Pipe upsetting, also called tube upsetting, is a procedure to use pressure to shorten the billet height and enlarge the diameter (lateral dimension). It is the basic forming method in the plastic forming procedure. After this process, our steel pipes acquire high strength and long service life. We can also avoid joint cracking.
Production Line LST pipe upsetting production line is configured with three GTR120/160 medium frequency induction heating furnaces, one 630-ton tube upsetting machine and one auxiliary machine. We can process 20,000 tons of tubings and 10,000 tons of drill pipes annually.
Technological Process of Pipe Upsetting Steel pipes are sent to the induction furnace. They are driven by induction furnace trolley and then can be heated by the furnace. This tube upsetting process may include twice or three times heating. When the temperature is reached, pipes are moved to the upsetting machine. The hold-down cylinder will press the pipe body and moves forward to make the end of steel pipes become thicker. According to technical requirements, we can do pipe upsetting several times to thicken pipe end diameter. At last, we do polishing for the outside burrs and inside burrs. The tube upsetting process is thus finished.
Pipe upsetting easily produces some defects.
1) Bend and Skew Caused by the followings:
a. During the tube upsetting process, the ratio of length and diameter is more than 2.5-3.
b. The end surface is not perpendicular to the pipe axis.
c. The hitting power is not straight.
d. Pipe billet is not heated uniformly or unevenly.
2) Surface Cracking and Folding
If we do pipe upsetting for the curved billets that are not straightened timely, they will become more curved and even not suitable for tube upsetting. Going on straightening will cause serious cracking on the bending part. The dimension of some pipe materials meets the relevant requirements, but the surface is not smooth with obvious hammered imprinting. When we do pipe upsetting, it is easy to cause folding.
During the tube upsetting process, the ratio of length and diameter should be less than 2.5.
The end surface should be perpendicular to the pipe axis. The forging force should be straight. The pipe upsetting force should be big enough otherwise interlayer will be easily formed.
We also need to consider the metal plasticity and control its deformation degree. For the metal with high hardness, strong tube upsetting can easily cause longitudinal crack.