The paper presents the experimental results on the determination of melt parameters such as the energy of the boundary, contact angle, density and kinematic viscosity of low and medium alloy steels at different temperatures, as well as the dispersion of their dendritic structure in solidified castings. The analysis of the data obtained allowed revealing using mathematical models the influence of the chemical composition and temperature of melts on their properties and the dendritic structure of castings. It was established the variation of the melt parameters depending on the particular chemical elements of steels as C, Si, Mn, O, P, V, Cr. The established analytical dependences shown that increasing density and viscosity contributes to the dispersion of the dendritic structure and viscosity is of the major effect. The derived quantitative patterns allows to evaluate structure formation of cast structural low and medium alloy steels.
The formation process of one of the most common casting defects, a shrinkage depression concerned to shrinkage cavity, was studied. The methodology, device and the experimental set up were developed to study the shrinkage cavity growth. The kinetics of vacuum formation in the cavity of the spherical casting of Al-Si-Mg alloy at its solidification in the sand-and-clay form was investigated. The data were analysed taking in mind the temperature variation in the centre of crystallizing casting. The causes of the shrinkage depression in castings were clarified. It was determined that atmospheric pressure leads to the retraction and curvature of metal layer on the surface of the casting with lower strength below which the shrinkage cavity is formed. To avoid such defects it was recommended to use the external or internal chills, feeders and other known technological methods. Deep shrinkage cavities inside the castings could be removed with an air flow through a thin tubular needle of austenitic steels for medical injections.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.