Due to the high pouring temperature of steel castings, which typically ranges from 1520 to 1620 ℃, the surface of the cavity is heated by the thermal radiation of the molten steel during the pouring process, which is prone to volume expansion, causing problems such as separation of the surface layer from the inner layer, and collapse of molding sand. Large steel castings have a large amount of molten steel to be poured, and generally require rapid pouring at low temperatures to minimize harmful effects such as thermal radiation from the molten steel on the surface of the mold cavity.
The steel casting of the intermediate pressure inner cylinder adopts an open gating system with a split face up and a sliding ladle bottom pouring. This scheme is conducive to the smooth filling of the cavity with liquid metal, the easy discharge of cavity gas, the reduction of liquid metal oxidation, and the avoidance of entrainment and slag inclusion; Reduce the impact of liquid metal on the sand core and mold cavity, and prevent defects such as sand inclusion caused by sand washing; Avoiding excessive temperature differences between various parts and reducing the shrinkage stress of steel castings is beneficial to reducing the occurrence of cracks.
When the metal liquid filling of steel castings just exceeds the critical speed of 0.55 m/s, the metal liquid only slightly falls back, forming the first surface fold; Continue to increase the filling speed, and the potential harm of metal flow ejection and falling back will become more apparent. To ensure a smooth inflow of molten steel during the filling process, the inflow speed of the inner gate is less than 0.55 m/s.
The pouring parameters are calculated through the gating system design software, and the results are as follows: the pouring weight is 19.8 t, using 12 # steel ladle, 1 ϕ 80 mm sliding inner gate, 4 nos ϕ 100 mm inner gate, pouring speed 0.54 m/s, pouring time 166 s.