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The difference between common steel pipe specification and spiral welded pipe
Feb 11, 2019

The difference between common steel pipe specification and spiral welded pipeAccording to different welding methods can be divided into arc welding pipe, high frequency or low frequency resistance welding pipe, gas welding pipe, furnace welding pipe, bondi pipe.According to the shape of the weld, it can be divided into straight welded pipe and spiral pipe.Welded steel tubes are used in oil drilling and machinery manufacturing.Φ 219 - Φ 2032, wall thickness 5-18 mm, material Q235, Q345, X42-70 level.


Φ 219 - Φ 2032, wall thickness 5-18 mm, material Q235, Q345, X42-70 level.Spiral welded steel pipe refers to the steel belt or steel plate bending deformation into a circular, square shape and then welded, the surface of the joint steel pipe.According to different welding methods can be divided into arc welding pipe, high frequency or low frequency resistance welding pipe, gas welding pipe, furnace welding pipe, bondi pipe.According to the shape of the weld, it can be divided into straight welded pipe and spiral welded pipe.Welded steel tubes are used in oil drilling and machinery manufacturing.Furnace welded pipe can be used as water gas pipe, etc.Spiral welded pipe is used for oil and gas transportation, pipe pile, bridge pier, etc.Compared with seamless steel tubes, welded steel tubes have lower cost and higher production efficiency.Straight welded pipe production process is simple, high production efficiency, low cost, rapid development.The strength of spiral welded pipe is generally higher than that of straight welded pipe. The welded pipe with larger diameter can be produced with narrower billet, and the welded pipe with different diameter can be produced with the same width billet.


However, compared with straight pipe of the same length, the weld length increases by 30-100%, and the production speed is lower.Therefore, the welding pipe with smaller diameter is mostly straight seam welding, while the welding pipe with large diameter is mostly spiral welded submerged arc welding pipe, which is used to shape hot rolled strip steel according to the spiral shape, and to make spiral seam steel pipe (also known as spiral welded pipe and spiral pipe) through the welding of inner seam and outer seam by submerged arc automatic welding.Spiral steel pipe can be widely used in the production of large diameter steel pipe for the following reasons: 1) as long as the forming Angle is changed, it can be used to produce all kinds of steel pipe with the same width of steel strip;2) due to continuous bending forming, the fixed length of steel tube is not limited;3) the spiral shape of the weld is evenly distributed on the circumference of the entire steel pipe, so the steel pipe has high dimensional accuracy and high strength;4) easy to change the size, suitable for small batch, multi-variety steel pipe production.


Production process of steel pipe:Single wire or double wire submerged arc welding shall be adopted for the butt joint of strip head and tail, and automatic submerged arc welding shall be adopted after the steel pipe is rolled.(3) before forming, the strip is treated by leveling, cutting and planing, surface cleaning, conveying and bending.(4) the electric contact pressure gauge is used to control the pressure of pressing down the oil cylinder on both sides of the conveyor to ensure the smooth conveying of the steel strip.Technological process of spiral steel tube (high-precision seamless steel tube,DIN2391 precision seamless steel tube, cold-drawn precision bright tube) :(1) raw materials are strip steel coil, welding wire and flux.Before being put into operation, it must pass strict physical and chemical inspection.



(2) single wire or double wire submerged arc welding shall be adopted for butt joint of strip head and tail, and automatic submerged arc welding shall be adopted for repair welding after rolled into steel tubes.(3) before forming, the strip is treated by leveling, cutting and planing, surface cleaning, conveying and bending.(4) the electric contact pressure gauge is used to control the pressure of pressing down the oil cylinder on both sides of the conveyor to ensure the smooth conveying of the steel strip.(5) adopt external control or internal control roller forming.(6) the welding seam clearance control device is adopted to ensure that the welding seam clearance meets the welding requirements, and the pipe diameter, the amount of offset and the welding seam clearance are strictly controlled.(7) both internal and external welding are conducted by Lincoln welder for single wire or double wire submerged arc welding, so as to obtain stable welding specifications.(8) all welded welds are inspected by online continuous ultrasonic automatic flaw detector, ensuring 100% coverage of non-destructive testing of spiral welds.If there are defects, automatic alarm and spray mark, production workers according to this at any time to adjust the process parameters, eliminate defects in time.(9) air plasma cutting machine is used to cut the spiral steel pipes into single ones.(10) after cutting into a single steel tube, the first three steel tubes in each batch shall be subject to a strict first-inspection system to check the mechanical properties, chemical composition, melting state, surface quality of the steel tube and non-destructive inspection to ensure that the pipe manufacturing process is qualified before it can be formally put into production.(11) the part marked by continuous acoustic wave inspection on the weld shall be subject to manual ultrasonic and X-ray reexamination. If there is any defect, it shall be subject to non-destructive inspection again after repair until the defect is confirmed to be eliminated.(12) the pipe where the butt weld of the strip and the t-joint intersecting the spiral weld are located shall be inspected by X-ray television or film.(13) each steel pipe is hydrostatic tested, and the pressure is sealed radially.The test pressure and time are strictly controlled by the microcomputer testing device of water pressure of steel tube.(14) the pipe end is machined to ensure the verticality, bevel Angle and blunt edge of the end face are accurately controlled.