After the seamless steel pipe is straightened, the initial inspection of the soot is performed to determine the length of the cutting head and the tail. The purpose of the seamless steel pipe cutting is to remove the ends with cracks, knots, ridges, tears and uneven wall thickness to obtain the required fixed-length seamless steel pipe.
In addition, the defects that are difficult to save after being inspected after the examination are removed, such as internal folds, internal scars, and severe wall thickness unevenness. Generally, the cutting of the former is performed on the line, while the latter is cut off offline.
The heat preservation time of the seamless steel tube during heat treatment should ensure that the steel tube in the furnace can be completely fired, the temperature is uniform, and the desired tissue transformation is completed, thereby obtaining uniform structure and performance. Generally, the heating temperature can be increased to shorten the holding time.
In the low-temperature annealing (including softening, stress relieving and recrystallization annealing), the annealing temperature is closer to the lower critical point A1, the faster the recovery of the seamless steel pipe, the more complete the effect of eliminating work hardening, therefore, the holding time can also be appropriate. shorten.
