Quenching and Partitioning Process Development to Replace Hot Stamping of High Strength Automotive Steel
- Colorado School of Mines, Golden, CO (United States)
The present project investigated Quenching and Partitioning (Q&P) to process cold rolled steels to develop high strength sheet steels that exhibit superior ductility compared to available grades with the intent to allow forming of high strength parts at room temperature to provide an alternative to hot stamping of parts. Hot stamping of boron alloyed steel is the current technology to manufacture thinner gauge sections in automotive structures to guarantee anti-intrusion during collisions whilst improving fuel efficiency by decreasing vehicle weight. Hot stamping involves reheating steel to 900 °C or higher followed by deformation and quenching in the die to produce ultra-high strength materials. Hot stamping requires significant energy to reheat the steel and is less productive than traditional room temperature stamping operations. Stamping at elevated temperature was developed due to the lack of available steels with strength levels of interest possessing sufficient ductility enabling traditional room temperature forming. This process is seeing growing demand within the automotive industry and, given the reheating step in this operation, increased energy consumption during part manufacturing results. The present research program focused on the development of steel grades via Q&P processing that exhibit high strength and formability enabling room temperature forming to replace hot stamping. The main project objective consisted of developing sheet steels exhibiting minimum ultimate tensile strength levels of 1200 MPa in combination with minimum tensile elongation levels of 15 pct using Q&P processing through judicious alloy design and heat treating parameter definition. In addition, detailed microstructural characterization and study of properties, processing and microstructure interrelationships were pursued to develop strategies to further enhance tensile properties. In order to accomplish these objectives, alloy design was conducted towards achieving the target properties. Twelve alloys were designed and laboratory produced involving melting, alloying, casting, hot rolling, and cold rolling to obtain sheet steels of approximately 1 mm thickness. Q&P processing of the samples was then conducted. Target properties were achieved and substantially exceeded demonstrating success in the developed and employed alloy design approaches. The best combinations of tensile properties were found at approximately 1550 MPa with a total elongation in excess of 20 pct clearly showing the potential for replacement of hot stamping to produce advanced high strength steels.
- Research Organization:
- Colorado School of Mines, Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office
- DOE Contract Number:
- EE0005765
- OSTI ID:
- 1419775
- Report Number(s):
- DOE-Mines-0005765
- Country of Publication:
- United States
- Language:
- English
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