Structural characteristics of Cr.Mo steels micro-alloyed with mischmetal after heat treatment

Drápala Jaromír - VŠB TU Ostrava (Czech Republic)

Co-authors: Pavel Machovčák, Silvie Brožová, Petr Jonštab, Ivo Szurman, Vu The Ha, Gabriela Kostiuková

In the paper the results of the experimental study of behaviour of mischmetal and non-ferrous metals in 42CrMo4 steel will be presented. The samples were prepared with micro-alloying of mischmetal and pure cerium by application of plasma metallurgy and of medium frequency melting with centrifugal casting. Alloying with cerium was carried out with use of filled profile. The next samples were taken from two ingots which were casted in the VHM’s steelworks (the standard time of casting lasted about 14 minutes). Three samples were prepared by using of the forging machine. Chemical composition, macro- and microstructure (light optical microscope, SEM), X-ray EDX chemical microanalysis, macro- and microhardness of all samples were obtained. Cerium addition resulted in the formation of micrometer size inclusions which can be utilized for controlling the grain size structure of steel castings. The majority of the particles have settled at the bottom part of the casting, indicating that the convection flow during solidification was very weak. The rare-earth metals (REM) addition slightly diminished hardness of the steel. A segregation phenomena in the distribution of cerium in the volume of special steels after relatively quick crystallization process was found.

Keywords: CrMo steel, rare-earth metals, microstructure, interaction, segregation

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