1. Appearance inspection.
The appearance inspection of welded joints is a cumbersome but widely used inspection method, and is an important part of the inspection. It is mainly to find defects on the surface of the weld and deviations in size, and to inspect with the naked eye, with the help of gauges and magnifying glasses. If there are defects on the surface of the weld, there is a possibility of defects inside the weld. Therefore, the weld surface of the spiral welded pipe shall not have defects such as broken arc, burn-through, cracks, scars, folds, arc pits, etc. The weld shape should be even and regular, and the transition should be smooth.
There are several types of weld seams for spiral welded steel pipes:
Steel strip butt weld seam: Steel strip butt weld seam is the weld seam where the steel plate or steel strip on the spiral seam steel pipe is connected at the head and tail;
Butt weld seam: It is a circular weld seam formed by connecting two sections of steel pipe together;
Positioning weld seam: It is a weld seam used to fix the butt edge before the final welding. After the two edges of the tube blank are heated to the welding temperature, they are squeezed by the extrusion roller to form a common metal grain that penetrates and crystallizes each other, and finally forms a strong weld seam.
If the extrusion pressure of the spiral steel pipe is too small, the number of common crystals will be reduced, and the strength of the weld metal will be reduced, and cracks will appear after the force is applied; if the extrusion pressure is too large, the molten metal will be squeezed out of the weld seam. Not only does it reduce the strength of the weld seam, but it will also produce a large number of internal and external burrs, and even produce defects such as weld seams.
During the forming process, the steel plate deforms evenly, the residual stress is small, and no scratches are produced on the surface. The processed spiral steel pipe has greater sensitivity in the size specification range of diameter and wall thickness, especially in the small and medium diameter thick wall pipe, which has advantages that other processes cannot compare with, and can meet users' more requirements in terms of spiral steel pipe specifications. The advanced double-sided submerged arc welding process can complete welding in the best position, and it is not easy to show defects such as misalignment, welding deviation and incomplete penetration, and it is easy to control the welding quality.
2. Physical inspection:
The physical inspection method is a method of measuring or inspecting by applying some physical phenomena.The inspection of internal defects of materials or workpieces generally adopts non-destructive testing methods, which include ultrasonic testing, radiographic testing, penetration testing, magnetic testing, etc. Strength test of pressure vessels: In addition to the sealing test, pressure vessels must also undergo strength tests, which are commonly water pressure tests and air pressure tests.They can both test the density of welds of containers and pipelines working under pressure, and air pressure tests are more flexible and faster than water pressure tests. At the same time, the products after the test do not need to be drained, which is especially suitable for products that are difficult to drain. However, the risk of the test is greater than that of the water pressure test. When conducting the test, the corresponding safety and technical measures must be adhered to to prevent accidents during the test.
