Welding knowledge: basic knowledge of welded steel pipe

【Summary Description】 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. Welded steel pipe: used in oil drilling and machinery manufacturing, etc. Furnace welded pipe: can be used as water gas pipe, etc., large diameter straight seam welded pipe for high pressure oil and gas transportation, etc. Spiral welded pipes are used for oil and gas transportation, pipe piles, piers, etc. According to the shape of the weld 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 the straight seam welded pipe, can use a narrow billet to produce larger diameter welded pipe, can also use the same width of the blank to produce different diameter welded pipe. However, compared with the same length of the straight seam welded pipe, the weld length increased by 30~100%, the production speed is low. Therefore, most of the small diameter welded pipes are welded by straight seam welding, and most of the large diameter welded pipes are welded by spiral welding. Spiral seam welded steel pipes are divided into automatic submerged arc welded steel pipes and high frequency welded steel pipes. a. Spiral seam automatic submerged arc welded steel pipes are divided into Class A pipes and Class B pipes according to the pressure of the conveying medium. Grade pipes are generally welded with ordinary carbon steel Q235, Q235F and ordinary low-alloy structural steel 16Mn, and grade B pipes are welded with Q235, Q235F, Q195 and other steels for low-pressure fluid delivery pipes. B. spiral seam high frequency welded steel pipe spiral seam high frequency welded steel pipe there is no uniform product standard, generally made of ordinary carbon steel Q235, Q235F and other steel materials. According to the use is divided into ordinary welded pipe, galvanized welded pipe, blown oxygen welded pipe; steel wire casing, metric welded pipe. Idler tube, deep well water pump tube, automobile tube, transformer tube, electric welding thin-walled tube, electric welding special-shaped tube, spiral welded tube, etc. 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 low carbon steel that is easy to weld. Steel pipes must undergo water pressure, bending, flattening and other tests, which have certain requirements for surface quality. Typically, the delivery length is 4-10 meters, usually requiring a fixed length (or double length) delivery. The specification of welded pipe is expressed in nominal diameter (mm or inch). The nominal diameter is different from the actual diameter. Welded pipe according to the provisions of the wall thickness of ordinary steel pipe and thick steel pipe two. Steel pipes are divided into threaded and non-threaded types according to the form of pipe ends. Galvanized steel pipe: In order to improve the corrosion resistance of the steel pipe, the general steel pipe (black pipe) is galvanized. There are two types of galvanized steel pipes: hot-dip galvanized and electro-galvanized. The hot-dip galvanizing layer is thick and the electroplating cost is low. Oxygen blowing welded pipe: used for steel-making oxygen blowing pipe, generally with small diameter welded steel pipe, specifications from 3/8 inch -2 inch eight. Made of 08,10,15,20 or Q195-Q235 steel. To prevent corrosion, some are aluminized. Wire casing: It is also a kind of ordinary carbon steel welded steel pipe, which is used in concrete and various structural power distribution projects. Commonly used nominal diameter is 13-76mm. The wall of the wire casing is relatively thin, and it is mostly used after coating or galvanizing, and cold bending test is required. Metric welded pipe: its specification is expressed in the form of seamless pipe. The welded steel pipe is expressed by outer diameter * wall thickness mm. It is welded with ordinary carbon steel, high-quality carbon steel or ordinary low alloy steel with hot or cold belt, or with hot spot after welding and then made by cold drawing method. Metric welded pipes are divided into ordinary energy pipes and thin-walled pipes, which are generally used for structural parts, such as transmission shafts, or conveying fluids, while thin-walled pipes are used in the production of furniture, lamps, etc. to ensure the strength and bending test of steel pipes. Roller tube: used for welded steel pipes for belt conveyor rollers, generally made of Q215, Q235A, B steel and No. 20 steel, with a diameter of 63.5 -219.0mm. There are certain requirements for the bending of the pipe. The end face should be perpendicular to the center line and have ovality. Generally, water pressure and flattening tests should be carried out. Transformer tube: used to make transformer cooling tubes and other heat exchangers, made of ordinary carbon steel, requiring flattening, flaring, bending and hydraulic testing. The steel pipe has fixed length or multi-section transportation, and there are certain requirements for the bending degree of the steel pipe. Special-shaped pipe: square pipe, rectangular pipe, hat-shaped pipe, hollow plastic steel door and window steel pipe welded by ordinary carbon-bonded structural steel and 16Mn steel strip, mainly used for agricultural machinery components, steel doors and windows, etc. Welded thin-walled tubes: mainly used for making furniture, toys, lamps, etc. At present, thin-walled pipes made of stainless steel belts are widely used, such as high-end furniture, decoration, fences, etc. Spiral welded pipe: It is a low-carbon carbon structural steel or low-alloy structural steel strip based on a certain helix angle.

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