The wave detection technology of straight seam steel pipe weld seam is a detection technology that has gradually emerged in recent years, which is of great significance for improving the stability of straight seam steel pipe. Regarding the specific application and common problems of straight seam steel pipe wave detection, we will bring you a specific content introduction:
First, what are the common welding defects in welds? How is each formed? Common defects in welds include pores, slag inclusions, incomplete penetration, incomplete fusion, and cracks.
1. Pores are the cavities formed in the weld metal that absorb excess gas or gas generated by metallurgical reactions when the welding pool is at a high temperature during the welding process. It is too late to escape before cooling and solidification. The main reason for the formation is that the electrode or flux is not dried before welding, and the dirt on the surface of the weldment is not cleaned.
2. Incomplete penetration refers to the phenomenon that the base metal at the root of the welded joint is not penetrated. The main reason is that the welding current is too small, the strip speed is too fast or the welding specification is improper.
3. Unfused means that there is no fusion between the filler metal and the base metal or between the filler metal and the filler metal. The main reason for non-fusion is that the groove is not clean, the speed of the strip is too fast, the welding current is too small, and the angle of the welding rod is improper.
4. Slag inclusion: refers to the slag or non-metallic inclusions remaining in the weld metal after welding. The main reason for slag inclusion is that the welding current is too small, the welding speed is too fast, and the cleaning is not clean so the slag or non-metallic inclusions are too late to float.
5. Crack: refers to the crack that is partially broken in the heat-affected zone of the weld or base metal during or after welding. Cracks can be divided into hot cracks, cold cracks, and reheat cracks according to their causes. Hot cracks are caused by improper welding processes during welding; cold cracks are caused by excessive welding stress, high hydrogen content in the welding rod flux, or excessive rigidity difference of the weldment. Therefore, it is also called a delayed crack; a reheat crack is generally the crack generated by reheating (stress relief heat treatment or another heating process) of weldment after welding.
Second, in weld seam wave flaw detection, why is shear wave flaw detection often used?
Pores and slag inclusions in the weld are three-dimensional defects and are less harmful. Cracks, incomplete penetration, and incomplete fusion are planar defects, which are very harmful. In weld flaw detection, due to the influence of high reinforcement and dangerous defects such as cracks, incomplete penetration, and incomplete fusion in welds, they are often perpendicular to or at an angle to the detection surface, so shear wave flaw detection is generally used.
Third, what principles should be used to select the K value of the probe when shear wave flaw detection welds are used? The choice of probe K value should be considered from the following three aspects:
1. Enable the sound beam to scan the entire weld section.
2. Make the center line of the sound beam perpendicular to the main dangerous defects as much as possible.
3. Ensure sufficient flaw detection sensitivity.
Fourth, what are the basic scanning methods of the angled probe during weld flaw detection, and what are the main functions of each?
Zigzag inspection is a scanning method in which front and rear, left and right, and corner scanning are used simultaneously, and the probe moves in a zigzag shape. The weld seam can be inspected for defects.
Left and right scanning: the scanning method in which the probe moves in parallel along the direction of the weld. The longitudinal flaw length of the weld can be inferred.
Front and rear scanning: infer the depth of the defect and its height.
Corner scanning: determine the directionality of defects.
Front and back, left and right, and corner scanning is carried out at the same time, and relatively large echoes of defects can be found, and then the location of defects can be determined.
Surround Scan: Infer defect shape.
Parallel, oblique parallel inspection and cross-scan inspection: detect transverse defects in welds and heat-affected zones.
Tandem scanning: to detect planar defects perpendicular to the flaw detection surface.
Fifth, in weld flaw detection, how to determine the position of the defect in the weld? After the defect wave is found in the weld flaw detection, the position of the defect in the actual weld should be determined according to the position of the defect wave on the oscilloscope screen. The defect positioning methods are divided into:
1. Sound path positioning method: When the instrument adjusts the scanning speed according to the sound path 1:n, it is used to determine the defect position.
2. Horizontal positioning method: when the instrument adjusts the scanning speed according to the horizontal 1:n, it is used to determine the defect position.
3. Depth positioning method: when the instrument adjusts the scanning speed according to the depth 1:n, it is used to determine the defect position.
6. What are the methods for measuring the length of defect indication in weld flaw detection? What situations does each apply to? In flaw detection, if the defects located on or above the quantitative line are found, the indicated length of the defect wave should be measured.
The JB/T4130.3-2005 standard stipulates that when the defect wave has only one high point, use the 6dB method to measure its indicated length. When the defect wave has multiple high points and the wave height of the endpoint is in zone II, use the endpoint 6dB method to measure its indicated length.
Post time: Mar-20-2023