The uneven deformation of seamless tube during cold drawing results in additional stress, which remains in the residual stress of tube after cold drawing. The non-uniform deformation degree of seamless pipe determines the magnitude and distribution of residual stress.


Deformation of cold drawn steel is determined by deformation characteristics. Because the processing of tube wall does not involve the mandrel and the thickness of tube wall does not change much after deformation, there is a great difference between the deformation conditions of inner and outer layers, which leads to the deformation of seamless tube, resulting in uneven deformation.


During the deformation process, the metal near the inner surface of the seamless tube first enters the plastic deformation state, and the metal flows along the axis without being affected by friction. As a result, the non-uniformity of the axial deformation along the thickness direction appears. As a result, the natural extension of the outer layer of seamless tube is significantly lower than that of the inner layer. In this way, the axial and tangential additional tensile deformation and additional tensile stress of the outer layer of seamless tube reach the maximum value; on the contrary, when the maximum stress is reached, the axial and tangential additional compressive deformation and compressive stress of the inner layer of seamless tube remain in the tube after deformation.


In summary, due to the uneven deformation of the seamless tube after air gap, there are large residual stresses in the seamless tube. It is necessary to find an effective method to reduce the residual stresses in the seamless tube. Reduce the harm of vertical splitting.