In the process of producing submerged arc steel pipes, the temperature must be strictly controlled to ensure the reliability of welding. If the temperature is too low, the welding position may not reach the temperature required for welding. When most of the metal structures are still solid, it is difficult for the metals at both ends to penetrate each other and combine. When the temperature is too high, there are many metals in the molten state at the welding position. The texture of these parts is very soft and has corresponding fluidity. They may carry molten droplets. When such metal drops, there is also not enough metal to penetrate each other. And during welding, there will be some unevenness with welds to form molten holes. Therefore, the integrated sewage treatment equipment manufacturer reminds us that the temperature should be strictly controlled during the production process of submerged arc steel pipes. Regular manufacturers have good control technology, so they can achieve temperature control requirements during the production process to ensure product quality, so we need to buy submerged arc steel pipes from regular manufacturers.

Submerged arc steel pipes can be used for liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural use: as piling pipes, bridges; for docks, roads, building structures, etc. Submerged arc steel pipes are spiral seam steel pipes made of strip steel coils as raw materials, extruded at room temperature, and welded by automatic double-wire double-sided submerged arc welding. The strip steel is butt-jointed head and tail, using single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after rolling into steel pipes. Externally controlled or internally controlled roller forming is used. Both internal and external welding are performed by single-wire or double-wire submerged arc welding with foreign Lincoln electric welding machines, to obtain stable welding specifications.

What inspections do submerged arc steel pipes need to undergo after production?
(1) Hydrostatic test: The expanded steel pipes are inspected one by one on a hydrostatic test machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;
(2) Expansion: The submerged arc steel pipe is expanded along its entire length to improve the dimensional accuracy of the steel pipe and the distribution of stress inside the steel pipe;
(3) X-ray inspection II: X-ray industrial television inspection and pipe end weld filming are performed on the steel pipes after expansion and hydrostatic test;
(4) Magnetic particle inspection of pipe ends: This inspection is performed to detect defects at the pipe ends;
(5) X-ray Line inspection I: X-ray industrial television inspection of internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;
(6) Inspect the internal and external welds of spiral steel pipes and the parent materials on both sides of the welds;
(7) Acoustic inspection II: Perform acoustic inspection again to check the defects that may occur in straight seam welded steel pipes after expansion and water pressure;
(8) Chamfering: Process the pipe ends of the steel pipes that have passed the inspection to achieve the required pipe end groove size;
(9) Anti-corrosion and coating: Anti-corrosion and coating are performed on the qualified steel pipes according to user requirements.

Submerged arc steel pipe fittings and assemblies prefabricated in the processing plant must be completed, that is, all welds have been welded, flange interfaces have been installed, long-term pads have been installed, and all flange bolts have been inserted and tightened. The deviation of the outer dimensions of the submerged arc steel pipe assembly compared with the design value shall not exceed the following provisions; when the outer dimensions of the submerged arc steel pipe assembly are 3m, the deviation is ±5mm. When the outer dimensions of the submerged arc steel pipe assembly increase by 1m, the deviation value can increase by ±2mm, but the total deviation value cannot be greater than ±15mm.

Manually welded assemblies with flange interfaces or valves must be subjected to experiments. All assemblies should be marked according to the short pipe specifications in the drawings, and their outlet ends should be closed with blind plates or thread plugs. The outlet flange of the assembly can be welded firmly if the flange bolt holes are evenly distributed. If it is a flange connected to the equipment or a flange connected to the branch flange of other assemblies, it can only be welded at the end of the pipe, and it can only be welded after it is transported to the installation site for positioning. The assembly should also be equipped with valves, welded with short pipes for installing instruments for sewage and vent pipes, and the elevation marks for installing sliding brackets. The prefabricated pipe section should be cleaned inside. Submerged arc steel pipe assemblies should take into account the convenience of transportation and installation, and have adjustable joints. At the same time, they should have sufficient rigidity and should not produce long-term deformation.