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

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

Second, different concepts
1. Straight seam steel pipe: Straight seam steel pipe is a steel pipe in which the 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.

Third, different uses
1. Straight seam steel pipe: Straight seam steel pipe is mainly used in water supply projects, the petrochemical industry, the chemical industry, the electric 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 purposes: piling pipes, bridges; pipes for docks, roads, building structures, etc.
2. Seamless steel pipe: Seamless steel pipe has a hollow section and is widely used as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, coal gas, water, and certain solid materials. Compared with solid steel materials such as round steel, steel pipes are lighter in weight when the bending and torsional strength are the same, and they are an economical cross-section steel material.

Fourth, seamless steel pipe quality requirements
1. Chemical composition of steel: The chemical composition of steel is the most important factor affecting the performance of seamless steel pipes. It is also the main basis for formulating pipe rolling process parameters and steel pipe heat treatment process parameters.
(1) Alloying elements: intentionally added, according to purpose;
(2) Residual elements: brought in from steelmaking and properly controlled;
(3) Harmful elements: strict control (As, Sn, Sb, Bi, Pb), gases (N, H, O); refining outside the furnace or electro slag remelting: improving the uniformity of the chemical composition of the steel and the purity of the steel degree, reducing non-metallic inclusions in the tube blank and improving its distribution pattern.
2. Geometric dimensional accuracy and shape of steel pipes
(1) Steel pipe outer diameter accuracy: It depends on the method of determining (reducing) diameter, equipment operation conditions, process system, etc. Allowable 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.; wall thickness allowable deviation: ρ= (S-Si)/Si× 100% S: cross-section or minimum wall thickness; Si: nominal wall thickness mm;
(4) Steel pipe ovality: indicates the degree of out-of-roundness of the steel pipe;
(5) Steel pipe length: normal length, fixed (multiple) length, and length tolerance;
(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 slope: indicates the degree of inclination between the steel pipe end face and the steel pipe cross-section;
(8) Steel pipe end bevel angle and blunt edge.