Relation Between the Microstructure of Cold Resistant Steel 20GL and Some Parameters of the Melting Process

Resumo

The microstructure, impact toughness and melting parameters of cold-resistant steel 20GL are studied. The impact toughness of the steel at negative temperature (KCV^-60) is shown to be affected the most by the size of the primary (natural) grains of the metal. The size of the natural grains is shown to be dependent on the content of oxygen and (to a less degree) of silicon. Introduction of an elevated amount of slag-forming materials and aluminum into liquid metal provides the required (at most 0.005–0.008 wt.%) content of oxygen and an impact toughness (KCV^-60) no less than 0.167 MJ/m². Influence of the nonmetallic inclusions, of the size of actual grains, and of the content of pearlitic phase on KCV^-60 in normalized steel has not been detected or was not obvious.