The mechanical properties of die castings correlate with the inner structure of a casting, distribution of the eutectic phases, and with the content and distribution of porous cavities in the casting volume. This submitted paper deals with the issue of the possibility to influence the basic parameters affecting the quality of castings through structural modifications of the gating system. The structural parameter under assessment is the gate height. In the case of the diverse height of the gate, five sets of castings were produced. The individual sets of castings were subjected to examination of selected mechanical properties, i.e., of permanent deformation and surface hardness. At the same time, the individual sets of castings were subjected to metallographic examination of the eutectic structure of the casting. It was proved that the gate height influences the aforementioned properties of the castings and significantly affects the ratio of the eutectic phases in the volume of the casting. The conclusion describes the mutual correlation between the gate structure, the mechanical properties of the casting, and its structural composition.
The design of the gating system and the adjustment of the technological parameters of high pressure die casting are closely correlated. Correct connection of the gating system structure and technological parameters will be reflected in the final casting quality. Significant influence on the filling progress of a mold cavity has a gate and its geometry. Within the gate, the final increasing of melt flow velocity arises and determines the filling mode. The contribution is devoted to the influence of the gate height on selected technological parameters. The obtained data are being evaluated and on the basis of the experimental results assessment, the recommendations applicable in the foundry industry are being deduced.
Experimental studies of the wheel rim workpieces with additional technological corrugations have been carried out the results of which showed the ineffectiveness of this technique in profiling to increase thickness of the radial profile junctions of the semi-finished product. The comparison of profiling methods was carried out according to the Cochran's criterion and Student t-test. The additional experiments aimed at the determination of the flexural strain on differently shaped workpieces confirmed the impossibility of creation of the upthrust in the meridional direction during the deformation of the closed shells with straightening of the technological seats (corrugations). It is determined that the seats on the shell unbend in the tangential direction, the bending moments are damped nearthe site of the load application.
Distribution of gasses to the cast volume and volume of pores can be maintained within the acceptable limits by means of correct setting of technological parameters of casting and by selection of suitable structure and gating system arrangement. The main idea of this paper solves the issue of suitability of die casting adjustment—i.e., change of technological parameters or change of structural solution of the gating system—with regards to inner soundness of casts produced in die casting process. Parameters which were compared included height of a gate and velocity of a piston. The melt velocity in the gate was used as a correlating factor between the gate height and piston velocity. The evaluated parameter was gas entrapment in the cast at the end of the filling phase of die casting cycle and at the same time percentage of porosity in the samples taken from the main runner. On the basis of the performed experiments it was proved that the change of technological parameters, particularly of pressing velocity of the piston, directly influences distribution of gasses to the cast volume.
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