Causes and measures of pipe weld porosity
Weld pipe weld porosity affects not only the pipeline denseness, resulting pipeline leakage and corrosion will be induced point seriously reduce the weld strength and toughness. Factors weld porosity are: the flux in the water, dirt, oxide and iron filings, welding ingredients and cover thickness, surface quality steel and steel side plates processing, welding technology and steel molding processes.
Related prevention measures:
1. Flux ingredients. CaF2 and SiO2 containing an appropriate amount of welding, the reaction will absorb large amounts of H2, generating a high stability of the HF insoluble in the liquid metal, thereby preventing the formation of hydrogen gas holes.
2. The bulk thickness of the flux is generally 25-45mm, large solder particle size, bulk density hour take the maximum thickness, whereas the minimum value; high current, low welding speed accumulation take the maximum thickness, whereas the minimum value addition, summer or air humidity, flux recovery should be dried before use.
3. The surface-treated steel sheet. To avoid open-book leveling off oxide scale and other debris into the molding process, the board should be set cleaning device.
4. Steel plate edge processing. Steel plate edge should be set rust and burr removal device to reduce the possible generation of holes. Removing device installed in the best position after the milling machine and disc shear, the structure of the device is the active wire wheel side two up and down position adjustable gap, the upper and lower clamping plate edge.
5. Weld profile. Weld forming factor is too small, narrow and deep weld shape, gas and inclusion is not easy to leak out, easy to form pores and slag. General weld coefficient control in 1.3-1.5, thick-walled pipe maximum value, minimum value of thin-walled.
6. Reduce secondary magnetic field. To reduce the influence of magnetic blow should be made on the workpiece welding cable connection location only possible away from the welding terminal, to avoid some welding cable secondary magnetic field generated in the workpiece.
7. Workmanship. Should be appropriate to reduce or increase the speed of the welding current, thereby delaying the crystallization rate of the weld metal bath in order to facilitate the escape of gas, at the same time, if the strip delivery location instability, should be timely adjusted to eliminate frequent fine-tuning after the adoption of the front axle or bridge to maintain molding, causing gas to escape difficult.