① According to the ratio of cross-sectional area, it is divided into closed gating system and open gating system.
The closed gating system can ensure that the liquid iron can fill the mold cavity smoothly and rapidly during the filling process, and the impact on the mold can be reduced at the same time. In open gating system, the cross-sectional area of cross runner and inner runner is large, and the velocity of molten iron is slow and stable, which can avoid turbulence and further oxidation during the filling process of molten iron, thus effectively reducing the formation of secondary slag.
② According to the position of the runner on the casting, it can be divided into top pouring type, bottom pouring type, middle pouring type and ladder type.
Top gating system means that the ingate is located at the top of the casting pouring position. The main advantages are: the cavity is easy to be filled to avoid casting defects due to the thin wall; due to the top-down filling, the top-down temperature gradient at the end of pouring is formed, which is conducive to the formation of top-down sequential feeding under the action of gravity; the feeding efficiency of riser is improved, the amount of molten metal is saved, and the process yield is improved. The main disadvantages are as follows: the filling process is completed by the falling of molten iron from top to bottom. If the pressure head is too high, there will be a lot of spatter, scattered flow and oxidation; the impact of high temperature molten iron on the bottom surface of the mold is large, and even produces sand washing; the slag blocking ability of the gating system is poor.
Bottom gating system means that the ingate is located at the bottom of the casting pouring position. Its main advantages are: the filling process of molten metal is relatively stable; the position of internal runner is submerged in molten iron during the whole process from pouring, so as to avoid splashing and oxidation of molten iron; it is conducive to the full play of slag blocking function of cross runner. The main disadvantages are as follows: the high temperature molten iron entering the mold at the late pouring stage is at the bottom of the pouring position, which is not conducive to the formation of the top-down temperature gradient required by sequential solidification and riser feeding; the runner position is easy to form overheating.
Intermediate injection gating system refers to that the ingate is located at a certain position in the middle of the casting pouring position. It has both advantages and disadvantages of top and bottom pouring systems.
The stepped gating system refers to that the inner runner is arranged in layers on the casting. Its main advantages are: the liquid iron filling is carried out in layers according to the actual needs to realize the top-down sequential filling; the molten iron filling head is reduced to make the filling process stable; the temperature of molten iron pouring into the mold cavity after the top layer is higher than that at the bottom, which can realize sequential solidification and casting feeding under the action of gravity; it can effectively reduce casting defects such as shrinkage cavity and cold shut. The main disadvantages are: inaccurate calculation in process design can easily lead to molten iron entering into each layer of runner at the same time.