First, different classifications
1. Straight seam steel pipe: divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe
2. Seamless steel pipe: seamless pipe is divided into hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe, top pipe, etc. According to the cross-sectional shape, seamless steel pipe is divided into round and special-shaped pipes. Special-shaped pipes have square, oval, triangle, hexagon, melon seed, star, winged pipe, and many other complex shapes.
Second, different concepts
1. Straight seam steel pipe: Straight seam steel pipe is a steel pipe with a weld parallel to the longitudinal direction of the steel pipe.
2. Seamless steel pipe: A steel pipe made of a whole piece of metal with no seams on the surface is called a seamless steel pipe.
Third, different uses
1. Straight seam steel pipe: Straight seam steel pipe is mainly used in tap water engineering, the petrochemical industry, the chemical industry, the power industry, agricultural irrigation, and urban construction. For liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural use: used as piling pipes, bridges; pipes for docks, roads, building structures, etc.
2. Seamless steel pipe: Seamless steel pipe has a hollow cross-section and is widely used as a pipeline for conveying fluids, such as pipelines for conveying oil, natural gas, coal gas, water, and certain solid materials. Compared with solid steel such as round steel, steel pipe is lighter in weight when the bending and torsional strength are the same, and is an economical cross-section steel.
Fourth, quality requirements for seamless steel pipes
1. Chemical composition of steel: The chemical composition of steel is one of the most important factors affecting the performance of seamless steel pipes, and is also the main basis for formulating rolling process parameters and steel pipe heat treatment process parameters.
(1) Alloy elements: intentionally added, according to the purpose;
(2) Residual elements: brought in during steelmaking, appropriately controlled;
(3) Harmful elements: strictly controlled (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, reduce non-metallic inclusions in the tube blank and improve their distribution morphology.
2. Geometric dimensional accuracy and shape of steel pipes
(1) External diameter accuracy of steel pipes: depends on the sizing (reduction) method, equipment operation, process system, etc. Permissible deviation of outer diameter δ=（D-Di）/Di ×100% D: or minimum outer diameter in mm;
(2) Nominal outer diameter in mm;
(3) Steel pipe wall thickness accuracy: related to the heating quality of the tube blank, the process design parameters and adjustment parameters of each deformation process, the quality of the tool and its lubrication quality, etc.; Permissible deviation of wall thickness: ρ=（S-Si）/Si×100% S: or minimum wall thickness on the cross-section; Si: nominal wall thickness in mm;
(4) Steel pipe ovality: indicates the degree of non-circularity of the steel pipe;
(5) Steel pipe length: normal length, fixed (multiple) length, and allowable deviation of length;
(6) Steel pipe curvature: indicates the curvature of the steel pipe: curvature per meter of steel pipe length, curvature of the entire length of the steel pipe;
(7) Steel pipe end face cutting bevel: indicates the degree of inclination of the steel pipe end face and the steel pipe cross section;
(8) Steel pipe end face groove angle and blunt edge.
Post time: Jan-10-2025