In the welding process, the commonly used stainless steel electrodes in life can be divided into: chromium stainless steel electrodes and chromium nickel stainless steel electrodes.
Chromium stainless steel electrode has certain corrosion resistance and heat resistance. It is usually selected as some materials for power stations, chemical, petroleum and other equipment. However, the weldability of chromium stainless steel electrodes is usually poor. Attention should be paid to the welding process, heat treatment conditions and selection of suitable welding electrodes.
Chromium-nickel stainless steel electrode has good corrosion resistance and oxidation resistance, and it is widely used in the fields of fertilizer, petroleum and medical machinery manufacturing. In order to prevent intergranular corrosion caused by heating, the welding current should not be too large, about 20% less than that of carbon steel electrodes, the arc should not be too long, and the interlayer cooling is fast, so narrow bead welding is better.
Key points and precautions when welding stainless steel:
1. Power supply with vertical external characteristics, the welding wire is connected to the negative pole.
1. Generally suitable for welding thin plates below 6mm. It has the characteristics of beautiful appearance after the welding seam is formed, and less welding deformation.
2. The protective gas is argon with a purity of 99.99%. When the welding current is 50150A, the argon flow rate is 810L/min, and when the welding current is 150250A, the argon flow rate is 1215L/min.
3. The length of the tungsten electrode protruding from the gas nozzle is preferably 45 mm. The area with poor shielding such as fillet welding is 23mm, and the groove depth is 56mm. The distance from the nozzle to the workpiece is usually no more than 15mm.
4. In order to prevent welding pores, if there is rust or oil stains, it is necessary to clean the welded parts in time.
5. When welding ordinary steel, the length of the welding arc should be 24mm, and when welding stainless steel, the length of the welding arc should be 13mm. If the time is too long, the protection effect is not good.
6. In order to prevent the back side of the bottom weld bead from being oxidized when the bottom is connected, it is necessary to use gas protection.
7. In order to protect the welding pool with argon gas and facilitate the welding operation, the intermediate line between the tungsten electrode and the welding part should generally maintain an angle of 8085°, and the angle between the filler metal wire and the surface of the workpiece should be as small as possible. Approximately 10°.
8. Ventilation and windproof. In windy places, please take measures to block the network and take appropriate indoor ventilation measures.
2. A welding power source with flat characteristics, the welding wire is connected to the positive electrode.
1. The arc length of stainless steel and MIG welding are generally welded under spray transition conditions, and the voltage should be adjusted to an arc length of 46mm.
2. Windproof. MIG welding is more susceptible to wind, because wind may cause pores, so when the wind speed is higher than 0.5m/sec, it is necessary to take timely wind protection measures.