Nissan Motor Co., Ltd. announced in late 2011 the world’s first* Ultra High Tensile Strength Steel rated at 1.2 gigapascals (GPa) which is highly formable, to the extent that it can be used for cold pressing structural body parts. To be deployed globally in models across the Nissan lineup from 2013, it will reduce vehicle body weight by up to 15 kilograms, representing a significant step in improving environmental impact as well as driving performance.
Developed in collaboration with Nippon Steel Corporation and Kobe Steel, Ltd., 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.
This new breakthrough 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. 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 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, Nissan’s 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.