Thin-walled stainless steel pipe is a new type of energy-saving and environmentally friendly pipe with good corrosion resistance, long life, reliable connection of pipe fittings, and moderate price. Argon welding is used for high-pressure stainless steel pipelines with high cleanliness and engineering quality requirements. It is widely used in industrial and boiler pipeline installation projects. With the development of the national economy, argon electric welding of thin-walled stainless steel pipes will be a new trend in the installation of industrial and boiler piping systems.
How should the thin-walled stainless steel welded pipe be welded?
1 Features
The connection of thin-walled stainless steel pipes using argon electric welding has the following advantages over manual arc welding and argon arc welding:
1.1 Welding quality is good: according to the welding process evaluation, select the appropriate welding wire, tungsten electrode, welding process parameters and protective gas that meet the requirements of the purity, which can make the weld root be well integrated. When performing radiographic inspection, the pass rate is significantly higher.
1.2 High efficiency: the same welder uses the argon welding process and the manual arc welding process to weld the same welding port. The welding efficiency of the argon welding process is 2 to 4 times that of the manual arc welding and 1 to 2 times that of the argon arc welding , Significantly shorten the construction period.
2.3 Low cost: After comprehensive measurement, it is found that argon arc welding can reduce the overall construction cost by 10 to 20% than manual arc welding, and can reduce the overall construction cost by 5 to 15% than argon arc welding, and the welding joint is well formed and the repair rate is low , Reducing the overall cost.
2 Scope of application
This construction method is mainly suitable for the installation of thin-walled stainless steel industry and boiler pipes with high welding quality. The diameter of the welded pipe is DN10mm ~ DN230mm, and the thickness of the pipe wall is 1.5 ~ 6mm.
3 Process principle
Argon argon welding is to weld the bottom of the weld seam by argon arc welding, and then use the welding method of the arc welding cover surface. First, determine the angle and position of each welding zone for the circumferential butt weld of the pipe, and then determine the parameters of each zone: Preheating temperature, welding temperature, current, welding pulse, argon flow rate, etc., it combines the advantages of the two welding methods, and can ensure the quality of the project.
4 Process flow and operation points
4.1 Process flow
Construction preparation → pipe cutting → bevel processing → bevel inner and outer surface cleaning → electrode drying → DC welding machine adjusting current → welding pairing → locating spot welding → bottom welding → cover welding → appearance inspection → flaw detection
4.2 Operational points
4.2.1 Construction preparation:
1) Strictly control the purchase of materials, conduct material testing and mechanical performance re-inspection according to regulations, and do a good job in welding process evaluation, grade welder training, technical disclosure, etc.
2) Electrode drying: This process uses stainless steel alkaline electrode, the drying temperature is 350-380 ℃, the drying time is 1--2 hours, and the dried electrode is placed in a 110-150 ℃ incubator , The electrode used on site is stored in the heat preservation barrel.
3) Process parameter selection:
①Preheating temperature control: the general preheating temperature is controlled at 180-200 ℃, and the preheating time is 1-3 minutes.
② Welding track inclination: When the inclination is too small, bridging is more likely to occur, while the inclination is too large, it is easy to produce virtual welding. The inclination of the track should be controlled between 5 ° and 7 °.
③Welding temperature: The welding temperature should be controlled at 250 ± 5 ℃.
④Use orthogonal test method to find the most ideal parameter value.
