A detailed explanation of surface treatment and processing methods of thick-walled steel pipes

Thick-walled steel pipes have a wide variety of steel types and specifications, and their performance requirements are also various. All of these should be differentiated as user requirements or working conditions change. Generally, steel pipe products are classified according to cross-sectional shape, production method, pipe material, connection method, coating characteristics, use, etc. Thick-walled steel pipes can be divided into round steel pipes and special-shaped steel pipes according to the cross-sectional shape. Special-shaped thick-walled steel pipes refer to steel pipes with various non-circular cross-sections, including square tubes, rectangular tubes, elliptical tubes, flat elliptical tubes, semicircular tubes, hexagonal tubes, hexagonal inner tubes, and unequal hexagonal tubes. Tube, equilateral triangular tube, pentagonal plum tube, octagonal tube, convex tube, double convex tube. Double-concave tube, multi-concave tube, melon-shaped tube, flat tube, diamond-shaped tube, star-shaped tube, parallelogram tube, ribbed tube, drop-shaped tube, inner finned tube, twisted tube, B-shaped tube, D-shaped tube Type tubes, and multi-layer tubes, etc. Thick-walled steel pipes are further divided into steel pipes with equal cross-sections and steel pipes with variable cross-sections according to the longitudinal section shape. Variable cross-section (or variable cross-section) steel pipe refers to a steel pipe that undergoes periodic or non-periodic changes in cross-sectional shape, inner and outer diameters, and wall thickness along the length of the pipe. It mainly includes an outer tapered tube, inner tapered tube, outer stepped tube, inner stepped tube, periodic section tube, corrugated tube, spiral tube, steel pipe with cooling fins, gun barrel with double lines, etc.

To improve the service life of oil and gas pipelines, surface treatment is usually carried out to facilitate the firm combination of thick-walled steel pipes and anti-corrosion layers. The common treatment methods are cleaning, tool rust removal, pickling, spray shot blasting, and rust removal.

1. Surface pickling of straight seam steel pipe

Common pickling methods include chemical and electrolytic methods. However, only chemical pickling is used for the anti-corrosion of pipelines. Chemical pickling can achieve the cleanliness and roughness of the steel pipe surface, which is convenient for the subsequent anchor lines. Usually, as a reprocessing after shot peening (sand).

2. Spray shot blasting to remove rust

The high-power motor drives the blades to rotate at high speed, so that steel sand, steel shots, iron wire segments, minerals, and other abrasives are sprayed and projected on the surface of the steel pipe under the action of centrifugal force. On the one hand, rust, oxygen reactants, and dirt, on the other hand, the steel pipe Under the violent impact and friction of abrasives, the required uniform roughness is achieved.

3. Thick-walled steel pipe cleaning

Grease, dust, lubricants, and organic matter adhered to the surface of thick-walled steel pipes are usually cleaned with solvents and emulsions. However, for the rust, oxygen reaction skin, and welding slag on the surface of the steel pipe cannot be removed, other treatment methods are needed.

4. Use tools to remove rust on straight seam steel pipes

Oxygen-reactive skin, rust, and welding slag on the surface of steel pipes can be cleaned and polished with a wire brush. There are two types of derusting tools: manual and power. The derusting of manual tools can reach the Sa2 level, and the derusting of power tools can reach the Sa3 level. If the surface of the steel pipe is attached to a particularly strong oxygen-reactive skin, it may not be cleaned with the help of tools, so other methods need to be found.

Among the four surface treatment methods for thick-walled steel pipes, shot blasting is the ideal treatment method for pipe rust removal. Generally, shot blasting is mainly used for the inner surface treatment of steel pipes, and shot blasting is mainly used for the outer surface treatment of steel pipes.

The main processing method of thick-walled steel pipe is rolling, which is the pressure processing of passing the steel metal billet through the gap (various shapes) of a pair of rotating rolls. Due to the compression of the rolls, the cross-section of the material is reduced and the length of the thick-walled steel pipe is increased. Method, which is a common production method for the production of steel, is mainly used to produce steel profiles, plates, and pipes. Divided into cold rolling and hot rolling. Forging steel: a pressure processing method that uses the reciprocating impact force of a forging hammer or the pressure of a press to change the blank into the shape and size we need. It is generally divided into free-forging and die-forging seamless steel pipes. Steel pipes are still indispensable materials for various conventional weapons. Gun barrels, barrels, etc. must be made of steel pipes. Steel pipes can be divided into round pipes and special-shaped pipes according to the shape of the cross-sectional area. Because under the premise that the circumference is equal, the area of the circle is large, and more fluid can be transported with a circular tube. In addition, when the circular section of thick-walled steel pipe is subjected to internal or external radial pressure, the force is relatively uniform. Therefore, most of the thick-walled steel pipes are round pipes. The steel pipe has a hollow cross-section and is widely used as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water, and certain solid materials. Compared with solid steel such as round steel, the seamless steel pipe is lighter in weight when the bending and torsional strength is the same. The thick-walled steel pipe is an economical cross-section steel, which is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobiles, etc. Drive shafts, bicycle frames, and steel scaffolding for building construction.