How to choose the overall argon filling and partial argon filling for argon arc welding?

When welding stainless steel by argon arc welding, due to the high affinity of stainless steel and oxygen, if the welding seam protection measures are not taken, the weld metal on the back is easily oxidized during the welding process, the alloying elements are burned, and welding defects are easily generated, causing The mechanical properties and corrosion resistance of the weld metal decrease. During 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 pipelines generally adopts methods such as filling argon in the tube, self-shielded welding wire and welding protective agent without argon filling, 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, the back protection and precautions of argon-filled stainless steel argon arc welded pipe will be introduced. 1. Filling the tube with argon for protection: The method of filling the tube with argon is to prevent oxidation of the back of the weld. The argon filling method mainly includes overall argon filling and partial argon filling. 1. Overall argon filling method: For small-diameter pipes or when the pipe fittings are short, the overall argon filling can be used, and this method is relatively simple. The method of filling argon as a whole: seal both ends with tape (paper shell, rubber sheet, etc.), fill one end of the tube with argon, and make a 3-5mm discharge hole on the top of the other end of the seal, mainly to prevent the inside of the tube when the arc ends. The argon gas pressure is too large, which makes it difficult to end the arc of the joint, resulting in pits and other defects. In addition, in order to prevent a large amount of argon gas from being discharged in the gap between the counterparts, a section of the nozzle can be sealed with paper tape in advance, leaving only the length of the welder for one continuous welding until the welding is completed. 2. Local argon filling method: When the pipe diameter is large and the pipeline is long, if the pipe is directly filled with argon, the welding quality is not easy to guarantee, and a large amount of argon gas will be wasted, increasing the maintenance cost. In order to save argon, the method of partial argon filling can be used. Local filling of argon can be done by water-soluble paper method. Before pairing, stick water-soluble paper 150mm from both sides of the welded joint in the tube to form a set of temporary blocking plates, and then use an argon-filled needle to fill the tube with argon gas at the gap between the opposite ports. When the pipeline system is subjected to the hydrostatic test, the water-soluble paper is quickly dissolved in the water and is discharged with the water without causing adverse effects. In addition, argon-filled fixtures can be made for partial argon-filling protection. Before welding, the argon-filled fixture blocking plates are placed on both sides of the tube in advance, and the fixture is pulled out of the tube after welding is completed. This method is suitable for ground prefabrication of stainless steel pipes, which is simple and easy to implement. 2. Judgment of the effect of argon protection: The effect of argon protection can be judged according to the color of the weld. During the welding process, the welder can adjust the shielding gas according to the color, so that the welding seam can achieve better protection effect. Its color is silver white, golden yellow is the best, blue is good, red-gray is better, gray is bad, gray-black is the worst. 3. Precautions for argon filling protection (1) During argon arc welding, the back of the weld should be supplied with air in advance, and the flow rate should be appropriately increased. After the air is discharged, the flow rate will gradually decrease. During the welding process, the tube should be filled with argon continuously. When the welding is stopped, the gas is stopped after the welding, so that the welding seam can be fully protected. In addition, special attention should be paid to the fact that welding can only be carried out after the air is exhausted, otherwise the protective effect of argon filling will be affected. (2) Argon gas 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, the eddy current will be brought into the air during welding, and the protection effect will be deteriorated. (3) The argon 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 protection effect of argon filling is better. (4) In order to reduce the loss of argon gas in the tube from the gap between the counterparts, affect the protection effect, and increase the cost, paper tape can be pasted along the gap between the welds before welding, leaving only the length of the welder to start arc welding. In actual work, the protection method on the back of the weld should be flexibly selected according to the factors such as the amount of welding works, pipe specifications, process requirements and applicability of operation, so as to ensure the welding quality.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods