How to check the welding quality of elbow pipe fittings？
1. Appearance inspection of elbow pipe fittings: generally, the naked eye survey is the main method. Through appearance inspection, it can find the appearance defects of welding elbow pipe fittings, and sometimes use 5-20 times magnifying glass to investigate. Such as edge biting, porosity, welding tumors, surface cracks, slag inclusion and penetration, etc. The shape dimension of the weld can also be measured by the welding detector or sample.
2. Nondestructive inspection of elbow pipe fittings: inspection of slag, porosity, cracks and other defects hidden in the weld. X – ray inspection is to use X – ray to take pictures of the welding seam, according to the negative impression to determine whether there are internal defects, the number and type of defects. Now the most widely used is the selection of X-ray inspection, as well as ultrasonic inspection and magnetic inspection. Then according to the product skill requirements to identify whether the weld is qualified. At this point, reflected waves appear on the screen. According to the comparison and identification of these reflected waves with normal waves, the size and location of the defect can be determined. Ultrasonic flaw detection is much simpler than X-ray, so it is widely used. However, ultrasonic inspection can only be judged by the operation experience, and can not leave the inspection basis. The ultrasonic beam is sent from the probe into the metal, and when it reaches the metal-air interface, it refracts and passes through the weld. If there are defects in the weld, the ultrasonic beam will be reflected to the probe and be borne, for the internal defects of the weld surface is not deep and the appearance of the very small cracks, magnetic flaw detection can also be used.
3. The mechanical properties of elbow pipe test: nondestructive testing can find the inherent defects of the weld, but can not clarify the mechanical properties of the metal in the heat affected zone of the weld, so sometimes to make tension, impact, bending and other experiments on the welded joint. These experiments are done by the experimental board. The test plate used is best welded together with the longitudinal seam of the cylinder to ensure consistent construction conditions. Then the mechanical properties of the test plate are tested. In practice, only the welding joints of new steel are tested in this respect.
4. Elbow pipe pressure test and pressure test: for the pressure vessel sealing requirements, water pressure test and (or) pressure test, to check the sealing and pressure ability of the weld. The method is to inject 1.25-1.5 times the working pressure of water or equal to the working pressure of gas (mostly with air) into the container, stay for a certain time, and then investigate the pressure drop in the container, and investigate whether there is leakage outside, according to these can identify whether the weld is qualified.
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