Large-diameter straight seam welded pipe is a general name, which is produced by steel strips, and the pipes welded by high-frequency welding equipment are called straight seam welded pipes. (It gets its name because the welding of the steel pipe is in a straight line). Among them, according to different uses, there are different subsequent 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 325 or more are called large pipes. caliber steel pipe. The welding process used for large-diameter thick-walled straight seam steel pipes is double-sided submerged arc welding technology. It can also be manually welded after the steel pipes are formed. The general detection method is flaw detection. Unqualified products need to be welded again. Large-diameter thick-walled straight seam steel pipes are generally suitable for fluid liquid transportation, steel structure support, and piling, and are widely used in petrochemical, construction, water supply engineering, electric power industry, agricultural irrigation, urban construction, etc. The steel pipe should be able to withstand the internal pressure, carry out the 2.5Mpa pressure test every hour, and keep it without leakage for one minute. The method of eddy current flaw detection is allowed to replace the hydrostatic test. The molding methods mainly include UOE, RBE, JCOE, etc., among which JCOE has a high usage rate. It can also be threaded at the end of the pipe according to the customer's requirements, also known as threaded or unthreaded.
Introduction of rust removal method for large diameter straight seam steel pipe:
Use solvents and emulsions to clean the surface of large-diameter straight seam steel pipes to remove oil, grease, dust, lubricants, and similar organic substances, but it cannot remove rust, scale, welding flux, etc. on the surface of large-diameter straight seam steel pipes. only as an aid.
2. Tool derusting
Mainly use tools such as wire brushes to polish the surface of large-diameter straight seam steel pipes, which can remove loose or raised scales, rust, welding slag, etc. The rust removal by hand tools can reach the Sa2 level, and the power tool rust removal can reach the Sa3 level. If the surface of the large-diameter straight seam steel pipe is firmly oxidized, the rust removal effect of the tool is not ideal, and the anchor pattern depth required for anti-corrosion construction cannot be reached.
Generally, chemical and electrolytic methods are used for pickling treatment. Only chemical pickling is used for pipeline anticorrosion, which can remove scale, rust, and old coatings. Sometimes it can be used as retreatment after sandblasting and rust removal. Although chemical cleaning can achieve the cleanliness and roughness of the surface, its anchor pattern is shallow and it is easy to pollute the environment.
4. Spray (throw) to remove rust
Spraying (throwing) rust removal is driven by a high-power motor to rotate the spraying (throwing) blades at high speed, so that steel sand, steel shots, iron wire segments, minerals, and other abrasives are sprayed (throwing) on the surface of the steel pipe under the action of centrifugal force, not only rust, oxides and dirt can be removed, but also the required uniform roughness can be achieved under the violent impact and friction of abrasives.
The production process of large diameter straight seam steel pipe:
The production process of large-diameter straight seam steel pipes generally includes hot rolling, hot coiling, casting, and other production methods. Generally, large-diameter thick-walled steel pipes will use double-sided submerged arc welding production technology. Welding, straightening, flat head, and other processes meet the requirements of petrochemical standards.
Large-diameter straight seam steel pipes are mainly used for body support parts, such as bridge piling, submarine piling, and high-rise building piling.
The materials used for large-diameter straight seam steel pipes are generally Q345B and Q345C. Areas with lower temperatures will also use Q345D, and Q345E large-diameter straight seam steel pipes are mostly used in large-scale steel structure construction.