Bottom pouring type pouring system and pouring method for large-scale nodular cast iron wind power main rack casting

The invention discloses a nodular cast iron bottom pouring type pouring system and a pouring method for a large wind power main rack casting, belongs to a nodular cast iron sand casting technology, and aims to solve the problems that the existing slag filtering means is that a slag filtering sheet or a slag blocking channel is arranged in a straight pouring gate or an inner pouring gate, or the slag collecting amount is limited, and inclusions generated in a transverse pouring gate cannot be blocked. In order to solve the problems that molten metal flows through a bottom channel through gate control, splashing of the molten metal is effectively controlled, and inclusions are reduced; the two groups of symmetrical pouring gates comprise a straight pouring gate connected with the bottom of the pouring cup through a right-angle curve, a transverse pouring gate with a trapezoidal cross section, a plurality of groups of T-shaped or square slag collecting ladles communicated with the transverse pouring gate, and U-