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Welding is a process in which the material of the workpiece to be welded (the same or different) is heated, pressurized or both, and whether the filler material is used is selected to make the material of the workpiece achieve the combination between atoms and form a long-time connection. So what are the key points and precautions of stainless steel welding?
1. What kind of welding rod or wire is used to weld stainless steel?
Stainless steel electrodes can be divided into chromium stainless steel electrodes and chromium nickel stainless steel electrodes. In these two types of electrodes, those that meet the national standard shall be assessed according to the provisions of the national standard GB / t983-2012.
Chromium stainless steel has certain corrosion resistance (oxidizing acid, cavitation) and heat resistance. It is usually selected as equipment materials for power station, chemical industry, petroleum and so on. However, the weldability of chromium stainless steel is generally poor. Attention should be paid to the welding process, heat treatment conditions and the selection of appropriate electrodes. Chromium nickel stainless steel electrode has good corrosion resistance and is widely used in the fields of chemical industry, chemical fertilizer and petroleum. In order to prevent intergranular corrosion due to heating, the welding current should not be too large, which is about 20% smaller than that of carbon steel electrode. The arc should not be too long and the interlayer should be cooled quickly. Narrow weld bead is appropriate.
2. Key points and precautions for stainless steel welding
1、 The power supply with vertical external characteristics is adopted, and the positive polarity is adopted in DC (the welding wire is connected to the negative pole)
1. It is generally suitable for the welding of thin plates below 6mm, with the characteristics of beautiful weld formation and small welding deformation.
2. The shielding gas is argon with a purity of 99.99%. When the argon flow is 150 ~ 15L / min, the argon flow is 150A ~ 15L / min.
3. The length of tungsten electrode protruding from the gas nozzle is preferably 4 ~ 5mm. It is 2 ~ 3mm in the place with poor shielding performance such as fillet welding, 5 ~ 6mm in the place with deep groove, and the distance from the nozzle to the working is generally no more than 15mm.
4. In order to prevent the occurrence of welding pores, the welding parts must be cleaned if there is rust, oil stain, etc.
5. When welding ordinary steel, the length of welding arc is 2 ~ 4mm; When welding stainless steel, it is better to use 1 ~ 3mm. If it is too long, the protection effect is not good.
6. During butt backing, in order to prevent the back of the underlying weld bead from being oxidized, the back also needs to be protected by gas.
7. In order to protect the welding pool well with argon and facilitate the welding operation, the tungsten electrode line and the workpiece at the welding position shall generally maintain an angle of 80 ° ~ 85 °, and the included angle between the filler wire and the workpiece surface shall be as small as possible, generally about 10 °.
8. Windproof and ventilation. Where there is wind, please take measures to block the net, and take appropriate ventilation measures indoors.