What should you pay attention to when welding seamless steel tubes
1. To prevent the back surface of the bottom bead from being oxidized when performing butt backing, gas back protection is also required.
2. In order to prevent the appearance of welding pores in special-shaped pipes, if there is rust or oil stains on the welding parts, it must be cleaned up.
3. Dry elongation, general welding current is about 5mm when 250A or less, and about 20-25mm when 250A or more.
4. Use flat welding power, reverse polarity when DC welding. Welding can be performed with a general CO2 welding machine, but the pressure of the wire feeding wheel should be slightly loosened.
5. Arc length, MIG welding of stainless steel special-shaped pipe, generally welding under the condition of spray transition, the voltage should be adjusted to the arc length of 4-6mm.
6. Special-shaped pipe MIG welding is susceptible to the wind, and sometimes the breeze creates pores, so wind prevention measures should be taken where the wind speed is above 0.5m / sec.
7. The length of the tungsten electrode protruding from the gas nozzle is preferably 4-5mm. It is 2-3mm in areas with poor shielding, such as fillet welding, and 5-6mm in the depth of the slot. The distance from the nozzle to the work generally does not exceed 5mm.
8. In order to protect the weld pool well with argon gas and facilitate the welding operation, the tungsten electrode centerline and the welding workpiece should generally maintain an angle of 80-85 °. The angle between the filler wire and the surface of the special-shaped pipe should be as small as possible. , Generally about 0 °.
9. The positive polarity is generally suitable for welding special-shaped pipes below 6mm in direct current. It has the characteristics of beautiful welding seam formation and small welding deformation. The protective gas is argon with a purity of 99.99%. When the welding current is 50-50A, the argon flow is 8-0L / min, and when the current is 50-250A, the argon flow is 2-5L / min.