Views: 1 Author: Site Editor Publish Time: 2020-08-17 Origin: Site
Spiral steel pipe is a spiral seam steel pipe made of strip steel coils as raw material, often warm-extruded under urban pressure, spirally bent and formed by automatic double-wire double-sided submerged arc welding process for inner seam and outer seam welding. The raw materials are strip steel coils, welding wire, and flux.
Steel coils must undergo strict physical and chemical inspections before being put into use. The strip head and tail are butt jointed by single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after coiling into steel pipe. Before forming, the strip undergoes leveling, edge trimming, edge planing, surface cleaning and conveying, and pre-bending treatment. Electric contact pressure gauges are used to control the pressure of the cylinders on both sides of the conveyor to ensure the smooth delivery of the strip.
After the welding is completed, radiographic inspection shall be carried out for the welds of the spiral steel pipe and the intersecting joints of the spiral welds. Each steel pipe must undergo a corresponding hydrostatic pressure test. The pressure is radially sealed. The test pressure and time will be strictly controlled by the steel pipe hydraulic microcomputer detection device, and the test parameters will be printed.
The spiral shape of the weld is evenly distributed on the circumference of the spiral tube, so the spiral tube has high dimensional accuracy and strong strength. With the same wall thickness, the spiral steel pipe can withstand greater pressure. And because it is continuously bent and formed, the length of the spiral tube is not limited, and the length can be set at will.
The defect of the weld of the spiral steel pipe is "oblique defect". During use, the main stress direction of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than that of the straight seam pipe; secondly, because the pipeline steel is a rolled steel plate, the impact toughness has a large anisotropy, and it is rolled along. The CVN value in the direction can be 3 times higher than the CVN value perpendicular to the rolling direction.