The quality of the tube billet is the basic factor that determines the quality of seamless steel pipes for medium and low pressure boilers. In order to ensure the smooth progress of the perforation process and obtain high-quality medium and low pressure seamless boiler tubes, strict requirements must be put forward on the chemical composition, geometric dimensions, surface quality, macrostructure, macrostructure, physical properties, and chemical properties of the tube blank.

①The surface quality of the tube billet determines the surface quality of the medium and low pressure seamless boiler steel pipes. Therefore, the surface of the tube blank is not allowed to have visible defects, such as cracks, inclusions, scars, pores, iron sheets, joints, and sharp scratches, pits, and indentations with a depth of more than 1.00mm.

②The macrostructure defects of the tube blank are directly related to the internal quality of the boiler tube. Including center porosity, shrinkage cavity, subcutaneous crack, middle crack, center crack test and subcutaneous bubbles.

③Geometric size and shape requirements.
Diameter: Different specifications of boiler tube billets are delivered according to different outer diameter tolerances.
Ovality: The ovality should not be greater than 0.75 of the diameter tolerance.
Curvature: The bend per meter of the tube blank shall not be greater than 6mm, and the total bend shall not be greater than 0.6% of the total length.