Back protection method for welding stainless steel tube

With the rapid development of the petrochemical industry, stainless steel materials(such as stainless seamless steel pipe) have been widely used, which has also put forward higher requirements for the welding of pipes and plates, and has gradually eliminated the previous stainless steel arc welding priming method. When using argon arc welding for primer welding, argon arc welding for primer is faster and cleaner than arc welding. At the same time, some problems also arise.

During the welding process, since the back of the stainless steel argon arc welding primer is easily oxidized and causes defects, back protection measures must be taken to ensure the mechanical properties and corrosion resistance of the weld. Therefore, effective protection must be taken when welding stainless steel tubes.

1. Protective cover filled with argon protection method

This method is often used in the welding of large-diameter stainless steel pipes. The protective cover is connected to a metal pipe and an argon gas hose. The argon gas valve is opened to fill the protective cover with argon gas. The advantages of this method are concentrated protection and less argon gas waste.

2. Local argon filling protection method

For pipelines with small local space and short dimensions, it is easy to use local protection. Method: seal the pipeline welding joint with tape (to prevent air leakage), seal both ends of the pipeline with sponge, rubber, paper shell, etc., and connect the argon hose from Insert one end and fill it with argon gas, and it is best to make a small hole in the sealing area of the other end of the pipe. This will facilitate the final welding joint and will not cause dents due to excessive internal pressure;

During welding, in order to prevent a large amount of argon gas from being discharged from the weld seam, the weld sealing tape should be torn off and welded in sections. This can reduce the loss of argon gas and effectively protect the weld seam. This method is characterized by waste, slow argon filling, and high cost.

3. Direct argon filling method in the welding joint

For pipelines that are too long and have slightly larger diameters, local argon filling is too wasteful, the quality cannot be guaranteed, and the project cost is too high. In order to save costs, the direct argon filling method at the welded joint can be used.

4. Plugging method on both sides of the weld seam

Process the sponge into a plug with a slightly larger diameter for the pipe and connect the two pieces of sponge with a wire at a distance of 300-400 mm to make a double plug. Connect one end of the plug to a longer section of steel wire. When the two pieces meet, plug the plug at the key point first. Weld 150-200 mm on both sides of the weld. The long iron wire at one end should be longer than the length of the pipe at one end of the weld and expose the pipe end. One end of the small metal pipe is flattened, and the other end is connected to the argon hose. The flattened end is inserted into the aligned weld. Seam, fill with argon, and the best insertion direction is the uppermost part, so that before the bottom welding of the final joint, the small tube can be pulled out and welded by the remaining gas in the pipe. After welding, use wire to pull out the plug.

5. Argon gas protection judgment

The protective effect of argon gas can be judged according to the color of the internal weld, so that the operator can adjust the argon gas according to the color to achieve the best protection effect. White and golden yellow are most suitable.

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