Manufacturing process for steel components with a bainitic structure
A manufacturing process for steel components with a predominantly bainitic structure is proposed, which avoids the conventionally required long production times and enables large-scale production.
Steel components with a bainitic structure can exhibit a comparatively high tensile strength of more than 1.9 GPa. Consequently, if there are any technical requirements for a steel component, it can be produced with a lower weight. Low-weight components can contribute to the overall mass reduction of products. In case of vehicles this can have a positive impact on the fuel economy. Especially in the automotive industry/sector, the mechanical properties of bainite are desirable for load-bearing and/or safety-relevant applications. The implementation mostly fails due to very complex and time intensive production processes. Typically, up to eight hours of holding time (at the desired conversion temperature) are required for the production of bainite steel. However, this is often not acceptable/economical for mass production of components in the automotive and/or steel industry.
Scientists from the Clausthal University of Technology have developed a novel approach for the production of steel components with comparatively high strengths. At the same time the production times and costs are significantly reduced. The choice of the component blank (with specific austenitization temperature as well as chemical/elemental composition) is on key factor. In a first step, the component blank is cooled to a conversion temperature. The cooling rate is chosen in such a way that the formation of ferrite and perlite is essentially suppressed. The component blank is banitized at a temperature of 300°C with a conversion time of less than two hours. The result is a steel component with at least 80% bainite content and a tensile strength of at least 1.9 GPa. Fig 1a) schematically depicts the production process. According to the present invention, nano-bainite can be produced in less than one hour by continuous cooling and by using a cooling rate of 0.02 Ks-1. This cooling rate can be easily achieved during the production process of steels, e.g. in stacks of large thick products or in a coiled strip. Fig 1b) exemplarily shows a steel with a nano-bainitic structure. In Fig. 2 the stress-strain data are shown for bainitic steels with different chemical compositions and at different bainitization progression.
Fig. 2: Mechanical behavior of bainitic steels with different chemical compositions. Data are shown for different bainitization progression (source: Dr. Mohamed Soliman; adaptation after patent application).
- Conversion time less than two hours
- Steel components with a bainite content of at least 80% and a tensile strength of at least 1.9 GPa
- Significantly reduced bainitization duration enables mass production of steel components
- Reduced energy input
- Reduced production costs
- Structural components of vehicles (e.g. cars, trucks and ships)
- Steel industry
- Rolling bearings
- Plating/armored protection
The manufacturing process has been successfully developed. The strength of the steel components has been experimentally approved.
German patent application granted: DE102012017143B3
Patent holder: Clausthal University of Technology
M. Soliman, H. Palkowski “Development of the low temperature bainite” Archives of Civil and Mechanical Engineering 16 (2016) 403-412. Link to publication
Dr. Mirza Mackovic
Patent Manager Technology
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