Influence of chemical composition on the hot tearing formation of cast steel

Hot tears initiate under stress and strain, when the solid crystals are partially separated by the liquid film. At this stage, the overall strength of the hot spot of the casting is very low. The tendency of alloys to hot tearing depends on the temperature range in which the cracks can initiate. It has been assumed, that process of the cracks formation starts at the temperature of grains interlocking. The change of the length and chemical composition of liquid film separating the grains during solidification have been studied, using the simulation model for the growth of equiaxed grains. Mechanical properties of samples of the different cast steels in the solidification range, have been tested to define the lowest temperature of the hot tearing. Thus, for each chemical composition of the tested steel the range of brittleness could be calculated. The fractured surfaces were examined using Kevex X-ray analyzer coupled with scanning microscope. It was found that the examined regions were, at least partly, covered by the liquid phase rich in sulfur.