Welded steel pipe is divided into two kinds according to its welding seam shape-straight seam steel pipe and spiral steel pipe.

Steel pipe seam porosity affects not only the density of pipe welds, resulting pipeline leak, and will become a point of corrosion-induced, severely reducing weld strength and toughness.

Weld porosity factors are: the flux of water, dirt, and the iron oxide, the thickness of the welded components and coverage, and the surface quality of steel sheet processing side plates, the welding process and the pipe forming process and so on.

Relevant control measures are as below:

1.A flux component.When containing an appropriate amount of CaF2 and SiO2,  the welding processing will absorb large amounts of H2,and generate HF which with a high stability and does not dissolved in the liquid metal , thereby preventing the formation of hydrogen gas holes.

2.Accumulation thickness of flux is generally 25-45mm.When Flux is with big particles degree  and small density, take the maximum accumulation thickness, whereas the minimum value; high current, low welding speed take the maximum thickness, whereas the minimum value. Besides, when in summer or high humidity days, flux recovery should be dried before use.

3 Steel surface treatment. To avoid uncoiling leveling off of iron oxide and other debris falling into the molding process, the board cleaning device should be set up .

4 Steel plate edge treatment. Rust and burrs removal device should be set in the steel plate edge to reduce the possibility of porosity forming . The best location to install the clear device is near the 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.

5 Welding line profile. Welding form factor is too small,weld shape is narrow and deep , gas and inclusion is not easy to leak out and easy to form pores and slag. General weld factor control in 1.3-1.5, thick-walled pipe choose the maximum value,and minimum value of thin-walled.

6 Reducing the secondary magnetic field. To reduce the effects of magnetic blow, the connector position on the workpiece should keep away from the terminal part of the welding cable to avoid the secondary magnetic field generated in the workpiece.

7 Technology：Should appropriately reduce the welding speed or increase the current, thereby delaying the crystallization rate of the weld metal bath, in order to make it easy to release the gas, while if the delivery position is unstable, the strip should be timely adjusted to eliminate the front axle through frequent trimming or Bridge maintained forming, causing gas to escape difficult.