When the width of the steel strip is less than the allowable deviation, the squeezing force of the welded steel pipe will be reduced, which will cause the welding of the steel pipe loose, and cracks or open-end pipe will appear. When the width of the strip is greater than the allowable deviation,the squeezing force will be increased when the steel pipe is welded, which will cause tip, welding or burr welding defects appearing on the weld of the steel pipe. Therefore, the fluctuation of the strip width not only affects the accuracy of the steel pipe's outer diameter, but also seriously affects the surface quality of the steel pipe.
About the steel pipe that requires the same section wall thickness difference does not exceed the specified value (that is to say the uniformity of the steel pipe wall thickness is high), the fluctuation of strip thickness will transfer the allowable value that exceeds the thickness difference of one steel strip to the wall thickness difference of finished steel pipe, which will waste a large number of steel pipe for the thickness of the pipe exceeds the allowable deviation. Thickness fluctuations not only affect the thickness accuracy of the finished steel pipe, at the same time, the difference of steel strip's thickness will cause the extrusion pressure and welding temperature are instability while the steel pipe in the welding, which will result in welded steel pipe weld quality instability.
In addition, the existence of interlayer, impurities, trachoma and other material defects in the interior of steel is also an important factor to affect the quality of steel pipe .
Therefore, before welding the steel strip , we should check the surface quality and geometric size of each steel strip. For the steel strip that the quality does not meet the standard requirements, we shouldn't carry out production to avoid unnecessary losses.
