Electric welding is quite simple to say, but it is actually quite complicated. Pipeline can be said to be the most difficult to weld with many angles. The angle of welded pipe is more important, that is, the angle between covered electrode and weld is generally >; =90 degrees, the current is, for example, the current at the bottom of the weld is small and the current at the top of the weld is much larger. Climbing welding and vertical seam naturally look similar, but the current is also different.
Welding method: According to different welding methods, it can be divided into arc welded pipe, high-frequency or low-frequency resistance welded pipe, gas welded pipe, furnace welded pipe and Bondi pipe.
Welded steel pipe: used for oil drilling and machinery manufacturing.
Furnace welded pipe: can be used as water gas pipeline, etc. Large diameter straight welded pipe is used for high pressure oil and gas transportation. Spiral welded pipe is used for oil and gas transportation, pipe piles, piers, etc.
Extended data:
GB/T309 1- 1993 (galvanized welded steel pipe for low-pressure fluid transportation). Mainly used for conveying water, gas, air, oil, heating hot water or steam and other general low-pressure fluids. Its representative material is Q235A grade steel.
GB/T3092- 1993 (galvanized welded steel pipe for low-pressure fluid transportation). Mainly used for conveying water, gas, air, oil, heating hot water or steam and other general low-pressure fluids. Its representative material is Q235A grade steel.
Gb/t14291-1992 (welded steel pipe for conveying mining fluid). It is mainly used for straight seam welded steel pipes in mine air pressure, drainage and gas discharge in shaft. Its representative materials are Q235A and B grade steel. GB/T 14980- 1994 (large diameter welded steel pipe for low-pressure fluid transportation). Mainly used for conveying water, sewage, gas, air, heating steam and other low-pressure fluids. Its representative material is Q235A grade steel.
Gb/t12770-1991(stainless steel welded steel pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, hotel decoration and other mechanical parts and structural parts. The representative materials are 0Cr 13, 1Cr 17, 0cr19ni118Ni9, 0cr18ni.
Gb/t12771-1991(welded stainless steel pipe for liquid transportation). Mainly used for conveying low-pressure corrosive media. The representative materials are 0Cr 13, 0Cr 19Ni9, 00cr19ni1,00Cr 17, 0cr18ni/kloc-.
Welding requirements:
1) All relevant construction schemes shall be submitted before welding construction, and professional technical disclosure shall be made in different procedures before each procedure operation. The plans to be submitted include: clean pipeline construction plan, clean pipeline welding procedure and endoscope detection procedure;
2) Welders shall be trained and qualified by relevant labor departments and hold special operation certificates. The welder who operates the automatic welding machine shall provide corresponding training certification materials for automatic welding of clean pipes.
3) According to the design requirements and technical requirements, conduct special quality training for all personnel involved in the construction of special clean pipes, and make clear the correct practices and operation requirements;
4) Purifying gas (used for the inner surface of welded pipe) and shielding gas (used as the protective layer of external welding part) for welding shall provide complete quality certificates, including oxygen content and moisture content.
5) In the weld seam that cannot be welded automatically, excellent welders can be selected for manual welding.
6) All welds shall be free of corrosion spots, pinholes, corrosion traces and spot welding traces, the internal and external surfaces shall be free from obvious unevenness, and the welding wave shall be even and straight;
7) During the construction, strict inspection must be carried out according to the technical disclosure requirements of the scheme and process;
8) Precast welds and on-site welds shall be inspected by endoscope in time according to the requirements of inspection proportion. When X-ray nondestructive testing is needed, random inspection shall be carried out according to the proportion required by the design;
Records of welding construction process shall be established in time and truly. When the project site management has special requirements, it should be implemented according to its special requirements.
References:
Baidu encyclopedia-welded steel pipe