The causes and prevention methods of the stomata of the spiral steel pipe
welds, the shortcomings of the spiral steel pipe weld zone are stomata, hot cracks, and undercuts. Spiral steel pipe weld porosity not only affects the fineness of the pipe weld, but also constitutes the leakage of the pipe, and will become the induction point of corrosion, severely reducing the weld strength and durability.
The elements of the weld hole are: moisture, dirt, scale and iron filings in the flux, welding composition and masking thickness, appearance quality of the steel plate, steel plate edge treatment, welding process and steel tube forming process. Flux composition. When welding contains proper amount of CaF2 and SiO2, it will reverberate and absorb a lot of H2. The HF which is highly stable and insoluble in liquid metal can then avoid the formation of hydrogen pores.
Bubbles. Bubbles occur mostly in the center of the bead. The main reason is that hydrogen is still hidden inside the weld metal by means of bubbles. Therefore, it is necessary to eliminate the rust, oil, moisture and moisture of the wire and weld. Gas and other substances, and secondly it is necessary to dry the flux well to remove moisture. In addition, it is also useful to increase the current, lower the welding speed, and slow down the condensation rate of the molten metal.
The deposition thickness of the flux is generally 25-45mm, the flux particle size is large, the density is small, the stacking thickness takes the maximum value, and the minimum value is taken; the large current, the low welding speed stacking thickness takes the maximum value, and the minimum value, in addition, the summer or the air When the humidity is high, the recovered flux should be dried before use. Sulfur cracking (sulphur-induced cracking).