What are the rust removal methods for large-diameter straight seam welded steel pipes

"Large-diameter straight seam welded steel pipe" is a general term referring to steel pipes produced using steel strips and welded straight seams on high-frequency welding equipment. Different subsequent production processes are involved depending on the intended use.

Generally, straight seam steel pipes with a diameter of 325 mm or larger are called large-diameter straight seam steel pipes. The welding process for large-diameter thick-walled straight seam steel pipes is double-sided submerged arc welding. Manual welding can also be performed after the steel pipe is formed. The common inspection method is flaw detection; products that pass flaw detection can be shipped. Defective products need to be re-welded. Large-diameter thick-walled straight seam steel pipes are generally suitable for fluid transportation, steel structure support, piling, and are widely used in petrochemicals, construction, water supply projects, power industry, agricultural irrigation, and urban construction. The steel pipe should be able to withstand internal pressure; a 2.5 MPa pressure test should be conducted, maintaining no leakage for one minute. Eddy current testing is permitted as an alternative to the hydrostatic test. The main forming methods include UOE, RBE, and JCOE, with JCOE being the most widely used. Threading can also be applied to the pipe ends according to customer requirements, also known as threaded or unthreaded processing.

Methods for rust removal of large-diameter straight seam steel pipes:
1. Cleaning: Using solvents and emulsions to clean the surface of large-diameter straight seam steel pipes to remove oil, grease, dust, lubricants, and similar organic matter. However, it cannot remove rust, scale, welding flux, etc., from the surface of large-diameter straight seam steel pipes; it is only used as an auxiliary method in anti-corrosion production.
2. Tool rust removal: Mainly using tools such as wire brushes to grind the surface of large-diameter straight seam steel pipes, which can remove loose or raised scale, rust, welding slag, etc. Manual tool rust removal can achieve Sa2 grade, while power tool rust removal can achieve Sa3 grade. If the surface of the large-diameter straight seam steel pipe has firmly attached iron oxide scale, tool rust removal is not ideal and cannot achieve the anchor pattern depth required for anti-corrosion construction.
3. Pickling: Pickling is generally performed using both chemical and electrolytic methods. Pipeline corrosion protection uses only chemical pickling, which removes scale, rust, and old coatings. It can sometimes be used as a post-treatment after sandblasting. While chemical cleaning can achieve a high degree of cleanliness and roughness, it results in shallow surface texture and can easily pollute the environment.
4. Blasting: Blasting uses a high-powered motor to drive the blasting blades at high speed, causing abrasive materials such as steel shot, steel grit, wire segments, and minerals to be blasted onto the steel pipe surface under centrifugal force. This not only removes rust, oxides, and dirt, but also, for large-diameter straight seam steel pipes, achieves the required uniform roughness under the intense impact and friction of the abrasive.