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                                   Shrinkage of stainless steel castings




When stainless steel castings shrink, they are affected by some external resistance, in addition to chemical composition, temperature and phase change. The shrinkage of the casting in the mold is only hindered by the friction between the metal surface and the surface of the mold, which is called free shrinkage; if the shrinkage of the casting in the mold is otherwise hindered, it is said to be resistively shrinkage. It is obvious that for the same alloy, the resistive shrinkage is less than the free shrinkage.
Stainless steel castings are subject to the following resistances when shrinking in the mold.
(1) Friction of the surface of the mold. When the casting shrinks, the friction between the surface and the surface of the mold, the magnitude of the frictional resistance is related to the weight of the casting, the smoothness of the surface of the mold, and the surface coating of the mold.
(2) Thermal resistance. When the shrinkage time and speed of each part of the casting are inconsistent, and the resistance is restricted to each other and cannot be freely contracted, it is called thermal resistance. Therefore, the generation of thermal resistance is related to the structure of the casting.
(3) Mechanical resistance. When the stainless steel casting shrinks, it is resisted by the mold and the core, and cannot be freely contracted. This resistance is called mechanical resistance. The amount of this resistance depends on the strength and retractability of the mold and core, the position of the box or core, and the thickness and length of the casting itself. Mechanical resistance reduces the amount of shrinkage of the casting.

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