What is the difference between straight seam steel pipe and seamless steel pipe

A. Different categories
1. Straight seam steel pipe: divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe
2. Seamless steel pipes: seamless pipes are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, jacking pipes, etc. According to the cross-sectional shape, seamless steel tubes are divided into two types: round and special-shaped, and special-shaped tubes have various complex shapes such as square, oval, triangular, hexagonal, melon-shaped, star-shaped, and finned tubes.

B. Different concepts
1. Straight seam steel pipe: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe.
2. Seamless steel pipe: A steel pipe made of a single piece of metal with no seams on the surface is called a seamless steel pipe.

C. Different uses
1. Straight seam steel pipe: Straight seam steel pipe is mainly used in water supply engineering, the petrochemical industry, the chemical industry, the electric power industry, agricultural irrigation, and urban construction. Used for liquid transportation: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipes, as bridges; pipes for wharves, roads, building structures, etc.
2. Seamless steel pipe: Seamless steel pipe has a hollow cross-section and is widely used as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water, and certain solid materials. Compared with solid steel such as round steel, the steel pipe is lighter in weight when the bending and torsional strength is the same, and it is an economical section of steel.

Quality requirements for seamless steel pipes
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 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. Steel pipe geometric dimension accuracy and shape
(1) The accuracy of the outer diameter of the 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) Steel pipe wall thickness accuracy: 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 the wall thickness: ρ=(S-Si)/Si× 100% S: cross-section or minimum wall thickness; Si: nominal wall thickness mm;
(4) Ovality of steel pipe: indicates the degree of out-of-roundness of the steel pipe;
(5) Steel pipe length: normal length, fixed (double) ruler length, length tolerance;
(6) Curvature of the steel pipe: indicates the curvature of the steel pipe: the curvature of the length of the steel pipe per meter, the curvature of the full length of the steel pipe;
(7) Cutting slope of steel pipe end face: indicates the degree of inclination between the end face of the steel pipe and the cross-section of the steel pipe;
(8) The bevel angle and blunt edge of the end face of the steel pipe.


Post time: Apr-14-2023