Whole Argon Filling And Partial Argon Filling in Argon Arc Welding

When argon arc welding is used to weld stainless steel, due to the high affinity between stainless steel and oxygen, if no weld protection measures are taken, the weld metal on the back is easily oxidized during the welding process, alloy elements are burned, and welding defects are prone to occur, resulting in The mechanical properties and corrosion resistance of the weld metal decrease.

In argon arc welding of stainless steel pipes, in order to ensure the welding quality of the back of the weld, effective protective measures must be taken.

Argon arc welding of stainless steel pipes generally adopts argon filling in the pipe, self-shielding welding wire an argon-free welding protective agent, etc., which can well prevent the oxidation of the back of the weld, so that the mechanical properties and corrosion resistance of the weld can be effectively guaranteed.

Now we will introduce the argon-filled back protection and precautions of the stainless steel argon arc welded pipe.

1. Overall argon filling method

For small-diameter pipes or short pipe fittings, argon filling can be used as a whole, which is relatively simple.

The method of filling argon as a whole: seal both ends with adhesive tape (paper shell, rubber plate, etc.), fill argon gas from one end of the tube, and make a 3-5mm discharge hole on the top of the other end of the seal, mainly to prevent the arc from falling inside the tube. Argon gas pressure is too high, resulting in difficulty in arc closing of joints, and defects such as pits.

In addition, in order to prevent a large amount of argon gas from being discharged in the gap between the counterparts, the paper tape can be used to seal a section of the nozzle in advance, leaving only the length of continuous welding for the welder until the welding is completed.

2. Partial argon filling method

When the pipe diameter is large and the pipeline is long, if argon is directly filled into the pipe, the welding quality is not easy to guarantee, and a large amount of argon will be wasted, which will increase the maintenance cost.

In order to save argon, partial argon can be used. Partial argon can be filled with water-soluble paper. Before the alignment, paste water-soluble paper on both sides of the pipe at a distance of 150 mm from the welding port to form a set of temporary blocking boards, and then fill the pipe with argon gas at the gap between the ports.

When the piping system undergoes a hydrostatic test, the water-soluble paper will quickly dissolve in water and be discharged with the water without causing adverse effects. In addition, an argon-filled fixture can be made for partial argon-filled protection. Before welding, place the blocking plates of the argon-filled fixture on both sides of the pipe, and pull the fixture out of the pipe after welding. This method is suitable for the ground prefabrication of stainless steel pipes and is simple and easy to implement.

(2) Argon flow should be appropriate. If the flow rate is too small, the protection is not good, and the back of the weld is easy to oxidize; if the flow rate is too large, eddy currents will be generated during welding and the air will be brought into the air, and the protection effect will also deteriorate.

(3) The argon gas inlet should be placed as low as possible in the closed section, and the air discharge hole should be placed at a higher position in the closed section. Because argon is heavier than air, filling argon from a lower position can easily ensure a higher concentration, and the protective effect of argon filling is better.

(4) In order to reduce the loss of argon gas in the pipe from the gap between the counterparts, which will affect the protection effect and increase the cost, the paper tape can be pasted along the gap of the weld before welding, leaving only the length for the welder to start arc welding.

In actual work, the protection method for the back of the weld should be flexibly selected according to factors such as welding engineering quantity, pipe specifications, process requirements, and applicability of operation to ensure welding quality.