1. The quality of the pipe and intermediate pipe of the seamless steel pipe is unqualified, and the geometrical dimensions are not satisfactory. The longitudinal and transverse wall thicknesses are severely uneven, the bending and ellipticity are too large, the chemical composition is incompatible, and the mechanical properties are not. with.
2. Failure to comply with the operating procedures for each preparatory process before drawing seamless steel tubes. The main ones are incorrect hammer process, improper chemical treatment and heat treatment, burrs at the pipe end, low quality of grinding, and defects during transportation.
3. Failure to follow the procedures for the extubation process. The performance is inconsistent in the center line of the seamless steel pipe, the installation of the extruding die is not correct, the opening speed is too fast, the tool is improperly matched, the diameter of the mandrel rod is too large or too small, the deformation is too large, and the mandrel is not fed in time. Wait;
4. The quality of the extruding die and the mandrel are not good, including poor finish, low hardness and strength, inconsistent size, incorrect mounting of the carbide mold, etc.
5. The tube puller is out of repair. For example, the tilting of the pull-out trolley, the mold base or the extubation die itself is not installed correctly on the center frame.