Cold-drawn residual stress of seamless pipe

Uneven deformation of seamless pipe during cold drawing can cause additional stress. After cold drawing, this additional stress still exists in the residual stress of the pipe. The degree of uneven deformation of seamless steel pipe determines the magnitude and distribution of residual stress.

The deformation of cold drawn steel is determined by the deformation characteristics. Since the pipe wall processing does not involve the axis in the stretching process, the thickness of the pipe wall does not change much after deformation, so the deformation conditions and deformation conditions of the inner and outer layers lead to a seamless carbon steel pipe, resulting in uneven deformation.

During the deformation process, the metal near the inner surface of the seamless tube first enters a state of plastic deformation, and the metal flows along the axis without being affected by friction. As a result, the axial deformation along the thickness direction is not uniform, and the natural elongation of the outer layer of the seamless pipe is lower than that of the inner layer. In this way the additional axial and tangential tensile deformation and additional tensile stress of the outer layer are maximized. On the contrary, when the maximum stress is reached, the axial and tangential compressive deformation and compressive stress of the inner layer of the seamless tube increase, and the residual stress in the tube after deformation also increases.

In summary, due to the uneven deformation of the seamless steel pipe after the air gap, the residual stress in the seamless steel pipe is large. Therefore, it is necessary to find an effective method to reduce the residual stress of the air duct, thereby reducing the harm of vertical splitting.

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