Seamless pipes are divided into hot-rolled (extruded) seamless steel pipes and cold-drawn (rolled) seamless steel pipes due to different manufacturing processes. Cold drawn seamless tubing are divided into round tubes and special-shaped tubes. Perforation is the most important forming process in the production of hot-rolled tubes, and its task is to perforate a solid billet into a hollow billet (capillary).
In order to avoid the formation of holes in the process of oblique piercing of seamless steel pipes, the following measures can be taken:
1. Adopt large feed angle. As the feed angle increases, the axial velocity of the rolled piece increases. This reduces the number of cycles of repeated stress in the deformation zone and avoids the formation of voids in the seamless steel pipe.
2. Reduce the pass elliptic coefficient. The ellipticity coefficient of the pass is small, that is, the ellipticity of the pass is small, so that the lateral deformation of the rolled piece in the pass formed by the roll and the guide plate is small, thereby reducing the transverse tensile stress and preventing the seamless steel pipe from forming holes. Active guides prevent cavity formation. Generally, the guide plate has a large frictional resistance to the rolled piece, while the active guide plate has a small frictional resistance to the rolled piece, which is beneficial to the longitudinal deformation of the rolled piece, reduces uneven deformation, increases the critical reduction rate of the rolled piece, and prevents the formation of voids.
3. Increase top thrust. The jacking thrust during skew rolling means that when the rolled piece starts to bite, a thrust is applied to the rolled piece to promote it to enter the deformation zone for rolling. This can improve the rolling efficiency, reduce the number of repeated rolling of the rolled piece in the deformation zone, and prevent the seamless steel pipe from forming voids.
In order to avoid the formation of holes in the process of oblique piercing of seamless steel pipes, the following measures can be taken:
1. Adopt large feed angle. As the feed angle increases, the axial velocity of the rolled piece increases. This reduces the number of cycles of repeated stress in the deformation zone and avoids the formation of voids in the seamless steel pipe.
2. Reduce the pass elliptic coefficient. The ellipticity coefficient of the pass is small, that is, the ellipticity of the pass is small, so that the lateral deformation of the rolled piece in the pass formed by the roll and the guide plate is small, thereby reducing the transverse tensile stress and preventing the seamless steel pipe from forming holes. Active guides prevent cavity formation. Generally, the guide plate has a large frictional resistance to the rolled piece, while the active guide plate has a small frictional resistance to the rolled piece, which is beneficial to the longitudinal deformation of the rolled piece, reduces uneven deformation, increases the critical reduction rate of the rolled piece, and prevents the formation of voids.
3. Increase top thrust. The jacking thrust during skew rolling means that when the rolled piece starts to bite, a thrust is applied to the rolled piece to promote it to enter the deformation zone for rolling. This can improve the rolling efficiency, reduce the number of repeated rolling of the rolled piece in the deformation zone, and prevent the seamless steel pipe from forming voids.
