With the sustained development of economy, all countries are vigorously developing the energy industry. Long-distance oil and gas pipelines are an important way of energy security. In the process of anticorrosion construction of oil (gas) pipelines, the treatment method of anticorrosion steel pipes is one of the key factors that determine the anticorrosion service life of pipelines, and it is the premise of whether the anticorrosion layer and steel pipes can be firmly combined. Therefore, in strict accordance with the requirements of anticorrosion coating specification for steel pipe surface, we should constantly explore and summarize, and constantly improve the treatment method of anticorrosion steel pipe. This paper introduces the anti-corrosion treatment method of anti-corrosion spiral steel pipe for drainage.
1. Anticorrosion Process of Water Steel Pipe
1) Clean the steel surface with solvent and emulsion to remove oil, grease, dust, lubricant and similar organic matter, but it can't remove rust, scale and flux on the steel surface, so it is only used as an auxiliary means in anti-corrosion production.
2) Tool derusting mainly uses tools such as wire brushes to polish the steel surface, which can remove loose or warped scale, rust, welding slag, etc.
The treatment method of manual anti-corrosion steel pipes for spiral steel pipes can reach Sa2 level, and the derusting of power tools can reach Sa3 level. If the surface of steel is attached with firm scale, the tool derusting effect is not ideal, and the anchor depth required by anti-corrosion construction cannot be reached.
3) Pickling is generally done by chemical and electrolytic methods. Chemical pickling is only used for pipeline anticorrosion, which can remove scale, rust and old coating, and sometimes it can be used as reprocessing after sand blasting and rust removal.
Although chemical cleaning can make the surface clean and rough to a certain extent, its anchor lines are shallow and easy to pollute the environment.
4) Spraying (throwing) derusting Spraying (throwing) derusting is to spray (throwing) the steel pipe surface with abrasive materials such as steel sand, steel shot, iron wire segment and minerals under the centrifugal force by driving the spraying (throwing) blades to rotate at a high speed through a high-power motor. The treatment method of anticorrosive steel pipes can not only completely remove rust, oxides and dirt, but also achieve the required uniformity of steel pipes under the violent impact and friction of abrasive materials. After derusting by spraying (blasting), not only can the physical adsorption on the pipe surface be expanded, but also the mechanical adhesion between the anticorrosive coating and the pipe surface can be enhanced. Therefore, the treatment method of anti-corrosion steel pipes with spiral steel pipes is an ideal rust removal method for pipeline anti-corrosion.
2. The performance of spiral steel pipe for water
If the gap is too small, the proximity effect will increase, and the welding heat will be too large, which will lead to weld burn-out. Or deep pits are formed after the weld is extruded and rolled, which affects the surface quality of the weld. After the two edges of the tube blank are heated to the welding temperature, under the extrusion of the extrusion roller, common metal grains are formed to infiltrate and crystallize with each other, and finally a firm weld seam is formed. If the extrusion pressure is too small, the number of common crystals will be small, the strength of weld metal will decrease, and cracking will occur after stress. If the extrusion pressure is too large, it will melt.
The water spiral steel pipe is used to feed the strip steel into the welded pipe mill. After rolling by multiple rollers, the strip steel is gradually rolled up to form a round tube blank with an open gap. Adjust the pressing amount of the extrusion roller to control the weld gap to 1~3mm and make the two ends of the weld flush.
If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the weld crystal will be indirectly defective, resulting in incomplete fusion or cracking.
If the gap is too small, the proximity effect will increase, and the welding heat will be too large, which will lead to weld burn-out. Or deep pits are formed after the weld is extruded and rolled, which affects the surface quality of the weld.
After the two edges of the tube blank are heated to the welding temperature, under the extrusion of the extrusion roller, common metal grains are formed to infiltrate and crystallize with each other, and finally a firm weld seam is formed.
If the extrusion pressure of spiral steel pipe is too small, the number of common crystals will be small, the strength of weld metal will decrease, and cracking will occur after stress. If the extrusion force is too large, the molten metal will be extruded from the weld, which not only reduces the weld strength, but also produces a large number of internal and external burrs, and even causes defects such as welding lap seam.
