Factors that Cause Porosity in LSAW Steel Pipes

We know that the quality of the welded seam determines the quality of the LSAW steel pipe. Once the porosity of the LSAW steel pipe, it will not only affect the tightness of the welded pipe, cause leaks in the pipe, but also become an induced point of corrosion. Reduce weld strength and toughness. 

In general, moisture, dirt, scale and iron filings in the flux, welding composition and thickness, surface quality of the steel plate, treatment of the steel plate side plate, welding process and steel pipe forming process, etc. may be the cause of the porosity of the weld. Therefore, during welding, if the welding temperature is high, the weld seam will be over-burned to form a perforation. When it contains the
appropriate amount of CaF2 and SiO2, it will react and absorb a large amount of H2, generating HF with high stability and insolubility in liquid metal. Prevent the formation of hydrogen holes; the forming factor of the weld is too small, the shape of the weld is narrow and deep, gas and inclusions are not easy to float out, and pores and slag are easy to be formed; rust and Deburring device to reduce the possibility of pores.

Welding temperature is a key parameter that affects the quality of the weld. The position of the removal device is best installed after the edge milling machine and disc shears. The structure of the device is two active steel wire wheels with adjustable gaps on one side, and the plate edges are pressed up and down. Flux accumulation thickness is generally 25-45mm, the flux granularity is large, the density is small, the maximum thickness is set to the maximum value, and vice versa; the minimum value; high current, low soldering speed, the maximum thickness is set to the maximum value, otherwise the minimum value, 

in addition, summer or When the air humidity is high, the recovered flux should be dried and then used; in order to reduce the influence of magnetic bias, the connection position of the welding cable on the workpiece should only be far away from the welding terminal to avoid the secondary magnetic field generated by the welding cable on the workpiece; The welding speed should be appropriately reduced or the current should be increased to delay the crystallization speed of the weld pool metal to facilitate gas escape. At the same time, if the strip delivery position is unstable, it should be adjusted in time to prevent frequent fine adjustment of the front axle or rear axle. The bridge is maintained to be formed, which makes it difficult for gas to escape; in order to avoid uncoiling and leveling off of iron oxide and other debris entering the forming process, a plate surface cleaning device should be provided.

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