1, appearance inspection: the naked eye is generally the main observation, sometimes with a 5-20 times magnifying glass for observation. Through the appearance inspection, welded elbow weld surface defects can be found, such as biting edge, weld tumor, surface cracks, porosity, slag and weld penetration. The shape and size of the weld seam can also be measured using a weld port detector or sample plate.

2, non-destructive testing: detection of defects such as slag, porosity, cracks hidden inside the weld. Currently the most common use is the use of X-ray inspection, ultrasonic flaw detection and magnetic flaw detection. X-ray inspection is the use of X-ray photography of the weld, according to the negative image to determine the presence of internal defects, the number and type of defects. Then according to the product technical requirements to assess whether the weld is qualified. The basic principle of ultrasonic flaw detection is shown in the figure below. When the ultrasonic beam reaches the metal-air interface, it is refracted and passes through the weld. If there is a defect in the weld, the ultrasonic beam will be reflected to the probe and be accepted, and then the reflected waves will appear on the fluorescent screen. According to these reflected waves and normal wave comparison, identification, you can determine the size and location of the defect. Ultrasonic flaw detection is much simpler than radiography, and therefore widely used. However, ultrasonic flaw detection can often only be based on operational experience to make a judgment, and can not leave the test based. For the weld surface is not deep internal defects and surface cracks very small, but also can use magnetic flaw detection.

3, water pressure test and air pressure test: for the requirement of sealing the pressurized container, water pressure test and (or) air pressure test to check the seal of the weld and the ability to withstand pressure. The method is injected into the container 1.25-1.5 times the working pressure of water or gas equal to the working pressure (mostly with air), stay for a certain period of time, and then observe the pressure drop in the container, and external observation of leakage, according to which the weld can be assessed whether qualified.

4, the mechanical properties of the elbow test: nondestructive flaw detection can find defects inherent in the weld, but can not explain how the mechanical properties of the metal in the heat-affected zone of the weld, so sometimes the welded joint to be tensile, impact, bending and other tests. These tests are completed by the test plate. The test plate used is best welded together with the cylinder longitudinal seam to ensure consistent construction conditions. The test plate is then subjected to mechanical properties tests. In practice, this test is generally performed only on welded joints of new steel grades.