Application of subsidy scheme in casting process

Through the discussion and application of metal subsidy, dark subsidy and heat subsidy, it can be seen that these three different subsidy methods have their own advantages and disadvantages. The characteristics of the three subsidy processes are compared as follows:

Subsidy SchemeProcess characteristicsApplication scenario
Metal subsidiesSimple and direct, with strong operability; It is difficult to grind and will remain on the casting; Resulting in casting weight increase or affecting part assembly;Wide application, applicable to all kinds of structures, non machined surfaces need to propose design changes to customers.
Covert subsidyIt does not need to be polished and will not increase weight on the casting; It is necessary to add sand blocks or inserts.The shape of the dark subsidy is limited by the shape of the feeding channel, and its draft direction needs to be considered.
Thermal subsidyIt does not need to be polished and will not increase weight on the casting; The metal utilization ratio is improved; The operability is relatively complex;For complex casting surface; The heat allowance shall be placed in the sand mold (core) in advance.

The application of the subsidy scheme requires the cooperation of risers, and the designed risers shall comply with the following basic conditions for sequential solidification:

(1) The solidification time of the riser shall be greater than or equal to the solidification time of the casting.

(2) In the whole solidification process of the casting, the feeding channel between the riser and the feeding position should be unobstructed, which requires the coordinated use of the riser and the gating system, the chill, the subsidy scheme, etc., so that the casting can realize sequential solidification from the end area far from the riser to the riser.

(3) The riser shall have sufficient volume to ensure that there is enough molten metal to supplement the liquid shrinkage and solidification shrinkage of the casting.

In the actual process design and production, the problems encountered will be more complicated than simple models and examples. We need to analyze the actual casting structure and production line to determine the most suitable feeding process. On the premise that the products meet the standards, we should fully consider reducing material consumption and reducing labor intensity.

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