Deviation wall thickness of seamless steel pipe

In recent years, the proportion of seamless steel pipe in China’s steel production is growing, including seamless steel pipe wall thickness deviation is the importance of the quality one of the indicators due to its wide use and the higher its quality requirements. The thickness deviation directly affect the seamless steel pipe use.

Deviation produced in the piercing mill piercing process.
Piercing machine plug with the support plunger in the perforation of the first frame centering roll formed between a cantilever structure, so that the irregular beating of the plug in the piercing process, so that the plug will be in the tube Shouli Bu resulting in the generation of the thickness deviation.

Equipment manufacturing precision and structure.
Due to the poor stability of the piercing mill rolls and the guide plate in the device manufacturing, makes the device larger perforation beating impact of tube thickness; vintage centering roll structures are generally due to the upper roller and the lower roller is not transmission, an institution the centering roll center in the actual installation and adjustment is not easy to identify the three centering roll to hold fast mandrel theoretical center of the circle, so that will be caused by the perforation top the rod by centering roll to hold fast to produce radial Shouli Bu, stability is poor, resulting in the generation of wall deviation.

Installation and adjustment of the equipment line.
Units installed in the old-fashioned perforated accustomed “under rolling” method, the so-called “under rolling” is the centerline of the center line of the punch and ejector car is not in a horizontal line, but to make the puncher centerline ejector car centerline of a few millimeters, so piercing process rolling is relatively stable, but also can reduce the perforation in cards, etc., but it would be the center line of the mandrel and the tube is not a result of the tube deviation of the wall thickness of the perforation process.

The billets of the heating process.
Billets of the heating process is very important, and if the heating billets uneven heating, and thus will produce the yin and yang side, so that the plug in the piercing process Unevenness occurred offset, resulting in the low temperature surface of the capillary wall thickness of the piercing mill, high temperature surface wall thin .

The lower of the tube material.
The level of quality of tube feeding steel pipe wall thickness deviation also have a great impact, because of the to use horse sings like shearing machine the material cutter edge quality is not high, the resulting cross-section is more serious puncher head instantly bite into the generated cross-section sliding, as well as causing eccentricity and wall thickness deviation.

Impact Tools accuracy.
Destroyed when the time of piercing billets the correct geometry of the deformation zone, i.e. the tool imprecise head oval, such as a punching machine, punching machine plug rear bore eccentric, continue to use excessive wear, uneven wear of the upper and lower guide plate and roll easily cause uneven pipe wall thickness.

Using automatic pipe rolling mill.
Automatic pipe rolling mill is a vertical mill, it will cause the wall thickness deviation in the actual production process, mainly the “ears” part is obvious.

Seen in this light, to take effective measures, seamless steel pipe wall thickness deviation can really get a lot of improvement, and then for the subsequent processes, such as hot-rolled, cold-rolled or cold drawn to provide excellent shortage tube. As a large number of non-hot-rolled pipes delivered, in the order of the processing is generally cold-rolled and cold-drawn. The cold rolling mandrel role makes steel pipe wall thickness deviation can be corrected, while cold drawn not cold drawing the core floating head is in the process of drawing state, sensory seems cold drawn steel pipe and the wall thickness deviation is reduced, substantially only the absolute value of the wall thickness is reduced, the relative deviation of the wall thickness does not much change occurs. Therefore, in order to reduce the thickness deviation of a seamless steel pipe, the best resolved in the piercing process. Because, although later in the hot rolling step, such as rolling, are rounded can also reduce the mother pipe wall thickness deviation, but the corrective effect is limited, much less on the punching machine to control well. Of course, you can also reach the the purpose of reducing the pipe wall thickness deviation in the cold rolling mill, but the use of a cold rolling mill and use than drawing machine, theory and practice has proved that only the the shortage tube wall thickness deviation control perforation stage to better solution seamless quality of the finished product and not the cost of lower productivity and improve cost.


Post time: Oct-30-2019