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

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 steel pipe is divided into hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe, pipe jacking, etc. According to the cross-sectional shape, the seamless steel pipe is divided into two types: round and special-shaped.

Second, the concept is different

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 without 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 engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction. For liquid transportation: water supply, drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structure: for piling pipe, for bridge; for wharf, road, building structure, 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, 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 is economical section steel.

Quality requirements for seamless steel pipes

First, the chemical composition of the steel: the chemical composition of the steel is the most important factor affecting the performance of the seamless steel pipe, and it is also the main basis for formulating the parameters of the rolling process and the heat treatment process of the steel pipe.

(1) Alloying elements: intentionally added, according to the purpose;

(2) Residual elements: brought into steelmaking, and properly controlled;

(3) Harmful elements: strictly control (As, Sn, Sb, Bi, Pb), gas (N, H, O); out-of-furnace refining 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 their distribution.

Second, the geometric accuracy and shape of the steel pipe

(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. Allowable deviation of outer diameter δ=(D-Di)/Di ×100% D: or minimum outer diameter mm;

(2) Nominal outer diameter mm;

(3) Steel tube wall thickness accuracy: related to the heating quality of the tube blank, process design parameters and adjustment parameters of each deformation process, tool quality, and its lubrication quality, etc.; wall thickness tolerance: 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) Length of steel pipe: normal length, fixed (multiple) ruler length, length allowable deviation;

(6) Bending degree of steel pipe: Indicates the bending degree of the steel pipe: the bending degree of the steel pipe length per meter, the bending degree of the whole length of the steel pipe;

(7) The inclination of the end face of the steel pipe: indicates the inclination of the end face of the steel pipe and the cross-section of the steel pipe;

(8) Bevel angle and blunt edge of steel pipe end face.