The mathematical model and numerical simulations of the solidification of a cylindrical shaped casting, which take into account the process of filling the mould cavity by liquid metal and feeding the casting through the riser during its solidification, are presented in the paper. Mutual dependence of thermal and flow phenomena were taken into account because have an essential influence on solidification process. The effect of the riser shape on the effectiveness of feeding of the solidifying casting was determined. In order to obtain the casting without shrinkage defects, an appropriate selection of riser shape was made, which is important for foundry practice. Numerical calculations of the solidification process of system consisting of the casting and the conical or cylindrical riser were carried out. The velocity fields have been obtained from the solution of momentum equations and continuity equation, while temperature fields from solving the equation of heat conductivity containing the convection term. Changes in thermo-physical parameters as a function of temperature were considered. The finite element method (FEM) was used to solve the problem.
The paper includes validation studies of the flow module of the NovaFlow&Solid simulation code. Experiments of ductile iron and gray iron casting in a spiral test of castability were carried out. Casting experiments were then carried out in industrial conditions in the Ferrex Foundry in Poznań and the results are the castability spiral length and local cast iron rate during mould cavity pouring. Simulation tests using NovaFlow&Solid Control Volume code were made. The technological castability test was used to determine thermal-physical data through simplified inversion problem. Influence of physical parameters in the database of simulation code on the spiral length obtained as the result of simulation was analyzed. It was found that critical fraction of capillary flow CLFdown has the biggest impact on cast iron castability in the simulation code. The simulations resulted in defining parameters of gray iron GJL 250 and ductile iron GJS-400-15. For the parameters set, the length of castability spiral in simulations was in accordance with casting experiments.
The rebuilding technologies are used to develop surface of ladle. Among many welding methods currently used to obtain surface layer without defects one of the most effective way of rebuilding is using metal arc welding. This additional material gives more possibilities to make expected quality of rebuild surface. Chemical composition, property and economic factors allow to use metal wire. Because of these reasons, solid wire gives opportunity to be wildly used as material to rebuild or repair the surface in different sectors of industry. The paper shows a few ways to rebuild the surface in the massive cast with the use of metal active gas welding for repair. The work presents studies of defect in the massive cast. It contains the pictures of microstructures and defects. The method of removing defects and the results of checking by visual and penetrant testing methods are shown. The paper describes the methodology of repair the ladle with metal active gas welding, preheating process and standards nondestructive testing method.
The article describes the detection of a defect in a cast iron casting. It analyzes the cause of the crack in the Turbine Component casting. In this article, we are focusing on a particular turbine casting that is commonly used in automobiles as one of the components for turbochargers. The turbine is a casting made of ductile cast iron with a visible crack on the naked eye. The formation of cracks in castings is a common but undesirable phenomenon in the foundry practice. It is important to identify the errors, but also to know the cause of defects in castings. The solution is a detailed error analysis. In this paper I used metallographic analysis and magnetic powder method. The crack formation is due to tension in the casting, which results in tensile, shear, or shear forces. The crack formation kinetics is difficult because it is still very low during hardening and shortly after the casting is overloaded. The crack is most often due to core resistance or shrinkage molds that begin after the surface layer is tightened when the strength of the material is negligible to the end of the crystallisation.