The production process of general seamless steel pipes can be divided into two types: cold drawing and hot rolling. The production process of cold-rolled seamless steel pipes is generally more complex than that of hot-rolled ones. First, the pipe billets undergo three-roll continuous rolling. After extrusion, a sizing test is carried out. If there are no corresponding cracks on the surface, the round pipes are cut by a cutting machine into billets with a length of approximately 1 meter. Then they enter the annealing process. For annealing, acid liquids are used for pickling. During pickling, attention should be paid to whether a large number of bubbles are generated on the surface; if a large number of bubbles are produced, it indicates that the quality of the steel pipes fails to meet the corresponding standards. In terms of appearance, cold-rolled seamless steel pipes are shorter than hot-rolled seamless steel pipes. The wall thickness of cold-rolled seamless steel pipes is generally smaller than that of hot-rolled seamless steel pipes, but their surface looks brighter than that of thick-walled seamless steel pipes, with no much roughness on the surface and no many burrs on the caliber.

The delivery state of hot-rolled seamless steel pipes is generally the hot-rolled state after heat treatment. After passing quality inspection, hot-rolled seamless steel pipes undergo strict manual selection by workers. After quality inspection, the surface is oiled, followed by multiple cold-drawing tests. After hot rolling, a piercing test is conducted; if the piercing and diameter expansion are too large, straightening correction is required. After straightening, the pipes are transported to a flaw detector by a conveying device for a flaw detection test. Finally, labels are attached, specifications are arranged, and the pipes are placed in the warehouse.

Steel grades, mechanical properties, cold-drawn (rolled) pipes, machined pipes: For 20# steel, the tensile strength σb (N/mm²) is ≥510 for cold-drawn (rolled) pipes and ≥390 for machined pipes; the elongation δ5 (%) is ≥5 for cold-drawn (rolled) pipes and ≥20 for machined pipes. For 45# steel, the tensile strength σb (N/mm²) is ≥647 for cold-drawn (rolled) pipes and ≥590 for machined pipes; the elongation δ5 (%) is ≥4 for cold-drawn (rolled) pipes and ≥4 for machined pipes.

Processing methods, cylinder diameter, length, straightness, dimensional accuracy, inner hole roughness: For cold rolling, the cylinder diameter is 30-100, the length is ≤12M, the straightness is 3-1.0, the dimensional accuracy is H8-H10, and the inner hole roughness is 4-1.6. For cold drawing, the cylinder diameter is 30-250, the length is ≤12M, the dimensional accuracy is H8-H10, and the inner hole roughness is 8-1.6. For honing, the cylinder diameter is 40-500, the length is ≤12M, the straightness is 1000, the dimensional accuracy is H8-H9, and the inner hole roughness is 4-0.8. For rolling, the cylinder diameter is 40-400, the length is ≤7M, the dimensional accuracy is H8, and the inner hole roughness is 4.