Four quality inspection aspects of elbow welding


Release time:

2022-09-14

1. Appearance inspection: Generally, it is mainly observed with the naked eye, and sometimes with a magnifying glass of 5-20 times. Through visual inspection, it can be found that the surface defects of the welded elbow, such as undercut, weld flash, surface crack, porosity, slag inclusion and welding penetration, etc. The outer dimensions of the weld can also be measured with a weld joint detector or a template.

Four quality inspection aspects of elbow welding

1. Appearance inspection: Generally, it is mainly observed with the naked eye, and sometimes with a magnifying glass of 5-20 times. Through visual inspection, it can be found that the surface defects of the welded elbow, such as undercut, weld flash, surface crack, porosity, slag inclusion and welding penetration, etc. The outer dimensions of the weld can also be measured with a weld joint detector or a template.

2. Non-destructive inspection: inspection of defects such as slag inclusions, pores, and cracks hidden in the weld. At present, the most common use is the use of X-ray inspection, as well as ultrasonic flaw detection and magnetic flaw detection. X-ray inspection is to use X-rays to photograph the weld, and to judge whether there are internal defects, the number and type of defects according to the negative image. Then evaluate whether the weld is qualified according to the technical requirements of the product. The basic principle of ultrasonic flaw detection is shown in the figure below. The ultrasonic beam is emitted by the probe and transmitted to the metal. When the ultrasonic beam is transmitted to the interface between the metal and the air, it is refracted and passed through the weld. If there is a defect in the weld, the ultrasonic beam will be reflected to the probe and accepted, and the reflected wave will appear on the screen. According to the comparison and identification of these reflected waves and normal waves, the size and location of the defect can be determined. Ultrasonic flaw detection is much simpler than X-ray photography, so it is widely used. However, ultrasonic flaw detection can often only be judged by operating experience, and no inspection basis can be left. Magnetic flaw detection can also be used for internal defects that are not deep from the surface of the weld and tiny cracks on the surface.

3. Hydrostatic test and air pressure test: For pressure vessels that require tightness, a hydrostatic test and/or an air pressure test must be carried out to check the tightness and pressure-bearing capacity of the weld. The method is to inject 1.25-1.5 times the working pressure of clean water or gas equal to the working pressure (mostly air) into the container, stay for a certain time, and then observe the pressure drop in the container, and observe whether there is leakage externally. , according to which the qualification of the weld can be assessed.

4. Mechanical performance test of elbow: NDT can find the inherent defects of the weld, but it cannot explain the mechanical properties of the metal in the heat-affected zone of the weld, so sometimes tensile, impact, bending and other tests are required for welded joints. These tests are performed with test panels. The test plate used is preferably welded together with the longitudinal seam of the cylinder to ensure consistent construction conditions. The test panels were then tested for mechanical properties. In actual production, this test is generally only performed on welded joints of new steel grades.

penetration,undercut, template