Piercing is the core primary forming process of seamless steel tube production. Unreasonable piercing roll speed, roll gap, plug position and feed angle will lead to unstable metal flow during tube billet perforation, easily causing inner micro-cracks, inner fold defects and serious wall thickness eccentricity. These quality problems directly reduce the dimensional accuracy and mechanical stability of finished steel tubes, resulting in batch rejection and low pass rate in downstream pipeline and mechanical processing applications.

Aiming at the common defects in the piercing process, systematic parameter optimization is carried out. First, optimize the feed angle and rolling angle of the piercing mill. A reasonable angle matching can make the tube billet obtain uniform circumferential compression and axial extension during deformation, avoid local stress concentration inside the metal, and effectively suppress the initiation and expansion of inner surface micro-cracks caused by uneven deformation.

Precisely calibrate the roll gap and plug penetration depth. Excessive roll gap will cause insufficient compression and irregular wall thickness, while too small gap will increase extrusion stress and produce internal defects. By adjusting the plug front position and floating support parameters, the central deformation zone is stabilized, the metal filling uniformity of the inner wall is improved, and the wall thickness difference between the upper, lower, left and right sections of the steel tube is reduced significantly.

Optimize the piercing temperature control system. Too high rolling temperature will cause coarse grain structure and reduce thermal stability; too low temperature will increase metal deformation resistance and induce shear cracks. Formulate segmented temperature parameters according to different steel grades, ensure the billet is pierced in the optimal plastic temperature range, and improve metal fluidity and forming consistency.

Optimize the rolling speed matching mechanism. Unstable piercing speed will cause periodic fluctuation of wall thickness. By setting variable speed control and stable feeding logic, the transient deformation difference in the piercing process is eliminated, and the overall wall thickness uniformity of the tube body is improved. At the same time, improve the plug cooling system to keep the surface temperature stable, prevent local overheating adhesion, and reduce inner surface scratch defects.

Establish post-piercing quality inspection and feedback mechanism. Use ultrasonic testing and wall thickness scanning equipment to detect inner crack defects and eccentricity data in real time. Form parameter correction database for different steel grades and tube specifications, realize closed-loop adjustment of piercing process parameters, and continuously optimize process stability.

Through the overall optimization of seamless steel tube piercing process parameters, the problems of inner surface cracks and wall thickness eccentricity are effectively solved, the dimensional accuracy and internal quality consistency of finished tubes are improved, and the product qualification rate and engineering application reliability are greatly enhanced.