High tensile steel is up to six times stronger than conventional steel, and helped Volkswagen reduce the new Golf’s weight by about 100 kg, while also saving money. “Aluminum is about a third of the weight of conventional steel but costs three times as much,” says Reuters (let them answer the fuming mails by irate nerds who insist that such a statement is utter nonsense.)

“Volkswagen is using high-strength steels in increasing amounts. It is a very cost effective way of reducing weight,” Armin Plath, VW’s head of materials research and manufacturing, told Reuters in an interview. “Using new innovations in steel engineering… it is possible to reduce weight without the use for more costly materials such as aluminum and carbon fiber.” Volkswagen uses hot formed advanced high strength and ultra-high-strength steel. Other companies also increasingly use these materials.

However, Volkswagen may have to change its mind after all. Said Plath:

“If you now want to go beyond what is currently achievable, then maybe it will be required to use other materials such as aluminum and fiber re-enforced plastics.”

Bertel Schmitt
Bertel Schmitt

Bertel Schmitt comes back to journalism after taking a 35 year break in advertising and marketing. He ran and owned advertising agencies in Duesseldorf, Germany, and New York City. Volkswagen A.G. was Bertel's most important corporate account. Schmitt's advertising and marketing career touched many corners of the industry with a special focus on automotive products and services. Since 2004, he lives in Japan and China with his wife <a href="http://www.tomokoandbertel.com"> Tomoko </a>. Bertel Schmitt is a founding board member of the <a href="http://www.offshoresuperseries.com"> Offshore Super Series </a>, an American offshore powerboat racing organization. He is co-owner of the racing team Typhoon.

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  • Thornmark Thornmark on Jan 25, 2013

    Seems Honda did this with the new Accord: "High-Strength Steel The 2013 Accord unit-body uses 55.8-percent high-tensile steel, more than in any previous Accord. In addition, 17.2-percent of the steel is now grade 780, 980 and 1,500 – extremely high grades that have never before been used in any Accord. This contributes to higher body rigidity and reduced weight, which directly benefits ride and handling, interior quietness, performance and efficiency and long-term durability. The measured improvements in rigidity are significant. In static tests, bending rigidity is up 34 percent and torsional rigidity is up 42-percent compared to the previous-generation Accord. In dynamic tests, front lateral rigidity is up 16 percent and rear vertical rigidity is up 39-percent." http://www.hondanews.com/channels/honda-automobiles/releases/2013-honda-accord-body

  • Zackman Zackman on Jan 25, 2013

    Man, just when Morgan had wood perfected!

    • Morea Morea on Jan 25, 2013

      And the C6 Corvette has balsa wood in its floor pan as a noise deadener!

  • Morea Morea on Jan 25, 2013

    Another significant point is the number of different materials used in the body. If each color in the above figure represents a different metal and/or forming process then it becomes clear how highly engineered the frame really is. (Also nice to see the TTAC B&B has a good share of engineers and metallurgists!)

  • DannyEQS DannyEQS on Jan 26, 2013

    The choice of aluminum vs steel depends on many aspects of the part, the process, and the application. First, some general parameters. A typical Body in White (BIW) has on the order of 250 individual stamped parts. A steel-intensive BIW will weigh about 1000 pounds, and probably less. There are dozens of different grades used throughout the BIW, ranging from the lower strength 18,000 pounds per square inch (18,000 psi = 18 ksi = 125 MPa) to 10x that strength. The lowest strength steel is typically found on fenders which have a relatively complex shape. The highest strength steels are associated with components involved in crash protection. Skin panels are around 0.75mm thick (0.03 inch), while the structural components are up to 2.5mm (0.10 inch). The body style of a steel-intensive vehicle is usually a monocoque or unibody construction, which makes extensive use of stamped components. Unibody construction techniques cab be applied to aluminum-intensive vehicles, or a space-frame construction may be chosen. A space-frame will make much greater use of aluminum extrusions, and would have stamped aluminum sheets only for hang-on panels. The discussion below applies primarily to stamped components. Aluminum is 1/3 the density of steel. Meaning that an identical part made of aluminum will be 1/3 the weight of an identical part made of steel. But... aluminum has 1/3 the elastic modulus of steel. This means that for a given shape, aluminum is 1/3 as stiff as steel, and that aluminum has 3x more springback than steel. (Springback is a measure of how well the stamped part stays in the desired shape.) Because aluminum is 1/3 as stiff as steel, it is necessary to increase the thickness of the aluminum version of the part in question. So what might be 1.8 mm in steel needs to be 2.2 mm in aluminum (as an example - the part functional requirements determines the necessary thickness increase.) Even with this increased thickness, the aluminum part will likely weigh less than a comparable steel part. But...On a per-pound basis, sheet aluminum is more expensive than sheet steel. For a given part, there is usually a cost-advantage for steel. This gets magnified because the steels that are available today have a much better balance of strength vs formability, meaning that they are higher strength yet can be formed to the desired shape. What this translates to is that what needed to be 1.8 mm made from previous generations of steel can now be made from 1.4 mm. The higher strength balances out the lower thickness. Of course, there is a cost premium for these steels on a per-pound basis, but since the part is now made from thinner steel, it is not necessary to buy as much. This minimizes the financial impact. Now consider the amount of sheet metal thrown away. About half of the sheet metal purchased for a vehicle makes it on to the final product – and not because there is anything wrong with the quality. In the forming process, it is necessary to have additional metal around the perimeter of most parts to control the metal flow. This is called the binder and addendum. Although this metal is necessary to form the panel, it gets trimmed off the final product and winds up in the scrap chute. Then there is what is called “engineered scrap”. Think about the window opening area in a door. That area gets cut out in the final product. For every vehicle, there is on the order of 500 to 1000 pounds of scrap produced. If it is steel scrap, it can be bundled together and recycled. Multiple grades of steel can be mixed together and recycled with no constraints. However, the situation is different with aluminum. There are primarily 2 families of aluminum grades used in automotive construction – the 5XXX series and the 6XXX series. In general, the 5XXX series has higher strength while the 6XXX series has greater formability. Unfortunately, the elements that give 5XXX the higher strength are detrimental to the properties of 6XXX alloys. This means that instead of a manufacturing facility having one common scrap conveyer system (like that has been used for steel), if that facility will make aluminum-intensive vehicles, the scrap needs to be segregated. Of course it's possible to do so, but this comes at a cost to the facility. What about an actual assembled vehicle? Somehow, the parts need to be attached to each other. For steel, resistance spot welding has been used for many years. RSW of sheet aluminum is much more challenging - the electrical resistance of aluminum is much lower than steel (meaning it's a better conductor), and there is a thin layer of aluminum oxide on the sheet surface that must be accounted for. So to get around these hurdles, a different approach is used all together - self piercing rivets is a common approach. In sufficient volumes, this could come close to being the same per-vehicle cost as spot welding. Aren't there aluminum-intensive vehicles on the road now? Of course. But look at the nameplates. They are probably the vehicles that are not what most would call mass-market. Because these vehicles cost more, it is easier for the manufacturer to recoup the additional manufacturing cost. As the selling price decreases, it becomes more challenging to get it to be cost-neutral. That is, unless the cost equation changes. And that's where fuel economy and CO2 comes into play. If the BIW can be made lighter, then there can be a reduction in the engine/powertrain which can lead to further reductions in the vehicle weight. These reductions are needed for automakers to meet the current and future CAFE / emissions requirements. While the lighter weight is great for meeting these constraints, remember that the automaker needs to also meet safety/crash requirements. For that, strength and stiffness are critically important. Every automaker will balance these requirements with the lowest manufacturing cost. Some companies will stay with steel-intensive vehicles (but make use of higher strength grades), some companies will incorporate as much aluminum (and other lighter-weight metals like magnesium) as possible, and others will expand their use of carbon fiber and other composites. But one thing is certain... every company will need to make significant changes in their parts, processes, and products to accommodate the regulations. Thanks for reading through this - it turned out much longer than I thought it would be. -Danny www.EQSgroup.com www.Learning4M.com

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