Welded steel pipes refer to steel pipes with seams on the surface that are welded after bending and deforming steel strips or steel plates into round or square shapes. The billet used for welded steel pipe is steel plate or strip steel. This article mainly introduces the types of welded steel pipes, let’s take a look!
1. According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency resistance welded pipe, gas welded pipe, furnace welded pipe, Bondi pipe, etc.
Electric welded steel pipe: used in oil drilling and machinery manufacturing, etc.
Furnace welded pipe: can be used as water gas pipe, etc., large-diameter longitudinally welded pipe is used for high pressure oil and gas transportation, etc.; spiral welded pipe is used for oil and gas transportation, pipe piles, bridge piers, etc.
2. According to the weld shape, it can be divided into straight seam welded pipe and spiral welded pipe.
Longitudinal welded pipe: simple production process, high production efficiency, low cost, and rapid development.
Spiral welded pipe: The strength is generally higher than that of straight seam welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can also be used to produce welded pipes with different pipe diameters. But compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes use straight seam welding, and the large diameter welded pipes mostly use spiral welding.
Spiral seam welded steel pipes are divided into two types: automatic submerged arc welded steel pipes and high-frequency welded steel pipes.
a. Spiral longitudinal welded pipe seam automatic submerged arc welded steel pipes are divided into two types: Class A pipe and Class B pipe according to the pressure of the conveying medium. Class A pipes are generally welded with ordinary carbon steel Q235, Q235F and ordinary low-alloy structural steel 16Mn. Class B pipes are welded with steels such as Q235, Q235F, Q195, etc., and are used as low-pressure fluid conveying pipes.
b. Spiral seam high-frequency welded steel pipe. There is no uniform product standard for spiral seam high-frequency welded steel pipe. It is generally made of ordinary carbon steel Q235, Q235F and other steels.
3. According to the purpose, it is divided into general welded pipes, galvanized welded pipes, oxygen-blowing welded pipes, wire casings, metric welded pipes, roller pipes, deep well pump pipes, automotive pipes, transformer pipes, electric welded thin-walled pipes, electric welded special-shaped pipes and spirals. Welded pipe.
General welded pipe: General welded pipe is used to transport low-pressure fluid. Made of Q195A, Q215A, Q235A steel. It can also be made of other mild steel that is easy to weld. Steel pipes need to be subjected to water pressure, bending, flattening and other experiments, and there are certain requirements for surface quality. Usually the delivery length is 4-10m, and fixed-length (or double-length) delivery is often required. The specifications of welded pipes are expressed by the nominal diameter (mm or inches). The nominal diameter is different from the actual. Welded pipes are divided into two types: ordinary steel pipes and thickened steel pipes according to the specified wall thickness. The steel pipes are divided into threaded and non-threaded types according to the tube end form.
Galvanized steel pipe: In order to improve the corrosion resistance of the steel pipe, the general steel pipe (black pipe) is galvanized. Galvanized steel pipes are divided into two types: hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thick and the cost of electro-galvanizing is low.
Oxygen-blowing welded pipe: Used as a steel-making oxygen-blowing pipe, generally small-diameter welded steel pipes, with eight specifications ranging from 3/8 inch to 2 inch. It is made of 08, 10, 15, 20 or Q195-Q235 steel belt. In order to prevent corrosion, some are aluminized.
Wire casing: It is also an ordinary carbon steel electric welded steel pipe, used in concrete and various structural power distribution projects. The commonly used nominal diameter is from 13-76mm. The wall of the wire sleeve is thin, and most of it is used after coating or galvanizing, and a cold bending test is required.
Metric welded pipe: The specification is in the form of seamless pipe, and the welded steel pipe expressed by outer diameter * wall thickness in millimeters, using ordinary carbon steel, high-quality carbon steel or general energy low-alloy steel for hot strip, cold strip welding, or after hot strip welding Then it is made by cold dialing method. Metric welded pipes are divided into ordinary energy and thin-walled pipes, and are commonly used as structural parts, such as transmission shafts or conveying fluids. Thin-walled pipes are used to produce furniture, lamps, etc., and the strength and bending test of the steel pipe must be ensured.
Roller tube: Electric welded steel pipe for the roller of belt conveyor, generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for the tube bending, end face to be perpendicular to the centerline, and ellipticity. Generally, water pressure and flattening tests are carried out.
Transformer tube: It is used to manufacture transformer radiator tubes and other heat exchangers. It is made of ordinary carbon steel and requires flattening, flaring, bending, and hydraulic tests. Steel pipes are delivered in fixed-length or double-length, and there are certain requirements for the bending of the steel pipe.
Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, hollow rubber steel doors and windows welded by ordinary carbon structure steel and 16Mn steel strips, mainly used for agricultural machinery parts, steel windows and doors, etc.
Welded thin-walled pipe: mainly used to make furniture, toys, lamps, etc. At present, thin-walled pipes made of stainless steel belts are widely used, such as high-end furniture, decoration, and fences.
Spiral welded pipe: It is made by rolling low-carbon carbon structural steel or low-alloy structural steel strip into a tube blank at a certain spiral angle (called forming angle), and then welding the tube seam together. It can be made with a narrower Strip steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes can be welded on one side or on both sides. Welded pipes should be guaranteed to meet the requirements for hydraulic test, tensile strength and cold bending performance of the weld.
4. According to the shape of the end, it is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe.
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