How to deal with pit defects in seamless carbon steel pipes?

Posted by zora li on September 14th, 2023

In the production of seamless carbon steel pipes, regular holes and pits are mainly caused by uneven deformation. The key to solving the problem is to reduce uneven deformation. In order to solve this problem, the hot-rolled seamless steel pipe can be improved by fine-tuning the continuous rolling mill, appropriately reducing the deformation of the continuous rolling mill, uniformizing the billet and capillary temperature, and reducing the vibration of the continuous rolling mill. .

1. The appropriate adjustment of the continuous rolling mill should follow the principle of equal flow and continuous flow, avoid a reasonable amount of deformation while avoiding rolling between steel frames, and prevent the holes of the front rolling mill from being overfilled or underfilled. Seriously, the deformation of the rolling stock on each rolling mill should be relatively uniform. When the continuous roll wear is serious, the influence of roll wear on rolling should also be considered.

2. In order to reduce the longitudinal unevenness, the deformation of the continuous rolling mill can be appropriately reduced, and a small amount of deformation can be pushed to the hole. At the same time, the pore geometry is tightly controlled. Sometimes, the length of the capillary rolled out with seven ejector pins is uneven, and the ejector pin in question is removed in time.

3. The uneven temperature of the billet and the capillary tube causes uneven deformation, because the deformation resistance of the rolled piece at different temperatures is different, the deformation resistance of the high temperature part is low, and it is easy to deform; the deformation resistance of the low temperature part is high, and it is not easy to deform. The heating uniformity of the annular heating furnace is much worse than that of the stepped heating furnace, which has high requirements for improving production efficiency. When the temperature is not good, the wall thickness deviation of the capillary is very serious, which will adversely affect the subsequent rolling deformation. It is also necessary to reduce the temperature drop, especially the local temperature drop, during the transportation of the billet and capillary, so as to avoid local plastic degradation, which may cause holes or depressions.

4. Reduce the vibration of the continuous rolling mill. During rolling, the rolling machine will produce different degrees of vibration, especially the vibration of the mandrel is very violent, which is not good for rolling, so it is necessary to reduce its influence. The speed and speed limit of the continuous rolling mill can be adjusted to avoid the vibration frequency during rolling and the natural vibration frequency of the rolling mill.