Welded Structural Steel Pipe

The main parameters of welded steel pipes for structural use: caliber, wall thickness, length, welding technology, and whether surface anti-corrosion and heat preservation treatment is required.

Welded pipes are classified by use: general welded pipes, galvanized welded pipes, oxygen-blown welded pipes, wire casings, metric welded pipes, idler tubes, deep well pump tubes, automotive tubes, transformer tubes, electric-welded thin-walled pipes, electric-welded special-shaped pipes and spiral welded pipes.

General welded pipe: General welded pipe is used to convey low-pressure fluid. Made of Q195A, Q215A, Q235A steel. It can also be manufactured from other mild steels that are easy to weld. Steel pipes are subject to water pressure, bending, flattening and other tests, and have certain requirements for surface quality. Usually, the delivery length is 4-10m, and it is often required to deliver in fixed length (or double length). The specification of the welded pipe is represented by the nominal diameter (mm or inch). The nominal diameter is different from the actual one. The welded pipe has two types of ordinary steel pipe and thickened steel pipe according to the specified wall thickness. The steel pipe is divided into two types: threaded and unthreaded according to the pipe end form.

Galvanized steel pipe: In order to improve the corrosion resistance of steel pipes, general steel pipes (black pipes) are galvanized. There are two types of galvanized steel pipes: hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thicker and the cost of electric galvanizing is low.

Oxygen-blowing welded pipe: used for steelmaking and oxygen-blowing pipe, generally small-diameter welded steel pipes, with eight types of specifications ranging from 3/8 inch to 2 inch. Made of 08, 10, 15, 20 or Q195-Q235 steel strip. In order to prevent corrosion, some are aluminized.

Wire casing steel tube: that is, ordinary carbon steel electric-welded steel pipe, used in concrete and various structural power distribution projects, and the commonly used nominal diameter is from 13-76mm. The wall of the wire casing is relatively thin, and it is mostly used after coating or galvanizing, and a cold bending test is required.

Metric welded pipe: the specification is used as a seamless pipe form, and the welded steel pipe represented by the outer diameter * wall thickness in millimeters is welded with ordinary carbon steel, high-quality carbon steel or ordinary low-alloy steel with hot or cold bands, or with hot bands Then it is made by cold drawing method. Metric welded pipes are divided into ordinary energy and thin-walled pipes, which are generally used as structural parts, such as transmission shafts, or conveying fluids, and thin-walled pipes are used to produce furniture, lamps, etc., and the strength and bending test of steel pipes must be ensured.

Roller tube: used for belt conveyor roller electric welded steel pipe, generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for the bending degree of the pipe, the end surface should be perpendicular to the center line, and the ellipticity, and the water pressure and flattening tests are generally carried out.

Transformer tubes: used to manufacture transformer cooling tubes and other heat exchangers, made of ordinary carbon steel, requiring flattening, flaring, bending, and hydraulic tests. Steel pipes are delivered in fixed length or multiple lengths, and there are certain requirements for the bending degree of steel pipes.

Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, hollow plastic steel doors and windows steel pipes welded by ordinary carbon-bonded structural steel and 16Mn steel strips, mainly used as agricultural machinery components, steel windows and doors, etc.

Welded thin-walled tube: mainly used to make furniture, toys, lamps, etc. Thin-walled tubes made of stainless steel strips are widely used in high-end furniture, decoration, fences, etc.

Spiral welded pipe: It is made by rolling low-carbon carbon structural steel or low-alloy structural steel strip into a tube blank according to a certain helical angle (called forming angle), and then welding the pipe seam. It can be made with narrower Strip steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas transmission pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipes should ensure that the hydraulic test, the tensile strength of the weld and the cold bending performance must meet the regulations.