1. Chemical composition of steel: The chemical composition of steel is the most important factor affecting the performance of seamless steel pipes, and it is also the main basis for formulating the parameters of the rolling process and heat treatment of seamless steel pipes.
(1) Alloying elements: intentionally added, according to the application;
(2) Residual elements: brought in by steelmaking, properly controlled;
(3) Harmful elements: strictly control (As, Sn, Sb, Bi, Pb), gas (N, H, O); refining outside the furnace or electro slag remelting: improve the uniformity of chemical composition in steel and the purity of steel Degree, reduce the non-metallic inclusions in the tube blank and improve its distribution.
2. Geometric dimension accuracy and shape of seamless steel pipe
(1) The accuracy of the outer diameter of the seamless steel pipe: depends on the method of determining (reducing) the diameter, the operation of the equipment, and the processing system. Permissible deviation of outer diameter δ=(D-Di)/Di ×100% D: or minimum outer diameter mm;
(2) Nominal outer diameter mm;
(3) Wall thickness accuracy of seamless steel pipe: It is related to the heating quality of the tube blank, the process design parameters and adjustment parameters of each deformation process, the tool quality and its lubrication quality, etc.; the allowable deviation of wall thickness: ρ=(S-Si)/ Si×100% S: cross-section or minimum wall thickness; Si: nominal wall thickness mm;
(4) Ovality of seamless steel pipe: indicates the degree of out-of-roundness of seamless steel pipe;
(5) Length of seamless steel pipe: normal length, fixed (double) ruler length, length tolerance;
(6) Bending degree of seamless steel pipe: Indicates the bending degree of seamless steel pipe: the bending degree per meter of seamless steel pipe length, the bending degree of the full length of seamless steel pipe;
(7) Cutting slope of seamless steel pipe end face: Indicates the degree of inclination between the end face of seamless steel pipe and the cross-section of seamless steel pipe;
(8) The groove angle and blunt edge of the end face of the seamless steel pipe.
Post time: Jul-17-2023