Large-diameter straight seam welded pipe is a general term. It is produced by steel strips. All pipes welded by high-frequency welding equipment are called straight seam welded pipes. (It is named because the welding part of the steel pipe is in a straight line). According to different uses, there are different post-production processes. (It can be roughly divided into scaffolding pipes, fluid pipes, wire casings, bracket pipes, guardrail pipes, etc.)
Generally, straight seam steel pipes with a diameter of more than 325 are called large-diameter steel pipes. The welding process used for large-diameter thick-walled straight seam steel pipes is double-sided submerged arc welding technology, and manual welding can also be performed after the steel pipe is formed. The generally used detection method is flaw detection. After the flaw detection is qualified, it can be shipped. Unqualified products need to be re-welded. Large-diameter thick-walled straight seam steel pipes are generally suitable for the transportation of fluids and liquids, the support of steel structures, and piling. They are widely used in petrochemicals, construction, tap water projects, power industry, agricultural irrigation, urban construction, etc. The steel pipe should be able to withstand the internal pressure, conduct a 2.5Mpa pressure test at the same time, and maintain no leakage for one minute. Eddy’s current flaw detection is allowed to replace the water pressure test. The main forming methods are UOE, RBE, JCOE, etc., among which JCOE has a high usage rate. It can also be threaded at the pipe end according to customer requirements, also called threaded and unthreaded.
First, the rust removal method of large-diameter straight seam steel pipe is introduced:
1. Cleaning: Use solvents and emulsions to clean the surface of large-diameter straight seam steel pipes to remove oil, grease, dust, lubricants, and similar organic matter, but it cannot remove rust, oxide scale, welding flux, etc. on the surface of large-diameter straight seam steel pipes, so it is only used as an auxiliary means in anti-corrosion production.
2. Tool rust removal: Mainly use tools such as wire brushes to polish the surface of large-diameter straight seam steel pipes, which can remove loose or raised oxide scales, rust, welding slag, etc. Manual tools can achieve Sa2-level rust removal, and power tools can achieve Sa3-level rust removal. If the surface of large-diameter straight seam steel pipes is firmly attached to an iron oxide scale, the tool rust removal effect is not ideal, and the anchor pattern depth required for anti-corrosion construction cannot be achieved.
3. Pickling: Generally, chemical and electrolytic methods are used for pickling. Pipeline anti-corrosion only uses chemical pickling, which can remove oxide scale, rust, and old coating. Sometimes it can be used as a re-treatment after sandblasting rust removal. Although chemical cleaning can achieve the best cleanliness and roughness on the surface, its anchor pattern is shallow and easy to pollute the environment.
4. Spray (blast) rust removal: Spray (blast) rust removal uses a high-power motor to drive the spray (blast) blade to rotate at high speed, so that steel sand, steel shot, wire segment, minerals, and other abrasives are sprayed (blasted) on the surface of the steel pipe under the action of centrifugal force. Not only can rust, oxides, and dirt be removed but also large-diameter straight seam steel pipes can achieve the required uniform roughness under the violent impact and friction of abrasives.
Second, the production process of large-diameter straight seam steel pipes:
The production process of large-diameter straight seam steel pipes generally includes hot rolling, hot coiling, casting, and other production methods. Large-diameter thick-walled steel pipes are generally processed using double-sided submerged arc welding production processes. The products are subjected to multiple processes such as bending, seaming, internal welding, external welding, straightening, and flat heads to meet the requirements of petrochemical standards.
The use of large-diameter straight seam steel pipes is mainly used for body support parts, such as bridge piling, seam piling, and high-rise building piling.
The materials used for large-diameter straight seam steel pipes are generally Q345B and Q345C. Q345D and Q345E large-diameter straight seam steel pipes are also used in areas with lower temperatures. They are mostly used in large-scale steel structure construction.
Post time: Dec-27-2024