Straight seam steel pipe is often used in the construction of tap water industry, petrochemical industry, etc. It is a steel pipe with the weld parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe, etc. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is relatively fast. Compared with spiral welded pipe, it has the advantage of fast production speed.
First, what is a straight seam steel pipe
General welded pipe: General welded pipe is used to transport low-pressure fluid. Made of Q195, Q215A, Q235A steel, Q235B ordinary carbon. It can also be made of easy-to-weld 0317 standard model 6012 and steel mother 755 mild steel. The steel pipe must undergo water pressure, bending, flattening, and other experiments, and has certain requirements for surface quality. The delivery length is usually 4-10m, and fixed-length (or multiple-length) delivery is often required. The specifications of welded pipes are expressed in nominal diameter (mm or inch). The nominal diameter is different from the actual diameter. According to the specified wall thickness, welded pipes are divided into ordinary steel pipes and thickened steel pipes. According to the form of the pipe end, steel pipes are divided into threaded and non-threaded. The welding process used for submerged arc welded straight seam steel pipes is submerged arc welding technology, which uses filler welding and particle-shielded flux submerged arc. The production diameter can reach 1500mm. LSAW is the English abbreviation for submerged arc welded straight seam steel pipes. The production processes of submerged arc welded straight seam steel pipes include JCOE forming technology and coil forming submerged arc welding technology. When the diameter is large, two steel plates may be used for coiling, which will form a double weld. The standards that can be implemented are the GB/T3091-2008 low-pressure fluid steel pipe production standard, GB/T9711.1-2 -1997 petroleum and natural gas steel pipe production and use standard, and the American API 5L pipeline steel pipe implementation standard. Production materials: Q195A-Q345E; 245R; Q345QA-D; L245-L485; X42-X70. The main pressure parameters are 2ST/T, S is the yield strength, and T is the wall thickness. Submerged arc welding has developed into double-wire submerged arc welding and multi-wire submerged arc welding, and the efficiency is further improved.
Second, the production process of straight seam steel pipes
Straight seam steel pipes can be divided into high-frequency straight seam steel pipes and submerged arc welding straight seam steel pipes according to the production process. Submerged arc welding straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. according to their different forming methods. The following introduces the most common high-frequency straight seam steel pipes and submerged arc welding straight seam steel pipe forming processes.
Submerged arc welding process
1. Plate detection: After the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipe enters the production line, the whole plate is first subjected to ultrasonic inspection;
2. Edge milling: The two edges of the steel plate are double-sided milled by the edge milling machine to achieve the required plate width, plate edge parallelism, and groove shape;
3. Pre-bending edge: The plate edge is pre-bent by the pre-bending machine so that the plate edge has the required curvature;
4. Forming: On the JCO forming machine, the first half of the pre-bent steel plate is pressed into a "J" shape through multiple-step punching, and then the other half of the steel plate is bent in the same way to form a "C" shape, and finally an open "O" shape is formed
5. Pre-welding: The formed straight seam welded steel pipe is seamed and continuously welded by gas-shielded welding (MAG);
6. Internal welding: The inner side of the straight seam steel pipe is welded by longitudinal multi-wire submerged arc welding (up to four wires);
7. External welding: longitudinal multi-wire submerged arc welding is used to weld on the outside of the straight seam submerged arc welded steel pipe;
8. Ultrasonic inspection I: 100% inspection of the internal and external welds of the straight seam welded steel pipe and the parent materials on both sides of the weld;
9. X-ray inspection I: 100% X-ray industrial television inspection of the internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;
10. Diameter expansion: The entire length of the submerged arc welded straight seam steel pipe is expanded to improve the dimensional accuracy of the steel pipe and improve the distribution of stress in the steel pipe;
11. Water pressure test: The expanded steel pipes are inspected one by one on a water pressure testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;
12. Chamfering: The steel pipes that have passed the inspection are processed at the pipe end to achieve the required pipe end groove size;
13. Ultrasonic inspection II: Ultrasonic inspection is performed again on each pipe to check for possible defects in the straight seam welded steel pipe after diameter expansion and water pressure;
14. X-ray inspection II: X-ray industrial television inspection and pipe end weld filming of steel pipes after expansion and water pressure test;
15. Magnetic particle inspection of pipe ends: This inspection is carried out to find defects at the pipe ends;
16. Anti-corrosion and coating: Qualified steel pipes are anti-corrosion and coated according to user requirements.
Third, the use of straight seam steel pipes
Straight seam steel pipes are mainly used in tap water projects, the petrochemical industry, the chemical industry, the power industry, agricultural irrigation, and urban construction. For liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural use: as piling pipes, bridges; docks, roads, building structures, etc.
What is the production process of straight seam steel pipes into steel bent pipes?
1. What is a steel bent pipe: Steel bent pipes are bent using a set of bending dies. Regardless of the type of machine equipment, most of them use steel bent pipes, which are mainly used for oil, gas, and liquid transportation, and they occupy a very important position in aircraft and their engines.
2. Steel elbows can bend various profile sections: almost all sections of aluminum, steel, stainless steel, copper, and other metal profiles, and pipes (spiral steel pipes, straight seam steel pipes, seamless steel pipes) can be bent. Steel elbows have good bending qualities. Materials that have been sprayed, electroplated, polished, brushed, etc. can be bent directly without damaging the surface of the material.
3. The materials of variable diameter steel elbows: cast iron, stainless steel, alloy steel, forgeable cast iron, carbon steel, non-ferrous metals plastics, etc.
4. Connection with steel pipes: direct welding (the most commonly used method) flange welding, hot melt connection, threaded connection, socket connection, etc.
According to the production process, it is divided into: welding elbow, stamping elbow, casting elbow, etc.
Steel elbows are commonly used connecting pipe fittings in pipeline installation, used for connection at the end of the pipeline. Other names: 90-degree bend, right angle bend. Uses: used for two steel pipes with the same or different nominal diameters to make the pipeline turn at a certain angle.
5. Classification of steel elbows:
1) According to the material, it can be divided into carbon steel, cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon asphalt, PPC, etc.
2) According to the manufacturing method, it can be divided into pushing, pressing, forging, casting, etc.
3) According to the manufacturing standard, it can be divided into national standard, electrical standard, water standard, American standard, German standard, Japanese standard, Russian standard, etc.
4) According to its true radius of curvature, it can be divided into long-radius elbow and short-radius elbow. Long radius elbow means that its curvature radius is equal to 1.5 times the outer diameter of the steel pipe, that is, R=1.5D. Short radius elbow means that its curvature true radius is equal to the outer diameter of the steel pipe, that is, R=1.0D (D is the straightness of the elbow, R is the true radius of curvature).
5) If classified by pressure level: there are about 17 types, which are the same as the American steel pipe standards, including Sch5, Sch10s, Sch10, STD, Sch60, Sch80s, Sch100, Sch120, Sch140, Sch160, XXS, among which STD and XXS are the most commonly used.
