How is the dimensional accuracy of stainless steel seamless pipes controlled?

The dimensional accuracy control of stainless steel seamless pipes is a complex and meticulous process, mainly involving the following key steps and measures:

Selection and Preparation of Raw Materials: High-quality stainless steel billets must be selected as raw materials, and their chemical composition and physical properties must meet relevant standards. The cutting and pretreatment of the raw materials must ensure precise dimensions, reducing errors in subsequent processing.

Piercing Process Control: During the piercing process, factors such as the diameter of the tapered tool, the piercing speed, and the operating condition of the piercing machine will all affect the initial dimensional accuracy of the pipe. By precisely controlling these parameters, it ensures that the inner and outer diameters and wall thickness of the pierced pipe meet the design requirements.

Rolling and Drawing: Rolling and drawing are crucial steps in controlling the dimensional accuracy of the pipes. By adjusting parameters such as the gap between the rollers, the rolling speed, and the drawing force, the deformation of the pipe can be precisely controlled to achieve accurate dimensional control. Multiple inspections and corrections are also necessary during rolling and drawing to ensure the stability of the pipe dimensions.

Temperature Control: Temperature is a critical parameter during rolling and drawing. By controlling the temperature of the heating furnace and the rolling/drawing equipment, it ensures that the pipes are processed at appropriate temperatures, preventing dimensional changes caused by excessively high or low temperatures.

Subsequent Treatment: Pickling treatment can remove oxides and impurities from the surface of the pipes, improving surface smoothness and indirectly enhancing dimensional accuracy. Annealing treatment can eliminate processing stress, improve the mechanical properties of the pipes, and help stabilize the dimensions of the pipes.

Quality Inspection and Correction: Finished pipes must undergo strict quality inspections, including dimensional measurement and wall thickness detection. Pipes that do not meet the requirements need to be corrected or reprocessed until they satisfy the design specifications.

Specific Control Indicators: Typically, the length of steel pipes (random length) for hot-rolled pipes ranges from 1.5 to 10 meters, and for hot-extruded pipes, it is 1 meter or more. For cold-drawn (rolled) pipes with a wall thickness of 0.5 to 1.0 mm, the length ranges from 1.0 to 7 meters, and for those with a wall thickness greater than 1.0 mm, the length ranges from 1.5 to 8 meters. The diameter of hot-rolled (hot-extruded) pipes ranges from 54 to 480 mm in 45 varieties, with wall thicknesses from 4.5 to 45 mm in 36 varieties. The diameter of cold-drawn (rolled) pipes ranges from 6 to 200 mm in 65 varieties, with wall thicknesses from 0.5 to 21 mm in 39 varieties. The inner and outer surfaces of the steel pipes must be free from defects such as cracks, folds, checks, cracks, rolling laps, delaminations, and scabs. Both ends of the steel pipes should be cut at right angles, and burrs should be removed.

The dimensional accuracy control of stainless steel seamless pipes is a complex process involving multiple steps and parameters. By precisely controlling raw materials, piercing processes, rolling and drawing, temperature, subsequent treatments, and quality inspections, high-precision dimensional control can be achieved, ensuring that the quality of the pipes meets design requirements.