Nissan introduces new 1.2 GPa ultra high tensile strength steel with high formability; reduction in body weight of up to 15 kg
Nissan Motor Co., Ltd., in collaboration with Nippon Steel Corporation and Kobe Steel, Ltd., has developed Ultra High Tensile Strength Steel rated at 1.2 gigapascals (GPa). From 2013, this new, highly formable steel will be produced as steel plates for use in cold pressing structural body parts. To be deployed globally in models across the Nissan lineup, it will reduce vehicle body weight by up to 15 kilograms (33 pounds).
The new Ultra High Tensile Strength Steel will be used for center pillar reinforcements, front and side roof rails and other key structural components. By exceeding the structural body performance of previous materials with less thickness, the new steel will contribute to increased dynamic performance and fuel economy.
The new material will also contribute to lower total costs including that of manufacturing, as superior cold-pressing formability supports mass production.
Nissan says that the new material overcomes significant obstacles. Until now, high tensile strength steel involved a critical trade-off: increased strength came with increased rigidity and a consequent reduction in press formability. Maintaining quality in spot-welding has also been an ongoing challenge. Traditionally, only high tensile steel rated up to 980 megapascals (MPa) can be used in cold pressing structural body parts, requiring complex press work, the company said.
The new 1.2 GPa steel, combined with Nissan-developed advances in welding methodology, overcomes both obstacles.
Development of the new material was realized by a breakthrough in the ability to control its structural formation at the sub-micron level in combining hard and soft layers to achieve both strength and formability.
Once the new material was developed, extensive experimentation was required to develop an optimal spot-welding methodology. This has been achieved with a proprietary process that involves careful optimization of welding pressure, current volume and power distribution.
By adopting the new material to various parts of the vehicle, the new 1.2GPa Ultra High Tensile Strength Steel with High Formability will contribute significantly to overall vehicle weight savings without adding the extra cost required by other lightweight materials, such as aluminum, Nissan said.