Test items
The testing items of welded steel pipes include: surface defects, shape, size, weight, tensile test, flattening test, galvanized layer weight, galvanized layer uniformity, galvanized layer surface quality, galvanized layer adhesion, etc. Choose appropriate testing items based on your actual needs.
Project technical requirements
Surface defects: The inner and outer surfaces of the steel pipe are required to be smooth, and folding, broken lines, delamination, lap welding, arc breakage, burn-through and other defects whose depth after grinding exceeds the deviation of the wall thickness are not allowed. These defects should be completely removed, and the remaining wall thickness at the removed location should not be less than the minimum allowable wall thickness deviation. Other local defects whose depth does not exceed the deviation below the wall thickness are allowed to exist.
Tensile strength: The tensile strength of the steel pipe should not be less than 370MPa.
Lower yield strength: During the yielding period of the steel pipe sample, the minimum stress excluding the initial instantaneous effect should not be less than 235MPa.
Elongation after fracture: After the specified stress is removed from the steel pipe sample, the ratio of the elongation to the original gauge length should not be less than 15%.
In terms of flattening performance: it is required that when the distance between the two flat plates is 2/3 of the outer diameter of the steel pipe, no cracks or cracks are allowed in the weld. When the distance between the two flat plates is 1/3 of the outer diameter of the steel pipe, no cracks or cracks are allowed in the welding seam. No cracks or rips are allowed, and continue to flatten until the pipe wall is snug. The entire flattening process does not allow for delamination or metal overburning.
Weight of the galvanized layer: When measuring the weight of the zinc layer of the steel pipe, the total weight per unit area of the galvanized layer on the inner and outer surfaces of the steel pipe should not be less than 300g/m².
Uniformity of galvanized layer: The steel pipe sample does not appear red when immersed in copper sulfate solution for 5 consecutive times.
Galvanized layer adhesion: After the steel pipe passes the galvanized layer adhesion test, the zinc layer is not allowed to peel off on the sample.
Surface quality of galvanized layer: The galvanized layer on the inner and outer surfaces of the steel pipe should be complete. Black spots and bubbles that are not coated with zinc are not allowed to exist. Small rough surfaces and local zinc tumors are allowed to exist.
