Negative pressure is necessary to measure black alloy LFC. Negative pressure is to increase the strength and rigidity of sand important assurance measures, but also the model of gasification products excluded major initiatives. The size of the negative pressure and the holding time with casting material and the cluster model structure and paint-related. For good ventilation, paint coating thickness of less than 1mm, the negative pressure of the cast iron is generally 0.04 ~ 0.06MPa, whichever is the upper limit for steel castings. For aluminum casting the negative pressure control in general 0.02 ~ 0.03MPa. Negative pressure holding time depends on the model cluster structure, depending on the model number of clusters in each box is large, it may be appropriate to extend the negative hold time. Generally solidified crust reaches a certain thickness can it go negative in the casting surface. For thicker coatings and coating permeability poor circumstances, it may be appropriate to increase the negative pressure and the holding time.
Because there are models in the casting process model gasification needs to absorb heat, so LFC casting temperature should be slightly higher than sand casting. For different alloys, compared with sand casting, lost foam casting pouring temperature control in higher than sand casting 30 ~ 50 ℃. This liquid metal heat up 30 ~ 50 ℃ can meet the needs of the gasification thermal model. Pouring the casting temperature is too low prone to insufficient water, cold traps, wrinkled skin and other defects. Pouring temperature of castings prone to sticky sand and other defects.
LFC casting operation is intermittent pouring most taboo, so easily lead to casting to produce cold shut defect, that is, first molten metal poured into the lower temperature, resulting in between and after pouring cold separator liquid metal. In addition, the EPC casting system to use more closed-casting system, in order to maintain smooth casting. In this regard, in the form of a cup with a pouring gate operation it is smooth close. When pouring the cup holding the gate level remain stable, smooth dynamic head the cast. |
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