How to pay attention to safety in stainless steel welding?Date:2018/7/28 16:21:54
1. use vertical external characteristic power supply, DC adopts positive polarity (wire to negative electrode).
2. generally suitable for welding below 6mm thin plate, with beautiful weld appearance and small welding deformation.
The 3. gas is argon, and the purity is 99.99%. When the welding current is 50 "150A, the argon flow rate is 8" 10L/min, when the current is 150 "250A, the argon flow rate is 12" 15L/min.
4. the length of the tungsten pole from the gas nozzle, to 4 "5mm is good, in the corner welding and other obscured places is 2" 3mm, in the depth of the slotting place is 5 "6mm, the nozzle to work the distance is generally not more than 15mm.
5. in order to prevent the appearance of welding porosity, rust and oil stains must be cleaned up.
6. Welding arc length, welding ordinary steel, 2 "4mm is better, while welding stainless steel, 1" 3mm is better, too long is not good protection effect.
7. when the bottom is butted, the backside also needs gas protection to prevent the oxidation of the back side of the bottom bead.
8. in order to protect the welding pool well and facilitate the welding operation, the center line of the tungsten pole and the welding place should keep the angle of 80 "85 degrees, and the angle between the filler wire and the workpiece surface should be as small as possible, usually about 10 degrees.
9. wind and air change. In the windy area, please take the measures of blocking the net, while indoors, it is necessary to take appropriate ventilation measures.
Key points and notices of stainless steel MIG welding
1. adopt flat special welding power source, and reverse polarity is adopted when DC is used.
2. generally pure argon (purity is 99.99%) or Ar 2%O2, and the flow rate is 20 "25L/min".
3. Arc length, stainless steel MIG welding, generally under the condition of spray transfer welding, voltage to adjust to the length of the arc in 4 "6 mm degree.
4. windproof. MIG welding is susceptible to wind. Sometimes it can be done as wind to produce air holes, so wind speed above 0.5m/sec should be taken windproof measures.
Key points and attentions of stainless steel cored wire
1. adopt flat special welding power source and reverse polarity when DC welding. Welding can be done with a general CO2 welder, but the pressure of the wire feed wheel should be slightly loosened.
2. the protection gas is generally carbon dioxide gas, and the gas flow rate is 20 "25L/min".
3. the distance between the 3. welding nozzle and the workpiece is 15 "25mm".
4. dry extension length, the general welding current is less than 250A, about 15mm, when 250A is above, about 20 "25mm is more suitable."
1. Chromium stainless steel has certain corrosion resistance (oxidizing acid, organic acid, cavitation corrosion), heat resistance and wear resistance. Usually used in power plants, chemicals, and petroleum
Materials such as equipment. Chromium stainless steel weldability is poor, attention should be paid to welding technology, heat treatment conditions and suitable welding electrodes.
2. CR 13 stainless steel is more hardened after welding and easy to crack. If the same type of chromium stainless steel electrode (G202, G207) is used for welding, it is necessary to preheat above 300 C and slow cooling treatment around 700 C after welding. If the weldment cannot be heat treated after welding, chrome nickel stainless steel electrodes (A107 and A207) shall be used.
3. The weldability of Cr-17 stainless steel is better than that of Cr-13 stainless steel by adding appropriate stable elements Ti, Nb and Mo to improve corrosion resistance and weldability. The same type of chromium stainless steel electrode (G302, G307) should be preheated above 200 C and tempered around 800 C after welding. If the weldments are not heat treated, chrome nickel stainless steel electrodes (A107 and A207) shall be used.
4. Chromium-nickel stainless steel electrode has good corrosion resistance and oxidation resistance, and is widely used in chemical industry, fertilizer, petroleum, medical machinery manufacturing.
5. When chromium nickel stainless steel is welded, carbides are repeatedly heated to reduce corrosion resistance and mechanical properties.
6. Chrome nickel stainless steel has titanium calcium type and low hydrogen type. The titanium calcium type can be used for AC and DC, but when the AC welding is shallow, it is easy to turn red at the same time, so the DC power is used as far as possible. The diameter of 4 and below can be used for all position weldments, 5 and above for flat welding and fillet welding.
7, the welding rod should be dry in use, the titanium calcium type should be dried at 150 degrees for 1 hours, the low hydrogen type should be dried at 200-250 C for 1 hours (not repeated drying for many times, otherwise the skin is easily cracked and peeled), preventing the welding rod from sticking oil and other dirt, so as to avoid the increase of carbon content and the quality of the welding parts.
8. The welding current should not be too large to prevent the welding current from heating, which is 20% less than that of carbon steel electrode. The arc should not be too long and interlayer fast cold, so it is suitable for narrow welding channel.