9th ECCC European Continuous Casting Conference – ECCC 2017

The demands for AHSS have gradually increased due to their ability to reduce vehicle weight as a means to save energy, and to reduce the environmental impact. However, the successful design of AHSS often require the addition of large amounts of alloying elements such as aluminum, which make it difficult to cast sound slabs without surface defects. When casting high aluminum AHSS, due to the reaction between aluminum in steel and silica in mold flux, the viscosity and crystallization characteristics of the mold slag changes drastically, and deteriorates mold lubrication. Therefore, it is critical to limit the reaction between Al in steel and mold slag and at the same time to provide consistent and adequate mold slag in-use properties. This study will describes two possible countermeasures for successful casting of high aluminum AHSS. Firstly, an innovative continuous casting process based on molten mold flux feeding technology will be introduced. In this process, molten mold flux is fed into the casting mold to enhance the thermal insulation of the meniscus and, hence, the lubrication between the solidifying steel shell and the copper mold. Enhancement of both the castability and the surface quality of high-aluminum advanced high-strength steel (AHSS) slabs is one of the most important advantages when the new process has been applied into the commercial continuous casting process. Secondly, development of non-traditional lime-alumina based mold fluxes which have the potential to reduce slag-steel interaction during casting of high aluminum AHSS will also be dealt. Several trial casts of 1.45% Al TRIP steel using the lime-alumina based mold fluxes have been critically assessed in terms of stability of chemistry and mold performances. The crystallization behavior of lime-alumina based mold fluxes has been investigated in order to clarify the effects of phase evolution, crystallization kinetics, and morphology on casting performance.