Why can't stainless steel be welded with carbon steel electrode?
Why can't stainless steel be welded with carbon steel electrode?
What kind of welding rod is used for welding stainless steel pipe ?
Stainless steel electrode can be divided into chromium stainless steel electrode and chromium nickel stainless steel electrode.
Chromium stainless steel has certain corrosion resistance (oxidizing acid, organic 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 oxidation 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.
Key points and precautions of stainless steel pipe welding
一、 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 welding with wall thickness 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 welding current is 50~150a, the argon flow is 8~10l/min; when the welding current is 150~250a, the argon flow is 12~15l/min.
3. The length of tungsten electrode protruding from the gas nozzle is preferably 4 ~ 5mm. Where the working distance of the nozzle is not more than 2 ~ 6mm, the working distance of the nozzle is not more than 2 ~ 6mm.
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 angle between the center line of tungsten electrode and the workpiece at the welding position shall be generally maintained at 80 ° ~ 85 °, and the included angle between filler wire and 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.
二、 Key points and precautions for MIG welding of 904L UNS s08904 stainless steel.
1. Flat special welding power supply is adopted, and reverse polarity is adopted in DC (welding wire is connected to positive electrode)
2. Generally, pure argon (99.99% purity) or ar+2%o2 is used, and the flow rate is 20~25l/min.
3. The arc length and MIG welding of stainless steel are generally welded under the condition of spray transition, and the voltage should be adjusted to the extent that the arc length is 4 ~ 6mm.
4. Windbreak. MIG welding is easily affected by wind, and air holes are easy to be generated in windy places. Therefore, windproof measures should be taken in places with wind speed above 0.5m/s.
Service pressure of AISI 316, UNS s31603 stainless steel pipes and fittings
三、 Key points and precautions of stainless steel flux cored wire welding。
1. Flat welding power supply is adopted, and reverse polarity is adopted during DC welding. Ordinary CO2 welding machine can be used for welding, but please loosen the pressure of wire feeding wheel slightly.
2. The shielding gas is generally carbon dioxide, and the gas flow rate is 20 ~ 25L / min.
3. The distance between the welding nozzle and the workpiece should be 15 ~ 25mm.
4. Generally, when the welding current is below 250A, the dry extension length is about 15mm, and when the welding current is above 250A, it is about 20 ~ 25mm.
The welding of stainless steel pipe and stainless steel pipe fittings. The connection mode of stainless steel pipe and stainless steel flange is butt welding, flat welding and socket welding.
from: worldsteelasia
Email: emma@worldsteelasia.com
