Analysis and preventive measures of sand hole and slag hole defect in nodular cast iron roller

1. Defect analysis

(1) The slag cleaning treatment of molten iron is not complete;

(2) The results show that the design of gating system is unreasonable, the slag blocking effect is not good, the molten iron entering the mold cavity is not stable, and the secondary oxidation forms oxide slag;

(3) The tip sand treatment of the ingate is not in place, and the sand is washed during pouring;

(4) The riser design is unreasonable, and the first strand of dirty molten iron can not completely overflow the casting.

2. Preventive measures

(1) Strengthen the slag removing treatment of smelting pouring to improve the purification quality of molten iron;

(2) The semi open gating system is adopted, the flow resistance is set between the sprue and the transverse sprue, and the slag collection section of more than 100 mm is set at the end of the transverse sprue;

(3) The inclined joint is used at the contact between the ingate and the barrel, as shown in the figure, to avoid the sand inclusion caused by the sharp sand washing off at the ingate entrance;

(4) One overflow insulating riser is set on each end face of the two shaft heads. One end of the sprue is an open riser, and the other end is a blind riser. It has the dual functions of feeding and overflow, so that the molten iron inclusion can overflow out of the casting;

(5) It can increase the rising speed of liquid iron level in the mold cavity and fill the mold quickly, so as to avoid the sand inclusion defect caused by long-time baking of the upper mold.