The SSAW welding process is known for its efficiency and suitability for large-diameter pipes. It produces pipes with a spiral seam, making them suitable for applications such as oil and gas transmission, water pipelines, and structural uses. This article will talk about welding process of SSAW steel pipe.
The SSAW steel pipe initiates the welding process by feeding a steel strip into the welded pipe unit and subsequently rolling it through multiple rollers. Gradually, the strip is wound into a circular billet with open gaps. The pressure of the squeeze roller is carefully adjusted to maintain the weld gap within the range of 1 to 3 mm, ensuring that the weld ends are flush.
In instances where the gap is excessively large, the proximity effect weakens, leading to insufficient eddy current heat. This results in a poor intergranular joint, with the weld potentially remaining unfused or developing cracks.
Conversely, if the gap is too small, the proximity effect intensifies, causing the welding heat to rise excessively. This may result in the burning of the weld seam. Alternatively, the weld seam might be excessively squeezed and rolled, forming a deep pit that adversely affects the surface quality of the weld.
Upon heating both ends of the pipe to the welding temperature, ordinary metal grains form as a result of the squeeze roller's pressure. These grains penetrate and crystallize with each other, ultimately forming a robust weld. In cases where the extrusion force is insufficient, the number of eutectics formed is limited, leading to decreased weld metal strength and the occurrence of cracks under stress. Conversely, excessive extrusion force can result in cracks in the molten metal squeezed out of the weld. This not only diminishes weld strength but also gives rise to numerous internal and external burrs, and may even lead to defects such as welding gaps.
United Steel Industry is professional manufacturer of SSAW steel pipe in China, if you want to know more about it, please feel free to contact:sales@usisteels.com
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