Surface treatment method of LSAW steel pipe

LSAW steel pipe is the general name of high frequency straight seam, submerged arc straight seam, electric welding straight seam, pipeline straight seam, etc. High-frequency straight seam steel pipe adopts the epitaxial effect of high-frequency current to produce high temperature and external extrusion of both ends of the steel plate in a short period of time, which is a kind of real electrode-free base metal butt joint.

Taking hot rolled coil as raw material, the wall thickness of ERW high-frequency LSAW steel pipe can be controlled at about ±0.2mm, and the end of the steel pipe adopts the American APL standard or GB/T9711.1 standard, with the end of the pipe being cut and the length of the conveyance being fixed. In recent years, ERW steel pipe has been widely used as the main steel pipe of urban pipeline network in natural gas pipeline network projects and natural gas enterprises. At present, ERW high-frequency LSAW steel pipe accounts for 60% of the proportion of steel pipe used in the world.

The surface treatment of LSAW steel pipe is one of the key factors to determine the anticorrosive service life of the pipeline, which is the premise of whether the anticorrosive coating and the steel pipe can be firmly combined, and the research shows that the service life of the anticorrosive coating depends on the type of coating, the quality of the coating, and the construction environment, and the influence of the surface treatment of LSAW steel pipe on the service life of the anticorrosive coating is about 50 percent. Therefore, it should be in strict accordance with the requirements of the specification of anti-corrosion coating on the surface of steel pipe, and constantly explore and summarize the surface treatment method of steel pipe.

1. The cleaning of straight seam steel pipe uses solvents and emulsions to clean the steel surface to remove oil, grease, dust, lubricants and similar organic matter, but cannot remove the oxide skin, steel surface rust, flux, etc., and can only be used as an auxiliary means of anti-corrosion production.

2. If the steel surface is firmly attached to the iron oxide scale, its descaling effect is not ideal, can not meet the requirements of anti-corrosion construction on the depth of anchoring particles. LSAW steel pipe descaling tools mainly use steel wire brush and other tools to polish the steel surface, manual descaling can reach SA2 level, and power tool descaling can reach SA3 level, which can remove loose or raised oxide scale, rust, welding slag and so on.

3. The pickling of straight seam steel pipe is generally treated by chemical and electrolytic methods, which can be used as reprocessing after sandblasting and rust removal. Although chemical cleaning can make the surface reach a certain degree of cleanliness and roughness, its anchoring particles are shallow and easy to pollute the environment, and pipeline anticorrosive can only be treated by chemical pickling to remove oxidized scale, iron rust and old coatings.