Steel-technology development specialist NanoSteel is expanding its customer base for the new advanced high-strength alloys currently undergoing testing by OEMs and Tier 1s, as global automotive demand for stronger, lighter vehicle structures increases.
The Rhode Island-based company, which emerged on the auto-steel scene 12 years ago, also is working with additional steel mills to produce the AHSS sheet, according to David Paratore, CEO and President.
Last spring, NanoSteel delivered its first production-scale AHSS to GM and other OEMs for initial evaluations. (GM Ventures, the automaker's venture-capital arm, is a lead shareholder.) Joint development partner AK Steel was the first steel producer to manufacture this AHSS using traditional slab casting.
NanoSteel metallurgists delivered the breakthroughs necessary to enable the slab casting process in early 2014. The technique typically uses 8- to 10-in (203- to 254-mm) thick steel slabs to produce automotive sheet, Paratore explained to Automotive Engineering.
Since then, the two companies have been overcoming hurdles to commercialize the product. In Paratore’s words, NanoSteel is now focused on execution, not technology.
“We needed to pay our dues, so to speak,” he said. “We went through all the ups and downs that come with taking a new material from the lab to commercial scale, but we’re over those hurdles now. And we’re pretty confident we could produce the material on a regular basis.”
One of those hurdles was designing an alloy that could create the desired microstructures at much slower cooling rates. “Originally, our materials needed to rapidly solidify,” Paratore noted. “One of the major breakthroughs that we needed was to make our materials resilient to cooling rate. Now we can withstand the cooling rate that is natural in a 10-in-thick piece of steel.”
Another challenge was narrowing the initial liquid-to-solid temperature gap. “Our alloys typically had a very large gap between the two, around 150 to 170°C," he said. "That much energy had to be pulled out during the solidification during the casting process, which was too much. So we had to design an alloy that also shrunk that gap to a reasonable number for steel mills’ equipment.”
NanoSteel now affectionately refers to its materials as LGs, for “low gaps.” Refinements have also resulted in “substantially” improved properties and enhanced lightweighting capability, said Paratore.
Tensile strength of the material supplied to GM is approximately 1200 MPa and ductility is measured as 50% elongation. The company has “quite a few [other] alloys already designed and ‘sitting on the shelf,’” Paratore revealed. He said the next product will most likely be higher strength but sacrifice some ductility—for example, in the range of 1500 MPa and 30% elongation.
NanoSteel is marketing its AHSS as being both easy to produce and to work. Production involves conventional alloying elements with standard slab casting equipment. Stamping and forming of parts is done at room temperature without additional manufacturing infrastructure or investment, such as that required for ‘hot’ stamped parts, he claimed.
“Our intent is to be able to produce our steels in all the major processes for automotive—electric arc furnace (EAF) and blast furnace in the creation of the actual melt,” Paratore said. Thin slabs—less than 5 in (127 mm) thick—is another goal.
“Those are the other pieces of this puzzle that we want to move along simultaneously," he asserted, "because one of the fundamentals to NanoSteel’s business model is global availability.”