Spiral steel pipe seam weld porosity affects not only dense, causing pipeline leak, which will become a point of corrosion-induced, severely reducing weld strength and toughness. Weld porosity factors are: the flux of water, dirt, iron oxide, and welding the cover composition and thickness of the steel sheet and the surface quality of steel side plates treatment, welding and pipe forming process and other processes. Flux ingredients. CaF2 and SiO2 containing an appropriate amount of welding, the reaction will absorb a large amount of H2, without generating a high stability of the liquid metal is dissolved in HF, thereby preventing the formation of hydrogen gas holes. Bubbles. Bubbles occur in the center of the weld bead, which is mainly in the form of hydrogen gas bubbles remain hidden inside the weld metal, therefore, measures to eliminate such defects must be removed by first welding wire and rust, oil, water and moisture other substances, followed by drying the flux must remove moisture well. Moreover, the current increase, reducing the welding speed, slowing down the speed of solidification of the molten metal is very effective. Accumulation thickness flux is generally 25-45mm, solder large particle size, density hour accumulation take the maximum thickness, whereas the minimum value; high current, low welding speed stacking thickness maximum value, minimum value and vice versa, in addition, summer or air humidity, flux recovery should be dried before use. Sulfur crack (sulfur-induced cracking). Sulfur segregation with a strong welding plate (particularly flexible boiling steel) with sulfur segregation into the weld metal sulfides produced cracks. The reason is that the presence of hydrogen-containing low-melting zone in the segregation of sulfur in steel and iron sulfide. So, to prevent this situation generates, uses less sulfur segregation band semi-killed steel or killed steel is also clear efficiency. Second, clean the weld surface and flux and dry is also very necessary. Steel surface treatment. To avoid uncoiling leveling off of iron oxide and other debris into the molding process, the board should be set up cleaning device. Thermal cracking. In submerged arc welding, the inner weld hot cracking, and particularly in the arc of the arc crater cracks occur easily. To eliminate this crack, usually in the extinction of the arc and plate fitted and welded at the ends of the coil can be reversed and the spiral steel pipe welded into the stitch welding. Heat stress is a big crack in the weld time or when a high si weld metal in the most prone. Steel plate edge treatment. Steel plate edge should be set to remove rust and burrs devices to reduce possible pores. Clear device installed in the best location and disc cutting edge milling machines, structure of the device is the active wire wheel while two position adjustable gap down, up and down the compression plate edges. Involved in the welding slag. Is involved in the remaining part of the slag welding slag in the weld metal. Weld profile. Weld's form 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 factor control in 1.3-1.5, thick-walled spiral pipe maximum value, minimum value of thin-walled. Penetration of the poor. Inside and outside the weld metal overlap is not enough, and sometimes lack of penetration. This situation is called a lack of penetration degrees. Reduce secondary magnetic field.
To reduce the effects of magnetic blow, so that the connector position on the workpiece away from the welding cable welding is only possible terminal portion of the welding cable to avoid the secondary magnetic field generated in the workpiece. Undercut. Undercut is a V-shaped groove along the edge of the seam weld centerline. Undercut under welding speed, current, voltage, and other conditions resulting in inappropriate. Which is too high welding speed than the current does not fit easily cause undercut defects. Workmanship. Should be appropriate to reduce the welding speed or increase the current, thereby delaying the crystallization rate of the weld metal bath, in order to escape the gas, while the delivery position is unstable if the strip should be timely adjusted to eliminate the front axle through frequent trimming or Bridge to maintain shape, causing gas to escape difficult.
