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Internal thermal stress
During the cooling of a body from a given temperature, the loss of temperature is unevenly distributed over the body unless the process of cooling is very slow. Normally, some areas cool faster than others, contracting accordingly faster than the parts that are still warm. The different degrees of contraction lead to the accumulation of internal stress in the cooling body which affects solder joints and cast parts. Therefore, thorough annealing is indispensable before use, especially in the case of large castings; otherwise deformation may occur.