Welded pipe type: spiral welded pipe

Spiral welded pipe: The low carbon carbon structural steel or low alloy structural steel strip is rolled into a tube blank according to a certain helix Angle (called forming Angle), and then the pipe joint is welded together. It can be made of narrow strip steel to produce large diameter steel pipe. The specifications are expressed by outer diameter * wall thickness, and the welded pipe should ensure that the hydraulic test, tensile strength and cold bending performance of the weld should meet the requirements.

Material

Q235A, Q235B, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, 16Mn, 20#, Q345, L245, L290, 40#, 60#, X42, X46, X70, X80.

Use

Spiral welded pipe is mainly used in tap water engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, urban construction in China. For liquid transportation: water supply, drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structure: for piling pipe, as a bridge; Pipe for wharf, road, building structure, etc.

Production technology

Spiral welded pipe is also a kind of welding pipe equipment, its strength is generally higher than that of straight welded pipe, can be used to produce a narrower blank pipe diameter larger welded pipe, can also be used to produce the same width blank pipe diameter of different welded pipe. But compared with the same length of straight seam pipe, the weld length is increased by 30~100%, and the production speed is lower. Therefore, small diameter welded pipe mostly adopts straight seam welding, large diameter welded pipe mostly adopts spiral welding.

Production technology of spiral steel pipe: It is a spiral seam steel pipe with strip coil plate as raw material, extruded at constant temperature and welded by automatic double-wire double-sided submerged arc welding process.

1, raw materials, namely strip coil, welding wire, flux. Strict physical and chemical inspection is required before being put into operation.

2. The butt butt of strip steel is made of single wire or double wire submerged arc welding, and automatic submerged arc welding is adopted to repair welding after being rolled into steel pipe.

3, before forming, strip steel after leveling, cutting edge, planing edge, surface cleaning and conveying and bending treatment.

4. Electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth transmission of the strip.

5, the use of external control or internal control roller forming.

6. The weld gap control device is adopted to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of wrong side and the weld gap are strictly controlled.

7, both internal and external welding using the United States Lincoln welding machine for single wire or double wire submerged arc welding, so as to obtain stable welding specifications.

8. The welding seams are inspected by online continuous ultrasonic automatic injury instrument, ensuring 100% non-destructive testing coverage of spiral welds. If there are defects, automatic alarm and spraying mark, production workers at any time to adjust the process parameters, timely elimination of defects.

9. Use air plasma cutting machine to cut the steel pipe into a single piece.

10. After cutting into a single steel pipe, each batch of steel pipe head three to carry out a strict first inspection system, check the mechanical properties of the weld, chemical composition, melting condition, surface quality of the steel pipe and through non-destructive inspection, to ensure that the pipe process qualified, before formally put into production. 11. The parts with continuous sonic inspection marks on the weld shall be reviewed by manual ultrasonic and X-ray. If there are defects, they shall be nondestructive tested again after repair until it is confirmed that the defects have been eliminated.

12. The butt welding weld of strip steel and the pipe where the T-joint intersects with the spiral weld are all inspected by X-ray TV or film.

13. Each steel pipe is tested by hydrostatic pressure, and the pressure is sealed radial. The test pressure and time are strictly controlled by the microcomputer measuring device of steel pipe water pressure. Test parameters are automatically printed and recorded.

14, pipe end machining, so that the end face perpendicularity, groove Angle and blunt edge can be accurately controlled.

Anticorrosive spiral welded pipe technology

Because the individual quality of spiral welded pipe is relatively large, so must be stacked in the outdoor, but it will be difficult to avoid the sun and rain, so the problem of rust has been plagued by spiral welded pipe storage time and conditions. Therefore, it is necessary for us to have a comprehensive answer to the knowledge of spiral welded pipe rust prevention.

The main use of wire brush and other tools to polish the steel surface, spiral welding pipe cleaning and preheating can remove loose or warped oxide skin, rust, welding slag, etc. Hand tools can reach Sa2 level, power tools can reach Sa3 level, if the steel surface is firmly attached to the oxide sheet, the tool rust removal effect is not ideal, can not reach the anticorrosive construction requirements of anchor grain depth.

Pickling uses solvents and emulsions to clean the surface of welded steel pipe (welded pipe) used for low-pressure fluid transportation to remove oil, grease, dust, lubricant and similar organic matter, but it can not remove rust, oxide skin, welding flux, etc., so it is only used as an auxiliary means in anti-corrosion production.

General use of chemical and electrolytic two methods to do pickling treatment, pipeline anticorrosion only chemical pickling, can remove oxide skin, rust, old coating, sometimes it can be used as sand blasting after the reprocessing. Chemical cleaning can make the surface to a certain degree of cleanliness and roughness, but its anchor pattern is shallow, and easy to pollute the spiral welded pipe stacking environment.

The reasonable use of means to clean the rusty pipe fittings to ensure that the pipe fittings will serve the production for a long time and create more production benefits.