Excessively large gaps can lead to reduced proximity effects, insufficient eddy current heat, poor intergranular bonding of the weld seam, and ultimately result in incomplete fusion or cracking.
Excessively small gaps, on the other hand, can cause increased proximity effects, excessive welding heat, leading to burn-through of the weld seam; or the formation of deep pits after extrusion and rolling, affecting the surface quality of the weld seam.
After heating both edges of the tube blank to the welding temperature, under the compression of squeeze rolls, common metallic grains interpenetrate and crystallize, ultimately forming a solid weld seam. If the extrusion force during spiral steel tube welding is too small, the number of common crystals formed will be limited, reducing the metal strength of the weld seam and potentially causing cracking under stress. Conversely, excessive extrusion force can squeeze out molten metal from the weld seam, not only weakening the weld strength but also generating numerous internal and external burrs, and even causing defects such as overlapping seams.
Not only is welding bias unnecessary, but the internal and external weld seams should be maintained at 1-3mm. The spiral angle of the spiral tube weld seam is typically 50-75 degrees, resulting in a combined stress that is 60-85% of the principal stress in directly welded pipes. Under the same working pressure, the wall thickness of a spiral pipe is reduced compared to a straight-welded pipe of the same diameter.
During the forming process of spiral steel tubes, the steel plate undergoes uniform deformation with minimal residual stress and no surface scratches. The processed spiral steel tubes offer greater flexibility in terms of diameter and wall thickness dimensions and specifications.
Spiral steel tubes can be utilized for liquid transportation (water supply and drainage), natural gas transportation (gas, steam, liquefied petroleum gas), and structural applications (pile pipes, beams, docks, roads, and piping for building structures).
