How Much Do You Know about Galvanized Steel Pipe Welding?

Dec. 21, 2020

Many industries now use galvanized steel pipe, because this material is more convenient to use, and the quality of the product is obvious to all. Can galvanized pipe be welded? What are the welding characteristics and processes of galvanized steel pipes? Everyone will have doubts about this, so next, the galvanized steel pipe supplier will introduce galvanized steel pipe welding to you.

Welding characteristics of galvanized steel pipe

Galvanized steel pipe is widely used in all walks of life. The advantage of using galvanized steel is to use metallic zinc that can form a dense oxide protective layer in the air to protect the internal steel structure. In the case of welding or scratching, due to the existence of the Zn-Fe galvanic cell, the relatively active galvanized part can be used as a sacrificial anode, delaying the corrosion of steel, and has good corrosion resistance. However, due to the presence of the galvanized layer, cracks, pores, and slag inclusions are prone to occur during welding, and it is difficult to obtain good welding quality.

Galvanized Steel Pipe

The welding process of galvanized steel pipe

Galvanized steel pipes are generally coated with a layer of zinc outside of low-carbon steel, and the galvanized layer is generally 20um thick. The melting point of zinc is 419°C and the boiling point is about 908°C. In welding, zinc melts into a liquid floating on the surface of the molten pool or at the root of the weld.

Zinc has a large solid solubility in iron. The zinc liquid will etch the weld metal deeply along the grain boundary, and the low melting point zinc will form "liquid metal embrittlement". At the same time, zinc and iron can form brittle compounds between metals, such as Fe3Zn10, FeZn10, and so on. These brittle phases reduce the plasticity of the weld metal and cause cracks under tensile stress.

How to weld galvanized steel pipe?

The manufacturing process of galvanized welded steel pipe is like this. First, the pipe body is pickled. After pickling, it is cleaned in an ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride. Then sent to the hot-dip plating tank. 

Achieve the integration of the galvanized layer and the tube body. Uniformity of the galvanized layer Galvanized steel pipe shall be tested for the uniformity of the galvanized layer. The hydraulic test shall be carried out on the black pipe. Eddy current testing may also be used instead of the hydraulic test. The galvanized layer of the galvanized welded steel pipe water supply pipeline is guaranteed to be intact, without scratches on the surface, the pipeline is straight, and there is no blockage of stolen goods inside. Check that the threads of the pipe fittings are intact and there are no blisters cracks. 

Galvanized welded steel pipes are now used in traditional applications such as water pipes and gas pipes. They are also widely used in oil wells, oil pipelines, chemical equipment, mines and coal mine pipelines and heaters, and heat exchange tubes. If you want more information about high quality galvanized steel pipes, please contact us.

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