February 16, 2018

New high-strength steels can reduce vehicle emissions

High-performance lightweight materials ideal automotive and other manufacturing industries

One of the most direct and effective ways to improve the fuel efficiency of vehicle – and thereby lower greenhouse gas emissions – is to reduce the vehicle’s weight. However, this can come at the cost of vehicle safety.

For example, every 10 per cent reduction in total vehicle weight achieves an average fuel economy improvement of 4.9 per cent; however, a decrease of 100kg in the weight of a car can also cause a 3–4.5 per cent increase in safety risk.

One way forward is to develop new materials that are lighter and stronger than those they replace. Responding to the needs of vehicle manufacturers, steel makers around the world are developing new advanced high strength steels (AHSSs) that are both lighter and stronger than conventional steel, offering improved fuel efficiency without compromising safety.

According to an environmental case study reported by the World Steel Association, the use of every 1kg of AHSSs in a five-passenger family car could achieve a total life cycle saving of 8kg greenhouse gas, which corresponds to a 5.7 per cent reduction in greenhouse gas emissions over the full life cycle of the vehicle.

In a paper published in the influential journal Progress in Materials Science, “Thermomechanical processing of advanced high strength steels”, University of Wollongong (UOW) researchers Professor Zhengyi Jiang and Dr Jingwei Zhao provide a comprehensive review of the first, second and third generations of AHSSs and also of Nano Hiten steels, another type of high-performance steel used in the automotive industry.

Thermomechanical processing is a metallurgical process that combines mechanical processes (such as forging or rolling) with thermal processes (heat treatment, water quenching, heating and cooling at various rates) into a single process.

Professor Jiang, from UOW’s School of Mechanical, Materials, Mechatronics and Biomedical Engineering, said AHSSs are complex and sophisticated materials, with microstructures that are controlled by precise thermomechanical processing technologies.

“Advanced high strength steels are regarded as the most promising materials for vehicles in the 21st century due to the unique combination of excellent performance and competitive cost,” Professor Jiang said.

“The unique metallurgical properties and processing methods of AHSSs will enable the automotive industry to meet requirements for safety, efficiency, emissions, manufacturability, durability and quality at relatively low cost.”

Professor Jiang said research into the thermomechanical processing of AHSSs in the laboratory was essential for the optimal design of processing conditions by precise control of temperature, strain, strain rate, heat treatment and cooling parameters.

“As each type of AHSS has a unique application in vehicles, specified thermomechanical processing technologies should be developed to produce high quality AHSS products where they might be best employed to meet mechanical property demands for the automotive parts,” he said.

The paper provides a comprehensive review for those who are developing, making, using and designing AHSSs and their thermomechanical processing technologies.

Professor Jiang’s research group is equipped with powerful facilities for the research on steel processing and manufacturing, including Hille 100 rolling mill, rolls cross and shifting system, accelerated ultrafast water-cooling systems and lubricant emulsification machine, and has been conducting research in this area for more than 27 years.

Professor Jiang and Dr Zhao’s research was funded by an Australian Research Council (ARC) Discovery Projects grant, ARC Future Fellowships grants, and by the Baosteel-Australia Joint Research and Development Centre Research and Development Fund.