In the hydraulic test of the ERW pipe/tube, it is often found that the rupture opening is broken off from the weld line of the ERW steel pipe, which indicates that the strength of the welded part is lower than that of the base metal. Through the experimental analysis, it is found that the thickness of the sample in the weld is reduced if the internal scratching groove is formed on the inner surface of the steel pipe during the removal of the burr in the weld. In tensile tests, samples are easily broken from this point.
The water pressure test of the water supply pipeline is a means to evaluate the final quality of the steel pipe laying. Generally speaking, we have two requirements for the static hydraulic pressure test: one is to correctly reflect the leakage of the pipeline; second, the pressure test without problems, and the interface will not be damaged by the pressure test. On the contrary, it will affect the quality of the project, or rework, retest, resulting in waste, and even no personal safety accidents.
In addition, when API SPEC 5L is used for the tensile test of the weld, the residual height is selected to remove or retain the weld, and the weld breaks often occur. This indicates that the strength of ERW steel pipe weld is lower than that of base metal. There are two reasons for the analysis: first, the strength of the welded joint of the steel tube is lower than the strength of the base metal; the second is to scrape the inner surface of the steel pipe when the burr is removed in the weld. Due to the unreasonable transition between the welding position and the base material, the trench or the residual burr will cause the stress concentration, so the overall structure strength of the weld is lower than the structure strength of the matrix material. Therefore, the transition shape between the welded parts of the steel pipe and the base metal should be optimized to ensure the overall quality of the steel pipe.
