The advantage of thick-walled straight seam steel pipe is that the online heat treatment process of the weld eliminates welding stress, refines the metallographic grains of the heat-affected zone, and improves the physical and mechanical properties. Western developed countries attach importance to the application of HFW/ERW welded pipes. For example, Greece and Japan produce HFWф610mm×25.4mmX60 and X65 steel grade welded pipes respectively to replace seamless steel pipes and thick-walled straight seam steel pipes. There is a misunderstanding in China that HFW/ERW welded pipes can be used for pipes below ф406mm, and thick-walled straight seam steel pipes should be used for pipes above ф406mm, which leads to the development of HFW/ERW units in the direction of producing thick-walled straight seam steel pipe products.
The direction of structural adjustment of high-frequency straight seam welded pipes in the future is to advance into high-grade and large-wall thick product series. The typical process is the “F.F.X forming + hot stretching and reducing diameter + full pipe heat treatment” mode to meet the market demand for oil and gas pipelines, submarine pipelines, and oil well pipes. The high-frequency straight seam welded pipe heat treatment mode can also be used to develop building structure pipes, boiler pipes, and marine pipelines for thick-walled straight seam steel pipes. High-frequency straight seam welded pipes should also pursue product diversification and produce precision pipes such as automobiles, light industry, chemicals, textiles, food, medical care, medium and low-pressure boilers, household appliances, construction, and container pipes.
The basic process of daily maintenance of thick-walled straight seam steel pipe cantilever crane.
1. When hanging and lifting thick-walled straight seam steel pipes, the wire rope is not allowed to be pulled obliquely to prevent the wire rope from slipping out of the groove.
2. Pay attention during operation to ensure personnel and equipment.
3. Check the switches before and after the trolley frequently to see if the switches with the maximum limit of the hook rise are good and sensitive.
4. Lubrication points such as gears, sprockets, chains, and ropes of thick-walled straight seam steel pipes should be refueled regularly.
5. When operating the cantilever crane, you must work closely with the hanging personnel and obey the hanging command.
6. The hook should be fully loaded with coils.
7. The wire rope should be replaced when 10% of the strands are broken.
8. Check the lifting brake of the hook frequently to see if it is good and sensitive.
The production process of large-diameter thick-walled straight seam steel pipe is automatic submerged arc welding, and the process procedures are 1 pre-bending, 2 pre-welding, 3 internal and external welding, 4 rounding straightening, and 5 port processing. Large-diameter thick-walled seam steel pipes are becoming more and more important in the steel pipe application industry. The main application industries of large-diameter thick-walled straight seam steel pipes include water conservancy projects, steel structures, the power industry, the chemical industry, urban planning construction, irrigation, long-distance oil and gas pipelines, bridge piling, and submarine oil pipelines.
1. Thick-walled straight seam steel pipe and steel plate flaw detection: Before the steel plate for manufacturing large-diameter thick-walled straight seam welded steel pipe is put into production, the first step is to conduct a preliminary wave inspection of the steel pipe plate;
2. Steel plate milling: The milling machine developed and researched by the thick-walled straight seam steel pipe is used to mill the steel plate, and the steel plate is formed into a V-shaped groove shape;
3. JCOE forming: The JCO forming machine imported from Germany stamps the steel plate multiple times to form a “J” shape, and then the other end of the steel plate is made into a “C” shape using the same process, and finally an open “O” shape is formed.
4. Open pre-welding: The thick-walled straight seam steel pipe blank with a formed opening is pre-welded and the seams are closed. Here, padding-type shallow welding is used.
5. Internal welding after pre-welding: Lincoln double-sided automatic submerged arc welding machine performs submerged arc automatic welding on the inner weld of thick-walled straight seam steel pipe;
b. External welding: Double-sided automatic submerged arc welding machine performs submerged arc automatic welding on the outer weld of thick-walled straight seam steel pipe;
6. Cold expansion (reduction): Precision expansion of thick-walled straight seam steel pipe improves the precision size of thick-walled straight seam steel pipe and reduces the internal stress of steel pipe.
7. Non-destructive control of industrial TV assembly line operation of thick-walled straight seam steel pipe I: 100% strict inspection of the inner and outer welds of straight seam welded steel pipe and adjacent parent materials, working speed: 2.5 meters/minute.
8. Product water pressure test: The steel pipes are tested one by one on the water pressure testing machine to ensure the test pressure.
9. Port processing: Qualified thick-walled straight seam steel pipes are processed to meet the required form of the pipe end.
10. Steel pipe anti-corrosion: Thick-walled straight seam steel pipes are coated with anti-corrosion coating and related work according to the contract process.
From the existing technology, the hot delivery and hot charging furnace technology of continuous casting round billets can be promoted in continuous rolling tube production lines and some AR and ASSEL rolling mill production lines to achieve 100% continuous casting round billets. The online quenching heat treatment process of large-diameter seamless steel pipes has been successfully used in Valin Hengyang Steel Pipe, which has simplified the production process of alloy steel pipes and reduced energy consumption and heat treatment costs per ton of steel. The products of the “piercing + cold drawing (rolling)” unit can adapt to market demand and user recognition, and still have vitality at this stage; the hot rolling seamless steel pipe unit below ф76mm is defined as backward production capacity, and their is still controversy in the industry.
Post time: Dec-30-2024