Alongside suppliers of metals, plastics, reinforced carbon fiber and composites, vehicle designers race to comply with global fuel economy mandates

December 2016 - Automakers continuously evolve the way they specify, test, validate and source materials and work them into a complex design and production system. As the deadlines approach to comply with standards on reducing greenhouse gas emissions and improving fuel economy across the spectrum of passenger vehicles, OEMs and their suppliers have become ever more integrated in their mutual desire to deliver the best product at the best value.

Modern Metals reviewed the efforts of a handful of materials manufacturers and two major automotive customers to highlight developments that will dominate the market from now through the next decade. 

Steel grades

In early November, ArcelorMittal introduced a second generation of advanced high-strength steels (AHSS). It launched new press hardenable steels (PHS) Ductibor 1000 and Usibor 2000; and martensitic steels MartINsite M1700 and M2000. The company is also preparing to expand its family of third-generation AHSS (which today includes Fortiform 1050 in Europe) starting in 2017. Together, these grades help automakers further reduce body-in-white weight to improve fuel economy without compromising vehicle safety or performance.

Brian Aranha, executive vice president- global automotive for ArcelorMittal, says that samples of Ductibor 1000 are available to North American customers for qualification testing. Typical applications include energy absorption parts such as front and rear rails and lower B-pillars.

Usibor 2000, an aluminum-silicon coated PHS, enables automakers to fabricate parts with complicated geometry at a very high strength without formability or springback challenges. Typical applications include strength-critical passenger compartment parts such as rockers, pillars, roof rails and cross members. Commercial production of Usibor 2000 in North America will begin in late summer 2017.

“Looking ahead, the scope of hot stamping products in vehicles will continue to increase with the release of more advanced products like Usibor 2000, which offers 10 to 15 percent weight savings when compared to existing hot stamping solutions,” Aranha says.

Compatible with standard press hardening technologies and processes, combining Usibor 2000 with Ductibor 1000 or other PHS into laser-welded blanks offers weight savings, improved crash behavior and cost savings through material and manufacturing optimization, according to the steelmaker.

The new MartINsite products work for “anti-intrusion parts such as bumper and door beams,” explains Aranha. M1700 and M2000 will be available for OEM qualifications by mid-2017 and ready for commercial production in early 2018.

ArcelorMittal is also investing in AM/NS Calvert, its Alabama joint venture with Nippon Steel and Sumitomo Metals Corp., to produce high formability, cold-stamping steels. These have strengths similar to the strongest dual-phase steels, but with higher ductility and cold formability.

ArcelorMittal will produce cold-rolled and galvanized/galvannealed versions of HF 980 and HF 1180 in North America, targeting OEM qualifications by mid-2017. Commercial production, beginning with the cold-rolled grades, will occur in late 2017. HF grades are suited for components limited by energy absorption, such as front and rear rails and upper motor compartment rails.

AK Steel Holding Corp., Middletown, Ohio, is innovating as well with the introduction of NexMet. CEO Roger K. Newport says this family of products is designed to enable AK’s automotive customers to meet current and future CAFE standards. NexMet 440EX is an exposed surface quality product combining high yield and tensile strength at thinner gauges to facilitate lightweight automotive designs. 440EX is meant for applications where appearance and dent resistance are critical, such as on the exposed panels of cars and trucks. NexMet 1000 and NexMet 1200 will be available for customer qualifications in early 2017.

After its success with aluminum in its F-150, Ford Motor Co.’s 2017 Super Duty pickup trucks are now built with an aluminum body. Novelis supplies sheet for it.

AK Steel this year upgraded its hot-dip galvanizing line at Dearborn Works in Michigan, opened a research and innovation center and expanded its R&D workforce by 35 percent, Newport told investors in an earnings call.

Kirk W. Reich, AK Steel’s senior vice president of manufacturing, says the NexMet grades “allow us to nearly double the elongation of the product for the same strength level. We’ll be providing samples early next year.”

New automotive grades provide the company with “a platform for growth [and help to] fight the intrusion of aluminum and other products,” Reich says. “These products do the lightweighting that aluminum has been touted to do and are in the same neighborhood as the amount of lightweighting that we get [but] for a much better cost.”

In addition, automakers don’t have to switch stamping machinery from one material to another. 

Nucor Corp. has broken ground on a $230 million cold mill complex in Arkansas, with annual rolling capacity of 500,000 tons. It should open in late 2018. “This supports our strategy of moving up the value chain and growing our participation in the automotive market,” Chairman, President and CEO John Ferriola told investors in late October. “The mill will allow us to cold reduce to both lighter gauge and much higher strength levels, to meet our customers’ lightweighting goals.”

The Specialty Cold Mill Complex will also broaden the automotive capability of Nucor’s galvanizing lines at its Alabama and South Carolina sheet mills. The joint venture agreement Nucor inked with JFE Steel of Japan, says Ferriola, “will finally put to bed this argument about whether or not automotive-grade steel can be made in an electric-arc furnace shop.”

Aluminum grades

Constellium N.V. in October opened a €180 million finishing line at its plant in Neuf-Brisach, France, to supply up to 100,000 tons of automotive body sheet. 

The line features high-speed thermal treatment, precise temperature control, highly efficient quench hardening as well as greater flexibility on the thickness of processed alloys. These  technologies will enable Constellium to manufacture products for automotive closure inners, outers and body-in-white. The line is in the final stage of the qualification phase and has already started commercial production.

On the heels of launching a new plant in Bowling Green, Kentucky, with its joint venture partner UACJ Corp., Constellium’s finishing line in France “is another critical step in the execution of our worldwide automotive growth strategy,” CEO Jean-Marc Germain stated.

In Europe, stricter regulation of vehicles’ CO2 emissions have resulted in greater demand for aluminum. With the rising importance of lightweighting, aluminim automotive body sheet volumes are expected to reach 700,000 tons in 2020, up from 230,000 tons in 2012, according to Constellium.

The 2016 Cadillac ATS-V coupe has a strong yet light architecture using ultra-high-strength steel and aluminum, plus carbon fiber for the hood.

Meanwhile, Novelis is celebrating the penetration it’s made into the bodies and structures of luxury vehicles. The company’s efforts are personified in models from Cadillac, BMW, Mercedes and Jaguar/Land Rover; and with its development of Advanz Fusion e200 products, which combines high formability with hemming performance. The achieved draw depth with Fusion e200 exceeds other 6000 series alloys and can make bending radii smaller than 0.2 mm after a 15 percent pre-strain, according to Don Whitacre, senior technical development manager for Novelis North America.

The company commissioned a third automotive finishing line in Oswego, New York, this past May. Spending $120 million, Novelis expanded its supply of high-strength aluminum alloy for Ford Motor Co.’s F-Series trucks.

“Automakers are seeking alternative materials to cut vehicle weight while maintaining strength and safety requirements,” Novelis President and CEO Steve Fisher stated during the commissioning. That line rolls aluminum sheet for the body and cargo box of the 2017 F-Series Super Duty lineup, helping to reduce overall vehicle weight by up to 350 pounds.

“Aluminum is favored among designers and engineers to help meet 2025 fuel economy standards. Aluminum achieves a 40 percent body mass reduction and 12 percent reduction in curb weight,” Matthias Kapp, engineering manager-automotive, for Sapa Extrusions North America, said during the Global Automotive Lightweighting Materials (GALM) conference, held in Detroit in August. 

Carmakers are now applying the material to electric vehicles, he adds. In a comparison, “the EV steel car had a 375 kg body weight and the EV aluminum car body mass was 213 kg—43 percent lower.” Further, aluminum used in a battery pack saved 11 percent compared with a battery featuring steel parts.

Sapa Group makes strong, lightweight extrusions starting with the right melting process, the right casting technology and by being able to optimize the billet, says Kapp. “We focused on crash properties, elongation and strength.”

The company is also working with customers to devise standards for bend tests with extrusions, similar to tests used for sheet products.

Research and testing

General Motors Co. and Ford Motor Co. are among the global carmakers that have carefully assessed the materials strategy they need to meet European, North American and other international standards to reduce emissions and boost mileage per gallon in the next decade.

Curt D. Horvath, technical fellow for GM, speaking at the GALM conference, showed tables comparing strength-to-weight ratios for different steel and aluminum grades, stiffness-to-weight ratios and ductility.

GM’s goal “is to optimize the application of materials” and employ a mixed material strategy that includes advanced and ultra-high-strength steels, aluminum sheet, castings and extrusions, Horvath said.

In modeling new vehicles with structure integration CAE simulation tools, GM spent more than 50 million computational hours on designing the stiffer and lighter Cadillac CT6, more than 10 million computation hours on the Chevrolet Malibu and over 9 million computational hours on the Chevrolet Camaro. As a result, the Malibu consumes a variety of steel grades and the CT6 consumes 13 different materials. The luxury model features an aluminum-intensive structure, advanced- and ultra-high-strength steels and multiple joining methods, said Horvath. 

The Malibu and Camaro shed 300 and pounds, respectively, and the Cadillac XT5 is nearly 280 pounds lighter than the current SRX. Six models shed a combined 2,400 pounds, potentially saving 15 million gallons of fuel and reducing carbon dioxide emissions by 137,000 metric tons, per year, according to Horvath. Separately, GM is also validating material models for crash simulation of carbon fiber composite structures.

With the goal of lightweighting the chassis, Ford has been developing both a magnesium and a carbon fiber composite subframe, according to a GALM presentation by Xiaoming Chen, John Uicker and David Wagner. A CAE-driven design on the magnesium subframe so far meets all stiffness, durability and strength requirements. The prototype produced by Ford saved 30 percent off the weight of the existing subframe. Ford will next conduct testing for corrosion mitigation, component strength and fatigue, bolt loads and others. The carbon fiber composite rear subframe saves 43 percent of the weight of the previous model. Working with Cosma International and Magna Exteriors, Ford is assured that high-volume CF production is feasible but further tests and investigation are needed. 

These are just some of the parts and components undergoing tests, including  joining methods such as welding and adhesives; for strength and ductility through a wide variety of forming processes; for load capacity; and more.

Under every feasible simulation, total cost and value are being compared, and every material producer is working to commercialize and scale up their ability to meet mass production targets. 

The U.S. Environmental Protection Agency reported that about 3.5 percent of projected model-year 2016 production could meet the 2025 CO2 emissions targets but those comprise solely hybrids, plug-in hybrids, electric vehicles and hydrogen fuel cell vehicles. 

“Since the 2025 standards are nearly a decade away, there’s considerable time for continued improvements in gasoline[-powered] vehicle technology to occur,” the agency stated. The thoughtful and considered race to the finish line should benefit the automakers, their suppliers and especially the health of the planet. MM