Possibility of Utilization of Gate Geometry to Modify the Mechanical and Structural Properties of Castings on the Al-Si Basis

Abstract

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.

Research and Evaluation of the Influence of the Construction of the Gate and the Influence of the Piston Velocity on the Distribution of Gases into the Volume of the Casting

“…As it becomes evident according to Figure 4 , reducing cross-section of the runner and increasing velocity of pressing piston resulted in increase of gas entrapment in the cast. As the velocity in the gate is relatively on the constant level for the individual pairing parameters (filling mode of the mold shaping cavity determines the melt velocity in the gate [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 33 ]), it is inevitable to focus on evaluation of the flow in the runners.…”

“…From the point of view of structure, the sole parameter influencing the method of filling of the mold shaping cavity is the gate area S G . As the gate area is in this case the function of width and height of the gate and width is constant according to [ 23 ], the only variable parameter is the gate height b n ( Figure 1 ) [ 24 ]. Table 1 presents the evaluated constant and variable structural parameters of the gate.…”

“…As the mean thickness of the cast h reaches the value of 2 mm for the particular cast and maximal cast length l (in this case it is the cast diameter) reaches the value of 116.5 mm, the melt velocity in the gate for reference gating system is determined to the value of v G1 = 35 m·s −1 . By means of continuity Equation (1) and taking into consideration the closed system [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], piston velocity is determined v P1 = 2.8 m·s −1 : S G × v G = S P × v P , …”

“…Right in the gate final acceleration of the melt flow occurs as well as its forming before entering the mold shaping cavity. Velocity in the gate determines the filling mode of the mold shaping cavity on the basis of which it is possible to predict development of the gas entrapment in the cast volume [ 24 , 25 , 26 , 27 , 28 ].…”

“…The objective pursued is to achieve reduction of distribution of gases to the cast volume during die casting cycle. On the basis of knowledge and information published in [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ] it is possible to understand the system of filling chamber—shaping cavity—as a closed system (pipeline). On the basis of hydrodynamics it can be thus assumed that velocity in the gate with preservation of constant flow rate of the melt is influenced by the cross section of the gate or by velocity of the piston.…”