Machine table casting will undergo volume shrinkage or expansion during solidification and subsequent cooling. This volume change is often restricted by the outside world and the various parts of the machine tool casting and cannot be carried out freely, so casting stress occurs. If the cause of the stress is eliminated, the casting stress will be eliminated. This kind of stress is called temporary casting stress. If the casting stress still exists after the cause of the stress is eliminated, this stress is called the casting residual stress.

cast iron machine table

 

During the process of solidification and subsequent cooling of machine table casting, due to different wall thicknesses and different cooling conditions, the temperature and degree of phase transformation of each part will be different, resulting in different volume changes of each part of the machine table casting. If the casting alloy is already in an elastic state at this time, the various parts of the machine table casting will have mutual constraints. Casting residual stress is often this kind of stress caused by different temperatures and different degrees of phase transformation.

 

Stress relief annealing is to heat the machine table casting at a certain temperature, and then slowly cool it to eliminate the residual stress in the machine tool casting. For gray cast iron, stress-relieving annealing can stabilize the geometry of the machine table casting and reduce the deformation after cutting.