Research of modification influence on cracking resistance of cast iron in moulds

Abstract

The research is devoted to determination of influence of grey iron modification technology; this gray iron is used for manufacture of steel casting moulds. Difficult operating conditions stipulate strict requirements both on construction of moulds and on their materials. These moulds materials should reliably withstand to effect of cast steel with the temperature 1600-1700 °C, as well as to thermal shock which is directly proportional to this temperature, to essential cyclic thermal stresses and deformations. Peculiar operating conditions of moulds (such as high heating temperature, mounting on movable and stationary runners, intensive traffic routes etc.) hamper conduction of the required investigations directly during their operation. The research was carried out on physical models of moulds for consumable electrodes of vacuum arc remelting with geometrical similarity scale 1:10. The following mould models for consumable electrodes, cast of iron, were tested: modified by ferrosilicon FS65 (according to the GOST 1415-93), modified by primary aluminium A99 (according to the GOST 11069-2001), modified by vanadium slag ShVD-1 (according to the technical specification TU 14-11-178-86), modified by ferrosilicobarium FSB-30 and by silicomishmetal SIMISh-1. These modifiers were selected owing to their wide use at production facilities. Thereby, the conducted tests were aimed to examine the features of moulds walls deformation and stress-strain state on the models of gray and modified cast iron; they allowed to assess the advantages and disadvantages of obtained structure and graphite inclusions forms. They will also help to develop the most rational form of external surface for moulds designed for section and sheet metal, previously determining destruction features. Application of thinwalled moulds with rational form can provide substantial decrease of their specific consumption. Examination of metal quality which was cast in pilot (lightened) moulds with curved external surface displayed that metal macrostructure for pilot and usual ingots is the same.