Quantitative Characterization of a Belt-cast High-Manganese Steel Microstructure

The description of the solidification process in casting processes with varying product thickness is characterized based on solidification structures, segregations as well as the primary and secondary microstructure. In near-net-shape casting processes, it is particularly challenging to achieve microstructure homogeneity in the as-cast condition, since the degree of forming in production processes up to hot or cold strip is lower than in the production of slabs or thin slabs. The density of shrinkage porosity in belt-cast high-manganese steel (HMnS) will be determined quantitatively using polished microsections. Following the visualization of the primary cast structure, light microscopic images will be obtained using different tint etches. For the evaluation of secondary dendrite arm spacing (SDAS), internally developed software based on ImageJ and Matlab will be used.

Corrosion behavior and electrochemical corrosion of a high manganese steel in simulated marine splash zone

The corrosion behavior of a high manganese steel in simulated marine splash zone environment was studied by dry-wet cyclic corrosion experiment and electrochemical experiment. Corrosion kinetics, composition, surface morphology, cross-section morphology, element distribution, valence state, polarization curve and electrochemical impedance spectroscopy were analyzed with the aim of characterizing the characteristics of corrosion product films. The results show that in chloride-containing environment, in the initial corrosion products, Mn oxides with porous structure lead to higher corrosion rate. As corrosion extends, the formation of alloy element oxides in corrosion products changes the corrosion properties of rust layers at different stages. Mo oxides form a stable passivation film, which reduces the influence of chloride ion on corrosion. Ni oxides in the inner rust layer facilitate the transformation of goethite, and Cr oxides in the outer rust layer increase the densification of the rust layer. The stability and compactness of Fe3O4, α-FeOOH and FeCr2O4 in the later corrosion products inhibit the corrosion action of manganese iron oxides and slow down the corrosion rate. With the corrosion durations, the corrosion current density of the sample with the corrosion product film first increases and then decreases, and the corrosion potential first moves negative and then shifts in a positive direction subsequently, indicating that the protective effect of the corrosion product film is gradually significant.

Different Phenomena Encountered during Dilatometry of Low-density Steels

In recent decades, highly alloyed low-density steels are being developed to reduce the weight of different automotive parts. Dilatometry can be a very useful experimental technique to understand phase transformations during heating or cooling of new low-density steel alloys. When performing dilatometry measurements some assumptions are made such as the homogeneity of the sample material tested during the experiment. In this study, dilatometry tests were performed for two different low-density steels, and the variations of the composition between the surface and the inner part of the sample were analyzed. The migration of manganese by diffusion from the interior of the samples and finally its evaporation on the surface under vacuum were observed. This compositional gradient generated in the samples may influence the veracity and interpretation of the results obtained in dilatometry when working with high manganese steel alloys. The detachment of surface grains created by this compositional change near the surface of the samples is also investigated.