Commonly used
spiral steel pipes do not use Q235 material. Commonly used spiral steel pipe materials in China generally include Q235A, Q235B, Q345, L245, L290, X42, X52, X60, X70, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb materials.
Spiral pipes, also called spiral steel pipes or spiral welded pipes, are made by rolling low carbon structural steel or low alloy structural steel strips into pipe blanks at a certain spiral angle (called forming angle) and then welding the pipe seams. , which can produce large-diameter steel pipes from narrower strips.
Spiral steel pipe production process
(1) The raw materials are steel strip coil, welding wire, and flux. They must undergo strict physical and chemical inspections before being put into use.
(2) For the head-to-tail butt joint of the steel strip, single-wire or double-wire submerged arc welding is used, and automatic submerged arc welding is used for repair welding after being rolled into a steel pipe.
(3) Before forming, the strip steel undergoes leveling, trimming, planing, surface cleaning, transportation, and pre-bending.
(4) Electric contact pressure gauges are used to control the pressure of the cylinders on both sides of the conveyor to ensure smooth conveying of the strip.
(5) Adopt external control or internal control roller forming.
(6) A weld gap control device is used to ensure that the weld gap meets the welding requirements. The pipe diameter, offset amount, and weld gap are strictly controlled.
(7) Both internal and external welding use American Lincoln welding machines for single-wire or double-wire submerged arc welding to obtain stable welding specifications.
(8) All completed welds have been inspected by an online continuous ultrasonic automatic flaw detector, ensuring 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically alarm and spray mark, so that production workers can adjust the process parameters at any time to eliminate defects in time.
(9) Use an air plasma cutting machine to cut the steel pipe into individual pieces.
(10) After being cut into individual steel pipes, each batch of steel pipes must undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, the surface quality of the steel pipes, and non-destructive testing to ensure that the pipe making process is qualified. Only then can it be officially put into production.
(11) The areas with continuous sonic flaw detection marks on the welds will undergo manual ultrasonic and X-ray re-examination. If there are indeed defects, they will be repaired and then undergo non-destructive inspection again until it is confirmed that the defects have been eliminated.
(12) The steel strip butt welds and the pipes where the T-shaped joints intersect with the spiral welds are all inspected by X-ray television or film.
(13) Each steel pipe has been tested by hydrostatic pressure, and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Test parameters are automatically printed and recorded.
(14) The pipe end is machined to accurately control the end face verticality, bevel angle, and blunt edge.
Surface treatment methods of spiral steel pipe:
1. Cleaning: Use solvents and emulsions to clean the surface of the steel to remove oil, grease, dust, lubricants, and similar organic matter. However, it cannot remove rust, oxide scale, flux, etc. on the surface of steel, so it is only used in anti-corrosion production. As an auxiliary means.
2. Tool rust removal: First, use tools such as wire brushes to polish the surface of the steel to remove loose or lifted oxide scales, rust, welding slag, etc. The rust removal of hand tools can reach the Sa2 level, and the rust removal of power tools can reach the Sa3 level. If there is a strong iron oxide scale attached to the surface of the steel, the rust removal effect of the tool will be unsatisfactory and the anchor pattern depth required for anti-corrosion construction will not be reached.
3. Pickling: Chemical and electrolytic methods are generally used for pickling treatment. Only chemical pickling is used for pipeline anti-corrosion, which can remove scale, rust, and old coatings. Sometimes it can be used as a reprocessing after sandblasting and rust removal. Although chemical cleaning can make the surface reach a certain degree of cleanliness and roughness, its anchor lines are shallow and it can easily cause pollution to the environment.
4. Spray (throw) rust removal: Spray (throw) rust removal is driven by a high-power motor to rotate the spray (throw) blade at high speed, so that steel sand, steel shot, wire segments, minerals, and other abrasives are rotated under the effect of centrifugal force. Spraying (throwing) the surface of the steel pipe can not only completely remove rust, oxides, and dirt, but also the steel pipe can achieve the required uniform roughness under the action of the strong impact and friction of the abrasive. After spraying (throwing) rust removal, it can not only expand the physical adsorption effect on the pipe surface but also strengthen the mechanical adhesion effect between the anti-corrosion layer and the pipe surface. Therefore, spray (throwing) rust removal is an ideal rust removal method for pipeline anti-corrosion. Generally speaking, shot blasting (sand) rust removal is mainly used for internal and external surface treatment of pipes, and shot blasting (sand) rust removal is mainly used for surface treatment of pipes.
Uses of spiral steel pipes: Spiral pipes are mainly used in water supply projects, the petrochemical industry, the chemical industry, the electric power industry, agricultural irrigation, and urban construction. They are among the 20 key products developed in our country. For liquid transportation: water supply, drainage, sewage treatment projects, mud transportation, ocean water transportation. For gas transportation: coal gas, steam, liquefied petroleum gas. Structural use: piling pipes, bridges; pipes for docks, roads, building structures, marine piling pipes, etc.
